Polymer-metal complexes as emerging catalysts for electrochemical reduction of carbon dioxide

A class of metal-doped polyanilines (PANIs) was synthesized and investigated as electrocatalysts for the carbon dioxide reduction reaction (CO2RR). These materials show good affinity for the electrode substrate and allow to obtain stable binder-free electrodes, avoiding the utilization of expensive ionomer and additives. The emeraldine-base polyaniline (EB-PANI), in absence of metal dopant, shows negligible electrocatalytic activity and selectivity toward the CO2RR. Such behavior significantly improves once EB-PANI is doped with an appropriate cationic metal (Mn, Cu or Sn). In particular, the Sn-PANI outperforms other metal-doped samples, showing a good turnover frequency of 72.2 h−1 for the CO2RR at − 0.99 V vs the reversible hydrogen electrode and thus satisfactory activity of metal single atoms. Moreover, the Sn-PANI also displays impressive stability with a 100% retention of the CO2RR selectivity and an enhanced current density of 4.0 mA cm−2 in a 10-h test. PANI, a relatively low-cost substrate, demonstrates to be easily complexed with different metal cations and thus shows high tailorability. Complexing metal with conductive polymer represents an emerging strategy to realize active and stable metal single-atom catalysts, allowing efficient utilization of metals, especially the raw and precious ones.