CN215218657U - Ni/NiO reference electrode for molten salt electrolyte - Google Patents

Abstract

The utility model discloses a Ni/NiO reference electrode for molten salt electrolyte, which comprises an electrode sleeve, a nickel wire electrode and reference salt; the electrode sleeve is a tube body with an opening at the upper end; inert gas is filled in the tube body; the reference salt is arranged at the bottom of the electrode sleeve; the lower end of the nickel wire electrode is covered with a nickel oxide layer, and the nickel wire electrode is inserted into the reference salt and extends out of the electrode sleeve; the upper end opening of the electrode casing is sealed by high-temperature sealant; the reference salt is carbonate or chloride. The Ni/NiO reference electrode provided by the utility model has long service life, good stability and reproducibility of electrode potential, and is suitable for being used in a molten salt electrolyte system within the range of 200-2000 ℃.

Description

Ni/NiO reference electrode for molten salt electrolyte

Technical Field

The utility model belongs to the electrode field, concretely relates to a Ni/NiO reference electrode for molten salt electrolyte.

Background

The high-temperature molten salt electrolyte has very important application in the fields of electrolytic metallurgy, corrosion and protection, environmental protection, resource recycling, fuel cells and the like, and the electrochemical research in the high-temperature molten salt plays a crucial role in understanding the mechanism process of relevant application scenes and promoting the progress of relevant technologies. The reference electrode is an indispensable part in electrochemical research, and for high-temperature molten salt electrolyte, how to prepare the reference electrode with high electrode potential stability, good electrode potential reproducibility and long service life is a bottleneck problem which troubles researchers. The most highly used of the chloride and carbonate systems are Ag/AgCl and Ag/Ag₂SO₄Reference electrode of the type comprising AgCl or Ag inserted by a silver wire₂SO₄And (4) carrying out encapsulation on the bottom of the electrode sleeve of the reference salt, and then putting into use. The electrode has proved to have short-term use stability, the optimal use time is about 7 days, and the electrode potential is seriously drifted after the electrode is used for a long time, thereby influencing the electrochemical test result. In a fluoride molten salt system, platinum wires/sheets are immersed in molten salt to serve as pseudo-reference electrodes, and the electrodes are not high in electrode potential stability and poor in reproducibility and are not suitable for long-term use. And Ag/AgCl, Ag/Ag₂SO₄And the platinum wire/sheet electrode contains noble metal, and the manufacturing cost is also a large factor for limiting the expanded production of the electrode. Therefore, it is necessary to develop a reference electrode which has high electrode potential stability, good electrode potential reproducibility, long service life, low cost, simple process and is suitable for high-temperature molten salt electrolyte.

SUMMERY OF THE UTILITY MODEL

To the technical problem, the utility model provides a Ni/NiO reference electrode for in fused salt, this electrode preparation is simple, can be in the fused salt kind steady operation. The invention designs a more practical Ni/NiO redox couple based on the design principle of the reference electrode, and manufactures the corresponding reference electrode based on the basic principle.

The utility model provides a technical scheme as follows:

a Ni/NiO reference electrode for molten salt electrolyte comprises an electrode sleeve, a nickel wire electrode and reference salt;

the electrode sleeve is a tube body with an opening at the upper end; inert gas is filled in the tube body;

the reference salt is arranged at the bottom of the electrode sleeve;

the lower end of the nickel wire electrode is covered with a nickel oxide layer, and the nickel wire electrode is inserted into the reference salt and extends out of the electrode sleeve;

the upper end opening of the electrode casing is sealed by high-temperature sealant;

the reference salt is carbonate or chloride.

Furthermore, the electrode sleeve is made of insulating aluminum oxide ceramics, the outer diameter of the electrode sleeve is 6-28mm, the inner diameter of the electrode sleeve is 4-26mm, the length of the electrode sleeve is 5-80 cm, and the thickness of the electrode sleeve is 1-5 mm.

Still further, the material of the electrode sleeve is selected from one of beta-alumina, zirconia and mullite.

Furthermore, the diameter of the nickel wire is 0.2-3mm, and the purity is 99-99.999%.

Furthermore, the nickel wire is reserved at least 0.5cm outside the electrode sleeve.

Furthermore, the nickel oxide layer spirally surrounds the lower end of the nickel wire electrode.

Further, the thickness of the nickel oxide is 0.01-0.3 mm

Further, the inert gas is N₂Or Ar.

Further, the carbonate is selected from Li₂CO₃、Na₂CO₃、K₂CO₃、CaCO₃、MgCO₃、BaCO₃And the like, in any one or more of these combinations. Preferably Li₂CO₃-Na₂CO₃-K₂CO₃。

Further, the chloride salt is selected from LiCl, NaCl, KCl and CaCl₂、MgCl₂、BaCl₂And the like, in any one or more of these combinations. MgCl-KCl is preferred.

The preparation method of the reference electrode comprises the following steps:

(1) accurately weighing a certain mass of molten salt (alkali metal/alkaline earth metal salt), and quickly moving the molten salt into a clean crucible;

(2) transferring the crucible into a furnace chamber of an electric furnace which is heated in advance, sealing the furnace cover, keeping an inert atmosphere, and keeping the temperature of 150-350 ℃ for drying for 12-48 h;

(3) after drying, heating the furnace until the molten salt is completely melted, then cooling to 20-150 ℃, taking out the crucible, completely wrapping the crucible with tinfoil, and putting the crucible into a glove box;

(4) smashing the crucible in a glove box, taking out salt blocks, and grinding the salt blocks into fine powder by using an agate mortar for later use;

(5) accurately weighing reference salt, grinding the reference salt to be uniform, and pouring the ground reference salt into an electrode sleeve;

(6) coating nickel oxide dissolved in ammonia water on the surface of the nickel wire, and obtaining the nickel wire covered with the nickel oxide after the ammonia water is volatilized;

(7) inserting a nickel wire into the electrode sleeve to touch the bottom, and reserving a metal wire with enough length on the pipe orifice side;

(8) and (4) taking a proper amount of high-temperature sealant to seal the opening of the electrode tube, and taking out the glove box after the electrode tube is dried and solidified.

The utility model has the advantages that:

(1) the preparation process is simple, and a single preparation step is easy to operate;

(2) the materials used for preparation are cheap and easy to obtain, so that the manufacturing cost of the product is greatly reduced;

(3) the nickel wire used in the method is covered with nickel oxide to form a Ni/NiO reference electrode, and the Ni/NiO reference electrode has excellent potential stability and reproducibility;

(4) the effective service time of the Ni/NiO reference electrode is long enough to be maintained properly for continuous use for at least 1 month.

Drawings

FIG. 1 is a schematic diagram of an apparatus for a Ni/NiO reference electrode; in the figure, 1-high temperature sealant, 2-nickel wire, 3-electrode sleeve, 4-inert gas, 5-reference salt and 6-nickel oxide layer;

FIG. 2 is a LSV plot of the precipitation potential of alkali metals;

FIG. 3 is a graph showing the change of the precipitation potential of an alkali metal with time.

Detailed Description

The present invention will be further described with reference to specific embodiments, but the present invention is not limited thereto.

Example 1

The Ni/NiO reference electrode has a structure shown in figure 1, and comprises an electrode sleeve 3, a nickel wire electrode 2 and reference salt 5;

the electrode sleeve 3 is a mullite tube with an opening at the upper end; inert gas 4 is filled in the tube body;

the reference salt 5 is arranged at the bottom of the mullite tube;

the lower end of the nickel wire 2 electrode is covered with a nickel oxide layer 6, and the nickel oxide layer is inserted into the reference salt 5 and extends out of the electrode sleeve;

the opening at the upper end of the electrode sleeve 3 is sealed by high-temperature sealant 1;

the reference salt 5 is a carbonate.

The carbonate of this example consists of Li in a molar ratio of 43.5:31.5:25₂CO₃-Na₂CO₃-K₂CO₃The solid powder composition is prepared by the following steps: (1) quickly pouring 10g of solid powder with the molar ratio into a clean alumina crucible, transferring the alumina crucible into a furnace chamber of an electric furnace which is heated in advance, sealing the furnace cover, keeping Ar atmosphere, and drying for 12-24 hours at the temperature of 300 ℃ under 250-; (2) and after drying, heating the furnace to 650 ℃ (the heating rate is 5 ℃/min), preserving the heat for 3-6 h at the temperature until the salt is completely melted, then cooling to about 100 ℃ at 3 ℃/min, taking out the crucible when the crucible is hot, completely wrapping the crucible with tin foil, putting the crucible into a glove box, smashing the crucible after cooling, taking out salt blocks, and grinding the salt blocks into fine powder by using an agate mortar.

The nickel wire electrode covered with the nickel oxide coating in this example was prepared as follows: and spirally coating nickel oxide dissolved in ammonia water on the surface of the nickel wire, and obtaining the nickel wire covered with the nickel oxide after the ammonia water is volatilized.

Fig. 2 is the calibration result of reference electrode, the utility model discloses a three electrode system, WE is Ni silk, CE platinized titanium, RE is Ni/NiO, get negative pole alkali metal and precipitate the potential and be the calibration reference, and the result is shown in the figure, under the test of passing through about 90h, removes initial 0 ~ 2 h's solid electrolyte stable stage, in the test of subsequent nearly 90h, alkali metal precipitates the potential and does not have obvious change, explains that the electrode potential of reference electrode is extremely stable.

FIG. 3 is a summary of the alkali metal precipitation potential in the calibration result of the reference electrode, and it can be seen from the figure that, at the initial stage of the test, the alkali metal precipitation potential is more negative, near-1.98V, and at the later 2-4 h, the alkali metal precipitation potential gradually stabilizes near-1.935V, and statistical analysis of standard deviation of the alkali metal precipitation potential at different times is performed, and the value is 0.01116, and as seen from mathematical statistics rules, the value indicates that the data have a small degree of dispersion, which indicates that the electrode potential of the Ni/NiO reference electrode in the invention is sufficiently stable. Meanwhile, the results also show that the mullite solid electrolyte needs an infiltration process in molten salt, the conductivity of the mullite solid electrolyte can be stabilized after the mullite solid electrolyte is completely infiltrated, and the electrode potential of the reference electrode can be stabilized.

Table 1 shows the results of the electrode potential reproducibility test of Ni/NiO reference electrodes prepared in the same batch, the test method is as follows: open circuit potentials were tested between two Ni/NiO reference electrodes of the same batch, and each two electrodes were tested against each other until all electrodes were tested. As shown in the figure, the test result of the open circuit potential between every 2 Ni/NiO reference electrodes of 4 Ni/NiO reference electrodes is shown, the potential difference does not exceed +/-5 mV, and the test requirement of the repeatability of the reference electrodes is met. This result indicates that the Ni/NiO reference electrode of the present invention is suitable for use in high temperature molten salt electrolytes, and can provide stable reference potential for the experimenters for basic electrochemical studies.

TABLE 1 results of the Ni/NiO reference electrode reproducibility test in example 1

Example 2

The structure of the reference electrode is the same as in example 1, differing only in the composition of the reference salt.

The reference salts of this example were prepared from a molar ratio of 30.6: 69.4 MgCl-KCl solid powder composition, the preparation method is as follows: (1) quickly pouring 10g of solid powder with the molar ratio into a clean alumina crucible, transferring the alumina crucible into a furnace chamber of an electric furnace which is heated in advance, sealing the furnace cover, keeping Ar atmosphere, and keeping the temperature of 250-300 ℃ for drying for 12-24 h; (2) and after drying, heating the furnace to 650 ℃ (the heating rate is 5 ℃/min), preserving the heat for 3-6 h at the temperature until the salt is completely melted, then cooling to about 100 ℃ at 3 ℃/min, taking out the crucible when the crucible is hot, completely wrapping the crucible with tin foil, putting the crucible into a glove box, smashing the crucible after cooling, taking out salt blocks, and grinding the salt blocks into fine powder by using an agate mortar.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (8)

1. A Ni/NiO reference electrode for molten salt electrolyte is characterized by comprising an electrode sleeve, a nickel wire electrode and reference salt;

the electrode sleeve is a tube body with an opening at the upper end; inert gas is filled in the tube body;

the reference salt is arranged at the bottom of the electrode sleeve;

the lower end of the nickel wire electrode is covered with a nickel oxide layer, and the nickel wire electrode is inserted into the reference salt and extends out of the electrode sleeve;

the upper end opening of the electrode casing is sealed by high-temperature sealant;

the reference salt is carbonate or chloride.

2. The electrode of claim 1, wherein the electrode casing is an insulating alumina ceramic having an outer diameter of 6-28mm and an inner diameter of 4-26 mm.

3. The electrode of claim 2, wherein the material of the electrode sleeve is selected from one of beta-alumina, zirconia, mullite.

4. The electrode of claim 1, wherein the nickel wire has a diameter of 0.2-3 mm.

5. The electrode of claim 1, wherein the nickel wire is reserved at least 0.5cm outside the electrode sheath.

6. The electrode of claim 1 wherein the nickel oxide layer is helically wrapped around the nickel wire electrode lower end.

7. The electrode of claim 1, wherein the nickel oxide has a thickness of 0.01 to 0.3 mm.

8. The electrode of claim 1, wherein the inert gas is N₂Or Ar.

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