Electrocatalytic Hydrogen Production with a Molecular Cobalt Complex in Aqueous Solution

Abstract

AbstractHerein, we present the synthesis of a cobalt complex with a pentadentate ligand platform and its application in the electrochemical hydrogen evolution reaction (LCF3=2,6‐bis(methoxybis(4‐trifluormethyl‐1H‐imidazol‐2‐yl)methyl)pyridine). The complex is active in neutral to acidic solvent mixtures containing 50 % water. Electronic tuning in the ligand backbone, that is introduction of electron‐withdrawing CF3‐groups, shifts the onset potential of the catalytic wave to less negative potentials. NMR and UV/Vis studies indicate that the CoIII complex is deprotonated twice in the ligand backbone under neutral conditions. Reduction is accompanied by protonation, as indicated by pH‐dependent CV measurements, and the CoI state initiates catalysis. The result suggests that the pentadentate ligand is an ideal platform for cobalt catalysts in the oxidative and reductive water splitting reaction.