Iron, manganese co-doped Ni3S2 nanoflowers in situ assembled by ultrathin nanosheets as a robust electrocatalyst for oxygen evolution reaction

Multicomponent Interface and Electronic Structure Engineering in Ir-Doped CoMO4-Co(OH)2 (M = W and Mo) Enable Promoted Oxygen Evolution Reaction

The core principles of multicomponent interface and electronic structure engineering are essential in designing high-performance catalysts for the oxygen evolution reaction (OER). However, combining these aspects within a catalyst is a significant challenge. In this investigation, a novel approach involving the development of hybrid Ir-doped CoMO4-Co(OH)2 (M = W and Mo) hollow nanoboxes was introduced, enabling remarkably efficient water oxidation electrocatalysis. Constructed from ultrathin nanosheet-assembled hollow nanoboxes, these structures boast a wealth of active centers for intermediate species, which in turn enhance both charge transfer and mass transport capabilities. Moreover, the compelling electronic and synergistic effects arising from the interaction between CoMO4 and Co(OH)2 significantly bolster OER electrocatalysis by facilitating efficient electron transfer. The introduction of Ir atoms serves to strategically adjust the electronic structure, fine-tune its electronic state, and operate as active centers to enhance OER electrocatalysis, thus diminishing the overpotential. This configuration results in Ir-CoWO4-Co(OH)2 and Ir-CoMoO4-Co(OH)2 exhibiting impressively low overpotentials of 252 and 261 mV, respectively, to 10 mA cm-2. Utilized in conjunction with the Pt/C catalyst in a two-electrode system for overall water splitting, a mere 1.53 V cell potential is needed to achieve the desired 10 mA cm-2 current density.

Designing core-shell heterostructure arrays based on snowflake NiCoFe-LTH shelled over W2N-WC nanowires as an advanced bi-functional electrocatalyst for boosting alkaline water/seawater electrolysis

The pursuit of efficient and sustainable hydrogen production through water splitting has led to intensive research in the field of electrocatalysis. However, the impediment posed by sluggish reaction kinetics has served as a significant barrier. This challenge has inspired the development of electrocatalysts characterized by high activity, abundance in earth's resources, and long-term stability. In addressing this obstacle, it is imperative to meticulously fine-tune the structure, morphology, and electronic state of electrocatalysts. By systematically manipulating these key parameters, the full potential of electrocatalysts can unleash, enhancing their catalytic activity and overall performance. Hence in this study, a novel heterostructure is designed, showcasing core-shell architectures achieved by covering W2N-WC nanowire arrays with tri-metallic Nickel-Cobalt-Iron layered triple hydroxide nanosheets on carbon felt support (NiCoFe-LTH/W2N-WC/CF). By integrating the different virtue such as binder free electrode design, synergistic effect between different components, core-shell structural advantages, high exposed active sites, high electrical conductivity and heterostructure design, NiCoFe-LTH/W2N-WC/CF demonstrates striking catalytic performances under alkaline conditions. The substantiation of all the mentioned advantages has been validated through electrochemical data in this study. According to these results NiCoFe-LTH/W2N-WC/CF achieves a current density of 10 mA cm-2 needs overpotential values of 101 mV for HER and 206 mV for OER, respectively. Moreover, as a bi-functional electrocatalyst for overall water splitting, a two-electrode device needs a voltage of 1.543 V and 1.569 V to reach a current density of 10 mA cm-2 for alkaline water and alkaline seawater electrolysis, respectively. Briefly, this research with attempting to combination of different factors try to present a promising stride towards advancing bi-functional catalytic activity with tailored architectures for practical green hydrogen production via electrochemical water splitting process.

FeCoNi molybdenum-based oxides for efficient electrocatalytic oxygen evolution reaction

The search for highly efficient and inexpensive electrocatalysts is crucial to the advancement of environmentally friendly and sustainable energy sources. Here, adopting a one-step hydrothermal method, we have effectively fabricated a self-supported multi-metal molybdenum-based oxide (FeCoNi-MoO4) on nickel foam (NF). In addition to changing the catalyst's microstructure, the introducing of Fe and Co, enhanced its active center count, improved its electronic structure, and in turn reduced the difficulty for high-valence Ni and Fe species to form, which accelerates the oxygen evolution reaction (OER) kinetics by promoting the development of the actual active materials, NiOOH and FeOOH. FeCoNi-MoO4 has outstanding OER performance, requiring just 204 mV overpotentials at 10 mA cm-2 and 271 mV at 100 mA cm-2. Its exceptional OER kinetics at both low and high currents are indicated by a Tafel slope of 50.6 mV dec-1, which is attributed to the combined effect of its multi-metal composition and a higher number of active sites. Moreover, the FeCoNi-MoO4 electrode was operated continuously for over 48 h. Furthermore, the density functional theory (DFT) results demonstrated that the introducing of Fe and Co, which quickens the rate of electron transfer during the electrocatalytic process, improves the ability of oxygen intermediate species to adsorb, and ultimately lowers the overpotential, is responsible for the increased electrocatalytic activity of FeCoNi-MoO4. This work offers hope for further developments in the sector by proposing an efficient approach for creating multi-active electrocatalysts that are stable, economical, and efficient.

Facile and scalable synthesis of Ni3S2/Fe3O4 nanoblocks as an efficient and stable electrocatalyst for oxygen evolution reaction

This study employed a one-step hydrothermal process to synthesize Ni3S2/Fe3O4 nanoblocks in situ on nickel foam (NF). The resulting Ni3S2/Fe3O4/NF catalyst demonstrates exceptional electrocatalytic activity for the oxygen evolution reaction (OER) and robust long-term stability. It achieves a low overpotential of only 220 mV for a current density of 10 mA cm-2 with a Tafel slope of 54.1 mV dec-1 and remains stable in 1.0 M KOH for 66 h. The binder-free self-supported three-dimensional nanoblocks enhance the reaction region and long-term stability. Electronic interactions between Fe3O4 and Ni3S2, coupled with heterogeneous interfaces, optimize the electronic structure, fostering the formation of highly reactive species. Density-functional theory (DFT) calculations confirm that Ni3S2/Fe3O4, with a heterogeneous interfacial structure, modulates the chemisorption of reaction intermediates on the catalyst surface, optimizing the Gibbs free energies (ΔG) of oxygen-containing intermediates. The synergistic effect between the two active materials within the heterogeneous structure enhances OER catalytic performance. This finding offers a valuable approach to designing efficient and stable OER electrocatalysts.

Nanosheet-assembled transition metal sulfides nanoflowers derived from CoMo-MOF for efficient oxygen evolution reaction

Oxygen evolution reaction (OER) is a multi-electron transfer process, whose intrinsic sluggish dynamic restricts the whole process of overall water splitting (OWS). To address this issue, a porous transition metal sulfide (TMS) catalyst with rich heterojunctions was prepared by vulcanization and trace Fe doping of CoMo-based metal-organic framework (MOF). In this work, the nanoflower composed of ultrathin 2D nanosheets anchored on a nickel foam presents a layered interface that contributes to the exposure of active regions. The resulting electrode denoted as Fe@CoMo2S4/Ni3S2/NF required a low overpotential (η10 = 167 mV @ 10 mA cm-2, η50 = 260 mV @ 50 mA cm-2) in 1.0 M KOH for OER and a small cell voltage (E = 1.513 V @ 10 mA cm-2) to power OWS when coupled with commercial Pt/C. It also exhibited splendid morphological and chemical stability with virtually invariant polarization curve and flower-like appearance after 1000 CV cycles, as well as long-term durability over 100 h with a constant current density of 10 mA cm-2. This work revealed the multi-anionic regulation mechanism in the surface reconstruction of sulfide electrocatalysts, and verified that Co/Mo/Ni-based oxysulfide was the true active substance of OER, which inspired the understanding and design of multi-anionic regulated electrocatalysts.

An efficient cerium dioxide incorporated nickel cobalt phosphide complex as electrocatalyst for All-pH hydrogen evolution reaction and overall water splitting

Transition metal phosphides (TMPs) have been considered as potential electrocatalysts with adjustable valence states, metal characteristics, and phase diversity. However, it is necessary but remains a major challenge to obtain efficient and durable TMPs catalysts, which can realize efficiently for not only all-pH hydrogen evolution reaction (HER), but also oxygen evolution reaction (OER). Hence, cerium dioxide incorporated nickel cobalt phosphide growth on nickel foam (CeO2/NiCoP) is fabricated by hydrothermal and phosphating reaction. CeO2/NiCoP shows excellent activity for all-pH HER (overpotentials of 48, 58 and 72 mV in alkaline, neutral and acidic solution at the current density of 10 mA cm-2), and has a small OER overpotential (231 mV @ 10 mA cm-2). Moreover, the voltage of overall water splitting in alkaline solution and simulated seawater electrolyte is only 1.46 and 1.41 V (10 mA cm-2), respectively, coupled with outstanding operational stability and corrosion resistance. Further mechanism research shows that CeO2/NiCoP possesses rich heterointerfaces, which serves more exposed active sites and possesses a promising superhydrophilic and superaerophobic surface. Density functional theory calculations manifest that CeO2/NiCoP has appropriate energy for intermediates of reactions. This work provides a deep insight into the CeO2/NiCoP catalyst for high-performance water/seawater electrolysis.

Polymer self-assembly guided heterogeneous structure engineering towards high-performance low-frequency electromagnetic wave absorption

Magnetic-dielectric synergy is currently regarded as among the most effective approaches to achieve low-frequency electromagnetic wave absorption (EMA). However, designing and fabricating EMA materials with tunable magnetic-dielectric balance towards high-performance low-frequency EMA remains challenging. Herein, a polymer self-assembly guided heterogeneous structure engineering strategy is proposed to fabricate hierarchical magnetic-dielectric nanocomposite. Polymer assemblies not only can be employed as intermediates to encapsulate metal-organic frameworks and load metal hydroxide, but also that they play a crucial role for the in-situ formation of polycrystalline FeCo/Co composite nanoparticles. As a result, the minimum reflection loss (RLmin) can reach -59.61 dB at 5.4 GHz (4.8 mm) with a 20 wt% filler loading, while the effective absorption bandwidth (EAB, RLmin ≤ -10 dB) is 2.16 GHz, exhibiting excellent low-frequency EMA performance. Systematic investigations demonstrate that hierarchical mesoporous carbon matrix that supports FeCo/Co composite nanoparticles is beneficial for optimizing impedance matching and increasing attenuation capacity. In general, this study opens up new prospects for developing magnetic-dielectric EMA materials using a polymer self-assembly guided heterogeneous structure engineering strategy, which may receive significant attention in future research.

Phytochemical-assisted green synthesis of CuFeOx nano-rose electrocatalysts for oxygen evolution reaction in alkaline media

This study represents a green synthesis method for fabricating an oxygen evolution reaction (OER) electrode by depositing two-dimensional CuFeO_x on nickel foam (NF). Two-dimensional CuFeO_x was deposited on NF using in situ hydrothermal synthesis in the presence of Aloe vera extract. This phytochemical-assisted synthesis of CuFeO_x resulted in a unique nano-rose-like morphology (petal diameter 30-70 nm), which significantly improved the electrochemical surface area of the electrode. The synthesized electrode was analyzed for its OER electrocatalytic activity and it was observed that using 75% Aloe vera extract in the phytochemical-assisted synthesis of CuFeO_x resulted in improved OER electrocatalytic performance by attaining an overpotential of 310 mV for 50 mA cm^-2 and 410 mV for 100 mA cm^-2. The electrode also sustained robust stability throughout the 50 h of chronopotentiometry studies under alkaline electrolyte conditions, demonstrating its potential as an efficient OER electrode material. This study highlights the promising use of Aloe vera extract as a green and cost-effective way to synthesize efficient OER electrode materials.

Redox-Active and Urea-Engineered-Entangled MOFs for High-Efficiency Water Oxidation and Elevated Temperature Advanced CO2 Separation Cum Organic-Site-Driven Mild-Condition Cycloaddition

Development of the multifaceted metal-organic framework (MOF) with in situ engineered task-specific sites can promise proficient oxygen evolution reaction (OER) and high-temperature adsorption cum mild-condition fixation of CO₂. In fact, effective assimilation of these attributes onto a single material with advance performance characteristics is practically imperative in view of renewable energy application and carbon-footprint reduction. Herein, we developed a three-fold interpenetrated robust Co(II) framework that embraces both redox-active and hydrogen-bond donor moieties inside the microporous channel. The activated MOF demonstrates notable OER catalysis in alkaline medium via quasi-reversible Co²⁺/Co³⁺ couple and unveils low overpotential with impressive 53.5 mV/dec Tafel slope that overpowers some benchmark, commercial, as well as contemporary materials. In particular, significantly increased turnover frequency (3.313 s^-1 at 400 mV) and fairly low charge-transfer resistance (3.02 Ω) compared to Co₃O₄, NiO, and majority of redox-active MOFs together with 91% Faradaic efficiency and notable framework durability after multiple OER cycles endorse high-performance water oxidation. Pore-wall decked urea groups benefit appreciable CO₂ adsorption even at elevated temperatures with considerable MOF-CO₂ interactions and exhibit recurrent capture-release cycles at diverse temperatures. Interestingly, CO₂ selectivity displays radical upsurge with temperature rise, affording 40% improved CO₂/N₂ value of 200 at 313 K, which outperforms many porous adsorbents and delineates real-time CO₂ scavenging potential. The guest-free MOF effectively catalyzes solvent-free CO₂ cycloaddition with broad substrate tolerance and satisfactory reusability under relatively mild condition. Opposed to the common Lewis acid-mediated reaction, two-point hydrogen-bonding activates the substrate, as supported from controlled experiments, juxtaposing the performance of an un-functionalized MOF and fluorescence modification-derived framework-epoxide interaction, providing valuable insights on unconventional cycloaddition route in the MOF.

Polymetallic sulfide nanosheet arrays with composite structure as a highly efficient oxygen evolution electrocatalyst

Designing an earth-abundant and cost-effective electrocatalyst for oxygen evolution reaction (OER) is the crux to the hydrogen production by water electrolysis on industrial scale. Herein, we developed a trimetallic sulfide hybrid of CoS_1.097/Fe_1-xS/Ni₃S₂/NF nanoarrays by the combination of morphology optimization and interface modulation. The unique morphology of ultrathin nanosheets significantly enriches the reaction sites of the catalyst, while the abundant heterogeneous interfaces effectively regulate the local electron structure and thus intrinsically enhances the catalytic activity of the material. As a result, the catalyst delivers the superior OER performance with the ultralow overpotential of 229 mV at the current density of 50 mA cm^-2 and Tafel slope of 30.2 mV dec^-1. Furthermore, the current density of the material keeps constant for 50 h in 1.0 M KOH. This work proposes a strategy for the synthesis of polymetallic sulfide catalysts with composite structure as an efficient OER catalyst by morphology optimization and interface modulation.

In Situ Fabrication of Mn-Doped NiMoO4 Rod-like Arrays as High Performance OER Electrocatalyst

The slow kinetics of the oxygen evolution reaction (OER) is one of the significant reasons limiting the development of electrochemical hydrolysis. Doping metallic elements and building layered structures have been considered effective strategies for improving the electrocatalytic performance of the materials. Herein, we report flower-like nanosheet arrays of Mn-doped-NiMoO₄/NF (where NF is nickel foam) on nickel foam by a two-step hydrothermal method and a one-step calcination method. The doping manganese metal ion not only modulated the morphologies of the nickel nanosheet but also altered the electronic structure of the nickel center, which could be the result of superior electrocatalytic performance. The Mn-doped-NiMoO₄/NF electrocatalysts obtained at the optimum reaction time and the optimum Mn doping showed excellent OER activity, requiring overpotentials of 236 mV and 309 mV to drive 10 mA cm^-2 (62 mV lower than the pure NiMoO₄/NF) and 50 mA cm^-2 current densities, respectively. Furthermore, the high catalytic activity was maintained after continuous operation at a current density of 10 mA cm^-2 of 76 h in 1 M KOH. This work provides a new method to construct a high-efficiency, low-cost, stable transition metal electrocatalyst for OER electrocatalysts by using a heteroatom doping strategy.

Cobalt-based co-ordination complex-derived nanostructure for efficient oxygen evolution reaction in acidic and alkaline medium

Electrochemical water splitting is one of the most important method for energy conversion and storage. For this, the design and development of a low-cost robust electrocatalyst are highly desirable. In this study, Cobalt-based electrocatalyst for Oxygen Evolution Reaction was synthesized by thermal treatment of Cobalt-dehydroacetic acid (Co-DHA). The as-synthesized Co nanostructures and Co-DHA crystals were characterized with powder X-ray diffraction, X-ray photoelectron spectroscopy thermo-gravimetric analysis, and field emission scanning electron microscopy. The electrochemical O₂ evolution study shows the overpotential (at 10 mV/cm⁻²) correspond to 294 mV vs reference hydrogen electrode (RHE) for K-300 (Co₃O₄@300), whereas K-500 (Co₃O₄@500) shows 170 mV vs RHE values in 1 M KOH solution, respectively. Similar trends have been observed for electrochemical O₂ evolution studies in 0.5 M H₂SO₄, where K-300 and K-500 shows the overpotential (at 10mV/cm⁻²) of 234 mV vs RHE, and 199 mV vs RHE, respectively. The outcomes show better catalytic efficiency of K-500 as compared to K-300.

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Simple one pot synthesis for precursor of Co₃O₄.

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Enhanced activity for oxygen evolution reaction.

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Efficient performance and stability in both acidic and alkaline medium.

A sulfur defective Mn-doped Ni3S2-xnanosheet for enhanced overall water splitting

Non-precious and stable electrocatalysts towards both oxygen and hydrogen evolution reaction (OER/HER) are essential for effective overall water splitting in alkaline solution. In this study, a sulfur defective and manganese-doped nickel sulfide nanosheet that uniformly grown on nickel foam substrate (Mn-Ni₃S_2-x@NF) is synthesized. In alkaline solution, the Mn-Ni₃S_2-x@NF showed a low overpotential of 76 and 110 mV for OER and HER at 10 mA cm^-2, respectively, together exhibiting excellent stability for both OER and HER reaction. It was confirmed by the experimental results that sulfur defects and Mn-doping synergistically optimized the electronic structure of Mn-Ni₃S_2-xwith increased electrical conductivity and enhanced OER/HER activity. Moreover, amorphous nickel oxyhydroxide (NiOOH) was observed byin situRaman during the OER condition, suggesting NiOOH is the active phase for OER reaction. Furthermore, the electrolyzer assembled by Mn-Ni₃S_2-x@NF merely needs 1.46 V to reach 10 mA cm^-2and shows good stability as well. This study provides a feasible way to prepare high-efficiency bifunctional catalysts for overall water splitting.

Facile deposition of palladium oxide (PdO) nanoparticles on CoNi2S4microstructures towards enhanced oxygen evolution reaction

Strong demand for renewable energy resources and clean environments have inspired scientists and researchers across the globe to carry out research activities on energy provision, conversion, and storage devices. In this context, development of outperform, stable, and durable electrocatalysts has been identified as one of the major objectives for oxygen evolution reaction (OER). Herein, we offer facile approach for the deposition of few palladium oxide (PdO) nanoparticles on the cobalt-nickel bi-metallic sulphide (CoNi₂S₄) microstructures represented as PdO@ CoNi₂S₄using ultraviolet light (UV) reduction method. The morphology, crystalline structure, and chemical composition of the as-prepared PdO@ CoNi₂S₄composite were probed through scanning electron microscopy, powder x-ray diffraction, high resolution transmission electron microscopy, energy dispersive spectroscopy and x-ray photoelectron spectroscopy techniques. The combined physical characterization results revealed that ultraviolet light (UV) light promoted the facile deposition of PdO nanoparticles of 10 nm size onto the CoNi₂S₄and the fabricated PdO@ CoNi₂S₄composite has a remarkable activity towards OER in alkaline media. Significantly, it exhibited a low onset potential of 1.41 V versus reversible hydrogen electrode (RHE) and a low overpotential of 230 mV at 10 mA cm^-2. Additionally, the fabricated PdO@ CoNi₂S₄composite has a marked stability of 45 h. Electrochemical impedance spectroscopy has shown that the PdO@CoNi₂S₄composite has a low charge transfer resistance of 86.3 Ohms, which favours the OER kinetics. The PdO@ CoNi₂S₄composite provided the multiple number of active sites, which favoured the enhanced OER activity. Taken together, this new class of material could be utilized in energy conversion and storage as well as sensing applications.

An in situ generated 3D porous nanostructure on 2D nanosheets to boost the oxygen evolution reaction for water-splitting

Efficient oxygen evolution reaction (OER) electrocatalysts can accelerate the reaction kinetics of water-splitting for large-scale hydrogen generation. In this work, 2D nanosheets decorated with a 3D porous nanostructure, including Fe, Co and Ni elements, are developed via anodic cyclic voltammetry scanning (ACVs) in the presence of sodium sulfide (FeCoNi-NS-ACVs). The formed 2D nanosheets provide metal ions during ACVs to generate a 3D porous structure and also construct a hierarchical morphology to favor the transport of the electrolyte and release of produced gas bubbles. What's more, the developed FeCoNi-NS-ACVs possesses superhydrophilic and excellent electroconductivity properties. Benefiting from the above merits, FeCoNi-NS-ACVs exhibits excellent electrocatalytic performances for the OER with low overpotentials of 170 mV and 198 mV to drive 50 mA cm^-2 and 100 mA cm^-2, respectively, with a small Tafel slope of 64 mV dec^-1 and remarkable durability over 50 h. Moreover, the FeCoNi-NS-ACVs also exhibits outstanding electrocatalytic activity and stability toward overall water-splitting.

Three-dimensional self-supporting catalyst with NiFe alloy/oxyhydroxide supported on high-surface cobalt hydroxide nanosheet array for overall water splitting

The development of available dual-function electrocatalysts is of great significance to the effective storage of excess electricity. Here, we obtained a three-dimensional Co(OH)₂ nanosheet with high surface area on nickel foam (Co(OH)₂/NF) via conventional hydrothermal. NiFe-coated Co(OH)₂ nanosheet array (NiFe@Co(OH)₂ NSAs/NF) was further constructed by electrodeposition for water splitting. By optimizing and regulating the deposition time, NiFe@Co(OH)₂ NSAs/NF with a deposition time of 500 s (NiFe-500@Co(OH)₂ NSAs/NF) only needs 98 mV of overpotential and can be stabilized for 100 h for hydrogen evolution at 10 mA cm^-2 due to the rich density active components for NiFe alloy/oxyhydroxide layer and interaction with Co(OH)₂ nanosheets. Thanks to the excellent 3D nanosheet array structure and the close integration between Co(OH)₂ and the upper layer NiFe, NiFe@Co(OH)₂ NSAs/NF with a deposition time of 200 s (NiFe-200@Co(OH)₂ NSAs/NF) can provide 10 mA cm^-2 with only 204 mV and maintain constant catalysis within 100 h. Therefore, the constructed NiFe@Co(OH)₂ NSAs/NF (500||200) double-electrode cell for water splitting requires only 1.58 V drive potential and can maintain 24 h durability at 10 mA cm^-2. The design of the catalyst opens up new ideas for the large-scale application of transition metals in water splitting.

Regulation of Morphology and Electrochemical Properties of Ni0.85Se via Fe Doping for Overall Water Splitting and Supercapacitor

The Fe-doped Ni0.85Se nanosheets array on Ni foam was synthesized successfully through one-step solvothermal method as effective binder-free multifunctional catalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), overall...

Superimposed OER and UOR performances by the interaction of each component in an Fe–Mn electrocatalyst

An Fe–Mn based OER and UOR bifunctional catalyst is synthesized through electrodeposition. Mn serves as a co-catalyst of Fe for OER. Both Mn and Fe act as active sites for UOR.

Hierarchical CoMoO4@CoFe-LDH heterostructure as a highly effective catalyst to boost electrocatalytic water oxidation

The oxygen evolution reaction (OER) has become the main barrier to electrochemical water splitting, owing to sluggish kinetics. To accelerate the OER process, a nature-abundant non-noble metal catalyst with outstanding...

In-situ construction of 3D hetero-structured sulfur-doped nanoflower-like FeNi LDH decorated with NiCo Prussian blue analogue cubes as efficient electrocatalysts for boosting oxygen evolution reaction

At present, it is urgent for us to develop non-noble metal-based catalysts with abundant reserves and high efficiency towards oxygen evolution reaction (OER) in water electrolysis devices. Herein, cubic NiCo-Prussian blue analogue (PBA)/ flower-like FeNi layered double hydroxide (LDH) heterostructure was facilely in-situ formed on porous nickel foam (NF) via hydrothermal strategy coupled by subsequent sulfurizing treatment (named as S-FeNi LDH@PBA/NF), showing largely facilitated electron transfer over homogeneous counterpart. Also, we investigated the effects of different Fe/Ni feeding ratios on their catalytic properties in some detail. The as-prepared S-FeNi LDH@PBA/NF demonstrated the superior OER activity (e.g. only 243 mV of overpotential required for 50 mA cm^-2) and stability. Accordingly, using the catalyst as anode, the home-assembled S-FeNi LDH@PBA/NF//Pt/C/NF electrolyzer exhibited small Tafel slope (83.1 mV dec^-1) and ultra-stability, showing the potential feasibility in practical water electrolysis. This strategy provides a hopeful model to enhance the OER performance by effectively constructing advanced catalyst with promising heterostructure and optimal electronic structure.

Nanowire-structured FeP-CoP arrays as highly active and stable bifunctional electrocatalyst synergistically promoting high-current overall water splitting

The design and construction of highly efficient and durable non-noble metal bifunctional catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media is essential for developing the hydrogen economy. To achieve this goal, we have developed a bifunctional nanowire-structured FeP-CoP array catalyst on carbon cloth with uniform distribution through in-situ hydrothermal growth and phosphating treatment. The unique nanowire array structure and the strong electronic interaction between FeP and CoP species have been confirmed. Electrochemical studies have found that the designed Fe_0.14Co_0.86-P/CC catalyst appears excellent HER (130 mV@10 mA cm^-2)/OER (270 mV@10 mA cm^-2) activity and stability. Moreover, the bifunctional Fe_0.14Co_0.86-P/CC^(+/-) catalyst is also used in simulated industrial water splitting system, where the pair catalyst requires about 1.95 and 2.14 V to reach 500 and 1000 mA cm^-2, even superior to the control RuO₂⁽⁺⁾||Pt/C^(-) catalyst, showing good industrial application prospects. These excellent electrocatalytic properties are attributed to the synergy between FeP and CoP species as well as the unique microstructure, which can accelerate charge transfer, expose more active sites and enhance electrolyte diffusion and gas emissions.

An ingeniously assembled metal-organic framework on the surface of FeMn co-doped Ni(OH)2 as a high-efficiency electrocatalyst for the oxygen evolution reaction

To overcome the problem of the sluggish kinetics of the oxygen evolution reaction (OER), it is of great significance to develop an efficient and stable non-noble metal-based OER catalyst for electrocatalytic energy conversion and storage. Herein, a complex of a metal-organic framework and hydroxide is synthesized by performing a ligand etching strategy on FeMn co-doped Ni(OH)₂ nanosheets in situ grown on nickel foam (FeMn-Ni(OH)₂@MOF/NF). Benefiting from the unique sheet-on-sheet hierarchical structure, multi-metal active nodes and two active materials grown in situ, the resulting FeMn-Ni(OH)₂@MOF/NF demonstrated brilliant OER activity with an overpotential of 199 mV to achieve a current density of 10 mA cm^-2 and long-term stability. This research will provide a new strategy for the design of high-performance OER electrocatalysts.

Iron, rhodium-codoped Ni2P nanosheets arrays supported on nickel foam as an efficient bifunctional electrocatalyst for overall water splitting

To enhance the overall water splitting efficiency, it is widely attractive yet challenging to develop low price, abundance and efficient bifunctional electrocatalysts towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, Fe,Rh-codoped Ni₂P nanosheets arrays were in situ anchored on three-dimension (3D) Ni foam under hydrothermal condition and successive phosphorization, denoted as Fe,Rh-Ni₂P/NF for simplicity. The unique nanosheets arrays effectively enriched the active sites with easy accessibility. By virtue of the unique sheet-like arrays and 3D porous conductive substrate, the prepared Fe,Rh-Ni₂P/NF showed the low overpotentials of 226 mV at 30 mA cm^-2 towards the OER and 73 mV at 10 mA cm^-2 for the HER. Moreover, the electrocatalyst effectively worked as anode and cathode for overall water splitting system, showing a small voltage of 1.62 V to drive a current density of 10 mA cm^-2. The present work provides alternative option for fabricating advanced catalysts in electrocatalysis and energy devices.

Coupling SnS2 and rGO aerogel to CuS for enhanced light-assisted OER electrocatalysis

In order to harvest more light wavelengths to improve the light-assisted electrochemical water splitting capacity, we developed a novel heterostructure of three-dimensional (3D) flower-like CuS architecture with accompanying SnS2 nanoparticles and reduced graphene oxide (rGO) aerogel for outstanding light-assisted electrocatalytic OER performance and good stability. The excellent catalytic kinetics, effective capturing of visible light, and rapid charge transfer of the CuS/SnS2/rGO (CSr) heterostructure were demonstrated. The overpotential (264 mV@10 mA cm-2) under light-assisted conditions is 20% lower than that under light-chopped conditions. SnS2 can harvest more light wavelengths and this boosts its intrinsic activity. However, with the increase of the SnS2 content, the OER activity decreases. The combination of the CS heterostructure and the rGO conductive aerogel achieves rapid charge transfer. Furthermore, the possible mechanism of the light-assisted electrocatalytic OER was also proposed. Overall, this work provides new insights into the simple and scalable fabrication of a highly efficient, low-cost, and stable non-noble-metal-based electrocatalyst.

Novel heterostructure Cu2S/Ni3S2 coral-like nanoarrays on Ni foam to enhance hydrogen evolution reaction in alkaline media

We fabricated a heterostructure Cu2S/Ni3S2 nanosheet array, which can accelerate charge transfer and provide more active sites. This work provides a promising non-noble metal electrocatalyst for water splitting under alkaline conditions.