Visible Light Photocatalysis Research Articles

Transition metal-doped CuO nanosheets for enhanced visible-light photocatalysis

Herein, we report a comprehensive investigation of Zn- and Fe-doped CuO nanosheets as promising photocatalysts for the degradation of organic dyes. These nanosheets were synthesized via a hydrothermal process and thoroughly characterized through spectroscopic and microscopic techniques. Photocatalytic degradation experiments using methylene blue (MB) and malachite green (MG) revealed a marked increase in efficiency within the doped CuO nanosheets when compared to their undoped counterparts. The degradation kinetics showed MB following a zero-order model and MG following a first-order model. In particular, Zn and Fe-doped CuO nanosheets outperformed undoped CuO, degrading 66% and 73% of MB and 85% and 90% of MG within specific timeframes, while undoped CuO achieved 62% and 76% degradation, respectively. Computational analysis conducted with Gaussian 09 software pinpointed reactive sites susceptible to radical and electrophilic attacks in the dyes. The enhanced performance is credited to transition metal doping, which induces a red shift in the optical band gap, thereby improving visible light absorption and diminishing electron-hole recombination. This study underscores the potential of transition metal doping in bandgap engineering for efficient visible light-assisted photocatalytic remediation.

Bio-Inspired Supramolecular Self-Assembled Carbon Nitride Nanostructures for Photocatalytic Water Splitting.

Fast production of hydrogen and oxygen in large amounts at an economic rate is the need of the hour to cater to the needs of the most awaited hydrogen energy, a futuristic renewable energy solution. Production of hydrogen through simple water splitting via visible light photocatalytic approach using sunlight is considered as one of the most promising and sustainable approaches for generating clean fuels. For this purpose, a variety of catalytic techniques and novel catalysts have been investigated. Among these catalysts, carbon nitride is presently deemed as one of the best candidates for the visible light photocatalysis due to its unique molecular structure and adequate visible-range bandgap. Its bandgap can be further engineered by structural and morphological manipulation or by doping/hybridization. Among numerous synthetic approaches for carbon nitrides, supramolecular self-assembly is one of the recently developed elegant bottom-up strategies as it is bio-inspired and provides a facile and eco-friendly route to synthesize high surface area carbon nitride with superior morphological features and other semiconducting and catalytic properties. The current review article broadly covers supramolecular self-assembly synthesis of carbon nitride nanostructures and their photocatalytic water-splitting applications and provides a comprehensive outlook on future directions.

Efficient visible-light photocatalysis of chloramphenicol using novel engineered biochar-based Ti-doped Bi2WO6 composite: Mechanisms, degradation pathways, and applications

A novel engineered biochar (ACB)-based Ti-doped Bi2WO6 composite (Ti-Bi2WO6@ACB) was synthesized via a one-step hydrothermal reaction for the efficient degradation of chloramphenicol (CAP) and extensive environmental applications. Multiple characterization techniques, CAP degradation effects, total organic carbon (TOC) removal, effects of environmental factors, recycling tests, actual wastewater treatment, enhancement strategies, and disinfection effects were systematically evaluated. It was found that Ti-Bi2WO6@ACB is a Ti3+ self-doped TiO2/Bi2WO6/ACB ternary heterogeneous photocatalyst. The introduction of ACB and Ti doping enhanced the elemental composition, oxygen-containing functional groups, defect structure (oxygen vacancies), visible-light absorption, and active sites. Moreover, Ti-Bi2WO6@ACB effectively inhibited the recombination of photogenerated carriers. The removal efficiency of Ti-Bi2WO6@ACB for 50 mg⋅L−1 CAP was 92.44 % at 120 min of irradiation, and the TOC removal rate was 67.72 %, which was significantly higher than that of the control treatment. Ti-Bi2WO6@ACB is reusable and photostable, with approximately 99 % sterilization of Staphylococcus aureus and Escherichia coli within 10 min of light irradiation and 48 h of cultivation. The addition of H2O2, ultrasonication, heating, and blowing air in the system improved the photocatalytic efficiency. The ultrasound enhancement mechanisms are related to the effects of cavitation, microjets, and photocatalysis coupled with sonocatalysis. CAP degradation was dominated by OH, O2−, and h+. The doping of Ti3+/TiO2 generated more defects and O2−, and the ACB acted as a carrier to prevent the agglomeration of TiO2 and Bi2WO6. Further, the degradation process of CAP was documented and the degradation pathways may include hydroxylation addition, methanol denaturation, substitution, C–N bond breaking, oxidation, hydrolysis, and decarboxylation reactions. The research presents fresh insights into the development of high-performance engineered biochar-based composite for environmental detoxification.

Visible-Light-Active BiOI/TiO2 Heterojunction Photocatalysts for Remediation of Crude Oil-Contaminated Water.

In this study, BiOI-sensitized TiO2 (BiOI/TiO2) nanocomposites with different levels of BiOI deposited via sequential ionic layer adsorption and reaction (SILAR) have been explored for the degradation of methyl orange, 4-chlorophenol (4-CP), and crude oil in water under visible (>400 nm) irradiation with excellent degradation performance. The reaction progress for methyl orange and 4-chlorophenol was monitored by a UV-vis spectrophotometer, and the degradation of the crude oil hydrocarbons was determined by GC-MS. The BiOI/TiO2 heterojunction improves separation of photogenerated charges, which enhances the degradation efficiency. Evaluation of the visible-light photocatalytic performance of the synthesized catalysts against methyl orange degradation confirmed that four SILAR cycles are the optimal deposition condition for the best degradation efficiency. The efficiency was further confirmed by degrading 4-CP and crude oil, achieving 38.30 and 85.62% degradation, respectively, compared with 0.0% (4-CP) and 70.56% (crude oil) achieved by TiO2. The efficiency of TiO2 in degrading crude oil was mainly due to adsorption along with photolysis. This study provides a simple and cost-effective alternative to traditional remediation methods requiring high energy consumption for remediation of crude oil-polluted water and refinery wastewater using visible-light photocatalysis along with adsorption.

Photocatalytic properties and antibacterial mechanisms of microbial-derived ZnS/CuS nanocomposites

The urgency to combat antibiotic-resistant bacterial infections requires new antibacterial materials and methods. Utilizing Shewanella onesidensis metabolism, biological zinc/copper sulfide (bio-ZnS/CuS) composites with excellent visible-light photocatalysis effects and broad-spectrum antibacterial activity were synthesized. During synthesis, over 95% of heavy metal ions were recovered from wastewater through co-precipitation to form metal sulfides. The biocomposite with Zn/Cu ratio at 1/9 (Zn1S/Cu9S) showed the best photocatalytic performance. Under visible-light catalysis of Zn1S/Cu9S, 98.02 ± 0.13% of methylene blue and 81.74 ± 2.12% of rhodamine B were rapidly removed, while sterilization rates exceeded 99.99% against Escherichia coli and 99.98% against Staphylococcus aureus. The biocomposite showed a nanostructure with sizes between 5 and 20 nm. Characterizations including X-ray photoelectron spectroscopy, UV-Vis absorption spectra, and photoluminescence spectra proved its excellent visible light response capacity (>400 nm) and energy utilization efficiency. Scavenging experiments demonstrated photogenerated holes and hydrogen peroxide as the major reactive oxygen species (ROS) that induce bacterial death. Toxicological studies revealed that ROS attacked bacterial cells by damaging membranes, inhibiting energy metabolism, breaking the antioxidant defense system, and compromising DNA integrity. This research presents innovative solutions for tackling bacterial infections and heavy metal contamination through the advancement of microbial synthetic functional nanomaterials.

Fabrication of next-generation multifunctional LBG-s-AgNPs@ g-C3N4 NS hybrid nanostructures for environmental applications

Toxic industrial wastes and microbial pathogens in water pose a continuous threat to aquatic life as well as alarming situations for humans. Developing advanced materials with an environmentally friendly approach is always preferable for heterogeneous visible light photocatalysis. As a green reducing tool, LBG-s-AgNPs@ g-C3N4 NS hybrid nanostructures were anchored onto graphitic carbon nitride (g-C3N4) using an environmentally friendly approach of anchoring/decorating AgNPs onto g-C3N4. With the help of advanced techniques, the fabricated hybrid nanostructures were characterized. Using a sheet like matrix of g-C3N4, nanosized and well-defined uniform AgNPs displayed good antibacterial activity as well as superior photodegradation of hazardous dyes, including methylene blue (MB) and Rhodamine B (RhB). Based on the disc diffusion method, three pathogenic microorganisms of clinical significance can be identified by showing the magnitude of their susceptibility. As a result, the following antimicrobial potency was obtained: E. coli ≥ M. luteus ≥ S. aureus. In this study, green synthesized (biogenic) AgNPs decorated with g-C3N4 were found to be more potent antimicrobials than traditional AgNPs. Under visible light irradiation, LBG-s-AgNPs@g-C3N4 NS (0.01 M) demonstrated superior photocatalytic performance: ∼100% RhB degradation and ∼99% of MB degradation in 160 min. LBG-s-AgNPs@g-C3N4 NS showed the highest kinetic rate, 3.44 × 10−2 min−1, which is 27.74 times for the control activity in case of MB dye. While in case of RhB dye LBG-s-AgNPs@g-C3N4 NS showed the highest kinetic rate, 2.26 × 10−2 min−1, which is 17.51 times for the control activity. Due to the surface plasmon resonance (SPR) and reduction in recombination of the electrons and holes generated during photocatalysis, anchoring AgNPs to g-C3N4 further enhanced the photocatalytic degradation of dyes. Using this photocatalyst, hazardous dyes can be efficiently and rapidly degraded, allowing it to be applied for wastewater treatment contaminated with dyes. It also showed remarkable antimicrobial activity towards Gram-ve/Gram + ve pathogens.

Diastereoselective Hydroacylation of Cyclopropenes by Visible-Light Photocatalysis.

An efficient and general strategy for the hydroacylation of cyclopropene is disclosed for synthesizing various 2-acylcyclopropane derivatives under mild reaction conditions. High functional group tolerance of this protocol features a novel route to access a divergent synthesis of acylated cyclopropane in a diastereoselective manner by photoinduced decarboxylation of α-ketoacid followed by acyl radical addition to cyclopropene. Additionally, the regioselective addition of acyl radical at the least substituted olefinic carbon center with trans-selective fashion makes this protocol more appealing toward natural product development.

Adsorption and Visible Photocatalytic Synergistic Removal of a Cationic Dye with the Composite Material BiVO4/MgAl–LDHs

Adsorption and photocatalysis are effective in removing organic pollutants from wastewater. This study is based on the memory effects of MgAl–layered double hydroxides (MgAl–LDHs) after high-temperature calcination. By introducing bismuth vanadate (BiVO4) during the reformation of the layered structure via contact with water, a composite material BiVO4/MgAl–LDHs with enhanced adsorption and visible light catalytic performance was synthesized. The effects of the calcination temperature, ratio, initial methylene blue (MB) concentration, and catalyst dosage on the adsorption and photocatalytic performance were investigated. The BiVO4/MgAl–LDHs showed better photocatalytic performance than the pure BiVO4 and MgAl–LDHs. Under the optimal conditions, the proportion of MB adsorbed in 20 min was 66.1%, and the percentage of MB degraded during 100 min of photolysis was 92.4%. The composite photocatalyst showed good chemical stability and cyclability, and the adsorption-degradation rate was 86% after four cycles. Analyses of the adsorption and photocatalytic mechanisms for the composite material showed that synergistic adsorption and visible light photocatalysis contributed to the excellent catalytic performance of the BiVO4/MgAl–LDHs. A highly adsorbent photocatalytic composite material exhibiting outstanding performance was prepared via a simple, cost-effective, and environmentally friendly method, providing reference information for the removal of organic pollutants from liquids.

Merging Visible Light Photocatalysis and P(III)‐Directed C−H Activation by a Single Catalyst: Modular Assembly of P‐Alkyne Hybrid Ligands

AbstractMetal‐catalyzed C−H activation strategies provide an efficient approach for synthesis by minimizing atom, step, and redox economy. Developing milder, greener, and more effective protocols for these strategies is always highly desirable to the scientific community. In this study, the utilization of a single rhodium complex enabled the visible‐light‐induced late‐stage C−H activation of biaryl‐type phosphines with alkynyl bromides, employing inherent phosphorus atoms as directing groups. This chemistry combines P(III)‐directed C−H activation with visible light photocatalysis, under exogenous photosensitizer‐free conditions, offering a unique platform for ligand design and preparation. Furthermore, this study also explores the asymmetric catalysis and coordination chemistry of the resulting P‐alkyne hybrid ligands with specific transition metals. Experimental results and density functional theory calculations demonstrate the mechanistic intricacies of this transformation.

Merging Visible Light Photocatalysis and P(III)-Directed C-H Activation by a Single Catalyst: Modular Assembly of P-Alkyne Hybrid Ligands.

Metal-catalyzed C-H activation strategies provide an efficient approach for synthesis by minimizing atom, step, and redox economy. Developing milder, greener, and more effective protocols for these strategies is always highly desirable to the scientific community. In this study, the utilization of a single rhodium complex enabled the visible-light-induced late-stage C-H activation of biaryl-type phosphines with alkynyl bromides, employing inherent phosphorus atoms as directing groups. This chemistry combines P(III)-directed C-H activation with visible light photocatalysis, under exogenous photosensitizer-free conditions, offering a unique platform for ligand design and preparation. Furthermore, this study also explores the asymmetric catalysis and coordination chemistry of the resulting P-alkyne hybrid ligands with specific transition metals. Experimental results and density functional theory calculations demonstrate the mechanistic intricacies of this transformation.

Enhanced degradation of micropollutants by visible light photocatalysts with strong oxygen activation ability

Visible light photocatalysis is widely considered a sustainable approach to break down micropollutants without chemical addition. To promote the output of photogenerated carriers under visible light, a Z-scheme plasmonic photocatalyst Bi-CeO2/Ag0/BiO2 was designed and fabricated to activate dissolved oxygen in water for micropollutant degradation. The doped Bi not only improved the separation of electron-hole, but also narrowed the band gap of CeO2 to enhance its absorption of visible light. Notably, metallic silver (Ag0) works as an electronic transmission vehicle from Bi-CeO2 to BiO2 in a Z-scheme mechanism. Likewise, the surface plasmon resonance effect of Ag0 also enhanced the absorption of visible light. Furthermore, the Bi doping induced abundant surface oxygen vacancies on CeO2 for enhanced capability and selectivity towards O2 adsorption and activation, which favored the generation of O2•− by photogenerated electrons to degrade sulfamethoxazole, enrofloxacin, and bisphenol A. Theoretical calculation results also confirmed the O2•−-driven degradation pathway for sulfamethoxazole. Therefore, the Z-scheme Bi-CeO2/Ag0/BiO2 not only extends the photocatalytic reactivity of CeO2-based catalysts to the visible light range, but also provides a chemical-free method to effectively degrade micropollutants.

Process efficiency and life cycle assessment of novel waste-derived Chl/TiO2 photocatalyst for rhodamine B removal

Visible-light photocatalysis is a promising approach toward cleaner production and environmental impact reduction. Dye sensitization of TiO2 nanoparticles with chlorophyll (Chl) pigments is a potential alternative for the improvement of photocatalysis efficiency but must be modified for higher activity in visible light. Herein, a novel and green Chl/TiO2 photocatalyst was constructed for rhodamine B removal using the TiO2 waste of the gas refinery Clause process, sensitized with extracted chlorophyll from orange tree leaf pigments. The effects of pH, pigment ratios, photocatalyst dosage, and temperature on the Chl/TiO2 photocatalyst performance accompanied by its environmental impacts were investigated. The results indicated that the pristine TiO2 before sensitization could degrade ~30 % of rhodamine B while the photocatalytic activity was enhanced to ~98 % after modification by 0.6 wt% chlorophyll pigments. The optimum conditions were achieved at 25 mg/l Chl/TiO2, pH = 4, and 50 mg/l rhodamine B after 2 h irradiation of visible light (LED lamp 50 W). Recycling studies showed a rhodamine B decolorization of 90 % after 5 cycles and demonstrated that Chl/TiO2 is a promising heterogeneous photocatalyst for the long-term removal of dyes from wastewater. The Chl/TiO2 followed the pseudo-first-order kinetic model and illustrated negative impacts on global warming (6.3 kg CO2) and terrestrial ecotoxicity (10.7 kg 1.4-DCB) from a life cycle assessment (LCA) perspective, originating from electricity consumption and acetone. Summing up, the present study offers a new and eco-efficient photocatalyst to facilitate wastewater treatment in real-world applications and gives perspectives to manage its long-term concern.

Experimental and Computational Studies on Cobalt(I)‐Catalyzed Regioselective Allylic Alkylation Reactions

AbstractHere, we report the development of cobalt(I)‐catalyzed regioselective allylic alkylation reactions of tertiary allyl carbonates with 1,3‐dicarbonyl compounds. A family of well‐defined tetrahedral cobalt(I) complexes bearing commercially available bidentate bis(phosphine) ligands [(P,P)Co(PPh3)Cl] are synthesized and explored as catalysts in allylic alkylation reactions. The catalyst [(dppp)Co(PPh3)Cl] (dppp=1,3‐Bis(diphenylphosphino)propane) enables the alkylation of a large variety of tertiary allyl carbonates with high yields and excellent regioselectivity for the branched product. Remarkably, this methodology is selective for the activation of tertiary allyl carbonates even in the presence of secondary allyl carbonates. This contrasts with the selectivity observed in cobalt‐catalyzed allylic alkylations enabled by visible light photocatalysis. Mechanistic insights by means of experimental and computational investigations support a Co(I)/Co(III) catalytic cycle.

Experimental and Computational Studies on Cobalt(I)-Catalyzed Regioselective Allylic Alkylation Reactions.

Here, we report the development of cobalt(I)-catalyzed regioselective allylic alkylation reactions of tertiary allyl carbonates with 1,3-dicarbonyl compounds. A family of well-defined tetrahedral cobalt(I) complexes bearing commercially available bidentate bis(phosphine) ligands [(P,P)Co(PPh3 )Cl] are synthesized and explored as catalysts in allylic alkylation reactions. The catalyst [(dppp)Co(PPh3 )Cl] (dppp=1,3-Bis(diphenylphosphino)propane) enables the alkylation of a large variety of tertiary allyl carbonates with high yields and excellent regioselectivity for the branched product. Remarkably, this methodology is selective for the activation of tertiary allyl carbonates even in the presence of secondary allyl carbonates. This contrasts with the selectivity observed in cobalt-catalyzed allylic alkylations enabled by visible light photocatalysis. Mechanistic insights by means of experimental and computational investigations support a Co(I)/Co(III) catalytic cycle.

Removal of cadmium through adsorption and visible light photocatalysis from polluted wastewater by mechano-chemically synthesized FeS nanopowder

Removal of cadmium through adsorption and visible light photocatalysis from polluted wastewater by mechano-chemically synthesized FeS nanopowder

A study on the applicability of thin film over powder for visible light photocatalysis

Copper oxide nanoparticles (CuO-NPs) powder and copper oxide thin films (CuO-TFs) have been studied to reveal their applicability in photodegradation. The CuO-TFs are found to be better photocatalysts as compared to powder form in the photodegradation of methylene blue (MB) dye solution. The photocatalytic effect of CuO-TFs (0.83 mg of deposited CuO), CuO-NPs powder (0.83 mg), and self-degradation of MB dye solution are found to be 83.91%, 52.40%, and 25.8% respectively. The FESEM images reveal that CuO-NPs are more prone to agglomeration than CuO-TFs. The average particle size of CuO-NPs and CuO-TFs are found to be 6.90 nm and 6.07 nm respectively. XPS analysis reveals lesser oxygen defects in CuO-TFs, which results in higher MB photodegradation activity as compared to CuO-NPs. The specific surface area of CuO-NPs and CuO-TFs are found to be 33.714 m2/g and 20.668 m2/g. The easy reusability and photocatalytic performance manifest CuO-TFs as better photocatalysts.

Mesoporous black TiO2 hollow shells with controlled cavity size for enhanced visible light photocatalysis.

Black TiO2 formed by introducing lattice disorder into pristine TiO2 has a narrowed band gap and suppresses the recombination of charge carriers. This provides a potential strategy for visible light photocatalysis. However, the microstructural design of black TiO2 for a higher optimization of visible light is still in high demand. In this work, we proposed the preparation of black TiO2 hollow shells with controllable cavity diameters using silica spheres as templates for the cavities and the NaBH4 reduction method. The decreased cavity size resulted in a hollow shell with an enhanced visible-light absorption and improved photocatalytic performance. Moreover, we demonstrated that this cavity can be combined with gold nanoparticles (AuNPs) to form AuNPs@black TiO2 yolk-shells. The AuNPs provided additional visible light absorption and promoted the separation of photogenerated carriers in the yolk-shell structures. This further improved the photocatalysis, the degradation rate of Cr(VI) can reach 0.066 min-1. Our work evaluated the effect of the cavity size on the photocatalytic performance of hollow and yolk-shell structures and provided concepts for the further enhancement of visible-light photocatalysis.

Hydrogen production by visible light photocatalysis with Chl@g-C3N4/Ti3C2Tx S-scheme heterojunction

Sustainable conversion of solar energy to hydrogen energy by photocatalytic splitting of water through the use of semiconductor photocatalytic materials is considered to be a promising and sustainable alternative proposal to replace conventional fossil fuels. However, efficient solar-driven photocatalytic hydrogen production has remained a great challenge due to the prevailing problems of existing semiconductor photocatalytic materials. It is shown that constructing heterostructures is a very powerful way to improve the photocatalytic hydrogen production capacity of composites under visible light. Therefore, in this work, an organic heterojunction structure based on chlorophyll (Chl) molecules and graphitic carbon nitride (g-C3N4) is reported and exploited for efficient solar energy-driven photocatalytic hydrogen evolution reaction (HER). Meanwhile, noble metal-free photocatalysts were successfully constructed with Ti3C2Tx MXene nanosheets through a simple stepwise complexation process of Chl, g-C3N4, and Ti3C2Tx for the achievement of HER for the photocatalytic decomposition of water. The results show that the optimal Chl@g-C3N4/Ti3C2Tx organic heterojunction composite has a remarkably advanced HER performance of 131 μmol/h/gcat, as compared with the traditional Chl@Ti3C2Tx and g-C3N4/Ti3C2Tx composites. The results provide new ideas for exploring MXene based catalysts for highly efficient conversion of solar energy.

Metal-free synthesis of nitriles from aldehydes and ammonium by visible-light photocatalysis

Metal-free synthesis of nitriles from aldehydes and ammonium by visible-light photocatalysis

Synthesis and characterization of enhanced visible light-driven C-doped ZnO-2D GO/g-C3N4 heterojunction photocatalyst

Well-designed 2D graphene oxide-modified polymeric graphitic carbon nitride composite nanosheets (GO/g-C3N4) as desirable sensitizers and catalytic substrates for optimising the visible light-driven photocatalytic performance of ZnO-based photocatalysts have been investigated. Herein, 2D GO/g-C3N4 composite nanosheets are first developed by ultrasonic and hydrothermal methods, and then coupled with ZnO nanoparticles to prepare a series of ternary GO/g-C3N4-ZnO heterojunction composites with vary GO loading concentrations. Characterization of the photocatalysts was carried out by SEM, TEM, XPS, XRD, DRS, photoluminescence (PL) spectroscopy; evaluation of the visible light photocatalytic activity was performed by degrading an aqueous methylene blue (MB) solution. XPS studies showed that the formation of a ZnC bond in 15 % GO/g-C3N4-ZnO is due to the replacement of oxygen by carbon, indicating the construction of a hybrid heterojunction composed of C-doped ZnO and visible light sensitive GO/g-C3N4 composite nanosheets. The photodegradation performance of 15 % GO/g-C3N4-ZnO is 5.3, 2.9, and 2.2 times higher than that of pure ZnO, g-C3N4, and g-C3N4-ZnO, respectively. Due to the increase of GO loading in GO/g-C3N4 composite nanosheets, some characteristics of efficient visible light photocatalysis, such as a wider light absorption range, fluorescence quenching in the PL spectrum, excellent optical response in photocurrent measurement, and good stability，were confirmed and can be attributed to the electronic interaction between heterostructures and the effective transfer of photogenerated electrons in these ternary nanocomposites. This work may provide a new promising pathway for the construction of easily prepared 2D GO/g-C3N4 hybrid-modified nanocomposites, which is a hopeful material for wastewater control.