Enhanced quinoline degradation by 3D stack Z-scheme photoelectrocatalytic system with Ag-TNTs photoanode and CN-CNWs photocathode

A novel 3D Stack Z-scheme photoelectrocatalytic (PEC) system was set up with Ag-TiO2/Ti nanotubes (Ag-TNTs) photoanode and g-C3N4/Cu2O/Cu nanowires (CN-CNWs) photocathode to realize efficient quinoline removal. Multiple mesh photoelectrodes were arranged in an alternating form (anode-cathode-anode) in the reactor to make full use of light and increase the contact possibility between catalysts and contaminants. Results suggested that the PEC system, CN-CNWs photocathode and O-2 condition could enhance the quinoline removal. Radical quenching experiment confirmed that hydroxyl radical (.OH) was dominant reactive oxygen species (ROS) in the PEC system and superoxide radical (.O-2(-)) generated on cathode was the reason for the increased quinoline removal efficiency with O-2. Compared with Cu2O/Cu, the CN-CNWs photocathode generated more H2O2 under different conditions. The mechanism was proposed: Driven by the bias, the anode electrons and cathode holes recombined and realized the simultaneous oxidation and reduction as a Z-scheme. It enhanced the reactions on both photoelectrodes and improved the system efficiency. This study provided a new and promising insight into the development of a novel PEC system for environmental remediation.