O, N-doping high specific surface area microporous carbon materials derived from gram-positive bacteria and its outstanding performance for supercapacitors

Abstract To develop special structure nanomaterials from nature with large specific surface areas and conduct appropriate doping may be effective ways to improve the performance of carbon-basing energy storage devices and mobile power supplies. Pure Gram-positive bacteria carbon material with dense microporous structure and properly self O, N-doping was developed towards highly performance supercapacitors for the first time. The structural characterization and electrochemial survey show that carbon derived from Gram-positive bacteria can bring unexpected material properties for its layered and nitrogen, oxygen containing peptidoglycan cell wall structure. Specifically, bifidobacterium yogurt starter powder as a representative of Gram-positive bacteria was employed and pre-carbonized at 450 °C, then re-carbonized at 700, 800 and 900 °C with KOH activated, respectively. The as-prepared Gram-positive bacteria carbons (GpBCs) have inherited the bacteria's cell wall structure to some extent, which makes the specific surface area as high as 2877 m2/g. When the mess ratio of the precursor to KOH was 1: 2 and re-carbonized at 800 °C, the sample named GpBC-800-2 exhibited a medium specific surface area (2436 m2/g), and possessed proper oxygen(11.20%) and nitrogen(0.56%) doping. For further electrochemial measurement, GpBC-800-2 delivered a specific capacitance of 220 F/g and a 94.5% retention after 10000 cycles in 6 M KOH at the current density of 1 A/g in three-electrode system. For further assessment on symmetry devices, 30 F/g specific capacitance was obtained and 97.8% retention after 10000 cycles were achieved in 6 M KOH at the current density of 1 A/g for symmetry devices. The constructed devices presented an energy density of 4.2 Wh/kg at the power density of 0.5 kW/kg, and still remained 3.19 Wh/kg at the power density of 5 kW/kg. Results of this work have given a first glance for pure Garm-positive bacteria carbon materials in supercapacitor application.