Visible-light-driven Z-scheme Bi2Sn2O7/CuBi2O4 heterojunction photocatalysts for the degradation of methylene blue and rhodamine B dyes

Degrading the organic compounds using the photocatalysis is a potential technology to control the environmental pollution. Concerned with this problem, a one-step hydrothermal approach was used to synthesise novel (1-x)Bi₂Sn₂O₇-xCuBi₂O₄ heterojunctions (where x = 0.05, 0.10, 0.15 and 0.20 wt.%). The compounds were investigated using XRD, FESEM, EDX, HRTEM, XPS, FTIR, UV-DRS, BET, EIS and PL techniques. The degradation of methylene blue (MB), rhodamine B (Rh B) and phenol were used to examine the photocatalytic activity (PCA) of Bi₂Sn₂O₇-CuBi₂O₄ heterojunctions. 0.90Bi₂Sn₂O₇–0.10CuBi₂O₄ heterojunction exhibited the highest PCA than pure Bi₂Sn₂O₇ and CuBi₂O₄. The enhanced specific surface area and the improved charge separations were primarily accountable for the enhanced PCA of these heterojunctions. The plausible mechanism of high PCA of these heterojunctions was comprehensively understood through the precisely computed energy band potentials and the performed free-radical trapping experiments. The trapping investigations showed that h⁺ and \(O_{2}^{ \cdot - }\) play important roles, with \(O_{2}^{ \cdot - }\) being the most prominent species. After four cycles, the heterojunction still effectively degraded the contaminants.