Hollow carbon nanosheets with predominant mesopores have been demonstrated as a promising electrode material for supercapacitor , but their low specific surface area with relatively low micropore proportion limits their specific capacitance and energy density . Herein, we develop a novel extrusion plant microtube strategy to synthesize micron-sized nitrogen-doped hollow porous carbon nanosheets (MNHPCS) from dandelion fluff having the specific natural thin-wall and hollow tubular bundled structure through high-pressure extrusion, carbonization and KOH activation. The optimized MNHPCS displays strutted bilayer nanosheet structure, large SSA of 1593 m 2 g −1 , high micoporosity of 71.2 % and high heteroatom content (5.2 at.% for N, 7.0 at.% for O). Importantly, MNHPCS prepared by the new technique overcomes the drawbacks of hollow carbon nanosheets and presents an excellent capacitance of 378 F g −1 at 0.5 A g −1 and rate capability of 57 % at 80 A g −1 in 6 M KOH. Furthermore, the energy density of MNHPCS//MNHPCS based supercapacitor in EMIMBF 4 can reach up to 84 Wh kg −1 . Most importantly, MNHPCS can be easily achieved from various plant wastes having hollow tubular structure, which would provide a clearly method on selecting plant precursors for producing hollow porous carbon nanosheets applied on supercapacitors.
Gaseous Hg 0 is one of the most deadly and hard-to-dispose pollutants. The oxidation of Hg 0 is a promising route, but the rational design and synthesis of highly efficient catalysts still remain grand challenges. Herein, CuO@Cu 2 O (or Cu x O) heterostructured nanoparticles uniformly monodispersing on porous carbon monolith were designed and successfully synthesized using oligo( m -phenylenediamine)-Cu 2+ complex as raw material. The Cu x O-carbon catalyst contains ∼28 wt% of Cu. Based on density functional theory calculation, the CuO@Cu 2 O junction interfaces can accelerate the Hg 0 oxidation by significantly reducing the energy barriers of reaction. Only 1 mg of the catalyst can catalyze the oxidation of more than 90 % of Hg 0 with [HCl] = 0.5 ppm, [O 2 ] = 6 vol%, T = 150 °C. The poisoning effect of either SO 2 or H 2 O on the catalysts is weak. Moreover, a long-term test confirmed that the Hg 0 oxidation rate can maintain more than 90 % even in the co-presence of SO 2 (5000 ppm) and H 2 O (10 vol%).
Structured porous carbon materials have been extensively applied for catalyst, sensor, adsorbent, energy storage materials and many others. However, the preparation of such carbon materials in a controllable way remains a significant challenge. In this work, 3D printing has been employed to prepare porous carbon structures with tailorable pore sizes. A starch/gelatin ink has been applied as carbon source with SiO 2 monodispersed spheres as hard template. The process exhibits an excellent printing accuracy. Controllable meso and macro structures can be thereby obtained. The printed monolithic structures have been used as metal-free catalysts for the selective oxidation of benzyl alcohol, as an illustration. The monolithic and meso/macro-porous structure has a remarkable influence on the reaction rate. A high conversion with high benzaldehyde selectivity has been achieved. The 3D printing strategy provides us a simple, low cost and reliable way of fabricating carbon structures with designable meso/macro-pores, which is promising for many other applications beyond catalysis.
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