Versatile TiO2 bandgap modification with metal, non-metal, noble metal, carbon material, and semiconductor for the photoelectrochemical water splitting and photocatalytic dye degradation performance

Abstract

TiO2 is a flexible material for photocatalytic applications owing to its convenient redox potential, eco-friendliness, and abundance. However, TiO2 requires minor adjustments to improve its absorption ability and to suppress charge carrier recombination. Hence, simple chemical procedures have been used to modify TiO2 by using metals (e.g., Ni), non-metals (e.g., N), noble metals (e.g., Ag), carbon materials (e.g., carbon nanofibers), and semiconductors (Fe2O3) as dopants or by forming composites. The photoelectrochemical (PEC) water splitting and photocatalytic dye degradation performance of the synthesized materials were compared. Fe2O3-TiO2 composite performed admirably in both reactions owing to its unique absorption strength and the formation of the heterojunction interface. Fe2O3-TiO2 demonstrated azo dye degradation efficiency of 94.4%. The Fe2O3-TiO2 photoelectrode in the PEC system exhibited a photocurrent response of 0.244 amp/cm2. This outstanding performance is due to the formation of the heterojunction interface that is attributable to the p-type and n-type semiconductor characteristics of the composite. Moreover, the noticeable absorption strength of Fe2O3-TiO2 enables the generation of additional charge carriers and effectively reduces the recombination rate owing to the formation of the heterojunction interface. Characterization techniques including X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, fluorescence spectroscopy, scanning electron microscopy, and transmission electron microscopy, were used to investigate the photocatalytic characteristics. This study promotes the development of new heterojunction semiconductors and dopants for photocatalytic applications.