A preparation method of a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure

Abstract

The application relates to a preparation method of a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure, and relates to a preparation method of a direct dimethyl ether fuel cell anode catalyst. In order to solve the problem that the Pt-based anode catalyst used by the existing direct dimethyl ether fuel cell has low catalytic activity due to the influence of poisoning, the application adopts a glucose carbonization method to prepare a novel porous carbon-coated tin dioxide SnO2@PC nanostructure carrier with SnO2 as the core and porous carbon as the shell, then deposits Pt nano-particles on the SnO2@PC nanostructure carrier, and successfully prepares the Pt / SnO2@PC catalyst with the three-phase interface structure. The three-phase interface structure is favorable for reducing the poisoning effect of toxic intermediates on Pt, improving the catalyst performance, significantly improving the dimethyl ether electrocatalytic activity and stability, thereby prolonging the endurance time and service life of the DDFC, and the catalyst shows the highest activity and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a direct dimethyl ether fuel cell anode catalyst. BACKGROUND

[0002] Dimethyl ether (DME) is considered as an alternative fuel for fuel cells due to its high energy density, low toxicity and low permeation effect through Nafion membrane. At ambient temperature, DME can be compressed into a liquid at 5 bar pressure and has a boiling point as low as -24℃. In addition, there is no carbon-carbon bond breaking in DME, which can effectively improve the electrocatalytic oxidation activity.

[0003] Direct dimethyl ether fuel cell (DDFC) is a direct conductive polymer fuel cell that converts the chemical energy of dimethyl ether fuel and oxidant into electrical energy through electrochemical discharge in one step, has high energy conversion efficiency, and is noiseless and pollution-free. The fuel dimethyl ether of direct dimethyl ether fuel cell is a renewable energy source, and dimethyl ether is abundant in source, easy to compress into a liquid, and convenient to store. Direct dimethyl ether fuel cell has the advantages of simple charging method, fast starting speed, no noise, safety and reliability. Direct dimethyl ether fuel cell has high energy density and high energy conversion efficiency, can quickly convert chemical energy into electrical energy, has small energy loss, long-term discharge stability of the battery, long service life, and can effectively reduce energy waste.

[0004] Pt-based catalysts are widely used as DME electrocatalysts. However, the catalytic activity and easy poisoning of Pt-based catalysts greatly hinder the large-scale application of direct dimethyl ether fuel cell (DDFC).

[0005] Metal oxides such as SnO2 are usually used as cocatalysts because they have good cocatalytic effect, electrochemical stability, corrosion resistance and lower cost. Similar to methanol oxidation, -CO ads which can be further oxidized to CO2 as a toxic intermediate, is the rate-limiting step in the oxidation of dimethyl ether. SnO2 can promote the dissociation of OH ads species, thereby helping to remove CO ads adsorbed on platinum active sites. However, SnO2 has low electronic conductivity, so the dimethyl ether oxidation performance of Pt / SnO2 catalyst is low. SUMMARY

[0006] The present application proposes a preparation method of a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure to solve the problem that the catalytic activity of the Pt-based anode catalyst used in the existing direct dimethyl ether fuel cell is low due to the influence of poisoning.

[0007] The preparation method of the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure according to the present application is carried out according to the following steps:

[0008] I. Preparation of SnO2@C carrier material

[0009] 1-2 g of glucose is weighed out and added to 30-50 ml of deionized water and ultrasonically dissolved to obtain a glucose solution; then 0.5-2 g of SnO2 is added to the glucose solution and stirred thoroughly, and the solution is transferred to a high-pressure reaction kettle for hydrothermal reaction; the solid product obtained by the hydrothermal reaction is washed and dried, and then calcined to obtain the SnO2@C carrier material;

[0010] The process of the hydrothermal reaction is: hydrothermal reaction at 170-200 DEG C for 20-24 h;

[0011] The process of the calcination is: calcination at 400-500 DEG C for 1-3 h, and the calcination atmosphere is nitrogen;

[0012] II. Preparation of SnO2@PC material

[0013] 1-3 g of SnO2@C carrier material and 0.05-0.2 g of pore-forming agent are weighed out and mixed, and then transferred to 20-40 ml of deionized water for stirring treatment for 20-24 h; after the stirring treatment, drying is performed, and then calcination is performed; after the calcination, the calcination product is washed and dried to obtain the SnO2@PC material;

[0014] The pore-forming agent is KOH;

[0015] The process of the calcination is: calcination at 600-800 DEG C for 5-7 h, and the calcination atmosphere is nitrogen;

[0016] III. Preparation of Pt / SnO2@PC catalyst with three-phase interface structure

[0017] 45-55 mg of SnO2@PC material is ultrasonically treated in 40-60 ml of deionized water for 0.5-1.5 h, and then magnetically stirred for 1.5-3 h; then 1-2 ml of chloroplatinic acid solution is added to the reaction solution, the pH value of the reaction solution is adjusted to 7-8, and then 60-70 ml of NaBH4 solution is added and stirred for 10-12 h; finally, washing and drying are performed to obtain the Pt / SnO2@PC catalyst with three-phase interface structure.

[0018] This invention utilizes a glucose carbonization method to prepare a novel porous carbon-coated tin dioxide (SnO2)@PC nanostructure support with SnO2 as the core and porous carbon (PC) as the shell. Pt nanoparticles are then deposited on the SnO2@PC nanostructure support, successfully preparing a Pt / SnO2@PC catalyst with a three-phase interface structure. During the pore-forming process, the support needs to be heated to 700℃. This heating process creates numerous defects on the PC surface, and the increased number of defects promotes the formation of tiny platinum nanoparticles, increasing the number of Pt active sites. Simultaneously, during heating, oxygen-containing groups such as C=O, COC, CO, and C-OH on the porous carbon surface are partially removed, reducing the likelihood of Pt nanoparticle deposition on the carbon surface. Meanwhile, the exposed tin dioxide surface at the carbon pores has abundant OH groups. ads Pt nanoparticles can preferentially deposit on the exposed tin dioxide surface at carbon pores. BET results show that the average size of carbon pores is 3-4 nm, and TEM results show that the Pt size is about 2-3 nm. Each carbon pore can accommodate 2-3 Pt nanoparticles. Pt particles can contact carbon and tin dioxide simultaneously to form a three-phase interface structure of Pt, SnO2 and PC.

[0019] In the Pt / SnO2@PC catalyst with a three-phase interface structure, porous carbon (PC) constructs a conductive network on the SnO2 surface, thereby improving the conductivity of SnO2 and enhancing its co-catalyst ability. The abundant OH groups on the SnO2 surface... ads The group can oxidize and remove the toxic intermediate CO adsorbed on Pt. ads The release of Pt active sites enhances the catalyst's electro-oxidation activity for dimethyl ether. By adjusting the number of functional groups on the PC layer surface and the pore size of the porous carbon, Pt particles can be directionally deposited at the three-phase interface, successfully constructing a three-phase interface structure. This three-phase interface structure helps reduce the poisoning effect of toxic intermediates on Pt, thereby improving catalyst performance.

[0020] Pt / SnO2@PC, as an anode catalyst for DDFC, possesses a unique three-phase interface structure and synergistic effects among its components, significantly enhancing the electrocatalytic activity and stability of dimethyl ether. This extends the endurance and lifespan of DDFC, with the Pt / SnO2@PC catalyst achieving a mass activity of 236 mA mg. -1 pt It is 2.2 times that of Pt / C. After 1000 cycles of accelerated potential cycling (APCT) test, the electrochemical active surface area (EAS) of Pt / SnO2@PC catalyst as DDFC anode catalyst decreased by only 29.75%, which is less than the 58.10% of Pt / C catalyst, indicating that Pt / SnO2@PC catalyst exhibits the highest activity and stability. Attached Figure Description

[0021] Figure 1 N2adsorption-desorption plots for Sn02@C and Sn02@PC;

[0022] Figure 2 Pore size distribution plots for Sn02@C and Sn02@PC;

[0023] Figure 3 FTIR spectra of Pt / Sn02@C and Pt / Sn02@PC;

[0024] Figure 4 XRD patterns of Pt / C, Pt / Sn02@C and Pt / Sn02@PC catalysts;

[0025] Figure 5 EDAX pattern of Pt / Sn02@C;

[0026] Figure 6 EDAX pattern of Pt / Sn02@PC (b);

[0027] Figure 7 TEM images and particle size distribution plots of Pt / C (a), Pt / Sn02@C (b) and Pt / Sn02@PC (c);

[0028] Figure 8 HRTEM image of Pt / Sn02@PC catalyst (a); wherein, Figure 8 b is a magnified view of the HRTEM image. Figure 8

[0029] Cyclic voltammograms (CV) of Pt / C, Pt / Sn02@C and Pt / Sn02@PC in 0.5 M H2S04solution. -1 H2SO4solution. Figure 9

[0030] Cyclic voltammograms of Pt / C, Pt / Sn02@C and Pt / Sn02@PC in 0.5 M H2S04and 1.5 M CH3OCH3solution; Figure 10

[0031] Mass activity (MA) plots of Pt / C, Pt / Sn02@C and Pt / Sn02@PC in 0.5 M H2S04and 1.5 M CH3OCH3solution; Figure 11

[0032] Chronoamperometric plots for dimethyl ether electro-oxidation on Pt / C, Pt / Sn02@C and Pt / Sn02@PC catalysts; Figure 12

[0033] Chronoamperometric plots for dimethyl ether electro-oxidation on Pt / C, Pt / Sn02@C and Pt / Sn02@PC catalysts;Figure 13 Figure showing the trend of the change in the electrochemically active area of Pt / C, Pt / SnO2@C and Pt / SnO2@PC during the accelerated aging test;

[0034] Figure 14 Figure showing the normalized curve of the electrochemically active area of Pt / C, Pt / SnO2@C and Pt / SnO2@PC during the accelerated aging test;

[0035] Figure 15 EIS Nyquist plot of the electro-oxidation of dimethyl ether on Pt / C, Pt / SnO2@C and Pt / SnO2@PC;

[0036] Figure 16 Power density curve of the discharge of the direct dimethyl ether fuel cell (3). DETAILED DESCRIPTION

[0037] The technical solution of the present application is not limited to the following specific embodiments, but also includes any reasonable combination of the specific embodiments.

[0038] Specific embodiment one: the preparation method of the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure in this embodiment is carried out according to the following steps:

[0039] I. Preparation of SnO2@C carrier material

[0040] 1-2 g of glucose was weighed and added to 30-50 ml of deionized water and dissolved by ultrasonic, to obtain a glucose solution; then 0.5-2 g of SnO2 was added to the glucose solution and stirred thoroughly, and the solution was transferred to a high-pressure reaction kettle for hydrothermal reaction; the solid product obtained by the hydrothermal reaction was washed and dried, and then calcined to obtain the SnO2@C carrier material;

[0041] The hydrothermal reaction process is: hydrothermal reaction at 170-200 ℃ for 20-24 h;

[0042] The calcination process is: calcination at 400-500 ℃ for 1-3 h, and the calcination atmosphere is nitrogen;

[0043] II. Preparation of SnO2@PC material

[0044] 1-3 g of SnO2@C carrier material and 0.05-0.2 g of pore-forming agent were weighed and mixed, and then transferred to 20-40 ml of deionized water for stirring treatment for 20-24 h, and then dried and calcined. After calcination, the calcined product was washed and dried to obtain the SnO2@PC material;

[0045] The pore-forming agent is KOH;

[0046] The calcination process is: calcination at 600-800℃ for 5-7h, and the calcination atmosphere is nitrogen;

[0047] III. Preparation of Pt / SnO2@PC catalyst with three-phase interface structure

[0048] 45-55mg SnO2@PC material is placed in 40-60mL deionized water and ultrasonic treated for 0.5-1.5h, and then magnetically stirred for 1.5-3h; then 1-2mL chloroplatinic acid solution is added to the reaction solution, the pH value of the reaction solution is adjusted to 7-8, then 60-70mL NaBH4 solution is added and stirred for 10-12h; finally, washing and drying are carried out to obtain the Pt / SnO2@PC catalyst with three-phase interface structure.

[0049] In this embodiment, a novel SnO2@PC nanostructured carrier with SnO2 as the core and porous carbon (PC) as the shell is prepared by glucose carbonization method, and then Pt nanoparticles are deposited on the SnO2@PC nanostructured carrier to successfully prepare the Pt / SnO2@PC catalyst with three-phase interface structure. In the pore forming process, the carrier needs to be heated to 700℃, and the heating process forms many defects on the surface of PC, and the increase in the number of defects can promote the formation of small platinum nanoparticles and increase the number of Pt active sites. At the same time, the oxygen-containing groups on the surface of porous carbon such as C=O, C-O-C, C-O, C-OH, etc. are partially removed during the heating process, and the possibility of Pt nanoparticles deposition on the carbon surface is reduced, while the exposed SnO2 surface at the carbon pores has abundant OH ads groups, and Pt nanoparticles can preferentially deposit on the exposed SnO2 surface at the carbon pores. The BET results show that the average size of the carbon pores is 3-4nm, and the TEM results show that the size of Pt is about 2-3nm, and each carbon pore can accommodate 2-3 Pt nanoparticles, and Pt particles can contact with carbon and SnO2 at the same time, forming a three-phase interface structure of Pt, SnO2 and PC.

[0050] In the Pt / SnO2@PC catalyst with three-phase interface structure, the porous carbon (PC) constructs a conductive network on the surface of SnO2, thereby improving the conductivity of SnO2 and enhancing the cocatalyst ability of SnO2. The abundant OH ads groups on the surface of SnO2 can oxidize and remove the toxic intermediate CO ads adsorbed on Pt, release Pt active sites, and improve the electro-oxidation activity of the catalyst for dimethyl ether. By adjusting the number of functional groups on the surface of the PC layer and the pore size of the porous carbon, Pt particles can be deposited at the three-phase interface, and a three-phase interface structure can be successfully constructed. The three-phase interface structure is beneficial to reduce the poisoning effect of toxic intermediates on Pt and improve the performance of the catalyst.

[0051] Pt / SnO2@PC as the anode catalyst of DDFC has a special three-phase interface structure and a synergistic effect between the components, which significantly improves the electrocatalytic activity and stability of dimethyl ether, thereby prolonging the endurance time and service life of DDFC. The mass activity of the Pt / SnO2@PC catalyst can reach 236 mAmg -1 pt , which is 2.2 times that of Pt / C. After the accelerated potential cycle test (APCT) of Pt / SnO2@PC as the anode catalyst of DDFC for 1000 cycles, the electrochemical active surface area (EAS) of the Pt / SnO2@PC catalyst only decreases by 29.75%, which is less than 58.10% of the Pt / C catalyst, indicating that the Pt / SnO2@PC catalyst shows the highest activity and stability.

[0052] Specific embodiment two: The difference between this embodiment and specific embodiment one is that the washing in step one uses anhydrous ethanol and deionized water in sequence.

[0053] Specific embodiment three: The difference between this embodiment and specific embodiment one or two is that the drying process in step one is vacuum drying at 70-100°C for 5-7h.

[0054] Specific embodiment four: The difference between this embodiment and any one of specific embodiments one to three is that the washing in step two uses HCl solution, anhydrous ethanol and deionized water in sequence, and the concentration of the HCl solution is 0.8-1.5 mol / L -1 .

[0055] Specific embodiment five: The difference between this embodiment and any one of specific embodiments one to four is that the drying process in step two is vacuum drying at 70-100°C for 5-7h.

[0056] Specific embodiment six: The difference between this embodiment and any one of specific embodiments one to five is that the adjustment of the pH value of the reaction solution in step three uses Na2CO4.

[0057] Specific embodiment seven: The difference between this embodiment and any one of specific embodiments one to six is that the concentration of the chloroplatinic acid solution in step three is 0.01-0.015 mol / L -1 .

[0058] Specific embodiment eight: The difference between this embodiment and any one of specific embodiments one to seven is that the concentration of the NaBH4 solution in step three is 0.04-0.06 mol / L -1 .

[0059] Specific embodiment nine: the difference between this embodiment and one of the specific embodiments one to eight is that the drying process in step three is vacuum drying at 70-100°C for 5-8h.

[0060] Specific embodiment ten: the difference between this embodiment and one of the specific embodiments one to nine is that the washing in step three is washing with deionized water.

[0061] Example 1

[0062] The preparation method of the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure in this example is carried out according to the following steps:

[0063] I. Preparation of SnO2@C carrier material

[0064] 2g of glucose was weighed and added to 40ml of deionized water and ultrasonically dissolved to obtain a glucose solution; then 1g of SnO2 was added to the glucose solution and stirred thoroughly, and the solution was transferred to a high-pressure reaction kettle for hydrothermal reaction at 180°C for 24h; the obtained solid product was sequentially washed with anhydrous ethanol and deionized water and vacuum dried at 80°C for 6h, and then calcined at 400°C for 2h, with nitrogen as the calcination atmosphere, to obtain the SnO2@C carrier material;

[0065] II. Preparation of SnO2@PC material

[0066] 2g of SnO2@C carrier material and 0.11g of pore-forming agent KOH were weighed and mixed, and then transferred to 30ml of deionized water for stirring treatment for 24h, and then dried, and then calcined at 700°C for 6h, with nitrogen as the calcination atmosphere; after calcination, the calcined product was sequentially washed with an HCl solution, anhydrous ethanol and deionized water; the concentration of the HCl solution was 1mol / L -1 , and vacuum drying was carried out at 80°C for 6h;

[0067] III. Preparation of Pt / SnO2@PC catalyst with three-phase interface structure

[0068] 50mg of SnO2@PC material was ultrasonically treated in 50ml of deionized water for 1h, and then magnetically stirred for 2h; then 1.5ml of chloroplatinic acid solution with a concentration of 0.01428mol / L -1 was added to the reaction solution, Na2CO4 was used to adjust the pH value of the reaction solution to 7-8, then a NaBH4 solution with a concentration of 0.05mol / L -1 was added and stirred for 12h; finally, deionized water washing and vacuum drying at 80°C for 6h were carried out to obtain the Pt / SnO2@PC catalyst with three-phase interface structure;

[0069] Physical characterization: The microstructure and elemental mapping of Pt / C, Pt / SnO2@C, and Pt / SnO2@PC catalysts were observed using transmission electron microscopy (TEM, FEI-TALOS-F200X). The elemental composition and content of the catalysts were analyzed using coupled energy-dispersive X-ray spectroscopy (EDAX, superX-eds). X-ray diffraction (XRD, Rigaku-smartlab) patterns of the catalyst materials were plotted using a CuKa X-ray source at a scanning temperature of 5 °C·s. -1 Pore ​​size and specific surface area were measured using a Brunauer-Emmett-Teller (BET, 3Flex 5.00) instrument.

[0070] Chemical characterization: Electrochemical tests were performed at 25°C using a PARSTAT4000 electrochemical workstation, employing a three-electrode system with a glassy carbon disk electrode as the working electrode and a 1cm Pt sheet as the electrode. 2 The working electrode was used as the counter electrode, and the Hg / Hg₂SO₄ electrode as the reference electrode. The working electrode was prepared as follows: 3 mg of catalyst was dispersed in 1 mL of isopropanol and sonicated for 5 min. Then, 4.0 mL of deionized water and 25.0 μL of Nafion solution were added, and the resulting solution was sonicated for 20 min to prepare a homogeneous suspension. 5 μL of the solution was added to the surface of the glassy carbon electrode, followed by 5 μL of Nafion solution. The prepared electrode was dried before electrochemical testing. A solution of 0.5 M H₂SO₄ and 1.5 M CH₃OCH₃ was used as the electrolyte. Cyclic voltammetry (CV) was performed with a potential range of 0 V–1.7 V (vs. RHE) and a scan rate of 50 mV·s. -1 The specific formula for calculating the electrochemically active surface area (ESA) of a catalyst is as follows:

[0071] ESA = Q H / (Q C ×g catalyst )

[0072] Q H Q represents the charge generated by hydrogen adsorption / desorption. C The estimated constant representing the adsorption / desorption of hydrogen atoms in a monolayer (0.21 mC·cm⁻¹) -2 ), g catalyst The mass of the Pt nanoparticles in the working electrode is given. Accelerated aging test (APCT) was used to observe the catalyst at 50 mV·s. -1 Stability at scan rate. Electrochemical impedance spectroscopy (EIS) was measured at a potential of 1.3 V (vs. RHE) from 100 kHz to 0.01 Hz with an AC amplitude of 5 mV. Chronopotential curves were obtained at 0.5 mol·L⁻¹. -1 H2SO4 and 1.5 mol·L-1 The test was carried out in a solution of CH3OCH3, and the test time was 1000 s.

[0073] Figure 1 N2adsorption-desorption curves of SnO2@C and SnO2@PC; Figure 2 The pore size distribution of SnO2@C and SnO2@PC; SnO2@C and SnO2@PC both showed typical type IV isotherms, indicating the presence of abundant mesopores in the two supports. The pore size of SnO2@C and SnO2@PC was mainly distributed in the range of 3-4 nm, indicating that the pore size of the two catalysts was relatively uniform. Table 1 shows the specific surface area and average pore size of SnO2@C and SnO2@PC. The average pore size of SnO2@C and SnO2@PC was 3.92 nm and 3.89 nm, respectively, and the specific surface area was 48.53 m 2 ·g -1 and 97.22 m 2 ·g -1 These results demonstrate that the specific surface area of SnO2@PC is significantly higher than that of SnO2@C. The larger specific surface area is due to the pore-forming effect of KOH, which can expose more SnO2, facilitating the formation of more three-phase interface structures.

[0074] Table 1 Specific surface area and pore size of SnO2@C and SnO2@PC

[0075]

[0076] Figure 3 FTIR spectra of Pt / SnO2@C and Pt / SnO2@PC; FTIR spectra showed a strong absorption peak at 3438 cm -1 , which may be caused by the stretching vibration of O-H in hydroxyl, carboxyl or adsorbed water. The peak centered at 1385 cm -1 can be attributed to the bending vibration of O-H. The two peaks at 1168 cm -1 and 1078 cm -1 are attributed to the stretching vibration of C-O-C and C-O, respectively. The peak at 1670 cm -1A weak peak corresponding to C=0 was observed in the range. The surface oxygen functional groups (C=0, C-O-C, COOH) will provide abundant active sites for platinum nanoparticles, thereby hindering the agglomeration of platinum nanoparticles. Compared with Pt / Sn02@C, there are fewer oxygen functional groups on the surface of Pt / Sn02@PC, which indicates that the PC layer on the surface of Pt / Sn02@PC provides fewer active sites and can deposit fewer platinum nanoparticles. The presence of Sn02surface hydroxyl groups is a direct anchoring site for platinum nanoparticles, further promoting the deposition of platinum nanoparticles. More platinum nanoparticles will preferentially deposit on the interface of C and Sn02, forming more three-phase interface structures, thereby further improving the electrocatalytic oxidation activity of dimethyl ether.

[0077] Figure 4 XRD patterns of Pt / C, Pt / Sn02@C and Pt / Sn02@PC catalysts; the diffraction peak at 26.3° is attributed to C (002), which is produced by glucose carbonization. The diffraction peaks at 26.6°, 33.9° and 51.8° correspond to Sn02(110), Sn02(101) and Sn02(211), respectively. The diffraction peaks at 39.8°, 46.2°, 67.5° and 81.3° can be attributed to Pt (111), Pt (200), Pt (220) and Pt (311), indicating that the Pt in the catalyst is face-centered cubic structure (fcc). Based on the Pt (111) crystal plane, the average particle size of Pt in the Pt / Sn02@PC catalyst was calculated to be 2.9 nm by Scherrer's formula. The average particle size of Pt in Pt / C and Pt / Sn02@C catalysts was 3.6 nm and 3.1 nm, respectively.

[0078] Figure 5 EDAX pattern of Pt / Sn02@C; Figure 6 EDAX pattern of Pt / Sn02@PC (b); the peak of Pt element further proves that Pt nanoparticles are successfully deposited on the Sn02@C and Sn02@PC composite carrier. The Pt loading of Pt / Sn02@C and Pt / Sn02@PC catalysts is about 14.4wt% and 15.9wt%, close to the theoretical value of 20wt.%. It is because the high-temperature heating during the formation of pores by KOH leads to the reduction of functional groups on the surface of the carbon layer. Therefore, there are fewer Pt nanoparticles loaded on the surface of carbon, and the Pt loading mass on the surface of the carrier is reduced. Further, it is indicated that more Pt nanoparticles are deposited at the three-phase interface, which not only saves the amount of Pt, but also improves the utilization rate of noble metals. The content of C in Pt / Sn02@C and Pt / Sn02@PC catalysts is 24.5wt% and 16.7wt%, respectively. The Sn02content is 51.1wt% and 57.4wt%, respectively.

[0079] Figure 7 TEM images and particle size distribution of Pt / C (a), Pt / Sn02@C (b) and Pt / Sn02@PC (c); as Figure 7 a and b, the platinum nanoparticles on the surface of Pt / C catalyst and the edge of Pt / Sn02@C catalyst were severely agglomerated. Compared with Pt / C and Pt / Sn02@C catalysts, under the condition of high-temperature pore-forming treatment using KOH, as Figure 7 c, the platinum nanoparticles on the surface of Pt / Sn02@PC catalyst were more evenly and orderly dispersed. In addition, from the particle size distribution graph, it can be seen that the average diameter of the platinum nanoparticles distributed on the surface of the three catalysts changed significantly. The average diameters of Pt / C, Pt / Sn02@C and Pt / Sn02@PC were 3.5 nm, 3.1 nm and 2.7 nm, respectively. This result is consistent with the above XRD result. This is because the many defects present on the PC shell provide more active sites for platinum nanoparticles and refine the grain size of platinum, which helps to stabilize smaller platinum nanoparticles on the surface of Pt / Sn02@PC. In addition, the functional groups on the carbon layer on the surface of the Pt / Sn02@PC catalyst are also reduced, and more platinum nanoparticles are deposited on the three-phase interface, thereby improving the ability of the catalyst.

[0080] Figure 8 HRTEM image of Pt / Sn02@PC catalyst; Figure 8 b is a locally magnified HRTEM image. Different lattice spacings of 0.2631 nm and 0.2230 nm correspond to Sn02(101) and Pt(111) planes, respectively. In addition, the carbon layer produced by glucose carbonization can also be observed. FFT obtained the diffraction images of Pt(111) and Sn02(101), further proving the existence of (fcc) Pt(111), Sn02(101) and carbon layer. As Figure 8 b shows that the Pt / Sn02@PC catalyst has abundant three-phase (i.e. Pt, Sn02 and PC) interfaces. The Pt nanoparticles are deposited on the C-Sn02 interface, indicating that there is interaction between them, which improves the performance of the Pt-based catalyst and further enhances the electrocatalytic oxidation activity of dimethyl ether.

[0081] Figure 9 Cyclic voltammograms (CV) of Pt / C, Pt / Sn02@C and Pt / Sn02@PC in 0.5 mol L -1 H2SO4 solution. There are typical hydrogen and oxygen adsorption / desorption curves in the CV. The EAS values of the three catalysts are listed in Table 2. The EAS of Pt / Sn02@PC is 55.33 m 2 ·g -1 , which is much higher than the 27.6 m 2 ·g-1 This indicates that the electrochemical activity of Pt / SnO2@PC catalyst is significantly higher than that of Pt / C, which is due to the defects in the porous carbon layer of Pt / SnO2@PC catalyst promoting the uniform dispersion of Pt nanoparticles. Therefore, the Pt / SnO2@PC catalyst has the highest EAS value and DME activity.

[0082] Figure 10 The cyclic voltammograms of Pt / C, Pt / SnO2@C and Pt / SnO2@PC catalysts in 0.5 M H2SO4 and 1.5 M CH3OCH3 solution; Figure 11 The mass activity (MA) plots of Pt / C, Pt / SnO2@C and Pt / SnO2@PC catalysts in 0.5 M H2SO4 and 1.5 M CH3OCH3 solution; the peak potential of the three catalysts for dimethyl ether electro-oxidation is 1.1 V. As can be seen from Table 1, the addition of SnO2 significantly improves the DME electrocatalytic oxidation ability of the catalyst. As shown in Figure 10 , the mass activity of the DME catalyst increases in the order of Pt / C < Pt / SnO2@C < Pt / SnO2@PC. The mass activity of Pt / SnO2@PC reaches 236 mA mg -1 Pt ( Figure 11 ), which is 1.3 times and 2.2 times that of Pt / SnO2@C and Pt / C. This may be due to the OH ads groups on the surface of SnO2 can promote the oxidation of CO ads , release the active sites of Pt, and further adsorb DME oxides. The reduction of carbon functional groups on the surface of the porous carbon promotes the deposition of Pt particles at the contact interface of PC and SnO2, forming more three-phase interface structures, thereby improving the DME electro-oxidation performance of the Pt / SnO2@PC catalyst.

[0083] Figure 12 The chronoamperograms of dimethyl ether electro-oxidation on Pt / C, Pt / SnO2@C and Pt / SnO2@PC;

[0084] Pt / SnO2@PC has the slowest downward trend. After 1000 s, the current density of Pt / SnO2@PC in DME is as high as

[0085] 14.59 mA·cm -2 , with the best stability. This may be due to SnO2 providing OH ads , thereby enhancing the oxidation ability of CO intermediates. In addition, OH adsThe Pt particles are anchored and can hinder the aggregation of Pt nanoparticles. Therefore, the stability of the electrocatalyst is enhanced. In addition, the three-phase interface structure of the Pt / Sn02@PC catalyst is increased, which fully plays the catalytic effect of Sn02, thereby improving the stability of the catalyst.

[0086] Figure 13 The trend chart of the change of the electrochemical active area of Pt / C, Pt / Sn02@C and Pt / Sn02@PC during the accelerated aging test process; Figure 14 The normalized curve of the electrochemical active area of Pt / C, Pt / Sn02@C and Pt / Sn02@PC during the accelerated aging test process; with the increase of the cycle number, the EAS of the three catalysts shows a downward trend. Among them, the EAS attenuation of the Pt / Sn02@PC catalyst is the smallest. According to Table 2, after 1000 times of APCT cycle, the EAS of the Pt / Sn02@PC catalyst only attenuates by 29.75%, which is lower than that of other catalysts, which again proves its superior stability.

[0087] Figure 15 The EIS Nyquist plot of dimethyl ether electro-oxidation on Pt / C, Pt / Sn02@C and Pt / Sn02@PC; the diameter of the semicircle usually corresponds to the electron transfer resistance. As Figure 15 and Table 2 show, the electron transfer resistance (8.64 Ω·cm -2 ) of Pt / Sn02@PC is lower than that of Pt / C and Pt / Sn02@C. This is because Sn02 can dissociate water to form OH ads groups, thereby promoting the oxidation of intermediate CO ads and accelerating the DME electro-oxidation reaction rate, thereby improving the DME electro-oxidation activity of the catalyst. In addition, the three-phase interface structure in the Pt / Sn02@PC catalyst helps the contact between Pt and Sn02@PC. It can further improve the DME electro-oxidation activity.

[0088] Figure 16 The power density curve of the discharge of the direct dimethyl ether fuel cell (3), which can be seen from Figure 16 , that the maximum power density of the direct dimethyl ether fuel cell (3) is 38.14 mw·cm -2 .

[0089] Table 2 Electrochemical test results of three catalysts

[0090]

[0091]

[0092] In Table 3, the DME electro-oxidation activity of Pt / Sn02@PC was compared with other catalysts reported in the literature. Pt / Sn02@PC has a higher EAS value and a higher exchange current density. The performance of DME electro-oxidation using Pt / Sn02@PC catalyst is significantly higher than other reported catalysts. Among them, Literature 1: Kashyap, Diwakar, Hanan Teller, and Alex Schechter. "Dimethyl ether oxidation on an active Sn02 / Pt / C catalyst for high-power fuel cells." ChemElectroChem 6.9 (2019): 2407-2414. Literature 2: Gebru MG, Subramanian P, Beisky P, et al. "Chemical-Dealloying-Derived PtPdPb-Based Multi metallic Nanoparticles: Dimethyl Ether Electrocatalysis and Fuel Cell Application." ACS Applied Materials & Interfaces 15.49 (2023): 56930-56944. Literature 3: Kubanova, M. S., A. B. Kuriganova, and N. V. Smirnova. "Electrooxidation of Dimethyl Ether on Pt / Ti02–C Catalysts." Russian Journal of Electrochemistry 58.10 (2022): 916-926. Literature 4: Gebru M G, Teller H, Subramanian P, et al. "Nonthermal Plasma-Modified Carbon-Carrying Sn-Based Ternary Nanocatalyst for High-Performance Direct Dimethyl Ether Fuel Cells." Energy Technology 10.11 2022: 2200835.

[0093] Table 3

[0094]

Claims

1. A method for preparing a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure, characterized in that: The preparation method of the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure is carried out according to the following steps: I. Preparation of SnO2@C support materials Weigh 1-2g of glucose, add it to 30-50ml of deionized water and sonicate to dissolve it to obtain a glucose solution; then add 0.5-2g of SnO2 to the glucose solution and stir thoroughly. Transfer the solution to a high-pressure reactor for hydrothermal reaction; wash and dry the solid product obtained from the hydrothermal reaction, and then calcine it to obtain SnO2@C support material. The hydrothermal reaction process is as follows: hydrothermal reaction at 170-200℃ for 20-24 hours; The calcination process is as follows: calcination at 400-500℃ for 1-3 hours, with nitrogen atmosphere. II. Preparation of SnO2@PC materials Weigh 1-3g of SnO2@C carrier material and 0.05-0.2g of pore-forming agent, mix them, and transfer them to 20-40mL of deionized water. Stir for 20-24h. After stirring, dry the mixture and then calcine it. After calcine, wash and dry the calcined product to obtain SnO2@PC material. The pore-forming agent is KOH; The calcination process is as follows: calcination at 600-800℃ for 5-7 hours, with nitrogen atmosphere. III. Preparation of Pt / SnO2@PC catalysts with a three-phase interface structure 45–55 mg of SnO2@PC material was placed in 40–60 mL of deionized water and sonicated for 0.5–1.5 h, followed by magnetic stirring for 1.5–3 h. Then, 1–2 mL of chloroplatinic acid solution was added to the reaction solution to adjust the pH to 7–8, followed by the addition of 60–70 mL of NaBH4 solution and stirring for 10–12 h. Finally, the mixture was washed and dried to obtain a Pt / SnO2@PC catalyst with a three-phase interface structure.

2. The method for preparing the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure according to claim 1, characterized in that: The washing process described in step one involves sequentially washing with anhydrous ethanol and deionized water.

3. The method for preparing the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure according to claim 1, characterized in that: The drying process described in step one is as follows: vacuum drying at 70–100°C for 5–7 hours.

4. The method for preparing the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure according to claim 1, characterized in that: The washing process in step two involves sequentially washing with HCl solution, anhydrous ethanol, and deionized water, wherein the concentration of the HCl solution is 0.8–1.5 mol / L. -1 .

5. The method for preparing the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure according to claim 1, characterized in that: The drying process described in step two is as follows: vacuum drying at 70–100°C for 5–7 hours.

6. The method for preparing the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure according to claim 1, characterized in that: In step three, the pH of the reaction solution is adjusted using Na2CO4.

7. The method for preparing the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure according to claim 1, characterized in that: The concentration of the chloroplatinic acid solution in step three is 0.01–0.015 mol / L. -1 .

8. The method for preparing the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure according to claim 1, characterized in that: The concentration of the NaBH4 solution in step three is 0.04–0.06 mol / L. -1 .

9. The method for preparing the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure according to claim 1, characterized in that: The drying process described in step three is as follows: vacuum drying at 70–100°C for 5–8 hours.

10. The method for preparing the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure according to claim 1, characterized in that: Step 3 involves washing with deionized water.

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