Investigation of formic acid oxidation on Ti/IrO2 electrodes

A model has been proposed according to which the voltammetric charge involved in the Ti/IrO₂ electrodes is due to two contributions: a faradaic contribution due to surface redox activities at the IrO₂ coating and a non-faradaic contribution due to the charging of electrical double layer (). The later has been proposed as a tool for the estimation of the relative surface area of the Ti/IrO₂ electrodes.Differential electrochemical mass spectrometry (DEMS) measurements using H₂¹⁸O has demonstrated that we are dealing with an active electrode in which the surface redox couple IrO₃/IrO₂ acts as mediator in the oxidation of formic acid (FA).From the voltammetric measurements using different IrO₂ loading and FA concentrations, the kinetic parameters of FA oxidation via the surface redox couple IrO₃/IrO₂ have been determined.Finally a model has been proposed considering that FA oxidation at Ti/IrO₂ anodes is controlled by mass transfer. The good agreement between the experimental results and the model indicates that the surface reaction between FA and the electrogenerated IrO₃ is a fast reaction.