Significant impact of γ-Al2O3 facet structure on the character and performance of surface Co-Mo sulfides for CO removal in H2 fuel via water gas shift

Three morphologically uniform γ-Al 2 O 3 crystallites [Al 2 O 3 hexagonal plates (Al 2 O 3 -HP), stacked hexagonal plates (Al 2 O 3 -SHP) and rods (Al 2 O 3 -R)] were controllably synthesized. The Co-Mo oxide precursor was loaded on these γ-Al 2 O 3 substrates via aqueous incipient wetness impregnation and transformed to the sulfides under 10% H 2 S/H 2 (v/v) atmosphere. The mainly exposed facet of Al 2 O 3 -HP and Al 2 O 3 -SHP was identified to be the (1   1   0) and (1   0   0)/(1   1   1), respectively; whereas a polycrystalline structure was observed over Al 2 O 3 -R. The original structural feature of oxide precursors, i.e., 2D polymeric/monomeric as well as 3D polymeric/MoO 3 species substantially varied over Al 2 O 3 -HP, Al 2 O 3 -SHP, and Al 2 O 3 -R, which in turn determines the effectiveness in sulfidation of surface oxide precursors. The richness of MoS 2 /Co 9 S 8 /Co-Mo-S species, and less fraction of partially sulphurated CoMoO x S 2 as well as CoO x /SO x 2− entities were recognized over Al 2 O 3 -HP. Based on the areal activity at 250 °C, the sulfides-Al 2 O 3 (1   1   0) interface is approximately 6–13.8 times more active than the poly-crystalline or commercial γ-Al 2 O 3 supported sulfides for water gas shift (WGS) in a hydrogen-rich stream. The sulfides-Al 2 O 3 (1   1   0) interface also notably outperformed the sulfides-Al 2 O 3 (1   0   0)/(1   1   1) interfaces for the reaction.