Visible Light Photocatalytic Activity Research Articles

Greatly increased visible-light photocatalytic activity of SnS2/carbon nanotube composite for Cr(VI) reduction: Insights into effects of solid acid structure

A composite of SnS2 and carbon nanotube (CNT) was successfully synthesized as a visible-light-driven photocatalyst with a mechanochemical method. In comparing with SnS2, the SnS2/CNT composite improved much the photocatalytic removal of Cr(VI) in acidic condition, which was confirmed to its special solid acid structure. During the synthesis of the SnS2/CNT composite by ball milling, S-C p-π bonding was formed between sulfur atoms in SnS2 and carbon atoms in CNT. The generated S-C p-π bonding enhanced the transfer of photo-induced electrons in the bulk phase of the composite photocatalyst under visible light irradiation. Moreover, the persistent radical sites on CNT were able to trap photo-induced electrons and served as conjugated acid sites in the photocatalysis, which increased surface concentration of protons through their association with H+. These made the catalyst have a solid acid structure with plentiful surface protons, promoting the interfacial electron transfer between the catalysts and Cr(VI) and increasing the source of H+ for the reduction of Cr(VI). As a result, the photocatalytic reduction rate of Cr(VI) on the SnS2/CNT composite were dramatically enhanced, being about 800% that on SnS2. On the basis of various characterizations and probe experiments, we confirmed the significance of the solid acid structure of the photocatalyst and clarified the catalytic mechanism of the new photocatalyst. Our finding may provide a new strategy to prepare highly active photocatalysts for proton-involved reactions.

Fabrication of structural defects and carboxyl groups on graphitic carbon nitride with enhanced visible light photocatalytic activity

Structural defects and surface functional group defects engineering in graphitic carbon nitride (g-C3N4) have great significance for optimizing its electron structure and photocatalytic activity. In this study, g-C3N4 was prepared via a solvothermal method without high-temperature calcination, and then carboxyl group defects-containing g-C3N4 was synthesized through post-modification. FTIR and XPS verified the presence of highly favorable carboxyl groups. Morphological and photoelectrical experiments verified that adding branched chains with carboxyl groups onto g-C3N4 effectively increased the specific surface area and pore volume of g-C3N4, improved the absorption of visible light and enhanced the separation and migration of photogenerated carriers. As a result, the modified g-C3N4 (CN-COOH) had a high bisphenol A (BPA) photocatalytic degradation of 99.6% at 60 min and a high kinetics constant of 0.067 min−1, which was 13.4 times that of the original g-C3N4 under visible light irradiation. In addition, CN-COOH showed high photocatalytic stability with photocatalytic activity decreased by only 1.5% after 5 cycles. Active species capture experiments have demonstrated that •O2− and holes are the main active substances in the BPA photocatalytic process. These findings open a new avenue for precise carboxyl modification of g-C3N4 via an environmentally-friendly post-modification approach and provide the mechanism of carboxyl defects of g-C3N4 photocatalysts on prompting photogenerated charge separation.

A flower-like metal-organic frameworks fabricated BiOCl heterojunction with enhanced visible light photocatalytic activity

The design and construction of appropriate photocatalysts in heterojunction mode is an effective way to improve photocatalytic performance. Herein, a metal-organic frameworks (MOFs) fabricated heterojunction constructed by MOF-902(Ti) and BiOCl (noted as TB) was developed to treat efficiently antibiotic tetracycline (TC) under visible light irradiation. TB exhibits a higher photodegradation ability than MOF-902(Ti) and BiOCl. Various characterization including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and scanning electron microscope (SEM), etc. verify the formation of TB heterojunction, which improves significantly the visible light response, increases the specific surface area/pore volume, promotes effectively charged carriers separation and transfer, and ultimately enhances greatly the photocatalytic performance. Reactive species trapping demonstrates that·O2-, e-, and h+ participate cooperatively in the photodegradation of TC. A possible mechanism for the enhanced photocatalytic activity of TB heterojunction is proposed.

Controllable Al2O3 coating makes TiO2 photocatalysts active under visible light by pulsed chemical vapor deposition

TiO2 catalysts, modified by coating Al2O3, presented high visible-light photocatalytic activity. Al2O3 nano-films were successfully deposited onto TiO2 particles using AlCl3 as a precursor via the pulsed chemical vapor deposition process. And, the alumina was anchored onto TiO2 surface via Ti–O–Al bonds. The morphology, constitution, photocatalytic activity and photoelectrochemical performance of the Al2O3-coated TiO2 were characterized. Controllable Al2O3 coating increased the oxygen vacancies and hydroxyl groups, and induced the formation of surface disordered TiO2 layer, which enhanced light absorption, increased charge carrier separation and transfer efficiency, and surface redox efficiency. Therefore, the TiO2/Al2O3 catalyst obtained via the pulsed chemical vapor deposition technique may break through the limitation of the band gap, and the pulsed chemical vapor deposition provided an effective strategy for the TiO2 production with active defective sites.

Controllable fabrication of Bi4Ti3O12/C/Bi2S3/MoS2 heterojunction with effective suppression of Bi2S3 assisted by amorphous carbon interlayer for significantly enhanced photocatalysis

BackgroundFabricating heterojunctions by combining with MoS2 is efficient to boost the visible light photocatalytic activity of Bi4Ti3O12 (BTO) but limited by the concurrent formation of Bi2S3 nanorods by in-situ ion exchange reaction. MethodsAn amorphous carbon interlayer that can effectively protect the BTO fibrous structure and suppress the Bi2S3 generation was introduced to construct Bi4Ti3O12/C/Bi2S3/MoS2 (BCBM) composites with enhanced photocatalytic activity. The BCBM fibers were fabricated by electrospinning and subsequent hydrothermal growth of carbon and MoS2. Significant findingsOwing to the important roles of carbon interlayer to keep the integrity of the BTO fibrous structure and provide charge transfer channel, fast separation of photoinduced carriers happens on the semiconductor interface between BTO and MoS2 to improve the visible light photocatalytic activity. The optimum BCBM displays a photocatalytic efficiency of 88.4% and apparent constant of 0.0148 min−1 towards degrading RhB, which are much higher relative to the Bi4Ti3O12/Bi2S3/MoS2 composites prepared without the carbon interlayer. Moreover, it is demonstrated that the thickness of carbon interlayer is crucial for fabricating high-performance BTO heterojunctions with MoS2. The design and results in this work may broaden the horizon to construct the Bi-based semiconductor photocatalyst with high photocatalytic performance.

Construction of novel fluorescent synergistic photocatalytic double Z-scheme photocatalyst for efficient antifouling of polydimethylsiloxane coatings

It has been challenging to enhance the static antifouling (AF) performance of silicone AF coatings using low-cost, high-performance, and environmentally friendly materials. In this work, a graphite-phase carbon nitride/titanium dioxide nanotubes/Sr2MgSi2O7:(Eu2+, Dy3+) long afterglow powder (g-C3N4/TNTs/SLAP, CTS) ternary double Z-scheme heterostructure photocatalyst was designed based on the application of photocatalytic technology in the field of AF and environmental remediation and the function of fluorescent corals and Watasenia scintillans emitting fluorescence to prevent the adhesion of fouling organisms. Then, this composite photocatalyst was dispersed in polydimethylsiloxane resin (PDMS) to prepare g-C3N4/TNTs/SLAP/PDMS (P-CTS) biomimetic fluorescent synergistic photocatalytic AF coating. The double Z-scheme heterostructure formed between the CTS enhances the carrier separation and transport efficiency, thus conferring excellent visible light photocatalytic activity on the CTS. At the same time, the fluorescence emitted by SLAP as a “light store” at night not only prolongs the photocatalytic activity but also inhibits the adhesion of fouling organisms. The results showed that the minimum attachment rates of S. aureus, E. coli, and benthic diatoms of P-CTS were 1.65 %, 1.40 %, and 10.20 %, respectively, under simulated natural diurnal conditions. This novel biomimetic fluorescent synergistic photocatalytic AF coating has good potential applications in marine AF and environmental remediation.

Improved Visible-Light Photocatalytic H2 Evolution of G-C3N4 Nanosheets by Constructing Heterojunctions with Nano-Sized Poly(3-Thiophenecarboxylic Acid) and Coordinating Fe(III).

It is highly desirable to enhance the photogenerated charge separation of g-C3N4 by constructing efficient heterojunctions, especially with an additional organic constitution for solar-hydrogen conversion. Herein, g-C3N4 nanosheets have been modified controllably with nano-sized poly(3-thiophenecarboxylic acid) (PTA) through in situ photopolymerization and then coordinated with Fe(III) via the -COOH groups of modified PTA, forming an interface of tightly contacted nanoheterojunctions between the Fe(III)-coordinated PTA and g-C3N4. The resulting ratio-optimized nanoheterojunction displays a ~4.6-fold enhancement of the visible-light photocatalytic H2 evolution activity compared to bare g-C3N4. Based on the surface photovoltage spectra, measurements of the amount of •OH produced, photoluminescence (PL) spectra, photoelectrochemical curves, and single-wavelength photocurrent action spectra, it was confirmed that the improved photoactivity of g-C3N4 is attributed to the significantly promoted charge separation by the transfer of high-energy electrons from the lowest unoccupied molecular orbital (LUMO) of g-C3N4 to the modified PTA via the formed tight interface, dependent on the hydrogen bond interaction between the -COOH of PTA and the -NH2 of g-C3N4, and the continuous transfer to the coordinated Fe(III) with -OH favorable for connection with Pt as the cocatalyst. This study demonstrates a feasible strategy for solar-light-driven energy production over the large family of g-C3N4 heterojunction photocatalysts with exceptional visible-light activities.

A unique and well-designed 2D graphitic carbon nitride with sponge-like architecture for enhanced visible-light photocatalytic activity

A unique and well-designed 2D graphitic carbon nitride (g-CN) with sponge-like architecture has been successfully synthesized by engineering supramolecular self-assembly and well-organized SiO2 nanoparticles. The resulting material showed great optical and textural characteristics with plenty of open and uniform pores, which are very helpful whether for multiple light scattering or mass transfer. The formation of boosted delocalized π-conjugated electrons at the molecular level and condensed heptazine building blocks result in enhanced carrier density and charge transfer dynamics. Optical emission spectroscopy and time‐resolved fluorescence lifetime (TRPL) strongly confirmed the enhancement of light harvesting and prolonged charge carrier lifetime. The optimized sample exhibited a degradation performance of 95% of bisphenol A (BPA, 10 mg L–1) after 60 min under visible–light irradiation at pH = 5. All the scavenging experiments, probing experiments as well as electron paramagnetic resonance (EPR) confirm that •O2– is the dominant reactive species that fragments bisphenol A. Interestingly, density functional theory (DFT) calculations unveil that the BPA interaction with a modified g-CN containing porous structure is energetically more favorable than non-porous pure g-CN. Moreover, the toxicity assessment showed that the final degradation products were placed in the non-harmful category based on acute and chronic toxicity. This study presents a promising strategy to modify the g-CN properties and provides an efficient technique for boosting its visible–light photocatalytic activity.

Enhancement in anaerobic biogas conversion by visible light photocatalytic Pre-treatment of rice husk with indium vanadate decorated titanium dioxide nanocomposite

Production of biogas from crop wastes via the biological route is one of the most demanding and promising technologies for energy generation for sustainable development. The incorporation of photocatalytic pretreatment as a robust catalytic technique has been reported to enhance the overall efficiency of the anaerobic process. Rice husk has been pretreated using Indium Vanadate decorated Titania nanocomposite to enhance its biodegradability for biogas production. Scanning electron microscopy confirmed the deformities and crevices that may support the role of the photocatalytic pretreatment in the subsequent anaerobic degradation process. FT-IR spectroscopy investigated the structural characteristics of pretreated and photolyzed rice husk samples. Gas chromatography was used to quantify the CH4 content of biogas yield after different treatments of rice husk. Photocatalytic pretreatment of rice husk showed 2.8 times higher cumulative biogas production than raw or untreated rice husk. Statistical analysis showed a significant difference between natural and pretreated rice husk biogas yield with a p-value of < 0.01. The results suggest that visible light active photocatalysis is an efficient pretreatment method that can facilitate the microbes to degrade the rigid rice husk for enhanced biogas production via the anaerobic digestion process.

Construction of PCN-222 and Atomically Thin 2D CNs Van Der Waals Heterojunction for Enhanced Visible Light Photocatalytic Hydrogen Production.

Atomically thin two-dimensional (2D) CN sheets have attracted extensive attention in the field of photocatalysis because of their shorter diffusion path of photogenerated carriers and abundant surface reaction sites than bulk CN. However, 2D CNs still exhibit poor visible-light photocatalytic activity because of a strong quantum size effect. Here, PCN-222/CNs vdWHs were successfully constructed using the electrostatic self-assembly method. The results showed that PCN-222/CNs vdWHs with 1 wt.% PCN-222 enhanced the absorption range of CNs from 420 to 438 nm, which improved the absorption capacity of visible light. Additionally, the hydrogen production rate of 1 wt.% PCN-222/CNs is four times that of the pristine 2D CNs. This study provides a simple and effective strategy for 2D CN-based photocatalysts to promote visible light absorption.

MIL-53(Fe)@BiOBr/TCN/Ti photoanode assembled visible light responsive photocatalytic fuel cell to enhance rhodamine B degradation and electricity generation

In this research, MIL-53(Fe)@BiOBr/TCN/Ti photoanode was created using the secondary silica sol drop coating method, and assembled with Cu cathode to form photocatalytic fuel cell (PFC) to degrade rhodamine B and generate electricity. The resulting PFC has high visible light response and photocatalytic activity. It has a rhodamine B degradation efficiency of 92.19%, a maximum power density of 6.2 μW cm−2, and a maximum photocurrent density of 0.11 mA cm−2. Its strong photocatalysis capabilities benefits from the wider light absorption range and lower charge carrier recombination rate of the photoanode. The double Z-scheme heterojunction formed among BiOBr, MIL-53(Fe) and TCN in the composite catalyst of the photoanode provide more transfer channels for photogenerated e− and encourage the separation of e−-h+ pairs. ∙OH and ∙O-2 are the main active substances for rhodamine B degradation. This study offers a novel approach to the development of high-efficiency photoanodes for PFC.

Visible light photocatalytic activity in BiFeO3 glass-ceramics

Bismuth Ferrite (BiFeO3) being a visible light active ferroelectric material is a potential candidate for removing industrial dyes from water through the photocatalysis process. To take advantage of the BiFeO3 phase, glass-ceramic with composition Bi2O3–Fe2O3–BaO–B2O3 was fabricated through a conventional melt and quench process. The desired bismuth ferrite (BiFeO3) phase was achieved by optimizing heat treatment temperature (480° C) duration for 2, 4, and 12 h. Each fabricated sample was then utilized for dye cleaning application via photocatalysis process with visible light as an exciting source, where the sample heat-treated at 480 °C for 2 h has shown the maximum Methylene Blue (MB) dye degradation of ∼69% in 300 min. Further, the stability of the fabricated samples was checked through their XRD pattern and SEM micrographs taken before and after the photocatalysis process. At last, MB dye degradation was also calculated through a colorimetric response of MB dye with RGB (red, green, and blue) values obtained by an app of a smartphone.

Bio-capped and green synthesis of ZnO/g-C3N4 nanocomposites and its improved antibiotic and photocatalytic activities: An exceptional approach towards environmental remediation

In this research study, we have synthesized the bio-capped ZnO/g-C3N4 nanocomposites by employing lemon juice (Citrus limon) as a stabilizer and mediator. Fruitfully, lemon juice which contains various acidic functional groups and citric acid has the capability to block the surface of g-C3N4 from chemical reactivity and activated the surface of g-C3N4 for various reactions. Consequently, the agglomeration behavior and controlled shape of g-C3N4 has also been achieved. Our experimental results i.e. XRD, TEM, HRTEM, PL, FS, XPS, and PEC have confirmed that the lemon juice mediated and green g-C3N4 (L-CN) has good performances and remarkable visible light photocatalytic activities as compared to the chemically synthesized g-C3N4 (CN). Furthermore, the small surface area and low charge separation of g-C3N4 is upgraded by coupling with ZnO nanoparticles. It is proved that the coupling of ZnO worked as a facilitator and photoelectron modulator to enhance the charge separation of g-C3N4. Compared to pristine lemon mediated green g-C3N4 (L-CN), the most active sample 5ZnO/L-CN showed ∼5-fold improvement in activities for ciprofloxacin (CIP) and methylene blue (MB) degradation. More specifically, the mineralization process and degradation pathways, and the mineralization process of ciprofloxacin (CIP) and methylene blue (MB) are suggested. Finally, our present novel research work will provide new access to synthesize the eco-friendly and bio-caped green g-C3N4 nanomaterials and their employment for pollutants degradation and environmental purification.

Cerium and carbon-sulfur codoped mesoporous TiO2 nanocomposites for boosting visible light photocatalytic activity

Ce and C–S codoped mesoporous TiO2 nanocomposites were synthesized via a sol-gel method integrated with an evaporation-induced self-assembly approach. The basic physicochemical characteristics of the synthetic samples were analyzed via a series of characterization techniques. The results reveal that C–S and Ce codoping on mesoporous TiO2 enhances the photocatalytic activity owing to the synergistic effect caused by narrowing the band gap, enhancing adsorption, trapping and transferring the excited e–/h+ pairs and suppressing the recombination of e–/h+ pairs. Furthermore, the obtained C,S–TiO2/CeO2 materials exhibit large specific surface areas and numerous pores which not only effectively improve the adsorption-enrichment capability, but also supply multi-dimensional mass and electron transfer channels. The photodegradation efficiency of RhB by C,S–TiO2/CeO2 within 40 min is nearly 100%, and its degradation efficiency is 6.63 times that of undoped TiO2. Recycling experiments show that mesoporous C,S–TiO2/CeO2 shows excellent recoverability and stability. Furthermore, by trapping experiments, •O2–, h+ and •OH are the predominant active species and a possible reaction mechanism is proposed.

Visible light photocatalytic activity of a FeCo metal-organic framework for degradation of acetaminophen and 2,4-dichlorophenoxyacetic acid and a nematode-based ecological assessment

The present work reports the solvothermal synthesis of a bimetallic (FeCo) metal-organic framework (MOF) for the sunlight-driven photocatalytic degradation of acetaminophen (AAP) and 2,4-dichlorophenoxyacetic acid (2,4-D). The FeCo-MOF was confirmed by various analytical techniques. The as-prepared FeCo-MOF displayed improved light absorbance in the visible region and a bandgap energy of 1.73 eV. Photoluminescence spectra showed that the FeCo-MOF exhibited a lower charge carrier recombination rate than bare Fe- or Co-MOFs. The FeCo-MOF achieved a maximum AAP conversion rate (rate constant 0.031/min) of 97.4% in 180 min than bare Fe-MOF (66%) or Co-MOF (73%). A scavenger study showed that the superoxide anion radicals were responsible for the degradations of AAP and 2,4-D. The catalyst proved stable after five recycles with no change in AAP degradation efficiency. On the other hand, under the same conditions, the FeCo-MOF photodegraded 2,4-D by 79.8%. A kinetic study showed that the degradations of AAP and 2,4-D exhibited pseudo-first-order kinetics. In addition, the ecotoxicity results showed that degraded 2,4-D altered the survival, development, reproduction, intracellular redox status, and expression pattern of stress-responsive genes in the Caenorhabditis elegans model.

Enhanced visible-light photocatalytic activity of Ni(1-x)BixTiO3 prepared by solvothermal method

In this study, a new Ni(1-x)BixTiO3 tannate-based perovskite with excellent photocatalytic properties under visible light was developed. Ni(1-x)BixTiO3 was prepared by a solvothermal method coupled with a sol–gel method. The Ni(1-x)BixTiO3 photocatalyst showed better light absorption than NiTiO3 in the UV and visible light regions. The bandgap energy (∼2.21 eV) of Ni(1-x)BixTiO3 was also smaller than that of NiTiO3. In the decomposition reaction of methylene blue and phenol under visible light (550–650 nm), the decomposition efficiency of the Ni(1-x)BixTiO3 photocatalyst was higher than that of NiTiO3. Among the Ni(1-x)BixTiO3 photocatalysts, Ni0.8Bi0.2TiO3 showed the highest visible light photocatalytic performance.

Interfacial chemical bond modulated ultrathin PbBiO2Cl/Bi2O3 Z-scheme heterojunction for promoting charge separation and enhancing photocatalytic activity

Rational design of heterojunction can effectively promote photogenerated charge separation, which is considered to be an effective strategy to enhance the photocatalytic activity. Here, 2D ultrathin PbBiO2Cl/Bi2O3 heterojunction was synthesized in situ by glucose assisted one-step hydrothermal reaction followed by calcination. The theoretical calculations and experimental results indicate that the ultrathin PbBiO2Cl/Bi2O3 heterojunction has a direct Z-scheme band structure modulated by the interfacial chemical bonds of Pb-O and Bi-O, which can significantly improve the charge separation efficiency, thereby enhancing the photocatalytic activity. The full spectrum photocatalytic activity of the ultrathin PbBiO2Cl/Bi2O3 heterojunction is 10 and 30 times higher than that of pristine PbBiO2Cl and Bi2O3, and the visible light photocatalytic activity is 13.5 and 112.3 times higher than that of pristine PbBiO2Cl and Bi2O3, respectively. This work provides a new strategy for in situ construction of ultrathin Z-scheme heterojunction with efficient charge separation modulated by interfacial chemical bonds.

In-situ fabrication of MoO3 hexagonal flowers decorated with Co3O4 microrods with enhanced photocatalytic activity and stability under visible light irradiation

In the recent years, semiconductor photocatalyst has become an environmentally friendly solution for the oxidative elimination of emerging wastewater contaminants under visible light irradiance. Though, the large bandgap energy (Eg) and fast recombination of charge carriers are still problems for the definite application. Here, excellent photocatalytic activity of MoO3 based photocatalyst was explored by decorating Co3O4 microrods with MoO3 hexagonal flowers with lower concentrations (1.0, 3.0, 5.0, 7.0 wt%) of Co3O4 to form novel p-n heterojunctions of Co3O4/MoO3 via hydrothermal synthesis. The as-synthesized 3% Co3O4/MoO3 nanocomposite revealed enormously improved visible light photocatalytic activity for the degradation of rhodamine B (RhB) and alizarin yellow (AY) dyes as compared to other samples due to the development of the p-n junction between p-Co3O4 and n-MoO3. The improved 3.0 wt% Co3O4-loaded MoO3 had a total removal of 91% RhB and 67% AY after 120 min of visible-light exposure with high recyclability and stability after five cycles. The developed p-n heterojunction between 3.0 wt% Co3O4 and MoO3 decreases Eg up to 2.16 eV, shows broader visible light absorption and improved photocharge separation as compared to pristine MoO3. The utilization of this novel heterojunction photocatalyst for the degradation of both dyes is the focus of this research. Furthermore, the trapping experiments and enhanced photocatalytic mechanism was proposed also.

A novel recoverable 1D core-shell cotton fiber@ZnIn2S4 composite with improved photoactivity for H2 evolution under visible light

The problems of low activity, high cost and difficulty in recycle of photocatalysts limit their practical application. Coupling photocatalyst with abundant and natural organic material is one of feasible strategies to achieve high photoactivity and low cost of photocatalysts. Herein, one-dimensional (1D) cotton fiber@ZnIn2S4 (CF@ZIS)·composites with a novel core-shell structure were synthesized by coupling ZIS with inexpensive and natural abundance CF via a simple one-pot hydrothermal process. The microstructure, crystalline structures, optical properties and electrochemical property of CF@ZIS were investigated. ZIS nanosheets were in-situ attached on the CF surface, obtaining the CF@ZIS core-shell structure. This core-shell structure significantly suppressed the self-assembly of ZIS nanosheets made almost all ZIS nanosheets exposed to visible light, improving the utilization of light and meanwhile affording more reactive sites. The as-synthesized CF@ZIS showed improved photoactivity for efficient hydrogen production under visible-light irradiation. By replacing the half ZIS by cheap CF, the CF@ZIS-50 photocatalyst exhibited the optimal visible-light photocatalytic activity, which is 2 times than pure ZIS in hydrogen production. The enhanced photoactivity of CF@ZIS photocatalyst should be attributed to the uniform in-situ growth of ZIS nanosheets on the CF surface, the reduction of CF, and the intimate interface between ZIS and CF, resulting in the boosted separation and transfer of photogenerated charges. Additionally, due to the fibrous morphology of CF, the CF@ZIS photocatalyst showed excellent recoverability and photostability. This work provides a promising approach for designing highly efficient and low cost photocatalysts by using natural organic materials.

A TiO2/Si carrier derived from photovoltaic solid waste to assemble Ag3PO4/Co3(PO4)2/TiO2/Si heterostructure for enhancing visible-light photocatalytic activity

The rapid development of the photovoltaic solar industry has generated a huge amount of retired waste silicon panels. The management and value-added recycling of silicon wafer waste are highly important for both environmental remediation and economic efficiency. In this work, waste solar silicon wafers were ball-milled to obtain silicon powder that was employed to prepare TiO2/Si by hydrothermal synthesis, which then was converted to support Ag3PO4 and Co3(PO4)2 with a co-precipitation method to yield Ag3PO4/Co3(PO4)2/TiO2/Si (APO/CPO/TIO/Si) composite catalyst. The photocatalytic properties of the materials doped with different concentrations of APO or CPO were examined using methyl orange (MO) degradation rate as a performance metric. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectrometer (DRS), and ultraviolet-visible spectrophotometer (UV–vis) were used to characterize and analyze the morphology, grain size, material phase, and photocatalytic performance of the samples, respectively. Furthermore, the mechanism derived for the APO/CPO/TIO/Si catalyst in the photocatalytic degradation revealed that superoxide radical (•O2-), singlet oxygen (1O2), and hydroxyl radical (•OH) are the major active substances during the photocatalytic process, the enhanced photocatalytic activity contributing to a heterojunction electron transfer pathway. This work provides a promising approach for waste solar panels management as well as a high-performance photocatalyst for environmental decontamination.