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Thermochemical storage (TCS) offers a number of advantages over sensible and latent heat based thermal energy storage (TES) technologies, including low heat loss, small volume change and high energy density. However, two of key technological challenges are low cycle stability and slow charging and discharging kinetics. We report here a novel composite TCS material made from MgSO4 and diatomite using an impregnation method. The structures, sorption kinetics, thermal properties and cycle stability of the composite were investigated by using several analytical techniques including scanning electron microscope, surface area measurements, Raman microscope, thermal gravitational analyzer, dynamic vapor sorption analyzer and differential scanning calorimeter. The results show that the porous structure of the diatomite provides water vapor transport channels and contact area between water vapor and MgSO4, leading to an increased hydration rate of MgSO4, hydration state and cycle stability compared with pure MgSO4, and an improved sorption capacity and thermal performance. When MgSO4 in the composites reaches ∼60% by mass, the diatomite tends to be saturated with more MgSO4 in a high hydrated state, resulting in a superior heat storage performance with an energy storage density of 772.9 kJ/kg and a water adsorption capacity of 0.37 g/g in a low to medium temperature range of 80–150 °C.

Sorption based thermochemical energy storage using salt hydrates offers several potential advantages if engineered properly, compared with sensible and latent heat storage technologies, including low heat loss, small volume change and high energy density. Two of key technological challenges are low mechanical structure stability, which determines the life-span; and slow charging and discharging kinetics, which depends largely on mass and heat transfer. As the heat and mass transfer relates to structure and composition of thermochemical storage materials, the two key challenging aspects are coupled and the use of engineered composite thermochemical materials provides an avenue to address the challenges. In this paper, we report a novel thermochemical storage composite material, consisting of magnesium sulfate (MgSO4, the thermochemical storage material) and expanded graphite (EG, heat transfer enhancer and structural stabiliser), prepared by impregnation of MgSO4 into EG. The composite has been characterized by various methods, including scanning electron microscopy (SEM), differential scanning calorimeter (DSC), thermogravimetry (TG), transient plane heat source method and dynamic vapor sorption (DVS). The results showed that the MgSO4-EG composite containing 60% MgSO4 displayed superior heat and mass transfer properties. The hydration time of MgSO4 was shorten to about 1/4 of its pure and original form and the thermal conductivity was increased by more than 84.8% through the MgSO4 impregnation into EG.

A strategy to improve its photocatalytic performance is still a challenge for the novel Sillen–Aurivillius perovskite type Bi4NbO8Br. Herein, novel Pt modified Bi4NbO8Br composites (Pt/BNB) with sufficient oxygen vacancies were successfully fabricated via a facile in situ chemical reduction method. For one thing, the deposition of Pt nanoparticles brings about a Mott–Schottky effect at the interface to accept photo-induced electrons, leading to an efficient charge separation. For another thing, the electronic metal–support interaction of Pt and Bi4NbO8Br decreases the formation energy of oxygen defects, which could serve as active sites for O2 activation. On account of the synergetic effect of Pt and oxygen vacancies, the dominant active species-photogenerated holes are accumulated on the surface of the photocatalysts, while the additional superoxide radicals are also involved. Hence, Pt/BNB performed with excellent photocatalytic activities in the degradation of wastewater contaminants, and the kinetic rate was 4.64, 10.21, 5.53, 9.80, 1.71 and 4.05 times, respectively, those of pristine Bi4NbO8Br towards methyl orange, rhodamine B, 2,4-dichlorophenol, p-nitrophenol, ciprofloxacin and tetracycline hydrochloride.

The development of bifunctional catalysts with a delicate structure, high efficiency, and good durability for the oxygen evolution reaction (ORR) and oxygen evolution reaction (OER) is crucial to renewable Zn-air batteries. In this work, Co0.7Fe0.3 alloy nanoparticles (NPs) confined in N-doped carbon with a yolk-shell structure in multi-beaded fibers were prepared as a bifunctional electrocatalyst. The confinement structure was composed of an N-doped graphitized carbon shell and a core formed by numerous Co0.7Fe0.3 NPs, and was evenly threaded into a one-dimensional fiber. Moreover, this distinctive hierarchical structure featured abundant mesopores, a high BET surface area of 743.8 m2 g-1, good electronic conductivity, and uniformly distributed Co0.7Fe0.3/Co(Fe)-Nx coupling active sites. Therefore, the experimentally optimized Co0.7Fe0.3@NC2:1-800 showed excellent OER performance (overpotential reached 314 mV at 10 mA cm-2) that far exceeded RuO2 (353 mV), and good ORR catalytic performance (half-wave potential of 0.827 V) comparable to Pt/C (0.818 V). Impressively, the Co0.7Fe0.3@NC2:1-800 Zn-air battery delivered a higher open circuit voltage of 1.449 V, large power density of 85.7 mW cm-2, and outstanding charge-discharge cycling stability compared with the commercial RuO2 + 20 wt% Pt/C catalyst. This work provides new ideas for the structural design of electrocatalysts and energy conversion systems.

The strategy to improve the photocatalytic removal efficiencies towards organic pollutants is still a challenge for the novel Sillen–Aurivillius perovskite type Bi4NbO8Cl. Herein, we report carbon-supported TiO2/Bi4NbO8Cl (C-TiO2/Bi4NbO8Cl) heterostructures with enhanced charge separation efficiency, which were fabricated via molten-salt flux process. The carbon-supported TiO2 particles were derived from MXene Ti3C2 precursors, and attached on plate-like Bi4NbO8Cl, acting as electron-traps to achieve supressed recombination of photo-induced charges. The improved charge separation confers C-TiO2/Bi4NbO8Cl heterostructures superior photocatalytic performance with 53% higher than pristine Bi4NbO8Cl, towards rhodamine B removal with the help of photo-induced holes. Moreover, the C-TiO2/Bi4NbO8Cl heterostructures can be expanded to deal with other water contaminants, such as methyl orange, ciprofloxacin and 2,4-dichlorophenol with 44, 25 and 13% promotion, respectively, and thus the study offers a series of efficient photocatalysts for water purification.

Fabrication of transition metal phosphides/carbon hybrids as electrocatalysts for oxygen reduction reaction (ORR) has great significance for developing clean energy conversion and storage devices based on earth abundant elements. In this work, we prepared 3D N,P-codoped porous carbon supported with ultrasmall Fe2P nanoparticles (Fe2P/NPC) as high-efficient ORR catalyst by a simple grinding-calcination strategy. As the pore-forming agent, ZnO nanospheres can be in-situ eliminated and generate abundant porous structures which are beneficial to mass transfer. Meanwhile, the large BET surface area (1288 m2 g−1) and pore volume (1.23 cm3 g−1) of Fe2P/NPC can provide more contact active centres for ORR. In alkaline solution, Fe2P/NPC performs excellent ORR activity with the positive onset potential (0.997 V) and half-wave potential (0.872 V), which are more positive than those of the commercial Pt/C (0.977 and 0.812 V). In addition, Fe2P/NPC can be used as air cathode catalyst in a Zn-air battery whose open circuit voltage (1.469 V) is larger than that of the commercial Pt/C (1.332 V) based one. This work provides new strategy to prepare transition metal phosphides/carbon hybrids for electrocatalysis and clean energy conversion systems.

Rational design of isolated metal atom doped carbon catalysts is essential for revealing the essence of high activity for the oxygen reduction reaction (ORR), which can promote the development of robust catalysts for clean energy conversion devices. Herein, we report a simple one-step strategy to prepare Fe and Co atomically supported on N-doped nanocarbon (FeCo-IA/NC) from metal–organic frameworks with excellent ORR activity. The isolated Fe–N4 and Co–N4 sites are characterized by atomic-resolution aberration-corrected scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy. The electrochemical results and density functional theory calculations indicate that the synergetic effect between Fe–N4 and Co–N4 accounts for the enhanced ORR activity. Benefiting from the large BET surface area, microporous feature, and high content (85%) of pyridinic and graphitic N, the well-designed catalyst exhibits better ORR activity (half-wave potential of 0.88 V) and Zn–air battery performances (higher open circuit potential and power density) than commercial Pt/C. This work may lay a foundation for further exploring efficient non-precious metal-based catalysts for the ORR and developing clean energy conversion devices.

Sodium-ion (Na-ion) hybrid capacitors as a novel electrochemical energy storage device have triggered considerable attention in recent years. However, the sluggish kinetics at anode and low specific capacity at cathode greatly hinder the overall performance output of Na-ion hybrid capacitors. Herein, we design a high-performance quasi-solid-state Na-ion hybrid capacitor assembled with the Mo2N quantum dots coupled carbon nanotubes as anode, decoupled hierarchical carbon nanotubes as cathode, and a porous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane based gel electrolyte. For the anode, the uniformly dispersed Mo2N quantum dots offer abundant ion-accessible active sites and shortened ion diffusion path, which effectively accelerate Na ion storage kinetics. After decoupling and activation, the hierarchical carbon nanotubes with high specific surface area and numerous in-plane nanopores contribute to fast reversible anion adsorption and desorption, greatly boosting the specific capacity. Additionally, the low-tortuosity nanotubular electrode microstructure with open framework is conducive to unimpeded electrolyte ion permeation and thereby can maximize the utilization of active materials. Benefiting from the elaborate electrode architecture engineering and rational device configuration, the assembled quasi-solid-state Na-ion hybrid capacitor can achieve a high energy density of 100.6 Wh kg−1 at a power density of 117.5 W kg−1, which is among the best compared with other Na-ion hybrid capacitors. The demonstration of proof-of-concept of the quasi-solid-state Na-ion hybrid capacitors offers new insights into rational design of high-energy-density hybrid energy storage systems.

The development of transition metal nitrides/carbon hybrids with well-organized morphology, outstanding efficiency and durability for Zn-air batteries are of great urgency. Herein, a morphology-controlled strategy to efficiently fabricate uniform Co4N nanoparticles anchored on N-doped carbon (Co4N@NC-m) is reported. The diameters and distribution of Co4N nanocrystals can be tuned to be homogeneous profited by abundant N sources in melamine. Moreover, thanks to the advantages of higher nitrogen doping content, better electrical conductivity, higher degree of graphitization, and larger electrochemical surface area, Co4N@NC-m possesses excellent oxygen reduction reaction (half-wave potential of 0.87 V) and oxygen evolution reaction (overpotential of 398 mV at 10 mA cm−2) activities in basic solution. The Zn-air battery fabricated with Co4N@NC-m owns higher open circuit voltage (1.490 V), larger power density, and better rechargeability than those of the commercial IrO2 + 20% Pt/C catalysts, which proves the potential application in practical energy conversion devices.

Developing efficient water-splitting electrocatalysts with high mass activity is in urgent need for large-scale sustainable production of hydrogen but, still remains as a big challenge. Herein, we report a one-pot method to fabricate a series of core@shell Ni@RuM (M=Ni or Co) nanocrystals (NCs) with Ni as the core and tunable RuM (M=Ni or Co) as the alloy shell for efficient water-splitting catalysis. Among these core@shell NCs, the obtained Ni@RuNi NCs exhibit the highest intrinsic activity for hydrogen evolution reaction (HER) and possess an outstanding mass activity of 1590 mA mgRu−1 at 0.07 V vs. reversible hydrogen electrode (RHE), which is 1.7 times higher than that of commercial Pt/C ( 950 mA mgPt−1 ). As for oxygen evolution reaction (OER), the prepared Ni@Ru0.4Co0.6 NCs with optimized shell composition achieve more enhanced mass activity of 270 mA mgRu−1 at 1.56 V vs. RHE, approaching three times higher than that of commercial RuO2 ( 89 mA mgRu−1 ). The superb mass activity of these Ni@RuM (M=Ni or Co) NCs can be attributed to their core@shell structure and modulated electronic structure through alloying with Ni or Co metal in the shell.

The development of electrochemical energy conversion and storage devices (e.g., fuel cells, metal–air batteries, and water splitting) offers new opportunities to address global energy challenges; h...

Heteroatom doped carbon based hierarchical nanostructures are one of most interesting electrode materials for boosting oxygen reduction reaction (ORR) owing to the active electronic structure and appealing structural stability. Herein we demonstrated a ‘polymerization-dissolution’ method to prepare a highly stable Fe, N, S tri-heteroatom doped core-shell carbon (HCSC) nanostructural ORR catalyst. The unique advantages, including the uniformly dispersed N, S and Fe–N active sites, and the special leaf-like core-shell nanostructure, endow the optimized HCSC catalyst (HCSC-IV-H) owning high-efficient ORR activity. Moreover, a Zn–air battery assembled with HCSC-IV-H exhibits a higher open potential (1.430 V) and lower discharge overpotential, comparing with the commercial IrO2 + 20% Pt/C catalyst. The present work highlights a novel strategy to construct highly efficient heteroatom doped nano-carbon materials for renewable energy storage and conversion devices.

MXenes as a new class of 2D materials have recently been widely applied in energy storage, electrocatalysis, sensors, adsorption, water purification, and so on, due to their tunable versatile properties. Herein, we demonstrate a simple, rapid and highly-sensitive sensing platform based on ultrathin two-dimensional MXene Ti3C2 nanosheets (Ti3C2 NSs) for selective analysis of Human papillomavirus (HPV), a major human pathogens and causative agents of cervical cancer. Ultrathin Ti3C2 NSs, obtained by exfoliating their layered HF-etched powder, exhibit high fluorescence quenching ability to dye-labeled single-stranded DNA (ssDNA) and different affinities for ssDNA and double-stranded DNA (dsDNA). Under the fluorescence quenching effect of Ti3C2 NSs, ssDNA probe (P) shows the minimal fluorescent emission. After the formation of duplex structure with its complementary target, ssDNA (T), the fluorescence intensity enhances evidently. Exonuclease III (Exo III) was used to improve the sensitivity by promoting more fluorescence enhancement. This magnified fluorescent sensor for HPV-18 detection shows a low detection limit of 100 pM and a high specificity. Furthermore, the developed DNA sensor can be employed to determine PCR amplified HPV-18 from cervical scrapes samples. It highlights ultrathin Ti3C2 NSs as a potential candidate for construction of fluorescence DNA biosensors with excellent performances.

Tuning reactive metal-support interaction (RMSI) is a promising approach to optimizing catalytic active sites via the electronic, geometric and compositional effects. In general, the RMSI is conducted on the reducible oxides via a high-temperature reaction (>550 °C). Herein we report a strong RMSI between Pt single atom (PtSA) and non-oxide-based g-C3N4 built by an in-situ photocatalytic reduction method at a sub-zero temperature. The experimental observation confirms that the rich N vacancies in g-C3N4 produce an obvious electron-deficient effect, which greatly enhances the RMSI. This strong RMSI contributes to the highest PtSA coverage density of 0.35 mg m−2 reported to date in carbon-based materials and outstanding H2-evolution activity of 174.5 mmol g−1 h−1 per PtSA relative to those on the electron-rich g-C3N4. The structure simulation reveals that the RMSI can not only stabilize the PtSA on the electron-deficient g-C3N4 via the strong chemical bond between PtSA and the two-coordinated C (C2C) sites caused by the N vacancies, but also promises the PtSA with an optimized electronic and geometric structures for capturing photogenerated electrons and producing H2. This finding opens a new channel for designing and manipulating single atom-loaded photocatalyst via the RMSI at a sub-zero low temperature.

Flexible and rechargeable Zn–air batteries, because of their high energy density, low cost, and environmental and human benignity, are one kind of the most attractive energy systems for future wear...

This report presents a simple method to produce an ultrasmall-Fe7C3/N-doped porous carbon hybrid (u-Fe7C3@NC) as an excellent oxygen reduction reaction (ORR) electrocatalyst. A zinc–air battery assembled with u-Fe7C3@NC performs at a higher open potential (1.486 V) and at a lower discharge overpotential compared with the commercial Pt/C catalyst.

Potassium-ion batteries (KIBs) are emerging as the prospective alternatives to lithium-ion batteries in energy storage systems owing to the sufficient resources and relatively low cost of K-related materials. However, serious volume expansion and low specific capacity are found in most materials systems resulting from the large intrinsic radius of K

The development of bifunctional catalysts with a delicate structure, high efficiency, and good durability for the oxygen evolution reaction (ORR) and oxygen evolution reaction (OER) is crucial to renewable Zn-air batteries. In this work, Co

Developing noble metal-free bifunctional oxygen electrocatalysts is vital for metal–air batteries. Herein, we present a facile approach to fabricating N-doped carbon nanosheet networks with metal nanoparticles (M/N-CNSNs) readily converted from metal–organic frameworks. The resultant Co/N-CNSNs show superior bifunctional oxygen catalytic activity attributed to the efficient active sites and fast mass diffusion enabled by the nanosheet structure. It is worth noting that the first-principles studies prove the Co/N–C sites to be the oxygen reduction reaction active sites, where the most favorable ones are the carbon atoms next to Co-coordinated pyridinic N. Interestingly, the cobalt content plays an important role in Co/N–C sites but was not directly involved in the catalytic process. In a Zn–air battery, a small voltage gap without obvious voltage loss is found for the Co/N-CNSNs. This facile approach enables scalable synthesis, representing an essential step toward the popularization of metal–air batteries.

Over the past several decades, extensive efforts have been undertaken to find methods to synthesize advanced electrocatalysts that possess rationally controllable sizes, shapes, crystallinities, compositions and structures for efficient energy conversion technologies. Of these methods, the one-pot seedless synthetic method in aqueous solution at ambient temperature has attracted extensive attention from researchers because it is a simple, inexpensive, energy-efficient, safe and less toxic method for the synthesis of electrocatalytic nanomaterials. In this review, recent developments in one-pot seedless synthetic strategies for the design of various structures of Au, Pt, Pd, Ag and multimetallic nanocrystals in aqueous solutions at ambient temperatures will be introduced, primarily focusing on the structure–electrocatalytic performance relationships of the as-prepared metal nanocrystals. Current challenges and outlooks for future research directions will also be provided in this promising research field.

A liquid-like poly(ionic liquid) (PIL) with a very low glass transition temperature of −51 °C and a thermal decomposition temperature of 202.7 °C was synthesized. A PIL-based electrolyte by mixing this poly(ionic liquid) with additives of 10 wt % propylene carbonate and 0.1 M LiClO4 is proved to be an excellent electrolyte for lithium-ion battery. The obtained PIL-based electrolyte exhibits a high ionic conductivity of 8.3 × 10–5 S cm–1 at 25 °C and 2.0 × 10–4 S cm–1 at 60 °C and a wide electrochemical potential window up to 5.61 V at 25 °C and 4.14 V at 60 °C. The Li/LiFePO4 batteries equipped with this PIL-based electrolyte achieve high capacity, outstanding cycling stability and rate capability at 25 °C, and even improved performance at high temperature like 60 °C. Such excellent performances of batteries are attributed to the formation of stable solid-electrolyte interface film at the lithium-electrolyte interface and the stability of electrolyte during cycling.

Silicon (Si) is a promising anode candidate for lithium-ion batteries (LIBs) owing to its unprecedented theoretical capacity of 4200 mA h g−1 and earth-abundant supply (26.2 wt%). Nevertheless, the huge volume expansion and unstable solid-electrolyte interface (SEI) of Si in multiple cycles make it very hard to simultaneously achieve high-energy and long-term cycle life for applications in large-scale renewable energy storage. Herein, we demonstrate a new class of Si/SiOx@void@nitrogen-doped carbon double-shelled hollow superstructure (Si/SiOx-DSHS) electrodes that are capable of accommodating huge volume changes without pulverization during cycling. Benefiting from the unique double-shelled hollow superstructure, Si/SiOx-DSHSs can facilitate the formation of a highly stable SEI layer and provide superior kinetics toward Li+-ion storage. The diffusion-controlled process and the capacitance-type reaction can work together to endow Si/SiOx-DSHSs with remarkable electrochemical characteristics, especially at high current density. These important characteristics make Si/SiOx-DSHSs deliver a large reversible capacity (1290 mA h g−1 at 0.1C), high first-cycle coulombic efficiency (71.7%), superior rate capability (360 mA h g−1 at 10C), and excellent cycling behavior up to 1000 cycles with a small capacity decay of 10.2%. The Si/SiOx-DSHSs are among the best Si-based anode materials for LIBs reported to date.

The dehydrogenation and conversion of methanol into 1,1-dimethoxymethane (DMM) was achieved over noble metal-free photocatalyst CdS/Ni2P under visible light. This photocatalytic process for methanol-to-H2 and DMM conversion is efficient and atom economic, with an optimal rate and selectivity of DMM of 188.42 mmol g−1 h−1 and 82.93%, respectively. This work supplies a new green approach for the direct efficient conversion of methanol into DMM and provides a promising avenue for sustainable bio-methanol applications.

Development of excellent bi-functional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) remains a key issue for the commercialization of various electrochemical devices such as fuel cells and metal-air batteries. Herein, we report the synthesis and electrocatalytic performance of mesoporous nanostructured spinel-type MFe2O4 (M = Co, Mn, Ni) oxides which can serve as alternative low-cost bi-functional electrocatalysts for ORR/OER. Loaded on XC-72 carbon support, the MFe2O4 spinel oxides show the M-dependent catalytic activities with CoFe2O4 being the most active electrocatalyst followed by MnFe2O4 and NiFe2O4 for ORR. For the OER, however, the activity increases in the order: MnFe2O4

Lignin extracted from trees is one of the most abundant biopolymers on Earth. Quinone, a substructure in lignin, can be used for energy storage via reversible redox reactions through absorbing and releasing electrons and protons. However, these efforts have encountered hindrances, such as short life cycle, low cycling efficiency, and a high self-discharge rate. All of these issues are related to electrode dissolution by electrolyte solvents and the insulating nature of lignin. Addressing these critical challenges, for the first time, we use a reconfigurable and hierarchical graphene cage to capture the lignin by mimicking the prey-trapping of venus flytraps. The reconfigurable graphene confines the lignin within the electrode to prevent dissolution, while acting as a three-dimensional current collector to provide efficient electron transport pathways during the electrochemical reaction. This bioinspired design enables the best cycling performance of lignin reported so far at 88% capacitance retention for ...

MoS2 is a promising electrode material for energy storage. However, the intrinsic multilayer pure metallic MoS2 (M-MoS2) has not been investigated for use in supercapacitors. Here, an ultrafast rate supercapacitor with extraordinary capacitance using a multilayer M-MoS2–H2O system is first investigated. Intrinsic M-MoS2 with a monolayer of water molecules covering both sides of nanosheets is obtained through a hydrothermal method with water as solvent. The super electrical conductivity of the as-prepared pure M-MoS2 is beneficial to electron transport for high power supercapacitor. Meanwhile, nanochannels between the layers of M-MoS2–H2O with a distance of ∼1.18 nm are favorable for increasing the specific space for ion diffusion and enlarging the surface area for ion adsorption. By virtue of this, M-MoS2–H2O reaches a high capacitance of 380 F/g at a scan rate of 5 mV/s and still maintains 105 F/g at scan rate of 10 V/s. Furthermore, the specific capacitance of the symmetric supercapacitor based on M-MoS...

The ever-increasing power and energy demands for modern consumer electronics and electric vehicles are driving the pursuit of energy-storage technologies beyond the current horizon. Pseudocapacitive charge storage is one of the most effective and promising approaches to fill this technology gap, owing to its potential to deliver both high power and energy densities. Typically, titanium niobium oxides (TiNbxO2+2.5x (x = 2, 5 and 24)) with intrinsic pseudocapacitance, high safety and theoretical capacities of 388–402 mA h g−1 are recognized as promising anode materials for lithium-ion batteries. However, their poor conductivity and low Li+-ion diffusion coefficient are known to be the major hurdles limiting the full utilization of their pseudocapacitive effects, leading to their lackluster rate capabilities. Herein, we employ a facile electrospinning method to prepare one-dimensional hierarchically porous ZrNb24O62 nanowires (P-ZrNb24O62) with an ultra-large Li+-ion diffusion coefficient as a new intercalating pseudocapacitive material for boosting Li+-ion storage. The P-ZrNb24O62 exhibits excellent electrochemical performances, including a high reversible capacity (320 mA h g−1 at 0.1C), safe working potential (∼1.67 V vs. Li/Li+), high initial coulombic efficiency (90.1%), outstanding rate capability (182 mA h g−1 at 30C) and durable long-term cyclability (90.2% capacity retention over 1500 cycles).

This study presents an in situ route to produce 3D Fe–N doped metal organic framework@carbon nanotubes/graphene (Fe-MOF@CNTs-G) hybrids as efficient oxygen reduction reaction (ORR) catalysts in both basic and acidic solutions. A rechargeable zinc–air battery assembled with Fe-MOF@CNTs-G exhibits a lower charge/discharge overpotential than the commercial IrO2 + 20% Pt/C catalyst.

The strategy to improve the photocatalytic performance is still a challenge for the novel Sillen-Aurivillius perovskite type Bi

Potassium-ion batteries (KIBs) have come into the spotlight in large-scale energy storage systems because of cost-effective and abundant potassium resources. However, the poor rate performance and problematic cycle life of existing electrode materials are the main bottlenecks to future potential applications. Here, the first example of preparing 3D hierarchical nanoboxes multidimensionally assembled from interlayer-expanded nano-2D MoS2 @dot-like Co9 S8 embedded into a nitrogen and sulfur codoped porous carbon matrix (Co9 S8 /NSC@MoS2 @NSC) for greatly boosting the electrochemical properties of KIBs in terms of reversible capacity, rate capability, and cycling lifespan, is reported. Benefiting from the synergistic effects, Co9 S8 /NSC@MoS2 @NSC manifest a very high reversible capacity of 403 mAh g-1 at 100 mA g-1 after 100 cycles, an unprecedented rate capability of 141 mAh g-1 at 3000 mA g-1 over 800 cycles, and a negligible capacity decay of 0.02% cycle-1 , boosting promising applications in high-performance KIBs. Density functional theory calculations demonstrate that Co9 S8 /NSC@MoS2 @NSC nanoboxes have large adsorption energy and low diffusion barriers during K-ion storage reactions, implying fast K-ion diffusion capability. This work may enlighten the design and construction of advanced electrode materials combined with strong chemical bonding and integrated functional advantages for future large-scale stationary energy storage.

This report presents a simple method to produce an ultrasmall-Fe7C3/N-doped porous carbon hybrid (u-Fe7C3@NC) as an excellent oxygen reduction reaction (ORR) electrocatalyst. A zinc-air battery assembled with u-Fe7C3@NC performs at a higher open potential (1.486 V) and at a lower discharge overpotential compared with the commercial Pt/C catalyst.

Despite its very high capacity (4200 mAh g–1), the widespread application of the silicon anode is still hampered by severe volume changes (up to 300%) during cycling, which results in electrical contact loss and thus dramatic capacity fading with poor cycle life. To address this challenge, 3D advanced Mxene/Si-based superstructures including MXene matrix, silicon, SiOx layer, and nitrogen-doped carbon (MXene/Si@SiOx@C) in a layer-by-layer manner were rationally designed and fabricated for boosting lithium-ion batteries (LIBs). The MXene/Si@SiOx@C anode takes the advantages of high Li+ ion capacity offered by Si, mechanical stability by the synergistic effect of SiOx, MXene, and N-doped carbon coating, and excellent structural stability by forming a strong Ti–N bond among the layers. Such an interesting superstructure boosts the lithium storage performance (390 mAh g–1 with 99.9% Coulombic efficiency and 76.4% capacity retention after 1000 cycles at 10 C) and effectively suppresses electrode swelling only ...

Despite its very high capacity (4200 mAh g

Rational design of electrocatalysts to replace the noble-metal-based materials for oxygen reactions is highly desirable but challenging for rechargeable metal–air batteries. Herein, we demonstrate a unique two stage encapsulation strategy to regulate the structure and performance of catalysts featured with thin graphene nanosheets coupling with full encapsulated ultrafine and high-loaded (∼25 wt %) transition metal nanoparticles (TMs@NCX) for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). By optimizing the electronic modulation effect from suitable metal cores, the best NiFe@NCX catalyst exhibits high stability and activity with an onset potential of 1.03 V for ORR and an overpotential of only 0.23 V at 10 mA cm–2 for OER, which is superior to commercial Pt/C and IrO2 catalysts. Rechargeable Zn–air battery using NiFe@NCX catalyst exhibited an unprecedented small charge–discharge overpotential of 0.78 V at 50 mA cm–2, high reversibility, and stability, holding great promise for the pr...

Discharging of the aprotic Li-O2 battery relies on the O2 reduction reaction (ORR) forming solid Li2 O2 in the positive electrode, which is often characterized by a sharp voltage drop (that is, sudden death) at the end of discharge, delivering a capacity far below its theoretical promise. Toward unlocking the energy capabilities of Li-O2 batteries, it is crucial to have a fundamental understanding of the origin of sudden death in terms of reactive sites and transport limitations. Herein, a mechanistic study is presented on a model system of Au|Li2 O2 |Li(+) electrolyte, in which the Au electrode was passivated with a thin Li2 O2 film by discharging to the state of sudden death. Direct conductivity measurement of the Li2 O2 film and in situ spectroscopic study of ORR using (18) O2 for passivation and (16) O2 for further discharging provide compelling evidence that ORR (and O2 evolution reaction as well) occurs at the buried interface of Au|Li2 O2 and is limited by electron instead of Li(+) and O2 transport.

Discharging of the aprotic Li–O2 battery relies on the oxygen reduction reaction (ORR) producing Li2O2 in the positive electrode, which remains incompletely understood. Here, we report a mechanistic study of the Li-ORR on a model system, i.e., an Au electrode in a Li+ dimethyl sulfoxide (DMSO) electrolyte. By spectroscopic identification of the reaction intermediates coupled with density functional theory calculations, we conclude that the formation of O2– and LiO2 in the Li-ORR critically depends on electrode potentials and determines the Li2O2 formation mechanism. At low overpotentials (> 2.0 V vs Li/Li+) O2– is identified to be the first surface intermediate, which diffuses into the bulk electrolyte and forms Li2O2 therein via a solution-mediated disproportionation mechanism. At high overpotentials (ca. 2.0–1.6 V vs Li/Li+) LiO2 has been observed, which can rapidly transform to Li2O2 by further electro-reduction, suggesting a surface-mediated mechanism. The solution-mediated Li2O2 formation that can ac...

Silver nanoparticles(Ag NPs) were prepared by dealloying Mg-Ag alloy precursor. The obtained Ag NPs have an average ligament size of (50±10) nm. Electrocatalytic activity of Ag NPs towards oxygen reduction reaction( ORR) in 0.1 mol/L NaOH solution was assessed via cyclic voltammetry(CV), rotating ring disk electrode(RRDE) techniques, and electrochemical impedance spectroscopy(EIS). The electrochemical active area for the ORR was evaluated by means of the charge of the underpotential deposition(UPD) of lead(Pb) on Ag NPs. The CV results indicate that Ag NPs have a higher current density and more positive onset potential than the bulk Ag electrode. RRDE was employed to determine kinetic parameters for O2 reduction. Ag NPs exhibit a higher kinetic current density of 25.84 mA/cm2 and a rate constant of 5.45×10–2 cm/s at–0.35 V vs. Hg/HgO. The number of electrons(n) involved in ORR is close to 4. Further, EIS data show significantly low charge transfer resistances on the Ag NPs electrode. The results indicate that the prepared Ag NPs have a high activity and are promising catalyst for ORR in alkaline solution.