A sodium-doped lanthanum titanate / borate composite catalytic material and its preparation method and application

Abstract

The present invention discloses a sodium-doped lanthanum titanate / borate composite catalytic material and its preparation method and application. The sodium-doped lanthanum titanate / borate composite catalytic material is La 1.33‑x Na 3x Ti2O6 / Na3La2(BO3)3 composite material, the La 1.33‑x Na 3x In the Ti2O6 / Na3La2(BO3)3 composite material, the molar fraction of Na3La2(BO3)3 is 35% to 75%; the La 1.33‑x Na 3x In Ti2O6, 3x is 0.16 to 0.54. It is prepared by uniformly mixing lamellar lanthanum titanate and sodium borohydride in a specific mass ratio, followed by annealing in an inert atmosphere. This composite catalytic material exhibits excellent interfacial contact, effectively improving carrier separation and migration efficiency, accelerating electron transfer, and exhibiting excellent photocatalytic performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor photocatalytic hydrogen production, and particularly relates to a sodium-doped lanthanum titanate / borate composite catalytic material, a preparation method thereof, and applications thereof. Background Art

[0002] Hydrogen is an ideal clean energy source with great development potential. As a renewable secondary energy source, it not only has the characteristics of rapid reaction speed and high calorific value, but also produces only water as a combustion product, thus simultaneously alleviating energy crises and environmental pollution. Compared with traditional hydrogen production methods, solar photocatalytic water splitting offers advantages such as economic efficiency, cleanliness, and safety, and has been called the "holy grail" of chemistry. Therefore, focusing on research on solar photocatalytic water splitting is of great significance to the sustainable development of the national economy and the protection of the ecological environment.

[0003] The current conversion efficiency of solar-powered photocatalytic water splitting to hydrogen remains relatively low, and the lack of efficient photocatalysts remains a bottleneck restricting industrial development. Therefore, the preparation and development of efficient photocatalysts is essential. Perovskite-type composite oxides, due to their high structural stability and tunable physical and chemical properties, hold great promise for applications in solar energy conversion, such as photocatalytic hydrogen production. However, like most photocatalysts, single perovskite-type oxide materials suffer from limitations such as a narrow photoresponse range and severe electron-hole recombination. Consequently, extensive research has focused on modifying perovskite-type oxides to enhance their photocatalytic activity. Among these modification methods, constructing heterostructures has proven to be an effective strategy for improving photocatalytic activity by enhancing light absorption, accelerating carrier separation, and stimulating more reactive sites. Traditional heterojunction photocatalysts require two separate phases for synthesis, resulting in complex reactions, stringent lattice matching requirements, and difficulty achieving rapid interfacial charge transfer. Therefore, the development of highly photocatalytically active perovskite-type oxide-based composite photocatalysts with well-defined interfacial features and simple preparation methods is crucial. Summary of the Invention

[0004] In view of the defects and shortcomings of existing perovskite-type oxide-based photocatalysts, the first object of the present invention is to provide a sodium-doped lanthanum titanate / borate composite catalytic material with good interface characteristics, excellent photolysis hydrogen production performance and good stability.

[0005] The second object of the present invention is to provide a method for preparing a sodium-doped lanthanum titanate / borate composite catalytic material.

[0006] The third object of the present invention is to provide an application of a sodium-doped lanthanum titanate / borate composite catalytic material.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a sodium-doped lanthanum titanate / borate composite catalytic material, wherein the sodium-doped lanthanum titanate / borate composite catalytic material is composed of La 1.33-x Na 3x Ti2O6 and Na3La2(BO3)3 are composited, and in the sodium-doped lanthanum titanate / borate composite catalytic material, the molar fraction of Na3La2(BO3)3 is 35% to 75%; the La 1.33-x Na 3x In Ti2O6, 3x is 0.16~0.54.

[0009] The present invention provides a sodium-doped lanthanum titanate / borate composite catalytic material composed of La 1.33-x Na 3x Ti2O6 and Na3La2(BO3)3 are composited and have a well-matched interface structure, which can improve the activity and stability of the photocatalytic material.

[0010] In a preferred embodiment, the molar fraction of Na3La2(BO3)3 in the sodium-doped lanthanum titanate / borate composite catalytic material is 49% to 73%; 1.33-x Na 3x In Ti2O6, 3x is 0.33~0.54.

[0011] When La 1.33-x Na 3x Na in the A site of Ti2O6 lattice + When the ion content 3x is 0.33-0.54 and the molar percentage of Na3La2(BO3)3 in the composite material is 49%-73%, the sodium-doped lanthanum titanate / borate composite catalytic material has excellent photocatalytic hydrogen production performance.

[0012] Further preferably, in the sodium-doped lanthanum titanate / borate composite catalytic material, the molar fraction of Na3La2(BO3)3 is 65% to 73%; 1.33-x Na 3x In Ti2O6, 3x is 0.48~0.54.

[0013] More preferably, in the sodium-doped lanthanum titanate / borate composite catalytic material, the molar fraction of Na3La2(BO3)3 is 65%, and the La 1.33-x Na 3x In Ti2O6, 3x is 0.48. When the chemical composition is 35% La 1.17 Na 0.48 Ti2O6 / 65%Na3La2(BO3)3 has the best photocatalytic hydrogen production performance.

[0014] The present invention also provides a method for preparing a sodium-doped lanthanum titanate / borate composite catalytic material, comprising mixing La2Ti2O7 and NaBH4 to obtain a precursor, and annealing the mixture under a protective atmosphere. In the precursor, the mass ratio of La2Ti2O7:NaBH4 is 1:0.3-0.6; the annealing temperature is 550-850°C, preferably 650°C, and the annealing time is 0.5-8h, preferably 3-3.5h.

[0015] The preparation method provided by the present invention utilizes NaBH4 to induce the in-situ conversion of La2Ti2O7 into La 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3, only needs to strictly control the mass ratio of La2Ti2O7 and NaBH4, and through one-step annealing, La with good interface characteristics can be obtained. 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3 composite material. Of course, the annealing temperature and mass ratio need to be effectively controlled. If NaBH4 is added excessively, it will destroy the generated La 1.33-x Na 3x Ti2O6 crystal structure, if NaBH4 is added too little, NaBH4 cannot induce the in-situ conversion of La2Ti2O7 into La 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3; When the annealing temperature is too low, it is difficult to meet the activation energy required for the phase transformation of La2Ti2O7 and the Na + It is difficult for ions to diffuse across the barrier into La2Ti2O7 to generate La 1.33-x Na 3x Ti2O6 phase. When the annealing temperature is too high, Na + The diffusion rate is too fast, and it is difficult to control the La2Ti2O7 and NaBH4 mass ratio by controlling the annealing time. 1.33-x Na 3x Ti2O6 phase Na + In addition, when the excess Na + Ion infiltration will destroy La 1.33-x Na 3x The lattice stability of the Ti2O6 phase causes it to decompose into amorphous TiO2 / La2O3.

[0016] In addition, the preparation method provided by the present invention can control the final product La by controlling the mass ratio of La2Ti2O7 and NaBH4 and controlling the annealing temperature and time. 1.33-x Na 3xThe doping content x of Na in Ti2O6 / Na3La2(BO3)3 and the proportion of Na3La2(BO3)3 are controlled to obtain a sodium-doped lanthanum titanate / borate composite catalytic material with specific composition and excellent performance. The inventors found that at a certain temperature, when the mass ratio of La2Ti2O7 to NaBH4 decreases, the final product La 1.33- x Na 3x The doping content x of Na in Ti2O6 / Na3La2(BO3)3 and the proportion of Na3La2(BO3)3 will increase; when the mass ratio of La2Ti2O7 to NaBH4 is fixed, when the annealing temperature is increased or the reaction time is increased, the final product La 1.33-x Na 3x The doping content x of Na in Ti2O6 / Na3La2(BO3)3 and the proportion of Na3La2(BO3)3 will both increase.

[0017] In a preferred embodiment, the La2Ti2O7 is in the form of lamellar sheets. The inventors have found that the lamellar structure can increase the specific surface area of La2Ti2O7, which is beneficial for the full contact between La2Ti2O7 and NaBH4 during the annealing process, accelerating the ion exchange process at the interface between the two phases, thereby promoting the La 1.33-x Na 3x Growth of Ti2O6 / Na3La2(BO3)3 composite catalytic materials. If bulk La2Ti2O7 raw materials are used, the annealing time required to obtain the composite catalytic material will be prolonged, and the uniformity of the resulting composite structure and good interface contact will be difficult to ensure.

[0018] In a preferred embodiment, the preparation process of La2Ti2O7 is as follows: a lanthanum source and a titanium source are prepared according to the chemical formula of La2Ti2O7, dissolved in an aqueous solution, stirred for 15-30 minutes, and then a sodium hydroxide solution is added to obtain a suspended liquid, and the resultant is obtained by hydrothermal reaction.

[0019] In a preferred embodiment, the lanthanum source is lanthanum nitrate, and the titanium source is titanium sulfate.

[0020] In a preferred embodiment, the temperature of the hydrothermal reaction is 230-250° C., and the time of the hydrothermal reaction is 23-25 hours.

[0021] In actual operation, the solid-liquid separation process is as follows: after the hydrothermal reaction is completed, the solution is naturally cooled to room temperature, and the supernatant solution is poured out to obtain a solid precipitate. The resulting solid precipitate is washed three times with deionized water and then ethanol. The centrifuge tube containing the precipitate is then placed in an insulated box and kept at 60-70°C under vacuum for 6-8 hours. The resulting powder is the lamellar La2Ti2O7.

[0022] Further preferably, in the precursor, the mass ratio is La2Ti2O7:NaBH4=1:0.4~0.6.

[0023] Preferably, the protective atmosphere is N2.

[0024] In a preferred embodiment, the annealing process is as follows: firstly heating to 550-850°C at a heating rate of 1-10°C / min, keeping the temperature for 0.5-8h, and then cooling to 25-100°C at a cooling rate of 1-10°C / min.

[0025] Further preferably, the annealing process is: first heating to 650°C at a heating rate of 5°C / min, keeping the temperature for 3-3.5h, and then cooling to 25-100°C at a cooling rate of 5°C / min.

[0026] In the actual operation process, the annealed sample was filtered and washed with a large amount of clean water until NaBH4 was dissolved, washed with ethanol three times, and dried to obtain La 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3 composite material.

[0027] The present invention also provides an application of a sodium-doped lanthanum titanate / borate composite catalytic material, wherein the sodium-doped lanthanum titanate / borate composite catalytic material is applied to photocatalytic hydrogen production.

[0028] Principles and advantages

[0029] The present invention provides a sodium-doped lanthanum titanate / borate composite catalytic material composed of La 1.33-x Na 3x Ti2O6 and Na3La2(BO3)3 are composited, which has a well-matched interface structure and can improve the activity and stability of photocatalytic materials. 1.33-x Na 3x Na in the A site of Ti2O6 lattice + The ion content 3x is 0.33-0.54, the molar percentage of Na3La2(BO3)3 in the composite material is 49%-73%, especially the chemical composition is 35% La 1.17 Na 0.48 Ti2O6 / 65% Na3La2(BO3)3 has the best photocatalytic hydrogen production performance.

[0030] The sodium-doped lanthanum titanate / borate composite catalytic material provided by the present invention is in situ grown by exchanging ions between sheets of La2Ti2O7 and NaBH4, wherein Na + Ions diffuse from the NaBH4 side across the interface into the La2Ti2O7 surface, inducing La 1.33-x Na3x Ti2O6 grows, and La / O dissolves from the La2Ti2O7 side interface due to the charge balance requirement and reacts with NaBH4 to form Na3La2(BO3)3. Since the growth rate of the crystal in the above process is controlled by the interface diffusion process, solid La 1.33- x Na 3x The Ti2O6 / Na3La2(BO3)3 composite structure gradually grows outward from the interface between the two phases, forming a close contact interface with mutually matched lattices.

[0031] The preparation method provided by the present invention utilizes NaBH4 to induce the in-situ conversion of La2Ti2O7 into La 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3, only needs to strictly control the mass ratio of La2Ti2O7 and NaBH4, and through one-step annealing, La with good interface characteristics can be obtained. 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3 composite material. Of course, the annealing temperature and mass ratio need to be effectively controlled. If NaBH4 is added excessively, it will destroy the generated La 1.33-x Na 3x Ti2O6 crystal structure, if NaBH4 is added too little, NaBH4 cannot induce the in-situ conversion of La2Ti2O7 into La 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3; When the annealing temperature is too low, it is difficult to meet the activation energy required for the phase transformation of La2Ti2O7 and the Na + It is difficult for ions to diffuse across the barrier into La2Ti2O7 to generate La 1.33-x Na 3x Ti2O6 phase. When the annealing temperature is too high, Na + The diffusion rate is too fast, and it is difficult to control the La2Ti2O7 and NaBH4 mass ratio by controlling the annealing time. 1.33-x Na 3x Ti2O6 phase Na + In addition, when the excess Na + Ion infiltration will destroy La 1.33-x Na 3x The lattice stability of the Ti2O6 phase causes it to decompose into amorphous TiO2 / La2O3.

[0032] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects:

[0033] 1) La of the present invention 1.33-x Na 3xTi2O6 / Na3La2(BO3)3 catalytic material has good interface characteristics, high catalytic activity and good stability, and can be widely used as a photocatalyst.

[0034] 2) The method of using NaBH4 to induce La2Ti2O7 conversion in the present invention can selectively prepare amorphous La2Ti2O7 materials or in-situ synthesize La2Ti2O7 by changing the mass ratio of NaBH4 at a lower temperature. 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3 composite photocatalyst; this method has the advantages of wide application range, simple process, mild reaction conditions and mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the XRD pattern of the La2Ti2O7 material prepared in Example 1.

[0036] Figure 2 This is the SEM image of the La2Ti2O7 material prepared in Example 1.

[0037] Figure 3 These are the XRD patterns of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0038] Figure 4 These are Raman spectra of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0039] Figure 5 La prepared in Example 1 1.33-x Na 3x EDSMAPPING diagram of Ti2O6 / Na3La2(BO3)3 catalytic material.

[0040] Figure 6 La prepared in Example 1 1.33-x Na 3x TEM image of Ti2O6 / Na3La2(BO3)3 catalytic material.

[0041] Figure 7 This is a graph showing the change in hydrogen production rate over time for the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0042] Figure 8 This is a graph of the average hydrogen production rates of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below with reference to non-limiting specific examples.

[0044] The reagents used in the examples of the present invention are all commercially available.

[0045] Example 1

[0046] Preparation of La2Ti2O7 flakes:

[0047] According to the molar ratio of La:Ti = 1:1, 4.33g of lanthanum nitrate and 2.40g of titanium sulfate were weighed and dissolved in 65mL of aqueous solution. Stir for 15 minutes to fully dissolve to obtain a clear solution. Then, 10mL of 0.1M sodium hydroxide solution was added under vigorous stirring to form a suspension solution.

[0048] The obtained suspension was poured into an autoclave, placed in an insulated box, heated to 230° C. for 24 hours, and then naturally cooled to room temperature; the supernatant solution was poured out to obtain a precipitate.

[0049] The obtained precipitate was washed three times with deionized water and ethanol in turn, centrifuged at a speed of 12000 r / min for 4 minutes, and then dried in an insulated box at 60°C for 12 hours. After grinding, flaky La2Ti2O7 was obtained.

[0050] Figure 1 This is the XRD pattern of the La2Ti2O7 material prepared in Example 1.

[0051] Figure 2 This is the SEM image of the La2Ti2O7 material prepared in Example 1. It can be seen from the figure that the obtained La2Ti2O7 material is a flaky nanostructure.

[0052] 2. Preparation of La2Ti2O7 and NaBH4 mixture precursor:

[0053] Mix 300 mg La2Ti2O7 and 120 mg NaBH4 in a mass ratio of 5:2 and grind for 20 min to ensure uniform dispersion.

[0054] 3. High temperature annealing modification:

[0055] The precursor mixture was sealed in a tube furnace and purged with nitrogen for 30 minutes to remove air from the quartz tube. The temperature was then raised to 650°C at a rate of 5°C / min and held for 2 hours before being naturally cooled to 80°C and removed. Nitrogen was continuously introduced into the quartz tube as a protective atmosphere throughout the annealing process to obtain a solid product.

[0056] 4. Washing and drying

[0057] The solid product obtained in step 3 was filtered and washed with a large amount of deionized water, washed three times with ethanol, centrifuged at a speed of 12000 r / min for 4 minutes, and dried in an insulated box at 60°C for 12 hours. After grinding, powdered La 1.33- x Na 3x Ti2O6 / Na3La2(BO3)3 catalytic material.

[0058] The chemical formula of the catalytic material obtained in Example 1 is: La 1.17 Na 0.48 Ti2O6 / Na3La2(BO3)3; wherein the molar fraction of Na3La2(BO3)3 is 65%.

[0059] Figure 3 The XRD patterns of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in FIG. 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3 catalytic material has a crystalline structure.

[0060] Figure 4 The Raman spectra of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in FIG. 1.33-x Na 3x La in Ti2O6 / Na3La2(BO3)3 catalytic material 1.33-x Na 3x Raman vibration modes corresponding to Ti2O6 and Na3La2(BO3)3.

[0061] Figure 5 La prepared in Example 1 1.33-x Na 3x EDSMAPPING diagram of Ti2O6 / Na3La2(BO3)3 catalytic material. It can be seen that the La prepared in Example 1 1.33-x Na 3x Na, B, Ti, La and O are evenly distributed in the Ti2O6 / Na3La2(BO3)3 catalytic material.

[0062] Figure 6 La prepared in Example 1 1.33-x Na 3x TEM image of Ti2O6 / Na3La2(BO3)3 catalytic material. As can be seen from the figure, the obtained La 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3 has a good contact interface structure.

[0063] 4. Photocatalytic performance test

[0064] The performance of the photocatalyst was determined through experimental data of photocatalytic hydrogen production. In a closed-circulation vacuum system, 50 mg of photocatalyst was uniformly dispersed in 100 mL of a sacrificial agent solution, which was a diethanolamine solution with a volume fraction of 10 vol%. A 300 W xenon lamp was used as the light source for the entire experiment. A filter (λ ≥ 420 nm) was used as the cutoff wavelength. When the circulating condensation system was in operation, the circulating temperature was set to 10 ° C. The hydrogen production process of the photocatalyst was analyzed using a gas chromatograph (GC4000).

[0065] Figure 7 The graph of hydrogen production rate over time shows that the La obtained in Example 1 1.33-x Na 3x The hydrogen production rate of Ti2O6 / Na3La2(BO3)3 catalytic material increases steadily with the increase of illumination time, with the fastest growth rate.

[0066] Figure 8 The average hydrogen production rate diagram is shown in the figure. It can be seen from the figure that the La obtained in Example 1 1.33-x Na 3x The photocatalytic hydrogen production rate of Ti2O6 / Na3La2(BO3)3 was 660 μmol g -1 h -1 , with the best photocatalytic activity.

[0067] Example 2

[0068] Compared with Example 1, in the preparation of the La2Ti2O7 and NaBH4 mixture precursor, 300 mg of La2Ti2O7 and 60 mg of NaBH4 were mixed at a mass ratio of 10:3 and ground for 20 minutes to ensure uniform dispersion. The remaining steps were consistent with Example 1.

[0069] The chemical formula of the catalytic material obtained in Example 2 is: La 1.22 Na 0.33 Ti2O6 / Na3La2(BO3)3, where the molar fraction of Na3La2(BO3)3 is 49%.

[0070] Figure 3 The XRD patterns of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in FIG. 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3 has a crystal structure.

[0071] Figure 4The Raman spectra of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3 are shown in FIG. 1.33-x Na 3x La in Ti2O6 / Na3La2(BO3)3 catalytic material 1.33-x Na 3x Raman vibration modes corresponding to Ti2O6 and Na3La2(BO3)3.

[0072] Figure 7 The graph of hydrogen production rate over time shows that the La obtained in Example 2 1.33-x Na 3x The hydrogen production rate of Ti2O6 / Na3La2(BO3)3 catalytic material increases steadily with the increase of illumination time.

[0073] Figure 8 The average hydrogen production rate diagram is shown in the figure. It can be seen from the figure that the La obtained in Example 2 1.33-x Na 3x The photocatalytic hydrogen production rate of Ti2O6 / Na3La2(BO3)3 was 230 μmol g -1 h -1 , and has good visible light photocatalytic activity.

[0074] Example 3

[0075] Compared with Example 1, in the preparation of the La2Ti2O7 and NaBH4 mixture precursor, 300 mg of La2Ti2O7 and 120 mg of NaBH4 were mixed at a mass ratio of 5:3 and ground for 20 minutes to ensure uniform dispersion. The remaining steps were consistent with Example 1.

[0076] The chemical formula of the catalytic material obtained in Example 2 is: La 1.15 Na 0.54 Ti2O6 / Na3La2(BO3)3, where the molar fraction of Na3La2(BO3)3 is 73%.

[0077] Figure 3 The XRD patterns of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in FIG. 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3 has a crystal structure.

[0078] Figure 4 The Raman spectra of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in FIG.1.33-x Na 3x La in Ti2O6 / Na3La2(BO3)3 catalytic material 1.33-x Na 3x Raman vibration modes corresponding to Ti2O6 and Na3La2(BO3)3.

[0079] Figure 7 The graph of hydrogen production rate over time shows that the La obtained in Example 3 1.33-x Na 3x The hydrogen production rate of Ti2O6 / Na3La2(BO3)3 catalytic material increases steadily with the increase of illumination time.

[0080] Figure 8 The average hydrogen production rate diagram is shown in the figure. It can be seen from the figure that the La obtained in Example 3 1.33-x Na 3x The photocatalytic hydrogen production rate of Ti2O6 / Na3La2(BO3)3 was 420 μmol g -1 h -1 , with suboptimal visible light photocatalytic activity.

[0081] Comparative Example 1

[0082] Compared with Example 1, in the preparation of the La2Ti2O7 and NaBH4 mixture precursor, 300 mg of La2Ti2O7 and 300 mg of NaBH4 were mixed at a mass ratio of 1:1 and ground for 20 minutes to ensure uniform dispersion. The remaining steps were consistent with Example 1.

[0083] The chemical formula of the catalytic material obtained in Comparative Example 1 is: Na3La2(BO3)3 / TiO2 / La2O3.

[0084] Figure 3 The XRD patterns of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown. As can be seen from the figure, the composite catalytic material obtained in Example 3 is composed of a Na3La2(BO3)3 crystalline phase and an amorphous phase of lanthanum / titanium oxide, indicating that excessive addition of NaBH4 will destroy the generated La 1.33-x Na 3x Ti2O6 crystal structure.

[0085] Figure 4 The Raman spectra of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in FIG. 1.33-x Na 3xThe vibration mode of Ti2O6 completely disappears, and only the Raman vibration mode of Na3La2(BO3)3 exists, indicating that the La / Ti oxide is completely amorphous under the condition of excessive NaBH4 addition.

[0086] Figure 7 3 is a graph showing the change of hydrogen production rate over time. It can be seen from the graph that the hydrogen production rate of the lanthanum titanium amorphous oxide / Na3La2(BO3)3 catalytic material obtained in Comparative Example 1 steadily increases with the increase of illumination time.

[0087] Figure 8 The average hydrogen production rate diagram shows that the photocatalytic hydrogen production rate of lanthanum titanium amorphous oxide / Na3La2(BO3)3 obtained in Comparative Example 1 is 63μmolg -1 h -1 , and has visible light photocatalytic activity.

[0088] Comparative Example 2

[0089] Compared with Example 1, in the preparation of the La2Ti2O7 and NaBH4 mixture precursor, 300 mg of La2Ti2O7 and 30 mg of NaBH4 were mixed at a mass ratio of 10:1 and ground for 20 minutes to ensure uniform dispersion. The remaining steps were consistent with Example 1.

[0090] The chemical formula of the catalytic material obtained in Comparative Example 2 is: La2Ti2O7.

[0091] Figure 3 The XRD patterns of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown. As can be seen from the figure, the composite catalytic material obtained in Example 4 is composed of an amorphous phase.

[0092] Figure 4 The Raman spectra of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown. It can be observed from the figure that the catalytic material obtained in Example 4 is composed of amorphous La2Ti2O7, and its Raman vibration mode is consistent with that of the original La2Ti2O7.

[0093] Figure 7 Graph showing the change of hydrogen production rate over time. From the graph, we can see that the hydrogen production rate of the amorphous La2Ti2O7 catalytic material obtained in Comparative Example 2 does not react with the increase of illumination time.

[0094] Figure 8 2 is a graph of average hydrogen production rate. As can be seen from the graph, the La2Ti2O7 catalytic material obtained in Comparative Example 2 is consistent with the original La2Ti2O7 and does not show visible light photocatalytic hydrogen production activity.

[0095] Comparative Example 3

[0096] Compared with Example 1, in the preparation of the La2Ti2O7 and NaBH4 mixture precursor, 300 mg of La2Ti2O7 and 60 mg of NaBH4 were mixed at a mass ratio of 5:1 and ground for 20 minutes to ensure uniform dispersion. The remaining steps were consistent with Example 1.

[0097] The chemical formula of the catalytic material obtained in Comparative Example 3 is: La 1.28 Na 0.16 Ti2O6 / Na3La2(BO3)3, where the molar fraction of Na3La2(BO3)3 is 37%.

[0098] Figure 3 The XRD patterns of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in FIG. 1.33-x Na 3x Ti2O6 / Na3La2(BO3)3 has a crystal structure.

[0099] Figure 4 The Raman spectra of the catalytic materials prepared in Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are shown in FIG. 1.33-x Na 3x La in Ti2O6 / Na3La2(BO3)3 catalytic material 1.33-x Na 3x Raman vibration modes corresponding to Ti2O6 and Na3La2(BO3)3.

[0100] Figure 7 The graph of hydrogen production rate changing with time shows that the La obtained in Comparative Example 3 1.33-x Na 3x The hydrogen production rate of Ti2O6 / Na3La2(BO3)3 catalytic material increases steadily with the increase of illumination time.

[0101] Figure 8 The average hydrogen production rate diagram is shown in the figure. It can be seen from the figure that the La obtained in Comparative Example 3 1.33-x Na 3x The photocatalytic hydrogen production rate of Ti2O6 / Na3La2(BO3)3 was 15 μmol g -1 h -1 , and has weak visible light photocatalytic activity.

Claims

1. A method for preparing a sodium-doped lanthanum titanate / borate composite catalytic material, characterized by: La2Ti2O7 and NaBH4 are mixed to obtain a precursor, and the precursor is annealed under a protective atmosphere, wherein the precursor has a mass ratio of La2Ti2O7:NaBH4=1:0.3-0.6; the annealing temperature is 550-850°C, and the annealing time is 0.5-8h; The sodium-doped lanthanum titanate / borate composite catalytic material is composed of La 1.33-x Na 3x Ti2O6 and Na3La2(BO3)3 are composited, and in the sodium-doped lanthanum titanate / borate composite catalytic material, the molar fraction of Na3La2(BO3)3 is 35% to 75%; the La 1.33-x Na 3x In Ti2O6, 3x is 0.16~0.

54.

2. The method for preparing a sodium-doped lanthanum titanate / borate composite catalytic material according to claim 1, characterized in that: The La2Ti2O7 is in the form of lamellar sheets.

3. The method for preparing a sodium-doped lanthanum titanate / borate composite catalytic material according to claim 1, characterized in that: The preparation process of La2Ti2O7 is as follows: lanthanum source and titanium source are prepared according to the chemical formula of La2Ti2O7, dissolved in aqueous solution, stirred for 15-30 minutes, and then sodium hydroxide solution is added to obtain a suspended liquid, and the resultant is obtained by hydrothermal reaction; The lanthanum source is lanthanum nitrate, and the titanium source is titanium sulfate; The temperature of the hydrothermal reaction is 230-250° C., and the time of the hydrothermal reaction is 23-25 h.

4. The method for preparing a sodium-doped lanthanum titanate / borate composite catalytic material according to claim 1, characterized in that: In the precursor, the mass ratio is La2Ti2O7:NaBH4=1:0.4~0.

6.

5. The method for preparing a sodium-doped lanthanum titanate / borate composite catalytic material according to claim 1, characterized in that: The protective atmosphere is N2; The annealing process is: firstly heating to 550-850°C at a heating rate of 1-10°C / min, keeping the temperature for 0.5-8h, and then cooling to 25-100°C at a cooling rate of 1-10°C / min.

6. The method for preparing a sodium-doped lanthanum titanate / borate composite catalytic material according to claim 1, characterized in that: The annealing process is as follows: firstly heating to 650°C at a heating rate of 5°C / min, keeping the temperature for 3-3.5h, and then cooling to 25-100°C at a cooling rate of 5°C / min.

7. The method for preparing a sodium-doped lanthanum titanate / borate composite catalytic material according to claim 1, characterized in that: In the sodium-doped lanthanum titanate / borate composite catalytic material, the molar fraction of Na3La2(BO3)3 is 49% to 73%; 1.33-x Na 3x In Ti2O6, 3x is 0.33~0.

54.

8. The method for preparing a sodium-doped lanthanum titanate / borate composite catalytic material according to claim 1, characterized in that: In the sodium-doped lanthanum titanate / borate composite catalytic material, the molar fraction of Na3La2(BO3)3 is 65% to 73%; 1.33-x Na 3x In Ti2O6, 3x is 0.48~0.

54.

9. Use of a sodium-doped lanthanum titanate / borate composite catalytic material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The sodium-doped lanthanum titanate / borate composite catalytic material is applied to photocatalytic hydrogen production.

Images