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.

Molecular sieving carbon (MSC) for separating O2-N2 and CO2-CH4 has been prepared through chemical vapor deposition (CVD) of methane and benzene on activated carbon spheres (ACS) derived from polystyrene sulfonate beads. The validity of the material for assessment of molecular sieving behavior for O2-N2 and CO2-CH4 pair of gases was assessed by the kinetic adsorption of the corresponding gases at 25℃. It was observed that methane cracking on ACS lead to deposition of carbon mostly in whole length of pores rather than in pore entrance, resulting in a reduction in adsorption capacity. MSC showing good selectivity for CO2-CH4 and O2-N2 separation was obtained through benzene cracking on ACS with benzene entrantment of 0.40×10-4 g/ml at cracking temperature of 725℃ for a period of 90 minutes resulting in a selectivity of 3.31:1.00 for O2-N2 and 8.00:1.00 for CO2-CH4 pair of gases respectively.