Demystify the unique hydrogen spillover effect in electrocatalytic hydrogen evolution

Abstract

Hydrogen spillover, involving the migration of active hydrogen species between high-affinity sites and weak adsorption sites on the catalyst surface, has recently garnered attention for its unique reaction mechanism and accelerated reaction kinetics. However, this migration process is thermodynamically unfavorable, as it necessitates overcoming significant interfacial barriers. Thus, hydrogen spillover is not commonly observed in hydrogen evolution reaction (HER) catalysis. A thorough understanding of hydrogen spillover is crucial for designing advanced HER catalysts with low-energy-barrier interfaces that facilitate hydrogen migration. In this review, we analyze the fundamental characteristics of hydrogen spillover and provide a comprehensive overview of its effects in the context of recent advances in HER. We summarize the various manifestations of hydrogen spillover observed in early HER catalysis and describe feasible physicochemical and electrochemical characterization methods to validate the occurrence of this phenomenon. Additionally, we discuss different strategies to modulate the kinetic barriers associated with interfacial hydrogen spillover in detail, which are essential for the efficient design and synthesis of advanced HER catalysts that leverage this effect. Finally, we present the challenges and future perspectives related to the hydrogen spillover effect in HER catalysis, offering guidance for expanding its application in catalytic reactions.