A Synthetic Nickel Electrocatalyst with a Turnover Frequency Above 100,000 s −1 for H 2 Production

Abstract

Reduction of acids to molecular hydrogen as a means of storing energy is catalyzed by platinum, but its low abundance and high cost are problematic. Precisely controlled delivery of protons is critical in hydrogenase enzymes in nature that catalyze hydrogen (H₂) production using earth-abundant metals (iron and nickel). Here, we report that a synthetic nickel complex, [Ni(P^Ph₂N^Ph)₂](BF₄)₂, (P^Ph₂N^Ph = 1,3,6-triphenyl-1-aza-3,6-diphosphacycloheptane), catalyzes the production of H₂ using protonated dimethylformamide as the proton source, with turnover frequencies of 33,000 per second (s⁻¹) in dry acetonitrile and 106,000 s⁻¹ in the presence of 1.2 M of water, at a potential of –1.13 volt (versus the ferrocenium/ferrocene couple). The mechanistic implications of these remarkably fast catalysts point to a key role of pendant amines that function as proton relays.