Oxidative adsorption and hydrogen-mediated desorption of parabanic acid on Pt(111) electrodes

The adsorption properties of parabanic acid (PBA) on Pt(111) electrodes are described. The process takes place with charge transfer at potentials higher than 0.175 V. The PBA adlayer is particularly stable against oxidation or CO adsorption but is desorbed upon hydrogen adsorption. Comparison between voltammetric charges and charge displacement experiments, carried out at low potentials, enables the estimation of the PBA contribution to the overall voltammetric charge. Spectroelectroelectrochemical experiments suggest that PBA adsorption takes place through one of its nitrogen atoms, after breaking of the corresponding NH bond. The kinetics of the PBA adlayer desorption takes place through an instantaneous nucleation and growth mechanism, linked to the adsorption of hydrogen atoms.