JP4855983B2 - Method for producing diamond electrode - Google Patents

Description

The present invention relates to a method for producing a diamond electrode having a needle-like projection arrangement structure on its surface, which can be used for various applications.

  Electrodes or catalyst carriers used in fuel cells, sensors, and reactors utilizing electrochemical reactions preferably have good electrical conductivity, are chemically inert and physically strong, and have a large surface area. As an electrode or catalyst carrier that satisfies these conditions, a conductive diamond electrode doped with impurities such as boron can be cited. In particular, a diamond electrode having a needle-like protrusion arrangement structure on the surface is attracting attention because it easily achieves a large surface area (see Patent Documents 1 and 2).

In the above Patent Document 1, anodized porous alumina having a through-hole is placed on a diamond substrate as a mask, gold having plasma etching resistance is deposited by vacuum deposition, and after removing the anodized porous alumina, A technique for obtaining a structure in which needle-shaped diamonds having a diameter of 20 nm are regularly arranged by performing oxygen plasma etching on a diamond substrate using vapor deposition dots as a mask is disclosed. Moreover, the said patent document 2 is disclosing the technique which makes a diamond surface ciliate by irradiating hydrogen plasma.
Japanese Patent No. 3020155 JP 2001-348296 A

  The physical properties of the diamond surface vary greatly depending on the type of terminal element, and hydrogen-terminated diamond is a conductor having a hydrophobic surface and a p-type conduction mechanism. When hydrogen-terminated diamond is used for the anode electrode, its surface is gradually oxidized to oxygen-terminated diamond exhibiting completely different characteristics. Thus, hydrogen-terminated diamond has the disadvantage that the surface state changes over time. On the other hand, oxygen-terminated diamond has a hydrophilic surface and exhibits electrical insulation.

  Since the technique of Patent Document 1 uses oxygen plasma etching, the diamond surface becomes oxygen-terminated diamond, resulting in a decrease in electrical conductivity. On the other hand, in the technique of Patent Document 2 described above, ciliary diamond is formed using hydrogen plasma etching, so that the surface of this ciliated diamond is initially low in electrode resistance and good electrochemical like hydrogen-terminated diamond. Although it exhibits characteristics, the surface is oxygen-terminated with repeated use and gradually changes over time.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method for producing a diamond electrode having a large surface area, high electrical conductivity on the surface, and electrochemical characteristics that hardly change over time.

(1) The invention of claim 1
A diamond base material doped with an dopant at an average concentration of 3 × 10 ²⁰ to 8 × 10 ²¹ atoms / cm ³ is subjected to dry etching with oxygen gas in a region from the surface of the diamond substrate to a depth of 0.2 μm. By processing the surface of the diamond substrate until the dopant concentration Cs is 1.01 to 2.0 times the average concentration, a needle-like protrusion arrangement structure is formed on the surface of the diamond substrate. The gist of the manufacturing method of the diamond electrode is as follows.

Since the diamond electrode manufactured according to the present invention has a needle-like projection arrangement structure on the surface, the surface area is large. In the vicinity of the surface, the average dopant concentration Ca has a dopant region in a range of 3 × 10 ²⁰ ~8 × 10 ²¹ atoms / cm ^3, a high electrical conductivity at the surface.

The present invention is, for example, can be manufactured diamond electrode as follows. That is, while de Panto is 3 × 10 ²⁰ ~8 × 10 ²¹ atoms / cm ³ in average concentration doped (added) diamond substrate, dry etching with oxygen gas (e.g., plasma etching, reactive ion etching, etc. By processing the surface of the diamond base material by etching using plasma of the above, a needle-like projection arrangement structure can be formed on the surface of the diamond base material.

  Conventionally, dry etching using oxygen gas is known to have a high etching effect on carbon materials such as diamond by the action of ions and radicals in oxygen plasma. However, when etching with oxygen plasma is performed on a carbon material, generally, the surface of the carbon material is etched uniformly or only slightly uneven (see paragraph “0008” of Patent Document 2). ). Therefore, in order to form an acicular protrusion arrangement structure by etching with oxygen plasma, as shown in FIG. 8, formation of a diamond thin film, formation of an aluminum layer, resist application, photomask exposure, development-cleaning, aluminum layer Therefore, a photolithographic process consisting of a number of processes including etching, resist removal, and oxygen plasma etching is required.

The present inventors have, by performing dry etching with oxygen gas to added diamond at a concentration of each species dopant 3 × 10 ²⁰ ~8 × 10 ²¹ atoms / cm ³ such as boron, acicular nano-order It has been found that a structure in which protrusions are regularly arranged is formed on the surface.

If each type dopant such as boron is subjected to etching by oxygen plasma with respect to the diamond substrate is added, oxide dopant near the diamond substrate surface to produce combines with oxygen in the plasma and the dopant atom itself However, it acts as a mask resistant to oxygen plasma. Etching by oxygen plasma selectively proceeds under the influence of this mask, and as a result, a needle-like projection arrangement structure is formed on the surface of the diamond substrate. In addition, it is clear from the results of depth ion analysis of secondary ion mass spectrometry (SIMS) that boron atoms, etc. inside etched out are recombined at the tip of the protrusion. It has become.

  Due to this fact, the inventors of the present application have a diamond having a needle-like protrusion arrangement structure obtained by the above method on the surface, and is a material exhibiting high electrical conductivity in which boron or the like is doped at a higher concentration at the tip of the protrusion. I found out. In other words, since the oxygen plasma irradiation is performed, the diamond surface is oxygen-terminated and stable, and the needle-shaped protrusion-structured diamond with the high-concentration boron-doped layer has electrochemical characteristics superior to those of the hydrogen-terminated diamond. Show.

  In addition, about the kind of dopant added to diamond, the dopant from which the characteristic suitable for the use of the diamond to manufacture can be used can be used. For example, when manufacturing a diamond material having the characteristics of a p-type semiconductor, a p-type dopant such as boron may be used. Further, when manufacturing a diamond material having the characteristics of an n-type semiconductor, an n-type dopant such as phosphorus may be used.

  According to the above manufacturing method, a step such as a photolithography process is not required for etching using oxygen plasma, and thus a significant improvement in productivity can be realized. In addition, since the dopant existing in the vicinity of the surface of the diamond base material acts as a very fine mask at the atomic level, the needle shape is much finer and has a higher aspect ratio than the needle-like protrusions formed through lithography. A protrusion arrangement structure can be formed. Therefore, it is possible to provide diamond having excellent electrode characteristics with a large surface area.

  Furthermore, by changing the dopant concentration, the arrangement density of the mask due to the dopant existing on the surface of the diamond changes. That is, by controlling the concentration of the dopant added to the diamond, the arrangement density of the needle-like protrusions formed on the diamond surface can be controlled, so that a diamond electrode having a suitable surface shape can be provided depending on the application. In addition, since the manufacturing method does not require a step such as photolithography, it can be applied not only to a planar two-dimensional material but also to a three-dimensional material such as a spherical shape.

  The process of etching the diamond substrate with oxygen plasma may be any etching method such as reactive ion etching using a high frequency as a plasma generation source, reactive beam etching, or reactive ion etching using a microwave as a plasma generation source. May be used. For example, when etching a diamond base material by reactive ion etching using a high frequency as a plasma generation source, the pressure is 5 to 100 Pa, more preferably 10 to 50 Pa in an oxygen gas atmosphere. An acicular protrusion arrangement structure can be formed. An arbitrary value can be selected as the high-frequency output. When the output is low, the etching rate is slow. When the output is high, the aspect ratio of the needle-like protrusion can be increased even in the same processing time.

Also, the protrusion diameter increases almost in proportion to the processing time. For example, when reactive ion etching is performed under the conditions of a high-frequency output of 300 W and an oxygen gas pressure of 20 Pa, when the processing time is as short as 30 seconds, the surface has a granular fine particle A protrusion (approximately 5 nm) is formed, and when treated for 15 minutes, diamond needle-shaped protrusions having an average diameter of approximately 25 nm and a length of approximately 300 nm are formed. Naturally, as the diameter increases, the density of the needle-like projections decreases, but it was still observed that the needles were formed at a high density of 3.8 × 10 ¹⁰ pieces / cm ² even in the 15-minute treatment.

  By the way, the method for producing diamond as a base material is not limited to chemical vapor deposition such as microwave plasma CVD or hot filament CVD, but may be a high temperature and high pressure method. Further, the timing of adding the dopant to diamond may be added in the process of producing diamond as a base material, or may be added by ion implantation after the diamond is produced.

The diamond electrode of the present invention thus obtained can be used as it is for an industrial electrolysis electrode or a chemical sensor electrode. In addition, by supporting a metal catalyst, an enzyme catalyst, or the like, application to a chemical sensor electrode or a fuel cell electrode with improved selectivity becomes possible .

In the diamond electrode produced according to the present invention, the dopant concentration Cs in the region from the surface of the diamond substrate to a depth of 0.2 μm is 1.01 to 2.0 times (preferably 1.015 to 1.05) the average concentration in the diamond substrate. 1.7), the conductivity is even higher.

(2 ) The invention of claim 2
The gist of the method for producing a diamond electrode according to claim 1 , wherein the dopant is boron.

The diamond electrode manufactured according to the present invention has the characteristics of a p-type semiconductor because the dopant is boron .

  The present invention will be described based on examples.

a) Production of Diamond Electrode FIG. 2A is a schematic diagram showing a production process of a diamond electrode having a needle-like projection arrangement structure on the surface. First, as shown in (1) of FIG. 2A, a boron-doped diamond thin film 2a to which boron is added is formed on a substrate 1.

  An example of a method for producing the boron-doped diamond thin film 2a is a microwave plasma CVD method. First, a diamond seed crystal is nucleated by mechanical polishing on the substrate 1 (n-Si (111) substrate). Then, boron-doped diamond thin film 2a is formed by a microwave plasma CVD method using a gas generated by bubbling a solution of boron oxide in a mixed solvent of acetone and methanol (boron solution) with hydrogen gas as a carbon source and a boron source. Is generated on the substrate 1.

In an experiment conducted by the inventors of the present invention, a thickness of about 7 hours was generated under the condition that the B / C ratio in the boron solution was 10,000 ppm and the microwave frequency was 2.45 GHz. An 18 μm boron-doped diamond thin film was obtained. That is, the film formation rate was 2.6 μm / h. The boron atoms in the produced boron-doped diamond thin film were uniformly distributed in the thin film, and the concentration was found to be about 2 × 10 ²¹ atoms / cm ³ from the SIMS measurement results.

  Next, as shown in (2) of FIG. 2 (a), the surface of the boron-doped diamond thin film 2a obtained in (1) of FIG. 2 (a) is etched by oxygen plasma to form boron. A large number of needle-like protrusions 3 are formed on the surface of the doped diamond thin film 2a.

  As an example of an etching method using oxygen plasma, reactive ion etching using a high frequency as a plasma generation source can be given. First, a substrate 1 on which a boron-doped diamond thin film 2a is deposited is placed on an electrode of a parallel plate type reactive ion etching apparatus (reactive ion etching apparatus RIE-10NR, manufactured by Samco Corporation), and 100% oxygen gas is used as an etching gas. Etching is performed for a predetermined time at a high frequency of 13.56 MHz and a high frequency output of 300 W in an atmosphere of a gas pressure of 20 Pa. By this etching process, as shown in FIGS. 2A and 2B, a structure in which needle-like protrusions 3 are regularly arranged at high density on the surface of the boron-doped diamond thin film 2a is formed. The

  In Example 1, as shown in Table 1, the etching process was performed for 30 seconds, 5 minutes, 10 minutes, and 60 minutes, and the diamond electrodes manufactured in each case were set to 1A to 1D. .

Further, the diamond electrode 1C was further subjected to an anodic oxidation treatment to obtain a diamond electrode 1E. This anodic oxidation treatment was carried out in a 0.5 M sulfuric acid aqueous solution by using a diamond electrode as an anode electrode and by 3 V vs. Ag / AgCl, constant voltage electrolysis for 30 minutes. Energizing current is about 17 mA / cm ^2, the quantity of electricity was approximately 31C / cm ^2.

  According to the above manufacturing method, when forming the needle-like projection arrangement structure, a process such as a photolithography process as shown in FIG. 8 is not required, and thus a significant improvement in productivity can be realized. Further, since boron existing in the vicinity of the surface of the diamond base material acts as a very fine mask at the atomic level, it is much finer and finer than the needle-like protrusions (FIG. 8B) formed through the lithography process. A needle-like protrusion arrangement structure (FIG. 2B) having a high aspect ratio can be formed. Further, since this manufacturing method does not require a step such as photolithography, it can be applied not only to a planar two-dimensional material but also to a three-dimensional material such as a spherical shape.

b) Manufacture of Electrode of Comparative Example A boron-doped diamond thin film 2a was formed on the surface of the substrate 1 in the same manner as in a) above, but a diamond electrode R1 that was not etched by oxygen plasma was used. In addition, a boron-doped diamond thin film 2a is formed on the surface of the substrate 1 in the same manner as in the above a), and the same anodic oxidation treatment as that of the diamond electrode 1E is performed without performing etching with oxygen plasma. To do. The manufacturing conditions for these diamond electrodes R1 and R2 are also shown in Table 1 above.

c) Measurement of boron concentration on outermost surface of diamond electrode For each of diamond electrodes 1C, 1D, and R1, using a secondary ion mass spectrometer (IMS-6f, manufactured by CAMCA), a region from the outermost surface to 20 nm, And the average concentration of boron in the region from the outermost surface to 200 nm was measured. The measurement conditions were that the sample was irradiated with O ₂ ⁺ at 5.5 kV to measure positive secondary ions. Moreover, the boron concentration conversion was performed using a standard sample having a known concentration, and the depth conversion was performed by actually measuring the crater depth after the measurement. The measurement results are shown in Table 2.

As shown in Table 2, when viewed in terms of the average boron concentration in the region from the outermost surface to 200 nm, the values at the diamond electrodes 1C and 1D are compared with the average boron concentration of the entire diamond electrode R1 (without etching by oxygen plasma). , Increased by 1.5% and 62.6%, respectively.

d) Observation of surface shape of diamond electrode The surface of the diamond electrode 1C was observed with an electron microscope. The observation photograph is shown in FIG. As apparent from FIG. 3, the diamond electrode 1C had a needle-like protrusion arrangement structure on the surface.

e) Test of electrochemical characteristics The diamond electrodes 1C, 1E, R1, and R2 were examined for electrochemical responses to various redox species by cyclic voltammetry. As the redox species, iron cyano complex, ruthenium ammine complex, and iron were used. The concentration of the redox species is 1 mM. When the iron cyano complex and the ruthenium ammine complex are used, the scanning speed is set to 10 mV / s using a test solution in which 0.1 M potassium chloride and iron are dissolved in 0.1 M perchloric acid. Measurement was performed with setting.

  In addition, an iron cyano complex, a ruthenium ammine complex, and iron are each subjected to an oxidation-reduction reaction as represented by the following chemical formulas 1 to 3.

Among the obtained cyclic voltammograms, the case of the diamond electrode 1C is shown in FIG. As is clear from FIG. 4, responses with small peak separation (difference in oxidation-reduction potential) were confirmed for various compounds in a wide range of potential regions. This means that when applied to an electrode for electrochemical measurement, a good response can be realized for a wide range of target substances.

  Table 3 shows the results of cyclic voltammograms for each electrode and the electron transfer rate constant determined by the Nicholson method (Analytical Chemistry 37 (1965) 1351.).

The diamond electrodes 1C and 1E showed fast electron transfer rate constants on the order of 10 ⁻² regardless of the difference in redox species. In addition, the value of the diamond electrode 1E subjected to the anodizing treatment showed a value similar to that of the diamond electrode 1C not subjected to the anodizing treatment, which means that the surface of the diamond electrode 1C has already been sufficiently oxidized. This indicates that the surface is in an electrochemically stable state where oxidation does not proceed any further.

  On the other hand, the results of the diamond electrode R1 which is hydrogen-terminated diamond and the diamond electrode R2 obtained by anodizing the diamond electrode indicate that the hydrogen-terminated surface is electrochemically unstable. Furthermore, the diamond electrode R1 showed a fast electron transfer rate with respect to the iron cyano complex as shown in JP-A No. 2001-348296, and showed a good result even with the ruthenium ammine complex. However, the reaction of divalent and trivalent iron ions is 1/20 compared to the reactions of other iron cyano complexes and ruthenium ammine complexes, compared with diamond electrodes 1C and 1E having a needle-like projection arrangement structure on the surface. The electron transfer rate constant was as slow as 1/30.

  Further, the surface of the diamond electrode R2 which is oxygen-terminated by the anodizing treatment and is stable is an electrical insulator in the vicinity of the surface, and the surface is negatively charged with a carbonyl group or a hydroxyl group. As a result of the electrostatic repulsion between the iron cyano complex and the charged cyano complex, the electron transfer rate constant was significantly reduced.

  The excellent results of the diamond electrodes 1C and 1E are considered to be caused by the following factors. First of all, since the manufacturing method is oxygen plasma etching, the surface of the formed needle is oxygen-terminated which is stable both chemically and electrochemically.

  Secondly, in the diamond electrode R2 having a flat surface form that has been anodized, it is negatively charged over the entire plane, whereas the diamond electrodes 1C and 1E having a needle-like protrusion arrangement structure on the surface have protrusion side surfaces. Therefore, the negative charging effect is mitigated, and the structure is such that electrostatic interaction is difficult to work. Furthermore, as described above, the boron atoms inside the etched-out portion are recombined at the tip of the protrusion, so that it has high electrical conductivity even in the vicinity of the surface.

Third, although the diamond electrodes 1C and 1E alleviate the electrostatic interaction, the electron transfer speed is significantly improved as compared with the diamond electrodes R1 and R2, as seen in the reaction of iron. Because. This is because the electron transfer rate constant, which was 2.7 × 10 ⁻³ cm / s at the diamond electrode R1, was 8.7 × 10 ⁻³ due to electrostatic attraction in the negatively charged diamond electrode R2, which was anodized. In the diamond electrodes 1C and 1E which are improved to cm / s and have a needle-like projection arrangement structure on the surface, iron ions attracted by electrostatic attraction are encapsulated between the needle-like projections. It is thought that it improved dramatically to 10 < ^-3 > cm / s and 8.3 * 10 < ^-3 > cm / s. In other words, it can be said that the third factor is derived from the acicular protrusion structure.

f) Measurement of contact angle on electrode surface In order to see the difference in the surface termination of each electrode, the contact angle of water was measured with a contact angle measuring instrument (OCA 15Plus, DataPhysics Instrument GmbH). The results are shown in Table 1 above. A contact angle of 73 degrees in the diamond electrode R1 made of hydrogen-terminated diamond indicates that the surface is hydrophobic, and a contact angle in the diamond electrodes 1A, 1B, 1C, 1D, 1E, and R2 is 20 degrees or less. This means that, as a result of the introduction of the oxygen-containing group on the surface, the affinity with water was improved and the surface became hydrophilic. In other words, the diamond electrodes 1A, 1B, 1C, 1D, 1E, and R2 are oxygen-terminated with chemically stable surfaces.

  A two-chamber electrolysis cell 10 as shown in FIG. 5 was prepared. The anode electrode 11 and the cathode electrode (platinum mesh) 13 are respectively disposed in 1 M sulfuric acid (20 mL) 18 through a diaphragm (Nafion 117, manufactured by DuPont). As the anode electrode 11, any one of the diamond electrodes 1C and R1 manufactured in Example 1 was used.

  When a current is passed between both electrodes by the DC power source 17, the sulfuric acid aqueous solution is electrolyzed and ozone gas is generated from the anode electrolysis chamber 19. The generated ozone gas is passed through the pipe 21 to 10 mL of pure water in which the measurement reagent is previously dissolved. Then, the ozone water concentration of pure water in which the measuring reagent is dissolved is measured with a dissolved ozone meter (manufactured by Kasahara Chemical Co., Ltd., dissolved ozone 03-2Z). The electrolytic cell 10 is always kept at 15 degrees or less by an ice water bath.

  FIG. 6 shows the ozone generation amount with respect to the energization current value when the diamond electrode 1C is used as the anode electrode 11 and when the diamond electrode R1 is used. The value on the horizontal axis in FIG. 6 is the current value per geometric surface area. When the diamond electrode 1C was used, water was more efficiently electrolyzed than when the diamond electrode R1 was used, and the amount of ozone generated was twice or more. This is presumably because the diamond electrode 1C has a needle-like protrusion arrangement structure on the surface, has a large surface area, and has high hydrophilicity, so that water can easily enter between the needle-like protrusions.

Evaluation of materials suitable for the enzyme catalyst support was carried out as follows.
a) Production of enzyme catalyst-carrying electrode Diamond electrodes 1B, 1C, 1D, R1, and R2 produced in Example 1 were prepared as carriers for the enzyme catalyst-carrying electrode. As other carriers, conductive diamond-like carbon R3, glassy carbon R4, and carbon R5 were prepared.

  Next, an enzyme was immobilized on each carrier to complete an enzyme catalyst-carrying electrode. Specifically, 50 mg of glucose oxidase (20,000 units, manufactured by Wako Pure Chemical Industries, Ltd.) as an enzyme and 100 mg of cetyltrimethylammonium bromide as a cross-linking agent were dissolved in 10 mL of 0.1 M phosphate buffer (pH 7). Each carrier was dipped in, stored after refrigeration overnight, and taken out and dried sufficiently at room temperature, and then 5% Nafion aqueous solution was applied and dried.

b) Electrochemical measurement Electrochemical measurement was performed by connecting a tripolar cell with the enzyme-supported electrode prepared as described above as a working electrode, a platinum coil as a counter electrode, and Ag / AgCl as a reference electrode to a potentiostat. . A solution prepared by dissolving 0.5 mM ferrocenecarboxylic acid as a mediator in 0.1 M phosphate buffer (pH 7) was used as a blank, and a solution prepared by dissolving glucose so as to be 10 mM was used as a sample. The sun click voltammogram was measured at a scanning speed of 1 mV / s. The results are shown in Table 4.

As shown in Table 4, when the carrier was a diamond electrode 1B, 1C, or 1D having a needle-like projection arrangement structure on the surface, the amount of the enzyme supported was increased and the reaction initiation potential was sufficiently low. The reason for this is considered to be the surface modification of the diamond electrodes 1B, 1C, and 1D and the formation of the acicular protrusion arrangement structure. From these results, it is clear that the diamond electrodes 1B, 1C, and 1D are suitable as enzyme-supporting electrodes and can be applied to enzyme sensors and enzyme-catalyzed fuel cells.

  On the other hand, in the case of the diamond electrode R1, the glassy carbon R4, and the conductive diamond-like carbon R3 whose carrier is untreated diamond, the surface is inactive, the bond with the enzyme is weak, and the response to glucose is small. It was not seen at all. In the case of the anodized diamond electrode R2 as a support, oxygen-containing groups were formed on the surface, and as a result, the glucose response was seen as a result of improved binding to the enzyme. However, the reaction initiation potential increased due to the increase in surface resistance. When this is applied to a glucose sensor, there is a concern that the selectivity is deteriorated, and it leads to a decrease in extraction voltage when used as an anode electrode of a biofuel cell. When the carrier was carbon R5, the electric capacity was large and the reactivity was hindered.

The manufacturing method is basically the same as that of the diamond electrode 1C of Example 1, except that the concentration of boron atoms in the boron-doped diamond thin film is 3 × 10 ²⁰ atoms / cm ³ , as measured by SIMS, Diamond electrodes 4A and 4C were manufactured by a manufacturing method of 8 × 10 ²¹ pieces / cm ³ .

  For the diamond electrodes 4A and 4C, as in Example 1, measurement of the boron concentration on the outermost surface of the diamond electrode (how much the boron concentration is increased on the outermost surface), observation of the surface shape of the diamond electrode, electricity When the test of chemical characteristics and the measurement of the contact angle on the electrode surface were performed, the results were almost the same as those of the diamond electrode 1C.

It is explanatory drawing showing the structure of the enzyme carrying | support electrode using the support | carrier which has an acicular protrusion arrangement | sequence structure. (A) is explanatory drawing showing the manufacturing method of the diamond electrode which has an acicular protrusion arrangement | sequence structure on the surface, (b) is a top view of the diamond electrode manufactured by (a). It is a surface photograph of the diamond electrode which has a needle-like projection arrangement structure on the surface. It is a cyclic voltammogram for various redox species. It is explanatory drawing showing the structure of a two-chamber electrolysis cell. It is a graph showing the relationship between the energization current value and ozone generation amount when each electrode is used. It is explanatory drawing showing the structure of the enzyme carrying | support electrode using the support | carrier with a flat surface form. (A) is explanatory drawing showing the method of manufacturing the diamond electrode which has an acicular projection arrangement | sequence structure on the surface using a photolithographic process, (b) is a top view of the diamond electrode manufactured by (a). .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate 2a ... Boron dope diamond thin film 3 ... Needle-like protrusion 10 ... Two-chamber electrolysis cell 11 ... Anode electrode 13 ... Cathode electrode 15 ... Diaphragm 17 ... DC power source 19 ... anode electrolysis chamber 21 ... piping 101 ... catalyst 102 ... binder 103 ... carrier 104 ... glucose 105 ... mediator 106 ... flow of electrons

Claims (2)

3x10 dopant ²⁰ ~ 8x10 ^{twenty one} Piece / cm ^Three A dopant concentration Cs in a region from the surface of the diamond substrate to a depth of 0.2 μm is 1.01 to 2.0 of the average concentration by dry etching with oxygen gas on a diamond base material doped with an average concentration of A method for producing a diamond electrode, characterized in that a needle-like protrusion arrangement structure is formed on a surface of a diamond base material by treating the surface of the diamond base material until it is doubled. The method for producing a diamond electrode according to claim 1 , wherein the dopant is boron.