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Open AccessFeature PaperArticle

Boosting Catalytic Combustion of Ethanol by Tuning Morphologies and Exposed Crystal Facets of α-Mn₂O₃

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Catalysts 2023, 13(5), 865; https://doi.org/10.3390/catal13050865 - 10 May 2023

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Abstract

Three types of α-Mn₂O₃ catalysts with different well-defined morphologies (cubic, truncated octahedra and octahedra) and exposed crystal facets have been successfully prepared via hydrothermal processes, and evaluated for ethanol total oxidation with low ethanol concentration at low temperatures. The α-Mn [...] Read more.

Three types of α-Mn₂O₃ catalysts with different well-defined morphologies (cubic, truncated octahedra and octahedra) and exposed crystal facets have been successfully prepared via hydrothermal processes, and evaluated for ethanol total oxidation with low ethanol concentration at low temperatures. The α-Mn₂O₃-cubic catalyst shows a superior catalytic reaction rate than that of α-Mn₂O₃-truncated octahedra and α-Mn₂O₃-octahedra under high space velocity of 192,000 mL/(g·h). Based on the characterization results obtained from XRD, BET, FE-SEM, HR-TEM, FT-IR, H₂-TPR, XPS, ethanol-TPD, and CO-TPSR techniques, the observed morphology-dependent reactivity of α-Mn₂O₃ catalysts can be correlated to the good low-temperature reducibility, abundant surface Mn⁴⁺ and adsorbed reactive oxygen species, which was originated from the exposed (001) crystal planes. Through tuning the morphology and exposed (001) crystal facet of α-Mn₂O₃, a highly active ethanol oxidation catalyst with high selectivity and excellent stability is obtained. The developed approach may be applied broadly to the development of the design principles for high-performance low-cost and environmentally friendly Mn-based oxidation catalysts. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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Open AccessArticle

Heterogeneous Chitosan@copper Catalyzed Selective C(sp³)–H Sulfonylation of Ketone Hydrazones with Sodium Sulfinates: Direct Access to β-Ketosulfones

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Catalysts 2023, 13(4), 726; https://doi.org/10.3390/catal13040726 - 12 Apr 2023

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Abstract

The exploration of inexpensive and stable heterogeneous catalysts for C–S coupling reactions remains a challenging issue. Herein, we successfully prepared a new biomass-derived copper catalyst and applied it to the selective C(sp³)–H-directed sulfonylation of ketone hydrazones with commercial sodium sulfinates. The [...] Read more.

The exploration of inexpensive and stable heterogeneous catalysts for C–S coupling reactions remains a challenging issue. Herein, we successfully prepared a new biomass-derived copper catalyst and applied it to the selective C(sp³)–H-directed sulfonylation of ketone hydrazones with commercial sodium sulfinates. The catalyst was characterized using different spectroscopic and microscopic techniques. Importantly, the prepared biomass-supported Cu catalyst catalyzed the C–S coupling reaction with considerably high activity. A variety of aryl and alkyl sulfinates were converted to the corresponding sulfones with good yields. In particular, the heterogeneous catalyst could be recovered easily after the synthesis and consecutively used at least five times with no appreciable decrease in the catalytic activity. Lastly, the copper catalyst is expected to have further applications in organic reactions catalyzed by Cu/CuO₂. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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Open AccessFeature PaperArticle

Cationic Covalent Triazine Network: A Metal-Free Catalyst for Effective Acetylene Hydrochlorination

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Catalysts 2023, 13(2), 432; https://doi.org/10.3390/catal13020432 - 17 Feb 2023

Viewed by 712

Abstract

Vinyl chloride, the monomer of polyvinyl chloride, is produced primarily via acetylene hydrochlorination catalyzed by environmentally toxic carbon-supported HgCl₂. Recently, nitrogen-doped carbon materials have been explored as metal-free catalysts to substitute toxic HgCl₂. Herein, we describe the development of [...] Read more.

Vinyl chloride, the monomer of polyvinyl chloride, is produced primarily via acetylene hydrochlorination catalyzed by environmentally toxic carbon-supported HgCl₂. Recently, nitrogen-doped carbon materials have been explored as metal-free catalysts to substitute toxic HgCl₂. Herein, we describe the development of a cationic covalent triazine network (cCTN, cCTN-700) that selectively catalyzes acetylene hydrochlorination. cCTN-700 exhibited excellent catalytic activity with initial acetylene conversion, reaching ~99% and a vinyl chloride selectivity of >98% at 200 °C during a 45 h test. X-ray photoelectron spectroscopy, temperature programmed desorption, and charge calculation results revealed that the active sites for the catalytic reaction were the carbon atoms bonded to the pyridinic N and positively charged nitrogen atoms (viologenic N⁺) of the viologen moieties in cCTN-700, similar to the active sites in Au-based catalysts but different from the those in previously reported nitrogen-doped carbon materials. This research focuses on using cationic covalent triazine polymers for selective acetylene hydrochlorination. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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Open AccessArticle

A Comparison of the Sensing Behavior for Pt-Mo/C-, Pt-Zr/C-, Pt-Fe-Ir/C-, and Pt/C-Modified Glassy Carbon Electrodes for the Oxidation of Ascorbic Acid and Dopamine

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Catalysts 2023, 13(2), 337; https://doi.org/10.3390/catal13020337 - 02 Feb 2023

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Abstract

This study compares the sensing performance for platinum-molybdenum-, platinum-zirconium-, platinum-iron-iridium-, and platinum-modified electrodes in terms of the amperometric detection of ascorbic acid (AA) and dopamine (DA). The Pt, Pt-Mo, Pt-Zr, and Pt-Fe-Ir electrocatalysts are fabricated by chemical reduction on a carbon black support [...] Read more.

This study compares the sensing performance for platinum-molybdenum-, platinum-zirconium-, platinum-iron-iridium-, and platinum-modified electrodes in terms of the amperometric detection of ascorbic acid (AA) and dopamine (DA). The Pt, Pt-Mo, Pt-Zr, and Pt-Fe-Ir electrocatalysts are fabricated by chemical reduction on a carbon black support (XC-72) and are further modified on a glassy carbon electrode (GCE) as sensing electrodes. The Pt-Mo/C/GCE exhibits better electrocatalytic activity toward AA and DA than the Pt/C/GCE, Pt-Zr/C/GCE, and Pt-Fe-Ir/C/GCE. The Pt-Mo/C/GCE exhibits a sensitivity of 31.29 µA mM⁻¹ to AA at 0.3 V vs. Ag/AgCl and a sensitivity of 72.24 µA mM⁻¹ to DA at 0.6 V vs. Ag/AgCl and is reproducible and stable. This electrode has a respective limit of detection of 7.69 and 6.14 µM for AA and DA. Sucrose, citric acid, tartaric acid, and uric acid do not interfere with AA and DA detection. The diffusion coefficient and kinetic parameters, such as the catalytic rate constant and the heterogeneous rate constant for AA and DA, are determined using electrochemical approaches. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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Open AccessArticle

Non-Conventional Synthesis and Repetitive Application of Magnetic Visible Light Photocatalyst Powder Consisting of Bi-Layered C-Doped TiO₂ and Ni Particles

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Catalysts 2023, 13(1), 169; https://doi.org/10.3390/catal13010169 - 11 Jan 2023

Cited by 2 | Viewed by 753

Abstract

In the current study, a non-conventional application of the magnetron sputtering technique was proposed. A four-step synthesis procedure allowed us to produce a magnetic photocatalyst powder consisting of bi-layered particles with carbon-doped TiO₂ on one side, and metallic Ni on the other [...] Read more.

In the current study, a non-conventional application of the magnetron sputtering technique was proposed. A four-step synthesis procedure allowed us to produce a magnetic photocatalyst powder consisting of bi-layered particles with carbon-doped TiO₂ on one side, and metallic Ni on the other side. XRD, SEM and EDS methods were used for sample characterization. It was determined, that after the sputtering process optimization, the bandgap of carbon-doped TiO₂ was reduced to approximately 3.1 eV and its light adsorption increased over the whole visible light spectrum. The repetitive Rhodamine B solution bleaching with magnetic photocatalyst powder and visible light showed interesting evolvement of photocatalyst efficiency. After the first cycle, Rhodamine B concentration was reduced by just 35%. However, after the second cycle, the reduction had already reached nearly 50%. Photocatalytic bleaching efficiency continued to improve rapidly until higher than 95% of Rhodamine B concentration reduction was achieved (at tenth cycle). For the next ten cycles, photocatalytic bleaching efficiency remained relatively stable. The initial gain in efficiency was attributed to the magnetic photocatalyst particle size reduction from an initial diameter of 100–150 µm to 5 µm. Naturally, the 20–30 times size reduction resulted in a remarkably increased active surface area, which was a key factor for the increased performance. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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Open AccessFeature PaperArticle

Evaluation of Structural and Functional Properties of La_0.6Sr_0.4MnO₃ Perovskite Prepared by the Fast Solution Combustion Approach

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José Jiménez Rodríguez

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Ramalinga Viswanathan Mangalaraja

Catalysts 2022, 12(12), 1636; https://doi.org/10.3390/catal12121636 - 13 Dec 2022

Viewed by 694

Abstract

A series of La_0.6Sr_0.4MnO₃ (LSM) perovskite was made using the rapid solution combustion method, which was calcined by varying the temperatures. In order to determine how the calcination temperature affected the nanopowders produced and calcined at various temperatures, [...] Read more.

A series of La_0.6Sr_0.4MnO₃ (LSM) perovskite was made using the rapid solution combustion method, which was calcined by varying the temperatures. In order to determine how the calcination temperature affected the nanopowders produced and calcined at various temperatures, their microstructural, morphological, compositional, optical, and electrical properties were analyzed using corresponding characterization tools. The XRD results showed the coexistence of the rhombohedral polymorphs R-3c and Pm-3m for the perovskite phase under a calcination temperature of 1400 °C, which were eliminated with increased calcination temperature. The average grain size was found to increase with increasing calcination temperature. The EDS analysis showed better agreement of the stoichiometry with the theoretical composition. The apparent porosity decreased with increasing temperature due to the coalescence of sintering pores. The sample obtained after calcination at 1500 °C showed 10.3% porosity. The hardness also improved with increasing calcination temperature and reached a maximum value of 0.4 GPa, which matched the bulk density. A similar trend was observed in the resistivity studies as a function of temperature, and all the samples exhibited a low resistivity of ~1.4 Ω·cm in the temperature range of 500–600 °C. The optical characterization showed broad absorption at 560–660 nm and bandwidth values between 3.70 and 3.95 eV, according to the applied heat treatment. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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Open AccessArticle

Synthesis of Ce_0.1La_0.9MnO₃ Perovskite for Degradation of Endocrine-Disrupting Chemicals under Visible Photons

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Madappa C. Maridevaru

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Afreen Hooriya Naceruddin

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Belqasem Aljafari

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Sambandam Anandan

Catalysts 2022, 12(10), 1258; https://doi.org/10.3390/catal12101258 - 17 Oct 2022

Viewed by 911

Abstract

The UN Environmental Protection Agency has recognized 4-n-Nonylphenol (NP) and bisphenol A (BPA) as among the most hazardous chemicals, and it is essential to minimize their concentrations in the wastewater stream. These industrial chemicals have been witnessed to cause endocrine disruption. [...] Read more.

The UN Environmental Protection Agency has recognized 4-n-Nonylphenol (NP) and bisphenol A (BPA) as among the most hazardous chemicals, and it is essential to minimize their concentrations in the wastewater stream. These industrial chemicals have been witnessed to cause endocrine disruption. This report describes the straightforward hydrothermal approach adopted to produce Ce_0.1La_0.9MnO₃ (CLMO) perovskite’s structure. Several physiochemical characterization approaches were performed to understand the Ce_0.1La_0.9MnO₃ (CLMO) perovskite crystalline phase, element composition, optical properties, microscopic topography, and molecular oxidation state. Here, applying visible photon irradiation, the photocatalytic capability of these CLMO nanostructures was evaluated for the elimination of NP and BPA contaminants. To optimize the reaction kinetics, the photodegradation of NP and BPA pollutants on CLMO, perovskite was studied as a specification of pH, catalyst dosage, and initial pollutant concentration. Correspondingly, 92% and 94% of NP and BPA pollutants are degraded over CLMO surfaces within 120 and 240 min, respectively. Since NP and BPA pollutants have apparent rate constants of 0.0226 min⁻¹ and 0.0278 min⁻¹, respectively, they can be satisfactorily fitted by pseudo-first-order kinetics. The decomposition of NP and BPA contaminants is further evidenced by performing FT-IR analysis. Owing to its outstanding photocatalytic execution and simplistic separation, these outcomes suggest that CLMO is an intriguing catalyst for the efficacious removal of NP and BPA toxicants from the aqueous phase. This is pertinent for the treatment of endocrine-disrupting substances in bioremediation. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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Open AccessArticle

Systematic Incorporation of Gold Nanoparticles onto Mesoporous Titanium Oxide Particles for Green Catalysts

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Catalysts 2021, 11(4), 451; https://doi.org/10.3390/catal11040451 - 31 Mar 2021

Cited by 1 | Viewed by 1371

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This report describes the systematic incorporation of gold nanoparticles (AuNPs) onto mesoporous TiO₂ (MPT) particles without strong attractive forces to efficiently serve as reactive and recyclable catalysts in the homocoupling of arylboronic acid in green reaction conditions. Unlike using nonporous TiO₂ [...] Read more.

This report describes the systematic incorporation of gold nanoparticles (AuNPs) onto mesoporous TiO₂ (MPT) particles without strong attractive forces to efficiently serve as reactive and recyclable catalysts in the homocoupling of arylboronic acid in green reaction conditions. Unlike using nonporous TiO₂ particles and conventional SiO₂ particles as supporting materials, the employment of MPT particles significantly improves the loading efficiency of AuNPs. The incorporated AuNPs are less than 10 nm in diameter, regardless of the amount of applied gold ions, and their surfaces, free from any modifiers, act as highly reactive catalytic sites to notably improve the yields in the homocoupling reaction. The overall physical properties of the AuNPs integrated onto the MPT particles are thoroughly examined as functions of the gold content, and their catalytic functions, including the rate of reaction, activation energy, and recyclability, are also evaluated. While the rate of reaction slightly increases with the improved loading efficiency of AuNPs, the apparent activation energies do not clearly show any correlation with the size or distribution of the AuNPs under our reaction conditions. Understanding the formation of these types of composite particles and their catalytic functions could lead to the development of highly practical, quasi-homogeneous catalysts in environmentally friendly reaction conditions. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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Open AccessArticle

Microwave-Assisted Solvothermal Synthesis of Chalcogenide Composite Photocatalyst and Its Photocatalytic CO₂ Reduction Activity under Simulated Solar Light

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Catalysts 2020, 10(7), 789; https://doi.org/10.3390/catal10070789 - 15 Jul 2020

Cited by 7 | Viewed by 1674

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A novel heterostructure consisting of Ru and Cu co-doped ZnS nanopowders (RCZS) into a MoS₂-graphene hybrid (MSG) is successfully prepared by the microwave-assisted solvothermal approach. RCZS nanopowders are fabricated on the surface of MSG, which produces a nanoscale interfacial between RCZS [...] Read more.

A novel heterostructure consisting of Ru and Cu co-doped ZnS nanopowders (RCZS) into a MoS₂-graphene hybrid (MSG) is successfully prepared by the microwave-assisted solvothermal approach. RCZS nanopowders are fabricated on the surface of MSG, which produces a nanoscale interfacial between RCZS and MSG. As the photo-excited electrons of RCZS can easily migrate to MoS₂ through graphene by hindering the electron and hole (e^– and h⁺) recombination, the photocatalytic activity could be improved by effective charge transfer. As RCZS are anchored onto the MSG, the photoluminescence intensity of the chalcogenide composite photocatalyst obviously decreases. In addition, a quaternary ruthenium and copper-based chalcogenide RCZS/MSG is able to improve the harvest and utilization of light. With the increase in the concentrations of Ru until 4 mol%, the band gap significantly decreases from 3.52 to 2.73 eV. At the same time, moderate modification by ruthenium can decrease the PL intensity compared to the pristine CZS/MSG sample, which indicates the enhancement of e^– and h⁺ separation by Ru addition. The photocatalytic activity of as-synthesized chalcogenide composite photocatalysts is evaluated by the photocatalytic carbon dioxide reduction. Optimized operation conditions for carbon dioxide reduction have been performed, including the concentration of NaOH solution, the amount of RCZS/MSG photocatalyst, and the content of co-doped ruthenium. The doping of ruthenium would efficiently improve the performance of the photocatalytic activity for carbon dioxide reduction. The optimal conditions, such as the concentration of 2 M NaOH and the 0.5RCZS/MSG dosage of 0.05 g L^–1, provide the maximum methane gas yield of 58.6 μmol h⁻¹ g^–1. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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Open AccessArticle

Preparation and Photocatalytic Properties of Heterostructured Ceria/Polyaniline Nanoparticles

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Catalysts 2020, 10(7), 732; https://doi.org/10.3390/catal10070732 - 02 Jul 2020

Cited by 5 | Viewed by 1868

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Cerium dioxide (CeO₂, ceria), a promising and abundant catalytic material with high-efficiency, nontoxicity, photochemical stability, and affordability, can be used as a photocatalyst to photocatalytically degrade organics and split water for hydrogen production under ultraviolet (UV) irradiation (about 5% of solar [...] Read more.

Cerium dioxide (CeO₂, ceria), a promising and abundant catalytic material with high-efficiency, nontoxicity, photochemical stability, and affordability, can be used as a photocatalyst to photocatalytically degrade organics and split water for hydrogen production under ultraviolet (UV) irradiation (about 5% of solar energy). However, the applications of the CeO₂ photocatalyst are limited due to low photocatalytic efficiency under sunlight irradiation. In this study, a nanosized CeO₂ powder was prepared by the precipitation method. Subsequently, various amounts of polyaniline (PANI) nanoparticles were deposited onto the surface of the CeO₂ nanoparticles to form a heterostructure by the polymerization method. The crystal structure, morphology, surface and optical properties of the CeO₂/PANI nanoparticles were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-Vis) absorption spectroscopy, and photoluminescence (PL). Experimental results demonstrated that PANI deposition improved the light absorption of CeO₂ nanoparticles in the visible light region. The heterostructured CeO₂/PANI nanoparticle with 4 wt % PANI deposition exhibited optimal photocatalytic activities with a hydrogen production rate of 462 μmolg⁻¹ within 6 h and a methyl orange (MO) degradation rate of 45% within 4 h under visible light irradiation. The photocatalytic mechanisms of the composite powder are also proposed in this report. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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Open AccessArticle

Synthesis of Hydroxy Sodalite from Coal Fly Ash for Biodiesel Production from Waste-Derived Maggot Oil

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Juvet Malonda Shabani

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Omotola Babajide

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Oluwaseun Oyekola

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Leslie Petrik

Catalysts 2019, 9(12), 1052; https://doi.org/10.3390/catal9121052 - 11 Dec 2019

Cited by 18 | Viewed by 2949

Abstract

Zeolites are aluminosilicate crystalline materials known for their unique characteristics, and have been prominent for nearly half a century due to their wide and important industrial applications. The production of zeolites, however, remains a challenge due to the high cost of commercial reagents [...] Read more.

Zeolites are aluminosilicate crystalline materials known for their unique characteristics, and have been prominent for nearly half a century due to their wide and important industrial applications. The production of zeolites, however, remains a challenge due to the high cost of commercial reagents conventionally used as feedstocks. In the current study, hydroxy sodalite (HS) zeolite samples were synthesised from coal fly ash feedstock by a direct hydrothermal synthesis method. The effects of hydrothermal crystallisation synthesis time on phase crystallinity, crystal size, and morphology of the formed HS were investigated. The prepared samples were characterised using XRD, SEM, EDS and FT-IR techniques. The XRD results of the samples prepared with varying synthesis times confirmed the formation of HS from low to high phase purity and crystallinity from 11 to over 98%. The SEM results reflected gradual variation in crystal morphology, of which highly crystalline HS samples were associated with hexagonal-cubic and cubic-platelet crystals. The FTIR, depicting zeolite characteristics of T–O and T–O–T stretching vibrations in the molecular framework, further confirmed the formation of HS zeolites for samples obtained above the 24-h synthesis time. These zeolite samples were then evaluated for their catalytic activities in the conversion of maggot oil to biodiesel. The application of the various hydroxy sodalite samples for the transesterification of maggot oil yielded up to 84.10% biodiesel (FAME) with physicochemical properties that were in compliance with the biodiesel specification standards. This study investigated the novel use of a coal fly ash-derived, heterogeneous HS catalyst in biodiesel production from maggot oil, and indicates its potential to enhance biodiesel yield and quality upon process optimisation tests. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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