One stable electrocatalyst for two evolution reactions by one-pot combustion synthesis

NiFeO_x is a high-active electrocatalyst for oxygen evolution reaction (OER) in alkaline media, which gradually deactivate in the long run due to Fe loss from the active sites into media solution during electrocatalysis. Herein, we propose a promising stable CeNiFeO_x electrocatalyst for oxygen and hydrogen evolution reactions (OER&HER) by a facile one-pot combustion synthesis. The X-ray diffraction (XRD) results indicate that both nickel and iron ions are successfully incorporated into ceria lattices to form a pure fluorite phase of CeNiFeO_x nanopowders, indicating a new achievement of as high as 20% of Ni/Fe solubility in the ceria lattice for the first time. The electrochemical measurements indicate that CeNiFeO_x exhibits the high OER activity of NiFeO_x electrocatalyst and the enhanced stability of oxygen evolution electrocatalysts. The Ce_0.8Ni_0.15Fe_0.05O_x with a single phase of cubic fluorite structure among all shows the most efficient activity with the overpotential of 325 mV for OER and 337 mV for HER at the current density of 10 mA cm⁻² in 1 M KOH than the pure CeO_x, NiFeO_x and other CeNiFeO_x nanoelectrocatalysts. After 1000 cycles, the Ce_0.8Ni_0.15Fe_0.05O_x nano electrocatalyst exhibits the remarkably improved stability for OER compared to NiFeO_x electrocatalyst. These findings demonstrate a facile approach to develop high-active and durable electrocatalysts under alkaline conditions for overall water splitting.     

Ni3S2-MoSx nanorods grown on Ni foam as high-efficient electrocatalysts for overall water splitting

In order to solve the problem of large overpotential in water electrolysis for hydrogen production, transition metal sulfides are promising bifunctional electrocatalysts for hydrogen evolution reaction/oxygen evolution reaction that can significantly reduce overpotential. In this work, Ni₃S₂ and amorphous MoS_x nanorods directly grown on Ni foam (Ni₃S₂-MoS_x/NF) were prepared via one-step solvothermal process, which were used as a high-efficient electrocatalyst for overall water splitting. The Ni₃S₂-MoS_x/NF composite exhibits very low overpotentials of 65 and 312 mV to reach 10 mA cm⁻² and 50 mA cm⁻² in 1.0 M KOH for HER and OER, respectively. Besides, it exhibits a low Tafel slope (81 mV dec⁻¹ for HER, 103 mV dec⁻¹ for OER), high exchange current density (1.51 mA cm⁻² for HER, 0.26 mA cm⁻² for OER), and remarkable long-term cycle stability. This work provides new perspective for further the development of highly effective non-noble-metal materials in the energy field.     

Porous NiFe alloys synthesized via freeze casting as bifunctional electrocatalysts for oxygen and hydrogen evolution reaction

Binder-free NiFe-based electrocatalyst with aligned pore channels has been prepared by freeze casting and served as a bifunctional catalytic electrode for oxygen and hydrogen evolution reaction (OER and HER). The synergistic effects between Ni and Fe result in the high electrocatalytic performance of porous NiFe electrodes. In 1.0 M KOH, porous Ni₇Fe₃ attains 100 mA cm⁻² at an overpotential of 388 mV with a Tafel slope of 35.8 mV dec⁻¹ for OER, and porous Ni₉Fe₁ exhibits a low overpotential of 347 mV at 100 mA cm⁻² with a Tafel slope of 121.0 mV dec⁻¹ for HER. The Ni₉Fe₁//Ni₉Fe₁ requires a low cell voltage of 1.69 V to deliver 10 mA cm⁻² current density for overall water splitting. The excellent durability at a high current density of porous NiFe electrodes has been confirmed during OER, HER and overall water splitting. The fine electrocatalytic performances of the porous NiFe-based electrodes owing to the three-dimensionally well-connected scaffolds, aligned pore channels, and bimetallic synergy, offering excellent charge/ion transfer efficiency and sizeable active surface area. Freeze casting can be applied to design and synthesize various three-dimensionally porous non-precious metal-based electrocatalysts with controllable multiphase for energy conversion and storage.     

Efficient overall water splitting using nickel boride-based electrocatalysts

Currently there is tremendous interest in the discovery of low cost and efficient electrocatalysts for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). In this work, iron-doped nickel boride (Fe_xNi_1-xB) and nickel boride (NiB) were successfully grown on 3D self-supporting graphene (SSG) electrodes via a one-step reduction approach. The Fe_0.2Ni_0.8B/SSG electrode required a very low overpotential of only 263 mV for OER (the best OER activity achieved to date for a metal boride). NiB/SSG showed modest OER performance but excellent HER activity. A water electrolyzer comprising Fe_0.2Ni_0.8B/SSG and NiB/SSG delivered a current density of 10 mA cm⁻² at a voltage of only 1.62 V. Further, the Fe_0.2Ni_0.8B/SSG and NiB/SSG catalysts showed excellent stability with no deactivation observed over 14 h of testing. Results demonstrate that nickel boride-based electrocatalysts are promising lost cost alternatives to precious metal-based electrocatalysts for OER, HER and overall water splitting.     

First insight on Mo(II) as electrocatalytically active species for oxygen evolution reaction

The replacement of noble metals with earth-abundant metals is still a big challenge for the practical application of electrocatalysis. In this work, we have developed the Mo_xC-modified alloy@nitrogen-doped carbon hybrid electrocatalysts (Mo_xC-alloy@NC, alloy: FeCo, NiCo) for oxygen evolution reaction (OER) by a simple thermolysis method. Compared with FeCo@NC and NiCo@NC, the OER performances of Mo_xC-FeCo@NC and MoC-NiCo@NC are greatly enhanced, mainly due to the improved electrical conductivity by the introduce of Mo_xC. Moreover, Mo_xC-FeCo@NC exhibits a smaller Tafel slope (80 mV/dec) and a lower overpotential (318 mV) at 10 mA cm⁻² in 1 M KOH solution, compared with MoC-NiCo@NC (186 mV/dec, 352 mV). In consideration of a lower BET area (6.6 m² g⁻¹) of Mo_xC-FeCo@NC than those of MoC-NiCo@NC (25.4 m² g⁻²), the remarkable electrocatalytic activity of Mo_xC-FeCo@NC is mainly attributed to the presence of Mo(II) acting as the OER active species. Although Mo as hydrogen evolution reaction (HER) active species is well known, Mo(II) as the OER active species has not been reported before.     

Core-shell Ni3Fe-based nanocomposites for the oxygen evolution reaction

To deal with energy and environmental issues, it is necessary to exploit efficient and stable electrocatalysts for the generation of clean hydrogen. Herein, we describe the synthesis of bimetallic Fe/Ni alloy encapsulated by amorphous carbon shells via a facile annealing strategy for electrocatalytic oxygen evolution reaction (OER). The ferric nickel tartrate annealed at 800 °C (Ni₃Fe₁O_x@C-800) exhibits a low OER overpotential of 264 mV at 10 mA cm^?2 and good stability in alkaline media. Compared with monometallic counterpart, bimetallic Ni₃Fe-based nanocomposites show lower OER barrier (ca. 324 kJ mol^?1) due to a cooperation mechanism between Ni and Fe sites in promoting electrocatalytic water oxidation. Compared with those annealed at other temperatures, the enhanced OER performance of Ni₃Fe₁O_x@C-800 can be ascribed to the large electrochemical surface area for exposing more active sites, smaller charge transfer, and better intrinsic activity of Ni₃Fe-based sites.     

Nanorod-like NiFe metal-organic frameworks for oxygen evolution in alkaline seawater media

Searching for highly active and durable oxygen evolution reaction (OER) electrocatalysts is the key to break through the bottleneck of overall water splitting. Here, we prepare Ni_xFe-BDC (H₂BDC = terephthalic acid) nanorods with different Ni/Fe ratios by a facile solvothermal method for the OER. The optimal Ni₃Fe-BDC exhibits a low overpotential (η₁₀) of 265 mV and a Tafel slope of 90 mV·dec⁻¹ in 1 M KOH. Moreover, it shows a low η₁₀ of 280 mV and excellent stability in the mixture of 1 M NaCl and 1 M KOH, which has strong corrosion resistance to Cl⁻ anions. The role of Fe³⁺ not only increases the charge transfer rate of Ni₃Fe-BDC, but also affects the specific surface area of the catalyst with high electrochemical activity. Kinetic studies show that both Fe and Ni sites act as active centers, which catalyze synergistically to reduce the reaction kinetic energy barrier. Characterization results of the used Ni₃Fe-BDC reveal that the in situ formed rod-like Ni₃FeOOH is the active site for the OER.     

Pomegranate-like Ni-doped cobalt boride implanted in B,N-doped carbon nanocages for enhanced electrochemical oxygen evolution

The development of efficient and stable transition metal boride electrocatalysts for oxygen evolution reaction (OER) is critical for energy conversion and environmental protection. Herein, we synthesized B, N-doped carbon layer encapsulated the Ni-doped Co_xB nanocages electrocatalyst (denoted as Ni-Co_xB@BNC) via a high-temperature boronizing, derived from Ni-doped cobalt-based zeolite imidazole frame (NiCo-ZIF), toward enhanced electrochemical alkaline oxygen evolution reaction. The Ni-Co_xB@BNC electrocatalyst synthesized at 550 °C exhibits excellent OER activity with a low overpotential of 274 mV and a Tafel slope of 80 mV dec⁻¹ at a current density of 10 mA cm⁻², which is better than precious metal RuO₂. The synergistic effect between B, N-doped carbon layer and Ni-doped Co_xB in Ni-Co_xB@BNC leads to higher OER catalytic activity. The B, N-doped carbon layer provides additional active sites, which accelerates charge transport and enhances the conductivity of Ni-Co_xB@BNC during OER. In addition, it also protects the pomegranate seed-like Ni-Co_xB nanoparticles inside, improving the stability of the Ni-Co_xB@BNC material. This work unambiguously elucidates the design and preparation strategy of transition metal boride implanted B, N-doped carbon nanocage electrocatalysts derived from controlled bimetallic ZIF precursor.     

Partially crystallized Ni–Fe oxyhydroxides promotes oxygen evolution

The slow oxygen evolution reaction (OER) kinetics influences hydrogen production efficiency from water splitting. To break through the bottleneck of water splitting, it is urgent to develop efficient and economic electrocatalysts. Although NiFe-based catalysts exhibit outstanding OER activity, the complicated preparation process limits their large-scale synthesis and applications. Here, partially crystallized nickel-iron oxyhydroxides are synthesized by a facile sol-gel method. When the Fe/Ni mole ratio is 0.5:1, the NiFe_0.5(OH)_x catalyst shows superior OER performance with a low OER overpotential of 265 mV and good durability. Kinetic studies show that the energy barrier of NiFe_0.5(OH)_x is only 31.5 kJ mol^?1, much smaller than those of Ni(OH)_x (41.0 kJ mol^?1) and Fe(OH)_x (44.8 kJ mol^?1). The synergistic action between Ni and Fe sites not only facilitates mass and charge transfer, but also promotes the formation of 1OOH intermediate for the OER.     

The effect of Fe on chemical stability and oxygen evolution performance of high surface area SrTix-1FexO3-δ mixed ionic-electronic conductors in alkaline media

Development of environmentally friendly, high performing oxygen evolution reaction (OER) catalysts is an important research challenge. In this work, iron doped strontium titanates with a general formula SrTi_1-xFe_xO_3-δ (x = 0.35, 0.50, 0.70, 0.90, and 1.00) denoted as STFx, were synthesized via a solid state reaction technique and characterized in terms of oxygen evolution reaction electrocatalysis in an alkaline electrolyte (0.1 M KOH). The produced powders were characterized by a high specific surface area (>20 m² g⁻¹), beneficial for OER. The evaluation of specific activity indicated the following trend of increasing performance: STF35 < STF50 < STF70 < SFO < STF90. The lowest overpotential at 10 mAcm⁻² _GEO of 410 mV (350 mV at 25 μA cm⁻²_OX) was achieved by STF90 with the corresponding Tafel slope of 60 mV dec⁻¹. The two materials with the highest Fe content (i.e. STF90 and SFO) showed, however, poor chemical stability in alkaline solution demonstrated by the dissolution of Sr. Based on the good electrochemical performance (~460 mV at 10 mA cm⁻²_GEO, ~405 mV at 25 μA cm⁻²_OX) and chemical stability for at least 30 days (no Sr dissolution) of STF50, it can be considered an interesting, working at room temperature OER catalyst based on non-toxic and abundant elements.     

Tunable Fe/N co-doped 3D porous graphene with high density Fe-Nx sites as the efficient bifunctional oxygen electrocatalyst for Zn-air batteries

Nitrogen-doped transition metal materials display promising potential as bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, Fe/N co-doped three-dimensional (3D) porous graphene (FeN-3D-PG) is prepared via a template method using sodium alginate as the carbon source and low polymerization degree melamine resin as the nitrogen source. The low polymerization degree melamine resin can form complexes with Fe³⁺ in the aqueous solution and further forms high density Fe-N_x active sites during pyrolysis. Meanwhile, the formed 3D porous structure efficiently promotes the uniform distribution of Fe-N_x active sites. The FeN-3D-PG catalyst exhibits pH-independent ORR activity. For OER, the catalyst possesses a low over potential (370 mV at 10 mA cm⁻²) in alkaline electrolyte. The Zn-air batteries (ZABs) using FeN-3D-PG as cathode exhibits a power density up to 212 mW cm⁻², a high specific capacity of 651 mAh g⁻¹, and the charge-discharge stability of 80 h. This work provides new sight to transition metal materials based ZABs with excellent performance.     

Investigation of the electrocatalytic performance for oxygen evolution reaction of Fe-doped lanthanum nickelate deposited on pyrolytic graphite sheets

Perovskite-type metal oxides have emerged as important materials in renewable energy because the high electrocatalytic performance for oxygen evolution reaction (OER). Hence, we perform a study on the electrocatalytic properties of LaNi_1-xFe_xO₃ (x = 0.0, 0.3, 0.6, and 0.9 mol%) for OER, mainly analyzing the influence provoked by the incorporation of Fe³⁺ in the lattice as well as the use of pyrolytic graphite sheet (PGS) as a potential substrate for electrocatalysis. These perovskites were synthesized by the co-precipitation method. The thin film electrodes were prepared depositing the obtained powders on PGS substrates via drop-casting. Depending on the Fe³⁺ level, structural changes and morphological modifications were identified for these materials. The highest electrocatalytic activity for OER was detected for LaNi_0.4Fe_0.6O₃. Besides the low charge transfer resistance, LaNi_0.4Fe_0.6O₃ exhibited a lower overpotential (439 mV) and a smaller Tafel slope (52 mV dec⁻¹) than the LaNiO₃ (465 mV and 76 mV dec⁻¹).     

Fe doped metal organic framework (Ni)/carbon black nanosheet as highly active electrocatalyst for oxygen evolution reaction

To alleviate the sluggish oxygen evolution reaction (OER) kinetics, it's urgent to develop electrocatalysts with high activity and low cost. In this work, Fe doped metal organic frameworks (Ni)/carbon black composites were synthesized via a facile hydrothermal method. Benefiting from the direct use of metal organic frameworks (MOFs) for OER, numerous and highly dispersed active sites are exposed to the electrolyte and reactants. By regulating Ni/Fe ratios, a high electrochemical active surface area (ECSA) and high relative surface content of active Ni³⁺ species are obtained, which mainly contribute to the high OER activity. Besides, the introduced carbon black (CB) was found to enhance the charge-transfer efficiency of the electrocatalysts, which is also favorable for OER. The optimal Ni9Fe1-BDC-0.15CB electrocatalyst shows excellent OER activity with the low overpotential of ~290 mV at 10 mA cm⁻² and the Tafel slope of ~76.1 mV dec⁻¹, which is comparable to RuO₂ and other MOFs-based OER electrocatalysts reported in recent years.     

The 3D ultra-thin Cu1-xNixS/NF nanosheet as a highly efficient and stable electrocatalyst for overall water splitting

In recent years, the exploration of efficient and stable noble-metal-free electrocatalysts is becoming increasingly important, used mainly for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). In this work, a new ultrathin porous Cu_1-xNi_xS/NF nanosheets array was constructed on the 3D nickel skeleton by two-step method: hydrothermal method and vulcanization method. Through these two processes, Cu_1-xNi_xS/NF has a larger specific surface area than that of foamed nickel (NF) and Cu_1-xNi_xO/NF. The Cu_1-xNi_xS/NF materials show excellent catalytic activity by accelerating the electron transfer rate and increase the amount of H₂ and O₂ produced. The lower overpotential was obtained only 350 mV at 20 mA cm⁻² for OER, not only that, but also the same phenomenon is pointed out in HER, optimal Cu_1-xNi_xS/NF presents low overpotentials of 189 mV to reach a current density of 10 mA cm⁻² in 1.0 M KOH for HER. Both OER and HER shows a lower Tafel slope: 51.2 mV dec⁻¹ and 127.2 mV dec⁻¹, subsequently, the overall water splitting activity of Cu_1-xNi_xS/NF was investigated, and the low cell voltage was 1.64 V (current density 10 mA cm⁻²). It can be stable for 14 h during the overall water splitting reaction. These results fully demonstrate that Cu_1-xNi_xS/NF non-precious metal materials can be invoked become one of the effective catalysts for overall water splitting, providing a richer resource for energy storage.     

In situ construction of heterostructure NiSe–NiO nanoarrays with rich oxygen vacancy on MXene for efficient oxygen evolution

Developing high-efficiency, non-noble, earth-available electrocatalysts for the oxygen evolution reaction (OER) is vital for electrochemical energy conversion, but it is still challenging. Herein, we ingeniously designed a partial selenization method to construct NiSe–NiO heterostructure grown in situ on Ta₄C₃T_x MXene (denoted as NiSe–NiO/Ta₄C₃T_x MXene). NiSe–NiO/Ta₄C₃T_x MXene's plethora of heterointerfaces provides a wealth of active sites, fast charge and mass transfer, and favorable adsorption energies for OER intermediates, all of which contribute synergistically to the oxidation of alkaline water. As expected, taking advantage of the strong chemical and electron synergistic effects of NiSe and NiO, the synthesized NiSe–NiO/Ta₄C₃T_x MXene exhibits excellent activity for OER with a low overpotential of 255 mV at 10 mA cm⁻², a small Tafel slope of 47.4 mV dec⁻¹, as well as excellent long-term stability, exceeding that of its competitors. This study offers a novel synthetic route toward developing high-performance OER electrocatalysts for renewable energy conversion/storage systems and beyond by optimizing the catalysts' composition and architecture.     

High-performance bifunctional Fe-doped molybdenum oxide-based electrocatalysts with in situ grown epitaxial heterojunctions for overall water splitting

The design and development of low-cost, abundant reserves, high catalytic activity and durability bifunctional electrocatalysts for water splitting are of great significance. Here, simple hydrothermal and hydrogen reduction methods were used to fabricate a uniform distribution of Fe-doped MoO₂/MoO₃ sheets with abundant oxygen vacancies and heterojunctions on etched nickel foam (ENF). The Fe– MoO₂/MoO₃/ENF exhibited a small overpotential of 36 mV at 10 mA cm⁻² for hydrogen evolution reaction (HER), an excellent oxygen evolution reaction (OER) overpotential of 310 mV at 100 mA cm⁻² and outstanding stabilities of 95 h and 120 h for the HER and OER, respectively. As both cathode and anode catalysts, the heterogeneously structured Fe– MoO₂/MoO₃/ENF required a low cell voltage of 1.57 V at 10 mA cm⁻². Density functional theory (DFT) calculations show that Fe doping and MoO₂/MoO₃ heterojunctions can significantly reduce the band gap of the electrode, accelerate electron transport and reduce the potential barrier for water splitting. This work provides a new approach for designing metal ion doping and heterostructure formation that may be adapted to transition metal oxides for water splitting.     

Bifunctional electrocatalysts for water splitting from a bimetallic (V doped-NixFey) Metal–Organic framework MOF@Graphene oxide composite

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 H₂SO₄ 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_xFe_y-MOF/GO electrocatalyst. Besides, the water electrolyzed products were analysed by gas chromatography to get clear insights on the formed H₂ and O₂ products.     

Enriched oxygen vacancy promoted heteroatoms (B,P, N,and S) doped CeO2: Challenging electrocatalysts for oxygen evolution reaction (OER) in alkaline medium

Increasing worldwide energy consumption has prompted considerable study into energy generation and energy storage systems in recent years. Chemical fuels may be produced efficiently via electrocatalytic water splitting, which uses electric and solar power. The development of efficient anodic electrocatalysts for efficient oxygen evolution reaction (OER) is a greater concern of present energy research. Cerium oxide (CeO₂) are promising electrocatalysts that exhibit outstanding OER but their reduced stability obstructs the practical application. A novel strategy was established to construct an effective catalyst of heteroatom (N, B, P and S) doped CeO₂ matrix were prepared. Moreover, the doping of heteroatoms into the CeO₂ matrix processes the improved electronic conductivity, reactive sites, increases the electrochemical catalytic activity, which enhances the water oxidation reaction. Consequently, well-suited alkaline electrolysers were brought together for water oxidation to ideal OER electrocatalytic activity. The OER activity of the electrocatalysts follows the order of S–CeO₂ (190 mV@10 mA cm⁻²), N– CeO₂ (220 mV @10 mA cm⁻²), P– CeO₂ (230 mV @10 mA cm⁻²), B–CeO₂ (250 mV @10 mA cm⁻²) and CeO₂ (260 mV @10 mA cm⁻²) in 1 M of KOH. From the kinetics analysis, Tafel slope value achieved for catalysts CeO₂, B–CeO_2, P–CeO₂, N–CeO₂ and S–CeO₂ are 142 mV dec⁻¹,121 mV dec⁻¹, 102 mV dec⁻¹, 98 mV dec⁻¹ and 83 mV dec⁻¹ respectively. These results validate that the S–CeO₂ electrode is prominent for OER performance with the requirement of cell voltage of 1.42 V at 10 mA cm⁻² current density. In addition, sulphur doped CeO₂ relatively have excellent stability through chrono-potentiometric analysis lasting for 20 h. Although the heteroatoms doped CeO₂ is acts as anode material, the preparation method is widespread, which will reduce the synthesis cost and streamline the preparation of electrode for OER. This research effort delivers a complete advantage for the development of robust, environmentally friendly and highly dynamic electrocatalysts for OER activity.     

Electrodeposition of Ni–Fe–Mn ternary nanosheets as affordable and efficient electrocatalyst for both hydrogen and oxygen evolution reactions

The synthesis of high performance and economical electrocatalysts in the process of overall water splitting is very important for the production of hydrogen energy and has become one of the most important challenges. Here, various Ni, Ni–Fe, Ni–Mn nanosheets and Ni–Fe–Mn ternary nanosheets were created using cost-effective, versatile and binder-free electrochemical deposition methods, and the electrocatalytic activity of various electrodes for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were investigated in an alkaline environment. Due to the high electrochemical active surface area due to the fabrication of nanosheets, the synergistic effect between different elements on the electronic structure, the high wettability due to the formation of nanosheets and the quick detachment of formed gasses from the electrode, the Ni–Fe–Mn nanosheets electrode showed excellent electrocatalytic activity. In order to deliver the 10 mA cm⁻² current density in HER and OER processes, this electrode required values of 64 mV and 230 mV overpotential, respectively. Also, the stability test showed that after 10 h of electrolysis at a current density of 100 mA cm⁻², the overpotential changes was very small (less than 4%), indicating that the electrode was excellent electrostatic stability. Also, when using as a bi-functional electrode in the full water splitting system, it only needed a cell voltage of 1528 V to deliver a current of 10 mA cm⁻². The results of this study indicate a new strategy for the synthesis of active and stable electrocatalysts.     

Local electronic structure modulation of NiVP@NiFeV-LDH electrode for high-efficiency oxygen evolution reaction

The emergence of alternative sustainable energy technologies has stimulated the utilisation of high-efficiency, cost-effective electrodes for renewable energy conversion. The oxygen evolution reaction (OER) is critical for water splitting and rechargeable metal-air batteries. However, the identification of efficient and robust non-noble-metal-based OER electrocatalysts remains a major hurdle for large-scale hydrogen production. Herein, NiVP@NiFeV-LDH heterojunction catalysts were constructed by phosphidation and hydrothermal processing, because OER activity can be improved by coupling NiVP and NiFeV-LDH. NiVP@NiFeV-LDH/NF exhibited remarkable OER performance with an ultralow overpotential of 317 mV at a current density of 100 mA cm⁻² and a Tafel slope of 83.0 mV dec⁻¹ in an alkaline environment. The high efficiency of NiVP@NiFeV-LDH/NF is attributed to increased mass and electron transport because of array structure formation and interfacial electronic structure optimisation, respectively. This work provides a novel approach for augmenting the OER performance of non-noble-metal-based electrocatalysts for energy conversion applications.