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US-20260125802-A1 - WATER ELECTROLYSIS USING IRON-DOPED ZIF-8 CATALYSTS

US20260125802A1US 20260125802 A1US20260125802 A1US 20260125802A1US-20260125802-A1

Abstract

A method of oxygen evolution comprising contacting a working electrode including an iron-doped zeolitic imidazolate framework-8 (Fe-ZIF-8), a counter electrode, and a reference electrode with an aqueous electrolytic solution, applying a potential, and forming oxygen at the working electrode. The iron-doped ZIF-8 includes iron in an amount of 5 to 55 weight percent relative to the combined weight of iron and zinc in the iron-doped ZIF-8. The Fe-ZIF-8 structures are nanoparticles with a longest dimension of 0.5 to 5 μm. The working electrode has an overpotential of 180 to 190 mV vs RHE at a current density of 10 mA/cm 2 .

Inventors

  • Munzir Hamedelniel Mohamed SULIMAN
  • Muhammad Usman
  • Aasif HELAL

Assignees

  • KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS

Dates

Publication Date
20260507
Application Date
20241108
Priority Date
20241104

Claims (20)

  1. 1 : A method of oxygen evolution, comprising: contacting a working electrode comprising an iron-doped zeolitic imidazolate framework-8, a counter electrode, and a reference electrode with an aqueous electrolytic solution, wherein the iron-doped zeolitic imidazolate framework-8 comprises iron in an amount of 5 to 55 percent by weight based on the total weight of iron and zinc in the iron-doped zeolitic imidazolate framework-8, wherein the iron-doped zeolitic imidazolate framework-8 is in the form of nanoparticles with a longest dimension of 0.5 to 5 μm, applying a potential; and forming oxygen at the working electrode, wherein the working electrode has an overpotential of 180 to 190 mV vs RHE at a current density of 10 mA/cm 2 .
  2. 2 : The method of claim 1 , further comprising: forming the iron-doped zeolitic imidazolate framework-8 by: dissolving 2-methylimidazole in a polar solvent to form a first solution; dissolving a zinc salt and an iron salt in a polar solvent to form a second solution; mixing the first solution and the second solution to form a precipitate; collecting and washing the precipitate; and drying the precipitate at a temperature of 50 to 70° C. for 8 to 24 hours to form the iron-doped zeolitic imidazolate framework-8.
  3. 3 : The method of claim 1 , wherein the working electrode is a nickel foam substrate coated with a mixture comprising the iron-doped zeolitic imidazolate framework-8 and a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer.
  4. 4 : The method of claim 3 , further comprising: forming the working electrode by: dispersing the iron-doped zeolitic imidazolate framework-8, the sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, and a polar solvent in water to form a mixture; sonicating the mixture for 10 to 30 minutes; and coating the mixture onto the nickel foam substrate.
  5. 5 : The method of claim 4 , wherein 50 to 150 μL of the mixture is coated onto the nickel foam substrate.
  6. 6 : The method of claim 4 , wherein the coating includes spray coating the mixture onto the nickel foam substrate.
  7. 7 : The method of claim 1 , wherein the iron-doped zeolitic imidazolate framework-8 comprises iron in an amount of 5 to 15 percent by weight based on the total weight of iron and zinc in the iron-doped zeolitic imidazolate framework-8 and the iron-doped zeolitic imidazolate framework-8 is in the form of nanoparticles with a longest dimension of 0.1 to 1 μm.
  8. 8 : The method of claim 1 , wherein the working electrode has an overpotential of 260 to 280 mV vs RHE at a current density of 55 mA/cm 2 .
  9. 9 : The method of claim 1 , wherein the working electrode has an overpotential of 460 to 480 mV vs RHE at a current density of 150 mA/cm 2 .
  10. 10 : The method of claim 1 , wherein the working electrode is stable for 20 to 28 hours at a current density of 50 mA/cm 2 .
  11. 11 : The method of claim 1 , wherein the working electrode has a double-layer capacitance of 8 to 12 mF/cm 2 .
  12. 12 : The method of claim 1 , wherein the working electrode has a charge transfer resistance of 0.2 to 0.6 Ω/cm 2 .
  13. 13 : The method of claim 1 , wherein a working area of the working electrode is 0.1 to 2 cm 2 .
  14. 14 : The method of claim 1 , wherein the counter electrode is a platinum wire.
  15. 15 : The method of claim 1 , wherein the reference electrode is a mercury/mercury oxide (Hg/HgO) electrode.
  16. 16 : The method of claim 1 , wherein the aqueous electrolytic solution comprises potassium hydroxide.
  17. 17 : The method of claim 1 , wherein the iron-doped zeolitic imidazolate framework-8 comprises iron in an amount of 5 to 15 percent by weight based on the total weight of iron and zinc in the iron-doped zeolitic imidazolate framework-8.
  18. 18 : The method of claim 1 , further comprising: producing hydrogen at the working electrode.
  19. 19 : The method of claim 1 , further comprising: producing formate at the working electrode.
  20. 20 : The method of claim 1 , further comprising: producing a hydrogenated product at the working electrode.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present disclosure claims the benefit of Saudi patent application Ser. No. 1020246174 filed on Nov. 4, 2024, with the Saudi Authority for Intellectual Property Office, which is incorporated herein by reference in its entirety. BACKGROUND Technical Field The present disclosure is directed to an electrocatalyst, particularly to an iron doped zeolitic imidazolate framework (Fe-doped ZIF-8)-based electrocatalyst for water-splitting. Description of 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 nor impliedly admitted as prior art against the present disclosure. Hydrogen production through electrolysis is a technology in the transition to a clean energy future, offering benefits of sustainability, energy storage, and economic growth. Hydrogen is a versatile fuel that can be used in various sectors, including transportation, industry, and power generation. Electrolysis, the process of using electricity to split water molecules into hydrogen and oxygen, offers a method to produce hydrogen without emitting greenhouse gases. This method is a promising technology for transitioning to a low-carbon economy and reducing use of fossil fuels [Yan, Z. et al., Renewable electricity storage using electrolysis. Proceedings of the National Academy of Sciences, 2020, 117, 12558-12563]. Although electrolysis is a promising method for hydrogen production, challenges exist and need to be addressed to enhance viability. One challenge that exists is production cost, as electrolysis requires a large amount of energy, typically sourced from renewable but intermittent sources, such as wind or solar power. The fluctuating availability of these energy sources can lead to inconsistencies in hydrogen production. Additionally, efficiency of the electrolysis process is a concern. Current technologies can have varying efficiencies, which may not justify the energy expenditure in all situations. Advancements in electrolyzer design and materials are needed to improve efficiency and reduce operational costs. Finding cost-effective ways to produce and store hydrogen can assist with widespread adoption of renewable processes. Addressing cost, efficiency, and infrastructure challenges may lead to water electrolysis playing a role in the future energy processes by facilitating the integration of renewable energy sources and reducing greenhouse gas emissions. Water splitting, the process of breaking water (H2O) molecules into its constituent elements, hydrogen (H2) and oxygen (O2), may occur through electrolysis. This process may use a two-electrode setup where a cathode and an anode are immersed in an electrolyte solution (typically water with an electrolyte like potassium hydroxide (KOH) or sodium hydroxide (NaOH). When an electric current is applied, water molecules near the anode are oxidized, releasing oxygen gas, while water molecules near the cathode are reducing, producing hydrogen gas. Zeolitic imidazolate frameworks (ZIFs) are a type of metal-organic framework (MOF) that demonstrate potentials for various application, including gas storage and separation and water splitting due to properties that enhance their performance as catalysts in electrolysis processes. ZIFs possess a high surface area and a porous structure, which provide ample active sites for catalytic reactions. The chemical composition and structure of ZIFs can be easily modified, and ZIFs exhibit excellent thermal and chemical stability; however, a limitation of ZIFs is their low conductivity, which hinders their effectiveness in certain electrochemical processes. To address low conductivity issues of ZIFs, the introduction of dopants or guest molecules into ZIF structures to improve the charge transport properties has been explored [Wang, N. et al, Fe/Ni bimetallic organic framework with varying anions as robust electrocatalyst for oxygen evolution reaction. Int J Hydrogen Energy, 2022, 47, 15, 9295-9300]. Another method of addressing low conductivity involves modifying the ZIF structure by incorporating conductive materials or introducing defects to enhance electrical conductivity. Metal doping, such as iron or zinc doping, in zeolitic imidazolate frameworks (ZIFs) can offers several advantages, such as enhancing the electrical conductivity of ZIFs and making them more suitable for electrochemical applications [Shahzad A. et al., Cobalt containing bimetallic ZIFs and their derivatives as OER electrocatalysts: A critical review. Coord Chem Rev, 2023, 477, 214925]. Additionally, metal dopants can influence the catalytic properties of ZIFs, improving their efficiency in various chemical reactions, including hydrogen production throug