Electrocatalysis, which can store electrical energy from renewable sources like solar and wind in chemical bonds, is an attractive solution to activating abundant small molecule precursors. The continual rise of atmospheric carbon dioxide (CO₂) concentrations and their association with climate change have inspired efforts to designate CO₂ as a C₁ feedstock for renewable energy-mediated conversions. If successful, this would provide an alternative to non-renewable petrochemical sources and ‘close the loop’ on carbon emissions; however, a significant knowledge and technological gap still exists for this strategy to be effective. The fundamental scientific challenge at the core of catalytic CO₂ conversion is in understanding how selective activation occurs at active sites and using this knowledge to optimize the catalytic response.

Previous results have suggested that molecular Cr complexes show low activity and stability in homogeneous CO₂RR, failing to produce quantifiable reduction products. This has led the field to assume that the higher d electron counts in late transition metals make them privileged for CO₂RR. However, with proper ligand design, electronic coupling between redox-active portions of the ligand and Cr ions can be favored, enabling selective CO₂ activation in the presence of proton donors. This can be enhanced by the inclusion of redox mediators which bind to the Cr center opposite to the site of CO₂ activation, increasing catalytic activity. In recent studies, we have identified both alternative redox mediators based on phosphorus and examined how the secondary coordination sphere can be used to modulate activity.

Amelia Reid

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