Electrolysis of ammonium carbamate: a voltammetric and X-ray photoelectron spectroscopic investigation into the modification of carbon electrodes

Uchiyama et al. report that a glassy C (GC) electrode modified with surface amino groups via the electrochem. oxidn. of ammonium carbamate can react with catechol in a 1,4-Michael addn. through the surface amino groups. This was deduced from XPS data and the observation of a new reversible couple at less pos. potentials than the catechol redox couple, which was attributed to a quinone-imine-like adduct. Identical voltammetry is obsd. at an unmodified GC electrode that was oxidatively pre-treated in an identical fashion to that reported by Uchiyama et al. but in the absence of ammonium carbamate and any other sources of N. XPS characterization of a graphite electrode before and after electrolysis in ammonium carbamate soln. suggests that the N species on the C surface may not be as amino groups, but may due to adsorbed ammonium ions or the formation of amides. It is not the surface amino groups that are reacting with catechol, and alternative explanations are discussed. [on SciFinder(R)]