WO2007094429A1

WO2007094429A1 - Electrode material and energy conversion device using same

Info

Publication number: WO2007094429A1
Application number: PCT/JP2007/052770
Authority: WO
Inventors: Tsutomu Kajino; Norihiko Setoyama; Keiko Uemura; Yoshiaki Fukushima; Hisao Kato; Seiya Tsujimura; Kenji Kano
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2006-02-17
Filing date: 2007-02-15
Publication date: 2007-08-23
Also published as: JP2007218795A; JP4811048B2

Abstract

Disclosed is an electrode material comprising a carbon porous body and an oxidation-reduction enzyme supported by the carbon porous body.

Description

Specification

Electrode material and energy conversion device using the same

Technical field

[0001] The present invention relates to an electrode material and an energy conversion device using the same, and more particularly to an electrode material made of a carbon composite material and an energy conversion device using the same. Background art

[0002] Conventionally, various studies on porous bodies have been conducted, and application to a carrier such as a catalyst or an electrode material has been studied using its adsorptivity. Various carbon composite materials in which such a porous body is used as a carrier and a functional molecule is supported on the carrier are disclosed.

[0003] An example is A.Vinu et ai., Adsorption of Cytochrome C on New Mesoporous

Carbon Molecular Sieves ", J. Phys. Chem. B, 2003, Vol. 107, p.8297-8299 (Reference 1) discloses a carbon composite material in which cytochrome C is supported on a mesoporous carbon molecular sieve. And

[0004] However, in the above-mentioned document 1, there is no description that a carbon composite material in which cytochrome C is supported on a mesoporous carbon molecular sieve is applied to an electrode material. Disclosure of the invention

[0005] The present invention has been made in view of the above-described problems of the prior art, and can provide sufficient stability and excellent activity of the support component, and can efficiently achieve the efficiency between the support and the support component. It is an object of the present invention to provide an electrode material capable of efficient electronic conduction and an energy conversion device using the same.

[0006] As a result of intensive studies to achieve the above object, the present inventors obtain sufficient stability and excellent activity of the loaded component by loading the oxidoreductase on the carbon porous body. Thus, it was found that an electrode material capable of efficient electron conduction between the carrier and the supported component was obtained, and the present invention was completed.

That is, the electrode material of the present invention comprises a carbon porous body and an oxidoreductase supported on the carbon porous body. [0008] The carbon porous body that is effective in the present invention has a specific surface area of 100 m ² Zg or more and a pore diameter distribution region of 2ηπ! Based on the total pore volume in the range of ~ lOOnm, the pore volume in the range of ± 25% of the average pore diameter is preferably 60% or more.

[0009] Further, as the carbon porous body that is useful in the present invention, an X-ray diffraction peak is not observed in the scan region 2 Θ = 0.5 to 10 ° (CuK line), and adsorption and desorption isotherm In the calculated pore size distribution, if the pore size value at the top of the distribution peak is in the range of 1 nm or more and less than lOnm, the pore size range of d 2 nm with respect to the pore size value (d). If the pore size value at the top of the distribution peak is in the range of 10 nm or more and 50 η m or less, (0) with respect to the pore size value (D) 75 XD) to (1.25 XD) A carbon gel containing 60% or more of the total pore volume in the pore diameter region is preferable.

[0010] In the present invention, the pore diameter value of the carbon gel force distribution peak top is 1

Preferable to be ~ 20nm! /.

[0011] Further, in the present invention, it is preferable that the carbon gel force average particle diameter is composed of primary particles having a particle diameter of 2 to 50 nm.

[0012] In addition, the acid reductase that is effective in the present invention is preferably at least one enzyme selected from the group powers of laccase and pyrilvin oxidase.

[0013] Furthermore, it is preferable that the electrode material of the present invention further includes an electron transmission material supported on the carbon porous body.

[0014] Further, in the electrode material of the present invention, the carbon porous body has pores, and at least a part of the acid-reductase is supported in the pores. I prefer to be there.

[0015] Furthermore, an energy conversion device of the present invention comprises the electrode material of the present invention.

[0016] According to the present invention, an electrode material capable of obtaining sufficient stability and excellent activity of the supported component and capable of efficient electron conduction between the carrier and the supported component and the same are used. An energy conversion device can be provided. Brief Description of Drawings

[0017] FIG. 1 is a cyclic voltammogram obtained using an electrode whose surface is modified with the electrode material obtained in Example 5.

[FIG. 2] FIG. 2 is a cyclic voltammogram obtained using an electrode whose surface is modified with the electrode material obtained in Comparative Example 1.

[Fig. 3] Fig. 3 is a cyclic voltammogram obtained by using an electrode obtained by modifying the electrode material obtained in Example 7 and Comparative Example 2 on the surface.

[FIG. 4] FIG. 4 is a cyclic voltammogram showing the cyclic voltagram shown in FIG. 3 in an enlarged range of 200 to 100 μΑ current.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail according to preferred embodiments thereof.

The electrode material of the present invention includes a carbon porous body and an acid reductase supported on the carbon porous body.

[0020] (porous carbon body)

As the carbon porous body according to the present invention, mesoporous carbon particles or carbon gels, which are carbon porous bodies having a specific surface area, pore diameter and pore volume, which can sufficiently improve the stability and activity of the supported component. Is contained, and so-called carbon black is not contained.

[0021] The average pore diameter of such a carbon porous body is preferably 2 to 50 nm, particularly preferably 2 to 20 nm! /. If the average pore diameter of the carbon porous body is less than 2 nm, the pore size tends to be smaller than the size of the supported component, and the adsorptivity tends to decrease. There is a tendency for the specific surface area to decrease and the adsorptivity to decrease. Further, when the average pore diameter of the carbon porous body exceeds 20 nm, there is a tendency that inconvenience is likely to occur when a part of the supporting component is supported.

[0022] In addition, from the viewpoint of preventing a reduction in the amount of the supported component, the average pore size of the carbon porous body according to the present invention is preferably equal to or larger than the molecular size of the supported component. More preferably, it is about 1 to 1.25 times the diameter. When the average pore diameter of the carbon porous material that is useful in the present invention is as described above, the supported component is finely matched to the molecular diameter. Because it is fixed in the pores, the outer wall of the pores suppress structural changes that occur when the supported component is deactivated by heat, so that the deactivated supported component can be prevented and the thermal stability is improved. Tend to.

[0023] Further, as a carbon porous body that is useful in the present invention, the pore size distribution region is 2ηπ! Based on the total pore volume in the range of ~ lOOnm, those having a pore volume in the range of ± 25% of the average pore diameter of 60% or more are preferable. If the uniformity of the pore size is worse than this, there will be more pore components other than the optimum pore size for supporting the oxidative reduction enzyme and other supporting components, and the stability and activity of the acid reduction enzyme will be sufficiently improved. There is a tendency to ヽ.

[0024] The specific surface area of the porous carbon material according to the present invention is preferably 100 m ² / g or more, more preferably 500 to 1000 m ² Zg. When the specific surface area force of the carbon porous body is less than Sl00m ² Zg, the contact area with the supporting component is reduced and the pores taking in the supporting component are reduced, so that the adsorptivity tends to be low.

[0025] Further, the pore volume of the carbon porous body according to the present invention is not particularly limited because it varies depending on the specific surface area and the average pore diameter, but is preferably 0.1 to 50 mlZg, and 0.2. More preferably, it is -2.5 mlZg.

[0026] From the viewpoint of preventing a reduction in the amount of the supported component, among the pores of the carbon porous body according to the present invention, pores having a pore diameter equal to or larger than the molecular diameter of the oxidoreductase are used. The total volume is preferably equal to or greater than the total volume of the supported acid reductase.

[0027] The specific surface area, average pore diameter and pore volume of the carbon porous body according to the present invention can be determined by the methods described below. That is, the carbon porous body is put in a predetermined container, cooled to liquid nitrogen temperature (196 ° C.), nitrogen gas is introduced into the container, and the adsorption amount is obtained by a constant volume method or a gravimetric method. Next, the pressure of the introduced nitrogen gas is gradually increased, and the nitrogen gas adsorption isotherm is obtained by plotting the nitrogen gas adsorption amount with respect to each equilibrium pressure. Using this nitrogen adsorption isotherm, the specific surface area, average pore diameter and pore volume can be calculated by the SPE (Subtracting Pore Effect) method (K.Kaneko, C.Ishii, M.Ruike,

H. Kuwabara, Carbon 30, 1075, 1986). The above SPE method is α-plot method, t-top s

This is a method to calculate the specific surface area etc. by removing the effect of the micropore strength and potential field by performing micropore analysis by the lot method etc. The calculation is more accurate than the BET method.

[0028] Further, the mesoporous carbon particles are based on the whole pore volume in the pore size distribution of 2 to 100 nm, 2 to: the pore volume in the pore size distribution of LOnm is 80% or more, The carbon particles have mesopores. Examples of methods for measuring such pore size distribution include XRD and nitrogen adsorption methods.

[0029] The method for producing such mesoporous carbon particles is not particularly limited, and for example, the following method can be employed. That is, porous particles such as silica and titer are adsorbed and impregnated with organic molecules such as sucrose and furfuryl alcohol, and then carbonized in an inert atmosphere. Thereafter, mesoporous carbon particles having porous particles such as silica in a bowl shape can be produced by dissolving and removing the particles in a bowl shape such as silica with hydrofluoric acid or NaOHZEtOH. For example, silica mesoporous MCM-48 can be used as a porous porous particle.

[0030] The carbon gel satisfies the following conditions (i) to (ii).

(i) In X-ray diffraction measurement (XRD), V and X-ray diffraction peaks are not observed in the scan region 20 = 0.5 to 10 ° (CuK line).

(ii) In the pore size distribution in which the adsorption / desorption isotherm force is also calculated, if the pore size value at the top of the distribution peak is in the range of 1 nm or more and less than lOnm, d is 2 nm with respect to the pore size value (d). When the pore size region contains 60% or more of the total pore volume and the pore size value of the distribution peak top is in the range of lOnm or more and 50nm or less, the pore size value (D) More than 60% of the total pore volume is included in the pore diameter region of (0.75 XD) to (1.25 XD) nm.

[0031] Here, the X-ray diffraction peak means that a periodic structure having a d value corresponding to the peak angle is present in the sample. Therefore, carbon-based porous materials with one or more peaks in the scan region 2 Θ = 0.5 to 10 ° (CuK line) are regularly arranged with a period of 0.9 to 17.7 nm. This is so-called mesoporous carbon (MPC). In the case of mesoporous carbon such as carrier strength, there is a tendency that sufficient improvement in stability and activation with respect to the supported component is not achieved.

[0032] The carbon gel has an X-ray rotation in a scan region 20 = 0.5 to 10 ° (CuK line). Folded peaks are not observed, and the pores do not have a periodic array structure, but have a three-dimensional network structure connected to each other. By using such a carbon gel as a carrier, the reason and the activity are surprisingly improved, although the reason is not clear.

[0033] In X-ray diffraction measurement (XRD), a peak intensity ratio with respect to background noise intensity of less than 3 is not recognized as an X-ray diffraction peak. That is, “X-ray diffraction peaks are not observed in the scan region 2 0 = 0.5 to 10 ° (CuK line)” means that the background in the scan region 2 Θ = 0.5 to 10 ° (CuK line). No X-ray diffraction peak with a ratio of peak intensity to noise intensity of 3 or more is observed.

[0034] Further, the carbon gel is an aggregate having the primary particle force, and in the pore size distribution calculated from the adsorption / desorption isotherm, (ii 1) the pore size value of the distribution peak top is not less than lnm and less than lOnm. In the range of the pore diameter value (d), the pore diameter region of d 2 nm contains 60% or more of the total pore volume, and (ii-2) the distribution peak top When the pore diameter value of s is in the range of lOnm or more and 50 nm or less, all pores are in the pore diameter region of (0.75 XD) to (1.25 XD) nm with respect to the pore diameter value (D). It contains more than 60% of capacity. If the uniformity of the pore diameter is worse than this, the number of pore components other than the optimum pore diameter for supporting an enzyme or the like increases, and the obtained effect is reduced.

[0035] Further, the pore size value of the distribution peak top of the carbon gel is preferably 1 to 20 nm. When the pore size value of the carbon gel is less than 1 nm, the pore size is often smaller than the size of the supported component, and the adsorptivity is reduced. On the other hand, when it exceeds 50 nm, the specific surface area is reduced. And the adsorptivity decreases. Further, if the pore diameter value of the carbon gel exceeds 20 nm, there is a tendency that inconvenience is likely to occur when the supporting component is supported.

[0036] The carbon gel is preferably one having an average particle size of primary particle force of 2 to 50 nm, more preferably an average particle size of 20 nm. If the average particle size of the primary particles constituting the carbon gel is less than 2 nm, the size of the pores is often smaller than the size of the supported component, and the adsorptivity is reduced, whereas if the average particle size exceeds 50 nm. The specific surface area is reduced and the adsorptivity is reduced. [0037] The method for producing such a carbon gel is not particularly limited, and can be suitably produced by employing a conventionally known method. Examples of a method for producing such a carbon gel include the method described below.

[0038] That is, first, according to the method described in the literature (RW Pekala, CT Alviso, FM Kong, and SS Hulsey, J. Non-cryst. Solids vol. 145, p. 90 (1992)). To synthesize an organic gel. That is, phenols such as resorcinol and aldehydes such as formaldehyde are reacted in the presence of an alkali catalyst or an acid catalyst, followed by aging to obtain an organic gel composed of phenol resin. Next, after drying the obtained organic gel, it is possible to obtain a carbon gel by baking it in an inert atmosphere and carbonizing it.

[0039] (oxidoreductase)

A suitable enzyme suitable for the present invention is appropriately selected depending on whether the electrode material of the present invention is used as the positive electrode material or the negative electrode material.

[0040] When the electrode material of the present invention is used as a material on the positive electrode side, the acid-reducing enzyme according to the present invention is not particularly limited as long as it is an enzyme that can receive electrons by reaction. Especially preferred is laccase bilirubin oxidase, which can catalyze the reaction that produces water using tons and oxygen as substrates.

[0041] On the other hand, when the electrode material of the present invention is used as a negative electrode material, the oxidoreductase according to the present invention is not particularly limited as long as it is an enzyme capable of releasing an electron by reaction, and alcohol is converted to acid. Examples thereof include alcohol dehydrogenase capable of catalyzing a reaction that releases electrons, aldehyde dehydrogenase that oxidizes aldehyde and formic acid, and formate dehydrogenase. In addition, as such an acid-reducing enzyme used for the electrode material on the negative electrode side, a corresponding oxidase such as oxidase or dehydrogenase can be used according to the raw material for supplying electrons. Specifically, Alcohol oxidase using alcohol as a raw material, organic acid dehydrogenase using organic acid such as formic acid as a raw material, and glucose oxidase such as glucose oxidase and glucose dehydrogenase using saccharide as a raw material are preferable. Furthermore, hydrogenase from hydrogen is also preferably used. It can be done.

[0042] (Electrode material)

As described above, the electrode material of the present invention comprises a carbon porous body and an acid reductase supported on the carbon porous body.

[0043] In the electrode material of the present invention, the amount of acid reductase supported on the carbon porous body is not particularly limited as long as the enzyme activity is shown, but the obtained electrode material has sufficient oxidoreductase. From the viewpoint of exhibiting activity, it is preferable that the loading amount of the oxidoreductase is about 0.01 to 80 parts by mass with respect to 100 parts by mass of the carbon porous body.

[0044] In addition, the method for obtaining the electrode material of the present invention by supporting an oxidoreductase on a carbon porous body is not particularly limited, and methods such as a sublimation method and an impregnation method can be employed. The following impregnation method is more preferred. That is, first, the acid reductase is dissolved in water or a buffer solution so as to have a concentration at which precipitation does not occur (preferably 0.1 mgZml to 1000 mgZml). Then, suspend the porous carbon body at a temperature (preferably 0 ° C to 50 ° C) that does not freeze the solution and does not denature the oxidoreductase, and it is preferable for at least 5 minutes or more. In this case, the acid reductase is immobilized in the pores of the carbon porous body by contacting the acid reductase with the carbon porous body for 30 minutes or more to obtain the electrode material of the present invention.

[0045] The concentration when the carbon porous body is suspended in the above solution is not particularly limited, but is preferably about 0.1 to lOOOOmgZml. Further, after the supporting step, there is a step of further separating the porous carbon composite material from the solution by performing centrifugal separation or the like, and removing the liquid component by performing drying or the like. It is possible to have a step of obtaining the carbon porous composite material in a state of being!

[0046] The electrode material of the present invention preferably further comprises an electron transfer substance supported on the carbon porous body. By further supporting an electron transfer substance in addition to the acid reductase on the carbon porous body, the electron transfer substance and the oxidoreductase combine to tend to enable more efficient electron conduction. is there. Examples of such electron transfer materials include electron transfer proteins such as cytochrome C and ferredoxin, metal complexes such as osmium (Os) complex and ruthenium (Ru) complex, and organic compounds having an electron transfer function. Note that the electrode material of the present invention has an amount of the electron transfer material carried on the porous carbon body. It is preferred to be in excess of the amount of acid reductase.

[0047] As a method for supporting the electron transfer substance on the carbon porous body, a method similar to the method for supporting the oxidoreductase on the carbon porous body as described above can be employed. Further, the electron transfer substance and the oxidoreductase may be simultaneously supported on the carbon porous body.

[0048] Further, in the electrode material of the present invention, it is preferable that the carbon porous body has pores and at least a part of the oxidoreductase is supported in the pores. preferable. The amount of the acid reductase supported in the pores of such a carbon porous body is not particularly limited and can be appropriately adjusted according to the design of the target electrode material, and is necessary for desired power generation. Prefer to be in quantity.

[0049] Next, the energy conversion device of the present invention will be described. That is, the energy conversion device of the present invention comprises the electrode material of the present invention. Examples of such energy conversion devices include biosensors, fuel cells, and solar cells.

[0050] Examples of such a biosensor include a sensor provided with the electrode material of the present invention in a detection unit for detecting a biological component or the like. In this way, by providing the biosensor with the electrode material of the present invention, electron transfer between the enzyme and the electrode is efficiently performed, so that highly sensitive sensing is possible. Moreover, the manufacturing method of such a nanosensor is not particularly limited, and a known manufacturing method can be appropriately employed. The biological components generally mean living organisms included in the category of living organisms and all tissues and cells constituting these, and are further manufactured and processed using such materials as raw materials. Foods etc. are also included in biological components. Moreover, as such a biosensor, it is only necessary to select the oxidoreductase contained in the electrode material of the present invention according to the component in the living body to be detected.

[0051] Examples of the fuel cell or the solar cell include those having the electrode material of the present invention on the electrode for the fuel cell or the solar cell.

[0052] Such an electrode for a fuel cell or the solar cell can be obtained, for example, by modifying the electrode material of the present invention on the surface of an electrode core material having a predetermined shape. Ma Such a core material is not particularly limited, and various materials that can be used for electrodes of fuel cells and solar cells can be used. Further, the method for obtaining the electrode by modifying the electrode material of the present invention on the surface of the core material is not particularly limited. For example, a suspension obtained by dispersing the electrode material of the present invention in an organic solvent is used as the core material. A method in which the electrode material of the present invention is modified on the surface of the core material and a solution in which a porous carbon body is suspended is applied to the surface of the core material, and a carbon porous material is applied to the surface of the core material. Examples thereof include a method for producing an electrode by modifying the body and then supporting the oxidoreductase on the strong porous body.

Example

Hereinafter, the present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to the following examples.

[0054] (Synthesis Examples 1 to 5: Synthesis of carbon gel)

First, the literature (RW Pekala, CT Alviso, FM Kong, and SS Hulsey, J. Non-cryst. Solids vol. 145, p. 90 (1992)) went. That is, resorcinol 5.5g (Wako Pure Chemical Industries) and sodium carbonate 26.5mg (Wako Pure Chemical Industries) were dissolved in 16.9g of distilled water, and then 37% formaldehyde aqueous solution 8.lg (Wako Pure Chemical Industries) was added. Stir and mix. The mixed solution became light yellow and transparent. The molar ratio of each component is as follows.

Resorcinol: Sodium carbonate: Formaldehyde = 200: 1: 400

Next, the solution prepared as described above was further diluted with water to obtain an organic gel while controlling the pore diameter. That is, prepare a solution by diluting the stock solution prepared as described above from 0.1 to 3 times by volume (volume ratio) (Synthesis example 1: dilution factor 0.1 times, synthesis example 2: dilution factor). 0. 5 times, Synthesis example 3: Dilution ratio 1 time, Synthesis example 4: Dilution ratio 3 times, Synthesis example 5: Dilution ratio 2 times), put these solutions in vials, seal tightly, and keep at room temperature for 24 hours The hydrated organic gel was obtained by standing at 50 ° C. for 24 hours and then at 90 ° C. for 72 hours.

[0055] Next, the obtained organic gel was dried as follows. That is, first, a hydrated organic gel was immersed in acetone (Wako Pure Chemicals) as an exchange solvent in order to remove moisture in the organic gel. The water in the gel diffuses into the acetone and the water in the gel The minutes were completely replaced with acetone. At this time, the substitution rate of water was further improved by exchanging acetone as a substitution solvent several times with a new one. Subsequently, the immersion solvent was changed to n-pentane (Wako Pure Chemical Industries), and the solvent exchange-immersion was repeated in the same manner as above until the acetone power in the organic gel—pentane was completely replaced. And the dried organic gel was obtained by air-drying the organic gel solvent-substituted by n-pentane.

[0056] Next, the obtained dried organic gel was carbonized as follows to obtain a carbon gel. That is, the carbonization of the gel was carried out by heating the dried organic gel under a nitrogen stream (flow rate 300 mlZmin) at 1000 ° C. The heating time was 6 hours.

[0057] <X-ray diffraction measurement (XRD)>

The carbon gel obtained in Synthesis Examples 1 to 5 and the mesoporous force obtained in Comparative Synthesis Example 1 were measured for X-ray diffraction, and the carbon gels obtained in Synthesis Examples 1 to 5 were measured. X-ray diffraction peak in the scan region 20 = 0.5 to 10 ° (CuK line) was not confirmed. Because of this, the carbon gels obtained in Synthesis Examples 1 to 5 have a structure in which the pores do not have a periodic array structure, but the pores are interconnected, and a three-dimensional network structure. It has been confirmed that

Nitrogen adsorption measurements were performed on the carbon gels obtained in Synthesis Examples 1 to 5, and the pore size distribution of the carbon gel was determined based on the obtained nitrogen adsorption isotherms. As a result, Synthesis Example 1

The pore size of the carbon gel obtained in ~ 5 is distributed only in the range of 2 to about 40 nm, the pore volume in the range of ± 25% of the average pore diameter is 60% or more, and the average pore diameter It was confirmed that 60% or more of the total pore volume was included in the range of 2 nm, and it was confirmed that the distribution shape force had highly uniform pores. The average pore diameters of the carbon gels obtained in Synthesis Examples 1 to 5 were as shown in Table 1.

[0059] [Table 1] Dilution factor Average fine particle L diameter Ratio table E¾

(Volume ratio) (nm) (m V g) Synthesis example 1 0. 1 times 3. 9 545 Synthesis example 2 0.5 times 8. 0 393 Synthesis example 3 1 times 10. 1 656 Synthesis example 4 3 times 36. 3 653 Synthesis example 5 2 times 22. 0 850

[0060] (Examples 1 to 4)

The electrode material of the present invention was manufactured using the carbon gel obtained in Synthesis Examples 1 to 4. That is, first, pyrilvinoxydase (BOD) was dissolved in distilled water as an enzyme to prepare a 0.7 mgZml enzyme solution. Next, 0.5 ml of the enzyme solution was added to 12.5 mg of each carbon gel, and gently mixed overnight at 4 ° C to immobilize the enzyme on each carbon gel. Thereafter, the carbon gel on which the enzyme is immobilized is separated and collected from the enzyme solution by centrifugation, and washed three times with 5 ml of distilled water to repeat the electrode material of the present invention (Example 1: Carbon obtained in Synthesis Example 1). Example 2: Using the carbon gel obtained in Synthesis Example 2, Example 3: Using the carbon gel obtained in Synthesis Example 3, Example 4: Using the carbon gel obtained in Synthesis Example 4 Use).

[0061] <Measurement of immobilized amount of enzyme>

The amount of enzyme immobilized was determined by calculating the amount of enzyme in the enzyme solution before and after immobilization based on the absorbance at 280 nm, and the amount of enzyme immobilized on the carbon gel was calculated. In the electrode materials obtained in Examples 2 to 4 having an average pore diameter larger than the molecular diameter of the enzyme (BOD: 6.4 nm) estimated from the molecular weight of the enzyme, almost the entire amount of the enzyme added was immobilized. It is certain that f * i¾.

[0062] <Thermal stability test of immobilized enzyme>

BOD fixed on a porous carbon body using the electrode materials obtained in Examples 2-4 The thermal stability of was evaluated. 12. 5 mg of each electrode material is suspended in 1 ml of 50 mM phosphate buffer (pH 7.5), heat-treated at 60 ° C for a specified time (5-60 minutes), then cooled sufficiently in ice, Thereafter, each electrode material was collected by centrifugation.

[0063] Next, 2.5 ml of a substrate solution (2.5 mM ferrocyan sodium, 50 mM phosphate buffer (pH 7.5), oxygen saturation) was added to each of the collected electrode materials, and the temperature was 37 ° C. After stirring for 25 minutes, the mixture was cooled and the absorbance at 420 nm of the supernatant was measured to determine the residual activity (relative activity with 100% of the activity before heat treatment). Table 2 shows the results obtained.

[0064] As can be seen from the results shown in Table 2, it was confirmed that any of the electrode materials obtained in Examples 2 to 4 had sufficient thermal stability. In addition, in the electrode materials (Examples 2 to 3) in which the enzyme was immobilized on the carbon gels obtained in Synthesis Example 2 and Synthesis Example 3 having pores corresponding to the size of the enzyme molecule, the immobilization was performed. It was confirmed that the thermal stability of the enzyme was higher.

[0065] [Table 2]

[0066] (Example 5)

First, a suspension was prepared by suspending 20 mg of the carbon gel obtained in Synthesis Example 2 in n-methylpyrrolidone (NMP) containing 10% polybutydifluoride. Next, the suspension was spin-coated (1 500 rpm) by 10 1 times on the surface of a φ6Zφ3 Dallas carbon (GC) cylindrical electrode to obtain a carbon porous body modified electrode. Next, the carbon porous body decorated electrode obtained was immersed in a 5 μΜ enzyme (BOD) aqueous solution at 4 ° C for a while, then MilliQ After washing with water three times, the BOD is fixed on a carbon porous body (carbon gel) modified on the electrode surface, and the electrode material of the present invention is produced on the surface of the electrode. A modified electrode was obtained.

[0067] (Example 6)

ADH was applied to the carbon porous body (carbon gel) modified on the electrode surface in the same manner as in Example 5 except that 5 μΜ alcohol dehydrogenase (ADH) aqueous solution was used instead of 5 μΜ enzyme (BOD) aqueous solution. The electrode material of the present invention was manufactured on the surface of the electrode, and an electrode having the surface modified with the electrode material of the present invention was obtained.

[0068] (Comparative Example 1)

In addition, a carbon porous body (carbon gel) modified on the electrode surface was prepared in the same manner as in Example 5 except that a 5 μΜ electron transfer protein (cytochrome C) aqueous solution was used instead of the 5 μΜ enzyme (BOD) aqueous solution. The electrode material for comparison was prepared by immobilizing cytochrome C on the electrode surface, and carrying the cytochrome C on carbon gel on the electrode surface, and an electrode having the electrode material for comparison modified on the surface was obtained.

[0069] <Electrical property test of electrode>

Using the electrode material obtained in Example 5 and Comparative Example 1 whose surface was modified, and using 0.1 M phosphate buffer (ρΗ7.0) saturated with oxygen or argon as an electrolyte, the cyclic voltamgram method (Example) 5: Electric potential of each electrode was measured by electric potential sweep (sweep speed 20mV Z seconds) between electric potentials 0-600mV, Comparative Example 1: Potential sweep (sweep speed 20mVZ seconds) between electric potentials 0-600mV . The cyclic voltamgram obtained using the electrode whose surface was modified with the electrode material obtained in Example 5 is shown in FIG. 1, and the electrode material obtained in Comparative Example 1 was modified on the surface. Figure 2 shows the cyclic voltammogram obtained using the electrode.

[0070] As is apparent from the cyclic voltamgram force shown in FIG. 1, the electrode material of the present invention (Example 5) in which BOD is fixed to a carbon gel is modified on the surface! On the other hand, no reduction current was observed in the absence of oxygen as an enzyme substrate, but a reduction current was observed in the presence of oxygen. From these results, in the electrode material of the present invention (Example 5), direct electron transfer occurs between the enzyme and the electrode, and the reduction current efficiently flows. It was confirmed that

[0071] On the other hand, as can be seen from the cyclic voltamgram force shown in FIG. 2, in the electrode whose surface was modified with a comparative electrode material (Comparative Example 1) in which cytochrome C was fixed on carbon gel. No reduction current was observed even in the presence of oxygen. From these results, it was confirmed that in the electrode material for comparison (Comparative Example 1), there is no enzyme that reacts with oxygen as a substrate, and therefore no reduction current flows only with the electron transfer protein. It was done.

[0072] Next, the electrode material obtained in Example 6 was used on an electrode whose surface was modified, and contained 1% alcohol. 0.1M phosphate buffer (pH 7.0) or no alcohol. Electrical characteristics were measured by cyclic voltamgram method using IM acid buffer (pH 7.0) as electrolyte.

[0073] As a result of the measurement, when 0.1 M phosphate buffer (pH 7.0) containing 1% alcohol was used as the electrolyte, a characteristic acid-acid current was observed. On the other hand, when 0.1 M phosphate buffer (pH 7.0) containing no alcohol was used as the electrolyte, no current was observed. From these results, it was confirmed that in the electrode material of the present invention (Example 6), direct electron transfer occurred between the enzyme and the electrode, and the oxidation current flowed efficiently.

[Example 7]

First, 10 mg of the carbon gel obtained in Synthesis Example 5 was suspended in n-methylpyrrolidone (NMP) 201 containing 0.1% polyvinyl difluoride. Next, 1 μl of the suspension was applied to the surface of a QCM electrode having a diameter of 5 mm and dried at 60 ° C. to obtain a carbon porous body modified electrode using PVDF as a binder. Next, the obtained carbon porous body modified electrode was immersed in a 5 μΜ enzyme (BOD) aqueous solution at 4 ° C for a while and then washed three times with Milli Q water to modify the electrode surface. BOD was fixed on a carbon porous body (carbon gel) to produce the electrode material of the present invention on the surface of the electrode, and an electrode having the surface modified with the electrode material of the present invention was obtained.

[0075] (Comparative Example 2)

A comparative electrode was obtained in the same manner as in Example 7 except that carbon black (ketchen black) was used instead of the carbon gel lOmg obtained in Synthesis Example 5. <Electric property test of electrode>

Using the electrode obtained by modifying the electrode material obtained in Example 7 and Comparative Example 2 on the surface, and using 50 mM phosphate buffer (pH 7.0) as the electrolyte, the electrolyte solution is cyclically stirred or stirred. The electrical characteristics of each electrode were measured by the voltamgram method (potential sweep between potentials 0 and 600 mV (sweep speed 20 mVZ sec)). The obtained cyclic voltagram is shown in Fig. 3, and the cyclic voltagram showing the cyclic voltagram shown in Fig. 3 in an enlarged range of 200 to 100 µΑ is shown in Fig. 4.

[0077] As is apparent from the cyclic voltammograms shown in Figs. 3 and 4, the oxidation current in a stationary state is obtained by using carbon black for the electrode obtained in Example 7 using carbon gel. It was confirmed that it was about 3 times the electrode obtained in Comparative Example 2. In addition, the current value did not change even when the electrode obtained in Comparative Example 2 using carbon black was stirred, whereas in the electrode obtained in Example 7 using carbon gel, By stirring the electrolyte solution and increasing the amount of dissolved oxygen as a reaction substrate, it was confirmed that a larger acid current flows and an oxidation current about 10 times that of the electrode obtained in Comparative Example 2 flows. .

[0078] From these results, in the electrode obtained using carbon black (Comparative Example 2), the electron transfer between the enzyme and the electrode carrier is reaction-controlled, whereas the carbon gel is used. In the electrode obtained by using (Example 7), it is considered that the mass transfer of the reaction substrate becomes the reaction rate-determining rate! / It was confirmed that the electron transfer between the enzyme and the electrode was efficiently achieved. Industrial applicability

[0079] As described above, according to the present invention, an electrode capable of obtaining sufficient stability and excellent activity of the carrier component and capable of efficient electron conduction between the carrier and the carrier component. Materials can be provided.

Therefore, the electrode material of the present invention is useful as a material used for an electrode of a fuel cell.

Claims

The scope of the claims

[1] An electrode material comprising a carbon porous body and an oxidoreductase supported on the carbon porous body.

[2] The carbon porous body has a specific surface area of 100 m ² Zg or more and a pore diameter distribution region in a range of ± 25% of the average pore diameter based on the total pore volume in the range of S2 nm to 100 nm. 2. The electrode material according to claim 1, having a pore capacity of 60% or more.

[3] X-ray diffraction peak is not recognized in the carbon porous body force scan region 2 Θ = 0.5 to 10 ° (CuK line), and the distribution peak When the pore diameter value of the top is in the range of 1 nm or more and less than lOnm, the pore diameter value of d ± 2 nm with respect to the pore diameter value (d) contains 60% or more of the total pore volume, In addition, when the pore size value of the distribution peak top is in the range of lOnm or more and 50nm or less, the pore diameter range of (0.75 XD) to (1.25 XD) nm with respect to the pore diameter value (D). 2. The electrode material according to claim 1, wherein the electrode material is a carbon gel containing 60% or more of the total pore capacity.

[4] The electrode material according to claim 3, wherein the carbon gel force distribution peak top has a pore diameter value of 1 to 20 nm.

[5] The electrode material according to claim 3, wherein the carbon gel force has an average particle size of primary particle force of 2 to 50 nm.

6. The electrode material according to claim 1, wherein the oxidoreductase is at least one enzyme selected from the group power of laccase and pyrilbinoxytase.

7. The electrode material according to claim 1, further comprising an electron transfer material supported on the carbon porous body.

[8] The electrode material according to [1], wherein the carbon porous body has pores, and at least a part of the acid reductase is supported in the pores.

[9] An energy conversion device comprising the electrode material according to any one of claims 1 to 8.