Non-noble-metal electrocatalysts for oxygen evolution reaction toward seawater splitting: A review

The direct electrolytic splitting of abundant seawater instead of scarce freshwater is an ideal strategy for producing clean and renewable hydrogen (H2) fuels. The oxygen evolution reaction (OER) is a vital half-reaction that occurs during electrochemical seawater splitting. However, OER suffers from sluggish four-electron transfer kinetics and competitive chlorine evolution reactions in seawater. Noble metal-based catalysts such as IrO2 and RuO2 are considered to have state-of-the-art OER electrocatalytic activity, but the low reserves and high prices of these noble metals significantly limit their large-scale application. Recently, efforts have been made to explore efficient, robust, and anti-chlorine-corrosion non-noble-metal OER electrocatalysts for seawater splitting such as oxides, hydroxides, phosphides, nitrides, chalcogenides, alloys, and composites. An in-depth understanding of the fundamentals of seawater electrolysis and the design principle of electrode materials is important for promoting seawater-splitting technology. In this review, we first introduce fundamental reactions in seawater electrolytes. Subsequently, construction strategies for OER electrocatalysts for seawater splitting are introduced. Finally, present challenges and perspectives regarding non-noble-metal OER electrocatalysts for commercial H2 production by seawater splitting are discussed.