My main focus during my Ph.D. study is to the application of electrochemistry in water treatment. Examples are membrane fouling and recovery on an inorganic conductive membrane using electrochemical impedance spectroscopy, mechanistic study of the validity of hydroxyl radical probe used in electrochemical processes, and surface passivation and regeneration on a substoichiometric TiO2 electrode using scanning electrochemical microscope.
- Membrane fouling and recovery using electrochemical impedance spectroscopy
Traditional membrane fouling detections are ineffective, for example, filtration law cannot be applied to large systems, imaging technique such as SEM, requires the destruction of membrane. Use of electrochemical impedance spectroscopy to detect membrane fouling takes advantage of the conductive nature of the Magneli phase inorganic membrane. This method injects a sinusoidal alternating potential signal with different frequencies into the asymmetric membrane, the penetration depth of this signal inversely depends on the frequency, and therefore different layers of the membrane can be resolved under different frequency regime. We have successfully constructed a mathematical transmission line model to simulation different fouling mechanisms, and justified with experiments.
- Mechanistic study of the validity of hydroxyl radical probe used in electrochemical processes
As a reactive oxygen species, hydroxyl radicals have been extensively used in several water treatment processes, such as advanced oxidation processes and electrochemical advanced oxidation processes. Meanwhile, hydroxyl radicals in the redox flow battery and flow cell cathode from the oxygen reduction reaction could damage the organic membrane separator. Researchers in the electrochemical area always use the hydroxyl radical probes in other system to the electrochemical systems without questioning the validity, due to the neglect of direct electron transfer under a low applied potential. In this work, we examined four most commonly used hydroxyl radical probes found in the literature, and found the terephthalic acid and benzoquinone are the best candidates, at the same time, it should be noted that benzoquinone can be easily reduced at the cathode side to produce hydroquinone, a divided cell need to be adopted if used.
So my experience has trained me to a electrochemist, membrane and water treatment scientist.