Enhanced Solar Photothermal Catalysis over Solution Plasma Activated TiO₂

Colored wide-bandgap semiconductor oxides with abundant mid-gap states have long been regarded as promising visible light responsive photocatalysts. However, their catalytic activities are hampered by charge recombination at deep level defects, which constitutes the critical challenge to practical applications of these oxide photocatalysts. To address the challenge, a strategy is proposed here that includes creating shallow-level defects above the deep-level defects and thermal activating the migration of trapped electrons out of the deep-level defects via these shallow defects. A simple and scalable solution plasma processing (SPP) technique is developed to process the presynthesized yellow TiO₂ with numerous oxygen vacancies (Ov), which incorporates hydrogen dopants into the TiO₂ lattice and creates shallow-level defects above deep level of Ov, meanwhile retaining the original visible absorption of the colored TiO₂. At elevated temperature, the SPP-treated TiO₂ exhibits a 300 times higher conversion rate for CO₂ reduction under solar light irradiation and a 7.5 times higher removal rate of acetaldehyde under UV light irradiation, suggesting the effectiveness of the proposed strategy to enhance the photoactivity of colored wide-bandgap oxides for energy and environmental applications.