Investigation of fuel cell processes in low temperature fuel cells

Abstract

At the institute of Technical Thermodynamics of the DLR physical and electrochemical methods have been used to characterize fuel cell components and processes in fuel cells. For this purpose various methods e.g. V-i curves, electrochemical impedance spec¬troscopy (EIS), current density measurements, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and porosimetry are applied. The techniques are used to characterize and support the development and improvement of the pa¬tented DLR-dry spraying technique for the manufacturing of electrodes and MEAs for PEFC. The electrochemical methods allow to investigate the electrochemical perfor¬mance in fuel cell configuration; in contrast, the physical methods are used in order to investigate the influence of variations in the manufacturing processes and to develop a production near quality control. Another application of these analytic methods is the investigation of the processes du¬ring fuel cell operation. The main topic in this field are the study of degradation pro¬cesses. The electrochemical methods especially the electrochemical impedance spectroscopy and the current density measurements can be used as in-situ spectro¬scopy, whereby these in-situ methods do not allow to distinguish different degrada¬tion processes. The physical methods will be used to investigate not used compo¬nents and for the post-mortem analysis; whereby these investigations allow to indentify degradation mechanisms. By combination of the physical and electrochemical methods the observed degradation effects can be interpreted.