Patent Application
20230279556
This patent application claims the benefit and priority of the Chinese Patent Application No. CN 202210195071.6 filed on Mar. 1, 2022. The entire disclosure of the above application is incorporated herein by reference.
The present disclosure relates to an electrolysis cell system and a method for preparing hydrogen and oxygen.
The use of an acidic cation exchange membrane in a form of H+ for PEM electrolysis has the following disadvantages that an extremely expensive iridium-containing catalyst is required; the plate material of an anode for an oxidation reaction must be titanium, and an expensive iridium coating is required.
The use of an anion exchange membrane for alkaline electrolysis has the following disadvantages that the membrane has a short service life, and the operating temperature is low.
When a porous separator is used for alkaline electrolysis, the pressure difference between hydrogen and oxygen chambers must be controlled very carefully to avoid gas mixing. In addition, bubbles generated in an electrolyte deteriorate the conductivity of the gap between an electrode and the porous separator.
The application U.S. Pat. No. 8,936,704B1 discloses a technology for preparing hydrogen by electrolysis with an adjustable operating capacity, which relates to a low gas purity of a liquid alkaline electrolyte at a low load, posing a hidden danger of explosion.
The technical problem to be solved in the present disclosure is to overcome defects in the prior art, including the use of precious metal materials, short membrane service life, low operating temperature, high operating requirements and low safety, thereby providing an electrolysis cell system and a method for preparing hydrogen and oxygen. The electrolysis cell system of the present disclosure features low material cost, long membrane service life, high operating temperature, low operating requirements and high safety; when used in the preparation of hydrogen and oxygen, it can obtain gas with relatively high purity.
The present disclosure solves the above-mentioned technical problem through the following technical solutions:
The present disclosure provides an electrolysis cell system, wherein the electrolysis cell system includes:
In the present disclosure, the cation exchange membrane in alkali-ion form is preferably a perfluorinated sulfonic acid membrane in alkali-ion form, further preferably a perfluorinated sulfonic acid membrane in sodium-ion form or a perfluorinated sulfonic acid membrane in potassium-ion form, e.g. a perfluorinated sulfonic acid membrane in sodium-ion form (PFSA-Na). The perfluorinated sulfonic acid membrane is a copolymer with polytetrafluoroethylene as the main chain, a sulfonic acid group as the end group, and perfluorinated vinyl ether as the side chain.
In the present disclosure, the thickness of the cation exchange membrane in alkali-ion form is preferably 8-170 μm, further preferably 15-60 μm, e.g. 50 μm.
In the present disclosure, the equivalent weight (EW) of the cation exchange membrane in alkali-ion form is preferably 700-1,500, further preferably 900-1,100. Wherein the equivalent weight is defined as the weight of the cation exchange membrane in alkali-ion form containing 1 mol of sulfonic acid groups with alkali ions, with a unit of g/mol.
In the present disclosure, the anode catalyst includes conventional transition metals in the art, and preferably includes one or more of Mn, Fe, Co, Ni and Cu, such as stainless steel or nickel powder.
In the present disclosure, the cathode catalyst is preferably a nickel catalyst, more preferably nickel with a high surface area; preferably, the amount of the nickel catalyst is 10 mg/cm2.
In the present disclosure, the cathode catalyst can also be a Pt/C catalyst; preferably, the loading of the Pt/C catalyst is 0-0.25 mg/cm2 rather than 0, more preferably 0.09 mg/cm2 or 0.2 mg/cm2.
In the present disclosure, the aqueous alkaline electrolyte is preferably an alkali metal hydroxide solution, further preferably a NaOH aqueous solution or a KOH aqueous solution, e.g. the NaOH aqueous solution.
Wherein, the inlet concentration of the NaOH aqueous solution can be 1-15 mol/L, preferably 2.5-4 mol/L. At a low current density, the concentration of the NaOH aqueous solution remains stable by means of reverse diffusion through the membrane; at a high current density, however, the inlet concentration of the NaOH aqueous solution must be controlled, so as to balance the concentration difference outside the battery, and prevent a voltage increase caused by great changes in the concentration of the NaOH aqueous solution during electrolysis.
The present disclosure further provides a method for preparing hydrogen and oxygen, wherein, the electrolysis cell system is used to prepare hydrogen and oxygen by electrolysis, wherein hydrogen is discharged from the cathode chamber outlet, and oxygen is discharged from the anode chamber outlet.
Wherein, the aqueous alkaline electrolyte can be fed by the following method: mixing the aqueous alkaline electrolyte flowing out from the anode chamber outlet and the aqueous alkaline electrolyte flowing out from the cathode chamber outlet to obtain a mixed solution, and then passing the mixed solution into the anode chamber inlet and the cathode chamber inlet respectively, to enter the anode chamber and the cathode chamber.
Alternatively, passing the aqueous alkaline electrolyte flowing out from the anode chamber outlet into the cathode chamber inlet to enter the cathode chamber; and passing the aqueous alkaline electrolyte flowing out from the cathode chamber outlet into the anode chamber inlet to enter the anode chamber. In this case, the voltage of the electrolysis cell is relatively lower at a given current density.
Wherein, the operating temperature of the electrolysis cell system is preferably 80-150° C., further preferably 90-110° C.
On the basis of conforming to general knowledge in the art, the preferred conditions can be in any combination, i.e. obtaining preferred examples of the present disclosure.
All reagents and raw materials used in the present disclosure are commercially available.
The present disclosure achieves the following positive and progressive effects:
The present disclosure is further illustrated by the following examples without limiting thereto. Experimental methods without specific conditions indicated in the examples are selected according to conventional methods and conditions or instructions for use of commodities.
An electrolysis cell system in Examples 1-13 of the present disclosure is shown in
The anode chamber inlet 3 and the cathode chamber inlet 6 are used for flow-in of the aqueous alkaline electrolyte; the anode chamber outlet 1 and the cathode chamber outlet 4 are used for flow-out of the aqueous alkaline electrolyte and discharges of gases.
The cation exchange membrane in alkali-ion form 8 in Examples 1-13 is a perfluorinated sulfonic acid membrane in sodium-ion form, with an equivalent weight of 1,100, a thickness of 50 μm and a surface area of 25 cm2-; 10 mg/cm2 nickel powder is used as the anode catalyst 7 in Examples 1-13; Pt/C is used as the cathode catalyst 9, the loading of the cathode catalyst 9 is 0.09 mg/cm2 in Example 1 or 0.2 mg/cm2 in Examples 2-13.
A NaOH aqueous solution with a concentration of 3 mol/L was passed into an electrolysis cell from the anode chamber inlet 3 and the cathode chamber inlet 6 respectively. A power supply was connected for electrolysis at an operating temperature of 90° C. Hydrogen was discharged from the cathode chamber outlet 4, and oxygen was discharged from the anode chamber outlet 1. A NaOH aqueous solution flowing out from the anode chamber outlet 1 and a NaOH aqueous solution flowing out from the cathode chamber outlet 4 was mixed and then passed into the cathode chamber inlet 6 and the anode chamber inlet 3.
A NaOH aqueous solution with a concentration of 3 mol/L was passed into an electrolysis cell from the anode chamber inlet 3 and the cathode chamber inlet 6 respectively. A power supply was connected for electrolysis at an operating temperature of 70° C. Hydrogen was discharged from the cathode chamber outlet 4, and oxygen was discharged from the anode chamber outlet 1. A NaOH aqueous solution flowing out from the anode chamber outlet 1 and a NaOH aqueous solution flowing out from the cathode chamber outlet 4 was mixed and then passed into the cathode chamber inlet 6 and the anode chamber inlet 3.
A power supply was connected for electrolysis at an operating temperature of 80° C. and under the same other conditions as example 2.
A power supply was connected for electrolysis at an operating temperature of 90° C. and under the same other conditions as example 2.
A power supply was connected for electrolysis at an operating temperature of 100° C. and under the same other conditions as example 2.
A NaOH aqueous solution with a concentration of 5 mol/L was passed into an electrolysis cell from the anode chamber inlet 3 and the cathode chamber inlet 6 respectively. A power supply was connected for electrolysis at an operating temperature of 70° C. Hydrogen was discharged from the cathode chamber outlet 4, and oxygen was discharged from the anode chamber outlet 1. A NaOH aqueous solution flowing out from the anode chamber outlet 1 and a NaOH aqueous solution flowing out from the cathode chamber outlet 4 was mixed and then passed into the cathode chamber inlet 6 and the anode chamber inlet 3.
A power supply was connected for electrolysis at an operating temperature of 80° C. and under the same other conditions as example 6.
A power supply was connected for electrolysis at an operating temperature of 90° C. and under the same other conditions as example 6.
A power supply was connected for electrolysis at an operating temperature of 100° C. and under the same other conditions as example 6.
A NaOH aqueous solution with a concentration of 7.5 mol/L was passed into an electrolysis cell from the anode chamber inlet 3 and the cathode chamber inlet 6 respectively. A power supply was connected for electrolysis at an operating temperature of 70° C. Hydrogen was discharged from the cathode chamber outlet 4, and oxygen was discharged from the anode chamber outlet 1. A NaOH aqueous solution flowing out from the anode chamber outlet 1 and a NaOH aqueous solution flowing out from the cathode chamber outlet 4 was mixed and then passed into the cathode chamber inlet 6 and the anode chamber inlet 3.
A power supply was connected for electrolysis at an operating temperature of 80° C. and under the same other conditions as example 10.
A power supply was connected for electrolysis at an operating temperature of 90° C. and under the same other conditions as example 10.
A power supply was connected for electrolysis at an operating temperature of 100° C. and under the same other conditions as example 10.
Conventional PEM electrolysis and a system thereof in the art were adopted. The membrane was Nafion 1135, the anode catalyst was 1.5 mg/cm2 IrO2, the cathode catalyst was 0.1 mg/cm2 Pt/C, and the anode and the cathode of a gas diffusion layer were titanium fiber felt and carbon fiber cloth respectively.
An electrolysis cell system in Examples 1-13 and Comparative example 1 was adopted. According to conditions in Examples 1-13 and Comparative example 1, the system was operated at different current densities, and voltage values were recorded, respectively.
According to conditions in Example 1, the system was operated at different current densities, voltage values were recorded, and a U/I curve shown in
According to conditions in Examples 2-13, the system was operated at different current densities, and voltage values were recorded. Voltage and current value records in Examples 2-13 are shown in Table 1.
According to conditions in Examples 4 and 5, the system was operated at different current densities, voltage values were recorded, and a U/I curve shown in
According to conditions in Examples 2-13, the system was operated at different current densities, voltage values were recorded, and graphs of a relation between U and temperature (T) at different current densities (I) shown in
According to conditions in Examples 4, 8 and 12, the system was operated at different current densities, voltage values were recorded, and a U/I curve at different NaOH concentrations shown in
According to conditions in Example 5 and Comparative example 1, the system was operated under different currents, voltage values were recorded, and a U/I curve shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022101950716 | Mar 2022 | CN | national |
