Method for inducing Mo2C phase change through Zn < 2 + >
By inducing a phase transition in Mo2C using Zn²⁺, a MoC/Mo2C composite material was prepared, solving the problem of controlling the ratio of MoC and Mo2C phases in the existing technology and achieving excellent oxygen reduction performance and stability in fuel cells.
Patent Information
- Application Number
- CN202511507742.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-21
- Publication Date
- 2026-02-03
AI Technical Summary
Existing technologies have failed to effectively control the ratio of MoC and Mo2C phases, and have not addressed their application in the oxygen reduction reaction of fuel cells.
MoC/Mo2C composite materials were prepared by inducing a phase transition of Mo2C with Zn²⁺. The ratio of the two phases was controlled by mixing molybdate and Zn²⁺ salt in deionized water, stirring and adding aniline, adjusting the pH and evaporating, and then carbonizing with magnesium powder and dicyandiamide under an inert atmosphere to obtain the MoC/Mo2C composite material.
The prepared MoC/Mo2C composite material exhibits excellent oxygen reduction activity and stability in fuel cells, with a half-wave potential greater than 0.7 V, and a more stable two-phase interface with higher activity.
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Figure CN121460596A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of material preparation, and particularly relates to a method for inducing Mo2C phase change by Zn2+. BACKGROUND
[0002] There are four different phase structures of molybdenum carbide: alpha-MoC, beta-Mo2C, eta-MoC and gamma-MoC. Among them, beta-Mo2C and gamma-MoC have very similar hexagonal crystal structures, except that their stacking sequences are different. The valence band shape of beta-Mo2C is very similar to that of Pt and has excellent conductivity and electrochemical stability, and is a cheap substitute for noble metal platinum, and is often used as a proton exchange membrane fuel cell oxygen reduction catalyst. However, beta-Mo2C has a higher density near the Fermi level and poor stability, and gamma-MoC has a stoichiometric ratio of 1:1 and is the most stable molybdenum carbide structure. The electron density around the Mo site mainly depends on C in the lattice, and as the C increases, the electron density around Mo decreases, so introducing gamma-MoC into beta-Mo2C to construct a heterojunction is expected to regulate the electronic structure of MoC / Mo2C and achieve synergistic improvement of its catalytic performance.
[0003] The currently reported literature only involves the preparation method of MoC / Mo2C composite material, and there is no related report on the preparation of composite material by ion-induced Mo2C phase change. 2+ The Mo2C phase change is induced by introducing Zn 2+ into the Mo2C phase, so that part of the Mo2C phase is converted into the MoC phase to form a MoC / Mo2C composite material. This ion-induced phase change method can make the interface between Mo2C and MoC more stable and more active.
[0004] An existing preparation method of two-dimensional sheet layer carbon-based molybdenum carbide (MoC and Mo2C) composite material does not involve the regulation of the proportion of MoC and Mo2C two phases in the composite material, nor the application of the molybdenum carbide composite material in the fuel cell oxygen reduction reaction.
[0005] Another method uses a melt method combined with a carbon thermal reduction method to prepare alpha-MoC / graphene composite material and apply it to catalytic oxygen reduction reaction, but does not involve the conversion and regulation between MoC and Mo2C two phases.
[0006] A method uses MoO3-EDA precursor as a template and tannic acid as a carbon source to in-situ synthesize Mo2C@C nanorods and apply them to catalytic oxygen reduction reaction, but does not involve the conversion and regulation between MoC and Mo2C two phases. SUMMARY
[0007] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for inducing Mo2C phase change by Zn2+ The method for inducing Mo2C phase change has excellent catalytic oxygen reduction performance and excellent stability, and the synthesis method is easy to operate, environmentally friendly, efficient and low in cost.
[0008] To achieve the above-mentioned goal, the application provides a Zn 2+ The method for inducing Mo2C phase change comprises the following steps: Step one, disperse molybdate and Zn2+ salt in deionized water according to the atomic ratio of Zn to Mo of 0.1-1, stir and add aniline, adjust the pH of the solution with hydrochloric acid to obtain a mixed solution; Step two, stir and evaporate the mixed solution, collect the solid product to obtain MoOn@PANI precursor; Step three, grind and mix the MoOn@PANI precursor, magnesium powder, endothermic agent and dicyandiamide according to the mass ratio, the mass ratio of MoOn@PANI precursor, magnesium powder and dicyandiamide is (1-4):1:(1-2), then perform carbonization treatment under inert atmosphere, and naturally cool to room temperature; Step four, wash the carbonized product with acid to remove the above-mentioned reaction by-products, then rinse and dry to obtain MoC / Mo2C composite material.
[0009] Further, the molybdate is ammonium molybdate or sodium molybdate; the Zn2+ salt is zinc nitrate, zinc chloride or zinc sulfate, and the molybdate is one of (NH4)6Mo7O 24 4H2O and Na2MoO4.
[0010] Further, in step one, the atomic ratio of Zn to Mo is 0.2-0.5.
[0011] Further, in step three, the temperature of the carbonization treatment is 600-900°C.
[0012] Further, in step four, use hydrochloric acid with a concentration of 1 M for washing, and perform vacuum drying at 80°C.
[0013] Further, in step three, the heating rate of the carbonization treatment is 5°C / min.
[0014] Further, in step three, the holding time is 2-7h.
[0015] Further, in step one, the pH range of the mixed solution is 2-5.
[0016] The MoC / Mo2C composite material prepared by the method, characterized in that the composite material contains MoC phase and Mo2C phase, and the mass ratio of the two phases is controlled by the atomic ratio of Zn to Mo in the range of 0.1-1.
[0017] Further, the mass ratio of the MoC phase to the Mo2C phase in the composite material is between 0.41 and 0.71.
[0018] Advantages: The present application has the following advantages: (1) According to the method, the electrocatalytic electrode material prepared contains Mo2C and MoC two phases, and the ratio of the two phases is controlled by the atomic ratio of Zn 2+ introduction amount, the ratio of Mo2C and MoC two phases can be adjusted according to the demand.
[0019] (2) According to the method, the MoC / Mo2C composite material prepared has a more stable two-phase interface and higher activity, and has excellent oxygen reduction activity: the half-wave potential in 0.1 M KOH is greater than 0.7 V. BRIEF DESCRIPTION OF DRAWINGS
[0020] Figure 1 X-ray diffraction (XRD) spectrum of the electrode prepared in Example 1, Example 2, Example 3 and Comparative Example 1.
[0021] Figure 2 XRD spectrum of the electrode prepared in Comparative Examples 1-6.
[0022] Figure 3 XRD spectrum of the electrode prepared in Comparative Examples 7 and 8.
[0023] Figure 4 Scanning electron microscope (SEM) image of the electrode prepared in Example 1.
[0024] Figure 5 Transmission electron microscope (TEM) image of the electrode prepared in Example 1. DETAILED DESCRIPTION
[0025] In order to make the purpose, content and advantages of the present application clearer, the specific embodiments of the present application are described in further detail below.
[0026] The present application provides a Zn 2+ The method for inducing Mo2C phase change comprises the following specific steps: Step 1: disperse molybdate and Zn 2+ salt in deionized water in a certain proportion, stir thoroughly, add aniline during stirring, and adjust the pH of the solution with HCl.
[0027] Step 2: The above mixed solution is vigorously stirred and evaporated at a certain temperature, and the solid product is collected to obtain MoO. n @PANI precursor.
[0028] Step 3: Add MoO n PANI precursor, Mg powder, NaCl, and dicyandiamide are thoroughly ground and mixed in a mortar, then carbonized in a tube furnace under an argon atmosphere, and naturally cooled to room temperature. NaCl acts as an endothermic agent to prevent excessive heat generation from the Mg powder; therefore, its mass only needs to be sufficient for endothermic purposes. It can be the same as the mass of Mg powder.
[0029] Step 4: Wash with HCl to remove the above reaction byproducts, then rinse several times with deionized water and ethanol, and vacuum dry to obtain the MoC / Mo2C composite material.
[0030] Furthermore, the molybdate is (NH4)6Mo7O 24 • One of 4H2O, Na2MoO4, Zn 2+ Salt is one of Zn(NO3)2‧6H2O, ZnCl, and ZnSO4.
[0031] Furthermore, the atomic ratio of Zn to Mo is 0.1 to 1; the pH range of the solution is 2 to 5.
[0032] Furthermore, the temperature at which the solution is stirred and evaporated is >50°C.
[0033] Furthermore, the MoO n The mass ratio of PANI, Mg, and dicyandiamide is (1~4):1:(1~2).
[0034] Furthermore, the carbonization temperature is 600~900°C, and the heating rate is 5°C / min. -1 The heat preservation time is 2~7 hours. Example
[0035] Step 1: Add 3 mmol (NH4)6Mo7O 24 • 4H2O and 2.1 mmol Zn(NO3)2·6H2O (Zn:Mo atomic ratio of 0.1) powder were dispersed in 30 mL of deionized water, stirred thoroughly, and 4 mL of aniline was added. The pH was adjusted to ~4 by adding 1 M HCl dropwise. Subsequently, the resulting mixed solution was vigorously stirred and evaporated at 80 °C. The solid product was collected, which is the preparation of MoO2 using the polymerization reaction of aniline. n @PANI precursor.
[0036] Step 2: 0.5 g Zn-MoO n@PANI precursor, 0.3 g Mg powder, 0.3 g NaCl (endothermic agent), and 0.5 g dicyandiamide were thoroughly ground and mixed in a mortar. The mixture was then carbonized in a tube furnace under an argon atmosphere at 5 °C for 1 minute. ‒1 The temperature was increased to 750 °C at a rate of [missing information], held at that temperature for 5 h, and then naturally cooled to room temperature. The product was washed with 1 M HCl to remove reaction byproducts, then rinsed several times with deionized water and ethanol, and dried under vacuum at 80 °C for 24 h to obtain the target Zn-MoC / Mo2C electrode. The prepared Zn-MoC / Mo2C catalytic electrode had a MoC to Mo2C two-phase ratio of 0.41, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH was 0.72 V. Example
[0037] The preparation of the Zn-MoC / Mo2C electrocatalytic electrode is the same as in Example 1, except that: in step one, the amount of Zn(NO3)2‧6H2O powder added is 4.2 mmol (Zn to Mo atomic ratio is 0.2), the ratio of MoC to Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode is 0.54, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH is 0.75 V. Example
[0038] The preparation of the Zn-MoC / Mo2C electrocatalytic electrode is the same as in Example 1, except that: in step one, the amount of Zn(NO3)2‧6H2O powder added is 10.5 mmol (Zn to Mo atomic ratio is 0.5), the ratio of MoC to Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode is 0.71, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH is 0.70 V. Example
[0039] The preparation of the Zn-MoC / Mo2C electrocatalytic electrode is the same as in Example 1, except that step two involves Zn-MoO. n The amount of @PANI precursor added was 0.2 g, and the ratio of MoC to Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode was 0.54, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH was 0.71 V. Example
[0040] The preparation of the Zn-MoC / Mo2C electrocatalytic electrode is the same as in Example 1, except that step two involves Zn-MoO. nThe amount of @PANI precursor added was 0.6 g, and the ratio of MoC to Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode was 0.54, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH was 0.75 V. Example
[0041] The preparation of the Zn-MoC / Mo2C electrocatalytic electrode is the same as in Example 1, except that step two involves Zn-MoO. n The amount of @PANI precursor added was 0.8 g, and the ratio of MoC to Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode was 0.54, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH was 0.74 V.
[0042] Comparative Example 1 without Zn 2+ Comparative Examples 2-6, Zn 2+ The amount introduced was too small, compared to proportions 7-8, where Zn was present in the smaller amount. 2+ The amount of Zn-MoC / Mo2C nanoparticles introduced was too large; in Comparative Example 9, no Zn-MoC / Mo2C nanoparticles were loaded; in Comparative Example 10, the amount of Zn-MoC / Mo2C nanoparticles loaded was too small; and in Comparative Example 11, the amount of Zn-MoC / Mo2C nanoparticles loaded was too large.
[0043] Comparative Example 1: The preparation of the catalytic electrode is the same as in Example 1, except that: the amount of Zn(NO3)2‧6H2O powder added in step one is 0 mmol (Zn, Mo atomic ratio is 0), the ratio of MoC and Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode is 0, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH is 0.5 V.
[0044] Comparative Example 2: The preparation of the catalytic electrode is the same as in Example 1, except that: in step one, the amount of Zn(NO3)2‧6H2O powder added is 0.21 mmol (Zn, Mo atomic ratio is 0.01), the ratio of MoC and Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode is 0, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH is 0.55 V.
[0045] Comparative Example 3: The preparation of the catalytic electrode is the same as in Example 1, except that: in step one, the amount of Zn(NO3)2‧6H2O powder added is 0.63 mmol (Zn, Mo atomic ratio is 0.03), the ratio of MoC and Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode is 0, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH is 0.55 V.
[0046] Comparative Example 4: The preparation of the catalytic electrode is the same as in Example 1, except that: in step one, the amount of Zn(NO3)2‧6H2O powder added is 1.05 mmol (Zn, Mo atomic ratio is 0.05), the ratio of MoC and Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode is 0, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH is 0.58 V.
[0047] Comparative Example 5: The preparation of the catalytic electrode is the same as in Example 1, except that: in step one, the amount of Zn(NO3)2‧6H2O powder added is 1.47 mmol (Zn, Mo atomic ratio is 0.07), the ratio of MoC to Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode is 0.23, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH is 0.62 V.
[0048] Comparative Example 6: The preparation of the catalytic electrode is the same as in Example 1, except that: in step one, the amount of Zn(NO3)2‧6H2O powder added is 1.89 mmol (Zn, Mo atomic ratio is 0.09), the ratio of MoC to Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode is 0.29, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH is 0.62 V.
[0049] Comparative Example 7: The preparation of the catalytic electrode is the same as in Example 1, except that: in step one, the amount of Zn(NO3)2‧6H2O powder added is 12.6 mmol (Zn, Mo atomic ratio is 0.6), the ratio of MoC to Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode is 0.64, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH is 0.62 V.
[0050] Comparative Example 8: The preparation of the catalytic electrode is the same as in Example 1, except that: in step one, the amount of Zn(NO3)2‧6H2O powder added is 16.8 mmol (Zn, Mo atomic ratio is 0.8), the ratio of MoC to Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode is 0.51, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH is 0.62 V.
[0051] Comparative Example 9: The preparation of the catalytic electrode is the same as in Example 1, except that: step two Zn-MoO nThe amount of @PANI precursor added was 0 g, and the prepared Zn-MoC / Mo2C catalytic electrode did not contain MoC and Mo2C, and the half-wave potential of the oxygen reduction reaction in 0.1 M KOH was 0.3 V.
[0052] Comparative Example 10: The preparation of the catalytic electrode is the same as in Example 1, except that: step two Zn-MoO n The amount of @PANI precursor added was 0.1 g, and the ratio of MoC to Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode was 0.54. The half-wave potential of the oxygen reduction reaction in 0.1M KOH was 0.33 V.
[0053] Comparative Example 11: The preparation of the catalytic electrode is the same as in Example 1, except that: step two Zn-MoO n The amount of @PANI precursor added was 1 g, and the ratio of MoC to Mo2C phases in the prepared Zn-MoC / Mo2C catalytic electrode was 0.54, and the half-wave potential of the oxygen reduction reaction in 0.1M KOH was 0.67 V.
[0054] As can be seen from the above embodiments and comparative examples: Zn 2+ The introduction of [a specific ingredient] can promote the conversion of Mo2C to MoC, and the incorporation of Zn [another ingredient] can also promote the conversion of Mo2C to MoC. 2+ The amount of energy can regulate the ratio between Mo2C and MoC, and the excess Zn 2+ The introduction of Zn will disrupt the crystal structure of molybdenum carbide and reduce its catalytic oxygen reduction performance; 2+ Insufficient introduction of Mo2C is not enough to induce the conversion of Mo2C to MoC, thus failing to form a two-phase synergistic catalytic oxygen reduction reaction, resulting in a decrease in the oxygen reduction reaction activity of the catalytic electrode.
[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A type of Zn 2+ The method for inducing a Mo2C phase transition is characterized by, Includes the following steps: Step 1: Disperse molybdate and Zn²⁺ salt in deionized water at an atomic ratio of Zn to Mo of 0.1 to 1, stir and add aniline, and adjust the pH of the solution with hydrochloric acid to obtain a mixed solution; Step 2: Stir and evaporate the mixed solution, collect the solid product, and obtain the MoOn@PANI precursor; Step 3: Grind and mix the MoOn@PANI precursor, magnesium powder, endothermic agent and dicyandiamide in a mass ratio of (1~4):1:(1~2). Then, carbonize the mixture under an inert atmosphere and allow it to cool naturally to room temperature. Step 4: Wash the carbonized product with acid to remove the above-mentioned reaction byproducts, then rinse and dry to obtain the MoC / Mo2C composite material.
2. The method according to claim 1, characterized in that, The molybdate is ammonium molybdate or sodium molybdate; the Zn²⁺ salt is zinc nitrate, zinc chloride, or zinc sulfate; and the molybdate is (NH₄)₆Mo₇O. 24 • One of 4H2O and Na2MoO4.
3. The method according to claim 1, characterized in that, In step one, the atomic ratio of Zn to Mo is 0.2 to 0.
5.
4. The method according to claim 1, characterized in that, In step three, the carbonization temperature is 600~900°C.
5. The method according to claim 1, characterized in that, In step four, the mixture is washed with 1 M hydrochloric acid and then vacuum dried at 80 °C.
6. The method according to claim 1, characterized in that, In step three, the heating rate of the carbonization process is 5 °C / min.
7. The method according to claim 1, characterized in that, In step three, the heat preservation time is 2 to 7 hours.
8. The method according to claim 1, characterized in that, In step one, the pH range of the mixed solution is 2 to 5.
9. A MoC / Mo2C composite material prepared by the method according to any one of claims 1-8, characterized in that, The composite material contains a MoC phase and a Mo2C phase, and the mass ratio of the two phases is controlled within the range of 0.1 to 1 by the atomic ratio of Zn to Mo.
10. The MoC / Mo2C composite material according to claim 9, characterized in that, The mass ratio of MoC phase to Mo2C phase in the composite material is between 0.41 and 0.71.