Compensating the impurities on the Cu surface by MOFs for enhanced hydrocarbon production in the electrochemical reduction of carbon dioxide

Abstract Copper (Cu) provides a cost-effective means of producing value-added fuels through the electrochemical reduction of carbon dioxide (CO2RR). However, we observed the production of hydrocarbons via CO2RR on commercial Cu films is less efficient because of the surface impurities, i.e., Fe. Carbon monoxide (CO), a reaction intermediate of CO2RR to hydrocarbons, binds strongly to the Fe sites and interrupts the production of hydrocarbons, resulting in an active hydrogen evolution reaction (HER). Herein, we report a method of blocking the effect of Fe impurities on the Cu surface through the preferential growth of nano-sized metal-organic frameworks (MOFs) on Fe site. When zirconium (Zr)-based MOFs (UiO-66) forms a compensating layer on Cu film via the terephthalic acid (TPA)-Fe coordination bond, the UiO-66 coated Cu film (UiO-66@Cu) presents significantly improved hydrocarbon Faradaic efficiency (FE) of 37.59% compared to 14.68% FE on commercial Cu film (99.9% purity) by suppressing HER. According to X-ray photoelectron spectroscopy (XPS) analysis, the UiO-66 ligand binds to entire metallic Fe site on the Cu surface, while metallic Cu is retained. Thus, UiO-66@Cu provides active sites of Cu for CO2RR and leads to highly efficient and selective production of hydrocarbons.