Enhanced photocatalytic performance through the ferroelectric synergistic effect of p-n heterojunction BiFeO3/TiO2 under visible-light irradiation

A BiFeO₃/TiO₂ p-n heterojunction photocatalyst with ferroelectric synergistic effect under visible-light irradiation was developed through facile hydrolysis and precipitation by forming nanospheres of TiO₂ on BiFeO₃ nanocube to improve the photocatalytic efficiency. Analyses of the microstructure, optical properties, and photoelectrochemical performance indicate the formation of a core–shell heterostructure of BiFeO₃/TiO₂ with excellent energy band matching. The BiFeO₃/TiO₂ p-n heterojunction has enlarged specific surface area, higher sensitivity to visible-light, and improved separation and transfer efficiency of photoelectron-hole pairs than single TiO₂ and BiFeO₃. Moreover, the composite exhibits superior photocatalytic degradation performance for methylene blue (MB) and common antibiotic tetracycline (TC) under UV and visible-light irradiation. The MB degradation rate within 180 min reaches 78.4% and 90.4% under UV and visible-light irradiation, respectively. Furthermore, the enhanced photocatalytic mechanism of BiFeO₃/TiO₂ is explored by photoluminescence (PL), electrochemical impedance spectroscopy (EIS), transient photocurrent analysis, radical quenching, and band structure characterization.     

Ultrasound-assisted synthesis of high-efficiency Ag3PO4/CeO2 heterojunction photocatalyst

The Ag₃PO₄/CeO₂ heterojunction photocatalyst prepared by an ultrasound-assisted method exhibits an enhanced photocatalytic activity compared to pure Ag₃PO₄, CeO₂, and Ag₃PO₄/CeO₂ obtained without ultrasound action. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and ultraviolet–visible absorption spectroscopy (UV–vis), and the effects of ultrasound on the physicochemical properties and photocatalytic activity of Ag₃PO₄/CeO₂ are discussed. Results show that the ultrasound-assisted synthesis method significantly improves the photocatalytic ability. The mechanism about the improvement was discussed in details.     

Increasing the photocatalytic and fungicide activities of Ag3PO4 microcrystals under visible-light irradiation

The present study reports for the first time the performance of silver phosphate (Ag₃PO₄) microcrystals as photocatalyst (degradation of Rodamine B-RhB) and antifungal agent (against Candida albicans–C. albicans) under visible-light irradiation (455 nm). Ag₃PO₄ microcrystals were synthesized by a simple co-precipitation (CP) method at room temperature. The structural and electronic properties of the as-synthetized Ag₃PO₄ have been investigated before and after 4 cycles of RhB degradation under visible light using X-ray diffraction (XRD), micro-Raman spectroscopy, UV–Vis spectrophotometer and field emission scanning electron microscopy (FE-SEM) images. The antifungal activity was analyzed in planktonic cells and 48h-biofilm of C. albicans by colony forming units (CFU) counting, confocal laser and FE-SE microscopies. Statistical analysis was carried out using SPSS software. Morphological and structural modifications of Ag₃PO₄ were observed upon recycling. After 4 recycles, the material maintained its photodegradation property; an eightfold increase in the efficiency of Ag₃PO₄ was observed in planktonic cells and a two fold increase in biofilm when irradiated under visible light. Thus, higher antifungal effectiveness against C. albicans was obtained when associated with visible-light irradiation.     

Fabrication and photocatalytic performance of one-dimensional Ag3PO4 sensitized SrTiO3 nanowire

The 1D Ag₃PO₄ sensitized SrTiO₃ nanowires are prepared by simple route of electrospinning-in situ deposition technique. The results of the thermogravimetry (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive Spectrometer (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV–Visible diffuse reflectance spectroscopy (UV–Vis) indicate that the Ag₃PO₄ nanoparticles has been deposited on the surface of the SrTiO₃ nanowires successfully. Experimental results showed that compared with pure SrTiO₃, the as-prepared 1D Ag₃PO₄ sensitized SrTiO₃ nanowires exhibit obvious enhancement of photocatalytic performance and stability. Especially, the Ag₃PO₄/SrTiO₃ (3AS sample) had a satisfactory photocatalytic activity for degrading methylene blue (MB) more than 98% under visible light irradiation. As to pure SrTiO₃ and Ag₃PO₄, only 9.8% and 49% of MB was decomposed after 35?min irradiation respectively. Furthermore, the mechanism of the enhancing photocatalytic activity could be ascribed to the nano-heterojunction of the Ag₃PO₄/SrTiO₃, the visible light response of the Ag₃PO₄, and the 1D structure of the nanowires.     

Dual Z-scheme heterojunction g-C3N4/Ag3PO4/AgBr photocatalyst with enhanced visible-light photocatalytic activity

Recently, there has been a significant interest in developing high-performance photocatalysts for removing organic pollutants from water environment. Herein, a ternary graphitic C₃N₄ (g-C₃N₄)/Ag₃PO₄/AgBr composite photocatalyst is synthesized using an in-situ precipitation-anion-exchange process and characterized by several spectroscopic and microscopic techniques. During the photocatalytic reaction, X-ray photoelectron spectroscopy clearly illustrated the formation of metallic Ag on the g-C₃N₄/Ag₃PO₄/AgBr composite surface. The ternary composite photocatalyst demonstrated an increased photoactivity under visible light (>420 nm), achieving a complete decolorization of methyl orange (MO) in 5 min. The ternary g-C₃N₄/Ag₃PO₄/AgBr hybrid was also applied to the 2-chlorophenol degradation under visible light, further confirming its excellent photocatalytic activity. In addition, quenching experiments revealed that holes (h⁺) and O₂^?– were the major attack species in the decolorization of MO. The enhanced photoactivity of g-C₃N₄/Ag₃PO₄/AgBr results from the efficient transfer/separation of photoinduced charges with the dual Z-scheme pathway and the charge recombination sites on the formed Ag particles.     

Selective photocatalytic degradation of azodyes in NiO/Ag3VO4 suspension

BACKGROUND: This work deals with the development of an active heterogeneous catalyst for selective organic synthesis under both visible light and UV irradiation to utilize efficiently solar light. Very few studies have been reported on the selective photooxidation performance of multimetal oxide materials under visible light irradiation. The photocatalytic degradation of azodyes was investigated systematically in aqueous NiO/Ag₃VO₄ dispersion under visible light irradiation. RESULTS: The catalyst NiO/Ag₃VO₄ showed high activity and selectivity for the photodegradation of the nonbiodegradable azodyes acid red B, reactive brilliant red X‐3B, and acid orange 7. From total organic carbon (TOC), Fourier transform infrared spectroscopy (FTIR), and gas chromatography/mass spectroscopy analyses, the tested azodyes were selectively oxidized into aromatic and aliphatic acids without any decrease of TOC. The high photooxidation selectivity also applied to UV light irradiation. Electron spin resonance and radical scavenger studies suggest that the anionic superoxide radical O₂^?? was the predominant active species in the photocatalytic reaction. CONCLUSION: The selectivity of NiO/Ag₃VO₄ for the oxidation of azodyes was not affected by the energy of light (UV and visible light). This approach allows effective controlled oxidation but avoids undesirable mineralization into CO₂ and H₂O. Copyright © 2010 Society of Chemical Industry     

Facile one-pot synthesis of a BiOBr/Bi2WO6 heterojunction with enhanced visible-light photocatalytic activity for tetracycline degradation

Photocatalytic removal of tetracycline (TC) from the wastewater is of great value in the chemical and environmental engineering field. Here, we introduced a facile one-step method for the synthesis of BiOBr/Bi₂WO₆ heterojunctions by using cheap CTAB as the Br source. We showed the possibility of our method to fine-tune the content of BiOBr in the produced BiOBr/Bi₂WO₆ by simply changing the dosage of cetyltrimethylammonium bromide (CTAB), providing a platform for the delicate tuning of the visible-light absorbance ability of the composites. With a suitable heterojunction structure of BiOBr/Bi₂WO₆-0.2, it exhibited an ultrarapid photocatalytic activity towards TC (20 mg·L^-1), with a competitive removal efficiency of 88.1% within 60 min and an ultrahigh removal rate of 0.0349 min^-1. It could also be robustly recycled for at least 5 cycles with slight removal efficiency loss. We demonstrated that this exciting photocatalytic performance was due to the highly decreased recombination of photoinduced electrons and holes on our composites by constructing this heterojunction structure, and the resulting OH and contributed to the effective degradation of TC to CO₂.     

Z-scheme AgSCN/Ag3PO4/C3N4 heterojunction with excellent photocatalytic degradation of ibuprofen

To develop a novel photocatalyst with high catalytic performance under sunlight, AgSCN/Ag₃PO₄/C₃N₄ heterojunction photocatalyst with Z-mechanism has been prepared, which demonstrates excellent photocatalytic performance for ibuprofen degradation. The catalytic activity of AgSCN/Ag₃PO₄/C₃N₄ is 1.5 and 3.3 times that of AgSCN/Ag₃PO₄ and Ag₃PO₄, respectively. The cyclic degradation number of AgSCN/Ag₃PO₄/C₃N₄ increases to seven because of the protection of AgSCN and C₃N₄ to Ag₃PO₄. The excellent photocatalytic performance of the AgSCN/Ag₃PO₄/C₃N₄ is attributed from the Z-mechanism with efficient separation efficiency of electron hole pair.     

Ag3PO4 quantum dots loaded on the surface of leaf-like InVO4/BiVO4 heterojunction with enhanced photocatalytic activity

Leaf-like InVO₄/BiVO₄ nanoarchitectures with scale of 2 μm–5 μm were prepared by a facile hydrothermal method. Ag₃PO₄ quantum dots (QDs) were then deposited onto the surface of leaf-like InVO₄/BiVO₄ crystals via a simple deposition–precipitation technique. The photocatalytic tests displayed that the Ag₃PO₄/InVO₄/BiVO₄ nanocomposite possesses a much higher rate for degradation of rhodamine B (Rh B) than the sum of BiVO₄, InVO₄, Ag₃PO₄, Ag₃PO₄/InVO₄, Ag₃PO₄/BiVO₄ or InVO₄/BiVO₄ under visible light irradiation. The observed improvement in photocatalytic performance is associated with the extended absorption in the visible light region resulting from the Ag₃PO₄ QD loading, the high specific surface area, and the effective separation of photogenerated carriers at the Ag₃PO₄/InVO₄/BiVO₄ interfaces.     

Ag3PO4/g-C3N4异质结催化剂可见光降解黄连素

采用原位生长法制备Ag₃PO₄/g-C₃N₄异质结催化剂,在可见光照射下,催化氧化降解废水中的药物大分子黄连素。通过X射线衍射（XRD）、扫描电镜（SEM）、X射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-vis DRS）分析催化剂的组成和结构,并测试了Ag₃PO₄/g-C₃N₄降解黄连素的光催化活性。结果表明：利用可见光照射,g-C₃N₄掺杂量为0.7 g时,Ag₃PO₄/g-C₃N₄对黄连素的光催化降解活性最好,可见光反应15 min降解率达到100%,重复4次实验后降解率降至73.2%,其具有较好的光稳定性。自由基捕获实验证明h⁺和·O₂^-在降解黄连素废水中起主要作用,结合UV-vis DRS分析可知,Ag₃PO₄/g-C₃N₄遵循Z型异质结机理。     

Synthesis of a CoTiO3/BiOBr heterojunction composite with enhanced photocatalytic performance

A novel heterojunction CoTiO₃/BiOBr nanocomposite with enhanced photocatalytic performance was synthesized by a precipitation-deposition method. The samples were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis spectrophotometry. Moreover, the photocatalytic activities were evaluated by decomposing the dye molecule Rhodamine B under visible light irradiation. The results showed that high photocatalytic performance can be achieved on the heterojunction photocatalysts, with the 0.15CoTiO₃/0.85BiOBr composite displaying the highest activity. The results of the study concluded that it was the introduction of CoTiO₃ into the catalyst that mainly enhanced the activity of the photocatalyst by promoting the separation of the electron-hole group on the interface between BiOBr and CoTiO₃.     

In-situ deposition of Ag3PO4 on TiO2 nanosheets dominated by (001) facets for enhanced photocatalytic activities and recyclability

Ag₃PO₄/TiO₂ nanosheet (TNS) heterojunction photocatalysts with almost 100% exposed (001) facets were fabricated via a facile in situ growth process. The Ag₃PO₄/TNS exhibited remarkable photocatalytic activity for the degradation of rhodamine B (RhB) and it was significantly more recyclable under sunlight compared with Ag₃PO₄. The RhB degradation efficiency was 99.11% after 50 min of sunlight irradiation, and was 85.8% after three cycles. The photocatalytic degradation mechanism of RhB over the Ag₃PO₄/TNS heterojunctions is driven by both photogenerated holes (h⁺) and ·O₂⁻ radicals. This efficient and reusable Ag₃PO₄/TNS heterojunction photocatalyst is not only suitable for fundamental research but also has potential for practical applications in the energy and environmental fields. This study demonstrates that applying morphology engineering to heterojunctions is useful for developing composite photocatalysts with greatly improved properties.     

Synthesis,characterization, and visible-light photocatalytic activity of transition metals doped ZTO nanoparticles

Transition metals doping has been proved to be a feasible way for tuning the physical properties on the surface and bulk of nanomaterials and also for the good performance in decontamination of emerging pollutants. In this context, doped samples of zinc tin oxide or zinc stannate nanoparticles (ZTO NPs) by several transition metals were synthesized in order to enhance the optical absorbance with the aims of reducing the band gap and therefore ameliorated their photocatalytic activity. They were characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy, Raman spectroscopy and photoluminescence. The XRD patterns and the microscopic observations showed the formation of spherical nanoparticles with an average size of about 30 nm and highly pure ZTO phase with an inverse spinel structure. The Raman spectra were dominated by bands relatives to the F2g (2) and A1g symmetries modes of inverse spinel structure. The band gap Eg is estimated to be 3.75 eV for the undoped sample, and 3.67, 3.64, 3.78 and 3.21 eV, for 2% Fe, 2% Mg, 2% Gd, and 2% Mn doped ZTO samples, respectively.Furthermore, the undoped ZTO NPs have the intrinsic problem of recombination of photogenerated charge carriers. We have shown that the reduction of the band gap and oxygen vacancies resulting from the doping effect could be a useful tool for trapping and avoid the recombination of electrons coming from photosensitized rhodamine B (RhB) under visible light irradiation. Owing to the structural advantages and low band gap, 2% Mn doped ZTO NPs, with the kinetic rate constants k of 0.024 min⁻¹, show enhanced performance for the elimination of RhB in aqueous solution compared to undoped and other doped ZTO NPs.     

Construction of g-C3N4 nanotube/Ag3PO4 S-scheme heterojunction for enhanced photocatalytic oxygen generation

Heterojunction engineering is considered as a hopeful approach to ameliorate the separation of photogenerated carriers of photocatalysts, realizing efficient water-splitting performance. In this study, an organic-inorganic S-scheme of a one-dimensional g-C₃N₄ nanotube (TCN)/Ag₃PO₄ photocatalytic system with high photocatalytic water oxidation activity was designed by coupling g-C₃N₄ nanotubes over Ag₃PO₄ particles through a chemical coprecipitation method. The TCN/Ag₃PO₄ heterojunction demonstrated excellent photocatalytic O₂ production with an O₂ evolution rate of up to 370.2 μmol·L^?1·h^?1. X-ray photoelectron spectroscopy analysis showed that electron migration between TCN and Ag₃PO₄ led to the formation of an internal electric field pointing from TCN to Ag₃PO₄, which drove the S-scheme charge transfer mode between TCN and Ag₃PO₄. Accordingly, the TCN/Ag₃PO₄ heterojunction possessed fast charge separation and high redox ability, leading to high photoactivity and photostability. This research provides a new strategy for fabricating highly efficient inorganic-organic S-scheme photocatalysts for O₂ production.     

Solvent-induced controllable synthesis of recyclable Ag2CO3 catalysts with enhanced visible light photocatalytic activity

The quest for cost-effective environmental remediation has motivated the research for highly efficient and stable photocatalysts capable of degrading pollutants under visible-light illumination. Ag-based visible-light-responsive photocatalysts demonstrate alluring properties and applications in the elimination of organic pollutants in wastewater, however they often suffer from inherent photo-corrosion under illumination. Herein, we report the facile solution-phase synthesis of silver carbonate (Ag₂CO₃) microcrystals with varied morphological features in different solvents. The size and morphology of Ag₂CO₃ materials can be tuned on the basis of varying types and ratios of solvents. The specific synthetic method allows the orientation controllable growth of Ag₂CO₃ microcrystals with variable length-to-diameter ratios, with the surface harvesting more solar energy, and the photocatalyst suppressing the electron-hole recombination. The enhancement in both the photocatalytic activity and photostability of Ag₂CO₃ catalysts is evident when AgNO₃ and NaHCO₃ are employed as stabilizers. Operating in the presence of 0.02 M stabilizer, the photocatalyst demonstrates highly efficient and robust degradation performance of higher than 95% in 5 successive times towards typical organic dye rhodamine B (RhB). Active holes and reactive oxygen-containing superhydroxyl radicals (·O²⁻) are determined by trapping experiments to be the main species responsible for improved photocatalytic performance. This work provides new insights into the development of high-performance, recyclable Ag-based photocatalytic materials for energy and environmental applications.     

NiTiO3/Ag3PO4 composites with improved photocatalytic activity under visible-light irradiation

A series of NiTiO₃/Ag₃PO₄ composites were prepared by a simple ion-exchange deposition method. The composition and morphology of the samples were determined by XRD, EDS and SEM. UV–vis DRS was used to characterize their optical absorption properties. The loading of NiTiO₃ could promote the efficient separation of photoinduced electron-hole pairs and enhance the charge carrier transport to improve the photocatalytic activity. The APO-5 composite exhibited the best photocatalytic activity for the degradation of methyl violet (MV). Kinetics studies indicated that the APO-5 composite showed an apparent rate constant of 0.115 min⁻¹, which was 2.61 times that of pure Ag₃PO₄.     

La3+掺杂对BiPO4光催化活性的影响

采用一步水热合成法制备La3+掺杂BiPO4纳米粉末,利用XRD、EDS、SEM、BET、UV-Vis、XPS等手段对La3+-BiPO4的形貌、结构、光谱特征、表面化学组成等做了表征和分析。以亚甲基蓝为目标污染物,考察了La3+-BiPO4的催化活性,并探讨了La掺杂提高BiPO4光催化性能的机理。结果表明：La掺杂使纳米BiPO4的晶粒生长受到抑制,比表面积增加,带隙变宽,出现氧空位,光生电子-空穴对复合几率降低。La3+-BiPO4光催化活性明显高于未掺杂的BiPO4,紫外光照射下,90 min 内,2% La3+-BiPO4对亚甲基蓝的降解率可达95%,光催化反应速率是BiPO4的3.7倍。     

Ag3PO4/g-C3N4复合材料制备及其光催化性能

采用原位沉淀法制备了Ag3PO4/g-C3N4复合材料，利用XRD、SEM、TEM、UV-Vis DRS和PL等技术对其进行表征。结果显示，g-C3N4呈现二维片状结构，Ag3PO4为立方晶相的类球状结构，且均匀分布在g-C3N4表面。以亚甲基蓝（MB）为模拟污染物，考察g-C3N4与Ag3PO4的不同摩尔比对MB降解率的影响。结果表明，在Ag3PO4/g-C3N4的摩尔比为1:0.7时，Ag3PO4/g-C3N4复合材料的光催化活性最佳，可见光照30 min后MB降解率即达到100%。光催化剂稳定性较好，重复使用5次，MB降解率仍达到85.24%。降解机理研究表明，h 和e-是降解MB的主要活性物质。     

The stabilization effect of surface capping on photocatalytic activity and recyclable stability of Ag3PO4

We find the stabilization effect of surface capping on the adsorption capacity and photocatalytic activity of Ag₃PO₄ in the recycling. The citrate anion complex (CAC) as the surface capping is confirmed to be constituted by citrate anion and silver citrate complex. The adsorption capacity of Ag₃PO₄ with CAC capping exhibits little increase in the subsequent cycle, whereas the one of the bare Ag₃PO₄ decreases by 25.8% for methylene blue (MB). The photocatalytic activity of Ag₃PO₄ with CAC capping is maintained, compared to marked 10% decrease of bare Ag₃PO₄ for degrading MB.     

Ag3PO4/g-C3N4复合材料的制备及其光催化性能

以硝酸银和三聚氰胺为原料,采用原位沉淀法制备了Ag3PO4/g-C3N4复合材料,利用XRD、SEM、TEM、UV-Vis DRS和PL等技术对其进行了表征.结果显示,g-C3N4呈二维片状结构,Ag3PO4为立方晶相的类球状结构,且均匀分布在g-C3N4表面.以亚甲基蓝(MB)为模拟污染物,考察g-C3N4与Ag3P...