Natural-gel derived, N-doped, ordered and interconnected 1D nanocarbon threads as efficient supercapacitor electrode materials

Abstract

A natural hydrogel has been successfully templated into a nitrogen doped interconnected 1D nanostructure by a hard templating method using an SBA-15 template. With urea as the nitrogen doping agent a high nitrogen percentage of 7.0 at% was achieved. Urea was seen to play a role in increasing the order and compactness of the final carbon product. By snipping the carbon into nano 1D threads a fairly high surface area up to 837 m² g⁻¹ was achieved with a high density of mesopores characterized by a pore size of 4–5 nm and a pore volume of 0.87–0.89 cm³ g⁻¹. The mesoporous architecture was channel type with an average width of ∼4 nm. With these characteristics the material represents an architecture that is adequate for high power supercapacitor electrode applications. Indeed, it was seen to deliver a capacity of 285 F g⁻¹ at a current density of 1 A g⁻¹ with only a small percentage loss in this initial capacitance value at a higher current density of 10 A g⁻¹ (210 F g⁻¹). These values suggest a high capacity retention of 74% up to 10 A g⁻¹ and 62% capacitance retention (176 F g⁻¹) at an extremely high current density of 40 A g⁻¹. The cycling stability of the material is also commendable as 96% capacity retention is recorded after 2000 charging–discharging cycles implemented at a high current density of 10 A g⁻¹.