Catalysis of Nickel-Based gold single-atom alloy for NO-CO reaction: Theoretical insight into role of gold atom in enhancing catalytic activity

Abstract

Single-atom alloy (SAA) attracts great interest recently as excellent heterogeneous catalyst. Herein, the catalysis of Ni-based Au SAA for NO-CO reaction is investigated using DFT calculations. Under lean conditions, N2 formation occurs to produce NiOx surface, as observed experimentally, because CO2 formation cannot occur due to easy desorption of CO. Under rich conditions, CO2 formation occurs with small Ea value to afford (N)2-adsorbed surface. Next catalytic cycle starts with (N)2(NO)2-adsorbed surface because N2 formation needs larger Ea value but NO adsorption readily occurs with considerable energy stabilization. As Au-content increases, d-valence-band center lowers in energy to increase activation barrier for N–O bond cleavage of NO but decrease those of CO2 and N2 formations. Thus, rate-limiting step is N2 formation in low Au-content but N–O bond cleavage in high Au-content. A volcano-plot is presented against Au-content. The optimal Au-content is about 6 % on catalyst surface.