Controllable synthesis of 2D amorphous carbon and partially graphitic carbon materials: Large improvement of electrochemical performance by the redox additive of sulfanilic acid azochromotrop in KOH electrolyte

In this work, by simply heating trisodium citrate dihydrate as sole precursor at 800 °C, novel 2D amorphous carbon material (the SC-blank sample) occurs, whose high surface area and large pore volume can reach up to 1015.8 m2 g−1 and 2.0 cm3 g−1, respectively. Furthermore, we present a synchronous carbonization and graphitization method to produce partially graphitic carbon materials. When heating the mixture of trisodium citrate dihydrate and nickel nitrate hexahydrate as template and graphitization catalyst (the mass ratio of 7:1) at 800 °C, the resulting SC-7:1 sample’s surface area has decreased to be 682.8 m2 g−1 due to its improved graphitization degree, together with a lower capacity, but a better rate capability. More importantly, in order to further enhance capacity, certain amount of sulfanilic acid azochromotrop (abbr. SAA) serving as redox additive has been introduced into KOH electrolyte. Notably, the SC-blank sample incorporated with SAA redox additive (12 mmol L−1) indicates a largely enhanced capacity of 164 mAh g−1 when measured at 3 A g−1, which is much larger than that of the pristine one (20 mAh g−1). To sum up, the SAA is an efficient redox additive for elevating the capacity.