Light-driven enhancement of CO2 hydrogenation via nickel loading and oxygen vacancy formed on indium oxide

Photothermal catalysis is an efficient approach for CO₂ conversion. Herein, the light-driven enhancement of CO₂ hydrogenation via nickel loading and oxygen vacancy formed on indium oxide was investigated. The 5.17 wt% Ni/In₂O_3-x catalyst exhibited a CO₂ conversion of ∼32 % with a CO production rate of 14.4 mmol g_cat⁻¹ h⁻¹ under visible light irradiation at 300 °C. The photothermal catalytic activity was four times that of the thermocatalytic reaction and over twice that of In₂O_3-x under the same photothermal conditions. Structural characterization methods, including XRD, TEM, H₂-TPR, CO₂-TPD, and XPS, confirmed the importance of suppressing the over-reduction of the Ni–In₂O_3-x interface, to maintain both metallic Ni and oxygen vacancies for the photothermal CO₂ conversion. UV–vis absorption, PL, XPS, and DFT calculation results verified the positive effect of the Ni loading and the formation of oxygen vacancies on enhancing visible light absorption and photoelectron-hole separation of Ni/In₂O_3-x, thus providing more photoelectrons for CO₂ conversion to CO. Additionally, the increasing metallic Ni phase and the regeneration of oxygen vacancies induced by visible light irradiation were discovered. The synergistic effect of the Ni loading and oxygen vacancies on In₂O_3-x plays a key role in enhancing the photothermal catalytic CO₂ hydrogenation.