A Comprehensive Route for Safe and Sustainable Graphene Oxide Synthesis

Abstract For almost sixty years, the modified Hummers method has been used to oxidise graphite with the radicals of KMnO 4 (MnO 3+ ) to produce graphene oxide (GO) with the use of H 2 O 2 as a terminating chemical in the reaction. NaNO₃ has traditionally been employed as a catalyst in the Hummers method, but its use is associated with the release of toxic byproducts such as NO₂ and N₂O₄. Moreover, recent studies have shown that excessive H₂O₂ can reduce GO, rendering it hydrophobic and causing partial precipitation. In this study, we propose a variation to the conventional method by reducing the dosage of NaNO₃ and eliminating the use of H₂O₂. This approach is experimentally evaluated and compared with conventional protocols that employ both NaNO 3 and H₂O₂. The results highlight that minimising NaNO 3 avoids the high risk of releasing hazardous NOₓ species, and H 2 O 2 -free reaction helps to obtain more stable rGO (a high-quality colloidal dispersion with chemical modification). The colloidal solution retains its stability for up to three months for rGO suspension.