Preparation method of iridium-based catalyst for anode of hydrogen-oxygen fuel cell
阅读说明：本技术 一种氢氧燃料电池阳极铱基催化剂的制备方法 (Preparation method of iridium-based catalyst for anode of hydrogen-oxygen fuel cell ) 是由 陶思成 史瑞祥 谢鑫 于 2018-08-07 设计创作，主要内容包括：本发明提供一种氢氧燃料电池阳极铱基催化剂的制备方法，属于燃料电池技术领域。本发明首先将铱前驱体、功能化碳载体以及柠檬酸钠均匀分散在溶剂中，搅拌一段时间后，将该混合液均匀地平铺在有机聚合物薄膜上，再水浴蒸干；最后通过在还原气氛热处理，制备出颗粒均匀分散的碳载铱基催化剂。本发明大大简化了传统铱基催化剂的制备方法，所制备的催化剂催化活性高、产量大、一致性好、粒径小、高分散，且制备工艺简单，可实现高效低成本催化剂的批量化生产，并广泛应用于氢氧燃料电池。(The invention provides a preparation method of an iridium-based catalyst of an anode of a hydrogen-oxygen fuel cell, belonging to the technical field of fuel cells. Firstly, uniformly dispersing an iridium precursor, a functionalized carbon carrier and sodium citrate in a solvent, stirring for a period of time, uniformly spreading the mixed solution on an organic polymer film, and evaporating in a water bath; finally, the carbon-supported iridium-based catalyst with uniformly dispersed particles is prepared by heat treatment in a reducing atmosphere. The invention greatly simplifies the preparation method of the traditional iridium-based catalyst, and the prepared catalyst has high catalytic activity, high yield, good consistency, small particle size, high dispersion and simple preparation process, can realize the batch production of the catalyst with high efficiency and low cost, and is widely applied to oxyhydrogen fuel cells.)
1. A method for preparing iridium-based catalyst of anode of hydrogen-oxygen fuel cell includes such steps as
(1) Functionalization of carbon supports
Weighing 8 g of commercial Vulcan XC-72 carbon powder in a 500ml round-bottom flask, adding 100-320 ml of concentrated nitric acid, heating and refluxing until boiling begins, reacting for 2-8 h, cooling to room temperature, adding water for dilution, performing suction filtration and washing until the pH value is close to 7, drying, and performing ball milling to obtain functional Vulcan XC-72 carbon powder;
the method is characterized in that:
(2) iridium precursor adsorbed on functionalized carbon
Respectively weighing the functionalized Vulcan XC-72 carbon powder obtained in the step (1), an iridium precursor and sodium citrate according to the mass ratio of the functionalized Vulcan XC-72 carbon powder to the iridium to the sodium citrate of 1: 0.05-2: 0.1-12; firstly, adding functional Vulcan XC-72 carbon powder into deionized water, and performing ultrasonic dispersion for 10-60 minutes to form a uniformly dispersed functional Vulcan XC-72 carbon powder mixed solution, wherein the mass concentration of the functional Vulcan XC-72 carbon powder is 3-100 mg/ml; then sequentially adding an iridium precursor and sodium citrate, stirring for 2-24 hours, transferring the obtained liquid onto a tiled organic polymer film, evaporating by a water bath at 50-80 ℃, and grinding into powder;
(3) preparation of carbon-supported iridium-based catalyst
And (3) carrying out heat treatment on the obtained powder for 1-3 hours at 200-800 ℃ in a mixed atmosphere of reducing gas and inert gas in a volume ratio of 1: 1-1: 20 and a total gas flow rate of 50-200 ml/min, and naturally cooling in the mixed atmosphere. And finally, dispersing the powder prepared in batches in 50-500 ml of deionized water, ultrasonically washing for 5-30 minutes, stirring and washing for 1-4 hours, filtering and washing for 3-10 times, and vacuum drying to obtain the carbon-supported iridium-based catalyst.
2. The method of claim 1, wherein the iridium precursor is selected from the group consisting of chloroiridic acid, sodium chloroiridate and sodium chloroiridate.
3. The method for preparing the iridium-based catalyst of the anode of the hydrogen-oxygen fuel cell according to claim 1, wherein the steps (2) and (3) of the preparation method are as follows:
(2) iridium precursor adsorbed on functionalized carbon
Respectively weighing the functionalized Vulcan XC-72 carbon powder, an iridium precursor and sodium citrate obtained in the step (1) according to the mass ratio of the functionalized Vulcan XC-72 carbon powder to the iridium to the sodium citrate of 1: 0.33: 2; firstly, adding functional Vulcan XC-72 carbon powder (8 g) into deionized water, and ultrasonically dispersing for 30 minutes to form uniformly dispersed functional Vulcan XC-72 carbon powder mixed solution, wherein the mass concentration of the functional Vulcan XC-72 carbon powder is 100 mg/ml; then adding an iridium precursor and sodium citrate in sequence, stirring for 24 hours, transferring the obtained liquid to a flat organic polymer film, evaporating by a water bath at 72 ℃, and grinding into powder.
(3) Preparation of iridium carbon catalyst
The powder obtained above was heat-treated at 500 ℃ for 2 hours in a mixed atmosphere of hydrogen and nitrogen in a volume ratio of 1: 6 and a total gas flow rate of 70 ml/min, and naturally cooled in the mixed atmosphere. And finally, dispersing the powder prepared in batches in 150 ml of deionized water, ultrasonically washing for 10 minutes, stirring and washing for 4 hours, filtering and washing for 4 times, and drying in vacuum to obtain the iridium-carbon catalyst.
4. The method for preparing the iridium-based catalyst of the anode of the hydrogen-oxygen fuel cell according to claim 1, wherein the steps (2) and (3) of the preparation method are as follows:
(2) iridium precursor adsorbed on functionalized carbon
Respectively weighing the functionalized Vulcan XC-72 carbon powder, iridium precursor and sodium citrate obtained in the step (1) according to the mass ratio of the functionalized Vulcan XC-72 carbon powder to iridium to sodium citrate of 1: 0.25: 1.5; firstly, adding functional Vulcan XC-72 carbon powder (0.16 g) into deionized water, and ultrasonically dispersing for 30 minutes to form uniformly dispersed functional Vulcan XC-72 carbon powder mixed liquid, wherein the mass concentration of the functional Vulcan XC-72 carbon powder is 4 mg/ml; then adding an iridium precursor and sodium citrate in sequence, stirring for 24 hours, transferring the obtained liquid to a flat organic polymer film, evaporating by a water bath at 72 ℃, and grinding into powder.
(3) Preparation of iridium carbon catalyst
The powder obtained above was heat-treated at 500 ℃ for 2 hours in a mixed atmosphere of hydrogen and nitrogen in a volume ratio of 1: 6 and a total gas flow rate of 70 ml/min, and naturally cooled in the mixed atmosphere. And finally, dispersing the powder prepared in batches in 150 ml of deionized water, ultrasonically washing for 10 minutes, stirring and washing for 4 hours, filtering and washing for 4 times, and drying in vacuum to obtain the iridium-carbon catalyst.
Technical Field
The invention belongs to the technical field of fuel cells, and particularly relates to a preparation method of an iridium-based catalyst of an anode of a hydrogen-oxygen fuel cell.
Background
The hydrogen-oxygen fuel cell is a device for directly converting chemical energy in hydrogen into electric energy, has the outstanding characteristics of high energy density, high power density, high energy conversion efficiency, no pollution, quick start at room temperature and the like, and is considered to be the best power cell of future electric vehicles. However, the use of a large amount of noble metal platinum as a catalyst in hydrogen-oxygen fuel cells leads to high cost, and restricts the large-scale commercial promotion of the fuel cells. The development of the non-platinum catalyst of the anode of the hydrogen-oxygen fuel cell has important significance for reducing the cost of the fuel cell and realizing the large-scale commercialization of fuel cell automobiles.
The iridium-metal-catalyzed hydrogen oxidation reaction has the characteristics of low overpotential and high reaction rate, is considered to be one of potential platinum replacement catalysts, and is paid much attention by researchers. Literature [ int.j.hydrogen.energy, 2010, 35: 5528-5538 discloses a method for synthesizing IrV/C catalyst by hydrothermal reduction, which comprises the steps of firstly using 120 ℃ ethylene glycol solvent to thermally reduce Ir and V precursors, and then annealing at 200 ℃ in a reducing atmosphere to obtain IrV/C catalyst. Literature [ j.phys.chem.c, 2011, 115: 9894 & 9902 & reports a synthesis method of IrNi/C core-shell structure catalyst, which adopts NaBH4 as a reducing agent metal precursor, and then carries out high-temperature treatment at 600 ℃ in a reducing atmosphere to obtain the IrNi/C core-shell structure catalyst. Chinese invention patent CN101411012A discloses a method for manufacturing a catalyst for a fuel cell, which comprises the steps of forming hydroxides of various metal salts on a conductive carrier by adjusting the pH value, and alloying through two steps of heat treatment to prepare a ternary alloy catalyst containing platinum, base metal and iridium. Literature [ j. mater. chem.a, 2014, 2: 10098-10103 and the Chinese patent CN103331172A disclose a method for preparing a fuel cell Ir-based anode catalyst particle size agent, which comprises the steps of firstly forming nickel-ammonia complex cations by using concentrated ammonia water as a complexing agent, then evaporating to dryness in a water bath to prepare a carbon-supported iridium nickel complex, and then reducing in a hydrogen atmosphere to prepare the carbon-supported IrNi alloy catalyst. Although all the iridium-based catalysts prepared by the method have certain hydrogen oxidation activity, the catalytic performance is still difficult to compare favorably with that of a platinum-based catalyst, and the catalytic activity cannot meet the requirement of practical application of a fuel cell; and the preparation process is complex and tedious, has large pollution, and is difficult to realize green and batch preparation of the catalyst.
Disclosure of Invention
The invention aims to provide a preparation method of an iridium-based catalyst of an anode of a hydrogen-oxygen fuel cell, aiming at the problems of complicated process, high cost, incapability of mass production and insufficient activity of the existing preparation method of the iridium-based catalyst. Firstly, uniformly dispersing an iridium precursor, a functionalized carbon carrier and sodium citrate in a solvent, stirring for a period of time, uniformly distributing the mixed solution on an organic polymer film, and evaporating in a water bath; finally, the carbon-supported iridium-based catalyst with uniformly dispersed particles is prepared by heat treatment in a reducing atmosphere. The invention greatly simplifies the traditional iridium-based catalyst preparation method, and the prepared catalyst has high activity, high yield, good consistency, small particle size and high dispersion, so that the metal utilization rate and the hydrogen oxidation activity are effectively improved, and the bulk production can be realized.
The purpose of the invention is realized as follows: a method for preparing iridium-based catalyst of anode of hydrogen-oxygen fuel cell includes such steps as
(1) Functionalization of carbon supports
Weighing 8 g of commercial Vulcan XC-72 carbon powder in a 500ml round-bottom flask, adding 100-320 ml of concentrated nitric acid, heating and refluxing until boiling begins, reacting for 2-8 h, cooling to room temperature, adding water for dilution, performing suction filtration and washing until the pH value is close to 7, drying, and performing ball milling to obtain the functionalized Vulcan XC-72 carbon powder.
(2) Iridium precursor adsorbed on functionalized carbon
Respectively weighing the functionalized Vulcan XC-72 carbon powder obtained in the step (1), an iridium precursor and sodium citrate according to the mass ratio of the functionalized Vulcan XC-72 carbon powder to the iridium to the sodium citrate of 1: 0.05-2: 0.1-12; firstly, adding functional Vulcan XC-72 carbon powder into deionized water, and performing ultrasonic dispersion for 10-60 minutes to form a uniformly dispersed functional Vulcan XC-72 carbon powder mixed solution, wherein the mass concentration of the functional Vulcan XC-72 carbon powder is 3-100 mg/ml; and then sequentially adding an iridium precursor and sodium citrate, stirring for 2-24 hours, transferring the obtained liquid onto a flat organic polymer film, evaporating by a water bath at 50-80 ℃, and grinding into powder.
Wherein the iridium precursor is one of chloro-iridic acid, sodium chloro-iridate and sodium chloro-iridite.
(3) Preparation of carbon-supported iridium-based catalyst
And (3) carrying out heat treatment on the obtained powder for 1-3 hours at 200-800 ℃ in a mixed atmosphere of reducing gas and inert gas in a volume ratio of 1: 1-1: 20 and a total gas flow rate of 50-200 ml/min, and naturally cooling in the mixed atmosphere. And finally, dispersing the powder prepared in batches in 50-500 ml of deionized water, ultrasonically washing for 5-30 minutes, stirring and washing for 1-4 hours, filtering and washing for 3-10 times, and vacuum drying to obtain the carbon-supported iridium-based catalyst.
After the technical scheme is adopted, the invention mainly has the following advantages:
(1) the invention utilizes the water bath evaporation on the tiled organic polymer film to dry, overcomes the defects of long time and large energy consumption of the water bath evaporation, fully exerts the function of controlling the particle diameter of the formed particles by the sodium citrate, solves the problems of difficult extraction, large loss, easy deliquescence and the like of the evaporation product caused by adding the sodium citrate, and also solves the problems of poor consistency and difficult uniform dispersion of chemical components in batch production, thereby obtaining the ultrafine nanoparticles with high yield, uniform chemical components and uniform distribution, and greatly improving the metal utilization rate and the catalyst activity.
(2) The method has the advantages that alloying, a hydrothermal reduction step, a pH value regulation step and a centrifugal washing step are not needed, the product is directly subjected to water bath evaporation and distillation treatment by reducing gas to synthesize the catalyst, and finally, the catalyst with clean surface, high dispersion and high activity can be obtained by simple cleaning.
(3) The catalyst prepared in batch by the method has no difference in activity with the catalyst prepared in trace, and the front and back purification processes are simple and easy to implement, so the method is suitable for the commercialized low-cost batch production of the iridium-based catalyst.
(4) Compared with the existing commercial platinum-based catalyst, the carbon-supported iridium-based catalyst prepared by the method has high activity comparable to that of the existing commercial platinum-based catalyst, has obvious cost advantage and can effectively reduce the cost of a fuel cell.
The method is simple and easy to implement, safe to operate, low in production cost, excellent in product performance and very suitable for batch production. The carbon-supported iridium-based catalyst prepared by the method has high-efficiency catalytic hydrogen oxidation performance, can replace a platinum-based catalyst to be applied to the field of fuel cells, particularly to a hydrogen anode of a proton exchange membrane fuel cell, and can realize large-scale commercial production of the catalyst.
Drawings
Fig. 1 is a High Resolution Transmission Electron Microscope (HRTEM) image of the iridium carbon catalyst prepared in example 1.
FIG. 2 is a plot of the linear scan of the hydrogen oxidation of the iridium carbon catalyst prepared in example 1 and a commercial Pt/C (20% by weight platinum) catalyst from Jonhson-Matthey corporation, UK, comparative experiment 1. Curve a is a hydrogen oxidation linear scan curve using the iridium carbon catalyst prepared in example 1 as a working electrode, a silver/silver chloride electrode as a reference electrode, a platinum ring as a counter electrode, a hydrogen-saturated 0.1 mol/liter of aqueous chloric acid solution as an electrolyte, and a scan rate of 10 mv/sec. Curve B is a hydrogen oxidation linear scan curve using a commercial Pt/C catalyst from Jonhson-Matthey, uk, as a working electrode, a silver/silver chloride electrode as a reference electrode, a platinum ring as a counter electrode, a hydrogen saturated 0.1 mol/perchloric acid aqueous solution as an electrolyte, and a scan rate of 10 mv/sec. Wherein the iridium loading capacity and the platinum loading capacity on the working electrode are both 5 micrograms, and the rotating speed of the electrode is 1600 revolutions per minute.
FIG. 3 is a plot of the linear scan of hydrogen oxidation for the iridium-carbon catalyst prepared in example 1 and a commercial PtRu/C (20% by mass platinum) catalyst from Jonhson-Matthey corporation, UK,
Fig. 4 is a graph of a hydrogen oxidation linear scan of the iridium carbon catalyst prepared in example 1 and example 2. Curve a is a linear scan curve of hydrogen hydroxide with the iridium carbon catalyst prepared in example 2 as the working electrode, the silver/silver chloride electrode as the reference electrode, the platinum ring as the counter electrode, the hydrogen-saturated 0.1mol/l aqueous solution of potassium hydroxide as the electrolyte, and the scan rate of 10 mv/s. Curve B is a hydrogen hydroxide linear scan curve with the iridium carbon catalyst prepared in example 1 as the working electrode, the silver/silver chloride electrode as the reference electrode, the platinum ring as the counter electrode, the hydrogen-saturated 0.1mol/l aqueous solution of potassium hydroxide as the electrolyte, and the scan rate of 10 mv/sec. Wherein the iridium loading capacity of the working electrode is 5 micrograms, and the rotating speed of the electrode is 1600 revolutions per minute.
Figure 5 is a plot of the hydrogen oxidation linear scan of the iridium carbon catalyst prepared in example 1 and the iridium nickel alloy on carbon catalyst from
Detailed Description
The present invention will be further described with reference to the following specific embodiments.