CN104649224A

CN104649224A - Expanded graphite/LiBH4 composite hydrogen storage material and preparation method thereof

Info

Publication number: CN104649224A
Application number: CN201510063138.0A
Authority: CN
Inventors: 孙立贤; 蔡荣; 徐芬; 邹勇进; 褚海亮; 张焕芝
Original assignee: Guilin University of Electronic Technology
Current assignee: Guilin University of Electronic Technology
Priority date: 2015-02-06
Filing date: 2015-02-06
Publication date: 2015-05-27
Anticipated expiration: 2035-02-06
Also published as: CN104649224B

Abstract

The invention discloses an expanded graphite/LiBH4 composite hydrogen storage material and a preparation method thereof. The expanded graphite/LiBH4 composite hydrogen storage material is prepared by adsorbing tetrahydrofuran solution of LiBH4, ultrasonically oscillating, drying in vacuum and the like by taking porous expanded graphite as a support material and LiBH4 as a hydrogen storage material through the capillary absorption action of the porous expanded graphite and a vacuum impregnation technology. The preparation method disclosed by the invention is simple in preparation process and lower in cost; LiBH4 can be effectively loaded in the expanded graphite; products having higher yield can be obtained within a short time; and the prepared composite hydrogen storage material has good hydrogen storage property.

Description

A kind of expanded graphite/LiBH 4composite hydrogen storage material and preparation method thereof

Technical field

The present invention relates to hydrogen storage material technical field of modification, specifically use porous expanded graphite load LiBH ₄prepare composite hydrogen storage material, make it have good hydrogen storage property.

Background technology

Socioeconomic high speed development, the demand of the mankind to the energy constantly increases, traditional fossil energy shortage and serious environmental problem, makes human knowledge be society urgent problem to the reproducible clear energy sources of searching.Hydrogen can be produced from water, and products of combustion is also water, and has the high characteristic of mass energy density, is a kind of desirable renewable clear energy sources.But the storage of hydrogen and transport significantly limit hydrogen applying as the energy.At present, conventional storage hydrogen mode is high-pressure gaseous storage hydrogen, liquid storage hydrogen and solid-state storage hydrogen.Solid-state storage hydrogen has the features such as energy density is high, safe, is considered to very promising storage hydrogen mode.Lithium borohydride (LiBH ₄) as a kind of solid-state hydrogen storage material, there is higher quality hydrogen-storage density (18.4 wt%), but hydrogen discharging temperature is high, hydrogen discharging speed is slow, cycle performance is poor, serious its applying as hydrogen storage material of obstruction.In order to improve LiBH ₄hydrogen storage property, the methods such as part anion/cation is replaced by using, catalysis doping and nanometer confinement effectively raise LiBH ₄hydrogen storage property.In order to reduce LiBH further ₄suction hydrogen discharging temperature and improve the hydrogen desorption capacity of whole system, the method using the synergy of nanometer confinement and catalysis to improve LiBH4 hydrogen storage property receives concern.

Patent CN102718183A " LiBH4/RGO high hydrogen storage composite hydrogen storage material and preparation thereof " discloses and adopts melt infiltration method or high speed ball milled to be dispersed in the duct of the standby RGO of chemistry redox legal system by LiBH4 under protection of inert gas atmosphere, improves LiBH ₄hydrogen storage property.At present, LiBH ₄the hydrogen storage property of system material does not also reach performance requriements, therefore finds suitable carrier and improves LiBH further ₄hydrogen storage property.Carbon material has the features such as quality is light, good stability, therefore uses carbon material as load LiBH ₄carrier be more satisfactory selection.Expanded graphite has the advantages that specific surface area is large, pore size distribution is wide, and preparation is simple simultaneously, has good adsorptive power, so be a kind of proper solid support material.

Summary of the invention

The object of the invention is for existing LiBH ₄hydrogen discharging temperature is high, and the dispersed shortcoming such as bad after dehydrogenation, by using porous expanded graphite load LiBH ₄prepare composite hydrogen storage material, by LiBH ₄be dispersed in the reticulated structure of expanded graphite, after degassed, still there is better dispersiveness, and there is good hydrogen storage property.

The present invention uses retort furnace to prepare porous expanded graphite, adopts method load LiBH in expanded graphite of dipping ₄, obtain load LiBH ₄expanded graphite composite hydrogen storage material, and study expanded graphite to LiBH ₄the impact of hydrogen storage property.

The technical scheme realizing the object of the invention is:

A kind of expanded graphite/LiBH ₄composite hydrogen storage material, comprises expanded graphite meterial and LiBH ₄material, expanded graphite meterial is that the laminar structured reticulated structure be staggered into exists mesoporous, LiBH ₄be dispersed in expanded graphite reticulated structure,

Wherein, expanded graphite has aperture, specific surface area>=40.005 m of 2 ~ 12 nm ²/ g.

Described hydrogen storage material general formula is (100-x) expanded graphite+xLiBH ₄, the mass percent of x is 46.9 ~ 67.0 wt%, has good preservation performance to hydrogen.

Described composite hydrogen storage material initial dehydrogenated temperature is less than 120 DEG C, and at 360 DEG C, vacuum, hydrogen desorption capacity is 4.2 ~ 8.8 wt%.

Described expanded graphite/LiBH ₄the preparation of composite hydrogen storage material is obtained by the method for solution impregnation under protection of inert gas and anhydrous and oxygen-free environment.

Described expanded graphite/LiBH ₄the preparation of composite hydrogen storage material, comprises the steps:

1) expansible black lead is placed in baking oven dry;

2) dried expansible black lead uniform spreading is sprinkling upon bottom corundum crucible, crucible is put into retort furnace calcining, obtained expanded graphite;

3) obtained expanded graphite is put into flask, in expanded graphite, instill LiBH in an inert atmosphere ₄tetrahydrofuran solution, sonic oscillation, vacuumize drying, obtain composite solids;

4) composite solids is degassed on physical adsorption appearance, obtains expanded graphite/LiBH ₄composite hydrogen storage material.

Oven drying temperature described in step 1) is 100 ~ 120 DEG C; Time of drying is at 12 more than h.

Step 2) described crucible is Al ₂o ₃crucible; Spreading thickness is not more than 1mm; Muffle furnace 900 DEG C; Operating time is 40 s.

Step 3) obtains composite solids by the method for solution impregnation, by control LiBH ₄the dripping quantity of solution can control LiBH in matrix material ₄content.

Vacuumize dry point two stages described in step 3), the first stage is dry 5 h at-0.05 MPa vacuum tightness 50 DEG C; Subordinate phase is dry 12 more than h at-0.1 MPa vacuum tightness 50 DEG C; Two stages adopt water-bath temperature control method.

Degassing temperature described in step 4) is 81 DEG C, operating time 12 more than h.

To the expanded graphite/LiBH of preparation ₄composite hydrogen storage material carries out the test of hydrogen storage property, and specific operation process is:

1) take about 0.1 g sample, at 360 DEG C, vacuum, carry out the test of PCT degassing kinetics.

2) take the sample of about 6 mg, in the argon gas atmosphere of 20 mL/min flow velocitys, under 10 DEG C/min heat-up rate condition, carry out TG test.

3), before getting dehydrogenation, the sample after dehydrogenation carries out SEM test.

Expanded graphite/LiBH of the present invention ₄composite hydrogen storage material, tool has the following advantages:

1. preparation method is simple, and cost is lower.Adopt the method for solution impregnation, the product with higher yields can be obtained at short notice.

2. the amount by controlling to add solution can obtain load difference amount LiBH ₄expanded graphite/LiBH ₄composite hydrogen storage material.

3. composite hydrogen storage material starts desorption temperature lower than 120 DEG C, and main desorption temperature reduces more than 100 DEG C.

Accompanying drawing explanation

Fig. 1 is embodiment expanded graphite/LiBH ₄the SEM photo of composite hydrogen storage material (E1).

Fig. 2 is the aperture structure distribution schematic diagram of embodiment expanded graphite.

Fig. 3 is embodiment expanded graphite N ₂adsorption curve and expanded graphite/LiBH ₄composite hydrogen storage material is at nitrogen adsorption, the desorption contrast schematic diagram of 77K.

Fig. 4 is embodiment LiBH ₄charge capacity is the expanded graphite/LiBH of 46.9 wt% and 67.0 wt% ₄composite hydrogen storage material and pure LiBH ₄at 360 DEG C, PCT dehydrogenation kinetics contrast schematic diagram under vacuum condition.

Fig. 5 is embodiment LiBH ₄charge capacity is the expanded graphite/LiBH of 46.9wt % and 67.0 wt% ₄composite hydrogen storage material and pure LiBH ₄in the argon gas atmosphere that flow velocity is 20 mL/min, the TG curve synoptic diagram of 10 DEG C/min heat-up rate.

Embodiment

Below in conjunction with drawings and Examples, content of the present invention is further described, but is not limitation of the invention.

Embodiment

A kind of expanded graphite/LiBH4 composite hydrogen storage material (E1), comprises 53.1 wt% expanded graphite meterials and 46.9 wt%LiBH4 materials.

A kind of expanded graphite/LiBH4 composite hydrogen storage material (E2), comprises 33 wt% expanded graphite meterials and 67 wt%LiBH4 materials.

Expanded graphite meterial is that the laminar structured reticulated structure be staggered into exists mesoporous, and LiBH4 is dispersed in expanded graphite reticulated structure, and wherein, expanded graphite has the aperture of 2 ~ 12 nm, specific surface area is 40.005 m2/g.

Above-mentioned two kinds of expanded graphite/LiBH ₄the preparation of composite hydrogen storage material, specifically comprises the steps,

1) expansible black lead is placed in 100 ~ 120 DEG C of baking ovens dry, the time is not less than 20 h;

2) dried expansible black lead uniform spreading is sprinkling upon Al ₂o ₃crucible bottom, thickness is not more than 1 mm, crucible is put into the retort furnace calcining 40s of 900 DEG C, obtained expanded graphite;

3) take expanded graphite 0.1 g, under protection of inert gas, instill the LiBH of 4 mol/L ₄tetrahydrofuran solution 1 ~ 4 mL, after sonic oscillation 30 min, dry 5 h under-0.05 MPa vacuum tightness, then vacuum tightness is brought up to dry 12 more than the h of-0.1 MPa, obtain composite solids;

4) by composite solids degassed 12 more than h under 81 DEG C of conditions on physical adsorption appearance, expanded graphite/LiBH is obtained ₄composite hydrogen storage material.

To described expanded graphite N ₂absorption property test is carried out in Quantachrome company physical adsorption appearance (autosorb-iQ), and specific operation process is:

1) take about 0.1 g sample, at vacuum condition 200 DEG C, degassed 12 h, accurately take sample quality after cooling.

2) put into instrument after taking sample quality, select hydrogen at the adsorption process of 77 K, with computer monitor its at various pressures to the absorption situation of hydrogen.

To embodiment expanded graphite/LiBH ₄the hydrogen storage property test of composite hydrogen storage material is what to carry out on Setsys Evo and PCTPro of SETARAM company production, and concrete operations are as follows:

1) TG test: take about 6 mg sample, carry out under 20 mL/min high-purity argon gas atmosphere, 10 DEG C/min heat-up rate, by the releasing situation of hydrogen under computer recording differing temps.

2) PCT test: take about 0.1 g sample, at vacuum condition 360 DEG C, selects kinetic test program, computer recording LiBH ₄hydrogen desorption capacity.

Fig. 1 is embodiment expanded graphite/LiBH ₄the SEM photo of composite hydrogen storage material (E1); LiBH is described ₄load, on expanded graphite, is filled with the pore passage structure in expanded graphite.

Fig. 2 is the aperture structure distribution schematic diagram of embodiment expanded graphite; Illustrate that expanded graphite aperture is mainly distributed as 2 ~ 12 nm.

Fig. 3 is the expanded graphite N of embodiment ₂adsorption curve and expanded graphite/LiBH ₄composite hydrogen storage material is at nitrogen adsorption, the desorption contrast schematic diagram of 77K; As can be seen from the figure expanded graphite/LiBH ₄the nitrogen adsorption amount of composite hydrogen storage material comparatively expanded graphite significantly reduces, and the LiBH of load is described ₄be filled with the pore passage structure in expanded graphite, thus reduce the specific surface area of expanded graphite, decrease nitrogen adsorption amount.

Fig. 4 is embodiment LiBH ₄charge capacity is the expanded graphite/LiBH of 46.9 wt% and 67.0 wt% ₄composite hydrogen storage material and pure LiBH ₄at 360 DEG C, PCT dehydrogenation kinetics contrast schematic diagram under vacuum condition; LiBH is described ₄charge capacity LiBH in mixture when being 46.9 wt% ₄amount of dehydrogenation be 8.8 wt%, the LiBH in mixture when charge capacity is 67.0 wt% ₄amount of dehydrogenation reduce to 4.2 wt%.

Fig. 5 is embodiment LiBH ₄charge capacity is the expanded graphite/LiBH of 46.9 %wt and 67.0 wt% ₄composite hydrogen storage material and pure LiBH ₄in the argon gas atmosphere that flow velocity is 20 mL/min, the TG curve synoptic diagram of 10 DEG C/min heat-up rate.LiBH is described ₄when charge capacity is 46.9 %wt, matrix material starts dehydrogenation at 120 DEG C, LiBH ₄compound substance LiBH when charge capacity is 46.9 %wt and 67.0 wt% ₄main desorption temperature pure LiBH ₄reduce more than 100 DEG C.

Claims

1. expanded graphite/LiBH ₄composite hydrogen storage material, is characterized in that: comprise expanded graphite meterial and LiBH ₄material, expanded graphite meterial is that the laminar structured reticulated structure be staggered into exists mesoporous, LiBH ₄be dispersed in expanded graphite reticulated structure,

2. composite hydrogen storage material according to claim 1, is characterized in that: described hydrogen storage material general formula is (100-x) expanded graphite+xLiBH ₄, the mass percent of x is 46.9 ~ 67.0 wt%.

3. the composite hydrogen storage material according to any one of claim 1-2, is characterized in that: described composite hydrogen storage material initial dehydrogenated temperature is less than 120 DEG C, and at 360 DEG C, vacuum, hydrogen desorption capacity is 4.2 ~ 8.8 wt%.

4. the preparation method of the composite hydrogen storage material according to any one of claim 1-2, is characterized in that, comprises the steps:

1) expansible black lead is placed in baking oven dry;

3) obtained expanded graphite is put into flask, in expanded graphite, instill LiBH in an inert atmosphere ₄tetrahydrofuran solution, sonic oscillation, vacuumizes drying, obtains composite solids;

4) composite solids is degassed on physical adsorption appearance, obtain expanded graphite/LiBH ₄composite hydrogen storage material.

5. the preparation method of composite hydrogen storage material according to claim 4, is characterized in that: oven drying temperature described in step 1) is 100 ~ 120 DEG C; Time of drying is at 12 more than h.

6. the preparation method of composite hydrogen storage material according to claim 4, is characterized in that: step 2) described crucible is Al ₂o ₃crucible; Expansible black lead spreading thickness is not more than 1mm; Muffle furnace is 900 DEG C; Calcination time is 40 s.

7. the preparation method of composite hydrogen storage material according to claim 4, is characterized in that: the drying that vacuumizes described in step 3) divides two stages, and the first stage is dry 5 h at-0.05 MPa vacuum tightness 50 DEG C; Subordinate phase is dry 12 more than h at-0.1 MPa vacuum tightness 50 DEG C; Two stages adopt water-bath temperature control method.

8. the preparation method of composite hydrogen storage material according to claim 4, is characterized in that: degassing temperature described in step 4) is 81 DEG C, operating time 12 more than h.