CN110813328A

CN110813328A - BiInOCl porous microsphere photocatalyst with hierarchical structure and preparation method thereof

Info

Publication number: CN110813328A
Application number: CN201911012826.9A
Authority: CN
Inventors: 李卫兵; 张延光; 田景; 王晓东; 方珂
Original assignee: Qingdao University of Science and Technology
Current assignee: Qingdao University of Science and Technology
Priority date: 2019-10-23
Filing date: 2019-10-23
Publication date: 2020-02-21

Abstract

The invention belongs to the technical field of photocatalysis, and particularly relates to a BiInOCl porous microsphere photocatalyst with a hierarchical structure; also relates to a preparation method of the BiInOCl porous microsphere photocatalyst with the hierarchical structure. The BiInOCl porous microsphere photocatalyst with the hierarchical structure is prepared by taking bismuth nitrate, indium nitrate, hydrochloric acid and ethylene glycol as basic raw materials through a simple one-step hydrothermal method. The invention has the advantages of good photocatalytic performance, and the performance of degrading norfloxacin, rhodamine B, methyl orange and methylene blue by full-light photocatalysis is obviously improved compared with the prior art.

Description

BiInOCl porous microsphere photocatalyst with hierarchical structure and preparation method thereof

Technical Field

The invention belongs to the technical field of photocatalysis, and particularly relates to a BiInOCl porous microsphere photocatalyst with a hierarchical structure; the invention also relates to a preparation method of the BiInOCl porous microsphere photocatalyst with the hierarchical structure.

Background

The photocatalytic technology is a green technology with important application prospect in the field of energy and environment, organic dirt can be thoroughly degraded into carbon dioxide and water under the illumination, and meanwhile, the photocatalytic material has no loss and can be recycled, so that the photocatalytic material is widely researched. At present, TiO is the main widely studied photocatalyst₂、 g-C₃N₄、CdS、BiVO₄、WO₃BiOX, etc., wherein BiOX (X ═ Cl, Br, I) is attracting attention as a novel photocatalyst due to its unique electric, optical, catalytic properties, and its unique lamellar structure [ Bi₂O₂]²⁺The built-in electric field formed by the element X can effectively reduce the recombination of photo-generated electrons and holes, and therefore, the photocatalyst has higher photocatalytic activity.

The band structure of BiOX can be adjusted by adjusting X in the BiOX semiconductor. BiOX has a larger atomic number of halogen atom X and a smaller forbidden band width of BiOX, i.e., BiOCl (. about.3.2 eV), BiOBr (. about.2.7 eV), and BiOI (. about.1.7 eV). Researches show that the energy band regulation of the BiOX semiconductor can be realized through the solid solution of the X atoms. E.g. jiaet al by regulating BiOCl_1-xBr_xThe value of x in (x is 0, 0.5, 1) realizes the transition of the forbidden band width from 3.37eV to 2.92eV to 2.83eV, and realizes the simultaneous regulation and control of the conduction band position and the valence band position. Lu et al also found by targeting BiOBr_xI_1-xThe adjustment of x in (x is 0-0.5) can realize BiOBr_xI_1-xAnd adjusting the position of the conduction band, the valence band and the width of the forbidden band. Although the band gap of the semiconductor can be reduced and the photoresponse range of the semiconductor can be widened by the solid solution of the halogen atoms, the energy of free radicals generated by light excitation is reduced due to the band gap shortening, and the full degradation is not facilitated. To widen the semiconductor within a certain rangeThe energy of free radicals can be improved due to the width of the forbidden band, and the energy-saving material has better complete decomposition capability on pollutants or water, so that the material also has very good industrial application value.

Besides regulating the X atom in the BiOX, the regulation of the Bi site atom can also realize the energy band regulation of the BiOX. Since Pb and Bi are positioned in the same period and have similar atomic radii, the regulation and control of the Bi position in BiOX are easy to realize. The research finds that Pb²⁺Can be inserted into [ Bi ]₂O₂]²⁺Interlaminar, Pb 6s²The orbit occupies a higher energy state at the top of a Valence Band (VBM), the Pb 6p orbit occupies a lower energy state at the bottom of a Conduction Band (CBM), and the hybrid states of the VBM and the CBM can respectively reduce the effective mass of holes and electrons, prolong the service life of excited-state carriers and improve the photocatalytic activity. However, Pb is a heavy metal, has strong biological toxicity and causes three-fold harm. Therefore, a more green element is required to be searched for regulating and controlling the Bi bitcell of BiOX so as to realize the regulation of the BiOX energy band structure and better realize the application of the BiOX energy band structure in the field of photocatalysis.

In and Bi are positioned In adjacent periods, In and Bi are both In a valence of +3, and the atomic radius of In is slightly smaller than Bi, so that lattice distortion is likely to occur due to mismatching of the atomic radius In the solid solution process. In addition, In is very easy to hydrolyze to form a local acidic environment, so that the local kinetics of the growth reaction is changed, and the possibility of regulating and controlling the microscopic morphology of the product is realized.

Disclosure of Invention

One of the purposes of the invention is to provide a BiInOCl porous microsphere photocatalyst with a hierarchical structure, which has good photocatalytic performance, and the performance of degrading norfloxacin, rhodamine B, methyl orange and methylene blue by full-light photocatalysis is obviously improved compared with the prior art.

In order to solve the technical problems, the invention adopts the following technical scheme: a BiInOCl porous microsphere photocatalyst with a hierarchical structure is prepared by taking bismuth nitrate, indium nitrate, hydrochloric acid and ethylene glycol as basic raw materials and adopting a simple one-step hydrothermal method.

In of the BiInOCl porous microsphere photocatalyst is 1:0.5, 1:1, 1:2 and 1: 3.

Preferably, In is 1:2 of Bi: In of the Bi In ocl porous microsphere photocatalyst.

Another object of the present invention is to provide a method for preparing a BiInOCl porous microsphere photocatalyst with a hierarchical structure, which comprises the following steps:

(1) preparing sample solutions in different proportions: firstly, 4 beakers with the specification of 100mL are taken, 80mL of ethylene glycol is added, and then 0.4mmol of Bi (NO) is added respectively₃)₃Adding 0.2mmol, 0.4mmol, 0.8mmol and 1.2mmol of In (NO) respectively₃)₃Finally, 0.4mmol of HCl solution is added and stirred for 30min until complete dissolution.

(2) Hydrothermal reaction: the prepared samples with different proportions are added into a 100mL reaction kettle and placed in an electrothermal blowing dry box at 140 ℃ for reaction for 24 hours.

(3) Washing and drying: and naturally cooling the hydrothermal reaction kettle to room temperature, washing with deionized water, washing with ethanol, and drying at 60 ℃ to obtain the prepared sample.

In the invention, the In is dissolved into the BiOCl In a solid way, the structure of the BiOCl still presents a microsphere structure, and the specific surface area is greatly increased. The research on photoelectrochemistry and photocatalysis performance discovers that the BiInOCl-1:2 sample has the best photoelectrochemistry performance and the performance of degrading norfloxacin through photocatalysis. Researches find that the main reasons for improving the photoelectrochemistry and the photocatalytic performance of BiInOCl-1:2 are as follows: firstly, the adsorption capacity of the BiInOCl-1:2 sample is enhanced by the larger specific surface area, and the number of active sites is increased; and secondly, the solid solution of In enables the valence band of BiInOCl to move positively and pulls the conduction band to move negatively, so that the oxidation capability and the reduction capability are enhanced simultaneously. Meanwhile, radical detection shows that a large number of hydroxyl radicals and superoxide radicals exist in the solution at the same time, so that the redox capability of the BiInOCl is improved, and the BiInOCl has higher photoelectrochemistry and photocatalysis performances.

The BiInOCl porous microsphere photocatalyst with the hierarchical structure prepared by the invention has the ratio of Bi to InWhen the ratio is 1:2, the catalyst has the best photoelectrochemical property and the property of degrading norfloxacin by photocatalysis. Under the irradiation of all light, the photo-generated current density is-61.11 muA/cm²The degradation efficiency of the sample to norfloxacin in 5Min BiInOCl-1:2 can reach 96%, and the degradation efficiency is improved by 9.6 times compared with that of pure BiOCl. The research shows that the reason for improving the photocatalytic performance of the BiInOCl-1:2 photocatalyst is as follows: firstly, the large specific surface area of BiInOCl is beneficial to the adsorption of BiInOCl on pollutants, and the number of active sites of BiInOCl is increased; and secondly, the introduction of In enables the valence band of BiInOCl to be positively shifted, the conduction band to be negatively shifted, and the oxidation capability and the reduction capability to be improved. And BiInOCl can generate more superoxide radicals and hydroxyl free radicals compared with BiOCl, so that BiInOCl has stronger oxidizing capability.

Compared with the prior art, the invention has the beneficial effects that:

(1) the BiInOCl solid solution microspheres with high specific surface area are successfully prepared by a simple one-step hydrothermal method, and the preparation method is simple; the large specific surface area of the BiInOCl solid solution can better adsorb substances to be degraded and removed onto active sites, so that the substances are oxidized and removed.

(2) The formation of the BiInOCl solid solution can simultaneously regulate and control the positions of a conduction band and a valence band of BiOCl, so that the conduction band is moved positively and negatively, and the redox capability of photoproduction holes and electrons is enhanced. Meanwhile, BiInOCl can generate more superoxide radicals and hydroxyl radicals compared with BiOCl, so that BiInOCl has stronger oxidizing capability. The BiInOCl solid solution has stronger oxidation-reduction capability, so the BiInOCl solid solution has better application prospect in the aspect of difficultly-degraded pollutants.

Drawings

FIG. 1 is a series of sample SEM topographies;

wherein, FIG. 1A is the SEM morphology of BiOCl, FIG. 1B is the SEM morphology of the In-dissolved BiInOCl photocatalyst sample (BiInOCl-1:0.5) of example 1, FIG. 1C is the SEM morphology of the In-dissolved BiInOCl photocatalyst sample (BiInOCl-1:1) of example 2, FIG. 1D is the SEM morphology of the In-dissolved BiInOCl photocatalyst sample (BiInOCl-1:2) of example 3, and FIG. 1E is the SEM morphology of the In-dissolved BiInOCl photocatalyst sample (BiInOCl-1:3) of example 4;

FIG. 2 is a TEM image under low and high magnification of BiInOCl and the In-solutionized BiInOCl photocatalyst sample of example 3 (BiInOCl-1: 2);

wherein FIG. 2A is a TEM image under a low power lens of BiOCl, FIG. 2B is a TEM image under a high power lens of BiOCl, FIG. 2C is a TEM image under a low power lens of an In-dissolved BiInOCl photocatalyst sample (BiInOCl-1:2) of example 3, and FIG. 2D is a TEM image under a high power lens of an In-dissolved BiInOCl photocatalyst sample (BiInOCl-1:2) of example 3;

FIG. 3 shows the results of the element distribution test of the In-dissolved BiInOCl photocatalyst sample (BiInOCl-1:2) of example 3;

FIG. 4 is an EDS energy spectrum of an In solid solution BiInOCl photocatalyst sample (BiInOCl-1:2) of example 3;

FIG. 5 shows XPS results for BiOCl and the In solid solution BiInOCl photocatalyst sample of example 3 (BiInOCl-1: 2);

wherein, fig. 5A is a total spectrum, fig. 5B is an XPS result of Bi4f, fig. 5C is an XPS result of Cl2p, fig. 5D is an XPS result of O1s, and fig. 5E is an XPS result of In 3D;

FIG. 6 is N for a series of samples₂Adsorption/desorption isotherms and pore size profiles of the series of samples;

wherein, FIG. 6A is N of the series of samples₂Adsorption/desorption isotherms, fig. 6B is a pore size distribution plot for a series of samples;

FIG. 7 is a graph of the UV/VIS diffuse reflectance spectrum and the energy band width of the semiconductor for a series of samples;

wherein, fig. 7A is an ultraviolet/visible diffuse reflection spectrum of the series of samples, and fig. 7B is a band width diagram of a semiconductor of the series of samples;

FIG. 8 shows a series of samples at 0.1mol/L Na₂SO₄A graph of the change of the photo-generated current density in the solution with time;

FIG. 9 is a graph of photocatalytic degradation performance of a series of samples;

wherein, fig. 9A is a graph of the effect of a series of samples on degrading 10mg/L norfloxacin at full light, fig. 9B is a graph of the ultraviolet-visible diffuse reflection absorption spectrum of the In solid solution BiInOCl photocatalyst sample (BiInOCl-1:2) of example 3 on degrading norfloxacin, fig. 9C is a graph of the cycle stability of the In solid solution BiInOCl photocatalyst sample (BiInOCl-1:2) of example 3 on degrading norfloxacin at full light, and fig. 9D is a graph of the degradation effect of the In solid solution BiInOCl photocatalyst sample (BiInOCl-1:2) of example 3 on different materials at full light;

FIG. 10 is the results of testing the electrochemical impedance and Mott Schottky of the In solid solution BiInOCl photocatalyst sample of example 3 (BiInOCl-1: 2);

wherein, FIG. 10A is the electrochemical impedance spectrum of the In-dissolved BiInOCl photocatalyst sample (BiInOCl-1:2) of example 3, FIG. 10B is the Mott Schottky diagram of the In-dissolved BiInOCl photocatalyst sample (BiInOCl-1:2) of example 3,

FIG. 11 is an electron paramagnetic resonance spectrum of BiInOCl and the In solid solution BiInOCl photocatalyst sample of example 3 (BiInOCl-1: 2);

wherein, FIG. 11A is the electron paramagnetic resonance spectrum of the superoxide radical of BiOCl and the BiInOCl photocatalyst sample (BiInOCl-1:2) with In solid solution of example 3, and FIG. 11B is the electron paramagnetic resonance spectrum of the hydroxyl radical of BiOCl and the BiInOCl photocatalyst sample (BiInOCl-1:2) with In solid solution of example 3;

Detailed Description

The following examples are given to facilitate a better understanding of the invention, but do not limit the invention. The experimental procedures in the following examples are conventional unless otherwise specified.

Example 1

A BiInOCl porous microsphere photocatalyst with a hierarchical structure is prepared by taking bismuth nitrate, indium nitrate, hydrochloric acid and ethylene glycol as basic raw materials through a simple one-step hydrothermal method, wherein the ratio of Bi to In is 1: 0.5.

The preparation method of the BiInOCl porous microsphere photocatalyst with the hierarchical structure comprises the following steps:

(1) preparing sample solutionLiquid: firstly, 1 beaker with the specification of 100mL is taken, 80mL of ethylene glycol is added, and then 0.4mmol of Bi (NO) is added₃)₃Then, 0.2mmol of In (NO) was added₃)₃Finally, 0.4mmol of HCl solution is added and stirred for 30min until complete dissolution.

Example 2

A BiInOCl porous microsphere photocatalyst with a hierarchical structure is prepared by taking bismuth nitrate, indium nitrate, hydrochloric acid and ethylene glycol as basic raw materials through a simple one-step hydrothermal method, wherein the ratio of Bi to In is 1: 1.

(1) preparing a sample solution: firstly, 1 beaker with the specification of 100mL is taken, 80mL of ethylene glycol is added, and then 0.4mmol of Bi (NO) is added₃)₃Then, 0.4mmol of In (NO) was added₃)₃Finally, 0.4mmol of HCl solution is added and stirred for 30min until complete dissolution.

Example 3

A BiInOCl porous microsphere photocatalyst with a hierarchical structure is prepared by taking bismuth nitrate, indium nitrate, hydrochloric acid and ethylene glycol as basic raw materials through a simple one-step hydrothermal method, wherein the ratio of Bi to In is 1: 2.

(1) preparing a sample solution: firstly, 1 beaker with the specification of 100mL is taken, 80mL of ethylene glycol is added, and then 0.4mmol of Bi (NO) is added₃)₃Then, 0.8mmol of In (NO) was added₃)₃Finally, 0.4mmol of HCl solution is added and stirred for 30min until complete dissolution.

Example 4

A BiInOCl porous microsphere photocatalyst with a hierarchical structure is prepared by taking bismuth nitrate, indium nitrate, hydrochloric acid and ethylene glycol as basic raw materials through a simple one-step hydrothermal method, wherein the ratio of Bi to In is 1: 3.

(1) preparing a sample solution: firstly, 1 beaker with the specification of 100mL is taken, 80mL of ethylene glycol is added, and then 0.4mmol of Bi (NO) is added₃)₃1.2mmol of In (NO) was added₃)₃Finally, 0.4mmol of HCl solution is added and stirred for 30min until complete dissolution.

Results of the experiment

FIG. 1 is an SEM image of a series of samples, and BiOCl in FIG. 1A shows a microneedle-assembled microspherical structure with a particle size of about 6-8 μm. In FIG. 1B, when the ratio of Bi to In is 1:0.5, the needle shape becomes fine and the surface becomes smooth, but the size of the microspheres is not substantially changed. In FIG. 1C, when the ratio of Bi to In is 1:1, the surface of the microsphere is not smooth and fluffy, and the surface is loose. In FIG. 1D, when the ratio of Bi to In is 1:2, the surface of the sphere has a porous structure, and the particle size of the microsphere begins to decrease. At a ratio of Bi to In of 1:3 In FIG. 1E, the microspheres become irregular and remain porous.

In order to further observe the micro-morphology of the prepared series of samples, a TEM test is carried out on the samples, and FIGS. 2A and 2B are TEM images of a sample BiOCl under a low-power microscope and a high-power microscope respectively, wherein the BiOCl under the low-power microscope is in a microsphere structure, a core is large, the structure is compact, and the surface is in a rough amorphous state; the high power lens BiOCl has clear lattice fringes, wherein 0.195nm and 0.22nm correspond to the (200) and (112) crystal planes of BiOCl, respectively. FIG. 2C is a TEM image of a BiInOCl-1:2 sample under a low power microscope, and it is found that BiInOCl-1:2 also exhibits a microsphere structure, but has a smaller core and is relatively loose and has a smoother surface than BiOCl. FIG. 2D is a TEM image of BiInOCl-1:2 under a high power microscope, and BiInOCl-1:2 is observed to exist only in a lattice width of 0.31 nm.

To further test the element distribution in the BiInOCl-1:2 photocatalysis, we performed element distribution tests on BiInOCl-1:2 samples, and the relevant results are shown in FIG. 3. The bright spots of different colors In the figure represent the distribution of different elements In the BiInOCl-1:2 sample, and Bi, In, O and Cl are uniformly distributed on the microsphere In the figure, which shows that Bi, In, O and Cl are uniformly distributed on the microsphere.

To further test the elemental species in the BiInOCl-1:2 photocatalysis, we performed EDS testing on BiInOCl-1:2 samples with the relevant results shown in FIG. 4. In the figure, the elements C except Bi, In, O and Cl come from the environment, the existence of Cu is used as a carrier when EDS test is carried out, and no other elements except C and Cu exist, which indicates that the sample prepared by the method is relatively pure and has no impurities.

FIG. 5 shows XPS results for BiOCl and the In solid solution BiInOCl photocatalyst sample of example 3 (BiInOCl-1: 2). FIG. 5A, curve a, is a BiOCl sampleCurve a has a peak of C1s in addition to several peaks of Bi4f, Cl2p and O1s, wherein C is derived from the instrument per se; curve b is the total spectrum of BiInOCl-1:2, curve a has a peak of C1s In addition to the presence of several peaks of Bi4f, Cl2p, O1 and In3d, and curves a and b have no other impurity elements except carbon of the apparatus, which indicates that the sample prepared by the method is relatively pure and has no impurity, which is consistent with the results of EDS and Mapping. FIG. 5B is an XPS plot of Bi4f, in which 159.38eV and 164.69eV correspond to Bi4f_7/2And Bi4f_5/2This is due to Bi³⁺. The BiInOCl-1:2 sample was at Bi4f compared to pure BiOCl_7/2And Bi4f_5/2The binding energy becomes large, which is probably due to the fracture of Bi-O, so that the electron density of the Bi surface increases, thereby increasing the binding energy. FIG. 5C is an XPS plot of Cl2p, with 198.1eV and 199.7eV corresponding to Cl2p, respectively_3/2And Cl2p_1/2The binding energy of Cl2p in the BiInOCl-1:2 sample was not significantly changed compared to BiOCl, indicating that the chemical state of Cl was not changed in the formation of BiInOCl. Three binding energies at 530.37eV, 532.03eV, 533.2eV were obtained by XPS peak separation software processing (as shown in FIG. 5D), indicating the presence of three states of oxygen in the BiOCl sample. The binding energies of 530.37eV, 532.03eV, and 533.2eV correspond to the binding energy of lattice oxygen Bi-O in BiOCl, hydroxyl groups adsorbed on the surface of the material, and water adsorbed on the surface, respectively. 445.4eV and 453eV In FIG. 5E correspond to In3d, respectively_5/2And In3d_3/2The binding energy of (1).

To verify the reason why the BiInOCl-1:2 microsphere structure became loose, we further performed N2 adsorption/desorption isotherms and pore size distribution tests on the prepared samples. N for the respective series of samples in FIGS. 6A and 6B₂Adsorption/desorption isotherms and pore size distribution. N is a radical of₂The specific surface areas of BiOCl, BiInOCl-1:0.5, BiInOCl-1:1, BiInOCl-1:2 and BiInOCl-1:3 measured on the adsorption/desorption isotherm were 11.02 m²/g、25.02m²/g、71.32m²/g、102.03m²G and 75.84m²The data show that different proportions of indium can greatly improve the specific surface area of the sample, and the BiInOCl-1:2 sampleThe specific surface area of the BiOCl sample is 9.26 times that of the BiOCl sample, and the specific surface area is larger when the ratio of Bi to In is 1:2, so that the adsorption of pollutants In the degradation process is facilitated. The pore size distribution diagram shows that the average pore size is larger as the indium content is increased, but the surface of the microsphere is damaged when the indium content is too high, so that the specific surface area is still smaller than that of BiInOCl-1:2 even though the pore size of BiInOCl-1:3 is larger than that of BiInOCl-1:2, and the solid solution of indium leads the microsphere to become loose and be in a porous state according to the test result of TEM.

The light absorption properties of the series of samples can be measured by UV-visible diffuse reflectance, as shown In FIG. 7A for the UV-visible diffuse reflectance spectra of BiOCl, BiInOCl-1:0.5, BiInOCl-1:1, BiInOCl-1:2 and BiInOCl-1:3, it can be seen from the graphs that the absorption band edge of BiOCl In the a-curve is about 700nm due to the large number of oxygen vacancies In BiOCl. when the ratio of Bi: In is 1:0.5, the absorption band edge undergoes a blue shift to about 400nm, when the ratio of Bi: In is 1:1, the absorption band edge undergoes a blue shift to about 375nm, when the ratio of Bi: In is further increased to 1:2, the absorption band edge undergoes a further blue shift to about 370nm, when the ratio of Bi: In is further increased to 1:3, the absorption band edge undergoes a red shift as compared to InOCl-1:2, the absorption band edge shifts to about 375nm when the ratio of Bi: In is increased to about 375nm, when the ratio of Bi: In is further increased to 1:3, the absorption band edge shifts to a certain amount of the sample, and when the absorption band edge shift is calculated according to the reflection spectrum of the spectrum of BiOCl-visible light is increased, the spectrum of BiIn, the spectrum of BiOCl-visible spectrum of the spectrum of BiIn, the spectrum of BiOCl, the spectrum of^1/nIt can be seen from fig. 7B that the energy gap of BiOCl is about 1.77eV, while the energy gap becomes larger with different ratios of indium added, where the energy gap of BiInOCl-1:2 is the largest, about 3.6 eV.

The photoelectrochemical properties of the prepared samples can be characterized by the magnitude of the photo-generated current density under illumination, and fig. 8 is a graph of the photo-generated current density of the series of samples under illumination as a function of time. As can be seen from the observation of FIG. 8, the photo-generated current density in the graph is all negative, indicating that we made the productThe prepared series of photoelectrodes are all made of p-type semiconductor materials. Curve a is a plot of photo-generated current density versus time for the prepared BiOCl sample, which was only-7.42. mu.A/cm after 3 cycles of testing²I.e. it generates a smaller amount of photogenerated carriers under illumination; curve b is the photo-generated current density of the prepared BiInOCl-1:0.5 sample as a function of time, and the photo-generated current density is about-10.23 muA/cm after 3 cycles²Compared with the BiOCl sample, the method is slightly improved, which shows that the solid solution of a low proportion of In has less influence on the photoelectrochemical property of the BiOCl; curve c is a plot of photo-generated current density versus time for the BiInOCl-1:1 sample, which was found to be about-58.31 μ A/cm after stabilization of the photo-generated current over three cycles²Is 7.86 times that of the BiOCl sample, which shows that the proportion of Bi to In reaches 1:1, so that the photoelectrochemical performance of the sample is greatly improved. The curve d is a graph of the relationship between the photo-generated current density and the time of the prepared BiInOCl-1:2 sample, and the observation of the curve d can find that the photo-generated current density is continuously increased to-61.11 muA/cm along with the continuous increase of the In adding amount²8.23 times that of pure BiOCl; with the continuous increase of the added amount of In, the photo-generated current density of the BiInOCl-1:3 sample is greatly improved compared with that of pure BiOCl, but is reduced compared with that of the BiInOCl-1:2 sample, because the excessively high added amount of In damages the surface structure of the material and hinders the transfer of photo-generated carriers.

The photocatalytic degradation performance of the prepared series of samples can be characterized by the performance of photocatalytic degradation of norfloxacin, for example, curves a, b, c, d, e in fig. 9A are the degradation effect of samples BiOCl, BiInOCl-1:0.5, BiInOCl-1:1, BiInOCl-1:2 and BiInOCl-1:3 on norfloxacin with the concentration of 10mg/L under full light irradiation. The first 30min is the adsorption of the sample on norfloxacin, and the adsorption effect of BiOCl on norfloxacin can be found to be poor, while the adsorption effect of the sample on norfloxacin is improved to different degrees after different amounts of indium are added. In the curve a, when the degradation time is 5min, the degradation efficiency of BiOCl on norfloxacin is only 10%; when the degradation time is 20min, the degradation efficiency of BiOCl on norfloxacin is 33%. When the degradation time in the curve b is 5min, the degradation efficiency of BiInOCl-1:0.5 on norfloxacin is only 25 percent; when the degradation time is 20min, the degradation efficiency of BiInOCl-1:0.5 on norfloxacin reaches 73%, and compared with BiOCl, the degradation efficiency is improved to a certain extent. When the degradation time in the curve c is 5min, the degradation efficiency of BiInOCl-1:1 on norfloxacin can reach 80%, and complete degradation can be achieved within 20 min. When the degradation time in the curve d is 5min, the degradation efficiency of BiInOCl-1:2 on norfloxacin can reach 96 percent, and almost complete degradation can be achieved. When the degradation time in the curve e is 5min, the degradation efficiency of BiInOCl-1:3 on norfloxacin can reach 86%, and the norfloxacin can be completely degraded in 10 min. Fig. 9B shows that in the process of degrading norfloxacin, a BiInOCl-1:2 sample degrades ultraviolet visible absorption spectra at different times, two characteristic peaks exist at 275nm and 325nm, which respectively correspond to an aromatic ring and a piperazine ring of norfloxacin, and the peak intensities of the two characteristic peaks gradually decrease with the extension of the degradation time, which indicates that both the aromatic ring and the piperazine ring undergo a certain ring-opening reaction and may be finally degraded into carbon dioxide and water. In order to study the stability of photocatalytic degradation of the sample, the BiInOCl-1:2 sample with the best degradation performance was subjected to a cycle stability test, as shown in FIG. 9C, during the test, after degradation, the norfloxacin containing the sample was centrifuged to remove the supernatant, and the obtained sample was washed with water several times to remove adsorbed norfloxacin, and then norfloxacin was continuously added for degradation. We found that the degradation efficiency at 5min was 96% in the first test, and the degradation efficiency at 5min was still 93.7% in the fourth degradation test, which was only reduced by 2.3%, indicating that the sample had high stability and could be recycled many times. According to researches, the sample has a better degradation effect and better stability, and in order to research the universality of sample application, a plurality of dyes are selected for degradation, and as shown in FIG. 9D, the concentrations of the dyes used in the degradation process are all 10 mg/L. The BiInOCl-1:2 sample is found to have good degradation effects on methyl orange, rhodamine B and methylene blue, and the degradation efficiency within 10min can reach more than 90%, which shows that the prepared sample has good degradation effect on colorless pollutants and is also suitable for degradation removal of dyes.

In order to further study the reason for the improvement of BiInOCl-1:2 photoelectrochemical properties, the series of samples were subjected to electrochemical impedance and Mott Schottky test. Fig. 10A shows an electrochemical impedance spectrum of the prepared sample. The point in the graph is data obtained by actual tests, the size of the impedance arc radius in the graph corresponds to the migration and conversion speed of the current carrier, the smaller the impedance arc radius is, the faster the migration and conversion speed of the current carrier is, and observation can find that the impedance arc radius of the BiInOCl-1:2 sample is the smallest, and the fastest the migration and conversion speed of the current carrier is. Therefore, compared with a BiOCl sample, the material has higher photoproduction current density and performance of photocatalytic degradation of norfloxacin. The mott schottky can be used to test p-type and n-type of semiconductor, and can be used to roughly estimate the carrier concentration of the sample and the conduction band potential of p-type semiconductor material or the valence band potential of n-type semiconductor material, as shown in fig. 10B for the mott schottky test results for the series of samples. First, the positive and negative slopes of the mott schottky test can determine the p and n types of the semiconductor, the semiconductor is an n type semiconductor if the slope is regular, and the semiconductor is a p type semiconductor if the slope is negative. The slope of the curve is observed, and the slope of the sample is all negative, which indicates that the prepared sample is all p-type semiconductor, and the result is consistent with the i-t test result. Then, the intersection of the slope of the mott schottky curve and the coordinate axis can approximate the conduction band potential or the valence band potential of the semiconductor, the p-type semiconductor estimates the valence band potential, and the n-type semiconductor estimates the conduction band potential. As can be seen from the observation curves, the valence band potential of the BiOCl sample is about 1.76V, while the valence band potential of the BiInOCl-1:2 sample is shifted to 2.06V, and the valence band of the semiconductor is capable of enhancing the oxidation capability of photogenerated holes on the valence band.

The superoxide radical and hydroxyl radical are active species with oxidizability, and in order to research the reason of the improvement of photocatalytic performance and photoelectrochemical performance, the existence condition of the active radicals of BiOCl and BiInOCl-1:2 samples is further researched. FIGS. 11A and 11B show the presence of superoxide and hydroxyl radicals, respectively, in BiOCl and BiInOCl-1:2 samples under total light. In fig. 11A, BiOCl in the dark state does not generate superoxide radical, and after 4min of illumination, very weak signal peaks of superoxide radical with a signal intensity ratio of 1:1:1:1 were detected in the BiOCl sample, and the signal intensity of superoxide radical generated by BiOCl increased with time, indicating that the amount of superoxide radical generated by BiOCl increased with time. The BiInOCl-1:2 sample does not generate superoxide radical in a dark state, and also generates a signal peak of the superoxide radical after illumination for 4min, but the intensity of the signal peak of the superoxide radical of the BiInOCl-1:2 sample is stronger than that of the signal peak of the superoxide radical of the BiInOCl-1:2 sample, which shows that the BiInOCl-1:2 sample generates more superoxide radical than the BiOCl sample under the same illumination condition. Similarly, BiOCl in the dark state in FIG. 11B did not generate hydroxyl radicals, and after 4min of added illumination, very weak signal peaks of hydroxyl radicals with a 1:2:2:1 signal intensity ratio were detected in the BiOCl sample, and the signal intensity of the hydroxyl radicals generated by BiOCl increased with time, indicating that the amount of hydroxyl radicals generated by BiOCl increased with time. The BiInOCl-1:2 sample does not generate hydroxyl radicals in a dark state, and also generates a signal peak of the hydroxyl radicals after illumination for 4min, but the signal peak intensity of the hydroxyl radicals of the BiInOCl-1:2 sample is stronger than that of the BiOCl, which shows that the BiInOCl-1:2 sample generates more hydroxyl radicals than the BiOCl under the same illumination condition. Compared with BiOCl, BiInOCl-1:2 generates more superoxide radicals and hydroxyl radicals, and the valence band potential of BiInOCl-1:2 is corrected, so that the conclusion that the oxidizing capability is stronger is consistent.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications can be made without departing from the principles of the invention and these modifications are to be considered within the scope of the invention.

Claims

1. A BiInOCl porous microsphere photocatalyst with a hierarchical structure is characterized in that: bismuth nitrate, indium nitrate, hydrochloric acid and ethylene glycol are used as basic raw materials, and a BiInOCl porous microsphere photocatalyst with a hierarchical structure is prepared by a simple one-step hydrothermal method.

2. The hierarchical BiInOCl porous microsphere photocatalyst as claimed in claim 1, which is characterized in that: the Bi: In of the BiInOCl porous microsphere photocatalyst is 1:0.5, 1:1, 1:2 and 1: 3.

3. The hierarchical BiInOCl porous microsphere photocatalyst as claimed in claim 1, which is characterized in that: the Bi: In ═ 1:2 of the BiInOCl porous microsphere photocatalyst is the optimal proportion.

4. A method for preparing the bi inocl porous microsphere photocatalyst with a hierarchical structure as claimed in any one of claims 1 to 3, which is characterized by comprising the following steps:

(1) preparing sample solutions in different proportions: firstly, 4 beakers with the specification of 100mL are taken, 80mL of ethylene glycol is added, and then 0.4mmol of Bi (NO) is added respectively₃)₃Adding 0.2mmol, 0.4mmol, 0.8mmol and 1.2mmol of In (NO) respectively₃)₃Finally, adding 0.4mmol of HCl solution, and stirring for 30min until the HCl solution is completely dissolved;

(2) hydrothermal reaction: adding the prepared samples with different proportions into a 100mL reaction kettle, and placing the reaction kettle in an electrothermal blowing dry box at the temperature of 140 ℃ for reaction for 24 hours;