Remarkably enhanced catalytic performance in CoOx/Bi4Ti3O12 heterostructures for methyl orange degradation via piezocatalysis and piezo-photocatalysis

ZnSnO3-derived ZnSnO3/ZIF-8 composites with enhanced adsorption and photocatalytic activity in RhB degradation and CO2 reduction

This study aims to increase the photoactivity of ZnSnO3 by modifying it with zeolitic imidazolate framework-8 (ZIF-8). The composite catalyst was prepared by a straightforward hydrothermal method using ZnSnO3 as the zinc source. The in-situ generated ZnSnO3/ZIF-8 composite exhibits a strong interaction between ZnSnO3 and ZIF-8, which benefits electron transfer. Band structure analysis shows that ZIF-8 has a higher conduction band and a lower valence band than ZnSnO3, and cannot form a typical heterojunction. However, defects in ZIF-8 may act as electron traps, accepting electrons from the conduction band of ZnSnO3. This atypical heterojunction results in the spatial separation of charge carriers within the composite. The transient photocurrent response, electrochemical impedance spectroscopy, and photoluminescence analysis confirmed this hypothesis. Meanwhile, ZIF-8 also plays a role in adsorbing dyes and concentrating reactants due to its extremely high specific surface area. Therefore, the ZnSnO3/ZIF-8 composite exhibits significantly improved photocatalytic performance in Rhodamine B degradation. The degradation rate of the best sample was 10.4 times that of ZnSnO3. Active species capture experiments showed that holes and superoxide radicals were the main active species. Additionally, the ZnSnO3/ZIF-8 composite showed enhanced photocatalytic activity in CO2 reduction. This study may show new insights into the design of efficient photocatalytic materials using metal-organic framework materials.

A novel 3D Fe2O3@ZnBi2O4 n-p heterojunction with high photocatalytic activity under visible light

A novel n-p Fe2O3@ZnBi2O4 (FZB) heterojunction with a unique 3D structure was fabricated in two simple steps to break down MB under visible light. First, the polymer gel combustion technique was employed to fabricate a 3D Fe2O3 framework. Next, a microwave-assisted precipitation approach was used to incorporate 3D ZnBi2O4 flakes onto the framework surface. FZB can effectively collect a broad range of UV-Vis light and sunlight. Surprisingly, the core-shell p-n heterojunction structure makes it easier for photogenerated charges to move and separate. This is because the semiconductor parts are better connected and the electric field is inside the two junctions. UV-Vis-DRS, EIS, PL, and XPS analyses confirmed this phenomenon. As a result, n-p FZB, with a Fe2O3/ZnBi2O4 molar ratio of 2 : 1, showed the highest photocatalytic activity, increasing the reaction rate by 4.2 times compared to Fe2O3 and 2.8 times compared to ZnBi2O4. Exposure to light for 100 min at a concentration of 0.7 g L-1 the FZB catalyst and pH = 9 led to the breakdown of more than 95% of the 50 ppm MB solution. In addition, the photodegradation of MB by n-p FZB increased the reaction rate by 2.15 times by adding hydrogen peroxide (H2O2), which is known as the photo-Fenton reaction. The efficacy showed remarkable photocatalytic activity, which increased the reaction rate by 5.95 times when persulfate was used. Finally, after examination of the energy band structure of the materials and the findings regarding the function of the oxidizing sites in the photocatalytic process, a reaction mechanism was proposed.

Designing CuO@rGO-MoS2 Nanocomposite with Bird's-Nest Like Structure as Peroxymonosulfate Activator for the Efficient Degradation of Rhodamine B

A straightforward, single-stage hydrothermal approach was utilized to synthesize a unique CuO@rGO-MoS2 nanocomposite, featuring a nest-mimicking architecture. It has highly efficient heterogeneous catalyzed property that can catalyze and activate the peroxymonosulfate (PMS) by means of radical (•OH, SO4•-, and O2•-) and nonradical (1O2) pathways to generate ROS for the rapid degradation of the organic dye rhodamine B (Rh.B). Graphene oxide, which has high specific surface, serves as an excellent carrier which achieves a homogeneous dispersion of the main catalyst component and gives a series of oxygen-containing functional groups that become active centers for nonradical route activation. Through experimental and DFT calculation, it was revealed that MoS2 as a cocatalyst accelerated the redox cycle of the Cu active center during the activation of PMS via catalysis, further enhancing the catalytic activity of the nanocomposites. And thus the CuO@rGO-MoS2/PMS system with bird's-nest like structure achieves rapid degradation of Rh.B in a short period, and the decomposition efficiency of Rh.B reaches 99% within 30 min duration of the reaction. Besides, this system exhibits excellent resistance to environmental interference, demonstrating commendable degradation efficiency across broad pH spectrum (pH 5-11) and high levels of common interfering ions (Cl-, NO3-, SO42-, etc.). To conclude, this study tried to propose and validate a catalyst design idea based on catalytic activation of peroxymonosulfate by selecting appropriate main catalysts, cocatalysts, and catalyst carriers to achieve improved catalytic performance and stability of the catalysts, and the synthesized catalysts CuO@rGO-MoS2 by this design strategy have shown good degradation performances in real wastewater.

Bi4Ti3O12 Crystallized in 40Bi2O3-40B2O3-20TiO2 Glass Matrix for Photo-Piezocatalytic Dye Degradation

The coupling of photocatalysis and piezocatalysis has gained significant interest among researchers. In this study, we present the photo-piezocatalytic activity exhibited by bismuth titanate (Bi4Ti3O12) glass-ceramics (BTO-GC). BTO-GC samples were prepared in a glass system of 40Bi2O3-40B2O3-20TiO2 (in mol %) by using the melt-quench technique. The catalyst was characterized by the X-ray diffraction (XRD) technique and Raman spectroscopy for its structure and phase analysis. Surface morphology and chemical composition were analyzed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The catalytic performance of BTO-GC was evaluated in photocatalysis, piezocatalysis, and photo-piezocatalysis processes. Methylene blue (MB) dye degradation was evaluated by using a UV-Vis spectrophotometer. A maximum degradation performance of ~86% was achieved in the solar light photocatalysis process. This study highlights the synergistic photo-piezocatalytic performance in glass-ceramics and advances the understanding of its underlying mechanism.

Piezocatalytic techniques and materials for degradation of organic pollutants from aqueous solution

With the rapid development of industry, agriculture, and urbanization, various organic pollutants have accumulated in natural water, posing a potential threat to both the ecological environment and human beings, and removing organic pollutants from water is an urgent priority. Piezoelectric techniques, with the advantages of green, simple operation, and high efficiency, are highly sought after in the degradation of environmental organic pollutants. Moreover, combining piezoelectric techniques with advanced oxidation processes (AOPs), photocatalysis, or electrocatalysis can further effectively promote the efficient degradation of target pollutants. Therefore, a perspective is presented on the recent progress of piezoelectric techniques for the degradation of various organic pollutants from aqueous solutions. The classification of various piezoelectric materials, as well as modification strategies for improving piezocatalysis, are first systematically summarized. Furthermore, the latest research on piezocatalysis and its combination with other technologies, such as AOPs, photocatalysis, and electrocatalysis, in the degradation of environmental pollutants is discussed. The potential mechanisms of piezocatalysis are also analyzed in depth. Finally, the urgent challenges and future opportunities for piezoelectric techniques in the degradation of organic pollutants are provided.

Application of catalytic technology based on the piezoelectric effect in wastewater purification

The demands of human life and industrial activities result in a significant influx of toxic contaminants into aquatic ecosystems. In particular, organic pollutants such as antibiotics and dye molecules, bacteria, and heavy metal ions are represented, posing a severe risk to the health and continued existence of living organisms. The method of removing pollutants from water bodies by utilizing the principle of the piezoelectric effect in combination with chemical catalytic processes is superior to other wastewater purification technologies because it can collect water energy, mechanical energy, etc. to achieve cleanliness and high removal efficiency. Herein, we briefly introduced the piezoelectric mechanisms and then reviewed the latest advances in the design and synthesis of piezoelectric materials, followed by a summary of applications based on the principle of piezoelectric effect to degrade pollutants in water for wastewater purification. Moreover, water purification technologies incorporating the piezoelectric effect, including piezoelectric effect-assisted membrane filtration, activation of persulfate, and battery electrocatalysis are elaborated. Finally, future challenges and research directions for the piezoelectric effect are proposed.

Enhanced piezocatalytic RhB degradation with ZnSnO3 Nanocube-modified Bi4Ti3O12 composite catalyst by harnessing ultrasonic energy

With the increasing demand for effective methods to address environmental pollution, piezocatalysis has emerged as a promising approach for pollutant degradation under mechanical energy. However, the development of highly efficient piezocatalytic materials remains a challenge. This study aimed to increase the piezocatalytic activity of bismuth titanate (Bi4Ti3O12) by modifying it with zinc stannate (ZnSnO3) nanocubes. The composite catalysts were synthesized using a straightforward deposition and calcination process. The calcination process ensured the tight adhesion of ZnSnO3 nanocubes to the Bi4Ti3O12 surface, while facilitating strong interactions between ZnSnO3 and Bi4Ti3O12, which enhanced electron transfer and heterojunction structure formation. Band structure analysis indicated that Bi4Ti3O12 has higher conduction band and valence band potentials than ZnSnO3, forming a type-II heterojunction. Bi4Ti3O12 possesses a higher Fermi level than ZnSnO3, resulting in interfacial electron drift and formation of a built-in electric field, which further promotes the directional transfer and separation efficiency of charge carriers within the composite catalyst. This hypothesis was confirmed by surface photovoltage spectroscopy, piezoelectric current response, and electrochemical analysis. Consequently, the ZnSnO3/Bi4Ti3O12 composite exhibited significantly improved piezocatalytic performance in RhB degradation, achieving a degradation efficiency of 80 % within 90 min under ultrasonic vibration. The degradation rate of the optimal sample was 8.2 times that of Bi4Ti3O12 and 6.3 times that of ZnSnO3. Additionally, experiments to detect reactive species were conducted to elucidate the mechanism behind the piezocatalytic RhB degradation. Holes and hydroxyl radicals were the main reactive species. This study may offer new insights into the design of efficient piezocatalytic materials.

Analysis of the electrical conductivity and activation energies of bismuth titanate (Bi4Ti3O12)

In this study, bismuth titanate (Bi4Ti3O12) was synthesized from pure solid compounds and structurally characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The electrical properties were evaluated by measuring the electrical conductivity of Bi4Ti3O12 at various oxygen partial pressures (pO2 = 10-5 and 10-8 atm) and temperatures (450 °C-750 °C). The electrical conductivity behavior was assessed during the heating and cooling processes. The material activation energies were determined based on the heating curve, which displayed Arrhenius-type behavior and activation energy slope changes, which could be attributed to point defects. When the temperature was increased from 450 °C to 750 °C at oxygen partial pressures pO2 = 10-5 atm, the electrical conductivity increased by about 62.9 %, whereas when the temperature decreased from 750 °C to 450 °C, the electrical conductivity was reduced by 35.95 %. The electrical behavior of Bi4Ti3O12 was analyzed by establishing its electrical conductivity and chemical activity under different oxygen partial pressures and heating-cooling conditions can allow the synthesis of materials with attractive characteristics for electronic applications.

Enhanced piezocatalytic and piezo-photocatalytic dye degradation via S-scheme mechanism with photodeposited nickel oxide nanoparticles on PbBiO2Br nanosheets

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 PbBiO2Br 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/PbBiO2Br composite exhibits efficient performance in piezocatalytic RhB degradation. The optimal sample is the NiO/PbBiO2Br 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 PbBiO2Br. 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/PbBiO2Br composite. A comprehensive exploration of the charge migration mechanism at the NiO/PbBiO2Br 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 PbBiO2Br 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 PbBiO2Br 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.

Construction of a Bi2S3/Bi0.5Na0.5TiO3 Composite Catalyst with S Vacancies for Efficient Piezo-Photocatalytic Hydrogen Production

Photocatalytic hydrogen production with low environmental and economic costs is expected to be a powerful means to alleviate energy and environmental problems. However, how to inhibit the rapid recombination of photogenerated carriers is a challenge that photocatalytic hydrogen production has to face. In this study, the coupling of the piezoelectric effect and vacancy engineering into the photocatalytic reaction process synergistically promoted carrier separation, thereby promoting the improvement of hydrogen production performance. Specifically, the novel dual piezoelectric Bi2S3/Bi0.5Na0.5TiO3 (BS-12/BNT) piezo-photocatalyst rich in S vacancies was synthesized by an impregnation method. The hydrogen generation rate of 5% BS-12/BNT under the combined impact of light and ultrasound was up to 1019.39 μmol/g/h, which is 9.5 times higher than that of pure BNT. Various characterization analyses have confirmed that the piezoelectric-photocatalytic activity of BS/BNT composite materials is significantly improved, mainly due to the introduction of S vacancies and piezoelectric fields, which enhance the absorption of sunlight, reduce interface resistance, and so raise the photogenerated carriers' separation efficiency. In addition, the stability of BS/BNT is significantly better than that of the previously synthesized catalysts. Finally, according to the results of XPS, UV-vis, and ESR, the active groups and possible electron transfer paths generated during the piezoelectric-photocatalytic hydrogen production process were studied. This work presents a new approach to promote hydrogen production performance through the synergistic effect of the piezoelectric effect and S vacancies.

Piezoelectric Effect-Mediating Reactive Oxygen Species in NiTiO3 Nanorods for Photocatalytic Removal of U(VI)

Piezoelectric catalysis could convert mechanical energy into chemical energy, which can combine with solar energy for a high-efficiency piezo-photocatalysis reaction. In this work, NiTiO3 nanorods were synthesized via the sol-gel method and initially employed for the removal of U(VI) from radioactive-contaminated water. The NiTiO3 nanorods will generate an internal electric field in an ultrasonic environment, which could greatly improve the performance of piezo-photocatalysis in reducing U(VI) by promoting the generation of photoexcited electrons and reactive oxygen species (ROS). After exposure to visible light and ultrasound for 3 h, the NTO-R-1 exhibited superb U(VI) degradation efficiency of 93.91%, which was 2.58, 6.15, and 6.68 times greater than those of visible light, ultrasonic irradiation, and dark, respectively. Moreover, photoexcited electrons and oxygen-active species play a decisive role in the piezo-photocatalysis process. Therefore, NiTiO3 with excellent piezo-photocatalysis properties exhibits good potential for the development of efficient wastewater purification catalysts and also helps to probe the possible mechanism of piezo-photocatalysis removal of U(VI) in wastewater.

Ultrasonic-driven degradation of organic pollutants using piezoelectric catalysts WS2/Bi2WO6 heterojunction composites

Water pollution has been made worse by the widespread use of organic dyes and their discharge, which has coincided with the industry's rapid development. Piezoelectric catalysis, as an effective wastewater purification method with promising applications, can enhance the catalyst activity by collecting tiny vibrations in nature and is not limited by sunlight. In this work, we designed and synthesized intriguing WS2/Bi2WO6 heterojunction nanocomposites, investigated their shape, structure, and piezoelectric characteristics using a range of characterization techniques, and used ultrasound to accelerate the organic dye Rhodamine B (RhB) degradation in wastewater. In comparison to the pristine monomaterials, the results demonstrated that the heterojunction composites demonstrated excellent degradation and stability of RhB under ultrasonic circumstances. The existence of heterojunctions and the internal piezoelectric field created by ultrasonic driving work in concert to boost catalytic performance, and the organic dye's rate of degradation is further accelerated by the carriers that are mutually transferred between the composites.

Ultrasonic controllable synthesis of sulfur-functionalized metal-organic frameworks (S-MOFs) and their application in piezo-photocatalytic rapid reduction of hexavalent chromium (Cr)

The United Nations' Sustainable Development Goals (SDGs) are significant in guiding modern scientific research. In recent years, scholars have paid much attention to MOFs materials as green materials. However, piezo catalysis of MOFs materials has not been widely studied. Piezoelectric materials can convert mechanical energy into electrical energy, while MOFs are effective photocatalysts for removing pollutants. Therefore, it is crucial to design MOFs with piezoelectric properties and photosensitivity. In this study, sulfur-functionalized metal-organic frameworks (S-MOFs) were prepared using organic sulfur-functionalized ligand (H2TDC) ultrasonic synthesis to enhance their piezoelectric properties and visible light absorption. The study demonstrated that the S-MOFs significantly enhanced the reduction of a 10 mg/L solution of hexavalent chromium to 99.4 % within 10 min, using only 15 mg of catalyst. The orbital energy level differences of the elements were analyzed using piezo response force microscopy (PFM) and X-ray photoelectron spectroscopy (XPS). The results showed that MOFs functionalized with sulfur atom ligands have a built-in electric field that facilitates charge separation and migration. This study presents a new approach to enhance the piezoelectric properties of MOFs, which broadens their potential applications in piezo catalysis and piezo-photocatalysis. Additionally, it provides a sustainable method for reducing hexavalent chromium, contributing to the achievement of sustainable development goals, specifically SDG-6, SDG-7, SDG-9, and SDG-12.

Recent advances of piezo-catalysis and photocatalysis for efficient environmental remediation

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.

Piezoelectric Polarization and Sulfur Vacancy Enhanced Photocatalytic Hydrogen Evolution Performance of Bi2S3/ZnSn(OH)6 Piezo-photocatalyst

The combination of piezoelectric catalysis and photocatalysis could effectively enhance the carrier separation efficiency and further improve the hydrogen production activity. However, piezoelectric polarization always suffers from a low polarization strength, which severely restricts its actual applications. In this study, we successfully synthesized a novel sulfur vacancy-rich Bi2S3/ZnSn (OH)6 (BS-12/ZSH) piezo-photocatalyst for hydrogen evolution through water splitting. Notably, the piezo-photocatalytic hydrogen generation rate of the 8% BS-12/ZSH catalyst (336.21 μmol/g/h) was superior to that of pristine ZSH (29.71 μmol/g/h) and BS-12 (21.66 μmol/g/h). In addition, the hydrogen generation for 8% BS-12/ZSH (336.21 μmol/g/h) under ultrasonic coupling illumination was significantly higher than that under single illumination (52.09 μmol/g/h) and ultrasound (121.90 μmol/g/h), owing to the cooperative interaction of the sulfur vacancy and piezoelectric field. Various characterization analyses confirmed that (1) the introduction of sulfur vacancies in BS-12 provided more active sites, (2) BS-12 with sulfur vacancies acted as a co-catalyst to accelerate the hydrogen production rate, and (3) the piezoelectric field eliminated the electrostatic shielding and offered an additional driving force, which effectively promoted the separation of electron-hole pairs. This research clearly reveals the synergistic effect between piezocatalysis and photocatalysis as well as offers a promising sight for the rational design of high-efficiency piezo-photocatalysts.

MoS2@MWCNTs with Rich Vacancy Defects for Effective Piezocatalytic Degradation of Norfloxacin via Innergenerated-H2O2: Enhanced Nonradical Pathway and Synergistic Mechanism with Radical Pathway

Molybdenum disulfide (MoS2)-based materials for piezocatalysis are unsatisfactory due to their low actual piezoelectric coefficient and poor electrical conductivity. Herein, 1T/3R phase MoS2 grown in situ on multiwalled carbon nanotubes (MWCNTs) was proposed. MoS2@MWCNTs exhibited the interwoven morphology of thin nanoflowers and tubes, and the piezoelectric response of MoS2@MWCNTs was 4.07 times higher than that of MoS2 via piezoresponse force microscopy (PFM) characterization. MoS2@MWCNTs exhibited superior activity with a 91% degradation rate of norfloxacin (NOR) after actually working 24 min (as for rhodamine B, reached 100% within 18 min) by pulse-mode ultrasonic vibration-triggered piezocatalysis. It was found that piezocatalysis for removing pollutants was attributed to the synergistic effect of free radicals (•OH and O2•-) and nonfree radical (1O2, key role) pathways, together with the innergenerated-H2O2 promoting the degradation rate. 1O2 can be generated by electron transfer and energy transfer pathways. The presence of oxygen vacancies (OVs) induced the transformation of O2 to 1O2 by triplet energy transfer. The fast charge transfer in MoS2@MWCNTs heterostructure and the coexistence of sulfur vacancies and OVs enhanced charge carrier separation resulting in a prominent piezoelectric effect. This work opens up new avenues for the development of efficient piezocatalysts that can be utilized for environmental purification.

Synthesis of Efficient S-Scheme Heterostructures Composed of BiPO4 and KNbO3 for Photocatalytic N2 Fixation and Water Purification

The preparation of catalysts with heterojunction structures is a strategy to achieve efficient charge separation and high photocatalytic activity of photocatalysts. In this work, BiPO4/KNbO3 heterostructure photocatalysts were fabricated by a combination of hydrothermal and precipitation methods and subsequently employed in catalyzing N2-to-NH3 conversion and RhB degradation under light illumination. Morphological analysis revealed the effective dispersion of BiPO4 on KNbO3 nanocubes. Band structure analysis suggests that KNbO3 and BiPO4 exhibit suitable band potentials to form an S-scheme heterojunction. Under the joint action of the built-in electric field at the interface, energy band bending, and Coulomb attraction force, photogenerated electrons and holes with low redox performance are consumed, while those with high redox performance are effectively spatially separated. Consequently, the BiPO4/KNbO3 shows enhanced photocatalytic activity. The NH3 production rate of the optimal sample is 2.6 and 5.8 times higher than that of KNbO3 and BiPO4, respectively. The enhanced photoactivity of BiPO4/KNbO3 is also observed in the photocatalytic degradation of RhB. This study offers valuable insights for the design and preparation of S-scheme heterojunction photocatalysts.

Activities of BiFeO3/carbon-dots catalysts in piezo-photocatalytic degradation of ciprofloxacin upon light/ultrasonic excitation

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).

Macroscopic Spontaneous Piezopolarization and Oxygen-Vacancy Coupled Robust NaNbO3/FeOOH Heterojunction for Pharmaceutical Drug Degradation and O2 Evolution: Combined Experimental and Theoretical Study

Prompt recombination of photoproduced charges in bulk and surface of a photocatalyst significantly impedes catalytic efficiency. To address these challenges, FeOOH nanorods (NRs) anchored NaNbO3 (NNO) piezoelectric microcubes (MCs) have been fabricated for ciprofloxacin (CIP) degradation and oxygen evolution through water splitting by coupling macroscopic spontaneous piezoelectric polarization and a built-in electric field. The local electric field induced by surface oxygen vacancies (Ovs) and orientation of FeOOH NRs over NNO MCs afford the polarization electric field a significant boost, driving the quick separation/migration of charge carriers from bulk to the surface. The polarized NNO/FeOOH composite with ample Ovs demonstrates an outstanding piezophotocatalytic CIP degradation of 93% in 1 h, higher than pristine materials (NNO and FeOOH), and a high O2 evolution rate of 1155 μmol h-1. The effect of piezoelectric polarization on the catalytic activity is supplemented by theoretical simulations. This work offers an avenue for selective pollutant remediation and water splitting through the rational design of piezoelectric polarization-mediated heterostructure systems with surface Ovs.