KR101198215B1 - Apparatus and method for photoelectrochemical hydrogen production using by preparation of electrodeposited Pt on TiO2 natubular electrode as cathode, natural seawater and concentrated seawater electrolytes obtained from membrane process - Google Patents

Abstract

The present invention relates to a photoelectrochemical hydrogen production apparatus using a concentrated seawater electrolyte prepared from a titania cathode, a platinum-supported nanotube structure, natural seawater and a membrane, and an object thereof. and then to the foundation of TiO ₂ carrying a small amount of platinum to facilitate electron transfer a TiO ₂ nano-tubes in order to increase the tuning hydrogen claim of the cathode to efficient production of improved Pt / TiO ₂ the cathode, than by using the electrode It is an object of the present invention to provide a photoelectrochemical hydrogen production apparatus and a method for producing the same using a concentrated TiO ₂ cathode, a platinum-supported nanotube structure, a natural seawater, and a membrane made of a membrane capable of practical application.
To this end, the photoelectrochemical hydrogen production apparatus according to the present invention, in the photoelectrochemical hydrogen production apparatus, in the apparatus for producing hydrogen using a concentrated seawater electrolyte having a general seawater and total dissolved component (TDS) higher than the general seawater, the metal, A titania photon anode which is formed by stacking nanotubes such that the photocatalyst titania (TiO ₂ ) has a constant arrangement by anodization and is exposed to light when exposed to light; A cathode supported by platinum from a platinum precursor based on the titania flounder node, and capable of generating hydrogen; An anode electrolyte unit for accommodating general seawater and various concentrated seawater electrolytes and having a flatfish node immersed therein; A cathode electrolyte unit for accommodating general seawater and various concentrated seawater electrolytes, in which platinum of various contents is supported on titania cathodes, and the cathodes are immersed in seawater electrolytes; Nanofiltration membranes to allow ion exchange between various kinds of seawater electrolytes and electrolyte portions; And a solar cell connected to the titania cathode electrode and the titania cathode electrode on which the platinum is supported and formed to be exposed to light.

Description

      Apparatus and method for photoelectrochemical hydrogen production using by preparation of electrodeposited Pt on TiO2 natubular electrode using platinum-supported nanotube-structured titania cathode, natural seawater and concentrated seawater electrolyte prepared from membrane as cathode, natural seawater and concentrated seawater electrolytes obtained from membrane process}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectrochemical hydrogen production apparatus using a concentrated seawater electrolyte prepared from a platinum-supported nanotube-structured TiO ₂ cathode, natural seawater and a membrane, and more particularly, to photochemistry in a photoelectrochemical cell. Hydrogen is produced through the reaction, but in order to utilize the TiO ₂ electrode of the nanotube structure as a photocathode and to increase hydrogen ion reduction ability in the same nanotube structure of TiO ₂ , various seawater electrolytes are supported. Apparatus for producing a photoelectrochemical hydrogen using a TiO ₂ cathode having a nanotube structure loaded with platinum and a concentrated seawater electrolyte prepared from a natural seawater and a membrane for supplying a photoelectrochemical cell to produce hydrogen through a photochemical reaction. It is about.

      Rapid industrialization after the Industrial Revolution was accomplished by fossil fuels such as coal and petroleum as energy sources, but excessive use of fossil fuels caused global warming due to the generation of carbon dioxide. Due to reserves, the development of new alternative energy sources is urgent.

      As an alternative energy source, hydrogen can be easily stored like conventional fossil fuels, can be produced from water or organic materials, and has almost no pollution. Therefore, countries around the world can efficiently produce and easily store hydrogen. It is struggling to develop

      In producing hydrogen, the ultimate raw material is expected to be water in the coming years of the hydrogen economy, and electrolysis or photochemical hydrogen production processes will be required. However, the hydrogen production process through water decomposition is expected to cause a global water shortage because a large amount of water must be input.

      At present, the global water consumption is estimated at about 272 trillion liters, including drinking water, agricultural water and industrial water, and the water consumption in the 2030s, when the hydrogen economy will come, is expected to be up to twice that. Therefore, if only about 2-3% of the world's water resources are used as raw materials for hydrogen production, the water shortage will surely become a reality. Therefore, it is necessary to use seawater, the most abundant resource in nature, as a raw material. Hydrogen production process is required.

      At present, some electrolysis processes are used to produce hydrogen from seawater or to obtain by-products. However, there are disadvantages of low efficiency and requiring electricity as a separate energy source. In addition, there is also a photochemical hydrogen production method using the sunlight as a natural energy source, because the efficiency is reduced by the pure water decomposition is increasing its efficiency through various additives. On the other hand, since there are various ionic components in seawater, it is expected that if used as an electrolyte for photochemical hydrogen production, it will greatly contribute to the effective utilization of water resources required for hydrogen production in the future.

      In recent years, seawater desalination technology has attracted much attention in order to secure drinking water and industrial water all over the world along with energy problems. In Korea, seawater desalination technology is under development to overcome this problem. The seawater desalination method uses an evaporation method, an electrodialysis method, a membrane process, etc., and consumes a lot of energy to separate salts in seawater.

      Therefore, it is a recent trend to adopt a method using a membrane process having a relatively low energy consumption among seawater desalination methods.

      The seawater desalination process by the membrane undergoes a process of desalination by desalting ions in seawater by applying high pressure energy, which inevitably results in concentrated water containing a high concentration of salt, which is discharged to the shore. Secondary problems of coastal ecosystem pollution can be caused.

      In order to solve this problem, researches on utilizing concentrated seawater components are underway, and the concentrated effluent generated during seawater desalination is linked with the photoelectrochemical hydrogen production method (ultimately, hydrogen production method using solar light). The ripple effect is great when energy is produced.

The hydrogen production method using the solar light is to use the characteristics of the photocatalyst, the photocatalyst utilization technology has been used a lot in the treatment of environmental pollutants in the past, by reducing the proton (H ⁺ ) and hydrogen by using sunlight It can be used in manufacturing.

      The term 'photocatalyst' is used when referring to a 'catalyst for accelerating the photoreaction', and in order to become a 'photocatalyst', the condition as a general 'catalyst' must be satisfied as well as not directly consumed by participating in the reaction. The reaction rate should be accelerated by providing a mechanism path different from the existing photoreaction. In the latter case, this means that the turn-over ratio per active site must exceed 1.0.

In order for the photocatalyst to exhibit photochemical activity, light energy of more than the band energy or the band gap energy (E _g ) is required, which is a valence band (VB), which is the band of the highest energy occupied by the electrons, The difference in conduction band (CB), the lowest energy band not occupied by electrons, is a forbidden interval that electrons cannot occupy, and excites the electrons / holes pairs in the Is the minimum energy that can be generated.

Along with the band gap energy, what is important is the relative position of the covalent and conducting bands (Fermi energy (E _f ), which is made in detail by the position of these bands), which is the redox couple in the aqueous solution from the photocatalyst. This is because it plays an important role in determining whether electrons move and transfer electrons.

As photocatalyst materials having the above characteristics, semiconductor metal oxides are mainly used. Examples thereof include tungsten trioxide (WO ₃ ), zinc oxide (ZnO), silicon carbide (SiC), cadmium sulfide (CdS), and gallium arsenide. (GaAs) and the like, but usually, titania (TiO ₂ ) having an anatase structure is used. This is because stability, such as excellent efficiency, relatively low cost, smooth supply, and no corrosiveness has been confirmed.

The present invention is based on TiO ₂ of nanotube structure through anodization, which can be made at a relatively low price instead of the platinum electrode which is widely used in the conventional method of producing hydrogen from water or aqueous solution in the photoelectrochemical hydrogen production method. In order to increase the hydrogen production rate of the cathode, a small amount of platinum is supported on TiO ₂ nanotubes, which are easy to transfer electrons, to improve efficiency, and then the Pt / TiO ₂ cathode electrode can be manufactured with improved efficiency. It is an object of the present invention to provide a photoelectrochemical hydrogen production apparatus using a concentrated seawater electrolyte prepared from a TiO ₂ cathode having a nanotube structure, and a natural seawater and a membrane loaded with platinum.

That is, it is prepared from TiO ₂ cathode, natural sea water, and membrane of nanotube structure loaded with platinum, which enables to produce hydrogen efficiently and economically by utilizing concentrated seawater, which is abundant resources in nature, and concentrated ions. It is to provide a photoelectrochemical hydrogen production apparatus using a concentrated seawater electrolyte and a method of manufacturing the same.

In order to achieve the above object, a photoelectrochemical hydrogen production apparatus using a concentrated seawater electrolyte prepared from a TiO ₂ cathode, a natural seawater, and a membrane having a platinum-supported nanotube structure according to the present invention includes a general seawater and a photoelectrochemical hydrogen production apparatus. In a device for producing hydrogen by using a concentrated seawater electrolyte having a total dissolved component (TDS) higher than that of general seawater, the nanotubes are arranged on the surface of the metal titanium support such that the photocatalyst titania (TiO ₂ ) has a constant arrangement by anodization. A titania photon anode formed by stacking and exposed to light to exhibit photoactivity; A cathode supported by platinum from a platinum precursor based on the titania flounder node, and capable of generating hydrogen; An anode electrolyte unit for accommodating general seawater and various concentrated seawater electrolytes and having a flatfish node immersed therein; A cathode electrolyte unit for accommodating general seawater and various concentrated seawater electrolytes, in which platinum of various contents is supported on titania cathodes, and the cathodes are immersed in seawater electrolytes; Nanofiltration membranes to allow ion exchange between various kinds of seawater electrolytes and electrolyte portions; And a solar cell connected to the titania cathode and the titania cathode electrode on which the platinum is supported and formed to be exposed to light.

      Preferably, the titania photoanode is characterized in that the pure titania nanotubes are formed on the titanium support.

      Preferably, the cathode is supported on the basis of the titania photon anode, but the platinum is 0.01 to 0.5 parts by weight based on 100 parts by weight of the electrolyte, characterized in that the counter electrode for supporting the platinum As iron or platinum coil is used, it is characterized in that it is manufactured as a current of 0.005 to 0.015 [A] is applied for 3 to 10 minutes.

      In addition, the cathode is a 1.5 to 2.5 in a flow rate range of 350 to 450 ml / min 5 to 15% hydrogen / argon mixed gas at a temperature of 450 to 550 ℃ to firmly support platinum and exhibit a photocatalyst-specific crystal structure It is characterized in that the heat treatment for a time.

On the other hand, the photoelectrochemical hydrogen production method using a concentrated seawater electrolyte prepared from a TiO ₂ cathode, a platinum-supported nanotube structure, natural seawater and a membrane, the general seawater from which the particulate matter is removed in the photochemical hydrogen production apparatus described above It is characterized in that the hydrogen is prepared by feeding the electrolyte.

      In addition, it is characterized by producing a hydrogen by supplying a concentrated seawater electrolyte having a concentration of total dissolved component (TDS) higher than the general seawater concentrated by the nanofiltration membrane in the above-described photochemical hydrogen production apparatus as an electrolyte.

      In addition, the above-mentioned photochemical hydrogen production apparatus is further concentrated by reverse osmosis membrane using the concentrated seawater electrolyte prepared by the nanofiltration membrane, and the total dissolved component (TDS) concentration is higher than that of the general seawater electrolyte and the nanofiltration membrane. Hydrogen is produced by supplying a high concentration of seawater electrolyte to the electrolyte.

      Here, the seawater electrolyte supplied for hydrogen production through the method as described above is divided into general seawater and seawater concentrated by the membrane.

      General seawater electrolyte is seawater with 33,500 mg / l total dissolved solids (TDS) taken from the east coast of Korea, and removes particulate matter from seawater by 0.45 um pretreatment filter and removes Supplied to.

      In the case of the concentrated seawater electrolyte, a seawater reservoir for storing seawater after removal of particulate matter by a 0.45 um pretreatment filter as in the general seawater and a membrane necessary for the purpose are provided to separate / concentrate ions in seawater. A seawater supply unit having a membrane cell and a seawater pipe for supplying seawater from the seawater reservoir to the membrane cell, and a high pressure pump installed at the seawater supply pipe to provide a supply pressure, and an ion component is separated by the membrane cell. A separate seawater discharge portion for discharging the separated seawater having a TDS (total dissolved component) concentration lower than that of general seawater, and the concentrated seawater having a higher TDS concentration than the general seawater is discharged to the seawater storage portion due to the concentration of ions by the membrane cell. Seawater according to the method disclosed in the applicant's application number 10-2010-0074834 This is made be.

      The allowable operating range of the membrane cell is preferably operated at less than 100 atm, and the concentrated seawater electrolyte (Seawater II) supplies general seawater (Seawater I), and is operated by nanofiltration (NF) inside the membrane cell. Concentrated seawater electrolyte produced at 20 atm pressure, and another concentrated seawater electrolyte (Seawater III) is a reverse osmosis, inside the membrane cell by using a seawater II (Seawater II) prepared from nanofiltration membrane RO) A seawater electrolyte produced by the membrane at 40 atm.

      Concentrated seawater electrolytes (Seawater II, III) prepared by the membrane operating conditions described above have a high total dissolved ingredient (TDS) concentration of about 46,000, respectively, compared to the total dissolved ingredient (TDS) 33,500 mg / l of seawater I It has a concentration of more than mg / l (Seawater II), about 59,260 mg / l (Seawater III) means that the ionic components in the seawater is more concentrated by the membrane.

      According to the present invention made as described above, the effect of overcoming the problem of low efficiency of the conventional photocatalyst hydrolysis tank production apparatus, and the problem of low efficiency of the slurry photocatalyst as photocathode and cathode Will be.

      In addition, the present invention takes advantage of the photocatalytic charge pair generating ability of the photocatalyst and the ability to reduce the protons of the cathode, using immobilized tubular titania prepared by anodization as photocathode and cathode, and supporting platinum on the cathode. By improving the proton reduction capacity, the hydrogen production rate can be improved, and the nano-energy membrane applied as a cell and ion bridge, which is a zero energy consumption type applied voltage device, is applied to the most abundant seawater resources or By using concentrated seawater, it is possible to maximize the efficiency of hydrogen production, thereby economically producing hydrogen.

In addition, compared to the cost of the large area of the electrode when using the existing platinum cathode, compared to the existing platinum electrode by using a small amount of platinum precursor on the nanotube TiO ₂ to improve the hydrogen production rate economically It can be effective.

      On the other hand, the present invention is expected to receive the spotlight desalination process in order to diversify the water resources in order to overcome this situation in the situation that water shortage is being realized at home and abroad in the future, the concentrated seawater generated in the seawater desalination process directly Or after the post-treatment can be used as an electrolyte for producing hydrogen, it is possible to enable an environmentally friendly hydrogen production.

1 is a configuration showing an embodiment of a seawater electrolyte separation / concentration apparatus applied to the photoelectrochemical hydrogen production using a concentrated seawater electrolyte prepared from a TiO ₂ cathode, a natural seawater and a membrane of a platinum-supported nanotube structure according to the present invention Degree,
2 is a view showing the configuration of a photoelectrochemical hydrogen production apparatus using a concentrated seawater electrolyte prepared from a TiO ₂ cathode, a natural seawater and a membrane having a platinum-supported nanotube structure;
Figure 3 is a graph showing the hydrogen production rate results by the Pt / TiO ₂ cathode according to the pure titania photon anode and platinum loading in the present invention,
4 is a view showing the XRD analysis of the platinum-supported 0.2 wt.% Pt / TiO ₂ cathode electrode in the present invention,
5a and 5b is a view showing the SEM analysis of the optimum 0.2 wt.% Pt / TiO ₂ cathode electrode loaded with platinum in the present invention,
5c and 5d show the results of TEM analysis of an optimal 0.2 wt.% Pt / TiO ₂ cathode electrode loaded with platinum in the present invention;
6a is a view showing the results of operating the nanofiltration membrane for the production of concentrated seawater electrolyte (Seawater II) in the present invention,
Figure 6b is a view showing the reverse osmosis membrane operation results for the production of concentrated seawater electrolyte (Seawater III) in the present invention,
FIG. 7 is a graph showing the results of hydrogen production using pure titania photocathode and 0.2 wt.% Pt / TiO ₂ cathode electrode, general seawater electrolyte (Seawater I) and concentrated seawater electrolyte (Seawater II, III). .

First, a photoelectrochemical hydrogen production apparatus using a concentrated seawater electrolyte prepared from a TiO ₂ cathode, a platinum-supported nanotube structure, natural seawater, and a membrane according to the present invention, and a seawater electrolyte separation / concentration device applied to the method of manufacturing the same. An embodiment is described as follows.

1 is a configuration showing an embodiment of a seawater electrolyte separation / concentration apparatus applied to the photoelectrochemical hydrogen production using a concentrated seawater electrolyte prepared from a TiO ₂ cathode, a natural seawater and a membrane of a platinum-supported nanotube structure according to the present invention In addition, the seawater electrolyte separator / concentrator is configured to supply seawater to the membrane cell from the seawater reservoir 10 for storing seawater, the membrane cell 20 for separating / concentrating ionic components in seawater, and the seawater reservoir. Separated seawater discharge unit for discharging seawater having a concentration of TDS (total dissolved component) lower than natural seawater by separating the ions by the seawater supply unit 30 and the membrane cell 20. 40) and concentrated seawater which concentrates ions by the membrane cell 20 and discharges seawater having a TDS concentration higher than natural seawater (called 'concentrated seawater') to the seawater reservoir 10. It is configured to include a chulbu 50.

      The seawater storage unit 10 stores the seawater in which the particulate matter is removed from the natural seawater.

      That is, natural seawater is a general seawater taken from the east coast of Korea, for example, and stores seawater from which particulate matter exceeding 0.45 μm is removed through a filter 11a of 0.45 μm or less.

      When particulate matter exceeding 0.45 μm is present in the seawater, hydrogen is produced for a long time through the photoelectrochemical hydrogen production apparatus described below, and the tube-type photosensitive electrode (i.e., titania photoanode) is used during the photochemical reaction. Particulate matter may be deposited to inhibit photochemical reactions or cause problems such as clogging of analytical equipment when analyzing the composition of seawater.

      Therefore, as a pretreatment process for the separation / concentration of sea water is to filter particulate matter from natural sea water.

      In general, Total Dissolved Solids (TDS), which is an indicator of salt concentration in seawater, was 33,500 mg / l, and the hydrogen ion concentration (pH) was 7.98.

      The salinity of seawater distributed on the earth varies according to region and season, but in Korea, TDS is between 31,500 and 34,600 mg / l depending on the region and water temperature distribution. Based on these data, it can be seen that the seawater used in the present invention is also within the range.

      The seawater storage unit 10 of the present embodiment has a seawater storage tank 11 containing seawater, and a seawater temperature control unit 12 having a coolant circulation coil 12a immersed in the seawater storage tank 11 to circulate the cooling water. Consists of The filter 11a is provided in the seawater storage tank 11.

      In addition, the seawater temperature controller 12 increases the temperature of the seawater due to an increase in the temperature of the high pressure pump 32 when the membrane cell 20 is operated in the seawater recirculation filtration mode as described below. It is provided to prevent or to maintain a constant temperature of the supply sea water, to allow the coolant to circulate through the coolant circulation coil 12a to increase the heat exchange efficiency.

      The membrane cell 20 is made of stainless steel, and can be pressurized up to 100 atm, considering the recovery rate of seawater electrolyte and the appropriate level of operation time, it is preferable to operate at 20 to 40 atm. The detailed description will be described later.

      The membrane cell 20 is provided with a nanofiltration membrane or a reverse osmosis membrane (not shown), and operated in a cross-flow filtration mode to remove ions in seawater. Separation / concentration.

      Then, the separated seawater having a lower ion concentration than the seawater supplied from the seawater supply unit 30 (that is, 'supply seawater') is sent to the separated seawater discharge unit 40, and the concentrated seawater having a higher ion concentration than the supplied seawater discharges the concentrated seawater. Send to section 50.

      The seawater supply unit 30 is installed in the seawater supply pipe 31 for supplying seawater from the seawater storage unit 10 to the membrane cell 20, and in the conduit of the seawater supply pipe 31 to be installed in the membrane cell 20. It is provided with the high pressure pump 32 which provides the pressure required, ie, supply pressure. In addition, the seawater supply pipe 31 is provided with a damper 33 for removing or minimizing vibrations that may occur in the seawater supply pipe 31 due to the supply pressure during the high pressure operation of the high pressure pump 32.

      In addition, the seawater supply pipe 31 is provided with a seawater supply pressure gauge 34, particularly at the inlet side of the membrane cell 20, to supply the supply pressure of seawater provided to the membrane cell 20 through the seawater supply pipe 31. Measure it.

      In the pipeline of the seawater supply pipe 31, a safety valve 35 and a bypass pipe 36 are installed. When the seawater supply pressure of the seawater measured by the seawater supply pressure gauge 34 rises rapidly, The safety valve 35 is opened and the seawater supplied to the membrane cell 20 is diverted to the seawater reservoir 10 through the bypass pipe 36, so that safe operation is achieved.

      The separated seawater discharge part 40 of the present embodiment is provided with a separated seawater pipe 41 through which the ions are separated by the membrane cell 20 and the seawater having a lower TDS concentration than the natural seawater is discharged to the outside.

      The separated seawater pipe 41 is provided with a separated seawater pressure gauge 42 for measuring the discharge pressure of the separated seawater, and a separated seawater flowmeter 43 for measuring the flow rate of the separated seawater.

      In addition, a separate seawater recovery pipe 44 branched from the separate seawater pipe 41 is provided, which separates the seawater when the membrane cell 20 is operated by the supplied seawater recycle filtration method. It is to be recovered to the sea water storage (10).

      In addition, the separated seawater sampling section 45 branches from the separated seawater pipe 41 as a pipe for collecting and analyzing a sample of the separated seawater, if necessary.

      At the branch points of the separated seawater pipe 41, the separated seawater recovery pipe 44, and the separated seawater sampling section 45, a separate seawater direction switching valve 46 for changing the flow path of the seawater is provided.

      The concentrated seawater discharge section 50 of the present embodiment is provided with a concentrated seawater pipe 51 in which the concentrated seawater is recovered from the membrane cell 20 to the seawater storage section, and the discharge pressure of the concentrated seawater pipe 51 is provided. The concentrated seawater pressure gauge 52 and the concentrated seawater flowmeter 53 which measure a flow volume, respectively are provided.

      In addition, the concentrated seawater pipe 51 is provided with a flow rate control valve 54 for controlling the flow rate of the concentrated seawater. The flow rate of the concentrated seawater and the separated seawater and the membrane cell by fine adjustment of the flow rate control valve 54 are provided. It is possible to fluctuate the pressure.

      In addition, a concentrated seawater sampling section 55 branched from the concentrated seawater piping 51 is provided to collect samples of the concentrated seawater, and the branch of these concentrated seawater piping 51 and the concentrated seawater sampling section 55 is provided. The branch is provided with a concentrated seawater diverting valve 56 for changing the flow path of the concentrated seawater.

      Meanwhile, 0.45 um of pre-filtered general seawater electrolyte (hereinafter referred to as 'Seawater I') and polyamide nanofiltration membrane alone process to prepare seawater electrolyte and seawater concentrated by the nanofiltration membrane The raw material is divided into concentrated seawater prepared by reverse osmosis membrane of the same material.

      The concentrated seawater electrolyte prepared by the nanofiltration membrane used in the present invention (called 'Seawater II'), and the more concentrated seawater electrolyte by reverse osmosis membrane after nanofiltration (this is called 'Seawater III') Can be.

      Analysis of the main components of the concentrated seawater electrolyte (Seawater II, III) by the general seawater (Seawater I) and membrane used in the present invention are shown in Table 1.

      * Analysis of major components of seawater electrolyte Seawater i
(General seawater) Seawater ii
(Concentrated seawater) Seawater iii
(Concentrated seawater) Membrane process NA ⁺ NF NF + RO Hydrogen ion concentration (pH) 7.9 8.0 8.1 Total dissolved ingredient concentration (TDS, mg / L) 33,500 46,000 59,260 Sodium (mg / L) 10,080 11,709 12,520 Potassium (mg / L) 581 655 906 Calcium (mg / L) 385 643 650 Magnesium (mg / L) 1,194 2,059 2,317 Chloride (mg / L) 18,870 28,810 35,240 Sulfate (mg / L) 2,628 3,831 5,212

NA +: Not applicable.

      The operation for producing the seawater electrolyte in the seawater electrolyte separation / concentration apparatus applied to the present invention is pressurized to obtain an electrolyte recovery rate of 25% in the supplied seawater recycle filtration method.

      When the area of the membrane is small, it is preferable to operate by supply seawater recycle filtration to accumulate ion concentration, and the calculation of electrolyte recovery in the supply seawater recycle filtration can be calculated by Equation 1.

In Formula 1, 'R' is an electrolyte recovery rate, and means a percentage of the amount of seawater (V _P ) separated from the membrane relative to the amount of seawater (V _F ) supplied.

      Based on the recovery rate of 25%, the recovery time of the seawater electrolyte has a short advantage in the recovery rate of less than that, but the concentration efficiency is low, the concentration efficiency can be increased to obtain more recovery rate, but the production time is longer or the inorganic scale on the membrane surface It is more likely to form.

      In the present invention, the allowable operating pressure range of the membrane cell 20 for preparing the seawater electrolyte is 100 atm or less, and the operating pressure varies depending on the characteristics of the membrane described in the membrane cell 20.

      The operating allowable pressure of the nanofiltration membrane used in the present invention is 10 to 30 atm and 40 to 60 atm for the reverse osmosis membrane.

      In the case of operating pressure in the present invention, when operating at a pressure lower than 10 atm, the operating time for obtaining a seawater electrolyte recovery rate of 25% is long, when the pressure exceeds 60 atm to obtain a seawater electrolyte recovery rate of 25% Running time is shorter, but the likelihood of inorganic scales forming on the membrane surface increases.

      Next, a description will be given of the photoelectrochemical hydrogen production apparatus of the present invention using the seawater electrolyte (Seawater II, III) concentrated by the seawater I or the seawater electrolyte separation / concentration device configured as described above.

FIG. 2 is a view showing the configuration of a photoelectrochemical hydrogen production apparatus using a concentrated seawater electrolyte prepared from a TiO ₂ cathode, a natural seawater, and a membrane having a platinum-supported nanotube structure, the apparatus comprising a titania photon anode 110; While receiving the seawater electrolyte, platinum is supported in Titania based on the anode electrolyte portion 120 and the lightfish node 110 on which the titania photonic anode 110 is immersed to receive hydrogen 130, which generates hydrogen. While interposed between the cathode electrolyte portion 140, the anode electrolyte portion 120 and the cathode electrolyte portion 140, the cathode 130 is immersed between the anode electrolyte portion 120 and the cathode electrolyte portion 140 Nanofiltration membrane 150 to enable ion exchange in the solar cell 160 and a solar cell 160 exposed to light by being connected to the titania light-anode 110 and the cathode 130 by wires. It is open configuration.

The titania photoanode 110 is formed by stacking a photocatalyst titania (TiO ₂ ) in a tubular shape by anodization on a surface of a metal titanium support, and is exposed to light such as sunlight.

      That is, the titania photon anode 110 has a structure in which the tubular titania, which is a photocatalytic material, is integrally formed and bonded to the surface of the metallic titanium, which is a support, through an anodization reaction.

      At this time, the hollow side of each titania tube is facing outward while making a right angle with the surface of the metal titanium support.

      In other words, Titania tubes, which are layers of transition metal oxides, are stacked and arranged on the surface of the metal titanium support, and a voltage is applied to the solar cell 160 between the titania photoanode 110 and the cathode 130. As the electrons move in one direction, the redox reaction can be separated and caused.

The anodic oxidation of the titania flounder node 110, after washing the metal titanium support, 1 to 3 parts by weight of ammonium fluoride (NH ₄ F) and 2 to 4 parts by weight of water (H ₂ O) based on 100 parts by weight of the total electrolyte And 93 to 97 parts by weight of ethylene glycol (C ₂ H ₆ O ₂ ) in a mixed component electrolyte solution using a copper or platinum coil as a negative electrode as a counter electrode to oxidize a metal titanium support as a positive electrode.

      At this time, if the content of ammonium fluoride is less than 1 part by weight, it is difficult to form a tubular oxide film, and when it exceeds 3 parts by weight, the tubular oxide film is deformed into a non-uniform form.

      In addition, when the water content is less than 2 parts by weight, it is difficult to dissolve the ammonium fluoride. When it exceeds 4 parts by weight, the viscosity of the electrolyte is lowered, and thus, the rate of anodization may be changed. And, in the case of ethylene glycol is less than 93 parts by weight, the etching rate of the oxide is faster, if it exceeds 97 parts by weight it is difficult to form a long oxide tube.

      In the anodization, the applied voltage is 40 to 60 [V] and the applied current is 0.05 to 0.15 [A].

      At this time, if the applied voltage is less than 40 [V], the generation of oxide becomes irregular, and if it exceeds 60 [V], desorption of the oxide occurs.

      If the applied current is less than 0.05 [A], anodization is not performed or proceeds very slowly, and if it exceeds 0.15 [A], the anode burns. The time required for anodizing is approximately 1 to 3 hours.

      In the present invention, after preparing to the pre-heat treatment step of forming a crystal of the pure titania nanotube electrode used as the photoanode 110, it is used as the cathode 130 by supporting various amounts of platinum (Pt).

The iron or platinum coil in the platinum precursor ^{_{(H 2 PtCl 6. 6H 2}} O) solution with different concentrations of the counter electrode and is supported by the pure titania electrode and the anodic oxidation reaction.

      In this case, when platinum (Pt) is supported to manufacture the cathode 130, platinum may be used in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the electrolyte.

      When the platinum is 0.01 parts by weight or less, the effect of supporting is hardly seen, and when it is 0.5 parts by weight or more, platinum particles may not be dispersed and aggregated inside and outside of the titania nanotube wall, thereby causing more platinum to be seen. Because you can't.

      In addition, the range of 0.005 to 0.015 [A] is appropriate for the platinum-supported applied current range.

      When the applied current is 0.005 [A] or less, platinum is not effectively supported on the titania nanotubes, and when the applied current is 0.015 [A] or more, the platinum particles may not be effectively dispersed and aggregated.

      The platinum supporting time is in the range of 3 to 10 minutes.

      When the supporting time is 3 minutes or less, it is a time range in which the supporting effect of platinum is not seen, and when the supporting time is 10 minutes or more, no supporting effect is seen.

      After such anodization and platinum support, heat treatment of the photon anode 110 and the cathode 130 to be oxidized in a furnace in which the atmosphere gas and the processing temperature can be controlled is required.

      First, in the case of the flounder node 110, the titania flounder node 110 is heat-treated at 450 to 650 ° C while supplying 400 to 600 ml of oxygen per unit surface area of the metal titanium support.

      This heat treatment is a process for crystallizing the amorphous oxide layer produced by anodization into a uniform structure.

      If the oxygen supply amount does not reach 400ml / min during the heat treatment process, the time for forming the oxide layer may become long, and the oxide layer may be unstable. If the amount exceeds 600ml / min, no more effect is obtained.

      The heat treatment time for the titania photon anode 110 is changed depending on the oxygen supply amount, the heat treatment temperature, the surface area of the metal titanium support, etc., and generally takes about 1 to 3 hours.

      If the heat treatment temperature is less than 450 ° C., crystallization to an anatase structure becomes difficult, and if it exceeds 650 ° C., a rutile structure may be generated. Therefore, heat treatment is preferably performed in a temperature range of 450 to 650 ° C.

      In addition, after the platinum-supported cathode 130 is manufactured, the 5 to 15% hydrogen / argon mixed gas is heat-treated at 450 to 550 ° C. for 1.5 to 2.5 hours at a flow rate of 350 to 450 ml / min.

      This heat treatment is intended to crystallize the amorphous titania into a certain structure and at the same time ensure that the supported platinum particles are firmly supported on the titania nanotube wall.

      At this time, when the heat treatment temperature is 450 ° C. or less, it is difficult to form anatase, which is an intrinsic crystal structure of titania, and when 650 ° C. or more, a rutile having a relatively large crystal structure is formed, which may interfere with even distribution of platinum particles.

      The hydrogen / argon mixed gas used during the heat treatment has no effect on the platinum support when it is less than 5%, and more than 15% cannot be expected.

      If the flow rate of the mixed gas is less than 350 ml / min platinum supporting time to the titania crystal structure takes a long time, more than 450 ml / min is difficult to obtain more effects.

      In addition, when the heat treatment time is 1.5 hours or less, the formation of titania crystals and platinum support is unstable, and when 2.5 hours or more, titania may be detached from the cathode 130 electrode.

      Through the process described above to form a titania photon anode (110) formed on the surface of the metal titanium support with a tubular oxide layer having an area having a photosensitivity, when irradiated with ultraviolet or sunlight photoelectrochemical reaction from seawater It can be used as an electrode that causes.

      That is, when the titania photon anode 110 is irradiated with light equal to or greater than the bandgap energy of the photocatalytic material titania, electrons / holes are generated, and electrons / holes are separated by the potential difference applied by the solar cell 160. .

      The remaining holes oxidize the seawater to generate oxygen and chlorine gas and protons, and electrons moved to the platinum-supported cathode 130 through the conductive wire are cathodes from the anode electrolyte portion 120 through the nanofiltration membrane 150. Hydrogen is generated by effectively reducing the protons moved to the electrolyte unit 140.

      The nanofiltration membrane 150 is preferably used having a fraction molecular weight of 200 made of polyamide having a relatively high chemical resistance to seawater.

      When the fractional molecular weight is less than 200, ion exchange may not be easy, and thus the circuit configuration may not be made smoothly so that the amount of hydrogen is generated. When the fractional molecular weight is larger than 200, the anode electrolyte portion 120 and the cathode are used. The seawater electrolyte of the electrolyte unit 140 is not suitable because it is easily moved.

On the other hand, the solar cell 160 may use a single crystal or polycrystalline silicon solar cell, the minimum applied voltage is preferably in the range of 1.0 to 3.0 [V].

      Next, test examples for the photoelectrochemical hydrogen production apparatus according to the present invention configured as described above will be described.

      ≪ Test Example 1 >

400 ml of oxygen atmosphere after anodizing the mixed component electrolyte solution (ammonium fluoride (NH ₄ F) + water (H ₂ O) + ethylene glycol (C ₂ H ₆ O ₂ )) for 1.5 hours under a constant voltage of 0.1 [A]. Titania photon anode 110 of the present invention obtained by heat treatment at 450 ℃ for 2 hours / min was prepared.

For a cathode 130, supporting the platinum above flounder node 110 after the same oxidation anode and prepared with various concentrations of 0.05, 0.1, 0.2, 0.4 wt .% Of the platinum precursor them ^{_{(H 2 PtCl 6. 6H 2}} O ) After reacting iron with a counter electrode at a constant current of 0.01 [A] for 5 minutes, the platinum supporting cathode 130 of the present invention was heat-treated at 500 ° C. for 10 hours at 400 ml / min in a 10% hydrogen / argon mixed gas atmosphere. Prepared.

      At this time, the seawater electrolyte used was a common seawater electrolyte (Seawater I) in which only particulate matter was removed using a pretreatment filter.

      3 is a result of testing the hydrogen production rate by the cathode 130 and the pure titania photocathode 110 and the general seawater electrolyte (Seawater I) loaded with platinum at various concentrations of the present invention.

Referring to the result of FIG. 3, the amount of hydrogen generated in the 0.2 wt.% Pt / TiO ₂ cathode was the highest, and the result was 0.2 wt.% Pt / TiO ₂ (205 ± 15 mmol / hr-cm ² ), 0.1 wt.% Pt / TiO ₂ (162 ± 9.8 mmol / hr-cm ² ), 0.05 wt.% Pt / TiO ₂ (158.7 ± 5.1 mmol / hr-cm ² ), 0.4 wt.% Pt / TiO ₂ (156 ± 10.5 mmol / hr-cm ² ) followed by 0 wt.% Pt / TiO ₂ (103.2 ± 8.6 mmol / hr-cm ² ).

4 is an XRD analysis result of 0.2 wt.% Pt / TiO ₂ cathode having the highest hydrogen production rate among the cathode 130 electrodes.

      Titania on the electrode surface produced by anodization exists in an amorphous state before heat treatment, and crystals are formed by heat treatment after platinum is supported.

      In the figure of FIG. 4, an anatase, which is a crystal structure of titania, was formed through heat treatment at 500 ° C. for 2 hours, resulting in inherent peaks at diffraction angles (2θ) of 25.4 °, 48 °, and 53 °. The peaks were supported and detected at diffraction angles (2θ) 39 °, 45 °, 66 ° and 77 °. In addition, due to the growth of titania on the Ti surface, Ti-specific peaks were detected at diffraction angles (2θ) of 38 °, 63 ° and 71 °.

      5A to 5D show electron microscope analysis results of the cathode 130 electrode.

      As shown in Figure 5a and 5b, it can be observed through the SEM that the titania of the nanotube structure grew on the surface of the titanium in a constant arrangement.

      The length of the titania nanotubes is about 7-8 um, the diameter of the tubes is about 70-90 nm, and the thickness of the nanotube walls is about 30-40 nm.

      5C and 5D show that in the TEM results, the platinum particles are evenly supported on the inner and outer nanotube walls to disperse the black dots.

At this time, the diameter of the platinum particles was 10 nm or less.

      ≪ Test Example 2 &

      Supply general seawater (Seawater I in [Table 1]) from which particulate matter is removed through 0.45㎛ filter, and supply 20water pressure using nanofiltration membrane to adjust 25% of electrolyte recovery rate by recirculating feedwater. By performing the operation for the concentrated seawater electrolyte (Seawater II) was prepared.

      In addition, the concentrated seawater electrolyte (Seawater II) produced from the nano-filtration is supplied to the seawater by applying a pressure of 40 atm, and the concentrated seawater electrolyte (Seawater III) from the operation for adjusting the electrolyte recovery rate 25% by the recycled seawater filtration method. Prepared.

      To obtain the concentrated seawater electrolyte (Seawater II) from the nanofiltration membrane as shown in Figure 6a took about 40 hours of operation time at 20 atm.

      Flux decreases with initial operation time due to the deposition of inorganic ions on the membrane surface to form fouling.

      At this time, the total dissolved component (TDS) concentration of the prepared seawater electrolyte was about 46,000 mg / l (see [Table 1]), and the concentration rate of about 37% compared to about 33,500 mg / l of TDS of general seawater electrolyte (Seawater I). It is showing.

      6b took about 17 hours of operation time at 40 atm to obtain a concentrated seawater electrolyte (Seawater III) from the reverse osmosis membrane.

      Since the flux is operated at a high pressure it can be seen that it takes a short time to obtain a recovery rate of 25% than the nanofiltration membrane operation time.

      Compared to the initial flux, the present invention shows a decreasing trend. In the present invention, since the highly concentrated seawater electrolyte is filtered through the raw material, the fouling due to inorganic ions may be severe.

As shown in the results, the total dissolved component (TDS) of about 46,000 mg / l of the concentrated seawater electrolyte raw material operation resulted in TDS of about 59,260 mg / l (see Table 1) with a concentration of about 77% compared to the general seawater Can be obtained.

      <Test Example 3>

      Hydrogen was prepared by supplying the cathode electrode and the seawater electrolyte prepared by the above <Test Example 1> and <Experimental Example 2> to the photoelectrochemical hydrogen production apparatus of the present invention.

FIG. 7 commonly used a 0.2 wt.% Pt / TiO ₂ cathode and a pure titania photocathode selected in Test Example 1.

      7 is a concentrated seawater electrolyte prepared by the combination of the general seawater electrolyte prepared in Test Example 2 (Seawater I), a nanofiltration membrane (Seawater II), nanofiltration and reverse osmosis membrane ( Seawter III) was fed to the electrolyte of photoelectrochemical hydrogen production.

      As a result of the hydrogen production rate of FIG. 7, it can be seen that the hydrogen production rate in the concentrated seawater electrolyte is improved as compared to the general seawater electrolyte.

In addition, in the concentrated seawater electrolyte, the total dissolved component (TDS) concentration was increased, that is, the efficiency was high in the hydrogen production using the seawater electrolyte (Seawater III) with high concentration efficiency.

In the above described the present invention based on the preferred embodiment, the present invention is not limited to the above embodiment, various modifications by those skilled in the art within the scope of the technical idea of the present invention Of course this is possible.

10: seawater reservoir, 11: seawater reservoir,
11a: filter, 12: seawater temperature control unit,
12a: cooling water circulation coil, 20: membrane cell,
30: seawater supply unit, 31: seawater supply piping,
32: high pressure pump, 33: damper,
34: seawater supply pressure gauge, 35: safety valve,
36: bypass piping, 40: separated sea water discharge,
41: separated seawater pipe, 42: separated seawater pressure gauge,
43: separate seawater flow meter, 44: separated seawater recovery pipe,
45: separated seawater sampling section, 46: diverted seawater direction switching valve,
50: concentrated seawater discharge part, 51: concentrated seawater pipe,
52: concentrated seawater pressure gauge, 53: concentrated seawater flow meter,
54: flow control valve, 55: concentrated seawater sampling unit,
56: concentrated seawater diverter valve, 110: titania flounder node,
120: anode electrolyte portion, 130: cathode,
140: cathode electrolyte portion, 150: nanofiltration membrane,
160: solar cell.

Claims (8)

In the device for producing hydrogen using a concentrated seawater electrolyte having a general seawater and total dissolved component (TDS) higher than the general seawater in a photoelectrochemical hydrogen production device,
A titania photon anode which is formed by stacking nanotubes such that photocatalyst titania (TiO ₂ ) has a constant arrangement by anodization on a surface of a metal titanium support and is exposed to light;
A cathode supported by platinum from a platinum precursor based on the titania flounder node, and capable of generating hydrogen;
An anode electrolyte unit for accommodating general seawater and various concentrated seawater electrolytes and having a flatfish node immersed therein;
A cathode electrolyte unit for accommodating general seawater and various concentrated seawater electrolytes, in which platinum of various contents is supported on titania cathodes, and the cathodes are immersed in seawater electrolytes;
Nanofiltration membranes to allow ion exchange between various kinds of seawater electrolytes and electrolyte portions;
TiO ₂ cathode of the platinum-supported nanotube structure, natural sea water and comprising a solar cell connected to the titania cathode and the titania cathode electrode loaded with platinum and exposed to light; Photoelectrochemical hydrogen production apparatus using the concentrated seawater electrolyte prepared from the membrane. The method of claim 1,
The titania photocathode is a photoelectrochemical hydrogen production apparatus using a concentrated seawater electrolyte prepared from a TiO ₂ cathode, a nanotube-structured platinum-supported natural seawater, and a membrane, wherein pure titania nanotubes are formed on a titanium support. . The method of claim 1,
The cathode is a platinum-supported TiO ₂ cathode of the platinum nanotube structure, characterized in that the platinum is supported on the basis of the titania photon anode, the platinum is produced 0.01 to 0.5 parts by weight based on 100 parts by weight of the electrolyte, natural Photoelectrochemical hydrogen production apparatus using concentrated seawater electrolyte prepared from seawater and membranes. The method of claim 1,
The cathode is used as a counter electrode for supporting the platinum, or a platinum coil, and is prepared by applying a current of 0.005 to 0.015 [A] for 3 to 10 minutes of the platinum-supported nanotube structure Photoelectrochemical hydrogen production apparatus using concentrated seawater electrolyte prepared from TiO ₂ cathode, natural seawater and membrane. The method of claim 1,
The cathode is a 1.5 to 2.5 hours at a flow rate of 350 to 450 ml / min 5 to 15% hydrogen / argon mixed gas at a temperature of 450 to 550 ℃ to firmly support platinum and exhibit a photocatalyst-specific crystal structure An apparatus for producing a photoelectrochemical hydrogen using a concentrated seawater electrolyte prepared from a TiO ₂ cathode, a platinum-supported nanotube structure, natural seawater and a membrane, which is heat-treated. The TiO ₂ having a platinum-supported nanotube structure, wherein hydrogen is produced by supplying general seawater from which particulate matter is removed to the photochemical hydrogen production apparatus according to any one of claims 1 to 5. Photoelectrochemical hydrogen production method using concentrated seawater electrolyte prepared from cathode, natural seawater and membrane. The method for producing hydrogen by supplying a concentrated seawater electrolyte having a total dissolved component (TDS) concentration higher than that of general seawater to an electrolyte in a photochemical hydrogen production apparatus according to any one of claims 1 to 5 A photoelectrochemical hydrogen production method using a concentrated seawater electrolyte prepared from a TiO ₂ cathode, a platinum-supported nanotube structure, natural seawater and a membrane, characterized in that the. In the photochemical hydrogen production apparatus according to any one of claims 1 to 5, the concentrated seawater electrolyte prepared by the nanofiltration membrane is further concentrated by reverse osmosis membrane as a raw material, and the general seawater electrolyte and the nanofiltration membrane concentrated seawater electrolyte Using a concentrated seawater electrolyte prepared from TiO ₂ cathode, natural seawater and membrane of a platinum-supported nanotube structure, which supplies hydrogen by supplying a concentrated seawater electrolyte having a higher total dissolved component (TDS) concentration to the electrolyte. Photoelectrochemical hydrogen production method.

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