Block co-polymer templated mesoporous carbon–Nafion hybrid membranes for polymer electrolyte fuel cells under reduced relative humidity

Abstract

Sulfonic acid-functionalized mesoporous carbon (sMC) is explored as a potential hydrophilic inorganic filler to realize a hybrid membrane with Nafion for polymer electrolyte fuel cell (PEFC) applications under reduced relative humidity (RH). The functionalization of MC is performed by sulfonic acid-containing aryl radicals to increase the number of sulfonate groups per unit volume of carbon domain. Hybrid membranes are obtained by embedding sMC on Nafion matrix, thereby providing high absorption of water and fast proton-transport across the electrolyte membrane under low RH values. Proton conductivity of the Nafion–sMC (0.25wt%) hybrid membrane at 20% RH is 7.9×10−2Scm−1, which is 2.5 order of magnitude higher than that of a pristine recast Nafion membrane. A PEFC comprising Nafion–sMC hybrid membrane delivers a peak power density of 660mWcm−2 at a load current density of 1600mAcm−2 while operating at optimum temperature of 70°C under 20% RH and ambient pressure. By contrast, a peak power density of only 150mWcm−2 at a load current density of 380mAcm−2 is achieved with the pristine recast Nafion membrane under identical conditions. The Nafion–sMC hybrid membrane seems more promising at low RH PEFC operation to address many critical problems associated with commercial Nafion membrane.