Direct deposition of isolated metal atoms onto substrates has been recognized as a simple route to obtain high performance supported atomically dispersed metals (SACs), however, the agglomeration driven by high surface energy is difficult to avoid.

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.

The electronic structure of transition meatal oxides is in the predominant position among mostly central reactions, such as oxygen electroncatalysis, for the applications in energy storage. Herein, cobalt‐based catalysts are developed by taking the advantage of the strong electronegativity of halogen elements, whose activity and stability are also guaranteed. A “theory–calculation–experiment” research system is proposed to sort out the relationship between the electronegativity of heteroatoms and the electronic structure of layered CoO/F, CoO/Cl, and CoO/Br, for the electrochemical oxygen evolution reaction (OER). Experiments corresponding to calculations also verify that the stronger the electronegativity of the halide ions in the cobalt oxide catalyst, the more obvious the improvement of OER performance. By understanding the electronegative screening of halogen modification, a new perspective on designing principles for water‐splitting devices based on bandgap‐engineered metal oxides is proposed.

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