Sm-Induced Symmetry-Broken Ru Centers for Boosting Acidic Water Oxidation

Ruthenium oxide (RuO 2 ) as a promising acidic oxygen evolution reaction (OER) electrocatalyst for proton exchange membrane water electrolyzers still suffers from severe excessive oxidation and Ru dissolution, leading to the loss of activity. Herein, a Sm doping in amorphous/crystalline heterophase RuO 2 (AC-Sm-RuO 2 ) catalyst is designed for boosting the acidic OER catalytic performance by altering the electronic properties and number of active sites. The representative AC-Sm-RuO 2 displays robust OER performance with an overpotential of 200 mV to achieve 10 mA cm –2, and significantly enhanced stability compared to synthesized RuO 2 (S-RuO 2 ) and commercial RuO 2 (Com. RuO 2 ). Electrochemical measurements combined with advanced characterizations reveal that the high activity in AC-Sm-RuO 2 originated from the symmetry-broken Ru active sites, which lowers the formation energy barrier of *OOH; meanwhile, the improved stability arises from the strong interplay within the local Ru–O–Sm units and the characteristics of the amorphous/crystalline hybrid. This work emphasizes the effective means to design high-performance acidic OER catalysts via the synergy of microstructure symmetry disturbance and crystal phase engineering.