Marco Papasizza (one of Angel Cuesta Ciscar's PhD students) was awarded his PhD for his "In situ infrared study of electrocatalytic CO2 reduction and other interfacial processes in ionic liquid-water mixtures".
The main goal of Marco’s thesis was to apply in situ infrared spectroscopy to improve our understanding of electrocatalytic CO2 reduction (a potential technology for renewable energy storage and synthesis of fuels) in imidazolium-based ionic liquid-water mixtures. His work shows that CO is the main adsorbed product of CO2 reduction on Au electrodes, like in aqueous media. Experiments yielded no evidence of intermediates proposed in the literature. The spectra revealed hydrogen-bond-free water and bulk-like water populations in the mixture and parallel computational work predicts that hydrogen-bond-free water may stabilise the CO2− radical generated after the first electron transfer and account for the low overpotentials observed in this kind of medium. The significance of this work is, first, to question previous hypotheses on CO2 reduction intermediates in ionic liquids by failing to detect species proposed in the literature. Second, it shows that the interfacial behaviour of water populations is complex and worth investigating in more depth. Third, the results emphasise the importance of performing careful blank experiments in ionic liquid systems, because signals not connected to the reaction itself may be confused for intermediates of CO2 reduction or other electrocatalytic processes.