A composite of platelet-like orientated BiVO4 fused with MIL-125(Ti): Synthesis and characterization

Philani Vusumuzi Hlophe,Langelihle Nsikayezwe Dlamini,Lwazi Charles Mahlalela

doi:10.1038/s41598-019-46498-w

Philani Vusumuzi Hlophe, Langelihle Nsikayezwe Dlamini + Show 1 more

Open Access

https://doi.org/10.1038/s41598-019-46498-w

Copy DOI

Journal: Scientific Reports	Publication Date: Jul 11, 2019
Citations: 38	License type: open-access

Affiliation: University of Johannesburg

Abstract

The development of heterojunctions is the current focus of the scientific community as these materials are visible light active and the staggered positioning of their band edges combats electron-hole recombination which is the downside of most photocatalysts. In this work, a two- step hydrothermal synthesis protocol was utilized to fabricate a novel observable-light active material, composed of platelet-like BiVO4 and a titanium-based metal organic framework (MOF) called MIL-125(Ti). The tuning of specific morphologies, such as platelet-like in BiVO4, provides the exposure of most reactive facets which are more reactive towards photooxidation of organics in water, thus increasing their efficiency. The as-synthesized heterojunction was characterized by Transmission electron microscopy (TEM), scanning transmission microscopy (SEM), X-Ray diffraction (XRD), Raman spectroscopy, ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS), X-Ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectra. The formation of the heterojunction lead to a positive shift of the 3-2 Bi:Ti valence band (VB) (1.78 eV) when compared to 1.27 eV VB position of BiVO4. The PL and photoelectrochemical measurements revealed that the heterojunction photocatalyst designated 3-2 Bi-Ti demonstrated inhibited recombination rate (platelet-like BiVO4 > 3-2 Bi:Ti (PM) > MIL-125 > 1–1 Bi:Ti > 2–3 Bi:Ti > 3-2 Bi:Ti) and highly efficient interfacial charge shuttle between platelet-like BiVO4 and MIL-125(Ti) through the formed n-n junction.

Highlights

Several photocatalyst uses have been reported in literature and they include uses such as for storage of energy, sterilization, self-cleaning, air purification and wastewater treatment[1,2]
Further justification of the fabrication of the aforementioned materials is presented in Figs S3–5 (SEM-EDS mapping) which showed the presence of bismuth, vanadium, titanium, carbon and oxygen
The results revealed that the different heterojunctions were successfully synthesized

Summary

Introduction

Several photocatalyst uses have been reported in literature and they include uses such as for storage of energy, sterilization, self-cleaning, air purification and wastewater treatment[1,2] Work in these areas have been vastly explored using TiO2 as the base photocatalyst[3]. Even though there are available visible light active photocatalysts that have been used in photodegradation, such as BiVO4 and WO3, they further face an issue with fast electron-hole pairs recombination[5,6]. Heterojunction formation is a spatial separation technique which is band-edge offset dependant These band-edge offsets separate electrons and holes by directing these charge carriers to different materials via a junction[8]. Considerable attention has been given to bismuth vanadate (BiVO4) due to its narrow band gap of 2.4–2.5 eV, low-cost, nontoxicity, and favourable valence band position.

Methods

Results

Conclusion