Activation of CO 2 by Direct Cleavage Triggered by Photoelectrons on Rutile TiO 2 (110).

The initial activation of the inert CO 2 is a key step in its photoreduction to valuable chemicals. This process was proposed to proceed mainly by CO 2 accepting a photoelectron to form a CO 2 •- radical or by CO 2 accepting two photoelectrons and a proton to form the HCOO - anion on the prototypical rutile TiO 2 (110) surface. Here, we reveal a new mechanism, in which CO 2 is directly cleaved to CO and the adsorbed O 2- anion under the trigger of two photoelectrons, by using density functional theory calculations with the HSE06 hybrid functional. The newly revealed mechanism is more favorable than the two previously proposed pathways. Furthermore, our results show that the deficiency of photoelectrons on the catalyst surface is a potential reason for the current low efficiency of CO 2 photoreduction.