Structure-sensitivity and Electrolyte Effects in CO2 Electroreduction: From Model Studies to Applications

Aiming to reduce anthropogenic CO2 emissions, there is an urgent demand to develop more efficient and affordable technologies which convert CO2 into valuable feedstock molecules. The use of renewable electricity is a promising and sustainable approach to overcome this environmental issue, while producing valuable chemicals and clean fuels. However, the CO2 electroreduction reaction (CO2RR) still shows two main gaps: poor selectivity and required large overpotentials make the process not profitable enough. To overcome these challenges, model studies on single-crystalline surfaces aiming to find the relations between surface structure/electrolyte interactions and activity/selectivity are necessary. In these model studies, tuning the electrolyte composition is also key for the fundamental understanding of the CO2RR. In this review, we first discuss the structure-activity-selectivity relations from studies on well-ordered surfaces, i. e., single crystalline electrodes, for the CO2RR. We then summarise the role of the electrolyte, presenting work on classical aqueous solvents as well as non-aqueous electrolytes such as ionic liquids. We illustrate the importance of carrying out studies on well-defined electrified interfaces in order to get deep fundamental insights on the mechanism of the CO2RR, as well as scaling the process for real applications. Ultimately, this knowledge will be essential to rationally design the catalyst with tailored activity and selectivity for CO2 reduction.