Electrocatalytic oxidation of methanol and other short chain aliphatic alcohols on glassy carbon electrodes modified with conductive films derived from Ni-(N,N′-bis(2,5-dihydroxybenzylidene)-1,2-diaminobenzene)

Complexes of nickel(II) with the ligand N,N′-bis(2,5-dihydroxybenzylidene)-1,2-diaminobenzene (Ni^II-DHS) can be electropolymerized onto glassy carbon surfaces in alkaline solution to give electroactive films strongly adhered on the electrode surface. In alkaline solution, these poly-[Ni^II-DHS]/GC films present the typical voltammetric response of a surface-immobilized redox couple, as can be anticipated for the Ni²⁺/Ni³⁺ transitions into the film. In addition, the films exhibit a potent and persistent electrocatalytic activity towards the oxidation of methanol. The electrocatalytic currents are, at least, 80 times higher than those obtained for the oxidation of methanol at electrodes modified with nickel hydroxide films in alkaline solutions. In addition, the current is proportional to the concentration of methanol from 0.050 to 0.30 μM. The detection limit and the sensitivity were found to be 26 ± 2 nM and 7.4 × 10⁻² ± 6 × 10⁻³ A cm² mol⁻¹ M⁻¹, respectively. Electrodes modified with poly-[Ni^II-DHS]/GC films show a moderate electrocatalytic activity towards the oxidation of other aliphatic short chain alcohols, such as: ethanol, 1-propanol, 2-propanol and n-butanol. In all cases the catalytic currents present linear dependences with the concentration of alcohol in alkaline solution. The analytical properties of these potential alcohol sensors have also been studied.