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Catalysts
Special Issues
Photocatalysis in Air Purification
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Photocatalysis in Air Purification

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

Deadline for manuscript submissions: closed (29 February 2024) | Viewed by 10560

Special Issue Editors

Dr. Adrián Pastor Espejo

E-Mail Website
Guest Editor
Departamento de Química Inorgánica, Instituto Químico Para la Energía y Medioambiente (IQUEMA), Universidad de Córdoba, Campus de Rabanales, E-14014 Córdoba, Spain
Interests: solid-state chemistry; photocatalysis; environment; NOx; layered double hydroxides
Prof. Dr. Luis Sánchez Granados

E-Mail Website
Guest Editor
Departamento de Química Inorgánica, Instituto Químico Para la Energía y Medioambiente (IQUEMA), Universidad de Córdoba, Campus de Rabanales, E-14014 Córdoba, Spain
Interests: solid-state chemistry; photocatalysis; environment; NOx; nanomaterials

Special Issue Information

Dear Colleagues,

Having clean air in the environment has become a high-priority objective within environmental policy and sustainable development strategies. The World Health Organization recently established (September 2021) the new guideline limits for atmospheric pollutants, meaning that 99% of world population breathe in polluted air. In order to deal with this problem, photocatalysis has emerged as a technology with the ability to remove pollutant gases, such as NOx, CO2, or VOCs. This technology is at the forefront (more than 16,000 search results in 2022 only; Google Scholar) due to its mild conditions to work and the possibility of using the sunlight.

In order to promote an effective practical depollution of outdoor/indoor atmospheres, new materials have been developed, through the creation of new modifications in their chemical structure (doping and defects), their morphology (0D, 1D, 2D and 3D systems), and hierarchical structure (hybrid composites, electronic heterojunctions, membranes, etc.). Thus, new or improved functionalities for the application of these systems as air purification photocatalysts have been created. In this sense, those are also applied as photocatalytic additives to build materials (ceramics, mortars, pavements, paints, etc.) and perform air-cleaning operations at urban centres.

Therefore, this Special Issue compiles the most important recent advances in photocatalytic materials for air purification and aims to act as a meeting forum for acknowledged experts in this field.

Dr. Adrián Pastor Espejo
Prof. Dr. Luis Granados
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 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

  • photocatalysis
  • depollution
  • NOx
  • CO2
  • VOCs
  • nanomaterials
  • additives
  • building materials

Published Papers (6 papers)

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Research

27 pages, 8016 KiB  
Article
Development of Photocatalytic Coatings for Building Materials with Bi2O3-ZnO Nanoparticles
by Víctor M. Tena-Santafé, José M. Fernández, Claudio Fernández-Acevedo, Tamara Oroz-Mateo, Íñigo Navarro-Blasco and José I. Álvarez
Catalysts 2023, 13(11), 1412; https://doi.org/10.3390/catal13111412 - 03 Nov 2023
Viewed by 1251
Abstract
The aim of this study was to develop versatile coatings that can protect the stone surfaces of Architectural Heritage. Two different 3D media, namely superhydrophobic (SPHB) and hydro-oleophobic (OHB), were utilized as host matrices for nanostructured photocatalysts (Bi2O3-ZnO 8/92). [...] Read more.
The aim of this study was to develop versatile coatings that can protect the stone surfaces of Architectural Heritage. Two different 3D media, namely superhydrophobic (SPHB) and hydro-oleophobic (OHB), were utilized as host matrices for nanostructured photocatalysts (Bi2O3-ZnO 8/92). These photocatalysts were sensitive to visible light to enhance their efficiency when exposed to sunlight. To prevent the nanophotocatalyst from clumping together in the 3D media, non-ionic dispersant additives (Tween20, TritonX-100, and Brij35) were incorporated. The optimized suspensions were then applied to various substrates such as sandstone, limestone, and granite. The effectiveness of the coatings was assessed by evaluating the hydrophobicity, oleophobicity, and photocatalytic activity of the coated substrates. The Bi2O3-ZnO photocatalyst exhibited higher activity in the SPHB medium compared to the OHB medium. To simulate real-life conditions, the coated substrates were subjected to accelerated weathering tests to predict their durability. Despite a significant reduction in their thickness, the coatings demonstrated sustained hydrophobic efficiency and self-cleaning capability after the accelerated ageing tests. Full article
(This article belongs to the Special Issue Photocatalysis in Air Purification)
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21 pages, 4893 KiB  
Article
Zn-Cr Layered Double Hydroxides for Photocatalytic Transformation of CO2 under Visible Light Irradiation: The Effect of the Metal Ratio and Interlayer Anion
by Dolores G. Gil-Gavilán, Daniel Cosano, Juan Amaro-Gahete, Miguel Castillo-Rodríguez, Dolores Esquivel, José R. Ruiz and Francisco J. Romero-Salguero
Catalysts 2023, 13(10), 1364; https://doi.org/10.3390/catal13101364 - 12 Oct 2023
Cited by 1 | Viewed by 1267
Abstract
Carbon dioxide is the main gas responsible for the greenhouse effect. Over the last few years, the research focus of many studies has been to transform CO2 into valuable products (CO, HCOOH, HCHO, CH3OH and CH4), since it [...] Read more.
Carbon dioxide is the main gas responsible for the greenhouse effect. Over the last few years, the research focus of many studies has been to transform CO2 into valuable products (CO, HCOOH, HCHO, CH3OH and CH4), since it would contribute to mitigating global warming and environmental pollution. Layered double hydroxides (LDHs) are two-dimensional materials with high CO2 adsorption capacity and compositional flexibility with potential catalytic properties to be applied in CO2 reduction processes. Herein, Zn-Cr LDH-based materials with different metal ratio and interlayer anions, i.e., chloride (Cl−), graphene quantum dots (GQDs), sodium dodecyl sulfate (SDS) and sodium deoxycholate (SDC), have been prepared by a co-precipitation method and characterized by different techniques. The influence of the interlayer inorganic and organic anions and the metal ratio on the application of Zn-Cr LDHs as catalysts for the photocatalytic CO2 reduction reaction under visible light irradiation is unprecedentedly reported. The catalytic tests have been carried out with Ru(bpy)32+ as photosensitizer (PS) and triethanolamine as sacrificial electron donor (ED) at λ = 450 nm. All LDHs materials exhibited good photocatalytic activity towards CO. Among them, LDH3-SDC showed the best catalytic performance, achieving 10,977 µmol CO g−1 at 24 h under visible light irradiation with a CO selectivity of 88%. This study provides pertinent findings about the modified physicochemical features of Zn-Cr LDHs, such as particle size, surface area and the nature of the interlayer anion, and how they influence the catalytic activity in CO2 photoreduction. Full article
(This article belongs to the Special Issue Photocatalysis in Air Purification)
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23 pages, 4699 KiB  
Article
ZnO/TiO2 Composite Thin-Film Photocatalysts for Gas-Phase Oxidation of Ethanol
by Ibrahim Sanusi and Catherine B. Almquist
Catalysts 2023, 13(8), 1203; https://doi.org/10.3390/catal13081203 - 11 Aug 2023
Cited by 2 | Viewed by 1419
Abstract
The aim of this project is to investigate the photocatalytic activity of ZnO/TiO2 composite films for the gas-phase oxidation of ethanol. Pure TiO2, pure ZnO, and their composites were formulated using a sol-gel synthesis method, and the resulting powders were [...] Read more.
The aim of this project is to investigate the photocatalytic activity of ZnO/TiO2 composite films for the gas-phase oxidation of ethanol. Pure TiO2, pure ZnO, and their composites were formulated using a sol-gel synthesis method, and the resulting powders were cast and dried as thin films in a flat-plate ultraviolet light-emitting diode (UV LED) reactor. P25 TiO2 and commercially available ZnO were also used for comparison. The structural, morphological, and optical characteristics of the materials were characterized. The photocatalytic oxidation of ethanol vapors in air after 24 h of reactor operation was used to assess the relative photocatalytic activity of the ZnO/TiO2 composite films. Our results show that as ZnO content increased in the coupled semiconductor materials, the apparent photocatalytic activity decreased. In this study, pure ZnO (both sol-gel and purchased) had the least photocatalytic activity for vapor-phase ethanol oxidation in our test apparatus. For gas-phase photocatalysis, surface area was shown to be a critical feature for photocatalytic activity. However, the inherent photocatalytic activity of the materials was not decoupled from the effects of surface area in this study. Full article
(This article belongs to the Special Issue Photocatalysis in Air Purification)
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12 pages, 6066 KiB  
Article
Metal Bi Loaded Bi2Ti2O7/CaTiO3 for Enhanced Photocatalytic Efficiency for NO Removal under Visible Light
by Diyuan Du, Menglin Shi, Qingqing Guo, Yanqin Zhang, Ahmed A. Allam, Ahmed Rady and Chuanyi Wang
Catalysts 2023, 13(8), 1169; https://doi.org/10.3390/catal13081169 - 30 Jul 2023
Cited by 2 | Viewed by 833
Abstract
NO has caused many serious environmental problems and even seriously threatened human health. The development of a cheap and efficient method to remove NO from the air has become an urgent need. In this paper, a novel nanocomposite metal-semiconductor photocatalyst Bi-Bi2Ti [...] Read more.
NO has caused many serious environmental problems and even seriously threatened human health. The development of a cheap and efficient method to remove NO from the air has become an urgent need. In this paper, a novel nanocomposite metal-semiconductor photocatalyst Bi-Bi2Ti2O7/CaTiO3 was prepared. Compared to the original Bi2Ti2O7/CaTiO3, the modification by the metal Bi increased its photocatalytic activity from 25% to 64% under visible light irradiation. The improved photoactivity owns to the SPR effect and the electron capture effect of Bi metals in metal-semiconductor loaded systems improving the separation efficiency of electron-hole pairs and significantly improving the light absorption capacity of the composite photocatalyst. The capture experiment of active species showed that •OH, •O2−, h+ and e− are the main active species in the photocatalytic conversion of NO. This work provides new insights into the conformational relationships of Ti-based photocatalysts for NO removal. Full article
(This article belongs to the Special Issue Photocatalysis in Air Purification)
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11 pages, 4665 KiB  
Article
Improving Separation Efficiency of Photogenerated Charges through Combination of Conductive Polythiophene for Selective Production of CH4
by Yiqiang Deng, Lingxiao Tu, Ping Wang, Shijian Chen, Man Zhang, Yong Xu and Weili Dai
Catalysts 2023, 13(7), 1142; https://doi.org/10.3390/catal13071142 - 23 Jul 2023
Viewed by 865
Abstract
In today’s society, mankind is confronted with two major problems: the energy crisis and the greenhouse effect. Artificial photosynthesis can use solar energy to convert the greenhouse gas CO2 into high-value compounds, which is an ideal solution to alleviate the energy crisis [...] Read more.
In today’s society, mankind is confronted with two major problems: the energy crisis and the greenhouse effect. Artificial photosynthesis can use solar energy to convert the greenhouse gas CO2 into high-value compounds, which is an ideal solution to alleviate the energy crisis and solve the problem of global warming. The combination of ZnO and polythiophenes (PTh) can make up for each other’s drawbacks, thus improving the photoresponse behavior and separation efficiency of the photogenerated carriers. The PTh layer can transfer photogenerated electrons to ZnO, thereby extending the lifetime of the photogenerated charges. The production rate of CH4 from the photoreduction of CO2 with ZnO/PTh10 is 4.3 times that of pure ZnO, and the selectivity of CH4 is increased from 70.2% to 92.2%. The conductive PTh can absorb photons to induce π–π* transition, and the photogenerated electrons can transfer from the LUMO to the conduction band (CB) of ZnO, thus more electrons are involved in the reduction of CO2. Full article
(This article belongs to the Special Issue Photocatalysis in Air Purification)
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19 pages, 9612 KiB  
Article
Effects of Mott–Schottky Frequency Selection and Other Controlling Factors on Flat-Band Potential and Band-Edge Position Determination of TiO2
by Siaw Foon Lee, Eva Jimenez-Relinque, Isabel Martinez and Marta Castellote
Catalysts 2023, 13(6), 1000; https://doi.org/10.3390/catal13061000 - 13 Jun 2023
Cited by 7 | Viewed by 4172
Abstract
The use of titanium dioxide for tackling environmental pollution has attracted great research interest recently. The potential of a photocatalyst in removing contaminants depends mainly on its conduction and valence-band edges relative to the standard potential of reactive oxygen species. One of the [...] Read more.
The use of titanium dioxide for tackling environmental pollution has attracted great research interest recently. The potential of a photocatalyst in removing contaminants depends mainly on its conduction and valence-band edges relative to the standard potential of reactive oxygen species. One of the methods used in determining these band-edge positions is via the Mott–Schottky analysis. Thus, the aim of this work was to investigate the influence of the Mott–Schottky frequency and different electrochemical conditions on flat-band potential values and band-edge positions of pure anatase or Degussa P25, calcined or uncalcined in a 0.2 M Na2SO4 solution. The results showed that the shift in the flat-band potential was not so frequency-dependent in the Mott–Schottky analysis, however, other reasons, such as immersion duration leading to thenardite Na2SO4 salt deposition on the surface, irradiation of sources and the change in the pH of the solution (in the range of 1.64–12.11) were also responsible for it. In general, both the calcined anatase and P25 had a less negative value of the flat-band potential compared to the uncalcined. On the other hand, the calcined anatase had a tendency to have a less negative value of the flat-band potential than the calcined P25. From this study, the frequency range for obtaining the flat-band potential within one standard deviation in the Mott–Schottky at a single-frequency analysis was found to be between 200 and 2000 Hz. The energy difference between the Fermi level and the conduction band edge for anatase and P25, either calcined or uncalcined, was 0.097–0.186 and 0.084–0.192 eV, respectively. On the other hand, the band-edge position of anatase or P25 tended to shift upwards when it was repeatedly used in the photoelectrochemical analysis. Full article
(This article belongs to the Special Issue Photocatalysis in Air Purification)
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