Holey Reduced Graphene Oxide Coupled with an Mo₂ N-Mo₂ C Heterojunction for Efficient Hydrogen Evolution

An in situ catalytic etching strategy is developed to fabricate holey reduced graphene oxide along with simultaneous coupling with a small-sized Mo₂ N-Mo₂ C heterojunction (Mo₂ N-Mo₂ C/HGr). The method includes the first immobilization of H₃ PMo₁₂ O₄₀ (PMo₁₂ ) clusters on graphite oxide (GO), followed by calcination in air and NH₃ to form Mo₂ N-Mo₂ C/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 Mo₂ N-Mo₂ C heterojunction on HGr. The hybrid exhibits superior activity towards the hydrogen evolution reaction with low onset potentials of 11 mV (0.5 m H₂ SO₄ ) 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 Mo₂ N-Mo₂ C/HGr is ascribed to its small size, the heterojunction of Mo₂ N-Mo₂ C, and the good charge/mass-transfer ability of HGr, as supported by a series of experiments and theoretical calculations.