Controlling product selectivity in hybrid gas/liquid reactors using gas conditions, voltage, and temperature

For the conversion of CO₂ into fuels and chemical feedstocks, hybrid gas/liquid-fed electrochemical flow reactors provide advantages in selectivity and production rates over traditional liquid phase reactors. However, fundamental questions remain about how to optimize conditions to produce desired products. Using an alkaline electrolyte to suppress hydrogen formation and a gas diffusion electrode catalyst composed of copper nanoparticles on carbon nanospikes, we investigate how hydrocarbon product selectivity in the CO₂ reduction reaction in hybrid reactors depends on three experimentally controllable parameters: (1) supply of dry or humidified CO₂ gas, (2) applied potential, and (3) electrolyte temperature. Changing from dry to humidified CO₂ dramatically alters product selectivity from C₂ products ethanol and acetic acid to ethylene and C₁ products formic acid and methane. Water vapor evidently influences product selectivity of reactions that occur on the gas-facing side of the catalyst by adding a source of protons that alters reaction pathways and intermediates.