Iridium oxide nano-catalyst and preparation method thereof, and PEM water electrolysis hydrogen production process

Abstract

The invention relates to the technical field of electro-catalysis, in particular to an iridium oxide nano-catalyst, a preparation method thereof and a PEM water electrolysis hydrogen production process. The preparation method of the iridium oxide nano-catalyst provided by the invention comprises the following steps: mixing an iridium precursor, a solvent, small organic molecules and alkali metal nitrate to obtain a mixed solution; and then drying the mixed solution to remove the solvent, grinding the obtained solid, and calcining to obtain the iridium oxide nano-catalyst. The iridium oxide nanoneedle with a one-dimensional structure is prepared by introducing small organic molecules containing specific characteristic groups and regulating and controlling the morphology of an iridium catalyst, has the advantages of large specific surface area, high catalytic activity, good conductivity and the like, can effectively improve the OER catalytic activity, and is simple in preparation method and suitable for large-scale industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalysis, and particularly to an iridium oxide nanocatalyst and a preparation method thereof, as well as a PEM water electrolysis hydrogen production process. Background Art

[0002] The over-reliance on fossil energy has led to increasingly serious environmental problems, such as air pollution, water pollution, and global warming. To address these challenges, the development and utilization of renewable green energy have become the focus of global research. Currently, the solution of decomposing water into hydrogen and oxygen using electricity generated from renewable energy is called the "green hydrogen" solution, and exploring low-cost water electrolysis hydrogen production devices and efficient water electrolysis catalysts is of great significance for promoting the development of "green hydrogen".

[0003] Proton exchange membrane water electrolysis technology (PEM) is an efficient water electrolysis hydrogen production technology with advantages such as high efficiency, low energy consumption, and environmental friendliness, and is widely used in the hydrogen energy field. A proton exchange membrane water electrolyzer (referred to as a PEM water electrolyzer) efficiently decomposes water into hydrogen and oxygen through a specific device. The core component of the PEM water electrolyzer device is the membrane electrode assembly, which is composed of a proton exchange membrane and anode and cathode electrode materials; during PEM water electrolysis, the proton exchange membrane serves as an electrolyte, and specific chemical reactions occur at the anode and cathode: at the anode, water is decomposed into oxygen, protons, and electrons, and at the cathode, protons accept electrons and are reduced to hydrogen. However, due to the extreme acidic working environment in the PEM water electrolyzer, the choice of anode catalyst and cathode catalyst is very limited, and usually only platinum-based noble metal catalysts with strong acid resistance can be selected. Currently, commercial water electrolysis hydrogen production anode catalysts are mainly Ir-based oxide catalysts.

[0004] Currently, the synthesis methods of iridium dioxide catalysts mainly include low-temperature synthesis methods, such as hydrolysis methods in alkaline media, sol-gel methods, etc. As a result, the prepared iridium dioxide catalysts often have low crystallinity, many defects, and poor stability. Relatively speaking, the Adams method can effectively prepare iridium dioxide catalysts with high crystallinity, but it is difficult to control the particle size and morphology, and it is easy to agglomerate, resulting in a decrease in catalytic activity, thus limiting its industrial application in PEM devices. Summary of the Invention

[0005] In view of this, the present invention provides an iridium oxide nanocatalyst and a preparation method thereof, as well as a PEM water electrolysis hydrogen production process. The iridium oxide nanocatalyst prepared by the present invention is mainly in the form of one-dimensional iridium oxide nanoneedles in morphology, which can effectively improve the catalytic activity of the oxygen evolution reaction in water electrolysis.

[0006] The present invention provides a preparation method of an iridium oxide nanocatalyst, comprising the following steps:

[0007] (A) Mix an iridium precursor, a solvent, an organic small molecule, and an alkali metal nitrate to obtain a mixed solution;

[0008] (B) Dry the mixed solution to obtain a solid;

[0009] (C) Calcinate the solid to obtain an iridium oxide nanocatalyst;

[0010] Among them,

[0011] The organic small molecule is an organic compound containing a characteristic group; the characteristic group is at least one of an amino group-containing group, -COOH, and -SH; among them, the amino group-containing group is at least one of -NH2, -NH2-CO-NH2, and -CONH2.

[0012] Preferably, in step (A), the organic small molecule is at least one of L-arginine, acetic acid, ethanethiol, acetamide, and ethylenediamine.

[0013] Preferably, in step (A), the iridium precursor is at least one of chloroiridic acid, iridium acetylacetonate, iridium chloride, and potassium chloroiridate.

[0014] Preferably, in step (A), the alkali metal nitrate is at least one of lithium nitrate, sodium nitrate, and potassium nitrate.

[0015] Preferably, in step (A), the mass ratio of the organic small molecule to the iridium precursor is (0.01 - 0.1)∶0.1;

[0016] The molar ratio of the iridium precursor to the alkali metal nitrate is (0.01 - 10)∶10.

[0017] Preferably, in step (A), the solvent is water.

[0018] Preferably, in step (C), the calcination temperature is 500 - 700 °C and the time is 0.5 - 5 h.

[0019] Preferably, step (A) specifically includes:

[0020] (A1) Mix the iridium precursor and the solvent to obtain an iridium precursor solution;

[0021] (A2) Mix the iridium precursor solution with the organic small molecule and the alkali metal nitrate to obtain a mixed solution.

[0022] The present invention also provides an iridium oxide nanocatalyst prepared by the preparation method described in the above technical solution.

[0023] The present invention also provides a PEM electrolytic water hydrogen production process, wherein the anode oxygen evolution catalyst comprises the iridium oxide nanocatalyst described in the above technical solution.

[0024] The preparation method of the iridium oxide nanocatalyst provided by the present invention is to mix an iridium precursor, a solvent, an organic small molecule, and an alkali metal nitrate to obtain a mixed solution; then, the solvent is removed by drying the mixed solution, and the obtained solid is ground and then calcined to obtain the iridium oxide nanocatalyst. The present invention introduces an organic small molecule containing specific characteristic groups to regulate the morphology of the iridium catalyst, and prepares one-dimensional iridium oxide nanoneedles, which have the advantages of large specific surface area, high catalytic activity, good conductivity, etc., can effectively improve the OER catalytic activity, and its preparation method is simple and suitable for large-scale industrial application. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0026] Figure 1 XRD patterns of the IrO2 nanocatalysts obtained in Examples 1-4 of the present invention;

[0027] Figure 2 TEM image of the IrO2 nanocatalyst obtained in Example 1 of the present invention;

[0028] Figure 3 OER catalytic activity test effect diagram of the IrO2 nanocatalyst obtained in Example 1 of the present invention;

[0029] Figure 4 TEM image of the IrO2 nanocatalyst obtained in Example 2 of the present invention;

[0030] Figure 5 TEM image of the IrO2 nanocatalyst obtained in Example 3 of the present invention;

[0031] Figure 6 TEM image of the IrO2 nanocatalyst obtained in Example 4 of the present invention. Detailed Embodiments

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0033] In this text, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, and also includes an open technical solution containing the listed features.

[0034] As used herein, the term "and / or" includes any and all combinations of one or more of the related listed items.

[0035] In this text, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0036] In this text, regarding the units of data ranges, if the unit is only attached after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 50~100℃ means that the units of the left endpoint "50" and the right endpoint "100" are both ℃.

[0037] The present invention provides a method for preparing an iridium oxide nanocatalyst, comprising the following steps:

[0038] (A) Mixing an iridium precursor, a solvent, an organic small molecule, and an alkali metal nitrate to obtain a mixed solution;

[0039] (B) Drying the mixed solution to obtain a solid;

[0040] (C) Calcining the solid to obtain an iridium oxide nanocatalyst;

[0041] Wherein,

[0042] The organic small molecule is an organic compound containing a characteristic group; the characteristic group is at least one of an amino group-containing group, -COOH, and -SH; wherein, the amino group-containing group is at least one of -NH2, -NH2-CO-NH2, and -CONH2.

[0043] The present invention first mixes an iridium precursor, a solvent, an organic small molecule, and an alkali metal nitrate to obtain a mixed solution; then, dries the mixed solution to remove the solvent, and then grinds the obtained solid and calcines it to obtain an iridium oxide nanocatalyst. The iridium oxide nanocatalyst obtained by the present invention mainly has a one-dimensional nanostructure nanoneedle with a high aspect ratio, which can achieve high catalytic stability and fast mass transfer kinetics of the catalyst, and is of great significance for industrial PEM water electrolysis for hydrogen production.

[0044] Regarding step (A):

[0045] (A) Mix an iridium precursor, a solvent, an organic small molecule, and an alkali metal nitrate to obtain a mixed solution.

[0046] In the present invention, the iridium precursor is preferably at least one of chloroiridic acid, iridium acetylacetonate, iridium chloride, and potassium chloroiridate, and more preferably chloroiridic acid. The present invention has no special limitation on the source of the iridium precursor, and it can be a commercially available product or prepared according to known preparation methods in the art.

[0047] In the present invention, the solvent is preferably water. The water is preferably deionized water. In the present invention, the dosage ratio of the iridium precursor to the solvent is preferably (10 - 100) mg∶(1 - 10) mL.

[0048] In the present invention, the organic small molecule is an organic compound containing a characteristic group; wherein, the characteristic group is at least one of an amino group-containing group, -COOH (carboxyl group), and -SH (mercapto group); the amino group-containing group is at least one of -NH2 (amino group), -NH2-CO-NH2 (guanidyl group), and -CONH2 (amide group). In the present invention, preferably, the organic small molecule is at least one of L-arginine (where the characteristic groups are amino -NH2, carboxyl -COOH, and guanidyl -NH2-CO-NH2), acetic acid (carboxyl -COOH), ethanethiol (mercapto -SH), acetamide (amide -CONH2), and ethylenediamine (amino -NH2). In the present invention, more preferably, an organic small molecule containing an amino group as the characteristic group is used, and specifically more preferably at least one of L-arginine, acetamide, and ethylenediamine. In the present invention, most preferably, the organic small molecule is acetamide; using the above-mentioned specific organic small molecule containing an amino group is more conducive to the formation of the nano-needle morphology and more conducive to improving the OER catalytic activity compared to using organic small molecules containing other characteristic groups.

[0049] In the present invention, the mass ratio of the organic small molecule to the iridium precursor is preferably (0.01 - 0.1)∶0.1, and specifically can be 0.01∶0.1, 0.02∶0.1, 0.03∶0.1, 0.04∶0.1, 0.05∶0.1, 0.06∶0.1, 0.07∶0.1, 0.08∶0.1, 0.09∶0.1, 0.1∶0.1, and more preferably (0.01 - 0.05)∶0.1.

[0050] In the present invention, the alkali metal nitrate is preferably at least one of lithium nitrate, sodium nitrate, and potassium nitrate. In the present invention, the molar ratio of the iridium precursor to the alkali metal nitrate is preferably (0.01 - 10)∶10, specifically 0.01∶10, 0.1∶10, 1∶10, 2∶10, 3∶10, 4∶10, 5∶10, 6∶10, 7∶10, 8∶10, 9∶10, 10∶10, and more preferably (0.01 - 5)∶10.

[0051] In the present invention, step (A) preferably specifically includes:

[0052] (A1) Mix the iridium precursor with a solvent to obtain an iridium precursor solution;

[0053] (A2) Mix the iridium precursor solution with an organic small molecule and an alkali metal nitrate to obtain a mixed solution.

[0054] In steps (A1) - (A2): There are no special restrictions on the mixing method. The materials can be mixed evenly according to the conventional mixing methods in the art, such as stirring and mixing.

[0055] Regarding step (B):

[0056] (B) Dry the mixed solution to obtain a solid.

[0057] In the present invention, the drying temperature is preferably 50 - 100 °C, more preferably 60 - 90 °C. Specifically, the mixed solution can be placed in an oven for drying. By drying, the solvent is evaporated to dryness, thereby obtaining a solid.

[0058] Regarding step (C):

[0059] (C) Calcinate the solid to obtain an iridium oxide nanocatalyst.

[0060] In the present invention, it is preferred to first grind the solid obtained by drying, and then perform calcination.

[0061] In the present invention, the calcination temperature is preferably 500 - 700 °C, specifically 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, and more preferably 550 - 600 °C. In the present invention, the calcination time is preferably 0.5 - 5 h, specifically 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, and more preferably 0.5 - 3 h. The calcination can be carried out in a muffle furnace. After calcination, an iridium oxide (IrO2) nanocatalyst is obtained.

[0062] The present invention also provides an iridium oxide nanocatalyst prepared by the preparation method described in the above technical solution. In the present invention, the morphology of the iridium oxide nanocatalyst is mainly iridium oxide nanoneedles with a one-dimensional structure.

[0063] The present invention also provides an application of the iridium oxide nanocatalyst described in the above technical solution as an electrocatalyst for the oxygen evolution reaction in acidic medium.

[0064] The present invention also provides a PEM water electrolysis hydrogen production process, in which the anode oxygen evolution catalyst includes the iridium oxide nanocatalyst described in the above technical solution. That is, the above iridium oxide nanocatalyst is used as an electrocatalyst for the oxygen evolution reaction in acidic medium in the PEM water electrolysis hydrogen production process.

[0065] The preparation method of the iridium oxide nanocatalyst provided by the present invention comprises mixing an iridium precursor, a solvent, an organic small molecule, and an alkali metal nitrate to obtain a mixed solution; then, drying the mixed solution to remove the solvent, and then grinding the obtained solid and calcining it to obtain the iridium oxide nanocatalyst. The present invention introduces an organic small molecule containing specific characteristic groups to regulate the morphology of the iridium catalyst, and prepares iridium oxide nanoneedles with a one-dimensional structure; it has a uniform morphology and high OER catalytic activity, and can be used as an anode oxygen evolution catalyst in PEM water electrolysis hydrogen production to improve the hydrogen production effect. Among them, the present invention prepares iridium oxide catalysts with different morphologies by regulating organic small molecules with different characteristic groups. The use of amino groups has high stability for the synthesis of nanoneedles, and this one-dimensional nanoneedle structure can significantly improve the catalytic activity and stability of the iridium oxide catalyst, providing a new choice for the preparation of commercial anode catalyst layers for water electrolysis hydrogen production, and its preparation method is simple and suitable for large-scale industrial applications.

[0066] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0067] Example 1

[0068] 1. Preparation of iridium oxide nanocatalyst

[0069] (A) Take 0.098 g of iridium chloride acid, and then add 5 mL of deionized water to mix it evenly to obtain an iridium precursor solution. Then, add 0.02 g of acetamide and stir at room temperature for 5 min; then add 0.76 g of sodium nitrate and continue to stir at room temperature for 25 min to obtain a mixed solution.

[0070] (B) Place the mixed solution in an oven to dry until the solvent is completely evaporated to obtain a solid.

[0071] (C) Grind the solid evenly and calcine it in a muffle furnace at 550 °C for 2 h to obtain the IrO2 nanocatalyst.

[0072] 2. Product testing

[0073] (1) XRD and TEM characterization

[0074] Perform XRD and TEM characterization on the obtained IrO2 nanocatalyst respectively. The results are as Figure 1-2 shown. Figure 1 This is the XRD pattern of the IrO2 nanocatalyst obtained in Examples 1-3 of the present invention (in the figure, the label IrO2 + C2H5NO represents the sample of Example 1, the label IrO2 + HAc represents the sample of Example 2, the label IrO2 + C2H5SH represents the sample of Example 3, and the label IrO2 + C2H5NO (IrCl3) represents the sample of Example 4). Figure 2 This is the TEM image of the IrO2 nanocatalyst obtained in Example 1 of the present invention. It can be seen that the obtained IrO2 nanocatalyst conforms to the rutile iridium oxide phase, has high crystallinity, and the morphology is mainly one-dimensional IrO2 nanoneedle materials.

[0075] (2) OER catalytic activity test:

[0076] Use the prepared IrO2 nanocatalyst (m C2H5NO : m Ir = 0.2:1) for testing in a PEM water electrolysis device, and adopt a two-electrode test; use a commercial platinum-carbon catalyst as the hydrogen evolution reaction at the cathode, and use the IrO2 nanocatalyst as the oxygen evolution reaction at the anode. After preparing the catalyst on both the anode and cathode into a membrane electrode by the spraying-rolling method, the anode catalyst loading is 0.5 mg Ir / cm 2 , and the cathode catalyst loading is 0.1 mg Pt / cm 2 , and assemble it into a PEM device. Obtain the polarization curve of water electrolysis under the test conditions of 80 °C. The results are as Figure 3 shown. At a current density of 2 A / cm 2 , its potential is 1.78 V, which significantly improves the catalytic activity compared with commercial IrO2 (the potential is 2.02 V). It shows that this catalyst can be used as an anode oxygen evolution catalyst for PEM water electrolysis to produce hydrogen and improve the catalytic activity.

[0077] Example 2

[0078] 1. Preparation of iridium oxide nanocatalyst

[0079] Perform according to Example 1, except that the organic small molecule acetamide is replaced with ethanethiol.

[0080] 2. Product Testing

[0081] The obtained IrO2 nanocatalysts were characterized by XRD and TEM respectively, and the results are as Figure 1 , Figure 4 shown. It can be seen from Figure 1 that the IrO2 nanocatalyst obtained in this example conforms to the rutile iridium oxide phase. It can be seen from Figure 4 that the morphology of the obtained IrO2 nanocatalyst only shows some nanorods, presenting as non-uniform nanoparticles.

[0082] The OER catalytic activity test was carried out according to the test method in Example 1. The results showed that at a current density of 2 A / cm 2 , its potential was 1.82 V. The OER catalytic activity was improved compared with commercial IrO2, but decreased compared with Example 1.

[0083] Example 3

[0084] 1. Preparation of Iridium Oxide Nanocatalyst

[0085] Implemented according to Example 1, except that the organic small molecule acetamide was replaced with acetic acid.

[0086] 2. Product Testing

[0087] The obtained IrO2 nanocatalysts were characterized by XRD and TEM respectively, and the results are as Figure 1 , Figure 5 shown. It can be seen from Figure 1 that the IrO2 nanocatalyst obtained in this example also conforms to the rutile iridium oxide phase. It can be seen from Figure 5 that the morphology of the obtained IrO2 nanocatalyst presents as nanoparticles.

[0088] The OER catalytic activity test was carried out according to the test method in Example 1. The results showed that at a current density of 2 A / cm 2 , its potential was 1.88 V. The OER catalytic activity was improved compared with commercial IrO2, but decreased compared with Example 1.

[0089] Example 4

[0090] 1. Preparation of Iridium Oxide Nanocatalyst

[0091] Implemented according to Example 1, except that chloroiridic acid was replaced with iridium trichloride.

[0092] 2. Product Testing

[0093] The obtained IrO2 nanocatalysts were characterized by XRD and TEM respectively, and the results are as Figure 1 , Figure 6 shown. It can be seen fromFigure 1 It can be seen that the obtained IrO2 nanocatalyst in this example also conforms to the rutile iridium oxide phase and has high crystallinity. From Figure 6 it can be seen that the morphology of the obtained IrO2 nanocatalyst is nanoneedles.

[0094] According to the test method in Example 1, the OER catalytic activity was tested. The results showed that at a current density of 2 A / cm 2 its potential was 1.79 V, and the OER catalytic activity was improved compared with commercial IrO2 and was close to the performance of Example 1.

[0095] The effects of the IrO2 nanocatalysts obtained in Examples 1-4 are summarized in Table 1:

[0096] Table 1: Effects of the IrO2 nanocatalysts obtained in Examples 1-4

[0097] Morphology Potential in OER catalytic activity test, V <![CDATA[Commercial IrO2]]> -- 2.02 Example 1 One-dimensional nanoneedle-like 1.78 Example 2 Only partial nanorods appear, non-uniform nanoparticles 1.82 Example 3 Nanoparticles 1.88 Example 4 One-dimensional nanoneedle-like 1.79

[0098] In summary, the obtained IrO2 nanocatalyst of the present invention can improve the OER catalytic activity compared with commercial IrO2. At the same time, it can also be seen from Examples 1-4 that the present invention prepares iridium oxide catalysts with different morphologies by regulating organic small molecules with different characteristic groups, indicating that different groups have different effects on the morphology of the iridium oxide catalyst, and the amino group (corresponding to Example 1 and Example 4) has high stability for the synthesis of nanoneedles and is most conducive to the formation of the nanoneedle morphology. The prepared iridium oxide nanoneedle catalyst has a uniform morphology and high OER catalytic activity.

[0099] In this article, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in the technical field of the present invention, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements approximately the same as the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A preparation method of an iridium oxide nanocatalyst, characterized in that, It includes the following steps: (A) Mix an iridium precursor, a solvent, an organic small molecule, and an alkali metal nitrate to obtain a mixed solution; (B) Dry the mixed solution to obtain a solid; (C) Calcinate the solid to obtain an iridium oxide nanocatalyst; Wherein, The organic small molecule is an organic compound containing a characteristic group; the characteristic group is at least one of an amino group-containing group, -COOH, and -SH; wherein, the amino group-containing group is at least one of -NH2, -NH2-CO-NH2, and -CONH2.

2. The preparation method according to claim 1, characterized in that, In step (A), the organic small molecule is at least one of L-arginine, acetic acid, ethanethiol, acetamide, and ethylenediamine.

3. The preparation method according to claim 1, wherein In step (A), the iridium precursor is at least one of chloroiridic acid, iridium acetylacetonate, iridium chloride, and potassium chloroiridate.

4. The preparation method according to claim 1, characterized in that, In step (A), the alkali metal nitrate is at least one of lithium nitrate, sodium nitrate, and potassium nitrate.

5. The preparation method according to claim 1, characterized in that, In step (A), the mass ratio of the organic small molecule to the iridium precursor is (0.01 - 0.1):0.1; The molar ratio of the iridium precursor to the alkali metal nitrate is (0.01 - 10):

10.

6. The preparation method according to claim 1, characterized in that, In step (A), the solvent is water.

7. The preparation method according to claim 1, characterized in that, In step (C), the calcination temperature is 500 - 700 °C and the time is 0.5 - 5 h.

8. The preparation method according to claim 1, characterized in that, Step (A) specifically includes: (A1) Mix the iridium precursor and the solvent to obtain an iridium precursor solution; (A2) Mix the iridium precursor solution with the organic small molecule and the alkali metal nitrate to obtain a mixed solution.

9. An iridium oxide nanocatalyst prepared by the preparation method according to any one of claims 1 - 8.

10. A PEM electrolytic water hydrogen production process, characterized in that, The anodic oxygen evolution catalyst therein includes the iridium oxide nanocatalyst according to claim 9.

Images