A platinum-rhodium alloy supported titanium dioxide catalyst, its preparation method and application

Abstract

The present invention discloses a platinum-rhodium alloy supported titanium dioxide catalyst, its preparation method and application, which relate to the field of catalytic technology. The present invention includes the following steps: Step 1: Prepare a precursor solution of Pt and a precursor solution of Rh; Step 2: Mix the Pt and Rh precursor solutions, and add TiO₂ into the mixed Pt and Rh precursor solution for solvothermal reaction to obtain a sample; Step 3: Wash the obtained sample and perform vacuum drying. The prepared titanium dioxide supported platinum-rhodium alloy catalyst of the present invention can efficiently photoreduce CO to C₂H₄, and the yield in 3 hours is as high as 362.94 μmol gcat⁻¹; the catalyst prepared by the present invention has high activity and high selectivity, exceeding the photocatalytic reduction performance of most of the currently reported CO, especially it can produce C₂H₄, and the selectivity of C₂H₄ is close to 50%.

Description

Technical Field

[0001] The present invention belongs to the field of catalysis. Specifically, it relates to a platinum-rhodium alloy supported titanium dioxide catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] CO is one of the exhaust gases inevitably produced by the combustion of fossil fuels, which will cause serious harm to human health and the ecological environment. At the same time, CO is also an important intermediate molecule for the conversion and utilization of carbon resources and can be used to prepare more other high-value-added energy fuels or chemical products. At present, powerful external driving forces are required for the effective conversion of CO. For example, the conversion reaction generally needs to be carried out under high temperature and high pressure conditions. Therefore, it has broad application prospects but is extremely challenging to achieve the directional preparation of high-value-added fuels and chemicals from CO through low-energy-consuming and environmentally friendly methods. Compared with thermal energy and electrical energy, solar energy in nature is an inexhaustible green clean energy. Therefore, the catalytic conversion method of photocatalytic CO has far-reaching significance and has attracted extensive research attention. However, it is extremely difficult to drive the catalytic conversion of CO with low-energy light.

[0003] Therefore, developing a functional catalyst with high-efficiency CO photoreduction performance has great practical value and value orientation. However, for pure semiconductors, the adsorption of CO is generally weak, which limits the photocatalytic performance of CO. In recent years, the deposition method of metal cocatalysts (Pd, Pt, Rh, Au, etc.) has been widely used to expand the light absorption region of pure titanium dioxide and enhance the adsorption ability of reactants. Therefore, attempting to develop a simple and general method to synthesize a catalyst for efficient CO reduction has great research and application value.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a synthesis method for preparing a platinum-rhodium alloy catalyst supported on commercial TiO2 by a one-step solvothermal co-reduction method. The method provided by the present invention has high simplicity, is suitable for large-scale preparation, and the obtained catalyst has a leading photocatalytic activity and good stability at present.

[0006] To solve the above technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a platinum-rhodium alloy supported titanium dioxide catalyst includes the following steps:

[0008] Step 1: Prepare a precursor solution of Pt and a precursor solution of Rh; wherein, the concentrations of the Pt and Rh precursor solutions are both 1.0 mg mL -1; The precursor solution of Pt was prepared by dissolving platinum tetraammine nitrate in ethylene glycol solvent, and the precursor solution of Rh was prepared by dissolving rhodium chloride in ethylene glycol solvent;

[0009] Step 2: Mix the Pt and Rh precursor solutions, and add TiO2 into the mixed solution of Pt and Rh precursors for solvothermal reaction to obtain a sample; among them, when TiO2 is added into the mixed solution of Pt and Rh precursors, the solvothermal reaction temperature is 180 - 200 °C, and the solvothermal reaction duration is 10 - 12 hours; more specifically, take 0.5 mL of Pt precursor solution and 1.0 mL of Rh precursor solution, mix them thoroughly and continuously drop them into a certain volume of ethylene glycol solvent, then add 0.05 - 1.00 g of TiO2 powder into it, and stir ultrasonically for 30 min;

[0010] Step 3: Wash the obtained sample and perform vacuum drying; among them, the sample obtained from the hydrothermal reaction needs to be repeatedly washed with absolute ethanol and ultrapure water, and finally vacuum dried; the temperature of vacuum drying is 60 - 70 °C; the obtained final sample is highly dispersed on the P25 substrate, and the ratio of platinum to rhodium in it is about 1:4.

[0011] A titanium dioxide catalyst loaded with platinum-rhodium alloy, prepared by the preparation method described in any one of the above.

[0012] An application of a titanium dioxide catalyst loaded with platinum-rhodium alloy, applied to photocatalytic CO reduction.

[0013] After adopting the above technical solutions, the present invention has the following beneficial effects compared with the prior art. Of course, any product implementing the present invention does not necessarily need to achieve all the advantages described below:

[0014] The TiO2-supported platinum-rhodium alloy catalyst prepared by the present invention can efficiently photocatalytically reduce CO to C b H4, and the yield in 3 hours is as high as 362.94 μmol gcat -1 .

[0015] The catalyst prepared by the present invention has high activity and high selectivity, exceeding the photocatalytic reduction performance of most of the currently reported CO, especially it can produce C2H4, and the selectivity of C2H4 is close to 50%.

[0016] The catalyst prepared by the present invention also has excellent photocatalytic stability and is suitable for the long-term photocatalytic CO reduction reaction.

[0017] The following further describes the specific embodiments of the present invention in detail with reference to the drawings. Description of the Drawings

[0018] The accompanying drawings in the following description are merely some embodiments. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts. In the drawings:

[0019] Figure 1 It is the X-ray diffraction pattern of the commercial TiO₂-supported platinum-rhodium alloy catalyst obtained in Example 1;

[0020] Figure 2 It is the scanning transmission electron microscope image of the commercial TiO₂-supported platinum-rhodium alloy catalyst obtained in Example 1;

[0021] Figure 3 It is the aberration-corrected scanning tunneling electron microscope photograph of the commercial TiO₂-supported platinum-rhodium alloy catalyst obtained in Example 1;

[0022] Figure 4 It is the photocatalytic CO reduction activity diagram of the commercial TiO₂-supported platinum-rhodium alloy catalyst obtained in Example 1;

[0023] Figure 5 It is the photoelectric property diagram (a: transient photocurrent, b: electrochemical impedance, c: linear sweep voltammetry, and d: Mott-Schottky test) of the commercial TiO₂-supported platinum-rhodium alloy catalyst obtained in Example 1;

[0024] Figure 6 It is the performance stability test of the commercial TiO₂-supported platinum-rhodium alloy catalyst obtained in Example 1.

[0025] It should be noted that these drawings and textual descriptions are not intended to limit the scope of the concept of the present invention in any way, but to illustrate the concept of the present invention to those skilled in the art by referring to specific embodiments. Detailed Description of the Invention

[0026] Now, the present invention will be further described in detail with reference to the accompanying drawings.

[0027] Please refer to Figure 1-6 As shown, in this embodiment, a method for preparing a titanium dioxide catalyst supported by a platinum-rhodium alloy is provided, including the following steps:

[0028] Step 1: Prepare a precursor solution of Pt and a precursor solution of Rh; wherein, the concentrations of both the Pt and Rh precursor solutions are 1.0 mg mL -1 ; The preparation of the Pt precursor solution is to dissolve platinum diamine nitrate in an ethylene glycol solvent, and the preparation of the Rh precursor solution is to dissolve rhodium chloride in an ethylene glycol solvent;

[0029] Step 2: Mix the Pt and Rh precursor solutions, and add TiO2 into the mixed Pt and Rh precursor solution for solvothermal reaction to obtain a sample; wherein, when adding TiO2 into the mixed Pt and Rh precursor solution, the solvothermal reaction temperature is 180 - 200 °C, and the solvothermal reaction duration is 10 - 12 hours; more specifically, take 0.5 mL of the Pt precursor solution and 1.0 mL of the Rh precursor solution, fully mix them evenly, then continuously drop them into a certain volume of ethylene glycol solvent, and then add 0.05 - 1.00 g of TiO2 powder into it, and stir ultrasonically for 30 min;

[0030] Step 3: Wash the obtained sample and perform vacuum drying; wherein, the sample obtained from the hydrothermal reaction needs to be repeatedly washed with absolute ethanol and ultrapure water, and finally vacuum dried; the temperature of vacuum drying is 60 - 70 °C; the obtained final sample is highly dispersed on the P25 substrate, and the platinum:rhodium ratio therein is about 1:4.

[0031] A titanium dioxide catalyst supported by a platinum-rhodium alloy, prepared by the preparation method according to any one of the above.

[0032] An application of a titanium dioxide catalyst supported by a platinum-rhodium alloy, applied to photocatalytic CO reduction.

[0033] The TiO2-supported platinum-rhodium alloy catalyst prepared by the present invention can efficiently photocatalytically reduce CO to C2H4, and the yield in 3 hours is as high as 362.94 μmol gcat -1 .

[0034] The catalyst prepared by the present invention has high activity and high selectivity, exceeding the photocatalytic reduction performance of most of the currently reported CO, especially it can produce C2H4, and the selectivity of C2H4 is close to 50%.

[0035] The catalyst prepared by the present invention also has excellent photocatalytic stability and is suitable for the long-term photocatalytic CO reduction reaction.

[0036] The present invention first uses platinum salt and rhodium salt as raw materials, and utilizes the suitable reducibility and relatively large viscosity of ethylene glycol and other characteristics as the reaction solvent and reducing agent, so that the reduction and growth rates of the two metals are more suitable and controllable, providing the possibility for the mixing between the two metal atoms. By performing a long-time high-temperature solvothermal reaction, a more thermodynamically stable supported solid solution alloy is formed.

[0037] The performance of the material is evaluated by a photocatalytic CO reduction evaluation system. The light source for the photocatalytic experiment is 300 W, and the reactor used is made of quartz. The drugs used in the following examples are all commercially available products without special instructions, and the methods used are all conventional methods in the art without special instructions.

[0038] Example 1: First, prepare the precursor solution of Pt (tetraammineplatinum nitrate dispersed in ethylene glycol solvent with a concentration of 1.0 mg mL-1) and the precursor solution of Rh (rhodium chloride dispersed in ethylene glycol solvent with a concentration of 1.0 mg mL-1). Measure 0.5 mL of the platinum solution and 1.0 mL of the rhodium solution respectively, add them to the ethylene glycol solution and mix evenly. Then, put 0.05 g of TiO2 into the mixed solution of Pt and Rh precursors, carry out hydrothermal reaction at 180 °C for 12 hours. After cooling to room temperature, wash the obtained sample and dry it under vacuum at 60 °C overnight. Grind the sample thoroughly.

[0039] Characterize the Pt-Rh alloy supported on TiO2 (commercial) photocatalyst, and the results are shown in Figures 1 to 4 . Figure 1 is the X-ray diffraction pattern of the commercial TiO2 supported Pt-Rh alloy catalyst obtained in Example 1. The results show that the main body of the catalyst is still TiO2, but the diffraction peaks of the Pt-Rh alloy can still be observed; Figure 2 is the scanning transmission electron microscope image of the commercial TiO2 supported Pt-Rh alloy catalyst obtained in Example 1, showing that the Pt-Rh alloy is evenly dispersed on the commercial TiO2, and the average particle size is about 8 - 10 nm; Figure 3 is the aberration-corrected scanning tunneling electron microscope photograph of the commercial TiO2 supported Pt-Rh alloy catalyst obtained in Example 1, showing the clear atomic distribution of the Pt-Rh alloy. It can be seen that the brighter atoms are Pt and the relatively darker ones are Rh atoms. The disordered arrangement of bright and dark Pt and Rh atoms can be seen, indicating the synthesis of a Pt-Rh solid solution alloy.

[0040] Carry out photocatalytic tests on the above commercial TiO2 supported Pt-Rh alloy catalyst. The test process is as follows: The reactivity of the sample was evaluated using a quartz reactor. Disperse 10 mg of the photocatalyst in 30 mL of solution and sonicate for 30 minutes. Before illumination (300 W xenon lamp, 320 - 780 nm), use argon to remove the air inside the reactor, and then evacuate the reactor. Subsequently, add argon (99.99%) and CO gas (99.99%) to the closed reactor, and the volume ratio of Ar to CO is 4:1. Use a fully automatic online gas chromatograph (GC9790ⅡPlus, Fuli) to regularly measure the gas products, and use an FID detector to detect CO, CH4, C2H, and C2H6. The test results are shown in Figure 4 , Figure 4 is the photocatalytic CO reduction activity diagram of the commercial TiO2 supported Pt-Rh solid solution alloy catalyst obtained in Example 1. After 3 h of reaction, the yield of the reduction product C2H4 can reach 362.94 μmol gcat -1 , and the selectivity is close to 50%.

[0041] The photoelectric properties of the photocatalytic materials were further tested. Figure 5 , Figure 5 To verify the photoelectric properties of the commercial TiO2-supported platinum-rhodium alloy catalysts obtained in Example 1, the photoelectric performance of the four materials was characterized using transient photocurrent, electrochemical impedance spectroscopy, linear sweep voltammetry, and Mott-Schottky spectroscopy. The results showed that under illumination, the Pt-Rh / TiO2 catalyst generated a higher photocurrent and facilitated the migration of photogenerated carriers across the surface. Compared with the other three materials, Pt-Rh / TiO2 exhibited a higher reduction current density. Mott-Schottky spectroscopy at the same frequency (1000 Hz) confirmed that all four catalysts were n-type semiconductors, while Pt-Rh / TiO2 exhibited a smaller slope relative to the other samples, indicating a higher charge carrier concentration.

[0042] Figure 6 The performance stability test of the commercial TiO2-loaded platinum-rhodium alloy catalyst obtained in Example 1 was carried out. The test results showed that the prepared catalyst had excellent photocatalytic stability.

[0043] In the present invention, all experimental parameters are strictly considered, including the selection of platinum source and rhodium source, solvent concentration, reaction temperature and time.

[0044] Example 2: The present invention provides a method for preparing a commercial TiO2-supported platinum-rhodium alloy catalyst by a one-step solvent thermal method, which comprises the following steps:

[0045] Step 1: Dissolve tetraammine platinum nitrate and rhodium chloride in ethylene glycol solvent (the concentration of platinum solution and rhodium solution are both 1.0 mg mL -1 ), stir and mix evenly;

[0046] Step 2: Add the obtained mixed platinum-rhodium solution to the ethylene glycol solution and stir to mix evenly;

[0047] Step 3: Add 0.05-1.00 g of TiO2 (P25) to the mixed solution in step 2 above and mix thoroughly under ultrasonic stirring;

[0048] Step 4: The mixed solution prepared in step 3 was placed in a polytetrafluoroethylene-lined stainless steel autoclave for hydrothermal reaction at 180-200°C for 10-12 h.

[0049] Specifically, the sample obtained by the reaction in step 4 is cooled to room temperature.

[0050] Specifically, the cooled sample was repeatedly washed by centrifugation with anhydrous ethanol and ultrapure water for more than 6 times.

[0051] Specifically, the centrifuged product is placed in a vacuum drying oven and dried overnight at 60-70 °C.

[0052] The present invention is not limited to the above embodiments. Any person should know that structural changes made under the inspiration of the present invention, as long as they have the same or similar technical solutions as the present invention, all fall within the protection scope of the present invention. The technologies, shapes, and structures not described in detail in the present invention are all well-known technologies.

Claims

1. Application of a platinum-rhodium alloy supported titanium dioxide catalyst, characterized in that, Applied to photocatalytic CO reduction to ethylene, characterized in that, a preparation method of a platinum-rhodium alloy supported titanium dioxide catalyst, comprising the following steps: Step 1: Prepare a precursor solution of Pt and a precursor solution of Rh; Step 2: Mix the Pt and Rh precursor solutions, and add TiO2 into the mixed Pt and Rh precursor solution for solvothermal reaction to obtain a sample; The TiO2 is P25; Step 3: Wash the obtained sample and perform vacuum drying; the concentrations of both the Pt and Rh precursor solutions are 1.0 mg mL -1 ; In Step 1, the precursor solution of Pt is prepared by dissolving platinum diamine dinitrate in ethylene glycol solvent, and the precursor solution of Rh is prepared by dissolving rhodium chloride in ethylene glycol solvent; In Step 2, TiO2 is added into the mixed Pt and Rh precursor solution, the solvothermal reaction temperature is 180 - 200 °C, and the solvothermal reaction duration is 10 - 12 hours; In Step 2, take 0.5 mL of the Pt precursor solution and 1.0 mL of the Rh precursor solution, mix them thoroughly and continuously drop them into a certain volume of ethylene glycol solvent, then add 0.05 - 1.00 g of TiO2 powder into it, and stir ultrasonically for 30 min; In Step 3: The sample obtained from the hydrothermal reaction should be repeatedly washed with absolute ethanol and ultrapure water, and finally dried in vacuum; In Step 3, the vacuum drying temperature is 60 - 70 °C; In Step 3: The obtained platinum-rhodium alloy is highly dispersed on the P25 substrate, and the ratio of platinum to rhodium in it is 1:4.

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