Electron/hole piezocatalysis in chemical reactions

The emergence of piezocatalysts has led to advancements in catalyst design through the development of new technologies. Electron/hole piezocatalysis, a novel form of catalysis, utilizes piezoelectric materials that are stimulated by mechanical energy. This stimulation generates electrons and holes, which prove highly effective in promoting inefficient reactions, designing new reactions, and facilitating challenging chemical reactions and transformations. This review provides a concise historical account of electron/hole catalysis and the concept of piezoelectricity. Additionally, it explores various types of piezocatalysts, including piezoceramics (both lead-free and lead-based), piezopolymers, and piezocomposites. Notably, lead-free piezoceramics such as barium titanate and zinc oxide, as well as piezopolymers like polyvinylidene fluoride in β-phase and polyacrylonitrile in planar zigzag conformation, have gained significant recognition. The piezoelectric coefficient of polymers can be enhanced by adjusting the processing parameters and employing techniques such as blending, filler addition, stretching, and composite formation with piezo/non-piezo additives. Furthermore, piezoelectricity has been observed in unique materials such as ionic liquids, metal–organic frameworks, graphitic carbon nitride, black phosphorus, and MXenes. This review also presents recent research findings on the utilization of piezoelectric materials in various applications, including water splitting, water remediation, organic synthesis, and polymerization/crosslinking.