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Over the past five decades, anthropogenic carbon dioxide (CO₂) emissions have increased from 2 Gigatons to 10 Gigatons. This rise in atmospheric CO₂ levels has been correlated with a rise in global average temperatures and negative environmental effects. As a result, developing technologies capable of utilizing and reducing excess CO₂ emissions is one of the grand engineering challenges of the 21^st century.

Electrochemical reduction of CO₂ to value-added chemicals (such as carbon monoxide (CO), methanol, formic acid, and ethylene) provides a promising solution to this problem. However, one major issue is the high overpotential associated with CO₂ reduction – although the full-cell thermodynamic equilibrium potential for CO₂ reduction to CO is 1.34 volts, a significant overpotential is required to form the CO₂^* intermediate. Reducing this overpotential reduces the cell energy requirement, thereby improving process economics and energy efficiency.

In this work, we will highlight recent advances in lowering cell overpotentials for the electrochemical reduction of CO₂ to CO. First, we examine the effect of electrolyte composition on the cell potential required for CO₂ reduction. Using potassium hydroxide (KOH) as an electrolyte, overpotentials of only 0.26 V are possible. Second, we examine the effects of gold nanoparticles supported on multi-walled carbon nanotubes as a cathode catalyst for CO₂ reduction to CO. In combination with KOH electrolyte, this catalyst has the lowest overpotential (0.16 V) reported in literature. Third, we report the effect of alternate (non-oxygen evolution) anodic reactions. Using oxidation of glycerol, an onset potential of just 0.85 V is possible.