Previous studies indicated that the Ni-based cermet anode for proton conducting solid oxide fuel cells (PC-SOFC) seemed to have better tolerance against poisoning by low-ppm-level hydrogen sulfide (H₂S) compared to conventional oxide-ion conducting SOFC, but the detail and the origin for such a difference are not known. In this study, an in-depth investigation was carried out to reveal the differences in H₂S poisoning behavior for PC-SOFC (based on BaZe_0.1Ce_0.7Y_0.1Yb_0.1O₃ (BZCYYb) electrolyte and Ni-BZCYYb cermet anode) versus conventional oxide ion conducting SOFC (based on yttria-stabilized-zirconia (YSZ) electrolyte and Ni-YSZ cermet anode) using both electrolyte supported full cells and anode symmetrical cells from 750 to 450^oC. In addition, a dense Ni-BZCYYb composite pellet to simulate the cermet anode was exposed to hydrogen fuel with ppm-level H₂S and then characterized using tools such as XRD, SEM/EDS, and secondary ion mass spectroscopy (SIMS). The implications of the results on the sulfur poisoning mechanism as well as the overall anode hydrogen electrochemical oxidation process for PC-SOFC, including the potential electrocatalytic role proton conducting oxide electrolytes might play will be discussed, and the directions for future work including the use of cells with patterned metal electrodes will be pointed out.