Indium hydroxide photocatalyst containing hydroxyl vacancy as well as preparation method and application of indium hydroxide photocatalyst

Abstract

The invention relates to an indium hydroxide photocatalyst containing hydroxyl vacancy and a preparation method and application thereof, and the preparation method of the catalyst comprises the following steps: (1) preparing a clear sodium oleate aqueous solution by using deionized water, slowly adding a compound containing In < 3 + > into the clear sodium oleate aqueous solution to obtain a mixed solution with floccules, and then adjusting the pH value of the mixed solution to 3-6; and (2) carrying out hydrothermal reaction on the mixed solution obtained in the step (1), centrifuging, washing and drying to obtain the indium hydroxide containing the hydroxyl vacancy. The catalyst disclosed by the invention has a relatively wide light absorption range, the CO2 reduction capacity of the catalyst under a xenon lamp is greatly improved, the catalyst shows excellent selectivity of reducing CO2 into ethanol, and meanwhile, the photocatalyst has low resistivity, rapid carrier transfer capacity, high photon-generated carrier separation capacity and low carrier recombination rate; the good CO2 reduction cycle stability is realized, and the like.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, and relates to an indium hydroxide photocatalyst containing hydroxyl vacancies, its preparation method, and its application. Background Technology

[0002] Faced with surging energy demands driven by global industrialization and population growth, our long-standing reliance on fossil fuels is not only facing depletion, but the excessive carbon dioxide released from their combustion is also contributing to severe climate change. Converting atmospheric CO2 into valuable resources, rather than treating it as pure waste, has become a global consensus for achieving sustainable development. Simulating natural photosynthesis and using solar energy to drive CO2 reduction is widely recognized as a promising solution. It holds the promise of simultaneously addressing the two major challenges of the greenhouse effect and the energy crisis, providing crucial support for our journey towards a carbon-neutral future. Among the many possible conversion products, multi-carbon fuels generated through C / C coupling reactions, particularly ethanol, are highly favored due to their high energy density, ease of storage and transportation, and perfect compatibility with existing energy infrastructure. However, the efficient and selective conversion of inert CO2 molecules into ethanol is a complex process involving multiple electron-proton transfers, and its reaction pathway is fraught with challenges. Therefore, developing novel and efficient photocatalysts, much like designing a skilled "molecular craftsman" capable of precisely controlling the binding energy of reaction intermediates and guiding the reaction towards the desired ethanol product, has become an important but also challenging problem.

[0003] Traditional photocatalytic strategies, such as defect engineering, heterostructure building, and surface modification, have been extensively studied, but have long faced three major bottlenecks: (1) semiconductors (such as TiO2 and ZnO) have wide band gaps and limited visible light absorption; (2) CO2 mass transfer efficiency is low, and the concentration of reactants at active sites is insufficient, which promotes the side reaction hydrogen evolution (HER); (3) in the complex reaction network, C1 and C2 are difficult to react. 2+ The competing pathways reduce the selectivity of the target product.

[0004] Indium hydroxide (In(OH)3) has attracted attention as a novel photocatalytic CO2 reduction catalyst due to its good adsorption and activation ability for CO2 molecules and its tunable morphology. However, In(OH)3 still faces the following problems in photocatalytic CO2RR applications: (1) its ability to utilize light is limited, its intrinsic band gap is relatively wide, and it mainly responds to ultraviolet light; (2) the separation and migration efficiency of photogenerated carriers is low, which leads to easy recombination of electron-hole pairs.

[0005] To overcome the aforementioned limitations, this invention proposes optimizing the reaction pathway by constructing locally confined active site pairs. Inspired by the synergistic effect of spatially separated active sites in tandem catalysis strategies, we designed a type of active site pair on the In(OH)3 surface, composed of hydroxyl vacancies (Ov) and adjacent surface hydroxyl groups (–OH), mimicking the synergistic catalytic function of Lewis acid-base pairs. The Ov site acts as an electron enrichment center, enhancing CO2 adsorption and activation, and promoting the formation of CO intermediates; while the adjacent –OH site acts as a proton source, promoting the hydrogenation step. The close spatial arrangement of these two sites effectively lowers the reaction energy barrier of C–C coupling. Simultaneously, by controlling the surface Ov density, the material is endowed with local hydrophobic properties, creating a CO2-rich microenvironment at the gas-liquid-solid three-phase interface, effectively suppressing hydrogen evolution side reactions, increasing the surface coverage and residence time of CO intermediates, thereby guiding the reaction pathway towards ethanol formation. This strategy not only achieves electronic structure regulation of active sites but also breaks through the limitations of traditional photocatalysts in C… 2+ Limitations on product selectivity.

[0006] This invention is proposed to solve the above-mentioned problems and provide solutions. Summary of the Invention

[0007] The purpose of this invention is to provide an indium hydroxide photocatalyst containing hydroxyl vacancies, its preparation method, and its applications. This addresses the technical problems of poor CO2 reduction performance caused by the low light absorption and easy recombination of photogenerated carriers in indium hydroxide as a photocatalytic material. The prepared catalyst exhibits high light absorption, with an absorption edge reaching 367 nm, and minimal carrier recombination. Under xenon lamp irradiation, the reduction rate to ethanol can reach up to 73.6 μmol·h⁻¹. -1 ·g -1 .

[0008] The objective of this invention can be achieved through the following technical solutions: On the one hand, this invention proposes a method for preparing an indium hydroxide photocatalyst containing hydroxyl vacancies, comprising the following steps: (1) Prepare a clear sodium oleate aqueous solution using deionized water, and remove the sodium oleate containing In. 3+ The compound was slowly added to the clarified sodium oleate aqueous solution to obtain a mixture with flocculent matter, and then the pH of the mixture was adjusted to 3-6. (2) The mixture obtained in step (1) is subjected to hydrothermal reaction, and indium hydroxide containing hydroxyl vacancies is obtained by centrifugation, washing and drying.

[0009] In step (1), the In-containing compound must be added after the sodium oleate has completely dissolved. 3+ The compound, slowly added, contains In 3+The optimal rate for the compound is 0.01 g / s.

[0010] Furthermore, in step (1), the concentration of the sodium oleate aqueous solution is preferably 0.06 mmol / ml. Of course, the concentration here can also be adjusted according to the preparation needs. At the same time, during the dropping process, the dropping rate is controlled at 0.5 ml / min.

[0011] Furthermore, in step (1), sodium oleate and In 3+ The optimal molar ratio is 3:1.

[0012] In step (1), the In-containing 3+ The preferred compound is indium nitrate or its hydrate.

[0013] In step (1), the reagent used to adjust the pH is preferably dilute nitric acid, and the optimal concentration of the dilute nitric acid solution is 1M.

[0014] Furthermore, in step (2), the hydrothermal reaction temperature is 160℃ and the time is 18h.

[0015] Furthermore, in step (2), the optimal pH value of the solution before hydrothermal treatment should be 3.

[0016] Furthermore, in step (2), the washing process should adopt the optimal mixing ratio of isopropanol:ethanol:water volume ratio of 2:1:1.

[0017] The preparation principle and process of this invention are as follows: ① Using sodium oleate as a structure directing agent, its carboxyl functional group interacts with In 3+ Metal ions undergo chemisorption to form stable metal soaps. This substance can preferentially and selectively adsorb onto the high-energy crystal planes of In(OH)3, inhibiting its anisotropic growth, which is key to inducing the formation of plate-like structures. ② By precisely adjusting the pH value of the reaction system, the form in which sodium oleate exists can be controlled. Under lower pH conditions, sodium oleate reacts with H+. + The combination generates oleic acid molecules, which can self-assemble into layered micelles through hydrogen bonds and van der Waals forces. Their unionized carboxyl groups can further form an intermolecular hydrogen bond network, serving as a soft template to guide the directional growth of In(OH)3 crystal nuclei into ultrathin nanosheets. ③ Under high temperature and high pressure hydrothermal conditions, crystals preferentially grow along the crystal plane stabilized by the structure-directing agent. In a strongly acidic microenvironment, H... + The combined effect of etching and rapid crystallization kinetics not only limits the size of the crystal, but also directly induces the removal of hydroxyl groups (-OH) in the crystal lattice during the growth process, thereby generating a large number of hydroxyl vacancies (Ov) in situ and in a controllable manner. ④ The formed Ov and adjacent surface hydroxyl groups (–OH) spatially constitute a hindered Lewis acid-base pair. Ov, as an electron-rich region (Lewis acid site), enhances CO2 adsorption and activation, while the adjacent –OH (Lewis base site) promotes proton transfer. The synergistic effect of these two factors significantly lowers the energy barrier for CO2 activation and C–C coupling. Simultaneously, the introduction of Ov reduces surface energy, endowing the material with localized hydrophobic properties. ⑤ The generation of vacancies in indium hydroxide causes a redistribution of electrons, thereby changing the d-band center of the catalyst and further improving the photocatalytic reduction performance of CO2; ⑥ The electronic structure of indium hydroxide theoretically matches the energy required to reduce CO2 to ethanol, and this modification greatly improves the photocatalytic reduction performance of CO2.

[0018] On the other hand, this invention proposes an indium hydroxide photocatalyst containing hydroxyl vacancies, which is prepared using the method described above. Containing In, O, and H elements, the indium hydroxide has a nanosheet structure with square sheets approximately 20 nm in size. The optimal pH for the synthesis of this indium hydroxide quantum dot photocatalyst containing hydroxyl vacancies is 3. Its absorption edge can reach 367 nm, and carrier recombination is minimal. Under xenon lamp irradiation, the reduction rate to ethanol can reach up to 73.6 μmol·h⁻¹. -1 ·g -1 .

[0019] The series of In(OH)3 materials synthesized via a solvothermal method employing the synergistic effect of acid regulation and structure-directing agents exhibit unique localized structural features in the obtained In(OH)3 ultrathin nanosheets with controllable hydroxyl vacancies (Ov) and surface hydroxyl groups (–OH). Compared to traditional bulk In(OH)3, this ultrathin structure possesses a larger specific surface area and a shorter charge migration path, which is beneficial for the efficient separation and migration of photogenerated carriers. Furthermore, the ultrathin structure promotes the spatial formation of hindered Lewis acid-base pairs between surface Ov and –OH, where Ov acts as an electron enrichment center, enhancing CO2 adsorption and activation, while –OH promotes proton transfer; the synergistic effect significantly reduces the C–C coupling barrier. Simultaneously, the introduction of Ov imparts hydrophobic properties to the material surface, constructing a CO2-rich reaction microenvironment at the gas-liquid-solid three-phase interface, effectively suppressing hydrogen evolution side reactions, increasing the coverage of *CO intermediates, and guiding the reaction pathway towards ethanol. This structural design provides an ideal platform for atomically controlled catalytic microenvironment regulation.

[0020] Furthermore, this invention also provides an application of an indium hydroxide photocatalyst containing hydroxyl vacancies. Specifically, this tandem photocatalyst is used for the photocatalytic reduction of CO2 to CH3CH2OH, exhibiting good photocatalytic activity in the UV-Vis region and excellent cycling stability. It can reduce CO2 to CH3CH2OH in pure water without the addition of sacrificial agents.

[0021] The indium hydroxide photocatalyst containing hydroxyl vacancies of the present invention, as a novel photocatalyst, has the following advantages in the application of photocatalytic reduction of CO2: ① The two-dimensional ultrathin sheet structure has a large specific surface area, providing more surface active sites; ②The ultrathin structure significantly shortens the charge migration path, effectively promoting the separation and migration of photogenerated carriers; ③ The hydroxyl vacancies (Ov) constructed on the surface form hindered Lewis acid-base pairs with adjacent hydroxyl groups (–OH). Ov acts as an electron enrichment center to enhance CO2 adsorption activation, and –OH promotes proton transfer, thus synergistically reducing C–C coupling energy. ④ The introduction of hydroxyl vacancies optimized the band structure of the material, reducing the band gap of B-In(OH)3 to 2.4 eV and significantly broadening the visible light absorption range; ⑤ The formation of a hydrophobic microenvironment on the surface promotes the enrichment of CO2 at the gas-liquid-solid three-phase interface, effectively suppresses hydrogen evolution side reactions, and improves the coverage of CO intermediates. ⑥ By precisely controlling the synthesis pH value, the concentration of hydroxyl vacancies can be constructed in a controllable manner, providing a new paradigm for the rational design of catalytic microenvironments.

[0022] The present invention discloses an indium hydroxide photocatalyst containing hydroxyl vacancies, which constructs an ultrathin nanosheet structure with a specific local microenvironment by precisely controlling the synthesis conditions. This enables precise control of the carbon dioxide reduction reaction pathway, resulting in better absorption and utilization of light, thus promoting the development of photocatalysts and having significant practical applications for making fuller use of sunlight.

[0023] The present invention discloses an indium hydroxide photocatalyst containing hydroxyl vacancies, which, compared with traditional indium hydroxide materials, has a wider light absorption range, superior carbon dioxide adsorption capacity, high CO2 reduction performance, low resistivity, rapid transfer of free carriers, high photogenerated carrier separation capability, low carrier recombination rate, good CO2 reduction cycle stability, and higher carbon-carbon coupling selectivity.

[0024] This invention discloses an indium hydroxide photocatalyst containing hydroxyl vacancies. The hydroxyl vacancies on the surface form synergistic active sites with adjacent hydroxyl groups, providing an ideal reaction microenvironment for the targeted activation of carbon dioxide molecules. Simultaneously, the hydrophobic properties formed on the material surface effectively suppress side reactions and promote the enrichment and transformation of key reaction intermediates. The preparation process is very simple, suitable for industrial-scale production, and has high economic and practical value.

[0025] The present invention discloses an indium hydroxide photocatalyst containing hydroxyl vacancies, which applies a local microenvironment regulation strategy to the field of photocatalytic carbon dioxide reduction. By constructing hindered Lewis acid-base pairs, the reaction pathway is effectively guided, exhibiting efficient and selective carbon dioxide reduction to ethanol performance, and demonstrating excellent photocatalytic activity and cycle stability under sacrificial agent-free conditions.

[0026] This invention discloses an indium hydroxide photocatalyst containing hydroxyl vacancies. Indium hydroxide is applied to the photocatalytic reduction of CO2. This material is a p-generation metal oxide semiconductor, a photocatalyst with unique oxygen affinity. The addition of hydroxyl vacancies and microenvironment modification effectively promotes the separation and transfer of photogenerated electrons and holes, inhibits their recombination, and suppresses other reactions, exhibiting highly efficient and selective CO2 reduction to ethanol. Furthermore, it demonstrates good photocatalytic activity in the UV-Vis region and excellent cycling stability. Under xenon lamp irradiation, the CO2 to ethanol reduction rate can reach up to 73.6 μmol·h⁻¹. -1 ·g -1 . Compared with the prior art, the indium hydroxide photocatalyst containing hydroxyl vacancies of the present invention has the advantages of simple preparation process, strong visible light response, high carrier separation efficiency, good product selectivity, and no need for precious metal co-catalyst. Moreover, the preparation method is simple to operate, low in cost, and environmentally friendly, which meets the requirements of green and sustainable development. Attached Figure Description

[0027] Figure 1 This is a scanning electron microscope image of the indium hydroxide photocatalyst rich in hydroxyl vacancies obtained in Example 1. Figure 2 This is a transmission electron microscope (TEM) image of the indium hydroxide photocatalyst rich in hydroxyl vacancies obtained in Example 1. Figure 3 This is a high-resolution transmission electron microscope image of the indium hydroxide photocatalyst rich in hydroxyl vacancies obtained in Example 1. Figure 4 The elemental distribution electron microscope image of the indium hydroxide photocatalyst rich in hydroxyl vacancies obtained in Example 1 is shown. Figure 5 X-ray electron diffraction patterns of the photocatalysts obtained in Examples 1-2 and Comparative Example 1; Figure 6 The X-ray photoelectron spectra of the photocatalysts obtained in Examples 1-2 and Comparative Example 1 are shown below. Figure 7 Fourier transform infrared spectra of the photocatalysts obtained in Examples 1-2 and Comparative Example 1; Figure 8 The Raman spectra of the photocatalysts obtained in Examples 1-2 and Comparative Example 1 are shown below. Figure 9 The UV-Vis diffuse reflectance spectra of the photocatalysts obtained in Examples 1-2 and Comparative Example 1 are shown. Figure 10 The photocurrent diagrams of the photocatalysts obtained in Examples 1-2 and Comparative Example 1 under xenon lamp irradiation are shown. Figure 11 Electrochemical impedance spectroscopy (EIS) diagrams of the photocatalysts obtained in Examples 1-2 and Comparative Example 1; Figure 12 The graph shows the CO2 reduction rate of the photocatalysts obtained in Examples 1-2 and Comparative Example 1 under xenon lamp irradiation. Figure 13 The graph shows the relationship between the reduction of CO2 by the photocatalyst obtained in Example 1 into other products under xenon lamp irradiation and the number of cycles. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0029] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0030] In this invention, the electrochemical performance was tested using an electrochemical workstation, specifically the Chenhua electrochemical workstation, model CHI760E.

[0031] CO2 reduction performance test used 500M 1 H NMR and gas chromatography.

[0032] The electrochemical performance testing methods in the various embodiments of the present invention are as follows: 7.5 mg of indium hydroxide photocatalyst, 1 mg of ethyl cellulose, 1 mL of α-terpineol, and 0.5 mL of ethanol were mixed and then sonicated at a power of 60 W and a frequency of 40 kHz for 12 h to obtain a slurry. The slurry obtained above was coated onto FTO glass with a coating thickness controlled at 0.5-1 mm and dried in an oven at 60°C to obtain an electrochemical test working electrode. Subsequently, the electrochemical performance was tested at an electrochemical workstation.

[0033] Example 1 An indium hydroxide photocatalyst rich in hydroxyl vacancies, mainly containing three elements: In, O, and H, is prepared by a method including the following steps: (1) Preparation of aqueous solution of sodium oleate Take 3 mmol of sodium oleate and add it to 50 mL of water. Heat the water to 40 °C and stir until a clear solution is formed to obtain an aqueous solution of sodium oleate. (2) Preparation of materials for indium hydroxide reactor with defects 1 mmol of indium nitrate hydrate was slowly added to an aqueous solution of sodium oleate to obtain a mixture containing flocculent material. The resulting mixture was adjusted to pH 3 with 1 M dilute nitric acid to obtain a solution with white granular precipitate.

[0034] (3) Preparation of defective indium hydroxide The mixture of the above-mentioned white granular precipitate was transferred to a polytetrafluoroethylene reactor for hydrothermal reaction at 160°C for 18 h. Then, the mixture obtained from the above hydrothermal reaction was centrifuged at 10,000 r / min for 20 min, and the resulting precipitate was washed by centrifugation at 10,000 r / min for 20 min with a solution of isopropanol:ethanol:water in a volume ratio of 2:1:1. Repeat the centrifugation and washing process 7-8 times. Dry the resulting filter cake at a controlled temperature of 60°C to obtain indium hydroxide rich in hydroxyl vacancies, denoted as B-In(OH)3.

[0035] Example 2: Compared with Example 1, most of them are the same, except that in step (2), the pH is adjusted to 6 and then washed and centrifuged with water and heat. It is indium hydroxide containing some hydroxyl vacancies, denoted as Y-In(OH)3.

[0036] Comparative Example 1: Compared with Example 1, most of them are the same, except that in step (2), the pH is adjusted to 11 and then washed and centrifuged with water and heat. It is indium hydroxide without hydroxyl vacancies, denoted as W-In(OH)3.

[0037] The hydroxyl-rich indium hydroxide obtained above was scanned using a scanning electron microscope at 35,000x magnification. The resulting scanning electron microscope image is shown below. Figure 1 As shown, from Figure 1 As can be seen, indium hydroxide rich in hydroxyl vacancies exhibits a plate-like structure.

[0038] The obtained indium hydroxide photocatalyst rich in hydroxyl vacancies was scanned at 100 nm using transmission electron microscopy. The resulting transmission electron microscopy image is shown below. Figure 2 As shown, from Figure 2 As can be seen, indium hydroxide rich in hydroxyl vacancies has a nanosheet structure and no particles are formed, which indicates that indium hydroxide rich in hydroxyl vacancies is not a nanoparticle.

[0039] The obtained indium hydroxide photocatalyst rich in hydroxyl vacancies was scanned at 5 nm using a transmission electron microscope (TEM). The resulting TEM image is shown below. Figure 3 As shown, from Figure 3 It can be seen that it has 0.28 nm lattice fringes, which conform to the typical (220) crystal plane characteristics of indium hydroxide.

[0040] The obtained indium hydroxide photocatalyst rich in hydroxyl vacancies was scanned at 500 nm using a transmission electron microscope. The elemental distribution is shown below. Figure 4 As shown, from Figure 4 It can be seen that the material contains In and O elements, and the elements are evenly distributed; The indium hydroxide photocatalysts obtained in Example 1, Example 2, and Comparative Example 1 were measured using X-ray diffraction, and the obtained XRD patterns are shown below. Figure 5 As shown, Figure 5 In the diagram, the horizontal axis represents the 2θ angle, and the vertical axis represents the diffraction peak intensity. B-In(OH)3 represents the indium hydroxide photocatalyst rich in hydroxyl vacancies obtained in Example 1; Y-In(OH)3 represents the indium hydroxide photocatalyst containing partially hydroxyl vacancies obtained in Example 2; and W-In(OH)3 represents the indium hydroxide photocatalyst without hydroxyl vacancies obtained in Comparative Example 1. Figure 5 It can be seen that they are all pure phases. The photocatalysts obtained in Examples 1-2 and Comparative Example 1 were measured using X-ray photoelectron spectroscopy. The XPS spectra obtained by XPSPEAK41 software analysis are shown below. Figure 6 As shown, the In indium hydroxide photocatalyst rich in hydroxyl vacancies is in its most electron-rich state.

[0041] The photocatalysts obtained in Examples 1-2 and Comparative Example 1 were measured using Fourier transform infrared spectroscopy, and the obtained Fourier transform infrared spectra are shown below. Figure 7 As shown, Figure 7In the figure, the horizontal axis represents wavenumber, and the vertical axis represents absorbance. B-In(OH)3 represents the indium hydroxide photocatalyst rich in hydroxyl vacancies obtained in Example 1; Y-In(OH)3 represents the indium hydroxide photocatalyst containing partially hydroxyl vacancies obtained in Example 2; and W-In(OH)3 represents the indium hydroxide photocatalyst without hydroxyl vacancies obtained in Comparative Example 1. Figure 7 As can be seen from the results, the indium hydroxide photocatalysts obtained in Examples 1-2 and Comparative Example 1 all possess characteristic functional groups, and their peak intensity decreases with the generation of hydroxyl vacancies.

[0042] The photocatalysts obtained in Examples 1-2 and Comparative Example 1 were measured using Raman spectroscopy, and the resulting Raman spectra are shown below. Figure 8 As shown, Figure 8 In the figure, the horizontal axis represents Raman shift, and the vertical axis represents intensity. B-In(OH)3 represents the indium hydroxide photocatalyst rich in hydroxyl vacancies obtained in Example 1; Y-In(OH)3 represents the indium hydroxide photocatalyst containing partially hydroxyl vacancies obtained in Example 2; and W-In(OH)3 represents the indium hydroxide photocatalyst without hydroxyl vacancies obtained in Comparative Example 1. Figure 8 As can be seen from the results, the indium hydroxide photocatalysts obtained in Examples 1-2 and Comparative Example 1 all have characteristic peaks, and their peak intensity decreases with the generation of hydroxyl vacancies.

[0043] The photocatalysts obtained in Examples 1-2 and Comparative Example 1 were measured using a UV-Vis spectrophotometer, and the obtained UV-Vis diffuse reflectance spectra are shown below. Figure 9 As shown, Figure 9 In the figure, the horizontal axis represents wavelength, and the vertical axis represents absorptivity. B-In(OH)3 represents the indium hydroxide photocatalyst rich in hydroxyl vacancies obtained in Example 1; Y-In(OH)3 represents the indium hydroxide photocatalyst containing partially hydroxyl vacancies obtained in Example 2; and W-In(OH)3 represents the indium hydroxide photocatalyst without hydroxyl vacancies obtained in Comparative Example 1. Figure 9 It can be seen that the absorption edge of the indium hydroxide photocatalyst rich in hydroxyl vacancies is red-shifted compared to that without hydroxyl vacancies. This indicates that hydroxyl vacancies broaden the light absorption range of the material. The reason for this may be that hydroxyl vacancies create new defect energy levels, which leads to band gap hybridization and narrows the band gap of B-In(OH)3, thus causing a red-shift in the absorption edge.

[0044] The photocatalysts obtained in Examples 1-2 and Comparative Example 1 were measured using an electrochemical workstation (model: CHI760E, manufacturer: Shanghai Chenhua). The photocurrent performance at a bias voltage of 0.2V is shown in the figure below. Figure 10As shown, the horizontal axis represents time, and the vertical axis represents photocurrent. B-In(OH)3 represents the indium hydroxide photocatalyst rich in hydroxyl vacancies obtained in Example 1; Y-In(OH)3 represents the indium hydroxide photocatalyst containing partially hydroxyl vacancies obtained in Example 2; and W-In(OH)3 represents the indium hydroxide photocatalyst without hydroxyl vacancies obtained in Comparative Example 1. Figure 10 As can be seen, no current is generated when the lamp is off, but a photocurrent is generated when the lamp is on. This indicates that under visible light excitation, the indium hydroxide photocatalyst rich in hydroxyl vacancies has the best photogenerated electron-hole pair separation, resulting in a large current.

[0045] The photocatalysts obtained in Examples 1-2 and Comparative Example 1 were measured using an electrochemical workstation (model: CHI760E, manufacturer: Shanghai Chenhua). The AC impedance diagrams obtained at frequencies of 1,000,000-0.01 Hz are shown below. Figure 11 As shown, the horizontal axis represents the real impedance, and the vertical axis represents the imaginary impedance. B-In(OH)3 represents the indium hydroxide photocatalyst rich in hydroxyl vacancies obtained in Example 1, Y-In(OH)3 represents the indium hydroxide photocatalyst containing some hydroxyl vacancies obtained in Example 2, and W-In(OH)3 represents the indium hydroxide photocatalyst without hydroxyl vacancies obtained in Comparative Example 1. Figure 11 As can be seen from the data, the radius of the semicircle in the quetis spectrum of the indium hydroxide photocatalyst rich in hydroxyl vacancies is smaller than that of the indium hydroxide photocatalyst without hydroxyl vacancies. This indicates that the impedance of the indium hydroxide photocatalyst rich in hydroxyl vacancies is smaller than that of the indium hydroxide photocatalyst without hydroxyl vacancies, which is beneficial to the transfer of photogenerated carriers.

[0046] Photocatalytic CO2 reduction performance test The photocatalysts obtained in Examples 1-2 and Comparative Example 1 were measured using liquid nuclear magnetic resonance (LMR) and gas chromatography (GC). The CO2 reduction test process was as follows: 10 mg of the above photocatalyst was placed in a sealed reactor, and 10 mL of deionized water was added. The reactor was then sonicated at 60 W and 40 kHz for 10 min. After sealing the reactor, a vacuum was applied, and CO2 was introduced. The reactor was then placed under a 300 W xenon lamp irradiation with circulating cooling water for CO2 reduction testing. Measurements were taken every 1 h of irradiation using LMR and GC. The obtained CO2 reduction data are shown below. Figure 12 As shown, the vertical axis represents the yield of the product per gram of catalyst per hour, and the horizontal axis represents the sample. The height of the bars in the bar chart represents the amount of the product generated. B-In(OH)3 photocatalyst was used for the photocatalytic reduction of CO2. The amount of B-In(OH)3 used as the catalyst was 10 mg. Under visible light irradiation, the rate of catalytic reduction of CO2 to CH3CH2OH for 10 h was 73.6 μmol·g. -1·h -1 .from Figure 12 It can be seen that the indium hydroxide photocatalysts B-In(OH)3 and Y-In(OH)3 containing hydroxyl vacancies have significantly higher CO2 reduction yields to ethanol than the indium hydroxide photocatalyst W-In(OH)3 without hydroxyl vacancies. Among them, the indium hydroxide photocatalyst B-In(OH)3 rich in hydroxyl vacancies obtained in Example 1 has the best performance. This indicates that the addition of hydroxyl vacancies greatly improves the CO2 reduction performance of indium hydroxide. This may be because the addition of hydroxyl vacancies greatly improves the local microenvironment, inhibits the generation of other reaction pathways to a certain extent, enhances light absorption and CO2 adsorption, and thus greatly improves the CO2 reduction performance.

[0047] The photocatalyst obtained in Example 1 was measured using liquid nuclear magnetic resonance (LMR) and gas chromatography (GC). The CO2 reduction test process was as follows: 10 mg of the above photocatalyst was placed in a sealed reactor, and 10 mL of deionized water was added. The reactor was then sonicated at 60 W and 40 kHz for 10 min. The reactor was then sealed, evacuated, and CO2 was introduced. With circulating cooling water added, the reactor was placed under a 300 W xenon lamp for CO2 reduction testing. Measurements were taken every 1 h of irradiation using LMR and GC. The obtained CO2 reduction data are shown below. Figure 13 As shown, the system is cycled every 6 hours for a total of 10 cycles. The resulting ethanol production performance graph is shown below. Figure 13 As shown, from Figure 13 As can be seen, the indium hydroxide photocatalyst rich in hydroxyl vacancies can still maintain a high ethanol yield after 10 cycles, which shows that the indium hydroxide photocatalyst rich in hydroxyl vacancies obtained in this invention has good stability.

[0048] In summary, the indium hydroxide photocatalyst containing hydroxyl vacancies of the present invention exhibits excellent electrochemical performance. When applied to the photocatalytic reduction of CO2, its product shows good selectivity for ethanol, with a maximum ethanol production rate of 73.6 μmol·g. -1 ·h -1 Furthermore, its preparation method is characterized by simple operation and low production cost.

[0049] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing an indium hydroxide photocatalyst containing a hydroxyl vacancy, characterized by, The method comprises the following steps: (1) A clear sodium oleate aqueous solution is prepared using deionized water, and a compound containing In 3+ is slowly added into the clear sodium oleate aqueous solution to obtain a mixed solution with flocculation, and then the pH value of the mixed solution is adjusted to 3-6; (2) subjecting the mixed solution obtained in step (1) to a hydrothermal reaction, and obtaining indium hydroxide containing hydroxyl vacancies through centrifugation, washing and drying.

2. The method of claim 1, wherein the method is characterized by, In step (1), the molar ratio of sodium oleate and In 3+ was 3:

1.

3. The method of claim 1, wherein the method is characterized by, In step (1), the compound containing In 3+ is preferably indium nitrate or a hydrate thereof.

4. The method of claim 1, wherein the method is characterized by, In step (1), the reagent used for adjusting pH is dilute nitric acid.

5. The method of claim 1, wherein the method is characterized by: The concentration of the aqueous sodium oleate solution is 0.06 mmol / mL.

6. The method of claim 1, wherein the method is characterized by: In step (2), the temperature of the hydrothermal reaction is 160°C, and the time is 18 h. 7.Indium hydroxide photocatalyst containing hydroxyl vacancies, which is prepared by the method according to any one of claims 1-6.

8. Use of an indium hydroxide photocatalyst containing hydroxyl vacancies according to claim 7, characterized in that, It is used for photocatalytic reduction of CO2 to CH3CH2OH. 9.The application according to claim 8, wherein CO2 is photocatalytically reduced to CH3CH2OH by visible light.

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