Stabilizing High-Valence Copper(I) Sites with Cu-Ni Interfaces Enhances Electroreduction of CO 2 to C 2+ Products.

In this study, the copper-nickel (Cu-Ni) bimetallic electrocatalysts for electrochemical CO 2 reduction reaction(CO 2 RR) are fabricated by taking the finely designed poly(ionic liquids) (PIL) containing abundant Salen and imidazolium chelating sites as the surficial layer, wherein Cu-Ni, PIL-Cu and PIL-Ni interaction can be readily regulated by different synthetic scheme. As a proof of concept, Cu@Salen-PIL@Ni(NO 3 ) 2 and Cu@Salen-PIL(Ni) hybrids differ significantly in the types and distribution of Ni species and Cu species at the surface, thereby delivering distinct Cu-Ni cooperation fashion for the CO 2 RR. Remarkably, Cu@Salen-PIL@Ni(NO 3 ) 2 provides a C2+ faradaic efficiency (FE C2+ ) of 80.9% with partial current density (j C 2+ ) of 262.9 mA cm -2 at -0.80 V (versus reversible hydrogen electrode, RHE) in 1 m KOH in a flow cell, while Cu@Salen-PIL(Ni) delivers the optimal FE C2+ of 63.8% at j C2+ of 146.7 mA cm -2 at -0.78 V. Mechanistic studies indicates that the presence of Cu-Ni interfaces in Cu@Salen-PIL@Ni(NO 3 ) 2 accounts for the preserve of high-valence Cu(I) species under CO 2 RR conditions. It results in a high activity of both CO 2 -to-CO conversion and C-C coupling while inhibition of the competitive HER.