Two-dimensional bimetal hydroxide single-layer nanosheets for selective ion transport

Abstract

The invention belongs to the technical field of salinity difference power generation, and relates to a two-dimensional double-metal hydroxide single-layer nanosheet for selective ion transmission, and the application is that the anionic two-dimensional double-metal hydroxide single-layer nanosheet is prepared into a film and then is arranged between two salt solutions with concentration difference to serve as a power generation device, so that salinity difference power generation is realized. According to the invention, the anionic two-dimensional double-metal hydroxide single-layer nanosheet is used as a salinity difference electrogenesis membrane material for the first time, and has very excellent power density performance.

Description

Technical Field

[0001] The invention relates to application of an anionic two-dimensional double metal hydroxide monolayer nanosheet in generating electricity using a salt difference, and belongs to the technical field of generating electricity using a salt difference. Background Art

[0002] Reverse electrodialysis technology is one of the methods that can effectively capture osmotic energy and has been deeply studied and developed. Nanofluid membrane is the key component of reverse electrodialysis technology to extract osmotic energy, and the excellence of its performance determines the efficiency of energy conversion.

[0003] Traditional nanofluid membranes cannot achieve the minimum energy density standard for commercialization due to insufficient ion selectivity and insufficient ion transport. At present, many two-dimensional materials including graphene, graphene oxide, molybdenum disulfide, carbon nanotubes and framework materials (MOFs, COFs, ZIFs, etc.) have been used to study osmotic energy conversion due to their rich surface functional groups and modifiability. Compared with the original simple polymer materials, the nanoscale pores and functionalized surfaces of two-dimensional materials can promote the transmembrane transport and selective passage of ions. However, most of the nanomaterials reported so far have weak electrostatic interactions with ions in the solution, resulting in low efficiency of salt difference power generation, which in turn affects the power density performance of salt difference power generation. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides an anionic two-dimensional double metal hydroxide monolayer nanosheet for generating electricity from salinity differences.

[0005] The technical solution for realizing the present invention is: application of anionic two-dimensional double metal hydroxide monolayer nanosheets in salt difference electricity generation.

[0006] Preferably, the application refers to preparing anionic two-dimensional double metal hydroxide monolayer nanosheets into a film and placing it between two salt solutions with a concentration difference as a power generation device to achieve salt difference power generation.

[0007] Preferably, the application comprises the following steps:

[0008] Step 1, a certain volume of anionic two-dimensional double metal hydroxide single-layer nanosheet suspension is subjected to vacuum filtration on a filter membrane to obtain a filter membrane with a single-layer nanosheet deposit;

[0009] Step 2, after vacuum drying the filter membrane with the single-layer nanosheet deposit, peeling off the membrane layer from the filter membrane to obtain a nanofluid membrane of a certain thickness;

[0010] Step 3, fixing the nanofluid membrane between two insulating gaskets with a certain pore size, installing the gasket in the middle of an H-type electrolytic cell to prepare a two-chamber electrolytic cell;

[0011] Step 4: Place two salt solutions of different concentrations in the left and right chambers of the electrolytic cell respectively to achieve salt difference electricity generation.

[0012] Specifically, the anionic two-dimensional double metal hydroxide monolayer nanosheet is any one of Ni-Al LDH, Mg-Al LDH, Mg-Fe LDH, Ni-Fe LDH, Zn-Al LDH, Co-Al LDH, and Cu-Al LDH, preferably Ni-Al LDH.

[0013] Specifically, in step 1, the concentration of the anionic two-dimensional double metal hydroxide monolayer nanosheet suspension is 0.5 to 1.5 g / L.

[0014] Specifically, in step 1, the filter membrane is any one of a PTFE filter membrane, a PVDF filter membrane, a cellulose filter membrane, and a double-pass anodized aluminum oxide filter membrane (AAO), preferably AAO.

[0015] Specifically, in step 1, the pressure of the reduced pressure filtration is 200 to 900 mbar.

[0016] Specifically, in step 2, the vacuum drying temperature is 20 to 90° C., and the drying time is 1 to 5 days.

[0017] Specifically, in step 2, the thickness of the nanofluid film is 2 to 50 μm.

[0018] Specifically, in step 3, the aperture of the insulating gasket is 0.1 to 10 mm.

[0019] Specifically, in step 4, the salt in the salt solution is any one of sodium salt, potassium salt, magnesium salt, calcium salt, chloride salt, nitrate, and sulfate, preferably sodium chloride.

[0020] Specifically, in step 4, the concentration difference between the two salt solutions is 5 to 500 times.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) For the first time, anionic two-dimensional double hydroxide monolayer nanosheets were used as membrane materials for salt gradient power generation, with very excellent power density performance.

[0023] (2) Compared with other electricity-generating materials, the atomically thin thickness of two-dimensional nanosheets can enhance the electrostatic interaction between the material and the ions in the solution, and the prepared nanofluid membrane can form an ordered confined fast ion transport channel, thereby improving the electricity generation efficiency.

[0024] (3) The preparation method of the power-generating membrane material is simple. The power-generating material with the best performance can be obtained by simply controlling the type, ratio and concentration of the reactants. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the process of using the two-dimensional double metal hydroxide monolayer nanosheets described in the present invention to generate electricity through salt difference.

[0026] Figure 2 This is the AFM image of the Ni-Al LDH sample in Example 1.

[0027] Figure 3 This is the SEM image of the Ni-Al LDH sample in Example 1.

[0028] Figure 4 This is the XRD pattern of the Ni-Al LDH sample in Example 1.

[0029] Figure 5 This is the Raman image of the Ni-Al LDH sample in Example 1.

[0030] Figure 6 This is the FT-IR graph of the Ni-Al LDH sample in Example 1.

[0031] Figure 7 This is the power density curve of the Ni-Al LDH sample in Example 1 as a salt difference power generation membrane material in a NaCl environment.

[0032] Figure 8 The power density curve of the Ni-Al LDH prepared in Example 1 as the salt difference power generation membrane material in a Ca2Cl environment.

[0033] Fig. 9 The power density curve of the Ni-Al LDH prepared in Example 1 as the salt difference power generation membrane material in a Mg2Cl environment.

[0034] Fig.10 The power density curve of the Ni-Al LDH prepared in Example 1 as the salt difference power generation membrane material in a KCl environment.

[0035] Fig.11 The power density curve of the Ni-Al LDH prepared in Example 1 as the salt difference power generation membrane material in a LiCl environment.

[0036] Fig.12 This is the IV curve of the Ni-Al LDH sample in Example 1 as a salt difference power generation membrane material in a NaCl environment. DETAILED DESCRIPTION

[0037] The present invention will be further described below through specific embodiments and accompanying drawings.

[0038] The concept of the present invention is: the present invention forms a nanofluid membrane with micro / nano channels by preparing anionic two-dimensional double metal hydroxide monolayer nanosheets, so that ions can selectively move from concentrated salt solution to dilute salt solution under the drive of salinity gradient to generate electricity. On the one hand, due to its two-dimensional morphology with ultra-thin atomic thickness, the electrostatic interaction between the material and the ions in the solution is enhanced, and the ions in the solution can be more effectively transmitted in the micro-nano channels, thereby further improving the conversion efficiency; on the other hand, the preparation method is simple, and the optimal performance of the electricity-generating material can be obtained by simply controlling the type, proportion and concentration of the reactants.

[0039] Since Ni-Al LDH, Mg-Al LDH, Mg-Fe LDH, Ni-Fe LDH, Zn-Al LDH, Co-Al LDH, and Cu-Al LDH are all two-dimensional nanosheets with ultra-thin thickness at the atomic level, are positively charged, and have similar physicochemical properties, the present invention is only described using Ni-Al LDH as an example.

[0040] Combination Figure 1 The use of the anionic two-dimensional double metal hydroxide monolayer nanosheet in the salt difference power generation of the present invention comprises the following steps:

[0041] Step 1, prepare double metal hydroxide powder according to the method described in the existing literature, wash the prepared double metal hydroxide powder with deionized water and ethanol three times, and dry it in a drying oven at 30°C. Then, intercalate and exfoliate with a mixed solution of sodium chloride and dilute hydrochloric acid, sodium dodecyl sulfate (SDS) solution and formamide solution to obtain a two-dimensional double metal hydroxide monolayer nanosheet suspension.

[0042] Step 2: After filtering the nanosheet suspension in step 1 through a filter membrane at a pressure of 800 mbar for about 1.5 days, the nanosheet suspension is dried at 30° C. to obtain a nanofluid membrane.

[0043] Step 3, fix the nanofluid membrane in step 2 between two insulating gaskets with a certain pore size, and ensure that the holes on both sides of the gaskets are covered by the nanofluid membrane, and then align the gaskets and place them in an H-type electrolytic cell to obtain a two-chamber electrolytic cell divided into left and right chambers by the nanofluid membrane. Two salt solutions with a concentration difference of 5 to 500 times are placed in the left and right chambers of the electrolytic cell to achieve salt difference electricity generation.

[0044] Example 1

[0045] (1) Weigh 0.4944 g AlCl3·6H2O, 0.9736 g NiCl2·6H2O and 0.5380 g urea, dissolve in 128 mL pure water, place the mixed solution on a magnetic stirrer and stir at a speed of about 300 r / min for 1 h, pour the stirred mixed solution into a 200 mL reactor liner, place the reactor in a vacuum drying oven at 190°C, and perform hydrothermal reaction for 48 h.

[0046] (2) After the reactor was cooled to room temperature, the inner tank was taken out and the solid at the bottom was centrifuged at 8000 rpm for 5 min to obtain a light green powder, which was washed three times with pure water and anhydrous ethanol (20000 rpm for 5 min) respectively, and finally dried in a drying oven at 30 °C to obtain Ni-Al LDH-CO3 2- powder.

[0047] (3) Weigh 1g of Ni-Al LDH-CO3 from step 2 2- Powder, pour it into 1L NaCl (1mol / L)-HCl (3.3mmol / L) mixed solution, build a gas loop, exhaust the air in the conical flask with argon, make the whole reaction system completely in argon environment, seal the container, place it on the speed-adjustable oscillator and oscillate for 12h to carry out ion exchange reaction. Centrifuge the vibrated light green suspension at 20000rpm for 5min, remove the supernatant, and wash the solid three times with pure water and anhydrous ethanol respectively. After washing, dry the solid in a 30℃ vacuum drying oven to obtain Ni-Al LDH-Cl- powder.

[0048] (4) Weigh 0.7 g of the Ni-Al LDH-Cl-powder prepared in step 3 and pour it into 700 mL of 0.1 mol / L SDS solution. Repeat the subsequent steps in step 3 to obtain Ni-Al LDH-SDS-powder.

[0049] (5) Weigh 1 g of Ni-Al LDH-SDS-powder from step 4, place it in 1000 mL of formamide, purge with argon, seal the container, and oscillate it at 160 rpm in a speed-controlled oscillator for 4 days. In order to remove the unpeeled particles, the obtained light green translucent suspension needs to be further processed by centrifugation at 2000 rpm for 10 minutes. The supernatant is retained to obtain a well-dispersed and stable nanosheet suspension, which is subjected to AFM testing, such as Figure 2 As shown in FIG. 1 , the exfoliated Ni-Al LDH nanosheets are single-layer nanosheets with a thickness of about 0.8 nm. The exfoliated nanosheet suspension is freeze-dried to obtain Ni-Al LDH nanosheet powder, which is then subjected to SEM testing. Figure 3 As shown, the material has a two-dimensional sheet structure composed of nanosheets.

[0050] (6) Use AAO with a diameter of 50 mm and a pore size of 80-100 nm as the filter membrane, assemble the filtration device, and connect the vacuum pump. Absorb a certain volume of the nanosheet suspension in step 5, slowly and evenly add it to the container, turn on the vacuum pump, and filter at a pressure of 800 mbar for about 1.5 days. After the filtration is completed, put the product together with the AAO filter membrane into a vacuum drying oven at 30°C for drying. After drying, peel off the film layer from the AAO filter membrane to obtain a Ni-Al LDH nanofluid membrane with a certain thickness. Perform XRD test on it, as shown Figure 4 As shown in Figure 1, three diffraction peaks appeared in the XRD spectrum at 7.4°, 14.9° and 22.6°, which are the out-of-plane reflections of 003, 006 and 009 of the two-dimensional layered structure. Raman test was performed on it, as shown in Figure 1. Figure 5 As shown, 493cm -1 and 556cm -1 The characteristic peaks at 982 cm-1 can be attributed to the vibration of Ni-OH and Al-OH, while the -1 and 1062cm -1 The two characteristic peaks are caused by the vibration of OH, which proves the successful preparation of Ni-Al LDH nanofluid membrane. FT-IR test is performed on it, such as Figure 6 As shown, 444cm -1 and 552cm -1 The characteristic peaks at 1062 cm-1 can be attributed to the vibration of Ni-OH and Al-OH, while the -1 The characteristic peak at is caused by the vibration of OH, which proves the successful preparation of Ni-Al LDH nanofluid membrane.

[0051] (7) The nanofluid membrane in step 6 is fixed between two insulating gaskets with a pore size of 0.2 mm, ensuring that the holes on both sides of the gaskets are covered, and then the gaskets are aligned and placed in an H-type electrolytic cell to obtain a two-chamber electrolytic cell divided into left and right chambers by the nanofluid membrane. In order to verify the effect of 5 groups of different salt solutions (NaCl, CaCl2, MgCl2, KCl, LiCl) on the power density of Ni-Al LDH nanofluid membrane, the left chamber of the electrolytic cell is a 0.5M salt solution, and the right chamber of the electrolytic cell is a 0.01M corresponding salt solution. At room temperature, an external resistance box is connected, and the current under different resistances is recorded by a multi-function source meter. The power density curves of the same type of salt solutions with different concentrations are tested, such as Figure 7 As shown in Figure 2, the power density is 7.1 W m in a salinity difference environment of 50 times that of NaCl. -2 , indicating that the material has good salt difference electricity generation performance. Figure 8 As shown, the power density is 10.0 W m in a salinity difference environment of 50 times that of CaCl2. -2 .like Fig. 9As shown in Figure 2, the power density is 10.2 W m in a salinity difference environment of 50 times that of MgCl2. -2 .like Fig.10 As shown, the power density is 1.6 W m in a salinity difference environment of 50 times that of KCl. -2 .like Fig.11 As shown in Figure 2, the power density is 5.9 W m in a salinity difference environment of 50 times that of LiCl. -2 The multifunctional source meter is directly connected to the positive and negative electrodes of the two-chamber electrolytic cell containing the Ni-Al LDH nanofluid membrane to test its IV curve, such as Fig.12 As shown, an open circuit voltage of 61 mV and a short circuit current of 11.7 μA can be generated in a salinity difference environment of 50 times that of NaCl.

Claims

1. Application of anionic two-dimensional double hydroxide monolayer nanosheets in salt gradient power generation.

2. The use according to claim 1, characterized in that The application refers to preparing anionic two-dimensional double metal hydroxide monolayer nanosheets into a film and placing it between two salt solutions with a concentration difference as an electricity generating device to achieve salt difference electricity generation.

3. The use according to claim 1, characterized in that The application comprises the following steps: Step 1, a certain volume of anionic two-dimensional double metal hydroxide single-layer nanosheet suspension is filtered under reduced pressure on a filter membrane to obtain a filter membrane with a single-layer nanosheet deposit; Step 2, after vacuum drying the filter membrane with the single-layer nanosheet deposit, peeling off the membrane layer from the filter membrane to obtain a nanofluid membrane of a certain thickness; Step 3, fixing the nanofluid membrane between two insulating gaskets with a certain pore size, installing the gasket in the middle of an H-type electrolytic cell to prepare a two-chamber electrolytic cell; Step 4: Place two salt solutions of different concentrations in the left and right chambers of the electrolytic cell respectively to achieve salt difference electricity generation.

4. The use according to claim 3, characterized in that The anionic two-dimensional double metal hydroxide monolayer nanosheet is any one of Ni-Al LDH, Mg-Al LDH, Mg-Fe LDH, Ni-Fe LDH, Zn-Al LDH, Co-Al LDH, and Cu-Al LDH, preferably Ni-Al LDH.

5. The use according to claim 3, characterized in that In step 1, the concentration of the anionic two-dimensional double hydroxide monolayer nanosheet suspension is 0.5-1.5 g / L.

6. The use according to claim 3, characterized in that In step 1, the filter membrane is any one of a PTFE filter membrane, a PVDF filter membrane, a cellulose filter membrane, and a double-pass anodized aluminum oxide filter membrane (AAO), preferably AAO.

7. The use according to claim 3, characterized in that In step 2, the thickness of the nanofluid film is 2~50 µm.

8. The use according to claim 3, characterized in that In step 4, the salt in the salt solution is any one of sodium salt, potassium salt, magnesium salt, calcium salt, chloride salt, nitrate and sulfate, preferably sodium chloride.

9. The use according to claim 3, characterized in that In step 4, the concentration difference between the two salt solutions is 5 to 500 times.

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