Eliminating redox-mediated electron transfer mechanisms on molecular catalysts enables CO2 conversion to ethanol

Abstract Molecular catalysts play a significant role in chemical transformations, utilizing changes in redox states to facilitate reactions. In the broadening field of carbon dioxide (CO 2 ) electrolysis to value-added products, catalyst choice strongly impacts product formation. To date molecular electrocatalysts have efficiently produced single-carbon products from CO 2 1–3 but have struggled to achieve the carbon-carbon coupling step needed to reach highly valued multi-carbon products. Conversely, copper acts as the only reliable bulk metal that enables carbon-carbon coupling, but leads to broad C2+ product spectrums. 3–5 Here we designed a molecular electrocatalyst system that subverts the traditional redox-mediated reaction mechanisms of organometallic compounds, facilitating electrochemical CO 2 -to-ethanol yields of 96% at optimal conditions with trace methanol and C3 products. By coupling iron tetraphenylporphyrin (Fe-TPP) with a nickel electrode, we fixed the iron oxidation state during electrocatalytic CO 2 reduction to enable further reductions and coupling of *CO intermediates. This represents a marked behavioural shift compared to the same metalloporphyrin deposited onto carbon-based electrodes. Extending the approach to a 3D porous nickel support with adsorbed Fe-TPP, we attain ethanol faradaic efficiencies of 68% +/- 3.2% at -0.3 V vs a reversible hydrogen electrode (pH = 7.7) with partial ethanol current densities of -21 mA cm -2 . Separately we demonstrate maintained ethanol production over 60 hours of operation. Further consideration of the wide parameter space of molecular catalyst and metal electrodes shows promise for additional novel chemistries and achievable metrics.