Enhancement of the degradation ability for organic pollutants via the synergistic effect of photoelectrocatalysis on a self-assembled perylene diimide (SA-PDI) thin film

A self-assembled perylene diimide (SA-PDI) film was prepared on an indium-tin-oxide (ITO) substrate and acted as a photoanode for the photoelectrocatalytic (PEC) degradation of some emerging contaminants under visible light irradiation (λ > 420 nm) and applied voltage. Due to the synergistic effect, the photocatalytic degradation rate by the SA-PDI film under visible light irradiation and an applied voltage of 2.1 V was 2.72 times and 14.5 times those of the PC and EC processes, respectively. The visible light irradiation not only generated a promoting effect on electrocatalytic (EC) oxidation at potentials above 1.2 V but also generated many more h+ for promoting the electrocatalytic oxidation of phenol. Furthermore, an applied voltage above 1.2 V could effectively improve the separation rate of electrons from the SA-PDI electrodes to the Pt electrodes, and then, much more O2- and OH could be generated for improving the photocatalytic (PC) oxidation efficiency. Therefore, the h+, OH and O2- could improve the synergistic effect of phenol oxidation during the PEC process. Moreover, the SA-PDI film appeared to have satisfactory stability in the PEC process. The SA-PDI film was also proven to be effective for two other contaminants, namely, 2,4-dichlorophenol, and ciprofloxacin.