Microwave-Heated Graphene Realizes Ultrafast Energy Conversion and Thermal Storage

Thermal energy storage using common phase change materials (PCMs) usually suffers from a long time consumption, uneven temperature, and low efficiency. An electromagnetic induction heating method with the advantages of rapidness and heating from the inside out might mitigate these issues. Two-dimensional graphene owns a single atomic layer structure and a large number of exposed chemical bonds; therefore, making fast electromagnetic wave absorption and thermal conduction becomes possible. Herein, we realized a fast, uniform, and repeatable thermal conversion through microwave heating graphene and paraffin composite. Graphene acts as a bridge for linking microwaves and paraffin. It absorbs microwaves as a result of the existence of microenergy levels and transmits energy to paraffin in the form of thermal energy. As a consequence, the composite can be rapidly heated to the phase transition temperature (58 °C) within 1 min and the thermal effect can be maintained after 30 cycles. The enthalpy of composite is 190.04 J g–1, even with 1 wt % loading of graphene. Moreover, this method can be safely handled in the air because the composite has almost no mass loss below 159.9 °C. In summary, the proposed strategy of microwave-heated graphene–PCMs has great application potential in thermal management and energy conversion.