High temperature low vacuum synthesis of a freestanding three-dimensional graphene nano-ribbon foam electrode

The fabrication of a freestanding three-dimensional (3D) graphene nano-ribbon open cell foam electrode is reported based upon a facile high temperature (1700 degrees C) low vacuum (50 Torr) process. The graphene nano-ribbon (GNR) foam comprises on average 4 graphene layers and has an O/C ratio of 0.14; a quasi-graphene structure. This unique material is demonstrated to be electrochemically useful, with the electrochemical properties and resultant electroanalytical performance of the novel freestanding 3D GNR foam electrode reported for the first time. Electrochemical characterisation is performed via cyclic voltammetry in aqueous solutions using a range of electro-active redox probes and biologically relevant analytes, namely potassium ferrocyanide(II), hexaammineruthenium(III) chloride, uric acid (UA), acetaminophen (AP) and dopamine hydrochloride (DA). Analytical performance is evaluated and benchmarked through comparisons of the 3D GNR foam to other carbon based 3D foam electrodes, namely pristine graphene and reticulated vitreous carbon (RVC) alternatives. We show that the 3D GNR foam electrode possesses favourable heterogeneous electron transfer (HET) properties when compared to the alternative carbon based 3D foams, likely due to improved coverage of reactive edge plane like-sites/defects on its structure. In terms of the electroanalytical response of the 3D GNR foam electrode, it is found to give rise to an improved linear range and limit of detection towards some analytes; however, in certain cases the alternative carbon based 3D foams out-performed the GNR foam. These findings question the need of 'only' fast HET properties and suggest a compromise is required (for improved sensing capabilities to be realised) between HET speeds, the presence/absence of oxygenated species and the accessibility of the electrode's active surface area. This work offers insight to those working in the field of electrochemistry, particularly electroanalysis and those searching for new carbon based 3D foam electrode materials.