Enriching surface oxygen vacancies of spinel Co3O4 to boost H2O adsorption for HER in alkaline media

Abstract

Oxygen-defective Co₃O_2.64S_0.33 (namely CoO_0.88S_0.11) particulate spheres (PS) were prepared via the solid-state sulfurization of spinel Co₃O₄ at 300 °C in an Ar atmosphere. The introduction of sulfur (S) atoms was found to enrich the surface oxygen vacancies (V_so) remarkably in the as-derived CoO_0.88S_0.11 PS relative to pristine Co₃O₄ and CoS₂, thus offering more active sites for catalytic reactions. Theoretical calculations were also performed to justify that the enrichment of V_so is favorable to boost the adsorption of H₂O molecules. As a result, these CoO_0.88S_0.11 PS with exposed (111) facets demonstrated enhanced electrocatalytic performance in H₂ evolution reaction (HER) with a low overpotential (OP) of 83 mV to realize a current density of 10 mA cm⁻², and a high turnover frequency (TOF) of 1.589 H₂ s⁻¹ was obtained in 1 M KOH aqueous electrolyte.