CN1132675C - Hydrogen storing metal or alloy modified one-dimensional hydrogen storing carbon nano-material - Google Patents

Abstract

A one-dimensional nano carbon hydrogen storage material modified by hydrogen storage metal or hydrogen storage alloy. The hydrogen storage material is a high-performance hydrogen storage material prepared by doping or depositing hydrogen storage metal or hydrogen storage alloy on the surface of one-dimensional nano carbon etched by microwave plasma. The one-dimensional nanocarbon is carbon nanotubes or nanocarbon fibers or a mixture of the two in any proportion, and the carbon nanotubes are single-walled or multi-walled carbon nanotubes with a diameter greater than 0.4nm. The hydrogen storage metals include exothermic soluble metals of groups IA to IVB in the periodic table, and endothermic soluble metals of groups VB to VIII except the exothermic soluble metal Pd. The hydrogen storage alloy is crystalline rare earth nickel-based AB ₅ type alloy, zirconium-based or titanium-based Laves-based AB ₂ -type alloy, titanium-nickel-based and titanium-iron-based AB type alloy, magnesium-based A ₂ B type alloy or the above-mentioned Any one of hydrogen storage alloys or two or more binary or multi-element amorphous hydrogen storage alloys. The hydrogen storage capacity of the hydrogen storage material of the present invention is 3.5-5.5 wt%.

Description

One-dimensional nanocarbon hydrogen storage materials modified by hydrogen storage metals or hydrogen storage alloys

technical field

The invention relates to a one-dimensional nano-carbon high-performance hydrogen storage material modified by a hydrogen-storage metal or a hydrogen-storage alloy, in particular to doping or depositing a hydrogen-storage metal or a hydrogen-storage alloy on the surface of a one-dimensional nano-carbon etched by microwave plasma The prepared high-performance hydrogen storage materials.

Background technique

Currently commonly used hydrogen storage technologies mainly include compressed hydrogen storage, liquefied hydrogen storage, metal hydrogen storage and low-temperature adsorption hydrogen storage. Generally, the weight hydrogen storage ratio of compressed hydrogen storage is relatively low; although the hydrogen storage capacity of liquefied hydrogen storage has been improved, but to maintain the liquid hydrogen state, the system needs a temperature not higher than -252.6°C, and the energy consumption is relatively large. Activated carbon A similar problem exists with hydrogen storage. The volume capacity of metal hydrogen storage is large, and the hydrogen adsorption volume is often more than 100 times the volume of hydrogen storage metal or hydrogen storage alloy, but its weight hydrogen storage capacity is relatively low, and there are still problems such as slow hydrogen absorption and desorption speed.

One-dimensional nanocarbon materials such as carbon nanofibers and carbon nanotubes have generally attracted the attention of scholars from various countries due to their advantages such as low working temperature, moderate working pressure, large hydrogen storage ratio by weight, and good shape selectivity. In 1997, American Dillon et al. reported that the hydrogen adsorption capacity of single-walled carbon nanotubes (SWNTs) was much larger than that of activated carbon, and speculated that the hydrogen storage capacity of SWNTs was 5-10 wt%. In 1998, Chambers et al. reported that the hydrogen storage capacity of carbon nanofibers at 12Mpa was as high as 22.3 liters of hydrogen per gram of carbon nanofibers. In 1999, Singapore Chen et al. reported that the hydrogen storage capacity of multi-walled carbon nanotubes (MWNTs) doped with Li and K reached 20wt% and 14wt%, respectively. But in fact, the experimental results of Chambers and Chen were not reproducible, and their experimental results were considered to be affected by water. In recent years, Japan's Toyota Corporation's invention patent (JP10-072201) has reported a preparation technology for a hydrogen storage alloy/carbon nanotube (carbon nanofiber) composite material. At room temperature, its hydrogen storage capacity can reach up to 10 wt%. . In addition, Toshiba has also prepared a hydrogen storage alloy/carbon nanotube (carbon nanofiber) composite material doped with alkali metal ions, and its hydrogen storage capacity is 1-8wt% (JP 2001-146408). In recent years, my country has made some progress in the hydrogen storage of one-dimensional nanocarbons. In 1999, the invention patent of the Shenyang Metal Research Institute of the Chinese Academy of Sciences reported that the hydrogen storage capacity of the prepared single-walled carbon nanotubes was 4.2wt% (ZL991122902.4), and the carbon nanofibers had a hydrogen storage capacity as high as 10-12wt% (CN12779953A) . Nankai University adopts a method different from Toyota's to prepare hydrogen storage alloy/carbon nanotube composite hydrogen storage material, and its hydrogen storage capacity is 2.5-5.2wt% (WO01/53550A1, CN00100500.7). However, it should be noted that the carbon nanotubes or carbon nanofibers that can be repeatedly verified at present are 1 to 4.5 wt%, and the one-dimensional nanocarbon hydrogen storage still requires an initial pressure of more than 10 MPa.

Contents of the invention

The purpose of the present invention is to provide a hydrogen storage metal or hydrogen storage alloy modified one-dimensional nano-carbon high-performance hydrogen storage material and a preparation method thereof.

The hydrogen storage material for realizing the purpose of the present invention is a hydrogen storage material made by doping or depositing a hydrogen storage metal or a hydrogen storage alloy on the surface of one-dimensional nano carbon etched by microwave plasma. Microwave plasma etching is used to etch the surface of one-dimensional nano-carbon, so as to increase and increase the diffusion channel of hydrogen from the surface to the inside, so that more hydrogen can enter the interior of one-dimensional nano-carbon. After that, Doping or depositing hydrogen storage metal or hydrogen storage alloy on the etched one-dimensional nano carbon surface. The main function of hydrogen storage metals or hydrogen storage alloys is to convert hydrogen molecules into hydrogen atoms through catalysis, adsorption or absorption, so as to accelerate the diffusion rate of hydrogen into the interior of one-dimensional nanocarbons, reduce the diffusion resistance of hydrogen, and not only improve the performance of one-dimensional nanocarbons. The hydrogen storage performance of the material, and under the condition of room temperature and 5-7MPa, the hydrogen storage and release platform tends to be better. Therefore, the hydrogen storage metal or hydrogen storage alloy modified one-dimensional nanocarbon high-performance hydrogen storage materials make up to a certain extent the deficiency of hydrogen storage due to the single use of one-dimensional nanocarbon or hydrogen storage alloy materials.

The one-dimensional nano-carbon in the present invention is carbon nanotube or nano-carbon fiber, or a mixture of the two. Wherein, the carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes. Single-walled carbon nanotubes are prepared by a hydrogen arc discharge method, and multi-walled carbon nanotubes and nanocarbon fibers are prepared by a catalytic cracking method. The invention is also applicable to one-dimensional nano carbon materials prepared by other methods.

The microwave plasma etching described in the present invention is mainly performed on a microwave plasma generating device. The main working parameters of the device are: the etching power is usually 0.3~3Kw, the etching temperature is 300~1500℃, the processing pressure is 6.0×10 ² ~6.0×10 ³ Pa, the etching gas is hydrogen, and the condition gas is nitrogen or argon gas or a mixture of both. Under the condition of nitrogen or argon, the proportion of hydrogen is more than 80%, and that of nitrogen or argon is less than 20%; for the mixed condition gas, the sum of nitrogen and argon is not more than 20%.

The hydrogen storage metals of the present invention include exothermic soluble metals of groups IA-IVB in the periodic table, and endothermic soluble metals of groups VB-VIII except the exothermic soluble metal Pd. The hydrogen storage alloy is crystalline rare earth nickel-based AB ₅ alloy, zirconium-based or titanium-based Laves-based AB ₂ -type alloy, titanium-nickel-based and titanium-iron-based AB-type alloy, magnesium-based A ₂ B-type alloy; or Any one of the above-mentioned hydrogen storage alloys or two or more binary or multi-element amorphous hydrogen storage alloys.

The hydrogen storage alloy rare earth nickel system AB ₅ type composition described in the present invention is LNi _nxyz Co _x N _y M _z , L is mischmetal, La, Ce, Nd, Pr, Y, N and M are Mn, V respectively , Cr, Al, Fe, Cu, Zn, Sn, 4≤n≤6≤x≤, 02, 0≤y≤2, 0≤z≤2; zirconium-based or titanium-based or rare-earth nickel-based Laves phase system AB ₂ Type alloy composition is KNi _abcd V _b G _c J _d , K is Zr, Ti, Hf, mixed rare earth metals, La, Ce, Nd, Pr, Y, G and J are Co, Mn, Cr, Al, Fe, Cu, Zn, Sn, 1.2≤a≤2.8, 0≤b≤2, 0≤c≤2, 0≤d≤2; titanium-nickel or titanium-iron AB type alloy composition is HNi _mki F _e kP _i , H is Zr, Hf, P is Co, Mn, V, Cr, Al, Cu, Zn, Sn, 0.6≤m1.5, 0≤k≤1.5, 0≤j≤1, magnesium-based alloy A ₂ B type The alloy composition is Mg _gf E _f Ni _fpg Co _p T _q , E is Ca, Zr, Ti, Hf, mixed rare earth metals, La, Ce, Nd, Pr, Y, Ti is Mn, V, Cr, Al, Fe, Cu, Zn, Sn, 0.8≤g≤2.5, 0≤f≤1, 0≤p≤0.6, 0≤q≤0.6.

The one-dimensional nano-carbon material of hydrogen storage metal or alloy described in the present invention can be prepared by methods such as chemical co-precipitation reduction method, vacuum deposition method, sputtering method or CVD method.

The specific preparation process of the hydrogen storage material of the present invention is as follows:

1. Preparation of one-dimensional carbon nanomaterials. The single-wall carbon nanotubes are mainly prepared by hydrogen arc discharge method, and the purity is greater than 50%; the multi-wall carbon nanotubes or nano-carbon fibers are prepared by catalytic cracking method, and the purity is greater than 70%.

2. Pretreatment of one-dimensional carbon nanomaterials. Grind the prepared one-dimensional nanomaterials into NaOH solution, heat to reflux and ultrasonically oscillate to improve the dispersion of one-dimensional nanocarbons; after that, oxidize the one-dimensional nanocarbons, wash with deionized water, and dry , the one-dimensional nano-carbon with a purity greater than 90% is prepared. After oxidation treatment, the specific surface area of one-dimensional nanocarbon increases, and most of the fullerenes cages at both ends of carbon nanotubes (diameter>0.4nm) are opened, which is beneficial for hydrogen to enter the internal storage of the tube.

3. Etching the pretreated one-dimensional nanocarbon with microwave plasma. The common power of etching is 0.3~3kW, the etching temperature is 300~1500℃, the processing pressure is 6.0×10 ² ～6.0×10 ³ Pa; the etching gas is hydrogen, and the condition gas is nitrogen or argon or a mixture of the two . Under the condition of nitrogen or argon, the proportion of hydrogen is generally greater than 80%, and that of nitrogen or argon is less than 20%; for mixed condition gases, the sum of nitrogen and argon should not exceed 20%.

4. Prepare one-dimensional nano-carbon composite materials modified by hydrogen storage metal or hydrogen storage alloy by chemical co-precipitation reduction method, vacuum deposition method, sputtering method or CVD method. After that, it is roasted under nitrogen or argon at 200-700°C for 1-2 hours, so that the prepared hydrogen-storage metal or hydrogen-storage alloy is combined with one-dimensional nano-carbon more closely, so as to obtain a hydrogen-storage metal or hydrogen-storage alloy modified Dimensional nanocarbon hydrogen storage materials.

Detailed ways

The present invention is described in detail below by way of examples.

Example 1

The single-wall carbon nanotube is prepared by a hydrogen arc discharge method, and the prepared single-wall carbon nanotube has a purity of 60%, a tube diameter of 1-40 nm, and a tube length of 10-100 μm. After it was ground, it was placed in NaOH solution, heated to reflux and ultrasonically oscillated for 1 h, washed with deionized water and dried. Afterwards, the single-walled carbon nanotubes were oxidized in mixed acid (concentrated H ₂ SO ₄ :concentrated HNO ₃ =3:1), heated to reflux for 1 hour, washed with deionized water and dried. The pretreated single-walled carbon nanotubes were subjected to microwave plasma etching. The etching gas is hydrogen, the etching power is 2.5kW, the temperature is 1200°C, the etching time is 2h, and the processing pressure is 6.0×10 ² Pa. Under the conditions of hydrogen purity of 99.9999%, initial pressure of 7MPa and room temperature, the hydrogen storage capacity of the etched single-wall carbon nanotube is 4wt%. 200ml of PdCl ₂ solution was prepared, mixed with 2g of etched single-walled carbon nanotubes and stirred for 1 hour at a stirring speed of 800r/min. Afterwards, pass through H ₂ to react, and the reaction temperature is 100°C. The reaction product was washed, dried, and calcined at 300° C. for 2 h under argon to prepare palladium-modified single-walled carbon nanotubes. The results of TEM, XRD, electron diffraction and energy spectrum studies show that there are metal layers and single metal particles on the surface of single-walled carbon nanotubes, the wrapping rate is about 55%, and its main component is metal Pd (>99%), which is extremely A small part is Fe, Co, Ni and other impurities. Under the same test conditions, the hydrogen storage capacity of the etched single-walled carbon nanotubes is 5.5 wt%.

Example 2

Multi-walled carbon nanotubes are prepared by catalytic cracking. The prepared multi-walled carbon nanotubes have a purity of 75 percent, a tube diameter of 10-80 nm, and a tube length of 20-100 μm. The pretreatment, microwave plasma etching process and hydrogen storage test conditions of the multi-walled carbon nanotubes are the same as in Example 1. Tests show that the etched multi-walled carbon nanotubes have a hydrogen storage capacity of 2.5 wt%. The hydrogen storage capacity of palladium-modified multi-walled carbon nanotubes is 3.5wt%. The results of TEM, XRD, electron diffraction and energy spectrum studies show that the metal on the surface of multi-walled carbon nanotubes mostly exists in a layered or single particle state, with a wrapping rate of about 65%, and its main component is metal Pd (>98%) , a very small part is Fe, Co, Ni and other impurities.

Example 3

Carbon nanofibers are prepared by catalytic cracking. The prepared nano-carbon fiber has a purity of 78 percent, a tube diameter of 80-100 nm, and a tube length of more than 0.1 mm. The pretreatment of carbon nanofibers, microwave plasma etching process and hydrogen storage test conditions are the same as in Example 1. Tests show that the etched carbon nanofibers have a hydrogen storage capacity of 3.8 wt%. The hydrogen storage capacity of palladium-modified carbon nanofibers is 5wt%. The results of TEM, XRD, electron diffraction and energy spectrum studies show that the metal on the surface of carbon nanofibers mostly exists in a layered or single particle state, with a wrapping rate of about 50%, and its main component is metal Pd (>98%), with very little Part of it is Fe, Co, Ni and other impurities.

Example 4

The preparation of multi-walled carbon nanotubes is the same as in Example 2, and the pretreatment, microwave plasma etching process and hydrogen storage test conditions are the same as in Example 1. Stir and blend 2g of etched multi-walled carbon nanotubes with 20g of liquid VCl ₄ at a high speed, heat and pass H ₂ to react after mixing uniformly. Then, the reaction product was moved into a tube furnace and reacted with H ₂ for 2 h at a reaction temperature of 1250 °C. The reaction product was washed and calcined at 300° C. under argon for 2 hours to prepare vanadium-modified multi-walled carbon nanotubes. The results of TEM, XRD, electron diffraction and energy spectrum studies show that the metal on the surface of multi-walled carbon nanotubes mostly exists in a layered or single particle state, with a wrapping rate of about 60%, and its main component is metal V (>90%) , a small part is V ₂ O ₃ (about 9%) and impurities such as Fe, Co, Ni. The hydrogen storage capacity of the V-modified multi-walled carbon nanotubes is 3.8 wt%.

Example 5

The preparation of carbon nanofibers is the same as in Example 3, and its pretreatment, microwave plasma etching process and hydrogen storage test conditions are the same as in Example 1. Mix NiCl ₂ and LaCl ₃ solutions of the same concentration uniformly at a volume ratio of 5:1, add 2 g of etched and ground carbon nanofibers to the mixture, stir with an electric motor at a stirring speed of 500 r/min, and slowly add Na ₂ CO ₃ solution, after complete reaction, suction filtration, deionized water washing and vacuum drying process to prepare LaNi ₅ precursor La ₂ O ₃ ·10NiO attached to the surface of carbon nanofibers. The reaction product was transferred into a tube furnace, and reacted with H ₂ at a reaction temperature of 1000°C. The reaction product is washed. And calcined at 300°C for 2h under the protection of argon to prepare LaNi ₅ modified carbon nanofibers. The results of TEM, XRD, electron diffraction and energy spectrum studies show that the metal on the surface of carbon nanofibers mostly exists in a layered or single particle state, with a wrapping rate of about 50%, and its main component is metal LaNi ₅ (>98%), which is extremely A small part is Fe, Co, Ni and other impurities. The hydrogen storage capacity of LaNi ₅ modified carbon nanofibers is 4.5wt%.

Claims (7)

1, the one-dimensional nano carbon hydrogen storage material modified of a kind of hydrogen storage metal or hydrogen storage alloy is characterized in that this hydrogen storage material is through the high performance hydrogen storage material that mixes on the unidimensional nanocarbon surface of microwave plasma-etching or deposition hydrogen storage metal or hydrogen storage alloy are prepared into.

2, hydrogen storage material as claimed in claim 1 is characterized in that described～dimension nano-sized carbon is carbon nanotube or carbon nano fiber.

3, hydrogen storage material as claimed in claim 1 is characterized in that described carbon nanotube is single wall or multi-walled carbon nano-tubes.

4, hydrogen storage material as claimed in claim 1 is characterized in that described one-dimensional nano carbon is carbon nanotube or the carbon nano fiber mixture by the arbitrary proportion proportioning.

5, hydrogen storage material as claimed in claim 1, it is characterized in that described hydrogen storage metal be IA in the periodic table of elements～

IVB family heat release lysotype metal, the heat absorption lysotype metal of VB～VIII family except that heat release lysotype metal Pd.

6, hydrogen storage material as claimed in claim 1 is characterized in that described hydrogen storage alloy is that crystalline state rare earth nickel is AB ₅Type alloy, zirconium base or titanium base Laves are AB ₂Type alloy, nickel titante series and ferrotianium are AB type alloy, magnesium base A ₂The Type B alloy.

7, hydrogen storage material as claimed in claim 1 is characterized in that described hydrogen storage alloy is an amorphous alloy, and being selected from rare earth nickel is AB ₅Type alloy, zirconium base or titanium base Laves are AB ₂Type alloy, nickel titante series and ferrotianium are AB type alloy, magnesium base A ₂Any one or two kinds of above binary or the polynary amorphous hydrogen storage alloys of Type B alloy.