Electrochemical performance of Cu- and Ag-doped carbon aerogels

Cu- and Ag-doped carbon aerogels were prepared by carbonization at 900 °C of organic aerogels obtained from resorcinol and formaldehyde, using copper or silver acetate as catalyst, respectively. A reference sample was also prepared using potassium carbonate as catalyst. Metal-doped carbon aerogels were activated with oxygen at 300 °C up to a 20% burn-off. Activation increased the surface area and total micropore volume of the Cu-doped carbon aerogel but did not modify the mesopore volume, and largely increased the oxygen content of this aerogel. By contrast, oxygen activation had practically no effect on the surface area and total micropore volume of the Ag-doped carbon aerogel, and produced slight changes in the other textural parameters. The oxygen content was lower in the activated Ag-doped carbon aerogel than in the similarly activated Cu-doped carbon aerogel. Gravimetric capacitances are higher in Cu-doped than in Ag-doped carbon aerogels and oxygen activation produced a marked increase of capacitance and a decrease in the equivalent series resistance (ESR) in both aerogel types. This is attributed to an activation-induced increase in textural parameters and metal content. The activated Cu-doped carbon aerogel shows the highest gravimetric and volumetric capacitances, 192 F g^-1 and 98 F cm^-3, respectively. This volumetric capacitance is higher than that generally required for practical applications in small-volume devices. There is practically no capacitance fading in any sample after 2000 cycles.