Interaction of H2S with Au(111) and Au(100): A comparative investigation with microkinetic modeling based on dispersion corrected first-principles calculations

[Display omitted] •H2S binds Au(111) and Au(100) in an intact form at low temperature, in line with prior experimental results.•Almost all constituent elementary steps in the reaction of H2S with the two model surfaces follow a B EP relationship.•Au(100) is more active than Au(111) toward the initial hydrogen abstraction from H2S.•The less densely packed (100) facet is not as reactive as Au(111) for the second dissociation of SH species.•The S product comes from SH dissociation, not from SH disproportionation, on both surfaces. Using density functional predictions with van der Waals and thermal corrections, followed by a microkinetics, we report the reaction of hydrogen sulfide (H2S) under experimentally relevant circumstances on the model surfaces Au(111) and Au(100) that are present in actual Au nanoparticles. For low coverage of interest, the theoretical binding enthalpy of this species onto the hexagonal (111) facet is identified to better match the corresponding TPD findings relative to the square (100) case. The reaction sensitivities of all examined elementary steps involving SH species to the substrate structure originate from a much stronger binding of SH groups to Au(100). Through our detailed microkinetic modeling, it is determined that adsorbed H2S begins to partially dissociate on Au(111) at 190 K, while a lower temperature of 170 K is found for Au(100). Unexpectedly, the less densely packed (100) face demonstrates a rise in onset temperature of subsequent SH decomposition from 183 K at the close-packed (111) facet to 215 K. For both surfaces, the direct dissociation of SH is confirmed as the efficient mechanism to yield elemental sulfur instead of SH disproportionation. This study verifies that the disproportionation step is reversed during the cycle and becomes the consumption route for sulfur adatoms.