Selenium vacancy-rich CoSe2 ultrathin nanomeshes with abundant active sites for electrocatalytic oxygen evolution

Abstract

CoSe₂ is a promising electrocatalyst for the oxygen evolution reaction (OER), benefiting from its suitable electronic configuration and inherent metallic behavior. However, the low ratio of electrolyte-accessible active sites suppresses the OER performance of pure CoSe₂. Engineering CoSe₂ into a two-dimensional ultrathin nanomesh structure with abundant selenium vacancies is expected to increase its number of active sites and hence improve the OER activity, but, its synthesis is highly challenging. In this work, CoSe₂ ultrathin nanomeshes with abundant selenium vacancies (CoSe₂ UNM_vac) were prepared through plasma treatment on CoSe₂–diethylenetriamine (DETA) layered hybrids. The as-obtained CoSe₂ UNM_vac exhibited an excellent OER performance with a low overpotential of 284 mV at 10 mA cm⁻², a small Tafel slope of 46.3 mV dec⁻¹, good stability over 20 h and a large mass activity of 789.1 A g⁻¹ at an overpotential of 300 mV. The greatly enhanced OER activity could be ascribed to the large number of highly active sites on the surface, which are exposed to the electrolyte.