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CN-121295232-B - Iridium catalyst and preparation and application thereof

CN121295232BCN 121295232 BCN121295232 BCN 121295232BCN-121295232-B

Abstract

The invention relates to the technical field of catalysts, in particular to an iridium catalyst and preparation and application thereof, which utilizes a small amount of oxalic acid to regulate and control hydrolysis kinetics of iridium precursors, the pH and the temperature are precisely controlled step by step, and the iridium hydroxide hydrate precursor is precipitated and anchored on the surface of the carrier in situ, so that the iridium species are ensured to be uniformly distributed in the subsequent precipitation process. The two-step heat treatment method of stabilization and ultralow temperature reduction is utilized to induce precipitation of sodium chloride crystals as pore-forming agents, the active phase of simple substance iridium is precisely controlled to be 5-8 nm through the space confinement effect, active point aggregation caused by high-temperature sintering is avoided, and abundant pore canal structures are constructed by removing sodium chloride through subsequent pickling.

Inventors

  • Tao Huabing
  • XIAO MEIYI
  • HU TIAN
  • Lao Kejie
  • ZHENG NANFENG
  • FANG XIAOLIANG

Assignees

  • 厦门大学

Dates

Publication Date
20260512
Application Date
20251215

Claims (10)

  1. 1. A method for preparing an iridium catalyst, comprising the steps of: step 1, mixing a sodium chloride aqueous solution, a carrier, an iridium precursor and oxalic acid to obtain a first mixed solution; The iridium precursor is H 2 IrCl 6 , and the carrier is TiO 2 ; Step 2, performing first temperature control on the first mixed solution to 70-75 ℃, adding NaOH aqueous solution to adjust the pH of the first mixed solution to 9-10, and performing second temperature control on the first mixed solution to 30-40 ℃ to obtain second mixed solution; Step 3, adding NaOH solution to adjust the pH value of the second mixed solution to 10-11, precipitating to obtain a third mixed solution, and removing free liquid of the third mixed solution to obtain a precipitate; Step 4, in an air atmosphere, drying the precipitate, and performing heat treatment at 180-200 ℃ to obtain a precursor; Step 5, in a reducing gas atmosphere, carrying out fifth temperature control on the precursor to 80-120 ℃, and reducing the precursor; and 6, pickling and drying the precursor after the reduction treatment to obtain the supported metal iridium catalyst.
  2. 2. The method according to claim 1, wherein in the step 1, the aqueous solution of sodium chloride is saturated aqueous solution of sodium chloride at 45 to 70 ℃, and/or the mass of the carrier added per 1L of the aqueous solution of sodium chloride in the step 1 is 20 to 40g, and/or the mass of the iridium precursor added per 1L of the aqueous solution of sodium chloride in the step 1 is 40 to 80g, and/or the mass of the oxalic acid added per 1L of the aqueous solution of sodium chloride in the step 1 is 1 to 5g.
  3. 3. The method for preparing an iridium catalyst according to claim 1, wherein the concentration of the aqueous NaOH solution is 5 to 40wt%.
  4. 4. The method according to claim 1, wherein in the step 3, the second mixed solution is further stirred after the pH is adjusted, and/or the third mixed solution is further aged before the free liquid of the third mixed solution is removed in the step 3.
  5. 5. The method for preparing iridium catalyst according to claim 1, wherein in the step 4, the temperature at which the precipitate is dried is 70 ℃ to 80 ℃, and/or in the step 5, the reducing gas atmosphere is a mixture of hydrogen and inert gas, the volume ratio of the hydrogen to the inert gas is 1 (2-5), and the inert gas is selected from any one or a mixture of nitrogen, argon and helium.
  6. 6. The method for producing an iridium catalyst according to claim 1, wherein in the step 6, the acid used for acid washing is hydrochloric acid or nitric acid, or a mixture thereof, and/or wherein in the step 6, the acid concentration used for acid washing is 10 to 30wt%.
  7. 7. An iridium catalyst characterized by being obtained by the production method according to any one of claims 1 to 6.
  8. 8. A membrane electrode comprises a cathode catalytic layer and an anode catalytic layer, wherein the cathode catalytic layer and the anode catalytic layer are respectively arranged on two opposite sides of a proton exchange membrane, and the membrane electrode is characterized in that the anode catalytic layer comprises the iridium catalyst as claimed in claim 7.
  9. 9. The membrane electrode assembly according to claim 8, wherein the iridium catalyst comprises (a) a TiO 2 carrier, (b) elemental iridium nanoparticles supported on the TiO 2 carrier, the elemental iridium nanoparticles having a particle size ranging from 5 nm to 8 nm, and (c) a porous structure formed in the catalyst and constructed after elution of a sacrificial template.
  10. 10. A method of making a membrane electrode according to any one of claims 8 or 9, comprising the steps of: s1, mixing a water/alcohol mixed solvent, an ionomer and the iridium catalyst, and grinding to obtain slurry; s2, coating the slurry on a transfer film, and drying to form the transfer film coated with the anode layer; And S3, respectively transferring the transfer film coated with the Pt-based catalyst and the transfer film coated with the anode layer to two sides of the proton exchange film to obtain the catalyst coated membrane electrode.

Description

Iridium catalyst and preparation and application thereof Technical Field The invention relates to the technical field of catalysts, and particularly discloses an iridium catalyst and preparation and application thereof. Background Proton Exchange Membrane Water Electrolysis (PEMWE) has rapidly developed due to its fast response, high efficiency, and good purity of hydrogen production. The PEM electrolyzer is mainly composed of a bipolar plate, a gas diffusion layer, a proton exchange membrane and an electrode catalytic layer, wherein an anode Oxygen Evolution Reaction (OER) is a speed control step, and the performance of an anode catalyst determines the hydrogen production efficiency, stability and cost. Although the iridium-based catalyst can keep activity and stability under strong acid and high potential, the iridium resource is scarce and the cost is high, so that the iridium-based catalyst becomes a key bottleneck for restricting PEMWE industrialization. Therefore, the development of a novel catalyst with low iridium loading, high activity and durability is a core direction. The key to improving iridium utilization is to increase the effective active sites. The specific surface area and the number of active sites can be obviously improved by preparing the nano iridium material, and the atomic utilization rate can be further improved by dispersing Ir by using a carrier, so that the synthesis of the supported nano iridium catalyst is an effective strategy for reducing the dosage of Ir. The liquid phase polyol reduction method and the high temperature gas phase reduction method are easy to cause particle growth and agglomeration, high dispersion and high purity simple substance iridium are difficult to obtain, and the simple accumulation is unfavorable for mass transfer under large current, for example, in a noble metal oxide catalyst for water electrolysis of patent CN1874841A, a deposition-precipitation method is adopted, an iridium precursor is subjected to pH value adjustment precipitation in the presence of an inorganic oxide carrier with high specific surface area, finally high temperature roasting is carried out in air, the method uses high temperature roasting at about 400 ℃ to cause serious particle sintering and growth, the precise control of the particle size of an active point is not realized, the mass transfer structure of the catalyst only depends on passive accumulation of carrier particles, the simple accumulation is unfavorable for mass transfer under large current, the precipitation process adopts one-step pH adjustment, the realization of high uniform dispersion and anchoring of the active point is unfavorable, the surface of the iridium precursor is subjected to pH value adjustment of the carrier, the precursor is further dripped into the surface of the carrier, the carrier is uniformly adsorbed on the surface, the surface of the carrier is subjected to drying, the carrier is subjected to thermal reduction, the particle size is difficult to realize, the precise control of the particle size is difficult to realize, the natural accumulation is difficult to realize, the natural particle diameter control is difficult to realize, the natural particle diameter is easy to realize, and the natural particle diameter control is difficult to realize by adopting the thermal carrier, and the precise particle accumulation is easy to realize, The existing method depends on high-temperature treatment, strong reducing agent or complex multi-step reaction, so that the energy consumption is high, the particle size and distribution are difficult to control, and the microscopic mass transfer state of the carrier is poor, so that a novel method which is simple in process, mild in condition, capable of generating high-activity iridium species in a large-scale manner and accurate is needed. Disclosure of Invention Aiming at the problems in the prior art, the first aspect of the invention provides a preparation method of an iridium catalyst, which comprises the following steps: Step 1, mixing aqueous solution of sodium chloride, a carrier, an iridium precursor and oxalic acid to obtain a first mixed solution; Step 2, performing first temperature control on the first mixed solution, adding NaOH aqueous solution to adjust the pH value of the first mixed solution, and performing second temperature control on the first mixed solution to obtain second mixed solution; step 3, adding NaOH solution to adjust the pH of the second mixed solution, precipitating to obtain a third mixed solution, carrying out third temperature control on the third mixed solution, and removing free liquid of the third mixed solution to obtain a precipitate; Step 4, drying the precipitate in an air atmosphere, and performing heat treatment to obtain a precursor; Step 5, in a reducing atmosphere, carrying out fifth temperature control on the precursor, and reducing the precursor; and 6, pickling and drying the precursor after the reduction tr