Robust reduced graphene oxide paper fabricated with a household non-stick frying pan: A large-area freestanding flexible substrate for supercapacitors

Inspired by cooking omelettes, a facile, low-cost and scalable method involving the use of a readily available household non-stick frying pan is introduced to fabricate large-area freestanding reduced graphene oxide (RGO) paper. The as-fabricated RGO paper is robust enough to bear sandpaper polishing, bending/folding, and hydrothermal and electrochemical deposition processes without obvious structure/performance degradation. As a demonstration, the as-obtained RGO papers were directly used as universal flexible substrates for high performance supercapacitors (SCs). Thus, WO₃ and PPy, which are two distinctive active materials, were loaded onto the RGO paper via a hydrothermal process and electrodeposition process, respectively, which are two typical fabrication methods for high performance SC electrodes. The resultant WO₃- and PPy-RGO paper, which act as negative and positive electrodes, respectively, were further assembled into a flexible asymmetric supercapacitor (ASC), achieving a high energy density of 0.23 mW h cm^-3 at a power density of 7.3 mW cm^-3 when normalized to the whole volume. Moreover, benefiting from the robust flexible RGO substrate, the performance of the ASC showed great stability under different bending angles and after repeated bending/folding. These exciting results demonstrate that our robust RGO paper is an ideal universal substrate for different active materials synthesized via various processing methods, which show its great potential in an all-solid energy storage system with excellent flexibility and robustness.