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Advances in Techniques for Characterization of Non-Stoichiometric Oxides and Their Applications in Catalysis

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A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Catalytic Materials".

Deadline for manuscript submissions: closed (30 April 2020) | Viewed by 15573

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Special Issue Editors

Dr. Marta Boaro

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Guest Editor

Università degli Studi di Udine, Polytechnic Department of Engineering and Architecture, Udine, Italy
Interests: catalysis and electrocatysis for energy and environmental applications, metal oxide catalysts, ceria-based materials, solid oxide fuel cell material, solar biofuels

Prof. Dr. Xiang Wang

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Guest Editor

Key Laboratory of Jiangxi Province for Environment and Energy Catalysis, College of Chemistry and Chemical Engineering, Nanchang University, Nanchang 330031, China
Interests: heterogeneous and industrial catalysis for air pollution control and clean energy transformation; rare earth metal oxide catalysis; structure and reactivity relationship of metal oxides; solid surface structural chemistry
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Antonella Glisenti

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Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy
Interests: catalysis and electrocatalysis for energy and environmental applications (SOFC/SOEC, TWC, and DeNOx); green hydrogen synthesis and storage; oxide-based catalysts; perovskites

Special Issue Information

Dear Colleagues,

Non-stoichiometric oxides such as ceria-based materials, perovskites of transition metals, or related perovskite structures are important classes of catalysts with applications in the field of energy services, electrochemical devices, and environment depollution. Their surface and bulk physico-chemical properties, the redox behavior, and, consequently, their catalytic activity are controlled by the nature and chemistry of their defects, which, in turn, depend on the treatment history of these oxides and their operating conditions.

Operando studies or in-house characterizations with advanced techniques of analysis and progress in the different types of spectroscopies and in transient measurement techniques have allowed a deeper understanding of the relationship between defect chemistry and activity of these materials, thus highlighting the key parameters that rule the mechanisms of catalytic reactions in which these materials are involved. This Special Issue aims at gathering research papers, mini reviews, and perspective articles that demonstrate the relevance of using advanced techniques of characterization and a multi-analytical approach for relating catalytic and electrocatalytic properties of these oxides to their structure and to specific arrangements of defects.

Prof. Marta Boaro
Prof. Xiang Wang
Prof. Antonella Glisenti
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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. Catalysts is an international peer-reviewed open access monthly 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 2700 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

Spectroscopic operando techniques;
defects chemistry characterization;
in situ analysis;
catalysis for energy and environment;
non-stoichiometric oxides;
perovskites and related structures;
ceria-based materials;
electrocatalysis;
DRIFT;
XPS;
Raman analyses;
transient methods for catalyst characterization;
mechanism of reactions.

Published Papers (4 papers)

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Research

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13 pages, 2791 KiB

Open AccessArticle

Electrochemical Response of Highly Porous Percolative CGO Electrospun Membranes

by Rafael Hubert Silva, Vincenzo Esposito, Apiwat Dankeaw, Carlos Pérez Bergmann and Debora Marani

Catalysts 2020, 10(7), 756; https://doi.org/10.3390/catal10070756 - 8 Jul 2020

Viewed by 1959

Abstract

Electrochemical Impedance Spectroscopy (EIS) is here used to characterize highly porous Ce_0.9Gd_0.1O_1.95 (CGO, ca. 90% vol. of porosity) free-supporting nano-fibrous thick (100μm) membranes, fabricated via an electrospinning technique. The investigation of the calcination temperature influence on the microstructure indicates an evolution of the single nanofiber’s microstructure with a gradual grain growth from densely packed polycrystalline to pearl collar-like structures at increasing temperatures. This evolution is accompanied by brittleness for samples treated at temperatures above 800 °C. The electrochemical characterization suggests an ionic percolative conductivity that exploits both the bulk-lattice conduction along the individual nanofibers and interfacial conduction across different nanofibers at their intersections. Optimized membranes treated at 600 and 700 °C exhibit a similar electrochemical bulk response, but different interfacial electrochemical behavior (low frequency) associated with a grain size effect. Full article

(This article belongs to the Special Issue Advances in Techniques for Characterization of Non-Stoichiometric Oxides and Their Applications in Catalysis)

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11 pages, 1944 KiB

Open AccessCommunication

Evoked Methane Photocatalytic Conversion to C2 Oxygenates over Ceria with Oxygen Vacancy

by Jin Du, Wei Chen, Gangfeng Wu, Yanfang Song, Xiao Dong, Guihua Li, Jianhui Fang, Wei Wei and Yuhan Sun

Catalysts 2020, 10(2), 196; https://doi.org/10.3390/catal10020196 - 6 Feb 2020

Cited by 25 | Viewed by 3714

Abstract

Direct conversion of methane to its oxygenate derivatives remains highly attractive while challenging owing to the intrinsic chemical inertness of CH₄. Photocatalysis arises as a promising green strategy which could stimulate water splitting to produce oxidative radicals for methane C–H activation and subsequent C–C coupling. However, synthesis of a photocatalyst with an appropriate capability of methane oxidation by water remains a challenge using an effective and viable approach. Herein, ceria nanoparticles with abundant oxygen vacancies prepared by calcinating commercial CeO₂ powder at high temperatures in argon are reported to capably produce ethanol and aldehyde from CH₄ photocatalytic oxidation under ambient conditions. Although high-temperature calcinations lead to lower light adsorptions and increased band gaps to some extent, deficient CeO₂ nanoparticles with oxygen vacancies and surface Ce^III species are formed, which are crucial for methane photocatalytic conversion. The ceria catalyst as-calcinated at 1100 °C had the highest oxygen vacancy concentration and Ce^III content, achieving an ethanol production rate of 11.4 µmol·g_cat⁻¹·h⁻¹ with a selectivity of 91.5%. Additional experimental results suggested that the product aldehyde was from the oxidation of ethanol during the photocatalytic conversion of CH₄. Full article

(This article belongs to the Special Issue Advances in Techniques for Characterization of Non-Stoichiometric Oxides and Their Applications in Catalysis)

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12 pages, 1791 KiB

Open AccessArticle

In Situ Investigations on the Facile Synthesis and Catalytic Performance of CeO₂-Pt/Al₂O₃ Catalyst

by Chengxiong Wang, Dezhi Ren, Junchen Du, Qinggao Qin, Aimin Zhang, Li Chen, Hao Cui, Jialin Chen and Yunkun Zhao

Catalysts 2020, 10(2), 143; https://doi.org/10.3390/catal10020143 - 21 Jan 2020

Cited by 7 | Viewed by 2464

Abstract

Ceria-modified Pt/Al₂O₃ catalyst has been commonly prepared by the impregnation of platinum on ceria-modified alumina and widely applied in the chemical industry and automotive industry. The in situ diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS), and thermogravimetric (TG) analysis techniques were employed to investigate the typical mechanisms of the bis(ethanolammonium)hexahydroxyplatinate(IV) and cerium nitrate decomposition catalyzed by Pt^δ+ species for the facile synthesis of CeO₂-Pt/Al₂O₃ catalyst. It was found that Pt⁴⁺-catalyzed decomposition of cerium nitrate leads to the higher dispersity of ceria and forming more active oxygen species, on the basis of X-ray diffraction (XRD) and H₂ temperature-programmed reduction (H₂-TPR) results. The in situ activity measurements were also performed to investigate the reaction mechanisms and the specific activities for the catalytic CO, NO, C₃H₆ and C₃H₈ co-oxidation. The results indicate that undesirable N₂O by-product is formed by the selective catalytic reduction (SCR) of NO by C₃H₆ below 350 °C. The cerium addition effectively improves the activity of catalytic oxidation, but exhibits an increased N₂O yield, due to the increased reducibility. Full article

(This article belongs to the Special Issue Advances in Techniques for Characterization of Non-Stoichiometric Oxides and Their Applications in Catalysis)

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Review

Jump to: Research

48 pages, 5337 KiB

Open AccessFeature PaperReview

Ceria-Based Catalysts Studied by Near Ambient Pressure X-ray Photoelectron Spectroscopy: A Review

by Xènia Garcia, Lluís Soler, Núria J. Divins, Xavier Vendrell, Isabel Serrano, Ilaria Lucentini, Jordi Prat, Eduardo Solano, Massimo Tallarida, Carlos Escudero and Jordi Llorca

Catalysts 2020, 10(3), 286; https://doi.org/10.3390/catal10030286 - 3 Mar 2020

Cited by 44 | Viewed by 6877

Abstract

The development of better catalysts is a passionate topic at the forefront of modern science, where operando techniques are necessary to identify the nature of the active sites. The surface of a solid catalyst is dynamic and dependent on the reaction environment and, therefore, the catalytic active sites may only be formed under specific reaction conditions and may not be stable either in air or under high vacuum conditions. The identification of the active sites and the understanding of their behaviour are essential information towards a rational catalyst design. One of the most powerful operando techniques for the study of active sites is near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), which is particularly sensitive to the surface and sub-surface of solids. Here we review the use of NAP-XPS for the study of ceria-based catalysts, widely used in a large number of industrial processes due to their excellent oxygen storage capacity and well-established redox properties. Full article

(This article belongs to the Special Issue Advances in Techniques for Characterization of Non-Stoichiometric Oxides and Their Applications in Catalysis)

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