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[Display omitted] • SrBi 4 Ti 4 O 15 /Ag 2 O p-n heterojunction piezo-photocatalysts are synthesized by molten salt method and chemical precipitation method. • The coupling of piezoelectric effect and photocatalysis significantly improves the performance of pollutant degradation. • The piezoelectric property of SrBi 4 Ti 4 O 15 optimized by electric field polarization promotes the piezo-photocatalytic performance of SrBi 4 Ti 4 O 15 /Ag 2 O markedly. • The polarized SrBi 4 Ti 4 O 15 -0.20Ag 2 O piezo-photocatalyst degrades almost 100 % of RhB within 6 min, accompanied by a high rate constant (k = 0.8949 min−1). Ferroelectric materials will generate an internal electric field when subjected to force, thus assisting to separate the photogenerated carriers. Here, a ferroelectric SrBi 4 Ti 4 O 15 /Ag 2 O p-n heterojunction catalyst is designed, inducing the remarkable enhancement of photocatalytic degradation performance by piezoelectric effect under the direct current electric field. The polarized SrBi 4 Ti 4 O 15 /Ag 2 O degrades 99.54 % Rhodamine B (RhB) within 6 min when exposed to light and ultrasonic vibration simultaneously, with an ultra-high degradation rate constant (k = 0.8949 min−1), which is 3.24 times of photocatalytic degradation rate (0.2765 min−1) and 17.38 times of the piezocatalytic degradation rate (0.0515 min−1). Moreover, SrBi 4 Ti 4 O 15 /Ag 2 O piezo-photocatalyst presents excellent degradation effect on methylene blue (MB), methyl violet (MV), methyl orange (MO) and tetracycline (TC). The piezoelectric effect induced by ultrasonic vibration provides a built-in electric field, which significantly enhances the separation of photoexcited carriers, consequently improving the photocatalytic degradation properties of SrBi 4 Ti 4 O 15 /Ag 2 O. This study provides a valuable reference for designing efficient photocatalysts by coupling photocatalysis and piezoelectric effect. [ABSTRACT FROM AUTHOR]

[Display omitted] • Improved activity by synergy of Z-scheme and piezoelectricity was firstly proposed. • The promotion mechanism of piezoelectricity on dual Z-scheme is explained. • The prepared material has strong anti-interference ability. • The degradation path of nitenpyram is explained in detail. • The toxicity of NTP's intermediate products was also analyzed. A highly active catalyst AgI/Ag 3 PO 4 /BaTiO 3 with the synergistic effect of photocatalysis and piezoelectricity was prepared, which can remove 100 % of Nitenpyram (NTP) in a wide pH range within 10 min. This piezo-photocatalyst AgI/Ag 3 PO 4 /BaTiO 3 with dual Z-scheme shows a higher NTP degradation rate than their mono-material and binary composites. The apparent rate constant of AgI/Ag 3 PO 4 /BaTiO 3 in NTP removal is 2.12 times higher than the second-performing catalyst. In the quenching experiment, h+ and ·O 2 – were observed to be the main active substance in NTP degradation and the former contributes the most. The dual Z-scheme mechanism and the built-in electric field are both beneficial for the separation of electron-hole pairs, as well as the extension of the photo-generated carrier lifetime. At last, the effect factor experiments proved that the prepared AgI/Ag 3 PO 4 /BaTiO 3 catalyst owns stable and efficient activity. This work provides novel guidance for the construction of highly efficient and stable piezo-photocatalytic heterojunction catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new strategy that simulated lymphatic reflux to enhance intratumoral delivery. • Clarifying effect and mechanism of piezo-photocatalysis in hydrodynamic therapy. • Schottky barrier at metal–semiconductor contact would enhance catalytic efficiency. • Enhanced HDT promoted the decrease of tumor interstitial fluid pressure by 53.62%. • Intratumoral accumulation of nanomedicine was 18.78 times the normal level. Due to high TIFP caused by blocked lymphatic reflux, nanomedicine delivery is restricted in the depth of tumors. In our previous work, we demonstrated an anticipated strategy of hydrodynamic therapy by photocatalytic water splitting to reduce TIFP, which enhances delivery efficiency and antitumor efficacy. Herein, we designed a novel nanomedicine (CPL@M) as "nano-lymphatic vessels" for enhancing intratumoral delivery by coupling piezo-photocatalysis. The piezocatalysis was coupled with in situ photocatalysis to achieve higher rate (56.42 μL·h−1·g−1), which leads to the decrease of TIFP by 53.62 %. Then, the blood perfusion was drastically increased, which improved the tumor accumulation by 18.78 times compared to that of nanomedicine without water splitting. Furthermore, ROS and Pt (II) have the potent activities for tumor elimination. This strategy provides a deeper insight into coupling piezo-photocatalytic water splitting for reducing TIFP and enhancing intratumoral delivery, which opens up a new direction of nano-catalysis medicine. [ABSTRACT FROM AUTHOR]

The synergistic piezo-photocatalysis with enhanced efficiency for degrading obstinate pollutants in wastewater is considered as an advanced way to ameliorate the global water contamination. In this work, we report a facile route to construct the Bi 0.5 Na 0.5 TiO 3 @Ag composite by photoreduction of AgNO 3 to obtain Ag on Bi 0.5 Na 0.5 TiO 3 nanoparticles. And the composite was used to degrade three representative pollutants, i.e. ciprofloxacin, methyl orange and mitoxantrone hydrochloride. Remarkably, for methyl orange solution with the initial concentration of 10 mg/L, the degradation rate constant of the composite reached 0.051 min−1. H+ and •O 2 − play a major role in this degradation process, verified by the radical quenching experiments. The absorption platform of Bi 0.5 Na 0.5 TiO 3 was located in the UV region, after introducing Ag in the composite, the absorption region broadened to both UV and visible light, greatly promoting the response to light. Simultaneously, the induced piezo-potential by mechanical energy in Bi 0.5 Na 0.5 TiO 3 hindered the carrier recombination, resulting in high-efficiency synergistic piezo-photocatalytic process. This work provides a paradigm to innovate both material and catalytic way for degrading multiple organic pollutants. • BNT@Ag composite was constructed by direct addition of AgNO 3. • Efficient piezo-photocatalytic synergistic effect was achieved. • Absorb both UV and visible light for higher utilization ratio of light energy. • Maintain good catalytic performance in varying environment. [ABSTRACT FROM AUTHOR]

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.)

[Display omitted] • Flower-like SrBi 4 Ti 4 O 15 /BiOCl heterojunction piezo-photocatalysts are synthesized by molten salt method and hydrothermal method. • Photocatalytic performance of SrBi 4 Ti 4 O 15 /BiOCl catalysts are significantly improved through piezoelectric effect. • The electric-polarized SBTO-0.6BOC piezo-photocatalyst degrade almost 100 % of RhB within 7 min, accompanied by a high rate constant (k = 0.7313 min−1). Combining photocatalyst with piezoelectric materials is an effective way to promote the performance of photocatalysis. Herein, a flower-like SrBi 4 Ti 4 O 15 /BiOCl composite is proposed and its photocatalytic degradation performance is effectively improved by piezoelectric effect. SrBi 4 Ti 4 O 15 /BiOCl heterojunction is prepared by molten salt method and hydrothermal method, and the polarization is carried out under the action of direct current high voltage electric field. Piezoelectric effect offers a built-in polarization field for improving the separation efficiency of photogenerated electrons and holes. Hence, under the synergistic action of ultrasound and light, the degradation rate constant of polarized SrBi 4 Ti 4 O 15 /BiOCl to RhB dye reaches 0.7313 min−1, which is 13.13 and 2.53 times that of pure SrBi 4 Ti 4 O 15 and SrBi 4 Ti 4 O 15 /BiOCl under light only, exceeding almost vast majority piezo-photocatalysts reported. This study provides an efficient and feasible piezo-photocatalyst for pollutant treatment, and contributing to comprehending the mechanism of piezoelectric effect to improve the photocatalytic performance. [ABSTRACT FROM AUTHOR]

Piezoelectric semiconductor nanomaterials have been intensively developed for piezo-photocatalysis, in which the built-in electric field generated by piezoelectricity can accelerate the seperation and transfer of photogenerated carriers. However, the challenges of poor recyclability and secondary pollution must be solved for large-scale applications. In this study, a three-dimensional porous poly(vinylidene difluoride) (PVDF) composite foam containing piezoelectric semiconductor Bi 0.5 Na 0.5 TiO 3 (BNT) nanofibers are fabricated. The BNT nanofibers prepared by electrospinning exhibit excellent piezoelectric activity, strong photoexcited response, and low charge transfer resistance. The fabricated BNT/PVDF composite foams display favorable flexibility and hierarchical pore structure, which can easily deform to construct a built-in electric field via bi-piezoelectric integration and owns abundant active sites for catalytic reactions. The PVDF matrix has a dominant electroactive β-phase, responsible for its high piezoelectricity. As a result, the BNT/PVDF composite foam exhibits strong piezo-photocatalytic activity. The degradation of highly-concentrated RhB solution (C 0 = 50 mg/L) reaches 90.8% within 180 min. This work provides a feasible piezo-photocatalytic material for large-scale applications. • BNT nanofibers show high piezoelectricity and strong photoresponse. • BNT/PVDF foams show favorable flexibility and hierarchical pore structure. • High-concentration RhB (50 mg/L) solution is effectively degraded. [ABSTRACT FROM AUTHOR]

Understanding of the structural–performance correlations allow for the rational design of piezo-photocatalytic materials with profound benefits for catalytic activity. In this study, the ZnAl layered double hydroxides (ZnAl-LDHs) with different thickness are applied in the piezo-photocatalytic process for carbamazepine (CBZ) pollutants degradation. The piezo-photocatalytic efficiency of ultra-thin ZnAl-LDHs sheets (ZnAl-U) reaches 95.8 % with the reaction rate constant of 0.148 min-1 for CBZ degradation, being 1.61 and 3.02 times of the thin ZnAl-LDH (ZnAl-T) and bulks ZnAl-LDHs (ZnAl-B), respectively. This result is attributed to that ZnAl-U is more sensitive towards light irradiation and external stress than ZnAl-T and ZnAl-B, thus producing higher current and more reactive oxygen species (O 2 •−, HO• and 1O 2) for piezo-photocatalytic degradation of CBZ. At the same time, the piezo-photocatalytic rate constant of ZnAl-U is 3.36 times of the sum of the individual piezocatalysis and photocatalysis, which is due to that the piezoelectric field boosts the separation of photo-induced electron-hole pairs and modulates the alignment of band energy, resulting in a synergetic enhanced piezo-photocatalytic reaction. This work discloses the significance of structure on the ZnAl-LDHs piezo-photocatalytic performance, and highlights the role of piezoelectric field on the improvement of photocatalytic process. [Display omitted] • Different thicknesses of ZnAl-LDHs possess different piezo-photoelectric activity. • Photo-induced charges are separated better by the piezo-field of thinner ZnAl-LDHs. • Ultrathin ZnAl-LDHs exhibit a superb piezo-photocatalytic activity for CBZ removal. [ABSTRACT FROM AUTHOR]

Persistent organic pollution (POPS) with the feature of difficult to be degraded, highly toxic and global spread has become a challenge for the whole human beings. Recently, piezo-photoelectric catalysis is emerging as a promising way to degrade organic pollutions. In order to avoid the secondary pollution caused by the difficult recycling of powder catalyst, a three-dimensional barium titanate (BaTiO 3 , BT) scaffold is prepared by direct writing technique in this study, of which the surface is decorated by titanium oxide (TiO 2 , TO) nanowire arrays. Piezoelectric potential can be generated in the BT scaffold, especially in the direction parallel to the direct writing printing, and the piezoelectric electric field can effectively promote the separation of photo-generated carriers. This design of the structure can effectively produce a larger deformation compared with the bulk structure in the catalytic process, and it can also increase the contact area between the catalyzer and solution with enhanced reactive site. Due to the piezo-phototronic coupling effect, BT piezoelectric ceramic scaffold with TiO 2 array exhibits an excellent dye degradation efficiency, of which the rate constant reaches approximately 0.109 min−1 for 100 mL of 10 mg/L of indigo carmine (IC) degradation. This work demonstrated that 3D piezoelectric ceramics by direct ink writing method shows a great potential in promoting the practical application of catalysis. [Display omitted] • 3D BaTiO 3 scaffold decorated with TiO 2 nanowire arrays was applied in photo-piezoelectric catalysis for the first time. • The superior piezo-photocatalytic properties was achieved with a rate constant of 0.11 min−1 for degrading of 10 mg/L IC. • It was revealed that the generated potential was enhanced when the direction of printing is parallel to the force. [ABSTRACT FROM AUTHOR]

Bi 4 Ti 3 O 12 is one of the Aurivillius-type layered perovskite oxides with superior photocatalytic effect, however, the further enhancement of this effect is limited by the high recombination rate of photo-generated carriers. Here, piezo-phototronic effect was employed to significantly improve the photocatalytic performance of Bi 4 Ti 3 O 12 nanoplates synthesized by molten-salt method. Under light and ultrasonic excitations, the screening effect of the built-in electric field caused by ferroelectric polarization can be broken by the alternating piezoelectric potential due to the periodic mechanical stress, and thus the reaction rate k of piezo-photocatalytic degradation of RhB reaches 0.1414 min−1 which is 5.6 times of piezocatalytic k value and 2.1 times of photocatalytic k value. This k value is much larger than that of Bi 4 Ti 3 O 12 nanoplates and Bi 4 Ti 3 O 12 nanoflowers synthesized by solid-state reaction method and hydrothermal method, respectively. Due to the good balance of size, shape, crystallinity and specific surface area, Bi 4 Ti 3 O 12 nanoplates synthesized by molten-salt method exhibit better piezo-photocatalytic performance for degrading RhB. This work is helpful to develop other efficient piezo-photocatalysts. [Display omitted] • The monodisperse and highly crystalline Bi 4 Ti 3 O 12 nanoplates were synthesized by one-step molten-salt method. • Photocatalytic performance was significantly improved through piezotronic effect. • The reaction rate of piezo-photocatalytic degradation of RhB reaches 0.1414 min−1. [ABSTRACT FROM AUTHOR]

Herein, a g-C 3 N 4 /PDI-g-C 3 N 4 homojunction has been fabricated for piezo-photocatalytic atrazine removal and exhibited better performance than individual photocatalysis or piezocatalysis. The introduction of PDI induces the π-π interaction facilitating electrons migration, and twists the g-C 3 N 4 plane into a more polar porous structure with enhanced piezoelectricity. The homojunction facilitates the photoelectron transfer at the g-C 3 N 4 /PDI-g-C 3 N 4 interfaces. The photoelectricity and the piezoelectricity of g-C 3 N 4 /PDI-g-C 3 N 4 were assessed. The finite element simulation showed that the porous structure of the g-C 3 N 4 /PDI-g-C 3 N 4 is essential to the enhanced piezoelectricity. Astonishingly, the piezo-photocatalytic atrazine degradation rate under an optimized condition (pH=2.97) reached 94% within 60 min. Moreover, the g-C 3 N 4 /PDI-g-C 3 N 4 homojunction produced 625.54 μM H 2 O 2 during the one-hour piezo-photocatalysis. Given the quenching experiments, reactive species detection and the electronic band of g-C 3 N 4 /PDI-g-C 3 N 4 , the piezo-photocatalytic mechanism has been proposed. In addition, the degradation pathways and the reduced intermediates toxicity intermediates of atrazine have been investigated. [Display omitted] • Unique g-C 3 N 4 /PDI-g-C 3 N 4 (CNPC) homojunction have been fabricated. • CNPC showed superior piezo-photocatalytic atrazine removal and H 2 O 2 generation. • The π-π stacked CNPC homojunction facilitated the charge transfer. • The enhanced polarity of CNPC is responsible for the piezoelectricity increases. • The results indicated the reduced toxicity of intermediates in the system. [ABSTRACT FROM AUTHOR]

Ferroelectric materials can generate a built-in electric field under strain, which can produce reactive oxygen species (ROS) for in-situ piezocatalysis via a series of redox reactions, or enhance photocatalytic activities through the separation of the photoinduced electron and hole pairs. In this study, the synergistic piezo-phototronic effect is enhanced by increasing the inner piezopotential of ferroelectric nanofibers in fibrous piezoelectric/oxide semiconductor heterostructures. Ferroelectric BaTiO 3 nanofibers are fabricated by a sol-gel assisted electrospinning and subsequent annealing at 700 ºC for 2 h, 4 h, and 6 h, respectively (denoted as BT2H, BT4H, and BT6H). Piezoelectric force microscopy results reveal that the necklace-like BT6H nanofibers demonstrate the highest local piezoelectric coefficient d 33 (42.7 pm V−1) than BT2H (26.3 pm V−1) and BT4H (37.8 pm V−1) nanofibers because BT6H nanofibers are composed of highly crystallized electric dipoles with single domain nanostructures. Additionally, BT6H@TiO 2 core-shell nanofibers are synthesized by a wet-chemical coating of TiO 2 on BT6H nanofibers. Under both ultrasound and UV light irradiations, BT6H@TiO 2 core-shell nanofibers exhibit a high piezo-photocatalytic degradation rate constant of 6 × 10−2 min−1 because of the enhancement of the piezotronic effect by the high piezoelectricity of electric dipoles that promote the separation of the photoinduced electron and hole pairs. The enhancement of the synergistic piezo-phototronic effect is ascribed to the highly active reaction sites that are confined into the high specific surface area of the one-dimensional fibrous boundary of BT6H@TiO 2 core-shell nanofibers, beneficial for the migration of the interfacial charge carriers. This study presents a simple approach to improve the piezo-photocatalysis through modulating the crystallization and the size of electric dipoles, providing an efficient pathway for underpinning the coupling mechanism between the enhancement of local ferro/piezoelectricity and piezo-phototronic effect. [Display omitted] • Local ferro/piezoelectricity is probed by piezoelectric force microscopy. • Piezoelectricity of BaTiO 3 nanofibers increases with the size of electric dipoles. • The increase of local piezotronic effect improves photochemical reactivity. • Modulation of piezoelectricity of BaTiO 3 nanofibers results in an enhanced piezo-photocatalysis of BaTiO 3 @TiO 2 core-shell nanofibers. [ABSTRACT FROM AUTHOR]

In this study, a semiconducting BaTiO 3 @C (BT@C) core-shell structure was successfully prepared via a one-step hydrothermal method assisted by glucose. The exposed Ti4+ on the BT surface was reduced to Ti3+ by glucose during the hydrothermal process, resulting in the formation of a mass of oxygen vacancies. Meanwhile, excess glucose was carbonized and the carbon accumulated on the BT surface to form a BT@C core-shell structure, and the thickness of the carbon shell gradually increased with increasing glucose concentration. The effect of glucose concentration on the phase compositions and morphologies of BT@C nanoparticles was investigated. The as-prepared BT@C composites exhibited the higher piezo-photodegradation capability for rhodamine B compared with the raw BT duo to the combination with semiconductor property and piezoelectric effect. The method utilized in this study to fabricate semiconducting BT@C core-shell structured composite can be extended to synthesize the other piezoelectric /ferroelectric@C composites and will open up great potential in the field of piezo-photocatalysis and environmental purification. In this study, a semiconducting BaTiO 3 @C (BT@C) core-shell structure was successfully prepared via a one-step hydrothermal method assisted by glucose. The exposed Ti4+ on the BT surface was reduced to Ti3+ by glucose during the hydrothermal process, resulting in the formation of a mass of oxygen vacancies. Meanwhile, excess glucose was carbonized and the carbon accumulated on the BT surface to form a BT@C core-shell structure, and the thickness of the carbon shell gradually increased with increasing glucose concentration. The effect of glucose concentration on the phase compositions and morphologies of BT@C nanoparticles was investigated. The as-prepared BT@C composites exhibited the higher piezo-photodegradation capability for rhodamine B compared with the raw BT duo to the combination with semiconductor property and piezoelectric effect. The method utilized in this study to fabricate semiconducting BT@C core-shell structured composite can be extended to synthesize the other piezoelectric /ferroelectric@C composites and will open up great potential in the field of piezo-photocatalysis and environmental purification. [Display omitted] • The semiconducting BT@C core-shell structure was successfully prepared. • BT@C nanocomposites exhibit the excellent piezo-photocatalysis activity. • The semi-conductivity is caused by the reduction of BT and oxygen vacancy defects. • The coupling of piezoelectric effect and semiconductor property plays a key role. [ABSTRACT FROM AUTHOR]

The induced built-in electric field by piezoelectric materials has proven to be one of the most effective strategies for modulating the charge-transfer pathway and inhibiting carrier recombination. In this work, a series of core-shell structured BaTiO 3 @TiO 2 nanowires (BT@TiO 2 NWs) heterojunctions were synthesized and the significant coupling effects between BaTiO 3 (BT) and TiO 2 resulted in surperior piezo-photocatalytic performance, which was demonstrated by three typical types of dyes with high concentrations. The degradation efficiency of 30 mg/L Rhodamine B (RhB), Methylene blue (MB) and Indigo Carmine (IC) solutions by 0.5 g/L BT@TiO 2 NWs reached 99.5% in 75 min, 99.8% in 105 min and 99.7% in 45 min, respectively, which are much higher than piezo-photocatalysis systems reported before. To reveal the coupling mechanisms, photoelectrochemical measurements and band diagram analysis were carried out. The carrier concentration was increased from 2.28 × 1017 cm−3 to 4.91 × 1018 cm−3 and the lifetime of charges was improved from 50.37 ms to 60.98 ms due to the construction of a heterojunction between TiO 2 and BT. It was proposed that the tilting and bending of the energy band caused by the introduction of a piezoelectric polarization can facilitate carrier separation both in the bulk phase and at the surfaces of semiconductors, resulting in outstanding piezo-photocatalytic properties for highly concentrated dye degradation. This work provides a universal catalyzer for highly concentrated dye degradation. [Display omitted] • BaTiO 3 @TiO 2 core-shell nanowires were applied in photo-piezoelectric catalysis for the first time. • The outstanding piezo-photocatalytic properties for high concentrated dye degradation was achieved. • The mechanism of piezo-photoelectric coupling effect of BT@TiO 2 heterojunction was revealed. [ABSTRACT FROM AUTHOR]

Piezo-photocatalysis (implement by ultrasound vibration and UV-vis light irradiation), a new-emerging strategy, can suppress the rapid recombination of electrons and holes to enhance the catalytic performance. The modulation of interface structures (e.g., the introduction of oxygen vacancies, OVs) plays a significant role in the charge-transfer and the catalytic activity. In this paper, the AgNbO 3 (ANO) powder was prepared by a facile hydrothermal method. Based on this, we introduce OVs into ANO successfully by annealing in N 2 (ANO-N 2). The ANO-N 2 with OVs exhibits much better piezo-photocatalytic activity for degradation of Rhodamine B (RhB) than the ANO. The result found that OVs can narrow the band gap and improve the UV-vis light absorption, and most importantly, promote the separation of electron hole pairs under electric field to enhance the piezo-photocatalytic performance. The work thus supplies an in-depth understanding of the mechanism between OVs and piezo-photocatalytic performance. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • BaTiO 3 /La 2 Ti 2 O 7 shows good piezoelectric potential under ultrasonic vibration. • The polarization electric field can regulate charge carriers at the interface. • Ultrasound vibration enhances the visible light activity of BaTiO 3 /La 2 Ti 2 O 7. The separation efficiency of photogenerated carriers in photocatalysis is one of the key factors limiting the overall performance. The polarization field modification of piezoelectric materials is considered to be an effective strategy to regulate their photocatalytic performance. In this study, novel heterojunction photocatalysts that combine piezoelectric BaTiO 3 nanorods and La 2 Ti 2 O 7 nanosheets were synthesized and the polarization electric field promoted the bulk charge separation, while regulating the migration and separation of the carriers at the heterojunction interface. Under the combined action of visible light and ultrasonic, the piezo-photocatalytic degradation efficiency of CIP over BaTiO 3 /La 2 Ti 2 O 7 composites increased by 24% and 12.5% compared with its photocatalytic and piezocatalytic degradation efficiency, respectively. Furthermore, the finite element simulation shows that BaTiO 3 /La 2 Ti 2 O 7 heterojunctions have a stronger piezoelectric potential difference compared to pure BaTiO 3. Our findings provide insights into the development of piezo-photocatalysts that can effectively degrade pollutants under visible light. [ABSTRACT FROM AUTHOR]

The secondary recombination of photogenic charge carriers caused by structural defects at the interface of BaTiO 3 /KNbO 3 heterojunction is successfully suppressed by the built-in electric field generated by the piezoelectric effect in BaTiO 3 and KNbO 3. BaTiO 3 /KNbO 3 composite photocatalyst exhibits excellent degradation performance for direct lake blue 5B dye (DLB 5B) under the synergistic effect of piezocatalysis and photocatalysis. [Display omitted] • BaTiO 3 /KNbO 3 heterostructure photocatalysts were successfully prepared for the first time. • BaTiO 3 /KNbO 3 presented good piezo-photocatalytic activity in degrading direct lake blue 5B dye under light irradiation and ultrasonic vibration. • The synergistic effect of piezocatalysis and photocatalysis on the separation and transfer of charge carriers was proposed. In order to reduce the secondary recombination of photogenic charge carriers caused by the structural defects at the interface of traditional heterostructure photocatlysts, and the charge shielding effect of static condition on the built-in electric field in ferroelectric/piezoelectric photocatalyst, two typical piezoelectric photocatalysts, BaTiO 3 and KNbO 3 , were successfully compounded into a series of BaTiO 3 /KNbO 3 heterostructure photocatalysts for the first time. BaTiO 3 nanoparticles with good crystallinity are uniformly distributed on the surface of KNbO 3 prism to form the BaTiO 3 /KNbO 3 heterostructure. The piezo-response force microscopy (PFM) results and piezo-photocatalytic degradation experiments stimulated by ultrasonic vibration and light irradiation show that the separation efficiency of photogenic charge carriers and degradation performance are enhanced by the synergistic effect of piezocatalysis and photocatalysis. The piezo-photocatalytic degradation efficiency of BaTiO 3 /KNbO 3 over direct lake blue 5B dye can reach up to 93.3%. The reaction rate constant of 0.3BaTiO 3 /0.7KNbO 3 over the target dye is 4.44 and 8.57 times higher than that of BaTiO 3 and KNbO 3. This work will provide a promising paradigm to degrade organic pollutants by using synergetic effect of piezocatalysis and photocatalysis, which perhaps facilitates the practical applications of piezo-photocatalytic technology in the environmental field. [ABSTRACT FROM AUTHOR]

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.)

The coupling between piezoelectricity and photoexcitation has recently been emerged as an effective strategy to improve the catalytic performance of semiconductors. Lead-free Bi 0.5 Na 0.5 TiO 3 (BNT) is a promising system for effective piezo-photocatalysis owing to its favorable piezoelectricity, photoexcited response, and electrical conductivity. In this work, one-dimensional BNT nanorods prepared by a high-temperature molten-salt method were developed for piezo-photocatalysis applications for the first time, which exhibited excellent catalytic activity. The degradation efficiency of RhB solution (initial concentration C 0 = 5 mg/L) in the presence of BNT nanorods reached 95% in 30 min, leading to a high first-order rate constant k of 0.094 min−1. For reveal the underlying mechanisms, the piezoresponse characterization, piezoelectric potential simulation, band diagram analysis, and photoelectrochemical measurements were carried out, and the BNT nanospheres synthesized by hydrothermal method were simultaneously studied for comparison. A higher piezoelectric coefficient d 33 * of 200 pm/V and a larger potential output under pressure were achieved in the BNT nanorods. The BNT nanorods also displayed the narrower band gap, stronger photocurrent response, and lower charge transfer resistance. These merits enabled the BNT nanorods to exhibit strong piezo-photocatalytic activity. Moreover, it was found that the BNT nanorods showed better piezo-photocatalytic activity for cationic dyes (RhB and MB) than anionic dyes (MO). For RhB, MB, and MO solutions with C 0 of 10 mg/L, k values of 0.041, 0.075, and 0.013 min−1 were achieved, respectively. [Display omitted] • Highly-crystalline, tough, and durable BNT nanorods were prepared by a molten-salt method. • The BNT nanorods show large piezoelectric potential and effective separation of photogenerated carriers. • The k value reaches 0.094 min−1 for RhB degradation via the BNT nanorods and piezo-phototronic coupling effect. [ABSTRACT FROM AUTHOR]

An efficient method for constructing p-n heterojunctions by loading p-type BiOI nanosheets on the surface of n-type ZnO nanorods is reported. The core-shell heterojunctions of BiOI/ZnO NRs show enhanced catalytic activity for the degradation of organic pollutants such as Bisphenol A with the synergetic piezoelectric effect. • The p-n heterojunction of BiOI/ZnO NRs was built to improve the separation of charge carriers. • The introduction of BiOI nanosheets extends the absorption range of ZnO to the visible region. • Photocatalytic activity was improved by coupling piezoelectric effect with build-in field. • Removal rate of Bisphenol A was 100 % within 30 min under concurrent visible light and ultrasonic vibration. p-n Heterojunctions of BiOI/ZnO nanorod arrays (BiOI/ZnO NRs) were prepared by loading the p-type BiOI nanosheets on the n-type ZnO nanorod arrays for efficient removal of organic contaminants in water during the piezo-photocatalytic degradation. Under concurrent visible-light irradiation and ultrasonic vibration, the bisphenol solution (50 mL, 10 mg/L) could be completely degraded within 30 min by 10 mg of 0.15 BiOI/ZnO NRs. It shows a dramatically-enhanced degradation efficiency under light irradiation and ultrasonic vibration, which is four times as high as that only under light irradiation. The excellent piezo-photocatalytic ability of BiOI/ZnO NRs could be attributed to the piezoelectric effect coupling with photocatalytic process. Under the irradiation of light, the electron-hole pairs were generated in BiOI nanosheets, and the piezoelectric potential is created inside the highly oriented one-dimensional ZnO nanorods by ultrasonic vibration, which can accelerate the migration of photogenerated carriers. It shows a strategy to effectively enhance the photocatalytic activity through utilizing the internal piezoelectric potential, which is generated by the one-dimensional nanorods with piezoelectric properties under ultrasonic vibration. So, it can promote the separation and prolong the lifetime of photogenerated carriers, and result in high-efficient degradation of organic contaminants. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) as green oxidants are of great importance for environmental and biological applications. Photocatalysis is one of the major routes for ROS evolution, which is seriously restricted by rapid charge recombination. Herein, piezocatalysis and photocatalysis (i.e., piezo–photocatalysis) are coupled to efficiently produce superoxide radicals (•O2−), hydrogen peroxide (H2O2), and hydroxyl radicals (•OH) via oxygen reduction reaction (ORR), by using Bi4NbO8X (X = Cl, Br) single crystalline nanoplates. Significantly, the piezo‐photocatalytic process leads to the highest ORR performance of the Bi4NbO8Br nanoplates, exhibiting •O2−, H2O2, and •OH evolution rates of 98.7, 792, and 33.2 µmol g−1 h−1, respectively. The formation of a polarized electric field and band bending allows directional separation of charge carriers, promoting the catalytic activity. Furthermore, the reductive active sites are found enriched on all the facets in the piezo–photocatalytic process, also contributing to the ORR. By piezo–photodeposition of Pt to artificially plant reductive reactive sites, the Bi4NbO8Br plates demonstrate largely enhanced photocatalytic H2 production activity with a rate of 203.7 µmol g−1 h−1. The present work advances piezo–photocatalysis as a new route for ROS generation, but also discloses the potential of piezo–photocatalytic active sites enriching for H2 evolution. [ABSTRACT FROM AUTHOR]