The anodic passivation of carbon electrodes

Based on literature data, the mechanism of anodic passivation of carbon electrodes is discussed. It is proposed that the first step of the anodic passivation process involves the electro-oxidation of carbon to CO(g), while the second step involves the parallel reactions of electro-oxidation of CO(g) to CO 2 (g), and oligomerization of CO(g) to C 6 O 6 (aq) [triquinoyl]. The standard redox potential for C 6 O 6 (aq)/6C is calculated to be +0.77 V, which is consistent with the observed passivation of carbon in the potential range of +1.0 to +1.7 V (vs. NHE).