Oxygen defect based cobalt-doped-NiMoO4 hierarchical hollow nanosheet-based-nanosphere for oxygen evolution reaction

Abstract

Hollow structures with a hierarchical architecture and multi-composition have attracted extensive interest because of their fascinating physicochemical properties as well as wide applications. To improve the efficiency of overall water splitting, highly active and stable electrocatalysts are highly desirable. A novel high-efficiency oxygen defect based hierarchical hollow nanosheet-based-nanosphere Co–NiMoO₄-HNS electrocatalyst for oxygen evolution was arranged by doping Co on a Ni-MoEG yolk/shell nanosphere. Co–NiMoO₄-HNS has a greater hydrophilicity and smaller band gap than that of NiMoO₄-CS. Post OER characterization indicates that the main active phase of the Co₂–NiMoO₄-HNS catalysts toward the OER are amorphous Ni³⁺, Co³⁺, and H–O and the high-valent Mo (+6) can make nickel and cobalt better maintain Ni³⁺ and Co³⁺ sites. Remarkably, this hierarchical hollow Co₂–NiMoO₄-HNS catalyst exhibits a favorable catalytic performance toward the oxygen evolution reaction (OER) with a receivable overpotential of 270 mV achieving a current density of 10 mA cm⁻² and a Tafel slope of 65 mV dec⁻¹. In expansion, as an electrocatalyst, Co₂–NiMo₄-HNS appeared to have a great long-term steadiness in the electrolyte. This work may give a broad hypothetical and specialized background for plans of cost-effective bifunctional electrocatalysts.