Constructing Hydrogen Migration Channel from Atomic Clusters to Single Atom for Superior Electrocatalytic Hydrogen Evolution with Ultralow Pt Loading

Developing highly active and durable cathode catalysts using minimal use of noble metal remains a grand challenge for proton exchange membrane water electrolyzer. Herein we design a Pt-based sub-nanometric catalysts featuring coexisting single atoms and atomic clusters anchored on sulfur-doped carbon. This dual-active-site architecture enables independent optimization of active hydrogen (H*) formation and subsequent recombination kinetics, thus breaking the limitation of Sabatier principle. Specially, by introducing a secondary transition metal such as Mn, the interfacial charge distribution and work function of Pt clusters is regulated, promoting both H* formation and migration. Meanwhile, the neighboring electron-deficient Pt single atoms facilitate H* recombination kinetics. The catalyst with 3.6 wt% Pt loading achieves a recorded mass activity of 14.48 A mg^-1 at 15 mV, exceeding commercial 40wt% Pt/C by 41-fold. When integrated into an electrolyzer, the catalyst demonstrates exceptional activity and stability with only 10% Pt loading relative to commercial benchmark, representing a critical advancement toward practical green hydrogen production. Also, the direct evidences of H* formation, migration and recombination process are confirmed by operando experiments and theoretical calculations for the first time, which offers new concept for decoupling of HER reaction and rational design of catalysts.