Molecular Hybrid Materials for Selective CO₂ Electroreduction to Multicarbon Products

Abstract Electrochemical devices, using renewable energy sources, for CO 2 reduction (CO 2 R) coupled with water oxidation is an attractive strategy for the carbon‐neutral generation of solar fuels and chemical feedstocks. Highly reduced multi‐carbon (C 2+ ) products (e.g., ethylene, ethanol, and propanol) are among the most attractive CO 2 R chemicals because of their commercial value and high energy densities. Here a new molecular hybrid material is reported that combines the capacity of molecular CO 2 R catalyst to generate CO with the capacity of Cu(0) materials to achieve C 2+ products and further tune their reactivity with organic modifiers. A Fe‐A 2 B 2 porphyrin containing two quaternary ammonium groups that set the right CO 2 R onset potential for a synergistic tandem performance with Cu 2 O nanocubes as the precursors is prepared. Furthermore, Fe‐A 2 B 2 porphyrin is functionalized with two thiolate substituents in order to covalently anchor the molecular catalyst onto Cu providing an intimate interaction and great stability. The structural design enables a substantially enriched CO species adsorbed on Cu facilitated by the iron porphyrin catalyst that in turn facilitates the evolution of C 2+ products, as demonstrated by in situ Raman spectroscopy. In addition, the whole electrode is further coated with phenyl modifiers that regulate the proton content and hydrophilicity in the neighborhood of the active centers. This approach affords Faradaic efficiencies in the range of 50% for ethylene and 77% for C 2+ products at an applied potential of −1.05 V versus RHE.