TiO2/polydopamine S-scheme heterojunction photocatalyst with enhanced CO2-reduction selectivity

Photocatalytic CO2 conversion into solar fuels has been a promising strategy to utilize abundant solar energy and alleviate greenhouse effect. Herein, a series of polydopamine-modified TiO2 (TiO2@PDA) hollow spheres were fabricated by in situ self-polymerization of dopamine to systematically investigate the effect of PDA wrapping on the photocatalytic CO2 reduction activities of TiO2. Among all TiO2@PDA composite photocatalysts, the highest value of methane yield (1.50 μmol h−1 g−1) was achieved with 0.5 % PDA, which was 5 times than that of pure TiO2 (0.30 μmol h−1 g−1). The improvement of photocatalytic activity and methane selectivity was ascribed to the enhanced light absorption, promoted CO2 adsorption capacity, increased reduction power of photogenerated electrons, as well as efficient separation and transfer of photogenerated charge carriers induced by the S-scheme heterojunction between TiO2 and PDA. This work provides a facile surface modification method with cost-effective polymer materials in photocatalytic CO2 conversion.