Construction of Metal-N₂O₂ Sites on Poly(ionic liquid) for Highly Efficient Electrocatalytic CO₂ Reduction

In this study, atomically dispersed metal catalysts of Salen-PIL(M) (M = Zn and Cu) for electrochemical CO₂-to-C₁ conversion were fabricated by polymerization of a vinyl-decorated ionic liquid (IL) monomer bearing a Salen-M moiety with para-diethylbenzene. The characterization results indicated that the Salen-Zn/Cu complex was atomically dispersed in the PIL skeleton. They differed significantly in the electron transfer speed to CO₂, CO affinity, and H₂O activation, which influenced both the activity and selectivity toward CO or CH₄. Besides, the formation of CO₂^•-* and H₂O activation were related to the tolerance of the pH range. Meanwhile, the adjustment of the interfacial H₂O content by introducing a hydrophobic IL benefited the competitive CO₂RR versus HER on Salen-PIL(Zn/Cu) catalysts. As a result, Salen-PIL(Zn) provided a CO faradaic efficiency (FE_CO) of 90.1% with a partial current density (j_CO) of 90.1 mA cm^-2 at -0.85 V, while a FE_CH4 of 54.5% with j_CH4 of 272.5 mA cm^-2 at -1.60 V was obtained on Salen-PIL(Cu).