LAUSR

Abstract Electrocatalytic water splitting in acid electrolyte is considered as one of the promising strategies to generate hydrogen. However, the industrial applications of electrolytic water are mainly hindered by the oxygen evolution reaction (OER) due to the high overpotential. Therefore, it is critical to develop highly active and durable electrocatalysts to reduce the overpotential. This work reports ultra-small Sn-RuO2 nanoparticles supported on N‑doped carbon polyhedral are successfully synthesized through dipping and annealing. Integrating the merits of metal–organic frameworks (MOFs) and dopant atoms, the optimized catalyst Sn-RuO2@NPC displays a low overpotential of 178 mV at 10 mA cm−2 and excellent long-term stability after continuous testing of 150 hours in the acidic media, which surpassed most Ru-based OER catalysts. The density functional theory (DFT) calculations reveal that doping Sn into RuO2 could effectively improve the intrinsic OER activity of adjacent Ru sites, thereby reducing the Gibbs free energy of rate-determining steps. Notably, the crystal orbital Hamilton population (COHP) shows that the binding strength between catalytic active sites (Ru sites) and reaction intermediates (*O) is decreased due to the presence of Sn, which results in more easily forming the next reaction intermediates (*OOH) and then improving the water splitting activity. This work provides a new insight into an effective method of efficient electrocatalysts for water splitting in acidic media.