TWI661149B - Method for storing and releasing hydrogen gas - Google Patents

Abstract

A method for storing and releasing hydrogen, comprising the steps of: providing a palladium copper alloy having a nanostructure; contacting the palladium copper alloy with hydrogen to generate a spontaneous chemical reaction which dissociates hydrogen into hydrogen Protons, and enter the palladium copper alloy as hydrogen protons; and a voltage is applied to the palladium copper alloy containing hydrogen protons to release hydrogen. Using the palladium-copper alloy to carry out the method of the present invention can improve the efficiency and safety of hydrogen storage and hydrogen release processes, and reduce the required material cost and energy.

Description

Method for storing and releasing hydrogen

The invention relates to a method for storing and releasing hydrogen, and in particular to a method for storing and releasing hydrogen using a bimetallic nano alloy.

The advantages of hydrogen as an energy source are its large calorific value, cleanness, and abundant resources, which can be described as inexhaustible and inexhaustible. Therefore, it is hailed as one of the most promising new energy sources in the 21st century. However, to achieve the use of hydrogen energy, three key issues must be addressed: the production of large quantities of cheap hydrogen, the storage and transportation of hydrogen, and the use of hydrogen.

In terms of hydrogen storage and transportation, compressed gas storage method and liquid hydrogen storage method are currently commonly used storage methods. However, the use of steel cylinders to store and transport high-pressure gaseous hydrogen is dangerous, and the amount of hydrogen stored is small and the cost is high. Liquid hydrogen has a higher density than gaseous hydrogen, but the liquefaction temperature of hydrogen is minus 239.7 degrees Celsius. It needs to provide good insulation protection equipment and consume a lot of energy during storage.

In 1964, researchers JJ Reilly and RH Wisqall of the Brook-Haven Laboratory discovered the hydrogen storage characteristics of Mg ₂ Ni alloys. In 1969, the Philips laboratory found that LaNi ₅ alloy had good hydrogen storage properties. In 1974, JJ Reilly and RH Wisqall discovered TiFe hydrogen storage alloys. These major discoveries have begun the research of metal hydride hydrogen storage materials. This solid metal alloy has a hydrogen storage density of about 1,000 times that of hydrogen, which is the same as or more than liquid hydrogen, without the risk of explosion, and has the advantage of zero loss. It can store hydrogen for a long time, and can be stored without complicated containers. It can also obtain high-purity hydrogen, which is a cost-effective hydrogen storage method.

Generally, hydrogen storage alloys or hydrogen storage metals use metal alloys or metals to react with hydrogen to form alloy hydrides or metal hydrides, so that hydrogen is stored in a solid form. If the conditions are changed slightly, the alloy hydride or metal hydride will Releases hydrogen and changes back to alloys or metals. Therefore, it is very convenient to use hydrogen storage alloy or metal to store hydrogen, transport hydrogen, and use hydrogen. Although some pure metals such as palladium and uranium have better hydrogen storage functions, they are more expensive. Although some alloys have not the best hydrogen storage performance, they are relatively cheap. Therefore, "hydrogen storage alloys" are the most important in the development and utilization of hydrogen energy. Desirable materials.

All metal elements in the periodic table can react with hydrogen to form hydrides. The nature of the reaction can be roughly divided into two types. The first metal easily reacts with hydrogen to form a stable hydride, and it emits heat during the reaction. It is called an exothermic metal (A), such as Ti, Zr, Mg, V, and rare earth elements. Another metal has a smaller affinity with hydrogen, and it is not easy to generate hydrides. It needs to absorb heat during the reaction with hydrogen. It is called an endothermic metal (B), such as Fe, Co, Ni, Cr, etc. The exothermic metal (A) has a strong affinity with hydrogen, has a high hydrogen absorption amount, and is not easy to release hydrogen; the endothermic metal (B) has opposite properties. Generally, hydrogen storage alloys are formed by combining these two metals with different characteristics. The molecular formula is expressed by AmBn (such as AB, A2B, AB2, AB5, AB3, AB7, etc.). This type of hydrogen storage alloy is mainly controlled by element A. The hydrogen storage capacity, and the B element controls the reversibility of hydrogen absorption and release, in order to improve the thermodynamic and dynamic properties of the alloy's hydrogen absorption and release, and the appropriate m and n ratios can be adjusted to prepare hydrogen storage alloys with excellent characteristics.

The methods of alloy hydrogen storage can be divided into physical hydrogen storage and chemical hydrogen storage. Physical hydrogen storage is a porous hydrogen storage material that is physically adsorbed, so that hydrogen molecules accumulate on the surface of the material, but do not react with the material. Xue response. Chemical hydrogen storage is a reversible reaction between hydrogen storage alloy and hydrogen at a certain temperature and pressure to generate metal solid solution and metal hydride. This reversible reaction is exothermic when hydrogen is absorbed, and hydrogen is released when it absorbs heat.

However, there are still some shortcomings in hydrogen storage using solid metal alloys, including: excessive hydrogen protons embedded during hydrogen storage cannot be stably fixed in the metal lattice, resulting in shortened service life and long-term possible collapse of the metal lattice , Thereby irreversibly reducing the amount of hydrogen storage and safety.

In order to solve the above problems, the inventors hope to use a new solid metal alloy to store and release hydrogen. In addition to stably absorbing a large number of hydrogen protons, the amount of precious metals can be reduced, and the efficiency of the hydrogen storage and hydrogen release processes can be increased. .

An object of the present invention is to provide a method for storing and releasing hydrogen, which adopts a hydrogen storage alloy with excellent performance, which can store hydrogen in a stable and large amount, increase the efficiency of hydrogen storage and hydrogen release processes, and reduce hydrogen storage and release Energy required for the hydrogen process and reduced use of precious metals.

In order to achieve the above object, the present invention provides a method for storing and releasing hydrogen, including: providing a palladium-copper alloy having a nanostructure, such as a core-shell structure or nanowire; when storing hydrogen, the palladium-copper alloy Contact with hydrogen to generate a spontaneous chemical reaction that dissociates hydrogen into hydrogen protons and enters the palladium copper alloy in the form of hydrogen protons; and applies a voltage to the palladium copper alloy containing hydrogen protons To release hydrogen.

In one embodiment, the voltage of the above method ranges from 1V to 2V.

In one embodiment, the weight percentage of copper in the palladium-copper alloy can be in the range of 3% to 70%, 3% to 40%, or 5% to 25%, and the remaining component is palladium.

In one embodiment, the above method further includes: controlling the operating flow rate of hydrogen to a flow rate range of 30-50 cm / min, and contacting the hydrogen with the palladium copper alloy.

The palladium-copper alloy used in the present invention has a structure as small as a nanometer and a stable nanometer structure, so it can store hydrogen in a stable and large amount. For the reaction process of hydrogen storage and hydrogen release, palladium-copper alloys all have good catalytic efficiency, and their activation energy and adsorption energy are both quite low. Therefore, the energy required for hydrogen storage and hydrogen release processes is quite low, and their The price is cheaper than other single metals with excellent hydrogen storage performance.

100‧‧‧ Hydrogen storage device

110‧‧‧Hydrogen storage cavity

120‧‧‧palladium copper alloy

130‧‧‧ Power

PdCu-H‧‧‧ Hydrogen Protons Adsorbed by Palladium Copper Alloy

IS‧‧‧Hydrogen molecules dissociate on the surface of the palladium copper alloy to the initial state of the adsorption process

TS‧‧‧Hydrogen molecules dissociate on the surface of the palladium-copper alloy to the transition state of being adsorbed

FS‧‧‧Hydrogen molecules dissociate on the surface of the palladium copper alloy to the final state of the adsorption process

E _TS ‧‧‧Activation Energy

FIG. 1 is a schematic diagram of a hydrogen storage device according to an embodiment of the present invention.

FIG. 1A is a particle size distribution diagram of palladium-copper alloy nano particles having a core-shell structure.

FIG. 2 is a schematic diagram of a palladium-copper alloy core-shell structure according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of energy levels of an initial state, a transition state, and a final state of a hydrogen molecule dissociation reaction according to an embodiment of the present invention.

4 is a hydrogen free energy diagram using different metals as hydrogen evolution reaction catalysts.

FIG. 5 is a volcanic map drawn based on the Gibbs free energy of hydrogen protons adsorbed by different metals and the exchange current density of the metal.

The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms mentioned in the following embodiments, such as: up, down, left, right, front or rear, etc., are merely directions for referring to the accompanying drawings. Therefore, these directional terms are only used to illustrate and not to limit the present invention.

FIG. 1 is a schematic diagram of a hydrogen storage device according to an embodiment of the present invention, which is used to implement a method for storing and releasing hydrogen. The hydrogen storage device 100 includes a hydrogen storage cavity 110 and a power source 130. The inner layer of the hydrogen storage cavity 110 is made using a novel palladium-copper alloy 120 to allow hydrogen to flow in and be stored in the palladium-copper alloy 120. The two poles of the power source 130 are electrically connected to the palladium copper alloy 120 to apply a bias or current to the palladium copper alloy to reduce the hydrogen protons in the palladium copper alloy 120 to hydrogen and release them.

In this embodiment, the palladium-copper alloy 120 is a bimetal alloy having a nano-structure. The weight percentage of the copper content therein may be 3% -70%, 3% -40%, and a preferred range is 5% -25%. In the palladium copper alloy of this embodiment, the weight percentage of copper metal is 25%, and the remaining components are palladium metal.

In one embodiment, the nanostructure of the palladium-copper alloy is a metal cluster with a core-shell structure. FIG. 1A is a particle size distribution diagram of palladium-copper alloy nano particles having a core-shell structure, showing that the size of most palladium-copper alloy nano particles falls within a particle size range of 3 to 5 nm, and a preferred particle size is 4.5 nm . In another embodiment, the nanostructure of the palladium-copper alloy can be a nanowire with a wire diameter as small as a nanometer. The core-shell structure or the form of nanowires can not only maintain the stability of the nanostructure and avoid explosions, but also its lattice arrangement is suitable for hydrogen protons to be embedded therein and has the property of easily adsorbing hydrogen, so the safety of hydrogen storage can be improved. In addition, the palladium-copper alloy has a relatively low hydrogen adsorption energy, which can increase the catalytic efficiency of the hydrogen release process.

It is worth mentioning that, published by Neil M. Wilson and David W. Flaherty in the Journal of the American Chemical Society (J.Am.Chem.Soc. 2016, 138,574-586.) In 2016, "Mechanism for the Direct Synthesis of H ₂ O ₂ on Pd Clusters: Heterolytic Reaction Pathways at the Liquid-Solid Interface "Scheme 1 on page 578 has revealed that palladium metal can spontaneously dissociate hydrogen molecules. In addition, copper metal has good catalytic properties, which can reduce the activation energy required for hydrogen molecule dissociation and the adsorption energy of hydrogen. Therefore, in this embodiment, a palladium-copper alloy made of two metals, palladium and copper, is in contact with hydrogen to spontaneously generate a hydrogen evolution reaction (HER) between the gas phase and the solid phase, so that hydrogen molecules dissociate themselves Is a hydrogen proton. It should be noted that the reaction between the gas phase and the solid phase has nothing to do with the conventional process of hydrolyzing liquid phase to produce hydrogen.

When hydrogen is stored, the hydrogen is controlled to pass through the hydrogen storage chamber 110 at a flow rate of 35.5 cm / min, and the hydrogen is brought into contact with the inner layer of the palladium copper alloy 120 to generate an spontaneous hydrogen evolution reaction. The spontaneous hydrogen evolution reaction dissociates hydrogen into hydrogen protons. . Next, the dissociated hydrogen protons are embedded in the interstitial spaces of the palladium copper alloy to complete the storage of hydrogen. In one embodiment, the operating flow rate of hydrogen ranges from 30-50 cm / min.

In order to reduce the hydrogen protons in the palladium copper alloy 120 to hydrogen and release them, the power source 120 applies a voltage of 1V to the palladium copper alloy 120 containing hydrogen protons to combine hydrogen protons with each other and add electrons to generate hydrogen. In one embodiment, the applied voltage range may be 1V ~ 2V. When the applied voltage or current conditions are different, different hydrogen release rates can be obtained. It is worth noting that the hydrogen release process of the present invention is achieved by applying a voltage, which is not the same as the practice of adjusting the temperature and pressure in the conventional technology to cause the alloy to absorb heat and emit hydrogen. The method and thermodynamics of the invention are discussed It has nothing to do with the endothermic and exothermic heat.

FIG. 2 is a schematic diagram of a method for manufacturing a palladium copper alloy 120 according to an embodiment of the present invention, and also shows a core-shell structure of the palladium copper alloy 120.

Material: 20% by weight of Palladium on carbon (Pd / C) as the core material. The precursor of copper is CuCl ₂ . 2H ₂ O. HPLC grade ethanol.

Synthetic steps of palladium-copper alloy 120: Put 0.266 g of palladium-carbon catalyst in 50 ml of mixed solvent [ethanol-water (1: 1)], and perform sonicating treatment for 1 hour to form a uniform palladium-carbon suspension liquid. The palladium-carbon suspension was then treated with hydrogen for 2 hours with constant stirring to complete the pretreatment step. Then, 50 ml of a 5 × 10 ^-3 M CuCl ₂ aqueous solution was added to the reaction flask containing the pretreated palladium-carbon suspension and stirred under a constant hydrogen purge for 6 hours to obtain nano particles of the palladium-copper alloy 120 . Nano particles of the palladium-copper alloy 120 were then separated from its solvent using a high-power centrifugal pump (20,000 rpm, 30 minutes). Finally, the nano particles of the palladium copper alloy 120 obtained by centrifugation were dried in an air oven at 80 ° C. for about 8 hours.

FIG. 3 is a schematic diagram of energy levels of an initial state, a transition state, and a final state of a hydrogen molecule dissociation reaction. In a hydrogen molecule dissociation reaction model of an embodiment, the process of dissociating hydrogen molecules on the surface of the palladium copper alloy 120 to be adsorbed by the palladium copper alloy 120 is divided into an initial state IS, a transition state TS, and a final state FS. The "initial state IS" is the molecular configuration and the most stable energy state when hydrogen molecules are adsorbed on the surface of the palladium copper alloy 120. The "transition state TS" is an energy state that the hydrogen molecules need to absorb to start dissociating between hydrogen and hydrogen on the surface of the palladium copper alloy 120. The "final state FS" is an energy state in which two independent hydrogen protons are formed on the surface of the palladium-copper alloy 120 after hydrogen molecules are dissociated. The energy difference between the transition state TS and the initial state IS in FIG. 3 is the activation energy E _TS . The following table lists experimental data of activation energy E _TS and adsorption energy of hydrogen molecules. Here, "adsorption energy" refers to the net energy of hydrogen molecules adsorbed on the surface of palladium copper alloy 120. It can be seen from the table below that the adsorption energy of hydrogen molecules by the palladium-copper alloy 120 is lower than that of pure palladium metal or copper metal for the hydrogen molecules, so the voltage required for the hydrogen release process can be reduced.

FIG. 4 shows hydrogen free energy using different metals as catalysts for the hydrogen evolution reaction. The horizontal axis is the reaction direction and the vertical axis is the hydrogen free energy. The hydrogen free energy of different metals in FIG. 4 is represented by different forms of line segments. Since the hydrogen free energy of the palladium-copper alloy 120 is higher than that of gold, platinum, nickel, molybdenum, platinum-bismuth alloys, etc., it can be judged that the dissociated hydrogen protons are higher in the nanoscale palladium copper alloy lattice than gold. , Platinum, platinum bismuth alloy and other metal materials are relatively stable. In addition, the price of palladium-copper alloy 120 is cheaper than materials containing metals such as gold and platinum, and it is also cheaper than the price of palladium single metal. Therefore, the palladium-copper alloy in this case is a cheaper and more stable hydrogen storage material.

As shown in FIG. 5, the Gibbs free energy of hydrogen protons adsorbed by different metals and the exchange current density of the metals are plotted into a Volcano plot. The horizontal axis of Figure 5 is the Gibbs free energy of the hydrogen protons adsorbed by the metal in the figure. The Gibbs free energy is obtained from the electron density functional theory (DFT); the vertical axis is the exchange current density (units) : A / cm ² ), which is a function of the Gibbs free energy of hydrogen protons. Figure 5 shows that when the palladium-copper alloy 120 is used as a hydrogen storage material, its electrochemical properties and hydrogen free energy are close to the single metal material "platinum" with excellent hydrogen storage performance. Therefore, when considering price and efficiency, it can be replaced Platinum metal is used as an ideal hydrogen storage material.

The invention generates spontaneous hydrogen evolution reaction at the interface between the gas phase and the solid phase by contacting the palladium copper alloy with hydrogen, which can more effectively and quickly dissociate hydrogen molecules into hydrogen protons, and embed them in the interstitial space of the palladium copper nano alloy In particular, it has a stable nanostructure, so it can improve the safety and hydrogen storage capacity of the hydrogen storage and hydrogen release process, and it will be used in battery production technology for electric vehicles. Since the present invention uses low-cost copper as the second element of the alloy, its excellent electrical conductivity and hydrogen proton affinity properties make the palladium-copper alloy cost-effective.

However, the above are only preferred embodiments of the present invention. The scope of implementation of the present invention, that is, the simple equivalent changes and modifications made according to the scope of the patent application and the description of the invention, are still within the scope of the patent of the present invention. In addition, any embodiment of the present invention or the scope of patent application does not need to achieve all the purposes or advantages or features disclosed by the invention. In addition, the abstract and the title are only used to assist the search of patent documents, and are not intended to limit the scope of rights of the present invention.

Claims (7)

A method for storing and releasing hydrogen includes: providing a palladium-copper alloy having a nanostructure; contacting the palladium-copper alloy with hydrogen to generate an spontaneous chemical reaction that dissociates hydrogen into hydrogen protons And into the palladium copper alloy in the form of hydrogen protons; and applying a voltage to the palladium copper alloy containing hydrogen protons to release hydrogen. The method for storing and releasing hydrogen according to item 1 of the scope of patent application, wherein the voltage ranges from 1V to 2V. The method for storing and releasing hydrogen described in item 1 of the scope of patent application, wherein the nanostructure of the palladium copper alloy is selected from one of a core-shell structure and a nanowire. The method for storing and releasing hydrogen according to item 3 of the scope of the patent application, wherein in the palladium copper alloy, the weight percentage of copper is 3% to 70%, and the remaining component is palladium. The method for storing and releasing hydrogen according to item 3 of the scope of the patent application, wherein in the palladium copper alloy, the weight percentage of copper is 3% to 40%, and the remaining component is palladium. The method for storing and releasing hydrogen according to item 3 of the scope of the patent application, wherein in the palladium copper alloy, the weight percentage of copper is 5% to 25%, and the remaining component is palladium. The method for storing and releasing hydrogen as described in item 1 of the scope of the patent application, further comprises: controlling the operating flow rate of the hydrogen gas within a flow rate range of 30-50 cm / min, and bringing the hydrogen gas into contact with the palladium copper alloy.