A fundamental understanding of the origin of oxygen evolution reaction (OER) activity of transition-metal-based electrocatalysts, especially for single precious metal atoms supported on layered double hydroxides (LDHs), is highly required for the design of efficient electrocatalysts toward further energy conversion technologies. Here, we aim toward single-atom Au supported on NiFe LDH (sAu/NiFe LDH) to clarify the activity origin of LDHs system and a 6-fold OER activity enhancement by 0.4 wt % sAu decoration. Combining with theoretical calculations, the active behavior of NiFe LDH results from the in situ generated NiFe oxyhydroxide from LDH during the OER process. With the presence of sAu, sAu/NiFe LDH possesses an overpotential of 0.21 V in contrast to the calculated result (0.18 V). We ascribe the excellent OER activity of sAu/NiFe LDH to the charge redistribution of active Fe as well as its surrounding atoms causing by the neighboring sAu on NiFe oxyhydroxide stabilized by interfacial CO32– and H2O in...

Single-Atom Au/NiFe Layered Double Hydroxide Electrocatalyst: Probing the Origin of Activity for Oxygen Evolution Reaction

Recent Progress on Multimetal Oxide Catalysts for the Oxygen Evolution Reaction

Highly Active Trimetallic NiFeCr Layered Double Hydroxide Electrocatalysts for Oxygen Evolution Reaction

Layered double hydroxide (LDH)-based materials have attracted widespread attention in various applications due to their unique layered structure with high specific surface area and unique electron distribution, resulting in a good electrocatalytic performance. Moreover, the existence of multiple metal cations invests a flexible tunability in the host layers; the unique intercalation characteristics lead to flexible ion exchange and exfoliation. Thus, their electrocatalytic performance can be tuned by regulating the morphology, composition, intercalation ion, and exfoliation. However, the poor conductivity limits their electrocatalytic performance, which therefore has motivated researchers to combine them with conductive materials to improve their electrocatalytic performance. Another factor hampering their electrocatalytic activity is their large lateral size and the bulk thickness of LDHs. Introducing defects and tuning electronic structure in LDH-based materials are considered to be effective strategies to increase the number of active sites and enhance their intrinsic activity. Given the unique advantages of LDH-based materials, their derivatives have been also used as advanced electrocatalysts for water splitting. Here, recent progress on LDHs and their derivatives as advanced electrocatalysts for water splitting is summarized, current strategies for their designing are proposed, and significant challenges and perspectives of LDHs are discussed.

Recent Progress on Layered Double Hydroxides and Their Derivatives for Electrocatalytic Water Splitting

Efficient Electrocatalytic and Photoelectrochemical Hydrogen Generation Using MoS2 and Related Compounds

Finding efficient electrocatalysts for oxygen evolution reaction (OER) that can be effectively integrated with semiconductors is significantly challenging for solar-driven photo-electrochemical (PEC) water splitting. Herein, amorphous cobalt–iron hydroxide (CoFeH) nanosheets are synthesized by facile electrodeposition as an efficient catalyst for both electrochemical and PEC water oxidation. As a result of the high electrochemically active surface area and the amorphous nature, the optimized amorphous CoFeH nanosheets exhibit superior OER catalytic activity in alkaline environment with a small overpotential (280 mV) to achieve significant oxygen evolution (j = 10 mA cm−2) and a low Tafel slope (28 mV dec−1). Furthermore, CoFeH nanosheets are simply integrated with BiVO4 semiconductor to construct CoFeH/BiVO4 photoanodes that exhibit a significantly enhanced photocurrent density of 2.48 mA cm−2 (at 1.23 V vs reversible hydrogen electrode (RHE)) and a much lower onset potential of 0.23 V (vs RHE) for PEC-OER. Careful electrochemical and optical studies reveal that the improved OER kinetics and high-quality interface at the CoFeH/BiVO4 junction, as well as the excellent optical transparency of CoFeH nanosheets, contribute to the high PEC performance. This study establishes amorphous CoFeH nanosheets as a highly competitive candidate for electrochemical and PEC water oxidation and provides general guidelines for designing efficient PEC systems.

Amorphous Cobalt–Iron Hydroxide Nanosheet Electrocatalyst for Efficient Electrochemical and Photo-Electrochemical Oxygen Evolution

Three-dimensional (3D) semiconductor photoelectrodes are promising for improving the efficiency of photoelectrochemical (PEC) water splitting for hydrogen generation, but a high-quality heterojunction between the semiconductor and the carefully selected high-performance electrocatalyst is crucial. Here, we report the rational design of a novel 3D p-Si/NiCoSex core/shell nanopillar (NP) array photocathode via uniform photo-assisted electrodeposition of NiCoSex electrocatalyst on bamboo shoot-like Si NP array backbones. We demonstrate its enhanced PEC performance with a photocurrent density of −37.5 mA cm−2 at 0 V (vs. RHE) under simulated 100 mW cm−2 (1 Sun) irradiation with an AM 1.5 G filter, which is the highest value reported for p-type Si photocathodes. The synergistic effects of the excellent light harvesting of the Si NP array core and the good optical transparency, as well as the excellent electrocatalytic activity of the NiCoSex shell, boost the production and utilization of photogenerated electrons. The design of p-Si/NiCoSex core/shell NP arrays offers a new strategy for preparing highly efficient photoelectrochemical solar energy conversion devices.

A p-Si/NiCoSex core/shell nanopillar array photocathode for enhanced photoelectrochemical hydrogen production

A non-enzymatic hydrogen peroxide sensor based on vertical NiO nanosheets supported on the graphite sheet

Exploring efficient and cheap oxygen evolution reaction (OER) electrocatalysts is of great significance for electrochemical water splitting. Herein, we successfully prepared an efficient ternary electrocatalyst of porous cobalt oxynitride (Co3 Ox Ny ) nanosheets by a simple nitridation strategy. Specifically, CoON PNS-400 (cobalt oxynitride with porous nanosheet structure obtained at 400 o C) offered a low OER overpotential of 0.23 V to achieve the catalytic current density of 10 mA cm-2 and a small Tafel slope of 48 mV dec-1 in alkali media, outperforming most of the first-row transition-metal-based OER electrocatalysts. The calculated density of states (DOS) analysis and electron spin resonance (ESR) measurements revealed that the introduction of foreign N atoms into pristine Co3 O4 nanosheets can optimize the electronic structure and create more oxygen vacancies, thus leading to enhanced electrical conductivity. Density functional theory (DFT) calculations demonstrated that the foreign N atoms can also improve the energetics for OER by modulating the free energy for adsorbed intermediates (OOH*, OH*, O*), further improving the OER electrocatalytic activity of CoON PNS-400. This work provides a possibility for rationally designing ternary transition-metal compounds as advanced OER electrocatalysts.

Wei Liu

Papers

Amorphous Cobalt–Iron Hydroxide Nanosheet Electrocatalyst for Efficient Electrochemical and Photo-Electrochemical Oxygen Evolution

A p-Si/NiCoSex core/shell nanopillar array photocathode for enhanced photoelectrochemical hydrogen production

A non-enzymatic hydrogen peroxide sensor based on vertical NiO nanosheets supported on the graphite sheet

Porous Cobalt Oxynitride Nanosheets for Efficient Electrocatalytic Water Oxidation

Gel-incorporated PbS and PbI2 single-crystals