Copper/alkaline earth metal oxide interfaces for electrochemical CO₂-to-alcohol conversion by selective hydrogenation

Multicarbon alcohols produced by electrochemical CO₂ reduction (CO₂RR) are attractive alternatives to fossil fuels; however, the selectivity towards alcohols in CO₂RR remains low, a result of competing hydrocarbon (that is, ethylene) production. Here we report on Cu catalysts decorated with different alkaline earth metal oxides (MOs). We found that BaO delivers a Faradaic efficiency of 61% towards C₂₊ alcohols. At an industry-relevant current density of 400 mA cm⁻², the ratio of alcohols to hydrocarbon reached 3:1. Mechanistic studies, including in operando X-ray absorption spectroscopy, in situ Raman spectroscopy and density functional theory calculations, suggested that the increased selectivity towards alcohols originates from sites at the MO/Cu interface. Furthermore, computational studies indicated that the incorporation of MOs favours a hydroxy-containing C₂ intermediate (*HCCHOH) over the hydrocarbon intermediate (*HCC) at interfacial Cu sites on the path to alcohol products. We also propose that the relative bond strengths of Cu–COH and C–OH correlate with the selectivity for alcohol over hydrocarbon.