Nickel Complexes with Non‐innocent Ligands as Highly Active Electrocatalysts for Hydrogen Evolution.

Rational design of a molecular catalyst for a hydrogen evolution reaction (HER) with both high rates and low overpotential remains a challenge. Here we report a series of Ni‐based catalysts incorporating non‐innocent ligands and aimed at reduction of the overpotential by reserving electrons in the ligand, which could decouple the correlation between metal center reduction and metal hydride formation. The third‐order rate constant of our catalysts can be increased by 2 orders of magnitude without increase of overpotential by altering the substituents in the imide since the electronic effect of substituents can change the kinetics of metal hydride formation dramatically. Furthermore, constructing a proton shuttle in the ligand further improves the activity. The catalyst with both of these features can catalyze HER at a turnover frequency of 2572 s–1 with low concentrations of acid and an extremely high third‐order rate constant of 2.7×106 M–2·s–1 at a low overpotential. Regulation of metal center reduction and metal hydride formation for HER — lower overpotentials and faster reaction rates. [ABSTRACT FROM AUTHOR]