Superior Photocatalytic Activity of Polypyrrole Polymer Nanostructuresprepared by Radiolysis in Water and Dichloromethane

Abstract

Conjugated polymers have emerged as very active photocatalysts under visible light. Among these materials, nanostructured polypyrrole (PPy) has recently been used as photocatalyst for degradation of environmental pollutants under UV as well as visible light. In the present study, we specifically explored the photocatalytic activity of conducting PPy synthesized by radiolysis, either in water (PPy_H2O) or in dichloromethane solvent (PPy_DCM), in the absence of any dopant or template. The successful preparation of both kinds of conducting polymers was confirmed by complementary spectroscopic techniques and morphological characterizations. Besides, the photocatalytic activity of both materials was evaluated in the degradation of phenol as model pollutant in aqueous solution. PPy_H2O as well as PPy_DCM were found to exhibit remarkably high photocatalytic activity under both UV and visible light. These organic photocatalysts remain very stable after several cycles, and thus easily reusable. Interestingly, PPy_DCM clearly appears as the most efficient photocatalyst, due to its longer chain length, its doped nature, its lower optical band gap and its large extended absorption band from the UV to the near infrared region. The present work definitely validates radiation chemistry as an alternative approach to synthesize conducting polymer-based photocatalysts. The obtained results also highlight the fact that radiosynthesized PPy, especially those prepared in dichloromethane, constitute promising candidates for water depollution.

Keywords: Radiolysis, Conducting polymers, Polypyrrole, Photocatalysis, Organic Photocatalysts