Efficient Anodic Degradation of Phenol Paired to Improved Cathodic Production of H2O2 at BDD Electrodes

Abstract

Electrochemical degradation of phenol (PhOH) with simultaneous reduction of O2(g) to H2O2 in acidic media was performed in an H-type divided cell (500 mL), separated with a cationic membrane (Nafion 424). Boron-doped diamond (BDD) electrodes were used as anode and cathode. The study was divided into three stages: (a) Electroanalytical study of the oxygen reduction reaction (ORR) to H2O2 by hydrodynamic linear-sweep voltammetry with a BDD-RDE in acidic and alkaline solutions; (b) galvanostatic ORR to H2O2 at BDD electrode in acidic solution (unpaired system); (c) pairing the anodic PhOH degradation with the H2O2 cathodic production at BDD electrodes. The best production of H2O2 under our conditions with the unpaired system was 250.1 mg L−1 at 1.5 mA cm−2 after 540 min of electrolysis, the highest reported to date for BDD electrode in acidic media. Total mineralization of 100 mg L−1 of PhOH in the paired system required a higher current density (i.e., 2.5 mA cm−2); in spite of this, the process is one order of magnitude faster than any electrochemical process previously reported.