Simultaneous electrochemical production of hydrogen peroxide and degradation of organic pollutants

We investigated the effect of org. pollutants on the prodn. of hydrogen peroxide (H_2O_2) in the presence of Na_2SO_4 as an electrolyte under oxygen condition. TiO_2/IrO_2, graphite rod, and Ag/AgCl were used as an anode, a cathode, and a ref. electrode, resp. The electrochem. prodn. of H_2O_2 was significantly enhanced in the presence of org. pollutants. This result is ascribed to that the presence of org. pollutants reduces the anodic decompn. of H_2O_2. Org. pollutants prevent the surface complexation between hydroxyl group on the anode surface and H_2O_2. Furthermore, they can be acted as a scavenger of surface-bound hydroxyl radicals that decomp. H_2O_2. We also confirmed that the prodn. of H_2O_2 coupled with the degrdn. of org. pollutants at acidic pH than that at alk. condition. H_2O_2 is mainly produced via the proton coupled electron transfer (PCET) to oxygen. Org. pollutants are highly degraded at acidic condition, because they are electrostatically attracted with the anode surface and surface-bound OH radicals are more generated at a lower pH. This result indicates that the acidic pH provides a better condition for the degrdn. of org. pollutants and prodn. of H_2O_2