Molecules

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18 pages, 4757 KiB

Open AccessArticle

Highly Porous Carbon Flakes Derived from Cellulose and Nickel Phosphide Heterostructure towards Efficient Electrocatalysis of Oxygen Evolution Reaction

by Ewa Mijowska, Karolina Pietrusewicz and Klaudia Maślana

Molecules 2024, 29(2), 352; https://doi.org/10.3390/molecules29020352 - 10 Jan 2024

Cited by 2 | Viewed by 1033

Abstract

This study delves into the pressing challenges of climate change and the escalating carbon dioxide (CO₂) emissions by exploring hydrogen technology as a sustainable alternative. In particular, there is focus on nickel phosphide-based electrocatalysts, known for their promising performance in hydrogen [...] Read more.

This study delves into the pressing challenges of climate change and the escalating carbon dioxide (CO₂) emissions by exploring hydrogen technology as a sustainable alternative. In particular, there is focus on nickel phosphide-based electrocatalysts, known for their promising performance in hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs). Therefore, here we have designed a facile strategy to deliver highly porous carbon flakes derived from cellulose fibers via carbonization at 850 °C, yielding highly porous structures and outstanding specific surface area (SSAcel_carb_850_act = 3164 m²/g) after activation. As-fabricated carbon was utilized as a support for Ni₁₂P₅ with an optimized mass ratio. Electrochemical testing revealed that the composite of Ni₁₂P₅ and carbon flakes with a ratio of 100:1, respectively, exhibited the most favorable kinetics for the oxygen evolution reaction (OER). Importantly, the durability tests of this sample demonstrated the most stable behavior and lowest potential change under high current density among the studied samples, making it a promising candidate in practical applications. Moreover, the analysis of electrocatalysts after an OER does not show any changes, indicating that the sample does not undergo undesired intermediate reactions and that unwanted products are not released, explaining its stable behavior. This provides a straightforward approach for creating a cellulose-derived composite with enhanced electroactivity and durability. Full article

(This article belongs to the Special Issue Porous Materials as Catalysts and Sorbents)

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13 pages, 2079 KiB

Open AccessArticle

Influence of ZSM-5 Crystal Size on Methanol-to-Olefin (MTO) vs. Ethanol-to-Aromatics (ETA) Conversion

by Daniel Dittmann, Elif Kaya, Dennis Strassheim and Michael Dyballa

Molecules 2023, 28(24), 8046; https://doi.org/10.3390/molecules28248046 - 12 Dec 2023

Viewed by 1122

Abstract

Crystal size is a key parameter of zeolites applied as catalysts. Herein, ZSM-5 crystals with similar physicochemical and acid properties, few defects, and aluminum exclusively in tetrahedral coordination are synthesized and the influence of the crystal size on the MTO and ETA conversion [...] Read more.

Crystal size is a key parameter of zeolites applied as catalysts. Herein, ZSM-5 crystals with similar physicochemical and acid properties, few defects, and aluminum exclusively in tetrahedral coordination are synthesized and the influence of the crystal size on the MTO and ETA conversion is investigated. Short olefins are the main products of the MTO conversion, whereas larger olefins and aromatics dominate the products after ETA conversion. In the case of both feeds, an increased crystal size decreases the catalyst’s lifetime. The MTO conversion over larger ZSM-5 altered the product distribution, which was not the case for the ETA conversion. The reason is that the instantly available aromatics during ETA conversion lead to fast coking and zeolite crystals only active in the outer layers. Thus, the different reactivity of different-sized ZSM-5 is direct proof of a different conversion mechanism for both alcohols. Full article

(This article belongs to the Special Issue Porous Materials as Catalysts and Sorbents)

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13 pages, 9296 KiB

Open AccessArticle

Mesoporous-Layered Double Oxide/MCM-41 Composite with Enhanced Catalytic Performance for Cyclopentanone Aldol Condensation

by Jinfan Yang, Ning Shang, Jiachen Wang and Huimin Liu

Molecules 2023, 28(23), 7920; https://doi.org/10.3390/molecules28237920 - 3 Dec 2023

Viewed by 881

Abstract

Layered double oxides are widely employed in catalyzing the aldol condensation for producing biofuels, but its selectivity and stability need to be further improved. Herein, a novel MCM-41-supported Mg–Al-layered double oxide (LDO/MCM-41) was prepared via the in situ integration of a sol–gel process [...] Read more.

Layered double oxides are widely employed in catalyzing the aldol condensation for producing biofuels, but its selectivity and stability need to be further improved. Herein, a novel MCM-41-supported Mg–Al-layered double oxide (LDO/MCM-41) was prepared via the in situ integration of a sol–gel process and coprecipitation, followed by calcination. This composite was first employed to catalyze the self-condensation of cyclopentanone for producing high-density cycloalkane precursors. LDO/MCM-41 possessed large specific surface area, uniform pore size distribution, abundant medium basic sites and Bronsted acid sites. Compared with the bulk LDO, LDO/MCM-41 exhibited a higher selectivity for C10 and C15 oxygenates at 150 °C (93.4% vs. 84.6%). The selectivity for C15 was especially enhanced on LDO/MCM-41, which was three times greater than that on LDO. The stability test showed that naked LDO with stronger basic strength had a rapid initial activity, while it suffered an obvious deactivation due to its poor carbon balance. LDO/MCM-41 with lower basic strength had an enhanced stability even with a lower initial activity. Under the optimum conditions (50% LDO loading, 170 °C, 7 h), the cyclopentanone conversion on LDO/MCM-41 reached 77.8%, with a 60% yield of C10 and 15.2% yield of C15. Full article

(This article belongs to the Special Issue Porous Materials as Catalysts and Sorbents)

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20 pages, 2173 KiB

Open AccessArticle

Removal of Methyl Red from Aqueous Solution Using Biochar Derived from Fennel Seeds

by Dorota Paluch, Aleksandra Bazan-Wozniak, Robert Wolski, Agnieszka Nosal-Wiercińska and Robert Pietrzak

Molecules 2023, 28(23), 7786; https://doi.org/10.3390/molecules28237786 - 26 Nov 2023

Cited by 5 | Viewed by 867

Abstract

In this study, fennel (Foeniculum vulgare) seeds were used as a precursor to obtain carbon adsorbents through physical activation with carbon dioxide and chemical activation by impregnating the precursor with sodium carbonate. The physical activation involved the carbonization of the precursor [...] Read more.

In this study, fennel (Foeniculum vulgare) seeds were used as a precursor to obtain carbon adsorbents through physical activation with carbon dioxide and chemical activation by impregnating the precursor with sodium carbonate. The physical activation involved the carbonization of the precursor at a temperature of 600 °C for 60 min and activation at a temperature of 800 °C for 30 min with carbon dioxide. Chemical activation included impregnation of the precursor with sodium carbonate at a mass ratio of a precursor to activator of 1:2. The mixture was activated in a nitrogen atmosphere with a flow rate at a temperature of 700 °C for 45 min. The resulting biochar samples were washed with 5% hydrochloric acid and subsequently rinsed with boiling distilled water. The biochar adsorbents were characterized using low-temperature nitrogen adsorption–desorption isotherms, Boehm titration, and pH measurements of their aqueous extracts. The specific surface area of the obtained adsorbents ranged from 89 to 345 m²/g. Biochar adsorbents exhibit a predominance of acidic groups over basic groups on their surfaces. The sorption capacities of the obtained samples towards an aqueous solution of methyl red range from 26 to 135 mg/g. Based on adsorption studies, it was found that the adsorption of the dye on the obtained biochar materials follows a pseudo-second-order model. The Freundlich isotherm best describes the studied process, indicating the formation of a multilayer of adsorbate on the adsorbent surface. The efficacy of adsorption in aqueous solutions of methyl red was found to increase with the elevation of the process temperature. Moreover, thermodynamic studies have shown that the adsorption process is spontaneous and endothermic. Consequently, this work provides a description of the physicochemical parameters of two biochars obtained by physical and chemical activation of a little-studied precursor—fennel seeds—and studies on their potential use as adsorbents for contaminants from the aqueous phase. Full article

(This article belongs to the Special Issue Porous Materials as Catalysts and Sorbents)

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18 pages, 5137 KiB

Open AccessArticle

Nanoshaped Cerium Oxide with Nickel as a Non-Noble Metal Catalyst for CO₂ Thermochemical Reactions

by Jarosław Serafin and Jordi Llorca

Molecules 2023, 28(7), 2926; https://doi.org/10.3390/molecules28072926 - 24 Mar 2023

Cited by 4 | Viewed by 1651

Abstract

Four different nanoshapes of cerium dioxide have been prepared (polycrystals, rods, cubes, and octahedra) and have been decorated with different metals (Ru, Pd, Au, Pt, Cu, and Ni) by incipient wetness impregnation (IWI) and ball milling (BM) methods. After an initial analysis based [...] Read more.

Four different nanoshapes of cerium dioxide have been prepared (polycrystals, rods, cubes, and octahedra) and have been decorated with different metals (Ru, Pd, Au, Pt, Cu, and Ni) by incipient wetness impregnation (IWI) and ball milling (BM) methods. After an initial analysis based on oxygen consumption from CO₂ pulse chemisorption, Ni-like metal, and two forms of CeO₂ cubes and rods were selected for further research. Catalysts were characterized using the Brunauer-Emmett-Teller formula (BET), X-ray spectroscopy (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV–visible spectrophotometry (UV-Vis), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction (H₂-TPR) and CO₂ pulse chemisorption, and used to reduce of CO₂ into CO (CO₂ splitting). Adding metals to cerium dioxide enhanced the ability of CeO₂ to release oxygen and concomitant reactivity toward the reduction of CO₂. The effect of the metal precursor and concentration were evaluated. The highest CO₂ splitting value was achieved for 2% Ni/CeO₂-rods prepared by ball milling using Ni nitrate (412 µmol/g_cat) and the H₂ consumption (453.2 µmol/g_cat) confirms the good redox ability of this catalyst. Full article

(This article belongs to the Special Issue Porous Materials as Catalysts and Sorbents)

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14 pages, 2835 KiB

Open AccessArticle

Synthesis of Pillar[5]arene- and Phosphazene-Linked Porous Organic Polymers for Highly Efficient Adsorption of Uranium

by Xiaoxiao Zhao, Ziyi Liu, Shuguang Zhang, Mehdi Hassan, Chunxin Ma, Zhenzhong Liu and Weitao Gong

Molecules 2023, 28(3), 1029; https://doi.org/10.3390/molecules28031029 - 19 Jan 2023

Cited by 3 | Viewed by 1872

Abstract

It is crucial to design efficient adsorbents for uranium from natural seawater with wide adaptability, effectiveness, and environmental safety. Porous organic polymers (POPs) provide superb tunable porosity and stability among developed porous materials. In this work, two new POPs, i.e., HCCP-P5-1 and HCCP-P5-2 [...] Read more.

It is crucial to design efficient adsorbents for uranium from natural seawater with wide adaptability, effectiveness, and environmental safety. Porous organic polymers (POPs) provide superb tunable porosity and stability among developed porous materials. In this work, two new POPs, i.e., HCCP-P5-1 and HCCP-P5-2 were rationally designed and constructed by linked with macrocyclic pillar[5]arene as the monomer and hexachlorophosphate as the core via a macrocycle-to-framework strategy. Both pillar[5]arene-containing POPs exhibited high uranium adsorption capacity compared with previously reported macrocycle-free counterparts. The isothermal adsorption curves and kinetic studies showed that the adsorption of POPs on uranium was consistent with the Langmuir model and the pseudo-second-order kinetic model. Especially, HCCP-P5-1 has reached 537.81 mg/g, which is greater than most POPs that have been reported. Meanwhile, the comparison between both HCCP-P5-1 and HCCP-P5-2 can illustrate that the adsorption capacity and stability could be adjusted by the monomer ratio. This work provides a new idea for the design and construction of uranium adsorbents from macrocycle-derived POPs. Full article

(This article belongs to the Special Issue Porous Materials as Catalysts and Sorbents)

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21 pages, 5384 KiB

Open AccessArticle

Impact of TiO₂ Reduction and Cu Doping on Bacteria Inactivation under Artificial Solar Light Irradiation

by Piotr Rychtowski, Oliwia Paszkiewicz, Maria Carmen Román-Martínez, Maria Ángeles Lillo-Ródenas, Agata Markowska-Szczupak and Beata Tryba

Molecules 2022, 27(24), 9032; https://doi.org/10.3390/molecules27249032 - 18 Dec 2022

Cited by 2 | Viewed by 1203

Abstract

Preparation of TiO₂ using the hydrothermal treatment in NH₄OH solution and subsequent thermal heating at 500–700 °C in Ar was performed in order to introduce some titania surface defects. The highest amount of oxygen vacancies and Ti³⁺ surface defects [...] Read more.

Preparation of TiO₂ using the hydrothermal treatment in NH₄OH solution and subsequent thermal heating at 500–700 °C in Ar was performed in order to introduce some titania surface defects. The highest amount of oxygen vacancies and Ti³⁺ surface defects were observed for a sample heat-treated at 500 °C. The presence of these surface defects enhanced photocatalytic properties of titania towards the deactivation of two bacteria species, E. coli and S. epidermidis, under artificial solar lamp irradiation. Further modification of TiO₂ was targeted towards the doping of Cu species. Cu doping was realized through the impregnation of the titania surface by Cu species supplied from various copper salts in an aqueous solution and the subsequent heating at 500 °C in Ar. The following precursors were used as a source of Cu: CuSO₄, CuNO₃ or Cu(CH₃COO)₂. Cu doping was performed for raw TiO₂ after a hydrothermal process with and without NH₄OH addition. The obtained results indicate that Cu species were deposited on the titania surface defects in the case of reduced TiO₂, but on the TiO₂ without NH₄OH modification, Cu species were attached through the titania adsorbed hydroxyl groups. Cu doping on TiO₂ increased the absorption of light in the visible range. Rapid inactivation of E. coli within 30 min was obtained for the ammonia-reduced TiO₂ heated at 500 °C and TiO₂ doped with Cu from CuSO₄ solution. Photocatalytic deactivation of S. epidermidis was greatly enhanced through Cu doping on TiO₂. Impregnation of TiO₂ with CuSO₄ was the most effective for inactivation of both E. coli and S. epidermidis. Full article

(This article belongs to the Special Issue Porous Materials as Catalysts and Sorbents)

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12 pages, 3279 KiB

Open AccessArticle

W-SBA-15 as an Effective Catalyst for the Epoxidation of 1,5,9-Cyclododecatriene

by Marcin Kujbida, Agnieszka Wróblewska, Grzegorz Lewandowski, Piotr Miądlicki and Beata Michalkiewicz

Molecules 2022, 27(24), 8769; https://doi.org/10.3390/molecules27248769 - 10 Dec 2022

Viewed by 949

Abstract

The results of a study on the epoxidation of 1,5,9-cyclododecatriene (CDT) on a W-SBA-15 catalyst using the batch and half-periodic methods are presented. During this study, the activity of the W-SBA-15 catalyst was compared to that of the Ti-SBA-15 catalyst, and the W-SBA-15 [...] Read more.

The results of a study on the epoxidation of 1,5,9-cyclododecatriene (CDT) on a W-SBA-15 catalyst using the batch and half-periodic methods are presented. During this study, the activity of the W-SBA-15 catalyst was compared to that of the Ti-SBA-15 catalyst, and the W-SBA-15 catalyst was found to be about 20 times more active than the Ti-SBA-15 catalyst. The highest CDT conversion so far, amounting to 86 mol%, was obtained after carrying out the 4 h epoxidation process. Conducting the studied process using the semi-batch method did not result in the significant improvement in value functions describing this process (CDT conversion and selectivity of CDT transformation to ECDD), but the fastest H₂O₂ dosing rate (246 µL/h) allowed us to obtain 9 mol% higher CDT conversion in comparison to the batch method. Full article

(This article belongs to the Special Issue Porous Materials as Catalysts and Sorbents)

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