H 2 S Poisoning of Proton Conducting Solid Oxide Fuel Cell and Comparison with Conventional Oxide-Ion Conducting Solid Oxide Fuel Cell

Abstract

The electrochemical response of proton conducting solid oxide fuel cells (PC-SOFC) with Ni-BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) cermet anode by low-ppm(v) level hydrogen sulfide (H 2 S) was studied using both electrolyte-supported cells and anode symmetrical cells at 750-450°C. Upon the introduction of H 2 S, both types of cells show small but observable increase in the electrode apparent interfacial resistance (R ai) with no change in ohmic resistance. In addition, secondary-ion mass spectroscopy (SIMS) analysis on Ni-BZCYYb composite pellets after exposure to H 2 S showed a strong correlation between the distributions of barium and sulfur species, yet both were complementary to the distribution of nickel species. The results indicate that PC-SOFC are still subjected to poisoning by low ppm(v)-level H 2 S at intermediate temperature. However, the H 2 S poisoning effect (in terms of relative increase in interfacial resistance) for PC-SOFC appearsmuch smaller than for conventional oxide-ion conducting SOFC with Ni-yttria stabilized zirconia (Ni-YSZ) cermet anode and YSZ electrolyte. Such a difference in H 2 S poisoning behavior is hypothesized to be related to the different anode reaction process for PC-SOFC versus conventional oxide-ion conducting SOFC and the potential (electro-)catalytic role that proton conducting ceramic electrolyte might play in the anode reaction. The directions for future study are also pointed out.