CATALYST FOR A FUEL CELL

The present invention provides a process for preparing a catalyst precursor, said process comprising the steps of (i) providing PtXalloy particles on a support material and (ii) applying a shell of X to the PtXalloy particles to provide a catalyst precursor comprising particles having a PtXcore and an X shell. The ratio of a to b is in the range of and including 10:1 to 1:2.5 and X is Co, Ni, Y, Gd, Sc or Cu. Also provided is a process for preparing a catalyst material.