Photoelectrochemical performance of multi-layered BiOx-TiO2/Ti electrodes for degradation of phenol and production of molecular hydrogen in water

Multi-layered BiOx-TiO2 electrodes were used for the oxidation of chemical contaminants coupled with the production of H-2 characterized by a synergistic enhancement. The BiOx-TiO2 electrodes were composed of a mixed-metal oxide array involving an under layer of TaOx-IrOx, a middle layer of BiOx-SnO2, and a top layer of BiOx-TiO2 deposited in a series on both sides of Ti foil. Cyclic voltammograms showed that the BiOx-TiO2 electrodes had an electrocatalytic activity for oxidation of phenol that was enhanced by 70% under illumination with AM 1.5 light. When the BiOx-TiO2 anode was coupled with a stainless steel cathode in a Na2SO4 electrolyte with phenol and irradiated with UV light at an applied DC voltage, the anodic phenol oxidation rate and the cathodic H-2 production rates were enhanced by factors of four and three, respectively, as compared to the sum of each light irradiation and direct DC electrolysis. These synergistic effects depend on the specific electrode composition and decrease on TaOx-IrOx and BiOx-SnO2 anodes in the absence of a top layer of BiOx-TiO2. These results indicate that the BiOx-TiO2 layer functions as the key photo-electrocatalyst. The heavy doping level of Bi (25 mol%) in TiO2 increases the electric conductivity of the parent TiO2. (c) 2011 Elsevier B.V. All rights reserved.