Preparation of porous PPy-TiO2 composites: Improved visible light photoactivity and the mechanism

Novel hierarchically macroporous PPy-TiO2 composites were synthesized by polymerization of pyrrole with macro/mesoporous TiO2 as a photosensitizer and template. Complete hybridization was realized because the dual porous structure of the sensitizing material was efficient to infiltrate the pyrrole monomer into its interior and introduce UV photons penetrating the porous network for local polymerization. The collective performance favors the fabrication of hybrids with a well-adhered interface between the polymer monomer and the inorganic sensitizing material. The covalent bonding interaction between N and Ti atoms was proved by FTIR, XPS, Raman spectrum and elemental analysis. Mechanisms about the polymerization and interface interaction were discussed in terms of semiconductor photocatalysis. The photo response of the composites is shifted into visible light spectrum (2.67-2.92 eV), showing a band gap narrowing as compared to 3.18 eV of the bare TiO2. The sample of PPy-TiO2-24 shows the higher photoactivity and photocurrent than other composites and the TiO2 under visible light irradiation due to its ordered macropores, uniform PPy sensitizer layer, and relatively less hole-electron recombination rate. This work demonstrates the preparation of organic-inorganic composites with new nanostructures and enhanced visible light properties, and the mechanisms. (C) 2013 Elsevier B.V. All rights reserved.