Selective Photothermal Reduction of CO₂ to CO over Ni-Nanoparticle/N-Doped CeO₂ Nanocomposite Catalysts

Photothermal reverse water gas shift reaction is one of the promising methods to palliate global energy and environmental issues. Searching for catalysts with high activity and CO selectivity for CO2 conversion has been attracting extensive attention. In this work, Ni nanoparticle-loaded N-doped CeO2 (Ni/N-CeO2) composite catalysts were synthesized using a three-step method. Under light irradiation, the optimal Ni/N5.0-CeO2 exhibited a CO yield rate of 20.9 mmol·gcat–1·h–1 with almost 100% of CO selectivity via photothermal CO2 reduction. As a comparison, Ni/CeO2, without nitrogen doping, showed a high CH4 selectivity. The strong light absorption of Ni/N5.0-CeO2 mainly by loading of Ni nanoparticles and the enhanced adsorption/activation of CO2 molecules due to increased oxygen vacancies in N5.0-CeO2 by N-doping were supposed to account for the excellent catalytic performances. The doping of nitrogen was of particular importance for the formation of N–H bonds, which could modulate the reaction pathway for promoting the reduction of CO2 toward CO while suppressing the undesirable CO2 methanation process.