Electrocatalytic hydrogen evolution reaction by a Ni(N2O2) complex based on 2,2′-bipyridine

Abstract

In the face of rising atmospheric carbon dioxide (CO₂) emissions from fossil fuel combustion, the hydrogen evolution reaction (HER) continues to attract attention as a method for generating a carbon-neutral energy source for use in fuel cells. Since some of the best-known catalysts use precious metals like platinum, which have low natural abundance and high cost, developing efficient Earth abundant transition metal catalysts for HER is an important objective. Building off previous work with transition metal catalysts bearing 2,2′-bipyridine-based ligand frameworks, this work reports the electrochemical analysis of a molecular nickel(II) complex, which can act as an electrocatalyst for the HER with a faradaic efficiency for H₂ of 94 ± 8% and turnover frequencies of 103 ± 6 s⁻¹ when pentafluorophenol is used as a proton donor. Computational studies of the Ni catalyst suggest that non-covalent interactions between the proton donor and ligand heteroatoms are relevant to the mechanism for electrocatalytic HER.