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The advancement of effective and robust catalysts that can replace the precious-metal-based benchmarks for electrocatalytic overall water splitting is a highly fashionable approach to exploring sustainable energy utilization and addressing environmental issues. Herein, we demonstrate a facile single-step fabrication of NiS-NiS 2 nanoparticles in situ grown on the layered porous sulfur-doped graphitic carbon nitride nanosheets (NiS-NiS 2 /SGCN) act as bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline medium. Further, an increasing the Ni precursor (fixed sulfur source) increases the formation of NiS-NiS 2 on the surface of SGCN (labeled as NS-1.0, NS-2.0, and NS-3.0). Structural and morphological studies such as PXRD, XPS, FTIR, HR-TEM, etc., revealed a uniform distribution of NiS/NiS 2 on the surface of S-g-C 3 N 4 nanosheets. The OER and HER activity of NiS-NiS 2 /SGCN nanohybrid were significantly enhanced by increasing the affinity of accessible surface-active edge sites, interfacial contact allows effective modification of electronic structure, high structural porosity, redox-active centers of Ni2+/Ni3+, and rich in sulfur vacancy. In addition, the enhancement of the exposure of the edge sites is improved by their attachment to a sulfur-doped g-C 3 N 4 framework. As a result, in the half-cell experiments, the NiS-NiS 2 /SGCN (NS-3.0) catalyst exhibited enhanced performance in both OER and HER, requiring an overpotential of 298 mV to reach 50 mA/cm2 for OER and −144 mV to reach 10 mA/cm2 for HER. Furthermore, the constructed electrolyzer using Ni-S 3.0 as the cathode and anode required a cell voltage of 1.66 V to yield 50 mA/cm2 in overall water splitting. This study may inspire the in-situ synthesis of different metal sulfides on SGCN to provide a unique interfacial approach for improving the performance of bifunctional non-precious electrocatalysts. NiS-NiS2/SGCN as Bifunctional Electrocatalysts for HER and OER in an alkaline medium. [Display omitted] • Single-step fabrication of NiS-NiS 2 grown insitu on sulfur-doped graphitic carbon nitride. • NiS-NiS 2 /SGCN/NF exhibited a low OER overpotential of 298 mV (at 50 mA/cm2). • NiS-NiS 2 /SGCN/NF showed a low HER overpotential of −144 mV (at 10 mA/cm2). • NiS-NiS 2 /SGCN/NF electrode acts as a bifunctional electrocatalyst in alkaline media. [ABSTRACT FROM AUTHOR]

In recent years, the electrocatalytic nitrogen reduction reaction (NRR) has attracted considerable attention as a promising method for ammonia synthesis. Currently, various diatomic catalysts (DACs) composed of metal and non-metal combinations have been studied and reported for the NRR. These catalysts have been proven the ability to lower the reaction overpotential and enhance its activity. Among them, DACs supported on two-dimensional nitride materials have been widely applied in the NRR. In this work, ten heteronuclear diatomic catalysts supported on nitrogen-doped graphene were constructed. The research results demonstrated that MoCrN 6 -G exhibited the best catalytic performance among these catalysts due to its lowest overpotential (0.45 V) and low desorption free energy (0.15 eV) of NH 3 , as well as a higher selectivity for NRR compared to the hydrogen evolution reaction. It is worth emphasizing that the d-band center (ε d) is considered as a descriptor for rapidly screening efficient NRR electrocatalysts, further guiding the rational design of catalysts. [Display omitted] • Construced ten stable nitrogen-doped graphene supported heteronuclear diatomic catalysts. • The MoCrN 6 -G catalyst exhibited the lowest overpotential (0.45 V) during the NRR. • NH 3 can easily dissociate from the MoCrN 6 -G catalyst surface due to a desorption free energy of only 0.15 eV. • The MoCrN 6 -G catalyst demonstrated inhibitory effects towards the HER and showed high thermodynamic stability. • The d-band center (ε d) can serve as a predictive descriptor for rapidly screening highly active NRR catalysts. [ABSTRACT FROM AUTHOR]

The activation of lattice oxygen oxidation mechanism (LOM) will endow iridium‐based electrocatalysts with desired acid‐available water oxidation activity, compared to the conventional adsorbate evolution mechanism (AEM). However, the inherent symmetric [IrO6] octahedra of commercial Ir‐based catalysts generally thermodynamically favor the AEM pathway contributing to the moderate water oxidation performance. Here, based on typical layered Ca2IrO4 (CIO) modeled materials, the d‐orbitals electron repulsion strategy is demonstrated, via constructing asymmetrically polarized Ir‒O‒Ru configuration in Ru‐CIO, to effectively activate the lattice oxygen participating in water oxidation process for decent oxygen‐related electrocatalytic activity. Specifically, a great increase of ≈700‐fold and ≈170‐fold in mass activity and turnover frequency, respectively, has been realized for the optimal Ru‐CIO electrocatalyst in an acid medium relative to the commercial IrO2 electrocatalysts, where a small overpotential of only 175 mV is required for achieving 10 mA cmgeo‒2. In situ X‐ray fine structure spectroscopies combined with in situ 18O‐ isotope‐labeled differential electrochemical mass spectrometry analyses reveal that desirable LOM has been boosted by the activated lattice oxygen and the flexible Ir(3+δ)+ active sites of asymmetric [IrO6] octahedra, which results in superior OER kinetics for Ir‐based oxide catalysts. [ABSTRACT FROM AUTHOR]

The electrocatalytic performance of a Fe65Co10Si12.5B12.5 Fe-based compounds toward alkaline hydrogen evolution reaction (HER) is enhanced by dealloying. The dealloying process produced a large number of nanosheets on the surface of NS-Fe65Co10Si12.5B12.5, which greatly increased the specific surface area of the electrode. When the dealloying time is 3 h, the overpotential of NS-Fe65Co10Si12.5B12.5 is only 175.1 mV at 1.0 M KOH and 10 mA cm−2, while under the same conditions, the overpotential of Fe65Co10Si12.5B12.5 is 215 mV, which is reduced. In addition, dealloying treated electrodes also show better HER performance than un-dealloying treated electrodes. With the increase in Co doping amount, the overpotential of the hydrogen evolution reaction decreases, and the hydrogen evolution activity is the best when the addition amount of Co is 10%. This work not only provides a basic understanding of the relationship between surface activity and the dealloying of HER catalysts, but also paves a new way for doping transition metal elements in Fe-based electrocatalysts working in alkaline media. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) over perovskite oxides, upon undergoing a lattice oxygen oxidation mechanism, is strongly oxygen vacancy‐correlated as determined by the oxygen ion diffusivity. Despite substantial efforts having been devoted to tuning the oxygen vacancy concentration in perovskite oxides, the impact of the concomitant altering of oxygen vacancy ordering is often underestimated. In particular, the underlying mechanism of how the ordering and the concentration of oxygen vacancy affect the lattice OER, and how to well balance them still remain inadequately understood. Herein, a series of Sr1−xCaxCo0.5Fe0.5O3−δ with gradually increased oxygen vacancy concentration and ordering are synthesized. Theoretical calculations indicated that a higher oxygen vacancy concentration promoted the lattice oxygen migration, whereas a higher oxygen vacancy ordering impeded it. Particularly, Sr0.5Ca0.5Co0.5Fe0.5O3−δ with a relatively higher oxygen vacancy concentration and a lower ordering displayed the maximum oxygen diffusion rate and the optimal OER activity, affording a current density of 10 mA cm−2 at a quite low overpotential of 310.2 mV, together with a small Tafel slope of 55.87 mV dec−1. This study sheds light on the critical influence of oxygen vacancy configuration on the lattice OER, and paves a compromised avenue to screen and design advanced electrocatalysts for various electrochemical devices. [ABSTRACT FROM AUTHOR]

The development of electricity‐driven oxygen evolution reaction (OER) is a potent solution for energy storage applications. In recent years, there is a surge in interest in designing transition metal‐based catalysts with stable linkages, presenting an efficient alternative to noble metal‐based electrocatalysts. Transition metal complexes linked by salen ligands garner considerable attention due to their capacity to chelate and stabilize metal ions. This work presents a novel approach by strategically incorporating the metal–salen core into a porous organic polymer (POP) backbone, thereby fabricating a highly effective electrocatalyst for oxygen evolution. The judicious selection of metal–salen active sites, coupled with the intramolecular free volume (IMFV) of the triptycene core and the high specific surface area of the salen–POPs, result in superior OER activity. By precisely tuning the structure through variation of the transition metal in the salen unit, deep insights are gained into their electrocatalytic behavior. Notably, the most efficient catalyst, Ni‐DHDA‐TAT, exhibits an impressively low overpotential (η10) of ≈ 270 mV at a current density of 10 mA cm−2 for OER (in 1 m KOH). Further, Ni‐DHDA‐TAT retains its activity even after 50 h of chronoamperometry and 1000 cyclic voltammetry cycles with negligible degradation in its initial performance. [ABSTRACT FROM AUTHOR]

Water splitting is an important approach to hydrogen production. But the efficiency of the process is always controlled by the oxygen evolution reaction process. In this study, a three-dimensional nickel–molybdenum binary nanoarray microstructure electrocatalyst is successfully synthesized. It is grown uniformly on Ni foam using a hydrothermal method. Attributed to their unique nanostructure and controllable nature, the Ni-Mo-based nanoarray samples show superior reactivity and durability in oxygen evolution reactions. The series of Ni-Mo-based electrocatalysts presents a competitive overpotential of 296 mV at 10 mA·cm−2 for an OER in 1.0 M KOH, corresponding with a low Tafel slope of 121 mV dec−1. The three-dimensional nanostructure has a large double-layer capacitance and plenty of channels for ion transfer, which demonstrates more active sites and improved charge transmission. This study provides a valuable reference for the development of non-precious catalysts for water splitting. [ABSTRACT FROM AUTHOR]

The efficient electrosynthesis of hydrogen peroxide (H2O2) via two‐electron oxygen reduction reaction (2e− ORR) in neutral media is undoubtedly a practical route, but the limited comprehension of electrocatalysts has hindered the system advancement. Herein, we present the design of model catalysts comprising mesoporous carbon spheres‐supported Pd nanoparticles for H2O2 electrosynthesis at near‐zero overpotential with approximately 95 % selectivity in a neutral electrolyte. Impressively, the optimized Pd/MCS‐8 electrocatalyst in a flow cell device achieves an exceptional H2O2 yield of 15.77 mol gcatalyst−1 h−1, generating a neutral H2O2 solution with an accumulated concentration of 6.43 wt %, a level sufficiently high for medical disinfection. Finite element simulation and experimental results suggest that mesoporous carbon carriers promote O2 enrichment and localized pH elevation, establishing a favorable microenvironment for 2e− ORR in neutral media. Density functional theory calculations reveal that the robust interaction between Pd nanoparticles and the carbon carriers optimized the adsorption of OOH* at the carbon edge, ensuring high active 2e− process. These findings offer new insights into carbon‐loaded electrocatalysts for efficient 2e− ORR in neutral media, emphasizing the role of carrier engineering in constructing favorable microenvironments and synergizing active sites. [ABSTRACT FROM AUTHOR]

Refining synthesis strategies for metal–organic framework (MOF)-based catalysts to improve their performance and stability in an oxygen evolution reaction (OER) is a big challenge. In this study, a series of nanostructured electrocatalysts were synthesized through a solvothermal method by growing MOFs and metal–triazolates (METs) on nickel foam (NF) substrates (named MET-M/NF, M = Fe, Co, Cu), and these electrocatalysts could be used directly as OER self-supporting electrodes. Among these electrocatalysts, MET-Fe/NF exhibited the best OER performance, requiring only an overpotential of 122 mV at a current density of 10 mA cm−2 and showing remarkable stability over 15 h. The experimental results uncovered that MET-Fe/NF underwent an in situ structural reconstruction, resulting in the formation of numerous iron/nickel (oxy)hydroxides with high OER activity. Furthermore, in a two-electrode water-splitting setup, MET-Fe/NF only required 1.463 V to achieve a current density of 10 mA cm−2. Highlighting its potential for practical applications. This work provides insight into the design and development of efficient MOF-based OER catalysts. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting is an ideal alternative to obtain hydrogen, which is a renewable and clean source of energy with a high calorific value. Designing a highly stable and affordable catalyst is a critical need for achieving the desired electrocatalytic efficacy. Three-dimensional (3D) nanomaterials (NMs) have a hierarchical or interconnected network or framework-like structure with commendable mechanical stability. They possess large surface area and electroactive sites, which have garnered immense scientific interest in the past few years. Different 3D NMs that have been used for electrocatalysis of water are the central focus of this review. There are only a handful of reports discussing them in the literature, but none of them comprehensively cover various 3D NMs as water-splitting catalysts. In addition, the basic concepts of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as well as various metrics affecting water splitting kinetics, have been highlighted in detail. In the end, hurdles in the design and commercialization of highly stable water-splitting catalysts and their possible remedies have been discussed along with. [Display omitted] • Electrochemical water splitting is a plausible approach for producing hydrogen. • 3D nanostructured electrocatalysts have enhanced the efficacy of water splitting. • Fabrication and electrocatalytic activity of 3D nanocatalysts have been focussed. • Various metrics affecting the water splitting kinetics have also been discussed. • Hurdles in design and commercialization of these catalysts have been highlighted. [ABSTRACT FROM AUTHOR]

The design of high‐entropy single‐atom catalysts (HESAC) with 5.2 times higher entropy compared to single‐atom catalysts (SAC) is proposed, by using four different metals (FeCoNiRu‐HESAC) for oxygen reduction reaction (ORR). Fe active sites with intermetallic distances of 6.1 Å exhibit a low ORR overpotential of 0.44 V, which originates from weakening the adsorption of OH intermediates. Based on density functional theory (DFT) findings, the FeCoNiRu‐HESAC with a nitrogen‐doped sample were synthesized. The atomic structures are confirmed with X‐ray photoelectron spectroscopy (XPS), X‐ray absorption (XAS), and scanning transmission electron microscopy (STEM). The predicted high catalytic activity is experimentally verified, finding that FeCoNiRu‐HESAC has overpotentials of 0.41 and 0.37 V with Tafel slopes of 101 and 210 mVdec−1 at the current density of 1 mA cm−2 and the kinetic current densities of 8.2 and 5.3 mA cm−2, respectively, in acidic and alkaline electrolytes. These results are comparable with Pt/C. The FeCoNiRu‐HESAC is used for Zinc–air battery applications with an open circuit potential of 1.39 V and power density of 0.16 W cm−2. Therefore, a strategy guided by DFT is provided for the rational design of HESAC which can be replaced with high‐cost Pt catalysts toward ORR and beyond. [ABSTRACT FROM AUTHOR]

Facile preparation of low-cost electrocatalysts for an efficient oxygen evolution reaction (OER) is significant but remains a big challenge. Herein, a novel and facile strategy for transforming intrinsic non-stoichiometric ultrathin Co5(O9.48H8.52)NO3 nanosheets into oxygen-vacancy enriched Co3O4/CoOOH heterostructure nanosheets for an efficient OER was developed. The as-synthesized Co3O4/CoOOH heterostructure nanosheets displayed excellent OER performances, showing an extremely low overpotential of 260 mV at a current density of 10 mA cm−2, a relatively small Tafel slope of 52 mV dec−1, and a long-term durability of at least 20 h. This work provides a new way for the production of oxygen vacancies on metal (oxy)hydroxide nanosheets through electric-field assisted in situ transformation of non-stoichiometric metal oxyhydroxide nanosheets. [ABSTRACT FROM AUTHOR]

An advance of highly efficient nanostructured electrocatalysts based on non-noble metals for water electrolysis and urea oxidation reaction (UOR) are of great significance for urea-enriched wastewater remediation and producing hydrogen. Herein, we report V x Ni 1-x O catalysts supported on three-dimensional Ni-foam scaffold for catalytic water and urea electrolysis. V x Ni 1-x O catalysts show rapid water and urea electrolysis due to enhanced electrochemical surface area (ECSA). Most important of all, the urea oxidation reaction has a lower potential of 1.418V vs RHE as compared to oxygen evolution reaction (1.684 V vs RHE) system to generate 100 mA/cm2. Additionally, a two-electrode cell for bi-functional water electrolysis generates 100 mA/cm2 at a potential of 2.10 V at 20 °C and just 1.86 V at 60 °C temperature due to regulated the adsorption/desorption of intermediates species, enhanced charge and mass transport, and easier desorption of oxygen molecules from the anode. The stability of V x Ni 1-x O catalyst was measured at 1000 mA/cm2 current density for up to 17 h. • Doping energy strategy to design a vertical V x Ni 1-x O nanosheets for water and urea electrolysis. • Overpotential of 454 mV for OER and 271 mV for HER at 100 mA/cm2. • Maximum current of 1000 mA/cm2 is achieved at a cell potential of 2.3 V. • V 0.1 Ni 0.9 O catalyst shows he stability for 17 h at 1000 mA/cm2. • Urea electrolysis system has a lower cell potential of 1.418V at 100 mA/cm2. [ABSTRACT FROM AUTHOR]

Designing electrocatalysts for electrochemical water splitting to generate renewable energy has been a prospective interest throughout the previous decade. The efficiency of electrochemical water splitting, however, is impeded by the sluggish kinetics of the oxygen evolution reaction (OER). Herein, the heterostructure of layered double hydroxides (NiFe-LDH) and MXene (Ti 3 C 2 T x) were synthesized via hydrothermal (NiFe-LDH/Ti 3 C 2 T x -H) and physical mixing (NiFe-LDH/Ti 3 C 2 T x -P) methods. The NiFe-LDH/Ti 3 C 2 T x -H exhibited an overpotential of 269 mV at 10 mA cm−2, indicating superior performance as compared to NiFe-LDH/Ti 3 C 2 T x -P (353 mV) and RuO 2 (313 mV). The double layer capacitance (C dl) of NiFe-LDH/Ti 3 C 2 T x -H was higher (2.05 mF cm−2) as compared to NiFe-LDH/Ti 3 C 2 T x -P (1.63 mF cm−2), thus indicating more active sites for improving reaction kinetics. Additionally, the NiFe-LDH/Ti 3 C 2 T x -H electrocatalyst retained stable performance (96.1%) after 10 h of chronopotentiometry at a constant current density of 10 mA cm−2. [Display omitted] • Synthesized novel NiFe-LDH/Ti 3 C 2 T x -H heterostructure via hydrothermal route. • Uniform growth of NiFe-LDH prevents the agglomeration of NiFe-LDH and Ti 3 C 2 T x. • The strong interfacial interactions enhance the catalytic efficiency. • NiFe-LDH/Ti 3 C 2 T x -H exhibited a lower overpotential of 269 mV at 10 mA cm−2 for OER. [ABSTRACT FROM AUTHOR]

In the realm of sustainable and environmentally friendly "green-hydrogen" fuel demand, water electrolysis stands as a pathway of hope for the extraction of renewable hydrogen. However, the durability and efficiency of electrocatalysts have been a major challenge in this process, owing to factors like the high costs of noble catalysts (Pt, Ir, Ru, etc.) and their limited stability. Layered Nickel-iron double hydroxides (NiFe-LDH) have shown potential as low-cost and efficient electrocatalysts because of their suitable electronic configuration and distinguished orbital confinement. However, their durability In the realm of sustainable and environmentally friendly "green-hydrogen" fuel demand, water electrolysis stands as a pathway of hope for the extraction of renewable hydrogen. However, the durability and efficiency of electrocatalysts have been a major challenge in this process, owing to factors like the high costs of noble catalysts (Pt, Ir, Ru, etc.) and their limited stability. Layered Nickel-iron double hydroxides (NiFe-LDH) have shown potential as low-cost and efficient electrocatalysts because of their suitable electronic configuration and distinguished orbital confinement. However, their performance and durability in corrosive alkaline water at high current density remain limited. In this regard, one can make the nano-composites of this NiFe-LDH with high electronic conductivity materials and layered structures like VSe 2. With this motivation, this work presents a novel electrocatalyst, NiFe-LDH, supported with VSe 2 nanosheets ( V Se 2 / NiFe − LDH), designed to address these challenges and enhance water splitting efficiency. Experimental results demonstrate that the heterostructure synergistically reduces charge transfer resistance, increases exposure of active sites, and enhances oxygen gas evolution ability. Consequently, the V Se 2 / NiFe − LDH electrocatalyst demonstrated superior sustainability, maintaining an elevated current density (500 mA cm − 2 ) for over 50 h of continuous electrolysis without noticeable degradation. This research opens up new possibilities and shows that nano-compositing can be a good option for achieving efficient and durable electrocatalysts in alkaline water splitting, thereby contributing to sustainable hydrogen production. [Display omitted] • Facile hydro/solvothermal preparation of composites of NiFe-LDH and VSe 2. • Enhanced Oxygen and Hydrogen evolution were observed. • Decreased charge transfer resistance was noticed. • Durable up to about 50 h for overall water splitting at a high current density of 500 mA cm − 2. [ABSTRACT FROM AUTHOR]

Cu2O doped with atomically dispersed Rh (Rh:Cu2O) is synthesized with a wet chemical method. It shows higher activity and faradaic efficiency at lower overpotential for reduction of CO2 to C2+ products, especially C2H4, than pristine Cu2O. We found that introducing Rh promotes CO2 adsorption, *CO hydrogenation to *CHO and their coupling to O*CCHO intermediates, which contributes to enhanced catalytic performance. [ABSTRACT FROM AUTHOR]

A novel Fe, Co-CeO 2 /CeF 3 @MXene heterostructure with Fe-Co dual active sites and oxygen vacancies has been prepared for alkaline water/real seawater OER. [Display omitted] • Fe, Co-CeO 2 /CeF 3 @MXene heterostructure with Fe-Co dual active sites was synthesized by energy-free consumption co-deposition method. • Fe，Co-CeO 2 /CeF 3 @MXene can function as highly effective electrocatalyst toward OER. • The adsorption evolution mechanism and the lattice oxygen mechanism synergistically enhanced the OER activity. • Wind and solar-energy-assisted water electrolysis devices show their promising prospects for green hydrogen production sustainably. Exploring low-cost, high-activity, and structurally stable nonprecious metal electrocatalysts for sluggish oxygen evolution reaction (OER) is paramount for water electrolysis. Herein, we successfully prepare a novel Fe,Co-CeO 2 /CeF 3 @MXene heterostructure with Fe–Co dual active sites and oxygen vacancies for alkaline OER using an energy-free consumption co-deposition method. Impressively, Fe,Co-CeO 2 /CeF 3 @MXene achieves an ultralow overpotential of 192 mV and a long-term stability of 110 h at 10 mA cm−2 without structural changes, thereby outperforming the commercial IrO 2 (345 mV). In addition, Fe,Co-CeO 2 /CeF 3 @MXene exhibits much superior activity (271 mV) and durability to IrO 2 (385 mV) in the real seawater OER. Wind- and solar energy-assisted water electrolysis devices show their promising prospects for sustainable green hydrogen production. Characterization techniques and theoretical calculations reveal that the Fe,Co co-implanted CeO 2 /CeF 3 heterostructure effectively degrades the energy barrier of the OER and optimizes the adsorption strength of *OH, *O, and *OOH intermediates. It exhibits the dual coupling mechanism of the adsorbed evolution and lattice oxygen mechanisms, which synergistically improves the OER performance. This work provides a facile and efficacious strategy for synthesizing a new class of heterostructures to achieve significant enhancement in the activity and stability of OER catalysts. [ABSTRACT FROM AUTHOR]

Herein, a novel Pt anchoring WO3 nanoarray catalyst is reported and its application as HzOR and HER bifunctional electrocatalysts which shown to have superior bifunctional performance for HzOR/HER under alkaline conditions. The Pt/WO3/NF requires an ultrasmall overpotential of 34.6 and 226.38 mV to achieve 10 and 100 mA cm−2 for the hydrazine oxidation reaction (HzOR), respectively. When used for HER-HzOR electrolysis, Pt/WO3/NF requires low voltages of 0.717 V and 1.049 V at 100 and 200 mA cm−2, respectively. [ABSTRACT FROM AUTHOR]

Nickel-iron oxy/hydroxides (NiFeOxHy) emerge as an attractive type of electrocatalysts for alkaline water oxidation reaction (WOR), but which encounter a huge challenge in stability, especially at industrial-grade large current density due to uncontrollable Fe leakage. Here, we tailor the Fe coordination by a MXene-mediated reconfiguration strategy for the resultant NiFeOxHy catalyst to alleviate Fe leakage and thus reinforce the WOR stability. The introduction of ultrafine MXene with surface dangling bonds in the electrochemical reconfiguration over Ni-Fe Prussian blue analogue induces the covalent hybridization of NiFeOxHy/MXene, which not only accelerates WOR kinetics but also improves Fe oxidation resistance against segregation. As a result, the NiFeOxHy coupled with MXene exhibits an extraordinary durability at ampere-level current density over 1,000 h for alkaline WOR with an ultralow overpotential of only 307 mV. This work provides a broad avenue and mechanistic insights for the development of nickel-iron catalysts toward industrial applications. [ABSTRACT FROM AUTHOR]

The electrocatalytic splitting of water to produce hydrogen is regarded as an efficient and promising strategy but is limited by its large overpotential; thus, a highly efficient electrocatalyst is urgently needed. Mixed metal doping is an important strategy in defect engineering because the heteroatoms can change the intrinsic structure to form defects by affecting the atomic coordination mode and adjusting the electronic structure, which is often accompanied by morphological changes. Herein, two-dimensional layered bimetallic Co–pydc containing axially coordinated water molecules was selected by producing surface defects through Fe doping in Co centers as bifunctional electrocatalysts for OER and HER. The optimized Co0.59Fe0.41–pydc possesses outstanding OER performance with the lowest overpotential of 262 mV to reach j = 10 mA cm−2, and Co0.75Fe0.25–pydc possesses superior HER performance with the lowest overpotential of 96 mV at j = 10 mA cm−2. Furthermore, the overall water splitting device assembled with Co0.59Fe0.41–pydc@NF//Co0.59Fe0.41–pydc@NF affords a current density of 10 mA cm−2 at only 1.687 V. This work emphasizes the surface defects formed by tuning the electronic structure of metal centres accompanied with morphological changes of bimetallic dopants for efficient overall water splitting. [ABSTRACT FROM AUTHOR]

Developing a cost-effective, efficient, and eco-friendly electrocatalyst made from non-noble materials for the hydrogen evolution reaction (HER) is challenging. This research paper presents an application of the nickel sulfide (Ni 3 S 2) nanowires-filled multiwalled carbon nanotubes (CNTs) synthesized on carbon cloth (CC) (Ni 3 S 2 @CNTs/CC) as an efficient HER electrocatalyst. The performance of Ni 3 S 2 @CNTs/CC as a working electrode was examined for its hydrogen evolution ability. In a 1.0 M KOH solution, Ni 3 S 2 @CNTs/CC requires cathodic overpotentials of 381 mV and 549 mV to generate current densities of 10 mA/cm2 and 100 mA/cm2, respectively. Electrochemical impedance measurements showed a low charge transfer resistance value of 3.3 Ω for Ni 3 S 2 @CNTs/CC. The evaluation of the electrochemically active surface area revealed that Ni 3 S 2 @CNTs/CC has more electrochemical active sites and a higher roughness factor than pristine CC. Most importantly, the current density of Ni 3 S 2 @CNTs/CC did not significantly degrade after 3000 CV cycles and 12 h of constant HER. These findings suggest that Ni 3 S 2 @CNTs/CC is a cost-effective, highly functional, and stable electrode material for HER in a strongly alkaline medium. [Display omitted] • Application of novel Ni 3 S 2 @CNTs/CC acting as an electrocatalyst for HER is reported for the first time. • The synthesized Ni 3 S 2 @CNTs promote water dissociation by facilitating the electron transfer process. • The enhanced catalytic HER activity of Ni 3 S 2 @CNTs/CC is attributed to the synthesized Ni 3 S 2 @CNTs on the CC substrate. • Ni 3 S 2 @CNTs/CC acts as a binder-free, flexible HER electrocatalyst. [ABSTRACT FROM AUTHOR]

The construction of efficient, sustainable, and low-cost nonprecious metal electrocatalysts for oxygen evolution reaction (OER) is necessary for the realization of electrocatalytic overall water splitting. Herein, the PW 6 Mo 6 /ZIF-67@NF is prepared using a simple coprecipitation method. Characterization results indicate that the PW 6 Mo 6 induces the exposure of Co nodes in ZIF-67, which can act as catalytic active sites for OER. Meanwhile, the introduction of PW 6 Mo 6 improves the conductivity and electrochemical active surface area of ZIF-67, which further enhances the OER performance. The electrochemical test results show that the PW 6 Mo 6 /ZIF-67@NF exhibit an ultralow overpotential of 201 mV at 10 mA cm−2 and a small Tafel slope of 55 mV dec−1 for OER, which is lower than that of ZIF-67@NF (329 mV, 286 mV dec−1). Our study demonstrates the potential of polyoxometalate and ZIF composites to decrease the barriers of OER and provides a feasible approach for exploring economical and practical electrocatalysts. The etching of PW 6 Mo 6 induces the exposure of Co active sites in ZIF-67, thereby PW 6 Mo 6 /ZIF-67@NF exhibit an ultralow overpotential of 201 mV at 10 mA cm−2 and a small Tafel slope of 55 mV dec−1 for OER. [Display omitted] • The PW 6 Mo 6 /ZIF-67@NF with exposed Co nodes was successfully prepared using a coprecipitation method. • The introduction of PW 6 Mo 6 improved the conductivity and electrochemical active surface area of ZIF-67. • The ZIF-67 framework prevents the dissolution of PW 6 Mo 6 in the electrolyte, thus increasing the stability. • The PW 6 Mo 6 /ZIF-67@NF exhibited an ultralow overpotential and a small Tafel slope for OER. [ABSTRACT FROM AUTHOR]

Constructing bifunctional electrocatalysts is essential for efficient water splitting. Rational interface engineering is an effective method for modifying active sites and promoting electronic charge transfer, resulting in improved water splitting efficiency. In this study, we designed a metal-free, 2D structure of graphene and boron nitride (h-BN). 2D stacking of two different layers generated abundant interfaces as well as huge electrochemical active sites. As a result, the graphene/h-BN stacked structure has a very low overpotential of 28 mV (for 10 mA/cm2 current density) for hydrogen evolution. At the same time, a significantly low overpotential of 360 mV (for 50 mA/cm2 current density) was achieved for oxygen evolution. The stacked structure of graphene/h-BN has been effectively utilized as a promising cathode and anode in a two-electrode system for accomplishing overall water splitting. Thus, our investigation suggests that rational construction of heterogeneous interfaces by stacking different 2D nanostructures can accelerate the overall water splitting by maximizing the electrochemical performance. [Display omitted] • Graphene layer was engineered by stacking h-BN • 2D stacking generated abundant interfaces as well as huge electrochemical active sites • A very low overpotential of 28 mV (for 10 mA/cm2 current density) for hydrogen evolution • Overpotential for OER was significantly low 360 mV (for 50 mA/cm2 current density) [ABSTRACT FROM AUTHOR]

The free standing CoFe@PANI bifunctional electrocatalyst display high electrocatalytic activity for OER (overpotential of 230 mV @10 mA cm−2) and MOR (specific current density of 120 mA cm−2) in alkaline medium. [Display omitted] Developing inexpensive, highly electrochemically active, and stable catalysts towards electrochemical studies remains challenge for researchers. In this regard, binder-free CoFe@PANI composite electrocatalyst is deposited on nickel foam (NF) substrate via successive electrodeposition of polyaniline (PANI) and CoFe-LDH at Room temperature (RT). As deposited binder-free CoFe@PANI electrocatalyst displays high electrocatalytic activity towards oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) in alkaline media. In CoFe@PANI structure, interfacing of high-electron conducting PANI establishes strong interconnection with CoFe-LDH by tuning electronic structures, which accelerates the electrochemical performance towards OER and MOR. For OER, CoFe@PANI requires low overpotential (η 10) of 237 mV to reach current density (I d) of 10 mA cm−2 and displays low Tafel slope value of 46 mV dec−1 in 1 M KOH solution. Also, it displayed specific I d of 120 mA cm−2, when it was tested for MOR in 1 M KOH with 0.5 M methanol solution. The superior electrocatalytic activity of CoFe@PANI is mainly ascribed to high electrochemical active surface area (ECSA), abundant active sites and fast electron transfer between electrocatalyst and electrode surface. Of note, the current work may open new era for design and development of non-precious highly active and stable hybrid electrocatalysts at RT for various applications. [ABSTRACT FROM AUTHOR]

Heterostructures based on transition metal chalcogenides/oxides have gained significant interest in the application of electrochemical hydrogen evolution reaction (HER) due to their distinct characteristics and excellent electrocatalytic activity. Herein, we developed an earth-abundant, low-cost, and light-sensitive CuS/NiO (CSNO) heterostructure electrocatalyst via a facile co-precipitation method and fabricated it on silver-modified conducting cellulose paper for HER. Under all pH level, the performance of the visible light-sensitive HER catalyst has been examined. With the illumination of light, HER performance at all pH, which conserves energy has been seen. In basic media, the value of overpotential was improved to −290 mV vs RHE at 20 mA/cm2 under light-illuminating conditions. Similarly, with light illumination, the overpotential of the CSNO10/Ag- modified paper is reduced to −363 mV and −312 mV vs RHE in an acidic and in a near-neutral medium, respectively. In addition to that, the values of the Tafel slopes and charge-transfer resistance also decreased indicating relatively faster HER kinetics in the presence of light at all pH levels. Also, The CSNO10 electrode exhibits stability of more than 24 h in 1 M PBS with an overpotential of −368 mV vs RHE at 20 mA/cm2. The overall performance of the CuS/NiO heterostructure is a good sign to be explored it as a low-cost and efficient electrocatalyst for the large-scale production of green hydrogen (H 2). • We developed a light-sensitive CuS/NiO heterostructure electrocatalysts. • CSNO electrocatalyst shows pH universal HER performance. • CSNO shows an overpotential of −413 mV and −363 mV in light and dark. • CSNO electrocatalyst exhibits excellent stability upto 24 h. [ABSTRACT FROM AUTHOR]

The hydrothermal method is a frequently used approach for synthesizing HER electrocatalysts. However, a weak tolerance to high temperature is an intrinsic property of carbon cloth (CC) in most situations, and CC-based catalysts, which require complex technological processes in low-temperature environments, exhibit weak stability and electrochemical performance. Hence, we provide a new solution for these issues. In this work, MoO3-NiSx films of 9H5E-CC catalysts are synthesized, first through electrodeposition to form Ni particles on CC and then through a hydrothermal reaction to reform the reaction. The advantages of this synthetic process include mild reaction conditions and convenient operation. The obtained MoO3-NiSx film presents excellent catalytic activity and stability for HER. MoO3-NiSx film requires only a low overpotential of 142 mV to drive 10 mA cm−2 for HER in 1.0 m KOH, and the obtained 9H5E-CF film only needs 294 mV to achieve 50 mA cm−2 for OER. Remarkably, they also show excellent OER, HER, and full water splitting long-term electrochemical stability, maintaining their performance for at least 72 h. This work can be expanded to provide a new strategy for the fabrication of stable, high-performing electrodes using simple, mild reaction conditions. [ABSTRACT FROM AUTHOR]

Hydrogen has enormous commercial potential as a secondary energy source because of its high calorific value, clean combustion byproducts, and multiple production methods. Electrocatalytic water splitting is a viable alternative to the conventional methane steam reforming technique, as it operates under mild conditions, produces high‐quality hydrogen, and has a sustainable production process that requires less energy. Electrocatalysts composed of precious metals like Pt, Au, Ru, and Ag are commonly used in the investigation of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Nevertheless, their limited availability and expensive cost restrict practical use. In contrast, electrocatalysts that do not contain precious metals are readily available, cost‐effective, environmentally friendly, and possess electrocatalytic performance equal to that of noble metals. However, considerable research effort must be devoted to create cost‐effective and high‐performing catalysts. This article provides a comprehensive examination of the reaction mechanism involved in electrocatalytic water splitting in both acidic and basic environments. Additionally, recent breakthroughs in catalysts for both the hydrogen evolution and oxygen evolution reactions are also discussed. The structure‐activity relationship of the catalyst was deep‐going discussed, together with the prospects of current obstacles and potential for electrocatalytic water splitting, aiming at provide valuable perspectives for the advancement of economical and efficient electrocatalysts on an industrial scale. [ABSTRACT FROM AUTHOR]

A well-dispersed Ni nano electrocatalyst boosts the kinetics and decreases the reaction overpotential of Li 2 S 4 reduction, providing more spaces for the concentration difference overpotential and allowing more soluble polysulfide intermediates farther away (l 2) from the surface of conductive materials to be reduced based on Fick's first law, significantly improving the sulfur utilization. Consequently, excellent rate performance, high areal capacity, and stable cycle performance are exhibited. [Display omitted] The lithium-sulfur battery (Li-S) has been considered a promising energy storage system, however, in the practical application of Li-S batteries, considerable challenges remain. One challenge is the low kinetics involved in the conversion of Li 2 S 4 to Li 2 S. Here, we reveal that highly dispersed Ni nanoparticles play a unique role in the reduction of Li 2 S 4. Ni-porous carbon (Ni-PC) decorated in situ on a free-standing carbon nanotube sponge (CNTS/Ni-PC) enriches the current response of liquid phase Li 2 S 4 and Li 2 S 2 around the cathode more than 8.1 and 5.7 times higher than that of the CNTS blank sample, respectively, greatly boosting the kinetics and decreasing the reaction overpotential of Li 2 S 4 reduction (lower Tafel slope and larger current response). Thus, with the same total overpotential, more space is provided for the concentration difference overpotential, allowing the more soluble polysulfide intermediates farther away from the surface of the conductive materials to be reduced based on the "wane and wax" strategy, and significantly improving the sulfur utilization. Consequently, S@CNTS/Ni-PC delivers excellent rate performance (812.4 mAh·g−1 at 2C) and a remarkable areal capacity of 10.1 mAh·cm−2. This work provides a viable strategy for designing a target catalyst to enhance the conversion kinetics in the Li 2 S 4 reduction process. [ABSTRACT FROM AUTHOR]

In this research, highly efficient heterogeneous bifunctional (BF) electrocatalysts (ECs) have been strategically designed by Fe coordination (CR) complexes, [Fe2L2(H2O)2Cl2] (C1) and [Fe2L2(H2O)2(SO4)].2(CH4O) (C2) where the high seven CR number synergistically modifies the electronic environment of the Fe centre for facilitation of H2O electrolysis. The electronic status of Fe and its adjacent atomic sites have been further modified by the replacement of −Cl− in C1 by −SO42− in C2. Interestingly, compared to C1, the O−S−O bridged C2 reveals superior BF activity with extremely low overpotential (η) at 10 mA cm−2 (140 mVOER, 62 mVHER) and small Tafel slope (120.9 mV dec−1OER, 45.8 mV dec−1HER). Additionally, C2 also facilitates a high‐performance alkaline H2O electrolyzer with cell voltage of 1.54 V at 10 mA cm−2 and exhibits remarkable long‐term stability. Thus, exploration of the intrinsic properties of metal–organic framework (MOF)‐based ECs opens up a new approach to the rational design of a wide range of molecular catalysts. [ABSTRACT FROM AUTHOR]

Hetero-structured NiFeCr–S/NiS nanosheet arrays supported on nickel foam (NiFeCr–S/NiS/NF) were prepared by sulfurizing the hetero-structured hybrid of NiFeCr-layered double hydroxides/NiS/NF (NiFeCr-LDH/NiS/NF) through sequential hydrothermal method and vapour deposition method. Benefiting from the abundant NiS/NiFeCr–S interfaces and the two-dimensional nanosheet structure, the as-prepared catalyst displays an overpotential at 10 mA cm−2 of 94 mV for oxygen evolution reaction and 131 mV for hydrogen evolution reaction, respectively, which is better than the non-sulfurized NiFeCr-LDH/NiS/NF and NiFeCr-LDHs/NF, as well as the sulfurized NiFeCr–S/NF and NiS/NF. In the self-assembled device using NiFeCr–S/NiS/NF as both cathode and anode, the overall water splitting reaction can be driven at 1.53 V of cell voltage to achieve the current density of 10 mA cm−2. • Low overpotential of 121 mV at 20 mA cm−2 for oxygen evolution reaction. • Low overpotential of 119 mV at 10 mA cm−2 for hydrogen evolution reaction. • Driving the overall water splitting reaction at a cell voltage of 1.53 V to achieve the current density of 10 mA cm−2. • Hetero-structured NiFeCr–S/NiS nanosheet arrays. • High electrocatalytic activity and stability as electrocatalysts for overall water splitting reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiCoCu LDH electrocatalyst were prepared by a reflex method. • Fabricated ternary NiCoCu LDH exhibit excellent activities for HER and OER. • For the OER and HER, NiCoCu LDH greatly reduces overpotential as low as 87 and 224 mV at 10 mA cm−2. • A constant robust stability was maintained at a current density of 100 mA cm−2 after 10 h. This study focuses on the electrochemical properties of layered double hydroxide (LDH), which is a specific structure of NiCoCu LDH, and the active species therein, rather than the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) of ternary NiCoCu LDH materials. Six types of catalysts were synthesized using the reflux condenser method and coated onto a nickel foam support electrode. Compared to bare, binary, and ternary electrocatalysts, the NiCoCu LDH electrocatalyst exhibited higher stability. The double layer capacitance (Cdl) of the NiCoCu LDH (12.3 mF cm−2) is greater than that of the bare and binary electrocatalysts, indicating that the NiCoCu LDH electrocatalyst has a larger electrochemical active surface area. In addition, the NiCoCu LDH electrocatalyst has a lower overpotential of 87 mV and 224 mV for the HER and OER, respectively, indicating its excellent activity with the bare and binary electrocatalysts. Finally, it is demonstrated that the structural characteristics of the NiCoCu LDH contribute to its excellent stability in long-term HER and OER tests. [ABSTRACT FROM AUTHOR]

Transition-metal sulfides (TMSs) have indeed drawn dramatic interest as a potential species of electrocatalysts by virtue of their unique structural features. However, their poor stability and inherent activity have impeded their use in electrocatalytic water splitting. Here, we provide a rational design of a hierarchical nanostructured electrocatalyst containing CeOx-decorated NiCo-layered double hydroxide (LDH) coupled with Ni3S2 protrusions formed on a Ni foam (NF). Specifically, the as-prepared electrocatalyst, denoted as Ni2Co1 LDH-CeOx/Ni3S2@NF, presents only 250 and 300 mV overpotential at ±100 mA cm−2, respectively, along with the Tafel slope values of 92 and 52 mV dec−1, as well remarkable long-term life for water splitting in an alkaline electrolyte. Based on systematic experiments and theoretical analysis, the superior electrocatalytic property in terms of Ni2Co1 LDH-CeOx/Ni3S2@NF can be imputed to the following reasons: the porous framework of Ni3S2@NF provides a largely surface area and high conductivity; the NiCo LDH nanosheets provide enriched active sites and favorable adsorption ability; the oxygen-vacancy-rich CeOx optimizes the electronic configuration. Overall, these factors work synergistically to expedite the catalytic kinetics of splitting water. Our work concentrates on a rational interface to devise efficient, multifunctional, and serviceable electrocatalysts for future applications. [ABSTRACT FROM AUTHOR]

As one of the best electrocatalysts for the hydrogen evolution reaction, platinum catalysts are a benchmark for the performance evaluation of new catalysts. However, platinum catalysts reported in the literature show diverse electrocatalytic performances, resulting in the lack of a common reference standard. In this study, we investigated several factors that affect the performance of platinum catalysts by performing experimental measurements and data processing. These factors included the solution resistance, electrolyte temperature, loading quantity, catalyst microstructure, and normalization method of the current density. Finally, we recommended criteria for the performance evaluation of electrocatalysts. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) performance of nanosized iridium oxide-nanosheet-like based electrocatalysts synthesized by a modified Adams method is reported in this work. Cysteamine hydrochloride was introduced during the synthesis of IrO 2 to induce the evolution of nanosheet-like morphology from spherical particles. The IrO 2 crystallinity prepared by the modified Adams method was greatly affected by calcination temperature. When the temperature increases to 400 °C, the resulted iridium oxide transitions from pseudo-amorphous to crystal rutile type. Electrochemical evaluation results show that the IrO 2 synthesized at 400 °C performs the best in terms of enhanced mass activity (1.104 A mg−1@1.6 V) and lower overpotential (315 mV@10 mA cm−2) as compared with the counterparts prepared at other temperatures. Ta 2 O 5 with different molar ratios of Ir/Ta was incorporated to further improve the stability of iridium oxide and to reduce its usage as anode catalyst. Ultrathin IrO 2 –Ta 2 O 5 nanosheets with optimized Ir/Ta = 7: 3 M ratio outperform the commercial IrO 2 benchmark in terms of OER activity and stability. The overpotential of IrO 2 –Ta 2 O 5 (7: 3) is at 326 mV@10 mA cm−2, and its mass activity is as high as 0.9 A mg−1@1.6 V. Chronopotentiometry and chronoamperometry tests verify its excellent durability. • Amorphous IrO 2 and IrO 2 –Ta 2 O 5 were synthesized by modified Adams method. • IrO 2 –Ta 2 O 5 (7: 3) shows OER activity of 0.9 A mg−1 and overpotential of 326 mV@10 mA cm−2. • IrO 2 –Ta 2 O 5 (7: 3) also exhibits excellent stability. [ABSTRACT FROM AUTHOR]

This paper introduces a comprehensive research experiment regarding the synthesis and characterization of electrocatalysts for electrochemical water splitting. In this experiment, the electrocatalysts (Cu-MoS2/CNTs) were prepared by hydrothermal and wet chemical methods. Then, the electrochemical performance of the catalysts was evaluated by voltammetry and electrochemical impedance spectroscopy (EIS) techniques, which helped consolidate students' understanding and learning of the concepts of irreversible electrode and overpotential. They are helpful to stimulate students' scientific research interests and improve students' comprehensive experimental abilities through the synthesis and optimization of electrocatalysts. [ABSTRACT FROM AUTHOR]

The development of economical and highly efficient electrocatalysts is crucial for the oxygen evolution reaction in water electrolysis, which is associated with producing clean and sustainable hydrogen fuel. For this purpose, we successfully elaborated a new series of LaCo 1-x Zn x O 3 oxides (x = 0, 0.1, 0.2, 0.3 and 0.4) via a facile sol-gel route and investigated their structural, morphological and electrochemical properties for a possible use as electrocatalysts toward oxygen evolution reaction in a basic solution. Among the developed materials, the LaCo 0.9 Zn 0.1 O 3 electrocatalyst displays a remarkable performance; an overpotential of merely 327 mV is needed to generate a specified current density of 10 mA.cm−2 geo ; a current density of around 73.41 mA cm−2 at 450 mV, almost twice as high compared to the pristine electrocatalyst; a faster reaction kinetic with a lower Tafel slope of ∼92 mV.dec−1 and an activity loss of less than 4% after 24 h of utilization. [Display omitted] • LaCo 1-x Zn x O 3 electrocatalysts with different Zn content (x) were synthesized via the sol-gel route. • Interesting behaviors were observed in the structural and electrocatalytic properties. • The LaCo 0.9 Zn 0.1 O 3 electrocatalyst shows the best electrocatalytic activity with the faster kinetic. • The LaCo 0.9 Zn 0.1 O 3 exhibits good stability toward the OER over 24 h. [ABSTRACT FROM AUTHOR]

The development of highly efficient binary heterostructures with enhanced electrocatalytic activities is vital for reducing the energy consumed by the hydrogen evolution reaction (HER). Herein, we successfully design and synthesize an eco-friendly Ag 3 PO 4 /1T-2H MoS 2 heterostructure to catalyze the HER process. Micromorphology and microstructure studies show that the Ag 3 PO 4 nanoclusters are well dispersed with abundant catalytically active sites on the surface of the 1T-2H MoS 2 nanoflowers. X-ray photoelectron spectroscopy confirms the stable oxidation state and electronic interactions in the 2 wt% Ag 3 PO 4 /1T-2H MoS 2 nanostructure. Benefitting from the strong electronic interactions and advantages of abundant heterogeneous interfaces and catalytically active sites, the 2 wt% Ag 3 PO 4 /1T-2H MoS 2 heterostructure delivers excellent and durable electrochemical HER activity in alkaline solution, with a low overpotential of 149 mV for the HER at 10 mA cm−2, in clear improvement over 1T-2H MoS 2. The enhanced electrocatalytic activity is ascribed to the abundant catalytically active sites, rapid charge transport, and Ag 3 PO 4 /1T-2H MoS 2 synergism. This study provides a novel strategy for exploring and synthesizing low-cost binary electrocatalysts that enhance the electrochemical HER performance in energy-conversion applications. [Display omitted] • Ag 3 PO 4 /1T-2H MoS 2 material was synthesized by ultrasonication. • 2 wt% Ag 3 PO 4 /1T-2H MoS 2 exhibited the best HER performance among all electrocatalysts in 1 M KOH. • 2 wt% Ag 3 PO 4 /1T-2H MoS 2 showed 149 mV low overpotential for HER. • The synergistic effect between Ag 3 PO 4 and 1T-2H MoS 2 significantly improves the electrochemical activity. [ABSTRACT FROM AUTHOR]

As traditional energy structures transition to new sources, hydrogen is receiving significant research attention owing to its potential as a clean energy source. The most significant problem with electrochemical hydrogen evolution is the need for highly efficient catalysts to drive the overpotential required to generate hydrogen gas by electrolyzing water. Experiments have shown that the addition of appropriate materials can reduce the energy required for hydrogen production by electrolysis of water and enable it to play a greater catalytic role in these evolution reactions. Therefore, more complex material compositions are required to obtain these high-performance materials. This study investigates the preparation of hydrogen production catalysts for cathodes. First, rod-like NiMoO4/NiMo is grown on NF (Nickel Foam) using a hydrothermal method. This is used as a core framework, and it provides a higher specific surface area and electron transfer channels. Next, spherical NiS is generated on the NF/NiMo4/NiMo, thus ultimately achieving efficient electrochemical hydrogen evolution. The NF/NiMo4/NiMo@NiS material exhibits a remarkably low overpotential of only 36 mV for the hydrogen evolution reaction (HER) at a current density of 10 mA·cm−2 in a potassium hydroxide solution, indicating its potential use in energy-related applications for HER processes. [ABSTRACT FROM AUTHOR]

Developing a robust and highly efficient electrocatalyst for the oxygen evolution reaction (OER) is required, due to its sluggish mechanism and high overpotential. Here, we present the Ti 3 C 2 T x and ZIF-67 composites (MXene/ZIF-67) for an efficient OER. The MXene/ZIF-67_1:10 exhibits an overpotential of 366 mV, which is better than MXene (548 mV) and RuO 2 (395 mV). Moreover, it shows improved electrochemical stability at 20 mA·cm− 2 with only a 0.2% increase in potential after 5 h, while RuO 2 with an overpotential loss of 3.5%. After an increase in the current density of 10–20 mA cm−2 the potential increase by 7.4%, while in RuO 2 by 25.3%. To reveal the observed performance, the composite's robustness and explain each component's role. Moreover, a detailed OER mechanism is discussed. It was realized via in situ Raman microscopy and XRD which allowed the revealing of the active species responsible for boosting OER. • MXene/ZIF-67 composite was designed for OER. • MXene/ZIF-67 presented outstanding electrocatalytic activity in OER. • MXene/ZIF-67 structures exhibit robust stability at high current density for a long time. • In situ Raman and XRD were applied to revile the mechanism of OER. [ABSTRACT FROM AUTHOR]

Transition metal-based nanomaterials exhibit promising potential as highly active and low-cost electrocatalysts for alkaline water splitting, which can be achieved via elaborating compositional modulation and structural manipulation. This, however, normally involves multiple or even complex synthetic procedures. Herein, we report a simple one-step sulfidation of FeMnZn multi-metal skeletons for the preparation of highly efficient electrocatalysts. The incorporation of Mn and Zn induced a hierarchical nano/micro sheet-to-sheet morphology supported on an open porous skeleton (FeMnZn/Mn-FeS, FMZS2), which not only facilitates electron/ion transport but also expands the accessible surface. Meanwhile, Mn is introduced to optimize the adsorption/desorption ability of intermediates on the S sites in FeS. The resultant effect leads to remarkable electrocatalytic performance with good durability. Notably, the optimized FMZS2 delivers 20 mA cm−2 at a low overpotential of 118 mV for the HER and 100 mA cm−2 at an overpotential of 390 mV for the OER, outperforming Pt/C and IrO2 catalysts, respectively. Moreover, the assembled alkaline electrolyzer also has good overall water splitting capability, which is better than that of the noble metal ones. [ABSTRACT FROM AUTHOR]

Theoretical calculation results unveil that the reconstructed Co(Ni)OOH on FeNiCo-MOF during OER processes is beneficial to improve the OER activity. Experimentally, to achieve 2D trimetallic FeNiCo-MOF nanosheets, a facile room-temperature dispersion approach is employed. Such 2D nanosheets reveal an OER overpotential as low as 239 mV at 10 mA cm−2 and excellent long-term stability in 1M KOH. Undoubtedly, this work highlights the great potential of directly utilizing MOF nanosheets as OER electrocatalysts. [ABSTRACT FROM AUTHOR]

Molecular electrocatalysts for CO2‐to‐CO conversion often operate at large overpotentials, due to the large barrier for C−O bond cleavage. Illustrated with ruthenium polypyridyl catalysts, we herein propose a mechanistic route that involves one metal center that acts as both Lewis base and Lewis acid at different stages of the catalytic cycle, by density functional theory in corroboration with experimental FTIR. The nucleophilic character of the Ru center manifests itself in the initial attack on CO2 to form [Ru‐CO2]0, while its electrophilic character allows for the formation of a 5‐membered metallacyclic intermediate, [Ru‐CO2CO2]0,c, by addition of a second CO2 molecule and intramolecular cyclization. The calculated activation barrier for C−O bond cleavage via the metallacycle is decreased by 34.9 kcal mol−1 as compared to the non‐cyclic adduct in the two electron reduced state of complex 1. Such metallacyclic intermediates in electrocatalytic CO2 reduction offer a new design feature that can be implemented consciously in future catalyst designs. [ABSTRACT FROM AUTHOR]

Single‐atom Fe‐N‐C (denoted as Fe1‐N‐C) catalysts exhibit inadequate bifunctional activities to conquer the sluggish oxygen reduction and evolution reaction (ORR/OER), hindering their practical applications in rechargeable Zn‐air batteries (ZABs). Here, by employing Fe1‐N‐C hollow nanorods as ORR‐active support, OER‐active NiFe‐layered double hydroxide (NiFe‐LDH) nanodots are evenly decorated through a spatially confined process to form NiFe‐LDH/Fe1‐N‐C heterostructure hollow nanorods with abundant accessible catalytic sites. The NiFe‐LDH/Fe1‐N‐C heterostructure not only enhances the ORR activity of pristine Fe1‐N‐C but also realizes efficient bifunctional ORR/OER activity in one monolithic catalyst. Theoretical calculations reveal that introducing NiFe‐LDH nanodots results in donation of electrons to the Fe1‐N‐C matrix and thus lowers the Fe‐d band center of the Fe‐N4 sites, dramatically narrowing the energy barriers of the ORR rate‐limiting steps. As a result, NiFe‐LDH/Fe1‐N‐C nanorods deliver remarkable ORR activity with a half‐wave potential of 0.90 V versus reversible hydrogen electrode, surpassing bare Fe1‐N‐C and commercial Pt/C. Impressively, the integrated NiFe‐LDH/Fe1‐N‐C catalysts show outstanding bifunctional performance with a small overpotential gap of only 0.65 V. The liquid‐state ZABs with NiFe‐LDH/Fe1‐N‐C as an air‐cathode catalyst deliver a peak power density of 205 mW cm−2 and long‐term cycling stability of up to 400 h. [ABSTRACT FROM AUTHOR]

A binder-free, self-supporting and substrate-rejuvenating electrocatalytic electrode based on nonnoble elements is widely acknowledged as the most potential candidate for feasible water splitting. Through the consecutive surface treatment including Fe-leaching in a simple KSCN solution, anodic polarization and chronopotentiometric aging in KOH solution, a commercially available 4J40 INVAR alloy was adopted in this work to fabricate an anode for oxygen evolution in alkaline media. Featuring all above advantages over most state-of-the-art OER electrocatalysts, the 4J40 electrode after being stabilized by CP-aging needs an overpotential of only 241 mV to achieve the current density of 10 mA cm−2 in 1 M KOH, in addition to its stability tested at the lower and higher current densities, respectively. The controlling OER mechanisms were discussed accordingly, with the Fe-doped nickel-based oxyhydroxide and the nickel peroxide being considered correspondingly as the main OER-enhancing species before and after CP-aging. [Display omitted] • 4J40 INVAR alloy was Fe-leached in KSCN solution to modulate Ni/Fe ratio. • OER-active (oxy)hydroxides were obtained on alloy surface by LSV polarizations. • Anode based on this alloy was stabilized by CP-aging for efficient and stable OER. • Oxyhydroxide and peroxide are OER-enhancing respectively before and after CP-aging. • Current density of 10 mA cm−2 was attained at overpotential of 241 mV in 1 M KOH. [ABSTRACT FROM AUTHOR]

Bismuth‐based electrocatalysts are promising candidates for electrochemical CO2 reduction to formate attributing to the accelerated formation of *OCHO intermediate, while the high‐energy consumption remains a major challenge for practicability. Herein, we present the ultrathin Bi2O2CO3 nanosheets with abundant oxygen vacancy (Vo‐BOC‐NS) reconstructed from S, N‐co‐doped bismuth oxides that can act as durable electrocatalyst for CO2‐to‐formate conversion with faradic efficiency (FEformate) of >95%, partial current density of 286 mA cm−2 with energy efficiency of 73.8% at −0.62 V (vs. RHE) and low overpotential of 200 mV in a flow electrolyzer. The theoretical calculations decipher that the oxygen vacancy can optimize *OCOH adsorption/desorption for the accelerated conversion kinetics. The pair‐electrosynthesis tactic of formate co‐production can enable a superior FEformate of >90% at wide cell voltage of 2–3.3 V and total yield rate of 3742 μmol cm−2 h−1 at 3.3 V, suggesting great potential for future industrialization. [ABSTRACT FROM AUTHOR]

An ongoing challenge still lies in the exploration of proficient electrocatalysts from earth-abundant non-precious metals instead of noble metal-based catalysts for clean hydrogen energy through large-Scale electrochemical water splitting. However, developing a non-precious transition metals based, stable electrocatalyst for cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) is important challenge for modern energy conversion technology. In this report Vanadium doped bimetallic nickel-iron nanoarray, fabricated by carbon supported architecture through carbonization process for electrochemical water splitting. Three types of catalysts were prepared in different molar ratio of Ni/Fe. The electrocatalytic performance demonstrated that the catalyst with equal mole ratio (0.06:0.06) of Ni/Fe possess high catalytic activity for both OER and HER in alkaline and acidic medium. Besides, our findings revealed that the doping of vanadium could play a strong synergetic effect with Ni/Fe, which provide a small overpotential of 90 mV and 210 mV at 10 mA cm−2 for HER and OER respectively compared to the other two catalyst counterparts. Also, the catalyst with 1:1 (Ni/Fe) molar ratio showed a high current density of 208 mA cm−2 for HER at 0.5 M H 2 SO 4 and 579 mA cm−2 for OER at 1 M KOH solution, the both current densities are much higher than the other two catalysts (different Ni/Fe ratio). In addition, the presented catalysts showed extremely good durability, reflecting in more than 20 h of consistent Chronoamprometry study at fixed overpotential η = 250 mV without any visible voltage elevation. Similarly, the (Ni/Fe) equal ratio catalyst showed better corrosion potential 0.209 V vs Ag/AgCl and lower current density 0.594 × 10−12 A cm−2 in high alkaline medium. The V-doping, MOF/GO surface defects are significantly increased the corrosion potential of the V-Ni x Fe y -MOF/GO electrocatalyst. Besides, the water electrolyzed products were analysed by gas chromatography to get clear insights on the formed H 2 and O 2 products. [Display omitted] • V-doped bimetallic nickel-iron nanoarray, fabricated by carbon supported architecture through carbonization. • The V-Nix: Fey MOF/GO were characterized by Raman, PXRD, FESEM, TEM and XPS. • V–Ni 0.06 : Fe 0.06 MOF/GO showed lower overpotential of 90 mV and 210 V for HER and OER. • The water electrolyzed products were analysed by gas chromatography. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of novel high-entropy amorphous compounds have been synthesized. • FeCoNiMnBPO x show a low overpotential of 248 mV at 10 mA cm−2. • Leaching of boron and phosphorus promotes surface reconstruction. Efficient, cost-effective and durable electrocatalysts are highly required to overcome the slow kinetics and high overpotential of oxygen evolution reaction (OER). Here we report a series of novel amorphous high-entropy borophosphate catalysts FeCoNiMBPO x (M = Mg, Al, Cr, Mn) prepared by a low-temperature reduction method. The leaching of boron and phosphorus accelerates the surface self-reconstruction of FeCoNiMnBPO x , and the subsequently formed high-oxidation-state metal-OOH species is beneficial to improve the catalyst performance. Moreover, the unique amorphous structure with abundant defects provides more active sites for OER. As a return, all the samples exhibit excellent OER activity and stability. Among them, FeCoNiMnBPO x with the highest conductivity and the largest electrochemical active surface area (ECSA) exhibits the best electrocatalytic performance, requiring only low overpotentials of 248 mV and 294 mV to reach current densities of 10 mA cm−2 and 100 mA cm−2, respectively. This sample also shows an exceptional durability for 50 h without a significant increase in potential, which is superior to that of the benchmark RuO 2 electrocatalyst. The combination of the adsorbate evolution mechanism (AEM) and the lattice oxygen-mediated mechanism (LOM) are responsible for the excellent catalyst performance. This work provides new ideas for designing high-activity multiple-element catalysts. [ABSTRACT FROM AUTHOR]

The transition metal phosphates are earth-abundant minerals that have been shown to perform well in electrocatalytic water splitting, whereas these catalysts still tend to have excessively high overpotentials and slow kinetics in HER and OER processes. In the present work, hybrid catalysts consisting of Pt quantum dots doped NiP (NiP-Pt) nano-embroidery spheres and Co(OH) 2 nanosheets were successfully prepared by two-step electrodeposition method. The excellent catalytic performance of the catalyst relies principally on the synergistic interaction between NiP and Pt quantum dots. Additionally, the NiP-Pt exhibits strong electronic interactions at the interface with Co(OH) 2. Consequently, the catalyst has a strong catalytic performance in terms of HER and OER catalytic performance. In terms of HER, an overpotential of only 40 mV is required when the current density reaches 10 mA cm−2, corresponding to a Tafel slope of 49.85 mV · dec−1. At the same time, the catalyst also performs well at OER, with a current density of 10 mA cm−2 at an overpotential of 186 mV and a Tafel slope of 53.049 mV · dec−1 much less than most electrocatalysts. This study involving electrodeposition and doping of quantum dots provides a new idea for the efficient synthesis of fundamental HER and OER bifunctional catalysts. [Display omitted] • Interface engineering of Pt QDs doped NiP and Co(OH) 2 promotes electrocatalytic water splitting. • Nano-embroidered NiP-Pt/Co(OH) 2 catalyst on NF is prepared by two-step electrodeposition. • NiP-Pt/Co(OH) 2 requires overpotentials of 40 and 186 mV to achieve 10 mA·cm−2 for HER and OER in alkaline electrolytes. • NiP-Pt/Co(OH) 2 exhibits excellent stability after 1000 CV cycles for HER and OER reactions. • The doping of Pt quantum dots promotes HER, while Co(OH) 2 contributes OER activity during the reaction process. [ABSTRACT FROM AUTHOR]