Alkali metals are commonly used to promote heterogeneous catalysts. For instance, K can enhance the MoS₂-catalyzed synthesis of methanethiol, an important industrial chemical, from CO/H₂/H₂S. Herein, we not only demonstrate that the synergy increases with alkali cation size (Cs > Rb > K > Na) but also that alkali sulfides themselves are the active sites. The alkali-normalized methanethiol formation rate of Cs sulfide is nearly the same as that of Cs-promoted MoS₂ with a much lower yield of unwanted methane. Kinetic measurements show that methanethiol on alkali sulfides is formed via the reaction 3 CO + 2 H₂S → COS + CO₂ + CH₃SH. This represents a first example of H₂S as a hydrogen donor for the formation of the thiol counterpart of methanol. The role of MoS₂ is that of a promoter that disperses alkali and provides spillover H from H₂ dissociation.

碱金属通常用于促进多相催化剂。例如，K 可以增强 MoS ₂催化从 CO/H ₂ /H ₂ S合成甲硫醇，甲硫醇是一种重要的工业化学品。在此，我们不仅证明了协同作用随着碱金属阳离子尺寸（Cs > Rb > K > Na) 而且碱金属硫化物本身就是活性位点。Cs 硫化物的碱标准化甲硫醇形成速率与 Cs 促进的 MoS ₂几乎相同，但不需要的甲烷产率要低得多。动力学测量表明，碱金属硫化物上的甲硫醇是通过反应 3 CO + 2 H ₂ S → COS + CO ₂  + CH _{3 形成的}SH。这代表了 H ₂ S 作为氢供体用于形成甲醇的硫醇对应物的第一个例子。MoS ₂的作用是分散碱并提供来自H ₂解离的溢出H的促进剂。