An electrochemical device and a proton conducting medium for use in an electrochemical device having a proton conducting electrolyte comprising the formula: H.sub.aM.sub.bQ.nH.sub.2O where H is a proton, M is a cation, Q is the fluoroborate or fluoroheteroborate anion, n ranges from 0.01 to 1000, a ranges from 0.01 to 2 and b ranges from 0 to 2, a and b are chosen to render the formula electrically neutral, and when b is greater than 0, the ratio of b to a is less than 100 to 1.