Surface Science Study on the Stability of Various Catalyst Materials for DMFC

Abstract

This contribution presents exemplary investigations by surface science methods for the investigation of electrodes and catalyst systems in fuel cells. The aim is to illustrate the information gain which is obtained with the combination of physical analysis even of complex system. Particularly, systems for DMFC application were selected. The examples range from commercially available catalysts and their electrodes to model systems with novel experimental composition. For platinum alloy catalysts on the anode side XPS analysis shows that the non-noble alloy metals are dissolved. On the cathode an agglomeration of the platinum can be observed by electron microscopies, whereby the agglomeration results in a loss of active surface area. The investigated RuSe catalysts are significantly changed due to electrochemical operation, whereby the non active species is dissolved. Investigations of model systems are presented that show that a core-shell catalyst structures help to stabilize nonnoble components.

Investigation of Local Degradation Effects

“…By separating the components some information about changes in the vertical direction can be obtained. The degradation of PTFE in the electrode and in the GDL [12] was investigated by XPS. With XPS the carbon in carbon black and in the PTFE or electrolyte material can be clearly distinguished.…”

Investigation of the Degradation of Hydrophobized Carbon Structures in PEFC

“…During long-term operation of PEFC the performance decreases due to the degradation of the fuel cell components. Unfortunately, one of the degradation processes leads to an alteration of the hydrophobicity of the GDL and the reaction layer [1]. Due to a partial decomposition of the PTFE the hydrophobicity of the components will be reduced and consequently the water balance is changed.…”