Preparation method and application of platinum-based catalyst with tin oxide hollow nanofiber as carrier

Abstract

The application relates to the technical field of proton exchange membrane fuel cells, in particular to a preparation method and application of a platinum-based catalyst taking tin oxide hollow nanofibers as carriers. Through an electrostatic spinning process, SnCl2 / C nanofiber materials are prepared in advance, and after high-temperature oxidation, SnO2 hollow nanofiber carriers are obtained; then, platinum nanoparticles are loaded on the above carriers by using a mode of physical adsorption followed by thermal adsorption to obtain a Pt(5)-SnO2 catalyst material. In the application, the platinum nanoparticles are loaded on the tin oxide hollow nanofiber carriers, the high-activity action of the platinum nanoparticles is utilized, the corrosion resistance of the tin oxide and the high-efficiency charge transmission action are utilized to coordinate and optimize the adsorption action on the intermediate of an acidic hydrogen oxidation (HOR) reaction, the CO poisoning resistance and the phosphoric acid poisoning resistance of the material are improved, and finally the acidic HOR catalytic activity is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of proton exchange membrane fuel cell, and particularly relates to a preparation method and application of a platinum-based catalyst with tin oxide hollow nanofiber as a carrier. BACKGROUND

[0002] Proton exchange membrane fuel cell (PEMFC) is considered as one of the high-efficiency and sustainable electrochemical energy conversion devices, and carbon-supported platinum-based catalyst is a universal anode catalyst. Under the working condition of PEMFC (0.6-0.8V and pH<1), the carbon support of Pt nanoparticles is easily corroded, leading to the generation of CO and structural damage. In addition, during the start-stop operation of PEMFC, due to the existence of reverse current, the local potential of the cathode will reach 1.5V, which greatly aggravates the further oxidation of the carbon support. Previous studies have shown that after 4000min of constant potential test at 1.5V potential, the carbon weight loss due to corrosion is about 19%. After the corrosion of carbon, the Pt nanoparticles on the surface of the carbon support tend to dissolve and migrate, leading to the decline of catalytic performance. At the same time, the weak interaction between Pt and the carbon support makes the Pt particles also easy to migrate and aggregate, and considering this, it is an urgent need for the development of PEMFC technology to find an electrochemically stable and conductive support material with stronger interaction with Pt nanoparticles to replace carbon.

[0003] Metal oxides, such as TiO2, SnO2 and CeO2, have been investigated as alternative electrocatalyst supports due to their high electrochemical stability and tunable metal-support interactions. Among them, tin dioxide (SnO2) is considered as a promising electrocatalyst support due to its abundant reserves, environmental friendliness, stable chemical properties, and large-scale mesoporous structure, which is conducive to faster charge transfer. SnO2 is also a semiconductor metal oxide, and its surface composition has excellent electron mobility and stability, making it an important n-type semiconductor with a wide band gap of 3.6 eV, which has been widely used in lithium ion batteries, photocatalyst oxidation, etc. The SnO2 materials currently studied are usually in the form of low specific surface area, which is not conducive to charge transfer, so methods such as nanotubes, nanostructured nanorods, hollow nanospheres, and nanosheets have been developed to generate SnO2 nanostructures to increase their surface area. In this paper, carbon nanofibers are used as a carrier template to stabilize SnO2, and Pt nanoparticles are embedded on the surface of SnO2 hollow nanofibers, which not only increases the specific surface area of the material to expose more active sites, but also constructs a hollow nanochannel that is conducive to charge transfer. In the case of loading Pt nanoparticles on SnO2, not only can it promote the dispersion of Pt nanoparticles, but also can reasonably and effectively distribute the adsorbed hydrogen on the active sites during the HOR reaction. Considering that Pt has a high chemical affinity for CO and is easily poisoned by CO, SnO2 as a carrier of Pt nanoparticles helps to weaken the binding of CO on Pt, and the Pt-O-Sn interface plays a key role in electron transfer. At the same time, high-temperature proton exchange membrane fuel cells (HT-PEMFC) use liquid phosphoric acid as electrolyte, and Pt-based catalysts have a strong adsorption effect on phosphoric acid anions (H2PO4 - ), which causes a large amount of catalytic sites to be poisoned, thereby greatly reducing the HOR activity. The SnO2 carrier can reduce the adsorption free energy of platinum nanoparticles on phosphoric acid, thereby reducing phosphoric acid poisoning. Moreover, in high-temperature operating systems, the high stability of the SnO2 carrier prevents the separation of metal nanoparticles, so it not only avoids poisoning in fuel cells but also maintains its stability. In-depth research in this area will have the potential for a huge breakthrough in improving the quality activity, cycle stability, etc. of the HOR catalyst, and will also be a strategy worth exploring to improve the power density of high-temperature proton exchange membrane fuel cell anode materials. SUMMARY

[0004] The application aims to solve the problems in the prior art and provides a preparation method and application of a platinum-based catalyst with tin oxide hollow nanofibers as a carrier. The structural stability and excellent electronic conductivity of SnO2 are fully utilized, and Pt nanoparticles are combined to fully exert the reasonable adsorption and desorption of active sites and reaction intermediates and resist the poisoning of CO and phosphoric acid on the active sites. Therefore, the prepared Pt (5) -SnO2 hollow nanofibers exhibit excellent activity and stability as acidic hydrogen oxidation electrocatalyst materials.

[0005] To achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0006] A preparation method of a platinum-based catalyst with tin oxide hollow nanofibers as a carrier, comprising the following steps:

[0007] Step S1, preparing SnCl2 / C nanofiber material

[0008] Stannous chloride (SnCl2) and polyvinylpyrrolidone (PVP) are respectively added into a mixed solvent of N,N-dimethylformamide (DMF) and ethanol, stirred at room temperature for 12 hours, and then the solution is transferred into a syringe. An electrostatic spinning machine is used, and aluminum foil is used as a collector to collect the spinning fibers to obtain SnCl2 / C nanofiber material.

[0009] Step S2, preparing SnO2 hollow nanofiber

[0010] The SnCl2 / C nanofiber material is placed in a muffle furnace for pre-oxidation and high-temperature oxidation to obtain SnO2 hollow nanofiber.

[0011] Step S3, preparing Pt (5) -SnO2 hollow nanofiber

[0012] The SnO2 hollow nanofiber and potassium chloroplatinate (K2PtCl4) are dissolved in deionized water and stirred, and sodium borohydride (NaBH4) aqueous solution is added for reduction, and then centrifugal drying is performed to obtain Pt / SnO2. Then, heat treatment is performed in an inert atmosphere to obtain Pt (5) -SnO2 hollow nanofiber.

[0013] Preferably, in step S1, the mass ratio of SnCl2 to PVP is 1:2, and the volume ratio of DMF to ethanol is 1:1.

[0014] Preferably, in step S1, the electrostatic spinning machine uses aluminum foil as a collector to collect the spinning fibers, and the parameter settings are as follows: flow rate is 0.04-0.12 mm / min -1 , applied voltage is 10-25 kV, and the distance from the nozzle tip to the receiving plate is 8-20 cm.

[0015] Preferably, in step S2, the pre-oxidation is heated to 100-300°C at a heating rate of 1-4°C / min, and held for 1-4h; the high-temperature oxidation is heated to 400-600°C at a heating rate of 3-8°C / min, and held for 2-4h.

[0016] Preferably, in step S3, the mass ratio of K2PtCl4 and SnO2 is 1:20, the mass of NaBH4 in the aqueous NaBH4 solution is 0.1-1g, the reduction time is 1-12h, the drying temperature is 50-80°C, and the drying time is 8-12h.

[0017] Preferably, in step S3, the inert atmosphere for the heat treatment is N2 / NH3, the heat treatment is heated to a temperature of 300-800°C at a heating rate of 1-10°C / min, and held for 1-5h.

[0018] A platinum-based catalyst Pt-SnO2 prepared by the above preparation method (5) -SnO2, wherein the platinum-based catalyst Pt (5) -SnO2 exhibits a hollow long nanofiber structure composed of SnO2 nanoparticles, has an average inner diameter of 150±20nm and an average outer diameter of 200±50nm, and has Pt nanoparticles uniformly embedded in the surface of the nanofiber, wherein the large specific surface area of the hollow nanofiber increases the number of exposed active sites, the good electrical conductivity of SnO2, and the unique structure of the hollow nanofiber play a role in facilitating charge transfer during the reaction, and the Pt nanoparticles are stabilized so as not to fall off, thereby improving the activity and stability of the Pt (5) -SnO2 catalyst in an acidic HOR. Due to the excellent electron mobility, stability, and large band gap of the SnO2 surface composition, the catalyst can avoid poisoning of the Pt active sites by CO and reduce adsorption of phosphoric acid on the Pt sites during the reaction, which is beneficial to reducing CO poisoning and phosphoric acid poisoning of the catalyst when it is applied to an anode material of a high-temperature proton exchange membrane fuel cell.

[0019] The application also provides a platinum-based catalyst Pt-SnO2 prepared by the above preparation method (5) -SnO2 in an acidic hydrogen oxidation reaction, specifically, a platinum-based catalyst Pt-SnO2 (5) -SnO2, wherein the rare earth metal oxide exhibits a long hollow nanofiber structure, and Pt nanoparticles are uniformly embedded in the surface of the nanofiber, wherein the SnO2 carrier can effectively adjust the electronic structure of the Pt nanoparticles, greatly reduces adsorption of CO and phosphoric acid anions on the active sites, and optimizes HBE in the HOR reaction.

[0020] By adopting the technical scheme, SnCl2 and PVP are added into DMF and ethanol solvents, mixed uniformly, and SnCl2 / C nanofiber material is prepared in advance through an electrostatic spinning process, and after pre-oxidation and high-temperature oxidation, carbon nanofiber templates are oxidized to form long and hollow SnO2 nanofiber material, which has regular and uniform morphology, and the average inner diameter is 150±20 nm and the average outer diameter is 200±50 nm. Pt nanoparticles are loaded on the surface of the stable hollow nanofiber, and because the catalyst material has a large specific surface area, the exposure rate of Pt active sites is increased. In addition, SnO2 acts as a carrier of Pt nanoparticles, which weakens the combination of CO and Pt, greatly reducing the poisoning effect of CO on the catalyst. Because Pt-based catalysts have a strong adsorption effect on phosphate anions (H2PO4-), the catalyst sites in the fuel cell are usually poisoned, and the SnO2 carrier can reduce the adsorption free energy of platinum nanoparticles for phosphoric acid, thereby reducing the poisoning of phosphoric acid. Moreover, the unabsorbed phosphoric acid can increase the ion flowability of the electrolyte, thereby accelerating the charge transfer rate of the electrolyte and the electrode surface, and improving the HOR reaction kinetics. Because the surface composition of the SnO2 carrier has excellent electron mobility and stability, it can not only promote the dispersion of Pt nanoparticles, but also reasonably and effectively distribute the adsorbed hydrogen on the active sites during the HOR reaction, significantly improving the overall HOR activity and stability of the catalyst.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] 1. The present application uses a simple electrospinning-reduction-thermal adsorption method to prepare a Pt (5) -SnO2 hollow nanofiber electrocatalyst with excellent electrochemical activity, high stability, good CO poisoning resistance and phosphoric acid tolerance.

[0023] 2. The SnO2 carrier used in the present application is abundant in reserves, environmentally friendly, and chemically stable, and the surface composition has excellent electron mobility, which is beneficial to faster charge transmission.

[0024] 3. The Pt (5) -SnO2 catalyst of the present application has regular morphology, and the SnO2 carrier adjusts the electronic structure and adsorption binding energy of Pt, optimizes the combination strength of Pt and H, promotes the adsorption and desorption of reaction intermediates, and finally realizes the improvement of HOR catalytic activity. Moreover, the Pt (5)-SnO2 has the characteristics of large specific area, rich and uniform active sites, high current density, excellent stability and good anti-poisoning properties, compared with conventional Pt-based materials, the prepared Pt (5) -SnO2 hollow nanofiber has unique structural characteristics and carrier advantages, and is a potential hydrogen oxidation electrocatalyst material, which is expected to have a broad application prospect in the future energy industry. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 SEM atlas of the platinum-based catalyst prepared for the embodiment 1 of the present application;

[0026] Figure 2 TEM atlas of the platinum-based catalyst prepared for the embodiment 1 of the present application;

[0027] Figure 3 AC-STEM atlas of the platinum-based catalyst prepared for the embodiment 1 of the present application;

[0028] Figure 4 XRD atlas of the platinum-based catalyst prepared for the embodiment 1 of the present application;

[0029] Figure 5 Tafel curve atlas of the platinum-based catalyst prepared for the embodiment 1 of the present application;

[0030] Figure 6 LSV curve comparison atlas of the materials obtained from the embodiment 1 and comparative examples 1 and 2 of the present application;

[0031] Figure 7 Micro-polarization region linear fitting curve comparison atlas of the materials obtained from the embodiment 1 and comparative examples 1 and 2 of the present application;

[0032] Figure 8 Phosphoric acid resistance test curve atlas of the platinum-based catalyst prepared for the embodiment 1 of the present application;

[0033] Figure 9 Anti-CO poisoning test curve atlas of the platinum-based catalyst prepared for the embodiment 1 of the present application. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings, so that the people skilled in the art can better understand the advantages and features of the present application, and the protection scope of the present application can be defined more clearly. The described embodiments of the present application are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the people skilled in the art without creative labor are within the protection scope of the present application.

[0035] Embodiment 1:

[0036] A method for preparing a platinum-based catalyst with tin oxide hollow nanofiber as a carrier, comprising the following steps:

[0037] 1) Preparation of SnCl2 / C nanofiber material: 0.5 g of stannous chloride (SnCl2) and 1 g of polyvinylpyrrolidone (PVP) were added to 6 mL of N,N-dimethylformamide (DMF) and 6 mL of ethanol mixed solvent, respectively, stirred at room temperature for 12 h, and then the solution was transferred to a 10 mL syringe. An electrospinning machine was used, and the parameter settings were as follows: flow rate was 0.06 mm / min, applied voltage was 20 kV, distance from nozzle tip to receiving plate was 15 cm, aluminum foil was used as a collector to collect the spun fibers, and SnCl2 / C nanofiber material was collected; -1

[0038] 2) Preparation of SnO2 hollow nanofiber: the SnCl2 / C nanofiber material was placed in a muffle furnace for pre-oxidation, with a heating rate of 2 ℃ / min, first pre-oxidized at 150 ℃ for 2 h, and then high-temperature oxidized at 500 ℃ with a heating rate of 5 ℃ / min to obtain SnO2 hollow nanofiber;

[0039] 3) Preparation of Pt (5) -SnO2 hollow nanofiber: 100 mg of SnO2 hollow nanofiber and 5 mg of potassium chloroplatinate (K2PtCl4) were dissolved in 50 mL of deionized water, stirred, and 0.5 g of sodium borohydride (NaBH4) aqueous solution was added for reduction for 8 h, then centrifuged and dried to obtain Pt / SnO2, which was placed in a tube furnace and heat-treated at 300 ℃ under N2 atmosphere with a heating rate of 2 ℃ / min, and kept at this temperature for 3 h, and then cooled to room temperature to obtain Pt (5) -SnO2 hollow nanofiber.

[0040] The platinum-based catalyst Pt (5) -SnO2 with tin oxide hollow nanofiber as a carrier prepared in Example 1 was physically characterized by SEM, TEM, XRD, etc. From the SEM Figure 1 ), it can be seen that the material is composed of interwoven hollow nanofibers, with an average inner diameter of 150±20 nm and an average outer diameter of 200±50 nm, and the TEM spectrum Figure 2 ) can also clearly show the structural characteristics of the hollow fibers, with a wall thickness of 30±20 nm. The AC-STEM spectrum Figure 3 ) shows that Pt nanoparticles are uniformly embedded and exposed on the surface of SnO2. From the Figure 4 ​XRD patterns can be seen, the diffraction peaks of the material and Sn02standard card completely consistent (JCPDS card, 41-1445), to prove the successful preparation of Sn02, no obvious Pt related diffraction peak is due to the amount of Pt doped is very small, while the (002) crystal surface corresponding to the diffraction peak of graphitized carbon.

[0041] From the Tafel curve ( Figure 5 ) or micro-polarization region linear fitting curve ( Figure 7 ) can be calculated out of the higher exchange current density, indicating that it has a faster reaction kinetics rate.

[0042] The above results show that the material as an acidic hydroxide electrocatalyst material has good application prospect.

[0043] Example 2:

[0044] In this embodiment, different from example 1, the amount of SnCl2in step 1 is changed to 1g, and the rest is the same as example 1.

[0045] Example 3:

[0046] In this embodiment, different from example 1, the amount of PVP in step 1 is changed to 250mg, and the rest is the same as example 1.

[0047] Example 4:

[0048] In this embodiment, different from example 1, the amount of DMF in step 1 is changed to 12mL, and the rest is the same as example 1.

[0049] Example 5:

[0050] In this embodiment, different from example 1, the amount of ethanol in step 1 is changed to 12mL, and the rest is the same as example 1.

[0051] Example 6:

[0052] In this embodiment, different from example 1, the flow rate in step 1 is changed to 0.08mm min -1 , and the rest is the same as example 1.

[0053] Example 7:

[0054] In this embodiment, different from example 1, the voltage applied in step 1 is changed to 18kV, and the rest is the same as example 1.

[0055] Example 8:

[0056] In this embodiment, different from example 1, the distance from the nozzle tip to the receiving plate in step 1 is changed to 10cm, and the rest is the same as example 1.

[0057] Example 9:

[0058] In this example, the temperature ramping rate of pre-oxidation in step 2 was changed to 3°C / min, and the rest was the same as example 1.

[0059] Example 10:

[0060] In this example, the temperature of pre-oxidation in step 2 was changed to 200°C, and the rest was the same as example 1.

[0061] Example 11:

[0062] In this example, the time of pre-oxidation in step 2 was changed to 3h, and the rest was the same as example 1.

[0063] Example 12:

[0064] In this example, the amount of SnO2 in step 2 was changed to 200mg, and the rest was the same as example 1.

[0065] Example 13:

[0066] In this example, the amount of K2PtCl4 in step 2 was changed to 10mg, and the rest was the same as example 1.

[0067] Example 14:

[0068] In this example, the amount of NaBH4 in step 2 was changed to 0.2g, and the rest was the same as example 1.

[0069] Example 15:

[0070] In this example, the reduction time of NaBH4 in step 2 was changed to 2h, and the rest was the same as example 1.

[0071] Example 16:

[0072] In this example, the temperature ramping rate of heat treatment in step 2 was changed to 5°C / min, and the rest was the same as example 1.

[0073] Example 17:

[0074] In this example, the temperature of heat treatment in step 2 was changed to 600°C, and the rest was the same as example 1.

[0075] Example 18:

[0076] In this example, the difference from Example 1 is that the length of heat treatment in Step 2 is changed to 4h, and the rest is the same as Example 1.

[0077] Comparative Example 1:

[0078] The difference from Example 1 is only that the amount of K2PtCl4 added is 10mg, and the rest of the implementation conditions remain unchanged.

[0079] Comparative Example 2:

[0080] The difference from Example 1 is only that K2PtCl4 is not added, and the rest of the implementation conditions remain unchanged.

[0081] The materials of Example 1, Comparative Examples 1-2 were tested for hydrogen oxidation reaction, and electrochemical measurements were performed using a CHI 660E workstation in a three-electrode system in a 0.1M HCIO4 solution, with a graphite rod and a mercury / mercury oxide electrode as the counter electrode and reference electrode, respectively. 5mg of catalyst was mixed with 100uL of Nafion (5wt.%), then 600uL of deionized water and 300u of ethanol were added to prepare a catalyst ink. After ultrasonic treatment for 30min, 10μL of catalyst ink was uniformly dropped on a glassy carbon electrode with an area of 0.196cm 2 , and dried at room temperature as the working electrode. In a H2-saturated electrolyte, the scan rate was 5mV s -1 , the scan rate was 0.02-1.02V or 0.1-0.5V (vs. RHE), the scan rate was 1600rpm, and the LSV curve was obtained on the RDE, and the LSV test results are shown in Figure 6 , Pt (5) -SnO2 exhibited its superior current density, and the performance of the comparative sample Pt (10) -SnO2 was slightly worse than that of Pt (5) -SnO2, and pure SnO2 basically did not exist. In a 0.1M HCIO4 electrolyte, 0.01M, 0.05M and 0.1M of H3PO4 were added respectively, and the phosphoric acid resistance was tested by LSV, and it can be obviously seen that with the increase of phosphoric acid concentration, the current density also increases, which shows that the Pt active site in Pt (5) -SnO2 is not only not poisoned by phosphoric acid, but also due to the presence of phosphoric acid ions, the ion concentration in the electrolyte is increased, the charge flow is increased, and the reaction rate is improved. CO stripping voltammetry measurement was carried out in a 0.1M HCIO4 solution. Before the test, pure N2 was input into the electrolyte to remove the air in the electrolyte. Then, the electrode was kept under bubbling CO gas at 0.1V vs. RHE for 15min, and then the electrolyte was purged with N2 for 30min to completely remove CO in the solution, leaving only a layer of CO on the surface of the working electrode, and the current density was measured at 20mV s -1The anti-CO poisoning test curve was obtained by recording the CO stripping voltammetry from 0.05 V to 1.1 V (vs. RHE), and the test results are shown in Figure 9 As shown in the figure, the CO stripping peak of Pt (5) -SnO2 has a low and obvious CO stripping peak starting potential, indicating that the CO adsorbed on the surface of the catalyst is easy to be oxidized and desorbed, further strengthening the CO tolerance of the catalyst, thus exhibiting the Pt (5) -SnO2 has the advantage of anti-CO poisoning.

[0082] In summary, by loading platinum nanoparticles on the tin oxide hollow nanofiber carrier, the high activity of platinum nanoparticles and the corrosion resistance and high efficient charge transport of tin oxide are used to coordinate and optimize the adsorption of the intermediate of the acidic HOR reaction, and the anti-CO poisoning and anti-phosphoric acid poisoning performance of the material are improved, and finally the acidic HOR catalytic activity is improved.

[0083] The description and practice disclosed in the present application are easy to think and understand for ordinary skilled persons in the technical field, and some improvements and refinements can be made without departing from the principles of the present application. Therefore, the modifications or improvements made without departing from the spirit of the present application should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a platinum-based catalyst with tin oxide hollow nanofibers as a carrier, characterized by, The method comprises the following steps: Step S1, preparing SnCl2 / C nanofiber material Stannous chloride (SnCl2) and polyvinylpyrrolidone (PVP) are respectively added into a mixed solvent of N,N-dimethylformamide (DMF) and ethanol, stirred at room temperature for 12 hours, and then the solution is transferred into a syringe; an electrostatic spinning machine is used to collect the spinning fibers by using aluminum foil as a collector, and SnCl2 / C nanofiber material is collected; Step S2, preparing SnO2 hollow nanofiber The SnCl2 / C nanofiber material is pre-oxidized in a muffle furnace, and then high-temperature oxidation is performed to obtain SnO2 hollow nanofiber; Step S3, preparation of Pt (5) Sn02hollow nanofibers SnO2hollow nanofibers were stirred with potassium chloroplatinate (K2PtCl4) in deionized water, and then reduced by adding aqueous sodium borohydride (NaBH4) solution, and then centrifuged and dried to obtain Pt / SnO2, which was then heat-treated under an inert atmosphere to obtain Pt (5) -SnO2hollow nanofibers.

2. The method for preparing a platinum-based catalyst with tin oxide hollow nanofiber as a carrier according to claim 1, characterized in that, In step S1, the mass ratio of SnCl2 and PVP is 1:2, and the volume ratio of DMF and ethanol is 1:

1.

3. The method for preparing a platinum-based catalyst with tin oxide hollow nanofibers as a carrier according to claim 1, characterized in that, In step S1, the electrospinning machine collects the spun fibers using an aluminum foil as a collector. The parameters are set as follows: flow rate of 0.04-0.12 mm / min, applied voltage of 10-25 kV, and distance from the nozzle tip to the receiving plate of 8-20 cm. -1 , applied voltage of 10-25 kV, and distance from the nozzle tip to the receiving plate of 8-20 cm.

4. The method for preparing a platinum-based catalyst with tin oxide hollow nanofibers as a carrier according to claim 1, characterized in that, In step S2, the pre-oxidation is heated to 100-300℃ at a heating rate of 1-4℃ / min, and the temperature is kept for 1-4h; the high-temperature oxidation is heated to 400-600℃ at a heating rate of 3-8℃ / min, and the temperature is kept for 2-4h.

5. The method for preparing a platinum-based catalyst using tin oxide hollow nanofibers as a support according to claim 1, characterized in that, In step S3, the mass ratio of K2PtCl4 and SnO2 is 1:20, the mass of NaBH4 in the NaBH4 aqueous solution is 0.1g-1g, the reduction time is 1-12h, the drying temperature is 50-80℃, and the drying time is 8-12h.

6. The method of claim 1, wherein the method of preparing a platinum-based catalyst using tin oxide hollow nanofibers as a carrier is characterized by, In step S3, the inert atmosphere for heat treatment is N2 / NH3, the heat treatment is heated to 300-800℃ at a heating rate of 1-10℃ / min, and the temperature is kept for 1-5h.

7. A platinum-based catalyst Pt-SnO2 prepared by the method according to any one of claims 1 to 6. (5) -SnO2.

8. A platinum-based catalyst Pt-SnO2 prepared by the method according to any one of claims 1 to 6. (5) Use of SnO2 in acid hydroxylation reactions.

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