Imidazole-imidazolate pair as organo-electrocatalyst for CO2 reduction on ZIF-8 material

The electrochemical reduction of CO2 to value-added products is hindered by its thermodynamic stability and by the large energy required to chemically activate the molecule. With this respect, forcing CO2 in a non-linear geometry would induce an internal electron charge rearrangement which would facilitate further electrochemical transformations. In this work, we achieved this goal through the design of a dual function electro-organocatalyst, which exploits the ability of the imidazolate (Im-) lone pair to bind CO2 via nucleophilic attack and then electrochemically reduce it. To give structural stability to the Im- based catalyst, the imidazoles species are incorporated into a solid structure, namely ZIF-8. Once activated by the organic Im- ligand, CO2 is electrochemically reduced to CO when a bias is applied to ZIF-8. The catalyst proposed in our study was first devised by computer aided design based on Density functional Theory simulations and then realized in laboratory. Our results demonstrate that ZIF-8 supported on conductive CNTs presents surface Im- active sites which convert CO2 into CO with a high faradaic efficiency (70.4 %) at −1.2 V vs reversible hydrogen electrode, by combining chemical activation with electrochemical catalysis.