Novel p–n Heterojunction Nanocomposite: TiO₂ QDs/ZnBi₂O₄ Photocatalyst with Considerably Enhanced Photocatalytic Activity under Visible-Light Irradiation

Abstract

The practical and widespread application of photocatalysts is limited by the problem of visible-light absorption, the immediate recombination of photogenerated electron–hole pairs, and the low number of active sites on their surface. We synthesized a series of novel TiO2 QDs/ZnBi2O4 nanocomposites through the hydrothermal method to overcome these problems. The formation of nanocomposites and their features were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, photocurrent, field-emission scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy, photoluminescence, Brunauer–Emmett–Teller, ultraviolet–visible diffuse reflection spectroscopy, and total organic carbon techniques. Among the different ratios of nanocomposites, the TiO2 QDs/ZnBi2O4 (10%) displayed the highest photocatalytic activity under visible-light irradiation, and the corresponding rhodamine B (RhB) degradation rate constant was 1022 × 10–4 min–1, which was nearly 77 and 5.9 times that of the TiO2 and TiO2 QD samples, respectively. In light of the mechanism study, the photocatalytic activity improvement can be ascribed to the p–n heterojunction formation, which led to an increase in the visible-light absorption, suppression of electron–hole recombination, and promotion of charge-carrier transfer. h+, •O2 –, and •OH were also identified as active species responsible for RhB photodegradation through the scavenging test. Phenol, Congo red, malachite green, and methyl orange were also degraded as various pollutants to ensure the prepared nanocomposites’ potential for practical applications. The nanocomposite stability was assessed during reuse evaluation experiments and showed good stability after four consecutive cycles. This work proposes a novel nanocomposite and provides an overview of its features for future applications.

Self-Assembly of a 3D Hollow BiOBr@Bi-MOF Heterostructure with Enhanced Photocatalytic Degradation of Dyes

“…Photocatalytic degradation has been considered to be an effective and promising method for removing organic dyes from industrial wastewater, − where the separation of photogenerated charge carriers and the effective absorption of dye molecules are crucial in the degradation processes . Thanks to their strong ability to capture dye molecules, high surface area, flexible skeleton structure, diversified functions, and intriguing tailorable features, metal–organic frameworks (MOFs) seem to be a promising porous photocatalyst in realizing the efficient degradation of dyes, − while MOFs themselves exhibit very poor transmission/separation efficiency of photogenerated charge carriers and limited visible light adsorption ability. − Consequently, several efficient inorganic semiconductor/MOF-based heterojunctions, such as TiO 2 @MOF, CdS–NRs/MOF, g-C 3 N 4 /MOF, and BiOBr/MIL-53­(Fe), − were developed to significantly improve their photocatalytic performance.…”

In situ synthesis of holey g-C3N4 nanosheets decorated by hydroxyapatite nanospheres as efficient visible light photocatalyst

“…The operational procedure of the reusability test includes collection of the nanocomposite powder by centrifuge aer each catalytic experiment, washing, and drying for reusing. [47][48][49] The obtained results showed that photocatalytic nanopowder composite has high catalytic performance even aer 5 runs (see Fig. 4Sb (ESI le †)).…”

Substantial enhancement in the photocatalytic degradation of organic/inorganic pollutants in water and photoelectrochemical activity using TiO2@Ag@LaFeO3 core–shell nanorods

“…In particular, LaFeO 3 is known as a p-type semiconductor, while TiO 2 shows an n-type feature. 33 It is worth mentioning that the Fermi energy ( E F ) for the n-type semiconductor is ∼0.1 V below the E CB , whereas the E F is 0.1 V above the VB for the p-type semiconductor. 34 Prior to the formation of the junction, the photogenerated electrons and holes on the CB and VB of LaFeO 3 are not transferred to the TiO 2 NRs due to the unmatched position of the CB and the VB.…”