Abstract
Electrochemical water splitting driven by clean and sustainable energy sources to produce hydrogen is an efficient and environmentally friendly energy conversion technology. Water splitting involves hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), in which OER is the limiting factor and has attracted extensive research interest in the past few years. Conventional noble-metal-based OER electrocatalysts like IrO2 and RuO2 suffer from the limitations of high cost and scarce availability. Developing innovative alternative nonnoble metal electrocatalysts with high catalytic activity and long-term durability to boost the OER process remains a significant challenge. Among all of the candidates for OER catalysis, self-supported layered double hydroxides (LDHs) have emerged as one of the most promising types of electrocatalysts due to their unique layered structures and high electrocatalytic activity. In this review, we summarize the recent progress on self-supported LDHs and highlight their electrochemical catalytic performance. Specifically, synthesis methods, structural and compositional parameters, and influential factors for optimizing OER performance are discussed in detail. Finally, the remaining challenges facing the development of self-supported LDHs are discussed and perspectives on their potential for use in industrial hydrogen production through water splitting are provided to suggest future research directions.
Highlights
The emission of greenhouse gases and other environmental pollution issues related to the consumption of fossil fuels such as coal, petroleum, and natural gas has aroused intensive research interest in renewable energy technologies [1,2,3,4]
The thickness and crystallinity of the layered double hydroxides (LDHs) can be adjusted by changing the deposition parameters, such as the current density and working time, while its chemical composition can be controlled by changing the metal salts in the electrolyte
The sulfurization of NiCoFe LDHs could result in a small portion of the hydroxyl ions being substituted by S2, effectively promoting electrical conductivity through the construction of Ni–S and Co–S bonds, which are more favorable for electron transfer
Summary
The emission of greenhouse gases and other environmental pollution issues related to the consumption of fossil fuels such as coal, petroleum, and natural gas has aroused intensive research interest in renewable energy technologies [1,2,3,4]. Conventional precious-metal-based electrocatalysts like IrO2 and RuO2 exhibit excellent OER performance [26] Their high cost, scarce availability, and instability in alkaline. LDH-based materials have been developed as promising OER electrocatalysts due to their various advantages, such as low cost, abundance, and favorable water adsorption, the poor durability and low intrinsic conductivity (10−13–10−17 S cm−1) of the powdery LDHs greatly hinder their electrocatalytic performance and practical application [33]. LDHs grown in situ on conductive supports toward water splitting [35, 36] In addition to their excellent chargetransfer ability, conventional supports like nickel foam (NF), copper foam (CF), and carbon cloth (CC) can provide a large surface area for active electrocatalysts to grow [10, 37]. The remaining challenges and future outlook for the design and synthesis of novel self-supported LDH electrocatalysts are discussed to provide direction for further research
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