Influence of thermal treatment atmosphere on N-doped carbon spheres for wastewater treatment and supercapacitor applications

Carbon-based materials have emerged as some of the most proficient materials for diverse applications including wastewater treatment and energy storage devices. In the present report, N-doped carbon spheres synthesized from soy flour and glucose were thermally treated at 900 °C in argon (Ar) or nitrogen (N2) atmospheres. Apart from the morphological changes the samples also undergo graphitization as well as conversion of the doped-N functionalities to more stable functionalities. The thermal treatment under inert gas for both the cases resulted in porous samples with micropores. Ar atmosphere resulted in larger diameter micropores (>1 nm) as compared with N2 (0.8 nm). Pore formation mechanism has been proposed for differences in the micropore size and distribution as well as graphitization temperature for the two gases. The adsorption and photocatalytic performance of carbons were studied using neutral (p-nitrophenol, PNP), cationic (methylene blue, MB), and anionic (eriochrome black-T, EBT) model pollutants. The sample heat-treated under Ar showed maximum %decolorization under dark as well as UV irradiation. The kinetics of the adsorption as well as adsorption mechanisms of model pollutants onto the surface of the heat-treated samples has been studied. The supercapacitve performance of all the samples was studied using cyclic voltametery and galvanostatic charge−discharge curves. Ar heat-treated sample showed the best supercapacitve performance with a total capacitance of 59.06 F/g.