CN111962091A - Water electrolysis method and device - Google Patents
Water electrolysis method and device Download PDFInfo
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Abstract
The invention discloses a water electrolysis method and a device, wherein a flow battery and a water electrolysis structure are combined, so that the flow battery can replace a single buffer medium in water electrolysis by a conventional step method, and only the spatial relationship of hydrogen evolution reaction and oxygen evolution reaction in the water electrolysis is decoupled, so that the hydrogen evolution reaction and the oxygen evolution reaction are generated in different spaces, the mixing of hydrogen and oxygen can be avoided, and the purity of the generated oxygen and hydrogen is greatly improved; meanwhile, the hydrogen evolution reaction and the oxygen evolution reaction can be simultaneously generated, so that the hydrogen and the oxygen can be simultaneously generated, the time required by hydrogen production in the step-by-step electrolysis water can be shortened, and the reaction efficiency is improved.
Description
Technical Field
The invention relates to the technical field of electrochemistry, in particular to a water electrolysis method and a water electrolysis device.
Background
Hydrogen gas has the most prominent advantage as an energy source because the combustion product is only water, and hydrogen is therefore considered to be the most desirable energy source material. At present, in order to produce hydrogen, hydrogen can be produced by electrolyzing water, wherein the water can be electrolyzed by a step method. Specifically, an 'electron-coupling-proton buffering medium' is introduced in the reaction process of the electrolyzed water, and the hydrogen evolution reaction and the oxygen evolution reaction of the electrolyzed water can be separated in time and space through the action of the buffering medium, so that the hydrogen production and the oxygen production are two independent steps.
However, when water is electrolyzed by the step method, hydrogen and oxygen are not simultaneously generated, and although the purity of the generated hydrogen and oxygen is high, the time for generating hydrogen and oxygen is long, and the efficiency is reduced.
Therefore, the technical problem to be solved by the technical staff in the field is how to reduce the reaction time, improve the reaction efficiency and ensure that the generated hydrogen and oxygen have higher purity while electrolyzing water to obtain hydrogen and oxygen.
Disclosure of Invention
The embodiment of the invention provides a water electrolysis method and a water electrolysis device, which are used for reducing reaction time, improving reaction efficiency and ensuring that the generated hydrogen and oxygen have higher purity while electrolyzing water to obtain hydrogen and oxygen.
In a first aspect, an embodiment of the present invention provides an electrolytic water device, including:
a flow battery for: generating an active substance;
and an electrolyzed water structure for: under the action of the active substances generated by the flow battery and under the driving of energy, water molecules are electrolyzed, and hydrogen and oxygen are generated simultaneously;
wherein the energy comprises: electrical energy input externally, or chemical energy generated by adjusting parameters of the flow battery.
In a second aspect, an embodiment of the present invention provides a method for electrolyzing water, including:
the flow battery generates active materials;
the electrolytic water structure electrolyzes water molecules under the action of the active substances and the driving of energy, and simultaneously separates out hydrogen and oxygen;
wherein the energy comprises: electrical energy input from outside, or chemical energy generated by adjusting parameters of a flow battery in the water electrolysis device.
The invention has the following beneficial effects:
according to the water electrolysis method and the water electrolysis device provided by the embodiment of the invention, the flow battery is combined with the water electrolysis structure, so that the flow battery can replace a single buffer medium in water electrolysis by a conventional step method, and only the spatial relationship between hydrogen evolution reaction and oxygen evolution reaction in the water electrolysis is decoupled, so that the hydrogen evolution reaction and the oxygen evolution reaction are generated in different spaces, the mixing of hydrogen and oxygen can be avoided, and the purity of the generated hydrogen and oxygen is greatly improved; meanwhile, the hydrogen evolution reaction and the oxygen evolution reaction can be simultaneously generated, so that the hydrogen and the oxygen can be simultaneously generated, the time required by hydrogen production in the step-by-step electrolysis water can be shortened, and the reaction efficiency is improved.
Drawings
FIG. 1 is a schematic structural view of an electrolytic water device provided in an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of an electrolytic water device provided in an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of another water electrolysis apparatus provided in the embodiment of the present invention;
FIG. 4 is a schematic structural diagram of another water electrolysis apparatus provided in the embodiment of the present invention;
FIG. 5 is a schematic diagram of a result of a cyclic voltammetry test provided in an embodiment of the present invention;
FIG. 6 is a graphical representation of the results of another cyclic voltammetry test provided in an example of the invention;
FIG. 7 is a flow chart of a method of electrolyzing water provided in an embodiment of the present invention.
Wherein, 1-a first pump, 2-a second pump, 3-a third pump, 4-a fourth pump, 5-a fifth pump, 6-a sixth pump, 7-a seventh pump, 8-an eighth pump, 10-a flow battery, 11-a positive storage tank, 12-a negative storage tank, 13-an electrochemical battery, m0, m1, m 2-a diaphragm, G1-a first polar plate, G2-a second polar plate, 20-an electrolytic water structure, 21, 22-medium storage tank, 23-anode catalytic bed, 24-cathode catalytic bed, 30a, 30 b-first cavity, 40a, 40 b-second cavity, k 1-first storage space, k 2-second storage space, k 3-third storage space, k 4-fourth storage space, F1-first valve, F2-second valve.
Detailed Description
The following will explain in detail a specific embodiment of a method and apparatus for electrolyzing water according to an embodiment of the present invention with reference to the accompanying drawings. It should be noted that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
An embodiment of the present invention provides an electrolytic water device, as shown in fig. 1, which may include:
a flow battery 10 for: generating an active substance;
and an electrolytic water structure 20 for: under the action of active substances generated by the flow battery 10 and driven by energy, water molecules are electrolyzed, and hydrogen and oxygen are generated simultaneously;
wherein the energy comprises: electrical energy input externally, or chemical energy generated by adjusting parameters of flow battery 10.
Therefore, by combining the flow battery and the water electrolysis structure, the flow battery can replace a single buffer medium (the buffer medium can be understood as an oxidation-reduction buffer medium) in water electrolysis by a conventional step method, and only the spatial relationship between the hydrogen evolution reaction and the oxygen evolution reaction in the water electrolysis is decoupled, so that the hydrogen evolution reaction and the oxygen evolution reaction occur in different spaces, the separation of the hydrogen evolution reaction and the oxygen evolution reaction in the spaces is realized, the mixing and cross permeation of hydrogen and oxygen can be avoided, the purity of the generated hydrogen and oxygen is greatly improved, and the safety of hydrogen production is improved; meanwhile, the hydrogen evolution reaction and the oxygen evolution reaction can be simultaneously generated, so that the hydrogen and the oxygen can be simultaneously generated, the time required by hydrogen production in the step-by-step electrolysis water can be shortened, and the reaction efficiency is improved.
In addition, in the aspect of energy setting, external input electric energy (such as electric energy generated by external input direct current or new energy power generation) can be adopted, and chemical energy generated by adjusting parameters of the flow battery can be adopted, so that in an actual situation, driving energy can be selected according to the actual situation to meet the requirements of different application scenes, and the design flexibility is improved.
In addition, the design of combining the water electrolysis structure with the flow battery can break through the limitation that the traditional flow battery is limited by the concentration of the electrolyte and causes low energy density, and the electric energy can be converted into the chemical energy and the chemical energy can be converted into the hydrogen and the oxygen which can be independently stored and transported through the auxiliary hydrogen production structure (namely the water electrolysis structure). Because the hydrogen and the oxygen can be separated from the system in a storage and transportation mode, the capacity of the whole device is not limited by the upper limit theoretically, and the device has wide application prospect.
Optionally, in an embodiment of the present invention, the electrolytic water structure is specifically configured to:
and adjusting the potential of the active material in the flow battery according to the adjustment of the pH value of the flow battery, so that water molecules are electrolyzed under the action of the active material and the driving of the adjusted potential.
In practical situations, when water molecules are electrolyzed, an oxidation-reduction reaction needs to occur, a certain potential is needed for the oxidation-reduction reaction, and when the potential meets a certain requirement, the oxidation-reduction reaction can be effectively and automatically performed without external input of electric energy, so that the energy for driving the oxidation-reduction reaction is chemical energy.
Therefore, in order to be able to drive the progress of the redox reaction by chemical energy, the pH value of the electrolyte in the flow battery may be adjusted, and the potential of the active material in the electrolyte may be adjusted by the pH value so that the potential may be adjusted to a potential required for the redox reaction, thereby achieving chemical energy driving.
Therefore, the redox reaction is driven by chemical energy, the consumption of external energy can be reduced, the energy consumption of electrolyzed water is further reduced, and the completion of the electrolyzed water can be realized on the basis of energy conservation.
In specific implementation, in the embodiment of the present invention, the following manners may be adopted when the flow battery and the electrolytic water structure are configured:
mode 1:
optionally, in the embodiment of the present invention, the flow battery and the water electrolysis structure are two structures which operate independently.
That is, although the flow cell can provide active substances for the water electrolysis structure, so that the water electrolysis structure can electrolyze water molecules to generate hydrogen and oxygen, the design in the embodiment of the invention can enable the flow cell to operate alone, that is, the operation of the flow cell can be free from the influence of the water electrolysis structure; in a similar way, the water electrolysis structure can also be operated independently, namely the operation of the water electrolysis structure can not be influenced by the flow battery, so that the flow battery and the water electrolysis structure can be operated independently, and the interference caused by the mutual influence between the flow battery and the water electrolysis structure is avoided.
Specifically, in the embodiment of the present invention, in this mode 1, when the flow cell and the electrolytic water structure are provided, the following can be adopted:
case 1:
optionally, in an embodiment of the present invention, as shown in fig. 2, the flow battery includes: a negative reservoir 12 for holding negative electrolyte, a positive reservoir 11 for holding positive electrolyte, and an electrochemical cell 13; the electrochemical cell 13 comprises a plurality of chambers, with separators (e.g., m0, m1, and m2) disposed between different chambers, each chamber being connected to an external power source;
the electrolytic water structure includes: two medium reservoirs (e.g., 21 and 22) for holding reaction medium;
the positive reservoir 11, the negative reservoir 12, and the two medium reservoirs (e.g., 21 and 22) are located in different chambers, respectively, and are connected to different chambers, respectively.
That is, in case 1, the energy for driving the electrolytic water structure to work is externally input electric energy, and by adjusting the externally input electric energy, the work of the electrolytic water structure can be adjusted, and at the same time, the flow battery can be supplied with energy to generate active substances, so that the electrolytic water can generate hydrogen and oxygen simultaneously.
Moreover, through the arrangement, the flow battery and the electrolytic water structure can be independent of each other, the flow battery and the electrolytic water structure can operate independently without interference, and the working efficiency of the flow battery and the electrolytic water structure is improved.
Optionally, in an embodiment of the present invention, as shown in fig. 2, the flow battery may further include: a first pump 1 disposed between the negative reservoir 12 and the electrochemical cell 13, and a second pump 2 disposed between the positive reservoir 11 and the electrochemical cell 13;
the electrolytic water structure further includes: a third pump 3 arranged between one of the media reservoirs (e.g. 21) and the electrochemical cell 13, and a fourth pump 4 arranged between the other media reservoir (e.g. 22) and the electrochemical cell 13.
In this manner, the negative electrolyte in the negative reservoir and the positive electrolyte in the positive reservoir can be delivered to the electrochemical cell by the first pump and the second pump, respectively, so that the negative electrolyte and the positive electrolyte can react in the electrochemical cell to produce an active material.
And the reaction media in the two media storage tanks can be respectively conveyed to the electrochemical cell through the third pump and the fourth pump, so that the active substance and the reaction media are subjected to oxidation-reduction reaction under the driving of external electric energy, and then hydrogen and oxygen are simultaneously generated, and the electrolysis of water is realized.
Alternatively, in an embodiment of the present invention, as shown in fig. 2, the electrochemical cell 13 includes: the first pole plate G1 is positioned on one side of the first cavity, which is far away from the second cavity, and the second pole plate G2 is positioned on one side of the second cavity, which is far away from the first cavity;
the water electrolysis structure comprises catalytic structures (catalytic beds shown as 23 and 24) respectively arranged between the first polar plate G1 and the first chamber and between the second polar plate G2 and the second chamber.
Wherein, since the active substance is located in the electrochemical cell, the reaction medium is also delivered to the electrochemical cell, and the catalytic structure is also provided in the electrochemical cell, the redox reaction is carried out in the electrochemical cell such that both hydrogen and oxygen are generated in the electrochemical cell.
The mixed substance carrying the oxygen and the reaction solution may then be transported through a conduit (not shown in fig. 2) connected to the electrochemical cell, and subjected to a treatment that separates and collects the oxygen; similarly, the mixture of hydrogen and the reaction solution may be transported through a pipe (not shown in fig. 2) connected to the electrochemical cell, and then subjected to a certain treatment, so that hydrogen may be separated and collected.
Thus, the generated hydrogen and oxygen can be collected and stored for subsequent use.
To illustrate, the media reservoir 21 optionally needs to be connected to the second chamber, labeled 2, and, when connected, can be accessed from the top of the second chamber (i.e., the uppermost of the second chamber labeled 2 in fig. 2) and also from the side of the second chamber; thus, in fig. 2, the medium reservoir 21 is shown accessed from the side of the second chamber, and the surface medium reservoir 21 is not connected to the second plate 22.
Similarly, the medium reservoir 22 is connected to the first chamber labeled 1 in the same manner as described above, and the description of the repeated points is omitted.
Optionally, in an embodiment of the present invention, a flow battery includes: a negative electrolyte and a positive electrolyte;
the negative electrolyte includes: hydroxide ions, and anthraquinone and/or anthraquinone derivatives;
the positive electrolyte includes: hydroxyl ions, and ferrocyanide ions.
Among them, the derivatives of anthraquinone can be, but are not limited to: 2,3,6, 7-tetrahydroxyanthraquinone (which may be abbreviated as THAQ), 2, 6-dihydroxyanthraquinone (which may be abbreviated as 2,6-DHAQ), or 1, 5-dimethyl-2, 6-dihydroxyanthraquinone.
The ferrocyanide ions may be provided by salts of ferrocyanide ions, and the salts of ferrocyanide ions may be, but are not limited to: sodium ferrocyanide, potassium ferrocyanide, ammonium ferrocyanide, sodium ferrocyanide, potassium ferrocyanide, ammonium ferrocyanide and other salts.
Also, the concentration of the hydroxide ions in the negative electrolyte and the positive electrolyte may be set to, but not limited to, 0.01moL/L to 4moL/L, and the pH may be set to, but not limited to, 12 to-2.
The water electrolysis process will be described below with reference to the structure shown in FIG. 2.
Take 2,6-DHAQ with alkaline negative electrolyte and sodium ferricyanate with alkaline positive electrolyte as examples.
Stage one:
when the external circuit I is connected and the external circuits II and III are disconnected, the flow battery can be charged; during charging, 2,6-DHAQ can be transported to the third chamber by the action of the first pump 1 and the second pump 2, and ferrocyanide ions (hereinafter abbreviated as Fe (CN))6 4-) Transferring into a fourth chamber to convert 2,6-DHAQ into 2,6-DHAQ, Fe (CN)6 4-Loss of electrons to Fe (CN)6 3-。
Therefore, in the above process, the circulation of the electrolyte is as shown in a and B, respectively.
And a second stage:
the external circuit (I) is turned off, and the external circuits (II) and (III) are respectively turned on.
For external circuit (c):
the lye in the medium reservoir 22 can be transported into the first chamber by the action of the fourth pump 4, since the catalytic structure (cathode catalytic bed as shown in 24) is arranged between the first plate G1 and the first chamber and there is 2,6-reDHAQ in the third chamber, so that now a reduction reaction can take place, the reaction equation being as follows:
2,6-reDHAQ+2H2O+2e-→2,6-DHAQ+H2↑+2OH-；
that is, hydrogen gas may be generated in the electrochemical cell at this time, and the hydrogen gas may be transported through a pipeline and collected and stored through a series of processes.
Also, the above reaction may be referred to as a hydrogen evolution reaction, which includes a cathode reaction and an anode reaction, wherein:
and (3) cathode reaction: 2H2O+2e-→H2↑+2OH-；
And (3) anode reaction: 2,6-reDHAQ-2e-→2,6-DHAQ。
For external circuit (c):
the lye in the medium tank 21 can be fed into the second chamber by the action of the third pump 3, thanks to the catalytic structure (anodic catalytic bed, shown as 23) arranged between the second plate G2 and the second chamber, and the presence of fe (cn) in the fourth chamber6 3-So that oxidation reactions can now take place, the reaction formula is as follows:
4Fe(CN)6 3-+4OH--4e-→4Fe(CN)6 4-+O2↑+2H2O；
that is, oxygen may be generated in the electrochemical cell at this point, and this oxygen may be piped away and collected and stored through a series of processes.
Also, the above reaction may be referred to as an oxygen evolution reaction, which includes a cathodic reaction and an anodic reaction, wherein:
and (3) cathode reaction: 2Fe (CN)6 3-+2e-→2Fe(CN)6 4-；
And (3) anode reaction: 4OH--4e-→O2↑+2H2O。
That is, when the external circuits are simultaneously connected, hydrogen and oxygen can be simultaneously generated, thereby reducing the time consumed for preparing oxygen and hydrogen and improving the reaction efficiency; meanwhile, because the oxygen and the hydrogen are generated in different chambers, the oxygen and the hydrogen can be prevented from permeating and mixing, and the prepared hydrogen and the oxygen can have higher purity.
Therefore, in the above process, the circulation process of the electrolyte is the circulation shown by a | | C and B | | D, respectively.
In practical terms, the first stage and the second stage are cyclically and alternately performed, so that hydrogen and oxygen can be simultaneously obtained while the flow battery and the electrolytic water structure can be independently operated.
Case 2:
optionally, in an embodiment of the present invention, as shown in fig. 3, the method includes: a first cavity 30b and a second cavity 40b, and an electrochemical cell 13;
the electrochemical cell 13 comprises a plurality of chambers, with a separator m0 disposed between different chambers; the first cavity 30b and the second cavity 40b are respectively connected with different chambers;
the first cavity 30b includes: a first storage space k1 and a second storage space k2 independent of each other, the first storage space k1 containing a positive electrolyte and an anode catalytic bed 23;
the second cavity 40b includes: a third storage space k3 and a fourth storage space k4, independent of each other, the third storage space k3 containing a negative electrolyte and a cathode catalytic bed 24;
further comprising: a first valve F1 disposed outside the first chamber 30b and connected to the first storage space k1 and the second storage space k2, respectively, and a second valve F2 disposed outside the second chamber 40b and connected to the third storage space k3 and the fourth storage space k4, respectively.
Wherein the structure in the first chamber except the anode catalytic bed, the structure in the second chamber except the cathode catalytic bed, and the electrochemical cell constitute a flow battery; the first storage space and the third storage space constitute an electrolyzed water structure.
In this case 2, the redox reaction can be driven by chemical energy, that is: the concentration of hydroxyl ions in the negative electrolyte and the positive electrolyte can be adjusted, and further the pH value of the electrolyte is adjusted, so that the electrolyte has a proper potential, the oxidation-reduction reaction is driven to proceed, and the electrolysis of water is realized.
Of course, in practical cases, the second storage space may contain a small amount of positive electrolyte, or may be empty; similarly, the fourth storage space may contain a small amount of negative electrolyte, or may be empty. It may be set according to actual conditions as long as a surplus space is provided in the second storage space and the fourth storage space so as to store the active material.
Alternatively, in an embodiment of the present invention, as shown in fig. 3, two chambers may be provided to simplify the structure of the electrochemical cell 13, thereby simplifying the structure of the water electrolysis apparatus.
Alternatively, in the embodiment of the present invention, as shown in fig. 3, a fifth pump 5 is disposed between the first chamber 30b and the electrochemical cell 13, and a sixth pump 6 is disposed between the second chamber 40b and the electrochemical cell 13.
Also, as shown in fig. 3, the first plate G1 and the second plate G2 of the electrochemical cell 13 need to be connected to an external power source, and the electrochemical cell 13 can be supplied with electric energy by the external power source to charge the flow cell, so that the flow cell generates active substances.
In this way, through the arrangement of the fifth pump and the sixth pump, the positive electrolyte in the first storage space can be conveyed into the electrochemical cell, meanwhile, the negative electrolyte in the third storage space can be conveyed into the electrochemical cell, and when an external power supply provides electric energy, the flow cell can be charged to generate active substances; and continuously, under the action of the fifth pump and the sixth pump, the active substances can be respectively conveyed to the second storage space and the fourth storage space for accumulation, and when the active substances are accumulated to a certain degree, the first valve and the second valve can be opened, so that the active substances respectively enter the first storage space and the third storage space through the first valve and the second valve and react with the corresponding catalytic bed to generate oxygen and hydrogen.
Therefore, in the process of electrolyzing water, the first storage space and the third storage space can have higher concentration of active substances, so that the oxidation-reduction reaction can be accelerated, and the reaction rate can be improved.
Alternatively, in the embodiment of the present invention, the setting of the negative electrolyte and the positive electrolyte may be referred to the setting in case 1, and repeated descriptions are omitted.
Alternatively, in an embodiment of the present invention, when both the negative electrolyte and the positive electrolyte are alkaline electrolytes, then:
the catalyst in the anode catalytic bed may include, but is not limited to:
noble metal-based catalysts resistant to alkaline corrosion, for example: at least one metal such as iridium, ruthenium, rhodium, etc., or an oxide or oxide composite;
or a composite of a noble metal catalyst resistant to alkaline corrosion and a carbon material having a high specific surface area;
or, the noble metal catalyst with alkali corrosion resistance is coated on a metallic titanium substrate or a nickel substrate.
Among them, since the electrolyte is alkaline, from the viewpoint of cost saving, an alkaline-resistant inexpensive metal catalyst may be used instead of the noble metal catalyst, and the selectable inexpensive catalysts may include, but are not limited to: transition metal compounds, such as metallic cobalt, nickel phosphide, nitride, oxide and phosphorus nitride.
The catalyst in the cathode catalyst bed may include, but is not limited to:
noble metal-based catalysts resistant to alkaline corrosion, for example: at least one of platinum, platinum black, platinum oxide, or a platinum alloy doped with nitrogen, phosphorus, or the like;
or a composite of a noble metal catalyst resistant to alkaline corrosion and a carbon material having a high specific surface area (for example, graphene, carbon nanotubes, carbon black, etc.).
Among them, since the electrolyte is alkaline, from the viewpoint of cost saving, an alkaline-resistant inexpensive metal catalyst may be used instead of the noble metal catalyst, and the selectable inexpensive catalysts may include, but are not limited to: transition metal compounds such as metallic nickel, molybdenum, tungsten phosphide, nitride, oxide, carbide and phosphorus nitride.
The water electrolysis process will be described below with the structure shown in FIG. 3.
Take 2,6-DHAQ with alkaline negative electrolyte and sodium ferricyanate with alkaline positive electrolyte as examples.
Stage one:
upon activation of the fifth pump 5 and the sixth pump 6, Fe (CN) in positive electrolyte in the first storage space k1 may be pumped6 4-Into the left chamber in fig. 3 (hereinafter referred to as chamber 1), while also the 2,6-DHAQ in the negative electrolyte in the third storage space k3 can be transferred into the right chamber in fig. 3 (hereinafter referred to as chamber 2); when the external power supply supplies power, the flow battery is charged, so that Fe (CN) in the chamber 16 4-Loss of electrons to Fe (CN)6 3-The 2,6-DHAQ in chamber 2 gets electrons to become 2, 6-reDHAQ.
Then, continuing to drive the fifth pump 5 and the sixth pump 6, Fe (CN)6 3-And 2,6-reDHAQ into the second storage space k2 and the fourth storage space k4, respectively, such that Fe (CN)6 3-Accumulation is performed in the second storage space k2 and 2,6-reDHAQ is accumulated in the fourth storage space k 4.
And a second stage:
for the second cavity 40 b:
when the 2,6-reDHAQ in the fourth storage space k4 has accumulated to a certain extent (which can be controlled according to practical conditions), the second valve F2 can be opened to allow the 2,6-reDHAQ in the third storage space k3 to contact with the cathode catalyst bed, the pH value of the negative electrolyte can be adjusted by adjusting the concentration of hydroxide ions due to the presence of hydroxide ions in the third storage space k3, and the reduction reaction in the third storage space k3 can be driven when the potential of the negative electrolyte reaches a certain value, and the reaction formula is as follows:
2,6-reDHAQ+2H2O+2e-→2,6-DHAQ+H2↑+2OH-；
that is, hydrogen gas may be generated in the third storage space k3 at this time, and the hydrogen gas may be delivered through a pipe (not shown in fig. 3) and collected and stored through a series of processes.
For the first cavity 30 b:
to be Fe (CN) in the second storage space k26 3-To a certain extent (can be based onActual situation controlling), the first valve F1 can be opened, so that fe (cn) in the first storage space k16 3-In contact with the anode catalytic bed 23, since hydroxyl ions are present in the first storage space k1, the pH of the positive electrolyte can be adjusted by adjusting the concentration of hydroxyl ions, and the oxidation reaction in the first storage space k1 can be driven when the potential of the positive electrolyte reaches a certain value, and the reaction formula is as follows:
4Fe(CN)6 3-+4OH--4e-→4Fe(CN)6 4-+O2↑+2H2O；
that is, oxygen may be generated in the first storage space k1, and the oxygen may be transported out through a pipeline (not shown in fig. 3) and collected after a series of treatments or directly exhausted.
Mode 2:
optionally, in an embodiment of the present invention, the flow battery and the electrolytic water structure are an integral structure.
That is to say, the flow battery and the water electrolysis structure are arranged together, and although the flow battery and the water electrolysis structure cannot operate independently, the structure is compact, so that the integration level of the water electrolysis device can be improved, and the volume of the water electrolysis device can be reduced.
Optionally, in an embodiment of the present invention, as shown in fig. 4, the method includes: a first cavity 30a and a second cavity 40a, and an electrochemical cell 13;
the electrochemical cell 13 comprises a plurality of chambers, with a separator m0 disposed between different chambers; the first cavity 30a and the second cavity 40a are respectively connected with different chambers;
the first chamber 30a contains a positive electrolyte and an anode catalytic bed 23, and the second chamber 40a contains a negative electrolyte and a cathode catalytic bed 24.
Therefore, the flow battery and the water electrolysis structure can be integrally arranged, water can be electrolyzed while the flow battery works, the time required by water electrolysis can be reduced integrally, and the electrolysis efficiency can be improved.
Alternatively, in the embodiment of the present invention, as shown in fig. 4, a seventh pump 7 is disposed between the first chamber 30a and the electrochemical cells 13, and an eighth pump 8 is disposed between the electrochemical cells 13 in the second chamber 40 a;
the electrochemical cell 13 includes a first plate G1 and a second plate G2, and the first plate G1 and the second plate G2 are connected to an external power source.
Therefore, the electrolyte in the first cavity and the electrolyte in the second cavity can be conveyed to the electrochemical cell through the seventh pump and the eighth pump, the flow cell can be charged through electric energy provided by an external power supply, active electrolyte (namely active substances) is generated in the electrochemical cell, the active electrolyte is input into the first cavity and the second cavity through pipelines, oxidation-reduction reaction occurs under the action of respective catalytic beds, water electrolysis is realized, and hydrogen and oxygen are simultaneously prepared.
Alternatively, in the embodiment of the present invention, the setting of the negative electrolyte and the positive electrolyte may be referred to the setting in case 1, and repeated descriptions are omitted.
Moreover, the arrangement of the anode catalytic bed and the cathode catalytic bed can be referred to the arrangement in case 2, and the repeated description is omitted.
The water electrolysis process will be described below with reference to the structure shown in FIG. 4.
Take 2,6-DHAQ with alkaline negative electrolyte and sodium ferricyanate with alkaline positive electrolyte as examples.
Upon activation of the seventh pump 7 and the eighth pump 8, Fe (CN) in the positive electrolyte in the first chamber 30a may be injected6 4-Into the left chamber in fig. 4 (hereinafter referred to as chamber 1), while the 2,6-DHAQ in the negative electrolyte in the second chamber 40a can also be transferred into the right chamber in fig. 4 (hereinafter referred to as chamber 2); when the external power supply supplies power, the flow battery is charged, so that Fe (CN) in the chamber 16 4-Loss of electrons to Fe (CN)6 3-The 2,6-DHAQ in chamber 2 gets electrons to become 2, 6-reDHAQ.
Then, continuing to drive the seventh pump 7 and the eighth pump 8, Fe (CN)6 3-And 2,6-reDHAQ, respectivelyInto the first and second cavities 30a and 40 a.
For the second cavity 40 a:
2,6-reDHAQ is in contact with the cathode catalytic bed 24, and because hydroxide ions exist in the cavity, the pH value of the negative electrolyte can be adjusted by adjusting the concentration of the hydroxide ions, and the reduction reaction in the cavity can be driven when the potential of the negative electrolyte reaches a certain value, and the reaction formula is as follows:
2,6-reDHAQ+2H2O+2e-→2,6-DHAQ+H2↑+2OH-；
that is, hydrogen gas may be generated in the second chamber 40a, and the hydrogen gas may be transported out through a pipe (not shown in fig. 4) and collected and stored through a series of processes.
For the first cavity 30 a:
Fe(CN)6 3-and anode catalytic bed 23, and because there is hydroxyl ion in the chamber, the pH of the positive electrolyte can be adjusted by adjusting the concentration of hydroxyl ion, and when the potential of the positive electrolyte reaches a certain value, the oxidation reaction can be driven to occur in the chamber, and the reaction formula is as follows:
4Fe(CN)6 3-+4OH--4e-→4Fe(CN)6 4-+O2↑+2H2O；
that is, oxygen may be generated in the first chamber 30a, and the oxygen may be transported out through a pipeline (not shown in fig. 4), and collected and stored after a series of processes.
That is, with the structure shown in fig. 4, the electrolysis of water molecules can be driven by chemical energy to produce hydrogen and oxygen, so that the consumption of external energy can be reduced, and the effect of energy saving can be achieved.
In order to verify that the alkaline flow battery constructed by the 2,6-DHAQ and the sodium ferricyanide can replace a single buffer medium in the electrolyzed water by a conventional step method, and a cyclic voltammetry test is carried out.
Testing one:
1.1, preparation:
preparing active substance electrolyte of 2,6-DHAQ and ferrocyanide, wherein the concentration of the active substance can be 0.2mmoL/L, and the medium in the electrolyte can be potassium hydroxide solution with pH value of 14.
1.2, test conditions:
the cyclic voltammetry test adopts a three-electrode system, the working electrode is a glassy carbon electrode, the reference electrode is an Ag/AgCl electrode (the parameter is 3M NaCl, 213mVvs. SHE), the counter electrode is a platinum electrode, and the test is carried out by using an AUTUlab electrochemical workstation and a ring disk electrode.
The test conditions included: the scanning speed is 100mV/s, and the scanning range is-1.6V-1.2V.
1.3, test results:
referring to the test result diagram shown in fig. 5, it can be seen that:
the redox peak potentials of 2,6-DHAQ and ferrocyanide are both in the middle of the initial potentials for hydrogen evolution (i.e., reduction, which can be represented by HER) and oxygen evolution (i.e., oxidation, which can be represented by OER) under the same conditions.
Wherein the redox peak of 2,6-DHAQ has a potential of about 0.68V (vs. SHE), and the redox peak of ferrocyanide has a potential of about 0.5V (vs. SHE).
From the above results, it can be determined that:
2,6-DHAQ and ferrocyanide can be used as a buffering medium for electron-proton coupling in the step-by-step hydrogen production reaction by water electrolysis to realize water electrolysis.
And (2) testing:
2.1, preparation:
preparing an active substance electrolyte of 2,3,6,7-THAQ and ferrocyanide, wherein the concentration of the active substance can be 0.2mmoL/L, and the medium in the electrolyte can be a potassium hydroxide solution with the pH value of 14.
2.2, test conditions:
the cyclic voltammetry test adopts a three-electrode system, the working electrode is a glassy carbon electrode, the reference electrode is an Ag/AgCl electrode (the parameter is 3M NaCl, 213mVvs. SHE), the counter electrode is a platinum electrode, and the test is carried out by using an AUTUlab electrochemical workstation and a ring disk electrode.
The test conditions included: the scanning speed is 100mV/s, and the scanning range is-1.4V-1.0V.
2.3, test results:
referring to the test result diagram shown in fig. 6, it can be seen that:
the redox potential of 2,3,6,7-THAQ is about 0.80V (vs. SHE) and the redox peak of ferrocyanide is about 0.5V (vs. SHE), both in the middle of the initial potentials of hydrogen evolution (i.e. reduction) and oxygen evolution (i.e. oxidation) under the same conditions.
From the above results, it can be determined that:
2,3,6,7-THAQ and ferrocyanide can be used as a buffering medium for electron-proton coupling in the step-by-step hydrogen production reaction by water electrolysis to realize water electrolysis.
Based on the same inventive concept, an embodiment of the present invention provides a method for electrolyzing water, as shown in fig. 7, including:
s701, generating active substances by the flow battery;
s702, electrolyzing water molecules by an electrolytic water structure under the action of active substances and the driving of energy, and simultaneously separating out hydrogen and oxygen; wherein the energy comprises: electrical energy input from the outside, or chemical energy generated by adjusting parameters of a flow battery in the water electrolysis device.
By combining the flow battery and the water electrolysis structure, the flow battery can replace a single buffer medium in the water electrolysis by a conventional step method, and only the spatial relationship between the hydrogen evolution reaction and the oxygen evolution reaction in the water electrolysis is decoupled, so that the hydrogen evolution reaction and the oxygen evolution reaction occur in different spaces, the mixing of hydrogen and oxygen can be avoided, and the purity of the generated oxygen and hydrogen is greatly improved; meanwhile, the hydrogen evolution reaction and the oxygen evolution reaction can be simultaneously generated, so that hydrogen and oxygen can be simultaneously generated, the time required by hydrogen production and oxygen production in the electrolyzed water can be shortened, and the reaction efficiency is improved.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (11)
1. An apparatus for electrolyzing water, comprising:
a flow battery for: generating an active substance;
and an electrolyzed water structure for: under the action of the active substances generated by the flow battery and under the driving of energy, water molecules are electrolyzed, and hydrogen and oxygen are generated simultaneously;
wherein the energy comprises: electrical energy input externally, or chemical energy generated by adjusting parameters of the flow battery.
2. The electrolytic water device of claim 1, wherein the electrolytic water structure is specifically configured to:
and adjusting the potential of the active material in the flow battery according to the adjustment of the pH value of the flow battery, so that the water molecules are electrolyzed under the action of the active material and the driving of the adjusted potential.
3. The electrolytic water device of claim 1 wherein the flow battery and the electrolytic water structure are two structures that operate independently of each other.
4. The electrolytic water device of claim 3, wherein the flow battery comprises: a negative reservoir for holding a negative electrolyte, a positive reservoir for holding a positive electrolyte, and an electrochemical cell; the electrochemical cell comprises a plurality of chambers, wherein diaphragms are arranged among different chambers, and each chamber is connected with an external power supply;
the electrolytic water structure includes: two medium storage tanks for placing reaction medium;
the positive storage tank, the negative storage tank and the two medium storage tanks are respectively positioned in different cavities and are respectively connected with different cavities.
5. The electrolytic water device of claim 4, wherein the electrochemical cell comprises: the device comprises a first chamber, a second chamber, a third chamber and a fourth chamber which are positioned between the first chamber and the second chamber, a first polar plate positioned on one side of the first chamber, which is far away from the second chamber, and a second polar plate positioned on one side of the second chamber, which is far away from the first chamber;
the water electrolysis structure comprises a catalytic structure, and the catalytic structure is respectively arranged between the first polar plate and the first cavity and between the second polar plate and the second cavity.
6. The electrolytic water device of claim 3, comprising: a first cavity and a second cavity, and an electrochemical cell;
the electrochemical cell comprises a plurality of chambers, and separators are arranged among the chambers; the first cavity and the second cavity are respectively connected with different cavities;
the first cavity includes: a first storage space and a second storage space which are independent from each other, wherein the first storage space contains positive electrolyte and an anode catalytic bed;
the second cavity includes: a third storage space and a fourth storage space which are independent of each other, wherein the third storage space contains negative electrolyte and a cathode catalyst bed;
further comprising: the first valve is arranged outside the first cavity and is respectively connected with the first storage space and the second storage space, and the second valve is arranged outside the second cavity and is respectively connected with the third storage space and the fourth storage space.
7. The electrolytic water device of claim 6, wherein there are two chambers.
8. The electrolytic water device of claim 1, wherein the flow battery is a unitary structure with the electrolytic water structure.
9. The electrolytic water device of claim 8, comprising: a first cavity and a second cavity, and an electrochemical cell;
the electrochemical cell comprises a plurality of chambers, and separators are arranged among the chambers; the first cavity and the second cavity are respectively connected with different cavities;
the first cavity is filled with positive electrolyte and an anode catalytic bed, and the second cavity is filled with negative electrolyte and a cathode catalytic bed.
10. The electrolytic water device of claim 1, wherein the flow battery comprises: a negative electrolyte and a positive electrolyte;
the negative electrolyte includes: hydroxide ions, and anthraquinone and/or anthraquinone derivatives;
the positive electrolyte includes: the hydroxide ion, and the ferrocyanide ion.
11. A method of electrolyzing water, comprising:
the flow battery generates active materials;
the electrolytic water structure electrolyzes water molecules under the action of the active substances and the driving of energy, and simultaneously separates out hydrogen and oxygen;
wherein the energy comprises: electrical energy input from outside, or chemical energy generated by adjusting parameters of a flow battery in the water electrolysis device.
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