Yttria-stabilized barium zirconate surface reactivity at elevated temperatures
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Research Letter
Yttria-stabilized barium zirconate surface reactivity at elevated temperatures Märtha M. Welander, Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59715, USA Daniel J. Goettlich, Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59715, USA; Montana Materials Science Program, Montana State University, Bozeman, MT 59715, USA Tanner J. Henning, Montana Materials Science Program, Montana State University, Bozeman, MT 59715, USA Robert A. Walker , Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59715, USA; Montana Materials Science Program, Montana State University, Bozeman, MT 59715, USA Address all correspondence to Robert A. Walker at [email protected] (Received 29 April 2020; accepted 28 May 2020)
Abstract Material changes in yttrium-doped barium zirconate, BaZr0.8Y0.2O3–x, were studied using in situ Raman spectroscopy and ex situ x-ray photoelectron spectroscopy analysis. During in situ Raman analysis, samples were heated to temperatures of 300–600 °C and exposed to both dry and humidified H2 atmospheres. At the lower temperatures (300–450 °C), a new vibrational peak appears in the Raman spectra during exposure to humidified H2. The appearance of this feature is reversible, dependent on previous sample history, and possibly results from new, secondary phase formation or lattice distortion.
Introduction As energy conversion strategies evolve to meet an increasing demand for clean, sustainable power production, solid oxide electrochemical cells have drawn attention for their ability to efficiently convert fuel into electricity (as a fuel cell) or species, such as CO2 and H2O, into high value products, including CO and H2, through electrolysis. While solid oxide fuel cells (SOFCs) have matured to the point where they are now produced commercially, high-temperature proton ceramic fuel cells (PCFCs) are a newer technology that has begun attracting interest.[1–4] PCFCs are attractive relative to SOFCs because of the low activation energy associated with proton transport and correspondingly lower device operating temperatures. SOFCs require that oxide anions diffuse from the cathode to the anode through a solid oxide electrolyte—typically yttria-stabilized zirconia (YSZ)—and the ∼100 kJ/mol activation energy for oxide diffusion requires that SOFCs operate at temperatures of 650 °C and higher.[2] In contrast, the activation energy for proton conduction through PCFC electrolytes is only ∼50 kJ/mol[5] and PCFCs can operate at temperatures as low as 300 °C. Additionally, PCFCs have higher conversion efficiencies with hydrocarbon fuels because water is produced at the cathode and does not dilute the anode fuel stream. An added PCFC asset is higher resistance to carbon accumulation due to reverse Boudouard reactions.[2,6–8] Despite these appealing properties, however, PCFC development is limited by uncertainties surrounding the materials used as PCFC electrolytes and electrodes. Specifically, questions about material
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