Indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst and preparation method and application thereof

Abstract

The application provides an indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst and a preparation method and application thereof. The preparation method is as follows: first, an indium oxide electrospinning precursor solution is prepared, then a niobium pentoxide electrospinning precursor solution is prepared, the two solutions are mixed and stirred, and an indium oxide-niobium pentoxide precursor is obtained through an electrospinning technology; and then, the indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst is obtained through high-temperature calcination in air. The catalyst shows enhanced CO2 reduction activity and CO selectivity under the irradiation of ultraviolet visible light. The photo-generated electrons with strong reduction capacity on the conduction band of the niobium pentoxide and the photo-generated holes with strong oxidation capacity on the valence band of the indium oxide are spatially separated in the catalyst, thereby participating in the photocatalytic reaction. Meanwhile, the efficient adsorption and activation of CO2 molecules on the surface of the niobium pentoxide make the catalyst show enhanced CO2 reduction activity and CO selectivity under the irradiation of ultraviolet visible light.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalytic material synthesis and application, and particularly relates to an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] Excessive emission of carbon dioxide (CO2) disrupts the natural carbon cycle, leading to serious environmental pollution problems and exacerbating the greenhouse effect. Solar energy is a clean, pollution-free, inexhaustible and renewable energy source, but it is difficult to store due to its large day / night and seasonal variations. Using inexpensive and efficient photocatalytic technology to convert CO2 into solar fuels with high added value is one of the most promising strategies to solve the above problems.

[0003] Niobium pentoxide (Nb2O5) is a non-toxic and stable oxide with a high conduction band position and strong reduction ability, which has attracted great attention in the field of photocatalysis. Preliminary density functional theory calculations show that compared with free CO2 molecules, the bond length and bond angle of CO2 molecules adsorbed on Nb2O5 will change, and the two oxygen atoms in CO2 can form chemical bonds with Nb atoms in Nb2O5, indicating that Nb2O5 has great potential to adsorb and activate stable CO2 molecules during CO2 photoreduction. However, the recombination rate of photo-generated electrons and holes in single Nb2O5 is fast, resulting in low photocatalytic efficiency.

[0004] Indium oxide (In2O3) has a narrow band gap (about 2.9 eV) and visible light absorption characteristics. Compared with Nb2O5, the energy band position of In2O3 is relatively low, and the oxidation ability is strong, which is more inclined to be used as an oxidation-type photocatalyst.

[0005] How to make good use of the intrinsic characteristics and advantages of In2O3 and Nb2O5, and construct a composite nanofiber ladder-type heterojunction photocatalyst by coupling the two phases through a simple one-step method, which can not only realize efficient separation of photo-generated electrons and holes in space, but also retain photo-generated carriers with strong reduction and oxidation ability to participate in photocatalytic reaction, to promote photocatalytic CO2 and help achieve the "double carbon" goal, is a technical problem to be solved for realizing green development at present. SUMMARY

[0006] The purpose of the present application is to provide an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst and a preparation method and application thereof to overcome the above-mentioned deficiencies of the prior art.

[0007] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0008] The first object of the present application is to provide a preparation method of indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst, which comprises the following specific steps:

[0009] Step S1, preparation of indium oxide nanofiber precursor solution: dissolve indium source in N,N-dimethylformamide, then add polymer and stir until dissolved to obtain indium oxide nanofiber precursor solution;

[0010] Step S2, preparation of niobium pentoxide nanofiber precursor solution: dissolve niobium source in water and stir until dissolved to obtain niobium pentoxide nanofiber precursor solution;

[0011] Step S3, preparation of indium oxide-niobium pentoxide composite nanofiber precursor solution: add the niobium pentoxide nanofiber precursor solution obtained in step S2 to the indium oxide nanofiber precursor solution obtained in step S1, and stir until mixed uniformly to obtain the indium oxide-niobium pentoxide composite nanofiber precursor solution;

[0012] Step S4, synthesis of indium oxide-niobium pentoxide composite nanofiber precursor: obtain amorphous indium oxide-niobium pentoxide composite nanofiber precursor by electrospinning method from the precursor solution obtained in step S3;

[0013] Step S5, crystallization treatment of indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst: calcine the amorphous indium oxide-niobium pentoxide composite nanofiber collected in step S4 in air atmosphere to obtain yellowish crystallized indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst.

[0014] Further, in step S1, the mass ratio of indium source to N,N-dimethylformamide is 1:10-1:50, the indium source is indium nitrate hydrate or indium acetate hydrate, the polymer is polyvinylpyrrolidone, the molecular weight of polyvinylpyrrolidone is 90000 or 1300000, and the mass ratio of polyvinylpyrrolidone to N,N-dimethylformamide is 1:2-1:10.

[0015] Further, in step S2, the niobium source is ammonium niobate oxalate hydrate or ethoxy niobium or hydrated niobium oxalate, the molar ratio of niobium source to indium source is 1:100-30:100, and the mass ratio of niobium source to water is 1:10-1:100.

[0016] Further, in step S3, the stirring time of the mixed niobium pentoxide nanofiber precursor solution and indium oxide nanofiber precursor solution is 12-24 hours.

[0017] Further, in step S4, the distance between the spinning needle and the receiving plate in the electrospinning process is kept at 10-20 cm, the voltage is 10-20 kV, and the spinning rate is 0.1-1.0 mL h -1 .

[0018] Further, in step S5, the calcination temperature is 400-800 DEG C, and the time is 1-4 hours.

[0019] The second object of the present application is to provide an indium oxide-diniobium pentoxide composite nanofiber gradient heterojunction photocatalyst prepared by the preparation method described above.

[0020] Further, the diameter of the indium oxide-diniobium pentoxide composite nanofiber structure is about 50-100 nm, and the molar ratio of diniobium pentoxide to indium oxide in the composite nanofiber is (1-30):100.

[0021] The third object of the present application is to provide an application of the indium oxide-diniobium pentoxide composite nanofiber gradient heterojunction photocatalyst described above in catalytic reduction of CO2.

[0022] The fourth object of the present application is to provide a method for catalytic reduction of CO2, in which the indium oxide-diniobium pentoxide composite nanofiber gradient heterojunction photocatalyst described in claim 7 or 8 is used to reduce CO2 into CO under ultraviolet-visible light.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] (1) The present application provides a preparation method of an indium oxide-diniobium pentoxide composite nanofiber gradient heterojunction photocatalyst, which prepares the indium oxide-diniobium pentoxide composite nanofiber gradient heterojunction photocatalyst through a simple one-step electrospinning technology. Specifically, an indium oxide electrospinning precursor solution is prepared first, then a diniobium pentoxide electrospinning precursor solution is prepared, the two solutions are mixed and stirred to obtain an indium oxide-diniobium pentoxide mixed electrospinning precursor solution, and an indium oxide-diniobium pentoxide precursor is obtained through electrospinning technology; the obtained indium oxide-diniobium pentoxide precursor is calcined at high temperature in air to obtain a crystallized indium oxide-diniobium pentoxide composite nanofiber gradient heterojunction photocatalyst. The composite nanofiber gradient heterojunction photocatalyst exhibits enhanced CO2 reduction activity and CO selectivity under the irradiation of ultraviolet-visible light.

[0025] (2) The indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst provided by the application is a gradient heterojunction photocatalyst in which the indium oxide is an oxidation-type photocatalyst and the niobium pentoxide is a reduction-type photocatalyst, the indium oxide and the niobium pentoxide are coupled to construct the gradient heterojunction composite photocatalyst through a one-step method, the photo-generated electrons with strong reduction ability on the conduction band of the niobium pentoxide and the photo-generated holes with strong oxidation ability on the valence band of the indium oxide are separated in space, thereby participating in the photocatalytic reaction, and the catalyst is more conducive to enhancing the CO2 reduction activity and converting CO2 into CO, thanks to the efficient adsorption and activation of CO2 molecules on the surface of the niobium pentoxide.

[0026] (3) The method has simple process, convenient operation, easily available raw materials, no need for complex equipment, low production cost, and is very suitable for large-scale industrial production.

[0027] (4) The indium oxide and the niobium pentoxide in the indium oxide-niobium pentoxide composite nanofiber material provided by the application form a gradient heterojunction, so that the photo-generated electrons with strong reduction ability on the conduction band of the niobium pentoxide and the photo-generated holes with strong oxidation ability on the valence band of the indium oxide are effectively separated, and meanwhile, CO2 molecules can be efficiently adsorbed and activated on the surface of the catalyst, so that the indium oxide-niobium pentoxide composite nanofiber material exhibits excellent activity in CO2 photoreduction, and provides a new idea for relieving the increasingly serious energy shortage and environmental pollution problem and helping to achieve the “double carbon” goal. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a scanning electron microscope photo of the indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst prepared in the application.

[0029] Figure 2a It is a transmission electron microscope photo of the indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst prepared in the application.

[0030] Figure 2b It is a high-resolution transmission electron microscope photo of the indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst prepared in the application.

[0031] Figure 3 It is an X-ray diffraction spectrum of the material prepared in the application.

[0032] Figure 4 It is an ultraviolet-visible diffuse emission absorption spectrum of the material prepared in the application.

[0033] Figures 5a-5cA graph of the photocatalytic CO2 reduction performance of the material prepared in Example 1 and Comparative Examples 1-3 of the present application is shown. DETAILED DESCRIPTION

[0034] In order to make the objects, technical solutions, and advantages of the present application clearer, the embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0035] Example 1

[0036] The present embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0037] The specific steps are as follows:

[0038] Step S1, preparation of an indium oxide nanofiber precursor solution: an indium nitrate hydrate and PVP completely dissolved solution is prepared with DMF as a solvent, the molecular weight of PVP is 1300000, the mass ratio of indium nitrate hydrate to DMF is 1:30, the mass ratio of PVP to DMF is 1:6, and a clear and transparent solution is obtained;

[0039] Step S2, preparation of a niobium pentoxide nanofiber precursor solution: ammonium niobate oxalate is dissolved in water, the molar ratio of niobium source to indium source is 10:100, the mass ratio of ammonium niobate oxalate to water is 1:60, and a clear and transparent solution is obtained after complete dissolution;

[0040] Step S3, preparation of an indium oxide-niobium pentoxide composite nanofiber precursor solution: the niobium pentoxide nanofiber precursor solution obtained in step S2 is added to the indium oxide nanofiber precursor solution obtained in step S1, and stirring is performed for 24 hours until the mixture is uniform, and a clear and transparent solution is obtained;

[0041] Step S4, synthesis of an indium oxide-niobium pentoxide composite nanofiber precursor: the indium oxide-niobium pentoxide composite nanofiber precursor solution obtained in step S3 is subjected to electrospinning, the distance between the spinning needle and the receiving plate is kept at 10 cm, the voltage is 20 kV, and the spinning rate is 0.4 mL h -1 , to obtain the indium oxide-niobium pentoxide composite nanofiber precursor;

[0042] Step S5, crystallization treatment of the indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst: the amorphous indium oxide-niobium pentoxide composite nanofiber collected in step S4 is calcined at 600 DEG C for 2 hours in air to obtain a yellowish indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst.

[0043] Example 2

[0044] The present embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst.

[0045] The present embodiment is basically the same as example 1, except that in step S1, the mass ratio of indium acetate hydrate to DMF is 1:30.

[0046] Example 3

[0047] The present embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst.

[0048] The present embodiment is basically the same as example 1, except that in step S1, the mass ratio of indium acetate hydrate to DMF is 1:30.

[0049] Example 4

[0050] The present embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst.

[0051] The present embodiment is basically the same as example 1, except that in step S1, the mass ratio of indium acetate hydrate to DMF is 1:30.

[0052] Example 5

[0053] The present embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst.

[0054] The present embodiment is basically the same as example 1, except that in step S1, the mass ratio of indium acetate hydrate to DMF is 1:30.

[0055] Example 6

[0056] The present embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst.

[0057] The present embodiment is basically the same as example 1, except that in step S1, the mass ratio of indium acetate hydrate to DMF is 1:30.

[0058] Example 7

[0059] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0060] The embodiment is basically the same as that in example 1, except that in step S1, the mass ratio of PVP to DMF is 1:10.

[0061] Example 8

[0062] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0063] The embodiment is basically the same as that in example 1, except that in step S2, the ethoxy niobium is dissolved in water.

[0064] Example 9

[0065] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0066] The embodiment is basically the same as that in example 1, except that in step S2, the niobium oxalate hydrate is dissolved in water.

[0067] Example 10

[0068] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0069] The embodiment is basically the same as that in example 1, except that in step S2, the molar ratio of the niobium source to the indium source is 1:100.

[0070] Example 11

[0071] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0072] The embodiment is basically the same as that in example 1, except that in step S2, the molar ratio of the niobium source to the indium source is 30:100.

[0073] Example 12

[0074] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0075] The embodiment is basically the same as that in example 1, except that in step S2, the mass ratio of the ammonium niobate oxalate to water is 1:10.

[0076] Example 13

[0077] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0078] The embodiment 1 is basically the same, except that: in step S2, the mass ratio of ammonium niobate oxalate to water is 1:100.

[0079] Embodiment 14

[0080] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0081] The embodiment 1 is basically the same, except that: in step S3, stirring for 12 hours until the mixture is uniform, to obtain a clear and transparent solution.

[0082] Embodiment 15

[0083] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0084] The embodiment 1 is basically the same, except that: in step S4, the distance between the spinning needle and the receiving plate is kept at 20 cm.

[0085] Embodiment 16

[0086] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0087] The embodiment 1 is basically the same, except that: in step S4, the voltage is 10 kV.

[0088] Embodiment 17

[0089] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0090] The embodiment 1 is basically the same, except that: in step S4, the spinning rate is 0.1 mL h -1 .

[0091] Embodiment 18

[0092] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0093] The embodiment 1 is basically the same, except that: in step S4, the spinning rate is 1.0 mL h -1 .

[0094] Embodiment 19

[0095] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0096] The same as example 1, except that in step S5, calcination is performed at 400℃ for 2 hours.

[0097] Example 20

[0098] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0099] The same as example 1, except that in step S5, calcination is performed at 800℃ for 2 hours.

[0100] Example 21

[0101] The embodiment provides a preparation method of an indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst.

[0102] The same as example 1, except that in step S5, calcination is performed at 600℃ for 4 hours.

[0103] Comparative example 1

[0104] The preparation method of the indium oxide nanofiber is as follows:

[0105] In step S1, an indium nitrate hydrate and PVP completely dissolved solution is prepared by taking DMF as a solvent, the molecular weight of the PVP is 1300000, the mass ratio of the indium nitrate hydrate to the DMF is 1:30, the mass ratio of the PVP to the DMF is 1:6, and a clear and transparent solution is obtained;

[0106] In step S2, the clear and transparent solution obtained in step S1 is subjected to electrostatic spinning, the distance between a spinning needle and a receiving plate is kept to be 10cm, the voltage is 20kV, the spinning rate is 0.4mL h -1 , and an indium oxide nanofiber precursor is obtained.

[0107] In step S3, the amorphous indium oxide nanofiber collected in step S2 is calcined at 600℃ for 2 hours in an air atmosphere, and a yellowish indium oxide nanofiber is obtained.

[0108] Comparative example 2

[0109] The preparation method of the niobium pentoxide nanofiber is as follows:

[0110] In step S1, an ammonium niobate oxalate solution is prepared by dissolving the ammonium niobate oxalate in water, the mass ratio of the ammonium niobate oxalate to the water is 1:60, and a clear and transparent solution is obtained.

[0111] Step S2, synthesis of the nanofiber precursor of niobium pentoxide: the clear and transparent solution obtained was electrospun, the distance between the needle and the receiving plate was kept at 10 cm, the voltage was 20 kV, and the spinning rate was 0.8 mL h -1 , to obtain the nanofiber precursor of niobium pentoxide;

[0112] Step S3, crystallization treatment of the nanofiber of niobium pentoxide: the amorphous nanofiber of niobium pentoxide collected in step S2 was calcined at 600°C for 2 hours in an air atmosphere, to obtain the crystallized white nanofiber of niobium pentoxide.

[0113] Comparative Example 3

[0114] The preparation method of the physical mixture of indium oxide-niobium pentoxide is as follows:

[0115] Step S1, preparation of the solution of the nanofiber precursor of indium oxide: a solution of indium nitrate hydrate and PVP completely dissolved was prepared with DMF as the solvent, the molecular weight of PVP was 1300000, the mass ratio of indium nitrate hydrate to DMF was 1:30, and the mass ratio of PVP to DMF was 1:6, to obtain a clear and transparent solution;

[0116] Step S2, synthesis of the nanofiber precursor of indium oxide: the clear and transparent solution obtained in step S1 was electrospun, the distance between the needle and the receiving plate was kept at 10 cm, the voltage was 20 kV, and the spinning rate was 0.4 mL h -1 , to obtain the nanofiber precursor of indium oxide;

[0117] Step S3, crystallization treatment of the nanofiber of indium oxide: the amorphous nanofiber of indium oxide collected in step S2 was calcined at 600°C for 2 hours in an air atmosphere, to obtain the crystallized light yellow nanofiber of indium oxide;

[0118] Step S4, preparation of the solution of the nanofiber precursor of niobium pentoxide: ammonium niobate oxalate was dissolved in water, the mass ratio of ammonium niobate oxalate to water was 1:60, to obtain a clear and transparent solution;

[0119] Step S5, synthesis of the nanofiber precursor of niobium pentoxide: the clear and transparent solution obtained was electrospun, the distance between the needle and the receiving plate was kept at 10 cm, the voltage was 20 kV, and the spinning rate was 0.8 mL h -1 , to obtain the nanofiber precursor of niobium pentoxide;

[0120] Step S6, crystallization treatment of the nanofiber of niobium pentoxide: the amorphous nanofiber of niobium pentoxide collected in step S5 was calcined at 600°C for 2 hours in an air atmosphere, to obtain the crystallized white nanofiber of niobium pentoxide;

[0121] Step S7, Synthesis of Indium Oxide-Niobium Pentoxide Physical Hybrid Material: The indium oxide nanofibers collected in step S3 and the niobium pentoxide nanofibers collected in step S6 are physically mixed to prepare an indium oxide-niobium pentoxide composite material, wherein the molar ratio of niobium pentoxide nanofibers to indium oxide nanofibers is 10:100.

[0122] To better illustrate the performance of the indium oxide-niobium pentoxide composite nanofiber ladder-type heterojunction photocatalyst prepared in this invention, the applicant conducted the following research:

[0123] Performance characterization:

[0124] The indium oxide-niobium pentoxide composite nanofiber ladder-shaped heterojunction photocatalyst was characterized by scanning electron microscopy (SEM), and all examples 1-21 exhibited similar morphologies. Taking Example 1 as an example, refer to... Figure 1 and Figure 2a ,Depend on Figure 1 It can be seen that the fiber diameter of the indium oxide-niobium pentoxide composite nanofiber ladder heterojunction photocatalyst prepared by a simple one-step electrospinning method is 50-100 nm; Figure 2a It can be seen that the indium oxide-niobium pentoxide composite nanofiber ladder heterojunction photocatalyst exhibits a very uniform fibrous morphology and a rough surface; Figure 2a The inset is an energy-dispersive X-ray spectrum showing the presence of In, Nb, and O elements in the composite nanofibers, confirming the presence of indium oxide and niobium pentoxide in the composite nanofibers.

[0125] refer to Figure 2b The high-resolution transmission electron microscopy image shows two sets of lattice fringes with spacings of 0.29, 0.41, 0.39 and 0.31 nm, corresponding to indium oxide (222) and (211) and niobium pentoxide (001) and (200) crystal planes, respectively.

[0126] refer to Figure 3 The figures show the X-ray diffraction patterns of the materials obtained in Example 1 and Comparative Examples 1-3. The diffraction peaks of pure indium oxide nanofibers and niobium pentoxide nanofibers correspond perfectly to their standard cards (PDF#71-2195, PDF#30-0873); due to the lower loading of niobium pentoxide relative to indium oxide, no characteristic diffraction peaks for niobium pentoxide were observed in the indium oxide-niobium pentoxide composite nanofiber ladder heterojunction photocatalyst.

[0127] refer to Figure 4UV-Vis diffuse reflectance absorption spectra of the materials obtained in Example 1 and Comparative Examples 1-3 were measured. As can be seen from the figure, the absorption band edges of indium oxide and niobium pentoxide are located at about 425 and 390 nm, respectively; compared with pure niobium pentoxide nanofibers, the UV-Vis light absorption characteristics of the indium oxide-niobium pentoxide composite nanofibers are slightly improved, which is attributed to the strong light absorption capacity of indium oxide, further proving the presence of niobium pentoxide in the composite nanofiber gradient heterojunction photocatalyst.

[0128] In order to better illustrate the effect of the indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst of the present application in the application of catalyzing CO2, the present applicant has also carried out the following research:

[0129] Photocatalytic activity test: photocatalytic reduction of CO2 was carried out in an online gas closed system equipped with a gas circulation pump, and a 300 W xenon lamp was used as the light source. During the experiment, the composite materials obtained in Example 1 and Comparative Examples 1-3, 2 mM of molecular catalyst [RuII(bpy)3]Cl2.6H2O, 10 mM of sacrificial agent 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH), 30 mL of acetonitrile and a small amount of H2O were added into the quartz reactor. After the reaction system was pumped to a vacuum state, about 60 kPa of high-purity CO2 gas (99.999%) was introduced. After adsorption equilibrium, the xenon lamp was turned on to start irradiation. A gas chromatograph (GC-2030, Shimadzu) equipped with a dielectric barrier discharge plasma detector (BID) was used to detect the CO2 reduction products. Standard mixed gases were used to calibrate the retention time values of the gases, so as to determine the types of photocatalytic CO2 reduction products. At the same time, two groups of blank experiments were designed, one group of experiments without the introduction of CO2 gas, and the other group of experiments without the light source, and the results showed that the existence of CO2 and light source were the two most critical factors for photocatalytic reduction of CO2.

[0130] Reference Figures 5a-5c and Table 1, the photocatalytic CO2 reduction performance comparison chart and data statistics table of the materials prepared in Example 1 and Comparative Examples 1-3. From Figure 5a and 5b it can be seen that the indium oxide-niobium pentoxide composite nanofiber gradient heterojunction photocatalyst exhibits the best CO2 reduction activity, in which the generation rate of CO is 18.6 mmol g -1 , the generation rate of H2 is 0.8 mmol g -1 , and the CO selectivity reaches ~96%, which is much higher than the catalytic activity and CO selectivity of pure indium oxide nanofibers, pure niobium pentoxide nanofibers and physical mixed materials of indium oxide nanofibers and niobium pentoxide nanofibers. At the same time, several control experiments were carried out, such asFigure 5c As shown, experiment I represents the reaction system without [RuII(bpy)3]Cl2 . 6H2O and BIH, experiment II represents the reaction system without BIH, and experiment III represents the reaction system without [RuII(bpy)3]Cl2 . 6H2O, and experiment IV represents the reaction system without indium oxide-niobium pentoxide composite nanofiber ladder heterojunction photocatalyst. By comparing the results, it is confirmed that the molecular catalyst and hole sacrificial agent help to significantly improve the photocatalytic efficiency.

[0131] Table 1.

[0132] Sample name CO production rate (mmol g -1 ) H2 production rate (mmol g -1 ) Example 1 In2O3@Nb2O5 18.6 0.8 Comparative Example 1 In2O3 3.0 0.5 Comparative Example 2 [Nb2O5] 8.8 0.9 Comparative Example 3 In2O3 + Nb2O5 16.3 0.8

[0133] The above not involved, applicable to the prior art.

[0134] Although some specific embodiments of the present application have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present application, and those skilled in the art can make various modifications or supplements or use similar ways to replace the described specific embodiments, but will not deviate from the direction of the present application or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modification, equivalent replacement, improvement, etc. made according to the technical essence of the present application to the above embodiments shall be included in the protection scope of the present application.

Claims

1. A method of catalytic reduction of CO2, characterized by, The application discloses a method for preparing an indium oxide-niobium pentoxide composite nanofiber ladder-shaped heterojunction photocatalyst. S1, preparation of an indium oxide nanofiber precursor solution: dissolving an indium source in N,N-dimethylformamide, and then adding a polymer and stirring until the polymer is dissolved to obtain the indium oxide nanofiber precursor solution; the indium source is indium nitrate hydrate or indium acetate hydrate; the polymer is polyvinylpyrrolidone, and the molecular weight of the polyvinylpyrrolidone is 90000 or 1300000; the mass ratio of the polyvinylpyrrolidone to N,N-dimethylformamide is 1:2-1:10, and the mass ratio of the indium source to N,N-dimethylformamide is 1:10-1:50; S2, preparation of a niobium pentoxide nanofiber precursor solution: dissolving a niobium source in water and stirring until the niobium source is dissolved to obtain the niobium pentoxide nanofiber precursor solution; the niobium source is ammonium niobate oxalate hydrate, ethoxy niobium or hydrated niobium oxalate; the molar ratio of the niobium source to the indium source is 1:100-30:100, and the mass ratio of the niobium source to water is 1:10-1:100; S3, preparation of an indium oxide-niobium pentoxide composite nanofiber precursor solution: adding the niobium pentoxide nanofiber precursor solution obtained in step S2 into the indium oxide nanofiber precursor solution obtained in step S1, and stirring until the solution is uniformly mixed to obtain the indium oxide-niobium pentoxide composite nanofiber precursor solution; S4, synthesis of indium oxide-niobium pentoxide composite nanofiber precursor: the precursor solution obtained in step S3 is used to obtain amorphous indium oxide-niobium pentoxide composite nanofiber precursor by electrospinning method; in the electrospinning process, the distance between the spinning needle and the receiving plate is kept at 10-20 cm, the voltage is 10-20 kV, and the spinning rate is 0.1-1.0 mLh -1 ; S5, crystallization treatment of the indium oxide-niobium pentoxide composite nanofiber ladder-shaped heterojunction photocatalyst: calcining the amorphous indium oxide-niobium pentoxide composite nanofiber precursor collected in step S4 in an air atmosphere, the calcination temperature is 400-800 DEG C, and the calcination time is 1-4 hours, so that the crystallized light yellow indium oxide-niobium pentoxide composite nanofiber ladder-shaped heterojunction photocatalyst is obtained.

2. The method of claim 1, wherein, In step S3, the stirring time is 12-24 hours.

3. The method of claim 2, wherein, The diameter of the indium oxide-niobium pentoxide composite nanofiber structure is 50-100 nm.

4. The method of claim 3, wherein, The molar ratio of the niobium pentoxide to the indium oxide in the composite nanofiber is (1-30):100.

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