Fabrication of TiO2/Fe2O3/CdS systems: effects of Fe2O3 and CdS content on superior photocatalytic activity

Abstract

A heterostructured material of CdS and Fe₂O₃ nanoparticle-modified TiO₂ nanotube array (NTA) photoelectrode (TiO₂/Fe₂O₃/CdS) is reported in this work. TiO₂/Fe₂O₃ was prepared by annealing TiO₂ NTAs pre-loaded with Fe(OH)₃, which was uniformly clung to TiO₂ NTAs using sequential chemical bath deposition (S-CBD). Subsequently, CdS nanoparticles were deposited on TiO₂/Fe₂O₃ using the successive ion layer adsorption and reaction (SILAR) technique. Three-dimensional (3D) TiO₂/Fe₂O₃/CdS samples generated a photocurrent of approximately 4.92 mA cm⁻², with a photoconversion efficiency of 4.36%, which is more than 20 times higher than that of bare TiO₂ NTAs (0.22%) and 6 times that of TiO₂/Fe₂O₃ (0.71%). The photocatalytic activity was evaluated by the degradation of p-nitrophenol (PNP) under visible light (λ > 420 nm). The TiO₂/Fe₂O₃/CdS exhibited the best photocatalytic activity among all samples. Almost all PNP was degraded by TiO₂/Fe₂O₃/CdS within 120 min. The enhancement of photocatalytic activity could be attributed to the promoted photo-induced electron and hole separation and migration on the basis of photoluminescence spectra, photocurrent measurements, and open-circuit photovoltage responses. In addition, the newly synthesized TiO₂/Fe₂O₃/CdS can maintain high photocatalytic efficiency for five reuse cycles. Our findings provide a new idea for the low cost synthesis of high performance photocatalysts for the photodegradation of organic pollutants in aqueous solution.