Highly efficient molecular nickel catalysts for electrochemical hydrogen production from neutral water.

A series of nickel complexes containing N5-pentadentate ligands with different amine-to-pyridine ratios were studied for electrochemical H2 production in neutral water and the one with a diamine-tripyridine ligand displays a TON of up to 308,000 over 60 h electrolysis at -1.25 V vs. SHE, with a Faradaic efficiency of ∼91%.