Effect of precipitant on the performances and structures of Au/ZnO catalysts for CO oxidation

Various Au/ZnO catalysts were prepared by a coprecipitation method with four kinds of precipitants, Na2CO3, NaOH and NH4OH, and the catalytic performance of CO oxidation at an ambient temperature and humidity were studied. It was found that the precipitants play an important role for the Au/ZnO catalyst structure, such as the precursors, the particle size of ZnO and metallic gold and the BET surface area of Au/ZnO catalysts. The sample prepared by using NH4OH as precipitant exhibited a lower activity and poorer stability, while the Au/ZnO catalysts prepared by other three precipitants can maintain CO completely oxidized to CO2 for at least 1 100 h. The feed gas mixture can result in sintering of metallic gold and accumulation of carbonate-like species on the surface of Au/ZnO catalysts during the CO oxidation process. The stability is related to the rate of gold sintering and the amount of hydrozincite formed on the catalyst surface.