Journal
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
Volume 46, Issue 38, Pages 20023-20036Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijhydene.2021.03.104
Keywords
Yttria-stabilised zirconia (YSZ); Oxygen isotope exchange; Water vapour presence; Surface structure; Rate-determining stage; H-1-NMR
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Funding
- Ministry of Science and Higher Education of the Russian Federation [AAAA-A19-119020190078-6]
- Act 211 of the Government of the Russian Federation [02.A03.21.0006]
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The study investigated the oxygen surface kinetics and mechanisms of oxygen interaction with yttria-stabilised zirconia nano-sized powder in dry and humid oxygen atmospheres. It was found that the presence of water in the atmosphere decreases the heterogeneous oxygen exchange rate, and differences in isotopic exchange mechanisms were observed between dry and humid atmospheres.
The oxygen surface kinetics and mechanism of oxygen interaction between oxygen from the gas phase and yttria-stabilised zirconia nano-sized powder have been studied by pulse O-18/O-16 isotope exchange (PIE) in dry (O-2) and humid (mixture O-2 + H2O with pH(2)O = 2.6 kPa at T = 22 degrees C) oxygen atmospheres in comparison with micro-sized powder. Dependences of the heterogeneous oxygen exchange rate (r(H)) in the temperature range from 550 to 900 degrees C, and oxygen partial pressure range in the carrier gas and pulses of 5-19% have been obtained. It has been established that the presence of water causes a decrease in the heterogeneous oxygen exchange rate due to the presence of strongly bound hydroxyl groups in the nanopores of the sample. Differences between the mechanisms of isotopic exchange for dry and humid atmospheres have been found in this temperature range (550-700 degrees C). The observed differences are associated with the interaction of the gas phase and hydroxyls in the adsorbed layer of the oxide. An original method for the separation of the contributions of three types of oxygen exchange for dry and humid atmospheres has been proposed. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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