Magnesium oxide scaffolded preparation of N, O self-doped biochar with super-hydrophilic surface for aqueous supercapacitor with desired energy density

To assemble electrochemical supercapacitor with attractive energy density, heteroatoms self-doped biochar with hydrophilic surface and natural pore system is prepared by pyrolyzing Flammulina velutipes (FV) pickled with Mg (CH3COO)(2) for the first time. The resultant biochar FVB-2-900 displays a super hydrophilicity. It also shows specific surface area of 1174.2 m(2)center dot g(-1) and pore volume up to 1.57 cm(3)center dot g(-1). Due to its N, O co-doped hydrophilic surface, the electrode based on it displays a specific capacitance of 470.5 F center dot g(-1) at current density of 0.5 A center dot g(-1) in three-electrode system. Its outstanding energy density of 18.0 Wh center dot kg(-1) is calculated at power density of 0.7004 kW center dot kg(-1) in the electrolyte 1.0 M H2SO4 for the assembled symmetric super-capacitor. Furthermore, a higher energy density of 26.1 Wh center dot kg(-1) at power density of 1.0 kW center dot kg(-1) is recorded in the electrolyte 1.0 M Na2SO4. It also exhibits a good cyclic stability of 100 % retention rate after 10,000 cycles at 5.0 A center dot g(-1). The simple synthesis process, outstanding property, and excellent electrochemical super-capacitor performance make the biochar FVB-2-900 a competitive candidate in the green energy storage.

Automated summary

Heteroatoms self-doped biochar with hydrophilic surface and natural pore system, prepared from Flammulina velutipes pickled with Mg (CH3COO)(2), exhibits high specific surface area and pore volume. The electrode based on this biochar shows high specific capacitance and energy density, as well as good cyclic stability. The biochar's simple synthesis process, outstanding properties, and excellent electrochemical performance make it a promising candidate for green energy storage.