Methanol, Ethanol and Glycerol oxidation study by graphite-epoxy composite electrodes with graphene-anchored nickel oxyhydroxide nanoparticles.

Alcohols have been widely employed in different applications from solvents to fuels but today the main concern is their energy value as fuel. This work reports a graphite-epoxy composite electrode with nickel oxyhydroxide nanoparticles anchored in reduced graphene oxide for the electrooxidation of methanol, ethanol and glycerol, aiming for future application in electronic tongues for biofuel quality control. The electrode was formed by a graphite-epoxy graphite compound with cyclic voltammetry electrodeposited reduced graphene oxide and nickel oxyhydroxide nanoparticles formed by the decomposition in NaOH alkaline solution of cyclic voltammetry electrodeposited nickel hexacyanoferrate. FE-SEM studies were performed to confirm NiOOH nanoparticle morphology; EDX was applied to analyze chemical composition and ImageJ software was applied to size nanoparticles: the average size of the NiOOH nanoparticles was 61±16 nm. To verify the performance of the prepared electrode, it was applied in the electrooxidation of alcohols in alkaline medium by cyclic voltammetry. By performing different calibration experiments of methanol, ethanol and glycerol it was possible to extract some information about the electrode in the presence of alcohols. The LOD for methanol, ethanol and glycerol were 2.16 mM, 2.73 mM and 0.09 mM, respectively, with sensitivity values of 1.32 µA mM^-1, 1.80 µA mM^-1 and 24.60 µA mM^-1, also for methanol, ethanol and glycerol. Multivariate inspection of the data using Principal Component Analysis (performed with use of the ClustVis online tool) demonstrated the potential ability to discriminate between the different alcohols, whereas the explained variance with the first two components was as high as 89.7%.