Mass transfer effects on ZrO2 oxygen concentration cells exposed to non-equilibrium H2-O2 mixtures

We report further studies of ZrO₂ oxygen concentration cells exposed to non-equilibrium gas mixtures. Substantial shifts of cell voltage-(H₂/O₂) composition curves are produced by changes in the gas flow rate past the cell. At high flow rates, there is an abrupt voltage step at about 2.2 times the H₂/O₂ stoichiometric ratio. At low flow rates this voltage step occurs at stoichiometry. These findings are understood on the basis of mass transfer to a heterogeneous catalyst/electrode surface.