Determining the width of the electrochemically active electrode area along the triple phase boundary

The width of the active electrode area along the triple phase boundary, TPB, was determined using a novel method based on ac impedance measurements between two interdigitated electrodes. The theoretical basis is presented and... [ view full abstract ]

The width of the active electrode area along the triple phase boundary, TPB, was determined using a novel method based on ac impedance measurements between two interdigitated electrodes. The theoretical basis is presented and used to derive the width for gold electrodes applied onto the solid electrolyte (SE) Y₂O₃ stabilized ZrO₂ (YSZ). Gold electrodes were used in the demonstration of the method due to their ion blocking nature and poor cathodic properties which requires that all or at least most of the electrochemical reaction steps take place on the free surface of the SE near the TPB. The width δ was determined in operando to be 0.4, 0.3 and 0.2 μm at 250, 275 and 300 °C, respectively, decreasing with increasing temperature. In addition, the ionic conductivity of YSZ at those low temperatures was also determined. [1]

[1] Solid State Ionics, 303, (2017), 70–77