Ultrafast Electrocatalytic H2 Evolution from Water Achieved by a Cobalt-NHC Catalyst

Development of highly active catalysts for water oxidation and reduction is one of the crucial targets in artificial photosynthesis. However, chemists still face a great challenge in advancing the molecular-level understanding of these catalytic processes. Here we succeed in raising two orders of magnitude in the turnover frequency (TOF) of electrocatalysis for hydrogen evolution reaction (HER) under neutral aqueous conditions (pH 7.0). The title N-heterocyclic carbene cobalt catalyst (Co-NHC1) is demonstrated to achieve an unprecedented TOF of 33 million s-1, which is by far higher than the highest value reported to date (TOF = 0.1 million s-1 at pH 7.0). We also show that the HER electrocatalyzed by Co-NHC1 rapidly proceeds as a diffusion-limited reaction via two successive concerted proton-electron transfer (CPET) pathways.