Waste cigarette butt-derived B, N doped bifunctional hierarchical mesoporous carbon for supercapacitor and oxygen reduction reaction

Utilization of hazardous waste into valuable materials is the prime need globally. Herein, discarded cigarette filters (a harmful waste/environmental hazard) were utilized to produce heteroatom (Nitrogen and Boron) doped hierarchical mesoporous carbon nanocomposite (NHMC and B-NHMC) via simple elegant hydrothermal route. The fabricated hierarchical mesoporous carbons (HMC), N-doped carbon (NHMC) and boron doped carbon (B-NHMC) composite exhibited high surface area about to 972, 1283 and 1869 m(2) g(-1) respectively with the mesoporosity (similar to 13-16 nm). Scanning electron microscopy confirmed the hierarchical nature of the produced carbon. Elemental analysis (CHN) established the presence of C, H, N, B and O elements. Electrochemical studies showed remarkable super-capacitive behavior in 6 M KOH electrolyte. The specific capacitance of the fabricated electrode materials HMC, NHMC and B-NHMC was observed 309, 325 and 365 F g(-1) respectively and was calculated through CV graphs at a potential of 2 mV s(-1). Moreover, GCD showed an enhanced specific capacitance of 320, 355 and 373 F g(-1) at a current density of 0.5 A g(-1) for HMC, NHMC and B-NHMC sample electrodes. The capacitance retention graphs showed high retention of 91%, 93% and 95% after 5000 segments of charge discharge curves of HMC, NHMC and B-NHMC electrodes, which confirmed an excellent capacitance retention exhibited by the materials. An excellent electrocatalytic performance was exhibited by B-NHMC material for oxygen reduction reaction (ORR) with an onset and half wave potential of 0.975, 0.835 V respectively in O-2 saturated 0.1 M KOH electrolyte, The value of Tafel slope of B-NHMC catalyst was examined 89.5 mV dec(-1), which shows a close agreement with commercial Pt/C (20%) 87.7 mV dec(-1), demonstrating good kinetic properties of B-NHMC catalyst, which is near about the commercial Pt/C (20%). The average number of electrons transferred during the ORR process is 3.96, which is found a close resemblance with the ideal four electrons ORR process. Thus, discarded cigarette filters can be smartly utilized as waste to manufacture heteroatom doped (N and B) hierarchical mesoporous carbon (NHMC/B-NHMC) composite at commercial scale to solve the municipality and environmental issue and to utilize in energy storage system and fuel cells.

Automated summary

In this study, discarded cigarette filters were transformed into valuable materials by using a hydrothermal method to produce heteroatom-doped hierarchical mesoporous carbon nanocomposite. The fabricated composite exhibited high surface area and mesoporosity, and showed remarkable super-capacitive behavior and electrocatalytic performance. Therefore, this research is significant for the efficient utilization of hazardous waste, solving environmental issues, and applications in energy storage systems and fuel cells.