Piezo-Photocatalytic Flowing Synthesis of Hydrogen Peroxide in Water Using a Piezoelectric Heterojunction

The exploration of photocatalysts that can combine external energy in photocatalytic H₂O₂ production to boost production efficiency is highly desirable for the sustainable utilization of solar energy. Herein, a piezo-photocatalytic flowing synthesis strategy has been proposed for the overall reaction production of H₂O₂ using a piezoelectric heterojunction (BiOCl/Zn-TCPP). The thus-generated piezoelectric heterojunction with the integration of visible-light response, prominent piezoelectric properties, and favorable redox ability can efficiently improve the separation and transport efficiency of photogenerated carriers under the synergistic effect of ultrasound and light. Remarkably, the piezo-photocatalytic H₂O₂ production rate over BiOCl/Zn-TCPP is 202,200 μM h^–1 g^–1, achieving a 44-fold increase in H₂O₂ activity of BiOCl/Zn-TCPP without piezoelectric potential, even superior to most semiconductor-based catalysts in photocatalysis. Notably, in a continuous flowing setup, it achieves an H₂O₂ concentration of 1.38 wt % after 10 h with a production rate of 407 μM h^–1 under sunlight and air, which can be successfully applied as an antibacterial agent and readily stored as a solid phase (i.e., Na₂CO₃·1.5 H₂O₂) for easy storage or transportation. This work might provide new insights required for the development of external energy-assisted photocatalytic systems in an efficient H₂O₂ flowing synthesis and applications.