Poly-Amide Modified Copper Foam Electrodes for Enhanced\nElectrochemical Reduction of Carbon Dioxide

Abstract

A strategy to modulate\nthe electrocatalytic activity of copper\ntoward CO₂ reduction involving adsorption of acrylamide,\nacrylic acid, and allylamine polymers is presented. Modification of\nelectrodeposited copper foam with poly­(acrylamide) leads to a significant\nenhancement in faradaic efficiency for ethylene from 13% (unmodified\nfoam) to 26% at −0.96 V vs RHE, whereas methane yield is unaffected.\nEffects from crystalline phase distribution and copper oxide phases\nare ruled out as the source of enhancement through XPS and in situ\nXRD analysis. DFT calculations reveal that poly­(acrylamide) adsorbs\non the copper surface via the oxygen atom on the carbonyl groups and\nenhances ethylene formation by (i) charge donation to the copper surface\nthat activates CO for dimerization, (ii) chemical stabilization of\nthe CO dimer (a key intermediate for C₂ products) by hydrogen-bond\ninteractions with the −NH₂ group, and (iii) facilitating\nthe adsorption of CO molecules near the polymer, increasing local\nsurface coverage. Poly­(acrylamide) with copper acts as a multipoint\nbinding catalytic system where the interplay between activation and\nstabilization of intermediates results in enhanced selectivity toward\nethylene formation. Modification with poly­(acrylic acid) which has\na similar structure to poly­(acrylamide) also shows some enhancement\nin activity but is unstable, whereas poly­(allylamine) completely suppresses\nCO₂ reduction in favor of the hydrogen evolution reaction.