DFT + U study of the CO + NOx reaction on a CeO2(110)-supported Au nanoparticle

The adsorption and reactions of CO and NOx on a Au6 nanoparticle supported on the CeO2(110) surface have been studied using density functional theory calculations corrected by on-site Coulomb interactions (DFT + U). The results show that CO can strongly adsorb on the top site of the Au nanoparticle with an adsorption energy of ∼1.2 eV, while the adsorption of NO on both the Au nanoparticle and the interface between the nanoparticle and the CeO2 support is generally much weaker. However, at the interface, formation of the N2O2 dimer followed by cleavage of the terminal N–O bond is an effective way to decompose NOx. For the complete process, the first step of the CO + N2O2 reaction can readily occur in Langmuir-Hinshelwood mode with an activation energy of only ∼0.4 eV, leading to the formation of N2O and CO2 via an intermediate ONNOCO species. In contrast, the second step to eliminate N2O requires a rather high energy barrier of ∼1.8 eV through a Eley-Rideal type collision reaction. Further analyses show that the unique electronic properties of Ce can induce the electron transfer and localization from supported Au to surface Ce cations, which then promotes the formation of negatively charged N2O2. Moreover, the structural flexibility of the Au nanoparticle also facilitates the adsorbed CO to approach and react with N2O2 at the interface.

Graphical AbstractCeO2(110)-supported Au6 clusters strongly favor adsorption of CO on the Au top site and N2O2 at reduced interfacial Ce3+ cations, and exhibit unique catalytic activity toward subsequent CO + NOx redox reactions for CO2 and N2 formation.Figure optionsDownload full-size imageDownload as PowerPoint slide