Patent ID: 7220693

Claim:
A method of forming an element comprising a reaction layer for use in an electrochemical cell, the steps comprising: a) providing a carbon-supported catalyst; b) mixing said carbon-supported catalyst with a proton conduction enhancing material; c) forming an element comprising a reaction layer from a mixture resulting from said mixing step (b); and d) after said forming step (c), directly sulfonating said element with a sulfonating agent comprising at least one of the inorganic salts from the group (NH 4 ) 2 SO 4 , NH 4 HSO 4 , (NH 4 ) 2 SO 3 , (NH 4 ) 2 S 2 O 8 , (NH 4 ) 2 S 2 O 3 , and NH 4 SO 3 CF 3 ; whereby a C—SO 3 H linkage is formed with said carbon-supported catalyst.