Theoretical design principles of metal catalysts for selective ammonia oxidation from high throughput computation

Abstract

Selective catalytic oxidation of ammonia (NH₃-SCO) is a ubiquitous process in exhaust aftertreatment, yet making catalysts with high reactivity and selectivity at low working temperatures remains a great challenge, due to the trade-off between activity and selectivity under operating conditions. We present here a microkinetic-based high throughput computational study on ammonia selective oxidation catalysts and outline the basic requirements and design principles of a good NH₃-SCO catalyst. The complete ammonia selective oxidation process is demonstrated on the low-index facets of representative metals (Ag, Au, Cu, Ir, Pd, Pt, Rh and Ru), and the NH₃ oxidation rates, product selectivity and reactivity orders of different metallic catalysts are evaluated quantitatively. It is revealed that the binding abilities of N and O atoms could be used as effective descriptors of catalytic performance arising from the existence of linear scaling relations among surface adsorbates. The ruling laws of catalytic performance state that moderate N binding energy (−5.00 ∼ −4.00 eV) exhibits the most favorable catalytic activity, on top of which strengthened O binding could further promote N₂ selectivity. Based on the guiding principles, a series of alloy systems are batch screened and some potential catalysts with good activity and selectivity are proposed. Our study lays out a general theoretical framework for the design of metallic catalysts and their property tuning for NH₃-SCO.