Enhanced Photocatalytic Activity of Z-Scheme Bi2WO6/P25 Heterojunctions via 7,7,8,8-Tetracyanoquinodimethane Modification

Efficient interfacial charge transfer is crucial for improving the photocatalytic performance of semiconductor heterojunctions under visible-light irradiation. In this study, Bi2WO6/P25 heterojunction photocatalysts modified with 7,7,8,8-tetracyanoquinodimethane (TCNQ) were prepared to enhance visible-light photocatalytic activity. The optimized sample with a TCNQ mass ratio of 0.3% exhibited the highest activity for rhodamine B degradation, achieving a degradation rate approximately 6.0 times higher than that of pure Bi2WO6 and 1.7 times higher than that of the pristine Bi2WO6/P25 heterojunction. The degradation rates of phenol were 6.5 times and 2.3 times higher for Bi2WO6 and BP-5, respectively. The enhanced photocatalytic performance was mainly attributed to the modification of TCNQ, which enhanced the electron transfer from P25 to Bi2WO6, establishing a multi-stage electron transfer mechanism involving P25 → Bi2WO6 → TCNQ. This molecular surface modification strategy provides new insights for the rational design of high-performance photocatalytic materials.