Double-layer supercapacitors ( SCs) based on carbon quantum dots (CQDs) are a novel and highly potential electrical energy storage technology. They have a high-power density (Pd) and a long span life, which are desirable for electric automobiles, however, their specific capacitance (Csp) needs to be improved. Here, we introduce an affordable and environmentally sustainable method to enhance the capacitance of Boron-Sulphur doped carbon quantum dots (B,S-CQDs) from Oloptum miliaceum (Grass) via the hydrothermal method. The findings show that heteroatom-doping might greatly enhance the Csp and energy density (Ed) when compared to undoped CQDs. As a consequence, the B,S-CQDs demonstrate a high Csp of 390 F g− 1 at 0.1 A g− 1 and 152 F g− 1 at 1.0 A g− 1, revealing excellent rate performance. Along with the electrode demonstrates superb coulombic efficiency with only 2% efficiency loss after 3000 cycles. Furthermore, the B,S-CQDs with a wide voltage range of 0.8 V yields a remarkable Ed of 48.0 Wh kg− 1 and Pd of 524 W kg− 1. These promising findings demonstrate an economical and environmentally friendly electrode material for high-performance SCs. This study offers ideas for the design and preparation of SCs electrode materials and represents a major endeavour to turn waste biomass (smilograss) into a useful electrode material.

B, S doped zero-dimensional carbon quantum dots from bio-waste for high density supercapacitors
    Abstract
    1 Introduction
    2 Experimental section
        2.1 Reagents and electrodes
        2.2 Preparation of B,S-CQDs from Oloptum miliaceum leaves
        2.3 Morphological characterizations
        2.4 Electrochemical characterization
        2.5 Theoretical details
    3 Results and analysis
        3.1 Optical studies of B,S-CQDs
        3.2 Vibrational studies of B,S-CQDs
        3.3 Zeta potential
        3.4 Structural studies of B,S-CQDs
        3.5 Morphological studies of B,S-CQDs
    4 Texture characterization
    5 Electrochemical studies
        5.1 DFT results
    6 Conclusion
    References

• Suman(Department of Chemistry, Chaudhary Devi Lal University, Sirsa 125055, India)
• Gita Rani(Department of Chemistry, Chaudhary Devi Lal University, Sirsa 125055, India) Corresponding author
• Bhawna(Department of Chemistry, Chaudhary Devi Lal University, Sirsa 125055, India)
• Siddharth(Department of Chemistry, Chaudhary Devi Lal University, Sirsa 125055, India)
• Harish Kumar(Department of Chemistry, Central University of Haryana, Mahendergarh 123033, India)
• Jai Devi(Department of Chemistry, Guru Jambheshwar University of Science and Technology, Hisar 125001, Haryana, India)