NOVELTY - A proton-conductive material has a distance between adjacent clusters of 5-20 Angstrom .    USE - The material is used for a solid polymer electrolyte membrane for a fuel cell (claimed). It can be used as electrolyte membrane for electrolyzing hydrohalic acid, for electrolyzing water, for electrolyzing sodium chloride, an oxygen condenser, a humidity sensor, and gas sensor.    ADVANTAGE - The proton-conductive material exhibits high proton conductivity even when it is not highly moisturized. A high proton conductivity of a 10-2 S/cm order can be obtained even at an extremely low temperature by reducing the cluster-to-cluster distance to less than or equal to 20 Angstrom . The fuel cells can operate at greater than or equal to 100 degrees C and have higher operation efficiency and a higher capacity. The use of the proton-conductive material makes it possible to remove the components and parts related to the low-temperature operation and the moisturization. The production cost of fuel cells can be reduced.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for producing a proton-conductive material, comprising obtaining trialkylsilane-alkylsulfonic acid by oxidizing mercapto group of mercaptoalkyl trialkoxysilane, converting an alkoxy group of trialkoxysilane-alkylsulfonic acid to a hydroxyl group, and obtaining a proton-conductive material by polymerization using a sol-gel method, where the trialkoxysilane-alkylsulfonic acid in which the alkoxy group has been converted to the hydroxyl group is used as a starting material which is a monomer compound. The alkoxy group of tetralkoxysilane is converted to a hydroxyl group and used as the monomer compound.    DESCRIPTION OF DRAWING(S) - The drawing is a graph illustrating the relation between the cluster-to-cluster distance and the proton conductivity for the proton-conductive material (designated by +), Nafion 112 (designated by black square), Nafion 115 (designated by x), and Nafion 1500 (designated by empty square), at 80 degree Celsius and at 20%RH.