Stalin Joseph

Enhanced Supercapacitor Performance of N‐Doped Mesoporous Carbons Prepared from a Gelatin Biomolecule

Nitrogen-containing mesoporous carbon electrodes with tunable pore diameters for supercapacitor applications are synthesized by the nanocasting technique using a naturally abundant gelatin polymer as the single precursor for nitrogen and carbon.

Diaminotetrazine based mesoporous C3N6 with a well-ordered 3D cubic structure and its excellent photocatalytic performance for hydrogen evolution

Novel nitrogen enriched diamino-s-tetrazine based highly ordered 3D mesoporous carbon nitride (MCN-9) hybrid materials with a body centered cubic Ia3d structure having high specific surface areas, large pore volumes, and tunable pore diameters were prepared by employing 3D body centered cubic KIT-6 mesoporous silica having a gyroidal porous structure and various pore diameters as the sacrificial hard template through a simple self-condensation followed by polymerization reaction of aminoguanidine hydrochloride inside the nanochannels of the KIT-6 template. Characterization results reveal that the prepared materials exhibit a 3D porous structure with well-defined mesopores and possess excellent physical parameters including high surface areas (157–346 m2 g−1), large pore volumes (0.36–0.63 cm3 g−1), different pore diameters (5.5–6.0 nm) and a high N/C ratio of 1.87, which is much higher than that of ideal C3N4 (1.33). The deep yellow colored MCN-9 with a 3D porous structure also shows good absorption properties with a tunable narrow bandgap of 2.25–2.5 eV, which is again much lower than that of C3N4 (2.7 eV) and helps to achieve much higher photocatalytic water splitting activity than non-porous C3N4 and other carbon nitrides under visible light irradiation.

Highly Crystalline Mesoporous C60 with Ordered Pores: A Class of Nanomaterials for Energy Applications

Highly ordered mesoporous C60 with a well-ordered porous structure and a high crystallinity is prepared through the nanohard templating method using a saturated solution of C60 in 1-chloronaphthalene (51 mg mL-1 ) as a C60 precursor and SBA-15 as a hard template. The high solubility of C60 in 1-chloronaphthalene helps not only to encapsulate a huge amount of the C60 into the mesopores of the template but also supports the oligomerization of C60 and the formation of crystalline walls made of C60 . The obtained mesoporous C60 exhibits a rod-shaped morphology, a high specific surface area (680 m2  g-1 ), tuneable pores, and a highly crystalline wall structure. This exciting ordered mesoporous C60 offers high supercapacitive performance and a high selectivity to H2 O2 production and methanol tolerance for ORR. This simple strategy could be adopted to make a series of mesoporous fullerenes with different structures and carbon atoms as a new class of energy materials.

Metal organic framework derived mesoporous carbon nitrides with a high specific surface area and chromium oxide nanoparticles for CO2 and hydrogen adsorption

In this work, we report a simple and versatile method for the preparation of mesoporous carbon nitrides (MCNs) functionalized with highly dispersed chromium oxide nanoparticles by using a metal organic framework, MIL-100(Cr), as a template and aminoguanidine hydrochloride (AG) as a high nitrogen content single molecular precursor. We are able to synthesise these metal oxide functionalized MCN materials with single step carbonization but without using any toxic template removal process using HF or NaOH. The absence of a washing procedure with toxic acid also allows the incorporation of a large amount of metal oxide particles inside the porous channels of MCNs. The obtained MCN materials exhibit a high specific surface area and a large pore volume. The AG to template ratios are varied to control the amine functional groups and the textural parameters including the specific surface area and pore volume. It is found that the AG to template ratio of 1.5 is the best condition to obtain MCNs with a specific surface area of 1294 m2 g−1, which is the highest value reported so far for MCN-based materials. FT-IR and XPS results reveal that the prepared materials contain free NH2 groups within the CN network which help to anchor metal oxide nanoparticles and provide highly dispersed basic sites. These functionalized MCN materials are also used as adsorbents for CO2 capture. Among the materials studied, the MCN with the highest specific surface area shows the largest CO2 adsorption capacity (16.8 mmol g−1) which is much higher than those of MCN materials prepared from SBA-15 and KIT-6, activated carbon, MIL-100(Cr), SBA-15, and multiwalled carbon nanotubes. This high adsorption capacity is mainly due to the strong synergistic effect between the MCN with high specific surface area and highly dispersed metal oxide nanoparticles.

Heteroatom functionalized activated porous biocarbons and their excellent performance for CO2 capture at high pressure

Activated biocarbons with a porous structure and nitrogen functionalities are synthesized from the prolific waste biomass, Arundo donax, and an organic material, chitosan, by a simple one step chemical activation with ZnCl2. The nitrogen functional groups in the porous activated biocarbons are significantly increased by the addition of chitosan in the synthesis mixture. The textural properties and N content can easily be tuned by varying the amount of activating agent and the carbonization temperature. The optimized biocarbon sample was obtained at a fairly low carbonization temperature of 500 °C by employing an impregnation mass ratio of ZnCl2 to Arundo donax/chitosan of 3. This optimized material exhibits the best specific surface area of 1863 m2 g−1, pore volume of 1.0 cm3 g−1 and nitrogen content of 5.4 wt%. The presence of nitrogen functionalities on the materials provides a negatively charged surface which is critical for the adsorption of CO2 molecules which are acidic in nature. The sample shows remarkable adsorption capacities of 18.2 mmol g−1 at 0 °C/30 bar and 13.1 mmol g−1 at 25 °C/30 bar under the conditions corresponding to pre-combustion CO2 capture from flue gas streams. High CO2 adsorption values of 3.6 mmol g−1 at 0 °C/1 bar and 2.1 mmol g−1 at 25 °C/1 bar are also observed under post-combustion CO2 capture conditions of the material. The N-doped activated biocarbon shows an exceptionally high value of isoelectric heat of adsorption (32.2 kJ mol−1), indicating that the surface polarity generated by N dopant plays a crucial role in enhancing interactions between CO2 and porous N-doped activated biocarbons.

Cobalt oxide functionalized nanoporous carbon electrodes and their excellent supercapacitive performance

Nanoporous carbon (CMK-3-150) functionalized with different amounts of cobalt oxide (CoO) nanoparticles was synthesized by an incipient wetness impregnation technique for supercapacitor application. The characterization results reveal that the specific surface area and pore volume of the CoO functionalized CMK-3-150 marginally decrease upon increasing the amount of the CoO whereas the pore diameter and the structure of the CMK-3-150 were not affected even after the functionalization. The electrochemical measurements show that the specific capacitance of the electrodes was enhanced after the functionalization with CoO. Among the electrodes studied, CMK-3-150 functionalized with 15 wt% CoO shows an excellent cycling stability and specific capacitance of 331 F g−1, which is ca. two times higher than that of the pure nanoporous carbon. This enhanced performance is due to the combined contribution of electrical double layer capacitance and pseudocapacitance. A symmetric supercapacitor device based on the CMK-3-150–15Co electrode gives the maximum energy density of 29.67 W h kg−1 at a power density of 0.07 kW kg−1.

Effect of Heat Treatment on the Nitrogen Content and Its Role on the CO2 Adsorption Capacity of Highly Ordered Mesoporous Carbon Nitride

Mesoporous carbon nitrides (MCNs) with rod-shaped morphology and tunable nitrogen contents have been synthesized through a calcination-free method by using ethanol-washed mesoporous SBA-15 as templates at different carbonization temperatures. Carbon tetrachloride and ethylenediamine were used as the sources of carbon and nitrogen, respectively. The resulting MCN materials were characterized with low- and high-angle powder XRD, nitrogen adsorption, high-resolution (HR) SEM, HR-TEM, elemental analysis, X-ray photoelectron spectroscopy, and X-ray absorption near-edge structure techniques. The carbonization temperature plays a critical role in controlling not only the crystallinity, but also the nitrogen content and textural parameters of the samples, including specific surface area and specific pore volume. The nitrogen content of MCN decreases with a concomitant increase in specific surface area and specific pore volume, as well as the crystallinity of the samples, as the carbonization temperature is increased. The results also reveal that the structural order of the materials is retained, even after heat treatment at temperatures up to 900 °C with a significant reduction of the nitrogen content, but the structure is partially damaged at 1000 °C. The carbon dioxide adsorption capacity of these materials is not only dependent on the textural parameters, but also on the nitrogen content. The MCN prepared at 900 °C, which has an optimum BET surface area and nitrogen content, registers a carbon dioxide adsorption capacity of 20.1 mmol g-1 at 273 K and 30 bar, which is much higher than that of mesoporous silica, MCN-1, activated carbon, and multiwalled carbon nanotubes.

Mesoporous Gallosilicate with 3 D Architecture as a Robust Energy-Efficient Heterogeneous Catalyst for Diphenylmethane Production

Herein, we report the preparation of 3 D mesoporous gallosilicate with Ia3d symmetry (GaKIT‐6) and different gallium contents using Pluronic P123. The incorporation of gallium into the silica framework of KIT‐6 is difficult if the usual synthesis method of KIT‐6 is followed, because it requires a large amount of HCl in the synthesis mixture. Therefore, the amount of HCl in the synthesis mixture is reduced to suitably adjust the solution pH so as to incorporate a large amount of gallium into the silica framework of KIT‐6. The low‐angle powder XRD results confirm that all the samples demonstrate well‐ordered and a cubic 3 D structure with Ia3d symmetry. However, the wide‐angle XRD patterns show no peaks at the higher angle, which confirms the absence of gallium oxide nanoparticles in the nanochannels and the incorporation of gallium atoms into the silica framework. The nitrogen adsorption and electron microscopy studies reveal that the samples demonstrate excellent textural features with well‐ordered mesoporous structures having spherical morphology. The analysis of the solid‐state 29Si MAS NMR spectra confirms that the gallium atoms are bonded tetragonally with the silica framework of KIT‐6. Furthermore, the catalytic performance of the materials has been investigated in the benzylation of benzene, with benzyl chloride as a benzylating agent. The catalytic activity of GaKIT‐6 increases with an increase in gallium content in the catalyst. GaKIT‐6 with a Si/Ga molar ratio of 7 demonstrates much better catalytic activity than do several reported 1 D and 2 D heteroatom‐incorporated mesoporous materials. In addition, the GaKIT‐6 catalyst is found to be highly active even at reaction temperatures as low as 313 K, which demonstrates a high benzyl chloride conversion and diphenylmethane selectivity. The catalytic activity of the GaKIT‐6 catalyst is retained even after the recyclability test, which confirms that the GaKIT‐6 catalyst is highly stable and can be used thrice without affecting its structural order.