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.