Lamellar membrane with orderly aligned glycine molecules for efficient proton conduction

Abstract

Proton conduction is essential for proton exchange membrane (PEM) in hydrogen fuel cell. However, the proton conductivity of most PEMs is limited by the inferior continuity of transport channels and random arrangement of transfer carriers. Here, charged vermiculite lamellar membrane with orderly aligned glycine molecules in the interlayer channel is fabricated. We demonstrate that sulfonic acid-grafted channel induces and interacts with the end amino groups of glycine molecules, forming ordered acid-base pairs along the wall. Meantime, the carboxyl groups at the other end are located in the middle of channel, forming continuous hydrogen bond networks. Such molecule arrangement creates long-range hoping highways for proton conduction. The Vr-SO3H@Gly membrane (∼8 μm in thickness) with 10.2 wt% glycine obtains horizontal conductivity of 378.5 mS cm−1 at 90 °C and 100% RH, 2.2 times of that of commercial Nafion membrane. Moreover, the molecule arrangement is stable helped by the strong channel-glycine and glycine-glycine interactions, rendering excellent conduction stability. These then bring high hydrogen fuel cell performances with maximum current density and power density of 604 mA cm−2 and 184 mW cm−2, respectively, which are superior to Nafion and most reported 2D lamellar PEMs. This study should provide insights in developing advanced lamellar membranes for application in proton conduction field.