Kinetics and Mechanism of the Hydrogen Peroxide Reduction Reaction on a Graphite Carbon Nitride Sensor

The kinetics and mechanism of the hydrogen peroxide reduction reaction (HPRR) on a recently proposed carbon-based electrode is studied by means of experiments and simulations. The electrode is highly oriented pyrolytic graphite (HOPG) modified by the deposition of a graphite carbon nitride (g-C3N4) film. Current transients obtained from chronoamperometry measurements allow us to propose a kinetic model for the HPRR on the surface. The model produces excellent fits of current transients, providing sensible rate constants for each electrocatalytic step. The rate constants obtained are consistent with low energy barriers for each step, suggesting outstanding electrocatalytic activity of the g-C3N4/HOPG electrode. Moreover, different trends are found for low and high analyte concentrations, evidencing a change in the reaction mechanism. To clarify the mechanisms involved in the reaction, first-principles atomistic simulations were performed. The different reaction steps were modeled at the substrate/water interface, including solvent environment through continuum embedding approaches. The simulated thermodynamics and kinetics of the different processes show that a significant role in the electrocatalytic activity of the system is associated with the geometrical rearrangements of the interface, with a critical role played by the corrugation/decorrugation processes of the outermost sheet of the electrode.