TW201427770A - Manufacturing method of cathod catalyst and ozone-generating device - Google Patents

Abstract

The instant disclosure relates to a manufacturing method of cathode catalyst, comprising the following steps. The first step is mixing an organic medium with an iron-based starting material and a nitrogen-based starting material to form a mixture. The next step is adding a carbon material to the mixture, and subsequently executing a heating process to form a solid-state precursor. The next step is grinding the solid-state precursor to form precursory powder. The last step is calcining the precursory powder under NH3 atmosphere to form powder catalyst, and the powder catalyst can reduce the activation energy of hydrogen ion reacting with oxygen to make water. The instant disclosure further provides an ozone-generating device.

Description

Cathode catalyst preparation method and ozone generating device

The invention relates to a cathode catalyst, in particular to a cathode catalyst and an ozone generating device which are applied to an ozone generator and can catalyze the reaction of hydrogen ions generated by the anode to generate water to avoid hydrogen generation.

Ozone is a substance known to be highly oxidizing in nature, and its oxidizing power is about 3,000 times higher than that of chloride. It does not resemble chlorine and remains in the environment for a long time. Therefore, it is rapidly expanding its use in various industrial fields.

At present, the common methods for generating ozone include ultraviolet light method, high pressure discharge method and water electrolysis method. Among them, ultraviolet light method and high pressure discharge method are widely used in industry and home, and still have the following disadvantages: 1. Higher consumption Can; 2. More complex system composition; 3. High manufacturing cost; 4. Need to dissolve the gas in the gas phase in the liquid phase; therefore, the method of generating ozone by using water electrolysis technology has arisen.

Generally, the water electrolysis ozone generating device comprises a solid polymer electrolyte membrane (cation exchange membrane) and a sealed anode and a cathode disposed on both sides thereof, and is used for a cation exchange membrane and an electrode catalyst (for example, an electrode catalyst for an anode). The cathode electrode catalyst is subjected to a water electrolysis reaction using a liquid-loaded interface (three phase interface) to generate ozone from the anode and hydrogen from the cathode.

However, in the process of performing the water electrolysis reaction, the hydrogen gas generated by the three-phase interface of the cathode catalyst, the cation exchange membrane and the water is driven by the pressure inside the bubble to reach the cathode through the cation exchange membrane, and is mixed. The phenomenon of outward discharge in oxygen.

According to the Young-Laplace formula P _g -P _L =2 γ/r (P _g : pressure inside the bubble; P _L : liquid pressure; γ: surface tension of the liquid; r: bubble radius), when the liquid pressure is fixed, the bubble The smaller the diameter, the greater the pressure inside the bubble. Accordingly, the purity of the ozone generated is lowered or the gas current efficiency is lowered (i.e., the performance of the water ozone generating device is lowered).

Furthermore, in the ozone generating device for generating ozone, oxygen, and hydrogen, it is possible to exceed the minimum limit of hydrogen explosion due to the movement of hydrogen to the cathode (hydrogen accounts for 4.65 volumes of the mixed gas of ozone, oxygen, and hydrogen). Percentage), especially at high current densities, is a high concentration of gas generated from the electrode, which is more likely to cause safety concerns. In addition, the hydrogen ions generated are likely to cause electrode corrosion and reduce the service life of the electrode.

The reason is that the inventors have felt the shortcomings of the prior art mentioned above, and based on their experience in manufacturing and technology accumulation of water ozone generating devices, after continuous research, experimentation and improvement, finally developed and designed a practical one. this invention.

The object of the present invention is to provide a method for preparing a cathode catalyst suitable for a long-acting ozone generator for producing ozone, which can prevent the generation of hydrogen gas with safety concerns and increase the stability of the ozone generator. .

According to an embodiment of the present invention, the method for preparing the cathode catalyst comprises the steps of: first, mixing an at least iron-containing starting material with a nitrogen-containing starting material in an organic medium to form a mixture; then, a carbon material is added to the mixture and heat treated to form a solid precursor; thereafter, the solid precursor is ground to form a precursor powder; and finally, the precursor powder is Ammonia-containing environment Sintering is carried out to form a cathode catalyst.

According to the above cathode catalyst, the present invention further provides an ozone generating device comprising a cation exchange membrane, an anode water tank and a cathode water tank; the anode water tank is disposed on one side of the cation exchange membrane and has a connection to the cation exchange An anode on one surface of the film, wherein the anode comprises an anode substrate and an anode catalyst layer formed on the anode substrate; the cathode sink is disposed on the other side of the cation exchange film and has a connection to the cation exchange film The cathode of the other surface, wherein the cathode comprises a cathode substrate and a cathode catalyst layer formed on the cathode substrate, and the cathode catalyst layer comprises the cathode catalyst prepared by the above preparation method.

In summary, the cathode catalyst provided by the embodiment of the present invention contains at least three elements of iron, nitrogen and carbon. When the anode of the ozone generating device converts water into ozone, the incident hydrogen ions pass through the cation exchange membrane to The cathode reacts with the cathode catalyst of the present invention and oxygen to form water, thereby effectively avoiding hydrogen generation with safety concerns and reducing the possibility of hydrogen ions corroding the electrode, thereby increasing the safety and stability of the ozone generating device.

Hereinafter, the method for producing the ozone generating device and the cathode catalyst of the present invention will be described in detail based on the respective drawings, and the ozone generating device can stably generate ozone for a long period of time.

Please refer to FIG. 1 , which is a schematic top view of an ozone generating device according to an embodiment of the present invention; the ozone generating device 100 includes a cation exchange film 1 , an anode water tank 2 , and a cathode water tank 3 .

The anode water tank 2 is disposed on one side of the cation exchange membrane 1 and has an anode 21 connected to one surface of the cation exchange membrane 1. Further, an anode chamber 22 is further formed between the tank body of the anode water tank 2 and the anode 21. The anode 21 includes an anode base 211 and an anode catalyst layer 212 formed on the anode base 211. The anode base 211 is a conductive porous structure, and one surface of the anode catalyst layer 212 is connected to the anode base 211. The other surface is attached to the cation exchange membrane 1 and can be used to generate ozone.

The cathode water tank 3 is disposed on the other side of the cation exchange membrane 1 and has a cathode 31 connected to the other surface of the cation exchange membrane 1. Further, a cathode body of the cathode water tank 3 is formed between the tank body and the cathode 31. The cathode chamber 32 includes a cathode substrate 311 and a cathode catalyst layer 312 formed on the cathode substrate 311. One surface of the cathode catalyst layer 312 is connected to the cathode substrate 311, and the other surface is connected to the cation exchange film 1. It can be used to produce hydrogen and oxygen.

In the present embodiment, the cation exchange membrane 1 is most suitable as a perfluorosulfonic acid cation exchange membrane, which has high cation selective permeability, high chemical stability and thermal stability, high mechanical strength, and low electrolyte diffusion. Rate, low resistance and other advantages.

On the anode side of the cation exchange membrane 1, the anode substrate 211 is generally of a structure having conductivity, oxidation resistance, sufficient release of the generated gas, and sufficient circulation of the electrolyte; for example, paper or roll may be used. A carbon fiber body (carbon paper or carbon cloth) or a metal such as titanium, tantalum, niobium or zirconium is used as the porous body, the mesh body, the fibrous body or the foam of the substrate, but is not limited thereto. In more detail, the porous body described above may be composed of fluororesin mixed metal particles, wherein the fluororesin is most PTFE. Suitably; alternatively, the porous body may be a porous metal plate or a sintered metal fiber.

The anode catalyst layer 212 can be formed on the surface of the anode substrate 211 by a material having a high oxygen overvoltage by electrolytic plating, thermal decomposition, coating, hot pressing, or the like, and can be used as the material of the anode catalyst layer 212. It is lead dioxide or conductive diamond.

On the cathode side of the cation exchange membrane 1, the cathode substrate 311 may be a porous or reticulated body of a carbonaceous fiber (carbon paper or carbon cloth) or a metal such as nickel, stainless steel or zirconium as a substrate. The fibrous body and the foam; it is worth mentioning that the cathode catalyst layer 312 of the present invention comprises a cathode catalyst prepared by the following production method.

Please refer to FIG. 2 , which is a schematic flow chart of a method for preparing a cathode catalyst according to a first embodiment of the present invention. The specific contents of each step will be described in detail below:

Step 1: Mixing at least an iron-containing starting material with a nitrogen-containing starting material in an organic medium to form a mixture. In this embodiment, the at least iron-containing starting material is selected from the group consisting of ferrous acetate (Fe(C ₂ H ₃ O ₂ ) ₂ ), and the at least nitrogen-containing starting material is selected from the group consisting of phenanthroline The organic medium is selected from the group consisting of ethanol; further, the ferrous acetate and the phenanthroline are mixed in ethanol at a molar concentration ratio of 1.7:11.1, and uniformly mixed by solid state for about 12 hours to form a mixture; During the mixing process, the iron ions of ferrous acetate first form a chelate with phenanthroline and then redesolve in ethanol.

Step 2: A carbon material is added to the mixture and heat treated to form a solid precursor. Specifically, the carbon material may be selected from the group consisting of carbon black, graphite whisker, amorphous carbon, activated carbon, mesoporous carbon, porous carbon fiber, Nano carbon fiber, carbon nanotube or carbon fiber, and carbon material particle size less than 10 microns; further, the heat treatment is to put a mixture of carbon material into the oven to a temperature between 60 ° C and 80 ° C Heating is carried out and the temperature is maintained for 8 to 16 hours to remove the solvent to form a solid precursor.

Step 3: The solid precursor is ground to form a precursor powder. In the step of grinding, the solid precursor is placed in a ball mill jar and ball milled with a zirconium ball for 2 to 4 hours to form a precursor powder.

Step 4: The precursor powder is calcined in an ammonia-containing environment to prepare a cathode catalyst. In the step of performing the calcination, the precursor powder is placed in a high-temperature furnace through ammonia gas, and calcined at a temperature between 500 ° C and 1000 ° C for 1 to 3 hours to prepare a powdery cathode catalyst. It includes at least three elements of iron, nitrogen and carbon. Further, the powdery cathode catalyst is uniformly mixed with a resin to form a paste, which is then applied to the surface of the cathode substrate 311, and after drying, forms a cathode catalyst layer 312.

Please refer to FIG. 3, which is an X-ray diffraction pattern of a cathode catalyst prepared by using different temperatures for calcination. Specifically, it is shown that the precursor powder formed by the steps 1 to 3 is formed into a crystal phase of a cathode catalyst which is respectively calcined at different temperatures; as shown in the figure, at 500 ° C to 600 ° C medium no generation of iron-nitrogen phase; calcination of the catalyst at 700 deg.] C to 900 deg.] C with obvious Fe ₂ N phase; Xia fired at 1000 ℃ the catalyst completely transformed into Fe ₂ N FeN _0.056.

Please refer to FIG. 4, which is an activity test diagram of the oxygen reduction reaction of the cathode catalyst prepared by using different temperatures for calcination, wherein the Y-axis of the graph shows the ring current from top to bottom. The density with the disc current. Specifically, it is made by simmering at different temperatures. The cathode catalyst is carried on the disk electrode of a rotating ring-disc electrode (RRDE), and the redox reaction (oxygen reduction) is measured by linear voltammetry in an oxygen-rich 0.5 M aqueous sulfuric acid solution. Reaction, ORP) activity.

As shown in the figure, the half-wave potential of the cathode catalyst of the present invention shifts to a high potential as the temperature of the calcination rises, indicating that the activity of the redox reaction increases with the temperature of the calcination. Increasing; however, when the calcination temperature is higher than 800 ° C, the half-wave potential of the cathode catalyst of the present invention shifts to a low potential as the calcination temperature rises. In addition, the activity of the catalyst is derived according to the calculation method of the literature theory. The result indicates that the onset potential of the catalyst determines the adsorption energy of oxygen adsorption on the surface of the catalyst. In other words, the lower the initial potential, the onset. The higher the energy.

It can be seen that the cathode catalyst having a calcining temperature of 700 ° C to 800 ° C not only has the highest half-wave potential, but also effectively reduces the adsorption energy of oxygen, so in step 4, the temperature between 700 ° C and 800 ° C For the best calcination temperature.

Please refer to FIG. 5, which is a graph showing the relationship between the hydrogen peroxide generation rate and the electron transfer number versus potential of a cathode catalyst prepared by calcination at different temperatures. It can be seen that the cathode catalyst with a calcination temperature between 500 ° C and 800 ° C catalyzes the redox reaction of four electron paths (as shown in Formula I); the cathode contact with a calcination temperature between 900 ° C and 1000 ° C The medium catalyzes the redox reaction of the two electron paths (as shown in Formula II) to produce a higher level of hydrogen peroxide (hydrogen peroxide).

O ₂ +4H ⁺ +4e ^- → 2H ₂ O (Formula I)

O ₂ +2H ⁺ +2e ^- → H ₂ O ₂ (Formula II)

As described above, the cathode catalyst of the present invention contains Fe ₂ N and the Fe ₂ N system is mounted on a carbonaceous carrier, and can catalyze a four-electron conversion reaction between hydrogen ions and oxygen to form water; in other words, the application is as described. The cathode catalyst ozone generating device can convert the hydrogen ions generated by the anode into water to avoid the formation of hydrogen gas, thereby increasing the safety and stability of the ozone generating device; furthermore, the ozone generating device can also avoid the electrode suffering from The erosion of hydrogen ions increases the life of the electrode.

[Second embodiment]

Please refer to FIG. 6 , which is a graph showing the relationship between the potential and the potential of at least iron containing materials. It should be mentioned that the iron ion activity of ferrous acetate, ferrous sulfate (FeSO ₄ ) and ferrous oxalate (FeC ₂ O ₄ ) can be inferred from the slope of the current density drop in each curve. The greater the slope, the better the activity. .

As shown in the figure, there is no significant difference in the slope of the three, so in the first step, the at least iron-containing starting material may be selected from ferrous sulfate or ferrous oxalate; further, ferrous sulfate and phosphorus Nitrogen phenanthrene is mixed in ethanol at a molar concentration ratio of 2.8:11.1.

In addition, ferrous oxalate and phenanthroline are mixed in ethanol at a molar concentration ratio of 1.5:11.1 to form a mixture; in addition, the organic medium may be selected from the group consisting of methanol, ethanol, butanol according to the needs of practical applications. One of isopropyl alcohol and propanol. Thereafter, steps 2 to 4 are also performed to form the cathode catalyst of the present invention.

In summary, the cathode catalyst and ozone generating device provided by the embodiments of the present invention have the following advantages:

1. The preparation method of the cathode catalyst of the invention is simple and rapid, and the cost is lower than that of the noble metal such as platinum, so it has great development value.

2. The cathode catalyst prepared by the above preparation method has better four-electron conversion efficiency and can catalyze four-electron conversion between hydrogen ions and oxygen. The reaction generates water to prevent hydrogen ions from eroding the electrode, and can reduce the probability of occurrence of a side reaction of the two-electron conversion to produce hydrogen peroxide.

3. When the anode of the ozone generating device of the present invention converts water into ozone, the incident hydrogen ions pass through the cation exchange membrane to the cathode, and react with the above cathode catalyst and oxygen to form water, thereby effectively avoiding safety. The suspected hydrogen is generated and reduces the possibility of hydrogen ions corroding the electrode, thereby increasing the safety and stability of the ozone generating device.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and the equivalents of the present invention are intended to be included within the scope of the present invention.

100‧‧‧Ozone generating device

1‧‧‧Cation exchange membrane

2‧‧‧Anode sink

21‧‧‧Anode

211‧‧‧Anode substrate

212‧‧‧Anode catalyst layer

22‧‧‧Anode chamber

3‧‧‧cathode sink

31‧‧‧ cathode

311‧‧‧ Cathode Matrix

312‧‧‧ Cathode catalyst layer

32‧‧‧Cathode chamber

1 is a schematic cross-sectional view of an ozone generating device of the present invention; FIG. 2 is a schematic flow chart of a method for preparing a cathodic catalyst according to the present invention; and FIG. 3 is a schematic view of a method for preparing a cathodic catalyst according to the present invention. X-ray diffraction diagram of the medium; FIG. 4 is an activity test diagram of the oxygen reduction reaction of the cathode catalyst prepared by calcining at different temperatures according to the preparation method of the cathode catalyst of the present invention; FIG. 5 is a cathode catalyst of the present invention. The preparation method is a graph showing the relationship between the hydrogen peroxide generation rate and the electron transfer number to the potential of the cathode catalyst prepared by calcination at different temperatures; and FIG. 6 is a graph showing at least the various irons used in the preparation method of the cathode catalyst of the present invention. A plot of current density versus potential for the starting material.

100‧‧‧Ozone generating device

1‧‧‧Cation exchange membrane

2‧‧‧Anode sink

21‧‧‧Anode

211‧‧‧Anode substrate

212‧‧‧Anode catalyst layer

22‧‧‧Anode chamber

3‧‧‧cathode sink

31‧‧‧ cathode

311‧‧‧ Cathode Matrix

312‧‧‧ Cathode catalyst layer

32‧‧‧Cathode chamber

Claims (10)

A method for preparing a cathode catalyst, comprising the steps of: mixing a starting material containing at least iron with an at least nitrogen-containing starting material in an organic medium to form a mixture; adding a carbon material to the The mixture is heat treated to form a solid precursor; the solid precursor is ground to form a precursor powder; and the precursor powder is calcined in an ammonia-containing environment to form a cathode catalyst. The method for preparing a cathode catalyst according to claim 1, wherein the at least iron-containing starting material is one selected from the group consisting of ferrous acetate, ferrous sulfate and ferrous oxalate, the at least nitrogen-containing The starting material is phenanthroline. The method for preparing a cathode catalyst according to claim 1, wherein the organic medium is one selected from the group consisting of methanol, ethanol, butanol, isopropanol and propanol. The method for preparing a cathode catalyst according to claim 1, wherein the at least iron-containing starting material and the at least nitrogen-containing starting material are mixed at a molar concentration ratio of 1.5 to 2.8:11.1. In organic media. The method for preparing a cathode catalyst according to claim 1, wherein the carbon material is carbon black, graphite whisker, amorphous carbon, activated carbon, mesoporous carbon, porous carbon fiber, nano carbon fiber, and nanometer. Carbon tube or carbon fiber, the heat treatment is carried out in an oven at a temperature between 60 ° C and 80 ° C for 8 to 16 hours. The method for preparing a cathode catalyst according to claim 1, wherein in the step of grinding, the solid precursor is placed in a ball mill and ball milled by zirconium balls for 2 to 4 hours to form the precursor. powder. The method for preparing a cathode catalyst according to claim 1, wherein in the step of calcining, the precursor powder is placed in a high temperature furnace of ammonia gas at a temperature between 500 ° C and 1000 ° C. The cathode catalyst was prepared by heating for 1 to 3 hours. An ozone generating device comprising: a cation exchange membrane; an anode water tank disposed on one side of the cation exchange membrane and having an anode connected to a surface of the cation exchange membrane, wherein the anode comprises an anode substrate and a cathode An anode catalyst layer formed on the anode substrate; and a cathode water tank disposed on the other side of the cation exchange membrane and having a cathode connected to the other surface of the cation exchange membrane, wherein the cathode comprises a cathode a substrate and a cathode catalyst layer formed on the cathode substrate, and the cathode catalyst layer comprises a cathode catalyst prepared by the method for preparing a cathode catalyst according to claim 1. The ozone generating device of claim 8, wherein the anode substrate is carbon paper or carbon cloth, and the cathode substrate is platinum, copper, cerium oxide, lead dioxide, carbon cloth, carbon paper or a combination thereof. The ozone generating device according to claim 8, wherein the cathode catalyst layer is formed by mixing the cathode catalyst with a resin into a paste, applying the surface to the surface of the cathode substrate, and drying.