Graphitic carbon nitride-based photocatalysts: Toward efficient organic transformation for value-added chemicals production

Valorization of Waste Tungsten Filament into mpg-C3N4-WO3 Photocatalyst: A Sustainable e-Waste Management and Wastewater Treatment

The waste of tungsten filament materials in the environment is one of the reasons for environmental pollution, and it is very dangerous to animals and plants. To date, not much attention has been given to its utility or recyclability. Herein, the present work reported the synthesis of tungsten trioxide nanoparticles (WO₃ NPs) by the utilization of cost-free waste tungsten filament by a simple calcination method. A mesoporous graphitic carbon nitride-tungsten trioxide (mpg-C₃N₄-WO₃) composite designed from the WO₃ NPs produced from tungsten filament waste and thiourea as a carbon and nitrogen precursor by a one-step calcination method. The synthesized samples were characterized and confirmed by different characterization techniques. The photocatalytic behavior of the synthesized mpg-C₃N₄-WO₃ composite was assessed, with respect to the effect of initial pH, amount of photocatalyst, dye concentration, and reaction time, as well for the degradation of Methylene Blue (MB) dye under sunlight. The best photocatalytic performance (92%) was achieved using mpg-C₃N₄-WO₃ with experimental condition ([photocatalyst] = 100 mg/L, [MB]₀ = 10 mg/L, pH 8, and time = 120 min) under sunlight irradiation with excellent photostability than that of isolated mpg-C₃N₄ and WO₃ NPs. The histotoxicological studies also showed that the photodegraded products of MB were found to be nontoxic and did not structurally changes in the gill architecture as well as brain tissues of freshwater fish Labeo rohita.

Highly Efficient Solar Light Driven g-C3N4@Cs0.33WO3 Heterojunction for the Photodegradation of Colorless Antibiotics

This study facilitates the synthesis of a graphitic carbon nitride/cesium tungsten oxide (g-C₃N₄@Cs_0.33WO₃) heterojunction using a solvothermal method. The photocatalytic activities of the prepared samples were examined for the photodegradation of colorless antibiotics, namely tetracycline, enrofloxacin, and ciprofloxacin, as well as cationic and anionic dyes, such as methyl orange, rhodamine B, neutral red, and methylene blue, under full-spectrum solar light. We have purposely selected different kinds of wastewater pollutants of colorless antibiotics and cationic and anionic organic dyes to investigate the potential application of this heterojunction toward different groups of water pollutants. The results revealed that the g-C₃N₄@Cs_0.33WO₃ heterojunction showed an outstanding photocatalytic activity toward all the pollutants with concentrations of 20 ppm each at pH 3 by photocatalytically removing 97% of tetracycline within 3 h, 98% of enrofloxacin within 2 h, 97% of ciprofloxacin within 2.25 h, 98% of methylene blue in 1 h, 99% of rhodamine B within 2 h, 99% of neutral red in 1.25 h, and 95% of methyl orange in 2 h. These findings indicate that the developed photocatalyst possesses excellent photocatalytic properties toward seven different water pollutants that make it a universal photocatalyst. The developed g-C₃N₄@Cs_0.33WO₃ oxide heterojunction also presented a photocatalytic performance better than those of reported solar light active photocatalysts for photodegradation of rhodamine B and tetracycline. The efficient photocatalytic performance of the heterojunction can be ascribed to its extended light-absorbing ability, effective charge separation and fast charge transfer properties, and a high surface area. Moreover, an active species detection experiment also confirmed that superoxide radicals, hydroxyl radicals, and holes played significant roles in the photocatalysis of the organic dyes and tetracycline.

Simple Low Temperature Technique to Synthesize Sillenite Bismuth Ferrite with Promising Photocatalytic Performance

Sillenite-type members of the bismuth ferrite family have demonstrated outstanding potential as novel photocatalysts in environmental remediation such as organic pollutant degradation. This investigation has developed a low temperature one-step hydrothermal technique to fabricate sillenite bismuth ferrite Bi₂₅FeO₄₀ (S-BFO) via co-substitution of 10% Gd and 10% Cr in Bi and Fe sites of BiFeO₃, respectively, by tuning hydrothermal reaction temperatures. Rietveld refined X-ray diffraction patterns of the as-synthesized powder materials revealed the formation of S-BFO at a reaction temperature of 120-160 °C. A further increase in the reaction temperature destroyed the desired sillenite structure. With the increase in the reaction temperature from 120 to 160 °C, the morphology of S-BFO gradually changed from irregular shape to spherical powder nanomaterials. The high-resolution TEM imaging demonstrated the polycrystalline nature of the S-BFO(160) nanopowders synthesized at 160 °C. The as-synthesized samples exhibited considerably high absorbance in the visible region of the solar spectrum, with the lowest band gap of 1.76 eV for the sample S-BFO(160). Interestingly, S-BFO(160) exhibited the highest photocatalytic performance under solar irradiation, toward the degradation of rhodamine B and methylene blue dyes owing to homogeneous phase distribution, regular powder-like morphology, lowest band gap, and quenching of electron-hole pair recombination. The photodegradation of a colorless organic pollutant (ciprofloxacin) was also examined to ensure that the degradation is photocatalytic and not dye-sensitized. In summary, Gd and Cr co-doping have proven to be a compelling energy-saving and low-cost approach for the formulation of sillenite-phase bismuth ferrite with promising photocatalytic activity.

Nano-architectural design of TiO2 for high performance photocatalytic degradation of organic pollutant: A review

In the past several decades, significant efforts have been paid toward photocatalytic degradation of organic pollutants in environmental research. During the past years, titanium dioxide nano-architectures (TiO₂ NAs) have been widely used in water purification applications with photocatalytic degradation processes under Uv/Vis light illumination. Photocatalysis process with nano-architectural design of TiO₂ is viewed as an efficient procedure for directly channeling solar energy into water treatment reactions. The considerable band-gap values and the subsequent short life time of photo-generated charge carriers are showed among the limitations of this approach. One of these effective efforts is the using of oxidation processes with advance semiconductor photocatalyst NAs for degradation the organic pollutants under UV/Vis irradiation. Among them, nano-architectural design of TiO₂ photocatalyst (such as Janus, yolk-shell (Y@S), hollow microspheres (HMSs) and nano-belt) is an effective way to improve oxidation processes for increasing photocatalytic activity in water treatment applications. In the light of the above issues, this study tends to provide a critical overview of the used strategies for preparing TiO₂ photocatalysts with desirable physicochemical properties like enhanced absorption of light, low density, high surface area, photo-stability, and charge-carrier behavior. Among the various nanoarchitectural design of TiO₂, the Y@S and HMSs have created a great appeal given their considerable large surface area, low density, homogeneous catalytic environment, favorable light harvesting properties, and enhanced molecular diffusion kinetics of the particles. In this review was summarized the developments that have been made for nano-architectural design of TiO2 photocatalyst. Additional focus is placed on the realization of interfacial charge and the possibility of achieving charge carriers separation for these NAs as electron migration is the extremely important factor for increasing the photocatalytic activity.

Constructing novel graphitic carbon nitride-based nanocomposites - From the perspective of material dimensions and interfacial characteristics

Two-dimensional (2D) graphitic carbon nitride (g-C₃N₄), a fascinating metal-free conjugated polymer, has garnered immense interest in the fields of solar power generation and environmental remediation. The construction of g-C₃N₄-based nanocomposites with materials of various dimensions can further improve their photocatalytic activities by surface area enlargement, bandgap tuning, heterojunction formation, etc. In this paper, we comprehensively reviewed the design, synthesis, and functionalities of g-C₃N₄-based nanocomposites based on their applications in hydrogen evolution, CO₂ reduction, and pollutants removal. We provided detailed analyses on the integration of 2D g-C₃N₄ with zero-, one-, two-, and three-dimensional materials with a focus on their interfacial characteristics and functional improvement. This review aims to stimulate fresh ideas on the interfacial engineering of g-C₃N₄-based nanocomposites to broaden their future applications.

Magnetic recyclable heterogeneous catalyst Fe3O4/g-C3N4 for tetracycline hydrochloride degradation via photo-Fenton process under visible light

Antibiotic pollution of water resources is a global problem, and the development of new treatments for destroying antibiotics in water is a priority research. We successfully manufactured recyclable magnetic Fe₃O₄/g-C₃N₄ through the electrostatic self-assembly method. Selecting tetracycline (TC) as the target pollutant, using Fe₃O₄/g-C₃N₄ and H₂O₂ developed a heterogeneous optical Fenton system to remove TC under visible light. Fe₃O₄/g-C₃N₄ was systematically characterized by SEM, TEM, XRD, FTIR, XPS, DRS, and electrochemical methods. The removal efficiency of 7% Fe₃O₄/g-C₃N₄ at pH = 3, H₂O₂ = 5 mM, and catalyst dosage of 1.0 g/L can reach 99.8%. After magnetic separation, the Fe₃O₄/g-C₃N₄ photocatalyst can be recycled five times with minimal efficiency loss. The excellent degradation performance of the prepared catalyst may be attributed to the proper coupling interface between Fe₃O₄ and g-C₃N₄ which promotes the separation and transfer of photogenerated electrons. Photogenerated electrons can also accelerate the conversion of Fe³⁺ to Fe²⁺, thereby producing more ˙OH. The new Fe₃O₄/g-C₃N₄ can be used as a raw material for advanced oxidation of water contaminated by refractory antibiotics.

Visible-Light Driven H2O-to-H2O2 Reaction by Nitrogen-Enriched Resins for Photocatalytic Oxidation of an Organic Pollutant in Wastewater

A photocatalytic H₂O-to-H₂O₂ reaction for sustainable organic wastewater treatment is environmentally attractive. Phenolic resins, inexpensive metal-free photocatalysts, are capable of harvesting visible light. Herein, novel nitrogen-enriched resin photocatalysts with a desired band-gap energy (1.83-1.98 eV) for harvesting visible light were prepared by copolymerization of resorcinol and melem for simultaneous photocatalytic H₂O-to-H₂O₂ and oxidation of methylene blue. Under visible light irradiation for 5 h, very high yields of H₂O₂ (870-975 μM of H₂O₂/g/h) by RFM resin photocatalysts could be achieved. The photocatalytic H₂O₂ for reactive oxygen species (^•OH) and photogenerated h⁺ could account for high conversion (40% conversion under visible light irradiation within 3 h) in oxidation of methylene blue. Such unique low-cost metal-free resins demonstrate the visible light photocatalytic H₂O-to-H₂O₂ reaction which can synergize with the oxidation of organic pollutants in wastewater.

Plasmonic and bi-piezoelectric enhanced photocatalysis using PVDF/ZnO/Au nanobrush

The photocatalytic degradation, as an environmental-friendly technology, has great significance for cost-effective and efficient catalysis processes, wherein piezo-photocatalysis can significantly increase the catalytic degradation rate using both solar and mechanical energy. Here, a ternary heterostructure PVDF/ZnO/Au (PZA) nanobrush photocatalyst with high piezo-photocatalytic efficiency was presented via low-temperature hydrothermal and chemical reduction methods. Under both solar and mechanical energy, the current response and degradation rate of the as-synthesized PZA nanobrush all increase significantly compared with that under solar alone and under mechanical energy alone, and the excellent recyclability is investigated. It is found that the PZA nanobrush with ultrasonic-assisted piezo-photocatalysis completely degrade MO of 20 mg/L in 60 min, which exhibits greater enhancement of photocatalytic activity than with stirring-assisted piezo-photocatalysis due to higher power. The high piezo-photocatalytic activity of PZA nanobrush is attributed to the surface plasmon resonance (SPR) coupling of Au and built-in electric field originating from the ZnO and PVDF, which can increase the absorption of visible light, promote the charge transfer and separation of photogenerated electrons/holes. This work introduces the SPR and bipiezotronic effect to improve plasmonic photocatalysis with PZA heterostructures, which offers a new solution in green technologies to design high-performance catalysts for the environmental remediation.

Synthesis of novel CuNb2O6/g-C3N4 binary photocatalyst towards efficient visible light reduction of Cr (VI) and dyes degradation for environmental remediation

The further development of an efficient and sustainable water treatment requires the development of a very active and controllable photocatalyst. The heterojunction is a promising site where the activity of such a photocatalyst can be enhanced. Organic dyes have become a severe concern in recent years owing to their significant presence in wastewater. Hexavalent Chromium (Cr (VI)) is a potential carcinogen also exhibiting great persistence in wastewater. So, a low-waste, high-performance materials is required to eliminate organic dyes and Cr (VI) from wastewater. In this study, CNO/g-CN (CuNb₂O₆/g-C₃N₄) photocatalyst synthesized via co-precipitation, followed by calcination which were characterized using physiochemical and photo-electrochemical approaches to identify their structural, photochemical and optical traits. The uniqueness of the synthesized photocatalyst is due to both its efficient photo-reduction of Cr (VI) and photo-degradation of Rhodamine B (RhB), Methylene Blue (MB) and Methyl Orange (MO) under visible light. The CNO/g-CN composite with 30% CNO heterojunctions exhibited the highest photocatalytic activity with Cr (VI) 92.80% photoreduction and efficiency degradation for RhB, MB, MO of 99.6%, 98.50%, 99.0%, respectively, with constant rate (k). This efficient photocatalytic activity is attributed to the lower recombination rate of electron-hole pairs. Free radical trapping experiments showed that ^•O₂^- and h⁺ play an important role in the photodegradation. The study, therefore, opens an alternative route in the synthesis of very efficient binary photocatalysts for application in environmental remediation.

Photoredox Cross-Dehydrogenative Coupling of N-Aryl Glycines Mediated by Mesoporous Graphitic Carbon Nitride: An Environmentally Friendly Approach to the Synthesis of Non-Proteinogenic α-Amino Acids (NPAAs) Decorated with Indoles

Indole-decorated glycine derivatives are prepared through an environmentally benign cross-dehydrogenative coupling between N-aryl glycine analogues and indoles (yield of ≤81%). Merging heterogeneous organocatalysis and photocatalysis, C–H functionalization has been achieved by selective C-2 oxidation of N-aryl glycines to afford the electrophilic imine followed by Friedel–Crafts alkylation with indole. The sustainability of the process has been taken into account in the reaction design through the implementation of a metal-free recyclable heterogeneous photocatalyst and a green reaction medium. Scale-up of the benchmark reaction (gram scale, yield of 69%) and recycling experiments (over seven runs without a loss of efficiency) have been performed to prove the robustness of the protocol. Finally, mechanistic studies were conducted employing electron paramagnetic resonance spectroscopy to unveil the roles of the photocatalyst and oxygen in the formation of odd-electron species.

Carbon-Based Nanocatalysts (CnCs) for Biomass Valorization and Hazardous Organics Remediation

The continuous increase of the demand in merchandise and fuels augments the need of modern approaches for the mass-production of renewable chemicals derived from abundant feedstocks, like biomass, as well as for the water and soil remediation pollution resulting from the anthropogenic discharge of organic compounds. Towards these directions and within the concept of circular (bio)economy, the development of efficient and sustainable catalytic processes is of paramount importance. Within this context, the design of novel catalysts play a key role, with carbon-based nanocatalysts (CnCs) representing one of the most promising class of materials. In this review, a wide range of CnCs utilized for biomass valorization towards valuable chemicals production, and for environmental remediation applications are summarized and discussed. Emphasis is given in particular on the catalytic production of 5-hydroxymethylfurfural (5-HMF) from cellulose or starch-rich food waste, the hydrogenolysis of lignin towards high bio-oil yields enriched predominately in alkyl and oxygenated phenolic monomers, the photocatalytic, sonocatalytic or sonophotocatalytic selective partial oxidation of 5-HMF to 2,5-diformylfuran (DFF) and the decomposition of organic pollutants in aqueous matrixes. The carbonaceous materials were utilized as stand-alone catalysts or as supports of (nano)metals are various types of activated micro/mesoporous carbons, graphene/graphite and the chemically modified counterparts like graphite oxide and reduced graphite oxide, carbon nanotubes, carbon quantum dots, graphitic carbon nitride, and fullerenes.

Environment Friendly g-C3N4-Based Catalysts and Their Recent Strategy in Organic Transformations

Organic molecules synthesized in an environmentally friendly manner have excellent therapeutic potential. The entire preparation technique was examined in the existence of a light source, implying that light has been replaced by heating and the usage of dangerous chemicals has decreased, resulting in less pollution of the environment. The advantages of these nanocarbon catalysts include high efficiency, environmentally friendly synthesis, eco-friendly, inexpensive, and non-corrodible. In organic transformations, solid metal base/metal-free catalysts produce better results. Here, the metal-free semiconductor g-C₃N₄ was used to demonstrate the catalytic behavior of organic conversions. g-C₃N₄ is a two-dimensional material and a p‑type semiconductor to enhance the photocatalytic activity. The excellent properties of g-C₃N₄ sheet lead to the support of metals to form metal-organic frameworks. Most of the reactions gained positive response under visible light irradiation. This review will inspire readers in widen the applications of g-C₃N₄ based catalyst in various organic transformation reactions.

Tuning the surface and optical properties of graphitic carbon nitride by incorporation of alkali metals (Na, K, Cs and Rb): Effect on photocatalytic removal of organic pollutants

Alkali metals have been known for their intercalation properties and can be employed for the separation of stacking in sheet-like materials. In this work, alkali metals (Na, K, Rb and Cs) have been systematically incorporated in varying concentrations in g-C₃N₄ sheets and their effect on resulting optical, surface and photocatalytic properties have been explored in detail. It was observed that the optical, electronic and surface properties of g-C₃N₄ were altered upon the incorporation of different alkali metal ions. The band gap and specific surface area of resulting materials were decreased as compared to the pristine g-C₃N₄. In addition, the alkali metal incorporation in g-C₃N₄ sheets showed the formation of cyanide groups and nitrogen vacancies in the resulted materials. Further, the photocatalytic activity of g-C₃N₄ and alkali metal incorporated g-C₃N₄ was calculated by studying the degradation of acid red 94 dye under visible light irradiation. It was observed that the photocatalytic activity of pristine g-C₃N₄ sheets was decreased with an increase in the concentration of alkali salt used during the synthesis of alkali metal incorporated g-C₃N₄. This decrease in the activity could arise due to the decreased surface area, detrimental amount of nitrogen vacancies and high concentration of alkali metal ions incorporated in the structural framework of g-C₃N₄ sheets. This work provides a unique example of the adverse effect of alkali metal ions on photocatalytic activity of g-C₃N₄ and paves future directions for the improvement of the performance of g-C₃N₄ based materials.

Visible-light-driven photocatalytic disinfection by S-scheme α-Fe2O3/g-C3N4 heterojunction: Bactericidal performance and mechanism insight

High-performance photocatalytic applications require to develop heterostructures between two semiconductors with matched band energy levels to facilitate charge-carrier separation. The S-scheme photocatalytic system has great potential to be explored, in terms of the improvement of charge separation, however, small efforts have been made in photocatalytic disinfection application. In this study, a non-toxic and low-cost S-scheme photocatalytic system composed of α-Fe₂O₃ and g-C₃N₄ was fabricated by in-suit production of g-C₃N₄ and firstly applied into water disinfection. The α-Fe₂O₃/g-C₃N₄ junction demonstrated an enhanced activity for photocatalytic bacterial inactivation, with the complete inactivation of 7 log₁₀ cfu·mL^-1 of Escherichia coli K-12 cells within 120 min under visible light irradiation. Its logarithmic bacterial inactivation efficiency was nearly 7 times better than that of single g-C₃N₄. The experimental results suggested that the effective prevention of charge-carrier recombination led to an improved generation of reactive oxygen species (ROSs), resulting in impressive disinfection performance. Moreover, the DNA gel electrophoresis experiments validated the reason for the irreversible death of bacteria, which was the leakage and destruction of chromosomal DNA. In addition, this S-scheme heterojunction also showed excellent photocatalytic disinfection performance in authentic water matrices (including tap water, secondary treated sewage effluent, and surface water) under visible light irradiation. Hence, the α-Fe₂O₃/g-C₃N₄ composite has great potential for sustainable and efficient photocatalytic disinfection applications.

Graphitic carbon nitride/NH2-MIL-101(Fe) composite for environmental remediation: Visible-light-assisted photocatalytic degradation of acetaminophen and reduction of hexavalent chromium

Herein, an efficient photocatalyst composed of graphitic carbon nitrate and iron-based metal-organic framework (g-C₃N₄/NH₂-MIL-101(Fe)) composite was fabricated by a solvothermal method for the degradation of acetaminophen (AAP) and reduction of Cr(VI) under sunlight illumination. The composite was confirmed by X-ray diffraction. UV-visible spectra showed that the bare g-C₃N₄, pure Fe-MOF, and composite harvest solar light effectively. The photocatalytic experiment indicated that the composite exhibited superior reduction efficiency of Cr(VI) (66%) compared to the bare g-C₃N₄ (35%) and pure Fe-MOF (51%) at pH 7. As the pH decreases from 9 to 2, the reduction efficiency increased. The highest Cr(VI) reduction (91%) was observed at pH 2. On the other hand, the catalyst degraded 94% of AAP at pH 7 compared to the bare g-C₃N₄ (42%) and pure Fe-MOF (60%) in the presence of hydrogen peroxide. A radical scavenger experiment endorsed that the generation of superoxide radicals was the main reason for the AAP degradation. The cyclic stability test indicated that there was no substantial decrease in the degradation efficiency of AAP after ten repeated cycles. The kinetic studies showed that the photodegradation of AAP and reduction Cr(VI) was well-fitted to the first-order kinetics. Gas chromatography-mass spectrometry analysis showed that hydroquinone, aliphatic carboxylic acids, monohydroxy, and dihydroxy paracetamol were the main products formed as a result of such degradation process. Therefore, the iron-based MOF and their composites can be used as effective photocatalysts for pollutants degradation.

Constructing porous intramolecular donor–acceptor integrated carbon nitride doped with m-aminophenol for boosting photocatalytic degradation and hydrogen evolution activity

A porous intramolecular D–A integrated carbon nitride with boosted photocatalytic activity was constructed via thermal melting followed by thermal copolymerization of m-aminophenol with urea.

The enhancement mechanism of ultra-active Ag3PO4 modified by tungsten and the effective degradation towards phenolic pollutants

A novel strategy of W modification was applied to overcome the disadvantages of Ag₃PO₄. Ultra-active Ag₃PO₄ with different W doping ratios were successfully synthesized by facile chemical precipitation method, among which 0.5%W-AP showed the best results. Meanwhile, the stability and yield were enhanced. XRD, Raman and ESR etc. were employed to investigate the morphology, structure and optical properties of samples. It was proved W⁶⁺ entered into the Ag₃PO₄ lattice, occupied the position of P⁵⁺ and doped in the form of WO₄^2-. The significant improvement of photocatalytic performance of W doped Ag₃PO₄ was attributed to the change of morphology, the decrease of particle size, the increase of crystallinity, the shrink of band gap energy and the reduction of photo-induced carriers recombination rate with W doping. The photocatalytic mechanism analysis showed h⁺ was the main oxidative species in the photocatalytic process, •O₂^- and •OH played minor roles. Under visible light irradiation, the impacts of the important operating parameters on the typical phenolic pollutants, phenol and bisphenol A, were evaluated with 0.5%W-AP. It was confirmed that 68% and 82% of phenol and bisphenol A were respectively degraded within 15 min and 40 min under optimized photocatalytic parameters: 0.4 g/L catalyst dosage, 20 mg/L pollutant concentration, pH 5.7 and 125 mW/cm² irradiation intensity, and the corresponding K' were 2.14 and 5.50 times of undoped samples. This work provides a new approach for effective degradation towards phenolic pollutants by Ag₃PO₄ with ultra-high photocatalytic activity, high applicability and enhanced stability and yield.

Facile fabrication of novel Fe3O4-SnO2-gC3N4 ternary nanocomposites and their photocatalytic properties towards the degradation of carbofuran

Herein, Fe₃O₄-SnO₂ nanoheterojunction has been synthesized and successfully encapsulated in gC₃N₄ matrix using a novel hydrothermal technique. The synthesized material was characterized using sophisticated analytical methods like XRD, TEM, BET, UV-Vis, VSM and XPS to evaluate structural, morphological, optical, magnetic and surface chemical properties. The hybrid nanostructure Fe₃O₄-SnO₂-gC₃N₄ has been utilized for the LED light-induced photocatalytic degradation of carbofuran. The catalyst exhibited notable photocatalytic performance under visible light with an efficiency of ~89% and pseudo first order rate constant of 0.015 min^-1. The result of change in variables like catalyst dose, pollutant concentration, pH and contact time on the photodegradation efficiency and degradation kinetics was studied. The incorporation of Fe₃O₄ improved the magnetic separation of the catalyst after several cycles of operation, thereby improving the practical utility of the catalyst system to tackle organic pollutants.

Synthesis and characterization of Cr2AlC MAX phase for photocatalytic applications

MAX phase, a layered ternary carbide/nitride, displays both ceramic and metallic properties, which has significantly attracted the materials research. In this work, Cr₂AlC MAX phase powder with high purity was fabricated via a facile and cost-effective pressure-less sintering methodology and utilized for photocatalytic degradation of different organic pollutants for the first time. Various characterization techniques were used for confirming the morphological and other physico-chemical properties of the catalyst. Cr₂AlC MAX phase with a low band gap of 1.28 eV has shown 99% efficiency in the degradation of malachite green, an organic pollutant under visible light irradiation. The scavenger studies conclude that, O₂^•-and h⁺ as the active species during the photocatalytic reaction. Furthermore, the kinetic study revealed that the reaction obeys pseudo-first-order kinetics and can be reused for four cycles without losing the activity. This novel approach can give new insight into the potential application of MAX phase materials in the field of wastewater treatment under visible light irradiation.

Microwave-assisted synthesis of ZnAl-LDH/g-C3N4 composite for degradation of antibiotic ciprofloxacin under visible-light illumination

Ciprofloxacin (CIP) is a fluoroquinolone family antibiotic pollutant. CIP existence in water environment has been rising very fast in day-to-day life and subsequently, it gives enormous health issues for humans because of its potent biological activity. To encounter this, current researchers are focusing on the development of highly efficient visible light semiconductor nanocomposites with potential photocatalytic activity. In the present work, we have successfully synthesized highly efficient zinc-aluminum layered double hydroxides with graphitic carbon nitride (ZALDH/CN) composites via a simple microwave irradiation method first time for the degradation of CIP under visible light. The fabricated materials are subsequently characterized by various spectroscopic techniques. UV-Vis DRS, TRFL, XRD, FT-IR, BET, FE-SEM, TEM, and XPS for optical, crystal structure, morphological, and elemental analysis. The main reactive intermediates which are formed during the photocatalytic degradation process were analyzed by LC-MS analysis. It is worth to note that, the optimized ZALDH/CN-10 composite showed the highest photo-degradation rate constant of 1.22 × 10^-2 min^-1 with 84.10% degradation is higher than bare CN and ZALDH photocatalysts. Based on the electron-hole pair trapping experiment results, possible CIP photo-degradation mechanism was also explained in the present study. With all results, this work demonstrates the ZALDH/CN composite materials showed a high synergistic effect with more specific surface area. Highest specific surface area leads to enhanced visible light adsorption capacity. Subsequently improved number of catalytically active sites. Furthermore, as compared with pure materials, composites of ZALDH/CN are having low electron-hole pair recombination. Consequently, the composites ZALDH/CN showed superior photocatalytic activity for antibiotic pollutant CIP degradation under visible-light illumination.

In-situ fabrication of novel flower like MoS2/CoTiO3 nanorod heterostructures for the recyclable degradation of ciprofloxacin and bisphenol A under sunlight

Effectual degradation of toxic water contaminants is a crucial step in water purification and designing an efficient semiconductor based hybrid structure photocatalyst is a good approach to achieve this. Benefiting from the combination of semiconductors, a series of novel visible-light active flower-like MoS₂/CoTiO₃ nanorod heterostructures with excellent morphological contact interface were prepared through a facile in-situ hydrothermal process. These heterostructures were well characterized and demonstrated high photocatalytic performance for ciprofloxacin (CIP) and bisphenol A (BPA) under sunlight irradiation. Compared to pristine CoTiO₃ and MoS₂, the optimal catalyst (5 wt% MoS₂/CoTiO₃) presented 39.97 and 22.32 times higher activity for CIP degradation and 26.85 and 15.66 times higher activity for BPA degradation, respectively. This improved activity can be accounted for the effective interfacial contact which promotes the efficient charge carriers separation and reduce its recombination. The catalyst exhibited decent stability and was potentially reused for five cycles without significant loss in activity. Furthermore, based on active species scavenging experiments the plausible photodegradation mechanism is discussed in detail.

Visible light-conducting polymer nanocomposites as efficient photocatalysts for the treatment of organic pollutants in wastewater

This review compiles recent advances and challenges on photocatalytic treatment of wastewater using nanoparticles, nanocomposites, and polymer nanocomposites as photocatalyst. The review provides an overview of the fundamental principles of photocatalytic treatment along the recent advances on photocatalytic treatment, especially on the modification strategies and operational conditions to enhance treatment efficiency and removal of recalcitrant organic contaminants. The different types of photocatalysts along the key factors influencing their performance are also critically discussed and recommendations for future research are provided.

Photocatalytic Penicillin Degradation Performance and the Mechanism of the Fragmented TiO2 Modified by CdS Quantum Dots

In this study, a novel method was adopted to construct a CdS-TiO₂ heterostructure to degrade penicillin under sunlight. A potato extract was used during the synthesis process of CdS QDs as a stabilizer and a modifier. The CdS-TiO₂ composite with a heterostructure delivers high photocatalytic degradation efficiency. In detail, 0.6 mg/mL of CdS-TiO₂ can successfully decompose penicillin after 2 h, and 5‰ CdS-TiO₂ shows the optimal degradation efficiency with the degradation rate reaching 88%. Furthermore, the underlying mechanisms of the penicillin decomposition reaction were investigated by the EPR test and trapping experiment. It was found that the high photocatalytic degradation efficiency was attributed to the heterojunction of CdS-TiO₂, which successfully suppresses the recombination of the conduction band of CdS and the valence band of TiO₂. Moreover, it was confirmed that the reaction is the O₂-consuming process, and introducing O₂ can greatly accelerate the generation of a superoxide radical during the photocatalytic degradation process, which eventually improves the degradation of penicillin and shortens the degradation time. Finally, this work provides the possible penicillin degradation pathways, which will inspire the researchers to explore and design novel photocatalysts in the field of wastewater treatment in the future.