Properties of PdAu and PtCu alloy surfaces for the adsorption and catalytic reduction of O 2 and NO by H 2

Abstract

The adsorption and catalytic properties of PdAu and PtC alloy surfaces were investigated under low pressure conditions, with the real surface composition being monitored using Auger electron spectroscopy. Flash desorption experiments on O 2 and NO, and steady state kinetic experiments involving the reduction of these substances by H 2 were performed on polycrystalline alloy surfaces. For the PdAu system, O 2 desorption was promoted by gold, as shown by the shift of O 2 desorption toward lower temperature and a linear decrease in the saturated amount of O 2 adsorption with increase in gold content. For the PtCu system, O 2 desorption was retarded by copper i.e. the O 2 desorption temperature shifted upward with increase in copper content. In both the alloy systems, catalytic activities for the above reactions were significantly suppressed by the addition of gold or copper to the platinum group metals. The drop was more pronounced for NO reduction, suggesting that a larger ensemble of active platinum group metal atoms are necessary for NO dissociation.