New metal persulfido compositions of matter are described. In one embodiment the metal is molybdenum and the metal persulfido complex mimics the structure and function of the triangular active edge site fragments of MoS2, a material that is the current industry standard for petroleum hydro desulfurization, as well as a promising low-cost alternative to platinum for electrocatalytic hydrogen production. This molecular [(PY5W2)MoS2]x+ containing catalyst is capable of generating hydrogen from acidic-buffered water or even seawater at very low overpotentials at a turnover frequency rate in excess of 500 moles H2 per mole catalyst per second, with a turnover number (over a 20 hour period) of at least 19,000,000 moles H2 per mole of catalyst.