Preparation method of modified electrolyte for alkaline electrolyzed water and modified electrolyte

Abstract

The present application discloses a preparation method of a modified electrolyte for alkaline electrolyzed water and the modified electrolyte. The modified electrolyte includes an electrolyte solution and a hydrogen phosphate additive. By adding the hydrogen phosphate additive to the electrolyte solution and stirring it, the modified electrolyte is generated. The modified electrolyte prepared by the present application is non-toxic and environmentally friendly, and can change the electron arrangement on the surface of the electrode during the electrolysis process, exposing more active sites on the electrode surface, thereby significantly reducing the cathodic hydrogen evolution overpotential. At the same time, the addition of the hydrogen phosphate increases the ion concentration in the electrolyte, promotes the dissociation of water, and reduces the electrolyte resistance. Both of the above aspects achieve the purpose of reducing the energy consumption of the electrolytic cell.

Description

Technical Field

[0001] The present invention belongs to the field of hydrogen production by electrolysis of water, and particularly relates to a preparation method of a modified electrolyte for alkaline electrolysis of water and the modified electrolyte. Background Art

[0002] With the overuse of fossil fuels, the problems of energy shortage and environmental pollution have become increasingly serious. Developing and utilizing clean and renewable new energy is an effective means to address energy shortage and environmental pollution problems. Among the developed new energies, hydrogen has the highest calorific value and clean combustion products, making it an ideal clean and renewable energy source. Electrolysis of water is an efficient, clean and promising hydrogen production technology. In particular, the alkaline water electrolysis hydrogen production technology has a simple process and low cost. It is the earliest developed hydrogen production technology in electrolysis of water, and also the most commercially mature and largest-scale developed hydrogen production technology at present.

[0003] In the alkaline water electrolysis hydrogen production technology, the energy consumption of the electrolysis system is a very key technical index. Lower energy consumption can greatly reduce the use cost of the electrolyzer and is also one of the key indexes for reducing the hydrogen production cost. In terms of the electrolysis principle, reducing the overpotential of the electrode, the diaphragm resistance, and the electrolyte resistance can all reduce the energy consumption of the electrolyzer. Among them, the electrode overpotential is affected by factors such as electrode material, electrode coating process, solution composition, temperature, and current density. The two ways of electrode material (using noble metal electrodes) and electrode coating are complex in process and very high in cost. In contrast, changing the composition of the alkaline electrolyte and directly adding additives to the electrolyte is a simpler and quicker method with very low cost. However, increasing potassium hydroxide in the potassium hydroxide electrolyte solution to increase its concentration and thus increase the ionic conductivity can reduce the energy consumption of the electrolyzer, but the effect is not significant. This method is also applicable to sodium hydroxide. Adding K2Cr2O7 to the electrolyte, when oxidation occurs, Cr6+ becomes Cr3+, and the impurities on the electrode surface are strongly oxidized, increasing the surface activity of the electrode and reducing the interpolar voltage (Wang Di, Energy conservation and consumption reduction in the process of water electrolysis, China Molybdenum Industry, 1998, 22, 3, 46 - 48). Adding salicylate-based ionic liquids to the alkaline electrolyte can also enhance the HER performance, but the effect of the ionic liquid is not obvious after the temperature rises (Luis A. et al, Towards tailoring of electrolyte additives for efficient alkaline water electrolysis: salicylate-based ionic liquids, ACS Appl. Energy Mater. 2018, 1, 9, 4731 - 4742)

[0004] In the process of implementing the existing technology, the inventor found that:

[0005] Although the method of adding additives to the electrolyte can significantly reduce the energy consumption of the electrolytic cell, the additives have strong toxicity and negative impacts on the environment.

[0006] Therefore, the present application provides a technical solution for preparing a modified electrolyte for alkaline electrolyzed water, which is non-toxic, environmentally friendly, and can significantly reduce the energy consumption of the electrolytic cell, so as to solve the problems in the prior art that although the energy consumption of the electrolytic cell can be reduced, the additives have strong toxicity and negative impacts on the environment. Summary of the Invention

[0007] In order to overcome the defects and deficiencies existing in the prior art, the present application provides a technical solution for preparing a modified electrolyte for alkaline electrolyzed water, which is non-toxic, environmentally friendly, and can reduce the energy consumption of the electrolytic cell, so that the modified electrolyte prepared by this method can reduce the electrolysis energy consumption of the electrolytic cell, thereby solving the problems in the prior art that although the energy consumption of the electrolytic cell can be reduced, the additives have strong toxicity and negative impacts on the environment.

[0008] To achieve the above object, the present invention provides the following technical solution: A method for preparing a modified electrolyte for alkaline electrolyzed water, the modified electrolyte includes an electrolyte solution and a hydrogen phosphate additive, and the hydrogen phosphate additive is added to the electrolyte solution and stirred to generate the modified electrolyte.

[0009] Further, the electrolyte is an alkaline electrolyte;

[0010] The alkaline electrolyte is one of potassium hydroxide and sodium hydroxide.

[0011] Further, the molar concentration of potassium hydroxide in the electrolyte solution is 1 mol / L to 7 mol / L, and the molar concentration of sodium hydroxide in the electrolyte solution is 1 mol / L - 10 mol / L.

[0012] Further, the mass fraction ratio of potassium hydroxide in the electrolyte solution is 10 wt% - 35 wt%.

[0013] Further, the hydrogen phosphate additive is at least one of potassium dihydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, and ammonium hydrogen phosphate.

[0014] Further, the molar concentration of the hydrogen phosphate additive in the electrolyte solution is 0.005 mol / L to 0.5 mol / L.

[0015] In addition, the present application also provides a modified electrolyte prepared according to the above preparation method.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The modified electrolyte prepared by this application is non-toxic, environmentally friendly, and can change the electron arrangement on the electrode surface during the electrolysis process, exposing more active sites on the electrode surface, thereby significantly reducing the cathodic hydrogen evolution overpotential. At the same time, the addition of hydrogen phosphate increases the ion concentration in the electrolyte, promotes the dissociation of water, and reduces the electrolyte resistance. Both of the above aspects achieve the purpose of reducing the energy consumption of the electrolytic cell. In addition, the usage method is simple. Only need to add a quantitative additive to the prepared electrolyte, or add a quantitative additive to the electrolyte in the running electrolytic cell at regular intervals. Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the overpotential test results of the comparative example and Examples 1-4;

[0019] Figure 2 It is a schematic diagram of the upper electrolytic cell test results of the comparative example and Examples 1-4; Detailed Embodiments

[0020] The present invention will be further described below in conjunction with the embodiments.

[0021] Comparative Example

[0022] Use 1M potassium hydroxide aqueous solution as the electrolyte for testing the hydrogen evolution overpotential and 30% wt potassium hydroxide aqueous solution as the electrolyte for the upper electrolytic cell test (blank control electrolyte).

[0023] Example 1

[0024] Prepare a modified electrolyte by the preparation method of a modified electrolyte for alkaline water electrolysis provided by this application.

[0025] Select dipotassium hydrogen phosphate as the hydrogen phosphate additive A and add it to 1M potassium hydroxide aqueous solution to make the concentration of dipotassium hydrogen phosphate in its solution 0.05 mol / L to prepare the modified electrolyte A1;

[0026] Select dipotassium hydrogen phosphate as the hydrogen phosphate additive A and add it to 30% wt potassium hydroxide aqueous solution to make the concentration of dipotassium hydrogen phosphate in its solution 0.05 mol / L to prepare the modified electrolyte A2.

[0027] Example 2

[0028] Prepare a modified electrolyte by the preparation method of a modified electrolyte for alkaline water electrolysis provided by this application.

[0029] Select potassium dihydrogen phosphate as the hydrogen phosphate additive B and add it to 1M potassium hydroxide aqueous solution to make the concentration of potassium dihydrogen phosphate in its solution 0.05 mol / L to prepare the modified electrolyte B1;

[0030] Potassium dihydrogen phosphate was selected as the hydrogen phosphate additive B and added to the 30% wt potassium hydroxide aqueous solution to make the concentration of potassium dihydrogen phosphate in the solution 0.05 mol / L, and the modified electrolyte B2 was prepared.

[0031] Example 3

[0032] The modified electrolyte was prepared by the preparation method of a modified electrolyte for alkaline electrolyzed water provided by this application.

[0033] Disodium hydrogen phosphate was selected as the hydrogen phosphate additive C and added to the 1M potassium hydroxide aqueous solution to make the concentration of disodium hydrogen phosphate in the solution 0.05 mol / L, and the modified electrolyte C1 was prepared;

[0034] Disodium hydrogen phosphate was selected as the hydrogen phosphate additive C and added to the 30% wt potassium hydroxide aqueous solution to make the concentration of disodium hydrogen phosphate in the solution 0.05 mol / L, and the modified electrolyte C2 was prepared.

[0035] Example 4

[0036] The modified electrolyte was prepared by the preparation method of a modified electrolyte for alkaline electrolyzed water provided by this application.

[0037] Ammonium hydrogen phosphate was selected as the hydrogen phosphate additive D and added to the 1M potassium hydroxide aqueous solution to make the concentration of ammonium hydrogen phosphate in the solution 0.05 mol / L, and the modified electrolyte D1 was prepared;

[0038] Ammonium hydrogen phosphate was selected as the hydrogen phosphate additive D and added to the 30% wt potassium hydroxide aqueous solution to make the concentration of ammonium hydrogen phosphate in the solution 0.05 mol / L, and the modified electrolyte D2 was prepared.

[0039] Effect experiment

[0040] 1. The hydrogen evolution reaction (HER) performance tests were carried out on the blank control electrolyte 1M potassium hydroxide aqueous solution in the comparative example and the modified electrolytes A1, B1, C1, and D1 in Examples 1-4. The specific detection is as follows:

[0041] Detection method: In the standard three-electrode system, the working electrode was a 46-mesh nickel mesh sprayed with Raney nickel, the counter electrode was a graphite rod, and the reference electrode was Hg / HgO. It was correctly connected and installed on the Autolab electrochemical workstation. The 1M potassium hydroxide aqueous solution in the comparative example and the modified electrolytes A1, B1, C1, and D1 in Examples 1-4 were respectively poured into the electrolytic cell for linear sweep voltammetry (LSV) test. The electrolyte temperature was room temperature 25°C, and the test voltage range was 0V to -0.67V (vs RHE).

[0042] The test results are shown in Table 1 below and Figure 1 the corresponding overpotential test results.

[0043] Table 1

[0044]

[0045] From the data in Table 1 and Figure 1 , it can be seen by comparison that for the modified electrolytes in Examples 1 to 4, the hydrogen evolution overpotential of the electrodes is significantly lower than that in Comparative Example 1, and the reduction value is between 40 mV and 50 mV.

[0046] 2. Performance tests were carried out on the blank control electrolyte of 30% wt potassium hydroxide aqueous solution in the comparative example and the modified electrolytes A2, B2, C2, and D2 in Examples 1 to 4 using a small electrolytic cell with a nipple structure at 1 NL / h.

[0047] Detection method: A 46-mesh Raney nickel mesh was used as the electrode. During operation, the electrolyte temperature was controlled at 80 °C, and a constant current mode electrolysis was selected. The current density was set at 2500 A / m 2 , and the continuous electrolysis time was 7 hours. During the electrolysis process, the voltage of the electrolytic cell was recorded every 1 hour by the system.

[0048] The test results are shown in Table 2 below and Figure 2 the corresponding electrolytic cell test results.

[0049] Table 2

[0050]

[0051]

[0052] According to Table 2 above and Figure 2 , it can be seen by comparison that for the modified electrolytes in Examples 1 to 4, the average voltage of the electrolytic cell is lower than that in Comparative Example 1, and the reduction value is more than 100 mV.

[0053] Combining the hydrogen evolution reaction (HER) performance test and the performance test using a small electrolytic cell with a nipple structure at 1 NL / h. It can be seen that in the case of gas production, the modified electrolyte has a more obvious effect on reducing the cell voltage of the electrolytic cell, which also shows that the modified electrolyte not only significantly reduces the overpotential of hydrogen evolution at the cathode, but also increases the ion concentration in the electrolyte, promotes the dissociation of water, or reduces the gas content in the electrolyte, thereby reducing the electrolyte resistance. Therefore, the modified electrolyte of the present invention significantly reduces the energy consumption of the electrolytic cell.

[0054] The above are only the preferred embodiments of the present invention, and the scope of implementation of the present invention cannot be limited thereby. That is, all simple equivalent changes and modifications made according to the content recorded in the claims of the present invention and the specification of the invention still fall within the scope covered by the claims of the present invention. In addition, the abstract part and the title are only used to assist in the search of patent documents and are not used to limit the scope of rights of the present invention.

Claims

1. A preparation method of a modified electrolyte for alkaline electrolyzed water, characterized in that: The modified electrolyte includes an alkaline electrolyte solution and a hydrogen phosphate additive. By adding the hydrogen phosphate additive to the alkaline electrolyte solution and stirring it, a modified electrolyte is generated. The molar concentration of the hydrogen phosphate additive in the electrolyte solution is 0.005 mol / L to 0.5 mol / L. The alkaline electrolyte is one of potassium hydroxide and sodium hydroxide. The molar concentration of potassium hydroxide in the electrolyte solution is 1 mol / L to 7 mol / L, and the molar concentration of sodium hydroxide in the electrolyte solution is 1 mol / L to 10 mol / L.

2. The preparation method of the modified electrolyte for alkaline electrolyzed water according to claim 1, characterized in that, The mass fraction of potassium hydroxide in the electrolyte solution is 10 wt% - 35 wt%.

3. The preparation method of the modified electrolyte for alkaline electrolyzed water according to claim 1, characterized in that, The hydrogen phosphate additive is at least one of potassium dihydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, and ammonium hydrogen phosphate.

4. A modified electrolyte prepared by the preparation method according to any one of claims 1 to 3.

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