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 m2 g−1 respectively with the mesoporosity (~ 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 O2 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.