Unveiling the mysteries of hydrogen spillover phenomenon in hydrogen evolution reaction: Fundamentals, evidence and enhancement strategies

The phenomenon of hydrogen spillover is a dynamic behavior during catalytic reactions and has been a prominent area of research in the field of thermal catalysis. This concept has become a new focus of research in the field of hydrogen evolution reaction (HER) in recent years. The hydrogen spillover effect has a pivotal effect on modulating the active sites of catalysts and enhancing catalytic activity, which also provides a novel perspective for optimizing HER catalysts. While some advancements have been achieved in understanding the hydrogen spillover phenomenon, the existing review is deficient in a systematic overview of the mechanism of hydrogen spillover occurrence during HER and a summary of the evidence to confirm the occurrence of the hydrogen spillover phenomenon particularly. Furthermore, a comprehensive summary of the specific strategies to optimize the catalytic system using this effect is lacking. In light of the aforementioned considerations, this review aims to conduct a comprehensive summary of the fundamental mechanisms underlying the phenomenon of hydrogen spillover, with a particular focus on the evidence presented in experimental studies. Following a comprehensive examination of the underlying mechanism and supporting evidence, the discussion turns to the question of how the hydrogen spillover effect can be strategically enhanced to optimize the overall performance of HER. Finally, the opportunities and challenges facing this research area are discussed, and potential future research directions are outlined. This review not only enhances comprehension of how hydrogen spillover occurs in the HER process but also offers invaluable theoretical insight and practical strategies for the creation of new and efficient catalysts.