Unveiling the effect of structural asymmetry on photocatalytic performance: Bi-substituted Y2Sn2O7 system with mechanistic insight

Abstract

This study investigated the impact of structural distortion on the photocatalytic activity of Bi-substituted Y₂Sn₂O₇. By tuning the electronic structure of Y₂Sn₂O₇ through Bi substitution, its charge carrier (electron–hole pair, e⁻/h⁺) dynamics, including surface transfer, lifetime, and recombination pathways, were modulated. A series of Bi-substituted Y₂Sn₂O₇ photocatalysts was synthesized and thoroughly characterized. Subsequently, their photocatalytic performance was evaluated by degrading para-chlorophenol (p-CP) (one of the major synthons of dioxins and furans) under UV and visible light irradiation. Our findings revealed a strong correlation between photocatalytic activity and different structural factors, such as the bandgap, flat band potential, and surface charge. In-depth XPS and EPR analysis highlighted the influence of oxygen vacancies on charge carrier trapping within the pyrochlore/tetragonal structures. Furthermore, it was demonstrated that the structural asymmetry of Bi-substituted Y₂Sn₂O₇ significantly impacted its photocatalytic efficiency via the formation of various intermediates during the photo-oxidation of p-CP and their mechanistic roles. Finally, femtosecond dynamics studies provided insights into the dominant role of either holes (h⁺) or alternative pathways in the photo-oxidation process. This work provides a comprehensive understanding of the interplay among the structural parameters, electronic properties, and photocatalytic activity of Bi-substituted Y₂Sn₂O₇ systems.