CN111215056A - Preparation method and application of low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst - Google Patents
Preparation method and application of low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst Download PDFInfo
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- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 94
- 239000001301 oxygen Substances 0.000 title claims abstract description 94
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 94
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- 230000009467 reduction Effects 0.000 title claims abstract description 77
- 239000010411 electrocatalyst Substances 0.000 title claims abstract description 73
- 238000002360 preparation method Methods 0.000 title abstract description 29
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
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- UKVIEHSSVKSQBA-UHFFFAOYSA-N methane;palladium Chemical compound C.[Pd] UKVIEHSSVKSQBA-UHFFFAOYSA-N 0.000 description 1
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- 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
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/44—Palladium
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- B01J35/00—Catalysts, in general, characterised by their form or physical properties
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- B01J35/33—Electric or magnetic properties
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01J35/391—Physical properties of the active metal ingredient
- B01J35/394—Metal dispersion value, e.g. percentage or fraction
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- 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
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- 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
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Abstract
The invention adopts a method that a high molecular template agent and a carbon source precursor are self-assembled to synthesize the hollow polymer ball in a hydrothermal process, and then a simple and convenient double-solvent dipping method is provided to successfully prepare PdCl4 2‑Loaded on a hollow polymer ball, finally placing the reactant in a programmable atmosphere tube furnace, and carbonizing at the high temperature of 900 ℃ by 500 plus materials to obtain the low-load Pd/hollow carbon ball oxygen reduction electrocatalyst (Pd-HCS) which can be used as an efficient ORR electrocatalyst in an alkaline environment. The low-load Pd-HCS oxygen reduction electrocatalyst obtained by the method has higher specific surface area, good conductivity and enough active sites, and shows more excellent oxygen reduction electrocatalytic performance, good stability and excellent activity of resisting methanol poisoning. The preparation method has simple processThe method has low cost and certain universality, and has certain guiding significance for designing and developing a novel fuel cell cathode oxygen reduction electrocatalyst.
Description
Technical Field
The invention belongs to the field of chemical energy materials, particularly relates to preparation of a hollow carbon sphere oxygen reduction electrocatalyst, and particularly relates to a preparation method and application of a low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst for catalyzing reduction of cathode oxygen of a fuel cell into water.
Background
In recent years, due to exhaustion of conventional fossil energy and increasing environmental pollution, research and development of novel efficient, low-cost, and clean and renewable energy conversion and storage technologies, such as fuel cells, zinc-air cells, and water decomposition technologies, are in great demand. Among them, the fuel cell is the most rapidly developed, is considered as the energy star in the 21 st century, can directly convert the chemical energy in the fuel and the oxidant into the electric energy, is not limited by the Carnot cycle, and has the conversion efficiency of more than 60 percent; and the product is water, so that the cleaning agent is high-efficiency and pollution-free.
The electrode of the fuel cell is an electrochemical reaction site where the fuel undergoes an oxidation reaction and the oxidant undergoes a reduction reaction, and the electrode can be mainly divided into two parts, one of which is an Anode (Anode) and the other is a Cathode (Cathode), and the thickness is generally 200-; the structure of the fuel cell is different from that of a plate electrode of a general cell in that the electrode of the fuel cell has a porous structure, so that most of fuel and oxidant (such as oxygen, hydrogen, etc.) can pass through the porous structure. The oxygen reduction reaction generated at the cathode of the fuel cell relates to a multi-electron reaction process, the dynamics is slow, so that the commercialization promotion process of the fuel cell is not stopped, so that the existence of an electrocatalyst is generally needed to greatly improve the oxygen reduction reaction rate of the fuel cell, and the current commonly used commercial electrocatalyst is still a noble metal Pt/C catalyst, but the large-scale use of the fuel cell is limited by the defects of rare metal Pt element, high price, easy poisoning and the like. In order to increase the power density of the fuel cell and reduce the development cost of the fuel cell, it is necessary to not only achieve mass production of key materials such as the electrocatalyst as soon as possible, but also reduce the amount of platinum in the electrocatalyst. In order to reduce the development cost of cathode oxygen reduction electrocatalysts, numerous researchers are devoted to developing and researching novel Pt-based and non-Pt-based electrocatalysts, and the catalytic activity and stability of the catalyst are ensured while the loading capacity of noble metals is reduced.
Pd has very similar properties to Pt (in the same group of the periodic table of elements, with the same fcc crystal structure, similar atomic sizes), and is inexpensive compared to Pt, and its abundance on earth is at least 50 times that of Pt, and thus can be a good substitute for Pt catalysts in fuel cells. However, due to the inherent tendency of metal atoms to migrate and aggregate into nanoparticles, surface energy is reduced by aggregation, with the particle size increasing, directly resulting in a reduction in the activity of the nanoelectrocatalyst. Therefore, fine control of the dispersion of Pd nanoparticles is required to improve their electrocatalytic activity, which is a challenging problem. To solve this problem, a highly conductive carbon material is combined with Pd nanoparticles to achieve a desired uniform dispersion effect, which not only facilitates charge transport, but also provides abundant active sites to immobilize Pd nanoparticles. At present, a carbon carrier material which is commonly used is a carbon black material which has high conductivity, higher specific surface area and low price, and a commercial Pt/C oxygen reduction electrocatalyst is prepared by loading noble metal Pt on the carbon black material. However, as the loading of the catalyst increases, the particle size of the metal particles increases rapidly on the surface of the carbon black, and the catalyst is agglomerated to lower the stability and activity of the catalyst, resulting in waste of precious metals. The novel carbon carrier materials (hollow carbon spheres, mesoporous carbon) have high specific surface area, good conductivity and good corrosion resistance, and become the key point of research.
In recent years, various noble metal/carbon composite materials have received attention from researchers due to their excellent oxygen reduction catalytic activity. For example, the subject group such as Lorenzo designs Pd/mesoporous carbon, Pt/mesoporous carbon, Pd/graphene and Pt/hollow carbon sphere composite materials ((1) Lorenzo periini, Christian duranate, et al, acsappl. mater. interface 2015,7,1170-1179.(2) sabinasmin, yurijo, seungjon jeon. applied surface science,2017,406, 226-234. (3) guanghuiwangetal, naturaterials, 2014,13,293-300), and it was found that a strong interaction force exists between the carbon material and the precious metal, which is helpful for the dispersion of the metal particles and improves the electrocatalytic activity thereof. However, the preparation of the above catalyst has the following problems: (1) various carbon materials need to be pretreated, and amino groups are additionally introduced to anchor metal particles, so that the acting force between the metal particles and a carrier is enhanced, and the dispersity of the Pd nanoparticles is improved; (2) has a certain particle agglomeration phenomenon, and is preparedThe process is complicated, the time consumption is long, the cost is high, and the industrial production is difficult. These problems are mainly due to the metal precursor ions being negatively charged noble metal ions (PtCl) in the same solution4 2-、PdCl4 2-) And a large amount of oxygen-containing functional groups with negative charges exist on the carbon precursor material, and electrostatic repulsive force exists, so that the loaded noble metal nano particles have a certain agglomeration phenomenon. If a simple double-solvent impregnation method is used for replacing single-solvent synthesis, pores have certain capillary action force in two solutions, noble metal ions are adsorbed onto a carbon precursor by the capillary action force, electrostatic repulsion between a negatively charged carboxyl functionalized carbon sphere precursor and negatively charged ions can be overcome, rich oxygen-containing functional groups derived from a triblock copolymer Pluronic cP123, sodium oleate and DA and nitrogen-containing groups derived from HMT are utilized for anchoring and promoting uniform dispersion of Pd nanoparticles in a high-temperature process, and therefore high electrocatalytic activity and atom utilization rate are achieved.
Disclosure of Invention
In view of the above problems, the technical problem to be solved by the present invention is to provide a low-loaded Pd/hollow carbon sphere oxygen reduction electrocatalyst with low cost, high performance and high stability.
In order to solve the technical problems, the invention adopts the technical scheme that:
the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst has a diameter of about 130-180nm and a shell thickness of about 20-40 nm.
Preferably, the diameter is about 150nm, the shell thickness is about 20nm, and the mass fraction of Pd is 1.7%.
The preparation method of the nano material comprises the following steps:
(a) a hydrothermal process: weighing a proper amount of template agent and a carbon source precursor, respectively preparing aqueous solutions A and B, stirring and mixing at room temperature to obtain a micelle solution C, then putting the solution C into a polytetrafluoroethylene reaction kettle, placing the polytetrafluoroethylene reaction kettle into an oven, heating the polytetrafluoroethylene reaction kettle to a specific temperature from room temperature at a certain heating rate, carrying out heat preservation for a period of time, carrying out hydrothermal reaction, then naturally cooling to room temperature, centrifuging at a high rotating speed, taking out a solid at the bottom, washing the solid with deionized water and ethanol for multiple times, and drying the obtained precipitate to obtain a hollow polymer sphere precursor HPS;
(b) and (3) dipping: weighing a certain amount of hollow polymer sphere precursor HPS, dispersing in an organic solvent, performing ultrasonic treatment for a period of time, uniformly stirring to obtain dispersion liquid D, weighing a proper amount of Na2PdCl4Dissolving in deionized water, performing ultrasonic homogenization to obtain a solution E, gradually dripping the solution E into the dispersion D in the stirring process of the dispersion D to obtain a solution F, evaporating under the stirring condition, and then placing in a vacuum drying oven for vacuum drying to obtain a Pd/hollow polymer sphere precursor;
(c) and (3) calcining: and placing the porcelain boat containing the Pd/hollow polymer sphere precursor in a programmable atmosphere tube furnace, raising the temperature to a specific temperature at a certain heating rate, carrying out high-temperature calcination in an inert atmosphere, carrying out heat preservation for a period of time, and then naturally cooling to room temperature to obtain the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst Pd-HCS.
Preferably, in step (a), the templating agent is: the triblock copolymer Pluronic cP123 and sodium oleate are adopted, and the molar ratio of the Pluronic cP123 to the sodium oleate is 1: 16-1: 64.
Preferably, in step (a), the carbon source precursor is: the composite material comprises Hexamethylenetetramine (HMT) and 2, 4-Dihydroxybenzoic Acid (DA), wherein the molar ratio of the hexamethylenetetramine to the 2, 4-dihydroxybenzoic acid is 1: 1-1: 3, and the molar ratio of a triblock copolymer Pluronic cP123 to the Hexamethylenetetramine (HMT) is 1: 60-1: 70.
Preferably, in the step (a), the heating rate is 1-4 ℃/min, the heat preservation temperature is 100-180 ℃, and the heat preservation time is 1-8 h.
Preferably, in step (b), the noble metal salt is: na (Na)2PdCl4The mass ratio of the noble metal salt to the hollow polymer sphere precursor HPS is 1: 10-1: 100, the vacuum drying temperature is 25-80 ℃, and the drying time is 6-48 h.
Preferably, in step (b), the organic solvent used to disperse the hollow polymer sphere precursor HPS is pentane.
Preferably, in the step (c), the heating rate is 1-10 ℃/min, the calcining temperature is 500-900 ℃, and the temperature is kept for 0.5-6 h under the inert atmosphere of nitrogen and argon.
The method for modifying the glassy carbon electrode by the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst comprises the following steps: ultrasonically dispersing a low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst in a Nafion solution to obtain 2mg/mL ink dispersion, uniformly dripping the ink dispersion on a glassy carbon electrode by using a micro syringe, and baking under an infrared lamp, wherein the Nafion solution is a mixed solution of water, isopropanol and Nafion in a volume ratio of 4:1: 0.1.
Compared with the prior art, the invention has the beneficial effects that:
(1) the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst provided by the invention has the advantages of concentrated particle size distribution and uniform shell thickness, is expected to realize stable mass production, and has stable performance when being applied to fuel cell electrode materials.
(2) The low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst Pd nano-particles provided by the invention have good dispersibility, promote the adsorption of oxygen molecules in the oxygen reduction reaction process, reduce the overpotential of the oxygen reduction reaction, can quickly realize the adsorption of oxygen and reduce in an alkaline environment when being applied to the cathode oxygen reduction of a fuel cell, and show excellent electrochemical properties: has a half-wave potential and current density comparable to commercial Pt/C electrocatalysts; and has good stability under long-time cycle test and excellent methanol poisoning resistance.
(3) The invention adopts the hollow carbon spheres as the load matrix, and the hollow carbon spheres have the advantages of good conductivity, larger pore volume, higher specific surface area and the like. The abundant oxygen-containing functional groups derived from the triblock copolymer PluronicP123, sodium oleate and DA and the nitrogen-containing functional groups derived from HMT favour anchoring and promote uniform dispersion of Pd nanoparticles. Due to the synergistic effect between the nitrogen-containing functional group and the oxygen-containing functional group, the aggregation and migration of the Pd nanoparticles are prevented in the pyrolysis process. Therefore, the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst with uniformly distributed Pd nano particles is synthesized.
(4) The Pd nano-particles are successfully loaded on the hollow carbon spheres by adopting a simple double-solvent impregnation method, the double-solvent impregnation method is based on a hydrophobic solvent (pentane) and a hydrophilic solvent (water), the former solution disperses a large amount of HPS and plays a key role in smoothly carrying out the impregnation process, and the latter solution contains a metal precursor and can be adsorbed in pores by the capillary force of pores.
(5) The invention provides a low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst, wherein the mass fraction of Pd is 1.7%, the mass fraction of Pt in commercial Pt/C is 20%, the raw material reserves of the preparation method are rich, the price is relatively low, the preparation process is simple, the obtained low-load Pd-HCS electrocatalyst has the oxygen reduction catalytic performance equivalent to that of the commercial Pt/C, and the low-load Pd-HCS electrocatalyst has certain guiding significance for the commercial application of fuel cells.
Drawings
FIG. 1 is a TEM photograph of low loading Pd/hollow carbon sphere oxygen reduction electrocatalysts prepared at different calcination temperatures in examples 2-4: a is Pd-HCS-500; TEM images with B being Pd-HCS-700 and C being Pd-HCS-900;
FIG. 2 is an XRD diffraction pattern of the hollow carbon sphere nanomaterial (HCS) prepared in example 1 and the low loading Pd/hollow carbon sphere oxygen reduction electrocatalyst in examples 2-4;
FIG. 3 is a linear scan plot of ORR catalytic activity of HCS-700 prepared in example 1, Pd-HCS-700 prepared in example 3, and a commercial Pt/C catalyst;
FIG. 4 is a linear scan plot of ORR catalytic activity for Pd-HCS-500, Pd-HCS-700, and Pd-HCS-900 catalysts prepared in examples 2-4;
FIG. 5 is a cyclic voltammogram of the Pd-HCS-700 modified glassy carbon electrode prepared in example 3 in a 0.1M potassium hydroxide solution containing 1M methanol at a sweep rate of 10 mV/s;
FIG. 6 is a linear plot of ORR catalytic activity of the Pd-HCS-700 catalyst prepared in example 2 after 1, 3500 and 10000 cyclic voltammetry scans;
figure 7 is a linear plot of ORR catalytic activity of commercial Pt/C catalysts after 1, 3500 and 10000 cyclic voltammetry scans.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the present invention is not limited to the examples.
Example 1 preparation of hollow carbon sphere nanomaterial (HCS-700)
In order to compare the performance difference between the Pd-free hollow carbon sphere oxygen reduction electrocatalyst and the low-loaded Pd/hollow carbon sphere oxygen reduction electrocatalyst, a Hollow Carbon Sphere (HCS) was first prepared, and the specific preparation method included the following steps:
(a) a hydrothermal process: 54mg of template Pluronic cP123 and 90mg of sodium oleate were weighed out to prepare aqueous solution A with concentrations of 0.375mmol/L and 12mmol/L, respectively. 231mg of 2, 4-Dihydroxybenzoic Acid (DA) and 88mg of Hexamethylenetetramine (HMT) are weighed out and prepared into aqueous solutions with the concentrations of 20mmol/L and 8.3mmol/L respectively, and the aqueous solutions are fully stirred and dissolved for 30min to obtain a solution B. And then slowly adding the solution A into the solution B in the stirring process, and continuously stirring for 30min to obtain a micelle solution C. And then transferring the solution C into a polytetrafluoroethylene reaction kettle, placing the reaction kettle in an oven, carrying out temperature preservation for 2h at the temperature rising rate of 1 ℃/min to 160 ℃, then naturally cooling to room temperature, centrifuging for 20min at the rotating speed of 10000rpm, repeatedly carrying out deionized water/ethanol cleaning for 3 times, and placing the obtained reddish brown precipitate in a vacuum oven at the temperature of 50 ℃ for drying for 24h to obtain the hollow polymer sphere precursor HPS.
(b) And (3) calcining: placing the ceramic boat containing the hollow polymer ball precursor HPS in a programmable atmosphere tube furnace, and heating to 700 ℃ at the speed of 2 ℃/min in a programmed manner at N2Calcining at high temperature in the atmosphere, keeping the temperature for 3h, and naturally cooling to room temperature to obtain the hollow carbon sphere nano material (HCS-700).
Example 2 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-500)
A preparation method of a low-load Pd/hollow carbon sphere nano material comprises the following steps:
(a) a hydrothermal process: 54mg of template Pluronic cP123 and 90mg of sodium oleate were weighed out to prepare aqueous solution A with concentrations of 0.375mmol/L and 12mmol/L, respectively. 231mg of 2, 4-Dihydroxybenzoic Acid (DA) and 88mg of Hexamethylenetetramine (HMT) are weighed out and prepared into aqueous solutions with the concentrations of 20mmol/L and 8.3mmol/L respectively, and the aqueous solutions are fully stirred and dissolved for 30min to obtain a solution B. And then slowly adding the solution A into the solution B in the stirring process, and continuously stirring for 30min to obtain a micelle solution C. And then transferring the solution C into a polytetrafluoroethylene reaction kettle, placing the reaction kettle in an oven, carrying out temperature preservation for 2h at the temperature rising rate of 1 ℃/min to 160 ℃, then naturally cooling to room temperature, centrifuging for 20min at the rotating speed of 10000rpm, repeatedly carrying out deionized water/ethanol cleaning for 3 times, and placing the obtained reddish brown precipitate in a vacuum oven at the temperature of 50 ℃ for drying for 24h to obtain the hollow polymer sphere precursor HPS.
(b) And (3) dipping: adopting a double-solvent immersion method, weighing 50mgHPS, dispersing in pentane, ultrasonically stirring uniformly to obtain dispersion liquid D, weighing 2mgNa2PdCl4Dissolving in deionized water, and performing ultrasonic treatment to obtain solution E. Gradually dripping the solution E into the solution D in the stirring process of the solution D to obtain a solution F, stirring for 30min, then opening a bottle cap, evaporating at room temperature for 2-24h, and then putting into a vacuum oven, drying at 50 ℃ for 12-48h to obtain the Pd/hollow polymer sphere precursor.
(c) And (3) calcining: placing the ceramic boat containing the Pd/hollow polymer ball precursor in a programmable atmosphere tube furnace, and heating to 500 ℃ at the speed of 2 ℃/min by a program at N2Calcining at high temperature in the atmosphere, preserving the heat for 3 hours, and then naturally cooling to room temperature to obtain the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-500).
Example 3 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-700)
A preparation method of a low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst comprises the following steps:
(a) a hydrothermal process: 54mg of template Pluronic cP123 and 90mg of sodium oleate were weighed out to prepare aqueous solution A with concentrations of 0.375mmol/L and 12mmol/L, respectively. 231mg of 2, 4-Dihydroxybenzoic Acid (DA) and 88mg of Hexamethylenetetramine (HMT) are weighed out and prepared into aqueous solutions with the concentrations of 20mmol/L and 8.3mmol/L respectively, and the aqueous solutions are fully stirred and dissolved for 30min to obtain a solution B. And then slowly adding the solution A into the solution B in the stirring process, and continuously stirring for 30min to obtain a micelle solution C. And then transferring the solution C into a polytetrafluoroethylene reaction kettle, placing the reaction kettle in an oven, carrying out temperature preservation for 2h at the temperature rising rate of 1 ℃/min to 160 ℃, then naturally cooling to room temperature, centrifuging for 20min at the rotating speed of 10000rpm, repeatedly carrying out deionized water/ethanol cleaning for 3 times, and placing the obtained reddish brown precipitate in a vacuum oven at the temperature of 50 ℃ for drying for 24h to obtain the hollow polymer sphere precursor HPS.
(b) And (3) dipping: adopting a double-solvent immersion method, weighing 50mgHPS, dispersing in pentane, ultrasonically stirring uniformly to obtain dispersion liquid D, weighing 2mgNa2PdCl4Dissolving in deionized water, and performing ultrasonic treatment to obtain solution E. Gradually dripping the solution E into the solution D in the stirring process of the solution D to obtain a solution F, stirring for 30min, then opening a bottle cap, evaporating at room temperature for 2-24h, and then putting into a vacuum oven, drying at 50 ℃ for 12-48h to obtain the Pd/hollow polymer sphere precursor.
(c) And (3) calcining: placing the ceramic boat containing the Pd/hollow polymer ball precursor in a programmable atmosphere tube furnace, and heating to 700 ℃ at the speed of 2 ℃/min by a program at the temperature of N2Calcining at high temperature in the atmosphere, preserving the heat for 3 hours, and then naturally cooling to room temperature to obtain the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-700).
Example 4 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-900)
A preparation method of a low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst comprises the following steps:
(a) a hydrothermal process: 54mg of template Pluronic cP123 and 90mg of sodium oleate were weighed out to prepare aqueous solution A with concentrations of 0.375mmol/L and 12mmol/L, respectively. 231mg of 2, 4-Dihydroxybenzoic Acid (DA) and 88mg of Hexamethylenetetramine (HMT) are weighed out and prepared into aqueous solutions with the concentrations of 20mmol/L and 8.3mmol/L respectively, and the aqueous solutions are fully stirred and dissolved for 30min to obtain a solution B. And then slowly adding the solution A into the solution B in the stirring process, and continuously stirring for 30min to obtain a micelle solution C. And then transferring the solution C into a polytetrafluoroethylene reaction kettle, placing the reaction kettle in an oven, carrying out temperature preservation for 2h at the temperature rising rate of 1 ℃/min to 160 ℃, then naturally cooling to room temperature, centrifuging for 20min at the rotating speed of 10000rpm, repeatedly carrying out deionized water/ethanol cleaning for 3 times, and placing the obtained reddish brown precipitate in a vacuum oven at the temperature of 50 ℃ for drying for 24h to obtain the hollow polymer sphere precursor HPS.
(b) And (3) dipping: adopting a double-solvent immersion method, weighing 50mgHPS, dispersing in pentane, ultrasonically stirring uniformly to obtain dispersion liquid D, weighing 2mgNa2PdCl4Dissolving in deionized water, and performing ultrasonic treatment to obtain solution E. Gradually dripping the solution E into the solution D in the stirring process of the solution D to obtain a solution F, stirring for 30min, then opening a bottle cap, evaporating at room temperature for 2-24h, and then putting into a vacuum oven, drying at 50 ℃ for 12-48h to obtain the Pd/hollow polymer sphere precursor.
(c) And (3) calcining: placing the ceramic boat containing the Pd/hollow polymer ball precursor in a programmable atmosphere tube furnace, and heating to 900 ℃ at the speed of 2 ℃/min2Calcining at high temperature in the atmosphere, preserving the heat for 3 hours, and then naturally cooling to room temperature to obtain the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-900).
Example 5 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-5-700)
Samples were prepared in the same manner as in example 3, except that: HPS and Na in double-solvent impregnation process2PdCl4The amount of (c) added.
Example 6 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-6-700)
Samples were prepared in the same manner as in example 3, except that: HPS and Na in double-solvent impregnation process2PdCl4The amount of (c) added.
Example 7 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-7-700)
Samples were prepared in the same manner as in example 3, except that: HPS and Na in double-solvent impregnation process2PdCl4The amount of (c) added.
Example 8 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-8-700)
In the same manner as in example 3The samples were prepared except that: HPS and Na in double-solvent impregnation process2PdCl4The amount of (c) added.
Example 9 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-9-700)
Samples were prepared in the same manner as in example 3, except that: HPS and Na in double-solvent impregnation process2PdCl4The amount of (c) added.
Example 10 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-10-700)
Samples were prepared in the same manner as in example 3, except that: HPS and Na in double-solvent impregnation process2PdCl4The amount of (c) added.
Example 11 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-11-700)
Samples were prepared in the same manner as in example 3, except that: HPS and Na in double-solvent impregnation process2PdCl4The amount of (c) added.
Example 12 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-12-700)
Samples were prepared in the same manner as in example 3, except that: HPS and Na in double-solvent impregnation process2PdCl4The amount of (c) added.
Example 13 preparation of Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst (Pd-HCS-13-700)
Samples were prepared in the same manner as in example 3, except that: HPS and Na in double-solvent impregnation process2PdCl4The amount of (c) added.
Table 1 shows Pluronic cP123, sodium oleate, Hexamethylenetetramine (HMT), 2, 4-dihydroxybenzoic acid, HPS, Na from examples 1-132PdCl4Summary of the amounts added and calcination temperatures.
TABLE 1
Example 14 method for modifying glassy carbon electrode with low Pd/hollow carbon sphere oxygen reduction electrocatalyst
Ultrasonically dispersing the prepared low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst catalyst in a Nafion solution to obtain 2mg/mL ink dispersion liquid, wherein the Nafion solution is a mixed solution of water, isopropanol and Nafion in a volume ratio of 4:1:0.1, uniformly dripping the mixed solution on a glassy carbon electrode by using a micro-syringe, and baking under an infrared lamp to obtain the catalyst modified electrode.
Example 15 test of oxygen reduction catalytic reaction Performance of a glassy carbon electrode modified by a Low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst
In 0.1MKOH electrolyte solution, a three-electrode system is adopted to carry out electrochemical test on the catalyst, a glassy carbon electrode modified by a low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst is taken as a working electrode, a saturated Ag/AgCl electrode is taken as a reference electrode, a Pt wire is taken as a counter electrode, and an Shanghai Hua CHI-842D electrochemical workstation and a Japanese ALSRRDE-3A rotating disc device are adopted to carry out oxygen reduction catalytic reaction performance test on the catalyst modified electrode. The oxygen reduction catalytic activity was tested in a 0.1m koh solution saturated with oxygen.
The specific operation is as follows: at the constant temperature of 25 ℃, introducing oxygen into the electrolyte for about 30min in advance to saturate the oxygen in the solution, and then scanning an oxygen reduction polarization curve from high potential 0V to low potential-0.5V at a scanning rate of 10 mV/s. The electrode modified by the hollow carbon sphere or the glassy carbon electrode modified by the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst, which is obtained by the invention, is placed in an oxygen-saturated 0.1M potassium hydroxide solution to carry out a cathode oxygen reduction reaction test of a fuel cell, and the activity parameters for representing the oxygen reduction reaction comprise the initial potential, half-wave potential and limiting current density of the oxygen reduction reaction.
Example 16 ICP Mass fraction test
Firstly carrying out acid dissolution digestion on a Pd-HCS-700 catalyst sample, then using a 5% nitric acid solution to fix the volume to 20mL, filtering, taking 10mL solution to dilute to 100mL, and carrying out ICP-OES: agilent725 from Agilent, USA tests to obtain the Pd content in the solution.
FIG. 1 is a TEM photograph of the low-loaded Pd/hollow carbon sphere oxygen reduction electrocatalyst prepared at different calcination temperatures in examples 2-4, and it can be seen from FIG. 1 that the three low-loaded Pd/hollow carbon spheres prepared in examples 2-4 have uniform size, the size range is about 130-180nm in diameter, the shell thickness is about 20-40nm, and it can be seen from B that the Pd-HCS-700 nano carbon sphere is about 150nm in diameter, and the shell thickness is about 20 nm. FIG. 2 is an XRD diffraction pattern of the four carbon sphere nano-materials prepared in examples 1-4, and it can be seen from the figure that at 500 ℃, the Pd-HCS-500 catalyst exists mainly in the form of PdO, when the temperature rises to 700 ℃ and 900 ℃, the PdO is converted into Pd elementary substance, and the existence of Pd is favorable for promoting the occurrence of ORR reaction.
To compare the difference in the noble metal content between the low-loaded Pd/hollow carbon sphere oxygen reduction electrocatalyst prepared according to the present invention and the commercial Pt/C electrocatalyst, the Pd-HCS-700 catalyst prepared in example 3 was subjected to the ICP test, and the mass fraction of Pd in the Pd-HCS-700 was 1.7%, while the mass fraction of Pt in the commercial Pt/C was 20%.
FIG. 3 shows the results of the ORR catalytic activity tests for Pd-HCS-700, HCS-700 and commercial Pt/C catalysts. As can be seen from fig. 3, the modified electrode of the obtained Pd-HCS-700 catalyst has optimal catalytic activity for oxygen reduction, with a half-wave potential of 0.802V (vs. rhe), which is comparable to the performance of a commercial Pt/C catalyst with a half-wave potential of 0.804V (vs. rhe), and is of great significance for promoting the commercialization process of fuel cells.
FIG. 4 is a linear scanning curve of ORR catalytic activities of Pd-HCS-500, Pd-HCS-700 and Pd-HCS-900 catalysts, and it can be seen from FIG. 4 that the oxygen reduction catalytic activity of Pd-HCS-500 is low, while the oxygen reduction catalytic activities of Pd-HCS-700 and Pd-HCS-900 are high, and it can be seen from the XRD diffraction pattern in FIG. 2 that Pd-HCS-500 exists mainly in the form of PdO, and PdO in Pd-HCS-700 and Pd-HCS-900 is converted into Pd, so that the catalytic activity is high.
Fig. 5 is a cyclic voltammogram of the Pd-HCS-700 catalyst modified glassy carbon electrode prepared in example 3 in 0.1M potassium hydroxide solution containing 1M methanol, and it can be seen from the cyclic voltammogram that the modified electrode of the Pd-HCS-700 catalyst obtained in example 2 has no obvious methanol oxidation peak after 1M methanol is added, and the oxygen reduction reaction peak is not substantially shifted negatively, which indicates that the low-loading Pd/hollow carbon sphere oxygen reduction electrocatalyst prepared by us has good methanol poisoning resistance.
FIGS. 6 and 7 are linear plots of ORR catalytic activity after 1, 3500 and 10000 cyclic voltammetry scans for Pd-HCS-700 and commercial Pt/C catalysts, respectively. It can be seen from the figure that the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst Pd-HCS-700 prepared in example 3 has no significant change in initial potential and half-wave potential after 10000 cycles of cycle, while the commercial Pt/C catalyst has significant negative shift in initial potential and half-wave potential after 10000 cycles of cycle, which indicates that the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst prepared by us has good stability.
Combining the above examples and test results, the low-loading Pd/hollow carbon sphere oxygen reduction electrocatalyst provided by the invention has uniform outer diameter and wall thickness and narrow particle size distribution, has equivalent oxygen reduction catalytic activity compared with commercial Pt/C catalyst, but has higher methanol poisoning resistance and stability than commercial Pt/C catalyst. In addition, the preparation process is simple, the mass fraction of the metal in the obtained low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst is much lower than that of a commercial Pt/C catalyst, so that the preparation and application costs of the catalyst are undoubtedly greatly reduced, and the preparation method has an immeasurable promoting effect on the popularization and application of fuel cells.
While there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be understood by those skilled in the art that the invention is not limited by the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.
Claims (10)
1. A low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst is characterized in that: the diameter is about 130-180nm, and the shell thickness is about 20-40 nm.
2. The low loading Pd/hollow carbon sphere oxygen reduction electrocatalyst according to claim 1, characterized in that: the diameter is about 150nm, the shell thickness is about 20nm, and the mass fraction of Pd is 1.7%.
3. A method for preparing a low-loaded Pd/hollow carbon sphere oxygen reduction electrocatalyst according to claim 1, characterized by comprising the steps of:
(a) a hydrothermal process: weighing a proper amount of template agent and a carbon source precursor, respectively preparing aqueous solutions A and B, stirring and mixing at room temperature to obtain a micelle solution C, then putting the solution C into a polytetrafluoroethylene reaction kettle, placing the polytetrafluoroethylene reaction kettle into an oven, heating the polytetrafluoroethylene reaction kettle to a specific temperature from room temperature at a certain heating rate, carrying out heat preservation for a period of time, carrying out hydrothermal reaction, then naturally cooling to room temperature, centrifuging at a high rotating speed, taking out a solid at the bottom, washing the solid with deionized water and ethanol for multiple times, and drying the obtained precipitate to obtain a hollow polymer sphere precursor HPS;
(b) and (3) dipping: weighing a certain amount of hollow polymer sphere precursor HPS, dispersing in an organic solvent, performing ultrasonic treatment for a period of time, uniformly stirring to obtain dispersion liquid D, weighing a proper amount of Na2PdCl4Dissolving in deionized water, performing ultrasonic homogenization to obtain a solution E, gradually dripping the solution E into the dispersion D in the stirring process of the dispersion D to obtain a solution F, evaporating under the stirring condition, and then placing in a vacuum drying oven for vacuum drying to obtain a Pd/hollow polymer sphere precursor;
(c) and (3) calcining: and placing the porcelain boat containing the Pd/hollow polymer sphere precursor in a programmable atmosphere tube furnace, raising the temperature to a specific temperature at a certain heating rate, carrying out high-temperature calcination in an inert atmosphere, carrying out heat preservation for a period of time, and then naturally cooling to room temperature to obtain the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst Pd-HCS.
4. The method for preparing the low-loading Pd/hollow carbon sphere oxygen reduction electrocatalyst according to claim 3, characterized in that: in step (a), the templating agent is: the triblock copolymer Pluronic P123 and sodium oleate are adopted, and the molar ratio of the Pluronic P123 to the sodium oleate is 1: 16-1: 64.
5. The method for preparing the low-loading Pd/hollow carbon sphere oxygen reduction electrocatalyst according to claim 3, characterized in that: in step (a), the carbon source precursor is: the composite material comprises Hexamethylenetetramine (HMT) and 2, 4-Dihydroxybenzoic Acid (DA), wherein the molar ratio of the hexamethylenetetramine to the 2, 4-dihydroxybenzoic acid is 1: 1-1: 3, and the molar ratio of a triblock copolymer Pluronic P123 to the Hexamethylenetetramine (HMT) is 1: 60-1: 70.
6. The method for preparing the low-loading Pd/hollow carbon sphere oxygen reduction electrocatalyst according to claim 3, characterized in that: in the step (a), the heating rate is 1-4 ℃/min, the heat preservation temperature is 100-180 ℃, and the heat preservation time is 1-8 h.
7. The method for preparing the low-loading Pd/hollow carbon sphere oxygen reduction electrocatalyst according to claim 3, characterized in that: in step (b), the noble metal salt is: na (Na)2PdCl4The mass ratio of the noble metal salt to the hollow polymer sphere precursor HPS is 1: 10-1: 100, the vacuum drying temperature is 25-80 ℃, and the drying time is 6-48 h.
8. The method for preparing the low-loading Pd/hollow carbon sphere oxygen reduction electrocatalyst according to claim 3, characterized in that: in step (b), the organic solvent used to disperse the hollow polymer sphere precursor HPS is pentane.
9. The method for preparing a low-loading Pd/hollow carbon sphere oxygen reduction electrocatalyst according to any one of claims 2 to 8, wherein: in the step (c), the heating rate is 1-10 ℃/min, the calcining temperature is 500-900 ℃, and the temperature is kept for 0.5-6 h under the inert atmosphere of nitrogen and argon.
10. The method for modifying the glassy carbon electrode by the low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst according to claim 1, characterized by comprising the steps of: ultrasonically dispersing a low-load Pd/hollow carbon sphere oxygen reduction electrocatalyst in a Nafion solution to obtain 2mg/mL ink dispersion, uniformly dripping the ink dispersion on a glassy carbon electrode by using a micro syringe, and baking under an infrared lamp, wherein the Nafion solution is a mixed solution of water, isopropanol and Nafion in a volume ratio of 4:1: 0.1.
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| CN111729680A (en) * | 2020-06-18 | 2020-10-02 | 同济大学 | High-efficiency bifunctional oxygen electrocatalyst with heterostructure and preparation and application thereof |
| CN113649004A (en) * | 2021-07-07 | 2021-11-16 | 中国科学院合肥物质科学研究院 | Hollow carbon sphere loaded metal particle catalyst and preparation method and application thereof |
| CN113649004B (en) * | 2021-07-07 | 2023-10-13 | 中国科学院合肥物质科学研究院 | Hollow carbon sphere supported metal particle catalyst and preparation method and application thereof |
| CN113611887A (en) * | 2021-08-04 | 2021-11-05 | 北京航空航天大学 | Preparation method of low-platinum-loading carbon corrosion-resistant fuel cell catalyst |
| CN113611887B (en) * | 2021-08-04 | 2023-03-31 | 北京航空航天大学 | Preparation method of low-platinum-loading carbon corrosion-resistant fuel cell catalyst |
| CN114050281A (en) * | 2021-11-02 | 2022-02-15 | 湖北大学 | Hollow carbon nanosphere composite catalyst and preparation method and application thereof |
| CN114050281B (en) * | 2021-11-02 | 2023-12-15 | 湖北大学 | Hollow carbon nano sphere composite catalyst and preparation method and application thereof |
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