Synergistically Tuning Graphene Layer and Active Sites for Flexible Zn–Air Batteries

Abstract

Fewer layer graphene principally has a higher surface area to support more catalytic sites for energy conversion, but it is still challenging to synthesize monolayer graphene without oxidation from graphite at a low cost. Here, a method for synergistically thinning graphene layers and constructing catalytic sites to create a superior bifunctional oxygen catalyst through vapor intercalation of multi‐layer graphene or its derivatives is described. The synthesized small sheet sizes of 1–2 layer graphene‐supported FeN4 and FeCo active sites exhibit superior reversible activity of oxygen reduction and evolution reactions with a low overall overpotential of 0.648 V. The sheet‐shaped catalyst is further used to fabricate flexible soft‐packed and wearable cable‐type quasi‐solid‐state zinc–air batteries, achieving high performances (>188 mW cm−2, >450 cycles) and enabling smartphone charging. DFT calculations reveal that fewer layer graphene coupled with atomic FeN4 and alloy FeCo sites enables lower Gibbs free energy for favorable OOH* intermediate adsorption/desorption benefiting superior oxygen redox process. This study introduces a strategy for scalable synthesis of 1–2 layer graphene from cheap microcrystalline graphite minerals for wearable and durable energy devices.