Pillared Graphene for Supercapacitor Applications

Abstract

Since the discovery of graphene in 2004 [1], it has been considered a “Wonder” material with lots of potential due to its attractive properties. Owing to such properties, graphene is theoretically expected to have an electrochemical double layer capacitance of 550 F/g [2]. However, due to the high cost and difficulty of producing and handling single sheets of graphene, the presence of graphene in the market was hindered. Luckily, many methods were devised to synthesize graphene-like materials that would be easier and cheaper to produce. Unfortunately such methods end up producing reduced Graphene Oxide (rGO) with stacked graphene layers due to pi-pi interactions, which impedes the full utilisation of the graphene’s surface area. Pillaring the graphene using organic linkers was proven to be one of the useful techniques in partially preventing the restacking of the graphene sheets in rGO [3].Herein, three molecular pillars with different chemical nature and lengths will be presented as pillaring agents for graphene and the performance of their corresponding pillared graphene assemblies as electrode materials for supercapacitors will be assessed against that of rGO as a reference sample. To assess the success of the pillaring technique and to decipher the chemical composition of the samples, various characterization techniques were employed such as XRD, TGA, XPS, EA, SEM, FT-IR, Raman spectroscopy and conductivity measurements. Different electrolytes were used to test the electrochemical performance in different environments (acidic and neutral with different cation sizes). The pillared graphene assemblies demonstrated an enhanced capacitive performance compared to reference samples and a correlation between such performance and the different physico-chemical characteristics is to be highlighted.