Physico-Chemical nanomaterials science

The influence of thermal salt melt treatment of g-C3N4 upon their photocatalytic activity in the reaction of selective oxidation of benzyl alcohol under visible light
Shvalagin V.V.1, Siroshenko Yu.E.1, Kompanets M.O.1,2, Dmitryeva E.V.2, Kuzmenko A.B.2, Kuchmiy S.Ya.1
1 Photochemistry department, L.V. Pisarzhevskii Institute of Physical Chemistry of the NAS of Ukraine. Prospect Nauki, 31, Kyiv, Ukraine. 
E-mail: vitaliy.shvalagin@gmail.com
2 National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, 37, Prosp. Peremohy, Kyiv, 03056, Ukraine.

Under condition of thermal treatment of graphitic carbon nitride (g-C3N4) in KCl+LiCl melt it was obtained crystalline g-C3N4(T) with layered structure (Fig. a, b), high capability to absorb visible light and absence of luminescence, main reason of photogenerated charges decay. 

Fig. - SEM images of g-C3N4 (a), g-C3N4(Т) nanostructures (b) and kinetic curves of benzaldehyde formation during the benzyl alcohol oxidation in the presence of g-C3N4 тa g-C3N4(Т) (с).

Photocatalytic activity of g-C3N4(T) in visible light benzyl alcohol (BAlc) aerobic (both air and oxygen) oxidation to benzaldehyde (BAld) far exceeds activity of g-C3N4 (Fig. c). Under optimal conditions the rate of BAlc formation in the presence of g-C3N4(T) is higher than 3,6 ммоль h−1 g−1 along with conversion of BAlc of 81% and selectivity of BAld of 96%.
Higher photocatalytic activity of g-C3N4(T) can be explained in the following terms: smaller particle size, caused the efficient transfer of photogenerated charges to the active centers, where redox transformations occurred; increased visible light absorption; increased crystallinity and decreased number of defects – the centers of charges recombination.