Self-sensitized brown-TiO₂ photocatalyst for highly efficient CO₂ reduction under ambient conditions

Solar-powered photocatalytic CO₂ reduction offers great potential for carbon fixation. Conventional wide-bandgap semiconductors absorb little visible light. Dye sensitization improves absorption but reduces photoelectron transfer efficiency, limiting photocatalytic performance. This work reports a self-sensitized anatase brown titanium dioxide (B-TiO₂) catalyst developed through an optimized two-step method. Comprehensive experimental and computational analyses reveal that B-TiO₂ extends its spectral absorption edge to 601.94 nm, over 43.69 % compared to P25, significantly enhancing visible light absorbance. The surface of B-TiO₂ characterized by oxygen vacancies, Ti³⁺ species, and lattice defects, which are crucial for its markedly improved photocatalytic activity. Under irradiation from a 300 W Xe-lamp, the self-sensitized B-TiO₂ catalyst achieves an impressive total charge-transferred electron number of 570.84 μmol·g⁻¹·h⁻¹ and a CO₂ conversion rate of 142.05 μmol·g⁻¹·h⁻¹. Furthermore, the photocatalytic mechanism was investigated in detail. This innovative self-sensitized catalyst offers a promising strategy for developing high-efficiency photocatalysts, potentially advancing the field of photocatalytic CO₂ reduction.