Excess Se-doped MoSe2 and nitrogen-doped reduced graphene oxide composite as electrocatalyst for hydrogen evolution and oxygen reduction reaction

Noble metal catalysts (e.g., Pt, Ru, and Ir) are expensive and scarce and cannot be synthesized at a large scale. The cheap and stable chalcogenides seem to be an attractive alternative and are most likely to replace the precious metal catalysts. However, the poor conductivity, limited number of active sites, and other properties of the chalcogenides limit their applications. In this work, we synthesized defect-rich MoSe2 with nitrogen-doped reduced graphene oxide (MoSe2/NG) in a simple hydrothermal process by introducing excess Se precursor. The catalyst with optimal performance (MoSe2/NG-4) exhibits good bifunctional properties in the oxygen reduction reaction and hydrogen evolution reaction (HER). It exhibits a small overpotential of 120 mV at a current density of 10 mA cm −2 in the HER, with a smaller Tafel slope of 69 mV dec−1, which is much lower than the values of most reported most reported Mo-based catalysts. Besides, it behaves as an effective catalyst in the ORR and adopts a four-electron reaction pathway. This excellent bifunctional catalytic property is mainly due to the rich heterostructure of MoSe2/NG-4 and synergistic effect of nitrogen doping, excellent conductivity of graphene, and the rich active sites. This work provides a new approach for the synthesis and application of chalcogenides and their complexes in the field of catalysis.