Catalytic oxidation of NO at low concentrations by carbon nanofibers near room temperature
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摘要: 采用聚丙烯腈 (PAN)作为静电纺丝前驱体，通过静电纺丝法制备了炭纳米纤维，经预氧化和炭化处理，得到了孔隙率高、比表面积大的PAN基炭纳米纤维 (PCNFs)。通过控制前驱体溶液的浓度，可以得到不同直径的PCNFs。制备的样品在室温 (20 °C)下能去除低浓度的NO (5×10−5)。结果表明，炭纳米纤维的微观结构可以影响其对NO的催化性能。CNFs直径越小，微孔越发达，比表面积越大，吸附和催化氧化效果越好。Abstract: Polyacrylonitrile (PAN) nanofibers obtained by electrospinning were used to prepare PAN-based carbon nanofibers (PCNFs) by pre-oxidation, carbonization and high-temperature treatment in NH3. The PCNFs were used for the removal of low concentrations of NO (5×10−5) near room temperature (20 °C) by catalytic oxidation. Results indicated that the PCNFs had high porosity and a large specific surface area, and their diameters could be regulated by changing the PAN concentration. The smaller the diameter of the PCNFs the more micropores were developed, and the larger the specific surface area the better the adsorption and catalytic oxidation performance.
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Key words:
- Electrospinning /
- Porous carbon nanofibers /
- NO removal /
- Catalytic oxidation
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Figure 1. Macro morphologies of nanofibers: (a) as-spun nanofibers, (b) pre-oxidized nanofibers and (c) nanofibers after activation with NH3.
Figure 2. (a-f) SEM images of CNFs at different PAN concentrations at 800 °C: (a) 8 wt.%, (b) 10 wt.%, (c) 12 wt.%, (d) 15 wt%, (e) 18 wt.% and (f) 20 wt.%, and (g-l) SEM images of NH3 activated CNFs at 800 °C with different concentrations of PAN: (g) 8 wt.%, (h) 10 wt.%, (i) 12 wt.%, (j) 15 wt.%, (k) 18 wt.% and (l) 20 wt.%, and (m) average diameters of carbonized CNFs and (n) average diameters of the activated CNFs.
Figure 3. (a) Adsorption and desorption curves of CNFs activated by NH3 at 800 °C, (b) pore size distributions of CNFs at 800 °C, (c) Raman spectra of CNFs at 800 °C, (d) Raman spectra of NH3 activated CNFs at 800 °C, (e) SSA of NH3-activated CNFs at 800 °C, (f) ID/IG values of carbonized CNFs at 800 °C and (g) ID/IG values of NH3-activated CNFs at 800 °C.
Figure 4. (a-f) Removal of NO by CNFs at different concentrations of PAN at the same carbonization temperature: (a) 8 wt.%, (b) 10 wt.%, (c) 12 wt.%, (d) 15 wt.%, (e)18 wt.%, (f) 20 wt.%, (g−l) Removal of NO by PCNFs at different PAN concentrations obtained at the same activation temperature: (g) 8 wt.%, (h) 10 wt.%, (i) 12 wt.%, (j) 15 wt.%, (k) 18 wt.%, (l) 20 wt.% and conversion of NO to NO2 by (m) CNFs and (n) PCNFs.
Table 1. Pore parameters of PCNFs activated at 800 °C.
PCNFs Burn-off(wt%) SSA
(cm3 g−1)Pore volume
(cm3 g−1)Micropore
volume
ratio (%)BET TPV Vmicro Vmeso PCNF-N8 54.28 313.09 0.2095 0.1957 0.0138 93.4 PCNF-N10 55.30 333.61 0.2222 0.2085 0.0137 93.8 PCNF-N12 58.75 351.51 0.2312 0.2193 0.0227 94.9 PCNF-N15 59.00 354.80 0.2357 0.2263 0.0094 96.0 PCNF-N18 58.75 342.75 0.2207 0.2197 0.0010 99.5 PCNF-N20 56.15 348.47 0.2235 0.2218 0.0017 99.2 
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