High Corrosion Resistance of NiFe-Layered Double Hydroxide Catalyst for Stable Seawater Electrolysis Promoted by Phosphate Intercalation

Molybdate-Modified NiOOH for Efficient Methanol-Assisted Seawater Electrolysis

Seawater electrolysis holds great promise for sustainable, green hydrogen production but faces challenges of high overpotentials and competing chlorine evolution reaction (CER). Replacing the oxygen evolution reaction with the methanol oxidation reaction (MOR) presents a compelling alternative due to its lower anodic potential which mitigates the risk of CER. While NiOOH is known for its MOR activity, its performance is limited by sluggish non-electrochemical kinetics and Cl-induced degradation. Herein, a MoO4 2--modified NiOOH electrocatalyst is reported that significantly enhances MOR-assisted seawater splitting efficiency. In situ leached MoO4 2- from the heterojunction optimizes methanol adsorption and facilitates proton migration, thereby accelerating the non-electrochemical steps in MOR. Additionally, the adsorbed MoO4 2- effectively repels Cl-, protecting the electrodes from Cl--induced corrosion. The MOR-assisted electrolyzer using NiMo||Ni(OH)2/NiMoO₄ requires only 1.312 V to achieve 10 mA cm-2, substantially lower than conventional alkaline seawater electrolysis (1.576 V). Furthermore, it demonstrates remarkable stability, sustaining high current densities (up to 1.0 A cm-2) for over 130 h. This work presents a promising strategy for designing high-performance electrocatalysts for efficient and sustainable green hydrogen production from seawater.

Polycalmagite Coating Enables Long-Term Alkaline Seawater Oxidation Over NiFe Layered Double Hydroxide

Renewable energy-powered seawater electrolysis is a green and attractive technique for producing high-purity hydrogen. However, severe chlorideions (Cl-) and their derivatives tend to corrode anodic catalysts at ampere-level current densities and hinder the application of seawater-to-H2 systems. Herein, a polycalmagite (PCM)-coated NiFe layered double hydroxide is presented on Ni foam (NiFe LDH@PCM/NF) that exhibits exceptional stability in alkaline seawater. PCM not only acts as a conductive layer to reduce charge transfer resistance of the anodes but also as a polymer-based protective layer to inhibit Cl- adsorption and stabilize metal ions oxidation due to its own anions and strong adhesion, thereby increasing activity and stability during alkaline seawater. Thus, NiFe LDH@PCM/NF only needs a low overpotential of 364 mV to reach up to 1000 mA cm-2 and maintains operation for 500 h without activity degradation. Moreover, a minimal amount of hypochlorite can be detected in electrolyte after a 500-h stability test. This development affords a significant exploration in creating durable and efficient anodes, highlighting the importance of polymer coating toward anti-corrosion in alkaline seawater oxidation.

Transition Metal-Coordinated Polymer Achieves Stable Seawater Oxidation over NiFe Layered Double Hydroxide

Seawater electrolysis has emerged as a promising approach for the generation of hydrogen energy, but the production of deleterious chlorine derivatives (e.g., chloride and hypochlorite) presents a significant challenge due to the severe corrosion at the anode. Transition metal-coordinated polymers have garnered attention as promising electrocatalysts for alkaline seawater oxidation (ASO), attributed to their remarkable chlorine corrosion resistance, high conductivity, and facile synthesis. In this study, we employ an anodic oxidation-electrodeposition strategy to grow NiFe-polyaniline on NiFe layered double hydroxide supported on Ni foam (NiFe LDH@NiFe-PANI/NF) as a highly efficient catalyst for ASO. We demonstrate stable ASO at industrial-level current densities (j) by employing a synergistic strategy that integrates NiFe-PANI, which offers resistance to chlorine-induced corrosion, and molybdate, which effectively repels chloride anions. In alkaline seawater, NiFe LDH@NiFe-PANI/NF requires 380 mV to sustain a j of 1000 mA cm-2, and it exhibits continuous operation for 500 h at a j of 1000 mA cm-2. Besides, the anion-exchange membrane electrolyzer consisting of NiFe LDH@NiFe-PANI/NF requires a voltage of 2.16 V to drive 300 mA cm-2. Notably, it can operate stably for 120 h, highlighting its potential for sustainable energy applications.

Robust Damage-Sensing and Corrosion-Warning Polymeric Coatings: a New Approach to Visually Monitor the Degradation Dynamics of Coated Mg-Alloys

Corrosion and degradation of magnesium (Mg) alloy result in serious damage and limit its application in new-energy automobile industry. Considerable protective coating is proposed, yet it is hindered by the difficulties in avoiding and visually monitoring coating micro-damage and localized metal corrosion. Herein, a novel anticorrosion coating system with autonomously monitoring multiple levels of damages in coated Mg-alloy system, is proposed. In this design, the top layer of coating consists of polymethyl methacrylate (PMMA) microcapsules containing crystal violet lactone (CVL) and polyurethane resin dispersed with SiO2 nanoparticles. Upon surface damage, the presence of SiO2 triggers the chromogenic reaction of CVL liberated from ruptured microcapsules, resulting in an immediate blue coloration to highlight coating damage. Meanwhile, the primer coating incorporates PMMA microcapsules with a phenolphthalein (PHP) core, which timely reveals alkaline corrosion pits at Mg alloy/coating interface by generating pink coloration. Furthermore, the microcapsules-embedded coating exhibits superior corrosion resistance. The failure evolution dynamics of coating-Mg system, including both the external coating damage and internal localized corrosion, can be visually indicated. This work provides an innovative strategy to tailor and monitor the degradation of coated Mg alloys, thereby presenting promising prospects for application in automotive anticorrosion engineering.

Optimizing the stability of NiFeOOH via oxyanion intercalation for water oxidation at large current densities

In alkaline water splitting, transition metals (Ni, Fe) have received extensive attention, and NiFe-oxyhydroxide (NiFeOOH) is regarded as an exceptionally active electrocatalysts for oxygen evolution reaction (OER). However, maintaining the long-term stability of NiFeOOH at high current densities is challenging due to Fe segregation and catalyst degradation. Herein, this study proposes an approach to enhancing the stability of the Ni/Fe-O covalent bond by intercalating oxyanions (NO3-, PO43-, SO42-, and SeO42-) into the NiFeOOH substrate, improving its resistance to bond breakage. And the NiFeOOH-NO3- electrocatalyst was found to be optimal, achieving an overpotential of 311 mV and stable performance at 1 A cm-2 for several hundred hours. Consequently, NiFeOOH-NO3- exhibited a significantly improved OER stability, with a mere 3.33 % stability attenuation after 100 h, compared to 13.19 % for pristine NiFeOOH. Notably, the presence of NO3- in NiFeOOH effectively mitigates Fe segregation, leading to a fourfold enhancement in long-term stability relative to that of NiFeOOH without NO3- modification. Theoretical calculations show that the introduction of NO3- effectively shifts metal 3d band centers of NiFeOOH closer to the Fermi level. It is suggested that the oxyanions lead to increased strength of the Ni/Fe-O bonds, thereby inhibiting the dissolution of Fe and enhancing the stability of NiFeOOH phase. This research represents a significant advance in controlling Fe segregation to stabilize NiFe-based electrocatalysts for high-current-density water oxidation.

Expanded Negative Electrostatic Network-Assisted Seawater Oxidation and High-Salinity Seawater Reutilization

Coastal/offshore renewable energy sources combined with seawater splitting offer an attractive means for large-scale H2 electrosynthesis in the future. However, designing anodes proves rather challenging, as surface chlorine chemistry must be blocked, particularly at high current densities (J). Additionally, waste seawater with increased salinity produced after long-term electrolysis would impair the whole process sustainability. Here, we convert seawater to O2 selectively, on hydroxides, by building phytate-based expanded negative electrostatic networks (ENENs) with electrostatically repulsive capacities and higher negative charge coverage ranges than those of common inorganic polyatomic anions. With surface ENENs, even typically unstable CoFe hydroxides perform nicely toward alkaline seawater oxidation at activities of >1 A cm-2. CoFe hydroxides with phytate-based ENENs exhibit prolonged lifespans of 1000 h at J of 1 A cm-2 and 900 h at J of 2 A cm-2 and thus rival the best seawater oxidation anodes. Direct introduction of trace phytates to seawater weakens corrosion tendency on conventional CoFe hydroxides as well, extending the life of hydroxides by ∼28 times at J of 2 A cm-2. A wide range of materials all obtain prolonged lifetimes in the presence of ENENs, validating universal applicability. Mechanisms are studied using theoretical computations under working conditions and ex situ/in situ characterizations. We demonstrate a potentially viable way to sustainably reutilize high-salinity wastewater, which is a long-standing but neglected issue. Series-connected devices exhibit good resistance to low temperature operation and are more eco-friendly than current organic electrolyte-based energy storage devices.

Engineering d-p Orbital Hybridization in Mo-O Species of Medium-Entropy Metal Oxides as Highly Active and Stable Electrocatalysts toward Ampere-Level Water/Seawater Splitting

Optimizing the electronic structure of electrocatalysts is of particular importance to enhance the intrinsic activity of active sites in water/seawater. Herein, a series of medium-entropy metal oxides of X(NiMo)O2/NF (X = Mn, Fe, Co, Cu and Zn) is designed via a rapid carbothermal shocking method. Among them, the optimized medium-entropy metal oxide (FeNiMo)O2/NF delivered remarkable HER performance, where the overpotentials as low as 110 and 141 mV are realized at 1000 mA cm-2 (@60 °C) in water and seawater. Meanwhile, medium-entropy metal oxide (FeNiMo)O2/NF only required overpotentials of as low as 330 and 380 mV to drive 1000 mA cm-2 for OER in water and seawater (@60 °C). Theoretical calculations showed that the multiple-metal synergistic effect in medium-entropy metal oxides can effectively enhance the d-p orbital hybridization of Mo─O bond, reduce the energy barrier of H* adsorbed at the Mo sites. Meanwhile, Fe sites in medium-entropy metal oxide can act as the real OER active center, resulting in a good bifunctional activity. In all, this work provides a feasible strategy for the development of highly active and stable medium-entropy metal oxide electrocatalysts for ampere-level water/seawater splitting.

Ultrafast Room-Temperature Synthesis of Phosphate-Intercalated NiFe Layered Double Hydroxides for High-Performance Alkaline Seawater Oxidation

Quick and easy synthetic methods and highly efficient catalytic performance are equally important to anodic oxygen evolution reaction (OER) electrocatalysts for alkaline seawater electrolysis. Herein, we report a facile one-step route to in situ growing PO43- intercalated NiFe layered double hydroxides (NiFe-LDH) on Ni foam (denoted as NiFe-P/NF) by a room-temperature immersion for several minutes. This ultrafast approach transforms the NF surface into a rough PO43- intercalated NiFe-LDH overlayer, which demonstrates outstanding OER performance in both alkaline simulated and natural seawaters owing to good hydrophilic interface and the electrostatic repulsion of PO43- against Cl- anions. Density functional theory calculations reveal that the intercalated PO43- can not only promote electron transfer but also prevent Cl- from entering the interlayer and simultaneously inhibit the migration of Cl- over the NiFe-LDH surface. In alkaline simulated and natural seawater electrolytes, NiFe-P/NF needs low overpotentials of 248 and 298 mV to achieve a current density of 100 mA cm-2, respectively. NiFe-P/NF can stably run over 42 h in an alkaline high-salty electrolyte (1 M KOH + 2.5 M NaCl) at 250 mA cm-2, more than 70 times that of NiFe/NF (0.6 h), emphasizing the critical role of the intercalated PO43- anions on the excellent durability. This study offers a new strategy to modify commercial NF to prepare efficient and stable OER catalysts for seawater electrolysis.

Upcycling of Spent LiFePO4 Cathodes to Heterostructured Electrocatalysts for Stable Direct Seawater Splitting

The pursuit of carbon-neutral energy has intensified the interest in green hydrogen production from direct seawater electrolysis, given the scarcity of freshwater resources. While Ni-based catalysts are known for their robust activity in alkaline water oxidation, their catalytic sites are prone to rapid degradation in the chlorine-rich environments of seawater, leading to limited operation time. Herein, we report a Ni(OH)2 catalyst interfaced with laser-ablated LiFePO4 (Ni(OH)2/L-LFP), derived from spent Li-ion batteries (LIBs), as an effective and stable electrocatalyst for direct seawater oxidation. Our comprehensive analyses reveal that the PO4 3- species, formed around L-LFP, effectively repels Cl- ions during seawater oxidation, mitigating corrosion. Simultaneously, the interface between in situ generated NiOOH and Fe3(PO4)2 enhances OH- adsorption and electron transfer during the oxygen evolution reaction. This synergistic effect leads to a low overpotential of 237 mV to attain a current density of 10 mA cm-2 and remarkable durability, with only a 3.3 % activity loss after 600 h at 100 mA cm-2 in alkaline seawater. Our findings present a viable strategy for repurposing spent LIBs into high-performance catalysts for sustainable seawater electrolysis, contributing to the advancement of green hydrogen production technologies.

Progress in Anode Stability Improvement for Seawater Electrolysis to Produce Hydrogen

Seawater electrolysis for hydrogen production is a sustainable and economical approach that can mitigate the energy crisis and global warming issues. Although various catalysts/electrodes with excellent activities have been developed for high-efficiency seawater electrolysis, their unsatisfactory durability, especially for anodes, severely impedes their industrial applications. In this review, attention is paid to the factors that affect the stability of anodes and the corresponding strategies for designing catalytic materials to prolong the anode's lifetime. In addition, two important aspects-electrolyte optimization and electrolyzer design-with respect to anode stability improvement are summarized. Furthermore, several methods for rapid stability assessment are proposed for the fast screening of both highly active and stable catalysts/electrodes. Finally, perspectives on future investigations aimed at improving the stability of seawater electrolysis systems are outlined.

Reinforcing 2D Single-Crystal Bi2O2CO3 with Additional Interlayer Carbonates by CO2-Assisted Solid-to-Solid Phase Transition

A facile gaseous CO2 mediated solid-to-solid transformation principle is adopted to insert additional CO3 2- anions into the thin single-crystal nanosheets of Bi2O2CO3, which is built of periodic arrays of intrinsic CO3 2- anions and (Bi2O2)2+ layers. The additional CO3 2- anions create abundant defects. The Bi2O2CO3 nanosheets with rich interlayer CO3 2- exhibit superior electronic properties and charge transfer kinetics than the pristine single-crystal 2D Bi2O2CO3 and display enhanced catalytic activity in photocatalytic CO2 reduction reaction and the photocatalytic oxidative degradation of organic pollutants. This work thus illustrates interlayer engineering as a flexible means to build layered 2D materials with excellent properties.

Unraveling the crucial contribution of additive chromate to efficient and stable alkaline seawater oxidation on Ni-based layered double hydroxides

Seawater electrolysis to generate hydrogen offers a clean, green, and sustainable solution for new energy. However, the catalytic activity and durability of anodic catalysts are plagued by the corrosion and competitive oxidation reactions of chloride in high concentrations. In this study, we find that the additive CrO42- anions in the electrolyte can not only promote the formation and stabilization of the metal oxyhydroxide active phase but also greatly mitigate the adverse effect of Cl- on the anode. Linear sweep voltammetry, accelerated corrosion experiments, corrosion polarization curves, and charge transfer resistance results indicate that the addition of CrO42- distinctly improves oxygen evolution reaction (OER) kinetics and corrosion resistance in alkaline seawater electrolytes. Especially, the introduction of CrO42- even in the highly concentrated NaCl (2.5 M) electrolyte prolongs the durability of NiFe-LDH to almost five times the case without CrO42-. Density functional theory calculations also reveal that the adsorption of CrO42- can tune the electronic configuration of active sites of metal oxyhydroxides, enhance conductivity, and optimize the intermediate adsorption energies. This anionic additive strategy can give a better enlightenment for the development of efficient and stable oxygen evolution reactions for seawater electrolysis.

Tungstate Intercalated NiFe Layered Double Hydroxide Enables Long-Term Alkaline Seawater Oxidation

Renewable electricity-driven seawater splitting presents a green, effective, and promising strategy for building hydrogen (H2)-based energy systems (e.g., storing wind power as H2), especially in many coastal cities. The abundance of Cl- in seawater, however, will cause severe corrosion of anode catalyst during the seawater electrolysis, and thus affect the long-term stability of the catalyst. Herein, seawater oxidation performances of NiFe layered double hydroxides (LDH), a classic oxygen (O2) evolution material, can be boosted by employing tungstate (WO4 2-) as the intercalated guest. Notably, insertion of WO4 2- to LDH layers upgrades the reaction kinetics and selectivity, attaining higher current densities with ≈100% O2 generation efficiency in alkaline seawater. Moreover, after a 350 h test at 1000 mA cm-2, only trace active chlorine can be detected in the electrolyte. Additionally, O2 evolution follows lattice oxygen mechanism on NiFe LDH with intercalated WO4 2-.

Activating and Stabilizing a Reversible four Electron Redox Reaction of I-/I+ for Aqueous Zn-Iodine Battery

Low capacity and poor cycle stability greatly inhibit the development of zinc-iodine batteries. Herein, a high-performance Zn-iodine battery has been reached by designing and optimizing both electrode and electrolyte. The Br- is introduced as the activator to trigger I+, and coupled with I+ forming interhalogen to stabilize I+ to achieve a four-electron reaction, which greatly promotes the capacity. And the Ni-Fe-I LDH nanoflowers serve as the confinement host to enable the reactions of I-/I+ occurring in the layer due to the spacious and stable interlayer spacing of Ni-Fe-I LDH, which effectively suppresses the iodine-species shuttle ensuring high cycling stability. As a result, the electrochemical performance is greatly enhanced, especially in specific capacity (as high as 350 mAh g-1 at 1 A g-1 far higher than two-electron transfer Zn-iodine batteries) and cycling performance (94.6 % capacity retention after 10000 cycles). This strategy provides a new way to realize high capacity and long-term stability of Zn-iodine batteries.

Oxalate anions-intercalated NiFe layered double hydroxide as a highly active and stable electrocatalyst for alkaline seawater oxidation

Seawater electrolysis is gaining recognition as a promising method for hydrogen production. However, severe anode corrosion caused by the high concentration of chloride ions (Cl-) poses a challenge for the long-term oxygen evolution reaction. Herein, an anti-corrosion strategy of oxalate anions intercalation in NiFe layered double hydroxide on nickel foam (NiFe-C2O42- LDH/NF) is proposed. The intercalation of these highly negatively charged C2O42- serves to establish electrostatic repulsion and impede Cl- adsorption. In alkaline seawater, NiFe-C2O42- LDH/NF requires an overpotential of 337 mV to gain the large current density of 1000 mA cm-2 and operates continuously for 500 h. The intercalation of C2O42- is demonstrated to significantly boost the activity and stability of NiFe LDH-based materials during alkaline seawater oxidation.

Intercalated and Surface-Adsorbed Phosphate Anions in NiFe Layered Double-Hydroxide Catalysts Synergistically Enhancing Oxygen Evolution Reaction Activity

The oxygen evolution reaction (OER), a crucial semireaction in water electrolysis and rechargeable metal-air batteries, is vital for carbon neutrality. Hindered by a slow proton-coupled electron transfer, an efficient catalyst activating the formation of an O-H bond is essential. Here, we proposed a straightforward one-step hydrothermal procedure for fabricating PO43--modified NiFe layered double-hydroxide (NiFe LDH) catalysts and investigated the role of PO43- anions in enhancing OER. Phosphate amounts can efficiently regulate LDH morphology, crystallinity, composition, and electronic configuration. The optimized sample showed a low overpotential of 267 mV at 10 mA cm-2. Density functional theory calculations revealed that intercalated and surface-adsorbed PO43- anions in NiFe LDH reduced the Gibbs free energy in the rate-determining step of *OOH formation, balancing oxygen-containing intermediate adsorption/dissociation and promoting the OER. Intercalated phosphate ions accelerated precatalyst dehydrogenation kinetics, leading to a rapid reconstruction into active NiFe oxyhydroxide species. Surface-adsorbed PO43- interacted favorably with adsorbed *OOH on the active Ni sites, stabilizing *OOH. Overall, the synergistic effects of intercalated and surface-adsorbed PO43- anions significantly contributed to enhanced OER activity. Achieving optimal catalytic activity requires a delicate equilibrium between thermodynamic and kinetic factors by meticulously regulating the quantity of introduced PO43- ions. This endeavor will facilitate a deeper comprehension of the influence of anions in electrocatalysis for OER.

The Recent Progresses of Electrodes and Electrolysers for Seawater Electrolysis

The utilization of renewable energy for hydrogen production presents a promising pathway towards achieving carbon neutrality in energy consumption. Water electrolysis, utilizing pure water, has proven to be a robust technology for clean hydrogen production. Recently, seawater electrolysis has emerged as an attractive alternative due to the limitations of deep-sea regions imposed by the transmission capacity of long-distance undersea cables. However, seawater electrolysis faces several challenges, including the slow kinetics of the oxygen evolution reaction (OER), the competing chlorine evolution reaction (CER) processes, electrode degradation caused by chloride ions, and the formation of precipitates on the cathode. The electrode and catalyst materials are corroded by the Cl- under long-term operations. Numerous efforts have been made to address these issues arising from impurities in the seawater. This review focuses on recent progress in developing high-performance electrodes and electrolyser designs for efficient seawater electrolysis. Its aim is to provide a systematic and insightful introduction and discussion on seawater electrolysers and electrodes with the hope of promoting the utilization of offshore renewable energy sources through seawater electrolysis.

In-situ fabrication of bimetallic FeCo2O4-FeCo2S4 heterostructure for high-efficient alkaline freshwater/seawater electrolysis

Rational construction of bifunctional electrocatalysts with long-term stability and high electrocatalytic activity is of great importance, but it is challenging to obtain highly efficient non-precious metal-based catalysts for overall seawater electrolysis. Herein, a nickel foam (NF) self-supporting CoFe-layered double hydroxide (CoFe-LDH/NF) was directly converted into FeCo2O4-FeCo2S4 heterostructure via hydrothermal method in 50 mM Na2S solution, instead of FeCo2O4@FeCo2S4 core-shell structure. The FeCo2O4-FeCo2S4 heterojunction shows nanosheets structure with rough surface (the thickness of ∼ 198.9 nm), which provides rich oxide/sulfide interfaces, high electrochemical active area, a large number of active sites, as well as fast charge and mass transfer. In 1.0 M KOH solution, 1.0 M KOH + 0.5 M NaCl, and alkaline natural seawater, the FeCo2O4-FeCo2S4 heterojunction exhibits eminently electrocatalytic performance, with overpotentials of η-100 = 225 mV, η-100 = 233 mV, and η-100 = 238 mV for OER, as well as η-100 = 271 mV, η-100 = 273 mV, and η-100 = 277 mV for HER, respectively. Furthermore, self-supporting FeCo2O4-FeCo2S4 electrode (FeCo2O4-FeCo2S4/NF) as the cathode and anode of an electrolyzer exhibits a lower cell voltage of E-100 = 1.75 V in alkaline seawater than those of FeCo2S4/NF (1.77 V), CoFe-LDH/NF (1.87 V), and FeCo2O4/NF (1.91 V). Specifically, FeCo2O4-FeCo2S4 electrolyzer can stably produce hydrogen for over 48 h in alkaline freshwater/seawater electrolyte. These outstanding electrocatalytic performances and corrosion resistance to salty-water can be attributed to the surface reconstruction behavior of the FeCo2O4-FeCo2S4/NF catalyst during OER, which leads to the in-situ formation of metal oxyhydroxides. In particular, the FeCo2O4-FeCo2S4 heterojunction is also very competitive among most state-of-the-art non-noble metal-based catalysts, whether in KOH or alkaline salty-water electrolytes.

Concerning the stability of seawater electrolysis: a corrosion mechanism study of halide on Ni-based anode

The corrosive anions (e.g., Cl-) have been recognized as the origins to cause severe corrosion of anode during seawater electrolysis, while in experiments it is found that natural seawater (~0.41 M Cl-) is usually more corrosive than simulated seawater (~0.5 M Cl-). Here we elucidate that besides Cl-, Br- in seawater is even more harmful to Ni-based anodes because of the inferior corrosion resistance and faster corrosion kinetics in bromide than in chloride. Experimental and simulated results reveal that Cl- corrodes locally to form narrow-deep pits while Br- etches extensively to generate shallow-wide pits, which can be attributed to the fast diffusion kinetics of Cl- and the lower reaction energy of Br- in the passivation layer. Additionally, for the Ni-based electrodes with catalysts (e.g., NiFe-LDH) loading on the surface, Br- causes extensive spalling of the catalyst layer, resulting in rapid performance degradation. This work clearly points out that, in addition to anti-Cl- corrosion, designing anti-Br- corrosion anodes is even more crucial for future application of seawater electrolysis.

Facile method to activate substrate for oxygen evolution by a galvanic-cell reaction

NiFe layered double hydroxide (NiFe LDH) is a promising material with multiple functions. In this communication, a novel method is used to prepare NiFe LDH. This synthesis method is achieved via galvanic-cell corrosion between nickel and iron substrates in aqueous solutions containing a halogen group anion (e.g., Cl) at ambient temperature. The as-prepared NiFe LDH electrodes are developed as electrocatalysts for the oxygen evolution reaction (OER) and exhibit excellent catalytic activities and durability. This work provides an energy-efficient, cost-effective, and scaled-up corrosion engineering approach for manufacturing NiFe LDH materials.

Recent Advances of Modified Ni (Co, Fe)-Based LDH 2D Materials for Water Splitting

Water splitting technology is an efficient approach to produce hydrogen (H₂) as an energy carrier, which can address the problems of environmental deterioration and energy shortage well, as well as establishment of a clean and sustainable hydrogen economy powered by renewable energy sources due to the green reaction of H₂ with O₂. The efficiency of H₂ production by water splitting technology is intimately related with the reactions on the electrode. Nowadays, the efficient electrocatalysts in water splitting reactions are the precious metal-based materials, i.e., Pt/C, RuO₂, and IrO₂. Ni (Co, Fe)-based layered double hydroxides (LDH) two-dimensional (2D) materials are the typical non-precious metal-based materials in water splitting with their advantages including low cost, excellent electrocatalytic performance, and simple preparation methods. They exhibit great potential for the substitution of precious metal-based materials. This review summarizes the recent progress of Ni (Co, Fe)-based LDH 2D materials for water splitting, and mainly focuses on discussing and analyzing the different strategies for modifying LDH materials towards high electrocatalytic performance. We also discuss recent achievements, including their electronic structure, electrocatalytic performance, catalytic center, preparation process, and catalytic mechanism. Furthermore, the characterization progress in revealing the electronic structure and catalytic mechanism of LDH is highlighted in this review. Finally, we put forward some future perspectives relating to design and explore advanced LDH catalysts in water splitting.