Enhancement of charge efficiency for a capacitive deionization cell using carbon xerogel with modified potential of zero charge

The use of tetraethyl orthosilicate to modify carbon xerogel materials results in the formation of silica oxide and carboxylic functional groups at the carbon's surface. Voltammetric characterization indicates that the potential of zero charge (PZC) of the modified samples was positively shifted to the extent affected by dip-coating repetitions. Cycling tests were performed at 1.2 V for 15 cycles in a flow-through cell with ~ 4 mM deaerated NaCl. The average charge efficiency of the cell was significantly enhanced from ~ 60% to ~ 86% when the modified electrode served as the cathode. This increase in efficiency was mainly attributed to the shifting of the PZC at the cathode towards the cell short-circuit potential, thereby reducing co-ion repulsion at the cathode.