Advances in Piezoelectric Polarization Enhanced Photocatalytic Energy Conversion

Semiconductor-based photocatalysis is an efficient technology that reduces energy consumption and environmental pollution; however, it is impeded by Coulombic attraction-induced charge recombination, which reduces solar conversion efficiency. The internal electric field induced by heterointerface engineering, defect engineering, heteroatom doping, ferroelectric polarization, and polar surface terminations intervening in the uniform charge distribution can drive the directional migration of photogenerated electrons and holes, suppressing the charge recombination and back-reaction of intermediate species. However, the built-in electric field is static and easily shielded by internal active carriers and externally charged ions, which is detrimental to successive charge separation. Moreover, the internal electric field that relies solely on the structural design of the catalyst often requires complex preparation processes and is disqualified from simple and efficient solar energy conversion. By coupling the piezoelectric effect with the photoexcitation feature in piezo-photocatalysis, charge carrier dynamics can be persistently modulated. The noncentrosymmetric structures of piezoelectrics result in the deviation of positive and negative charge centers with the exerted external stress, generating nonzero dipole moments and polarization charges on the opposite terminals of the crystal. On the one hand, the polarized bound charges and initiated piezoelectric polarization field by mechanical stress promote the separation and transfer of photoinduced charges in both the bulk and on the surface of the catalyst, facilitating more active carriers to participate in the surface reaction. On the other hand, the accumulation of piezoelectric polarization charges on the surface contributes to the upward or downward bending of the band, which can flexibly manipulate the charge transfer behavior at the heterojunction interface, further steering the spatial distribution of electrons and holes. In addition, band tilting induced by piezoelectric polarization can also modulate the energy band structure of the catalyst to match the redox potential of the target reaction, breaking the intrinsic thermodynamic restriction. Hence, the coupling of solar and mechanical energy significantly improves the efficiency of catalytic energy conversion. As a complex reaction process of piezo-photocatalysis, diverse enhancement strategies have been implemented; however, there are few systematic and pertinent overviews for high-performance piezo-photocatalyst design. This study introduces the mechanism of piezoelectric polarization-enhanced photocatalysis and summarizes the catalytic enhancement strategy based on the piezo-photocatalysis reaction process, including morphology and polarization regulation, heterostructure construction, and surface engineering. Meanwhile, recent advances in piezo-photocatalysis for energy applications have been reviewed. Finally, the problems and challenges associated with the development of piezo-photocatalysis are analyzed and discussed.

Automated summary

Semiconductor-based photocatalysis is an efficient technology for reducing energy consumption and environmental pollution, but charge recombination limits its efficiency. Piezo-photocatalysis, by coupling the piezoelectric effect with photoexcitation, can modulate charge carrier dynamics and improve catalytic energy conversion efficiency. This study introduces the mechanism and enhancement strategies of piezo-photocatalysis and reviews recent advances in energy applications. It also analyzes the challenges in the development of piezo-photocatalysis.