NOVELTY - Proton-conducting electrolyte membrane for a fuel cell, which is impermeable for reaction components of a fuel cell reaction, with a perforated, nonconductive glass or ceramic support, infiltrated with a proton-conducting material suitable for selective conduction of protons through the membrane, has an outer proton-conducting coating, which is insoluble in water and methanol, on at least one side as diffusion barrier.    USE - The electrolyte membrane is used for producing a membrane electrode array or fuel cell (stack); and the membrane and array are used in fuel cells, especially direct methanol or reformate fuel cells (all claimed). Fuel cells with the membrane or array and mobile or stationary systems, especially a vehicle or an energy system for a building, with the fuel cell (stack) are claimed.    ADVANTAGE - Existing membrane electrode arrays for fuel cells use organic polymers as proton-exchanging membrane but their conductivity depends on maintaining a suitable water content, which cannot be guaranteed at temperatures above 100 degrees C and is generally impossible in reformate or direct methanol fuel cells. Existing inorganic proton conductors cannot be made into the thin membrane films with low surface resistance and high power density needed in lightweight cells. Electrolyte membranes of ceramic material on a metal support are unsuitable, as they tend to delaminate. Membranes of proton conductor without metal supports cannot be used in direct methanol fuel cells supplied with a liquid water/methanol mixture on the anode side, as gradual leaching of electrolyte causes a considerable loss of power density with time. The diffusion barrier eliminates this drawback. As it is very thin, it has little effect on the proton conductivity of the membrane. The membrane has higher proton conductivity than polymer membranes at low atmospheric humidity. The membrane electrode array has low total resistance and suitable mechanical properties, e.g. tensile strength and flexibility, for use under extreme conditions, e.g. in a vehicle, tolerates operating temperatures above 80 degrees C, avoids short-circuit and cross-over problems and can be produced easily.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) Electrolyte membrane made by infiltration of a flexible, perforated, nonconducting glass or ceramic support with a first mixture containing an immobilizable hydroxysilylalkyl-acid (I) of sulfur (S) or phosphorus (P) or its salt or a mixture containing a Bronsted acid and/or (I) or its salt and a sol precursor for aluminum (Al), silicon (Si), titanium (Ti), zirconium (Zr) and/or P oxide, followed by consolidation, then application of a second mixture to at least one side and consolidation to the diffusion barrier;    (2) Production of the electrolyte membrane by making an electrolyte membrane, applying a mixture to at least one side and consolidating this to the diffusion barrier;    (3) Membrane electrode array for a fuel cell, comprising the membrane with diffusion barrier and, on opposite sides, porous, electroconductive anode and cathode films comprising a catalyst for the anode and cathode reaction, a proton-conducting component and optionally a catalyst support;    (4) Production of this array by coating each side of the electrolyte membrane with diffusion barrier(s), simultaneously or consecutively, with a mixture of a condensable precursor for the proton-conducting electrode layer, a catalyst (precursor) for the anode or cathode reaction and optionally a catalyst support and/or pore former and producing a firm bond between these layers.