1. Technical Field
The present application relates to a reactor including a solid electrolyte.
2. Description of the Related Art
In recent years, hydrogen has received attention as a clean energy source. A fuel cell that generates power using hydrogen is known as a device that uses hydrogen. As is well known, the fuel cell includes an anode, a cathode, and an electrolyte held between the anode and the cathode. As the electrolyte, for example, a solid electrolyte capable of conducting protons (hydrogen ions) can be used, and as the solid electrolyte, solid polymer films such as Nafion (registered trademark), and perovskite-type oxides are known.
U.S. Pat. No. 7,993,785 discloses a structure of a fuel cell that uses a MEMS (Micro Electro-Mechanical System) process (see
It is required to improve reliability by suppressing damage of a solid electrolyte due to, for example, mechanical impact from outside.
The following is provided as an exemplary embodiment of the present disclosure:
a reactor comprising: a solid electrolyte having a first surface and a second surface, a plurality of first electrodes arranged on the first surface, a plurality of second electrodes arranged on the second surface, a first substrate including a plurality of first chambers each formed of a first recess on one principal plane, a second substrate including a plurality of second chambers each formed of a second recess on one principal plane; and an external power supply. A bottom of each of the first recess is opposite to one of the plurality of the first electrodes. A bottom of each of the second recess is opposite to one of the plurality of the second electrodes. Each first electrode includes a first catalyst. Each second electrode includes a second catalyst. The first substrate is arranged on the first surface in such a manner that each first chamber is interposed between the first substrate and the first surface. The second substrate is arranged on the second surface in such a manner that each second chamber is interposed between the second substrate and the second surface. At least one of the plurality of the first chambers overlaps two or more second chambers, when viewed from a direction perpendicular to the one principal surface of the first substrate. The external power supply is electrically interposed between the plurality of the first electrodes and the plurality of the second electrodes in such a manner that a voltage difference is generated between the plurality of the first electrodes and the plurality of the second electrodes.
According to the present disclosure, there is provided a reactor with improved reliability, which ensures that damage to a solid electrolyte can be suppressed.
First, an outline of one aspect of the present disclosure will be described.
A reactor as one aspect of the present disclosure comprises a solid electrolyte having a first surface and a second surface, a plurality of first electrodes arranged on the first surface, a plurality of second electrodes arranged on the second surface, a first substrate including a plurality of first chambers each formed of a first recess on one principal plane, a second substrate including a plurality of second chambers each formed of a second recess on one principal plane; and an external power supply. A bottom of each of the first recess is opposite to one of the plurality of the first electrodes. A bottom of each of the second recess is opposite to one of the plurality of the second electrodes. Each first electrode includes a first catalyst. Each second electrode includes a second catalyst. The first substrate is arranged on the first surface in such a manner that each first chamber is interposed between the first substrate and the first surface. The second substrate is arranged on the second surface in such a manner that each second chamber is interposed between the second substrate and the second surface. At least one of the plurality of the first chambers overlaps two or more second chambers, when viewed from a direction perpendicular to the one principal surface of the first substrate. The external power supply is electrically interposed between the plurality of the first electrodes and the plurality of the second electrodes in such a manner that a voltage difference is generated between the plurality of the first electrodes and the plurality of the second electrodes.
In a certain aspect, the reactor further comprises a joining layer arranged between the solid electrolyte and the first substrate.
In a certain aspect, the second substrate is electrically conductive. The second substrate is electrically connected to the external power supply in such a manner that the a voltage having the same polarity as that of the second electrode is applied to the second substrate.
In a certain aspect, the second substrate is electrically conductive. The second substrate is electrically connected to the external power supply in such a manner that a voltage having the same polarity as that of the first electrode is applied to the second substrate.
In a certain aspect, a distance between an outer edge of the second electrode and the second substrate on the second surface is larger than a thickness of the solid electrolyte.
In a certain aspect, the first substrate is electrically conductive. The first substrate is electrically connected to the external power supply in such a manner that a voltage having the same polarity as that of the second electrode is applied to the first substrate.
In a certain aspect, the plurality of first chambers each have a circular or polygonal shape when viewed from a direction perpendicular to the one main surface of the first substrate. The plurality of first chambers are arranged so as to form a lattice pattern.
In a certain aspect, a carrier in the solid electrolyte is a hydrogen ion or an oxygen ion.
A method for activating the reactor as one aspect of the present disclosure comprises
(a) preparing a reactor comprising:
a solid electrolyte having a first surface and a second surface;
a plurality of first electrodes arranged on the first surface;
a plurality of second electrodes arranged on the second surface;
a first substrate including a plurality of first chambers each formed of a first recess on one principal plane;
a second substrate including a plurality of second chambers each formed of a second recess on one principal plane; and
an external power supply,
wherein
a bottom of each of the first recess is opposite to one of the plurality of the first electrodes;
a bottom of each of the second recess is opposite to one of the plurality of the second electrodes;
each first electrode includes a first catalyst;
each second electrode includes a second catalyst;
the first substrate is arranged on the first surface in such a manner that each first chamber is interposed between the first substrate and the first surface;
the second substrate is arranged on the second surface in such a manner that each second chamber is interposed between the second substrate and the second surface;
at least one of the plurality of the first chambers overlaps two or more second chambers of the plurality of the second chambers, when viewed from a direction perpendicular to the one principal surface of the first substrate;
the external power supply is electrically interposed between the plurality of the first electrodes and the plurality of the second electrodes;
the second substrate is electrically conductive; and
the second substrate is electrically connected to the external power supply in such a manner that a voltage having the same polarity as that of the second electrode is applied to the second substrate;
(b) applying voltages, which have mutually different polarities, to the first electrode and the second electrode; and
(c) applying to the second substrate a voltage having the same polarity as that of the voltage applied to the second electrode.
A method for activating the reactor as one aspect of the present disclosure comprises
(a) preparing a reactor comprising:
a solid electrolyte having a first surface and a second surface;
a plurality of first electrodes arranged on the first surface;
a plurality of second electrodes arranged on the second surface;
a first substrate including a plurality of first chambers each formed of a first recess on one principal plane;
a second substrate including a plurality of second chambers each formed of a second recess on one principal plane; and
an external power supply,
wherein
a bottom of each of the first recess is opposite to one of the plurality of the first electrodes;
a bottom of each of the second recess is opposite to one of the plurality of the second electrodes;
each first electrode includes a first catalyst;
each second electrode includes a second catalyst;
the first substrate is arranged on the first surface in such a manner that each first chamber is interposed between the first substrate and the first surface;
the second substrate is arranged on the second surface in such a manner that each second chamber is interposed between the second substrate and the second surface;
at least one of the plurality of the first chambers overlaps two or more second chambers of the plurality of the second chambers, when viewed from a direction perpendicular to the one principal surface of the first substrate;
the external power supply is electrically interposed between the plurality of the first electrodes and the plurality of the second electrodes;
the second substrate is electrically conductive; and
the second substrate is electrically connected to the external power supply in such a manner that a voltage having the same polarity as that of the first electrode is applied to the second substrate.
(b) applying voltages, which have mutually different polarities, to the first electrode and the second electrode; and
(c) applying to the second substrate a voltage having the same polarity as that of the voltage applied to the first electrode.
A method for activating the reactor as one aspect of the present disclosure comprises
(a) preparing a reactor comprising:
a solid electrolyte having a first surface and a second surface;
a plurality of first electrodes arranged on the first surface;
a plurality of second electrodes arranged on the second surface;
a first substrate including a plurality of first chambers each formed of a first recess on one principal plane;
a second substrate including a plurality of second chambers each formed of a second recess on one principal plane; and
an external power supply,
wherein
a bottom of each of the first recess is opposite to one of the plurality of the first electrodes;
a bottom of each of the second recess is opposite to one of the plurality of the second electrodes;
each first electrode includes a first catalyst;
each second electrode includes a second catalyst;
the first substrate is arranged on the first surface in such a manner that each first chamber is interposed between the first substrate and the first surface;
the second substrate is arranged on the second surface in such a manner that each second chamber is interposed between the second substrate and the second surface;
at least one of the plurality of the first chambers overlaps two or more second chambers of the plurality of the second chambers, when viewed from a direction perpendicular to the one principal surface of the first substrate;
the external power supply is electrically interposed between the plurality of the first electrodes and the plurality of the second electrodes;
the first substrate is electrically conductive; and
the first substrate is electrically connected to the external power supply in such a manner that a voltage having the same polarity as that of the second electrode is applied to the first substrate;
(b) applying voltages, which have mutually different polarities, to the first electrode and the second electrode; and
(c) applying to the second substrate a voltage having the same polarity as that of the voltage applied to the first electrode.
Exemplary embodiments of the present disclosure will be described below with reference to the drawings.
Reactor 100 shown in
Upper substrate 102a is arranged on main surface S1 of solid electrolyte 101. As illustrated, upper substrate 102a has a plurality of recesses 107a formed so as to correspond, respectively, to a plurality of cathodes 103a. Upper substrate 102a is arranged on solid electrolyte 101 in such a manner that recesses 107a face main surface S1. Thus, a plurality of first chambers 104a each having one of a plurality of cathodes 103a are formed. Similarly, lower substrate 102b is arranged on main surface S2 of solid electrolyte 101. Lower substrate 102b has a plurality of recesses 107b formed so as to correspond, respectively, to a plurality of anodes 103b. Recesses 107b are arranged on solid electrolyte 101 so as to face main surface S2. Thus, a plurality of second chambers 104b each having one of a plurality of anodes 103b are formed.
In
In the illustrated example, first chamber 104a has a circular shape when viewed from a direction perpendicular to upper substrate 102a. In
In the example shown in
As illustrated in
A structure in which more portions of a solid electrolyte are supported by a substrate can be provided as compared to a conventional configuration in which a space over one main surface of a solid electrolyte overlaps a space over the other main surface. According to the present disclosure, more portions of solid electrolyte 101 can be supported by surface Sa of upper substrate 102 and/or surface Sb of lower substrate 102b on the solid electrolyte 101 side as schematically shown in
According to the present disclosure, the solid electrolyte is relatively easily made thin because more portions of the solid electrolyte can be supported by the substrate. By making the solid electrolyte thin, the ion conductivity of the solid electrolyte can be improved. Therefore, the operation temperature of the reactor can be lowered. Since the area of portions of the solid electrolyte, where both main surfaces are exposed to the space (e.g. space in the first chamber and space in the second chamber), can be reduced, damage to the solid electrolyte can be suppressed even when the solid electrolyte is made thin. Damage to the solid electrolyte due to, for example, a difference in pressure between a reactant (liquid or gas) supplied to the space over one main surface of the solid electrolyte and a reactant (liquid or gas) supplied to the space over the other main surface, and thermal impact at the time of starting or stopping operation of the reactor can be suppressed. Therefore, a reactor having improved reliability can be provided. Such a reactor is prepared by a user. In other words, the user procures the reactor.
Configurations of components and operation of the reactor in the present disclosure will be described more in detail below.
<Solid Electrolyte>
Solid electrolyte 101 is, for example, a proton conductive organic film or solid oxide. For example, a perovskite-type oxide (generally represented by the chemical formula: ABO3) as a proton conductor can be used as the solid electrolyte. When at least one alkali earth metal selected from the group consisting of Ba, Sr and Ca is placed at site A situated at a top of a cubic crystal, at least one element selected from the group consisting of Zr, Hf, Y, La, Ce, Gd, In, Ga, Al and Ru is placed at site B situated at the body center of the cubic crystal, and O (oxygen) is placed at a site situated at the face center of the cubic crystal, a good proton conductor can be obtained.
For example, solid electrolyte 101 has a thickness of from 0.5 μm to 2 μm (inclusive). By making the solid electrolyte thin, proton conductivity can be improved, so that power generation efficiency can be improved, for example, when reactor 100 is used as a fuel cell. In a conventional structure as shown in FIG. 1 in U.S. Pat. No. 7,993,785, it is difficult to make a solid electrolyte thin while sufficient mechanical strength is secured. According to the present disclosure, first chambers 104a and second chambers 104b are arranged such that each first chamber 104a and each second chamber 104b do not completely overlap each other. Therefore, even if mechanical impact is applied, damage to solid electrolyte 101 can be suppressed. Therefore, a solid electrolyte having a thickness in the above-mentioned range is relatively easily used.
<First Electrode and Second Electrode>
Cathode 103a and anode 103b each have a catalyst. For example, when reactor 100 is made to operate as a fuel cell, cathode 103a has a catalyst that reduces oxygen, and anode 103b has a catalyst that oxidizes hydrogen. Cathode 103a is formed of, for example, a material having proton permeability (conductivity), electron conductivity and a catalytic function. Examples of the material include metals such as platinum (Pt) and solid oxides such as SrRuO3. Cathode 103a may have a laminated structure of a metal and a solid oxide. Cathode 103a is not required to be formed of a single material having all of proton permeability, electron conductivity and a catalytic function, and may be formed of, for example, a laminated structure of an electrode having electron conductivity and a catalyst. Anode 103b can be formed using a material similar to that of cathode 103a. Materials of cathode 103a and anode 103b can be appropriately changed according to the intended use of reactor 100. Therefore, anode 103b is not required to have a structure identical to that of cathode 103a.
As shown in
<Upper Substrate and Lower Substrate>
As has been described with reference to
Upper substrate 102a includes a plurality of first fluid inlets 105a and a plurality of first fluid outlets 106a provided so as to correspond, respectively, to a plurality of first chambers 104a. As illustrated, fluid inlet 105a and fluid outlet 106a communicate with first chamber 104a. Lower substrate 102b includes a plurality of second fluid inlets 105b and a plurality of second fluid outlets 106b provided so as to correspond, respectively, to a plurality of second chambers 104b. As illustrated, fluid inlet 105b and fluid outlet 106b communicate with second chamber 104b. That is, reactor 100 has a plurality of channels capable of supplying a gas or a liquid independently to cathode 103a in each first chamber 104a, and a plurality of channels capable of supplying a gas or a liquid independently to anode 103b in each second chamber 104b. These channels provided in reactor 100 are each kept air-tight and water-tight, and configured to ensure that fluids introduced into the channels are not mixed together. Therefore, in first chambers 104a and second chambers 104b, reactions of substances introduced into the chambers independently proceed.
Examples of a material of upper substrate 102a include silicon, glass and quartz. Upper substrate 102a may be a layer formed on a main surface of solid electrolyte 101 by PVD (Physical Vapor Deposition), CVD (Chemical Vapor Deposition), electroforming or the like and formed of an oxide, a nitride or a metal (e.g. nickel (Ni)). A material similar to that of upper substrate 102a can be used for lower substrate 102b. For example, when a silicon substrate is used for upper substrate 102a or lower substrate 102b, recesses, fluid inlets and fluid outlets can be easily formed by dry etching, wet etching or the like. The shape of each of upper substrate 102a and lower substrate 102b is not limited to a plate shape as illustrated in
Depending on the intended use of the reactor, the channel for introducing a reactant and the channel for discharging a reactant may be identical. That is, one of the fluid inlet and the fluid outlet may be omitted. For example, when a proton conductor is used as solid electrolyte 101, reactor 100 can be used as a hydrogen gas sensor. When reactor 100 is used as a hydrogen gas sensor, a gas to be measured and a gas as a reference (e.g. air) are introduced into first chamber 104a and second chamber 104b, respectively. When these gases are introduced, protons corresponding to the partial pressure of hydrogen in the gas to be measured move through the solid electrolyte. At this time, first electrode 103a and second electrode 103b function as a sensing electrode and a counter electrode, respectively. Specifically, a current having a magnitude corresponding to the concentration of hydrogen in the gas to be measured passes between first electrode 103a and second electrode 103b. A substance in first chamber 104a and a substance in second chamber 104b are not changed before and after measurement. Therefore, the channel for introducing a gas to be measured and the channel for discharging a gas to be measured may be identical. Similarly, the channel for introducing a gas as a reference and the channel for discharging a gas as a reference may be identical.
<Operation of Reactor>
One example of operation of rector 100 will now be described.
When a proton conductor is used as solid electrolyte 101, for example, a reactant (e.g. hydrogen) is introduced from fluid inlet 105b into second chamber 104b. As described above, second chambers 104b are mutually independent, and fluid inlets 105b and fluid outlets 106b are formed individually in second chambers 104b. Fluid inlets 105b communicating with second chambers 104b are connected to, for example, a first reactant storage vessel (not illustrated).
The reactant introduced from fluid inlet 105b comes into contact with anode 103b in second chamber 104b. By an action of anode 103b, protons are pulled out from the reactant, and introduced into solid electrolyte 101. The protons in solid electrolyte 101 arrive at cathode 103a by means of at least one of a concentration gradient of the protons, a difference in partial pressure (of hydrogen) between second chamber 104b and first chamber 104a facing second chamber 104b, and a difference in voltage applied between anode 103b and cathode 103a. First chambers 104a each having cathode 103a therein are mutually independent similarly to second chambers 104b, and fluid inlets 105a and fluid outlets 106a are formed individually in first chambers 104a. Fluid inlets 105a communicating with first chambers 104a are connected to, for example, a second reactant storage vessel (not illustrated). A product in each first chamber 104a is collected through fluid outlet 106a.
Reactor 100 can be used for various intended uses according to the combination of anode 103b and cathode 103a to be used. Reactor 100 can be used for hydrogenation devices, dehydrogenation devices, hydrogen sensors and so on as well as fuel cells. Here, an example of using reactor 100 to perform electrolysis of water vapor and hydrogenation of a substance to be hydrogenated will be described. Hereinafter, a device to be used for electrolysis of water vapor and hydrogenation of a substance to be hydrogenated may be referred to as a “water vapor electrolysis and hydrogenation device.”
When reactor 100 is used as a water vapor electrolysis and hydrogenation device, an anode containing a catalyst that oxidizes hydrogen in a gas containing water is used, and a cathode containing a hydrogenation catalyst is used. Examples of the catalyst that oxidizes hydrogen in a gas containing water, and the hydrogenation catalyst include metals and alloys containing Pt.
Turn to
During operation of the water vapor electrolysis and hydrogenation device, the whole water vapor electrolysis and hydrogenation device is kept at about 300° C., and, for example, water vapor is introduced into second chamber 104b through fluid inlet 105b. For example, toluene (C6H5CH3) is introduced into first chamber 104a through fluid inlet 105a. Further, external power source 108 is connected to cathode 103a and anode 103b, and a potential difference (e.g. 1.5 V) is applied between the anode and the cathode. In second chamber 104b, water vapor is brought into contact with anode 103b, whereby protons are pulled out from water vapor (water). Protons generated in anode 103b move through solid electrolyte 101 to arrive at cathode 103a. Toluene is brought into contact with cathode 103a to be hydrogenated. Thus, methylcyclohexane (C6H11CH3) can be obtained in first chamber 104a.
Usually, in a reactor using a solid oxide as a solid electrolyte, the above-mentioned reaction is achieved at a temperature ranging from 400° C. to 800° C. On the other hand, according to the present disclosure, a so-called organic hydride such as methylcyclohexane can also be obtained by activating the reactor at a temperature of, for example, about 300° C. According to the present disclosure, damage to solid electrolyte 101 by mechanical impact can be suppressed, and therefore a solid electrolyte having a thickness of, for example, about several micrometers can also be used. By using a solid electrolyte having a thickness of about several micrometers, a higher ion conductivity can be achieved. Therefore, the operation temperature of the reactor can be set to be lower than before.
<Method for Manufacturing Reactor>
One example of a method for manufacturing a reactor according to the present disclosure will be described with reference to
First, Pt film 13b, solid electrolyte 101 and Pt film 13a are sequentially formed on silicon (Si) substrate 10 as shown in
For formation of Pt film 13b, solid electrolyte 101 and Pt film 13a, for example, a sputtering method can be used. Thicknesses of Pt film 13b, solid electrolyte 101 and Pt film 13a are, for example, 20 nm, 1 μm and 20 nm, respectively. As solid electrolyte 101, a perovskite-type oxide having BaZrO3 as a backbone with site B partially substituted with Y (yttrium) can be used. The method for forming the layers is not limited to a sputtering method, and a PLD (Pulsed Laser Deposition) method, a vacuum deposition method, an ion plating method, a CVD method, MBE (Molecular Beam Epitaxy) or the like may be used.
Next, Pt film 13a as an uppermost layer is patterned by photolithography. Thus, cathode 103a can be formed. Here, as shown in
Next, two single crystal Si substrates 12a and 12b each provided with a thermal oxide film having a thickness of 1 μm are provided. Thicknesses of these substrates are, for example, about 500 μm.
Next, as shown in
Next, as shown in
Next, as shown in
It is to be noted that a plurality of recesses 107b are formed such that when Si substrate 12a is superimposed on Si substrate 12b in such a manner that surface Sa of Si substrate 12a faces surface Sb of Si substrate 12b, the contours of the openings on one substrate do not coincide with the contours of the openings on the other substrate. More specifically, at least one of perpendicular projections of the openings on Si substrate 12a to a surface parallel to surface Sa (or surface Sb) overlaps two or more of perpendicular projections of the openings on Si substrate 12b to a surface parallel to surface Sa (or surface Sb) (see
Next, as shown in
Next, as shown in
Next, Si substrate 10 is removed by wet etching from a side opposite to the surface to which upper substrate 102a is joined. Dry etching may be used instead of wet etching. In formation of an epitaxial multilayer film on Si substrate 10, a sacrificial layer may be formed on Si substrate 10 beforehand, followed by removing Si substrate 10 by an epitaxial lift-off method, sacrificial layer etching, or the like.
Next, as shown in
Thereafter, in the same manner as in the case of upper substrate 102a, solid electrolyte 101 having anodes 103b on main surface S2 and lower substrate 102b provided with a plurality of recesses 107b are pressurized while being subjected to heating and application of a voltage, whereby these components are anode-joined. At this time, lower substrate 102b is arranged on main surface S2 of solid electrolyte 101 in such a manner that each one of a plurality of recesses 107b faces each one of a plurality of anodes 103b. Reactor 100 shown in
In the example described above, an electrode is formed with solid electrolyte 101 supported by a substrate (Si substrate 10 or upper substrate 102a). Therefore, unlike a method of joining an electrode/solid electrolyte/electrode laminate to a substrate, occurrence of defects such as pinholes in a solid electrolyte can be suppressed even when a relatively thin solid electrolyte is used. Further, occurrence of damage to a solid electrolyte due to mechanical impact in a manufacturing process can be suppressed. Therefore, a reactor having improved reliability can be obtained.
For example, between adjacent cathodes, a wiring (not illustrated) that connects the cathodes to each other is provided as described above. In the example described above, the wiring between the cathodes is electrically isolated from upper substrate 102a by a thermal oxide film of upper substrate 102a. Similarly, for example, the wiring between adjacent anodes is electrically isolated from lower substrate 102b by a thermal oxide film of lower substrate 102b.
As shown in
By joining solid electrolyte 101 and upper substrate 102a (or lower substrate 102b) to each other with the joining layer interposed therebetween, leakage of a reactant between adjacent first chambers (or adjacent second chambers) can be suppressed. A similar effect is obtained when upper substrate 102a (or lower substrate 102b) is formed by the foregoing various film formation methods. For example, by coating a surface of the wiring using an insulating material, joining layer 107 can be formed from a metallized ceramic layer. When an insulating material is used as a material of joining layer 107, the degree of freedom of design of the wiring between cathodes and/or anodes is improved, and therefore the degree of freedom of design of the shape, arrangement and so on of first chambers 104a and/or second chambers 104b is also improved.
As illustrated in
An electrically conductive substrate may be used as an upper substrate or a lower substrate.
As is apparent from
As is apparent from
As is apparent from
Further, electrically conductive upper substrate 102a may be connected to the high potential section of external power source 108 as shown in
As is apparent from
In a configuration ensuring that a voltage having the same polarity as that of a voltage applied to cathode 103a can be applied to lower substrate 102b as illustrated in
In the examples shown in
As described above, according to the present disclosure, there can be provided a reactor with improved reliability, which ensures that damage to a solid electrolyte due to mechanical impact and thermal impact at the time of starting or stopping operation can be suppressed. According to the present disclosure, damage to the solid electrolyte is suppressed, and therefore the solid electrolyte is relatively easily made thin. Therefore, a higher ion conductivity can be achieved, so that the reactor can be activated at an operation temperature of, for example, about 300° C.
As the solid electrolyte, not only a proton conductor but also an oxygen ion conductor formed of a solid oxide may be used, and therefore carriers in the solid electrolyte may be oxygen ions.
The reactor according to the present disclosure can be used for fuel cells, hydrogenation devices, dehydrogenation devices, water vapor electrolysis devices, water vapor electrolysis and hydrogenation devices and so on. The reactor according to the present disclosure can also be used as a gas sensor such as a hydrogen sensor or an oxygen sensor by measuring an electromotive force generated between a first electrode and a second electrode.
Number | Date | Country | Kind |
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2014-092801 | Apr 2014 | JP | national |