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