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1.
The effects of bromine treatment on the hydrogen storage properties of multi-walled carbon nanotubes
S. MirershadiA. Reyhani S.Z. MortazaviB. Safibonab M. Khabazian Esfahani 《International Journal of Hydrogen Energy》2011,36(24):15622-15631
The effects of bromine treatment on the properties of multi-walled carbon nanotubes (MWCNTs) such as surface porosity, sp2 hybridization, functional groups and hydrogen storage capacity were studied and compared with treated MWCNTs by HCl, HNO3 and H2SO4 acids. The treatments affect the graphitization properties (sp2 hybridization) and porous structures of MWCNTs by enlarging the specific surface area and the micro-pore volume. In addition, the hydrogen storage capacity of the treated MWCNTs was also investigated by volumetric technique. It is found that the destroying of sp2 hybridization of bromine treated MWCNTs increases hydrogen adsorption sites and decreases hydrogen desorption temperature. 相似文献
2.
Oxygen‐modified multiwalled carbon nanotubes: physicochemical properties and capacitor functionality
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Edwin T. Mombeshora Patrick G. Ndungu A. L. Leigh Jarvis Vincent O. Nyamori 《国际能源研究杂志》2017,41(8):1182-1201
Multiwalled carbon nanotubes (MWCNTs) have found numerous applications in energy conversion systems. The current work focused on the introduction of oxygen moieties onto the walls of MWCNTs by five different reagents and investigating the associated physicochemical properties. Oxygen‐containing groups were introduced onto MWCNTs using an ultrasound water‐bath treatment with HNO3, HCl, H2O2 or HCl/HNO3 solution. Physicochemical properties were characterised by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman, thermal gravimetric analysis, textural characteristics, cyclic voltammetry and electrochemical impedance spectroscopy. The study focus was mainly on linking the physicochemical properties of oxygen‐functionalised MWCNTs and suitability in electrochemical capacitors using group one sulfates. From the Fourier transform infrared spectroscopy KBr pellet protocol, peaks at 3400, 2370 and 1170 cm?1 suggest oxygen‐containing functionalities on MWCNTs. HNO3 treatment introduced highest oxygen‐containing moieties and achieved highest specific capacitance in Li2SO4 and Na2SO4 electrolytes of 36.200 F g?1 (77 times better than pristine) and 45.100 F g?1 (2.5 times enhancement), respectively. For K2SO4, it was 33.600 F g?1 (4.9 times better) with HNO3/HCl‐treated samples. Oxygen‐functionalised MWCNTs displayed both pseudo and electrochemical double‐layer mechanism of enhanced charge storage and cycle stability in group one sulfates electrolytes. The dominating charge storage mechanism was pseudo, and Na2SO4 was the best electrolyte amongst the three group one sulfates investigated. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
3.
《International Journal of Hydrogen Energy》2023,48(5):1930-1942
The present work investigates the effect of acid functionalization of multiwalled carbon nanotubes (MWCNTs) on the physisorption based mechanism of hydrogen storage at room temperature. For this purpose, a suite of functionalized CNT samples is synthesized and subjected to a comprehensive range of material characterization techniques and hydrogen storage measurements. Nitric acid (HNO3) and the mixture of sulphuric acid and nitric acid (H2SO4:HNO3) are used for the synthesis at oxidation temperatures of 80 °C and 100 °C. Electron microscopy and X-ray photoelectron spectroscopy results reveal that acid functionalization causes major alternation in the physicochemical properties of the CNTs due to the varied concentration of oxygen functional groups. Particularly, the H2SO4:HNO3 functionalized sample at 100 °C is found to have the highest interlayer spacing, oxygen to carbon ratio (26.09 at. %), defect content, and specific surface area (215.3 m2/g). These features collectively contribute to substantially improved hydrogen storage properties, including a ~150% increase in the hydrogen storage capacity at 298 K and 50 bar. Furthermore, kinetic analysis shows that the desorption follows a multiple diffusion process which is sensitive to the oxygen functional groups and structural defects, hence reducing the rate of desorption; whereas the adsorption is controlled by a more rapid, three-dimensional diffusion process. 相似文献
4.
Dan Lin Xing Xie Yan Zhao Gang Chen Le Zeng 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(3):282-287
To investigate the effects of acid treatments on the chemical structure and pyrolysis behavior of coal, we examined the low-rank Zhundong coal pretreated by four single acids (HCl, HF, H2SO4, HNO3) and a combined acid (HCl-HF-HCl). Our results indicated that the carboxylic and phenolic hydroxyl contents of the coal increased, while the aliphatic and aromatic hydrogen contents decreased after leaching. Nitric acid destroyed long aliphatic chains in coal, which caused the key pyrolysis stage to occur at lower temperature, the number of volatiles increased, and the pyrolysis rate improved. 相似文献
5.
Hydrogen storage capacities of raw, oxidized, purified and Fe-doped multi-walled carbon nanotubes (MWCNTs) were studied by electrochemical method. Based on transmission electron microscopy and Raman spectroscopic data, thermal oxidation removed defective graphite shells at the outer walls of MWCNTs. The analysis results indicated that the acid treatment dissolved most of the catalysts and opened some tips of the MWCNTs. Thermal gravimetric analysis and differential scanning calorimetry results illustrated that by oxidation and purification of MWCNTs, the weight loss peak shifts toward a higher temperature. N2 adsorption isotherms of the purified and oxidized MWCNTs showed an increase in N2 adsorption below P/Po = 0.05, suggesting that microporous structures exist in the purified and oxidized MWCNTs. The electrochemical results revealed that the Fe-doped MWCNTs produced the highest hydrogen storage capacities compared to the other samples in various sweep rates. According to electrochemical analyses, the peak currents of hydrogen adsorption/desorption increased by increasing the catalyst's active surface. 相似文献
6.
《International Journal of Hydrogen Energy》2020,45(3):2017-2021
Clinoptilolite from Gördes (Turkey) was treated with HCl, HNO3 and H2SO4 solutions of varying concentrations (from 2.0 M to 6.0 M) at 90 °C for 4 h to evaluate its potential for possible applications in hydrogen storage. X-ray diffraction, X-ray fluorescence and nitrogen adsorption techniques were applied for characterization of the zeolites. Hydrogen adsorption capacities of clinoptilolite samples were found in the range between 1.609 and 2.391 mmol/g. The effects of the acid modification process on the structure and hence hydrogen adsorption was evaluated according to the obtained results. 相似文献
7.
Pin-Ju Tsai Cheng-Hsien Yang Wei-Che Hsu Wen-Ta Tsai Jeng-Kuei Chang 《International Journal of Hydrogen Energy》2012
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
8.
I.A. Panagiotopoulos R.R. Bakker T. de Vrije P.A.M. Claassen E.G. Koukios 《International Journal of Hydrogen Energy》2012
The main objective of this study was to use the fermentability test to investigate the feasibility of applying various dilute acids in the pretreatment of barley straw for biological hydrogen production. At a fixed acid loading of 1% (w/w dry matter) 28–32% of barley straw was converted to soluble monomeric sugars, while at a fixed combined severity of −0.8 30–32% of the straw was converted to soluble monomeric sugars. With fermentability tests at sugar concentrations 10 and 20 g/L the extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus showed good hydrogen production on hydrolysates of straw pretreated with H3PO4 and H2SO4, and to a lesser extent, HNO3. The fermentability of the hydrolysate of straw pretreated with HCl was lower compared to the other acids but equally high as that of pure sugars. At sugar concentration 30 g/L the fermentability of all hydrolysates was low. 相似文献
9.
Pt–Ru catalysts supported on mesoporous carbon nitride (MCN), multiwall carbon nano tubes (MWCNTs), treated MWCNTs (t-MWCNTS) and Vulcan-XC were prepared using co-impregnation reduction method for the oxidation of ethanol in direct ethanol fuel cell (DEFC) to study the effect of support material. The MCN support was prepared using SBA-15 as template and t-MWCNTs were prepared by refluxing in HNO3 and H2SO4 mixture (1:3) using MWCNTs. XRD shows the formation of Pt–Ru bi-metallic catalyst with size ranges from 7 to 17 nm using different supports. The catalyst and its supports were characterized by physically and electrochemically. Linear sweep voltammetry, cyclic voltammetry and chrono amperometry studies of the above systems reveal that MCN supported Pt–Ru catalyst shows higher electro-catalytic activity towards ethanol oxidation compared to Pt–Ru in treated t-MWCNTs, MWCNts and Vulcan-XC supports. The performance of DEFC based on maximum power density is found to be in the order Pt–Ru/MCN > Pt–Ru/t-MWCNTs > Pt–Ru/MWCNTs > Pt–Ru/Vulcan-XC. The Pt–Ru/MCN shows highest power density of 61.1 mW cm−2 at 100 °C, 1 bar pressure with catalyst loading of 2 mg cm−2 using 2 M ethanol feed. 相似文献
10.
《International Journal of Hydrogen Energy》2022,47(49):21253-21260
In this work, the effect on the physico-chemical properties of Nafion 117 membrane due to the treatment with HCl, H2SO4 and HNO3 was studied. Water uptake, crystallinity, proton conductivity and water dynamics were evaluated on treated and non-treated membranes. An increase in the water uptake and conductivity and a decrease in the crystallinity were observed in treated membranes in comparison with the untreated one. The water dynamics, studied by spin-spin NMR relaxometry, suggests that treated membranes have a more uniform channel size distribution. The treatment with HCl and HNO3 showed higher conductivity and water uptake than H2SO4. 相似文献
11.
Cafer Saka Mustafa Salih Eygi̇ Asım Balbay 《International Journal of Hydrogen Energy》2021,46(5):3876-3886
Inorganic acids such as hydrochloric acid (HCl), nitric acid (HNO3) and sulphuric acid (H2SO4) are generally used in the acid modification of clays. Here, CoB catalyst was synthesized on the acetic acid-activated kaolin support material (CH3COOH -kaolin- CoB) with an alternative approach. This prepared catalyst, firstly, was used to catalyze the hydrolysis of NaBH4 (NaBH4-HR). The structure of the raw kaolin, kaolin-CH3COOH, and CH3COOH-kaolin-CoB samples were characterized by X-ray diffraction spectroscopy (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscope (SEM), and nitrogen adsorption. At the same time, this catalyst performance was examined by Co loading, NaBH4 concentration, NaOH concentration, temperature and reusability parameters. The end times of this hydrolysis reaction using raw kaolin-CoB and CH3COOH-kaolin-CoB were found to be approximately 140 and 245 min, respectively. The maximum hydrogen generation rates (HGRs) obtained at temperatures 30 °C and 50 °C were 1533 and 3400 mL/min/gcatalyst, respectively. At the same time, the activation energy was found to be 49.41 kJ/mol. 相似文献
12.
J. Gülen 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2013,35(3):231-237
Abstract Coals are heterogeneous, complex noncrystalline macromolecules having both organic and inorganic materials that contain some inorganic constituents. Some techniques have been applied to this fossil fuel in order to remove these undesired inorganic parts from the organic part. Chemical demineralization is one of the suitable methods for removal of inorganic elements although it is an expensive way. But by this method, many elements are leached effectively from the lignite body from the point of economic view because these inorganic parts may cause some undesired deleterious effects. In this study, the demineralization effect of some aqueous acids of 5% such as HCl, H2SO4, HNO3, and HF was studied. The effect of these mineral acids was shown by X-ray spectroscopy. 相似文献
13.
David Luxembourg Gilles Flamant Eric Bêche Jean-Louis Sans Joseph Giral Vincent Goetz 《International Journal of Hydrogen Energy》2007
Samples of single wall carbon nanotubes (SWNTs) were prepared using a solar reactor. Graphite targets containing different catalysts (Ni/Co, Ni/Y, Ni/Ce) allowed the synthesis of SWNTs soot in which nanotubes had different diameter distributions. Several consecutive stages of HCl treatment and thermal oxidation in air (HCl protocol) purified the samples. Another protocol involving HNO3 treatment and H2O2 oxidation (HNO3 protocol) was also used. Isotherms of hydrogen adsorption were volumetrically measured at 253 K under pressures below 6 MPa on raw and treated samples. The highest adsorption capacity (0.7 wt%) was measured on raw soot. HCl protocol clearly increases the BET surface area (SBET) and the microporous volume (W0(N2)) measured by N2 at 77 K of the treated samples with respect to the as-produced materials, whereas HNO3 protocol decreases them. A correlation between textural properties and hydrogen storage capacities is discussed. 相似文献
14.
Zhijun Zhang Liang Zhao Li Zhuang Yanan Li Hanyu Zhang 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2019,41(13):1605-1614
The effect of acid treatment on mineral removal and pyrolysis of Longkou oil shale were investigated. X-ray diffraction (XRD) and X-ray fluorescence (XRF) indicated that the HCl treatment can remove the calcite, the H2SO4 treatment can convert the calcite to CaSO4, and the HF treatment can remove the quartz and convert the calcite to CaF2; moreover, all three treatments cannot remove the pyrite in the oil shale. Oil shale was individually treated with HCl, H2SO4, and HF before conducted the pyrolysis experiment. The pyrolysis results showed that oil shale treated with H2SO4 or HF almost equally enhanced the oil yield, while HCl treatment had a negative effect on the oil yield. Thermogravimetry (TG) analysis indicated that the carbonates had a catalytic effect, sulfates may also had a catalytic effect and the silicates had an inhibitive effect on the decomposition of kerogen. Combining the TG analysis, oil yield and the price of every acid, the H2SO4 treatment was considered to be the best method to treat oil shale.Moreover, the carbonate minerals can be removed after H2SO4 treatment, so it would reduce the amount of pyrolysis feed to increase production efficiency. 相似文献
15.
《International Journal of Hydrogen Energy》2022,47(88):37385-37393
This study was conducted to investigate the properties of hydrolysates obtained from acid and alkali hydrolysis and to evaluate the feasibility of employing them for bio-hydrogen production. High sugar concentrations of 16.8 g/L and 13.3 g/L were present in 0.5% and 1.0% H2SO4 hydrolysates, respectively. However, H2SO4 hydrolysis resulted in large amounts of short-chain fatty acids (SCFAs) and furan derivatives, which were removed by detoxification. In bio-hydrogen production, 1.0% H2SO4 hydrolysate showed a 55.6 mL of highest hydrogen production and 1.14 mol-H2/mol-hexose equivalentadded of hydrogen yield. In control and 1.0% NaOH hydrolysate, 29.7 mL and 36.9 mL of hydrogen were produced, respectively. Interestingly, relatively high acetate and butyrate production resulted in lactate reduction. Also, NH4OH hydrolysate produced less than 10 mL of hydrogen. Thus, these results indicate that hydrogen production and metabolite distribution can vary depending on the sugars and by-product composition in the hydrolysate. 相似文献
16.
Chuanmin Ruan Maggie Paulose Oomman K. Varghese Craig A. Grimes 《Solar Energy Materials & Solar Cells》2006,90(9):1283-1295
We examine the photoelectrochemical properties of highly ordered titanium dioxide nanotube-array photoanodes, fabricated by anodization of titanium in a nitric acid/hydrofluoric acid electrolyte, with and without the addition of boric acid. Under UV–Vis illumination the photocurrent densities achieved with TiO2 nanotube-arrays fabricated in the H3BO3–HNO3–HF electrolyte are a factor of seven greater than the TiO2 nanotube-array samples obtained in the commonly used HNO3–HF electrolyte, indicating the ability to control the photoelectrochemical response of the highly ordered nanotube arrays by tailoring the electrolyte composition. For 560 nm long boric-acid fabricated nanotube arrays, a photoconversion efficiency of 7.9% is achieved upon a 320–400 nm illumination at an intensity of 98 mW/cm2, with hydrogen generated by water photoelectrolysis at the power-time normalized rate of 1708-μmol/h W (42 ml/h W). The resulting nanotube-arrays demonstrate excellent photocorrosion stability, with no detectable degradation in photoconversion properties over 6 months of testing. While the titania bandgap is not suitable for high visible spectrum efficiencies, the high photoconversion efficiency achieved under UV illumination indicates the suitability of the highly ordered nanotube-array architecture for hydrogen generation by water photoelectrolysis. 相似文献
17.
Sanjay Kumar Gurpreet Kaur Anjali Joshi 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2019,41(12):1508-1517
The aim of the study is to enhance the production and performance of biodiesel from non-food feedstock seeds of citrus maxima through base catalyzed transesterification process. The Performance of biodiesel was increased by the blends with butanol-diesel (Biodiesel + Butanol + Diesel) in different proportions. The obtained biodiesel and its blends were characterized by ASTM. In this study, Glycerol was obtained as a by-product of citrus maxima biodiesel. Crude glycerol was purified by the H3PO4, H2SO4, HCl, and HNO3. The characterization of glycerol included Flash Point, ash Content, alkalinity, FT-IR, etc.. 相似文献
18.
D. Morales-Acosta Luis A. Godinez L. Álvarez-Contreras 《Journal of power sources》2010,195(2):461-9275
Pd-Co and Pd catalysts were prepared by the impregnation synthesis method at low temperature on multi-walled carbon nanotubes (MWCNTs). The nanotubes were synthesized by spray pyrolysis technique. Both catalysts were obtained with high homogeneous distribution and particle size around 4 nm. The morphology, composition and electrocatalytic properties were investigated by transmission electron microscopy, scanning electron microscopy-energy dispersive X-ray analysis, X-ray diffraction and electrochemical measurements, respectively. The electrocatalytic activity of Pd and PdCo/MWCNTs catalysts was investigated in terms of formic acid electrooxidation at low concentration in H2SO4 aqueous solution. The results obtained from voltamperometric studies showed that the current density achieved with the PdCo/MWCNTs catalyst is 3 times higher than that reached with the Pd/MWCNTs catalyst. The onset potential for formic acid electrooxidation on PdCo/MWCNTs electrocatalyst showed a negative shift ca. 50 mV compared with Pd/MWCNTs. 相似文献
19.
Hydrogen adsorption capacity of Multiwalled carbon nanotubes (MWCNTs) decorated with Nickel (Ni) nanoparticles has been presented at room temperature and under moderate pressures of 4–20 bar. The functionalization of carbon nanotubes was carried by H2SO4-HNO3 reducing agents and the Ni supported MWCNTs (Ni-MWCNTs) were prepared by wet chemical method. The structure and morphology characterization of samples were performed by XRD, TEM, EDX and SEM analyses. These nanotubes then subjected to hydrogenation step by using Sievert's-like apparatus. The hydrogenation of the Ni-MWCNTs was performed at 298 K and moderate hydrogen pressures of 4–20 bar. The obtained results show that there is a correlation between hydrogen storage capacity and hydrogen pressure that; as the pressure was increased, hydrogen uptake capacity enhanced due to physisorption. In addition, maximum hydrogen storage capacity of Ni-MWCNTs was found to be 0.298 wt % at room temperature and under pressure of 20 bar. 相似文献
20.
《International Journal of Hydrogen Energy》2019,44(20):9771-9778
The sulfur–iodine (SI) cycle is deemed to be one of the most promising alternative methods for large-scale hydrogen production by water splitting, free of CO2 emissions. Decomposition of hydrogen iodide is a pivotal reaction that produces hydrogen. The homogeneous conversion of hydrogen iodide is only 2.2% even at 773 K [1]. A suitable catalyst should be selected to reduce the decomposition temperature of HI and attain reaction yields approaching to the thermodynamic equilibrium conversion. However, residual H2SO4 could not be avoided in the SI cycle because of incomplete purification. The H2SO4 present in the HI feeding stream may lead to the poisoning of HI decomposition catalysts. In this study, the activity and sulfur poisoning of Ru and Ni catalysts loaded on carbon and alumina, respectively, were investigated at 773 K. HI conversion efficiency markedly decreased from 21% to 10% with H2SO4 (3000 ppm) present, which was reversible when H2SO4 was withdrawn in the case of Ru/C. In the case of Ru/C and Ni/Al2O3, catalyst deactivation depends on the concentration of H2SO4; the higher the concentration of H2SO4, the greater the severity of deactivation. Catalysts before and after sulfur poisoning were characterized by transmission electron microscopy (TEM), energy-dispersive X-Ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Experimental results and characterization of poisoned and fresh catalysts indicate that the catalyst deactivation could be ascribed to the competitive adsorption of sulfur species and change in its surface properties. 相似文献