Membrane-free electrolytic water step-by-step hydrogen production system

Abstract

The system comprises an electrochemical reaction module and an electrolyte circulating module, and the electrochemical reaction module comprises an anode chamber, an insulating diaphragm, a cathode chamber and an external direct-current power supply; the electrolyte circulation module comprises a hydrogen separation pool, a regeneration circulation pool and a buffer pool; the hydrogen separation tank is used for receiving the anode electrode liquid which flows out of the anode chamber and is subjected to the reaction and the cathode electrode liquid which flows out of the cathode chamber and is subjected to the reaction, and converging to form a circulating electrolyte solution so as to realize separation of a hydrogen product; the regeneration circulating pool is used for catalyzing regeneration of the circulating electrolyte solution in the hydrogen separation pool and releasing oxygen; the buffer pool is used for fully mixing the solution in the regeneration circulating pool and then circulating the solution into the electrochemical reaction module. According to the invention, the time-space step-by-step preparation of hydrogen and oxygen can be realized under the membrane-free condition, and the efficient production and continuous operation of the process can be realized at room temperature.

Description

Technical Field

[0001] The invention relates to the field of hydrogen production by water electrolysis, and in particular to a membraneless water electrolysis stepwise hydrogen production system. Background Art

[0002] Hydrogen energy has attracted wide attention due to its high combustion calorific value, clean and pollution-free. It is currently the most promising clean energy and has been applied in many fields such as electricity, transportation, and industry. At present, the main methods for preparing hydrogen are coal gasification, petroleum cracking, and water decomposition. Among them, water electrolysis has the advantages of high efficiency, simple operation, environmental friendliness, and no pollution. It is a recognized green hydrogen production method.

[0003] However, the traditional one-step water electrolysis method faces many challenges. The hydrogen and oxygen generated by alkaline water electrolysis are easily mixed, which is not suitable for large-scale application in the context of green electricity. However, expensive ion exchange membranes restrict water electrolysis systems that use diaphragms or membranes as separators. Current water electrolysis technology cannot compete with low-cost gray hydrogen from fossil fuels in terms of cost, which limits its potential for scale-up. By making the two half reactions of water electrolysis independent, hydrogen and oxygen can be produced at different times, spaces and reaction conditions, and disruptive processes have become a promising route to reduce system costs. Summary of the invention

[0004] The object of the present invention is to provide a membraneless water electrolysis stepwise hydrogen production system, which greatly reduces the cost and can achieve hydrogen (H 2 ) and oxygen (O 2 ) can realize step-by-step preparation in time and space under membrane-free conditions, and can achieve efficient production and continuous operation of the process at room temperature.

[0005] In one aspect of the present invention, the present invention provides a membraneless water electrolysis stepwise hydrogen production system. According to an embodiment of the present invention, the system comprises:

[0006] An electrochemical reaction module, the electrochemical reaction module comprising an anode chamber, an insulating diaphragm, a cathode chamber and an external DC power supply; the anode chamber is provided with an anode catalytic electrode and an anode electrode liquid; the cathode chamber is provided with a cathode catalytic electrode and a cathode electrode liquid;

[0007] An electrolyte circulation module, the electrolyte circulation module includes a hydrogen separation cell, a regeneration circulation cell and a buffer cell; the hydrogen separation cell is used to receive the anode electrode liquid that has completed the reaction flowing out of the anode chamber and the cathode electrode liquid that has completed the reaction flowing out of the cathode chamber, and merge them to form a circulating electrolyte solution to achieve separation of hydrogen products; the regeneration circulation cell is used to catalyze the regeneration of the circulating electrolyte solution in the hydrogen separation cell and release oxygen; the buffer cell is used to fully mix the solution in the regeneration circulation cell and recirculate it into the electrochemical reaction module.

[0008] The membraneless water electrolysis step-by-step hydrogen production system can generate H at the cathode 2 At the same time, the products of the anode reaction are reused in the chemical reaction to regenerate and release O 2 and the original electrolyte (KBr), and its subsequent solution is directly circulated into the cathode chamber and the anode chamber for the electrochemical reaction raw material again. 2 and O 2 The spatiotemporal decoupling of the preparation process and the absence of expensive ion exchange membranes in the entire reaction effectively solve the high cost of water electrolysis and the safety issues caused by gas shuttling.

[0009] In addition, the membraneless water electrolysis stepwise hydrogen production system according to the above embodiment of the present invention may also have the following additional technical features:

[0010] In some embodiments of the present invention, the anode electrode solution and the cathode electrode solution are both electrolyte solutions whose solute is potassium bromide.

[0011] In some embodiments of the present invention, the cathode catalytic electrode includes a conductive substrate, a main material bonded to the conductive substrate, and metal ions embedded in the main material by an electrochemical ion embedding method, wherein the main material is an embedded electrode material having an ion accommodating space or an electrode material that can undergo ion embedding-extraction reactions.

[0012] In some embodiments of the present invention, the method for preparing the cathode catalytic electrode comprises the following steps: using an electrolytic cell, embedding metal chromium ions into a main material by an electrochemical ion method to obtain the cathode catalytic electrode, wherein the electrolytic cell comprises a cathode electrode, a reference electrode, an anode electrode and an electrolyte solution. 2 O 7 2 - ) is reduced and deposited on the cathode, forming a semi-permeable membrane of chromium hydroxide (Cr(OH) 3 ), which can significantly suppress the side reaction processes present in the cathode while allowing HER to proceed.

[0013] In some embodiments of the present invention, the cathode electrode is one of porous nickel foam, nickel molybdenum foam, and ruthenium or platinum electrode loaded on nickel foam as a substrate, wherein the pores of the nickel molybdenum foam are 110ppi.

[0014] In some embodiments of the present invention, the electrochemical ion method is as follows: a constant current charge-discharge method is used to perform charge-discharge treatment, and during the charge-discharge process, the metal chromium ions are embedded in the main material.

[0015] In some embodiments of the present invention, the electrochemical ion method comprises the following steps: placing one of potassium dichromate powder, vanadium pentoxide powder, and sodium orthovanadate powder in an electrolyte solution, stirring to fully dissolve, and then electroplating, wherein the electroplating adopts an external direct current with a current density of -50 to -500 mA / cm 2 The electroplating time is 15 to 45 minutes.

[0016] In some embodiments of the present invention, the stirring time is 2 to 10 minutes, and the stirring rate is 500 to 1000 rpm.

[0017] In some embodiments of the present invention, the anode catalytic electrode is an iridium-plated titanium mesh or a ruthenium-plated titanium felt.

[0018] In some embodiments of the present invention, the insulating membrane is a qualitative filter paper, which can effectively prevent the positive and negative electrodes from directly contacting each other and thus causing a short circuit.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) After the electrolyte solution of the present invention is electrochemically converted in a membraneless electrolytic cell, the product is reduced in a regeneration cell (bromate is reduced to bromide ions, BrO 3 - →2Br - +3O 2 ), thereby achieving the regeneration of the electrolyte and realizing the purpose of recycling the electrolyte. In the electrolytic cell, the protons near the cathode combine to generate H under the catalytic conditions of the applied current. 2 At the same time, the bromide ions in the electrolyte react with the OH - The bromate ions in the electrolyte solution after electrolysis are reduced to bromide ions and produce oxygen under the action of the catalyst, which effectively solves the hydrogen and oxygen mixing problem in the electrolytic water system and realizes the time and space decoupling of hydrogen and oxygen. The membraneless electrolytic cell system provided by the present invention has good stability and is stable at a current density of about -100 mA / cm 2 After 8.5 hours of continuous use, the cell voltage is relatively stable. 2 The Faradaic efficiency remains at 65%.

[0021] 2) In the present invention, the water electrolysis reaction is decoupled in time and space, so that the oxygen evolution reaction and the hydrogen evolution reaction are respectively carried out in two different reaction vessels, and the oxygen evolution reaction is a controllable reaction. No membrane component is required between the positive and negative electrodes of the entire reaction system to separate the reactions.

[0022] 3) The present invention directly uses potassium bromide electrolyte as the raw material of the electrolytic cell to electrolyze water. The Faraday efficiency of hydrogen in the reaction process can reach 99.48%. The positive and negative electrodes of the system are equipped with an insulating diaphragm (qualitative filter paper) to prevent the positive and negative electrodes from directly contacting each other. The electrolyte circulates to the cathode at a flow rate of 30 mL / min through a peristaltic pump and then flows into the anode area through the filter paper.

[0023] 4) The catalyst obtained by electroplating in the present invention can promote HER to a great extent, inhibit most of the side reactions in the system, and increase H 2 The selectivity can be effectively operated without a diaphragm, greatly reducing the cost. At the same time, it can be operated at a higher current density (-500mA / cm 2 ) conditions, which is of great significance for commercial applications.

[0024] 5) The present invention uses chromium electroplating on a nickel-molybdenum foam electrode as a catalytic electrode, and shows excellent performance in the experiment of electrolyzing water to produce hydrogen in a membraneless electrolytic cell. 2 , when the full cell voltage is -2.35V, 99.48% H 2 The Faraday efficiency is very high, and in the case of the electrode combination, the overall cell voltage is low, at -2.35 V. When using a 1.5 M KBr solution, the current density is between -100 and -500 mA / cm 2 H can still be efficiently produced 2 . At industrial current density (-500mA / cm 2 ) can maintain electrolysis stability and product distribution for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic structural diagram of a system for producing hydrogen by membraneless water electrolysis stepwise in Example 16 of the present invention, in which: 1, anode chamber; 2, insulating diaphragm; 3, cathode chamber; 4, anode catalytic electrode; 5, cathode catalytic electrode; 6, hydrogen separation tank; 7, regeneration circulation tank; 8, buffer tank; 9, peristaltic pump 1; 10, peristaltic pump 2; 11, peristaltic pump 3;

[0026] Figure 2 Schematic diagram of the structure of the electrolytic cell in Example 1 of the present invention (left), and a schematic diagram of the reaction principle of the anode, cathode in the electrolytic cell and the regeneration device in Example 16 (right);

[0027] Figure 3 Detailed diagram of the membraneless electrolytic cell assembly (a) and the sealing method diagram of the flow battery (b) in Example 10 of the present invention;

[0028] Figure 4This is a field emission transmission electron microscope (TEM) image of the cathode catalytic electrode in Example 1 of the present invention;

[0029] Figure 5 X-ray photoelectron spectroscopy (XPS) graphs of the cathode catalytic electrodes prepared in Example 1 and Comparative Example 1 of the present invention, wherein (a) is a high-resolution XPS spectrum of Mo 3p, and (b) is a high-resolution XPS spectrum of Cr 2p;

[0030] Figure 6 The performance diagram of the electrolytic cells in Comparative Example 1 and Examples 1-4 of the present invention, wherein (a) is the H of the electrolytic cells in Example 1 and Comparative Example 1. 2 Faraday efficiency comparison diagram, (b) is a comparison diagram of the voltage (compared to the standard Ag / AgCl electrode) in the electrolytic cells of Example 1 and Comparative Example 1 over time, (c) is the H of the electrolytic cells of Examples 1-4 2 Faraday efficiency comparison diagram, (d) is a comparison diagram of the voltage (compared to the standard Ag / AgCl electrode) in the electrolytic cell of Example 1-2 over time;

[0031] Figure 7 The performance diagram of the electrolytic cell in Example 1 and Example 5 of the present invention, wherein (a) is the H of the electrolytic cell in Example 1 and Example 5 2 Faraday efficiency comparison chart, (b) is a comparison chart of the change of electrolytic cell voltage (compared to the standard Ag / AgCl electrode) over time in Example 1 and Example 5;

[0032] Figure 8 The performance diagram of the electrolytic cell of Example 1 and Examples 6-9 of the present invention, wherein (a) is the H of the electrolytic cell in Example 6 and Example 7 2 Faraday efficiency comparison chart, (b) H of the electrolytic cells in Examples 1, 8, and 9 2 Faraday efficiency comparison chart;

[0033] Fig. 9 The performance diagram of the electrochemical reaction module of Examples 10-15 of the present invention, wherein (a) is the H of the electrochemical reaction module in Examples 10-15. 2 Faraday efficiency comparison diagram, (b) is a diagram showing the relationship between the electrolytic cell voltage and current density of the membraneless water electrolysis stepwise hydrogen production system in Example 16;

[0034] Fig.10 The voltage and H of the electrolytic cell when the membraneless water electrolysis stepwise hydrogen production system in Example 16 of the present invention continuously works for 8.5 hours 2 Faraday efficiency variation diagram. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] The method for preparing a cathode catalytic electrode comprises the following steps:

[0038] Use Figure 2 The electrolytic cell shown in the figure comprises a cathode electrode, an Ag / AgCl reference electrode, and an anode electrode. The anode electrode is a platinum-plated titanium felt, and the cathode electrode is a nickel-molybdenum foam. A 0.1 mol / L, pH=8 PBS phosphate buffer solution (source leaf) is selected as the solvent, 1.5 M potassium bromide is added to dissolve in the above solvent, and then a 1 mol / L potassium hydroxide solution is added to adjust the pH to 8 to obtain an electrolyte solution. 3.8 mM of the additive potassium dichromate is added to the electrolyte solution, and fully dissolved for 5 minutes, with a stirring rate of 700 rpm; then electroplating is carried out under the condition of an external current, and the electroplating current is: -100 mA / cm 2 , the electroplating time is: 30min. An air inlet is set above the electrolytic cell to introduce purge gas N 2 (20 sccm), and the generated H 2 The content was detected by chromatography.

[0039] The system undergoes the following reaction on the cathode electrode surface: 2H + +2e - →H 2 .

[0040] The following reaction occurs on the anode electrode surface: Br - +3H 2 O→BrO 3 - +6H + +6e - .

[0041] like Figure 4 As shown, a chromium protective layer is indeed formed on the cathode surface during the electroplating process, which confirms that chromium is effectively loaded on the cathode surface.

[0042] The electrochemical performance was tested using an electrochemical workstation (CHI 1140C).

[0043] Example 2

[0044] Preparation method of cathode catalytic electrode. The difference between this embodiment and embodiment 1 is that the cathode electrode is nickel foam and the test current density is -100mA / cm 2 , other conditions and steps are the same as those in Example 1.

[0045] Example 3

[0046] Preparation method of cathode catalytic electrode. The difference between this embodiment and embodiment 1 is that the cathode electrode is nickel molybdenum foam loaded with ruthenium. The preparation conditions are as follows: the nickel foam metal is placed in a ruthenium chloride solution with a concentration of 1mM and immersed for 5min. The test current density is -100mA / cm 2 , other conditions and steps are the same as those in Example 1.

[0047] Example 4

[0048] Preparation method of cathode catalytic electrode. The difference between this embodiment and embodiment 1 is that the cathode electrode is nickel-molybdenum foam loaded with platinum. The preparation conditions are as follows: the nickel foam is placed in a 1mM chloroplatinic acid solution and immersed for 5 minutes. The test current density is -100mA / cm 2 , other conditions and steps are the same as those in Example 1.

[0049] Example 5

[0050] Preparation method of cathode catalytic electrode. The difference between this embodiment and embodiment 1 is that the solvent in the electrolyte solution is changed to 0.1M PBS phosphate buffer solution with pH=7, and KOH is added to adjust the pH to 7. The test current density is -100mA / cm 2 , other conditions and steps are the same as those in Example 1.

[0051] like Figure 7 As shown in a, by comparing and analyzing the hydrogen Faraday efficiency at different pH values, it can be seen that when the electrolyte pH is 8, the overall Faraday efficiency of the system is maintained at about 95% and the system is relatively stable as a whole. Figure 7 b It can be seen that increasing the pH under different pH conditions can effectively inhibit the occurrence of side reactions.

[0052] Example 6

[0053] Preparation method of cathode catalytic electrode. The difference between this embodiment and embodiment 1 is that potassium dichromate additive is not added to the electrolyte solution, and the test current density is -100mA / cm 2 , other conditions and steps are the same as those in Example 1.

[0054] Example 7

[0055] Preparation method of cathode catalytic electrode, the difference between this embodiment and embodiment 1 is that: the cathode electrode is firstly 2 The cathode material after electroplating was placed in an electrolyte containing 3.8 mM potassium dichromate additive to load chromium. Subsequently, the cathode material prepared above was placed in an electrolyte without potassium dichromate for electroplating. The test current density was -100 mA / cm 2 , other conditions and steps are the same as those in Example 1.

[0056] Figure 8 a. The cathode electrode material is modified by first electroplating it in an electrolyte system containing chromium for 30 minutes to obtain a chromium-loaded nickel-molybdenum foam electrode, and then placing it in a chromium-free electrolyte system (the same ratio as the above electrolyte but without potassium dichromate) and an electrolyte system containing chromium, respectively. The investigation shows that the chromium layer obtained by electroplating during the electrolysis process is a dynamic process. If the electroplated nickel-molybdenum foam electrode is to still have good stability and hydrogen evolution Faraday efficiency in the subsequent system, it should be placed in a chromium-containing electrolyte atmosphere.

[0057] Example 8

[0058] Preparation method of cathode catalytic electrode. The difference between this embodiment and embodiment 1 is that the additive added to the electrolyte solution is vanadium pentoxide, and the test current density is -100mA / cm 2 , other conditions and steps are the same as those in Example 1.

[0059] Example 9

[0060] Preparation method of cathode catalytic electrode. The difference between this embodiment and embodiment 1 is that the additive added to the electrolyte solution is sodium orthovanadate, and the test current density is -100mA / cm 2 , other conditions and steps are the same as those in Example 1.

[0061] Comparative Example 1

[0062] The preparation method of the cathode catalytic electrode is different from Example 1 only in that potassium dichromate powder is not added, and other conditions and steps are the same as Example 1.

[0063] The cathode catalytic electrodes prepared in Example 1 and Comparative Example 1 were subjected to morphological tests: field emission scanning electron microscopy (S4800) was used for characterization, with an accelerating voltage (EHT) of 3 kV, a working distance (WD) of 8.6 mm, and a detector type of SE2 detector; transmission electron microscopy (Jeol JEM-2100) was used for characterization, with an operating voltage of 200 kV. The results of the scanning electron microscope showed that the surface of the cathode catalytic electrode synthesized in Example 1 was electroplated with chromium to form an effective chromium protective layer, which could effectively inhibit side reactions during the electroplating process.

[0064] The cathode catalytic electrodes prepared in Example 1 and Comparative Example 1 were characterized by an X-ray tube as a cathode using an X-ray photoelectron spectrometer (VG ESCA2000). All data were calibrated using the C1s peak of 284.8 eV as the internal standard. The test results show that the surface of the cathode catalytic electrode prepared in Example 1 did not change before and after the reaction, as shown in the Mo 3p spectrum (5a). Combined with the Cr 2p spectrum, it can be seen that the valence state of the Cr metal in the catalyst is +3 (576.6 eV) and +6 (586.6 eV), indicating that the performance of the catalyst metal (nickel molybdenum) has not changed after the chromium is loaded on the surface of the nickel molybdenum foam, as shown in FIG. Figure 5 The +6 valence may come from the additive in the electrolyte (K 2 Cr 2 O 7 ) is a proof that chromium hydroxide is formed on the electrode surface.

[0065] Figure 6 ab shows that the chromium loading of the cathode can effectively improve the Faradaic efficiency of the hydrogen reaction, according to Figure 6 The cell voltage data of b shows that chromium loaded on the cathode can effectively inhibit the side reactions of the cathode and stabilize the cell voltage. Figure 6 c It can be seen that Example 1 (nickel molybdenum foam) shows the best H compared with Example 2 (nickel foam), 3 (nickel foam loaded with ruthenium), and 4 (nickel foam loaded with platinum). 2 Faraday efficiency. Figure 6 In d, the electrolytic cell pressures of nickel-molybdenum foam and nickel foam are compared. It can be seen that Example 1 has a lower cell pressure than Example 2, so the overall performance of nickel-molybdenum foam is better.

[0066] Example 10

[0067] like Figure 3 As shown in a, the electrochemical reaction module includes an anode chamber, an insulating diaphragm, a cathode chamber and an external DC power supply; the anode chamber is equipped with an anode catalytic electrode and an anode electrode liquid; the cathode chamber is equipped with a cathode catalytic electrode and a cathode electrode liquid.

[0068] Specifically, the anode chamber is surrounded by an anode plate and an insulating diaphragm, and the anode catalytic electrode is arranged between the anode plate and the insulating diaphragm and is bonded to both; the cathode chamber is surrounded by a cathode plate and an insulating diaphragm, and the cathode catalytic electrode is arranged between the cathode plate and the insulating diaphragm and is bonded to both. Among them, the anode catalytic electrode adopts platinum-coated titanium felt, and the electrochemical reaction area is 1×1cm 2 ; The cathode electrode is made of nickel-molybdenum foam, and the electrochemical reaction area is 1×1cm 2 ; The insulating diaphragm is made of qualitative filter paper; the anode plate and the cathode plate are both 6.5cm×6.5cm graphite plates, which can be disassembled and assembled using fastening bolts.

[0069] The components of the anode electrode liquid and the cathode electrode liquid are the same, both of which are potassium bromide electrolyte solutions. The preparation method is as follows: select 0.1mol / L, pH=8 PBS phosphate buffer solution (source leaf) as the solvent, add 1.5M potassium bromide to dissolve in the above solvent, and then add 1mol / L potassium hydroxide solution to adjust the pH to 8. Add 3.8mM potassium dichromate additive to the electrolyte solution, fully dissolve for 5min, and stir at a rate of 700rpm; then add -100mA / cm 2 Electroplating was carried out for 30 min under current conditions.

[0070] The flow rate of the cathode electrode liquid is 30mL / min. A cathode guide channel is arranged on the cathode plate. The cathode guide channel is distributed in a serpentine shape from bottom to top. The serpentine groove cooperates with the cathode catalytic electrode bonded thereon to form a cathode guide channel. The lower port of the cathode guide channel serves as the cathode liquid inlet, and the upper port is opened as the cathode liquid outlet. The cathode liquid enters the cathode guide channel after passing through the cathode catalytic electrode, and then flows out from the upper port.

[0071] Figure 3 b specifically shows the assembly sequence of the electrochemical reaction modules, which are grouped in order of 1-1', 2-2', 3-3', and 4-4'. Installing them in a diagonal order can ensure good sealing of the flow battery device and prevent the internal electrode material from shifting.

[0072] The performance test was carried out by an electrochemical workstation (CHI 1140C) with a test current density of -100 mA / cm 2 .

[0073] Embodiment 11

[0074] An electrochemical reaction module, the difference between this embodiment and embodiment 10 is that the test current density is -50mA / cm 2 , other conditions and steps are the same as those in Example 10.

[0075] Example 12

[0076] An electrochemical reaction module, the difference between this embodiment and embodiment 10 is that the test current density is -150mA / cm 2 , other conditions and steps are the same as those in Example 10.

[0077] Example 13

[0078] An electrochemical reaction module, the difference between this embodiment and embodiment 10 is that the test current density is -200mA / cm 2 , other conditions and steps are the same as those in Example 10.

[0079] Embodiment 14

[0080] An electrochemical reaction module, the difference between this embodiment and embodiment 10 is that the test current density is -300mA / cm 2 , other conditions and steps are the same as those in Example 10.

[0081] Embodiment 15

[0082] An electrochemical reaction module, the difference between this embodiment and embodiment 10 is that the test current density is -500mA / cm 2 , other conditions and steps are the same as those in Example 10.

[0083] The electrolytic cells of Examples 1-4, 8-9 and the electrochemical reaction modules of Examples 10-15 were subjected to Faraday efficiency tests: Ar was used as a carrier gas, and the gas phase product distribution was determined by using gas chromatography (GC2060) combined with a thermal conductivity detector (TCD).

[0084] H 2 Faraday efficiency calculation formula:

[0085] Where z is H 2 where n is the number of moles of reactant (mol), F is the Faraday constant (96485 C / mol), and Q is the total amount of electricity input during the reaction.

[0086] To obtain the average value and error bar, all Faraday efficiency measurements were repeated three times. The results of gas chromatography showed that the outlet gas composition was mainly H 2 , where H 2 The results were analyzed by TCD in gas chromatography. Figure 6 (c), 8(b), 9(b), and the specific results are summarized in Table 1.

[0087] Table 1 Faraday efficiency of the electrolytic cells of Examples 1-4, 8-9 and the electrochemical reaction modules of Examples 10-15

[0088]

[0089] like Fig. 9 As shown in a, the Faraday efficiency of hydrogen evolution and the cell pressure at the corresponding time were measured at different current densities. 2 The hydrogen Faraday efficiency under these conditions can reach up to 78%, and the overall electrochemical activity can still be maintained at a high current density.

[0090] The electrolytic cells of Examples 1, 5 and Comparative Example 1 and the electrochemical reaction modules of Examples 11-15 were subjected to voltage tests: wherein the electrolytic cells of Examples 1, 5 and Comparative Example 1 were tested using a two-electrode electrolysis method, and the potential difference between the cathode and the anode was the voltage of the electrolytic cell. The electrochemical reaction modules of Examples 11-15 were tested using a three-electrode electrolysis method, which were the anode and cathode and the standard Ag / AgCl reference electrode, respectively, and the measured voltage was the potential difference between the cathode and the silver chloride reference electrode. Fig. 9 As shown in b, the voltage of the electrolytic cell is different under different current densities. Generally speaking, as the electrolysis current density increases, the electrolytic cell voltage gradually increases.

[0091] Example 16

[0092] A membraneless water electrolysis stepwise hydrogen production system comprises an electrochemical reaction module and an electrolyte circulation module.

[0093] The electrochemical reaction module includes an anode chamber 1, an insulating diaphragm 2, a cathode chamber 3 and an external DC power supply; the anode chamber 1 has an anode catalytic electrode 4 and an anode electrode liquid built in; the cathode chamber 3 has a cathode catalytic electrode 5 and a cathode electrode liquid built in; specifically, the electrochemical reaction module used in this embodiment is the electrochemical reaction module of Example 10.

[0094] The electrolyte circulation module includes a hydrogen separation tank 6, a regeneration circulation tank 7 and a buffer tank 8; the hydrogen separation tank 6 is used to receive the anode electrode liquid that has finished the reaction flowing out of the anode chamber 1 and the cathode electrode liquid that has finished the reaction flowing out of the cathode chamber 3, and merge them to form a circulating electrolyte solution to achieve the separation of hydrogen products; the regeneration circulation tank 7 is used to catalyze the regeneration of the circulating electrolyte solution in the hydrogen separation tank 6 and release oxygen, and the circulating electrolyte solution in the hydrogen separation tank 6 enters the regeneration circulation tank 7 through a peristaltic pump 1 9; the buffer tank 8 is used to fully mix the solution in the regeneration circulation tank 7 and then recirculate it into the electrochemical reaction module, the solution in the regeneration circulation tank 7 enters the buffer tank 8 through a peristaltic pump 2 10, and the solution in the buffer tank 8 enters the electrochemical reaction module through a peristaltic pump 3 11. The electrolyte solution circulation speed of the peristaltic pump 3 11 is 30mL / min, and the electrolyte solution circulates into the cathode and then flows into the anode area through the filter paper.

[0095] In the electrolytic cell system, H is generated at the cathode 2 ; Bromate (BrO 3 - ) and H + ; The liquid produced by the cathode and anode is recovered to the gas separation pool, and the bromate ions (BrO 3 - ) solution is pumped into the regeneration tank, where it is reduced to bromide ions under the action of the catalyst and releases O 2 (The specific reaction formula is as follows: Regeneration: BrO 3 - →2Br - +3O 2 ) ; thus achieving H 2 and O 2 Decoupling in time and space effectively solves the problems of gas crossover and high cost in current proton exchange membrane water electrolysis.

[0096] The stability of the membraneless water electrolysis stepwise hydrogen production system was tested: During the test, a constant -100mA / cm was applied to the flow cell. 2 The current density was set at 1000V, and the voltage change of the electrolytic cell was monitored by an electrochemical workstation. The experimental test results showed that the voltage of the electrolytic cell remained almost unchanged at around -3V during the 8.5h long-term electrolysis process. 2 The Faraday efficiency was maintained at 65%. This proved that the chromium-modified nickel-molybdenum foam electrode and the membraneless water electrolysis system can maintain good stability, providing application prospects for industrialization.

[0097] As shown in Figure b, the membraneless water electrolysis step-by-step hydrogen production system can be operated at -100 mA / cm 2 It can maintain stability for a long time under the conditions.

[0098] Fig.10 The graph of the electrolytic cell voltage and H2 Faraday efficiency changes when the liquid flow battery system of the present invention continuously works for 8.5 hours. It is found that the system still maintains good stability during the 8.5 hours of applied current, and the overall hydrogen Faraday efficiency is still maintained at more than 65%. This shows that the membraneless water electrolysis stepwise hydrogen production system has a certain stability under long-term conditions.

[0099] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A membraneless water electrolysis stepwise hydrogen production system, characterized in that: include: An electrochemical reaction module, the electrochemical reaction module comprising an anode chamber, an insulating diaphragm, a cathode chamber and an external DC power supply; the anode chamber is provided with an anode catalytic electrode and an anode electrode liquid; The cathode chamber is provided with a cathode catalytic electrode and a cathode electrode liquid; An electrolyte circulation module, the electrolyte circulation module includes a hydrogen separation cell, a regeneration circulation cell and a buffer cell; the hydrogen separation cell is used to receive the anode electrode liquid that has completed the reaction flowing out of the anode chamber and the cathode electrode liquid that has completed the reaction flowing out of the cathode chamber, and merge them to form a circulating electrolyte solution to achieve separation of hydrogen products; the regeneration circulation cell is used to catalyze the regeneration of the circulating electrolyte solution in the hydrogen separation cell and release oxygen; the buffer cell is used to fully mix the solution in the regeneration circulation cell and recirculate it into the electrochemical reaction module.

2. A membraneless water electrolysis stepwise hydrogen production system according to claim 1, characterized in that: The anode electrode solution and the cathode electrode solution are both electrolyte solutions with potassium bromide as the solute.

3. A membraneless water electrolysis stepwise hydrogen production system according to claim 1, characterized in that: The cathode catalytic electrode includes a conductive substrate, a main material bonded to the conductive substrate, and metal ions embedded in the main material by an electrochemical ion embedding method, wherein the main material is an embedded electrode material with ion accommodation space or an electrode material that can undergo ion embedding-extraction reaction.

4. A membraneless water electrolysis stepwise hydrogen production system according to claim 3, characterized in that: The preparation method of the cathode catalytic electrode comprises the following steps: using an electrolytic cell, embedding metal chromium ions into a main material by an electrochemical ion method to obtain the cathode catalytic electrode, wherein the electrolytic cell comprises a cathode electrode, a reference electrode, an anode electrode and an electrolyte solution.

5. A membraneless water electrolysis stepwise hydrogen production system according to claim 4, characterized in that: The cathode electrode is one of porous nickel foam, nickel molybdenum foam, and ruthenium or platinum electrode loaded on nickel foam as a substrate.

6. A membraneless water electrolysis stepwise hydrogen production system according to claim 4, characterized in that: The electrochemical ion method is as follows: a constant current charge-discharge method is used to perform charge-discharge treatment, and during the charge-discharge process, the metal chromium ions are embedded in the main material.

7. A membraneless water electrolysis stepwise hydrogen production system according to claim 6, characterized in that: The electrochemical ion method comprises the following steps: placing one of potassium dichromate powder, vanadium pentoxide powder and sodium orthovanadate powder in an electrolyte solution, stirring to fully dissolve, and then electroplating, wherein the electroplating adopts external direct current with a current density of -50 to -500 mA / cm 2 The electroplating time is 15 to 45 minutes.

8. A membraneless water electrolysis stepwise hydrogen production system according to claim 7, characterized in that: The stirring time is 2 to 10 minutes, and the stirring speed is 500 to 1000 rpm.

9. The membraneless water electrolysis stepwise hydrogen production system according to claim 1, characterized in that: The anode catalytic electrode is an iridium-plated titanium mesh or a ruthenium-plated titanium felt.

10. The membraneless water electrolysis stepwise hydrogen production system according to claim 1, characterized in that: The insulating diaphragm is qualitative filter paper.

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