Photoelectrocatalytic decomposition of dye in aqueous solution using Nafion as an electrolyte

In this research, methylene blue (MB) was use as a pollutant to investigate the capability of dye degradation of photocatalytic (UV/TiO2) and photoelectrocatalytic (UV/TiO2/bias) reaction, and also the condition for UV/TiO2/bias process was optimized. The photocatalytic process with bias potential was conducted in aqueous supporting electrolyte and with a proton exchange membrane (Nafion 117). Comparing with the general use of aqueous electrolyte (e.g. NaSO4, KCl, or NaCl) in photoelectrocatalytic process, this study was focused on the application of proton exchange membrane as a solid electrolyte for the photoelectrocatalytic decomposition of MB. The degradation of MB was experimentally studied by a varied reaction condition (i.e. solution pH value, UV light intensity, initial dye concentration, gas introduction, supporting electrolyte concentration, and bias potential). Degradation of MB was enhanced in UV/TiO2/bias process as compared to that carried out in UV/TiO2 process, especially as the Nafion membrane was applied (UV/TiO2/Nafion process). The photodegradation rates could also be boosted by increasing the concentration of supporting electrolyte, concentration of dissolving oxygen and UV light intensity. In UV/TiO2/Nafion process, the rate constants of MB degradation increased as increasing bias potential to a certain level, and then it leveled off. The suitable bias potentials for experiments conducted at pH 5.3 and 7.0 were found to be 0.5 and 0.6 V, respectively.