JP2018045985A - Method for manufacturing microbial fuel cell by molybdenum nitride cathode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost, high-performance microbial fuel cell which is high in redox catalyst efficiency and superior in electrochemical performance.SOLUTION: A high-performance microbial fuel cell with a molybdenum nitride cathode comprises the cathode and an anode. The anode is a piece of blank carbon paper. The cathode is manufactured by coating a piece of carbon paper with a Nafion solution in which the concentration of a molybdenum nitride mixed therein is 5 wt.%. The molybdenum nitride is obtained by: causing a hydrothermal reaction of a mixture solution including ammonium molybdate, nitric acid and water at 180°C for 5 hours to obtain oxidized molybdenum powder; and then, performing a thermal treatment on the oxidized molybdenum powder at 300-900°C for 1 hour under an ammonia gas atmosphere, thereby to obtain the molybdenum nitride as a final product.SELECTED DRAWING: Figure 1

Description

  The present invention relates to the technical field of microbial fuel cells, and specifically to a high performance microbial fuel cell with a molybdenum nitride cathode.

  Microbial fuel cells (MFCs) technology uses microorganisms as a catalyst to decompose organic substances in water by its metabolic action to produce protons and electrons, which enter the cathode through an external circuit, and the protons pass through an ion exchange membrane to the cathode. To reach. At the cathode, the oxidizing agent (electron acceptor) reacts with the reached electrons and protons to produce a reduction product. When the outer circuit contacts the negative electrode, the MFCs can support the operation of the negative electrode if the electrical energy generated by the MFCs is sufficient. MFCs are novel systems that have the dual effect of purification of contaminated water and energy recovery.

  Currently reported oxidants (electron acceptors) selected for MFCs-based cathodes include ferrocyanide, permanganate, and oxygen, in which oxygen is obtained directly from the air. Therefore, the reference potential of the oxidation-reduction reaction is about 0.8 V, which is higher than most reduction reaction potentials, which is advantageous for improving the voltage of MFCs. Thus, oxygen now becomes a very common cathode acceptor.

  The oxidation-reduction reaction at the cathode has a severe polar development and a slow reaction rate under a non-catalytic condition. At present, commercial platinum-carbon (Pt / C) is generally used, but this catalyst is very expensive and disadvantageous for practical application of MFCs, so it is highly efficient and inexpensive. Developing redox catalysts and replacing expensive Pt / C is a research focus in the field of microbial fuel cells.

  An object of the present invention is to provide a high-performance microbial fuel cell using a molybdenum nitride cathode, which has features such as high efficiency of the redox catalyst, excellent electrochemical performance, and low cost.

The present invention is realized by the following technical scheme.
The present invention is a high-performance microbial fuel cell with a molybdenum nitride cathode including a cathode and an anode, wherein the anode is blank carbon paper, and the cathode has a mixed concentration of molybdenum nitride of 5 wt. The solution is manufactured by applying it to carbon paper.

  Further, the molybdenum nitride is manufactured by the following method. That is, a mixed solution containing ammonium molybdate, nitric acid and water was hydrothermally reacted at 180 ° C. for 5 hours to obtain molybdenum oxide powder, and then heat-treated at 300 to 900 ° C. for 1 hour in an ammonia gas atmosphere. To obtain the final molybdenum nitride.

  Furthermore, the heat treatment temperature of the molybdenum oxide powder in an ammonia gas atmosphere is 700 to 800 ° C.

  Further, the microbial fuel cell has a sandwiched two-chamber microbial fuel cell structure and includes a cathode chamber, an anode chamber, and an ion exchange membrane installed between the cathode chamber and the anode chamber.

  Further, the microbial fuel cell further contains an anolyte, and the anolyte is produced by the following method. That is, a mixture of 10.0 g sodium hydrogen carbonate, 11.2 g disodium hydrogen phosphate, 10.0 g anhydrous glucose and 5 g yeast extract was dissolved in a beaker, 0.8707 g HNQ was further added and stirred uniformly, and then the solution was fixed at 1000 mL. Place in a bottle and make a constant volume.

The microbial fuel cell using the molybdenum nitride cathode of the present invention has the following beneficial effects.
First, the efficiency of the redox catalyst is high. The present invention has submitted a novel microbial fuel cell using molybdenum nitride as a cathodic redox catalyst. The maximum peak current magnitude of the molybdenum nitride catalyst approaches commercial Pt / C, with an average electron mobility of 3.97 under different potentials, approaching commercial Pt / C 4.08. This indicates that molybdenum nitride belongs to a four-electron transfer mechanism, like platinum-carbon, in catalytic redox, and promotes redox efficiently.
Second, the electrochemical performance is excellent. The maximum power density and corresponding current density of microbial fuel cells containing ² mg / cm ² molybdenum nitride cathode catalyst are 9.24 W / m ³ and 37.40 A / m ³ respectively, but 0.5 mg / The maximum power density and the corresponding current density of microbial fuel cell containing cm ² commercial Pt / C cathode catalyst are 12.49 W / m ³ and 43.50 A / m ³ respectively.
Third, the cost is low. The maximum power density and corresponding current density of molybdenum nitride composite cathode microbial fuel cell reach 73.97% and 85.98% respectively of commercial Pt / C electrodes, but the price of cobalt molybdenum composite nitride material is low and mass production Can significantly reduce the operating cost of microbial fuel cells.

It is an XRD figure of molybdenum nitride. 5 is a linear scanning graph measured with a rotating ring disk electrode device of a molybdenum nitride electrode at 400 rpm in a neutral buffer solution. Figure 5 is a linear scan graph of glassy carbon electrode modified with molybdenum nitride and commercial Pt / C. It is the output density graph and polarization graph (calculated by the volume of an anode chamber) of the microbial fuel cell of the cathode catalyst containing ² mg / cm <2> molybdenum nitride (sample 3). FIG. ² is a power density graph and polarization graph (calculated by the volume of the anode chamber) of a microbial fuel cell with a cathode catalyst containing 0.5 mg / cm ² of commercial Pt / C.

  In order that those skilled in the art can better understand the technical solution of the present invention, the product of the present invention will be described in more detail below by combining the embodiments and the drawings.

  The present invention discloses a high performance microbial fuel cell with a molybdenum nitride cathode, which includes a cathode and an anode, the anode is blank carbon paper, and the cathode has a mixed concentration of molybdenum nitride of 5 wt.%. A (Nafion) solution is applied to carbon paper.

  Further, the molybdenum nitride is manufactured by the following method. That is, a mixed solution containing ammonium molybdate, nitric acid and water was hydrothermally reacted at 180 ° C. for 5 hours to obtain molybdenum oxide powder, and then heat-treated at 300 to 900 ° C. for 1 hour in an ammonia gas atmosphere. To obtain the final molybdenum nitride.

  Furthermore, the treatment temperature of the molybdenum oxide powder in an ammonia gas atmosphere is 700 to 800 ° C.

  Further, the microbial fuel cell has a sandwiched two-chamber microbial fuel cell structure, and includes a cathode chamber, an anode chamber, and an ion exchange membrane installed between the cathode chamber and the anode chamber.

  Further, the microbial fuel cell further contains an anolyte, and the anolyte is produced by the following method. In other words, a mixture of 10.0 g sodium bicarbonate, 11.2 g disodium hydrogen phosphate, 10.0 g anhydrous glucose and 5 g yeast extract was dissolved in a vicat, and 0.8707 g HNQ was further added and stirred uniformly. Place in a bottle and make a constant volume.

  In order to further study the microbial fuel cell of the present invention, the technical solution of the present invention will be specifically described in Example 1 and Example 2, respectively.

Example 1
The present invention discloses a high-performance microbial fuel cell using a molybdenum nitride cathode, and a method for manufacturing, assembling and testing the molybdenum nitride cathode is as follows.
First step, production and characterization of catalytic molybdenum nitride. A mixed solution containing ammonium molybdate, nitric acid and water was hydrothermally reacted at 180 ° C. for 5 hours to obtain molybdenum oxide powder (corresponding sample 1). The structure of molybdenum oxide was measured by XRD, and the result is shown in FIG. 1 (corresponding sample 1). Subsequently, the obtained molybdenum oxide powder was heat-treated at 500 ° C. for 1 hour in an ammonia gas atmosphere to obtain a final molybdenum nitride. The measurement result of the structure is as shown in FIG. 1 (corresponding sample 2). The result of the linear scan test is shown in Fig. 2 (corresponding sample 2).

The second step, the production of the redox catalyst modified electrode, specifically includes the following steps.
Preparation of glassy carbon electrode: Glassy carbon electrode (3 mm diameter) is polished before use. Specifically, polishing was first performed with α-Al ₂ O ₃ powder on abrasive paper, and then ultrasonically cleaned with deionized water.

  Working electrode of molybdenum nitride: Take 1.5mg molybdenum nitride and 3.5g activated carbon, drop 300μL 1% Nafion solution and 100μL isopropanol respectively, then ultrasonically disperse in ice water bath for 30 minutes to form a uniform liquid did. Subsequently, 5.5 μL of the liquid was taken, applied to a polished glassy carbon electrode, and dried at room temperature to obtain a working electrode.

The study of the third step, a linear scan of the catalyst for redox performance, includes the following steps.
The PBS buffer solution contains 2.45 g / L disodium hydrogen phosphate solids and 4.576 g / L sodium monohydrogen phosphate solids.

  Measured by linear scanning voltammetry. This measurement was performed with a traditional three-electrode electrochemical Ikeko, using Ag / AgCl (saturated potassium chloride) as a reference electrode, a platinum electrode as a counter electrode, and a working electrode as a molybdenum nitride electrode.

Prior to measurement, high purity N ₂ gas is passed through the bottom of the PBS buffer for 15 minutes to remove a portion of the impurity gas dissolved in the solution, and the electrode is activated by cyclic voltammetry (CV). After that, high-purity O ₂ gas was saturated at the bottom of the electrolytic solution for 15 minutes, and the state of the high-purity O ₂ gas was maintained at the liquid level of the electrolytic solution during measurement.

Example 2
The difference between Example 2 and Example 1 was that the final molybdenum nitride was obtained because molybdenum oxide had a heat treatment temperature of 700 ° C. in an ammonia gas atmosphere. The measurement result of the structure is as shown in FIG. 1 (corresponding sample 3), and the linear scanning measurement result is as shown in FIG. 2 (corresponding sample 3).

Example 3
The difference between Example 3 and Example 1 was that the final molybdenum nitride was obtained because molybdenum oxide had a heat treatment temperature of 900 ° C. in an ammonia gas atmosphere. The measurement results of the structure are as shown in FIG. 1 (corresponding sample 4), and the linear scanning measurement results are as shown in FIG. 2 (corresponding sample 4).

As can be seen from the XRD results in FIG. 1, as the heat treatment temperature increases, the valence of molybdenum oxide decreases from +6 to +4, +2, and then to +1, and gradually increases to Mo ₃ N ₂ and MoN. become. The main component of Example 2 is Mo ₃ N ₂ with a small amount of MoO ₂ crystal peak.

As can be seen from the linear scanning result of FIG. 2, the redox peak current expressed in Example 2 is relatively large, and the redox peak potential of Example 2 is about 0.15 V. Much more than Example 3. This explains that Mo ₃ N ₂ mixed with the MoO ₂ crystal obtained under the heat treatment condition of Example 2 is superior in catalytic performance for redox.

Control Example 1
In order to evaluate the performance of the molybdenum nitride cathode of the microbial fuel cell of the present invention, a comparative evaluation was performed as Control Example 1 by replacing the molybdenum nitride electrode with a commercial Pt / C working electrode. A method for producing a commercial Pt / C working electrode is as follows. That is, take 5 mg of commercial Pt / C, drop 300 μL 1% Nafion solution and 100 μL isopropanol respectively, then ultrasonically disperse in an ice water bath for 30 minutes to form a uniform liquid, 5.5 μL of the liquid was taken and applied to a polished glassy carbon electrode and dried at room temperature to obtain a working electrode.

  Using a rotating ring disk electrode device, a control study was conducted on the redox catalyst performance of Example 2 and commercial Pt / C, and the results are shown in FIG.

  In FIG. 3, a is the molybdenum nitride electrode of Example 2 (corresponding sample 3), b is a commercial Pt / C electrode, and both a and b are under different rotational speeds in neutral buffer. FIG. c and d are Koutecky-Levich graphs under different potentials obtained from a and b, respectively.

  As can be seen from FIG. 3, under the same rotational speed, the magnitude of the maximum peak current of molybdenum nitride approaches commercial Pt / C, and the average electron mobility under different potentials is 3.97. It approaches Pt / C 4.08. This indicates that molybdenum nitride belongs to the four-electron transfer mechanism in catalytic oxidation-reduction like platinum-carbon, and promotes oxidation-reduction efficiently.

  Furthermore, on the basis of electrode research, the electrode was assembled into a battery and a control study was conducted. Specific examples are shown in Example 4 and Control Example 2.

Example 4
The present invention discloses a high performance microbial fuel cell with a molybdenum nitride cathode, and its manufacturing, assembly and testing methods are as follows.
In the first step, a catalyst was applied to one side of 2 × 3 cm ² carbon paper on which a molybdenum nitride cathode was manufactured, and a waterproof layer was applied to the other side.

(1) Production of waterproof layer: 5 mL 60% PTFE solution was taken and dissolved in a 100 mL beaker, and 55 mL distilled water was added and mixed uniformly to obtain a 5% PTFE solution. Next, the PTEF dispersion was uniformly applied to the surface of the carbon paper with a paint brush, dried at room temperature for 10 minutes, and then dried in a muffle furnace at 370 ° C. for 10 minutes. In the same manner, the above operation was repeated to form a three-layer PTEF waterproof layer on carbon paper.

(2) Production of catalyst layer:
Molybdenum nitride (taken ² mg / cm ² based on the waterproof layer area) was taken and polished sufficiently, and 88 μL of 5% Nafion solution and 0.5 mL of absolute ethanol were added and dispersed uniformly with ultrasound for 30 minutes. . The uniformly dispersed catalyst was uniformly applied to carbon paper on which a waterproof layer was formed, and dried naturally at room temperature for 24 hours.

Second Step, Production of Anode The anode was a blank 2 × 2 cm ² standard carbon paper, and the carbon paper was connected with a copper wire. Mainly prevents metallic copper from dissolving in the battery operation process, and prevents the generation of heavy metal ions having a toxic effect on microorganisms. Seal the connection between carbon paper and copper wire with epoxy resin (prepare epoxy resin and solidifying agent 1: 1).

Third step, assembly operation of microbial fuel cell and test anolyte: Dissolve a mixture of 10.0g sodium bicarbonate, 11.2g disodium hydrogen phosphate, 10.0g anhydrous glucose and 5g yeast extract in a beaker and add 0.8707gHNQ After stirring uniformly, the solution was placed in a 1000 mL constant volume bottle to make a constant volume and prepared.

  The air cathode microbial fuel cell has a sandwich structure, and the center of the cathode tail gate having a maximum liquid volume of 20 mL of the anode is an open window 2 cm × 3 cm, and the cathode is exposed to the air.

  Starting the battery and measuring the power density polarization graph: 18 mL of anolyte was placed in the reactor and high purity nitrogen gas was passed through for 15 minutes. After the gas passage was completed, 2 mL of the E. coli culture solution was taken into the reactor, and the top inlet of the reactor was sealed with a rubber stopper to keep the reactor sealed. After the open circuit voltage of the battery was stabilized, the batteries were loaded with different electrical resistances in order, and the system automatically recorded the voltage value, output density, current density, etc. of the outputs of the different load resistances. The specific measurement result is as shown in FIG.

Control Example 2
A cathode of a microbial fuel cell using a Pt / C cathode as an anode, and the method for producing and testing the microbial fuel cell is as follows.
The operation of the first step, the production of the Pt / C cathode, is the same as in Example 4, and the catalyst loading is 0.5 mg / cm ² .

  The second step, the production and operation of the anode are the same as in Example 4.

  The third step, the assembly operation of the microbial fuel cell and the test operation are the same as in Example 4, and the specific measurement results are as shown in FIG.

As can be seen from FIGS. 4 and 5, the open circuit potential of a microbial fuel cell containing ² mg / cm ² of a molybdenum nitride cathode catalyst is 0.481 V and the open circuit of a commercial Pt / C cathode catalyst of 0.5 mg / cm ^2. The potential is slightly lower than 0.56V.

The maximum power density and corresponding current density of microbial fuel cells containing ² mg / cm ² molybdenum nitride cathode catalyst are 9.24 W / m ³ and 37.40 A / m ³ respectively, but 0.5 mg / The maximum power density and the corresponding current density of cathode catalyst microbial fuel cell containing commercial Pt / C of cm ² are 12.49 W / m ³ and 43.50 A / m ³ respectively.

  Therefore, the maximum power density and corresponding current density of molybdenum nitride composite cathode microbial fuel cell reach 73.97% and 85.98% respectively for commercial Pt / C electrodes, but the price of cobalt-molybdenum composite nitride material is low, Since mass production is possible, the operating cost of the microbial fuel cell is greatly reduced.

  The foregoing is only a relatively preferred embodiment of the invention and is not a formally limiting to the invention. A person skilled in the art can smoothly implement the present invention based on the drawings in the specification and the above description. However, as long as an engineer who is familiar with this technical field does not remove the technical solution of the present invention, it is not possible to make a slight change, modification, or change using the above technical contents. Is an equivalent embodiment of the present invention. At the same time, any equivalent changes, modifications, transitions, etc. made to the above embodiments based on the substantial technique of the present invention are within the protection scope of the technical solution of the present invention.

The present invention relates to the technical field of microbial fuel cells, and specifically to a method for producing a high-performance microbial fuel cell using a molybdenum nitride cathode.

The present invention is realized by the following technical scheme.
The present invention relates to a high-performance microbial fuel cell using a molybdenum nitride cathode including a cathode and an anode, wherein the anode is carbon paper , and the cathode is a Nafion solution having a mixed concentration of molybdenum nitride of 5 wt.%. Is applied to carbon paper.

Further, the microbial fuel cell has a two-chamber microbial fuel cell structure including a cathode chamber and an anode chamber, and includes a cathode chamber, an anode chamber, and an ion exchange membrane installed between the cathode chamber and the anode chamber.

The present invention discloses a high-performance microbial fuel cell with a molybdenum nitride cathode, which includes a cathode and an anode, the anode is carbon paper , and the cathode is Nafion (mixed concentration of molybdenum nitride of 5 wt.%). Nafion) solution is applied to carbon paper.

Further, the microbial fuel cell has a two-chamber microbial fuel cell structure including a cathode chamber and an anode chamber, and includes a cathode chamber, an anode chamber, and an ion exchange membrane installed between the cathode chamber and the anode chamber.

Second Step, Production of Anode The anode was 2 × 2 cm ² standard carbon paper, and the carbon paper was connected with a copper wire. Mainly prevents metallic copper from dissolving in the battery operation process, and prevents the generation of heavy metal ions having a toxic effect on microorganisms. Seal the connection between carbon paper and copper wire with epoxy resin (prepare epoxy resin and solidifying agent 1: 1).

Claims (5)

A microorganism comprising a molybdenum nitride cathode, comprising a cathode and an anode, wherein the anode is blank carbon paper, and the cathode is produced by applying a Nafion solution having a molybdenum nitride mixed concentration of 5 wt.% To carbon paper. Fuel cell. A mixed solution containing ammonium molybdate, nitric acid and water was hydrothermally reacted at 180 ° C. for 5 hours to obtain molybdenum oxide powder, and then heat-treated at 300 to 900 ° C. for 1 hour in an ammonia gas atmosphere. The microbial fuel cell with a molybdenum nitride cathode according to claim 1, wherein the molybdenum nitride is produced by a method of obtaining molybdenum nitride. The microbial fuel cell with a molybdenum nitride cathode according to claim 1 or 2, wherein the heat treatment temperature of the molybdenum oxide powder in an ammonia gas atmosphere is 700 to 800 ° C. The microbial fuel cell has a sandwich-type two-chamber microbial fuel cell structure, and includes a cathode chamber, an anode chamber, and an ion exchange membrane installed between the cathode chamber and the anode chamber. Microbial fuel cell with molybdenum nitride cathode. The microbial fuel cell further comprises an anolyte, and a mixture of 10.0 g sodium bicarbonate, 11.2 g disodium hydrogen phosphate, 10.0 g anhydrous glucose and 5 g yeast extract is dissolved in a beaker, and further 0.8707 g 2-hydroxy-1, 5. The nitriding solution according to claim 4, wherein the anolyte is produced by adding 4-naphthoquinone (HNQ) and stirring uniformly, and then placing the solution in a 1000 mL constant volume bottle and measuring the volume. Microbial fuel cell with molybdenum cathode.

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