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Nanomaterials
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Nanoparticles and Nanostructures for Sustainable Heterogeneous Catalysis and Electrocatalysis
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Nanoparticles and Nanostructures for Sustainable Heterogeneous Catalysis and Electrocatalysis

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Energy and Catalysis".

Deadline for manuscript submissions: closed (30 September 2021) | Viewed by 16728

Special Issue Editors

Prof. Dr. Simelys Hernández

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Guest Editor
Catalytic Reaction Engineering for Sustainable Technologies (CREST) group, Department of Applied Science and Technology (DISAT), Politecnico di Torino, 10129 Torino, Italy
Interests: photocatalysis; electrocatalysis; heterogeneous catalysis; adsorption; CO2 capture and conversion; nanomaterials; renewable energy storage; waste water treatment; artificial photosynthesis
Special Issues, Collections and Topics in MDPI journals
Dr. José Luis Cagide Fajín

E-Mail Website
Guest Editor
Laboratório Associado para a Química Verde (LAQV@REQUIMTE),Faculty of Sciences, University of Oporto, Rua do Campo Alegre, s/n, 4169-007 Oporto, Portugal
Interests: heterogeneous catalysis; nanostructured catalysts; adsorption; surface Science; Density Funtional Theory (DFT) calculations; quantum mechanics

Special Issue Information

Dear Colleagues,

The development of environmentally friendly, cost-effective, and sustainable technologies to improve current chemical processes and to sustain the long-term energy economy, based on a zero-carbon footprint, are among the most critical challenges that we are facing today. In recent years, nanostructured materials have attracted considerable interest owing to their enhanced active surface area, which promotes improved catalytic activity and tuneability of many chemical reactions. Moreover, nanoparticle-based heterogeneous catalysts have the advantage of reducing operative costs due to the facile separation of the catalyst from the products and the use of mild operative conditions. However, there are still challenges, such as stability, activity, and selectivity, which limit the actual application of nanocatalysts materials in emerging applications, like electrochemical and thermochemical CO2 conversion processes, degradations of emerging pollutants by photo/electrochemical and sonocatalytic technologies, among others.

This Special Issue of Nanomaterials will present state-of-the-art research on the various challenging issues that have to still be solved for the practical application of new nanoparticle and nanostructured materials in different fields, including heterogeneous catalytic process, electrocatalysis, photocatalysis, and sonocatalysis. High-quality short communications, research papers covering recent experimental and theoretical advances, as well as comprehensive reviews addressing novel and state-of-the-art outcomes in nanocatalysts and nanostructured electrode materials will be accepted. Special attention will be paid to novel synthesis procedures, electrodes preparation methods, advanced in-situ/operando characterization, and the practical application of novel nanocatalyst materials with outstanding performances.


Prof. Dr. Simelys Hernández
Dr. José Luis Cagide Fajín
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Nanomaterials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • nanoparticles
  • heterogeneous catalysis
  • electrocatalysis
  • photocatalysis
  • sonocatalysis
  • carbon capture and conversion
  • energy

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Published Papers (6 papers)

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Research

17 pages, 2918 KiB  
Article
N2O Hydrogenation on Silver Doped Gold Catalysts, a DFT Study
by José L. C. Fajín and Maria Natália D. S. Cordeiro
Nanomaterials 2022, 12(3), 394; https://doi.org/10.3390/nano12030394 - 25 Jan 2022
Cited by 2 | Viewed by 2243
Abstract
In this study, the full reaction mechanism for N2O hydrogenation on silver doped Au(210) surfaces was investigated in order to clarify the experimental observations. Density functional theory (DFT) calculations were used to state the most favorable reaction paths for individual steps [...] Read more.
In this study, the full reaction mechanism for N2O hydrogenation on silver doped Au(210) surfaces was investigated in order to clarify the experimental observations. Density functional theory (DFT) calculations were used to state the most favorable reaction paths for individual steps involved in the N2O hydrogenation. From the DFT results, the activation energy barriers, rate constants and reaction energies for the individual steps were determined, which made it possible to elucidate the most favorable reaction mechanism for the global catalytic process. It was found that the N2O dissociation occurs in surface regions where silver atoms are present, while hydrogen dissociation occurs in pure gold regions of the catalyst or in regions with a low silver content. Likewise, N2O dissociation is the rate determining step of the global process, while water formation from O adatoms double hydrogenation and N2 and H2O desorptions are reaction steps limited by low activation energy barriers, and therefore, the latter are easily carried out. Moreover, water formation occurs in the edges between the regions where hydrogen and N2O are dissociated. Interestingly, a good dispersion of the silver atoms in the surface is necessary to avoid catalyst poison by O adatoms accumulation, which are strongly adsorbed on the surface. Full article
(This article belongs to the Special Issue Nanoparticles and Nanostructures for Sustainable Heterogeneous Catalysis and Electrocatalysis)
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27 pages, 6287 KiB  
Article
CuZnAl-Oxide Nanopyramidal Mesoporous Materials for the Electrocatalytic CO2 Reduction to Syngas: Tuning of H2/CO Ratio
by Hilmar Guzmán, Daniela Roldán, Adriano Sacco, Micaela Castellino, Marco Fontana, Nunzio Russo and Simelys Hernández
Nanomaterials 2021, 11(11), 3052; https://doi.org/10.3390/nano11113052 - 13 Nov 2021
Cited by 16 | Viewed by 3231
Abstract
Inspired by the knowledge of the thermocatalytic CO2 reduction process, novel nanocrystalline CuZnAl-oxide based catalysts with pyramidal mesoporous structures are here proposed for the CO2 electrochemical reduction under ambient conditions. The XPS analyses revealed that the co-presence of ZnO and Al [...] Read more.
Inspired by the knowledge of the thermocatalytic CO2 reduction process, novel nanocrystalline CuZnAl-oxide based catalysts with pyramidal mesoporous structures are here proposed for the CO2 electrochemical reduction under ambient conditions. The XPS analyses revealed that the co-presence of ZnO and Al2O3 into the Cu-based catalyst stabilize the CuO crystalline structure and introduce basic sites on the ternary as-synthesized catalyst. In contrast, the as-prepared CuZn- and Cu-based materials contain a higher amount of superficial Cu0 and Cu1+ species. The CuZnAl-catalyst exhibited enhanced catalytic performance for the CO and H2 production, reaching a Faradaic efficiency (FE) towards syngas of almost 95% at −0.89 V vs. RHE and a remarkable current density of up to 90 mA cm−2 for the CO2 reduction at −2.4 V vs. RHE. The physico-chemical characterizations confirmed that the pyramidal mesoporous structure of this material, which is constituted by a high pore volume and small CuO crystals, plays a fundamental role in its low diffusional mass-transfer resistance. The CO-productivity on the CuZnAl-catalyst increased at more negative applied potentials, leading to the production of syngas with a tunable H2/CO ratio (from 2 to 7), depending on the applied potential. These results pave the way to substitute state-of-the-art noble metals (e.g., Ag, Au) with this abundant and cost-effective catalyst to produce syngas. Moreover, the post-reaction analyses demonstrated the stabilization of Cu2O species, avoiding its complete reduction to Cu0 under the CO2 electroreduction conditions. Full article
(This article belongs to the Special Issue Nanoparticles and Nanostructures for Sustainable Heterogeneous Catalysis and Electrocatalysis)
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16 pages, 4279 KiB  
Article
Dielectric Properties and Spectral Characteristics of Photocatalytic Constant of TiO2 Nanoparticles Doped with Cobalt
by Valentin G. Bessergenev, José F. Mariano, Maria Conceição Mateus, João P. Lourenço, Adwaa Ahmed, Martin Hantusch, Eberhard Burkel and Ana Maria Botelho do Rego
Nanomaterials 2021, 11(10), 2519; https://doi.org/10.3390/nano11102519 - 27 Sep 2021
Cited by 1 | Viewed by 1926
Abstract
Dielectric properties and spectral dependence of the photocatalytic constant of Co doped P25 Degussa powder were studied. Doping of TiO2 matrix with cobalt was achieved by precipitation method using of Tris(diethylditiocarbamate)Co(III) precursor (CoDtc–Co[(C2H5)2NCS2]3 [...] Read more.
Dielectric properties and spectral dependence of the photocatalytic constant of Co doped P25 Degussa powder were studied. Doping of TiO2 matrix with cobalt was achieved by precipitation method using of Tris(diethylditiocarbamate)Co(III) precursor (CoDtc–Co[(C2H5)2NCS2]3). Five different Co contents with nominal Co/Ti atomic ratios of 0.005, 0.01, 0.02, 0.05 and 0.10 were chosen. Along with TiO2:Co samples, a few samples of nanopowders prepared by Sol-Gel method were also studied. As it follows from XPS and NMR studies, there is a concentration limit (TiO2:0.1Co) where cobalt atoms can be uniformly distributed across the TiO2 matrix before metallic clusters start to form. It was also shown that CoTiO3 phases are formed during annealing at high temperatures. From the temperature dependence of the dielectric constant it can be concluded that the relaxation processes still take place even at temperatures below 400 °C and that oxygen defect Ti–O octahedron reorientation take place at higher temperatures. The spectral dependency of the photocatalytic constant reveals the presence of some electronic states inside the energy gap of TiO2 for all nanopowdered samples. Full article
(This article belongs to the Special Issue Nanoparticles and Nanostructures for Sustainable Heterogeneous Catalysis and Electrocatalysis)
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16 pages, 4554 KiB  
Article
Optimization of α-Fe2O3 Nanopillars Diameters for Photoelectrochemical Enhancement of α-Fe2O3-TiO2 Heterojunction
by Herme G. Baldovi
Nanomaterials 2021, 11(8), 2019; https://doi.org/10.3390/nano11082019 - 7 Aug 2021
Cited by 10 | Viewed by 2684
Abstract
Global warming is pushing the world to seek to green energy sources and hydrogen is a good candidate to substitute fossil fuels in the short term. In future, it is expected that production of hydrogen will be carried out through photo-electrocatalysis. In this [...] Read more.
Global warming is pushing the world to seek to green energy sources and hydrogen is a good candidate to substitute fossil fuels in the short term. In future, it is expected that production of hydrogen will be carried out through photo-electrocatalysis. In this way, suitable electrodes that acts as photoanode absorbing the incident light are needed to catalyse water splitting reaction. Hematite (α-Fe2O3) is one of the most attractive semiconductors for this purpose since it is a low-cost material and it has a suitable band gap of 2.1 eV, which allows the absorption of the visible region. Although, hematite has drawbacks such as low carrier mobility and short holes diffusion lengths, that here it has been tried to overcome by nanoengineering the material, and by using a semiconductor as a scaffold that enhances charge carrier separation processes in the electrode. In this work, we fabricate ultrathin quasi transparent electrodes composed by highly ordered and self-standing hematite nanopillars of a few tens of nanometers length on FTO and TiO2 supports. Photoanodes were fabricated utilizing electron beam evaporation technique and anodized aluminum oxide templates with well-defined pores diameters. Thus, the activity of the compact layer hematite photoanode is compared with the photoanodes fabricated with nanopillars of controllable diameters (i.e., 90, 260 and 400 nm) to study their influence on charge separation processes. Results indicated that optimal α-Fe2O3 photoanodes performance are obtained when nanopillars reach hundreds of nanometers in diameter, achieving for photoanodes with 400 nm nanopillars onto TiO2 supports the highest photocurrent density values. Full article
(This article belongs to the Special Issue Nanoparticles and Nanostructures for Sustainable Heterogeneous Catalysis and Electrocatalysis)
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14 pages, 5623 KiB  
Article
Bifunctional Ag-Decorated CeO2 Nanorods Catalysts for Promoted Photodegradation of Methyl Orange and Photocatalytic Hydrogen Evolution
by Jinwen Liu, Li Zhang, Yifei Sun and Yang Luo
Nanomaterials 2021, 11(5), 1104; https://doi.org/10.3390/nano11051104 - 24 Apr 2021
Cited by 24 | Viewed by 2950
Abstract
The photodegradation of organic pollutants and photocatalytic hydrogen generation from water by semiconductor catalysts are regarded as the of the most promising strategies to resolve the crisis of global environmental issues. Herein, we successfully designed and prepared a series of silver-decorated CeO2 [...] Read more.
The photodegradation of organic pollutants and photocatalytic hydrogen generation from water by semiconductor catalysts are regarded as the of the most promising strategies to resolve the crisis of global environmental issues. Herein, we successfully designed and prepared a series of silver-decorated CeO2(Ag/CeO2) photocatalysts with different morphologies by a facile hydrothermal route. The physical properties, charge transfer behavior and photocatalytic performances (degradation and hydrogen evolution) over diverse catalysts with nanocubes, nanoparticles and nanorods shapes were comprehensively studied. It was found that the Ag-decorated CeO2 nanorods (Ag/R-CeO2) demonstrate the best activity for both photocatalytic methyl orange (MO) degradation and photocatalytic H2 production reaction with attractive stability during cycling tests, suggesting its desirable practical potential. The superior performance of Ag/R-CeO2 can be ascribed to (1) the facilitated light absorption due to enriched surface oxygen vacancies (OVs) and plasmonic Ag nanoparticles on nanorods, (2) the facilitated photo-excited charge carrier (e−-h+) separation efficiency on a metal/oxide hybrid structure and (3) the promoted formation of active reaction intermediates on surface-enriched Ag and oxygen vacancies reactive sites on Ag/CeO2 nanorods. This study provides a valuable discovery of the utilization of abundant solar energy for diverse catalytic processes. Full article
(This article belongs to the Special Issue Nanoparticles and Nanostructures for Sustainable Heterogeneous Catalysis and Electrocatalysis)
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18 pages, 5130 KiB  
Article
Effects of Crystallite Sizes of Pt/HZSM-5 Zeolite Catalysts on the Hydrodeoxygenation of Guaiacol
by Haonan Duan, Yajie Tian, Siyuan Gong, Bofeng Zhang, Zongjing Lu, Yinqiang Xia, Yawei Shi and Congzhen Qiao
Nanomaterials 2020, 10(11), 2246; https://doi.org/10.3390/nano10112246 - 12 Nov 2020
Cited by 17 | Viewed by 2666
Abstract
Herein, Pt/HZSM-5 zeolite catalysts with different crystallite sizes ranging from nanosheet (~2 nm) to bulk crystals (~1.5 μm) have been prepared for the hydrodeoxygenation of guaiacol, and their effects on the reaction pathway and product selectivity were explored. HZSM-5 zeolites prepared by seeding [...] Read more.
Herein, Pt/HZSM-5 zeolite catalysts with different crystallite sizes ranging from nanosheet (~2 nm) to bulk crystals (~1.5 μm) have been prepared for the hydrodeoxygenation of guaiacol, and their effects on the reaction pathway and product selectivity were explored. HZSM-5 zeolites prepared by seeding (Pt/Z-40: ~40 nm) or templating (Pt/NS-2: ~2 nm) fabricated intra-crystalline mesopores and thus enhanced the reaction rate by promoting the diffusion of various molecules, especially the bulky ones such as guaiacol and 2-methoxycyclohexanol, leading to a higher cyclohexane selectivity of up to 80 wt % (both for Pt/Z-40 and Pt/NS-2) compared to 70 wt % for bulky HZSM-5 (Pt/CZ: ~1.5 μm) at 250 °C and 120 min. Furthermore, decreased crystallite sizes more effectively promoted the dispersion of Pt particles than bulky HZSM-5 (Pt/Z-400: ~400 nm and Pt/CZ). The relatively low distance between Pt and acidic sites on the Pt/Z-40 catalyst enhanced the metal/support interaction and induced the reaction between the guaiacol molecules adsorbed on the acidic sites and the metal-activated hydrogen species, which was found more favorable for deoxygenation than for hydrogenation of oxygen-containing molecules. In addition, Pt/NS-2 catalyst with a highly exposed surface facilitated more diverse reaction pathways such as alkyl transfer and isomerization. Full article
(This article belongs to the Special Issue Nanoparticles and Nanostructures for Sustainable Heterogeneous Catalysis and Electrocatalysis)
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