Studying Functional Electrode Structures with Combined Scanning Probe Techniques

Abstract

In this article, the study of the active electrode surfaces of a special type of fuel cells, solid oxide fuel cells (SOFCs), is described. The high conversion efficiency of this type of fuel cells is connected with a high working temperature, which makes the material selection difficult and causes thermal degradation processes, limiting the life time of the cells. We investigated the topography, conductivity phenomena, and chemical composition of such electrode surfaces in the nanoscale regime with several atomic force microscopy (AFM)-based techniques. Of particular interest was the grain size distribution of the surfaces in order to optimize their production process. The results of the AFM experiments were compared with those obtained by XRD measurements. The AFM achieved grain height data inaccessible by SEM. Nanoscale material contrast was obtained by applying the technique of Chemical Contrast Imaging (CCI) developed in our group. These measurements indicated possible phase separations in the electrode surfaces. The local electronic conductivity and differences between crystallites and grain boundaries were studied by Conductive AFM (C-AFM) and Electrostatic Force Microscopy (EFM). The theory, implementation and testing of this method and the results are discussed.