Surface Engineering of CeO2 Catalysts: Differences Between Solid Solution Based and Interfacially Designed Ce1-xMxO2 and MO/CeO2 (M = Zn, Mn) in CO2 Hydrogenation Reaction

Zn- and Mn-doped Cerium-oxide based catalyst textured as a solid solutional as well as interfacial form was compared in CO2 hydrogenation reaction to understand the role of texture as well as dopant type. Ce0.9M0.1O2 (M = Zn, Mn) solid solution was prepared by hydrothermal method and CeO2 supported 10 mol% metal oxide (Metal = Zn, Mn) were prepared by wet impregnation method, where the catalysts were characterized by XRD, N-2 adsorption/desorption isotherm, TEM, Raman spectra, HAADF-STEM and H-2-TPR. During the CO2 activation reaction, CO was the major product with minor amounts of methane, ethane, methanol and ethanol. In the case of the Zn-doped CeO2 catalyst, the presence of Zn improved catalytic activity in both solid solutional and interfacial form due to the synergetic effect of Zn-Ce-based oxide. However, for MnOx/CeO2 catalysts, the CO2 consumption rate significantly decreased for 10 mol% MnOx/CeO2, Ce0.9Mn0.1O2 and Mn3O4, where the MnOx addition inhibits the reduction of CeO2. In the case of the pure CeO2, DRIFTS spectra show that formate intermediate formed by reaction between activated CO2 and OH transformed into methoxy species through formaldehyde intermediates, which leads to the formation of small amount of methanol and ethanol. Graphic