Turning the activity of Cr–Ce mixed oxide towards thermocatalytic NO oxidation and photocatalytic CO2 reduction via the formation of yolk shell structure hollow microspheres

Abstract

Cr–Ce mixed oxides microspheres will have considerable potential in thermocatalytic NO oxidation and photocatalytic CO2 reduction reaction (CO2RR) if their low porosity and expensive synthetic expenditure can be overcome. To avoid these obstacles, a facile and economical strategy was adopted to synthesize double-shelled hollow Cr–Ce mixed oxide microspheres. The highly active multipurpose catalyst achieved an ultrahigh thermocatalytic NO oxidation efficiency at low temperatures, and provided high yields of CH4 and CH3OH during the photocatalytic CO2RR. For NO oxidation, the optimized catalyst provided over 40% NO removal at 150 °C, which was ascribed to the reduced aggregation of the active subunits and the increased active species availability. Further, the exposed surface could generate an increased content of Cr6+ and Oβ, which played the key role in NO oxidation. For CO2 photocatalytic reduction, the superior behavior originated from the reduced band gap and the effective separation of photoinduced charge carriers. This study opens up new possibilities of using Cr–Ce mixed oxides for application in catalysis.