CN113355682B - Iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material, preparation method and application thereof - Google Patents
Iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material, preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses an iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material, a preparation method and application thereof. The preparation method comprises the following steps: the liquid phase reaction system mainly composed of hydrogen fluoride, hydroxide, cobalt salt, ferrous salt and water is reacted under the protection of nitrogen, and the iron doped trifluoro cobaltate oxygen evolution electrocatalytic material is obtained. The invention also discloses application of the electrocatalytic material as an oxygen evolution electrocatalyst in hydrogen production by water electrolysis. The preparation process of the electrocatalytic material is simple, raw materials are cheap and easy to obtain, the oxygen evolution overpotential of the electrocatalytic material in a 1.0mol/LKOH solution is lower than that of an iridium noble metal electrode under the same condition, and the oxygen evolution electrocatalytic performance and the electrocatalytic stability are excellent, so that the electrocatalytic material is expected to be applied to large-scale production of photovoltaic, wind power and hydroelectric hydrogen.
Description
Technical Field
The invention relates to an electrocatalytic oxygen evolution material, in particular to a preparation method of an iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material taking cobalt ions as coordination center ions and fluorine ions as ligands, and application of the electrocatalytic oxygen evolution material in the aspect of electrocatalytic oxygen evolution in water electrolysis hydrogen production, belonging to the technical field of renewable energy materials.
Background
The solar photovoltaic water electrolysis hydrogen production, wind energy water electrolysis hydrogen production or hydroelectric power generation hydrogen production is an important method for obtaining clean hydrogen energy. Noble metals ruthenium and iridium and their oxides are well-known oxygen evolution electrocatalysts with excellent performance. The publication No. CN112853391A discloses a preparation method of ruthenium oxide supported double metal hydroxide and application of the ruthenium oxide supported double metal hydroxide in electrocatalytic oxygen evolution, and the publication No. CN112760677A discloses an iridium-tungsten alloy nano material, a preparation method of the iridium-tungsten alloy nano material and application of the iridium-tungsten alloy nano material as an acidic oxygen evolution reaction catalyst. The research on inexpensive and efficient non-noble metal catalysts is a key for realizing low-cost water electrolysis hydrogen production, and is also an effective way for producing hydrogen by using renewable energy sources.
The complete reaction of electrolyzed water involves a cathodic hydrogen evolution reaction of 2 electron transfer and an anodic oxygen evolution reaction of 4 electron transfer.
2H + +2e＝H 2 Cathode 2 electron transfer reaction
4OH - -4e＝H 2 O+O 2 Anode 4 electron transfer reaction
Only if the energy consumption of the whole reaction is reduced, the current efficiency of the electrolyzed water can be truly improved, and the low energy consumption and high efficiency hydrogen production can be realized. From the reaction mechanism, the mechanism of the 4 electron transfer reaction is more complex than that of the 2 electron transfer reaction, and the reaction resistance or the reaction energy barrier is also much larger. Therefore, reducing the reaction energy barrier of 4-electron oxygen evolution reaction is the key to reducing energy consumption in the electrolytic water hydrogen production reaction.
Although some transition metal oxides or hydroxides are used as oxygen evolution electrocatalytic materials, their oxygen evolution overpotential is still large and cannot meet the requirements of practical applications. In particular, excessive hydrogen ions generated by oxygen evolution may locally dissolve the transition metal oxide or hydroxide electrode, thereby affecting the electrolysis efficiency and the service life thereof.
Disclosure of Invention
In order to overcome the defects of the existing electrolytic water oxygen evolution electrocatalyst, reduce energy consumption and improve current efficiency, the invention aims to design a novel iron-doped trifluoro cobaltate oxygen evolution electrocatalyst material, a preparation method thereof and application of the novel iron-doped trifluoro cobaltate oxygen evolution electrocatalyst material in the aspect of hydrogen production by water electrolysis.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a preparation method of an iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material, which comprises the following steps: the uniform water phase mixed reaction system mainly composed of hydrogen fluoride, hydroxide, cobalt salt, ferrous salt and water reacts for 0.5 to 2 hours at the temperature of-2 to 99 ℃ under the protection of nitrogen to obtain the iron doped trifluoro compoundCobaltate oxygen evolution electrocatalytic material of formula MCo (1-x) Fe x F 3 M represents a charge balance ion, and 0 < x < 1.
In some embodiments, the preparation method specifically includes:
electrolyte is added into the mixed solution of hydrogen fluoride and hydroxide, and the temperature of the mixed solution is controlled below minus 2 ℃;
and (3) mixing and grinding cobalt salt and ferrous salt, directly adding the mixture into the mixed solution, carrying out ultrasonic oscillation, and then heating to 85-99 ℃ to continue to react for 0.5-2h to obtain the iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material.
In some embodiments, the molar ratio of ferrous salt to cobalt salt is y:1, wherein y > 0, preferably 0 < y < 1.
The embodiment of the invention also provides the iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material prepared by the method, the crystal structure of the material is a perovskite type cubic crystal system, and the space group is P m 3 m A space group represented by the chemical formula MCo (1-x) Fe x F 3 M represents a charge balance ion, and 0 < x < 1.
The embodiment of the invention also provides application of the iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material as an oxygen evolution electrocatalyst in the field of water electrolysis hydrogen production.
Correspondingly, the embodiment of the invention also provides a method for producing hydrogen by water electrolysis, which comprises the following steps:
preparing the iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material into an iron-doped trifluoro cobaltate electrode, wherein the iron-doped trifluoro cobaltate electrode comprises a carbon paste electrode, a nickel-based electrode, a titanium-based electrode or a stainless steel-based electrode;
the iron-doped trifluoro cobaltate electrode is used as an oxygen evolution electrode, nickel is used as a hydrogen evolution electrode, and is matched with an alkaline aqueous solution to form an electrolytic water hydrogen production system, and the electrolytic water hydrogen production is realized by electrifying between the oxygen evolution electrode and the hydrogen evolution electrode.
Compared with the prior art, the preparation process is simple, the raw materials are cheap and easy to obtain, cobalt ions are adopted as central ions, a certain amount of iron ions are doped, potassium ions or sodium ions are adopted as charge balance ions, fluorine ions are adopted as ligands, the novel electrocatalytic oxygen evolution material is generated through the coordination reaction of the cobalt ions and the ligands in a solvent, and the oxygen evolution overpotential of the electrocatalytic material in a 1.0mol/LKOH solution is lower than that of an iridium noble metal electrode under the same condition, so that the electrocatalytic oxygen evolution material has excellent oxygen evolution performance and electrocatalytic stability, and is expected to be applied to large-scale hydrogen production in photovoltaic, wind power and hydropower.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings may be obtained according to the drawings without inventive effort to those skilled in the art.
FIG. 1 is a schematic diagram of KeFF in an exemplary embodiment of the present invention 3 、KCoF 3 、KCo 0.75 Fe 0.25 F 3 X-ray powder diffraction pattern of (2);
FIG. 2A is a KCo in an exemplary embodiment of the present invention 0.75 Fe 0.25 F 3 Is a transmission electron microscope image;
FIG. 2B is a KCo in an exemplary embodiment of the present invention 0.75 Fe 0.25 F 3 Is a pattern of electron diffraction patterns;
FIG. 2C is a KCo in an exemplary embodiment of the present invention 0.75 Fe 0.25 F 3 Is a high power transmission electron microscope image;
FIG. 2D is a KCoF in an exemplary embodiment of the invention 3 Is a transmission electron microscope image;
FIG. 2E is a KCoF in an exemplary embodiment of the invention 3 Is a pattern of electron diffraction patterns;
FIG. 2F is a KCoF in an exemplary embodiment of the invention 3 Is a high power transmission electron microscope image;
FIG. 2G is a KeFF in an exemplary embodiment of the invention 3 Is a transmission electron microscope image;
FIG. 2H is an exemplary embodiment of the present inventionKFEF in the examples 3 Is a pattern of electron diffraction patterns;
FIG. 2I is a schematic diagram of KeFF in an exemplary embodiment of the invention 3 Is a high power transmission electron microscope image;
FIG. 3 is a diagram of graphite, KFEF F in an exemplary embodiment of the invention 3 、IrO 2 、KCoF 3 、KCo (1-x) Fe x F 3 Is a linear sweep oxygen evolution voltammogram;
FIG. 4 is a KCo in an exemplary embodiment of the present invention 0.75 Fe 0.25 F 3 Oxygen evolution i-t graph of (c).
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following detailed description of the embodiments of the present invention will be given with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the invention shown in the drawings and described in accordance with the drawings are merely exemplary and the invention is not limited to these embodiments.
It should be noted here that, in order to avoid obscuring the present invention due to unnecessary details, only structures and/or processing steps closely related to the solution according to the present invention are shown in the drawings, while other details not greatly related to the present invention are omitted.
One aspect of the embodiment of the invention provides a preparation method of a novel iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material and application of the novel iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material in water electrolysis hydrogen production. The preparation method adopts cobalt ions as central ions, is doped with a certain amount of iron ions, adopts potassium ions or sodium ions as charge balance ions, adopts fluorine ions as ligands, and generates the novel electrocatalytic oxygen evolution material through the coordination reaction of the cobalt ions and the ligands in a solvent.
In some exemplary embodiments, the method of preparing includes: the uniform water phase mixed reaction system mainly composed of hydrogen fluoride, hydroxide, cobalt salt, ferrous salt and water reacts for 0.5 to 2 hours at the temperature of-2 to 99 ℃ under the protection of nitrogen to obtain the iron doped trifluoro cobaltate oxygen evolution electrocatalytic material with the chemical formula of MCo (1-x) Fe x F 3 M represents electricityThe charge balance ion is more than 0 and less than 1.
Further, M includes potassium ions, sodium ions, etc., but is not limited thereto.
In some exemplary embodiments, the method of preparing further comprises: introducing nitrogen into the uniform water phase mixed reaction system to deoxidize for more than 20 minutes.
In some exemplary embodiments, the preparation method specifically includes:
adding electrolyte into the mixed solution of hydrogen fluoride and hydroxide, introducing nitrogen to remove oxygen for more than 20 minutes, and controlling the temperature of the mixed solution below-2 ℃;
grinding cobalt salt and ferrous salt, directly adding the ground cobalt salt and ferrous salt into the mixed solution for introducing nitrogen and deoxidizing, carrying out ultrasonic oscillation, and then heating to 85-99 ℃ for continuous reaction for 0.5-2h to obtain the iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material.
In other exemplary embodiments, the preparation method may further include: directly taking fluoride solution, introducing nitrogen to remove oxygen for more than 20 minutes, and controlling the temperature of the solution to be-2 ℃ in order to prevent metal ions from hydrolyzing. To reach-2 ℃, electrolyte is added according to a numerical principle.
Further, the fluoride used in the present invention includes potassium fluoride, sodium fluoride, etc., but is not limited thereto.
Further, the electrolyte includes any one or a combination of two or more of calcium chloride, potassium sulfate, sodium sulfate, potassium nitrate, sodium nitrate, potassium chloride, sodium chloride, glucose, and the like, but is not limited thereto.
Further, the ultrasonic oscillation time is less than 10 hours.
In some exemplary embodiments, the preparation method specifically includes: mixing hydrofluoric acid and hydroxide solution to obtain the fluoride solution, wherein the hydroxide solution comprises potassium hydroxide and/or sodium hydroxide solution and the like.
In some exemplary embodiments, the molar ratio of ferrous salt to cobalt salt is y:1, wherein y > 0, preferably 0 < y < 1.
In some exemplary embodiments, the cobalt salt includes, but is not limited to, sulfuric acidCobalt (CoSO) 4 ) Cobalt chloride (CoCl) 2 ) Cobalt nitrate Co (NO) 3 ) 2 And the like, or a combination of any one or two or more thereof.
In some exemplary embodiments, the ferrous salts include, but are not limited to, ferrous ammonium sulfate Fe (NH) 4 ) 2 (SO 4 ) 2 。
In some exemplary embodiments, the method of preparing further comprises: after the reaction is completed, standing and layering are carried out, solids are separated, washing and drying are carried out, and the iron doped trifluoro cobaltate oxygen evolution electrocatalytic material is obtained.
In some more specific exemplary embodiments, the preparation method of the iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material specifically comprises the following steps:
(1) Taking 50mL of 3mol/L KF, and controlling the temperature of the solution to be minus 2 ℃ to prevent metal ions from hydrolyzing;
(2) In order to reach-2 ℃, a certain amount of electrolyte is added according to a principle of digitality, so that the temperature of the solution can be reduced to-2 ℃; further taking 0.05mol of cobalt salt for further increasing KCoF 3 Adding a certain amount of Fe (II) salt into cobalt salt, wherein the molar ratio of Fe (II) to Co can be (0-1): 1, even the molar amount of Fe (II) may be greater than the molar amount of Co. The XRD diffraction peak of the alloy shifts according to the different contents of Fe (II);
(3) Electrolytes added according to the principle of colligation include, but are not limited to, calcium chloride, potassium sulfate, sodium sulfate, potassium nitrate, sodium nitrate, potassium chloride, sodium chloride, and even substances with colligation such as glucose that can reduce temperature;
(4) Grinding cobalt salt and Fe (II) salt, directly adding into the KF solution, and ultrasonically stirring for 0.0-10.0h; then the temperature is increased to 85-99 ℃, and the product is obtained after continuous reaction. Standing for layering, separating out solid, washing and drying to obtain the iron doped trifluoro cobaltate oxygen evolution electrocatalyst.
In another aspect, the invention provides an iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material prepared by the method, which has a perovskite type cubic crystal system and a space group of P m 3 m A space group represented by the chemical formula MCo (1-x) Fe x F 3 M represents a charge balance ion, and 0 < x < 1.
Further, M includes potassium ions, sodium ions, etc., but is not limited thereto.
In another aspect, the embodiment of the invention provides application of the iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material as an oxygen evolution electrocatalyst in the field of water electrolysis hydrogen production.
Accordingly, another aspect of an embodiment of the present invention also provides a method for producing hydrogen by electrolysis of water, including:
preparing the iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material into an iron-doped trifluoro cobaltate electrode, wherein the iron-doped trifluoro cobaltate electrode comprises a carbon paste electrode, a nickel-based electrode, a titanium-based electrode or a stainless steel-based electrode;
the iron-doped trifluoro cobaltate electrode is used as an oxygen evolution electrode, nickel is used as a hydrogen evolution electrode, and is matched with an alkaline aqueous solution to form an electrolytic water hydrogen production system, and the electrolytic water hydrogen production is realized by electrifying between the oxygen evolution electrode and the hydrogen evolution electrode.
By means of the technical scheme, the preparation process is simple, raw materials are low in cost and easy to obtain, cobalt ions are adopted as central ions, a certain amount of iron ions are doped, potassium ions or sodium ions are adopted as charge balance ions, fluorine ions are adopted as ligands, a novel electrocatalytic oxygen evolution material is generated through the coordination reaction of the cobalt ions and the ligands in a solvent, and the oxygen evolution overpotential of the electrocatalytic material in a 1.0mol/LKOH solution is lower than that of an iridium noble metal electrode under the same condition, so that the electrocatalytic oxygen evolution material has excellent oxygen evolution performance and electrocatalytic stability, and is expected to be applied to large-scale production of photovoltaic, wind power and hydroelectric hydrogen.
The technical solution of the present invention will be described in further detail below with reference to a number of preferred embodiments and accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. It should be noted that the examples described below are intended to facilitate the understanding of the present invention and are not intended to limit the present invention in any way. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. The experimental methods, in which specific conditions are not noted in the following examples, are generally conducted under conventional conditions or under conditions recommended by the manufacturer.
Comparative example 1
Potassium trifluorocobaltate KCoF 3 Is prepared from the following steps: to prevent metal ions from hydrolyzing, 3mol/LKF mL was taken and the temperature of the solution was controlled to-2 ℃. In order to reach-2 ℃, solid NaCl is added according to the principle of digitality to saturate the mixture; taking 0.05mol of cobalt salt, grinding, directly adding into the KF solution, and carrying out ultrasonic oscillation for 0.0-10.0h; then keeping the temperature rising rate of 1 ℃/min to 85 ℃, and continuing the reaction for 0.5-2h to obtain the product. Standing for layering, separating out solid, washing and drying to obtain oxygen evolution electrocatalyst KCoF 3 The X-ray powder diffraction pattern is shown as curve a in FIG. 1, and corresponds to the diffraction pattern corresponding to the standard card number JCPDS 18-1006.
Comparative example 2
Similarly, potassium trifluorocobaltate KFEF 3 As comparative example 2, the resulting diffraction pattern is shown as curve b in FIG. 1.
Comparative example 3
Taking 0.15mmol KF or NH 4 F, grinding and mixing 0.05mol of cobalt chloride, placing the mixture into a tube furnace, heating to 350 ℃ under the protection of nitrogen flow, keeping the temperature for 2-5 hours, and collecting the obtained product to measure XRD diffraction data of the product, wherein the diffraction pattern of the product is similar to a curve a in figure 1.
Example 1
KCo 0.75 Fe 0.25 F 3 Is prepared from the following steps: taking 50mL of hydrofluoric acid with the concentration of 3mol/L, adding 55mL of KOH with the concentration of 3mol/L, introducing nitrogen, and deoxidizing for 20 minutes; mixing and grinding 0.0375mol of cobalt sulfate and 0.0125mol of ferrous ammonium sulfate, directly adding the mixture into the solution, maintaining the temperature at 95 ℃ under the condition of ultrasonic oscillation, and reacting for 1h to obtain the product. Standing for layering, separating out solid, washing and drying to obtain oxygen evolution electrocatalyst KCo 0.75 Fe 0.25 F 3 The XRD diffraction pattern is shown in curve c of FIG. 1.
Example 2
KCo 0.5 Fe 0.5 F 3 Is prepared from the following steps: taking 50mL of 3mol/L KF, introducing nitrogen, and deoxidizing for 25 minutes; to prevent the metal ions from hydrolyzing, the solution temperature was controlled to-2 ℃. In order to reach-2 ℃, solid NaCl is added according to the principle of digitality to saturate the mixture; grinding 0.025mol of cobalt chloride and 0.025mol of ferrous ammonium sulfate, directly adding the ground cobalt chloride and the ferrous ammonium sulfate into the solution, and carrying out ultrasonic oscillation for 0.0-10.0h; then the temperature is increased to 99 ℃ and the reaction is continued for 0.5h to obtain the product. Standing for layering, separating out solid, washing and drying to obtain oxygen evolution electrocatalyst KCo 0.5 Fe 0.5 F 3 The XRD diffractogram is similar to curve c in figure 1.
Example 3
KCo 0.6 Fe 0.4 F 3 Is prepared from the following steps: taking 50mL of 3mol/L KF, introducing nitrogen, and deoxidizing for 30 minutes; to prevent the metal ions from hydrolyzing, the solution temperature was controlled to-2 ℃. In order to reach-2 ℃, solid NaCl is added according to the principle of digitality to saturate the mixture; then 0.03mol of cobalt nitrate and 0.02mol of ferrous ammonium sulfate are taken, grinded and then directly added into the solution, and ultrasonic oscillation is carried out for 0.0-10.0h; then the temperature is increased to 85 ℃, and the reaction is continued for 2 hours to obtain the product. Standing for layering, separating out solid, washing and drying to obtain oxygen evolution electrocatalyst KCo 0.6 Fe 0.4 F 3 The XRD diffractogram is similar to curve c in figure 1.
The inventors also compared KCoF of comparative example 1 3 KFEF of comparative example 2 3 And KCo obtained in example 1 0.75 Fe 0.25 F 3 Characterization and testing of various properties were performed with the following results:
first, embodiment 1 of the present invention is to further improve KCoF 3 Adding a certain amount of Fe (II) salt into cobalt salt, wherein the molar ratio of Fe (II) to Co can be (0-1): 1, even the molar amount of Fe (II) may be greater than the molar amount of Co. The XRD diffraction peak of the alloy shifts according to the content of Fe (II). Referring to FIG. 1, KCoF 3 、KFeF 3 And KCo 0.75 Fe 0.25 F 3 XRD pattern of the sample. From the diffraction pattern, KCoF 3 Diffraction peaks of the electrocatalyst at 2θ= 21.842 °,31.064 °,38.285 ° are respectively opposite toCorresponds to KCoF 3 (100), (110) and (111) crystal face index (JCPDS 18-1006), keFF 3 Diffraction peaks of the sample at 2θ= 21.724 °,30.845 °,38.001 ° correspond to kfefs, respectively 3 (100), (110) and (111) crystal face index (JCPCDS 20-0895). Iron doped fluoride KCo 0.75 Fe 0.25 F 3 Diffraction angle and interplanar spacing at 2θ= 21.722 °,30.864 °,38.025 ° are both between those of the single metal fluoride KCoF 3 With KeFF 3 In between, it is shown that the bimetal of Co, fe changes the unit cell size.
Second, the present inventors also compared KCoF of comparative example 1 3 KFEF of comparative example 2 3 And KCo obtained in example 1 0.75 Fe 0.25 F 3 Transmission electron microscopy was performed and the results showed that KCo 0.75 Fe 0.25 F 3 ，KCoF 3 And KFEF 3 The morphology, diffraction spots and interplanar spacing of KCoF are shown in FIGS. 2A-2C 3 The morphology, diffraction spots and interplanar spacing of KFEF are shown in FIGS. 2D-2F 3 The morphology, diffraction spots and interplanar spacing of (c) are shown in figures 2G-2I. The results of the interplanar spacing are consistent with those of powder diffraction, further showing that the resulting product is perovskite-type fluoride.
Third, the present inventors also compared KCoF of comparative example 1 3 KFEF of comparative example 2 3 And KCo obtained in example 1 0.75 Fe 0.25 F 3 After oxygen evolution performance test, the inventor synthesizes a series of KCo (1-x) FexF 3 Electrocatalyst, 0.15g KCo was weighed (1-x) FexF 3 The catalyst is made into a carbon paste electrode, and a linear scanning curve in 1.0mol/LKOH is shown in FIG. 3, wherein a curve a represents graphite, a curve b represents KFEF, and a curve c represents IrO 2 Curve d represents KCo f and curve e represents KCo 0.25 Fe 0.75 F 3 Curve f represents KCo 0.5 Fe 0.5 F 3 Curve g represents KCo 0.75 Fe 0.25 F 3 。KCoF 3 And the oxygen evolution overpotential of the iron-doped potassium trifluorocobaltate is lower than that of the noble metal iridium. At a current density of 10 mA/cm, each electrode materialThe oxygen evolution parameters of the material are shown in table 1. KCo (KCo) (1-x) FexF 3 (x<1.0 More overpotential for oxygen evolution of electrocatalyst than noble metals Ir or IrO 2 And the oxygen evolution performance is excellent, and the energy consumption of the electrolyzed water can be effectively reduced.
TABLE 1 oxygen evolution Performance of a series of electrodes
Fourth, the inventors also performed on the synthesized KCo 0.75 Fe 0.25 F 3 Stability of electrocatalyst was tested
To test KCo 0.75 Fe 0.25 F 3 The electrode oxygen evolution stability of (2) was measured by performing an i-t scan at 0.6V (vs. SCE), and FIG. 4 is a graph showing the scan for 6 hours. The initial current was 39mA/cm 2 The current density of the electrode at the end was approximately 44mA/cm 2 The current density increases.
Example 4
Taking a series of KCos prepared by the invention (1-x) Fe x F 3 0.15g of the carbon paste is added into 0.45 g of graphite powder, ground by a mortar, added with a proper amount of silica gel oil and uniformly mixed to obtain the carbon paste. Injecting carbon paste into polytetrafluoroethylene tube with diameter of 3mm, compacting and copper wire to form KCo-containing material (1-x) Fe x F 3 Carbon paste electrodes of oxygen evolution electrocatalysts. The carbon paste electrode is used as an oxygen evolution electrocatalyst, the foam nickel is used as a hydrogen evolution electrode, water is electrolyzed in 1.0mol/LKOH alkaline solution under the pressure of 1.6V tank, oxygen evolution can be observed at the anode, and hydrogen evolution can be observed at the cathode.
In summary, the novel electrocatalytic oxygen evolution material is prepared by adopting cobalt ions as central ions, doping a certain amount of iron ions, taking potassium ions or sodium ions as charge balance ions, taking fluorine ions as ligands and performing coordination reaction of the cobalt ions and the ligands in a solvent, and has excellent oxygen evolution performance and electrocatalytic stability.
It should be understood that the above embodiments are merely for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the present invention and implement the same according to the present invention without limiting the scope of the present invention. All equivalent changes or modifications made in accordance with the spirit of the present invention should be construed to be included in the scope of the present invention.
Claims (9)
1. The preparation method of the iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material is characterized by comprising the following steps of: the uniform water phase mixed reaction system mainly composed of hydrogen fluoride, potassium hydroxide, cobalt salt, ferrous salt and water is reacted for 0.5 to 2 hours at the temperature of-2 to 99 ℃ under the protection of nitrogen, and the iron doped trifluoro cobaltate oxygen evolution electrocatalytic material is obtained, and the chemical formula is MCo (1-x) Fe x F 3 M represents potassium ion, x=0.25, i.e. the chemical formula is KCo 0.75 Fe 0.25 F 3 The crystal structure of the iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material is a perovskite type cubic crystal system, and the space group is P m 3 m Space group.
2. The preparation method according to claim 1, characterized by comprising: introducing nitrogen into the uniform water phase mixed reaction system to deoxidize for more than 20 minutes.
3. The preparation method according to claim 1, characterized by comprising the following steps:
electrolyte is added into the mixed solution of hydrogen fluoride and potassium hydroxide, and the temperature of the mixed solution is controlled below minus 2 ℃;
and (3) mixing and grinding cobalt salt and ferrous salt, directly adding the mixture into the mixed solution, carrying out ultrasonic oscillation, and then heating to 85-99 ℃ to continue to react for 0.5-2h to obtain the iron-doped trifluoro cobaltate oxygen evolution electrocatalytic material.
4. A method of preparation according to claim 3, characterized in that: the electrolyte is selected from any one or more than two of potassium sulfate, sodium sulfate, potassium nitrate, sodium nitrate, potassium chloride, sodium chloride and calcium chloride; and/or the ultrasonic oscillation time is less than 10 hours.
5. The method of manufacturing according to claim 1, characterized in that: the cobalt salt is selected from any one or more than two of cobalt sulfate, cobalt chloride and cobalt nitrate; and/or the ferrous salt is ferrous ammonium sulfate.
6. The method for producing according to claim 1, characterized by further comprising: after the reaction is completed, standing and layering are carried out, solids are separated, washing and drying are carried out, and the iron doped trifluoro cobaltate oxygen evolution electrocatalytic material is obtained.
7. An iron-doped trifluorocobaltate oxygen evolution electrocatalytic material prepared by the process of any one of claims 1-6.
8. The use of the iron-doped trifluorocobaltate oxygen evolution electrocatalyst material according to claim 7 as an oxygen evolution electrocatalyst in the field of hydrogen production by electrolysis of water.
9. A method for producing hydrogen by electrolysis of water, comprising:
forming the iron-doped trifluorocobaltate oxygen evolution electrocatalytic material of claim 7 into an iron-doped trifluorocobaltate electrode comprising a carbon paste electrode, a nickel-based electrode, a titanium-based electrode, or a stainless steel-based electrode;
the iron-doped trifluoro cobaltate electrode is used as an oxygen evolution electrode, nickel is used as a hydrogen evolution electrode, and is matched with an alkaline aqueous solution to form an electrolytic water hydrogen production system, and the electrolytic water hydrogen production is realized by electrifying between the oxygen evolution electrode and the hydrogen evolution electrode.
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