The SSA adsorption rate and productivity linearly increases from -1.0 V to -1.4 V after which they stay the same (Figure ). The 24 % increase in both the adsorption rate and productivity indicates that a wider potential window leads to faster CO2 hydrolysis, possibly due to faster depletion of H + ions in the bulk solution. Similar to volumetric adsorption capacity, the productivity also approximately doubles compared to previous best results, possibly due to the combined effect of using higher voltage window and improved mass transfer of GR-AC electrodes. The coulombic efficiency (ηc) stays around 99 % at -1 V and -1.2 V, reduces to 91 % at -1.4 V, and further reduces to 82 % at -1.6 V (Figure ). Reduced ηc at high voltage windows may be attributed to enhanced irreversible, pseudocapacitive contributions from surface functionalities, hydrogen sorption, and faradaic leakage current from water decomposition. By continuously running the SSA cycles at -1.4 V for multiple cycles, a coulombic efficiency of 96 % was achieved without any performance loss in SSA adsorption capacity (Figure ), arguing that after a few cycles the most irreversibly redox-active functionalities from the activated carbon surface are removed, and the electrodes can be fully reversibly charged. Previous studies have shown that increasing the voltage window of aqueous supercapacitors above 1.5-1.6 V results in carbon oxidation at the anode and hydrogen evolution at the cathode, irreversible charge losses, and high leakage currents that significantly degrades the supercapacitors long-term performance. Therefore, the optimal voltage window for SSA with GR-AC electrodes in the NaHCO3 electrolyte used in the current study would be -1.4 V. The energy efficiency (ηe) stays above 60 % up to -1.2 V, reduces to 50 % at -1.4 V, and further reduces to 40 % at -1.6 V (Figure ). Since additional energy is required to store additional charges in the pores at higher voltage, an increased energy loss is observed at higher voltages (Table ). Previous SSA studies have shown that ηe as high as 80 % can be achieved by using very concentrated electrolytes (e.g. 5 M NaCl), or alternative salt solutions (e.g., 1 M MgBr2) , arguing that there is a room for improvement in ηe values.