KR102123618B1 - Method for fabricating metallic phosphate thin film and electrochemical catalyst electrode using the same - Google Patents

Abstract

The present invention relates to a method for preparing a metal phosphate thin film and an electrochemical catalyst electrode using the same, (a) preparing an acidic aqueous solution having a pH of 2 or more and 5 or less, (b) phosphoric acid that can be precipitated within the pH range Adding anions to the acidic aqueous solution to form a coating solution, (c) immersing a metal substrate containing a metal ionized within the pH range of the coating solution in the coating solution, (d) of the metal substrate The metal is ionized to form a metal ion, increasing the pH of the coating solution, and (e) forming a metal phosphate thin film on at least a portion of the metal substrate by combining and depositing the phosphate anion with the metal ion. It is characterized by including.

Description

Method for manufacturing metal phosphate thin film and electrochemical catalyst electrode using the same {METHOD FOR FABRICATING METALLIC PHOSPHATE THIN FILM AND ELECTROCHEMICAL CATALYST ELECTRODE USING THE SAME}

The present invention relates to a method for manufacturing a metal phosphate thin film and an electrochemical catalyst electrode using the same. More specifically, the present invention relates to a method of manufacturing a metal phosphate thin film that deposits phosphate by adjusting the pH of a solution and an electrochemical catalyst electrode using the same.

Recently, the metal phosphate electrode has attracted attention due to its excellent reactivity and stability. In order to apply this to the electrocatalytic reaction, most metal phosphate electrodes are made using phosphine (PH ₃ ) gas in a high temperature environment. A metal phosphate thin film is prepared by using chemical vapor deposition (CVD) using a metal nanoparticle precursor and a phosphate precursor at a high temperature of 200°C to 500°C.

However, in a high-temperature environment, the phosphate precursor has a problem of being changed into a highly toxic phosphine (PH ₃ ) gas, and has a disadvantage in that productivity is reduced due to a long coating time.

The present invention is to solve a number of problems, including the problems as described above, it is an object to provide a method of manufacturing a metal phosphate thin film in a short time at a low temperature by adjusting the pH of the solution.

In addition, an object of the present invention is to produce an electrochemical catalyst electrode having high reactivity and stability and excellent performance by forming a metal phosphate thin film to which a transition metal cation is added.

However, these problems are exemplary, and the scope of the present invention is not limited thereby.

According to one aspect of the present invention for solving the above problems, (a) preparing an acidic aqueous solution having a pH of 2 or more and 5 or less, (b) phosphate anions that can be precipitated within the pH range are added to the acidic aqueous solution. Forming a coating solution by adding, (c) immersing a metal substrate containing a metal ionized within a pH range of the coating solution in the coating solution, (d) metal of the metal substrate is ionized to form metal ions Forming and increasing the pH of the coating solution and (e) forming a metal phosphate thin film on at least a portion of the metal substrate by combining and depositing the phosphate anion with the metal ion. A manufacturing method is provided.

In addition, according to an embodiment of the present invention, in step (e), as the pH increases, the precipitation rate of the phosphate anion may be greater than the ionization rate of the metal.

In addition, according to an embodiment of the present invention, the coating solution further includes at least one transition metal cation that improves catalytic activity, and in step (e), the phosphoric acid anion is combined with the metal ion and the transition metal cation. And can be precipitated.

In addition, according to an embodiment of the present invention, the coating solution may further include nitrite ions (Nitrite ion, [NO ₂ ] ^- ) to accelerate the increase in pH.

In addition, according to an embodiment of the present invention, the coating solution may have a temperature range of 50 ℃ to 90 ℃.

In addition, according to an embodiment of the present invention, the metal substrate is iron (Fe), nickel (Ni), zinc (Zn), calcium (Ca), magnesium (Mg), manganese (Mn), copper (Cu) And it may include at least any one or a combination of metals selected from the group consisting of chromium (Cr).

In addition, according to one embodiment of the present invention, the transition metal cation is nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), ruthenium (Ru), copper (Cu), iridium (Ir) ), magnesium (Mg), calcium (Ca), and zinc (Zn).

Further, according to an embodiment of the present invention, the metal phosphate thin film may include porous metal phosphate particles having a size of 1 μm to 3 μm.

And, according to another embodiment of the present invention for solving the above problems, there is provided an electrochemical catalyst electrode comprising a metal phosphate thin film on at least a portion of the surface.

According to one embodiment of the present invention made as described above, it is possible to manufacture a metal phosphate thin film in a short time at a low temperature by adjusting the pH of the solution.

In addition, the present invention can form a metal phosphate thin film to which a transition metal cation is added, to produce an electrochemical catalyst electrode having high reactivity and stability and excellent performance.

Of course, the scope of the present invention is not limited by these effects.

1 is a flow chart showing a method of manufacturing a metal phosphate thin film according to an embodiment of the present invention.
2 and 3 are schematic views showing a method of manufacturing a metal phosphate thin film according to an embodiment of the present invention.
Figure 4 is a scanning electron microscope (Scanning Electron Microscope, SEM) photograph showing the surface of a metal phosphate thin film according to an embodiment of the present invention.
Figure 5 shows the current density (Current density) of the electrode in the oxygen generation reaction experiment of Comparative Example 1, Examples 1 to 4.
6 shows a change in current density according to the number of times of the oxygen generation reaction experiment of Example 1.
7 is a graph showing the current density in the oxygen generation reaction experiment according to the concentration of cobalt (Co) added to the manganese phosphate thin film according to an experimental example of the present invention.
8 is a scanning electron microscope (SEM) photograph showing the surface of the electrode of Example 6 according to an experimental example of the present invention before and after the oxygen generation reaction experiment.
9 is a graph showing the results of an oxygen generating reaction experiment of an electrode according to an electrolyte concentration according to an experimental example of the present invention.
10 shows the results of experiments of durability of the electrode of Example 6 when the pH of the electrolyte according to the experimental example of the present invention is 14.
11 is a graph showing the water oxidation reaction activity of the electrode according to the zinc phosphate thin film formation temperature according to an experimental example of the present invention.
12 is a graph showing the water oxidation reaction activity of the electrode according to the zinc phosphate thin film formation time according to an experimental example of the present invention.
13 is a graph showing the water oxidation reaction activity of the electrode according to the amount of transition metal cation added when forming a zinc phosphate thin film according to an experimental example of the present invention.
14 is a graph showing the water oxidation reaction activity of an electrode according to the content of metal cations of a metal substrate added to a coating solution when forming a zinc phosphate thin film according to an experimental example of the present invention.
15 is a graph showing the water oxidation reaction activity of an electrode according to whether a second transition metal cation is included in forming a zinc phosphate thin film according to an experimental example of the present invention.
16 and 17 are photographs and graphs showing the surface properties of a zinc phosphate thin film electrode according to an embodiment of the present invention.
18 and 19 are graphs showing the atomic distribution on the surface of a zinc phosphate thin film electrode according to an embodiment of the present invention.
20 is a graph showing the current density in the water oxidation experiment of the electrode according to an embodiment of the present invention.
21 and 22 are graphs showing cyclic voltammetry (CV) analysis results of water oxidation experiments of electrodes according to Examples and Comparative Examples of the present invention.
23 is a graph showing the results of a cyclic voltammetry (CV) analysis during a water oxidation experiment of an electrode according to pH of an electrolyte according to an embodiment and a comparative example of the present invention.
24 is a photograph showing a process of performing a water oxidation experiment using an electrode on which a metal phosphate thin film is formed according to an embodiment of the present invention.

For a detailed description of the present invention, which will be described later, reference is made to the accompanying drawings that illustrate, by way of example, specific embodiments in which the present invention may be practiced. These examples are described in detail enough to enable those skilled in the art to practice the present invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain shapes, structures, and properties described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in relation to one embodiment. In addition, it should be understood that the location or placement of individual components within each disclosed embodiment can be changed without departing from the spirit and scope of the invention. Therefore, the following detailed description is not intended to be taken in a limiting sense, and the scope of the present invention, if appropriately described, is limited only by the appended claims, along with all ranges equivalent to those claimed. In the drawings, similar reference numerals refer to the same or similar functions across various aspects, and length, area, thickness, and the like may be exaggerated for convenience.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to enable those skilled in the art to easily implement the present invention.

1 to 3, a method of manufacturing a metal phosphate thin film according to an embodiment of the present invention (S100) will be described. 1 is a flow chart showing a method of manufacturing a metal phosphate thin film 100 according to an embodiment of the present invention, and FIGS. 2 and 3 show a method of manufacturing a metal phosphate thin film 100 according to an embodiment of the present invention It is a schematic diagram.

According to Figure 1, the manufacturing method of the metal phosphate thin film 100 (S100), (a) pH 2 or more, 5 or less steps to prepare an acidic aqueous solution (210) (S110), (b) within the pH range Forming a coating solution 200 by adding the phosphate anion 220 that can be precipitated to the acidic aqueous solution 210 (S120), (c) containing a metal ionized within the pH range of the coating solution 200 Step of immersing the metal substrate 300 in the coating solution 200 (S130), (d) the metal of the metal substrate 300 is ionized to form metal ions 320 and increase the pH of the coating solution 200 Steps (S140) and (e) may include the step (S150) of forming a metal phosphate thin film 100 on at least a portion of the metal substrate 300 by combining and depositing the phosphate anion 220 with the metal ion 320. have.

The conventional method for forming a metal phosphate thin film was prepared by using a chemical vapor deposition (CVD) method in which the phosphoric acid precursor is in a high temperature environment of 200°C to 500°C. However, this has a problem that the phosphate precursor becomes toxic phosphine (PH ₃ ) in a high temperature environment. To prevent this, the present invention is characterized by using a phenomenon in which a phosphate anion is precipitated in a low temperature, acidic environment.

First, (a) in the step (S110) of preparing the acidic aqueous solution 210, the acidic aqueous solution 210 may have a pH of 2 or more and 5 or less. Referring to the Pourbiax diagram of phosphoric acid, the phosphate anion (PO ₄ ^3- ) 220 may be precipitated as a solid at pH 2 or higher.

Next, (b) a coating solution 200 is formed by adding a phosphate anion 220 that can be precipitated within the pH range to the acidic aqueous solution 210 (S120). The coating solution 200 may include a raw material that forms the metal phosphate thin film 100. Among them, the phosphate anion 220 may be precipitated as a solid at pH 2 or higher as described above.

The coating solution 200 may further include other components that can be added to the metal phosphate thin film 100 other than the phosphate anion 220. For example, the other component may be a second metal element that enhances the catalytic activity of the metal phosphate thin film 100, or other additives. On the other hand, the coating solution 200 may be formed by preparing a pH-adjusted acidic aqueous solution 210 and sequentially adding the phosphate anion 220, and simultaneously adding the phosphate anion 220 to the acidic aqueous solution 210. The coating solution 200 may be formed by adjusting the pH.

In addition, according to an embodiment of the present invention, the coating solution 200 may have a temperature range of 50 ℃ to 90 ℃. In the conventional case, a metal phosphate thin film was formed by making the phosphate precursor into a gaseous state in a high temperature environment of at least 200°C. On the other hand, in the case of the present invention, the phosphate anion 220 and the metal ion 320 are combined and precipitated according to the change in the pH of the coating solution 200 to form a metal phosphate thin film 100. 100) is possible. Preferably, the coating solution 200 may have a temperature range of 60 ℃ to 70 ℃.

Then, (c) a metal substrate 300 containing metal as a raw material for forming the metal phosphate thin film 100 is immersed in the coating solution 200 (S130). The metal substrate 300 may include metal that is ionized within the pH range of the coating solution 200. The metal substrate 300 may be cleaned by sequentially performing a base treatment and an acid treatment before being prepared in the coating solution 200.

The metal of the metal substrate 300, for example, iron (Fe), nickel (Ni), manganese (Mn), or the like, may be ionized to the metal ion 320 at a pH of 5 or less. To form the metal phosphate thin film 100, a state in which metal may exist in the form of ions and a pH corresponding to an interface where phosphate anions 220 may be precipitated as a solid by combining with metal ions 320 are selected. An acidic aqueous solution 210 is prepared. Preferably, the pH of the acidic aqueous solution 210 may be 2.5.

2 When reference to (c) of Figure 3, the metal substrate 300 is the corrosion in the coating solution (200) metal ions (M ⁺⁾ (320) and the electron (e ^-) emits. Thereafter, the metal ions 320 and the phosphate anions 220 are combined and precipitated to form the metal phosphate thin film 100 in a region where the metal substrate 300 is corroded. The metal substrate 300 is not necessarily in a flat shape, and may have various shapes depending on the case. For example, the metal substrate 300 may have a cylindrical shape, or may have a porous foam shape. As the method in which the metal substrate 300 is immersed in the coating solution 200, a method commonly used may be adopted. Preferably, after the metal phosphate thin film 100 is formed, a method of dipping to facilitate the washing process may be used.

In this case, the metal substrate 300 is made of iron (Fe), nickel (Ni), zinc (Zn), calcium (Ca), magnesium (Mg), manganese (Mn), copper (Cu), and chromium (Cr). It may include at least any one or a combination of metals selected from the group. Preferably, the metal substrate 300 may be a metal foil including iron (Fe) or nickel (Ni).

Thereafter, (d) the metal of the metal substrate 300 contacted with the coating solution 200 is ionized to form the metal ion 320, and the pH of the coating solution 200 may be increased (S140 ). 2 and reference to (c) of Figure 3, at the same time as the metal ion (M ⁺⁾ (320) is formed when the metal of the metal substrate 300 is ionized, the electron (e ^-) to form. Hydrogen ions contained in the coating solution (200) of the acid (H ⁺⁾ are electron (e ^-), the concentration of the reaction is hydrogen gas (H _2), the coating solution 200, hydrogen ions (H ⁺⁾ of It lowers and the pH increases. At this time, the temperature of the coating solution 200 may be heated to 50°C to 90°C to induce corrosion of the metal substrate 300.

Meanwhile, according to an embodiment of the present invention, the coating solution 200 may further include a nitrite ion ([NO ₂ ] ^- ) 280 that accelerates an increase in pH. The nitrite ion 280 is slightly acidic basic by an acid-base reaction in an aqueous solution. That is, it is added to the coating solution 200 including the acidic aqueous solution 210 to increase the pH faster. Therefore, nitrite ions 280 may be further included in the coating solution 200 so that the phosphate anions 220 may be precipitated to accelerate the increase in pH.

Next, (e) the phosphate anion 220 is combined with the metal ion 320 and precipitated to form a metal phosphate thin film 100 on at least a portion of the metal substrate 300 (S150). The phosphate anion 220 and the metal ion 320 may form a strong bonding force in the coating solution 200. Since they each have a negative charge (-) and a positive charge (+), they can be combined with each other by electrostatic attraction. The phosphate anion 220 is precipitated as a solid as the pH is increased, and the metal phosphate thin film 100 may be formed on the metal substrate 300 together with the combined metal ions 320.

At this time, according to an embodiment of the present invention, (e) in the step (S150) of forming the metal phosphate thin film 100, as the pH increases, the precipitation rate of the phosphate anion 220 becomes larger than the ionization rate of the metal. Can be.

Referring to FIGS. 2 and 3 (d) and (e), when the pH of the coating solution 200 increases, the rate at which the metal is corroded and ionized initially is faster than the precipitation rate of the phosphate anion 220. At this time, without the precipitation of the phosphate anion 220, it forms a bond with the metal ion 320. Then, the precipitation rate of the phosphate anion 220 increases as the pH increases by reduction of the hydrogen ion (H ⁺ ). When the deposition rate of the phosphate anion 220 is greater than the ionization rate of the metal, the metal ion 320 and the phosphate anion 220 are deposited on the metal substrate 300 to form the metal phosphate thin film 100. At this time, the metal phosphate thin film 100 may be formed on at least a portion of the metal substrate 300, and preferably may be formed in a region where the metal substrate 300 is corroded. The process of washing with distilled water may be further performed on the metal substrate 300 on which the metal phosphate thin film 100 is formed through the above process.

On the other hand, according to one embodiment of the present invention, the coating solution 200 further comprises at least one transition metal cation 280 that improves catalytic activity, and (e) phosphoric acid in the step of forming the metal phosphate thin film 100 The anion 220 may be combined with the metal ion 320 and the transition metal cation 280 and be precipitated.

The metal phosphate thin film 100 may include only the metal constituting the metal substrate 300, but may be included in the metal phosphate thin film 100 by adding other metal ions to the coating solution 200. In this case, the added metal ion may be a transition metal cation 280 that improves the catalytic activity of the metal phosphate thin film 100. When the metal phosphate thin film 100 is prepared by adding a transition metal, the activity of the electrochemical catalytic reaction may be improved. In addition, it is also possible to prepare a catalyst electrode capable of selectively acting on a desired reaction by varying the type and composition of the transition metal. When the phosphate anion 220 is deposited, the metal ions 320 and the transition metal cations 280 may be deposited together to be included in the metal phosphate thin film 100.

At this time, according to an embodiment of the present invention, the transition metal cation 280 is nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), ruthenium (Ru), copper (Cu), iridium It may be at least one selected from the group consisting of (Ir), magnesium (Mg), calcium (Ca), and zinc (Zn), or a combination thereof. Preferably, the transition metal cation 280 may be nickel (Ni), cobalt (Co), or a combination thereof.

The manufacturing method (S100) of the metal phosphate thin film 100 of the present invention has the advantage that the metal phosphate thin film 100 having excellent reactivity and stability can be manufactured by shortening the process time at a low temperature compared to the conventional method. In particular, since the low-temperature coating solution 200 is used, a problem in which phosphine (PH ₃ ) toxic substances are generated in a high-temperature environment can be solved. In addition, since the thin film coating method is used as an inexpensive raw material, it can have competitiveness in mass production.

Meanwhile, according to an embodiment of the present invention, the electrochemical catalyst electrode 500 may include the metal phosphate thin film 100 on at least a portion of the surface. The metal phosphate thin film 100 may be formed on at least a portion of the metal substrate 300. Referring to FIG. 3, a metal substrate 300 providing a raw material of metal included in the metal phosphate thin film 100 may be a base material of the electrochemical catalyst electrode 500. The metal phosphate thin film 100 formed according to the above-described process may be formed in at least a partial region of the metal substrate 300, preferably in a region where the metal substrate 300 is corroded to produce the electrochemical catalyst electrode 500. have. In addition, the type and content of the metal substrate 300 and the transition metal cation 280 may be varied to manufacture the electrochemical catalyst electrode 500 applicable to a desired reaction.

Figure 4 is a scanning electron microscope (Scanning Electron Microscope, SEM) photograph showing the surface of a metal phosphate thin film according to an embodiment of the present invention.

Referring to FIG. 4, it can be seen that a phosphate anion 220, a metal ion 320 and a transition metal cation 280 are deposited on the metal substrate 300 to form a metal phosphate thin film 100. The metal phosphate thin film 100 may include porous metal phosphate particles 110 having a size of 1 μm to 3 μm. Since the metal phosphate particle 110 is formed with a lattice stress, performance is superior to that of a conventional oxide catalyst. In particular, when forming the porous metal phosphate particles 110 in a few μm unit, the lattice stress may be greater. In addition, the electrochemical catalyst electrode 500 on which the metal phosphate thin film 100 is formed can be manufactured by selecting the type of the transition metal cation 280 and the metal substrate 300 added to the coating solution 200. The catalyst used varies depending on the electrochemical reaction, and accordingly, the composition of the coating solution 200 may be changed and the metal phosphate thin film 100 may be prepared.

Hereinafter, examples and experimental examples for helping understanding of the present invention will be described. However, the following Examples and Experimental Examples are only to help understanding of the present invention, and the Examples and Experimental Examples of the present invention are not limited to the following Examples and Experimental Examples.

Example

1.Manganese phosphate thin film (MnPi) electrode using stainless steel (SS) substrate

Metal phosphate thin film by using stainless steel as the metal substrate 300 and adding cobalt (Co), iridium (Ir) and ruthenium (Ru) based on manganese (Mn) as the transition metal cation 260 An experimental example using the electrode formed (100) will be described.

First, in the present embodiment, when the method for manufacturing a manganese phosphate thin film (MnPi) is prepared, stainless steel (SS) is prepared by the metal substrate 300 and a pretreatment process of the metal substrate is performed. The stainless steel substrate is treated with 40 mL of 0.2 M NaOH aqueous solution in a degrease soultion at 60° C. for 8 minutes. At this time, the degreasing agent is processed while rotating at 200 rpm. Subsequently, the mixture is washed for 1 minute in distilled water, treated with 40 mL of a 10% concentration aqueous HCl solution for 5 minutes at room temperature, and then washed twice with distilled water for 1 minute.

Thereafter, 40 mL of an aqueous solution in which 0.12 g of K-104A, a manganese phosphate compound, and 0.12 g of K-104B (manganese phosphate-based surface control agent of BCC) was dissolved was used as a surface activating soulution, and the pretreated metal was used. The substrate is surface-treated for 1 minute. The surface treatment is performed by rotating the metal substrate at 300 rpm in a manganese phosphate-based aqueous solution.

Subsequently, a phosphate thin film is formed using 40 mL of an aqueous solution containing 3.2 g MN100 and a second transition metal cation sulfate (MSO ₄ ) as a manganese phosphate solution (Mn Phosphating solution), which is a coating solution. At this time, the process of forming the phosphate thin film is processed at 94°C for 10 minutes.

Finally, the metal substrate on which the metal phosphate thin film is formed is washed with distilled water and annealed at 300° C. for 5 hours.

The manganese phosphate thin film (MnPi) prepared by the above method includes a metal element dissolved in stainless steel (SS), a manganese cation, and a second transition metal cation and phosphate added separately.

Hereinafter, comparative examples and examples prepared by varying conditions in the method of manufacturing the manganese phosphate thin film (MnPi) will be described.

Comparative Example 1: Pure stainless steel (SS) electrode (Bare SS)

A stainless steel (SS) substrate without surface treatment was prepared, and this is referred to as Comparative Example 1.

Example 1: Manganese Phosphate Thin Film (MnPi) electrode (SS+MnPi)

In the above method of manufacturing a manganese phosphate thin film (MnPi), a manganese phosphate thin film is formed in the same manner, except that a manganese phosphate solution is prepared without adding a sulfate (MSO ₄ ) containing a second transition metal cation. A steel (SS) electrode is prepared, which is referred to as Example 1.

Example 2: Manganese-iridium phosphate thin film (MnIrPi) electrode (SS+5MnIrPi)

In the production method of Example 1, the second transition metal cation of the manganese phosphate solution is prepared in the same manner except that iridium (Ir) is used. 5 mM IrSO ₄ is added from the manganese phosphate solution, and in the same manner as above, a stainless steel (SS) electrode having a manganese metal phosphate thin film is prepared, which is referred to as Example 2.

Example 3: Manganese-ruthenium phosphate thin film (MnRuPi) electrode (SS+5MnRuPi)

In the preparation method of Example 1, the second transition metal cation of the manganese phosphate solution is prepared in the same manner, except that ruthenium (Ru) is used. 5 mM RuSO ₄ is added from the manganese phosphate solution, and in the same manner as above, a stainless steel (SS) electrode having a manganese metal phosphate thin film is prepared, which is referred to as Example 3.

Example 4: Manganese-cobalt phosphate thin film (MnCoPi) electrode (SS+10MnCoPi)

In the production method of Example 1, the second transition metal cation of the manganese phosphate solution is prepared in the same manner except that cobalt (Co) is used. In a manganese phosphate solution, 10 mM CoSO ₄ is added, and in the same manner as above, a stainless steel (SS) electrode having a manganese metal phosphate thin film is prepared, which is referred to as Example 4.

Example 5: Manganese-cobalt phosphate thin film (MnCoPi) electrode (SS+100MnCoPi)

In the preparation method of Example 4, it was prepared in the same manner except that the concentration of cobalt (Co) in the manganese phosphate solution was used differently. In the manganese phosphate solution, 100 mM CoSO ₄ is added, and in the same manner as above, a stainless steel (SS) electrode having a manganese metal phosphate thin film is prepared, which is referred to as Example 5.

Example 6: Manganese-cobalt phosphate thin film (MnCoPi) electrode (SS+200MnCoPi)

In the preparation method of Example 4, it was prepared in the same manner except that the concentration of cobalt (Co) in the manganese phosphate solution was used differently. In the manganese phosphate solution, 200 mM CoSO ₄ is added, and in the same manner as above, a stainless steel (SS) electrode having a manganese metal phosphate thin film is prepared, which is referred to as Example 6.

Example 7: Manganese-cobalt phosphate thin film (MnCoPi) electrode (SS+500MnCoPi)

In the preparation method of Example 4, it was prepared in the same manner except that the concentration of cobalt (Co) in the manganese phosphate solution was used differently. In the manganese phosphate solution, 500 mM CoSO ₄ is added, and in the same manner as above, a stainless steel (SS) electrode having a manganese metal phosphate thin film is prepared, which is referred to as Example 7.

Example 8: Manganese-cobalt phosphate thin film (MnCoPi) electrode (SS+1000MnCoPi)

In the preparation method of Example 4, it was prepared in the same manner except that the concentration of cobalt (Co) in the manganese phosphate solution was used differently. In the manganese phosphate solution, 10000 mM CoSO ₄ is added, and in the same manner as above, a stainless steel (SS) electrode having a manganese metal phosphate thin film is prepared, which is referred to as Example 8.

[Table 1] below is a table summarizing comparative examples and examples in the preparation of a manganese phosphate thin film (MnPi).

Comparative Example 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Remark Bare SS MnPi MnIrPi 5/200
MnRuCo
Pi 10
MnCoPi 100
MnCoPi 200
MnCoPi 500
MnCoPi 1000
MnCoPi Board SS SS SS SS SS SS SS SS SS Metal cations - Mn Mn Mn Mn Mn Mn Mn Mn Transition metal
Cation
(mM) - - Ir
(5mM) Ru(5mM)
Co
(200mM) Co
(10mM) Co
(100mM) Co
(200mM) Co
(500mM) Co
(1000mM)

Hereinafter, an experiment for the activity of the electrochemical catalyst electrode using the electrodes of Comparative Example 1 and Examples 1 to 8 will be described.

Experimental Example 1: Oxygen generation reaction (OER) experiment of manganese phosphate thin film

5 and 6, the oxygen generation reaction (OER) experiment of Comparative Example 1 and Example 1 will be described. Figure 5 shows the current density (Current density) of the electrode in the oxygen generation reaction experiment of Comparative Examples 1 and Examples 1 to 4, Figure 6 shows the current density change according to the number of times of the oxygen generation reaction experiment of Example 1 .

Comparative Example 1, Examples 1 to 4, the working electrode (Working Electrode, WE), the carbon electrode (Carbon cloth), the counter electrode (Counter Electrode, CE), and Ag/AgCl (3 M NaCl) as the reference electrode (Reference electrode), and the electrolyte is a 1 M aqueous KOH solution to form a three-electrode cell.

Referring to FIG. 5, it can be seen that the current densities are higher when the electrodes of Examples 1 to 4 in which the manganese phosphate thin film is formed have the same voltage. Among them, it can be seen that the electrode of Example 4 further comprising cobalt (Co) as a transition metal cation shows the best current density. This means that when another transition metal cation is further added to the metal phosphate thin film, the performance of the electrode is improved. In particular, when more cobalt (Co) ions are added, the performance improvement of the electrode can be maximized.

And, referring to Figure 6, it can be seen that the electrode of Example 1 increases in current density according to the number of times of the oxygen generation reaction experiment. When more than 20 repetition experiments were performed, it can be seen that the amount of change in current density decreased and stabilized. That is, it means that the electrode on which the metal phosphate thin film is formed is stabilized as the number of times of use increases, thereby exhibiting stable performance as a catalyst electrode.

Experimental Example 2: Oxygen generation reaction (OER) experiment according to the concentration of cobalt (Co)

Using the electrodes of Examples 4 to 8, an oxygen generation reaction (OER) experiment according to the concentration of cobalt (Co) added as a transition metal cation is performed. 7 is a graph showing the current density in the oxygen generation reaction experiment according to the concentration of cobalt (Co) added to the manganese phosphate thin film according to an experimental example of the present invention.

The electrode of Examples 4 to 8 is a working electrode, a platinum wire (Pt wire) is a counter electrode, and Hg/HgO (1M KOH) is used as a reference electrode, and the electrolyte is a 1 M KOH aqueous solution to form a 3-electrode cell (Cell). To form.

7 (a) and (b), as the concentration of cobalt (Co) ions added during the manufacture of the manganese phosphate thin film (MnPi) increases, the current density increases and then 200 mM of cobalt (Co) ions are added. When you do, you can see that the current density is the highest. That is, when the manganese phosphate thin film (200MnCoPi) is prepared by adding 200 mM of cobalt (Co) ion, it means that the efficiency of the electrode can be maximized.

7(c) and 7(d) are graphs showing the current density change when the oxygen generation reaction experiment was repeatedly performed using the electrode of Example 6 prepared by adding 200 mM of cobalt (Co) ion. It can be seen that the current density increases as the experiment is repeated and then stabilizes when repeated more than 170 times. And, (d) of FIG. 7 shows the results when the oxygen generation reaction experiment was repeatedly performed 170 times, and then the electrolyte was replaced and the experiment was performed again. Even if the electrolyte is replaced, there is no change in the current density, which means that the performance of the electrode is stabilized in over 170 repeated experiments.

8 is a scanning electron microscope (SEM) photograph showing the surface of the electrode of Example 6 according to an experimental example of the present invention before and after the oxygen generation reaction experiment. 8(a) and 8(b) show the state before the experiment, and it can be seen that the manganese phosphate thin film (200MnCoPi) containing cobalt formed hexagonal columnar particles. However, as shown in FIGS. 8(c) and 8(d), after 170 or more repeated experiments, it can be seen that after the electrode of Example 6 was stabilized, the surface became rough and porous particles were formed. This means that porous particles are formed on the surface of the metal phosphate thin film, and the lattice stress increases to increase the catalyst efficiency.

Experimental Example 3: Oxygen generation reaction (OER) experiment according to the pH of the electrolyte

Using the electrode of Example 6 (200MnCoPi), an oxygen generation reaction experiment according to the concentration of the electrolyte is performed. Under the same conditions as in Experimental Example 2, the electrolyte was adjusted using 0.5 M of potassium phosphate potassium (KPi) to control the concentration of the electrolyte and an oxygen evolution reaction experiment was performed. 9 is a graph showing the results of an oxygen generating reaction experiment of an electrode according to an electrolyte concentration according to an experimental example of the present invention. FIG. 9(a) shows the current density of the electrode in the oxygen generation reaction experiment when the NHE (Normal hydrogen electrode) is used, and FIG. 9(b) is based on the RHE (Reversible hydrogen electrode).

Referring to FIG. 9, it can be seen that the current density is higher in the neutral case (pH 7.00) than in the case where the electrolyte is acidic (pH 3.02). This means that the electrode on which the metal phosphate thin film of the present invention is formed has high efficiency at a pH of 7 at which most of the electrochemical reactions are performed.

On the other hand, Figure 10 shows the results of testing the durability of the electrode of Example 6, when the pH of the electrolyte is 14, according to an experimental example of the present invention.

As the working electrode, the electrode of Example 6 (200MnCoPi) was used as a counter electrode, and carbon electrode (Carbon cloth) and a reference electrode were used as Hg/HgO (1 M KOH), and 1 M KOH aqueous solution was used as the electrolyte to obtain oxygen at pH 14 Occurrence reaction experiments are performed. Then, the voltage at a constant current density was measured according to the experiment time.

Referring to FIG. 10, it can be seen that the voltage of the electrode changes as the experiment time passes, but the voltage stabilizes after a certain period of time, especially after 15 hours. That is, it can be seen that the electrode on which the metal phosphate thin film of the present invention was formed is stabilized over time in the electrochemical reaction and has a constant catalytic electrode efficiency.

2. Manganese Phosphate Thin Film (MnPi) Electrode Using Nickel (Ni) Substrate

Hereinafter, a metal phosphate thin film 100 is prepared by using nickel (Nickel, Ni) as the metal substrate 300 and iron (Fe) based on zinc (Zn) as the transition metal cation 260. An example will be described.

First, in the present embodiment, a method of manufacturing a zinc phosphate thin film (ZnPi) is prepared, and nickel (Ni) is prepared as the metal substrate 300 and a pretreatment process of the metal substrate is performed. The metal substrate is treated with 40 mL of 0.2 M NaOH aqueous solution in a degrease soultion at 60° C. for 8 minutes. At this time, the metal substrate is rotated at 200 rpm and processed. Subsequently, the mixture is washed for 1 minute in distilled water, treated with 40 mL of a 10% concentration aqueous HCl solution for 5 minutes at room temperature, and then washed twice with distilled water for 1 minute.

Subsequently, the pretreated metal substrate is surface-treated for 1 minute using 40 mL of an aqueous solution in which 0.4 g of a phosphoric acid-based compound K-107A (manganese phosphate-based surface modifier of BCC) is dissolved as a surface activating soulution. . The surface treatment is performed by rotating the metal substrate at 200 rpm in a zinc phosphate-based aqueous solution.

Thereafter, as a coating solution, an aqueous solution of 50 mL of zinc phosphate solution (Zn Phosphating solution), zinc sulfate (ZnSO ₄ ), and iron sulfate (FeSO ₄ ), which is a sulfate (MSO ₄ ) containing a second transition metal cation, is used. To form a thin film of phosphate.

In this case, the zinc phosphate solution includes 10 mL of phosphoric acid (H ₃ O ₄ ), 2 mL of nitric acid (HNO ₃ ), 0.2 g of sodium fluoride (NaF), 0.02 g of sodium triphosphate (Na ₅ P ₃ O ₁₀ ), K··· _{Na · tartrate tetrahydrate (C 4 H} 6 O 6 · K · Na · 4H 2 O) 0.5 g, sodium anywhere chamber sulfonate _{(Soudium dedocyl benzene sulfonate, C 18} H 30 -SO 3 - + Na)) 0.005 g, And potassium nitrite (Potassium nitrite, KNO ₂ ) 2 g of distilled water is mixed in 1000 mL, and the pH is adjusted to 2.5 with a 2 M NaOH aqueous solution.

Finally, the metal substrate on which the metal phosphate thin film is formed is washed with distilled water. The zinc phosphate thin film (ZnPi) prepared by the above method includes a nickel (Ni) element dissolved in a nickel (Ni) substrate, a zinc cation, an iron (Fe) cation and a phosphate added separately. Hereinafter, optimization experiments according to the performance of the electrode on which the metal phosphate thin film is formed by varying the conditions in the method for manufacturing the zinc phosphate thin film (ZnPi) will be described.

Experimental Example 4: Measurement of water oxidation reaction activity according to the temperature of zinc phosphate thin film formation

In this experimental example, the water oxidation reaction activity of the zinc phosphate thin film (ZnPi) electrode prepared differently according to the temperature in the above manufacturing method will be described.

In the zinc phosphate thin film manufacturing method, the temperature of forming the phosphate thin film is 25°C, 70°C, 80°C and 90°C, respectively, and is performed for 8 minutes to prepare a phosphate thin film containing iron.

11 is a graph showing water oxidation reaction activity of an electrode according to a zinc phosphate thin film formation temperature according to an experimental example of the present invention. Referring to (a), (b), (c), and (d) of FIG. 11, the water oxidation reaction activity increases as the temperature increases when the zinc phosphate thin film is formed, but the temperature is the highest at temperatures between 70°C and 80°C. It can be seen that it has a high current density. However, referring to FIG. 11(e), it can be seen that the reproducibility of the electrode having the zinc phosphate thin film formed at a temperature of 70° C. or higher is poor. That is, it can be seen that, in the present experimental example, when the zinc phosphate thin film was formed, it was performed at a temperature of 70°C.

Experimental Example 5: Measurement of water oxidation reaction activity over time of zinc phosphate thin film formation

In this experimental example, the water oxidation reaction activity of the zinc phosphate thin film (ZnPi) electrode prepared differently with time in the above manufacturing method will be described.

In the zinc phosphate thin film production method, the temperature in the process of forming the phosphate thin film is 70° C., and the time is 10 minutes, 20 minutes, 40 minutes and 80 minutes, respectively, to prepare a phosphate thin film containing iron.

12 is a graph showing the water oxidation reaction activity of the electrode according to the zinc phosphate thin film formation time according to an experimental example of the present invention. Referring to FIG. 12, when the zinc phosphate thin film is formed, the water oxidation reaction activity increases as time increases, but it can be seen that it has the highest current density when it is performed for 40 minutes. That is, it can be seen that the present experimental example is an optimal condition that is performed for 40 minutes when forming a zinc phosphate thin film.

Experimental Example 6: Measurement of water oxidation reaction activity according to the content of transition metal cations when forming a zinc phosphate thin film

In this experimental example, the water oxidation reaction activity of a zinc phosphate thin film (ZnPi) electrode prepared with a different content of transition metal cations in the above manufacturing method will be described.

In the zinc phosphate thin film production method, the temperature in the process of forming the phosphate thin film is 70° C., the time is 40 minutes, the content of zinc ions ([Zn ²⁺ ]), the content of zinc ions and iron ions ([Zn ²⁺ ] and [Fe ²⁺ ]) to prepare phosphate thin films containing iron, which are referred to as Examples 13 to 16, respectively. At this time, the content ratio of zinc ions and iron ions is fixed at 1:3 ([Zn ²⁺ ]/[Fe ²⁺ ] = 1/3), and is prepared by varying the amount added to the coating solution.

13 is a graph showing the water oxidation reaction activity of an electrode according to the amount to which a transition metal cation is added when forming a zinc phosphate thin film according to an experimental example of the present invention.

Referring to (a) of FIG. 13, it can be seen that zinc ion ([Zn ²⁺ ]) when forming a zinc phosphate thin film has the highest current density when 10 mM. And, referring to (b) and (c) of FIG. 13, the content ratio of zinc ions and iron ions is 1:3, and when 10 mM and 30 mM are added, respectively, it can be seen that it has the highest current density. have. That is, in the present experimental example, it can be seen that when forming a zinc phosphate thin film, it is optimal to prepare a zinc phosphate thin film by adding 10 mM of zinc ion and 30 mM of iron ion.

Meanwhile, FIG. 14 is a graph showing the water oxidation reaction activity of an electrode according to the content of metal cations of a metal substrate added to a coating solution when forming a zinc phosphate thin film, according to an experimental example of the present invention. Referring to FIG. 14, it can be seen that as the nickel (Ni) ion used as a metal substrate was further added to the coating solution, the current density decreased. It can be seen that, when forming the zinc phosphate thin film, it is an optimal condition to not add more metal cations of the metal substrate.

In addition, FIG. 15 is a graph showing the water oxidation reaction activity of an electrode according to whether a second transition metal cation is included in forming a zinc phosphate thin film according to an experimental example of the present invention. Referring to FIG. 15, it can be seen that the current density is higher when the zinc phosphate thin film includes nickel as a metal cation, zinc as a transition metal cation, and iron as a second transition metal cation. That is, when two or more kinds of transition metal cations are included, it means that the activity of the electrode is further improved.

Referring to the above experimental examples, the electrode formed with the zinc phosphate thin film was coated with a coating solution containing 10 mM of zinc ion (ZnSO ₄ ) and 30 mM of iron ion (FeSO ₄ ) in the above method for 40 minutes at 70°C. It can be seen that under the conditions of processing, the performance of the electrode can be maximized.

3. Physical property analysis of zinc phosphate thin film electrode (ZnPi) using nickel (Ni) substrate

Hereinafter, physical property analysis of the manganese phosphate thin film electrode according to the experimental results of the "2. Zinc phosphate thin film electrode using a nickel substrate" will be described.

Example 9: Zinc phosphate thin film (Zn(Ni)FePi) electrode containing iron (Fe)

First, it is the same method as the manufacturing method of the experimental result of "2. Zinc Phosphate Thin Film Electrode Using Nickel Substrate", and the coating solution containing 10 mM of zinc ion (ZnSO ₄ ) and 30 mM of iron ion (FeSO ₄ ) 70 An electrode in which a zinc phosphate thin film (Mn(Ni)FePi) containing iron is formed on a nickel (Ni) substrate under conditions of processing at 40° C. for 40 minutes, is referred to as “Example 9”.

Example 10: Stabilized zinc phosphate thin film electrode (Zn(Ni)FeOx)

The electrode (Zn(Ni)FePi) of Example 9 was repeatedly subjected to a water oxidation experiment to prepare a stabilized electrode. The electrode of Example 9 was used as a working electrode, a carbon electrode as a counter electrode, and Hg/HgO (1 M KOH) as a reference electrode, and a 3-electrode cell was constructed with an aqueous 1 M KOH solution of pH 14 as an electrolyte. do. The water oxidation experiment using the electrode of Example 9 was repeated 150 times to convert the phosphate (Pi) of the electrode into a hydroxyl group (-OH). The electrode (Zn(Ni)FeOx) formed at this time is referred to as “Example 10”.

Comparative Example 2: Nickel-iron electrode (e-NiFeOx) using electroplating

A nickel-iron electrode (e-NiFeOx) is prepared by electroplating iron ions on a nickel substrate using a conventional method, which is referred to as Comparative Example 2.

Next, physical properties of Examples 9 and 10 will be described with reference to FIGS. 16 to 19.

16 and 17 are photographs and graphs showing the surface properties of a zinc phosphate thin film electrode according to an embodiment of the present invention. (A), (b), (c), and (d) of FIG. 16 are SEM photographs and atomic force microscopy (AFM) photographs of the surface and cross-section of the Example 9 electrode, and FIG. 17(e), (f), (g) and (h) are SEM and AFM photographs of the surface and cross section of the Example 10 electrode.

16 and 17, it can be seen that the surfaces of Examples 9 and 10 have a rough surface by forming a zinc phosphate thin film. The case of Example 10 appears to have a relatively even surface. This shows that the AFM graphs and photographs of Examples 9 and 10 show a decrease in roughness or variation in atomic distribution according to the depth of the zinc phosphate thin film. That is, since the electrode of Example 9 in which the first phosphate thin film was formed repeated 150 water oxidation experiments, it means that the electrode of Example 10 was stabilized and had a certain level of performance compared to Example 9.

18 and 19 are graphs showing the atomic distribution on the surface of a zinc phosphate thin film electrode according to an embodiment of the present invention.

Referring to FIG. 18, the atomic distributions of the electrode surfaces of Example 9 and Example 10 can be seen. Both electrodes appear to contain elements of nickel, iron and zinc. In the case of nickel, it is a metal cation melted from the metal substrate, and iron and zinc are transition metal cations added to the coating solution. On the other hand, referring to (c) of FIG. 18, Example 10 appears to have almost no phosphorus (P) content, which means that 150 water oxidation experiments are repeated to replace phosphate (Pi) with hydroxyl groups (OH). do.

19(a) is an example 9 electrode surface, and FIG. 19(b) is an analysis result using an energy dispersive spectroscope (EDS) of the electrode surface of Example 10. Referring to FIG. 19, the types and contents of atoms distributed on the surface of the electrode of Example 9 and Example 10 can be seen.

20 is a graph showing the current density in the water oxidation experiment of the electrode according to an embodiment of the present invention. FIG. 20 shows that the current density increases during the manufacture of Example 10 by repeatedly performing the water oxidation experiment of the electrode of Example 9. This means that the performance of the electrode as Example 9 was improved as the surface properties of the zinc phosphate thin film changed and stabilized while performing the water oxidation experiment.

Next, the performance of Examples and Comparative Examples of the present invention will be described with reference to FIGS. 21 to 24.

21 and 22 are graphs showing cyclic voltammetry (CV) analysis results of water oxidation experiments of electrodes according to Examples and Comparative Examples of the present invention. Using the electrode of Example 10 and the electrode of Comparative Example 2, a water oxidation experiment is performed in a 1M KOH aqueous solution. 21 and 22, it can be seen that the electrode of Example 10 in which the phosphate thin film was formed according to an embodiment of the present invention has better performance than the electrode of Comparative Example 2 prepared through a conventional electroplating method. have.

23 is a graph showing the results of a cyclic voltammetry (CV) analysis in the water oxidation experiment of an electrode according to the pH of an electrolyte according to an embodiment and a comparative example of the present invention. 23A and 23B show the results of experiments using the electrode of Example 10 and FIGS. 23C and 23D using the electrode of Comparative Example 2. In the water oxidation experiment, an aqueous KOH solution was used as the electrolyte, and the pH was adjusted by varying the concentration. Referring to FIG. 23, it can be seen that the current density increases as the pH of both electrodes increases. However, when comparing the two electrodes, it can be seen that the electrode of Example 10 has a very high current density compared to the electrode of Comparative Example 2. This means that the metal phosphate thin film according to the present invention has better electrode performance than the conventional electroplating method.

24 is a photograph showing a process of performing a water oxidation experiment using an electrode on which a metal phosphate thin film is formed according to an embodiment of the present invention.

According to FIG. 24, when the constant current of 20 mA/cm ² was applied using the electrode of Example 10, the amount of oxygen generated with time was measured. As a result, it can be seen that 0.4 mL of oxygen is generated every 30 minutes. This is a value corresponding to about 97% of Faraday efficiency (FE). That is, it can be seen that the electrode on which the metal phosphate thin film was formed according to one embodiment of the present invention has excellent efficiency as an electrochemical catalyst.

As described above, as a result of comparing Examples 1 to 8 with Comparative Example 1, the electrodes of Examples 1 to 8 in which a metal phosphate thin film was formed than a pure stainless steel substrate exhibited better performance in an oxygen evolution reaction (OER) experiment. You can see that In addition, when the transition metal cation is further added in a specific content, performance improvement of the electrode on which the metal phosphate thin film is formed can be maximized.

In addition, as a result of comparing Examples 9, 10 and Comparative Example 2, when forming a zinc phosphate thin film containing iron on a nickel substrate, it is possible to maximize electrode performance by controlling optimal process conditions. It can be seen that the electrode manufactured through the above method has superior performance in terms of current density and durability compared to the electrode manufactured through the conventional electroplating method.

Therefore, the method for producing a metal phosphate thin film of the present invention can be prepared in a short time at a low temperature using a phenomenon in which a phosphate anion is precipitated as a solid by adjusting the pH of the solution. In addition, an electrochemical catalyst electrode containing transition metal and phosphate and forming porous metal phosphate particles has high reactivity and stability, and has excellent performance.

The present invention has been illustrated and described with reference to preferred embodiments, as described above, but is not limited to the above embodiments and is varied by those skilled in the art to which the present invention pertains without departing from the spirit of the present invention. Modifications and modifications are possible. Such modifications and variations are to be considered as falling within the scope of the invention and appended claims.

100: metal phosphate thin film
110: metal phosphate particles
200: coating solution
210: acidic aqueous solution
220: phosphate anion
260: transition metal cation
280: [NO _2] ^- anion
300: metal substrate
320: metal ion
500: electrochemical catalyst electrode

Claims (9)

(a) preparing an acidic aqueous solution having a pH of 2 or more and 5 or less;
(b) adding a phosphate anion that can precipitate within the pH range to the acidic aqueous solution to form a coating solution;
(c) immersing a metal substrate containing a metal ionized within the pH range of the coating solution in the coating solution;
(d) the metal of the metal substrate is ionized to form metal ions, and increasing the pH of the coating solution; And
(e) forming a metal phosphate thin film on at least a portion of the metal substrate by combining and depositing the phosphate anion with the metal ion;
Including,
In step (e), as the pH increases, the precipitation rate of the phosphate anion becomes greater than the ionization rate of the metal,
A metal phosphate thin film comprising the same metal as the metal substrate is formed, and a metal phosphate thin film is formed in the region of the metal substrate corroded in step (d),
The metal substrate includes nickel (Ni), and the coating solution further includes two kinds of zinc (Zn) ions and iron (Fe) ions, which are transition metal cations for improving catalytic activity,
In the step (e), the method of manufacturing a metal phosphate thin film, wherein the phosphate anion binds and precipitates with the metal ion and the transition metal cation. delete delete According to claim 1,
The coating solution further comprises a nitrite ion (Nitrite ion, [NO ₂ ] ^- ) for accelerating the increase of the pH, the method for producing a metal phosphate thin film. According to claim 1,
The coating solution has a temperature range of 50 ℃ to 90 ℃, a method for producing a metal phosphate thin film. delete delete According to claim 1,
The metal phosphate thin film is a method of manufacturing a metal phosphate thin film containing porous metal phosphate particles having a size of 1 μm to 3 μm. An electrochemical catalyst electrode comprising a metal phosphate thin film on at least a portion of a surface,
The metal phosphate thin film is formed by the method of manufacturing a metal phosphate thin film of any one of claims 1, 4, 5, and 8, an electrochemical catalyst electrode.

Images