Catalysts

14 pages, 2425 KiB

Open AccessArticle

Efficient Removal of Methylene Blue Using an Organic–Inorganic Hybrid Polyoxometalate as a Dual-Action Catalyst for Oxidation and Reduction

by Lu Chen, Haowen Cui, Feng Jiang, Lingyan Kong, Baoli Fei and Xiang Mei

Catalysts 2024, 14(9), 576; https://doi.org/10.3390/catal14090576 (registering DOI) - 29 Aug 2024

Abstract

An organic–inorganic hybrid polyoxometalate (POM) CoPMoV [PMo^VI₈V^IV₄V^V₂O₄₂][Co(Phen)₂(H₂O)]₂[TEA]₂•H₃O•3H₂O (Phen = 1,10-phenanthroline, TEA = triethylamine) prepared by hydrothermal synthesis was explored as [...] Read more.

An organic–inorganic hybrid polyoxometalate (POM) CoPMoV [PMo^VI₈V^IV₄V^V₂O₄₂][Co(Phen)₂(H₂O)]₂[TEA]₂•H₃O•3H₂O (Phen = 1,10-phenanthroline, TEA = triethylamine) prepared by hydrothermal synthesis was explored as a heterogeneous catalysts to remove methylene blue (MB) through Fenton-like reaction and catalytic reduction. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) were employed to characterize CoPMoV. The MB removal rates for the Fenton-like reaction and the catalytic reduction were 91.6% (120 min) and 97.5% (2 min), respectively, under optimum conditions. CoPMoV demonstrated excellent stability and recyclability in the Fenton-like reaction and catalytic reduction, which was confirmed by 5 cycle tests. Plausible mechanisms for MB degradation and reduction have also been proposed. Benefiting from the excellent redox properties of cobalt and [PMo^VI₈V^IV₄V^V₂O₄₂]⁵⁻ anion, CoPMoV could act as a Fenton-like and reductive catalyst for the removal of MB. This study provides a green and facile strategy to design POM-based organic–inorganic material for dye wastewater treatment via oxidation and reduction. Full article

(This article belongs to the Special Issue Advanced Catalysis for Energy and Environmental Applications)

26 pages, 4954 KiB

Open AccessReview

A Critical Review of Clay Mineral-Based Photocatalysts for Wastewater Treatment

by Yaozhong Qi, Sikai Zhao, Yanbai Shen, Xiaoyu Jiang, Haiyi Lv, Cong Han, Wenbao Liu and Qiang Zhao

Catalysts 2024, 14(9), 575; https://doi.org/10.3390/catal14090575 - 29 Aug 2024

Abstract

This review critically examines the latest advancements in clay mineral-based photocatalysts for water purification. Clay minerals, owing to their natural abundance, low cost, and unique physicochemical properties, have emerged as promising candidates for enhancing photocatalytic efficiency. This article delves into various activation methods [...] Read more.

This review critically examines the latest advancements in clay mineral-based photocatalysts for water purification. Clay minerals, owing to their natural abundance, low cost, and unique physicochemical properties, have emerged as promising candidates for enhancing photocatalytic efficiency. This article delves into various activation methods for clay minerals, including acid, alkali, calcination, and mechanochemical activation, highlighting their roles in enhancing surface area, creating active sites, and improving photocatalytic performance. Moreover, the review explores various modification strategies for photocatalysts, such as doping with metal and non-metal ions, deposition of metals, and the design of heterojunctions, to further boost photocatalytic activity. In particular, the utilization of kaolinite, montmorillonite, attapulgite, and sepiolite as clay mineral supports for photocatalysts is discussed in detail, showcasing their potential in wastewater treatment. The review underscores the significant strides made in the development of clay mineral-based photocatalysts, highlighting their effectiveness in degrading organic contaminants under light exposure. Nevertheless, there are persisting challenges such as the optimization of loading quantities, improvement in compatibility between clay minerals and photocatalysts, and reduction in preparation costs for large-scale applications. In summary, this review offers valuable insights into the current status of clay mineral-based photocatalysts for water purification, thereby stimulating future research in this promising field. Full article

(This article belongs to the Section Photocatalysis)

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20 pages, 2572 KiB

Open AccessArticle

Waste Biomass Utilization for the Production of Adsorbent and Value-Added Products for Investigation of the Resultant Adsorption and Methanol Electro-Oxidation

by Hala Mohamed, Abeer Enaiet Allah, Doaa Essam, Ahmed A. Farghali, Ahmed A. Allam, Sarah I. Othman, Abdalla Abdelwahab and Rehab Mahmoud

Catalysts 2024, 14(9), 574; https://doi.org/10.3390/catal14090574 (registering DOI) - 29 Aug 2024

Abstract

Waste valorization is necessary in today’s society to achieve a sustainable economy and prosperity. In this work, a novel approach to the waste valorization of cuttlebone was investigated. This material was ground and calcined at 900 °C for 5 h in an inert [...] Read more.

Waste valorization is necessary in today’s society to achieve a sustainable economy and prosperity. In this work, a novel approach to the waste valorization of cuttlebone was investigated. This material was ground and calcined at 900 °C for 5 h in an inert atmosphere. The resulting calcined cuttlebone (CCB) was characterized using XRD, SEM, FTIR, BET, TGA, Zetasizer, and potential methods. The main phases in the CCB were determined to be CaO, MgO, Ca₃(PO₄)₂, and residual carbon. CCB was investigated as an adsorbent for the removal of dye from simulated wastewater streams. The maximum adsorption capacities for rhodamine B and crystal violet dyes were estimated to be 519 and 921 mg/g, respectively. For both dyes, the Avrami model was the best-fit model for representing adsorption kinetics. The study of adsorbent regeneration for CV as a representative example involved the use of several chemical solvents. Ethanol solvent was shown to have the highest adsorbent regeneration method efficiency, reaching 65.20%. In addition, CCB was investigated for methanol electro-oxidation for energy generation. As the methanol concentration increased, the maximum current density produced by the CCB increased, reaching approximately 50 mA/cm². This work paves the way toward waste valorization of natural matter for sustainable production and consumption of material, as per the requirements of the circular economy principles. Full article

(This article belongs to the Section Biomass Catalysis)

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19 pages, 5632 KiB

Open AccessArticle

UiO-67 Metal–Organic Framework as Advanced Adsorbent for Antiviral Drugs from Water Environment

by Sitah Almotiry, Basma G. Alhogbi, Mohamed Abdel Salam and Mariusz Jaremko

Catalysts 2024, 14(9), 573; https://doi.org/10.3390/catal14090573 (registering DOI) - 29 Aug 2024

Abstract

Metal–organic frameworks (MOFs) have attained significant usage as adsorbents for antiviral medicines in contemporary times. This study focused on synthesizing a UiO-67 metal–organic framework using the hydrothermal method. The synthesized framework was then characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy [...] Read more.

Metal–organic frameworks (MOFs) have attained significant usage as adsorbents for antiviral medicines in contemporary times. This study focused on synthesizing a UiO-67 metal–organic framework using the hydrothermal method. The synthesized framework was then characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analyses (TGA), and zeta potential measurements. The UiO-67 was then employed for the purpose of assessing the efficiency of various adsorption factors in the removal of antiviral medicines from aqueous solutions, including drugs such as ritonavir (RTV) and lopinavir (LPV), which were extensively used for the treatment of coronavirus (COVID-19) during the pandemic. The variables examined were the quantity of adsorbent used, different pH of the solution, temperature, and contact duration. The experimental findings indicate that the highest level of RTV elimination was 91.2% and of experimental adsorption capacity (q_e_,exp) was 9.7 mg/g and for LPV this was 85.9%, and (q_e_,exp) 8.9 mg/g, using 50 mg of UiO-67 at a pH 8, temperature of 298 K, and for 120 min. The impact of contact duration and temperature on the kinetics of adsorption was examined by employing pseudo-first-order and pseudo-second-order kinetic models. The experimental results showed a good match with the pseudo-second-order kinetic model with value of R² 0.99 and the q_e_,calc was 9.7 RTV and 8.9 mg/g LPV, which is a good match with q_e_,exp. Also, based on diffusion kinetic studies, the adsorption was confirmed to be catalytic in nature on the surface of the UiO-67 MOFs. A thermodynamic analysis of adsorption was conducted, whereby calculations for the Gibbs free energy change (∆G), enthalpy change (∆H), and entropy change (∆S) were performed. The positive ∆H values confirm the endothermic nature of the adsorption of RTV and LPV by UiO-67. The ΔG values exhibited negativity across all temperatures, suggesting the spontaneous nature of the adsorption process of RTV and LPV by UiO-67 from an aqueous solution. UiO-67 was shown to be highly effective in extracting RTV and LPV from real environmental samples. Full article

(This article belongs to the Special Issue Catalytic Energy Conversion and Catalytic Environmental Purification)

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16 pages, 2753 KiB

Open AccessFeature PaperArticle

Promoted Ru/PrO_x Catalysts for Mild Ammonia Synthesis

by Samuel M. Drummond, Jennifer Naglic, Thossaporn Onsree, Santosh K. Balijepalli, Alexis Allegro, Stephanie N. Orraca Albino, Katherine M. O’Connell and Jochen Lauterbach

Catalysts 2024, 14(9), 572; https://doi.org/10.3390/catal14090572 (registering DOI) - 29 Aug 2024

Abstract

Ammonia synthesis is one of the most important chemical reactions. Due to thermodynamic restrictions and the reaction requirements of the current commercial iron catalysts, it is also one of the worst reactions for carbon dioxide emissions and energy usage. Ruthenium-based catalysts can substantially [...] Read more.

Ammonia synthesis is one of the most important chemical reactions. Due to thermodynamic restrictions and the reaction requirements of the current commercial iron catalysts, it is also one of the worst reactions for carbon dioxide emissions and energy usage. Ruthenium-based catalysts can substantially improve the environmental impact as they operate at lower pressures and temperatures. In this work, we provide a screening of more than 40 metals as possible promoter options based on a Ru/Pr₂O₃ catalyst. Cesium was the best alkali promoter and was held constant for the series of double-promoted catalysts. Ten formulations outperformed the Ru-Cs/PrO_x benchmark, with barium being the best second promoter studied and the most cost-effective option. Designs of experiments were utilized to optimize both the pretreatment conditions and the promoter weight loadings of the doubly promoted catalyst. As a result, optimization led to a more than five-fold increase in activity compared to the unpromoted catalyst, therefore creating the possibility for low-ruthenium ammonia synthesis catalysts to be used at scale. Further, we have explored the roles of promoters using kinetic analysis, X-ray Photoelectron Spectroscopy (XPS), and in situ infrared spectroscopy. Here, we have shown that the role of barium is to act as a hydrogen scavenger and donor, which may permit new active sites for the catalyst, and have demonstrated that the associative reaction mechanism is likely used for the unpromoted Ru/PrO_x catalyst with hydrogenation of the triple bond of the dinitrogen occurring before any dinitrogen bond breakage. Full article

(This article belongs to the Section Nanostructured Catalysts)

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18 pages, 2811 KiB

Open AccessFeature PaperArticle

Are Rh Catalysts a Suitable Choice for Bio-Oil Reforming? The Case of a Commercial Rh Catalyst in the Combined H₂O and CO₂ Reforming of Bio-Oil

by José Valecillos, Leire Landa, Gorka Elordi, Aingeru Remiro, Javier Bilbao and Ana Guadalupe Gayubo

Catalysts 2024, 14(9), 571; https://doi.org/10.3390/catal14090571 (registering DOI) - 29 Aug 2024

Abstract

Bio-oil combined steam/dry reforming (CSDR) with H₂O and CO₂ as reactants is an attractive route for the joint valorization of CO₂ and biomass towards the sustainable production of syngas (H₂ + CO). The technological development of the process [...] Read more.

Bio-oil combined steam/dry reforming (CSDR) with H₂O and CO₂ as reactants is an attractive route for the joint valorization of CO₂ and biomass towards the sustainable production of syngas (H₂ + CO). The technological development of the process requires the use of an active and stable catalyst, but also special attention should be paid to its regeneration capacity due to the unavoidable and quite rapid catalyst deactivation in the reforming of bio-oil. In this work, a commercial Rh/ZDC (zirconium-doped ceria) catalyst was tested for reaction–regeneration cycles in the bio-oil CSDR in a fluidized bed reactor, which is beneficial for attaining an isothermal operation and, moreover, minimizes catalyst deactivation by coke deposition compared to a fixed-bed reactor. The fresh, spent, and regenerated catalysts were characterized using either N₂ physisorption, H₂-TPR, TPO, SEM, TEM, or XRD. The Rh/ZDC catalyst is initially highly active for the syngas production (yield of 77% and H₂/CO ratio of 1.2) and for valorizing CO₂ (conversion of 22%) at 700 °C, with space time of 0.125 g_catalyst h (g_oxygenates)⁻¹ and CO₂/H₂O/C ratio of 0.6/0.5/1. The catalyst activity evolves in different periods that evidence a selective deactivation of the catalyst for the reforming reactions of the different compounds, with the CH₄ reforming reactions (with both steam and CO₂) being more rapidly affected by catalyst deactivation than the reforming of hydrocarbons or oxygenates. After regeneration, the catalyst’s textural properties are not completely restored and there is a change in the Rh–support interaction that irreversibly deactivates the catalyst for the CH₄ reforming reactions (both SR and DR). As a result, the coke formed over the regenerated catalyst is different from that over the fresh catalyst, being an amorphous mass (of probably turbostractic nature) that encapsulates the catalyst and causes rapid deactivation. Full article

(This article belongs to the Special Issue Catalytic Reforming and Hydrogen Production: From the Past to the Future)

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16 pages, 3545 KiB

Open AccessArticle

Engineered CoS/Ni₃S₂ Heterointerface Catalysts Grown Directly on Carbon Paper as an Efficient Electrocatalyst for Urea Oxidation

by Saba A. Aladeemy, Prabhakarn Arunachalam, Abdullah M. Al-Mayouf, P. N. Sudha, A. Rekha, A. Vidhya, J. Hemapriya, Srinivasan Latha, P. Supriya Prasad, S. Pavithra, Raja Arunadevi and Salah T. Hameed

Catalysts 2024, 14(9), 570; https://doi.org/10.3390/catal14090570 - 28 Aug 2024

Viewed by 205

Abstract

Developing highly efficient and stable electrocatalysts for urea electro-oxidation reactions (UORs) will improve wastewater treatment and energy conversion. A low-cost cobalt sulfide-anchored nickel sulfide electrode (CoS/Ni₃S₂@CP) was synthesized by electrodeposition in DMSO solutions and found to be highly effective [...] Read more.

Developing highly efficient and stable electrocatalysts for urea electro-oxidation reactions (UORs) will improve wastewater treatment and energy conversion. A low-cost cobalt sulfide-anchored nickel sulfide electrode (CoS/Ni₃S₂@CP) was synthesized by electrodeposition in DMSO solutions and found to be highly effective and long-lasting. The morphology and composition of catalyst surfaces were examined using comprehensive physicochemical and electrochemical characterization. Specifically, CoS/Ni₃S₂@CP electrodes require a potential of 1.52 volts for a 50 mA/cm² current, confirming CoS in the heterointerface CoS/Ni₃S₂@CP catalyst. Further, the optimized CoS/Ni₃S₂@CP catalyst shows a decrease of 100 mV in the onset potential (1.32 V_RHE) for UORs compared to bare Ni₃S₂@CP catalysts (1.42 V_RHE), demonstrating much greater performance of UORs. As compared to Ni₃S₂@CP, CoS/Ni₃S₂@CP exhibits twofold greater UOR efficiency as a result of a larger electroactive surface area. The results obtained indicate that the synthetic CoS/Ni₃S₂@CP catalyst may be a favorable electrode material for managing urea-rich wastewater and generating H₂. Full article

(This article belongs to the Section Electrocatalysis)

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34 pages, 8841 KiB

Open AccessReview

Research Progress of Pt-Based Catalysts toward Cathodic Oxygen Reduction Reactions for Proton Exchange Membrane Fuel Cells

by Yue Chen, Zhiyin Huang, Jiefen Yu, Haiyi Wang, Yukuan Qin, Lixin Xing and Lei Du

Catalysts 2024, 14(9), 569; https://doi.org/10.3390/catal14090569 - 28 Aug 2024

Viewed by 126

Abstract

Proton exchange membrane fuel cells (PEMFCs) have been considered by many countries and enterprises because of their cleanness and efficiency. However, due to their high cost and low platinum utilization rate, the commercialization process of PEMFC is severely limited. The cathode catalyst layer [...] Read more.

Proton exchange membrane fuel cells (PEMFCs) have been considered by many countries and enterprises because of their cleanness and efficiency. However, due to their high cost and low platinum utilization rate, the commercialization process of PEMFC is severely limited. The cathode catalyst layer (CCL) plays an important role in manipulating the performance and lifespan of PEMFCs, which makes them one of the most significant research focuses in this community. In the CCL, the intrinsic activity and stability of the catalysts determine the performance and lifetime of the catalyst layer. In this paper, the composition and working principle of the PEMFC and cathode catalyst layer are briefly introduced, focusing on Pt-based catalysts for oxygen reduction reactions (ORRs). The research progress of Pt-based catalysts in the past five years is particularly reviewed, mainly concentrating on the development status of emerging Pt-based catalysts which are popular in the current research field, including novel concepts like phase regulation (intermetallic alloys and high-entropy alloys), interface engineering (coupled low-Pt/Pt-free catalysts), and single-atom catalysts. Finally, the future research and development directions of Pt-based ORR catalysts are summarized and prospected. Full article

(This article belongs to the Special Issue Powering the Future: Advances of Catalysis in Batteries)

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11 pages, 1027 KiB

Open AccessFeature PaperArticle

Catalytic Valorization of Organic Solid Waste: A Pilot-Scale Run of Sugarcane Bagasse

by Zhaofei Li, Ali Omidkar and Hua Song

Catalysts 2024, 14(9), 568; https://doi.org/10.3390/catal14090568 - 28 Aug 2024

Viewed by 221

Abstract

Organic solid waste treatment is crucial for enhancing environmental sustainability, promoting economic growth, and improving public health. Following our previous organic solid waste upgrading technique, a further two-step pilot-scale run, using sugarcane bagasse as the feedstock, has been successfully conducted with long-term stability. [...] Read more.

Organic solid waste treatment is crucial for enhancing environmental sustainability, promoting economic growth, and improving public health. Following our previous organic solid waste upgrading technique, a further two-step pilot-scale run, using sugarcane bagasse as the feedstock, has been successfully conducted with long-term stability. Firstly, the sugarcane bagasse was treated under mild conditions (400 °C and 1 bar of CH₄), and this catalytic Methanolysis treatment resulted in a bio-oil with a yield of 60.5 wt.%. Following that, it was subjected to a catalytic Methano-Refining process (400 °C and 50 bar of CH₄) to achieve high-quality renewable fuel with a liquid yield of 95.0 wt.%. Additionally, this renewable fuel can be regarded as an ideal diesel component with a high cetane number, high heating values, a low freezing point, low density and viscosity, and low oxygen, nitrogen, and sulfur contents. The successful pilot-scale catalytic upgrading of sugarcane bagasse further verified the effectiveness of this methane-assisted organic solid waste upgrading technique and confirmed the high flexibility of this innovative technology for processing a wide spectrum of agricultural and forestry residues. This study will shed light on the further valorization of organic solid waste and other carbonaceous materials. Full article

(This article belongs to the Special Issue Catalyzing the Sustainable Process Paradigm)

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15 pages, 3890 KiB

Open AccessArticle

Rational Engineering of Nanostructured NiS/GO/PVA for Efficient Photocatalytic Degradation of Organic Pollutants

by Arafat Toghan, Naglaa Roushdy, Hanan Alhussain and Noha A. Elessawy

Catalysts 2024, 14(9), 567; https://doi.org/10.3390/catal14090567 - 28 Aug 2024

Viewed by 299

Abstract

A novel nanocomposite film synthesized from an inexpensive and easily accessible polymer such as poly (vinyl alcohol) (PVA), which is coated with nickel sulfide (NiS) and graphene oxide (GO), was obtained from used drinking-water bottles. The produced coated film was examined as a [...] Read more.

A novel nanocomposite film synthesized from an inexpensive and easily accessible polymer such as poly (vinyl alcohol) (PVA), which is coated with nickel sulfide (NiS) and graphene oxide (GO), was obtained from used drinking-water bottles. The produced coated film was examined as a potential photocatalyst film for wastewater treatment promotion in a batch system for the removal of methylene blue (MB) and tetracycline (TC) antibiotics. The experimental results show that the presence of GO significantly increases the photocatalytic efficiency of NiS, and the MB and TC degradation results proved that the incorporation of GO with NiS led to a more than one-and-a-half-fold increase in the removal percentage in comparison with the NiS/PVA-coated film. After 30 min of illumination using GO/NiS/PVA-coated film, the removal efficiency reached 86% for MB and 64% for TC. The photodegradation kinetic rate followed the pseudo-first-order rate. Furthermore, the response surface methodology (RSM) model was utilized to study and optimize several operating parameters. The ideal circumstances to achieve 91% elimination of MB are 12 mg L⁻¹ MB initial concentration, two lamps, and an illumination time of 15 min; however, to achieve 85% TC removal, 11 mg L⁻¹ TC initial concentration, two lamps, and a 45 min illumination time should be used. The fabricated nanocomposite photocatalyst film seems to have promise for use in water purification systems. Full article

(This article belongs to the Special Issue Advancement in Photocatalysis for Environmental Applications)

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11 pages, 8418 KiB

Open AccessArticle

Comparative Study on Ethanol-Based Oxygenate Synthesis via Syngas over Monometallic Rh Catalysts Supported on Different Zr-MOFs

by Ruiqi Yu, Xiangjiang Duan, Xuanwang Yu, Xiang Zheng, Haifang Mao and Jun Yu

Catalysts 2024, 14(9), 566; https://doi.org/10.3390/catal14090566 - 27 Aug 2024

Viewed by 279

Abstract

Three types of Zr-based metal–organic frameworks (Zr-MOFs) were employed as supports to prepare monometallic Rh catalysts by the impregnation method. The effects of the structural properties of Zr-MOFs on their supported monometallic Rh catalysts for syngas conversion were investigated. The results showed that, [...] Read more.

Three types of Zr-based metal–organic frameworks (Zr-MOFs) were employed as supports to prepare monometallic Rh catalysts by the impregnation method. The effects of the structural properties of Zr-MOFs on their supported monometallic Rh catalysts for syngas conversion were investigated. The results showed that, compared to catalysts with Rh@MOF-808 and Rh@UiO-66, Rh@UiO-67 had higher CO conversion and C₂⁺ oxygenate selectivity. The state of the Rh site is affected by the different structure of the Zr-MOFs, which is responsible for the difference in catalytic performance. The relatively higher Rh dispersion on the UiO-67 support boosted its CO adsorption ability, and Rh@UiO-67 having the best C₂⁺ oxygenate selectivity was mainly attributed to it having the highest Rh⁺/Rh⁰ ratio. Full article

(This article belongs to the Special Issue Latest Advances and Prospects of Nanomaterials for Catalysis and Energy Storage)

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3 pages, 155 KiB

Open AccessEditorial

Catalysts for Sustainable Hydrogen Production: Preparation, Applications and Process Integration, 2nd Edition

by Concetta Ruocco and Marco Martino

Catalysts 2024, 14(9), 565; https://doi.org/10.3390/catal14090565 - 26 Aug 2024

Viewed by 242

Abstract

The effects of climate change are now evident all over the world [...] Full article

(This article belongs to the Special Issue Catalysts for Sustainable Hydrogen Production: Preparation, Applications and Process Integration, 2nd Edition)

3 pages, 135 KiB

Open AccessEditorial

Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section “Catalytic Materials”

by Leonarda Francesca Liotta, Narendra Kumar and Konstantin Ivanov Hadjiivanov

Catalysts 2024, 14(9), 564; https://doi.org/10.3390/catal14090564 - 26 Aug 2024

Viewed by 250

Abstract

The Special Issue “Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section “Catalytic Materials” contains 14 peer-reviewed research articles and 1 review paper (Contributions 1–15), which broadly focus on the field of homogeneous and heterogeneous catalysis, [...] Read more.

The Special Issue “Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section “Catalytic Materials” contains 14 peer-reviewed research articles and 1 review paper (Contributions 1–15), which broadly focus on the field of homogeneous and heterogeneous catalysis, with an emphasis on synthesis, physico-chemical characterizations, and applications in several environmental protection reactions, such as CO₂ valorization, NOx SCR, removal of VOCs, photocatalysis [...] Full article

(This article belongs to the Special Issue Exclusive Papers of the Editorial Board Members and Topical Advisory Panel Members of Catalysts in Section "Catalytic Materials")

12 pages, 2678 KiB

Open AccessArticle

Hydrogen Co-Combustion of Aromatic Volatile Organic Compounds over Pd/Al₂O₃ Catalyst

by Lutf Ullah, Sehrish Munsif, Long Cao, Palle Ramana Murthy, Jing-Cai Zhang and Wei-Zhen Li

Catalysts 2024, 14(9), 563; https://doi.org/10.3390/catal14090563 - 26 Aug 2024

Viewed by 268

Abstract

Catalytic combustion is an effective strategy for alleviating volatile organic compounds (VOCs), including hydrocarbons and aromatic compounds, mostly derived from the petrochemical and pharmaceutical industries. We employed Pd/Al₂O₃ as a catalyst for combusting aromatic VOCs via hydrogen catalytic combustion. It [...] Read more.

Catalytic combustion is an effective strategy for alleviating volatile organic compounds (VOCs), including hydrocarbons and aromatic compounds, mostly derived from the petrochemical and pharmaceutical industries. We employed Pd/Al₂O₃ as a catalyst for combusting aromatic VOCs via hydrogen catalytic combustion. It differs from conventional approaches that do not necessitate additional electric heating. Briefly, when hydrogen (H₂) is introduced below its lower explosive limit of 4% on the Pd/Al₂O₃ catalyst, it completely oxidizes important aromatic VOCs like benzene, toluene, ethyl benzene, and xylene to carbon dioxide and water. The catalytic performance of the integrated system remains stable even after long-term use. Therefore, hydrogen co-combustion on the Pd/Al₂O₃ catalyst can provide onsite heating for a facility without needing external electric heat. The catalytic performance shows no significant dependence on the sizes of Pd nanoparticles in both fresh and spent conditions, as demonstrated by XRD, XPS, and STEM analyses. Therefore, renewable green hydrogen can effectively reduce aromatic VOC pollutants, providing a more energy-efficient alternative. Our findings suggest that this integrated process is promising for converting aromatic VOCs into carbon dioxide and water without electric heating. Full article

(This article belongs to the Section Industrial Catalysis)

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20 pages, 1254 KiB

Open AccessArticle

Numerical Investigation of Equilibrium and Kinetic Aspects for Hydrogenation of CO₂

by Rakhi and Fabian Mauss

Catalysts 2024, 14(9), 562; https://doi.org/10.3390/catal14090562 - 26 Aug 2024

Viewed by 283

Abstract

Even if huge efforts are made to push alternative mobility concepts, such as electric cars and fuel-cell-powered cars, the significance and use of liquid fuels is anticipated to stay high during the 2030s. Biomethane and synthetic natural gas (SNG) might play a major [...] Read more.

Even if huge efforts are made to push alternative mobility concepts, such as electric cars and fuel-cell-powered cars, the significance and use of liquid fuels is anticipated to stay high during the 2030s. Biomethane and synthetic natural gas (SNG) might play a major role in this context, as they are raw material for chemical industry that is easy to be stored and distribute via existing infrastructure, and are a versatile energy carrier for power generation and mobile applications. Since biomethane and synthetic natural gas are suitable for power generation and for mobile applications, they can therefore replace natural gas without any infrastructure changes, thus playing a major role.In this paper, we aim to comprehend the direct production of synthetic natural gas from

{CO}_{2}

and

H_{2}

in a Sabatier process based on a thermodynamic analysis as well as a multi-step kinetic approach. For this purpose, we thoroughly discuss

{CO}_{2}

methanation to control emissions in order to maximize the methane formation along with minimizing the CO formation and to understand the complex methanation process. We consider an equilibrium and kinetic modeling study on the NiO-

{SiO}_{2}

catalyst for methanation focusing on

{CO}_{2}

-derived SNG. The thermodynamic analysis of

{CO}_{2}

hydrogenation is preformed to define the optimal process parameters followed by the kinetic simulations for catalyst development. The investigation presented in this paper can also be used for developing machine learning algorithms for methanation processes. Full article

(This article belongs to the Section Computational Catalysis)

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15 pages, 6407 KiB

Open AccessArticle

Improvement of Power Density and COD Removal in a Sediment Microbial Fuel Cell with α-FeOOH Nanoparticles

by Monica Mejía-López, Orlando Lastres, José Luis Alemán-Ramírez, Antonio Verde, José Campos Alvarez, Soleyda Torres-Arellano, Gabriela N. Trejo-Díaz, Pathiyamattom J. Sebastian and Laura Verea

Catalysts 2024, 14(9), 561; https://doi.org/10.3390/catal14090561 - 26 Aug 2024

Viewed by 373

Abstract

Sediment microbial fuel cells (SMFC) are bioelectrochemical systems that can use different wastes for energy production. This work studied the implementation of nanoparticles (NPs) of α-FeOOH (goethite, which is well-known as a photoactive catalyst) in the electrodes of an SMFC for its potential [...] Read more.

Sediment microbial fuel cells (SMFC) are bioelectrochemical systems that can use different wastes for energy production. This work studied the implementation of nanoparticles (NPs) of α-FeOOH (goethite, which is well-known as a photoactive catalyst) in the electrodes of an SMFC for its potential use for dye removal. The results obtained demonstrate the feasibility of the NPs activation with the electrical potential generated in the electrodes in the SMFC instead of the activation with light. The NPs of α-FeOOH were synthesized using a hydrothermal process, and the feasibility of a conductive bio-composite (biofilm and NPs) formation was proven by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and electrochemical techniques. The improvement of the power density in the cell was more than twelve times higher with the application of the bio-composite, and it is attributed mostly to the presence of NPs. The results also demonstrate the NPs effect on the increase of the electron transfer, which resulted in 99% of the COD removal. The total electrical energy produced in 30 days in the SMFC was 1.2 kWh based on 1 m² of the geometric area of the anode. The results confirm that NPs of α-FeOOH can be used to improve organic matter removal. Moreover, the energy produced due to its activation through the potential generated between the electrodes suggests the feasibility of its implementation for dye removal. Full article

(This article belongs to the Special Issue Feature Papers in Section "Biomass Catalysis")

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27 pages, 5134 KiB

Open AccessReview

Advancements in Cobalt-Based Catalysts for Enhanced CO₂ Hydrogenation: Mechanisms, Applications, and Future Directions: A Short Review

by Xixue He, Xinyu Wang and Hao Xu

Catalysts 2024, 14(9), 560; https://doi.org/10.3390/catal14090560 - 25 Aug 2024

Viewed by 473

Abstract

In 2020, China put forward the national energy and economic development strategy goal of “carbon peak and carbon neutrality”; in this context, the hydrogenation of carbon dioxide into clean energy and high-value-added chemicals can effectively alleviate the current environmental pressure. This process represents [...] Read more.

In 2020, China put forward the national energy and economic development strategy goal of “carbon peak and carbon neutrality”; in this context, the hydrogenation of carbon dioxide into clean energy and high-value-added chemicals can effectively alleviate the current environmental pressure. This process represents a crucial avenue for the advancement of green energy and the realisation of a sustainable energy development strategy. Among the efficient catalysts designed for CO₂ hydrogenation reactions, transition metal cobalt has garnered extensive attention from researchers due to its relatively abundant reserves and low economic cost. This paper first introduces the thermodynamic process of carbon dioxide hydrogenation and discusses methods to improve the efficiency of the catalytic reaction from a thermodynamic perspective. It then briefly describes the reaction mechanism of cobalt-based catalysts in the carbon dioxide hydrogenation reaction. Based on this understanding, this paper reviews recent research on the application of cobalt-based catalysts in the hydrogenation of carbon dioxide to produce methane, hydrocarbon chemicals, and alcohols. Finally, the methods to improve the catalytic efficiency of these catalysts are discussed, and future research directions are proposed. Full article

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9 pages, 4147 KiB

Open AccessArticle

Fabrication of Platinum-Decorated NiCo-Layered Double Hydroxide Nanoflowers for Electrocatalytic Ammonia Oxidation Reaction

by Xinyue Wang, Yujie Gong, Hongli Cai, Yue Han, Jiali Gu, Liang Zhang and Chun Zhao

Catalysts 2024, 14(9), 559; https://doi.org/10.3390/catal14090559 - 25 Aug 2024

Viewed by 394

Abstract

The complete anodic oxidation of ammonia is an important part of direct ammonia fuel cells. Fabricating a high-performance electrocatalyst for ammonia oxidation reaction is meaningful for developing a direct ammonia fuel cell. Herein, we designed one platinum-decorated NiCo-layered double hydroxide nanoflower on Ni [...] Read more.

The complete anodic oxidation of ammonia is an important part of direct ammonia fuel cells. Fabricating a high-performance electrocatalyst for ammonia oxidation reaction is meaningful for developing a direct ammonia fuel cell. Herein, we designed one platinum-decorated NiCo-layered double hydroxide nanoflower on Ni foam (Pt-NiCo-LDH-Ni foam) and measured the electrocatalytic performance via the cyclic voltammetry (CV) technique. The experimental results demonstrated that the optimized Pt-NiCo-LDH-Ni foam showed great electrocatalytic performance, with a low overpotential with a value of −0.573 V, a high current density of 17.75 mA cm⁻² for the ammonia oxidation reaction, and good stability. Full article

(This article belongs to the Section Electrocatalysis)

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13 pages, 2635 KiB

Open AccessReview

TiO₂-Supported Catalysts in Low-Temperature Selective Reduction of NO_x with NH₃: A Review of Recent Progress

by Xue Bian, Jing Wang, Yuting Bai, Yanping Li, Wenyuan Wu and Yuming Yang

Catalysts 2024, 14(9), 558; https://doi.org/10.3390/catal14090558 - 25 Aug 2024

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Abstract

Selective catalytic reduction (SCR) stands out as a pivotal method for curbing NO_x emissions from flue gas. The support, crucially, for SCR efficacy, loads and interacts with the active components within the catalyst. The catalysts could be amplified by the denitration performance [...] Read more.

Selective catalytic reduction (SCR) stands out as a pivotal method for curbing NO_x emissions from flue gas. The support, crucially, for SCR efficacy, loads and interacts with the active components within the catalyst. The catalysts could be amplified by the denitration performance of the catalyst by enhancements in support pore structure, acidity, and mechanical robustness. These improvements ensure efficient interaction between the support and active materials, thereby optimizing the structure and property of the catalysts. TiO₂ is the most commonly used support of the NH₃-SCR catalyst. The catalyst with TiO₂ support has poor thermal stability and a narrow temperature range, which can be improved. This paper reviews the research progress on the effects of various aspects of TiO₂ support on the NH₃-SCR catalyst’s performance, focusing on the TiO₂ crystal type, TiO₂ crystal surface, different TiO₂ structures, TiO₂ support preparation methods, and the effects of TiO₂-X composite support on the NH₃-SCR catalyst’s performance. The reaction mechanism, denitrification performance, and anti-SO₂/H₂O poisoning performance and mechanism of TiO₂ support with different characteristics were described. At the same time, the development trend of the NH₃-SCR catalyst using TiO₂ as the support is prospected. It is hoped that this work can provide optimization ideas for SCR catalyst research. Full article

(This article belongs to the Special Issue Recent Catalytic Progresses for Environmental Remediation and Pollutant Degradation)

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16 pages, 12257 KiB

Open AccessArticle

Catalytic Application of POSS–COF-[(Co(acetate)₂] for Selective Reduction of Nitriles to Amines

by Anosha Rubab, Manzar Sohail, Riyadh H. Alshammari, Ayman Nafady, Md. A. Wahab and Ahmed Abdala

Catalysts 2024, 14(9), 557; https://doi.org/10.3390/catal14090557 - 25 Aug 2024

Viewed by 319

Abstract

We report the reticular synthesis and structural investigations through the spectroscopic analysis of a novel polyhedral oligomeric silsesquioxane (POSS)-modified framework, hereby ascribed as a catalyst for the selective reduction of aryl nitriles to amines. The integration of the unique features of the polyhedral [...] Read more.

We report the reticular synthesis and structural investigations through the spectroscopic analysis of a novel polyhedral oligomeric silsesquioxane (POSS)-modified framework, hereby ascribed as a catalyst for the selective reduction of aryl nitriles to amines. The integration of the unique features of the polyhedral oligomeric silsesquioxane with 2,2′-Bipyridine-4,4′-dicarboxaldehyde and subsequently coordination to cobalt acetate manifests a distinctive feature, which is a stable covalent bond between Co and the functionalized POSS, effectively preventing catalyst leaching. The cobalt acetate-modified POSS–COF, synthesized with this approach, underwent a comprehensive characterization employing various analytical techniques including FTIR, XRD, SEM, XPS, TGA, and ²⁹Si NMR. This thorough characterization provides a detailed insight into the structural and chemical attributes of the catalyst. Our catalyst, with its exceptional catalytic efficiency in catalyzing reduction reactions compared to its homogeneous counterparts, and its distinctive three-dimensional metalated POSS system, shows outstanding catalytic performance attributed to its diverse coordination interactions with ligands. Moreover, this catalyst presents additional merits, such as facile recovery and recyclability, making it a promising candidate for sustainable and efficient catalytic processes and thus instilling hope for a greener future. Full article

(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)

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17 pages, 9575 KiB

Open AccessArticle

Activation of Peroxymonosulfate by Fe, O Co-Embedded Biochar for the Degradation of Tetracycline: Performance and Mechanisms

by Yufang Tao, Shenshen Sun, Yunzhen Hu, Shijie Gong, Shiyun Bao, Huihui Li, Xinyi Zhang, Zhe Yuan and Xiaogang Wu

Catalysts 2024, 14(9), 556; https://doi.org/10.3390/catal14090556 - 24 Aug 2024

Viewed by 308

Abstract

In recent years, pollution stemming from pharmaceuticals has garnered widespread global concern, which exacerbates the ecological risk to both surface and groundwater. In the current study, Fe and O co-embedded biochar (Fe-O-BC) was synthesized through a one-step pyrolysis procedure with corncob serving as [...] Read more.

In recent years, pollution stemming from pharmaceuticals has garnered widespread global concern, which exacerbates the ecological risk to both surface and groundwater. In the current study, Fe and O co-embedded biochar (Fe-O-BC) was synthesized through a one-step pyrolysis procedure with corncob serving as the feedstock. The fabricated Fe-O-BC catalysts were characterized by various techniques and were employed for the activation of peroxymonosulfate (PMS) to degrade tetracycline (TC). TC was rapidly degraded within 40 min, with a degradation rate of 0.1225 min⁻¹, which was much higher than those for O-BC/PMS (0.0228 min⁻¹) and Fe-BC/PMS (0.0271 min⁻¹) under the same conditions. The effects of PMS dosage, Fe-O-BC dose, initial pH value and coexisting anions for TC degradation were investigated. Finally, the mechanism of TC oxidation in the catalytic system was implored through experiments of determining the active sites and radical scavenging experiments. The C-O-Fe bond in the catalyst was confirmed to be the dominant active sites accelerating TC degradation. Free diffused HO^•, the surface-bound HO^• and SO₄^•− and O₂^•−participated in the reaction and absorbed SO₄^•−, and HO^• predominantly contributed to TC degradation. This study provides an efficient and green alternative for pharmaceutical wastewater treatment by Fe and O co-doped catalyst-induced heterogeneous process. Full article

(This article belongs to the Special Issue Recent Catalytic Progresses for Environmental Remediation and Pollutant Degradation)

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10 pages, 4022 KiB

Open AccessArticle

Spartina alterniflora-Derived Carbons for High-Performance Oxygen Reduction Reaction (ORR) Catalysts

by Xinmeng Hao, Yougui Zhou, Lihua Guo, Huipeng Li, Hong Shang and Xuanhe Liu

Catalysts 2024, 14(9), 555; https://doi.org/10.3390/catal14090555 - 24 Aug 2024

Viewed by 329

Abstract

Being an alien species, Spartina alterniflora has occupied the living space of native animals and plants, causing irreversible damage to the environment. Converting Spartina alterniflora into carbon or its derivatives offers a valuable solution to manage both invasive biomass and an energy shortage. [...] Read more.

Being an alien species, Spartina alterniflora has occupied the living space of native animals and plants, causing irreversible damage to the environment. Converting Spartina alterniflora into carbon or its derivatives offers a valuable solution to manage both invasive biomass and an energy shortage. Herein, through a simple activation process, we successfully prepared Spartina alterniflora-derived carbon (SAC) and its N-doped derivative SANC, and used them as metal-free catalysts for an oxygen reduction reaction (ORR). SAC exhibits good electrochemical performance and holds significant potential in catalysis. After N-doping by melamine as a nitrogen source, electronegativity is redistributed in SANC, leading to enhanced performance (a half-wave potential of 0.716 V vs. RHE, and a four-electron transfer pathway with a H₂O₂ yield of only 2.05%). This work presents a straightforward and cost-effective approach to the usage of obsolete invasive biomass and shows great potential in energy generation. Full article

(This article belongs to the Special Issue Porous Materials as Efficient Catalysts: Synthesis, Characterization and Applications)

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12 pages, 4555 KiB

Open AccessFeature PaperArticle

Boosting Benzene’s Ozone Catalytic Oxidation at Mild Temperatures over Highly Dispersed Ag-Doped Mn₃O₄

by Hao Guo, Liwei Cen, Kui Deng, Wenlong Mo, Hojo Hajime, Di Hu, Pan Zhang, Wenfeng Shangguan, Haibao Huang and Hisahiro Einaga

Catalysts 2024, 14(9), 554; https://doi.org/10.3390/catal14090554 - 23 Aug 2024

Viewed by 305

Abstract

Transition metal oxides show high activity while still facing the challenges of low mineralization and poor durability in the ozone catalytic oxidation (OCO) of volatile organic compounds (VOCs). Improving the oxygen mobility and low-temperature reducibility of transition metal oxides was found to be [...] Read more.

Transition metal oxides show high activity while still facing the challenges of low mineralization and poor durability in the ozone catalytic oxidation (OCO) of volatile organic compounds (VOCs). Improving the oxygen mobility and low-temperature reducibility of transition metal oxides was found to be an effective way to address the above challenges. Here, highly dispersed Ag was added to Mn₃O₄ via the co-precipitation oxalate route, and the obtained Ag/Mn₃O₄ exhibited higher mineralization and stability in benzene catalytic ozonation at room temperature. Compared to Mn₃O₄, the concentration of CO₂ formed from benzene oxidation over Ag/Mn₃O₄ was significantly increased, from 585.4 ppm to 810.9 ppm, while CO generation was greatly suppressed to only one tenth of its original value (194 ppm vs. 19 ppm). In addition, Ag/Mn₃O₄ exhibited higher catalytic stability than Mn₃O₄. The introduction of Ag obviously improved the oxygen mobility and low-temperature reducibility of Mn₃O₄. Moreover, the highly dispersed Ag also promoted the activity of surface oxygen species and the chemisorption of benzene on Mn₃O₄. The above physicochemical properties contributed to the excellent catalytic performance and durability of Ag/Mn₃O₄. This research could shed light on the improvement in VOC mineralization via ozone catalytic oxidation. Full article

(This article belongs to the Special Issue Catalytic Energy Conversion and Catalytic Environmental Purification)

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Catalysts, Volume 14, Issue 9 (September 2024) – 23 articles

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