Photoelectron Storage at the WO 3 /TiO 2 Interface: Modeling in Ambient Conditions from First-Principles Calculations

Using first-principles calculations, we showed that the monoclinic WO 3 (001) preferentially forms a reconstructed monolayer on the anatase TiO 2 (001) surface. We thoroughly examined the structure of the WO 3 /TiO 2 surface under ambient conditions, i.e., in equilibrium with gas-phase O 2 /H 2 O or H 2 /H 2 O under a range of pressure and temperature or in aqueous solution under a range of pH and electrochemical potential. Based on the WO 3 /TiO 2 surface structures at different potentials, we proposed the proton-coupled electron-transfer (PCET) reaction pathway during charging and oxygen reduction reaction (ORR) pathways during discharging, which account for its reversible electron storage ability. With electronic structure analysis, we depicted the charge separation effect of WO 3 on TiO 2 and the electron storage effect of WO 3 .