Bifunctional Electrocatalysts For Water Splitting Research Articles

Self-supporting trace Pt-decorated ternary metal phosphide as efficient bifunctional electrocatalyst for water splitting

Compared to monofunctional catalysts, the preparation of bifunctional materials with HER and OER activities holds greater significance for the separation of hydrogen from water electrolysis. In this study, we synthesized a self-supported bifunctional catalyst using ternary transition metal (Ni, Fe, Co) phosphide adorned with trace Pt for water splitting (P-Fe6Co3Ni/Pt/NF). As the main catalytic kernel toward HER, the Pt nanoparticles underwent uniform in situ reduction on the Ni foam, avoiding clustering due to the protective effect of iron and cobalt phosphides. This exposed more active sites, improving HER kinetics. In the OER process, the deposited Fe and Co were confirmed to play a pivotal role and will undergo oxidation to oxyhydroxides during structural reconstruction. In addition to enhancing conductivity, the Mott-Schottky test revealed that Pt can facilitate the formation of more active sites, leading to a lower potential for the OER reaction. Ultimately, P-Fe6Co3Ni/Pt/NF required only an overpotential of 32.8mV in HER to reach the current density of 10mAcm-2, demonstrating excellent OER activity with a low overpotential of 259.9mV at current density of 20mAcm-2. When employed as cathode and anode in water electrolysis, P-Fe6Co3Ni/Pt/NF necessitated only 1.6V cell voltage to achieve the current density of 10mAcm-2. This study provides a reference for designing other highly efficient Pt-based electrocatalyst, thereby promoting the widespread application of water electrolysis in hydrogen production.

Enhanced Electrocatalytic Capacity of Two POM@NH2‐MIL‐101(Fe) Composites for Oxygen Evolution Reaction

AbstractThe development and exploration of efficient bifunctional electrocatalysts for water splitting are in high demand and have garnered significant attention in recent years. Herein, by incorporating the advantages of catalytically active polyoxometalates (POMs) and structural stable metal–organic frameworks (MOFs), two POM@MOFs composite materials, Ni4Mo12@Fe and Co4Mo12@Fe, have been successfully prepared via the encapsulation of POMs anions, [MoV12O30(μ2‐OH)10H2{NiII4(H2O)12}]∙14H2O (noted as Ni4Mo12) and [MoV12O30(μ2‐OH)10 H2{CoII(H2O)3}4]∙12H2O (noted as Co4Mo12), into the cavities of MOFs NH2‐MIL‐101(Fe), respectively. Compared to each individual components, Ni4Mo12@Fe and Co4Mo12@Fe composites, as heterogeneous electrocatalysts, both showed enhanced electrocatalytic capacities for efficient oxygen evolution reaction (OER) under alkaline conditions with overpotentials of 332.64 mV for Ni4Mo12@Fe and 352.64 mV for Co4Mo12@Fe at 10 mA cm−2. Additionally, the enhanced electrocatalytic capacities of these two composites could also achieve towards hydrogen evolution reaction (HER). Such a POMs‐assisted strategy for the formation of POM@MOFs composites, described here, paves a new avenue for the development of highly economical, active nonnoble metal bifunctional electrocatalysts for OER and HER.

Chemical coupling engineered exceptional overall water splitting of autogenic NiS/FeS/NiFeOOH heterostructure

The commercial application of hydrogen production is heavily subjected to the expensive and complex fabrication of required bifunctional catalysts integrated with good oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) activity. Herein, a simple one-spot hydrothermal technique is advocated to simplify the synthesis of NiS/FeS/NiFeOOH heterostructure (denoted as NiFeS) and achieve exceptional bifunctional electrocatalyst for water splitting. Such NiFeS heterostructure reveals multi-synergistic heterointerfaces with chemical coupling to provide more accessible active sites, regulate electronic structure of the active center and enhance interfacial charge transfer, enabling a significant contribution in improving the catalysis. Therefore, the OER overpotential of NiFeS catalyst is only 249 mV to supply 100 mA cm−2 current density, and the overpotential for HER reaches to 153 mV at 10 mA cm−2. When constructed into a lab-made electrode system, it confirms a remarkable cell voltage of only 1.51 V at 10 mA cm−2 for water splitting, along with an exceptional durability up to 100 h at 100 mA cm−2. This study gives a novel insight into heterostructure engineering for the construction of bifunctional electrocatalysts.

NiP/Fe3P/MoP@NF nanoblocks as a bifunctional electrocatalyst for water splitting in alkaline seawater and urea solution

Compared with conventional electrolytic fresh water for hydrogen generation, electrolytic seawater for hydrogen production is more cost-effective, because seawater resources are rich, and fresh water resources are short. However, there are many impurity ions in seawater, especially chloride ions, which have great corrosion on the catalyst, so it is a major factor restricting the development of electrolytic seawater. In this study, a novel NiP/Fe3P/MoP@NF catalyst was made via conventional hydrothermal and phosphating method. Experimental results show that the overpotential of NiP/Fe3P/MoP@NF catalyst in the current density of 10 mA cm−2 is just 40 mV for hydrogen evolution reaction (HER) and the overpotential of NiP/Fe3P/MoP@NF catalyst in the same condition is 135 mV for oxygen evolution reaction (OER) in 1 M KOH and seawater solution. In electrolyte solution of 0.5 M urea and 1 M KOH, the overpotential of NiP/Fe3P/MoP@NF catalyst in the same current density of 10 mA cm−2 is 51 mV for HER. Furthermore, the whole alkaline seawater splitting requires an applied voltage of 1.66 V at current density of 10 mA cm−2. Experimental results show that the increased catalytic activity is assigned to the rapid electron transport rate, the exposure of more activity sites, and their synergistic catalysis. The density functional theory (DFT) can show that MoP has the best Gibbs free energy for hydrogen and electrical conductivity compared with NiP and Fe3P, thus enhancing the catalytic performance of NiP/Fe3P/MoP@NF. The paper proposes novel ideas concerning the exploration of catalysts in alkaline seawater and urea solution.

MOFs-derived 3D hierarchical CoFe2O4/RuO2 hollow nanosheet array for efficient overall water splitting

Accelerating hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics process is crucial to the development of transition metal oxide based materials as bifunctional catalysts for overall water splitting. Herein, a heterostructured CoFe2O4/RuO2 hollow hierarchical nanosheet array (FeRu-CoOx) has been designed by using MOF as template followed by simultaneous etching-doping process combined with calcination for enhanced HER performance without compromise of OER activity. The MOF-derived FeRu-CoOx exhibits an enhancement on HER performance with 58 mV overpotential to achieve 10 mA cm-2 and a small Tafel slop of 73.1 mV dec-1 in the alkaline solution, compared to CoFe2O4 counterpart (Fe-CoOx) using monometallic Fe etching and doping. In addition, the FeRu-CoOx electrode also shows good OER activity (10 mA cm-2 at an overpotential of 229 mV), better than those of Fe-CoOx (239 mV) and commercial RuO2 electrodes (270 mV). The introduction of Ru helps the construction of heterostructure, which is in favor of exposure of active sites, increasing the electron interaction between different composites, and accelerating charge transfer. The alkali electrolyzer using FeRu-CoOx as cathode and anode shows a small cell voltage with only 1.48 V at 10 mA cm-2 and good tolerance toward long-term stability. The MOF template combined with etching-doping strategy to construct hierarchical and heterostructured materials gives a way to develop advanced bifunctional electrocatalysts for water splitting.

Bifunctional Noble-Metal Free Ternary Chalcogenide Electrocatalysts for Water Splitting

With the ever-increasing global energy demand, the development of renewable energy technologies is crucial to fulfilling the energy requirements in a sustainable manner. Hydrogen has emerged as a promising energy carrier that can provide emission-free energy for end-use applications. Among the several pathways of hydrogen production, green hydrogen production by electrochemical water splitting using renewable energy is an emission-free, efficient energy conversion technology. Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) occur at the cathode and anode, respectively. Water splits into hydrogen and oxygen at the thermodynamic potential of 1.23 V; however, overpotentials are observed experimentally due to the kinetic barriers, which increases the required potential for water splitting. Catalysts lower the required overpotentials, making the process more energy efficient. A significant issue with large-scale hydrogen production by water electrolysis is that the state-of-the-art catalysts for HER and OER are based on precious metals and thus are limited by their high cost and net production capacity. Thus, there is a lot of interest in developing noble-metal-free electrocatalysts based on earth-abundant materials that can efficiently lower the associated overpotentials for the two halves of the water-splitting reaction.A large number of late transition metal-based ternary complex oxides have been investigated for their catalytic performance towards water splitting, where fine-tuning of the properties using compositional engineering has been demonstrated. Binary sulfides, selenides, and phosphides have also been explored as candidates for water splitting. Recently, early transition metal-based ternary complex materials have emerged as a novel class of electronic materials with applications in infrared optics and photovoltaics. However, similar chalcogenide compositions based on late-transition metals remain underexplored.We have synthesized a series of LaMS3 (M = Mn, Fe, Co, Ni) materials by high-temperature sulfurization of corresponding ternary oxides, using carbon disulfide (CS2) as the sulfurizing agent. The LaMS3 compounds are isostructural and crystallize in the hexagonal P 63 space group. When tested for catalytic performance towards water splitting, they demonstrate good activity towards both HER and OER, with LaNiS3 (LNS) being the most active material, and a periodic activity trend is observed, where LNS > LCS >> LFS > LMS. For OER in alkaline electrolyte, LNS demonstrates an overpotential of 373 mV at 10mA/cm2 in 1.0 M KOH, and a low Tafel slope value of 48 mV/dec. The long-term stability was tested using chronopotentiometry measurements, and LNS shows excellent stability, with negligible change in overpotential over several hours. For HER testing in both acidic and alkaline electrolyte, LNS again seems to be the most active material, and a periodic activity trend in the HER activity of LaMS3 materials, similar to the OER activity trend, is observed. LNS has an overpotential of 340 mV in 0.5 M H2SO4 and 362 mV in 1.0 M KOH, indicating that LNS is catalytically active over a wide range of pH levels. LNS also shows excellent long-term stability towards HER in both acidic and alkaline electrolyte. We also compared the activity of LaMS3 materials with their ternary oxide counterparts from which they were synthesized, and the LaMS3 compounds outperform the LaMO3 compounds, demonstrating lower overpotentials and Tafel slope values for both HER and OER, with the HER overpotentials for LaMO3 materials being > 250 mV higher compared to LaMS3, for both acidic and alkaline electrolytes. The catalytic activity of the LaMS3 series towards both HER and OER, along with their excellent long-term stability, makes these materials promising candidates for bifunctional electrocatalysts for water splitting while offering a wide compositional range that allows for further optimization of their performance.

Highly Durable Compositionally Variant Bifunctional Tetrametallic Ni–Co–Mn–Fe Phosphide Electrocatalysts Synthesized by a Facile Electrodeposition Method for High-Performance Overall Water Splitting

In the recent few decades, the demand for green sources of energy that are clean and sustainable became very essential to reduce the greenhouse and global warming problems. Consequently, there is an increasing demand to identify nonprecious, cheap bifunctional electrocatalysts for water splitting. Herein, nanosheets of different earth-abundant Ni, Co, Mn, and Fe combinations are electrodeposited over commercial Ti mesh and tested for the overall water splitting. The bare Ti mesh requires overpotentials of −486.6 mV at −10 mA cm–2 and 534.5 mV at 10 mA cm–2 for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. However, the electrodeposited catalysts show much higher catalytic activity for both HER and OER with overpotentials of −300 and 279 mV at −10 and 10 mA cm–2, respectively, lowering the overpotential needed to drive the OER by 50%. Nevertheless, to enhance the electrocatalytic performance of the fabricated catalysts, they are phosphidized using different phosphorous precursors. The resulted NiCoMnFe–P catalysts exhibit much lower HER overpotential (−200 mV at −10 mA cm–2), which is 40% lower than that needed by the bare Ti mesh. For the overall water splitting, a cell voltage of 1.71 V is recorded to achieve a current density of 10 mA cm–2. Lastly, the stability test of the overall device reveals very high stability with current retention of 90% over 22 h of continuous electrolysis. Furthermore, the synergy between the metallic components in the absence and presence of P is elucidated using density functional theory calculations, revealing optimized G H* and G H2O* for the HER reaction over the P-top site of the MnFeCoNiP catalyst. In addition, the calculations explain the superiority of the NiCoMnFe catalyst over the NiCoMnFeP counterpart for the OER.

Electronic modulation of MOF-derived CoxMnyB nanosheet arrays toward efficient bifunctional electrocatalysts for water splitting

The design of robust and efficient bifunctional electrocatalysts for total water splitting is of paramount importance for the advancement of sustainable energy conversion technologies. To fully exploit the electrocatalytic capabilities of transition metal borides, we integrate manganese-incorporated cobalt boride (CoxMnyB) nanoarrays derived from metal-organic frameworks (MOFs). CoxMnyB nanosheet arrays exhibit pronounced electronic modulation, indicating superior electrochemical behavior. CoxMnyB can served as a binder-free catalytic electrode, which exhibits bifunctional electrocatalytic activity of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). CoxMnyB demonstrates an overpotential ∼ 277 mV under 10 mA cm−2 and a Tafel slope of 71 mV dec-1 for HER. It also exhibits optimised OER characteristics, with a potential of 1.54 V at a current density of 10 mA cm−2 and the lowest Tafel slope of 62 mV dec-1. CoxMnyB catalysts emerge as promising candidates for bifunctional electrocatalysts in overall water splitting, delivering remarkable and enduring electrocatalytic functionalities. The intricate mechanisms governing the electrocatalytic performance of the CoxMnyB bifunctional catalyst are systematically discussed in relation to nanostructure, conductive behavior, and the covalent bonding nature of metal-metalloid borides. Density functional theory (DFT) calculations reveal a reduced hydrogen binding energy at the catalyst surface and a weakened energy barrier of OOH*. This study suggests a favourable and feasible pathway for deploying metal borides in high-efficiency electrocatalysis and energy storage applications.

Structural investigation of Cr2CTx/NiFe2O4 MXene composite as a bifunctional electrocatalyst for water splitting

The electrocatalytic water splitting offers great potential as an environmentally friendly and sustainable method to produce hydrogen and oxygen, the former serving as a renewable alternative to traditional fossil fuels. MXene, a novel two-dimensional (2D) layered class of materials, has gained enormous attention as an electrocatalyst for water splitting. This versatile material can be tailored to enhance its electroactive surface sites and stability toward electrocatalytic performance. Herein, we have designed a 2D hybrid material, Cr2CTx/NiFe2O4, via an in-situ hydrothermal approach. NiFe2O4 spheres decorated on layered-Cr2CTx are subjected to analysis using XRD, FTIR, TGA, XPS, FESEM, HRTEM-SAED, and optical profilometry. The synthesized hybrid MXene material shows outstanding activity for overall water splitting compared to Cr2CTx and NiFe2O4. Cr2CTx/NiFe2O4 exhibits an overpotential of 144 mV and 159 mV at a current density of 10 mA cm−2 for hydrogen evolution and oxygen evolution reactions, respectively, and achieves a cell potential of 1.69 V for overall water splitting. This study reveals valuable insights on bi-functional 2D hybrid MXene materials for electrocatalytic water splitting.

Enhanced activity of electrodeposited WO3 thin films as bi-functional electrocatalysts for water splitting

The ultimate goal of the hydrogen economy is to develop an efficient and cost-effective electrocatalyst that can accelerate hydrogen synthesis from water without or with little additional energy. This study describes a unique surface modified electrodeposited nano-sized tungsten oxide (WO3) as an intriguing bi-functional electrocatalyst for OER in alkaline and HER in acidic conditions. The nano-WO3 was synthesized hydrothermally and electrodeposited on a fluorinated tin oxide (FTO) electrode. The highly uniform distribution of the WO3@FTO catalyst results in negligible charge transfer resistance, a large electroactive surface area, and increased water-splitting potential. During oxygen evolution reaction (OER), electrodeposited WO3@FTO initiates water splitting at an overpotential (η) of just 240 mV and represents a turnover frequency (TOF) of 0.59 sec−1. These results are comparable to previously reported electrocatalysts. Under an alkaline electrolyte, a current density of 15 mA/cm2 remained constant for several hours, indicating the high stability and durability of the electrodeposited WO3@FTO electrode. The electrode also performed well in hydrogen evolution reactions (HER). A Tafel slope of 46 mV/dec and −28 mV/dec was found for OER and HER, respectively, indicating an enhanced kinetics rate of reaction taking place at the electrode surface. Furthermore, in acidic conditions, the electrode represents a lower HER overpotential of 104 mV. The work provides a significant understanding of electrodeposited WO3@FTO electrodes and their role in electrochemical water splitting.

Sulfurization of bimetallic (Co and Fe) oxide and alloy decorated on multi-walled carbon nanotubes as efficient bifunctional electrocatalyst for water splitting

The advancement in electrocatalysis, particularly in the development of efficient catalysts for hydrogen and oxygen evolution reactions (HER and OER), is crucial for sustainable energy generation through processes like overall water splitting. A notable bifunctional electrocatalyst, CoFe2O4/Co7Fe3, has been engineered to facilitate both OER and HER concurrently, aiming to reduce overpotentials. In the pursuit of further enhancing catalytic efficiency, a morphological transformation has been achieved by introducing a sulphur source and multi-walled carbon nanotubes (MWCNTs) into the catalyst system, resulting in S–CoFe2O4/Co7Fe3/MWCNTs. This modification has significantly improved the activity for both OER and HER. An onset overpotential of 250 mV@10 mAcm−2 for the OER and 270 mV@50 mAcm−2 for the HER, indicating efficient catalytic activity at relatively low overpotentials. S–CoFe2O4/Co7Fe3/MWCNTs display an outstanding long-term stability in alkaline electrolytes, with minimal Tafel slopes of 77 mV/dec for the OER and 70 mV/dec for the HER, suggesting sustained catalytic performance over extended periods. Furthermore, when employed as both the cathode and anode in the context of complete water splitting, S–CoFe2O4/Co7Fe3/MWCNTs demonstrate an impressive cell voltage of 1.52 V at a current density of 10 mA cm−2 in a 1 M KOH solution, showcasing its viability for practical applications. Given its cost-effectiveness and superior activity, S–CoFe2O4/Co7Fe3/MWCNTs hold significant promise for widespread applications in overall water splitting electrocatalysis, contributing to the advancement of cleaner and sustainable fuel generation technologies.

Shifting the Oxygen-Evolution Reaction Pathway via Cation Engineering to Activate Lattice Oxygen in Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) as promising electrocatalysts have been widely studied, but their performance is limited by conductivity and coordinating saturation. This study proposes a cationic (V) modification strategy and evaluates its effect on the electrocatalytic performance of CoFe-MOF nanosheet arrays. The optimal V-CoFe-MOF/NF electrocatalyst exhibits excellent oxygen-evolution reaction (OER)/hydrogen-evolution reaction (HER) performance (231 mV at 100 mA cm-2/86 mV at 10 mA cm-2) in alkaline conditions, with its OER durability exceeding 400 h without evident degradation. Furthermore, as a bifunctional electrocatalyst for water splitting, a small cell voltage is achieved (1.60 V at 10 mA cm-2). The practicability of the catalyst is further evaluated by membrane electrode assembly (MEA), showing outstanding activity (1.53 V at 10 mA cm-2) and long-term stability (at 300 mA cm-2). Moreover, our results reveal the apparent reconstruction properties of V-CoFe-MOF/NF in alkaline electrolytes, where the partially dissolved V promotes the formation of more active β-MOOH. The mechanism study shows the OER mechanism shifts to a lattice oxygen oxidation mechanism (LOM) after V doping, which directly avoids complex multistep adsorption mechanism and reduces reaction energy. This study provides a cation mediated strategy for designing efficient electrocatalysts.

Electron Manipulation and Surface Reconstruction of Bimetallic Iron-Nickel Phosphide Nanotubes for Enhanced Alkaline Water Electrolysis.

Developing high-efficiency and stable bifunctional electrocatalysts for water splitting remains a great challenge. Herein, NiMoO4 nanowires as sacrificial templates to synthesize Mo-doped NiFe Prussian blue analogs are employed, which can be easily phosphorized to Mo-doped Fe2xNi2(1-x)P nanotubes (Mo-FeNiP NTs). This synthesis method enables the controlled etching of NiMoO4 nanowires that results in a unique hollow nanotube architecture. As a bifunctional catalyst, the Mo-FeNiP NTs present lower overpotential and Tafel slope of 151.3 (232.6) mV at 100 mA cm-2 and 76.2 (64.7) mV dec-1 for HER (OER), respectively. Additionally, it only requires an ultralow cell voltage of 1.47 V to achieve 10 mA cm-2 for overall water splitting and can steadily operate for 200 h at 100 mA cm-2. First-principles calculations demonstrate that Mo doping can effectively adjust the electron redistribution of the Ni hollow sites to optimize the hydrogen adsorption-free energy for HER. Besides, in situ Raman characterization reveals the dissolving of doped Mo can promote a rapid surface reconstruction on Mo-FeNiP NTs to dynamically stable (Fe)Ni-oxyhydroxide layers, serving as the actual active species for OER. The work proposes a rational approach addressed by electron manipulation and surface reconstruction of bimetallic phosphides to regulate both the HER and OER activity.

Transient potential oscillation-driven vertically-aligned cobalt hydroxide nanosheet as non-noble bifunctional electrocatalyst for water splitting

Transient potential oscillation-driven vertically-aligned cobalt hydroxide nanosheet as non-noble bifunctional electrocatalyst for water splitting

Deep eutectic solvent-induced controllable synthesis of bifunctional Ni–Fe–P catalysts for electrochemical water splitting

Developing electrocatalysts with excellent activity, high stability, and low cost is vital for large-scale hydrogen production through electrochemical water splitting. Herein, a bifunctional Ni–Fe–P catalyst in situ grown on Fe foam (Ni–Fe–P/FF) is developed by a simple one-step solvothermal process in the deep eutectic solvent (DES) of ethylene glycol and choline chloride (named Ethaline). The unique solvent environment of Ethaline assisted with the regulating effect of the introduced Fe(III) ions shows an essential role in governing the preparation process. The developed Ni–Fe–P/FF acts as the efficient bifunctional electrocatalyst for water splitting in 1.0 M KOH, requiring overpotentials of 82 mV (229 mV) and 263 mV (370 mV) to deliver 10 mA cm−2 (100 mA cm−2) for oxygen and hydrogen evolution reactions, respectively. Furthermore, the self-supported catalyst-assembled electrolyzer also exhibits good catalytic performance with a low voltage of 1.83 V to drive 100 mA cm−2 and good stability over 100 h. This work offers a facile approach to fabricating high-performance bifunctional Ni–Fe–P electrocatalysts to catalyze water splitting.

Tuning the Activity and Stability of CoCr-LDH by Forming a Heterostructure on Surface-Oxidized Nickel Foam for Enhanced Water-Splitting Performance.

The development of low-cost, efficient catalysts for electrocatalytic water splitting to generate green hydrogen is a hot topic among researchers. Herein, we have developed a highly efficient heterostructure of CoCr-LDH on NiO on nickel foam (NF) for the first time. The preparation strategy follows the simple annealing of a cleaned NF without using any Ni salt precursor, followed by the growth of CoCr-LDH nanosheets over the surface-oxidized NF. The CoCr-LDH/NiO/NF catalyst shows excellent electrocatalytic activity and stability toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in a 1 M KOH solution. For OER, only 253 mV and for HER, only 185 mV overpotentials are required to attain a 50 mA cm-2 current density. Also, the long-term stability of both the OER and HER for 60 h proves its robustness. The turnover frequency value for the OER increased 1.85 times after the heterostructure formation compared to bare CoCr-LDH. The calculated Faradaic efficiency values of 97.4 and 94.75% for the OER and HER revealed the high intrinsic activity of the heterostructure. Moreover, the heterostructure only needs 1.57 V of cell voltage when acting as both the anode and the cathode to achieve a 10 mA cm-2 current density. The long-term stability of 60 h for the total water-splitting process proves its excellent performance. Several systematic pre- and post-experiment characterizations prove its durable nature. These excellent OER and HER activities and stabilities are attributed to the surface-modified electronic structure and thin nanosheet-like surface morphology of the heterostructure. The thin, wide, and modified surface of the catalyst facilitates the diffusion of ions (reactants) and gas molecules (products) at the electrode/electrolyte interface. Furthermore, electron transfer from n-type CoCr-LDH to p-type NiO results in enhanced electronic conductivity. This study demonstates the effective design of a self-supported heterostructure with minimal synthetic steps to generate a bifunctional electrocatalyst for water splitting, contributing to the greater cause of green hydrogen economy.

In situ hierarchical self-assembly of NiFeHCF nanoparticles on nickel foam: highly active and ultra-stable bifunctional electrocatalysts for water splitting and their environmental assessment towards green energy

To obtain high catalytic activity and stability for commercial green hydrogen generation without requiring extra energy, NiFeHCF@NF was synthesized using a unique all-in-one approach.

Zr-doped heterostructure interface to tune the electronic structure of bi-functional electrocatalysts for water splitting

Electrocatalysts for water splitting with earth-abundant materials are proposed to obtain high activity and durability simultaneously by a Zr-doping interface based on physical chemistry and materials science for engineering applications.

Synergistic coupling of reduced graphene oxide with Ni0.85Se for highly active bifunctional electrocatalyst for water splitting

Electrochemical water splitting can provide eco-friendly fuel. Nevertheless, this method requires efficient bifunctional electrocatalysts. In this study, a bifunctional electrocatalyst was synthesized by coating Ni0.85Se and hydrothermally-reduced graphene oxide on nickel foam (NF) using two-step electrodeposition. Moreover, graphene oxide was reduced through hydrothermal means prior to the pulse reverse electrodeposition. As confirmed by FT-IR, hydrothermally and electrochemically reduced graphene oxide on NF (HERGO) reveals a higher reduction degree in comparison to electrochemically-reduced graphene oxide on NF (ERGO). Ni0.85Se covered HERGO through the on-off cathodic pulse electrodeposition. Therefore, excellent electrocatalytic activity was obtained using the synergetic effect of RGO and Ni0.85Se. The ECSA values of 431 and 3500 cm2 were attained through coating HERGO and Ni0.85Se/HERGO on bare NF, respectively. The Ni0.85Se/HERGO revealed Ƞ10 of 67 and 230 mV for HER and OER, respectively. For overall water splitting, the Ni0.85Se/HERGO ǁ Ni0.85Se/HERGO device requaired 1.533 V at 10 mA/cm2.

Economic and binder-free synthesis of NiCo2O4 nanosheets on a Flexible stainless steel mesh as a bifunctional electrode for water splitting

Water as a green source of hydrogen has attracted the attention of researchers considering its potential applications in the energy sector. Thus, developing efficient bifunctional electrocatalysts for water splitting is a potential challenge perceived by researchers exploring the development of sustainable energy technologies. With this motive, the present study focuses on the preparation of the highly active, economic, binder-free, and bifunctional NiCo2O4 nanosheets@ Flexible Stainless Steel Mesh substrate (NCO@FSSM) electrocatalyst via reflux condensation method for the bulk O2 and H2 production. The influence of reflux condensation temperatures (100, 120, 140 °C) on the morphology and electrocatalytic activity is investigated. Electrocatalytic properties for NCO@FSSM synthesized at 120 °C were noted exhibiting smaller overpotentials for oxygen evolution reaction (OER, 310 mV) and hydrogen evolution reaction (HER, 79 mV) at 10 mA cm−2, which were lowest among the previously reported Ni, and Co-based electrodes. Additionally, the scale-up experiments with NCO-120@FSSM film (8 cm X 8 cm) as an anode and FSSM as a cathode and vice-versa, in a specially designed scale-up electrochemical cell revealed steady electrocatalytic performance. The real-time water splitting was studied for 25 h and was noted to produce 7.4 L of (O2) and 11.5 L of hydrogen (H2).