Self-adaptive copper pairs on CuO(111) boosting ammonia catalytic combustion

Abstract

Copper oxides exhibit outstanding performance in ammonia catalytic combustion, but a limited understanding of reaction mechanisms and the nature of active sites under operating conditions hinders further catalyst optimization. Utilizing density functional theory-based microkinetic simulations, we herein establish a comprehensive reaction mechanism on CuO(111), which enables the successful prediction of the experimental light-off temperature and identifies the self-adaptive copper pairs as key active sites. The NH₂ coupling over the copper pairs is the critical step for N₂ formation, which, along with H₂O production, governs the overall reaction rate. Interestingly, the copper atom pairs can adjust their atomic distance ranging from 2.42 to 2.90 Å and their oxidation states between Cu^I and Cu^II in response to the adsorbed intermediates, thereby facilitating the catalytic cycle and specifically inhibiting NH₂ dehydrogenation. Moreover, reducing copper pair distance through surface compressive strain can further lower the activation energies of rate-determining steps and enhance the reactivity.