the layer 2 the layer 4 is disposed on the surface 3a of the layer 3 and upon addition of electrolyte cancels or compensates for the curling or bending of the matrix resulting from the layer 3 thereby causing the matrix 1 to remain substantially flat no special attention must therefore be given to the matrix upon subsequent incorporation into the fuel cell the layer 3 preferably is formed from carbon having a particle size of approximately 500 angstroms and a surface are greater than 100 square meters per gram the concentration of ptfe may be from 1 10 with a concentration of 3 6 being preferable the layers 2 and 4 on the other hand may be formed from silicon carbide of particle size 0 5 to 10 microns the concentration of ptfe in these layers may also be from 1 10 with a range of 4 6 being preferable the overall thickness of the matrix i e the three layers may range from 0 005 to 0 040 inches with a range of 0 008 to 0 012 inches being preferable individual thickness for the layer 3 may range from 0 002 inches to 0 0020 inches and for the layers 2 and 4 from 0 0005 inches to 0 010 inches it should be noted that the principles of the invention are applicable as well to the situation where the layer 3 expands to a lesser degree than the similar greater expanding layers 2 and 4 in such case the layer 4 will likewise compensate for any bending or curling to result in a flat matrix 1.