Ferrocobalt oxalate / foamed nickel composite material and preparation method and application thereof

Abstract

The invention relates to the technical field of electrode materials, and particularly discloses a ferrocobalt oxalate / foamed nickel composite material and a preparation method and application thereof. Nanometer flower-shaped cobalt iron oxalate (CoFeC2O4) is loaded on a foamed nickel substrate through a simple coprecipitation method. Through the synergistic effect of components and morphology, the hydrazine oxidation reaction can be started at a lower overpotential, the reaction kinetics process is accelerated, meanwhile, the cathode hydrogen evolution reaction is promoted, and the efficiency of the whole water electrolysis hydrogen production system is synergistically improved; the chemical property of the ferrocobalt oxalate is relatively stable, and the structure and catalytic performance of the ferrocobalt oxalate can be maintained for a long time; in addition, the raw materials cobalt and iron are abundant in reserves, the cost is far lower than that of a noble metal catalyst, the preparation process is simple, the material can be prepared at the room temperature, industrial large-scale production is facilitated, the material shows huge application potential in the field of hydrazine oxidation assisted water electrolysis hydrogen production, and efficient and sustainable development of the hydrogen energy industry is expected to be promoted.

Description

Technical Field

[0001] The invention relates to the technical field of electrode materials, and in particular to a cobalt iron oxalate / nickel foam composite material and a preparation method and application thereof. Background Art

[0002] With the rapid development of the global economy and the over-reliance on traditional fossil energy, the energy crisis is becoming increasingly serious. At the same time, the use of traditional energy has brought about serious environmental problems, such as global climate change caused by greenhouse gas emissions. In this context, hydrogen energy has received widespread attention as a clean, efficient and sustainable energy carrier. The only product of hydrogen combustion is water, which is pollution-free and has a high energy density, making it an ideal energy substitute. It is particularly important to explore green and efficient hydrogen production methods. Among them, hydrogen production by water electrolysis is considered to be a clean technology to solve problems such as environmental pollution and fossil energy consumption because of its simple operation, large processing capacity and long operating time.

[0003] The water electrolysis process includes two half reactions: oxygen evolution reaction at the anode and hydrogen evolution reaction at the cathode. The oxygen evolution reaction at the anode involves a four-electron transfer process, which has a high overpotential and slow kinetics, limiting the efficiency of water electrolysis. Therefore, replacing the oxygen evolution reaction with a thermodynamically more favorable small molecule oxidation reaction can significantly reduce the voltage required for electrolysis and improve the efficiency of hydrogen production by water electrolysis. Hydrazine is a hydrogen energy carrier with high energy density, and the hydrazine oxidation reaction only produces nitrogen and water, without greenhouse gases such as carbon dioxide. The hydrazine oxidation reaction (-0.33V vs.RHE) has a lower theoretical reaction potential than the oxygen evolution reaction (1.23V vs.RHE). Therefore, using the hydrazine oxidation reaction as the anode and combining it with the cathode half reaction of hydrogen evolution by water electrolysis can achieve efficient production of hydrogen.

[0004] At present, commercial hydrazine oxidation catalysts are still mainly based on precious metals (platinum, palladium, etc.) with high intrinsic catalytic activity. However, the shortage of precious metal reserves and high prices restrict their large-scale application. In order to reduce costs, people are also constantly studying other non-precious metal hydrogen evolution catalysts, but their activity in catalyzing hydrazine oxidation needs to be improved. Therefore, the development of cheap, efficient and stable electrochemical catalytic materials is of great significance for the development of hydrazine oxidation-assisted water electrolysis hydrogen production technology. Summary of the invention

[0005] In view of the problem that the existing non-precious metal hydrogen evolution catalyst has low catalytic activity for hydrazine oxidation reaction, the present invention provides a cobalt iron oxalate / nickel foam composite material and a preparation method and application thereof.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0007] A cobalt iron oxalate / nickel foam composite material comprises a nickel foam matrix and nano-flower-shaped cobalt iron oxalate loaded on the nickel foam matrix; wherein the chemical formula of the cobalt iron oxalate is CoFeC2O4.

[0008] Compared with the prior art, the cobalt oxalate iron / nickel foam composite material provided by the present invention has oxalate ions (C2O4 2— ) can form specific chemical bonds and coordination environments with cobalt ions and ferrous ions, adjust the electron cloud density of the metal center, thereby improving the adsorption / desorption process of reactants and reaction intermediates, and promoting the rapid progress of the catalytic reaction; at the same time, in the electrochemical environment, such as alkaline or acidic electrolyte, the combination of oxalate in CoFeC2O4 and metal ions can make it have better chemical stability, not easy to dissolve, decompose or structurally destroy, thereby improving the stability of the composite material; in addition, oxalate ions also act as proton carriers or electron transfer media to promote the progress of electrochemical reactions.

[0009] Nano flower-shaped cobalt iron oxalate has a large specific surface area, and each of its petal-shaped nanosheets can participate in the reaction as an active site, greatly increasing the contact area with the electrolyte and the reactant, so that more reactants can react on the catalyst surface, thereby improving the catalytic efficiency; the nano flower-shaped structure can also effectively shorten the ion diffusion path, and the diffusion distance of ions in the nano flower-shaped cobalt iron oxalate is shorter than that of block or granular materials, and can reach the active site faster for reaction, reducing the energy loss in the ion diffusion process and improving the reaction rate; and the nanosheets intersect in the nano flower-shaped structure, which is conducive to the rapid transmission of electrons between different petals or branches, and constructs an efficient electronic conduction network; in addition, there are gaps and channels between the petals or branches of the nano flower, forming an open three-dimensional structure, so that reactants and product molecules can diffuse in and out of the catalyst surface more easily, reducing diffusion restrictions. Therefore, the cobalt iron oxalate provided by the present invention has excellent electrocatalytic activity and has broad application prospects in the field of electrochemical catalysis.

[0010] Furthermore, the loading amount of the nanoflower-shaped cobalt iron oxalate is 1 mg / cm 2 ~2mg / cm 2 .

[0011] The present invention also provides a method for preparing the cobalt iron oxalate / nickel foam composite material, comprising the following steps:

[0012] The nickel foam is added into an alcohol solution of a soluble cobalt salt and a soluble iron salt, and an alcohol solution of oxalic acid is slowly added thereto, and the mixture is allowed to stand for reaction to obtain a cobalt iron oxalate / nickel foam composite material.

[0013] The preparation method of the cobalt oxalate iron / nickel foam composite material provided by the present invention prepares cobalt oxalate iron (CoFeC2O4) loaded on the surface of nickel foam by a simple coprecipitation method. The synthesis method is simple, the raw materials used are all non-toxic or low-toxic reagents, the reaction risk is low, and it is suitable for large-scale production and application.

[0014] Optionally, the nickel foam needs to be pretreated before the coprecipitation reaction to remove impurities and oxides on the surface of the nickel foam.

[0015] Furthermore, the nickel foam is cut into small pieces and then added into 2 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol for ultrasonic treatment for 20 to 30 minutes respectively, and then dried to obtain a clean nickel foam matrix.

[0016] Furthermore, the soluble cobalt salt is cobalt nitrate.

[0017] Furthermore, the soluble iron salt is ferric nitrate.

[0018] Furthermore, the molar ratio of the soluble cobalt salt, the soluble iron salt and the oxalic acid is (6-9):(1-4):(0.8-1).

[0019] Furthermore, in the alcohol solution of the soluble cobalt salt and the soluble iron salt, the concentration of the soluble cobalt salt is 6 mmol / L to 9 mmol / L, and the concentration of the soluble iron salt is 1 mmol / L to 4 mmol / L.

[0020] Furthermore, the concentration of the oxalic acid alcohol solution is 0.8 mol / L to 1 mol / L.

[0021] Furthermore, the temperature of the static reaction is 20° C. to 40° C., and the static reaction time is 3 h to 4 h.

[0022] The present invention significantly improves the catalytic activity of the cobalt iron oxalate / nickel foam composite material through the coordinated regulation of morphology and composition, provides a superior composite electrode material for electrocatalytic reactions, and the preparation method has a wide range of raw material sources, low price, simple and easy preparation process, high preparation efficiency, can be mass-produced, and has broad application prospects.

[0023] The present invention also provides the use of the cobalt iron oxalate / nickel foam composite material in hydrazine oxidation-assisted water electrolysis to produce hydrogen.

[0024] The invention also provides application of the cobalt iron oxalate / nickel foam composite material in a hydrazine hydrate fuel cell.

[0025] The cobalt iron oxalate / nickel foam prepared by the present invention can start the hydrazine oxidation reaction with a lower overpotential through the synergistic effect of composition and morphology, accelerate the reaction kinetics, and also promote the cathode hydrogen evolution reaction, synergistically improving the efficiency of the entire water electrolysis hydrogen production system; and the cobalt iron oxalate itself has relatively stable chemical properties and can maintain its own structure and catalytic performance for a long time, which is conducive to significantly improving the service life of the electrode material; in addition, the raw materials of cobalt and iron are abundant in reserves, the cost is much lower than that of precious metal catalysts, and the preparation process is simple, the material can be prepared at room temperature, which is conducive to industrial large-scale production, and shows great application potential in the field of hydrazine oxidation-assisted water electrolysis hydrogen production, and is expected to promote the efficient and sustainable development of the hydrogen energy industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image of cobalt iron oxalate / nickel foam prepared in Example 1 of the present invention;

[0027] Figure 2 This is the X-ray diffraction pattern of cobalt iron oxalate / nickel foam prepared in Example 1 of the present invention;

[0028] Figure 3 This is an X-ray photoelectron spectrum of cobalt iron oxalate / nickel foam prepared in Example 1 of the present invention;

[0029] Figure 4 Linear scanning curves of the oxygen evolution reaction of the cobalt iron oxalate / nickel foam prepared in Example 1 of the present invention in a 1 mol / L potassium hydroxide solution and the hydrazine oxidation reaction in a solution containing 1 mol / L hydrazine and 1 mol / L potassium hydroxide;

[0030] Figure 5 Linear scanning curves of hydrazine oxidation reaction of the catalysts prepared in Example 1 of the present invention and Comparative Examples 1 to 3 in a solution containing 1 mol / L hydrazine and 1 mol / L potassium hydroxide;

[0031] Figure 6 This is a linear scanning curve of the cobalt iron oxalate / nickel foam prepared in Example 1 of the present invention in hydrazine oxidation-assisted water electrolysis to produce hydrogen (OHzS) in a solution containing 1 mol / L hydrazine and 1 mol / L potassium hydroxide. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] In order to better illustrate the present invention, further examples are given below.

[0034] Example 1

[0035] A method for preparing cobalt iron oxalate / nickel foam comprises the following steps:

[0036] Step 1: Cut the nickel foam into 1*2cm 2 The small pieces were ultrasonically cleaned for 30 min with 2 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol respectively, and dried to obtain a foamed nickel matrix;

[0037] Step 2: Place the cleaned nickel foam substrate into a solution containing 40 mL of anhydrous ethanol, 0.093 g of Co(NO3)2·6H2O, and 0.032 g of Fe(NO3)3·9H2O, and slowly drop a mixed solution of 40 mL of anhydrous ethanol and 3 g of oxalic acid into the above solution. After the addition is completed, let it stand at room temperature for 3 hours, take out the nickel foam, wash it, and dry it to obtain cobalt iron oxalate / nickel foam.

[0038] Example 2

[0039] A method for preparing cobalt iron oxalate / nickel foam comprises the following steps:

[0040] Step 1: Cut the nickel foam into 1*2cm 2 The small pieces were ultrasonically cleaned for 30 min with 2 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol respectively, and dried to obtain a foamed nickel matrix;

[0041] Step 2: Place the cleaned nickel foam substrate into a solution containing 40 mL of anhydrous ethanol, 0.081 g of Co(NO3)2·6H2O, and 0.048 g of Fe(NO3)3·9H2O, and slowly drop a mixed solution of 40 mL of anhydrous ethanol and 2.9 g of oxalic acid into the above solution. After the addition is completed, let it stand at room temperature for 3 hours, take out the nickel foam, wash it, and dry it to obtain cobalt iron oxalate / nickel foam.

[0042] Example 3

[0043] A method for preparing cobalt iron oxalate / nickel foam comprises the following steps:

[0044] Step 1: Cut the nickel foam into 1*2cm 2 The small pieces were ultrasonically cleaned for 30 min with 2 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol respectively, and dried to obtain a foamed nickel matrix;

[0045] Step 2: Place the cleaned nickel foam substrate into a solution containing 40 mL of anhydrous ethanol, 0.070 g of Co(NO3)2·6H2O, and 0.064 g of Fe(NO3)3·9H2O, and slowly drop a mixed solution of 40 mL of anhydrous ethanol and 3.4 g of oxalic acid into the above solution. After the addition is completed, let it stand at room temperature for 3 hours, take out the nickel foam, wash it, and dry it to obtain cobalt iron oxalate / nickel foam.

[0046] Example 4

[0047] A method for preparing cobalt iron oxalate / nickel foam comprises the following steps:

[0048] Step 1: Cut the nickel foam into 1*2cm 2 The small pieces were ultrasonically cleaned for 30 min with 2 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol respectively, and dried to obtain a foamed nickel matrix;

[0049] Step 2: Place the cleaned nickel foam substrate into a solution containing 40 mL of anhydrous ethanol, 0.104 g of Co(NO3)2·6H2O, and 0.018 g of Fe(NO3)3·9H2O, and slowly drop a mixed solution of 40 mL of anhydrous ethanol and 3.6 g of oxalic acid into the above solution. After the addition is completed, let it stand at room temperature for 3 hours, take out the nickel foam, wash it, and dry it to obtain cobalt iron oxalate / nickel foam.

[0050] Comparative Example 1

[0051] This comparative example provides a method for preparing cobalt oxalate / nickel foam, which is different from Example 1 in that ferric nitrate is replaced by an equimolar amount of cobalt nitrate, and specifically comprises the following steps:

[0052] Step 1: Cut the nickel foam into 1*2cm 2 The small pieces were ultrasonically cleaned for 30 min with 2 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol respectively, and dried to obtain a foamed nickel matrix;

[0053] Step 2: Place the cleaned nickel foam substrate into a solution containing 40 mL of anhydrous ethanol and 0.116 g of Co(NO3)2·6H2O, and slowly drop a mixed solution of 40 mL of anhydrous ethanol and 3 g of oxalic acid into the above solution. After the addition is completed, let it stand at room temperature for 3 hours, take out the nickel foam, wash it, and dry it to obtain cobalt oxalate / nickel foam.

[0054] Comparative Example 2

[0055] This comparative example provides a method for preparing ferrous oxalate / nickel foam, which is different from Example 1 in that cobalt nitrate is replaced by an equal molar amount of ferric nitrate, and specifically comprises the following steps:

[0056] Step 1: Cut the nickel foam into 1*2cm 2 The small pieces were ultrasonically cleaned for 30 min with 2 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol respectively, and dried to obtain a foamed nickel matrix;

[0057] Step 2: Place the cleaned nickel foam substrate into a solution containing 40 mL of anhydrous ethanol and 0.162 g of Fe(NO3)3·9H2O, and slowly drop a mixed solution of 40 mL of anhydrous ethanol and 3 g of oxalic acid into the above solution. After the addition is completed, let it stand at room temperature for 3 hours, take out the nickel foam, wash it, and dry it to obtain ferrous oxalate / nickel foam.

[0058] Comparative Example 3

[0059] This comparative example provides a method for preparing nickel iron oxalate / nickel foam, which is different from Example 1 in that cobalt nitrate is replaced by an equimolar amount of nickel nitrate, and specifically comprises the following steps:

[0060] Step 1: Cut the nickel foam into 1*2cm 2 The small pieces were ultrasonically cleaned for 30 min with 2 mol / L hydrochloric acid solution, deionized water and anhydrous ethanol respectively, and dried to obtain a foamed nickel matrix;

[0061] Step 2: Place the cleaned nickel foam substrate into a solution containing 40 mL of anhydrous ethanol, 0.093 g of Ni(NO3)2·6H2O, and 0.032 g of Fe(NO3)3·9H2O, and slowly drop a mixed solution of 40 mL of anhydrous ethanol and 3 g of oxalic acid into the above solution. After the addition is completed, let it stand at room temperature for 3 hours, take out the nickel foam, wash it, and dry it to obtain nickel iron oxalate / nickel foam.

[0062] Material characterization

[0063] The SEM image of the cobalt iron oxalate / nickel foam prepared in Example 1 is as follows: Figure 1 As shown in the figure, it can be seen that cobalt iron oxalate has a nanoflower-like structure with a diameter of about 5 μm. The nanosheets are cross-linked with each other and have a large exposed specific surface area.

[0064] The XRD pattern of cobalt iron oxalate / nickel foam prepared in Example 1 is as follows: Figure 2 As shown in the figure, it can be seen that the characteristic diffraction peak is located between the corresponding cobalt oxalate and ferrous oxalate diffraction peaks, indicating that cobalt and iron elements are mixed at the atomic level in the product, confirming that the final product is CoFe(II)C2O4.

[0065] The XPS image of the cobalt iron oxalate / nickel foam prepared in Example 1 is as follows: Figure 3 As shown, the XPS spectrum shows obvious C, O, Co and Fe peaks, further proving the formation of cobalt iron oxalate.

[0066] Performance Testing

[0067] A three-electrode system was used, with the cobalt iron oxalate / nickel foam prepared in Example 1 as the working electrode, graphite as the counter electrode, and Ag / AgCl as the reference electrode, to test the linear scanning curves of the oxygen evolution reaction of the cobalt iron oxalate / nickel foam prepared in Example 1 in a 1 mol / L potassium hydroxide solution and the hydrazine oxidation reaction in a solution containing 1 mol / L hydrazine and 1 mol / L potassium hydroxide. Figure 4 As shown. Figure 4 It can be seen that the anode current density reaches 10mA / cm 2 When the voltage is 1.282V, the oxygen evolution reaction requires a voltage of 1.282V, while the hydrazine hydrate oxidation only requires 0.761V.

[0068] The three-electrode system was used to test the linear scanning curve of the hydrazine oxidation reaction of the cobalt iron oxalate / nickel foam prepared in Example 1 and Comparative Examples 1 to 3 in a solution containing 1 mol / L hydrazine and 1 mol / L potassium hydroxide. Figure 5 As shown. Figure 5 It can be seen that the anode current reaches 10mA / cm 2 When the voltage of Example 1 is 0.761V, the voltage of Comparative Example 1 is 0.794V, the voltage of Comparative Example 2 is 0.862V, and the voltage of Comparative Example 3 is 0.772V.

[0069] Figure 6 The test system is a 1 mol / L potassium hydroxide solution containing 1 mol / L hydrazine and 1 mol / L potassium hydroxide solution. Figure 6 It can be seen that at 100mA / cm 2 Under the current density, when there is no hydrazine in the electrolyte, the water decomposition voltage of the whole water electrolysis system (OWS) is 1.75V; when there is hydrazine in the electrolyte, the water decomposition voltage of the hydrazine oxidation assisted whole water electrolysis system (OHzS) is 0.38V, which is 1.37V lower. 2 Under the current density, when the electrolyte does not contain hydrazine, the water decomposition voltage of OWS is 1.94V; when the electrolyte contains hydrazine, the water decomposition voltage of OHzS is 0.61V, which is reduced by 1.33V.

[0070] Replacing the oxygen evolution reaction with the hydrazine oxidation reaction can reduce the electricity cost of water electrolysis to produce hydrogen by about 69%, confirming the energy-saving effect of hydrazine oxidation-assisted water electrolysis to produce hydrogen.

[0071] The cobalt iron oxalate / nickel foam prepared in Examples 2 to 4 can achieve technical effects substantially equivalent to those in Example 1.

[0072] In summary, the preparation method of the cobalt iron oxalate / nickel foam of the present invention is simple in process operation and easy to synthesize. The obtained cobalt iron oxalate / nickel foam has good chemical stability, abundant active sites and good electrical conductivity, exhibits excellent electrocatalytic activity in catalyzing hydrazine oxidation reaction, and has broad energy application prospects.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A cobalt iron oxalate / nickel foam composite material, characterized in that: It comprises a foamed nickel matrix and nano-flower-shaped cobalt iron oxalate loaded on the foamed nickel matrix; wherein the chemical formula of the cobalt iron oxalate is CoFeC2O4.

2. The cobalt iron oxalate / nickel foam composite material according to claim 1, characterized in that: The loading amount of the nano flower-shaped cobalt iron oxalate is 1 mg / cm 2 ~2mg / cm 2 .

3. The method for preparing the cobalt iron oxalate / nickel foam composite material according to claim 1 or 2, characterized in that: The steps include: The nickel foam is added into an alcohol solution of a soluble cobalt salt and a soluble iron salt, and an alcohol solution of oxalic acid is slowly added thereto, and the mixture is allowed to stand for reaction to obtain a cobalt iron oxalate / nickel foam composite material.

4. The method for preparing the cobalt iron oxalate / nickel foam composite material according to claim 3, characterized in that: The soluble cobalt salt is cobalt nitrate; and / or The soluble iron salt is ferric nitrate.

5. The method for preparing the cobalt iron oxalate / nickel foam composite material according to claim 3 or 4, characterized in that: The molar ratio of the soluble cobalt salt, the soluble iron salt and the oxalic acid is (6-9):(1-4):(0.8-1).

6. The method for preparing the cobalt iron oxalate / nickel foam composite material according to claim 3, characterized in that: In the alcohol solution of the soluble cobalt salt and the soluble iron salt, the concentration of the soluble cobalt salt is 6 mmol / L to 9 mmol / L, and the concentration of the soluble iron salt is 1 mmol / L to 4 mmol / L.

7. The method for preparing the cobalt iron oxalate / nickel foam composite material according to claim 3, characterized in that: The concentration of the oxalic acid alcohol solution is 0.8 mol / L to 1 mol / L.

8. The method for preparing the cobalt iron oxalate / nickel foam composite material according to claim 3, characterized in that: The temperature of the static reaction is 20° C. to 40° C., and the time of the static reaction is 3 h to 4 h.

9. Use of the cobalt iron oxalate / nickel foam composite material according to claim 1 or 2 in hydrazine oxidation-assisted water electrolysis to produce hydrogen.

10. Use of the cobalt iron oxalate / nickel foam composite material according to claim 1 or 2 in a hydrazine hydrate fuel cell.

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