Ru/Se‐RuO₂ Composites via Controlled Selenization Strategy for Enhanced Acidic Oxygen Evolution

Abstract The introduction of electronegative non‐metallic heterostructures is promisingly desired to develop Ru‐based oxide catalysts, which have higher activity and robust stability for acidic oxygen evolution reaction (OER). Developing scalable synthetic strategies and enlightening the mechanism understanding of the enhancement is imperative but still challenging. Herein, a facile selenium‐assisted reduction approach is reported to fabricate the partially reduced nano‐sized Ru with mixed‐valence Se species immobilization, directly from commercial RuO 2 through ball milling and annealing procedures. The obtained Ru/Se‐RuO 2 composites demonstrate superior electrocatalytic performance toward acidic OER with small overpotentials of 190 and 240 mV at 10 and 100 mA cm −2 , a Tafel slope of only 43.7 mV dec −1 , and no detectable activity decay under operation for 24 h. Experimental results further demonstrate a synergistic effect including enhanced electron transfer interaction by the formation of Ru/RuO 2 heterostructures and more available active sites due to Se doping. Theoretical calculations indicate that slight Se doping and metallic Ru loading can significantly decrease the free energy change for the formation of *OOH intermediate, and thus dramatically promotes the OER performance. This strategy offers a promising strategy for the development of non‐metallic elements incorporated high‐performance catalysts and related water electrocatalytic devices for sustainable energy applications.