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1.
The effects of different amounts palladium loading on the hydrogen sorption characteristics of double-walled carbon nanotubes (DWCNTs) have been investigated. The physical properties of the pristine DWCNTs and Pd/DWCNTs were systematically characterized by X-ray diffraction, transmission electron microscopy, and Brunauer–Emmett–Teller surface area measurements. Pd nanoparticles were loaded on DWCNT surfaces for the dissociation of H2 into atomic hydrogen, which spills over to the defect sites on the DWCNTs. When we use different Pd content, the particle size and dispersion will be different, which affects the hydrogen storage capacity of the DWCNTs. In this work, the hydrogen storage capacities were measured at ambient temperature and found to be 1.7, 1.85, 3.0, and 2.0 wt% for pristine DWCNTS, 1.0 wt%Pd/DWCNTs, 2.0 wt%Pd/DWCNTs, and 3.0 wt%Pd/DWCNTs, respectively. We found that the hydrogen storage capacity can be enhanced by loading with Pd nanoparticles and selecting a suitable content. Furthermore, the sorption can be attributed to the chemical reaction between the atomic hydrogen and the dangling bonds of the DWCNTs.  相似文献   

2.
Double-walled carbon nanotubes (DWCNTs) were modified for enhanced hydrogen storage by employing a combination of two techniques: KOH activation for the formation of defects on DWCNT surfaces and loading of the DWCNTs with nanocrystalline Pd. The physical properties of the pristine DWCNTs and chemically modified DWCNTs were systematically characterised by X-ray diffraction, transmission electron microscopy, Raman spectroscopy and Brunauer–Emmett–Teller (BET) surface area measurements. The amounts of hydrogen storage capacity were measured at ambient temperature and found to be 1.7, 2.0, 3.7, and 2.8 wt% for pristine DWCNTS, 2 wt% Pd DWCNTs, activated DWCNTs, and 2 wt% Pd activated DWCNTs, respectively. Hydrogen molecules could be adsorbed on defect sites created by chemical activation in DWCNTs through van der Waals forces. For Pd nanoparticle loaded DWCNTs, H2 molecules could be dissociated into atomic hydrogen and adsorbed on defect sites. We found that the hydrogen storage capacity of DWCNTs can be significantly enhanced by chemical activation or loading with Pd nanoparticles.  相似文献   

3.
The use of hydrogen as an energy carrier is an attractive solution toward addressing global energy issues and reducing the effects of climate change. Design of new materials with high hydrogen sorption capacity and high stability is critical for hydrogen purification and storage. In this study, titanium dioxide nanotubes (TiO2NTs) were modified with palladium nanoparticles (PdNPs) utilizing a facile photo-assisted chemical deposition approach. Electrochemical anodization was employed for the direct growth of TiO2NTs. The PdNP functionalized TiO2NTs (TiO2NT/Pd) were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The hydrogen sorption behaviours and stability of the TiO2NT/Pd nanocomposites were investigated and compared with nanoporous Pd networks that were deposited on a bulk titanium substrate (Ti/Pd) using cyclic voltammetry (CV) and chronoamperometry (CA). Our studies show that the TiO2NT/Pd nanocomposites possess a much higher hydrogen storage capacity, faster kinetics for hydrogen sorption and desorption, and higher stability than the nanoporous Pd.  相似文献   

4.
A novel in situ synthesis of Pd nanoparticles supported in hollow carbon spheres (HCS) is reported. The size of the nanoparticles can be tuned via application of different Pd precursors. The hydrogen storage properties of Pd supported in HCS under room temperature were examined at partial pressures. We observed significant difference between the storage capacities of two samples containing Pd nanoparticles with different diameter distributions. The results showed that the sample with suitable diameters of Pd nanoparticles was more favorable for the H2 storage, even lower mass of Pd was used. The maximum hydrogen storage of 0.36 wt % exhibited the sample with Pd nanoparticles with the diameter of 11 nm (measured at 298 K and 24 bar) and it was enhanced by the factor of two in respect to the pristine HCS. The enhanced storage capacity is due to cumulative hydrogen adsorption by HCS and Pd nanoparticles. We also propose the mechanism of hydrogen storage in our material.  相似文献   

5.
Decoration with transition metal catalysts has been reported to enhance H2 storage capacity of carbon materials at ambient temperature. Furthermore, it has been proposed that surface oxygen groups may improve the process. In this study, a carbon molecular sieve was subjected to controlled oxidation and consequent doping with Pd nanoparticles. The H2 sorption performance of the pristine and oxidized, undoped and doped materials was examined at 298 K up to 20 bar. It was found that the non-oxidized carbon-Pd composite did not show any spillover based sorption increase. On the other hand the oxidized samples reveal a slight enhancement that could be attributed to a weak chemisorption process initiated by the so-called ‘‘spillover’’ effect. Overall, the contribution of spillover to the total hydrogen storage capacity of this system (under the conditions studied) was not found to be of great significance.  相似文献   

6.
Three activated carbons (ACs) having apparent surface areas ranging from 2450 to 3200 m2/g were doped with Pd nanoparticles at different levels within the range 1.3–10.0 wt.%. Excess hydrogen storage capacities were measured at 77 and 298 K at pressures up to 8 MPa. We show that hydrogen storage at 298 K depends on Pd content at pressures up to 2–3 MPa, below which the stored amount is low (<0.2 wt.%). At higher pressures, the micropore volume controls H2 storage capacity. At 77 K, Pd doping has a negative effect on hydrogen storage whatever the pressure considered. From N2 adsorption at 77 K, TPR, XRD, TEM, and H2 chemisorption studies, we concluded that: (i) Pd particles remained mainly decorating the outer surface of the ACs; (ii) increasing Pd content produced an increase of the metal particle size; (iii) ACs with higher surface area produced smaller metallic nanoparticles at a given Pd content.  相似文献   

7.
Development of advanced hydrogen storage materials with high capacity and stability is vital to achieve an envisaged hydrogen economy. Here, we report a uniformly dispersed Pd nanoparticles on the boron-doped reduced graphene oxide (Pd/B-rGO) as a novel nanocomposite for efficient hydrogen storage. The effects of the incorporation of Pd NPs and the substitution of boron atoms into the graphene-based nanomaterial matrix on the electrochemical hydrogen up-taking and releasing were comparatively studied using electrochemical techniques, and duly supported by density functional theory (DFT) calculations. The discharge capacities of the Pd-rGO and Pd/B-rGO nanocomposites were determined to be over 45 and 128 times higher than that of the Pd NPs, respectively, showing that the B doping and the rGO support played significant roles in the enhancement of the hydrogen storage capability. Moreover, the galvanostatic charging and discharging cycling tests demonstrated a high stability and efficient kinetics of the Pd/B-rGO nanocomposite in the H2SO4 electrolyte for hydrogen up-taking and release.  相似文献   

8.
Corncob-derived activated carbon (CAC) was prepared by potassium hydroxide activation. The Pt/Pd-doped CAC samples were prepared by two-step reduction method (ethylene glycol reduction plus hydrogen reduction). The as-obtained samples were characterized by N2-sorption, TEM and XRD. The results show the texture of CAC is varied after doping Pt/Pd. The Pd particles are easier to grow up than Pt particles on the surface of activated carbon. For containing Pt samples, the pore size distributions are different from original sample and Pd loaded sample. The hydrogen uptake results show excess hydrogen uptake capacity on the Pt/Pd-doped CAC samples are higher than pure CAC at 298 K, which should be attributed to hydrogen spillover effects. The 2.5%Pt and 2.5%Pd hybrid doped CAC sample shows the highest hydrogen uptake capacity (1.65 wt%) at 298 K and 180 bar, The particle size and distribution of Pt/Pd catalysts could play a crucial role on hydrogen uptake by spillover. The total hydrogen storage capacity analysis show that total H2 storage capacities for all samples are similar, and spillover enhanced H2 uptakes of metal-doped samples could not well support total H2 storage capacity. The total pore volume of porous materials also is a key factor to affect total hydrogen storage capacity.  相似文献   

9.
Hydrogen storage properties of carbon nanotubes (CNTs) modified by oxidative etching and decoration of Pd spillover catalysts are investigated. A mixed H2SO4/H2O2 solution containing ferrous ions (Fe2+) is useful to open the caps, to shorten the length, and to generate defects on CNTs. The Pd catalysts are deposited on the CNTs with the aid of supercritical carbon dioxide (scCO2); as a result, a highly dispersed Pd nanoparticles and an intimate connection between Pd and carbon surface can be obtained. Combination of the two approaches can optimize a hydrogen spillover reaction on CNTs, resulting in a superior hydrogen storage capacity of 1.54 wt% (at 25 °C and 6.89 MPa), which corresponds to an enhancement factor of ∼4.5 as compared to that of pristine CNTs.  相似文献   

10.
Nano-CeO2 supports, which have different structure from different preparation methods, were used to prepare nano-Pd/CeO2 catalysts. The hydrogen storage capacity of prepared nano-Pd/CeO2 catalysts were studied via vapor phase benzene hydrogenation and cyclohexane dehydrogenation reactions. Results show that the prepared Pd/CeO2 catalysts exhibit excellent benzene hydrogenation and cyclohexane dehydrogenation performances. The catalytic performance of the Pd/CeO2 catalysts is related to the dispersion of metallic Pd, hydrogen adsorption-desorption ability and structure of Pd/CeO2 catalysts and so on. And those properties are also directly affected by the morphology and mesoporous structure of the prepared nano-Pd/CeO2 catalysts that can be regulated by CeO2 support preparation methods. The synergistic effect between metal Pd, CeO2 support and their structures can effectively promote benzene hydrogenation and cyclohexane dehydrogenation, thus promoting hydrogen storage capacity. The prepared Pd/CeO2-HT catalyst, which has high specific surface area, developed pore structure and highly dispersed metal Pd species, exhibits superior catalytic performances. And, the Pd/CeO2-HT catalyst exhibits superior catalytic hydrogen storage performances. The benzene conversion over it at 200 °C reaches 99.5%. Whereas the cyclohexane conversion at 450 °C is 65.3%, and the H2 production capacity is 73.77 g/h.  相似文献   

11.
The high pressure H2 sorption isotherms for vanadium pentoxide foam (VOF) were obtained at a liquid nitrogen temperature. The enhancement of hydrogen storage capacity occurred in as-prepared VOF (∼1.0 wt%) in contrast to that in pristine vanadium pentoxide (∼0.2 wt%). The maximum capacity of hydrogen storage (∼2.0 wt%) was achieved by thermal annealing at Ta = 623 K. The enhancement of hydrogen storage in VOF is attributed to the morphological modulation by thermal annealing.  相似文献   

12.
In this work, track-etched poly (ethylene terephthalate) (PET) membranes having different pore sizes were functionalized by the carboxylic groups and the amino groups. Palladium (Pd) nanoparticles of average diameter 5 nm were synthesized chemically and deposited onto pore walls as well as on the surface of these pristine and functionalized membranes. Effect of Pd nanoparticles binding on these membranes were explored and aminated membrane were found to bind more Pd nanoparticles due to its affinity. The morphology of these composite membranes is characterized by Scanning Electron Microscope (SEM) for confirmation of Pd nanoparticle deposition on pore wall as well as on the surface. Gas permeability of functionalized and non-functionalized membranes for hydrogen and carbon dioxide has been examined. From the gas permeability data of hydrogen (H2) and carbon dioxide (CO2) gases, it was observed that these membranes have higher permeability for H2 as compared with CO2. Due to absorption of hydrogen by Pd nanoparticles selectivity of H2 over CO2 was found higher as compared to without Pd embedded membranes. Such type of membranes can be used to develop hydrogen selective nanofilters for purification/separation technology.  相似文献   

13.
In this work we report a theoretical study on the atomic and molecular hydrogen adsorption onto Pd-decorated graphene monolayer and carbon nanotubes by a semi-empirical tight-binding method. We first investigated the preferential adsorption geometry, considering different adsorption sites on the carbon surface, and then studied the evolution of the chemical bonding by evaluation of the overlap population (OP) and crystal orbital overlap population (COOP). Our results show that strong C–Pd and H–Pd bonds are formed during atomic hydrogen adsorption, with an important role in the bonding of C 2pz and Pd 5s, 5pz and 4dz2 orbitals. The hydrogen storage mechanism in Pd-doped carbon-based materials seems to involve the dissociation of H2 molecule on the decoration points and the bonding between resultant atomic hydrogen and the carbon surface.  相似文献   

14.
It is still a challenging task to achieve the rapid detection of hydrogen (H2) with the rapid development of hydrogen energy sector. In this work, the H2 sensing capabilities of pristine and Pd-modified SnO2 nanoparticles with the size of ~7 nm were systematically evaluated. The SnO2 nanoparticles were synthesized via hydrothermal method and Pd modification was performed using impregnation route. Pd modification remarkably upgraded the H2 sensing performances compared with the pristine SnO2 gas sensor. The working temperature of SnO2 decreased from 300 °C to 125 °C after Pd loading. Among the prepared Pd/SnO2 gas sensors, 0.50 at.% Pd/SnO2 sensor exhibited the highest response magnitude of 254 toward 500 ppm H2 and rapid response/recovery time of 1/22 s at 125 °C. The enhanced H2 sensing capabilities by Pd modification may be related to the catalytic effect and the resistance modulation.  相似文献   

15.
Carbon nanotubes are considered important materials for hydrogen storage. Although the C–H interaction is very weak at room temperature, the incorporation of highly dispersed Pd nanoparticles increases the H2 adsorption on carbon surfaces. In this work we performed density functional theory studies of H2 adsorption on single walled carbon nanotubes (SWCNTs) with C-vacancies and a Pd decoration. We used the VASP and SIESTA codes. Our calculations show that Pd adsorption is favored on the C-vacancies of the (5,5) SWCNT, while H2 adsorption also occurs preferentially on C-defective sites.  相似文献   

16.
Hydrogen adsorption on porous materials is one of the possible methods proposed for hydrogen storage for transport applications. One way for increasing adsorption at room temperature is the inclusion of metal nanoparticles to increase hydrogen–surface interactions. In this study, ordered mesoporous carbon materials were synthesized by replication of nanostructured mesoporous SBA-15 silica. The combination of different carbon precursors allowed to tailor the textural, structural and chemical properties of the materials. These carbons were used for the synthesis of hybrid nanostructured carbon/palladium materials with different sizes of metal nanoparticles. The hydrogen sorption isotherms were measured at 77 K and 298 K between 0.1 and 8 MPa. Hydrogen storage capacities strongly correlate with the textural properties of the carbon at 77 K. At room temperature, Pd nanoparticles enhance hydrogen storage capacity by reversible formation of hydride PdHx and through the spillover mechanism. The hydrogen uptake depends on the combined influences of metal particle size and of carbon chemical properties. Carbons obtained from sucrose precursors lead to the hybrid materials with the highest storage capacities since they exhibits a large microporous volume and a high density of oxygenated surface groups.  相似文献   

17.
High-energy density and low cost magnesium nanoparticles (Mg NPs)-based material are being sought to meet increasing capable of hydrogen (H2) storage demand. Here, a kind of air-stable Mg NPs supported on porous structured multi-walled carbon tubes-polymethyl methacrylate (MWCNTs-PMMA) template is prepared owing to reversible well-distributed, dispersed and small-sized Mg/MgH2 NPs. The aim is to improve the H2 storage capacity, hydrogen sorption kinetics and thermodynamics of nano Mg-based system without using catalyst. The organic Mg precursor was directly in-situ reduced to metallic Mg NPs in MWCNTs-PMMA template by lithium naphthalide. The size distribution of reduced Mg nanoparticles is around 3.6 ± 0.2 nm, confirmed by XRD and TEM analyses, which is due to the strong interaction between Mg NPs and MWCNTs-PMMA via PMMA binding Mg2+, as well as the confinement of porous template hindered the growth and agglomeration of Mg NPs. Moreover, except H2, O2 and H2O molecules can't infiltrate the porous structure of MWCNTs-PMMA resulted in the presence of air stable Mg NPs in the MWCNTs-PMMA. The work provides a new scope to prepare nano metal-based composite for H2 storage.  相似文献   

18.
Acidic etching and Pt particle decoration were applied to modify the hydrogen absorption behavior of carbon nanotubes (CNTs). Two different acidic solutions, namely H2SO4/HNO3 and FeSO4/H2SO4/H2O2, were used for etching treatment. A novel electroless deposition process, incorporating supercritical CO2 (sc-CO2) fluid, was used to decorate finely-dispersed nano-sized Pt particles on CNTs. The hydrogen storage capacities of various modified CNTs were measured by using a high pressure thermal gravimetric microbalance (HPTGA). The experimental results showed that acidic etching could increase the surface defect density and lead to open-up of the caps of CNTs, resulting in an increase in the active adsorption site for physical sorption of H2. The electroless deposition of nano-Pt particles on CNTs, using conventional electrolyte, could promote chemical sorption of hydrogen via spillover mechanism. By employing sc-CO2 bath, the Pt particle size became much finer and more uniformly distributed on the surfaces of CNTs, giving rise to a high hydrogen storage capacity. When a hybrid process including sc-CO2 Pt decoration following acidic etching was applied to modify CNTs, a substantial enhancement of hydrogen storage capacity (about 2.7 wt%) was observed.  相似文献   

19.
The nanometric carbon CMK‐3 modified with Pt was synthesized and applied as a reservoir for hydrogen uptake. We found that the newly synthesized hybrid composites exhibited significantly enhanced H2 storage. The approach that we have followed includes synthesis of nanostructures with the experimental study of its adsorption capacity and storage properties. In summary, we have shown that CMK‐3 ordered porous carbon modified with Pt nanoclusters is a promising material for hydrogen uptake. The samples were characterized by X‐ray diffraction, N2 isotherms, X‐ray photoelectron spectra and transmission electron microscopy. The nanoparticles of Pt (~1.7 nm) incorporated onto the nanostructured carbon CMK‐3 showed higher hydrogen uptake at low and high pressures (3.3 wt% of H2 sorption at 10 bar and 77 K) than CMK‐3. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

20.
In the present work, the effect of carbon shell around size selected palladium (Pd) nanoparticles on hydrogen (H2) sensing has been studied by investigating the sensing response of Pd-C core-shell nanoparticles having a fixed core size and different shell thickness. The H2 sensing response of sensors based on Pd and Pd-C nanoparticles deposited on SiO2 and graphene substrate has been measured over a temperature range of 25 °C–150 °C. It is observed that Pd-C nanoparticle sensor shows higher sensitivity with increase in shell thickness and faster response/recovery in comparison to that of Pd nanoparticle samples. Pd-C nanoparticles show room temperature H2 sensitivity in contrast to Pd nanoparticles which respond only at higher temperatures. Role of carbon shell is also understood by investigating H2 sensing properties of Pd and Pd-C nanoparticles on graphene substrates. These results show that higher catalytic activity and electronic interaction at Pd-C interface, a complete coverage and protection of Pd surface by carbon and presence of structural defects in nanoparticle core are important for room temperature and higher sensing response.  相似文献   

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