Metal organic framework-ionic liquid hybrid catalysts for the selective electrochemical reduction of CO2 to CH4

Abstract

The electrochemical reduction of CO2 towards hydrocarbons is a promising technology that can utilize CO2 and prevent its atmospheric accumulation while simultaneously storing renewable energy. However, current CO2 electrolyzers remain impractical on a large scale due to the low current densities and faradaic efficiencies (FE) on various electrocatalysts. In this study, hybrid HKUST-1 metal-organic framework–fluorinated imidazolium-based room temperature ionic liquid (RTIL) electrocatalysts are designed to selectively reduce CO2 to CH4. An impressive FE of 65.5% towards CH4 at −1.13 V is achieved for the HKUST-1/[BMIM][PF6] hybrid, with a stable FE greater than 50% maintained for at least 9 h in an H-cell. The observed improvements are attributed to the increased local CO2 concentration and the improved CO2-to-CH4 thermodynamics in the presence of the RTIL molecules adsorbed on the HKUST-1-derived Cu clusters. These findings offer a novel approach of immobilizing RTIL co-catalysts within porous frameworks for CO2 electroreduction applications.