Electrocatalysts For Alkaline Water Electrolysis Research Articles

H2S-Treated Nickel Foam Electrocatalyst for Alkaline Water Electrolysis under Industrial Conditions

H₂S-Treated Nickel Foam Electrocatalyst for Alkaline Water Electrolysis under Industrial Conditions

Facile and fast route of electrodepositing chloride ion-modified NiFePt layered double hydroxides for hydrogen evolution reaction

NiFe-based layered double hydroxide (LDH) is a promising electrocatalyst for alkaline water electrolysis because of the low cost and earth abundance of Ni and Fe, as well as their characteristic layered structure resulting in high electrocatalytic performance. However, its hydrogen evolution reaction (HER) activity is still insufficient compared to existing catalysts. Additionally, the hydrothermal method, a common LDH fabrication method, can be time-consuming and complicated. Herein, we suggest a facile route for the preparation of HER catalyst within tens of seconds using one-pot electrodeposition with only a few ionic additives. A trace amount of Pt ion was added to enhance the HER performance and chloride (Cl−) ion was used to increase the specific surface area of the catalyst as well as to control the reduction of Pt ion for Pt-O bonding. Consequently, the 2.5 mmol Cl− ion treated NiFePt LDH (NiFePt_Cl LDH) requires an overpotential of only 52 mV to reach a current density of 100 mA cm−2 and significantly improved durability, with an overpotential increase of only 7 mV at 100 mA cm−2 after 1,000 cyclic voltammetry scans.

Alkaline Water Electrolysis for Green Hydrogen Production.

ConspectusThe global energy landscape is undergoing significant change. Hydrogen is seen as the energy carrier of the future and will be a key element in the development of more sustainable industry and society. However, hydrogen is currently produced mainly from fossil fuels, and this needs to change. Alkaline water electrolysis with advanced technology has the most significant potential for this transition to produce large-scale green hydrogen by utilizing renewable energy. The assembly of industrial electrolyzer plants is more complex on a larger scale, but it follows a basic working principle, which involves two half-cells of anode and cathode sites where the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) occur. Out of the two reactions, the OER is more challenging both thermodynamically and kinetically. Besides having access to renewable electricity, developing durable and abundant electrocatalysts for the OER remains a challenge in large-scale alkaline water electrolysis. Among different physicochemical properties, the electrocatalyst surface and its interaction with water and reaction intermediates, as well as formed molecular hydrogen and oxygen, play an essential role in the catalytic performance and the reaction mechanism. In particular, the binding strengths between the catalyst surface and intermediates determine the rate-limiting step and electrocatalytic performance.This Account gives some insights into the status of the hydrogen economy and basic principles of alkaline water electrolysis by covering its fundamentals as well as industrial developments. Further, the HER and OER reaction mechanisms of alkaline water electrolysis and selected electrocatalyst progress for both half-reactions are briefly discussed. The Adsorbate Evolution Mechanism and the Lattice Oxygen Mechanism for the OER are explained with specific references. This Account also deliberates on the author's selected contributions to the development of transition metal-based electrocatalysts for alkaline water electrolysis with an emphasis on OER. The focus is particularly given to the enhancement of intrinsic activity, the role of eg-filling, phase segregation, and defect structure of cobalt-based electrocatalysts for OER. Structural modification and phase transformation of the cobalt oxide electrocatalyst under working conditions are further deliberated. In addition, the creation of new active surface species and the activation of cobalt- and nickel-based electrocatalysts through iron uptake from the alkaline electrolyte are discussed. In the end, this Account provides a brief overview of challenges related to large-scale production and utilization of green hydrogen.

Nanocrystalline (NixCo(1-x))3(PO4)2@FeSe2/NF as a promising OER electrocatalyst for alkaline water electrolysis

Affordable and sustainable hydrogen production is the need of the hour owing to the mounting global pursuit for the hydrogen economy. Water splitting is the premier go-to method to produce green hydrogen at a larger scale in which the half-cell Oxygen Evolution Reaction (OER) demands a larger amount of energy expenditure due to its sluggish kinetics. Hence, designing an efficient OER electrocatalyst, especially for alkaline water electrolysis that offers alternatives to the usage of precious group metals is a pressing priority. Herein, we report a novel nanocrystalline electrocatalyst consisting of two components, namely cobalt nickel phosphate and iron diselenide synthesised via a two-step electrodeposition at room temperature. The combination of the two components on the porous nickel foam substrate exhibits an overpotential of 272 mV at 100 mA/cm2 in 1 M KOH showing a low Tafel slope of a mere 38 mV/dec with appreciable retention even after 24 h of stability test at a relatively higher current density. The surface reconstruction that occurs when FeSe2 is electrodeposited on (Ni0.35Co0.65)3(PO4)2@NF and the synergy between the two components is the primary reason for the improved performance. Thus, this work highlights the ambient synthesis of a highly durable earth-abundant metal-based electrocatalyst which exceeds the performance of the standard Ru/C by a decent margin.

Multi-interface engineering of nickel-based electrocatalysts for alkaline hydrogen evolution reaction

High gravimetric energy density and zero carbon emission of hydrogen have motivated hydrogen energy to be an attractive alternative to fossil fuels. Electrochemical water splitting in alkaline medium, driven by green electricity from renewable sources, has been mentioned as a potential solution for sustainable hydrogen production. Hydrogen evolution reaction (HER), as a cathodic half-reaction of water splitting, requires additional overpotential to obtain protons via water adsorption/dissociation, suffering from slow kinetics in alkaline solution. Robust and active nickel (Ni)-based electrocatalyst is a promising candidate for achieving precious-metal comparable performance owing to its platinum-like electronic structures with more efficient electrical power consumption. Various modification strategies have been explored on Ni-based catalysts, among which multi-interface engineering is one of the most effective routines to optimize both the intrinsic activity of Ni-based electrocatalysts and the extrinsic stacked component limitations. Herein, we systematically summarize the recent progress of multi-interface engineering of Ni-based electrocatalysts to improve their alkaline HER catalytic activity. The origin of sluggish alkaline HER kinetics is first discussed. Subsequently, three kinds of interfaces, geometrically and reactively, conductive substrate/electrocatalyst interface, electrocatalyst internal heterointerface, and electrocatalyst/electrolyte interface, were cataloged and discussed on their contribution mechanisms toward alkaline HER. Particular focuses lie on the microstructural and electronic modulation of key intermediates with energetically favorable adsorption/desorption behaviors via rationally designed interfaces. Finally, challenges and perspectives for multi-interface engineering are discussed. We hope that this review will be inspiring and beneficial for the exploration of efficient Ni-based electrocatalysts for alkaline water electrolysis.

Benchmarking Activity and Stability of Layered Double Hydroxides (LDHs) Electrocatalysts for Alkaline Water Electrolysis

In order to reduce the cost of producing hydrogen through water electrolysis, novel technologies must be improved. Recently, the merging of conventional alkaline electrolysis (AEL) and proton exchange membrane electrolysis (PEM) has led to the development of anion exchange membrane electrolysis (AEMWE), which offers several advantages over AEL and PEM. In a nutshell, this technique employs cheap, abundant, and easily available (non-geostrategic) transition metals with anionic exchange membranes, overcoming the drawbacks of AEL and PEM.[1]To reach the readiness level of this technology, new and scalable synthetic routes for catalysts that lower the overpotential of the sluggish oxygen evolution reaction (OER) are required. Amongst all the OER catalysts reported in the literature, Layered Double Hydroxides (LDHs) have gained increasing attention due to their low overpotentials and stabilities.[2] Besides, electrochemical protocols to determine the activity and stability of these catalysts in different electrochemical cells must be established to understand their properties. Thus, this work focuses on the advantages and limitations of different electrochemical techniques, such as rotating disk electrode (RDE), three-electrode cells, and single-cell tests, to determine the activity and stability of two different LDHs. Unlike laboratory scale LDHs ‒prepared by hydrothermal treatment (HT-LDH)‒ room temperature synthesized LDHs (RT-LDH) can be prepared in kilogram quantities and present chemical structure and morphology differences. In this work, the LDHs have been characterized with spectroscopic techniques to correlate the chemical structure and morphology of the materials to their electrochemical response by RDE, three-electrode cells, and single-cell measurements.All in all, the scalable RT-LDH presents higher activity compared to HT-LDH in all three techniques. On the one hand, small current densities can only be reached by RDE, and the short-term stability of the materials is affected by the catalyst layer interface. On the other side, single-cell test measurements require long operational times, and the contribution of the membrane degradation to the overall cell voltage is still unclear. Thus, three-electrode cell measurements offer the possibility of characterizing LDHs at relevant current densities in a fast and straightforward manner, without membrane contributions, and are further employed in this work to study the stability of these systems.

A novel polyaniline based nanocomposite derived from used tea biomass: a promising electrocatalyst for oxygen evolution reaction

A potential electrocatalyst for alkaline water electrolysis was prepared by using an inexpensive used tea dust biomass wherein the used tea dust biomass was subjected for calcination followed by polymerization with varied amounts of monomer, aniline, to prepare nanocomposites. The thoroughly characterized nanocomposites were tested as potential electrocatalysts for oxygen evolution reaction (OER). The nanocomposite prepared using 5 mL of aniline requires an overpotential of only 380 mV (1.61 V vs RHE) to generate the current density of 250 mA cm−2 while the sample prepared without aniline requires 450 mV (1.68 V vs RHE) to generate the same amount of current density. Adding optimum amounts of polyaniline increases the number of active sites and conductivity, which are beneficial to facilitate OER. This study demonstrates successful conversion of tea waste biomass, produced in every home, into potential electrocatalyst, which can be used to generate environmentally benign carbon free hydrogen fuel.

One-Step Electrodeposition of NiMoP/NF as an Efficient and Cost-Effective Cathodic Electrocatalyst for Alkaline Water Electrolysis

One-Step Electrodeposition of NiMoP/NF as an Efficient and Cost-Effective Cathodic Electrocatalyst for Alkaline Water Electrolysis

Bimetallic Cu–Ni core–shell nanoparticles anchored N-doped reduced graphene oxide as a high-performance bifunctional electrocatalyst for alkaline water splitting

Water electrolysis is regarded as the most promising method for developing sustainable energy technologies. However, low-cost bifunctional electrocatalysts with high efficacy and long-term stability are required to make this method economically viable. Core-shell nanoparticles, which comprise a thin layer of a catalytically active shell surrounding a subsurface core, have recently emerged as cutting-edge electrocatalysts for effective water electrolysis. Herein, we systematically fabricated distinct bimetallic Cu–Ni particles by tuning the Cu:Ni ratios, and then anchored them to an N-doped reduced graphene oxide (NRG) backbone for alkaline water splitting. A Cu:Ni molar ratio of 1:1 was determined to be optimal for forming an effective core–shell configuration, affording favorable adsorption energies toward reactants. The Cu–Ni(1:1) core–shell nanoparticles anchored NRG, termed Cu–Ni(1:1)@NRG, displayed excellent performance toward the H2 evolution reaction (HER) and oxygen evolution reaction (OER), with overpotentials at 10 mA cm−2 of 107 and 310 mV, respectively, versus a reversible hydrogen electrode (RHE). This current density (10 mA cm−2) was attained at a low cell voltage of 1.64 V when Cu–Ni(1:1)@NRG was used as the bifunctional electrocatalyst for alkaline water electrolysis. Furthermore, the Cu–Ni(1:1)@NRG electrocatalyst exhibited outstanding long-term stability in prolonged electrocatalytic studies at a constant current density.

Investigation of Charge–Discharging Behavior of Metal Oxide–Based Anode Electrocatalysts for Alkaline Water Electrolysis to Suppress Degradation due to Reverse Current

In the bipolar-type alkaline water electrolysis powered by renewable energy, electrocatalysts are degraded by repeated potential change associated with the generation of reverse current. If an electrode has large discharge capacity, the opposite electrode on the same bipolar plate is degraded by the reverse current. In this study, discharge capacity of various transition metal-based electrocatalysts was investigated to clarify the determining factors of electrocatalysts on the reverse current and durability. The discharge capacities from 1.5 to 0.5 V vs. RHE (Qdc,0.5) of electrocatalysts are proportional to the surface area in most cases. The proportionality coefficient, corresponding to the specific capacity, is 1.0 C·m–2 for Co3O4 and 2.3 C·m–2 for manganese-based electrocatalysts. The substitution of Co3+ in Co3O4 with Ni3+ increased Qdc,0.5. The upper limit of theoretical specific capacity for Co3O4 is estimated to be 1.699 C·m–2, meaning the former and latter cases correspond to 2- and 1-electron reactions, respectively, per a cation at the surface. The discharge capacities of the elctrocatalysts increased because of the dissolution and recrystallization of nickel and/or cobalt into metal hydroxides. The increase in the capacities of Co3O4 and NiCo2O4 during ten charge–discharge cycles was below 2–9% and 0.5–38%, respectively. Therefore, if a cathode electrocatalyst with relatively low redox durability is used on the one side of a bipolar plate, it is necessary to control optimum discharge capacity of the anode by changing surface area and constituent metal cations to minimize the generation of reverse current.Graphical

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Quad-metallic MOF-derived carbon-armored pseudo-high entropy alloys as a bifunctional electrocatalyst for alkaline water electrolysis at high current densities

A quad-metallic pseudo-HEA catalyst, FeCoNiMo@C, was developed for water electrolysis, exhibiting outstanding bifunctional catalytic efficiency and stability, 500 mA cm−2@1.725 V and a 3.4% decay after a 50 h operation at 500 mA cm−2.

(Invited) Designing Microscale Structures for Enhanced Function of Electrocatalysts for Alkaline Water Electrolysis

Water electrolysis has already been implemented for many decades on an industrial scale. It does, however, remain an active area of research and development for the pursuit of materials that have enhanced electrocatalytic performance and prolonged durability. For example, the accumulation of gas bubbles on the surfaces of electrodes during water electrolysis remains a challenge. Persistent bubbles on the surfaces of electrocatalysts can block electrolyte access to the electrode and reduce the electrochemically active surface area. At current densities that are relevant to industrial applications an extensive portion of the electrode can become covered with bubbles. There are a range of solutions that are being utilized in industrial settings, but also additional solutions being sought to optimize the efficiency of these systems. These solutions include applied shear flows across the surfaces of the electrodes, the implementation of ultrasonic induced cavitation, and an increase in electrolyte temperature. These solutions require further expenditures of energy and decrease the overall energy efficiency of the system. Alternative approaches may yield a lower energy demand for maintaining accessibility of the electrolyte to the electrochemically active surface area. One approach is through the design of electrode surface architectures that can assist with the removal of gas bubbles during water electrolysis. This work includes a review of the progress made in preparing structured electrodes for the alkaline based water electrolysis and specifically for the oxygen evolution reaction. These structures can influence the dynamics that occur at the electrode-electrolyte interface, such as the growth, coalescence, and release of oxygen gas bubbles. Understanding the correlations between the structures on the electrodes and their influence on the function of these materials towards the gas evolution are sought to guide the future development of optimal surface structures that are self-cleaning. Designs of electrode surface architectures are sought that can improve the efficiency of electrodes toward this and other gas evolution reactions.

Facile construction of porous and heterostructured molybdenum nitride/carbide nanobelt arrays for large current hydrogen evolution reaction

The development of cost-effective, highly efficient and stable electrocatalysts for alkaline water electrolysis at a large current density has attracted considerable attention. Herein, we reported a one-dimensional (1D) porous Mo2C/Mo2N heterostructured electrocatalyst on carbon cloth as robust electrode for large current hydrogen evolution reaction (HER). The MoO3 nanobelt arrays and urea were used as the metal and non-metal sources to fabricate the electrocatalyst by one-step thermal reaction. Due to the in-situ formed abundant high active interfaces and porous structure, the Mo2C/Mo2N electrocatalyst shows enhanced HER activity and kinetics, as exemplified by low overpotentials of 54, 73, and 96 mV at a current density of 10 mA cm−2 and small Tafel slopes of 48, 59 and 60 mV dec−1 in alkaline, neutral and acid media, respectively. Furthermore, the optimal Mo2C/Mo2N catalyst only requires a low overpotential of 290 mV to reach a large current density of 500 mA cm−2 in alkaline media, which is superior to commercial Pt/C catalyst (368 mV) and better than those of recently reported Mo-based electrocatalysts. This work paves a facile strategy to construct highly efficient and low-cost electrocatalyst for water splitting, which could be extended to fabricate other heterostructured electrocatalyst for electrocatalysis and energy conversion.

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.

Anodized Steel: The Most Promising Bifunctional Electrocatalyst for Alkaline Water Electrolysis in Industry

AbstractElectrolysis of water, especially alkaline water electrolysis (AWE), is the most promising technology to produce hydrogen in industry. However, only 4% of the total hydrogen is produced in this way because the electrode materials are expensive, inefficient, or unstable. Here, it is reported that the large‐scale 3D printed martensitic steel (AerMet100) can be the bifunctional electrode for AWE with high catalytic performance, which may dramatically increase the green‐hydrogen percentage in the market and provide strategic planning for energy management. It is found that the martensitic steel by fast anodization (3 min) can realize ultra‐high hydrogen and oxygen evolution reactions (HER and OER), and excellent stability at high current densities. Particularly, this electrocatalyst shows a low overpotential of 3.18 V and long‐term stability over 140 h at 570 mA cm−2 in overall water splitting. Additionally, the treated large‐scale steel can work well under a very high current up to 20 A. This study demonstrates that martensitic steel can be commercialized as a highly efficient catalyst for industrial hydrogen production in AWE, which should provide solutions to the energy crisis and environmental pollution.

Studies on Co3O4–NiO nanocomposites for potential electrocatalyst for alkaline water electrolysis

Studies on Co3O4–NiO nanocomposites for potential electrocatalyst for alkaline water electrolysis

Hierarchical porous nickel supported NiFeOxHy nanosheets for efficient and robust oxygen evolution electrocatalyst under industrial condition

As an ideal clean energy carrier, hydrogen is regarded as the most promising alternative to replace fossil fuels in the future energy system. Compared to the traditional steam reforming process, water electrolysis is an innovative method for green hydrogen production. The oxygen evolution reaction (OER) with slow kinetics limits the efficiency of water electrolysis, thus, the fabrication of efficient and robust electrocatalysts for OER is highly desirable to promote the development of hydrogen industry. Herein, we developed a robust OER electrocatalyst by coupling NiFeOxHy nanosheets with porous nickel (PN) substrate via bubble template method. The NiFeOxHy-PN electrocatalyst displays superior electrocatalytic performance, the overpotential for OER at 100 mA cm−2 and 1000 mA cm−2 are 265 mV and 326 mV, respectively. Especially, the NiFeOxHy-PN exhibits better activity and durability than the commercial Raney nickel (RN) in alkaline water electrolysis under industrial conditions, which indicates its potential for industrial application. This work provides an efficient strategy to synthesize advanced electrocatalyst for alkaline water electrolysis.

Pulse electrodeposited CoFeNiP as a highly active and stable electrocatalyst for alkaline water electrolysis

A high-performance CoFeNiP/NF bifunctional catalyst for water splitting was prepared via a pulse-electrodeposition method. Doping with iron and nickel significantly modulates the electronic state of CoP, resulting in enhanced activity and stability.

Benchmarking Perovskite Electrocatalysts’ OER Activity as Candidate Materials for Industrial Alkaline Water Electrolysis

The selection and evaluation of electrocatalysts as candidate materials for industrial alkaline water electrolysis is fundamental in the development of promising energy storage and sustainable fuels for future energy infrastructure. However, the oxygen evolution reaction (OER) activities of various electrocatalysts already reported in previous studies are not standardized. This work reports on the use of perovskite materials (LaFeO3, LaCoO3, LaNiO3, PrCoO3, Pr0.8Sr0.2CoO3, and Pr0.8Ba0.2CoO3) as OER electrocatalysts for alkaline water electrolysis. A facile co-precipitation technique with subsequent thermal annealing (at 700 °C in air) was performed. Industrial requirements and criteria (cost and ease of scaling up) were well-considered for the selection of the materials. The highest OER activity was observed in LaNiO3 among the La-based perovskites, and in Pr0.8Sr0.2CoO3 among the Pr-based perovskites. Moreover, the formation of double perovskites (Pr0.8Sr0.2CoO3 and Pr0.8Ba0.2CoO3) improved the OER activity of PrCoO3. This work highlights that the simple characterization and electrochemical tests performed are considered the initial step in evaluating candidate catalyst materials to be used for industrial alkaline water electrolysis.