M.Sc Thesis

M.Sc StudentKedem Shahar
SubjectComposite Nano-Fibers for Enhanced Photocatalytic Activity
DepartmentDepartment of Chemical Engineering
Supervisors PROFESSOR EMERITUS Yachin Cohen
PROF. Yaron Paz


Composite photocatalysts, based on TiO2 and a carbonaceous inert support, are becoming more and more popular in the field of photocatalysis.  This popularity reflects the success of the “Adsorb & Shuttle” (A&S) approach, according to which contaminants are first adsorbed on a substrate and subsequently diffuse to the TiO2 domains, where they are degraded.  This method was found to be very effective in the degradation of contaminants that otherwise hardly adsorb on the photocatalyst.  To achieve substantial composite photoactivity it is required to obtain good adherence between the photocatalyst and the inert components, as well as to achieve high surface area in the composite structure.  Although the surface area is not the only important parameter for high photocatalytic activity, it is quite understood that photocatalysis, being a surface phenomenon, may gain significantly by being performed on high surface area systems.  It is for this reason, that a nanofibrous structure may have an obvious advantage.

The research objective was to fabricate and characterize highly reactive, composite polymer nanofibers for photocatalytic degradation of contaminants. Composite nanofibers containing nanometric TiO2 particles and Multi Walled Carbon Nanotubes (MWCNT) dispersed in poly(acrylonitrile) (PAN) were prepared by the electrospinning (ES) technique. The structure and quality of the precursor dispersions were evaluated by Cryo-transmission electron microscopy (cryo-TEM). The fabricated nanofibers, the diameters of which were in the 20-200 nm range, contained well-oriented nanotubes and spherical TiO2 nanoparticles in close proximity. TEM images showed that the presence of carbon nanotubes reduces the extent by which the polymeric matrix is degraded upon exposure to UV light.  These findings were independently corroborated by complementary FTIR measurements, according to which the reduced self-degradation of the matrix was accompanied by an enhanced ability to photo-decompose model contaminants.