CN106207203B - A kind of nano-sheet Ni (OH)2Catalyst and its preparation method and application - Google Patents

Abstract

A nano flake Ni(OH) ₂ catalyst and its preparation method and application. The invention discloses a preparation method of a nanosheet Ni(OH) ₂ catalyst, comprising: (1) immersing a pure nickel substrate in an electrolyte; the electrolyte contains: 0.2 to 3mol L ^‑1 of ^F‑ ; 0.1 to 1mol L ^-1 NH ₄ ⁺ ; 2-7mol L ^- 1 ethylene glycol; 5-10mol L ^-1 glycerol; 0.1-0.5mol L ^- 1 Na ₂ WO ₄ 2H ₂ O; (2 ) is prepared by constant current anodic oxidation; (3) the sample treated in step (2) is subjected to hydrothermal treatment, and after the hydrothermal treatment, it is washed and dried to obtain a nanosheet-like Ni(OH) ₂ catalyst. The invention also discloses the nano flake Ni(OH) ₂ catalyst obtained by the above preparation method and its application. The nano catalyst prepared by the invention has high electrocatalytic activity, good cycle stability and CO poisoning resistance, and the preparation process is simple, efficient and low in cost.

Description

A kind of nano flake Ni (OH) 2 catalyst and its preparation method and application

technical field

The invention relates to the fields of electrocatalysis and fuel cells, in particular to a nanosheet Ni(OH) ₂ catalyst, a preparation method and application thereof.

Background technique

In recent years, direct methanol fuel cells (DMFCs) have received extensive research and attention due to their advantages such as low operating temperature, high energy utilization efficiency, convenient fuel storage, and low pollutant emissions. However, the commercial application of acidic DMFCs based on platinum-based catalysts is facing some critical issues, such as slow oxidation kinetics, methanol permeation, high catalyst cost, and oversensitivity to toxic CO intermediates, etc. In contrast, alkaline DMFCs are attracting increasing attention due to their enhanced reaction kinetics and less pollutant emissions, as well as a wide range of electrode material choices. Non-noble metals and cheap metals can be used as catalysts in alkaline DMFC, among which nickel-based materials (such as metal nickel, nickel alloys and nickel compounds, etc.) have high electrocatalytic activity, low price and good cycle stability And other advantages, it is considered to be a very promising non-platinum-based basic DMFC catalyst material.

The anode catalytic electrode is an important part of DMFC and plays a decisive role in the performance of DMFC. Catalytic activity largely depends on the surface morphology and crystal structure of the catalyst. Nanotechnology has been proven to be an effective method to improve the catalytic activity of electrodes. A large number of studies have been devoted to the preparation of nickel-based catalyst materials with various morphologies and structures by different methods, such as atomic layer deposition, sol-gel method, chemical deposition method and electrochemical deposition method. Although the above preparation methods have made some progress, most of the processes are still too complicated to carry out large-scale industrial production, or additives and conductive agents need to be used in the preparation process, which reduces the catalytic activity of the catalyst. At the same time, most of the prepared nickel-based catalysts have weak binding force with the conductive substrate, which will cause phase transition, structural damage or loss of active materials during long-term recycling, which greatly affects the performance of the battery. Therefore, the study of a simple and efficient method to prepare Ni-based catalyst materials with high electrocatalytic activity and high stability is of great importance, but at the same time, it faces great challenges.

Anodic oxidation treatment is a common electrochemical method for preparing nano-oxidized films. It has been successfully applied to metal materials such as aluminum, titanium, zirconium, iron and niobium. The structure and morphology of the prepared anodized nano-films It is easy to control and design, and has excellent electrochemical performance, and is widely used in supercapacitors, solar cells, sensors and catalysts and other fields. However, due to the high solubility of nickel oxides in commonly used anodizing electrolytes, it is difficult to control the structure and morphology of the prepared film, and usually only severe localized Dissolution or electropolishing phenomena. Therefore, so far, there is no research report on the preparation of nickel-based thin film catalysts by anodic oxidation.

Contents of the invention

In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, one of the purposes of the present invention is to provide a nanosheet Ni(OH) ₂ catalyst with strong catalytic activity and good cycle stability.

The second object of the present invention is to provide a preparation method of the above-mentioned nanosheet Ni(OH) _2catalyst , and the preparation process is simple.

The third object of the present invention is to provide the application of above-mentioned nano flake Ni(OH) ₂ catalyst.

The object of the present invention is achieved through the following technical solutions:

A kind of nano flake Ni (OH) The preparation method of _catalyst , comprises the following steps:

(1) Immerse the pure nickel substrate in the electrolyte;

The electrolyte contains: 0.2 to 3 mol L ^-1 of F ^- ; 0.1 to 1 mol L ^-1 of NH ₄ ⁺ ; 2 to 7 mol L ^-1 of ethylene glycol; 5 to 10 mol L ^-1 of glycerol; 0.1 ˜0.5 mol L ⁻¹ of Na ₂ WO ₄ 2H ₂ O;

(2) Preparation by constant current anodic oxidation, the current density is 30-100mA cm ^-2 , the electrolyte temperature is 10-30°C, and the oxidation time is 5-15min;

(3) Carry out hydrothermal treatment to the sample treated in step (2), after hydrothermal treatment, directly clean with deionized water and then blow dry to obtain nanosheet Ni(OH) ₂ catalyst.

Step (2) Before the constant current anodization, the voltage is boosted to 3-4.5V at a rate of 5-20mV s ^-1 and kept for 1-5min, and then the constant-current anodization is performed.

The pure nickel substrate described in step (1) is a nickel sheet or nickel foam.

The specific conditions for the hydrothermal treatment in step (3) are: the filling degree of the hydrothermal kettle is less than 50%, the treatment temperature is 100-200° C., and the hydrothermal time is 2-5 hours.

The hydrothermal solution of the hydrothermal treatment contains: 1-3 mol L ^-1 of LiOH; 2-5 mol L ^-1 of isopropanol; 0.5-2 mol L ^-1 of dimethyl phosphate.

The pure nickel substrate described in step (1) is a pretreated nickel substrate, and the pretreatment is:

The nickel substrate was ultrasonically cleaned in acetone and alcohol solutions for 10-15 minutes to remove the oil and oxide layer on the surface, and finally it was taken out and dried to obtain a pure nickel substrate with a clean surface.

The constant current anodization in step (2) adopts a three-electrode system, with a pure nickel substrate as a working electrode, a pure platinum sheet as a counter electrode, and a saturated calomel electrode as a reference electrode.

The nanosheet Ni(OH) ₂ catalyst is prepared by the preparation method of the nanosheet Ni(OH) ₂ catalyst.

The application of the nano-flaky Ni(OH) ₂ catalyst is as an anode catalytic electrode of a direct methanol fuel cell.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

(1) The nano-flaky Ni(OH) _catalyst of the present invention has strong catalytic activity. In the process of electrocatalytic oxidation of methanol, the nanosheet Ni(OH) ₂ film has an oxidation voltage of 0.67V vs. Hg/HgO and an oxidation current density of up to 72mA cm ^-2 . It has the characteristics of anti-CO poisoning.

(2) The nanosheet Ni(OH) _catalyst of the present invention has good cycle stability. During the long-term cycle test, the nanosheet-like Ni(OH) ₂ film exhibited durable cycle stability, with a residual of 84% of the peak current after 1000 cycles, and a strong mechanical stability properties and electrochemical stability.

(3) nano-flaky Ni(OH) of the present inventionThe preparation method of the _catalyst adopts specific anodic oxidation technology to directly generate a nano-flaky nickel-based compound film layer in situ on the nickel substrate, and there is a film layer between the film layer and the substrate Strong mechanical binding force can effectively avoid the agglomeration of nanoparticles and the loss of active substances.

(4) The preparation method of the nanosheet Ni(OH) ₂ catalyst of the present invention further optimizes the organizational structure of the film layer through hydrothermal post-treatment, and improves the catalytic performance of the film layer.

(5) The preparation method of the nano-flaky Ni(OH) _2catalyst of the present invention has a simple process. Anodizing technology has short processing time, low working voltage, simple processing technology, can be easily transplanted and enlarged, has a wide range of applications, and is suitable for large-scale production.

(6) The nanosheet Ni(OH) _catalyst of the present invention is low in cost. Because nickel is abundant in nature and cheap, the use of nickel as a catalyst for direct methanol fuel cells overcomes the disadvantages of high cost of traditional precious metals such as platinum and ruthenium.

Description of drawings

FIG. 1 is a schematic diagram of an anodizing device used in an embodiment of the present invention.

Fig. 2 is the XRD test result of the nanosheet Ni(OH) ₂ film layer prepared in Example 1 of the present invention.

Fig. 3 is the SEM image of the nanosheet Ni(OH) ₂ film layer prepared in Example 1 of the present invention.

FIG. 4 is a CV test chart of the electrocatalytic oxidation of methanol by the nanosheet-like Ni(OH) ₂ film layer prepared in Example 1 of the present invention and the film layers prepared in Comparative Samples 1-3.

Fig. 5 is a long-term stability test graph of the nanosheet-like Ni(OH) ₂ film layer prepared in Example 1 of the present invention and the film layer prepared in Comparative Samples 1-3 for electrocatalytic oxidation of methanol.

FIG. 6A is a chronoamperometry diagram of the electrocatalytic oxidation of methanol by the nanosheet Ni(OH) ₂ film layer prepared in Example 1 of the present invention.

6B is a graph showing the relationship between the steady-state current and the concentration of methanol for the electrocatalytic oxidation of methanol by the nano-flaky Ni(OH) ₂ film layer prepared in Example 1 of the present invention.

FIG. 7A is a high-magnification SEM image of the nanosheet Ni(OH) ₂ film layer prepared in Example 2 of the present invention.

FIG. 7B is a low-magnification SEM image of the nanosheet Ni(OH) ₂ film layer prepared in Example 2 of the present invention.

Fig. 8 is the CV test chart of the electrocatalytic oxidation of methanol by the nanosheet Ni(OH) ₂ film layer prepared in Example 2 of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

Example 1

The nano flake Ni of this implementation (OH) The preparation method of _catalyst , comprises the following steps:

(1) Use a pure nickel sheet with a thickness of 0.2mm and a purity of 96.6% as the base metal, cut it into a rectangle of 3.5cm × 0.5cm, and the upper part with a length of 1.5cm is the clamping part, which is used to connect with the Connection, the lower part with a length of 2cm is the actual use part, which is immersed in the electrolyte to participate in the anodic oxidation reaction.

(2) Use acetone and alcohol to remove the oil stain and oxide layer on the surface of the nickel sheet in an ultrasonic environment. The amount of acetone and alcohol is just enough to cover the nickel sheet sample. First, ultrasonically clean it in the acetone solution for 10 minutes, and then put it in the alcohol solution. Ultrasonic cleaning for 10 minutes; after ultrasonic degreasing, rinse with deionized water and dry.

(3) Add 1 mol L ^-1 of ammonium fluoride, 5 mol L ^-1 of ethylene glycol, 8 mol L ^-1 of glycerol and 0.3 mol L ^-1 of Na ₂ WO ₄ 2H ₂ O into the container to prepare electrolytic Fix one end of the cleaned nickel sheet on the anode fixture, and immerse the other end in the electrolyte for anodizing. The anodizing device is CHI 660D electrochemical workstation 1 produced by Shanghai Chenhua Instrument Co., Ltd., as shown in Figure 1 , using a three-electrode system, with nickel sheet 2 as the working electrode, pure platinum sheet 3 as the counter electrode, and a saturated calomel electrode 4 ( ^SCE ) as the reference electrode. V, kept at a constant voltage of 3.5V for 2min, and then prepared by constant current anodic oxidation, the oxidation current was 85mA cm ^-2 , the oxidation time was 10min, and the temperature of the electrolyte was 25°C.

(4) After waiting for the oxidation time to end, remove the sample, clean the surface with deionized water and dry it for later use.

(5) Carry out hydrothermal post-treatment to the sample after anodic oxidation, the hydrothermal solution adopts the LiOH of 1mol L ^-1 , the isopropanol of 3molL ^-1 and the dimethyl phosphate of 1mol L ^-1 , the solution and the sample that configure Add it to a 50mL hydrothermal kettle, and the volume of the added solution is 20mL, accounting for 40% of the volume of the hydrothermal kettle.

(6) After closing the hydrothermal kettle, put it into a KMT-F9 box-type resistance furnace for heating. The hydrothermal temperature is 150°C, and the hydrothermal time is 3h. After hydrothermal heating, directly take out the sample with deionized water After cleaning the surface and blowing it dry, a nano-flaky Ni(OH) ₂ film is obtained.

In order to better illustrate the performance of the nanosheet Ni(OH) ₂ catalyst prepared by the present invention, comparative samples 1-3 were prepared in this example, and their test results were compared with those of the present invention. Wherein the preparation process of each comparison sample is as follows:

Comparative sample 1:

(1) Use a pure nickel sheet with a thickness of 0.2mm and a purity of 96.6% as the base metal, cut it into a rectangle of 3.5cm × 0.5cm, and the upper part with a length of 1.5cm is the clamping part, which is used to connect with the Connection, the lower part with a length of 2cm is the actual use part, which is immersed in the electrolyte to participate in the anodic oxidation reaction.

(2) Use acetone and alcohol to remove the oil stain and oxide layer on the surface of the nickel sheet in an ultrasonic environment. The amount of acetone and alcohol is just enough to cover the nickel sheet sample. First, ultrasonically clean it in the acetone solution for 10 minutes, and then put it in the alcohol solution. Ultrasonic cleaning for 10 minutes; after ultrasonic degreasing, rinse with deionized water and dry.

(3) Add 1 mol L ^-1 of ammonium fluoride, 5 mol L ^-1 of ethylene glycol, 8 mol L ^-1 of glycerol and 0.3 mol L ^-1 of Na ₂ WO ₄ 2H ₂ O into the container to prepare electrolytic One end of the cleaned nickel sheet was fixed on the anode fixture, and the other end was immersed in the electrolyte for anodic oxidation. The anodic oxidation device was a CHI 660D electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd., using a three-electrode system. The nickel sheet is used as the working electrode, the pure platinum sheet is used as the counter electrode, and the saturated calomel electrode (SCE) is used as the reference electrode. First, the voltage is boosted to 3.5V at a boost rate of 10mV s ^-1 , and the voltage is kept constant at 3.5V. After keeping for 2 minutes, it was prepared by constant current anodic oxidation, the oxidation current was 85mA cm ^-2 , the oxidation time was 10 minutes, and the temperature of the electrolyte was 25°C.

(4) After waiting for the oxidation time to end, remove the sample, clean the surface with deionized water and dry it for later use.

(5) Carry out hydrothermal post-treatment to the sample after anodic oxidation, the hydrothermal solution adopts the NaOH of 1mol L ^-1 , the isopropanol of 3molL ^-1 and the dimethyl phosphate of 1mol L ^-1 , the solution and the sample that configure Add it to a 50mL hydrothermal kettle, and the volume of the added solution is 20mL, accounting for 40% of the volume of the hydrothermal kettle.

(6) After closing the hydrothermal kettle, put it into a KMT-F9 box-type resistance furnace for heating. The hydrothermal temperature is 150°C, and the hydrothermal time is 3h. After hydrothermal heating, directly take out the sample with deionized water Blow dry after cleaning the surface.

Comparative sample 2:

(1) Use a pure nickel sheet with a thickness of 0.2mm and a purity of 96.6% as the base metal, cut it into a rectangle of 3.5cm × 0.5cm, and the upper part with a length of 1.5cm is the clamping part, which is used to connect with the Connection, the lower part with a length of 2cm is the actual use part, which is immersed in the electrolyte to participate in the anodic oxidation reaction.

(2) Use acetone and alcohol to remove the oil stain and oxide layer on the surface of the nickel sheet in an ultrasonic environment. The amount of acetone and alcohol is just enough to cover the nickel sheet sample. First, ultrasonically clean it in the acetone solution for 10 minutes, and then put it in the alcohol solution. Ultrasonic cleaning for 10 minutes; after ultrasonic degreasing, rinse with deionized water and dry.

(3) Add 1 mol L ^-1 of ammonium fluoride, 5 mol L ^-1 of ethylene glycol, 8 mol L ^-1 of glycerol and 0.3 mol L ^-1 of Na ₂ WO ₄ 2H ₂ O into the container to prepare electrolytic One end of the cleaned nickel sheet was fixed on the anode fixture, and the other end was immersed in the electrolyte for anodic oxidation. The anodic oxidation device was a CHI 660D electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd., using a three-electrode system. The nickel sheet is used as the working electrode, the pure platinum sheet is used as the counter electrode, and the saturated calomel electrode (SCE) is used as the reference electrode. First, the voltage is boosted to 3.5V at a boost rate of 10mV s ^-1 , and the voltage is kept constant at 3.5V. After keeping for 2 minutes, it was prepared by constant current anodic oxidation, the oxidation current was 85mA cm ^-2 , the oxidation time was 10 minutes, and the temperature of the electrolyte was 25°C.

(4) After waiting for the oxidation time to end, remove the sample, clean the surface with deionized water and dry it for later use.

(5) Carry out hydrothermal post-treatment to the sample after anodic oxidation, the hydrothermal solution adopts the KOH of 1mol L ^-1 , the isopropanol of 3mol L ^-1 and the dimethyl phosphate of 1mol L ^-1 , the solution that configures and The sample is added to a 50mL hydrothermal kettle, and the volume of the added solution is 20mL, accounting for 40% of the volume of the hydrothermal kettle.

(6) After closing the hydrothermal kettle, put it into a KMT-F9 box-type resistance furnace for heating. The hydrothermal temperature is 150°C, and the hydrothermal time is 3h. After hydrothermal heating, directly take out the sample with deionized water Blow dry after cleaning the surface.

Comparative sample 3

(1) Use a pure nickel sheet with a thickness of 0.2mm and a purity of 96.6% as the base metal, cut it into a rectangle of 3.5cm × 0.5cm, and the upper part with a length of 1.5cm is the clamping part, which is used to connect with the Connection, the lower part with a length of 2cm is the actual use part, which is immersed in the electrolyte to participate in the anodic oxidation reaction.

(2) Use acetone and alcohol to remove the oil stain and oxide layer on the surface of the nickel sheet in an ultrasonic environment. The amount of acetone and alcohol is just enough to cover the nickel sheet sample. First, ultrasonically clean it in the acetone solution for 10 minutes, and then put it in the alcohol solution. Ultrasonic cleaning for 10 minutes; after ultrasonic degreasing, rinse with deionized water and dry.

(3) Add 1 mol L ^-1 of ammonium fluoride, 5 mol L ^-1 of ethylene glycol, 8 mol L ^-1 of glycerol and 0.3 mol L ^-1 of Na ₂ WO ₄ 2H ₂ O into the container to prepare electrolytic One end of the cleaned nickel sheet was fixed on the anode fixture, and the other end was immersed in the electrolyte for anodic oxidation. The anodic oxidation device was a CHI 660D electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd., using a three-electrode system. The nickel sheet is used as the working electrode, the pure platinum sheet is used as the counter electrode, and the saturated calomel electrode (SCE) is used as the reference electrode. First, the voltage is boosted to 3.5V at a boost rate of 10mV s ^-1 , and the voltage is kept constant at 3.5V. After keeping for 2 minutes, it was prepared by constant current anodic oxidation, the oxidation current was 85mA cm ^-2 , the oxidation time was 10 minutes, and the temperature of the electrolyte was 25°C.

(4) After waiting for the oxidation time to end, remove the sample, clean it with deionized water and dry it.

The structure of the nanosheet Ni( _OH ) film layer prepared in this embodiment is characterized, and its XRD test result is as shown in Figure 2 (wherein the emission peak of nickel comes from the matrix), as can be seen from the figure, in water After heat treatment, the composition of the film layer is all β-Ni(OH) ₂ (JCPDS card No.14-117).

The surface morphology of the nano-flaky Ni(OH) ₂ film layer prepared in this embodiment is characterized, and its SEM test result is shown in Figure 3. It can be observed from the figure that after anodic oxidation and hydrothermal treatment, the final prepared A large number of 3D nanosheet structures are produced on the surface of the film layer.

The nano-flaky Ni(OH) _film layer prepared in this embodiment and the film layer prepared in comparative sample 1, comparative sample 2 and comparative sample 3 are used for DMFC anode catalyst, and the electrocatalytic activity of the electrode catalyst of gained and electrochemical stability were measured.

Fig. 4 shows that the nanosheet Ni(OH) ₂ films prepared in this embodiment and the film layer prepared in the comparative sample 1, the comparative sample 2 and the comparative sample 3 are in 0.1mol L ^-1 NaOH and 1mol L ^-1 methanol solution The cyclic voltammetry test curve (CV) in. It can be seen from the figure that the samples without hydroheating and the samples after hydroheating with LiOH, NaOH and KOH solutions all showed a certain catalytic ability to methanol, but the catalytic performance of the samples after hydroheating with LiOH solution was obviously lower Superior to other samples, its oxidation voltage is 0.67V vs. Hg/HgO, which is the smallest among the four, and the oxidation current density is 72mA cm ^-2 , which is the highest among the four, indicating that the nano The sheet-like Ni(OH) ₂ thin films exhibited the highest catalytic activity for the oxidation of methanol. A new oxidation peak appeared in the reverse scan, which represented the elimination reaction of the residual carbon intermediates formed during the forward scan, and the retrace curve did not cross the forward scan curve, reflecting the nanoscale Flaky Ni(OH) ₂ films have good resistance to intermediate poisoning.

Fig. 5 shows that the nano-flaky Ni(OH) ₂ films prepared in this example and the film layers prepared in Comparative Sample 1, Comparative Sample 2 and Comparative Sample 3 were prepared in 0.1mol L ^-1 NaOH+1mol L ^-1 CH ₃ Long-term CV cycle test results in OH solution. It can be seen from the figure that compared with before the test, after 1000 cycles, the remaining amount of peak current density reached 84% after hydrothermal treatment of LiOH solution, while the sample without hydrothermal treatment and NaOH , KOH solution after hydroheating the remaining amount of the peak current density of the sample were 45%, 65% and 55%, which proves that the nanosheet Ni(OH) ₂ film after LiOH solution hydroheating has the best Electrocatalytic cycle stability.

Fig. 6A is the chronoamperometry (CA) diagram of the nano-flaky Ni(OH) ₂ film prepared in this example in 0.1mol L ^-1 NaOH solution before and after adding methanol, and the selected step potential is 0.67V (ie The potential of methanol oxidation peak), the time is greater than 1h. For each chronoamperometry curve, the oxidation current decreased rapidly within the first 20s, and then gradually tended to a stable state. When methanol is added to the solution, the measured value of the steady-state current is much higher than that measured without adding methanol, which is consistent with the previous CV test results, further illustrating the oxidation of methanol by the nanosheet Ni(OH) ₂ film Has high catalytic activity. Moreover, the current value of the CA test for more than one hour is very stable, indicating that the nanosheet Ni(OH) ₂ film has good tolerance and anti-poisoning to the intermediate product of methanol oxidation reaction.

Figure 6B shows the relationship between the CA steady-state current and methanol concentration of the nanosheet Ni(OH) ₂ film prepared in this example. It can be seen from the curve that when the potential step reaches a steady state, the oxidation current gradually increases with the increase of the methanol concentration until the methanol concentration increases to 3mol L ^-1 , at which time the steady state current does not increase significantly , reaching a platform. The methanol saturation concentration (3mol L ^-1 ) of the nanosheet Ni(OH) ₂ film is much higher than that of other reported Ni-based catalysts (<1mol L ^-1 ), showing stronger catalytic kinetics.

Example 2

The nano flake Ni of this implementation (OH) The preparation method of _catalyst , comprises the following steps:

(1) Use nickel foam with a thickness of 0.5mm and a purity of 96.6% as the base metal, cut it into a rectangle of 3.5cm × 0.5cm, and the upper part with a length of 1.5cm is the clamping part, which is used to connect with the fixture , the lower part with a length of 2cm is the actual use part, which is immersed in the electrolyte to participate in the anodic oxidation reaction.

(2) Use acetone and alcohol to remove the oil stain and oxide layer on the surface of the nickel foam in an ultrasonic environment. The amount of acetone and alcohol is just enough to cover the nickel sheet sample. First, ultrasonically clean it in the acetone solution for 10 minutes, and then put it in the alcohol solution. Ultrasonic cleaning for 10 minutes; after ultrasonic degreasing, rinse with deionized water and dry.

(3) Add 0.5 mol L ^-1 of ammonium fluoride, 5 mol L ^-1 of ethylene glycol, 8 mol L ^-1 of glycerol and 0.4 mol L ^-1 of Na ₂ WO ₄ 2H ₂ O into the container to prepare Electrolyte, fix one end of the cleaned nickel sheet on the anode fixture, and immerse the other end in the electrolyte for anodic oxidation. The anodic oxidation device is CHI 660D electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd., using a three-electrode system. The nickel sheet is used as the working electrode, the pure platinum sheet is used as the counter electrode, and the saturated calomel electrode (SCE) is used as the reference electrode. First, the voltage is boosted to 3V at a boosting speed of 10mV s ^-1 , and the voltage is maintained at a constant voltage of 3V. After 2 minutes, it was prepared by constant current anodic oxidation, the oxidation current was 100mA cm ^-2 , the oxidation time was 10 minutes, and the temperature of the electrolyte was 25°C.

(4) After waiting for the oxidation time to end, remove the sample, clean the surface with deionized water and dry it for later use.

(5) Carry out hydrothermal post-treatment to the sample after anodic oxidation, the hydrothermal solution adopts the LiOH of 1mol L ^-1 , the isopropanol of 3molL ^-1 and the dimethyl phosphate of 1mol L ^-1 , the solution and the sample that configure Add it to a 50mL hydrothermal kettle, and the volume of the added solution is 20mL, accounting for 40% of the volume of the hydrothermal kettle.

(6) Close the hydrothermal kettle and place it in a KMT-F9 box-type resistance furnace for heating. The hydrothermal temperature is 150°C and the hydrothermal time is 3h. After cleaning the surface, blow dry, that is.

The structure and surface morphology of the nanosheet Ni(OH) film _layer prepared in this embodiment are characterized, and its catalytic performance is detected:

Fig. 7A, Fig. 7 B are the SEM picture of the nano-flaky Ni(OH) ₂ film prepared on the nickel foam substrate, as can be seen from the figure, the nano-flaky Ni(OH) ₂ film prepared on the nickel foam substrate The thin film has a similar structure to the film layer grown on the nickel substrate; and, because the 3D structure of the foamed nickel material itself has a high specific surface area, it can provide more active sites for methanol oxidation, making it catalytically active be further enhanced.

Figure 8 shows the CV test results of the nanosheet Ni(OH) ₂ film prepared on the foamed nickel substrate in 0.1mol L ^-1 NaOH + 1molL ^-1 CH ₃ OH solution. It can be seen from the CV diagram that methanol The peak current density of the electrocatalytic oxidation on the nickel foam base film is very high, reaching 170mA cm ^-2 , and the oxidation peak voltage is 0.72V, which shows a higher catalytic performance than the film prepared by using the nickel substrate. active.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the embodiment, and any other changes, modifications, substitutions and combinations made without departing from the spirit and principle of the present invention , simplification, all should be equivalent replacement methods, and are all included in the protection scope of the present invention.

Claims (8)

1. a kind of nano sheet Ni (OH) The preparation method of _catalyst is characterized in that, comprises the following steps: (1) Immerse the pure nickel substrate in the electrolyte; The electrolyte contains: 0.2 to 3 mol L ^-1 of F ^- ; 0.1 to 1 mol L ^-1 of NH ₄ ⁺ ; 2 to 7 mol L ^-1 of ethylene glycol; 5 to 10 mol L ^-1 of glycerol; 0.1 ˜0.5 mol L ⁻¹ of Na ₂ WO ₄ 2H ₂ O; (2) Preparation by constant current anodic oxidation, the current density is 30-100mA cm ^-2 , the electrolyte temperature is 10-30°C, and the oxidation time is 5-15min; (3) carry out hydrothermal treatment to the sample after step (2) process, after hydrothermal treatment, directly blow dry after cleaning with deionized water, obtain _nano flake Ni(OH) Catalyst; The hydrothermal solution of the hydrothermal treatment contains: 1-3 mol L ^-1 of LiOH; 2-5 mol L ^-1 of isopropanol; 0.5-2 mol L ^-1 of dimethyl phosphate. 2. The preparation method of nano-flaky Ni(OH) _2catalyst according to claim 1, characterized in that, before step (2) carries out constant-current anodic oxidation, earlier with the rate boost of 5～20mV s ^-1 To 3 ~ 4.5V, keep 1 ~ 5min, and then carry out constant current anodic oxidation. 3. nano-flaky Ni(OH) according to claim _1. The preparation method of catalyst is characterized in that, the pure nickel substrate described in step (1) is nickel sheet or foamed nickel. 4. nano-flaky Ni(OH) according to claim ₁ The preparation method of the catalyst is characterized in that, the hydrothermal treatment described in step (3), the specific conditions are: the filling degree of the hydrothermal kettle is less than 50%, and the temperature The temperature is 100~200℃, and the water heating time is 2~5h. 5. nano flake Ni according to claim 1 (OH) The preparation method of _catalyst is characterized in that, the pure nickel matrix described in step (1) is the nickel matrix through pretreatment, and described pretreatment is: The nickel substrate was ultrasonically cleaned in acetone and alcohol solutions for 10-15 minutes to remove the oil and oxide layer on the surface, and finally it was taken out and dried to obtain a pure nickel substrate with a clean surface. 6. nano-flaky Ni(OH) according to claim ₁ The preparation method of catalyzer is characterized in that, the described constant-current anodic oxidation of step (2) adopts three-electrode system, is working electrode with pure nickel matrix, pure platinum The slice is the counter electrode, and the saturated calomel electrode is the reference electrode. 7. The nano-flaky Ni (OH) ₂ catalyst prepared by the preparation method of the nano-flaky Ni (OH) ₂ catalyst described in any one of claims 1 to 6. 8. The nanosheet Ni(OH) of claim _7. The application of the catalyst is characterized in that, as the anode catalytic electrode of the direct methanol fuel cell.