Recent Advances with Sulfonated Silica Ceramic Carbon Electrodes for Fuel Cells

Abstract

Sulfonated silica-based ceramic carbon electrodes (SS-CCE) are prepared using low-cost organosilane precursors that are mixed with the carbon-supported platinum (Pt/C) catalyst in monomer form, and subsequently polymerized and coated onto a gas diffusion layer in a single step. Our lab has demonstrated that that SS-CCEs can achieve similar H2/O2 fuel cell performance as conventional Nafion-based electrodes [1, 2]. Furthermore, these electrode structures display excellent tolerance to dry operating conditions, due to the proton conductivity of the sulfonic acid moiety and the hygroscopic nature of the SiO2 backbone. This is a major advantage over conventional Nafion-based fuel cell electrodes which require the use of heavily humidified gas feeds and are limited to temperature below 80 °C. Therefore SS-CCEs have great potential to improve PEMFC efficiency by reducing parasitic power losses required for gas humidification. Furthermore, they have the potential to reduce the required catalyst loading and extend the operating temperature range of PEMFCs. While these results have been promising, there are few detailed studies of SS-CCE structure-property. Likewise, their durability in operating fuel cells have yet to be proven. In this presentation, we will give an overview of our group’s recent progress towards optimization the synthesis and structure of SS-CCEs. In particular, we have found hydrothermal conditions to be a promising way to enhance performance, promoting a more homogenous distribution of silicate ionomer and more effective bonding to the carbon surface [3]. Likewise, accelerated stress tests indicate that the silicate ionomer also serves to stability the Pt catalysts and enhance its durability [4]. This, along with their tolerance to high temperatures/low relative humidity conditions leads to improved stability of SS-CCE-based fuel cell systems.