Facilitating alkaline hydrogen evolution of Ru@Fe-NC with ultra-low overpotential: Optimized d-band center and lowered energy barrier for water dissociation

The strong hydrogen binding affinity on Ru surfaces and their intrinsic aggregation tendency pose significant challenges to the hydrogen evolution reaction (HER) activity of Ru-based electrocatalysts. The construction of active electrocatalysts composed of partially dispersed nanoparticles (NPs) and individual single atomic site with robust thermodynamic stability, has emerged as a viable alternative to benchmark commercial HER electrocatalyst. Herein, a multi-step strategy was designed to synthesize Ru_NP@Fe_SA-NC electrocatalyst, and a robust interaction between uniformly dispersed Ru NPs and embedded single-atom Fe sites was uncovered, which not only regulates the particle size of Ru NPs but also controls the spin state and electronic configuration of Fe single atom. Moreover, magnetic characterization reveals that the synergetic effect induces a high spin state of the Fe atom with unpaired electrons in the 3d orbitals, which enhances the adsorption of intermediates and accelerates the reaction kinetics. The as obtained electrocatalyst demonstrates a low overpotential of 13 mV at 10 mA cm⁻² in alkaline condition. Remarkably, theoretical calculation indicates that the outstanding performance of Ru_NP@Fe_SA-NC stems from the Fe optimized electronic structure of the Ru site, which downshifts the d-band center, reduces the energy barriers for water dissociation and optimizes H* desorption, thereby promoting HER. This study presents an innovative approach to utilize Fe_SA-NC to stabilize Ru NPs and reduce the energy barrier, contributing to an ideal HER performance.