Electrochemical conversion of CO2 to value-added products is an attractive approach for mitigation of emissions and energy decentralization by storing electricity in the form of chemical bonds. With efforts towards commercialization, recent emphasis on vapor-fed reactors have allowed for higher current densities. These vapor-fed reactors provide significant advantages compared to similar aqueous-phase systems due to increased mass transport of reactants, reaction area, and tuning of catalyst and reaction environment. In particular, the gas diffusion electrode (GDE) architecture allows for CO2 to be delivered directly to the catalyst in vapor phase, thus decoupling the partial pressure of CO2 from the concentration of water. Previous studies using GDEs have shown considerable activity and selectivity towards carbon monoxide and ethylene in highly alkaline electrolytes (pH &gt; 14). In this work, we demonstrate advanced manufacturing (AM) for rapid development and testing for improved performance across an evolution of reactor designs in bulk pH neutral conditions (pH &lt; 8). We observe and discuss activation- and mixed-control regimes for a variety of CO2 flow and electrochemical potential conditions. Furthermore, we use transport modeling to define a dimensionless number (Da) to identify mass transport regimes considering the effects of underlying mass transport mechanisms and the competing hydrogen evolution reaction. These systems provide effective delivery of CO2 and result in increased CO dimerization to multi-carbon products with high selectivity (&gt;85% FE towards C2+). Using AM vapor-fed reactors, up to 16.6% CO2 conversion is achieved with high ethylene (3.67%) and ethanol (3.66%) yields compared to the literature. We propose AM as a promising approach for accelerating reactor design and understanding governing phenomena while de-risking scale-up and optimization for industrial implementation.

Advanced manufacturing for electrosynthesis of fuels and chemicals from CO2

ACS Fall 2021

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