Catalysts

Editorial

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2 pages, 170 KiB

Open AccessEditorial

Special Issue: New Trends in Photo (Electro)catalysis: From Wastewater Treatment to Energy Production

by Simonetta Palmas

Catalysts 2021, 11(5), 586; https://doi.org/10.3390/catal11050586 - 30 Apr 2021

Cited by 2 | Viewed by 1459

Abstract

This Special Issue aimed at focusing on photo- and photo-electrocatalytic processes specifically devoted to present both new catalytic materials and possible applications in environmental and energetic fields [...] Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

Research

Jump to: Editorial, Review

10 pages, 1608 KiB

Open AccessArticle

Enhanced Photocatalytic Activity of Semiconductor Nanocomposites Doped with Ag Nanoclusters Under UV and Visible Light

by Jorge González-Rodríguez, Lucía Fernández, Yanina B. Bava, David Buceta, Carlos Vázquez-Vázquez, Manuel Arturo López-Quintela, Gumersindo Feijoo and Maria Teresa Moreira

Catalysts 2020, 10(1), 31; https://doi.org/10.3390/catal10010031 - 26 Dec 2019

Cited by 18 | Viewed by 3869

Abstract

Emerging contaminants (ECs) represent a wide range of compounds, whose complete elimination from wastewaters by conventional methods is not always guaranteed, posing human and environmental risks. Advanced oxidation processes (AOPs), based on the generation of highly oxidizing species, lead to the degradation of [...] Read more.

Emerging contaminants (ECs) represent a wide range of compounds, whose complete elimination from wastewaters by conventional methods is not always guaranteed, posing human and environmental risks. Advanced oxidation processes (AOPs), based on the generation of highly oxidizing species, lead to the degradation of these ECs. In this context, TiO₂ and ZnO are the most widely used inorganic photocatalysts, mainly due to their low cost and wide availability. The addition of small amounts of nanoclusters may imply enhanced light absorption and an attenuation effect on the recombination rate of electron/hole pairs, resulting in improved photocatalytic activity. In this work, we propose the use of silver nanoclusters deposited on ZnO nanoparticles (ZnO–Ag), with a view to evaluating their catalytic activity under both ultraviolet A (UVA) and visible light, in order to reduce energetic requirements in prospective applications on a larger scale. The catalysts were produced and then characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and inductively coupled plasma-optical emission spectrometry (ICP-OES). As proof of concept of the capacity of photocatalysts doped with nanoclusters, experiments were carried out to remove the azo dye Orange II (OII). The results demonstrated the high photocatalytic efficiency achieved thanks to the incorporation of nanoclusters, especially evident in the experiments performed under white light. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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15 pages, 4299 KiB

Open AccessArticle

Niobium Oxide Catalysts as Emerging Material for Textile Wastewater Reuse: Photocatalytic Decolorization of Azo Dyes

by Alexsandro Jhones dos Santos, Luana Márcia Bezerra Batista, Carlos Alberto Martínez-Huitle, Ana Paula de Melo Alves and Sergi Garcia-Segura

Catalysts 2019, 9(12), 1070; https://doi.org/10.3390/catal9121070 - 14 Dec 2019

Cited by 40 | Viewed by 4934

Abstract

Niobium-based metal oxides are emerging semiconductor materials with barely explored properties for photocatalytic wastewater remediation. Brazil possesses the greatest reserves of niobium worldwide, being a natural resource that is barely exploited. Environmental applications of solar active niobium photocatalysts can provide opportunities in the [...] Read more.

Niobium-based metal oxides are emerging semiconductor materials with barely explored properties for photocatalytic wastewater remediation. Brazil possesses the greatest reserves of niobium worldwide, being a natural resource that is barely exploited. Environmental applications of solar active niobium photocatalysts can provide opportunities in the developing areas of Northeast Brazil, which receives over 22 MJ m² of natural sunlight irradiation annually. The application of photocatalytic treatment could incentivize water reuse practices in small and mid-sized textile businesses in the region. This work reports the facile synthesis of Nb₂O₅ catalysts and explores their performance for the treatment of colored azo dye effluents. The high photoactivity of this alternative photocatalyst makes it possible to quickly obtain complete decolorization, in less than 40 min of treatment. The optimal operational conditions are defined as 1.0 g L⁻¹ Nb₂O₅ loading in slurry, 0.2 M of H₂O₂, pH 5.0 to treat up to 15 mg L⁻¹ of methyl orange solution. To evaluate reutilization without photocatalytic activity loss, the Nb₂O₅ was recovered after the experience and reused, showing the same decolorization rate after several cycles. Therefore, Nb₂O₅ appears to be a promising photocatalytic material with potential applicability in wastewater treatment due to its innocuous character and high stability. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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16 pages, 6923 KiB

Open AccessArticle

Preparation and Analysis of Ni–Co Catalyst Use for Electricity Production and COD Reduction in Microbial Fuel Cells

by Paweł P. Włodarczyk and Barbara Włodarczyk

Catalysts 2019, 9(12), 1042; https://doi.org/10.3390/catal9121042 - 8 Dec 2019

Cited by 16 | Viewed by 3044

Abstract

Microbial fuel cells (MFCs) are devices than can contribute to the development of new technologies using renewable energy sources or waste products for energy production. Moreover, MFCs can realize wastewater pre-treatment, e.g., reduction of the chemical oxygen demand (COD). This research covered preparation [...] Read more.

Microbial fuel cells (MFCs) are devices than can contribute to the development of new technologies using renewable energy sources or waste products for energy production. Moreover, MFCs can realize wastewater pre-treatment, e.g., reduction of the chemical oxygen demand (COD). This research covered preparation and analysis of a catalyst and measurements of changes in the concentration of COD in the MFC with a Ni–Co cathode. Analysis of the catalyst included measurements of the electroless potential of Ni–Co electrodes oxidized for 1–10 h, and the influence of anodic charge on the catalytic activity of the Ni–Co alloy (for four alloys: 15, 25, 50, and 75% concentration of Co). For the Ni–Co alloy containing 15% of Co oxidized for 8 h, after the third anodic charge the best catalytic parameters was obtained. During the MFC operation, it was noted that the COD reduction time (to 90% efficiency) was similar to the reduction time during wastewater aeration. However, the characteristic of the aeration curve was preferred to the curve obtained during the MFC operation. The electricity measurements during the MFC operation showed that power equal to 7.19 mW was obtained (at a current density of 0.47 mA·cm⁻²). Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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13 pages, 6265 KiB

Open AccessArticle

Wastewater Treatment and Electricity Production in a Microbial Fuel Cell with Cu–B Alloy as the Cathode Catalyst

by Paweł P. Włodarczyk and Barbara Włodarczyk

Catalysts 2019, 9(7), 572; https://doi.org/10.3390/catal9070572 - 28 Jun 2019

Cited by 30 | Viewed by 5818

Abstract

The possibility of wastewater treatment and electricity production using a microbial fuel cell with Cu–B alloy as the cathode catalyst is presented in this paper. Our research covered the catalyst preparation; measurements of the electroless potential of electrodes with the Cu–B catalyst, measurements [...] Read more.

The possibility of wastewater treatment and electricity production using a microbial fuel cell with Cu–B alloy as the cathode catalyst is presented in this paper. Our research covered the catalyst preparation; measurements of the electroless potential of electrodes with the Cu–B catalyst, measurements of the influence of anodic charge on the catalytic activity of the Cu–B alloy, electricity production in a microbial fuel cell (with a Cu–B cathode), and a comparison of changes in the concentration of chemical oxygen demand (COD), NH₄⁺, and NO₃^– in three reactors: one excluding aeration, one with aeration, and during microbial fuel cell operation (with a Cu–B cathode). During the experiments, electricity production equal to 0.21–0.35 mA·cm⁻² was obtained. The use of a microbial fuel cell (MFC) with Cu–B offers a similar reduction time for COD to that resulting from the application of aeration. The measured reduction of NH₄⁺ was unchanged when compared with cases employing MFCs, and it was found that effectiveness of about 90% can be achieved for NO₃^– reduction. From the results of this study, we conclude that Cu–B can be employed to play the role of a cathode catalyst in applications of microbial fuel cells employed for wastewater treatment and the production of electricity. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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16 pages, 6775 KiB

Open AccessFeature PaperArticle

Porous Ni Photocathodes Obtained by Selective Corrosion of Ni-Cu Films: Synthesis and Photoelectrochemical Characterization

by Laura Mais, Simonetta Palmas, Michele Mascia, Elisa Sechi, Maria Francesca Casula, Jesus Rodriguez and Annalisa Vacca

Catalysts 2019, 9(5), 453; https://doi.org/10.3390/catal9050453 - 16 May 2019

Cited by 11 | Viewed by 3315

Abstract

In this work, a dealloying technique is proposed as a synthesis method to obtain highly porous Nickel electrodes starting from Ni-Cu co-deposit: pulsed corrosion is applied adopting different corrosion and relaxation times. Different morphologies, pore size distribution and residual copper amount were obtained [...] Read more.

In this work, a dealloying technique is proposed as a synthesis method to obtain highly porous Nickel electrodes starting from Ni-Cu co-deposit: pulsed corrosion is applied adopting different corrosion and relaxation times. Different morphologies, pore size distribution and residual copper amount were obtained depending on the corrosion conditions. For the developed electrodes, the surface roughness factor, R_f, was evaluated by electrochemical impedance spectroscopy (EIS). The hydrogen evolution reaction (HER) on these electrodes was evaluated by means of steady-state polarization curves, and the related parameters were derived by Tafel analysis. Finally, a thin layer of NiO on the porous structures was obtained to exploit the semiconductor characteristic of the oxide, so that an extra-photopotential was obtained by the simulated solar light action. Results demonstrate greater apparent activity of the developed electrodes towards HER in comparison with commercial smooth Ni electrode, which can be mainly attributed to the large R_f obtained with the proposed technique. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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13 pages, 3122 KiB

Open AccessArticle

Effect of the Degree of Inversion on the Photoelectrochemical Activity of Spinel ZnFe₂O₄

by Luis I. Granone, Konstantin Nikitin, Alexei Emeline, Ralf Dillert and Detlef W. Bahnemann

Catalysts 2019, 9(5), 434; https://doi.org/10.3390/catal9050434 - 9 May 2019

Cited by 20 | Viewed by 3369

Abstract

Physicochemical properties of spinel ZnFe₂O₄ (ZFO) are known to be strongly affected by the distribution of the cations within the oxygen lattice. In this work, the correlation between the degree of inversion, the electronic transitions, the work function, and the [...] Read more.

Physicochemical properties of spinel ZnFe₂O₄ (ZFO) are known to be strongly affected by the distribution of the cations within the oxygen lattice. In this work, the correlation between the degree of inversion, the electronic transitions, the work function, and the photoelectrochemical activity of ZFO was investigated. By room-temperature photoluminescence measurements, three electronic transitions at approximately 625, 547, and 464 nm (1.98, 2.27, and 2.67 eV, respectively) were observed for the samples with different cation distributions. The transitions at 625 and 547 nm were assigned to near-band-edge electron-hole recombination processes involving O^2- 2p and Fe³⁺ 3d levels. The transition at 464 nm, which has a longer lifetime, was assigned to the relaxation of the excited states produced after electron excitations from O^2- 2p to Zn²⁺ 4s levels. Thus, under illumination with wavelengths shorter than 464 nm, electron-hole pairs are produced in ZFO by two apparently independent mechanisms. Furthermore, the charge carriers generated by the O²⁻ 2p to Zn²⁺ 4s electronic transition at 464 nm were found to have a higher incident photon-to-current efficiency than the ones generated by the O²⁻ 2p to Fe³⁺ 3d electronic transition. As the degree of inversion of ZFO increases, the probability of a transition involving the Zn²⁺ 4s levels increases and the probability of a transition involving the Fe³⁺ 3d levels decreases. This effect contributes to the increase in the photoelectrochemical efficiency observed for the ZFO photoanodes having a larger cation distribution. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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21 pages, 5009 KiB

Open AccessArticle

Integrated Au/TiO₂ Nanostructured Photoanodes for Photoelectrochemical Organics Degradation

by Roberto Matarrese, Michele Mascia, Annalisa Vacca, Laura Mais, Elisabetta M. Usai, Matteo Ghidelli, Luca Mascaretti, Beatrice R. Bricchi, Valeria Russo, Carlo S. Casari, Andrea Li Bassi, Isabella Nova and Simonetta Palmas

Catalysts 2019, 9(4), 340; https://doi.org/10.3390/catal9040340 - 5 Apr 2019

Cited by 20 | Viewed by 4008

Abstract

In this work, hierarchical Au/TiO₂ nanostructures were studied as possible photoanodes for water splitting and bisphenol A (BPA) oxidation. TiO₂ samples were synthetized by Pulsed Laser Deposition (PLD), while Au nanoparticles (NPs) were differently dispersed (i.e., NPs at the bottom or [...] Read more.

In this work, hierarchical Au/TiO₂ nanostructures were studied as possible photoanodes for water splitting and bisphenol A (BPA) oxidation. TiO₂ samples were synthetized by Pulsed Laser Deposition (PLD), while Au nanoparticles (NPs) were differently dispersed (i.e., NPs at the bottom or at the top of the TiO₂, as well as integrated TiO₂/Au-NPs assemblies). Voltammetric scans and electrochemical impedance spectroscopy analysis were used to correlate the morphology of samples with their electrochemical properties; the working mechanism was investigated in the dark and in the presence of a light radiation, under neutral pH conditions towards the possible oxidation of both bisphenol A (BPA) and water molecules. Different behavior of the samples was observed, which may be attributed mainly to the distributions of Au NPs and to their dimension as well. In particular, the presence of NPs at the bottom seems to be the crucial point for the working mechanism of the structure, thanks to scattering effects that likely allow to better exploit the radiation. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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13 pages, 2752 KiB

Open AccessArticle

The Role of Mediated Oxidation on the Electro-irradiated Treatment of Amoxicillin and Ampicillin Polluted Wastewater

by Fernando L. Silva, Cristina Sáez, Marcos R.V. Lanza, Pablo Cañizares and Manuel A. Rodrigo

Catalysts 2019, 9(1), 9; https://doi.org/10.3390/catal9010009 - 24 Dec 2018

Cited by 23 | Viewed by 3035

Abstract

In this work, the electrolysis, photoelectrolysis and sonoelectrolysis with diamond electrodes of amoxicillin (AMX) and ampicillin (AMP) solutions were studied in the context of the search for technologies capable of removing antibiotics from liquid wastes. Single-irradiation processes (sonolysis and photolysis) were also evaluated [...] Read more.

In this work, the electrolysis, photoelectrolysis and sonoelectrolysis with diamond electrodes of amoxicillin (AMX) and ampicillin (AMP) solutions were studied in the context of the search for technologies capable of removing antibiotics from liquid wastes. Single-irradiation processes (sonolysis and photolysis) were also evaluated for comparison. Results showed that AMX and AMP are completely degraded and mineralized by electrolysis in both chloride and sulfate media, although the efficiency is higher in the presence of chloride. The effect of the current density on mineralization efficiency is not relevant and this may be related to the role of mediated oxidation. Irradiation by ultraviolet light or ultrasound (US) waves does not produce a synergistic effect on the mineralization of AMX and AMP solutions. This indicates that the massive formation of radicals during the combined processes can favor their recombination to form stable and less reactive species. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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19 pages, 11119 KiB

Open AccessFeature PaperArticle

Ag/Ag₂O as a Co-Catalyst in TiO₂ Photocatalysis: Effect of the Co-Catalyst/Photocatalyst Mass Ratio

by Soukaina Akel, Ralf Dillert, Narmina O. Balayeva, Redouan Boughaled, Julian Koch, Mohammed El Azzouzi and Detlef W. Bahnemann

Catalysts 2018, 8(12), 647; https://doi.org/10.3390/catal8120647 - 10 Dec 2018

Cited by 64 | Viewed by 7509

Abstract

Mixtures and composites of Ag/Ag₂O and TiO₂ (P25) with varying mass ratios of Ag/Ag₂O were prepared, employing two methods. Mechanical mixtures (TM) were obtained by the sonication of a suspension containing TiO₂ and Ag/Ag₂O. Composites [...] Read more.

Mixtures and composites of Ag/Ag₂O and TiO₂ (P25) with varying mass ratios of Ag/Ag₂O were prepared, employing two methods. Mechanical mixtures (TM) were obtained by the sonication of a suspension containing TiO₂ and Ag/Ag₂O. Composites (TC) were prepared by a precipitation method employing TiO₂ and AgNO₃. Powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ag(0) and Ag₂O. The activity of the materials was determined employing methylene blue (MB) as the probe compound. Bleaching of MB was observed in the presence of all materials. The bleaching rate was found to increase with increasing amounts of TiO₂ under UV/vis light. In contrast, the MB bleaching rate decreased with increasing TiO₂ content upon visible light illumination. XRD and XPS data indicate that Ag₂O acts as an electron acceptor in the light-induced reaction of MB and is transformed by reduction of Ag⁺, yielding Ag(0). As a second light-induced reaction, the evolution of molecular hydrogen from aqueous methanol was investigated. Significant H₂ evolution rates were only determined in the presence of materials containing more than 50 mass% of TiO₂. The experimental results suggest that Ag/Ag₂O is not stable under the experimental conditions. Therefore, to address Ag/Ag₂O as a (photo)catalytically active material does not seem appropriate. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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13 pages, 2788 KiB

Open AccessArticle

TiO₂-SiO₂-PMMA Terpolymer Floating Device for the Photocatalytic Remediation of Water and Gas Phase Pollutants

by Valentina Sabatini, Luca Rimoldi, Laura Tripaldi, Daniela Meroni, Hermes Farina, Marco Aldo Ortenzi and Silvia Ardizzone

Catalysts 2018, 8(11), 568; https://doi.org/10.3390/catal8110568 - 21 Nov 2018

Cited by 8 | Viewed by 4388

Abstract

Floating photocatalytic devices are highly sought-after as they represent good candidates for practical application in pollutant remediation of large water basins. Here, we present a multilayer floating device for the photocatalytic remediation of contaminants present in water as well as of volatile species [...] Read more.

Floating photocatalytic devices are highly sought-after as they represent good candidates for practical application in pollutant remediation of large water basins. Here, we present a multilayer floating device for the photocatalytic remediation of contaminants present in water as well as of volatile species close to the water surface. The device was prepared on a novel tailored ter-polymer substrate based on methylmethacrylate, α-methylstyrene and perfluoroctyl methacrylate. The ad hoc synthesized support presents optimal characteristics in terms of buoyancy, transparency, gas permeability, mechanical, UV and thermal stability. The adhesion of the TiO₂ top layer was favoured by the adopted casting procedure, followed by a corona pre-treatment and by the deposition of an intermediate SiO₂ layer, the latter aimed also at protecting the polymer support from photocatalytic oxidation. The device was characterized by contact angle measurement, UV-vis transmittance and scanning electron microscopy. The final device was tested for the photocatalytic degradation of an emerging water pollutant as well as of vapors of a model volatile organic compound. Relevant activity was observed also under simulated solar irradiation and the device showed good stability and recyclability, prospecting its use for the photocatalytic degradation of pollutants in large water basins. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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Review

Jump to: Editorial, Research

37 pages, 6574 KiB

Open AccessReview

A Review on the Pathways of the Improved Structural Characteristics and Photocatalytic Performance of Titanium Dioxide (TiO₂) Thin Films Fabricated by the Magnetron-Sputtering Technique

by Yu-Hsiang Wang, Kazi Hasibur Rahman, Chih-Chao Wu and Kuan-Chung Chen

Catalysts 2020, 10(6), 598; https://doi.org/10.3390/catal10060598 - 27 May 2020

Cited by 61 | Viewed by 6956

Abstract

Titanium dioxide (TiO₂) thin films are used for a broad range of applications such as wastewater treatment, photocatalytic degradation activity, water splitting, antibacterial and also in biomedical applications. There is a wide range of synthesis techniques for the deposition of TiO [...] Read more.

Titanium dioxide (TiO₂) thin films are used for a broad range of applications such as wastewater treatment, photocatalytic degradation activity, water splitting, antibacterial and also in biomedical applications. There is a wide range of synthesis techniques for the deposition of TiO₂ thin films, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), both of which are well known deposition methods. Layer by layer deposition with good homogeneity, even thickness and good adhesive nature is possible by using the PVD technique, with the products being used for photocatalytic applications. This review studies the effects of magnetron sputtering conditions on TiO₂ films. This innovative technique can enhance the photocatalytic activity by increasing the thickness of the film higher than any other methods. The main purpose of this article is to review the effects of DC and RF magnetron sputtering conditions on the preparation of TiO₂ thin films for photocatalysis. The characteristics of TiO₂ films (i.e., structure, composition, and crystallinity) are affected significantly by the substrate type, the sputtering power, the distance between substrate and target, working pressure, argon/oxygen ratio, deposition time, substrate temperature, dopant types, and finally the annealing treatment. The photocatalytic activity and optical properties, including the degree of crystallinity, band gap (E_g), refractive index (n), transmittance (T), and extinction coefficient (k), of TiO₂ films are dependent on the above- mentioned film characteristics. Optimal TiO₂ films should have a small particle size, a strong degree of crystallinity, a low band gap, a low contact angle, a high refractive index, transmittance, and extinction coefficient. Finally, metallic and nonmetallic dopants can be added to enhance the photocatalytic activity of TiO₂ films by narrowing the band gap. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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30 pages, 5150 KiB

Open AccessReview

Synthesis and Surface Modification of TiO₂-Based Photocatalysts for the Conversion of CO₂

by Samar Al Jitan, Giovanni Palmisano and Corrado Garlisi

Catalysts 2020, 10(2), 227; https://doi.org/10.3390/catal10020227 - 14 Feb 2020

Cited by 114 | Viewed by 10077

Abstract

Among all greenhouse gases, CO₂ is considered the most potent and the largest contributor to global warming. In this review, photocatalysis is presented as a promising technology to address the current global concern of industrial CO₂ emissions. Photocatalysis utilizes a semiconductor [...] Read more.

Among all greenhouse gases, CO₂ is considered the most potent and the largest contributor to global warming. In this review, photocatalysis is presented as a promising technology to address the current global concern of industrial CO₂ emissions. Photocatalysis utilizes a semiconductor material under renewable solar energy to reduce CO₂ into an array of high-value fuels including methane, methanol, formaldehyde and formic acid. Herein, the kinetic and thermodynamic principles of CO₂ photoreduction are thoroughly discussed and the CO₂ reduction mechanism and pathways are described. Methods to enhance the adsorption of CO₂ on the surface of semiconductors are also presented. Due to its efficient photoactivity, high stability, low cost, and safety, the semiconductor TiO₂ is currently being widely investigated for its photocatalytic ability in reducing CO₂ when suitably modified. The recent TiO₂ synthesis and modification strategies that may be employed to enhance the efficiency of the CO₂ photoreduction process are described. These modification techniques, including metal deposition, metal/non-metal doping, carbon-based material loading, semiconductor heterostructures, and dispersion on high surface area supports, aim to improve the light absorption, charge separation, and active surface of TiO₂ in addition to increasing product yield and selectivity. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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17 pages, 3586 KiB

Open AccessReview

Graphitic Carbon Nitride Materials for Photocatalytic Hydrogen Production via Water Splitting: A Short Review

by Seong Jun Mun and Soo-Jin Park

Catalysts 2019, 9(10), 805; https://doi.org/10.3390/catal9100805 - 25 Sep 2019

Cited by 70 | Viewed by 14319

Abstract

The generation of photocatalytic hydrogen via water splitting under light irradiation is attracting much attention as an alternative to solve such problems as global warming and to increase interest in clean energy. However, due to the low efficiency and selectivity of photocatalytic hydrogen [...] Read more.

The generation of photocatalytic hydrogen via water splitting under light irradiation is attracting much attention as an alternative to solve such problems as global warming and to increase interest in clean energy. However, due to the low efficiency and selectivity of photocatalytic hydrogen production under solar energy, a major challenge persists to improve the performance of photocatalytic hydrogen production through water splitting. In recent years, graphitic carbon nitride (g-C₃N₄), a non-metal photocatalyst, has emerged as an attractive material for photocatalytic hydrogen production. However, the fast recombination of photoexcited electron–hole pairs limits the rate of hydrogen evolution and various methods such as modification, heterojunctions with semiconductors, and metal and non-metal doping have been applied to solve this problem. In this review, we cover the rational design of g-C₃N₄-based photocatalysts achieved using methods such as modification, metal and non-metal doping, and heterojunctions, and we summarize recent achievements in their application as hydrogen production photocatalysts. In addition, future research and prospects of hydrogen-producing photocatalysts are also reviewed. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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25 pages, 3328 KiB

Open AccessReview

Recent Progress on Metal Sulfide Composite Nanomaterials for Photocatalytic Hydrogen Production

by Sher Ling Lee and Chi-Jung Chang

Catalysts 2019, 9(5), 457; https://doi.org/10.3390/catal9050457 - 17 May 2019

Cited by 69 | Viewed by 6446

Abstract

Metal sulfide-based photocatalysts have gained much attention due to their outstanding photocatalytic properties. This review paper discusses recent developments on metal sulfide-based nanomaterials for H₂ production, acting as either photocatalysts or cocatalysts, especially in the last decade. Recent progress on key experimental [...] Read more.

Metal sulfide-based photocatalysts have gained much attention due to their outstanding photocatalytic properties. This review paper discusses recent developments on metal sulfide-based nanomaterials for H₂ production, acting as either photocatalysts or cocatalysts, especially in the last decade. Recent progress on key experimental parameters, in-situ characterization methods, and the performance of the metal sulfide photocatalysts are systematically discussed, including the forms of heterogeneous composite photocatalysts, immobilized photocatalysts, and magnetically separable photocatalysts. Some methods have been studied to solve the problem of rapid recombination of photoinduced carriers. The electronic density of photocatalysts can be investigated by in-situ C K-edge near edge X-ray absorption fine structure (NEXAFS) spectra to study the mechanism of the photocatalytic process. The effects of crystal properties, nanostructure, cocatalyst, sacrificial agent, electrically conductive materials, doping, calcination, crystal size, and pH on the performance of composite photocatalysts are presented. Moreover, the facet effect and light trapping (or light harvesting) effect, which can improve the photocatalytic activity, are also discussed. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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32 pages, 9086 KiB

Open AccessEditor’s ChoiceReview

Advanced Design and Synthesis of Composite Photocatalysts for the Remediation of Wastewater: A Review

by Jianlong Ge, Yifan Zhang, Young-Jung Heo and Soo-Jin Park

Catalysts 2019, 9(2), 122; https://doi.org/10.3390/catal9020122 - 30 Jan 2019

Cited by 204 | Viewed by 12098

Abstract

Serious water pollution and the exhausting of fossil resources have become worldwide urgent issues yet to be solved. Solar energy driving photocatalysis processes based on semiconductor catalysts is considered to be the most promising technique for the remediation of wastewater. However, the relatively [...] Read more.

Serious water pollution and the exhausting of fossil resources have become worldwide urgent issues yet to be solved. Solar energy driving photocatalysis processes based on semiconductor catalysts is considered to be the most promising technique for the remediation of wastewater. However, the relatively low photocatalytic efficiency remains a critical limitation for the practical use of the photocatalysts. To solve this problem, numerous strategies have been developed for the preparation of advanced photocatalysts. Particularly, incorporating a semiconductor with various functional components from atoms to individual semiconductors or metals to form a composite catalyst have become a facile approach for the design of high-efficiency catalysts. Herein, the recent progress in the development of novel photocatalysts for wastewater treatment via various methods in the sight of composite techniques are systematically discussed. Moreover, a brief summary of the current challenges and an outlook for the development of composite photocatalysts in the area of wastewater treatment are provided. Full article

(This article belongs to the Special Issue New Trends in Photo(Electro)catalysis: From Wastewater Treatment to Energy Production)

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