Catalyst coated membranes and preparation methods for fuel cells

A method of preparing a catalyst coated membrane assembly for a solid polymer electrolyte fuel cell, the catalyst coated membrane assembly comprising a solid polymer electrolyte membrane comprising a proton-conducting membrane ionomer, first and second catalyst layers comprising first and second catalysts respectively and first and second ionomers respectively and bonded to opposite sides of the solid polymer electrolyte membrane, and a porous polymer sheet at the interface between the second catalyst layer and the solid polymer electrolyte membrane and bonded to both, and wherein the pores of the porous polymer sheet comprise the solid polymer membrane electrolyte and the second catalyst layer;

• the method comprising:
• coating a first catalyst ink comprising the first catalyst and the first ionomer onto a supporting substrate;
• drying the first catalyst ink coating, thereby form ling the first catalyst layer;
• coating a membrane ionomer solution comprising the membrane ionomer onto the first catalyst layer;
• applying the porous polymer sheet to the wet membrane ionomer solution coating wherein the membrane ionomer solution partially fills the pores of the porous polymer sheet;
• drying and annealing the membrane ionomer coating, thereby forming the solid polymer electrolyte membrane;
• applying a second catalyst ink comprising the second catalyst and the second ionomer to the porous polymer sheet wherein the second catalyst ink fills the remaining pores of the porous polymer sheet;
• and
• drying the second catalyst ink coating, thereby forming the second catalyst layer.