Special Issue "Nanomaterials in Photo(Electro)catalysis"

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Photocatalysis".

Deadline for manuscript submissions: closed (30 September 2020).

Special Issue Editors

Prof. Dr. Roberto Comparelli
E-Mail Website
Guest Editor
National Research Council–Institute for Physical Chemical Processes (CNR-IPCF), Bari, Italy
Interests: photocatalysis; visible light active photocatalysts; inorganic nanocrystals; hybrid nanocomposites; plasmonics nanoparticles; nanocrystal functionalization; solar energy conversion
Special Issues and Collections in MDPI journals
Dr. Francesca Petronella
E-Mail Website
Guest Editor
National Research Council–Institute for Physical Chemical Processes (CNR-IPCF), Bari, Italy
Interests: nanomaterials, photocatalysis, colloidal synthesis, colloidal nanoparticles, hybrid nanocomposites, plasmonic nanoparticles, functionalization
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Photoactive nanomaterials are receiving increasing attention due to their potential application in light-driven redox processes for the degradation of water and gas-phase pollutants and in the field of energy conversion and production.

Modern material science offers a toolbox to finely tune nanomaterial size/shape-dependent chemical-physical properties, thus allowing one to fully exploit the great potential of photoactive materials. In addition, post-synthesis manipulation of nanomaterials plays a key role to integrate them in photo-reactors or to deposit them on large surfaces in order to allow easy recovery of the catalysts and prevent any release of nanopowders in the environment. The great potential of photocatalytic process can be further boosted up by applying an external differential potential to the catalyst in order to increase the yield of light's conversion into chemical energy.

The potential application of photoactive nanomaterials in the environmental field includes the abatement of organic pollutant in water, water disinfection, and the abatement of gas-phase pollutants in outdoor and indoor applications. Urgent environmental challenges, such as the production of green fuels and solar energy conversion, are further application fields where the development of photoactive nanomaterials with improved properties is essential.

We invite contributors to submit original research papers or reviews that account for recent advances in the field of photoactive nanomaterials for the degradation of pollutants; for energy conversion; and for energy production assisted by UV, visible, or solar light.

Dr. Roberto Comparelli
Dr. Francesca Petronella
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Photo(electro)chemistry
  • Photoactive nanomaterial synthesis
  • Supported photocatalysts
  • Advanced oxidation processes
  • Water treatments
  • Gas-phase pollutants
  • Water splitting
  • H2 generation
  • CO2 reduction

Published Papers (12 papers)

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Editorial

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Editorial
Nanomaterials in Photo (Electro) Catalysis
Catalysts 2021, 11(2), 149; https://doi.org/10.3390/catal11020149 - 21 Jan 2021
Viewed by 435
Abstract
The increasing rate of water and air pollution dramatically impacts natural ecosystems and human health causing depletion of biodiversity, climate changes, spreading of respiratory diseases, and, as a consequence, negatively impacting the world economy [...] Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)

Research

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Article
Low Temperature Synthesis of Photocatalytic Mesoporous TiO2 Nanomaterials
Catalysts 2020, 10(8), 893; https://doi.org/10.3390/catal10080893 - 07 Aug 2020
Cited by 5 | Viewed by 1246
Abstract
We report the synthesis of mesoporous TiO2 nanostructures based on the decomposition of TiOSO4 in aqueous alkaline solution at room temperature, followed by mild thermal treatment (110 °C) in an oven and suitable to yield up to 40 g of product [...] Read more.
We report the synthesis of mesoporous TiO2 nanostructures based on the decomposition of TiOSO4 in aqueous alkaline solution at room temperature, followed by mild thermal treatment (110 °C) in an oven and suitable to yield up to 40 g of product per batch. The duration of the thermal treatment was found to be crucial to control crystalline phase composition, specific surface area, surface chemistry and, accordingly, the photocatalytic properties of the obtained TiO2 nanocrystals. The thorough investigation of the prepared samples allowed us to explain the relationship between the structure of the obtained nanoparticles and their photocatalytic behavior, that was tested in a model reaction. In addition, the advantage of the mild treatment against a harsher calcination at 450 °C was illustrated. The proposed approach represents a facile and sustainable route to promptly access an effective photocatalyst, thus holding a significant promise for the development of solutions suitable to real technological application in environmental depollution. Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)
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Article
Physical Origin of Diminishing Photocatalytic Efficiency for Recycled TiO2 Nanotubes and Ag-Loaded TiO2 Nanotubes in Organic Aqueous Solution
Catalysts 2020, 10(7), 737; https://doi.org/10.3390/catal10070737 - 03 Jul 2020
Cited by 4 | Viewed by 637
Abstract
Arrays of titania nanotubes (TiO2NTs) were developed by electrochemical anodization and doped with silver on their surface by photodeposition to achieve TiO2NTs/Ag. It is found that only anatase TiO2NTs were formed, with the preferential growth direction perpendicular [...] Read more.
Arrays of titania nanotubes (TiO2NTs) were developed by electrochemical anodization and doped with silver on their surface by photodeposition to achieve TiO2NTs/Ag. It is found that only anatase TiO2NTs were formed, with the preferential growth direction perpendicular to the titanium substrate, and with the length and diameter of ~2 µm and 90–120 nm, respectively. The presence of Ag on the surface of TiO2NTs was also confirmed. The TiO2NTs and TiO2NTs/Ag were used as photocatalysts to decolorize the methylene blue (MB) aqueous solution. The photodegradation efficiency (PDE) is as high as 83% for TiO2NTs and 98% for TiO2NTs/Ag photocatalysts. This work focused on the investigation of the stability and recyclability of these photocatalysts in terms of efficiency and its physical origin by surface analysis using X-ray photoelectron spectroscopy (XPS). It is found that PDE diminishes from 83% to 76% in TiO2NTs upon eight recycling runs and from 98% to 80% in TiO2NTs/Ag upon six recycling runs. The XPS analysis revealed that the physical origin of diminishing efficiency is the carbon contamination on the surface of recycled TiO2NTs and a combination of carbon contamination and Ag leaching in recycled TiO2NTs/Ag. Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)
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Article
The Spinning Voltage Influence on the Growth of ZnO-rGO Nanorods for Photocatalytic Degradation of Methyl Orange Dye
Catalysts 2020, 10(6), 660; https://doi.org/10.3390/catal10060660 - 12 Jun 2020
Cited by 6 | Viewed by 865
Abstract
In this work, well-designed zinc oxide-reduced graphene oxide (ZnO-rGO) nanorods (NRs) were synthesized by a hydrothermal method using electrospun ZnO-rGO seed layers. The ZnO-rGO seed layers were fabricated on fluorine-doped tin oxide (FTO) glass substrates through calcined of electrospun nanofibers at 400 °C [...] Read more.
In this work, well-designed zinc oxide-reduced graphene oxide (ZnO-rGO) nanorods (NRs) were synthesized by a hydrothermal method using electrospun ZnO-rGO seed layers. The ZnO-rGO seed layers were fabricated on fluorine-doped tin oxide (FTO) glass substrates through calcined of electrospun nanofibers at 400 °C in the air for 1 h. The nanofibers were prepared by electrospinning different spinning voltages and a spinning solution containing zinc acetate, polyvinyl pyrrolidone, and 0.2 wt% rGO. From a detailed characterization using various analytical techniques, for instance, X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS), the dependence of the structure, morphology, and optical properties of the ZnO-rGO NRs was demonstrated. The photocatalytic activities of ZnO-rGO nanorods were evaluated through the degradation of dye methyl orange (MO). The results show that the change of spinning voltages and the coupling of rGO with ZnO improved photodecomposition efficiency as compared to pure ZnO. The highest photocatalytic efficiency was obtained for the ZnO-rGO NRs prepared with a spinning voltage of 40 kV. Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)
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Article
Structurally and Compositionally Tunable Absorption Properties of [email protected] Nanocatalysts for Plasmonic Photocatalytic Degradation of Environmental Pollutants
Catalysts 2020, 10(4), 405; https://doi.org/10.3390/catal10040405 - 08 Apr 2020
Cited by 1 | Viewed by 883
Abstract
Composite nanomaterials having Ag nanoparticles (NPs) that decorate nanostructured AgCl (Ag/AgCl) are promising as plasmonic photocatalysts because of the visible-light absorption of Ag NPs. However, the narrow absorption bands of Ag NPs near 400 nm cause inefficient absorption in the visible range and, [...] Read more.
Composite nanomaterials having Ag nanoparticles (NPs) that decorate nanostructured AgCl (Ag/AgCl) are promising as plasmonic photocatalysts because of the visible-light absorption of Ag NPs. However, the narrow absorption bands of Ag NPs near 400 nm cause inefficient absorption in the visible range and, consequently, unsatisfactory photocatalytic activity of Ag/AgCl nanomaterials. In this study, we introduce a new class of AgCl-based photocatalysts that are decorated with bimetallic Ag and Au NPs ([email protected] NPs) for visible-light-driven photocatalytic degradation of organic pollutants. Polyvinylpyrrolidone induces selective reduction of noble metal precursors on AgCl while leaving AgCl intact. The extended composition of the decorating NPs red-shifts the absorption band to 550–650 nm, which allows the catalysts to take advantage of more energy in the visible range for improved efficiency. Furthermore, we control the structures of the [email protected] NPs, and investigate their correlation with photocatalytic properties. The versatility, chemical stability, and practical application of the [email protected] NPs are demonstrated using various organic pollutants, recycling experiments, and natural aqueous media, respectively. Our fundamental investigation on the synthesis and applications of AgCl-based nano-photocatalysts is highly valuable for designing plasmonic photocatalysts and expanding their utilization. Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)
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Article
Exploiting Direct Current Plasma Electrolytic Oxidation to Boost Photoelectrocatalysis
Catalysts 2020, 10(3), 325; https://doi.org/10.3390/catal10030325 - 14 Mar 2020
Cited by 8 | Viewed by 920
Abstract
In this study, we report an investigation of the photoelectrochemical activity of TiO2 films formed by DC plasma electrolytic oxidation (PEO) at a variable potential in a sulfuric acid electrolyte at 0 and 25 °C. The surface morphology was mainly determined by [...] Read more.
In this study, we report an investigation of the photoelectrochemical activity of TiO2 films formed by DC plasma electrolytic oxidation (PEO) at a variable potential in a sulfuric acid electrolyte at 0 and 25 °C. The surface morphology was mainly determined by the oxide-forming potential. X-Ray Diffraction and Raman analyses showed that the relative amount of the anatase and rutile phases varied from 100% anatase at low potential (110–130 V) to 100% rutile at high potential (180–200 V), while mixed-phase oxide films formed at intermediate potential. Correspondingly, the band gap of the TiO2 films decreased from about 3.20 eV (pure anatase) to 2.94 eV (pure rutile) and was red-shifted about 0.1 eV by reducing the electrolyte temperature from 25 °C to 0 °C. Glow-Discharge Optical Emission Spectroscopy (GD-OES) and X-ray Photoelectron Spectroscopy (XPS) analyses evidenced S-containing species located preferentially close to the TiO2/Ti interface. The photoelectrochemical activity was assessed by measuring the incident photon-to-current efficiency (IPCE) under Ultraviolet C (UV-C) irradiation, which showed a non-gaussian normal trend as a function of the PEO cell potential, with maximum values exceeding 80%. Photoelectrocatalytic activity was assessed by decolorization of model solutions containing methylene blue. Photoanodes having higher IPCE values showed faster decolorization kinetics. Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)
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Article
Selective Oxidation of Benzyl Alcohol by Ag/Pd/m-BiVO4 Microspheres under Visible Light Irradiation
Catalysts 2020, 10(2), 266; https://doi.org/10.3390/catal10020266 - 22 Feb 2020
Cited by 6 | Viewed by 1300
Abstract
A series of Ag/Pd/m-BiVO4 (monoclinic) bimetallic photocatalytic materials with different loading amounts and different mass ratios of Ag and Pd were synthesized by a hydrothermal method and an NaBH4 reduction method. The Ag/Pd/m-BiVO4 photocatalyst with a total Ag and Pd [...] Read more.
A series of Ag/Pd/m-BiVO4 (monoclinic) bimetallic photocatalytic materials with different loading amounts and different mass ratios of Ag and Pd were synthesized by a hydrothermal method and an NaBH4 reduction method. The Ag/Pd/m-BiVO4 photocatalyst with a total Ag and Pd loading of 2 wt% and an Ag-to-Pd mass ratio of 2:1 can selectively oxidize benzyl alcohol to benzaldehyde under visible light irradiation, the conversion rate was up to 89.9%, and the selectivity was greater than 99%. The conversion rate on Ag/Pd/m-BiVO4 was higher than those on Ag/m-BiVO4 and Pd/m-BiVO4. The photocatalysts were characterized by X-ray powder diffraction (XRD), ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, N2 adsorption-desorption isothermal curves (BET) and other means. The effects of different light wavelengths and light intensities were compared. Then, the effects of different alcohol derivatives on the reactions were explored. The cycle experiments proved that the Ag/Pd/m-BiVO4 photocatalyst had good light stability and thermal stability. In addition, the capturing experiment of active species shows that the selective oxidation of benzyl alcohol is mainly accomplished through the synergistic action of h+, e, •OH and •O2. Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)
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Article
Degradation of Carbamazepine by Photo(electro)catalysis on Nanostructured TiO2 Meshes: Transformation Products and Reaction Pathways
Catalysts 2020, 10(2), 169; https://doi.org/10.3390/catal10020169 - 01 Feb 2020
Cited by 15 | Viewed by 1158
Abstract
Carbamazepine (CBZ) is a pharmaceutical compound recalcitrant to conventional wastewater treatment plants and widely detected in wastewater bodies. In the present study, advanced oxidation processes for carbamazepine removal are investigated, with particular regard to the degradation pathways of carbamazepine by photoelectrocatalysis and conventional [...] Read more.
Carbamazepine (CBZ) is a pharmaceutical compound recalcitrant to conventional wastewater treatment plants and widely detected in wastewater bodies. In the present study, advanced oxidation processes for carbamazepine removal are investigated, with particular regard to the degradation pathways of carbamazepine by photoelectrocatalysis and conventional photocatalysis. Photoelectrocatalysis was carried out onto TiO2 meshes obtained by Plasma Electrolytic Oxidation, a well-known technique in the field of industrial surface treatments, in view of an easy scale-up of the process. By photoelectrocatalysis, 99% of carbamazepine was removed in 55 min while only 65% removal was achieved by photolysis. The investigation of the transformation products (TPs) was carried out by means of UPLC-QTOF/MS/MS. Several new TPs were identified and accordingly reaction pathways were proposed. Above 80 min the transformation products disappear, probably forming organic acids of low-molecular weight as final degradation products. The results demonstrated that photoelectrocatalysis onto TiO2 meshes obtained by plasma electrolytic oxidation is a useful alternative to common advanced oxidation processes as wastewater tertiary treatment aimed at removing compounds of emerging concern. Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)
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Article
Doping of Chlorine from a Neoprene Adhesive Enhances Degradation Efficiency of Dyes by Structured TiO2-Coated Photocatalytic Fabrics
Catalysts 2020, 10(1), 69; https://doi.org/10.3390/catal10010069 - 02 Jan 2020
Cited by 9 | Viewed by 978
Abstract
We demonstrate that using neoprene as a binder during the fabrication of TiO2-coated fabrics enhances the rates of photodegradation of dyes by the fabrics. The neoprene binder simultaneously modifies the surface of the TiO2 particles with Cl and dopes the [...] Read more.
We demonstrate that using neoprene as a binder during the fabrication of TiO2-coated fabrics enhances the rates of photodegradation of dyes by the fabrics. The neoprene binder simultaneously modifies the surface of the TiO2 particles with Cl and dopes the TiO2 with Cl, without requiring high temperatures or other harsh laboratory treatments. The adsorption of chlorine on the surface and doping of the lattice with chlorine were confirmed by X-ray photoelectron spectroscopy. The chloride ions adsorbed onto the TiO2 surface introduces a negative surface charge that enhances electrostatic adsorption of cationic dyes, and greatly improves the self-sensitizing degradation performance of the dyes. Chloride ions replace lattice oxygen atoms in TiO2, inducing lattice oxygen vacancies, that reduce the apparent band gap of the TiO2 particles, enhancing its absorption of visible light, and further increasing the photocatalytic activity of the composite-coated fabric. The degradation rates of RhB and MB over 50 min were 95.2% and 96.0%, respectively. The degradation rate for MO reached 95.4% after 180 min. We also show that •OH and •O2− are active agents in the dye-degradation mechanism. Moreover, the photocatalytic performance of the composite-coated fabric was unchanged after eight cycles of photocatalytic degradation of RhB, demonstrating that the photocatalyst-coated fabrics was highly recyclable. Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)
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Article
Low-Cost Synthesis of Cu-Modified Immobilized Nanoporous TiO2 for Photocatalytic Degradation of 1H-Benzotriazole
Catalysts 2020, 10(1), 19; https://doi.org/10.3390/catal10010019 - 21 Dec 2019
Cited by 5 | Viewed by 1071
Abstract
Cu-modified immobilized nanoporous TiO2 photocatalysts, prepared by electrochemical anodization of titanium foils, were obtained via four different synthesis methods: hydrothermal synthesis, anodization with Cu source, electrodeposition, and spin-coating, using two different copper sources, Cu(NO3)2 and Cu(acac)2. The [...] Read more.
Cu-modified immobilized nanoporous TiO2 photocatalysts, prepared by electrochemical anodization of titanium foils, were obtained via four different synthesis methods: hydrothermal synthesis, anodization with Cu source, electrodeposition, and spin-coating, using two different copper sources, Cu(NO3)2 and Cu(acac)2. The objective of this research was to investigate how copper modifications can improve the photocatalytic activity of immobilized nanoporous TiO2 under the UV/solar light irradiation. The best photocatalytic performances were obtained for Cu-modifications using spin-coating. Therefore, the effect of irradiated catalyst surface areas on the adsorption of model pollutants, methylene blue (MB) and 1H-benzotriazole (BT), was examined for samples with Cu-modification by the spin-coating technique. The mechanisms responsible for increased degradation of MB and BT at high Cu concentrations (0.25 M and 0.5 M) and decreased degradation at low Cu loadings (0.0625 M and 0.125 M) were explained. 1H-benzotriazole was used to study the photocatalytic activity of the given samples because it is highly toxic and present in most water systems. The characterization of the synthesized Cu-modified photocatalysts in terms of phase composition, crystal structure, and morphology were investigated using X-ray Diffraction, Raman Spectroscopy, Scanning Electron Microscopy, and Energy Dispersive X-ray spectroscopy. Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)
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Article
Eco-Toxicological and Kinetic Evaluation of TiO2 and ZnO Nanophotocatalysts in Degradation of Organic Dye
Catalysts 2019, 9(10), 871; https://doi.org/10.3390/catal9100871 - 21 Oct 2019
Cited by 7 | Viewed by 1304
Abstract
In this study, the photocatalytic degradation of azo dye “Food Black 1” (FB1) was investigated using TiO2 and ZnO nanoparticles under ultraviolet (UV) light. The performances of the two photocatalysts were evaluated in terms of key parameters (e.g., decolorization, dearomatization, mineralization, and [...] Read more.
In this study, the photocatalytic degradation of azo dye “Food Black 1” (FB1) was investigated using TiO2 and ZnO nanoparticles under ultraviolet (UV) light. The performances of the two photocatalysts were evaluated in terms of key parameters (e.g., decolorization, dearomatization, mineralization, and detoxification of dye) in relation to variables including pre-adsorption period, pH, and temperature. Under acidic conditions (pH 5), the ZnO catalyst underwent photocorrosion to increase the concentration of zinc ions in the system, thereby increasing the toxic properties of the treated effluent. In contrast, TiO2 efficiently catalyzed the degradation of the dye at pH 5 following the Langmuir–Hinshelwood (L–H) kinetic model. The overall results of this study indicate that the decolorization rate of TiO2 on the target dye was far superior to ZnO (i.e., by 1.5 times) at optimum catalyst loading under UV light. Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)
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Review

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Review
Recent Developments in Synthesis and Photocatalytic Applications of Carbon Dots
Catalysts 2020, 10(3), 320; https://doi.org/10.3390/catal10030320 - 11 Mar 2020
Cited by 10 | Viewed by 1554
Abstract
The tunable photoluminescent and photocatalytic properties of carbon dots (CDs) via chemical surface modification have drawn increased attention to this emerging class of carbon nanomaterials. Herein, we summarize the advances in CD synthesis and modification, with a focus on surface functionalization, element doping, [...] Read more.
The tunable photoluminescent and photocatalytic properties of carbon dots (CDs) via chemical surface modification have drawn increased attention to this emerging class of carbon nanomaterials. Herein, we summarize the advances in CD synthesis and modification, with a focus on surface functionalization, element doping, passivation, and nanocomposite formation with metal oxides, transition metal chalcogenides, or graphitic carbon nitrides. The effects of CD size and functionalization on photocatalytic properties are discussed, along with the photocatalytic applications of CDs in energy conversion, water splitting, hydrogen evolution, water treatment, and chemical degradation. In particular, the enzyme-mimetic and photodynamic applications of CDs for bio-related uses are thoroughly reviewed. Full article
(This article belongs to the Special Issue Nanomaterials in Photo(Electro)catalysis)
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