Long-Lasting Non-hydrogenated Dark Titanium Dioxide: Medium Vacuum Anneal for Enhanced Visible Activity of Modified Multiphase Photocatalysts

Multiphase TiO2 was stably modified by vacuum treatment for a dramatic improvement in visible-light absorption and photocatalytic reactivity. The samples were made of rutile-brookite, bare or N doped, and were grown on reduced graphene oxide. The stable introduction of Ti3+ species and oxygen vacancies resulting in mitigated electron-hole recombination was identified as the main responsible factor, along with a change in surface charges.