Electrochemical reduction of CO2 to value added fuels has emerged as a strategy to combat global climate change, while fulfilling the need for portable, renewable fuels. Inorganic molecular catalysts can perform the CO2RR electrochemically. However, achieving selective CO2 reduction to formate or CO in the presence of protons and electrons is difficult as the parasitic H2 evolution reaction is often favored. Existing approaches have relied on tuning thermodynamic parameters to achieve selectivity. Yet, scaling relationships dictate only complexes accessible at very reducing potentials can perform adequately. As an alternative approach, kinetic barriers can be modulated to suppress H2 evolution. We hypothesized formation of a hydrophobic pocket around a metal-hydride center would raise the kinetic barrier of approaching protons, without inhibiting the approach of non-polar CO2. Therefore, CO2 reduction would be kinetically favored over H2 evolution, selectively forming C1 CO2 reduction products without concomitant H2 evolution. To examine this effect, metal complexes with hydrophobic groups around the metal center and water-solubilizing moieties remote of the active site were studied.

Controlling selectivity in CO2 reduction electrocatalysts with secondary sphere effects

ACS Fall 2021

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