Photothermal catalytic reduction of CO 2 is a powerful way to promote carbon neutralization goals. However, there are few reports on the deactivation of the photothermal CO 2 reduction reaction. Here, we observed an interesting deactivation phenomenon of photothermal CO 2 conversion over TiO 2−x H x (black TiO 2 ). Despite the presence of a reducing atmosphere of H 2 , the oxygen vacancy concentration of TiO 2−x H x is reduced, resulting in the deactivation of photothermal CO 2 reduction. After Ni is modified onto TiO 2−x H x , Ni can activate H 2 to form H s , and the oxygen vacancy concentration of Ni/TiO 2−x H x may be maintained, thus solving the deactivation problem in photothermal CO 2 hydrogenation.
It is difficult to design a new single‐component photocatalyst to simultaneously possess a bandgap small enough to absorb most of sunlight and strong redox ability to reduce CO2 into value‐added chemical fuels. Herein, bandgap engineering of nickel vanadate compounds (NixV2O5+x, x = 1, 2, 3) is rationally designed to overcome the above challenge. Through changing the Ni:V ratio, the bandgap and band edge positions of nickel vanadates can be regulated, enabling Ni2V2O7 and Ni3V2O8 to reduce CO2 in the presence of water under visible light irradiation that do not exist in NiV2O6. Ni 3d orbitals of Ni2V2O7 and Ni3V2O8 replace V 3d orbitals of NiV2O6 and hybridize with O 2p orbitals to form the valence band maximums, resulting in their negative shifts. Meanwhile, the relatively weaker effect of the crystal field in VO4 tetrahedron over Ni2V2O7 and Ni3V2O8 results in less V 3d split, thus making the conduction band edges to shift upward. In addition, higher concentration of oxygen vacancies over Ni2V2O7 can further enhance its photocatalytic activity for CO2 conversion into CO with nearly 100% selectivity by prolonging the lifetime of photogenerated carriers and improving the chemisorption of CO2.
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