Titanium Oxide Electrocatalytic Membrane Filtration: "Two Faces" of Oxygen Vacancies in Generation and Transformation of Reactive Oxygen Species

Oxygenvacancies show "two faces" toward ROSgeneration and transformation during metal oxide electrocatalyticmembrane filtration, acting as promoters at low concentrations butinhibitors at high concentrations. Oxygen vacancies are crucial to the production of reactiveoxygenspecies (ROS) in the metal oxide electrocatalytic membrane (MO x EM) process. Here, using cathodic TiO x EM as a model, we thoroughly reveal theroles of oxygen vacancies in ROS generation and transformation. Oxygenvacancies significantly promote H2O2 and (OH)-O-& BULL; production at low concentrations (increment <35%)but inhibit their production at high concentrations (increment >35%).Electrochemical analysis discloses that the enhancement of ROS productionprofits from the acceleration of charge transfer kinetics by bothbulk and surface oxygen vacancies, whereas we attribute the declinein ROS production to the strong adsorption of ROS by surface oxygenvacancies. It is strongly supported by theoretical calculations thatreveal the promoted adsorption of *OOH and *OH by oxygen vacancies,which intensifies the capture and scavenging of H2O2 and (OH)-O-& BULL;. Moreover, the gradual increaseof interaction time between ROS and oxygen vacancies (from & SIM;1to & SIM;5 s) notably reduces the generation and transformationefficiency of ROS, further highlighting the detrimental impact ofoxygen vacancies. In summary, oxygen vacancies show "two faces"toward ROS generation and transformation, acting as ROS promotersat low concentrations but inhibitors at high concentrations. A mediumoxygen vacancy concentration is preferred for ROS production, thuscausing impressive pollutant removal (>95% removal of bisphenolAwithin 1.2-1.5 s at 360-440 LMH). This study providesguidance on regulating ROS generation and transformation by manipulatingthe oxygen vacancy concentration to enhance the decontamination efficiencyof MO x EMs.