First-Principles Study of Photochemical Activation of CO$_2$ by Ti-based Oxides

The photochemical conversion of CO$_2$ and H$_2$O into energy-bearing hydrocarbon fuels provides an attractive way of mitigating the green-house gas CO$_2$ and utilizing solar energy as a sustainable energy source. However, due to the high reduction potential and chemical inertness of CO$_2$ molecules, the conversion rate of CO$_2$ is impractically low. The activation of CO$_2$ is critical in facilitating further reactions. By carrying out first-principles calculations of reaction pathways from CO$_2$ to CO$_2^{-}$ anions on Ti-based oxides including zeolites in the presence of photoexcited electrons, we have studied the initial step of CO$_2$ activation via 1e transfer. It is shown that the CO$_2$ reactivity of these surfaces strongly depends on the crystal structure, surface orientation, and presence of defects. This opens a new dimension in surface structure modification to enhance the CO$_2$ adsorption and reduction on semiconductor surfaces.