Method For Splitting Research Articles

In-Situ Sulfuration of Ni(OH)2 to Heterostructured Ni3S2/Ni(OH)2@Ni Catalyst for Efficient Water Splitting.

The exploring and developing non-precious transition metal-based catalysts for practical water electrolysis with the low cost, high efficiency and easy macroscopic preparation was still a challenge. Herein, Ni3S2/Ni(OH)2 heterojunction with different sulfuration time was proposed and hydrothermally synthesized using a simple two-step approach, which served as a bifunctional electrocatalyst for water splitting in alkaline solution at industrial temperature. Among these catalysts, Ni3S2/Ni(OH)2-5h displayed the smallest overpotentials (237 mV@100 mA cm-2 and 360 mV@100 mA cm-2) for OER and HER at room temperature, along with low Tafel slopes of 62.0 mV dec-1 and 80.8 mV dec-1 respectively. Furthermore, working at high temperature Ni3S2/Ni(OH)2-5h exhibited even lower overpotential of 82 mV@100 mA cm-2 at 70 °C for OER and 325 mV@100 mA cm-2 at 60 °C for HER. The excellent performance was ascribed to the heterojunction accelerating the charge transfer, hierarchical interconnected structure promoting the mass transfer and the synergistic effect between the components of Ni3S2 and Ni(OH)2. This work could provide a promising route for promoting the electrocatalytic performance of Ni-based catalyst with a simple sulfuration method for industrial water splitting, which could expand to other non-noble metal-based materials for enhancing the electrocatalytic activities.

Self-supported bifunctional porous Ni–Fe-based electrode via one-step reduction method for efficient water splitting

Efficient, inexpensive, and robust bifunctional electrodes are crucial for water splitting. Herein, the three-dimensional hierarchical porous nickel-iron (Ni–Fe)- based monolith is directly fabricated through a one-step reduction approach of their oxide precursors under a hydrogen atmosphere. The Ni–Fe alloy as the active material of water splitting is simultaneously formed during the reduction process and water is the only by-product, which is facile and environmentally friendly. The effects of the reduction temperatures and the Fe contents on the microstructures and composition of the obtained Ni–Fe samples are systematically investigated. The optimized Ni–Fe-based monolith is used as a self-supporting electrode for oxygen evolution reaction, its electro-oxidized derivatives show a low overpotential of 217 mV at 10 mA cm−2 and an ultralow Tafel slope of 31 mV dec−1 in 1 M KOH. Furthermore, the electrolyzer consisting of the bifunctional electrode demonstrates outstanding performance of 1.49 V at 10 mA cm−2 and exceptional long-term stability over 1000 h at 50 mA cm−2, surpassing the majority of alkaline electrolyzers utilizing Ni–Fe-based electrodes.

Surface engineering of CuO-Cu2O heterojunction thin films for improved photoelectrochemical water splitting

The efficient production of green hydrogen poses a significant challenge that requires the development of active, low-cost, and stable catalysts. Copper oxide has emerged as a highly effective photocatalyst for water splitting, offering the advantages of being nontoxic, abundant, and inexpensive. Nonetheless, the photoelectrochemical water splitting (PEC) process can be enhanced through surface modification. In this study, we utilized single-source precursors for aerosol-assisted chemical vapor deposition (AACVD) in order to deposit thin films of copper oxide (CuO-Cu2O) heterojunctions onto a substrate composed of fluorine-doped tin oxide (FTO). The chosen precursor for this purpose was copper (II) nitrate hemi(pentahydrate). To further optimize the CuO-Cu2O films, a novel acid treatment involving the addition of varying quantities of acetic acid (AA) to the precursor solution was employed. Remarkably, this acid treatment resulted in a significant improvement in the photocurrent density of the CuO-Cu2O heterojunction. Notably, a 3 mL acid-treated CuO-Cu2O thin film exhibited an impressive photocurrent measure of −6.8 mA/cm2 at 0.0 V vs RHE in 0.5 M Na2SO4 electrolyte, compared to the performance of the untreated CuO-Cu2O thin film (−2.8 mA/cm2 at 0.0 V vs RHE). This catalyst demonstrated stability and a threefold increase in hydrogen production performance. The increase in photocurrent densities is closely linked to the influence of AA on two key factors: particle growth and structural defects, such as oxygen vacancies. This relationship has been confirmed through the examination of SEM, AFM, and PL spectra results. The findings of this study not only offer a novel approach to catalyst design but also propose a practical method for photoelectrochemical water splitting. This method holds great promise for achieving sustainable and renewable energy sources, as well as efficient green hydrogen production.

Recent advances on hydrogen generation based on inorganic metal oxide nano-catalyst using water electrolysis approach

Abstract Today world is looking for a cheap, environment friendly and efficient substitute of fossil fuel. Because due to large consumption of the fossil fuels on daily basis in whole world, emission of hazardous gases have produced lethal effects on human being. In this scenario hydrogen energy has emerged in form of clean, renewable and more efficient energy. Now the key challenge is that efficient production of the green hydrogen at commercial scale to meet demand of hydrogen. The electrolysis of water is the best pathway to achieve efficient hydrogen production. For this purpose the synthesis and improvement of low cast, active as well as stable catalysts or electrolysis is prerequisite for hydrogen production by electro-catalytic method for splitting of water. Main focus of this review is that, how we can perform the electrolysis of water by various techniques using novel methods especially electro-catalysts in term of activity, efficiency, large surface area, porosity, and stability. This will be performed by the method of two-half cell reaction one is the Hydrogen Evolution Reaction (HER) other one Oxygen Evolution Reaction (OER), where reaction proceeded in both medium acidic as well as alkaline phases. Particular attention is given to produce green clean hydrogen production from usable water and its physical and chemical storages for further uses for the support of human sustainability. Basically the recent strategy is to prepare, design and development of nanoscale materials/composite with non-noble metals and with also nanostructured with noble-metals will be discussed in this approach. The increased efficiency and utility have been the focal points of the use of diverse materials from different classes. To increase the electro-catalytic efficiency in OER and HER, we will discuss about new analyses methods and insights into studying the chemical compositions, shapes, surface area, porosity, and synergy of catalysts and the active sites of nanostructured electro-catalysts. This review will further provide the picture of current state of developments as well as recent progress for mechanized efficient production of clean hydrogen (i.e., HER) from water by electrocatalytic method using various nanoscale materials in a broad scale.

Large-area, flexible bimetallic phosphorus-based electrodes for prolong-stable industrial grade overall seawater splitting

The economical and efficient preparation of highly stable electrodes for hydrogen from water splitting is one of the current challenges. Herein, a flexible and durable bifunctional nickel–cobalt-phosphide electrode is constructed in situ on hydrophilicity filter paper (NiCoP@HP) via a one-step mild electroless plating method for industrial-scale water splitting. The bimetallic synergy of Ni-Co facilitates efficient electron transfer, while the electronegativity of phosphide contributes to high intrinsic activity, and the flexible paper substrate allow the electrode to be folded and bent. The NiCoP@HP electrodes exhibit outstanding performance for the hydrogen/oxygen evolution reaction (HER/OER), with low overpotentials only 43 mV and 164 mV at a current density of 10 mA cm−2 in simulated seawater (1.0 M KOH + 0.5 M NaCl). Importantly, the NiCoP@HP electrode demonstrates long-term stability, operating for over 1440 h at a current density of 500 mA cm−2 in 1.0 M KOH + 0.5 M NaCl and 1.0 M KOH + Seawater, respectively. This universally applicable method allows the preparation of a range of highly efficient catalytic electrodes (Fe, Mo, W, etc.). This work provides a simple, scalable, and versatile approach for the in situ construction of noble metal-free, highly efficient, and cost-effective bifunctional electrocatalysts, opening new possibilities for industrial-scale water splitting.

Ternary dual S-scheme In2O3/SnIn4S8/CdS heterojunctions for boosted light-to-hydrogen conversion

Developing artificial S-scheme systems with highly active catalysts is significant to long-term solar-to-hydrogen conversion. Herein, CdS nanodots-modified hierarchical In2O3/SnIn4S8 hollow nanotubes were synthesized by an oil bath method for water splitting. Benefiting from the synergy among the hollow structure, tiny size effect, matched energy level positions, and abundant coupling heterointerfaces, the optimized nanohybrid attains an impressive photocatalytic hydrogen evolution rate of 110.4 µmol/h, and the corresponding apparent quantum yield reaches 9.7% at 420 nm. On In2O3/SnIn4S8/CdS interfaces, the migration of photoinduced electrons from both CdS and In2O3 to SnIn4S8via intense electronic interactions contributes to the ternary dual S-scheme modes, which are beneficial to promote faster spatial charge separation, deliver better visible light-harvesting ability, and provide more reaction active sites with high potentials. This work reveals protocols for rational design of on-demand S-scheme heterojunctions for sustainably converting solar energy into hydrogen in the absence of precious metals.

Construction of a transition-metal sulfide heterojunction photocatalyst driven by a built-in electric field for efficient hydrogen evolution under visible light

Photocatalytic H2 evolution is of prime importance in the energy crisis and in lessening environmental pollution. Adopting a single semiconductor as a photocatalyst remains a formidable challenge. However, the construction of an S-scheme heterojunction is a promising method for efficient water splitting. In this work, CdS nanoparticles were loaded onto NiS nanosheets to form CdS/NiS nanocomposites using hollow Ni(OH)2 as a precursor. The differences in the Fermi energy levels between the two components of CdS and NiS resulted in the formation of a built-in electric field in the nanocomposite. Density functional theory (DFT) calculations reveal that the S-scheme charge transfer driven by the built-in electric field can accelerate the effective separation of photogenerated carriers, which is conducive to efficient photocatalytic hydrogen evolution. The hydrogen evolution rate of the optimized photocatalyst is 39.68 mmol·g−1 h−1, which is 6.69 times that of CdS under visible light. This work provides a novel strategy to construct effective photocatalysts to relieve the environmental and energy crisis.

Performance comparison of TCR-pMHC prediction tools reveals a strong data dependency.

The interaction of T-cell receptors with peptide-major histocompatibility complex molecules (TCR-pMHC) plays a crucial role in adaptive immune responses. Currently there are various models aiming at predicting TCR-pMHC binding, while a standard dataset and procedure to compare the performance of these approaches is still missing. In this work we provide a general method for data collection, preprocessing, splitting and generation of negative examples, as well as comprehensive datasets to compare TCR-pMHC prediction models. We collected, harmonized, and merged all the major publicly available TCR-pMHC binding data and compared the performance of five state-of-the-art deep learning models (TITAN, NetTCR-2.0, ERGO, DLpTCR and ImRex) using this data. Our performance evaluation focuses on two scenarios: 1) different splitting methods for generating training and testing data to assess model generalization and 2) different data versions that vary in size and peptide imbalance to assess model robustness. Our results indicate that the five contemporary models do not generalize to peptides that have not been in the training set. We can also show that model performance is strongly dependent on the data balance and size, which indicates a relatively low model robustness. These results suggest that TCR-pMHC binding prediction remains highly challenging and requires further high quality data and novel algorithmic approaches.

Bias-free visible light-driven photoelectrochemical water splitting of type II ZnO/CuS core/shell heterojunction nanotube arrays

Solar-driven water splitting of semiconductor photoelectrodes via photoelectrochemical (PEC) cell has been regarded as the most promising approach to mitigate the energy crisis and environmental issues in the future. In this work, CuS nanoparticles (NPs) are deposited on ZnO nanotube arrays (ZnO/CuS NTAs) via successive ion layer absorption and reaction method for PEC water splitting under visible light irradiation without applying bias. The excellent light harvesting capacity of CuS NPs from visible to near infrared region not only expands the light harvesting of ZnO NTAs into near infrared region, but also substantially boosts light absorption ranging from 300 to 800 nm. Moreover, CuS NPs coupled on ZnO NTAs can establish a type-II band alignment between ZnO and CuS. Consequently, the ZnO/CuS NTAs photoanode exhibits the significantly boosted PEC water splitting performance under visible light illumination (λ > 420 nm) without applying bias. The photocurrent density of the ZnO/CuS NTAs photoanode is 21.2 μA/cm2, which is increased by 9 times compared to that of the pure ZnO NTAs photoanode. The enhancement in PEC water splitting performance for ZnO/CuS NTAs is attributed to (i) the cooperative actions of ZnO and CuS; (ii) significant enhancement in light absorption from the visible to near infrared region achieved by CuS NPs and (iii) efficient charge carrier separation achieved by type-II band alignment.

Co(OH)2 Nanoflowers Decorated α-NiMoO4 Nanowires as a Bifunctional Electrocatalyst for Efficient Overall Water Splitting

The development of bifunctional electrocatalysts with high catalytic activity and cyclic stability is an effective method for electrocatalytic water splitting. Herein, a promising hydroxide/oxide Co(OH)2/α-NiMoO4 NWs/CC heterostructure with nanoflowers decorating the nanowires was fabricated on a carbon cloth (CC) substrate via hydrothermal and calcination methods. In contrast to one-dimensional nanomaterials, the interfaces of Co(OH)2 nanoflowers and α-NiMoO4 nanowires on CC provide more active sites for electrocatalytic reactions; therefore, they exhibit obviously enhanced electrocatalytic activities in overall water splitting. Specifically, the Co(OH)2/α-NiMoO4 NWs/CC electrodes exhibit an overpotential of 183.01 mV for hydrogen evolution reaction (HER) and of 170.26 mV for oxygen evolution reactions (OER) at the current density of 10 mA cm−2 in 1.0 M KOH. Moreover, the electrocatalytic oxygen evolution reaction (OER) activity of the Co(OH)2/α-NiMoO4 NWs/CC electrocatalyst was enhanced after long-term stability tests.

Molten salt-assisted synthesis of nitrogen-vacancy crystalline graphitic carbon nitride with tunable band structures for efficient photocatalytic overall water splitting

The photocatalytic overall water splitting performance of graphitic carbon nitride (g-C3N4) has still been restricted by its inefficient charge separation efficiency. Herein, nitrogen-vacancy crystalline g-C3N4 nanosheets (g-C3N4-D) with tunable band structures were successfully prepared by the alkali-molten salt-assisted method for efficient photocatalytic overall water splitting. Among them, g-C3N4-D2 not only combines the advantages of the amorphous and crystalline state of two-dimensional g-C3N4 nanosheets, but also introduces nitrogen vacancy to adjust the bandgap structures of crystalline g-C3N4 by an alkali etching, thus improving the light energy utilization and charge separation efficiency. TEM and EPR spectrum prove the existence of N defects in the crystalline g-C3N4. The excellent and stable photocatalytic overall water splitting activity with H2 and O2 evolution rate of 49.60 μmol g−1 h−1 and 24.71 μmol g−1 h−1 was obtained over g-C3N4-D2 with Pt and Co3O4 nanorods as cocatalysts (Pt/g-C3N4-D2/3%Co3O4 NRs) under AM 1.5G simulated light irradiation. In the half-reaction experiments, the maximum H2 evolution rate of Pt/g-C3N4-D2/3%Co3O4 NRs is 3.78 mmol g−1 h−1 with a significant quantum efficiency of 11.94 % at 400 nm, and the solar-hydrogen conversion efficiency (STH) is 1.48 %. The photocatalytic water oxidation activity of Pt/g-C3N4-D2/5%Co3O4 NRs is 42.34 μmol g−1 h−1. Additionally, the potential mechanism of photocatalytic overall water splitting was testified by in-situ XPS. This work provides a simple strategy for further advancing the potential application of g-C3N4 by molten salt-assisted alkali etching to introduce N vacancies to regulate the band gap of crystalline g-C3N4 for photocatalytic overall water splitting.

In-situ growth of hierarchical trifunctional Co4S3/Ni3S2@MoS2 core-shell nanosheet array on nickel foam for overall water splitting and supercapacitor

It is an enormous challenge to construct the cheap and effective multifunctional electrocatalysts for energy storage and conversion applications. Herein, a ZIF-67 derived Co4S3/Ni3S2@MoS2 core-shell nanosheet arrays were successfully developed on nickel foam via a simple two-step hydrothermal vulcanization method for electrocatalytic water splitting and supercapacitors. For overall water splitting, CNM 0.5 required the overpotentials of 96 and 269 mV at 10 mA cm−2 and 100 mA cm−2 for HER and OER in 1 M KOH. The dual-electrode electrolytic cell assembled from CNM 0.5 required only 1.447 V at 10 mA cm−2, and had nearly 100% Faraday efficiency and long-term stability (40 h). When used as the electrode for supercapacitors, CNM 0.5 had a large specific capacitance of 1238 F g−1 at 1 A g−1 current density and exceptional durability (85% retention after 2000 cycles). The ASC device assembled with CNM 0.5 provided the high-energy density of 41.2 W h kg−1 and long cycle-life (87% after 2000 cycles). The unique core-shell morphology with abundant active reactive edge sites would be beneficial for charge reduction and the volume shrinking/swelling during the rapid charge/discharge process. The well-ordered and vertically aligned nanosheet arrays possessed good conductivity and small interface resistance, which would facilitate the electron transfer and electrolyte penetration, ion insertion and de-intercalation.

Harvesting Hydropower via a Magnetoelastic Generator for Sustainable Water Splitting.

Energy consumption and the resulting climate change are the two major challenges to human sustainability. Hydrogen (H2) is a form of environmentally friendly renewable energy with an extremely high energy density of 143 MJ kg-1. Water splitting is a practical and cost-effective approach to generate H2 through the decomposition of H2O by electrolysis with an external power supply. Herein, we introduce a compelling platform technology for self-powered water splitting by using a soft magnetoelastic generator to convert hydropower into electricity as a sustainable power supply for electrolysis. At a rotating speed of 469 rpm, the hydropower harvester is able to convert flowing kinetic energy into electricity and produce a high current density of 2.99 mA cm-2 at a low resistance of 60 Ω. The magnetoelastic generator is intrinsically waterproof since the magnetic field can penetrate the water molecules. As a demonstration, the device maintained a stable electrical output even in underwater situations after over 7,000 cyclic operations. The generated electricity from hydropower could produce H2 at a rate of 1.93 × 10-3 mL min-1. In conclusion, this work provides a compelling method for self-powered water splitting by using flowing kinetic energy.

Flexible on-chip droplet generation, switching and splitting via controllable hydrodynamics

Flexible droplet preparation and manipulation are significant for lots applications such as immunoreaction and monocellular culture. Herein, we present a novel method for effective on-chip droplet generation, splitting and switching via controllable hydrodynamics. The microchannel of the designed chip has 6 inlets and 3 three outlets. The water solution is injected from a specific inlet (inlet d), and the other 5 inlets are used to inject oil fluids. Under the shearing effect of immiscible oils, the water phase breaks into dispersed droplets first, and the generated droplets can be further split into daughter drops or switched into side outlets from the middle outlet. To investigate the hydrodynamic droplet manipulation behaviors, a two-dimensional simulation model based on phase-field method is established. Utilizing the computational model, we systematically analyze the influences of the flow rates of continuous and dispersed fluids and the manipulation modes on droplet generation, splitting and switching. The numerical results indicate that the droplets can be generated with controlled sizes. For instance, at Qd = 5 μL/min and Qc1,2 = 5 μL/min, the droplet diameter decreases from 89.2 μm to 49.2 μm as Qs1,2 gradually rises from 15 μL/min to 40 μL/min. Moreover, the prepared droplets can realize on-demand splitting and switching. When Qd, Qc1,2, and Qs1,2 are fixed at 5 μL/min, 5 μL/min and 25 μL/min, respectively, the generated droplet is split into different proportional daughter drops with the rising of Qs3 (or Qs4) at first, and finally it is switched into the side-outlets when Qs3 (or Qs4) is higher than 80 μL/min. Therefore, this proposed droplet manipulation approach will be promising for various applications, and the numerical simulations can provide useful guidelines on the design and operation of droplet-based microfluidic systems.

Eigenfunction method for splitting of energy levels in quantum mechanics

In this work, we illustrate the use of eigenfunction method (EFM) in quantum mechanics by taking a specific example namely the splitting of energy levels under perturbation. Initially, the symmetry group of the Hamiltonian is taken to be [Formula: see text] which under the action of a perturbing potential changes to a lower symmetry namely [Formula: see text]. We have constructed an irreducible basis using the EFM for both the symmetries and show the simplifications that ensure the calculation of the expectation value of the perturbing Hamiltonian.

Dynamic self-optimization of hierarchical NiAl architecture catalysing oxygen evolution reaction in alkaline water electrolysis

Engineering highly active earth-abundant oxygen evolution electrode (OEE) with a promising method for alkaline water splitting is an extraordinarily honorable challenge. In this work, a facile and effective strategy has been developed to obtain a self-supported OEE (marked as HNA-CA-ECA) with defect-rich (Ni(OH)2/NiOOH hybrid) nanosheets that serve as the active sites, in situ generating over an equally important electrically conductive NiAl with hierarchical architecture to drive proficient catalysis. Notably, the HNA-CA-ECA catalyst shows superior activity toward OER with the overpotentials of 193 mV to reach a geometrical catalytic current density of 10 mA/cm2 with a very low Tafel slope of 39 mV/dec, surpassing the performance of the-state-of-the art IrO2, which requires an overpotential of 216 mV yielding catalytic current density of 10 mA/cm2 with a Tafel slope of 65 mV/dec. Interestingly, there was no significant performance loss of the HNA-CA-ECA catalyst after continuous 168 h electrolysis operation at a high current density of 800 mA/cm2 with an ultra-low overpotential of 229 mV in 6 M KOH at 353 K. Such a remarkable feature lies in the synergistic effect of the engineered high intrinsic activity, extremely huge catalytic surface area, and accelerated electron/ion transport. Moreover, the novel methodology of integrating the defect-rich nickel (oxy) hydroxide nanosheets (crystal defects) and formation of hierarchically porous architecture (morphology defects) presented in this work can broaden horizons and provide new dimensions in the design of highly active and stable electrocatalysts for alkaline water electrolysis.

Synergistic modulation of inverse spinel Fe3O4 by doping with chromium and nitrogen for efficient electrocatalytic water splitting

Earth-abundant Fe-based oxides have drawn less attention in electrocatalytic water splitting owing to the inferior intrinsic activity and poor conductivity. Therefore, developing an effective method to increase the catalytic performance of Fe-based oxides is of great importance for the practical application. Herein, a novel Cr/N co-doped Fe3O4 electrocatalyst (denoted as Cr-Fe3O4-N/NF) is designed and prepared by a simple immersion treatment followed by a calcination method for efficient water splitting. The resultant Cr-Fe3O4-N/NF shows significant catalytic activity for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with overpotentials of 218 and 95 mV at 10 mA cm–2. Furthermore, the water splitting system using Cr-Fe3O4-N/NF could afford a current density of 10 mA cm–2 at 1.53 V, which is superior to two-electrode system composed of Pt/C and RuO2. The high activities are attributed to the synergistic effect between Cr and N element doping. Specifically, the introduction of electron-deficient Cr is conductive to accelerate the dissociation process of water, adsorption process of intermediates, adjust the electronic structure. Simultaneously, N doping can increase the adsorption of H intermediates, provide more active sites for hydrogen absorption, and improve the electrical conductivity. This study provides a new strategy for Cr and N co-doped metal oxides electrocatalysts for high-performance water splitting.

G-C3N4-modulated bifunctional SnO2@g-C3N4@SnS2 hollow nanospheres for efficient electrochemical overall water splitting

An efficient bifunctional electrocatalyst is developed by bifunctional group construction method for electrochemical overall water splitting. Herein, a self-assembly method using silicon dioxide (SiO2) as template is proposed, in which tin dioxide (SnO2) and tin disulfide (SnS2) are constructed on the inner and outer walls of graphitic carbon nitride (g-C3N4) hollow nanospheres respectively, realizing the dual function of different interfaces controlled by g-C3N4 as the main body. Benefit from this design, the inner wall SnO2@g-C3N4 play a major contribution to oxygen evolution reaction (OER), while the outer wall g-C3N4@SnS2 contribute more to hydrogen evolution reaction (HER). Specifically, the adjustment of C element enhances the adsorption of *H at the edge S site, and the adjustment of N element optimizes the adsorption of OER reactant and the intermediate, thereby improving the bifunctional electrocatalytic activity. The test results show that the electrocatalytic material SnO2@g-C3N4@SnS2 exhibits an excellent electrocatalytic performance of OER and HER in alkaline medium. In addition, low voltage and 48 h stability of SnO2@g-C3N4@SnS2 are also demonstrated in the overall water splitting test. This work paves an avenue for design and control of bifunctional electrocatalysts with separable active sites.

Hierarchical 3D flower like cobalt hydroxide as an efficient bifunctional electrocatalyst for water splitting

• Transition metal oxide/hydroxides grown on nickel foam (NF) by hydrothermal method. • Co(OH) 2 /NF showed higher OER activity with low overpotential of 230 mV@10 mA cm -2 . • MnO 2 /NF delivered better HER activity with an overpotential of 150 mV@10 mA cm -2 . • The Co(OH) 2 ||Co(OH) 2 electrolyzer demonstrated a cell voltage of 1.61 V@10 mA cm -2 . • The electrolyzer offered an excellent long-term stability of 80 hours@100 mA cm -2 . The development of cost-effective and extremely stable bifunctional electrocatalysts is highly challenging due to the sluggish kinetics of oxygen evolution reaction (OER) compared to hydrogen evolution reaction (HER). So finding a suitable electrocatalyst for the respective OER and HER activity is highly essential. The best OER and HER electrocatalyst demands enhanced kinetics with increased surface area, active sites, and lower charge transfer resistances at the interfaces. Hence, improving the efficiency of an electrocatalyst for bifunctional activity would be advantageous for OWS. Here, we have reported nickel hydroxide (Ni(OH) 2 ), manganese dioxide (MnO 2 ), and cobalt hydroxide (Co(OH) 2 ) self-supported transition metal oxide/hydroxides grown nickel foam (NF) substrate by simple hydrothermal method for overall water splitting (OWS) in alkaline medium. The Co(OH) 2 /NF show a low overpotential of 230 mV for OER, whereas MnO 2 /NF exhibits low overpotential of 150 mV for HER to accomplish a current density of 10 mA cm −2 . Though, MnO 2 exhibits low overpotential for HER, the current density is lower compared to Co(OH) 2 due to lower surface area and conductivity. The full electrolyzer constructed from Co(OH) 2 ||Co(OH) 2 show a lowest cell voltage of 1.61 V and with an anion exchange membrane H-cell delivers a cell voltage of 1.68 V at 10 mA cm −2 in 1M KOH. A long-term stability studies (80 hours) on Co(OH) 2 ||Co(OH) 2 demonstrate robustness of the prepared electrodes and confirms the superior bifunctional electrocatalytic activity to replace the expensive noble metals.

Ru doping NiCoP hetero-nanowires with modulated electronic structure for efficient overall water splitting

Herein, a novel Ru-doped bimetal phosphide (Ru-NiCoP) heterostructure electrocatalyst on Ni foam is successfully synthesized through a multi-step hydrothermal reaction, ion exchange, and phosphorization method for efficient overall water splitting in alkaline media. The doping of Ru and P can effectively optimize the electronic structure and expose more active sites. The unique 3D interconnected nanowires not only ensures the uniform distribution of Ru coupled with NiCoP, but also endows the Ru-NiCoP/NF with the large ECSA, the fast electron transport and the favorable reaction kinetics attributes. Benefiting from the compositional and structural advantages, Ru-NiCoP/NF catalyst exhibits significantly enhancedcatalytic activities along with excellent stability, only needing 32.3 mV at 10 mA cm−2 for HER and 233.8 mV at 50 mA cm−2 for OER. In particular, when Ru-NiCoP/NF is employed as both cathode and anode electrodes,a small voltage of 1.50 V is required to reach 30 mA cm−2for overall water splittingwith an impressive stability. This study provides an alternative strategyon the design and development of high performance catalysts foroverall water splittingand other energy conversion fields.