Modeling the Performance of A Flow-Through Gas Diffusion Electrode for Electrochemical Reduction of CO or CO <sub>2</sub>
Yikai Chen, Nathan S. Lewis, Chengxiang Xiang
Abstract
A flow-through gas diffusion electrode (GDE) consisting of agglomerate catalysts for CO or CO 2 reduction, gas channels for reactants, aqueous electrolytes for ionic transport, and metallic current collectors was simulated and evaluated using a numerical model. The geometric partial current densities and Faradaic Efficiencies (FE) for CH 4 , C 2 H 4 and H 2 generation in GDEs were calculated and compared to the behavior of analogous aqueous-based planar electrodes. The pH-dependent kinetics for CH 4 and C 2 H 4 generation were used to represent the intrinsic catalytic characteristics for the agglomerate catalyst. The modeling indicated that relative to planar electrodes for either CO reduction (COR) or CO 2 reduction (CO 2 R), substantial increases in electrochemical reduction rates and Faradaic efficiencies are expected when flow-through GDEs are used. The spatially resolved pH and reaction rates within the flow-through GDEs were also simulated for two different operating pHs, and the resulting transport losses were analyzed quantitatively. For CO 2 reduction, substantial loss of CO 2 via chemical reaction with the locally alkaline electrolyte was observed due to the increased pH in operating GDEs.