Photodeposition of earth-abundant cocatalysts in photocatalytic water splitting: Methods, functions, and mechanisms

Photocatalytic water splitting based on semiconductor photocatalysts is a promising approach for producing carbon-neutral, sustainable, and clean H2 fuel. Cocatalyst loading, which is an appealing strategy, has been extensively employed to improve the photocatalytic efficiency semiconductors. In view of the high cost and rare preservation of noble metal cocatalysts that significantly hinder their utilization for large-scale energy production, various cocatalysts comprising earth-abundant elements have been developed as noble-metal-free candidates using different methods to boost photocatalytic water splitting. Among these preparation strategies, photodeposition has attracted tremendous attention in the deposition of earth-abundant cocatalysts owing to its simplicity and moderate availability, improved interfacial charge separation and transfer, and abundant active sites on the surface. In this review, we first summarize the deposition principles, deposition advantages, categories of cocatalysts, roles of cocatalysts, influencing factors, modification strategies, and design considerations in the photodeposition of earth-abundant cocatalysts. The photodeposited earth-abundant cocatalysts for the photocatalytic H2 evolution half reaction, photocatalytic O2 evolution half reaction, and overall photocatalytic water splitting are discussed. Finally, some perspectives on the challenges and possible future directions for the photodeposition of earth-abundant cocatalysts in photocatalytic water splitting are presented.