Preparation method of selenium-bismuth oxide nanosheet and heterojunction type photoelectrode based on preparation method
阅读说明：本技术 一种硒氧化铋纳米片的制备方法及基于其的异质结型光电极 (Preparation method of selenium-bismuth oxide nanosheet and heterojunction type photoelectrode based on preparation method ) 是由 李国华 周雪 王宁 项曙光 胡鑫 于 2020-11-23 设计创作，主要内容包括：本发明公开了一种硒氧化铋纳米片的制备方法及基于其的异质结型光电极,是通过改进Bi-2O-2Se纳米片的合成工艺,获得了形貌均匀、不团聚且厚度极薄的Bi-2O-2Se纳米片,然后通过合适的工艺方法将其与WO-3纳米板构建为异质结光电极,二者表现出极强的协同增效作用,所得异质结具有优异的PEC性能。本发明Bi-2O-2Se纳米片的制备方法与异质结的构建方法,都具有方法简单、安全性能高和无污染的优势。(The invention discloses a preparation method of a selenium-bismuth oxide nanosheet and a heterojunction type photoelectrode based on the selenium-bismuth oxide nanosheet, which is realized by improving Bi 2 O 2 The synthesis process of the Se nanosheet obtains Bi with uniform appearance, no agglomeration and extremely thin thickness 2 O 2 Se nanosheets, which are then reacted with WO by a suitable process 3 The nano plate is constructed into a heterojunction photoelectrode, the heterojunction photoelectrode and the photoelectrode have strong synergistic interaction, and the obtained heterojunction has excellent PEC performance. Bi of the invention 2 O 2 The preparation method of the Se nanosheet and the construction method of the heterojunction have the advantages of simple method, high safety performance and no pollution.)
1. A preparation method of a selenium bismuth oxide nanosheet is characterized by comprising the following steps:
step 1, adding bismuth ammonium citrate and sodium selenite into deionized water, heating and stirring until the bismuth ammonium citrate and the sodium selenite are fully dissolved, then adding a KOH solution, and continuously stirring uniformly to obtain a precursor solution;
step 2, transferring the precursor liquid into a reaction kettle, and carrying out hydrothermal reaction at the temperature of 180 ℃ and 210 ℃ for 24-36 hours; after the reaction is finished, the reaction solution is dispersed evenly by ultrasonic, centrifuged and filteredFiltering, washing and drying the obtained precipitate to obtain Bi2O2Se nanosheet powder.
2. The method of claim 1, wherein: in the step 1, the concentration of the KOH solution is 2-4mol/L, and the dosage ratio of the sodium selenite, the ammonium bismuth citrate, the deionized water and the KOH solution is 1mmoL:1-3mmoL:5-20mL:20-40 mL.
3. The method of claim 1, wherein: in step 1, the temperature for heating and stirring is 20-40 ℃.
4. The method of claim 1, wherein: in the step 2, the filling degree of the precursor liquid added into the reaction kettle is 50-60%.
5. The method of claim 1, wherein: in the step 2, the cleaning is alternately cleaning by deionized water and absolute ethyl alcohol; the drying is carried out for 5 to 8 hours under the condition of 60 to 80 ℃ of a vacuum drying oven.
6. A bismuth oxide selenide nanosheet prepared by the preparation method defined in any one of claims 1-5.
7. A heterojunction photoelectrode based on bismuth selenide nanosheets as defined in claim 6, wherein: the photoelectrode is prepared by applying the Bi of claim 62O2Se nanosheet and WO3The nano plate is constructed into a heterojunction structure so as to obtain the nano plate.
8. The heterojunction type photoelectrode of claim 7, wherein: the photoelectrode takes conductive glass as a substrate, and WO which grows vertically is synthesized on the surface of the conductive glass by a hydrothermal method3An array of nanoplates, followed by applying the Bi of claim 62O2Solution spin coating of Se nanoplates onto the WO3Of arrays of nanoplatesSurface, thereby obtaining.
9. A method for fabricating a heterojunction type photoelectrode as claimed in claim 7 or 8, comprising the steps of:
step 1, dissolving sodium tungstate and ammonium oxalate in deionized water, stirring uniformly at room temperature, and then sequentially adding HCl and H2O2Mixing with ethanol under stirring to obtain WO3A precursor solution;
preparing ethanol and APTES into a mixed solution according to the volume ratio of 100:1, then putting the cleaned conductive glass into the mixed solution, shaking for 1-2h, taking out, washing and drying;
placing the treated conductive glass into the WO3Reacting in the precursor solution in a water bath kettle at the temperature of 80-100 ℃ for 180-250 minutes; after the reaction is finished, cooling to room temperature, taking out the conductive glass, washing and drying to obtain WO3A film;
subjecting the obtained WO3Annealing the film in a muffle furnace at 400-600 ℃ for 1.5-3h to synthesize vertically grown WO on the surface of the conductive glass3A nanoplate array;
step 2 of adding the Bi of claim 62O2Dissolving Se nanosheet in isopropanol, then dropwise adding a proper amount of nafion solution, and uniformly stirring by ultrasonic to obtain Bi2O2Se solution;
step 3, adding Bi obtained in step 22O2Se solution is coated on the growth substrate with WO3Naturally drying the conductive glass surface of the nano plate array, and then heating the conductive glass surface on a heating table at 100 ℃ for 15-20 min;
step 4, annealing the conductive glass treated in the step 3 in a glove box filled with Ar gas at the temperature of 180 ℃ for 1-3h to form WO3/Bi2O2Se heterojunction photoelectrode.
10. The method of manufacturing according to claim 9, wherein:
in step 1, sodium tungstate, ammonium oxalate, deionized water, HCl with the concentration of 10-12mol/L and H with the concentration of 9.5-10mol/L2O2The dosage ratio of the ethanol to the ethanol is 1mmol:0.5-1mmol:20-35mL:5-7mL:5-6mL:20-30 mL;
in step 2, Bi2O2The dosage ratio of the Se nano-sheet, the isopropanol and the nafion solution is 0.2-0.4g, 10-20mL and 0.1-0.3 mL.
Technical Field
The invention belongs to the field of photoelectricity, and particularly relates to a preparation method of a selenium bismuth oxide nanosheet and a heterojunction type photoelectrode based on the preparation method.
Background
With the development of global economy, fossil fuels are excessively consumed, resulting in environmental problems becoming more and more serious. Sunlight is one of the most outstanding renewable energy sources due to its inexhaustible, versatile, abundant and environmentally friendly characteristics. By efficiently coupling solar energy with electrochemical mechanisms, a wide range of photo-electrochemical (PEC) devices have been explored, such as sensors, solar cells and water splitting devices (nat. rev. mater.,2016, volume 1, page 15010). Therefore, intensive research on materials and structures having excellent PEC properties and further improvement of the properties thereof, thereby improving the PEC conversion rate, is one of important research subjects.
Based on the excellent optical, electrical and non-toxic properties, many studies have been focused on bismuth-based semiconductors such as bismuth salt (BiVO) in recent years4，Bi2MoO6，Bi2WO6，Bi2O2Se), bismuth oxyhalide (binox (X ═ Cl, Br, I), bismuth sulfide (Bi)2S3) (adv.mater.,2017, volume 29, page 1702387) and bismuth sulfide (Bi)2O2S，Bi9O7.5S6，Bi2OS2) Etc. (PCCP,2018, volume 20, pages 20340-20346). Selenium bismuth oxide (Bi)2O2Se) have also recently begun to attract attention in the industry, e.g. Bi in ultra-thin 2D structures2O2The hydrothermal synthesis method of the Se nanosheet is reported, and the Se nanosheet is prepared from bismuth ammonium citrate serving as a bismuth source and sodium selenite serving as a selenium source, and has the thickness of about 4.7nm (ADVANCED MATERIALS TECHNOLOGIES, 2020, volume 5). Two-dimensional material Bi2O2Se exhibits extremely high mobility, excellent stability, adjustable bandgap and excellent mechanical properties, and theoretically should exhibit excellent performance in the electronic and optoelectronic fields. However, it has been conventionally proposed to use Bi2O2Se has been studied mainly on its thermoelectric properties, but its PEC properties are poor and it is difficult to form a film.
The construction of heterojunctions is an effective method of enhancing PEC performance in nanostructure design, by which two or more semiconductor materials with matched energy bands can be composited together, and then by inhibiting recombination, the separation and transfer of photogenerated electron holes can be improved. However, the research of the invention finds that the Bi prepared according to the existing hydrothermal synthesis process2O2The Se nanosheet is difficult to combine with other semiconductor materials to form a heterojunction structure. Study its originThus, probably because such wet chemical synthesis methods are generally accompanied by agglomeration and non-uniformity, Bi is obtained2O2The Se nanosheets are also too thick to allow them to be effectively composited with other semiconductor materials. Therefore, Bi is first required to be synthesized2O2And (3) searching the process conditions of the Se nanosheets to change the microscopic morphology of the Se nanosheets. Meanwhile, the research of the invention also finds that the appearance and the type of another selected semiconductor material can greatly influence the performance of the obtained heterojunction. The invention screens a plurality of materials and discovers tungsten trioxide (WO)3) Or a suitable material. Tungsten trioxide (WO)3) Have the advantage of being non-toxic, stable and corrosion resistant, and are one of the materials recognized in PEC applications. But WO3There are other drawbacks in PEC applications, such as: relatively wide band gap (2.8 eV), slow hole kinetics, low charge transfer at the semiconductor/electrolyte Interface, high rate of photo-generated electron-hole recombination (J.colloid Interface Sci.,2018, Vol.510, pp.20-31; appl.Catal.B-environ.,2018, Vol.220, pp.417-428; ACS appl.Mater.interfaces,2017, Vol.9, pp.40235-40243).
Disclosure of Invention
Based on the defects of the prior art, the invention provides a preparation method of a selenium-bismuth oxide nanosheet and a heterojunction type photoelectrode based on the preparation method, and the technical problems to be solved are that: firstly, by improving the synthesis process of the selenium bismuth oxide nanosheets, the selenium bismuth oxide nanosheets which are uniform in appearance, free of agglomeration and extremely thin in thickness are obtained; then, based on the obtained selenium bismuth oxide nanosheets, a suitable second semiconductor material is screened and constructed into a heterojunction with excellent PEC performance.
In order to realize the purpose of the invention, the following technical scheme is adopted:
the invention firstly discloses a preparation method of a selenium bismuth oxide nanosheet, which comprises the following steps:
step 1, adding bismuth ammonium citrate and sodium selenite into deionized water, heating and stirring until the bismuth ammonium citrate and the sodium selenite are fully dissolved, then adding a KOH solution, and continuously stirring uniformly to obtain a precursor solution;
step 2, transferring the precursor liquid into a reaction kettle, and carrying out hydrothermal reaction at the temperature of 180 ℃ and 210 ℃ for 24-36 hours; after the reaction is finished, the reaction solution is dispersed evenly by ultrasonic, centrifuged and filtered, and the obtained precipitate is cleaned and dried to obtain Bi2O2Se nanosheet powder.
Preferably, in the step 1, the concentration of the KOH solution is 2-4mol/L, and the dosage ratio of the sodium selenite, the ammonium bismuth citrate, the deionized water and the KOH solution is 1mmoL:1-3mmoL:5-20mL:20-40 mL.
Preferably, in step 1, the temperature for heating and stirring is 20-40 ℃.
Preferably, in step 2, the filling degree of the precursor solution added into the reaction kettle is 50-60%.
Preferably, in the step 2, the cleaning is performed by alternately cleaning with deionized water and absolute ethyl alcohol; the drying is carried out for 5 to 8 hours under the condition of 60 to 80 ℃ of a vacuum drying oven.
The invention also discloses a heterojunction photoelectrode which is prepared by the Bi prepared by the method2O2Se nanosheet and WO3The nano plate is constructed into a heterojunction structure so as to obtain the nano plate. Specifically, the method comprises the steps of taking conductive glass as a substrate, and synthesizing vertically grown WO on the surface of the conductive glass by a hydrothermal method3Nano plate array, and preparing Bi by the above method2O2Solution spin coating of Se nanoplates onto the WO3A surface of a nanoplate array.
The invention relates to a manufacturing method of a heterojunction type photoelectrode, which comprises the following steps:
step 1, dissolving sodium tungstate and ammonium oxalate in deionized water, stirring uniformly at room temperature, and then sequentially adding HCl and H2O2Mixing with ethanol under stirring to obtain WO3A precursor solution;
preparing ethanol and APTES into a mixed solution according to the volume ratio of 100:1, then putting the cleaned conductive glass into the mixed solution, shaking for 1-2h, taking out, washing and drying;
placing the treated conductive glass into the WO3In the precursor solution, thenReacting in a water bath kettle at 80-100 ℃ for 180-250 minutes; after the reaction is finished, cooling to room temperature, taking out the conductive glass, washing and drying to obtain WO3A film;
subjecting the obtained WO3Annealing the film in a muffle furnace at 400-600 ℃ for 1.5-3h to synthesize vertically grown WO on the surface of the conductive glass3A nanoplate array;
step 2 of adding the Bi of claim 62O2Dissolving Se nanosheet in isopropanol, then dropwise adding a proper amount of nafion solution, and uniformly stirring by ultrasonic to obtain Bi2O2Se solution;
step 3, adding Bi obtained in step 22O2Se solution is coated on the growth substrate with WO3Naturally drying the conductive glass surface of the nano plate array, and then heating the conductive glass surface on a heating table at 100 ℃ for 15-20 min;
step 4, annealing the conductive glass treated in the step 3 in a glove box filled with Ar gas at the temperature of 180 ℃ for 1-3h to form WO3/Bi2O2Se heterojunction photoelectrode.
Preferably: in step 1, sodium tungstate, ammonium oxalate, deionized water, HCl with the concentration of 10-12mol/L and H with the concentration of 9.5-10mol/L2O2The dosage ratio of the ethanol to the ethanol is 1mmol:0.5-1mmol:20-35mL:5-7mL:5-6mL:20-30 mL; in step 2, Bi2O2The dosage ratio of the Se nano-sheet, the isopropanol and the nafion solution is 0.2-0.4g, 10-20mL and 0.1-0.3 mL.
The invention has the beneficial effects that:
1. the invention improves Bi2O2The synthesis process of the Se nanosheet obtains Bi with uniform appearance, no agglomeration and extremely thin thickness2O2Se nanosheets, which are then reacted with WO by a suitable process3The nano plate is constructed into a heterojunction photoelectrode, the heterojunction photoelectrode and the photoelectrode have strong synergistic interaction, and the obtained heterojunction has excellent PEC performance.
2. The nanometer material is used as a microscopic material, the shape and the performance of the product can be greatly changed by slight change of the preparation method, and the result has strong contingency. The invention discovers that the raw material proportion, the reaction temperature, the filling ratio of a reaction kettle and the like can influence the appearance of the product, particularly Bi2O2The thickness and the shape uniformity of the Se nanosheet have great influence, and the Bi with the required extremely thin thickness (less than 3.5nm) is obtained through the cooperation of all process conditions2O2Se nanosheet.
3. Bi of the invention2O2The preparation method of the Se nanosheet and the construction method of the heterojunction have the advantages of simple method, high safety performance and no pollution.
Drawings
FIG. 1 shows WO prepared in example 1 of the present invention3Nano plate, Bi2O2Se nanosheet and WO3/Bi2O2An X-ray diffraction pattern of a Se heterojunction;
FIG. 2 shows Bi prepared in example 1 of the present invention2O2Scanning electron microscopy of Se nanoplates;
FIG. 3 shows Bi prepared in example 1 of the present invention2O2High resolution transmission electron microscope images of Se nanoplates;
FIG. 4 shows WO prepared in example 1 of the present invention3Nano plate, Bi2O2Se nanosheet and WO3/Bi2O2A current-time curve test chart of the Se heterojunction;
FIG. 5 shows WO prepared in example 1 of the present invention3Nano plate, Bi2O2Se nanosheet and WO3/Bi2O2And (3) a linear sweep voltammetry test chart of the Se heterojunction.
Detailed Description
The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.
Example 1
Step 1, dissolving 2.7mmol sodium tungstate and 2.4mmol ammonium oxalate in 66mL deionized water, and stirring at room temperature15min, then 18mL of HCl with the concentration of 12mol/L is dropwise added and stirred for 15min, and 16mL of H with the concentration of 9.7mol/L is dropwise added2O2Stirring for 10min, and finally adding 60mL of ethanol into the solution and stirring for 30min to obtain WO3A precursor solution; preparing ethanol and APTES into a mixed solution according to the volume ratio of 100:1, then putting the cleaned conductive glass into the mixed solution, shaking for 1-2h, taking out, washing and drying; placing the treated FTO conductive glass into WO3Reacting in the precursor solution in a water bath kettle at 85 ℃ for 200 minutes; after the reaction is finished, cooling to room temperature, taking out the conductive glass, washing the conductive glass with deionized water, and drying at 60 ℃ for 10 hours to obtain WO3A film; subjecting the obtained WO3Annealing the film in a muffle furnace at 500 ℃ for 2h to synthesize vertically grown WO on the surface of the conductive glass3An array of nanoplates.
Step 2, adding 4mmol of bismuth ammonium citrate and 2mmol of sodium selenite into 20mL of deionized water, heating and stirring at 35 ℃ for 15min, then adding 54mL of 3.7mol/L KOH solution, and stirring for 2h to obtain a precursor solution; transferring 60mL of precursor solution into a 100mL reaction kettle, and carrying out hydrothermal reaction at 200 ℃ for 30 hours; after the reaction is finished, the reaction solution is dispersed evenly by ultrasonic, centrifuged and filtered, the obtained precipitate is alternately cleaned for 6 times by absolute ethyl alcohol and deionized water and dried for 8 hours at 70 ℃ in a vacuum drying oven, and then Bi is obtained2O2Se nanosheet powder.
Step 3, adding 0.15g of Bi2O2Dissolving Se nanosheet in 15mL of isopropanol, ultrasonically stirring for 1 hour, then dropwise adding 200 mu L of nafion solution, ultrasonically stirring for 30 minutes to obtain Bi2O2Se solution.
Step 4, taking 25 mu L of Bi2O2And (3) spin-coating the glass obtained in the step (1) with Se solution, naturally drying for 30 minutes after 5 times of spin-coating, and heating for 15 minutes on a hot table at 100 ℃.
Step 5, annealing the conductive glass treated in the step 4 for 90min at 200 ℃ in a glove box filled with Ar gas to form WO3/Bi2O2Se heterojunction photoelectrode.
FIG. 1 shows the WO prepared in this example3Nano plate, Bi2O2Se nanosheet and WO3/Bi2O2XRD pattern of Se heterojunction, from which WO can be seen3/Bi2O2Se has obvious peaks on (002), (004), (006) and (008) planes, which indicates that the Se is WO3And Bi2O2Se composite heterojunction structure.
FIG. 2 shows Bi prepared in example 1 of the present invention2O2Scanning electron microscopy of Se nanoplates, from which it can be seen that the product is lamellar.
FIG. 3 shows Bi prepared in this example2O2Single crystal structure of Se nanosheet, having a lattice fringe spacing of 0.29nm as measured in the figure, corresponding to Bi2O2The (004) plane of Se.
WO obtained in this example3/Bi2O2The Se heterojunction is used as a photoelectrode, and the performance of the Se heterojunction is tested according to the following steps:
in an electrochemical workstation, Ag/AgCl is used as a reference electrode, Pt is used as a counter electrode, and 0.2mol of Na2SO4A three electrode test was performed for the electrolyte solution. Under the irradiation of simulated sunlight, a linear sweep voltammetry test is carried out by using a voltage of 0-0.9, and an I-T test is carried out by using a voltage of 0.8V. The illumination area is 0.25cm2The period is 20 s.
For comparison, this example also prepares WO3Photoelectrode (i.e., the sample obtained in step 1 above) and Bi2O2Se nanosheet photoelectrode (i.e. replacing the conductive glass of the step 4 above with non-grown WO)3Conductive glass of a nanoplate array) and the same test was performed.
FIG. 4 shows the WO prepared in this example3Nano plate, Bi2O2Se nanosheet and WO3/Bi2O2The Se heterojunction simulates a current-time curve map under the irradiation of sunlight. It can be seen that: bi2O2Although Se is a good thermoelectric material, the PEC performance is poor, and in a three-electrode test with 0.2mol of sodium sulfate as an electrolyte solution, when a bias voltage of 0.8V is applied, Bi is added2O2Light dark current of SeCan only reach microampere level or even smaller, and the difference of two current-voltage curves is extremely small and almost becomes a straight line. At a voltage of 0.8V, WO3The photocurrent of the light source reaches 0.0502mA, and the dark current is about 0.023 mv. And when a 0.8V bias is applied, WO3/Bi2O2The photocurrent of the Se heterojunction was 0.12mA (greater than WO alone)3) Dark current of 0.018mA (less than WO alone)3) This fully illustrates the heterojunction structure making Bi2O2The PEC performance of Se is greatly improved, and WO is fully described3And Bi2O2Synergistic effect of Se on PEC performance. Furthermore, WO3/Bi2O2The reaction time for the rise and fall of the Se heterojunction was 6ms, and it can be seen that the absorption response rate remained unchanged. This rapid decline is facilitated by the WO prepared3/Bi2O2The S heterojunction array has fewer defects.
FIG. 5 shows the WO prepared in this example3Nano plate, Bi2O2Se nanosheet and WO3/Bi2O2The linear sweep voltammetry curve test chart of Se can verify Bi2O2The PEC performance of Se is poor, but the performance of Se is greatly improved after the Se forms a heterojunction, and the Se has good photoresponse.
The above description is only exemplary of the present invention and should not be taken as limiting the invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.