Advanced Measurement and Modeling Techniques for Improved SOFC Cathodes

Abstract

The goal of this project was to develop an improved understanding of factors governing performance and degradation of mixed-conducting SOFC cathodes. Two new diagnostic tools were developed to help achieve this goal: 1) microelectrode half-cells for improved isolation of cathode impedance on thin electrolytes, and 2) nonlinear electrochemical impedance spectroscopy (NLEIS), a variant of traditional impedance that allows workers to probe nonlinear rates as a function of frequency. After reporting on the development and efficacy of these tools, this document reports on the use of these and other tools to better understand performance and degradation of cathodes based on the mixed conductor La 1-x Sr x CoO 3-δ (LSC) on gadolinia or samaria-doped ceria (GDC or SDC). We describe the use of NLEIS to measure O 2 exchange on thin-film LSC electrodes, and show that O 2 exchange is most likely governed by dissociative adsorption. We also describe parametric studies of porous LSC electrodes using impedance and NLEIS. Our results suggest that O 2 exchange and ion transport co-limit performance under most relevant conditions, but it is O 2 exchange that is most sensitive to processing, and subject to the greatest degradation and sample-to-sample variation. We recommend further work that focuses on electrodes of well-defined or characterized geometry, and probes the details of surface structure, composition, and impurities. Parallel work on primarily electronic conductors (LSM) would also be of benefit to developers, and to improved understanding of surface vs. bulk diffusion.

Lower and upper bounds on CSL parameters from latent image formation and IGM heating

“…The second is to use standard classical Brownian motion formulae, as is done in the paper of Collett and Pearle [4]. In Adler [36], we calculate and compare the mean-square coordinate fluctuation predicted by the two methods, for the case of isotropic hard sphere scattering. We show that the two calculations give identical results, and so either method can be used to estimate collision backgrounds that may mask CSL effects.…”

Stochastic particle annihilation: a model of state reduction in relativistic quantum field theory

“…A general solution to the energy-based state diffusion with time-dependent coupling has recently been found [11]. At present, non-relativistic proposals are seen to have sufficiently negligible effects on the quantum scale in order to be indistinguishable from standard quantum theory for current experimental technologies [12]. At the same time these proposals offer a consistent understanding of classical and quantum domains.…”