CO 2 adsorption rate. This is confirmed by the degree of rate control analysis in Figure . dropping at more negative potentials due to H 2 OR promoted by K + microenvironments, while H 2 OR promoted by TMA + microenvironments is at least one order of magnitude lower (see Figure ). In the case of a fully hydrated Tokuyama membrane (λ = 11) in a CO 2 -saturated 0.1 M KHCO 3 electrode, [K + ] AEM = 0.012 M (all the bulk species' concentrations are reported in Table ). Nevertheless, for λ = 11, [K + ] OHP is close to the steric limit at strongly negative potentials, and at low magnitude potentials, it is higher than in the corresponding [K + ] b = 0.1 M liquid electrolyte, producing more K + microenvironments and therefore increasing the CO current density (Figure ). This is due to the presence of the fixed background charge in the domain, which pushes the mobile positive charges towards the negatively charged electrode. The presence of the fixed background charge does not affect