Preparation method of TiO2 / VIB group metal oxide composite photo-thermal catalyst

Abstract

The application relates to a preparation method of a TiO2 / VIB group metal oxide composite photothermal catalyst, and belongs to the technical fields of transition metal oxide composite catalyst materials, photothermal catalysis and solar fuel preparation. The method comprises the following steps: S1, TiO2 dispersion liquid preparation: forming a TiO2 dispersion liquid; S2, precursor compounding: mixing to form a reaction mixed liquid; S3, solvent thermal reaction: performing solvent thermal reaction on the reaction mixed liquid, so that VIB group metal oxides containing oxygen vacancies are in-situ nucleated and grown on the surface of TiO2 nanomaterials, in the pores or between the particles; and S4, post-treatment: separating, washing and drying the reaction product to obtain the TiO2 / VIB group metal oxide composite photothermal catalyst. The preparation method of the TiO2 / VIB group metal oxide composite photothermal catalyst is simple in preparation process, adjustable in component proportion, does not need a noble metal assistant catalyst, and is suitable for photothermal catalysis of CO2 reduction to prepare CO, CH4, CH3OH, HCOOH and other solar fuels and chemicals.

Description

Technical Field

[0001] This invention relates to the fields of transition metal oxide composite catalytic materials, photothermal catalysis, and solar fuel preparation technology, specifically a method for preparing a TiO2 / Group VIB metal oxide composite photothermal catalyst and its application in the carbon dioxide reduction reaction. Background Technology

[0002] The resource utilization of CO2 has become an important research direction in the energy and environment field. Catalytic reduction of CO2 into carbon-containing fuels and chemicals such as carbon monoxide, methane, methanol, and formic acid not only helps alleviate greenhouse gas emission pressures but also enables the recycling of carbon resources.

[0003] Photocatalytic CO2 reduction can be directly driven by solar energy, offering advantages such as mild reaction conditions and low energy consumption. However, traditional semiconductor photocatalytic systems generally suffer from problems such as narrow light absorption range, rapid recombination of photogenerated electrons and holes, and insufficient CO2 adsorption and activation capabilities, resulting in reaction efficiency and product selectivity that are difficult to meet the needs of practical applications.

[0004] Photothermal synergistic catalysis technology provides an effective approach to solving the above problems. Catalytic materials with photothermal conversion capabilities can convert light energy into local heat energy, increase the reaction interface temperature, and accelerate reaction kinetics; at the same time, the charge carriers generated by photoexcitation can participate in the surface redox process, thus forming a synergistic effect of photo-driven and thermally promoted catalysis.

[0005] Metal oxides possess advantages such as low cost, good stability, and tunable composition and defects, making them important material systems in the field of photothermal CO2 reduction. Among them, TiO2, as a typical n-type semiconductor, exhibits high chemical stability, strong resistance to photocorrosion, and abundant surface hydroxyl groups; however, its large band gap limits its utilization of visible and near-infrared light. Group VIB metal oxides, especially oxygen-vacancy-containing tungsten oxides, molybdenum oxides, and chromium oxides, typically possess visible to near-infrared light absorption, defect state modulation, and photothermal conversion capabilities, which can compensate for the insufficient spectral response of TiO2.

[0006] Existing composite photothermal catalysts still suffer from drawbacks such as complex preparation steps, difficulty in controlling component ratios, insufficient contact at the composite interface, and difficulty in simultaneously achieving photothermal conversion and carrier separation. Some systems also rely on noble metal co-catalysts, increasing preparation costs and limiting large-scale applications. Therefore, it is necessary to develop a TiO2-based composite photothermal catalyst system that is easy to prepare, has a tunable composition, tight interfacial bonding, and a protection range covering similar group VIB oxygen-deficient metal oxides. Summary of the Invention

[0007] This invention aims to address the problems of limited light absorption range of existing TiO2, insufficient carrier recombination and surface reaction efficiency of single oxygen-deficient metal oxides, and insufficient interfacial bonding of composite catalysts, and provides a TiO2 / Group VIB metal oxide composite photothermal catalyst and its preparation method.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for preparing a TiO2 / Group VIB metal oxide composite photothermal catalyst includes the following steps:

[0010] S1, TiO2 dispersion preparation: TiO2 nanomaterials are added to the reaction solvent and subjected to stirring, ultrasonication or a combination thereof to form a TiO2 dispersion;

[0011] S2, Precursor Combination: A Group VIB metal source is added to the TiO2 dispersion and mixed to form a reaction mixture;

[0012] S3, Solvothermal reaction: The reaction mixture is subjected to a solvothermal reaction to allow oxygen-vacant Group VIB metal oxides to nucleate and grow in situ on the surface, pores or between particles of TiO2 nanomaterials.

[0013] S4. Post-processing: The reaction products are separated, washed and dried to obtain TiO2 / Group VIB metal oxide composite photothermal catalyst.

[0014] Furthermore, the Group VIB metal is one or more of tungsten, molybdenum, and chromium, preferably tungsten or molybdenum, and more preferably tungsten; the Group VIB metal oxide is a non-stoichiometric oxide with oxygen vacancies, selected from WO3. 3-x W 18 O 49 MoO 3-x MoO2, Cr2O 3-x , tungsten-molybdenum composite oxides or combinations thereof, wherein 0 < x < 1.

[0015] Furthermore, the Group VIB metal source is one or more of the following: chlorides, nitrates, alkoxides, carbonyl compounds, acid salts, ammonium salts, or hydrates of Group VIB metals, preferably one or more of the following: tungsten chloride, tungsten hexachloride, sodium tungstate, ammonium metatungstate, ammonium molybdate, molybdenum chloride, chromate, or hydrates thereof.

[0016] Furthermore, the TiO2 nanomaterial is one or more of the following: anatase TiO2, rutile TiO2, brookite TiO2, mixed-crystal TiO2 containing anatase and rutile phases, commercial P25 type TiO2, TiO2 nanoparticles, TiO2 nanorods, TiO2 nanosheets, TiO2 nanotubes, or mesoporous TiO2; the reaction solvent is water, ethanol, ethylene glycol, isopropanol, n-butanol, benzyl alcohol, N,N-dimethylformamide, N-methylpyrrolidone, or a mixture thereof.

[0017] Furthermore, in S1, the amount of TiO2 nanomaterial added is 1% to 80% based on the mass fraction of TiO2 in the composite catalyst, preferably 5% to 60%, and more preferably 10% to 50%; in S3, the solvothermal reaction temperature is 100 to 240°C, and the reaction time is 2 to 36 hours.

[0018] Furthermore, after step S4, a heat treatment step is included, which is performed under air, nitrogen, argon, hydrogen-argon mixture or vacuum conditions, with a heat treatment temperature of 100-500°C and a time of 0.5-6 hours; or no heat treatment is performed to retain oxygen vacancies in the Group VIB metal oxide.

[0019] Furthermore, the oxygen-vacant Group VIB metal oxide is a nanosheet, nanorod, nanowire, nanoparticle, flower-like structure, bundle-like structure, porous cluster structure, or a combination thereof.

[0020] The present invention also provides a TiO2 / Group VIB metal oxide composite photothermal catalyst, wherein the composite photothermal catalyst comprises a TiO2 phase and a Group VIB metal oxide phase containing oxygen vacancies, the two forming a heterogeneous interface in contact with each other; the Group VIB metal oxide phase has visible to near-infrared light absorption capability and photothermal conversion capability, and the heterogeneous interface is used to promote the separation and migration of photogenerated charge carriers.

[0021] Furthermore, the group VIB metal oxide is W 18 O 49 The TiO2 is a P25 type TiO2 containing anatase and rutile phases, and the W 18 O 49 The catalyst is an oxygen-deficient tungsten oxide nanosheet, nanorod, or a flower-like structure assembled from them; the mass fraction of TiO2 relative to the composite photothermal catalyst is 1% to 80%, preferably 10% to 50%.

[0022] This invention also provides the application of a TiO2 / Group VIB metal oxide composite photothermal catalyst in the photothermal catalytic reduction reaction of CO2, wherein the products of the CO2 reduction reaction include CO, CH4, CH3OH, HCOOH or a combination thereof; the reaction is carried out in a CO2 atmosphere using water, water vapor, hydrogen, alcohols, amines or a combination thereof as proton sources or hydrogen sources, and the catalyst is irradiated with ultraviolet light, visible light, near-infrared light, simulated sunlight or a combination thereof; the composite photothermal catalyst can achieve CO2 photothermal reduction without loading a noble metal co-catalyst.

[0023] Compared with the prior art, the present invention provides a method for preparing a TiO2 / Group VIB metal oxide composite photothermal catalyst, which has the following beneficial effects:

[0024] 1. The preparation method of this TiO2 / Group VIB metal oxide composite photothermal catalyst uses TiO2 nanomaterials and Group VIB metal sources as raw materials to construct the composite interface in situ through solvothermal reaction. The preparation process is simple, the reaction conditions are mild, and it is suitable for composition and structure control.

[0025] 2. The preparation method of this TiO2 / Group VIB metal oxide composite photothermal catalyst expands the protection scope from single TiO2 / W 18 O 49 Extending to the TiO2 / Group VIB oxygen-deficient metal oxide system, Group VIB metal oxides such as tungsten, molybdenum, and chromium can all generate broad-spectrum absorption, defect states, and photothermal conversion characteristics through oxygen vacancies or non-stoichiometric structures, and can form functional complementarity with TiO2.

[0026] 3. The preparation method of the TiO2 / Group VIB metal oxide composite photothermal catalyst, in which the Group VIB metal oxide is nucleated and grown in situ in the presence of TiO2, is conducive to forming a tight and sufficient heterogeneous interface contact, and overcomes the problems of uneven dispersion and weak interface bonding caused by mechanical mixing.

[0027] 4. The preparation method of this TiO2 / Group VIB metal oxide composite photothermal catalyst can construct a heterojunction structure by combining the TiO2 phase with the Group VIB metal oxide phase containing oxygen vacancies, which promotes the directional migration and separation of photogenerated electrons and holes, reduces the carrier recombination probability, and provides more effective active carriers for the CO2 reduction reaction.

[0028] 5. The preparation method of the TiO2 / Group VIB metal oxide composite photothermal catalyst, wherein the Group VIB oxygen-deficient metal oxide can provide visible to near-infrared light absorption and photothermal conversion capabilities, and TiO2 can provide a stable semiconductor framework and surface reaction sites, and the two synergistically improve the efficiency of CO2 adsorption, activation and reduction reactions.

[0029] 6. The preparation method of this TiO2 / Group VIB metal oxide composite photothermal catalyst does not require the introduction of noble metal co-catalysts, and can choose not to perform high-temperature air calcination to retain the oxygen vacancy structure of the Group VIB metal oxide, which is beneficial to reduce costs and maintain broad-spectrum photothermal performance. Attached Figure Description

[0030] Figure 1 The TiO2 and W are used in the preparation method of the TiO2 / Group VIB metal oxide composite photothermal catalyst of this invention. 18 O 49 and TiO2 / W with different TiO2 loading 18 O 49 X-ray diffraction (XRD) pattern of the composite material.

[0031] Figure 2 The TiO2 and W are used in the preparation method of the TiO2 / Group VIB metal oxide composite photothermal catalyst of this invention. 18 O 49 and TiO2 / W 18 O 49 Scanning electron microscope (SEM) image of the composite material.

[0032] Figure 3 The TiO2 and W are used in the preparation method of the TiO2 / Group VIB metal oxide composite photothermal catalyst of this invention. 18 O 49 and different composite ratios of TiO2 / W 18 O 49 Photothermal catalytic CO2 reduction to CO performance of the sample.

[0033] Figure 4 The TiO2 and W are used in the preparation method of the TiO2 / Group VIB metal oxide composite photothermal catalyst of this invention. 18 O 49 With TiO2 / W 18 O 49 Photoluminescence (PL) spectrum of the -30% composite catalyst. Detailed Implementation

[0034] To further understand the present invention, the TiO2 / Group VIB metal oxide composite photothermal catalyst and its applications provided by the present invention are described in detail below with reference to embodiments and accompanying drawings. The scope of protection of the present invention is not limited to the following embodiments.

[0035] Please see Figures 1 to 4 .

[0036] Example 1: Sea urchin-shaped W 18 O 49 Catalyst preparation

[0037] A certain amount of tungsten chloride was weighed and added to 40 mL of anhydrous ethanol. The mixture was ultrasonically treated for 30 min and stirred to form a homogeneous solution. The solution was transferred to a polytetrafluoroethylene-lined reactor and solvothermal treated at 150–180 °C for 6–12 h. After the reaction was completed, the mixture was allowed to cool naturally. The resulting precipitate was washed with deionized water and ethanol, and then vacuum-dried overnight at 60 °C to obtain a sea urchin-like W. 18 O 49 catalyst.

[0038] Example 2: TiO2 / W 18 O 49 Preparation of composite catalysts

[0039] A certain amount of tungsten chloride was weighed and added to 40 mL of anhydrous ethanol. The mixture was sonicated for 30 min and stirred to form a clear or homogeneous solution. Commercial P25 TiO2 was weighed and added to the above solution. Sonication and stirring were continued to ensure thorough mixing of the TiO2 and the tungsten source. The mixture was transferred to a polytetrafluoroethylene-lined reactor and solvated at 150–180 °C for 6–12 h. After the reaction, the mixture was allowed to cool naturally. The resulting precipitate was washed with deionized water and ethanol, and then dried overnight at 60 °C to obtain TiO2 / W. 18 O 49 Composite catalyst.

[0040] By adjusting the amount of P25 type TiO2 fed, TiO2 / W were prepared respectively. 18 O 49 -10%, TiO2 / W 18 O 49 -30% and TiO2 / W 18 O 49 -50% of the sample. The percentage represents the proportion of TiO2 feed mass to the total TiO2 feed mass, calculated based on the tungsten source feed amount (W). 18 O 49 The percentage of the sum of theoretical masses.

[0041] Example 3: A general preparation method for TiO2 / Group VIB metal oxide composite catalysts

[0042] Except for replacing tungsten chloride with tungstate, metatungstate, molybdate, molybdenum chloride, chromate, or a combination thereof, the remaining steps can be performed as in Example 1 to obtain TiO2 / WO. 3-x TiO2 / MoO 3-x TiO2 / MoO2, TiO2 / Cr2O 3-x Alternatively, TiO2 / tungsten-molybdenum composite oxide catalysts can be used. By adjusting the solvent composition, reaction temperature, reaction time, and post-treatment atmosphere, the oxygen vacancy concentration, morphology, and photothermal properties of Group VIB metal oxides can be controlled.

[0043] Example 4: Photothermal catalytic CO2 reduction test

[0044] 10 mg of catalyst was weighed and uniformly dispersed at the bottom of the gas-solid reactor. 200 μL of deionized water was added as a proton source. After sealing, high-purity CO2 was introduced to purge air and establish a CO2 reaction atmosphere. Once the system reached adsorption-desorption equilibrium, a UV-Vis-NIR light source was turned on to initiate the photothermal catalytic reaction. After the reaction, a gas sample was extracted, and gas chromatography was used to quantitatively analyze CO and other products. The catalytic performance was evaluated based on the amount of CO generated per unit mass of catalyst and per unit time.

[0045] Test Example 1: Characterization of Crystal Phase and Morphology

[0046] like Figure 1 As shown in the figure, the characteristic diffraction peaks of the TiO2 sample can be matched with the anatase phase TiO2 standard card (PDF#84-1285) and the rutile phase TiO2 standard card (PDF#86-0148), respectively, indicating that the anatase and rutile phases coexist in the prepared TiO2. 18 O 49 The main diffraction peaks of the sample are similar to those of the monoclinic phase W. 18 O 49 The standard card (PDF#05-0392) matches. For different TiO2 / W ratios... 18 O 49 The composite sample showed both TiO2 and W in its diffraction pattern. 18 O 49 The characteristic diffraction peaks of TiO2 and W were observed, and no other obvious impurity phase peaks were observed, indicating that TiO2 and W... 18 O 49 Successful composite formation was achieved without the formation of new crystalline impurities during the process. Both TiO2 and W were observed in the composite sample. 18 O 49 The characteristic diffraction peaks indicate that the mixed-crystal structure of TiO2 is preserved during the solvothermal recombination process, and W 18 O 49 The crystal phase was successfully formed. As the amount of TiO2 added increased, the relative intensity of the TiO2-related diffraction peaks in the composite sample gradually increased, indicating that the composition of the composite material can be adjusted by the amount of TiO2 added.

[0047] like Figure 2 As shown, TiO2 is composed of nanoparticles and their aggregates, W 18 O 49 A flower-like structure formed by assembling sea urchin-shaped nanorods. In the composite sample, W... 18 O 49Nanostructures grow on the surface and around TiO2 particles, forming sufficient contact between the two components, providing a structural basis for interfacial charge transport and surface catalytic reactions.

[0048] Test Example 2: Photothermal catalytic CO2 reduction performance

[0049] like Figure 3 As shown, under the same photothermal catalytic testing conditions, single TiO2 and single W... 18 O 49 The CO production rates were 6.36 μmol·g. -1 ·h -1 and 13.50 μmol·g -1 ·h -1 TiO2 / W 18 O 49 -10%, TiO2 / W 18 O 49 -30% and TiO2 / W 18 O 49 The CO generation rates of the -50% composite samples were 195.24, 424.13, and 256.79 μmol·g⁻¹, respectively. -1 ·h -1 Among them, TiO2 / W 18 O 49 The -30% sample exhibited the highest CO formation rate, indicating that an appropriate ratio of TiO2 to W... 18 O 49 The composite material can significantly improve the photothermal CO2 reduction performance.

[0050] like Figure 4 As shown, compared to TiO2, TiO2 / W 18 O 49 The fluorescence emission intensity of the -30% composite catalyst decreased significantly, indicating that TiO2 and W 18 O 49 After recombination, a closely contacted heterojunction is formed. The built-in electric field generated by the heterojunction can drive the directional migration and efficient separation of photogenerated electrons and holes between the two phases, reduce the probability of carrier radiative recombination, and thus improve the photothermal synergistic catalytic performance.

[0051] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a TiO2 / Group VIB metal oxide composite photothermal catalyst, characterized in that, Includes the following steps: S1, TiO2 dispersion preparation: TiO2 nanomaterials are added to the reaction solvent and subjected to stirring, ultrasonication or a combination thereof to form a TiO2 dispersion; S2, Precursor Combination: A Group VIB metal source is added to the TiO2 dispersion and mixed to form a reaction mixture; S3, Solvothermal reaction: The reaction mixture is subjected to a solvothermal reaction to allow oxygen-vacant Group VIB metal oxides to nucleate and grow in situ on the surface, pores or between particles of TiO2 nanomaterials. S4. Post-processing: The reaction products are separated, washed and dried to obtain TiO2 / Group VIB metal oxide composite photothermal catalyst.

2. The method for preparing a TiO2 / Group VIB metal oxide composite photothermal catalyst according to claim 1, characterized in that, The Group VIB metal is one or more of tungsten, molybdenum, and chromium; the Group VIB metal oxide is a non-stoichiometric oxide with oxygen vacancies, selected from WO3. 3-x W 18 O 49 MoO 3-x MoO2, Cr2O 3-x , tungsten-molybdenum composite oxides or combinations thereof, wherein 0 < x < 1.

3. The method for preparing a TiO2 / Group VIB metal oxide composite photothermal catalyst according to claim 1, characterized in that, The group VIB metal source is one or more of the following: group VIB metal chloride, nitrate, alkoxide, carbonyl compound, acid salt, ammonium salt, or hydrate.

4. The method for preparing a TiO2 / Group VIB metal oxide composite photothermal catalyst according to claim 1, characterized in that, The TiO2 nanomaterial is one or more of the following: anatase TiO2, rutile TiO2, brookite TiO2, mixed-crystal TiO2 containing anatase and rutile phases, commercial P25 type TiO2, TiO2 nanoparticles, TiO2 nanorods, TiO2 nanosheets, TiO2 nanotubes, or mesoporous TiO2; the reaction solvent is water, ethanol, ethylene glycol, isopropanol, n-butanol, benzyl alcohol, N,N-dimethylformamide, N-methylpyrrolidone, or a mixture thereof.

5. The method for preparing a TiO2 / Group VIB metal oxide composite photothermal catalyst according to claim 1, characterized in that, The amount of TiO2 nanomaterial added in S1 is 1% to 80% based on the mass fraction of TiO2 in the composite catalyst; the solvothermal reaction temperature in S3 is 100 to 240°C, and the reaction time is 2 to 36 h.

6. The method for preparing a TiO2 / Group VIB metal oxide composite photothermal catalyst according to claim 1, characterized in that, The step following step S4 further includes a heat treatment under air, nitrogen, argon, a hydrogen-argon mixture, or vacuum conditions, with a heat treatment temperature of 100–500°C and a time of 0.5–6 h; or no heat treatment is performed to retain oxygen vacancies in the Group VIB metal oxide.

7. The method for preparing a TiO2 / Group VIB metal oxide composite photothermal catalyst according to claim 1, characterized in that, The oxygen-vacant Group VIB metal oxides are nanosheets, nanorods, nanowires, nanoparticles, flower-like structures, bundle-like structures, porous cluster structures, or combinations thereof.

8. A TiO2 / Group VIB metal oxide composite photothermal catalyst, prepared by the method for preparing the TiO2 / Group VIB metal oxide composite photothermal catalyst according to any one of claims 1-7, characterized in that, The composite photothermal catalyst comprises a TiO2 phase and a group VIB metal oxide phase containing oxygen vacancies, which form a heterogeneous interface in contact with each other; the group VIB metal oxide phase has visible to near-infrared light absorption capability and photothermal conversion capability, and the heterogeneous interface is used to promote the separation and migration of photogenerated carriers.

9. The TiO2 / Group VIB metal oxide composite photothermal catalyst according to claim 8, characterized in that, The group VIB metal oxide is W 18 O 49 The TiO2 is a P25 type TiO2 containing anatase and rutile phases, and the W 18 O 49 The catalyst is composed of oxygen-deficient tungsten oxide nanosheets, nanorods, or flower-like structures assembled from them; the mass fraction of TiO2 relative to the composite photothermal catalyst is 1% to 80%.

10. The application of the composite photothermal catalyst according to any one of claims 8-9 in the photothermal catalytic CO2 reduction reaction, characterized in that, The products of the CO2 reduction reaction include CO, CH4, CH3OH, HCOOH or combinations thereof; the reaction is carried out in a CO2 atmosphere using water, water vapor, hydrogen, alcohols, amines or combinations thereof as proton sources or hydrogen sources, and the catalyst is irradiated with ultraviolet light, visible light, near-infrared light, simulated sunlight or combinations thereof; the composite photothermal catalyst can achieve CO2 photothermal reduction without loading noble metal co-catalysts.

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