Scavenger-Supported Photocatalytic Evidence of an Extended Type I Electronic Structure of the TiO₂@Fe₂O₃ Interface

Abstract

Heterostructures of TiO 2 @Fe 2 O 3 with a specific electronic structure and morphology enable us to control the interfacial charge transport necessary for their efficient photocatalytic performance. In spite of the extensive research, there still remains a profound ambiguity as far as the band alignment at the interface of TiO 2 @Fe 2 O 3 is concerned. In this work, the extended type I heterojunction between anatase TiO 2 nanocrystals and α-Fe 2 O 3 hematite nanograins is proposed. Experimental evidence supporting this conclusion is based on direct measurements such as optical spectroscopy, X-ray photoemission spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), and the results of indirect studies of photocatalytic decomposition of rhodamine B (RhB) with selected scavengers of various active species of OH • , h • , e − , and • O 2 − . The presence of small 6−8 nm Fe 2 O 3 crystallites at the surface of TiO 2 has been confirmed in HRTEM images. Irregular 15−50 nm needle-like hematite grains could be observed in scanning electron micrographs. Substitutional incorporation of Fe 3+ ions into the TiO 2 crystal lattice is predicted by a 0.16% decrease in lattice parameter a and a 0.08% change of c, as well as by a shift of the Raman E g(1) peak from 143 cm −1 in pure TiO 2 to 149 cm −1 in Fe 2 O 3 -modified TiO 2 . Analysis of O 1s XPS spectra corroborates this conclusion, indicating the formation of oxygen vacancies at the surface of titanium(IV) oxide. The presence of the Fe 3+ impurity level in the forbidden band gap of TiO 2 is revealed by the 2.80 eV optical transition. The size effect is responsible for the absorption feature appearing at 2.48 eV. Increased photocatalytic activity within the visible range suggests that the electron transfer involves high energy levels of Fe 2 O 3 . Well-programed experiments with scavengers allow us to eliminate the less probable mechanisms of RhB photodecomposition and propose a band diagram of the TiO 2 @Fe 2 O 3 heterojunction.

Green Synthesis of TiO2 Nanoparticles in a Deep Eutectic Solvent for High‐Performance Photocatalysis: The Role of the Cosolvent

“…Due to its carcinogenetic and non-biodegradable nature, it is crucial to explore efficient methods and materials to remove RhB from wastewater and industrial effluents. [50][51][52] We have examined the potential of our TiO 2 nanoparticles as photocatalysts towards the degradation of RhB under UV light.…”

“…Rhodamin B (RhB) is a water‐soluble fluorescent dye of xanthene class that is extensively used in different industries for paper and textile dyeing as well as for the production of laser dye. Due to its carcinogenetic and non‐biodegradable nature, it is crucial to explore efficient methods and materials to remove RhB from wastewater and industrial effluents [50–52] . We have examined the potential of our TiO 2 nanoparticles as photocatalysts towards the degradation of RhB under UV light.…”

Design and development of a Sb2WO6/graphene oxide (2D) nanocomposite as novel electrochemical metal-ion sensor and improved photocatalyst for the degradation of tetracycline

“…58 To effectively identify the primary reactive oxygen species involved in the photocatalytic activity, photocatalysis tests were conducted in the presence of selected additives as radical scavengers. Isopropyl alcohol (IPA), ammonium oxalate (AO), and p -benzoquinone (BQ) were used as quenchers for the hydroxyl radicals (OH˙), photogenerated holes (h + ), and superoxide anion radicals (O 2 ˙ − ), respectively 59 (Fig. S4a, ESI†).…”

TiO2 Nanoparticles for Methylene Blue Dye Degradation: Effect of Calcination Temperature

“…While MB dye's efficiency is drastically reduced by the BQ quencher, this implies that superoxide radicals are the principal reactive species responsible for the decomposition of organic pollutants. 71…”