Effect of humidification at anode and cathode in proton-conducting SOFCs

Electrical conductivity measurements and hydrogen–oxygen fuel cell experiments were carried out at 600–800 °C using proton-conducting Yb-doped SrCeO3. The total conductivity increased with PO2 higher than 10−5 atm and decreased with respect to PH2O, suggesting that electron hole formation was suppressed in the presence of water. In fuel cell tests, the introduction of water to the oxygen cathode resulted in a lower OCV due to the converse hydrogen potential, but a higher ionic transport number in agreement with the conductivity measurements. The introduction of water to the hydrogen anode did not affect the OCV but improved (lowered) the area-specific resistance (ASR), probably by promotion of the uptake of protons through hydroxyl insertion.