The high frequency intercept on the real axis of the Nyquist plot (Rhf ∼ 55 Ω) can be largely attributed to the oxide ion conduction in the electrolyte (Rion,YSZ > 0.8 × Rhf) with small contributions from the electronic sheet resistance of the Ti+Pt grid (Reon,grid = ∼5–10 Ω) and the wiring resistance (Reon,wire = ∼2 Ω), see section S-4 for more details.