Preparation method and application of transition metal doped nickel-based composite material

Abstract

The invention relates to the technical field of catalysts, in particular to a preparation method and application of a transition metal doped nickel-based composite material, and the preparation method comprises the following steps: firstly, measuring nickel nitrate hexahydrate (or nickel chloride hexahydrate), ferric chloride and urea, and dissolving the three into deionized water to prepare a uniform metal precursor solution; then, the foamed nickel is subjected to surface pretreatment, ultrasonic cleaning is conducted through ethyl alcohol, acetone, a hydrochloric acid solution and deionized water in sequence, and surface impurities and an oxide layer are thoroughly removed; immersing the pretreated foamed nickel into the precursor solution, and completing the reaction at a set temperature for a set reaction time; and finally, alternately washing with deionized water and ethanol, and carrying out vacuum drying treatment to finally obtain the NiFe-LDH / NF composite material with the iron-doped nickel-based hydroxide nanosheet array vertically grown on the surface of the foamed nickel. The preparation process is simple and convenient to operate, the raw material cost is low, and a new technical direction is provided for development of the efficient non-noble metal electrolyzed water catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a preparation method of a transition metal-doped nickel-based composite material and application thereof. BACKGROUND

[0002] From the perspective of expanding the raw material resources for hydrogen production by water electrolysis, seawater, as the most abundant water resource on the earth's surface (about 97.5% of the total global water resources), can completely eliminate the dependence on limited fresh water if used directly for hydrogen production by electrolysis, especially suitable for hydrogen energy industry layout in areas lacking fresh water resources such as coastal areas, islands and deserts, and has irreplaceable strategic significance for realizing the resource sustainability of hydrogen energy production. However, in the scenario of electrolyzing seawater, the OER process faces more severe specific technical challenges: the high concentration of Cl - in seawater is easy to cause chlorine evolution reaction at the anode, which has a significant competitive relationship with OER, not only consumes electric energy to generate Cl2 by-product, resulting in a decrease in hydrogen purity, but also accelerates the oxidation corrosion of active sites of the catalyst; at the same time, the dissolved Ca 2+ and Mg 2+ in seawater are easy to combine with OH - on the electrode surface to generate Ca(OH)2 and Mg(OH)2 precipitates, forming a dense scale layer to block the active sites and increase the mass transfer resistance, resulting in rapid degradation of the catalyst performance. The existing non-noble metal OER catalysts are mostly designed for alkaline fresh water systems, and generally have the shortcomings of insufficient chlorine corrosion resistance and weak anti-scaling ability in seawater environment, which is difficult to meet the requirements of industrial continuous operation. Therefore, developing a non-noble metal OER catalyst with low cost, high OER catalytic activity and selectivity, strong chlorine corrosion resistance and anti-scaling ability has become a key requirement to break through the industrialization bottleneck of hydrogen production by electrolyzing seawater.

[0003] Among transition metal-based catalysts, nickel-iron layered double hydroxide (NiFe-LDH) exhibits OER activity close to noble metals in alkaline electrolyte due to its layered structure, controllable electronic properties and abundant active sites. The synergistic effect of Ni 2+ and Fe 3+ in the layer can optimize the adsorption energy of intermediates, and the open structure is also beneficial to mass transfer and gas release. Some optimized NiFe-LDH can have an overpotential as low as 250-300 mV at a current density of 1 M KOH 10 mA cm -2 . However, the existing NiFe-LDH still has obvious shortcomings: the industrial-grade high current density (>1000 mA cm -2)The performance is attenuated due to the dissolution of the active site and the structure collapse; the traditional preparation needs to coat the electrode with a high molecular binder, which easily covers the active site and increases the interface resistance; and the research on the electrolyte impurity interference, dynamic adaptability and seawater electrocatalytic corrosion resistance is still weak, the existing achievements focus on the optimization of low current density, lack of systematic exploration of failure mechanism and stability improvement under high current density, and the above bottlenecks need to be broken through by structure design and process innovation.

[0004] In view of the above problems, the NiFe-LDH-based catalyst with high activity, high stability and industrial applicability needs to be developed through structure design and preparation process innovation. For example, by in-situ growth of the catalyst through substrate loading strategy, the use of binder can be avoided, the contact impedance can be reduced and the active site can be maximized; by optimizing the electronic structure through adjusting the metal ratio, the metal-oxygen bond strength can be enhanced and the dissolution of active components can be inhibited; in addition, the multi-stage pore design can accelerate the release of bubbles and avoid mass transfer delay. The above improvement direction provides a feasible path for the performance breakthrough of the NiFe-LDH catalyst, but the structure-activity relationship and large-scale preparation technology still need to be further explored to meet the industrialization demand of water electrolysis for hydrogen production. SUMMARY

[0005] The purpose of the present application is to solve the problems existing in the prior art, and a preparation method of a transition metal doped nickel-based composite material and its application are proposed. By optimizing the metal ratio, substrate loading strategy and preparation process, the oxygen evolution reaction (OER) activity and long-term stability of the catalyst are significantly improved, and the energy consumption cost of water electrolysis for hydrogen production is reduced.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a transition metal doped nickel-based composite material, the transition metal doped nickel-based composite material is an iron doped nickel-based hydroxide nanosheet array grown on the surface of a nickel foam; the preparation method comprises the following steps:

[0008] Step 1, preparation of a precursor solution: respectively weigh nickel nitrate hexahydrate (or nickel chloride hexahydrate) and urea, and add different amounts of anhydrous iron chloride, dissolve the above raw materials in deionized water, stir until completely dissolved, and obtain a metal precursor solution;

[0009] Step 2, substrate pretreatment: the nickel foam is subjected to surface cleaning treatment;

[0010] Step 3, hydrothermal reaction: the precursor solution prepared in step 1 is transferred to a reaction kettle, the pretreated nickel foam is added, and the hydrothermal reaction is carried out;

[0011] Step 4: post-treatment: after the reaction is completed, the sample is taken out, washed and dried to obtain the transition metal doped nickel-based composite material.

[0012] Preferably, in step 1, the amounts of each raw material are as follows: nickel nitrate hexahydrate 0.1-0.2 g (or nickel chloride hexahydrate), urea 0.2-0.3 g, anhydrous ferric chloride 0.01 g-0.20 g, and the amount of deionized water required for dissolving the above raw materials is 30 mL-45 mL. Among them, the molar ratio of Ni to Fe is 1:0.2-1:2, and the amount of urea is an integer multiple of the total molar amount of metal salt. Here, the molar ratio of Ni to Fe is preferably 1:1-1:2, and the amount of urea is 3-5 times the total molar amount of metal salt.

[0013] Preferably, in step 1, the mass ratio of anhydrous ferric chloride corresponds to an iron element content of about 0.87%-11.77%. This iron element content range can be achieved by adjusting the amount of anhydrous ferric chloride, which can be optionally selected from the range of 0.01 g-0.20 g.

[0014] Preferably, in step 2, the pretreatment of the foamed nickel is ultrasonic cleaning in the following order: first, cleaning with ethanol for 20-40 min, then cleaning with acetone for 20-40 min, followed by cleaning with 3-5 mol / L HCl solution for 10 min (a total of 3 times), and finally cleaning with deionized water for 30 min (a total of 4-5 times). -1 Preferably, in step 2, the pretreatment of the foamed nickel is ultrasonic cleaning in the following order: first, cleaning with ethanol for 20-40 min, then cleaning with acetone for 20-40 min, followed by cleaning with 3-5 mol / L HCl solution for 10 min (a total of 3 times), and finally cleaning with deionized water for 30 min (a total of 4-5 times).

[0015] Preferably, in step 3, the temperature of the hydrothermal reaction is 120-160 ℃, and the reaction time is 6-8 h. Here, the preferred conditions for the hydrothermal reaction are a temperature of 125-130 ℃ and a time of 6 h.

[0016] Preferably, in step 3, the size of the foamed nickel is 2 cm×2 cm or 3 cm×3 cm.

[0017] Preferably, in step 4, the cleaning conditions are 3-5 times of alternate washing with deionized water and ethanol, the vacuum drying temperature is 45 ℃, and the drying time is 8 h.

[0018] The application also provides a transition metal-doped nickel-based composite material prepared by the above preparation method for use in oxygen evolution reaction (OER).

[0019] In practical applications: in a 1 M KOH electrolyte, the oxygen evolution reaction (OER) test results show that at a current density of 500 mAcm -2 -2, the overpotential is 0.45 V, and the Tafel slope is 0.12 V / dec. 1.5The overpotential of the LDH is 309 mV, and the overpotential of the Ni (OH)2 / NF is 539 mV; under the current density of 1000 mA cm -2 The overpotential of the LDH is 354 mV, and the overpotential of the Ni (OH)2 / NF is 718 mV. 1.5 The overpotential of the LDH is 354 mV, and the overpotential of the Ni (OH)2 / NF is 718 mV. 1.5 The LDH can continuously run for 500 hours under the constant current density of 2000 mA cm -2 The voltage has little change; under the constant current density of 2000 mA cm -2 The voltage has little change. Therefore, the NiFe-LDH / NF catalyst prepared by the application has excellent catalytic activity and stability under high current density, which is beneficial to realize industrial application in the electrolytic hydrogen industry.

[0020] By adopting the above technical scheme: the metal synergistic effect is precisely controlled by iron doping, and the nanosheet array is grown in situ without relying on a high molecular binder, which can maximize the exposure of the catalytically active sites and significantly reduce the interface contact resistance. In terms of application performance, it exhibits excellent oxygen evolution reaction (OER) catalytic activity in an alkaline electrolyte, and has stable running capacity under high current density, which can adapt to industrial scenarios such as water electrolysis hydrogen production and seawater electrocatalysis.

[0021] Compared with the prior art, the application has the following beneficial effects:

[0022] 1、The transition metal doped nickel-based composite material prepared by the application has excellent catalytic activity and stability, and the OER overpotential under the current density of 500 mA cm -2 The current density is 309 mV, which is significantly lower than that of the undoped iron Ni (OH)2 / NF catalyst (539 mV); under the current density of 1000 mA cm -2 The overpotential is 354 mV, which is 50.7% lower than that of the Ni (OH)2 / NF (718 mV), and exhibits high kinetic performance under high current density.

[0023] 2、The catalyst of the application can continuously run for 500 hours under the constant current density of 2000 mA cm -2 The voltage has little change; under the constant current density of 2000 mA cm -2 The voltage has little change, and the structural durability is significantly better than that of the traditional system.

[0024] 3、The application avoids the use of a high polymer binder through an in-situ growth process by a hydrothermal method, maximizes the exposure of active sites, reduces the interface contact resistance, and at the same time, the raw material cost is only 1 / 5 of that of a noble metal catalyst (such as IrO2), the preparation process is simple, the energy consumption is low, it is suitable for large-scale industrial production, and has great commercial application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Ni3Fe prepared for the application examples 1, 2, 3 and the comparative example 1 0.2 -LDH, Ni3Fe-LDH, Ni3Fe 1.5 XRD patterns of -LDH, Ni3Fe2-LDH;

[0026] Figure 2 TEM and EDS images of the catalyst of the application example 3;

[0027] Figure 3 Ni3Fe of the application 0.2 -LDH, Ni3Fe-LDH, Ni3Fe 1.5 Comparison chart of OER performance of -LDH, Ni3Fe2-LDH;

[0028] Figure 4 Stability test curve chart of the catalyst of the application example 3 in alkaline water and simulated seawater. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings, so that the people skilled in the art can better understand the advantages and features of the application, and the protection scope of the application is defined more clearly. The described embodiments of the application are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by the people skilled in the art without creative labor fall within the protection scope of the application.

[0030] Example 1:

[0031] Iron-doped nickel-based hydroxide nanosheet array electrolytic water catalyst Ni3Fe 0.2 Preparation method of -LDH:

[0032] (1) Preparation of the precursor solution:

[0033] a) Take 0.145 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O), 0.24 g of urea (CO(NH2)2), and 0.016 g of anhydrous ferric chloride (FeCl3) and add them to 37 mL of deionized water in sequence.

[0034] b) Stir magnetically for 30 min until complete dissolution, forming a uniform transparent solution.

[0035] (2) Hydrothermal reaction and in-situ loading:

[0036] a) Transfer the above solution to a 50 mL polytetrafluoroethylene-lined reaction kettle, and add pretreated nickel foam (NF, size 3 cm×3 cm) as the substrate.

[0037] b) Seal the reaction kettle and place it in a vacuum drying box, set the temperature to 130°C, and react for 6 h.

[0038] (3) Post-processing:

[0039] a) After the reaction is completed, naturally cool to room temperature, remove the nickel foam substrate, and rinse it with deionized water 5 times and with anhydrous ethanol 3 times.

[0040] b) Place the sample in a vacuum drying box and dry it at 45°C for 8 h to obtain a nickel-based catalyst with a 1.43% iron doping amount (labeled as Ni3Fe-LDH). 0.2

[0041] Example 2:

[0042] Method for preparing iron-doped nickel-based hydroxide nanosheet array electrolytic water catalyst Ni3Fe-LDH:

[0043] (1) Preparation of precursor solution:

[0044] a) Take 0.145 g of Ni(NO3)2·6H2O, 0.24 g of CO(NH2)2, and 0.08 g of FeCl3 and dissolve them in 37 mL of deionized water.

[0045] b) Stir magnetically for 30 min until complete dissolution, forming a uniform transparent solution.

[0046] (2) Hydrothermal reaction and in-situ loading:

[0047] a) Transfer the above solution to a 50 mL polytetrafluoroethylene-lined reaction kettle, and add pretreated nickel foam (NF, size 3 cm×3 cm) as the substrate.

[0048] ​b) Seal the reaction kettle and place it in a vacuum drying oven. Set the temperature to 130 °C and the reaction time to 6 h.

[0049] (3) Post-treatment:

[0050] a) After the reaction is completed, naturally cool to room temperature. Remove the foam nickel substrate and rinse it with deionized water 5 times and with anhydrous ethanol 3 times.

[0051] b) Place the sample in a vacuum drying oven and dry it at 45 °C for 8 h to obtain a nickel-based catalyst with an iron doping amount of 7.15% (labeled as Ni3Fe-LDH).

[0052] Example 3:

[0053] Preparation method of iron-doped nickel-based hydroxide nanosheet array electrolytic water catalyst Ni3Fe-LDH: 1.5

[0054] (1) Preparation of precursor solution:

[0055] a) Weigh 0.145 g of Ni(NO3)2·6H2O, 0.24 g of CO(NH2)2, and 0.12 g of FeCl3, and dissolve them in 37 mL of deionized water.

[0056] b) Stir magnetically for 30 min until completely dissolved to form a uniform transparent solution.

[0057] (2) Hydrothermal reaction and in-situ loading:

[0058] a) Transfer the above solution to a 50 mL polytetrafluoroethylene-lined reaction kettle and add pre-treated foam nickel (NF, size 3 cm x 3 cm) as the substrate.

[0059] b) Seal the reaction kettle and place it in a vacuum drying oven. Set the temperature to 130 °C and the reaction time to 6 h.

[0060] (3) Post-treatment:

[0061] a) After the reaction is completed, naturally cool to room temperature. Remove the foam nickel substrate and rinse it with deionized water 5 times and with anhydrous ethanol 3 times.

[0062] b) Place the sample in a vacuum drying oven and dry it at 45 °C for 8 h to obtain a nickel-based catalyst with an iron doping amount of 7.15% (labeled as Ni3Fe 1.5 -LDH).

[0063] Example 4:

[0064] ​Preparation method of iron-doped nickel-based hydroxide nanosheet array water electrolysis catalyst Ni3Fe2-LDH

[0065] (1) Preparation of precursor solution:

[0066] a) Take Ni(NO3)2·6H2O 0.145 g, CO(NH2)2 0.24 g, FeCl3 0.16 g, and dissolve in 37 mL of deionized water.

[0067] b) Stir for 30 min by magnetic force until completely dissolved to form a uniform transparent solution.

[0068] (2) Hydrothermal reaction and in-situ loading:

[0069] a) Transfer the above solution to a 50 mL polytetrafluoroethylene-lined reaction kettle, and add pretreated foam nickel (NF, size 3 cm×3 cm) as the substrate.

[0070] b) Seal the reaction kettle and place it in a vacuum drying box, set the temperature to 130°C, and react for 6 h.

[0071] (3) Post-processing

[0072] a) After the reaction is completed, naturally cool to room temperature, remove the foam nickel substrate, and rinse with deionized water for 5 times and anhydrous ethanol for 3 times.

[0073] b) Place the sample in a vacuum drying box and dry at 45°C for 8 h to obtain a nickel-based catalyst with an iron doping amount of 14.31% (labeled as Ni3Fe2-LDH).

[0074] Comparative Example 1:

[0075] Preparation method of iron-doped nickel-based hydroxide nanosheet array water electrolysis catalyst Ni3Fe2-LDH

[0076] (1) Preparation of precursor solution:

[0077] a) Only take Ni(NO3)2·6H2O 0.145 g, CO(NH2)2 0.24 g, and do not add FeCl3, and dissolve in 37 mL of deionized water.

[0078] b) Stir for 30 min by magnetic force until completely dissolved to form a uniform transparent solution.

[0079] (2) Hydrothermal reaction and in-situ loading:

[0080] a) The above solution was transferred to a 50 mL Teflon-lined reaction kettle, and pretreated foamed nickel (NF, size 3 cm x 3 cm) was added as a substrate.

[0081] b) The reaction kettle was sealed and placed in a vacuum drying box, and the temperature was set to 130°C, and the reaction time was 6 h.

[0082] (3) Post-treatment

[0083] a) After the reaction was completed, it was naturally cooled to room temperature, and the foamed nickel substrate was removed and washed with deionized water 5 times and absolute ethanol 3 times.

[0084] b) The sample was placed in a vacuum drying box and dried at 45°C for 8 h to obtain a nickel-based catalyst without iron doping (labeled as Ni(OH)2 / NF).

[0085] Electrochemical test

[0086] Ni3Fe of Example 1, Example 2, Example 3, Comparative Example 1 0.2 -LDH, Ni3Fe-LDH, Ni3Fe 1.5 The electrochemical performance of the Ni(OH)2 / NF catalyst was tested by an electrochemical workstation. The electrochemical workstation used was a Chenhua electrochemical workstation, model DH604 and DH630. The specific method is as follows:

[0087] A 1.0 mol L⁻¹ KOH solution was used as the electrolyte, a three-electrode system was used, and the Ni3Fe 0.2 -LDH prepared in Example 1, Ni3Fe-LDH prepared in Example 2, Ni3Fe 1.5 -LDH prepared in Example 3, Ni3Fe2-LDH prepared in Example 4, and Ni(OH)2 / NF prepared in Comparative Example 1 were used as working electrodes, respectively, a Hg / HgO electrode was used as a reference electrode, and a carbon rod electrode was used as a counter electrode, and the linear sweep voltammetry curves were tested.

[0088] OER performance test:

[0089] The Ni3Fe 0.2 -LDH, Ni3Fe-LDH, Ni3Fe 1.5 -LDH, Ni3Fe2-LDH, and commercial IrO2 were tested for OER performance, and the polarization curve graph (LSV graph) obtained is shown in Figure 3 At a current density of 500 mA cm -2 , the Ni3Fe 1.5The overpotential of -LDH is 309 mV, while the overpotential of Ni(OH)2 / NF is 539 mV. At 1000 mA cm⁻¹ -2 At current density, Ni3Fe 1.5 The overpotential of -LDH is 354 mV, while the overpotential of Ni(OH)2 / NF is 718 mV.

[0090] Stability test:

[0091] In 1 M KOH electrolyte at 2000 mA cm⁻¹ -2 Ni3Fe 1.5 -LDH voltage remained almost unchanged; in simulated seawater electrolyte at 2000 mA cm⁻¹ -2 Ni3Fe 1.5 The -LDH voltage changes, but the change is small.

[0092] In summary, the iron-doped nickel-based seawater OER catalyst prepared by this invention exhibits significantly better water electrolysis performance than the commercial noble metal catalyst IrO2. Furthermore, this catalyst demonstrates excellent catalytic activity and stability at high current densities, which is beneficial for its industrial application in the electrolytic hydrogen production industry.

[0093] The descriptions and practices disclosed in this invention are readily apparent and understandable to those skilled in the art, and various modifications and refinements can be made without departing from the principles of this invention. Therefore, any modifications or improvements made without departing from the spirit of this invention should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing a transition metal-doped nickel-based composite material, characterized in that, The transition metal-doped nickel-based composite material is an iron-doped nickel-based hydroxide nanosheet array grown on the surface of nickel foam; its preparation method includes the following steps: Step 1, Preparation of precursor solution: Weigh out nickel nitrate hexahydrate or nickel chloride hexahydrate and urea respectively, and add different masses of anhydrous ferric chloride. Dissolve the above raw materials in deionized water and stir until completely dissolved to obtain metal precursor solution. Step 2, Substrate Pretreatment: Clean the surface of the nickel foam; Step 3, hydrothermal reaction: Transfer the precursor solution prepared in step 1 to the reaction vessel, add the pretreated nickel foam, and carry out the hydrothermal reaction; Step 4: Post-processing: After the reaction is complete, the sample is taken out, cleaned and dried to obtain a transition metal doped nickel-based composite material.

2. The method for preparing a transition metal-doped nickel-based composite material according to claim 1, characterized in that, In step 1, the amounts of each raw material are as follows: 0.1-0.2 g of nickel nitrate hexahydrate or nickel chloride hexahydrate, 0.2-0.3 g of urea, and 0.01 g to 0.20 g of anhydrous ferric chloride. The amount of deionized water required to dissolve the above raw materials is 30 mL to 45 mL.

3. The method for preparing a transition metal-doped nickel-based composite material according to claim 1, characterized in that, In step 1, the mass ratio of anhydrous ferric chloride corresponds to an iron content of 0.87% to 11.77%.

4. The method for preparing a transition metal-doped nickel-based composite material according to claim 1, characterized in that, In step 2, the pretreatment of the nickel foam consists of sequential ultrasonic cleaning: first, cleaning with ethanol for 20-40 min, then with acetone for 20-40 min, followed by cleaning with 3-5 mol L... -1 Rinse with hydrochloric acid solution for 10 minutes, 3 times in total, and finally rinse with deionized water for 30 minutes, 4-5 times in total.

5. The method for preparing a transition metal-doped nickel-based composite material according to claim 1, characterized in that, In step 3, the hydrothermal reaction temperature is 120-160 ℃ and the reaction time is 6-8 h.

6. The method for preparing a transition metal-doped nickel-based composite material according to claim 1, characterized in that, In step 3, the size of the nickel foam is 2 cm × 2 cm or 3 cm × 3 cm.

7. The method for preparing a transition metal-doped nickel-based composite material according to claim 1, characterized in that, In step 4, the cleaning conditions are: rinsing with deionized water and ethanol alternately 3 to 5 times, vacuum drying temperature of 45 ℃, and drying time of 8 h.

8. The application of a transition metal-doped nickel-based composite material prepared by any one of claims 1-7 in the oxygen evolution reaction.

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