Biomass-Based Functionalized Graphene for Self-Rechargeable Zinc–Air Batteries

Commercial batteries are typically charged with electrical power systems and consume electrical energy for recharging. Chemically self-charging batteries are a class of electrochemical devices that use chemical reactions to recharge batteries without electrical grids. Herein, we report the fabrication of a self-rechargeable zinc–air battery that is capable of simultaneously harnessing and storing energy based on biomass-derived functionalized graphene nanosheets (f-GNS). The chemical energy was harnessed into electric power by the spontaneous and reversible redox reactions between the f-GNS and atmospheric oxygen. This enables the fabrication of an energy storage device capable of self-charging without using any catalyst or organic dye. For the realization of integrated energy harvesting, conversion, and storage by a facile and sustainable approach, the f-GNS synthesized by the hydrothermal carbonization of pears followed by mild acid oxidation was used as the active material in an alkaline solution. The self-rechargeable zinc–air battery delivered an initial open circuit voltage of ∼1.15 V and a maximum instantaneous peak power density of ∼250 mW cm–2. The zinc–air batteries can charge themselves at rest in 15 min and exhibit high reversibility and excellent durability over prolonged charge and discharge cycles. When connected in series and parallel, the zinc–air batteries can offer the desired voltage and current, respectively, for practical applications. This work opens an avenue for further advancement in the design of self-sustainable, next-generation aqueous zinc–air batteries for practical applications.