Promoting the electrocatalytic activity through the introduction of oxygen vacancies to core–shell NiO hollow sphere catalysts for efficient oxygen evolution

Abstract

NiO has been widely studied as a potential Earth-abundant electrocatalyst for the oxygen evolution reaction (OER). Defect engineering and constructing hollow nanostructures are effective methods to improve electrocatalytic performance, so exploring an efficient route to obtain NiO catalysts simultaneously possessing oxygen vacancies and hollow nanostructures is necessary. In this work, core–shell NiO_1−x hollow spheres with oxygen vacancies are prepared through a solvothermal strategy followed by thermal treatment under an H₂/Ar atmosphere. And the content of oxygen vacancies can be regulated by varying the calcination time. Importantly, the existence of rich oxygen vacancies in NiO and its unique core–shell hollow structure promote water adsorption and enhance charge transfer and thus the core–shell NiO_1−x hollow spheres show appealing electrocatalytic performance, demonstrating efficient OER electrocatalysis with an overpotential (η) of 360 mV (at 10 mA cm⁻²) and Tafel slope of 103.9 mV dec⁻¹ in an alkaline medium.