CN105576263A - High-performance fuel cell catalyst and preparation method thereof - Google Patents

Abstract

The invention relates to a high-performance fuel cell catalyst and a preparation method thereof. The high-performance fuel cell catalyst is composed of metal and metal oxide, and the metal oxide is positioned at edges and apex corners, having low coordination number, of surfaces of metal nanoparticles. The preparation method of the fuel cell catalyst of a novel structure is simple, convenient to operate and free of environment pollution; the fuel cell catalyst prepared by the method has high oxygen reduction reaction activity and stability and is suitable for fuel cell electrodes and especially suitable for electrolyte membrane fuel cell electrodes.

Description

A kind of high-performance fuel cell catalyst and preparation method thereof

technical field

The invention belongs to the field of fuel cell catalysts, in particular to a high-performance fuel cell catalyst and a preparation method thereof.

Background technique

Energy is closely related to social progress and the development of the national economy, and every step forward in human society is closely related to the development and utilization of energy. Every major breakthrough in human energy utilization is accompanied by scientific and technological progress, thereby promoting the development of productivity. With economic growth, technological progress, and population growth, the demand for energy in human society is increasing day by day. With the depletion of fossil energy and the seriousness of environmental pollution, if no effective alternative energy is found, human society will face a comprehensive energy crisis. As a power generation device that directly converts chemical energy into electrical energy, fuel cells are considered to be the preferred clean energy technology in the 21st century because of their high efficiency and environmental friendliness. Electrolyte membrane fuel cells are considered to be the most promising, most competitive, and most likely to achieve industrial applications due to their advantages of high efficiency, cleanliness, and low temperature [R.Borup, et al., Chem.Rev.107( 2007) 3904; R. Dillon, et al., J. Power Sources 127 (2004) 112]. As a key component of the fuel cell, the electrocatalytic performance of the electrode directly affects the overall performance of the fuel cell. The low cathode oxygen reduction reaction rate of electrolyte membrane fuel cells is a key factor restricting the commercialization of electrolyte membrane fuel cells [H.A.Gasteiger, et al., Science324(2009)48; M.K.Debe, Nature486(2012)43; Science 315 (2007) 493]. Platinum (Pt)-based catalysts are currently the best polymer fuel cell electrode catalysts due to their high activity and high stability, and are widely used in the cathode and anode of fuel cells [C. Chen, et al., Science343 (2014) 1339; L. Zhang, et al., Science 349 (2015) 412]. However, due to the scarcity and high price of Pt resources, and the low oxygen reduction reaction rate of the cathode compared with the anode of the polymer membrane fuel cell, it is necessary to increase the amount of Pt in the cathode, which greatly increases the cost of the fuel cell. Therefore, the development of new high-performance fuel cell catalysts has become one of the main research directions of fuel cells, which has important application value and scientific significance.

The development of new fuel cell catalysts can start from two aspects: one is to improve the reactivity and stability of the catalyst; the other is to reduce the amount of Pt while maintaining a high reactivity of the catalyst, that is, to increase the utilization efficiency of Pt. The electrocatalytic reactivity of the cathode and anode of the fuel cell varies with the adsorption strength of the metal atoms on the catalyst surface and the reaction intermediates, and follows the variation law of the volcano diagram. Taking the oxygen reduction reaction as an example, the oxygen reduction reaction activity of the catalyst first increases and then decreases with the increase of the adsorption strength of surface metal atoms and oxygen [J.Greeley, et al., Nat.Chem.1(2009)552]. Therefore, improving the reactivity of the catalyst can be achieved by changing the adsorption strength between the metal atoms on the catalyst surface and the reaction intermediates. Density functional theory calculation results show that the reduction of platinum-oxygen (Pt-O) bond energy by 0.2eV can lead to the highest oxygen reduction reaction activity, and, for Pt nanoparticles, the Pt-O bond on the flat crystal plane The bond energy is smaller than that of Pt-O bonds located on the corners and edges [J. Greeley, et al., Nat. Chem. 1 (2009) 552]. It can be seen that designing a new type of fuel cell catalyst structure allows Pt atoms to be located on the flat crystal plane of the surface of the catalyst nanoparticle to obtain a lower Pt-O bond energy, so that the metal oxide is located on the edge and top of the surface of the nanocatalyst particle. On the corner, the repulsion between the oxygen atoms in the metal oxide and the oxygen atoms adsorbed on the Pt surface can further reduce the adsorption strength of oxygen on the Pt surface, which is an effective and feasible method to improve the oxygen reduction reaction activity of the catalyst.

Contents of the invention

The purpose of the invention is to propose a high-performance fuel cell catalyst with lower cost and better alkali resistance and acid resistance.

In order to achieve the above object, the present invention adopts the following technical solutions:

A high-performance fuel cell catalyst, characterized in that: it is composed of metal and metal oxide; the metal forms metal nanoparticles with crystal planes, edges and vertex angles on the surface; the metal oxide is located on the edges and vertex angles on the surface of the metal nanoparticles .

The above-mentioned high-performance fuel cell catalyst is characterized in that: the metal nanoparticles are single metal nanoparticles, or alloy nanoparticles in the form of multiple metals, or metal nanoparticles with a core-shell structure; The particle size of metal nanoparticles is less than 50nm.

The above high-performance fuel cell catalyst is characterized in that the metal oxide is selected from one or more of titanium oxide, vanadium oxide, tungsten oxide, molybdenum oxide, niobium oxide, and chromium oxide.

Described a kind of high-performance fuel cell catalyst is characterized in that, when described metal nanoparticle is single metal nanoparticle, single metal refers to a kind of in platinum, palladium, gold; When described metal nanoparticle When it is a metal alloy nanoparticle, the metal alloy refers to two or more of gold, palladium, copper, nickel, cobalt, ruthenium, and iron; when the metal nanoparticle is a metal nanoparticle with a core-shell structure In the case of particles, the core metal in the core-shell metal refers to one or more mixtures of gold, palladium or ruthenium.

The preparation method of the high-performance fuel cell catalyst is characterized in that: when the metal nanoparticles are single metal nanoparticles, the specific steps are as follows:

(1) Weigh the carbon nanocarrier and place it in absolute ethanol to make a mixed liquid with a carbon concentration of 1-5g/ml, sonicate or stir for 10-60min;

(2) Add sodium citrate to the mixed liquid, the mass of the added sodium citrate is 0.5-5 times of the carbon mass, sonicate or stir for 10-60min;

(3) Add one or more of the salts containing titanium, vanadium, tungsten, molybdenum, niobium, and chromium elements into the mixed liquid, and then ultrasonically or stir for 10-60 minutes;

(4) Add a reducing agent to the mixed liquid. The amount of the added reducing agent is 1.5-20 times the total amount of the salt substances containing titanium, vanadium, tungsten, molybdenum, niobium, and chromium. Ultrasonic or stirring 10-120min;

(5) A salt containing platinum or palladium is added to the mixed liquid, and the amount of the salt containing platinum, gold or palladium added is that of titanium, vanadium, tungsten, molybdenum, niobium, and chromium 0.1-3 times the sum of the amount of salt substances, ultrasonic or stirring for 10-60min;

(6) Centrifuge, filter, wash with deionized water, and dry to prepare a metal oxide-modified single-metal nanoparticle catalyst;

The preparation method of the high-performance fuel cell catalyst is characterized in that: when the metal nanoparticles are metal alloy nanoparticles, the specific steps are as follows:

(1) Weigh the carbon nanocarrier and place it in absolute ethanol to make a mixed liquid with a carbon concentration of 1-5g/ml, sonicate or stir for 10-60min;

(2) Add sodium citrate to the mixed liquid, the mass of the added sodium citrate is 0.5-5 times of the carbon mass, sonicate or stir for 10-60min;

(3) Add one or more of the salts containing titanium, vanadium, tungsten, molybdenum, niobium, and chromium elements into the mixed liquid, and then ultrasonically or stir for 10-60 minutes;

(4) Add a reducing agent to the mixed liquid. The amount of the added reducing agent is 1.5-20 times the total amount of the salt substances containing titanium, vanadium, tungsten, molybdenum, niobium, and chromium. Ultrasonic or stirring 10-120min;

(5) Add platinum-containing salts and two or more salts containing gold, palladium, copper, nickel, cobalt, ruthenium, and iron elements into the mixed liquid, and the added salts containing platinum, gold, palladium, The sum of the salts of copper, nickel, cobalt, ruthenium and iron is 0.1-3 times the sum of the salts of titanium, vanadium, tungsten, molybdenum, niobium and chromium, ultrasonic or stirring for 10-60min ;

(6) Centrifuge, filter, wash with deionized water, and dry to prepare a metal alloy nanoparticle catalyst modified by metal oxide;

The preparation method of the high-performance fuel cell catalyst is characterized in that: when the metal nanoparticles are metal nanoparticles with a core-shell structure, the specific steps are as follows:

(1) Weigh the carbon nanocarrier and place it in absolute ethanol to make a mixed liquid with a carbon concentration of 1-5g/ml, sonicate or stir for 10-60min;

(2) Add sodium citrate to the mixed liquid, the mass of the added sodium citrate is 0.5-5 times of the carbon mass, sonicate or stir for 10-60min;

(3) Add one or more of the salts containing titanium, vanadium, tungsten, molybdenum, niobium, and chromium elements into the mixed liquid, and then ultrasonically or stir for 10-60 minutes;

(4) Add a reducing agent to the mixed liquid. The amount of the added reducing agent is 1.5-20 times the amount of the salt containing titanium, vanadium, tungsten, molybdenum, niobium, and chromium. Ultrasound or stir for 10 -120min;

(5) Add one or more salts containing gold, palladium, or ruthenium to the mixed liquid, and the total amount of salts containing gold, palladium, and ruthenium added is 0.1-3 times the sum of the salts of molybdenum, niobium, and chromium, ultrasonic or stirring for 10-60 minutes;

(6) Centrifuge, filter, wash with deionized water, and dry;

(7) Deposit a single layer of copper on the surface of the metal nanoparticles prepared in step (6) by using the underpotential deposition method, and no deposition occurs on the surface of the metal oxide, and then place it in a solution containing a platinum salt to undergo a displacement reaction, Replace copper with platinum to form a single layer of platinum, or repeat step (7) several times to deposit multiple layers of platinum on the surface of gold, palladium or ruthenium nanoparticles, that is, to obtain a metal oxide-modified core-shell structure metal nanoparticle catalyst .

The preparation method of the high-performance fuel cell catalyst is characterized in that: the carbon nanocarrier is selected from one or more mixtures of carbon black, carbon nanotubes, carbon nanofibers, graphene and the like.

Beneficial effects of the present invention:

The invention uses a simple preparation method to realize the atomic level regulation of the surface structure of the catalyst, so that the oxygen reduction reaction performance of the catalyst is greatly improved.

The preparation method of the fuel cell catalyst with a new structure described in the present invention is simple, easy to operate, and can be carried out at normal temperature without relying on large-scale and special devices and equipment, and it is easy to realize mass production without using toxic chemical reagents and causing no pollution. environment.

The fuel cell catalyst with a novel structure prepared by the invention greatly improves the oxygen reduction reaction activity of the catalyst because the oxygen adsorption strength on the Pt surface is effectively reduced. At the same time, the metal oxide is located at the edge and vertex with a lower coordination number, which can effectively reduce the overflow of the inner layer metal atoms, not only can better protect the inner layer atoms from corrosion, but also reduce the inner layer atoms. The blocking of Pt active sites caused by the overflow of layer metal atoms improves the stability of the catalyst.

The novel structure fuel cell catalyst prepared by the present invention, wherein the metal oxide-modified core-shell structure metal nanoparticle catalyst can effectively improve the catalyst activity and stability while greatly reducing the amount of Pt, is a very performance A fuel cell catalyst that is superior and extremely easy to realize commercial application.

Description of drawings

Fig. 1 Schematic diagram of the structure of the core-shell metal nanoparticle catalyst modified by the novel structure metal oxide.

Fig. 2 Scanning transmission microscope-electron energy loss spectroscopy element surface scanning diagram of titanium dioxide-modified gold nanoparticles.

Fig. 3 Schematic diagram comparing the oxygen reduction performance of titania-modified AuPt core-shell metal nanoparticle catalysts and commercial Pt catalysts.

Fig. 4 Schematic diagram of the stability of titanium dioxide-modified AuPt core-shell metal nanoparticle catalysts.

Fig. 5 Schematic diagram comparing the oxygen reduction performance of vanadium oxide-modified AuPt core-shell metal nanoparticle catalysts and commercial Pt catalysts.

Figure 6 Schematic diagram of the stability of vanadium oxide-modified AuPt core-shell metal nanoparticle catalysts.

detailed description

Example 1:

Weigh 140g of carbon black and place it in 50ml of absolute ethanol, after ultrasonication for 60min, add 300mg of sodium citrate to the mixed liquid, and ultrasonication for 30min. Then, 0.9 mmol of titanium isopropoxide was added to the mixed liquid and ultrasonicated for 30 min. Continue to add 2ml of 1mol/L lithium triethyl borohydride to the mixed liquid, and then add 0.1mmol of sodium chloroaurate after ultrasonic reaction for 30 minutes, and ultrasonic for 60 minutes. The mixed liquid was centrifuged, filtered, washed with deionized water, and then dried in a vacuum oven. Figure 1 is a scanning transmission microscope-electron energy loss spectroscopy (STEM-EELS) element content surface scan diagram of titanium dioxide-modified Au nanoparticles. It can be seen from Figure 1 that titanium is distributed in gold nanoparticles in titanium dioxide-modified gold nanoparticles prepared by this method. The surface of the particle, and concentrated on the edges and corners of the gold nanoparticles.

Example 2:

Weigh 140g of carbon black and place it in 50ml of absolute ethanol, after ultrasonication for 60min, add 300mg of sodium citrate to the mixed liquid, and ultrasonication for 30min. Then, 0.3 mmol of titanium isopropoxide was added to the mixed liquid and ultrasonicated for 30 min. Continue to add 2ml of 1mol/L lithium triethyl borohydride to the mixed liquid, add 0.1mmol of sodium chloroaurate after reacting for 30min, and ultrasonicate for 60min. The mixed liquid was centrifuged, filtered, washed with deionized water, and then dried in a vacuum oven. Finally, the underpotential deposition method is used to deposit a single layer of copper on the surface of the prepared gold nanoparticles, and no deposition occurs on the surface of titanium dioxide, and then it is placed in a solution containing a platinum salt to undergo a displacement reaction, so that the copper is replaced by platinum to form a single layer. Platinum, repeating this step can also deposit double-layer platinum on the surface of gold nanoparticles to prepare a titanium dioxide-modified gold (core)-platinum (shell) catalyst. Fig. 2 is a schematic diagram of the structure of a titanium dioxide-modified AuPt core-shell metal nanoparticle catalyst. Figure 3 is a comparison of the oxygen reduction reaction performance of the titania-modified gold (core)-platinum (shell) catalyst prepared by this method and the commercial Pt catalyst (Tanaka Kikinzoku International Inc., 10E50E, 46.6wt%Pt). It can be seen from Figure 3 that the surface area activity of the oxygen reduction reaction of the gold (core)-platinum (shell) catalyst modified by titanium dioxide is nearly 5 times that of the commercial Pt catalyst, and the mass activity of the oxygen reduction reaction is nearly that of the commercial Pt catalyst. 10 times. Figure 4 is a schematic diagram of the stability of the titanium dioxide-modified gold (core)-platinum (shell) catalyst prepared by this method. It can be seen from Figure 4 that after 10,000 potential cycles, the oxygen reduction reaction performance of the titanium dioxide-modified gold (core)-platinum (shell) catalyst has not declined at all, indicating that the titanium dioxide-modified gold (core)-platinum (shell) The catalyst has good stability.

Example 3:

Weigh 140g of carbon black and place it in 50ml of absolute ethanol, after ultrasonication for 60min, add 300mg of sodium citrate to the mixed liquid, and ultrasonication for 30min. Then add 0.8 mmol of vanadium dichloride to the mixed liquid, and ultrasonicate for 30 min. Continue to add 3ml of 1mol/L lithium triethyl borohydride to the mixed liquid, and then add 0.14mmol of sodium chloroaurate after ultrasonic reaction for 60 minutes, and ultrasonic for 60 minutes. The mixed liquid was centrifuged, filtered, washed with deionized water, and then dried in a vacuum oven. Finally, the underpotential deposition method is used to deposit a single layer of copper on the surface of the prepared gold nanoparticles, and no deposition occurs on the surface of vanadium oxide, and then it is placed in a solution containing a platinum salt to undergo a displacement reaction, so that the copper is replaced by platinum to form a single layer. Repeating this step can also deposit double-layer platinum on the surface of gold nanoparticles to prepare a vanadium oxide-modified gold (core)-platinum (shell) catalyst. Figure 5 is a comparison of the oxygen reduction reaction performance of the vanadium oxide-modified gold (core)-platinum (shell) catalyst prepared by this method and the commercial Pt catalyst (Tanaka Kikinzoku International Inc., 10E50E, 46.6wt%Pt). It can be seen from Figure 5 that the surface area activity of the oxygen reduction reaction of the vanadium oxide-modified gold (core)-platinum (shell) catalyst is more than five times that of the commercial Pt catalyst, and the mass activity of the oxygen reduction reaction is that of the commercial Pt catalyst. nearly 8 times. Figure 6 is a schematic diagram of the stability of the vanadium oxide-modified gold (core)-platinum (shell) catalyst prepared by this method. It can be seen from Figure 6 that after 6000 cycles of potential cycles, the oxygen reduction reaction performance of the vanadium oxide-modified gold (core)-platinum (shell) catalyst has not declined at all, indicating that the vanadium oxide-modified gold (core)-platinum ( Shell) catalysts have good stability.

Claims (8)

1. a high performance fuel cell catalyst, is characterized in that: be made up of metal and metal oxide; Metal forms the metal nanoparticle that surface has crystal face, rib and drift angle; On the rib that metal oxide is positioned at surfaces of metal nanoparticles and drift angle.

2. a kind of high performance fuel cell catalyst according to claim 1, is characterized in that: described metal nanoparticle is monometallic nano particle, or the alloy nano particle of various metals form, or has the metal nanoparticle of nucleocapsid structure; Described metal nanoparticle particle diameter is less than 50nm.

3. a kind of high performance fuel cell catalyst according to claim 1, is characterized in that, described metal oxide is selected from one or more the mixing in titanium oxide, vanadium oxide, tungsten oxide, molybdenum oxide, niobium oxide, chromium oxide.

4. a kind of high performance fuel cell catalyst according to claim 2, is characterized in that, when described metal nanoparticle is monometallic nano particle, monometallic refers to the one in platinum, palladium, gold; When described metal nanoparticle is metal alloy nanoparticles, metal alloy refers to containing two or more in gold, palladium, copper, nickel, cobalt, ruthenium, iron; When described metal nanoparticle is the metallic nanoparticle period of the day from 11 p.m. to 1 a.m with nucleocapsid structure, the core metal in core-shell type metal refers to one or more mixing of gold, palladium or ruthenium.

5. a preparation method for high performance fuel cell catalyst as claimed in claim 1, is characterized in that: when described metal nanoparticle is monometallic nano particle, its concrete steps are as follows:

(1) take carbon nano-carrier and be placed in absolute ethyl alcohol, make the mixing material that concentration of carbon is 1-5g/ml, ultrasonic or stirring 10-60min;

(2) in mixing material, add natrium citricum, the quality of the natrium citricum added is 0.5-5 times of carbonaceous amount, ultrasonic or stirring 10-60min;

(3) in mixing material, one or more mixing in the salt of titaniferous, vanadium, tungsten, molybdenum, niobium, chromium element are added, ultrasonic or stirring 10-60min;

(4) add in mixing material and go back original reagent, the amount of substance going back original reagent added be titaniferous, vanadium, tungsten, molybdenum, niobium, chromium element salts substances total amount 1.5-20 doubly, ultrasonic or stir 10-120min;

(5) in mixing material, add the salt of a kind of platiniferous or palladium element, the amount of the salts substances of the platiniferous added, gold or palladium element be titaniferous, vanadium, tungsten, molybdenum, niobium, chromium element salts substances amount summation 0.1-3 doubly, ultrasonic or stir 10-60min;

(6) centrifugal, filter, deionized water washing, dry, the monometallic nano-particle catalyst of obtained modified metal oxide, to obtain final product.

6. a preparation method for high performance fuel cell catalyst as claimed in claim 1, is characterized in that: when described metal nanoparticle is metal alloy nanoparticles, its concrete steps are as follows:

(1) take carbon nano-carrier and be placed in absolute ethyl alcohol, make the mixing material that concentration of carbon is 1-5g/ml, ultrasonic or stirring 10-60min;

(2) in mixing material, add natrium citricum, the quality of the natrium citricum added is 0.5-5 times of carbonaceous amount, ultrasonic or stirring 10-60min;

(3) in mixing material, one or more mixing in the salt of titaniferous, vanadium, tungsten, molybdenum, niobium, chromium element are added, ultrasonic or stirring 10-60min;

(4) add in mixing material and go back original reagent, the amount of substance going back original reagent added be titaniferous, vanadium, tungsten, molybdenum, niobium, chromium element salts substances total amount 1.5-20 doubly, ultrasonic or stir 10-120min;

(5) salt adding platiniferous element in mixing material with containing gold, palladium, copper, nickel, cobalt, ruthenium, ferro element salt two or more mix, the amount summation of the salts substances of the platiniferous added, gold, palladium, copper, nickel, cobalt, ruthenium, ferro element be titaniferous, vanadium, tungsten, molybdenum, niobium, chromium element salts substances amount summation 0.1-3 doubly, ultrasonic or stir 10-60min;

(6) centrifugal, filter, deionized water washing, dry, the metal alloy nanoparticles catalyst of obtained modified metal oxide.

7. a preparation method for high performance fuel cell catalyst as claimed in claim 1, is characterized in that: when described metal nanoparticle is the metallic nanoparticle period of the day from 11 p.m. to 1 a.m with nucleocapsid structure, its concrete steps are as follows:

(1) take carbon nano-carrier and be placed in absolute ethyl alcohol, make the mixing material that concentration of carbon is 1-5g/ml, ultrasonic or stirring 10-60min;

(2) in mixing material, add natrium citricum, the quality of the natrium citricum added is 0.5-5 times of carbonaceous amount, ultrasonic or stirring 10-60min;

(3) in mixing material, one or more mixing in the salt of titaniferous, vanadium, tungsten, molybdenum, niobium, chromium element are added, ultrasonic or stirring 10-60min;

(4) add in mixing material and go back original reagent, the amount of substance going back original reagent added be titaniferous, vanadium, tungsten, molybdenum, niobium, chromium element salts substances amount 1.5-20 doubly, ultrasonic or stir 10-120min;

(5) in mixing material, add one or more mixing of salt containing gold, palladium or ruthenium element, the amount summation of salts substances containing gold, palladium, ruthenium element added be titaniferous, vanadium, tungsten, molybdenum, niobium, chromium element salts substances amount summation 0.1-3 doubly, ultrasonic or stirring 10-60min;

(6) centrifugal, filter, deionized water washing, dry;

(7) the surfaces of metal nanoparticles deposited monolayers copper of underpotential deposition method obtained by step (6) is adopted, do not deposit at metal oxide surface, be placed on again in the solution containing platinum salt and displacement reaction occurs, copper is made to be formed individual layer platinum by platinum displacement, or repeat step (7) for several times to realize at gold, palladium or ruthenium nano particle surface deposition multilayer platinum, i.e. the core-shell structure metall nano-particle catalyst of obtained modified metal oxide.

8. the preparation method of the high performance fuel cell catalyst according to claim 5 or 6 or 7, is characterized in that: described carbon nano-carrier is selected from one or more mixing in carbon black, carbon nano-tube, carbon nano-fiber, Graphene etc.