It is not so transparent to determine the proton transference number (t(H+)) of a proton-conducting oxide, e.g., SrCe1-xYbxO3-delta, from a concentration-cell open-circuit voltage (U), because in this case U is, in general, no longer a path-independent state property. We clarify this issue to validate the concentration-cell method, and correctly determine t(H+) of SrCe0.95Yb0.05O3-delta. The experimental values for t(H+) are precisely documented in the ranges of oxygen activity -4

Keywords:Proton transference number;Open-circuit voltage;Concentration cell;SrCe1-xYbxO3-delta;Proton conductors