Promoting the electrocatalytic conversion of CO₂ to ethanol at ultra-low potential by fully exposing periodic low-index facets in hexagonal pyramidal Cu

The close correlation between the crystal facet exposure features of copper (Cu) catalysts and their CO₂ reduction reaction (CO₂RR) products has attracted significant research interest. Driving efficient CO₂ reduction to ethanol on Cu catalysts through appropriate facet tailoring techniques holds considerable research value. In this work, computational studies reveal that periodically alternating (100)/(110)/(111) facets arranged in an orderly manner on Cu catalysts can facilitate a smooth reaction pathway from CO₂ to ethanol via a facet-dependent relay catalysis mechanism. This implies that constructing structures with periodically alternating exposed facets is crucial for promoting ethanol formation. Guided by these theoretical insights, we adjusted the morphology of Cu catalyst in an electrodeposition fabrication strategy by changing the precursor of Cu. By leveraging the synergistic effect of sodium citrate chelation and anion-specific adsorption to precisely control release of Cu ion, the three-dimensional hexagonal pyramidal Cu catalyst was fabricated with periodically exposed (100) and (111) facets, and the interfacial strain engineering induced abundant (110) facets at the junctures. As predicted, the resulting hexagonal pyramidal Cu catalyst achieved a remarkably high Faradaic efficiency of 79.79 % for ethanol production at −0.125 V vs. RHE. Detailed in situ FTIR spectroscopy confirmed that the stepped (111)/(110)/(100) configurations facilitate a cascade reaction pathway towards ethanol. This work provides a successful framework for theoretically guided catalyst design and performance optimization, which may stimulate the study on overcoming inherent limitations in multi-carbon product synthesis through crystallographic phase engineering.