(Keynote) Detecting the Elusive Adsorbed CO2·- Intermediate on a Copper Electrode Using Operando Raman Spectroscopy and Pyridine As a Promoter: Implication for CO2 Electroreduction

Monday, 2 October 2017: 08:00
National Harbor 8 (Gaylord National Resort and Convention Center)


Electrochemical conversion of the abundant CO2 to fuels, polymers, drugs, and other materials using renewable energy is one of the most promising approaches that can help deploy this energy and reduce our dependence on fossil fuels. However, the rational development of a viable CO2 electroreduction system is hampered by a daunting lacunae in the mechanistic knowledge of this reaction. This is especially true with respect to the knowledge derived from experimental (electrochemical and operando spectroscopic) data. The problem stems from the complexity of both CO2 electroreduction per se and the great technical challenges to detect and identify the key reaction intermediates in operandi exactly on the same catalyst that is employed in the preparative electrolysis studies.

We address this technical challenge by employing advantages of the electrochemical surface-enhanced Raman scattering (SERS) method, which have been neglected in the earlier attempts to gain mechanistic insights into CO2 electroreduction. These advantages include the outstanding sensitivity of SERS to the species adsorbed on the ‘hot spots’ and the ability of this method to detect these species on real electrocatalysts in real time. Specifically, combining this method with Density Functional Theory (DFT) simulations and employing pyridine as the reaction promoter, we resolve the long-standing controversies about the mechanism of the formate and CO synthesis on a polycrystalline copper electrode in aqueous electrolytes, as well as on the promoting effects of pyridine. Correlating the microscopic results with the electrolysis and electrochemical data, we conclude that the formation of the CO2d- intermediate is the rate-determining step of the formate synthesis on Cu, while formate and CO share the same route.