Electrolyte emulsion and process for producing same

1. A membrane electrode assembly comprising:

an electrolyte membrane,

wherein the electrolyte membrane is obtained by a production method which comprises:

(1) applying an electrolyte emulsion to a substrate;

(2) drying the electrolyte emulsion applied to the substrate to provide an electrolyte membrane; and

(3) peeling the electrolyte membrane off from the substrate,

wherein the electrolyte emulsion applied to the substrate comprises:

(i) an aqueous medium; and

(ii) a fluoropolymer electrolyte dispersed in the aqueous medium,

wherein the fluoropolymer electrolyte dispersed in the aqueous medium comprises:

(a) ionic clusters that are 0.1 to 2.6 nm apart at 25° C. and relative humidity 50% RH as calculated by small angle X-ray measurement based on the following formula(I):

d= λ/2/sin(θ m )  (I)

wherein d is a distance between ionic clusters, λ, is an incident X-ray wavelength used in the small angle X-ray measurement, and θm is a Bragg angle which indicates a peak; and

(b) a monomer unit that has an SO 3 Z group, wherein Z is an alkali metal, an alkaline-earth metal, hydrogen, or NR 1 R 2 R 3 R 4 , wherein R 1 , R 2 , R 3 , and R 4 each are individually a C1-C3 alkyl group or hydrogen,

wherein the electrolyte has an equivalent weight (EW) of 250 or more and 700 or less, a proton conductivity of 0.1 S/cm or higher when measured at 110° C. and relative humidity 50% RH, and a ratio (the number of SO 2 F groups)/(the number of SO 3 Z groups) of 0 to 0.01, and

the electrolyte being a spherical particulate substance having an average particle size of 10 to 500 nm.

2. A membrane electrode assembly comprising:

an electrode catalyst layer,

wherein the electrode catalyst layer is obtained by a production method which comprises:

(1) dispersing composite particles comprising a catalyst metal and a conductive agent in an electrolyte emulsion to prepare an electrode catalyst composition;

(2) applying the electrode catalyst composition to a substrate; and

(3) drying the electrode catalyst composition applied to the substrate to provide an electrode catalyst layer,

wherein the electrolyte emulsion comprises:

(i) an aqueous medium; and

(ii) a fluoropolymer electrolyte dispersed in the aqueous medium,

wherein the fluoropolymer electrolyte comprises

(a) ionic clusters that are 0.1 to 2.6 nm apart at 25° C. and relative humidity 50% RH as calculated by small angle X-ray measurement based on the following formula(I):

d= λ/2/sin(θ m )  (I)

wherein d is a distance between ionic clusters, λ, is an incident X-ray wavelength used in the small angle X-ray measurement, and θm is a Bragg angle which indicates a peak; and

(b) a monomer unit that has an SO 3 Z group, wherein Z is an alkali metal, an alkaline-earth metal, hydrogen, or NR 1 R 2 R 3 R 4 , wherein R 1 , R 2 , R 3 , and R 4 each are individually a C1-C3 alkyl group or hydrogen,

wherein the electrolyte has an equivalent weight (EW) of 250 or more and 700 or less, a proton conductivity of 0.1 S/cm or higher when measured at 110° C. and relative humidity 50% RH, and a ratio (the number of SO 2 F groups)/(the number of SO 3 Z groups) of 0 to 0.01, and

the electrolyte being a spherical particulate substance having an average particle size of 10 to 500 nm.

3. A polymer electrolyte fuel cell, comprising the membrane electrode assembly according to claim 1 .

4. A polymer electrolyte fuel cell, comprising the membrane electrode assembly according to claim 2 .

5. A membrane electrode assembly comprising:

an electrolyte membrane comprising,

ionic clusters that are 0.1 to 2.6 nm apart at 25° C. and relative humidity 50% RH as calculated by small angle X-ray measurement based on the following formula (I):

d=λ/ 2/sin(θ m )  (I)

wherein d is a distance between ionic clusters, λ is an incident X-ray wavelength used in the small angle X-ray measurement, and θm is a Bragg angle which indicates a peak; and

a polymer comprising a monomer unit that has an SO 3 Z group, wherein Z is an alkali metal, an alkaline-earth metal, hydrogen, or NR 1 R 2 R 3 R 4 , wherein R 1 , R 2 , R 3 , and R 4 each are individually a C1-C3 alkyl group or hydrogen;

wherein the polymer has an equivalent weight (EW) of 250 or more and 700 or less, a proton conductivity of 0.1 S/cm or higher when measured at 110° C. and relative humidity 50% RH, a ratio (the number of SO 2 F groups)/(the number of SO 3 Z groups) of 0 to 0.01, and a spherical particulate substance having an average particle size of 10 to 500 nm.

6. A membrane electrode assembly comprising:

an electrode catalyst layer, said electrode catalyst layer comprising,

composite particles comprising a catalyst metal and a conductive agent;

ionic clusters that are 0.1 to 2.6 nm apart at 25° C. and relative humidity 50% RH as calculated by small angle X-ray measurement based on the following formula (I):

d =λ/2/sin(θ m )  (I)

wherein d is a distance between ionic clusters, λ is an incident X-ray wavelength used in the small angle X-ray measurement, and θm is a Bragg angle which indicates a peak; and

a polymer comprising a monomer unit that has an SO 3 Z group, wherein Z is an alkali metal, an alkaline-earth metal, hydrogen, or NR 1 R 2 R 3 R 4 , wherein R 1 , R 2 , R 3 , and R 4 each are individually a C1-C3 alkyl group or hydrogen;

wherein the polymer has an equivalent weight (EW) of 250 or more and 700 or less, a proton conductivity of 0.1 S/cm or higher when measured at 110° C. and relative humidity 50% RH, a ratio (the number of SO 2 F groups)/(the number of SO 3 Z groups) of 0 to 0.01, and a spherical particulate substance having an average particle size of 10 to 500 nm.

7. A polymer electrolyte fuel cell, comprising the membrane electrode assembly according to claim 5 .

8. A polymer electrolyte fuel cell, comprising the membrane electrode assembly according to claim 6 .