Quinones from Biopolymers and Small Molecules Milled into Graphite Electrodes

Abstract The redox reactions of quinones can be used in electrical energy storage systems. Biopolymers are one of the important sources for quinones due to sustainability and low cost. In this work, biomass materials that contain a large fraction of potential quinone groups are used to directly fabricate biomass/graphite hybrid material electrodes, without extraction or separation of the redox active components from other elements. Among these biomass electrodes based on barks, the bark from holm oak (Quercus ilex) and graphite hybrid electrode exhibits a discharge capacity of 20 mAh g⁻¹, with 68% capacity retention after 1000 cycles. Moreover, various quinone chemicals from the biological world are used to generate the quinone/graphite hybrid material electrodes that display higher quinone loadings at the carbon electrodes. The alizarin/graphite hybrid material electrode presents a capacity of 70 mAh g⁻¹, which is ≈30 times higher than that of the graphite electrode. It is demonstrated that barks and quinones are capable of exfoliating graphite into few‐layer graphene sheets with reduced crystallite size. Processing into electrodes is facilitated by the use of another biopolymer, proteins in the form of misfolded protein fibrils, which also help to improve the available charge in electrodes formed from biomass or quinones.