Enhancing CO₂ Electroreduction to Multicarbon Products by Modulating the Surface Microenvironment of Electrode with Polyethylene Glycol

Abstract

Modulating the surface microenvironment of electrodes stands as a pivotal aspect in enhancing the electrocatalytic performance for CO₂ electroreduction. Herein, we propose an innovative approach by incorporating a small amount of linear oligomer, polyethylene glycol (PEG), into Cu₂O catalysts during the preparation of the Cu_PEG electrode. The Faradaic efficiency (FE) toward multicarbon products (C₂₊) increases from 69.3 % over Cu electrode without PEG to 90.3 % over Cu_PEG electrode at 500 mA cm^-2 in 1 M KOH in a flow cell. In situ investigations and theoretical calculations reveal that PEG molecules significantly modify the microenvironment on the Cu surface through hydrogen bond interactions. This modification leads to the relaxation of Nafion, increasing the availability of active sites and enhancing the adsorption of *CO and *OH, which in turn promotes C-C coupling. Concurrently, the reconstructed hydrogen bond network reduces the presence of active hydrogen species, thereby inhibiting the hydrogen evolution reaction.