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US-12624468-B2 - Large scale, monodispersed octahedral BiVO4 microcrystals, photostability and water oxidation thereof

US12624468B2US 12624468 B2US12624468 B2US 12624468B2US-12624468-B2

Abstract

A method of preparing bismuth vanadate particles is described. The bismuth vanadate particles prepared via ultrasonication and hydrothermal treatment exhibit controlled morphology (e.g., octahedral shape) and crystallinity (e.g., tetragonal crystal symmetry). A photoelectrode containing bismuth vanadate particles and a method of using the photoelectrode in a photoelectrochemical cell for water splitting is also provided.

Inventors

  • Abuzar Khan
  • Ibrahim Khan
  • Mohd Yusuf Khan

Assignees

  • KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS

Dates

Publication Date
20260512
Application Date
20211020

Claims (11)

  1. 1 . A method of preparing bismuth vanadate particles, the method comprising: mixing a bismuth (III) salt and an acidic aqueous solution to form a bismuth mixture; mixing a metavanadate salt and a basic aqueous solution to form a vanadate mixture; mixing the vanadate mixture and the bismuth mixture to form a reaction mixture that is simultaneously subjected to ultrasonication; and hydrothermally treating the reaction mixture thereby forming the bismuth vanadate particles, wherein: the bismuth vanadate particles have an octahedral shape; and the bismuth vanadate particles comprise crystalline BiVO 4 having a tetragonal crystal symmetry.
  2. 2 . The method of claim 1 , wherein the bismuth vanadate particles have an average particle size in a range of 0.8-6 μm.
  3. 3 . The method of claim 1 , wherein the reaction mixture is subjected to ultrasonication at a frequency in a range of 17.5-22.5 kHz.
  4. 4 . The method of claim 1 , wherein the reaction mixture is subjected to ultrasonication at an amplitude in a range of from 18 to 48 microns for an ultrasonicator equipped with a horn of 0.5 inch diameter.
  5. 5 . The method of claim 4 , wherein the reaction mixture is subjected to ultrasonication at an amplitude in a range of from 28 to 35 microns for an ultrasonicator equipped with a horn of 0.5 inch diameter, and wherein the bismuth vanadate particles consist essentially of crystalline BiVO 4 having a tetragonal crystal symmetry.
  6. 6 . The method of claim 1 , wherein the reaction mixture is hydrothermally treated at a temperature of 100-250° C.
  7. 7 . The method of claim 1 , wherein the bismuth (III) salt is bismuth (III) nitrate.
  8. 8 . The method of claim 1 , wherein the metavanadate salt is ammonium metavanadate.
  9. 9 . The method of claim 1 , wherein the acidic aqueous solution comprises nitric acid, and the basic aqueous solution comprises sodium hydroxide.
  10. 10 . The method of claim 1 , wherein the bismuth mixture further comprises an ionic surfactant.
  11. 11 . The method of claim 10 , wherein the ionic surfactant is sodium dodecylbenzene sulfonate.

Description

BACKGROUND OF THE INVENTION Technical Field The present disclosure relates to a method of making bismuth vanadate particles, and a method of using bismuth vanadate particles as part of a photoelectrode for water splitting. Description of the Related Art The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention. Facet-controlling has become an attractive method to enhance the catalytic behavior of semiconducting photocatalysts through modification of their morphology and crystallinity. Photochemical processes including light absorption and charge separation could be improved using photocatalysts having a specifically designed morphology and surface atomic structures [Y. Zhao, R. Li, L. Mu, C. Li, Significance of Crystal Morphology Controlling in Semiconductor-Based Photocatalysis: A Case Study on BiVO4 Photocatalyst, Cryst. Growth Des. 17 (2017) 2923-2928, incorporated herein by reference in its entirety]. For instance, morphological and facet tuning of anatase TiO2 {001} facets created highly photoactive species. Because of the large surface area of {001} facets, the exposed facets of anatase TiO2 grown as a single crystal generated an efficient photoresponse. Controlling the morphology and crystallinity of Platonian-shaped (tetrahedra, hexahedra, octahedra, etc.) metal oxides and metal vanadates is a challenge to research efforts because less is known about their crystallization than non-Platonian shaped metal oxides [X. Wang, D. Liao, H. Yu, J. Yu, Highly efficient BiVO4 single-crystal photocatalyst with selective Ag2O—Ag modification: Orientation transport, rapid interfacial transfer and catalytic reaction, Dalt. Trans. 47 (2018) 6370-6377, incorporated herein by reference in its entirety]. Metal vanadates are an emerging class of photocatalytic materials for photoelectrochemical applications. Among metal vanadates, BiVO4 (BV) has attracted attention for satisfactory optoelectrical characteristics (e.g., a bandgap of ˜2.40 eV), along with ionic conductivity, ferroelasticity, acousto-optical, and photochromic properties. Further, BV possesses high chemical stability and low toxicity [K. Wenderich, G. Mul, Methods, Mechanism, and Applications of Photodeposition in Photocatalysis: A Review, Chem. Rev. 116 (2016) 14587-14619; S. Wang, G. Liu, L. Wang, Crystal Facet Engineering of Photoelectrodes for Photoelectrochemical Water Splitting, Chem. Rev. 119 (2019) 5192-5247; and J. K. Cooper, S. Gul, F. M. Toma, L. Chen, Y. S. Liu, J. Guo, J. W. Ager, J. Yano, I. D. Sharp, Indirect bandgap and optical properties of monoclinic bismuth vanadate, J. Phys. Chem. C. 119 (2015) 2969-2974, each incorporated herein by reference in their entirety]. Under visible light irradiation, BV materials can be used in photoelectrochemical (PEC) applications as photoanodes. Because of its suitable band positions, chemical stability, sensitivity to visible light, and low cost, BV may be an alternative photocatalyst to TiO2 for solar energy conversion and environmental protection applications [G.-L. Li, First-principles investigation of the surface properties of fergusonite-type monoclinic BiVO4 photocatalyst, RSC Adv. 7 (2017) 9130-9140; and H. Gong, N. Freudenberg, M. Nie, R. Van De Krol, K. Ellmer, BiVO4 photoanodes for water splitting with high injection efficiency, deposited by reactive magnetron co-sputtering, AIP Adv. 6 (2016), each incorporated herein by reference in their entirety]. In view of the forgoing, one objective of the present disclosure is to provide a method of preparing bismuth vanadate particles. The bismuth vanadate particles may be present on a conducting substrate to form a photoelectrode used, for example, in a photoelectrochemical cell for water splitting. BRIEF SUMMARY OF THE INVENTION According to a first aspect, the present disclosure relates to a method of preparing bismuth vanadate particles that have an octahedral shape and comprise crystalline BiVO4 having a tetragonal crystal symmetry. The method involves the steps of (i) mixing a bismuth(III) salt and an acidic aqueous solution to form a bismuth mixture, (ii) mixing a metavanadate salt and a basic aqueous solution to form a vanadate mixture, (iii) mixing the vanadate mixture and the bismuth mixture to form a reaction mixture that is simultaneously subjected to ultrasonication, and (iv) hydrothermally treating the reaction mixture, thereby forming the bismuth vanadate particles. In one embodiment, the bismuth vanadate particles have an average particle size in a range of 0.8-6 μm. In one embodiment, the reaction mixture is subjected to ultrasonication at a frequency in a range of 17.5-22.5 kHz. In one embod