Dual-phased Mo2C/Mo3N2/C nanosheets for efficient electrocatalytic hydrogen evolution

Abstract

Mo₂C is a promising electrocatalyst for hydrogen evolution reaction (HER) on account of its Pt-like electronic features. However, the electronic structure of pure Mo₂C is unfavourable for the desorption of H_ads; thus, Mo₂C exhibits poor catalytic performance. Herein, dual-phased Mo₂C/Mo₃N₂/C nanosheets with an abundant heterostructure is prepared as a high-performance and low-cost electrocatalyst for HER. Mo₂C/Mo₃N₂/C has low overpotentials of 76 and 121 mV at a current density of 10 mA cm⁻², with low Tafel slopes of 52.6 and 59.4 mV dec⁻¹, respectively, under alkaline and acidic conditions. Also, Mo₂C/Mo₃N₂/C shows outstanding long-term stability with negligible decay in 1 M KOH and in 0.5 M H₂SO₄ observed even after 3000 cycles. The excellent electrocatalytic performance of Mo₂C/Mo₃N₂/C is attributed to (1) the suitable ratio of Mo₂C : Mo₃N₂ and the synergistic effect that well controlled the state of H_ads, which is favourable for the Volmer–Heyrovsky/Tafel reaction; (2) the compounds Mo₂C and Mo₃N₂ on the nanoscale form abundant heterogeneous nanointerfaces to facilitate electron transfer; (3) the loose and porous structure of Mo₂C/Mo₃N₂/C created more active sites, which facilitated its contact with the electrolyte and also facilitated bubble release. This study provides a novel strategy for the preparation of highly efficient electrocatalysts with heterostructures for HER applications.