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

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 & Aring; and their oxidation states between CuI and CuII 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.