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 (FECO) of 90.1% with a partial current density (jCO) of 90.1 mA cm-2 at -0.85 V, while a FECH4 of 54.5% with jCH4 of 272.5 mA cm-2 at -1.60 V was obtained on Salen-PIL(Cu).
Keywords: CH4 production; CO production; CO2 electroreduction; metal−N2O2 sites; poly(ionic liquids).