Abstract:
In recent times, Graphene Oxide (GO) based materials have attracted considerable attention in
the development of electrodes for a wide range of electrochemical applications. However,
insulating nature of GO has limited the use of this material ‘as it is’ for above mentioned
applications. Further, the randomness of oxygen functionalities and their inhomogeneous
spatial distribution have a significant impact on the electronic properties of GO. Thus, the
investigation of electrochemistry behind this intriguing material is required to realize its
application potential. In this study, thin films of GO which were synthesized under different
oxidation conditions using Improved Hummers method were casted on glassy carbon (GC)
disk electrodes via drop casting. These GO coated electrodes were then electrochemically
characterized in the presence of two redox probes potassium ferricyanide and ruthenium(III)
hexammine chloride using cyclic voltammetry (CV) to study the effect of oxygen
functionalities on electron transfer properties of GOs. The CV results of these GO electrodes
for potassium ferricyanide at different scan rates indicate that the electron transfer process is
reversible. Further the electrochemically active surface area of GO electrodes measured was
much less compared to that of bare GC. This indicates that insulating area of the GO electrodes
is higher than the electrochemically active surface area owing to the surface bound oxygen
functionalities of GO. Thus, these GO electrodes shows high resistance to electron transfer
compared to the bare GC electrode. However, same GO electrodes in ruthenium(III)
hexammine chloride showed distinct electrochemical response characteristics to
electrocatalytic process due to the presence of oxygen functionalities. In this case, electron
transfer process is followed by a catalytic chemical process where electrogenerated reduced
ruthenium(III) hexammine chemically react with oxygen functionalities of GO and regenerates
the starting material ruthenium(III) hexammine. Further, significant variation can be observed
in the rate constants of the chemical reaction for these GO electrodes. Therefore, these GOs
can be used as electrode materials for electrochemical applications where oxygenated
electrocatalytic reactions are employed.
