Microstructured Au/Ni-fiber catalyst for low-temperature gas-phase alcohol oxidation: Evidence of Ni₂O₃-Au⁺ hybrid active sites

Microfirous-structured Au/Ni-fiber catalysts prepared by Au galvanic deposition method are active and selective for the gas-phase oxidation of alcohols. The nature of their excellent low-temperature activity is explored especially by means of X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES). An interesting NiO@Au ensemble nanostructure (i.e., partial coverage of Au particles with NiO segments) was clearly identified, which is governing the high low-temperature activity. XPS and XANES studies indicate that the NiO@Au ensembles provide a unique synergistic effect, inducing a high surface concentration of Ni₂O₃-Au⁺ hybrid active sites. The Ni₂O₃ specimens not only promote the formation of Au⁺ cations and stabilize them but also serve as active O species reservoir. It is also proposed that O₂ is activated on the oxygen vacancy of Ni₂O₃ and then the adsorbed O atoms spill over onto Au⁺ cations to react with alcohols.