A Unique Platinum/Titania/Polymer Based Hybrid Organic-Inorganic Heterostructure for Enhanced Photocatalytic Activity

Abstract

This work delineates synthesis, characterization, and photocatalytic activity of a ‘hybrid organic-inorganic’ catalyst system, that consists of titanium dioxide (TiO₂), platinum (Pt) and a conductive polymer (polypyrrole). The nanocomposite photocatalyst was developed to enhance exciton separation in the large band-gap oxide semiconductor (TiO₂) by depositing a noble metal co-catalyst (Pt) at the surface. The hybrid nanocomposite was constructed through sequential sequestration of the building blocks i.e., the monomer (pyrrole) and the metal (Pt) salt, using a photo-deposition technique. At the same time, improvement for light absorbance as compared to pristine TiO₂ was realized through the deposition of a conducting polymer (polypyrrole) at the surface of the semiconductor. The polypyrrole provides a pathway for hole migration, thereby increasing the overall lifetime of the separated charges. The benefit of this architecture is demonstrated through an enhanced degradation (~40% increase) of an industrial dye, methyl orange as a representative example, under visible-light illumination compared to unmodified TiO₂. Furthermore, photo(electro)chemical analysis of the composite offered valuable insights into the charge transport mechanism. It led to the conclusion that photo illumination results in the participating components to (a) enable visible light absorbance and, (b) facilitate charge separation and utilization at the hetero-interfaces leading to redox activity. Insights into the mechanism of charge separation and transport from chronopotentiometric analysis suggest that the assembly is successful and works as desired.