Holey Reduced Graphene Oxide Coupled with an Mo2N–Mo2C Heterojunction for Efficient Hydrogen Evolution

Abstract

An in situ catalytic etching strategy is developed to fabricate holey reduced graphene oxide along with simultaneous coupling with a small-sized Mo₂N–Mo₂C heterojunction (Mo₂N–Mo₂C/HGr). The method includes the first immobilization of H₃PMo₁₂O₄₀ (PMo₁₂) clusters on graphite oxide (GO), followed by calcination in air and NH₃ to form Mo₂N–Mo₂C/HGr. PMo₁₂ not only acts as the Mo heterojunction source, but also provides the Mo species that can in situ catalyze the decomposition of adjacent reduced GO to form HGr, while the released gas (CO) and introduced NH₃ simultaneously react with the Mo species to form an Mo₂N–Mo₂C heterojunction on HGr. The hybrid exhibits superior activity towards the hydrogen evolution reaction with low onset potentials of 11 mV (0.5 m H₂SO₄) and 18 mV (1 m KOH) as well as remarkable stability. The activity in alkaline media is also superior to Pt/C at large current densities (>88 mA cm⁻²). The good activity of Mo₂N–Mo₂C/HGr is ascribed to its small size, the heterojunction of Mo₂N–Mo₂C, and the good charge/mass-transfer ability of HGr, as supported by a series of experiments and theoretical calculations.

An in situ etching strategy is developed to fabricate holey reduced graphene oxide coupled to a small-sized Mo₂N–Mo₂C heterojunction (Mo₂N–Mo₂C/HGr). Through the intimate contact of the Mo₂N and Mo₂C heterojunction and good charge/mass-transfer ability of HGr, the hybrid benefits from its small size and exhibits superior electrocatalytic activity towards the hydrogen evolution reaction over a broad pH range.

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