Solar light-induced photoelectrocatalytic degradation of bisphenol-A on TiO2/ITO film anode and BDD cathode

The degradation of bisphenol-A (BPA), an endocrine disrupting compound, by means of photoelectrocatalytic (PEC), photocatalytic (PC) and electrochemical oxidation (EO) was investigated. An immobilized TiO2/ITO film, prepared by a sol–gel method, served as the photocatalyst and the anode, while boron-doped diamond (BDD) as the cathode. Photochemical reactions were induced by simulated solar radiation, while anodic bias in the range 0.04–0.32 mA/cm2 was applied to evaluate its effect on PC degradation, as well as the extent of direct EO. Experiments were conducted at initial BPA concentrations between 100 and 300 μg/L, solution pH between 1 and 9 and two different electrolytes, i.e. HClO4 and NaCl.Current application always improved substantially the performance of photocatalytic degradation with the extent of enhancement (computed from the pseudo-first order kinetic constants of PEC and PC) reaching values as high as 90%. The interaction between PC and EO was found to be synergistic rather than additive; this is thought to be due to (i) a more efficient separation of the photogenerated electrons and holes, and (ii) the enhanced formation of peroxide and other reactive oxygen species favored on the BDD cathode.BPA degradation rates generally increased with increasing applied current, at strongly acidic conditions and in the presence of NaCl as the supporting electrolyte; at the conditions in question, complete BPA conversion could be achieved in no longer than 60–90 min of reaction.

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► Bisphenol-A is degraded rapidly by photoelectrocatalysis on TiO2/ITO anode.
► Low currents promote considerably solar photocatalytic rates.
► Photocatalytic and electrochemical reactions act synergistically.
► BDD cathode seems to favor peroxide formation.