Special Issue "In Situ and Operando Vibrational Spectroscopy in Catalysis"

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

Deadline for manuscript submissions: closed (30 November 2020).

Special Issue Editors

Dr. Davide Ferri
E-Mail Website
Guest Editor
Catalysis for Energy, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
Interests: heterogeneous catalysis; environmental catalysis; operando spectroscopy; IR spectroscopy; perovskite-type oxides; functional materials
Special Issues and Collections in MDPI journals
Dr. Matteo Signorile
E-Mail Website
Guest Editor
Dipartimento di Chimica, NIS e INSTM, Università di Torino, Via P. Giuria 7, IT-10125, Torino, Italy
Interests: in situ/operando spectroscopy; vibrational spectroscopy; resonance Raman spectroscopy; zeolite-based catalysts; DFT molecular modelling; heterogeneous catalysis

Special Issue Information

Dear Colleagues,

Adsorption processes and heterogeneously catalyzed reactions take place at the surface of materials. Because of the low radiation energy involved, vibrational spectroscopies remain indispensable techniques providing unique information on key surface properties, including the molecular structure of active sites and the nature of acid and basic sites. This Special Issue on “In situ and operando vibrational spectroscopy” will provide updates on the recent advances in our understanding of catalytic and adsorption processes, taking place at the gas–solid and liquid-phase interfaces, using vibrational spectroscopy. Topics related to in situ characterization, operando characterization, elucidation of reaction mechanisms, adsorption, time-resolved experiments, modulation-type experiments, and isotope exchange will be of interest. Contributions to this Special Issue are expected to include structural analysis and properties assessment of active sites in catalysts and sorbents. Characterization of surface species during reaction would be just ideal. Submissions to this Special Issue are welcome in the form of original research papers or short reviews reflecting knowledge in the field of characterization of materials within the following thematic subjects: catalytic processes; adsorption for capture/storage/separation applications; processes on minerals and soils; electrocatalysis; and structure by in situ/operando spectroscopy.

Dr. Davide Ferri
Dr. Matteo Signorile
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 papers will be 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 2000 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

  • vibrational spectroscopy
  • in situ
  • operando
  • heterogeneous catalysis
  • materials
  • reaction mechanism
  • active site
  • surface properties
  • structure–activity relation

Published Papers (4 papers)

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Research

Open AccessFeature PaperArticle
Changes of Pd Oxidation State in Pd/Al2O3 Catalysts Using Modulated Excitation DRIFTS
Catalysts 2021, 11(1), 116; https://doi.org/10.3390/catal11010116 - 14 Jan 2021
Viewed by 414
Abstract
Infrared spectroscopy is typically not used to establish the oxidation state of metal-based catalysts. In this work, we show that the baseline of spectra collected in diffuse reflectance mode of a series of Pd/Al2O3 samples of increasing Pd content varies [...] Read more.
Infrared spectroscopy is typically not used to establish the oxidation state of metal-based catalysts. In this work, we show that the baseline of spectra collected in diffuse reflectance mode of a series of Pd/Al2O3 samples of increasing Pd content varies significantly and reversibly under alternate pulses of CO or H2 and O2. Moreover, these baseline changes are proportional to the Pd content in Pd/Al2O3 samples exhibiting comparable Pd particle size. Similar measurements by X-ray absorption spectroscopy on a different 2 wt.% Pd/Al2O3 confirm that the baseline changes reflect the reversible reduction-oxidation of Pd. Hence, we demonstrate that changes in oxidation state of metal-based catalysts can be determined using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and that this behavior is part of the spectral changes that are returned by experiments under operando conditions. Full article
(This article belongs to the Special Issue In Situ and Operando Vibrational Spectroscopy in Catalysis)
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Open AccessArticle
CO2 Methanation over Rh/CeO2 Studied with Infrared Modulation Excitation Spectroscopy and Phase Sensitive Detection
Catalysts 2020, 10(6), 601; https://doi.org/10.3390/catal10060601 - 29 May 2020
Cited by 1 | Viewed by 658
Abstract
Methane is a well-established fuel molecule whose production from CO2 through methanation garners increasing interest as an energy storage solution. While often produced with Ni based catalysts, other metals are of interest thanks to higher robustness and activity-selectivity numbers. The Rh/CeO2 [...] Read more.
Methane is a well-established fuel molecule whose production from CO 2 through methanation garners increasing interest as an energy storage solution. While often produced with Ni based catalysts, other metals are of interest thanks to higher robustness and activity-selectivity numbers. The Rh/CeO 2 catalyst has shown appreciable properties for CO 2 methanation and its structural dynamics has been studied in situ. However, the reaction pathway is unknown. Here, we present infrared modulation excitation spectroscopy measurements with phase sensitive detection of a Rh/CeO 2 catalyst adsorbate composition during H 2 pulsing (0–2 vol.%) to a constant CO 2 (0.5 vol.%) feed. Various carbonyl (CO) and carbonate (b-CO 3 /p-CO 3 ) ad-species clearly respond to the hydrogen stimulus, making them potential reaction intermediates. The different CO ad-species are likely intermediates for product CO and CH 4 but their individual contributions to the respective formations are not unambiguously ascertained. As for the carbonate dynamics, it might be linked to the reduction/oxidation of the CeO 2 surface upon H 2 pulsing. Formate (HCOO) ad-species are clearly visible but appear to be, if not spectators, linked to slow side reactions possibly also affected by CeO 2 redox processes. Full article
(This article belongs to the Special Issue In Situ and Operando Vibrational Spectroscopy in Catalysis)
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Open AccessFeature PaperArticle
The Effect of CO Partial Pressure on Important Kinetic Parameters of Methanation Reaction on Co-Based FTS Catalyst Studied by SSITKA-MS and Operando DRIFTS-MS Techniques
Catalysts 2020, 10(5), 583; https://doi.org/10.3390/catal10050583 - 22 May 2020
Viewed by 798
Abstract
A 20 wt% Co-0.05 wt% Pt/γ-Al2O3 catalyst was investigated to obtain a fundamental understanding of the effect of CO partial pressure (constant H2 partial pressure) on important kinetic parameters of the methanation reaction (x vol% CO/25 vol% H2 [...] Read more.
A 20 wt% Co-0.05 wt% Pt/γ-Al2O3 catalyst was investigated to obtain a fundamental understanding of the effect of CO partial pressure (constant H2 partial pressure) on important kinetic parameters of the methanation reaction (x vol% CO/25 vol% H2, x = 3, 5 and 7) by performing advanced transient isotopic and operando diffuse reflectance infrared Fourier transform spectroscopy–mass spectrometry (DRIFTS-MS) experiments. Steady State Isotopic Transient Kinetic Analysis (SSITKA) experiments conducted at 1.2 bar, 230 °C after 5 h in CO/H2 revealed that the surface coverages, θCO and θCHx and the mean residence times, τCO, and τCHx (s) of the reversibly adsorbed CO-s and active CHx-s (Cα) intermediates leading to CH4, respectively, increased with increasing CO partial pressure. On the contrary, the apparent activity (keff, s−1) of CHx-s intermediates, turnover frequency (TOF, s−1) of methanation reaction, and the CH4-selectivity (SCH4, %) were found to decrease. Transient isothermal hydrogenation (TIH) following the SSITKA step-gas switch provided important information regarding the reactivity and concentration of active (Cα) and inactive -CxHy (Cβ) carbonaceous species formed after 5 h in the CO/H2 reaction. The latter Cβ species were readily hydrogenated at 230 °C in 50%H2/Ar. The surface coverage of Cβ was found to vary only slightly with increasing CO partial pressure. Temperature-programmed hydrogenation (TPH) following SSITKA and TIH revealed that other types of inactive carbonaceous species (Cγ) were formed during Fischer-Tropsch Synthesis (FTS) and hydrogenated at elevated temperatures (250–550 °C). The amount of Cγ was found to significantly increase with increasing CO partial pressure. All carbonaceous species hydrogenated during TIH and TPH revealed large differences in their kinetics of hydrogenation with respect to the CO partial pressure in the CO/H2 reaction mixture. Operando DRIFTS-MS transient isothermal hydrogenation of adsorbed CO-s formed after 2 h in 5 vol% CO/25 vol% H2/Ar at 200 °C coupled with kinetic modeling (H-assisted CO hydrogenation) provided information regarding the relative reactivity (keff) for CH4 formation of the two kinds of linear-type adsorbed CO-s on the cobalt surface. Full article
(This article belongs to the Special Issue In Situ and Operando Vibrational Spectroscopy in Catalysis)
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Open AccessArticle
Volatile Hydrogen Intermediates of CO2 Methanation by Inelastic Neutron Scattering
Catalysts 2020, 10(4), 433; https://doi.org/10.3390/catal10040433 - 16 Apr 2020
Cited by 1 | Viewed by 921
Abstract
Despite vast research efforts, the detection of volatile intermediates of catalytic reactions remains a challenge: in addition to the compatibility of the technique to the harsh reaction conditions, a molecular understanding is hampered by the difficulty of extracting meaningful information from operando techniques [...] Read more.
Despite vast research efforts, the detection of volatile intermediates of catalytic reactions remains a challenge: in addition to the compatibility of the technique to the harsh reaction conditions, a molecular understanding is hampered by the difficulty of extracting meaningful information from operando techniques applied on complex materials. Diffusive reflectance infrared Fourier transform spectroscopy (DRIFTS) is a powerful method, but it is restricted by optical selection rules particularly affecting the detection of hydrogen. This gap can be filled by inelastic neutron scattering (INS). However, INS cannot be used on hydrogenated systems at temperatures higher than 20 K. We demonstrate how its use as a post-mortem method gives insights into the crucial intermediates during CO2 methanation on Ni/alumina-silica catalysts. We detect a variety of H–, O–, and C-based intermediates. A striking outcome is that hydrogen and oxygen are concurrently chemisorbed on the catalysts, a result that needs the combined effort of DRIFTS and INS. Full article
(This article belongs to the Special Issue In Situ and Operando Vibrational Spectroscopy in Catalysis)
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