KR20220100538A - Oxygen evolution reaction catalyst for seawater electrolysis and preparation method thereof - Google Patents

Abstract

The present invention relates to an oxygen generation reaction catalyst for seawater electrolysis and a preparation method thereof, and more specifically, to an oxygen generation reaction catalyst for seawater electrolysis comprising a metal oxide having an atomic-scale gap and a preparation method thereof. When the oxygen generation reaction catalyst for seawater electrolysis of the present invention is used at the anode during seawater electrolysis, the oxygen generation reaction catalyst exhibits the effect of generating oxygen by selectively proceeding an oxygen generation reaction more predominantly between a chlorine generation reaction and the oxygen generation reaction which can occur at the anode.

Description

OXYGEN EVOLUTION REACTION CATALYST FOR SEAWATER ELECTROLYSIS AND PREPARATION METHOD THEREOF

The present invention relates to an oxygen evolution catalyst for seawater electrolysis and a method for preparing the same, and more particularly, to an oxygen evolution catalyst for seawater electrolysis comprising a metal oxide having an atomic-scale gap formed therein, and production thereof it's about how

The initial seawater electrolysis process has been limited to chlorine production. However, chlorine production by seawater electrolysis is currently prohibited because the release of chlorine gas into the atmosphere destroys ozone and accelerates global warming. In general, chlorine in the form of chlorous acid is used for disinfection and bleaching, but has serious problems in practical use due to local corrosion and human toxicity due to chlorine gas.

In the conventional seawater electrolysis reaction, chlorine ions are oxidized at the anode to generate chlorine, and sodium hypochlorite for seawater sterilization is prepared by reacting this chlorine with sodium hydroxide generated at the cathode. For the positive electrode, an active material with excellent chlorine-generating electrode catalytic activity and low oxygen generation has been applied. Research on chlorine-generating positive electrode active material, a number of studies including a positive electrode for soda (soda) electrolysis for producing chlorine from high-concentration saline has been conducted. It has been confirmed that an electrode coated with a platinum group metal, alloy, and platinum group oxide on a Ti substrate has a characteristic of selectively generating chlorine first, and has been put to practical use.

The oxygen evolution equilibrium potential in a neutral solution is about 0.7 V, which is lower than the chlorine evolution equilibrium potential. However, whereas chlorine evolution is a simple reaction, oxygen evolution is a complex reaction compared to chlorine evolution. And since the actual oxygen generation potential is higher than the chlorine generation potential in seawater electrolysis, chlorine gas is preferentially generated in the seawater electrolysis reaction. In order to suppress the generation of chlorine gas generated at the anode during seawater electrolysis, a manganese dioxide electrode is used. Manganese dioxide oxide has recently been applied as an anode electrode for seawater electrolysis because it has an oxygen generation overvoltage lower than that of chlorine generation. In addition, research into adding various elements to improve oxygen generation efficiency is being attempted.

Republic of Korea Patent Registration No. 10-0383269

An object of the present invention is to provide a catalyst capable of selectively increasing the efficiency of an oxygen evolution reaction under conditions in which chlorine production is suppressed during seawater electrolysis.

An embodiment of the present invention provides an oxygen evolution catalyst for seawater electrolysis comprising a metal oxide having an atomic-scale gap formed therein.

The catalyst is an anode catalyst for seawater electrolysis, characterized in that it selectively increases the efficiency of the oxygen generation reaction among chlorine generation reaction and oxygen generation reaction during seawater electrolysis.

The average of the atom-unit gaps is 5 to 11 Å, but is not limited thereto.

The metal oxide is made in the form of MO _x (0<x≤4), wherein M is Mg, Al, Au, Ag, Cd, Co, Cr, Cu, In, Ir, Mo, Nb, Ni, Os, At least one selected from the group consisting of Pd, Pt, Rh, Ru, Sn, Ti, V, W, Zn, Sc, Y, Zr, Hf, Ta, Mn, Fe, Tc, and Re.

According to another embodiment of the present invention, there is provided an anode for seawater electrolysis comprising the oxygen evolution reaction catalyst.

According to another embodiment of the present invention, there is provided a seawater electrolysis system including the anode for seawater electrolysis.

According to another embodiment of the present invention, there is provided a method for preparing an oxygen evolution catalyst for seawater electrolysis, the method comprising the steps of: 1) electrochemically lithiating a metal oxide; and 2) removing the lithiated metal oxide. lithiation.

The lithiation may include applying a constant current and a cut-off voltage of 0 V to 3 V using an electrochemical cell.

The delithiation may include washing the lithiated metal oxide with an acid solution or raising the voltage to 3 V immediately after lithiation is performed.

The metal oxide is made in the form of MO _x (0<x≤4), wherein M is Mg, Al, Au, Ag, Cd, Co, Cr, Cu, In, Ir, Mo, Nb, Ni, Os, At least one selected from the group consisting of Pd, Pt, Rh, Ru, Sn, Ti, V, W, Zn, Sc, Y, Zr, Hf, Ta, Mn, Fe, Tc, and Re.

When the oxygen evolution catalyst for seawater electrolysis of the present invention is used for the anode during seawater electrolysis, it is possible to produce oxygen by selectively advancing the oxygen evolution reaction among the chlorine evolution reaction and the oxygen evolution reaction that may occur at the anode. show possible effects.

1(a) is a schematic diagram of the voltage profile of the lithiation process of RuO ₂ and the formation of atom-unit gaps during reaction with lithium ions, and FIG. 1 is a real-time transmission electron microscope (TEM) of the lithiation process of single RuO ₂ particles. Fig. fi is a real-time TEM analysis image of RuO ₂ particle clusters corresponding to the initial, I, II and III states in the voltage profile (a).
FIG. 2(a) is a lattice expansion graph of single RuO ₂ particles upon lithiation in real-time TEM analysis, FIG. 2(b) is the average particle size measured by TEM observation, and FIG. 2(c) is measured by TEM observation. It is a statistical analysis graph of the average inter-lattice spacing.
3 is a TEM image (left) for each stage of lithiation of catalyst groups treated through the lithiation method and a statistical graph (right) of the resulting gap. More than 150 gaps were investigated for each image and statistics were generated, and representative values were set as the names of gaps.
Figure 4 (a) is a graph showing the result of measuring the current density in the acid condition of 0.1 M HClO ₄ of the lithiated RuOx nanoparticles according to an embodiment of the present invention, Figure 4 (b) is a BET surface area It is a graph.
5 is an electrochemical evaluation graph for the oxygen evolution reaction (a) a graph of the electrochemical evaluation result through the linear scanning potential (LSV) for the oxygen evolution reaction in acidic, seawater, and basic aqueous solution; (b) Tafel plotting the change of electrochemical properties evaluated through linear scanning potential method in each aqueous solution; (c) This is a table summarizing the degree of increase in properties, and (d) is a comparison of the tendency of electrical double layer capacitance (EDLC) and catalytic activity. It shows that the unit gap played a role in improving the performance.
6 is a seawater electrolysis potential-pH diagram (Pourbaix diagram) graph.
7(a) is a current separation graph of the reaction of oxygen and chlorine generation using an electrochemical method. Among the oxygen and chlorine generated from the disk electrode using a rotating ring-disk electrode (RRDE) in an acid solution containing 0.5 M NaCl, FIG. It selectively separates only chlorine from the ring, and thus shows the selectivity of oxygen/chlorine by voltage; (b) is a graph comparing the selectivity of oxygen and chlorine in terms of faradaic efficiency; (c) is a graph using actual seawater to investigate the results of seawater-electrolyzer and the amount of oxygen generated in the low current (10mA cm ^-2 ) and high current (100mA cm ^-2 ) sections.

In the present specification, when a member is said to be located “on” another member, this includes not only a case in which a member is in contact with another member but also a case in which another member is present between the two members.

In the present specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

In an embodiment of the present invention, there is provided an oxygen evolution catalyst for seawater electrolysis comprising a metal oxide having an atomic-scale gap formed, wherein the catalyst is an anode catalyst for seawater electrolysis, It is characterized by selectively increasing the efficiency of the oxygen evolution reaction among the chlorine evolution reaction and the oxygen evolution reaction.

In the electrolysis of seawater, chlorine gas or oxygen is generated at the anode. Hydrogen is generated at the cathode. The electrode reaction taking place at the two electrodes in the electrolysis reactor is as follows;

[anode]

2Cl ^- → Cl ₂ (g) 1.358 V vs. RHE

2H₂O → O₂(g) + 4H⁺ + 4e^- 1.299 V vs. RHE

[cathode]

2H₂O + 2e^- → H₂(g) + 2OH^- 0 V vs. RHE

In seawater electrolysis, since the actual oxygen generation potential is higher than the chlorine generation potential, chlorine gas is preferentially generated in the seawater electrolysis reaction.

The oxygen generation reaction catalyst for seawater electrolysis of the present invention exhibits an effect of selectively increasing the oxygen generation reaction efficiency when used in an anode for seawater electrolysis to generate oxygen.

The atomic-scale gap of the metal oxide is formed by electrochemical lithiation and delithiation processes of the metal oxide, and the average of the atomic-scale gap is 5 to 11 Å, more preferably 6 to 8 Å, but not limited thereto.

The metal oxide is made in the form of MO _x (0<x≤4), wherein M is Mg, Al, Au, Ag, Cd, Co, Cr, Cu, In, Ir, Mo, Nb, Ni, Os, At least one selected from the group consisting of Pd, Pt, Rh, Ru, Sn, Ti, V, W, Zn, Sc, Y, Zr, Hf, Ta, Mn, Fe, Tc, and Re.

As the lithiation proceeded, that is, as the cut-off voltage of the electrochemical lithiation process increased, the atom-unit gap increased, and it was confirmed that the optimum efficiency of the oxygen evolution reaction was exhibited when the atom-unit gap was 6 to 8 Å. .

The atomic-scale gap is a space formed in an atomic-scale size, and may include a regular or irregular shape, and may be separated or connected to each other, but is not limited thereto.

According to another embodiment of the present invention, there is provided an anode for seawater electrolysis comprising the oxygen evolution reaction catalyst.

The oxygen evolution catalyst may be fixed by a current collector, and the current collector is selected from (i) a carbon-based carrier, (ii) a porous inorganic oxide such as zirconia, alumina, titania, silica, ceria, and (iii) zeolite. can be The carbon-based carrier is carbon black (carbon black), porous carbon (porous carbon), carbon nano tube (carbon nano tube, CNT), carbon nano horn (carbonnano horn), graphene (graphene), super P (super P) , carbon fiber, carbon sheet, Ketjen Black, acetylene black, carbon sphere, carbon ribbon, fullerene, activated carbon And it may be selected from a combination of two or more thereof, but is not limited thereto, and current collectors usable in the technical field of the present invention may be used without limitation.

According to another embodiment of the present invention, there is provided a seawater electrolysis system including the anode for seawater electrolysis. The seawater electrolysis system may further include a negative electrode and an electrolyte, and the negative electrode, the ion exchange membrane and the electrolyte may be those commonly used in the technical distribution of the seawater electrolysis system, and are not particularly limited.

According to another embodiment of the present invention, there is provided a method for preparing an oxygen evolution catalyst for seawater electrolysis, the method comprising the steps of: 1) electrochemically lithiating a metal oxide; and 2) removing the lithiated metal oxide. lithiation.

The metal oxide is made in the form of MO _x (0<x≤4), wherein M is Mg, Al, Au, Ag, Cd, Co, Cr, Cu, In, Ir, Mo, Nb, Ni, Os, At least one selected from the group consisting of Pd, Pt, Rh, Ru, Sn, Ti, V, W, Zn, Sc, Y, Zr, Hf, Ta, Mn, Fe, Tc, and Re. Preferably, the metal oxide is RuO ₂ .

The method may further include drying the metal oxide at a temperature of 100 to 200° C. before the lithiation.

The lithiation may include applying a constant current and a cut-off voltage of 0 V to 3 V using an electrochemical cell. The cut-off voltage may be preferably 0.5 V to 3 V, more preferably 0.5 V to 2 V, but is not limited thereto. According to the present inventor's experiment, it was confirmed that, when the cut-off voltage was 0.8 V, an atomic-unit gap of about 6-8 Å was formed, and the highest oxygen evolution reaction activity was exhibited at the atomic-unit gap of this level. .

An atomic-scale gap of the metal oxide may be controlled by a cut-off voltage of a process of electrochemically lithiating the metal oxide particles. This specifically means that the atom-unit gap can be controlled by the cut-off voltage during constant current discharge (lithiation), that is, the voltage at which lithiation is stopped.

In the lithiation process under the constant current condition, lithiation is uniformly performed on the entire surface of the metal oxide particle, and in order to prevent the ruthenium metal from being desorbed and removed from the surface of the nanoparticles due to rapid and partial lithiation, low current lithiation is performed It is advantageous to be As a specific example, the low current lithiation current is preferably about 1 mA/g to about 20 mA/g.

Specifically, the lithiation step includes a) a first electrode in which a material layer containing the ruthenium oxide is formed on a current collector, a second electrode of metallic lithium, a separator positioned between the first electrode and the second electrode, and an electrolyte manufacturing an electrochemical cell; and b) performing lithiation by applying a constant current and a cut-off voltage of 0 V to about 3 V or less using the prepared electrochemical cell.

The electrochemical cell of step a) may correspond to a conventional lithium half-cell using a metal oxide as an active material, and the lithiation of step b) may correspond to a constant current discharge process in a conventional lithium half-cell. Accordingly, it goes without saying that the cut-off voltage may be a voltage based on Li/Li ⁺ .

The first electrode may be prepared by applying a slurry including a metal oxide and an organic binder on a current collector and then drying the slurry. The organic binder can be used as long as it is a material commonly used in electrodes of lithium secondary batteries, and any polymer that does not chemically react with the electrolyte is sufficient. The second electrode may be a film or foil of metallic lithium, but is not limited thereto. In addition, the separator may be used as long as it is a microporous membrane used in a typical lithium secondary battery.

The electrolyte may be used without limitation as long as it is a conventional non-aqueous electrolyte that smoothly conducts lithium ions in a conventional lithium secondary battery, and the solvent of the electrolyte is generally used as a non-aqueous electrolyte in a lithium secondary battery. have.

Of course, after the lithiation of step b) is performed, the step of recovering the lithiated nanoparticles from the first electrode may be further performed, and the recovery is a solvent and solid-liquid separation for dissolving the organic binder of the first electrode. It may be performed using, but is not limited to.

In one embodiment of the present invention, the delithiation step may be performed through acid water washing (chemical delithiation), and the acid of acid water washing is limited as long as it is a conventional acid used to selectively remove lithium oxide and/or lithium. It may be used without, but is not limited to. For example, the acid may include formic acid or acetic acid, but is not limited by the type of acid used for acid washing.

In another embodiment of the present invention, the delithiation step may be performed by raising the voltage to 3 V immediately after the lithiation of step b) is performed (electrochemical delithiation).

The delithiation step may be performed by chemical delithiation or electrochemical delithiation, and chemical delithiation and electrochemical delithiation may be performed together.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention in more detail, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not limited by these examples according to the gist of the present invention. .

<Example> Preparation of Oxygen Generation Reaction Catalyst for Seawater Electrolysis Using Lithium Ion Coin Cell

The RuO ₂ powder was dried for 3 hours at 150 degrees Celsius in an Ar atmosphere. The RuO ₂ powder and binder (5wt% PVDF) were dispersed in NMP (N-methyl-2-pyrrolidinone) to prepare a slurry. The slurry was applied to high-purity Cu foil (99.9999%) and dried in a vacuum oven at a temperature of 80° C. for one day.

The dried RuO ₂ electrode was used as one electrode and high purity Li foil (99.9999%) was used as the opposite electrode, and 1M LiPF ₆ as an electrolyte was dissolved in EC (ethyl carbonate) and DEC (diethyl carbonate) mixed in a 1:1 volume ratio. A coin cell was manufactured using OCV (Open Circuit Voltage) showed a value of about 3 V or more.

In the lithiation process, a charging/discharging process was performed by applying a current of about 3 mA. The lithiation process was performed for the I state to 1.6 V (Example 1), the II state to 0.8 V (Example 2), and the III state to 0 V (Example 3).

After the lithiation process is performed, delithiation is performed by increasing the voltage to 3 V in all, and the resultant samples of each process step are washed with acetone, water, and 1 mM acetic acid solution, residual electrolyte, Li ₂ O, and The solid electrolyte interlayers were removed.

<Experimental example>

1. Morphological analysis of oxygen evolution catalyst for seawater electrolysis

The lithiation reaction for metal oxides in battery materials, especially catalysts called conversion materials, is as follows:

{MxRy + (y.n)A -> xM + yAnR}

Here, A = Li, Na, M = transition metal, and R = O, S, Se, P, H, etc.

In the case of lithiation, there are some differences depending on the material, but taking a metal oxide as an example, an intermediate product such as [LixMyOz] is formed when the conversion reaction from a metal oxide to a metal occurs.

Referring to FIG. 1A , when no current is applied to RuO ₂ , RuO ₂ remains as it is (bare), and when lithiation proceeds [LixRuyOz] (where x, y, and z are independently real numbers of 0.1 to 3) .) is formed (I state, Examples 1 and 2), and as lithiation proceeds further, Ru metal is formed (II→III state, Example 3). That is, the more progressed I→II→III, the more lithiation proceeded. In FIG. 1A , the X-axis may be used as both a specific capacity, a degree of lithiation, or a time of a lithiation process.

Ruthenium oxide during lithiation showed two voltage plateaus. The first voltage band was about 2V compared to lithium, and the second voltage range was around 1V (Fig. 1a).

The first section is a Faraday reaction for lithium insertion into RuO ₂ , and the second section is a conversion section to Ru metal, and the present inventors confirmed that an atomic gap was formed in the second section.

All samples were stopped after lithiation at each voltage step, and electrochemical delithiation was performed to remove Li ions remaining inside the catalyst.

In order to confirm the real-time change of RuO ₂ nanoparticles during the lithiation process, structural changes including lattice expansion and grain boundary formation were observed in real time through in-situ TEM analysis using a nano battery configuration inside the TEM (Fig. 1b-i). and FIG. 2), statistically analyzing the gaps created in each step, and using a representative value as the name of the gaps in the atomic unit (FIG. 3); 0-RuO ₂ , 7-RuO ₂ , 11-RuO ₂ , 14-RuO ₂ .

Referring to FIG. 2 , as a result of TEM image analysis, the average size of the particles did not show a significant difference within 50 nm at each stage, and after the conversion to Ru metal, the volume expansion and the amorphous effect of RuO ₂ resulted in dramatic changes in RuO 2 . It was confirmed that lithiation proceeded through structural changes.

To summarize the above results, 1) the initial metal oxide catalyst is cleaved to form small particles, and the surface area increases (the increase in surface area can be confirmed as a result of the EDLC in FIG. 4) 2) The atomic unit gap between the faces of the cleaved metal oxide catalyst (Atomic scale gap) can be formed (check the TEM images in FIGS. 1 and 2), and the atomic-scale gap size is sub-nanometer (<1 nm), specifically, metal oxide that can dramatically improve OER performance It is possible to form a three-dimensional channel with a level of about 6-8 Å, which is the distance between the surface of the catalyst.

The atom-unit gap formed by the lithiation was confirmed by the experiment below to dramatically improve the oxygen evolution reaction during seawater electrolysis.

2. Evaluation of electrochemical properties of oxygen evolution catalyst for seawater electrolysis

The electrochemical characteristic evaluation of the oxygen evolution catalyst for seawater electrolysis was measured using a Rotating Ring Disk Electrode (RRDE) equipment. A half battery cell was tested, and a glassy carbon electrode was used as an electrode.

10 mg of the catalyst was dissolved in 100 ul of binder (10wt% Nafion solution) and 900 ul of ethanol + IPA solvent. This ink-type catalyst was placed on a glassy carbon electrode, dried, and then electrochemical properties were measured.

A platinum wire was used as the counter electrode, and an acid, neutral Ag/AgCl electrode, and a base, Hg/HgO electrode were used as the reference electrode.

Both the oxygen evolution reaction (OER) and the chlorine evolution reaction (CER) were measured after purging the cell with Ar gas.

In the case of the experiment showing the electrochemical properties of FIG. 3 , the experiment was performed in an acid condition of 0.1 M HClO ₄ . Ag/AgCl was used as the reference electrode, and the experiment was performed while rotating the RRDE electrode at 1600 rpm. The potential range in the experiment was measured by the cyclic amperometric method by scanning the range of [1.1 V, 1.4 V] at 10 mV/s.

Referring to FIG. 4(a), the catalysts of Examples 1 and 2 were RuO ₂ (bare) without lithiation. and an increased current density of about 2 to 6 times compared to Example 3, which means that Examples 1 and 2 have a large electrochemical surface area, which is the surface area measurement of FIG. 4(b). consistent with the result.

However, in the case of Example 3, compared with Examples 1 and 2, the surface area of FIG. 4(b) was increased, but the electrochemical activity of FIG. 4(a) was rather decreased. This means that there is no linear correlation between the surface area of the catalyst and the electrochemical activity, but rather the electrochemical activity is affected by the atom-unit gaps produced in Examples 1 or 2.

3. Confirmation of oxygen evolution reaction of oxygen evolution catalyst for seawater electrolysis during seawater electrolysis

As mentioned in Vos et al. (2018), the binding energy of the ^OOH intermediate is stabilized, and when inferred based on the mechanism in which H of the ^OOH intermediate forms a hydrogen bond in the atomic gap, the reaction rate determining step (RDS) : rate determining step) is the desorption step of ^* OOH regardless of the liquid phase.

The present inventors used linear sweep voltammetry (LSV) to conduct electrochemical evaluation in acidity, seawater (pH=7.8), and basicity to confirm that the atomic gap causes improvement in the oxygen evolution reaction (Fig. 5a).

Referring to FIG. 5A , 7-RuO ₂ , that is, when the atom-unit gap is 7 angstroms (< 1 nm), the highest increase in activity was exhibited. This tendency was common in aqueous solutions of different pH. In addition, what showed the greatest degree of improvement was the improvement of 150 mV mentioned above in basic aqueous solution.

Further, Tafel analysis was performed based on the electrochemical performance of the LSV (FIG. 5b). By plotting and comparing overvoltage versus log (current density), when the slope is small, the improvement of the Faraday response and the improvement of RDS are shown.

Referring to Figure 5b, 0-RuO ₂ Compared to when 7-RuO ₂ It could be confirmed that the reduced Tafel slope, which shows the same trend regardless of the pH.

As mentioned in the previous results, in the case of a catalyst that undergoes lithiation, the surface area increases, and if the effect of a simple surface area increase is only an increase in the electrochemical capacitance (EDLC: electric double layer capacitance), the activity should also increase. . However, in 14-RuO ₂ , a case was confirmed that deviated from this tendency, which is consistent with the results of BET.

4. Change in selectivity of oxygen and chlorine generation reaction of oxygen evolution catalyst for seawater electrolysis during seawater electrolysis

Catalysts made through atomic-level spacing can ultimately produce hydrogen and oxygen through the splitting of water in seawater. However, a high concentration of chlorine ions is present as a component of seawater, and the oxygen evolution reaction and the chlorine evolution reaction show similar oxidation reaction theoretical potentials (FIG. 6).

At this time, the chlorine evolution reaction, which is a two-electron reaction, generates a relatively low overvoltage compared to the oxygen evolution reaction, which is a four-electron reaction, so it is very difficult to selectively separate only one reaction among the two competing reactions. In addition, it is known that these two reactions have a kind of correlation due to the sharing of an intermediate and an active site.

The pH of seawater is about 7-8, and when the electrolytic reaction starts, the [H ⁺ ] concentration generated as a by-product of the oxidation reaction increases and the pH is lowered on the electrode surface and the electrolyzer where the oxidation reaction occurs.

In this case, as in the electric potential-pH diagram of seawater electrolysis of FIG. 6 (Pourbaix diagram, KS Exner et al./Electrochimica Acta 120 (2014) 460-466), HOCl produced under high pH conditions in the oxidation reaction of Cl ⁻ is inhibited, and the CER reaction in which Cl ₂ is selectively generated is dominant.

[Oxygen evolution reaction (OER)]

= (1.229 + 0.059 pH) V vs. RHE2H ₂ O → O ₂ (g) + 4H ⁺ + 4e ^-

= (1.229 + 0.059 pH) V vs. RHE

[Chlorine evolution reaction (CER)]

= (1.358 + 0.059 pH) V vs. RHE2Cl ^- → Cl ₂ (g)

= (1.358 + 0.059 pH) V vs. RHE

The chlorine evolution reaction proceeds through the combination of ^* Cl and ^* Cl, and the size of the reaction intermediate is small compared to ^* OOH in the oxygen evolution reaction.

Therefore, when a catalyst with atomic-level spacing through lithiation is applied to chlorine evolution, the reaction of ^* OOH intermediate products in OER due to the atomic-unit gap (about 5 to 11 Å) formed by lithiation. Although the energy can be lowered, it is judged that the reaction energy of ^* Cl is not improved.

This can be seen through the partial currents of oxygen and chlorine in the graph of FIG. 7A.

In the separation of partial currents of oxygen and chlorine, electrochemical analysis using a rotating ring-disk electrode (RRDE) was introduced. Of the oxygen and chlorine generated at the disk electrode, only chlorine was reduced at the ring electrode, and the amount of chlorine generated was tracked. At this time, the comparison was performed by dividing the current of chlorine and the current of oxygen to separate the currents of the two competing reactions (FIG. 7a).

Through the above experiment, it was confirmed that the generation of oxygen was selectively improved according to the introduction of the interatomic gap through the comparison (solid line) of the oxygen evolution reaction. In addition, when the selectivity at this time is compared with the faradaic efficiency, it can be seen that the oxygen generation due to the introduction of interatomic gaps increases from 60 to 65% to 80%, and in the case of chlorine generation, the selectivity was confirmed to be reduced from 35% to 20% (FIG. 7b).

Therefore, in the case of the oxygen evolution catalyst for seawater electrolysis of the present invention, it was confirmed that the catalytic reaction efficiency of the oxygen evolution reaction increased due to the effect of atomic-level distance, but not in the case of the chlorine evolution reaction.

This means that it is possible to selectively increase the efficiency of the oxygen evolution reaction under the condition that chlorine production is suppressed during seawater electrolysis.

Therefore, when ruthenium oxide with atomic unit gaps formed by lithiation is applied to an electrode for a seawater battery, specifically, a positive electrode, it exhibits an effect of selectively preferentially promoting an oxygen evolution reaction among a chlorine evolution reaction and an oxygen evolution reaction.

The generation of oxygen and chlorine was evaluated by constructing a seawater-electrolyzer using actual seawater. Low current (10mA/cm ² ) It is possible to compare the voltage in the pressurized section and the resulting oxygen production ( FIG. 7c ).

It was possible to confirm the voltage band of the electrolyzer lowered by introducing the atom-unit gap, and in the case of oxygen generation, it showed a selectivity of 70 to 80%, which was within the error range of the electrochemical evaluation result in the half reaction (Fig. 7a). could confirm that it was.

By applying a high current (100 mA/cm ² ), it was confirmed that the same tendency was observed even in the high current region. Therefore, it is possible to confirm the possibility of efficient oxygen generation in actual seawater-electrolysis due to the introduction of the present technology.

Claims (10)

A catalyst for oxygen evolution for seawater electrolysis comprising a metal oxide having an atomic-scale gap.
According to claim 1,
The catalyst is an anode catalyst for seawater electrolysis, an oxygen evolution catalyst that selectively increases the efficiency of an oxygen evolution reaction among a chlorine evolution reaction and an oxygen evolution reaction during seawater electrolysis.
According to claim 1,
The average of the atom-unit gap is 5 to 11 Å of the oxygen evolution reaction catalyst.
According to claim 1,
The metal oxide is made in the form of MO _x (0<x≤4), wherein M is Mg, Al, Au, Ag, Cd, Co, Cr, Cu, In, Ir, Mo, Nb, Ni, Os, At least one oxygen evolution catalyst selected from the group consisting of Pd, Pt, Rh, Ru, Sn, Ti, V, W, Zn, Sc, Y, Zr, Hf, Ta, Mn, Fe, Tc, and Re.
The anode for seawater electrolysis comprising the catalyst of any one of claims 1 to 4.
Seawater electrolysis system comprising the anode for seawater electrolysis of claim 5.
1) electrochemical lithiation of the metal oxide; and
2) A method for preparing an oxygen evolution catalyst for seawater electrolysis, comprising the step of delithiating the lithiated metal oxide.
8. The method of claim 7,
The lithiation is a method for producing an oxygen evolution catalyst for seawater electrolysis comprising applying a constant current and a cut-off voltage of 0 V to 3 V using an electrochemical cell.
8. The method of claim 7,
The delithiation includes washing the lithiated metal oxide with an acid solution or immediately after lithiation is performed, increasing the voltage to 3 V.
8. The method of claim 7,
The metal oxide is made in the form of MO _x (0<x≤4), wherein M is Mg, Al, Au, Ag, Cd, Co, Cr, Cu, In, Ir, Mo, Nb, Ni, Os, Oxygen generation reaction for seawater electrolysis at least one selected from the group consisting of Pd, Pt, Rh, Ru, Sn, Ti, V, W, Zn, Sc, Y, Zr, Hf, Ta, Mn, Fe, Tc, and Re Catalyst preparation method.

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