Iridium-based multi-element alloy core-shell structure PEM electrolytic water catalyst doped with molybdenum and its preparation method

Abstract

The present invention discloses an iridium-based multi-element alloy core-shell structure PEM electrolysis water catalyst doped with molybdenum and a preparation method thereof, which relates to the technical field of electrocatalysts, and forms an electrocatalyst material with noble metal iridium as the outer shell, transition metals cobalt and iridium as the inner core, and transition metal molybdenum doped in the core-shell. Due to the good corrosion resistance of transition metal molybdenum, this structure can improve the stability of the catalyst, and the transition metals are inexpensive, which can reduce the cost of the catalyst and increase the activity between multi-metal catalysts; at the same time, by removing the excess metals on the surface and inside of the catalyst, the performance of the catalyst can be further improved. The catalyst prepared by the method of the present invention has high OER activity, good stability, low cost and is easy to industrialize, solves the deficiencies existing in the existing PEM electrolysis water for hydrogen production, and has important value in the field of electrochemical applications and practical engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of proton exchange membrane electrolytic water catalysts, in particular to an iridium-based multi-alloy core-shell structure PEM electrolytic water catalyst doped with molybdenum and a preparation method thereof. Background Art

[0002] In order to cope with the continuous depletion of traditional fossil energy and serious environmental pollution problems, it is urgent to develop green new energy. As a highly efficient and clean secondary energy source, hydrogen energy has received extensive attention. However, at present, the main method for producing hydrogen is still based on fossil fuels, which goes against the original intention of reducing the consumption of traditional energy. Therefore, it is necessary to develop green hydrogen production technologies mainly based on electrolytic water for hydrogen production. In recent years, the development of PEM electrolytic water (proton exchange membrane electrolytic water) hydrogen production technology has been rapid, which is an effective way for green hydrogen production. However, high costs and low corrosion resistance limit their large-scale commercial applications. An important reason is that the cost of the catalyst in the membrane electrode is too high, mainly composed of precious metals such as platinum and iridium. Also, due to the strong acid environment, it is difficult for general metals to work stably for a long time. Many researchers have tried to develop non-precious metal catalysts and their derivatives, but without the protection of platinum and iridium, such catalysts are difficult to resist the inherent corrosion and oxidation sensitivity problems during the electrolytic water process. Therefore, developing low-cost, highly efficient, and stable low-precious metal electrode materials is the key to realizing the large-scale application of PEM electrolytic water for hydrogen production.

[0003] Recent studies have shown that the stability, activity of the catalyst can be improved and the precious metal content can be reduced by adjusting the chemical composition and nanostructure of the catalyst. The chemical composition of the catalyst can be adjusted by doping transition metals (including Ni, Co, etc.). This method can not only reduce the precious metal content to achieve the purpose of cost reduction, but also improve the electrocatalytic activity because synergistic effects will occur between different metals, increasing the active sites. The nanostructure of the catalyst can be adjusted by forming core-shell structures, hollow structures, single atoms, cluster structures, etc. So far, most of the studies on iridium-based multi-catalysts can only meet one or two of the three factors of low cost, high efficiency, and stability, but there is no good method to achieve a balance among the three. Summary of the Invention

[0004] To overcome the defects in the above-mentioned prior art, the present invention provides an iridium-based multi-alloy core-shell structure PEM electrolytic water catalyst doped with molybdenum. The transition metals molybdenum and cobalt are combined with the precious metal iridium to form a special core-shell structure electrocatalyst, which has the characteristics of low cost, high efficiency, and stability.

[0005] To achieve the above object, the present invention adopts the following technical solutions, including:

[0006] The invention discloses a molybdenum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst, wherein the catalyst is a nano-spherical core-shell structure electrocatalyst; wherein the shell of the spherical core-shell structure is iridium, the core is iridium-cobalt, and the transition metal molybdenum is dispersed between the shell and the core.

[0007] The present invention also provides a method for preparing a molybdenum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst, comprising the following steps:

[0008] S1, taking iridium source, cobalt source, molybdenum source, surfactant, alcohol reducing agent and stabilizer into a beaker and mixing them thoroughly, and ultrasonically cleaning them in an ultrasonic cleaner for a set time, then moving them into a constant temperature water bath and stirring them on a magnetic stirrer to make all the raw materials basically dissolved, moving the sample obtained after stirring into an oil bath for heat preservation, and obtaining a solution with precipitation after cooling;

[0009] S2, centrifugally purify the solution with precipitate obtained in step S1 N times, N>1, to obtain a precipitate as the catalyst, marked as Mo x -IrCo y @Ir.

[0010] Preferably, the method further comprises the following steps:

[0011] S3, dispersing the precipitate obtained in step S2 in an etching solution, and after etching for a set time, obtaining an etched mixed solution;

[0012] S4, centrifugally purify the mixed solution after etching obtained in step S3 M times, M>1, and obtain the precipitate after etching as the catalyst, marked as Mo x -IrCo y @Ir-Etch.

[0013] Preferably, in step S1, the iridium source is selected from one of iridium acetylacetonate or iridium chloride; the cobalt source is selected from one of cobalt acetylacetonate or cobalt chloride; the molybdenum source is selected from molybdenum acetylacetonate; the surfactant is one of hexadecyltrimethylammonium chloride or hexadecyltrimethylammonium bromide; the stabilizer is oleylamine; and the alcohol reducing agent is 1,2-hexadecanediol.

[0014] Preferably, in step S1, the ultrasonic time is 10 min; and the temperature of the water bath is 70-80°C.

[0015] Preferably, in step S1, stirring is performed using a magnetic stirrer, the rotation speed of the magnetic stirrer is 1000 rpm, and the stirring time is 10 min; the insulation temperature of the oil bath pot is 260-270° C., the insulation time is 40-60 min, and the heat transfer oil is dimethyl silicone oil.

[0016] Preferably, in step S1, the molar ratio of the iridium source to the molybdenum / cobalt source is 0.5:0.6, and the molar ratio of the cobalt source to the molybdenum source is 1:2, 1:1, 2:1 or 1:0.

[0017] Preferably, in step S2, toluene in a set amount and methanol / absolute ethanol in a set amount are added for centrifugal purification, and the solution ratio is 1:2; the centrifugal purification time each time is 5 min; the first centrifugal rotation speed is 10,000 rpm, and the centrifugal rotation speed is 8,000 rpm for each subsequent time.

[0018] Preferably, in step S3, the etching solution is cerium nitrate and copper nitrate; the concentration ratio of cerium to copper in the etching solution is 0:1, 1:3, 1:2, 1:1, 2:1, 3:1 or 1:0; the etching time is 3, 6, 9, 12, 18 or 24 hours.

[0019] Preferably, in step S4, the centrifuged solution is 10 mL of absolute ethanol, the centrifugal purification time each time is 5 min, the first centrifugal rotation speed is 10,000 rpm, and the centrifugal rotation speed is 8,000 rpm for each subsequent time.

[0020] The advantages of the present invention are as follows:

[0021] (1) The present invention combines transition metals with noble metals to form a special core-shell structure electrocatalyst, which is an important method for cost reduction, efficiency improvement and stability enhancement, and has great scientific research potential and industrial prospects.

[0022] (2) The present invention uses inexpensive and abundant transition metals molybdenum and cobalt as partial substitutes for current commercial noble metal iridium catalysts, solves the problem of too high cost of PEM electrolytic water catalysts, and further improves the catalytic activity and stability of electrolytic water.

[0023] (3) For the doped molybdenum iridium-based multi-alloy core-shell structure PEM electrolytic water catalyst prepared by the present invention, during the PEM electrolytic water hydrogen production process, due to the doping of transition metal molybdenum, transition metal molybdenum has good corrosion resistance, improving the corrosion resistance and stability of the catalyst.

[0024] (4) The present invention adopts a combination of one-step synthesis method and selective etching method. Although different metals may produce synergistic effects during the synthesis process, uneven agglomeration and other phenomena may also occur. Through selective etching, redundant metal clusters and uneven degradation are removed, further enhancing the stability. During a 100-hour long-term test, the voltage increase is less than 1%, showing good stability.

[0025] (5) In the present invention, the prepared iridium-based multi-alloy core-shell structure PEM electrolytic water catalyst doped with molybdenum is used as the anode electrode material instead of the commercial iridium oxide catalyst for PEM electrolytic water hydrogen production, and its current density reaches 10 mA / m 2 The overpotential of the required voltage is only 206 mV, which is better than that of the commercial iridium oxide catalyst (272 mV). Moreover, the electrode has a fast response rate, small electrochemical impedance, and large electrochemical active area, significantly improving the catalytic activity of the oxygen evolution reaction.

[0026] (6) In the present invention, the prepared iridium-based multi-alloy core-shell structure PEM electrolytic water catalyst doped with molybdenum is used as the anode electrode material instead of the commercial iridium oxide catalyst for PEM electrolytic water hydrogen production. Due to the doping of transition metals cobalt and molybdenum, the content of precious metal iridium is significantly reduced. The content of iridium per unit area is about 0.1 mg / cm 2 , which is much lower than the content of iridium in commercial electrolytic cells (2 - 4 mg / cm 2 ), greatly reducing the cost of the catalyst.

[0027] (7) The preparation method of the present invention can also achieve large-scale preparation of materials by changing the content of each metal source, is easy to industrialize, and has important engineering application value for promoting the large-scale application of PEM electrolytic water hydrogen production.

[0028] (8) The catalyst prepared by the method of the present invention has high OER (oxygen evolution reaction) activity, good stability, low cost, and is easy to industrialize, solving the deficiencies existing in the current PEM electrolytic water hydrogen production, and has important value in the field of electrochemical applications and practical engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 TEM image of Mo 0.04 -IrCo 0.02 @Ir-Etch prepared in Example 1 of the present invention.

[0030] Figure 2 HRTEM image of Mo 0.04 -IrCo 0.02 @Ir-Etch prepared in Example 1 of the present invention.

[0031] Figure 3 HAADF-STEM image and elemental mapping image of Mo 0.04 -IrCo 0.02 @Ir-Etch prepared in Example 1 of the present invention.

[0032] Figure 4 EDX spectrum of Mo 0.04 -IrCo 0.02 @Ir-Etch prepared in Example 1 of the present invention.

[0033] Figure 5 Mo prepared in Example 1 of the present invention 0.04 -IrCo 0.02 XRD pattern of @Ir-Etch

[0034] Figure 6 Mo prepared in Example 1 of the present invention 0.04 -IrCo 0.02 XPS pattern of @Ir-Etch

[0035] Figure 7 Oxygen evolution polarization curves of the catalysts prepared in Examples 1 to 17 of the present invention and the comparative catalyst IrO2

[0036] Figure 8 Mo prepared in Examples 1, 16, and 17 of the present invention 0.04 -IrCo 0.02 @Ir-Etch, Mo 0.04 -IrCo 0.02 @Ir and IrCo 0.06 Tafel slope curves of @Ir

[0037] Figure 9 Mo prepared in Examples 1, 16, and 17 of the present invention 0.04 -IrCo 0.02 @Ir-Etch, Mo 0.04 -IrCo 0.02 @Ir and IrCo 0.06 Electrochemical impedance curves of @Ir

[0038] Figure 10 Mo prepared in Examples 1, 16, and 17 of the present invention 0.04 -IrCo 0.02 @Ir-Etch, Mo 0.04 -IrCo 0.02 @Ir and IrCo 0.06 CV curves and double-layer capacitance diagrams of @Ir corresponding to different scanning rates

[0039] Figure 11 Mo prepared in Examples 1, 16, and 17 of the present invention 0.04 -IrCo 0.02 @Ir-Etch, Mo 0.04 -IrCo 0.02 @Ir and IrCo 0.06 Stability curves of @Ir on glassy carbon electrode

[0040] Figure 12 Mo prepared in Example 1 of the present invention 0.04 -IrCo0.02 Long-term stability curve of @Ir-Etch on carbon paper electrode.

[0041] Figure 13 Schematic diagram of the catalyst preparation process of the present invention. Detailed implementation manners

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0043] A molybdenum-doped iridium-based multi-alloy core-shell structure PEM electrolytic water catalyst is a nano-spherical core-shell structure electrocatalyst; wherein, the outer shell of the spherical core-shell structure is iridium, the inner core is iridium-cobalt, and the transition metal molybdenum is dispersed between the outer shell and the inner core.

[0044] Furthermore, a part of the excess metal clusters can be removed by selective etching.

[0045] Example 1

[0046] As Figure 13 shown, the preparation method of the molybdenum-doped iridium-based multi-alloy core-shell structure PEM electrolytic water catalyst is as follows:

[0047] S1, weigh 10.3 mg of 1,2-hexadecanediol (alcohol reducing agent), 32 mg of cetyltrimethylammonium chloride (surfactant), 5.2 mg of cobalt acetylacetonate (cobalt source), and 24.5 mg of iridium acetylacetonate (iridium source) with a balance, and measure 5 mL of oleylamine solution (stabilizer) with a measuring cylinder, and place them all in a 25 mL heat-resistant beaker for mixing. Then, weigh 13.1 mg of molybdenum acetylacetonate (molybdenum source). In this Example 1, the molar ratio of the cobalt source to the molybdenum source is 1:2, and quickly pour it into the above mixture, and ultrasonicate it with an ultrasonic cleaner for about 10 min. Then, transfer the beaker to a water bath at about 80 °C and a magnetic stirrer for constant temperature stirring for 10 min, and adjust the rotation speed of the magnetic stirrer to 1000 rpm to make the raw materials mix evenly. At this time, the solution is light yellow. Finally, transfer the beaker to an oil bath preheated to 270 °C, take it out after keeping warm for 1 h, and wait for it to cool naturally to room temperature to obtain a black solution with precipitation.

[0048] S2. Pour the obtained black solution with precipitate into a 50 mL centrifuge tube. Measure 5 mL of toluene and 10 mL of methanol and pour them into the centrifuge tube simultaneously for mixing. Then centrifuge at a speed of 10000 rpm for 5 min. After taking it out, pour off the supernatant to obtain a black precipitate. To further purify the precipitate, pour in 5 mL of toluene and 10 mL of absolute ethanol for mixing, and centrifuge at a speed of 8000 rpm for 5 min. After taking it out, pour off the supernatant. Repeat the above steps several times, and the centrifugation speed is 8000 rpm each time thereafter until the supernatant is colorless and transparent. Finally, put the centrifugally purified black precipitate into a vacuum drying oven at 60 °C for drying for 6 h to obtain the dried black precipitate, marked as Mo 0.04 -IrCo 0.02 @Ir.

[0049] S3. Pour the obtained Mo 0.04 -IrCo 0.02 @Ir into 1 mL of absolute ethanol, and ultrasonicate it with an ultrasonic cleaner for 10 min to completely disperse it in the solution, denoted as solution A. Additionally, weigh 2.172 g of cerium nitrate and 0.938 g of copper nitrate (the concentration ratio of cerium nitrate to copper nitrate is 1:1) and dissolve them in 5 mL of deionized water. Stir with a magnetic stirrer at 1000 rpm for about 5 min to obtain solution B. Pour solution A into solution B, and ultrasonicate it with an ultrasonic cleaner for 10 min to completely disperse solution A in solution B. Let it stand at room temperature for 6 h to obtain the standing mixed solution.

[0050] S4. Pour the standing mixed solution into a 50 mL centrifuge tube. Measure 10 mL of absolute ethanol and pour it into the centrifuge tube. Centrifuge at a speed of 10000 rpm for 5 min. After taking it out, pour off the supernatant to obtain a black precipitate. To further purify the precipitate, pour in 10 mL of absolute ethanol and centrifuge at a speed of 8000 rpm for 5 min. After taking it out, pour off the supernatant. Repeat the above steps several times, and the centrifugation speed is 8000 rpm each time thereafter until the supernatant is colorless and transparent. Finally, put the centrifugally purified black precipitate into a vacuum drying oven at 60 °C for drying for 6 h to obtain the dried black precipitate, marked as Mo 0.04 -IrCo 0.02 @Ir-Etch.

[0051] Take the Mo 0.04 -IrCo 0.02 @Ir-Etch obtained in step S4 as the doped molybdenum-based iridium-based multi-alloy core-shell structure PEM electrolysis water catalyst prepared in Example 1 of the present invention.

[0052] Example 2

[0053] The difference from Example 1 is that in step S1, the dosages of cobalt acetylacetonate and molybdenum acetylacetonate are changed to 7.8 mg and 9.8 mg, that is, the molar ratio of the cobalt source to the molybdenum source is changed to 1:1, and the others are the same as in Example 1.

[0054] Example 3

[0055] The difference from Example 1 is that in step S1, the dosages of cobalt acetylacetonate and molybdenum acetylacetonate are changed to 10.4 mg and 6.6 mg, that is, the molar ratio of the cobalt source to the molybdenum source is changed to 2:1, and the others are the same as in Example 1.

[0056] Example 4

[0057] The difference from Example 1 is that in step S1, the dosages of cobalt acetylacetonate and molybdenum acetylacetonate are changed to 15.6 mg and 0 mg, that is, only the cobalt source is added and the molybdenum source is not added, and the others are the same as in Example 1.

[0058] Example 5

[0059] The difference from Example 1 is that in step S3, the dosages of cerium nitrate and copper nitrate are changed to 1.086 g and 1.407 g, that is, the concentration ratio of cerium nitrate to copper nitrate is changed to 1:3, and the others are the same as in Example 1.

[0060] Example 6

[0061] The difference from Example 1 is that in step S3, the dosages of cerium nitrate and copper nitrate are changed to 3.25 g and 0.469 g, that is, the concentration ratio of cerium nitrate to copper nitrate is changed to 3:1, and the others are the same as in Example 1.

[0062] Example 7

[0063] The difference from Example 1 is that in step S3, the dosages of cerium nitrate and copper nitrate are changed to 1.447 g and 1.251 g, that is, the concentration ratio of cerium nitrate to copper nitrate is changed to 1:2, and the others are the same as in Example 1.

[0064] Example 8

[0065] The difference from Example 1 is that in step S3, the dosages of cerium nitrate and copper nitrate are changed to 2.893 g and 0.626 g, that is, the concentration ratio of cerium nitrate to copper nitrate is changed to 2:1, and the others are the same as in Example 1.

[0066] Example 9

[0067] The difference from Example 1 is that in step S3, the dosages of cerium nitrate and copper nitrate are changed to 4.34 g and 0 g, that is, the concentration ratio of cerium nitrate to copper nitrate is changed to 1:0, and the others are the same as in Example 1.

[0068] Example 10

[0069] The difference from Example 1 is that in step S3, the dosages of cerium nitrate and copper nitrate are changed to 0 g and 1.88 g, that is, the concentration ratio of cerium nitrate to copper nitrate is changed to 0:1, and the others are the same as in Example 1.

[0070] Example 11

[0071] The difference from Example 1 is that in step S3, it is left standing at room temperature for 3 h, and the others are the same as in Example 1.

[0072] Example 12

[0073] The difference from Example 1 is that in step S3, it is left standing at room temperature for 9 h, and the others are the same as in Example 1.

[0074] Example 13

[0075] The difference from Example 1 is that in step S3, it is left standing at room temperature for 12 h, and the others are the same as in Example 1.

[0076] Example 14

[0077] The difference from Example 1 is that in step S3, it is left standing at room temperature for 18 h, and the others are the same as in Example 1.

[0078] Example 15

[0079] The difference from Example 1 is that in step S3, it is left standing at room temperature for 24 h, and the others are the same as in Example 1.

[0080] Example 16

[0081] The difference from Example 1 is that steps S3 and S4 are not carried out, and the others are the same as in Example 1. The Mo 0.04 -IrCo 0.02 @Ir obtained in step S2 is used as the doped molybdenum iridium-based multi-alloy core-shell structure PEM electrolytic water catalyst prepared in Example 16 of the present invention.

[0082] Example 17

[0083] The difference from Example 4 is that steps S3 and S4 are not carried out, and the others are the same as in Example 4. The dried black precipitate obtained in step S2 is labeled as IrCo 0.06 @Ir, and IrCo 0.06 @Ir is used as the doped molybdenum iridium-based multi-alloy core-shell structure PEM electrolytic water catalyst prepared in Example 17 of the present invention.

[0084] The catalysts prepared in the above examples were subjected to physical characterization tests, and the test results are as follows:

[0085] Figure 1 is the Mo prepared in Example 1 of the present invention 0.04 -IrCo 0.02 TEM image (transmission electron microscope image) of Mo Figure 1 -IrCo 0.04 -IrCo 0.02 @Ir-Etch. It can be observed that the catalyst prepared by combining the one-step synthesis method (i.e., steps S1-S2) and the selective etching method (i.e., steps S3-S4) shows a nanospherical structure with a petal-like protrusion on the surface as a whole. Such a morphology can expose more active sites and improve the catalytic activity.

[0086] Figure 2 is the Mo prepared in Example 1 of the present invention 0.04 -IrCo 0.02 HRTEM image (high-resolution transmission electron microscope image) of Mo Figure 2 -IrCo

[0087] Figure 3 @Ir-Etch. It can be observed that the diameter of the nanospheres is about 30-50 nm, and the lattice spacing is about 0.21 nm. 0.04 -IrCo 0.02 HAADF-STEM image (scanning transmission image) and elemental mapping images (elemental mapping images include line scan images and area scan images) of Mo Figure 3 -IrCo Figure 3 @Ir-Etch. In it, figure (a) is the HAADF-STEM image, figure (b) is the elemental area scan image of the mixture of Ir, Co, and Mo elements, figure (c) is the elemental line scan image of the mixture of Ir, Co, and Mo elements, and figures (d), (e), and (f) are the elemental area scan images of Ir, Co, and Mo elements alone, respectively. It can be observed that the catalyst presents a core of IrCo alloy protected by a Ir-rich shell, and molybdenum elements are evenly distributed in the IrCo core and the Ir-rich shell; the thickness of the shell is about 5-10 nm.

[0088] Figure 4 is the Mo prepared in Example 1 of the present invention 0.04 -IrCo 0.02 EDX energy spectrum of Mo Figure 4 -IrCo

[0089] Figure 5 @Ir-Etch. It can be observed that the elemental energy of Ir in the catalyst is the most obvious, followed by Co, while the characteristic peak of Mo is relatively weak. 0.04 -IrCo 0.02XRD pattern (X-ray diffraction pattern) of Ir-Etch. Refer to Figure 5 It can be observed that the lattice spacings of the three elements Ir, Co, and Mo are 0.222 nm (Ir, JCPDS: 00-006-0598), 0.205 nm (Co, JCPDS: 00-015-0806), and 0.233 nm (Mo, JCPDS: 01-088-2331) respectively. The lattice spacing of the multi-component composite catalyst is generally between the maximum and minimum spacings of the single elements. Therefore, Mo 0.04 -IrCo 0.02 @The lattice spacing of Ir-Etch should satisfy 0.205 - 0.233 nm, which is consistent with Figure 2 the lattice spacing of 0.21 nm measured by (HRTEM image).

[0090] Figure 6 are Mo prepared in Examples 1, 16, and 17 of the present invention 0.04 -IrCo 0.02 @Ir-Etch, Mo 0.04 -IrCo 0.02 @Ir, IrCo 0.06 XPS spectra (X-ray photoelectron spectra) of each element of @Ir, Figure 6 Among them, Figure (a) is the total spectrum, and Figures (b), (c), and (d) are the specific narrow spectra of the three elements Ir, Co, and Mo respectively. Since different elements will produce diffraction peaks at different abscissa positions under testing, and the diffraction peaks of each element will have different valence states, the valence state composition and element content of each element of this catalyst can be obtained through peak fitting. Refer to Figure 6 It can be observed that the three elements Ir, Co, and Mo exist. Among them, Ir mainly exists in the 0-valent and 4-valent states, Co mainly exists in the 0-valent, 2-valent, and 3-valent states, and Mo mainly exists in the 0-valent, 5-valent, and 6-valent states; in addition, with the occurrence of etching, Mo 0.04 -IrCo 0.02 @The characteristic peak area of Ir in Ir-Etch has no obvious change, while the characteristic peak areas of Co and Mo decrease significantly, indicating that etching only removes the excess Co and Mo.

[0091] The electrochemical performance of the catalysts prepared in the above examples was tested, and the test results are as follows:

[0092] The present invention uses a three-electrode system for electrochemical performance testing and evaluates it through the performance change of the oxygen evolution reaction in hydrogen production by electrolyzing water. The three-electrode system is divided into a working electrode, a counter electrode, and a reference electrode. Among them, the catalyst electrode is used as the working electrode, the platinum wire electrode is used as the counter electrode, the saturated silver chloride electrode is used as the reference electrode, and the electrolyte is 0.5 M H2SO4 solution.

[0093] The test conditions of the present invention are as follows:

[0094] Test temperature: room temperature (25 - 28 °C);

[0095] Linear sweep voltage range: 1.197 - 1.597 V (versus reversible hydrogen electrode);

[0096] Linear sweep rate: 5 mV / s;

[0097] Electrochemical impedance voltage: 1.5 V (versus reversible hydrogen electrode);

[0098] Frequency range of impedance test: 10 5 ~ 0.01 Hz;

[0099] CV cycle voltage range: 0.9 - 1.0 V (versus reversible hydrogen electrode);

[0100] Scan rate of CV test: 5, 10, 20, 40, 60, 80, 100 mV / s;

[0101] Constant current density for stability test: 10 mA / cm 2 .

[0102] The preparation method of the working electrode in the present invention is as follows: First, take 5 mg of the prepared catalyst and add it to 1 mL of absolute ethanol, and ultrasonicate for 20 min to form a well - mixed suspension.

[0103] (1) Glassy carbon electrode: Use a pipette to measure 5 μL of the suspension and drop it on a glassy carbon electrode with a diameter of 3 mm. After drying at room temperature for 10 - 15 min, repeat the above step once; then use a pipette to measure 5 μL of 0.2 wt% Nafion solution and drop it on the glassy carbon electrode, and dry it at room temperature for later use.

[0104] Meanwhile, use commercial IrO2 as a comparative catalyst and prepare a control working electrode according to the above method.

[0105] It should be noted that except for the long - term stability test, a glassy carbon electrode is used as the test electrode (working electrode).

[0106] (2) Carbon paper electrode: Cut the carbon paper into 1×1 cm 2 and ultrasonicate it in acetone, absolute ethanol, and deionized water for 10 min each, then put it in a drying oven at 60 °C and dry it for 2 h for later use. Use a pipette to measure 143 μL of the suspension and 71.5 μL of 0.2 wt% Nafion solution, mix them well, and then take 54 μL of the mixed solution and drop it on 1×1 cm 2On the carbon paper electrode, after drying in an oven at 60 °C for 5 - 10 min, repeat the above steps 3 times; finally, place it in an oven at 60 °C and dry for 6 h for later use.

[0107] Figure 7 are the oxygen evolution polarization curves of the catalysts prepared in all examples of the present invention and the comparative catalyst IrO2. Figure 7 Among them, in Figure (a), the oxygen evolution polarization curves of Examples 1 - 9 are shown, and in Figure (b), the oxygen evolution polarization curves of Examples 10 - 17 and the comparative catalyst IrO2 are shown. The overpotentials corresponding to each catalyst are shown in Table 1. It can be seen that: when the current density is 10 mA / cm 2 , the Mo 0.04 -IrCo 0.02 @Ir-Etch prepared in Example 1 has the optimal oxygen evolution catalytic activity, and the overpotential is only 206 mV.

[0108] Table 1 Overpotentials corresponding to each catalyst

[0109] ;

[0110] Figure 8 are the Tafel slope curves of Mo 0.04 -IrCo 0.02 @Ir-Etch, Mo 0.04 -IrCo 0.02 @Ir, and IrCo 0.06 @Ir prepared in Examples 1, 16, and 17. Refer to Figure 8 It can be observed that the Tafel slopes of Mo 0.04 -IrCo 0.02 @Ir-Etch, Mo 0.04 -IrCo 0.02 @Ir, and IrCo 0.06 @Ir are 59.7 mV / dec, 61.5 mV / dec, and 69.8 mV / dec respectively. The Tafel slope of Mo 0.04 -IrCo 0.02 @Ir-Etch is the smallest, indicating that its electrode response rate is the fastest.

[0111] Figure 9 are the electrochemical impedance curves of Mo 0.04 -IrCo 0.02 @Ir-Etch, Mo 0.04 -IrCo 0.02 @Ir, and IrCo 0.06 @Ir prepared in Examples 1, 16, and 17. Refer to Figure 9 It can be observed that Mo 0.04 -IrCo 0.02The semi - circular diameter of @Ir - Etch is the smallest, indicating that its electrochemical impedance value is the smallest.

[0112] Figure 10 For the Mo prepared in Examples 1, 16, and 17 0.04 -IrCo 0.02 @Ir - Etch, Mo 0.04 -IrCo 0.02 @Ir, IrCo 0.06 The CV curve and double - layer capacitance diagram of @Ir. Figure 10 Among them, Figures (a), (b), and (c) are respectively Mo 0.04 -IrCo 0.02 @Ir - Etch, Mo 0.04 -IrCo 0.02 @Ir, IrCo 0.06 The CV curve diagram of @Ir, and Figure (d) is the double - layer capacitance diagram. Refer to Figure 10 It can be observed that the double - layer capacitance value of Mo 0.04 -IrCo 0.02 @Ir - Etch is the largest, indicating that its electrochemically active area is the largest.

[0113] Figure 11 For the Mo prepared in Examples 1, 16, and 17 0.04 -IrCo 0.02 @Ir - Etch, Mo 0.04 -IrCo 0.02 @Ir, IrCo 0.06 The stability curve of @Ir. Refer to Figure 11 It can be observed that after 20h of testing, the voltage rise of Mo 0.04 -IrCo 0.02 @Ir - Etch (about 1.1%) < Mo 0.04 -IrCo 0.02 @Ir voltage rise (about 2.8%) < IrCo 0.06 @Ir voltage rise (about 3.7%), which proves that the doping of Mo element and the method of chemical etching both have a certain promoting effect on the improvement of catalyst stability.

[0114] Figure 12 For the Mo prepared in Example 1 0.04 -IrCo 0.02 The long - term stability curve of @Ir - Etch on the carbon paper electrode. Refer to Figure 12 It can be observed that after 100h of long - term testing, the voltage rise of Mo 0.04 -IrCo 0.02 @Ir - Etch is less than 1%, showing good stability of the catalyst.

[0115] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A molybdenum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst, characterized in that: The catalyst is a nano-spherical core-shell structure electrocatalyst; wherein the shell of the spherical core-shell structure is iridium, the core is iridium-cobalt, and the transition metal molybdenum is dispersed between the shell and the core.

2. A method for preparing a molybdenum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst, characterized in that: The following steps are involved: S1, taking iridium source, cobalt source, molybdenum source, surfactant, alcohol reducing agent and stabilizer into a beaker and mixing them thoroughly, and ultrasonically cleaning them in an ultrasonic cleaner for a set time, then moving them into a constant temperature water bath and stirring them on a magnetic stirrer to dissolve the raw materials, moving the sample obtained after stirring into an oil bath for heat preservation, and obtaining a solution with a precipitate after cooling; S2, centrifugally purify the solution with precipitate obtained in step S1 N times, N>1, to obtain a precipitate as the catalyst according to claim 1, marked as Mo x -IrCo y @Ir.

3. The method for preparing the platinum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst according to claim 2, characterized in that: The following steps are also included: S3, dispersing the precipitate obtained in step S2 in an etching solution, and after etching for a set time, obtaining an etched mixed solution; S4, centrifugally purify the mixed solution after etching obtained in step S3 M times, M>1, and obtain the precipitate after etching as the catalyst according to claim 1, marked as Mo x -IrCo y @Ir-Etch.

4. The method for preparing the platinum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst according to claim 2, characterized in that: In step S1, the iridium source is selected from one of iridium acetylacetonate and iridium chloride; the cobalt source is selected from one of cobalt acetylacetonate and cobalt chloride; the molybdenum source is selected from molybdenum acetylacetonate; the surfactant is one of hexadecyltrimethylammonium chloride and hexadecyltrimethylammonium bromide; the stabilizer is oleylamine; and the alcohol reducing agent is 1,2-hexadecanediol.

5. The method for preparing the platinum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst according to claim 2, characterized in that: In step S1, the ultrasonic time is 10 minutes; the temperature of the water bath is 70-80°C.

6. The method for preparing the platinum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst according to claim 2, characterized in that: In step S1, a magnetic stirrer is used for stirring, the rotation speed of the magnetic stirrer is 1000 rpm, and the stirring time is 10 minutes; the insulation temperature of the oil bath pot is 260-270° C., the insulation time is 40-60 minutes, and the heat transfer oil is dimethyl silicone oil.

7. The method for preparing the platinum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst according to claim 2, characterized in that: In step S1, the molar ratio of the iridium source to the molybdenum / cobalt source is 0.5:0.6, and the molar ratio of the cobalt source to the molybdenum source is 1:2, 1:1, and 2:

1.

8. The method for preparing the platinum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst according to claim 2, characterized in that: In step S2, a set amount of toluene and a set amount of methanol / anhydrous ethanol are added for the centrifugal purification, and the solution ratio is 1:2; each centrifugal purification time is 5 minutes; the first centrifugal speed is 10000 rpm, and the subsequent centrifugal speed is 8000 rpm.

9. The method for preparing the platinum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst according to claim 3, characterized in that: In step S3, the etching solution is cerium nitrate and copper nitrate; the concentration ratio of cerium to copper in the etching solution is 0:1, 1:3, 1:2, 1:1, 2:1, 3:1 or 1:0; and the etching time is 3, 6, 9, 12, 18 or 24 hours.

10. The method for preparing the molybdenum-doped iridium-based multi-element alloy core-shell structure PEM water electrolysis catalyst according to claim 3, characterized in that: In step S4, the centrifugal solution is 10 mL of anhydrous ethanol, the centrifugal purification time is 5 min each time, the first centrifugal speed is 10000 rpm, and the centrifugal speed is 8000 rpm each time thereafter.

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