Palladium-loaded amino modified titanium dioxide catalyst as well as preparation method and application thereof

Abstract

The invention provides a palladium-loaded amino modified titanium dioxide catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalyst synthesis and energy chemical industry. According to the method, the amino is loaded on the TiO2 carrier, the amino is beneficial to activating CO2 and enables the CO2 to present a bent structure phase, and the constructed amino alkaline site effectively avoids the use of an alkaline medium in the traditional process and realizes the efficient adsorption of CO2 and the reduction of activation energy, so that the preparation of a pure formic acid product by reducing CO2 without an alkaline solvent under the photo-thermal concerted catalysis condition can be realized. Meanwhile, Pd-loaded metal nanoparticles serve as active components, so that strong metal-carrier interaction is formed to promote activation of CO2 and H2, the photo-thermal conversion efficiency can be enhanced through the Pd metal surface plasma resonance effect, and the conversion rate and selectivity of the reaction for preparing pure formic acid through CO2 reduction under the condition of no alkaline solvent are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst synthesis and energy chemical industry, and in particular to a palladium-supported amino-modified titanium dioxide catalyst and a preparation method and application thereof. Background Art

[0002] With the rapid development of industrial production and the sustained growth of social economy, the consumption of fossil fuels has increased dramatically, and a large amount of carbon dioxide (CO2) has been emitted into the atmosphere. The rational use of CO2 can effectively reduce carbon emissions and improve economic benefits, which is of great significance to the realization of green and low-carbon development. Converting CO2 into high-value-added chemicals (such as methanol, formic acid, methane and other hydrocarbon chemicals) is an effective way to achieve carbon emission reduction. Among them, formic acid is a mild hydrogen storage carrier (volume hydrogen storage capacity is 53g·L -1 ), and the reduction of CO2 to formic acid is a process with 100% atomic utilization. However, CO2 is a very stable linear molecule (△G = -394.38 kJ·mol -1 ), the bond energy of C=O is 750 kJ·mol -1 Activating CO2 is difficult. Furthermore, the CO2 reduction process to produce formic acid (involving a gas-to-liquid phase transition) is thermodynamically unfavorable, typically requiring the addition of an organic or inorganic base to shift the thermodynamic equilibrium toward the forward reaction. However, currently used CO2 reduction to produce formic acid primarily involves electrochemical and thermochemical conversion pathways, but these methods suffer from low energy efficiency or severe heat loss.

[0003] Photothermal catalytic reduction of CO2 to formic acid is a promising alternative method. It significantly reduces the reaction activation energy through the synergistic light-heat effect, achieving efficient CO2 conversion under mild conditions. Compared with traditional electrochemical and thermochemical pathways, photothermal catalysis can directly use solar energy to drive the reaction, reducing external energy input. Currently, most research on photothermal catalytic reduction of CO2 to formic acid still relies on alkaline solvent systems. The product exists in the form of formate, and an additional acidification step is required to obtain pure formic acid. This not only increases process complexity but also results in resource waste. To optimize this process, it is of great research value to develop photothermal catalytic systems under alkaline solvent-free conditions to achieve direct production of pure formic acid by CO2 reduction. However, under alkaline-free conditions, due to the high activation energy barrier of CO2 molecules, its catalytic conversion efficiency is often difficult to reach the level of alkaline systems. To address this difficulty, it is necessary to design new catalysts and optimize the reaction mechanism to improve the conversion rate and selectivity of the CO2 reduction reaction to produce pure formic acid under alkaline solvent-free conditions. Summary of the Invention

[0004] The purpose of the present invention is to provide a palladium-supported amino-modified titanium dioxide catalyst and its preparation method and application, which can improve the conversion rate and selectivity of CO2 reduction to pure formic acid under alkaline solvent-free conditions.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a palladium-supported amino-modified titanium dioxide catalyst, comprising the following steps:

[0007] Mixing titanium dioxide, an amino functionalization reagent, and water to perform amino modification to obtain amino-modified titanium dioxide;

[0008] Mixing the amino-modified titanium dioxide with a palladium precursor and water for loading to obtain palladium-loaded modified titanium dioxide;

[0009] The palladium-supported modified titanium dioxide is mixed with a reducing agent and reduced to obtain a palladium-supported amino-modified titanium dioxide catalyst.

[0010] Preferably, the titanium dioxide is a mixture of anatase phase titanium dioxide and rutile phase titanium dioxide.

[0011] Preferably, the amino functionalization agent includes one or more of 3-aminopropyltriethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, tetraethylenepentamine and triethylenetetramine.

[0012] Preferably, the ratio of the titanium dioxide to the amino functionalization reagent is 0.2-0.5 g:0.2-0.5 mL; the amino modification temperature is room temperature, and the time is 10-24 h.

[0013] Preferably, the palladium precursor includes sodium tetrachloropalladate or palladium chloride; and the mass ratio of the palladium precursor to titanium dioxide is 0.003-0.006:0.2-0.5.

[0014] Preferably, the load temperature is room temperature, and the time is 10 to 48 hours.

[0015] Preferably, the reducing agent includes sodium borohydride; the mass ratio of the reducing agent to the palladium precursor is 4-6:3-6; the reduction temperature is room temperature, and the reduction time is 2-6 hours.

[0016] The present invention provides a palladium-supported amino-modified titanium dioxide catalyst prepared by the preparation method described in the above technical solution.

[0017] The present invention provides the use of the palladium-supported amino-modified titanium dioxide catalyst described in the above technical solution in the photothermal catalytic CO2 reduction to produce formic acid.

[0018] Preferably, the application method comprises: mixing a palladium-supported amino-modified titanium dioxide catalyst with water, and performing a photocatalytic reduction reaction under CO2 and H2 conditions to obtain formic acid; the concentration of the palladium-supported amino-modified titanium dioxide catalyst after mixing with water is 0.1 to 3 g·L -1 ; The pressure of the CO2 is 0.5~3MPa, the pressure of the H2 is 0.5~3MPa, and the time of the catalytic reduction reaction is 0.5~6h.

[0019] The present invention provides a preparation method of a palladium-supported amino-modified titanium dioxide catalyst (Pd / TiO2-NH), wherein amino groups are supported on a TiO2 carrier, and the adsorption between the surface alkaline sites and CO2 is utilized to regulate the reaction equilibrium, and the amino groups are beneficial to activating CO2, causing it to present a bent conformation. The constructed amino alkaline sites effectively avoid the use of alkaline media in conventional processes, achieve efficient adsorption of CO2 and reduced activation energy, thereby enabling the reduction of CO2 to produce pure formic acid products without alkaline solvents under conditions of photothermal synergistic catalysis. At the same time, by supporting Pd metal nanoparticles as active components, not only a strong metal-support interaction is formed, synergistically promoting the activation process of CO2 and H2, but also the Pd metal surface plasma resonance effect can enhance the photothermal conversion efficiency, significantly improving the conversion rate and selectivity of the CO2 reduction reaction to produce pure formic acid under conditions of alkaline solvent-free conditions.

[0020] In the catalyst prepared by the present invention, the TiO2 carrier generates photogenerated carriers (photogenerated electrons (e - ) and holes (h + ), photogenerated electrons (e - ) and holes (h + ) is very easy to composite, and the loaded metal palladium nanoparticles act as electron capture centers to promote e - and h + The separation of photogenerated electrons effectively activates CO2 molecules. At the same time, the surface plasmon resonance effect of the loaded metal Pd converts light energy into thermal energy, expands the absorption capacity of sunlight, and the photothermal effect synergistically improves the reaction kinetics, thereby realizing photothermal synergistic CO2 reduction to formic acid. Therefore, the Pd / TiO2-NH catalyst prepared by the present invention can use the entire solar spectrum as an energy source to achieve efficient utilization of solar energy. The Pd / TiO2-NH catalyst is used to construct a solar full-spectrum driven CO2 hydrogenation to formic acid photothermal synergistic catalytic system. The system achieves efficient reduction of CO2 under alkaline solvent-free conditions, directly obtains pure formic acid product, and significantly improves the conversion efficiency of solar energy to chemical energy through the synergistic effect of photocatalysis and thermal catalysis.

[0021] The present invention loads amino groups on a carrier as solid alkaline sites, replacing the role of liquid alkaline solvents in the CO2 hydrogenation reaction to produce formic acid, and can be used for the photothermal catalytic reduction of carbon dioxide to synthesize pure formic acid under alkaline solvent-free conditions.

[0022] Compared with traditional electrocatalytic / thermocatalytic pathways, the Pd / TiO2-NH2 catalyst in the present invention uses simulated sunlight (xenon lamp spectral range 300-1100nm, including the ultraviolet band (300-400nm), visible light band (400-700nm) and near-infrared band (700-1100nm)) as the sole energy source to achieve the green conversion of CO2 to formic acid through a photothermal synergistic catalytic mechanism. No additional heat input is required during the entire process, which reduces heat loss during heat transfer, increases the surface temperature of the catalyst in situ, avoids heat loss caused by traditional heat conduction, and effectively reduces process energy consumption.

[0023] The preparation method of the present invention has few operating steps, easy-to-control process conditions, and good industrial scale-up potential and practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The X-ray diffraction pattern of the Pd / TiO2-NH3 catalyst prepared in Example 1;

[0025] Figure 2 This is the infrared spectrum of the Pd / TiO2-NH3 catalyst prepared in Example 1;

[0026] Figure 3 This is a high performance liquid chromatogram of the Pd / TiO2 catalyst used in the photothermal catalytic CO2 reduction reaction in Comparative Example 1;

[0027] Figure 4 This is a high performance liquid chromatogram of the Pd / TiO2-NH2 catalyst used in the photothermal catalytic CO2 reduction reaction in Example 1;

[0028] Figure 5 This is the HPLC graph of the Pd / TiO2-NH2 catalyst used in the photothermal catalytic CO2 reduction reaction in Example 2. DETAILED DESCRIPTION

[0029] In the present invention, unless otherwise specified, the required raw materials or reagents are commercially available products well known to those skilled in the art.

[0030] The present invention provides a method for preparing a palladium-supported amino-modified titanium dioxide catalyst, comprising the following steps:

[0031] Mixing titanium dioxide, an amino functionalization reagent, and water to perform amino modification to obtain amino-modified titanium dioxide;

[0032] Mixing the amino-modified titanium dioxide with a palladium precursor and water for loading to obtain palladium-loaded modified titanium dioxide;

[0033] The palladium-supported modified titanium dioxide is mixed with a reducing agent and reduced to obtain a palladium-supported amino-modified titanium dioxide catalyst.

[0034] In the present invention, the titanium dioxide is preferably a mixture of anatase titanium dioxide and rutile titanium dioxide (titanium dioxide serves as a catalyst carrier). The present invention has no particular limitation on the ratio of the anatase titanium dioxide to the rutile titanium dioxide, and any ratio is acceptable. As a preferred embodiment, the mass ratio of the anatase titanium dioxide to the rutile titanium dioxide is more preferably 1 to 4:0 to 4 and not 0, and further preferably 3:1.

[0035] In the present invention, the amino-functionalized reagent preferably includes one or more of 3-aminopropyltriethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, tetraethylenepentamine and triethylenetetramine; when the amino-functionalized reagent is two or more of the above, the present invention has no special limitation on the ratio of different types of reagents, and can be adjusted according to actual needs.

[0036] In the present invention, the usage ratio of titanium dioxide to amino functionalization agent is preferably 0.2-0.5 g:0.2-0.5 mL, more preferably 0.2-0.4 g:0.2-0.3 mL, and further preferably 0.2 g:0.2 mL.

[0037] In the present invention, water is preferably added to titanium dioxide and mixed uniformly to obtain a suspension. An amino-functionalizing agent is then added dropwise to the suspension with continuous stirring at room temperature to modify the amino groups, thereby achieving limited immobilization of the amino groups on the support surface. The amount of water used is not particularly limited; it is sufficient to ensure uniform mixing of the materials.

[0038] In the present invention, the temperature for amino modification is preferably room temperature, and the time is preferably 10 to 24 hours, more preferably 12 to 16 hours, and even more preferably 12 hours.

[0039] After the amino modification is completed, the present invention preferably does not perform post-treatment, and the obtained amino-modified titanium dioxide mixed solution is loaded with metal palladium.

[0040] In the present invention, the palladium precursor preferably includes sodium tetrachloropalladate (Na2PdCl4) or palladium chloride (PdCl2); the mass ratio of the palladium precursor to titanium dioxide is preferably 0.003-0.006:0.2-0.5, more preferably 0.004-0.006:0.2-0.3, and further preferably 0.005:0.2.

[0041] In the present invention, the palladium precursor is preferably dissolved in water, and the obtained palladium precursor solution is dripped dropwise into the amino-modified titanium dioxide mixed solution, and stirred for loading; the concentration of the palladium precursor solution is preferably 0.02 g·mL -1 .

[0042] In the present invention, the temperature of the load is preferably room temperature, and the time is preferably 10 to 48 hours, more preferably 24 to 36 hours.

[0043] After the loading is completed, the present invention preferably does not perform post-treatment, and a reducing agent is added to the obtained mixture for reduction.

[0044] In the present invention, the reducing agent preferably includes sodium borohydride (NaBH4); the reducing agent is preferably used in the form of an aqueous reducing agent solution, and the concentration of the aqueous reducing agent solution is preferably 0.02 g·mL -1 .

[0045] In the present invention, the mass ratio of the reducing agent to the palladium precursor is preferably 4-6:3-6, more preferably 4:3-5.

[0046] The present invention preferably rapidly adds a freshly prepared sodium borohydride aqueous solution to the loaded mixture to carry out the reduction reaction at room temperature. The present invention does not specifically limit the process of preparing the sodium borohydride aqueous solution, and the sodium borohydride aqueous solution can be used immediately after preparation according to methods well known in the art.

[0047] In the present invention, the reduction temperature is preferably room temperature, and the reduction time is preferably 2 to 6 hours, more preferably 2 to 4 hours. The present invention completely reduces the palladium precursor to metallic palladium nanoparticles through reduction.

[0048] After the reduction is completed, the present invention preferably uses a suction filtration device to collect the solid product and washes it multiple times with deionized water; the resulting solid is placed in a vacuum drying oven, dried at 60° C. for 12 hours, and ground to obtain a Pd / TiO2-NH3 catalyst.

[0049] The present invention provides a palladium-supported amino-modified titanium dioxide catalyst prepared by the preparation method described in the above technical solution.

[0050] The present invention provides the use of the palladium-supported amino-modified titanium dioxide catalyst described in the above technical solution in the photothermal catalytic CO2 reduction to produce formic acid.

[0051] In the present invention, the application method preferably comprises: mixing the palladium-supported amino-modified titanium dioxide catalyst with water, and performing a photocatalytic reduction reaction under CO2 and H2 conditions to obtain formic acid.

[0052] In the present invention, the concentration of the palladium-supported amino-modified titanium dioxide catalyst after mixing with water is preferably 0.1 to 3 g·L -1 , more preferably 0.5 to 2 g·L -1 , more preferably 1 g·L -1 ; The pressure of the CO2 is preferably 0.5 to 3 MPa, more preferably 0.8 to 2 MPa, and further preferably 1 MPa. The pressure of the H2 is preferably 0.5 to 3 MPa, more preferably 0.8 to 2 MPa, and further preferably 1 MPa. The time of the catalytic reduction reaction is preferably 0.5 to 6 h, more preferably 1 to 3 h, and further preferably 1 h.

[0053] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The experimental methods described in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0054] The following experimental methods and detection methods, unless otherwise specified, are conventional methods; the following reagents and raw materials, unless otherwise specified, are commercially available.

[0055] Example 1

[0056] 0.2 g of titanium dioxide powder (mass ratio of anatase phase titanium dioxide to rutile phase titanium dioxide is 3:1) was weighed into a 100 mL beaker, and 50 mL of deionized water was added and mixed uniformly to obtain a suspension; 0.2 mL of N-methyl-3-aminopropyltrimethoxysilane was added dropwise to the suspension, and stirring was continued at room temperature for 12 h to obtain a mixed solution containing amino-modified titanium dioxide; 273 μL of sodium tetrachloropalladate (Na2PdCl4) aqueous solution (0.02 g mL) was added dropwise to the mixed solution. -1 ), stirring was continued for 24 h, and 213 μL of a freshly prepared sodium borohydride (NaBH4) aqueous solution (0.02 g mL -1 ), after reduction for 2 h, the solid product was collected by filtration, the residual material was washed with deionized water several times, dried in a vacuum oven at 60 ° C for 12 h, and ground to obtain Pd / TiO2-NH catalyst.

[0057] Example 2

[0058] 0.2 g of titanium dioxide powder (mass ratio of anatase phase titanium dioxide to rutile phase titanium dioxide is 3:1) was weighed into a 100 mL beaker, and 50 mL of deionized water was added and mixed uniformly to obtain a suspension; 0.2 mL of N-methyl-3-aminopropyltrimethoxysilane was added dropwise to the suspension, and stirring was continued at room temperature for 12 h to obtain a mixed solution containing amino-modified titanium dioxide; 166 μL of palladium chloride (PdCl2) aqueous solution (0.02 g mL) was added dropwise to the mixed solution. -1 ), stirring was continued for 24 h, and 213 μL of a freshly prepared sodium borohydride (NaBH4) aqueous solution (0.02 g mL -1 ), after reduction for 2 h, the solid product was collected by filtration, the residual material was washed with deionized water several times, dried in a vacuum oven at 60 ° C for 12 h, and ground to obtain Pd / TiO2-NH catalyst.

[0059] Comparative Example 1

[0060] Weigh 0.2 g of titanium dioxide powder (mass ratio of anatase phase titanium dioxide to rutile phase titanium dioxide is 3:1) into a 100 mL beaker, add 50 mL of deionized water and mix well to obtain a suspension, and add 273 μL of sodium tetrachloropalladate (Na2PdCl4) aqueous solution (0.02 g mL) dropwise into the suspension. -1 ), stirred at room temperature for 24 h, and then 213 μL of a freshly prepared sodium borohydride (NaBH4) aqueous solution (0.02 g mL -1 ), reduced for 2 h, filtered, washed with deionized water for several times, dried under vacuum at 60 °C for 12 h, and then ground to obtain Pd / TiO2 catalyst.

[0061] Structural characterization

[0062] Figure 1 The X-ray diffraction pattern of the Pd / TiO2-NH3 catalyst prepared in Example 1 is shown in FIG. Figure 1 The catalyst exhibits three main diffraction peaks at 2θ = 25.3°, 37.9°, and 48.1°, corresponding to the (101), (004), and (200) crystal planes of TiO2 (JCPDS no. 21-1272), respectively. No characteristic diffraction peaks of Pd were observed in the XRD pattern, which is due to the small size of the metallic Pd nanoparticles.

[0063] Figure 2 This is the infrared spectrum of the Pd / TiO2-NH catalyst prepared in Example 1. Figure 2 As shown, at 1463cm -1 、1657cm -1 The asymmetric stretching vibration peak of the primary amine NH bond and the bending vibration peak of the secondary amine NH bond appeared at , indicating that the catalyst was successfully synthesized.

[0064] Application Example 1

[0065] The heat required for the photocatalytic CO2 reduction reaction is provided only by the light source. A 300W xenon lamp with an AM 1.5 filter is used as the full-spectrum light source (spectral range 300-1100nm, photocurrent density 0.15W / cm 2 ) simulates the spectral characteristics of sunlight. 20 mL of deionized water and the Pd / TiO2-NH3 catalyst prepared in Example 1 or Example 2 were added to a 50 mL autoclave to a concentration of 1 g·L -1 After sealing the reactor, the remaining air was replaced with CO2 five times, and 1MPa of CO2 and 1MPa of H2 were introduced. Magnetic stirring (500 rpm) was used throughout the reaction to ensure uniform dispersion of the catalyst. The TOF value was used as an evaluation indicator for the production of formic acid by hydrogenation of carbon dioxide.

[0066] The results are shown in Table 1.

[0067] Table 1 Performance of Pd / TiO2-NH3 catalyst in Examples 1-2

[0068]

[0069] As shown in Table 1, the conversion frequency (TOF) of carbon dioxide hydrogenation to formic acid using the Pd / TiO2-NH2 catalyst prepared in the present invention in a non-alkaline solvent system (deionized water as the reaction medium, 1MPa CO2 and 1MPa H2, 300-1100nm full spectrum irradiation) reached 53.33h -1 .

[0070] Compared with similar catalysts reported previously, the Pd / TiO2-NH3 catalyst of the present invention has excellent catalytic activity. The TOF of the Pd / AC-SA catalyst in prior art 1 (Jiang Shuchao, Liu Xiaokong, Zhai Shengliang, et al. Additive-free CO2 hydrogenation to pure formic acid solution via amine-modified Pd catalyst at room temperature [J]. Green Chemistry, 2023, 25(15): 6025-6031) is 29.1 h -1, PdMn in existing technology 2 (Ci Xiuqin, Zhai Dong, Tu Rui, et al. Continuous production of pure formic acid solution from CO2 hydrogenation at roomtemperature via amine-functionalized PdMn nano-alloy[J]. Chemical Engineering Journal, 2024, 497: 154951.) 0.6 The TOF of the / AC-NH catalyst was 37.1h -1 .

[0071] Comparative Application Example 1

[0072] 20 mg of the Pd / TiO2 catalyst prepared in Comparative Example 1 and 20 mL of deionized water were added to a 50 mL autoclave. After the autoclave was sealed, the residual air was replaced with CO2 five times and filled with 1 MPa CO2 and 1 MPa H2. The reaction was carried out under a 300 W xenon lamp (AM 1.5 filter, spectral range 300-1100 nm, photocurrent density 0.15 W / cm 2 ) and reacted with magnetic stirring at 500 rpm for 1 h.

[0073] The products of Comparative Example 1 and Examples 1-2 were detected by HPLC under the following conditions: column temperature 35°C, detection wavelength 210 nm, flow rate 0.6 mL·min -1 , injection volume 1 μL, mobile phase is dilute H2SO4 solution (pH = 2.5).

[0074] The high performance liquid chromatography analysis of comparative example 1 did not detect formic acid product ( Figure 3 ), compared with the formic acid yields in Examples 1 to 2 ( Figures 4-5 This indicates that amino modification in the Pd / TiO2-NH2 catalyst of the present invention is a key factor in achieving carbon dioxide reduction to formic acid in the absence of alkaline solvent.

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a palladium-supported amino-modified titanium dioxide catalyst, characterized in that: The following steps are involved: Mixing titanium dioxide, an amino functionalization reagent, and water to perform amino modification to obtain amino-modified titanium dioxide; Mixing the amino-modified titanium dioxide with a palladium precursor and water for loading to obtain palladium-loaded modified titanium dioxide; The palladium-supported modified titanium dioxide is mixed with a reducing agent and reduced to obtain a palladium-supported amino-modified titanium dioxide catalyst.

2. The preparation method according to claim 1, characterized in that The titanium dioxide is a mixture of anatase phase titanium dioxide and rutile phase titanium dioxide.

3. The preparation method according to claim 1, characterized in that The amino functionalization reagent includes one or more of 3-aminopropyltriethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, (N,N-dimethyl-3-aminopropyl)trimethoxysilane, tetraethylenepentamine and triethylenetetramine.

4. The preparation method according to claim 1, characterized in that The dosage ratio of the titanium dioxide to the amino functionalization reagent is 0.2-0.5 g:0.2-0.5 mL; the amino modification temperature is room temperature, and the time is 10-24 hours.

5. The preparation method according to claim 1, characterized in that The palladium precursor includes sodium tetrachloropalladate or palladium chloride; the mass ratio of the palladium precursor to titanium dioxide is 0.003-0.006:0.2-0.

5.

6. The preparation method according to claim 1 or 5, characterized in that The load temperature is room temperature, and the time is 10 to 48 hours.

7. The preparation method according to claim 1, characterized in that The reducing agent includes sodium borohydride; the mass ratio of the reducing agent to the palladium precursor is 4-6:3-6; the reduction temperature is room temperature, and the reduction time is 2-6 hours.

8. The palladium-supported amino-modified titanium dioxide catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the palladium-supported amino-modified titanium dioxide catalyst according to claim 8 in the photothermal catalytic reduction of CO2 to produce formic acid.

10. The use according to claim 9, characterized in that The application method comprises: mixing a palladium-supported amino-modified titanium dioxide catalyst with water, and performing a photocatalytic reduction reaction under CO2 and H2 conditions to obtain formic acid; the concentration of the palladium-supported amino-modified titanium dioxide catalyst after mixing with water is 0.1 to 3 g·L -1 ; The pressure of the CO2 is 0.5~3MPa, the pressure of the H2 is 0.5~3MPa, and the time of the catalytic reduction reaction is 0.5~6h.

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