Hydroformylation-like Reactions Enable Electrochemical Pathways from CO2 to Extended Carbon Chains

Atomically precise active sites on electrode surfaces promise new chemical transformations that simultaneously exploit both the potent physical handle of applied voltage and the highly-tailored reactivity of well-defined active sites. Often, these catalysts have off-electrode analogs in biology or organometallic chemistry, and effectively leveraging these analogies requires an understanding of how catalysis at the active site is perturbed by the complex interplay of electrolyte species and electric fields at electrode interfaces. In this work, we dissect and design two atomically precise catalysts that leverage off-electrode analogies and enable an electrochemical pathway that converts CO2 to extended carbon chains. We show that a new electrified hydroformylation reaction can be used to achieve electrochemical C-C coupling. Hydroformylation is a well-studied thermochemical reaction that performs C-C coupling by appending CO to an olefin in the presence of H2 gas. We mimic homogeneous HFN catalysts on electrode surfaces using single atom-decorated nanoparticles. We show that electrochemistry can be used to circumvent the need to supply H2 as a reactant. Instead, protons, electrons, and CO can be used to hydroformylate a model substrate. Additionally, we study the electrochemical generation of CO, a necessary reactant for hydroformylation, via immobilized cobalt phthalocyanine (CoPc) catalysts. Through collecting kinetic data over a wide range of operating conditions and quantitatively comparing candidate mechanisms, we are able to demonstrate unexpected roles of both the electrolyte and applied potential on the reaction pathway. These studies build towards a more rigorous and quantitative understanding of how the many components of an electrode interface interact with and influence catalysis on atomically precise active sites. It is crucial to carve out this complexity if we wish to effectively import catalysts or design principles from other catalytic contexts onto electrified interfaces.