Investigating HPA functionalized mesoporous silica materials for use as high temperature proton exchange membranes

Medium temperature proton exchange membrane fuel cells (MT-PEMFCs) are solid-state energy conversion devices that electrochemically convert chemical energy (e.g., from alcohols) into electricity. MT-PEMFCs have advantages over low temperature fuel cells, such as elimination of carbon monoxide poisoning of the electrocatalyst [1], enhanced oxidation kinetics of alcohol fuels such as methanol [2], and the use of liquid fuels [3]. Heteropoly acids (HPA) such as phosphotungstic acid (HPW) can be used to impregnate ordered mesoporous silica (MSN) to make nanocomposite proton exchange membranes (PEMs) [4]. While these HPW MSN mixes have been studied extensively as catalysts [5], HPW MSNs have only recently be studied for use in MT-PEMFCs using methanol as a fuel [6]. Previous studies have investigated the correlations between physical stability, temperature, and fuel cell performance [6]. However, the structure of the HPW MSNs and how this affects the proton conduction efficiency and mechanism of proton conduction in these materials has not been investigated. In this project, MT-PEMFCs with HPW MSN have been studied using synchrotron, desktop and neutron scattering and spectroscopic techniques. The results show that the physical properties vary with increased HPW content, however further analysis is required to demonstrate the exact functional changes and how this impacts the proton conduction mechanism