A nickel(II) complex of 2,6-pyridinedicarboxylic acid ion, an efficient electro-catalyst for both hydrogen evolution and oxidation

Abstract A new electrocatalyst based on a nickel complex, [Ni(HL)2], is designed and provided by the reaction of NiCl2 with 2,6-pyridinedicarboxylic acid (H2L) in our group. Electrochemical investigations show that [Ni(HL)2] can electro-catalyze hydrogen evolution from acetic acid with a rate constant of 3454 M−2 s−1. [Ni(HL)2] also can electro-catalyze hydrogen oxidation with a rate constant of 2.047 × 104 M−2 s−1. The carboxyl group of [Ni(HL)2] may play critical roles in the catalytic hydrogen evolution and oxidation reactions. Moreover, the introduction of an electron-withdrawing group, -Cl at the pyridine of H2L leads to a decrease in the catalytic activity for hydrogen generation, and [Ni(HL)2] shows a more efficient activity than [Ni(HL-Cl)2] (H2L-Cl: 4-chloro-2,6-pyridinedicarboxylic acid). These findings can afford a new ideal for the design of electrocatalysts for both H2 evolution and H2 oxidation.