Synthetic waste derived graphitic carbon nitride (g-CN) and g-CN/carbon hybrid for supercapacitors

Synthesis of carbon-based quantum dots (QDs) from nitrogen containing organic molecules yields a large fraction of a carbonaceous byproduct composed of larger particles and flakes. While QDs are utilized in various applications, this residue is considered a waste and is thus discarded. In this work we have (i) extensively characterized the residual byproduct of autoclave-assisted solvent-free synthesis of QDs from citric acid and urea to deduce that its primary constituent is graphitic carbon nitride (g-CN), (ii) prepared a novel g-CN/ carbon (g-CN/ C) hybrid material by carbonizing the crude product mixture obtained during autoclave-assisted synthesis of QDs, and (iii) performed electrochemical analysis of both g-CN and g-CN/C hybrid for supercapacitor applications. The specific capacitance of g-CN and g-CN/C at a current density of 2 A/g are 138.33 F/g and 146.67 F/g respectively, with 100 % retention of capacitance up to 5000 charge-discharge cycles. This waste-derived, N -deficit carbon nitride and its hybrid are of immediate interest for supercapacitor electrode fabrication. Their evident thermal and electrochemical properties place them among the next-generation smart materials, which are expected to compete with the incumbent technology not just in terms of electrochemical performance but also in the measures of stability, cost, and scalability.