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 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 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 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. Catalysis: Reclaiming carbon dioxide A nanomaterial that helps convert carbon dioxide to more useful chemicals has been developed by researchers in China. One potential method is to convert the carbon dioxide into carbon monoxide using a reaction known as reverse water-gas shift, and then use further reactions to convert this into fuel, or produce useful chemicals such as methanol or methane. This reaction normally requires high temperatures, and a catalyst is required to make the conversion efficient at lower, more practical temperatures. Tierui Zhang from the Technical Institute of Physics and Chemistry in Beijing and co-workers developed a nanocomposite based on iron and cerium with excellent performance in converting carbon dioxide into carbon monoxide with hydrogen only under light irradiation. This result indicates the potential of solar-driven catalysis for transforming carbon dioxide into fuels. A series of FeO-CeO₂ nanocomposite catalysts (FeCe-x) were successfully fabricated by hydrogen reduction of hydroxide precursors at temperatures (x) between 200–600 °C. A FeCe-300 catalyst with a Fe:Ce ratio of 2-1 exhibited excellent performance for photothermal CO₂ hydrogenation to CO (CO selectivity = 99.87%, CO production rate 19.61 mmol h⁻¹ g_cat⁻¹, excellent stability). The FeO phase was effective in promoting the reverse water-gas shift (RWGS, CO₂ + H₂ → CO + H₂O). Catalysts prepared at higher reduction temperatures contained both Fe⁰ and FeO, with the Fe⁰ catalyzing the Sabatier reaction (CO₂ + 4H₂ → CH₄ + 2H₂O) and thus lowering FeCe-x catalyst selectivity to CO. [ABSTRACT FROM AUTHOR]