CN115799533A - Platinum-based catalyst and preparation method and application thereof - Google Patents
Platinum-based catalyst and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a platinum-based catalyst and a preparation method and application thereof. The preparation method of the platinum-based catalyst comprises the following steps: calcining a platinum-based catalyst precursor to obtain the catalyst; the platinum-based catalyst precursor comprises urea, a carbon source and platinum salt; the mass ratio of the urea to the carbon source is 1: (0.5-2). In the preparation method of the platinum-based catalyst, the urea is added, and the urea has a protection effect on the growth of nano particles under high-temperature decomposition, so that the agglomeration of the platinum-based catalyst particles is effectively inhibited, and the activity of an ORR reaction is obviously improved. Meanwhile, the method is simple, the conditions are controllable, and the large-scale production is easy to expand.
Description
Technical Field
The invention relates to a platinum-based catalyst, a preparation method and application thereof
Background
Fuel cells are classified into proton exchange membrane fuel cells, solid oxide fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, alkaline fuel cells, and the like, according to the difference in electrolyte in the membrane electrode. Among them, proton Exchange Membrane Fuel Cells (PEMFCs) are the most likely future energy devices for large-scale application due to their advantages of high efficiency, no pollution, and low noise, and are expected to be widely applied to new energy vehicles, distributed power stations, and various small electronic devices, especially having important application prospects in the transportation field.
Rational design of highly active, durable platinum-based bimetallic nanoelectrocatalysts is critical to the commercialization of Proton Exchange Membrane Fuel Cells (PEMFCs). Although specific electrocatalytic oxygen reduction (ORR) activity has been achieved by using different catalyst designs with platinum-based bimetallic nanostructures, the growth of the particles during synthesis, whether liquid phase reduction or impregnation calcination, remains difficult to control, and the small specific surface area exposed by the large particles provides limited catalytically active sites, which is detrimental to the performance of the ORR reaction.
At present, a metal precursor is uniformly dispersed in an organic solvent by a liquid phase method, metal is reduced by utilizing the reducibility of a liquid phase reducing agent, and the nucleation and growth of particles are controlled by a surfactant, a capping agent and the like, so that more uniform particles or particles with special shapes are obtained, but the removal of the surfactant in the production process is difficult, and the subsequent treatment process is complicated. Meanwhile, the alloying of the particles obtained by the liquid phase method is not ideal, and a better alloy phase needs to be formed by calcining, so that other effective ways for synthesizing the carbon-supported platinum-based alloy catalyst particles with high dispersion and small particle size are continuously explored at present.
Furthermore, the improvement of the ORR reactivity requires, on the one hand, the intrinsic activity of the individual Pt atoms to be improved and, on the other hand, the availability of Pt atoms, for example, the formation of Pt as binary alloys with transition metals, which are capable of being incorporated into the crystal latticeThe condensed alloy retains a large amount of the original metal, thereby imparting a continuous compressive surface lattice strain and enhancing the ORR reactivity of the platinum-based catalyst (Gan L, heggen M, rudi S, et al. Core-shell compositional fine structures of dealcoholized Pt) x Ni 1–x nanoparticles and their impact on oxygen reduction catalysis[J]Nano letters,2012,12 (10): 5423-5430). The catalytic reaction only occurs on the surface of the catalyst, the size of the platinum-based catalyst is reduced while an alloy phase is formed, the utilization rate of Pt atoms can be effectively improved, the catalytic activity of the whole platinum-based catalyst on the ORR reaction is improved, and the work on the aspect is almost prepared by a liquid phase method at present. Zhiwei Yang et al (Gummalla M, ball S C, condition D A, et al. Effect of particulate size and operating conditions on Pt 3 Co PEMFC cathode catalyst durability[J]Catalysts,2015,5 (2): 926-948) synthesized Pt at 4.9nm, 8.1nm and 14.8nm, respectively 3 Co intermetallic nanoparticles, fuel cell performance decreasing with particle size, with 4.9nm Pt 3 Co has the highest ORR activity. Different particle sizes of Pt for the same loading 3 Co nanoparticles, the distance between particles increases with increasing size, the number of particles decreases, resulting in a decrease in the intrinsic active sites available for reaction, and a decrease in the oxygen concentration at the catalyst surface; on the other hand, the larger the particle size, the greater the electrode resistance at proton transport, and the lower the catalytic activity with the increase in particle size.
At present, the price of the electrocatalyst, platinum group catalyst, used in the ORR reaction occupies 40% to 50% of the total price of PEMFC, and reducing the platinum loading, using cheap metal to partially or completely replace the metal platinum would be very beneficial for the commercialization of fuel cells.
Therefore, it is highly desirable to provide a platinum-based catalyst that is dimensionally controllable and has higher activity for ORR reactions.
Disclosure of Invention
In order to solve the problem of low catalytic ORR activity caused by difficulty in controlling the particle size of the catalyst in the calcining process in the prior art, the invention provides a platinum-based catalyst and a preparation method and application thereof, and the method can effectively improve the activity of the platinum-based catalyst in catalyzing the ORR reaction.
The invention adopts the following technical scheme to solve the technical problems:
the invention provides a preparation method of a platinum-based catalyst, which comprises the following steps: calcining a platinum-based catalyst precursor to obtain the catalyst;
wherein the platinum-based catalyst precursor comprises urea, a carbon source and a platinum salt;
wherein the mass ratio of the urea to the carbon source is 1: (0.5-2).
In the preparation method of the platinum-based catalyst, the urea is added, so that the growth of the nano particles is protected under high-temperature decomposition, the agglomeration of the platinum-based catalyst particles is effectively inhibited, and the activity of the ORR reaction is obviously improved. Meanwhile, the method is simple, the conditions are controllable, and the large-scale production is easy to expand.
In the present invention, the carbon source may be a carbon source capable of supporting metallic platinum after calcination, such as carbon black, which is conventional in the art.
In the present invention, the platinum salt is a platinum salt conventionally used in the art for preparing a platinum-based catalyst, and is, for example, chloroplatinic acid or platinum acetylacetonate.
In the present invention, the mass ratio of the urea to the carbon source is preferably 1: (0.6-1).
In a specific embodiment of the present invention, the mass ratio of the urea to the carbon source is 1.
In the present invention, the mass ratio of the carbon source to the platinum salt is preferably 1: (0.4-0.6), e.g., 1.
In the invention, the platinum-based catalyst precursor can be prepared by the following method: dispersing the urea, the carbon source and the platinum salt in a solvent to obtain a dispersion liquid, and then sequentially filtering and drying the dispersion liquid to obtain a solid, namely the platinum-based catalyst precursor.
Wherein, the dispersion can adopt the conventional method in the field, and preferably uses ultrasonic dispersion.
The dispersing time is only required to form a uniform dispersion liquid from the dispersed mixed liquid, and is preferably 30min to 2h, for example 30min.
Wherein the solvent is conventional in the art and can be selected according to the platinum salt, such as water or acetone. Preferably, when the platinum salt is chloroplatinic acid, the solvent is water; when the platinum salt is platinum acetylacetonate, the solvent is acetone.
Wherein, the drying can be conventional in the art, and can be selected according to actual situations, such as freeze drying or vacuum drying. Preferably, when the solvent is water, the drying is freeze drying; when the solvent is acetone, the drying is vacuum drying.
In the present invention, the platinum-based catalyst precursor may preferably further include a non-noble metal salt.
The invention adopts urea as a protective agent for controlling the particle size, decomposes the transition metal at high temperature according to different decomposition temperatures of corresponding metal salts and forms an alloy phase with platinum to be directly loaded on the carbon carrier, thus effectively reducing the size of the nano particles and obtaining the platinum-based catalyst particles with controllable particle size and ordered structures.
Wherein the non-noble metal of the non-noble metal salt is preferably a transition metal, such as nickel, iron or cobalt.
Wherein the non-noble metal salt may be NiCl 2 ·6H 2 O、CoCl 2 ·6H 2 O、FeCl 3 ·6H 2 One or more of O, nickel acetylacetonate, iron acetylacetonate, and cobalt acetylacetonate.
Wherein the mass ratio of the carbon source to the non-noble metal salt is preferably 1: (0.1-1.3), for example 1.
Wherein the mass ratio of the platinum salt to the non-noble metal salt is 1: (0.2-5), for example 1:0.27, 1:4.47.
in the present invention, the calcination may be carried out by a method conventional in the art, preferably by using a tube furnace, and more preferably, the calcination is carried out by: putting the platinum-based catalyst precursor into a porcelain ark, and putting the porcelain ark into a tube furnace for calcination.
In the present invention, the time and atmosphere of the calcination may be set according to actual conditions.
In the present invention, the temperature of the calcination may be 500 to 800 ℃, for example, 500 ℃, 600 ℃, 700 ℃ or 800 ℃.
In the present invention, the temperature increase rate of the calcination may be 2 to 10 ℃/min, for example, 2 ℃/min, 5 ℃/min or 10 ℃/min.
In the present invention, the calcination time may be 1 to 4 hours, for example, 1 hour, 2 hours or 4 hours.
In the present invention, the atmosphere for calcination may be a mixture of hydrogen and argon, preferably, the reaction atmospheres Ar and H 2 The ratio of the volume flow rates of (A) to (B) may be Ar/H 2 =0 to 10, e.g. Ar/H 2 ＝1、Ar/H 2 =5 or Ar/H 2 ＝10。
In the present invention, the calcination may be performed by a stepwise temperature rise, preferably a two-stepwise temperature rise.
In the present invention, the temperature of the first stage heating in the stepwise heating may be 500 to 700 ℃, for example, 500 ℃, 600 ℃ or 700 ℃.
In the present invention, the first temperature rise in the stepwise temperature rise may be performed for a holding time of 0 to 2 hours, for example, 2 hours.
In the present invention, the temperature of the second stage of the segmented temperature rise may be 700 to 900 ℃, for example, 800 ℃.
In the present invention, the holding time of the first stage of the stepwise temperature rise may be 0 to 2 hours, for example, 2 hours.
In the invention, the heating rate of the first stage and the second stage in the sectional heating can be 2-10 ℃/min, such as 2 ℃/min, 5 ℃/min or 10 ℃/min.
The invention also provides a platinum-based catalyst which is prepared by adopting the preparation method.
The present invention also provides a platinum-based catalyst comprising carbon and platinum; the carbon is used as a carrier to load the platinum;
wherein the diameter of the platinum-based catalyst particles is 3 to 12nm.
In a specific embodiment of the present invention, the diameter of the platinum-based catalyst refers to the average diameter of the platinum-based catalysts prepared in the same batch;
wherein the average diameter is obtained by calculating the particle size in the (111) crystal plane direction according to XRD and the following Scherrer formula and taking the average value of the three calculation results,
D (hkl) ＝Kλ/(βcosθ)；
wherein D is (hkl) Is the particle diameter; k is a constant; λ is the X-ray wavelength; beta is the half-height width of a diffraction peak; theta is the diffraction angle. In the above formula, the value of the constant K is related to the definition of beta, and beta is selected to be 0.89 corresponding to the half-width height of the (111) plane peak.
In the present invention, the diameter of the particles of the platinum-based catalyst is preferably 3.5 to 11.4nm.
In a specific embodiment of the present invention, the particle size of the platinum-based catalyst is 3.5nm, 5.18nm, 6.5nm, 6.6nm, 10.2nm, 11.4nm.
In the present invention, in the platinum-based catalyst, the amount of the platinum supported is preferably 10 to 30wt%, preferably 10 to 20wt%, for example 18wt%, and the amount of the platinum supported is the percentage of the mass of the platinum to the total mass of the platinum-based catalyst.
In the present invention, the platinum-based catalyst preferably further comprises a non-noble metal. The addition of the non-noble metal can play a synergistic role with the platinum, and shows better catalytic activity for catalyzing ORR reaction.
In a specific embodiment of the invention, the platinum-based catalyst is PtCo/C, ptFe/C, ptNi 3 C or PtNi 1.5 and/C, wherein the "/" is carbon as a carrier to load metal Pt and metal Co.
In the present invention, the mass activity of the platinum-based catalyst is preferably 0.22 to 0.72Amg Pt -1 。
The invention also provides an application of the platinum-based catalyst in catalyzing ORR reaction.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows:
(1) According to the invention, urea is used as a protective agent for controlling the particle size, so that particle agglomeration of platinum-based catalyst particles in a high-temperature calcination process is effectively inhibited, the platinum-based catalyst particles with controllable particle size and an ordered structure are obtained, and the activity of the platinum-based catalyst in catalyzing ORR reaction is further effectively improved.
(2) The preparation method has controllable conditions, effectively saves the cost and is easy to expand large-scale production.
Drawings
FIG. 1 shows B-PtNi prepared in example 1 1.5 XRD profile of/C
FIG. 2 shows B-PtNi prepared in example 1 1.5 ORR polarization curves for/C and commercial Pt/C
FIG. 3 is an XRD plot of B-PtCo/C prepared in example 2
FIG. 4 is the ORR polarization curves for B-PtCo/C and commercial Pt/C prepared in example 2
FIG. 5 is an XRD plot of B-PtFe/C prepared in example 3
FIG. 6 is the ORR polarization curves for B-PtFe/C and commercial Pt/C prepared in example 3
FIG. 7 is an XRD plot of B-PtFe/C-700 deg.C prepared in example 4
FIG. 8 is the ORR polarization curves for B-PtFe/C-700 deg.C and commercial Pt/C prepared in example 4
FIG. 9 shows B-PtNi prepared in example 5 3 XRD curve of/C-1 h
FIG. 10 shows B-PtNi prepared in example 5 3 ORR polarization curves for/C-1 h and commercial Pt/C
FIG. 11 shows B-PtNi prepared in example 6 3 XRD curve at C-700 deg.C
FIG. 12 shows B-PtNi prepared in example 6 3 ORR polarization curves at/C-700 ℃ and commercial Pt/C
FIG. 13 shows A-PtNi prepared in comparative example 1 1.5 XRD profile of/C
FIG. 14 shows A-PtNi prepared in comparative example 1 1.5 ORR polarization curves for/C and commercial Pt/C
FIG. 15 is an XRD plot of A-PtCo/C prepared in comparative example 2
FIG. 16 is the ORR polarization curves of A-PtCo/C and commercial Pt/C prepared in comparative example 2
FIG. 17 is an XRD plot of A-PtFe/C prepared in comparative example 3
FIG. 18 is an ORR polarization curve of A-PtFe/C and commercial Pt/C prepared in comparative example 3
FIG. 19 is an XRD plot of A-PtFe/C-700 ℃ prepared in comparative example 4
FIG. 20 is the ORR polarization curves of A-PtFe/C-700 ℃ and commercial Pt/C prepared in comparative example 4
FIG. 21 shows A-PtNi prepared in comparative example 5 3 XRD curve of/C-1 h
FIG. 22 shows A-PtNi prepared in comparative example 5 3 ORR polarization curves for/C-1 h and commercial Pt/C
FIG. 23 shows A-PtNi prepared in comparative example 6 3 XRD curve at C-700 deg.C
FIG. 24 shows A-PtNi prepared in comparative example 6 3 ORR polarization curves at C-700 ℃ and commercial Pt/C
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the invention thereto. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
In the present invention, the prefix B is an example added with urea, and the prefix A is a comparative example without urea.
Example 1
Preparation of B-PtNi 1.5 /C ORR nano-catalytic particle
Step (1): 40mg of urea, 30mg of Vulcan XC-72 carbon black and 1.68mL of H with the concentration of 10mg/mL 2 PtCl 6 Aqueous solution, 4.6mg NiCl 2 ·6H 2 O is dispersed in 10mL of deionized water to give a suspended aqueous solution containing carbon black, which isIn the method, the concentration of the carbon black is 3mg/mL, and a uniform dispersion water solution is obtained after ultrasonic treatment for 30 min;
step (2): removing water from the dispersed aqueous solution obtained in the step (1) through freeze drying to obtain black powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark in a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 =10, performing two-stage temperature rise, performing heat preservation at 600 ℃ for 2 hours, then performing heat preservation at 800 ℃ for 2 hours, wherein the temperature rise rate of the two-stage temperature rise is 2 ℃/min, calcining, and naturally cooling to obtain B-PtNi 1.5 Catalyst particles per C.
Example 2
Preparation of B-PtCo/C ORR nano-catalytic particles
Step (1): 40mg of urea, 30mg of Vulcan XC-72 carbon black, 16.2mg of Pt (acac) 2 9.8mg of CoCl 2 ·6H 2 Dispersing O in 20mL of acetone solution to obtain carbon black suspension acetone dispersion solution, wherein the concentration of the carbon black is 1.5mg/mL, and performing ultrasonic treatment for 50min to obtain uniform dispersion acetone solution;
step (2): removing the acetone solvent from the dispersed acetone solution obtained in the step (1) through vacuum drying to obtain black powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark in a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 And =1, the temperature is kept for 2h at 500 ℃ and then for 2h at 800 ℃ by two-stage temperature rise, wherein the temperature rise rate of the two-stage temperature rise is 5 ℃/min, and the B-PtCo/C catalyst particles are obtained by natural cooling after calcination.
Example 3
Preparation of B-PtFe/C ORR nano-catalytic particles
Step (1): 30mg of urea, 60mg of Vulcan XC-72 carbon black, 32.4mg of Pt (acac) 2 14.5mg FeCl 3 ·6H 2 Dispersing O in 60mL of acetone solution to obtain a carbon black suspension acetone dispersion solution, wherein the concentration of the carbon black is 1mg/mL, and performing ultrasonic treatment for 1.2h to obtain a uniform dispersion acetone solution;
step (2): removing the acetone solvent from the dispersed acetone solution obtained in the step (1) through vacuum drying to obtain black powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark into a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 And =1, the temperature is kept for 2h at 500 ℃ and then for 2h at 800 ℃ by two-stage temperature rise, wherein the temperature rise rate of the two-stage temperature rise is 10 ℃/min, and the B-PtFe/C catalyst particles are obtained by natural cooling after calcination.
Example 4
Preparation of B-PtFe/C-700 ℃ ORR nano catalytic particles
Step (1): 120mg of urea, 60mg of Vulcan XC-72 carbon black, 32.4mg of Pt (acac) 2 14.5mg FeCl 3 ·6H 2 Dispersing O in 100mL of acetone solution to obtain a carbon black suspension acetone dispersion solution, wherein the concentration of the carbon black is 0.6mg/mL, and performing ultrasonic treatment for 1.5h to obtain a uniform dispersion acetone solution;
step (2): removing the acetone solvent from the dispersed acetone solution obtained in the step (1) through vacuum drying to obtain black powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark in a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 And =1, the temperature is kept for 2h at 500 ℃ and then for 2h at 700 ℃ by two-stage temperature rise, wherein the temperature rise rate of the two-stage temperature rise is 10 ℃/min, and the catalyst particles at the temperature of B-PtFe/C-700 ℃ are obtained by natural cooling after calcination.
Example 5
Preparation of B-PtNi 3 /C-1h ORR nano catalytic particle
Step (1): 60mg of urea, 50mg of Vulcan XC-72 carbon black and 2.52mL of H with the concentration of 10mg/mL 2 PtCl 6 Aqueous solution, 58.6mg NiCl 2 ·6H 2 Dispersing the carbon black into 40mL of aqueous solution by using O to obtain a suspension water dispersion solution of the carbon black, wherein the concentration of the carbon black is 1.25mg/mL, and performing ultrasonic treatment for 1 hour to obtain a uniform dispersion water solution;
step (2): removing water from the dispersed aqueous solution obtained in the step (1) through freeze drying to obtainBlack powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark in a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 =1, heating to 600 ℃, then preserving heat for 1h, wherein the heating rate is 10 ℃/min, and naturally cooling to obtain B-PtNi 3 C-1h catalyst particles.
Example 6
Preparation of B-PtNi 3 ORR nano catalytic particle at C-700 DEG C
Step (1): 40mg of urea, 25mg of Vulcan XC-72 carbon black and 2.52mL of H with a concentration of 10mg/mL 2 PtCl 6 Aqueous solution, 29.3mg NiCl 2 ·6H 2 Dispersing O in 25mL of aqueous solution to obtain a carbon black suspension water dispersion solution, wherein the concentration of the carrier is 1mg/mL, and performing ultrasonic treatment for 40min to obtain a uniform dispersion water solution;
step (2): removing water from the dispersed aqueous solution obtained in the step (1) through freeze drying to obtain black powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark in a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 =5, heating to 700 ℃, keeping the temperature, wherein the heating rate is 10 ℃/min, and naturally cooling to obtain B-PtNi 3 Catalyst particles at C-700 ℃.
Comparative example 1
Preparation of A-PtNi 1.5 /C ORR nano-catalytic particle
Step (1): 30mg of Vulcan XC-72 carbon black, 1.68mL of H with a concentration of 10mg/mL 2 PtCl 6 Aqueous solution, 14.6mg NiCl 2 ·6H 2 Dispersing O in 10mL deionized water to obtain a carbon black suspension aqueous solution, wherein the concentration of the carrier is 3mg/mL, and performing ultrasonic treatment for 30min to obtain a uniform dispersion aqueous solution;
step (2): removing water from the dispersed aqueous solution obtained in the step (1) through freeze drying to obtain black powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark in a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 =10, by twoHeating in a sectional manner, firstly keeping the temperature at 600 ℃ for 2h, then keeping the temperature at 800 ℃ for 2h, wherein the heating rate of the two-sectional heating is 2 ℃/min, calcining, and naturally cooling to obtain A-PtNi 1.5 Catalyst particles per C.
Comparative example 2
Preparation of A-PtCo/C ORR nano-catalytic particles
Step (1): 30mg of Vulcan XC-72 carbon black, 16.2mg of Pt (acac) 2 9.8mg CoCl 2 ·6H 2 Dispersing O in 20mL of acetone solution to obtain carbon black suspension acetone dispersion solution, wherein the concentration of the carrier is 1.5mg/mL, and performing ultrasonic treatment for 50min to obtain uniform dispersion acetone solution;
step (2): removing the acetone solvent from the dispersed acetone solution obtained in the step (1) through vacuum drying to obtain black powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark in a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 And =1, carrying out two-stage heating, firstly carrying out heat preservation for 2h at 500 ℃ and then carrying out heat preservation for 2h at 800 ℃, wherein the heating rate of the two-stage heating is 5 ℃/min, and carrying out natural cooling after calcination to obtain the A-PtCo/C catalyst particles.
Comparative example 3
Preparation of A-PtFe/C ORR nano-catalytic particles
Step (1): 60mg of Vulcan XC-72 carbon black, 32.4mg of Pt (acac) 2 14.5mg of FeCl 3 ·6H 2 Dispersing O in 60mL of acetone solution to obtain a carbon black suspension acetone dispersion solution, wherein the concentration of the carrier is 1mg/mL, and performing ultrasonic treatment for 1.2h to obtain a uniform dispersion acetone solution;
step (2): removing the acetone solvent from the dispersed acetone solution obtained in the step (1) through vacuum drying to obtain black powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark into a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 =1, performing two-stage temperature rise, firstly performing heat preservation at 500 ℃ for 2 hours, and then performing heat preservation at 800 ℃ for 2 hours, wherein the temperature rise rate of the two-stage temperature rise is 10 ℃/min, calcining, and naturally cooling to obtain A-PtFe/C catalyst particles.
Comparative example 4
Preparation of A-PtFe/C-700 ℃ ORR nano catalytic particles
Step (1): 60mg of Vulcan XC-72 carbon black, 32.4mg of Pt (acac) 2 14.5mg of FeCl 3 ·6H 2 O was dispersed in 100mL of an acetone solution to obtain a carbon black-suspended acetone dispersion solution. Wherein the carrier concentration is 0.6mg/mL, and a uniform dispersed acetone solution is obtained after 1.5h of ultrasonic treatment;
step (2): removing the acetone solvent from the dispersed acetone solution obtained in the step (1) through vacuum drying to obtain black powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark in a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 And =1, carrying out two-stage heating, firstly carrying out heat preservation for 2h at 500 ℃, and then carrying out heat preservation for 2h at 700 ℃, wherein the heating rate of the two-stage heating is 10 ℃/min, and carrying out natural cooling after calcination to obtain the A-PtFe/C-700 ℃ catalyst particles.
Comparative example 5
Preparation of A-PtNi 3 /C-1h ORR nano catalytic particle
Step (1): 50mg of Vulcan XC-72 carbon black and 2.52mL of H with a concentration of 10mg/mL 2 PtCl 6 Aqueous solution, 58.6mg NiCl 2 ·6H 2 Dispersing O in 40mL of aqueous solution to obtain a carbon black suspension water dispersion solution, wherein the concentration of the carrier is 1.25mg/mL, and performing ultrasonic treatment for 1 hour to obtain a uniform dispersion water solution;
step (2): removing water from the dispersed aqueous solution obtained in the step (1) through freeze drying to obtain black powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark in a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 =1, heating to 600 ℃, keeping the temperature for 1h, wherein the heating rate is 10 ℃/min, and naturally cooling to obtain A-PtNi 3 C-1h catalyst particles.
Comparative example 6
Preparation of A-PtNi 3 ORR nano catalytic particle at/C-700 DEG C
Step (1): 25mg of Vulcan XC-72 carbon black and 2.52mL of H with a concentration of 10mg/mL 2 PtCl 6 Aqueous solution, 29.3mg NiCl 2 ·6H 2 O is dispersed in 25mL of water solution to obtain carbon black suspension water dispersion solution, wherein the carrier concentration is 1mg/mL, and uniform dispersion solution is obtained after ultrasonic treatment for 40 min;
step (2): removing water from the dispersed aqueous solution obtained in the step (1) through freeze drying to obtain black powder to be calcined; putting the prepared black powder into a porcelain ark and placing the porcelain ark in a tubular furnace; then controlling the reaction atmosphere Ar and H through an external gas pipeline 2 Volume flow rate ratio Ar/H of 2 =5, heating to 700 ℃, keeping the temperature, wherein the heating rate is 10 ℃/min, and naturally cooling to obtain A-PtNi 3 Catalyst particles at C-700 ℃.
Effect example 1
Test samples: platinum-based alloy catalyst particles obtained in examples 1 to 6 and comparative examples 1 to 6.
Test equipment and conditions: the phase structure of the catalyst and alloy particles was analyzed by D8 ADVANCE X-ray polycrystalline diffractometer (XRD). Wherein the scanning range is 10-90 degrees, the step length is 0.02 degree, and the scanning speed is 0.36 s/step.
The grain size in the (111) crystal face direction is obtained according to the Scherrer formula, and the broadening caused by stress is negligible compared with the broadening caused by the grain size when the grain size is less than 100nm by adopting a low-angle diffraction line. At this time, the Scherrer formula is applied, and the particle size can be calculated. The measured object is characterized by X-ray diffraction from a macroscopic angle, so the calculated particle size has more persuasiveness and universality.
D (hkl) ＝Kλ/(βcosθ)；
D (hkl) Is the diameter of the particle; k is a constant; λ is the X-ray wavelength; beta is the half-height width of a diffraction peak; theta is the diffraction angle. In the above formula, the value of the constant K is related to the definition of beta, wherein beta is selected to be 0.89 corresponding to the half-width height of the (111) plane peak.
The test results were as follows:
fig. 1, 3, 5, 7, 9 and 11 are XRD curves of the platinum-based alloy nanoparticles prepared in examples 1 to 6, respectively, and fig. 13, 15, 17, 19, 21 and 23 are XRD curves of the platinum-based alloy nanoparticles prepared in comparative examples 1 to 6, respectively. The sizes of the platinum-based alloy nanoparticles prepared in examples 1 to 6 and comparative examples 1 to 6 were calculated three times using the above-described method and averaged, and the results are shown in table 1 below.
By comparison, the platinum-based alloy nanoparticles prepared in examples 1 to 6 of the present invention have a significantly broadened half-peak and a significantly reduced particle size, as compared to those of comparative examples 1 to 6.
TABLE 1 average diameter of platinum-based alloy nanoparticles obtained in examples 1 to 6 and comparative examples 1 to 6
Effect example 2
Test samples: platinum-based alloy nanoparticles obtained in examples 1 to 6 and comparative examples 7 to 12.
Test equipment and conditions: transmission electron microscopy: inductively coupled plasma atomic emission spectrometry (ICP-OES)
The test results were as follows:
the metal element Pt of the platinum-based catalyst particles was analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-OES), and the relative content of the Pt element was substantially measured to be 10 to 20wt%, wherein the average loading amount of Pt in the catalysts prepared in examples 1 to 6 was 18wt%, and the concentration of Pt in the ink for testing was 0.90mgPt/mL. Wherein, the loading amount of the platinum is the mass percentage of the metal Pt in the total mass of the platinum-based catalyst.
Effect example 3
Test samples: platinum-based alloy catalyst particles obtained in examples 1 to 6 and comparative examples 1 to 6.
Test equipment and conditions: electrochemical testing was performed on a Rotating Disk Electrode (RDE) apparatus, and data was collected by the chenhua CHI760E electrochemical workstation. Adopts a three-electrode system, and Pt wires and a Saturated Calomel Electrode (SCE) are respectively used as counter electrodesAnd a reference electrode. The ORR polarization curve was obtained by Linear Sweep Voltammetry (LSV) testing. Testing in advance at O 2 Saturated 0.1M HClO 4 The sweep rate and the RDE speed were 10mV/s and 1600rpm, respectively.
The mass of the noble metal is taken as a standard for calculating mass activity, and the calculation formula of mass activity MA is as follows:
MA＝SA/m；
where SA is the specific activity of the catalyst and m is the Pt loading on the working electrode.
The test results were as follows:
fig. 2, 4, 6, 8, 10 and 12 are ORR polarization curves of the platinum-based alloy nanoparticles prepared in examples 1 to 6, respectively, and fig. 14, 16, 18, 20, 22 and 24 are ORR polarization curves of the platinum-based alloy nanoparticles prepared in comparative examples 1 to 6, respectively. In contrast, the platinum-based alloy nanoparticles prepared in examples 1 to 6 exhibited better ORR activity, i.e., better catalytic performance, compared to the commercial Pt/C shifted to the right (shifted in the high potential direction), while the platinum-based alloy nanoparticles prepared in comparative examples 1 to 6 exhibited poorer ORR activity, i.e., poorer catalytic performance, compared to the commercial Pt/C shifted to the left or hardly changed in the half-wave potential.
Table 2 shows the mass activities of the platinum-based alloy nanoparticles obtained in examples 1 to 6 and comparative examples 1 to 6, wherein the theoretical mass activity of the commercial PtC catalyst (the platinum loading in the commercial PtC catalyst is 20 wt%) was 0.09Amg Pt -1 。
TABLE 2 Mass Activity of platinum-based alloy nanoparticles obtained in examples 1 to 6 and comparative examples 1 to 6
As can be seen from Table 2, the ORR performance of the platinum-based alloy nanoparticles prepared in examples 1 to 6 of the present invention was better than that of the commercial platinum-carbon and the platinum-based alloy nanoparticles prepared in comparative examples 1 to 6.
The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, and combinations that do not depart from the spirit and principle of the present invention are equivalent.
Claims (10)
1. A preparation method of a platinum-based catalyst is characterized by comprising the following steps: calcining a platinum-based catalyst precursor to obtain the catalyst;
wherein the platinum-based catalyst precursor comprises urea, a carbon source and a platinum salt;
wherein the mass ratio of the urea to the carbon source is 1: (0.5-2).
2. The method for producing a platinum-based catalyst according to claim 1, wherein the carbon source is carbon black;
and/or the platinum salt is chloroplatinic acid or platinum acetylacetonate;
and/or the mass ratio of the urea to the carbon source is 1: (0.6-1);
and/or the mass ratio of the carbon source to the platinum salt is 1: (0.4-0.6), e.g., 1;
and/or the preparation method of the platinum-based catalyst precursor comprises the following steps: dispersing the urea, the carbon source and the platinum salt in a solvent to obtain a dispersion liquid, and filtering and drying the dispersion liquid in sequence to obtain a solid, namely the platinum-based catalyst precursor;
wherein the dispersion is preferably ultrasonic dispersion;
wherein the dispersing time is preferably 30 min-2 h;
wherein, the solvent is preferably water or acetone:
for example, when the platinum salt is chloroplatinic acid, the solvent is water;
for example, when the platinum salt is platinum acetylacetonate, the solvent is acetone;
wherein, the drying is preferably vacuum drying or freeze drying;
for example, when the solvent is water, the drying is freeze-drying;
for example, when the solvent is acetone, the drying is performed under vacuum.
3. The method of preparing a platinum-based catalyst according to claim 1, wherein the platinum-based catalyst precursor comprises a non-noble metal salt.
4. The method for preparing a platinum-based catalyst according to claim 3, wherein the non-noble metal of the non-noble metal salt is a transition metal such as nickel, iron or cobalt;
and/or, the non-noble metal salt is NiCl 2 ·6H 2 O、CoCl 2 ·6H 2 O、FeCl 3 ·6H 2 One or more of O, nickel acetylacetonate, iron acetylacetonate, and cobalt acetylacetonate;
and/or the mass ratio of the carbon source to the non-noble metal salt is 1: (0.1-1.3), such as 1;
and/or the mass ratio of the platinum salt to the non-noble metal salt is 1: (0.2-5), for example 1:0.27, 1:4.47.
5. the method for preparing a platinum-based catalyst according to claim 1, wherein the temperature of the calcination is in the range of 500 to 800 ℃, such as 600 ℃ or 700 ℃;
and/or the heating rate of the calcination is 2-10 ℃/min, for example 5 ℃/min;
and/or the calcination is carried out for a time of 1 to 4 hours, for example 2 hours;
and/or the calcining atmosphere is hydrogen-argon mixed gas.
6. The process for the preparation of a platinum-based catalyst according to any one of claims 1 to 5, wherein the calcination is a temperature increase in stages, preferably a two-stage temperature increase;
wherein the temperature of the first stage in the sectional heating is 500-700 ℃, for example 600 ℃;
wherein the heat preservation time of the first stage of temperature rise in the sectional type temperature rise is 0-2 h;
wherein the temperature of the second stage of the sectional heating is 700-900 ℃, for example 800 ℃;
wherein the heat preservation time of the first stage of temperature rise in the sectional type temperature rise is 0-2 h;
wherein, the heating rate of the first stage and the second stage of the sectional heating is 2-10 ℃/min, such as 5 ℃/min.
7. A platinum-based catalyst produced by the method for producing a platinum-based catalyst according to any one of claims 1 to 6.
8. A platinum-based catalyst, characterized by comprising carbon and platinum, said carbon supporting said platinum as a carrier;
wherein the diameter of the platinum-based catalyst particles is 3 to 12nm.
9. Platinum-based catalyst according to claim 8, wherein the particles of the platinum-based catalyst have a diameter of 3.5 to 11.4nm, such as 5.18nm, 6.5nm, 6.6nm or 10.2nm;
and/or, in the platinum-based catalyst, the loading amount of the platinum is 10-30 wt%, preferably 10-20 wt%, for example 18wt%, and the loading amount of the platinum is the percentage of the mass of the platinum to the total mass of the platinum-based catalyst;
and/or, the platinum-based catalyst comprises a non-noble metal; the non-noble metal is preferably nickel, iron or cobalt;
and/or the mass activity of the platinum-based catalyst is 0.22-0.72A mg Pt -1 。
10. Use of a platinum-based catalyst according to any one of claims 7 to 9 for catalysing the ORR reaction.
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