Photocatalysis: Research and Potential Open Access

Photocatalysis: Research and Potential—A New Means to Better Master Your Publishing Policy and Improve the Visibility of Your Articles

Plasmon Enhanced Nickel(II) Catalyst for Photocatalytic Lignin Model Cleavage

Photocatalytic-induced cleaving of the ether C–O bond in model lignin compounds was studied with a closely-coupled compo-site material consisting of Ni(OH)₂ and gold nanoparticles (NPs) on a zirconia support (Au/ZrO₂–Ni(OH)₂). The three important ether bond types consisting of α-O-4, β-O-4, and 4-O-5 linkages can all be cleaved using this catalyst at reaction temperatures 40, 85 and 95 °C when under low-flux visible light irradiation. The Au NPs action as a light-harvesting antenna provided light-generated hot electrons that reduced Ni²⁺ to Ni⁰. The Ni⁰ was the active catalytic site where reductive cleavage of ether C–O bonds occurred while it was oxidized to Ni²⁺ to complete the catalysis cycle. The plasmonic antenna system with supported Ni(OH)₂ exhibited better ability for the catalytic reductive ether cleavages under visible light irradiation compared to photocata-lysts of Au NPs and Ni²⁺ ions immobilized on alumina fibers.

SnS₂ Quantum Dots Decorated MoS₂ Nanosheets Enabling Efficient Photocatalytic H₂ Evolution in CO₂ Saturated Water

SnS₂/MoS₂ heterojunction nanocomposite was prepared by a one-step hydrothermal synthesis method. The nanocomposite exhibited much improved photocatalytic hydrogen evolution performance in CO₂ saturated solution compared with pure MoS₂ and SnS₂ samples. The improved photocatalytic activity was attributed to the S-scheme heterojunction structure between SnS₂ quantum dots and MoS₂ nanosheets which facilitate electron-hole separation both in MoS₂ and SnS₂. In the S-scheme structure, the strong reduction ability of SnS₂ quantum dots was well maintained for the improved H₂ evolution. In situ DRIFT studies allowed us to suggest reaction pathways from CO₂ and H₂O to photocatalytic H₂, CO, and CH₄ generation.

Photocatalytic Efficiency of Suspended and Immobilized TiO₂ P25 for Removing Myclobutanil, Penconazole and Their Commercial Formulations

Fungicide application in viticulture is a major source of surface and groundwater contamination. It is therefore essential to find solutions to stop this environmental pollution. Heterogeneous photocatalysis is an advanced oxidation method for the degradation and mineralization of organic pollutants in water. TiO₂ P25 photocatalyst in suspension has been used for removing the fungicides Myclobutanil and Penconazol, and their respective commercial formulations Systhane and Topas, in contaminated water. The apparent kinetic constants k_app of fungicides removal over 30 min batch treatment was higher for a mixture of pure molecules of Myclobutanil and Penconazol than for a mixture of their commercial formulations (17.5 × 10⁻³ by comparison with 10.3 × 10⁻³ min⁻¹ for Myclobutanil, and 10.0 × 10⁻³ by comparison with 2.80 × 10⁻³ min⁻¹ for Penconazol). TOC removal constants k_TOC were similar for the two mixtures, due to the presence of mineral and organic additives in the commercial formulations. To easily recover the photocatalyst after fungicide removal, TiO₂ P25 has been supported on β-SiC foam. Fungicides degradation was lower with supported photocatalysts than with the suspension of photocatalyst nanoparticles (NPs) because of a lower concentration of active sites on the supported photocatalyst than in the catalyst suspension. However, catalyst recovery and reuse after fungicide removal is obviously easier with TiO₂/β-SiC material than with a suspension of TiO₂ which requires long and expensive filtration operations.

Potential Role of Exciton in Photocatalysis

This article commemorates the outstanding Russian scientists E.F. Gross and A.N. Terenin. It revisits their successors’ efforts to develop Terenin’s idea of using excitons, discovered by Gross, for photocatalytic redox reactions on wide-gap semiconductors. Terenin proposed ZnO as the subject of study. To explore the possibility of replacing photogenerated electrons and holes in a redox reaction by an exciton being a quasi-neutral particle, the test reaction of the photoactivated oxygen isotope exchange (POIE) was studied. It was found that many years of initial unsuccessful attempts were due to the fact that the exciton energy is spent on luminescence. In our experiments, the excitons decayed non-radiatively, and the long-lived electron-donor F-type and hole V-type active centers were formed by creating the 2D surface nanostructure ZnO/ZnO_1−x/O⁻. These centers allowed to obtain the reaction efficiency 5–8 times higher than with the interband transitions. Thus, the developed 2D surface nanostructure ZnO/ZnO_1−x/O⁻ resolved the problem of using an exciton in photocatalysis and demonstrated the perspective of this nanostructure as an efficient photocatalyst.

New Trends on Photoswitchable Antibiotics: From Syntheses to Applications

Antibiotics are excreted in the environment after being used to treat bacterial infections in human and animals. These residues are poorly eliminated by the actual wastewater treatment processes, affecting animal, human and environmental health. This has led to the emergence of antibiotic resistance in bacterial pathogens. To combat this problem, photopharmacology has emerged in the last decades. This approach, based on the coupling of a drug with a photochromic component, is a promising way to control antibiotic activity by light irradiation and consequently limit antibioresistance. Thus, this review summarizes the study on the effect of the irradiation light on the antimicrobial activity of coupling compounds.

Fibrous SiC-based Mesoporous Solids for the Photocatalytic Degradation of Organic Pollutants under Artificial Light

SiC-based mesoporous solids with fibrous nanostructure were prepared by impregnation of a polycarbosilane precursor on annealed polyacrylonitrile (PAN) fibers and subsequent pyrolysis. The obtained material exhibits a mesoporous structure and has a specific surface area of ~20 m²/g. It has a semiconducting electronic character with a bandgap of 2.65 eV, i.e., in the visible range. Adsorption tests of methylene blue were performed on the material under dark conditions, which showed an adsorption amount of 78 wt%. The photocatalytic activity of the material was then evaluated for the degradation of the dye under artificial daylight irradiation over a period of 7 h. A degradation of 94 wt% was achieved. Regeneration and reuse of the material was also tested and resulted in 97 wt% degradation after reuse, indicating potential interest of the material as a contactor in environmental remediation devices.

Benzene Bridged Carbon Nitride for Efficient Photocatalytic Hydrogen Evolution

Turing the electronic structure by inserting certain functional groups in graphitic carbon nitride (g-C₃N₄, CN for short) skeleton through molecular doping is an effective way to improve its photocatalytic performance. Herein, we prepare a benzene bridged carbon nitride (BCN) by calcining urea and 1,3,5-tribromobenzene at elevated temperature. The introduction of benzene ring in g-C₃N₄ layers improves the separation efficiency and lifetime of photogenerated carriers, inhibits the recombination rate of electron/hole pairs, thus the performance of photocatalytic hydrogen evolution improves. The optimal hydrogen evolution rate of 1.5BCN reaches 1800 µmol/h·g, which is nine times that of the pure g-C₃N₄. DFT calculation proved the benzene bridged CN increased the distance of charge transfer (DCT) and the push-pull electronic effect of intramolecular electrons. This work may provide a pathway for preparing molecular doped g-C₃N₄ with improved photocatalytic performance.

Exploring Bi₄V₂O₁₁ as Photoanode for Water Splitting with a Wide Range of Solar Light Capture and Suitable Band Potential

Bi₄V₂O₁₁ possesses a bandgap of ~1.9 eV, and the band positions of minimum conduction band and maximum valence band straddle the redox potentials of H⁺/H₂ and O₂/H₂O. In the current work, photoanode made of particulate Bi₄V₂O₁₁ film displays a wide range of light adsorption. However, when the anode was fabricated by drop-casting and examined for photoelectrochemical water splitting, the photocurrent density of the pristine Bi₄V₂O₁₁ was low. Improvement has then been carried out by Mo-doping. The Mo-doped Bi₄V₂O₁₁ photoanode achieves a maximum photocurrent density of 0.3 mA/cm² after a post deposition necking treatment to improve the connectivity of the drop-cast particles in the film. This material also shows a stability with maintaining 80% photocurrent after 2 h test. Discussion has been made on the displayed performance in PEC water splitting of the Bi₄V₂O₁₁ materials. Potential solutions have been proposed for this type of promising photoanode material for water splitting.

Visible Light-Driven H₂O₂ Photoelectrocatalytic Synthesis Over a Tandem Electrode Strategy

Photocatalytic synthesis of hydrogen peroxide (H₂O₂) can be an environmentally friendly and energy-saving solution. However, the oxygen reduction reaction (ORR) rate is limited due to the low solubility of O₂ in water. In this study, a modified BiVO₄ (BVO) photoanode combined with an Sn-coordinated phthalocyanine gas diffusion electrode (SnPc-GDE) was employed for the synthesis of H₂O₂, and the oxy-gen reduction reaction rate was increased through a unique three-phase interface system. When visible light was irradiated on the BVO photoanode, the hole-electron pairs were excited and the oxygen evolution reaction (OER) was driven through the holes, and the excited electrons were transferred to the SnPc-GDE to reduce O₂ for the synthesis of H₂O₂. Oxygen vacancy enrichment on the BVO electrode was achieved by photoetching and annealing under an N₂ atmosphere, which effectively improved the carrier separation efficiency. Complexation with a WO₃ layer formed a built-in electric field, which further promoted the electron-hole pair separation. The SnPc catalyst-modified GDE electrode has the best selectivity for ORR and remains stable during long-term reactions. Under bias-free conditions, the generation rate of H₂O₂ reached 952.5 μM·L⁻¹·h⁻¹, with a Faradaic efficiency of 48.4%. This study provided a practical strategy for designing a highly efficient BVO/SnPc-GDE photoelectrochemical system to produce H₂O₂ based on improvement in electron-hole transmission efficiency and product selectivity.

Photocatalysis: Research and Potential—A New Means to Better Master Your Publishing Policy and Improve the Visibility of Your Articles

SnS₂ Quantum Dots Decorated MoS₂ Nanosheets Enabling Efficient Photocatalytic H₂ Evolution in CO₂ Saturated Water

SnS₂/MoS₂ heterojunction nanocomposite was prepared by a one-step hydrothermal synthesis method. The nanocomposite exhibited much improved photocatalytic hydrogen evolution performance in CO₂ saturated solution compared with pure MoS₂ and SnS₂ samples. The improved photocatalytic activity was attributed to the S-scheme heterojunction structure between SnS₂ quantum dots and MoS₂ nanosheets which facilitate electron-hole separation both in MoS₂ and SnS₂. In the S-scheme structure, the strong reduction ability of SnS₂ quantum dots was well maintained for the improved H₂ evolution. In situ DRIFT studies allowed us to suggest reaction pathways from CO₂ and H₂O to photocatalytic H₂, CO, and CH₄ generation.utf-8

Plasmon Enhanced Nickel(II) Catalyst for Photocatalytic Lignin Model Cleavage

Photocatalytic-induced cleaving of the ether C–O bond in model lignin compounds was studied with a closely-coupled compo-site material consisting of Ni(OH)₂ and gold nanoparticles (NPs) on a zirconia support (Au/ZrO₂–Ni(OH)₂). The three important ether bond types consisting of α-O-4, β-O-4, and 4-O-5 linkages can all be cleaved using this catalyst at reaction temperatures 40, 85 and 95 °C when under low-flux visible light irradiation. The Au NPs action as a light-harvesting antenna provided light-generated hot electrons that reduced Ni²⁺ to Ni⁰. The Ni⁰ was the active catalytic site where reductive cleavage of ether C–O bonds occurred while it was oxidized to Ni²⁺ to complete the catalysis cycle. The plasmonic antenna system with supported Ni(OH)₂ exhibited better ability for the catalytic reductive ether cleavages under visible light irradiation compared to photocata-lysts of Au NPs and Ni²⁺ ions immobilized on alumina fibers.utf-8

Photocatalytic Efficiency of Suspended and Immobilized TiO₂ P25 for Removing Myclobutanil, Penconazole and Their Commercial Formulations

Fungicide application in viticulture is a major source of surface and groundwater contamination. It is therefore essential to find solutions to stop this environmental pollution. Heterogeneous photocatalysis is an advanced oxidation method for the degradation and mineralization of organic pollutants in water. TiO₂ P25 photocatalyst in suspension has been used for removing the fungicides Myclobutanil and Penconazol, and their respective commercial formulations Systhane and Topas, in contaminated water. The apparent kinetic constants k_app of fungicides removal over 30 min batch treatment was higher for a mixture of pure molecules of Myclobutanil and Penconazol than for a mixture of their commercial formulations (17.5 × 10⁻³ by comparison with 10.3 × 10⁻³ min⁻¹ for Myclobutanil, and 10.0 × 10⁻³ by comparison with 2.80 × 10⁻³ min⁻¹ for Penconazol). TOC removal constants k_TOC were similar for the two mixtures, due to the presence of mineral and organic additives in the commercial formulations. To easily recover the photocatalyst after fungicide removal, TiO₂ P25 has been supported on β-SiC foam. Fungicides degradation was lower with supported photocatalysts than with the suspension of photocatalyst nanoparticles (NPs) because of a lower concentration of active sites on the supported photocatalyst than in the catalyst suspension. However, catalyst recovery and reuse after fungicide removal is obviously easier with TiO₂/β-SiC material than with a suspension of TiO₂ which requires long and expensive filtration operations.utf-8

New Trends on Photoswitchable Antibiotics: From Syntheses to Applications

Antibiotics are excreted in the environment after being used to treat bacterial infections in human and animals. These residues are poorly eliminated by the actual wastewater treatment processes, affecting animal, human and environmental health. This has led to the emergence of antibiotic resistance in bacterial pathogens. To combat this problem, photopharmacology has emerged in the last decades. This approach, based on the coupling of a drug with a photochromic component, is a promising way to control antibiotic activity by light irradiation and consequently limit antibioresistance. Thus, this review summarizes the study on the effect of the irradiation light on the antimicrobial activity of coupling compounds.utf-8

Potential Role of Exciton in Photocatalysis

This article commemorates the outstanding Russian scientists E.F. Gross and A.N. Terenin. It revisits their successors’ efforts to develop Terenin’s idea of using excitons, discovered by Gross, for photocatalytic redox reactions on wide-gap semiconductors. Terenin proposed ZnO as the subject of study. To explore the possibility of replacing photogenerated electrons and holes in a redox reaction by an exciton being a quasi-neutral particle, the test reaction of the photoactivated oxygen isotope exchange (POIE) was studied. It was found that many years of initial unsuccessful attempts were due to the fact that the exciton energy is spent on luminescence. In our experiments, the excitons decayed non-radiatively, and the long-lived electron-donor F-type and hole V-type active centers were formed by creating the 2D surface nanostructure ZnO/ZnO_1−x/O⁻. These centers allowed to obtain the reaction efficiency 5–8 times higher than with the interband transitions. Thus, the developed 2D surface nanostructure ZnO/ZnO_1−x/O⁻ resolved the problem of using an exciton in photocatalysis and demonstrated the perspective of this nanostructure as an efficient photocatalyst.utf-8

Fibrous SiC-based Mesoporous Solids for the Photocatalytic Degradation of Organic Pollutants under Artificial Light

SiC-based mesoporous solids with fibrous nanostructure were prepared by impregnation of a polycarbosilane precursor on annealed polyacrylonitrile (PAN) fibers and subsequent pyrolysis. The obtained material exhibits a mesoporous structure and has a specific surface area of ~20 m²/g. It has a semiconducting electronic character with a bandgap of 2.65 eV, i.e., in the visible range. Adsorption tests of methylene blue were performed on the material under dark conditions, which showed an adsorption amount of 78 wt%. The photocatalytic activity of the material was then evaluated for the degradation of the dye under artificial daylight irradiation over a period of 7 h. A degradation of 94 wt% was achieved. Regeneration and reuse of the material was also tested and resulted in 97 wt% degradation after reuse, indicating potential interest of the material as a contactor in environmental remediation devices.utf-8

Benzene Bridged Carbon Nitride for Efficient Photocatalytic Hydrogen Evolution

Turing the electronic structure by inserting certain functional groups in graphitic carbon nitride (g-C₃N₄, CN for short) skeleton through molecular doping is an effective way to improve its photocatalytic performance. Herein, we prepare a benzene bridged carbon nitride (BCN) by calcining urea and 1,3,5-tribromobenzene at elevated temperature. The introduction of benzene ring in g-C₃N₄ layers improves the separation efficiency and lifetime of photogenerated carriers, inhibits the recombination rate of electron/hole pairs, thus the performance of photocatalytic hydrogen evolution improves. The optimal hydrogen evolution rate of 1.5BCN reaches 1800 µmol/h·g, which is nine times that of the pure g-C₃N₄. DFT calculation proved the benzene bridged CN increased the distance of charge transfer (DCT) and the push-pull electronic effect of intramolecular electrons. This work may provide a pathway for preparing molecular doped g-C₃N₄ with improved photocatalytic performance.utf-8

Exploring Bi₄V₂O₁₁ as Photoanode for Water Splitting with a Wide Range of Solar Light Capture and Suitable Band Potential

Bi₄V₂O₁₁ possesses a bandgap of ~1.9 eV, and the band positions of minimum conduction band and maximum valence band straddle the redox potentials of H⁺/H₂ and O₂/H₂O. In the current work, photoanode made of particulate Bi₄V₂O₁₁ film displays a wide range of light adsorption. However, when the anode was fabricated by drop-casting and examined for photoelectrochemical water splitting, the photocurrent density of the pristine Bi₄V₂O₁₁ was low. Improvement has then been carried out by Mo-doping. The Mo-doped Bi₄V₂O₁₁ photoanode achieves a maximum photocurrent density of 0.3 mA/cm² after a post deposition necking treatment to improve the connectivity of the drop-cast particles in the film. This material also shows a stability with maintaining 80% photocurrent after 2 h test. Discussion has been made on the displayed performance in PEC water splitting of the Bi₄V₂O₁₁ materials. Potential solutions have been proposed for this type of promising photoanode material for water splitting.utf-8

Visible Light-Driven H₂O₂ Photoelectrocatalytic Synthesis Over a Tandem Electrode Strategy

Photocatalytic synthesis of hydrogen peroxide (H₂O₂) can be an environmentally friendly and energy-saving solution. However, the oxygen reduction reaction (ORR) rate is limited due to the low solubility of O₂ in water. In this study, a modified BiVO₄ (BVO) photoanode combined with an Sn-coordinated phthalocyanine gas diffusion electrode (SnPc-GDE) was employed for the synthesis of H₂O₂, and the oxy-gen reduction reaction rate was increased through a unique three-phase interface system. When visible light was irradiated on the BVO photoanode, the hole-electron pairs were excited and the oxygen evolution reaction (OER) was driven through the holes, and the excited electrons were transferred to the SnPc-GDE to reduce O₂ for the synthesis of H₂O₂. Oxygen vacancy enrichment on the BVO electrode was achieved by photoetching and annealing under an N₂ atmosphere, which effectively improved the carrier separation efficiency. Complexation with a WO₃ layer formed a built-in electric field, which further promoted the electron-hole pair separation. The SnPc catalyst-modified GDE electrode has the best selectivity for ORR and remains stable during long-term reactions. Under bias-free conditions, the generation rate of H₂O₂ reached 952.5 μM·L⁻¹·h⁻¹, with a Faradaic efficiency of 48.4%. This study provided a practical strategy for designing a highly efficient BVO/SnPc-GDE photoelectrochemical system to produce H₂O₂ based on improvement in electron-hole transmission efficiency and product selectivity.utf-8