Chemistry
Universität Mainz
Institut für Physik
Given the increase in global energy demands and consensus that carbon-based fuels are contributing to greater atmospheric CO2 levels and thereby accelerating global warming, there is a critical need to identify alternative, sustainable sources. Water splitting, the process by which a catalyst promotes the generation of oxygen and hydrogen gas from water is an attractive route for chemical fuel generation. Given the appropriate materials, this process is performed following photo-absorption, thereby making it a potentially carbon-neutral process. Water splitting was first tested by Fujishima and Honda using TiO2 as the source of hot electrons and holes. Several investigations have addressed water splitting on the most stable (101) surface, however chemical modification, e.g., fluorination of TiO2 are known to shift the exposed facets of anatase from (101) to (001). The emerging of new materials where (001) is the more common surface, calls for the understanding of the mechanism of water splitting at this interface as a reference for future generations of modified surfaces. In this project we aim to address the thermodynamics pathways for the successive dehydrogenation of water at the TiO2 (001)/ water interface. Free energy perturbation methods will be used to compute deprotonation free energies (pKa) and oxidation free energies (electrochemical potentials) from ab-initio molecular dynamics simulations. The advantage of using an atomistic approach, that explicitly includes the electronic structure, is that both solid and liquid phases are treated on the same level of theory and electronic polarization of the solid and liquid at the interface are both captured using Density Functional Theory (DFT).