Electronic structure and defect density co-modulation of CoSe2/CeO2 nanocomposite for bifunctional hydrogen oxidation and reduction reactions

Developing bifunctional non-precious metal electrocatalysts toward hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) in acid is seriously challenged in various applications, such as hydrogen purifiers, fuel cells, and water electrolyzers. Here, we report the development of CoSe2/CeO2 nanocomposite electrocatalyst improved by electrochemical tuning for efficient HOR and HER in acid. Electrochemical tuning is shown to generate Ce3+, Co3+, and oxygen vacancies on the surface of the nanocomposite, which are considered active sites for the adsorption and desorption of hydrogen species. The tuned catalyst (t-CoSe2/CeO2) indicates an impressive activity towards HOR and HER in 0.5 M H2SO4 solution, achieving an anodic current density of 1.8 mA cm−2 at 900 rpm and cathodic overpotential of 61 mV, respectively, outperforming the commercial Pt/C. Besides, the synthesized electrocatalyst delivers favorable HOR/HER durability. Our results suggest that the surface manipulation of CoSe2/CeO2 nanocomposite could provide promising insights for substituting precious electrocatalysts for HOR/HER.