Selective catalytic reduction of NO by CO over spinel CuFe2O4 catalyst: The vital role of oxygen vacancies

Oxygen vacancies are widely employed to augment the catalytic reactivity in the selective catalytic reduction of NO by CO (CO-SCR) process. Herein, the specific promotion mechanism of oxygen vacancies was intensively explored through a series of CuFe2O4 catalysts via experiments and density functional theory (DFT) simulations. After the modification of oxygen vacancies, NO conversion was enhanced by 20%-32% and N2 selectivity was improved. Characterizations revealed that the redox performance, NO adsorption and activation capacity, active centers, and acidic sites of CuFe2O4 can be improved by enriched oxygen vacancies, contributing to the superior CO-SCR performance. DFT results identified that the adsorption energies of reactants were elevated and the intermediate reaction energy barriers were decreased with more oxygen vacancies. Furthermore, the CO-SCR reaction pathways with CuFe2O4 catalyst were proposed according to in-situ test results: it follows the Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms in the low-temperature range (50-250 ℃) and the Marse-van-Krevelen (Mvk) mechanism in the high-temperature range (≥250 ℃). Overall, this work highlights the bright prospects of oxygen vacancies on the modification of CO-SCR catalysts.