Monomeric MoS 4 2– -Derived Polymeric Chains with Active Molecular Units for Efficient Hydrogen Evolution Reaction

Molybdenum sulfides have attracted widespread attention as promising nonprecious-metal catalysts for the hydrogen evolution reaction (HER). Since the MoS 2 edge was proposed as a major active site, molecular and polymeric analogues to the MoS 2 edge have been widely explored as the HER catalysts. In particular, amorphous MoS x coordination polymers have been considered as active HER catalysts because they are rich in unsaturated Mo–S coordination, which is the characteristic of the active MoS 2 edge. Herein, we report that the simple monomeric thiomolybdate (MoS 4 2– ) could adopt a polymeric chain structure, which exhibited high HER activity; its turnover frequency surpassed those of dimeric [Mo 2 S 12 ] 2– - and trimeric [Mo 3 S 13 ] 2– -derived MoS x catalysts. This high HER activity of monomeric MoS 4 2– is attributed to the polymerization of MoS 4 2– anions, generating active molecu…