BiOCl Nanoplates Doped with Fe³⁺ Ions for the Visible-Light Degradation of Aqueous Pollutants

Abstract

Two-dimensional (2D) layered ultrathin bismuth oxychloride nanoplate (BiOCl-UTN) photocatalysts are highly active only under ultraviolet light (energy band gap E g: 3.0–3.1 eV). Herein, unlike using conventional closed-vessel high-temperature synthetic routes, we prepared unprecedented well-crystalline 2D Fe3+ ion-incorporated BiOCl-UTNs [Fe­(III)-BiOCl-UTNs] having ultrathin thicknesses of about 4–5 nm and planar sizes of about 30–50 nm in an open vessel at room temperature and then used in photocatalysis under visible light. The present approach is poly­(sodium 4-styrenesulfonate) (PSS)-aided, in which the formation of the distinct intermediate composite [PSS-Bi­(OCH2CH2OH)-Fe3+] significantly inhibits the habitual spontaneous growth of BiOCl along the ⟨001⟩ plane and results in Fe­(III)-BiOCl-UTNs. The synthesis shows robust reproducibility and allows large-scale production (5.2 g) with a well-controlled morphology, size, and thickness. Instead of using a tedious high-speed centrifugation process, the Fe­(III)-BiOCl-UTN product is obtained via electrolyte sedimentation which is facile and cost-effective. The successful doping of Fe3+ ions into BiOCl-UTNs, the sustainable layered structure, and the stable lattice arrangement endow Fe­(III)-BiOCl-UTNs with a narrower band gap (E g: 2.55 eV). As-prepared Fe­(III)-BiOCl-UTNs exhibit enhanced separation of photoexcited electrons–holes, rapid transfer of excited electrons to the surface, and significant potential to suppress electron–hole recombination. Consequently, under visible light, Fe­(III)-BiOCl-UTNs achieved a substantially improved catalytic performance (>99%, five-cycle recyclability) to photoreduce Cr­(VI) ions and photodegrade rhodamine B from aqueous solutions. The present performance surpasses pristine BiOCl-UTNs and state-of-the-art photocatalysts. Moreover, we disclosed the morphological optimization, predominant role of e– and •O2 radicals, and typical photocatalytic reaction mechanism. This work offers the first facile and cost-effective alternative to fabricate the iron-doped layered photocatalyst with superior catalytic activity, extendable for other functional materials and diverse practical applications.

Screen-printed p–n BiOCl/BiFeO3 heterojunctions for efficient photocatalytic degradation of Rhodamine B

“…34 The first peak corresponds to A 1 external Bi–Cl stretching mode, while the second and third peaks are respectively A 1 and E g internal Bi–Cl stretching mode. 20,26 In the BiOCl spectrum, some residual contribution from the BFO powders underneath can still be observed at 73 and 167 cm −1 . The low-concentration Bi 2 O 3 phase is not detected in the Raman signal.…”

“…16,17 Undoped BFO and BiOCl also have direct and indirect energy bandgap energies ranging between 2.1-2.5 eV (BFO) and 3.0-3.4 eV (BiOCl). 13,14,[18][19][20][21] To further increase BiOCl's visible light absorption, many strategies have been explored including elemental doping, incorporation of oxygen vacancies, addition of co-catalysts, morphology control or creation of heterostructures. 11 Good heterostructures require a direct epitaxial contact between two different crystalline structures.…”

A review on bismuth oxyhalide based materials for photocatalysis

“…Numerous transition metal ions like Fe, 116,[119][120][121][122] Cu, 123 Zn, 124, 125 Ti, 118 Al, 126 Sn, 127 , and Mn 128 have been used as a dopant in BiOX substances. For instance, Mn doping in BiOCl with oxygen vacancies can contract the bandgap and expand the optical absorption to the visible and IR regions of light.…”

Construction of a hydrangea-like Bi2WO6/BiOCl composite as a high-performance photocatalyst

“…20 To overcome these problems, tailoring the microstructure, heteroatom doping and the construction of a heterojunction have been adopted as the most effective strategies. [21][22][23] Among the bismuthcontaining semiconductors, Bi 2 WO 6 and BiOCl have been widely reported as highly efficient photocatalysts due to their easy preparation and superior photoelectric properties. 24 In terms of their crystal structures, Bi 2 WO 6 has alternating perovskite-like (WO 4 ) 2À and (Bi 2 O 2 ) 2+ layers, which endows Bi 2 WO 6 with a moderate band gap (B2.7 eV) and the fast separation of photoinduced carriers.…”