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Piezo-photocatalysis materials that can combine the piezoelectric effect in photocatalytic processes are very attractive for promising applications in water splitting and contaminant degradation. The perovskite oxides with adjustable exposed crystal facets are expected to optimize the catalysis activities by exposing the high-energy planes. In this work, we develop a salt-assisted strategy that controllably prepares anisotropic SrTiO 3 particles with a large number of surface defects, which exhibit good piezo-photocatalytic features. The exposure of the crystal facets can be tuned by changing the assistants (NaCl or SrCl 2). The SrCl 2 can lead to the exposure of the (110) plane in one-dimensional SrTiO 3 particles and NaCl can induce the cubic SrTiO 3 particles with the exposure plane of (200). Attributed to the exposed high-energy facets and abundant oxygen vacancies, the latter show higher activities than the former in both water splitting and dye degradation under light irradiation and ultrasonic vibration. Our work provides an approach to optimize piezo-photocatalytic activities by tuning the exposed crystal facets. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) serve as one of the most promising candidates for hydrogen peroxide (H2O2) 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 H2O2 using COFs. Noteworthily, the ethenyl group‐modified Cz‐COFs (COF‐DH‐Eth) demonstrates a record‐high yield of H2O2 (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 H2O2 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 H2O2 generation, signifying that organic ligands with a twistable structure play a crucial role in creating broken symmetry structures, thereby establishing piezoelectric properties in COFs. [ABSTRACT FROM AUTHOR]

The piezoelectric effect is employed to enhance the photocatalytic process by enabling the efficient utilization of photogenerated electrons and holes. In this study, a defect‐engineered Na–Sm bimetal‐regulated layered ferroelectric material, SrBi2Nb2O9, is synthesized using a molten salt process, and exhibits excellent piezo‐photocatalytic performance in the synergistic removal of uranium [U(VI)] and tetracycline (TC) from wastewater. The incorporation of the Sm dopant creates an intermediate band structure, while the Na doping introduces empty orbitals into the conduction band, thereby enhancing the electrical conductivity, improving the electron mobility, and supplying sufficient electrons to promote catalytic reactions. Moreover, the doping induces an additional internal electric field, which combines the embedded field along the b‐axis with the polarization along the a‐axis. This combined effect enhances the anisotropic migration of photogenerated electrons and holes, facilitating their spatial separation. The doped SrBi2Nb2O9 can simultaneously remove 98% of U(VI) and degrade 99% of TC. Furthermore, a synergistic enhancement effect is observed between the U(VI) reduction and TC oxidation reactions, with the rate constant of U(VI) being 1.2 times higher than that of the individual system. This work presents an innovative strategy for designing layered ferroelectric catalysts able to simultaneously remove pollutants and optimize piezo‐photocatalytic redox reactions. [ABSTRACT FROM AUTHOR]

The piezoelectric effect is employed to enhance the photocatalytic process by enabling the efficient utilization of photogenerated electrons and holes. In this study, a defect‐engineered Na–Sm bimetal‐regulated layered ferroelectric material, SrBi2Nb2O9, is synthesized using a molten salt process, and exhibits excellent piezo‐photocatalytic performance in the synergistic removal of uranium [U(VI)] and tetracycline (TC) from wastewater. The incorporation of the Sm dopant creates an intermediate band structure, while the Na doping introduces empty orbitals into the conduction band, thereby enhancing the electrical conductivity, improving the electron mobility, and supplying sufficient electrons to promote catalytic reactions. Moreover, the doping induces an additional internal electric field, which combines the embedded field along the b‐axis with the polarization along the a‐axis. This combined effect enhances the anisotropic migration of photogenerated electrons and holes, facilitating their spatial separation. The doped SrBi2Nb2O9 can simultaneously remove 98% of U(VI) and degrade 99% of TC. Furthermore, a synergistic enhancement effect is observed between the U(VI) reduction and TC oxidation reactions, with the rate constant of U(VI) being 1.2 times higher than that of the individual system. This work presents an innovative strategy for designing layered ferroelectric catalysts able to simultaneously remove pollutants and optimize piezo‐photocatalytic redox reactions. [ABSTRACT FROM AUTHOR]

Piezocatalysis and piezo‐photocatalysis technology is a continuously developing catalytic technology based on the piezoelectric effect of catalysts, which breaks the barrier between mechanical and chemical energy. The piezoelectric polarization field formed by the mechanical deformation of piezoelectric materials is proven to effectively manipulate band structures, improve the separation of electron‐hole pairs and enhance the catalytic activity, thus alleviating energy crises and environmental issues. Herein, this review first introduces the technology of piezocatalysis and piezo‐photocatalysis, comprehensively summarizes the synthesis methods of piezo(photo)catalysis materials, and analyzes and discusses the measures to optimize the performance of piezo(photo)catalysts. The following systematically summarizes the characteristics and development of the current main piezo(photo)catalytic systems, and discusses the application of first principles calculations in piezo(photo)catalysis in combination with practical researches. Subsequently, the main application progress of piezo(photo)catalysis in environmental remediation, energy conversion, and biomedical therapy fields is presented. In the end, the current challenges, development direction, and future prospects are prospected. [ABSTRACT FROM AUTHOR]

Piezo-photocatalysis is a "green" approach to decompose various pollutants using natural clean energy. Herein, a series of ZnSnO 3 /C nanofibers with excellent piezo-photocatalytic activities were reported. The XRD, TEM and SEM, as well as XPS measurements were carried out and the results indicate that ZnSnO 3 /C nanofibers with the orthorhombic phase were fabricated successfully. The UV–vis absorbance spectra, photocurrent response, EIS curves and photoluminescence characteristics indicate that the incorporated C decreases the band gap of ZnSnO 3 and improves separation efficiency of photoinduced charge-hole pairs, which results in higher catalytic activity of ZnSnO 3 /C nanofibers. The photocatalytic, piezocatalytic and piezo-photocatalytic activities were investigated by degrading diclofenac. The ZnSnO 3 /C‒0.3 ‰ has the highest reaction constant among the series of catalysts. The reaction constat of ZnSnO 3 /C‒0.3 ‰ in photocatalysis process (0.0185 min−1) is 2.15 times that of ZnSnO 3. The reaction constat of ZnSnO 3 /C‒0.3 ‰ in piezo-photocatalysis process (0.0549 min−1) is 2.97 times that of ZnSnO 3 /C‒0.3 ‰ in photocatalysis and 3.47 times that of ZnSnO 3 in piezo-photocatalysis (0.0158 min−1). The •OH and e− radicals are key roles for degrading diclofenac in catalysis processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel S-scheme NiO/PbBiO 2 Br composites are synthesized through a hybrid approach combining hydrothermal and photodeposition methods. • NiO/PbBiO 2 Br composites demonstrate dual energy harvesting capabilities from solar and vibration sources. • A synergistic effect between piezocatalysis and photocatalysis is observed in NiO/PbBiO 2 Br. • NiO/PbBiO 2 Br exhibits significantly increased photoactivity in RhB degradation. • Enhanced charge separation efficiency is achieved in NiO/PbBiO 2 Br via an S-scheme mechanism. The fabrication of an S-scheme heterojunction demonstrates as an efficient strategy for achieving efficient charge separation and enhancing catalytic activity of piezocatalysts. In this study, a new S-scheme heterojunction was fabricated on the PbBiO 2 Br surface through the photo-deposition of NiO nanoparticles. It was then employed in the piezoelectric catalytic degradation of Rhodamine B (RhB). The results demonstrate that the NiO/PbBiO 2 Br composite exhibits efficient performance in piezocatalytic RhB degradation. The optimal sample is the NiO/PbBiO 2 Br synthesized after 2 h of irradiation, achieving a RhB degradation rate of 3.11 h−1, which is 12.4 times higher than that of pure PbBiO 2 Br. Simultaneous exposure to visible light and ultrasound further increases in the RhB degradation rate, reaching 4.60 h−1, highlighting the synergistic effect of light and piezoelectricity in the NiO/PbBiO 2 Br composite. A comprehensive exploration of the charge migration mechanism at the NiO/PbBiO 2 Br heterojunction was undertaken through electrochemical analyses, theoretical calculations, and in-situ X-ray photoelectron spectroscopy analysis. The outcomes reveal that p-type semiconductor NiO and n -type semiconductor PbBiO 2 Br possess matching band structures, establishing an S-scheme heterojunction structure at their interface. Under the combined effects of band bending, interface electric fields, and Coulomb attraction, electrons and holes migrate and accumulate on the conduction band of PbBiO 2 Br and valence band of NiO, respectively, thereby achieving effective spatial separation of charge carriers. The catalyst's synergistic photo-piezoelectric catalysis effect can be ascribed to its role in promoting the generation and separation of charge carriers under both light irradiation and the piezoelectric field. The results of this investigation offer valuable insights into the development and production of catalytic materials that exhibit outstanding performance through the synergy of piezocatalysis and photocatalysis. [ABSTRACT FROM AUTHOR]

The pursuit of high-performance piezo-photocatalysts through structural modifications has been a focal point of investigation within the realm of related scientific disciplines. In this study, we successfully designed Er-doped Bi 0.5 Na 0.5 TiO 3 –BaTiO 3 combined with rare earth ion doping and solid solution modification, and the prepared particles exhibited homogeneous grain sizes and optimized concentrations of oxygen vacancies (O V). The synergistic incorporation of O V (accelerator for catalytic reaction) and Er3+ results in an impressive 12-fold enhancement of the piezo-photocatalytic rate when degrading the Rhodamine B dye. The optimal composition 0.96BNT-0.04BT-Er demonstrates outstanding electrochemical properties, including a superior photocurrent response and minimal impedance, highlighting its exceptional performance in piezo-photocatalysis. The fundamental enhancement in catalytic performance can be attributed to the reconfiguration of the band structure of 0.96BNT-0.04BT-Er, which has been meticulously calculated utilizing DRS and VB-XPS and the internal mechanism was explained in detail. This research serves as a source of inspiration for the investigation of solid solutions among piezo-photocatalysts and sheds light on the vital role of band structure in governing catalytic performance. [ABSTRACT FROM AUTHOR]

Over time, industrialization, population expansion, building, and other human-related activities have made water contamination a major problem. As a result, steps towards waste water treatment must be taken. By using piezoelectric materials in the purifying process, a new area of waste water treatment known as piezo-photocatalysis has emerged. To improve the material's water purification effectiveness, the piezoelectric action is paired with sun irradiation in this case. Up until this point, photocatalysis has served as a sophisticated method for purification. Thus, the piezoelectric materials became the center of attention in the quest for cutting-edge technologies for water purification. Piezoelectric materials have other potential applications outside of water treatment, including hydrogen production and carbon dioxide adsorption. The lead, barium, KNN, and bismuth perovskite compounds that have seen extensive usage in wastewater treatment are covered in this paper. These materials have the potential to achieve an efficiency of almost 100% when they combine the effects of piezoelectricity with photocatalysis. Consequently, the function of piezoelectric materials in wastewater treatment and the mechanism of piezo-photocatalysis are covered extensively in this paper. [ABSTRACT FROM AUTHOR]

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Piezoelectric and triboelectric enhanced catalysis use mechanical stimuli to enhance the performance of catalysts in energy conversion and pollutant degradation. The electric field generated by piezoelectric materials can tune the charge migration behavior and redox kinetics of catalysts, leading to improved efficiency in energy conversion and pollutant degradation. Triboelectrification can also generate an electric field when two different materials come into contact, and this effect can be used to enhance catalytic reactions. Research in this area is still in its early stages, but it has the potential to significantly improve the efficiency of energy conversion and pollutant degradation and provide a promising method for environmental remediation. This review accounts for recent advancements in piezoelectricity and triboelectricity enhanced catalysis, covering basic understandings, catalyst design, and performance insights. Finally, challenges and future opportunities for piezoelectricity and triboelectricity enhanced catalysis are discussed.

Hydrogen peroxide (H2O2) production via oxygen (O2) reduction reaction (ORR) in pure water (H2O) through graphitic carbon nitrides (g‐C3N4)‐based piezo‐photocatalysts is an exciting approach in many current studies. However, the low Lewis‐acid properties of g‐C3N4 limited the catalytic performance because of the low O2 adsorption efficacy. To overcome this challenge, the interaction of g‐C3N4 precursors with various solvents are utilized to synthesize g‐C3N4, possessing multiple nitrogen‐vacant species via thermal shocking polymerization. These results suggest that the lack of nitrogen in g‐C3N4 and the incident introduction of oxygen‐functional groups enhance the Lewis acid‐base interactions and polarize the g‐C3N4 lattices, leading to the enormous enhancement. Furthermore, the catalytic mechanisms are thoroughly studied, with the formation of H2O2 proceeding via radical and water oxidation pathways, in which the roles of light and ultrasound are carefully investigated. Thus, these findings not only reinforce the potential view of metal‐free photocatalysts, accelerating the understanding of g‐C3N4 working principles to generate H2O2 based on the oxygen reduction and water oxidation reactions, but also propose a facile one‐step way for fabricating highly efficient and scalable photocatalysts to produce H2O2 without using sacrificial agents, pushing the practical application of in situ solar H2O2 toward real‐world scenarios. [ABSTRACT FROM AUTHOR]

A series of Na0.5Bi0.5TiO3-based catalysts were synthesized by using the solvothermal route. The successful synthesis of catalysts was confirmed by various measurements. The influence of Y3+ doping on the band gap was revealed by the UV–visible absorbance spectra. Their photocatalytic, piezocatalytic, and piezo-photocatalytic activities were investigated by degrading methylene blue. The results show that the Y3+ doping can enhance the catalytic activity of Na0.5Bi0.5TiO3 due to the more efficient harvesting of light, and the catalytic activity can be further enhanced by the support of polyacrylonitrile nanofibers on account of the existence of more active sites. The reaction constants of Na0.5Bi0.485Y0.015TiO3 and Na0.5Bi0.485Y0.015TiO3@PAN in photocatalysis processes are 0.0075 and 0.0112 min–1, which is 1.23 and 1.84 times as many as that of Na0.5Bi0.5TiO3. In addition, the catalysts show higher catalytic activities when the catalysis is carried out at the operating condition including both simulated sunlight irradiation and ultrasonic vibration. The reaction constant of Na0.5Bi0.485Y0.015TiO3@PAN in piezo-photocatalysis is 0.0381 min–1, which is 3.09 and 6.77 times of photocatalysis and piezocatalysis. The enhanced activity results from suppression of charge carrier recombination. The radicals of •O2– and h+ play actual roles in the catalytic processes. [ABSTRACT FROM AUTHOR]

The efficient degradation of organic pollutants in diverse environmental matrices can be achieved through the synergistic application of piezo‐catalysis and photocatalysis. The focus of this study is on understanding the fundamental principles and mechanisms that govern the collaborative action of piezoelectric and photocatalytic materials. Piezoelectric nanomaterials, under mechanical stress, generate piezo‐potential, which, when coupled with photocatalysts, enhances the generation and separation of charge carriers. The resulting cascade of redox reactions promotes the degradation of a wide spectrum of organic pollutants. The comprehensive investigation involves a variety of experimental techniques, including advanced spectroscopy and microscopy, to elucidate the intricate interplay between mechanical and photoinduced processes. The influence of key parameters, such as material composition, morphology, and external stimuli on the catalytic performance, is systematically explored. This study contributes to the increasing knowledge of environmental remediation and lays the foundation for the development of advanced technologies using piezo and photocatalysis for sustainable pollutant removal. [ABSTRACT FROM AUTHOR]

The development of a high-performance ferroelectric piezo-photocatalyst is an efficient strategy for advancing sustainability within the environmental and energy sectors. Yet, a major challenge lies in the creation of a strong polarized electric field that can effectively hinder charge recombination, both within the bulk and on the surface of catalysts. Herein, we synthesize a series of Nb-doped Bi4Ti3O12 nanosheets via a facile one-pot hydrothermal method to achieve synergistically enhanced piezo-photocatalytic performance in CO2 reduction and pollutant degradation. The optimized doped Bi4Ti3O12 demonstrates remarkable efficiency in the conversion of CO2 into CO, with a high production rate of 72.7 μmol∙g−1∙h−1 without using co-catalysts or any sacrificial agent, surpassing the performance of unmodified Bi4Ti3O12 by up to 4.69 folds. Additionally, our catalyst demonstrates ultra-fast piezo-photocatalytic degradation of organic pollutant Rhodamine B (RhB) at low concentrations and exceptional piezo-photocatalytic activity at high concentrations, outperforming most previously reported state-of-the-art catalysts. The systematic corroboration of catalyst characterization and experimental analysis reveals that the synergistic effect arises from the amplified macroscopic polarization induced by lattice distortion caused by the larger Nb ions, thereby improving piezo-photocatalytic efficiency. This research thus offers valuable insights into the direct design and fabrication of versatile catalytic systems, with applications spanning CO2 valorization and beyond.

[Display omitted] • Bismuth ferrite-derived Bi 2 O 2 CO 3 composite was prepared with one-pot hydrothermal method. • Z-scheme heterojunction was formed in this composite. • CO 2 dissolved in dichloromethane was used as carbon source for Bi 2 O 2 CO 3. • The prepared composite presented improved photocatalytic activity and piezoelectric activity. Piezoelectric materials can generate the built-in electric field under ultrasound assistance, which is beneficial to the separation of the photogenerated electron-hole pairs in photocatalysis. Meanwhile, the ultrasound stress usually leads to accelerate electron transfer and enhance catalytic activity. Thus, piezo-photocatalysis technique is believed to be one of the effective techniques for organic pollutant degradation. In this work, a binary piezoelectric integrated piezo-photocatalytic Z-Scheme heterojunction with bismuth ferrite (BFO) and bismuth oxycarbonate (Bi 2 O 2 CO 3 , BOC) based on the in situ production of Bi 2 O 2 CO 3 on Bi 25 FeO 40 surface in dichloromethane, where Bi 25 FeO 40 was employed as piezoelectric materials and Bi source, CO 2 dissolved in dichloromethane was used as carbon source. Under 60 min ultrasound and visible light irradiation, the optimal BFO/BOC presented a higher piezo-photocatalytic tetracycline (TC) degradation rate (95 %) than Bi 25 FeO 40 (30 %) and Bi 2 O 2 CO 3 (17 %). Moreover, the optimal BFO/BOC illustrated higher piezo-photocatalytic TC degradation rate under ultrasound and visible light irradiation than that under visible light condition and ultrasound condition, respectively. These results strongly demonstrated the synergistically piezo-photocatalytic degradation of TC by BFO and BOC. This work not only provides a novel piezo-photocatalyst for pollutant degradation, but also provides a novel method to prepare Bi 2 O 2 CO 3 -based piezo-photocatalytic composite catalyst. [ABSTRACT FROM AUTHOR]

Increasing active sites in catalysts is of utmost importance for catalytic processes. In this regime, single‐atom dispersing on graphitic carbon nitrides (g‐C3N4) to produce fine chemicals, such as hydrogen peroxide (H2O2), is of current interest due to not only enhancing catalytic performance but also reducing the loading of necessary metals. Herein, g‐C3N4 is engineered by atomically dispersing aluminum (Al) or indium (In) sites to provide catalytic active centers via one‐step thermal shock polymerization. The addition of Al and In sites can accelerate the catalytic efficacy owing to the Lewis acid–base interactions between these metals and oxygen (O2). Under catalytic conditions, the formation of oxygenic radicals will strongly be associated with the enhanced formation of H2O2, confirmed by in situ electron paramagnetic resonance spectroscopy. Furthermore, the empirical analyses from positron annihilation spectroscopy show that In atoms will occupy the near positions of carbon vacancies (VC) to form NVC@InO bonds. This replacement will produce the highest formation energy based on the density functional theory calculations, improving the stability of atom‐dispersive materials. Therefore, via the combination of experimental and theoretical proofs, this study suggests the exact location of In atoms in g‐C3N4 structures, which can help boost the catalytic production of H2O2. [ABSTRACT FROM AUTHOR]

The Na 0.5 Bi 0.5 TiO 3 and Na 0.5 Bi 0.5 TiO 3 @C core-shell catalysts were synthesized successfully using the solvothermal method. A few of Ti4+ was reduced to Ti3+ with the help of glucose in the solvothermal process, which results in the formation of oxygen vacancies in the NBT@C catalysts. Meanwhile, the excessive glucose was carbonized, which accumulated on the surface of Na 0.5 Bi 0.5 TiO 3 and formed Na 0.5 Bi 0.5 TiO 3 @C core-shell composites. The phase, microstructure, optical and piezoelectric properties, as well as the catalytic activities of the synthesized catalysts were characterized. The Na 0.5 Bi 0.5 TiO 3 @C core-shell composites show higher photocatalytic activity that of pure Na 0.5 Bi 0.5 TiO 3 on account of more visible light absorbance. And the piezo-photocatalytic activities to tetracycline of the synthesized catalysts are highest due to the synergetic effects of photocatalysis and piezocatalysis. [ABSTRACT FROM AUTHOR]

Elucidating the impact of heteroatoms in graphitic carbon nitrides (g‐C3N4) is of utmost importance to rationalize materials. Hence, in this study, oxygen‐doped g‐C3N4 containing trace amounts of halogen in the structures for piezo‐photosynthesis of hydrogen peroxides (H2O2) is fabricated. The findings reveal that oxygen atoms may be inserted into g‐C3N4 in‐plane structures, while halogen atoms tend to become intercalated between g‐C3N4 layers. Furthermore, the presence of ammonium molten salts (NH4X) during the synthesis alters the concentration of mono and cluster vacancies of carbon and nitrogen in the materials, certifying by positron annihilation spectroscopy (PAS). These defective contributions will be meaningfully accelerate catalytic performance by providing trapping states. Additionally, the decomposition of generated H2O2 can produce highly oxidative hydroxyl radicals, inducing degradations on the catalyst's structures and unexpectedly decreasing catalytic outcomes. From the mechanistic view, different reduction and oxidation channels will be play a pivotal role in generating H2O2. Moreover, the influence of ultrasound and light is also carefully investigated in the work to gain more insights into how the catalysts are triggered to improve catalytic performance. Thus, this study highlights the importance of carefully characterizing structures of g‐C3N4 to precisely understand the catalytic properties, benefiting catalytic design and development. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The separation of photogenerated electron–hole pairs is vitally important for photocatalysis, which can be effectively promoted by polarization field. However, it only manifests in piezoelectric/pyroelectric/ferroelectric materials that have a non-centrosymmetric structure. Here, we demonstrate that the polarization enhanced photocatalysis (with wide spectra from ultraviolet (UV) light to visible light) can be achieved in centrosymmetric semiconductors, such as δ-MnO2 and TiO2 nanosheets integrated nanoflowers, by using the strain-gradient-induced flexoelectric polarization that is always overlooked in polarization-enhanced catalysis. Under ultrasonic and illumination excitation, the organic pollutants (methylene blue (MB), etc.) can be effectively degraded within 30 min with excellent stability and repeatability. Compared with photocatalysis, the flexo-photocatalytic performance of above centrosymmetric semiconductors is substantially increased by 85%. Moreover, the factors related to flexo-photocatalysis such as material morphology, mechanical stimuli source, and adsorption are explored to deeply understand the mechanism of flexo-photocatalysis. This work opens up a way for high-performance photocatalysis in centrosymmetric semiconductors. [ABSTRACT FROM AUTHOR]

The enhancement of photocatalytic reactivity through the internal electric field has received much attention. The combination of the piezoelectric effect and the photo-exiting process facilitates the segregation of the photogenerated carriers, thereby boosting the piezo-photocatalytic activity. We have constructed g-C3N4/Ag/ZnO tri-component composites; with various g-C3N4 precursors to achieve reliable photo/piezo-photocatalysis for H2 production and Rhodamine B (RhB) dye degradation. We observed that urea-based g-C3N4/Ag/ZnO (UCAZ) tri-components exhibit a superior H2 production rate of 1125.5 μmol h−1 g−1 under photocatalytic conditions. When piezoelectric-potential was introduced into the photocatalysis reaction via ultrasonic, the H2 rate increased dramatically to 1637.5 μmol h−1 g−1, which is approximately 145% greater than that light irradiation alone.Similarly, the catalytic decomposition ratio of Rhodamine B (RhB) under the coexistence of ultrasound and light, and degradation efficiency reached 99% in 120 min, which is higher than the value of (42%, 0.0031 min−1) for piezo-catalysis and (80%, 0.01 min−1) for photocatalysis condition alone. The rate constant under synergistic simulation reaches 0.021 min−1, which is 200% and 645% times higher than the sole light and ultrasonic illumination. Additionally, RhB degradation of all the tri-components was performed under solar light (Sunlight) and ultrasound irradiation, and efficiency reached 99.5% in 45 min with a rate constant of 0.06 min−1, which is 300% higher than the piezo-photocatalytic under LED source. The enhanced performance of the g-C3N4/Ag/ZnO tricomponent is attributed to the high specific surface area (168 m2 g−1) and synergetic effect of piezo catalysis and photocatalysis.

In this work, a novel heterojunction composite Ag2S/KTaxNb1-xO3 was designed and synthesized through a combination of hydrothermal and precipitation procedures. The Ta/Nb ratio of the KTaxNb1-xO3 and the Ag2S content were optimized. The best 0.5% Ag2S/KTa0.5Nb0.5O3 (KTN) sample presents an enhanced photocatalytic performance in ammonia synthesis than KTN and Ag2S. Under simulated sunlight, the NH3 generation rate of 0.5% Ag2S/KTN reaches 2.0 times that of pure KTN. Under visible light, the reaction rate ratio of the two catalysts is 6.0. XRD, XPS, and TEM analysis revealed that Ag2S was intimately decorated on the KTN nanocubes surface, which promoted the electron transfer between the two semiconductors. The band structure investigation indicated that the Ag2S/KTN heterojunction established a type-II band alignment with intimate contact, thus realizing the effective transfer and separation of photogenerated carriers. The change in charge separation was considered as the main reason for the enhanced photocatalytic performance. Interestingly, the Ag2S/KTN composite exhibited higher NH3 generation performance under the combined action of ultrasonic vibration and simulated sunlight. The enhanced piezo-photocatalytic performance can be ascribed that the piezoelectric effect of KTN improved the bulk separation of charge carriers in KTN. This study not only provides a potential catalyst for photocatalytic nitrogen fixation but also shows new ideas for the design of highly efficient catalysts via semiconductor modification and external field coupling.

The limitation to enhancing photocatalytic performance in photocatalysts lies in the rapid recombination of photo‐induced electrons and holes. Herein, AgNbO3 photocatalysts were synthesized by the hydrothermal method. The effects of hydrothermal temperature on the microstructure and photocatalytic/piezo‐photocatalytic performances of AgNbO3 have been systematically investigated. The AgNbO3 cubes synthesized at 180 °C for 24 h exhibited the best photocatalytic/piezo‐photocatalytic performances among all samples. The corona poling as an important method of polarization engineering is applied to promote further the separation and migration of charge carriers in AgNbO3. The polarized AgNbO3 synthesized at 170 °C exhibited outstanding piezo‐photocatalytic performance, and a degradation rate of 95 % for RhB within 90 min and a high apparent rate constant of 0.02978 min−1 were achieved. On the one hand, the alternating piezoelectric field caused by ultrasonic‐assisted illumination destroyed the shielding effect and enhanced the separation of electron‐hole pairs. On the other hand, polarization engineering induced by corona poling promoted the separation and migration of photo‐induced carriers, thereby realizing more efficient utilization of these charges during the photocatalytic decomposition process. This work presents a facile way to achieve superior piezo‐photocatalytic performances of AgNbO3‐based photocatalyst via polarization engineering. [ABSTRACT FROM AUTHOR]

In this comprehensive review article, we delve into the critical intersection of environmental science and materials science. The introduction sets the stage by emphasizing the global water shortage crisis and the dire consequences of untreated effluents on ecosystems and human health. As we progress into the second section, we embark on an intricate exploration of piezoelectric and photocatalytic principles, illuminating their significance in wastewater treatment and sustainable energy production. The heart of our review is dedicated to a detailed analysis of the detrimental impacts of effluents on human health, underscoring the urgency of effective treatment methods. We dissected three key materials in the realm of piezo-photocatalysis: ZnO-based materials, BaTiO3-based materials, and bismuth-doped materials. Each material is scrutinized for its unique properties and applications in the removal of pollutants from wastewater, offering a comprehensive understanding of their potential to address this critical issue. Furthermore, our exploration extends to the realm of hydrogen production, where we discuss various types of hydrogen and the role of piezo-photocatalysis in generating clean and sustainable hydrogen. By illuminating the synergistic potential of these advanced materials and technologies, we pave the way for innovative solutions to the pressing challenges of water pollution and renewable energy production. This review article not only serves as a valuable resource for researchers and scholars in the fields of material science and environmental engineering but also underscores the pivotal role of interdisciplinary approaches in addressing complex global issues. [ABSTRACT FROM AUTHOR]

Oxygen vacancies are found to have significant effects on the piezo-photocatalytic performance. For this reason, Molar-like and Bamboo-like BaTiO 3 with the same tetragonal phase are synthesized by a two-step hydrothermal method. Molar-like BaTiO 3 exhibits a superior piezo-photocatalytic performance by degrading the organic dye indigo carmine (IC), whose kinetic constant of 0.099 min−1 is 1.80 times higher than that of Bamboo-like BaTiO 3. The same conclusion is drawn while the differences in specific surface areas are eliminated. There are more oxygen vacancies in Molar-like BaTiO 3 compared to Bamboo-like BaTiO 3 , as shown in XPS results. The oxygen vacancies are favorable for light adsorption and O 2 activation, thus an excellent photocatalytic performance is achieved. XRD refinements show that Molar-like BaTiO 3 has a slightly higher content of piezoelectric tetragonal phase and stronger lattice distortion than Bamboo-like BaTiO 3. However, the piezoelectric polarization of Molar-like BaTiO 3 is weakened and the number of effective carriers is reduced due to more oxygen vacancies. The presented work provides a profound reference for the structural design of catalysts. [ABSTRACT FROM AUTHOR]

In this work, a novel heterojunction composite Ag2S/KTaxNb1-xO3 was designed and synthesized through a combination of hydrothermal and precipitation procedures. The Ta/Nb ratio of the KTaxNb1-xO3 and the Ag2S content were optimized. The best 0.5% Ag2S/KTa0.5Nb0.5O3 (KTN) sample presents an enhanced photocatalytic performance in ammonia synthesis than KTN and Ag2S. Under simulated sunlight, the NH3 generation rate of 0.5% Ag2S/KTN reaches 2.0 times that of pure KTN. Under visible light, the reaction rate ratio of the two catalysts is 6.0. XRD, XPS, and TEM analysis revealed that Ag2S was intimately decorated on the KTN nanocubes surface, which promoted the electron transfer between the two semiconductors. The band structure investigation indicated that the Ag2S/KTN heterojunction established a type-II band alignment with intimate contact, thus realizing the effective transfer and separation of photogenerated carriers. The change in charge separation was considered as the main reason for the enhanced photocatalytic performance. Interestingly, the Ag2S/KTN composite exhibited higher NH3 generation performance under the combined action of ultrasonic vibration and simulated sunlight. The enhanced piezo-photocatalytic performance can be ascribed that the piezoelectric effect of KTN improved the bulk separation of charge carriers in KTN. This study not only provides a potential catalyst for photocatalytic nitrogen fixation but also shows new ideas for the design of highly efficient catalysts via semiconductor modification and external field coupling. [ABSTRACT FROM AUTHOR]

Designing catalysts that can effectively make use of renewable energy benefits to solve the current challenges of environmental pollution and increasing energy demands. Piezo-photocatalysis that can utilize solar energy and natural vibration-energy has emerged as a “green” technique. In this work, we fabricated BiFeO3/C nano composites that can harvest solar and vibration energies and degrade organic pollutants. The incorporated carbon quantum dots bring about more efficient visible light absorbance and separation of photoinduced electron-hole pairs. The piezoelectric polarization further suppresses the recombination of photoinduced electron-hole pairs. The catalysts own higher reaction rates in piezo-photocatalysis and the BiFeO3/C-0.12 shows the highest degradation efficiency (k-value of 0.0835 min−1).

Sodium bismuth titanate (Bi0.5Na0.5TiO3, BNT) is a typical lead-free piezoelectric material with perovskite structure, which exhibits great potential as piezo-photocatalyst but limited by the little response on visible light and insufficient carriers for efficient catalytic reactions. Herein, a novel BNT/CdS heterojunction was facilely synthesized by the two-step hydrothermal process for significantly enhanced piezo-photocatalytic degradation of organic dyes. The CdS nanoparticles with 35 nm in diameter are uniformly decorated on the highly crystallized BNT spheres. The obtained BNT/CdS heterojunction displays strong absorption of visible light because of the narrow band gap of CdS. Due to the strong built-in electric field under ultrasonic and efficient excitation by visible light, the photogenerated carriers can be efficiently separated at the BNT/CdS interface and migrate to the surface for catalytic reactions. As a result, the BNT/CdS shows much higher piezo-photocatalytic activity than that of BNT and can degrade 99% RhB within 60 min. Meanwhile, the piezo-photocatalytic performance of BNT/CdS is far better than that of individual photocatalysis or piezocatalysis. Moreover, the catalytic experiments in the presence of different scavengers indicate that ·O2− is the predominant active specie. The synthetic process is simple, low-cost, and controllable to produce high-performance BNT/CdS and is believed to show promising application prospect. [ABSTRACT FROM AUTHOR]

Sustainability in catalysis is increasingly becoming the primary target in academic and industrial studies. Regarding the material perspective, designing heterojunction nanocatalysts to produce small molecules, such as hydrogen peroxide (H2O2), has been an attractive research theme in recent decades. Nonetheless, most reported materials suffer from a complicated synthetic process with various steps and using unbenign solvents, hindering practical applications on an industrial scale. This study proposed a facile one-step way to fabricate heterostructured CdS/g-C3N4 nanocatalysts to produce H2O2 from water and oxygen under light and ultrasound irradiation. The results showed that the formation of H2O2 mainly relies on oxygen radical species. Oxygen is initially converted into superoxide via excited electrons from CdS, followed by the formation of singlet oxygen from the oxidation process in g-C3N4 sites. Interestingly, the formation of H2O2 in an inert atmosphere is associated with the in situ evolution of oxygen from water oxidation due to the suitable electronic band position of g-C3N4 to drive multioxidation reactions. Charge transfer characterizations illustrate the S-scheme mechanism in the catalytic process, giving a better understanding of the charge transportation phenomenon, thus providing a critical pathway in designing and developing heterojunction materials for catalysis with easier catalyst preparation and operation processes. [ABSTRACT FROM AUTHOR]

This study is the first to report the high performance of calcined natural sphalerite as a heterogeneous catalyst (Catalyst) in the piezo- and photocatalytic degradation of pharmaceuticals (bezafibrate and ceftriaxone) using high-frequency ultrasound (US, 1.7 MHz) and ultraviolet-light-emitting diodes (LED, 365 nm). The kinetic comparison showed that piezo-photocatalysis (LED + US + Catalyst) was more efficient than photocatalysis (LED + Catalyst) for degrading both contaminants in deionized water as well as in surface river water at natural pH (7.9). Despite reducing degradation rates (~1.7 times) in river water due to the scavenging effect of its constituents, ceftriaxone and bezafibrate were degraded by 77% and 48% after 1 h of exposure, respectively. Adding H2O2 increased the corresponding pseudo-first-order rate constants, and the complete degradation of ceftriaxone was achieved. However, the contribution of ultrasound at a given intensity was hidden, which resulted in a similar performance of piezo-photocatalysis and photocatalysis for treating river water. No pronounced synergy between the piezo- and photocatalytic processes was observed in the experimental conditions used. Nevertheless, the H2O2-assisted piezo-photocatalysis using high-frequency US, LED, and natural catalysts can be considered a novel and effective strategy for eliminating pharmaceuticals from real water without pH adjustment. [ABSTRACT FROM AUTHOR]

A novel heterojunction composite of CoOx/Bi4Ti3O12 was synthesized through a combination of molten salt and photodeposition methods. The optimal sample exhibited superior performance in the piezocatalytic degradation of methyl orange (MO) dye with a degradation rate of 1.09 h−1, which was 2.4 times higher than that of pristine Bi4Ti3O12. Various characterizations were conducted to reveal the fundamental nature accountable for the outstanding piezocatalytic performance of CoOx/Bi4Ti3O12. The investigation of the band structure indicated that the CoOx/Bi4Ti3O12 composite formed a type-I p-n heterojunction structure, with CoOx acting as a hole trapper to effectively separate and transfer piezogenerated carriers. Significantly, the MO degradation rate of the best CoOx/Bi4Ti3O12 sample further increased to 2.96 h−1 under combined ultrasonic vibration and simulated sunlight. The synergy between piezocatalysis and photocatalysis can be ascribed to the following factors. The photoexcitation process ensures the sufficient generation of charge carriers in the CoOx/Bi4Ti3O12, while the piezoelectric field within Bi4Ti3O12 promotes the separation of electron-hole pairs in the bulk phase. Furthermore, the heterojunction structure between Bi4Ti3O12 and CoOx significantly facilitates the surface separation of charge carriers. This increased involvement of free electrons and holes in the reaction leads to a remarkable enhancement in catalytic MO degradation. This work contributes to the understanding of the coupling mechanism between the piezoelectric effect and photocatalysis, and also provides a promising strategy for the development of efficient catalysts for wastewater treatment.

The built‐in electric field induced by piezoelectric effect for suppressing the electron–hole recombination has gained substantial attention recently. In this study, a novel Z‐scheme ZnSnO3/Bi2WO6 (ZSO/BWO) piezo‐photocatalyst with synergistic polarized electric field was synthesized by a simple impregnation method. The optimized 1% ZSO/BWO shows high piezo‐photodegradation efficiency (99.9%, 60 min) and mineralization (42%, 60 min) of diclofenac (DCF) under the synergistic action of ultrasound and light, far exceeding that under sole ultrasound or illumination. The remarkable enhanced piezo‐photocatalytic activity of ZSO/BWO composite was attributed to the increased absorption, improved charge transfer, Z‐scheme heterojunction, and tight surface contact between ZSO and BWO. Moreover, the Z‐scheme mechanism of ZSO/BWO composites is studied in depth and confirmed by the free radical capture experiment and electron spin resonance technology. In addition, the corresponding intermediates of DCF degradation and the possible degradation pathways that were proposed on ZSO/BWO composites were analyzed by liquid chromatography–mass spectrometry and DFT. This work offers an efficient approach for constructing and preparing the highly efficient piezo‐photocatalysts for converting solar and mechanical vibration energies. [ABSTRACT FROM AUTHOR]