New Trends in Photocatalysis: Photocatalytic Materials and Applications

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

Deadline for manuscript submissions: closed (10 January 2022) | Viewed by 20073

Special Issue Editors

1. Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, UK
2. Department of Chemical Engineering, Materials, and Industrial Production, University of Naples "Federico II", 80138 Napoli, Italy
Interests: advanced oxidation processes of micropollutants in aqueous solution; kinetic modeling; heterogeneous photocatalysis; continuous-flow microreactors
Special Issues, Collections and Topics in MDPI journals
Department of Chemical Engineering, University of Patras, University Campus, Caratheodory 1, 26504 Patras, Greece
Interests: wastewater treatment technologies; advanced oxidation processes (AOPs) (process integration, kinetics and mechanisms, transformation byproducts and properties and reaction networks, modeling and optimization, scale-up); industrial wastewater treatment and valorization (olive oil production, edible olives, textiles, cotton processing, wineries, leachates); emerging and persistent micro-pollutants in the water cycle (pharmaceuticals, endocrine disruptors, pesticides); inactivation of waterborne pathogens
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Photocatalysts represent a class of important materials for a wide range of processes, from the production of new pharmaceuticals to environmental applications. As a result, the number of studies investigating photocatalytic materials is steadily increasing, also showing an interesting level of interdisciplinary collaboration between chemists, engineers, and materials scientists. Recent trends focus on the design of catalysts at different hierarchical levels, ranging from molecular to plant-scale, within the more general framework of sustainability challenges and process intensification. Potential topics of interest for this Special Issue include, but are not limited to, the following aspects:

- Synthesis and characterization of novel photocatalysts

- Intensification of photocatalytic processes for the production of functional molecules

- Applications of photocatalysts in wastewater and air treatment

- Photocatalytic materials to address specific sustainability challenges

- Photocatalytic reactor and plant design

- Critical and perspective reviews on proposed aspects of photocatalysis

Dr. Danilo Russo
Prof. Dr. Dionissios Mantzavinos
Guest Editors

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Keywords

  • photocatalysts
  • photocatalysis
  • sustainability
  • material design
  • process intensification
  • environmental

Published Papers (8 papers)

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Research

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18 pages, 7781 KiB  
Article
Photo-Fenton-Like Treatment of Municipal Wastewater
by Yerkanat N. Kanafin, Ardak Makhatova, Vasilios Zarikas, Elizabeth Arkhangelsky and Stavros G. Poulopoulos
Catalysts 2021, 11(10), 1206; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11101206 - 08 Oct 2021
Cited by 12 | Viewed by 1810
Abstract
In this work, the photochemical treatment of a real municipal wastewater using a persulfate-driven photo-Fenton-like process was studied. The wastewater treatment efficiency was evaluated in terms of total carbon (TC), total organic carbon (TOC) and total nitrogen (TN) removal. Response surface methodology (RSM) [...] Read more.
In this work, the photochemical treatment of a real municipal wastewater using a persulfate-driven photo-Fenton-like process was studied. The wastewater treatment efficiency was evaluated in terms of total carbon (TC), total organic carbon (TOC) and total nitrogen (TN) removal. Response surface methodology (RSM) in conjunction Box-Behnken design (BBD) and multilayer artificial neural network (ANN) have been utilized for the optimization of the treatment process. The effects of four independent factors such as reaction time, pH, K2S2O8 concentration and K2S2O8/Fe2+ molar ratio on the TC, TOC and TN removal have been investigated. The process significant factors have been determined implementing Analysis of Variance (ANOVA). Both RSM and ANN accurately found the optimum conditions for the maximum removal of TOC (100% and 98.7%, theoretically), which resulted in complete mineralization of TOC at the reaction time of 106.06 min, pH of 7.7, persulfate concentration of 30 mM and K2S2O8/Fe2+ molar ratio of 7.5 for RSM and at the reaction time of 104.93 min, pH of 7.7, persulfate concentration of 30 mM and K2S2O8/Fe2+ molar ratio of 9.57 for ANN. On the contrary, the attempts to find the optimal conditions for the maximum TC and TN removal using statistical, and neural network models were not successful. Full article
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14 pages, 4721 KiB  
Communication
Valence Regulation of Ultrathin Cerium Vanadate Nanosheets for Enhanced Photocatalytic CO2 Reduction to CO
by Lujia Ding, Qiutong Han, Hong Lu, Yong Yang, Gang Lu, Hui Zhang, Xueqin Ran, Yingdong Xia, Ping Li, Yonghua Chen and Yong Zhou
Catalysts 2021, 11(9), 1115; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11091115 - 16 Sep 2021
Cited by 11 | Viewed by 2046
Abstract
Atomic valence state regulation is an advantageous approach for improving photocatalytic efficiency and product selectivity. However, it is difficult to precisely control the ratio of the different valence states on the surface and the relationship between the surface valence change and catalytic efficiency [...] Read more.
Atomic valence state regulation is an advantageous approach for improving photocatalytic efficiency and product selectivity. However, it is difficult to precisely control the ratio of the different valence states on the surface and the relationship between the surface valence change and catalytic efficiency in the photocatalytic reaction process is unclear. Herein, CeVO4 ultrathin nanosheets were fabricated by one-step solvothermal method with ethanolamine (MEA) as the structure-directing agent. The ratio of the concentrations of intrinsic Ce4+ and Ce3+ ions is precisely modulated from 19.82:100 to 13.33:100 changed by the volume of MEA added without morphology modification. The photocatalytic efficiency increases as the concentrations of intrinsic Ce4+ and Ce3+ ions decrease and CV3 (prepared with 3 mL of MEA) shows the highest CO generation rate approximately 6 and 14 times larger than CV (prepared without MEA) and CV1 (prepared with 1 mL of MEA), respectively, in the photocatalytic CO2 reduction. Interestingly, about 6.8% photo-induced Ce4+ ions were generated on the surface of the catalysts during the photocatalytic CO2 reduction without any phase and morphology changes for CV3. The photocatalytic reaction mechanism is proposed considering the intrinsic and photo-induced Ce4+ ions to obtain efficient photocatalysts. Full article
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19 pages, 4972 KiB  
Article
Enhanced Visible Light Photocatalytic Degradation of Methylene Blue by CdS-ZnS-BiPO4 Nanocomposites Prepared by a Solvent-Assisted Heating Method
by Hsin-Chan Tsai, Yu-Hui Peng, Po-Yu Wen, Tsunghsueh Wu and Yang-Wei Lin
Catalysts 2021, 11(9), 1095; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11091095 - 11 Sep 2021
Cited by 9 | Viewed by 1893
Abstract
In this study, a ternary CdS-ZnS-BiPO4 nanocomposite, synthesized by a solvent-assisted heating method, demonstrated the highest visible light-induced photocatalysis towards the degradation of methylene blue (MB) when comparing with BiPO4, CdS-BiPO4, and ZnS-BiPO4. Transmission electron microscopy [...] Read more.
In this study, a ternary CdS-ZnS-BiPO4 nanocomposite, synthesized by a solvent-assisted heating method, demonstrated the highest visible light-induced photocatalysis towards the degradation of methylene blue (MB) when comparing with BiPO4, CdS-BiPO4, and ZnS-BiPO4. Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) were used to characterize the prepared nanocomposites. From UV-DRS results, the energy band gap of the prepared BiPO4 structures was 4.51 eV. When CdS nanoparticles were deposited on BiPO4 surface by a solvent-assisted heating method, the prepared nanocomposites exhibited visible light-responsive photocatalytic degradation toward MB (20 ppm). At a molar ratio of Cd to Zn as 1:7, the prepared CdS-ZnS-BiPO4 nanocomposites exhibited the best photocatalytic activity in degrading 95% of MB dyes, out-performing pure BiPO4, CdS-BiPO4, and ZnS-BiPO4 due to its enhanced charge separation efficiency and the lowered carrier recombination from the efficient p-n junction of unprecedented ternary composites. The investigations on mechanism conclude that the major reactive species responsible for MB degradation are holes and oxygen radicals. For practicality, the degradation efficiency for different dyestuff (Fast Green FCF, Rhodamine 6G, Acid Blue 1, methyl orange, and methyl red) degradation in the different water matrix samples (pond water, seawater, and lake water) by the prepared CdS-ZnS-BiPO4 nanocomposites was evaluated. Full article
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9 pages, 7545 KiB  
Article
Refractory Metal Oxide–Doped Titanate Nanotubes: Synthesis and Photocatalytic Activity under UV/Visible Light Range
by Min-Sang Kim, Hyun-Joo Choi, Tohru Sekino, Young-Do Kim and Se-Hoon Kim
Catalysts 2021, 11(8), 987; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11080987 - 18 Aug 2021
Cited by 1 | Viewed by 1648
Abstract
This study synthesized refractory metal-oxide-doped titanate nanotubes (TNTs) using a hydrothermal process and investigated their photocatalytic activity under ultraviolet and visible light irradiation. Refractory metal doping ions such as Mo6+ and W6+ can be supplied from molybdenum oxide and tungsten oxide [...] Read more.
This study synthesized refractory metal-oxide-doped titanate nanotubes (TNTs) using a hydrothermal process and investigated their photocatalytic activity under ultraviolet and visible light irradiation. Refractory metal doping ions such as Mo6+ and W6+ can be supplied from molybdenum oxide and tungsten oxide sources. The refractory metal-doped TNT may act as an electron trap or enhance the adsorption capacity, which increases the number of active sites and promotes separation efficiency. Full article
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14 pages, 4281 KiB  
Article
Photocatalytic Degradation of Valsartan by MoS2/BiOCl Heterojunctions
by Eleni Grilla, Maria Nefeli Kagialari, Athanasia Petala, Zacharias Frontistis and Dionissios Mantzavinos
Catalysts 2021, 11(6), 650; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11060650 - 21 May 2021
Cited by 7 | Viewed by 2302
Abstract
In the present study, the removal of valsartan (VLS), an antihypertensive agent, under simulated solar radiation with the use of molybdenum sulfide-bismuth oxychloride composites (MoS2/BiOCl), of variable MoS2 content (0.1–10.0 wt.%) was investigated. The physicochemical properties of the photocatalysts were [...] Read more.
In the present study, the removal of valsartan (VLS), an antihypertensive agent, under simulated solar radiation with the use of molybdenum sulfide-bismuth oxychloride composites (MoS2/BiOCl), of variable MoS2 content (0.1–10.0 wt.%) was investigated. The physicochemical properties of the photocatalysts were examined by XRD, DRS, BET and TEM/HRTEM. Preliminary tests were conducted to examine the photocatalytic efficiency of the synthesized MoS2/BiOCl composites towards VLS degradation in ultrapure water (UPW). It was found that the activity of pure BiOCl is improved with the addition of MoS2. The degradation rate was maximized with the use of the catalyst containing 0.25 wt.% MoS2. It was also found that the increase in catalyst concentration (50–1000 mg/L) enhances VLS degradation. It was found that VLS removal decreased by increasing VLS concentration. The effect of the water matrix on VLS removal was studied by carrying out experiments in real and synthetic water matrices. VLS degradation in UPW was faster than in bottled water (BW) and wastewater (WW), mainly due to the existence of organic matter in real aqueous media. Lastly, 0.25 wt.% MoS2/BiOCl showed great stability after 360 min of irradiation, serving as a promising catalyst for water remediation of emerging contaminants under solar irradiation. Full article
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12 pages, 3703 KiB  
Article
Immobilization of TiO2 Nanoparticles in Hydrogels Based on Poly(methyl acrylate) and Succinamide Acid for the Photodegradation of Organic Dyes
by Xiaomeng You, Hailong Huang, Ran Zhang, Zhongli Yang, Min Xu, Xuelu Wang and Yefeng Yao
Catalysts 2021, 11(5), 613; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11050613 - 11 May 2021
Cited by 9 | Viewed by 2147
Abstract
Hydrogels have excellent properties that make them ideally suited as host matrices for the immobilization of photoreactive materials such as TiO2 nanoparticles that serve as catalysts in the photodegradation of organic dyes, which is of great importance in practical water pollution treatment [...] Read more.
Hydrogels have excellent properties that make them ideally suited as host matrices for the immobilization of photoreactive materials such as TiO2 nanoparticles that serve as catalysts in the photodegradation of organic dyes, which is of great importance in practical water pollution treatment applications. However, the application of hydrogels for this purpose remains poorly studied. The present study addresses this issue by developing two types of hydrogels based on poly(methyl acrylate) and succinamide acid with embedded TiO2 nanoparticles for use as photocatalysts in the photodegradation of organic dyes. The results of the analysis demonstrate that the TiO2 nanoparticles are distributed uniformly in the hydrogel matrices, and the hydrogels maintain their original structures after use. The photodegradation efficiencies of the developed TiO2-hydrogels are demonstrated to be reasonably close to that of freely distributed TiO2 nanoparticles in solution for four different organic dyes. In addition, the results of degradation-regeneration cycling tests demonstrate that immobilizing the TiO2 nanoparticles into the hydrogels greatly reduces their loss during utilization, and the photocatalysts can be easily reused. In fact, the two TiO2-hydrogels retain reasonably high photocatalytic degradation performance after four degradation-regeneration cycles. Full article
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22 pages, 5769 KiB  
Article
Photocatalytic Properties of Core-Shell Structured Wool-TiO2 Hybrid Composite Powders
by Haoshuai Gu, Hui Zhang, Xinyue Zhang, Yani Guo, Limeng Yang, Hailiang Wu and Ningtao Mao
Catalysts 2021, 11(1), 12; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11010012 - 24 Dec 2020
Cited by 9 | Viewed by 1932
Abstract
In this study, a special core–shell structured wool-TiO2 (WT) hybrid composite powder also having TiO2 nanoparticles incorporated inside cortical cells was reported. The wool pallets were pulverized from wool fibers using vibration-assisted ball milling technique and the WT powders having mesopores [...] Read more.
In this study, a special core–shell structured wool-TiO2 (WT) hybrid composite powder also having TiO2 nanoparticles incorporated inside cortical cells was reported. The wool pallets were pulverized from wool fibers using vibration-assisted ball milling technique and the WT powders having mesopores and macropores were produced in hydrothermal process. Experimental results indicated that the infiltrated TiO2 nanoparticles were amorphous structure, while the coated TiO2 nanoparticles were anatase phase structure. The crystallized TiO2 nanoparticles were grafted with wool pallets by the N−Ti4+/S−Ti4+/O−Ti4+ bonds. The BET surface area was measured as 153.5 m2/g and the particle sizes were in the 600–3600 nm and 4000–6500 nm ranges. The main reactive radical species of the WT powders were holes, and •O2, 1O2, and •OH were also involved in the photodegradation of MB dye under visible light irradiation. The experimental parameters for photodegradation of MB dye solution were optimized as follows: 0.25 g/L of WT powders was added in 40 mL of 3 mg/L MB dye solution containing 50 mL/L H2O2, which resulted in the increases of COD value of degraded MB dye solution up to 916.9 mg/L at 120 min. The WT powders could be used for repeatedly photodegradation of both anionic and cationic dyes. Full article
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Review

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26 pages, 3049 KiB  
Review
Photocatalytic Applications in Wastewater and Air Treatment: A Patent Review (2010–2020)
by Marica Muscetta and Danilo Russo
Catalysts 2021, 11(7), 834; https://0-doi-org.brum.beds.ac.uk/10.3390/catal11070834 - 09 Jul 2021
Cited by 19 | Viewed by 3920
Abstract
In this work, we reviewed the most significant patents of the last decade (2010–2020) in the fields of water and air photocatalytic treatment. Patents were discussed by identifying the recurrent addressed issues and presenting the proposed solutions. Adoption of TiO2 and/or modified-TiO [...] Read more.
In this work, we reviewed the most significant patents of the last decade (2010–2020) in the fields of water and air photocatalytic treatment. Patents were discussed by identifying the recurrent addressed issues and presenting the proposed solutions. Adoption of TiO2 and/or modified-TiO2-based material is still the most common choice of inventors, whereas many patents focus on the design of the plants/devices to improve efficiency of photocatalytic treatment by improving light utilization and contact between the phases. The review also highlights issues deriving from specific applications and outlines future trends in the field, such as the need for standardized testing and digitalization of monitoring and control. Full article
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