Highly dispersed platinum-nickel-molybdenum-nitrogen composite, preparation and application thereof

Abstract

The application belongs to the field of material chemistry, and particularly relates to a highly-dispersed platinum-nickel-molybdenum-nitrogen composite as well as a preparation method and application thereof. The platinum catalyst in the platinum-nickel-molybdenum-nitrogen composite is anchored on the nickel-molybdenum-nitrogen composite in a highly-dispersed manner, and has excellent activity beyond commercial platinum-carbon, and can also be stably operated for a long time in high-concentration simulated seawater. The composite is prepared through a hydrothermal process and a subsequent low-temperature nitriding process, and has a simple preparation process, low raw material cost and good practical application potential.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of material chemistry, and particularly relates to a highly-dispersed platinum-nickel-molybdenum-nitrogen composite and a preparation and application thereof. BACKGROUND

[0002] Sustainable large-scale water electrolysis is a promising clean energy technology. Platinum is the best catalyst for hydrogen evolution reaction (HER) due to its optimal d-band center and ideal adsorption / desorption energy for the active intermediate. However, the scarcity and high cost of platinum are the main bottlenecks for the large-scale application of water electrolysis. An excellent HER catalyst can not only greatly reduce the amount of platinum used, but also maintain high catalytic activity and long-term stability.

[0003] As a substitute for platinum, inexpensive nickel-based catalysts can efficiently break the H-OH bond and be used in industrial water electrolysis cells in alkaline media. However, the hydrophobicity of the surface of these materials makes it difficult for the electrolyte to penetrate, and the H * Strong adsorption at the active site hinders the progress of HER. For example, strategies such as strain engineering, electron regulation and hydrogen overflow effect have been used to optimize the performance of nickel-based catalysts, but the activity and stability of the resulting materials are still lower than that of Pt. Metal nitrides with higher activity have also been developed, but so far no catalyst has exceeded platinum in terms of current density and overpotential. SUMMARY

[0004] In view of the problems in the prior art, the application provides a highly-dispersed platinum-nickel-molybdenum-nitrogen composite and a preparation method and application thereof. The platinum catalyst in the platinum-nickel-molybdenum-nitrogen composite is anchored on the nickel-molybdenum-nitrogen composite in a highly-dispersed manner, has excellent activity beyond that of commercial platinum-carbon, and can also be stably operated for a long time in high-concentration simulated seawater. The composite is prepared by a hydrothermal process and a subsequent low-temperature nitriding process, has a simple preparation process, low raw material cost, and good practical application potential.

[0005] The application is achieved by the following technical solutions.

[0006] Firstly, the application provides a highly-dispersed platinum-nickel-molybdenum-nitrogen composite Pt-Ni@NiMoN / NF, wherein the molar ratio of nickel to molybdenum in the composite is 0.5-2.5:0.05-0.25.

[0007] Further, the platinum source in the composite is one or more of chloroplatinic acid, potassium chloroplatinate, chloroplatinic acid ammonia, potassium chloroplatous acid, platinum nitrate, sodium chloroplatous acid, platinum tetrachloride and platinum acetylacetone.

[0008] Further, the nickel source in the complex is one or more of nickel nitrate, nickel acetate, nickel chloride, nickel sulfate, nickel phthalocyanine, nickel acetylacetone, nickel perchlorate.

[0009] Further, the molybdenum source in the complex is one or more of ammonium molybdate, sodium molybdate, zinc molybdate, molybdenum chloride, molybdenum acetylacetone, molybdenum acetate.

[0010] Secondly, the application provides a preparation method of a highly dispersed platinum-nickel-molybdenum-nitrogen complex, comprising the following steps:

[0011] (1) Pretreatment of nickel foam metal, the specific operation steps being that the nickel foam is respectively placed in a freshly prepared hydrochloric acid solution, anhydrous ethanol and deionized water, and ultrasonic washing is performed to remove the surface nickel oxide and impurities, and then the treated nickel foam is placed in a vacuum drying oven for drying for standby;

[0012] (2) An appropriate amount of nickel salt, molybdenum salt and urea are weighed and placed in a clean beaker, and a certain volume of deionized water is poured into the beaker to form a clear solution; the nickel foam pretreated in step 1 is transferred into a reaction kettle together with the solution to perform hydrothermal reaction, and after natural cooling to room temperature, the obtained sample is taken out and washed with deionized water, and then dried in a vacuum oven to obtain NiMoO4 / NF;

[0013] (3) The platinum salt solution is placed in a beaker, and the NiMoO4 / NF obtained in step 2 is immersed in the platinum salt solution to perform ion exchange reaction, and after the reaction is completed, the sample is washed with deionized water and dried to obtain Pt-NiMoO4 / NF;

[0014] (4) The NiMoO4 / NF or Pt-NiMoO4 / NF is respectively placed in a tube furnace, ammonia gas is introduced, the pyrolysis temperature and time are set, and after the reaction is completed, the sample Ni@NiMoN / NF or Pt-Ni@NiMoN / NF is taken out.

[0015] Further, the size of the nickel foam in step 1 is 1.5*2.0-4.5*6.0 cm.

[0016] Further, the concentration of the hydrochloric acid solution in step 1 is 1-2 M.

[0017] Further, the ultrasonic washing time in step 1 is 10-15 minutes.

[0018] Further, the drying temperature in step 1 is 50-80°C.

[0019] Further, the nickel salt in step 2 is one or more of nickel nitrate, nickel acetate, nickel chloride, nickel sulfate, nickel phthalocyanine, nickel acetylacetone, nickel perchlorate, and the amount of the nickel salt added is 0.5-2.5 mmol.

[0020] Further, the molybdenum salt in step 2 is one or more of ammonium molybdate, sodium molybdate, zinc molybdate, molybdenum chloride, molybdenum acetylacetone, molybdenum acetate; the amount of the molybdenum salt added is 0.05-0.25 mmol.

[0021] Further, the amount of urea in step 2 is 1.0-6.0 mmol.

[0022] Further, the amount of deionized water added in step 2 is 5-100 ml.

[0023] Further, the hydrothermal reaction temperature in step 2 is 80-150℃; the reaction time is 6-12 h.

[0024] Further, the platinum salt in step 3 is one or more of chloroplatinic acid, potassium chloroplatinate, chloroplatinic acid amine, potassium chloroplatous acid, platinum nitrate, sodium chloroplatous acid, platinum tetrachloride, platinum acetylacetone.

[0025] Further, the solvent in the platinum salt solution in step 3 is one or more of water, methanol, ethanol, acetone, ethylene glycol, etc.; the concentration of the platinum salt solution is at least 0.1 mg / ml; preferably 0.1 mg / ml-5.0 mg / ml.

[0026] Further, the reaction time of ion exchange in step 3 is at least 0.5 h, preferably 0.5 h-4.0 h; the reaction temperature is room temperature.

[0027] Further, the pyrolysis temperature in step 4 is 300-600℃; the pyrolysis time is 0.5-5.0 h; the ammonia flow rate is set to 10-300 ml / min.

[0028] In addition, the application provides a use of a platinum-nickel-molybdenum-nitrogen complex in hydrogen evolution, specifically, the platinum-nickel-molybdenum-nitrogen complex is directly used as a working electrode.

[0029] Further, the platinum-nickel-molybdenum-nitrogen complex is used by the following method:

[0030] The platinum-nickel-molybdenum-nitrogen complex is directly used as a working electrode after tailoring, a carbon rod is used as a counter electrode, a mercury oxide electrode is used as a reference electrode (the internal filling liquid is 1.0 M / L potassium hydroxide solution), the electrolyte is 1.0 M / L potassium hydroxide or 1.0 M / L potassium hydroxide solution containing different concentrations of sodium chloride (0.5, 1.0 and 2.0 M / L). An electrochemical workstation is used as a test platform, and a typical three-electrode system is used to carry out a hydrogen evolution reaction.

[0031] Compared with the prior art, the application has the following beneficial effects:

[0032] Firstly, the present application provides a highly dispersed platinum-nickel-molybdenum-nitrogen composite, which has a catalytic performance far superior to that of commercially available platinum-carbon noble metal catalysts. The composite can achieve a current density of 10 mA / cm 2 with only 7 mV of overpotential, and the overpotential is only 90 mV even at a high current density of 500 mA / cm 2 , which is far lower than the 321 mV of the platinum-carbon catalyst.

[0033] Secondly, the present application provides a preparation method of the highly dispersed platinum-nickel-molybdenum-nitrogen composite. The preparation process is simple, and the required raw materials are cheap and easy to obtain. The catalyst prepared by the process also has excellent long-term stability and can be continuously and stably operated for 110 h at a high current density of 50 mA / cm 2 with almost no attenuation.

[0034] Finally, the present application provides an application of the highly dispersed platinum-nickel-molybdenum-nitrogen composite in electrocatalytic hydrogen evolution under alkaline conditions. The low Tafel slope and small charge transfer resistance of the sample indicate its excellent kinetic process. The highly dispersed platinum sites anchored in the nickel-molybdenum-nitrogen greatly improve the HER performance of pure nickel-molybdenum-nitrogen hybrid, so that it exhibits excellent electrocatalytic activity in alkaline medium. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 X-ray diffraction patterns of.Ni@NiMoN / NF and Pt-Ni@NiMoN / NF.

[0036] Figure 2 SEM, TEM and HRTEM images of Pt-Ni@NiMoN / NF.

[0037] Figure 3 lsv curves, Tafel slopes and exchange current densities (j0) of different catalyst samples.

[0038] Figure 4 lsv curves of Pt-Ni@NiMoN / NF and commercial Pt-C / NF catalysts in different concentrations of sodium chloride alkaline solution.

[0039] Figure 5 Long-term stability test of Pt-Ni@NiMoN / NF and Ni@NiMoN / NF catalysts in 1M KOH.

[0040] Figure 6 Long-term stability test of Pt-Ni@NiMoN / NF catalyst in 1M KOH+2.0M NaCl solution. DETAILED DESCRIPTION

[0041] The present application will be further described in the following detailed description of embodiments with reference to the drawings. It is understood that other embodiments can be practiced and that changes can be made without departing from the spirit or scope of the application. The following detailed description is not intended to limit the application, as claimed, to any one embodiment, but rather, for purposes of illustration only. The detailed description includes specific information for a practical example of the application, and is not intended to limit the scope of the application, which is solely defined by the appended claims.

[0042] Example 1

[0043] Pre-treatment of the nickel foam: Two pieces of nickel foam with a size of 1.5 x 2.0 cm were placed in a new 1M HC1, anhydrous ethanol and deionized water, respectively, for ultrasonic washing for 10 minutes, in order to remove the surface nickel oxide and impurities, and then the treated nickel foam was placed in a 60°C vacuum drying oven for drying for standby.

[0044] Preparation of NiMoO4 / NF: 1.5 mmol of nickel nitrate (hexahydrate), 0.25 mmol of ammonium molybdate (tetrahydrate) and 3.0 mmol of urea were weighed into a clean beaker, and then 20 ml of deionized water was added to form a clear solution. The pre-treated nickel foam was transferred to a 50 ml reaction kettle with the solution, and a hydrothermal reaction was performed at a reaction temperature of 90°C for 8h. After natural cooling to room temperature, the obtained sample (NiMoO4 / NF) was washed with deionized water, and then dried in a vacuum oven for standby.

[0045] Preparation of Pt-NiMoO4 / NF: First, 0.1 ml of chloroplatinic acid solution with a concentration of 10.0 mg / ml was transferred to a small beaker, and then deionized water was added to make up to 5.0 ml. Then, the NiMoO4 / NF prepared in the previous step was immersed in the solution, and an ion exchange reaction was performed at room temperature for 1.0 h. After the reaction was completed, the sample was taken out, washed with deionized water, and dried in a vacuum oven. The obtained sample was labeled as Pt-NiMoO4 / NF.

[0046] Preparation of Ni@NiMoN / NF and Pt-Ni@NiMoN / NF:

[0047] The sample (NiMoO4 / NF) obtained in step 2 was placed in a tube furnace with air exhausted, and high-purity ammonia gas was slowly introduced. The sample was pyrolyzed at a temperature above 300°C for 2.0 h. After the reaction was completed, the furnace was naturally cooled, and the obtained sample (Ni@NiMoN / NF) was taken out and placed in a dry place for subsequent testing;

[0048] The sample obtained in step 3 (Pt-NiMoO4 / NF) was placed in a tube furnace with air exhausted, high-purity ammonia gas was slowly introduced, and pyrolysis was performed at 300°C or above for 2.0 h. After the reaction was completed, the furnace was naturally cooled, and the obtained sample (Pt-Ni@NiMoN / NF) was taken out and placed in a dry place for subsequent testing.

[0049] Example 2

[0050] Pre-treatment of nickel foam: Two pieces of nickel foam with a size of 1.5 x 2.0 cm were placed in a newly configured 1M HCl, anhydrous ethanol, and deionized water, respectively, and each was ultrasonically washed for 10 minutes. The purpose was to remove the surface nickel oxide and impurities. Subsequently, the treated nickel foam was placed in a 60°C vacuum drying oven for drying.

[0051] Preparation of NiMoO4 / NF: 1.5 mmol of nickel nitrate (hexahydrate), 0.25 mmol of ammonium molybdate (tetrahydrate), and 3.0 mmol of urea were weighed and placed in a clean beaker, and 20 ml of deionized water was added to form a clear solution. The pretreated nickel foam was transferred to a 50 ml reaction kettle with the solution and subjected to a hydrothermal reaction. The reaction temperature was 90°C, and the time was 8 h. After natural cooling to room temperature, the obtained sample (NiMoO4 / NF) was washed with deionized water, and then dried in a vacuum oven for standby use.

[0052] Preparation of Pt-NiMoO4 / NF: First, 0.5 ml of chloroplatinic acid solution with a concentration of 10.0 mg / ml was transferred to a small beaker and diluted to 5.0 ml with deionized water. Subsequently, the NiMoO4 / NF prepared in the previous step was immersed in it, and an ion exchange reaction was performed at room temperature for 1.0 h. After the reaction was completed, the sample was taken out, rinsed with deionized water, and dried in a vacuum oven. The obtained sample was labeled as Pt-NiMoO4 / NF.

[0053] Preparation of Pt-Ni@NiMoN / NF:

[0054] The sample obtained in step 3 (Pt-NiMoO4 / NF) was placed in a tube furnace with air exhausted, high-purity ammonia gas was slowly introduced, and pyrolysis was performed at 300°C or above for 2.0 h. After the reaction was completed, the furnace was naturally cooled, and the obtained sample (Pt-Ni@NiMoN / NF) was taken out and placed in a dry place for subsequent testing.

[0055] Example 3

[0056] Pre-treatment of nickel foam: Two pieces of nickel foam with a size of 1.5 x 2.0 cm were placed in a newly configured 1M HCl, anhydrous ethanol, and deionized water, respectively, and each was ultrasonically washed for 10 minutes. The purpose was to remove the surface nickel oxide and impurities. Subsequently, the treated nickel foam was placed in a 60°C vacuum drying oven for drying.

[0057] Preparation of NiMoO4 / NF: 1.5 mmol of nickel nitrate (hexahydrate), 0.25 mmol of ammonium molybdate (tetrahydrate) and 3.0 mmol of urea were weighed into a clean beaker, and then poured into 20 ml of deionized water to form a clear solution. The pretreated nickel foam was transferred into a 50 ml reactor together with the solution, and a hydrothermal reaction was performed at a temperature of 90℃ for 8 h. After natural cooling to room temperature, the obtained sample (NiMoO4 / NF) was washed with deionized water, and then dried in a vacuum oven for standby use.

[0058] Preparation of Pt-NiMoO4 / NF: 2.5 ml of chloroplatinic acid solution with a concentration of 10.0 mg / ml was first transferred into a small beaker, and then diluted to 5.0 ml with deionized water. Subsequently, the NiMoO4 / NF prepared in the previous step was immersed in the solution, and an ion exchange reaction was performed at room temperature for 1.0 h. After the reaction was completed, the sample was taken out, washed with deionized water, and dried in a vacuum oven. The obtained sample was marked as Pt-NiMoO4 / NF.

[0059] Preparation of Pt-Ni@NiMoN / NF:

[0060] The sample (Pt-NiMoO4 / NF) obtained in the previous step was placed in a tube furnace with the air exhausted, and high-purity ammonia gas was slowly introduced. The sample was pyrolyzed at a temperature of 300℃ for 2.0 h. After the reaction was completed, the furnace was naturally cooled, and the obtained sample (Pt-Ni@NiMoN / NF) was taken out and placed in a dry place for subsequent testing.

[0061] Product characterization and testing

[0062] As can be seen from the X-ray diffraction results shown in Figure 1 As can be seen from the X-ray diffraction results shown in

[0063] As can be seen from the X-ray diffraction results shown in Figure 2The SEM, TEM, and HRTEM results show that the Pt-Ni@NiMoN / NF prepared in this invention exists in the form of nanorods with a large number of attached particles. Local HRTEM images reveal that the lattice spacing of the spherical particles is 0.203 nm, corresponding to the (111) crystal plane of Ni. The rod-shaped regions contain a large number of amorphous phases, with some areas showing weak lattice fringes and a lattice spacing of 0.246 nm, corresponding to the (100) crystal plane of Ni0.2Mo0.8N. No obvious platinum nanoparticles were observed in the HRTEM images, further confirming the high dispersion of platinum.

[0064] Performance Testing: An electrochemical workstation (model CHI 760E) from Shanghai Chenhua Instruments Co., Ltd. was used as the testing platform. A typical three-electrode system was employed to conduct detailed tests on the HER performance of the prepared catalyst. The Ni@NiMoN / NF or Pt-Ni@NiMoN / NF prepared in this invention was directly used as the working electrode after being cut, with a carbon rod as the counter electrode and a mercuric oxide electrode as the reference electrode (filled with a 1.0 M / L potassium hydroxide solution). The electrolyte was either a 1.0 M / L potassium hydroxide solution or a 1 M / L potassium hydroxide solution containing different concentrations of sodium chloride (0.5, 1.0, and 2.0 M / L). The test results were used to evaluate the HER performance of the catalyst prepared using this process.

[0065] Depend on Figure 3 It can be seen that the Pt-Ni@NiMoN / NF prepared by this process has the best catalytic activity at a current density of 10 mA / cm². 2 The required overpotential is only 7 mV, far lower than that of commercial platinum-carbon and other catalysts, and this trend becomes more pronounced with increasing overpotential. Furthermore, this catalyst exhibits the lowest Tafel slope and the largest j0, indicating its excellent electrochemical kinetics.

[0066] Depend on Figure 4 It can be seen that even when the sodium chloride concentration in the electrolyte increases to 2 M / L, the catalytic activity of Pt-Ni@NiMoN / NF does not show a significant decrease. In contrast, commercial platinum-carbon catalysts exhibit a continuous decline in catalytic performance with increasing sodium chloride concentration. This experimental result fully demonstrates that the prepared Pt-Ni@NiMoN / NF possesses excellent resistance to sodium chloride corrosion.

[0067] Long-term electrocatalytic stability is an important indicator for evaluating catalyst performance. Figure 5 It can be seen that Pt-Ni@NiMoN / NF at 50mA / cm 2The overpotential of Pt-Ni@NiMoN / NF only increased by 9 mV after 110 h of constant current test at a current density of 50 mA / cm2. In sharp contrast, the Ni@NiMoN / NF without Pt showed a high degree of decay at the beginning of the stability test. The above results further demonstrate that the introduction of highly dispersed Pt elements can greatly improve the catalytic activity and stability of Ni@NiMoN / NF.

[0068] By Figure 6 It can be seen that the Pt-Ni@NiMoN / NF catalyst can still be operated stably for up to 70 h without significant decay at a current density of 50 mA / cm2in a basic solution with a sodium chloride concentration as high as 2.0 M, which further demonstrates its excellent resistance to sodium chloride corrosion. 2 It can be seen that the Pt-Ni@NiMoN / NF catalyst can still be operated stably for up to 70 h without significant decay at a current density of 50 mA / cm2in a basic solution with a sodium chloride concentration as high as 2.0 M, which further demonstrates its excellent resistance to sodium chloride corrosion.

Claims

1. A method for preparing a highly dispersed platinum-nickel-molybdenum-nitrogen composite, characterized in that, Includes the following steps: (1) Pretreatment of nickel foam metal, the specific operation steps are as follows: Take the foam nickel and place it in freshly prepared hydrochloric acid solution, anhydrous ethanol and deionized water respectively, and ultrasonically wash it to remove nickel oxide and impurities on the surface. Then put the treated foam nickel into a vacuum drying oven to dry for later use. (2) Weigh appropriate amounts of nickel salt, molybdenum salt and urea in a clean beaker, and pour in a certain volume of deionized water to form a clear solution. Transfer the foamed nickel pretreated in step (1) and this solution to the reactor for hydrothermal reaction. After naturally cooling to room temperature, take out the obtained sample and wash it thoroughly with deionized water. Then dry it in a vacuum oven to obtain NiMoO4 / NF. (3) Place the platinum salt solution in a beaker, immerse the NiMoO4 / NF obtained in step (2) in it to carry out the ion exchange reaction, and after the reaction is completed, rinse with an appropriate amount of deionized water and dry thoroughly to obtain Pt-NiMoO4 / NF. (4) Place NiMoO4 / NF and Pt-NiMoO4 / NF in a tube furnace, introduce ammonia gas, set the pyrolysis temperature and time, allow the reaction to cool naturally after completion, and take out the obtained samples Ni@NiMoN / NF and Pt-Ni@NiMoN / NF.

2. The preparation method according to claim 1, characterized in that, The nickel salt mentioned in step (2) is one or more of nickel nitrate, nickel acetate, nickel chloride, nickel sulfate, nickel phthalocyanine, nickel acetylacetone, and nickel perchlorate; the amount of nickel salt added is 0.5~2.5 mmol.

3. The preparation method according to claim 1, characterized in that, The molybdenum salt mentioned in step (2) is one or more of ammonium molybdate, sodium molybdate, zinc molybdate, molybdenum chloride, molybdenum acetylacetonate, and molybdenum acetate; the amount of molybdenum salt added is 0.05~0.25 mmol.

4. The preparation method according to claim 1, characterized in that, The amount of urea mentioned in step (2) is 1.0~6.0 mmol.

5. The preparation method according to claim 1, characterized in that, The platinum salt mentioned in step (3) is one or more of the following: chloroplatinic acid, potassium chloroplatinate, ammonium chloroplatinate, potassium chloroplatinate, platinum nitrate, sodium chloroplatinate, platinum tetrachloride, and platinum acetylacetonate.

6. The preparation method according to claim 1, characterized in that, The solvent in the platinum salt solution in step (3) is one or more of water, methanol, ethanol, acetone, and ethylene glycol; the concentration of the platinum salt solution is 0.1 mg / ml to 5.0 mg / ml.

7. The preparation method according to claim 1, characterized in that, The reaction time for ion exchange in step (3) is 0.5 h to 4.0 h; the reaction temperature is room temperature.

8. The preparation method according to claim 1, characterized in that, The pyrolysis temperature in step (4) is 300-600℃; the pyrolysis time is 0.5-5.0h; and the ammonia flow rate is set to 10-300 ml / min.

9. A highly dispersed platinum-nickel-molybdenum-nitrogen composite Pt-Ni@NiMoN / NF prepared by the preparation method of claim 1, characterized in that, The molar ratio of nickel to molybdenum in the composite is 0.5~2.5:0.05~0.

25.

10. The application of a highly dispersed platinum-nickel-molybdenum-nitrogen complex prepared by the method of claim 1 in hydrogen evolution, characterized in that, Specifically, the platinum-nickel-molybdenum-nitrogen composite is used directly as the working electrode.

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