Hydrogen storage in nickel doped MCM-41

Hydrogen as an energy carrier is one of the best environmentally friendly alternatives to fossil fuel sources. The potential use of hydrogen results with increasing demand to hydrogen production and storage. Recent studies show that materials having high surface area, large pore size and high affinity to hydrogen have high hydrogen storage capacity. MCM-41 is silica based material having such properties and its hydrogen sorption properties can be improved by doping transition metals to the structure. Ni was chosen for this purpose as it is known with its hydrogen affinity. In this study, different amounts of Ni doped in MCM-41 that was produced by microwave heating to examine hydrogen storage capacity of Ni doped MCM-41 systems. The morphology and structure of the material was characterized by scanning electron microscope and X-ray diffraction analysis. Thermal stability of MCM-41 was examined by thermogravimetric analysis and it was seen that MCM-41s are hydrothermally stable. Surface area, pore size and adsorption capacity of MCM-41 were measured by Brunauer-Emmett-Teller (BET) method. It was observed that the material had large surface area around 1000 m2/g and roughly 2 nm pore size. It was found materials have uniform pore structure with hexagonal well-ordered arrangement. BET surface area, pore volume and pore diameters decreased as the metal loading increased. The hydrogen adsorption capacity measurements were achieved by the Intelligent Gravimetric Analyzer at room temperature and up to 10 bar pressure. It was observed that the hydrogen storage capacity of MCM-41 is strongly affected by metal doping

Hydrogen storage in single wall carbon nanotubes produced on iron catalyst

Hydrogen is a promising clean energy alternative to conventional energy sources. Hence, increasing demand on hydrogen as energy carrier enhances studies in hydrogen storage. Hydrogen should be safely and efficiently stored in order to overcome existing barriers in hydrogen usage. Single wall carbon nanotube (SWCNT) is an eligible material for hydrogen storage. In this study, SWCNTs were produced by catalytic chemical vapor deposition (CCVD) of acetylene (C2H2) on MgO powder substrate impregnated with Fe. Catalysts were prepared with Fe to MgO ratio of 5:100 using iron nitrate (Fe(NO3)3•9H2O) solution as Fe source. SWCNTs were synthesized at 800°C for 60 minutes. Nitric acid (HNO3), was used for purification of synthesized SWCNT. The aim of the research was to investigate hydrogen storage capacity of as produced and purified SWCNTs synthesized on Fe-MgO catalyst. The morphology and structure of the SWCNTs were characterized by transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. Thermal gravimetric analysis (TGA), and Raman spectroscopy were used for further characterization. Hydrogen storage capacities of SWCNTs were measured by high pressure volumetric analyzer using volumetric method at the cryogenic temperature and gas pressure up to 90 bar. It was found that the hydrogen adsorption capacities of these materials were around 1.9 and 5.3 wt% for as produced and purified SWCNTs respectively. With the fact that DOE target for 2015 is 5.5 wt%, it was seen that SWCNTs produced on Fe-MgO catalyst have good potential as hydrogen storage material

Hydrogen adsorption of carbon nanotubes grown on different catalysts

Single wall carbon nanotubes (SWCNTs) were synthesized by catalytic chemical vapor deposition of C2H2 at 800°C for 60 min. Catalysts were prepared by impregnation of transition metals (Fe, Co, Ni, V and bimetallic mixture of Fe-Co) on MgO powder substrate with a metal to MgO ratio of 5:100. After the synthesis, the samples were purified by liquid phase oxidation method with 1.5M HNO3 for 30 min at 210°C. The samples were characterized by thermal gravimetric analysis, scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The hydrogen storage capacities of purified SWCNTs were investigated by volumetric method. It was found that the hydrogen uptake was in the range of 2.76-5.25 wt% at cryogenic temperature and 100 bar pressure. The maximum capacity was obtained with purified SWCNTs produced on Fe catalyst whereas purified SWCNTs grown on Fe-Co catalyst had the minimum hydrogen uptake

Investigation of the effect of reaction time, weight ratio and type of catalyst on the yield of multi wall carbon nanotubes via chemical vapor deposition of acetylene

The synthesis of multi wall carbon nanotubes (MWCNTs) was studied using catalytic chemical vapor deposition of acetylene at 500°C for 30 and 60 min. Catalysts were prepared by impregnating Fe, Co, Ni, V, and bimetallic mixture of Fe-Co on MgO with a weight ratio of 1:100, 5:100 and 10:100. The effects of the reaction time, the type, and the weight ratio of the catalysts on the carbon yield of MWCNTs were investigated. Experimental results showed that the 10:100 weight ratio of Fe-Co:MgO had the highest carbon yield (81.97%) and the MWCNT to amorphous carbon ratio (100.6) whereas 10:100 V:MgO had the lowest carbon yield (8.44%). Statistical analyses indicated that increasing weight ratio enhanced the carbon efficiencies of Fe, Co, Fe-Co and Ni catalyst; moreover, increasing the reaction time had a positive effect on the carbon efficiencies of Fe and V catalysts

Effect of loading bimetallic mixture of Ni and Pd on hydrogen storage capacity of MCM-41

MCM-41 was produced by microwave irradiation, which allows high yield, improved product purity, increased reaction rate and crystallization. As transition metals enhance the hydrogen uptake, Pd and Ni were loaded on MCM-41 to increase the hydrogen storage capacity of the structure. The surface areas of the samples were measured by N-2 adsorption and it was observed that they had large surface area around 938-1369 m(2)/g. The successful incorporation of metals into the structure was confirmed by characterization using X-ray diffraction and X-ray photoelectron spectroscopy. The hydrogen adsorption capacities of the samples were measured by the Intelligent Gravimetric Analyzer at room temperature and up to 10 bar pressure. The hydrogen storage capacity of MCM-41 was improved by increasing content of bimetallic mixture of Pd and Ni. The maximum hydrogen uptake was obtained as 0.98 wt% with 10:100 Pd Ni:MCM-41

Effect of reaction time, weight ratio, and type of catalyst on the yield of single-wall carbon nanotubes synthesized by chemical vapor deposition of acetylene

The single wall carbon nanotubes (SWCNTs) were synthesized by catalytic chemical vapor deposition of C2H2 at 800°C for 30 and 60 minutes. The transition metals of Fe, Co, Ni, V, and bimetallic mixture of Fe-Co impregnated on MgO powder substrate with weight ratios of 1:100, 5:100 and 10:100 were used as catalysts. The effects of catalyst type, weight ratio, and the reaction time on carbon yield of SWCNTs were investigated. The statistical analyses showed that the 1:100 weight ratio of Co-MgO (60 min) had the highest carbon yield (55.99%). It was also found that the reaction time enhances the carbon efficiency of all catalysts whereas increase in weight ratio lowers the carbon efficiency for Fe, V, and Fe-Co; however the carbon efficiency of Co is not affected with change in weight ratio