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22. Electronic engineering and oxygen vacancy modification of La0.6Sr0.4FeO3−δ perovskite oxide by low-electronegativity sodium substitution for efficient CO2/CO fueled reversible solid oxide cells.

Author

Lin, Wanbin, Li, Yihang, Singh, Manish, Zhao, Huibin, Yang, Rui, Su, Pei-Chen, and Fan, Liangdong

Subjects
SOLID oxide fuel cells, FUEL cell electrodes, STRONTIUM, PEROVSKITE, OXIDATION-reduction reaction, SODIUM ions, OXYGEN
Abstract

Reversible solid oxide cells (RSOCs) hold enormous potential for efficient direct CO2 reduction or CO oxidation in terms of exceptional faradic efficiency and high reaction kinetics. The identification of an active fuel electrode is highly desirable for enhancing the performance of RSOCs. This study explores the use of a alkaline metal dopant (Na) to modify the perovskite oxide of Na2x(La0.6−xSr0.4−x)FeO3−δ (2x = 0, 0.10, 0.20) materials with powerful CO2 chemical adsorption capacity, high oxygen ion conductivity, and low average valence of Fe sites for CO2/CO redox reactions. The experimental results indicate that the cells with the NaLSF0.10 fuel electrode achieve a current density of 1.707 A cm−2 at 1.5 V/800 °C and excellent stability over 120 hours at 750 °C for pure CO2 electrolysis, approximately 33.4% improvement over the pristine sample. When operated under a mixed CO–CO2 atmosphere under RSOC mode, the cell outputs the performance of 1.589 A cm−2 at 1.5 V and 329 mW cm−2 at 800 °C, and demonstrates relatively durable operation over 25 cycles. The addition of low valence sodium ions with high basicity and low electronegativity reduces the oxygen vacancy formation energy, increases the concentration of oxygen vacancies and modifies the electronic structure of LSF, thus enhancing CO2 adsorption, dissociation processes and charge transfer steps as corroborated by the detailed experimental analysis. Combined with the acceptable anti-carbon deposition capability, we prove here a feasible strategy and provide new insights into designing novel electrodes for SOEC/RSOCs to effectively convert CO2 with potential for renewable energy storage. [ABSTRACT FROM AUTHOR]

Published
2024
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33. Processing Challenges and Delamination Prevention Methods in Titanium-Steel DED 3D Printing

Author

Andreu, Alberto, Kim, Sanglae, Kim, Insup, Kim, Jeong-Hwan, Noh, Jinhong, Lee, Suhan, Lee, Wonhee, Su, Pei-Chen, and Yoon, Yong-Jin

Abstract

Direct Energy Deposition (DED) 3D printing has gained significant importance in various industries due to its ability to fabricate complex and functional parts with reduced material waste, and to repair existing components. Titanium alloys, known for their exceptional mechanical properties and biocompatibility, are widely used in DED 3D printing applications, where they offer benefits such as lightweight design possibilities and high strength-to-weight ratio. However, given the high material cost of titanium alloys, certain applications can benefit from the coating capabilities of DED to achieve the advantages of titanium on a distinct material substrate. Nevertheless, challenges related to material incompatibility and the development of unwanted brittle phases still affect the successful deposition of titanium alloys on steel substrates with DED 3D printing. This paper investigates the processing challenges and reviews delamination prevention methods, specifically targeting titanium-steel interfaces. In particular, the formation of unwanted brittle Ti–Fe intermetallics and methods to circumvent their formation are explored. The findings of this research contribute to a deeper understanding of the processing challenges and delamination prevention methods in DED 3D printing.

Published
2024
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43. Applied current on the suppression of strontium segregation in Sr₂Fe₁.₅Mo₀.₅O₆₋δ electrode for improved oxygen evolution reaction

Author

Li, Hao-Yang, Su, Pei-Chen, and School of Mechanical and Aerospace Engineering

Subjects
Mechanical engineering [Engineering], Perovskite Electrode, Strontium Segregation
Abstract

Strontium surface segregation is the main issue that causes long-term performance degradation in strontium-containing electrodes for solid oxide electrolysis cells. In this research, we effectively suppress strontium segregation by applying an anodic current that drives the segregated strontium back to the perovskite lattice and mitigate electrode performance degradation. By monitoring the impedance of Sr2Fe1.5Mo0.5O6-δ (SFM) air electrode under open circuit voltage at high temperature with changing current densities over time, the degradation caused by strontium segregation is verified. The applied current successfully prevent the polarization resistance from increasing is observed. The cell with 0.8 A/cm2 of the applied current increase only 3% of polarization resistance as compared to the cell without applied current after testing at 800 ℃ for 24 h. The atomic ratio of strontium on the SFM electrode surface shows lower strontium content after undergoing applied current, which means that the strontium is indeed migrated back to perovskite lattice under the applied current and result in slower degradation of the SFM electrode. Ministry of Education (MOE) The authors thank the funding support of AcRF Tier 1 project RG181/18 (S) from Ministry of Education, Singapore.

Published
2023

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