Application of metasilicate-containing alkaline salt water (natural seawater) electrolyte in field of water electrolysis hydrogen production

Abstract

The invention aims to utilize salt water (natural seawater) for electrolytic hydrogen production. Due to the fact that the concentration of chloride ions in the salt water is high, a remarkable chlorine evolution reaction (ClOR) is triggered on an anode, and the electrolysis efficiency is greatly reduced. In addition, the corrosivity of chloride ions can damage the anode catalyst, so that the performance of the anode catalyst is rapidly reduced. In order to solve the problem, the invention provides a novel electrolyte formula, and metasilicate anions are added into the electrolyte to slow down the corrosion of chloride ions to an anode material, so that the service life of the anode material in a seawater hydrogen production system is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production by water electrolysis, and in particular to hydrogen production by water electrolysis in an alkaline salt water (natural seawater) system. Background Art

[0002] With the massive consumption of fossil energy and severe environmental problems, the development and utilization of sustainable clean energy has received increasing attention. Hydrogen (H2) is considered to be the most satisfactory clean energy carrier due to its high safety factor and high energy density. Among the many technologies being studied, water electrolysis powered by sustainable energy is considered to be a simple, environmentally friendly, and carbon-free method for producing high-purity hydrogen, providing a promising strategy to solve the outstanding problem between global energy demand and fuel supply. In general, water electrolysis includes hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and its biggest obstacle is the kinetic slow electrochemical process that requires overcoming large energy barriers. In addition, the worldwide shortage of high-purity water resources is also a bottleneck for the large-scale promotion of water electrolysis.

[0003] Since seawater is the most abundant water resource on Earth, it is considered a natural electrolyte for large-scale and low-cost hydrogen production. However, the presence of corrosive substances in seawater, such as chlorides, can further aggravate catalyst degradation. The stability and durability of seawater electrolysis catalysts are critical to ensure continued efficient and cost-effective hydrogen production. Catalyst degradation not only reduces the overall efficiency of the electrolysis process, but also requires frequent replacement, increasing operating costs and reducing the overall sustainability of the system. Recently, researchers have developed Ni-based compounds (such as hydroxides, sulfides, phosphides, and nitrides) grown directly on Ni substrates and demonstrated their effectiveness in OER and anti-corrosion properties. Despite great progress in catalyst anti-corrosion, the effect of adjusting electrolyte composition on anti-corrosion performance in saltwater (natural seawater) electrolytes has rarely been studied.

[0004] The present invention uses sodium metasilicate (NaSiO3) as a low-cost additive added to an alkaline salt water (natural seawater) electrolysis system. Due to the presence of metasilicate, the corrosion resistance of the anode material is greatly enhanced, and the service life of the anode material is significantly improved. Summary of the invention

[0005] Technical problems solved by the present invention:

[0006] By adding sodium metasilicate to prepare alkaline salt water (natural seawater) electrolyte, the shortcomings of anode materials such as easy corrosion and poor stability in seawater electrolysis systems can be solved.

[0007] The technical solution adopted by the present invention is:

[0008] An electrolyte is prepared by using sodium metasilicate and potassium hydroxide as solutes and salt water (natural seawater) as solvent, and its application in the field of hydrogen production by electrolyzing salt water (natural seawater).

[0009] The specific contents are as follows:

[0010] First, the present invention provides an alkaline salt water (natural seawater) electrolyte containing metasilicate.

[0011] The electrolyte involved in the present invention is a sodium metasilicate-potassium hydroxide-salt water (natural seawater) solution.

[0012] Salt water includes the following characteristics: 2.5 mol / L sodium chloride solution.

[0013] The electrolyte has the following characteristics: the solute is sodium metasilicate (NaSiO3) and potassium hydroxide (KOH), the concentration ratio is 0.15-0.35 mol / L: 1 mol / L, and the solvent is salt water (natural sea water). (Respectively marked as alkaline salt water, alkaline salt water + 0.15MSiO3 2- , alkaline salt water + 0.25M SiO3 2- , alkaline salt water + 0.35M SiO3 2- , alkaline natural seawater + 0.25M SiO3 2- ).

[0014] Second, the present invention provides the use of the aforementioned electrolyte in the electrolysis of salt water (natural seawater) to produce hydrogen.

[0015] The invention uses alkaline salt water (natural seawater) containing metasilicate as electrolyte. Due to the presence of metasilicate, the corrosion resistance of the anode material is improved and the service life of the material is increased.

[0016] The present invention uses cheap and non-toxic sodium metasilicate as an additive and adds it to an alkaline salt water (natural seawater) electrolyte. The electrolyte effectively avoids the problems of high pressure and high temperature, strong acid and strong alkali, strict environment, complex raw materials, and difficult preparation. The electrolyte has the advantages of cheap raw materials, simple preparation, easy repetition, easy amplification, and short preparation time. Therefore, it has broad prospects for industrial application.

[0017] The alkaline seawater electrolyte containing metasilicate obtained by the present invention (marked as alkaline natural seawater + 0.25MSiO3 2- ), has excellent corrosion resistance. The performance test was carried out using commercial nickel foam (marked as NF) or nickel processed nickel foam (made by covering commercial nickel foam with 5g nickel nitrate hexahydrate and calcining at 120°C for 10 hours, marked as XSN) as the anode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1The oxygen evolution reaction (OER) LSV test result diagram of each experiment;

[0019] Figure 2 This is a stability test diagram of NF in alkaline salt water electrolyte;

[0020] Figure 3 NF in alkaline salt water + 0.15M SiO3 2- Electrolyte stability test diagram;

[0021] Figure 4 NF in alkaline salt water + 0.25M SiO3 2- Electrolyte stability test diagram;

[0022] Figure 5 NF in alkaline salt water + 0.35M SiO3 2- Electrolyte stability test diagram;

[0023] Figure 6 For XSN in alkaline salt water + 0.25M SiO3 2- Electrolyte stability test chart

[0024] Figure 7 XSN in alkaline natural seawater + 0.25M SiO3 2- Electrolyte stability test chart

[0025] Figure 8 SEM images of each experimental sample; DETAILED DESCRIPTION

[0026] In order to more clearly explain the purpose, technical scheme and advantages of the embodiments of the present invention, the technical scheme in the embodiments will be described in detail below. If specific conditions are not particularly specified, the operation will be carried out according to the usual conditions or the recommendations of the manufacturer. When the manufacturer of the reagent or instrument is not particularly specified, it refers to the conventional products that can be purchased on the market.

[0027] Example

[0028] The alkaline salt water electrolyte containing metasilicate is prepared by dissolving 10.66g-24.87g of sodium metasilicate and 14.03g of potassium hydroxide in 250mL of salt water to prepare 1M KOH+0.15M SiO3 2- Saline solution, 1M KOH + 0.25M SiO3 2- Saline solution, 1M KOH+0.35M SiO3 2- Salt water solution.

[0029] The alkaline natural seawater electrolyte containing metasilicate is prepared by dissolving 17.76g of sodium metasilicate and 14.03g of potassium hydroxide in 250mL of natural seawater to prepare 1M KOH+0.25M SiO3 2- Natural seawater solution.

[0030] Comparative Example

[0031] The alkaline salt water electrolyte containing no metasilicate is prepared by dissolving 14.03 g potassium hydroxide in 250 mL salt water to prepare a 1 M KOH salt water solution.

[0032] The alkaline natural seawater electrolyte without metasilicate is prepared by dissolving 14.03 g potassium hydroxide in 250 mL natural seawater to prepare a 1 M KOH natural seawater solution.

[0033] The specific marks, anode materials, and parameter ratios in the embodiments are shown in Tables 1-3.

[0034] Table 1 Electrolyte number table

[0035]

[0036]

[0037] Table 2 Anode material table

[0038]

[0039] Table 3 Electrolyte parameter ratio table

[0040]

[0041] Test example

[0042] 1.LSV, EIS and IT testing

[0043] The performance of the electrolytes in the embodiments and comparative examples was tested. The test process was as follows: in a 1 mol / L KOH electrolyte, the electrolytic cell was configured with three electrodes, commercial nickel foam (NF) or nickel processed nickel foam (XSN) was the anode, mercury / mercury oxide (Hg / HgO) was the reference electrode, and platinum was the counter electrode. 2- , alkaline salt water + 0.25M SiO3 2- , alkaline salt water + 0.35M SiO3 2- , alkaline natural seawater + 0.25M SiO3 2- ) for OER testing.

[0044] Test results see Figure 1-7(NF@1 means the anode material is nickel foam and the electrolyte is alkaline salt water).

[0045] Figure 1 The LSV polarization curve of Figure 1 It can be seen that the electrolyte containing metasilicate has no obvious effect on the OER performance of the anode material. Even with the presence of metasilicate, the Yang family material can still maintain a high OER activity.

[0046] Figure 2-7 The stability test diagram of each anode material in each electrolyte. The OER stability test was carried out in salt water using commercial nickel foam as the anode. After about 0.8 hours, the current dropped significantly, indicating that the anode catalyst had been corroded. When the electrolyte was 1M KOH+0.15M SiO3 2- When the electrolyte is 1M KOH + 0.25M SiO3, the service life increases slightly, but it is still not enough to meet industrial requirements. 2- Saline solution and 1M KOH + 0.35M SiO3 2- In salt water solution, commercial nickel metal foam can be stable for at least 80 hours.

[0047] In order to be more suitable for industrial applications, XSN with better OER activity was used as the anode material. After testing, it was found that XSN with better OER activity was used as the anode material in 1M KOH+0.25M SiO3 2- In a saline electrolyte, the anode material can operate stably for at least 1337 hours using the chronoamperometry method with 150 mA as the evaluation standard. 2- When using natural seawater solution, the chronoamperometry is also used with 160 mA as the evaluation standard, and the anode material can operate stably for at least 1985 hours.

[0048] 2. Microstructure and chemical properties

[0049] The microstructure of the embodiment is shown in Figure 8 .

[0050] FIG9 is a SEM image of the anode material in each electrolyte. Figure 8 a is the SEM image of the original XSN, whose skeleton is intact and almost broken. Figure 8 b is the SEM image of XSN after 40 minutes of chronoamperometry test in saline solution. It can be clearly observed that most of it has been corroded and deformed. Figure 8 c is XSN in 1M KOH+0.25M SiO3 2- The SEM image after 40 minutes of chronoamperometry test in saline electrolyte clearly shows that the skeleton is almost not damaged. This is due to the SiO3 2-The presence of makes XSN anti-corrosion.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An alkaline salt water (natural seawater) with added metasilicate as electrolyte is used for electrochemical electrolysis of natural seawater to produce hydrogen.

2. The alkaline salt water (natural seawater) electrolyte containing metasilicate according to claim 1, Features The concentration of metasilicate is 0.15-0.35 mol / L.

3. The alkaline salt water (natural seawater) electrolyte containing metasilicate according to claims 1-2 can be applied to a variety of anode material systems.

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