Photoelectrocatalytic degradation of microcystin-LR using Ag/AgCl/TiO2 nanotube arrays electrode under visible light irradiation

• Ag/AgCl/TiO2 is effective for the photoelectrochemical degradation of microcystin-LR (MC-LR).
• The photogenerated h+, OH and O2- are the major ROS for the degradation of MC-LR.
• The degradation rate of MC-LR increases with the decrease of initial pH.
• Cl− can improve the degradation of MC-LR.

The fabrication of Ag/AgCl/TiO2 nanotube arrays electrode was achieved by a two-step method involving an electrochemical anodization process and an electrodeposition process. The Ag/AgCl/TiO2 nanotube arrays electrode was employed for the photoelectrocatalytic (PEC) degradation of microcystin-LR (MC-LR) and found to be an effective visible-light-driven (VLD) PEC material. The reactive oxidative species (ROS) are observed to be generated from the hole (h+) and electron (e−) in the PEC process. The mechanism for PEC degradation of the MC-LR is investigated using different scavengers and found that the major reactive species generated in situ are h+, OH and O2-, which are actually responsible for the degradation of MC-LR. The effect of operating parameters, such as initial pH of MC-LR solution and the type of anions, are studied. And the results show that the degradation of MC-LR was highly promoted in NaCl electrolyte, and the degradation was enhanced in an acid medium.