CN111900415A - Method for preparing metal-nitrogen co-doped oxygen reduction catalyst using electroplating sludge - Google Patents

Abstract

The invention discloses a method for preparing a metal-nitrogen co-doped oxygen reduction catalyst by using electroplating sludge. Electroplating sludge, melamine and corn stalk biomass powder are mixed and dissolved in ultrapure water in a certain proportion, and magnetically stirred at room temperature. After stirring, it was dried at 50-70 °C for 4 h, and then ground into powder after drying; then an appropriate amount of powder was taken, pyrolyzed at 950 °C under the protection of N ₂ for 2 h, cooled to below 100 °C and taken out; Soak and shake in hydrochloric acid, wash and dry to obtain a metal-nitrogen co-doped oxygen reduction catalyst based on electroplating sludge. The catalyst has an oxygen reduction catalytic activity comparable to that of commercial Pt/C, and has excellent stability, good methanol resistance, and simple preparation. Cathode catalysts offer an option.

Description

Method for preparing metal-nitrogen co-doped oxygen reduction catalyst using electroplating sludge

technical field

The invention relates to a method for preparing a metal-nitrogen co-doped oxygen reduction catalyst by using electroplating sludge, and belongs to the technical field of electrocatalysis and waste recycling.

Background technique

Fuel cell is an environment-friendly energy device with high efficiency and low noise, but its cathode oxygen reduction reaction overpotential is high, and its resistance to methanol is poor. The current commercialized Pt-based catalysts are expensive and the reserves of Pt are limited. It is necessary to develop non-precious metal-based catalysts with good catalytic performance, low price and large reserves to replace Pt-based catalysts. Non-precious metal-based oxygen reduction catalysts have brought new hope for fuel cells, especially metal-nitrogen/carbon-based catalysts.

Metal sources are important components in metal-nitrogen/carbon type catalysts. Electroplating sludge, which is the "final state" of wastewater treatment in the electroplating industry, contains a large amount of important metals such as copper, nickel, chromium, iron, and zinc with different contents. If it is not properly treated, it will cause pollution and damage to the environment. , but also has the potential to be a metal source. Using electroplating sludge as a metal source for metal-nitrogen/carbon catalysts will be a combination of waste utilization and environmental protection, but it has not been reported in the literature so far.

SUMMARY OF THE INVENTION

In order to solve the problems of the prior art, the object of the present invention is to overcome the deficiencies of the prior art, and to provide a method for preparing a metal-nitrogen co-doped oxygen reduction catalyst by utilizing electroplating sludge, which is easy to operate, requires a short preparation time, and uses The source of the metal is electroplating industrial waste, and the prepared catalyst has good oxygen reduction catalytic performance, which is comparable to the current commercial Pt/C, and also has good methanol resistance and durability.

In order to achieve the above-mentioned purpose of invention and creation, the present invention adopts the following technical solutions:

A method for preparing a metal-nitrogen co-doped oxygen reduction catalyst by utilizing electroplating sludge, comprising the following steps:

a. Dry and grind the corn stalks, and then pass the ground stalk powder through a 100-mesh sieve and collect it to obtain the stalk powder;

b. Mix the electroplating sludge, melamine and the sieved straw powder in step a, then dissolve in ultrapure water, stir magnetically for at least 4 hours at room temperature, and filter and separate to obtain solids after stirring, And dry at 50～70℃, and then grind the dried solids into powder mixture;

c. Take the mixture powder obtained in the step b, put it in a quartz boat, and pyrolyze the mixture under the protection of N ₂ at a temperature of not lower than 950 ° C for at least 2 hours, and then cool the cracking production area to not high At 100°C, the pyrolysis product is taken out to obtain pyrolysis metal-nitrogen modified biochar;

d. The biochar obtained in the step c is placed in hydrochloric acid with a concentration of not less than 1 mol/L, soaked and shaken for washing for at least 12 hours, and then washed with ultrapure water suction filtration until the pH is 7, and the washed product It is separated out and collected, and then dried at 50-70° C. to obtain a metal-nitrogen co-doped oxygen reduction catalyst.

As a preferred technical solution of the present invention, in the step b, the electroplating sludge, melamine and the sieved straw powder in the step a are mixed according to the ratio of raw material mass ratio of 1:20:4 .

As a preferred technical solution of the present invention, in the step c, the mixture powder obtained in the step b is taken, placed in a quartz boat, and in a vacuum tube furnace, the flow rate of the non-redox protective gas is not less than 200mL/min, Program the temperature from room temperature to not less than 100 °C, the heating rate is not less than 10 °C/min, and the constant temperature is maintained for at least 20 minutes. This operation is used to maintain the oxygen exhaust in the tube furnace and the biomass is in a dry state; At a heating rate of 10°C/min, heat to not lower than 950°C, and carbonize at a constant temperature for at least 2 hours; then cool the pyrolysis product obtained after the constant temperature carbonization treatment to not higher than 100°C, and take out the pyrolysis product to obtain pyrolysis metal. - Nitrogen-modified biochar.

As a preferred technical solution of the present invention, in the step d, the prepared metal-nitrogen co-doped oxygen reduction catalyst contains a mass percentage of metal not less than 0.65 wt.%, and a mass percentage of nitrogen not less than 4.76 wt.%.

As a further preferred technical solution of the present invention, in the step d, the prepared metal-nitrogen co-doped oxygen reduction catalyst contains a mass percentage of metal not less than 0.65 wt.%, and a mass percentage of nitrogen not less than 4.76wt.%, the mass percentage containing silicon is not less than 2.13wt.%, the mass percentage containing oxygen is not less than 14.35wt.%, and the balance is carbon and impurities.

A metal-nitrogen co-doped oxygen reduction catalyst is prepared by the method of the present invention using electroplating sludge to prepare a metal-nitrogen co-doped oxygen reduction catalyst.

Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant advantages:

1. The method of the present invention can prepare a metal-nitrogen co-doped oxygen reduction catalyst based on electroplating sludge. The catalyst has an oxygen reduction catalytic activity comparable to that of commercial Pt/C during testing, and has excellent stability and methanol resistance. Good performance and simple preparation, it is a good measure to "turn waste into treasure", and provides a choice for the cathode catalyst of fuel cells;

2. The method of the present invention is simple and easy to implement, low in cost, and suitable for popularization and use.

Description of drawings

Fig. 1 is the SEM and TEM test charts of the preparation method of the preferred embodiment of the present invention.

FIG. 2 is a comparison of the LSV diagrams of the metal-nitrogen co-doped oxygen reduction catalyst prepared in the preferred embodiment of the present invention and commercial Pt/C.

Figure 3 is a graph of methanol resistance test of a prior art commercial Pt/C oxygen reduction catalyst.

FIG. 4 is a test chart of methanol resistance of the metal-nitrogen co-doped oxygen reduction catalyst prepared in the preferred embodiment of the present invention.

Detailed ways

The above scheme will be further described below in conjunction with specific embodiments, and preferred embodiments of the present invention are described in detail as follows:

In this embodiment, a method for preparing a metal-nitrogen co-doped oxygen reduction catalyst using electroplating sludge, the steps are as follows:

a. Dry and grind the corn stalks, and then pass the ground stalk powder through a 100-mesh sieve and collect it to obtain the stalk powder;

b. The electroplating sludge, melamine and the sieved straw powder in the step a are mixed in a mass ratio of 1:20:4, then dissolved in ultrapure water, and magnetically stirred at room temperature for 4h, After stirring, the solid matter is obtained by filtration and separation, and dried at 50-70° C., and then the dried solid matter is ground into a mixture powder;

c. Take the mixture powder obtained in step b and place it in a quartz boat. In a vacuum tube furnace, the flow rate of the non-redox protective gas is 200mL/min, and the temperature is programmed from room temperature to 100°C, and the heating rate is 10°C/min. , the constant temperature is maintained for 20min, and this operation is used to maintain the oxygen exhaust in the tube furnace, and the biomass is in a dry state; then, at a heating rate of 10℃/min, heated to 950℃, constant temperature carbonization treatment for 2h; then constant temperature carbonization treatment The obtained pyrolysis product is cooled to 100°C, and the pyrolysis product is taken out to obtain pyrolysis metal-nitrogen modified biochar;

d. The biochar obtained in the step c is placed in hydrochloric acid with a concentration of 1 mol/L, soaked and shaken for 12 hours, and then washed with ultrapure water by suction filtration until the pH is 7, and the washed product is separated out and collected, and then dried at 50-70° C. to obtain a metal-nitrogen co-doped oxygen reduction catalyst.

Experimental test analysis:

The metal-nitrogen co-doped oxygen reduction catalyst prepared in this example was used as a test sample for property inspection.

In this example, the composition of the electroplating sludge is shown in Table 1.

Table 1. Electroplating sludge composition table

The composition analysis of the electroplating sludge used in this example shows that the electroplating sludge is mainly Fe and contains a small amount of mixture of other metals.

In this example, the composition of the prepared metal-nitrogen co-doped oxygen reduction catalyst is shown in Table 2.

Table 2. XPS composition analysis table of ES-N/BC samples

Table 2 is the XPS composition analysis table of the catalyst prepared in this example, and both metal and nitrogen have been successfully doped into the material.

Fig. 1 is the SEM and TEM test charts of the preparation method of this embodiment, wherein Fig. 1(a) is the SEM, and Fig. 1(b) is the TEM test chart. It can be seen from FIG. 1 that the material prepared in this example has a porous floc structure and has abundant edge structures. FIG. 2 is a comparison of the LSV diagrams of the metal-nitrogen co-doped oxygen reduction catalyst prepared in this example and commercial Pt/C. At -0.80V, the absolute value of the limiting current density of ES-N/BC reaches 5.094mA cm ^-2 respectively, which reaches and exceeds the 5.048mAcm ^-2 of commercial Pt/C. The catalytic activity of the catalyst prepared in the example is comparable to that of commercial Pt/C. /C is equivalent. Figure 3 is a graph of methanol resistance test of a prior art commercial Pt/C oxygen reduction catalyst. 4 is a test chart of methanol resistance of the metal-nitrogen co-doped oxygen reduction catalyst prepared in Example 1 of the present invention. It can be seen from Figure 3 and Figure 4 that commercial Pt/C has an obvious methanol reaction peak after adding methanol, and its anti-methanol performance is not good. However, the materials prepared in the examples have basically no change in the curve after the addition of methanol, and have good methanol resistance.

In this example, the method for preparing a metal-nitrogen co-doped oxygen reduction catalyst by using electroplating sludge, the electroplating sludge, melamine and corn stover biomass powder are mixed in a certain proportion and dissolved in ultrapure water, and the magnetic stirring is carried out at room temperature for 4 hours. After drying, it was dried at 50-70 °C, and ground into powder after drying; then an appropriate amount of powder was taken, pyrolyzed at 950 °C under the protection of N ₂ for 2 h, cooled to below 100 °C and taken out; the resultant was placed in 1 mol/L hydrochloric acid for Soaking and shaking, washing and drying to obtain a metal-nitrogen co-doped oxygen reduction catalyst based on electroplating sludge. The catalyst has an oxygen reduction catalytic activity comparable to that of commercial Pt/C, and has excellent stability, good methanol resistance, and simple preparation. Cathode catalysts offer an option.

The embodiments of the present invention have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned embodiments, and various changes can also be made according to the purpose of the invention and creation of the present invention. Changes, modifications, substitutions, combinations or simplifications should be equivalent substitution methods, as long as they meet the purpose of the present invention, as long as they do not deviate from the technical principles and inventive concepts of the present invention, all belong to the protection scope of the present invention.

Claims (6)

1. A method for preparing a metal-nitrogen codoped oxygen reduction catalyst by using electroplating sludge is characterized by comprising the following steps:

a. drying and grinding corn straws, and then sieving the ground straw powder with a 100-mesh sieve and collecting to obtain straw powder;

b. mixing electroplating sludge, melamine and the straw powder sieved in the step a, dissolving the mixture in ultrapure water, magnetically stirring the mixture at room temperature for at least 4 hours, filtering and separating the mixture after stirring to obtain solid matters, drying the solid matters at 50-70 ℃, and grinding the dried solid matters into mixture powder;

c. putting the mixture powder obtained in the step b into a quartz boat, and carrying out reaction at the temperature of not less than 950 ℃ and in N₂Pyrolyzing the mixture for at least 2 hours under protection, then cooling the pyrolysis product to be not higher than 100 ℃, and taking out the pyrolysis product to obtain pyrolytic metal-nitrogen modified biochar;

d. and c, placing the biochar obtained in the step c in hydrochloric acid with the concentration not lower than 1mol/L, soaking, shaking and washing for at least 12 hours, then performing suction filtration and washing with ultrapure water until the pH value is 7, separating and collecting washed products, and then drying at 50-70 ℃ to obtain the metal-nitrogen co-doped oxygen reduction catalyst.

2. The method for preparing the metal-nitrogen co-doped oxygen reduction catalyst by using electroplating sludge according to claim 1, wherein in the step b, the electroplating sludge, the melamine and the straw powder sieved in the step a are mixed according to a raw material mass ratio of 1:20: 4.

3. The method for preparing a metal-nitrogen co-doped oxygen reduction catalyst by using electroplating sludge according to claim 1, wherein in the step c, the mixture powder obtained in the step b is taken and placed in a quartz boat, a non-redox protection gas is introduced into a vacuum tube furnace, the flow rate is not lower than 200mL/min, the temperature is programmed to be not lower than 100 ℃ from room temperature, the heating rate is not lower than 10 ℃/min, the temperature is kept for at least 20min at constant temperature, so that the oxygen in the tube furnace is exhausted, and the biomass is in a dry state; then heating to be not less than 950 ℃ at the heating rate of not less than 10 ℃/min, and carrying out constant-temperature carbonization treatment for at least 2 h; and then cooling the pyrolysis product obtained after the constant-temperature carbonization treatment to be not higher than 100 ℃, and taking out the pyrolysis product to obtain the pyrolytic metal-nitrogen modified biochar.

4. The method for preparing a metal-nitrogen co-doped oxygen reduction catalyst by using electroplating sludge as claimed in claim 1, wherein in the step d, the prepared metal-nitrogen co-doped oxygen reduction catalyst contains not less than 0.65 wt.% of metal and not less than 4.76 wt.% of nitrogen.

5. The method for preparing a metal-nitrogen co-doped oxygen reduction catalyst by using electroplating sludge as claimed in claim 4, wherein in the step d, the prepared metal-nitrogen co-doped oxygen reduction catalyst contains not less than 0.65 wt.% of metal, not less than 4.76 wt.% of nitrogen, not less than 2.13 wt.% of silicon, not less than 14.35 wt.% of oxygen, and the balance of carbon and impurities.

6. A metal-nitrogen co-doped oxygen reduction catalyst, which is prepared by the method for preparing a metal-nitrogen co-doped oxygen reduction catalyst by using electroplating sludge according to claim 1.

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