METHOD OF PRODUCING ELECTRODE CATALYST, METHOD OF PRODUCING GAS DIFFUSION ELECTRODE, AND METHOD OF PRODUCING MEMBRANE/ELECTRODE ASSEMBLY

An object of the present invention is to provide a method of producing an electrode catalyst having excellent catalytic activity and excellent durability in an electrode catalyst layer of MEA for a PEFC. The method of producing an electrode catalyst having a porous carbon support that has nanopores having a pore diameter of 1 to 20 nm and a BET specific surface area of 700 to 900 m2/g, and catalyst particles containing Pt supported on the support, includes: a first step for preparing a powder in which the catalyst particles are supported on the support; and a second step for accommodating the powder obtained through the first step in a flow-type reactor, flowing NH3 gas through the reactor under conditions of a concentration of 10 to 100% and a pressure of 0.1 MPa to 0.5 MPa, and regulating the temperature in the reactor to 500 °C or more and less than the decomposition temperature of ammonia, keeping for 5 to 10 hours to chemically react the powder and the NH3 gas.