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In this paper, a novel Pt/CoP/C photo-electro synergistic catalyst was successfully synthesized by a hydrothermal method combined with phosphorus doping treatment. The addition of Vulcan XC-72R is in favor of effectively preventing agglomeration of active catalytic sites, resulting in more uniform and smaller Pt and CoP nanoparticles. The as-obtained Pt/CoP/C shows excellent photo-electro catalytic performance for the HER with simulated solar light irradiation. The optimal hydrogen production is 5384.18 mmol h−1 g−1, which is obviously higher than that of the commercial catalyst (20 wt% Pt/C: 4608.52 mmol h−1 g−1). The research results show that introducing cobalt phosphide into the Pt catalyst can improve the electrocatalytic activity and stability for the HER; in particular, the existence of Co3O4 in Pt/CoP/C leads to an efficient photo-electro catalysis under irradiation, which significantly improves the catalytic activity of Pt. The results above provide a novel strategy for the rational design of cost-effective Pt-based composites towards a fast HER. [ABSTRACT FROM AUTHOR]

The development of noble-metal-free electrocatalysts with high catalytic efficiency, low cost, and high durability in pH-universal media is encountering a bottleneck in practical applications. In this paper, Ni@MoN-700 coral hybrids were prepared using hydrogen evolution reaction (HER) catalysts, which were synthesized by a high-temperature reduction of NiMoO4 nanorods with urea. It was found that the annealing temperature seriously affects the surface morphology and chemical composition of the catalysts. Besides, structural reorganization occurred during the HER, which involved the joining of pyrrolic N, metal nitrogen, Mo3+, and Mo6+, governing the HER performance. Also, during the HER, Ni and Mo could synergistically improve the overall catalytic activity of the catalysts, via electronic interactions. These advantages endow Ni@MoN-700 with exceptional endurance and great HER activity, with a low overpotential of 30 mV and 76 mV at 10 mA cm−2 in alkaline and acidic media. These characteristics are similar to those of Pt under alkaline conditions. NiMoN catalysts show unusual activity and long-term stability, indicating a wide range of potential applications. [ABSTRACT FROM AUTHOR]

FeCo2O4 is a potential OER catalyst, but its catalytic activity still needs to be further improved due to its poor electrical conductivity and low material utilization. In this paper, we construct oxygen-vacancy-rich two dimensional FeCo2O4 nanosheet materials using a liquid-phase reduction strategy. Benefiting from its large specific surface area, numerous surface catalytic sites, enhanced electrical conductivity, and modulated electronic structure, the catalyst exhibits an overpotential of only 270 mV at a current density of 10 mA cm−2, which is lower than that of the original FeCo2O4 nanosheets (420 mV). At the same time, the catalyst can run steadily for 20 hours without obvious decay. [ABSTRACT FROM AUTHOR]

Developing low-cost high-efficient electrocatalysts for alkaline hydrogen evolution reaction (HER) is of critical significance in hydrogen production via alkaline electrolyzers. Herein, we prepared CeO2/Co4N heterostructure for the catalyst in alkaline HER, which introduced a synergistic effect within the CeO2 and Co4N catalytic sites that facilitates the two consecutive steps in alkaline HER reaction. More importantly, plasma treatment was further applied to the material to tune the electronic structure of the catalytic sites by creating multiple anion vacancies. The introduced O vacancies accelerated the H2O cleaving process on CeO2, while the N vacancies in Co4N optimized the H adsorption strength on the Co sites. The catalytic activity of the catalyst improved significantly after plasma treatment. It only required an overpotential of 36 mV@10 mA cm−2 for the HER operated in 1 M KOH electrolyte and provided one of the best precious metal-free catalysts ever reported. [ABSTRACT FROM AUTHOR]

The efficient production of hydrogen through water electrolysis requires stable, high-performance and rather cost-effective electrocatalysts to promote the hydrogen evolution reaction (HER). Platinum (Pt) is known to be a benchmark electrocatalyst for the HER, but its high-cost is a major obstacle for large-scale applications. Therefore, reducing Pt loading on electrodes, with a minimal influence on the electrochemical performance is of significant importance. Here, we report on the effective utilization of Pt through a simple two-step magneto-electrodeposition synthesis method, leading to the formation of uniformly dispersed Pt/NiCu electrocatalysts with an excellent catalytic activity. Under optimum conditions, NiCu substrates are fabricated under a vertical static magnetic field of 0.5 T, followed by pulsed electrodeposition of Pt under the same magnetic field. The electrocatalyst (0.5 T NiCu + 0.5 T Pt) exhibits a high stability and superior HER activity, characterized by low overpotentials of 10.6, 54.6, and 87.8 mV obtained at current densities of 10, 100, and 200 mA cm−2, respectively, accompanied by a small Tafel slope of 13.4 mV dec−1 in alkaline media (1 M KOH). This work provides a new approach enabling the optimum utilization of Pt-based electrocatalysts employed for the HER. [ABSTRACT FROM AUTHOR]

Transition metal/nitrogen-doped carbon catalysts (M–N–C) show superior catalytic activity in electrocatalytic CO2 reduction due to their high atomic efficiency. In this work, a series of electrocatalysts with cobalt phthalocyanine (CoPc) highly dispersed on M–N–C were prepared. Compared to the pure M–N–C materials, all CoPc/M–N–C catalysts showed a significantly enhanced activity for CO2 reduction and suppressed hydrogen evolution reaction. Among these catalysts, CoPc/Fe–N–C exhibits an outstanding activity and selectivity for CO2 reduction with 99% faradaic efficiency for CO at a potential of −0.48 V vs. RHE. Obviously, such a composite strategy is considered as one of the effective methods to improve the selectivity of CO2 to CO. [ABSTRACT FROM AUTHOR]

It is highly urgent to develop efficient and stable non-precious metal electrocatalysts for water splitting. Here, we have successfully prepared a phytic acid (PA)-treated NiFe layered double hydroxide (LDH) catalyst. NiFe-LDH(PA) exhibits excellent catalytic activity towards the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and overall water splitting (OWS) (η10 = 112 mV and η100 = 198 mV for the HER, η100 = 260 mV for the OER, and 1.69 V for OWS @ 100 mA cm−2) as well as remarkable stability during long-term testing (100 h for the HER, 90 h for the OER, and 100 h for OWS). The PA treatment accelerates the catalytic kinetics of NiFe-LDH(PA) and exposes more active sites, leading to enhanced charge transfer. This work demonstrates the significant potential of organic small molecules in modifying the performance of conventional catalysts. [ABSTRACT FROM AUTHOR]

New heteroleptic dppe appended Co(III)-dithiocarbamate (dtc) complex cations with compositions [Co(S2CNEt2)2(dppe)](PF6) (Co-Et), [Co(S2CNPri2)2(dppe)](PF6) (Co-Pr) and [Co(S2CNBun2)2(dppe)](PF6) (Co-Bu) have been synthesized and characterized by microanalysis, spectroscopic methods and crystallographic analysis. The single crystal X-ray diffraction results indicated that in all three complexes, the coordination environment around Co(III) is distorted octahedral and Co(III) is coordinated to four sulfur centers of the two dtc ligands and the two phosphorus centers of the dppe ligand. These complexes serve as precursors to yield cobalt sulfide/cobalt phosphide nano-composites dCo-Et, dCo-Pr and dCo-Bu by solvothermal decomposition of Co-Et, Co-Pr and Co-Bu, respectively. The decomposed materials have been characterized by PXRD and SEM-EDAX and explored as potential electrocatalysts for both oxygen evolution and hydrogen evolution reactions in basic and acidic media, respectively. Catalytic activity is dependent on the precursor complex and best OER and HER activities are observed for dCo-Bu with an η10 of 230 mV and a Tafel slope of 192.11 mV dec−1 for the OER and an η10 of 470 mV and a Tafel slope of 126.21 mV dec−1 for the HER. [ABSTRACT FROM AUTHOR]

The development of high-performance and highly stable electrocatalysts is crucial and challenging for the hydrogen evolution reaction (HER). MOFs complexed with SnS2 can form complexes with inserted structures, and their large specific surface area and numerous pores favor mass transfer, exposing the S active sites to more SnS2, improving the utilisation of the active sites and enhancing the catalytic activity for the HER. Structural collapse can be hindered to improve the stability of the HER composites. Herein, six different kinds of SnS2 were synthesized by a hydrothermal method under discrete conditions, and SI8-SnS2 was screened out to have optimal morphology and electrocatalytic performance. Two innovative SnS2@Ni-MOF and SnS2@HKUST-1 as efficient electrocatalysts were synthesized by a facile grinding method for hydrogen generation. SnS2@Ni-MOF and SnS2@HKUST-1 catalysts showed lower overpotentials of 117 mV and 142 mV at 10 mA cm−2 (η10) and smaller Tafel slopes (58 mV dec−1 and 93 mV dec−1) than six different kinds of SnS2, Ni-MOF and HKUST-1 in 0.5 M H2SO4. Meanwhile, the Cdl values for SnS2@Ni-MOF and SnS2@HKUST-1 were estimated to be 11.5 mF cm−2 and 8.0 mF cm−2, and the stabilities of SnS2, Ni-MOF, HKUST-1, SnS2@Ni-MOF, and SnS2@HKUST-1 were tested at a current density of 10 mA cm−2. The current densities of SnS2@Ni-MOF and SnS2@HKUST-1 were stable over 8 h compared to the pure samples, and SEM, XPS tests were run after the HER test, indicating that the materials have excellent electrocatalytic stability. The syntheses of SnS2@Ni-MOF and SnS2@HKUST-1 enhance their intrinsic catalytic activity, and the porous structure promotes mass transfer efficiency, thereby improving the HER performance, which will guide the development of new and promising electrocatalysts for HER. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cells (DMFC) are a promising new energy source. However, the lack of high-performance and low-cost methanol oxidation electrocatalysts hinders their commercial application. Firstly, we successfully prepared NENU-5-derived molybdenum carbide material (Cu-MoC) via a co-precipitation and high-temperature carbonization method using a material composed of a copper-based metal–organic skeleton and a molybdenum-based carbide as the main body. Secondly, PtCu nano-alloy catalysts (Pt/Cu-MoC) were prepared using a unique, spontaneous single replacement reaction after metal–organic skeleton (MOF) carbonization. Through the synergistic effect between Pt and Cu and the strong interaction between Mo2C and PtCu, the electronic structure of the Pt is modified, the energy of the d-band center is reduced, electron exchange is accelerated, and catalytic activity is enhanced. Compared with a commercial Pt/C catalyst in alkaline environments, the Pt0.10/Cu-MoC catalyst has a better MOR catalytic activity (563.25 mA mgPt−1), which is 1.5 times higher than that of commercial Pt/C (376.67 mA mgPt−1). The Pt0.10/Cu-MoC catalyst has an onset potential for CO oxidation that is 16 mV lower than that of commercial Pt/C, indicating better resistance to CO poisoning. Exploring carbon materials derived from MOFs with excellent junction support and using them as carriers to prepare Pt-based catalysts is a practical and feasible approach. It provides a way to develop new Pt-based catalysts that perform efficient MOR. [ABSTRACT FROM AUTHOR]

Subphthalocyanines (SubPcs) have emerged as promising organic dyes for the development of efficient artificial photosynthetic devices, offering intense absorption in the visible region along with excellent charge transport properties. In this study, four novel SubPc derivatives containing carboxylic acid and various peripheral substituents were synthesized as a panchromatic photosensitizer to prepare an efficient and stable TiO2-based photocatalytic system for co-catalyst-free photocatalytic hydrogen evolution. To compare the influence of the nature of the peripheral substituents on photocatalytic activity, SubPc derivatives (coded as SubPc 1–4) were decorated with substituents having different electron-donating capabilities, such as alkyl thio, benzodioxin, amine, and iodo units, respectively. Photocatalytic activities were examined in the presence of TEOA as a sacrificial agent under irradiation with λ > 400 nm without co-catalyst loading. SubPc 1/TiO2 shows the best photocatalytic activity among the SubPc-sensitized photocatalysts, with a hydrogen evolution rate of 0.176 mmol h−1. While the activity of all four SubPc-based photocatalysts increased significantly after 24 h irradiation, notably, SubPc 1/TiO2 exhibited remarkable catalytic activity, achieving a hydrogen evolution rate of 6.017 mmol with a high turnover number (TON) value of 12 279 for hydrogen production. This study highlights the potential of SubPc-based sensitizers for co-catalyst-free photocatalytic H2 production and offers valuable insights into the impact of peripheral units in SubPc/TiO2-based photocatalytic systems. [ABSTRACT FROM AUTHOR]

The practical application of CO2 electroreduction to CO driven by renewable electricity should simultaneously meet the requirements of low overpotential, high CO faradaic efficiency (FE), and low cost. Herein, a new strategy is reported to construct a porous nanoflower Ni–Al NC catalyst with excellent catalytic activity via p–d orbital hybridization of Al and Ni. The optimized Ni–Al NC catalyst exhibits an outstanding CO2 electroreduction activity with the maximum CO FE of 98%, low onset potential of −0.5 V vs. RHE, and wide FECO plateau (>90% from −0.7 to −1.0 V vs. RHE), showing great promise for practical applications. The experimental results showed that the p–d hybrid Ni–Al NC catalyst not only enriched its reaction sites but also withstood potential changes in the highly selective reduction of CO2 to CO. This study provides a catalyst design strategy for the efficient electrocatalytic reduction of CO2 to CO under varying potentials. [ABSTRACT FROM AUTHOR]

Catalysts with high catalytic activity and low cost are extremely significant for hydrogen production by water cracking. In this work, through simple electrospinning and carbonization methods, Ru with excellent catalytic activity is dispersed onto Fe4C to form Ru–Fe4C nanoparticles loaded on N-doped carbon nanofibers (Ru–Fe4C/NCNF), so that Ru can expose more active sites and thus improve HER catalytic activity. Meanwhile, the addition of low-cost Fe can reduce the use of noble metal Ru, thereby reducing the catalyst cost. On the other hand, the prepared Ru–Fe4C/NCNF can be used as a self-supporting working electrode and shows good stability. The experimental results show that the prepared Ru–Fe4C/NCNF can drive a current density of 10 mA cm−2 with only 106 mV in 1 M KOH, and more importantly, only 254 mV can produce a current density of 100 mA cm−2. At the same time, it shows excellent stability after continuously working for 100 h at a current density of 100 mA cm−2. This work provides a new thought to synthesize economical catalysts with high catalytic activity. [ABSTRACT FROM AUTHOR]

The development of cheap but high activity and strong stability OER electrocatalysts is of great significance to improve electrochemical energy storage and conversion efficiency. A kind of nickel–cobalt alloy nanoparticle coated with a defect-rich carbon layer derived from citric acid was developed as an advanced alkaline OER electrocatalyst by simply annealing the citrate-coordinated nickel–cobalt complex. The formation of the alloy has promoted internal electron transfer, and the catalyst features unique structural advantages. The metal center was confined to the citrate-derived defect-rich carbon layer structure, which reduced the agglomeration of nanoparticles, increased the electrical conductivity, and exposed more active sites. The as-synthesized Ni0.8Co0.2(CA) showed a remarkable catalytic activity (an overpotential of 200 mV at 10 mA cm−2 and a Tafel slope of 87 mV dec−1), which also had good long-term stability. This study will contribute to deeper understanding of ligand selection and the design of high-performance alloy catalysts. [ABSTRACT FROM AUTHOR]

Given the current energy shortage, hydrogen energy is an attractive option as a renewable green energy source. Electrocatalytic hydrogen production is a promising and efficient method with great potential for renewable energy. However, the main limiting factor is developing low-cost and high-efficiency imprinted hydrogen evolution reaction (HER) catalysts. This study utilized theoretical calculations to address the challenge of designing Ni-based catalysts for efficient electrocatalytic HER. Firstly, Ni(111) and Ni(311) were subjected to Co doping, and the catalytic activity of Ni–Co catalysts for the electrocatalytic HER was evaluated using the ΔGH_ads and EH2O_ads indices. Moreover, Mo-doping modification was carried out on catalysts with more negative EH2O_ads and smaller absolute values of ΔGH_ads to determine the optimal catalysts for the electrocatalytic HER. Through quantum chemical calculations, the Ni(311)–2Ni–1Co-3,4Mo catalyst with optimal HER catalytic activity was determined. Additionally, the density of states (DOS) values before and after the adsorption of H* and H2O were calculated, and the reaction pathways before and after doping were explored. The Ni(311)–2Ni–1Co-3,4Mo catalyst can dissociate H2O and adsorb H* with higher performance, proving its excellent electrocatalytic HER catalytic performance. The findings of this study may provide theoretical guidance for the experimental development of HER catalysts. [ABSTRACT FROM AUTHOR]

Focusing on renewable energy, we developed an efficient and robust catalyst for overall water splitting (OWS). Using density functional theory (DFT) as the guide, a combination electrode with bifunctional activities based on Co-based carbonate hydroxides (CCHs) and pyrenely-graphdiyne nanowalls (Pyr-GDY-NWs) with three-dimensional structures was designed, and then a series of experiments were attempted to prepare the combination electrode CCH@Pyr-GDY-NWs. From the data of theory and experiment, we found that the combination electrode CCH@Pyr-GDY-NWs exhibits an outstanding catalytic activity towards OWS. The design approach reported herein could open up a new avenue for the construction of three-dimensional Pyr-GDY-NW-based electrodes with high catalytic activity. [ABSTRACT FROM AUTHOR]

Efficient precious metal-free oxygen reduction reaction (ORR) electrocatalysts are key to reducing the cost of fuel cells and metal–air batteries. In this study, we synthesized Ce–Co-based N-doped porous carbon nanosheets (Ce–Co/N/C) by introducing a small amount of rare earth element Ce to improve the catalytic activity of Co-based electrocatalysts. Here, folic acid (FA) was used as a metal complex ligand, and Ce–Co/N/C was synthesized using a solvothermal method with molten salt template-assisted calcination. The resulting Ce–Co/N/C material exhibited superior ORR performance in alkaline media with a high half-wave potential of 0.893 V (vs. RHE), splendid stability and methanol resistance, which are significantly better than those of commercial 20% Pt/C. These favorable chemical properties are due to their advantageous composition and structure. Transmission electron microscopy and N2 adsorption–desorption experiments showed that the catalyst has a large specific surface area and a hierarchical pore structure. X-ray photoelectron spectroscopy revealed that the change in Co binding energy after Ce doping indicates the adjustment of the Co electronic structure, which optimizes the adsorption/desorption of oxygen-containing intermediates and greatly improves the catalytic activity for oxygen reduction. [ABSTRACT FROM AUTHOR]

Transition-metal-based metal–organic frameworks (MOFs) have received great interest for the development of low cost, platinum-free, non-precious water splitting electrocatalysts for hydrogen generation to resolve the energy crisis. Recent studies are mainly concerned with the use of MOFs as a self-sacrificing template for the synthesis of carbon-based electrocatalysts encapsulating metallic sites. However, the process often produces undesired metal nanoparticles, lowering the catalytic activity of the materials. This report explores a novel strategy to improve the intrinsic electrocatalytic activity of MOFs by a ligand substitution method. Ligands with different electron donating capacity have been used for the substitution process and the hydrogen evolution activity has been found to be greatly affected by the presence of different donor ligands. The MOF used in this work is designed with Ni as a metal center with 5-azido isophthalic acid as the primary linker. Subsequently, the MOF is functionalized with different organic moieties, i.e., N,N-dimethylethylenediamine (DMEDA) and 4-aminotetrafluoropyridine (4-ATFP) with rich non-metal catalytic active sites by means of post synthetic modification. A comparative study has been performed which shows the 4-ATFP functionalized MOF to have the best electrocatalytic activity among the three with significant performance in all three media, i.e. neutral, acidic and alkaline. Furthermore, theoretical approaches have been employed for the analysis of these experimental observations. [ABSTRACT FROM AUTHOR]

Developing noble-metal-free bifunctional electrocatalysts at an effective cost and with a high catalytic ability for hydrogen production via water-splitting is imperative, although a great bottleneck remains. Herein, we present a plasma engraving strategy to synthesize N-doped CoFeS on cobalt foam with a multi-interface and defect hierarchical structure. The N-doped CoFeS was synthesized using an ion exchange method to prepare the CoFe LDH precursor, followed by sulphidation and plasma-assisted engraving in nitrogen gas. The N-doped CoFeS requires an overpotential of 230 mV for the OER and 26 mV for the HER to reach a current density of 10 mA cm−2. It also shows an excellent catalytic activity towards overall water splitting, which requires a low voltage of 1.61 and 1.80 V to achieve a current density of 10 and 50 mA cm−2, respectively, in 1 M KOH. The super-catalytic properties can be attributed to the interface and defect structure, which induces a high intrinsic activity, a superior transfer coefficient, and abundant active sites. This work presents a novel approach to prepare noble-metal-free electrocatalyst with plenty of interface and defect sites for overall water splitting. [ABSTRACT FROM AUTHOR]

This study aims to improve the hydrogen evolution reaction (HER) catalytic activity of CuS-based electrocatalysts in basic media for efficient and cost-effective hydrogen production. CuS is a promising alternative to noble metal-based electrocatalysts due to its low cost and high stability, but individual CuS has not been established as a good HER electrocatalyst. Recent reports suggest combining Cu and Ni to increase the HER catalytic activity of Cu-based electrocatalysts. This study explores the synergy of Cu and Ni by decorating the surface of CuS with Ni for an effective HER. The results show that sulfurizing electrodeposited Cu2O with the Ni precursor increases the electrochemical performance, achieving an overpotential of 325 mV to achieve a current density of 100 mA cm−2. This study provides a promising approach for developing efficient and cost-effective HER electrocatalysts. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are a new category of polymer with well-defined porous and crystalline properties that consist of lightweight elements. Strong covalent linkages connect these elements. Because of these covalent bonds, these substances have advantages such as adjustable features, low density, and a large surface area. Owing to these fascinating features, these materials reveal a promising kind of porous framework. Since COFs are applicable in various areas of gas separation, catalysis, chemical sensing, and energy storage, these materials appeal to researchers. Materials that benefit from tunable porosity and high surface area could be appropriate and desirable choices as next-generation catalytic substances and provide a wonderful opportunity in the field of catalytic usage. They are suitable for such catalytic activities as hydrogen evolution reactions, CO2-to-CO conversion, and oxygen evolution reactions. There are several approaches to synthesizing COFs, including the solvothermal method, microwave method, sonochemical method, and mechanochemical method. The purpose of this review article is to present the latest and most significant applications of COFs as catalysts. With an emphasis on synthetic approaches, some novel fabricated COFs are also evaluated. [ABSTRACT FROM AUTHOR]

The development of highly efficient electrocatalysts for urea oxidation reaction (UOR) is crucial for reproducible and clean energy technologies. Herein, dual-phased nickel-based cost-effective catalyst nickel phosphide (Ni2P)-nickel metaphosphate (Ni2P4O12) microspheric nanoparticles were fabricated through a two-step hydrothermal-phosphorization process by preciously controlling the feeding ratios of the Ni precursor and the P source. It merely needs a potential of 1.35 V vs. RHE to deliver a current density of 10 mA cm−2 with a small Tafel slop of 55 mV dec−1 and maintains high catalytic activity for 10 h in 1.0 M KOH with 0.33 M urea solution. The synergy effect and modulation of the electronic structure between Ni2P and Ni2P4O12 could be the reason for the good UOR performance. This work provides a new perspective for the further design of high-performance electrocatalysts in diverse energy fields. [ABSTRACT FROM AUTHOR]

Defect engineering is a promising strategy that essentially tailors the specific surface area, energy band structure and photocatalytic properties of catalysts. Herein, a series of oxygen defect modified polyimides (PI-NaHCO3 (1 : 1, 1 : 4, and 1 : 8)) containing triazine rings have been synthesized via thermal polymerization by introducing an inorganic foaming agent NaHCO3 into the synthesis of classical polyimide (PI). During the polymerization and washing process, a large amount of gas generated by NaHCO3 breaks the imide bond connections in PI, resulting in the formation of oxygen defects. The experimental results revealed that with the introduction of oxygen defects, the band gap of PI broadened, and the absorption band edge exhibited a certain blue shift. However, the separation and transmission of photogenerated carriers were significantly enhanced, and the radiation recombination has been inhibited. Therefore, the photocatalytic activity of samples was significantly improved. Among them, PI-NaHCO3 (1 : 4) shows the optimal catalytic activity in photocatalytic benzylamine oxidation and photocatalytic hydrogen evolution experiments. Under irradiation using a 420 nm LED (10 W), the conversion and selectivity of benzylamine to corresponding imine are more than 99%. This work provides a new way for the design of defective polyimide materials. [ABSTRACT FROM AUTHOR]

The development of efficient, durable and economical catalysts based on non-precious metals for the controllable and fast hydrogen evolution from chemical hydrogen storage materials is highly desirable for the hydrogen economy. Herein, we introduce an advanced catalytic system by in situ encapsulating cobalt phosphide (CoP) nanoparticles into a quasi-metal–organic framework (quasi-Co-MOF-74) through a smart pyrolysis method. The designed synergic structure of CoP@quasi-Co-MOF-74 facilitates the efficient adsorption and activation of reactants, and achieves superior catalytic activity for the dehydrogenation of ammonia borane (AB). The extremely high hydrogen generation rate (HGR) of 9790 mL min−1 gcat−1 achieved by this catalytic system is 13.1, 4.4, and 46.5 times higher than that of quasi-Co-MOF-74, CoP, and CoP@C counterparts, respectively. Furthermore, CoP@quasi-Co-MOF-74 also delivers a high turnover frequency (TOF) of 55.9 min−1 and a low activation energy of 38.22 kJ mol−1 for the catalytic hydrolysis of AB, which compares favorably to most of the previously reported transition metal phosphide and cobalt-based catalysts. [ABSTRACT FROM AUTHOR]

The development of substantial, environment-friendly and low-cost electrocatalysts for an efficient oxygen reduction reaction (ORR) is essentially important for the production and storage of green energy which has sparked the curiosity of researchers for scalable production of metal-free electrocatalysts from biowaste. We report an easy transformation of chestnut-derived biowaste into reduced graphene oxide (rGO) and pyridinic-N-dominated nitrogen-doped rGO (NCS-rGO). The synthesized catalyst exhibits better ORR activity with an onset and half-wave potential of 0.93 V and 0.86 V, respectively, along with a high diffusion-limiting current density of 5.05 mA cm−2. Under alkaline conditions, we found that NCS-rGO shows an unusually high electrocatalytic activity that is superior to that of the commercial 20% Pt/C catalyst. More notably, the NCS-rGO-based ORR electrocatalyst manifests higher methanol tolerance, without deterioration in catalytic activity even in the presence of significant amount of methanol, outperforming the current state-of-the-art Pt electrocatalyst. Density functional theory (DFT) studies illustrate that pyridinic N is a decisive part of NCS-rGO to achieve the best ORR performance. [ABSTRACT FROM AUTHOR]

The exploration of efficient, stable, and economical electrocatalysts for oxygen evolution reaction (OER) is of great significance and challenge for the development of renewable energy. A series of Ni-based layered double hydroxides (LDHs) have been explored as promising electrocatalysts for OER on account of their earth abundance, low overpotential, and super stability. However, the low electrical conductivity of LDHs cannot satisfy the progressive requirements of water splitting. Herein, we introduce a template strategy to synthesize trimetallic nickel-chromium LDH–cobalt (NiCr-LDH–Co) nanosheets on nickel foam (NiCr-LDH–Co/NF) without any binders as efficient catalysts for OER. Compared with the reported NiCoCr-LDHs synthesized by one-step, our NiCr-LDH–Co/NF delivered a lower overpotential of 229.4 mV at 50 mA cm−2, which is even lower than that of all the reported bimetallic nickel-based LDHs (NiFe-LDH, NiCo-LDH, NiMn-LDH, NiTi-LDH, NiV-LDH, etc.) and the precious RuO2 catalyst. Furthermore, the NiCr-LDH–Co/NF was maintained for at least 24 h at a high current density of 50 mA cm−2 without much deviation in 1 M KOH solution. The effective integration of the layered structures of LDH and the high electronic conductivity of the Co element endow NiCr-LDH–Co/NF remarkable catalytic ability for the OER process. Furthermore, the strategy expands the possibility for improving the catalytic activity of trimetallic LDHs as OER catalysts. [ABSTRACT FROM AUTHOR]

The rational design of efficient electrocatalysts for nitrogen reduction reaction (NRR) to produce NH3 under ambient condition is a longstanding challenge. The graphene-based single-atom catalyst (SAC) has been revealed as a promising candidate. Previous studies mainly focused on the metal center coordinated with N atoms, while those coordinated with other heteroatoms were rarely reported. Herein, we theoretically investigated the effect of oxygen coordination on the performance of vanadium (V) SAC embedded in graphene (VO4/G) towards NRR owing to the fact that V with less d electrons usually exhibits high chemical activity. It is revealed that VO4/G with good stability can efficiently convert N2 into NH3 through a distal mechanism with a low limiting potential of −0.60 V, which is superior to the experimentally synthesized FeN4/G and FeO4/G SACs. Moreover, the stronger adsorption of N2 than the H atom renders the high NRR selectivity of VO4/G against the competing hydrogen evolution reaction, and the rapid removal of the produced NH3 endows VO4/G with excellent recyclability. The good stability, high catalytic activity and selectivity, and excellent recyclability make VO4/G a prospective NRR catalyst. This work provides a promising NRR electrocatalyst awaiting experimental exploration and will stimulate further studies on other coordination atoms beyond N for graphene-based SAC. [ABSTRACT FROM AUTHOR]

Developing efficient, durable, and noble-metal-free electrocatalysts is considered the Holy Grail of sustainable hydrogen production through water splitting. In light of the potential importance of carbon components in low-cost electrocatalysis, various innovative synthesis strategies offering better structural integrity and facile electronic communication between the carbon component and catalytically active component are highly sought after. In coherence with this concept, N and S dual-doped carbon-armored Co9S8 (Co9S8@NSC) nanomaterials are synthesized via an improvised solid-state pyrolysis of Co(II) and sulphanilic acid adduct. The as-obtained nanomaterials furnish a bifunctional electrocatalytic activity for overall alkaline water splitting. In particular, Co9S8@NSC-8 (synthesized at 800 °C) shows impressive bifunctional activity with very low overpotentials of 267 and 120 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, corresponding to a current density of 10 mA cm−2. The catalyst supports rapid reaction kinetics for both HER and OER with respective Tafel slopes of 85 and 48 mV dec−1. The full-cell measurement with Co9S8@NSC-8 at both electrodes demonstrates a remarkable performance towards simultaneous HER and OER production, yielding a current density of 10 and 80 mA cm−2 at low potentials of 1.6 and 2.4 V, respectively. The degree of graphitization and the status of N and S doping in the carbon shell of Co9S8@NSC reasonably explain the catalytic activity they have acquired. In the long-term durability test, the catalyst retains its activity after 10 h of electrocatalysis, reflecting impeccable stability in an alkaline environment. The superior electrocatalytic activity of Co9S8@NSC materials is mainly attributed to a strong interfacial interaction between the Co9S8 cores and N,S-doped carbon shells. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) are one of the ideal functional materials for the oxygen evolution reaction (OER) because of their special configuration and good electrochemical activity. Incorporating different divalent and trivalent metals into layered double hydroxides (LDHs) is an effective way to induce defects and generate abundant oxygen vacancies and adjust the morphology of the materials and thus enhance the intrinsic catalytic activity of the materials. In this work, a nano-flower-like Mg-doped NiCo-LDH (denoted as NiCoMg-LDH) was synthesized by a solvothermal method, and the effect of the molar ratio of Mg, Co and Ni on the electrochemical activity of NiCoMg-LDH was explored. The results showed that NiCoMg-LDH with the optimum molar ratio (Ni : Co : Mg = 3 : 3 : 0.3) exhibited excellent OER catalytic activity in 1.0 M KOH, with an overpotential of only 229 mV at a current density of 10 mA cm−2, a small Tafel slope of 31.0 mV dec−1, and an electrochemically active surface area (ECSA) of 410 cm2. This work provides a facile but effective method to improve the OER performance of layered double hydroxides. [ABSTRACT FROM AUTHOR]

The application of zeolite imidazolate framework (ZIF)-based nanomaterials for oxygen reduction reaction (ORRs) and supercapacitors (SCs) is drastically confined by their quick aggregation and irreversible fusion of metal nanoparticles. Herein, the impact of using the mesoporous silica-protected calcination strategy on the CuFe-ZIF composite is studied. To this end, the CuFe-ZIF catalyst was first prepared and then covered by mesoporous silica (mSiO2). The acquired CuFe-ZIF@mSiO2 was pyrolyzed at 900 °C under an Ar atmosphere. After pyrolysis and acid etching, the Cu@Fe–N–C nanomaterial was formed. The synthesized samples were evaluated by physical and electrochemical tests. According to the results, Cu@Fe–N–C with mSiO2 protection exhibited better ORR catalytic activity with an onset potential of −0.04 V vs. Ag/AgCl compared to the unprotected sample (−0.17 V vs. Ag/AgCl). Besides, its average electron transfer number was found to be 3.55, indicating a 4-electron pathway for ORR. Furthermore, it offered excellent performance in a supercapacitor by applying the mSiO2 cover, and the specific capacitance value significantly enhanced from 191 F g−1 to 341 F g−1 at a current density of 1 A g−1. Therefore, it can be deduced that by employing the mesoporous silica covers during calcination process, the electrochemical properties of CuFe-ZIF-based materials can be considerably improved. [ABSTRACT FROM AUTHOR]

Transition metal phosphides have been widely studied because of their low cost and good conductivity, attempting to replace precious metal-based materials as new electrochemical catalysts for oxygen evolution reaction. However, the existing high-performance phosphide catalysts for oxygen evolution reaction have bottlenecks such as difficulty to accurately determine the components and the catalytic mechanism. Therefore, in this study, we designed and synthesized FeP/CoP heterogeneous materials with a unique porous morphology as OER catalysts. The as-prepared heterogeneous materials have excellent OER catalytic activity and stability. The overpotential at 10 mA cm−2 is only 266 mV, and the Tafel slope is 60.86 mV dec−1. We believe that the good catalytic performance of the as-prepared material is mainly due to the unique morphology and redistribution of interfacial charges. The results of this study provide new ideas for designing efficient metal phosphide-based OER catalysts. [ABSTRACT FROM AUTHOR]

A composite cluster with core–shell structure composed of polyoxometalates (POMs) and graphdiyne (GDY) was synthesized and applied for the electrochemical oxygen evolution reaction (OER). Compared with the original POMs and GDY, the composite cluster Co4(PW9)2@GDY demonstrates superior performance and stable electrochemical OER. The core–shell composite cluster exhibited high performance for OER with low potentials and a small Tafel slope. Moreover, high catalytic activity of the cluster was achieved at a high current density. Co4(PW9)2@GDY has excellent catalytic performance and long stability due to its strong electron-transfer ability in the system, higher conductivity, and the structural advantage of pores in GDY. We also tested the OER synergism mechanism between POM and GDY. This would open access and guide us to synthesize novel clusters based on polyoxometalates and graphdiyne. [ABSTRACT FROM AUTHOR]

Designing catalysts with high electrochemical activity and stability for the oxygen evolution reaction (OER) is a pivotal step for sustainable water splitting. Interface engineering can represent a practical approach to enhance catalytic performance. In this work, a cyclic voltammetry (CV) technique as an intentional surface reconstruction strategy is utilized to promote FeCoNiCrVB as a highly active OER catalyst. The activated electrocatalyst manifests enhanced catalytic activity with a low overpotential of 237 mV at a current density of 10 mA cm-2 and a Tafel slope of 24.2 mV dec-1, compared with the pristine one (332 mV & 46.2 mV dec-1). The excellent activity and long-term stability make reconstructed FeCoNiCrVB a promising candidate to catalyze the OER process. The amorphous state, highly active sites and entropy engineering jointly contribute to its advanced OER performance. This work shows the great potential of multicomponent alloys as electrocatalysts, and provides new ideas for the enhancement of the OER activity by using an electrochemical surface reconstruction strategy. [ABSTRACT FROM AUTHOR]

Hydrogen energy is considered to be one of the ideal clean energies to replace fossil fuels because of its high energy density, renewability and environmental friendliness. The design and development of efficient, stable and low-cost hydrogen evolution reaction (HER) electrocatalysts is the key to driving the industrialization of hydrogen production technology from electrochemical water splitting. In this work, sulfur-doped Ni2P (S-Ni2P) electrocatalysts with a porous structure were synthesized by simple one-step hydrothermal reaction. The composition, structure, morphology and HER properties of S-Ni2P materials were regulated by adjusting the amount of sulfur doping. The results show that S-Ni2P catalysts display a better HER catalytic performance than pure Ni2P in acidic and alkaline electrolytes. Sulfur doping can significantly improve the catalytic activity of Ni2P. With the increase of content of doped sulfur, the HER performance of S-Ni2P materials is gradually improved. When the content of doped sulfur is 10%, the overpotentials of S10%-Ni2P in 0.5 M H2SO4 and 1 M KOH are 290 and 331 mV at 10 mA cm-2 with the Tafel slope of 67.1 and 104.1 mV dec-1, respectively, exhibiting the best HER catalytic activity among all S-Ni2P materials. This is mainly due to the unique porous structure of S-Ni2P, which can provide more catalytic active sites. At the same time, sulfur doping can adjust the electronic structure of Ni2P so as to improve the intrinsic activity of the materials. [ABSTRACT FROM AUTHOR]

Producing molecular hydrogen (H2) using water provides a sustainable approach for developing clean energy technologies. Herein, we report highly active ruthenium (Ru) clusters supported on iron oxide (Ru/Fe3O4) and Fe3O4/multi-walled carbon nanotubes (Ru/Fe3O4/MWCNTs) by simple electrochemical deposition in a neutral aqueous medium. The supported catalyst exhibits good hydrogen evolution reaction (HER) activity in an acidic environment. Cyclic voltammograms (CVs) of potassium ferrocyanide (K4[Fe(CN)6]) confirm that MWCNTs enhance the electron transfer process by decreasing the redox formal potential. The overpotentials of Ru/Fe3O4/MWCNTs and Ru/Fe3O4 electrocatalysts versus the reversible hydrogen electrode (RHE) were found to be 101 mV and 306 mV to reach a current density of 10 mA cm−2. As prepared, the catalyst displays good stability and retain its HER activity even after 1000 cycles. Furthermore, the stability of Ru/Fe3O4/MWCNTs was studied using the chronopotentiometric (CP) technique for 12 h and found negligible loss in the catalytic activity towards the HER. To explore the role of Ru and underneath MWCNTs in improving the catalytic performance of Fe3O4, density functional theory (DFT) calculations were carried out. DFT calculations indicate that the octahedral site of Ru/Fe3O4 favors the HER with a low overpotential. However, Ru/Fe3O4/MWCNTs are more efficient towards the HER, which could be due to the availability of both octahedral and tetrahedral catalytic sites. [ABSTRACT FROM AUTHOR]

Recently, much attention has been focused on the development of photocatalysts for hydrogen evolution. Up to now, efficient hydrogen generation is still greatly challenging due to the restraints of the surface redox reaction rate, and the introduction of a co-catalyst is one of the keys to this problem. Here, dual non-noble co-catalysts NixP and Mn3O4 were proposed and prepared on a g-C3N4/red phosphorus (CNP) hybrid structure with a high light adsorption capability by a two-step photo-deposition method. The photo-excited charge on the composite catalyst separate and transfer from C3N4 to red phosphorous due to a type I heterojunction structure. NixP and Mn3O4 act as reductive and oxidative co-catalysts, respectively. The hydrogen production rate was 5851.3 μmol g−1 h−1, 12.4 times that of pure CNP. The consistent catalytic activity in an actual 25 mL flask for hydrogen evolution over eight hours accumulated 245.08 μmol H2 under solar simulated irradiation. This work provides practical reference for the development of a novel inexpensive photocatalyst system. [ABSTRACT FROM AUTHOR]

There are potential applications for binuclear oxo-bridged iron complexes in biological processes, catalysts, and magnetic materials, and the design of new bridged-iron complexes is important. A new mono-oxo-bridged binuclear iron(III) complex, [(H2O)(bpc)Fe–O–Fe(bpc)(H2O)], is designed and provided by the reaction of FeCl3 with 1,2-bis(pyridine-2-carboxamido)-4,5-dichlorobenzene) (H2bpc) in our group. Structural investigations show that two ions are connected with a Fe–O–Fe angle of 180.0°, so it is a novel linear mono-oxo-bridged iron complex. Magnetic studies indicate that the iron(III) ions are in low spin (ls) states. Electrochemical investigations exhibit that [(H2O)(bpc)Fe–O–Fe(bpc)(H2O)] has FeIV/III, FeIII/II, and FeII/I couples at 0.689, −0.476, and −2.065 V versus Ag/AgNO3, respectively, and can electro-catalyze hydrogen evolution from acetic acid with a rate constant of 7561.95 M−1 s−1. [ABSTRACT FROM AUTHOR]

The search for efficient non-precious metal or earth-abundant electrocatalysts is the key to drive clean energy technologies to develop a hydrogen economy. Here, we have developed a simple and scalable strategy for the synthesis of bimetallic ZnCo2(OH)F rod-like nanoarrays supported on nickel foam. The electrochemical test results show that ZnCo2(OH)F/NF exhibited a good electrocatalytic performance in the hydrogen evolution reaction (HER) at 10 mA cm−2, with an overpotential of 121 mV, a significant Tafel slope value of 129.9 mV dec−1 and excellent stability at different current densities. Due to bimetallic hybridization, this material has excellent catalytic activity and good H* absorption free energy active sites, which indicate its operability in rational hydrogen production applications. This work provides a superior synthetic strategy for the effective design and rational fabrication of low-cost, highly active, and highly stable non-precious metal HER electrocatalysts for electricity-to-hydrogen applications. [ABSTRACT FROM AUTHOR]

The development of efficient and low-cost sustainable electrocatalytic hydrogen precipitation materials is an effective way to support the reduction of fossil fuel use. In recent years, in order to overcome the problem of the poor electrical conductivity of transition metal chalcogenides (TMCs), carbon-based materials and the MXene family have become popular TMC carriers. In this work, Cu2MoS4/Ti3C2Tx-30% materials with a special structure were synthesized for the first time via a simple and friendly solvothermal method. We successfully grew Cu2MoS4in situ on a MXene (Ti3C2Tx) via solvent heating, and Cu2MoS4/Ti3C2Tx-30% was bonded together by electrostatic adsorption to form a special structure. Its overpotential is 103 mV lower than that of pure Cu2MoS4 at a current density of 10 mA cm−2 in an acidic medium (0.5 M H2SO4). At the same time, under the same conditions, the Tafel slope is 37 mV dec−1 lower than that of pure Cu2MoS4. Critically, the heterostructure retains high catalytic activity within 20 h. All of this is attributed to the special structure of Cu2MoS4/Ti3C2Tx-30%, resulting in increased conductivity, electrochemically active surface area (ECSA), and stability. This provides new ideas for future discoveries relating to the synthesis of non-precious transition metal two-dimensional composites. [ABSTRACT FROM AUTHOR]

The development of highly active HER catalysts is of great significance for the preparation of high-purity green hydrogen. Although Pt has the best catalytic activity for the hydrogen evolution reaction, its high price and scarcity greatly reduce its large-scale industrial application prospects. Herein, we applied a simple method to synthesize an efficient HER catalyst (Ru@SGO), and its performance is comparable to that of Pt/C. Graphene is used as the substrate to improve the conductivity of the material, and sulfur doping is used to improve the catalytic performance. We treated graphene oxide with Lawesson reagent to obtain a sulfur-enriched graphene, then ruthenium nanoparticles were coated to obtain the efficient HER catalyst Ru@SGO. The results show that the high catalytic activity of Ru@SGO comes from ruthenium nanoparticles, and sulfur doping also plays an important role. For Ru@SGO, in 0.5 M H2SO4, the overpotential is 69 mV at 10 mA cm−2 and the Tafel slope is only 52 mV dec−1, which is higher than that of Ru@GO (96 mV, 79 mV dec−1). In 1 M KOH, the overpotential is only 33 mV at 10 mA cm−2 and the Tafel slope is only 56 mV dec−1, which is also higher than that of Ru@GO (73 mV, 128 mV dec−1). SCN− poisoning experiments show that ruthenium nanoparticles play a decisive role in the catalytic performance of the HER. In addition, sulfur doping changes the charge distribution of graphene and effectively improves the intrinsic activity of the catalyst. [ABSTRACT FROM AUTHOR]

To overcome the sluggish kinetics for catalytic hydrolysis of ammonium borane (AB) to generate hydrogen, it is crucially important to design advanced catalysts with tertiary pore structures and substantial surface-exposed active sites. In this study, we report an architecture engineering strategy to construct nitrogen-rich porous carbon nanosheets with hollow worm-like nanowires (h-NCNWs) using low-cost/non-toxic and easily available graphitic carbon nitride as a self-sacrificing template and nitrogen source. The obtained h-NCNWs enable the uniform deposition of ultrafine Rh nanoparticles (Rh/h-NCNWs). The resultant Rh/h-NCNW catalyst exhibits an excellent hydrogen production performance for AB hydrolysis without any alkali promoters. Specifically, the Rh/h-NCNW catalyst with a low Rh loading of 2.12 wt% delivers much higher catalytic activity with a turnover frequency of 1234 min−1. The hollow worm-like nanowires created in Rh/h-NCNWs can provide diverse flexible channels to facilitate the exposure of copious surface-active sites and mass transport for AB hydrolysis, thereby promoting hydrogen evolution rates. This study provides an efficient strategy to engineer the architecture of the catalyst support for upgrading Rh metal-catalyzed hydrogen evolution from AB hydrolysis. [ABSTRACT FROM AUTHOR]

The rational design and facile synthesis of high-efficiency, low-cost, and robust bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are pivotal for hydrogen generation for energy conversion and storage. With this in mind, the synergistic modulation of the architecture, composition, and crystallinity of a non-precious-metal electrocatalyst is considered to be an efficacious strategy to enhance its catalytic activity. Herein, we present a facile route for fabricating a hierarchical Ni-P/NiSex hetero-nanostructured material grown in situ on nickel foam (NF) (denoted as Ni-P/NiSex/NF), which can act as a bifunctional electrocatalyst, via electrodepositing amorphous Ni-P film on the surface of hydrothermally synthesized crystalline NiSex nanorod arrays. The distinctive superhydrophilic 3D structure and useful heterointerface not only afford the greater exposure of active sites, but this material also shows faster charge/mass transport and facilitates the departure of gas bubbles. Meanwhile, benefitting from the regulated electronic structure of NiSex and the synergistic effects of outer amorphous Ni-P and inner crystalline NiSex, the as-fabricated multiphase catalyst exhibits simultaneously excellent electrocatalytic performances during the HER (overpotentials of 98 and 165 mV at 10 and 100 mA cm-2, respectively) and OER (an overpotential of 320 mV at 100 mA cm-2) in 1 M KOH electrolyte. Impressively, a Ni-P/NiSex/NF sample presents robust stability (100 h) during the OER and HER at a large current density. Significantly, an ultralow cell voltage of 1.536 V is required to deliver a current density of 10 mA cm-2 in a two-electrode electrolyzer with Ni-P/NiSex/NF as both the anode and cathode for overall water splitting (OWS), with the demonstration of remarkable durability, and this material far outperforms many recently reported bifunctional electrocatalysts. This work provides a promising strategy for developing efficient bifunctional catalysts for hydrogen production based on the synergistic engineering of the nanostructure design, composition control, and the use of crystalline states. [ABSTRACT FROM AUTHOR]

A set of new class benzimidazole-derived dinuclear cobalt complexes, [CoII2(L1)2] (1) and [CoII2(L2)2] (2) as molecular electrocatalysts are employed in a homogeneous system for electrocatalytic proton reduction (where L1 = 2-{[2-(8-hydroxyquinolin-2-yl)-1H-benzimidazol-1-yl]methyl}quinolin-8-ol and L2 = 2-{[6-methyl-2-(8-hydroxyquinolin-2-yl)-1H-benzimidazol-1-yl]methyl}quinolin-8-ol). The catalysts 1 and 2 electrocatalyze efficiently in an organic medium with the addition of acetic acid to probe the catalysis resulting in 82–90% of faradaic efficiency for H2 evolution at an applied potential of −1.70 V vs. SCE. From the electrochemical responses, it was inferred that the methyl-substituted dinuclear analogue, [CoII2(L2)2], possesses more negative onset potential and an increased overpotential of 100 mV than its parent counterpart, displaying lower catalytic activity. Upon performing an open circuit potential test through the application of an external potential of −1.70 V and −2.10 V vs. SCE followed by further treatment with 24 equivalents of proton source, the initial species reverts to the CoIICoII state. No observable degradation of catalysts was observed during the process that ensures their high stability throughout the event. [ABSTRACT FROM AUTHOR]