WO2022142058A1

WO2022142058A1 - Preparation method for monodisperse noble metal catalyst and application thereof

Info

Publication number: WO2022142058A1
Application number: PCT/CN2021/092635
Authority: WO
Inventors: 葛君杰; 李阳; 邢巍; 王显; 杨小龙; 刘长鹏; 李晨阳; 梁亮; 金钊; 刘世伟
Original assignee: 中国科学院长春应用化学研究所
Priority date: 2020-12-28
Filing date: 2021-05-10
Publication date: 2022-07-07
Also published as: CN112952152A

Abstract

A method for preparing monodisperse noble metal catalyst, comprising: dissolving zinc acetate and ellagic acid in a first solvent, washing, and drying to obtain a carrier precursor (S11); dissolving the carrier precursor in a second solvent to obtain a carrier precursor solution; dissolving a noble metal salt in the second solvent to obtain a noble metal salt solution; adding the noble metal salt solution fractionally into the carrier precursor solution for reacting to obtain a catalyst precursor (S12); grinding and mixing the catalyst precursor and a nitrogen-containing organic substance, and performing a heat treatment in a reducing atmosphere to obtain a monodisperse noble metal catalyst (S13). The preparation method has a simple operation and mild conditions, and can obtain a catalyst that has ultra-low noble metal loading, ultrahigh activity and an ultrahigh noble metal utilization rate. The monodisperse noble metal catalyst obtained by the preparation method can be applied to the electrooxidation of carbon monoxide and the purification of carbon monoxide in hydrogen.

Description

A kind of preparation method and application of monodisperse precious metal catalyst

technical field

The present disclosure relates to the technical field of fuel cell catalysts, in particular to a preparation method and application of a monodisperse noble metal catalyst.

Background technique

As a clean and efficient energy conversion device, fuel cells have been a research hotspot for decades. Faced with the global energy crisis and environmental pollution problems, fuel cells have won the favor of people for their high efficiency beyond Carnot efficiency and cleanliness without pollutants. Among them, hydrogen-oxygen fuel cells (HOFC) are the most eye-catching. . HOFC is a power generation device that directly converts the chemical energy in hydrogen and oxygen into electrical energy. It has the characteristics of high theoretical specific energy, high energy conversion efficiency, and environmental friendliness. The product is only water and no other emissions such as greenhouse gas _CO2 . Among them, hydrogen has the characteristics of the highest specific energy density, abundant reserves and a wide range of sources, absolutely clean and pollution-free, convenient for storage, and suitable for changing application conditions and working environments. HOFC is very similar to the existing internal combustion engine vehicles in application scenarios. It has a long cruising range and convenient hydrogen refueling, so it has broad application prospects in automobiles.

However, the commercial application of hydrogen-oxygen fuel cells still faces many problems. For example, the problem of oxygen mass transfer at the cathode leads to a decrease in the activity of the cathode catalyst, the expensive metal platinum catalyst that the anode catalyst relies on is too expensive, and the noble metal platinum catalyst is easily poisoned and deactivated by trace amounts of CO. Especially the problem of CO poisoning, the sources of hydrogen can be roughly divided into three categories: steam methane reforming, coal gasification, water electrolysis and others. The first two technologies account for more than 95% of the production, while water electrolysis and other technologies produce less than 4%, and the hydrogen produced by the first two technologies contains CO. Among the many problems faced by the above hydrogen-oxygen fuel cells, the poisoning of the anode platinum-based catalyst by CO is one of the keys to the commercialization of HOFCs. One of the current solutions is to pre-oxidize the anode fuel with CO to prevent poisoning of platinum-based catalysts.

Existing technologies remove CO in hydrogen fuel by non-electrochemical methods, but the chemical energy of CO is wasted. For example, Xiao has synthesized Ni/CeO ₂ , Ni/Al ₂ O ₃ , and Ni/ZrO ₂ to chemically remove CO in H ₂ -rich environment in a high temperature environment (Xiao ML, Zhang L, Sang YY, Gao ZM). , Effects of supports and combined process on hydrogen purification over nickel supported catalysts. Journal of Rare Earths. 2020; 38: 52-58.); Mahmood prepared CuO-ZnO-Al ₂ O ₃ catalyst by co-precipitation method under high temperature conditions Under chemical catalysis of CO (Mahmood A. Ali Nemati K. Mehran R. Preparation of mesoporous nanocrystalline CuO-ZnO-Al ₂ O ₃ catalysts for the H ₂ purification using catalystic preferential oxidation of CO(CO-PROX). 2019;44:27401 -27411); Dong Jin Suh uses high temperature chemical catalysis to remove trace CO by loading Pt on zeolite (Dong Jin Suh, Chan Kwak, Jin-Hong Kim, Se Mann Kwon, Tae-Jin Park.Removal of carbon monoxide from hydrogen-rich fuels by selective low-temperature oxidation over base metal added platinum catalysts. 2005;142:70-74); Eun-Yong Ko chemically catalyzes CO in _H2 -rich at high temperature via synthesized Pt-Co/YSZ catalysts (Eun-Yong Ko, Eun Duck Park, Hyun Chul Lee, Doohwan Lee, Soonho Kim, Supproted Pt-Co catalysts for selective COoxidation in a hydrogen-rich stream. 2007;46:734-737.).

The above studies show that the catalysis of CO in _H2 -rich so far mainly relies on chemical catalysis under high temperature conditions, which has a great loss of energy, and the chemical energy of CO is also wasted.

Therefore, how to develop a more suitable solution to the problem of CO poisoning, without the need for high temperature, and using the chemical energy of CO to solve the above problems has become an urgent problem for many forward-looking researchers in this field. one.

SUMMARY OF THE INVENTION

(1) Technical problems to be solved

In view of the above problems, the present disclosure provides a preparation method and application of a monodisperse noble metal catalyst, which are used to at least partially solve the technical problems of traditional catalysts such as large energy loss in CO preoxidation and waste of CO chemical energy.

(2) Technical solutions

One aspect of the present disclosure provides a method for preparing a monodisperse precious metal catalyst, comprising: S11, dissolving zinc acetate and ellagic acid in a first solvent, washing and drying to obtain a carrier precursor; S12, dissolving the carrier precursor in a first solvent In the second solvent, a carrier precursor solution is obtained; the precious metal salt is dissolved in the second solvent to obtain a precious metal salt solution; the precious metal salt solution is added to the carrier precursor solution in stages to obtain a catalyst precursor; S13, the catalyst After grinding and mixing the precursor and the nitrogen-containing organic matter, heat treatment is performed in a reducing atmosphere to obtain a monodisperse noble metal catalyst.

Further, the nitrogen-containing organic matter in S13 includes one or more of urea, cyanamide, dicyandiamide, melamine and o-phenanthroline.

Further, the precious metals in the precious metal salts in S12 include one or more of Ru, Rh, Pd, Ir, Pt, Ag and Au; the salt types of the precious metal salts in S12 include acetylacetonate, chloride salts, nitrates, One or more of potassium chloride hydrochloride and sodium chloride hydrochloride.

Further, the first solvent in S11 includes one or more of methanol, N-methylpyrrolidone and ethanol; and the second solvent in S12 includes one or more of methanol, N-methylpyrrolidone and ethanol.

Further, the ratio of zinc acetate, ellagic acid, all solvents, precious metal salts and urea is [0.36～0.46g]:[0.216～0.316g]:[70～100ml]:[3～8mg]:[2～3g ].

Another aspect of the present disclosure provides a method for preparing a monodisperse precious metal catalyst, comprising: S21, dissolving a precious metal salt and zinc nitrate in a third solvent to obtain a third solution; dissolving a nitrogen-containing organic substance in a fourth solvent, obtaining a fourth solution; S22, mixing the third solution and the fourth solution, and reacting to obtain a catalyst precursor; S23, heat-treating the catalyst precursor in a reducing atmosphere to obtain a monodisperse noble metal catalyst.

Further, the nitrogen-containing organic matter in S21 includes 2-methylimidazole.

Further, the precious metal in the precious metal salt in S21 includes one or more of Ru, Rh, Pd, Ir, Pt, Ag and Au; the salt types of the precious metal salt in S21 include acetylacetonate, chloride salt, nitrate, One or more of potassium chloride hydrochloride and sodium chloride hydrochloride.

Further, the third solvent in S21 includes methanol and/or ethanol; the fourth solvent in S21 includes methanol and/or ethanol.

Further, the ratio of noble metal salt, zinc nitrate, 2-methylimidazole and all solvents is [15-100mg]:[4.0-6.0g]:[7-9g]:[130-150ml].

Another aspect of the present disclosure provides a method for preparing a monodisperse precious metal catalyst, comprising: S31, dispersing a carbon material in a fifth solvent to obtain a fifth solution; S32, dissolving a precious metal salt in a sixth solvent to obtain precious metal salt solution; adding the precious metal salt solution into the fifth solution, and mixing to obtain a catalyst precursor; S33, after grinding and mixing the catalyst precursor and the nitrogen-containing organic matter, heat treatment in a reducing atmosphere to obtain a monodisperse precious metal catalyst.

Further, the nitrogen-containing organic matter in S33 includes one or more of urea, cyanamide, dicyandiamide, melamine and o-phenanthroline.

Further, the precious metal in the precious metal salt in S32 includes one or more of Ru, Rh, Pd, Ir, Pt, Ag and Au; the salt types of the precious metal salt in S32 include acetylacetonate, chloride salt, nitrate, One or more of potassium chloride hydrochloride and sodium chloride hydrochloride.

Further, the fifth solvent in S31 includes one or more of methanol and ethanol; the sixth solvent in S32 includes one or more of methanol and ethanol.

Further, the ratio of carbon material, all solvents, precious metal salts and urea is [80-100mg]:[70-100ml]:[3-8mg]:[2-3g].

Another aspect of the present disclosure provides a fuel cell, the anode of the fuel cell includes the monodisperse noble metal catalyst obtained by the above-mentioned preparation method of the monodisperse noble metal catalyst, which is used for purifying CO in hydrogen and electro-oxidation of CO.

(3) Beneficial effects

The preparation method and application of a monodisperse noble metal catalyst provided by the embodiments of the present disclosure, the catalyst obtained by the preparation method has excellent electrocatalytic performance, and the electrochemical and battery performance are significantly improved while reducing the loading of noble metal. Moreover, the method is simple in operation, mild in conditions, does not need surfactants or templates, therefore does not require complicated operation steps such as washing with water, and is easy to produce on a large scale. Further, the monodisperse noble metal catalyst is used in the CO pre-oxidation of the anode fuel of the hydrogen-oxygen fuel cell, which can be carried out electrochemically under the condition of medium and low temperature.

Description of drawings

FIG. 1 schematically shows a schematic flowchart of a method for preparing a monodisperse precious metal catalyst according to an embodiment of the present disclosure;

FIG. 2 schematically shows a schematic flowchart of a method for preparing a monodisperse precious metal catalyst according to another embodiment of the present disclosure;

FIG. 3 schematically shows a schematic flowchart of a method for preparing a monodisperse noble metal catalyst according to another embodiment of the present disclosure;

Fig. 4 schematically shows the pure CO oxidation curve of the monodisperse noble metal catalyst prepared according to Example 1 of the present disclosure under different scan rate conditions in perchloric acid solution;

FIG. 5 schematically shows a comparison of the performance curves of catalysts with different noble metal contents to CO at a rotational speed of 1600 rpm according to an embodiment of the present disclosure;

FIG. 6 schematically shows the oxidation performance curve of commercial Pt/C (Pt/C-JM-20%) to CO according to an embodiment of the present disclosure;

Figure 7 schematically shows the _CO -O fuel cell performance of the monodisperse noble metal catalyst prepared according to Example 1 of the present disclosure at different temperatures;

FIG. 8 schematically shows the performance of the fuel cell when the monodisperse noble metal catalyst prepared according to Example 1 of the present disclosure is used as the anode gas of H ₂ with different CO contents;

FIG. 9 schematically shows the gas phase diagram of the tail gas of the monodisperse noble metal catalyst prepared according to Example 1 of the present disclosure when H ₂ with different CO contents is used as the anode gas after the battery test for 4 hours;

FIG. 10 schematically shows an X-ray diffraction (XRD) curve of a monodisperse noble metal catalyst prepared according to an embodiment of the present disclosure;

FIG. 11 schematically shows the spherical aberration corrected scanning transmission photo (HAADF-STEM) of the monodisperse noble metal catalyst prepared according to Example 1 of the present disclosure at a scale of 5 nm;

FIG. 12 schematically shows a transmission electron microscope (TEM) photo of the monodisperse noble metal catalyst prepared according to Example 1 of the present disclosure under a 20 nm scale;

FIG. 13 schematically shows a transmission electron microscope (TEM) photo of the monodisperse noble metal catalyst prepared according to Example 2 of the present disclosure under a 20 nm scale;

FIG. 14 schematically shows a transmission electron microscope (TEM) photograph at a scale of 50 nm of the monodisperse noble metal catalyst prepared according to Comparative Example 1 of the present disclosure.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below with reference to the specific embodiments and the accompanying drawings.

All the raw materials of the present disclosure are not particularly limited in their sources, and can be purchased in the market or prepared according to conventional methods well known to those skilled in the art.

All raw materials in the present disclosure are not particularly limited in their purity, and the present disclosure preferably adopts analytical purity or conventional purity requirements in the field of fuel cell materials.

All the raw materials and technological processes of the present disclosure, their grades or abbreviations belong to the conventional grades or abbreviations in the field, and each grade or abbreviation is clear and definite in the field of its related use. For purposes, it can be purchased from the market or prepared by conventional methods, or can be realized by using corresponding equipment.

The present disclosure provides a preparation method of a monodisperse noble metal catalyst and its application in fuel cells, carbon monoxide or CO electro-oxidation in the purification of hydrogen. The present disclosure applies a monodisperse precious metal catalyst to CO pre-oxidation in a fuel cell, and obtains a catalyst with low metal loading, high activity and CO pre-oxidation under medium and low temperature conditions. The catalyst solves the problem of CO poisoning of Pt-based catalysts in existing fossil fuel hydrogen production. The catalyst of the present disclosure is a monodisperse noble metal catalyst with a structure of MN or MNC, which can be used in CO electro-oxidation and CO-O ₂ fuel cells, has the ability to continuously purify different contents of CO in H ₂ gas, and the preparation method is simple and easy to operate. , conditions are mild.

An embodiment of the present disclosure provides a method for preparing a monodisperse precious metal catalyst, please refer to FIG. 1 , including: S11, dissolving zinc acetate and ellagic acid in a first solvent, washing and drying to obtain a carrier precursor; S12 , dissolving the carrier precursor in the second solvent to obtain a carrier precursor solution; dissolving the precious metal salt in the second solvent to obtain a precious metal salt solution; adding the precious metal salt solution to the carrier precursor solution in stages, and reacting to obtain a catalyst precursor body; S13, after grinding and mixing the catalyst precursor and the nitrogen-containing organic substance, heat treatment is performed in a reducing atmosphere to obtain a monodisperse noble metal catalyst.

Specifically, in S11, at room temperature, zinc acetate and ellagic acid were respectively dissolved in N-methylpyrrolidone, dispersed uniformly by ultrasonic, mixed and poured into a beaker, and stirred at room temperature to obtain a first suspension; wherein, at room temperature The stirring time can be 48h.

The first suspension is washed once with N-methylpyrrolidone and twice with ethanol, and then dried to obtain a carrier precursor; wherein, the drying temperature may be 60° C.; and the drying time may be 12 hours.

S12, dissolving the carrier precursor in ethanol, dispersing it uniformly by ultrasonic, then adding an ethanol solution of precious metal (including Ru/Rh/Pd/Ir/Pt/Ag/Au) salt, and stirring at room temperature to obtain a catalyst precursor; The stirring time can be 12h.

S13, grinding and mixing the catalyst precursor and urea, and reducing in a mixed atmosphere of 5-10% H ₂ /Ar (or 6%-9%, or 7%-8%) to obtain a monodisperse noble metal catalyst. Wherein, the reduction temperature can be 950°C; the reduction time can be 1.5h. Wherein, the time of ultrasonic dispersion is preferably 20-60 min, more preferably 30-50 min. The stirring speed is preferably 300 to 500 rpm, and more preferably 350 to 450 rpm.

On the basis of the above embodiment, the nitrogen-containing organic matter in S13 includes one or more of urea, cyanamide, dicyandiamide, melamine and o-phenanthroline.

The nitrogen-containing organic matter here has the technical effect of adding nitrogen elements in the preparation method.

On the basis of the above embodiments, the precious metals in the precious metal salts in S12 include one or more of Ru, Rh, Pd, Ir, Pt, Ag and Au; the salt types of the precious metal salts in S12 include acetylacetonate, chlorinated One or more of salt, nitrate, potassium chlorohydrochloride and sodium chlorohydrochloride.

Acetylacetonate has the advantages of suitable size and easy formation of M-N structures anchored by nitrogen elements.

On the basis of the above embodiment, the first solvent in S11 includes one or more of methanol, N-methylpyrrolidone and ethanol; the second solvent in S12 includes one or more of methanol, N-methylpyrrolidone and ethanol variety.

N-methylpyrrolidone has the advantage of easily dissolving ellagic acid, and methanol or ethanol has the advantages of non-toxicity, cheapness, and easy dissolving of organic and inorganic substances.

On the basis of the above embodiment, the ratio of zinc acetate, ellagic acid, all solvents, precious metal salts and urea is [0.36～0.46g]:[0.216～0.316g]:[70～100ml]:[3～8mg] : [2～3g].

Among them, the addition amount of zinc acetate is preferably 0.36 to 0.46 g, more preferably 0.38 to 0.44 g, and more preferably 0.40 to 0.42 g. The amount of ellagic acid added is preferably 0.216 to 0.316 g, more preferably 0.236 to 0.296 g, and more preferably 0.256 to 0.276 g. The added amount of all solvents is preferably 70-100 ml, more preferably 75-95 ml, and more preferably 80-90 ml. The amount of the noble metal salt to be added is preferably 3 to 8 mg, more preferably 4 to 7 mg, and more preferably 5 to 6 mg. The amount of urea added is preferably 2 to 3 g, more preferably 2.2 to 2.8 g, and more preferably 2.4 to 2.6 g.

The molar ratio of zinc acetate to ellagic acid is about 2.5, which is conducive to the formation of a uniform flower-like carrier of about 200-300 nm. Proper feeding of noble metal salts can form single-atom catalysts with metal loadings of less than 1%. Too much will lead to particle formation, and too little will lead to insufficient active sites. The appropriate ratio of urea to catalyst precursor is about 2 to 5 times, and it is easy to obtain a catalyst with higher nitrogen elements at this time.

Another embodiment of the present disclosure provides a method for preparing a monodisperse noble metal catalyst, please refer to FIG. 2, including: S21, dissolving noble metal salt and zinc nitrate in a third solvent to obtain a third solution; Dissolving in the fourth solvent to obtain a fourth solution; S22, mixing the third solution and the fourth solution, and reacting to obtain a catalyst precursor; S23, subjecting the catalyst precursor to heat treatment in a reducing atmosphere to obtain a monodisperse noble metal catalyst.

Specifically, in S21, at room temperature, first, noble metal salts (including Ru/Rh/Pd/Ir/Pt/Ag/Au) and zinc nitrate were dissolved in methanol, 2-methylimidazole was dissolved in methanol, and ultrasonicated respectively. Disperse uniformly, S22, mix and pour into a beaker, and stir at room temperature to obtain a catalyst precursor suspension; wherein, the stirring time at room temperature can be 24h. The catalyst precursor suspension is washed with ethanol, and then dried to obtain a catalyst precursor; wherein, the drying temperature may be 60° C.; and the drying time may be 12 hours.

S23, reducing the catalyst precursor in a mixed atmosphere of 5%-10% H ₂ /Ar (or 6%-9%, or 7%-8%) to obtain a monodisperse noble metal catalyst. Wherein, the reduction temperature can be 950°C; the reduction time can be 1h. Wherein, the time of ultrasonic dispersion is preferably 20-60 min, more preferably 30-50 min. The stirring speed is preferably 300 to 500 rpm, and more preferably 350 to 450 rpm.

On the basis of the above embodiment, the nitrogen-containing organic substance in S21 includes 2-methylimidazole.

The nitrogen-containing organic matter here has the technical effect of synthesizing a regular dodecahedron carrier and providing nitrogen elements in the preparation method.

On the basis of the above embodiment, the precious metals in the precious metal salts in S21 include one or more of Ru, Rh, Pd, Ir, Pt, Ag and Au; the salt types of the precious metal salts in S21 include acetylacetonate, chloride One or more of salt, nitrate, potassium chlorohydrochloride and sodium chlorohydrochloride.

On the basis of the above embodiment, the third solvent in S21 includes methanol and/or ethanol; the fourth solvent in S21 includes methanol and/or ethanol.

Methanol or ethanol has the advantages of non-toxic, cheap, and easy to dissolve organic and inorganic substances.

On the basis of the above embodiment, the ratio of noble metal salt, zinc nitrate, 2-methylimidazole and all solvents is [15-100mg]:[4.0-6.0g]:[7-9g]:[130-150ml].

The ratio of precious metal salt to zinc nitrate is preferably (15-100mg):(4.0-6.0g), more preferably (15-100mg):(4.2-5.8g), more preferably (15-100mg):(4.5- 5.5g), more preferably (15-100mg):(4.8-5.3g).

The ratio of noble metal salt to 2-methylimidazole is preferably (15-100mg):(7-9g), more preferably (15-100mg):(7.2-8.8g), more preferably (15-100mg):( 7.5 to 8.5 g), more preferably (15 to 100 mg): (7.8 to 8.3 g).

The ratio of precious metal salt to all solvents is preferably (15-100mg):(130-150ml), more preferably (15-100mg):(132-148ml), more preferably (15-100mg):(135-145ml) , more preferably (15 to 100 mg): (138 to 143 ml).

The amount of the noble metal salt can be preferably 25-90 mg, more preferably 35-80 mg, more preferably 45-70 mg, and more preferably 55-60 mg.

Appropriate ratios of zinc nitrate and 2-methylimidazole readily form uniform dodecahedral supports. Proper feeding of noble metal salts can form single-atom catalysts with metal loadings of less than 1%. Too much will lead to particle formation, and too little will lead to insufficient active sites.

Another embodiment of the present disclosure provides a method for preparing a monodisperse precious metal catalyst, please refer to FIG. 3 , including: S31, dispersing the carbon material in a fifth solvent to obtain a fifth solution; S32, dissolving a precious metal salt in the fifth solvent In six solvents, a precious metal salt solution is obtained; the precious metal salt solution is added into the fifth solution, and mixed to obtain a catalyst precursor; S33, after grinding and mixing the catalyst precursor and nitrogen-containing organic matter, heat treatment in a reducing atmosphere to obtain a monodisperse precious metal catalysts.

Monodisperse precious metal catalysts were prepared with commercial carbon supports such as XC-72, BP-2000, EC-300J:

S31, S32, disperse the commercial carbon carrier in an ethanol solution, disperse it uniformly by ultrasonic, then add an ethanol solution of a precious metal (including Ru/Rh/Pd/Ir/Pt/Ag/Au) salt, and stir at room temperature to obtain a catalyst precursor; Wherein, the stirring time at room temperature can be 12h.

S33, grinding and mixing the catalyst precursor and urea, and reducing in a mixed atmosphere of 5-10% H ₂ /Ar (or 6%-9%, or 7%-8%) to obtain a monodisperse noble metal catalyst. Wherein, the reduction temperature can be 950°C; the reduction time can be 1h. Wherein, the time of ultrasonic dispersion is preferably 20-60 min, more preferably 30-50 min. The stirring speed is preferably 300 to 500 rpm, and more preferably 350 to 450 rpm.

On the basis of the above embodiments, the nitrogen-containing organics in S33 include one or more of urea, cyanamide, dicyandiamide, melamine and o-phenanthroline.

On the basis of the above embodiment, the precious metals in the precious metal salts in S32 include one or more of Ru, Rh, Pd, Ir, Pt, Ag and Au; the salt types of the precious metal salts in S32 include acetylacetonate, chloride One or more of salt, nitrate, potassium chlorohydrochloride and sodium chlorohydrochloride.

On the basis of the above embodiment, the fifth solvent in S31 includes one or more of methanol and ethanol; the sixth solvent in S32 includes one or more of methanol and ethanol.

Methanol or ethanol has the advantages of being non-toxic, cheap, and easily dissolving organic and inorganic substances.

On the basis of the above embodiment, the ratio of carbon material, all solvents, precious metal salts and urea is [80-100mg]:[70-100ml]:[3-8mg]:[2-3g].

The addition amount of the carbon material is preferably 80 to 100 mg, more preferably 82 to 98 mg, more preferably 85 to 95 mg, and more preferably 88 to 93 mg. The added amount of all solvents is preferably 70-100 ml, more preferably 75-95 ml, and more preferably 80-90 ml. The amount of the noble metal salt to be added is preferably 3 to 8 mg, more preferably 4 to 7 mg, and more preferably 5 to 6 mg. The amount of urea added is preferably 2 to 3 g, more preferably 2.2 to 2.8 g, and more preferably 2.4 to 2.6 g.

A suitable charging ratio of carbon material and noble metal salt can form a single-atom catalyst with a metal loading of less than 1%. If it is too large, it is easy to form particles, and if it is too small, there will be insufficient active sites. The appropriate ratio of urea to catalyst precursor is about 2 to 5 times, and it is easy to obtain a catalyst with higher nitrogen elements at this time.

The above steps of the present disclosure provide the application of a monodisperse noble metal catalyst in CO pre-oxidation of high activity hydrogen-oxygen fuel cell, purification of carbon monoxide or CO electro-oxidation in hydrogen containing carbon monoxide, and a high-activity hydrogen-oxygen fuel cell. The present disclosure applies a monodisperse precious metal catalyst to CO pre-oxidation in a fuel cell, and obtains a catalyst with low metal loading, high activity and CO pre-oxidation under medium and low temperature conditions. The high-performance ultra-low noble metal loading (including Ru/Rh/Pd/Ir/Pt/Ag/Au) catalyst for CO pre-oxidation of anode fuel in hydrogen-oxygen fuel cells solves the problem of CO poisoning Pt base in existing fossil fuel hydrogen production. catalyst problem. The catalyst of the present disclosure is a monodisperse noble metal catalyst with a structure of MN or MNC, which can be used in CO electro-oxidation and CO-O ₂ fuel cells, and has the ability to continuously purify H ₂ gases with different CO contents.

The present disclosure provides a monodisperse catalyst for CO pre-oxidation in the anode fuel of a hydrogen-oxygen fuel cell with high activity and ultra-low loading, operating at medium and low temperature, and in an electrochemical manner. The working conditions of the present disclosure can be carried out electrochemically under medium and low temperature conditions. Moreover, the present disclosure controls the content of different precious metals when preparing the catalyst, so as to take into account the precious metal content when the highest catalytic activity is obtained. The catalyst provided by the present disclosure has excellent electrocatalytic performance, and has significantly improved electrochemical and battery performance while reducing the loading of noble metals. In addition, the method provided by the present disclosure is simple in operation, mild in conditions, and does not require surfactants or templates, so it does not require complicated operation steps such as washing with water, and is easy to produce on a large scale.

Another embodiment of the present disclosure provides a fuel cell, the anode of the fuel cell includes the monodisperse noble metal catalyst obtained by the above-mentioned preparation method of the monodisperse noble metal catalyst, and is used for purifying CO in hydrogen and electro-oxidation of CO.

Here fuel cells include hydrogen-oxygen fuel cells or CO-O ₂ fuel cells; monodispersion includes single-atom state dispersion or double-atom state dispersion; monodisperse precious metal catalysts are monodisperse precious metal electrochemical catalysts; monodisperse precious metal catalysts are MN precious metal catalysts or MNC noble metal catalyst, wherein M is noble metal, N is nitrogen, and C is carbon.

In the monodisperse noble metal catalyst, the content of noble metal is 0.01wt.% to 2.0wt.%, more preferably 0.05wt.% to 1.5wt.%, more preferably 0.1wt.% to 1.0wt.%, more preferably 0.3 wt.%～0.7wt.%.

The mass content of the monodisperse noble metal catalyst in the anode material is 5-30 μg cm ⁻² , more preferably 10-25 μg cm ⁻² , and more preferably 15-20 μg cm ⁻² .

Purification includes continuous purification; the applied temperature includes medium and low temperature; the range of medium and low temperature includes 20-100°C, more preferably 30-90°C, more preferably 40-80°C, more preferably 50-60°C.

The present disclosure provides a catalyst with low metal loading, high activity and CO pre-oxidation under medium and low temperature conditions, which can perform electrochemical pre-oxidation of hydrogen-oxygen fuel cell anode at medium and low temperature. Moreover, the preparation method has simple operation and mild conditions, and can obtain a catalyst with ultra-low noble metal loading, ultra-high activity, and ultra-high noble metal utilization rate.

The present disclosure will be described in detail below with two specific embodiments.

Example 1

(1) Dissolve 100 mg of acetylacetonate (including Ru/Rh/Pd/Ir/Pt/Ag/Au) and 4.0 g of zinc nitrate in 90 ml of methanol at room temperature, and disperse uniformly after ultrasonication for 30 minutes to obtain a first suspension ; At room temperature, dissolve 9g of 2-methylimidazole in 60ml of methanol, shake evenly to obtain a second suspension; Pour the first suspension and the second suspension into a beaker, stir at room temperature for 24h, to obtain The third suspension; the third suspension was washed three times with ethanol, wherein the rotation speed of the centrifuge was 8000rpm, and then dried at 60°C for 12 hours to obtain a catalyst precursor; the catalyst precursor was heated at 950°C with a 10wt.% hydrogen-argon gas mixture Reduction was carried out in an atmosphere for 1 h, wherein the flow rate of the mixed gas was 30 cc min ^-1 , and the tube furnace was heated from room temperature to 950 °C at a heating rate of 5 °C min ^-1 to obtain a monodisperse noble metal catalyst, which was marked as MNC.

(2) Add 50 μL of Nation solution with a mass fraction of 5% to a centrifuge tube containing 950 μL of ethanol solution, and then add 5 mg of the MNC catalyst prepared in step (1) to it, and ultrasonically disperse for 30 min to obtain a mixed solution; take 20 μL of the above solution It was drop-coated on a glassy carbon electrode and dried at room temperature to obtain a thin-film electrode; a three-electrode system with a commercial hydrogen standard electrode as the reference electrode and a graphite rod as the counter electrode was subjected to nitrogen deoxygenation and CO-saturated 0.1M HClO ₄ Activation and performance tests were performed in solution with a scan rate of 20 mV/s.

The results are shown in FIG. 4 , which is the pure CO oxidation curve of the monodisperse noble metal catalyst prepared in Example 1 of the present disclosure in a perchloric acid solution under different scan rates.

Figure 4 shows the LSV curves of pure CO oxidation of the M-N-C catalyst at different rotational speeds from 900 to 2500 rpm. It can be seen from Figure 1 that the initial oxidation potential of the M-N-C catalyst prepared in Example 1 to CO is about 0 mV.

Referring to Figure 5, Figure 5 is a comparison of the performance curves of catalysts with different noble metal contents on CO at a rotational speed of 1600 rpm.

Referring to FIG. 6, FIG. 6 is the oxidation performance curve of commercial Pt/C (Pt/C-JM-20%) for CO.

It can be seen from Figures 5 and 6 that the commercial Pt/C catalyst (Pt/C-JM-20%) was completely poisoned at low potentials, as shown in Figure 6. The performance comparison is shown in Figure 5.

(3) Dissolve the catalyst with isopropanol/water mixed solvent, disperse uniformly by ultrasonic for 1 h, and spray on the gore membrane (proton exchange membrane) with an effective area of 4 cm ² . The commercial Pt/C cathode catalyst was controlled at 0.1 mg _Pt cm ^-2 , and the MNC anode catalyst was controlled at 8 μg _M cm ^-2 . The relative humidity was 100%, the back pressure was maintained at 200 kPa, and the gas flow rate was 300 mL min ^-1 . Battery performance with pure CO as anode gas.

Referring to FIG. 7 , FIG. 7 shows the CO-O ₂ fuel cell performance of the monodisperse noble metal catalyst prepared in Example 1 of the present disclosure at different temperatures.

As shown in Figure 7, the cell performance of pure CO as anode gas.

Referring to FIG. 8 , FIG. 8 shows the performance of the fuel cell when the monodisperse noble metal catalyst prepared in Example 1 of the present disclosure is used as the anode gas of H ₂ with different CO contents.

As shown in Fig. 8, the cell performance of _H2 as anode gas with different CO contents.

Referring to FIG. 9 , FIG. 9 is a gas phase diagram of the tail gas of the monodisperse noble metal catalyst prepared in Example 1 of the present disclosure when H ₂ with different CO contents is used as the anode gas after the battery test for 4 hours.

As shown in Figure 9, after the battery was tested for 4 h when _H2 with different CO contents was used as the anode gas, the gas phase diagram of the exhaust gas showed that the catalyst had the ability to continuously purify _H2 gases with different CO contents.

(4) Weigh a certain amount of the M-N-C catalyst prepared in step (1) to measure XRD, and no metal phase is observed.

Referring to FIG. 10 , FIG. 10 is an X-ray diffraction (XRD) curve of the monodisperse noble metal catalyst prepared in the present disclosure.

(5) Weighing a certain amount of the M-N-C catalyst prepared in step (1) and measuring HAADF-STEM, it can be observed that the precious metal is in a monodispersed state and is uniform.

Referring to FIG. 11 , FIG. 11 is a spherical aberration-corrected scanning transmission photograph (HAADF-STEM) of the monodisperse noble metal catalyst prepared in Example 1 of the present disclosure at a scale of 5 nm.

(6) Weighing a certain amount of the M-N-C catalyst prepared in step (1) and measuring TEM, it can be observed that no nanoparticles are formed.

Referring to FIG. 12 , FIG. 12 is a transmission electron microscope (TEM) photograph of the monodisperse noble metal catalyst prepared in Example 1 of the present disclosure at a scale of 20 nm.

Example 2

(1) At room temperature, dissolve 15 mg of acetylacetonate (including Ru/Rh/Pd/Ir/Pt/Ag/Au) and 4.0 g of zinc nitrate in 90 ml of methanol, and disperse uniformly after ultrasonication for 30 minutes to obtain a first suspension ; At room temperature, dissolve 9g of 2-methylimidazole in 60ml of methanol, shake evenly to obtain a second suspension; Pour the first suspension and the second suspension into a beaker, stir at room temperature for 24h, to obtain The third suspension; the third suspension was washed three times with ethanol, wherein the rotation speed of the centrifuge was 8000rpm, and then dried at 60°C for 12 hours to obtain a catalyst precursor; the catalyst precursor was heated at 950°C with a 10wt.% hydrogen-argon gas mixture Reduction was carried out in an atmosphere for 1 h, wherein the flow rate of the mixed gas was 30 cc min ^-1 , and the tube furnace was heated from room temperature to 950 °C at a heating rate of 5 °C min ^-1 to obtain a monodisperse noble metal catalyst, marked as LMNC.

(2) 50 μL of Nation solution with a mass fraction of 5% was added to a centrifuge tube containing 950 μL of ethanol solution, and 5 mg of the LMNC catalyst prepared in step (1) was added to it, and ultrasonically dispersed for 30 min to obtain a mixed solution; 20 μL of the above solution was taken It was drop-coated on a glassy carbon electrode and dried at room temperature to obtain a thin-film electrode; a three-electrode system with a commercial hydrogen standard electrode as the reference electrode and a graphite rod as the counter electrode was subjected to nitrogen deoxygenation and CO-saturated 0.1M HClO ₄ Activation and performance tests were performed in solution with a scan rate of 20 mV/s.

The results are shown in Figure 5, which shows the LSV curve of pure CO oxidation of the L-M-N-C catalyst at 1600 rpm. It can be seen from Figure 5 that the initial oxidation potential of the L-M-N-C catalyst prepared in Example 2 to CO is about 100 mV.

(3) Weigh a certain amount of the L-M-N-C catalyst prepared in step (1) to measure XRD, and no metal phase is observed.

(4) Weighing a certain amount of the L-M-N-C catalyst prepared in step (1) and measuring TEM, it can be observed that no nanoparticles are formed.

Referring to FIG. 13 , FIG. 13 is a transmission electron microscope (TEM) photograph of the monodisperse noble metal catalyst prepared in Example 2 of the present disclosure at a scale of 20 nm.

Comparative Example 1

(1) At room temperature, dissolve 4.0g of zinc nitrate in 90ml of methanol, and disperse uniformly after ultrasonication for 30min to obtain the first suspension; at room temperature, dissolve 9g of 2-methylimidazole in 60ml of methanol, shake evenly, The second suspension was obtained; the first suspension and the second suspension were poured into a beaker, and stirred at room temperature for 24 hours to obtain a third suspension; the third suspension was washed three times with ethanol, wherein the centrifuge The rotation speed was 8000 rpm, and then dried at 60 °C for 12 h to obtain a catalyst precursor; the catalyst precursor was reduced at 950 °C under a 10 wt.% hydrogen-argon mixed gas atmosphere for 1 h, wherein the flow rate of the mixed gas was 30cc min ^-1 , and the tube furnace was heated from room temperature to The heating rate of 5°C min ^-1 was raised to 950°C to obtain a pure supported catalyst, which was marked as NC.

(2) 50 μL of Nation solution produced by Aldrich with a mass fraction of 5% was added to a beaker containing 950 μL of methanol solution, and 5 mg of the NC catalyst prepared in step (1) was added to it, and ultrasonically dispersed for 30 min to obtain a mixed solution; 20 μL of the above solution was drop-coated on a glassy carbon electrode, and dried at room temperature to obtain a thin-film electrode; a three-electrode system with a commercial hydrogen standard electrode as the reference electrode and a graphite rod as the counter electrode, after nitrogen deoxygenation and CO saturation at 0.1 Activation and performance tests _were performed in M HClO solution with a scan speed of 20mV/s.

It can be seen from Figure 5 that the N-C catalyst prepared in Comparative Example 1 has no catalytic performance for CO.

(3) Weigh a certain amount of the N-C catalyst prepared in step (1) to measure XRD, and no metal phase is observed.

Referring to Fig. 10, Fig. 10 shows the X-ray diffraction (XRD) curve of the monodisperse noble metal catalyst prepared in the present disclosure.

(4) Weighing a certain amount of the N-C catalyst prepared in step (1) and measuring TEM, it can be observed that no nanoparticles are formed.

Referring to FIG. 14 , FIG. 14 is a transmission electron microscope (TEM) photograph of the monodisperse noble metal catalyst prepared in Comparative Example 1 of the present disclosure at a scale of 50 nm.

The experimental results show that the monodisperse precious metal catalyst provided by the present disclosure is used for CO pre-oxidation of hydrogen-oxygen fuel cell anode fuel, the catalyst has excellent electrocatalytic performance, and the treatment method is simple to operate, and the production cycle is short; The battery performance has been significantly improved while the precious metal loading has been reduced.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present disclosure in detail. It should be understood that the above-mentioned specific embodiments are only specific embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure should be included within the protection scope of the present disclosure.

Claims

A method for preparing a monodisperse precious metal catalyst, comprising:

S11, dissolving zinc acetate and ellagic acid in the first solvent, washing and drying to obtain a carrier precursor;

S12, dissolving the carrier precursor in a second solvent to obtain a carrier precursor solution; dissolving a precious metal salt in the second solvent to obtain a precious metal salt solution; adding the precious metal salt solution to the carrier in stages In the precursor solution, the catalyst precursor is obtained by the reaction;

S13, after grinding and mixing the catalyst precursor and the nitrogen-containing organic substance, heat treatment is performed in a reducing atmosphere to obtain a monodisperse noble metal catalyst.
The method for preparing a monodisperse precious metal catalyst according to claim 1, wherein the nitrogen-containing organic matter in S13 comprises one or more of urea, cyanamide, dicyandiamide, melamine and o-phenanthroline .
The method for preparing a monodisperse precious metal catalyst according to claim 2, wherein the precious metal in the precious metal salt in S12 comprises one or more of Ru, Rh, Pd, Ir, Pt, Ag and Au; The salt types of the precious metal salt in the S12 include one or more of acetylacetonate, chloride salt, nitrate, potassium chloride hydrochloride and sodium chloride hydrochloride.
The method for preparing a monodisperse precious metal catalyst according to claim 1, wherein the first solvent in S11 comprises one or more of methanol, N-methylpyrrolidone and ethanol; the second solvent in S12 Including one or more of methanol, N-methylpyrrolidone and ethanol.
The method for preparing a monodisperse precious metal catalyst according to claim 2, wherein the ratio of the zinc acetate, ellagic acid, all solvents, precious metal salts and urea is [0.36～0.46g]:[0.216～0.316g ]:[70～100ml]:[3～8mg]:[2～3g].
A method for preparing a monodisperse precious metal catalyst, comprising:

S21, dissolving the precious metal salt and zinc nitrate in the third solvent to obtain the third solution; dissolving the nitrogen-containing organic matter in the fourth solvent to obtain the fourth solution;

S22, mixing the third solution with the fourth solution, and reacting to obtain a catalyst precursor;

S23, heat-treating the catalyst precursor in a reducing atmosphere to obtain a monodisperse noble metal catalyst.
The method for preparing a monodisperse noble metal catalyst according to claim 6, wherein the nitrogen-containing organic substance in the S21 comprises 2-methylimidazole.
The method for preparing a monodisperse precious metal catalyst according to claim 7, wherein the precious metal in the precious metal salt in S21 comprises one or more of Ru, Rh, Pd, Ir, Pt, Ag and Au; The salt types of the noble metal salt in the S21 include one or more of acetylacetonate, chloride salt, nitrate, potassium chloride hydrochloride and sodium chloride hydrochloride.
The method for preparing a monodisperse noble metal catalyst according to claim 6, wherein the third solvent in S21 comprises methanol and/or ethanol; the fourth solvent in S21 comprises methanol and/or ethanol.
The method for preparing a monodisperse precious metal catalyst according to claim 7, wherein the ratio of the precious metal salt, zinc nitrate, 2-methylimidazole and all the solvents is [15～100mg]:[4.0～6.0g] : [7～9g]: [130～150ml].
A method for preparing a monodisperse precious metal catalyst, comprising:

S31, the carbon material is dispersed in the fifth solvent to obtain the fifth solution;

S32, dissolving the precious metal salt in the sixth solvent to obtain a precious metal salt solution; adding the precious metal salt solution into the fifth solution, and mixing to obtain a catalyst precursor;

S33, after grinding and mixing the catalyst precursor and the nitrogen-containing organic substance, heat treatment is performed in a reducing atmosphere to obtain a monodisperse noble metal catalyst.
The method for preparing a monodisperse precious metal catalyst according to claim 11, wherein the nitrogen-containing organic matter in S33 comprises one or more of urea, cyanamide, dicyandiamide, melamine and o-phenanthroline .
The method for preparing a monodisperse precious metal catalyst according to claim 12, wherein the precious metal in the precious metal salt in S32 comprises one or more of Ru, Rh, Pd, Ir, Pt, Ag and Au; The salt types of the noble metal salt in the S32 include one or more of acetylacetonate, chloride salt, nitrate, potassium chloride hydrochloride and sodium chloride hydrochloride.
The method for preparing a monodisperse noble metal catalyst according to claim 11, wherein the fifth solvent in S31 comprises one or more of methanol and ethanol; the sixth solvent in S32 comprises methanol and ethanol one or more of.
The method for preparing a monodisperse precious metal catalyst according to claim 12, wherein the ratio of the carbon material, all solvents, precious metal salts and urea is [80～100mg]:[70～100ml]:[3～8mg ]: [2～3g].
A fuel cell, characterized in that the anode of the fuel cell comprises the product obtained by the method for preparing a monodisperse noble metal catalyst according to any one of claims 1 to 5 or 6 to 10 or 11 to 15. Monodisperse noble metal catalyst for CO purification in hydrogen and CO electro-oxidation.