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Bismuth-layered ferroelectric nanomaterials exhibit great potential for piezo-photocatalysis. However, a major challenge lies in the difficulty of recovering the catalytic powders, raising concerns regarding secondary pollution of water. In this work, a novel hierarchical porous ferroelectric ceramic containing {110} surface-exposed Bi 3.15 Nd 0.85 Ti 3 O 12 (BIT-Nd) nanosheet arrays is grown on a porous ceramic matrix for efficient and recyclable piezo-photocatalysis. By controlling the BIT-Nd loading level of the nanosheets, the piezo-photocatalytic degradation efficiency of a Rhodamine B(RhB) (C 0 = 10 mg L -1 ) solution reached an optimum value of 97.1% in 100 min with a first-order kinetic rate constant, k, of up to 0.0321 min -1 in Bi 3.15 Nd 0.85 Ti 3 O 12 -20 (BITNd-20) with a mass ratio of hydrothermal products to ceramics of 20%. In the presence of BITNd-20, a surprising H 2 yield rate of 130 µmol·h -1 is achieved without using any cocatalyst or scavenger. Specially, the beneficial role of snowflake structures on piezoelectric potential amplification and introducing nanosheets with exposed {110} surfaces on hydrogen evolution reaction (HER) activity, piezoelectric potential output, and catalytic performance of porous ceramics has been revealed. This unique design strategy provides a new approach to enhance the piezo-photocatalytic activity by addressing environmental issues and enhancing catalytic performance to yield cleaner energy., (© 2025 Wiley‐VCH GmbH.)

Covalent organic frameworks (COFs) serve as one of the most promising candidates for hydrogen peroxide (H 2 O 2 ) photosynthesis, while attaining high-performance COFs remains a formidable challenge due to the insufficient separation of photogenerated charges. Here, through the rational design of bicarbazole-based COFs (Cz-COFs), we showcase the first achievement in piezo-photocatalytic synthesis of H 2 O 2 using COFs. Noteworthily, the ethenyl group-modified Cz-COFs (COF-DH-Eth) demonstrates a record-high yield of H 2 O 2 (9212 μmol g -1  h -1 ) from air and pure water through piezo-photocatalysis, which is ca. 2.5 times higher than that of pristine Cz-COFs without ethenyl groups (COF-DH-H) under identical condition and COF-DH-Eth without ultrasonic treatment. The H 2 O 2 production rate originates from the synergistic effect between an ultrasonication-induced polarized electric field and the spatially separated multiple charge transfer channels, which significantly promote the utilization of photogenerated electrons by directional transfer from bicarbazole groups to the ethenyl group-modified benzene rings. Several Cz-COFs and bifluorenylidene-based COFs (COF-BFTB-H) with similar twisted monomers exhibit obvious piezoelectric performance for promoting H 2 O 2 generation, signifying that organic ligands with a twistable structure play a crucial role in creating broken symmetry structures, thereby establishing piezoelectric properties in COFs., (© 2024 Wiley-VCH GmbH.)

Polyaniline (PANI), a typical organic photocatalyst, has an adjustable structure and good stability, can be easily synthesized on a large scale, and is economical. PANI is doped with ions to regulate its internal structure and improve its photocatalytic performance. However, its photocatalytic performance is limited by the doping concentration and its intrinsic properties, hindering its further application. Herein, PANI films with a piezo-photocatalytic function are fabricated to improve photocatalytic performance and explore their self-powered environmental purification property. PANI/poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) sandwich films, with PVDF-HFP as the interlayer, are prepared by introducing a piezoelectric field into PANI photocatalysts, thereby achieving excellent piezo-photocatalytic performance. The as-fabricated piezo-photocatalyst degrades methyl orange at a rate of 91.2% after 60 min under magnetic stirring. Owing to the low Young's modulus of the all-organic catalyst, self-powered purification is realized using the PANI/PVDF-HFP film. Leaf surfaces are functionalized by loading the film in them for removing pollutants under sunlight and water flow. Thus, this study proposes a common strategy, wherein a piezoelectric interlayer is introduced to load the organic photocatalyst for preparing an all-organic piezo-photocatalyst. This piezo-photocatalyst can be easily recycled and responds to weak forces, realizing its application for self-powered environmental purification., (© 2024 Wiley‐VCH GmbH.)

Piezo-photocatalysis is a frontier technology for converting mechanical and solar energies into crucial chemical substances and has emerged as a promising and sustainable strategy for N 2 fixation. Here, for the first time, defects and piezoelectric field are synergized to achieve unprecedented piezo-photocatalytic nitrogen reduction reaction (NRR) activity and their collaborative catalytic mechanism is unraveled over BaTiO 3 with tunable oxygen vacancies (OVs). The introduced OVs change the local dipole state to strengthen the piezoelectric polarization of BaTiO 3 , resulting in a more efficient separation of photogenerated carrier. Ti 3+ sites adjacent to OVs promote N 2 chemisorption and activation through d-π back-donation with the help of the unpaired d-orbital electron. Furthermore, a piezoelectric polarization field could modulate the electronic structure of Ti 3+ to facilitate the activation and dissociation of N 2 , thereby substantially reducing the reaction barrier of the rate-limiting step. Benefitting from the synergistic reinforcement mechanism and optimized surface dynamics processes, an exceptional piezo-photocatalytic NH 3 evolution rate of 106.7 µmol g -1  h -1 is delivered by BaTiO 3 with moderate OVs, far surpassing that of previously reported piezocatalysts/piezo-photocatalysts. New perspectives are provided here for the rational design of an efficient piezo-photocatalytic system for the NRR., (© 2023 Wiley-VCH GmbH.)

Recently, piezoelectric-based catalysis has been demonstrated to be an efficient means and promising alternative to sunlight-driven photocatalysis, where mechanical vibrations trigger redox reactions. Here, 60 nm-size BiFeO 3 nanoparticles are shown to be very effective for piezo-degrading Rhodamine B (RhB) model dye with record degradation rate reaching 13 810 L mol -1  min -1 , and even 41 750 L mol -1  min -1 (i.e., 100% RhB degradation within 5 min) when piezocatalysis is synergistically combined with sunlight photocatalysis. These BiFeO 3 piezocatalytic nanoparticles are also demonstrated to be versatile toward several dyes and pharmaceutical pollutants, with over 80% piezo-decomposition within 120 min. The maintained high piezoelectric coefficient combined with low dielectric constant, high-elastic modulus, and the nanosized shape make these BiFeO 3  nanoparticles extremely efficient piezocatalysts. To avoid subsequent secondary pollution and enable their reusability, the BiFeO 3 nanoparticles are further embedded in a polymer P(VDF-TrFE) matrix. The as-designed flexible, chemically stable, and recyclable nanocomposites still keep remarkable piezocatalytic and piezo-photocatalytic performances (i.e., 92% and 100% RhB degradation, respectively, within 20 min). This work opens a new research avenue for BiFeO 3 that is the model multiferroic and offers a new platform for water cleaning, as well as other applications such as water splitting, CO 2 reduction, or surface purification., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

Herein, a twisty C-TiO 2 /PCN (CNT) Step-scheme (S-scheme) heterojunction is fabricated and applied to degrade ciprofloxacin (CIP) with the assistance of ultrasonic vibration and visible light irradiation. The nitrogen-rich twisty polymeric carbon nitride (PCN) can not only induce a non-centrosymmetric structure with enhanced polarity for a better piezoelectric effect but also provide abundant lone pair electrons to promote n→π* transition during photocatalysis. Its hybridization with C-TiO 2 particles can construct S-scheme heterojunction in CNT. During the piezo-photocatalysis, the strain-induced polarization electric field in the heterojunction can regulate the electron migration between the two components, resulting in a more effective CIP degradation. With the synergistic effect of ultrasonic vibration and visible light irradiation, the reaction rate constant of CIP degradation by CNT increases to 0.0517 min -1 , which is 1.86 times that of photocatalysis and 6.46 times that of ultrasound. This system exhibits a stable CIP decomposition efficiency under the interference of various environmental factors. In addition, the in-depth investigation found that three pathways and 12 major intermediates with reduced toxicity are produced after the reaction. Hopefully, the construction of this twisty CNT S-scheme heterojunction with enhanced piezo-photocatalytic effect offers inspiration for the design of environmentally functional materials., (© 2023 Wiley-VCH GmbH.)

As a consequence of rapid industrialization throughout the world, various environmental pollutants have begun to accumulate in water, air, and soil. This endangers the ecological environment of the earth, and environmental remediation has become an immediate priority. Among various environmental remediation techniques, piezocatalytic techniques, which uniquely take advantage of the piezoelectric effect, have attracted much attention. Piezoelectric effects allow pollutant degradation directly, while also enhancing photocatalysis by reducing the recombination of photogenerated carriers. In this Review, we provide a comprehensive summary of recent developments in piezocatalytic techniques for environmental remediation. The origin of the piezoelectric effect as well as classification of piezoelectric materials and their application in environmental remediation are systematically summarized. We also analyze the potential underlying mechanisms. Finally, urgent problems and the future development of piezocatalytic techniques are discussed., (© 2022 Wiley-VCH GmbH.)

The built-in electric field can be generated in the piezoelectric materials under mechanical stress. The resulting piezoelectric effect is beneficial to charge separation in photocatalysis. Meanwhile, the mechanical stress usually gives rise to accelerated mass transfer and enhanced catalytic activity. Unfortunately, it remains a challenge to differentiate the contribution of these two factors to catalytic performance. Herein, for the first time, isostructural metal-organic frameworks (MOFs), i.e., UiO-66-NH 2 (Zr) and UiO-66-NH 2 (Hf), are adopted for piezo-photocatalysis. Both MOFs, featuring the same structures except for diverse Zr/Hf-oxo clusters, possess distinctly different piezoelectric properties. Strikingly, UiO-66-NH 2 (Hf) exhibits ≈2.2 times of activity compared with that of UiO-66-NH 2 (Zr) under simultaneous light and ultrasonic irradiation, though both MOFs display similar activity in the photocatalytic H 2 production without ultrasonic irradiation. Given their similar pore features and mass transfer behaviors, the activity difference is unambiguously assignable to the piezoelectric effect. As a result, the contributions of the piezoelectric effect to the piezo-photocatalysis can be clearly distinguished owing to the stronger piezoelectric property of UiO-66-NH 2 (Hf)., (© 2021 Wiley-VCH GmbH.)