The conversion of CO2 by the virtue of sunlight has the great potential to produce useful fuels or valuable chemicals while decreasing CO2 emission from the traditional fossil fuels. Here, we use the first-principles calculations combined with the periodic continuum solvation model (PCSM) to explore the adsorption and reactivity of CO2 on rutile TiO2(110) in the water environment. The results exhibit that both adsorption structures and reactivity of CO2 are greatly affected by water coadsorption on rutile TiO2(110). In particular, the solvation effect can change the most stable adsorption configuration of CO2 and H2O on rutile TiO2(110). In addition, the detailed conversion mechanism of CO2 reduction is further explored in the water environment. The results reveal that the solvation effect cannot only greatly decrease the energy barrier of CO2 reduction but also affect the selectivity of the reaction processes. These results presented here show the importance of the aqueous solution, which should be helpful to understand the detailed reaction processes of photocatalysts.

We investigated the structural properties, dynamical behaviors, and vibrational spectra of the water film adsorbed on the Al-terminated α-Al 2 O 3 (0001) surface using first-principles molecular dynamics simulations. The simulations showed that the structural properties of the water film, such as the mass density, atom number density, orientation order and hydrogen bonds (HBs) of water molecules, are considerably affected by the Alterminated α-Al 2 O 3 (0001) surface along its normal direction. A new dissociation 1−4′ state via two different indirect and double indirect pathways was proposed, which is slightly more favorable than 1−4 state under the condition of multiple water layers. The blue-and red-shifting of vibrational spectra for different water layers was observed. The interfacial water in various adsorption configurations and its corresponding vibrational spectrum were explicitly identified. The "ice-like" and "liquid-like" peaks of vibrational spectra, which are observed in various experiments of water/hydroxylated α-Al 2 O 3 (0001) interface, were reproduced in our simulations. Our simulations suggest the "ice-like" peak mostly stems from the surface OH and the interfacial water molecules that experienced more HBs interactions, while the "liquid-like" peak results from the "liquid-like" water molecules. Our study provides novel insights into the complex structures and dynamical behaviors of interfacial water, upon water film adsorbing on the Al-terminated α-Al 2 O 3 (0001) surface.

We identified the states of intrinsic point defects underlying the self-diffusion in Si and clarified the change of dominant diffusion mechanism responsible for the self-diffusion over a wide temperature range using ab initio method. We presented a reliable self-diffusion model that the mechanisms of vacancies and selfinterstitials dominate below and above 1220 K, respectively. Our calculations provided a clear picture of Si self-diffusion at lower and higher temperature ascribed to single point defects rather than extended defects. The calculations also provided valuable information on the energy levels and the thermal equilibrium concentrations of point defects, which are highly controversial in experimental reports due to detection limits.

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