Heterojunction and Photothermal-Piezoelectric Polarization Effect Co-Driven BiOIO3-Bi2Te3 Photocatalysts for Efficient Mixed Pollutant Removal

Built-in electric field coupled piezoelectric polarization engineering is a promising method to adjust and boost the catalytic performance of photocatalysts. Herein, BiOIO₃-Bi₂Te₃ type-II heterojunction piezo-photocatalyst was proposed and prepared by a sequential hydro-solvothermal method. Due to the co-drive of the heterojunction and photothermal-piezoelectric polarization effect certified by piezoelectric force microscopy, COMSOL simulations, and infrared thermography, the photocatalytic degradation performance of the as-prepared BiOIO₃-Bi₂Te₃ on rhodamine B was dramatically improved under the co-excitation of visible light and ultrasound compared with under the single light irradiation and the single ultrasonic conditions. Typically, the BiOIO₃-Bi₂Te₃ photocatalyst always showed significantly better catalytic degradation performance than the pure Bi₂Te₃, BiOIO₃, and BiOIO₃/Bi₂Te₃ mechanical mixtures. Impressively, based on the optimal conditions obtained by systematically studying the effects of temperatures, ultrasound intensities, and inorganic salts on the piezo-photocatalytic rhodamine B degradation, the optimum composite ratio BiOIO₃-Bi₂Te₃-20 piezo-photocatalyst can also effectively remove tetracycline and Cr(VI), and also achieve the purpose of simultaneously removing a mixture of these three pollutants with good recycling stability. Such enhanced catalytic performance was mainly attributed to the disruptions of the electrostatic equilibrium and saturation effects of the built-in electric field under successive ultrasonic and photoinduced co-disturbance, thus enhancing the driving force of separation and migration of photogenerated carriers as verified by electrochemical tests, energy band structure theory, and DFT calculations. Based on which and the sacrificial agent experiments, the photocatalytic degradation mechanism was proposed. This research showcased the significant potential for environmental remediation using solar energy and mechanical energy cooperatively.