Photocatalytic Performances of Ag3PO4 Polypods for Degradation of Dye Pollutant under Natural Indoor Weak Light Irradiation

Optimization of Electron Transport Pathway: A Novel Strategy to Solve the Photocorrosion of Ag-Based Photocatalysts

Although Ag-containing photocatalysts exhibit excellent photocatalytic ability, they present great challenges owing to their photocorrosion and ease of reduction. Herein, an electron acceptor platform of Ag2O/La(OH)3/polyacrylonitrile (PAN) fiber was constructed using a heterojunction strategy and electrospinning technology to develop a novel photocatalytic membrane with a redesigned electron transport pathway. Computational and experimental results demonstrate that the optimized electron transport pathway included intercrystal electron transfer induced by the La-O bond between Ag2O and La(OH)3 as well as electron transfer between the catalyst crystal and electrophilic PAN membrane interface. In addition, the photocatalytic performance of the Ag2O/La(OH)3 membrane for tetracycline (TC) removal was still above 97% after five photocatalytic reaction cycles. Furthermore, the carrier life was greatly extended. Mechanistic study revealed that photogenerated holes on the Ag2O/La(OH)3 membrane were the main reactive species in TC degradation. Overall, this study proposes a novel electron transport pathway strategy that effectively solves the problems of photocatalyst photocorrosion and structural instability.

Graphene oxide-incorporated silver-based photocatalysts for enhanced degradation of organic toxins: a review

Environmental contamination and scarcity of energy have been deepening over the last few decades. Heterogeneous photocatalysis plays a prominent role in environmental remediation. The failure of earlier metal oxide systems like pure TiO₂ and ZnO as stable visible-light photocatalysts demanded more stable catalysts with high photodegradation efficiency. Silver-based semiconductor materials gained popularity as visible-light-responsive photocatalysts with a narrow bandgap. But their large-scale usage in natural water bodies for organic contaminant removal is minimal. The factors like self-photocorrosion and their slight solubility in water have prevented the commercial use. Various efforts have been made to improve their photocatalytic activity. This review focuses on those studies in which silver-based semiconductor materials are integrated with carbonaceous graphene oxide (GO) and reduced graphene oxide (RGO). The decoration of Ag-based semiconductor components on graphene oxide having high-surface area results in binary composites with enhanced visible-light photocatalytic activity and stability. It is found that the introduction of new efficient materials further increases the effectiveness of the system. So binary and ternary composites of GO and Ag-based materials are reviewed in this paper.

Ag3PO4-based photocatalysts and their application in organic-polluted wastewater treatment

Semiconductor photocatalysis technology has shown great potential in the field of organic pollutant removal, as it can use clean and pollution-free solar energy as driving force. The discovery of silver phosphate (Ag₃PO₄) is a major breakthrough in the field of visible light responsive semiconductor photocatalysis due to its robust capacity to absorb visible light < 520 nm. Furthermore, the holes produced in Ag₃PO₄ under light excitation possess a strong oxidation ability. However, the strong oxidation activity of Ag₃PO₄ is only achieved in the presence of electron sacrifice agents. Otherwise, photocorrosion would greatly reduce the reuse efficiency of Ag₃PO₄. This review thus focuses on the structural characteristics and preparation methods of Ag₃PO₄. Particularly, the recent advances in noble metal deposition, ion doping, and semiconductor coupling, as well as methods of magnetic composite modification for the improvement of catalytic activity and recycling efficiency of Ag₃PO₄-based catalysts, were also discussed, and all of these measures could enhance the catalytic performance of Ag₃PO₄ toward organic pollutants degradation. Additionally, some potential modification methods for Ag₃PO₄ were also proposed. This review thus provides insights into the advantages and disadvantages of the application of Ag₃PO₄ in the field of photocatalysis, clarifies the photocorrosion essence of Ag₃PO₄, and reveals the means to improve photocatalytic activity and stability of Ag₃PO₄. Furthermore, it provides a theoretical and methodological basis for studying Ag₃PO₄-based photocatalyst and also compiles valuable information regarding the photocatalytic treatment of organic polluted wastewater.

Sonochemical synthesis of ZnCo2O4/Ag3PO4 heterojunction photocatalysts for the degradation of organic pollutants and pathogens: a combined experimental and computational study

ZnCo2O4/Ag3PO4 heterostructure nanoparticles were prepared by a facile ultrasonic method and characterized by various techniques. The photocatalytic activity of ZnCo2O4/Ag3PO4 nanoparticles was investigated for the degradation of organic pollutants (methyl...

Novel Ag3PO4/boron-carbon-nitrogen photocatalyst for highly efficient degradation of organic pollutants under visible-light irradiation

Ag₃PO₄ is an indirect bandgap semiconductor with excellent photocatalytic activity. However, it has not been widely used so far for the treatment of polluted wastewaters. This scarce use in wastewater treatment can be mainly attributed to its large crystallite size, which would be due to rapid agglomeration during the synthesis process, as well as to the photo-corrosion problem affecting this material. Hence, it would be crucial to develop a photocatalytic system involving Ag₃PO₄ nanoparticles with enhanced properties, such as higher specific surface area and excellent photocatalytic stability. To meet this demand, a novel Ag₃PO₄/boron carbon nitrogen (Ag₃PO₄/BCN) composite photocatalyst was successfully prepared in the present study via electrostatically driven self-assembly and ion exchange processes. After characterization and assessment, it was shown that the as-prepared Ag₃PO₄/BCN nanocomposite photocatalyst not only contains smaller Ag₃PO₄ nanoparticles, but also exhibits an enhanced visible-light photocatalytic activity for Rhodamine B (RhB) Methyl Orange (MO) and Tetracycline (TC) and improved stability, without decrease after 5 cycles, compared with pure Ag₃PO₄ nanoparticles. Positive synergy between Ag₃PO₄ nanoparticles and BCN nanosheets, including the increase in the number of active adsorption sites, and the restriction of the formation of Ag due to the recombination of photogenerated electron-hole pairs in Ag₃PO₄ nanoparticles, are mainly responsible for the enhanced properties of the prepared catalyst. This study shows that Ag₃PO₄/BCN composite photocatalyst would be promising for wastewater treatment, which would be of clearly environmental and public health relevance.

Porous hollow Ag/Ag2S/Ag3PO4 nanocomposites as highly efficient heterojunction photocatalysts for the removal of antibiotics under simulated sunlight irradiation

Antibiotic pollutants are a serious and growing threat to human health and the environment that efficient measures must be taken to eliminate them. Here, we report the facile fabrication of porous hollow Ag/Ag₂S/Ag₃PO₄ heterostrucutres for efficient photocatalytic degradation of tetracycline under simulated sunlight irradiation. The morphology manipulation and hetero-nanocomposites construction through a coprecipitation-refluxing approach were applied to enhance the photocatalytic performance of the Ag/Ag₂S/Ag₃PO₄ products. The photodegradation outcomes indicated that the heterojunction Ag/Ag₂S/Ag₃PO₄ photocatalyst with a suitable band gap energy of 2.17 eV, has better degradation performance (∼95%) than individual Ag₂S and Ag₃PO₄ structures after 120 min of simulated sunlight irradiation, even after five recycles. The good photocatalytic activity of Ag/Ag₂S/Ag₃PO₄ nanocomposites could be mainly attributed to the unique hierarchical architectures, promoted visible-light harvesting, reduced a recombination and boosted separation of electron-hole pairs originated from the as-formed heterojunctions. Moreover, we proposed a photocatalytic degradation mechanism based on the radical scavenging results, which disclosed that the ^•O₂^- and ^•OH species perform essential tasks for the photodegradation of antibiotics by Ag/Ag₂S/Ag₃PO₄ nanocomposites.

Temperature-dependent phonon dynamics of Ag3PO4 microcrystals

In this work, we present the study of the temperature-dependent behavior of silver orthophosphate (Ag₃PO₄) microcrystals using in situ Raman scattering. The Ag₃PO₄ as-synthesized microcrystals were prepared by the precipitation method and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and infrared spectroscopy, and differential scanning calorimetry (DSC). Temperature-dependent phonon dynamics were performed on Ag₃PO₄ microcrystals and pointed to a first-order phase transition in the temperature range 500-515 °C: Phase I (25-500 °C) → Phase II (515-590 °C). The phase transition is reversible and a temperature hysteresis was observed during the heating - cooling process: Phase II (590-470 °C) → Phase I (455-25 °C). The reversible phase transition is related to the distortion of the tetrahedral symmetry of PO₄ caused by the decrease in the crystalline order. DSC analysis confirmed the results of temperature-dependent Raman spectroscopy.

Fabrication of AgCl/Ag3PO4/graphitic carbon nitride heterojunctions for enhanced visible light photocatalytic decomposition of methylene blue, methylparaben and E. coli

Herein, a novel ternary nanocomposite AgCl/Ag₃PO₄/g-C₃N₄ was successfully synthesized via sedimentation precipitation and ion exchange method. The photocatalytic performance of the as-prepared AgCl/Ag₃PO₄/g-C₃N₄ nanocomposite was investigated via photocatalytic degradation of methylene blue (MB), methylparaben (MPB) and inactivation of E. coli under visible light irradiation. The AgCl/Ag₃PO₄/g-C₃N₄ composite presented the optimal photocatalytic performance, degrading almost 100% MB and 100% MPB, respectively. The excellent stability of AgCl/Ag₃PO₄/g-C₃N₄ was also verified in the cycle operations; the degradation efficiency of MPB could still be maintained at 85.3% after five cycles of experiments. Moreover, the AgCl/Ag₃PO₄/g-C₃N₄ composite displayed more superior photocatalytic inactivation efficiency with 100% removal of E. coli (7-log) in 20 min under visible light irradiation. The efficient photo-generated charge separation originated from a strong interaction in the intimate contact interface, which was confirmed by the results of photocurrent and EIS measurements. In addition, radical trapping experiments revealed that hole (h⁺) was the predominant active species in the photocatalytic system. Based on the experimental results, a photocatalytic mechanism for the degradation of parabens over AgCl/Ag₃PO₄/g-C₃N₄ was also proposed. We believe that this work provides new insights into the multifunctional composite materials for the applications in solar photocatalytic degradation of harmful organic compounds and common pathogenic bacteria in wastewater.

A noval ternary nanocomposite AgCl/Ag₃PO₄/g-C₃N₄ was successfully synthesized for photocatalytic degradation of methylene blue, methylparaben and inactivation of E. coli under visible light irradiation, showing excellent photocatalytic degradation performance and stability.

Hierarchical Ag3PO4@ZnIn2S4 nanoscoparium: An innovative Z-scheme photocatalyst for highly efficient and predictable tetracycline degradation

Z-scheme photocatalyst preserved with superior oxidicability is an innovative photocatalyst system that can be used for efficient photocatalytic detoxification of antibiotics. In this study, Z-scheme Ag₃PO₄@ZnIn₂S₄ photocatalyst was constructed by decorating Ag₃PO₄ nanoparticles on ZnIn₂S₄ nanoscopariums. ZnIn₂S₄ nanoscopariums were prepared by self-templated strategy and given hierarchical structures. The hierarchical Ag₃PO₄@ZnIn₂S₄ provides more active sites for generating photogenerated carriers and large surface area for capturing tetracycline. The study results show that Ag₃PO₄@ZnIn₂S₄ performed excellently well in the photocatalytic degradation of tetracycline and also in protecting Ag₃PO₄ nanoparticles from photo-corrosion. The highest removal efficiency (up to 92.3%) was achieved from the optimal composites of Ag₃PO₄ and ZnIn₂S₄. In stability tests, Ag₃PO₄@ZnIn₂S₄ did not reduce the photocatalytic activity of degrading tetracycline after five successive runs. Active radical identification proves that the transfer behavior of electron and hole over Ag₃PO₄@ZnIn₂S₄ follows a direct Z-scheme mechanism. Furthermore, the transformation pathway for degrading tetracycline was proposed by combining the Fukui index prediction with Mass Spectra identification of intermediates. This work presents in-depth sights into a regulated degradation pathway from theoretical prediction and practical identification based on innovative Z-scheme photocatalyst.

Study on Visible Light Catalysis of Graphite Carbon Nitride-Silica Composite Material and Its Surface Treatment of Cement

Cement-based composite is one of the essential building materials that has been widely used in infrastructure and facilities. During the service of cement-based materials, the performance of cement-based materials will be affected after the cement surface is exposed to pollutants. Not only can the surface of cement treated with a photocatalyst degrade pollutants, but it can also protect the cement-based materials from being destroyed. In this study, graphite carbon nitride-silica composite materials were synthesized by thermal polymerization using nanosilica and urea as raw materials. The effect of nanosilica content and specific surface area were investigated with the optimal condition attained to be 0.15 g and 300 m2/g, respectively. An X-ray diffractometer, thermogravimetric analyzer, scanning electron microscope, a Brunauer–Emmett–Teller (BET) specific surface area analyzer and ultraviolet-visible spectrophotometer were utilized for the characterization of as-prepared graphite carbon nitride-silica composite materials. Subsequently, the surface of cement-based materials was treated with graphite carbon nitride-silica composite materials by the one-sided immersion and brushing methods for the study of photocatalytic performance. By comparing the degradation effect of Rhodamine B, it was found that the painting method is more suitable for the surface treatment of cement. In addition, through the reaction of calcium hydroxide and graphite carbon nitride-silica composite materials, it was found that the combination of graphite carbon nitride-silica composite materials and cement is through C-S-H gel.

An Emerging Visible-Light Organic-Inorganic Hybrid Perovskite for Photocatalytic Applications

The development of visible-light active photocatalysts is a current challenge especially energy and environmental-related fields. Herein, methylammonium lead iodide perovskite (MAIPb) was chosen as the novel semiconductor material for its ability of absorbing visible-light. An easily reproducible and efficient method was employed to synthesize the as-mentioned material. The sample was characterized by various techniques and has been used as visible-light photocatalyst for degradation of two model pollutants: rhodamine B (RhB) and methylene-blue (MB). The photo-degradation of RhB was found to achieve about 65% after 180 min of treatment. Moreover, the efficiency was enhanced to 100% by assisting the process with a small amount of H2O2. The visible-light activity of the photocatalyst was attributed to its ability to absorb light as well as to enhance separation of photogenerated carriers. The main outcome of the present work is the investigation of a hybrid perovskite as photocatalyst for wastewater treatment.

Selective oxidation of alcohols by using CoFe2O4/Ag2MoO4 as a visible-light-driven heterogeneous photocatalyst

Using a CoFe₂O₄/Ag₂MoO₄ heterostructure as a novel, stable, inexpensive, and reusable photocatalyst with high-performance for the oxidation of alcohols.

Porous oxygen-doped carbon nitride: supramolecular preassembly technology and photocatalytic degradation of organic pollutants under low-intensity light irradiation

In order to overcome photocatalytic technology application limitations in water due to weak light intensity, it is crucial to synthesize photocatalysts that respond to weak light. In this study, porous and oxygen-doped carbon nitride (CN-MC) was synthesized via supramolecular preassembly technology using melamine and cyanuric chloride. The carbon nitride catalyst produced via this technology has a relatively high surface area (63.2 m² g^-1), irregular pores, and oxygen doping characteristics, which enhance the light capture capacity, increase the number of reactive sites, and accelerate electron-hole separation efficiency. Thus, the CN-MC exhibited excellent photocatalytic activity during the degradation of organic pollutants Rhodamine B (RhB, 95% removal within 6 h) and tetracycline hydrochloride (TC-HCl, 70% removal within 6 h) under low-intensity light (the light intensity = 0.8~1.8 mW cm^-2 with a wavelength range of 300-700 nm). Mechanistic analysis showed that ·O₂^- and ·OH were the dominant active free radicals during RhB and TC-HCl photocatalytic degradation over CN-MC. The proposed synthesis strategy effectively improves the photocatalytic activity of graphite carbon nitride under weak light by producing a porous morphology and oxygen atom doping.

Fabrication of magnetic BaFe12O19/Ag3PO4 composites with an in situ photo-Fenton-like reaction for enhancing reactive oxygen species under visible light irradiation

An in situ photo-Fenton-like and magnetic recycle system, BaFe₁₂O₁₉/Ag₃PO₄ has been constructed. BaFe₁₂O₁₉ can catalyze the conversion of H₂O₂ to generate ROSs (˙O₂⁻ and ˙OH radicals) on the surface of Ag₃PO₄.

Antibiotic removal from water: A highly efficient silver phosphate-based Z-scheme photocatalytic system under natural solar light

Photocatalytic degradation is an alternative method to remove pharmaceutical compounds from water, however it is hard to achieve efficient rate because of the low efficiency of photocatalysts. In this study, an efficient Z-Scheme photocatalyst was constructed by integrating graphitic carbon nitride (CN) and reduced graphene oxide (rGO) with AP via a simple facile precipitation method. Excitedly, ternary AP/rGO/CN composite showed superior photocatalytic and anti-photocorrosion performances under both intense sunlight and weak indoor light irradiation. NOF can be completely degraded in only 30 min and about 85% of NOF can be mineralized after 2 h irradiation under intensive sunlight irradiation. rGO could work not only as a sheltering layer to protect AP from photocorrosion but also as a mediator for Z-Scheme electron transport, which can protect AP from the photoreduction. This strategy could be a promising method to construct photocatalytic system with high efficiency for the removal of antibiotics under natural light irradiation.

Surface modification of sludge-derived carbon by phosphoric acid as new electrocatalyst for degradation of acetophenone

Sludge-derived carbons (SCs) were modified by different acids and used as electrocatalyst for electrochemical oxidation degradation of acetophenone. The results showed that SC treated with phosphoric acid (H₃PO₄-SC) exhibited the highest catalytic activity. The degradation efficiency of acetophenone reached 87.0%, and TOC removal was 72.3% under the conditions of 100 mg L^-1 acetophenone, 90 mA cm^-2, and 180 min reaction time. The element content and chemical state of H₃PO₄-SC were measured by XRF, XRD, TGA, FTIR, and Mössbauer spectra, and the results indicated that ferric iron and phosphate on the surface of H₃PO₄-SC might play the main role in acetophenone degradation. The carbonyl-¹³C-labeled acetophenone was first used to investigate the degradation of acetophenone in electrochemical oxidation by NMR.

Synthesis, Structural Property, Photophysical Property, Photocatalytic Property of Novel ZnBiErO₄ under Visible Light Irradiation

A novel photocatalyst ZnBiErO₄ was firstly synthesized by solid-state reaction method and its structural and photocatalytic properties were analyzed by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-Vis diffuse reflectance. The results demonstrated that ZnBiErO₄ crystallized with tetragonal crystal structure with space group I41/A. The lattice parameters for ZnBiErO₄ were proved to be a = b = 10.255738 Å and c = 9.938888 Å. The band gap of ZnBiErO₄ was estimated to be about 1.69 eV. Compared with nitrogen doped TiO₂, ZnBiErO₄ showed excellent photocatalytic activities for degrading methyl blue during visible light irradiation. The photocatalytic degradation of methyl blue with ZnBiErO₄ or N-doped TiO₂ as catalyst followed the first-order reaction kinetics. Moreover, the apparent first-order rate constant of ZnBiErO₄ or N-doped TiO₂ was 0.01607 min⁻¹ or 0.00435 min⁻¹. The reduction of total organic carbon, formation of inorganic products, such as SO₄²⁻ and NO₃⁻ and the evolution of CO₂ revealed the continuous mineralization of methyl blue during the photocatalytic process. ZnBiErO₄ photocatalyst had great potential to purify textile industry wastewater.

Synthesis, Property Characterization and Photocatalytic Activity of the Polyaniline/BiYTi₂O₇ Polymer Composite

A new polyaniline/BiYTi₂O₇ polymer composite was synthesized by chemical oxidation in-situ polymerization method for the first time. The effect of polyaniline doping on structural and catalytic properties of BiYTi₂O₇ was reported. The structural properties of novel polyaniline/BiYTi₂O₇ have been characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and UV-Vis DRS. The results showed that BiYTi₂O₇ crystallized well with the pyrochlore-type structure, stable cubic crystal system by space group Fd3m. The lattice parameter or band gap energy of BiYTi₂O₇ was found to be a = 10.2132 Å or 2.349 eV, respectively. The novel polyaniline/BiYTi₂O₇ polymer composite possessed higher catalytic activity compared with BiYTi₂O₇ or nitrogen doped TiO₂ for photocatalytic degradation of Azocarmine G under visible light irradiation. Additionally, the Azocarmine G removal efficiency was boosted from 3.0% for undoped BiYTi₂O₇ to 78.0% for the 10% polyaniline-modified BiYTi₂O₇, after only 60 min of reaction. After visible light irradiation for 330 min with polyaniline/BiYTi₂O₇ polymer composite as photocatalyst, complete removal and mineralization of Azocarmine G was observed. The photocatalytic degradation of Azocarmine G followed first-order reaction kinetics. Ultimately, the promoter action of H₂O₂ for photocatalytic degradation of AG with BiYTi₂O₇ as catalyst in the wastewater was discovered.

Graphitic-C3N4 nanosheets: synergistic effects of hydrogenation and n/n junctions for enhanced photocatalytic activities

Synergistic effects of n/n junctions and hydrogenation have enhanced the optical, electronic and photocatalytic properties of graphitic C₃N₄ nanosheets.

Activation of peroxymonosulfate by graphitic carbon nitride loaded on activated carbon for organic pollutants degradation

Graphitic carbon nitride supported on activated carbon (g-C3N4/AC) was prepared through an in situ thermal approach and used as a metal free catalyst for pollutants degradation in the presence of peroxymonosulfate (PMS) without light irradiation. It was found that g-C3N4 was highly dispersed on the surface of AC with the increase of surface area and the exposition of more edges and defects. The much easier oxidation of C species in g-C3N4 to CO was also observed from XPS spectra. Acid Orange 7 (AO7) and other organic pollutants could be completely degraded by the g-C3N4/AC catalyst within 20min with PMS, while g-C3N4+PMS and AC+PMS showed no significant activity for the reaction. The performance of the catalyst was significantly influenced by the amount of g-C3N4 loaded on AC; but was nearly not affected by the initial solution pH and reaction temperature. In addition, the catalysts presented good stability. A nonradical mechanism accompanied by radical generation (HO and SO4(-)) in AO7 oxidation was proposed in the system. The CO groups play a key role in the process; while the exposure of more N-(C)3 group can further increase its electron density and basicity. This study can contribute to the development of green materials for sustainable remediation of aqueous organic pollutants.

Efficient photocatalytic degradation of tetracycline hydrochloride by Ag3PO4 under visible-light irradiation

A facile, environmental-friendly Ag3PO4-PN photocatalyst was synthesized by a simple precipitation method at room temperature in the presence of ammonia and polyvinyl pyrrolidone (PVP). As-synthesized samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy (UV-vis DRS). The enhancement of photocatalytic efficiency of Ag3PO4-PN is strongly dependent on the excellent photo-absorption capacity, sharp edges and corners, and synergistic effect of PVP and NH3·H2O. The effects of catalyst dosage, TC concentration and solution pH were explored with tetracycline hydrochloride (TC) as target contamination. The mineralization was evaluated by total organic carbon (TOC) analysis and determination of the concentration of inorganic ions such as NO3 (-) and Cl(-). Radical detection experiment indicated the h(+) and ·O(2-) are major active species in the degradation of TC by Ag3PO4-PN. Moreover, photocatalyst stability and regeneration experiments exhibited the favorable stability and rejuvenation ability, suggesting a promising prospect of practical application of Ag3PO4 in the wastewater treatment.

Silver nanoparticles modified reduced graphene oxide wrapped Ag3PO4/TiO2 visible-light-active photocatalysts with superior performance

Rational design of a novel Ag₃PO₄/TiO₂/Ag-rGO photocatalyst with both electron and hole pathways for charge separation.

Magnetically separable Ag3PO4/NiFe2O4 composites with enhanced photocatalytic activity

A step wise growth process of APO nuclei leads to developing interesting morphologies of APO/NFO composites.