Continuous oxygen vacancy engineering of the Co3O4 layer for an enhanced alkaline electrocatalytic hydrogen evolution reaction

Abstract

Precisely tailoring the oxygen vacancies (O_v) of Co oxide based electrocatalysts could be highly essential for boosting hydrogen evolution reaction (HER) performance in alkaline media. Here, a rapid synthesis of an O_v-engineered Co₃O₄ layer on Ni foam has been demonstrated through a solid-phase melting strategy, where the O_v content in the Co₃O₄ layer can be adjusted from 52% to 74% simply by changing melting temperature. After HER testing, this content is further adjusted to 22–45% with the same trend. Remarkably, the Co₃O₄ layer with a medium O_v content (32%) gives the highest mass activity of −2.12 A g⁻¹ at an overpotential of 200 mV for the alkaline electrocatalytic HER. Moreover, it only requires an ultrasmall overpotential of 203 mV to achieve −100 mA cm⁻², outperforming all reported Co₃O₄ electrocatalysts so far. The medium O_v content in the Co₃O₄ electrocatalyst could enhance reaction kinetics by optimizing catalytic intermediate adsorption during the alkaline HER. This feasible tactic to precisely control O_v may provide an avenue for exploring other advanced electrocatalysts.