Experimental demonstration of the path- and time-dependence of open-circuit voltage of galvanic cells involving a multinary compound under multiple chemical potential gradients

It was mathematically predicted and numerically demonstrated [Yoo and Martin, Phys. Chem. Chem. Phys. 12 (1210) 14699] that the open-circuit voltage U of a galvanic cell, involving a multinary compound with multiple ionic carriers subjected to multiple chemical potential differences, be path- and time-dependent, unlike a cell involving a pure binary or a multinary compound with a single type ionic carrier. The path- and time-dependence of U is now experimentally demonstrated with a galvanic cell, μ O 2 ′ , μ H 2 O ′ | SrC e 0.95 Y b 0.05 O 3 − δ | μ O 2 ″ , μ H 2 O ″ involving a proton-conducting, mixed ionic electronic conductor, e.g., SrCe0.95Yb0.05O3–δ with H+ and O2− as ionic carriers subjected to the chemical potential differences of oxygen and water. The results are compared with a cell involving a multinary Zr0.84Y0.16O1.92 but with a single type ionic carrier O2−, μ O 2 ′ , μ H 2 O ′ | Z r 0.84 Y 0.16 O 1.92 | μ O 2 ″ , μ H 2 O ″ where U is path-independent in any case and time-independent as long as the electrode equilibria prevail. Implications of the path- and time-dependence of U are discussed.