and 𝜌 𝑖 (𝑥 -) are the concentrations of species 𝑖 just above and just below the barrier, respectively, and 𝑑 b =0.5 mm is the thickness of the barrier. The interface between the electrolyte is also approximated by a diffusion barrier which is only permeable to CO2 (i.e. 𝐷 𝑖,𝑏 = 0 for all other species) and the thickness is set to the small 0.1 nm to ensure that gas and electrolyte concentrations are always in equilibrium at the interface, since this conversion is quasi-instanteneous . The overall resulting geometry of the computational model is schematically depicted in Figure . Here we see an axisymmetric model with charged nanochannels of radius 𝑅 c = 2.5 nm and length 𝐻 = 50 nm at either side of an electrolyte separator with the top channel in direct contact with a gas chamber. Additional uncharged channels of height 𝑅 c = 2.5 nm are placed to take the effectively uncharged pathways through the macropores in the electrode into account.