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.

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.

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.

One-step fabrication of Cu-doped Bi2MoO6 microflower for enhancing performance in photocatalytic nitrogen fixation.

This study enhances the photocatalytic N2 immobilization performance of Bi2MoO6 through Cu doping. Cu-doped Bi2MoO6 was synthesized via a simple solvothermal method. Various characterizations were implemented to examine the influence of Cu doping on the properties of Bi2MoO6. Results indicated that the doped Cu element had a valence state of + 2 and substituted the position of Bi3+. Cu doping exerted minimal effect on the morphology of Bi2MoO6 but largely influenced the energy band structure. The band gap was slightly narrowed, and the conduction band was raised, such that Cu-doped Bi2MoO6 could generate more electrons with stronger reducibility. Moreover, importantly, Cu doping reduced work function and improved charge separation efficiency, which was considered the major cause of enhanced photoactivity. In addition, the Cu-Bi2MoO6 catalyst exhibited higher capability in the adsorption and activation of N2. Under the combined effects of the aforementioned changes, Cu-Bi2MoO6 demonstrated considerably higher photocatalytic efficiency than Bi2MoO6. The optimized NH3 generation rate reached 302 µmol/L g-1h-1 and 157 µmol/L g-1h-1 under simulated solar light and visible light, respectively, both achieving about 2.2 times higher than that of Bi2MoO6. This work provides a successful example of improving photocatalytic N2 fixation, and it may show some light on the design and preparation of heteroatom-doped semiconductor photocatalysts for N2-to-NH3 conversion.

Novel Bi2WO6/ZnSnO3 heterojunction for the ultrasonic-vibration-driven piezocatalytic degradation of RhB.

This study designed and prepared a new piezoelectric catalytic nanomaterial, Bi2WO6/ZnSnO3, and applied it in piezocatalytic water purification. Results indicated that the composite had superior piezocatalytic efficiency and stability in rhodamine B (RhB) degradation under ultrasonic vibration. The Bi2WO6/ZnSnO3 sample with 10% Bi2WO6 had the optimum activity with a degradation rate of 2.15 h-1, which was 7.4 and 11.3 times that of ZnSnO3 and Bi2WO6, respectively. Various characterizations were conducted to study the morphology, structure, and piezoelectric properties of the Bi2WO6/ZnSnO3 composites and reveal the reasons for their improved piezocatalytic performance. Results showed that ZnSnO3 cubes were dispersed throughout the surface of Bi2WO6 nanosheets, which enhanced the specific surface area and facilitated the piezocatalytic reaction. Additionally, type-II heterojunction structures formed at the contact interface of Bi2WO6 and ZnSnO3, driving the migration of piezoelectric-induced electrons and holes. Accordingly, the separation efficiency of charge carriers improved, and the piezoelectric catalytic activity was significantly enhanced. This study may provide a potential composite catalyst and a promising idea for the design of highly efficient piezoelectric catalyst.

A novel NiO/BaTiO3 heterojunction for piezocatalytic water purification under ultrasonic vibration.

This work designed and prepared a novel heterojunction composite NiO/BaTiO3 through a method of photodeposition and used it in piezocatalytic dye removal for the first time. Results of the piezocatalytic test indicated that the NiO/BaTiO3 composite presented superior efficiency and stability in the RhB degradation under the vibration of ultrasonic waves. The best NiO/BaTiO3 sample synthesized under light irradiation for 2 h displayed an RhB degradation rate of 2.41 h-1, which was 6.3 times faster than that of pure BaTiO3. By optimizing the piezocatalytic reaction conditions, the degradation rate constant of NiO/BaTiO3 can further reach 4.14 h-1 A variety of systematic characterizations were executed to determine the reason for the excellent piezocatalytic performance of NiO/BaTiO3. The band potentials of NiO and BaTiO3 are found to coincide, and at their contact interface, they may create a type-II p-n heterojunction structure. Driven by the potential difference and the built-in electric field, piezoelectrically enriched charge carriers can migrate between NiO and BaTiO3, resulting in improved efficiency in charge separation and an increase in the piezoelectric catalytic performance. This study may provide a potential composite catalyst and a promising idea for the design of highly efficient catalysts in the field of piezoelectric catalysis.