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14 pages, 12632 KiB

Open AccessArticle

Facile Synthesis of Oxygen-Doped g-C₃N₄ Mesoporous Nanosheets for Significant Enhancement of Photocatalytic Hydrogen Evolution Performance

by Tiekun Jia, Jingjing Li, Zhao Deng, Dongsheng Yu and Joong Hee Lee

Materials 2024, 17(13), 3345; https://doi.org/10.3390/ma17133345 - 6 Jul 2024

Cited by 3 | Viewed by 1387

Abstract

In this work, oxygen-doped g-C₃N₄ mesoporous nanosheets (O-CNS) were synthesized via a facile recrystallization method with the assistance of H₂O₂. The crystal phase, chemical composition, morphological structure, optical property, electronic structure and electrochemical property of the [...] Read more.

In this work, oxygen-doped g-C₃N₄ mesoporous nanosheets (O-CNS) were synthesized via a facile recrystallization method with the assistance of H₂O₂. The crystal phase, chemical composition, morphological structure, optical property, electronic structure and electrochemical property of the prepared O-CNS samples were well investigated. The morphological observation combined with the nitrogen adsorption–desorption results demonstrated that the prepared O-CNS samples possessed nanosheet-like morphology with a porous structure. Doping O into g-C₃N₄ resulted in the augmentation of the specific surface area, which could provide more active sites for photocatalytic reactions. Simultaneously, the visible light absorption capacity of O-CNS samples was boosted owing to the regulation of O doping. The built energy level induced by the O doping could accelerate the migration rate of photoinduced carriers, and the porous structure was most likely to speed up the release of hydrogen during the photocatalytic hydrogen process. Resultantly, the photocatalytic hydrogen production rate of the optimized oxygen-doped g-C₃N₄ nanosheets reached up to 2012.9 μmol·h⁻¹·g⁻¹, which was 13.4 times higher than that of bulk g-C₃N₄. Thus, the significantly improved photocatalytic behavior was imputed to the synergistic effect of the porous structure, the increase in active sites, and the enhancement of visible light absorption and charge separation efficiency. Our research highlights that the synergistic effect caused by element doping will make a great contribution to the remarkable improvement in photocatalytic activity, providing a new inspiration for the construction of novel catalysts. Full article

(This article belongs to the Special Issue Synthesis, Modification and Utilization of Porous Materials as Adsorbents, Catalysts and Catalyst Supports)

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14 pages, 10335 KiB

Open AccessArticle

The Synthesis of Well-Dispersed and Uniform-Sized Zeolite NaY by Adding Non-Refluxed and Acid-Refluxed Cogon Grass

by Pakawan Sereerattanakorn, Pimwipa Tayraukham, Nattawut Osakoo, Panot Krukkratoke, Chalermpan Keawkumay, Jatuporn Wittayakun, Nichakorn Pornnongsan, Krittanun Deekamwong and Sanchai Prayoonpokarach

Materials 2023, 16(23), 7330; https://doi.org/10.3390/ma16237330 - 24 Nov 2023

Viewed by 1723

Abstract

Zeolite NaY synthesized from a typical procedure could suffer from agglomeration. Adding non-refluxed cogon grass (NG) to the synthesis gel could produce NaY with good dispersion and uniform crystal size. Small molecules produced from cogon grass in alkaline conditions could prevent agglomeration. The [...] Read more.

Zeolite NaY synthesized from a typical procedure could suffer from agglomeration. Adding non-refluxed cogon grass (NG) to the synthesis gel could produce NaY with good dispersion and uniform crystal size. Small molecules produced from cogon grass in alkaline conditions could prevent agglomeration. The obtained zeolite (Y-NG) has a crystallinity and surface area comparable to the synthesis without grass (Y-WG). Y-NG demonstrated similar paraquat adsorption capacity to Y-WG at high initial concentrations. On the other hand, the zeolite from the addition of acid-refluxed grass (Y-RG) has the lowest crystallinity, smallest surface area, and poorest paraquat adsorption capacity. The effect of grass amount on the zeolite structure was studied. One gram of cogon grass was the optimum amount to add to the synthesis gel. Full article

(This article belongs to the Special Issue Synthesis, Modification and Utilization of Porous Materials as Adsorbents, Catalysts and Catalyst Supports)

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31 pages, 5930 KiB

Open AccessArticle

Hydrogenation of Carbon Dioxide to Dimethyl Ether on CuO–ZnO/ZSM-5 Catalysts: Comparison of Powder and Electrospun Structures

by Aidin Nejadsalim, Hamid Reza Godini, Sanjay Ramesh Kumar, Fausto Gallucci, Delf Kober, Aleksander Gurlo and Oliver Görke

Materials 2023, 16(23), 7255; https://doi.org/10.3390/ma16237255 - 21 Nov 2023

Cited by 1 | Viewed by 1745

Abstract

The promising direct dimethyl ether (DME) production through CO₂ hydrogenation was systematically analyzed in this research by synthesizing, characterizing, and testing several catalytic structures. In doing so, various combinations of precipitation and impregnation of copper- and zinc-oxides (CuO–ZnO) over a ZSM-5 zeolite [...] Read more.

The promising direct dimethyl ether (DME) production through CO₂ hydrogenation was systematically analyzed in this research by synthesizing, characterizing, and testing several catalytic structures. In doing so, various combinations of precipitation and impregnation of copper- and zinc-oxides (CuO–ZnO) over a ZSM-5 zeolite structure were applied to synthesize the hybrid catalysts capable of hydrogenating carbon dioxide to methanol and dehydrating it to DME. The resulting catalytic structures, including the co-precipitated, sequentially precipitated, and sequentially impregnated CuO–ZnO/ZSM-5 catalysts, were prepared in the form of particle and electrospun fibers with distinguished chemical and structural features. They were then characterized using XRD, BET, XPS, ICP, TGA, SEM, and FIB-SEM/EDS analyses. Their catalytic performances were also tested and analyzed in light of their observed characteristics. It was observed that it is crucial to establish relatively small-size and well-distributed zeolite crystals across a hybrid catalytic structure to secure a distinguished DME selectivity and yield. This approach, along with other observed behaviors and the involved phenomena like catalyst particles and fibers, clusters of catalyst particles, or the whole catalytic bed, were analyzed and explained. In particular, the desired characteristics of a CuO–ZnO/ZSM-5 hybrid catalyst, synthesized in a single-pot processing of the precursors of all involved catalytically active elements, were found to be promising in guiding the future efforts in tailoring an efficient catalyst for this system. Full article

(This article belongs to the Special Issue Synthesis, Modification and Utilization of Porous Materials as Adsorbents, Catalysts and Catalyst Supports)

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15 pages, 3895 KiB

Open AccessArticle

Basic Properties of MgAl-Mixed Oxides in CO₂ Adsorption at High Temperature

by Dylan Chaillot, Vincent Folliard, Jocelyne Miehé-Brendlé, Aline Auroux, Liva Dzene and Simona Bennici

Materials 2023, 16(16), 5698; https://doi.org/10.3390/ma16165698 - 19 Aug 2023

Cited by 2 | Viewed by 1739

Abstract

The increase of consciousness towards global warming and the need to reduce greenhouse gas emissions lead to the necessity of finding alternative applications based on easy-to-use materials in order to control and reduce global CO₂ emissions. Layered Double Hydroxides (LDHs) and LDH-derived [...] Read more.

The increase of consciousness towards global warming and the need to reduce greenhouse gas emissions lead to the necessity of finding alternative applications based on easy-to-use materials in order to control and reduce global CO₂ emissions. Layered Double Hydroxides (LDHs) and LDH-derived materials are potentially good adsorbents for CO₂, thanks to their low cost, easy synthesis, high sorption capacity, and surface basicity. They have been intensively studied in CO₂ capture at high temperature, presenting variable sorption capacities for MgAl LDHs with the same composition, but prepared under different synthesis conditions. The ambient temperature coprecipitation synthesis method is an attractive one-step procedure to synthesize LDHs under mild conditions, with low energy consumption and short synthesis time. The present study is based on the synthesis and characterization of hydrotalcites by a mild-conditions coprecipitation process and the production of derived mixed oxides to be used as CO₂ adsorbents. A critical comparison to similar materials is reported. Moreover, the effect of the surface basicity of the derived mixed oxides (measured by adsorption calorimetry) and the CO₂ sorption capacity are discussed, showing a linear correlation between the amount of weak and very strong basic sites and the CO₂ adsorption behavior. Full article

(This article belongs to the Special Issue Synthesis, Modification and Utilization of Porous Materials as Adsorbents, Catalysts and Catalyst Supports)

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12 pages, 2005 KiB

Open AccessArticle

Hierarchical SAPO-34 Catalysts as Host for Cu Active Sites

by Julio C. Fernandes Pape Brito, Ivana Miletto, Leonardo Marchese, Daniel Ali, Muhammad Mohsin Azim, Karina Mathisen and Enrica Gianotti

Materials 2023, 16(16), 5694; https://doi.org/10.3390/ma16165694 - 19 Aug 2023

Cited by 1 | Viewed by 1336

Abstract

Cu-containing hierarchical SAPO-34 catalysts were synthesized by the bottom-up method using different mesoporogen templates: CTAB encapsulated within ordered mesoporous silica nanoparticles (MSNs) and sucrose. A high fraction of the Cu centers exchanged in the hierarchical SAPO-34 architecture with high mesopore surface area and [...] Read more.

Cu-containing hierarchical SAPO-34 catalysts were synthesized by the bottom-up method using different mesoporogen templates: CTAB encapsulated within ordered mesoporous silica nanoparticles (MSNs) and sucrose. A high fraction of the Cu centers exchanged in the hierarchical SAPO-34 architecture with high mesopore surface area and volume was achieved when CTAB was embedded within ordered mesoporous silica nanoparticles. Physicochemical characterization was performed by using structural and spectroscopic techniques to elucidate the properties of hierarchical SAPO-34 before and after Cu introduction. The speciation of the Cu sites, investigated by DR UV-Vis, and the results of the catalytic tests indicated that the synergy between the textural properties of the hierarchical SAPO-34 framework, the high Cu loading, and the coordination and localization of the Cu sites in the hierarchical architecture is the key point to obtaining good preliminary results in the NO selective catalytic reduction with hydrocarbons (HC-SCR). Full article

(This article belongs to the Special Issue Synthesis, Modification and Utilization of Porous Materials as Adsorbents, Catalysts and Catalyst Supports)

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9 pages, 2504 KiB

Open AccessCommunication

Enhancement of Hydrogen Adsorption on Spray-Synthesized HKUST-1 via Lithium Doping and Defect Creation

by Masaru Kubo, Tomoki Matsumoto and Manabu Shimada

Materials 2023, 16(15), 5416; https://doi.org/10.3390/ma16155416 - 2 Aug 2023

Cited by 4 | Viewed by 1426

Abstract

We prepared HKUST-1 (Cu₃BTC₂; BTC³⁻ = 1,3,5-benzenetricarboxylate) using a spray synthesis method with Li doping and defect created via partial replacement of H₃BTC with isophthalic acid (IP) to enhance the H₂ adsorption capacity. Li-doping was [...] Read more.

We prepared HKUST-1 (Cu₃BTC₂; BTC³⁻ = 1,3,5-benzenetricarboxylate) using a spray synthesis method with Li doping and defect created via partial replacement of H₃BTC with isophthalic acid (IP) to enhance the H₂ adsorption capacity. Li-doping was performed by incorporating LiNO₃ in HKUST-1 via spray synthesis and subsequent thermal treatment for decomposing NO₃⁻, which enhances H₂ uptake at 77 K and 1 bar per unit mass and per unit area from 2.37 wt% and 4.16 molecules/nm² for undoped HKUST-1 to 2.47 wt% and 4.33 molecules/nm², respectively. Defect creation via the replacement of the BTC³⁻ linker with the IP²⁻ linker slightly in HKUST-1 skeleton did not affect H₂ uptake. Both Li-doping and defect creation significantly enhanced H₂ uptake to 3.03 wt%, which was caused by the coordination of Li ions with free carboxylic groups of the created defects via IP replacement. Full article

(This article belongs to the Special Issue Synthesis, Modification and Utilization of Porous Materials as Adsorbents, Catalysts and Catalyst Supports)

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12 pages, 3650 KiB

Open AccessArticle

Synthesis and Characterization of Zeolite NaY Dispersed on Bamboo Wood

by Pimrapus Tawachkultanadilok, Nattawut Osakoo, Chalermpan Keawkumay, Krittanun Deekamwong, Narongrit Sosa, Catleya Rojviriya, Supinya Nijpanich, Narong Chanlek, Sanchai Prayoonpokarach and Jatuporn Wittayakun

Materials 2023, 16(14), 4946; https://doi.org/10.3390/ma16144946 - 11 Jul 2023

Cited by 5 | Viewed by 2240

Abstract

Zeolites in powder form have the potential to agglomerate, lowering access to active sites. Furthermore, a suspension of fine zeolite powder in liquid media is difficult to separate. Such drawbacks could be improved by dispersing zeolite crystals on support materials. This work demonstrates [...] Read more.

Zeolites in powder form have the potential to agglomerate, lowering access to active sites. Furthermore, a suspension of fine zeolite powder in liquid media is difficult to separate. Such drawbacks could be improved by dispersing zeolite crystals on support materials. This work demonstrates the dispersion of zeolite NaY crystals on bamboo wood by mixing the wood with zeolite gel before hydrothermal treatment. The syntheses were performed with acid-refluxed and non–refluxed wood. The phase of zeolites, particle distribution and morphology, zeolite content in the wood, and zeolite–wood interaction were investigated using X-ray diffraction, X-ray tomography, scanning electron microscopy, thermogravimetric analysis, nitrogen sorption analysis, and X-ray photoelectron spectroscopy. Higher zeolite content and better particle dispersion were obtained in the synthesis with the acid–refluxed wood. The composite of NaY on the acid-refluxed wood was demonstrated to be an effective adsorbent for Ni(II) ions in aqueous solutions, providing a higher adsorbed amount of Ni(II) per weight of NaY. Full article

(This article belongs to the Special Issue Synthesis, Modification and Utilization of Porous Materials as Adsorbents, Catalysts and Catalyst Supports)

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17 pages, 2131 KiB

Open AccessArticle

Formation of Ag-Fe Bimetallic Nano-Species on Mordenite Depending on the Initial Ratio of Components

by Yulia Kotolevich, Evgenii Khramov, Perla Sánchez-López, Alexey Pestryakov, Yan Zubavichus, Joel Antúnez-Garcia and Vitalii Petranovskii

Materials 2023, 16(8), 3026; https://doi.org/10.3390/ma16083026 - 11 Apr 2023

Cited by 2 | Viewed by 1932

Abstract

The formation and properties of silver and iron nanoscale components in the Ag-Fe bimetallic system deposited on mordenite depend on several parameters during their preparation. Previously, it was shown that an important condition for optimizing nano-center properties in a bimetallic catalyst is to [...] Read more.

The formation and properties of silver and iron nanoscale components in the Ag-Fe bimetallic system deposited on mordenite depend on several parameters during their preparation. Previously, it was shown that an important condition for optimizing nano-center properties in a bimetallic catalyst is to change the order of sequential deposition of components; the order “first Ag⁺, then Fe²⁺” was chosen as optimal. In this work, the influence of exact Ag/Fe atomic proportion on the system’s physicochemical properties was studied. This ratio has been confirmed to affect the stoichiometry of the reduction–oxidation processes involving Ag⁺ and Fe²⁺, as shown by XRD, DR UV-Vis, XPS, and XAFS data, while HRTEM, S_BET and TPD-NH₃ show little change. However, it was found the correlation between the occurrence and amount of the Fe³⁺ ions incorporated into the zeolite’s framework and the experimentally determined catalytic activities towards the model de-NOx reaction along the series of nanomaterials elucidated in this present paper. Full article

(This article belongs to the Special Issue Synthesis, Modification and Utilization of Porous Materials as Adsorbents, Catalysts and Catalyst Supports)

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20 pages, 5073 KiB

Open AccessArticle

Opportunities for Recycling PV Glass and Coal Fly Ash into Zeolite Materials Used for Removal of Heavy Metals (Cd, Cu, Pb) from Wastewater

by Maria Visa and Alexandru Enesca

Materials 2023, 16(1), 239; https://doi.org/10.3390/ma16010239 - 27 Dec 2022

Cited by 7 | Viewed by 2432

Abstract

This work shows the development and characterization of two zeolite structures by recycling PV glass and coal fly ash for the removal of cadmium, copper, and lead from synthetic solutions containing one or three cations. The materials were characterized in terms of crystalline [...] Read more.

This work shows the development and characterization of two zeolite structures by recycling PV glass and coal fly ash for the removal of cadmium, copper, and lead from synthetic solutions containing one or three cations. The materials were characterized in terms of crystalline structure (XRD), morphology (SEM, AFM), and specific surface. For increasing the heavy-metals removal efficiency, the adsorption conditions, such as substrate dosage, preliminary concentration, and contact time, were optimized. The pseudo-second-order kinetic model adsorption kinetics fit well to describe the activity of the zeolites ZFAGPV-A and ZFAGPV-S. The zeolite adsorption equilibrium data were expressed using Langmuir and Freundlich models. The highest adsorption capacities of the ZFAGPV-A zeolite are q_maxCd = 55.56 mg/g, q_maxCu = 60.11 mg/g, q_maxPb = 175.44 mg/g, and of ZFAGPV-S, are q_maxCd = 33.45 mg/g, q_maxCu = 54.95 mg/g, q_maxPb = 158.73 mg/g, respectively. This study demonstrated a new opportunity for waste recycling for applications in removing toxic heavy metals from wastewater. Full article

(This article belongs to the Special Issue Synthesis, Modification and Utilization of Porous Materials as Adsorbents, Catalysts and Catalyst Supports)

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