Contrasting photocatalytic performance of quantum-dot sensitized p-type and n-type TiO2 hierarchical nanocomposites under visible light

Abstract

In recent times, titanium dioxide (TiO2) has acquired greater attention owing to its efficient photocatalytic activity, low cost, stability, non-corrosive, high availability, and nontoxicity towards the environment and humans. However, two major drawbacks including a wide band gap of around ∼3.2 eV and a high recombination rate of the photogenerated charge carriers restrict its capability in practical application. In this work, we deposited metal chalcogenide-based quantum-dots of lead sulfide (PbS QDs) on P25-, p-type and n-type TiO2 nanoparticles by pseudo-successive ionic layer adsorption and reaction (p-SILAR) process to form hierarchical nanocomposite and studied the corresponding photocatalytic activity under visible light. Concurrently, improved optoelectronic characteristics were recorded for n-TiO2/PbS hierarchical nanocomposite due to low charge recombination evidenced from photoluminescence (PL) spectra and optimum PbS deposition evidenced from EDX analysis as compared to p-TiO2 and P25–TiO2. The n-TiO2/PbS hierarchical nanocomposite degrades 74.4% RhB dye under visible light in 120 min. The structural, morphological, and photocatalytic characteristics were investigated by scanning and transmission electron microscopy, PL spectra, UV–Vis spectrophotometry, and Fourier transforms infrared spectra. This work might offer new understandings on P25-, p- and n-TiO2/PbS hierarchical nanocomposites with improved photocatalytic performance for visible-light activated degradation of RhB.