N2O decomposition over CuO/CeO2 catalyst: New insights into reaction mechanism and inhibiting action of H2O and NO by operando techniques

Abstract

In this work, a combination of ex situ (STEM-EELS, STEM-EDX, H2-TPR and XPS), in situ (CO-DRIFTS) and operando (DR UV–vis and DRIFTS) approaches was used to probe the active sites and determine the mechanism of N2O decomposition over highly active 4wt.% Cu/CeO2 catalyst. In addition, reaction pathways of catalyst deactivation in the presence of NO and H2O were identified. The results of operando DR UV–vis spectroscopic tests suggest that [Cu−O−Cu]2+ sites play a crucial role in catalytic N2O decomposition pathway. Due to exposure of {100} and {110} high-energy surface planes, nanorod-shaped CeO2 support simultaneously exhibits enhancement of CuO/CeO2 redox properties through the presence of Ce3+/Ce4+ redox pair. Its dominant role of binuclear Cu+ site regeneration through the recombination and desorption of molecular oxygen is accompanied by its minor active participation in direct N2O decomposition. NO and H2O have completely different inhibiting action on the N2O decomposition reaction. Water molecules strongly and dissociatively bind to oxygen vacancy sites of CeO2 and block further oxygen transfer as well as regeneration of catalyst active sites. On the other hand, the effect of NO is expressed through competitive oxidation to NO2, which consumes labile oxygen from CeO2 and decelerates [Cu+ Cu+] active site regeneration.