Graphene oxide induced hydrothermal carbonization of egg proteins for high-performance supercapacitors

Hydrothermal carbonization (HTC) is a conventional method to synthesise biomass-derived carbon materials. However, hydrothermal treatment of proteins usually induces the decomposition of these biopolymers without forming carbonaceous materials. Here, we report the use of graphene oxide sheets as a template and catalyst to carbonize egg proteins via HTC. The resulting egg protein derived carbon/reduced graphene oxide (EDC/rGO) composite was further activated using KOH to produce a highly porous heteroatom-doped carbon material and used as an electrode material for a supercapacitor. The typical supercapacitor exhibited a high specific capacitance (482 F g(-1) at a current density of 0.1 A g(-1)), good rate capability and excellent cycling stability (similar to 100% capacitance retention after 10 000 cycles of charging and discharging at 5 A g(-1)). Considering the high efficiency of the HTC process and the low cost of eggs, this work demonstrates a facile approach to produce high-performance carbon-based electrode materials for supercapacitors.