A Bifunctional Electrode Room-Temperature Electro-Catalytic Methanol On-line Hydrogen Production System

Abstract

The present invention discloses a dual-functional electrode room-temperature electrocatalytic methanol on-line hydrogen production system. A dual-functional electrode room-temperature electrocatalytic methanol on-line hydrogen production system includes a high-pressure resistant reactor and a power supply. A first dual-functional electrode, a second dual-functional electrode and an electrolyte are arranged in the high-pressure resistant reactor. The first dual-functional electrode and the second dual-functional electrode are immersed in the electrolyte. The positive electrode and the negative electrode of the power supply are respectively connected to the first dual-functional electrode and the second dual-functional electrode in the high-pressure resistant reactor. The electrolyte is an aqueous solution mixed with methanol and alkali. By connecting the power supply and applying a voltage in the high-pressure resistant reactor, hydrogen evolution at the cathode and methanol oxidation at the anode can be achieved, and the final products are hydrogen and sodium formate. In the present invention, the positive and negative electrodes of the power supply are periodically exchanged, and the absolute value of the voltage remains unchanged. The positive and negative conversion of the electrodes is completed by an external power supply control system without any operation on the reaction device.

Description

Technical field:

[0001] The present invention relates to the technical field of electrocatalysis, and in particular to a dual-function electrode room-temperature electrocatalytic methanol online hydrogen production system. Background technology:

[0002] As a clean energy source, hydrogen has become a focal point in global energy development. Traditional fossil fuel hydrogen production technologies, including natural gas reforming, water gas production, and methanol pyrolysis, all produce a mixture of CO2 and hydrogen, inevitably resulting in fossil energy consumption and CO2 emissions. Hydrogen production through water electrolysis faces the challenge of hydrogen and oxygen separation, and the electrodes typically contain precious metals, resulting in high production costs and energy consumption. Therefore, developing new, low-carbon, low-energy, and low-cost hydrogen production technologies is crucial for the development of hydrogen energy. Summary of the invention:

[0003] The present invention solves the problems existing in the prior art and provides a dual-function electrode room-temperature electrocatalytic methanol online hydrogen production system. The online hydrogen production system proposed by the present invention utilizes dual-function nickel-molybdenum alloy thin film electrodes as cathode and anode, and methanol as electrolyte to directly electrocatalytically produce hydrogen, without the need for a diaphragm for hydrogen and oxygen separation.

[0004] The object of the present invention is to provide a bifunctional electrode room-temperature electrocatalytic methanol online hydrogen production system, comprising a high-pressure reactor and a power supply, wherein a first bifunctional electrode, a second bifunctional electrode and an electrolyte are arranged in the high-pressure reactor, the first bifunctional electrode and the second bifunctional electrode are immersed in the electrolyte, the first bifunctional electrode and the second bifunctional electrode are both bifunctional nickel-molybdenum alloy thin film electrodes, the distance between the first bifunctional electrode and the second bifunctional electrode is 2-10 mm, the positive electrode and the negative electrode of the power supply are respectively connected to the first bifunctional electrode and the second bifunctional electrode in the high-pressure reactor, the electrolyte is a mixed aqueous solution of methanol and alkali, and when the power supply is turned on and a voltage is applied in the high-pressure reactor, hydrogen evolution at the cathode and methanol oxidation at the anode can be achieved, and the final products are hydrogen and sodium formate. The positive and negative electrodes of the power supply are exchanged so that the positive electrode and the negative electrode of the power supply are respectively connected to the second bifunctional electrode and the first bifunctional electrode in the high-pressure reactor, the positive and negative pole conversion frequency of the power supply is 5-30 min / time, and the absolute value of the voltage remains unchanged, thereby realizing online hydrogen production from methanol.

[0005] The products of the on-line hydrogen production system proposed by the present invention are hydrogen and sodium formate, and the hydrogen can be directly output at high pressure. During the reaction process, methanol and alkali are replenished in real time to maintain a constant concentration. The present invention periodically exchanges the positive and negative electrodes of the power supply, and the absolute value of the voltage remains unchanged. That is, the hydrogen evolution cathode connected to the negative electrode of the power supply in the previous cycle is switched to the positive electrode of the power supply and becomes the anode for methanol oxidation reaction; the methanol oxidation anode connected to the positive electrode of the power supply in the previous cycle is switched to the negative electrode of the power supply and becomes the cathode for hydrogen evolution reaction. The frequency of electrode positive and negative conversion is 5 - 30 min / time, and the electrode positive and negative conversion is completed by an external power supply control system without any operation on the reaction device.

[0006] The present invention uses an electrode material without noble metals to prepare a highly selective bifunctional catalytic electrode. The developed hydrogen production technology uses a solution containing methanol and alkali as the electrolyte. Hydrogen is produced at the cathode, and methanol is electrocatalytically oxidized at the anode to obtain high-value formate, without the generation of CO2 and O2. There is no need for a diaphragm / proton exchange membrane, and the danger of hydrogen-oxygen mixture explosion in traditional hydrogen production equipment is avoided. The developed hydrogen production technology can directly use methanol and alkali solution to prepare hydrogen on-line, and high-pressure output of hydrogen can be achieved without the aid of a hydrogen compressor, that is, it can be produced and used immediately; the raw materials can be transported in liquid and solid states, avoiding the problems of high-pressure hydrogen storage and transportation, and greatly reducing the costs of hydrogen production, storage and transportation.

[0007] During the continuous process of positive and negative electrode exchange in the on-line hydrogen production system proposed by the present invention, the adsorption ability of the electrode to hydroxide ions is inhibited, thereby inhibiting the oxygen evolution reaction and no oxygen is generated.

[0008] Preferably, the bifunctional nickel-molybdenum alloy thin film electrode is prepared by combining DC magnetron co-sputtering method with electrochemical treatment.

[0009] Preferably, the bifunctional nickel-molybdenum alloy thin film electrode is specifically prepared by the following steps:

[0010] (1) Using the DC magnetron co-sputtering method, using high-purity nickel metal and high-purity molybdenum metal as target materials, deposit a nickel-molybdenum alloy thin film on the substrate;

[0011] (2) Take the nickel-molybdenum alloy thin film obtained in step (1) as the anode and place it in an aqueous solution mixture of methanol with a concentration of 1 - 10 mol / L and NaOH with a concentration of 1 - 10 mol / L, and perform electrochemical activation treatment by cyclic voltammetry to obtain a bifunctional nickel-molybdenum alloy thin film electrode.

[0012] Further preferably, the specific conditions of the DC magnetron co-sputtering method in step (1) are as follows: the sputtering power of the nickel target is 5-30 W, the sputtering power of the molybdenum target is 10-100 W, the sputtering power ratio of nickel to molybdenum is controlled to be 1:2-1:4, the deposition time is 150-1800 s, the substrate rotation speed is 0-25 r / min, the substrate temperature is 20°C-300°C, the chamber pressure during the sputtering process is 0.5-2.5 Pa, Ar gas is introduced during the sputtering process, and its flow rate is 1-100 sccm.

[0013] Further preferably, the substrate in step (1) is stainless steel, copper foam, copper sheet, nickel foam, nickel sheet, silicon wafer, conductive glass or carbon cloth, and molybdenum atoms in the nickel-molybdenum alloy film are distributed in the alloy in the form of single atoms.

[0014] Further preferably, the specific steps of the electrochemical activation treatment using cyclic voltammetry in step (2) are as follows: the nickel-molybdenum alloy film is scanned in the range of 1.0-1.35 V vs. RHE using cyclic voltammetry, the scanning rate is 5-20 mV / s, and the number of scanning cycles is 3-10 to perform electrochemical treatment.

[0015] Preferably, the concentration of methanol in the electrolyte is 0.5-8 mol / L, the concentration of the base is 0.5-8 mol / L, and the molar ratio of methanol to the base is 1:4-8:1.

[0016] Preferably, the base is sodium hydroxide or potassium hydroxide.

[0017] Preferably, the voltage applied in the high-pressure resistant reactor is 1.35-3 V.

[0018] Compared with the prior art, the present invention has the following advantages: the bifunctional electrode ambient temperature electrocatalytic methanol on-line hydrogen production system provided by the present invention has high-purity hydrogen as the gas product, no oxygen or CO2 is generated during the reaction process, it can directly realize ambient temperature electrocatalytic methanol safe on-line hydrogen production, no diaphragm is required for hydrogen-oxygen separation, the reaction rate does not decrease significantly with the increase of gas pressure, and high-pressure output of high-purity hydrogen can be directly achieved without a hydrogen compressor. The anode is a liquid-phase methanol oxidation reaction, and the product is sodium formate. Description of the drawings:

[0019] Figure 1 It is a schematic structural diagram of a bifunctional electrode ambient temperature electrocatalytic methanol on-line hydrogen production system of the present invention;

[0020] Figure 2 It is an X-ray photoelectron spectroscopy (XPS) diagram of the nickel-molybdenum alloy film in Example 1;

[0021] Figure 3 It is a high-angle annular dark field-scanning transmission electron image (HADDF image) of the nickel-molybdenum alloy film in Example 1;

[0022] Figure 4 It is the linear sweep voltammetry test chart (LSV) of the cathodic electrocatalytic hydrogen evolution performance in Example 2;

[0023] Figure 5 It is the linear sweep voltammetry test chart (LSV) of the anodic electrocatalytic oxidation of methanol performance in Example 2;

[0024] Figure 6 It is the gas chromatogram (GC) of the cathodic product in Example 2;

[0025] Figure 7 It is the ion chromatogram of the anodic product in Example 2;

[0026] Explanation of reference numerals: 1, high-pressure resistant reactor; 2, power supply; 3, first bifunctional electrode; 4, second bifunctional electrode; 5, electrolyte solution. Specific implementation manners:

[0027] The following examples are further descriptions of the present invention, rather than limitations to the present invention.

[0028] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. Unless otherwise specified, the experimental materials and reagents in this article are all conventional commercially available products in this technical field.

[0029] Example 1

[0030] A preparation method of a bifunctional nickel-molybdenum alloy thin film electrode, comprising the following steps:

[0031] (1) Deposit a nickel-molybdenum alloy thin film on a nickel foam substrate by direct current magnetron co-sputtering method. Use high-purity nickel metal and high-purity molybdenum metal as targets. The sputtering power of the nickel target is 15 W, the sputtering power of the molybdenum target is 50 W, the deposition time is controlled to be 600 s, the substrate rotation speed is 15 r / min, the substrate temperature is controlled to be 200 °C, the chamber pressure during the sputtering process is controlled to be 1.5 Pa, and Ar gas is introduced during the sputtering process, and its flow rate is controlled to be 30 sccm.

[0032] (2) Use the nickel-molybdenum alloy thin film prepared in step (1) as the anode and place it in an aqueous solution of methanol with a concentration of 8 mol / L and NaOH with a concentration of 8 mol / L. Control the molar ratio of methanol to sodium hydroxide to be 1:1. Use cyclic voltammetry (CV) to scan the nickel-molybdenum alloy thin film in the range of 1.15 V vs. RHE, the scanning rate is 10 mV / s, and the number of scanning cycles is 5. After electrochemical treatment, take out the thin film and wash it with pure water to obtain a bifunctional nickel-molybdenum alloy thin film electrode.

[0033] The nickel-molybdenum alloy thin film prepared in step (1) was characterized by X-ray photoelectron spectroscopy, and the results are as Figure 2 shown.

[0034] The high-angle annular dark field image-scanning transmission electron image (HADDF image) of the nickel-molybdenum alloy thin film prepared in step (1) is as Figure 3 shown. In the figure, the larger and brighter dots are molybdenum atoms, indicating that molybdenum atoms are distributed in the alloy catalyst in the form of single atoms.

[0035] Example 2

[0036] Referring to Example 1, the difference is that: the specific conditions of the DC magnetron co-sputtering method in step (1) are: the sputtering power of the nickel target is 5 W, the sputtering power of the molybdenum target is 10 W, the deposition time is 150 s, the substrate is stationary, the substrate temperature is 20 °C, the chamber pressure during the sputtering process is 0.5 Pa, and Ar gas is introduced during the sputtering process, and its flow rate is 1 sccm; in step (2), cyclic voltammetry was used to scan the nickel-molybdenum alloy thin film in the range of 1.0 V vs. RHE, the scanning rate was 5 mV / s, and the number of scanning cycles was 3 to perform electrochemical treatment.

[0037] Example 3

[0038] Referring to Example 1, the difference is that: the specific conditions of the DC magnetron co-sputtering method in step (1) are: the sputtering power of the nickel target is 25 W, the sputtering power of the molybdenum target is 100 W, the deposition time is 1800 s, the rotation speed of the substrate is 25 r / min, the substrate temperature is 300 °C, the chamber pressure during the sputtering process is 2.5 Pa, and Ar gas is introduced during the sputtering process, and its flow rate is 100 sccm; in step (2), cyclic voltammetry was used to scan the nickel-molybdenum alloy thin film in the range of 1.35 V vs. RHE, the scanning rate was 20 mV / s, and the number of scanning cycles was 10 to perform electrochemical treatment.

[0039] Example 4

[0040] A bifunctional electrode ambient-temperature electrocatalytic methanol in-situ hydrogen production system is as Figure 1As shown in the figure, it includes a high-voltage resistant reactor 1 and a power supply 2. Inside the high-voltage resistant reactor 1, there are a first bifunctional electrode 3, a second bifunctional electrode 4, and an electrolyte 5. The first bifunctional electrode 3 and the second bifunctional electrode 4 are immersed in the electrolyte 5. Both the first bifunctional electrode and the second bifunctional electrode are bifunctional nickel-molybdenum alloy thin film electrodes prepared in Example 1. The bifunctional electrode serves as both a cathode and an anode. The electrolyte is a mixed aqueous solution of methanol (concentration: 8 mol / L) and sodium hydroxide (concentration: 8 mol / L). The molar ratio of methanol to sodium hydroxide is controlled at 1:1, and the distance between the first bifunctional electrode and the second bifunctional electrode is controlled at 5 mm. Connect the DC power supply, and apply a voltage (2 V) in the high-voltage resistant reactor at room temperature. Methanol is oxidized at the anode, and the final products are hydrogen and sodium formate. The hydrogen can be directly output at high pressure. During the reaction process, methanol and alkali are replenished in real time to maintain a constant concentration. The positive and negative electrodes of the power supply are exchanged regularly, and the absolute value of the voltage remains unchanged. That is, the hydrogen evolution cathode connected to the negative electrode of the power supply in the previous cycle is switched to the positive electrode of the power supply and becomes the anode for methanol oxidation reaction; the methanol oxidation anode connected to the positive electrode of the power supply in the previous cycle is switched to the negative electrode of the power supply and becomes the cathode for hydrogen evolution reaction. The frequency of electrode positive and negative conversion is 15 min / time, and the electrode positive and negative conversion is completed by an external power supply control system without any operation on the reaction device.

[0041] Electrochemical tests on hydrogen evolution reaction (abbreviated as HER) and methanol oxidation reaction (abbreviated as MOR) were carried out on the above bifunctional electrode room-temperature electrocatalytic methanol in-situ hydrogen production system. The results are respectively as Figure 4 shown and as Figure 5 shown. Figure 4 and Figure 5 The alloy sample in is the bifunctional nickel-molybdenum alloy thin film electrode prepared in Example 1. The gas generated at the cathode was collected and tested using a gas chromatograph. The results are as Figure 6 shown, with hydrogen evolution at the cathode. The products at the anode were collected and tested using an ion chromatograph. The results are as Figure 7 shown, with methanol oxidation at the anode and the product being sodium formate.

[0042] Example 5

[0043] It is the same as Example 4, except that: the distance between the first bifunctional electrode and the second bifunctional electrode is 2 mm, the concentration of methanol in the electrolyte is 0.5 mol / L, the concentration of alkali is 0.5 mol / L, the molar ratio of methanol to alkali is 1:4, the alkali is potassium hydroxide, the voltage applied in the high-voltage resistant reactor is 1.35 V, and the frequency of power supply positive and negative electrode conversion is 5 min / time.

[0044] Example 6

[0045] Same as Example 4, except that: the distance between the first bifunctional electrode and the second bifunctional electrode is 10 mm, the concentration of methanol in the electrolyte is 8 mol / L, the concentration of the base is 8 mol / L, the molar ratio of methanol to the base is 8:1, and the voltage applied in the high-pressure resistant reactor is 3 V. The conversion frequency of the positive and negative poles of the power supply is 30 min / time.

[0046] The descriptions of the above embodiments are only used to help understand the technical solutions and their core ideas of the present invention. It should be pointed out that for those skilled in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A bifunctional electrode room-temperature electrocatalytic methanol on-line hydrogen production system, characterized in that, It includes a high-voltage resistant reactor and a power supply. Inside the high-voltage resistant reactor, there are a first bifunctional electrode, a second bifunctional electrode and an electrolyte. The first bifunctional electrode and the second bifunctional electrode are immersed in the electrolyte. Both the first bifunctional electrode and the second bifunctional electrode are bifunctional nickel-molybdenum alloy thin film electrodes. The distance between the first bifunctional electrode and the second bifunctional electrode is 2 - 10 mm. The positive and negative electrodes of the power supply are respectively connected to the first bifunctional electrode and the second bifunctional electrode inside the high-voltage resistant reactor. The electrolyte is an aqueous solution mixed with methanol and an alkali. By turning on the power supply and applying a voltage in the high-voltage resistant reactor, cathodic hydrogen evolution and anodic methanol oxidation can be achieved. The final products are hydrogen and sodium formate. By exchanging the positive and negative electrodes of the power supply so that the positive and negative electrodes of the power supply are respectively connected to the second bifunctional electrode and the first bifunctional electrode inside the high-voltage resistant reactor, and the switching frequency of the positive and negative electrodes of the power supply is 5 - 30 min / time, while the absolute value of the voltage remains unchanged, on-line hydrogen production from methanol can be realized. The bifunctional nickel-molybdenum alloy thin film electrode is prepared by combining direct current magnetron co-sputtering method and electrochemical treatment. The bifunctional nickel-molybdenum alloy thin film electrode is specifically prepared through the following steps: (1) Using the direct current magnetron co-sputtering method, high-purity nickel metal and high-purity molybdenum metal are used as target materials to deposit a nickel-molybdenum alloy thin film on the substrate. The specific conditions of the direct current magnetron co-sputtering method are as follows: the sputtering power of the nickel target is 5 - 30 W, the sputtering power of the molybdenum target is 10 - 100 W, the sputtering power ratio of nickel and molybdenum is controlled to be 1:2 - 1:4, the deposition time is 150 - 1800 s, the rotation speed of the substrate is 0 - 25 r / min, the substrate temperature is 20°C - 300°C, the chamber pressure during the sputtering process is 0.5 - 2.5 pa, Ar gas is introduced during the sputtering process, and its flow rate is 1 - 100 sccm. The molybdenum atoms in the nickel-molybdenum alloy thin film are distributed in the alloy in the form of single atoms. (2) Taking the nickel-molybdenum alloy thin film obtained in step (1) as the anode and placing it in an aqueous solution mixed with methanol with a concentration of 1 - 10 mol / L and NaOH with a concentration of 1 - 10 mol / L, cyclic voltammetry is used to scan the nickel-molybdenum alloy thin film in the range of 1.0 - 1.35 V vs. RHE. The scanning rate is 5 - 20 mV / s, and the number of scanning cycles is 3 - 10 cycles for electrochemical treatment to obtain a bifunctional nickel-molybdenum alloy thin film electrode.

2. The bifunctional electrode ambient-temperature electrocatalytic methanol on-line hydrogen production system according to claim 1, wherein The substrate described in step (1) is stainless steel, copper foam, copper sheet, nickel foam, nickel sheet, silicon wafer, conductive glass or carbon cloth.

3. The bifunctional electrode room-temperature electrocatalytic methanol on-line hydrogen production system according to claim 1, characterized in that, In the electrolyte, the concentration of methanol is 0.5 - 8 mol / L, the concentration of the alkali is 0.5 - 8 mol / L, and the molar ratio of methanol to the alkali is 1:4 - 8:

1.

4. The bifunctional electrode ambient temperature electrocatalytic methanol on-line hydrogen production system according to claim 1 or 3, characterized in that, The alkali is sodium hydroxide.

5. The bifunctional electrode ambient-temperature electrocatalytic methanol on-line hydrogen production system according to claim 1, characterized in that, The voltage applied in the high-voltage resistant reactor is 1.35 - 3 V.

Images