Chemical functionalization of carbon/polymer bipolar plate materials via oxygen plasma activation and subsequent silanization

A simple coating routine in order to tune the wettability of carbon/polymer bipolar plate materials is presented. Standard carbon/polypropylene composite materials as used for commercial bipolar plates for polymer-electrolyte-membrane fuel cell application are chemically modified via oxygen plasma activation and subsequent silanization using distinct precursor molecules including perfluorodecyltrichlorosilane and aminopropyltrimethoxysilane. For characterization of the samples contact angle measurements, infrared and Auger electron spectroscopy and scanning electron and atomic force microscopy are employed. Spectroscopic data provides direct evidence for successful functionalization of the substrates. Microscopic data reveals the inherent roughness of the micro-/nanostructured substrate surfaces. Depending on the particular silane precursor, the coating procedure yields hydrophilic and hydrophobic surfaces with static water contact angles ranging from 55° to 160°. The wettability of these substrates remains unchanged upon storage in clean air over a period of one year and more. Prospects of the coating procedure targeting the optimization of the water management in fuel cell applications are discussed.