Tailoring edge functionalization of graphene quantum dots for efficient two-electron oxygen reduction reaction

Electrochemical two-electron (2e⁻) oxygen reduction reaction (ORR) is a direct approach for H₂O₂ generation prompting as alternative revolution over a greener and more sustainable environment for the research community to feed the global energy demands over anthraquinone process. Oxidized carbonaceous materials are proven to accelerate the 2e⁻ ORR pathway due to the presence of oxygen functional moieties which either tunes the interfacial edge sites benefiting the H₂O₂ catalytic pathways or hinders the pathway due to the density of oxygenated active sites. Here, we demonstrated the synthesis of graphene quantum dots (GQDs) being heteroatomically doped with oxygen and nitrogen moiety on the edge sites. The O-GQDs possess a high atomic ratio of oxygen around ∼43.5 % specified to the carbonyl moieties with high density inducing enormous active sites for the H₂O₂ production. The O-GQDs are proven to attain >87 % selectivity and exhibits a mass activity of 84 A/g with Tafel slope of 62 mV/dec compared to all reported carbonaceous catalysts. In addition, for practical applicability of continuous H₂O₂ production we attained a higher yield of 1273.68 mmol/g h, faradaic efficiency of >94 % and a good catalytic stability of 50 h. Experimental and spectroscopical analyses affirm the presence of C=O moiety with greater elemental weight% aiding in catalytic active site in the favor of H₂O₂ generation.