Characterization of glucose electro-oxidation at Ni and Ni–Cr alloy electrodes

Electro-catalytic oxidation of glucose by the nickel oxy-hydroxide film developed in alkaline medium on different working electrodes materials (Ni, Ni–Cr (90:10) or Ni–Cr (80:20)) is demonstrated. In the presence of glucose the oxidation peak current of nickel hydroxide increases while that of the reverse process decreases. This is attributed to the mediation of nickel species in the electro-catalytic process. The electro-catalytic film is formed by using a potential scan program developed in our research group. This program facilitated the formation of stable proportions of Ni(II)/Ni(III) oxy-hydroxides which are necessary for the electro-catalysis study. The electrochemical behavior of the electrodes in 0.10 M NaOH and in the presence of glucose was characterized by cyclic voltammetry. The structural morphology and roughness of the oxy-hydroxides were characterized by using, scanning electron microscopy and atomic force microscopy. The nickel electrode, as well as nickel–chromium alloy electrodes, showed good catalytic activity for the anodic oxidation of glucose. A new and more complete reaction mechanism based on the electrochemical generation of a Ni(III) active site at the electrode surface and the formation of a complex between the analyte and this active site prior to the electron transfer step is proposed. The Ni–Cr (80:20) alloy electrode gave the highest oxidation peak current to glucose concentrations indicating a greater catalytic activity of the film, attributed to an increased roughness of the electro-catalytic film.

► SEM photomicrographs show homogeneous growth of the oxy-hydroxide layer.
► Chromium is homogeneously distributed in the matrix of nickel.
► The roughness of the oxy-hydroxide layer increases with the amount of chromium.
► Glucose is easily oxidized at oxy-hydroxide covered Ni or Ni–Cr alloy electrodes.
► The proposed mechanism allows fitting experimental calibration curves with theoretical data.