Unlocking Hydrogen-Bond Network-Mediated Directional Spillover Mechanism in Electrocatalytic Hydrogen Evolution

Hydrogen spillover offers a promising route to circumvent scaling relations in the electrocatalytic hydrogen evolution reaction (HER) by spatially decoupling the hydrogen adsorption and desorption steps. However, its practical application has been limited by sluggish spillover kinetics across heterogeneous interfaces. In this work, we propose a hydrogen-bond (H-bond) network-mediated spillover mechanism that bypasses conventional interfacial mediation. Within this mechanism, active hydrogen species (H*) generated on one component sequentially enter the H-bond network, undergo directional transport via Grotthuss-type H* hopping along the network, and ultimately uptake onto another component. To realize this concept, we designed a Pt/g-C₃N₄/CoP catalyst, in which Pt effectively enriches H* to establish a coverage gradient from Pt→g-C₃N₄→CoP; g-C₃N₄ optimizes the proximity of the H-bond network to facilitate H* shuttling and serves as H* relay sites; and CoP provides facile sites for H₂ desorption. This configuration enables efficient H-bond network-mediated spillover along the Pt→g-C₃N₄→CoP pathway, achieving an ultrahigh Pt-mass-normalized HER activity of 175.0 A mg_Pt ^-1 at -0.1 V vs. RHE in acidic medium. The mechanism elucidated here opens new avenues for catalyst design in multi-step hydrogen-involving electrocatalytic processes.