Modeling Hydrogen Sulfide Adsorption on Mo-Edge MoS2 Surfaces under Solid Oxide Fuel Cell Conditions

We examine the degree to which sulfur-based fuel contaminants, such as hydrogen sulfide (H2S), can adsorb on the molybdenum sulfide-based anode of a solid oxide fuel cell (SOFC) under normal SOFC conditions. Our examination takes into account multiple adsorption/desorption events involving H2S and the fuel (H-2). By means of a kinetic model that allows us to approximate the rate of adsorbed oxygen formation based on experimental O2- anion consumption at the triple-phase-boundary (TPB), we also consider the reaction mechanisms associated with the formation and desorption of H2O(g), SO2(g), and S-2(g). Preferred adsorption sites. energies, transition states, and kinetic barriers are calculated for the resulting species, SHx, OHx, SOx, and S-2 (x = 0-2). We have concluded that at typical SOFC operating conditions, the level of adsorbed sulfur on the MoS2 anode surface will not exceed 25% (one S surface atom for every one Mo surface atom).