Novel photoactivation promoted light-driven CO2 reduction by CH4 on Ni/CeO2 nanocomposite with high light-to-fuel efficiency and enhanced stability

Abstract The catalytic CO 2 reduction by CH 4 to synthesize fuels of CO and H 2 (CRM) supplies a prospective technology to address the global warming effect caused by greenhouse gas of CO 2 . Due to its highly endothermic characteristics, CRM can only proceed at high reaction temperature, resulting in excessive energy consumption and quick catalyst deactivation due to serious carbon. Herein, we report a nanocomposite of Ni/CeO 2 that exhibits high catalytic activity and good stability with focalized UV–vis-Infrared (UV–vis-IR) illumination without applying any other heater. It generates high production rates of H 2 and CO (6.53 and 6.27 mmol min −1  g −1 ), its light-to-fuel efficiency ( η ) is up to 11.1%. Ni/CeO 2 shows efficient catalytic activity with 11.0% of η even with focalized Vis-IR illumination of wavelengths above 690 nm. Based on the experimental evidences, it is found that the highly effective catalytic performance of Ni/CeO 2 under the focalized illumination originates from the efficient light-driven thermocatalytic CRM. It is discovered for the first time that a synergetic effect among Ni nanoparticles and CeO 2 remarkably facilitates the catalytic durability of the Ni/CeO 2 nanocomposite. We delve into the origin of the synergetic effect by combining evidences of XRD, TEM, TG-MS, FTIR, and isotope labelling: The lattice oxygen of CeO 2 in Ni/CeO 2 participates in the oxidation of C* species formed on Ni nanoparticles via the migration at the Ni/CeO 2 interface, thus significantly enhancing the catalytic stability due to the inhibition of carbon deposition. It is found that the solar-light-driven thermocatalytic activity of Ni/CeO 2 is considerably improved by a novel photoactivation, which is quite different from the conventional photocatalysis on semiconductor photocatalysts. The novel photoactivation is theoretically revealed by DFT calculation: The irradiation obviously decreases the activation energy of the dominant steps of the C and CH oxidations for CRM on metallic Ni, thus considerably improving the catalytic activity of metallic Ni.