Electrochemical capacitors (supercapacitors) have received considerable attention as promising energy storage devices for applications including transportation, load leveling, and personal electronic devices. Common features among electrochemical capacitors are high power density and cycle life, and although they may differ with respect to electrode material, many electrochemical capacitors employ some type of high surface area carbon electrode. With the emergence of graphene (a single atom thick layer of carbon), some recent attention has focused on using this material as a supercapacitor electrode with generally promising results. In this paper, we present imidazolium-functionalized graphene oxide supercapacitor electrodes. We compare these materials to unmodified graphene oxide. Our results indicate that the functionalized graphene oxide materials exhibit higher capacity than unmodified graphene oxide, leading us to conclude that these materials may be suitable for supercapacitor electrodes. In addition, we show that the functionalized graphene oxide materials exhibit a mix of double-layer and pseudocapacitance, which ultimately could further enhance material capacity. (C) 2015 Elsevier B.V. All rights reserved.