Proton Conductivity of Simple Ionic Hydroxides Part I: The Proton Conductivities of Al(OH)3, Ca(OH)2, and Mg(OH)2

Abstract Proton conductivity is an outstanding feature of Al(OH)3, Mg(OH)2, and Ca(OH)2 powders between room temperature and their respective dehydration temperatures. It can be measured by using Pd‐black electrodes in H2 either by d.c. conductivity measurements, applying high injection voltages (> 104 V/cm), or by thermopotential measurements. Two conductivity mechanisms are observed which can be assigned to proton conductivity σ*H and defect proton conductivity σH'. The activation energies σ'H are 1.65, 2.0, and 2.2 eV for Al(OH)3, Mg(OH)2, and Ca(OH)2 respectively. The activation energies σH* are lower, ranging between 0.5–1.0 eV. σ'H occurs 20–60 K below the on‐set temperature of dehydration. It is enhanced by the adsorption of CH3COOH vapor and suppressed by NH3 vapor acting as proton donator and proton acceptor or traps respectively.