Developing advanced catalysts with rapid hydrogen evolution reaction (HER) kinetics in alkaline media is vital for hydrogen production. Through the d–p orbital hybridization effect, the electronic structure and H* adsorption can be optimized on metal species. Herein, a N-doped hollow carbon (H-NPC)-supported Ru cluster (c-Ru@H-NPC) catalyst was constructed via carbonization of well-defined hollow metal–organic frameworks, followed by etching and anchoring of Ru clusters. The hollow structure could not alter the coordination number of Ru while exhibiting higher-level electron transfer, thereby strengthening the orbital hybridization. Additionally, finite element simulations indicated the acceleration of H2 diffusion for hollow structures. Furthermore, the N-doping strengthened the electron interaction of Ru–C by the d–p hybridization effect, which was confirmed by theoretical calculations and in situ Raman spectroscopy. Therefore, in alkaline/alkaline seawater media, c-Ru@H-NPC needed only 10/12 mV overpotentials and 1.52/1.55 V cell voltages to drive the HER and overall water splitting, respectively, at a current density of 10 mA cm−2, exhibiting outstanding catalytic activity. Meanwhile, the attenuation of current density was very small towards successive stability tests for >55 h at 10 mA cm−2. This work permits new insights into the design of high-performance metal cluster catalysts for the HER and other conversion reactions.
