RU2336604C1 - Method of producing proton-conducting polymer membranes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to technology of producing proton-conducting polymer membranes and can be used in hydrogen power engineering and in production of hard-polymer fuel elements. Method of producing membranes includes modification of films from polybenzimidazols by hydrated acid zirconium oxide, or hydrated silicon oxide. Then doping of these films with orthophosphoric acid is performed. Proton-conductivity of polymer membranes reaches 10^-3 m/cm at room temperature, and increases to 10^-1 m/cm at temperature 160°C.

EFFECT: elaboration of method of producing polymer membranes with higher proton-conductivity.

5 ex

Description

The invention relates to hydrogen energy and fuel cells, in particular to methods for producing proton-conducting polymer membranes used in solid polymer fuel cells.

Known methods for producing perfluorinated membranes of the type "Nafion", "Flemion" based on copolymers of tetrafluoroethylene with perfluorinated vinyl esters [1, 2, 3]. The disadvantages of the above methods is to obtain membranes with a high cost, the need to maintain high humidity to work in a fuel cell, as well as their tendency to degradation at temperatures above 100 ° C.

It is also known that finely dispersed hydrated zirconium acid phosphate [4, 5] and hydrated zirconium oxide have high ionic conductivity [6, 7].

The closest analogue is a method for producing polymer proton-conducting membranes based on polybenzimidazoles with a heteropoly acid and subsequent treatment with phosphoric acid [8]. However, the disadvantages of this method are the relatively low conductivity, leaching of phosphoric acid at high humidity and a decrease in ionic conductivity.

The purpose of the invention is to improve the proton conductivity of membranes based on polybenzimidazoles (PBI) and to increase the stability of this property in a humid atmosphere.

This goal is achieved by the development of polymer membranes based on polybenzimidazoles and their modification with acid zirconium phosphate, or hydrated zirconium oxide, or silicon oxide, followed by doping the obtained composites with phosphoric acid.

The method includes modifying films of polybenzimidazoles with acid zirconium phosphate or hydrated zirconia or hydrated silica and doping these films with phosphoric acid. The proton conductivity of polymer membranes at room temperature reaches 10 ⁻³ S / cm and increases to 10 ⁻¹ S / cm at a temperature of 160 ° C.

The introduction of zirconium acid phosphate into the polybenzimidazole polymer matrix was carried out by alternating the treatment of the initial membrane with phosphoric acid and subsequent processing of the membrane in solutions of zirconium propoxide or zirconium oxochloride. Hydrated zirconium oxide was introduced by hydrolysis of zirconium oxochloride with sodium hydroxide inside the membrane matrix or by hydrolysis of zirconium propoxide with water inside the membrane matrix. The introduction of silicon oxide was carried out by hydrolysis of tetraethoxysilane (TEOS) with water inside the membrane matrix.

The proposed method for producing proton-conducting membranes has the following advantages:

- the simplicity of the technology for producing composite films

- developed membranes are characterized by high thermal stability

- the resulting composite membranes have high ionic conductivity at low humidity and temperatures up to 160 ° C

- significantly less leaching of phosphoric acid when holding the membrane in a humid atmosphere. The conductivity of the membrane doped only with phosphoric acid decreases by 2 orders of magnitude after exposure to a humid atmosphere. The conductivity of samples doped with acid zirconium phosphate, or hydrated zirconium oxide, or hydrated silicon oxide, decreases by 1.5-2 times after exposure to a humid atmosphere.

A method of obtaining proton-conducting membranes is illustrated by the following examples.

Example 1. A sample of the PBI membrane was conditioned in concentrated phosphoric acid at 80 ° C. Then the membrane was treated in a 40% solution of zirconium propoxide in propanol-1 at 100 ° C. Next, the membrane was treated in concentrated phosphoric acid at 80 ° C. The treatment cycle was repeated with zirconium propoxide and phosphoric acid. For the most complete crystallization of zirconium acid phosphate, the membrane was subjected to heat treatment at 150 ° C and subsequent treatment in phosphoric acid at room temperature. Conductivity was measured using impedance spectroscopy by the two-electrode method. The conductivity of the obtained composite membrane reaches (1.5-5) × 10 ^-2 S / cm at 160 ° C.

Example 2. A membrane sample PBI was conditioned in concentrated phosphoric acid at 80 ° C. Then the membrane was treated in a concentrated solution of zirconium oxochloride at 100 ° C. Next, the membrane was treated in concentrated phosphoric acid at 80 ° C. The cycle of treatment with zirconium oxochloride and phosphoric acid was repeated. For the most complete crystallization of zirconium acid phosphate, the membrane was subjected to heat treatment at 150 ° C and subsequent treatment in phosphoric acid at room temperature. Conductivity was measured using impedance spectroscopy by the two-electrode method. The conductivity of the obtained composite membrane reaches (1.5-5) 10 ^-2 S / cm at 160 ° C.

Example 3. A sample of the PBI membrane was treated in a concentrated solution of zirconium oxochloride at 90 ° C. Then hydrolysis was carried out with a 0.2 M sodium hydroxide solution. The treatment cycle was repeated with zirconium oxochloride and sodium hydroxide. The membrane was then treated at room temperature with concentrated phosphoric acid. Conductivity was measured by impedance spectroscopy by the two-electrode method. The conductivity of the obtained composite membrane reaches from 2 × 10 ^-2 to 10 ^-1 S / cm at 160 ° C.

Example 4. A sample of the PBI membrane was treated in a 40% solution of zirconium propoxide in propanol-1 at 100 ° C. Next, hydrolysis was carried out by boiling in water. Then the membrane was dried at 150 ° C. After that, the membrane was treated at room temperature with concentrated phosphoric acid. Conductivity was measured by impedance spectroscopy by the two-electrode method. The conductivity of the obtained composite membrane reaches from 2 × 10 ^-2 to 10 ^-1 S / cm at 160 ° C.

Example 5. A sample of the PBI membrane was processed in TEOS at 165 ° C. Next, hydrolysis was carried out by boiling in water. Then the membrane was dried at 150 ° C. After that, the membrane was treated at room temperature with concentrated phosphoric acid. Conductivity was measured by impedance spectroscopy by the two-electrode method. The conductivity of the obtained composite membrane reaches (3-8) 10 ^-2 S / cm at 160 ° C.

Bibliography

1. Grot W.G. Macromol. Symp., 1994, 82161.

2. US Patent 3,718,627. 1973.

3. US Patent 4,433,082,1984.

4. Yaroslavtsev A.B., Mirakyan A.L., Chuvaev V.F., Sokolova L.N. // Journal. inorg Chem. 1997.T 42.№6 p. 900.

5. A. Clearfield // Chem. Rev. 88 (1988) 125.

6. Tarnopolsky V. A., Aliev A. D., Novikova S. A., Yaroslavtsev A. B. // Journal. inorg Chem. 2002.Vol. 47. No. 11. since 1763

7. G. Alberti // Inorganic Ion Exchange Membranes. 7.1.1776.

8. RF patent RU 2279906 C1.

Claims (1)

A method of producing a proton-conductive polymer membrane based on polybenzimidazoles by doping with polybenzimidazole films by acid, characterized in that before doping the polybenzimidazoles with phosphoric acid, the polybenzimidazoles are doped with either zirconium acid phosphate or hydrated zirconia or hydrated silica.