阅读说明：本技术 一种电解海水三联产的装置及其方法和用途 (Device for electrolyzing seawater for tri-generation, method and application thereof ) 是由 孙晓明 王士元 李鹏松 邝允 于 2019-10-11 设计创作，主要内容包括：本发明公开了一种电解海水三联产的装置,其包括：电压提供装置,阳极,阴极,隔膜,包含电解液的电解槽；其中,所述电解液包含碱液和氯化钠,其中碱液的浓度不小于3mol/L,所述阳极和阴极分别设置在所述电解槽中,与电解液接触,电压提供装置分别与所述阳极和阴极电连接；所述隔膜设置在所述电解槽中,分隔所述阳极和所述阴极,所述隔膜选自阴离子交换膜、阳离子交换膜或碱性隔膜。本发明还公开一种电解海水三联产的方法和上述装置的用途。本发明的电解过程中,在海水中加入碱液,使其浓度不小于3mol/L,即可实现电解海水三联产,即产氢气,产氧气,产氯化钠。(The invention discloses a device for electrolyzing seawater to produce three products, which comprises: a voltage supply, an anode, a cathode, a diaphragm, an electrolytic cell containing an electrolyte; the electrolyte comprises an alkali liquor and sodium chloride, wherein the concentration of the alkali liquor is not less than 3mol/L, the anode and the cathode are respectively arranged in the electrolytic cell and are in contact with the electrolyte, and the voltage supply device is respectively connected with the anode and the cathode; the diaphragm is arranged in the electrolytic cell and separates the anode and the cathode, and the diaphragm is selected from an anion exchange membrane, a cation exchange membrane or an alkaline diaphragm. The invention also discloses a method for electrolyzing the seawater for the tri-generation and the application of the device. In the electrolysis process, the alkali liquor is added into the seawater to ensure that the concentration of the alkali liquor is not less than 3mol/L, and the electrolysis of the seawater tri-generation, namely hydrogen production, oxygen production and sodium chloride production can be realized.)

1. An apparatus for triple co-production of electrolyzed seawater, comprising:

a voltage supply, an anode, a cathode, a diaphragm, an electrolytic cell containing an electrolyte;

wherein the electrolyte comprises alkali liquor and sodium chloride, the concentration of the alkali liquor is not less than 3mol/L, the anode and the cathode are respectively arranged in the electrolytic cell and are contacted with the electrolyte,

the voltage supply device is respectively connected with the anode and the cathode;

the diaphragm is arranged in the electrolytic cell and separates the anode and the cathode, and the diaphragm is selected from an anion exchange membrane, a cation exchange membrane or an alkaline diaphragm.

2. The apparatus of claim 1, wherein the anode is nickel-iron hydrotalcite or sulfide of nickel-iron loaded on a conductive current collector, and the anode can also directly use nickel mesh, nickel-iron mesh, foam nickel-iron, or stainless steel mesh; the cathode is nickel-molybdenum alloy, molybdenum disulfide or simple substance nickel loaded on the conductive current collector.

3. The apparatus of claim 1, wherein the conductive current collector of the anode is selected from nickel foam, nickel-iron foam, stainless steel mesh, ferronickel mesh, or nickel mesh, and the conductive current collector of the cathode is selected from copper foam, stainless steel mesh, nickel mesh, or ferronickel mesh.

4. Root of herbaceous plantThe apparatus according to claim 2, characterized in that said nickel iron sulfide contains two phases of nickel sulfide, said two phases of nickel sulfide being NiS and Ni₃S₂。

5. The apparatus according to claim 2, characterized in that the nickel iron sulfide contains two phases of nickel sulfide, which is obtained by a one-step process without adding nickel iron salt, by hydrothermal reaction of a conductive substrate containing nickel iron in a solution of thiourea.

6. The method for electrolyzing the tri-generation of seawater is characterized in that the device of claim 1 is utilized, the voltage supply device is started, the electrolysis reaction is carried out in the electrolytic cell, two products of oxygen and hydrogen are produced, and after the reaction is carried out for a period of time, three products of hydrogen, oxygen and sodium chloride crystals are produced at the same time.

7. The method of claim 6, wherein the anode is nickel iron hydrotalcite or a sulfide of nickel iron supported on a conductive current collector; the cathode is nickel-molybdenum alloy, molybdenum disulfide or simple substance nickel loaded on the conductive current collector.

8. The method according to claim 7, characterized in that the nickel iron sulphide contains two phases of nickel sulphide, the two phases of nickel sulphide being NiS and Ni₃S₂。

9. The method as claimed in claim 6, wherein the electrolytic cell has an operating voltage in the range of 1.4 to 3V and a current density in the range of 0.01 to 2Acm^-2The temperature range of electrolysis is 25-100 ℃.

10. Use of the apparatus of claim 1 for the simultaneous production of hydrogen, oxygen and sodium chloride crystals.

Technical Field

The invention belongs to the technical field of electrochemistry, and particularly relates to a device for electrolyzing seawater for tri-generation, a method and application thereof.

Background

At present, the most challenging problems facing the energy industry are the exhaustion of fossil fuels and the increase of energy demand, so the construction of high-efficiency energy storage devices and the development of earth-abundant alternative energy sources are very important. Hydrogen, as a clean chemical fuel, can alleviate this energy demand problem, and electrochemical water splitting is one of the promising green technologies for hydrogen production, converting sustainable renewable energy into hydrogen.

Seawater is extremely abundant in the earth and is considered to be the most potential source of electrolyte for electrolysis of water. However, seawater has high salinity, mainly containing sodium ions and chloride ions. In the process of electrolyzing seawater, the concentration of chloride ions in the electrolyte can be continuously increased along with the consumption of water, and the high-concentration chloride ions not only can seriously corrode an anode material, but also can promote the generation of chlorine evolution reaction to reduce the energy efficiency of the electrolyzed water.

Disclosure of Invention

In order to solve the problems, the method of adding high-concentration sodium hydroxide into seawater can reduce the solubility of sodium chloride by utilizing the same ion effect of sodium, inhibit the continuous increase of the concentration of chloride ions and effectively protect the anode material. In addition, the invention also accompanies supersaturated precipitation of sodium chloride under relatively low concentration in the process of electrolyzing the oxygen and hydrogen in the seawater, further reduces the highest concentration which can be reached by chloride ions in the electrolyte, and solves the problem that the anode of the electrolyzed seawater is easy to corrode. In the device of the invention, a temperature zone control system can also be added, namely: the electrolysis process is carried out in a high-temperature area, so that sodium chloride is prevented from being separated out on the surface of the electrode to reduce the performance of the anode; the process of separating out sodium chloride is carried out in a low-temperature region, and the separation out of sodium chloride is accelerated by the principle of reducing the solubility of sodium chloride.

The invention provides a device for electrolyzing seawater for tri-generation, which comprises:

a voltage supply, an anode, a cathode, a diaphragm, an electrolytic cell containing an electrolyte;

wherein the electrolyte comprises alkali liquor and sodium chloride, the concentration of the alkali liquor is not less than 3mol/L, the anode and the cathode are respectively arranged in the electrolytic cell and are contacted with the electrolyte,

the voltage supply device is respectively connected with the anode and the cathode;

the diaphragm is arranged in the electrolytic cell and separates the anode and the cathode, and the diaphragm is selected from an anion exchange membrane, a cation exchange membrane or an alkaline diaphragm.

Of course, in the electrolyte of the present invention, the sodium chloride may be replaced with seawater.

Preferably, the aqueous solution of sodium chloride can be replaced by seawater after removal of calcium and magnesium ions

Preferably, the alkali liquor is sodium hydroxide or potassium hydroxide.

In the electrolyte of the present invention, the sodium chloride concentration may be saturated or unsaturated.

Preferably, the anode is nickel-iron hydrotalcite or sulfide of nickel-iron loaded on a conductive current collector, and the anode can also directly use a nickel net, a nickel-iron net, foamed nickel-iron or a stainless steel net; the cathode is nickel-molybdenum alloy, molybdenum disulfide or simple substance nickel loaded on the conductive current collector.

Wherein the nickel iron hydrotalcite, nickel iron sulfide, nickel molybdenum alloy, or molybdenum disulfide may be synthesized by any suitable method and loaded onto the conductive current collector by any suitable method.

Preferably, the conductive current collector of the anode is selected from nickel foam, nickel-iron foam, stainless steel mesh, nickel-iron mesh or nickel mesh, and the conductive current collector of the cathode is selected from copper foam, stainless steel mesh, nickel mesh or nickel-iron mesh.

Preferably, the nickel iron sulfide contains two-phase nickel sulfide, wherein the two-phase nickel sulfide is NiS and Ni₃S₂. Wherein NiS can improve the activity of oxygen evolution reaction, and Ni₃S₂The corrosion resistance of the material in seawater can be improved.

Preferably, the nickel-iron sulfide contains two-phase nickel sulfide, and the two-phase nickel sulfide is prepared by a one-step method without adding nickel iron salt, and can be obtained by only carrying out hydrothermal reaction on a conductive substrate containing the nickel-iron in a solution of thiourea.

Preferably, the diaphragm function can prevent the mixing of hydrogen and oxygen in the electrolytic cell on one hand, and on the other hand, through the selective permeation of anions and cations of the diaphragm, the diaphragm is more favorable for increasing the concentration of the anode or cathode sodium chloride so as to enable sodium chloride crystals to be more easily separated out from the electrolyte.

The invention provides a method for electrolyzing seawater for tri-generation, which is carried out by utilizing the device of the first aspect, the voltage supply device is started, an electrolysis reaction is carried out in the electrolytic cell, two products of oxygen and hydrogen are generated, and after the reaction is carried out for a period of time, three products of hydrogen, oxygen and sodium chloride crystal are simultaneously generated.

Preferably, the anode is nickel iron hydrotalcite or sulfide of nickel iron loaded on a conductive current collector; the cathode is nickel-molybdenum alloy, molybdenum disulfide or simple substance nickel loaded on the conductive current collector.

Preferably, the nickel iron sulfide contains two-phase nickel sulfide, wherein the two-phase nickel sulfide is NiS and Ni₃S₂。

Preferably, the working voltage range of the electrolytic cell is 1.4-3V, and the current density range is 0.01-2 Acm^-2The temperature range of electrolysis is 25-100 ℃.

A third aspect of the invention provides the use of the apparatus of the first aspect for the simultaneous production of hydrogen, oxygen and sodium chloride crystals.

In a fourth aspect the invention provides the use of the apparatus of the first aspect to increase the rate of precipitation of sodium chloride crystals.

A fifth aspect of the invention provides the use of the apparatus of the first aspect for improving the corrosion resistance of the anode and the stability of the electrolysis apparatus.

Preferably, the diaphragm action makes it possible, on the one hand, to prevent the mixing of hydrogen and oxygen in the cell and, on the other hand, to increase the local sodium chloride concentration by virtue of the ionic conductivity of the diaphragm, so that sodium chloride crystals are more easily precipitated from the electrolyte.

In a preferred embodiment, the anode material is nickel-iron hydrotalcite material with foamed nickel as a base, and the preparation method comprises the following steps:

step 1: nickel nitrate and ferric nitrate were dissolved in deionized water and recorded as solution a.

Step 2: the nickel foam is then freed of the surface oxide film by hydrochloric acid and is ready for use.

And step 3: and (3) electrodepositing the nickel-iron hydrotalcite on the cathode by a constant current method. Wherein the cathode is the foam nickel cleaned in the step 2, the anode is a stainless steel net, and the electroplating solution is the solution A prepared in the step 1. And drying the foamed nickel for later use after the electrodeposition is finished.

Preferably, the mass concentration of the nickel nitrate in the step 1 is 0.01-0.5 mol/L, the mass concentration of the ferric nitrate is 0.001-0.4 mol/L, and the volume of the deionized water is 50 mL.

Preferably, the current density of the cathodic electrodeposition in the step 3 is 10-50 mA cm^-2The time of electrodeposition is 10-30 min.

In a preferred embodiment, the cathode material is nickel-molybdenum alloy based on copper foam, and the preparation method comprises the following steps:

step A: nickel sulfate, sodium citrate, ammonium molybdate and sodium chloride were dissolved in deionized water and designated solution B.

And B: the copper foam was then freed of surface oxides with hydrochloric acid and ready for use.

And C: the nickel-molybdenum alloy is electrodeposited under the condition of water bath heating.

Preferably, the mass concentration of the nickel sulfate in the step A is 0.01-0.1 mol/L, the mass concentration of the sodium citrate is 0.01-0.1 mol/L, the mass concentration of the ammonium molybdate is 0.0003-0.04 mol/L, and the mass concentration of the sodium chloride is 0.02-0.5 mol/L.

Preferably, the electrodeposition conditions in the step C are that the counter electrode is a platinum electrode, the reference electrode is a saturated calomel electrode, and the constant current electrodeposition current density is 100-400 mAcm^-2The electrodeposition time is 1200 to 4800 seconds.

In a preferred embodiment, the anode material can also be a nickel iron sulfide material obtained by taking foamed nickel iron as a substrate and vulcanizing under a hydrothermal condition, and the preparation method comprises the following steps:

step 1: the thiourea was dissolved in deionized water and designated solution a.

Step 2: removing the oxide film on the surface of the foamed nickel iron by hydrochloric acid for standby.

And step 3: transferring the solution A obtained in the step 1 into a hydrothermal kettle, and inserting the foamed nickel iron with the surface oxide film removed in the step 2 into the hydrothermal kettle.

And 4, step 4: and (3) putting the hydrothermal kettle obtained in the step (3) into an oven for reaction at the temperature of 120 ℃ for 12 hours.

Preferably, the amount concentration of the thiourea in the step 1 is 0.01-0.1 mol/L.

Preferably, the reaction temperature of the hydrothermal kettle in the step 4 in the oven ranges from 90 to 180 ℃, and the reaction time is 8 to 24 hours.

The invention has the following beneficial effects:

1. the method can directly utilize the extremely abundant seawater on the earth surface as the source of the electrolyte, reduces the dependence on fresh water resources in the hydrogen production process, and solves the problem of insufficient fresh water resources required by hydrogen production in arid areas with serious water shortage and high demand of fresh water resources.

2. In the electrolysis process, sodium hydroxide is added into the seawater to ensure that the concentration of the sodium hydroxide is not less than 3mol/L, and the electrolysis of the seawater tri-generation (hydrogen production, oxygen production and sodium chloride production) can be realized. On one hand, the high-concentration sodium hydroxide can effectively inhibit the generation of chlorine evolution reaction in seawater electrolysis, improve the electrolysis efficiency and enable energy to be utilized to the maximum extent. On the other hand, the high-concentration sodium hydroxide is added into the electrolyte, due to the same ion effect, the concentration of sodium ions in the electrolyte is increased after the sodium hydroxide is added, and meanwhile, water is reduced due to the occurrence of oxygen evolution and hydrogen evolution reactions in the electrolysis process, so that the concentration of chloride ions and sodium ions in the electrolyte is increased, the precipitation of high-purity sodium chloride crystals can be promoted, sodium chloride with important industrial, agricultural and medical significance can be produced while hydrogen is produced, the triple co-production of the electrolyzed seawater is realized, and the important industrial significance and the environmental protection significance are achieved.

3. The invention firstly discovers that an anion exchange membrane, a cation exchange membrane or an alkaline diaphragm is added in an electrolytic cell to separate a cathode from an anode, so that oxygen and hydrogen generated by electrolysis can be separated, and the concentration of sodium ions and chloride ions can be locally improved in an electrolyte through the ion conductivity of the diaphragm, the precipitation of sodium chloride crystals is accelerated, and the efficiency of the triple co-production of the electrolyzed seawater is greatly improved.

4. The invention discovers for the first time that in the triple co-production of the electrolytic seawater, the anode contains two-phase nickel sulfide (NiS phase and Ni)₃S₂The nickel-iron sulfide of the phase) solves the problems that the common alkaline electrolytic water electrode material is easy to corrode and inactivate and has poor circulation stability when being directly used in seawater electrolysis, the anode can stably work for at least 150 hours under the constant voltage of 1.68V, and the cyclic voltammetry curves before and after the stability test show that the nickel-iron sulfide material of the two-phase nickel sulfide can keep the original performance and has good stability. The principle is that the nickel sulfide of two phases has two-phase interfaces, the activity of the two-phase interfaces is higher, NiS can improve the activity of oxygen evolution reaction, and Ni is arranged at the interfaces₃S₂Is easy to be oxidized to release sulfate ions, and the sulfate ions are combined with carbonate ions contained in the electrolyte to form polyanion groups to be attached to the surface of the nickel iron sulfide. The polyanion shows electronegativity and can repel chloride ions in seawater, so that the chloride ions are far away from the active material, the corrosion of the electrode by the chloride ions is avoided, and the selectivity of the oxygen evolution reaction of the electrode is improved.

Drawings

FIG. 1 is an XRD representation of the sodium chloride crystals precipitated after 136 hours of operation of the seawater electrolysis apparatus of example 1.

FIG. 2 is a graph showing the current density at the electrode surface as a function of time during 136 hours of operation of the seawater electrolysis apparatus of example 1.

FIG. 3 is a graph showing the volumes of hydrogen and oxygen generated by electrolysis at different time intervals in the seawater electrolysis apparatus of example 1.

FIG. 4 is a graph showing the change of the quality of sodium chloride crystals obtained by electrolyzing seawater in the seawater electrolyzing apparatus of example 1 with respect to the time of electrolysis.

FIG. 5 is a graph of current density as a function of time during 37 hours of operation of the seawater electrolysis apparatus of example 4.

FIG. 6 is a plot of cyclic voltammetry for the electrode material before and after stability testing for example 5.

Detailed Description

The present invention will be further described with reference to the following embodiments.