A screening of carbon-based electrodes (GC, BDD, F-BDD) as non-catalytic reference materials for investigations in organic electrocatalysis

In a systematic cyclovoltammetric investigation of electrochemical organic processes, the electrocatalytic effects of the tested electrode materials (i.e., their ability to lower the activation barrier for the process) are conveniently quantified in terms of difference of the peak potential obtained on the catalytic electrode vs. the peak potential obtained on a cathode free of electrocatalytic effects (for the target process). Glassy carbon (GC), which has often been the favorite electrode material for mechanistic investigations of outer-sphere electron transfer processes, is here compared with as prepared, hydrogen-terminated boron-doped diamond (BDD) and fluorinated boron-doped diamond (F-BDD). They are also carbon-based materials but, to a higher degree, terminated with inert groups possibly preventing specific adsorption. Specifically, the comparison is carried out considering the electrocatalytic reduction of model organic halides. While the current densities are comparable, the reduction potentials are regularly shifted in the negative direction, in the sequence GC < BDD < F-BDD, consistently with the decreasing number of O groups and the increasing number of inert H and/or F atoms, the latter species possibly exerting even a repulsing effect towards the reacting halide adsorption.