PRODUCTION METHOD FOR ELECTRODE CATALYST, ELECTRODE CATALYST, COMPOSITION FOR FORMING GAS DIFFUSION ELECTRODE, GAS DIFFUSION ELECTRODE, MEMBRANE-ELECTRODE ASSEMBLY (MEA), AND FUEL CELL STACK

摘要

Provided is a production method for an electrode catalyst wherein an electrode catalyst that has sufficiently reduced chlorine (Cl) species content can be obtained by means of a simple operation, even when an electrode catalyst precursor that contains a high concentration of chlorine is used as a source material. A production method for an electrode catalyst that has a core-shell structure that includes a core part that is formed upon a support and includes a shell part that is formed so as to cover at least one portion of the surface of the core part. The method includes: a first step, step (1), wherein a first liquid is prepared by adding to ultrapure water an electrode catalyst precursor (I) that is produced using a chlorine (Cl)-species-containing material and that has a chlorine (Cl) species concentration as measured by x-ray fluorescence analysis that is equal to or higher than a first chlorine (Cl) concentration; and a second step, step (2), wherein the electrode catalyst precursor (I) is filtered and washed using ultrapure water until the electrical conductivity (ρ) of the obtained liquid is equal to or less than a first set value, and wherein a second liquid is prepared by dispersing the obtained electrode catalyst precursor (II) in ultrapure water.