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.