Ultrafast Microwave Carbonization of Waste Using Graphene Microreactor for Efficient Energy Storage

Abstract The traditional carbonization method for preparing carbon materials is hindered by high energy consumption and low efficiency. In this work, a microwave carbonization approach is employed to fabricate a carbonaceous electrode, comprising a graphene and hard carbon heterostructure (GHCH), by rapidly carbonizing waste paper in just 10 seconds using a graphene microreactor. A novel microwave carbonization mechanism is substantiated by combining experimental evidence with finite element simulations. Graphene absorbs microwaves, generating high‐frequency plasma electromagnetic waves, which “catalyze” the sample's rapid microwave absorption, leading to electric breakdown within the sample to initiate preliminary carbonization. Utilizing this ultra‐fast carbonization technique, the GHCH as anode of K‐ion batteries exhibits high reversible capacity and excellent cycle stability. Structural characterization confirms the orderly arrangement of carbon microcrystals, the presence of N and S heteroatoms, and a mesoporous structure within the GHCH electrode. In situ synchrotron X‐ray techniques are employed in this work to investigate the mesoporous structure of GHCH electrodes and the binding dynamics of K‐ions during the charge–discharge cycles. Density functional theory calculations further reveal that the incorporation of graphene facilitated K‐ion diffusion and electron transfer within the GHCH electrodes. In summary, microwave carbonization offers a sustainable and efficient pathway for synthesizing high‐performance carbon‐based electrode.