Direct oxidation fuel cell system and membrane electrode assembly thereof

A direct oxidation fuel cell system, comprising:

• at least one membrane electrode assembly comprising a proton-conductive electrolyte membrane, and an anode and a cathode sandwiching said electrolyte membrane, said assembly being sandwiched between an anode-side current collector plate and a cathode-side current collector plate;
• a liquid fuel source in fluid communication with the anode of said at least one membrane electrode assembly;
• and
• an oxidant source in fluid communication with the cathode of said at least one membrane electrode assembly,
• wherein said anode has an anode catalyst layer that comprises a first mixture of a first solid proton-conductive substance and a first catalyst,
• said cathode has a cathode catalyst layer that comprises a second mixture of a second solid proton-conductive substance and a second catalyst, and
• an equivalent weight EWa of the first proton-conductive substance contained in the anode catalyst layer of said anode is greater than an equivalent weight EWc of the second proton-conductive substance contained in the cathode catalyst layer of said cathode wherein the equivalent weight EWa of the first proton-conductive substance contained in the anode catalyst layer of said anode and the equivalent weight EWc of the second proton-conductive substance contained in the cathode catalyst layer of said cathode are 800 to 1200 g/Eq, and the difference between EWa and EWc is not less than 100 g/Eq.