Sustainable Production of Graphene from Solar-Driven Expanded Graphite

Scalable synthesis of graphene sheets is challenging due to the complex production processes. Few-layered graphene sheets with high lateral sizes (4–5 μm) through a state-of-the-art solar irradiation-driven liquid-phase exfoliation technique are achieved. The sunlight is directly used on the intercalated graphite flakes for just 0.5 s to achieve the graphite expansion. Using focused sunlight makes our solar expansion technique sustainable with zero energy demand (0 J). The total energy spent to produce 1 kg of graphene through this technique is only around 2.135 MJ. The produced graphene sheets show significant electrical conductivity (1586 S cm⁻¹) and high in-plane thermal conductivity (196.3 W mK⁻¹). The electromagnetic interference (EMI) shielding properties of solar graphene are evaluated in the X-band region, and it shows a very high shielding effectiveness of about 71.5 dB at a thickness of ≈80 μm with an absolute EMI shielding effectiveness of about 11983.7 dB cm² g⁻¹. Overall, this work provides a viable approach for the efficient, scalable production of graphene with reduced energy consumption and cost, contributing to the sustainable production of graphene.