An in situ hard template strategy coupled with NaOH activation is proposed to prepare hierarchical porous carbons with high surface area from biomass for high-performance supercapacitors. The preparation of the carbon includes the sol− gel process of lotus seed shell and sodium phytate, followed by carbonization and NaOH activation. The soluble sodium phytate is pyrolyzed to nano-Na 5 P 3 O 10 during carbonization and then reacts with NaOH to convert to nano-Na 2 CO 3 and nano-Na 3 PO 4 particles, which are encapsulated in the carbon matrix as the in situ hard templates and leave large mesopores/macropores after being removed in the subsequent washing treatment. Combined with the micropores created by NaOH activation, the as-prepared carbons possess developed hierarchical pores with a large surface area of 3188 m 2 g −1 and a pore volume of 3.2 cm 3 g −1 . Furthermore, the carbons are rich in the heteroatoms of O, N, and P originated from the biomass precursors and sodium phytate. As a result, the biomass-derived hierarchical porous carbon exhibits high capacitance (286 F g −1 at 0.5 A g −1 ), great rate performance (241 F g −1 at 200 A g −1 ), and excellent cycle stability in 6 M KOH electrolyte. Outstanding electrochemical performances are also achieved in 3 M H 2 SO 4 electrolyte. Thus, the biomass-derived carbon with hierarchical porous structure and outstanding performance is considered as a promising electrode material for high-rate and high-energy density supercapacitors, and the strategy based on the in situ template method opens a new door for the preparation of hierarchical porous carbons with high surface area from biomass precursors.
Nitrogen-rich, high surface area, hierarchical porous carbons were simply prepared by the pyrolysis of a nitrogen-containing organic salt, and exhibit excellent rate capability in supercapacitors.
The effect of different mass transfer ways in landfill leachate treatment by electrochemical oxidation was studied, the electrochemical oxidation rate, current efficiency and energy consumption were mainly discussed by four different mass transfer ways—including higher pressure water jet electrode, aeration, mixing and natural convection. The results show that mass transfer way has an important influence for NH4+-N and CODcr removal in electrochemical oxidation landfill leachate, high pressure water jet has high current efficiency, oxidation rate and lower energy consumption, which is 7.41 mg/L.min, 48% and 0.11 Kwh/gNH4+-N in electrolytic 6 hours, respectively. Different mass transfer ways have different mass transfer coefficient, improving mass transfer coefficient could increase transfer rate and the overall efficiency of system.
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