One-Step Green Hydrothermal Synthesis of Few-Layer Graphene Oxide from Humic Acid

The conventional synthesis route of graphene oxide (GO(G)), based on Hummers method, suffers from explosion risk, environmental concerns and a tedious synthesis process, which increases production costs and hinders its practical applications. Herein, we report a novel strategy for preparing few-layer graphene oxide (GO(H)) from humic acid via simple hydrothermal treatment. The formation of GO(H) is mainly attributed to the hydrolysis, oxidation and aromatization of humic acid under hydrothermal conditions. The as-prepared few-layer GO(H) has typical morphology (thin and crumpled sheets with the thickness of ~3.2 nm), crystal structure (a Raman I(D)/I(G) ratio of 1.09) and chemical composition (an X-ray Photoelectron Spectroscopy (XPS) O/C atomic ratio of 0.36) of few-layer GO(G). The thermally reduced GO(H) (r-GO(H)) delivers considerable area capacitance of 28 µF·cm(−2), high rate capability and low electrochemical resistance as supercapacitor electrodes. The described hydrothermal process shows great promise for the cheap, green and efficient synthesis of few-layer graphene oxide for advanced applications.