Zhong-Xia Wang,Hua Zhang,Fang Wang,Hao Cheng,Wen-Hui He,Yu-Hua Liu,Xue-Qin Huang,Peng-Fei Li
Piezoelectric materials with inherent mechanical–electric coupling effect are a crucial family of functional materials in high-end information technology. For practical applications, the transverse piezoelectric performance (d31 or d32) is mainly considered, because this parameter is a vitally important index to characterize the performance of piezoelectric thin films. However, the transverse piezoelectricity of the thin films as a key figure of merit is seldom mentioned in molecular ferroelectrics. Herein, we report that a new 1D halide perovskite ferroelectric N,N-dimethylallylammoniumCdCl3 (DMAACdCl3) exhibits an above room-temperature ferroelectric phase transition with a saturated polarization of 1.9 μC cm–2 and a coercive field of 5.0 kV cm–1. The thin film of DMAACdCl3 is successfully fabricated using an easy processing spinning method and maintains well ferroelectric properties verified by piezoresponse force microscopy (PFM). More significantly, the ferroelectric thin film offers superior transverse piezoelectricity with an in-plane piezoelectric response of about 41 pC N–1, which is about twice that of well-known piezoelectric polymer PVDF (21 pC N–1). Transverse piezoelectricity has been scarcely studied in molecular ferroelectrics, and its exploitation would play an important role in the design of next-generation smart piezoelectric devices.
An emerging approach that employs both light and vibration energy on binary photo-/piezoelectric semiconductor materials for efficient hydrogen (H 2 ) evolution has garnered considerable attention. ZnIn 2 S 4 (ZIS) is recognized as a promising visible-light-activated photocatalyst. However, its effectiveness is constraint by the slow separation dynamics of photoexcited carriers. Density functional theory (DFT) predictions have shown that the integration of piezoelectric BiFeO 3 (BFO) is conducive to the reduction of the H 2 adsorption free energy (ΔG H* ) for the photocatalytic H 2 evolution reaction, thereby enhancing the reaction kinetics. Informed by theoretical predictions, piezoelectric BFO polyhedron particles were successfully synthesized and incorporated with ZIS nanoflowers to create a ZIS/BFO heterojunction using an ultrasonic-assisted calcination method. When subjected to simultaneous ultrasonic treatment and visible-light irradiation, the optimal ZIS/BFO piezoelectric enhanced (piezo-enhanced) heterojunction exhibited a piezoelectric photocatalytic (piezo-photocatalytic) H 2 evolution rate approximately 6.6 times higher than that of pristine ZIS and about 3.0 times greater than the rate achieved under light-only conditions. Moreover, based on theoretical predictions and experimental results, a plausible mechanism and charge transfer route for the enhancement of piezo-photocatalytic performance were studied by the subsequent piezoelectric force microscopy (PFM) measurements and DFT calculations. The findings of this study strongly confirm that both the internal electric field of the step-scheme (S-Scheme) heterojunction and the alternating piezoelectric field generated by the vibration of BFO can enhance the transportation and separation of electron-hole pairs. This study presents a concept for the multipath utilization of light and vibrational energy to harness renewable energy from the environment.
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