Original self-assembled S-scheme BiOBr-(0 0 1)/Bi2SiO5/Bi heterojunction photocatalyst with rich oxygen vacancy for boosting CO2 reduction performance

Photocatalysis CO2 reduction into high-value-added chemical feedstocks is desirable for simultaneously addressing the solar energy storage, CO2 excess and energy shortage issues. In this work, a kind of original S-scheme BiOBr-(001)/Bi2SiO5/Bi (OSB) heterostructure photocatalyst with rich oxygen vacancies is in-situ synthesized, which significantly promotes the photocatalytic CO2 reduction performance. Interestingly, the lower formation energy of oxygen vacancy exhibits the easy feasibility on the BiOBr-(001) surface via the assistant of ultrasound. There exists the highest photocatalytic CO2 reduction activity to CO of 234.05 μmol g-1h-1 for OSB-20 sample (ultrasound time: 20 min), higher 3.3 times than OSB-0 sample (without ultrasound). Combined with experimental and calculated results, the significative formation mechanism, widened light-response range, highly-efficient separation/transfer paths and improved redox-reduction abilities of photogenerated electron-hole pairs for S-scheme OSB-20 heterostructure are investigated and proposed. Our findings provide new insights for the construction and synthesis of the S-scheme Bi-based heterojunction photocatalyst system.