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Biomass gasification technology under microwave irradiation is a new and novel method, and the energy conversion performances during the process play a guiding role in improving the energy conversion efficiencies and developing the gasification simulation models. In order to improve the energy utilization efficiency of microwave biomass gasification system, this study investigated and presented the energy conversion performances during biomass gasification process under microwave irradiation, and these were materialized through detailing (a) the energy conversion performance in the microwave heating stage, and (b) the energy conversion performance in the microwave assisted biomass gasification stage. Different forms of energies in the biomass microwave gasification process were calculated by the method given in this study based on the experimental data. The results showed that the useful energy (energy in silicon carbide (SiC), 18.73 kJ) accounted for 31.22% of the total energy input (electrical energy, 60.00 kJ) in the heating stage, and the useful energy (energy in the products, 758.55 kJ) accounted for 63.41% of the total energy input (electrical and biomass energy, 1196.28 kJ) in the gasification stage. During the whole biomass gasification process under microwave irradiation, the useful energy output (energy in the products, 758.55 kJ) accounted for 60.38% of the total energy input (electrical and biomass energy, 1256.28 kJ), and the energy in the gas (523.40 kJ) product played a dominate role in product energy (758.55 kJ). The energy loss mainly included the heat loss in the gas flow (89.20 kJ), magnetron loss (191.80 kJ) and microwave dissipation loss (198.00 kJ), which accounted for 7.10%, 15.27% and 15.76% of the total energy, respectively. The contents detailed in this study not only presented the energy conversion performances during microwave assisted gasification process but also supplied important data for developing gasification simulation models. • Energy conversion performances of microwave biomass air gasification were detailed. • Effects of gasification temperature and SiC loading were investigated. • The useful energy output accounted for 60.38% of the total energy input. • Energy loss was mainly by magnetron (15.27%) and microwave dissipation (15.76%). [ABSTRACT FROM AUTHOR]

In the scope of the rapid technological advancements, nanoparticles (NPs) have gained prominence due to their excellent and tunable biological, and physicochemical properties. Nowadays, different methods are used for their synthesis. In particular, the green synthesis of metal precursors for the synthesis of NPs, represents a cost-effective, environmentally friendly, and hazardous chemical-free method for developing a large variety of NPs. By exploiting plant extracts, the production rate of NPs is relatively faster. Due to fossil reserves and high fuel consumption, renewable and clean energy materials are urgently needed to improve environmental sustainability. With outstanding electrochemical and physicochemical characteristics, molybdenum-based NPs (Mo-NPs) are gaining increasing attention in the fields of energy conversion and storage. Considering the significance of Mo-NPs synthesized from greener routes and their energy applications, it is necessary to review recent trends and developments in this field. This review summarizes important research studies and future research guidelines for the preparation of Mo-NPs through green routes and their applications to meet global energy and environmental demands. Moreover, future research directions are also highlighted to achieve sustainable greener precursors and Mo-NPs based energy storage devices. [Display omitted] • An overview on research results and progress of Mo-NPs in energy applications. • An overview of different greener routes for the synthesis of Mo-NPs. • Important and interesting energy applications of Mo-NPs are highlighted. • Major accomplishments are summarized in different tables for instant information. • Existing challenges and possible explanations are summarized for future research. [ABSTRACT FROM AUTHOR]

The development of low-cost electrochemical catalytic nanomaterials for efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) through structural and composition control is a great challenge. Herein, a 3D hybrid structure is designed by an in-situ approach for growing 2D leaf-like nanosheet arrays on 1D electrospun nanofibers. The resultant catalysts composed of Cr-doped Co nanoparticle decorated N-doped carbon nanosheet and carbon nanofiber are synthesized by subsequent Cr3+ impregnation and heat treatment. The excellent properties of the as-prepared cathode benefit from the novel establishment of the 3D structure and the regulating mechanism of the electron density of Co after Cr doping, which simultaneously increases the mass and charge transfer process during the catalytic reaction. Consequently, Cr 0.10 -Co@NC exhibits excellent catalytic performance for the ORR (with a half-wave potential of 0.84 V) and OER (with an overpotential of 370 mV). When used in a homemade ZAB for evaluating their practical reversible performance, the device exhibits a higher open-circuit voltage (1.45 V) and a smaller potential gap (0.73 V) with excellent cycle durability of 110 h. This work offers a well-designed structure and development for synthesizing efficient and durable electrocatalysts in electrochemical energy conversion technologies. [Display omitted] • 3D hybrid structure was synthesized by growing 2D MOF on 1D electrospun nanofibers. • Cr-doped Co@NC has much-enhanced mass transfer and electrical conductivity. • Cr 0.10 -Co@NC has an excellent bifunctional catalytic performance of the ORR and OER. • The excellent stability of Cr 0.10 -Co@NC toward ORR and OER was confirmed. • Cr 0.10 -Co@NC exhibits outstanding performance in Zinc-air batteries. [ABSTRACT FROM AUTHOR]

The development of cost-effective, highly efficient and stable electrocatalysts for alkaline water electrolysis at a large current density has attracted considerable attention. Herein, we reported a one-dimensional (1D) porous Mo 2 C/Mo 2 N heterostructured electrocatalyst on carbon cloth as robust electrode for large current hydrogen evolution reaction (HER). The MoO 3 nanobelt arrays and urea were used as the metal and non-metal sources to fabricate the electrocatalyst by one-step thermal reaction. Due to the in-situ formed abundant high active interfaces and porous structure, the Mo 2 C/Mo 2 N electrocatalyst shows enhanced HER activity and kinetics, as exemplified by low overpotentials of 54, 73, and 96 mV at a current density of 10 mA cm−2 and small Tafel slopes of 48, 59 and 60 mV dec−1 in alkaline, neutral and acid media, respectively. Furthermore, the optimal Mo 2 C/Mo 2 N catalyst only requires a low overpotential of 290 mV to reach a large current density of 500 mA cm−2 in alkaline media, which is superior to commercial Pt/C catalyst (368 mV) and better than those of recently reported Mo-based electrocatalysts. This work paves a facile strategy to construct highly efficient and low-cost electrocatalyst for water splitting, which could be extended to fabricate other heterostructured electrocatalyst for electrocatalysis and energy conversion. [Display omitted] • Porous and heterostructured Mo 2 N–Mo 2 C nanobelts electrocatalyst was prepared by one-step thermal reaction. • The abundant high active interfaces and good accessibility of more reactants to active sites improve the HER performance. • The Mo 2 N–Mo 2 C electrocatalyst shows a low overpotential of 290 mV to reach 500 mA cm−2 in alkaline media. [ABSTRACT FROM AUTHOR]

Hydrogen is one of the popular abundant elements in the world and, it is rising as a preferential energy and has developed a tool for decarbonization. Recently, hydrogen has been considered as next generation fuel for cars, trucks, homes, etc, because of the arising of worse climate. In this present work, the cost-effective and efficient electrocatalyst of calcium molybdate nanostructures were successfully prepared with the help of non-ionic surfactant (PEG) through the co-precipitation method for hydrogen evolution reaction. In XRD spectra, the high crystallite peak observed at 28.4° value corresponded to (112) lattice planes confirmed the formation of calcium molybdate nanostructures. In Raman spectra, the existence of tetrahedral [MoO 4 ] clusters and octahedral [CaO 8 ] clusters confirmed tetragonal calcium molybdate nanostructures formation. In SEM analysis, unique morphologies such as dumbbell and spindle-like structures was observed, which was achieved by using the PEG. The pore volume, pore diameter and specific surface area of CaMoO4–6 ml PEG were found to be 0.149 cc/g, 11.685 nm and 28.07 m2/g respectively. Electrochemical performance confirmed that the CaMoO4–6 ml PEG nanostructures exhibited superior HER activity with the low 198 mV overpotential at 10 mA/cm2 and lesser 204 mV/dec Tafel slope value. The charge transfer resistance of CaMoO4–6 ml PEG was 0.65 Ω, which has smaller than that of other electrocatalysts such as pure CaMoO4 (24.9 Ω), CaMoO4–2 ml PEG (2.47 Ω) and CaMoO4–4 ml PEG (2.04 Ω). The excellent HER activity was explored elevated electronic conductivity, mesoporous nature, high surface area and, unique morphology. [Display omitted] • CaMoO4–6 ml PEG explored 0.149 cc/g, 11.685 nm pore volume and diameter, 28.07 m2/g surface area. • CaMoO4–6 ml PEG exhibited superior HER activity with 198 mV at 10 mA/cm2 and lesser Tafel slope value of 204 mV/dec. • Excellent HER activity attributed high electronic conductivity, mesoporous nature, large surface area and, unique morphology. [ABSTRACT FROM AUTHOR]

Constructing an efficient co-catalyst/photocatalyst system for charge separation boosting photocatalytic hydrogen generation is a vital challenge. Herein, highly-dispersed PdS nanoparticles (NPs) acting as an efficient hole co-catalyst has been decorated on the ultrathin In 2 S 3 nanosheets. The strong interactions between PdS and In 2 S 3 via Pd–S–In bonds enable an intimate interface junction. Due to the high capacity of PdS for the hole capture with the assistance of internal electric field, the photogenerated charge carriers are not only separated effectively, the semiconductor photocatalyst In 2 S 3 is also protected from the photo-oxidation. As expected, a remarkable H 2 production rate of 142.27 μmol/h has been achieved for 3PdS/In 2 S 3 nanocomposite, which is 149.8 times higher than that of the pristine In 2 S 3 nanosheets, and 13.3 times superior to the In 2 S 3 decorated with a reductive co-catalyst Pt. This work provides a new insight into the co-catalyst modification engineering for an efficient photocatalytic energy conversion. [Display omitted] • Efficient hole co-catalyst PdS NPs are anchored on the ultrathin In 2 S 3 nanosheets. • Internal electric field expedites holes from In 2 S 3 to PdS via the close interface. • Rapid charge recombination and photo-corrosion of In 2 S 3 are inhibited effectively. • 3PdS/In 2 S 3 composite shows a superior activity for photocatalytic H 2 production. [ABSTRACT FROM AUTHOR]

In this study, the effect of air addition to the air electrode on the long-term stability and efficiency of solid oxide cells for CO 2 electrolysis, with 23.8% CO as protective gas in the fuel electrode, has been investigated. The results show that without continuous purging of the air in the air electrode (Cell-1), the degradation rate was 8.37%/kh in the 1070 h electrolysis process, while with 5 L/min air supplied to the air electrode (Cell-2), the degradation rate was 24.41%/kh. Impedance analysis indicates that the degradation of Cell-1 was mainly because of the increase in O2− exchange polarization impedance, while the degradation of Cell-2 was caused mainly by the variation of ohmic impedance. The microstructural characterization indicated a decrease in active Ni in the fuel electrode in both Cell-1 and Cell-2, but the degree of nickel loss depended on the test time. At the outlet of the Cell-2, the appearance of carbon further explains the faster degradation rate, although the carbon deposition was not directly caused by the introduction of air into the air electrode. Energy spectral analysis shows that the air electrode in Cell-1 generated Sr rich phases, which indicates that the absence of air in the air electrode in the electrolysis process indeed causes more serious microstructure damage. The energy conversion efficiency could exceed 86% if the energy consumed for heating the air is ignored. This work provides a scenario for the application of solid oxide cells for CO 2 electrolysis without air purging in the air electrode. • 1070 h of CO 2 electrolysis was conducted with no gas in air electrode. • Energy conversion efficiency reached more than 86% at −200 mA cm−2 and 1.216 V. • The voltage degradation rate was 8.37%/kh with no gas in air electrode. • The loss of Ni (more than 3%) dominates the degradation of fuel electrode. • The formation of Sr rich phase dominates the deterioration of air electrode. [ABSTRACT FROM AUTHOR]

Herein, we report a new class of CdS/CuCo 2 S 4 dots-on-rods nanostructures that exhibit efficient visible-light-induced H 2 evolution from water. The material CuCo 2 S 4 nanodots over CdS nanorods are fabricated through controlled loading in a facile hydrothermal process and formed a heterojunction, maximizing the energy conversion, that shows advanced performance in photochemical H 2 evolution (rate: 33.32 mmol g−1h−1 and AQY: 13.2% at λ = 420 ± 15 nm) from water. The experimental and theoretical results on physical and chemical properties revealed that the photocatalytic system is positively correlated with the H 2 production rate and suggest that CuCo 2 S 4 nanodots in CdS nanorods plays a critical role in relative efficiency of the H 2 generation. The surprisingly high activity was attributed to enhanced charge carriers' separation and transfer efficiency, confirmed by the kinetic measurements (TAS) and further reinforced from the Kelvin probe force microscopy (KPFM) analysis and theoretical understanding. [Display omitted] • The newly developed CdS/CuCo 2 S 4 was prepared by two-step hydrothermal process. • CuCo 2 S 4 nanodots decorated on CdS nanorods forms nano-heterojunction. • CdS/CuCo 2 S 4 system exhibited H 2 evolution rate of 33.32 mmol g−1h−1. • Structural and electronic properties were computed by DFT studies. • TAS indicates fast charge separation across CdS/CuCo 2 S 4 hetero-junction. [ABSTRACT FROM AUTHOR]

Rational design of electrocatalycally active materials with excellent performance for renewable energy conversion is of great interest. We have developed a nanosheet array of Ni/Co metal-organic framework (MOF) grown on CoO modified Ni foam (CoO/NF) substrate via the solvothermal process. The high surface area and low resistance of Ni/Co-MOF@CoO/NF (NC@CoO/NF) catalyst contribute to efficient water splitting. We have prepared a series of NC-n/CoO/NF (n = 1–4) catalysts to optimize the molar ratio of the Co atom in Ni MOF-74. Among them, NC-2@CoO/NF shows an excellent electrochemical performance in alkaline medium, i.e., low overpotential of 290 and 139 mV for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. For a two-electrode system with NC-2@CoO/NF, a low cell voltage of 1.54 V at 10 mA cm−2 has been obtained for overall water splitting which is much smaller than that with commercial Ir/C– Pt/C pair. This excellent performance can be attributed to the synergistic effects of Ni/Co-MOF and CoO/NF. In addition, the as-prepared NC-2@CoO/NF exhibits excellent long-term stability. The computational simulation also supports experimental results. [Display omitted] • Highly porous Ni/Co bimetallic MOF were grown on CoO modified Ni Form. • As-synthesized catalysts showed an excellent HER and OER properties. • Computational simulation reveled the synergetic effects of Co on Ni-MOF. [ABSTRACT FROM AUTHOR]

With the development of microfabrication technology and micro devices, the demand for Power Micro Electro Mechanical System (Power MEMS) is ever-increasing. However, traditional chemical batteries are not suitable for Power MEMS due to their low energy density. The combustion of hydrogen and hydrocarbon fuels offers a more promising alternative to conventional batteries. However, micro combustion faces the problems of flame instability and low combustion efficiency. Therefore, improving flame stabilization and combustion efficiency in micro combustions is necessary. Studies have made considerable progress in these aspects over the last decade. This paper summarized these studies and classified the optimization schemes according to flame stabilization and combustion efficiency. Besides, research on the Field Synergy Principle was discussed. The synergy between the flow field and temperature gradient field in the micro-scale domain will become a key research area in the future. It is proposed to insert porous media in MTES and MTPVS and adopt catalytic combustion. Adding hydrogen to the mixed gas was recommended. The equivalence ratio of the mixed gas in the range of 0.9–1.1 would be best. The equivalence ratio is the ratio of the theoretical requirement of air with complete combustion to the actual supply of air. • Factors affecting the flame stability in micro combustors are summarized. • Factors affecting the residence time in micro combustors are summarized. • Factors affecting the global efficiency of micro combustors are summarized. • Future works to improve the performance of micro combustors are introduced. [ABSTRACT FROM AUTHOR]

The characters of transient heat transfer and solar absorption are analyzed based on the multiscale CeO 2 reduction to predict the H 2 production, and the results show that the heat absorption of CeO 2 is affected by the diameter and the value of concentration ratio. The proportion of energy absorbed by CeO 2 increases from 0.55% to 42.73% as the diameter of CeO 2 increases from 0.1 to 100 μm. However, the time required for 0.1 and 100 μm CeO 2 to reach 1775 K is 0.07 and 0.83 s, respectively. The peak of the solar-to-fuel energy conversion efficiency (η solar-fuel) for 1 μm CeO 2 is 16.43%, which is the maximum for all selected diameters. After the analysis of the radiation intensity of blackbody and the absorptance of 1 μm CeO 2 as a function of wavelength, we find that comparing with no cutoff wavelength coating, the peak of η solar-fuel increases from 16.43% to 18.91% as the cutoff wavelength is 600 nm. To reach the same temperature of 1773 K, it takes 0.15 and 0.05 s as C is 50 and 200, and η solar-fuel is improved from 14.43% to 17.93%. • Transient heat transfer and solar absorption are analyzed based on the multiscale CeO 2 reduction. • The effects of particle size, irradiation intensity and concentration ratio are considered. • All calculations are based on the variation of absorptance with wavelength for different diameter particles. • The solar-to-fuel energy conversion efficiency is improved with cutoff wavelength coating. [ABSTRACT FROM AUTHOR]

Due to their efficient and cleaner operation nature, proton exchange membrane fuel cells are considered energy conversion devices for various applications including transportation. However, the high manufacturing cost of the fuel cell system components remains the main barrier to their general acceptance and commercialization. The main strategy for lowering the cost of fuel cells which is critical for their general acceptance as alternative energy sources in a variety of applications is to lower the cost of the electrolyte and catalyst. An electrolyte is one of the most important components in the fuel cell and a major contributor to the cost (>$500/m2 for commercial Nafion® series). Nafion is widely used as an electrolyte in PEMs, but it has some limitations in addition to high costs such as low proton conductivity, high-temperature performance degradation, and high fuel crossover. Therefore, the development and manufacturing of low-cost and high-performance electrolyte membranes with higher conductivity (∼0.1 S·cm −1) at a wider temperature range is a top priority in the scientific community. Recent years have seen extensive research on the preparation, modification, and properties of PEMs such as non-Nafion membranes (SPI, PBI, polystyrene, polyphosphazene, SPAEK, SPEEK, SPAS, SPEN), and their composites by incorporating functionalized CNTs, GO as fillers to overcome their drawbacks. This paper provides a comprehensive review of membrane materials and manufacturing with a focus on PEMs. In particular, the review brings out the basic mechanism involved in proton conduction, important requirements, historical background, contending technologies, types, advantages and disadvantages, current developments, future goals, and directions design aspects related to thermodynamic and electrochemical principles, system assessment parameters, and the prospects and outlook. [Display omitted] • The PFSA membranes (Nafion®) have been widely used as commercial membranes in PEMFC and DMFC. • Nafion membranes possess issues like high cost, high-temperature degradation, oxygen leakage, and methanol permeability. • Non-Nafion electrolytes e.g. SPI, PBI, polystyrene, polyphosphazene, SAMCs, & chitosan-based membranes have been reviewed. • CNTs and GO-based composites have been proved as promising materials to replace Nafion membranes. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) is a common reaction in many sustainable energy conversion systems. However, it has become a bottleneck in the development of sustainable energy conversion systems because of its slow kinetics, especially in the common electrolytic water reaction. At present, although there are a lot of researches on OER's catalysts, it is still a great challenge. In this work, a new type of composite was prepared by simple co-precipitation method and Hydrothermal, which is composed of Ce-doped NiFe Layered Double Hydroxide (LDH) and MoSe 2. The electrochemical test results of OER show that the overpotential of 6.7%Ce–NiFe LDH@MoSe 2 is 221 mV at 10 mA/cm2, which is better than that of NiFe LDH (409 mV). And it is better than most of the reported OER catalysts in literature, including precious metal catalysts. Simultaneously, 6.7%Ce–NiFe LDH@MoSe 2 also has smaller Tafel slope (35.8mV/dec), larger ESCA (6689 cm2), long-time stability and selectivity with 92.1% Faraday efficiency. The excellent OER performance of 6.7%Ce–NiFe LDH@MoSe 2 benefits from the increase of active and defective sites and the interface coordination between MoSe 2 and Ce–NiFe LDH. • 6.7%Ce–NiFe LDH@MoSe 2 shows excellent OER performance than NiFe LDH. • The overpotential of 6.7%Ce–NiFe LDH@MoSe 2 is 221 mV with 35.8mV/dec Tafel slop at 10 mA/cm2. • 6.7%Ce–NiFe LDH@MoSe 2 (689 cm2) is nearly 9.6 times higher than that of NiFe LDH (64.75 cm2). • 6.7%Ce–NiFe LDH@MoSe 2 exhibits good selectivity with 92.1% Faradaic efficiency. • The excellent OER performance of 6.7%Ce–NiFe LDH@MoSe 2 benefits from the increase of active and defective sites. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) is a significant reaction in water splitting and energy conversion. However, high price and sluggish kinetics catalysts prevent commercial applications. Generally, noble metals (e.g., iridium and ruthenium), which are expensive and unstable, have been used as catalysts for OER because of their high electrocatalytic activity. In this study, we report a high-performance OER catalyst with oxygen vacancies comprising NiO/Co 3 O 4 nanohybrids. For OER, the NiO/Co 3 O 4 heterostructure show good electrocatalytic performance with a low overpotential of 330 mV. This is higher than those of NiO, Co 3 O 4 , and benchmark IrO 2 candidates at current density of 10 mA cm−2. Furthermore, the NiO/Co 3 O 4 nanohybrids show long-term electrochemical stability for 10 h. The present research results show that NiO/Co 3 O 4 heterostructure is an excellent electrocatalyst for OER. • NiO/Co 3 O 4 nanohybrids are synthesized by the hydrothermal method. • DDA plays a critical role in generating heterostructure. • The plentiful oxygen vacancies exist in heterostructure. • Oxygen vacancy enhances the OER kinetics and activities. [ABSTRACT FROM AUTHOR]

Hierarchical hybrid heterostructures are regarded to be promising materials for highly efficient bifunctional electrocatalysts and high-performance supercapacitors due to their intriguing morphological features and remarkable electrochemical properties. Herein, we demonstrate the rational construct of cost-effective MoO x @NiS 2 hybrid nanostructures as bifunctional electrocatalysts and the electrode material of supercapacitor. Microstructural analysis shows that the hybrid is a kind of hierarchical heterostructure composed of open and porous NiS 2 nanowrinkles in situ grown on non-stoichiometric MoO x nanorods, which greatly improves the conductivity, and effectively maximized the electrochemical surface area. As expected, the MoO x @NiS 2 hybrid show remarkable electrocatalytic performance in alkaline media, such as overpotentials of 101 mV at 10 mA cm−2 for hydrogen evolution reaction (HER) and 278 mV at 20 mA cm−2 for oxygen evolution reaction (OER), and a low cell voltage of 1.62 V to deliver a current density of 10 mA cm−2. Moreover, the hybrid nanostructures present a high specific capacitance 1050 A/g at 1 A/g with ultra-long stability in 6 M KOH. The strategy proposed here introduces a new perspective about the development of efficient earth-abundant bifunctional elecrocatalysts and electrode materials for superior energy conversion and storage devices. Open and porous NiS 2 nanowrinkles (shell) in situ grow on non-stoichiometric MoO x (core) to fabricate the MoO x @NiS 2 hierarchical hybrid heterostructures, which greatly improves the conductivity, specific surface area and forms the heterointerfaces. Thus, the MoO x @NiS 2 hybrid exhibits superior electrocatalytic performance for alkaline water splitting and holds great potential for supercapacitor application. [Display omitted] • Open and porous NiS 2 nanowrinkles in situ grow on non-stoichiometric MoO x nanorods. • The hybrid improves the conductivity, specific surface area and forms the heterointerfaces. • Superior catalytic activity for HER (η 10 = 101 V) and OER (η 20 = 278 mV) is achieved. • A high specific capacitance of 1050 A/g at 1 A/g with superior stability is obtained. [ABSTRACT FROM AUTHOR]

WO 3 has been recognized as a promising photoanode for the conversion of solar energy to hydrogen energy through photoelectrochemical water splitting. Herein, Zn-WO 3 nanorod arrays were synthesized by a two-step solvothermal method and then decorated with FeOOH and CoOOH dual co-catalysts layer through electrodeposition. Characterizations confirm the presence of abundant surface oxygen vacancies in Zn-WO 3 , leading to the increase of carriers with high mobility and thus improving the separation (from 63.7% to 92.0%) and injection (from 61.9% to 95.3%) efficiency of carriers. Meanwhile, the dual co-catalysts layer accelerates the transfer of the hole at the interface and inhibits the photocorrosion. Consequently, the optimal 9-Zn-WO 3 -Fe/Co exhibits the photocurrent of 3.63 mA/cm2 at 1.23 V vs. RHE, which is 90.7% of the theoretical value of WO 3 (ca. 4.0 mA/cm2). This work constructs a highly efficient and stable WO 3 photoanode by an integration strategy of transition metal doping and dual co-catalysts modification. [Display omitted] • A facile strategy to prepare Zn-doped WO 3 with dual co-catalysts is developed. • Multiple characterizations confirm the introduction of surface oxygen vacancies. • Effective carrier separation and transfer are achieved through the bulk and surface modification of WO 3. • The photocurrent density of 9-Zn-WO 3 -Fe/Co reaches 90.7% of the theoretical value of WO 3. [ABSTRACT FROM AUTHOR]

The multicomponent combinations of metals in nanoscale noble metal-free high-entropy materials possess distinctive physiochemical properties, which endow them with rich accessible active sites, strong synergistic effect, and entropy-stabilization effect, enabling them to be promising for driving electrocatalytic water splitting. Herein, an interview of the progress achieved for the synthesis of noble metal-free high-entropy materials and catalytic mechanisms toward water splitting is provided. Some typical synthesis strategies have been systematically reviewed to highlight the advances in synthesizing highly efficient and noble-metal-free high-entropy catalysts. Next, the distinctive advantages of high-entropy materials for the electrochemical water splitting are also manifested to show their great promise for serving as advanced electrocatalysts. Moreover, some representative examples regarding the electrocatalytic oxygen evolution reaction, hydrogen evolution reaction, and overall water splitting based on noble-metal-free high-entropy catalysts are also discussed. In the end, future directions and new energy conversion technologies that can be enabled by the application of noble-metal-free high-entropy materials are outlined. • Noble metal-free high-entropy materials show great promise for water electrolysis. • The synergistic and entropy-stabilization effect enable them to show high activity. • The advantages, synthesis methods, and representative high-entropy catalysts for water splitting are summarized. • The future challenges of noble metal-free high-entropy catalysts for industrial water electrolysis are also discussed. [ABSTRACT FROM AUTHOR]

The development of a highly active and stable hydrogen evolution photocatalyst is a key issue for achieving efficient and comprehensive water splitting, and it is still challenging for the scientific community and practical applications. Herein, we build up a novel visible-light-driven S-scheme in CdS/ZnTHPP binary nanosystem by simple sintering process ensuring the fast transfer of the photo-generated carriers, showing dark green upon simulated sunlight irradiation. Under an optimal condition, the highest hydrogen evolution turnover number (TON) reaches around 22,264 during 128 h irradiation, and the H 2 evolution rates of the best CdS/ZnTHPP binary nanosystem was boosted up to a 400 mmol/g under irradiation for 8 hours with a conversion rate over 10-fold-higher than that of pristine CdS NRs. The macrocyclic compound serves as a region of electron absorption assisting the fast and continuous consumption of photo-generated electrons in this system, thereby concurrently alleviating the recombination of electron-hole pairs. Theoretical analyses reveal that the active sites and the generation of H 2 are controlled by the thermodynamic process. This new finding provides a new approach to rationally designing an efficient solar-to-chemical conversion system. A novel visible-light-driven Z-scheme in CdS/ZnTHPP binary nanosystem was built up by a simple sintering process ensuring the fast transfer of the photo-generated carriers, showing a robust hydrogen evolution performance. [Display omitted] • A novel visible-light-driven Z-scheme in CdS/ZnTHPP binary nanosystem was built. • The best H 2 evolution rate of CdS/ZnTHPP was 400 mmol/g under irradiation for 8 hours. • Theoretical analyses reveal the active sites and the generation of H 2 are controlled by the thermodynamic process. [ABSTRACT FROM AUTHOR]

Developing a bi-functional material which can meet both electrochemical water splitting and supercapacitors (SCs) is a hot spot in current research. In this study, hierarchical zigzag-like phosphorus doped CuCo 2 O 4 nanosheets based 3D electrode materials were successfully synthesized via a hydrothermal method and followed by thermal treatment. Since the unique morphology of 2D nanosheets with zigzag-like edges could provide more reactive sites, which is not only conducive to the hydrogen evolution reaction (HER), but also conducive to the electrochemical energy storage. Meanwhile, the doping of phosphorus was adopted to improve the conductivity, which would further enhance the electrochemical properties of CuCo 2 O 4. Thereafter, its performance for HER and SCs in 1 M KOH were systematically investigated. As an electrode for HER, it only required a low overpotential of 152 mV to reach 10 mA cm−2 with a Tafel slope of 115.7 mV dec−1. Furthermore, I-t test result showed an excellent stability. As an electrode for SCs, it exhibited a high specific capacity of 896.9C g−1 at 1 A g−1 in three-electrode system. All in all, the obtained hierarchical zigzag-like phosphorus doped CuCo 2 O 4 nanosheets provided a feasible route for the design of bi-functional electrode materials both for energy conversion and storage. • The hierarchical zigzag-like P-doped CuCo 2 O 4 nanosheets based 3D electrode materials were successfully prepared. • P-doped CuCo 2 O 4 nanosheets based electrode exhibited improved electrocatalytic activity for HER and excellent stability. • P-doped CuCo 2 O 4 electrode materials can attain great specific capacitances of 1993 F g−1 and excellent endurance performance. • The synthesized zigzag-like P-doped CuCo 2 O 4 nanosheets can be sustainable bifunctional materials for HER and supercapacitors. [ABSTRACT FROM AUTHOR]

Herein, strongly coupled Ni 3 S 2 /MoS 2 hollow spheres derived from NiMo-based bimetal-organic frameworks are successfully synthesized for overall water splitting via a one-pot solvothermal method followed by sulfurization. A well-defined hollow spherical structure with a heterointerface between Ni 3 S 2 and MoS 2 is constructed using solvothermal and sulfurization processes. Owing to their bimetallic heterostructure, porous hollow carbon structure with large surface area, and numerous exposed active sites, the Ni 3 S 2 /MoS 2 hollow spheres are found to be efficient electrocatalysts for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The heterostructured Ni 3 S 2 /MoS 2 hollow spheres show small overpotentials of 303 and 166 mV to reach a current density of 10 mA cm−2 for the OER and HER in 1.0 M KOH, respectively. Furthermore, an overall water-splitting electrolyzer consisting of the Ni 3 S 2 /MoS 2 hollow spheres as both the anode and cathode requires a very low cell voltage of 1.62 V to drive a current density of 10 mA cm−2 with outstanding long-term stability for 100 h. Our findings offer a new pathway for the design and synthesis of electrochemically advanced bifunctional catalysts for various energy storage and conversion applications. [Display omitted] • Ni 3 S 2 /MoS 2 was synthesized using a one-pot solvothermal method followed by sulfurization. • The synergistic effect of binary metal and unique structure led to excellent OER and HER activity. • Ni 3 S 2 /MoS 2 hollow spheres indicated outstanding catalytic activities and stability. [ABSTRACT FROM AUTHOR]

Tailoring the surface chemistry of oxides has been widely used to adjust their catalytic behavior in the energy conversion and storage devices. Herein, nanorods of Ni2+-doped ceria (Ce 1-x Ni x O 2-δ , x = 0, 0.05, 0.1, 0.15) are synthesized via a modified hydrothermal method, and evaluated as the anode catalysts for reduced-temperature solid oxide fuel cells (SOFCs). X-Ray diffraction patterns of as-synthesized powders in air imply successful incorporation of Ni2+ into the fluorite lattice of ceria for x = 0.05 and 0.1, with a secondary phase of NiO observed for x = 0.15. Transmission electron microscopy (TEM) examination confirms a rod-like morphology with a diameter of 10–13 nm and a length of 55–105 nm. Exposure of these powders in H 2 at 600°C results in exsolution of some spherical Ni particles of 11 nm in diameter. Electrochemical measurements on both symmetrical anode fuel cells and functioning cathode-supported fuel cells show an order of the catalytic activity toward hydrogen oxidation - CeO 2-δ < Ce 0·95 Ni 0·05 O 2-δ < Ce 0·9 Ni 0·1 O 2-δ. The anode polarization resistances in 97% H 2 – 3% H 2 O are 0.24, 0.31 and 0.37 Ω⋅cm2 for Ce 0·9 Ni 0·1 O 2-δ , Ce 0·95 Ni 0·05 O 2-δ and CeO 2-δ at 600°C, respectively. Thin (La 0·9 Sr 0.1) (Ga 0.8 Mg 0.2)O 3-δ -electrolyte fuel cells with nanostructured SmBa 0.5 Sr 0·5 Co 2 O 5+δ cathodes and Ce 0·9 Ni 0·1 O 2-δ anodes yield the highest power densities among the investigated series of anodes, e.g. , 820 mW⋅cm−2 in 97% H 2 – 3% H 2 O and 598 mW⋅cm−2 in 68% CH 3 OH - 32% N 2. XPS analyses of reduced nanorods indicate that the highest catalytic activities of Ce 0·9 Ni 0·1 O 2-δ toward fuel oxidation reactions should be correlated to the presence of highly active Ni nanoparticles and increased surface active oxygen, as confirmed by substantially facilitated extraction of the lattice oxygen on the surface by H 2 in temperature-programmed reduction (TPR) measurements. • Nanorods of Ni2+-doped ceria are synthesized as the anode catalysts for SOFCs. • Maximum power densities of 820⋅mW cm−2 were achieved in H 2 at 600°C. • Maximum power densities of 598⋅mW cm−2 were achieved in CH 3 OH at 600°C. • Exsolution of nano-scale Ni particles were observed for Ni2+-doped ceria anodes. • Doping Ni2+ into ceria facilitated surface reduction at low temperatures. [ABSTRACT FROM AUTHOR]

A dual surface modification of an SOFC metallic interconnect with a Gd 2 O 3 layer and an MnCo 2 O 4 coating was evaluated. The tested samples were oxidized for 7000 h in air at 1073 K. Oxidation products were characterized using XRD, SEM-EDS, and confocal Raman imaging, and ASR was measured. The effect of gadolinium segregation at grain boundaries in Cr 2 O 3 was evaluated using S/TEM-EDS. Area specific-resistance was measured and fuel cell tests investigating electrochemical performance and Cr contamination of electrodes were also performed. The results show that the proposed dual modification was more advantageous than either modification applied separately. The fuel cell tests performed after aging in humidified hydrogen at 1073 K and involving an actual interconnect made of this dual-modified material showed that after 250 h of aging its electrochemical parameters were nearly identical to those of the non-aged reference electrode. Moreover, the modification protected the electrodes from Cr poisoning. [Display omitted] • Crofer 22 APU underwent single and dual modifications via dip-coating and/or EPD. • Dual modification reduced the oxidation rate to a larger degree than single ones. • Confocal Raman imaging allowed the phase compositions to be identified. • ASR of dual-modified material after 7000 h of oxidation was excellent. • Dual modification effectively protected electrode materials from Cr poisoning. [ABSTRACT FROM AUTHOR]

The development of electrocatalyst possessing superior oxygen reduction reaction (ORR) activity is highly desirable due to the low sluggish kinetics at the cathode of fuel cell. Here, CoFe 2 O 4 nanoparticles embedded in N-doped carbon nanotubes electrocatalyst (denoted as CoFe 2 O 4 -NC) is synthesized via polymerization of pyrrole, absorbing metal ion and annealing under Ar/NH 3 atmosphere. By in situ integrating the catalytically active CoFe 2 O 4 nanoparticles with the N-doped carbon nanotubes and enhancing electrical conductivity, the as-obtained electrocatalyst exhibits excellent ORR activity and long-term stability with a half-wave potential of 0.86 V and 10 h continuous cycling, outperforming the reported similar catalysts. This work opens a new path for the expansion of low cost and efficient ORR electrocatalysts to substitute Pt-based metals for energy storage and conversion devices. [Display omitted] • In situ synthesis of CoFe 2 O 4 nanoparticles embedded in N-doped carbon nanotubes. • CoFe 2 O 4 -NC exhibits excellent ORR activity with a half-wave potential of 0.86 V and long-term stability. • The immobilization of particles on carbon tube prevents the CoFe 2 O 4 nanoparticles from dissolving or aggregating. [ABSTRACT FROM AUTHOR]

The development of electrocatalysts with high activity and durability for oxygen reduction reaction (ORR) in acidic electrolyte environments remains a serious challenge for clean and efficient energy conversion. Synergistic effects between Pt and inexpensive metals, the d band center of Pt and catalyst morphology could adjust the adsorption and desorption of oxygen intermediates by the Pt. All the factors affect the catalytic performance of Pt-based nanocrystals. Here, we prepared Cu@PtCu 3 NWs with an average diameter of 74.9 nm for Cu and about 10 nm PtCu 3 layer. After etching, the Cu@PtCu 3 nanowires is transformed into PtCu nanotube structure, due to the removal of copper from the surface and interior. PtCu NTs for ORR shows excellent activities and durability due to the integration of structural advantages and synergistic effects. Notably, the mass activity and specific activity of PtCu NTs (0.105 A mg−1 Pt and 0.230 mA cm−2 Pt) are 2.0 and 3.8 times higher than that of commercial Pt/C (0.053 A mg−1 Pt and 0.06 mA cm−2 Pt). The etching process to change the morphology of the catalyst and alter the electronic structure of the catalyst is expected to be useful for the design of future structured Pt-based alloy nanocatalysts. [Display omitted] • Dealloyed PtCu nanotubes for efficient oxygen reduction reactions. • Synergistic interaction on bimetallic structures enhances catalytic activity. • Alloy nanotubes maintain high stability in durability tests. [ABSTRACT FROM AUTHOR]

Reasonable construction of heterostructure is of significance yet a great challenge towards efficient pH-universal catalysts for hydrogen evolution reaction (HER). Herein, a facial strategy coupling gas-phase nitridation with simultaneous heterogenization has been developed to synthesize heterostructure of one-dimensional (1D) Mo 3 N 2 nanorod decorated with ultrathin nitrogen-doped carbon layer (Mo 3 N 2 @NC NR). Thereinto, the collaborative interface of Mo 3 N 2 and NC is conducive to accomplish rapid electron transfer for reaction kinetics and weaken the Mo–H ads bond for boosting the intrinsic activity of catalysts. As expected, Mo 3 N 2 @NC NR delivers an excellent catalytic activity for HER with low overpotentials of 85, 129, and 162 mV to achieve a current density of 10 mA cm−2 in alkaline, acidic, and neutral electrolytes, respectively, and favorable long-term stability over a broad pH range. As for practical application in electrocatalytic water splitting (EWS) under alkaline, Mo 3 N 2 @NC NR || NiFe-LDH-based EWS also exhibits a low cell voltage of 1.55 V and favorable durability at a current density of 10 mA cm−2, even surpassing the Pt/C || RuO 2 -based EWS (1.60 V). Consequently, the proposed suitable methodology here may accelerate the development of Mo-based electrocatalysts in pH-universal non-noble metal materials for energy conversion. • A methodology coupling g as-phase nitridation with simultaneous heterogenization. • The collaborative interface markedly boosts the intrinsic activity of catalysts. • Mo 3 N 2 @NC exhibits superior activity and durability for HER in all pH electrolytes. [ABSTRACT FROM AUTHOR]

Due to the future uses of solar energy in different areas, such as the oxidation of fossil fuel-based contaminants, the reduction of carbon dioxide, heterogeneous photocatalysis, and the generation of inexhaustible and renewable hydrogen gas exploits semiconductors. As a metal free photocatalyst, graphitic carbon nitride (g-C 3 N 4) is classified to solve these energy hazards and ecological difficulties owing to its excellent electronic structure with band energy of about 2.7 eV, robust photochemical stability, and better light-harvesting efficiency. However, its photocatalytic performance is still insufficient due to a minor surface area and poor conductivity. Therefore, heterojunction formation by combining it with a giant band gap material is a potential approach to reestablish polarization in its distinctive band structure, increase its light absorption capacity and enhance its surface area. In this regard, various synthesis techniques have been applied so far to integrate g-C 3 N 4 and other materials for boosting its photocatalytic activity. So far, metal oxide, sulfides, and ferrites are three crucial groups of materials that have been identified and defined to be used to synthesize g-C 3 N 4 dependent nanocomposites. As a result, in this review, we have compiled a list of the most recent g-C 3 N 4 nanocomposites with their applications in solar energy adaptation and pollution control. This study concludes an overview about the next steps to study the nanomaterials based g-C 3 N 4 composites and a range of additional insights to solve the present problems. • This review addresses the properties and structures of g-C 3 N 4 photocatalyst structure. • Pros and cons of their synthesis techniques. • The types of the g-C 3 N 4 -based nanocomposite are emphasized. • Approaches to improve the photocatalytic activity of g-C 3 N 4. • The most up-to-date photocatalytic applications were thoroughly discussed. [ABSTRACT FROM AUTHOR]

Prompt recombination of photo-generated charges in semiconducting material strictly restrict photocatalytic process efficiency. Herein, coupling of Cu x P nanoparticles and PbTiO 3 nanoplates through inert atmosphere calcination process for outstanding H 2 production has been reported. Uniform edging distribution of Cu x P nanoparticles over PbTiO 3 nanoplates; witnessed from TEM analysis revealed an intimate material contact for charge transportation to the active reaction sites of catalyst surface. Besides, junction interface between Cu x P and PbTiO 3 component; confirmed from XPS and Mott-Schottky analysis yield an amplified photo/electro-chemical and catalytic performance. A stronger photocurrent density via., H 2 O 2 electron scavenger and larger photovoltage in junction material compared with PbTiO 3 counterpart; follows higher surface charge transfer efficiency and slower potential decay with longer charge carriers lifetime simultaneously. The PbTiO 3 nanoplates with an optimum amount of Cu x P have achieved maximum H 2 production attaining conversion efficiency of 9.72%. Consequently, a type-II energy band alignment mechanism has been proposed for enhanced H 2 production. Outstanding hydrogen production over Cu x P/PbTiO 3 p-n junction with energy conversion efficiency of 9.72%. [Display omitted] • Coupling of single domain PbTiO 3 with low-cost Cu x P via, built-in electric field. • Cu x P/PbTiO 3 junction interface resulted in outstanding H 2 production. • Hybrid shows high surface charge transfer efficiency and slow potential decay. [ABSTRACT FROM AUTHOR]

Herein, Ni-doped Mn 2 O 3 microspheres are successfully synthesized via the facile coprecipitation of metal ions and ammonium bicarbonates, followed by a heat treatment process. Ni-doped Mn 2 O 3 exhibits outstanding catalytic performance toward the oxygen reduction reaction (ORR) in alkaline media with a half-wave potential of 0.801 V, limiting current density of 6.02 mA cm−2 at 0.6 V vs. RHE, outstanding long-term durability, and strong tolerance to methanol. Furthermore, a Zn–air primary battery using Ni-doped Mn 2 O 3 as an air cathode shows high open-circuit voltage of 1.52 V and high power density of 88.2 mW cm−2, outperforming the commercial Pt/C cathode. The exceptional performance of the Ni-doped Mn 2 O 3 microspheres is ascribed to the hierarchical structure, optimized particle size, and Ni incorporation into Mn 2 O 3. The proposed synthesis strategy provides a new methodology for the design and fabrication of electrochemically active transition metal-doped materials as efficient electrocatalysts for a variety of energy storage and conversion reactions. [Display omitted] • Ni-doped Mn 2 O 3 are fabricated via a simple co-precipitation and annealing process. • Ni-doped Mn 2 O 3 shows outstanding activity and long-term durability toward ORR. • Zn-air primary battery using Ni-doped Mn 2 O 3 possess excellent performance. [ABSTRACT FROM AUTHOR]

The discovery of novel 2D-monoelemental materials with extraordinary physical, mechanical, thermal, optical and electronic properties has predicted many potential applications in various areas of technology based on the grounds of advanced sciences. The monoelemental two dimensional (2D) materials arouse a tremendous attention in different areas of science due to their unique properties and extensive applications. The 2D nanomaterials like Borophene and Bismuthene have emerged as effective nanomaterials due to their unique properties including large surface area, structural anisotropy, tunable band gap, and high carrier mobility. They are attracting increasing research interest in electronics, optoelectronics, and catalysis and also in energy storage and energy conversion applications. These materials are massively studied under theoretical approaches but many of its physical characteristics have still to be analyzed experimentally. This review article gives a detail theoretical and experimental information about the 2D-nanostructured Borophene and Bismuthene materials including their synthesis techniques, properties and also analyzed their advantages and disadvantages over each other. Further we performed an overview of the status of Borophene and Bismuthene in electrochemical and sensing applications including batteries, sensors, catalysis, and gas storage devices. Furthermore, we present our insight into the challenges, future perspective and opportunities, which would hopefully shed light on the great potential of this ever-expanding field. The nanomaterials like borophene and bismuthene have emerged as effective alternatives to graphene with excellent electrochemical properties finding potential applications in detecting and sensing devices. It is established that Borophene and Bismuthene find a large area of applications in developing conductors for electric and thermal appliances. Borophene has demonstrated incredible flexibility and high structural anisotropy and it is a material massively studied by theoretical approaches. However, many of its physical characteristics have still to be realized experimentally. In this review, we present a brief survey on preparation methods of 2D-nanostructured materials Borophene and Bismuthene. Also, an overview of the applications' status of Borophene in electrochemical area, batteries, sensors, and catalysis and gas storage devices is covered along with an assessment on 2D-nanostructured Bismuthene being an extremely efficient electrocatalyst. It is described that Bismuthene shows a modest cyclability for Li-ion batteries, Na-ion batteries and K-ion batteries. Bismuthene is typically obtained through a low-cost liquid exfoliation synthesis method, for batteries and other energy conversion devices. In the synthesis of 2D-nanomaterials, the removal of dissolved chemicals from the reaction solutions and improving the device efficiency are still challenging. Herein, electrochemical and sensing applications of 2D-nanostructured materials, along with the advantages and disadvantages are comprehensively reviewed. • 2D-nanomaterials suitable for electrochemical and sensing applications. • Classification of 2D-nanomaterials from Group III, IV, V and VI. • Fabrication methods of 2D-materials under top-down and bottom-up approaches. • Applicability of Borophene and Bismuthene in energy conversion, and sensors. [ABSTRACT FROM AUTHOR]

The rational design of highly efficient, economical and environment-friendly electrocatalysts is currently an important goal of research on renewable energy conversion and storage. Herein, a facile metod was developed to construct two-dimensional composites, which consist of exfoliated CoPS 3 nanosheets grafted onto defective N-doped carbon (DNC) derived from spent tea leaves. The CoPS 3 @DNC composites demonstrate remarkable oxygen evolution reaction (OER) performance in an alkaline medium, with an overpotential of 297 mV at 10 mA cm− 2 and a small Tafel slope of 51.8 mV dec−1, which is better than that of commercial IrO 2 catalysts. Our experimental evidence reveals that the enhanced OER performance of this hybrid catalyst can be attributed to the interfacial effect of exfoliated CoPS 3 and N-doped carbon defects (electron transfer from the CoPS 3 layer to DNC). This work suggests a promising interface engineering technique for developing highly efficient and non-precious OER catalysts based on layered transition-metal trichalcogenides. • A simple and economical route is developed for constructing CoPS 3 @DNC composites. • The charge transfer is demonstrated between CoPS 3 and defective N-doped carbon. • The CoPS 3 @DNC nanosheets exhibit outstanding catalytic activity for OER. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cell (SOFC) is an energy conversion device that can directly convert the chemical energy of carbonaceous fuels into electricity. Solving the problem of carbon deposition in the conventional nickel-based anode is essential to improving the performance of SOFC when operating on carbonaceous fuels. Although impressive progress has been made in the development of alternative anode materials, nickel-based anodes with superior catalytic activity for carbonaceous fuels are still the most promising anode for the commercialization of SOFCs. The deposition of a catalyst layer with high catalytic activity for carbonaceous fuels over the nickel-based anode has been demonstrated as an effective way to enhance the performance and long-term stability of hydrocarbon-based SOFC. This review introduces the working principles of the catalyst layers, discusses the recent progress of the catalyst layer materials for hydrocarbon-fueled SOFC and issues of the different catalyst layer materials. Finally, some of the future prospects and challenges of the catalyst layers are summarized in this review article. • Structural and working principles of the catalyst layers were presented. • Materials of the catalyst layer for the application in nickel-based anode were summarized. • Challenges for improving the performance of the catalyst layer were highlighted. [ABSTRACT FROM AUTHOR]

Developing a multifunctional and sustainable electrode material for hydrogen evolution reaction and supercapacitors is a highly feasible avenue for producing the high energy density and renewable energies. In our study, nanostructured NiCo 2 S 4 /Ni 3 S 2 /NF nanoarrays are rational developed in experiments via a simple hydrothermal reaction. Ascribed to the 3D nanostructured NiCo 2 S 4 /Ni 3 S 2 with numerous exposure active sites and large contact areas for the electrolyte, the binder-free feature of NiCo 2 S 4 /Ni 3 S 2 /NF facilitates a low charge transfer resistance, as well as the synergetic effect of NiCo 2 S 4 and Ni 3 S 2. The obtained electrocatalyst showed ultrahigh electrocatalytic activity with an overpotential of 111 mV at 10 mA cm−2 and a Tafel slope of 57 mV dec−1. In addition, the electrode showed an area specific capacity of 6.13 F cm−2 at 10 mA cm−2 and superior rate capability (2.72 F cm−2 at 80 mA cm−2), accompanied by excellent cycling stability. This results presented in our work can provide an effective strategy for rational design of other hybrid materials with excellent electrochemical performance in the application of electrocatalysis and supercapacitors. • A new preparation, it is first time to fabricate NiCo 2 S 4 /Ni 3 S 2 /NF nanostructure. • The NiCo 2 S 4 /Ni 3 S 2 /NF presents an overpotential of 111 mV and a Tafel slope of 57 mV·dec−1. • The NiCo 2 S 4 /Ni 3 S 2 /NF electrode shows high area specific capacity and good rate capability. • The NiCo 2 S 4 /Ni 3 S 2 /NF electrode shows excellent cycle stability. [ABSTRACT FROM AUTHOR]

It remains a challenge to explore economical, high-effective and long term stability electrocatalysts toward large-scale hydrogen production. This work utilizes surface engineering strategy to in-situ CoFe-Prussian Blue Analogues on NiCo-layered double hydroxides to obtain 3D hierarchical heterostructure precursor (NiCo–CoFe-PBA). After phosphatization, this precursor can be further transform into tri-metallic phosphide (NiCoP/CoFeP@NF) and directly act as efficient self-supported electrode for Water and Urea Electrolysis. Impressively, the obtained NiCoP/CoFeP@NF-12 (±) electrode shows excellent catalytic performance with only requires the cell voltage of 1.61 and 1.46 V to deliver 10 mA cm−2 in overall water splitting and urea electrolysis, respectively, which benefiting from the porous Ni foam (NF) substrate, large catalytic activity area, remarkable mass/electron transfer property, the synergistic effect of components as well as superhydrophilicity and superaerophobicity of electrode surface. In addition, the experimental results also confirm that urea-assisted system has energy saving advantage superior than traditional water splitting in alkaline electrolyte. Moreover, the hierarchical strategy can also be introduced to the construction of other intricate composites for the utilization in energy conversion and storage. 3D hierarchical heterostructure NiCoP/CoFeP@NF self-supported eletrocatalyst for overall Water and Urea Electrolysis. [Display omitted] • Combining CoFe-PBA with NiCo-LDH on Ni foam to form hierarchical NiCoP/CoFeP@NF. • The electrode surface exhibits superhydrophilic and superaerophobicity. • NiCoP/CoFeP@NF shows excellent overall water and urea electrolysis performance. [ABSTRACT FROM AUTHOR]

Binder-free NiFe-based electrocatalyst with aligned pore channels has been prepared by freeze casting and served as a bifunctional catalytic electrode for oxygen and hydrogen evolution reaction (OER and HER). The synergistic effects between Ni and Fe result in the high electrocatalytic performance of porous NiFe electrodes. In 1.0 M KOH, porous Ni 7 Fe 3 attains 100 mA cm−2 at an overpotential of 388 mV with a Tafel slope of 35.8 mV dec−1 for OER, and porous Ni 9 Fe 1 exhibits a low overpotential of 347 mV at 100 mA cm−2 with a Tafel slope of 121.0 mV dec−1 for HER. The Ni 9 Fe 1 //Ni 9 Fe 1 requires a low cell voltage of 1.69 V to deliver 10 mA cm−2 current density for overall water splitting. The excellent durability at a high current density of porous NiFe electrodes has been confirmed during OER, HER and overall water splitting. The fine electrocatalytic performances of the porous NiFe-based electrodes owing to the three-dimensionally well-connected scaffolds, aligned pore channels, and bimetallic synergy, offering excellent charge/ion transfer efficiency and sizeable active surface area. Freeze casting can be applied to design and synthesize various three-dimensionally porous non-precious metal-based electrocatalysts with controllable multiphase for energy conversion and storage. • Porous NiFe electrodes with aligned pore channels were fabricated via freeze casting. • The NiFe served as a self-supported bifunctional electrocatalyst for OER and HER. • NiFe electrode exhibited good electrocatalytic performance and durability. • The synergistic effect of NiOOH and FeOOH promoted OER activity. [ABSTRACT FROM AUTHOR]

Rational design of oxygen evolution reaction (OER) electrocatalysts with advance nanostructures and composition superiority is an urgent need to promote electrocatalytic property. In this research, we fabricate Fe–NiCoP/NiCoP/NF electrocatalyst for OER via the interfacial scaffolding strategy with Prussian-blue-analogue (PBA) followed by low-temperature phosphating. The cube-on-sheet multimetallic-TMPs-based nanoarchitecture of Fe–NiCoP/NiCoP/NF exhibits outstanding OER performance, which only requires the overpotential of 201 mV to achieve a current density of 10 mA cm−2 and possesses good durability up to 50 h in 1.0 M KOH solution. The superior OER property of Fe–NiCoP/NiCoP/NF is mainly characteristic to the rich composition that optimizes the electronic structure and the cube-on-sheet multimetallic-TMPs-based nanoarchitecture which can facilitate more effective active sites exposure and ultimately promote charge transfer at the same time. This research provides a new strategy for the construction of advanced nanoarrays structure and the improvement of the electrocatalytic performance of polymetallic phosphides, which offers its promising applications especially in energy storage and conversion technology. • Novel Fe–NiCoP/NiCoP cube-on-sheet nanoarchitecture is designed for water splitting. • The Fe–NiCoP/NiCoP/NF exhibits a low overpotential of 201 mV at 10 mA cm−2 for OER. • This unique cube-on-sheet nanoarchitecture contributes to the high OER activity. • The synergistic effect between multiple metals is responsible for the high OER activity. [ABSTRACT FROM AUTHOR]

Proton-conducting solid oxide fuel cells (P–SOFCs) are promising energy conversion devices that convert chemical energy directly to electrical energy. P–SOFCs have attracted significant attention in the past few years because of their superiority over the oxygen-ion-conducting solid oxide fuel cells (O–SOFCs) in terms of better feasibility of efficient operation at lower temperatures, non-dilution of fuel at the anode, and higher theoretical efficiency. This review focuses on the scientometric analysis of 1008 quality articles retrieved from the Scopus database. The historical trends and progress in P–SOFCs are presented starting from the inception of the demonstration of the concept of proton conductivity in solid oxide fuel cells from 1986 to 2021. Furthermore, the notable achievements in the material development of various components of P–SOFC are expounded. The scientometric analysis reveals that only 28% of the countries in the world are involved in P–SOFC research and the National Natural Science Foundation of China is the top featured funding sponsor for many research studies related to P–SOFC development. This article can serve as an easy guide for P–SOFC research enthusiasts to navigate through the overview of this research area and identify potential collaborators, funding sponsors, most impactful researchers, countries, and articles. • Scientometric analysis of 1008 SCI P–SOFC articles was conducted. • Notable achievements in material development for P–SOFCs are summarized. • The research trends and knowledge gaps of P–SOFCs are discussed. [ABSTRACT FROM AUTHOR]

Outer wall temperature and exergy efficiency of micro-combustor are very essential in determining micro-thermophotovoltaic energy conversion effectiveness. In this study, a swirl rib was designed to improve the thermal efficiency of micro-combustor since a swirl flow can be formed when the hydrogen/air mixture passes through the swirl rib, which increases the residence time and turbulence intensity of the mixture. Effects of position, height, spacing, and shape of the swirl rib on the thermal performance of a cylindrical micro-combustor were investigated numerically. The thermal performance shows different trends with the variation of these geometric parameters, and an optimum mean outer wall temperature of 1260 K is obtained at the distance between the inlet and the rib of 7 mm, the rib height of 1.2 mm and the rib spacing of 0.5 mm, but this optimum setting triggers the large pressure drop that impedes further improvement of the micro-combustor performance. To minimize this effect, three rip shapes including rectangle, trapezoid and inversed trapezoid was designed. The results show that the micro-combustor with trapezoidal rib presents better thermal performance. This study provides theoretical guidance for the optimal design of the hydrogen-fueled micro-combustor. • A swirl rib was proposed to improve micro-combustor performance was proposed. • Effects of the swirl rib on micro-combustor performance were investigated. • Outer wall temperature and exergy efficiency were promoted significantly. • The induced pressure drop problem by swirl rib can be controlled by adjusting rib shape. [ABSTRACT FROM AUTHOR]

Reversible solid oxide cell (RSOC) has attracted significant attention due to its multi-functionalities for energy conversion and storage. This device works as a fuel cell (FC) or an electrolyzer cell (EC) with superior efficiency. However, its dynamic response is complex and may cause a large overshoot of current operated in reversible cell mode, which impairs the long-term stability of RSOC. Although several works report the overshoot phenomenon, the mechanism and effects on cell performance are still unclear so far. In this work, we build a 3D dynamic planar RSOC model to investigate the detailed behavior of overshoot. The results show that the overshoot of current for RSOC can be caused under switching mode conditions. Especially a larger overshoot of current can be observed within switching mode from EC to FC. The overshoot of current is mainly caused by the load change, slower gas diffusion, and differentiated temperature distribution in RSOC. [Display omitted] • The mode-changing can cause a large overshoot of current in RSOCs. • A dynamic model of RSOCs is developed to elevate the overshoot and response time. • Load sizes, switching time and temperature effect on the dynamic performance. • The current overshoot is proportional to the variation of load change. [ABSTRACT FROM AUTHOR]

Two-dimensional layered molybdenum disulfide and molybdenum trioxide (α -MoO 3) have fascinating potential for complementary energy storage and conversion applications due to their high surface area and multiple oxidation states of Mo. We report a novel hierarchical 1T/2H MoS 2 /MoO 3 nanocomposite prepared by a scalable liquid-phase exfoliation and subsequent facile hydrothermal route. The growth of MoS 2 onto 2D α -MoO 3 creates a unique 2D/2D hierarchical structure, which reduces the aggregation of α -MoO 3 nanoflakes, improves the electrical conductivity of the composite electrode, and activates inert basal plane of MoS 2. The electrochemical measurements revealed that such a composite possessed higher specific capacitance and promoted capacitance retention in a symmetric supercapacitor assembly. The remarkably enhanced visible-light-driven photocatalytic performance of hybrid hierarchical architecture can be attributed to a few distinctive synergistic effects, including activated inert basal plane, facilitated interfacial charge transfer, and peculiar ultrathin nanosheet framework with a large surface area and high content of exposed edge sites. • Facile synthesis of bifunctional hierarchical 1T/2H MoS 2 /MoO 3 nanocomposite. • The nanocomposite exhibits excellent visible-light-driven catalytic performance. • The nanocomposite shows superior charge retention and higher specific capacitance. • The phase engineering of MoS 2 boosts energy conversion and storage performance. • A mechanism for enhanced photocatalytic performance was proposed. [ABSTRACT FROM AUTHOR]

Developing a highly active, low-cost, and durable nanostructured catalytic material is of significant interest in fuel cell applications owing to its efficient energy conversion, ease of preparation and operation, and reduced emission of pollutants. In this work, various ratio (0.01, 0.03, and 0.05 mmol) of cobalt (Co), and iron (Fe) doped nickel hydroxide (Ni(OH) 2) nanosheet arrays were grown on Ni foam surface (Co–Ni(OH) 2 and Fe–Ni(OH) 2) via a simple one-step process. The Co–Ni(OH) 2 and Fe–Ni(OH) 2 nanosheet array on Ni foam electrodes were explored as potential candidate towards electro-oxidation of urea. Notably, 0.03 mmol Co doped Ni(OH) 2 /Ni foam electrode displayed lowest-onset oxidation potential (0.21 V) and enhanced electro-oxidation of urea (59.7 mA) owing to its large amount of electrocatalytic active sites, densely assembled nanosheet array structures with porous surfaces, and electronic diffusion channels, which might promote interface electrochemical reaction. In addition, synergistic effect between Co metal with Ni(OH) 2 has also promotes enhanced electro-oxidation of urea in contrast to Fe–Ni(OH) 2 nanosheet array, Ni(OH) 2 , and Ni foam electrodes. Chronoamperometric i-t curve of Co–Ni(OH) 2 /Ni foam electrode obviously exhibited higher catalytic current, highly stable and durable properties in contrast to Fe–Ni(OH) 2 nanosheet arrays. As-fabricated Co–Ni(OH) 2 /Ni foam can be explored as a new type of potential low-cost catalyst for electro-oxidation of urea, which reveals promising use in future fuel cell energy applications. [Display omitted] • Co, Fe-doped Ni(OH) 2 nanosheet-network arrays prepared by one-step process. • Co, Fe-doped Ni(OH) 2 nanosheet-network arrays is used for electro-oxidation of urea. • Co, Fe-doped Ni(OH) 2 showed low-onset potential, higher catalytic activity and stability [ABSTRACT FROM AUTHOR]

Electrolysis of CO 2 into CO by using solid oxide electrolysis cells (SOECs) is an advanced and sustainable energy conversion technology in the production of chemical energy by electrical power. However, the development of SOECs is limited because of the lack of cathode with high activity and stability. Herein, La 0.75 Sr 0.25-x Ca x Cr 0.5 Mn 0.5 O 3 /Gd 0.1 Ce 0.9 O 2-δ (Ca x -LSCM/GDC, x = 0, 0.05, 0.1 and 0.15) composites were obtained by introducing Ca into the A-site of LSCM and developed as desirable cathodes for high-temperature electrolysis of CO 2. The electrode polarization resistance (Rp) for CO 2 electrochemistry reduction of the half-cell with the Ca 0.05 -LSCM/GDC cathode shows the minimal values within different temperature and voltage ranges, this cathode has a Rp value of 0.98 Ω cm2 at 800 °C under an applied voltage of 1.0 V, which is decreased by 32% compared with that of the LSCM/GDC cathode under the same test condition. The current density of the full cell with the configuration of Ca 0.05 -LSCM/GDC|ScSZ|LSM/GDC achieves 31% increase at 1.2 V and 800 °C compared with that of LSCM/GDC cell. Moreover, Ca 0.05 -LSCM full cell remains fairly stable after 100 h of continuous operation in pure CO 2 atmosphere. Results indicate that Ca doped LSCM may be a reliable cathode material for CO 2 electrolysis in SOECs. • Ca-doped LSCM is studied as fuel electrode for direct electrolysis of CO 2. • The introduction of Ca can decrease the Rp of LSCM. • The SOEC shows a current density as high as 0.44 A cm−2 at 1.6 V at 800 °C. • Ca 0.05 -LSCM cell presents excellent long-term stability for CO 2 electrolysis. [ABSTRACT FROM AUTHOR]

The paper proposes a combined approach between numerical modeling and experimental measurements for the analysis of a cogeneration system based on the reaction of liquid aluminum and water steam. Scrap aluminum is used for hydrogen production and the primary one is employed as an energy carrier to transport the energy from the alumina reduction system to the site of the suggested plant. The analysis focuses on the liquid aluminum injection phase immediately downstream the nozzle. High frequency thermo-cameras are employed to qualitatively assess the thermal behaviour the liquid aluminum jet. Fast imaging techniques are used to capture the multiphase flow pattern of the liquid metal jet during the injection phase. The experimental results are used to validate a 2D multi-phase CFD approach. The computational fluid dynamics model of the injection phase is created and used to extend the measurements and deepen the understanding of the thermo-fluid dynamics behaviour of the system. In particular, the influence of different nozzles diameters and different injection pressures on the liquid aluminum jet is investigated. A modular approach is adopted for the domain subdivision in order to represent accurately all the geometrical features, while the volume of fluid approach is used to model the multi-phase flow distribution in the real geometry under actual operating conditions. Finally, a good agreement between the measurements and the calculations is found. • Development of a new energy conversion system based on the Al–H2O reaction. • Experimental analysis of the liquid aluminium injection system and spray formation. • CFD analysis of the liquid aluminium spray formation. • Evaluation of the injector's nozzle geometry for application in a real system. [ABSTRACT FROM AUTHOR]

The economical, efficient and durable oxygen reduction catalysts facilitate the enhancement of electrochemical energy devices competitiveness towards widespread applications. In view of this, we provide an innovative sulfuration inducing method for the synthesis of ZnS and cobalt nanoparticles decorated N, S co-doped CNTs (ZnS/Co-NSCNTs) catalyst. S introduced into the zinc-based zeolitic imidazolate frameworks (ZIF-8) and cobalt-based zeolitic imidazolate frameworks (ZIF-67) precursors via pyrolysis, and induced the generation of ZnS/Co-NSCNTs have been confirmed by XRD, SEM, TEM, and XPS techniques. The key features including activity sites, transfer channels and adsorption energy back up the excellent electrocatalytic activity of the as-prepared ZnS/Co-NSCNTs towards oxygen reduction reactions (ORR). ZnS/Co-NSCNTs additionally exhibited a positive half-wave potential of 0.871 V (vs. RHE) with improved current density towards ORR. In alkaline medium, ZnS/Co-NSCNTs catalyst displayed a high tolerance towards methanol and an excellent long-term cycling stability. The observed onset potential for our prepared ZnS/Co-NSCNTs catalyst is analogous with the commercially available noble metal catalysts. Also, ZnS/Co-NSCNTs catalyst as a cathode in zinc-air battery displayed an enhanced electrochemical performance with a highly specific capacity of 750.1 mAh g−1, outstanding cycling stability, and high rate behavior. This work provides a new approach for the construction of stable low-cost alternative air-cathode catalysts for other energy conversion and storage applications. • Sulfuration induced ZIF-8/ZIF-67 to N and S co-doped carbon tube loaded ZnS and Co. • ZnS/Co-NSCNTs own rich transfer channels, activity sites, and low adsorption energy. • ZnS/Co-NSCNTs exhibit superb ORR activity and stability in Zn-air battery. [ABSTRACT FROM AUTHOR]

Modulating the intrinsic physicochemical properties of crystalline 2D materials by dint of defect engineering largely enables multi-functionality. Uniform thin layered nanosheets further self-assembled at micro scale forming embossing structures of δ-MnO 2 were fabricated by microwave irradiation technique. The irradiation of UV/O 3 impacts incorporation of oxygen vacancy into the pristine system. Furthermore, detailed structural, morphological, surface analytical and electrochemical investigations evidenced outstanding energy storage and conversion activities. The asymmetric device δ-MnO 2 -UVT//F-MWCNT with an extended potential window 1.5 V, exhibited maximum energy density of 39 Wh/kg at a power density of 468.75 W/kg. The defect structural design exhibited excellent electrocatalytic OER activity with lowest overpotential (η 20 , 300 mV) and Tafel slope (71 mV/dec). The efficiency and stability of the illuminated material showed outstanding performances. To support our experimental findings, we have presented the electronic structures and quantum capacitance for pristine δ-MnO 2 and δ-MnO 2 with O vacancy employing Density Functional Theory (DFT) simulations. Presence of O vacancy makes a semi-conducting to metallic transition. The oxygen vacancies delocalize the neighboring electrons around the low coordinated Mn atoms and these delocalized electrons can be easily moved into the conduction band resulting improved conductivity in the material. In addition, the computed quantum capacitance tendency is as follows, δ-MnO 2 -UVT > δ-MnO 2 which associates with the experimental supercapacitance behaviour of these systems. • 2D δ-MnO 2 nanostructures are synthesized adopting a facile microwave irradiation technique. • A naive and effective photochemical UV ozone illumination mediated defects in the 2D δ-phased MnO 2 material. • Applicability of defect engineered 2D birnessite δ-MnO 2 as bifunctional electrode for supercapacitors and OER is realized. • Asymmetric δ-MnO 2 -UVT//F-MWCNT (1.5 V) device exhibited maximum energy density of 39 Wh/kg at power density of 468.75 W/kg. • Defect structural design showed excellent electrocatalytic OER activity (overpotential η 20 , 300 mV, Tafel slope 71mV/dec). [ABSTRACT FROM AUTHOR]

Sonochemistry is considered as one of the cleaner pathways for hydrogen production. The present paper investigates the potential of this technique based upon mass, mass to energy and energy conversion metrics, using modelling and experimental approaches. Four scenarios are examined assuming four saturating gases, namely O 2 , air, N 2 and Ar, four acoustic frequencies, i.e., 20, 210, 326 and 488 kHz, and considering common acoustic intensities then common net electric power. The study revealed that Ar is the best fitting saturating gas for the sonochemical production of hydrogen. With a common acoustic intensity of 0.48 W/cm2, an optimum ratio of H 2 molar yield to acoustic energy intensity is retrieved at 210 kHz, while with a common net electric power of 87 W, the highest ratio of hydrogen yield to electric energy was observed at 20 kHz. Results were interpreted based upon emitter surface, energy conversion and distinction of calorimetric and cavitational energies. • Sono-H 2 is examined through mass, mass to energy and energy conversion metrics. • Ar is the best fitting saturating gas for the sonochemical production of hydrogen. • At 0.48 W/cm2, the optimal frequency for H 2 yield to acoustic intensity is 210 kHz. • At 87 W e , the highest ratio for H 2 yield to electric energy is observed at 20 kHz. • The optimal frequency for electric to acoustic energy conversion is 20 kHz. [ABSTRACT FROM AUTHOR]

Electrochemical energy technologies such as fuel cells, supercapacitors, and batteries are some of the most suitable energy storage and conversion devices to meet our needs proving the future generation's equitable opportunity to meet their own needs. For this purpose, an earth-abundant precursor such as biomass is the best candidate for the synthesis of the next generation of low-cost and green electrode materials. This review summarizes the most recent progress in biomass-derived carbons for use in fuel cells, supercapacitors and lithium-ion batteries, the physical-chemical properties, desired features, performances, and limitations for electrochemical energy technologies. Several thermochemical treatments such as chemical activation, template methods, doping and hydrothermal treatments have been reviewed. Finally, we provide the reader with comprehensive information of the challenges, future research efforts, advantages, limitations and opportunities which will be a fundamental insight for the future design of biomass-derived carbon electrode materials for electrochemical storage and conversion systems. • Cost-effective electrode materials are the big challenge for energy conversion and storage systems. • An earth-abundant precursor such as biomass is the best candidate for the next-generation of green electrode materials. • Biomass-derived carbon electrode materials have promising future in the field of energy storage and conversion. [ABSTRACT FROM AUTHOR]

We herein propose a dual ligand coordination strategy for deriving puissant non-noble metal electrocatalysts to substitute valuable platinum (Pt)-based materials toward oxygen reduction reaction (ORR), a key reaction in metal-air batteries and fuel cells. In brief, cobalt ions are firstly double-coordinated with proportionate 2-methylimidazole (2-MeIm) and benzimidazole (BIm) to obtain drum-like zeolitic imidazolate frameworks (D-ZIFs), which are then carbonized to output the final Co, N co-doped porous carbon (Co–N–PC D) catalyst inheriting the drum-like morphology of D-ZIFs. The Co–N–PC D is featured by mesopores and exhibits superb electrocatalytic behavior for ORR. Impressively, the half-wave potential of Co–N–PC D catalysts is 0.886 V with finer methanol-tolerance and stability than those of commercial Pt/C. Additionally, a zinc-air battery assembled from the Co–N–PC D displays an open-circuit voltage of 1.413 V, comparable to that of commercial Pt/C (1.455 V), suggesting the potentials of Co–N–PC D in practical energy conversion devices. [Display omitted] • Drum-like ZIFs (D-ZIFs) are prepared by Co2+, 2-methylimidazole and benzimidazole. • Pyrolysis of D-ZIFs precursor yields Co, N, co-doped porous carbons (Co–N–PC D). • The porous channels allow facile diffusion of O 2 to active species. • Co–N–PC D exhibits high performance for ORR and in zinc-air batteries. [ABSTRACT FROM AUTHOR]

The superadiabatic combustion in porous media contributes to the efficient conversion of methane to syngas. In this paper, a divergent packed bed burner of two-layer was proposed to obtain the characteristics of methane partial oxidation. The divergent angle, interface location and pellet diameter were used to study the temperature and species distributions. Results indicate that the upper limit of velocity gradually decreased as the equivalence ratio increased and the limit of the divergent burner is obviously higher than that of the cylindrical one. The increasing of the divergent angle within a certain range enhances the methane conversion and the 15° shows the best among the selected five angles. The mole fractions of H 2 and CO gradually decrease when the interface locations move from the cylindrical region to the divergent one. As the equivalence ratio increased from 1.3 to 3.5, the yields of H 2 and CO and the energy conversion efficiency of syngas increase first and then decrease, and the maximum efficiency of 45.9% appears at the equivalence ratio of 2.0. The divergent region weakens the influence of inlet velocities and contributes to the stability of reforming reactions. [Display omitted] • A divergent packed bed burner of two layers was designed. • Upper limit of velocity decreased with the increasing of equivalence ratio. • H 2 and CO fractions decrease as interface location moves to divergent one. • Divergent structure contributes to the reforming stability. [ABSTRACT FROM AUTHOR]

Coking is a major issue with the traditional Ni-based anodes when directly oxidizing CH 4 in solid oxide fuel cells (SOFCs). Dry reforming to convert CH 4 –CO 2 into CO–H 2 syngas before entering Ni-based anode may potentially be an effective and economical method to address the coking problem. Consequently, an on-cell reforming layer outside the Ni-based anode is expected to offer a unique solution for direct CH 4 –CO 2 SOFCs without coking. In this study, Ni-GDC anode-supported cells with and without a Sr 2 Co 0.4 Fe 1.2 Mo 0.4 O 6-δ (SCFM) layer outside the anode support have been fabricated and evaluated using either H 2 or CH 4 –CO 2 as fuel. Both types of cells show excellent electrochemical performance when H 2 is used as fuel, and the SCFM layer has negligible impact on the cell performance. When CH 4 –CO 2 is used as fuel, however, the electrochemical performance and durability of the cells with the SCFM layer are much better than those without the SCFM layer outside the Ni-GDC anode, indicating that the SCFM layer can efficiently perform dry reforming. This unique on-cell dry reforming design enables direct CH 4 –CO 2 solid oxide fuel cells and offers a very promising route for energy storage and conversion. • Sr 2 Co 0.4 Fe 1.2 Mo 0.4 O 6-δ catalytic reforming layer was added outside the anode support. • The reforming layer showed negligible effect on the cell performance fed with H 2. • Cell performance and durability are improved with reforming layer when fed with CH 4 –CO 2. [ABSTRACT FROM AUTHOR]