Enhancing the charge-storage performance of N-doped reduced graphene oxide aerogel supercapacitors by adsorption of the cationic electrolytes with single-stand deoxyribonucleic acid

Abstract

Single-stand deoxyribonucleic acid/N-doped reduced graphene oxide aerogel (ssDNA/N-doped rGO) composites were synthesized and used as the electrode materials for supercapacitors. The mass change of the electrolytes adsorbed on the ssDNA/N-doped rGO electrode during a charge/discharge process determined by an electrochemical quartz crystal microbalance (EQCM) at a cathodic potential range (−0.5 to −0.1 V vs. Ag/AgCl) is 10-fold higher than that at an anodic potential range (−0.1–0.3 V vs. Ag/AgCl). This is because the ssDNA having negatively charged phosphate and nitrogen-containing nucleobase groups prefers cationic electrolytes to anionic ones. An as-fabricated supercapacitor of the ssDNA/N-doped rGO with a coin-cell size (CR2016) provides 644 F/g at 0.5 A/g, which is 1.3-fold higher than that of the N-doped rGO device. The specific power and specific energy of the as-fabricated ssDNA/N-doped rGO device are ca. 30 Wh/kg and 4500 W/kg, respectively with a capacity retention of 94.1% over 2500 cycles. Two as-fabricated supercapacitor cells connected in series can supply electricity to the red LED over 10 min. The composite materials in this work may also be used in other applications where the functional groups of ssDNA can play an important role to the adsorption of the cationic electrolytes.