Catalytic reduction mechanism of deoxygenation of NO via the CO-reaction pathway using nanoalloy Ag7Au6 clusters: density functional theory investigation

Abstract

We used density functional theory calculations to investigate the catalytic potential of Ag₇Au₆ alloy nanoclusters for the reduction of NO by CO. The mechanism comprises two main reaction stages: reduction of NO to generate N₂O followed by deoxygenation of N₂O by CO to form N₂ and CO₂. These N₂ and CO₂ products desorb easily from the active Ag₇Au₆ site, thereby avoiding catalyst poisoning. Potential energy surfaces of the doublet- and quartet-states were systematically elucidated. No spin crossing was found during the entire reaction and our results show that the reaction preferably follows the doublet state pathway. The main reaction pathways take place at Ag₇Au₆ cluster facet sites, rather than at edge sites. The crucial step involves Ag₇Au₆-catalysed reduction of NO to generate N₂O; deoxygenation of NO via the CO-reaction pathway is kinetically more favorable than that in the absence of CO. The NO reduction to generate N₂O is the rate determining step with an energy barrier of 175.2 kJ mol⁻¹. Our results reveal that this catalysed reaction is both thermodynamically and kinetically favourable. We conclude that the Ag₇Au₆ nanocluster has potential as a highly active catalyst for conversion of CO and NO pollutants into non-harmful products under ambient conditions.