CN110586090B - Noble metal alloy shell-core catalyst prepared by using organic reducing agent and preparation method thereof - Google Patents

Noble metal alloy shell-core catalyst prepared by using organic reducing agent and preparation method thereof Download PDF

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CN110586090B
CN110586090B CN201910954309.7A CN201910954309A CN110586090B CN 110586090 B CN110586090 B CN 110586090B CN 201910954309 A CN201910954309 A CN 201910954309A CN 110586090 B CN110586090 B CN 110586090B
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catalyst
core
noble metal
shell
reducing agent
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CN110586090A (en
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赵卿
王诚
王建龙
孙连国
张泽坪
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Tsinghua University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48—Silver or gold
    • B01J23/52—Gold
    • B01J35/23—
    • B01J35/33—
    • B01J35/397—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/16—Reducing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8825—Methods for deposition of the catalytic active composition
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
    • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Abstract

The invention belongs to the technical field of fuel cells and electrochemical catalysis, and particularly relates to a high-performance superfine low-Pt shell-core catalyst prepared by an organic reduction method and a preparation method thereof. The invention provides a noble metal alloy shell-core catalyst, which comprises 90-96 at% of carbon atoms and 2-7 at% of O element atoms; the Pt loading on the surface is 0.1-2 at.%, and the metal particle size is 0.5-5 nm. The low platinum shell-core alloy catalyst is prepared by a method for controlling reduction by using an organic carboxyl and hydroxyl reducing agent, and shows excellent oxygen reduction activity and electrocatalysis performance under an acidic condition.

Description

Noble metal alloy shell-core catalyst prepared by using organic reducing agent and preparation method thereof
Technical Field
The invention belongs to the technical field of fuel cells and electrochemical catalysis, and particularly relates to a high-performance superfine low-Pt shell-core catalyst prepared by an organic reduction method and a preparation method thereof.
Background
The proton exchange membrane fuel cell is a reaction device for directly converting chemical energy of fuel into electric energy, is a key technology for the development of the current new energy automobile, has the advantages of low operation temperature, high starting speed, cleanness and high efficiency, and is an important direction for the development of the future new energy technology (Zipen Zhao et al, adv. Mater., 2019). The fuel cell comprises an electrode, an electrolyte, a current collecting material and an external circuit, wherein the electrode is a place where electrochemical reaction of the fuel cell occurs, comprises a noble metal catalyst and a proton conductor, and a high-loading Pt/C catalyst (Meixia Wu et al, Electrochimica Acta,2019) is mainly used at present. As a core material of a fuel cell, a catalyst determines the discharge performance and the service life of the cell, and the improvement of the comprehensive performance and the localization of the preparation technology are directly related to the core competitiveness of the fuel cell technology, and have important development significance and industrialization prospects (j.l. The oxygen reduction reaction is one of the most important processes for realizing energy conversion of the fuel cell, and the kinetic process of the fuel cell slowly needs to use a large amount of Pt noble metal catalyst, so that the cost of the fuel cell is high, and the commercialization process of the fuel cell is hindered (M.H.Lee et al, J.Power Sources, 2009). In recent years, much attention has been paid to the study of high activity, high stability, low Pt loading Pt-based core-shell catalysts (y.j.li, l.chen et al, electrochim. acta, 2016). Currently, the mainstream research for reducing the amount of Pt is to prepare a core-shell structure alloy catalyst, use relatively cheap metal in the catalyst, use high-catalytic-activity noble metal such as Pt on the catalyst shell layer, and distribute the noble metal with catalytic activity on the surface as much as possible, so as to significantly improve the utilization rate of the noble metal and reduce the catalyst cost (p.
The slow and delayed oxygen reduction kinetics are the determining steps of the catalytic process, and the improvement of the ORR activity of the catalyst has a decisive influence on the improvement of the catalytic efficiency of the fuel cell. The Pt-based catalyst is considered to have the best ORR catalytic activity, however, it is costly and has insufficient life. Therefore, research on improving Pt catalytic activity and utilization rate and increasing catalyst stability is the main research direction (Mufan Li et al, science, 2016; A.E. Alvarez et al, ChemCatchem, 2017). The non-noble transition metal and the Pd, Ag and other cheap noble metals have the electrocatalytic activity equivalent to that of Pt, have lower cost, can replace Pt to a certain extent, and are used for the ORR catalytic process. In addition, the bimetallic core-shell nano structure concentrates and distributes the noble metal on the shell layer, thereby reducing the using amount of the noble metal and improving the utilization rate of the noble metal. Alloy structure shell-core catalysts such as Pt @ M NPs (M ═ Fe, Co, Ni, Cu), Pd @ Ni NPs, Pt @ PtCo NPs, Pt @ FePd NPs, and the like all have high electrocatalytic activity, high specific mass activity, and good electrochemical stability (y.j.li, l.chen et al, electrochim.acta, 2016;strasser et al, nanomater energy, 2016; k.a. kuttiyiel et al, nanomater. energy, 2016). For the catalyst with a shell-core structure, the existence of the core metal can increase the unit noble metal active site, and the modification of the electronic structure on the surface of the catalyst is induced by the ligand and the strain effect, so that O is promoted2So that overall ORR activity is promoted (j.y.lee et al, j.alloy.comp, 2017). The invention has the significance that the noble metal alloy shell-core catalyst is prepared by a method of controlling reduction of carboxyl and hydroxyl organic matters, the electrochemical activity of the noble metal alloy shell-core catalyst is obviously superior to that of the traditional commercialized Pt/C, and the noble metal alloy shell-core catalyst has wide application prospect in the field of fuel cells and electrochemical catalysis.
Disclosure of Invention
Technical problem to be solved by the invention
The invention aims to provide a high-performance superfine low-Pt shell-core catalyst prepared by a method for controlling reduction of a carboxyl and hydroxyl organic matter, and the catalyst has excellent oxygen reduction activity and has important use and research values in the fields of oxygen reduction catalytic systems, electrocatalysis, fuel cells and the like.
Means for solving the technical problem
Aiming at the problems, the invention provides a high-performance superfine low-Pt shell-core catalyst and a preparation method thereof.
According to one embodiment of the present invention, there is provided a noble metal alloy shell-core catalyst having 90 to 96 at.% of carbon and 2 to 7 at.% of O element; the Pt loading on the surface is 0.1-2 at.%, and the metal particle size is 0.5-5 nm.
According to a second aspect of the present invention, there is provided a method for preparing a noble metal alloy shell-core catalyst using an organic reducing agent, comprising the steps of:
(1) organic reduction of the superfine metal core;
(2) coating a stable metal transition layer;
(3) carrying out organic reduction and growth on the noble metal shell;
(4) aging and growing the crystal;
(5) separating the product and removing the solvent.
In one embodiment, in step (1), the metal precursor is adsorbed on a carbon support under the protection of a surfactant, and a reducing agent is added to perform metal nuclear reduction.
In one embodiment, in the step (1), the surfactant is one or more selected from CTAB, CTAC, sodium dodecylbenzenesulfonate, sodium dodecylsulfonate, P123, F127, polyacrylamide, PVP, polyethylene glycol, polyethylene oxide, and the like; the metal precursor is selected from soluble strong oxidizing metal salts; the loaded carbon carrier is selected from a high-conductivity and high-specific-surface-area carbon conductive carbon material; the hydroxyl and carboxyl reducing agent is selected from one or more of hydroxyl and carboxyl organic salts;
in one embodiment, in step (2), a metal ion having strong oxidizing property with respect to the core metal is added to prepare the transition coating layer through a metal substitution reaction.
In one embodiment, in step (2), the strong oxidizing metal ion of the substitution reaction is derived from a high valent metal salt and is more oxidizing than the nuclear metal ion.
In one embodiment, in the step (3), a reducing agent is added to reduce and coat the noble metal shell.
In one embodiment, in step (3), the metal wrapped by the shell layer is one or more of Pt, Ir, Au and Os metals.
In one embodiment, in the step (4), a reducing agent is added to perform surface crystal aging growth.
In one embodiment, in step (4), the protective reducing agent comprises Na2SO3、K2SO3、NaBH4、KBH4、LiAlH4、SnCl2And hydrazine.
The invention has the advantages of
(1) The invention relates to a method for preparing a noble metal alloy shell-core ultrafine nano-particle catalyst by using an organic reducing agent to control reduction. Firstly, adding carboxyl and hydroxyl salt to carry out organic reduction of metal cores; then, preparing a stable transition layer structure through a displacement reaction; then, coating the surface layer noble metal by a method of reducing a noble metal shell layer by organic acid; then aging and growing the shell metal under the action of the slow-release reducing agent; finally, the catalyst with low platinum shell-core structure is obtained by centrifugation, drying and other methods.
(2) The invention belongs to the technical field of fuel cells and electrochemical catalysis, and relates to a technology for preparing high-performance superfine low-Pt shell-core nanoparticles by a method for controlling reduction of a carboxyl organic compound and a hydroxyl organic compound, wherein the catalyst has excellent oxygen reduction activity; the catalyst has the advantages of simple preparation method, adjustable metal components and loading capacity, high activity and stability, and important use and research values in the fields of oxygen reduction catalytic systems, electrocatalysis, fuel cells and the like.
(3) Electrochemical tests such as linear voltage scanning, cyclic voltammetry, EIS and the like prove that the catalyst has remarkably excellent ORR activity compared with 40% commercial Pt/C (JM company), improves the utilization rate of Pt, and has important significance for reducing the cost of the catalyst and reducing the use of noble metals such as Pt and the like.
(4) The catalyst forms an ultrafine shell-core structure with the size less than or equal to 5nm, and has uniform dispersion and distribution, high activity and good stability.
In conclusion, the low-platinum-shell-core alloy catalyst prepared by the method for controlling reduction by using the organic carboxyl and hydroxyl reducing agents shows excellent oxygen reduction activity and electrocatalytic performance under acidic conditions.
Further features of the present invention will become apparent from the following description of exemplary embodiments.
Drawings
FIG. 1 is a low magnification TEM topography of a catalyst prepared in example 1 of the present invention. FIG. 1(a) is a graph of catalyst morphology at the 20nm scale; FIG. 1(b) is a statistical view of catalyst particles.
Fig. 2 is an XRD pattern of the catalyst prepared in example 1 of the present invention.
FIG. 3 is an XPS elemental analysis chart of a catalyst prepared in example 1 of the present invention. (a) XPS peak profile of C1s, (b) XPS peak profile of O1s, (C) XPS peak profile of Pt4f, and (d) XPS peak profile of Ag.
FIG. 4 is a graph showing the electrochemical properties of the catalyst prepared in example 1 of the present invention. (a) Prepare a CV comparison of Ag @ Pt/C catalyst activity to a commercial 40% Pt/C (JM) catalyst; (b) preparation of an ORR chart of Ag @ Pt/C catalyst vs. commercial 40% Pt/C (JM) catalyst.
FIG. 5 is a graph showing the electrochemical properties of the catalyst prepared in example 2 of the present invention. (a) Prepare a graph of CV activity for Ag @ Pt/C catalyst versus a commercial 40% Pt/C (JM) catalyst; (b) preparation of an ORR chart of Ag @ Pt/C catalyst vs. commercial 40% Pt/C (JM) catalyst.
Detailed Description
One embodiment of the present disclosure will be specifically described below, but the present disclosure is not limited thereto.
The prepared low platinum shell-core alloy catalyst is characterized in that the surface element analysis of the catalyst is as follows: the prepared low platinum shell-core alloy catalyst has 90-96 at% of carbon atoms and 2-7 at% of O element atoms; the distribution loading of Pt on the surface is 0.1-2 at.%, and the metal particle size is 0.5-5 nm. The catalyst has low Pt consumption, but the oxygen reduction activity is superior to that of a commercial Pt/C catalyst, and the catalyst has important significance for reducing the cost of the catalyst and reducing the use of noble metals such as Pt and the like. The percentage of total doped metal on the surface of the catalyst is 0.1-3 at.%.
The method for preparing the noble metal alloy shell-core ultrafine nano-particle catalyst by using the organic reducing agent to control reduction comprises the following steps:
1) organic reduction of the ultrafine metal nuclei: fully adsorbing the metal precursor on a carbon carrier by an ultrasonic oscillation method under the protection action of a surfactant; heating and stirring, adding a carboxyl reducing agent and a hydroxyl reducing agent, and heating in an oil bath to reduce the metal nuclei; the temperature range of the carboxyl and hydroxyl reducing agents for reducing the metal core is 80-150 ℃, and the time is 30 min-3 h; the concentration of the nucleating metal ions is 0.01-0.5 mol/L, and the addition amount is 0.1-10 vt%; the adding amount of the carbon carrier is 0.025-0.15 wt.%; the addition amount of the surfactant is 0.01-0.8 wt.%, and the addition amount of the carboxyl and hydroxyl reducing agent is 0.1-5 wt.%.
Further, the surfactant for promoting ionic dispersion is preferably one or more of CTAB, CTAC, sodium dodecylbenzene sulfonate, P123, F127, polyacrylamide, PVP, polyethylene glycol, or polyethylene oxide;
the nucleating metal ions are from AgF and AgNO3、AgClO4、Na2PdCl4、(NH4)2PdCl6、PdCl2Soluble strongly oxidizable metal salts of ruthenium chloride, mainly comprising Ag+、Au+、Ru3+、Pd2+、Rh3+One or more than one of strong oxidizing metal ions after H is waited;
the load carbon carrier comprises high-conductivity and high-specific-surface-area carbon conductive carbon materials such as Vulcan XC-72, BP2000, EC300J, acetylene black, carbon nanotubes, graphene, Ketjenblack and the like;
the hydroxyl and carboxyl reducing agent is one or more of organic salts rich in hydroxyl carboxyl, such as sodium citrate, potassium citrate, sodium oxalate, sodium formate, sodium acetate, fatty acid, phosphatidylcholine, ammonium oxalate, disodium citrate, ferric ammonium citrate, heme iron and the like;
2) and (3) coating a stable metal transition layer: adjusting the temperature, adding metal ions with strong oxidizing property relative to the core metal, and preparing a transition coating layer through metal replacement reaction; the reaction temperature is 40-120 ℃, and the reaction time is 30 min-3 h; the concentration of the strong oxidizing metal ions is 0.001-0.1 mol/L, and the adding amount is 0.1-12 vt%;
the strong oxidation metal ions are from one or more of strong oxidation ions such as Pt, Ir, Au, Os and the like, and meet the metal activity sequence, and have stronger oxidation property relative to core ions;
the further reduced carboxyl and hydroxyl reducing agent comprises one or more of hydroxyl-rich organic acid reducing agents such as ascorbic acid, citric acid, oxalic acid, amino acid, lactic acid, glutamic acid, fumaric acid, gluconic acid, tannic acid, oxalic acid, succinic acid and the like;
3) carrying out organic reduction and growth on a noble metal shell layer: adding a carboxyl reducing agent and a hydroxyl reducing agent, stirring and heating, and reducing and wrapping the noble metal shell layer; further adding a carboxyl hydroxyl reducing agent, and carrying out reduction and coating reaction on the noble metal shell at the temperature of 40-130 ℃ for 2-6 h; the concentration of the shell metal ions is 0.001-0.2 mol/L, and the addition amount is 0.1-10 vt%; the addition amount of the further added carboxyl-hydroxyl reducing agent is 0.1-3 wt.%;
the metal wrapped by the outer shell layer is one or more than one of strong oxidizing ions such as strong oxidizing metals Pt, Ir, Au, Os and the like, and is fully wrapped and aged;
4) aging and growing of crystals: adding a reducing agent, adjusting the pH value, ensuring the slow release of the reducing agent, and performing surface crystal aging growth; adjusting the pH value to carry out surface crystal aging growth reaction at the temperature of 40-130 ℃ for 6-16 h;
further, the protective reducing agent comprises Na2SO3、K2SO3、NaBH4、KBH4、LiAlH4、SnCl2Hydrazine and the like are used for adjusting the pH value to be 7-14, and surface crystals are fully aged and grown;
the addition amount of the protective reducing agent is 0.06-0.4 wt.%; the pH regulator includes ammonia water, NaOH, KOH, and K2CO3、KHCO3、Na2CO3、NaHCO3And one or more than one of inorganic alkali, and the aging growth of the crystal is promoted under the constant-temperature stirring effect.
The metal component carrying capacity of the noble metal alloy shell-core catalyst prepared by the carboxyl and hydroxyl organic matter controlled reduction method is 2-40%, and the mass fraction of the carbon carrier is 60-98%.
5) Product separation and solvent removal treatment: carrying out desolventizing treatment, carrying out separation of suspension by centrifugation to obtain an ultrafine nano product, drying in a vacuum drying oven, and grinding to obtain a catalyst; the vacuum drying temperature is 40-100 ℃, and the time is 10-24 h.
The catalyst is dispersed ultrafine nanoparticles, has high oxygen reduction activity, is simple in preparation method, adjustable in metal component and loading capacity, high in activity and stability, and has important use and research values in the fields of oxygen reduction catalytic systems, electrocatalysis, fuel cells and the like.
Examples
The present invention is described in more detail by way of examples, but the present invention is not limited to the following examples. Unless otherwise specified, "part" means "part by mass".
Example 1
First, 1 wt.% of AgNO was mixed3Diluting the solution in 100mL of deionized water, adding 0.034g of protective surfactant CTAB and 0.7250 mg of supported carbon carrier XC-7250 mg, ultrasonically dispersing for 30min, heating to 105 ℃ in an oil bath, adding 10mL of 1 wt.% sodium citrate, and carrying out carboxyl and hydroxyl reduction at 105 ℃ for 1 h; cooling to 60 deg.C, adding 0.015mol/L H2PtCl63mL, and replacing for 2h at 60 ℃ to prepare a transition layer; mixing ascorbic acid 1.2g, H2PtCl6Dissolving 3mL of the mixture in 25mL of the solvent, mixing, adding the mixture, adjusting the pH to 10 with NaOH, performing carboxyl and hydroxyl reduction at 60 ℃ for 4 hours, and finally adding 0.2g of NaBH4Mixing with 0.06g NaOH mixed solution, stirring and aging overnight; centrifuging and drying to obtain the Ag @ Pt/C (60 ℃) catalyst. The physical characterization of the catalyst is shown in FIGS. 1-3, and the performance of the catalyst is shown in FIG. 4.
FIG. 1 is a low magnification TEM topography of the catalyst prepared in example 1, (a) it can be seen that the Ag @ Pt/C catalyst is ultrafine nanoparticles, uniformly distributed on the surface of the support; (b) the particle size distribution diagram of the catalyst obtained by a statistical method can be seen, the average size of the catalyst is 1.97nm and less than 2nm, the catalyst is an ultrafine nano particle, the maximum size is 2.88, and the minimum size is 1.01.
Figure 2 is an XRD pattern of the catalyst prepared in example 1 of the present invention. As shown in the figure, 2 θ is 24.371 ° is the peak position of the carbon support, the peak position of the catalyst is 2 θ is 38.570 °, 45.047 °, 65.724 °, 79.425 °, which is different from 38.119 °, 44.305 °, 64.452 °, 77.409 ° of Ag, and is different from 39.755 °, 46.234 °, 67.454 °, 81.245 ° of Pt, and the peak position moves to a low angle direction relative to Pt, which indicates that lattice expansion and lattice spacing become large, and Ag is doped in Pt atoms, which generates a significant tensile stress, thereby realizing alloying.
FIG. 3 is an XPS elemental analysis chart of a catalyst prepared in example 1 of the present invention. 93.26% of carbon atom on the surface of the catalyst, 4.89% of O atom, 0.68% of Ag atom and 1.18% of Pt atom; (a) XPS peak profile of C1s, (b) XPS peak profile of O1s, (C) XPS peak profile of Pt4f, and (d) XPS peak profile of Ag.
FIG. 4 is a graph showing the electrochemical properties of the catalyst prepared in example 1 of the present invention. (a) Prepare a CV comparison of Ag @ Pt/C catalyst activity to a commercial 40% Pt/C (JM) catalyst; (b) preparation of an ORR chart of Ag @ Pt/C catalyst vs. commercial 40% Pt/C (JM) catalyst.
Example 2
First, 1 wt.% of AgNO was mixed3Diluting the solution in 100mL of deionized water, adding 0.034g of protective surfactant CTAB and 0.7250 mg of supported carbon carrier XC-7250 mg, ultrasonically dispersing for 30min, heating to 105 ℃ in an oil bath, adding 10mL of 1 wt.% sodium citrate, and carrying out carboxyl and hydroxyl reduction at 105 ℃ for 1 h; maintaining the temperature at 105 ℃, adding 0.015mol/L H2PtCl 63 mL, and replacing for 2H at 105 ℃ to prepare a transition layer; mixing ascorbic acid 1.2g, H2PtCl63mL of the aqueous solution was dissolved in 25mL of the aqueous solution, mixed, added, adjusted to pH 10 with NaOH, and subjected to reduction of carboxyl and hydroxyl groups at 105 ℃ for 4 hours, and finally 0.2g of NaBH was added4Mixing with 0.06g NaOH mixed solution, stirring and aging overnight; centrifuging and drying to obtain the Ag @ Pt/C (60 ℃) catalyst. The catalyst performance is shown in figure 5.
FIG. 5 is a graph showing the electrochemical properties of the catalyst prepared in example 2 of the present invention. (a) Prepare a graph of CV activity for Ag @ Pt/C catalyst versus a commercial 40% Pt/C (JM) catalyst; (b) preparation of an ORR chart of Ag @ Pt/C catalyst vs. commercial 40% Pt/C (JM) catalyst.
Example 3
Electrochemical tests were performed in a three-electrode system to characterize the oxygen reduction activity of the catalyst. The electrolyte solution of the system is 0.1mol L-1HClO of4The counter electrode is a Pt sheet electrode, the reference electrode is a saturated calomel electrode, the cyclic voltammetry test electrolyte solution is saturated by N2, and the test system is Gamry 3000; the ORR test solution was saturated with O2. Preparation of the rotating disk electrode membrane catalysis layer: 40% Pt/C catalyst: 5mg of catalyst, 2.5mL isopropanol, and ultrasonic treatment; 50 mu L of 5 wt% Nafion solution is added, ultrasonic treatment is carried out, and 3.2 mu L of the dispersed slurry is coated on the surface of a rotating disc electrode to be used as a working electrode. Due to the low Ag @ Pt/C catalyst loading, the membrane catalyst layer is prepared: 5mg of catalyst and 2.5mL of isopropanol, and performing ultrasonic treatment; adding 50 mu L of 5 wt% Nafion solution, performing ultrasonic treatment, and coating 6.4 mu L of the dispersed slurry on the surface of a rotating disc electrode to serve as a working electrode.
Industrial applicability
The catalyst has excellent oxygen reduction activity and has important use and research values in the fields of oxygen reduction catalytic systems, electrocatalysis, fuel cells and the like.
The present invention is not limited to the above embodiments, and any changes or substitutions that can be easily made by those skilled in the art within the technical scope of the present invention are also within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (1)

1. A method for preparing a noble metal alloy shell-core catalyst by using an organic reducing agent is characterized in that the noble metal alloy shell-core catalyst comprises a carbon carrier, noble metal alloy shell-core particles are loaded on the carbon carrier, a stable metal transition layer is arranged between shells and cores, the carbon atomic percent of the catalyst is 90-96 at.%, and the atomic percent of an O element is 2-7 at.%; the Pt loading on the surface is 0.1-2 at.%, and the metal particle size is 0.5-5 nm;
the preparation of the catalyst comprises the following steps:
first, 1 wt.% of AgNO was mixed3Diluting the solution in 100mL of deionized water, adding 0.034g of a protective surfactant CTAB and 0.7250 mg of a supported carbon carrier XC-7250 mg, ultrasonically dispersing for 30min, heating the solution to 105 ℃ in an oil bath, adding 10mL of 1 wt.% sodium citrate, and carrying out carboxyl and hydroxyl reduction at the oil bath reduction temperature of 105 ℃ for 1 h; cooling to 60 deg.C, adding 0.015mol/L H2PtCl63mL, and replacing for 2h at 60 ℃ to prepare a transition layer; mixing ascorbic acid 1.2g, H2PtCl63mL, dissolved and mixed in 25mL, and addedAdjusting pH to 10 with NaOH, reducing carboxyl and hydroxyl at 60 deg.C for 4h, and adding 0.2g NaBH4Mixing with 0.06g NaOH mixed solution, stirring and aging overnight; centrifuging and drying to obtain the Ag @ Pt/C catalyst.
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