Patent ID: 7943272

Claim:
A method of preparing a metal catalyst comprising a conductive catalyst material and a coating layer formed of a water repellent material on a surface of the conductive catalyst material, the method comprising: mixing a water repellent material and a first solvent to obtain a water repellent material solution, wherein the water repellent material includes at least one of 2,2-bistrifluoromethyl-4,5-difluoro-1,3-dioxol tetrafluoroethylene copolymer, polytetrafluoroethylene, fluoridized ethylene propylene, and polyvinylidenefluoride; mixing a conductive catalyst material in the first solvent to obtain a conductive catalyst solution; mixing the conductive catalyst solution and the water repellent material solution to obtain a first mixture; dripping the first mixture into a second solvent to induce phase separation between the first solvent and the second solvent to cause the water repellent material to form the coating layer on the surface of the conductive catalyst wherein the second solvent being a non-solvent for the water repellent material; and removing the first and second solvents by drying the second mixture.