Titania thin films with red-shifted photoresponse: Non-stoichiometry and cation doping

The objective of this research is to synthesize TiO₂ nano-structured thin films with properties tailored for the photoreduction of CO₂ to CH₄ under UV and visible light. Our efforts are guided by the objectives of creating a high number of photoactive sites, optimizing charge separation, and increasing response to visible light for improved photo-efficiency. Reactive magnetron sputtering with partial pressure control of oxygen is utilized to fabricate mixed-phase TiO₂ films with novel nanostructures, high solid-solid interfacial areas and enhanced oxidative and reductive activities. Recent studies have focused on the role of non-stoichiometry (oxygen vacancies) and cation doping (Nb) in titania to influence the photoresponse and photocatalytic performance. Non-stiochiometric films show a strong red-shift and there is an optimal non-stiochiometry for films with respect to methane yield from CO₂ reduction. Nb-doped films were also prepared to evaluate the effect of cation doping on optical, chemical and physical properties.