Catalyst layer, membrane electrode assembly, and electrochemical cell

Abstract

A method of manufacturing a membrane electrode assembly, including: forming a catalyst layer precursor containing a mixture of a catalyst material and a pore-forming material on a substrate having a flatness of 60% or more; removing the pore-forming material from the catalyst layer precursor on the substrate, thereby forming a catalyst layer containing the catalyst material and having a porosity of 20 to 90% by volume; transferring the catalyst layer from the substrate to a gas diffusion layer, to provide an electrode; and bonding the catalyst layer of the electrode to an electrolyte membrane, to provide a membrane electrode assembly.

1 - 6 . (canceled) 
     
     
         7 : A method of manufacturing a membrane electrode assembly, the method comprising:
 forming a catalyst layer precursor comprising a mixture of a catalyst material and a pore-forming material on a substrate having a flatness of 60% or more;   removing the pore-forming material from the catalyst layer precursor on the substrate, thereby forming a catalyst layer comprising the catalyst material and having a porosity of 20 to 90% by volume;   transferring the catalyst layer from the substrate to a gas diffusion layer, to provide an electrode; and   bonding the catalyst layer of the electrode to an electrolyte membrane, to provide a membrane electrode assembly.   
     
     
         8 : The method of  claim 7 , further comprising: bonding a second catalyst layer of a second electrode to the electrolyte membrane. 
     
     
         9 : The method of  claim 7 , wherein the substrate has a flatness of 70% or more. 
     
     
         10 : The method of  claim 7 , wherein the catalyst layer has a single layer structure satisfies a relation:
     R   1   ≧R   0 ×1.2,
   wherein:   R 1  is an alignment ratio of the catalyst layer; and   R 0  is an alignment ratio of the catalyst material in powder form having a random crystalline plane distribution,   wherein each of the alignment ratios is calculated from a X-ray diffraction spectrum having a diffraction angle 2θ range from 10 to 90 degree measured using Cu-Kα-rays, and is defined as a ratio of a diffraction peak area contributed by the most closely packed crystalline planes of a material to a total area of all diffraction peaks of the same material at the 20 range from 10 to 90 degree.   
     
     
         11 : The method of  claim 7 , wherein a ratio of pores having a pore diameter ranging from 5 to 100 nm to all pores in the catalyst layer is 50% by vol or more. 
     
     
         12 : The method of  claim 10 , wherein a spacing of the most closely packed crystalline planes is in a range from 95 to 98% of a corresponding spacing of the catalyst material in powder form with random crystalline plane distribution. 
     
     
         13 : The method of  claim 7 , wherein the catalyst layer comprises 30 at % or more of platinum or iridium. 
     
     
         14 : The method of  claim 7 , wherein the catalyst layer comprises an alloy having a composition of formula (I):
   Pt y Ru z T 1-y-z   (I),
   
       wherein:
 0.2≦y≦0.8; 
 0≦z≦0.8; and 
 T is at least one element selected from the group consisting of W, Hf, Si, Mo, Ta, Ti, Zr, Ni, Co, Nb, V, Sn, Al, and Cr. 
 
     
     
         15 : The method of  claim 7 , wherein the catalyst layer comprises an alloy having a composition of formula (II):
   Pt u M 1-u   (II),
   
       wherein:
 0<u≦0.9; and 
 M is at least one element selected from the group consisting of Co, Ni, Fe, Mn, Ta, W, Hf, Si, Mo, Ti, Zr, Nb, V, Cr, Al, and Sn. 
 
     
     
         16 : The method of  claim 7 , wherein a thickness of the catalyst layer is from 20 nm to 10 μm. 
     
     
         17 : The method of  claim 10 , wherein the catalyst material comprises Pt, and each of the alignment ratios is calculated with the following equation:
     R =an area of (111)/[an area of(111)+an area of (200)+an area of (311)]   wherein the peaks ( 111 ), ( 200 ), and ( 311 ) are presented in the range from 10 to 90 degrees of the diffraction angle 2θ.   
     
     
         18 : The method of  claim 7 , wherein the catalyst layer precursor comprising the mixture of the catalyst material and the pore-forming material is sputtered on the substrate. 
     
     
         19 : A method of manufacturing an electrochemical cell, the method comprising:
 sandwiching a membrane electrode assembly obtained by the method of  claim 8  with a first separator and a second separator.