Abstract: An electrode membrane structure comprising: an annular support member and a circular membrane portion integrally molded into said annular support, said membrane support being formed of sufficiently thin gas diffusible material, at least in the circular membrane portion and having an array of perforations to facilitate removal or separation of the annular support from the membrane portion, said support and membrane portions including an intermediate annular transition zone therebetween wherein the membrane portion increases in thickness to the support such that the gas diffusible material may be molded to the sufficient thinness required for gas diffusibility and yet maintain stability of dimension.