Hierarchically bread-derived carbon foam decorated with defect engineering in reduced graphene oxide/carbon particle nanocomposites as electrode materials for solid-state supercapacitors

The rational design of defective sites and atomic structure of electrode materials for energy storage devices still remains a challenge. Herein, hierarchically activated carbon foam (ACF) from bread has been developed. The density functional theory (DFT) calculation reveals that oxygen defects can form in the reduced graphene oxide/ carbon particle (rGO/CP) derived from graphene oxide frameworks (GOFs) by adding the reducing agent. The synergistic effects of the internal porous architecture of ACF and external interface coupling formed by the defect-rich rGO/CP nanocomposites can provide more electrons to adsorb-OH anions resulting in superior electrochemical energy storage performance. Therefore, the ACF-rGO/large-scale carbon particle (ACF-rGO/ LCP) electrodes show ultrahigh specific capacitance (521 F g-1) at a current density of 0.5 A g-1 and outstanding cycling stability with capacitance retention of 96.4 % over 12,000 cycles. Furthermore, the assembled binder-free supercapacitor using KOH/polyvinyl alcohol (PVA) as a gel electrolyte, displays a high energy density of 27.5 W h kg-1 with a power density of 472 W kg-1, and a capacitance retention of 95.2 % after 12,000 cycles. This work provides a novel pathway to prepare high-performance supercapacitors via the treatment of food waste and the recycling of carbohydrate resources.