Ruthenium oxide modified nickel electrode for ascorbic acid detection

Electrodes of ruthenium oxide modified nickel were prepared by a thermal decomposition method. The stoichiometry of the modifier, RuO_x, was quantitatively determined to be a meta-stable phase, RuO₅. The electrodes were employed to sense ascorbic acid in alkaline solution with a high sensitivity, 296 μAcm^-2 mM^-1, and good selectivity for eight kinds of disturbing reagents. We found that the ascorbic acid was oxidized irreversibly in solution. To match with the variation of the morphology, the sensitivity reached a maximum when the RuO_x segregated with a nano-crystalline feature. We find that the substrate oxidized as the deposited RuO_x grew thicker. The feature of the deposited RuO_x changed from nano-particles to small islands resulting from the wetting effect of the substrate oxide, NiO; meanwhile the sensitivity decreased dramatically. The endurance of the RuO_x/Ni electrode also showed a good performance after 38 days of successive test.