Kinetic evaluation of direct NO decomposition and NO–CO reaction over dendrimer-derived bimetallic Ir–Au/Al2O3 catalysts

Abstract

The effects of Au on the catalytic performance of Ir metal towards NO reduction by CO and direct NO decomposition have been investigated over dendrimer-derived Ir–Au bimetallic catalyst. Results were also compared to a catalyst prepared by conventional incipient wetness impregnation of metal salts. Characterization of Ir–Au bimetallic samples using scanning transmission electron microscopy, H2 chemisorption and temperature programmed desorption of NO reveals that highly dispersed Ir–Au particles can be obtained by dendrimer templating method. In-situ transmission Fourier transform infrared spectroscopy following adsorption of probe molecules (i.e., CO and NO) on the dendrimer-derived Ir–Au bimetallic sample indicated the presence of electron transfer from Ir to Au sites. In contrast, a geometric effect of Au on Ir was observed over the conventional-derived sample, consistent with X-ray photoelectron spectroscopy measurements. These properties influence the catalytic performance, with higher selectivity towards N2O and a better intrinsic catalytic turnover frequency for reduction of NO by CO and NO decomposition observed for the dendrimer-derived sample. Overall, the results suggest that both NO–CO and NO decomposition reaction are structure-sensitive reactions.