In-situ surface enhanced Raman spectroscopy investigations on surface transformations of oxide derived copper electrodes during CO2RR

Abstract

We investigated the catalytic activity and C2 selectivity in electrochemical carbon dioxide reduction reac-tion (CO2RR) on two distinguished electrodeposited Cu oxides with distinct morphologies and structures. The electrode with a compact structure exhibited two times higher faradaic efficiencies of C2 products (40%). Through utilizing electrochemical surface-enhanced Raman spectroscopy (SERS), it was realized that the formation of a metastable phase (malachite) on electrode surfaces by consumption of HCO3- could cause a shift in local pH. The analysis of SERS indicated a strong correlation between the presence of the malachite phase and strongly-adsorbed CO on electrode surfaces, preventing dimerization and fur-ther reduction. This malachite phase terminating the surface can hinder the charge exchange and inter-fere with further reductions in C2 products.