Microstructure and Optical Bandgap of Cobalt Selenide Nanofilms

The slow kinetics of the oxygen evolution reaction (OER) greatly hinders the large-scale production of hydrogen fuel from water splitting. Although many OER electrocatalysts have been developed to negotiate this difficult reaction, substantial progresses in the design of cheap, robust, and efficient catalysts are still required and have been considered a huge challenge. Here, we report a composite material consisting of CoSe2 nanobelts anchored on nitrogen-doped reduced graphene oxides (denoted as NG-CoSe2) as a highly efficient OER electrocatalyst. In 0.1 M KOH, the new NG-CoSe2 catalyst afforded a current density of 10 mA cm(-2) at a small overpotential of mere 0.366 V and a small Tafel slope of ∼40 mV/decade, comparing favorably with the state-of-the-art RuO2 catalyst. This NG-CoSe2 catalyst also presents better stability than that of RuO2 under harsh OER cycling conditions. Such good OER performance is comparable to the best literature results and the synergistic effect was found to boost the OER performance. These results raise the possibility for the development of effective and robust OER electrodes by using cheap and easily prepared NG-CoSe2 to replace the expensive commercial catalysts such as RuO2 and IrO2.