Process for the preparation of magnesium-based hydrogen storage materials doped with oxides

Abstract

The application belongs to the field of hydrogen storage materials, and particularly relates to a preparation method of oxide doped MgH2 hydrogen storage material. Different nitrate salts and anhydrous citric acid are respectively dissolved in deionized water, and four clear transparent solutions are obtained by stirring the reaction at room temperature by using a magnetic stirrer; the reaction temperature is increased, and the stirring is continued to obtain four clear transparent gels; the obtained products are dried in a drying box to obtain fluffy solids, and then the fluffy solids are ground to obtain powdery solids; the powdery solids are subjected to programmed heating in a tube furnace and then calcination to obtain oxide powders; the obtained four kinds of oxide powders are respectively loaded into a ball mill tank together with MgH2 for ball milling, and four kinds of oxide doped magnesium-based hydrogen storage materials are obtained. The application has the advantages of simple process, convenient operation, improved hydrogen absorption rate of MgH2, and reduced initial hydrogen release temperature.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen storage materials, specifically relating to a method for preparing magnesium-based hydrogen storage materials doped with oxides. Background Technology

[0002] Metal hydride materials, as energy carriers with good hydrogen adsorption and reversible hydrogen storage capabilities, have attracted much attention in the field of hydrogen storage materials. Magnesium-based hydrogen storage materials are considered one of the most promising hydrogen storage materials for practical application due to the abundance of Mg in the Earth's crust, its low density, and its good cycle reversibility. However, some problems still need to be solved before practical application, such as high desorption temperature, the kinetic limitations of Mg / MgH2, and its susceptibility to oxidation in oxygen and air.

[0003] The reaction between hydrogen and Mg is exothermic, with an enthalpy of 74.5 kJ·(mol·L· ... -1 H2), entropy change is 135 J·(K -1 mol -1 The presence of H2 leads to a higher desorption temperature for MgH2, making the reaction less likely to proceed. This is significantly greater than that for 20-40 kJ / mol. -1 Practical requirements for metal hydrides. In addition, MgH2 is highly prone to agglomeration during hydrogen absorption and desorption, which is a problem that urgently needs to be solved in the application of magnesium-based hydrogen storage materials. MgH2 agglomeration leads to increased particle size, thereby hindering the hydrogen intake channels of magnesium, reducing the active sites for hydrogen absorption and desorption, and consequently affecting its subsequent hydrogen absorption and desorption processes, reducing cycle stability and hydrogen storage capacity. Currently, domestic and international efforts are focused on improving the kinetic performance of magnesium-based hydrogen storage. In Mg-based hydrogen storage systems, adding catalysts is the most effective method to improve the hydrogen absorption and desorption of MgH2. Metal oxide catalysts have a significant effect on improving the hydrogen storage performance of MgH2. Adding metal oxide composite catalysts can further improve the problem that MgH2 requires higher temperatures to achieve hydrogen absorption and desorption, and can also prevent the agglomeration of MgH2 particles, thereby achieving the goal of improving its hydrogen storage performance.

[0004] Existing catalyst systems have improved the hydrogen storage performance of MgH2 to varying degrees, but they generally suffer from high hydrogen absorption and desorption temperatures, which hinders their further application. Developing novel and efficient magnesium-based hydrogen storage catalysts is of great economic and practical significance. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art and provide a method for preparing magnesium-based hydrogen storage materials with doped oxides that have fast hydrogen absorption / desorption rates and low initial hydrogen desorption temperatures.

[0006] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0007] The preparation method of magnesium-based hydrogen storage materials doped with oxides includes the following steps:

[0008] Step 1: Dissolve anhydrous citric acid and nitrate in deionized water and stir at room temperature to obtain colorless, clear and transparent solutions respectively;

[0009] Step 2: Increase the reaction temperature and continue stirring to obtain a clear and transparent gel;

[0010] Step 3: Dry the product obtained in step 2 to obtain a fluffy solid, and then grind it to obtain a powdered solid.

[0011] Step 4: After the temperature is increased by the programmed process, the mixture is calcined to obtain oxide powder;

[0012] Step 5: Place the oxide powder obtained in Step 4 and MgH2 into a ball mill jar and ball mill; separate the alloy powder in a glove box to obtain the desired product, magnesium-based hydrogen storage material doped with oxide.

[0013] Further, in step 1, the nitrate is manganese nitrate (Mn(NO3)2·2H2O), zirconium oxynitrate (ZrO(NO3)2·2H2O), cerium nitrate (Ce(NO3)3·2H2O) or cobalt nitrate (Mn(NO3)2·2H2O).

[0014] Further, in step 1, according to the molar ratio of metal ions to citric acid of 1:1.2, and the concentrations of metal ions and citric acid of 0.02mol / L and 0.024mol / L, respectively, 4-5g of anhydrous citric acid and 4-6g of nitrate are dissolved in 30ml of deionized water.

[0015] Further, in step 1, the reaction is stirred at room temperature for 15-20 minutes; in step 2, the reaction temperature is increased to 80°C and stirring is continued for 4 hours; in step 3, the mixture is dried in an oven at 100°C for 24 hours.

[0016] Furthermore, in step 4, the temperature is increased to 600-750°C using a tube furnace at a rate of 7°C / min, and then calcined for 5 hours.

[0017] Further, in step 5, 0.5g of oxide powder obtained in step 4 and 4.5g of MgH2 are loaded into a ball mill jar.

[0018] Furthermore, in step 5, 200g of stainless steel balls are placed in the ball mill jar at a ball-to-material ratio of 40:1, and then sealed with an O-ring.

[0019] Further, in step 5, after sealing with an O-ring, the grinding jar is removed and filled with 0.2 MPa of high-purity argon gas.

[0020] Furthermore, in step 5, the ball milling conditions are: ball mill speed is 350 r / min, and ball milling time is 4 h.

[0021] Furthermore, in step 5, the ball milling is performed for 20 minutes using an alternating forward and reverse rotation method, with a 10-minute interval between each rotation. After the ball milling operation is completed, the stainless steel balls and alloy powder are separated in the glove box.

[0022] This invention presents a comparative study of novel magnesium-based hydrogen storage materials prepared by ball milling MgH2 with different metal oxides. The study found that MgH2 ball-milled with oxide dopant exhibits excellent hydrogen storage performance, a lower initial hydrogen release temperature, and a simple and inexpensive catalyst preparation method. Doping with 10 wt.% Mn3O4, ZrO2, CeO2, and Co3O4 all improves the hydrogen absorption rate of MgH2 to varying degrees. In particular, MgH2 doped with 10 wt.% ZrO2 shows the best performance, achieving a hydrogen absorption capacity of 5.587 wt.% within 10 minutes at 200°C, while pure MgH2 only achieves 1.089 wt.% under the same conditions. Under these conditions, MgH2 doped with 10 wt.% ZrO2 has a hydrogen absorption capacity nearly 5.1 times that of pure MgH2. Figure 5 As shown, the initial hydrogen decomposition temperatures of pure MgH2 and MgH2 doped with 10 wt.% Co3O4, CeO2, Mn3O4, and ZrO2 are 290℃, 270℃, 267℃, 225℃, and 220℃, respectively. This indicates that MgH2 doped with 10 wt.% ZrO2 exhibits the best performance, reducing the temperature by 70℃.

[0023] The data comparison above shows that MgH2 doped with 10wt.% ZrO2 has the fastest hydrogen absorption rate and the lowest initial hydrogen release temperature. Attached Figure Description

[0024] The present invention will now be described in detail through specific embodiments. These embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art. As used throughout the specification and claims, the terms "comprising" or "including" are open-ended and are interpreted as "comprising but not limited to". The following description is a preferred embodiment for carrying out the invention; however, this description is intended to illustrate the general principles of the specification and is not intended to limit the scope of the invention. The scope of protection of the invention is determined by the appended claims. Unless otherwise specified, all reagents and materials used in the present invention are commercially available.

[0025] Figure 1 These are the XRD patterns of ZrO2, Mn3O4, Co3O4, and CeO2 prepared by the sol-gel method;

[0026] Figure 2This is a graph showing the hydrogen absorption kinetics of MgH2 and MgH2 doped with 10 wt.% of different oxides at 200 °C.

[0027] Figure 3 These are the hydrogen absorption kinetics test results of MgH2 after ball milling at 200℃, 250℃, and 300℃;

[0028] Figure 4 The graphs show the hydrogen absorption kinetics of MgH2-doped 10wt.% ZrO2 powder after ball milling at 200℃, 250℃, and 300℃.

[0029] Figure 5 This is a graph showing the hydrogen desorption kinetics of TPD after MgH2 is doped with four different oxides. Detailed Implementation

[0030] The present invention will now be described in detail with reference to specific embodiments:

[0031] Example 1

[0032] The following procedure was performed in a glove box filled with high-purity argon: 5g of MgH2 was poured into a ball mill jar, and 200g of stainless steel balls were added, resulting in a ball-to-material ratio of 40:1. After sealing with an O-ring, the ball mill jar was removed, and high-purity argon gas at 0.2MPa was introduced into it. The ball mill was operated at 350 r / min for 4 hours, using a 20-minute cycle followed by a 10-minute interval of alternating forward and reverse rotation. After the ball milling was completed, the stainless steel balls and alloy powder were separated in the glove box.

[0033] Example 2

[0034] 8.6848 g of cerium nitrate hexahydrate as the initial raw material and 4.608 g of anhydrous citric acid as the complexing agent were dissolved in 30 ml of deionized water. The mixture was stirred at room temperature for 15 min to obtain a colorless, clear, and transparent solution. The solution was then stirred with a magnetic stirrer at 80 °C for 4 h to obtain a clear, transparent gel. This gel was dried in an oven at 100 °C for 24 h to obtain a white, fluffy solid, which was then ground into a powder. This powder was calcined in a tube furnace at 600 °C at a rate of 7 °C / min for 5 hours to obtain a white powder, which was cerium dioxide.

[0035] The following procedure was performed in a glove box filled with high-purity argon: 0.5g of cerium dioxide and 4.5g of MgH2 (10wt.%) were poured into a ball mill jar, along with 200g of stainless steel balls (ball-to-material ratio 40:1). The jar was sealed with an O-ring, and then the ball mill jar was removed and filled with 0.2MPa of high-purity argon. The ball mill was operated at 350 rpm for 4 hours, using alternating forward and reverse rotation for 20 minutes, followed by a 10-minute interval. After the ball milling was completed, the stainless steel balls and alloy powder were separated in the glove box.

[0036] Example 3

[0037] 5.821 g of cobalt nitrate hexahydrate as the initial raw material and 4.608 g of anhydrous citric acid as the complexing agent were dissolved in 30 ml of deionized water. The mixture was stirred at room temperature for 15 min to obtain a colorless, clear, and transparent solution. The solution was then stirred with a magnetic stirrer at 80 °C for 4 h to obtain a clear, transparent gel. This gel was dried in an oven at 100 °C for 24 h to obtain a purple, fluffy solid, which was then ground to obtain a pink powder. This powder was calcined in a tube furnace at 600 °C at a rate of 7 °C / min for 5 h to obtain a black powder, which was cobalt tetroxide.

[0038] The following procedure was performed in a glove box filled with high-purity argon: 0.5g of cobalt tetroxide and 4.5g of MgH2 (10wt.%) were poured into a ball mill jar, along with 200g of stainless steel balls (ball-to-material ratio 40:1). The jar was sealed with an O-ring, and then the ball mill jar was removed and filled with 0.2MPa of high-purity argon. The ball mill was operated at 350 rpm for 4 hours, using alternating forward and reverse rotation for 20 minutes, followed by a 10-minute interval. After the ball milling was completed, the stainless steel balls and alloy powder were separated in the glove box.

[0039] Example 4

[0040] 5.020 g of manganese nitrate tetrahydrate as the initial raw material and 4.608 g of anhydrous citric acid as the complexing agent were dissolved in 30 ml of deionized water. The mixture was stirred at room temperature for 15 min to obtain a colorless, clear, and transparent solution. The solution was then stirred with a magnetic stirrer at 80 °C for 4 h to obtain a clear, transparent gel. This gel was dried in an oven at 100 °C for 24 h to obtain a brown, fluffy solid, which was then ground to obtain a brown powder. This powder was calcined in a tube furnace at 600 °C at a rate of 7 °C / min for 5 h to obtain a black powder, which was manganese tetroxide.

[0041] The following procedure was performed in a glove box filled with high-purity argon: 0.5 g of manganese tetroxide and 4.5 g of MgH2 (10 wt.%) were poured into a ball mill jar, along with 200 g of stainless steel balls (ball-to-material ratio 40:1). The jar was sealed with an O-ring, and then the ball mill jar was removed and filled with 0.2 MPa of high-purity argon. The ball mill was operated at 350 r / min for 4 hours, using alternating forward and reverse rotation for 20 minutes, followed by a 10-minute interval. After the ball milling was completed, the stainless steel balls and alloy powder were separated in the glove box.

[0042] Example 5

[0043] 8.6848 g of zirconium oxynitrate as the initial raw material and 4.608 g of anhydrous citric acid as the complexing agent were dissolved in 30 ml of deionized water. The mixture was stirred at room temperature for 15 min to obtain a colorless, clear, and transparent solution. The solution was then stirred with a magnetic stirrer at 80 °C for 4 h to obtain a clear, transparent gel. This gel was dried in an oven at 100 °C for 24 h to obtain a white, fluffy solid, which was then ground into a powder. This powder was calcined in a tube furnace at 600 °C at a rate of 7 °C / min for 5 hours to obtain a white powder, which was zirconium dioxide.

[0044] The following procedure was performed in a glove box filled with high-purity argon: 0.5g of zirconium dioxide and 4.5g of MgH2 (10wt.%) were poured into a ball mill jar, along with 200g of stainless steel balls (ball-to-material ratio 40:1). The jar was sealed with an O-ring, and then the ball mill jar was removed and filled with 0.2MPa of high-purity argon. The ball mill was operated at 350 rpm for 4 hours, using alternating forward and reverse rotation for 20 minutes, followed by a 10-minute interval. After the ball milling was completed, the stainless steel balls and alloy powder were separated in the glove box.

[0045] This invention compares and studies the metal powders obtained by ball milling MgH2 with different metal oxides. It was found that MgH2 ball-milled with oxide dopant has good hydrogen storage performance, lower initial hydrogen release temperature, and the catalyst preparation method is simple and inexpensive.

[0046] from Figure 1 As can be seen, the XRD patterns of different metal oxides prepared by the sol-gel method are shown.

[0047] from Figure 2It can be seen that doping with 10 wt.% Co3O4, CeO2, Mn3O4, and ZrO2 can all improve the hydrogen absorption rate of MgH2 to varying degrees, especially MgH2 doped with 10 wt.% ZrO2, which shows the best performance. At 200℃, it can achieve a hydrogen absorption rate of 5.587 wt.% within 10 minutes, while pure MgH2 can only achieve 1.089 wt.% under the same conditions. Under these conditions, MgH2 doped with 10 wt.% ZrO2 has a hydrogen absorption rate nearly 5.1 times that of pure MgH2. Figure 3 , Figure 4 The graph shows the hydrogen absorption rates of MgH2 doped with pure MgH2 and 10 wt.% ZrO2 at different temperatures. Figure 3 , 4 It can be seen that at 200℃ and 250℃, doping with 10wt.% ZrO2 can increase the hydrogen absorption rate of MgH2. For example... Figure 5 As shown, the initial hydrogen decomposition temperatures of pure MgH2 and MgH2 doped with 10 wt.% Co3O4, CeO2, Mn3O4, and ZrO2 are 290℃, 270℃, 267℃, 225℃, and 220℃, respectively. This indicates that MgH2 doped with 10 wt.% ZrO2 exhibits the best performance, reducing the temperature by 70℃.

[0048] The data comparison above shows that MgH2 doped with 10wt.% ZrO2 has the fastest hydrogen absorption rate and the lowest initial hydrogen release temperature.

[0049] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various different choices and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. Process for the preparation of a doped oxide magnesium-based hydrogen storage material, characterized in that, Comprise the following steps in turn: Step 1, 4-5g anhydrous citric acid and 4-6g nitrate are dissolved in 30ml deionized water according to the molar ratio of metal ion to citric acid 1:1.2, and the concentration of metal ion and citric acid is 0.02mol / L and 0.024mol / L respectively; the reaction is stirred at room temperature for 15-20min; the nitrate is manganese nitrate, zirconyl nitrate, cerium nitrate or cobalt nitrate; Step 2, the reaction temperature is increased to 80℃, and the stirring is continued for 4h to obtain a clear transparent gel; Step 3, the product obtained in step 2 is dried in an oven at 100℃ for 24h to obtain a fluffy solid, and then ground to obtain a powdery solid; Step 4, the temperature is increased to 600-750℃ at a rate of 7℃ / min in a tube furnace, and then calcined for 5h to obtain an oxide powder; Step 5, 0.5g oxide powder obtained in step 4 and 4.5g MgH2 are loaded into a ball mill tank, 200g stainless steel balls are loaded into the ball mill tank, the ball-to-material ratio is 40:1, the ball mill tank is sealed after an O-ring is sleeved, the ball mill tank is taken out, 0.2MPa high-purity argon is filled into the ball mill tank, the ball milling conditions are as follows: the rotation speed of the ball mill is 350r / min; the ball mill is operated in a forward and reverse alternating mode for 20min, and the ball milling is performed for 4h with an interval of 10min; after the ball milling operation is completed, the stainless steel balls and the alloy powder are separated in a glove box to obtain the target product, a magnesium-based hydrogen storage material doped with an oxide.

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