Preparation method of Pt / SnO2 (at) PC direct dimethyl ether fuel cell anode catalyst with three-phase interface structure

Abstract

The invention discloses a preparation method of a Pt / SnO2 (at) 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. The problem that a Pt-based anode catalyst adopted by an existing direct dimethyl ether fuel cell is affected by poisoning and is low in catalytic activity is solved. According to the invention, a glucose carbonization method is adopted to prepare a novel porous carbon coated tin dioxide SnO2 (at) PC nano-structure carrier with SnO2 as a core and porous carbon as a shell, and then Pt nanoparticles are deposited on the SnO2 (at) PC nano-structure carrier, so that the Pt / SnO2 (at) PC catalyst with a three-phase interface structure is successfully prepared. The three-phase interface structure is favorable for reducing the poisoning effect of toxic intermediates on Pt and improving the performance of the catalyst, so that the electrocatalytic activity and stability of dimethyl ether are remarkably improved, the endurance time and the service life of DDFC are prolonged, and the catalyst shows the highest activity and stability.

Description

Technical Field

[0001] The invention relates to a method for preparing a direct dimethyl ether fuel cell anode catalyst. Background Art

[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°C. In addition, there is no carbon-carbon bond breakage 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 in one step through electrochemical discharge. It has high energy conversion efficiency and is noiseless and pollution-free. Dimethyl ether, the fuel of direct dimethyl ether fuel cell, is a renewable energy source. Dimethyl ether is abundant in source, easy to compress into liquid, and convenient to store. Direct dimethyl ether fuel cell is easy to charge, fast to start, noiseless, safe and reliable. Direct dimethyl ether fuel cell has high energy density and high energy conversion efficiency. It can quickly convert chemical energy into electrical energy with low energy loss. The battery has stable discharge for a long time and long service life, which can effectively reduce energy waste.

[0004] Pt-based catalysts are widely used as DME electrocatalysts. However, the catalytic activity and susceptibility to poisoning of Pt-based catalysts have greatly hindered the large-scale application of direct dimethyl ether fuel cells (DDFCs).

[0005] Metal oxides such as SnO2 are often used as promoters because of their good promoter effect, electrochemical stability, corrosion resistance and low cost. ads As a toxic intermediate, it can be further oxidized to CO2, which is the rate-limiting step in the oxidation of dimethyl ether. SnO2 can promote the dissociation of OH ads adsorption of species, thereby helping to remove CO adsorbed on the platinum active sites ads However, the electronic conductivity of SnO2 is low, so the DME oxidation performance of Pt / SnO2 catalyst is low. Summary of the invention

[0006] In order to solve the problem that the Pt-based anode catalyst used in the existing direct dimethyl ether fuel cell has low catalytic activity due to poisoning, the present invention provides a method for preparing a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure.

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

[0008] 1. Preparation of SnO2@C carrier material

[0009] Weigh 1-2g of glucose, add it to 30-50ml of deionized water and dissolve it by ultrasonic to obtain a glucose solution; then add 0.5-2g of SnO2 to the glucose solution and stir it thoroughly, transfer the solution to a high-pressure reactor, and perform a hydrothermal reaction; wash and dry the solid product obtained by the hydrothermal reaction, and then calcine it to obtain a SnO2@C carrier material;

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

[0011] The calcination process is as follows: calcining at 400-500° C. for 1-3 hours, with nitrogen as the calcination atmosphere;

[0012] 2. Preparation of SnO2@PC materials

[0013] Weigh 1-3 g of SnO2@C carrier material and 0.05-0.2 g of pore former, mix them, transfer them into 20-40 mL of deionized water, stir them for 20-24 h, dry them after the stirring, and then calcine them. After calcination, wash and dry the calcined product to obtain SnO2@PC material;

[0014] The pore-forming agent is KOH;

[0015] The calcination process is as follows: calcining at 600-800° C. for 5-7 hours in a nitrogen atmosphere;

[0016] 3. Preparation of Pt / SnO2@PC catalyst with three-phase interface structure

[0017] 45-55 mg SnO2@PC material is placed in 40-60 mL deionized water for ultrasonic treatment for 0.5-1.5 h, and then magnetically stirred for 1.5-3 h; then 1-2 mL 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 NaBH4 solution is added and stirred for 10-12 h; finally, it is washed and dried to obtain a Pt / SnO2@PC catalyst with a three-phase interface structure.

[0018] The present invention adopts the glucose carbonization method to prepare a novel porous carbon-coated tin dioxide SnO2@PC nanostructure carrier with SnO2 as the core and porous carbon (PC) as the shell, and then deposits Pt nanoparticles on the SnO2@PC nanostructure carrier to successfully prepare a Pt / SnO2@PC catalyst with a three-phase interface structure. During the pore-forming process, the carrier needs to be heated to 700°C. The heating process causes many defects to form on the PC surface. The increase in the number of defects can promote the formation of tiny platinum nanoparticles and increase the number of Pt active sites. At the same time, during the heating process, oxygen-containing groups such as C=O, COC, CO, C-OH, etc. on the porous carbon surface are partially removed, and the possibility of Pt nanoparticles depositing on the carbon surface is reduced, while the exposed tin dioxide surface at the carbon pores has rich OH ads Group, Pt nanoparticles can be preferentially deposited on the exposed tin dioxide surface at the carbon pores. BET results show that the average size of the carbon pores is 3-4nm, TEM results show that the Pt size is about 2-3nm, and each carbon pore can just accommodate 2-3 Pt nanoparticles. Pt particles can contact with carbon and tin dioxide at the same time 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 the catalyst co-catalyst ability of SnO2. ads The group can oxidatively remove the toxic intermediate CO adsorbed on Pt ads , releasing Pt active sites and improving the electro-oxidation activity of the catalyst for dimethyl ether. By adjusting the number of functional groups on the PC layer surface and the pore size of the porous carbon, the Pt particles can be oriented and deposited at the three-phase interface, successfully constructing a three-phase interface structure. The three-phase interface structure is conducive to reducing the poisoning effect of toxic intermediates on Pt and improving catalyst performance.

[0020] As the anode catalyst of DDFC, Pt / SnO2@PC 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 extending the endurance and service life of DDFC. The mass activity of Pt / SnO2@PC catalyst can reach 236mAmg -1 pt , which is 2.2 times that of Pt / C. After 1000 cycles of accelerated potential cycling test (APCT), the electrochemical active surface area (EAS) of Pt / SnO2@PC, a DDFC anode catalyst, decreased by only 29.75%, which is less than 58.10% of Pt / C catalyst, indicating that Pt / SnO2@PC catalyst shows the highest activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 N2 adsorption-desorption curves of SnO2@C and SnO2@PC;

[0022] Figure 2 The pore size distribution diagram of SnO2@C and SnO2@PC;

[0023] Figure 3 FTIR spectra of Pt / SnO2@C and Pt / SnO2@PC;

[0024] Figure 4 XRD patterns of Pt / C, Pt / SnO2@C and Pt / SnO2@PC catalysts;

[0025] Figure 5 EDAX diagram of Pt / SnO2@C;

[0026] Figure 6 EDAX diagram of Pt / SnO2@PC (b);

[0027] Figure 7 TEM images and particle size distribution diagrams of Pt / C (a), Pt / SnO2@C (b) and Pt / SnO2@PC (c);

[0028] Figure 8 HRTEM image of Pt / SnO2@PC catalyst ( Figure 8 a); among which, Figure 8 b is a locally enlarged HRTEM image.

[0029] Fig. 9 For Pt / C, Pt / SnO2@C and Pt / SnO2@PC at 0.5molL -1 Cyclic voltammogram (CV) in H2SO4 solution.

[0030] Fig.10 Cyclic voltammograms of Pt / C, Pt / SnO2@C and Pt / SnO2@PC in 0.5M H2SO4 and 1.5MCH3OCH3 solutions;

[0031] Fig.11 Mass activity (MA) diagram of Pt / C, Pt / SnO2@C and Pt / SnO2@PC in 0.5M H2SO4 and 1.5MCH3OCH3 solutions;

[0032] Fig.12 The chronoamperometric curves of dimethyl ether electrooxidation on Pt / C, Pt / SnO2@C and Pt / SnO2@PC;

[0033] Fig.13 The trend diagram of the electrochemical active area changes of Pt / C, Pt / SnO2@C and Pt / SnO2@PC during the accelerated aging test;

[0034] Fig.14 Normalized curves of electrochemical active areas of Pt / C, Pt / SnO2@C and Pt / SnO2@PC during accelerated aging tests;

[0035] Fig.15 EIS Nyquist plots of dimethyl ether electrooxidation on Pt / C, Pt / SnO2@C and Pt / SnO2@PC;

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

[0037] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any reasonable combination of the specific implementation modes.

[0038] Specific implementation method 1: The preparation method of the Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst with a three-phase interface structure in this implementation method is carried out according to the following steps:

[0039] 1. Preparation of SnO2@C carrier material

[0040] Weigh 1-2g of glucose, add it to 30-50ml of deionized water and dissolve it by ultrasonic to obtain a glucose solution; then add 0.5-2g of SnO2 to the glucose solution and stir it thoroughly, transfer the solution to a high-pressure reactor, and perform a hydrothermal reaction; wash and dry the solid product obtained by the hydrothermal reaction, and then calcine it to obtain a SnO2@C carrier material;

[0041] The process of the hydrothermal reaction is: hydrothermal reaction at 170-200° C. for 20-24 hours;

[0042] The calcination process is as follows: calcining at 400-500° C. for 1-3 hours, with nitrogen as the calcination atmosphere;

[0043] 2. Preparation of SnO2@PC materials

[0044] Weigh 1-3 g of SnO2@C carrier material and 0.05-0.2 g of pore former, mix them, transfer them into 20-40 mL of deionized water, stir them for 20-24 h, dry them after the stirring, and then calcine them. After calcination, wash and dry the calcined product to obtain SnO2@PC material;

[0045] The pore-forming agent is KOH;

[0046] The calcination process is as follows: calcining at 600-800° C. for 5-7 hours in a nitrogen atmosphere;

[0047] 3. Preparation of Pt / SnO2@PC catalyst with three-phase interface structure

[0048] 45-55 mg SnO2@PC material is placed in 40-60 mL deionized water for ultrasonic treatment for 0.5-1.5 h, and then magnetically stirred for 1.5-3 h; then 1-2 mL 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 NaBH4 solution is added and stirred for 10-12 h; finally, it is washed and dried to obtain a Pt / SnO2@PC catalyst with a three-phase interface structure.

[0049] In this embodiment, a new porous carbon-coated tin dioxide SnO2@PC nanostructure 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 nanostructure carrier to successfully prepare a Pt / SnO2@PC catalyst with a three-phase interface structure. During the pore-forming process, the carrier needs to be heated to 700°C. The heating process causes many defects to form on the PC surface. The increase in the number of defects can promote the formation of tiny platinum nanoparticles and increase the number of Pt active sites. At the same time, during the heating process, oxygen-containing groups such as C=O, COC, CO, C-OH, etc. on the porous carbon surface are partially removed, and the possibility of Pt nanoparticles depositing on the carbon surface is reduced. The exposed tin dioxide surface at the carbon pores has rich OH ads Group, Pt nanoparticles can be preferentially deposited on the exposed tin dioxide surface at the carbon pores. BET results show that the average size of the carbon pores is 3-4nm, TEM results show that the Pt size is about 2-3nm, and each carbon pore can just accommodate 2-3 Pt nanoparticles. Pt particles can contact with carbon and tin dioxide at the same time to form a three-phase interface structure of Pt, SnO2 and PC.

[0050] 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 the catalyst co-catalyst ability of SnO2. ads The group can oxidatively remove the toxic intermediate CO adsorbed on Pt ads , releasing Pt active sites and improving the electro-oxidation activity of the catalyst for dimethyl ether. By adjusting the number of functional groups on the PC layer surface and the pore size of the porous carbon, the Pt particles can be oriented and deposited at the three-phase interface, successfully constructing a three-phase interface structure. The three-phase interface structure is conducive to reducing the poisoning effect of toxic intermediates on Pt and improving catalyst performance.

[0051] As the anode catalyst of DDFC, Pt / SnO2@PC 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 extending the endurance and service life of DDFC. The mass activity of Pt / SnO2@PC catalyst can reach 236mAmg -1 pt , which is 2.2 times that of Pt / C. After 1000 cycles of accelerated potential cycling test (APCT), the electrochemical active surface area (EAS) of Pt / SnO2@PC, a DDFC anode catalyst, decreased by only 29.75%, which is less than 58.10% of Pt / C catalyst, indicating that Pt / SnO2@PC catalyst shows the highest activity and stability.

[0052] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that: the washing in step 1 is performed using anhydrous ethanol and deionized water in sequence.

[0053] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that: the drying process in step one is: vacuum drying at 70-100° C. for 5-7 hours.

[0054] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that: the washing in step 2 is carried out by washing with HCl solution, anhydrous ethanol and deionized water in sequence, and the concentration of the HCl solution is 0.8 to 1.5 mol / L -1 .

[0055] Specific implementation mode 5: This implementation mode is different from any one of specific implementation modes 1 to 4 in that: the drying process in step 2 is: vacuum drying at 70 to 100° C. for 5 to 7 hours.

[0056] Specific implementation method six: This implementation method is different from any one of specific implementation methods one to five in that: in step three, Na2CO4 is used to adjust the pH value of the reaction solution.

[0057] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that the concentration of the chloroplatinic acid solution in step 3 is 0.01 to 0.015 mol / L -1 .

[0058] Specific embodiment eight: This embodiment differs from specific embodiments one to seven in that the concentration of the NaBH4 solution in step three is 0.04-0.06 mol / L -1 .

[0059] Specific implementation method 9: This implementation method is different from any one of specific implementation methods 1 to 8 in that: the drying process described in step 3 is: vacuum drying at 70-100° C. for 5-8 hours.

[0060] Specific implementation method ten: This implementation method is different from any one of specific implementation methods one to nine in that: the washing in step three is performed 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 embodiment is carried out according to the following steps:

[0063] 1. Preparation of SnO2@C carrier material

[0064] Weigh 2g of glucose, add it to 40ml of deionized water and dissolve it by ultrasonic to obtain a glucose solution; then add 1g of SnO2 to the glucose solution and stir it thoroughly, transfer the solution to a high-pressure reactor, and perform a hydrothermal reaction at 180°C for 24h; the obtained solid product is washed with anhydrous ethanol and deionized water in turn and vacuum dried at 80°C for 6h, and then calcined at 400°C for 2h in a nitrogen atmosphere to obtain a SnO2@C carrier material;

[0065] 2. Preparation of SnO2@PC materials

[0066] 2 g of SnO2@C carrier material and 0.11 g of pore-forming agent KOH were weighed and mixed, and then transferred to 30 mL of deionized water and stirred for 24 h. After the stirring treatment, it was dried and then calcined at 700 ° C for 6 h in a nitrogen atmosphere. After calcination, the calcined product was washed with HCl solution, anhydrous ethanol and deionized water in sequence. The concentration of the HCl solution was 1 mol / L -1 ; and vacuum dried at 80°C for 6h;

[0067] 3. Preparation of Pt / SnO2@PC catalyst with three-phase interface structure

[0068] 50 mg SnO2@PC material was placed in 50 mL deionized water for ultrasonic treatment for 1 h, and then magnetically stirred for 2 h; then 1.5 mL of 0.01428 mol / L -1 The pH value of the reaction solution was adjusted to 7-8 with Na2CO4, and then 0.05 mol / L -1 NaBH4 solution and stirred for 12 h; finally, washed with deionized water and vacuum dried at 80 °C for 6 h to obtain a Pt / SnO2@PC catalyst with a three-phase interface structure;

[0069] Physical characterization: The micromorphology and elemental mapping of Pt / C, Pt / SnO2@C and Pt / SnO2@PC catalysts were observed by transmission electron microscopy (TEM, FEI-TALOS-F200X). The elemental composition and content of the catalysts were analyzed by coupled energy dispersive spectroscopy (EDAX, superX-eds). The X-ray diffraction (XRD, Rigaku-smartlab) patterns of the catalyst materials were drawn using a CuKaX-ray source with a scanning temperature of 5°C·s -1 The pore size and specific surface area were measured by Brunauer-Emmett-Teller (BET, 3Flex5.00).

[0070] Chemical characterization: Electrochemical tests were performed at 25 °C using a PARSTAT 4000 electrochemical workstation with a three-electrode system, a glassy carbon disk electrode as the working electrode, and a Pt sheet (1 cm 2 ) electrode was used as the counter electrode, and the Hg / Hg2SO4 electrode was used as the reference electrode. The working electrode was prepared as follows: 3 mg of the catalyst was dispersed in 1 mL of isopropanol and ultrasonically treated for 5 min. Then 4.0 mL of deionized water and 25.0 μL of Nafion solution were added, and the resulting solution was ultrasonically dispersed for 20 min to prepare a uniform 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 the electrochemical test. A solution of 0.5 M H2SO4 and 1.5 M CH3OCH3 was used as the electrolyte. When performing cyclic voltammetry (CV) tests, the potential test range was 0 V to 1.7 V (vs. RHE) and the scan rate was 50 mV·s -1 The specific calculation formula of the electrochemically active specific surface area (ESA) of the catalyst is as follows:

[0071] ESA=Q H / (Q C ×g catalyst )

[0072] Where Q H represents the charge generated by hydrogen adsorption / desorption, Q C The estimated constant for the adsorption / desorption of hydrogen atoms in a monolayer (0.21 mC·cm -2 ), g catalyst is the mass of Pt nanoparticles in the working electrode. The accelerated aging test (APCT) experiment 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) with a frequency of 100 kHz to 0.01 Hz and an AC amplitude of 5 mV. The chronopotentiometry curve was -1 H2SO4 and 1.5 mol·L-1 The test was carried out in a CH3OCH3 solution and the test time was 1000s.

[0073] Figure 1 N2 adsorption-desorption curves of SnO2@C and SnO2@PC; Figure 2 The pore size distribution diagram of SnO2@C and SnO2@PC; SnO2@C and SnO2@PC both show typical type IV isotherms, indicating that there are abundant mesopores in the two carriers. The pore sizes of SnO2@C and SnO2@PC are mainly distributed in the range of 3nm to 4nm, indicating that the pore sizes of the two catalysts are relatively uniform. Table 1 shows the specific surface area and average pore size of SnO2@C and SnO2@PC. The average pore sizes of SnO2@C and SnO2@PC are 3.92nm and 3.89nm, respectively, and the specific surface areas are 48.53m 2 ·g -1 and 97.22m 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 and is conducive to 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 at 3438cm -1 A strong absorption peak is shown at 1385 cm, which may be caused by the stretching vibration of hydroxyl, carboxyl or OH in adsorbed water. -1 The peak centered at 1168 cm-1 can be attributed to the bending vibration of OH. -1 and 1078cm -1 The two peaks at 1670 cm-1 are attributed to the stretching vibrations of COC and CO, respectively. -1A weak peak is observed in the range, corresponding to C=O. The surface oxygen functional groups (C=O, COC, COOH) will provide abundant active sites for Pt nanoparticles, thus hindering the agglomeration of Pt nanoparticles. Compared with Pt / SnO2@C, there are fewer oxygen functional groups on the surface of Pt / SnO2@PC, which indicates that the PC layer on the surface of Pt / SnO2@PC provides fewer active sites and can deposit fewer Pt nanoparticles. The presence of hydroxyl groups on the SnO2 surface is a direct anchoring site for Pt nanoparticles, further promoting the deposition of Pt nanoparticles. More Pt nanoparticles will preferentially deposit on the interface between C and SnO2, forming more three-phase interface structures, thereby further improving the electrocatalytic oxidation activity of dimethyl ether.

[0077] Figure 4 The XRD patterns of Pt / C, Pt / SnO2@C and Pt / SnO2@PC catalysts; the diffraction peak at 26.3° 2θ is attributed to C(002), which is produced by the carbonization of glucose. The diffraction peaks at 26.6°, 33.9° and 51.8° correspond to SnO2(110), SnO2(101) and SnO2(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 a face-centered cubic (fcc) structure. Based on the Pt(111) crystal plane, the average particle size of Pt in the Pt / SnO2@PC catalyst was calculated to be 2.9nm by the Scherrers formula. The average particle sizes of Pt in Pt / C and Pt / SnO2@C catalysts are 3.6nm and 3.1nm, respectively.

[0078] Figure 5 EDAX diagram of Pt / SnO2@C; Figure 6 EDAX diagram of Pt / SnO2@PC (b); the peak of Pt element further proves that Pt nanoparticles are successfully deposited on SnO2@C and SnO2@PC composite supports. The Pt loading of Pt / SnO2@C and Pt / SnO2@PC catalysts is about 14.4wt% and 15.9wt%, close to the theoretical value of 20wt.%. This is due to the high temperature heating during the pore formation process of KOH, which leads to a reduction in the functional groups on the surface of the carbon layer. Therefore, there are fewer Pt nanoparticles loaded on the carbon surface, and the Pt loading mass on the support surface is reduced. It further shows 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 precious metals. The C content in Pt / SnO2@C and Pt / SnO2@PC catalysts is 24.5wt% and 16.7wt%, respectively. The SnO2 content is 51.1wt% and 57.4wt%, respectively.

[0079] Figure 7 TEM images and particle size distribution diagrams of Pt / C (a), Pt / SnO2@C (b) and Pt / SnO2@PC (c); Figure 7 As shown in a and 7b, the platinum nanoparticles on the surface of Pt / C catalyst and the edge of Pt / SnO2@C catalyst are seriously agglomerated. Compared with Pt / C and Pt / SnO2@C catalysts, under the condition of high temperature pore formation by KOH, Figure 7 c. The platinum nanoparticles on the surface of the Pt / SnO2@PC catalyst are more evenly dispersed and ordered. In addition, it can be seen from the particle size distribution diagram that the average diameter of the platinum nanoparticles distributed on the surfaces of the three catalysts has changed significantly. The average diameters of Pt / C, Pt / SnO2@C and Pt / SnO2@PC are 3.5nm, 3.1nm and 2.7nm, respectively. This result is consistent with the above XRD results. This is because the many defects on the PC shell provide more active sites for platinum nanoparticles and refine the grain size of platinum, which helps to stabilize the smaller platinum nanoparticles on the surface of Pt / SnO2@PC. In addition, the functional groups on the carbon layer on the surface of the Pt / SnO2@PC catalyst are also reduced, and more platinum nanoparticles are deposited on the three-phase interface, thereby improving the capacity of the catalyst.

[0080] Figure 8 HRTEM image of Pt / SnO2@PC catalyst; Figure 8 b is a locally enlarged HRTEM image. The different lattice spacings of 0.2631nm and 0.2230nm correspond to the SnO2(101) and Pt(111) planes, respectively. In addition, the carbon layer produced by the carbonization of glucose can also be observed. FFT obtained the diffraction images of Pt(111) and SnO2(101), further proving the existence of (fcc)Pt(111), SnO2(101) and carbon layer. Figure 8 As shown in (b), the Pt / SnO2@PC catalyst has abundant three-phase (i.e., Pt, SnO2, and PC) interfaces. Pt nanoparticles are deposited on the C-SnO2 interface, indicating that there is an interaction between them, which improves the performance of Pt-based catalysts and further enhances the electrocatalytic oxidation activity of dimethyl ether.

[0081] Fig. 9 For Pt / C, Pt / SnO2@C and Pt / SnO2@PC at 0.5molL -1 Cyclic voltammogram (CV) in H2SO4 solution. There are typical hydrogen and oxygen adsorption / desorption curves in CV. The EAS values ​​of the three catalysts are listed in Table 2. The EAS of Pt / SnO2@PC is 55.33 m 2 ·g -1 , much higher than Pt / C's 27.6m 2 ·g-1 This indicates that the electrochemically active surface area (EAS) of the Pt / SnO2@PC catalyst is significantly higher than that of the Pt / C catalyst. This is because the presence of a large number of defects in the porous carbon layer of the Pt / SnO2@PC catalyst promotes the uniform dispersion of Pt nanoparticles. Therefore, the Pt / SnO2@PC catalyst exhibits the highest EAS value and DME electrooxidation activity.

[0082] Fig.10 Cyclic voltammograms of Pt / C, Pt / SnO2@C, and Pt / SnO2@PC catalysts in 0.5 M H2SO4 and 1.5 M CH3OCH3 solutions; Fig.11 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 solutions; the peak potential for the electrooxidation of dimethyl ether on the three catalysts is 1.1 V. As can be seen from Table 1, the addition of SnO2 significantly improves the electrocatalytic oxidation ability of the catalyst towards DME. As Fig.10 shown, the mass activity of the DME electrooxidation catalysts 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 ( Fig.11 ) and is 1.3 times and 2.2 times that of Pt / SnO2@C and Pt / C, respectively. This may be due to the fact that 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 oxide. The reduction of carbon functional groups on the surface of the porous carbon promotes the deposition of Pt particles at the contact interface between PC and SnO2, forming more triple-phase interface structures, thus improving the DME electrooxidation performance of the Pt / SnO2@PC catalyst.

[0083] Fig.12 Chronoamperograms of the electrooxidation of dimethyl ether on Pt / C, Pt / SnO2@C, and Pt / SnO2@PC;

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

[0085] 14.59 mA·cm -2 , indicating the best stability. This may be attributed to the fact that SnO2 can provide OH ads , thus enhancing the oxidation ability towards CO intermediates. In addition, OH adsIt plays an anchoring role on Pt particles and may hinder the aggregation of Pt nanoparticles. Therefore, the stability of the electrocatalyst is enhanced. In addition, the three-phase interface structure of the Pt / SnO2@PC catalyst increases, which fully exerts the catalytic effect of SnO2, thereby improving the stability of the catalyst.

[0086] Fig.13 The trend diagram of the electrochemical active area changes of Pt / C, Pt / SnO2@C and Pt / SnO2@PC during the accelerated aging test; Fig.14 The normalized curves of electrochemical active areas of Pt / C, Pt / SnO2@C and Pt / SnO2@PC during the accelerated aging test; the EAS of the three catalysts showed a downward trend with the increase in the number of cycles. Among them, the EAS attenuation of the Pt / SnO2@PC catalyst was the smallest. According to Table 2, after 1000 APCT cycles, the EAS of the Pt / SnO2@PC catalyst only decayed by 29.75%, which was lower than that of other catalysts, once again proving its superior stability.

[0087] Fig.15 Figure 2 is the EIS Nyquist plot of dimethyl ether electrooxidation on Pt / C, Pt / SnO2@C and Pt / SnO2@PC; the diameter of the semicircle usually corresponds to the electron transfer resistance. Fig.15 As shown in Table 2, the electron transfer resistance of Pt / SnO2@PC (8.64Ω·cm -2 ) is lower than Pt / C and Pt / SnO2@C. This is because SnO2 can dissociate water to form OH ads groups, thereby promoting the intermediate CO ads The oxidation of SnO2@PC and DME electro-oxidation reaction rate are accelerated, thereby improving the DME electro-oxidation activity of the catalyst. In addition, the three-phase interface structure in the Pt / SnO2@PC catalyst is conducive to the contact between Pt and SnO2@PC. It can further improve the DME electro-oxidation activity.

[0088] Fig.16 is the power density curve of the direct dimethyl ether fuel cell (3) discharge, given by Fig.16 It can be seen 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 electrooxidation activity of Pt / SnO2@PC is compared with other catalysts reported in the literature. Pt / SnO2@PC has a higher EAS value and a higher exchange current density. The performance of DME electrooxidation using Pt / SnO2@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 SnO2 / Pt / C cat alyst for high-power fuel cells." ChemElectroChem 6.9(2019):2407-2414. Document 2: Gebr u MG, Subramanian P, Bělsky P, et al. "Chemical-Dealloying-Derived PtPdPb-BasedMulti metallic Nanoparticles: Dimethyl Ether Electrocatalysis and Fuel Cell Application." ACSApplied Materials&Interfaces 15.49(2023):56930-56944. Document 3: Kubanova, MS, AB Kuriganova, and NVSmirnova. "Electrooxidation of DimethylEther on Pt / TiO2–CСatalysts." Russian Journal of Electrochemistry 58.10 (2022): 916-926. Document 4: Gebru MG, Teller H, Subramanian P, et al. "Nonthermal Plasma-Modified Carbon-Carrying Sn-Based Ternary Nanocatalyst for High-PerformanceDirect Dimethyl Ether Fuel Cells." Energy Technology 10.112022:2200835.

[0093] Table 3

[0094]

Claims

1. A method for preparing a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst having 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:

1. Preparation of SnO2@C carrier material Weigh 1-2g of glucose, add it to 30-50ml of deionized water and dissolve it by ultrasonic to obtain a glucose solution; then add 0.5-2g of SnO2 to the glucose solution and stir it thoroughly, transfer the solution to a high-pressure reactor, and perform a hydrothermal reaction; wash and dry the solid product obtained by the hydrothermal reaction, and then calcine it to obtain a SnO2@C carrier material; The process of the hydrothermal reaction is: hydrothermal reaction at 170-200° C. for 20-24 hours; The calcination process is as follows: calcining at 400-500° C. for 1-3 hours, with nitrogen as the calcination atmosphere; 2. Preparation of SnO2@PC materials Weigh 1-3 g of SnO2@C carrier material and 0.05-0.2 g of pore former, mix them, transfer them into 20-40 mL of deionized water, stir them for 20-24 h, dry them after the stirring, and then calcine them. After calcination, wash and dry the calcined product to obtain SnO2@PC material; The pore-forming agent is KOH; The calcination process is as follows: calcining at 600-800° C. for 5-7 hours in a nitrogen atmosphere; 3. Preparation of Pt / SnO2@PC catalyst with three-phase interface structure 45-55 mg SnO2@PC material is placed in 40-60 mL deionized water for ultrasonic treatment for 0.5-1.5 h, and then magnetically stirred for 1.5-3 h; then 1-2 mL 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 NaBH4 solution is added and stirred for 10-12 h; finally, it is washed and dried to obtain a Pt / SnO2@PC catalyst with a three-phase interface structure.

2. The method for preparing a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst having a three-phase interface structure according to claim 1, characterized in that: The washing in step 1 is carried out using anhydrous ethanol and deionized water in sequence.

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

4. The method for preparing a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst having a three-phase interface structure according to claim 1, characterized in that: The washing in step 2 is carried out by washing with HCl solution, anhydrous ethanol and deionized water in sequence, and the concentration of the HCl solution is 0.8-1.5 mol / L -1 .

5. The method for preparing a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst having a three-phase interface structure according to claim 1, characterized in that: The drying process in step 2 is: vacuum drying at 70-100° C. for 5-7 hours.

6. The method for preparing a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst having a three-phase interface structure according to claim 1, characterized in that: In step 3, Na2CO4 is used to adjust the pH value of the reaction solution.

7. The method for preparing a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst having a three-phase interface structure according to claim 1, characterized in that: The concentration of the chloroplatinic acid solution in step 3 is 0.01 to 0.015 mol / L -1 .

8. The method for preparing a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst having a three-phase interface structure according to claim 1, characterized in that: The concentration of the NaBH4 solution in step 3 is 0.04-0.06 mol / L -1 .

9. The method for preparing a Pt / SnO2@PC direct dimethyl ether fuel cell anode catalyst having a three-phase interface structure according to claim 1, characterized in that: The drying process in step 3 is: vacuum drying at 70-100° C. for 5-8 hours.

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

Images