CoGGH, a Gly-Gly-His tripeptide coordinated to a cobalt ion, is shown to catalyze the reduction of aqueous protons to hydrogen (H-2) in a light-driven reaction in water near neutral pH. Using [Ru(bpy)(3)](2+) as a photosensitizer and ascorbate as an electron donor, a turnover number up to 2200 with respect to CoGGH has been observed with the system remaining active for more than 48 h. The reaction conditions that favor H-2 production are consistent with a reductive quenching mechanism. Results also suggest that CoGGH is robust under these reaction conditions and loss of activity over time results from [Ru(bpy)(3)](2+) degradation.