Direct Donation of Protons from H₂O to CO₂ in Artificial Photosynthesis on the Anatase TiO₂(101) Surface
2019
Ji, Yongfei | Luo, Yi
Conversion of CO₂ and H₂O into value-added organic molecules via artificial photosynthesis is a promising solution to current energy and environment problems. In the reaction, it is generally believed that CO₂ is converted into organic molecules by photogenerated electrons and protons that result from photo-oxidation of H₂O. In this work, we investigate the possibility that H₂O, without being oxidized, directly donates protons to CO₂ and other intermediates adsorbed at the oxygen vacancy on the anatase TiO₂(101) surface. We found that this can greatly lower the barriers (by about 0.3 eV) for the hydrogenation of CO₂, CO, H₂CO, and CH₃O because less energy is required to displace these adsorbates to accept the proton (in H₂O). The OH– group produced in these reactions can recombine with a surface-adsorbed proton to form a new H₂O molecule, making H₂O a shuttling center of the adsorbed protons, or it can take part in the oxygen evolution reaction with a lower barrier. The results suggest that H₂O can play multiple roles in artificial photosynthesis and the reduction and oxidation parts of the reaction may have synergistic effects.
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