Hydrogen Evolution Catalyzed by an Iron Polypyridyl Complex in Aqueous Solutions

Iron complexes containing tetradentate monophenolate ligands have been found to be highly active for the electrocatalytic reduction of protons to hydrogen gas. Catalysis occurs at −1.17 V vs SCE in CH3CN with a turnover frequency of up to 1000 s–1 and a 660 mV overpotential. Interestingly, the catalyst activity is enhanced in the presence of water, achieving turnover frequencies of 3000 s–1 with an overpotential of 800 mV, making it one of the most active iron electrocatalysts currently reported. The catalyst is also capable of generating hydrogen from purely aqueous buffer solutions of pH 3–5 with Faradaic efficiencies of 98%.