Fractal growth of a fern-like nanostructured Cu2O film electrode for electrochemical reduction of CO2 to ethanol

Abstract

Coating an electrocatalytic material on a substrate without using a binder is a preferable method to prepare electrodes for CO₂ reduction. In this work, nanostructured film electrodes are prepared by electrodepositing Cu₂O on the surface of a stainless steel strip (SS-316) at −0.3, −0.4 and −0.5 V for 5 minutes, which are denoted as CuP3T5, CuP4T5 and CuP5T5, respectively. The structure and various morphologies of these film electrodes and their impact on electrochemical CO₂ reduction are studied. The film electrodes contain the Cu₂O phase with marigold flower-like morphology (CuP3T5) and branched-3D fern-like structures (CuP4T5 and CuP5T5). Among the three nanostructured Cu₂O film electrodes, the CuP4T5 film electrode shows the highest activity for CO₂ reduction to ethanol, analysed by linear sweep voltammetry study and gas chromatography. The CuP3T5, CuP4T5 and CuP5T5 film electrodes show maximum faradaic efficiencies of ∼29%, ∼80% and ∼51% for the ethanol product, respectively, at the potential of −1.1 V vs. Ag/AgCl. The highest faradaic efficiency is correlated with the fractal growth morphology of the CuP4T5 sample. The mechanism of CO₂ reduction to ethanol is elucidated by DFT calculations carried out on Cu₂O(111).