FeO–CeO2 nanocomposites: an efficient and highly selective catalyst system for photothermal CO2 reduction to CO

Solar-driven catalysis is a promising strategy for transforming CO 2 into fuels and valuable chemical feedstocks, with current research focusing primarily on increasing CO 2 conversion efficiency and product selectivity. Herein, a series of FeO–CeO 2 nanocomposite catalysts were successfully prepared by H 2 reduction of Fe(OH) 3 -Ce(OH) 3 precursors at temperatures ( x ) ranging from 200 to 600 °C (the obtained catalysts are denoted as FeCe- x ). An FeCe-300 catalyst with an Fe:Ce molar ratio of 2:1 demonstrated outstanding performance for photothermal CO 2 conversion to CO in the presence of H 2 under Xe lamp irradiation (CO 2 conversion, 43.63%; CO selectivity, 99.87%; CO production rate, 19.61 mmol h −1 g cat −1 ; stable operation over 50 h). Characterization studies using powder X-ray diffraction and high-resolution transmission electron microscopy determined that the active catalyst comprises FeO and CeO 2 nanoparticles. The selectivity to CO of the FeCe- x catalysts decreased as the reduction temperature ( x ) increased in the range of 300–500 °C due to the appearance of metallic Fe 0 , which introduced an additional reaction pathway for the production of CH 4 . In situ diffuse reflectance infrared Fourier transform spectroscopy identified formate, bicarbonate and methanol as important reaction intermediates during light-driven CO 2 hydrogenation over the FeCe- x catalysts, providing key mechanistic information needed to explain the product distributions of CO 2 hydrogenation on the different catalysts.