Enzymes such as carbon monoxide dehydrogenase (CODH) optimize CO2 conversion reactions by stabilizing reactive intermediates through non-covalent interactions (NCIs) in the secondary coordination sphere. Such NCIs are decoupled from the binding energetics of the catalytic sites and hence can lead to reaction pathways otherwise intractable in heterogeneous catalysis and can break scaling relationships that place limits on catalytic activity. Inspired by enzymes such as CODH, we introduce the heterobimetallic thiospinels—AD2S4, where A and D are first-row transition elements—as a class of materials competent for the electrochemical carbon dioxide reduction reaction (CO2RR) in neutral aqueous media, and whose catalytic activity can be tuned via NCIs through surface functionalization. Monodisperse AD2S4 nanoparticles are prepared via conventional colloidal synthetic methods, and sulfide exchange with functionalized thiolates is quantified by Fourier Transform Infrared and X-ray photoelectron spectroscopies. We find that the product distribution for the CO2RR on these functionalized nanoparticles depends on the pKa of the surface functional group, leading us to propose a mechanism in which hydrogen-bonding of reactive intermediates at the secondary coordination sphere plays an important role in accessing value-added products for CO2RR.

Tuning the product distribution of electrochemical carbon dioxide reduction through targeted non-covalent interactions with heterobimetallic thiospinel nanocatalysts

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