Linking Molybdenum–Sulfur Clusters for Electrocatalytic Hydrogen Evolution

Controlling the spatial arrangement of molecular catalysts on electrodes is critical to developing an optimal electrocatalyst. Mo-S clusters have shown great promise in catalyzing hydrogen evolution for the generation of carbon-free fuel from water. Here we report a synthetic approach to organize these molecular clusters into ordered dimers, cages, and chains through the use of organic linkers, as solved by single-crystal X-ray diffraction. We find that the linkage through the coordination bond between thiolate and Mo₃S₇ leads to (1) a 40-fold enhancement in turnover frequency compared with the unlinked cluster and (2) the periodic arrangement of clusters on the electrode with control over their distance, orientation, and density, thus enabling hydrogen evolution at high catalyst loading. The materials developed here require an overpotential of only 89 mV to achieve a current density of 10 mA cm^-2, outperforming other Mo-S catalysts (both molecular and solid-state).