A density functional theory study of the formation of COS from CO and H2S on cesium sulfide.

[Display omitted] • Computational study of CO + H 2 S → COS + H 2 reaction on Cs 2 S. • Six low Miller index planes of Cs 2 S considered. • Weak CO adsorption, strong dissociative H 2 S adsorption. • COS formed via Langmuir-Hinshelwood mechanism, involving COSH* surface intermediate. • Cs 2 S (0 0 1) facet determines overall reactivity nanoparticles. Alkali metals can promote the performance of MoS 2 in methanethiol (CH 3 SH) synthesis from CO/H 2 /H 2 S mixtures. Recently, it has been found that alkali sulfides and most prominently Cs 2 S can also catalyze the reaction between CO and H 2 S to COS and H 2 , COS acting as an intermediate in CH 3 SH formation (M. Yu et al. J. Catal. 2022, 405, 116 – 128). Here, we study the nature of the active sites and the mechanism of the CO + H 2 S → COS + H 2 reaction for the 6 low-index Miller planes of Cs 2 S. While CO adsorbs weakly, strong dissociative adsorption of H 2 S results in HS* and H* intermediates, which further stabilize the (0 0 1) facet as the dominant surface termination. The main reaction pathway towards COS involves the association of CO* and SH* to COSH* followed by its dehydrogenation in a Langmuir-Hinshelwood mechanism. Reactions of CO* with lattice S atoms have prohibitively high barriers due to the strong Cs-S bonds in Cs 2 S. Overall, the reaction rate is dominated by the (0 0 1) facet with small contributions of the (0 1 0), (0 1 1) and (1 0 1) surfaces. COSH* formation, its dehydrogenation to COS, and COS desorption compete as rate-controlling steps on these surfaces. [ABSTRACT FROM AUTHOR]