Effect of the resorcinol/catalyst ratio in the capacitive performance of carbon xerogels with potential use in sodium chloride removal from saline water

Carbon xerogels were prepared by the resorcinol–formaldehyde method as potential electrodes for the electroadsorption of sodium chloride from aqueous solution. This work evidences the relevance of the resorcinol-to-catalyst (R/C) ratio employed during the synthesis in the capacitive properties of these carbon xerogels. Raman spectra revealed a significant increase of the structural ordering from R/C = 355 to 480, while an opposite trend was detected for R/C = 500. X-ray photoelectron spectroscopy showed an increase in the contribution of hydroxyl groups for those xerogels with a less ordered structure. Similarly, surface area and micropore volume showed a maximum for R/C = 480. The textural changes fairly matched with capacitance values recorded by cyclic voltammetry. Thus, a value as high as 89 F g−1 was recorded for R/C = 480, which was confirmed by a higher electrosorption capacity of 0.1 mmol of NaCl g−1 as compared to only 0.087 and 0.07 mmol g−1 for R/C = 355 and 500, respectively. Also, a low internal resistance was determined for CXG480, revealing the optimized properties achieved for the xerogel with intermediate resorcinol/catalyst ratio.