Sodium carboxymethyl cellulose derived carbon aerogels synthesized by zinc nitrate hexahydrate and urea for supercapacitor electrodes

Carbon aerogel is one of the ideal materials for supercapacitor because of its high specific surface area and high conductivity. Sodium carboxymethyl cellulose (CMC-Na) has attracted much attention owing to its water solubility. In this work, we have provided a simple and facile strategy by zinc nitrate hexahydrate (Zn(NO3)2·6H2O) as an activative agent and urea (CO(NH2)2) as a nitrogen source to achieve the N/O co-doped carbon aerogels. Just as bread expands during baking, the introduction of these agents makes the materials expand and fluffy. By changing the amount of Zn(NO3)2·6H2O and CO(NH2)2, the microstructure and element content can be controlled. When the mass ratio of CMC-Na, Zn(NO3)2·6H2O and CO(NH2)2 was 2:1:4, we obtained the highest specific capacitance in a three-electrode system (248 F g−1 at 0.1 A g−1). This value was more than three times higher than that of pure CMC-Na derived carbon materials. In the symmetrical supercapacitor, the maximum specific capacitance was 129 F g−1 at 0.1 A g−1. It was assembled into a coin cell for long cycle stability test and the capacitance retention maintained 90 % at 30 A g−1 for 15,000 cycles. Compared with the traditional method of carbonization followed by activation, this work exhibits a simpler strategy by one-step carbonization and activation and shows the prospect of CMC-Na as a precursor of the carbon electrode in the field of energy storage.