CN111180750B - A kind of AgPdIr nano-alloy and preparation and use method thereof - Google Patents

Abstract

The invention relates to an AgPdIr nano-alloy and a preparation and use method. Ir is added to the AgPd nano-alloy to form an AgPdIr ternary nano-alloy. The use of AgPdIr ternary nanoalloy as a catalyst improves the catalytic activity and stability of formate oxidation reaction, and moves the onset potential and peak potential position of formate oxidation reaction to the negative potential direction, which improves the direct formate fuel cell. discharge voltage and energy efficiency. Using AgPdIr nanoalloy as the catalyst for formate oxidation reaction, the onset potential of formate oxidation reaction is 0.16-0.2V, the peak potential is 0.5-0.8V, and the potential is referenced to the reversible hydrogen electrode. The catalytic activity of formate oxidation reaction is 2.09-5.14A·mg ^-1 _Pd , and the catalytic activity of formate oxidation reaction is 0.82-1.54A·mg- ¹ _Pd after 4000s durability test, which is a commercialized Pd/C 1.29‑3.17 times and 7.45‑14 times the activity and durability.

Description

A kind of AgPdIr nano-alloy and its preparation and use method

technical field

The invention belongs to the technical field of fuel cells, relates to an AgPdIr nano-alloy and a preparation and use method thereof, in particular to an anode catalyst for a direct formate fuel cell and a preparation method thereof.

Background technique

With the increasingly serious energy crisis and environmental deterioration, it is urgent to develop a new clean energy to replace traditional fossil fuels. Direct formate fuel cell is a green and efficient energy conversion device with the advantages of non-toxicity, high conversion efficiency and good safety. Generally, the working environment of the direct formic acid fuel cell is alkaline, the anode is formate oxidation reaction, and the cathode is oxygen reduction reaction, and its theoretical voltage and theoretical power density are higher than other types of fuel cells. Therefore, in recent years, the research of direct formate fuel cells has attracted more and more attention.

At present, the problem that restricts the development of direct formate fuel cells is the lack of a formate oxidation catalyst with high catalytic activity and good stability. Currently, the widely used catalysts for formate oxidation are commercial Pt/C or Pd/C. Pt/C catalysts have low catalytic activity for formate oxidation, and are prone to poisoning during the catalytic reaction. Compared with Pt/C, commercial Pd/C catalysts have low price, high catalytic activity, and no poisoning phenomenon, which has become a research hotspot for formate oxidation catalysts. However, the metal Pd surface has a strong binding energy for the adsorbed hydrogen generated during the formate oxidation reaction. The intermediate product hydrogen adsorbed on the Pd surface occupies the catalytically active sites of Pd/C, causing its catalytic activity to drop rapidly, resulting in poor stability. Therefore, to accelerate the commercialization of direct formate fuel cells, it is necessary to develop Pd-based catalysts with higher catalytic activity and stability.

Generally, the main method to improve the catalytic activity and stability of Pd-based catalysts for formate oxidation is alloying. That is, by combining metal Pd with other different types of metals, a new type of Pd-based nano-alloy catalyst is formed, thereby improving the catalytic activity and stability of the Pd-based formate oxidation catalyst.

Chinese invention patent CN107017409A discloses a direct formate fuel cell with electro-alkali-salt co-production. In this battery system, PdAu bimetallic catalysts were used as anode catalysts instead of traditional Pt-based catalysts. Although the PdAu bimetallic catalyst reduces the cost of the battery, its cost is still high.

Chinese patent CN108417854A discloses a high-efficiency silver-palladium nano-alloy formate oxidation electrocatalyst and a preparation method. The AgPd nano-alloy proposed in the invention not only ensures the high-efficiency formate oxidation catalytic activity, but also improves the Pd poisoning problem through Ag alloying, thereby improving the stability of the catalytic material and prolonging the service life of the material.

Chinese invention patent CN108746659A discloses a flower-shaped AgPd nano-alloy and its preparation and use methods. In this invention, by using Apzc as a morphology control agent, an AgPd nano-alloy catalyst with flower-like morphology is synthesized, which exhibits excellent catalytic activity and stability.

Chinese invention patent CN108598508A discloses an AgPd nano-alloy formate oxidation catalyst and a surfactant-free treatment method for improving catalytic activity. In the invention, on the basis of the alloyed Pd-based nano-catalyst, an in-situ electrochemical potential cycling method is proposed to improve the catalytic activity of Ag-Pd nano-alloy formate oxidation.

In summary, although a lot of research has been done on Pd-based bimetallic nanoalloy formate oxidation catalysts, the current Pd-based nanocatalysts still have the following disadvantages: low onset potential for formate oxidation, and formic acid The peak potential of the salt oxidation reaction is biased towards the positive potential direction, which will lead to low cell output voltage and low fuel conversion efficiency when the direct formate fuel cell works.

SUMMARY OF THE INVENTION

technical problem to be solved

In order to avoid the deficiencies of the prior art, the present invention provides an AgPdIr nano-alloy and a preparation and use method, which overcomes the deficiencies of the Pd-based nano-formate oxidation reaction catalyst in the prior art.

Technical solutions

An AgPdIr nano-alloy, which is characterized in that: Ir is added to the AgPd nano-alloy to form an AgPdIr ternary nano-alloy catalyst, the morphology is a three-dimensional porous spherical structure assembled by nano-crystals, wherein: the composition atomic percentage range is Ag: 23 ~46, Pd: 49-73, Ir: 1-8.

The diameter of the balls in the three-dimensional porous spherical structure is 30-100 nanometers.

The size of the nanocrystals is 3-7 nanometers.

A method for preparing the AgPdIr nano-alloy, characterized in that the steps are as follows:

Step 2: Add 0.2-0.3 mL of sodium chloropalladate, 0.12-0.32 mL of chloroiridic acid and 0.1-0.2 mL of silver nitrate precursor solution with a concentration of 0.01 mol·L ^-1 in sequence to the hexadecyl chloride obtained in step 1. Alkylpyridine solution, and stir for 10 to 15 minutes to make it evenly mixed

Step 3: add the ascorbic acid solution to the solution obtained in step 2, then stop stirring, and stand for 2 to 4 hours at 25 to 50 °C;

Step 4: by centrifuging, washing with deionized water, and freeze-drying the solution in step 3 to obtain an AgPdIr nano-alloy formate oxidation reaction catalyst;

The proportion of each component in the above reaction is each part, which is doubled as required.

A method for using the AgPdIr nano-alloy, characterized in that: using the AgPdIr nano-alloy as a formate oxidation reaction catalyst, the initial potential of the formate oxidation reaction is 0.16-0.2V, and the peak potential is 0.5-0.8V, The potential is referenced to a reversible hydrogen electrode. The catalytic activity of formate oxidation reaction is 2.09-5.14A·mg ^-1 _Pd , and the catalytic activity of formate oxidation reaction is 0.82-1.54A·mg ^-1 _Pd after 4000s durability test, which is a commercial Pd/C 1.29-3.17 times and 7.45-14 times the activity and durability.

beneficial effect

The invention proposes an AgPdIr nano-alloy and a method for preparing and using the same. Ir is added to the AgPd nano-alloy to form an AgPdIr ternary nano-alloy. The use of AgPdIr ternary nanoalloy as a catalyst improves the catalytic activity and stability of formate oxidation reaction, and moves the onset potential and peak potential position of formate oxidation reaction to the negative potential direction, which improves the direct formate fuel cell. discharge voltage and energy efficiency.

In the present invention, the AgPdIr ternary nano-alloy catalyst has excellent catalytic activity and stability. Figure 2 shows the AgPdIr ternary nano-alloy catalyst and commercial Pd/C in N ₂ saturated 1M KOH+1M KCOOH solution It can be seen from the figure that the catalytic activity of the AgPdIr ternary nanoalloy catalyst is higher than that of the commercial Pd/C catalyst, showing a negatively shifted onset potential and peak potential. At 0.5 V (vs RHE), the current density of the AgPdIr ternary nanoalloy catalyst is 5.14 A·mg ^-1 _Pd , which is 3.17 times that of commercial Pd/C. Figure 3 shows the long-range durability test of AgPdIr ternary nanoalloy catalyst for formate oxidation reaction. The test results show that under the test condition of potential 0.624V (vs RHE), after 20000s long-term test, its formic acid The current density of the salt oxidation reaction is still 347 mA·mg ^-1 _Pd . Figure 4 shows the regeneration ability of the AgPdIr ternary nanoalloy catalyst for the formate oxidation reaction. It can be seen from the figure that after the 4000s test process, the AgPdIr ternary nanoalloy catalyst was washed with deionized water and put into a new electrolyte, and its formate oxidation reaction activity returned to the initial state. Figure 5 shows the cycle stability test of AgPdIr ternary nanoalloy catalyst for formate oxidation reaction. From the test results, it can be seen that after 500 cycles, its formate oxidation reaction activity is 41% of the initial value.

Description of drawings

Figure 1: Flow chart of preparation of AgPdIr ternary nanoalloy catalyst

Figure 2: Cyclic voltammetry curves of different kinds of catalysts in N ₂ saturated 1M KOH+1M KCOOH solution, curve 1 is the cyclic voltammetry curve of AgPdIr ternary nanoalloy catalyst; curve 2 is the commercial Pd/C Cyclic voltammetry curves.

Figure 3: Long-range durability test of formate oxidation reaction of AgPdIr ternary nanoalloy catalyst. The test method is time-current curve, the test potential is 0.624V (vs RHE), and the test time is 20000s.

Figure 4: The regeneration ability test of AgPdIr ternary nanoalloy catalyst for formate oxidation reaction. The test method is time-current curve, the test potential is 0.624V (vs RHE), and the test time is 4000s. Curve 1 is the first time-current curve, curve 2 is the second time-current curve, curve 3 is the third time-current curve, and curve 4 is the fourth time-current curve.

Figure 5: Cyclic stability test of AgPdIr ternary nano-alloy catalyst. The test method is cyclic voltammetry curve and the scan rate is 50mV/s. Curve 1 is the cyclic voltammetry curve of the first circle; Curve 2 is the cyclic voltammetry curve of the 200th circle; Curve 3 is the cyclic voltammetry curve of the 500th circle.

Detailed ways

The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

The main components of the electrocatalyst for formate oxidation reaction of the present invention are Ag, Pd and Ir, and the atomic percentages of the components are Ag: 23-46, Pd: 49-73, and Ir: 1-8. The AgPdIr nano-alloy is a single-phase solid solution alloy. The morphology of the AgPdIr nano-alloy is a three-dimensional porous spherical structure assembled by nano-crystals, the diameter of the sphere is 30-100 nanometers, and the size of the nano-crystals is 3-7 nanometers.

Using AgPdIr nanoalloy as the catalyst for formate oxidation reaction, the onset potential of formate oxidation reaction is 0.16-0.2V (vs RHE), and the peak potential is 0.5-0.8V (vs RHE). The catalytic activity is 2.09-5.14A·mg ^-1 _Pd , and the catalytic activity of formate oxidation reaction is 0.82-1.54A·mg ^-1 _Pd after 4000s durability test, which is 1.29% higher than commercial Pd/C activity and durability -3.17 times and 7.45-14 times.

Specific examples:

Example 1

18 mg of cetylpyridine chloride surfactant was dissolved in 5 mL of deionized water, sonicated for 10 minutes, and stirred for 10 minutes to form an aqueous cetylpyridine chloride solution. 0.267mL sodium chloropalladate (0.01mol·L ^-1 ), 0.12mL chloroiridic acid (0.01mol·L ^-1 ) and 0.13mL silver nitrate (0.01mol·L ^-1 ) aqueous solution were respectively added dropwise to the above to obtain The aqueous solution of cetylpyridine chloride was stirred for 10 minutes to form an aqueous precursor solution. 0.3 mL of ascorbic acid aqueous solution with a concentration of 0.1 mol·L ^-1 was prepared, and quickly added dropwise to the above-obtained precursor aqueous solution, the stirring was stopped, and the reaction was allowed to stand at 35° C. for 3 hours. After the reaction is completed, the obtained black solution is centrifuged and washed three times with deionized water, and finally freeze-dried for 12 hours to obtain the final Ag ₃₂ Pd ₆₆ Ir ₂ ternary nano-alloy catalyst. The electrochemical test results in _N2 -saturated 1M KOH ₊ 1M _KCOOH solution show that the _Ag32Pd66Ir2 ternary nanoalloy catalyst has a commercial current density for formate oxidation at 0.5V (vs RHE) 1.29 times that of the Pd/C catalyst.

Example 2

18 mg of cetylpyridine chloride surfactant was dissolved in 5 mL of deionized water, sonicated for 10 minutes, and stirred for 10 minutes to form an aqueous cetylpyridine chloride solution. 0.267mL sodium chloropalladate (0.01mol·L ^-1 ), 0.2mL chloroiridic acid (0.01mol·L ^-1 ) and 0.13mL silver nitrate (0.01mol·L ^-1 ) aqueous solution were respectively added dropwise to the above to obtain The aqueous solution of cetylpyridine chloride was stirred for 10 min to form an aqueous precursor solution. 0.3 mL of ascorbic acid aqueous solution with a concentration of 0.1 mol·L ^-1 was prepared, and quickly added dropwise to the above-obtained precursor aqueous solution, the stirring was stopped, and the reaction was allowed to stand at 35° C. for 3 hours. After the reaction is completed, the obtained black solution is centrifuged, washed with deionized water three times, and finally freeze-dried for 12 hours to obtain the final Ag ₃₀ Pd ₆₆ Ir ₄ ternary nano-alloy catalyst. The electrochemical test results in _N2 -saturated 1M KOH ₊ 1M _KCOOH solution show that the _Ag31Pd65Ir4 ternary nanoalloy catalyst has a commercial current density for formate oxidation at 0.5V (vs RHE) 3.17 times that of the Pd/C catalyst.

Example 3

18 mg of cetylpyridine chloride surfactant was dissolved in 5 mL of deionized water, sonicated for 10 minutes, and stirred for 10 minutes to form an aqueous cetylpyridine chloride solution. 0.267mL of sodium chloropalladate (0.01mol·L ^-1 ), 0.32mL of chloroiridic acid (0.01mol·L ^-1 ) and 0.13mL of silver nitrate (0.01mol·L ^-1 ) aqueous solution were respectively added dropwise to the above to obtain The aqueous solution of cetylpyridine chloride was stirred for 10 minutes to form an aqueous precursor solution. 0.3 mL of ascorbic acid aqueous solution with a concentration of 0.1 mol·L ^-1 was prepared, and quickly added dropwise to the above-obtained precursor aqueous solution, the stirring was stopped, and the reaction was allowed to stand at 35° C. for 3 hours. After the reaction is completed, the obtained black solution is centrifuged and washed three times with deionized water, and finally freeze-dried for 12 hours to obtain the final Ag ₂₈ Pd ₆₅ Ir ₇ ternary nano-alloy catalyst. The electrochemical test results in _{N2 -} saturated 1M KOH+1M _KCOOH solution show that the _Ag28Pd65Ir7 ternary nanoalloy catalyst has a commercial current density for formate oxidation at 0.5V (vs RHE) 2.54 times that of the Pd/C catalyst.

Example 4

18 mg of cetylpyridine chloride surfactant was dissolved in 5 mL of deionized water, sonicated for 10 minutes, and stirred for 10 minutes to form an aqueous cetylpyridine chloride solution. 0.3 mL of sodium chloropalladate (0.01 mol·L ^-1 ), 0.2 mL of chloroiridic acid (0.01 mol·L ^-1 ) and 0.1 mL of silver nitrate (0.01 mol·L ^-1 ) aqueous solution were sequentially added dropwise to the above obtained The aqueous solution of cetylpyridine chloride was stirred for 10 minutes to form an aqueous precursor solution. 0.3 mL of ascorbic acid aqueous solution with a concentration of 0.1 mol·L ^-1 was prepared, and quickly added dropwise to the above-obtained precursor aqueous solution, the stirring was stopped, and the reaction was allowed to stand at 35° C. for 3 hours. After the reaction is completed, the obtained black solution is centrifuged and washed three times with deionized water, and finally freeze-dried for 12 hours to obtain the final Ag ₂₃ Pd ₇₃ Ir ₄ ternary nano-alloy catalyst. The electrochemical test results in _N2 -saturated 1M KOH ₊ 1M _KCOOH solution show that the _Ag23Pd73Ir4 ternary nanoalloy catalyst has a commercial current density for formate oxidation at 0.5V (vs RHE) 2.41 times that of the Pd/C catalyst.

Example 5

18 mg of cetylpyridine chloride surfactant was dissolved in 5 mL of deionized water, sonicated for 10 minutes, and stirred for 10 minutes to form an aqueous cetylpyridine chloride solution. 0.2mL sodium chloropalladate (0.01mol·L ^-1 ), 0.2mL chloroiridic acid (0.01mol·L ^-1 ) and 0.2mL silver nitrate (0.01mol·L ^-1 ) aqueous solution were respectively added dropwise to the above obtained The aqueous solution of cetylpyridine chloride was stirred for 10 minutes to form an aqueous precursor solution. 0.3 mL of ascorbic acid aqueous solution with a concentration of 0.1 mol·L ^-1 was prepared, and quickly added dropwise to the above-obtained precursor aqueous solution, the stirring was stopped, and the reaction was allowed to stand at 35° C. for 3 hours. After the reaction is completed, the obtained black solution is centrifuged, washed with deionized water three times, and finally freeze-dried for 12 hours to obtain the final Ag ₄₆ Pd ₄₉ Ir ₅ ternary nano-alloy catalyst. The electrochemical test results in _{N2 -} saturated 1M KOH+1M _KCOOH solution show that the _Ag46Pd49Ir5 ternary nanoalloy catalyst has a commercial current density for formate oxidation at 0.5V (vs RHE) 1.89 times that of the Pd/C catalyst.

Claims (3)

1. An AgPdIr nanoalloy, which is characterized in that: adding Ir into AgPd nano alloy to form an AgPdIr ternary nano alloy catalyst, wherein the shape of the AgPdIr ternary nano alloy catalyst is a three-dimensional porous spherical structure assembled by nanocrystals, and the AgPd ternary nano alloy catalyst is characterized in that: the diameter of the ball in the three-dimensional porous spherical structure is 30-100 nanometers, the size of the nanocrystal is 3-7 nanometers, and the atomic percentage ranges of the components are Ag: 23-46, Pd: 49-73, Ir: 1 to 8.

2. A method for preparing the AgPdIr nanoalloy of claim 1, characterized by the following steps:

step 1: completely dissolving 17-25 mg of cetylpyridinium chloride surfactant into 5-7 mL of deionized water to form a transparent cetylpyridinium chloride aqueous solution;

step 2: the concentration is 0.01 mol.L ^-1 Sequentially adding 0.2-0.3 mL of sodium chloropalladate, 0.12-0.32 mL of chloroiridic acid and 0.1-0.2 mL of silver nitrate precursor solution into the cetylpyridinium chloride solution obtained in the step 1, and stirring for 10-15 minutes to uniformly mix the materials

And step 3: adding an ascorbic acid solution into the solution obtained in the step 2, stopping stirring, and standing and reacting for 2-4 hours at the temperature of 25-50 ℃;

and 4, step 4: processing the solution in the step 3 through centrifugal separation, deionized water cleaning and freeze drying to obtain the AgPdIr nano alloy formate oxidation reaction catalyst;

the proportion of each component in the reaction is each part, and is multiplied according to the requirement.

3. The use method of the AgPdIr nanoalloy according to claim 1, characterized in that: the AgPdIr nano alloy is used as a formate oxidation reaction catalyst, the initial potential of the formate oxidation reaction is 0.16-0.2V, the peak potential is 0.5-0.8V, and the potential is referred to a reversible hydrogen electrode; the catalytic activity of the formate oxidation reaction is 2.09-5.14 A.mg ^-1 _Pd The catalytic activity of the formate oxidation reaction is 0.82 to 1.54 A.mg after a 4000s durability test ^-1 _Pd Is prepared from1.29-3.17 times and 7.45-14 times the activity and durability of commercial Pd/C.

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