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16 pages, 4717 KiB

Open AccessArticle

A Study on the Evaluation Methods of Nitrogen Oxide Removal Performance of Photocatalytic Concrete for Outdoor Applications

by Hee-Ju Park, Sayed Mukit Hossain, Kiin Choi, Ho-Kyong Shon and Jong-Ho Kim

Catalysts 2022, 12(8), 846; https://doi.org/10.3390/catal12080846 - 02 Aug 2022

Cited by 2 | Viewed by 1693

Abstract

In Korea, the issue of particulate matter pollution is growing, and many solutions are being developed to deal with it. Photocatalytic technology has been found to be helpful in removing precursors such as nitrogen oxides that cause particulate matter. In a microcosm setup, [...] Read more.

In Korea, the issue of particulate matter pollution is growing, and many solutions are being developed to deal with it. Photocatalytic technology has been found to be helpful in removing precursors such as nitrogen oxides that cause particulate matter. In a microcosm setup, ISO 22197-1 has been successfully used to quantify the removal of nitrogen oxides from the specimen to which the photocatalyst is applied. However, owing to a lack of suitable tools, on-site measurement of real-scale efficacy is difficult. Depending on the substrate and surrounding circumstances at the application location, the photocatalyst may function at varying levels. Additionally, the expected photocatalytic effect may differ depending on the ambient air quality and sunlight irradiation intensity. This article describes two approaches for studying outdoor concrete photocatalysis. Standard gas measurement and dual-reactor measurement are the recommended evaluation approaches. The standard gas measurement method was found useful for assessing the applied photocatalyst itself as an outcome of field assessment. The performance of photocatalysts at different sites was found to be mutually exclusive and comparable. Over 180 min, on a building roof deck, the NO removal by the standard gas method was 0.68 ppm, whereas, at two shaded locations, the removal amount was 0.51 ppm (side wall) and 0.24 ppm (underpass) for 300 min. The dual reactor measurement approach, on the other hand, was discovered to be one of the most suitable methods for assessing how much of an improvement there has been in the air quality in areas where photocatalysts have been placed. Full article

(This article belongs to the Special Issue Photocatalytic Reaction Engineering for Energy Conversion, Water and Air Purification)

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22 pages, 5153 KiB

Open AccessArticle

Synthesis and Evaluation of FeSX/TiO₂ for the Photocatalytic Degradation of Phenol under Visible-Light Region

by Diego Alvarez-Bustos, Felipe Sanchez-Minero, Victor Santes, Issis Claudette Romero-Ibarra, José Antonio de los Reyes Heredia, Reyna Rios-Escobedo, Francisco Tzompantzi-Morales and Carlos Eduardo Santolalla-Vargas

Catalysts 2022, 12(5), 457; https://doi.org/10.3390/catal12050457 - 20 Apr 2022

Cited by 4 | Viewed by 2301

Abstract

In the present work, phenol was used as a model molecule to the photocatalytic evaluation of TiO₂ impregnated with iron sulphide and chlorine on a visible-light reactor. The iron–chlorine catalyst was prepared by incipient impregnation with the metal precursors, Fe (NO₃ [...] Read more.

In the present work, phenol was used as a model molecule to the photocatalytic evaluation of TiO₂ impregnated with iron sulphide and chlorine on a visible-light reactor. The iron–chlorine catalyst was prepared by incipient impregnation with the metal precursors, Fe (NO₃)₃ and NaCl on previously calcined TiO₂. The catalyst was sulphurized with H2S at 300 °C for 1 h. The catalysts were prepared at different chlorine concentrations using HYDRA chemical equilibrium diagrams to obtain different fractions of FeCl⁺. The oxide catalysts were characterized with diffuse reflectance (DRS UV–Vis) and temperature programmed reduction analysis (TPR). Sulphurized catalysts were characterized with Raman spectrometry and X-ray photoelectron spectrometry (XPS). The FeS–2Cl/TiO₂ catalyst presented 8.35 times higher photodegradation than TiO₂ and 6.4 times higher compared to the FeS–0.25Cl/TiO₂ catalyst. DRS and XPS showed similar results of band gap, proving that the catalyst remain stable after sulphurisation. The TPR results of FeS–2Cl/TiO₂ showed an increment of 86.29% in Fe²⁺/Fe³⁺ compared to FeS–0.25Cl/TiO₂. XPS and Raman results for oxide and sulphated iron species relation suggested that FeS–2Cl/TiO₂ decreased 4.45% compared to FeS–0.25Cl/TiO₂ catalyst. XPS semiquantitative for S/Fe results showed that the FeS–2Cl/TiO₂ catalyst increased 73.17% in comparison to FeS–0.25Cl/TiO₂. These results suggested the increment of sulphurisation degree for FeS–2Cl/TiO₂. In this regard, the catalyst characterization results showed that the presence of FeCl⁺ (0.85 fractions) in solution before impregnation promoted the active sulphide species maintaining the band gap and improved the degradation of phenol on visible light. Full article

(This article belongs to the Special Issue Photocatalytic Reaction Engineering for Energy Conversion, Water and Air Purification)

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18 pages, 6531 KiB

Open AccessFeature PaperArticle

H₂ Photoproduction Efficiency: Implications of the Reaction Mechanism as a Function of the Methanol/Water Mixture

by Irene Barba-Nieto, Gerardo Colón, Anna Kubacka and Marcos Fernández-García

Catalysts 2022, 12(4), 402; https://doi.org/10.3390/catal12040402 - 06 Apr 2022

Cited by 1 | Viewed by 1611

Abstract

The influence of the reaction pathway of the sacrificial molecule oxidation to generate hydrogen is here investigated for lean and rich methanol reaction mixtures. Pt-TiO₂ powders promoted or not with tin sulfide were used as catalysts. With the help of in situ [...] Read more.

The influence of the reaction pathway of the sacrificial molecule oxidation to generate hydrogen is here investigated for lean and rich methanol reaction mixtures. Pt-TiO₂ powders promoted or not with tin sulfide were used as catalysts. With the help of in situ infrared experiments under reaction conditions, methanol evolution was shown to take place by hole-related oxidation steps, with alkoxy and carbon-centered species as key radical species. The study analyzed quantitatively the fate and chemical use of the photons absorbed by the solids with the help of the quantum efficiency and the useful fraction of photons observables. Within this framework, the role of the sulfide component to promote photoactivity is interpreted, braiding chemical and photonic information. Full article

(This article belongs to the Special Issue Photocatalytic Reaction Engineering for Energy Conversion, Water and Air Purification)

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31 pages, 9150 KiB

Open AccessFeature PaperArticle

Kinetic Modeling and Quantum Yields: Hydrogen Production via Pd-TiO₂ Photocatalytic Water Splitting under Near-UV and Visible Light

by Bianca Rusinque, Salvador Escobedo and Hugo de Lasa

Catalysts 2022, 12(2), 113; https://doi.org/10.3390/catal12020113 - 18 Jan 2022

Cited by 2 | Viewed by 3144

Abstract

A palladium (Pd) doped mesoporous titanium dioxide (TiO₂) photocatalyst was used to produce hydrogen (H₂) via water splitting under both near-UV and visible light. Experiments were carried out in the Photo-CREC Water-II Reactor (PCW-II) using a 0.25 wt% Pd-TiO [...] Read more.

A palladium (Pd) doped mesoporous titanium dioxide (TiO₂) photocatalyst was used to produce hydrogen (H₂) via water splitting under both near-UV and visible light. Experiments were carried out in the Photo-CREC Water-II Reactor (PCW-II) using a 0.25 wt% Pd-TiO₂ photocatalyst, initial pH = 4 and 2.0 v/v% ethanol, as an organic scavenger. After 6 h of near-UV irradiation, this photocatalyst yielded 113 cm³ STP of hydrogen (H₂). Furthermore, after 1 h of near-UV photoreduction followed by 5 h of visible light, the 0.25 wt% Pd-TiO₂ photocatalyst yielded 5.25 cm³ STP of H₂. The same photocatalyst, photoreduced for 24 h under near-UV and subsequently exposed to 5 h of visible light, yielded 29 cm³ STP of H₂. It was observed that the promoted redox reactions led to the production of hydrogen and by-products such as methane, ethane, ethylene, acetaldehyde, carbon monoxide, carbon dioxide and hydrogen peroxide. These redox reactions could be modeled using an “in series-parallel” reaction network and Langmuir Hinshelwood based kinetics. The proposed rate equations were validated using statistical analysis for the experimental data and calculated kinetic parameters. Furthermore, Quantum yields (

{Q Y}_{H^{•}} %

) based on the H^• produced were also established at promising levels: (a) 34.8% under near-UV light and 1.00 g L⁻¹ photocatalyst concentration; (b) 8.8% under visible light and 0.15 g L⁻¹. photocatalyst concentration following 24 h of near-UV. Full article

(This article belongs to the Special Issue Photocatalytic Reaction Engineering for Energy Conversion, Water and Air Purification)

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11 pages, 3696 KiB

Open AccessArticle

Ionic Liquid-Assisted Synthesis of Ag₃PO₄ Spheres for Boosting Photodegradation Activity under Visible Light

by Beibei Zhang, Lu Zhang, Yulong Zhang, Chao Liu, Jiexiang Xia and Huaming Li

Catalysts 2021, 11(7), 788; https://doi.org/10.3390/catal11070788 - 28 Jun 2021

Cited by 4 | Viewed by 1622

Abstract

In this work, a simple chemical precipitation method was employed to prepare spherical-like Ag₃PO₄ material (IL-Ag₃PO₄) with exposed {111} facet in the presence of reactive ionic liquid 1-butyl-3-methylimidazole dihydrogen phosphate ([Omim]H₂PO₄). The [...] Read more.

In this work, a simple chemical precipitation method was employed to prepare spherical-like Ag₃PO₄ material (IL-Ag₃PO₄) with exposed {111} facet in the presence of reactive ionic liquid 1-butyl-3-methylimidazole dihydrogen phosphate ([Omim]H₂PO₄). The crystal structure, microstructure, optical properties, and visible-light photocatalytic performance of as-prepared materials were studied in detail. The addition of ionic liquids played a crucial role in forming spherical-like morphology of IL-Ag₃PO₄ sample. Compared with traditional Ag₃PO₄ material, the intensity ratio of {222}/{200} facets in XRD pattern of IL-Ag₃PO₄ was significantly enhanced, indicating the main {111} facets exposed on the surface of IL-Ag₃PO₄ sample. The presence of exposed {111} facet was advantageous for facilitating the charge carrier transfer and separation. The light-harvesting capacity of IL-Ag₃PO₄ was larger than that of Ag₃PO₄. The photocatalytic activity of samples was evaluated by degrading rhodamine B (RhB) and p-chlorophenol (4-CP) under visible light. The photodegradation efficiencies of IL-Ag₃PO₄ were 1.94 and 2.45 times higher than that of Ag₃PO₄ for RhB and 4-CP removal, respectively, attributing to a synergy from the exposed {111} facet and enhanced photoabsorption. Based on active species capturing experiments, holes (h⁺), and superoxide radical (•O₂⁻) were the main active species for visible-light-driven RhB photodegradation. This study will provide a promising prospect for designing and synthesizing ionic liquid-assisted photocatalysts with a high efficiency. Full article

(This article belongs to the Special Issue Photocatalytic Reaction Engineering for Energy Conversion, Water and Air Purification)

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27 pages, 6003 KiB

Open AccessFeature PaperArticle

Photocatalytic Conversion of Organic Pollutants in Air: Quantum Yields Using a Silver/Nitrogen/TiO₂ Mesoporous Semiconductor under Visible Light

by Adilah Sirivallop, Salvador Escobedo, Thanita Areerob, Hugo de Lasa and Siriluk Chiarakorn

Catalysts 2021, 11(5), 529; https://doi.org/10.3390/catal11050529 - 21 Apr 2021

Cited by 7 | Viewed by 2780

Abstract

This research studies the photocatalytic conversion of methanol (25–90 µmol/L range) as a volatile organic compound (VOC) surrogate into CO₂, using a N/Ag/TiO₂ photocatalyst under visible light irradiation in a Photo-CREC Air unit. The N/Ag/TiO₂ mesh supported photocatalyst is [...] Read more.

This research studies the photocatalytic conversion of methanol (25–90 µmol/L range) as a volatile organic compound (VOC) surrogate into CO₂, using a N/Ag/TiO₂ photocatalyst under visible light irradiation in a Photo-CREC Air unit. The N/Ag/TiO₂ mesh supported photocatalyst is prepared via the solvothermal method. While the bare-TiO₂ is inactive under visible light, the N/Ag/TiO₂ 2 wt.% loaded stainless-steel woven mesh displays 35% quantum yields, with 80% absorbed photons and 60% methanol conversion in a 110 min irradiation period. Results obtained are assigned to silver surface plasmon resonance, silver and nitrogen species synergistic impacts on band gap, and their influence on particle agglomerate size and semiconductor acidity. The determined quantum yields under visible light in a Photo-CREC Air unit, are the highest reported in the technical literature, that these authors are aware of, with this opening unique opportunity for the use of visible light for the purification of air from VOC contaminants. Full article

(This article belongs to the Special Issue Photocatalytic Reaction Engineering for Energy Conversion, Water and Air Purification)

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Review

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32 pages, 6833 KiB

Open AccessReview

The Challenges of Integrating the Principles of Green Chemistry and Green Engineering to Heterogeneous Photocatalysis to Treat Water and Produce Green H₂

by Fernanda Anaya-Rodríguez, Juan C. Durán-Álvarez, K. T. Drisya and Rodolfo Zanella

Catalysts 2023, 13(1), 154; https://doi.org/10.3390/catal13010154 - 09 Jan 2023

Cited by 7 | Viewed by 4428

Abstract

Nowadays, heterogeneous photocatalysis for water treatment and hydrogen production are topics gaining interest for scientists and developers from different areas, such as environmental technology and material science. Most of the efforts and resources are devoted to the development of new photocatalyst materials, while [...] Read more.

Nowadays, heterogeneous photocatalysis for water treatment and hydrogen production are topics gaining interest for scientists and developers from different areas, such as environmental technology and material science. Most of the efforts and resources are devoted to the development of new photocatalyst materials, while the modeling and development of reaction systems allowing for upscaling the process to pilot or industrial scale are scarce. In this work, we present what is known on the upscaling of heterogeneous photocatalysis to purify water and to produce green H₂. The types of reactors successfully used in water treatment plants are presented as study cases. The challenges of upscaling the photocatalysis process to produce green H₂ are explored from the perspectives of (a) the adaptation of photoreactors, (b) the competitiveness of the process, and (c) safety. Throughout the text, Green Chemistry and Engineering Principles are described and discussed on how they are currently being applied to the heterogeneous photocatalysis process along with the challenges that are ahead. Lastly, the role of automation and high-throughput methods in the upscaling following the Green Principles is discussed. Full article

(This article belongs to the Special Issue Photocatalytic Reaction Engineering for Energy Conversion, Water and Air Purification)

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35 pages, 5393 KiB

Open AccessFeature PaperReview

Synthesis and Performance of Photocatalysts for Photocatalytic Hydrogen Production: Future Perspectives

by Salvador Escobedo and Hugo de Lasa

Catalysts 2021, 11(12), 1505; https://doi.org/10.3390/catal11121505 - 10 Dec 2021

Cited by 11 | Viewed by 4838

Abstract

Photocatalysis for “green” hydrogen production is a technology of increasing importance that has been studied using both TiO₂–based and heterojunction composite-based semiconductors. Different irradiation sources and reactor units can be considered for the enhancement of photocatalysis. Current approaches also consider the [...] Read more.

Photocatalysis for “green” hydrogen production is a technology of increasing importance that has been studied using both TiO₂–based and heterojunction composite-based semiconductors. Different irradiation sources and reactor units can be considered for the enhancement of photocatalysis. Current approaches also consider the use of electron/hole scavengers, organic species, such as ethanol, that are “available” in agricultural waste, in communities around the world. Alternatively, organic pollutants present in wastewaters can be used as organic scavengers, reducing health and environmental concerns for plants, animals, and humans. Thus, photocatalysis may help reduce the carbon footprint of energy production by generating H₂, a friendly energy carrier, and by minimizing water contamination. This review discusses the most up-to-date and important information on photocatalysis for hydrogen production, providing a critical evaluation of: (1) The synthesis and characterization of semiconductor materials; (2) The design of photocatalytic reactors; (3) The reaction engineering of photocatalysis; (4) Photocatalysis energy efficiencies; and (5) The future opportunities for photocatalysis using artificial intelligence. Overall, this review describes the state-of-the-art of TiO₂–based and heterojunction composite-based semiconductors that produce H₂ from aqueous systems, demonstrating the viability of photocatalysis for “green” hydrogen production. Full article

(This article belongs to the Special Issue Photocatalytic Reaction Engineering for Energy Conversion, Water and Air Purification)

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