H2S adsorption and the effect of sulfur on the oxidation of Ni3Al(111)

We report the formation of a (2×2) sulfur adlayer by the adsorption of H2S on Ni3Al(111) at room temperature, followed by annealing to ∼1100 K. From Auger electron spectroscopy (AES) measurements, this pattern is consistent with a sulfur coverage (θS) of ≤0.25 monolayers (ML). A diffuse low-energy electron diffraction pattern with streaks, corresponding to θS=0.3 ML, was observed after sulfur adsorption at ∼800 K, but the (2×2) order was restored upon flash annealing to ∼1100 K. AES results rule out any aluminum enrichment or sulfide formation in the surface during exposure to H2S or thermal treatment. The presence of sulfur on the Ni3Al(111) surface retards its oxidation at room temperature. Sulfur is found to remain at the oxide/Ni3Al(111) interface during oxidation at ∼300 K.