A method for improving the stability of a proton-conductor electrolyte in carbon dioxide

Abstract

The application discloses a preparation method for improving stability of a proton conductor electrolyte in carbon dioxide, relates to the technical field of solid oxide batteries and solid oxide electrolysis cells, and is characterized by the following steps: through a nano-additive surface modification method, a nano-structure additive of an alkaline earth metal oxide, or a transition metal oxide, or a VA main group metal oxide is prepared on the surface of a barium cerate and a barium zirconate series electrolyte obtained through a solid phase reaction method by using a vacuum impregnation method, and an alkaline proton conductor electrolyte with a surface modification additive is obtained. The alkaline proton conductor electrolyte with the surface modification nano-structure additive obtained by the application can be applied to a proton type carbon hydrogen ceramic membrane fuel cell or high-temperature electrolysis carbon dioxide, so that the stability of the electrolyte can be effectively enhanced, and ohmic loss can be reduced, thereby greatly improving the performance and stability of the solid oxide fuel cell and the electrolysis cell under a carbon dioxide atmosphere.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of solid oxide cell and solid oxide electrolysis cell, and particularly relates to a preparation method for improving stability of proton conductor electrolyte in carbon dioxide. BACKGROUND

[0002] Solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) have become one of the energy conversion technologies that are concerned at present due to their high efficiency, low cost without noble metal catalyst and wide fuel application range because they can provide combined heat and power. According to the different ion-conducting electrolytes, SOFC and SOEC are mainly divided into oxygen ion type and proton type. The development of oxygen ion type conductor electrolyte is limited by the high activation energy of oxygen ion conduction. The ohmic resistance of the oxygen ion type conductor electrolyte is much larger than that of the proton type conductor electrolyte at medium and low temperatures. Therefore, the proton type SOFC / SOEC has become a hot research direction at home and abroad. At present, the proton type conductor electrolyte materials mainly include various element-doped barium zirconate, barium cerate, strontium zirconate and strontium cerate systems. Among them, barium zirconate and barium cerate have become the main electrolyte materials for proton type SOFC / SOEC due to their advantages of proton conductivity and stability. However, the proton type electrolyte usually adopts B-site doping to control the conductivity and stability, and the A-site is usually completely occupied by alkali metal ions. When the SOFC using hydrocarbon fuel or the SOEC electrolyzing CO2, acid-base reaction easily occurs to form conductive barrier phases such as carbonates, which increases the interfacial resistance. As a result, a large ohmic resistance is formed in the cell or electrolysis cell during operation, which leads to the decrease of performance and stability. How to maintain the high ion conductivity and stability of the proton conductor electrolyte in the presence of carbon dioxide and other acidic gases is one of the key problems for improving the performance and stability of the proton type SOFC and SOEC for high-temperature electrolysis of CO2.

[0003] At present, A-site partial substitution is used to reduce the alkalinity of the electrolyte, but it may cause the decrease of the conductivity of the proton conductor electrolyte. In addition, excessive element doping may cause large stress in the crystal structure, which may cause structural distortion and impurity phase precipitation during long-term operation, resulting in changes in composition and structure, increase of ohmic resistance, decrease of performance and stability problems. Therefore, the partial doping substitution method commonly used at present to improve the conductivity and stability of the proton conductor electrolyte still has some problems, which will limit the further popularization and large-scale application of the proton type solid oxide cell and electrolysis cell. SUMMARY

[0004] In order to solve the technical problem of the stability of the barium zirconate and barium cerate system material in the carbon dioxide acidic gas, the application discloses a preparation method for improving the stability of a proton conductor electrolyte in carbon dioxide, and a nano additive protection is constructed on the surface of the electrolyte by using a vacuum impregnation method, so that the acid-base reaction of the proton conductor electrolyte in the carbon dioxide is reduced, and the proton transmission activity is enhanced.

[0005] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme: a preparation method for improving the stability of a proton conductor electrolyte in carbon dioxide, comprising the following steps:

[0006] Step one, a nitrate solution containing alkaline earth metal ions, or a nitrate solution containing transition metal ions, or a nitrate solution containing VA main group metal ions is configured, and an appropriate amount of a complexing agent is added, the PH is adjusted, the volume is fixed, and a mixed solution of the complexing agent and the nitrate is obtained;

[0007] Step two, the mixed solution of the complexing agent and the nitrate obtained in step one is used for multiple vacuum impregnations of yttrium-doped barium zirconate or / and barium cerate powder according to the total amount of impregnation demand, the powder after each impregnation is subjected to low-temperature calcination, and the powder after the last impregnation is subjected to high-temperature calcination.

[0008] Further, in step one, the alkaline earth metal ions include one of magnesium ions, calcium ions and strontium ions; the transition metal ions include one of manganese ions, nickel ions, iron ions and zinc ions; and the VA main group metal ions are one of bismuth ions;

[0009] The fixed concentration of the metal ions in the solution is 0.05-0.25 mol / L, and the PH value is 5-6;

[0010] The complexing agent is one or two of glycine, ammonium citrate and EDTA, and the concentration of the complexing agent is 0.8-4.5 mol / L.

[0011] Further, in step two, the impregnation is performed in the order from high to low concentration when the mixed solution of the complexing agent and the nitrate is used for impregnation, and the vacuum degree is adjusted from low to high during the impregnation process.

[0012] The impregnation times are 5-15 times, and the vacuum degree ranges from 0.5 to 0.1 Mpa.

[0013] Further, the total amount of impregnation in step two is 0.5mol%, 1.0mol%, 2.0mol%, 3.0mol%, 4.0mol% of the molar amount of yttrium-doped barium zirconate or / and barium cerate powder, wherein the total amount of magnesium ion impregnation is 0.5mol%, 1.0mol%, 2.0mol%, 3.0mol%, 4.0mol%; the total amount of calcium ion impregnation is 0.5mol%, 4.0mol%; the total amount of strontium ion impregnation is 0.5mol%; the total amount of manganese ion impregnation is 1.0mol%, 2.0mol%, 3.0mol%; the total amount of nickel ion impregnation is 0.5mol%, 1.0mol%; the total amount of iron ion impregnation is 0.5mol%, 1.0mol%, 4.0mol%; the total amount of zinc ion impregnation is 1.0mol%; and the total amount of bismuth ion impregnation is 4.0mol%.

[0014] Further, in step two, the low-temperature calcination temperature is 300-450 degrees, and the calcination time is 2-4 hours, the high-temperature calcination temperature is 700-900 degrees, and the calcination time is 2-6 hours.

[0015] The beneficial effects of the present application are that the nano-structured additives on the surface of the electrolyte are composed of various metal oxides, on the one hand, the basicity of these metal oxides is lower than that of the barium-containing electrolyte oxide, which can effectively reduce the reaction activity of the strong basic barium-containing oxide on the surface of the electrolyte and the carbonate and other impurities generated by the acid carbon dioxide; on the other hand, the nano-structured additives and the electrolyte can form a high-activity heterojunction, which helps to improve the proton conductivity, thereby reducing the overall performance loss of the electrolyte and the adverse effects on stability.

[0016] The present application strictly selects alkaline earth metal ions, or transition metal ions, or VA main group metal ions and the corresponding total amount of impregnation, which is related to the action mode of the nano-structured additives with different ion properties and formed on the surface of the electrolyte, thereby breaking through the traditional idea of chemical doping modification of the internal crystal structure of the electrolyte material itself.

[0017] The present application adopts a method of combining chemical components and surface structure modification, and finally obtains a proton conductor electrolyte material with surface-modified nano-additives, which greatly improves the stability and ion transport activity in carbon dioxide, effectively reduces the ohmic resistance and improves the stability.

[0018] The method improves the conductivity and stability of the proton conductor electrolyte material in carbon dioxide, which is conducive to the development and application of high-temperature electrolysis of carbon dioxide by hydrocarbon fuel proton type SOFC and proton type SOEC. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The carbon dioxide temperature programmed desorption curve of Example 1 in BZY electrolyte impregnated with different molar contents of Mg 2+

[0020] ​Figure 2 Example 1 in BZY electrolyte impregnated with 4 mol% Mg 2+ Stability test chart of the prepared proton ceramic membrane fuel cell after 20 mL / min carbon dioxide is passed in;

[0021] Figure 3 Example 2 in BZY electrolyte impregnated with 0.5 mol% Ca 2+ , Ni 2+ , Fe 3+ , Sr 2+ Carbon dioxide temperature programmed desorption curve of the solution; Figure 3 Example 2 in BZY electrolyte impregnated with 0.5 mol% Fe 3+ SEM image;

[0022] Figure 4 Example 3 in BZY electrolyte impregnated with 4.0 mol% Bi 3+ , Ca 2+ , Fe 3+ Carbon dioxide temperature programmed desorption curve of the solution; Figure 4 Example 3 in BZY electrolyte impregnated with 4.0 mol% Ca 2+ SEM image; DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0024] Proton solid oxide fuel cells and electrolytic cells commonly use electrolytes including barium cerate and barium zirconate doped systems. Since the A sites are completely occupied by alkali earth metal ions with strong basicity and are prone to enrichment on the surface, the acid-base reaction is prone to occur when carbon dioxide exists in the product and reactant, resulting in a large interfacial resistance, and further resulting in problems such as increase of ohmic resistance, decrease of cell performance and stability, etc.

[0025] Example 1

[0026] 1.2820 g, 2.5641 g, 5.1282 g of Mg(NO3)2 6H2O were respectively dissolved in 40 mL of deionized water, continuously stirred and 9.0080 g of glycine was added, the pH was adjusted to 6 using nitric acid and ammonia water, and then the volume was made up in a 100 mL volumetric flask to obtain magnesium ion impregnation solutions of 0.05 mol / L, 0.1 mol / L and 0.2 mol / L, and the glycine concentration was 1.2 mol / L.

[0027] Adjust the vacuum degree to 0.4 Mpa, first immerse BaZr0.8Y0.2O3-δ(BZY) in 0.2 mol / L solution for 2 times, and calcine at 350 degrees for 2 hours after each time of immersion; then immerse in 0.1 Mpa 0.1 mol / L solution for 3 times, and calcine at 350 degrees for 2 hours after each time of immersion; then immerse in 0.05 Mpa 0.05 mol / L solution for 5 times, and calcine at 350 degrees for 2 hours after each time of immersion; and finally, after the last time of immersion, calcine at 800 degrees for 2 hours, to obtain a sample with a total amount of impregnation of 4 mol%.

[0028] Test Mg-4mol% by carbon dioxide temperature programmed desorption method, and the results are shown in Figure 1 Compared with pure BZY, no obvious carbon dioxide desorption peak is present at each temperature section.

[0029] Prepare the sample with a total amount of impregnation of 4 mol% into a proton ceramic membrane fuel cell for testing, and after 20 mL / min carbon dioxide is introduced, the performance remains stable for more than 80 hours, as shown in Figure 2 .

[0030] Example 2

[0031] Dissolve 2.0200 g and 8.0799 g Fe(NO3)3 9H2O respectively in 50 mL deionized water, continuously stir and add 19.4572 g ammonium citrate, adjust the PH to 6 by nitric acid and ammonia water, and then make up to volume in a 100 mL volumetric flask, to obtain 0.05 mol / L and 0.2 mol / L iron ion impregnation solutions respectively, and the ammonium citrate concentration is 0.8 mol / L.

[0032] Adjust the vacuum degree to 0.4 Mpa, first immerse BaZr0.8Y0.2O3-δ(BZY) in 0.2 mol / L solution for 2 times, and calcine at 350 degrees for 2 hours after each time of immersion; then immerse in 0.1 Mpa 0.05 mol / L solution for 3 times, and calcine at 350 degrees for 2 hours after each time of immersion; then immerse in 0.05 Mpa 0.05 mol / L solution for 5 times, and calcine at 350 degrees for 2 hours after each time of immersion; and finally, after the last time of immersion, calcine at 800 degrees for 2 hours, to obtain a sample with a total amount of impregnation of 4 mol%.

[0033] Test Fe-0.5mol% by carbon dioxide temperature programmed desorption method, and the results are shown in Figure 3 Compared with pure BZY, no carbon dioxide desorption peak is present, and some nano-structured particles are formed on the surface.

[0034] Prepare the sample with a total amount of impregnation of 0.5 mol% into a proton ceramic membrane fuel cell for testing, and after 10 mL / min carbon dioxide is introduced, the performance can remain stable for more than 50 hours.

[0035] Example 3

[0036] 1.1807g, 2.3614g, 5.9035g Ca (NO3) 2 4H2O were dissolved in 40mL deionized water respectively, stirring constantly and adding 7.5067g glycine, adjusting PH to 6 with nitric acid and ammonia water, then setting volume in 100mL volumetric flask, respectively obtaining 0.05mol / L, 0.1mol / L, 0.25mol / L calcium ion impregnation solution, glycine concentration is 1.0mol / L.

[0037] Adjusting vacuum degree to 0.3Mpa, first impregnating 0.25mol / L solution on BaZr 0.8 Y 0.2 O 3-δ (BZY) once, calcining at 350 degrees for 2 hours; then impregnating 0.1mol / L solution 4 times under 0.15Mpa, calcining at 350 degrees for 2 hours after each impregnation; again impregnating 0.05mol / L solution 5 times under 0.05Mpa, calcining at 350 degrees for 2 hours after each impregnation; finally calcining at 800 degrees for 2 hours, obtaining 4mol% sample in total impregnation amount.

[0038] Using carbon dioxide temperature programmed desorption method to test Ca-4mol%, results as shown in Figure 4 compared with pure BZY, no carbon dioxide desorption peak appears, and SEM shows that its surface is rich in a large number of nanoparticles.

[0039] Impregnation total amount of 4mol% sample is prepared into proton ceramic membrane fuel cell for testing, after passing in 10mL / min carbon dioxide, performance remains stable for more than 30 hours.

[0040] Of course, the above description is not a limitation on the present application, the present application is not limited to the above examples, changes, modifications, additions or substitutions made by the person skilled in the art within the essential scope of the present application, also should belong to the protection scope of the present application.

Claims

1. A method for improving the stability of a proton-conductor electrolyte in carbon dioxide, characterized by, It comprises the following steps: Step one, configure the nitrate solution containing alkaline earth metal ions, or the nitrate solution containing transition metal ions, or the nitrate solution containing VA main group metal ions, and add appropriate amount of complexing agent to it, adjust the PH, and then constant volume, to obtain the mixed solution of complexing agent and nitrate; Step two, use the mixed solution of complexing agent and nitrate obtained in step one to impregnate yttrium doped barium zirconate or / and barium cerate powder according to the total amount of impregnation demand, and then low temperature calcination is carried out after each impregnation, and high temperature calcination is carried out after the last impregnation, to obtain the final powder material of electrolyte; In step one, the alkaline earth metal ions include one of magnesium ion, calcium ion and strontium ion; the transition metal ions include one of manganese ion, nickel ion, iron ion and zinc ion; the VA main group metal ion is one of bismuth ion; The constant volume concentration of metal ions in the solution is 0.05-0.25 mol / L, and the PH value is 5-6; The complexing agent is one or two of glycine, ammonium citrate and EDTA, and the concentration of complexing agent is 0.8-4.5 mol / L; In step two, when impregnated with the mixed solution of complexing agent and nitrate, impregnation is carried out in the order from high to low concentration, and the vacuum degree is adjusted from low to high during impregnation; The impregnation times are 5-15 times, and the vacuum degree ranges from 0.5 to 0.1 Mpa.

2. The method of claim 1, wherein the proton-conductor electrolyte is stabilized in carbon dioxide. The total amount of impregnation in step two is the molar amount of yttrium doped barium zirconate or / and barium cerate powder, wherein the total amount of magnesium ion impregnation is 0.5 mol%, 1.0 mol%, 2.0 mol%, 3.0 mol% and 4.0 mol%; the total amount of calcium ion impregnation is 0.5 mol% and 4.0 mol%; the total amount of strontium ion impregnation is 0.5 mol%; the total amount of manganese ion impregnation is 1.0 mol%, 2.0 mol% and 3.0 mol%; the total amount of nickel ion impregnation is 0.5 mol% and 1.0 mol%; the total amount of iron ion impregnation is 0.5 mol%, 1.0 mol% and 4.0 mol%; the total amount of zinc ion impregnation is 1.0 mol%; and the total amount of bismuth ion impregnation is 4.0 mol%.

3. The method of claim 2, wherein the proton-conductor electrolyte is stabilized in carbon dioxide by adding a compound selected from the group consisting of a carbonate, a bicarbonate, a hydroxide, and a mixture thereof. In step two, the low temperature calcination temperature is 300-450 degrees, and the calcination time is 2-4 hours; the high temperature calcination temperature is 700-900 degrees, and the calcination time is 2-6 hours.

Images