Direct Z-scheme SnO2/Bi2Sn2O7 photocatalyst for antibiotics removal: Insight on the enhanced photocatalytic performance and promoted charge separation mechanism

Abstract A kind of direct Z-scheme SnO2/Bi2Sn2O7 heterojunction photocatalyst was fabricated aiming to explore the underlying photocatalyitc mechanism as well as the improved photocatalytic antibiotics degradation activity. Experimental results indicated that the existence of the built-in electric field between SnO2 and Bi2Sn2O7 led to a direct Z-scheme charge transfer. The efficient separation and fast transfer of photogenerated charge carriers contributed to boosting the photocatalytic performance of SnO2/Bi2Sn2O7. The optimal photocatalytic tetracycline degradation efficiency of SnO2/Bi2Sn2O7 was 88.4 %, which was 1.4-fold higher than that of pure Bi2Sn2O7 (62.9 %) and 12.5 times higher than pure SnO2 (7.1 %). Radical trapping experiments and electron paramagnetic results indicated that the photocatalytic degradation process in SnO2/Bi2Sn2O7 system was modulated by photogenerated electrons, holes and O 2− active species. This work may offer a new insight for enhancing the photocatalytic activity of Bi2Sn2O7 by constructing a direct Z-scheme heterojunction structure.