Effect of Humidity on C₁, C₂ Product Selectivity for CO₂ Reduction in a Hybrid Gas/Liquid Electrochemical Reactor

Hybrid gas/liquid-fed electrochemical flow reactors may become attractive alternatives for chemical synthesis once it is understood how catalytic product selectivity may be optimized through the control of gas phase reactants. Using a constant pH basic electrolyte to suppress the hydrogen evolution reaction, we explore how protonation by water vapor added to the flowing CO₂ supply affects the CO₂ reduction reaction. Although H₂ remains the dominant product, supplying dry CO₂ gas selectively produces more C₂ products than C₁. However, adding protons through water vapor changes selectivity toward C₁ products, increasing the overall faradaic efficiency of hydrocarbon production while reducing H₂ production.