Synthesis of Au-NiOx/ultrathin graphitic C3N4 nanocomposite for electrochemical non-platinum oxidation of methanol

The Au-NiO_x/g-C₃N₄ (graphitic C₃N₄) nanocomposite is synthesized and utilized as catalyst for the electrochemical oxidation of methanol in the alkaline electrolyte. Au and Ni nanoparticles are uniformly dispersed on ultrathin g-C₃N₄ nanosheets by in-situ synthesis with nickel nitrate and chloroauric acid as Ni and Au resource respectively. The structure, morphology and component of the prepared nanocomposites are characterized by different techniques like transmission electron microscopy, X-ray diffraction, elemental mapping image and X-ray photoelectron spectroscopy. The results prove that the nanoparticles are well-distributed and embedded in g-C₃N₄ nanosheets. The electrochemical performance of different nanocomposite for methanol oxidation reaction (MOR) is tested under alkaline conditions via electrochemical technologies. Compared to the pure g-C₃N₄ and Au/g-C₃N₄, the NiO_x/g-C₃N₄ exhibits electrochemical catalytic effect toward methanol electro-oxidation with the existence of Ni. This electrochemical catalytic performance is enhanced significantly for the Au-NiO_x/g-C₃N₄, whose oxidation peak current density is 2.32 times higher than NiO_x/g-C₃N₄. The slope value drew from the Tafel plots shows that the Au-NiO_x/g-C₃N₄ owns the lowest Tafel slope (67.00 mV/dec). After the 7200 s stability test, the Au-NiO_x/g-C₃N₄ catalyst can still maintain a high current density. Long-term stability and good anti-poisoning ability promise Au-NiO_x/g-C₃N₄ a competitive non-Pt catalyst for the methanol oxidation.