PHOTOCATALYTIC ACTIVITY OF NANO AND MICROCRYSTALLINE TIO2 HYBRID SYSTEMS INVOLVING PHTHALOCYANINE OR PORPHYRIN SENSITIZERS

Hybrid photocatalysts based on TiO2-anatase matrix, representing the both micro-and nano-structures, impregnated with selected lanthanide diphthalocyanine and metalloporphyrin sensitizers, were compared to evaluate their activity and effectiveness in a water suspension catalytic system designed to degrade 4-nitrophenol (4-NP) in a UV-stimulated reaction. Either type of the anatase catalyst was proved to be effective in mineralizing of 4-NP. However, kinetic studies confirmed that the composite's efficiency basically depends on the nature of the macromolecular sensitizer and to a minor extent on the dimensions (micro/nano) of the TiO2 particles. The apparent higher activity observed for the micro-TiO2 catalysts indicates improvement of the electron transfer between the sensitizer and the micro-crystalline structure of TiO2-anatase in contrast to the nano-crystalline matrix. The mechanistic aspects of the observed catalytic performances have been discussed.