An efficient electrocatalyst for the reduction of CO2 (CO2R) would enable the conversion of a major contributor to global warming into valuable carbon-based products. However, the complexity of the catalyst/electrolyte interface poses challenges in identifying how a change in an electrocatalyst affects the observed CO2R selectivity. Therefore, we employ a methodical experimental approach that focuses upon identifying which parameters play an important role in determining CO2R selectivity. First, we examined the effect of a series of organic modifiers on the CO2R selectivity of Cu. Cu surfaces were functionalized with molecular and polymeric modifiers featuring a wide variety of structural characteristics, including neutral and cationic species, protic and aprotic species, and species bearing various functional groups. The product distribution of these surfaces in the CO2R reaction was characterized at -0.7 V vs. RHE, focusing upon the selectivity between CO, formic acid and H2. This allowed classification of the organic structures based upon the promoted product. Finally, each class of modifiers was examined and key, common structural characteristics of the modifiers were identified. Through this systematic study, we find that these organic modifiers influence CO2R selectivity, not through structure-specific interactions, but rather due to bulk properties that influence the local surface environment. In this presentation, we describe the common features of these modifiers that emerge as key to changing the observed selectivity, and the ways in which these features offer insights into the mechanism. We expect that the identified structure-reactivity relationships will illuminate important design principles for novel, selective CO2R electrocatalysts and organic structures for CO2R devices.

Effect of organic modifiers on the local environment in the electrocatalytic reduction of CO2 at metallic surfaces

2019 Fall National Meeting

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