The kinetics of the oxidation and reduction of H2O2 at a Pt electrode: A differential electrochemical mass spectrometric study

- O2 mass signal and Faradaic currents have been measured simultaneously by DEMS.
- Partial currents for the oxidation and reduction reactions of H2O2 are estimated based on experiments.
- A complex reaction with an apparently high overpotential doesn't always mean slow kinetics.

The kinetics of the oxidation and reduction of hydrogen peroxide (HPOOR, HPORR) at a Pt electrode in 0.1 M HClO4 + 2 mM H2O2 are investigated by Differential Electrochemical Mass Spectrometry (DEMS) in a flow cell. The O2 mass signal was recorded during cyclic voltammetry, and its potential dependence follows the shape of the cyclic voltammogram. Partial currents for HPOOR and HPORR are estimated based on the O2 mass signal and the total Faradaic current. The onset overpotential for HPORR at the Pt electrode is above 0.6 V. It is limited by the thermodynamics of OHad desorption, as is also the case with ORR. The onset overpotential for HPOOR is below 0.1 V, due to the faster consumption of H2O2 through HPORR at these potentials and the small bulk H2O2 concentration used.