Pd-modified TiO2 electrode for electrochemical oxidation of hydrazine, formaldehyde and glucose

The electrocatalysis of the oxidation of hydrazine, formaldehyde and glucose on a nanoporous Pd-modified TiO2 electrode, prepared by the hydrothermal process, was investigated in 0.1 M NaOH solutions. The electrocatalytic activity of the Pd-modified TiO2 electrode for the electrochemical oxidation of hydrazine, formaldehyde and glucose is characterized by the low onset potentials of −0.80, −0.70 and −0.85 V (vs Ag,AgCl), respectively. Compared to the oxidation of formaldehyde and glucose, the hydrazine oxidation on the Pd-modified TiO2 presents the highest anodic oxidation current densities, showing that the Pd-modified TiO2 electrode is more electro-active for the hydrazine oxidation than for the oxidation of formaldehyde and glucose. Chronoamperograms at different concentrations of hydrazine and formaldehyde showed that the Pd-modified TiO2 electrode is a promising electrochemical sensor for the detection of hydrazine with a sensitivity of 0.554 mA cm−2 mM−1 and a detection limit of 0.023 mM, and for the detection of formaldehyde with a sensitivity of 0.20667 mA cm−2 mM−1 and a detection limit of 0.015 mM. However, it was found from the chronoamperometric responses at various glucose concentrations that a linear plot of the anodic oxidation current density versus glucose concentration developed only in the range of 7–35 mM glucose while an obvious deviation from the linear relationship was observed at both low and large glucose concentrations. Results show that the prepared Pd-modified TiO2 electrode could be applied to the direct liquid (hydrazine, formaldehyde, and glucose) fuel cells as an effective anodic catalyst, in addition to be a promising electrochemical sensor for the detection of hydrazine and formaldehyde.