Polythiophene-decorated copper via polypyrrole intermediary passivation layer for enhanced electrocatalytic reduction of carbon dioxide

Abstract

Copper is unique in catalyzing the electrochemical reduction of carbon dioxide (CO2RR) to produce C2+ hydrocarbons, but pristine Cu has a low selectivity and stability. In this study, a multilayered, N and S-containing polymer, polypyrrole (PPy), and polythiophene (PTh) were electrodeposited on polycrystalline Cu surface, and the CO2RR catalytic activity was investigated via Electrochemical Mass Spectrometry (EC-MS), Gas (GC) and Liquid (HPLC) Chromatography techniques. The PTh-PPy-Cu electrode exhibited lower CO2RR onset potential (−0.6 V vs RHE) and higher selectivity towards ethylene formation, when compared to bare Cu electrodes, as revealed by the EC-MS measurements. GC analyses also revealed that the PTh-PPy-Cu electrode exhibits higher faradaic efficiency for ethylene production than bare Cu (FE ∼ 1.4 to 7.0 %) at a relatively low overpotential (−1.0 V vs RHE). The improved selectivity of PTh-PPy-Cu for C2H4 was mainly attributed to the in-situ generated surface defects (grain boundaries), stabilized by the PTh overlayer, and to the strong hydrophobic characteristic of the polymer layer. This study could pave the way for fine-tuning the catalytic activity, selectivity, and stability of copper-containing catalysts by utilizing surface modification of metallic catalysts toward the CO2RR.