Catalysts and Photocatalysts Based on Mixed Metal Oxides

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

Deadline for manuscript submissions: closed (31 October 2023) | Viewed by 10598

Special Issue Editors

N.N. Semenov Federal Research Center for Chemical Physics, Russian Academy of Sciences, Kosygin st. 4, 119991 Moscow, Russia
Interests: catalysis; photocatalysis; metal oxides; doping; nano-semiconductors; EPR sprctroscopy
Laboratory of Photoactive Nanocomposite Materials, Saint-Petersburg State University, Ulyanovskaya Str. 1, Peterhof, 198504 Saint-Petersburg, Russia
Interests: photocatalysis; self-cleaning; superhydrophilic; antibacterial surfaces; metal and semiconductor particles; nanocristalyne transparent coatings; functional test according to DIN; CEN and ISO
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

It is well-known that in many practical applications and in fundamental research metal oxides have an extremely important role in heterogeneous catalysis. During the last two decades, they have also been used as nanostructured semiconductor photocatalysts. Doped and bare mixed oxides are based mainly on titanium dioxide, TiO2, and other transition metal complexes have revealed interesting features as self-cleaning, effective anti-bacterial and detoxicant materials. Every year, hundreds of new original articles and several reviews are published in leading scientific journals.

This Special Issue of Catalysts is dedicated to novel trends in the synthesis, characterization, properties, functional activity, and applications of mixed metal oxides of different types active in catalytic and photocatalytic reactions and processes. In this Special Issue we intend to gather specialists in chemistry, photochemistry, chemical catalysis, as well as photo- and photoelectrocatalysis. The Issue will include both original reports and short focused review papers to stimulate further developments in these fields. Given your innovative work in this area, we are convinced that your contribution is essential for the success of this project. It would also bring attention to the broader catalytic/photocatalytic community to the growing field of novel trends in practical aspects of the area.

Prof. Dr. Alexander Kokorin
Prof. Dr. Detlef W. Bahnemann
Guest Editors

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Keywords

  • catalysis
  • photocatalysis
  • metal oxides
  • doping
  • structure
  • properties
  • physical methods

Published Papers (9 papers)

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Research

22 pages, 17448 KiB  
Article
Effect of Copper Particle Size on the Surface Structure and Catalytic Activity of Cu–CeO2 Nanocomposites Prepared by Mechanochemical Synthesis in the Preferential CO Oxidation in a H2-Rich Stream (CO-PROX)
by Olga M. Zhigalina, Olga S. Morozova, Dmitry N. Khmelenin, Alla A. Firsova, Olga V. Silchenkova, Galina A. Vorobieva, Andrey V. Bukhtiyarov, Evgeny N. Cherkovskiy and Victoria G. Basu
Catalysts 2024, 14(4), 222; https://doi.org/10.3390/catal14040222 - 27 Mar 2024
Viewed by 219
Abstract
An effect of Cu powder dispersion and morphology on the surface structure and the physical–chemical and catalytic properties of Cu–CeO2 catalysts prepared by mechanochemical synthesis was studied in the preferential CO oxidation in a H2-rich stream (CO-PROX). Two catalysts, produced [...] Read more.
An effect of Cu powder dispersion and morphology on the surface structure and the physical–chemical and catalytic properties of Cu–CeO2 catalysts prepared by mechanochemical synthesis was studied in the preferential CO oxidation in a H2-rich stream (CO-PROX). Two catalysts, produced by 30 min ball-milling from CeO2 and 8 mass% of copper powders and with particle sizes of several tens (dendrite-like Cu) and 50–200 nm (spherical Cu obtained with levitation-jet method), respectively, were characterized by X-ray diffraction and electron microscopy methods, a temperature-programmed reduction with CO and H2, and with Fourier-transform infrared spectroscopy. The catalyst synthesized from the “large-scale” dendrite-like Cu powder, whose surface consisted of CuxO (Cu+) agglomerates located directly on the surface of facetted CeO2 crystals with a CeO2(111) and CeO2(100) crystal planes exposition, was approximately two times less active at 120–160 °C than the catalyst synthesized from the fine Cu powder, whose surface consisted of CuxO (Cu2+) clusters of 4–6 nm in size located on the steps of facetted CeO2 nanocrystals. Although a large part of CO2 reacted with a ceria surface to give carbonate-like species, no blockage of CO-activating centers was observed due to the surface architecture. The surface structure formed by the use of highly dispersed Cu powder is found to be a key factor responsible for the catalytic activity. Full article
(This article belongs to the Special Issue Catalysts and Photocatalysts Based on Mixed Metal Oxides)
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20 pages, 9332 KiB  
Article
Green Synthesis of Mixed ZnO-SnO2 Nanoparticles for Solar-Assisted Degradation of Synthetic Dyes
by Tahani Saad Algarni, Amal M. Al-Mohaimeed, Naaser A. Y. Abduh, Reem Abdulrahman Habab and Saad Mohammed Alqahtani
Catalysts 2023, 13(12), 1509; https://doi.org/10.3390/catal13121509 - 13 Dec 2023
Cited by 1 | Viewed by 1027
Abstract
In this work, ZnO, SnO2, and their mixed ZnO-SnO2(25%) nanoparticles (NPs) were successfully green synthesized in a straightforward manner with a low-cost and environmentally friendly approach using a banana peel extract. The synthesized nanophotocatalysts were characterized using various techniques [...] Read more.
In this work, ZnO, SnO2, and their mixed ZnO-SnO2(25%) nanoparticles (NPs) were successfully green synthesized in a straightforward manner with a low-cost and environmentally friendly approach using a banana peel extract. The synthesized nanophotocatalysts were characterized using various techniques including FTIR, XRD, UV-Vis, TEM, SEM, BET, PL, EDS, and TGA. The characterization results showed that the ZnO and SnO2 powders were crystallized in a hexagonal wurtzite and rutile-type tetragonal structures, respectively, and their mixed ZnO-SnO2(25%) NPs contain both structures. Also, it was found that the addition of SnO2 into the ZnO structure reduces the PL intensity of the latter, confirming better separation of electron/hole pairs. The average particle size of a ZnO-SnO2(25%) NP photocatalyst was found to be 7.23 nm. The cationic dyes methylene blue (MB) and crystal violet (CV) as well as the anionic dyes naphthol blue black (NBB) and Coomassie brilliant blue R 250 (CBB) were employed as model dyes to assess the dye removal efficiencies of the biosynthesized nanophotocatalysts under sunlight. In all cases, the mixed ZnO-SnO2(25%) NP photocatalyst showed much better photocatalytic activity than individual photocatalysts. The degradation percent of dyes using ZnO-SnO2(25%) NPs ranged between 92.2% and 98%. The efficient photocatalytic activity of ZnO-SnO2(25%) NPs is attributed to the effective charge separation and reduced electron/hole recombination rate. The kinetic study results conformed to a pseudo first-order reaction rationalized in terms of the Langmuir–Hinshelwood model. Furthermore, the results showed that the ZnO-SnO2(25%) NP photocatalyst is highly stable and could be recycled several times without a noticeable reduction in its catalytic activity towards dye removal. Full article
(This article belongs to the Special Issue Catalysts and Photocatalysts Based on Mixed Metal Oxides)
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14 pages, 1939 KiB  
Article
Cryogels from Pt/γ-Fe2O3 and Pd/γ-Fe2O3 NPs as Promising Electrocatalysts for Ethanol Oxidation Reaction
by Hadir Borg, Irene Morales, Daniel Kranz, Nadja C. Bigall and Dirk Dorfs
Catalysts 2023, 13(7), 1074; https://doi.org/10.3390/catal13071074 - 06 Jul 2023
Cited by 1 | Viewed by 1041
Abstract
Cryogels from noble metal NPs have proven to be highly efficient catalysts due to their high specific surface area which increases the mass transfer channels and catalytic active sites. By using metal oxides as co-catalysts, the costs of the material can be significantly [...] Read more.
Cryogels from noble metal NPs have proven to be highly efficient catalysts due to their high specific surface area which increases the mass transfer channels and catalytic active sites. By using metal oxides as co-catalysts, the costs of the material can be significantly reduced, while the catalytic activity can remain the same or even improve due to synergetic effects. In this work, we synthesize different cryogel thin films supported on modified ITO substrates from Pt, Pd nanoparticles (NPs), and mixtures of these noble metals with γ-Fe2O3 NPs in a very low concentration (1 wt% of the noble metal). Structural and elemental analysis of the samples are performed, along with the measurement and analysis of their catalytic activity. The electrocatalytic activity of the cryogels towards ethanol oxidation reaction (EOR) in alkaline media was evaluated by means of cyclic voltammetry. By mixing γ-Fe2O3 NPs with Pt or Pd NPs in the cryogel structure, we observe increased tolerance against poisonous surface intermediates produced during the EOR. Moreover, we observe an increase in the catalytic activity towards EOR in the case of the 1 wt% Pd/γ-Fe2O3 cryogel, making them promising materials for the development of direct ethanol fuel cells. Full article
(This article belongs to the Special Issue Catalysts and Photocatalysts Based on Mixed Metal Oxides)
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17 pages, 3713 KiB  
Article
Photodeposition of Hydroxyapatite into a Titanium Dioxide Nanotubular Layer Using Ca(EDTA) Complex Decomposition
by Veronika Yu. Yurova, Polina I. Zyrianova, Pavel V. Nesterov, Vyacheslav V. Goncharov, Ekaterina V. Skorb and Sviatlana A. Ulasevich
Catalysts 2023, 13(6), 993; https://doi.org/10.3390/catal13060993 - 09 Jun 2023
Cited by 2 | Viewed by 1194
Abstract
A new photocatalytic hydroxyapatite (HA) synthesis method has been developed. This method is based on the unique ability of the TiO2 photocatalyst to decompose the Ca(EDTA) complex under UV illumination. As a result, released Ca2+ ions react with PO43− [...] Read more.
A new photocatalytic hydroxyapatite (HA) synthesis method has been developed. This method is based on the unique ability of the TiO2 photocatalyst to decompose the Ca(EDTA) complex under UV illumination. As a result, released Ca2+ ions react with PO43− ions forming the HA particles. The photocatalytic formation of hydroxyapatite is found to have a fractional order, which may indicate the complex reaction mechanism and the presence of several limiting stages. The TNT-HA samples were studied by XRD, FTIR, SEM, GDOES, and biocompatibility study. High biocompatibility of the surfaces is proven by pre-osteoblast cell growth. Full article
(This article belongs to the Special Issue Catalysts and Photocatalysts Based on Mixed Metal Oxides)
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14 pages, 3357 KiB  
Article
Photocatalytic and Antimicrobial Activity of TiO2 Films Deposited on Fiber-Cement Surfaces
by Robson H. Rosa, Ricardo S. Silva, Lucas L. Nascimento, Monica H. Okura, Antonio Otavio T. Patrocinio and João A. Rossignolo
Catalysts 2023, 13(5), 861; https://doi.org/10.3390/catal13050861 - 09 May 2023
Cited by 1 | Viewed by 1489
Abstract
In this study, TiO2 films were deposited via the doctor blade technique on fiber-cement surfaces. Two types of nanoparticles (TiO2-P25 from Degussa and TiO2-PC105 from Tronox) were used to produce films. Scanning electron microscopy (SEM) and atomic force [...] Read more.
In this study, TiO2 films were deposited via the doctor blade technique on fiber-cement surfaces. Two types of nanoparticles (TiO2-P25 from Degussa and TiO2-PC105 from Tronox) were used to produce films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images revealed films with homogeneous and nanoparticulated morphology. The TiO2 PC105 film presented a lower roughness parameter (RMS) in relation to that of the TiO2 P25-based film. Both films exhibited high hydrophilicity when exposed to UV-A radiation (contact angle θ < 6°). The photocatalytic activity of the films was evaluated by standardized methylene blue dye degradation assays under UV-A irradiation (1.0 mW/cm2). The TiO2-PC105 film showed a photonic efficiency of ξ = 0.1%, while for the films obtained with TiO2-P25, ξ = 0.08%. The cement surface modified with the PC105 film was evaluated for antimicrobial activity through the use of multiple pathogens commonly found in hospitals. A considerably high efficiency was measured with visible light. Growth inhibition rates of 99.0% ± 0.2, 99.1% ± 0.2, 99.1% ± 0.2, 97.5% ± 0.5, 98.0% ± 0.5 and 98.0% ± 0.5 were found for Staphylococcus aureus, Klebsiella sp., Escherichia coli, Rhizobium sp., Fusarium sp. and Penicillium sp., respectively. The results show the self-cleaning ability and their potential use for protection, by preventing contamination of the fiber-cement surface and opening new possibilities for the use of this building material. Full article
(This article belongs to the Special Issue Catalysts and Photocatalysts Based on Mixed Metal Oxides)
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15 pages, 4285 KiB  
Article
Enhanced Titania Photocatalyst on Magnesium Oxide Support Doped with Molybdenum
by Anatoly Kulak and Alexander Kokorin
Catalysts 2023, 13(3), 454; https://doi.org/10.3390/catal13030454 - 21 Feb 2023
Cited by 1 | Viewed by 1158
Abstract
Titania photocatalysts supported on mesoporous MgO carriers doped with Mo(VI) ions were prepared and characterized by XRD, BET nitrogen adsorption, FT-IR, and EPR methods. The photocatalytic activity was evaluated by bleaching an aqueous dye solution in the presence of a dispersed photocatalyst and [...] Read more.
Titania photocatalysts supported on mesoporous MgO carriers doped with Mo(VI) ions were prepared and characterized by XRD, BET nitrogen adsorption, FT-IR, and EPR methods. The photocatalytic activity was evaluated by bleaching an aqueous dye solution in the presence of a dispersed photocatalyst and by bleaching the dry surface of a solid tablet of photocatalyst using rhodamine B and nigrosin as model organic pollutants. It was established that TiO2 photocatalyst based on MgO carrier doped with 1 wt.% Mo(VI) ions, with the ratio of MgO:TiO2 = 1:0.5, possessed the highest activity under UV radiation. The increase in the content of molybdenum up to 10 wt.% leads to the formation of a MoO3 nanophase on the MgO surface, the formation of an isotype nn heterojunction at the MoO3/TiO2 interface, and photocatalytic activity under the action of visible light. Full article
(This article belongs to the Special Issue Catalysts and Photocatalysts Based on Mixed Metal Oxides)
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14 pages, 4005 KiB  
Article
Template-Assisted SnO2: Synthesis, Composition, and Photoelectrocatalytical Properties
by Evgenii Gribov, Evgeny Koshevoy, Iuliia Chikunova and Valentin Parmon
Catalysts 2023, 13(1), 168; https://doi.org/10.3390/catal13010168 - 11 Jan 2023
Cited by 3 | Viewed by 1261
Abstract
A series of tin oxides were synthesized with polystyrene microspheres (250 nm) as the template. It was shown that an increase in the template content led to increasing specific pore volume and to the formation of bimodal pore structure with pores of 9 [...] Read more.
A series of tin oxides were synthesized with polystyrene microspheres (250 nm) as the template. It was shown that an increase in the template content led to increasing specific pore volume and to the formation of bimodal pore structure with pores of 9 and 70 nm in diameter. Addition of cetyltrimethylammonium bromide (CTAB) during synthesis led to the formation of friable structures (SEM data), to an increase in the average pore diameter from 19 to 111 nm, and to the formation of macropores of 80–400 nm in size. All materials had similar surface properties and cassiterite structure with 5.9–10.8 nm coherent scattering region (XRD data). Flat-band potentials of the samples were determined and their photoelectrocatalytic properties to oxidation of water and methanol were studied in the potential range of 0.4–1.6 V RHE. It was shown that the sample obtained using CTAB was characterized by lower flat-band potential value, but appeared significantly higher photocurrent in methanol oxidation, which resulted from enhanced macro-meso-porous structure to facilitate methanol pore diffusion. Full article
(This article belongs to the Special Issue Catalysts and Photocatalysts Based on Mixed Metal Oxides)
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15 pages, 2228 KiB  
Article
Synthesis of Catalytic Precursors Based on Mixed Ni-Al Oxides by Supercritical Antisolvent Co-Precipitation
by Nikolay S. Nesterov, Vera P. Pakharukova, Alexey A. Philippov, Evgeny Y. Gerasimov, Sergey V. Tsybulya and Oleg N. Martyanov
Catalysts 2022, 12(12), 1597; https://doi.org/10.3390/catal12121597 - 06 Dec 2022
Cited by 8 | Viewed by 1416
Abstract
Mixed Ni-Al oxide catalytic precursors with different elemental ratios (20, 50, and 80 wt.% Ni0) were synthesized using green supercritical antisolvent co-precipitation (SAS). The obtained oxide precursors and metal catalysts were characterized in detail by X-ray diffraction (XRD) analysis, atomic pair [...] Read more.
Mixed Ni-Al oxide catalytic precursors with different elemental ratios (20, 50, and 80 wt.% Ni0) were synthesized using green supercritical antisolvent co-precipitation (SAS). The obtained oxide precursors and metal catalysts were characterized in detail by X-ray diffraction (XRD) analysis, atomic pair distribution function (PDF) analysis, CO adsorption, and high-resolution transmission electron microscopy (HRTEM). It was found that the composition and structure of the Ni-Al precursors are related to the Ni content. The mixed Ni1−xAlxO oxide with NiO-based crystal structure was formed in the Ni-enriched sample, whereas the highly dispersed NiAl2O4 spinel was observed in the Al-enriched sample. The obtained metal catalysts were tested in the process of anisole H2-free hydrogenation. 2-PrOH was used as a hydrogen donor. The catalyst with 50 wt.% Ni0 demonstrated the highest activity in the hydrogenation process. Full article
(This article belongs to the Special Issue Catalysts and Photocatalysts Based on Mixed Metal Oxides)
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14 pages, 4567 KiB  
Article
Influence of the LaMn1−xFexO3 (x = 0–1) Composition on Catalytic Activities in the Reactions Involving Oxygen
by Lyubov Isupova, Vladimir Rogov, Evgenii Gerasimov and Igor Prosvirin
Catalysts 2022, 12(12), 1563; https://doi.org/10.3390/catal12121563 - 02 Dec 2022
Viewed by 861
Abstract
Perovskite samples of the LaMn1−xFexO3 (x = 0–1) series were prepared by the Pechini method; their physicochemical properties were studied using XRD, HRTEM, XPS, and BET, and their catalytic activity was estimated in nitrous oxide decomposition and methane [...] Read more.
Perovskite samples of the LaMn1−xFexO3 (x = 0–1) series were prepared by the Pechini method; their physicochemical properties were studied using XRD, HRTEM, XPS, and BET, and their catalytic activity was estimated in nitrous oxide decomposition and methane and CO oxidation reactions. In methane and CO oxidation reactions, all intermediate (0 < x < 1) samples of the series exhibited a lower catalytic activity normalized to the unit surface area as compared to the extreme terms, whereas in the nitrous oxide decomposition all intermediate samples were more active than extreme terms of the series. Different dependences of activities on the composition obtained in the study for the tested reactions involving the catalyst oxygen are caused by differences in the reaction mechanisms. Full article
(This article belongs to the Special Issue Catalysts and Photocatalysts Based on Mixed Metal Oxides)
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