High surface area, high porosity iridium-based catalysts and methods of making same

Abstract

Iridium-based catalysts and methods of making the catalysts are described. The catalyst comprises a catalytic material comprising nanosheets of iridium oxide or a mixture of iridium and iridium oxide. It may have a BET surface area of at least 50 m2 / g and a pore volume of at least 0.10 cc / g. The thickness of the nanosheet is less than 50 nm. The catalyst is prepared using an organic structure directing agent and an inorganic structure directing agent.

Description

[0001] Priority declaration

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 374,932 filed on September 8, 2022, the entire contents of which are incorporated herein by reference. Background Art

[0003] Hydrogen plays an important role in the path towards an environmentally friendly, low-carbon energy structure as an energy carrier for grid balancing or power-to-gas and power-to-liquid processes. Water electrolysis produces high-quality hydrogen by electrochemically decomposing water into hydrogen and oxygen; the reaction is given by the following equation 1. The water electrolysis process is an endothermic process, and electricity is the energy source. When the method is operated by renewable energy such as wind, solar or geothermal energy, water electrolysis has a zero carbon footprint. The main water electrolysis technologies include alkaline electrolysis, proton exchange membrane (PEM) water electrolysis (such as Figure 1 PEMWE as shown), anion exchange membrane (AEM) water electrolysis (such as Figure 2 AEMWE) and solid oxide water electrolysis shown.

[0004] like Figure 1 As shown, in the PEMWE system 100, the anode 105 and the cathode 110 are separated by a solid PEM electrolyte 115, such as the one shown in the trademark A fluorinated copolymer based on sulfonated tetrafluoroethylene sold by the Chemours company. The anode and cathode catalysts typically comprise IrO2 and Pt, respectively. At the positively charged anode 105, pure water 120 is oxidized to produce oxygen 125, electrons (e - ) and protons; the reaction is given by Equation 2. Protons are transported from the anode 105 to the cathode 110 through the proton-conducting PEM 115. At the negatively charged cathode 110, a reduction reaction occurs in which electrons from the cathode 110 are given to protons to form hydrogen 130; the reaction is given by Equation 3. The PEM 115 not only conducts protons from the anode 105 to the cathode 110, but also separates the H2 gas 130 and O2 gas 125 produced in the water electrolysis reaction. PEM water electrolysis is one of the advantageous methods for converting renewable energy into high-purity hydrogen, with the advantages of compact system design at high pressure difference, high current density, high efficiency, fast response, small footprint, low temperature (20°C to 90°C) operation, and high-purity oxygen byproduct. However, one of the main challenges of PEM water electrolysis is the high capital cost of the cell stack, including expensive acid-resistant stack hardware (such as Pt-coated Ti bipolar plates), expensive precious metal catalysts required for electrodes, and expensive PEMs.

[0005] Water electrolysis reaction: 2H2O→2H2+O2 (1)

[0006] Anodic oxidation reaction of PEMWE: 2H2O→O2+4H + +4e - (2)

[0007] Cathodic reduction reaction of PEMWE: 2H + +2e - →H2 (3)

[0008] AEMWE is a developing technology. Figure 2 As shown, in the AEMWE system 200, the anode 205 and the cathode 210 are separated by a solid AEM electrolyte 215. Typically, a water feed 220 with an added electrolyte (such as diluted KOH or K2CO3 or deionized water) is fed to the cathode side. The anode and cathode catalysts typically include Ni-based or Ni alloy catalysts that do not contain platinum group metals. At the negatively charged cathode 210, water is reduced to form hydrogen 225 and hydroxyl ions by adding four electrons; the reaction is given by Equation 4. The hydroxyl ions diffuse from the cathode 210 to the anode 205 through the AEM 215 that conducts hydroxyl ions. At the positively charged anode 205, the hydroxyl ions are recombined into water and oxygen 230; the reaction is given by Equation 5. The AEM 215 not only conducts hydroxyl ions from the cathode 210 to the anode 205, but also separates H2 225 and O2 230 produced in the water electrolysis reaction. The AEM 215 allows the production of hydrogen 225 with a very high purity of at least 99.9% at high pressures of up to 35 bar.

[0009] Cathodic reduction reaction of AEMWE: 4H2O+4e - →2H2+4OH - (4)

[0010] AEMWE's anodic oxidation reaction: 4OH - →2H2O+O2+4e - (5)

[0011] IrO2 is widely accepted as the most effective oxygen evolution reaction (OER) catalyst in PEM-WE due to its high activity and stability. However, the limited supply and high price of IrO2 restrict its use.

[0012] Therefore, there is a need for a highly active IrO2 that can be used at lower loadings and is comparable to commercial IrO x catalysts provide comparable or improved performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Figure 2 is a diagram of the PEMWE system.

[0014] Figure 2 AEMWE system diagram.

[0015] FIG. 3A to FIG. 3B is a scanning transmission electron microscope (STEM) image of the IrOx-bipyridine catalyst.

[0016] Figure 4 STEM image of IrOx-cysteamine catalyst.

[0017] Figure 5 Figure 2 is a graph showing the comparison of the OER activities of the following materials: (a) commercial catalysts; (b) IrO x- Cysteamine; and (c) IrO according to the present invention x -Bipyridine.

[0018] Figure 6 Figure 2 shows the polarization curves of a water electrolyzer containing: (a) a commercial catalyst; (b) IrO x- Cysteamine; and (c) IrO prepared according to the present invention x -Bipyridine. DETAILED DESCRIPTION

[0019] 2 mg / cm in the anode layer of catalyst coated membrane (CCM) for PEMWE 2 Ir x High loading of OER catalysts is required for state-of-the-art PEM water electrolyzers to maintain high performance and stability. x OER catalyst loading decreased to 0.5 mg / cm 2 or less results in low durability and low electrolyzer efficiency due to the very thin IrO-based x Poor mechanical stability of the anode catalyst layer and defects in the CCM. x Current state of the art commercial IrO nanoparticles x The catalyst has less contact between adjacent particles and is therefore prone to forming defects in the very thin anode coating on the PEM. x Low loading of OER catalysts results in defective coatings and poor electrical contact between the catalyst coating and the porous transport layer (PTL). Therefore, low loading catalyst coatings with defects lead to high cell / stack voltages, resulting in low electrolyzer efficiency. x The BET surface area of ​​the catalysts was less than 25 m 2 The BET surface areas of these commercial IrO x The pore volume of the catalyst is 0.05 cc / g or less.

[0020] The present invention provides a significant reduction in IrO x A solution for loading without sacrificing performance and durability. A family of new IrO2 catalysts for oxygen evolution reaction (OER) in PEMWE or AEMWE has been developed. The highly active iridium-based materials have high porosity, high surface area and nanosheet morphology. The nanosheets have at least one dimension (thickness) of the nanoscale of 1nm to 50nm and an aspect ratio of at least 5. CCMs prepared using high surface area, high porosity, highly active nanosheet IrO2 as OER catalysts have comparable performance to commercial IrO2 catalysts at lower IrO2 loadings.

[0021] The morphology of IrO2 is important. Specifically, when the IrO2 in the anode catalyst layer x When the load is low (e.g., 0.5 mg / cm 2 or lower). Commercial IrO2 has a spherical morphology, which introduces too many defects in the catalyst layer to maintain activity when the IrO2 loading is reduced. Due to the less overlap between adjacent particles, the defects in the thin IrO2 catalyst coating are usually areas without catalyst coating. In contrast, the nanosheet morphology maintains a continuous, well-connected catalyst layer structure in the thin catalyst coating, resulting in low resistance and good performance. IrO2 with the desired nanosheet morphology x There is a higher tendency to form a continuous anode catalyst layer without pinholes in CCM. The continuous catalyst layer structure provides IrO x The particles are in better contact with each other in the anode catalyst layer, resulting in lower resistance. A uniform anode catalyst layer also helps maintain low contact resistance with the porous transport layer.

[0022] The PEM electrolyzer test results (discussed below) show that under the same test conditions, the 2 The CCM of the catalyst of the present invention supported by IrO2 shows similarity to that of the catalyst with 1.0 mg / cm 2 Comparable performance to commercial IrO2 loaded.

[0023] The iridium-based catalyst comprises a catalytic material comprising nanosheets of iridium oxide or a mixture of iridium and iridium oxide.

[0024] The catalyst has at least 50m 2 / g, or at least 100m 2 / g, or at least 150m 2 / g, or at 50m 2 / g to 800m 2 / g range, or within 50m 2 / g to 700m 2 / g range, or within 50m2 / g to 600m 2 / g range, or within 50m 2 / g to 500m 2 / g range, or within 50m 2 / g to 400m 2 / g range, or within 50m 2 / g to 300m 2 The BET surface area is in the range of / g.

[0025] The catalyst has a pore volume of at least 0.10 cc / g, or at least 0.20 cc / g, or at least 0.30 cc / g, or in the range of 0.10 cc / g to 0.70 cc / g, in the range of 0.10 cc / g to 0.60 cc / g, or in the range of 0.10 cc / g to 0.50 cc / g, or in the range of 0.10 cc / g to 0.40 cc / g.

[0026] The catalyst has a nanosheet structure, wherein the thickness of the nanosheet is less than 50 nm, or less than 20 nm, or less than 10 nm, or less than 5 nm.

[0027] In one embodiment, the catalyst has a 2 / g to 800m 2 The pore volumes of the nanostructured carbon foams ranged from 0.20 cc / g to 0.70 cc / g.

[0028] The catalyst is prepared using an organic structure directing agent and an inorganic structure directing agent. The organic structure directing agent coordinates with the Ir precursor to form a coordination complex. Due to the steric hindrance of the organic structure directing agent, the presence of the coordination ligand affects the stacking of the Ir species in the solid state of the material. When calcined in a molten inorganic structure directing agent environment to remove the organic structure directing agent, a new IrO with a unique morphology is obtained due to the unique solid-state stacking of the Ir species. x Materials. Organic and inorganic structure-directing agents play important roles in determining the final IrO x The morphological aspect of the material plays an important role. During the synthesis, a solution is made of an iridium-based precursor in a solvent. An organic structure-directing template and an inorganic structure-directing template are added to the solution. The solution is heated, and the solvent is evaporated to form a solid residue, in which the inorganic structure-directing agent is mainly composed of Ir substances and the organic structure-directing agent is in its coordination sphere. The solid residue is dried and calcined to form an iridium-based catalyst. The characteristics of the catalyst are as described above.

[0029] The organic structure-directing template includes a plurality of heteroatoms, such as oxygen, nitrogen, sulfur and / or phosphorus, which can coordinate with the Ir metal center during heating. Suitable organic structure-directing templates include, but are not limited to, cysteamine, 2,2'-bipyridine, tripyridine, tris(2-aminoethyl)amine, ethylenediamine, 3-aminopropane-1-thiol, glycine, ethanolamine, polyethyleneimine, 1,2-bis(diphenylphosphine)ethane, or combinations thereof.

[0030] The inorganic structure directing agent is in a molten state at the calcination temperature. For example, when the material is calcined at 400°C, LiNO3 and NaNO3 can be used. When the material is calcined at 800°C, NaCl can be used. A mixture of inorganic structure directing agents can be used to obtain the desired intermediate temperature. Suitable inorganic structure directing templates include, but are not limited to, NaNO3, KNO3, LiNO3, NaCl, KCl, or combinations thereof.

[0031] Suitable heating temperatures include, but are not limited to, 30° C. to 200° C., or 30° C. to 150° C., or 30° C. to 100° C., or 30° C. to 80° C., or 50° C. to 200° C., or 50° C. to 150° C., or 50° C. to 100° C., or 50° C. to 80° C. Suitable heating times include, but are not limited to, 10 minutes to 240 minutes, or 10 minutes to 180 minutes, or 10 minutes to 120 minutes, or 10 minutes to 60 minutes, or 20 minutes to 240 minutes, or 20 minutes to 180 minutes, or 20 minutes to 120 minutes, or 20 minutes to 60 minutes, or 30 minutes to 240 minutes, or 30 minutes to 180 minutes, or 30 minutes to 120 minutes, or 30 to 60 minutes.

[0032] Suitable drying temperatures include, but are not limited to, 60° C. to 150° C., or 60° C. to 100° C., or 80° C. to 150° C., or 80° C. to 100° C. Suitable drying times include, but are not limited to, 20 minutes to 600 minutes, or 20 minutes to 600 minutes, 20 minutes to 300 minutes, or 20 minutes to 240 minutes, or 20 minutes to 120 minutes, or 30 minutes to 600 minutes, 30 minutes to 300 minutes, or 30 minutes to 240 minutes, or 30 minutes to 120 minutes.

[0033] Suitable calcination temperatures include, but are not limited to, 300° C. to 600° C., or 300° C. to 500° C., or 300° C. to 450° C., or 350° C. to 600° C., or 350° C. to 500° C., or 350° C. to 450° C. Suitable calcination times include, but are not limited to, 20 minutes to 120 minutes, or 20 minutes to 60 minutes, or 30 minutes to 120 minutes, or 30 minutes to 60 minutes.

[0034] In some embodiments, the iridium-based catalyst can be washed with water, or an organic solvent, or a combination thereof. Suitable organic solvents include, but are not limited to, alcohols, aldehydes, organic acids, ketones, ethers, acetates, or a combination thereof.

[0035] After washing, the catalyst can be dried to remove water and / or organic solvent. For example, drying can be carried out by heating or freeze drying. Suitable drying temperatures after washing include but are not limited to -50°C to 100°C, or -50°C to 80°C, or -50°C to 50°C, or -20°C to 100°C, or -20°C to 80°C, or -20°C to 50°C. Suitable drying times include but are not limited to 20 minutes to 500 minutes, or 20 minutes to 400 minutes, or 20 minutes to 360 minutes, or 20 minutes to 300 minutes, or 50 minutes to 500 minutes, or 50 minutes to 400 minutes, or 50 minutes to 360 minutes, or 50 minutes to 300 minutes, or 100 minutes to 500 minutes, or 100 minutes to 400 minutes, or 100 minutes to 360 minutes, or 100 minutes to 300 minutes.

[0036] Example

[0037] Example 1: Iridium Oxide Nanosheet Catalyst IrO x -Synthesis of Bipyridine

[0038] A sample of 200 mg of IrCl3 hydrate was mixed with 10 mL of water in a flask and subjected to ultrasonic treatment for 30 minutes at room temperature to completely dissolve the solid. Subsequently, 203 mg of 2,2'-bipyridine was added to the solution along with 4 g of NaNO3. The system was heated to 80°C in a water bath for 1 hour with continuous stirring. The solvent was evaporated in the same water bath, which took another hour. The recovered solid was ground into a fine powder and transferred to a calcining tray. It was dried in a calcining furnace at 110°C for 30 minutes, and then the temperature was raised to 450°C at 2°C / min. The temperature was maintained at 450°C for 30 minutes and then cooled to 50°C in air. After washing with H2O and methanol, 120 mg of IrO3 was recovered after drying in air at room temperature. x -bipyridine catalyst, which is a black solid. IrO was characterized by STEM x -Bipyridine catalyst. Figure 3A -B The STEM image shown in 1 confirms that IrO x -Bipyridine catalyst has thin nanosheet morphology.

[0039] Example 2: Iridium Oxide Nanosheet Catalyst IrO x -Synthesis of Cysteamine

[0040] A sample of 200 mg IrCl3 hydrate was mixed with 10 mL water in a flask and subjected to ultrasonic treatment for 30 minutes at room temperature to completely dissolve the solid. Subsequently, 100 mg cysteamine was added to the solution together with 4 g NaNO3. Under continuous stirring, the system was heated to 80 ° C in a water bath for 1 hour. The solvent was evaporated in the same water bath, which took about another hour. The recovered solid was ground into a fine powder and transferred to a calcining tray. It was dried at 110 ° C for 30 minutes in a calcining furnace, and then the temperature was raised to 450 ° C at 2 ° C / min. The temperature was maintained at 450 ° C for 30 minutes and then cooled to 50 ° C in air. After washing with H2O and methanol, 123 mg of IrO was recovered after drying in air at room temperature. x -cysteamine catalyst, which is a black solid. Characterization of IrO by STEM x -Cysteamine catalyst. Figure 4 The STEM image shown shows that IrO x -Cysteamine catalyst has thin nanosheet morphology.

[0041] Example 3: Evaluation of intrinsic oxygen evolution reaction (OER) activity of three iridium-based catalysts

[0042] A commercial IrO2 catalyst and two novel iridium-based catalysts prepared in Examples 1 and 2 were evaluated in a bench-top electrochemical test cell. The catalysts were prepared by mixing the catalysts and the iridium-based catalysts in a mixture of deionized water and ethanol. Catalyst ink was prepared by adding ionomer (5 wt % alcohol solution). The mixture was finely dispersed using an ultrasonic bath. An aliquot of 10 uL of the prepared ink was drop cast on a glassy carbon working electrode. After drying in air for 20 minutes, the electrode with the drop cast catalyst was placed in an electrochemical test cell along with a counter electrode made of a Pt sheet and a Ag / AgCl (4M KCl) reference electrode.

[0043] Linear sweep voltammetry (LSV) measurements were performed in the range of 0.5 V to 1.36 V (vs. Ag / AgCl) at a rate of 10 mV / s, and the results for all three samples were pooled in Figure 5 In LSV measurements, the current, a measure of the rate of the oxygen evolution reaction, is measured while sweeping the voltage applied to the working electrode (which serves as a measure of the energy applied to the reaction). An ideal OER catalyst has a high current at low applied voltage, for example, a catalyst that can reach 10 mA / cm at an overpotential of 250 mA. 2 .like Figure 5 As shown, IrO xThe -cysteamine catalyst had the best OER activity, as it had the highest OER current at any applied cell voltage (vs. Ag / AgCl) in the measured range. Commercial IrO2 was the least active catalyst, as it exhibited the lowest OER current at any applied cell voltage. Another notable feature of the two new Ir-based catalysts is the redox events that occur at applied voltages between 0.5V and 0.8V (vs. Ag / AgCl). This is believed to be due to the oxidation of Ir-related species, indicating that the catalyst is IrO x .

[0044] It should be noted that the potential range is catalyst dependent. Because the catalysts of the present invention are highly active, the potential can be stopped at 1.36 V. However, less active catalysts may require higher potentials to obtain a measurable current.

[0045] Example 4: Evaluation of water electrolysis performance of three iridium-based catalysts

[0046] The water electrolysis performance of the commercial IrO2 catalyst and the two novel catalysts prepared in Examples 1 and 2 were evaluated using a single water electrolyzer at 80°C and atmospheric pressure.

[0047] Commercial IrO2 catalyst coated membrane, IrO x -Cysteamine catalyst-coated membrane and IrO x A perfluorosulfonic acid polymer-based membrane with a thickness of 55 μm, a commercial Pt / C catalyst as a cathode coating on one side of the membrane for hydrogen evolution reaction (HER), and a commercial IrO2 catalyst (or IrO2) as an anode coating on the other side of the membrane for OER were used. x - Cysteamine thin nanosheet catalyst, or IrO x -bipyridine thin nanosheet catalyst). The Ir loading and Pt loading on the commercial IrO2 catalyst coated membrane were 0.9 mg / cm 2 and 0.15mg / cm 2 .IrO x -The Ir loading and Pt loading on the cysteamine catalyst coated membrane were 0.15 mg / cm 2 and 0.15mg / cm 2 .IrO x -Ir loading and Pt loading on the bipyridine catalyst coated membrane were 0.15 mg / cm 2 and 0.15mg / cm 2 The catalyst-coated membrane was placed between two Pt-coated Ti felts as anode and cathode porous transport layers to form a catalyst-coated membrane electrode assembly. Then, a test cell was installed using this catalyst-coated membrane electrode assembly.

[0048] Proton exchange membrane (PEM) water electrolysis test station (Scribner 600 electrolyzer test system) is used to evaluate commercial IrO2 catalyst coated membrane electrode assemblies, IrO x - Cysteamine catalyst coated membrane electrode assembly and IrO x -Bipyridine catalyst coated membrane electrode assembly with 5cm 2 The water electrolysis performance in a single electrolyzer with an active membrane area of ​​1000 μm was measured. The porous transport layer (PTL) and the compression factor (defined as the ratio between the sealing gasket thickness and the PTL thickness) were identical between these components. The test station included an integrated power supply, a potentiostat, an impedance analyzer for electrochemical impedance spectroscopy (EIS) and high frequency resistance (HFR), and real-time sensors for product flow rate and permeation monitoring. The test was performed at 80°C and 15 psig pressure. Ultrapure water was supplied to the anode of the cell at a flow rate of 100 mL / min. The polarization curves were plotted (each data point was held for 1 minute), as shown in Figure 6 shown.

[0049] Figure 6 Shown with 0.15mg / cm 2 Very low Ir loading IrO x -Cysteamine catalyst-coated membrane electrode assembly and IrO x -bipyridine catalyst-coated membrane electrode assembly showed a similar 2 The higher Ir-loaded commercial IrO2 catalyst-coated MEAs have comparable water electrolysis performance, as evidenced by comparable current densities at equal voltages.

[0050] Specific implementation plan

[0051] While the following is described in conjunction with specific embodiments, it should be understood that this description is intended to illustrate and not to limit the scope of the foregoing description and the appended claims.

[0052] A first embodiment of the present invention is an iridium-based catalyst comprising a catalytic material comprising nanosheets comprising iridium oxide or a mixture of iridium and iridium oxide and having a carbon content of at least 50 m 2 / g BET surface area and a pore volume of at least 0.10cc / g, and wherein the thickness of the nanosheet is less than 50nm. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the first embodiment in this paragraph, wherein the thickness of the nanosheet is less than 20nm. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the first embodiment in this paragraph, wherein the thickness of the nanosheet is less than 10nm. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the first embodiment in this paragraph, wherein the BET surface area is at least 100m 2 / g. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the first embodiment in this paragraph, wherein the BET surface area is at least 150 m 2 / g. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the first embodiment in this paragraph, wherein the BET surface area is 50m 2 / g to 800m 2 / g. An embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the first embodiment in this paragraph, wherein the BET surface area is within 50 m 2 / g to 300m 2 / g range. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the first embodiment in this paragraph, wherein the pore volume is at least 0.20cc / g. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the first embodiment in this paragraph, wherein the pore volume is at least 0.30cc / g. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the first embodiment in this paragraph, wherein the pore volume is in the range of 0.10cc / g to 0.70cc / g. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the first embodiment in this paragraph, wherein the pore volume is in the range of 0.10cc / g to 0.40cc / g. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the first embodiment in this paragraph, wherein the BET surface area is 50m 2 / g to 800m 2 / g, and the pore volume is in the range of 0.20cc / g to 0.70cc / g.

[0053] A second embodiment of the present invention is a method for preparing an iridium-based nanosheet catalyst, the method comprising providing a solution of an iridium-based precursor in a solvent; adding an organic structure-directing template and an inorganic structure-directing template to the solution; heating the solution having the organic structure-directing template and the inorganic structure-directing template and evaporating the solvent to form a solid residue; drying the solid residue; and calcining the solid residue to form an iridium-based catalyst, the iridium-based catalyst comprising thin nanosheets of iridium oxide or a mixture of iridium and iridium oxide, and having at least 50 m 2 / g of BET surface area and a pore volume of at least 0.10cc / g, and wherein the thickness of the nanosheet is less than 50nm. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the second embodiment in this paragraph, wherein the organic structure-directed template comprises cysteamine, 2,2'-bipyridine, tripyridine, tris(2-aminoethyl)amine, ethylenediamine, 3-aminopropane-1-thiol, glycine, ethanolamine, polyethyleneimine or a combination thereof. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the second embodiment in this paragraph, wherein the inorganic structure-directed template comprises NaNO3, KNO3, LiNO3, NaCl, KCl or a combination thereof.

[0054] One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the second embodiment in this paragraph, wherein the solution having the organic structure-directed template and the inorganic structure-directed template is heated at a temperature in the range of 300°C to 900°C for 10 minutes to 240 minutes. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the second embodiment in this paragraph, wherein the solid residue is dried at a temperature in the range of 350°C to 650°C for 20 minutes to 120 minutes. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the second embodiment in this paragraph, wherein the solid residue is calcined at a temperature in the range of 400°C to 500°C for 30 minutes to 60 minutes. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the second embodiment in this paragraph, further comprising washing the iridium-based catalyst with water, or an organic solvent, or a combination thereof. One embodiment of the present invention is one, any or all of the previous embodiments in this paragraph up to the second embodiment in this paragraph, wherein the BET surface area is 50 m 2 / g to 800m 2 / g, or the pore volume is in the range of 0.20cc / g to 0.70cc / g, or both.

[0055] Although there is no further detailed description, it is believed that those skilled in the art can utilize the present invention to the greatest extent by using the foregoing description and can easily determine the essential characteristics of the present invention without departing from the spirit and scope of the present invention to make various changes and modifications of the present invention and adapt it to various usages and conditions. Therefore, the aforementioned preferred specific embodiments should be understood as merely illustrative and not to limit the rest of the present disclosure in any way, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0056] In the foregoing, all temperatures are set forth in degrees Celsius and all parts and percentages are by weight unless otherwise indicated.

Claims

1. An iridium-based catalyst comprising: A catalytic material comprising nanosheets comprising iridium oxide or a mixture of iridium and iridium oxide and having a molecular weight of at least 50 m 2 / g and a pore volume of at least 0.10 cc / g, and wherein the nanosheets have a thickness of less than 50 nm.

2. The catalyst according to claim 1, wherein the thickness of the nanosheets is less than 20 nm.

3. The catalyst of claim 1, wherein the BET surface area is at least 100 m 2 / g.

4. The catalyst according to claim 1, wherein the BET surface area is 50 m 2 / g to 800m 2 / g range.

5. The catalyst of claim 1, wherein the pore volume is at least 0.20 cc / g. The catalyst of claim 1 , wherein the pore volume is in the range of 0.10 cc / g to 0.70 cc / g.

7. A method for preparing an iridium-based nanosheet catalyst, the method comprising: providing a solution of an iridium-based precursor in a solvent; adding an organic structure-directing template and an inorganic structure-directing template to the solution; heating the solution having the organic structure-directing template and the inorganic structure-directing template and evaporating the solvent to form a solid residue; drying the solid residue; as well as The solid residue is calcined to form an iridium-based catalyst comprising thin nanosheets of iridium oxide or a mixture of iridium and iridium oxide and having a carbon content of at least 50 m 2 / g and a pore volume of at least 0.10 cc / g, and wherein the nanosheets have a thickness of less than 50 nm.

8. The method according to claim 7, wherein the organic structure-directing template comprises cysteamine, 2,2'-bipyridine, tripyridine, tris(2-aminoethyl)amine, ethylenediamine, 3-aminopropane-1-thiol, glycine, ethanolamine, polyethyleneimine or a combination thereof; or wherein the inorganic structure-directing template comprises NaNO3, KNO3, LiNO3, NaCl, KCl or a combination thereof; or both of the above.

9. The method according to claim 7: wherein the solution having the organic structure guiding template and the inorganic structure guiding template is heated at a temperature ranging from 300° C. to 900° C. for 10 minutes to 240 minutes; or wherein the solid residue is dried at a temperature in the range of 350°C to 650°C for 20 minutes to 120 minutes; or wherein the solid residue is calcined at a temperature ranging from 400° C. to 500° C. for 30 minutes to 60 minutes; or a combination thereof.

10. The method according to claim 7, further comprising: The iridium-based catalyst is washed with water, or an organic solvent, or a combination thereof.

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