Revealing the Tunable Effects of Single Metal Atoms Supported on Nitrogen-Doped Carbon Nanotubes during NO Oxidation from Microkinetic Simulation

Abstract

NO oxidation is one of the most used catalytic routes for NO x removal, which is a pressing environmental issue. As an emerging new class of catalysts, single atom catalysts (SACs) have demonstrated competitive catalytic capabilities compared with conventional noble metals regarding NO oxidation. It is of pivotal importance to understand the working principle and screen the best candidate SAC in NO oxidation. To this end, five SACs (Fe, Co, Ni, Cu, and Pt) have been examined and compared, which exhibit unique and hitherto unusual catalytic properties for NO oxidation as revealed from first principles calculations. The turnover frequency (TOF) of the Co SAC is estimated to be 0.33 s–1, which exceeded that of the conventional NO oxidation catalyst. The nitrogen dopants on the carbon nanotube support effectively adjust the properties of metal atoms, which significantly enhanced the adsorption of reactants. The trend of calculated adsorption energies is consistent with the variable d-band center of single metal atoms. It was found Eley–Rideal (E–R) is more favorable than Langmuir–Hinshelwood (L–H) for all SACs. The calculated TOF of SACs is well correlated with the oxygen adsorption energy. The current work demonstrates the great potential of SACs in NO oxidation and verified the strategy of carbon support dopant engineering.

Design of single-atom catalysts for NO oxidation using OH radicals

“…Although its oxidation energy barrier is only 0.17 eV, its NO 2 desorption energy barrier is 1.5 eV, which also limits the reaction activity of the catalytic process. Si et al 19 conducted research on the oxidation of NO by O 2 using five SACs (Fe, Co, Ni, Cu, and Pt). Their findings revealed that nitrogen doping agents effectively modulate the electronic structure of metal active sites.…”