Polyethyleneimine-reinforced Sn/Cu foam dendritic self-supporting catalytic cathode for CO2 reduction to HCOOH

In this work, a novel catalytic cathode of polyethyleneimine (PEI)–Sn/Cu foam with dendritic structure was prepared by electrodeposition and impregnation. It was used in the electrocatalytic reduction of CO2 to HCOOH, and its performance in this process was evaluated. At −0.97 V vs. RHE, the faradaic efficiency and current density reached 92.3% and 57.1 mA cm−2, respectively, in a 0.5 M KHCO3 electrolyte. The HCOOH production rate reached 890.4 μmol h−1 cm−2, which exceeds those for most reported Sn catalysts. Density functional theory calculations showed that use of Sn/Cu foam is more conducive to HCOOH formation than use of Cu or Sn alone, and *OCHO is the main intermediate in HCOOH formation. The results of OH− adsorption experiments confirmed that the introduction of PEI enhanced the catalytic capacity of the Sn/Cu foam, stabilized CO2·− intermediates, and promoted HCOOH generation. These results will provide an attractive strategy for developing efficient catalysts with excellent activities and stabilities for CO2 electroreduction.