טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentShemer Guy
SubjectEnhanced Photocatalysis Baesd on Biasing of Interdigitated
Microelectrodes Made of Titanium Dioxide
DepartmentDepartment of Chemical Engineering
Supervisor Professor Yaron Paz


Abstract

Titanium dioxide (TiO2) is a well-known photocatalyst, capable of decomposing many organic and inorganic pollutants, and thus, suitable for purifying air and water. TiO2 has several disadvantages, most notably is its low quantum efficiency, which can be linked to its high recombination rate of electron-hole pairs.

Applying a small positive bias to the TiO2 electrode can significantly improve the photocatalytic properties of the TiO2.  To date, studies were done under conditions where the distance between the electrodes was quite considerable hence by-products formed at the anode (namely super-oxide) could hardly participate in the reactions on the TiO2 surface.

In this research, a device with interdigitated micro-electrodes made of TiO2 and Pt was proposed. The influence of a small applied bias and the distance between the micro-electrodes (50 to 100 m) on the photocatalytic properties of TiO2 was checked. For this purpose, a fabrication process was developed. The devices were characterized and tested (photocatalyticly).

The photocatalytic experiments were: photocatalysis in air (photoelectrodegradation of a chemisorbed organic monolayer was measured in air); photo-current measurements (photo-current vs. applied potential was measured); photocatalysis in water (photoelectrodegradation of a dye was measured).

From the photocatalysis experiments in air, an optimal positive applied bias in the range of 0 - 0.6 V was found.

From the photo-current experiments, a partial agreement with the theory and with results from the literature (on different systems) was observed.

From Photocatalysis experiments in water it was observed that applying a small bias can significantly enhance the photodegradation rate. Increasing the applied bias (in the range of 0 - 0.4 V) had a gradually decreasing effect on the improvement of the photodegradation rate.