For each charge/discharge cycle, the amount of CO 2 adsorbed was calculated by taking the difference between the peaks and troughs of the amount of gas in the reservoir. This was calculated from the pressure transducer data (smoothed over a window of 100 seconds) using the ideal gas equation 𝑝𝑉 = 𝑛𝑅𝑇. The volume of the reservoir was calculated during the process of dosing CO 2 into the cell, based on pressure measurements of the added gas (using Boyle's Law P 1 V 1 = P 2 V 2 ). The cell was kept in a 30 ºC incubator to control the temperature, though the initial temperature increase when first putting into the incubator is associated with the initial rise in the calculated amount of gas in the cell. To account for any linear changes in pressure over time each peak value was compared to the mean of the two adjacent troughs. The amount of gas adsorbed in one cycle was then normalized by the mass of carbon in the gas-exposed electrode to give the adsorption capacity in mmol/kg. The overall adsorption capacity was taken as the mean of adsorption capacities for each cycle, and the error calculated using a 95% confidence interval with the Student's t-test.