Electrodes For Water Splitting Research Articles

Synergizing superwetting and architected electrodes for high-rate water splitting.

Water splitting is one of the most promising technologies for generating green hydrogen. To meet industrial demand, it is essential to boost the operation current density to industrial levels, typically in the hundreds of mA cm-2. However, operating at these high current densities presents significant challenges, with bubble formation being one of the most critical issues. Efficient bubble management is crucial as it directly impacts the performance and stability of the water splitting process. Superwetting electrodes, which can enhance aerophobicity, are particularly favorable for facilitating bubble detachment and transport. By reducing bubble contact time and minimizing the size of detached bubbles, these electrodes help prevent blockage and maintain high catalytic efficiency. In this review, we aim to provide an overview of recent advancements in tackling bubble-related issues through the design and implementation of superwetting electrodes, including surface modification techniques and structural optimizations. We will also share our insights into the principles and mechanisms behind the design of superwetting electrodes, highlighting the key factors that influence their performance. Our review aims to guide future research directions and provides a solid foundation for developing more efficient and durable superwetting electrodes for high-rate water splitting.

Reinforcement of electrocatalytic overall water splitting by constructing Mo-doped NiFe LDH/NiS heterostructure

Electrochemical water splitting is considered to be an environmentally friendly and efficient method of hydrogen production. NiFe LDH is a well-known electrocatalyst for oxygen evolution, yet its effectiveness in HER has been suboptimal. In this research, we created a Mo-NiFe LDH@NiS catalyst on carbon cloth via cation doping and heterointerface construction of NiFe LDH. The resulting Mo-NiFe LDH@NiS/CC showed remarkable HER activity. Furthermore, when used as a bifunctional electrode for overall water splitting, Mo-NiFe LDH@NiS/CC operated at a cell voltage of 1.58V at a current density of 10mA/cm² and exhibited outstanding durability. This study emphasizes the significant enhancement in HER and overall water-splitting efficiency of NiFe LDH achieved through Mo doping and heterostructure engineering, advancing its potential for effective water splitting applications.

ZnMnCoS/rGO nanocomposite for an effective bifunctional electrode for overall water splitting and supercapacitor applications

Abstract Future energy storage and energy conversion devices will benefit from the development of active electrode materials that serve as both an electrocatalysts and an energy storage device. Recently, mixed metal sulfides are cheaper and have improved electrical and electrochemical performance than their oxide/hydroxide similarly has garnered a lot of interest for use in energy storage and electro catalysis applications. In this, mixed metal sulfides, as zinc manganese cobalt sulfide (ZMCS) and reduced graphene oxide composite zinc manganese cobalt sulfide (rZMCS) were successfully synthesized via hydrothermal route for overall water splitting and supercapacitor. The prepared materials are characterized through x-ray diffraction, x-ray photoelectron spectroscopy, Field emission scanning electron microscope, transmission electron microscope with elemental mapping and Brunauer–Emmett–Teller analysis. The ZMCS and rZMCS electrodes exhibit an over-potential of 258 and 170 mV for HER and 302 and 230 mV for OER at a density of current is 10 mA cm2 in 3 M KOH. Overall water splitting is carried out for rZMCS electrodes and it shows the long-term stability of 15 hrs. The specific capacitances of ZMCS and rZMCS electrodes are 1065 F g1 and 1167 F g1 at 1 A g1. The obtained electrode could maintain 96 % and 98 % until 5000 cycles. Asymmetric supercapacitor device rZMCS//rGO delivers a total amount of energy and power is 47.6 Wh kg1 and 925 W kg1 with could maintain 86 % upto 10000 cycles. The outcomes draw attention to the produced electrode able to be practical as a multifunctional electrode for energy storage and conversion devices.

Self-Supported Transition Metal Based-Textile Electrodes through Interfacial Assembly for Overall Water Splitting in Alkaline Media

Water splitting holds significant promise for sustainable hydrogen production without carbon emissions. To develop electrodes suitable for large-scale hydrogen generation, characteristics such as large surface area, low electrical resistance, high electrocatalytic activity, and enduring operational stability are paramount. In our investigation, we've engineered high-performance water-splitting electrodes (WSEs) with exceptionally low overpotentials and robust stability through a process integrating carbonization and interfacial assembly-induced electrodeposition. These electrodes feature high-quality electrocatalytic structures based on transition metals (Ni, Fe, and Co), facilitated by strong electronic interactions. They exhibit low sheet resistance akin to bulk metals, a porous 3D architecture with ample specific surface area, and robust interfacial adhesion between the textile-based support and electrocatalysts. Our methodology begins with textiles, transformed into hydrophilic conductive substrates via carbonization and acid treatment, with additional amine molecule incorporation to enhance support-electrocatalyst interactions. Notably, our hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrodes demonstrate extremely low overpotentials (12 mV at 10 mA cm−2 for HER, 186 mV at 50 mA cm−2 for OER) under alkaline conditions. Furthermore, our full-cell electrodes exhibit sustained water-splitting activity at diverse current density from 10 to 2000 mA cm−2 for at least 2100 hours in 1 M KOH solution. We anticipate that our methodology lays a foundational framework for the development of commercially viable, high-performance WSEs.

Comparison of O2 and H2 Crossover and Concurrent Faradaic Efficiency Loss of AEM and PEM Water Electrolysis Cells

PEM water electrolyzers (PEMWEs) are able to store fluctuating renewable energy as chemical energy in the form of hydrogen gas. Due to the low pH and high anode potentials, however, only scarce iridium-based catalysts are considered to be reasonably stable to be employed commercially. This significant drawback for large scale application encourages research into AEM water electrolyzers (AEMWEs). They are ought to combine the advantages of polymer electrolyte based water electrolysis technologies with operation at elevated pH that allows usage of non-PGM based OER catalysts.1 Though the overall cell reaction is the same whether run in acidic or alkaline environment, the water-splitting electrode switches from the anode to the cathode, which necessarily changes the direction of osmotic drag within the polymer electrolyte. Additionally, AEM cells are commonly operated in a liquid-liquid set-up where both sides are actively flushed with an alkaline electrolyte solution, which further complicates the understanding of interfacial effects, product formation and removal as well as limiting factors for the overall electrical efficiency (i.e., overpotential contributions) of the system.With AEMWE research still being at an infant state compared to PEMWE it is important to learn as much as possible form the established system to boost the understanding and therewith performance and lifetime of the new technology. Especially gas crossover has been identified as a significant driver for PEMWE degradation2-3 and is limiting the operating range due to the formation of explosive mixtures at the anode. Also, the faradaic efficiency loss stemming from gas crossover should not be neglected. With the extent of gas crossover being strongly dependent on a multitude of experimental parameters, it is difficult to quantitatively compare data from different research groups.In this study we show a 1:1 comparison of AEMWE and PEMWE single cell measurements with special focus on the gas crossover characteristics and the concurrent faradaic efficiency achieved for both technologies. We fixed the experimental parameters to be as close as possible (PTL structure, flow field design, compression etc.) in order for this in-house comparison to serve as a basis for a better understanding of crossover phenomena both in AEMWE and PEMWE cells. By thoroughly analyzing similarities and differences regarding crossover dependency on the operating range the most important mechanisms and therewith influencing factors for both technologies are discussed. Miller, H. A.; Bouzek, K.; Hnat, J.; Loos, S.; Bernäcker, C. I.; Weißgärber, T.; Röntzsch, L.; Meier-Haack, J., Green hydrogen from anion exchange membrane water electrolysis: a review of recent developments in critical materials and operating conditions. Sustainable Energy & Fuels 2020, 4, 2114-2133.Kuhnert, E.; Heidinger, M.; Sandu, D.; Hacker, V.; Bodner, M., Analysis of PEM Water Electrolyzer Failure Due to Induced Hydrogen Crossover in Catalyst-Coated PFSA Membranes. Membranes (Basel) 2023, 13.Weiß, A.; Siebel, A.; Bernt, M.; Shen, T. H.; Tileli, V.; Gasteiger, H. A., Impact of Intermittent Operation on Lifetime and Performance of a PEM Water Electrolyzer. J. Electrochem. Soc. 2019, 166, F487-F497.

Dual-synergistic effect of medium-entropy metal sulfoselenide nanoparticles toward efficient overall seawater splitting

Developing efficient and durable electrodes for overall water splitting (OWS) in seawater electrolytes is a major challenge. Herein, we synthesized highly active and stable Fe1.2(CoNi)1.8S3Se3 medium-entropy metal sulfoselenide (MESSe) nanoparticles for the electrodes. The Fe1.2(CoNi)1.8S3Se3 MESSe electrode exhibited excellent electrocatalytic performance in alkaline simulated seawater, with a η100 value of 156 mV for the hydrogen evolution reaction and 262 mV for the oxygen evolution reaction. Compared to Fe1.2(CoNi)1.8S6 sulfide and Fe1.2(CoNi)1.8Se6 selenide, the electronic structure of Fe1.2(CoNi)1.8S3Se3 MESSe positively modulates the adsorption/desorption process of *H/*OH intermediate and significantly reduces the free energy of the rate-determining step, thereby accelerating the reaction kinetics of both hydrogen/oxygen evolution reactions. The performance of OWS is significantly enhanced by utilizing the prepared electrode, enabling it to achieve 100 mA cm−2 with only 1.77 V in alkaline simulated seawater. Furthermore, the durability of the electrode is maintained at this high current density in alkaline simulated seawater, alkaline seawater as well as seawater electrolyte. This work will lay the foundation for the development of innovative medium-entropy metal sulfoselenides, promoting their application in a wide range of electrochemical energy systems operating under extreme conditions.

Promoting Nickel-Iron layered double hydroxide via In-situ sulfur doping for efficient bifunctional electrocatalysis and energy storage applications

Electrodes with multifunctional applications are essential to realize compact and cost-effective energy storage systems. Herein, we report the role of in-situ sulfur doping on nickel-iron-layered double hydroxide (NiFe-LDH) grown on nickel foam via the facile hydrothermal method. The effects of S-doping under different atomic percentages have been evaluated in terms of charge transport and morphological features. The in-situ mode of doping S helps to attain enhanced charge transport property without the detrimental S2− substitution in OH sites of NiFe-LDH. The 5 at% doped NiFe-LDH (NFS05) demonstrates enhanced OER and HER properties with lower overpotentials of 304 mV and 99 mV, respectively. The NFS05 electrode demonstrated bifunctional activity with a low cell voltage of 1.60 V (@10 mA/cm2) in overall alkaline electrolysis. The empowered NFS05 has also been incorporated as an electrode in a supercapacitor configuration in which it demonstrated high specific and aerial capacitances of 212 F/g and 240.3 F/cm2 at a current density of 0.25 A/g respectively. The improved electron density on the Ni and Fe sites via in-situ S doping together with enhanced surface-active sites are responsible for the NFS05’s superior electrode activity, which was decoded from X-ray photoelectron spectroscopy. This in-situ doping of S is found to be beneficial for realizing multifunctional electrodes for efficient electrochemical water splitting and energy storage systems with high stability.

Recycled industrial waste silicon steel as high-performance electrode for oxygen evolution reaction using electroless plating surface modification

Exploring the large-area, cost-effective, and high-performance electrocatalyticoxygen evolution reaction (OER) electrode for water splitting is of great significance. Inspiring from the ‘waste to resource’ toward the circular economy, herein, the waste silicon steels (SS) were transformed into high-performance CoxFe3-xP/SS OER electrode through a facile electroless plating method. The plating layer of CoxFe3-xP not only endows the CoxFe3-xP/SS with outstanding electrocatalytic OER activity but also improves the corrosion resistance and stability of CoxFe3-xP/SS. The obtained Co2Fe1P/SS electrode exhibits the lowest overpotential of 244 mV at a current density of 10 mA/cm2 in 1 M KOH with a low Tafel slope of 48.7 mV/dec. Even at high current densities and in 6 M KOH and alkaline seawater (seawater + 1 M KOH), the Co2Fe1P/SS electrode also shows relatively low overpotentials, as well as high long-term durability. Specially, a large-area Co2Fe1P/SS OER electrode(40 × 40 cm2)was successfully prepared via the electroless plating approach. Toward the CoxFe3-xP/SS, the bimetallic Co-Fe synergies and phosphating effect promote the exposure of active sites and charge transfer. In addition, generated M(OH)x/MOOH (M = Co or Fe) species during OER activation could synergize with CoxFe3-xP and contribute excellent catalytic activity and stability.

Can Carbon be Used as an Anode for Water Splitting?

Carbon materials, whose structural and electronic properties can be fine-tuned, are promising material solutions for many energy-related systems. However, due to the lack of fundamental understanding of the carbon surface chemistry, especially when they are used in electrolytes, the rapid development of carbon as electrodes has led to many widely accepted misunderstandings. Focusing on the case of carbon-based electrode for water splitting, this Viewpoint tries to highlight the main problems of the area and demonstrates/presents the dynamic carbon surface chemistry in the application. The role of carbon as an anode for water splitting is revealed and if it can be practically used in water splitting is discussed.

NiCoP nanoparticles distributed on N-doped carbon-nanosheets loading on nickel phosphide as self-supporting electrode for efficient overall water splitting

The investigation of a bifunctional self-supporting catalytic electrode holds significant practical importance for the application of overall water splitting. In this paper, a precursor with a large specific surface is constructed by growing ZIF-67 nanosheets on nickel foam. Subsequently, Ni–Co bimetallic phosphide particles (NiCoP) are obtained through phosphating, which distributed in N-doped carbon material and loaded on nickel phosphide (NiCoP@NC-Ni3P/NF), facilitating the overall water splitting. Due to its large specific surface area, the double electron regulation of Ni and Co, as well as the synergistic interaction between NiCoP and Ni3P, NiCoP@NC-Ni3P/NF exhibits excellent hydrogen/oxygen evolution properties, only requiring 125.6/288.4 mV to achieve 20 mA cm−2. Its performance of overall water splitting only requires an applied voltage of 1.54 V to reach 10 mA cm−2. Moreover, the NiCoP particles embedded in the nitrogen-doped carbon can effectively reduce electrolyte corrosion, ensuring exceptional catalyst stability.

Investigating the oxidative synthesis of copper oxide nanowires: Wettability and photoelectrochemical insights

In this report, we fabricated the copper oxide nanowires by thermally oxidizing copper foil in different ambient environments such as: air, argon, and oxygen. The as-synthesized samples showed very low reflectance properties, and the contact angle measurements revealed a wide range of contact angles, ranging from 32.6° to 101.6°. The difference in the wettability behavior was attributed to the varying proportions of cupric and cuprous oxide in the growth process, as well as the existence of oxygen vacancies. The presence of the adsorbed hydroxyl groups on the surface was found to greatly influence the hydrophilicity of the surface. Furthermore, the synthesized samples were tested as photoelectrochemical water-splitting electrodes to assess their performance. The photocurrent density of samples synthesized in air, argon, and oxygen was 1.02, 1.4, and 1.8 mA/cm2, respectively. The results showed that samples synthesized in an oxygen environment showed a lower charge transfer resistance at the electrode-electrolyte interface with the highest shift in flat band potential. The study demonstrates a cost-effective method to modify wetting properties and enhance the photoelectrochemical performance of the copper foil.

A nanoporous nickel–iron alloy seamlessly anchored into hierarchical porous nickel for efficient and extremely stable water splitting

The development of a robust, low-cost electrode for electrochemical water splitting is a challenging, but essential task for realizing hydrogen production under industrial conditions. Here, we seamlessly anchor nanoporous nickel–iron into a hierarchical porous nickel foam (npNi–Fe/HPNF) by a designed gaseous oxidation–reduction engineering for a commercial nickel foam. The three-dimensional hierarchical porous structure considerably enhances the specific surface area of the electrode, yielding abundant electrocatalytic sites that promote the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Moreover, owing to its mechanically robust, seamlessly anchored architecture, and remarkable superhydrophilicity/superaerophobicity, the electrolyzer composed of self-standing npNi–Fe/HPNF and its electro-activation derivative displays a current density of 10 mA cm−2 at 1.54 V, ultralong durability of more than 2000 h at 500 mA cm−2 in a 1 M KOH electrolyte, and high performance of 2 V at 1 A cm−2 in a quasi-industrial environment (5 M KOH and 70 °C), outperforming most alkaline electrolyzers based on state-of-the-art electrodes. Exceptional electrochemical performance and the ability to be prepared at a large scale (2500 cm2) make npNi–Fe/HPNF a promising candidate for industrial water splitting applications.

Hard X-ray Photoelectron Spectroscopy Probing Fe Segregation during the Oxygen Evolution Reaction.

NiFe electrocatalysts are among the most active phases for water splitting with regard to the alkaline oxygen evolution reaction (OER). The interplay between Ni and Fe, both at the surface and in the subsurface of the catalyst, is crucial to understanding such outstanding properties and remains a subject of debate. Various phenomena, ranging from the formation of oxides/(oxy)hydroxides to the associated segregation of certain species, occur during the electrochemical reactions and add another dimension of complexity that hinders the rational design of electrodes for water splitting. In this work, we have developed the procedure for the quantification of chemical depth profiling by XPS/HAXPES measurements and applied it to two NiFe electrodes with different porosities. The main outcome of this study is related to the surface reconstruction of the electrodes during the OER, followed at two different depths by means of X-ray photoelectron spectroscopy. We find that Fe initially segregates at the surface when exposed to ambient conditions, resulting in the formation of an inactive FeOx phase. In addition, the porosity of the catalyst plays a significant role in the segregation process and thus in the performance of the electrode. In particular, the higher porosity of the nanostructured sample is responsible for a more pronounced diffusion of Fe from the subsurface to the surface with a more effective suppression of the activity of the Ni1-xFexOOH phase. These results highlight the importance of the fact that the chemical state of the surface of a multielement system is a snapshot in time, dependent on both external parameters, such as the applied potential and the adjacent electrolyte, and the underlying bulk properties accessible with HAXPES.

Study on evaluating and optimizing surface property mechanisms of polyalloy for enhanced OER catalyses via electrodeposited technique coupled with molecular dynamics simulations

Polyalloy catalysts composed of non-precious metals exhibit considerable potentials for facilitating overall water splitting processes in alkaline environments. However, achieving evaluations and optimizations of surface property mechanisms of polyalloy for enhanced OER catalyses is the key scientific issue that urgently need to be solved. Electrodeposited technique coupled with molecular dynamics simulations (MDS) are the key to breaking through aforementioned bottlenecks. Moreover, accurately predicting selections of non-precious metal elements in these catalysts through molecular dynamics simulations poses a challenging task. Here, three distinct non-precious metal catalysts (i.e. Ni, NiCo, and NiCoFe) were successfully synthesized through a facile one-step electrodeposition approach under a three-electrode system, which were deposited onto carbon sheets. For the sake of evaluating catalytic properties, MDS were utilized to calculate contact angles on ideal surfaces, which were verified by experimental measurements. Furthermore, ternary alloy catalysts (i.e. NiCoFe) exhibited an overpotential of 254 mV at a current density of 10 mA cm2 and exhibited remarkable stability over a prolonged 150-hour testing period. Finally, main findings can further underscore potentials of utilizing electrodeposition to fabricate efficient non-precious metal catalytic electrodes for overall water splitting, as well as the feasibility of indirectly predicting electrocatalytic performances of such cost-effective catalysts via MDS.

Self-supporting sea urchin-like Ni-Mo nano-materials as asymmetric electrodes for overall water splitting

Self-supporting sea urchin-like Ni-Mo nano-materials as asymmetric electrodes for overall water splitting

Moisture-Stable CsSnBr2Cl Halide Perovskite: Electrochemical Insights in Aqueous Environments.

In this investigation, moisture-stable CsSnBr2Cl nanoparticles were synthesized by incorporating Cl into CsSnBr3 halide perovskite using the hot injection method. Various analyses including XRD, XPS, UV-vis absorbance, photoluminescence, and Mott-Schottky have confirmed that the structural properties, chemical states, optical properties, and electronic band structure of CsSnBr2Cl nanoparticles remain intact even after 75 days of water immersion, thereby conclusively demonstrating their moisture stability. In a three-electrode system, the comparative electrochemical performance of pristine CsSnBr3 nanoparticles and moisture-stable Cl-incorporated CsSnBr2Cl nanoparticles was evaluated in various aqueous electrolytes, including HCl, Na2SO4, and KOH. The results indicate that the CsSnBr2Cl electrode material exhibits superior electrochemical properties, such as a larger integrated cyclic voltammetry (CV) area, a wider potential window, longer charge-discharge times, and lower impedance parameters compared to the pristine CsSnBr3 nanoparticles. The electrochemical performance of CsSnBr2Cl nanoparticles was evaluated for potential applications in batteries, supercapacitors, fuel cells, and water splitting, with a focus on reaction kinetics, charge storage mechanisms, and impedance parameters. The electrochemical properties of the nanoparticles were assessed using a three-electrode configuration across various 0.5 M aqueous electrolytes (HCl, Na2SO4, and KOH). In HCl, the nanoparticles demonstrated impressive charge storage capability, achieving a capacitance of 474 F g-1 at 1 A g-1, affirming their suitability for energy storage devices. In Na2SO4(aq.), the nanoparticles exhibited excellent stability for supercapacitors, operating up to 1.6 V without significant oxygen evolution. Notably, in KOH, they demonstrated potential as effective water-splitting electrodes. The practical applicability of the nanoparticles was evaluated using a symmetric two-electrode configuration with HCl and Na2SO4 electrolytes. The capacitance values were 117 F g-1 in HCl and 70 F g-1 in Na2SO4 at 1 A g-1. Notably, after 5000 GCD cycles in HCl(aq.), the nanoparticles retained 93% of their capacitance and maintained 91% Coulombic efficiency. They also demonstrated stable operation across a temperature range of 3 to 60 °C, achieving an energy density of 5.83 W h kg-1 at a power density of 600 W kg-1. This study emphasizes the considerable potential of CsSnBr2Cl nanoparticles in advancing electrochemical energy storage technologies and sets a solid foundation for future research and development in metal halide perovskites.

Superhydrophilic and Underwater Superaerophobic Dual-Function Peony-Shaped Selenide Micro-nano Array Self-Supported Electrodes for High-Efficiency Overall Water Splitting Driven by Renewable Energy.

With the intensification of global environmental pollution and resource scarcity, hydrogen has garnered significant attention as an ideal alternative to fossil fuels due to its high energy density and nonpolluting nature. Consequently, the urgent development of electrocatalytic water-splitting electrodes for hydrogen production is imperative. In this study, a superwetting selenide catalytic electrode with a peony-flower-shaped micronano array (MoS2/Co0.8Fe0.2Se2/NixSey/nickel foam (NF)) was synthesized on NF via a two-step hydrothermal method. The optimal catalytic activity of cobalt-iron selenide was achieved by adjusting the Co/Fe ratio. The intrinsic catalytic activity of the electrodes was enhanced by incorporating transition metal selenides, which then served as a precursor for the subsequent loading of MoS2 nanoflowers on the surface to fully expose the active sites. Furthermore, the superwetting properties of the electrode accelerated electrolyte penetration and electron/mass transfer, while also facilitating bubble detachment from the electrode surface, thereby preventing "bubble shielding effect". This resulted in superior oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance, as well as overall water splitting capabilities. In a 1.0 M KOH solution, the electrode required only 166 and 195 mV overpotential to achieve a current density of 10 mA cm-2 for OER and HER, respectively. When functioning as a bifunctional catalytic electrode, only 1.60 V of voltage was necessary to drive the electrolyzer to reach a current density of 10 mA cm-2. Moreover, laboratory simulations of wind and solar energy-driven water splitting validated the feasibility of establishing a sustainable energy-to-hydrogen production chain. This work provides new insights into the preparation of low-overpotential, high-catalytic-activity superhydrophilic and underwater superaerophobic catalytic electrodes by rationally adjusting elemental ratios and exploring changes in electrode surface wettability.

In situ hydrothermal growth of Ni-based hydrogen phosphate polyhedrons on Ni foam for efficient hydrogen evolution reaction

Developing a cost-effective and stable electrocatalyst is the key to achieve the large-scale applications of water electrolysis to produce green hydrogen. Herein, an in situ hydrothermal growth strategy was put forward to prepare a novel self-supporting electrode, that is, Ni-based hydrogen phosphate polyhedrons supported on 3D Ni foam. This electrode was composed of crystalline (Ni(H2PO4)2·2H2O, Ni(H3P2O7)2·2H2O), and amorphous phase in which NiO nanoparticles formed. The amorphous phase connected polyhedrons to the Ni foam substrate, forming multifarious heterogeneous interfaces. Such a structure possessed large number of active sites, favored the fast reaction kinetics and electron transport rate, synergistically resulting in a superior alkaline HER performance. In alkaline electrolyte, the electrode only needed a small overpotential of 69 mV to reach the current density of 10 mA cm−2 with a small Tafel slope of 56 mV dec−1, and exhibited a good stability at the current density of 100 mA cm−2 for 50 h. This in situ hydrothermal growth strategy opened up a new route to green synthesis of cost-effective and stable 3D heterostructured self-supporting electrode for water-splitting.

Self-supported V–Cu2S catalysts for green hydrogen production through alkaline water electrolysis

In this study, we present self-supported vanadium-doped copper sulfide (Cu2S) electrodes as effective catalytic network for alkaline water electrolysis. The electrodes demonstrate a remarkably lower value of overpotential 375 mV for HER (hydrogen evolution reaction) and 403 mV for OER (oxygen evolution reaction) to generate 100 mA/cm2 current. A bi-functional electrolyzer incorporating these electrodes achieves a high current of 100 mA/cm2 at a cell voltage of 1.97 V. The positive influence of vanadium incorporation enhances the overall electrocatalytic activity of Cu2S and capable of generating the geometric current density of more than 500 mA/cm2 current for bi-functional electrolysis in industrial-scale alkaline electrolyte 5 M KOH at an elevated temperature of 60 °C, highlighting its potential for practical applications in renewable hydrogen production. Furthermore, the stability of electrodes was measured at different current densities at 20, 50 and 300 mA/cm2, suggesting the capabilities of electrodes for sustainable water electrolysis for green H2 and O2 production. DFT analyses confirms that the V-CusS exhibits superior performance owing to favourable H-adsorption energy on S-sites and minimum Gibb's free energy on V-sites. The study focuses on specific electrochemical performance metrics, offering insights into the promising utilization of vanadium-doped Cu2S electrodes for efficient water splitting in alkaline environments.

Strong electronic interaction in chromium-molybdenum dual incorporated few-layer cobalt sulfide nanosheets with lattice distortion for efficient bifunctional water splitting

The investigation into cost-effective and high-efficiency bifunctional electrocatalysts for electrochemical water splitting is crucial for advancing the conversion efficiency of intermittent energy systems. In this study, a novel dissolution-in situ precipitation method is introduced to synthesize few-layer CoS2 nanosheets incorporating dual cations (Cr, Mo), referred to as Cr/Mo-CoS2. The synergistic influence arising from robust dual dopant-induced coupling interactions and pronounced lattice distortions enhances the rate-determining steps of the HER and OER processes in Cr/Mo-CoS2 by optimizing the adsorption of H* and OOH* intermediates on the catalyst surface. The distinctive pinecone-like structure formed by these nanosheets provides numerous active sites and facilitates electron transfer during reactions. Consequently, the synthesized Cr/Mo-CoS2 nanosheets demonstrate superior catalytic activity, characterized by a low overpotential of 123.8 mV at 10 mA cm−2 for the hydrogen evolution reaction and 310.2 mV at 50 mA cm−2 for the oxygen evolution reaction, coupled with excellent durability in alkaline electrolytes. When utilized as bifunctional electrodes for comprehensive water splitting, Cr/Mo-CoS2 achieves a current density of 10 mA cm−2 at a cell voltage of 1.55 V. This research underscores the critical role of dual-cation doping-induced coupling interactions and significant lattice distortions in augmenting the performance of transition metal chalcogenide electrocatalysts.