Abstract master thesis Hilbert Heida - Friday February 24, 2023 - Starting at 15:00hr.
Rapid scan IR reflection-absorption spectroelectrochemistry to uncover the mechanism of electrochemical CO2 reduction on Cu
The electrochemical reduction of CO2 on Cu is a promising reaction to convert CO2 into C1 and C2 hydrocarbons. Previous (theoretical) studies have proposed a lot of different mechanisms,including many different pathways. Despite the effort to uncover the exact mechanism, the mechanism is still subject of debate. Spectroscopy techniques have been used to observe intermediates that appear during the reaction, to give more insight in the CO2 reduction mechanism. In this research, rapid scan infrared reflection absorption spectroscopy (IRRAS) with polarized light is used to obtain information in the presence of (adsorbed) species/intermediates on the Cu surface and in the diffusion layer while the reaction is taking place. Many peaks have been observed, some of which are not reported in previous studies. It was found that CH products can be formed under certain conditions and that the local pH close to the metal surface is of huge importance for the reaction. The CO2, HCO3– and CO32- IR bands are tracked and used to link them to an estimated local pH. CO, one of the most important intermediates, has not been observed in the electrochemical reduction of CO2. Our hypothesis is that the CO coverage on the Cu surface does not create a substantial IR absorbance signal within the time window of our measurements. Furthermore, using surface sensitive infrared reflection absorption spectroscopy experiments, a new type of reduction reaction is proposed. A HCO3– assisted CO2 reduction that yields monodentate adsorbed CO32- and adsorbed formate as products is proposed.