ALUMINA-BASED HETEROJUNCTION MATERIAL WITH ABUNDANT OXYGEN VACANCIES AND PREPARATION METHOD THEREOF

Abstract

Disclosed are an alumina-based heterojunction material with abundant oxygen vacancies and a preparation method thereof. The heterojunction material is composed of alumina with abundant oxygen vacancies and bismuth-rich bismuth oxychloride. The method includes mixing aluminum nitrate nonahydrate, bismuth nitrate pentahydrate, an ammonium salt and urea, each in certain amount, under stirring to obtain a mixture B, placing the mixture B in a muffle furnace, heating the mixture B and continuing the stirring to gradually melt the mixture B to form an ionic liquid B; and subjecting the ionic liquid B to a spontaneous combustion reaction in the muffle furnace to obtain a product B, and cooling the product B to room temperature to obtain the alumina-based heterojunction material with abundant oxygen vacancies.

Claims

1. An alumina-based heterojunction material with abundant oxygen vacancies, which is composed of Al.sub.2O.sub.3 with abundant oxygen vacancies and bismuth-rich bismuth oxychloride Bi.sub.12O.sub.17Cl.sub.2.

2. A method for preparing the Al.sub.2O.sub.3 with abundant oxygen vacancies as defined in claim 1, comprising mixing aluminum nitrate nonahydrate, an ammonium salt, and urea in a molar ratio of 1:(0.5-3.0):(0.5-2.0) under stirring to obtain a mixture A, placing the mixture A in a muffle furnace, and heating the mixture A at a temperature of 200-600° C. to gradually melt the mixture A to form an ionic liquid A; and maintaining the temperature, subjecting the ionic liquid A to a spontaneous combustion reaction in the muffle furnace to obtain a product A, and cooling the product A to room temperature to obtain the Al.sub.2O.sub.3 with abundant oxygen vacancies.

3. The method of claim 2, wherein the mixture A is heated at a temperature of 500° C.

4. The method of claim 2, wherein the ammonium salt comprises at least one ammonium halide selected from the group consisting of dimethylammonium chloride, trimethylammonium chloride, tetramethylammonium chloride, diethylammonium chloride, 2-bromoethylamine hydrobromate, tetrabutyl ammonium bromide, and tetraethylammonium iodide.

5. The method of claim 2, wherein the molar ratio of aluminum nitrate nonahydrate, the ammonium salt, and urea is in a range of 1:(0.5-1.5):(0.5-1.0).

6. The method of claim 2, wherein the molar ratio of aluminum nitrate nonahydrate, the ammonium salt, and urea is 1:1.5:0.5.

7. A method for preparing an alumina-based heterojunction material with abundant oxygen vacancies, comprising steps of a) mixing bismuth nitrate pentahydrate, aluminum nitrate nonahydrate, an ammonium salt, and urea under stirring in a molar ratio of 12:(1-4):2:(2-12) to obtain a mixture B, placing the mixture B in a muffle furnace, heating the mixture B at a temperature of 200-500° C. to gradually melt the mixture B to form an ionic liquid B, and continuing the stirring to be uniform; and b) maintaining the temperature, subjecting the ionic liquid B to a spontaneous combustion reaction in the muffle furnace to obtain a product B, and cooling the product B to room temperature to obtain the alumina-based heterojunction material with abundant oxygen vacancies.

8. The method of claim 7, wherein the molar ratio of bismuth nitrate pentahydrate, aluminum nitrate nonahydrate, the ammonium salt, and urea is in a range of 12:(1.5-3):2:(4-8).

9. The method of claim 7, wherein the mixture B is heated at a temperature of 300-450° C.

10. The method of claim 7, wherein the mixture B is heated at a temperature of 350-400° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 shows X-ray diffraction (XRD) patterns of the defective alumina prepared in Examples 1-4.

[0030] FIG. 2 shows ultraviolet-visible diffuse reflection spectroscopy (UV-Vis DRS) spectra of the defective alumina prepared in Examples 1-4.

[0031] FIG. 3 shows an electron paramagnetic resonance (EPR) spectrum of the defective alumina prepared in Example 1.

[0032] FIG. 4 shows a .sup.27Al nuclear magnetic resonance (.sup.27Al NMR) spectrum of the defective alumina prepared in Example 1.

[0033] FIG. 5 shows a N.sub.2 adsorption-desorption curve of the defective alumina prepared in Example 1.

[0034] FIG. 6 is a transmission electron microscope (TEM) image of the Al.sub.2O.sub.3/Bi.sub.12O.sub.17Cl.sub.2 composite prepared in Example 5.

[0035] FIG. 7 shows an oxygen temperature-programmed desorption (O.sub.2-TPD) curve of Al.sub.2O.sub.3/Bi.sub.12O.sub.17Cl.sub.2 composite prepared in Example 5.

[0036] FIG. 8 shows an electron paramagnetic resonance (EPR) spectrum of .circle-solid.O.sub.2.sup.− (EPR- .circle-solid.OH) in Al.sub.2O.sub.3/Bi.sub.12O.sub.17Cl.sub.2 composite prepared in Example 5.

[0037] FIG. 9 shows an electron paramagnetic resonance spectrum of .circle-solid.OH (EPR- .circle-solid.OH) in Al.sub.2O.sub.3/Bi.sub.12O.sub.17Cl.sub.2 composite prepared in Example 5.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The present disclosure is further described in detail below with reference to the drawings and specific examples. As used herein, the phrase “muffle furnace” means a furnace where materials are heated to produce changes in physiological properties.

Example 1

[0039] Al.sub.2O.sub.3 with unsaturated coordination and abundant oxygen vacancies was prepared as follows:

[0040] (1) Aluminum nitrate nonahydrate, diethylammonium chloride, and urea were mixed under stirring in a molar ratio of 1:0.5:2, obtaining a mixture A. The mixture A was then placed in a muffle furnace and heated to 200° C. In the muffle furnace, the mixture A was gradually melted to form an ionic liquid A.

[0041] (2) The above temperature was maintained in the muffle furnace, and the ionic liquid A was subjected to a spontaneous combustion reaction, obtaining a product A. The product A was cooled to room temperature, obtaining a pure Al.sub.2O.sub.3 with unsaturated coordination and abundant oxygen vacancies.

[0042] The obtained product was characterized by XRD, UV-Vis DRS, EPR, .sup.27Al NMR and N.sub.2 adsorption and desorption tests. The results are shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4 and FIG. 5 respectively.

[0043] The XRD patterns are shown in FIG. 1, which have scanning angle (2θ) as abscissa, and diffraction peak intensity as ordinate. From the XRD pattern {circle around (1)} in FIG. 1, it can be seen that the product has a pure Al.sub.2O.sub.3 phase.

[0044] The UV-Vis DRS spectra are shown in FIG. 2, which have wavelength as abscissa and intensity as ordinate. According to curve CD in FIG. 2, a band gap is calculated as about 4.927 eV according to a formula α(hv)=a(hv- E.sub.g).sup.2. Due to the wide band gap, the prepared Al.sub.2O.sub.3 material could not be excited by light, which makes it possible to act as an insulator for adsorbing oxygen and storing electrons.

[0045] The EPR spectrum is shown in FIG. 3, which has magnetic field intensity (B) as abscissa and signal intensity as ordinate. It can be seen from the curve CD in FIG. 3 that there is an obvious signal peak at g=2.000, which corresponds to the characteristic signal of oxygen vacancy, indicating the existence of oxygen vacancies in the prepared Al.sub.2O.sub.3 material.

[0046] The .sup.27Al NMR spectrum is shown in FIG. 4, which has chemical shift (ppm) as abscissa and absorption peak intensity as ordinate. It can be seen from the curve {circle around (1)} in FIG. 4 that there are four-coordinated alumina (14.98 ppm) and six-coordinated alumina (65.36 ppm).

[0047] The curve of N.sub.2 absorption and desorption is shown in FIG. 5, which has relative pressure as abscissa and quantity adsorbed as ordinate. In FIG. 5, “A” represents adsorption and “D” represents desorption. The curve in the inset of FIG. 5 has average pore diameter as abscissa, and dV/dD pore volume as ordinate. According to the curve {circle around (1)}, i.e. N.sub.2 adsorption-desorption curve in FIG. 5, the prepared Al.sub.2O.sub.3 material has a specific surface area of 45.2467 m.sup.2/g and an average pore diameter of 3.0120 nm. The obtained defective Al.sub.2O.sub.3 has large specific surface area.

Example 2

[0048] Al.sub.2O.sub.3 with unsaturated coordination and abundant oxygen vacancies was prepared as follows:

[0049] (1) Aluminum nitrate nonahydrate, diethylammonium chloride, trimethylammonium chloride, and urea were mixed under stirring in a molar ratio of 1:0.5:2.5:0.5, obtaining a mixture A. The mixture A was then placed in a muffle furnace and heated to 400° C. In the muffle furnace, the mixture A was gradually melted to form an ionic liquid A.

[0050] (2) The above temperature was maintained in the muffle furnace, and the ionic liquid A was subjected to a spontaneous combustion reaction, obtaining a product A., The product A was cooled to room temperature, obtaining the final product.

[0051] The obtained final product was characterized by XRD, and UV-Vis DRS. The results are shown in FIG. 1 (curve {circle around (2)}) and FIG. 2 ({circle around (2)}) respectively. The curve {circle around (2)} of the XRD patterns in FIG. 1 shows that the product has an Al.sub.2O.sub.3 crystalline phase. The curve {circle around (2)} of the UV-Vis DRS spectra in FIG. 2 shows that the alumina prepared in this example has the same light absorption characteristics as the alumina prepared with different raw material ratios in other examples.

Example 3

[0052] Al.sub.2O.sub.3 with unsaturated coordination and abundant oxygen vacancies was prepared as follows:

[0053] (1) Aluminum nitrate nonahydrate, tetrabutylammonium bromide, and urea were mixed under stirring in a molar ratio of 1:1:0.5, obtaining a mixture A. The mixture A was then placed in a muffle furnace and heated to 600° C. In the muffle furnace, the mixture A was gradually melted to form an ionic liquid A.

[0054] (2) The above temperature was maintained in the muffle furnace, and the ionic liquid A was subjected to a spontaneous combustion reaction, obtaining a product A. The product A was cooled to room temperature, obtaining a pure Al.sub.2O.sub.3 with unsaturated coordination and abundant oxygen vacancies.

[0055] The obtained product was characterized by XRD, and UV-Vis DRS. The results are shown in FIG. 1 (curve {circle around (3)}) and FIG. 2 (curve {circle around (3)}) respectively. The curve {circle around (3)} of the XRD patterns in FIG. 1 shows that the product has an Al.sub.2O.sub.3 crystalline phase. The curve {circle around (3)} of the UV-Vis DRS spectra in FIG. 2 shows that the alumina prepared in this example has the same light absorption characteristics as the alumina prepared with different raw material ratios in other examples.

Example 4

[0056] Al.sub.2O.sub.3 with unsaturated coordination and abundant oxygen vacancies was prepared as follows:

[0057] (1) Aluminum nitrate nonahydrate, tetrabutylammonium bromide, and urea were mixed under stirring in a molar ratio of 1:1.5:2, obtaining a mixture A. The mixture A was then placed in a muffle furnace and heated to 500° C. In the muffle furnace, the mixture A was gradually melted to form an ionic liquid A.

[0058] (2) The above temperature was maintained in the muffle furnace, and the ionic liquid A was subjected to a spontaneous combustion reaction, obtaining a product A. The product A was cooled to room temperature, obtaining a pure Al.sub.2O.sub.3 material with unsaturated coordination and abundant oxygen vacancies.

[0059] The obtained product was characterized by XRD, and UV-Vis DRS. The results are shown in FIG. 1 (curve {circle around (4)}) and FIG. 2 (curve {circle around (4)}) respectively. The curve {circle around (4)} of the XRD patterns in FIG. 1 indicates that the product is composed of Al.sub.2O.sub.3. The curve {circle around (4)} of the UV-Vis DRS spectra in FIG. 2 shows that the alumina prepared in this example has the same light absorption characteristics as the alumina prepared with different raw material ratios in other examples.

Example 5

[0060] A alumina-based heterojunction material with abundant oxygen vacancies was prepared by compounding Al.sub.2O.sub.3 with unsaturated coordination and abundant oxygen vacancies with Bi.sub.12O.sub.17Cl.sub.2 as follows:

[0061] (1) Bismuth nitrate pentahydrate, aluminum nitrate nonahydrate, diethylammonium chloride, and urea were mixed under stirring in a molar ratio of 12:2:2:6, obtaining a mixture B. The mixture B was then placed in a muffle furnace and heated to 500° C. In the muffle furnace, the mixture B was gradually melted to form an ionic liquid B.

[0062] (2) The above temperature was maintained in the muffle furnace, and the ionic liquid B was subjected to a spontaneous combustion reaction, obtaining a product B. The product B was then cooled to room temperature, obtaining a composite of Al.sub.2O.sub.3 and Bi.sub.12O.sub.17Cl.sub.2.

[0063] The obtained product sample was characterized by high resolution transmission electron microscope (HRTEM), O.sub.2-TPD, EPR- .circle-solid.O.sub.2.sup.− and EPR- .circle-solid.OH. The results are shown in FIG. 6, FIG. 7, FIG. 8 and FIG. 9 respectively.

[0064] In FIG. 6, lattice fringes of Bi.sub.12O.sub.17Cl.sub.2 can be observed, indicating the existence of Bi.sub.12O.sub.17Cl.sub.2, while the vague part is attributed to Al.sub.2O.sub.3, indicating that Al.sub.2O.sub.3 is closely combined with Bi.sub.12O.sub.17Cl.sub.2.

[0065] The O.sub.2-TPD spectrum is shown in FIG. 7, which has temperature as abscissa, and adsorption intensity as ordinate. It can be seen from FIG. 7 that the oxygen-adsorption ability is greatly improved after Bi.sub.12O.sub.17Cl.sub.2 is introduced into the alumina with oxygen vacancies, which is attributed to the dual functions of physical and chemical adsorption of molecular oxygen on alumina with oxygen vacancies.

[0066] FIG. 8 shows the EPR spectrum of .circle-solid.O.sub.2.sup.−, which is used to detect the amount of oxygen molecules activation product .circle-solid.O.sub.2.sup.− in the product sample and has magnetic field intensity (B) as abscissa, and signal intensity as ordinate. It can be seen from this figure that the amount of .circle-solid.O.sub.2.sup.− is higher than that of Bi.sub.12O.sub.17Cl.sub.2 in the Al.sub.2O.sub.3/Bi.sub.12O.sub.17Cl.sub.2 heterojunction photocatalyst, indicating that the introduction of alumina with abundant oxygen vacancies significantly improves the adsorption and activation of oxygen molecules and promotes the formation of reactive oxygen species .circle-solid.O.sub.2.sup.−.

[0067] FIG. 9 shows the EPR spectrum of .circle-solid.OH, which is used to detect the amount of activation product .circle-solid.OH of oxygen molecules in the product sample and has magnetic field intensity (B) as abscissa, and signal intensity as ordinate. It can be seen from this figure that the amount of .circle-solid.OH is higher than that of Bi.sub.12O.sub.17Cl.sub.2 in the Al.sub.2O.sub.3/Bi.sub.12O.sub.17Cl.sub.2 heterojunction photocatalyst, indicating that the introduction of alumina with abundant oxygen vacancies significantly improves the adsorption and activation of oxygen molecules and promotes the formation of reactive oxygen species .circle-solid.OH.

Example 6

[0068] An alumina-based heterojunction material with abundant oxygen vacancies was prepared by compounding Al.sub.2O.sub.3 with unsaturated coordination and abundant oxygen vacancies with Bi.sub.12O.sub.17Cl.sub.2 as follows:

[0069] (1) Bismuth nitrate pentahydrate, aluminum nitrate nonahydrate, diethylammonium chloride, and urea were mixed under stirring in a molar ratio of 12:1:2:3, obtaining a mixture B. The mixture B was then placed in a muffle furnace and heated to 500° C. In the muffle furnace, the mixture B was gradually melted to form an ionic liquid B.

[0070] (2) The above temperature was maintained in the muffle furnace, and the ionic liquid B was subjected to a spontaneous combustion reaction, obtaining a product B. The product B was then cooled to room temperature, obtaining a composite of Al.sub.2O.sub.3 and Bi.sub.12O.sub.17Cl.sub.2.

Example 7

[0071] An alumina-based heterojunction material with abundant oxygen vacancies was prepared by compounding Al.sub.2O.sub.3 with unsaturated coordination and abundant oxygen vacancies with Bi.sub.12O.sub.17Cl.sub.2 as follows:

[0072] (1) Bismuth nitrate pentahydrate, aluminum nitrate nonahydrate, trimethylammonium chloride, and urea were mixed under stirring in a molar ratio of 12:4:2:12, obtaining a mixture B. The mixture B was then placed in a muffle furnace and heated to 500° C. In the muffle furnace, the mixture B was gradually melted to form an ionic liquid B.

[0073] (2) The above temperature was maintained in the muffle furnace, and the ionic liquid B was subjected to a spontaneous combustion reaction, obtaining a product B. The product B was then cooled to room temperature, obtaining a composite of Al.sub.2O.sub.3 and Bi.sub.12O.sub.17Cl.sub.2.

Example 8

[0074] An alumina-based heterojunction material with abundant oxygen vacancies was prepared by compounding Al.sub.2O.sub.3 with unsaturated coordination and abundant oxygen vacancies with Bi.sub.12O.sub.17Cl.sub.2 as follows:

[0075] (1) Bismuth nitrate pentahydrate, aluminum nitrate nonahydrate, tetramethylammonium chloride, and urea were mixed under stirring in a molar ratio of 12:3:2:9, obtaining a mixture B. The mixture B was then placed in a muffle furnace and heated to 500° C. In the muffle furnace, the mixture B was gradually melted to form an ionic liquid B.

[0076] (2) The above temperature was maintained in the muffle furnace, and the ionic liquid B was subjected to a spontaneous combustion reaction, obtaining a product B. The product B was then cooled to room temperature, obtaining a composite of Al.sub.2O.sub.3 and Bi.sub.12O.sub.17Cl.sub.2, i.e., the alumina-based heterojunction material with abundant oxygen vacancies.