Low-Temperature Selective Catalytic Reduction of NO by CO in the Presence of O2 over Cu:Ce Catalysts Supported by Multiwalled Carbon Nanotubes

Abstract

The catalytic activity of a series of Cu–Ce catalysts supported on carbon nanotubes was studied for NO reduction by CO. The 20 wt % Cu1:Ce3/CNT catalyst showed the highest NOx conversion of 96% at 220 °C in the presence of oxygen (O2/CO ≤ 0.6). The catalytic activity of the CNT-supported catalysts was significantly enhanced due to synergistic interactions between surface oxygen vacancies and Cu+ species in the CNT-supported catalysts. Shifting of redox equilibrium to right (Cu2+ + Ce3+ ↔ Cu+ + Ce4+) resulted in creation of more reduced state Cu+. In the presence of excess oxygen (O2/CO ≥ 0.6), the catalyst can effectively catalyze the CO–O2 reaction and the NO + CO reaction did not occur. Compared with Cu1:Ce3/CNT catalyst, Cu1:Ce3 catalyst supported on activated carbon showed lower activity due to the lower Cu+/Cu2+. A possible reaction mechanism was proposed, providing insight into the catalytic reactions between NO and CO.