Two-dimensional oxide heterostructure nanofluid film for efficient ion transmission

Abstract

The invention belongs to the technical field of salinity difference power generation, and relates to a two-dimensional oxide heterostructure nanofluid film for efficient ion transmission, which comprises the following steps: preparing a two-dimensional oxide heterostructure material rich in cation defects into a film, and arranging the film between two salt solutions with concentration difference as a power generation device to realize salinity difference power generation. According to the invention, the two-dimensional oxide heterostructure rich in cation defects is used as the salinity difference electricity generation membrane material for the first time, and the power density performance is very excellent.

Description

Technical Field

[0001] The invention relates to application of a two-dimensional oxide heterostructure material rich in cation defects in salt difference power generation, belonging to the technical field of salt difference power generation. Background Art

[0002] A large amount of energy can be obtained from the salinity difference between seawater and freshwater, which is called "blue energy" and has great prospects. It is estimated that rivers flowing into the ocean worldwide can generate about 2 trillion watts of electricity, of which about 980 billion watts can be used, equivalent to 40% of the global 2400 billion watts of electricity used in 2018. In addition, the discharged wastewater can also provide an additional 18.5 billion watts of salinity gradient energy. Therefore, the development and utilization of osmotic energy is of great value. At present, a variety of technologies have been developed to effectively capture osmotic energy, among which reverse electrodialysis (RED) has a higher power density conversion capacity than pressure delayed osmosis (PRO) technology. In addition, RED technology can directly output the osmotic power stored in the salinity gradient from seawater and river water, which is conducive to the future production, maintenance and large-scale application of facilities. As a key component of RED technology, the performance of nanofluid membrane determines the efficiency and capacity of salt difference energy conversion.

[0003] At present, commercial nanofluid membranes include Nafion, AMI 7001, FKS-50, FAB-PK-130, etc. However, these membranes are expensive, the preparation process is complicated, and they do not have the potential for large-scale application. Therefore, researchers have developed other nanofluid membranes with excellent performance and low cost. At present, many two-dimensional materials including boron nitride, graphene oxide, molybdenum disulfide, Mxene and framework materials (MOFs, COFs, etc.) have been used to study salt difference energy conversion because of their rich surface functional groups and modifiability. However, most of the two-dimensional nanomaterials reported so far have weak interactions with ions in the solution, resulting in low power generation efficiency, 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 a two-dimensional oxide heterostructure material rich in cation defects for salt difference electricity generation.

[0005] The technical solution for realizing the present invention is: application of a two-dimensional oxide heterostructure material rich in cation defects in salt difference electricity generation.

[0006] Preferably, the application refers to preparing a two-dimensional oxide heterostructure material rich in cation defects 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 a suspension of a two-dimensional oxide heterostructure material rich in cation defects is subjected to vacuum filtration on a filter membrane to obtain a filter membrane with a two-dimensional heterostructure deposit;

[0009] Step 2, after vacuum drying the filter membrane with the two-dimensional heterogeneous structure 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 obtain 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 cation-defect-rich two-dimensional oxide heterostructure material is Ti 0.87 O2 / GO、Ti 0.91 O2 / GO 、 MnO2 / GO, Ca2Nb3O 10 / GO, preferably Ti 0.87 O2 / GO.

[0013] Specifically, in step 1, the concentration of the suspension of the two-dimensional oxide heterostructure material rich in cation defects is 0.5 to 10 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 (AAO) filter membrane, preferably a PTFE filter membrane.

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

[0016] Specifically, in step 2, the 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, a two-dimensional oxide heterostructure rich in cation defects was used as a membrane material for salt difference power generation, which has very excellent power density performance.

[0023] (2) Compared with other electricity-generating materials, the rich cationic defects in the two-dimensional oxide heterostructure can enhance the electrostatic interaction between the material and the ions in the solution, and the prepared nanofluid membrane can form an asymmetric 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 oxide heterostructure rich in cation defects described in the present invention to generate electricity through salt difference.

[0026] Figure 2 is Ti in Example 1 0.87 AFM image of O2 sample.

[0027] Figure 3 is Ti in Example 1 0.87 TEM image of O2 sample.

[0028] Figure 4 is Ti in Example 1 0.87 HAADF-STEM image of O2 sample.

[0029] Figure 5 is Ti in Example 1 0.87 XRD pattern of O2 sample.

[0030] Figure 6 is Ti in Example 1 0.87 Raman graph of O2 sample.

[0031] Figure 7 This is the AFM image of the GO sample in Example 1.

[0032] Figure 8 This is the TEM image of the GO sample in Example 1.

[0033] Fig. 9 This is the HRTEM image of the GO sample in Example 1.

[0034] Fig.10 This is the XRD pattern of the GO sample in Example 1.

[0035] Fig.11This is the Raman image of the GO sample in Example 1.

[0036] Fig.12 is Ti in Example 1 0.87 XRD pattern of O2 / GO sample.

[0037] Fig.13 is Ti in Example 1 0.87 Raman image of O2 / GO sample.

[0038] Fig.14 is Ti in Example 1 0.87 FT-IR image of O2 / GO sample.

[0039] Fig.15 The Ti prepared in Example 1 0.87 Power density curve of O2 / GO sample as salt difference power generation membrane material in NaCl environment.

[0040] Fig.16 The Ti prepared in Example 1 0.87 Power density curve of O2 / GO sample as salt difference power generation membrane material in Ca2Cl environment.

[0041] Fig.17 The Ti prepared in Example 1 0.87 Power density curve of O2 / GO sample as salt difference power generation membrane material in Mg2Cl environment.

[0042] Fig.18 The Ti prepared in Example 1 0.87 Power density curve of O2 / GO sample as salt difference power generation membrane material in KCl environment.

[0043] Fig.19 The Ti prepared in Example 1 0.87 Power density curve of O2 / GO sample as salt difference power generation membrane material in LiCl environment.

[0044] Fig. 20 is Ti in Example 1 0.87 IV curve of O2 / GO sample as salt difference electricity generating membrane material in NaCl environment. DETAILED DESCRIPTION

[0045] The present invention will be further described below through specific embodiments and accompanying drawings.

[0046] The concept of the present invention is: the present invention forms a nanofluid membrane with micro / nano channels by preparing a two-dimensional oxide heterostructure rich in cation defects, so that ions can selectively move from a concentrated salt solution to a dilute salt solution driven by a salinity gradient to generate electricity. On the one hand, due to the rich cation defects in the two-dimensional oxide heterostructure, 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.

[0047] Due to Ti 0.87 O. Ti 0.91 O2, MnO2, Ca2Nb3O 10 They are both atomically thin two-dimensional nanosheets and are negatively charged, so they are combined with the TiO2-assembled GO 0.87 O2 / GO、Ti 0.91 O2 / GO, MnO2 / GO, Ca2Nb3O 10 / GO heterostructure materials have similar physical and chemical properties, so the present invention only uses Ti 0.87 Take O2 / GO as an example for explanation.

[0048] Combination Figure 1 The use of the two-dimensional oxide heterostructure rich in cation defects in the present invention in generating electricity from salinity difference comprises the following steps:

[0049] Step 1, prepare a two-dimensional oxide nanosheet suspension rich in cation defects and a graphene oxide suspension with carbon defects according to the method described in the existing literature, ultrasonically mix a certain volume of the two-dimensional oxide nanosheet suspension rich in cation defects and the graphene oxide suspension in a certain proportion for 30 minutes, stir for 2 hours, and form a stable two-dimensional oxide heterostructure suspension rich in cation defects.

[0050] Step 2: The suspension in step 2 is filtered under a pressure of 800 mbar for about 1 day, and then dried at 25° C. to obtain a nanofluid membrane.

[0051] 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.

[0052] Example 1

[0053] (1) A mixture of 95 mmol TiO2, 22 mmol K2CO3 and 7 mmol Li2CO3 was ground and then heat treated at 1073 K for 1 h. The resulting solid was ground again for 30 min and then calcined at 1273 K for 20 h to obtain K 0.8 Ti 1.73 Li 0.27 O4 layered titanate. The generated K 0.8 Ti 1.73 Li 0.27 O4 in 1 mol L -1 The mixture was stirred in a hydrochloric acid solution for 3 days. It was washed with deionized water several times, filtered, and dried at 25°C overnight to obtain H 1.07 Ti 1.73 O4·H2O. Then, 2g H 1.07 Ti 1.73 O4·H2O was oscillated with 500 mL TBAOH aqueous solution for more than 14 days to obtain a stable monolayer Ti 0.87 O2 nanosheet colloidal suspension. AFM test was performed on it, such as Figure 2 As shown, the peeled Ti 0.87 The O2 nanosheets are single-layer nanosheets with a thickness of about 1.1 nm. TEM tests were performed on them. Figure 3 As shown in Figure 2, the material has a two-dimensional sheet structure composed of nanosheets. HAADF-STEM test was performed on it, as shown in Figure 2. Figure 4 As shown in Figure 2, many Ti defects are randomly distributed on the surface of the nanosheets, proving the successful preparation of cation-defect-rich two-dimensional transition metal oxide nanosheet materials. The exfoliated nanosheet suspension was freeze-dried to obtain Ti 0.87 O2 nanosheet powder, and XRD test was performed on it, such as Figure 5 As shown in the figure, three significant diffraction peaks appeared in the XRD spectrum at 5°, 10° and 15°, which are the 010, 020 and 030 out-of-plane reflections of the two-dimensional layered structure, proving that Ti 0.87 The successful preparation of O2 materials. 0.87 O2 nanosheet powder was subjected to Raman test, such as Figure 6 As shown, the Raman spectra are at 285, 448, and 704 cm -1 There are three characteristic peaks at 200-900 cm -1 Ti-O vibration within the range.

[0054] (2) Through 50mL single layer Ti 0.87 The O2 nanosheet colloidal suspension was ultrasonically mixed with 50 mL of monolayer GO suspension for 30 min and stirred for 2 h to prepare a stable TiO2 nanosheet colloidal suspension by liquid phase self-assembly. 0.87O2 / GO mixed suspension. AFM test was performed on the GO suspension, such as Figure 7 As shown in Figure 2, the exfoliated GO nanosheets are single-layer nanosheets with a thickness of about 0.8 nm. TEM tests were performed on the GO suspension. Figure 8 As shown in Figure 2, GO material has a two-dimensional sheet structure composed of nanosheets. HRTEM test of GO suspension, such as Fig. 9 As shown in Figure 2, many carbon defects are distributed on the surface of GO nanosheets, proving the successful preparation of GO nanosheet materials rich in cationic defects. The GO nanosheet suspension was freeze-dried to obtain GO nanosheet powder, which was subjected to XRD testing, as shown in Figure 2. Fig.10 As shown in the XRD spectrum, there is an obvious intensity peak at about 10.7° at 2θ value, corresponding to the 001 reflection, which proves the successful preparation of GO material. Raman test was performed on GO nanosheet powder, as shown in Fig.11 As shown, the Raman spectrum has two characteristic peaks D (1350cm -1 ) and G(1590cm -1 ), representing sp 3 Hybrid vibration of defects and sp 2 In-plane vibration of carbon atoms.

[0055] (3) Use a PTFE filter membrane with a diameter of 50 mm and a pore size of 220 nm, assemble the filtration device, and connect the vacuum pump. Absorb a certain volume of Ti in step 3. 0.87 The O2 / GO mixed suspension was slowly and evenly added to the container, and the vacuum pump was turned on to filter at a pressure of 800 mbar for about 1 day. After the filtration was completed, it was dried at room temperature. After drying, the Ti with a certain thickness could be peeled off from the PTFE filter membrane. 0.87 O2 / GO nanofluid film. XRD test was performed on it, such as Fig.12 As shown in Figure 1, the XRD spectrum shows three significant diffraction peaks at 5°, 10° and 15°, which are the 010, 020 and 030 out-of-plane reflections of the two-dimensional layered structure. Fig.13 As shown, two characteristic peaks (1350cm -1 ) and G peak (1590cm -1 ) represent sp 3 Hybrid vibration of defects and sp 2 The in-plane vibration of carbon atoms. FT-IR test is performed on it, such as Fig.14 As shown, the FT-IR spectrum shows that at 1050 cm -1 and 1627cm -1 There are two prominent bands at ∼650 cm-1, which can be attributed to the COC and C=C functional groups within the graphene oxide structure. -1There is a characteristic band at the location, which belongs to Ti 0.87 Ti-O functional group of O2 structure.

[0056] (4) The nanofluid membrane in step 3 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 the 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 Fig.15 As shown, the power density is 20.1Wm in a salinity difference environment of 50 times NaCl. -2 , indicating that the material has good salt difference electricity generation performance. Fig.16 As shown, the power density is 8.5 W m in a salinity difference environment of 50 times that of CaCl2. -2 .like Fig.17 As shown in Figure 2, the power density is 6.7 W m in a salinity difference environment of 50 times that of MgCl2. -2 .like Fig.18 As shown in Figure 2, the power density in an environment with a salt difference of 50 times that of KCl is 23.1 W m -2 .like Fig.19 As shown, the power density is 10.9Wm 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. 20 As shown, an open circuit voltage of 146.2 mV and a short circuit current of 22.2 μA can be generated in a salinity difference environment of 50 times that of NaCl.

Claims

1. Application of a two-dimensional oxide heterostructure material rich in cation defects in salt difference power generation.

2. The use according to claim 1, characterized in that The application refers to preparing a two-dimensional oxide heterostructure material rich in cation defects 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.

3. The use according to claim 1, characterized in that The application comprises the following steps: Step 1, a certain volume of a suspension of a two-dimensional oxide heterostructure material rich in cation defects is subjected to vacuum filtration on a filter membrane to obtain a filter membrane with a two-dimensional heterostructure deposit; Step 2, after vacuum drying the filter membrane with the two-dimensional heterogeneous structure 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 obtain 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 Cation-defect-rich two-dimensional oxide heterostructures for Ti 0.87 O2 / GO、Ti 0.91 O2 / GO, MnO2 / GO, Ca2Nb3O 10 / GO, preferably Ti 0.87 O2 / GO.

5. The use according to claim 3, characterized in that In step 1, the concentration of the suspension of the two-dimensional oxide heterostructure material rich in cation defects is 0.5~10 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 an AAO filter membrane, preferably a PTFE filter membrane.

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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