(DE4447126-A1)      Membrane electrode composite comprises a membrane contg. a polymeric cation exchanger with carboxylic, phosphonic or sulphonic acid gps., which is soluble in a solvent, and finely-divided metals, catalysing the formation of water from H2 and O2, applied to at least one side of the membrane. The novelty is that the part of the membrane covered with metal is porous but contains no closed pores and the metal can also be present in the pores.    Also claimed is a method for making the composite. The membrane is provided with a porous surface by a phase inversion process; treated with a soln. of a reducing agent for H2PtCl6; rinsed to remove reducing agent adhering to the surface; and placed in H2PtCl6 soln., so that Pt is deposited on its surface. Alternatively, the membrane with the porous surface is (partly) converted to salt by treatment with an aq. soln. of a K, Rb, Cs or ammonium salt and then on at least one side with H2PtCl6 to deposit a hardly soluble hexachloroplatinate on the surface, then rinsed and treated with reducing agent, so that Pt is deposited on the surface as firmly adhering aggregates. The non-solvent used in the phase inversion stage is water, opt. mixed with a polar aprotic solvent, or an aliphatic alcohol. After treatment with the first solvent, electroconductive C, opt. charged with metal catalyst, may be applied before rinsing or spraying with a second solvent, which is miscible with the first solvent but is a non-solvent for the membrane.    USE -   The composite is used in electrochemical cells, esp. as membrane/electrode unit in fuel cells and electrolysers (all claimed).    ADVANTAGE -   The unit has very large catalyst/fuel gas and catalyst/electrolyte specific interfaces and can be made easily. It also has very high activity.    (JP10507574-W)      Membrane electrode composite comprises a membrane contg. a polymeric cation exchanger with carboxylic, phosphonic or sulphonic acid gps., which is soluble in a solvent, and finely-divided metals, catalysing the formation of water from H2 and O2, applied to at least one side of the membrane. The novelty is that the part of the membrane covered with metal is porous but contains no closed pores and the metal can also be present in the pores.    Also claimed is a method for making the composite. The membrane is provided with a porous surface by a phase inversion process; treated with a soln. of a reducing agent for H2PtCl6; rinsed to remove reducing agent adhering to the surface; and placed in H2PtCl6 soln., so that Pt is deposited on its surface. Alternatively, the membrane with the porous surface is (partly) converted to salt by treatment with an aq. soln. of a K, Rb, Cs or ammonium salt and then on at least one side with H2PtCl6 to deposit a hardly soluble hexachloroplatinate on the surface, then rinsed and treated with reducing agent, so that Pt is deposited on the surface as firmly adhering aggregates. The non-solvent used in the phase inversion stage is water, opt. mixed with a polar aprotic solvent, or an aliphatic alcohol. After treatment with the first solvent, electroconductive C, opt. charged with metal catalyst, may be applied before rinsing or spraying with a second solvent, which is miscible with the first solvent but is a non-solvent for the membrane.    USE -   The composite is used in electrochemical cells, esp. as membrane/electrode unit in fuel cells and electrolysers (all claimed).    ADVANTAGE -   The unit has very large catalyst/fuel gas and catalyst/electrolyte specific interfaces and can be made easily. It also has very high activity.    (EP787368-B1)      Membrane electrode composite comprises a membrane contg. a polymeric cation exchanger with carboxylic, phosphonic or sulphonic acid gps., which is soluble in a solvent, and finely-divided metals, catalysing the formation of water from H2 and O2, applied to at least one side of the membrane. The novelty is that the part of the membrane covered with metal is porous but contains no closed pores and the metal can also be present in the pores.    Also claimed is a method for making the composite. The membrane is provided with a porous surface by a phase inversion process; treated with a soln. of a reducing agent for H2PtCl6; rinsed to remove reducing agent adhering to the surface; and placed in H2PtCl6 soln., so that Pt is deposited on its surface. Alternatively, the membrane with the porous surface is (partly) converted to salt by treatment with an aq. soln. of a K, Rb, Cs or ammonium salt and then on at least one side with H2PtCl6 to deposit a hardly soluble hexachloroplatinate on the surface, then rinsed and treated with reducing agent, so that Pt is deposited on the surface as firmly adhering aggregates. The non-solvent used in the phase inversion stage is water, opt. mixed with a polar aprotic solvent, or an aliphatic alcohol. After treatment with the first solvent, electroconductive C, opt. charged with metal catalyst, may be applied before rinsing or spraying with a second solvent, which is miscible with the first solvent but is a non-solvent for the membrane.    USE -   The composite is used in electrochemical cells, esp. as membrane/electrode unit in fuel cells and electrolysers (all claimed).    ADVANTAGE -   The unit has very large catalyst/fuel gas and catalyst/electrolyte specific interfaces and can be made easily. It also has very high activity.    (US5906716-A)      Membrane electrode composite comprises a membrane contg. a polymeric cation exchanger with carboxylic, phosphonic or sulphonic acid gps., which is soluble in a solvent, and finely-divided metals, catalysing the formation of water from H2 and O2, applied to at least one side of the membrane. The novelty is that the part of the membrane covered with metal is porous but contains no closed pores and the metal can also be present in the pores.    Also claimed is a method for making the composite. The membrane is provided with a porous surface by a phase inversion process; treated with a soln. of a reducing agent for H2PtCl6; rinsed to remove reducing agent adhering to the surface; and placed in H2PtCl6 soln., so that Pt is deposited on its surface. Alternatively, the membrane with the porous surface is (partly) converted to salt by treatment with an aq. soln. of a K, Rb, Cs or ammonium salt and then on at least one side with H2PtCl6 to deposit a hardly soluble hexachloroplatinate on the surface, then rinsed and treated with reducing agent, so that Pt is deposited on the surface as firmly adhering aggregates. The non-solvent used in the phase inversion stage is water, opt. mixed with a polar aprotic solvent, or an aliphatic alcohol. After treatment with the first solvent, electroconductive C, opt. charged with metal catalyst, may be applied before rinsing or spraying with a second solvent, which is miscible with the first solvent but is a non-solvent for the membrane.    USE -   The composite is used in electrochemical cells, esp. as membrane/electrode unit in fuel cells and electrolysers (all claimed).    ADVANTAGE -   The unit has very large catalyst/fuel gas and catalyst/electrolyte specific interfaces and can be made easily. It also has very high activity.