KR20170138813A - Photo-water splitting cell with photoanode coated Pt MEA and its manufacture - Google Patents

Abstract

The present invention relates to a method for manufacturing platinum membrane electrode assembly (MEA) for electrolysis and applying electric conductivity in addition to existing hydrogen ion conductivity through physical pore generation and platinum coating in a positive ion exchange membrane which is a main ingredient of MEA, and a platinum MEA, which independently receives sunlight without external wires and decomposes water, manufactured thereby. As hot wires are moved, electrical loss through wires is minimized. Moreover, external wires are not needed when large area and large scale electrolysis cells are installed, so costs and effort for installation costs and maintenance can be minimized.

Description

Technical Field The present invention relates to a membrane electrode assembly for photo-electrolytic hydrogen generation, a method of manufacturing the same, and a photovoltaic cell comprising the same,

The present invention relates to a membrane electrode assembly for photovoltaic electrolytic hydrogen generation, a method for producing the same, and a photovoltaic cell comprising the same.

The photocatalytic reaction generally proceeds in the following manner. In the case of the negative electrode reaction, the ionic behavior depends on the pH range.

[Reaction Scheme 1]

Photo-cathode for Hydrogen Evolution

2H ⁺ + 2e ^- → H ₂ low pH

2H ₂ O + 2e ^- → H ₂ + 2OH ^- high pH

[Reaction Scheme 2]

Photo-anode for Hydrogen Evolution

OH + H ₂ O [HO · OH] + H ⁺ + e ^-

[HO-OH] - > HO-OH

OH OH O + OH + e- + H ⁺

2O · OH → 2OH + O ₂

The photovoltaic electrolysis is a technique for decomposing water by receiving sunlight, and it also includes a method of linking a photovoltaic electrolytic device with a photovoltaic device. Korean Patent Registration No. 10-0806168 discloses a method for producing hydrogen energy by decomposing photocatalyst, which is performed by combining a photocatalytic water decomposition apparatus using sunlight and a solar cell capable of applying a voltage by sunlight And a method for producing hydrogen energy is described. This method is more rapid and widely known, but still needs further development because of the cost of the solar cell and the economics of the amount of alkaline or PEM type power receiving system. In Korean Patent No. 10-1541746, Platinum-loaded TiO ₂ and a Nafion layer on the TiO ₂ surface are impregnated with SnP ^{6 +} , and the final shape is SnP ^{6 +} / Nf / Pt-TiO ₂ form of visible light hydrolysis. Such TiO ₂ is a photocatalyst used in a form dispersed in water in which the diameter is in the range of 10 to 100 nm. In this case, it is difficult to bring about a contact between the catalyst particles, so that it is difficult to draw a dense reaction on the entire surface, And the efficiency of electrolytic solution is decreased due to poor dispersion.

In addition to the particle type technology, there is a tandem cell type that connects the solar cell with the water electrolytic cell. In addition, it is easy to form large-scale industrial area more easily, such as the Korean Patent No. 10-0766701, which maximizes the efficiency by aligning the fevroskite structure to nano-level among the iron oxide having high photoelectric conductivity by photoanode, Which is a slightly more complementary to the existing MEA technology, and its proven materials and manufacturing methods.

However, at present, the maximum optical water electrolysis efficiency of the present technology has many technical limitations to overcome by about 4%. In this invention, in order to increase the efficiency, an electronic loss which is generated as an electron flow in an external conductor, a platinum catalyst layer in which electrons flow, , And the busbar, which is connected to the external conductor, minimizes the ohmic loss, so that the photovoltaic electrolytic efficiency can be increased compared with the existing one.

The manufacturing technology and the application method of the Pt MEA of the present invention are based on the patent of Korean Patent No. 10-0930360 owned by L Chemtech. However, the substance used in the existing patent is not active in the photocatalytic reaction in case of Ta, And the like.

In order to overcome and solve the above problems, the present invention is constructed so as to have a technical differentiation from the existing patent by adding a processing process for imparting electrical conductivity thereto and a process for forming a photo anode.

According to an aspect of the present invention, there is provided a membrane electrode assembly for photochemical hydrogen generation, the membrane having an anode and a cathode on the surface of a cation-exchange electrolyte membrane, the anode having a passage formed through the interior of the electrolyte membrane, And a catalyst layer of a fixed platinum group element is electroless-plated to form a platinum catalyst layer in the form of a metal integrally with the electrolyte membrane.

In addition, according to the present invention, a negative electrode can be formed by coating a cathode catalyst such as TiO ₂ , Sn ₃ O ₄ , ZnO, WO ₃ or the like on the surface to be used as a cathode side on the formed platinum catalyst layer by electrospray or coating method such as doctor blade, decal, Characterized in that the cathode catalyst is coated in a plating or electrolytic plating mode and is active in the photovoltaic electrolysis.

According to another aspect of the present invention, there is provided a method of manufacturing a photovoltaic electrolytic solution-generating membrane electrode assembly having an anode and a cathode catalyst layer for forming electrodes on both surfaces of an electrolyte membrane, The pretreated electrolyte membrane is impregnated into a solution containing electrode catalyst ions to immobilize the ions on the surface and inside of the electrolyte membrane by forcibly forming the electrolyte membrane, and the electrode catalyst ions immobilized on the electrolyte membrane are reacted with a catalyst reduction by the adsorption-reduction method comprising: forming an electrode catalyst layer and the electrode catalyst layer is the side of the electrolyte membrane side coated on both surfaces of TiO _2, Sn ₃ O _4, ZnO, WO _3, etc. to the anode catalyst electrospray or electroless plating, or electrolytic A step of coating the electrolyte membrane by plating, and a step of coating one surface of the electrolyte membrane coated with both surfaces of the electrode catalyst layer by electroplating A tantalum plating step and a post-treatment step of cleaning the electrolyte membrane.

According to the present invention, in the adsorption-reduction step, any one or a mixture of at least one of iridium, manganese, cobalt, nickel, palladium, chromium and platinum can be used as the electrode catalyst.

According to another aspect of the present invention, there is provided a photovoltaic membrane electrode assembly including a positive electrode and a negative electrode on both surfaces of an electrolyte membrane and a lead wire connecting the positive electrode and the negative electrode to each other and a positive electrode and a negative electrode of the membrane electrode assembly, A separation plate and a frame made of quartz or PEEK transparent material having a permeability to solar light for blocking the anode chamber and a cathode chamber for the optical water electrolysis, respectively, and an anode chamber and a cathode chamber And a packing for preventing external leakage of a product and a product in the separator, the frame and the packing, wherein the anode penetrates the interior of the electrolyte membrane and is fixed using _{TiO 2, Sn 3 O 4,} ZnO, WO ₃ form the anode catalyst is coated on the platinum catalyst, and the cathode catalyst layer as the electrode catalyst layer of platinum Membrane configured to be characterized by having an electrode assembly.

According to the present invention, the optical water electrolysis is advantageous in that the CO ₂ generation is reduced by using the regenerative power as compared with the electrolysis using electricity, and that it can be used semi-permanently without a large deterioration once installed. In addition, the BOP manufacturing cost such as a DC power supply, a diffusion layer, and a current feeder, which occupies a relatively large cost in an electric power receiving apparatus using electricity, is minimized or eliminated.

When the membrane electrode assembly used for the photovoltaic electrolysis is manufactured using the Pt membrane electrode assembly of the present invention, mass production is possible and the know-how of the conventional membrane electrode assembly process control can be applied as it is. In addition, there is an advantage in that the existing optical water electrolytic cell can be compacted by forming a cell without leaving a lead outside, and energy loss such as lead resistance can be reduced.

1 is a cross-sectional view showing a layer structure of a Pt MEA coated with a positive electrode catalyst for photovoltaic electrolysis according to the present invention,
2 is a schematic view of an electrochemical cell system used in an embodiment of the present invention,
3 is a flow chart photoanode formation process of a Pt MEA manufacturing process,
Fig. 4 is a seman image of various nano sizes of the photoanode,
5 is a cross-sectional SEM measurement image of Pt-coated Pt-MEA for photovoltaic electrolysis,
FIG. 6 is a graph photocurrent of the photocathode generation rate of photocatalytic cell hydrolysis.

Best Mode for Carrying Out the Invention Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings, in which a membrane electrode assembly for photovoltaic electrolytic hydrogen generation according to the present invention, a method of manufacturing the same, and a photovoltaic cell having the same.

FIG. 1 is a cross-sectional view showing a structure of a photovoltaic electrolytic cell to be ultimately implemented in the present invention, and FIG. 3 is a block diagram showing a process of manufacturing a photovoltaic electrolytic hydrogen-generating membrane electrode assembly according to an embodiment of the present invention. A process of manufacturing the membrane electrode assembly according to the present invention will be described with reference to FIG.

The method of manufacturing the membrane electrode assembly according to the present invention uses an adsorption-reduction method and other coating methods, and is divided into three stages. The first step is a pretreatment step of the ion exchange membrane 110. The second step is a step of forming an air gap 150 to allow an electric current to flow between the anode and the cathode in the ion exchange membrane. (120, 130). In the fourth step, the anode catalyst 140 is coated on the anode side of the membrane electrode assembly having the platinum catalyst prepared in the first step.

The ion exchange membrane suitable for the production of the membrane electrode assembly according to the present invention is most preferably a perfluorinated sulfonic acid cation exchange membrane.

The first step, the preprocessing step, is as follows.

First, the surface of the ion exchange membrane is roughened by sandblasting or sandpaper to widen the reaction surface area. After the ion exchange membrane is roughened, the washing and cleaning steps are repeated to remove impurities in the ion exchange membrane. As a cleaning method, a method such as heating by adding pure water to remove foreign substances on the surface of the ion exchange membrane is used. The washing step is a step of heating in an acid solution such as sulfuric acid or hydrochloric acid. The pretreatment step consists of roughening the surface of the ion exchange membrane, washing with pure water, and heating in the acid, and it is preferable to repeat this process at least once.

The second step of forming the voids is as follows.

A void is formed in the cation exchange membrane to have a similar number of voids per unit area with a needle of constant thickness. At this time, when the density of the pores differs from one area to another, a phenomenon occurs in which a current flows into a certain area. Therefore, it is important to form pores at regular intervals to prevent this.

The adsorption step in the 3-1 step is as follows.

The adsorption step of the catalyst ion is to impregnate the ion exchange membrane into a solution in which the metal compound having an electrochemical catalytic function is dissolved by impregnating the ion exchange membrane at a predetermined temperature for a predetermined period of time to diffuse the metal ion into the ion exchange membrane capable of ion exchange. Affects the physical properties of the ion exchange membrane.

At this time, any one or a mixture of at least one of iridium, manganese, cobalt, nickel, palladium, chromium, and platinum is known as an applicable electrochemical catalyst. In order to permeate such a metal catalyst into the ion exchange membrane, compound _{Pt (NH 3) 4 Cl 2} , RuCl 3, IrCl 3, Mn (NO 3) 2, Co (NO 3) 2, Ni (NO 3) used as the precursor _{2, SnCl 3, PdCl 2,} CrCl 3 , etc. . As the electrode catalyst, a platinum catalyst which can be applied to the positive electrode and the negative electrode at the same time is preferable.

The concentration of the platinum catalyst reagent is suitably from 0.01 mmole to 5 mmole. At this time, when the concentration is lower than 0.01 mmole, the catalyst ion component into the ion exchange membrane is difficult to permeate, and when the concentration is higher than 5 mmole, unreacted catalyst exists and wastes expensive noble metal.

The temperature suitable for the metal ion adsorption step is 10 to 80 ° C. When the temperature is lower than 10 ° C, the penetration of the catalyst ions into the ion exchange membrane is difficult. When the temperature exceeds 80 ° C, the deformation of the ion exchange membrane is severe. 40 to 60 ° C.

The reduction step (platinum ion reduction process) in the step 3-2 is as follows.

The reduction process is a process of impregnating the ion exchange membrane to reduce the fixed metal catalyst ions to a metal catalyst using a reducing agent (e.g., NaBH ₄ ) and a reduction promoter (e.g., NH ₄ OH, NaOH). At this time, a reducing agent having a reducing function and a reducing accelerator (alkali component) for promoting reduction are put into a thermostatic chamber at a constant temperature and the solution is stirred at a low speed. In this case, the reduction temperature is preferably 20 to 80 ° C. When the temperature is lower than 20 ° C, the reduction efficiency is lowered due to the low reacting rate of the reducing agent and the alkali component promoting the elution function and reduction. There is a serious difficulty in operation. A more preferable reduction temperature is 40 to 70 占 폚.

When this electroplating step is completed, a post-treatment step of cleaning and storing with water or hydrochloric acid is performed.

As described above, the present invention may be repeated after the post-treatment step to increase the impregnation amount of the catalyst, that is, the adsorption-reduction step as the second step, the electroplating step, and the post-treatment step as the third step.

The anode coating step of the fourth step is as follows.

TiO ₂ , Sn ₃ O ₄ , ZnO, and WO ₃ , and the particles having a particle size of 10 to 100 nm are mixed with an ionomer prepared from the same material as the cation exchange membrane, and then the solution is applied by electrospray, inkjet printing or slot die , doctor blades, bar coaters, and sin coaters. When the catalyst layer is coated with a thick film too much, it may cause a problem in light transmittance. Therefore, it is very important to coat the catalyst layer with a thickness of about 10 to 50 nm or less.

The ionomer content of the same composition as that of the optimized cation exchange membrane is preferably 5 to 35 wt% based on the weight of the catalyst. The dispersion mainly uses IPA or ethylene glycol, and a dispersant such as glycerol for controlling the viscosity.

2 is a structural view of a unit electrochemical cell having a membrane electrode assembly manufactured by the present invention. As shown in FIG. 2, the unit electrochemical cell of the present invention comprises a membrane electrode assembly composed of a TiO ₂ catalyst as an anode catalyst as described above. Here, TiO ₂ on one side of the membrane electrode assembly 100 includes an ion exchange membrane 110, an ion exchange membrane (110) And a cathode 120 having an anode 140 having an electrode catalyst layer 140 composed of a platinum 130 and a platinum catalyst layer on the other side. At this time, the anode chamber 210 and the cathode chamber 220 formed by the anode 140 and the cathode 120 have a product and a reactant, which are opposed to each other. The anode chamber 210 is shielded from the outside by the frame 210 and the packing and the insulating member 250 and has a membrane electrode assembly 200 between the anode 220 and the anode chamber. The quartz window 240, which is capable of transmitting light in the visible light region where light is electrolyzed, is formed in the anode chamber 210 in the same manner as the light transmission area of 1 cm ² , and is then sealed with rubber packing to prevent insulation and leakage do. The assembly is assembled by bolts and nuts (270) having excellent strength such as stainless steel with constant force. The busbar plate 280 for supplying current is located between the membrane electrode assemblies 200 and supported by the support 260 to support the light source at a constant interval and height. A flow path 290 for supplying electrolytic water and an electrolyte to the anode chamber and the cathode chamber is formed.

[Example]

TiO ₂ particles were coated on the Pt MEA to a thickness of about 100 nm, and a photoelectrochemical cell having the same structure as shown in FIG. 2 was fabricated and used as a system as schematically shown in FIG. 2 to produce hydrogen. At this time, the reaction area of TiO ₂ blocks the light and the electrolyte through the colored Teflon tape or gasket, except for the maximum area of 1 cm ² , which is uniformly irradiated with the light source corresponding to 1 Sun. The test was conducted using 0.1 M NaOH as the electrolyte.

The photoelectrochemical cell fabricated as described above was fabricated and assembled into a cell cell as shown in FIG. 2, and the photocatalytic hydrogen generation efficiency of the cell was confirmed.

Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be understood that the invention is not limited to the disclosed embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as defined by the appended claims. Examples or modifications will also fall within the scope of the claims of this invention.

Claims (6)

A membrane electrode assembly for photochemical oxygen generation having a positive electrode and a negative electrode on both surfaces of an ion exchange membrane electrolyte,
Wherein the positive electrode is an electrode layer formed integrally by penetrating the inside of the electrolyte membrane and connected to the coating layer of the negative electrode by applying a photocatalyst on a fixed platinum catalyst, and the negative electrode is a platinum- Electrode assembly. The method according to claim 1,
The cathode may be formed by electro-spraying, a doctor blade, a roll coater, a bar coater, an applicator, a slot die or an inkjet coating on a film of any one of TiO ₂ , Sn ₃ O ₄ , ZnO and WO ₃ , Is formed by direct molding or by a decal method in which the film is formed on a transfer film of PTFE or PI and then transferred by hot pressing. The method according to claim 1,
When the negative electrode or anode is formed, a structure having regular pores of nano size of AAO or ATO is used as a template, or TiO ₂ , Sn ₃ O ₄ , ZnO, and WO ₃ synthesized in nano size are used as the template, Wherein the catalytic activity is maximized. The method according to claim 1,
An electrospray, a decal method or an impregnation-reduction (reduction impregnation) method is used by using a nano composite of Pt, Pd, Au or Ir as the positive electrode or supported on a carrier by carbon. . A PEEK material that can transmit light and has excellent mechanical strength is used as an anode chamber and a cathode chamber material. A quartz window with excellent light permeability is inserted into the reaction area of an anode chamber which directly receives light and receives light, And a separation plate for separating both the seals and the bus bars from each other so as to prevent water leakage. The method of claim 5,
Wherein the aqueous electrolyte is an aqueous solution containing an inorganic strong acid or an aqueous base or a neutral salt.

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