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15 pages, 4580 KiB

Open AccessArticle

One-Pot Synthesis of Iron-Modified Zeolite X and Characterization of the Obtained Materials

by Fabian N. Murrieta-Rico, Joel Antúnez-García, Rosario I. Yocupicio-Gaxiola, Jonathan Zamora, Armando Reyes Serrato and Vitalii Petranovskii

Catalysts 2023, 13(8), 1159; https://doi.org/10.3390/catal13081159 - 27 Jul 2023

Cited by 5 | Viewed by 1687

Abstract

Iron inclusion in the composition of the zeolite crystal structure endows it with new and useful properties. However, direct synthesis involving Fe, frequently creates unfavorable conditions that hinder the crystallization process and generate impurity phases. For this reason, novel methods, which include iron [...] Read more.

Iron inclusion in the composition of the zeolite crystal structure endows it with new and useful properties. However, direct synthesis involving Fe, frequently creates unfavorable conditions that hinder the crystallization process and generate impurity phases. For this reason, novel methods, which include iron within the zeolitic matrix, are being sought out. This article presents a one-pot synthesis of iron-modified zeolite X. The resulting materials were characterized, and their textural, electrical, and magnetic properties were studied. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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21 pages, 5108 KiB

Open AccessArticle

Porous Hybrid PVDF/BiFeO₃ Smart Composite with Magnetic, Piezophotocatalytic, and Light-Emission Properties

by Farid Orudzhev, Nariman Alikhanov, Abdulkarim Amirov, Alina Rabadanova, Daud Selimov, Abdulatip Shuaibov, Rashid Gulakhmedov, Magomed Abdurakhmanov, Asiyat Magomedova, Shikhgasan Ramazanov, Dinara Sobola, Kamal Giraev, Akhmed Amirov, Kamil Rabadanov, Sultanakhmed Gadzhimagomedov, Rabadanov Murtazali and Valeria Rodionova

Catalysts 2023, 13(5), 874; https://doi.org/10.3390/catal13050874 - 11 May 2023

Cited by 8 | Viewed by 2836

Abstract

The creation of multi-stimuli-sensitive composite polymer–inorganic materials is a practical scientific task. The combination of photoactive magneto-piezoelectric nanomaterials and ferroelectric polymers offers new properties that can help solve environmental and energy problems. Using the doctor blade casting method with the thermally induced phase [...] Read more.

The creation of multi-stimuli-sensitive composite polymer–inorganic materials is a practical scientific task. The combination of photoactive magneto-piezoelectric nanomaterials and ferroelectric polymers offers new properties that can help solve environmental and energy problems. Using the doctor blade casting method with the thermally induced phase separation (TIPS) technique, we synthesized a hybrid polymer–inorganic nanocomposite porous membrane based on polyvinylidene fluoride (PVDF) and bismuth ferrite (BiFeO₃/BFO). We studied the samples using transmission and scanning electron microscopy (TEM/SEM), infrared Fourier spectroscopy (FTIR), total transmission and diffuse reflection, fluorescence microscopy, photoluminescence (PL), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), vibrating-sample magnetometer (VSM), and piezopotential measurements. Our results demonstrate that the addition of BFO increases the proportion of the polar phase from 76.2% to 93.8% due to surface ion–dipole interaction. We also found that the sample exhibits laser-induced fluorescence, with maxima at 475 and 665 nm depending on the presence of nanoparticles in the polymer matrix. Furthermore, our piezo-photocatalytic experiments showed that under the combined actions of ultrasonic treatment and UV–visible light irradiation, the reaction rate increased by factors of 68, 13, 4.2, and 1.6 compared to sonolysis, photolysis, piezocatalysis, and photocatalysis, respectively. This behavior is explained by the piezoelectric potential and the narrowing of the band gap of the composite due to the mechanical stress caused by ultrasound. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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20 pages, 3149 KiB

Open AccessFeature PaperArticle

Photocatalytic Activity and Stability of Organically Modified Layered Perovskite-like Titanates HLnTiO₄ (Ln = La, Nd) in the Reaction of Hydrogen Evolution from Aqueous Methanol

by Sergei A. Kurnosenko, Vladimir V. Voytovich, Oleg I. Silyukov, Ivan A. Rodionov and Irina A. Zvereva

Catalysts 2023, 13(4), 749; https://doi.org/10.3390/catal13040749 - 14 Apr 2023

Cited by 5 | Viewed by 1390

Abstract

Two series of hybrid inorganic–organic materials, prepared via interlayer organic modification of protonated Ruddlesden–Popper phases HLnTiO₄ (Ln = La, Nd) with n-alkylamines and n-alkoxy groups of various lengths, have been systematically studied with respect to photocatalytic hydrogen evolution from aqueous [...] Read more.

Two series of hybrid inorganic–organic materials, prepared via interlayer organic modification of protonated Ruddlesden–Popper phases HLnTiO₄ (Ln = La, Nd) with n-alkylamines and n-alkoxy groups of various lengths, have been systematically studied with respect to photocatalytic hydrogen evolution from aqueous methanol under near-ultraviolet irradiation for the first time. Photocatalytic measurements were organized in such a way as to control a wide range of parameters, including the hydrogen generation rate, quantum efficiency of the reaction, potential dark activity of the sample, its actual volume concentration in the suspension, pH of the medium and stability of the photocatalytic material under the operating conditions. The insertion of the organic modifiers into the interlayer space of the titanates allowed obtaining new, more efficient photocatalytic materials, being up to 68 and 29 times superior in the activity in comparison with the initial unmodified compounds HLnTiO₄ and a reference photocatalyst TiO₂ P25 Degussa, respectively. The hydrogen evolution rate over the samples correlates with the extent of their interlayer hydration, as in the case of the inorganic–organic derivatives of other layered perovskites reported earlier. However, the HLnTiO₄-based samples demonstrate increased stability with regard to the photodegradation of the interlayer organic components as compared with related H₂Ln₂Ti₃O₁₀-based hybrid materials. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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15 pages, 3670 KiB

Open AccessEditor’s ChoiceArticle

Influence of the Valence of Iron on the NO Reduction by CO over Cu-Fe-Mordenite

by Yulia Kotolevich, Trino Zepeda-Partida, Rosario Yocupicio-Gaxiola, Joel Antúnez-Garcia, Luis Pelaez, Miguel Avalos-Borja, Pedro Jovanni Vázquez-Salas, Sergio Fuentes-Moyado and Vitalii Petranovskii

Catalysts 2023, 13(3), 484; https://doi.org/10.3390/catal13030484 - 27 Feb 2023

Cited by 2 | Viewed by 1336

Abstract

A comprehensive study of the catalytic properties of the copper-iron binary system supported on mordenite, depending on the iron valence—CuFe2MOR and CuFe3MOR—was carried out, and redox ability has been considered as a decisive factor in determining catalytic efficiency. Acidity was studied by TPD-NH [...] Read more.

A comprehensive study of the catalytic properties of the copper-iron binary system supported on mordenite, depending on the iron valence—CuFe2MOR and CuFe3MOR—was carried out, and redox ability has been considered as a decisive factor in determining catalytic efficiency. Acidity was studied by TPD-NH₃, DRIFT-OH, and DRT methods. The total acidity of both samples was high. The Brönsted acidity is similar for both bimetallic samples and is explained by the acidity of zeolite; Lewis acidity varies greatly and depends on the exchange cations. A screening DRIFT study of CO and NO has shown redox capacity and demonstrated a potential for using these materials as catalysts for ambient protection. CuFe2MOR demonstrated stable Cu and Fe species, while CuFe3MOR showed redox dynamic species. As expected, CuFe3MOR displayed higher catalytic performance in NO reduction via CO oxidation, because of the easily reduced intermediate NO-complex adsorbed on the metallic Cu and Fe sites, which were observed through in situ DRIFT study. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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17 pages, 6409 KiB

Open AccessArticle

MnO₂ Doped with Ag Nanoparticles and Their Applications in Antimicrobial and Photocatalytic Reactions

by G. Anguraj, R. Ashok Kumar, C. Inmozhi, R. Uthrakumar, Mohamed S. Elshikh, Saeedah Musaed Almutairi and K. Kaviyarasu

Catalysts 2023, 13(2), 397; https://doi.org/10.3390/catal13020397 - 12 Feb 2023

Cited by 17 | Viewed by 4000

Abstract

A wide range of nanoparticles have been produced for photocatalysis applications. Nonetheless, degrading organic dyes requires nanoparticles that are efficient and excellent. As a photocatalyst, pure manganese oxide (MnO₂) was prepared via a sol–gel method using silver (Ag) nanoparticles of transition [...] Read more.

A wide range of nanoparticles have been produced for photocatalysis applications. Nonetheless, degrading organic dyes requires nanoparticles that are efficient and excellent. As a photocatalyst, pure manganese oxide (MnO₂) was prepared via a sol–gel method using silver (Ag) nanoparticles of transition metal oxide. In addition to X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX), the crystal structure and elemental composition were analysed. According to XRD data, the transition metal of MnO₂ oxide is highly pure and has a small crystallite size. The presence of functional groups was confirmed and clarified using Fourier-transform infrared spectra (FTIR). By irradiating the transition pure and doped MnO₂ photocatalysts with visible light, the UV-vis, μ-Raman, and surface areas were determined. As a result, of using the photocatalysts with aqueous methylene blue (MB) solutions under visible light irradiation, the MnO₂ doped with Ag nanoparticles demonstrated high degradation efficiencies and were utilised to establish heterogeneous photocatalysis dominance. In this paper, we demonstrate that the photocatalytic efficiency of transition metal oxides is exclusively determined by the particle size and surface area of nano-sized materials. Due to their high surface charge ratio and different surface orientations, have the highest photocatalytic efficiency. Generally, MnO₂ doped with Ag nanoparticles is resistant to bacteria of both Gram-positive and Gram-negative types (B. sublittus and Escherichia coli). There is still a need for more research to be performed on reducing the toxicity of metal and metal oxide nanoparticles so that they can be used as an effective alternative to antibiotics and disinfectants, particularly for biomedical applications. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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14 pages, 4068 KiB

Open AccessArticle

Features of the Catalytic Cracking of Propane with a Step-Wise Change Pr_xYb_2−xZr₂O₇

by Ekaterina B. Markova, Alexander G. Cherednichenko, Sofia S. Smirnova, Tatiana F. Sheshko and Tatiana A. Kryuchkova

Catalysts 2023, 13(2), 396; https://doi.org/10.3390/catal13020396 - 11 Feb 2023

Cited by 3 | Viewed by 4118

Abstract

In this paper, the features of catalytic cracking of propane with a step-wise change in the composition of the catalyst from Pr₂Zr₂O₇ to Yb₂Zr₂O₇ were considered. For the research, samples of catalysts Pr [...] Read more.

In this paper, the features of catalytic cracking of propane with a step-wise change in the composition of the catalyst from Pr₂Zr₂O₇ to Yb₂Zr₂O₇ were considered. For the research, samples of catalysts Pr₂Zr₂O₇, (Pr_0.75Yb_0.25)₂Zr₂O₇, (Pr_0.5Yb_0.5)₂Zr₂O₇, (Pr_0.25Yb_0.75)₂Zr₂O₇ and Yb₂Zr₂O₇ were synthesized and analyzed. Analysis of the results from catalytic experiments showed that for the catalyst (Pr_0.25Yb_0.75)₂Zr₂O₇, at a temperature of 700 °C, the conversion of propane reaches values of 100%, but for Yb₂Zr₂O₇, this indicator decreases to 84%. The selectivity for ethylene is consistently reduced from 85% to 28% in several catalysts (Pr_0.75Yb_0.25)₂Zr₂O₇ > Pr₂Zr₂O₇ > (Pr_0.5Yb_0.5)₂Zr₂O₇ >(Pr_0.25Yb_0.75)₂Zr₂O₇ > Yb₂Zr₂O₇. An increase in the number of surface adsorption centers leads to a predominant rupture of the C–C bond in the propane molecule with the formation of ethylene. When ytterbium ions are introduced into the catalyst, the amount of ethylene in the reaction products decreases, but the selectivity for propylene increases in the series Pr₂Zr₂O₇ < (Pr_0.75Yb_0.25)₂Zr₂O₇ < (Pr_0.5Yb_0.5)₂Zr₂O₇ < Yb₂Zr₂O₇ < (Pr_0.25Yb_0.75)₂Zr₂O₇, which is associated with a decrease in the binding energy of carbon atoms in propane with the catalytic center during adsorption. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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22 pages, 6842 KiB

Open AccessArticle

Active Sites in H-Mordenite Catalysts Probed by NMR and FTIR

by Marina G. Shelyapina, Ekaterina A. Krylova, Anton S. Mazur, Alexey A. Tsyganenko, Yaroslav V. Shergin, Elizaveta A. Satikova and Vitalii Petranovskii

Catalysts 2023, 13(2), 344; https://doi.org/10.3390/catal13020344 - 3 Feb 2023

Cited by 5 | Viewed by 2503

Abstract

Mordenites are widely used in catalysis and environmental protection. The catalytic properties of mordenite are largely determined by the composition of its crystal framework, i.e., the SiO₂/Al₂O₃ molar ratio (MR), and the cationic form. In H-mordenites, the most [...] Read more.

Mordenites are widely used in catalysis and environmental protection. The catalytic properties of mordenite are largely determined by the composition of its crystal framework, i.e., the SiO₂/Al₂O₃ molar ratio (MR), and the cationic form. In H-mordenites, the most important characteristic becomes the structure and distribution of acid sites, which depends on the number and distribution of Al tetrahedra in the framework. In the present work, the local structure of these centers in H-mordenite catalysts with a nominal MR varied from 9.9 to 19.8 was studied in detail using a combination of magic angle spinning nuclear magnetic resonance (MAS NMR) and Fourier transform infrared spectroscopy (FTIR). ²⁷Al MAS NMR indicates the presence of extra-framework Al in most of the studied samples that results in a higher real MR of the zeolitic framework compared to the nominal value. Concentrations of Lewis and Brønsted acid sites, as well as of silanol groups were estimated by elemental analysis, NMR, and FTIR spectroscopy. The values of site concentrations obtained from band intensities of adsorbed CO and those of OH groups are compared with the amount of framework and extra-framework aluminum. The advantages and restrictions of different methods of active site characterization are discussed. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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14 pages, 3091 KiB

Open AccessArticle

Selectivity Control of CO₂ Reduction over Pt/g-C₃N₄ Photocatalysts under Visible Light

by Andrey A. Saraev, Anna Y. Kurenkova, Angelina V. Zhurenok, Evgeny Y. Gerasimov and Ekaterina A. Kozlova

Catalysts 2023, 13(2), 273; https://doi.org/10.3390/catal13020273 - 25 Jan 2023

Cited by 7 | Viewed by 2347

Abstract

Photocatalysts based on g-C₃N₄ have been investigated in the CO₂ reduction reaction under visible light irradiation (λ = 397, 427, 452 nm). Photocatalysts were prepared by melamine calcination at 500–600 °C with further platinum deposition (0.1–1.0 wt.%). The effect [...] Read more.

Photocatalysts based on g-C₃N₄ have been investigated in the CO₂ reduction reaction under visible light irradiation (λ = 397, 427, 452 nm). Photocatalysts were prepared by melamine calcination at 500–600 °C with further platinum deposition (0.1–1.0 wt.%). The effect of the preparation conditions of g-C₃N₄ and the method of platinum deposition on the physicochemical properties and activity of photocatalysts was studied. The photocatalysts were investigated by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, X-ray diffraction, high resolution transmission electron microscopy, UV-Vis spectroscopy, and low temperature nitrogen adsorption techniques. It has been found that the efficiency of CO₂ reduction is governed by the surface area of g-C₃N₄ and the presence of platinum in the metallic state, while the optimal content of platinum is 0.5 wt. %. The highest rate of CO₂ reduction achieved over Pt/g-C₃N₄ photocatalyst is 13.2 µmol h⁻¹ g⁻¹ (397 nm), which exceeds the activity of pristine g-C₃N₄ by 7 times. The most active photocatalysts was prepared by calcining melamine in air at 600 °C, followed by modification with platinum (0.5 wt.%). Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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16 pages, 5640 KiB

Open AccessArticle

Synthesis and Characterization of ZnO Doped TiO₂ Nanocomposites for Their Potential Photocatalytic and Antimicrobial Applications

by Anguraj Gunasekaran, Ashok Kumar Rajamani, Chandrasekar Masilamani, Inmozhi Chinnappan, Uthrakumar Ramamoorthy and Kasinathan Kaviyarasu

Catalysts 2023, 13(2), 215; https://doi.org/10.3390/catal13020215 - 17 Jan 2023

Cited by 12 | Viewed by 4408

Abstract

As a result of the sol-gel method, we were able to produce pure ZnO and ZnO-doped TiO₂ nanocomposites. The hexagonal wurtzite phase in ZnO products was discovered by powder X-ray diffraction (XRD). ZnO products are typically hexagonal wurtzite crystallites, formed according to [...] Read more.

As a result of the sol-gel method, we were able to produce pure ZnO and ZnO-doped TiO₂ nanocomposites. The hexagonal wurtzite phase in ZnO products was discovered by powder X-ray diffraction (XRD). ZnO products are typically hexagonal wurtzite crystallites, formed according to the Debye Scherrer formula. Nanocomposites with significant morphological changes were created using the sol-gel process, including those that resembled rocks. To determine the composition of Zn, O, and Ti atoms in the samples, a multidimensional X-ray analysis was performed. There is an energy gap between 3.61 eV, as determined by UV-vis spectroscopy. In this study, pure ZnO and ZnO-doped TiO₂ nanocomposites were used to study the degradation of methylene blue (MB) under visible light irradiation. Over an irradiation course of 6 h, a ZnO-doped TiO₂ composite (84%) were studied. As determined by the kinetic analysis, nanocomposites made from pure ZnO and ZnO-doped TiO₂ followed pseudo-first-order kinetics. In the presence of ZnO-doped TiO₂ nanocomposites, antibacterial activity was significantly improved. This was shown to be effective against Gram-positive and Gram-negative bacteria (Escherichia coli and B. sublittus). There is evidence that the metal oxide nanocomposites that are produced can be used as an appropriate antimicrobial and disinfection alternative, particularly in biomedical settings, as reported in more detail. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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13 pages, 3329 KiB

Open AccessArticle

Synthesis, Characterization and Photocatalytic Activity of Spherulite-like r-TiO₂ in Hydrogen Evolution Reaction and Methyl Violet Photodegradation

by Anastasia K. Bachina, Vadim I. Popkov, Anna S. Seroglazova, Maria O. Enikeeva, Anna Yu. Kurenkova, Ekaterina A. Kozlova, Evgeny Y. Gerasimov, Albina A. Valeeva and Andrey A. Rempel

Catalysts 2022, 12(12), 1546; https://doi.org/10.3390/catal12121546 - 1 Dec 2022

Cited by 7 | Viewed by 2042

Abstract

Synthesis and characterization of spherulite-like nanocrystalline titania with rutile structure (r-TiO₂) are described herein. The r-TiO₂ particles were synthesized via the convenient and low-cost hydrothermal treatment of TiO(C₆H₆O₇) titanyl citrate. The [...] Read more.

Synthesis and characterization of spherulite-like nanocrystalline titania with rutile structure (r-TiO₂) are described herein. The r-TiO₂ particles were synthesized via the convenient and low-cost hydrothermal treatment of TiO(C₆H₆O₇) titanyl citrate. The r-TiO₂ spherulites are micron-sized agglomerates of rod-shaped nanocrystals with characteristic sizes of 7(±2) × 43(±10) nm, oriented along (101) crystallographic direction, and separated by micropores, as revealed by SEM and TEM. PXRD and Raman spectroscopy confirmed the nanocrystalline nature of r-TiO₂ crystallites. BET analysis showed a high specific surface area of 102.6 m²/g and a pore volume of 6.22 mm³/g. Photocatalytic performances of the r-TiO₂ spherulites were investigated for the processes of methyl violet (MV) degradation in water and hydrogen evolution reaction (HER) in aqueous solutions of ethanol. The (MV) degradation kinetics was found to be first-order and the degradation rate coefficient is 2.38 × 10⁻² min⁻¹. The HER was performed using pure r-TiO₂ spherulites and nanocomposite r-TiO₂ spherulites with platinum deposited on the surface (r-TiO₂/Pt). It was discovered that the r-TiO₂/Pt nanocomposite has a 15-fold higher hydrogen evolution rate than pure r-TiO₂; their rates are 161 and 11 nmol/min, respectively. Thus, the facile synthesis route and the high photocatalytic performances of the obtained nanomaterials make them promising for commercial use in such photocatalytic processes as organic contamination degradation and hydrogen evolution. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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15 pages, 9510 KiB

Open AccessArticle

One Step Synthesis of Oxygen Defective Bi@Ba₂TiO₄/BaBi₄Ti₄O₁₅ Microsheet with Efficient Photocatalytic Activity for NO Removal

by Ting Gao, Ke Zhang, Qiuhui Zhu, Qingyun Tian, Hui Wang, Wei Zhang, Jiangyushan Liang, Jingqi Lin, Ahmed A. Allam, Jamaan S. Ajarem, Peter K. J. Robertson and Chuanyi Wang

Catalysts 2022, 12(11), 1455; https://doi.org/10.3390/catal12111455 - 17 Nov 2022

Cited by 4 | Viewed by 1943

Abstract

Photocatalysis is an effective technology for NO removal even at low concentrations in the ambient atmosphere. However, the low efficiency of this advanced process and the tendency of producing toxic byproducts hinder the practical application of photocatalysis. To overcome these problems, the Bi@Ba [...] Read more.

Photocatalysis is an effective technology for NO removal even at low concentrations in the ambient atmosphere. However, the low efficiency of this advanced process and the tendency of producing toxic byproducts hinder the practical application of photocatalysis. To overcome these problems, the Bi@Ba₂TiO₄/BaBi₄Ti₄O₁₅ photocatalytic composites were successfully prepared by a one-step hydrothermal method. The as-synthesized photocatalysts exhibited an efficient photocatalytic performance and generated low amounts of toxic byproducts. X-ray diffraction studies show that Bi³⁺ is successfully reduced on the surface of Ba₂TiO₄/BaBi₄Ti₄O₁₅ (BT/BBT). After L-Ascorbic acid (AA) modification, the photocatalytic NO removal efficiency of Bi@Ba₂TiO₄/BaBi₄Ti₄O₁₅ is increased from 25.55% to 67.88%, while the production of the toxic byproduct

{NO}_{2}

is reduced by 92.02%, where the initial concentration of NO is diluted to ca. 800 ppb by the gas stream and the flow rate is controlled at 301.98 mL·min⁻¹ in a 150 mL cylindrical reactor. Furthermore, ambient humidity has little effect on the photocatalytic performance of theBi@Ba₂TiO₄/BaBi₄Ti₄O₁₅, and the photocatalyst exhibits excellent reusability after repeated cleaning with deionized water. The improved photocatalytic effect is attributed to the addition of AA in BT/BBT being able to reduce Bi³⁺ ions to form Bi nanoparticles giving surface plasmon effect (SPR) and generate oxygen vacancies (OVs) at the same time, thereby improving the separation efficiency of photogenerated carriers, enhancing the light absorption, and increasing the specific surface areas. The present work could provide new insights into the design of high-performance photocatalysts and their potential applications in air purification, especially for NO removal. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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16 pages, 10183 KiB

Open AccessArticle

Electrochemical Activity of Original and Infiltrated Fe-Doped Ba(Ce,Zr,Y)O₃-Based Electrodes to Be Used for Protonic Ceramic Fuel Cells

by Liana R. Tarutina, Anna V. Kasyanova, George N. Starostin, Gennady K. Vdovin and Dmitry A. Medvedev

Catalysts 2022, 12(11), 1421; https://doi.org/10.3390/catal12111421 - 12 Nov 2022

Cited by 2 | Viewed by 2318

Abstract

Proton-ceramic fuel cells (PCFCs) are promising devices for electrochemical energy conversion purposes due to their combination of high energy efficiency, environmental friendliness, and high durability. In the present work, the polarization characteristics of promising electrodes for PCFCs based on BaFe_xCe_0.7−x [...] Read more.

Proton-ceramic fuel cells (PCFCs) are promising devices for electrochemical energy conversion purposes due to their combination of high energy efficiency, environmental friendliness, and high durability. In the present work, the polarization characteristics of promising electrodes for PCFCs based on BaFe_xCe_0.7−xZr_0.2Y_0.1O_3−δ (BCZYFx) are comprehensively studied. Along with the individual BCZYFx electrodes, we investigated a method for improving their electrochemical activity by introducing nanoparticles of PrO_x electrocatalysts into the porous structure of the electrode material. According to the experimental data, electroactivation allowed for the polarization resistances of the electrodes at 700 °C to be reduced from 1.16, 0.27, 0.62 Ω°cm² to 0.09, 0.13, 0.43 Ω°cm² for x = 0.5, 0.6, and 0.7, respectively. For a PCFC cell with an air electrode of BCZYF0.6 composition activated using PrO_x nanoparticles, it was possible to achieve a maximum specific power of 300 mW cm⁻² at 750 °C, which is competitive for a single cell with Co-free cathodes. The results obtained provide insight into the processes occurring in the studied electrodes after electroactivation. It is shown how the improvement of electrochemical characteristics of the electrode can be realized by a simple infiltration method in combination with a subsequent thermal treatment. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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13 pages, 3177 KiB

Open AccessArticle

Crystal Structure and Properties of Gd_1-xSr_xCo_1-yFe_yO_3-δ Oxides as Promising Materials for Catalytic and SOFC Application

by Tatiana V. Aksenova, Darya K. Mysik and Vladimir A. Cherepanov

Catalysts 2022, 12(11), 1344; https://doi.org/10.3390/catal12111344 - 2 Nov 2022

Cited by 6 | Viewed by 1761

Abstract

A series of samples with the overall composition Gd_1-xSr_xCo_1-yFe_yO_3-δ (x = 0.8; 0.9 and 0.1 ≤ y ≤ 0.9), which are promising materials for catalytic and SOFC application, was prepared by [...] Read more.

A series of samples with the overall composition Gd_1-xSr_xCo_1-yFe_yO_3-δ (x = 0.8; 0.9 and 0.1 ≤ y ≤ 0.9), which are promising materials for catalytic and SOFC application, was prepared by a glycerol nitrate technique. X-ray diffraction analysis allowed to describe Gd_0.2Sr_0.8Co_1-yFe_yO_3-δ with 0.1 ≤ y ≤ 0.5 in a tetragonal 2a_p × 2a_p × 4a_p superstructure (SG I4/mmm), while oxides with 0.6 ≤ y ≤ 0.9 exhibit cubic disordered perovskite structure (SG Pm-3m). All Gd_0.1Sr_0.9Fe_1-yCo_yO_3-δ oxides within the composition range 0.1 ≤ y ≤ 0.9 possess the cubic perovskite structure (SG Pm-3m). The structural parameters were refined using the Rietveld full-profile method. The changes of oxygen content in Gd_1-xSr_xCo_1-yFe_yO_3-δ versus temperature were determined by thermogravimetric analysis. The introduction of iron into the cobalt sublattice leads to a gradual increase in the unit cell parameters and unit cell volume, accompanied with increasing oxygen content. The temperature dependency of conductivity for Gd_0.2Sr_0.8Co_0.3Fe_0.7O_3-δ exhibits a maximum (284 S/cm) at ≈600 K in air. The positive value of the Seebeck coefficient indicates predominant p-type conductivity in the Gd_0.2Sr_0.8Co_0.3Fe_0.7O_3-δ complex oxide. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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10 pages, 3068 KiB

Open AccessArticle

The Effect of Transition Metal Substitution in the Perovskite-Type Oxides on the Physicochemical Properties and the Catalytic Performance in Diesel Soot Oxidation

by Liliya V. Yafarova, Grigory V. Mamontov, Irina V. Chislova, Oleg I. Silyukov and Irina A. Zvereva

Catalysts 2021, 11(10), 1256; https://doi.org/10.3390/catal11101256 - 19 Oct 2021

Cited by 6 | Viewed by 2617

Abstract

The paper is focused on the Fe for Co substitution effect on the redox and catalytic properties in the perovskite structure of GdFeO₃. The solid oxides with the composition GdFe_1−xCo_xO₃ (x = 0; 0.2; 0.5; 0.8; [...] Read more.

The paper is focused on the Fe for Co substitution effect on the redox and catalytic properties in the perovskite structure of GdFeO₃. The solid oxides with the composition GdFe_1−xCo_xO₃ (x = 0; 0.2; 0.5; 0.8; 1) were obtained by the sol-gel method and characterized by various methods: X-ray diffraction (XRD), temperature-programmed reduction (H₂-TPR), N₂ sorption, temperature-programmed desorption of oxygen (TPD-O₂), simultaneous thermal analysis (STA), and X-ray photoelectron spectroscopy (XPS). The H₂-TPR results showed that an increase in the cobalt content in the GdFe_1−xCo_xO₃ (x = 0; 0.2; 0.5; 0.8; 1) leads to a decrease in the reduction temperature. Using the TPD-O₂ and STA methods, the lattice oxygen mobility is increasing in the course of the substitution of Fe for Co. Thus, the Fe substitution in the perovskite leads to an improvement in the oxygen reaction ability. Experiments on the soot oxidation reveal that catalytic oxidation ability increases in the series: GdFe_0.5Co_0.5O₃ ˂ GdFe_0.2Co_0.8O₃ ˂ GdCoO₃, which is in good correlation with the increasing oxygen mobility according to H2-TPR, TPD-O_2, and STA results. The soot oxidation over GdFeO₃ and GdFe_0.8Co_0.2O₃ is not in this range due to the impurities of iron oxides and higher specific surface area. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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22 pages, 4377 KiB

Open AccessFeature PaperArticle

Synthesis of n-Alkoxy Derivatives of Layered Perovskite-Like Niobate HCa₂Nb₃O₁₀ and Study of Their Photocatalytic Activity for Hydrogen Production from an Aqueous Solution of Methanol

by Vladimir V. Voytovich, Sergey A. Kurnosenko, Oleg I. Silyukov, Ivan A. Rodionov, Alexander N. Bugrov, Iana A. Minich, Ekaterina N. Malygina and Irina A. Zvereva

Catalysts 2021, 11(8), 897; https://doi.org/10.3390/catal11080897 - 25 Jul 2021

Cited by 21 | Viewed by 2710

Abstract

A series of hybrid inorganic–organic niobates HCa₂Nb₃O₁₀×ROH, containing n-alkoxy groups of primary alcohols (R = Me, Et, Pr, Bu, Hx, and Dc) grafted in the interlayer space, has been studied for the first time in relation [...] Read more.

A series of hybrid inorganic–organic niobates HCa₂Nb₃O₁₀×ROH, containing n-alkoxy groups of primary alcohols (R = Me, Et, Pr, Bu, Hx, and Dc) grafted in the interlayer space, has been studied for the first time in relation to photocatalytic hydrogen generation from a model 1 mol % aqueous solution of methanol under ultraviolet irradiation. Photocatalytic activity was measured both for bare samples and for their composites with Pt nanoparticles as a cocatalyst. The advanced measurement scheme allowed monitoring the volume concentration of a sample in a suspension during the experiment, its pH, and possible exfoliation of layered compounds into nanolayers. In the series of n-alkoxy derivatives, the maximum rate of hydrogen evolution was achieved over a Pt-loaded ethoxy derivative HCa₂Nb₃O₁₀×EtOH/Pt. Its apparent quantum efficiency of 20.6% in the 220–350 nm range was found not to be caused by changes in the light absorption region or specific surface area upon ethanol grafting. Moreover, the amounts of hydrogen released during the measurements significantly exceeded those of interlayer organic components, indicating that hydrogen is generated from the reaction solution rather than from the hybrid material. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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Review

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43 pages, 14068 KiB

Open AccessReview

An Evaluation of the Biocatalyst for the Synthesis and Application of Zinc Oxide Nanoparticles for Water Remediation—A Review

by Nkosingiphile E. Zikalala, Shohreh Azizi, Sithembela A. Zikalala, Ilunga Kamika, Malik Maaza, Ali Akbar Zinatizadeh, Touhami Mokrani and Kasinathan Kaviyarasu

Catalysts 2022, 12(11), 1442; https://doi.org/10.3390/catal12111442 - 15 Nov 2022

Cited by 13 | Viewed by 3506

Abstract

Global water scarcity is threatening the lives of humans, and it is exacerbated by the contamination of water, which occurs because of increased industrialization and soaring population density. The available conventional physical and chemical water treatment techniques are hazardous to living organisms and [...] Read more.

Global water scarcity is threatening the lives of humans, and it is exacerbated by the contamination of water, which occurs because of increased industrialization and soaring population density. The available conventional physical and chemical water treatment techniques are hazardous to living organisms and are not environmentally friendly, as toxic chemical elements are used during these processes. Nanotechnology has presented a possible way in which to solve these issues by using unique materials with desirable properties. Zinc oxide nanoparticles (ZnO NPs) can be used effectively and efficiently for water treatment, along with other nanotechnologies. Owing to rising concerns regarding the environmental unfriendliness and toxicity of nanomaterials, ZnO NPs have recently been synthesized through biologically available and replenishable sources using a green chemistry or green synthesis protocol. The green-synthesized ZnO NPs are less toxic, more eco-friendly, and more biocompatible than other chemically and physically synthesized materials. In this article, the biogenic synthesis and characterization techniques of ZnO NPs using plants, bacteria, fungi, algae, and biological derivatives are reviewed and discussed. The applications of the biologically prepared ZnO NPs, when used for water treatment, are outlined. Additionally, their mechanisms of action, such as the photocatalytic degradation of dyes, the production of reactive oxygen species (ROS), the generation of compounds such as hydrogen peroxide and superoxide, Zn²⁺ release to degrade microbes, as well as their adsorbent properties with regard to heavy metals and other contaminants in water bodies, are explained. Furthermore, challenges facing the green synthesis of these nanomaterials are outlined. Future research should focus on how nanomaterials should reach the commercialization stage, and suggestions as to how this ought to be achieved are presented. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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