Oxidation of phenol on platinum electrodes rapidly leads to the formation of a passivating film on the surface of these electrodes. Studies of cyclic voltammetry and chronoamperometry combined with high-performance liquid chromatography (HPLC) analyses have shown that the presence of carbon black avoids these phenomena of passivation and thus allows the complete mineralization of phenol. The nature of carbon black and the pH value are two important factors which are studied here. VULCAN XC-72 R, an intrinsic p-type semiconductor, having a large specific area, showed all its efficiency when cyclic voltammetry experiments were carried out in an acid medium (pH 2.2). HPLC analyses revealed the appearance of several by-products such as hydroquinone and benzoquinone, and maleic and fumaric acids.