KR20190022277A - Photoelectrode comprising catalyst binding layer, preparing method for the photoelectrode, and photoelectrochemical cell comprising the photoelectrode - Google Patents

Abstract

The present invention provides a photoelectrode including a catalyst maintaining layer, a manufacturing method thereof, and a photoelectrochemical cell including the photoelectrode. The photoelectrode comprises: an electrode formed on a substrate; a photoactive layer formed on the electrode and generating electrons by receiving light; a catalyst maintaining layer formed on the photoactive layer and improving mobility of the electrons; and a catalyst layer formed on the catalyst maintaining layer and containing a metal catalyst. The photoelectric conversion efficiency of the photoelectrode can be improved.

Description

TECHNICAL FIELD [0001] The present invention relates to a photoelectrode including a catalyst holding layer, a method of manufacturing the same, and a photoelectrochemical cell including the photoelectrode. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a photoelectrode including a catalyst holding layer, a method for producing the same, and a photoelectrochemical cell including the photoelectrode.

Recently, as interest in environmentally friendly resources has increased, researches on hydrogen and oxygen generation systems using sunlight and water are underway.

In a water splitting photoelectrode, the photoelectrode generally has a structure of a substrate / electrode / photoactive layer / catalyst. When the photoelectrode is operated, water is reduced by generating electrons from the sunlight at the cathode, , The electrons are lost at the anode, and the water is oxidized to generate oxygen.

In this regard, Korean Patent No. 10-1724690 discloses a method for producing an iron-nickel-based water decomposition catalyst electrode by anodization and a water decomposition catalyst electrode produced thereby.

On the other hand, a metal catalyst is mainly used as a catalyst of the photoelectrode for a cathode. When such a metal catalyst is used, the metal catalyst is separated from the photoactive layer shortly after the oxidation-reduction reaction starts, There is a problem that the stability or sustainability of the electrode is deteriorated.

In the case of the conventional photoelectrode for a cathode, segregation of metal catalysts occurs, and the metal catalyst separated from the photoactive layer diffuses into the photoelectrode or the electrolyte, and the photoelectrons Chemical properties may be deteriorated.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a photoelectrode including a catalyst holding layer, a method of manufacturing the same, and a photoelectrochemical cell including the photoelectrode.

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

According to a first aspect of the present invention, there is provided an electrode comprising: 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 electrons; And a catalyst layer formed on the catalyst holding layer and containing a metal catalyst, wherein the catalyst holding layer binds the metal catalyst contained in the catalyst layer, And the photoelectrode for the cathode is reduced.

According to a second aspect of the present invention, there is provided an optical element comprising: a photoelectrode according to the first aspect of the present invention; A counter electrode electrically connected to the photoelectrode; And an electrolyte. ≪ IMAGE >

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming an electrode on a substrate; Forming a photoactive layer that receives light on the electrode and generates electrons; Forming a catalyst holding layer for improving the mobility of electrons on the photoactive layer; And a step of forming a catalyst layer containing a metal catalyst on the catalyst holding layer, wherein the catalyst holding layer binds the metal catalyst contained in the catalyst layer to form the metal And the separation of the catalyst from the catalyst layer is reduced.

According to embodiments of the present invention, the catalyst holding layer can improve the photoelectric conversion efficiency of the photoelectrode by improving the mobility of electrons generated in the photoactive layer. In addition, the catalyst holding layer can prevent corrosion of the internal structure of the electrode such as the substrate, the electrode, the photoactive layer, or the buffer layer in the electrolyte solution, thereby improving the stability and durability of the photoelectrode. In addition, the catalyst holding layer may be formed by binding the metal catalyst contained in the catalyst layer, thereby reducing the segregation of the metal catalyst from the catalyst layer and diffusing into the photoelectrode, It is possible to reduce the movement of the material to the electrolyte outside the photo-electrode, thereby reducing the catalyst loss and improving the photo-electrochemical characteristics (photoelectric conversion efficiency) and stability of the photo-electrode for the cathode.

According to embodiments of the present invention, the method for fabricating the photoelectrode for a cathode may include a step of forming the catalyst holding layer by a spray coating method in a non-vacuum method in which drying is performed at a low process temperature of 70 ° C, (30 minutes), the process is relatively simple and has an advantage of cost reduction.

Fig. 1 is a schematic view of an entire structure of a photoelectrode.
2B is a cross-sectional view illustrating a method of manufacturing a photoelectrode having a structure of electrode / photoactive layer / catalyst holding layer / catalyst layer, And a method of manufacturing a photoelectrode having a laminated structure of a support layer / catalyst layer.
3 is a schematic view showing a step of forming a catalyst holding layer.
Fig. 4 is a schematic view showing an effect obtained by including the catalyst holding layer. Fig.
5 is a graph showing the result of photoelectrochemical current-potential characteristic analysis of the photoelectrode.
6 is a graph showing the photoelectrochemical stability analysis results of the photoelectrode containing a Pt catalyst.
7 is a graph showing the results of XPS analysis of the amount of Pt catalyst remaining in the photoelectrode.
8 is a graph showing the stability analysis results of the photoelectrode containing Ni-Mo catalyst.
9 is a graph showing stability analysis results of the photoelectrode containing a Co catalyst.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is " on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

The terms " about ", " substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure.

The word " step (or step) " or " step " used to the extent that it is used throughout the specification does not mean " step for.

Throughout this specification, the term " combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

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

According to a first aspect of the present invention, there is provided an electrode comprising: 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 electrons; And a catalyst layer formed on the catalyst holding layer and containing a metal catalyst, wherein the catalyst holding layer binds the metal catalyst contained in the catalyst layer, And the photoelectrode for the cathode is reduced.

In one embodiment of the present invention, the photoelectrode may be used as a cathode. For example, when used for water splitting, the photoelectrode may be subjected to a reduction reaction in which hydrogen ions combine with electrons Hydrogen may be generated by, but is not limited to, hydrogen.

In one embodiment of the present invention, the photoelectrode for the cathode has a function of protecting the photoabsorption layer from the photoabsorption layer and the electrolyte that receives light from the external light source, and improving the charge transfer performance, And a catalyst layer that receives electrons passing through the post-catalyst holding layer generated from the light absorbing layer and undergoes an electrochemical reaction. However, the present invention is not limited thereto.

In one embodiment of the present invention, the catalyst holding layer of the photoelectrode for the cathode may improve the corrosion resistance of the photoelectrode by the electrolyte, improve the interfacial bonding strength between the photoactive layer and the metal catalyst or the buffer layer, and the metal catalyst , But the present invention is not limited thereto, and it may protect the inside of the photo-electrode, improve the charge transfer, and reduce or prevent diffusion of the metal catalyst into the photo-electrode.

In one embodiment of the present invention, 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 the present invention is not limited thereto.

In one embodiment of the present invention, the photoelectrode may have a stacking order of an electrode / a photoactive layer / a buffer layer / a catalyst holding layer / a catalyst layer or an electrode / a buffer layer / a photoactive layer / a catalyst holding layer / .

In one embodiment of the present invention, the catalyst holding layer may include, but not limited to, a carbonaceous material.

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

In one embodiment of the present invention, 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 support layer may be from about 0.3 nm to about 3 nm, from about 0.3 nm to about 2.5 nm, from about 0.3 nm to about 2 nm, from about 0.3 nm to about 1.5 nm, from 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, But is not limited to, from about 1.5 nm to about 2 nm, from about 2 nm to about 3 nm, from about 2 nm to about 2.5 nm, or from about 2.5 nm to about 3 nm.

In one embodiment of the present invention, when the thickness of the catalyst holding layer is less than about 0.3 nm, the absolute amount of the catalyst holding layer is decreased, so that the surface coverage is decreased, and corrosion due to electrolyte penetration and loss And when the thickness of the catalyst holding layer is larger than about 3 nm, the catalyst holding layers may be separated from each other by van der Waals force, and corrosion and catalyst loss may occur, but the present invention is not limited thereto.

In one embodiment of the present invention, the catalyst holding layer may improve the mobility of electrons within the catalyst holding layer, but the present invention is not limited thereto.

For example, when the reduced graphene oxide (rGO) is used as the catalyst holding layer, the carbon atom distance is reduced in the case of reduced graphene oxide (rGO) than in the unreduced graphene oxide (GO) But the present invention is not limited thereto.

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

In one embodiment of the present invention, the separation of the metal catalyst from the catalyst layer may include separating the metal catalyst into an electrolyte or diffusing into a photoelectrode internal structure (for example, a buffer layer), but is not limited thereto Do 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 an interface with the catalyst layer, The binding of the catalyst may reduce or prevent the metal catalyst from separating from the catalyst layer, but is not limited thereto.

In one embodiment herein, the functional group may include, but is not limited to, for example, an oxygenated species, a dangling bond, or a kink.

In one embodiment of the present invention, the catalyst layer may be formed of one selected from the group consisting of Pt, Co, Rh, Ir, Ru, Re, Au, Ag, Cu, Ni, Mo, Fe, Sn, Bi, Zn, Ga, , Cd, W, Ta, Nb, and combinations thereof. However, the present invention is not limited thereto.

In one embodiment of the present invention, since the catalyst layer of the photoelectrode for a cathode contains a metal catalyst, the photoelectrode has an appropriate binding energy for oxidation-reduction reaction (redox) in the electrolyte, but the present invention is not limited thereto. For example, when the binding energy between the hydrogen ion and the metal catalyst is too small, the hydrogen ion is likely to fall off and the reduction reaction is difficult to occur. When the binding energy is too large, the reduced hydrogen gas is difficult to desorb from the metal catalyst. But the present invention is not limited thereto.

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

In one embodiment of the present invention, the catalyst layer may be in the form of, for example, a nanoparticle, a thin film, or a 3D nanostructure, but is not limited thereto.

According to a second aspect of the present invention, there is provided an optical element comprising: a photoelectrode according to the first aspect of the present invention; A counter electrode electrically connected to the photoelectrode; And an electrolyte. ≪ IMAGE >

The entire contents of the light electrode of the first aspect of the present application can be applied to all of the second aspect of the present application, and the application of the second aspect of the present invention is not excluded because the description is omitted.

In one embodiment of the invention, the counter electrode and the electrolyte may be those commonly used in the art of optical electrode applications. For example, the counter electrode is Au, Cu, Ag, Pt, Pd, Rh, Ir, Re, Ni, Co, Mo, Nb, IrOx, RuOx, PdOx, may be NiOx electrode, and the electrolyte is H ⁺ OH ^- , but it is not limited thereto.

In one embodiment of the present invention, the photo-electrochemical cell may decompose water to generate hydrogen or oxygen, but is not limited thereto.

In one embodiment of the invention, the photo-electrochemical cell may be, but not limited to, reducing carbon dioxide.

According to a third aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming an electrode on a substrate; Forming a photoactive layer that receives light on the electrode and generates electrons; Forming a catalyst holding layer for improving the mobility of 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 invention, 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 invention, since the catalyst holding layer is formed by the spray coating method, it is completed within a short time (30 minutes) in a non-vacuum process at a low process temperature of 70 ° C, There are relatively simple features. Also, since the catalyst holding layer is formed by spray coating only two or three times, it is formed in an atomic layer unit and has almost the same transmittance as the glass substrate. As a result, rGO The loss of incident light caused by the incident light can be almost neglected.

Hereinafter, the present invention will be described in more detail with reference to the drawings and embodiments, and the scope of the present invention is not limited by the present embodiments.

[ Example ]

≪ Production of photoelectrode &

2 is a flowchart showing a method of manufacturing a photoelectrode according to an embodiment of the present invention. FIG. 2A is a cross-sectional view of the electrode / FIG. 2B is a flowchart illustrating a method of manufacturing a photoelectrode having a stacked structure of an electrode / a photoactive layer / a buffer layer / a catalyst holding layer / a catalyst layer.

The substrate 110 is made of a transparent and rigid glass substrate. However, it is not limited thereto and opaque or translucent 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 material, and stainless steel, SUS) or polyimide (PI) may be used, but the present invention is not limited thereto.

In this embodiment, molybdenum (Mo) is used for the electrode 120, and an electrode having a thickness of about 700 nm is formed through sputter deposition.

As the photoactive layer 130, Cu (In, Ga) Se ₂ (hereinafter, referred to as '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 and Ga were co-sputtered under the above conditions and Cu was sputtered thereon. As described above, formation of In, Ga / Cu is defined as one cycle. Through the above process, about 10 cycles were repeated until the thickness of the photoactive layer reached about 1.5 μm to about 1.7 μm. Finally, selenization was performed at about 400 ° C under selenium (Se) and overpressure conditions. Through this process, polycrystalline Cu _{0 . 9} (In _0.7 Ga _0.3 ) Se ₂ composition was prepared. In this example, the photoactive layer 130 was formed 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, a multinary chalcogenide. The polyvalent chalcogenide may include binary, ternary, quaternary chalcogenide, and the like. This material group may be a compound containing 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 a binary chalcogenide, SnS, SnSe, Sb₂S₃, Sb₂Se₃, CdTe, and the like, as a ternary chalcogenide, CuGaS₂(CGS), CuGaSe_{2 (}CGSe), CuInS_{2 (}CIS), CuInSe_{2 (}CISe), CuInTe₂, CuAlSe₂, AgInSe₂ , Or as a filament type chalcogenide, Cu (In, Ga) Se₂₍CIGS), Cu₂ZnSnS₄(CZTS), Cu₂ZnSnSe₄(CZTSe), Ag₂ZnSnS₄ And the like.

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

In the present embodiment, the photoactive layer is formed by the sputtering deposition method, so that the composition of the photoactive layer can be precisely controlled, and it is advantageous that the photoactive layer can be formed into a compact large large polycrystalline grain .

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

Materials that can be used as the buffer layer 140 in addition to CdS, for example, zinc sulfide (zinc sulfide; ZnS) sulfide, indium (indium sulfide; In ₂ S _3), zinc tin oxide (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 oxy sulfide, Cd (O, S), zinc sulfide oxide (Zn (O, S)), zinc selenium (ZnSe) and the like.

As the method for forming the buffer layer 140, the temperature of the water circulating containers (Water circulation bath) was maintained at 90 ℃, (a CdSO- ₄ 0.125 g was dissolved in 200 mL of deionized water), Cd precursor in the container, S precursor ( 1.52 g of Thiourea dissolved in 100 mL deionized water), and 40 mL (28 wt%) of ammonia. At this time, the glass / Mo / CIGS sample was put into the solution, and when the temperature of the inner bath reached 65 ° C, the sample was removed and rinsed with DI water. Thereafter, deionized water was removed with N ₂ guns. Unnecessary oxides formed on the CIGS surface of the photoactive layer 130 were removed by the above method 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 quickly 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 bandgap of about 2.2 to about 2.4 eV or more as a buffer layer, and a material having a high electron conductivity is advantageous.

In this embodiment, the buffer layer 140 is prepared by chemical bath deposition. In addition to the above-described buffer layer formation method, for example, a vacuum vapor deposition (thermal evaporation, thermal evaporation, sputtering, atomic layer deposition, molecular beam epitaxy, chemical vapor deposition, Or by a non-vacuum deposition (chemical bath deposition) method.

As the catalyst holding layer 150, reduced graphene oxide (rGO) was used in this embodiment. 3 is a schematic view showing a step of forming a catalyst holding layer in one embodiment of the present invention.

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

To prepare the reduced graphene oxide (rGO), graphene oxide (GO) powder was prepared in a "modified Hummer's method" manner. The graphene oxide (GO) was added to DI water and ultrasonicated for about 30 minutes to disperse uniformly. 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 vessel containing the mixed solution was stirred in a water bath heated to 95 캜 for 1 hour, and a black reduced graphene oxide suspension (rGO suspension) was prepared in the solution. The reduced graphene oxide suspension (rGO suspension) was filtered with a Teflon filter paper (0.22 um pore size) and the remaining powder was rinsed several times with ethanol and deionized water. The purified reduced graphene oxide powder (rGO powder) (0.01 mg / mL) was ultrasonicated in a mixed solution of deionized water and ethanol (3: 7) for 30 minutes. The reduced graphene oxide suspension (rGO suspension 152) was sprayed 2 to 3 times on 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, various concentrations of rGO layer were spray coated onto CIGS / CdS from the reduced graphene oxide suspension (rGO suspension 152) to 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 highly advantageous coating method for forming on a large-area substrate. Spray coating of the present embodiment is very advantageous in terms of cost 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, the process is completed within 30 minutes in a non-vacuum process at a low process temperature of 70 캜. Also, since the catalyst holding layer is formed by spray coating only two or three times, it is formed in an atomic layer unit and has almost the same transmittance as the glass substrate. As a result, rGO The loss of incident light caused by the incident light can be almost neglected.

The step of forming the catalyst holding layer may include, in addition to the spray coating method, a hydrazine hydrate treatment, a plasma exposure, a pulsed light exposure, a heat treatment with urea, , Direct heating in a furnace, and electrochemical reduction.

In addition to the above methods, 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.

FIG. 4 is a schematic view of a representative effect of a photo electrode including a catalyst holding layer in one embodiment of the present invention. FIG.

The reduced graphene oxide (rGO) produced by the present invention is a material in which graphene oxide (GO) is chemically reduced, and can maintain a very stable photoelectrochemical (PEC) form. Since the rGO is completely reduced in the GO, unnecessary chemical changes such as conversion from rGO to GO, which may occur during the photoelectrochemical hydrogen production reaction, do not occur. Thus, after about 7 hours of reaction, the rGO remains stable and retains the catalyst (e.g., Pt), resulting in catalyst segregation, in-diffusion, It is possible to effectively prevent catalyst loss such as desorption. This is because the rGO of the present invention 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 nanometers (about 5 nm or so), the surface of the buffer layer (CdS) can not be completely covered and thus the interface between the CdS and the electrolyte forms an interface have. However, when reduced graphene oxide (rGO) is formed as the catalyst holding layer, since there is no portion directly in contact with the electrolyte, the role of preventing corrosion can also be performed at the same time. Since rGO has a high electrical conductivity, it can effectively disperse photoexcited electrons by the Pt catalyst which exists spontaneously and reduce the electron-hole recombination at the surface, thereby reducing the charge transfer rate ). This can effectively reduce the voltage drop that can occur when a large amount of electrons are injected into one catalyst.

In this embodiment, a Pt catalyst is used as the catalyst layer 160, and the step of forming the catalyst layer 160 is as follows.

The CIGS photoelectrode where reduced graphene oxide (rGO) was formed was placed in a vacuum chamber and the Pt catalyst was subjected to e-beam evaporation. Slowly deposited at a rate of less than about 1 A / s, the Pt catalyst was induced to deposit in the form of nanoparticles.

The forming of the catalyst layer may be performed using a vacuum deposition method such as sputter deposition, pulsed laser deposition, atomic layer deposition, molecular beam epitaxy or non-vacuum deposition Such as electrodeposition, photodeposition, and the like.

<Catalyst The holding layer  Included The  Characteristics>

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

As a comparative example, photoelectrochemical current-potential characteristics of a CIGS / CdS / Pt optical cathode (reference) and an example CIGS / CdS / rGO / Pt optical cathode are shown. The photoelectrochemical properties of the polymer can be known.

For the experimental conditions, the CIGS photocathode generates charges by receiving light. Therefore, the experiment is performed under the condition of 1 sun light (1 sun, AM 1.5G / 100 mW / cm ² ) using a 300 W Xe lamp as a light source It went on. For the measurement, a "potentiostat" (current-potential source) was used, which measures the photocurrent by applying a potential.

The electrolyte was prepared with 0.5 M phosphate buffer (0.5 M Na ₂ SO ₄ , 0.5 M NaH ₂ PO ₄ , 0.5 M Na ₂ HPO ₄ ) and added with NaOH granules to have a pH of 6.8 . Because this experiment is a hydrogen production using CIGS photocathode, an electrolyte in which H ⁺ is dissolved excessively is suitable, and it can escape the risk of corrosion because it has a neutral pH of 6.8. Of course, even strong acid electrolytes such as H ₂ SO ₄ or HClO ₄ can react, but there is a risk of poor photoelectric stability.

For the measurement, three electrodes are required. Each electrode is a working electrode (WE), a counter electrode (CE), and a reference electrode (RE). In this embodiment, a CIGS photocathode was used as the working electrode, a Pt coil was used as the counter electrode, and Ag / AgCl (3 M KCl) was used as the reference electrode. 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 generation reaction, and the hole current corresponding to the potential is applied to the counter electrode And participate in the oxygen production reaction.

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

Table 1 shows the current density and the starting voltage value of the comparative example and the example shown in Fig.

[Table 1]

Table 1 above and as can be found in Figure 5, when the different concentrations (rGO-0.125, rGO-0.25 , rGO-1.5, and rGO-3) of rGO when the Pt catalyst is formed after the coating, compared with 0 V _RHE reference It can be seen that both the current density and the starting voltage are increased.

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

FIG. 6A is a CIGS / CdS / Pt optical cathode. FIG. 6B is a stability test of the photoelectrochemical stability of a CIGS / CdS / rGO-0.25 / Pt optical cathode. And the change of the photocurrent density was measured. The measurement was carried out at room temperature without agitation under the conditions of "potentiostat", three electrode system, 1 sun light, and 0.5 M phosphate buffer, which were the same as the measurement conditions of LSV.

1 When the sunlight (1 sun) was irradiated, the light was turned on and off every 30 seconds (light chopping). In other words, the photo current and the dark current are alternately measured in 30 seconds. In the case of the chronoamperometry measurement of more than 7 hours in both electrodes, an unnecessary electrochemical reaction Did not happen.

In Figure 6a, the photocurrent reduction is analyzed to be due to the loss of the Pt catalyst. This can be confirmed by the XPS measurement of FIG. 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 in various concentrations of rGO, the photocurrent density was maintained for more than about 7 hours and was found to be the most stable or sustainable.

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

FIG. 7A is a graph comparing the intensities of Pt 4f before and after the chronoam ferrometric hydrogen generation reaction of the CIGS / CdS / Pt optical cathodes and FIG. 7B is the CIGS / CdS / rGO-0.25 / .

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

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

FIGS. 8 and 9 are graphs showing the photoelectrochemical stability analysis results of the photoelectrode for a cathode when a Ni-Mo alloy and a Co catalyst are used as a metal catalyst for a photoelectrode for a cathode according to an embodiment of the present invention.

8 was the same as the method of manufacturing the photoelectrode of FIG. 6 except that a Ni-Mo alloy catalyst was used. The Ni-Mo alloy catalyst was Ni: Mo = 7: 3 , And electron beam (e-beam).

The photo-electrode for the cathode manufactured in FIG. 9 was the same as the photo-electrode manufacturing method of FIG. 6 except that a Co catalyst was used, and the Co catalyst was deposited to a thickness of 1.5 nm as an e-beam .

S: Injection device
100: photo electrode
110: substrate
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 a substrate;
A photoactive layer formed on the electrode and receiving light to generate electrons;
A catalyst which is formed on the photoactive layer and improves the mobility of the electrons
A holding layer; And
A catalyst layer formed on the catalyst holding layer and containing a metal catalyst;
And a second electrode,
Wherein the catalyst holding layer binds the metal catalyst contained in the catalyst layer to reduce separation of the metal catalyst from the catalyst layer.
The method according to claim 1,
Further comprising a buffer layer between the photoactive layer and the catalyst holding layer or between the electrode and the photoactive layer.
The method according to claim 1,
Wherein the catalyst holding layer comprises a carbonaceous material.
The method of claim 3,
The carbonaceous material may include reduced graphene oxide (rGO) or graphene oxide (GO)
And the photoelectrode for the cathode.
The method according to claim 1,
Wherein the thickness of the catalyst holding layer is 0.3 nm to 3 nm.
The method according to claim 1,
The catalyst layer may be formed of one selected from the group consisting of Pt, Co, Rh, Ir, Ru, Re, Au, Ag, Cu, Ni, Mo, Fe, Sn, Bi, Zn, Ga, Pb, Sn, Ti, In, Cd, , And combinations thereof. &Lt; Desc / Clms Page number 24 &gt;
The method according to claim 1,
Wherein the catalyst layer is in the form of a nanoparticle, a thin film, or a 3D nanostructure.
An optical device comprising: a photoelectrode for a cathode according to any one of claims 1 to 7;
A counter electrode electrically connected to the photoelectrode for the cathode; And
Electrolyte
And a second electrode.
9. The method of claim 8,
Wherein the photoelectrochemical cell decomposes water to generate hydrogen.
9. The method of claim 8,
Wherein the photo-electrochemical cell reduces carbon dioxide.
Forming an electrode on the substrate;
Forming a photoactive layer that receives light on the electrode and generates electrons;
Forming a catalyst holding layer for improving the mobility of electrons on the photoactive layer; And
Forming a catalyst layer containing a metal catalyst on the catalyst holding layer;
A method of manufacturing a photoelectrode for a cathode,
Wherein the catalyst holding layer binds the metal catalyst contained in the catalyst layer to reduce separation of the metal catalyst from the catalyst layer.
A method of manufacturing a photoelectrode for a cathode.
12. The method of claim 11,
Wherein the step of forming the catalyst holding layer includes a spray coating method.

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