Design of Cu-based bimetals for ammonia catalytic combustion via DFT-based microkinetic modeling

Abstract

Copper and its oxides possess excellent performance for ammonia catalytic combustion, but further improving the catalytic performance is still impeded by the limited understanding of the reaction mechanism. Herein, a density functional theory-based microkinetic study by considering the adsorbate-adsorbate interactions was performed to uncover the reaction mechanism under experimental conditions and further design the superior Cu-based bimetal catalysts. Our calculations demonstrate that the partially oxidized Cu(111) covered by oxygen atoms is the active phase. The ammonia consumption rate is not only constrained by strong adsorption of NH and O species but also suppressed by elementary reactions of NH coupling and O-assisted NH3 dehydrogenation from 400 to 800 K. Subsequently, two Cu-based bimetal catalysts, CuAg3 and CuAu3, cautiously designed by weakening the adsorption of NH and O species and reducing the activation barriers of the two rate-determining steps, possess superior catalytic performance than the copper in ammonia catalytic combustion. Overall, our studies not only reveal the reaction mechanism of ammonia catalytic combustion on Cu(111) but also provide important insights for the design of optimal catalysts including two predicted Cu-based bimetal catalysts.