Permeability Matters When Reducing CO₂ in an Electrochemical Flow Cell

Abstract

The highest performing cathodes for CO 2 electrolyzers are porous and exhibit high specific surface areas that serve to increase the density of CO 2 reduction catalyst sites. While porous electrodes increase CO 2 reduction activity, their high surface area can negatively impact the mass transport of products and reactants at high current densities (i.e., >100 mA cm −2 ). We demonstrate here the trade-off between the density of CO 2 reduction catalyst sites (specific surface area) and mass transport (permeability) for porous electrodes used for mediating the conversion of KHCO 3(aq) into CO (g) in an electrolyzer. This demonstration relied on porous electrodes containing a silver electrocatalyst deposited on carbon fibers of varying fiber diameters (0.5, 1, and 10 μm). Porous electrodes with the intermediate specific surface areas (fiber diameter = 1 μm) yielded the highest CO formation rates. This result shows that permeability should be considered when designing porous electrodes for CO 2 electrolysis.

MOF-Derived Ni Single-Atom Catalyst with Abundant Mesopores for Efficient Mass Transport in Electrolytic Bicarbonate Conversion

“…(e) Bicarbonate electrolysis performance of NaCl@Ni/Zn-6 and the state-of-the-art precious Ag-based catalysts. (Blue: Ag NPs; green: Ag NPs; purple: porous Ag foam; pink: Ag foam; light blue: Ag NPs; and light purple: Ag NPs).…”

Direct carbonate electrolysis into pure syngas

“…A low permeability resulted in insufficient in situ regeneration of reactant CO 2 . 49 We varied the CDL thickness between 10 to 50 mm and achieved a maximum CO FE of 46% (H 2 /CO ratio of 1.16) at 200 mA cm À2 with a 25 mm CDL (Fig. 3D).…”

Progress and Understanding of CO2/CO Electroreduction in Flow Electrolyzers

“…Another important role of the flow-field is to improve the mass transport. In this regard, the interdigitated flow-field is typically employed due to the strong forced convection in this configuration (Figure e) . Unlike the aforementioned four patterns, the channels of the interdigitated flow-field are disconnected from one another.…”

“…In this regard, the interdigitated flow-field is typically employed due to the strong forced convection in this configuration (Figure 23e). 212 Unlike the aforementioned four patterns, the channels of the interdigitated flow-field are disconnected from one another. To reach the outlet, the reactant flow must pass through the porous GDE in contact with the ribs of the flow channels, achieving an efficient mass transport of the reactant to the CL of the GDE.…”