Operando UV/Vis Analysis of the Synergy Effect between Copper and Gold in Nitric Oxide Reduction over Gold and Copper on Alumina Catalysts.

Mono- (Cu or Au) and bi-metallic AuCu nanoparticles were prepared by a modified polyol reduction method and deposited onto Al2O3 followed by calcination at 500°C in air. The synthesised catalysts were tested for their activity for NO reduction with CO in excess H2O between 50 and 500°C at a contact time relevant for automotive convertors. The bi-metallic catalysts showed a significantly higher activity than Cu/Al2O3 and Au/Al2O3, and the latter was inert for the target reaction. In addition, the activity depended greatly on the Au/Cu ratio, which thus demonstrates a synergy effect between these two metals. Operando UV/Vis spectroscopy provided direct evidence for the transformation of initially oxidised CuOx species into metallic Cu0, which is the only active species for NO reduction. Promotion with Au was found to accelerate the reduction of Cu2+/Cu+ to Cu0. [ABSTRACT FROM AUTHOR]