Cascade charge transfer mechanism optimization of g-C3N4/Bi@Bi2WO6 for efficient 2,4-DCP piezo-photocatalytic degradation

Abstract

The technique of ultrasonically mediated piezo-photocatalysis shows promising prospects in the fields of environment and energy. However, a more detailed exploration is needed to understand its underlying mechanisms. The present study demonstrates the successful enhancement of piezo-photocatalytic efficiency in a g-C3N4/Bi@Bi2WO6 (ωCBBW) composite by employing a bifunctional strategy. Approximately 91 % of the 2,4-dichlorophenol (2,4-DCP) is degraded by the cooperative interaction of ultrasonic and illumination, which is 1.7 times higher than that under photocatalytic and 2.1 times greater than under piezoelectric. The negative shifted flat band in Mott-Schottky is attributed to the regulation of the internal electric field by the piezoelectric effect, indicating the shielding of the Schottky barrier by the piezoelectric field. The strongest photocurrent density of 7.18 μA/cm2 shows a significant charge conduction behavior. Additionally, the Charge density difference suggests a preferential electron transfer from Bi to Bi2WO6 rather than g-C3N4. Based on work function and ESR spectroscopy, a novel mechanism is proposed for the transition from Type-II to S-scheme charge transfer in the piezo-photocatalytic system. This study establishes the profound influence of heterojunction materials, exhibiting both LSPR and piezoelectric properties, on photon conversion efficiency in piezo-photocatalytic systems, characterized by an augmented photocurrent density.