Multi-parameter optimization of the capacitance of Carbon Xerogel catalyzed by NaOH for application in supercapacitors and capacitive deionization systems.

Carbon Xerogel is an economic choice of material for electrodes with applications in Electric Double Layer Capacitors (EDLCs) and Capacitive DeIonization systems (CDI, particularly for desalination). The objective here is to optimize Carbon Xerogel's performance, specifically its capacitance, through multi-parameter optimization using Response Surface Methodology (RSM). We choose NaOH as the catalyst and select as the optimization parameters (i) the pH of the initial Resorcinol-Formaldehyde-Catalyst (RFC) solution, (ii) Reactants to Liquid mass ratio (R/L) of the RFC solution, and (iii) the Pyrolysis Temperature (PT). For a selected range of these three parameters, we obtain an optimum capacitance of Carbon Xerogel equal to 37.6 F/g with optimized parameters PT = 800, R/L = 30% and pH = 5.7. Through comparing Carbon Xerogel samples synthesized with Na2CO3 versus NaOH as the catalyst, we show that the capacitance not only depends on the pH of the initial RFC solution, but also is a strong function of the catalyst material.