Method for preparing high-purity hydrogen and amorphous-phase molybdenum oxide by membrane-free full-pH electrolyzed water

Abstract

The invention discloses a method for preparing high-purity hydrogen and amorphous-phase molybdenum oxide through membrane-free full-pH water electrolysis, and belongs to the field of hydrogen production through water electrolysis and the field of metallurgical electrochemical engineering. According to the method, metal molybdenum is used as an anode, a hydrogen evolution material is used as a cathode, and voltage is controlled to be applied in a full pH value range to decompose (sea) water to prepare high-purity hydrogen and amorphous-phase molybdenum oxide species. When the applied voltage reaches the oxidation potential of the metal molybdenum, the surface of the metal molybdenum anode is gradually subjected to electrooxidation to generate solid amorphous-phase molybdenum oxide species, and meanwhile, the cathode is subjected to hydrogen evolution reaction. Along with the increase of the applied voltage, the electrooxidation rate of the molybdenum anode is increased, and no oxygen is generated, so that high-purity hydrogen is obtained at the cathode. The metal molybdenum electrode material used in the method is rich in reserve, the water electrolysis device is simple, an expensive diaphragm material is not needed, the production cost is low, the energy consumption is low, the influence of the pH value and composition of the electrolyte is small, and the method can be widely applied to the field of membrane-free full-pH-value electrolysis (sea) water hydrogen production and the field of metallurgical electrochemical engineering.

Description

Technical Field

[0001] The invention relates to a method for producing hydrogen by electrolysis of water, in particular to a method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH electrolysis of water. Background Art

[0002] Hydrogen energy has the advantages of high energy density, only water as a byproduct of combustion, and wide sources. It is considered to be an ideal energy carrier material. In hydrogen production technology, the use of renewable energy to generate electricity to drive water decomposition to produce green hydrogen is considered to be one of the most promising methods to alleviate the energy crisis and solve the greenhouse effect. The hydrogen production reaction by water electrolysis includes the cathode hydrogen evolution reaction (HER) and the anode oxygen evolution reaction (OER). Compared with the HER process involving two-electron transfer, the OER process involves a complex four-electron transfer, resulting in slow kinetics and high overpotential. As a result, the OER process has become a bottleneck problem for hydrogen production by water electrolysis. In addition, scarce precious metal catalysts (such as IrO2 and RuO2), expensive proton and anion exchange membrane materials, and scarce fresh water resources further limit the large-scale application of water electrolysis technology.

[0003] At present, the membraneless hydrogen production technology of organic molecule electrooxidation coupled with alkaline water electrolysis can significantly reduce the anode oxidation potential, reduce energy consumption, and obtain high-purity hydrogen. However, this technology has problems such as difficult liquid product separation, high reaction conditions, complex large-scale electrolysis equipment, and the need to develop cheap, efficient, and stable anode catalysts, which hinders the large-scale application of this technology. Traditional alkaline diaphragm electrolyzers (ALK) and anion exchange membrane electrolyzers (AEM) can use cheap, efficient, and stable transition metal-based catalysts, but in traditional ALK technology, oxygen will pass through the diaphragm into the cathode side and mix with hydrogen, bringing safety hazards. Therefore, the electrolysis efficiency of this technology is low. AEM technology can prevent oxygen from mixing with hydrogen and obtain high-purity hydrogen, but the price of anion exchange membrane is relatively expensive. The proton exchange membrane used in proton exchange membrane electrolyzer (PEM) technology is relatively cheap compared to anion exchange membrane, but the use of expensive precious metal catalysts under acidic conditions and the OER process with a high overpotential limit the large-scale application of this technology. Using abundant seawater directly as electrolyte can significantly alleviate the problem of freshwater resource shortage, but the composition of seawater is complex, and there are problems such as poor stability of membrane materials and chlorine precipitation.

[0004] Therefore, it is of great significance to develop a universally applicable method for producing hydrogen by water electrolysis. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full pH water electrolysis. The method uses a metal molybdenum sheet as an anode, utilizes the advantage that the oxidation potential of metal molybdenum is much smaller than the oxygen evolution potential, significantly reduces the anode overpotential, and reduces the energy consumption of water electrolysis. The oxidation process of the metal molybdenum electrode is less affected by the pH value and composition of the electrolyte. The method is suitable for acidic, alkaline, neutral water electrolysis, as well as alkaline seawater and direct seawater electrolysis. The method does not require the use of expensive diaphragm materials, has low production cost and low energy consumption, and is suitable for industrial production.

[0006] The purpose of the present invention is achieved through the following technical solutions: A method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis, the method comprising the following steps: (1) Using metal molybdenum sheet as anode and hydrogen evolution material as cathode, membraneless water electrolysis is performed to produce hydrogen in electrolytes with full pH values ​​and pure seawater; (2) When the applied potential in the electrolyte is greater than the oxidation potential of metallic molybdenum, an electro-oxidation reaction occurs on the surface of the molybdenum anode to generate solid molybdenum oxide species without generating oxygen. At the same time, hydrogen is precipitated at the cathode to obtain high-purity hydrogen. (3) A membraneless water electrolysis hydrogen production device suitable for the hydrogen production method, comprising a device, a metal molybdenum anode, a hydrogen evolution cathode, a temperature measurement system, a stirring device, a hydrogen outlet, an electrolyte feed inlet and an electrolyte outlet.

[0007] In the method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis, the metallic molybdenum described in step (1) is industrial-grade metallic molybdenum with a molybdenum content of 90 to 99.999%.

[0008] The method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis, wherein the hydrogen-evolving material in step (1) is a single metal of Pt, Ru, Ir, Ru, Rh, Fe, Co, Ni, Mo, W, Mn, Ti, V, Ag, Au, Re, a multi-metal alloy, and an oxide, hydroxide, phosphide, nitride, sulfide, carbide, selenide and telluride containing at least one metal.

[0009] In the method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis, the full pH value range described in step (1) is 0 to 20.

[0010] In the method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis, the membrane described in step (1) is a proton exchange membrane and an anion exchange membrane.

[0011] The method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis, the full-pH electrolyte described in step (1) includes sulfuric acid, perchloric acid, potassium hydroxide, sodium hydroxide, lithium hydroxide, sodium sulfate, potassium sulfate, sodium chloride, potassium chloride, phosphate buffer solution and natural seawater and alkaline natural seawater solution.

[0012] In the method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis, the electrolyte temperature in step (2) is 20 to 80°C.

[0013] In the method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis, the applied potential in step (2) is 0.3 ~ 3.0 V vs. RHE.

[0014] In the method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis, the solid molybdenum oxide species in step (2) is amorphous molybdenum oxide, and the physical phase is at least one of molybdenum dioxide, molybdenum trioxide, and molybdenum dioxide and molybdenum trioxide containing oxygen defects.

[0015] In the method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis, the membraneless water electrolysis hydrogen production device suitable for the hydrogen production method described in step (3) should at least include a metal molybdenum anode, a hydrogen evolution cathode, a temperature measurement system, a stirring device, a hydrogen outlet, an electrolyte feed inlet and an electrolyte outlet.

[0016] The present invention has the following advantages and effects: This method uses metal molybdenum sheets as anodes, taking advantage of the fact that the oxidation potential of metal molybdenum is much lower than the oxygen evolution potential, significantly reducing the anode overpotential and reducing the energy consumption of water electrolysis.

[0017] In this method, as the potential increases, only electrode oxidation reaction occurs at the metal molybdenum anode without oxygen evolution, and high-purity hydrogen can be obtained under high current density or high voltage.

[0018] The oxidation process of the metal molybdenum electrode in this method is less affected by the pH value and composition of the electrolyte, and is suitable for electrolysis of acidic, alkaline, neutral water, as well as alkaline seawater and direct seawater electrolysis.

[0019] The anodization product of the method is a solid molybdenum oxide species, which is easy to separate and can be recycled as a raw material for use in the fields of metallurgy, electrochemistry, catalysis, optics and functional materials.

[0020] This method has abundant reserves of metal molybdenum sources and low prices, and does not require the use of expensive diaphragm materials. It has low production costs and low energy consumption, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1This is the XRD pattern of the metal molybdenum sheet anode; Figure 2 is the XRD pattern of the anodized product; Figure 3 The linear voltammetric curves at different temperatures in 0.5 M H2SO4 solution; Figure 4 Gas production at 2.0 V vs. RHE; Figure 5 Linear voltammetric curves at different temperatures in 1 M KOH solution; Figure 6 The linear voltammetric curves at different temperatures in 0.1 M Na2SO4 solution; Figure 7 The linear voltammetric curves at different temperatures in alkaline seawater solution; Figure 8 It is the linear voltammetric curve at different temperatures in natural seawater; Fig. 9 Schematic diagram of membraneless electrolysis of (sea) water to produce hydrogen. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with specific implementation methods, but the protection scope of the present invention is not limited to the following embodiments. It should be noted that all other embodiments without outstanding creativity within the scope of the claims of the present invention and not listed in this specification should belong to the protection scope of the present invention. Example 1

[0023] The metal molybdenum sheet (molybdenum content 99.95%) was used as the working electrode, the platinum sheet as the cathode, and the Ag / AgCl electrode as the reference electrode to conduct a membraneless water electrolysis hydrogen production test in H2SO4 electrolyte with pH = 0.3. The phases of the metal molybdenum sheet and the anodic oxidation product are Figure 1 and Figure 2 Given in.

[0024] Polarization curves were tested in electrolytes at 25, 40, 60, and 80 °C, with a voltage range of 0 to 1.5 V vs RHE and a scan rate of 0.002 V / s. The experimental results show that Figure 3 As shown in the figure, at 25, 40, 60 and 80 °C, when the applied potential was 1.23 V vs RHE, the current density reached 400, 490, 580 and 650 mA / cm2 respectively, and no oxygen was produced. When the applied potential was as high as 2.0 V vs RHE, the molybdenum anode still did not produce oxygen, as shown in the figure. Figure 4 As shown, high purity hydrogen can be obtained at high current density. Example 2

[0025] A metal molybdenum sheet (molybdenum content of 99.95%) was used as a working electrode, a platinum sheet was used as a cathode, and a Hg / HgO electrode was used as a reference electrode to conduct a membraneless water electrolysis hydrogen production test in a KOH electrolyte with a pH of 14. The metal molybdenum sheet and the anodic oxidation product were the same as in Example 1.

[0026] Polarization curves were tested in electrolytes at 25, 40, 60, and 80 °C, with a voltage range of 0 to 1.5 V vs RHE and a scan rate of 0.002 V / s. The experimental results show that Figure 5 As shown in the figure, at 25, 40, 60 and 80°C, when the applied potential was 1.23 V vs RHE, the current density at each temperature reached 230, 400, 520 and 660 mA / cm2, respectively, and no oxygen was produced. When the applied potential was as high as 2.0 V vs RHE, the molybdenum anode still did not produce oxygen, achieving high-purity hydrogen at high current density. Example 3

[0027] A metal molybdenum sheet (molybdenum content of 99.95%) was used as a working electrode, a platinum sheet was used as a cathode, and an Ag / AgCl electrode was used as a reference electrode to conduct a membraneless water electrolysis hydrogen production test in a Na2SO4 electrolyte with a pH of 6.4. The metal molybdenum sheet and the anodic oxidation product were the same as in Example 1.

[0028] Polarization curves were tested in electrolytes at 25, 40, 60, and 80 °C, with a voltage range of 0 to 1.5 V vs RHE and a scan rate of 0.002 V / s. The experimental results show that Figure 6 As shown in the figure, at 25, 40, 60 and 80°C, when the applied potential was 1.23 V vs RHE, the current density at each temperature reached 20, 40, 47 and 73 mA / cm2, respectively, and no oxygen was produced. When the applied potential was as high as 2.0 V vs RHE, the molybdenum anode still did not produce oxygen, achieving high-purity hydrogen at high current density. Example 4

[0029] A metal molybdenum sheet (molybdenum content of 99.95%) was used as a working electrode, a platinum sheet was used as a cathode, and a Hg / HgO electrode was used as a reference electrode to conduct a membraneless water electrolysis hydrogen production test in a KOH seawater solution at pH = 14. The metal molybdenum sheet and the anodic oxidation product were the same as in Example 1.

[0030] Polarization curves were tested in electrolytes at 25, 40, 60, and 80 °C, with a voltage range of 0 to 1.5 V vs RHE and a scan rate of 0.002 V / s. The experimental results show that Figure 7 As shown in the figure, at 25, 40, 60 and 80°C, when the applied potential was 1.23 V vs RHE, the current density at each temperature reached 230, 270, 380 and 460 mA / cm2, respectively, and no oxygen was produced. When the applied potential was as high as 2.0 V vs RHE, the molybdenum anode still did not produce oxygen, achieving high-purity hydrogen at high current density. Example 5

[0031] A metal molybdenum sheet (molybdenum content of 99.95%) was used as a working electrode, a platinum sheet was used as a cathode, and a Hg / HgO electrode was used as a reference electrode to conduct a membraneless water electrolysis hydrogen production test in natural seawater at pH = 8.4. The metal molybdenum sheet and the anodic oxidation product were the same as in Example 1.

[0032] Polarization curves were tested in electrolytes at 25, 40, 60, and 80 °C, with a voltage range of 0 to 1.5 V vs RHE and a scan rate of 0.002 V / s. The experimental results show that Figure 8 As shown in the figure, at 25, 40, 60 and 80°C, when the applied potential was 1.23 V vs RHE, the current density at each temperature reached 25, 45, 66 and 85 mA / cm2, respectively, and no oxygen was produced. When the applied potential was as high as 2.0 V vs RHE, the molybdenum anode still did not produce oxygen, achieving high-purity hydrogen at high current density. Example 6

[0033] The present invention relates to a membraneless full pH electrolysis device 1 for producing high-purity hydrogen and amorphous molybdenum oxide from (sea) water, such as Fig. 9 As shown, it includes a metal molybdenum anode 2, a hydrogen evolution cathode 3, a temperature measurement system 4, a stirring device 5, a hydrogen outlet 6, an electrolyte feed port 7 and an electrolyte outlet 8. During the operation of the device, the electrolyte continuously enters the electrolytic cell, and under the applied voltage, the hydrogen evolution cathode continuously precipitates hydrogen, and the gas is continuously discharged and collected from the hydrogen outlet; at the same time, the metal molybdenum anode is continuously oxidized, and the generated powdered molybdenum oxide species are continuously peeled off, dispersed into the electrolyte under strong stirring, and continuously discharged from the electrolyte outlet with the electrolyte.

[0034] The above disclosed embodiments of the invention are exemplary, and it cannot be understood that the scope of protection of the present invention is limited to the listed embodiments. These embodiments listed in this specification are to better illustrate the method and practical application effects of the present invention, so that people in the relevant technical field can better understand and use the present invention.

Claims

1. A method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full pH water electrolysis, characterized in that: The method The process includes: (1) Using metal molybdenum sheet as anode and hydrogen evolution material as cathode, membraneless water electrolysis is performed to produce hydrogen in electrolytes with full pH values ​​and pure seawater; (2) When the applied potential in the electrolyte is greater than the oxidation potential of metallic molybdenum, an electro-oxidation reaction occurs on the surface of the molybdenum anode to generate solid molybdenum oxide species without generating oxygen. At the same time, hydrogen is precipitated at the cathode to obtain high-purity hydrogen. (3) A membraneless water electrolysis hydrogen production device suitable for the hydrogen production method, comprising a device (1), a metal molybdenum anode (2), a hydrogen evolution cathode (3), a temperature measurement system (4), a stirring device (5), a hydrogen outlet (6), an electrolyte feed inlet (7) and an electrolyte outlet (8).

2. The method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full pH water electrolysis according to claim 1, characterized in that: The metallic molybdenum described in step (1) is industrial grade metallic molybdenum, and the molybdenum content is 90-99.999%.

3. The method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full pH water electrolysis according to claim 1, characterized in that: The hydrogen-generating material described in step (1) is a single metal of Pt, Ru, Ir, Ru, Rh, Fe, Co, Ni, Mo, W, Mn, Ti, V, Ag, Au, Re, a multi-metal alloy, and an oxide, hydroxide, phosphide, nitride, sulfide, carbide, selenide, and telluride containing at least one metal.

4. The method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full pH water electrolysis according to claim 1, characterized in that: The full pH range described in step (1) is 0 to 20.

5. The method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full pH water electrolysis according to claim 1, characterized in that: The membranes described in step (1) are proton exchange membranes and anion exchange membranes.

6. The method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis according to claim 1, characterized in that: The full pH value electrolyte described in step (1) includes sulfuric acid, perchloric acid, potassium hydroxide, sodium hydroxide, lithium hydroxide, sodium sulfate, potassium sulfate, sodium chloride, potassium chloride, phosphate buffer solution, natural seawater and alkaline natural seawater solution.

7. The method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis according to claim 1, characterized in that: The electrolyte temperature described in step (2) is 20 ~ 80 °C.

8. The method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis according to claim 1, characterized in that: The applied potential described in step (2) is 0.3 ~ 3.0 V vs. RHE.

9. The method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis according to claim 1, characterized in that: The solid molybdenum oxide species described in step (2) is amorphous molybdenum oxide, and the physical phase is at least one of molybdenum dioxide, molybdenum trioxide, and molybdenum dioxide and molybdenum trioxide containing oxygen defects.

10. The method for preparing high-purity hydrogen and amorphous molybdenum oxide by membraneless full-pH water electrolysis according to claim 1, characterized in that: The membraneless water electrolysis hydrogen production device suitable for the hydrogen production method described in step (3) should at least include a device (1), a metal molybdenum anode (2), a hydrogen evolution cathode (3), a temperature measurement system (4), a stirring device (5), a hydrogen outlet (6), an electrolyte feed port (7) and an electrolyte outlet (8).

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