首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The effect of chemical pre-treatment of the carbon support used for deposition of Pt nano-particles is reported. Data on particle size, distribution and their electocatalytic activity toward hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) are reported. Vulcan XC-72R carbon was pre-treated with 5% HNO3, 0.07 M H3PO4, 0.2 M KOH and 10% H2O2. The properties of carbon supports were studied by N2 adsorption and X-ray photoelectron spectroscopy (XPS). Chemical reduction with ethylene glycol (EG) was used to synthesize Pt on carbon supports and the differences in catalyst morphology were characterized using CO chemisorption, X-ray diffraction, energy dispersive X-ray analysis and transmission electron microscope techniques. The electrocatalytic activity of Pt/C catalysts toward HOR and ORR was examined by cyclic voltammetry (CV) on a rotating ring-disk electrode (RRDE) and compared with E-Tek Pt/C. The ORR was predominantly involved via four-electron process with the first electron transfer being the rate-determining step. However, the specific activity and mass activity were greatly influenced by the pre-treatment employed.  相似文献   

2.
Hydrogen is a sustainable, renewable and clean energy carrier that meets the increasing energy demand. Pure hydrogen is produced by the hydrolysis of sodium borohydride (NaBH4) using a catalyst. In this study, Ni/TiO2 catalysts were synthesized by the sol-gel technique and characterized by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) methods. The effects of Ni loading ratio (20–40%), catalyst amount (75–200 mg), the concentration of sodium hydroxide (NaOH, 0.25–1 M), initial amount of NaBH4 (75–125 mg) and the reaction temperature (20–60 °C) on hydrogen production performance were examined. The hydrogen yield (100%) and hydrogen production rate (110.87 mL/gcat.min) were determined at the reaction conditions of 5 mL of 0.25 M NaOH, 100 mg NaBH4, 100 mg Ni/TiO2, 60 °C. Reaction order and activation energy were calculated as 0.08 and 25.11 kJ/mol, respectively.  相似文献   

3.
The nanoparticles (NP), consisting of hydrazine grafted organo-silica with PdNPs embedded shell on the Fe3O4 core, were prepared to study the adsorption and interactions of hydrogen in PdNPs and their support matrix. This material is expected to find the applications in the hydrogen technology including catalysis. The PdNPs were formed spontaneously in the organo-silica shell on magnetite nanoparticles by the reduction of Pd2+ ions with grafted hydrazine in the organo-silica shell. Thus formed NPs, termed as Fe3O4-GTEOS@PdNPs, were also thermally treated at 1033 K in Ar atmosphere to convert organic components to carbon. The chemical composition, physical structure, and magnetic properties were studied by high resolution transmission electron microscopy, X-rays diffraction, Mössbauer spectroscopy and X-ray photoelectron spectroscopy for the characterizations of physical, chemical and magnetic changes occurred in the Fe3O4-GTEOS@PdNPs after hydrogen adsorption-desorption at varying temperatures with respect to that in unused one. The hydrogen adsorption pressure-composition (PC) isotherms in Fe3O4-GTEOS@PdNPs followed the expected trend from 173 to 303 K as expected from PdNPs. However, thermally treated Fe3O4-GTEOS@PdNPs were found to adsorb lower amount of hydrogen due to oxidation of Pd0 to PdO and morphological changes during heating in Ar atmosphere. The comparison of nH/nPd value (0.49) obtained for the PdNPs in Fe3O4-GTEOS@PdNPs with the values those reported in the literature for different Pd materials showed the decrease in nH/nPd value with decrease in the size of Pd particles. This was attributed to stronger Pd–H bond in a nanoscale palladium, which prevented hydrogen transfer to interior matrix as compared to bigger Pd particles. The hydrogen adsorption PC isotherm at 373 K in Fe3O4-GTEOS@PdNPs could not be obtained as the unknown chemical reaction happened in the sample during the experiment. The considerably higher H2 consumption in the Fe3O4-GTEOS@PdNPs occurred at 373 K than that expected from the hydrogen adsorption in the PdNPs alone.  相似文献   

4.
We report on an easy synthesis method for the preparation of a hybrid composite of Pt-loaded MWCNTs@MOF-5 [Zn4O(benzene-1,4-dicarboxylate)3] that greatly enhanced hydrogen storage capacity at room temperature. To prepare the composite, we first prepared Pt-loaded MWCNTs, which were then incorporated in-situ into the MOF-5 crystals. The obtained composite was characterized by various techniques such as powder X-ray diffractometry, optical microscopy, porosimetry by nitrogen adsorption, and hydrogen adsorption. The analyses confirmed that the product has a highly crystalline structure with a Langmuir specific surface area of over 2000 m2/g. The hybrid composite was shown to have a hydrogen storage capacity of 1.25 wt% at room temperature and 100 bar, and 1.89 wt% at cryogenic temperature and 1 bar. These H2 storage capacities represent significant increases over those of virgin MOF-5s and Pt-loaded MWCNTs.  相似文献   

5.
This study investigates the crystal structure and Pressure–composition (PC) isotherm of Nd2Ni7 prepared by annealing an arc-melted ingot at 1448 K for 10 h followed by ice-water quenching. The crystal structure was further refined by X-ray Rietveld analysis based on the Ce2Ni7-type structure. The lattice parameters were determined as a = 0.5001(1) nm and c = 2.4437(4) nm. A single plateau was observed during the first absorption–desorption cycle. In the first absorption cycle, the maximum hydrogen capacity reached 1.22 H/M (1.58 mass%) at 233 K. The absorption and desorption plateau pressures were approximately 1.0 and 0.002 MPa, respectively. In the first desorption process, 0.63 H/M of hydrogen remained in the sample. Further, a single sloping plateau was observed in the second absorption–desorption process. Heavy peak broadening was observed in the X-ray diffraction (XRD) profile after hydrogenation, with no detection of an amorphous phase.  相似文献   

6.
A new metal-organic framework [Fe3O(OOC-C6H4-COO)3(H2O)3]Cl·(H2O)x was synthesized with a specific surface area of 2823 m2/g and a lattice parameter of 88.61 Å. Isostructural with MIL-101, this compound exhibits similar hydrogen adsorption properties, with maximum adsorption capacity of 5.1wt.% H at 77 K. The adsorption enthalpy of hydrogen for MIL-101 and ITIM-1 (MIL-101Fe) at zero coverage was calculated for a wide temperature range of 77 K ÷ 324 K, considering corrections for the variation of hydrogen gas entropy with the temperature. The resulted adsorption enthalpy is 9.4 kJ/mol for MIL-101, in excellent agreement with the value reported in literature from microcalorimetric measurements, and a value of 10.4 kJ/mol at zero coverage was obtained for ITIM-1 (MIL-101Fe).  相似文献   

7.
A phase stability map of metallic magnesium powder, exposed to environmental conditions for 12 months (Mg-12M) and subjected to different high-energy ball-milling speeds and milling times, was constructed. Mg-12M−160 [½MgO-⅓Mg(OH)2-⅙hydromagnesite] and Mg-12M−640 [¼MgO-⅝Mg(OH)2-⅛hydromagnesite] composites were obtained changing the milling conditions. The correlation among the accumulated energy (ΔEaccum), the impact energy (ΔEhit), and the phase stability under different high-energy ball-milling conditions were generated. The Mg-12M−160 composite had a hydrogen storage capacity of 0.63 wt% at −196 °C and 8.3 bar, although further hydrogen adsorption at higher pressures is expected. Structural defects play a significant role in the adsorption capacity. A representation of the possible absorption mechanism is proposed.  相似文献   

8.
In this study, clinoptilolite (CLN), mordenite (MOR) and chabazite (CHA) from Turkey and those of H+-, Na+-, K+-, Li+-, Ca2+- and Mg2+- exchanged forms were investigated for hydrogen storage at 77 K using volumetric apparatus up to 100 kPa. Cation exchange procedures were carried out using 1.0 M HCI, KNO3, LiNO3, NaNO3, Mg(NO3)2 and Ca(NO3)2 solutions at 90 °C for 5 h. Structural characteristics of these zeolite samples were investigated using XRD, XRF and N2 adsorption techniques. Experimental results showed that the chabazite samples (0.474–1.082 wt %) had a higher hydrogen adsorption capacity than mordenite (0.224–0.337 wt %) and clinoptilolite (0.065–0.555 wt %) samples. The variations in the level of hydrogen adsorption of original and cation exchanged natural zeolites were discussed in terms of the induced differences in their structural properties.  相似文献   

9.
Hydrogen is a worldwide green energy carrier, however due its low storage capacity, it has yet to be widely used as an energy carrier. Therefore, the quantum chemical method is being employed in this investigation for better understand the hydrogen storage behaviour on Pt (n = 1-4) cluster decorated C48H16 sheet. The Pt(n = 1-4) clusters are strongly bonded on the surface of C48H16 sheet with binding energies of ?3.06, ?4.56, ?3.37, and ?4.03 eV respectively, while the charge transfer from Pt(n = 1-4) to C48H16 leaves an empty orbital in Pt atom, which will be crucial for H2 adsorption. Initially, the molecular hydrogen is adsorbed on Pt(n = 1-4) decorated C48H16 sheet through the Kubas interaction with adsorption energies of ?0.85, ?0.66, ?0.72, and ?0.57 eV respectively, while H–H bond is elongated due to the transfer of electron from σ (HH) orbital to unfilled d orbital of the Pt atom, resulting in a Kubas metal-dihydrogen complexes. Furthermore, the dissociative hydrogen atoms adsorbed on Pt(n = 1-4) decorated C48H16 sheet have adsorption energies of ?1.14 eV, ?1.02 eV, ?0.95 eV, and ?1.08 eV, which are greater than the molecular hydrogen adsorption on Pt(n = 1-4) cluster supported C48H16 sheet with lower activation energy of 0.007, 0.109, 0.046, and 0.081 eV respectively. To enhance the dissociative hydrogen adsorption energy, positive and negative external electric fields are applied in the charge transfer direction. Increasing the positive electric field makes H–H bond elongation and good adsorption, whereas increasing the negative electric field results H–H bond contraction and poor adsorption. Thus, by applying a sufficient electric field, the H2 adsorption and desorption processes are can be easily tailored.  相似文献   

10.
The adsorption equilibrium of hydrogen on graphene sheets (GS) was studied based on a sample of GS with SBET = 300 m2/g at the temperatures of 77.15 K–293.15 K and the pressures of 0 MPa–6 MPa. In the meantime, the adsorptions (Excess adsorption measurements) of hydrogen on granular coconut shell SAC-02 activated carbon (SBET = 2074 m2/g) and carbon nanofiber (CNFs, SBET = 205 m2/g) were investigated at the pressures of 0–8 MPa and the temperature of 77.15 K. The outcomes from experiments were used to determine the parameters in Toth equation by way of Non-linear fit. The absolute adsorption amounts of hydrogen on the GS, which were calculated from the equation, were used to calculate the isosteric heat of hydrogen adsorption by use of adsorption isosteres.  相似文献   

11.
Developing highly efficient, low-cost, and robust water splitting hydrogen production catalysts is critical for hydrogen energy applications. This study presents the synthesis of Co3O4/VO2 heterogeneous nanosheet structures on carbon cloth (Co3O4/VO2/CC). The obtained Co3O4/VO2/CC hybrid catalyst has a low overpotential of 108 mV at a current density of 10 mA cm?2, a Tafel slope of 98 mV dec?1, and high stability in 1.0 M KOH for 10 h. The experimental results and density functional theory (DFT) calculations results also show that Co3O4 coupled with VO2 in Co3O4/VO2/CC can optimize hydrogen adsorption energy and facilitate electron transport, thereby accelerating the catalytic kinetics for hydrogen evolution reaction (HER). This work also provided an alternative method to design and construct non-noble metal oxide-based catalysts for alkaline hydrogen production.  相似文献   

12.
The incorporation of nanoscale Co particles (with sizes from a few nanometres) into porous carbon aerogels (CAs) was investigated. Elemental maps of the nanoscale metal particles embedded within CA were obtained using energy filtered transmission electron microscopy. The microstructure of Co doped carbon aerogels was further investigated using small angle X-ray scattering and nitrogen adsorption at 77 K. The isosteric heat of adsorption (Qst) was investigated as a function of hydrogen uptake at temperatures from 77 K to 110 K over the pressure range of 0-0.25 MPa. The isosteric heat of adsorption at low H2 concentration for Co doped CA (9.0 kJ mol−1) was found to be higher than for pure CA (5.8 kJ mol−1).  相似文献   

13.
Hydrogen adsorption and desorption over Ru/SiO2 and Ru/Vulcan are investigated in terms of hydrogen storage and release characteristics by both dynamic and static experiments. Ru particle dispersions as a function of metal loading were determined by HR-TEM and volumetric chemisorption experiments. Vulcan was more accommodating for spillover hydrogen than SiO2. High Ru dispersions, i.e., small particle sizes, favored the amount of hydrogen spillover to Vulcan, as revealed by temperature programmed desorption (TPD) of hydrogen. TPD of hydrogen under He flow experiments over Ru/SiO2 and Ru/Vulcan materials revealed a low temperature process (up to 200 °C) attributed to desorption of weakly bound hydrogen from Ru metal surface. A high temperature process (above 450 °C) was attributed to diffusion of hydrogen from the support to the Ru particle and desorption at the Ru sites. Hydrogen adsorbs strongly on Ru metal, as indicated by the initial heats of H2 adsorption measured as 100 kJ/mol over 1 wt% Ru/Vulcan by adsorption calorimetry. At higher coverages, heat of adsorption of hydrogen was measured as 10 kJ/mol. Low heat of adsorption of hydrogen at high coverages indicate multilayer weak adsorption of hydrogen over the storage material, which can desorb at lower temperatures.  相似文献   

14.
We prepared activated carbons (ACs) that are among the best adsorbents for hydrogen storage. These ACs were prepared from anthracites and have surface areas (SBET) as high as 2772 m2 g−1. Anthracites activated with KOH presented the highest adsorption capacities with a maximum of 5.3 wt.% at 77 K and 4 MPa. Non-linearity between hydrogen uptake at 77 K and pore texture was confirmed, as soon as their SBET exceeded the theoretical limiting value of (geometrical) surface area, i.e., SBET > 2630 m2 g−1. We separated adsorption and compression contributions to total hydrogen storage. The amount of hydrogen stored is significantly increased by adsorption only at moderate pressure: 3 MPa and 0.15 MPa at 298 and 77 K, respectively. Hydrogen adsorption on ACs at high pressure, above 30 MPa at 298 K and 8 MPa at 77 K, has not interest because more gas can be stored by simply compression in the same tank volume.  相似文献   

15.
The purpose of this paper is to describe and evaluate the corrosion of carbon steel in crotonic acid for hydrogen production and using polysorbate 20 (NS), dioctyl sodium sulfosuccinate (AS) and benzalkonium chloride (CS) to control hydrogen evolution. Measurements were conducted in tested solutions using hydrogen evolution and electrochemical impedance spectroscopy (EIS) measurements and complemented by scan electron microscope (SEM) and energy dispersive X-ray (EDX) investigations. It is shown that the hydrogen generation rate obtained during the corrosion of carbon steel in crotonic acid increased with increase in acid concentration, temperature and immersion time. The addition of organic surfactants inhibits the hydrogen generation rate. The inhibition occurs through adsorption of organic surfactants on the metal surface. Adsorption processes followed the Langmuir isotherm. The order of effectiveness of the surfactants was AS > NS > CS. The values of activation energy (Ea) and heat of adsorption (Qads) were calculated and discussed.  相似文献   

16.
Hydrogen production through autothermal reforming of methane (ATR of CH4) over promoted Ni catalysts was studied. The control of the ability to self-activation and activity of Ni-M/Ce0.5Zr0.5O2/Al2O3 catalysts was achieved by tuning their reducibility through the application of different types (M = Pt, Pd, Re, Mo or Sn) and content (molar ratio M/Ni = 0.003, 0.01 or 0.03) of additive. The comparison of the efficiency and action mode of noble (M = Pt, Pd) and non-noble (M = Re, Mo, Sn) metal additives in the composition of Ni-M/Ce0.5Zr0.5O2/Al2O3 catalysts was performed using X-ray fluorescence analysis, N2 adsorption, X-ray diffraction, high-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction with hydrogen, and thermal analysis. The composition-characteristics-activity correlations were determined. It was shown that the introduction of a promoter does not affect the textural and structural properties of catalysts but influences their reducibility and performance in ATR of CH4. At the similar dispersion of NiO active component (11 ± 2 nm), the Ni2+ reduction is intensified in the following order of additives: Mo < Sn < Re ≤ Pd < Pt. It was found that for the activation of Ni and Ni–Sn catalysts before ATR of CH4 tests, the pre-reduction is required. On the contrary, the introduction of Pt, Pd and Re additives leads to the self-activation of catalysts under the reaction conditions and an increase of the H2 yield due to the enhanced reducibility of Ni2+. The efficient and stable catalyst for hydrogen production has been developed: in ATR of CH4 at 850 °C over an optimum 10Ni-0.9Re/Ce0.5Zr0.5O2/Al2O3 catalyst the H2 yield of 70% is attained. The designed catalyst has enhanced stability against oxidation and sintering of Ni active component as well as high resistance to coking.  相似文献   

17.
Developing high-efficiency electrocatalysts viable for pH-universal hydrogen evolution reaction (HER) has attracted great interest because hydrogen is a promising renewable energy carrier for replacing fossil fuels. Herein, we present a facile strategy for fabricating ultra-fine Ru nanoparticles (NPs) decorated V2O3 on the carbon cloth substrates as efficient and stable pH-universal catalysts for HER. Benefiting from the metallic property and electronic conductivity of V2O3 matrix, the optimized hybrid (Ru/V2O3-CC) exhibits excellent HER activities in a wide pH range, achieving lower overpotentials of 184, 219, and 221 mV at 100 mA cm−2 in 0.5 M H2SO4, 1.0 M KOH and 1.0 M phosphate-buffered saline, respectively. Moreover, the electrode remains superior stability with negligible degradation after 5000 cyclic voltammetry scanning whether in acidic, alkaline or neutral media. Experimental results, combined with theoretical calculations, demonstrate that the interaction between Ru NPs and the support V2O3 induces the local electronic density diversity, allowing optimization of the adsorption energy of Ru towards hydrogen intermediate H1, thus favoring the HER process.  相似文献   

18.
Herein, we report an inexpensive synthesis of sonochemical nickel and iron (M = Ni, Fe) doped Cu2ZnSnS4 (CZTS) and their utility as a nanoelectrodes for improved electrocatalytic water splitting performance. The as-synthesized electrode materials were characterized further by Transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman and X-ray photoelectron (XP) spectroscopic studies. Significantly, Ni doped CZTS electrocatalyst exhibits low overpotential approximately 214 and 400 mV for the hydrogen evolution reactions (HER) in 0.5 M H2SO4 and 1 M KOH electrolyte solutions respectively, and 1.29 V vs RHE for the oxygen evolution reactions (OER) in 1 M KOH at 10 mA/cm2 current density. Small Tafel slopes and tested durability for longer time i.e. upto 500 min for water splitting, demonstrates that Ni doped CZTS is efficient bifunctional electrocatalyst having high activity along with extraordinary current/potential stability. Moreover, Fe doped CZTS electrocatalyst shows relatively poor response, i.e. overpotential 300 mV in 0.5 M H2SO4 and 445 mV in 1.0 M KOH towards HER and overpotential 1.54 V for the OER in 1 M KOH reaches at 10 mA/cm2. This highly efficient bifunctional electrocatalysts that can meet the existing energy anxiety.  相似文献   

19.
In this work the hydrogen evolution reaction (HER) onto Ni–Sn alloy coatings deposited at different current densities from the bath containing 0.1 M Sn2+ and 0.1 M Ni2+ ions in the pyrophosphate–glycine solution, was investigated by polarization curves and electrochemical impedance spectroscopy (EIS) measurements. Their morphology and chemical composition were investigated by scanning electron microscopy equipped with an energy-dispersive X-ray spectroscopy (SEM-EDS), while the phase composition was investigated by X-ray powder diffraction (XRPD). It was shown that their chemical composition, phase composition and morphology depend on the deposition current density. In deposited samples all detected phases, face centered cubic (fcc) Ni, close packed (hcp) hexagonal Ni3Sn, hexagonal Ni(1+x)Sn (0 < x < 0.5) which adopts NiAs structure type and monoclinic Ni3Sn4 (CoSn structure type), were of low crystallinity. The increase of the Ni–Sn alloy coatings catalytic activity for HER in 6 M KOH with increasing the deposition current density was shown to be the consequence of the change of all three parameters: chemical composition, phase composition and morphology, with the effect of morphology being the most pronounced.  相似文献   

20.
With the increasing demand for environmental protection worldwide, metal-organic frameworks (MOFs) have been pivotal in the clean energy domain. Due to the high surface areas, large porosities and structural tunability, they are promising for the adsorption separation of H2/CH4 mixtures. High-throughput computational screening was adopted to identify the optimal adsorbents for hydrogen purification from 502 MOFs with open copper sites. Firstly, the adsorption performance of H2/CH4 mixture in 440 MOFs, which exhibit non-zero surface area and over -3.8 Å largest cavity diameter (LCD), was calculated using grand canonical Monte Carlo (GCMC) simulations at 300 K and various pressures. Secondly, we identified the top 9 high-performance MOFs by evaluating the ranking of candidate adsorbent performance according to a combination metric of adsorption performance score (APS, the product of adsorption capacity of CH4 and selectivity of CH4 over H2) and percent regenerability (R%). PCN-39 and MOF-505 exhibit high APS of 101 mol kg−1 and 67.9 mol kg−1, respectively, promising for hydrogen purification. Subsequently, the breakthrough curves of H2/CH4 mixture through the fixed bed packed with some optimal MOFs were predicted to evaluate their effects in practical hydrogen purification. UMODEH08 or UMOBEF04 exhibits the long dimensionless residence time over 30 of CH4 for the H2/CH4 separation. Finally, we also explored the behaviors of the radial distribution functions (RDF) and adsorption equilibrium configurations to further demonstrate how the selected MOFs differentiate CH4 from H2. The investigation on all these observations at molecular level will pave the way for the development of new materials for clean energy applications.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号