The Mechanism of Piezocatalysis: Energy Band Theory or Screening Charge Effect?

Abstract

Piezocatalysis, a newly emerging catalysis technology that relies on the piezopotential and piezoelectric properties of the catalysts, is attracting unprecedented research enthusiasm for applications in energy conversion, organic synthesis, and environmental remediation. Despite the rapid development in the past three years, the mechanism of piezocatalysis is still under debate. A fundamental understanding of the working principles of this technology should enable the future design and optimization of piezocatalysts. Herein, we provide an overview of the two popular theories used to explain the observed piezocatalysis: energy band theory and screening charge effect. A comprehensive discussion and clarification of the differences, relevance, evidence, and contradiction of the two mechanisms are provided. Finally, challenges and perspectives for future mechanistic studies are highlighted. Hopefully, this Review can help readers gain a better understanding of piezocatalysis and enable its application in their own research.

Piezoelectrically Mediated Reversible Addition–Fragmentation Chain-Transfer Polymerization

“…The surface of ZnO also plays a pivotal role in determining piezoreactivity. 6 After the US, the color of the ZnO sample (ZnO/TPMA) became gray (Figure S11a−c). The deposition of TPMA was further confirmed by the X-ray photoelectron spectroscopy (XPS) analysis.…”

“…The surface of ZnO also plays a pivotal role in determining piezoreactivity . After the US, the color of the ZnO sample (ZnO/TPMA) became gray (Figure S11a–c).…”

“…Synthetic materials are also subject to mechanical vibrations that often lead to the damage of materials. Mechanically mediated reactions that harness mechanical energy for constructive purposes have gained renewed interest in recent years. − For example, ultrasound (US) can initiate or enhance the reactions via acoustic cavitation in liquid (sonochemistry). − More recently, piezoelectrically mediated reactions that use the redox activities of piezoelectric nanoparticles under mechanical agitation have been reported. − They show advances in both solution and bulk reactions where acoustic cavitation is not sufficient to promote the reaction. Great efforts have been made for piezoelectrically mediated small molecular reactions, including water splitting, oxidative dye degradation, and C–C coupling. ,− …”

Catalytic Activity of BaTiO3 Nanoparticles for Wastewater Treatment: Piezo- or Sono-Driven?

“…Since the ionic exchanges between the surface and the surrounding medium strongly depend on the electrochemical potential of the piezoelectric surface, the mechanical strain-induced piezopotential therefore significantly affects the material’s electrochemical activity . The observed catalytic activities of such piezoelectric nanomaterials have been explained by two different models, namely, using energy band theory or describing them as resulting from charge screening effects . In energy band theory, which is inspired by the widely accepted photocatalysis model, the built-in piezoelectric potential is thought to be responsible for the separation and transport of the excited electron–hole pairs generated within the material to the surface, where they take part in the chemical reactions.…”

“…5 The observed catalytic activities of such piezoelectric nanomaterials have been explained by two different models, namely, using energy band theory or describing them as resulting from charge screening effects. 6 In energy band theory, which is inspired by the widely accepted photocatalysis model, the built-in piezoelectric potential is thought to be responsible for the separation and transport of the excited electron−hole pairs generated within the material to the surface, where they take part in the chemical reactions. In the charge screening effect, the piezoelectric potential generates surface-bound charges that are then compensated for or screened by free charges from outside the material.…”