Hydrogen Adsorption Capacity Research Articles

Synthesis of sulfur-doped porous carbons by soft and hard templating processes for CO2 and H2 adsorption

Sulfur-doped porous carbons were synthesized by two synthetic approaches, i.e. a direct one (soft-template) and an indirect one (hard-template). In the soft-template approach, a phenolic resin based on phloroglucinol or resorcinol and thiophene carboxaldehyde (TCA) was self-assembled with a triblock copolymer followed by carbonization in inert atmosphere. For the second method, zeolite beta was used as hard-template and infiltrated with carbon by chemical vapor deposition (CVD) process followed by H2S treatment. Mesoporous materials with uniform pore size and moderate apparent specific surface area (up to 635 m2 g−1) were obtained by soft-template route. The hard-template route, coupled with H2S post-treatment, allowed to obtain highly microporous/mesoporous materials having high apparent surface area (1700–2500 m2 g−1) and high total pore volume (1.25–1.95 cm3 g−1). High temperature or amounts of TCA induce a decrease of the microporosity and apparent surface area while the mesoporosity varies distinctly depending on the synthesis method used. The sulfur content could be easily modified by the amount of thiophene carboxaldehyde for the soft-templating route (up to 10.9 wt % at 600 °C) or by the H2S heat-treatment temperature for the hard-templating method. In the latter case, with the increase of the temperature up to 900 °C, high S-content was reached (up to 14.4 wt %). The influence of the carbon porosity and surface functionality on the H2 and CO2 adsorption was evaluated. Hard-templated carbons possessing well developed microporosity adsorb the highest amounts of H2 and CO2. The sulfur and oxygen groups lead to improvement of the hydrogen adsorption capacity and have less significant effect on CO2 storage.

Controllable Fe introduction into ordered mesoporous carbon with interconnected small pores for investigating Fe doping effect on hydrogen adsorption

Iron has been proved effective for hydrogen adsorption due to its high binding energy with hydrogen molecules. Here a series of iron-doped interconnected ordered mesoporous carbons (Fe/OMCs) with controllable doping level (zero to 9.11%) and large surface area were successfully prepared by adjusting the initial additive mass of ferric nitrate. The mesoporous carbon materials were characterized by means of nitrogen adsorption, pore size distribution, low-angle X-ray diffractometer, energy dispersive X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. The results show that the Fe/OMCs possess well-ordered mesostructured, intrinsic 3D network structure, and large surface area from 921 to 1378 m2 g−1. The low-angle XRD diffraction peaks of the Fe/OMC samples shifted slightly toward high angles, indicating the introduced Fe on the OMC prevents framework shrinkage during the calcination. The controllable iron particles with size of 20–40 nm partially embedded on the 3D network structure showed different state of iron particles, namely zero iron (α-Fe), magnetite (Fe3O4) and hematite (α-Fe2O3), and part of them kept naked in the pore, providing more available iron actives for hydrogen adsorption. Based on the unique structure, adsorption data of hydrogen on the OMC were collected to independently investigate the iron doping effect on the Fe/carbon composite surface interactions. The results indicate that hydrogen adsorption capacity is greatly enhanced with the iron content, and the sample Fe/OMC-9 with 9.11% iron content exhibits the highest hydrogen adsorption capacity of 1.10 wt%, 59% higher than the non-doped OMC. The high hydrogen adsorption is attributed to OMC's 3D porous network structure with well-dispersed iron nanoparticles partially exposed in the pore.

Preparation of activated carbon from empty fruit bunch for hydrogen storage

There are many advantages associated with the use of hydrogen as clean fuels, thus there is a need to search for good hydrogen adsorbents. Activated carbon (AC) from various sources has been tested as hydrogen adsorbents, with the exception of AC produced from empty fruit bunch (EFB). The aim of this study is to produce AC from EFB obtained in Malayisa, followed by testing on its hydrogen storage capacity. The AC samples were activated using physical and chemical processes. The total surface areas (SBET) and microporous structures of the ACs produced were in the range of 305–687m2/g and up to 94%, respectively. The hydrogen storage capacity was studied at constant temperature, 77K and pressure from ambient pressure up to 100bar. The hydrogen uptake increased occasionally from 0bar to 20bar and decreased above 20bar. EFB activated with 2M KOH demonstrated maximum hydrogen adsorption capacity with 2.14wt% hydrogen uptake at 20bar. More research is needed to improve the hydrogen adsorption capacity on AC, and to determine its potential applications other than mobile applications.

Preparation of different graphene nanostructures for hydrogen adsorption

In this study, different types of graphene were synthesized to investigate hydrogen adsorption capacity at different pressures (0–34 bar) at room temperature (298 K). Graphene and nanoporous graphene were prepared by Chemical Vapor Deposition (CVD) method, using methane as a carbon source at a temperature of 900 °C over copper plates and nickel oxide nanocatalyst. The nickel oxide nanocatalyst was prepared by sol–gel method, whereas graphene oxide was prepared through modified Hummer's method. The products were characterized by X-ray diffraction, field emission-scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller and Raman spectroscopy. The adsorption of hydrogen was done by volumetric method. High adsorption capacity was achieved in nanoporous graphene because of its high pore volume (2.11 cm3/g) and large specific surface area (850 m2/g). Hydrogen adsorption values for nanoporous graphene, graphene and graphene oxide were determined as 2.56, 1.70 and 0.74 wt%, respectively. In addition, the hydrogen adsorption of graphene nanostructures fitted nicely to the selected two-parameter and three-parameter adsorption isotherm models. The adsorption isotherm model coefficients have been found for a 0–34 bar pressure range. The parameter values for all adsorbents showed proper conformity to the model and experimental data. Copyright © 2016 John Wiley & Sons, Ltd.

Double-Confined Nickel Nanocatalyst Derived from Layered Double Hydroxide Precursor: Atomic Scale Insight into Microstructure Evolution

Double-confined nickel nanocatalyst Ni/Ni(Al)Ox/AlOx, with metal Ni nanoparticles implanted in the weakly crystalline Ni(Al)Ox matrix and embedded in amorphous AlOx networks, was facilely fabricated by hydrogen reduction of the NiAl-LDH precursor at a controlled temperature. Direct structure imaging of Ni and Al species revealed that subnanometer Ni0 clusters nucleate initially in the Ni(Al)Ox matrix. Subsequent growth of Ni0 clusters proceeds at the expense of the surrounding Ni(Al)Ox, accompanied by consecutive transfer of Al3+ from the central part to the near-surface, suggesting a mechanism of ion reverse migration. The Ni(Al)Ox interfacial shell is proposed to provide a strong connection with the metallic Ni and the AlOx network, improving the hydrogen adsorption capacity of the double-confined Ni catalyst and consequently the catalytic activity for dimethyl terephthalate hydrogenation to dimethyl cyclohexane-1,4-dicarboxylate, a prominent modification reagent and intermediate in the polymer industry...

A simulation study on the hydrogen storage properties of fullerene family molecules Cx(x = 56,60,70) and their hydrides

Hydrogen storage is a key factor for the application of hydrogen energy. From first principle calculation, we have acquired the energy barrier for hydrogen molecules to pass through the hexagonal rings and pentagonal rings of the fullerene. Then the absorption energy and energy barrier are used to analyze the hydrogen adsorption capacity of the fullerene family and their hydrides. We have also studied the hydrogen storage properties of the fullerene family and their hydrides by grand canonical Monte Carlo method. It is found that the weight density of hydrogen storage at ambient temperature and pressure can reach 7.71 wt.%. The results show that it is difficult for hydrogen to get into the carbon cage of the fullerene because of the high energy barrier, while it is beneficial to destroy the fullerene structure for the processes of absorption and desorption. Meanwhile, fullerene hydrogenation is an effective method to improve the hydrogen storage properties. Our study facilitates the design and synthesis of hydrogen storage materials, and provides theoretical support to improve the hydrogen storage capability for materials.

Effect of titanium on adsorption of hydrogen in β-cyclodextrin

The hydrogen adsorption capacity on β-cyclodextrin and the changes of adsorption influenced by titanium have been investigated through multiscale theoretical approach. The results show that, in the pristine β-cyclodextrin, hydrogen molecules intend to accumulate at the area outside edge of β-cyclodextrin. However, when β-cyclodextrin is modified by titanium, the accumulated fields of hydrogen molecules are changed. Furthermore, the calculations show that the frontier orbitals of β-cyclodextrin are evidently delocalized and the adsorption energy between β-cyclodextrin and hydrogen are enlarged for Ti modifying β-cyclodextrin.

Novel 2D micro-porous Metal-Organic Framework for hydrogen storage

A novel two dimensional Metal-Organic Framework (MOF) structured compound with trimesic acid (TMA), 1,10 Phenantroline (Phen) and Cu(II) building blocks were synthesized and characterized experimentally. Then Grand Canonical Monte Carlo (GCMC) simulation calculations used for determination of hydrogen adsorption capacity and surface characteristics of the compound theoretically. Three different regions were determined for the adsorbent, which were micro, micro/sub-meso spaces inside the adsorbent and the surface regions. It is found that the synthesized compound could uptake approx. 1.3 and 1.2 wt.% hydrogen at 77 K, 100 bars and 1 bar respectively. Thus the adsorbent that is synthesized in this work have strong hydrogen adsorption capability in comparison to the previously reported ones.

Enhanced hydrogen storage performance of reduced graphene oxide hybrids with nickel or its metallic mixtures based on spillover mechanism

In this work, as a fascinating 2-dimensional carbon material, reduced graphene oxide (rGO) has been decorated with Ni, Ni/Pd, and Ni/Ag/Pd nanoparticles on its surface to enhance its hydrogen storage performance based on the spillover mechanism. First, graphene oxide (GO) was fabricated from graphite by a modified Hummer method. Next the GO was dispersed in water and mixed with nickel chloride, palladium chloride, and/or silver nitrate to synthesize parental Ni(OH)2/GO, Ni(OH)2/Pd(OH)2/GO, and Ni(OH)2/Pd(OH)2/AgOH/GO hybrids through hydrothermal treatment with HMTA as a capping and precipitation agent. After in situ reduction of these parental hybrids with hydrogen flow and heat treatment at 350 °C, nanostructured Ni/rGO, Ni/Pd/rGO, and Ni/Ag/Pd/rGO hybrids were obtained. These Ni (Ni/Pd, or Ni/Ag/Pd)/rGO hybrids show great potential in hydrogen storage at ambient environment, as measured at room temperature (293.15 K) and 800 mmHg, 0.007, 0.13, and 0.055 wt% hydrogen adsorption capacity was obtained from the Ni/rGO, Ni/Pd/rGO, and Ni/Ag/Pd/rGO hybrids, respectively.

Preparation, characterization and hydrogen sorption study of MIL-101(Cr) pellets

The paper discusses the bulk (25 g/batch) synthesis of MIL-101(Cr) using acetic acid and its pelletization as hydrogen storage material for on-board automotive applications. The synthesized material was moulded into a shaped body (a pellet) using binders such as sodium salt of carboxy methyl cellulose (Na-CMC), starch (ST) and polyvinyl alcohol (PVA) as well as a pellet without binder. Pellets were prepared using an hydraulic press by applying different pressures (5, 10 and 15 tonnes; where 1 tonne per square metre = 9.80665 kPa). The research team investigated the effect of compression pressure on the pellet properties and also its hydrogen adsorption capacity. The surface area and micropore volume decreased with the increase of compression pressure. The Dubinin-Radushkevich (DR) equation was used to calculate micropore volume. The maximum hydrogen storage capacity obtained is 2.54 wt.% at temperature of 77 Kelvin (K) using 10% PVA as a binder at 10 tonnes compression pressure. MIL-101(Cr) pellets prepared without binder, compressed at 10 tonnes pressure, showed 3.10 wt.% hydrogen storage capacity at the temperature of 77 K.

Hydrogen storage capacity enhancement of MIL-53(Cr) by Pd loaded activated carbon doping

Metal organic frameworks (MOFs) have attracted great attention as adsorptive material for hydrogen storage because of their exceptionally high specific surface areas and chemically tunable structures. Fine structural properties of central chromium atoms in MIL-53 have been studied using XANES and EXAFS spectroscopies in the present work. Fourier transformed EXAFS (extended X-ray absorption fine structural) spectra of MIL-53 showed that the bond distance of Cr–O (first shell) was 1.959Å with a coordination number of about 4.7. The pre-edge XANES (X-ray absorption near edge structural) spectra of Cr atoms in MIL-53 exhibit an absorbance feature around 5988eV for the 1s to 3d transition which was forbidden by the selection rule in the case of perfect octahedral symmetry. However, the sharp feature at 6008eV and well defined shoulders at 6003eV were due to the dipole-allowed of 1s to 4pxy electron transition. These features of XANES spectra identified the existence of Cr(III) in MIL-53(Cr) structure. The synthesized MIL-53(Cr) adsorbs 1.45 wt% hydrogen measured at 77K and 60bar while after modification with Pd-loaded activated carbon (AC), the hydrogen adsorption capacity was increased to 1.92 wt% due to spillover effect of H2 molecules. The heat of adsorption was also calculated from both high-pressure hydrogen adsorption data using modified D-A model and from the low-pressure hydrogen adsorption data using the van't Hoff equation.

The Synthesis of Nitrogen-Doped Mesoporous Carbon Spheres for Hydrogen Storage

The nitrogen-doped mesoporous carbon spheres have been synthesized via soft-template and hydrothermal synthetic strategies using phenol/formaldehyde resins as carbon sources and melamine as a nitrogen source. The obtained carbon spheres exhibit a spherical morphology with a size range of 3-5 μm, which possess the narrow microporosity (ca. 1.2 nm) and mesoporosity (ca. 4 nm), large surface area (560-1200 m2 g-1) and high nitrogen contents (up to 15.7 wt%). Due to the well-developed porous structure and high nitrogen content, the carbon spheres show high performance for hydrogen storage, and the hydrogen adsorption capacities are in the range of 140-185 cm3 g-1, which is better than that of most activated carbons. The incorporation of nitrogen into carbons is favored for hydrogen uptake in low pressure.

Synthesis, structural characterization and hydrogen storage of nickel-containing mesoporous MCM-48 by electroless plating

Hydrogen is a promising fuel for it is clean, highly abundant and non-toxic, but on-board storage of hydrogen is still a challenge. So it is imperative to have an efficient method of hydrogen storage. The mesoporous MCM-48 especially the nickel-containing MCM-48 has great potential in hydrogen storage. MCM- 48 was prepared by hydrothermal synthesis. Then electroless plating technology was used to deposit Ni on the surface of MCM-48 under ultrasonic environment. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and N2 adsorption-desorption were employed to investigate the pore structure properties. The results showed that all the samples had Ia3d cubic structure and pore channels were highly ordered. Hydrogen adsorption studies showed that the MCM-48 after nickel plating adsorbed nearly twice the amount of hydrogen than pure MCM-48 at 2.0 MPa, 263 K. So we believe that a small amount of Ni can improve the capacity of hydrogen adsorption of MCM-48 efficiently.

Hydrogen storage on boron substituted carbon materials

Hydrogen storage capacity of boron substituted carbon materials synthesized by the carbonization of resorcinol and triethylborate as carbon and boron sources respectively is reported. The effects of the boron-doping and carbonization temperature and the role of functional groups have been investigated. The hydrogen adsorption capacity has been studied with a high pressure volumetric analyzer (HPVA) and a maximum of 5.9 wt% hydrogen storage capacity was observed at 298 K and 100 bar pressure. At 77 K in both carbon samples (namely BC-600 or BC-800) show only fractional weight percent of hydrogen sorption (1.1 and 0.5 wt%). The nearly 5 weight % hydrogen storage was obtained by loading heteroatom (B) to carbon sample at 298 K and 100 bar.

Kinetics of hydrogen adsorption on MgH2/CNT composite

Magnesium hydride (MgH2)–carbon nanotubes (CNT) composite has been prepared by high-energy ball milling method and their experimental and kinetic hydrogen adsorption studies was assessed. Hydrogen adsorption studies were performed by Sievert’s volumetric apparatus and kinetic evaluation was conducted by surface chemistry and Langmuir–Hinshelwood–Hougen–Watson (LHHW) type mode. Powder X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were performed. Hydrogen adsorption capacity of commercial MgH2, milled MgH2, and MgH2/CNT composite are found to be 0.04, 0.057, and 0.059g (H2)/g (MgH2) at 673K and hydrogen pressure of 4.6MPa. Addition of 5wt% of CNTs to MgH2 proved to be very critical to enhance hydrogen adsorption as well as to improve its kinetics. It was observed that hydrogen adsorption is not in quasi-state equilibrium and is modeled using kinetic rate laws.

Ambiguity in determining H2 adsorption capacity of carbon fiber by pressure technique

In this paper hydrogen adsorption capacity of carbon fibers is presented. These fibers are synthesized by pyrolysis of cotton fibers. Forty five varying parameters are applied for the pyrolysis of cotton to get carbon fiber of varied specific densities. Specific densities are calculated by (i) water displacement method and (ii) tapping method. Maximum hydrogen adsorption capacity is found to be 1.246 wt% if specific density value obtained by water displacement method is considered; whereas specific density obtained from tapping method showed 7.076 wt% hydrogen adsorption by the same carbon fibers.This paper imposes a question that since the measurement of density of carbon by these two method give different results which one should be accepted or is there a need to develop another method.

Synthesis and characteristics of magnesium inserted on porous silica materials by mechanical alloying

Impregnation of nanocrystalline magnesium and iron at different concentrations into Beta zeolite was studied employing two techniques: the Traditional Method (TM) and Mechanical Milling (MM). It is known that hydrogen is a potential fuel for the development of the society in a friendly environment with the world; however, there are great challenges for storage. Hydrides of metals are considered as a promising alternative in the areas of materials and energy. Both techniques employed in this study allowed the distribution of Mg and Fe metals in the porous of the Beta zeolite support, high surface area values and a promising adsorption capacity of hydrogen. Therefore, zeolites appeared as materials of interest in the field of alternative energy. The efficiency of impregnation of both techniques was evaluated and the samples were characterized by appropriate methods.

Experimental and simulation study on structural characterization and hydrogen storage of metal organic structured compounds

One of the barrier for common usage of hydrogen energy system is storing hydrogen efficiently. Especially for mobile applications, it is very important to store hydrogen in small spaces reversibly. Metal-organic framework (MOF) structured materials step forward with the ability of reversible hydrogen storage which meet the storage targets. The MOF structured compounds were synthesized using Cu(II) and Zn(II) metals, trimesic acid (benzene 1,3,5 tricarboxylic acid) (TMA) and 1,10 phenantroline (Phen) building blocks. The compounds were activated thermally at 398 K for 4 days under a vacuum for sorption experiments. Then, DTA/TGA, FT-IR, powder-XRD, BET surface area and elemental analysis techniques were used to determine the molecular structures of the synthesized compound. Finally, the hydrogen storage properties were measured at 77 K and 1 bar of hydrogen pressure. In addition to experimental investigations, hydrogen adsorption characteristics and performances of the compounds were also determined with the molecular simulation calculations. It is found that the Cu(II) and Zn(II) compounds could uptake 2.652 wt. % (sim. 2.434 wt. %) and 1.383 wt. % (1.187 wt. %) respectively, at 77 K and 1 bar pressure. Consequently, hydrogen adsorption mechanism and capacities of the compounds clarified. And it is found out that the compounds have good storage performance in comparison to the previously reported MOFs.

One-pot synthesis of tailored Pd–Co nanoalloy particles confined in mesoporous carbon

The synthesis of mesoporous carbon with confined PdCo nanoalloy particles by a one-pot soft-template approach is reported herein. The influence of metal precursor type, metal composition and annealing temperature on the carbon@PdCo material characteristics was systematically investigated. Small and homogeneously distributed PdCo nanoparticles in the carbon matrix were achieved. The PdCo particle size could be tuned from 8 to 25 nm and the metal composition proved to be the main parameter controlling the size. When the amount of Pd is low (Pd50Co50) the particle is small and increases with the increase of temperature. On the contrary, for richer Pd contents (Pd75Co25, Pd90Co10) the particle size is larger but they exhibit extremely high stability with no obvious modification of size between 450 and 800 °C. The tuned experimental parameters had less impact on the materials textural characteristics, they exhibit similar surface area and uniform pore size distribution. Among the materials, only the Pd rich alloys (Pd90Co10) are able to form metallic hydride and consequently, showing the highest hydrogen adsorption capacity.

Mineral magnetite as precursor in the synthesis of multi-walled carbon nanotubes and their capabilities of hydrogen adsorption

Mineral magnetite was used as metallic oxide catalysts in the synthesis of Multi-Walled Carbon Nanotubes (MWCNTs) by Aerosol Assisted Chemical Vapor Deposition (AACVD). The structural and morphological information of MWCNTs was obtained by X-ray Diffraction (XRD), Raman Spectroscopy (RS), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). The hydrogen storage capacity and the gas adsorption kinetics of the MWCNTs exposed to H2 at different pressures were determined using a quartz crystal microbalance (QCM). It was found that the hydrogen adsorption capacity was strongly dependent on the chemical, structural and morphological characteristics of the MWCNTs which, in turn, depend on the proportion of the starting materials (mineral magnetite and zeolite) used for the synthesis by AACVD. However, no a clear correlation was found between each one of these characteristics and the adsorption properties since the sample was affected by gas exposure during the H2 loading/unloading cycles. The maximum adsorption capacity was 1.76 wt% at 44 Torr of H2 exposure pressure. The adsorption kinetics was determined by in situ monitoring the QCM resonance frequency. As expected, a faster H2 adsorption kinetics of the MWCNTs occurred when the sample was exposed to higher H2 pressures. In general, there are measurable H2 adsorption between 60 s and 100 s before reaching saturation.