Electrochemically derived monolayer graphene with CVD-comparable optoelectrical properties and high capacitive...

Harnessing the exceptional properties of monolayer graphene (MG) requires scalable, cost-effective synthesis free from multi-layer graphene. While liquid-phase methods are inexpensive, they often produce oxidized, layer-polydisperse graphene with small flakes. Here, we present a liquid-phase method that synthesizes layer-monodisperse MG via engineered electrochemical exfoliation. Using a 98% H₂SO₄electrolyte, graphite was intercalated to stage I graphite bisulfate (GB) and subsequently exfoliated, followed by tuned ultrasonic agitation in NMP, achieving a high MG yield of ∼93.3%. This process results in large MG flakes (∼136µm²) with low defect density (I_D/I_G<0.1) and oxygen content of 2.8%. The MG also exhibits outstanding optoelectrical properties, including ∼96.86% transparency and high conductivity (∼2.45 × 10⁶S m^-1), comparable to CVD-synthesized graphene. Additionally, MG films demonstrate superior supercapacitive energy storage with a specific capacitance of ∼1363 F g^-1at 1 A g^-1, surpassing thicker graphene and reduced graphene oxide films.