Revealing the intrinsic nature of Cu- and Ce-doped Mn3O4 catalysts with positive and negative effects on CO oxidation using operando DRIFTS-MS

Abstract

Aiming at the problem of the poor performance of an Mn-MOF-74-derived Mn₃O₄ catalyst in low-temperature carbon monoxide (CO) oxidation, copper (Cu) and cerium (Ce) elements were used to modify the Mn₃O₄ catalyst to improve its performance in low-temperature CO oxidation. According to the results of catalytic performance testing, the CO oxidation activity of the Cu_0.3Mn_2.7O₄ catalyst was significantly improved compared with that of the pristine Mn₃O₄ catalyst, when a CO conversion rate of 90% was achieved at 118 °C. According to X-ray photoelectron spectroscopy and Brunauer–Emmett–Teller analyses, the (Mn²⁺ + Mn³⁺)/(Mn²⁺ + Mn³⁺ + Mn⁴⁺) ratio and the O_ads/O_total ratio increased after Cu doping, indicating promoted oxygen vacancy generation. In addition, the increased specific surface area was beneficial for the adsorption of reactant molecules and the exposure of active sites. According to H₂-temperature-programmed reduction characterization, Cu doping significantly enhanced the performance of the Cu_0.3Mn_2.7O₄ catalyst during low-temperature redox. Finally, these factors synergistically promoted the degradation of CO over the Cu_0.3Mn_2.7O₄ catalyst. In addition, operando diffuse reflectance Fourier transform infrared spectroscopy results suggested the presence of more terminal-type oxygen, which is essential for the catalytic oxidation of CO on the surface of the Cu_0.3Mn_2.7O₄ catalyst. Moreover, the Cu_0.3Mn_2.7O₄ catalyst also showed excellent resistance to carbonate, and remarkable stability.