A Water-soluble Cobalt(II) Compound Co(TCNQ)2, An Electrocatalyst for Hydrogen Evolution from Acetic Acid and Water

Background: The generation of hydrogen by electrochemical reduction of water, represents an attractive approach for storing the electrical energy transiently produced by renewable energy sources, and catalysts based on transition metal compounds are used to increase the reaction rate. Despite much progress in water reduction catalysis, structural complexity, insolubility in aqueous media and low pH conditions severely limit their practical utility. To meet this goal, we design an electrocatalyst based on Co(TCNQ)2 (TCNQ: 7,7,8,8-tetracyanoquinodimethane). This compound is water soluble and can catalyze proton or water reduction. Methods: The reaction of LiTCNQ with CoCl2.6H2O yields a cobalt-TCNQ compound, Co(TCNQ)2 1. This compound has been characterized by spectroscopic, physics-chemical and electro-chemical methods. Results: Electrochemical studies show that the electrocatalytic system formed by compound 1 achieves a turnover frequency (TOF) of 767 moles h-1 H2 from a neutral buffer solution (pH 7.0) at an overpotential (OP) of 0.638 V. Conlusions: The result suggests that the addition of TCNQ is the key feature for highly catalytic activity of 1. This can be attributed to the introduction of TCNQ- ion to cobalt center, stabilizing the low oxidation state of cobalt.