To help understand part of the mechanism that facilitates the carbon capture features of our device we construct a simple computational model that captures the rough features of the experimental system (see Methods for full details) by calculating the transport of CO2 and HCO3 - in an aqueous electrolyte consisting of nonreactive ions of valency ±1 with equilibrium concentration 100 mM. This computational model incorporates continuum transport equations that include Fickian diffusion, Ohmic conduction, and a source-sink term as a result of the chemical reaction