TECHNOLOGY FOCUS - POLYMERS - Preferred Method: Stage (A) involves preparation of a dispersion/suspension of polymer rather than a solution, preferably using PPA with a content of at least 85% (calculated as P2O5); the viscosity of the mixture may be adjusted between stages (B) and (C) by adding phosphoric acid. The membrane obtained in stage (C) is exposed to moisture at a certain temperature and for a certain time until it becomes self-supporting and removable from the substrate without damage. Stage (D) involves treatment for 10 seconds to 300 hours (preferably 1 minute to 200 hours) at 0-150 (preferably 10-120, especially 20-90) degreesC in presence of moisture, water, dilute phosphoric acid and/or steam. After this, the membrane may be surface-crosslinked by heating in the presence of oxygen, or possibly by irradiation with infra-red (IR) or near infra-red (NIR).Preferred Polymers: Polyazoles with repeating units of formula (I) and/or (II)Ar = a tetravalent, mono- or poly-nuclear (hetero)aromatic residue;Ar1 = a divalent (hetero)aromatic residue;Ar2 = a di- or tri-valent (hetero)aromatic residue;X = O, S or an amino group containing H and a 1-20C organic group, preferably alkyl, alkoxy or arylPreferred polyazoles are polybenzimidazole, poly(pyridines), poly(pyrimidines), polyimidazoles, polybenzthiazoles, polybenzoxazoles, polyoxadiazoles, polyquinoxalines, polythiadiazoles and poly(tetrazapyrenes), especially polymers with one or more repeating benzimidazole units of various formulae (24 units shown, including e.g. the formula below).n = 10 or more, preferably 100 or morePreferred Membranes: The membrane formed in stage (C) has a thickness of 20-2000 (preferably 30-1500, especially 50-1200) microns; the final self-supporting membrane (stage D) has a thickness of 15-400 (preferably 20-200, especially 20-150). The substrate used in stage (C) is an electrode and the membrane may also comprise a layer containing a catalyst.    TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Electrodes: Electrodes in which the membrane coating has a thickness of 2-300 (preferably 5-250, especially 10-100) microns.Preferred Units: Membrane-electrode units as above, containing other polyazole-based polymer membrane(s) and/or polymer blend membrane(s) containing polyazole-based polymer(s). EXAMPLE - A mixture of 10 g polybenzimidazole (PBI; inherent viscosity = 0.92 dl/g) and 90 g polyphosphoric acid (PPA; P2O5 content = 83.4%) was heated at 270degreesC under nitrogen for 14 hours, diluted with 33.33 g 85% phosphoric acid (PA), and cooled to 240degreesC over 1 hour with stirring, to give a 7.5% solution of PBI in 106.9% PPA. The hot solution was coated onto preheated (100degreesC) glass plates in a film thickness of 150 microns and left for 3 days under ambient conditions. Hydrolysis by atmospheric moisture gave a mechanically-stable membrane based on a PBI/PPA/PA system, with a total acid/PBI mol ratio of 13.2. This membrane showed specific conductivity values of 0.115, 0.099, 0.074, 0.081, 0.101, 0.118, 0.126 and 0.128 S/cm at 25, 40, 60, 80, 100, 120, 140 and 160degreesC respectively.