Enhancement of Charge Separation and NIR Light Harvesting through Construction of 2D-2D Bi4 O5 I2 /BiOBr:Yb3+ , Er3+ Z-Scheme Heterojunctions for Improved Full-Spectrum Photocatalytic Performance

A Novel In Situ Biosynthesized Bacterial Cellulose/MoS2/TiO2 Composite Film for Efficient Removal of Dyes and Pathogenic Bacteria from Industrial Wastewater under Sunlight Illumination

Developing multifunctional water purification materials is of great significance for the elimination of organic pollutants and bacterial pathogens in industrial wastewater. Herein, we report a novel green material, bacterial cellulose/molybdenum disulfide/titanium oxide (BC/MoS2/TiO2) composite film, through one-step in situ biosynthesis, and its application in industrial wastewater treatment. The systematic physicochemical characterization of BC/MoS2/TiO2 demonstrated that MoS2 and TiO2 were effectively incorporated into the BC porous network matrix. Meanwhile, BC/MoS2/TiO2 was absorbed in the UV, visible, and NIR regions with a bandgap of 1.93 eV, indicating that it can serve as a sunlight-excited photocatalyst. Further photocatalytic studies revealed that the synergistic effect of MoS2 and TiO2 enabled BC/MoS2/TiO2 to generate large amounts of •OH and O2•-, and the potential photocatalytic mechanism was investigated. Additionally, BC/MoS2/TiO2 exhibited higher photodegradation efficiencies against methylene blue (k = 0.01963 min-1) and rhodamine B (k = 0.01844 min-1), as well as better photodynamic and photothermal antibacterial performances against Staphylococcus aureus (99.9929%) and Escherichia coli (99.8935%) than BC/MoS2 or BC/TiO2 alone. BC/MoS2/TiO2 showed great reusability and maintained its effectiveness after four cycles. Overall, these results revealed that the biosynthesized BC/MoS2/TiO2 achieved favorable photodegradation of organic dye pollutants via a type I photodynamic pathway under sunlight illumination and synergistic photothermal and photodynamic antimicrobial activity, thus suggesting that this mild, green, and sustainable composite is a promising material for efficient antibacterial and degradation of industrial wastewater constituents.

Amorphous/Crystalline Interface of Bi/Bi4NbO8Cl Heterostructure for Improved Piezo-Photocatalysis

Efficient separation of photogenerated charges at the surface of photocatalysts is vital for achieving high photocatalytic activity. Here, a Bi/Bi4NbO8Cl heterostructure piezo-photocatalyst with an amorphous/crystalline interface (acBi/BNC) is prepared by in situ reduction using Bi4NbO8Cl as a self-sacrificial template. This ingenious design synergistically utilizes the advantages of the amorphous/crystalline interface structure, localized surface plasmon resonance effect, and piezoelectric field. The formation of amorphous/crystalline interfaces induces the generation of oxygen vacancies, and subsequently lattice distortions, thus improving the piezoelectric properties. Theoretical and experimental results demonstrate that the combination of piezoelectric field and amorphous/crystalline interface promotes the effective separation and migration of photogenerated charges between the bulk and surface of the catalysts. Under simultaneous light and ultrasound, the optimal heterostructure (acBi/BNC-3) exhibit superior photodegradation efficiency of tetracycline reached 80% within 5 min, and the reaction rate (2.78 × 10-1 min-1) is 7.8 and 5.4 times that of pure Bi4NbO8Cl (BNC) and crystalline Bi/Bi4NbO8Cl (cBi/BNC), respectively. Furthermore, the piezo-photocatalytic tetracycline degradation efficiency surpasses those under individual photocatalysis and piezocatalysis conditions. This work provides a novel rational design to improve the spatial charge separation of Bi-based catalysts and prepare high-performance piezo-photocatalysts via interface engineering.

Construction of Full-Spectrum-Response Bi3O4Br:Er3+@Bi2O3- x S-Scheme Heterojunction With [Bi─O] Tetrahedral Sharing by Integrated Upconversion and Photothermal Effect Toward Optimized Photocatalytic Performance

Designing and optimizing photocatalysts to maximize the use of sunlight and achieve fast charge transport remains a goal of photocatalysis technology. Herein, a full-spectrum-response Bi3O4Br:Er3+@Bi2O3- x core-shell S-scheme heterojunction is designed with [Bi─O] tetrahedral sharing using upconversion (UC) functionality, photothermal effects, and interfacial engineering. The UC function of Er3+ and plasmon resonance effect of Bi2O3- x greatly improves the utilization of sunlight. The equivalent layer structure of Bi3O4Br and Bi2O3- x facilitates the construction of high-quality S-scheme heterojunction interfaces with close atomic-level contact obtained from the [Bi─O] tetrahedral sharing and the resulting Bi3O4Br:Er3+@Bi2O3- x core-shell morphology, enabled efficient charge transfer. Furthermore, localized temperature increase, induced by photothermal effects, enhanced the chemical reaction kinetics. Benefiting from the distinctive construction, the Bi3O4Br:Er3+@Bi2O3- x heterojunctions exhibit excellent performance in the photocatalytic degradation of bisphenol A that is 2.40 times and 4.98 times greater than that of Bi3O4Br:Er3+ alone under full-spectrum light irradiation and near-infrared light irradiation, respectively. This work offers an innovative perspective for the design and fabrication of full-spectrum-response S-scheme heterojunction photocatalysts with efficient solar energy utilization based on high quality interfaces, UC functionality, and the photothermal effect.

Interfacial Engineering of a Z-Scheme Bi2O2S/NiTiO3 Heterojunction Photoanode for the Degradation of Sulfamethoxazole in Water

To develop a semiconductor interface with enhanced spatial separation of carriers under visible light irradiation for the photoelectrochemical (PEC) oxidation process, we explored the fabrication of a Bi2O2S/NiTiO3 heterojunction photoanode for the removal of sulfamethoxazole in water. The Bi2O2S/NiTiO3 photoanode was synthesized via an in situ hydrothermal process, and it exhibited better light absorption and charge separation, as well as a reduced rate of recombination of photoexcited charge species compared to pristine Bi2O2S and NiTiO3. The improved photoelectrocatalytic performance was attributed to the synergistic interaction between Bi2O2S and NiTiO3 and the presence of an S-O bond at the heterojunction interface, thus resulting in Z-scheme heterojunction formation. Various characterization methods such as XPS, UV-DRS, electrochemical impedance spectroscopy, photoluminescence, FESEM, TEM, and photocurrent response measurements were explored to explain the optical and electrochemical properties of the semiconductor heterojunction. The PEC degradation process was optimized, demonstrating a degradation efficiency removal of 80% for 5 mg/L sulfamethoxazole in water, with a TOC removal of 45.5%. A Z-scheme heterojunction formation mechanism was proposed to explain the enhanced photoelectrocatalytic activity of the photoanode. This work generally contributes to the development of efficient and sustainable photoanodes for environmental remediation.

Piezoelectric Heterojunctions as Bacteria-Killing Bone-Regenerative Implants

Heterojunctions are widely used in energy conversion, environmental remediation, and photodetection, but have not been fully explored in regenerative medicine. In particular, piezoelectric heterojunctions have never been examined in tissue regeneration. Here the development of piezoelectric heterojunctions is shown to promote bone regeneration while eradicating pathogenic bacteria through light-cellular force-electric coupling. Specifically, an array of heterojunctions (TiO2/Bi2WO6), made of piezoelectric nanocrystals (Bi2WO6) decorating TiO2 nanowires, is fabricated as a biocompatible implant. Upon exposure to near-infrared light, the piezoelectric heterojunctions generate reactive oxygen species and heat to kill bacteria through photodynamic and photothermal therapy, respectively. Meanwhile, the mechanical forces of the stem cells grown on the implant trigger the heterojunctions to produce electric fields that further promote osteogenesis to achieve osteointegration. The heterojunctions effectively suppress postoperative recurrent infections while promoting osseointegration through the local electric fields induced by cells. Therefore, the piezoelectric heterojunctions represent a promising antibacterial tissue-regenerative implant.

Designing Polychromatic Er3+/Yb3+-Codoped Bi2WO6 Upconverting Nanoparticles with Enhanced Visible-Light-Triggered Photocatalytic Properties toward Tetracycline Degradation

To address the unsatisfactory photodegradation capacities of photocatalysts, Er3+/Yb3+-codoped Bi2WO6 (Bi2WO6:Er3+/xYb3+) nanoparticles (NPs) with polychromatic upconversion (UC) emission and boosted visible-light-triggered photocatalytic abilities were designed. First-principles density functional theory was employed to study the impact of Er3+ and Yb3+ codoping on the electronic structure of Bi2WO6. Upon 980 nm excitation, the resultant NPs emitted polychromatic UC emissions caused by energy back transfer from Er3+ to Yb3+. Moreover, the involved UC emission mechanism was clarified through examining the pump power related to UC emission spectra. By investigating the visible-light-induced tetracycline (TC) decomposition, the photocatalytic activities of developed NPs were explored, where Bi2WO6:Er3+/0.07Yb3+ NP can degrade 81.76% of TC within 30 min, with a k value of 0.0552 min-1. Both the theoretical calculation and trapping results reveal that the •O2-, h+, and •OH were formed during the pollutant removal process. Additionally, the toxic TC can be photodegraded to nontoxic products via the synthesized photocatalysts, leading to wastewater purification. These achievements manifest that Bi2WO6:Er3+/xYb3+ NPs are promising visible-light-triggered photocatalysts to degrade pollutants, and our findings also propose a facile approach to regulate the photocatalytic activities of photocatalysts via utilizing doping and UC emission strategies.

Enhancing the near-infrared upconversion photocatalytic activity of ZnO/Bi3Ti2O8F:Yb3+, Er3+ by modulating the internal electric field through Z-scheme heterojunction construction

Exploring strategies to improve the near-infrared response of photocatalysts is an urgent challenge that can be overcome by utilizing upconversion (UC) luminescence to enhance photocatalysis. This paper reports the fabrication of a ZnO/Bi3Ti2O8F:Yb3+, Er3+ (ZnO/BTOFYE) Z-scheme heterojunction based on a Bi3Ti2O8F:Yb3+, Er3+ (BTOFYE) UC photocatalyst via electrostatic self-assembly. Fermi energy difference at the interface of BTOFYE and ZnO generates a strong internal electric field (IEF) in the Z-scheme heterojunction, offering a novel charge transfer mode that promotes carrier transfer and separation while retaining the strong redox capability. These results are confirmed through in situ X-ray photoelectron spectroscopy, in situ Kelvin probe force microscopy, electron spin resonance, and density functional theory calculations. In addition, the effect of the IEF on the UC luminescence process of Er3+ enhances the luminescence intensity, considerably improving the UC utilization efficiency. The optimal ZnO/BTOFYE degrades 64 % of ciprofloxacin in 120 min, which is 2.3 times more than that degraded by BTOFYE. Overall, the results of this study offer a reference for the rational development of high efficiency UC photocatalysts by generating IEF in Z-scheme heterojunctions.

Tuning Surface Electronics State of P-Doped In2.77S4/In(OH)3 toward Efficient Photoelectrochemical Water Oxidation

Indium sulfide with a two-dimensional layered structure offers a platform for catalyzing water oxidation by a photoelectrochemical process. However, the limited hole holders hinder the weak intrinsic catalytic activity. Here, the nonmetallic phosphorus atom is coordinated to In2.77S4/In(OH)3 through a bridge-bonded sulfur atom. By substituting the S position by the P dopant, the work function (surface potential) is regulated from 445 to 210 mV, and the lower surface potential is shown to be beneficial for holding the photogenerated holes. In2.77S4/In(OH)3/P introduces a built-in electric field under the difference of Fermi energy, and the direction is from the bulk to the surface. This band structure results in upward band bending at the interface of In2.77S4/In(OH)3 and P-doped sites, which is identified by density functional theory calculations (∼0.8 eV work function difference). In2.77S4/In(OH)3/P stands out with the highest oxidation efficiency (ηoxi = 70%) and charge separation efficiency (ηsep = 69%). Importantly, it delivers a remarkable water oxidation photocurrent density of 2.51 mA cm-2 under one sun of illumination.

Inorganic-Organic Dual-Ligand-Regulated Photocatalysis of CdS@ZnxCd1-xS@ZnS Quantum Dots for Lignin Valorization

In a dual-functional lignin valorization system, a harmonious oxidation and reduction rate is a prerequisite for high photocatalytic performance. Herein, an efficient and facile ligand manipulating strategy to balance the redox reaction process is exploited via decorating the surface of the CdS@ZnxCd1-xS@ZnS gradient-alloyed quantum dots with both inorganic ligands of hexafluorophosphate (PF6-) and organic ligands of mercaptopropionic acid (MPA). Inorganic ion ligands in this system provide a promotion for intermediator reduction reactions. By optimizing the ligand composition on the quantum dot surface, we achieve precise control over the extent of oxidation and reduction, enabling selective modification of reaction products; that is, the conversion rate of 2-phenoxy-1-phenylethanol reached 99%. Surface engineering by regulating the ligand type demonstrates that PF6- and thiocyanate (SCN-) inorganic ion ligands contribute significantly toward electron transfer, while MPA ligands have beneficial effects on the hole-transfer procedure, which is predominantly dependent on their steric hindrance, electrostatic action, and passivation effect. The present study offers insights into the development of efficient quantum dot photocatalysts for dual-functional biomass valorization through ligand design.

Improved Charge Separation and CO2 Affinity of In2O3 by K Doping with Accompanying Oxygen Vacancies for Boosted CO2 Photoreduction

The CO2 photocatalytic conversion efficiency of the semiconductor photocatalyst is always inhibited by the sluggish charge transfer and undesirable CO2 affinity. In this work, we prepare a series of K-doped In2O3 catalysts with concomitant oxygen vacancies (OV) via a hydrothermal method, followed by a low-temperature sintering treatment. Owing to the synergistic effect of K doping and OV, the charge separation and CO2 affinity of In2O3 are synchronously promoted. Particularly, when P/P0 = 0.010, at room temperature, the CO2 adsorption capacity of the optimal K-doped In2O3 (KIO-3) is 2336 cm3·g-1, reaching about 6000 times higher than that of In2O3 (0.39 cm3·g-1). As a result, in the absence of a cocatalyst or sacrificial agent, KIO-3 exhibits a CO evolution rate of 3.97 μmol·g-1·h-1 in a gas-solid reaction system, which is 7.6 times that of pristine In2O3 (0.52 μmol·g-1·h-1). This study provides a novel approach to the design and development of efficient photocatalysts for CO2 conversion by element doping.

Constructing BiOBr1-xIx-y with Abundant Surface Br Vacancies for Excellent Visible-Light Photodegradation Capability of High-Concentration Refractory Contaminants

Bismuth oxybromide (BiOBr) is a promising photocatalytic semiconductor material due to its unique hierarchical structure and band structure. However, its photocatalytic applications are restricted due to its narrow visible-light absorption range and poor photooxidation capability. In this study, BiOBr1-xIx-y with rich surface Br vacancies (BrVs-rich BiOBr1-xIx-y) was created via a facile indirect substitution strategy. Benefiting from the broadened visible-light response range and reduced recombination rate of photogenerated carriers, BiOBr1-xIx-y shows excellent visible-light photodegradation ability for high-concentration refractory contaminants, such as phenol, tetracycline, bisphenol A, rhodamine B, methyl orange, and even real wastewater. At the same time, the Br vacancies can regulate the band structure of BiOBr1-xIx-y and serve as trap states to promote charge separation, thus facilitating surface photoredox reactions. An in-depth investigation of the Br vacancy effect and photodegradation mechanism was conducted. This novel study revealed the significance of Br vacancies in enhancing the photocatalytic performance of BiOBr under visible light, providing a promising strategy for improving the utilization efficiency of sunlight in wastewater treatment.