Self-healing of super hydrophobic and hierarchical surfaces for gas diffusion layer

Abstract

Surface wettability of gas diffusion media (GDM) is one of the key issues related to the water management in fuel cells. In this study, a facile coating approach of combining carbon black and polydimethylsiloxane (PDMS) is developed to fabricate the gas diffusion layer (GDL) with super hydrophobic and hierarchical surfaces. Due to the Wenzel and Cassie's effect, the fabricated GDL shows the average contact angle as high as 158° and the roll angle less than 5°. Its super durability could be identified by the constant potential oxidation with the oxidization peak current approaching to 0.1 mA cm−2, an order of magnitude smaller than that of conventional GDL coated with polytetrafluoroethylene (PTFE) and carbon black (10/90 wt/wt). Furthermore, these hierarchical hydrophobic surfaces exhibit a recovery of hydrophobicity from 107° to 133° by heat treatment. The mechanism of the exceptional self-healing capability is investigated by microscopic and spectroscopic analysis. It is indicated that ring siloxanes with lower surface tension formed on GDL surface during heat treatment process. This paper provides a fundamental research on the hierarchical superhydrophobic surfaces of GDL and a promising solution to develop long-live super hydrophobic GDL.