One-pot synthesis of C/N co-doped TiO2 with rich oxygen vacancy for efficient photoreduction CO2-to-CO in pure water

Photocatalytic technology has emerged as a promising approach for addressing global energy and environmental challenges by enabling the conversion of CO2 into valuable chemicals. In this study, we successfully synthesized TiO2 co-doped with C and N, along with an abundant oxygen vacancy (referred to as C/N-TiO2-VO), utilizing a hydrothermal method. Through various characterization techniques, it has been confirmed that the C and N originated from N, N′-dimethylformamide (DMF), while the VO was mainly generated by isopropyl alcohol (IPA), acting as a reducing agent. These techniques also verified that C/N-TiO2-VO has the strong light absorption ability and longer fluorescence lifetime, all of which contribute to enhancing photocatalytic performance. More importantly, C/N-TiO2-VO exhibited exceptional performance in the photoreduction of CO2 to CO, achieving nearly 100 % selectivity in pure water, with a CO evolution rate of 53.97 μmol g−1 h−1. This rate was 10.8 and 8.1 times higher than that of TiO2 and C/N-TiO2, respectively. Further theoretical calculations illustrated that stronger local charges and defect levels are formed on the surface of C/N-TiO2-VO compared with TiO2(101), facilitating the dissociation of CO2 and the conversion of CO2 into *COOH intermediates. Furthermore, in situ DRIFTS results confirmed the formation of crucial intermediate *COOH during CO2 photoreduction. This study presents a viable approach for designing highly active photocatalysts through the synergistic effects of doping and vacancies. [Display omitted] •C/N-TiO2-VO photocatalysts were successfully prepared by one-step hydrothermal process using DMF as C and N source and IPA as reducing agent.•C, N co-doped and VO in C/N-TiO2-VO nanocrystals enhanced the separation efficiency of photo-generated carriers and inhibit carrier recombination.•C/N-TiO2-VO displayed a high CO selectivity of ∼100 % with a yield of 54.0 μmol g−1 h−1.