Electroreduction of CO2 to formate on amine modified Pb electrodes

Abstract

The electrocatalytic activity of islands-like aryl-aliphatic amines, aminophenyl and nitrophenyl derived Pb surfaces toward the electroreduction of CO₂ into formate was investigated. Diazonium chemistry was used to graft 4-aminomethylbenzene, 3-aminomethylbenzene, 4-(2-aminoethyl)benzene and nitrobenzene on the surface of Pb electrodes. Both scanning electron microscopy and X-ray photoelectron spectroscopy confirmed that organic layers are deposited at the surface of the electrodes, whose extent of grafting and thickness can be varied through the amine concentration in the grafting solution. The Pb-amine derived electrodes show enhanced activity and selectivity toward CO₂ reduction to formate. Compared to bare Pb, the cyclic voltammograms of amine modified electrodes showed higher current density in CO₂-saturated electrolyte and lower current density in Ar-saturated electrolyte. Stable electrolysis currents were recorded in most cases, and the best results were obtained for Pb modified with 4-aminomethylbenzene and a grafting extent of 6.3 × 10⁻⁷ mol cm⁻². In that case, a current density as high as −24.0 mA cm⁻² at −1.29 V vs. RHE was obtained, with a formate faradaic efficiency larger than 80%.