CN114921807A - Membrane electrode material for preparing sodium borohydride hydrogen storage by electrolyzing sodium metaborate and process - Google Patents

Abstract

The invention discloses a membrane electrode material and process for preparing sodium borohydride hydrogen storage by electrolysis of sodium metaborate. The Nafion membrane is separated to form two left and right symmetrical spaces, and the two chambers formed are respectively subjected to flow renewal of 50ml of metal ion solution and 50ml of NaBH4 alkaline solution. Using the flow cell to prepare the catalyst has the advantages of simple process, easy enlargement and popularization and application value.

Description

Membrane electrode material and process for preparing sodium borohydride hydrogen storage by electrolysis of sodium metaborate

technical field

The invention relates to a membrane electrode material and process for preparing sodium borohydride hydrogen storage by electrolysis of sodium metaborate. The material has excellent hydrogen storage performance, and the preparation device has a special flow structure, and belongs to the fields of hydrogen storage materials and sodium borohydride regeneration.

Background technique

Sodium borohydride (NaBH ₄ ) is an excellent hydrogen storage material, its hydrogen storage density can reach 10.8wt%, the regeneration product is pollution-free, and the hydrogen release purity is high, and it is also an ideal hydrogen source for fuel cells. Exchange membrane fuel cell (PEMFC) and direct borohydride fuel cell (DBFC) systems are promising candidates for hydrogen storage, but their high price, high hydrogen production cost, difficult regeneration, and the need for precious metal catalysts restrict their use. develop.

At present, in the field of electroreduction of sodium metaborate, scholars at home and abroad mainly use electroless plating method to prepare catalysts involved in the reaction. , He Min chemically plated nickel-based and cobalt-based rare earth composite electrodes with copper sheets as the base. During the process, it was found that due to the strong acidity of the Nafion membrane, the performance is stable in the long-term electrocatalysis process, which plays an extremely important role in reducing cost and energy consumption and improving the electrolysis efficiency. Therefore, the inventor chose to use the Nafion membrane as the substrate. The metal catalyst is also the key material of the membrane electrode, which has a decisive influence on the performance and stability of the membrane electrode. Therefore, in order to reduce the polarization overpotential, electrolysis voltage and energy consumption, it is necessary to prepare electrode catalytic materials with high activity, low overpotential and stable performance. In the previous work of the inventor's research group, several non-precious metals Pb, Sn, Bi, Zn, Cd, Cu, etc. were compared, and it was concluded that Pb has better catalytic activity in the process of electroreduction of sodium metaborate to prepare sodium borohydride. Based on the above situation, the inventors chose to prepare lead-based Nafion membrane electrode materials. In the early stage, they tried to use the immersion reduction method, the two-chamber method, and the flow plating method, and compared them in turn to gradually optimize and improve the performance. , the continuous circulation of the metal liquid and the reducing liquid can be realized, the liquid can be fully reacted, and the lead-based membrane electrode material plated out by flow has good catalytic performance.

SUMMARY OF THE INVENTION

Aiming at the problems of expensive catalyst cost and low concentration of sodium borohydride in the process of electrochemically reducing sodium metaborate to prepare sodium borohydride, the present invention proposes a membrane catalyst material for preparing sodium borohydride by electrochemically reducing sodium metaborate in a flow electrolytic cell .

To achieve the above-mentioned technical purpose and achieve the above-mentioned technical effect, the present invention is realized through the following technical solutions:

A membrane electrode material for preparing sodium borohydride hydrogen storage by electrochemically reducing sodium metaborate, characterized in that the preparation method comprises the following steps: respectively carrying out 50ml of a PbCl solution with a concentration of 0.025mol/L and a 50ml concentration of PbCl _on both sides of a flow cell. The flow of 0.1mol/L NaBH ₄ alkaline solution was renewed for 12h, that is, the steps of metal ion exchange and reduction of the coating were carried out simultaneously.

As a further improvement of the present invention, the electrochemical reduction of sodium metaborate to prepare a membrane electrode material for sodium borohydride hydrogen storage is characterized in that a Nafion membrane is used to prepare a lead-based membrane catalyst. .

As a further improvement of the present invention, the electrochemical reduction of sodium metaborate to prepare a membrane electrode material for sodium borohydride hydrogen storage is characterized in that the size of the membrane electrode is 30-100mm, and the actual size matches the mold.

As a further improvement of the present invention, the electrochemical reduction of sodium metaborate to prepare a membrane electrode material for sodium borohydride hydrogen storage is characterized in that: the flow cell is made of two customized polypropylene plates, each plate corresponding to two sides There is a 2-5mm diameter hole on the upper and lower sides, and the hole is connected to the hose for solution renewal through the flow pump. During preparation, the Nafion membrane was sandwiched between two plates and the entire device was fixed inside with screws. Two symmetrical spaces are formed by the Nafion membrane, and the two chambers formed are respectively subjected to the flow renewal of 50ml PbCl ₂ solution and NaBH ₄ lye.

As a further improvement of the present invention, the electrochemical reduction of sodium metaborate to prepare a membrane electrode material for sodium borohydride hydrogen storage is characterized in that: the left and right compartments separated into the same size are cuboid, and the length is 30-100mm , the width is 3-5mm, and the height is 30-100mm.

As a further improvement of the present invention, the electrochemical reduction of sodium metaborate to prepare a membrane electrode material for sodium borohydride hydrogen storage is characterized in that the outer length of the two plates is 50-120 mm, the outer width is 6-8 mm, and the height is 50-120 mm. 50-120mm.

Description of drawings

Fig. 1 is a three-dimensional schematic diagram of a flow cell (for coating);

Figure 2 is a schematic diagram of flow cell coating work;

Fig. 3 is the SEM image of flow cell lead plating film catalyst;

FIG. 4 is a graph showing the performance optimization of catalysts prepared under different PbCl ₂ solution concentrations in Example 1. FIG.

FIG. 5 is a linear voltammogram of electrolysis at different voltages for 0.5 h in Example 2. FIG.

6 is a linear voltammogram of flow electrolysis at different times when the electrolysis voltage is 3V in Example 3.

7 is a graph of NaBH ₄ generation rate and Faradaic efficiency graph of flow electrolysis at different times when the electrolysis voltage is 3V in Example 3.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Below in conjunction with accompanying drawing, the present invention is described in detail:

As shown in Figure 1 is the preparation device of the present invention, the preparation device includes two customized polypropylene plates and screws, the flow pipe connects the flow pump and the device (as shown in Figure 2), and each plate has a 2- 5mm diameter hole, the hole connects the hose for solution renewal through the flow pump. During preparation, the Nafion membrane was sandwiched between two plates and the entire device was fixed inside with screws. Two symmetrical spaces are formed by the Nafion membrane, and the two chambers formed are respectively subjected to the flow renewal of 50ml PbCl ₂ solution and NaBH ₄ lye. Figure 3 is an SEM image of the lead film catalyst, showing that a lamellar homogeneous structure has been prepared. .

Example 1: Use Nafion film lead plating to prepare catalyst, the size is 40*40mm, during preparation, the Nafion film is sandwiched between two plates and the whole device is fixed with screws. On both sides of the flow cell are 50ml of PbCl ₂ solution and 50ml of NaBH ₄ lye solution with a concentration of 0.1mol/L. The flow pump is used to fix the flow rate to make the solutions on both sides flow and update for 12h, that is, the exchange and reduction of metal ions in the coating The steps are performed simultaneously, wherein the concentrations of the PbCl ₂ solution are 0.0119, 0.0148, 0.0178, 0.0237, 0.025, 0.027, and 0.030 mol/L, respectively. Then a two-electrode electrode system was used, and NaBO ₂ lye was electrolyzed at 3.0V by using a flow electrolytic cell at normal temperature and normal pressure.

Example 2: Using Nafion film lead plating to prepare a catalyst, the size is 40*40mm. During preparation, the Nafion film is sandwiched between two plates and the entire device is fixed with screws. On both sides of the flow cell are 50ml of PbCl ₂ solution with a concentration of 0.025mol/L and 50ml of NaBH ₄ lye with a concentration of 0.1mol/L, and the flow pump is used to make the solutions on both sides flow and update for 12h, that is, the metal ion exchange of the coating And the restoration steps are carried out at the same time. Then a two-electrode electrode system was used, and the CHI660B electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd. was used as the power supply. Under normal temperature and pressure, NaBO ₂ was electrolyzed by a flow electrolytic cell at 2.6, 2.8, 3.0, 3.2, and 3.4V, respectively. lye.

Example 3: Using Nafion film lead plating to prepare a catalyst, the size is 40*40mm. During preparation, the Nafion film is sandwiched between two plates and the entire device is fixed with screws. On both sides of the flow cell are 50ml of PbCl ₂ solution with a concentration of 0.025mol/L and 50ml of NaBH ₄ lye with a concentration of 0.1mol/L, and the flow pump is used to make the solutions on both sides flow and update for 12h, that is, the metal ion exchange of the coating And the restoration steps are carried out at the same time. Then a two-electrode electrode system is used, and the CHI660B electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd. is used as the power supply. Under normal temperature and normal pressure, the electrolysis voltage is 3V, and the flow electrolysis 3.5, 4, 4.5, 5, 5.5, 6.5, 7.5, 8, 20h respectively electrolyze NaBO ₂ lye.

Performance Testing

The method for measuring the reduced sodium borohydride is as follows: after the electrolysis is completed, the gold electrode is used as the working electrode, the mercury-mercury oxide electrode is used as the reference electrode, the graphite electrode is used as the counter electrode, and the three electrodes are in the same cathode chamber. Amperometric or cyclic voltammetry to test the concentration of sodium borohydride in the electrolyzed solution, the test voltage range is -0.8-0V, the scanning speed is 0.05V/s, and whether there is an oxidation peak at about -0.5V through the scanning curve Determine whether sodium borohydride is formed.

As shown in Figure 4, which corresponds to the performance optimization diagram of the catalyst prepared in Example 1 with different concentrations of PbCl ₂ solution, it can be seen that the membrane prepared at the concentration of 0.025 mol/L has the best performance.

As shown in FIG. 5 , corresponding to the electrolyte Lsv diagram obtained by electrolysis at different voltages in Example 2, it can be seen that the electrolysis peak current is the largest at 3V, and the sodium borohydride concentration is the highest.

As shown in Figure 6, corresponding to the influence of different electrolysis times on electrolysis in Example 2, it can be seen that the longer the electrolysis time during the test, the higher the current and the higher the sodium borohydride concentration, indicating that the prepared lead film catalyst Material properties are good.

As shown in Figure 7, the generation rate and Faradaic efficiency diagram corresponding to different electrolysis time in Example 2, it can be seen that within 8h, the concentration of sodium borohydride increases with the increase of electrolysis time. However, when the electrolysis time reaches 20h, the concentration of sodium borohydride increases to a certain extent, but the Faradaic efficiency decreases significantly, indicating that most of the current has not been used for electrolysis of sodium metaborate. It is shown that, in a certain electrolysis time, the longer the electrolysis time is, the higher the concentration of sodium borohydride is, which indicates that the prepared lead film catalyst material has good performance.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (6)

1. A membrane electrode material for hydrogen storage of sodium borohydride prepared by electrochemical reduction of sodium metaborate is characterized by comprising the following steps: 50ml of 0.025mol/L PbCl is respectively carried out on both sides of the flow cell ₂ Solution and 50ml of NaBH with a concentration of 0.1mol/L ₄ And (4) updating the flow of the alkali liquor for 12h, namely simultaneously performing the steps of metal ion exchange and reduction of the coating.

2. The membrane electrode material for hydrogen storage and preparation of sodium borohydride by electrochemical reduction of sodium metaborate as claimed in claim 1, wherein: a Nafion membrane was used to prepare a lead-based membrane catalyst.

3. The membrane electrode material for hydrogen storage and preparation of sodium borohydride by electrochemical reduction of sodium metaborate as claimed in claim 1, wherein: the size of the membrane electrode is 30-100mm, and the actual size is matched with the mould.

4. The membrane electrode material for hydrogen storage and preparation of sodium borohydride by electrochemical reduction of sodium metaborate as claimed in claim 1, wherein: the flow cell is made of two customized polypropylene plates, the upper part and the lower part of the corresponding two sides of each plate are respectively provided with a hole with the diameter of 2-5mm, and the hole is connected with a hose to refresh the solution through a flow pump. During preparation, a Nafion membrane is clamped between two plates, and the whole device is fixed by screws. Two bilaterally symmetrical spaces are formed by separating Nafion films, and 50ml of PbCl is respectively carried out in the two formed chambers ₂ Solutions and NaBH ₄ And (4) flow updating of the alkali liquor.

5. The membrane electrode material for hydrogen storage and preparation of sodium borohydride by electrochemical reduction of sodium metaborate as claimed in claim 1, wherein: the left and right chambers are rectangular with the same size, the length is 30-100mm, the width is 3-5mm, and the height is 30-100 mm.

6. The membrane electrode material for hydrogen storage and preparation of sodium borohydride by electrochemical reduction of sodium metaborate as claimed in claim 1, wherein: the outer length of the two plates is 50-120mm, the outer width is 6-8mm, and the height is 50-120 mm.

Images