CCM composite

A CCM comprising a membrane having on one of the two surfaces a first electrocatalytic layer containing a catalyst and on the other one a second electrocatalytic layer containing a catalyst, wherein:

• the orthogonal projection of the perimeter of the first electrocatalytic layer on the second layer is distant from the perimeter of the second electrocatalytic layer at least 1 mm, preferably 2 mm in each point of said projection;
• the electrocatalytic layers and the membrane containing (per)fluorinated ionomers, the CCM having the following features:
• size variations, in the orthogonal directions of the plane xy, lower than 15%, more preferably lower than 10% after CCM dipping in demineralized water at 100° C. for 30 minutes, dried at 105° C. under vacuum for one hour;
• the CCM remains substantially unchanged after 60 cycles by dipping in water at 80° C. for 8 hours and then in water at the temperature of 25° C. for 16 hours.