N-doped MWCNTs from catalyst-free, direct pyrolysis of commercial glue

We report a unique, catalyst-free, direct pyrolysis process to obtain nitrogen-doped multiwall carbon nanotubes (N-MWCNTs). The process includes the polymerization of ethyl cyanoacrylate (ECA) based commercial super glue with aqueous NaCl solution. The resultant poly-ethyl cyanoacrylate (PECA)-NaCl composite was washed to remove NaCl and subsequently calcined at 1000 °C in an inert atmosphere to obtain carbon nanotubes. The field emission scanning electron microscopy and high-resolution transmission electron microscopy studies confirm that these are nitrogen-doped multiwall carbon nanotubes (N-MWCNTs) with diameters in the range of 80–110 nm. Compared to conventional MWCNTs, these nanotubes exhibit distinct multilayer stacking of carbon with short-range ordering with interlayer spacing slightly larger than graphitic carbon. XPS studies reveal the presence of doped nitrogen substituting for carbon atoms, whereas Raman spectroscopy data shows that these nitrogen-doped nanotubes exhibit nanocrystalline, graphitic carbon. Washing of PECA-NaCl composite results in the removal of NaCl leading to the unique porous PECA intermediate structure. These unique morphological changes and structural transformations of PECA in DI water along with the peculiar degradation behavior of PECA during the heat treatment process may be responsible for the formation of N-MWCNT

Near room temperature synthesis of sulfonated carbon nanoplates and their catalytic application

We demonstrate a unique one-pot synthesis approach to obtain sulfonated carbon nanoplates having elongated hexagonal morphology (S-ECN). The S-ECN were synthesized by dehydration of recrystallized sucrose and sodium chloride mixed crystals with concentrated sulfuric acid under ambient conditions. No additional heat treatment or elaborate experimental setup was necessary to obtain graphitic carbon nanoplates. Scanning electron microscopy (SEM) studies showed that presence of NaCl and recrystallization conditions played a crucial role in crystal habit modification of sucrose during recrystallization. Consequently, initial morphology of sucrose crystals was largely preserved in resultant carbon nanostructures. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy studies showed that S-ECN were partially graphitic with wider interplanar spacing compared to standard graphite. The elemental analysis (CHNS) and Fourier transform infrared (FTIR) spectroscopic studies confirm the presence of sulfur in the form of –SO3H group. The catalytic performance of the S-ECN was studied for hydroxyalkylation-alkylation (HAA) reaction of 2-methylfuran with furfural to produce C15 oxygenated hydrocarbon. The S-ECN showed up to 90% conversion of 2-methylfuran. Additionally, an empirical kinetic model was developed to obtain rate constant of HAA reaction and to correlate 2-methylfuran conversion under various reaction conditions. The experimental results matched reasonably well with the calculated 2-methylfuran conversion

Hard carbon derived from sepals of Palmyra palm fruit calyx as an anode for sodium-ion batteries

Hard carbons with large interlayer spacing, disordered structures and interconnected porosity at low cost, are considered as promising anode materials for sodium-ion batteries (NIB). In this work, we report the synthesis of hard carbon anode materials from sepals of palm fruit calyx (bio-waste) that are prepared by carbonization at moderate temperature between 500 °C and 900 °C. Electron microscopy studies show that the resultant hard carbon is highly porous with interconnected porous network. X-ray diffraction and Raman spectroscopic analyses indicate that the carbonized materials possess disordered structure with large interlayer spacing (0.37 nm). The electrochemical studies reveal that hard carbon which is pyrolyzed at 700 °C (WHC-700) shows better performance, delivering 397 mAh g−1 and 280 mAh g−1, initial discharge and charge capacities, respectively. Specific capacities of about 275 mAh g−1 and 175 mAh g−1 are achieved for WHC-700 material at a current density of 30 and 200 mA g−1, respectively. The sepals of Palmyra palm fruit calyx (bio-waste material) yield hard carbon material at moderate carbonization temperature with optimum microstructural properties and larger interlayer spacing. These attributes are responsible for their good electrochemical performance as an anode material for NIBs

Nitrogen-doped Graphene-like Carbon Nanosheets from Commercial Glue: Morphology, Phase Evolution and Li-ion Battery Performance

We report a two-step process to synthesize nitrogen-doped graphene-like carbon nanosheets (N-CNS), using commercially available ethyl cyanoacrylate based super glue as a carbon precursor. In this process, super glue is polymerized in aqueous NaCl solution, followed by carbonization at 1000 °C. The scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) studies show that the resultant material consists of micron-sized carbon nanosheets with wrinkled morphology. The HRTEM, X-ray diffraction (XRD), XPS and Raman spectroscopic studies confirm the formation of nanocrystalline and graphitic, nitrogen doped carbon nanosheets. Detailed FTIR analysis of the degradation products of the polymeric precursor (polyethyl cyanoacrylate) at various heat treatment temperatures in inert atmosphere reveals that, the polymer undergoes cyclization process similar to polyacrylonitrile (PAN) during carbonization to yield the N-CNS. The N-CNS used as an anode for lithium-ion battery shows stable reversible capacities of 480 mAh g-1 for 100 cycles, which indicates that N-CNS are promising material for lithium-ion battery application. In a broader perspective, unique chemical transformation of polyethyl cyanoacrylate to graphitic carbon may be useful to design new nanostructured carbons for a plethora of applications

In-situ formation of mesoporous SnO2@C nanocomposite electrode for supercapacitors

In this work, we report a supercapacitor based on SnO2@C composite electrode with better electrochemical performance. SnO2@C composite is synthesized from porous polymer beads by the impregnation method. The resultant composite is porous and retains uniform spherical morphology of polymer beads. The composite exhibits the bimodal distribution of pores with a specific surface area of 286 m2g−1. SnO2@C composite electrode show specific capacitance of 432 F g−1 at 1 A g−1 in 1M KOH electrolyte with capacitance retention of 95.5% for 2000 cycles. Besides, the composite electrode shows an energy density of 29.4 Wh kg−1 at a power density of 418 W kg−1 at 1 A g−1 current density. The optimize electrode design improves cyclic stability due to reducing crystal growth of SnO2 as well as diffusion kinetics because of the presence of bimodal pores which provides continuous electron path. The bimodal micropores and mesopores in carbon matrix have the accessibility of electrolyte to SnO2, improving overall electrochemical performance and therefore SnO2@C composite is suitable as electrode material for supercapacitors