Enhanced photocatalytic hydrogen evolution and CO2 to CH4 selectivity of Co3O4/Ti3+-TiO2 hollow S-scheme heterojunction via ZIF-67 self-template and Ti3+/Ov.

The potential would be an important issue for enhancing photocatalytic HER and CO 2 photoreduction selectivity. Herein, the Co 3 O 4 /Ti3+-TiO 2 hollow S-scheme heterojunction is fabricated via continuous light modification-chemical-annealing-reduction method. Evaluated by photocatalytic performance, the as-prepared Co 3 O 4 /Ti3+-TiO 2 hollow S-scheme heterojunction exhibits remarkable photocatalytic performance enhancement than single TiO 2 , including hydrogen evolution (∼396.16 μmol/g·h, ∼15 folds) and CO 2 photoreduction (H 2 /CH 4 /CO: ∼20.32/80.57/9.85 μmol/g·h, ∼20 folds), and achieves CO 2 photoreduction to CH 4 selectivity enhancement, which can be mainly ascribed to the synergism of Ti3+/O v and S-scheme heterojunction. There, Ti3+/O v can not only increase the solar efficiency, but also decrease the energy barrier of H+ and ∗CO photoreduction to enhance HER and CO 2 to CH 4 selectivity, including promote the H+ diffusion and CO 2 absorption. Additionally, the formed Co 3 O 4 /Ti3+-TiO 2 S-scheme heterojunction can promote the photo-generated carrier separation/transportation. Also, the hollow 3D structure obtained by ZIF-67 self-template can increase solar efficiency and stability. [Display omitted] • Ti3+/O v can decrease ∗CO photoreduction energy barrier to enhance CH 4 selectivity. • Ti3+/O v with shallow donor level can increase carrier concentration. • Heterojunction can promote carriers separation/transport via appropriate potential. • Hollow 3D structure can increase interface heterojunction and stability. • ZIF-67 self-template can decrease photocatalyst corrosion. [ABSTRACT FROM AUTHOR]