Mechanism insights into CO oxidation on a low-cost N doped pyrite: A molecular simulation study

Abstract

A comprehensive understanding of the effect of N doping on CO oxidation over FeS2 is prominently meaningful for fabricating a low-cost heteroatom catalyst with an optimum structure and satisfactory activity. Herein, periodic density functional theory (DFT) calculations were performed to investigate possible reaction mechanisms for CO oxidation over FeS2 and N doped FeS2 (N-FeS2). Two kinds of active oxygen species are observed on the catalyst surfaces, including the adsorbed O2 and atomic O. The results show that the CO first prefers to react with the atomic O formed by O2 dissociation (FeS2) and the adsorbed O2 (N-FeS). Comparing to FeS2, the energy barriers of CO oxidation over N-FeS2 are lower, which indicates that N doping can improve the activity for CO oxidation. The analyses of electronic structure evidence that N doping can modify the electronic density of the adjacent Fe atoms and thus form favorable electronic configurations for O2 adsorption, which facilitates O2 activation and the succeeding CO oxidation. The whole favorable CO oxidation cycle for N-FeS2 consists of three stages: O2 adsorption → first CO oxidation → second CO oxidation. Our findings can provide a fundamental understanding to develop N doped catalysts with high activity for CO abatement.