Preparation method and application of CeO2@Rh composite material

Abstract

The application discloses a preparation method and application of a CeO2@Rh composite material taking multi-walled carbon nanotubes (CNT) as a carrier. 3+ The method comprises the following steps: S1: precipitating Rh on the surface of CNT, preparing Rh / CNT through calcination, and ultrasonically dispersing the Rh / CNT in an ethanol solvent; S2: dissolving Ce(NO3)3 in the ethanol solvent; S3: adding the Ce(NO3)3 ethanol solution obtained in the step 2 into the suspension liquid obtained in the step 1, stirring to add NH4HCO3, centrifuging, washing with ethanol, and freeze-drying the precipitate; finally, collecting the precipitate, calcining at high temperature, and cooling to obtain an X-CeO2@Rh / CNT composite material (X is different calcination temperatures). The optimal composite material 400-CeO2@Rh / CNT provided by the application is superior to a commercial Pt / C in terms of HOR activity and stability in an alkaline environment, and can be applied to the field of catalytic hydrogen oxidation. The preparation method is simple, easy to control, and can be used to prepare a high-activity and high-stability HOR catalyst with good practical value and application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite materials, and provides a composite material and a preparation method and application thereof, in particular to a preparation method of a CeO2@Rh composite material taking multi-walled carbon nanotubes as a carrier. BACKGROUND

[0002] To help carbon neutralization, the development of fuel cells has attracted widespread attention, such as alkaline anion exchange membrane fuel cells (AEMFCs) and proton exchange membrane fuel cells (PEMFCs) based on hydrogen oxidation. AEMFCs and PEMFCs are composed of two half-reactions, namely the hydrogen oxidation reaction (HOR) at the anode and the oxygen reduction reaction (ORR) at the cathode. In acidic electrolyte, the slow kinetics of ORR and its high dosage of noble metal seriously limit the application of PEMFCs. In recent years, non-noble metal-based cathode electrocatalysts have fast ORR kinetics and excellent stability in alkaline environments, which has prompted AEMFCs to replace PEMFCs. Although great progress has been made in alkaline ORR, the kinetics of HOR becomes slow with the increase of pH, and even the most recognized Pt catalyst has its kinetics reduced to one hundredth of that under acidic conditions due to the inappropriate interaction between the Pt surface and the HOR intermediates (H* and OH*) in alkaline environments. Therefore, designing and synthesizing high-performance HOR catalysts is an urgent need for the development of AEMFCs.

[0003] According to the dual-function theory, not only the hydrogen binding energy (HBE) of the electrocatalyst has an important influence on its HOR activity, but also the hydroxyl binding energy (OHBE) is an important indicator for measuring its alkaline HOR catalyst. Therefore, an ideal HOR electrocatalyst can best balance the binding energy of the adsorbed intermediates (H* and OH*), which can be further proved by the Pt-Ni(OH)2 and Pt-Ru systems. Although Rh is considered as a HOR catalyst that can replace Pt, its HBE and low oxygen affinity affected by pH make the alkaline HOR performance of Rh still unsatisfactory. Studies have shown that the introduction of oxygen-affine metal oxides into Rh can make up for the deficiency of Rh in adsorbing oxygen-containing intermediates, and the interaction between Rh and metal oxides can adjust the electronic structure of Rh. Barman et al. partially oxidized Rh NPs / C in air to form a Rh-Rh2O3 interface, and the Rh surface provided active sites for the adsorption of H*, and Rh2O3 showed high oxygen affinity. Mu et al. added oxygen-affine metal species (OM = Co, Mn, Cr and Fe) to RuRh clusters to optimize the HBE of RuRh and increase its oxygen affinity, and the activity of RuRh-OM was 2 times higher than that of commercial Pt.

[0004] In summary, there are few reports on improving the basic HOR activity by adjusting the interaction strength between Rh and metal oxides. In order to further improve the performance of the material, the applicant constructed a CeO2@Rh heterostructure supported on multi-walled carbon nanotubes (X-CeO2@Rh / CNT, X is the pyrolysis temperature), adjusted the interaction strength between CeO2 and Rh by different pyrolysis temperatures, and obtained the best exchange current density and mass-normalized kinetic current density. This type of composite material greatly widens the application range of metal oxygen compounds and carbon materials, and its HOR activity and stability are much better than that of commercial Pt / C catalytic material. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings and deficiencies of the prior art, develop new high-performance electrochemical materials, and especially obtain composite materials that can be used in the field of electrochemical catalysis. The present inventors have conducted in-depth research and made a lot of creative efforts, and thus completed the present application.

[0006] Specifically, the technical solutions and contents of the present application relate to a preparation method and application of an X-CeO2@Rh / CNT composite material.

[0007] The preparation method of the X-CeO2@Rh / CNT composite material proposed in the present application has the following specific steps:

[0008] S1: Preparation of Rh / CNT ethanol suspension: carboxylated carbon nanotubes (CNT) are ultrasonically dispersed in a H2O / EtOH (ratio 1:1) mixed solution, RhCl3 / EtOH suspension is added, and stirring is performed at an appropriate speed for a period of time, then NH4HCO3 is added, and stirring is performed for a period of time, after which the obtained suspension is centrifuged at a certain speed, washed, and freeze-dried to collect black solid product. The product is placed in a H2 / Ar gas atmosphere, and calcination is performed under specific conditions (such as heating rate, calcination time, gas flow rate, and calcination temperature, etc.), and Rh / CNT is obtained after cooling. Finally, Rh / CNT is ultrasonically dispersed in an ethanol solvent to obtain Rh / CNT ethanol suspension.

[0009] S2: Preparation of Ce(NO3)3 ethanol solution: Ce(NO3)3 is stirred and dissolved in an ethanol solvent to prepare a certain concentration of Ce(NO3)3 ethanol solution;

[0010] S3: Preparation of X-CeO2@Rh / CNT composite material: The Ce(NO3)3 ethanol solution obtained in step 2 is mixed with the Rh / CNT ethanol suspension obtained in step 1, and after stirring at high speed for a period of time, NH4HCO3 is added to the obtained mixture, stirring for a period of time, high-speed centrifugation, ethanol washing, freeze-drying to collect the product, and placing the obtained product in an inert gas atmosphere, setting specific conditions for calcination (such as heating rate, calcination time, gas flow rate and calcination temperature, etc.), and after cooling, the X-CeO2@Rh / CNT composite material is obtained.

[0011] According to the above scheme, in step S1, specifically, 20-60 mg of carboxylated carbon nanotubes (CNT) are added to 40-120 ml of a H2O / EtOH mixed solution, and ultrasonic dispersion is performed for 10-60 min;

[0012] According to the above scheme, in step S1, specifically, 1-3 ml of RhCl3 / EtOH solution is added; stirring is performed at a speed of 200-1000 rpm for 10-60 min;

[0013] According to the above scheme, in step S1, 200-600 mg of NH4HCO3 is added, and stirring is performed for 2-10 h, and the obtained suspension is centrifuged at a speed of 8000-15000 rpm;

[0014] According to the above scheme, in step S1, specifically, calcination is performed at a temperature of 400-800℃ under a 5%-30% H2 / Ar gas atmosphere;

[0015] According to the above scheme, in step S1, specifically, 5-30 mg of Rh / CNT is added to 5-40 ml of an ethanol solvent, and ultrasonic dispersion is performed for 10-60 min;

[0016] According to the above scheme, in step S2, specifically, 3-12 mg of Ce(NO3)3 is added to 5-35 ml of an ethanol solvent;

[0017] According to the above scheme, in step S3, specifically, after the Ce(NO3)3 ethanol solution is mixed with the Rh / CNT ethanol suspension, stirring is performed at a speed of 200-1000 rpm for 10-60 min;

[0018] According to the above scheme, in step S3, specifically, after NH4HCO3 is added to the obtained mixture, stirring is performed at a speed of 200-1000 rpm for 2-10 h, the centrifuge speed is 8000-15000 rpm, the centrifugation time is 3-10 min, and the operation is repeated 2-6 times;

[0019] According to the above scheme, in step S3, the inert gas is nitrogen or argon, the calcination temperature is 100-800 DEG C, the gas flow rate is 50-150 sccm, and the temperature rising rate is 3-8 DEG C / min.

[0020] In summary, the X-CeO2@Rh / CNT composite material can be prepared by using the above method and is widely applied in the field of electrochemical catalysis.

[0021] The present application has the advantages that: the preparation method is simple, the CeO2 and Rh heterostructure is constructed, the pyrolysis temperature (300, 400 and 500 DEG C) is adjusted to adjust the interaction strength of CeO2 and Rh, and the best composite catalyst material 400-CeO2@Rh / CNT is screened out, which has high activity, high stability and other characteristics in the hydrogen oxidation reaction: 1. The exchange current density (0.54 mA cm PGM -2 ) is 1.67 times of the commercial Pt / C (0.33 mA cm PGM -2 ) 2. In the chronoamperometry test at a voltage of 0.1 V, the current value of the composite material only decreases by 11% within 12 h, while the current value of the commercial Pt / C decreases by 69%. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Fig. 1 is a scanning electron microscope (SEM) image and a high-resolution transmission electron microscope (HRTEM) image of the 400-CeO2@Rh / CNT composite material in the embodiment 1 of the present application.

[0023] a-c are a scanning electron microscope (SEM) image and a high-resolution transmission electron microscope (HRTEM) image of the 400-CeO2@Rh / CNT composite material;

[0024] d-f are a scanning electron microscope (SEM) image and a high-resolution transmission electron microscope (HRTEM) image of the 500-CeO2@Rh / CNT composite material;

[0025] g-i are a scanning electron microscope (SEM) image and a high-resolution transmission electron microscope (HRTEM) image of the 300-CeO2@Rh / CNT composite material;

[0026] Figure 2 Fig. 2 is an X-ray diffraction (XRD) pattern of the 400-CeO2@Rh / CNT, 500-CeO2@Rh / CNT, 300-CeO2@Rh / CNT, Rh / CNT and 400-CeO2 / CNT composite materials in the embodiment 1-4 of the present application;

[0027] Figure 3is the Raman spectrum of the 400-CeO2@Rh / CNT, 500-CeO2@Rh / CNT, 300-CeO2@Rh / CNT, Rh / CNT and 400-CeO2 / CNT composite material in the present application embodiment 1-4;

[0028] Figure 4 is the X-ray photoelectron spectrogram of the 400-CeO2@Rh / CNT, 500-CeO2@Rh / CNT, 300-CeO2@Rh / CNT, Rh / CNT and 400-CeO2 / CNT composite material in the present application embodiment 1-4;

[0029] Figure 5 is the electrochemical performance test diagram of the 400-CeO2@Rh / CNT, 500-CeO2@Rh / CNT, 300-CeO2@Rh / CNT composite material, Rh / CNT and commercial Pt / C in the present application embodiment 1, 2, 3. Figure 5 a is the linear sweep voltammetry curve diagram (1600 rpm, 5 mV s-1) of the 400-CeO2@Rh / CNT, 500-CeO2@Rh / CNT, 300-CeO2@Rh / CNT composite material, Rh / CNT and commercial Pt / C in the H2 saturated 0.1M KOH solution; Figure 5 b is the comparison diagram of the normalized exchange current density (j 0,s ) and the mass-normalized kinetic current density (j k,m ) of the 400-CeO2@Rh / CNT, 500-CeO2@Rh / CNT, 300-CeO2@Rh / CNT composite material, Rh / CNT and commercial Pt / C at the overpotential of 50 mV;

[0030] Figure 6 is the stability test result of the 400-CeO2@Rh / CNT, Rh / CNT and commercial Pt / C composite material in the present application embodiment 1, 2, 3. DETAILED DESCRIPTION

[0031] The present application will be described in detail below through specific drawings and embodiments, but the purpose and object of these exemplary drawings and embodiments are only used to exemplify the present application, and do not constitute any form of any limitation on the actual protection scope of the present application, and more do not limit the protection scope of the present application to this.

[0032] Example 1: Preparation of 400-CeO2@Rh / CNT

[0033] S1: Preparation of Rh / CNT: 40 mg of carboxylated carbon nanotubes were dispersed in 80 mL of H2O / EtOH (volume ratio of 1:1) and ultrasonically dispersed for 30 min. Then 2 mL of 0.1 M RhCl3 / EtOH solution was added to the above mixture and stirred at a speed of 600 rpm. After 30 min, 400 mg of NH4HCO3 was added and stirred for 5 h. The obtained suspension was centrifuged, washed, and freeze-dried to obtain a black solid. Finally, the black solid was calcined at a flow rate of 100 sccm of 20% H2 / Ar atmosphere at 600 °C for 2 h at a heating rate of 5 °C min -1 , to obtain Rh / CNT.

[0034] S2: 9.47 mg of Ce(NO3)3 was added to 20 mL of ethanol solution and stirred to disperse; 15 mg of Rh / CNT was added to 20 mL of ethanol solution and ultrasonically dispersed for 30 min; the Ce(NO3)3 ethanol solution was poured into the Rh / CNT ethanol suspension and stirred at a speed of 500 rpm for 5 h. After stirring, centrifugation was performed at 11000 rpm for 5 min to obtain a black precipitate, which was washed with ethanol three times and freeze-dried. The freeze-dried product was calcined at a flow rate of 100 sccm of Ar atmosphere at 400 °C for 1 h at a heating rate of 5 °C min -1 , to obtain 400-CeO2@Rh / CNT composite material.

[0035] Example 2: Preparation of 500-CeO2@Rh / CNT

[0036] Except that the calcination temperature in the above step S2 was replaced by 500 °C, the other operations were unchanged, thereby repeating the operation of Example 1 to prepare 500-CeO2@Rh / CNT composite material.

[0037] Example 3: Preparation of 300-CeO2@Rh / CNT

[0038] Except that the calcination temperature in the above step S2 was replaced by 300 °C, the other operations were unchanged, thereby repeating the operation of Example 1 to prepare 300-CeO2@Rh / CNT composite material.

[0039] Example 4: Preparation of 400-CeO2 / CNT

[0040] 9.47 mg Ce(NO3)3 was added into 20 ml ethanol solution and stirred to disperse; 15 mg CNT-COOH was added into 20 ml ethanol solution and ultrasonically dispersed for 30 min; the Ce(NO3)3 ethanol suspension was poured into the CNT-COOH ethanol suspension, and stirred at a speed of 500 rpm for 5 h. After stirring, centrifugation was performed at 11000 rpm for 5 min to obtain black precipitate, which was washed with ethanol for three times and freeze-dried. The product obtained after freeze-drying was calcined at 400 ℃ for 1 h under an atmosphere of 100 sccm Ar with a heating rate of 5 ℃ min -1 , and 400-CeO2 / CNT composite material was obtained after cooling.

[0041] Microscopic characterization and electrochemical performance test:

[0042] The 300-CeO2@Rh / CNT, 400-CeO2@Rh / CNT, 500-CeO2@Rh / CNT and 400-CeO2 / CNT composite materials obtained in Examples 1-4 were subjected to microscopic characterization and electrochemical performance test by the following experiments, and the results were as follows:

[0043] Preparation process of working electrode: 1 mL of H2O / isopropyl alcohol / 5wt% Nafion solution (volume ratio of 75:25:2.5) was added to 1 mg of electrocatalyst, and ultrasonic treatment was performed for 1 h to obtain 1 mg mL -1 of electrocatalyst ink. 20 μL of electrocatalyst dispersion was dropped onto the surface of a glassy carbon electrode (GCE, diameter of 5 mm), and naturally air-dried for testing. In a standard three-electrode system at 20 ℃, a rotating disc electrode (RDE) was connected to CHI 760E for electrochemical test. A saturated calomel electrode (SCE) and a graphite rod were used as the reference electrode and the counter electrode, respectively. Unless otherwise specified, all potentials were calculated to the reversible hydrogen electrode (RHE) and subjected to iR correction, and the specific operation was as follows: in a 0.1 M KOH solution saturated with H2, two platinum sheets were used as the working electrode and the counter electrode, respectively, and the SCE was used as the reference electrode for calibration, and the voltage was operated at a scan rate of 1 mV s -1 , and the average value of the two potentials at the current zero was taken as the thermodynamic potential of the hydrogen electrode reaction. All HOR tests were performed in a 0.1 M KOH solution saturated with H2. Before the HOR test, the electrocatalyst was activated in a H2 atmosphere at a potential range of -0.2-0.4 vs RHE until the cyclic voltammetry (CV) curve showed no obvious change. Linear sweep voltammetry curve (LSV) was obtained at a rotation speed of 1600 rpm. The parameter setting of LSV was that the potential range was -0.2-0.4 vs RHE, and the scan rate was 5 mV s -1 .

[0044] 1. Figure 1 Scanning electron microscope (SEM) images and high-resolution transmission electron microscope (HRTEM) images of 400-CeO2@Rh / CNT, 500-CeO2@Rh / CNT, and 300-CeO2@Rh / CNT. Figure 1 In c, 1f, and 1i, lattice fringes with inter-lattice spacing d of 0.32 nm and 0.22 nm can be clearly observed, corresponding to the (111) crystal plane of CeO2 and the (111) crystal plane of Rh, respectively, and a contact interface is clearly present. This result indicates that there is mutual contact between CeO2 and Rh.

[0045] 2. Figure 2 X-ray diffraction patterns of 400-CeO2@Rh / CNT and other comparative materials are shown. This further illustrates the successful preparation of the CeO2@Rh / CNT composite material and other comparative materials.

[0046] 3. Figure 3 Raman spectra of 400-CeO2@Rh / CNT and other comparative materials. CeO2 peaks are located at ~460, ~597, and ~1172 cm⁻¹. -1 , respectively corresponding to F 2g , D and 2LO. Compared to 400-CeO2 / CNT, CeO2@Rh / CNT has F 2g A negative wavenumber shift occurred, which may indicate an interaction between CeO2 and Rh. To further confirm the interaction between CeO2 and Rh, we calculated I... (D+2LO) / I (F2g) The ratio of oxygen vacancy concentration to 400-CeO2@Rh / CNT reflects the oxygen vacancy concentration. Fitting calculations revealed that the oxygen vacancy concentration, from highest to lowest, is: 400-CeO2@Rh / CNT > 500-CeO2@Rh / CNT > 300-CeO2@Rh / CNT > 400-CeO2 / CNT. This indicates that different pyrolysis temperatures lead to varying interaction strengths between CeO2 and Rh.

[0047] 4. Figure 4 X-ray photoelectron spectra of 400-CeO2@Rh / CNT and other comparative materials. Figure 4 a. Compared to Rh / CNT, 400-CeO2@Rh / CNT was found to have Rh... 0 3D 5 / 2 The binding energy shifts positively (Δ = +0.3 eV) for 500-CeO2@Rh / CNT. 0 3D 5 / 2 The binding energy shifts positively (Δ = +0.2 eV) for 300-CeO2@Rh / CNT. 0 3D 5 / 2a positive shift (Δ = +0.1 eV) is observed. This indicates that the electrons transfer from Rh to CeO2 after the formation of CeO2 / Rh heterostructure, and the interaction strength between CeO2 and Rh is in the order of 400-CeO2@Rh / CNT > 500-CeO2@Rh / CNT > 300-CeO2@Rh / CNT. O 1s spectra Figure 4 b) further proves the size of oxygen vacancy defect concentration, which is consistent with the results of Raman spectra.

[0048] 5、 Figure 5 For electrochemical performance test. Figure 5 a is the linear sweep voltammetry curve of 400-CeO2@Rh / CNT and other comparative materials in 0.1 M KOH solution saturated with H2, Figure 5 b is the normalized exchange current density (j 0,s ) and mass-normalized kinetic current density (j k,m ) at a potential of 50 mV. Figure 5 a shows that the limiting current density of 400-CeO2@Rh / CNT is the largest, followed by 500-CeO2@Rh / CNT and 300-CeO2@Rh / CNT, which are all better than commercial Pt / C; Figure 5 b shows that the exchange current density (0.54 mA cm PGM -2 ) of 400-CeO2@Rh / CNT is 1.67 times that of commercial Pt / C (0.33 mA cm PGM -2 ) and 2.82 times that of Rh / CNT, indicating that there is a synergistic promotion effect between CeO2 and Rh, and different pyrolysis temperatures will result in different interaction strengths between CeO2 and Rh, thereby improving the hydrogen oxidation performance to different degrees.

[0049] 6、 Figure 6 Stability test of 400-CeO2@Rh / CNT and other comparative materials. Figure 6 a is the CV comparison chart before and after the accelerated durability test (ADT). Compared with Pt / C and Rh / CNT, the limiting current density of 400-CeO2@Rh / CNT composite material does not change significantly after 10,000 cycles of voltammetry test, and the change degree of half-wave potential is small, which indicates that 400-CeO2@Rh / CNT has better stability. As shown in Figure 6 b, the i-t curve shows that 400-CeO2@Rh / CNT retains 88% of the HOR activity within 12 h. However, under the same conditions, the activities of Pt / C and Rh / CNT decrease by about 69% and 72%, respectively, further indicating that 400-CeO2@Rh / CNT has excellent stability.

[0050] It can be seen that in the embodiment, when the S2 calcination temperature is 400°C, the HOR activity and stability of the 400-CeO2@Rh / CNT composite material prepared in the alkaline environment are better than those of the commercial Pt / C, which is the most preferred condition.

[0051] It should be understood that the use of these examples is merely for the purpose of illustration of the present application and is not intended to limit the scope of the protection of the present application. Furthermore, it should also be understood that, after reading the disclosure of the present application, those skilled in the art can make various modifications, alterations and / or changes to the present application, and all these equivalent forms are also within the scope of protection defined by the appended claims of the present application.

Claims

1. A method for preparing an X-CeO2@Rh / CNT composite material, characterized in that: The X-CeO2@Rh / CNT composite material was prepared according to the following method: S1: Carboxylated carbon nanotubes were first ultrasonically dispersed in a 1:1 volume ratio H2O and EtOH mixed solution, RhCl3 / EtOH solution was added, and the mixture was stirred at an appropriate speed for the first time. Then NH4HCO3 was added, and the mixture was stirred a second time at the same stirring speed to obtain a suspension. The obtained suspension was centrifuged, washed, and freeze-dried to obtain an intermediate product. The intermediate product was calcined at high temperature and cooled under H2 / Ar mixed gas conditions to obtain Rh / CNT. Finally, Rh / CNT was ultrasonically dispersed in ethanol solvent for the second time to obtain Rh / CNT ethanol suspension. S2: Dissolve Ce(NO3)3 in ethanol solvent by stirring to prepare Ce(NO3)3 ethanol solution; S3: The Ce(NO3)3 ethanol solution obtained in step S2 is mixed with the Rh / CNT ethanol suspension obtained in step S1. After a period of high-speed stirring, NH4HCO3 is added. The suspension is obtained by a second stirring at the same stirring speed. The obtained suspension is centrifuged at high speed, washed, and freeze-dried to collect the product. The obtained product is calcined at high temperature under inert gas protection at a temperature of X, which is 300-500 ℃. After cooling, the X-CeO2@Rh / CNT composite material is obtained.

2. The preparation method according to claim 1, characterized in that: In step S1, the mass of the carboxylated carbon nanotubes is 20-60 mg, the volume of the H2O / EtOH mixed solution is 40-120 ml, and the first ultrasonic dispersion time is 10-60 min.

3. The preparation method according to claim 1, characterized in that: In step S1, the concentration of the RhCl3 / EtOH solution is 0.1 M, the volume is 1-3 ml, the first stirring speed is 200-1000 rpm and the stirring time is 10-60 min; the mass of the NH4HCO3 is 200-600 mg, the second stirring speed is 200-1000 rpm and the stirring time is 2-10 h; the centrifugation speed of the suspension is 8000-15000 rpm.

4. The preparation method according to claim 1, characterized in that: In step S1, the volume fraction of the H2 / Ar mixed gas is 5%-30%, the calcination temperature is 400-800 ℃, the mass of the Rh / CNT is 5-30 mg, the volume of the ethanol solvent is 5-40 ml, and the second ultrasonic dispersion time is 10-60 min.

5. The preparation method according to claim 1, characterized in that: In step S2, the mass of Ce(NO3)3 is 3-12 mg, and the volume of ethanol solvent is 5-35 ml.

6. The preparation method according to claim 1, characterized in that: In step S3, after mixing the Ce(NO3)3 ethanol solution and the Rh / CNT ethanol suspension, the first high-speed stirring speed is 200-1000 rpm and the stirring time is 10-60 min.

7. The preparation method according to claim 1, characterized in that: In step S3, the mass of NH4HCO3 is 200-600 mg, the second stirring speed is 200-1000 rpm, and the stirring time is 2-10 h.

8. The preparation method according to claim 1, characterized in that: In step S3, the centrifugation speed is 8000-15000 rpm, the centrifugation time is 3-10 min, and the number of operations is 2-6; the calcination temperature is 400 ℃, the gas flow rate is 50-150 sccm, and the heating rate is 3-8 ℃ / min.

9. An X-CeO2@Rh / CNT composite material prepared by the preparation method according to any one of claims 1-8.

10. The application of the X-CeO2@Rh / CNT composite material as described in claim 9 in the field of electrochemical catalytic hydrogenation reaction.

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