Insights into synergetic modulation of nickel sites over graphene by introducing tungsten and light for efficient methanol electrooxidation

Cut-lost, highly active and stable (photo-)electrocatalysts are earnestly expected to overcome high energy obstacles in methanol oxidation reaction (MOR). A hybrid of NiW/graphene (NiW/G) is prepared by a simple self-designed electrosynthesis method. During the process of electrosynthesis, exfoliation of bulky graphite into graphene and generation of multivalent NiW bimetal precursor are both achieved. This obtained composite displays superior photoelectrocatalytic performance towards MOR. As for NiW/G-light, its area activity (peak current) and mass activity (peak current) are up to 343.4 mA cm⁻² and 5960.7 mA mg⁻¹ respectively, much higher than NiW/G, Ni/G and W/G. Operando electrochemical impedance spectroscopy, in-situ Fourier transform infrared spectroscopy and other ex-situ techniques uncover that the excellent MOR performance for NiW/G-light results from synergetic modulation of nickel sites by introducing tungsten and light, which provides desired adsorption behavior and high electrochemical active surface area. It's found that introduction of W component promotes the formation of W-O-Ni(Ni³⁺) species, supporting more strong adsorption sites for methanol. This results in new reaction path between adsorbed methanol and OH* for producing formic acid. With application of light, the photo-generated hole promotes oxidation of residual Ni²⁺ into Ni³⁺ species, which provides additional formed NiOOH sites for MOR. It's concluded introduction of tungsten and light is efficient for greatly enhancing methanol electrooxidation. This work is highly instructive for application of self-designed electrosynthesis method to construct dimetal/graphene composite and photoelectric synergistic catalysis towards MOR.