Methodology for the study of mixed transport properties of a Zn-doped SrZr_0.9Y_0.1O_3−δ electrolyte under reducing conditions

Abstract

The mixed ionic-electronic transport properties of the protonic ceramic electrolyser material SrZr0.9Y0.1O3-, with the addition of 4mol% ZnO as sintering additive, are analysed under reducing conditions. The study is performed by means of an active-load modification of the classical electromotive-force method to account for the nonnegligible effect of the electrodes on the obtained electrical-transport numbers. The methodology is developed in detail in order to link the electrochemical criteria to simulated equivalent circuits. The observed electromotive force of the system is considerably affected by the introduction of the polarisation resistance of the electrodes in the corresponding analysis, resulting in a high deviation between the present results and those obtained by a classical analysis without attending to electrode effects. Under wet reducing conditions (pH2  0.05 atm, pH2O 3·10 3 10 2 atm), the oxide-ionic transport number is negligible in the range of 600900 ºC, whereas pure protonic conductivity is observed for temperatures ≤ 700 ºC and pH2O ≥ 5.6x10 3 atm. For higher temperatures and/or lower pH2O, mixed protonic-electronic conduction is exhibited. The electronic contribution under reducing conditions is consistent with ntype electronic behaviour.

Transport properties of acceptor-doped barium zirconate by electromotive force measurements

“…(5) introduces underestimation of the contribution of the ionic conduction. [25][26][27][28][29] It is necessary to take the electrode polarization into consideration. And the ionic transport numbers can be corrected using Eq.…”

Electromotive Force (emf) Determination of Transport Numbers for Native and Foreign Ions in Molten Alkali Metal Carbonates

“…The original derivation by Gorelov does not cover the case of multiple ions (native and foreign) responding independently to chemical gradients, but Pérez-Coll et al have recently proposed a modification for the case of oxides with oxide ion, proton, and electron transport. 33,34 For Liu's approach there have however not been attempts to expand the correction to cases with multiple ions and driving forces Figure 2. Corrected transport numbers (t corrected ) obtained using Liu's equation for different resistance ratios (R total includes R electrode ) and measured transport numbers (t measured = E obs /E N ).…”

Exploring the mixed transport properties of sulfur(vi)-doped Ba2In2O5 for intermediate-temperature electrochemical applications

“…Platinum paste was painted on each side of the pellets and fired at 900 ºC for 2 h to yield the contact electrodes. For this purpose the electromotive force was monitored as a function of a variable external resistance located in parallel to the system, as previously reported 32,33 . The experimental procedure was applied to dry/wet N 2 and O 2 atmospheres.…”

“…Under these conditions, an auxiliary-variable resistance located in parallel to the sample produces a modification of the measured electromotive force of the system (E M ) according to 32,33 . Simultaneously, a gradient of pH 2 O was established by exposing each gas flow to different levels of humidification controlled by mixing wet and dry gas fractions.…”