Oxygen Vacancy and Heteroatom Co-Engineering in WO3@Mn2WO4 Core–Shell Nanostructures for Advanced Tungsten-Based Electrocatalysis

Tungsten-based electrocatalysts are considered promising alternatives to noble metal catalysts for electrochemical water splitting; however, their practical application is severely limited by inherently sluggish reaction kinetics and low density of active sites. In this study, a rationally designed Co-doped WO3@Mn2WO4 core–shell nanostructure with oxygen vacancy modulation (Co-WO3@Mn2WO4-0.6-Ov) was fabricated via a facile hydrothermal synthesis combined with post-treatment using borohydride reduction. By precisely tuning the Co doping concentration (0, 0.3, 0.6, and 0.9 mM), the optimal catalytic performance was identified. Structural characterization confirmed the successful construction of the core–shell heterostructure and the effective modulation of the electronic structure of the W/Mn active sites through Co doping and oxygen vacancy engineering. Electrochemical measurements demonstrated that the optimized Co-WO3@Mn2WO4-0.6-Ov catalyst exhibits a Tafel slope as low as 53.8 mV dec-1 for the hydrogen evolution reaction (HER) under acidic condition of 0.5 M H2SO4, achieving the best performance among all prepared samples and reflecting significantly accelerated electrocatalytic kinetics. This synergistic strategy combining heteroatom doping and oxygen vacancy engineering is also applicable to overall water splitting, enabling a membrane electrode assembly to achieve excellent long-term stability for over 40 h in both acidic and alkaline media. The enhanced catalytic performance is attributed to the synergistic effects of Co doping, oxygen vacancies, and the core–shell structure, which collectively promote interfacial charge transfer and increase the exposure of active sites.