Surface structures and electrochemical activity of palladium-niobium binary alloy electrodes, and glucose biosensor with palladium-niobium binary alloy electrode

The electrochemical activities of binary metals in a Pd-Nb system were investigated as a function of their compositions, crystal structures, using a hydrogen peroxide and ascorbic acid redox reaction. High activities for the redox reaction of hydrogen peroxide were observed when an alloy of composition 75 atom% Pd-25 atom% Nb (Pd-25Nb) with Pd₃Nb phase was used. Tests on six electrodes showed that at a constant potential of 0.7V, the Pd-25Nb electrode had the best hydrogen peroxide detection capability (Pd-25Nb: 3.2 μA mm^-2; Pd: 2.4 μA mm^-2; Pt: 2.2 μA mm ^-2; Pd-10Nb: 1.8 μA mm^-2; Pd-30.8Nb: 2.4 μA mm ^-2; Pd-54.4Nb: 0.6 μA mm^-2 for 2mM hydrogen peroxide). And then, Pd-25Nb gave the best performance in terms of preferential hydrogen peroxide oxidation against ascorbic acid. Subsequently, the Pd-25Nb electrode which had excellent hydrogen peroxide detection capability, Pd and Pt were used for the fabrication of amperometric glucose sensors. To fabricate the glucose sensors, we coated the three electrodes first with γ- aminopropyltriethoxysilane, and then with crosslinked bovine serum albumin and glutaraldehyde containing glucose oxidase. Tests on the Pd-25Nb, Pd, and Pt electrode glucose sensors showed that the Pd-25Nb glucose sensor had a better glucose detection capability than the Pd and Pt glucose sensors: 0.468 μA mm^-2mM^-1 for the Pd-25Nb sensor, 0.307 μA mm ^-2mM^-1 for the Pd sensor, and 0.276 μA mm ^-2mM^-1 for the Pt sensor with 1.67mM glucose. We discuss the relation between electrode responses to both hydrogen peroxide and ascorbic acid and electrode surface structures.