KR102132825B1 - Photoelectrode comprising catalyst binding layer, preparing method for the photoelectrode, and photoelectrochemical cell comprising the photoelectrode - Google Patents

Abstract

The present application provides a photoelectrode comprising a catalyst holding layer, a method for manufacturing the same, and a photoelectrochemical cell comprising the photoelectrode.

Description

A photoelectrode comprising a catalyst holding layer, a method for manufacturing the same, and a photoelectrochemical cell comprising the photoelectrode TECHNICAL PHOTOELECTRODE COMPRISING CATALYST BINDING LAYER

The present application relates to a photoelectrode comprising a catalyst holding layer, a method for manufacturing the same, and a photoelectrochemical cell comprising the photoelectrode.

Recently, as interest in eco-friendly resources has increased, studies on hydrogen and oxygen generation systems using sunlight and water have been conducted.

In a water splitting photoelectrode, the photoelectrode generally has a structure of a substrate/electrode/photoactive layer/catalyst, and when the photoelectrode is operated, the cathode receives electrons from sunlight and water is reduced to produce hydrogen. At the anode, electrons are lost, and water is oxidized to produce oxygen.

In this regard, Korean Patent Registration No. 10-1724690 discloses a method for manufacturing an iron-nickel based water decomposition catalyst electrode through anodization and a water decomposition catalyst electrode prepared accordingly.

On the other hand, a metal catalyst is mainly used as a catalyst for the cathode photoelectrode, and when the metal catalyst is used, the metal catalyst is separated from the photoactive layer shortly after the oxidation-reduction reaction is started. There is a problem that the stability (stability) or the sustainability (sustainability) of the electrode is poor.

In addition, in the case of a conventional cathode photoelectrode, segregation between metal catalysts occurs, and the metal catalyst separated from the photoactive layer diffuses inside the photoelectrode or toward the electrolyte, and the photoelectron of the photoelectrode over time A problem that the chemical properties are deteriorated may occur.

An object of the present application is to provide a photoelectrode comprising a catalyst holding layer, a method for manufacturing the same, and a photoelectrochemical cell comprising the photoelectrode as invented to solve the above-mentioned problems.

However, the problems to be solved by the present application are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

The first aspect of the present application includes an electrode formed on a substrate; A photoactive layer formed on the electrode and receiving light to generate electrons; A catalyst holding layer formed on the photoactive layer and improving the mobility of the electrons; And a catalyst layer formed on the catalyst holding layer and containing a metal catalyst, wherein the catalyst holding layer binds a metal catalyst contained in the catalyst layer, so that the metal catalyst is the catalyst layer. Provided is a cathode for reducing the separation from the photoelectrode.

The second aspect of the present application includes a photoelectrode according to the first aspect of the present application; A counter electrode electrically connected to the photoelectrode; And it provides an electrochemical cell, comprising an electrolyte.

A third aspect of the present application includes forming an electrode on a substrate; Forming a photoactive layer that generates electrons by receiving light on the electrode; Forming a catalyst holding layer to improve the mobility of the electrons on the photoactive layer; And forming a catalyst layer containing a metal catalyst on the catalyst holding layer, wherein the catalyst holding layer binds a metal catalyst contained in the catalyst layer to the metal. It provides a method for manufacturing a cathode photoelectrode, which reduces the separation of the catalyst from the catalyst layer.

According to the embodiments of the present application, the catalyst holding layer may improve the mobility of electrons generated in the photoactive layer to improve the photoelectric conversion efficiency of the photoelectrode. In addition, the catalyst holding layer may improve the stability and durability of the photoelectrode by preventing corrosion of the internal structure of the electrode, such as a substrate, an electrode, a photoactive layer, or a buffer layer, in an electrolyte solution. In addition, the catalyst holding layer binds a metal catalyst contained in the catalyst layer, thereby reducing the segregation of the metal catalyst from being separated from the catalyst layer and diffusing into the photoelectrode or aggregating each other. It is possible to reduce the material from moving to the electrolyte outside the photoelectrode, thereby reducing catalyst loss and improving the photoelectrochemical properties (photoelectric conversion efficiency) and stability of the cathode photoelectrode.

According to the embodiments of the present application, the method for manufacturing the cathode photoelectrode is a fast time in a non-vacuum method in which drying is performed at a low process temperature of 70° C. by forming the catalyst holding layer by a spray coating method. Since it is finished within (30 minutes), the process is relatively simple, which has the advantage of cost reduction.

1 shows a schematic diagram of the overall structure of a photoelectrode.
Figure 2 is a flow chart showing a method of manufacturing a photoelectrode, Figure 2a is a method of manufacturing a photoelectrode having a layered structure of an electrode/photoactive layer/catalyst holding layer/catalyst layer, Figure 2b is an electrode/photoactive layer/buffer layer/catalyst It is a flow chart showing a method of manufacturing a photoelectrode having a stacked structure of a holding layer/catalyst layer.
3 is a schematic view showing a step of forming a catalyst holding layer.
4 is a schematic diagram of the effect obtained by including a catalyst holding layer.
5 is a graph showing the results of photoelectrochemical current-potential characteristics analysis of a photoelectrode.
6 is a graph showing the results of photoelectrochemical stability analysis of a photoelectrode containing a Pt catalyst.
7 is a graph showing the results of XPS analysis of the residual amount of Pt catalyst in the photoelectrode.
8 is a graph showing the stability analysis results of a photoelectrode containing a Ni-Mo catalyst.
9 is a graph showing the stability analysis results of a photoelectrode containing a Co catalyst.

Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present application pertains may easily practice. However, the present application may be implemented in various different forms and is not limited to the embodiments described herein. In addition, in order to clearly describe the present application in the drawings, parts irrelevant to the description are omitted, and like reference numerals are assigned to similar parts throughout the specification.

Throughout this specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. do.

Throughout this specification, when one member is positioned “on” another member, this includes not only the case where one member abuts another member, but also the case where another member exists between the two members.

Throughout the present specification, when a part “includes” a certain component, it means that the component may further include other components, not to exclude other components, unless otherwise stated.

The terms "about", "substantially", and the like, as used throughout this specification, are used in or at a value close to that value when manufacturing and material tolerances specific to the stated meaning are given, and are understood herein. To help, accurate or absolute figures are used to prevent unconscionable abusers from unduly using the disclosed disclosure.

The term “~(steps)” or “steps of” to the extent used throughout this specification does not mean “steps for”.

Throughout the present specification, the term “combination(s)” included in the expression of the marki form means one or more mixtures or combinations selected from the group consisting of the components described in the expression of the marki form, It means to include one or more selected from the group consisting of the above components.

Throughout this specification, the description of “A and/or B” means “A or B, or A and B”.

The first aspect of the present application includes an electrode formed on a substrate; A photoactive layer formed on the electrode and receiving light to generate electrons; A catalyst holding layer formed on the photoactive layer and improving the mobility of the electrons; And a catalyst layer formed on the catalyst holding layer and containing a metal catalyst, wherein the catalyst holding layer binds a metal catalyst contained in the catalyst layer, so that the metal catalyst is the catalyst layer. Provided is a cathode for reducing the separation from the photoelectrode.

In one embodiment of the present application, the photoelectrode may be used as a cathode, for example, when used for water splitting, in the photoelectrode, a hydrogen ion reacts with a reduction reaction in which electrons bind with electrons. Hydrogen may be generated, but is not limited thereto.

In one embodiment of the present application, the cathode photoelectrode protects a light absorbing layer that receives light from an external light source and a light absorbing layer from an electrolyte while simultaneously improving charge transfer performance and maintaining a catalyst that reduces or prevents separation of metal catalysts. It may be a photoelectrode including a layer and a catalyst layer generated by the light absorbing layer and passing through the catalyst holding layer to undergo an electrochemical reaction, but is not limited thereto.

In one embodiment of the present application, the catalytic holding layer of the cathode photoelectrode may improve corrosion resistance of the photoelectrode by the electrolyte, and improve the interfacial bonding force between the photoactive layer and the metal catalyst or the buffer layer and the metal catalyst, , May protect the inside of the photoelectrode, improve charge transfer, and serve to reduce or prevent diffusion of the metal catalyst into the photoelectrode, but are not limited thereto.

In one embodiment of the present application, the photoelectrode may further include a buffer layer between the photoactive layer and the catalyst holding layer or between the electrode and the photoactive layer, but is not limited thereto.

In one embodiment of the present application, the photoelectrode may have an electrode/photoactive layer/buffer layer/catalyst holding layer/catalyst layer or an electrode/buffer layer/photoactive layer/catalyst holding layer/catalyst layer stacking order, but is not limited thereto. .

In one embodiment of the present application, the catalyst holding layer may include a carbonaceous material, but is not limited thereto.

In one embodiment of the present application, the carbonaceous material may include reduced graphene oxide (rGO) or graphene oxide (GO), but is not limited thereto.

In one embodiment of the present application, the thickness of the catalyst holding layer may be about 0.3 nm to about 3 nm, but is not limited thereto.

For example, the thickness of the catalyst holding layer is about 0.3 nm to about 3 nm, about 0.3 nm to about 2.5 nm, about 0.3 nm to about 2 nm, about 0.3 nm to about 1.5 nm, about 0.3 nm to about 1 nm , About 1 nm to about 3 nm, about 1 nm to about 2.5 nm, about 1 nm to about 2 nm, about 1 nm to about 1.5 nm, about 1.5 nm to about 3 nm, about 1.5 nm to about 2.5 nm, about 1.5 nm to about 2 nm, about 2 nm to about 3 nm, about 2 nm to about 2.5 nm, or about 2.5 nm to about 3 nm, but is not limited thereto.

In one embodiment of the present application, when the thickness of the catalyst holding layer is less than about 0.3 nm, since the absolute amount of the catalyst holding layer decreases, surface coverage decreases, resulting in corrosion and catalyst loss due to electrolyte penetration. This may occur, and when the thickness of the catalyst holding layer is greater than about 3 nm, the catalyst holding layers may be separated from each other by van der Waals forces, and corrosion and loss of catalyst may occur, but are not limited thereto.

In one embodiment of the present application, the catalyst holding layer may be to improve the mobility of electrons inside the catalyst holding layer, but is not limited thereto.

For example, when the reduced graphene oxide (rGO) is used as the catalyst holding layer, the distance between carbon atoms is reduced in the case of reduced graphene oxide (rGO) than in the case of unreduced graphene oxide (GO). It may be to improve the mobility of electrons by shorter, but is not limited thereto.

In one embodiment of the present application, the catalyst holding layer may be to reduce or prevent separation of the metal catalyst from the catalyst layer by binding a metal catalyst contained in the catalyst layer, but is not limited thereto.

In one embodiment of the present application, the separation of the metal catalyst from the catalyst layer may include the separation of the metal catalyst into an electrolyte or diffusion into an internal structure of a photoelectrode (eg, a buffer layer), but is not limited thereto. Does not.

For example, when reduced graphene oxide (rGO) is used as the catalyst holding layer, the reduced graphene oxide may have a functional group at the interface with the catalyst layer, and the functional group may be the metal. By binding the catalyst, the metal catalyst can be reduced or prevented from being separated from the catalyst layer, but is not limited thereto.

In one embodiment of the present application, the functional group may include, but is not limited to, an oxidized species, an unsaturated bond, or a kink, for example.

In one embodiment of the present application, the catalyst layer is Pt, Co, Rh, Ir, Ru, Re, Au, Ag, Cu, Ni, Mo, Fe, Sn, Bi, Zn, Ga, Pb, Sn, Ti, In , Cd, W, Ta, Nb, and combinations thereof, but may include metal elements selected from the group.

In one embodiment of the present application, since the catalyst layer of the cathode photoelectrode contains a metal catalyst, the photoelectrode has an appropriate binding energy for an oxidation-reduction reaction (redox) in the electrolyte, and at the same time a high exchange current density. (exchange current density), but is not limited thereto. For example, if the binding energy between the hydrogen ion and the metal catalyst is too small, the hydrogen ion will fall off easily, so the reduction reaction is difficult to occur, and if the binding energy is too large, the reduced hydrogen gas is difficult to desorb from the metal catalyst, so the catalyst It can lower the activity, but is not limited thereto.

In one embodiment of the present application, the metal catalyst in the catalyst layer may be formed continuously or discontinuously, but is not limited thereto.

In one embodiment of the present application, the catalyst layer may be, for example, nanoparticles, thin films, or 3D nanostructures, but is not limited thereto.

The second aspect of the present application includes a photoelectrode according to the first aspect of the present application; A counter electrode electrically connected to the photoelectrode; And it provides an electrochemical cell, comprising an electrolyte.

All the contents related to the photoelectrode of the first aspect of the present application can be applied to all of the second aspect of the present application, and the application thereof is not excluded from the second aspect of the present application because the description is omitted.

In one embodiment of the present application, the counter electrode and the electrolyte may be generally used in the photoelectrode application field, which is a technical field of the present application. For example, the counter electrode may be Au, Cu, Ag, Pt, Pd, Rh, Ir, Re, Ni, Co, Mo, Nb, IrOx, RuOx, PdOx, NiOx electrode, and the electrolyte may be H ⁺ and It may be a solution having a value between 0 and 14 containing OH ^- , but is not limited thereto.

In one embodiment of the present application, the photoelectrochemical cell may be to generate hydrogen or oxygen by decomposing water, but is not limited thereto.

In one embodiment of the present application, the photoelectrochemical cell may be one that reduces carbon dioxide, but is not limited thereto.

A third aspect of the present application includes forming an electrode on a substrate; Forming a photoactive layer that generates electrons by receiving light on the electrode; Forming a catalyst holding layer to improve the mobility of the electrons on the photoactive layer; And forming a catalyst layer containing a metal catalyst on the catalyst holding layer.

In one embodiment of the present application, the step of forming the catalyst holding layer may include a spray coating method, but is not limited thereto.

In one embodiment of the present application, since the catalyst holding layer is formed by the spray coating method, it is terminated within a fast time (30 minutes) in a non-vacuum method at a low process temperature of 70° C. It has a relatively simple feature. In addition, since the catalyst holding layer is formed by spray coating of only 2 to 3 times, it is formed in units of atomic layers and has almost the same permeability as the glass substrate. There is an advantage that the loss of incident light can be almost neglected.

Hereinafter, the drawings and the embodiments of the present application will be described in more detail, and the scope of the present application is not limited by the examples.

[ Example ]

<Production of photoelectrodes>

1 is, in one embodiment of the present application, shows the overall schematic diagram of the photoelectrode, and FIG. 2 is a flow chart showing a method of manufacturing the photoelectrode in one embodiment of the present application, and FIG. 2a is the electrode/photoactive layer A method of manufacturing a photoelectrode having a layered structure of /catalyst holding layer/catalyst layer, and FIG. 2B is a flowchart showing a method of manufacturing a photoelectrode having a layered structure of electrode/photoactive layer/buffer layer/catalyst holding layer/catalyst layer.

As the substrate 110, a transparent and rigid one was used as a glass substrate. However, the present invention is not limited thereto, and an opaque or translucent one may be used, and a flexible one may also be used. For example, polyethylene terephthalate (PET), polyethylene naphthalate (PI), or colorless polyimide may be used as the transparent substrate, and stainless steel as an opaque substrate (stainless steel, SUS) or polyimide (PI) may be used, but is not limited thereto.

In the present embodiment, molybdenum (Mo) was used as the electrode 120, and an electrode having a thickness of about 700 nm was formed through a sputter deposition method.

As the photoactive layer 130, a Cu(In,Ga)Se ₂ (hereinafter “CIGS”) material was used.

The photoactive layer 130 was formed by a sputter deposition method, the temperature of the glass/Mo substrate was maintained at 350°C, and Ar was maintained at 3 mTorr for sputtering. In the above conditions, In and Ga were co-sputtered, and Cu was sputtered thereon. Forming In,Ga/Cu as described above was defined as one cycle. Through the above process, about 10 cycles were repeated until the thickness of the photoactive layer was about 1.5 μm to about 1.7 μm. Finally, heat treatment was performed under selenium (Se) overpressure conditions at around 400°C (selenization). Through this process, polycrystalline Cu _{0 . 9} (In _0.7 Ga _0.3 )Se ₂ composition was prepared, and in this embodiment, the photoactive layer 130 was manufactured to a thickness of about 1.5 μm. The prepared photoactive layer 130 absorbs light to generate charges (electron-hole pairs), and serves as a p-type semiconductor.

In addition to the CIGS, the photoactive layer 130 may include, for example, multinary chalcogenide. The polyvalent chalcogenide may include binary, ternary, quaternary chalcogenide, and the like. The material group may be a compound including at least one element of Cu, In, Ga, Zn, Sn, Sb, or Ag and at least one element of S, Se, Te, or Ge. For example, as binary chalcogenide SnS, SnSe, Sb ₂ S ₃ , Sb ₂ Se ₃ , CdTe, etc., as ternary chalcogenide CuGaS ₂ (CGS), CuGaSe _{2 (} CGSe), CuInS _{2 (} CIS), CuInSe _{2 (} CISe), CuInTe ₂ , CuAlSe ₂ , AgInSe ₂ As the quaternary chalcogenide, Cu(In,Ga)Se ₂₍ CIGS), Cu ₂ ZnSnS ₄ (CZTS), Cu ₂ ZnSnSe ₄ (CZTSe), Ag ₂ ZnSnS _4, etc. may be included.

The photoactive layer 130, in addition to the sputtering deposition method, as a vacuum deposition method, thermal co-evaporation, atomic layer deposition (ALD), molecular beam epitaxy, pulsed laser It may be formed by spin coating or electrodeposition as a non-vacuum deposition method, such as a vapor deposition method (pulsed laser deposition, PLD), or a chemical vapor deposition (CVD) method.

In this embodiment, the photoactive layer is formed by a sputtering deposition method, so that the composition of the photoactive layer can be precisely controlled, and there is an advantage that it can be made of a compact and large polycrystalline grain. .

As the buffer layer 140, CdS was used in this embodiment.

Materials that can be used as the buffer layer 140 include, in addition to CdS, for example, zinc sulfide (ZnS), indium sulfide (In ₂ S ₃ ), zinc tin oxide (Zn _x Sn) _y O _z ), zinc magnesium oxide (Zn _x Mg _y O _z ), zinc titanium oxide (Zn _x Ti _y O _z ), titanium oxide (TiO ₂ ), cadmium oxyoxide (cadmium oxy sulfide; Cd(O,S)), zinc sulfide oxide (Zn(O,S)), zinc selenium (ZnSe), and the like.

As a method of forming the buffer layer 140, the temperature of the water circulation bath was maintained at 90°C, in which Cd precursor (0.125 g of CdSO- ₄ dissolved in 200 mL deionized water), S precursor ( Thiourea 1.52 g) dissolved in 100 mL deionized water, and 40 mL (28 wt %) of ammonia were mixed. At this time, the glass/Mo/CIGS sample was placed in the solution, and when the temperature of the inner bath reached 65°C, the sample was removed and rinsed with DI water. Then, deionized water was removed with an N ₂ gun. By the above-described method, unnecessary oxides generated on the CIGS surface of the photoactive layer 130 were removed, and a buffer layer 140 having a thickness of about 50 nm was uniformly formed along the curvature of the photoactive layer 130.

The CdS buffer layer of the present embodiment is an n-type semiconductor, and can form a p-n junction with the photoactive layer to rapidly separate electron-holes. In particular, in order to minimize the loss of light reaching the photoactive layer, it is advantageous to use a material having a band gap of about 2.2 to about 2.4 eV or more as a buffer layer, and a material having high electron conductivity is advantageous.

In this embodiment, the buffer layer 140 was prepared by chemical bath deposition. In addition to the buffer layer forming method, for example, vacuum deposition (thermal evaporation method; thermal evaporation, sputtering; sputtering, atomic layer deposition method; atomic layer deposition, molecular beam epitaxy; molecular beam epitaxy, chemical vapor deposition method, chemical vapor deposition, etc.) and It may also be by non-vacuum deposition (chemical bath deposition).

In this embodiment, reduced graphene oxide (rGO) was used as the catalyst holding layer 150. 3 is a schematic diagram showing a step in which a catalyst holding layer is formed in one embodiment of the present application.

In addition to the reduced graphene oxide (rGO) as the catalyst holding layer, for example, graphene oxide (GO), graphene (graphene), graphite (graphite), and the like can be used.

In order to prepare the reduced graphene oxide (rGO), a graphene oxide (GO) powder was prepared in a "modified Hummer's method" method. The graphene oxide (GO) was placed in deionized water (DI water) and subjected to ultrasonication for about 30 minutes to uniformly disperse it. A graphene oxide dispersion (GO dispersion) was prepared by the above method (1 mg/mL). 10 mL of the graphene oxide dispersion (GO dispersion) was mixed with 2 mL (35 wt% in water) of hydrazine solution and 15 mL (28 wt %) of ammonia. The container containing the mixed solution was stirred for 1 hour in a water bath heated to 95°C, and as a result, a black reduced graphene oxide suspension (rGO suspension) was prepared in the solution. The reduced graphene oxide suspension (rGO suspension) was filtered with "Teflon filter paper" (0.22 um pore size) and the remaining powder was washed several times with ethanol and deionized water. The purified reduced graphene oxide powder (rGO powder) (0.01 mg/mL) was sonicated for 30 minutes in a mixed solution of deionized water and ethanol (3:7). The reduced graphene oxide suspension (rGO suspension: 152) was sprayed 2-3 times against CIGS/CdS on a substrate heated to 70° C. by a spray gun (S) having a nozzle size of about 0.3 mL. . As a result, rGO layers of various concentrations from the reduced graphene oxide suspension (rGO suspension: 152) were spray coated onto CIGS/CdS with a thickness of about 0.34 nm to about 1 nm.

The spray coating method used in this study is not limited by the roughness and geometric morphology of the material, and is a very advantageous coating method when formed on a large area substrate. The spray coating of this embodiment is also very cost-effective because methods such as spin coating and blade coating discard more than about 90% of the solution.

Since the catalyst holding layer is formed by the spray coating method, it is finished in 30 minutes in a non-vacuum method at a low process temperature of 70° C., and thus has a cost saving effect and a relatively simple process. In addition, since the catalyst holding layer is formed by spray coating of only 2 to 3 times, it is formed in units of atomic layers and has almost the same permeability as the glass substrate. There is an advantage that the loss of incident light can be almost neglected.

In the step of forming the catalyst holding layer, in addition to the spray coating method, hydrazine hydrate treatment, plasma treatment, pulsed light exposure, heat treatment with urea (heat treatment with urea) , Furnace heating (direct heating in a furnace), and electrochemical reduction (electrochemical reduction).

In addition to the above method, the step of forming the catalyst holding layer may include a solution-based coating method such as spin coating, blade coating, inkjet printing, dip coating. have.

4 is a schematic diagram of a representative effect of a photoelectrode including a catalyst holding layer in one embodiment of the present application.

The reduced graphene oxide (rGO) prepared herein is a chemically reduced material of graphene oxide (GO) and can maintain a very stable form in photoelectrochemical (PEC). Since the rGO is completely reduced in GO, unnecessary chemical changes such as the conversion from rGO to GO that may occur during the photoelectrochemical hydrogen production reaction do not occur. Therefore, after about 7 hours of reaction, rGO maintains a stable form and at the same time holds the catalyst (e.g., Pt), and can cause catalyst aggregation during PEC reaction, internal diffusion (in-diffusion), from the surface. Catalyst loss such as desorption can be effectively prevented. This is because rGO of the present application has various functional groups such as oxygenated species, dangling bonds, and kinks.

In addition, since the Pt catalyst is formed of nanoparticles having a size of several nm (about 5 nm or so), the surface of the buffer layer (CdS) cannot be completely covered, so that the interface between the CdS and the electrolyte forms (optical) corrosion. have. However, when the reduced graphene oxide (rGO) is formed as a catalyst holding layer, since there is no portion in direct contact with the electrolyte, a role of preventing corrosion can also be performed simultaneously. Since rGO has a high electrical conductivity, it effectively disperses photoexcited electrons with sparse Pt catalyst to reduce electron-hole recombination on the surface, thereby reducing charge transfer rate. ). As a result, it is possible to effectively reduce the voltage drop that may occur due to the concentration of many electrons in one catalyst.

In this embodiment, a Pt catalyst was used as the catalyst layer 160, and the steps in which the catalyst layer 160 is formed are as follows.

The CIGS photoelectrode on which the reduced graphene oxide (rGO) was formed was placed in a vacuum chamber and the Pt catalyst was e-beam evaporated. By slowly depositing at a rate of less than about 1 A/s, the Pt catalyst was induced to deposit in the form of nanoparticles.

The step of forming the catalyst layer is sputter deposition, pulsed laser deposition, atomic layer deposition, molecular beam epitaxy, or non-vacuum deposition as a vacuum deposition method. As it can include a method such as electroplating (electrodeposition), photodeposition (photodeposition).

<catalyst Holding layer Containing Photoelectrode Characteristics>

5 is a graph showing a photoelectrochemical current-potential characteristic analysis result of a photoelectrode in one embodiment of the present application.

Photoelectrochemical current-potential characteristics of CIGS/CdS/Pt optical cathode (reference) as a comparative example and CIGS/CdS/rGO/Pt optical cathode as an example, and a photoelectrode according to the concentration of rGO (volume concenstration, mL) The photoelectrochemical properties of can be seen.

Regarding the experimental conditions, the CIGS photocathode generates light and receives charge, so the experiment is performed under the condition of 1 sunlight (1 sun, AM 1.5G / 100 mW/cm ² ) using a 300 W intensity Xe lamp as a light source. It went on. For measurement, a "potentiostat" (current-potential source) was used, which is a method of measuring the photocurrent by applying a potential.

As the electrolyte, a 0.5 M phosphate buffer solution (phosphate buffer: 0.5 M Na ₂ SO ₄ , 0.5 M NaH ₂ PO ₄ , 0.5 M Na ₂ HPO ₄ ) was used, and was prepared to have a pH of 6.8 by adding NaOH granules. Became. Since this experiment is hydrogen production using CIGS photocathode, an electrolyte in which H ⁺ is excessively dissolved is suitable, and since it has a pH close to neutral, it can escape from the risk of corrosion. Of course, it is possible to react with a strongly acidic electrolyte such as H ₂ SO ₄ or HClO ₄ , but there may be a risk of poor photoelectrochemical stability.

Three electrodes are required for measurement (working electrode (WE), counter electrode (CE), reference electrode (RE)). In this embodiment, CIGS photocathode as a working electrode, Pt coil as a counter electrode, and Ag/AgCl (3 M KCl) as a reference electrode were used, respectively. When a potential is applied to the CIGS photocathode based on the reference electrode, the photoexcited electrons move to the CIGS photocathode/electrolyte surface to participate in the hydrogen production reaction, and the hole current corresponding to the potential is the counter electrode. It moves and participates in the oxygen production reaction.

The data were measured at room temperature, and the scan range was -0.2 V vs. The reversible hydrogen electrode (RHE) is 0.6 V _RHE (reduction to oxidation). The scan rate was 20 mV/sec, and the reaction proceeded without stirring the electrolyte. In FIG. 5, the dotted line represents dark current density and LSV is measured without incident light, indicating that the current is close to 0 in the measurement range. This means that there were no unnecessary electrochemical reactions other than the hydrogen production reaction.

Table 1 shows the current density and starting voltage values of Comparative Examples and Examples shown in FIG. 5.

[Table 1]

As can be seen from Table 1 and Figure 5, when the concentration of rGO (rGO-0.125, rGO-0.25, rGO-1.5, and rGO-3) is different, when Pt catalyst is formed after coating, it is compared based on 0 V _RHE It can be seen that both the current density and the starting voltage increased than in the example.

6 is a graph showing the results of photoelectrochemical stability analysis of a photoelectrode in an embodiment of the present application.

FIG. 6A shows the photoelectrochemical stability of the CIGS/CdS/Pt optical cathode, and FIG. 6B shows the photoelectrochemical stability of the CIGS/CdS/rGO-0.25/Pt optical cathode. It was applied to measure the change in photocurrent density. Under the conditions of "potentiostat", three electrode system, one sun, and 0.5 M phosphate buffer, which were the same as the measurement conditions of LSV, the mixture proceeded without stirring at room temperature.

When irradiating 1 sun, the measurement was performed by turning the light on and off every 30 seconds (light chopping). In other words, photocurrent and dark current are measured alternately on the basis of 30 seconds, and both electrodes are unnecessary electrochemical reactions other than hydrogen generation reaction during chronoamperometry measurement of 7 hours or more. Did not happen.

It is analyzed in FIG. 6A that the decrease in photocurrent is due to the loss of the Pt catalyst. This can be confirmed through the XPS measurement of FIG. 7. The applied potential was 0 V _RHE is, 0 V _RHE one photoelectric current density (photo-current density) is (broken line in Fig. 6) and the current density is equal to the time of 0 V _RHE at LSV of Figure 5 at the time. When rGO-0.25 was used among various concentrations of rGO, the photocurrent density persisted for more than about 7 hours, and it was confirmed that the stability or sustainability was highest.

7 is a graph showing an XPS analysis result for the Pt catalyst residual amount of the photoelectrode in one embodiment of the present application.

Figure 7a is a CIGS / CdS / Pt optical cathode, Figure 7b is a graph comparing the intensity (intensity) of Pt 4f before and after the chronoamperometry hydrogen production reaction of CIGS/CdS/rGO-0.25/Pt optical cathode. .

In the case of XPS, measurement was performed at a high vacuum of 1x10 ^-10 Torr, and monochromatic Al Kα (1486.6 eV) was used as an X-ray light source. The core level measurement of Pt 4f is the result of integrating 50 meV binding energy step size (x-axis) and 10 scans. The peak was calibrated based on "Adventitious Carbon 1s" (284.5 eV).

In the case of the comparative example CdS, the intensity (intensity) after the reaction was reduced (FIG. 7A), while in the case of the example rGO-0.25, it can be seen that the same intensity (intensity) is maintained during the reaction for 7 hours (FIG. 7B). Through this, it can be seen that the catalyst (Pt) of the comparative example CdS is lost during the reaction, but in the case of rGO-0.25, the catalyst layer is formed on the catalyst holding layer (rGO) without losing the catalyst.

8 and 9 are graphs showing the results of photoelectrochemical stability analysis of the photoelectrode for the cathode when Ni-Mo alloy and Co catalyst are used as metal catalysts for the cathode photoelectrode, respectively, in one embodiment of the present application.

The cathode photoelectrode prepared in FIG. 8 used the same method as the photoelectrode production method of FIG. 6, except that a Ni-Mo alloy catalyst was used, and the Ni-Mo alloy catalyst was Ni:Mo = 7:3 , E-beam was deposited to a thickness of 1.5 nm.

The cathode photoelectrode prepared in FIG. 9 was used in the same manner as the photoelectrode production method of FIG. 6, except that the Co catalyst was used, and the Co catalyst was deposited with an electron beam (e-beam) to a thickness of 1.5 nm. .

S: injection device
100: photoelectrode
110: description
120: electrode
130: photoactive layer
140: buffer layer
150: catalyst holding layer
152: reduced graphene oxide suspension
160: catalyst layer

Claims (12)

An electrode formed on the substrate;
A photoactive layer formed on the electrode and receiving light to generate electrons;
A catalytic holding layer formed on the photoactive layer to completely cover the photoactive layer and improving the mobility of the electrons; And
A catalyst layer formed on the catalyst holding layer and containing a metal catalyst
A cathode, comprising: a photoelectrode for a cathode,
The catalyst holding layer binds to a metal catalyst contained in the catalyst layer to reduce separation of the metal catalyst from the catalyst layer,
The catalytic holding layer comprises a carbonaceous material containing reduced graphene oxide (rGO), a cathode photoelectrode.
According to claim 1,
And a buffer layer between the photoactive layer and the catalyst holding layer or between the electrode and the photoactive layer.
delete delete According to claim 1,
The thickness of the catalyst holding layer is 0.3 nm to 3 nm, the cathode photoelectrode.
According to claim 1,
The catalyst layer is Pt, Co, Rh, Ir, Ru, Re, Au, Ag, Cu, Ni, Mo, Fe, Sn, Bi, Zn, Ga, Pb, Sn, Ti, In, Cd, W, Ta, Nb , And an element selected from the group consisting of combinations thereof.
According to claim 1,
The catalyst layer is in the form of nanoparticles (nanoparticles), thin films, or 3D nanostructures, cathode photoelectrodes.
The cathode for a cathode according to any one of claims 1, 2, 5 to 7;
A counter electrode electrically connected to the cathode photoelectrode; And
Electrolyte
A photoelectrochemical cell comprising a.
The method of claim 8,
The photoelectrochemical cell is to decompose water to generate hydrogen, a photoelectrochemical cell.
The method of claim 8,
The photoelectrochemical cell is to reduce carbon dioxide, a photoelectrochemical cell.
Forming an electrode on the substrate;
Forming a photoactive layer that generates electrons by receiving light on the electrode;
Forming a catalyst holding layer for improving the mobility of the electrons on the photoactive layer to completely cover the photoactive layer; And
Forming a catalyst layer containing a metal catalyst on the catalyst holding layer;
A method of manufacturing a cathode photoelectrode comprising:
The catalyst holding layer binds to a metal catalyst contained in the catalyst layer to reduce separation of the metal catalyst from the catalyst layer,
The catalyst holding layer is to include a carbonaceous material containing reduced graphene oxide (rGO),
Method for manufacturing cathode photoelectrode.
The method of claim 11,
The step of forming the catalyst holding layer includes a spray coating method, a method for manufacturing a cathode photoelectrode.

Images