Research

19 pages, 11661 KiB

Open AccessArticle

Unraveling the Structural and Compositional Peculiarities in CTAB-Templated CeO₂-ZrO₂-MnO_x Catalysts for Soot and CO Oxidation

by Maria V. Grabchenko, Natalia N. Mikheeva, Grigory V. Mamontov, Vicente Cortés Corberán, Kseniya A. Litvintseva, Valery A. Svetlichnyi, Olga V. Vodyankina and Mikhail A. Salaev

Nanomaterials 2023, 13(24), 3108; https://doi.org/10.3390/nano13243108 - 09 Dec 2023

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Abstract

Structure–performance relationships in functional catalysts allow for controlling their performance in a wide range of reaction conditions. Here, the structural and compositional peculiarities in CTAB-templated CeO₂-ZrO₂-MnO_x catalysts prepared by co-precipitation of precursors and their catalytic behavior in CO [...] Read more.

Structure–performance relationships in functional catalysts allow for controlling their performance in a wide range of reaction conditions. Here, the structural and compositional peculiarities in CTAB-templated CeO₂-ZrO₂-MnO_x catalysts prepared by co-precipitation of precursors and their catalytic behavior in CO oxidation and soot combustion are discussed. A complex of physical–chemical methods (low-temperature N₂ sorption, XRD, TPR-H₂, Raman, HR TEM, XPS) is used to elucidate the features of the formation of interphase boundaries, joint phases, and defects in multicomponent oxide systems. The addition of Mn and/or Zr dopant to ceria is shown to improve its performance in both reactions. Binary Ce-Mn catalysts demonstrate enhanced performance closely followed by the ternary oxide catalysts, which is due the formation of several types of active sites, namely, highly dispersed MnO_x species, oxide–oxide interfaces, and oxygen vacancies that can act individually and/or synergistically. Full article

(This article belongs to the Special Issue Application of Porous Nanomaterials in Energy Storage and Catalysis)

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16 pages, 11075 KiB

Open AccessArticle

Water Adsorption Dynamics on Metal–Organic Framework MOF-801: Comparative Study of Loose and Glued Grains, and Coatings

by Marina Solovyeva and Larisa Gordeeva

Nanomaterials 2023, 13(17), 2442; https://doi.org/10.3390/nano13172442 - 28 Aug 2023

Viewed by 1347

Abstract

Adsorption heat transformation and storage (AHTS) is an environmentally benign and energy-saving alternative to common compression chillers and heat pumps. The low specific power (SP) of adsorption systems is a key drawback that hinders their broader dissemination. The optimization of adsorption dynamics is [...] Read more.

Adsorption heat transformation and storage (AHTS) is an environmentally benign and energy-saving alternative to common compression chillers and heat pumps. The low specific power (SP) of adsorption systems is a key drawback that hinders their broader dissemination. The optimization of adsorption dynamics is a prerequisite for SP enhancement. In this work, we studied the dynamics of water vapor adsorption on MOF-801—a promising adsorbent for AHTS. For the first time, two configurations of compact MOF-801 bed, namely, grains glued to the surface of a metal support and thin adsorbent coatings, are prepared, and their porous structure is characterized. The water adsorption dynamics is compared with a common loose grains configuration. The main findings are: (a) the binder can both accelerate and decelerate the water adsorption, and its chemical nature is subject to careful selection; (b) at the initial time, heat transfer between the support and adsorbent bed controls the adsorption rate, and, at a longer time, mass transfer starts to affect it; (c) polyvinylpyrrolidone, bentonite, thermal grease, and hydroxyethylcellulose increase the heat transfer coefficients and accelerate adsorption; polyvinyl alcohol and polyaniline slow it down; and (d) for the coatings prepared with polyvinylpyrrolidone, an SP of 1.6–5.1 kW/kg can be achieved, which is about twice that for the loose grains. The new configurations can be recommended for effective but expensive adsorbents such as MOFs, and their implementation will contribute to the further spread of AHTS technology. Full article

(This article belongs to the Special Issue Application of Porous Nanomaterials in Energy Storage and Catalysis)

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17 pages, 3896 KiB

Open AccessArticle

Copper-Based Silica Nanotubes as Novel Catalysts for the Total Oxidation of Toluene

by Victor Deboos, Carla Calabrese, Jean-Marc Giraudon, Rino Morent, Nathalie De Geyter, Leonarda Francesca Liotta and Jean-François Lamonier

Nanomaterials 2023, 13(15), 2202; https://doi.org/10.3390/nano13152202 - 28 Jul 2023

Viewed by 718

Abstract

Cu (10 wt%) materials on silica nanotubes were prepared via two different synthetic approaches, co-synthesis and wetness impregnation on preformed SiO₂ nanotubes, both as dried or calcined materials, with Cu(NO₃)2.5H₂O as a material precursor. The obtained silica and [...] Read more.

Cu (10 wt%) materials on silica nanotubes were prepared via two different synthetic approaches, co-synthesis and wetness impregnation on preformed SiO₂ nanotubes, both as dried or calcined materials, with Cu(NO₃)2.5H₂O as a material precursor. The obtained silica and the Cu samples, after calcination at 550 °C for 5 h, were characterized by several techniques, such as TEM, N₂ physisorption, XRD, Raman, H₂-TPR and XPS, and tested for toluene oxidation in the 20–450 °C temperature range. A reference sample, Cu(10 wt%) over commercial silica, was also prepared. The copper-based silica nanotubes exhibited the best performances with respect to toluene oxidation. The Cu-based catalyst using dried silica nanotubes has the lowest T₅₀ (306 °C), the temperature required for 50% toluene conversion, compared with a T₅₀ of 345 °C obtained for the reference catalyst. The excellent catalytic properties of this catalyst were ascribed to the presence of easy copper (II) species finely dispersed (crystallite size of 13 nm) on the surface of silica nanotubes. The present data underlined the impact of the synthetic method on the catalyst properties and oxidation activity. Full article

(This article belongs to the Special Issue Application of Porous Nanomaterials in Energy Storage and Catalysis)

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23 pages, 1962 KiB

Open AccessArticle

Synthesis and Catalytic Activity for 2, 3, and 4-Nitrophenol Reduction of Green Catalysts Based on Cu, Ag and Au Nanoparticles Deposited on Polydopamine-Magnetite Porous Supports

by Helen K. Brown, Jamal El Haskouri, María D. Marcos, José Vicente Ros-Lis, Pedro Amorós, M. Ángeles Úbeda Picot and Francisco Pérez-Pla

Nanomaterials 2023, 13(15), 2162; https://doi.org/10.3390/nano13152162 - 25 Jul 2023

Cited by 1 | Viewed by 1092

Abstract

This work reports on the synthesis of nine materials containing Cu, Ag, Au, and Ag/Cu nanoparticles (NPs) deposited on magnetite particles coated with polydopamine (PDA). Ag NPs were deposited on two PDA@Fe3O4 supports differing in the thickness of the PDA film. The film [...] Read more.

This work reports on the synthesis of nine materials containing Cu, Ag, Au, and Ag/Cu nanoparticles (NPs) deposited on magnetite particles coated with polydopamine (PDA). Ag NPs were deposited on two PDA@Fe3O4 supports differing in the thickness of the PDA film. The film thickness was adjusted to impart a textural porosity to the material. During synthesis, Ag(I) was reduced with ascorbic acid (HA), photochemically, or with NaBH4, whereas Au(III), with HA, with the PDA cathecol groups, or NaBH4. For the material characterization, TGA, XRD, SEM, EDX, TEM, STEM-HAADF, and DLS were used. The catalytic activity towards reduction of 4-, 3- and 2-nitrophenol was tested and correlated with the synthesis method, film thickness, metal particle size and NO2 group position. An evaluation of the recyclability of the materials was carried out. In general, the catalysts prepared by using soft reducing agents and/or thin PDA films were the most active, while the materials reduced with NaBH4 remained unchanged longer in the reactor. The activity varied in the direction Au > Ag > Cu. However, the Ag-based materials showed a higher recyclability than those based on gold. It is worth noting that the Cu-containing catalyst, the most environmentally friendly, was as active as the best Ag-based catalyst. Full article

(This article belongs to the Special Issue Application of Porous Nanomaterials in Energy Storage and Catalysis)

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16 pages, 3932 KiB

Open AccessArticle

Highly Active Manganese Oxide from Electrolytic Manganese Anode Slime for Efficient Removal of Antibiotics Induced by Dissociation of Peroxymonosulfate

by He Zhang, Ruixue Xiong, Shijie Peng, Desheng Xu and Jun Ke

Nanomaterials 2023, 13(10), 1600; https://doi.org/10.3390/nano13101600 - 10 May 2023

Cited by 2 | Viewed by 995

Abstract

In this paper, high-activity manganese oxide was prepared from electrolytic manganese anode slime to realize the efficient removal of antibiotics. The effects of sulfuric acid concentration, ethanol dosage, liquid–solid ratio, leaching temperature and leaching time on the leaching of manganese from electrolytic manganese [...] Read more.

In this paper, high-activity manganese oxide was prepared from electrolytic manganese anode slime to realize the efficient removal of antibiotics. The effects of sulfuric acid concentration, ethanol dosage, liquid–solid ratio, leaching temperature and leaching time on the leaching of manganese from electrolytic manganese anode slime were systematically studied. Under the optimal conditions, the leaching rate of manganese reached 88.74%. In addition, a Mn₃O₄ catalyst was synthesized and used to activate hydrogen persulfate (PMS) to degrade tetracycline hydrochloride (TCH). The synthesized Mn₃O₄ was characterized by XRD, XPS, Raman, SEM and HRTEM. As a result, the prepared Mn₃O₄ is spherical, with high purity and crystallinity. The catalytic activity of Mn₃O₄ for PMS to degrade TCH was increased to 82.11%. In addition, after four cycles, the performance remained at 78.5%, showing excellent stability and recyclability. In addition, O₂⁻ and ¹O₂ are the main active species in the degradation reaction. The activity of Mn₃O₄ is attributed to it containing Mn(II) and Mn(III) at the same time, which can quickly realize the transformation of high-valence and low-valence manganese, promote the transfer of electrons and realize the degradation of organic pollutants. Full article

(This article belongs to the Special Issue Application of Porous Nanomaterials in Energy Storage and Catalysis)

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19 pages, 25463 KiB

Open AccessArticle

Carbonized Polydopamine-Based Nanocomposites: The Effect of Transition Metals on the Oxygen Electrocatalytic Activity

by Jesús Cebollada, David Sebastián, María Jesús Lázaro and Maria Victoria Martínez-Huerta

Nanomaterials 2023, 13(9), 1549; https://doi.org/10.3390/nano13091549 - 05 May 2023

Cited by 3 | Viewed by 1671

Abstract

The electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the most critical processes in renewable energy-related technologies, such as fuel cells, water electrolyzers, and unitized regenerative fuel cells. N-doped carbon composites have been demonstrated to be promising ORR/OER catalyst candidates [...] Read more.

The electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the most critical processes in renewable energy-related technologies, such as fuel cells, water electrolyzers, and unitized regenerative fuel cells. N-doped carbon composites have been demonstrated to be promising ORR/OER catalyst candidates because of their excellent electrical properties, tunable pore structure, and environmental compatibility. In this study, we prepared porous N-doped carbon nanocomposites (NC) by combining mussel-inspired polydopamine (PDA) chemistry and transition metals using a solvothermal carbonization strategy. The complexation between dopamine catechol groups and transition metal ions (Fe, Ni, Co, Zn, Mn, Cu, and Ti) results in hybrid structures with embedded metal nanoparticles converted to metal–NC composites after the carbonization process. The influence of the transition metals on the structural, morphological, and electrochemical properties was analyzed in detail. Among them, Cu, Co, Mn, and Fe N-doped carbon nanocomposites exhibit efficient catalytic activity and excellent stability toward ORR. This method improves the homogeneous distribution of the catalytically active sites. The metal nanoparticles in reduced (MnO, Fe₃C) or metallic (Cu, Co) oxidation states are protected by the N-doped carbon layers, thus further enhancing the ORR performance of the composites. Still, only Co nanocomposite is also effective toward OER with a potential bifunctional gap (ΔE) of 0.867 V. The formation of Co-N active sites during the carbonization process, and the strong coupling between Co nanoparticles and the N-doped carbon layer could promote the formation of defects and the interfacial electron transfer between the catalyst surface, and the reaction intermediates, increasing the bifunctional ORR/OER performance. Full article

(This article belongs to the Special Issue Application of Porous Nanomaterials in Energy Storage and Catalysis)

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16 pages, 3398 KiB

Open AccessArticle

Functionalized Biochars as Supports for Ru/C Catalysts: Tunable and Efficient Materials for γ-Valerolactone Production

by Charf Eddine Bounoukta, Cristina Megías-Sayago, Juan Carlos Navarro, Fatima Ammari, Svetlana Ivanova, Miguel Ángel Centeno and Jose Antonio Odriozola

Nanomaterials 2023, 13(6), 1129; https://doi.org/10.3390/nano13061129 - 22 Mar 2023

Cited by 3 | Viewed by 1549

Abstract

Cotton stalks-based biochars were prepared and used to synthetize Ru-supported catalysts for selective production of γ-valerolactone from levulinic acid in aqueous media. Different biochars’ pre-treatments (HNO₃, ZnCl₂, CO₂ or a combination of them) were carried out to activate [...] Read more.

Cotton stalks-based biochars were prepared and used to synthetize Ru-supported catalysts for selective production of γ-valerolactone from levulinic acid in aqueous media. Different biochars’ pre-treatments (HNO₃, ZnCl₂, CO₂ or a combination of them) were carried out to activate the final carbonaceous support. Nitric acid treatment resulted in microporous biochars with high surface area, whereas the chemical activation with ZnCl₂ substantially increases the mesoporous surface. The combination of both treatments led to a support with exceptional textural properties allowing the preparation of Ru/C catalyst with 1422 m²/g surface area, 1210 m²/g of it being a mesoporous surface. The impact of the biochars’ pre-treatments on the catalytic performance of Ru-based catalysts is fully discussed. Full article

(This article belongs to the Special Issue Application of Porous Nanomaterials in Energy Storage and Catalysis)

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14 pages, 4352 KiB

Open AccessArticle

A Comparison between Porous to Fully Dense Electrodeposited CuNi Films: Insights on Electrochemical Performance

by Xuejiao Wang, Jingyuan Bai, Meilin Zhang, Yuxi Chen, Longyi Fan, Zhou Yang, Jin Zhang and Renguo Guan

Nanomaterials 2023, 13(3), 491; https://doi.org/10.3390/nano13030491 - 25 Jan 2023

Cited by 2 | Viewed by 1549

Abstract

Nanostructuring of metals is nowadays considered as a promising strategy towards the development of materials with enhanced electrochemical performance. Porous and fully dense CuNi films were electrodeposited on a Cu plate by electrodeposition in view of their application as electrocatalytic materials for the [...] Read more.

Nanostructuring of metals is nowadays considered as a promising strategy towards the development of materials with enhanced electrochemical performance. Porous and fully dense CuNi films were electrodeposited on a Cu plate by electrodeposition in view of their application as electrocatalytic materials for the hydrogen evolution reaction (HER). Porous CuNi film were synthesized using the hydrogen bubble template electrodeposition method in an acidic electrolyte, while fully dense CuNi were electrodeposited from a citrate-sulphate bath with the addition of saccharine as a grain refiner. The prepared films were characterized chemically and morphologically by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The Rietveld analysis of the XRD data illustrates that both CuNi films have a nanosized crystallite size. Contact angle measurements reveal that the porous CuNi film exhibits remarkable superhydrophobic behavior, and fully dense CuNi film shows hydrophilicity. This is predominately ascribed to the surface roughness of the two films. The HER activity of the two prepared CuNi films were investigated in 1 M KOH solution at room temperature by polarization measurements and electrochemical impedance spectroscopy (EIS) technique. Porous CuNi exhibits an enhanced catalysis for HER with respect to fully dense CuNi. The HER kinetics for porous film is processed by the Volmer–Heyrovsky reaction, whereas the fully dense counterpart is Volmer-limited. This study presents a clear comparison of HER behavior between porous and fully dense CuNi films. Full article

(This article belongs to the Special Issue Application of Porous Nanomaterials in Energy Storage and Catalysis)

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