Atomic Force Microscopy

Abstract

Although atomic force microscopy (AFM) is an ex situ technique, the measuring conditions can be chosen rather close to operating conditions in a PEM fuel cell. The flexibility in the analyzed areas allows an overview of the sample as well as a highly resolved measurement on the nanometer scale. The signals recorded by AFM are on the one hand based on force interaction of the AFM tip with the sample surface, thereby delivering, that is, local friction, adhesion, stiffness, and energy loss. On the other hand, electrical properties such as electronic conductivity, ionic conductivity as well as surface potential, electrostatic force or reactivity can be retrieved. The AFM works in ambient air and in a humid or liquid environment, including an electrochemical cell. Hydrophilic and hydrophobic surface properties are especially important for water management in a PEM fuel cell and degradation processes can be followed by a comparison of samples in a fresh state and after operation.