a) Electronic Features: Changing the electronic features of the cation ring can affect its acidity, potentially improving or diminishing catalytic activity, or even introducing new reaction pathways. This particularly might be of high relevance for highly acidic cations. b) Bulkiness: Different substituents can impact the bulkiness of the cation, which in turn affects the interfacial interaction of the cation with the catalyst and adsorbed CO2. Bulky cations may also obstruct active sites at the same surface concentration. To ensure a fair comparison, it is advisable to compare substituents within the same functional family that have similar bulkiness. c) Hydrophobicity/Hydrophilicity: The hydrophobic or hydrophilic nature of the cation can influence the stability and mechanism of the non-aqueous CO2 conversion process, especially in the presence of residual water. The effect of water on cation chemistry depends on the cation's nature, and more acidic cations are more likely to experience significant impacts such as deprotonation and reaction with hydroxyl groups. d) Intrinsic Electronic Effects: The intrinsic electronic effects of the cation within the double layer can have an impact. Non-specific interactions with the electrode, including the image charge effect, can modify the electrostatic potential and the adsorption properties of the electrode for polar intermediates93-94. While these effects are expected to be similar for cations with the same charge density per volume94, they may differ for cations with significantly different bulkiness and charge density. Therefore, it is important to work with cations of similar bulkiness when studying specific chemical factors such as acidity.
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