Structure‐guided Capacitance Relationships in Oxidized Graphene Porous Materials Based Supercapacitors

Abstract

Supercapacitors formed from porous carbon and graphene‐oxide (GO) materials are usually dominated by either electric double‐layer capacitance, pseudo‐capacitance, or both. Due to these combined features, reduced GO materials have been shown to offer superior capacitance over typical nanoporous carbon materials; however, there is a significant variation in reported values, ranging between 25 and 350 F g−1. This undermines the structure (e.g., oxygen functionality and/or surface area)‐performance relationships for optimization of cost and scalable factors. This work demonstrates important structure‐controlled charge storage relationships. For this, a series of exfoliated graphene (EG) derivatives are produced via thermal‐shock exfoliation of GO precursors and following controlled graphitization of EG (GEG) generates materials with varied amounts of porosity, redox‐active oxygen groups and graphitic components. Experimental results show significantly varied capacitance values between 30 and 250 F g−1 at 1.0 A g−1 in GEG structures; this suggests that for a given specific surface area the redox‐active and hydrophilic oxygen content can boost the capacitance to 250–300% higher compared to typical mesoporous carbon materials. GEGs with identical oxygen functionality show a surface area governed capacitance. This allows to establish direct structure‐performance relationships between 1) redox‐active oxygen functional concentration and capacitance and 2) surface area and capacitance.