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Simultaneously enhancing the reaction kinetics, mass transport, and gas release during alkaline hydrogen evolution reaction (HER) is critical to minimizing the reaction polarization resistance, but remains a big challenge. Through rational design of a hierarchical multiheterogeneous three-dimensionally (3D) ordered macroporous Mo 2 C-embedded nitrogen-doped carbon with ultrafine Ru nanoclusters anchored on its surface (OMS Mo 2 C/NC-Ru), we realize both electronic and morphologic engineering of the catalyst to maximize the electrocatalysis performance.The formed Ru-NC heterostructure shows regulative electronic states and optimized adsorption energy with the intermediate H*, and the Mo 2 C-NC heterostructure accelerates the Volmer reaction due to the strong water dissociation ability as confirmed by theoretical calculations. Consequently, superior HER activity in alkaline solution with an extremely low overpotential of 15.5 mV at 10 mA cm −2 with the mass activity more than 17 times higher than that of the benchmark Pt/C, an ultrasmall Tafel slope of 22.7 mV dec −1 , and excellent electrocatalytic durability were achieved, attributing to the enhanced mass transport and favorable gas release process endowed from the unique OMS Mo 2 C/NC-Ru structure.By oxidizing OMS Mo 2 C/NC-Ru into OMS MoO 3 -RuO 2 catalyst, it can also be applied as efficient oxygen evolution electrocatalyst, enabling the

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The synergistic regulation of the electronic structures of transition-metal oxide-based catalysts via oxygen vacancy defects and singleatom doping is efficient to boost their oxygen evolution reaction (OER) performance, which remains challenging due to complex synthetic procedures. Herein, a facile defect-induced in situ single-atom deposition strategy is developed to anchor atomically dispersed Ru single-atom onto oxygen vacancy-rich cobalt oxides (Ru/Co 3 O 4−x ) based on the spontaneous redox reaction between Ru 3+ ions and nonstoichiometric Co 3 O 4−x . Accordingly, the as-prepared Ru/Co 3 O 4−x electrocatalyst with the coexistence of oxygen vacancies and Ru atoms exhibits excellent performances toward OER with a low overpotential of 280 mV at 10 mA cm −2 , a small Tafel slope value of 86.9 mV dec −1 , and good long-term stability in alkaline media. Furthermore, density functional theory calculations uncover that oxygen vacancy and atomically dispersed Ru could synergistically tailor electron decentralization and d-band center of Co atoms, further optimizing the adsorption of oxygen-based intermediates (*OH, *O, and *OOH) and reducing the reaction barriers of OER. This work proposes an available strategy for constructing electrocatalysts with abundant oxygen vacancies and atomically dispersed noble metal and presents a deep understanding of synergistic electronic engineering of transition-metal-based catalysts to boost oxygen evolution.

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