Kinetics of the Electrode Reaction at the  H 2 ‐  H 2 O  Porous Pt/Stabilized Zirconia Interface

Abstract

To elucidate the mechanism of the electrode reaction at the interface of H2-H20 porous Pt/stabilized zirconia, measurements were made on the electrode interface conductivity, ~, and the steady-state polarization current, I, as a function of H2 partial pressure, P~2, and H20 partial pressure, PH20, up to 800~ The rate of the electrode reaction at 700 to 800~ in H2-H20 atmospheres is faster than that in CO-CO2 and slower than that in 02 rich atmospheres by 1 to 2 orders of magnitude. The rate-determining reaction process was the exchange of adsorbed OH radicals between the Pt-and the stabilized zirconia-surface at the triple-phase boundary (TPB) of gas/Pt/stabilized zirconia. When the oxygen activity, a0, ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.122.253.228 Downloaded on 2015-05-25 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.122.253.228 Downloaded on 2015-05-25 to IP

Model for Solid Electrolyte Gas Electrode Reaction Kinetics; Key Concepts, Basic Model Construction, Extension of Models, New Experimental Techniques for Model Confirmation, and Future Prospects

“…Therefore, ohmic resistance compensation is necessary in the analysis of experimental data. 19,30,77,80 When P(O 2 )(ref ) is set different from P(O 2 ) of the reactant gas at WE, compensation for the difference is necessary to attain the correct G chem .…”

“…Discussion on the performance of reference and counter electrodes was made in several papers, 19,27,30,35 particularly in relation to gas sensors, 18,26,28,39 and new techniques. 40,51,68 Gas phase chemical potential is sensitive to impurity gas particularly when the reactant gas is much diluted or gas mixing Electrochemistry, 82(10), 819-829 (2014) ratio of oxidant and reductant gases is very far from unity.…”

“…TPB; 25,26,30,35,37,43 reaction with Pt electrode and stabilized zirconia electrolyte under reduced atmospheres Under reduced atmospheres with CO-CO 2 or H 2 -H 2 O, the coverage of O ad on the surface of Pt becomes low. Then, to progress the redox reaction, H ad or CO ad on Pt must pick up oxidant species from the oxide electrolyte surface across TPB.…”

“…25 In the H 2 -H 2 O atmospheres, the adsorbed species on SZ is O ad , OH ad , and H 2 O ad from the higher to the lower P(O 2 ). 30 The concluded rate determining reactions taking place between the adsorbed species on Pt surface and that on SZ surface across the TPB for CO-CO 2 at 800-1000°C are oxygen exchange under ordinary CO-CO 2 conditions and carbon exchange Electrochemistry, 82(10), 819-829 (2014) across TPB at the conditions close to carbon deposition. 25 In the H 2 -H 2 O atmospheres, OH exchange between the adsorbed species on Pt and SZ becomes the rate determining step.…”

“…25 In the H 2 -H 2 O atmospheres, OH exchange between the adsorbed species on Pt and SZ becomes the rate determining step. 30 The important model employed in this analysis is the following hypothesis; Let us consider the cross section of two surface X and Y to form the TPB composed of gas phase, surface X and surface Y. Species A adsorbs on X with the coverage H A (X) and species B adsorbs on Y with the coverage H B (Y).…”