CN102479956A

CN102479956A - Method for improving chemical stability of proton exchange membrane

Info

Publication number: CN102479956A
Application number: CN2010105668209A
Authority: CN
Inventors: 张华民; 肖少华; 李先锋
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2010-11-30
Filing date: 2010-11-30
Publication date: 2012-05-30

Abstract

The invention provides a method for improving chemical stability of a proton exchange membrane. According to the invention, a perfluorosulfonic acid proton exchange membrane is immersed in a solution containing one or more than two metal ions selected from the group consisting of Zr<4+>, Ca<2+>, Mg<2+> and Al<3+>, and introduction of one metal ion or more than two metal ions selected from the group consisting of Zr<4+>, Ca<2+>, Mg<2+> and Al<3+> into the perfluorosulfonic acid proton exchange membrane is realized through ion exchange. The method provided in the invention improves resistance of the proton exchange membrane to chemical degradation by modifying micro-morphology of ion clusters of the membrane.

Description

A kind of method that improves the PEM chemical stability

Technical field

The present invention relates to a kind of method that improves the ionic exchange film for fuel cell chemical stability, specifically a kind of method of passing through the microscopic appearance of modification PEM ion cluster with the anti-chemical degradation ability of raising film.

Background technology

Proton Exchange Membrane Fuel Cells (PEMFC) is a kind of chemical energy that will be stored in fuel and the oxidant is converted into electric energy through electrochemical reaction a energy conversion device; Have the startup of energy conversion efficiency high and low temperature, specific power and characteristics such as specific energy height, environmental friendliness; Be expected to have broad application prospects in one of alternative power source that becomes fixed power station, vehicle-mounted power source and portable power supply.In the low-carbon economy epoch in future, PEMFC will receive increasing concern as desirable vehicle-mounted power source.Yet the life-span of PEMFC under actual condition is unsatisfactory, is one of major obstacle of restriction PEMFC commercialization process, and wherein the chemical degradation of PEM is one of key factor that influences the PEMFC life-span.

Generally believe that at present the free radical that generates in the battery operation process has caused the chemical degradation of PEM.And the generation of free radical has two kinds of mechanism: 1) oxygen is penetrated into anode and hydrogen reaction generation H through film ₂O ₂2) hydrogen is penetrated into negative electrode and oxygen reaction generation H through film ₂O ₂, perhaps oxygen directly generates H through the two-electron reduction approach ₂O ₂The H that generates ₂O ₂Under catalyst action, decompose and generate free radical.Even also degraded is serious under the open circuit operating mode of high temperature low humidity for the excellent perfluoro sulfonic acid membrane of chemical stability.Therefore, the anti-chemical degradation performance of raising film just becomes an eager and important problem.

Essentially, the method for the anti-chemical degradation performance of raising film mainly contains two types: 1) suppress the generation of free radical as far as possible from the source; 2), free radical just destroyed before attacking film by quencher.Present research focuses mostly in second class methods.People such as Trogadas (Electrochemical and Solid State Letters; 2008.11 (7): p.B113-B116) propose ceria and can be used as renewable free radical quencher; The composite membrane of doping cerium dioxide shows good chemical stability in the accelerated tests (Open Circuit Voltage test, OCV test) in position.MnO ₂P.143-151) and ZrO (Zhao, Journal of Membrane Science, 2010.346 (1): ₂(Xiao, Journal of Power Sources, 2010.195 (24): p.8000-8005) also be used as H ₂O ₂Decomposition catalyst is doped in the film, has improved the chemical stability of film well.But first kind method is studied seldom, and it is significant that the angle of modifying from microscopic appearance goes to improve the chemical stability of film.

Summary of the invention

The object of the present invention is to provide a kind of method that improves the chemical stability of PEM under the battery operation condition through the microscopic appearance of modifying PEM.

Technical scheme of the present invention is following:

A kind of method that improves the PEM chemical stability is soaked in the perfluorinated sulfonic acid PEM and contains Zr ⁴⁺, Ca ²⁺, Mg ²⁺, Al ³⁺In a kind of or solution more than two kinds in, through ion-exchange the part sulfonic acid group is replaced as-SO3M (M=Zr ⁴⁺, Ca ²⁺, Mg ²⁺, Al ³⁺), in the perfluorinated sulfonic acid PEM, introduce Zr ⁴⁺, Ca ²⁺, Mg ²⁺, Al ³⁺In a kind of or metal ion more than two kinds.

Said solution is Zr ⁴⁺, Ca ²⁺, Mg ²⁺, Al ³⁺In a kind of or nitrate solution more than two kinds, Zr in the nitrate solution ⁴⁺, Ca ²⁺, Mg ²⁺Or Al ³⁺Concentration be 0.05-100mmol/L;

In the perfluorinated sulfonic acid PEM, introduce Zr ⁴⁺, Ca ²⁺, Mg ²⁺, Al ³⁺In amount a kind of or metal ion more than two kinds the 3-10% that is sulfonic acid group molal quantity in the perfluorinated sulfonic acid PEM.

Advantage of the present invention and characteristic effect are: 1) through trace metal ion (Zr ⁴⁺, Ca ²⁺, Mg ²⁺, Al ³⁺) modify the composition and the pattern of the ion cluster of perfluoro sulfonic acid membrane, alleviate perfluoro sulfonic acid membrane and cause-SO because of degraded ₃The degradation behavior of H polycondensation and generating-S-O-S-; 2) band trace-SO ₃M (M=Zr ⁴⁺, Ca ²⁺, Mg ²⁺, Al ³⁺) the water absorption of ion cluster of perfluoro sulfonic acid membrane decrease reacting gas (H ₂, O ₂) solvability in ion cluster can reduce, thereby reduce the reacting gas of film infiltration, reduce because reacting gas being penetrated into opposite side generating free radical and the membrane degradation that causes at catalyst surface; 3) method is simple, easy to operate, and trace introducing metal ion is little to the performance impact of film.

Description of drawings

Fig. 1 is Zr ⁴⁺-Nafion212 and comparative example be battery open circuit voltage curve over time in 24h OCV accelerated tests;

Fig. 2 is Zr ⁴⁺The comparison curves of-Nafion212 and the comparative example hydrogen permeate electric current before OCV;

Fig. 3 is Zr ⁴⁺-Nafion212 is at the hydrogen permeate change in current curve of 24h OCV accelerated tests caudacoria;

Fig. 4 is the correlation curve of comparative example hydrogen permeate electric current of film before and after 24h OCV accelerated tests.

Embodiment

Comparative example

Adopt Nafion212 and cathode and anode hot pressing to get three-in-one membrane electrode assembly, carry out activation after the assembled battery, carry out the chemical stability of continuous 24 hours OCV accelerated tests investigation films then; Operating condition is: battery temperature is 80 ℃; The humidification temperature is 64 ℃, and relative humidity is controlled at 50%, and hydrogen and oxygen induction air flow ratio are 40ml/min; Inlet pressure is 0.2MPa, moves 24h continuously.Experimental result shows: find that the OCV rate of decay is 7.6mV/h (Fig. 1), the hydrogen permeate electric current significantly becomes big (Fig. 4).

Embodiment 1

Preparation 1L 0.05mmol/L Zr (NO3) 4 solution immerse 10g perfluoro sulfonic acid membrane (Nafion212) in the solution, take out film behind the 24h and obtain micro-Zr ⁴⁺Type Nafion212 (is called for short Zr ⁴⁺-Nafion212), Zr ⁴⁺Molal quantity be in the perfluorinated sulfonic acid PEM sulfonic acid group molal quantity 20%.140 ℃ of hot pressings get three-in-one membrane electrode assembly, carry out activation after the assembled battery, in the open circuit accelerated tests, investigate the chemical stability of film then; Operating condition is: battery temperature is 80 ℃; The humidification temperature is 64 ℃, and relative humidity is controlled at 50%, and hydrogen and oxygen induction air flow ratio are 40ml/min; Inlet pressure is 0.2MPa, moves 24h continuously.

Experimental result shows: Zr ⁴⁺The open circuit fall off rate of-Nafion212 (OCV rate) obviously descends than comparative example, and OCV rate is 1mV/h (Fig. 1); As shown in Figure 2, Zr ⁴⁺The initial hydrogen impervious electric current of-Nafion212 diminishes than comparative example, and promptly hydrogen diminishes through the absolute magnitude that film is penetrated into opposite side, and the amount that generates free radical because of the reacting gas infiltration will reduce, and the degraded of film is inhibited; The hydrogen permeate electric current does not change basically before and after the OCV as shown in Figure 3, also verifies that the anti-chemical degradation ability of film is greatly improved.

Embodiment 2

Preparation 1L 0.05mmol/L Mg (NO ₃) ₂Solution immerses 10g perfluoro sulfonic acid membrane (Nafion212) in the solution, takes out film behind the 24h and obtains micro Mg ²⁺Type Nafion212 (is called for short Mg ²⁺-Nafion212), Mg ²⁺Molal quantity be in the perfluorinated sulfonic acid PEM sulfonic acid group molal quantity 10%.140 ℃ of hot pressings get three-in-one membrane electrode assembly, carry out activation after the assembled battery, in the open circuit accelerated tests, investigate the chemical stability of film then; Operating condition is: battery temperature is 80 ℃; The humidification temperature is 64 ℃, and relative humidity is controlled at 50%, and hydrogen and oxygen induction air flow ratio are 40ml/min; Inlet pressure is 0.2MPa, moves 24h continuously.

Embodiment 3

Preparation 1L 0.05mmol/L Ca (NO ₃) ₂Solution immerses 10g perfluoro sulfonic acid membrane (Nafion212) in the solution, takes out film behind the 24h and obtains micro-Ca ²⁺Type Nafion212 (is called for short Ca ²⁺-Nafion212), Ca ²⁺Molal quantity be in the perfluorinated sulfonic acid PEM sulfonic acid group molal quantity 10%.140 ℃ of hot pressings get three-in-one membrane electrode assembly, carry out activation after the assembled battery, in the open circuit accelerated tests, investigate the chemical stability of film then; Operating condition is: battery temperature is 80 ℃; The humidification temperature is 64 ℃, and relative humidity is controlled at 50%, and hydrogen and oxygen induction air flow ratio are 40ml/min; Inlet pressure is 0.2MPa, moves 24h continuously.

Embodiment 4

Preparation 1L 0.05mmol/L Al (NO ₃) ₃Solution immerses 10g perfluoro sulfonic acid membrane (Nafion212) in the solution, takes out film behind the 24h and obtains trace of Al ³⁺Type Nafion212 (is called for short Al ³⁺-Nafion212), Al ³⁺Molal quantity be in the perfluorinated sulfonic acid PEM sulfonic acid group molal quantity 15%.140 ℃ of hot pressings get three-in-one membrane electrode assembly, carry out activation after the assembled battery, in the open circuit accelerated tests, investigate the chemical stability of film then; Operating condition is: battery temperature is 80 ℃; The humidification temperature is 64 ℃, and relative humidity is controlled at 50%, and hydrogen and oxygen induction air flow ratio are 40ml/min; Inlet pressure is 0.2MPa, moves 24h continuously.

Claims

1. method that improves the PEM chemical stability is characterized in that:

The perfluorinated sulfonic acid PEM is soaked in contains Zr ⁴⁺, Ca ²⁺, Mg ²⁺, Al ³⁺In a kind of or solution more than two kinds in, in the perfluorinated sulfonic acid PEM, introduce Zr through ion-exchange ⁴⁺, Ca ²⁺, Mg ²⁺, Al ³⁺In a kind of or metal ion more than two kinds.

2. according to the described method of claim 1, it is characterized in that:

Said solution is Zr ⁴⁺, Ca ²⁺, Mg ²⁺, Al ³⁺In a kind of or nitrate solution more than two kinds, Zr in the nitrate solution ⁴⁺, Ca ²⁺, Mg ²⁺Or Al ³⁺Concentration be 0.05-100mmol/L.

3. according to the described method of claim 1, it is characterized in that:

In the perfluorinated sulfonic acid PEM, introduce Zr ⁴⁺, Ca ²⁺, Mg ²⁺, Al ³⁺In amount a kind of or metal ion more than two kinds the 3-20% that is sulfonic acid group molal quantity in the perfluorinated sulfonic acid PEM.