Chloroplatinic acid solid compound for preparing hydrogen fuel cell catalyst

Abstract

The invention discloses a chloroplatinic acid solid compound for preparing a hydrogen fuel cell catalyst, which is prepared by the following steps: firstly, putting platinum powder into a mixed solution consisting of a hydrochloric acid solution and a nitric acid solution, heating until the platinum powder is completely dissolved, and then carrying out nitrate removal treatment to obtain a nitrate-removed solution; heating the solution after saltpeter removal, and adding chlorate to obtain a solid precipitate; then at room temperature, adding water to dilute the solid precipitate, adding a reducing agent at one time, uniformly mixing, continuously stirring until fluffy sponge platinum solid is not separated out any more, and separating and cleaning to obtain sponge platinum; finally, under the heating condition, sponge platinum is dissolved in a mixed solvent composed of a hydrochloric acid solution and hydrogen peroxide, the heating condition is kept, the solvent is removed through concentration and evaporation, and a chloroplatinic acid solid is prepared. In the process of preparing the chloroplatinic acid solid compound, the reduction reaction conditions are improved, so that the activity of the prepared sponge platinum is protected, the activity of the prepared chloroplatinic acid product is improved and stabilized, and the stability and the electrochemical activity of the chloroplatinic acid product are improved.

Description

Technical Field

[0001] The invention belongs to the field of preparation of chloroplatinic acid for synthesizing hydrogen fuel cell catalysts, and in particular relates to a chloroplatinic acid solid compound for preparing hydrogen fuel cell catalysts. Background Art

[0002] Hydrogen fuel cell catalysts are currently at the core of research in the new energy sector. They are prepared by loading platinum compounds onto a carrier. Therefore, the activity and stability of chloroplatinic acid, a raw material for hydrogen fuel cell catalysts, directly impact the electrochemical activity and stability of hydrogen fuel cells. Improving the platinum activation performance of chloroplatinic acid and ensuring batch-to-batch stability are key control factors.

[0003] Prior art (such as application number CN117985782A) is reduced by adding alkali, and attempts to use without adding alkali to adjust pH directly to the acidic solution of platinum to reduce, find that elemental platinum can not be effectively reduced. The reason is that under acidic conditions, the elemental platinum nucleus reduced will be dissolved without reunion, and alkaline reducing agent will preferentially react with free acid so as to suppress reduction process to proceed;Although the alkali (ammonia, tetramethylammonium hydroxide etc.) without metal ion is replaced and neutralized with acid, it can not be effectively reduced after forming co-substance pair, and certain by-product (dichlorodiamine platinum, dichlorotetraamine platinum etc.) is generated, and its structural stability will not react with hydrazine hydrate.And in the process, metal ion is introduced and then it is necessary to carry out purification and impurity removal, the activity of intermediate can be caused to be gradually inactivated during cleaning and impurity removal, it is necessary to add reducing agent for secondary activation after cleaning to make sponge platinum keep high activity state, and then dissolved by hydrochloric acid, hydrogen peroxide mixed solution, this technique increases activation cost.

[0004] Based on this, a new preparation method of chloroplatinic acid solid compound is now provided, which can achieve full reduction by using non-metallic ions, improve activity performance, avoid activity deactivation, and has a simple process and is more suitable for large-scale production. Summary of the Invention

[0005] Purpose of the invention: The present invention provides a novel preparation process for obtaining a solid chloroplatinic acid compound with high activation performance.

[0006] Technical solution: The solid chloroplatinic acid compound used in the preparation of hydrogen fuel cell catalysts of the present invention is prepared by the following steps:

[0007] (1) Platinum powder is placed in a mixed solution consisting of a hydrochloric acid solution and a nitric acid solution, heated until completely dissolved, and then subjected to a nitric acid removal treatment to obtain a nitric acid removal solution;

[0008] (2) heating the solution after removing the nitrate and adding chloride salt to obtain a solid precipitate;

[0009] (3) At room temperature, the solid precipitate is diluted with water, and the reducing agent is added all at once, mixed evenly, and stirred continuously until fluffy sponge platinum solid no longer precipitates; the sponge platinum solid is then separated from the mother liquor and washed with water at room temperature to obtain sponge platinum; the mass ratio of the added volume of the reducing agent to the solid precipitate is (0.05-0.8 mL):1 g;

[0010] (4) dissolving sponge platinum in a mixed solvent consisting of hydrochloric acid solution and hydrogen peroxide under heating conditions; maintaining the heating conditions, concentrating and evaporating to remove the solvent, thereby obtaining chloroplatinic acid solid.

[0011] The present invention adopts a method combining precipitation and reduction processes, wherein platinum ions are first precipitated as ammonium chloroplatinate and then reduced to sponge platinum by a reducing agent, thereby deeply activating the platinum while avoiding the introduction of additional metal ions.

[0012] The core of the present invention is that the reduction process can be carried out at room temperature (0-30°C) by adding all the reducing agent at one time, so as to reduce the process cost while further stabilizing the activity of the prepared sponge platinum, avoiding the influence of temperature increase on the activity of platinum, and then preparing a highly active sponge platinum intermediate and then preparing the chloroplatinic acid compound; at the same time, under this condition, after adding an excess reducing agent to the dilution solution of ammonium chloroplatinate at one time, on the one hand, a one-time excess addition method is adopted to promote the full progress of the reduction reaction by improving the dispersion of the system; on the other hand, the excess reducing agent is dissolved in the system, and after determining that the reduction reaction is fully carried out, the excess reducing agent remaining in the system can be used to further suppress the re-oxidation reaction between the platinum in the system and the residual chloride ions, thereby avoiding the reduction of platinum activity caused by secondary oxidation of platinum and protecting the activity of platinum; in addition, the excess reducing agent can also be used to further stabilize the activity of platinum during the cleaning process of platinum precipitation, thereby reducing the influence of chloride ions on the activity of platinum during the cleaning process.

[0013] Furthermore, in step (1) of the method for preparing a solid chloroplatinic acid compound of the present invention, the mass concentration of the hydrochloric acid solution is 36-38%, and the mass concentration of the nitric acid solution is 65-68%; the volume ratio of the hydrochloric acid solution to the nitric acid solution is (4-5):1.

[0014] Furthermore, in step (1) of the method for preparing a solid chloroplatinic acid compound of the present invention, the heating temperature is 60-110° C.; and the nitrate removal treatment is to maintain the heating temperature until no yellowish-brown nitrogen oxide gas escapes.

[0015] Furthermore, in step (2) of the method for preparing a solid chloroplatinic acid compound of the present invention, the heating temperature is 80-100° C.; and the chloride salt is solid ammonium chloride or a saturated ammonium chloride solution.

[0016] Furthermore, in step (2) of the method for preparing a solid chloroplatinic acid compound of the present invention, the mass of the solid chloride salt added is 0.6-1 times the mass of the platinum powder.

[0017] Furthermore, in step (3) of the method for preparing the solid chloroplatinic acid compound of the present invention, the room temperature is 0-30° C., and the reaction time with continuous stirring after uniform mixing is 20-60 min.

[0018] Furthermore, in step (3) of the method for preparing the solid chloroplatinic acid compound of the present invention, the mass ratio of water to the fixed precipitate is (5-15):1.

[0019] Furthermore, in step (3) of the method for preparing a solid chloroplatinic acid compound of the present invention, the reducing agent is one or more of ascorbic acid, hydrazine hydrate and glucose.

[0020] Furthermore, in step (4) of the method for preparing a solid chloroplatinic acid compound of the present invention, the heating temperature is 80-100° C., the mass concentration of the hydrochloric acid solution is 36-38%, the mass concentration of the hydrogen peroxide is 30-35%, the volume ratio of the hydrochloric acid solution to the hydrogen peroxide is 2:(1-1.5), and the mass ratio of the added volume of the mixed solvent to the sponge platinum is (6-15 mL):1 g.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: by changing the reduction reaction conditions during the preparation of a solid chloroplatinic acid compound, the activity of the prepared sponge platinum is protected, the activity of the prepared chloroplatinic acid product is enhanced and stabilized, and its stability and electrochemical activity are improved. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described in detail below with reference to the embodiments.

[0023] It should be noted that the masses of the sponge platinum prepared in the following examples of the present invention and the initial platinum powder are substantially the same, with an error within the range of ±0.1 g.

[0024] Example 1

[0025] The preparation method of chloroplatinic acid in the present embodiment comprises the following steps:

[0026] (1) Take 50g of platinum powder, add 250mL of hydrochloric acid and 50mL of nitric acid, with a mass concentration of 38% hydrochloric acid and a mass concentration of 68% nitric acid, and heat to 90°C until the platinum powder is completely dissolved and no excess nitric acid escapes;

[0027] (2) heating the solution to 100° C., adding 220 g of a 17.7 wt % ammonium chloride solution to the solution, and filtering to obtain 113.6 g of ammonium chloroplatinate solid;

[0028] (3) Add 1500 g of water to the ammonium chloroplatinate solid and add 20 mL of 80% hydrazine hydrate to the solution at room temperature for reduction. The reaction is completed after 30 minutes, and fluffy sponge platinum solid is precipitated.

[0029] (4) After separating the sponge platinum from the mother liquor, add water and wash repeatedly until the conductivity of the washing liquid is less than 2μs / cm 2 ;

[0030] (5) Add 300 mL of 37% hydrochloric acid and 150 mL of 32% hydrogen peroxide to the platinum and dissolve at 80° C.; after filtering, continue to concentrate at 90° C. to a platinum content of 37.7%, and cool to obtain chloroplatinic acid solid.

[0031] Example 2

[0032] The preparation method of chloroplatinic acid in the present embodiment comprises the following steps:

[0033] (1) Take 50g of platinum powder, add 250mL of hydrochloric acid and 50mL of nitric acid, with a mass concentration of 38% hydrochloric acid and a mass concentration of 68% nitric acid, and heat to 95°C until the platinum powder is completely dissolved and no excess nitric acid escapes;

[0034] (2) maintaining the solution temperature at 95° C., adding 220 g of a 17.7 wt % ammonium chloride solution to the solution, and filtering to obtain 113.5 g of ammonium chloroplatinate solid;

[0035] (3) Add 1000 g of water to the ammonium chloroplatinate solid and add 50 mL of 40% ascorbic acid solution to the solution at room temperature for reduction. After 30 min of reduction, fluffy sponge platinum solids precipitate.

[0036] (4) After separating the sponge platinum from the mother liquor, add water and wash repeatedly until the conductivity of the washing liquid is less than 2μs / cm 2 ;

[0037] (5) Add 350 mL of 37% hydrochloric acid and 200 mL of 32% hydrogen peroxide to the platinum and dissolve at 90° C.; after filtering, continue to concentrate at 90° C. to a platinum content of 37.8%, and cool to obtain chloroplatinic acid solid.

[0038] Example 3

[0039] (1) Take 50g of platinum powder, add 250mL of hydrochloric acid and 50mL of nitric acid, with the mass concentration of hydrochloric acid being 38% and the mass concentration of nitric acid being 68%, and heat to 95°C until the platinum powder is completely dissolved and no excess nitric acid escapes;

[0040] (2) heating the solution to 100° C., adding 35 g of solid ammonium chloride to the solution, and filtering to obtain 113.7 g of solid ammonium chloroplatinate;

[0041] (3) Add 1200 g of water to dilute the ammonium chloroplatinate solid. At room temperature, add 40 mL of 20% glucose solution to the solution all at once for reduction. After the reduction is completed, sponge platinum solid is precipitated.

[0042] (4) After separating the sponge platinum from the mother liquor, add water and wash repeatedly until the conductivity of the washing liquid is less than 2μs / cm 2 ;

[0043] (5) Add 350 mL of 37% hydrochloric acid and 150 mL of 32% hydrogen peroxide to the platinum and dissolve at 95° C.; filter and continue to concentrate at 90° C. to a platinum content of 37.7%, and cool to obtain chloroplatinic acid solid.

[0044] Comparative Example 1

[0045] Comparative Example 1 is the same as Example 1, except that the reduction reaction is carried out at 90° C. The specific steps include:

[0046] (1) Take 50g of platinum powder, add 250mL of hydrochloric acid and 50mL of nitric acid, with the mass concentration of hydrochloric acid being 38% and the mass concentration of nitric acid being 68%, and heat to 90°C until the platinum powder is completely dissolved and no excess nitric acid escapes;

[0047] (2) heating the solution to 100° C., adding 220 g of a 17.7 wt % ammonium chloride solution to the solution, and filtering to obtain 113.6 g of ammonium chloroplatinate solid;

[0048] (3) Add 1500 g of water to the ammonium chloroplatinate solid and heat it to 90° C. Then add 20 mL of 80% hydrazine hydrate to the solution all at once for reduction. After 20 minutes, the reaction is complete and fluffy sponge platinum solid is precipitated.

[0049] (4) After separating the sponge platinum from the mother liquor, add water and wash repeatedly until the conductivity of the washing liquid is less than 2μs / cm 2 ;

[0050] (5) Add 300 mL of 37% hydrochloric acid and 150 mL of 32% hydrogen peroxide to the platinum and dissolve at 80° C.; after filtering, continue to concentrate at 90° C. to a platinum content of 37.7%, and cool to obtain chloroplatinic acid solid.

[0051] Comparative Example 2

[0052] The basic steps are the same as those in Example 1, except that the reduction is carried out by heating and adding hydrazine hydrate dropwise to fully reduce the platinum. Specifically, the steps include:

[0053] (1) Take 50g of platinum powder, add 250mL of hydrochloric acid and 50mL of nitric acid, with a mass concentration of 38% hydrochloric acid and a mass concentration of 68% nitric acid, and heat to 90°C until the platinum powder is completely dissolved and no excess nitric acid escapes;

[0054] (2) heating the solution to 100° C., adding 220 g of a 17.7 wt % ammonium chloride solution to the solution, and filtering to obtain 113.6 g of ammonium chloroplatinate solid;

[0055] (3) Add 1500 g of water to the ammonium chloroplatinate solid and heat it to 90° C. Then, add 15 mL of 80% hydrazine hydrate dropwise to the solution for reduction. After 30 min, the reaction is complete and fluffy sponge platinum solid is precipitated.

[0056] (4) After separating the sponge platinum from the mother liquor, add water and wash repeatedly until the conductivity of the washing liquid is less than 2μs / cm 2 ;

[0057] (5) Add 300 mL of 37% hydrochloric acid and 150 mL of 32% hydrogen peroxide to the platinum and dissolve at 80° C.; after filtering, continue to concentrate at 90° C. to a platinum content of 37.7%, and cool to obtain chloroplatinic acid solid.

[0058] Performance testing

[0059] The electrochemical performance of the chloroplatinic acid solids prepared in Examples 1-3 and Comparative Examples 1-2 was tested with reference to GB / T 20042.4-2009. The test results are shown in Table 1.

[0060] Table 1 Electrochemical properties of Examples 1-3 and Comparative Examples 1-2

[0061]

[0062] It should be noted that the catalyst performance tests of the above examples and comparative examples have a single error range of ±0.001V, and the experimental data are averaged by repeated sampling to ensure that the data results will not cause large deviations due to the test.

[0063] In the above performance test, the greater the current density, the better the catalyst performance. The catalyst standard is: 0.04A / cm 2 The current density must be greater than 0.890V; 2A / cm 2The current density must be greater than 0.640V, and the catalyst activity that meets this standard is qualified and effective; the above Examples 1-3 all meet the requirements, while the high temperature in Comparative Examples 1-2 affects the activity of platinum, resulting in a decrease in catalyst activity; and the performance of Comparative Example 1 is better than that of Comparative Example 2, which further proves that the reducing agent added once has a protective effect on platinum, and still has a protective effect on it even under heating conditions.

[0064] In addition to the above embodiments, it should be noted that the technical effects claimed in the present invention can be achieved by adopting the preparation process of the present invention and the specified parameter range, and therefore no further examples are given for verification.

[0065] For example, the mass concentration of the hydrochloric acid solution used in the present invention is 36-38%, the mass concentration of the nitric acid solution used is 65-68%, the volume ratio of the hydrochloric acid solution to the nitric acid solution in the nitric acid solution is (4-5):1, preferably 5:1; the amount ratio of platinum powder to the mixed solution is 1g:(6-8)mL, preferably 1g:8mL; the heating temperature in step (1) can be 60-110°C; after the nitrate is removed, the nitrate removal solution needs to be heated again, and its temperature can be 80-100°C. In step (3), the mass ratio of water to solid precipitate is (5-15):1, preferably 10:1; the reducing agent used can be one or more of ascorbic acid with a mass concentration of 40-80%, hydrazine hydrate with a mass concentration of 20-80%, or glucose with a mass concentration of 40-50%; the room temperature range can be 0-30°C; and in step (4), the heating temperature can be 80-100°C.

Claims

1. A chloroplatinic acid solid compound for preparing a hydrogen fuel cell catalyst, characterized in that: Prepared by the following steps: (1) Platinum powder is placed in a mixed solution consisting of a hydrochloric acid solution and a nitric acid solution, heated until completely dissolved, and then subjected to a nitric acid removal treatment to obtain a nitric acid removal solution; (2) heating the solution after removing the nitrate and adding chloride salt to obtain a solid precipitate; (3) At room temperature, the solid precipitate is diluted with water, and the reducing agent is added all at once, mixed evenly, and stirred continuously until fluffy sponge platinum solid no longer precipitates; the sponge platinum solid is then separated from the mother liquor and washed with water at room temperature to obtain sponge platinum; the mass ratio of the added volume of the reducing agent to the solid precipitate is (0.05-0.8 mL):1 g; (4) dissolving sponge platinum in a mixed solvent consisting of hydrochloric acid solution and hydrogen peroxide under heating conditions; maintaining the heating conditions, concentrating and evaporating to remove the solvent, thereby obtaining chloroplatinic acid solid.

2. The chloroplatinic acid solid compound according to claim 1, characterized in that In step (1), the mass concentration of the hydrochloric acid solution is 36-38%, and the mass concentration of the nitric acid solution is 65-68%; the volume ratio of the hydrochloric acid solution to the nitric acid solution is (4-5):

1.

3. The chloroplatinic acid solid compound according to claim 1, wherein In step (1), the ratio of the platinum powder to the mixed solution is 1 g: (6-8) mL.

4. The chloroplatinic acid solid compound according to claim 1, characterized in that In step (1), the heating temperature is 60-110° C.; the nitrate removal treatment is to maintain the heating temperature until no yellowish brown nitrogen oxide gas escapes.

5. The chloroplatinic acid solid compound according to claim 1, characterized in that In step (2), the heating temperature is 80-100° C.; and the chloride salt is solid ammonium chloride or saturated ammonium chloride solution.

6. The chloroplatinic acid solid compound according to claim 1, characterized in that In step (2), the mass of the chloride salt added is 0.6-1 times the mass of the platinum powder.

7. The chloroplatinic acid solid compound according to claim 1, characterized in that In step (3), the room temperature is 0-30° C., and the reaction time with continuous stirring after mixing is 20-60 min.

8. The chloroplatinic acid solid compound according to claim 1, characterized in that In step (3), the mass ratio of water to fixed precipitate used in the water dilution is (5-15):

1.

9. The chloroplatinic acid solid compound according to claim 1, characterized in that In step (3), the reducing agent includes at least one of ascorbic acid, hydrazine hydrate or glucose.

10. The chloroplatinic acid solid compound according to claim 1, characterized in that In step (4), the heating temperature is 80-100° C., the mass concentration of the hydrochloric acid solution is 36-38%, the mass concentration of the hydrogen peroxide is 30-35%, the volume ratio of the hydrochloric acid solution to the hydrogen peroxide is 1:(0.5-0.75), and the mass ratio of the added volume of the mixed solvent to the sponge platinum is (6-15 mL):1 g.

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