Fig. 4: Photo-assisted electrochemical oxidation processes.

a, Ultraviolet (UV)-electrolyser and photovoltaic (PV)-electrolyser system. b, Photoelectrochemical advanced oxidation (PECAO) system. c, Key properties of electrochemical advanced oxidation systems for practical wastewater treatment applications. The pretreatment reduces the interference of the influent water, whereas the continuous-flow mode enhances throughput capacity and operational stability. Under sunlight, the photoanode absorbs light energy to generate holes and electrons. A thin layer on the photoanode improves light utilization efficiency. The cathode catalyses oxygen reduction to produce reactive oxygen species (ROS), with electrolyte additives accelerating their generation. The mechanical durability of the electrodes determines their lifespan, directly influencing the overall device longevity. Low ohmic loss in the system minimizes unnecessary electrical consumption and improves operational stability. By coupling the photoanode and cathode, organic pollutants are efficiently removed. Furthermore, tuning catalytic properties and operating parameters can yield targeted value-added by-products, enhancing the economic viability of the process. D, degradation products; P, pollutants.