Nanocatalysts in photocatalytic water splitting for green hydrogen generation: Challenges and opportunities

Green hydrogen is a promising technology for sustainable energy production, with photocatalytic water splitting offering several advantages over wind/solar-powered water electrolysis. The focus of this review paper is on high-performance photocatalysts, which are key to improving the efficiency of photocatalytic hydrogen production. First, the general principles of photocatalytic hydrogen production and the factors affecting photocatalytic performance are summarized. Then, the conventional semiconductor photocatalysts including methods to improve their catalytic activities are comprehensively reviewed, which is followed by a detailed discussion of representative nano-photocatalysts. The performance of photocatalysts is affected by various factors, such as optical absorption, separation and transport efficiency of photocarriers, and redox capacity. The entire process of photocatalytic hydrogen production can be optimized through methods such as element doping, cocatalyst location, morphology adjustment, and heterojunction construction. Finally, photocatalysts of different dimensions, along with the challenges and future research directions, are summarized based on comparisons of numerous studies. This review provides a quick start guide for investigating the application of high-performance photocatalysts in green hydrogen production from photocatalytic hydrolysis, and offers insight into the latest advancements in photochemical conversion efficiency. It also provides a valuable reference for selecting nanomaterials and optimizing photocatalytic hydrogen production.