Ultrathin Bi4O5I2 nanosheets as an integrated piezo-photocatalyst: Super visible-light piezo-photocatalysis and synergistic catalytic mechanism

Abstract

Coupling piezocatalysis in the process of photocatalysis has aroused great interests of researchers to depress the serious recombination of photogenerated charge carriers. However, it still suffers from the inefficient catalytic activity and lacks in-depth understanding on their relationship. In this work, we report that outstanding piezo-photocatalytic activity is achieved over ultrathin Bi4O5I2 nanosheets, and disclose the synergistic catalytic mechanism. Piezoelectric force microscopy (PFM) and COMSOL simulation analysis reveal the strong piezoelectricity of the Bi4O5I2. Under simultaneous irradiation of visible light and ultrasonic, Bi4O5I2 ultrathin nanosheets exhibit a piezo-photocatalytic efficiency of tetracycline hydrochloride (TH) degradation of 88.3% within 8 min with a rate coefficient of 0.4703 min−1, which is 2.3-fold of the sum of the single photocatalysis and piezocatalysis, also far exceeding that of other previously reported piezo-photocatalyst. In situ electrochemical and electron paramagnetic resonance (EPR) under light, ultrasonic, and simultaneous light and ultrasonic conditions disclose that the synergistically enhanced charge separation and transfer and evolution of reactive species (superoxide radicals and holes) occur in the piezo-photocatalytic reaction process, which is derived from the piezoelectric field and band bending. This work emphasizes the effect of the piezoelectric field on strengthening the photocatalytic performance and further the understanding on synergistic piezo-photocatalytic mechanism.