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Steiner C, Malashchuk V, Kubinski D, Hagen G, Moos R. Microwave-Based State Diagnosis of Three-Way Catalysts: Impact Factors and Application Recommendations. SENSORS (BASEL, SWITZERLAND) 2024; 24:4091. [PMID: 39000871 PMCID: PMC11243869 DOI: 10.3390/s24134091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 06/13/2024] [Accepted: 06/18/2024] [Indexed: 07/16/2024]
Abstract
This study reassesses an overview of the potential of the radio frequency (RF)-based state diagnostics of three-way catalysts (TWC) based on a previous study with an emphasis on the defect chemistry of the catalyst material during reoxidation and reduction. Some data are based on the previous works but are newly processed, and the signal parameters resonant frequency and inverse quality factor are evaluated with respect to applicability. The RF-based method uses electromagnetic resonances in a cavity resonator to provide information on the storage level of the oxygen storage component. The analysis focuses on a holistic investigation and evaluation of the major effects influencing the RF signal during operation. On the one hand, the response to the oxygen storage behavior and the resolution of the measurement method are considered. Therefore, this study merges original data from multiple former publications to provide a comprehensive insight into important measurement effects and their defect chemistry background. On the other hand, the most important cross-sensitivities are discussed and their impact during operation is evaluated. Additionally, the effect of catalyst aging is analyzed. The effects are presented separately for the two resonant parameters: resonant frequency and (unloaded) quality factor. Overall, the data suggest that the quality factor has a way higher signal quality at low temperatures (<400 °C) and the resonant frequency is primarily suitable for high operating temperatures. At most operating points, the quality factor is even more robust against interferences such as exhaust gas stoichiometry and water content. Correctly estimating the catalyst temperature is the most important factor for reliable results, which can be achieved by combining the information of both resonant signals. In the end, the data indicate that microwave-based state diagnosis is a powerful system for evaluating the oxygen storage level over the entire operating range of a TWC. As a research tool and in its application, the system can therefore contribute to the improvement of the emission control of future gasoline vehicles.
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Affiliation(s)
- Carsten Steiner
- Bayreuth Engine Research Center (BERC), Department of Functional Materials, University of Bayreuth, 95447 Bayreuth, Germany
| | - Vladimir Malashchuk
- Bayreuth Engine Research Center (BERC), Department of Functional Materials, University of Bayreuth, 95447 Bayreuth, Germany
| | | | - Gunter Hagen
- Bayreuth Engine Research Center (BERC), Department of Functional Materials, University of Bayreuth, 95447 Bayreuth, Germany
| | - Ralf Moos
- Bayreuth Engine Research Center (BERC), Department of Functional Materials, University of Bayreuth, 95447 Bayreuth, Germany
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Sala EM, Mazzanti N, Chiabrera FM, Sanna S, Mogensen MB, Hendriksen PV, Ma Z, Simonsen SB, Chatzichristodoulou C. Unravelling the role of dopants in the electrocatalytic activity of ceria towards CO 2 reduction in solid oxide electrolysis cells. Phys Chem Chem Phys 2023; 25:3457-3471. [PMID: 36637049 DOI: 10.1039/d2cp05157e] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
CO2 reduction in Solid Oxide Electrolysis Cells (SOECs) is a key-technology for the transition to a sustainable energy infrastructure and chemical industry. Ceria (CeO2) holds great promise in developing highly efficient, cost-effective and durable fuel electrodes, due to its promising electrocatalytic properties, and proven ability to suppress carbon deposition and to tolerate high concentrations of impurities. In the present work, we investigate the intrinsic electrocatalytic activity of ceria towards CO2 reduction by means of electrochemical impedance spectroscopy (EIS) on model systems with well-defined geometry, composition and surface area. Aiming at the optimization of the intrinsic catalytic properties of the material, we systematically study the effect of different dopants (Zr, Gd, Pr and Bi) on the reaction rate under varying operating conditions (temperature, gas composition and applied polarization) relevant for SOECs. The electrochemical measurements reveal the dominant role of the surface defect chemistry of the material in the reaction rate, with doping having only a mild effect on the rate and activation energy of the reaction. By analyzing the pO2 and overpotential dependence of the reaction rate with a general micro-kinetic model, we are able to identify the second electron transfer as the rate limiting step of the process, highlighting the dominant role of surface polarons in the energy landscape. These insights on the correlation between the surface defects and the electrocatalytic activity of ceria open new directions for the development of highly performing ceria-based technological electrodes.
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Affiliation(s)
- Elena Marzia Sala
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, DK-2800, Kgs., Lyngby, Denmark.
| | - Nicola Mazzanti
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, DK-2800, Kgs., Lyngby, Denmark.
| | - Francesco M Chiabrera
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, DK-2800, Kgs., Lyngby, Denmark.
| | - Simone Sanna
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, DK-2800, Kgs., Lyngby, Denmark.
| | - Mogens B Mogensen
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, DK-2800, Kgs., Lyngby, Denmark.
| | - Peter V Hendriksen
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, DK-2800, Kgs., Lyngby, Denmark.
| | - Zhongtao Ma
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, DK-2800, Kgs., Lyngby, Denmark.
| | - Søren B Simonsen
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, DK-2800, Kgs., Lyngby, Denmark.
| | - Christodoulos Chatzichristodoulou
- Department of Energy Conversion and Storage, Technical University of Denmark, Fysikvej, Building 310, DK-2800, Kgs., Lyngby, Denmark.
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Zirconia-Based Nanomaterials for Alternative Energy Application: Concept of Research in Smart Laboratory. ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2022. [DOI: 10.1007/s13369-022-06976-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Steiner C, Hagen G, Kogut I, Fritze H, Moos R. Analysis of defect chemistry and microstructural effects of non-stoichiometric ceria by the high-temperature microwave cavity perturbation method. Ann Ital Chir 2022. [DOI: 10.1016/j.jeurceramsoc.2021.08.053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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Wulfmeier H, Kohlmann D, Defferriere T, Steiner C, Moos R, Tuller HL, Fritze H. Thin-film chemical expansion of ceria based solid solutions: laser vibrometry study. Z PHYS CHEM 2021. [DOI: 10.1515/zpch-2021-3125] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
The chemical expansion of Pr0.1Ce0.9O2–δ
(PCO) and CeO2–δ
thin films is investigated in the temperature range between 600 °C and 800 °C by laser Doppler vibrometry (LDV). It enables non-contact determination of nanometer scale changes in film thickness at high temperatures. The present study is the first systematic and detailed investigation of chemical expansion of doped and undoped ceria thin films at temperatures above 650 °C. The thin films were deposited on yttria stabilized zirconia substrates (YSZ), operated as an electrochemical oxygen pump, to periodically adjust the oxygen activity in the films, leading to reversible expansion and contraction of the film. This further leads to stresses in the underlying YSZ substrates, accompanied by bending of the overall devices. Film thickness changes and sample bending are found to reach up to 10 and several hundred nanometers, respectively, at excitation frequencies from 0.1 to 10 Hz and applied voltages from 0–0.75 V for PCO and 0–1 V for ceria. At low frequencies, equilibrium conditions are approached. As a consequence maximum thin-film expansion of PCO is expected due to full reduction of the Pr ions. The lower detection limit for displacements is found to be in the subnanometer range. At 800 °C and an excitation frequency of 1 Hz, the LDV shows a remarkable resolution of 0.3 nm which allows, for example, the characterization of materials with small levels of expansion, such as undoped ceria at high oxygen partial pressure. As the correlation between film expansion and sample bending is obtained through this study, a dimensional change of a free body consisting of the same material can be calculated using the high resolution characteristics of this system. A minimum detectable dimensional change of 5 pm is estimated even under challenging high-temperature conditions at 800 °C opening up opportunities to investigate electro-chemo-mechanical phenomena heretofore impossible to investigate. The expansion data are correlated with previous results on the oxygen nonstoichiometry of PCO thin films, and a defect model for bulk ceria solid solutions is adopted to calculate the cation and anion radii changes in the constrained films during chemical expansion. The constrained films exhibit anisotropic volume expansion with displacements perpendicular to the substrate plane nearly double that of bulk samples. The PCO films used here generate high total displacements of several 100 nm’s with high reproducibility. Consequently, PCO films are identified to be a potential core component of high-temperature actuators. They benefit not only from high displacements at temperatures where most piezoelectric materials no longer operate while exhibiting, low voltage operation and low energy consumption.
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Affiliation(s)
- Hendrik Wulfmeier
- Clausthal University of Technology, Institute of Energy Research and Physical Technologies , 38640 Goslar , Germany
| | - Dhyan Kohlmann
- Clausthal University of Technology, Institute of Energy Research and Physical Technologies , 38640 Goslar , Germany
| | - Thomas Defferriere
- Massachusetts Institute of Technology , Department of Materials Science and Engineering , Cambridge , MA , 02139 , USA
| | - Carsten Steiner
- University of Bayreuth , Department of Functional Materials , 95440 Bayreuth , Germany
| | - Ralf Moos
- University of Bayreuth , Department of Functional Materials , 95440 Bayreuth , Germany
| | - Harry L. Tuller
- Massachusetts Institute of Technology , Department of Materials Science and Engineering , Cambridge , MA , 02139 , USA
| | - Holger Fritze
- Clausthal University of Technology, Institute of Energy Research and Physical Technologies , 38640 Goslar , Germany
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