Thermo-Driven Photocatalytic Co2 Hydrogenation Over Niox/Nb2o5 Via Regulating the Electron Transfer Behavior of Reactant Gas Adsorption

The thermo-driven photocatalytic CO2 hydrogenation was studied for NiOx/Nb2O5 from the point of CO2 and H2 adsorption behavior. Photothermal synergistic and Ni modification dramatically changed the electron transfer behavior of CO2 adsorption (CO2 (ads)) and H2 (ads) via regulating Fermi level and providing Ni0 and VOs adsorption sites, respectively. The H2 (ads) at Ni0 site donates electrons to NiOx/Nb2O5 (pre-oxidized) and CO2 (ads) at VOs-Nb5+ or Ni0 sites accepts electrons from NiOx/Nb2O5 (pre-reduced), while NiOx/Nb2O5 displayed excellent photocatalytic activities. Furthermore, the in-situ DRIFTS results suggested that CO2 (ads) will form two reaction pathways on different adsorption sites, CO2 (ads) at Ni0 sites directly hydrogenated with H atoms (H2 molecule dissociates at Ni0 to form two H-atoms) to generate CH4 and C2H6 through COOH intermediate. The other one was CO2 (ads) form dimer CO2 • CO2δ- species at VOs-Nb5+ sites, and it will be further disproportioned to produce CO and CO3δ- species, then CO3δ- species were gradually hydrogenated to form CH4 and C2H6. Moreover, increasing the number of CO2/H2 molecules accepts/donates electrons will also improve the reduction degree of CO2. This work offers a new explanation for photothermal synergistic