Boosting light harvesting and charge separation over hollow double-shelled Ag@SrTiO3-TiO2 with Z-scheme heterostructure for highly efficient photocatalytic reduction of nitrate to N2

Abstract

Hollow double-shelled Ag@SrTiO₃-TiO₂ with Z-scheme heterostructure was constructed for highly efficient photocatalytic reduction of nitrate to N₂. The 3D finite-difference-time-domain analysis indicated that hollow double-shelled structure improved light harvesting due to multiple reflections. Photo-generated electrons transfer from SrTiO₃ to Ag⁰ caused by electron sink effect were utilized to reduce nitrate, while photo-generated electrons of TiO₂ migrated to SrTiO₃ via transport bridge of Ti³⁺ defects for electron–hole recombination. Such charge carriers migration pathway facilitated the construction of Z-scheme heterostructure, which enhanced charge separation yet still retained high redox powers. Both photogenerated electrons and CO₂⁻ played important role in photocatalytic denitrification. Furthermore, Ag⁰ acted as co-catalyst which not only promoted photogenerated electrons transfer to nitrate but also enhanced nitrate conversion selectivity to N₂. Combining the above advantages, nitrate removal rate and the nitrogen selectivity reached 97.2 % and 98.8 % within 60 min, respectively. Even after five cycles, it still remained satisfied photocatalytic activity and stability. In summary, this work proposed a feasible strategy to construct Z-scheme hollow double-shelled photocatalyst for efficient photocatalytic denitrification.