Activated Carbon Electrodes with Improved Sorption Capacity for Supercapacitive Swing Adsorption of Carbon Dioxide

Abstract

Global warming due to anthropogenic CO2 emissions demands the rapid development of efficient carbon capture technologies. Supercapacitive swing adsorption (SSA) is a technology that relies on the reversible charge and discharge of supercapacitor electrodes to selectively adsorb and desorb CO2. A current limitation of SSA is the low sorption capacity. Here, we investigate a series of activated carbons derived from biomass, coke, coal, and carbide as electrode materials for SSA. The energetic and adsorptive performance metrics are quantitatively analyzed and their relationship with double layer capacitance, real capacitance, imaginary capacitance, and diffusion resistance is studied. The results show that there is a strong positive correlation between specific capacitance and CO2 adsorption capacity. The highest gravimetric sorption capacity was measured for garlic-root derived activated carbons valuing 273 mmol.kg-1 for 4 cm2 electrodes having a specific capacitance of 257 F.g-1. This is a ~4-fold increase compared to BPL 4x6 carbon having a specific capacitance of 86 F.g-1 and an adsorption capacity of 70 mmol.Kg-1. Volumetric specific capacitances and volumetric sorption capacities are also correlated. The highest volumetric sorption capacity was found for garlic powder-derived activated carbon valuing 65.3 mol.m3 at a volumetric specific capacitance of 62.3 F.cm3 which is a two-fold increase compared to BPL 4x6 carbon which has a volumetric specific capacitance of 41.2 F/cm3 and a volumetric sorption capacity of 27.1 mol.m3. In addition, higher specific capacitance tends to improve the overall adsorption rate and productivity.

High‐Voltage Supercapacitive Swing Adsorption of Carbon Dioxide

“…We recently discovered that biomass‐derived activated carbons from garlic skin, garlic roots, and garlic clove powder lead to about 3–4 times increase of the gravimetric adsorption capacity and adsorption rate, and that there is a strong positive correlation between capacitance and CO 2 adsorption capacity. [ 12 ] Recently, Forse et al. reported that the gravimetric sorption capacity of SSA can be increased from 50 to 112 mmol kg −1 by charging the electrodes between −1 and +1 V instead of −1 and 0 V, but this approach resulted in a very high energy consumption (751 kJ mol −1 CO 2 ).…”

“…These resistance values are lesser than all the previously reported biomass‐derived electrodes used for SSA. [ 12 ] This signifies that the modified synthesis and electrode preparation procedure for garlic‐roots derived activated carbon electrodes is critical to achieve better electronic conductivity. A record low energy consumption of ≈70 kJ mol −1 is observed at −1 V (Figure 3e).…”

“…The charge efficiency (CE) of GR‐AC electrodes is around 0.3 up to −1.2 V which is higher than all the previously reported values. [ 12 ] The CE slightly reduces to 0.26 at −1.4 V, and further reduces to 0.21 at −1.6 V (Figure 3f). The improved charge efficiencies may be due to improved pore accessibility to H + /HCO 3 − /CO 3 2− , leading to a more effective removal of these ions from the chemical equilibrium.…”