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

Abstract

Solar-driven catalysis is a promising strategy for transforming CO2 into fuels and valuable chemical feedstocks, with current research focusing primarily on increasing CO2 conversion efficiency and product selectivity. Herein, a series of FeO–CeO2 nanocomposite catalysts were successfully prepared by H2 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 CO2 conversion to CO in the presence of H2 under Xe lamp irradiation (CO2 conversion, 43.63%; CO selectivity, 99.87%; CO production rate, 19.61 mmol h−1 gcat−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 CeO2 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 Fe0, which introduced an additional reaction pathway for the production of CH4. In situ diffuse reflectance infrared Fourier transform spectroscopy identified formate, bicarbonate and methanol as important reaction intermediates during light-driven CO2 hydrogenation over the FeCe-x catalysts, providing key mechanistic information needed to explain the product distributions of CO2 hydrogenation on the different catalysts.