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

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 electrolyteaccessible active sites suppresses the OER performance of pure CoSe2. Engineering CoSe2 into a two-dimensional ultrathin nanomesh structure with abundant seleniumvacancies 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 UNMvac) were prepared through plasma treatment on CoSe2-diethylenetriamine (DETA) layered hybrids. The as-obtained CoSe2 UNMvac exhibited an excellent OER performance with a low overpotential of 284 mV at 10 mAcm(-2), a small Tafel slope of 46.3mV 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.