CN100344021C

CN100344021C - Production of platinum/carbon catalyst from inorganic glue

Info

Publication number: CN100344021C
Application number: CNB2005100148245A
Authority: CN
Inventors: 田建华; 徐燕; 单忠强
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2005-08-23
Filing date: 2005-08-23
Publication date: 2007-10-17
Anticipated expiration: 2025-08-23
Also published as: CN1747208A

Abstract

The present invention relates to a method for preparing the inorganic colloid of a platinum / carbon catalyst, which comprises the following steps: 1) solid NaHSO3 is added in H2 PtCl6 water solution which contains 2.0 to 4.0g. L<-1> of Pt, the H2 PtCl6 water solution and the NaHSO3 are stirred under room temperature to react, and an intermediate body H3 Pt (SO3) 2OH is generated; 2) the pH value of a system is adjusted to be 4.8 to 5.5 by alkali water solution, H2 O2 is added in drops to form PtO2 colloid solution which contains 0.5 to 1.0 g. L<-1> of Pt, and alkali water solution is added in drops in the process of system reaction to control the pH value range; 3) carbon black is added in the PtO2 colloid solution to be fully mixed; 4) formaldehyde water solution is added under the condition of continuous stir so that PtO2 is fully reduced to be Pt, 5) solution is filtered, and the solution is washed for many times by deionized water of which the temperature is 50 DEG C to 100 DEG C to remove Cl<-> ions; 6) the solution is washed once again by absolute alcohol, and then the solution is dried under the protection of nitrogen; or the solution is directly dried by vacuum after the step 5) is completed. The added quantity of the solid NaHSO3 is that the mol ratio of H2 PtCl6 to the NaHSO3 is 1: 3 to 25. The mass percent concentration of the formalin is 5% to 12%, the reduction reaction time is from 1.5 hours to 4 hours, and the reduction reaction is carried out at the temperature of 30 DEG C to 50 DEG C. The prepared Pt/C catalyst has the characteristics of high Pt carrying capacity, small grain diameter, good dispersibility and uniform grain size distribution.

Description

The inorganic colloid method of preparation platinum/C catalyst

Technical field

The present invention relates to the Proton Exchange Membrane Fuel Cells technical field, particularly a kind of inorganic colloid method for preparing platinum/C catalyst.

Background technology

Fuel cell is a kind of efficient, eco-friendly Blast Furnace Top Gas Recovery Turbine Unit (TRT), and the chemical energy that it directly will be stored in fuel and the oxidant is converted into electric energy.In today that environment and the energy receive much concern, the research and development of fuel cell more and more are subjected to the attention of national governments.

Proton Exchange Membrane Fuel Cells (Proton Exchange Membrane Fuel Cell PEMFC) has the energy conversion efficiency height, and specific energy is big, start rapidly and series of advantages such as environmental friendliness, and be following most effective and one of the generation technology that cleans most.Membrane electrode (Membrane ﹠amp; Electrode Assembly is the parts of PEMFC most critical MEA), is the core that the PEMFC electrochemical reaction can efficiently be carried out, and membrane electrode is made up of gas diffusion layers, catalyst layer and proton exchange membrane usually.General carbon paper or the carbon cloth of handling through polytetrafluoroethylene (PTFE) that adopt of gas diffusion layers.Eelctro-catalyst adopts load type platinum/carbon (Pt/C) or platinum-ruthenium/carbon (Pt-Ru/C), and it is present hydrogen/oxygen (H ₂/ O ₂) or hydrogen/air (H ₂/ air) the first-selected high activity eelctro-catalyst of PEMFC.The general employing of proton exchange membrane has the perfluorinated sulfonic acid type proton exchange membrane (as the Nafion series membranes of du pont company) of high proton conductivity.

Eelctro-catalyst is to make among the PEMFC fuel and oxidant finish oxidation and reduction reaction conditio sune qua non respectively.Up to now, for being the PEMFC of fuel with hydrogen, it is the highest that Pt remains catalytic activity, the eelctro-catalyst that performance is the most stable.Under the PEMFC environment, the hydrogen of Pt catalysis, oxygen electrode process are as follows:

H ₂+Pt→2Pt-H→2H ⁺+Pt+2e ^-

O ₂+2e ^-+Pt→2Pt-O+2e ^-→2OH ^-+Pt

Because the resource and the price problem of precious metals pt, PEMFC generally adopts support type Pt/C catalyst, is about to metal Pt particulate load on the conductive carbon black surface.In order to satisfy the requirement of the big current work of PEMFC, in the used Pt/C catalyst carrying capacity of Pt up to 20%～40%, and in order to obtain high Pt utilance, require in the catalyst particle of Pt tiny, be evenly distributed and do not have agglomeration.

Traditional Pt/C method for preparing catalyst mainly contains immersion reduction method, ion-exchange, B  nnemann method, intercalation compound synthetic method and organic colloid method etc., prepare the Pt/C catalyst with these conventional methods and have a lot of problems: the Pt/C catalyst Pt grain diameter such as immersion reduction method and ion-exchange preparation is bigger, and the Pt particle is reunited easily; Intercalation compound synthetic method and B  nnemann method cost height, reaction condition are comparatively harsh, the preparation process complexity, and also impurity content is higher relatively in the product; Organic colloid method process conditions are restive, the product separation difficulty.In order to address the above problem, many in recent years researchers improve conventional method on the one hand, as improved liquid deposition reducing process and polyalcohol method on the immersion reduction method basis, and development on the basis of immersion reduction method and the solid reaction process that comes etc.; Utilize some new technologies and new method on the other hand, as microemulsion method, microwave method and vacuum sputtering etc.Since the preparation method of eelctro-catalyst and the structure that preparation technology determines eelctro-catalyst, and then influence its performance, thereby the research of Pt/C method for preparing catalyst and technology is the research and development focus in Proton Exchange Membrane Fuel Cells field in recent years always.

Summary of the invention

The present invention proposes a kind of inorganic colloid method for preparing platinum/C catalyst, and step is as follows:

1) be 2.0～4.0gL at Pt content ^-1H ₂PtCl ₆In the aqueous solution, middle adding solid NaHSO ₃, addition is H ₂PtCl ₆With NaHSO ₃Mol ratio 1: 3～25, stirring reaction under the room temperature generates intermediate H ₃Pt (SO ₃) ₂OH;

2) the pH value of using the alkaline aqueous solution regulation system drips H then 4.8～5.5 ₂O ₂, form Pt content at 0.5～1.0gL ^-1PtO ₂Colloidal solution, and in the system course of reaction, drip alkaline aqueous solution control pH value scope;

3) carbon black is joined PtO ₂It is fully mixed.

4) under continuous stirring condition, add formalin, make PtO ₂Fully be reduced into Pt.The mass percent concentration of formalin is 5%～12%, and the reduction reaction time is 1.5～4 hours, carries out under 30～50 ℃.

5) solution filters, and repeatedly washs with 50 ℃～100 ℃ deionized waters and removes Cl ^-Ion.

6) wash once more with absolute ethyl alcohol, dry under nitrogen protection then; Or above-mentioned steps 5) finish after directly vacuumize.

Described alkaline aqueous solution is NaOH or Na ₂CO ₃The aqueous solution.

Described carbon black fully stirs immersion with isopropyl alcohol and deionized water mixed solution before using, or the preceding heat treatment 20～40 minutes under 500～650 ℃ of nitrogen environments of carbon black use.

Use ultrasonic concussion fully to mix in the described step 3).

The present invention adopts the inorganic colloid legal system to be equipped with the new method of Pt/C catalyst, and this Pt/C catalyst has high electro catalytic activity to the hydrogen and the oxygen electrochemical reaction of carrying out in the fuel cell especially.Prepared Pt/C catalyst has that Pt carrying capacity height, particle diameter are little, the characteristics of good dispersion and even particle size distribution.As Fig. 1 and Fig. 2 is that (black particles is the Pt particle to transmission electron microscope on the photo for Transmission ElectronMicroscope, the design sketch according to the Pt/C catalyst of the present invention's preparation that TEM) characterizes.Instrument adopts TECNAIG2F-20 type field, Dutch Philip transmission electron microscope.The Pt/C catalyst (Fig. 1 and Fig. 2) of the present invention's preparation is through atomic absorption spectroscopy determination, and the content of Pt is respectively 19.4% and 19.5% mass fraction.

Description of drawings

Fig. 1: embodiment 1Pt/C catalyst transmission electron microscope picture;

Fig. 2: embodiment 2Pt/C catalyst transmission electron microscope picture.

Embodiment

Embodiment 1

1. getting 10mL Pt content is 2.38gL ^-1H ₂PtCl ₆Add 0.3g solid NaHSO in the solution ₃, stirring reaction under the room temperature.

2. use deionized water 20ml dilute solution, the pH value of the NaOH solution regulation system of usefulness 1mol/L drips the 30%H of 1ml then 5.0～5.4 then ₂O ₂, reaction generates PtO ₂Colloid.During reaction is carried out, splash into 5%NaOH solution continuously and keep the pH value of system 5.0～5.4.

3. 95mg carbon black (commercially available Vulcan XC-72) is added 5ml distilled water and 5ml isopropyl alcohol sonic oscillation 20min, join PtO again ₂In the colloidal solution, ultrasonic concussion 20 minutes, 6% formalin of adding 18ml under continuous mechanical agitation condition makes PtO then ₂Fully be reduced into Pt, reaction temperature is 50 ℃, 3 hours reaction time.

4. solution filters, and repeatedly washs with 80 ℃ of deionized waters and removes Cl ^-Behind the ion, direct 80 ℃ of vacuumizes 3 hours.

Implementation result is seen accompanying drawing 1.

Embodiment 2

1. getting 12mL Pt content is 4.0gL ^-1H ₂PtCl ₆Add 0.45g solid NaHSO in the solution ₃, stirring reaction under the room temperature.

2. use deionized water 50ml dilute solution, use the Na of 0.6mol/L then ₂CO ₃The pH value of solution regulation system drips the 30%H of 2ml then 4.8～5.2 ₂O ₂, reaction generates PtO ₂Colloid.During reaction is carried out, splash into the Na of 0.6mol/L continuously ₂CO ₃Solution keeps the pH value of system 4.8～5.2.

3. with 190mg carbon black (Vulcan XC-72) heat treatment 30 minutes under 600 ℃ of nitrogen environments.

4. the carbon black of handling well is joined PtO ₂In the colloidal solution, ultrasonic concussion 30 minutes, 10% formalin of adding 25ml under continuous mechanical agitation condition makes PtO then ₂Fully be reduced into Pt, reaction temperature is 45 ℃, 3 hours reaction time.

5. solution filters, and repeatedly washs with 80 ℃ of deionized waters and removes Cl ^-Behind the ion, use absolute ethanol washing, then 70 ℃ of dryings in nitrogen atmosphere.

Implementation result is seen accompanying drawing 2.

The present invention's method open and that disclose can be by using for reference this paper disclosure.Although method of the present invention is described by preferred embodiment, but those skilled in the art obviously can change method as herein described in not breaking away from content of the present invention, spirit and scope, more particularly, the replacement that all are similar and change apparent to those skilled in the artly, they are regarded as being included in spirit of the present invention, scope and the content.

Claims

1. inorganic colloid method for preparing platinum/C catalyst, step is as follows:

1) be 2.0～4.0gL at Pt content ^-1H ₂PtCl ₆In the aqueous solution, add solid NaHSO ₃, addition is H ₂PtCl ₆With NaHSO ₃Mol ratio 1: 3～25, stirring reaction under the room temperature generates intermediate H ₃Pt (SO ₃) ₂OH;

2) the pH value of using the alkaline aqueous solution regulation system drips H then 4.8～5.5 ₂O ₂, form Pt content at 0.5～1.0gL ^-1PtO ₂Colloidal solution, and in the system course of reaction, drip alkaline aqueous solution control pH value in 4.8～5.5 scopes;

3) carbon black is joined PtO ₂It is fully mixed;

4) under continuous stirring condition, add formalin, make PtO ₂Fully be reduced into Pt.The concentration of formalin is 5%～12% (mass percent), and the reduction reaction time is 1.5～4 hours, carries out under 30-50 ℃;

5) solution filters, and repeatedly washs with 50 ℃ of-100 ℃ of deionized waters and removes Cl ^-Ion;

2. a kind of inorganic colloid method for preparing platinum/C catalyst as claimed in claim 1 is characterized in that described alkaline aqueous solution is NaOH or Na ₂CO ₃The aqueous solution.

3. a kind of inorganic colloid method for preparing platinum/C catalyst as claimed in claim 1 is characterized in that fully stirring immersion with isopropyl alcohol and deionized water mixed solution before described carbon black uses.

4. a kind of inorganic colloid method for preparing platinum/C catalyst as claimed in claim 1, it is characterized in that described carbon black use before heat treatment 20～40 minutes under 500-650 ℃ of nitrogen environment.

5. a kind of inorganic colloid method for preparing platinum/C catalyst as claimed in claim 1 is characterized in that using in the described step 3) ultrasonic concussion fully to mix.