Unraveling a Graphene Exfoliation Technique Analogy in the Making of Ultrathin Nickel-Iron Oxyhydroxides@Nickel Foam to Promote the OER

PbS@NiFe-LDH heterojunction: an efficient photo-assisted electrocatalyst for the OER

Recently, photo-assisted electrocatalysis as an emerging catalytic approach that combines the technologies of photocatalysis and electrocatalysis has attracted great interest among researchers. Under this circumstance, the NiFe-LDH compounded with PbS based (PbS@NFHS) heterojunction with both photoactive and electrocatalytic properties was constructed for the first time through an ambient etching route and a subsequent low-temperature hydrothermal method. The as-prepared catalyst displayed a novel hierarchical 3D open structure based on nanosheets, which offered numerous electrochemically active sites, facilitated the swift diffusion of ions and enhanced both electrical conductivity and catalytic stability, thus significantly improving the catalytic performance. Furthermore, the charge redistribution in the p-n junction led to the formation of space-charge regions and a built-in electric field, which benefited the charge transfer and thereby enhanced the intrinsic activity. Under illumination, electrochemical tests showed that the overpotential was only 291 mV for the OER at 50 mA cm-2 in 1 M KOH solution, which was 50 mV lower than that without illumination. Moreover, the catalyst can maintain stability for 40 hours at a current of 10 mA cm-2 in 1 M KOH. Compared to the traditional electrocatalytic OER, this work employed a very promising photo-assisted electrocatalytic strategy, which could further broaden the wide application of NiFe-LDH.

Activity-Stability Relationships in Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is a critical process in various sustainable energy technologies. Despite substantial progress in catalyst development, the practical application of OER catalysts remains hindered by the ongoing challenge of balancing high catalytic activity with long-term stability. We explore the inverse trends often observed between activity and stability, drawing on key insights from both experimental and theoretical studies. Special focus is placed on the performance of different electrodes and their interaction with acidic and alkaline media across a range of electrochemical conditions. This Perspective integrates recent advancements to present a thorough framework for understanding the mechanisms underlying the activity-stability relationship, offering strategies for the rational design of next-generation OER catalysts that successfully meet the dual demands of activity and durability.

Fe,Ce Co-Doped Ni3S2/NiS Polymorphism Nanosheets With Improved Electrocatalytic Activity and Stability for Water Oxidation

Balancing the relationship between electrocatalytic activity and stability of sulfide catalysts during oxygen evolution reaction (OER) has been attracting extensive research interest. Here, a simple electrodeposition-vulcanization two-step route was designed to successfully construct nickel foam supported sheet-like Fe,Ce-codoped Ni3S2/NiS polymorphism catalyst (labeled as Fe,Ce-Ni3S2/NiS/NF). Electrochemical measurements showed that the as-obtained Fe,Ce-Ni3S2/NiS/NF electrode presented excellent OER electrocatalytic performances. In 1 M KOH solution, merely 173 and 234 mV of overpotentials were required to deliver the current densities of 10 and 100 mA cm-2, respectively. Further investigations revealed that the Fe,Ce co-doping regulated the electron density around Ni, which promoted the conversion of Ni towards the higher valence state and simultaneously, avoided the stability decrease of the catalyst caused by excessive oxidation corrosion. Moreover, the defects generated during vulcanization also contributed to promoting water oxidation. The present work provides a facile and feasible approach to balance the relationship between the stability and the activity of sulfide catalysts for OER.

Rapid Formation of Epitaxial Oxygen Evolution Reaction Catalysts on Dendrites with High Catalytic Activity and Stability

Oxygen evolution reaction is an essential but kinetically sluggish step in many energy storage and conversion processes and therefore is in pursuit of highly efficient and stable catalysts. Although nanosized transition-metal-based oxides/hydroxides exhibit high catalytic activity toward the oxygen evolution reaction (OER), many of them suffer from low stability at an anode current density in industrial scale. Herein, by combining a rapid epitaxial formation method with dynamic bubble-templated electrodeposition, we successfully developed single crystalline NiFeCu oxide catalysts with a hierarchical porous structure. It was found that the structure can facilitate fast electron transportation for the catalysts and retard the diffusion of the O atoms to the inner metallic current collector. The hierarchical pores inherited from the hydrogen bubble templates built ideal channels for the massive and rapid release of oxygen bubbles. As a consequence, the NiFeCu oxides catalyzed the OER more efficiently and steadily than the commercial RuO2 catalyst at an anode current density in industrial scale (300 mA/cm2). This work, by resolving the durability concerns for nanosized oxides, offers a series of highly efficient and stable catalysts for OER and a structure building strategy to boost the catalytic activity and stability for nonconductive catalysts.

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.

Oxygen-Plasma-Induced Hetero-Interface NiFe2O4/NiMoO4 Catalyst for Enhanced Electrochemical Oxygen Evolution

The electrolysis of water to produce hydrogen is an effective method for solving the rapid consumption of fossil fuel resources and the problem of global warming. The key to its success is to design an oxygen evolution reaction (OER) electrocatalyst with efficient conversion and reliable stability. Interface engineering is one of the most effective approaches for adjusting local electronic configurations. Adding other metal elements is also an effective way to enrich active sites and improve catalytic activity. Herein, high-valence iron in a heterogeneous interface of NiFe2O4/NiMoO4 composite was obtained through oxygen plasma to achieve excellent electrocatalytic activity and stability. In particular, 270 mV of overpotential is required to reach a current density of 50 mA cm-2, and the overpotential required to reach 500 mA cm-2 is only 309 mV. The electron transfer effect for high-valence iron was determined by X-ray photoelectron spectroscopy (XPS). The fast and irreversible reconstruction and the true active species in the catalytic process were identified by in situ Raman, ex situ XPS, and ex situ transmission electron microscopy (TEM) measurements. This work provides a feasible design guideline to modify electronic structures, promote a metal to an active oxidation state, and thus develop an electrocatalyst with enhanced OER performance.