NOVELTY - A proton-conducting membrane is formed using solid acid material in a solid phase.    USE - For electrochemical devices such as fuel cell, hydrogen separation membrane, or electrolysis cell.    ADVANTAGE - The solid acid material used for forming proton-conducting membrane has good conductivity in dry environment, conductivity which can be controlled to be either purely proton-conducting or both proton- and electron-conducting, and impermeability to gases and hydrocarbon liquids. The material is operative at elevated temperature (over 100 degreesC) and inexpensive. The structural binder mixed with the solid acid material enhances the mechanical integrity and/or chemical stability of the membrane. The membrane is impermeable to fluids such as gas and water and has high proton conductivity.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) Method for conducting proton across a barrier involves forming a membrane using solid acid material which is used to conduct protons.    (2) Fuel cell comprising a source of fuel and a proton-conducting membrane which is formed using solid acid material in a superprotonic phase.    (3) Operation of electrochemical device involves providing fuel to a proton-conducting membrane in which electrochemical reaction is carried out without humidifying the membrane.    (4) Proton- and electron-conducting membrane formed using solid acid material.    (5) Method for separating hydrogen from other materials involves chemically reacting hydrogen at the surface of proton- and electron-conducting membrane to decompose the hydrogen into proton and electron followed by passing the proton and electron through the membrane and blocking the passage of other materials including carbon monoxide.    (6) Method of using electrochemical device involves forming a solid acid material which is used to conduct protons.    (7) Formation of membrane-electrode assembly involves forming a composite film including a polymer and solid acid with a general formula of MaHb(XOt)c onto a backing layer such as graphite paper followed by forming electrodes on backing layer and hot pressing.