Piezo-Photocatalysis in Polymeric Photocatalytic Membranes for Wastewater Treatment

The integration of water purification processes, including photocatalytic processes and membrane technology in the form of photocatalytic membranes, is an effective solution to overcome the operational and performance limitations of both methods in water and wastewater treatment applications. Electron-hole recombination and limited access to light are the primary challenges for photocatalysts in photocatalytic membranes, a field that has garnered significant attention. In this context, incorporating the piezoelectric effect into photocatalytic membranes to form piezo-photocatalytic membranes is a promising approach to improve catalytic performance. This review comprehensively discusses the synergistic interaction between photocatalytic processes, membrane filtration, and piezoelectric effects. First, the fundamental concepts of piezoelectric semiconductors and the working principles of piezo-photocatalytic systems are introduced. Then, preparation strategies for piezo-photocatalysts and piezo-photocatalytic membranes are summarized. In addition, the role of piezo-photocatalysts in enhancing the efficiency of piezo-photocatalytic membranes for water and wastewater treatment applications is critically discussed. Finally, current challenges, limitations, and future research directions in this emerging field are presented. In piezo-photocatalytic membranes, the piezo-photocatalysts are not only optically active but also deform under mechanical stress, thereby generating an electric field. The electric field facilitates the separation of electron-hole pairs in the photocatalytic process and their transfer to the material surface, thereby enhancing oxidation-reduction reactions. These membranes demonstrate enhanced performance compared with traditional photocatalytic membranes, even under low-light conditions, due to piezoelectric activation. Overall, piezo-photocatalytic membranes are considered a promising strategy for overcoming the limitations of conventional photocatalytic membranes under both illuminated and low-light conditions.