Multi-metal alloy / Mo2C heterojunction nano material as well as preparation method and application thereof
Synthesis of polymetal alloy/Mo2C heterojunction nanomaterials by fast Joule thermal method solves the problem of insufficient catalyst stability and OER performance in alkaline seawater electrolysis, and achieves efficient water decomposition and long-term stability under harsh conditions.
Patent Information
- Application Number
- CN202411418514.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-12
- Publication Date
- 2024-12-10
AI Technical Summary
During the electrolysis of alkaline seawater, it is difficult for the catalyst to avoid chloride ion anodization reaction under high current density, resulting in anode corrosion and cathode H2 generation stopping. The existing high-entropy alloy catalysts are insufficient in harsh seawater conditions.
The rapid Joule thermal method is used to synthesize polymetal alloy/Mo2C heterojunction nanomaterials as precatalysts. The water decomposition is accelerated through the heterojunction interface between Mo2C and high-entropy alloys, dynamically adjust the reaction kinetics and repel Cl-, thereby improving the stability of the catalyst. and OER performance.
The good OER performance and excellent stability of high-entropy alloy/Mo2C heterojunction nanomaterials in alkaline seawater electrolysis are achieved, which significantly improves the intrinsic activity and selectivity of the catalyst and extends the duration of the electrolysis process.
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Figure CN119101951A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of hydrogen production by water electrolysis, and in particular relates to a multi-metal alloy / Mo2C heterojunction nanomaterial and a preparation method and application thereof. Background Art
[0002] The global energy and environmental crisis has prompted people to accelerate the exploration of renewable energy development. Hydrogen, as an energy-dense and carbon-neutral fuel, is an ideal alternative to limited fossil fuels. Electrolysis of water to produce hydrogen can achieve zero carbon emissions throughout the process and is considered an advanced strategy. Seawater is a potential raw material for electrolysis because it is superior to fresh water in terms of reserves and distribution. Although there is no consensus on the economic superiority of direct or indirect seawater electrolysis, various current research advances have shown prospects for practical application. Among the sub-research directions such as direct seawater electrolysis, alkaline seawater electrolysis, acidified seawater electrolysis, and asymmetric seawater electrolysis, alkaline seawater electrolysis has become the mainstream seawater electrolysis method because it does not require a continuous supply of alkali and can effectively prevent the chloride ion anodic oxidation reaction (COR). However, due to the Cl in seawater, the electrolysis of seawater is not as efficient as indirect seawater electrolysis. - At high levels, especially at high current densities, most catalysts find it difficult to avoid COR. As chloride ions completely corrode the anode, the cathode will stop producing H2, leading to electrolysis failure. Overall, alkaline seawater splitting technology provides an attractive route to hydrogen production, but still requires suitable anode catalysts to work efficiently and durably in chloride-rich environments.
[0003] The study found that during the electrolysis of water at the anode, the soluble anions produced by the oxidation pre-catalyst will be re-adsorbed on the surface of the active catalyst by electrostatic force under the action of the electric field. In addition to serving as sacrificial reagents for structural reconstruction, these inactive anions can also change the electronic environment of the active site and interact with some intermediates to regulate the reaction kinetics and improve the oxygen evolution reaction (OER) activity. In addition, in the seawater environment, the oxidizing ion SO4 2- ,PO4 3- and MoO4 2- The anions preferentially adsorb on the anode surface and repel Cl - , thus effectively alleviating the Cl - corrosion.
[0004] High entropy alloys (HEAs) have attracted extensive attention in aqueous anodic oxidation reaction (OER) electrocatalysis due to their active multi-element synergy. In addition, the structure of HEAs can be adjusted by controlling the composition and ratio of metal elements, resulting in enhanced OER performance of HEAs. However, there are few studies on the application of HEA catalysts in alkaline seawater electrolysis, and achieving long-term stability of HEA catalysts under harsh seawater conditions remains a major challenge. Summary of the invention
[0005] In order to solve the above problems, the present invention innovatively synthesized a nanomaterial with a heterojunction of a multi-metal alloy (preferably a high entropy alloy) and Mo2C by a rapid Joule heating method, and found that it can be used as a pre-catalyst in alkaline seawater electrolysis, and not only has good OER performance but also has excellent stability in alkaline seawater electrolysis.
[0006] Specifically, in one aspect, the present invention provides a multi-metal alloy / Mo2C heterojunction nanomaterial, which has a multi-metal alloy phase and a Mo2C phase, and a heterojunction interface is formed between the multi-metal alloy phase and the Mo2C phase.
[0007] Furthermore, the multi-metal alloy phase and the Mo2C phase in the multi-metal alloy / Mo2C heterojunction nanomaterial form a uniform heterojunction structure.
[0008] Furthermore, the multi-metal alloy is a bimetallic alloy, a trimetallic alloy or a high entropy alloy.
[0009] Furthermore, the metal is selected from Fe, Co, Ni or Cu.
[0010] Furthermore, the high entropy alloy is an alloy of Fe, Co, Ni and Cu.
[0011] Furthermore, the molar ratio between the metals in the multi-metal alloy is 1:1.
[0012] Furthermore, the molar ratio between the multi-metal alloy and Mo2C is 1:2~2:1.
[0013] In another aspect, the present invention provides a method for preparing the multi-metal alloy / Mo2C heterojunction nanomaterial as described herein, comprising: (1) subjecting a metal source of a plurality of metal ions to a solvothermal reaction with a molybdenum salt and 2,5-dihydroxyterephthalic acid in a solvent, and then collecting the reaction product, washing it, and drying it; (2) subjecting the dried product obtained in step (1) to Joule heating to obtain the multi-metal alloy / Mo2C heterojunction nanomaterial.
[0014] Further, the metal sources of the plurality of metal ions are hydrochlorides, nitrates, sulfates or acetates of at least two of Fe, Co, Ni and Cu. For example, the metal sources of the plurality of metal ions may include iron acetate tetrahydrate (Fe(CO2CH3)2·4H2O), 0.25 mmol cobalt chloride hexahydrate (CoCl2·6H2O), nickel chloride hexahydrate (NiCl2·6H2O), cupric chloride (CuCl2), etc.
[0015] Further, the molybdenum salt is a hydrochloride, nitrate, sulfate or acetate of molybdenum. For example, the molybdenum salt can be molybdenum chloride (MoCl5).
[0016] Further, the solvent is selected from one or more of water, ethanol, ethylene glycol, dimethylformamide, and dimethylacetamide. For example, the solvent can be a mixed solvent of dimethylformamide, ethanol and water.
[0017] Furthermore, the solvent thermal reaction is carried out at 100-150° C. for 12-36 hours.
[0018] Furthermore, the washing is performed using an alcohol solvent such as ethanol.
[0019] Furthermore, the drying is vacuum drying.
[0020] Furthermore, the conditions for the Joule heating are: applying a current of 90-120A, a discharge time of 15-60s, and an actual heating temperature of 600-800°C.
[0021] In another aspect, the present invention provides a use of the multi-metal alloy / Mo2C heterojunction nanomaterial as described herein or the multi-metal alloy / Mo2C heterojunction nanomaterial prepared by the method described herein in the electrolysis of water or the electrolysis of seawater (preferably alkaline seawater).
[0022] Furthermore, the multi-metal alloy / Mo2C heterojunction nanomaterial is used to prepare an OER electrocatalyst.
[0023] Beneficial Effects of the Invention
[0024] The present invention innovatively synthesizes a nanomaterial with a heterojunction of a multi-metal alloy (preferably a high entropy alloy) and Mo2C by a rapid Joule heating method, which can be used as a pre-catalyst in alkaline seawater electrolysis. Taking the high entropy alloy / Mo2C heterojunction nanomaterial (abbreviated as HEA-Mo2C in this article) as an example, through the analysis of its microstructure, it is found that HEA-Mo2C is a uniformly dispersed heterojunction structure. Electrochemical analysis shows that during the electrolysis process, the Mo2C segment is gradually oxidized to MoO4 2- , and adsorbed on the surface of active sites. At the same time, HEA also dynamically reconstructs itself into high entropy hydroxides to accelerate the kinetics of water decomposition. In situ infrared spectroscopy proved that during the reaction of HEA-Mo2C, due to MoO4 2- To Cl - The repulsive effect of OH - The adsorption of ions improves the selectivity of OER and the intrinsic activity of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1:(a) XRD characterization of HEA-Mo2C obtained at different heat treatment temperatures, (b) XRD characterization of heterojunction materials obtained by changing the types of alloying elements.
[0026] Figure 2 : (a) XRD characterization of NiFeCoCu and HEA-Mo2C without Mo2C, (b) Raman characterization of NiFeCoCu and HEA-Mo2C without Mo2C.
[0027] Figure 3 :(a) Projection electron microscope image of HEA-Mo2C, (b) Locally enlarged projection electron microscope image of HEA-Mo2C, (c) Enlarged image of the heterojunction area, (d) Enlarged image of the lattice of Mo2C and HEA areas and the corresponding schematic diagram of the lattice spacing, (e) Energy dispersive X-ray spectroscopy (EDS) element mapping diagram.
[0028] Figure 4 : (a) XPS overall spectrum of HEA-Mo2C, (b) Ni 2p, (c) Cu 2p, (d) Mo 3d, (e) Co 2p and (f) Fe2p XPS high-resolution spectra.
[0029] Figure 5 : Linear voltammetric reaction curves of HEA-Mo2C obtained at different heat treatment temperatures.
[0030] Figure 6 :OER performance of HEA-Mo2C and other nanomaterials in 1.0 M KOH + seawater: (a) polarization curves of different catalysts, (b) kinetic energy distribution at 10, 100 and 500 mA cm -2 (c) Overpotential comparison at, (c) Tafel slope, (d) Nengquist curve, (e) Double layer capacitance diagram, (f) Mass activity and electrochemical active area comparison of different catalysts, (g) Long-term stability comparison of HEA-Mo2C and NiFeCoCu. DETAILED DESCRIPTION
[0031] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.
[0032] Example 1
[0033] In this embodiment, a high entropy alloy / Mo2C heterojunction nanomaterial (abbreviated as HEA-Mo2C) was synthesized. The synthesis process was divided into two steps. The specific synthesis steps are as follows: In the first step, 0.25 mmol iron acetate tetrahydrate (Fe(CO2CH3)2·4H2O), 0.25 mmol cobalt chloride hexahydrate (CoCl2·6H2O), 0.25 mmol NiCl2·6H2O (nickel chloride hexahydrate), 0.75 mmol molybdenum chloride (MoCl5), 0.25 mmol copper chloride (CuCl2) and 0.34 mmol 2,5-dihydroxyterephthalic acid were dissolved in a mixture of 22.5 mL dimethylformamide DMF, 1.35 mL anhydrous ethanol and 1.35 mL deionized water, and the mixture was transferred to a 50 mL autoclave and heated to 120°C for 24 h. The product was collected by suction filtration, washed with ethanol 3 times, and vacuum dried at 80°C for 12 hours. h; the second step of the reaction is to place the dried product in a Joule heat heating device, set the program to apply 120 A current, the discharge time is 30 s, the actual heating temperature is 800 ° C, and the final product HEA-Mo2C is obtained.
[0034] Example 2
[0035] In this example, a high entropy alloy / Mo2C heterojunction nanomaterial was synthesized. The synthesis process was the same as that described in Example 1, with the only difference being that a 90 A current was applied during the Joule heating process, the discharge time was 30 s, the actual heating temperature was 600°C, and the final product was named HEA-Mo2C-30s / 600°C.
[0036] Example 3
[0037] In this example, a high entropy alloy / Mo2C heterojunction nanomaterial was synthesized. The synthesis process was the same as that described in Example 1, with the only difference being that a current of 110 A was applied during the Joule heating process, the discharge time was 30 s, the actual heating temperature was 700°C, and the final product was named HEA-Mo2C-30s / 700°C.
[0038] Example 4
[0039] In this embodiment, a bimetallic alloy / Mo2C heterojunction nanomaterial is synthesized. The synthesis process is the same as that described in Example 1, with the only difference being that the types of metal reactants in the first step of the synthesis reaction are reduced, i.e., cobalt chloride hexahydrate and copper chloride are removed. The final product obtained is a NiFe bimetallic alloy / Mo2C heterojunction nanomaterial, named NiFe-Mo2C.
[0040] Example 5
[0041] In this embodiment, a tri-metal alloy / Mo2C heterojunction nanomaterial is synthesized. The synthesis process is the same as that described in Example 1, with the only difference being that the type of metal reactant in the first step of the synthesis reaction is reduced, i.e., cupric chloride is removed, and the final product obtained is a NiFeCo tri-metal alloy / Mo2C heterojunction nanomaterial, named NiFeCo-Mo2C.
[0042] Comparative Example
[0043] In this comparative example, a four-metal NiFeCoCu high entropy alloy was synthesized. The synthesis process was the same as that described in Example 1, with the only difference being that molybdenum chloride was not added in the first step of the synthesis reaction.
[0044] Test Example 1: Structure and morphology characterization of samples prepared in the examples and comparative examples
[0045] Figure 1a shows the XRD results of HEA-Mo2C obtained under heat treatment at different temperatures. It can be observed that a small amount of Mo2C characteristic peaks appear at 600°C. As the reaction temperature increases, the characteristic peak intensity of Mo2C gradually increases. At 800°C, the characteristic peak intensity of Mo2C is relatively close to the peak intensity of HEA. It can be considered that the relative content of Mo2C is similar to that of the high entropy alloy HEA, forming a uniform heterojunction structure. Figure 1 b shows that by changing the types of elements in the alloy, bimetallic and trimetallic alloy heterojunction structure materials were successfully prepared, proving the versatility of this synthesis method.
[0046] like Figure 2 As shown in a, without adding Mo element to the precursor, a single-phase high entropy alloy can be formed. Figure 2 As shown in b, Raman spectroscopy was performed to characterize the samples. The metal oxidation peaks on the alloys were observed for all samples, and 802 cm-1 for HEA-Mo2C. -1 and 980cm -1 MoO formed by oxidation of Mo2C x The characteristic peaks further prove the existence of Mo2C substance.
[0047] In order to further observe the morphology and structure of HEA-Mo2C, it was characterized by transmission electron microscopy. Figure 3 (a) shows that HEA-Mo2C has a uniformly distributed spherical morphology with a size of approximately 30nm-80nm. Figure 3 (b) The structure is enlarged and HEA and Mo2C are symmetrically and evenly distributed, and the heterojunction interface is clearly visible. Figure 3c) The periodic arrangement of two different lattice stripes in the heterojunction region can be clearly observed. The lattices of the two regions were measured separately. The lattice spacing of 0.19nm corresponds to Mo2C (200), and the lattice spacing of 0.24nm corresponds to HEA (111), which confirms the existence of two phase structures ( Figure 3 d). Energy dispersive X-ray spectroscopy (EDS) elemental analysis showed that nickel, iron, cobalt and copper were distributed in the same area, and molybdenum was distributed alone in the Mo2C area, which directly proved the successful synthesis of HEA-Mo2C heterojunction material ( Figure 3 e).
[0048] In order to further reveal its chemical state information, XPS characterization was performed on the main sample HEA-Mo2C. From the XPS total spectrum, it can be seen that C, O, Fe, Ni, Cu, Mo, and Co exist ( Figure 4 a). From the 2p high-resolution images of Ni, Fe, Ni, Cu and Co, it can be observed that the metallic peak and the oxidized peak exist simultaneously, indicating that the surface of the high-entropy alloy is still slightly oxidized ( Figure 4 bf). The metallic state of Mo and the Mo x+ , indicating that a small amount of Mo is reduced to the metallic state.
[0049] Test Example 2: Electrochemical Performance and OER Performance Test of Samples Prepared in Examples and Comparative Examples
[0050] Figure 5 The electrochemical properties of HEA-Mo2C obtained under heat treatment at different temperatures were characterized. It can be observed that HEA-Mo2C obtained under 800℃ heat treatment has better electrochemical reaction performance than those obtained under 700℃ and 600℃.
[0051] The seawater OER performance of HEA-Mo2C was evaluated in 1 M KOH + seawater electrolyte, as Figure 6 As shown in Figure ac, HEA-Mo2C exhibits the best performance among all tested samples, reaching 100 mA cm at an overpotential of only 270 mV. -2 The current density of HEA-Mo2C is much lower than that of NiFeCo-Mo2C (321mV), NiFe-Mo2C (326mV) and NiFeCoCu (391mV). At the same time, the Tafel slope of HEA-Mo2C is also the lowest, only 35mV dec. -1 , compared with NiFeCo-Mo2C (53mV dec -1 )、NiFe-Mo2C(54mVdec -1 ) and NiFeCoCu (59mV dec -1) is small, indicating its fast kinetic characteristics. In addition, from the Nengquist plot, it can be seen that HEA-Mo2C has the smallest reaction resistance, which also proves that it has the best reaction kinetics ( Figure 6 d). The dual cell capacitance of different samples was calculated, and it was observed that HEA-Mo2C had the most active sites. The mass activity and electrochemical area normalized current density of different samples were compared, and HEA-Mo2C showed the best overall electrochemical performance, proving that the high entropy molybdenum carbide heterojunction material greatly enhances its electrocatalytic performance due to the synergistic effect of multiple elements ( Figure 6 f). Since molybdenum carbide materials are widely used in electrocatalytic seawater OER electrolysis, we compared the stability of NiFeCoCu materials without Mo2C and HEA-Mo2C in seawater electrolysis. It can be seen that the HEA-Mo2C heterojunction material has excellent stability and can stably electrolyze for more than 250h in a 1M KOH + seawater environment ( Figure 6 g).
[0052] It should be noted that the preferred embodiments of the present invention are given in the specification of the present invention, but the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not intended to be additional limitations on the content of the present invention. The purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. In addition, the above-mentioned technical features continue to be combined with each other to form various embodiments not listed above, which are all considered to be within the scope of the present invention specification; further, for ordinary technicians in this field, they can be improved or transformed according to the above description, and all these improvements and transformations should belong to the protection scope of the claims attached to the present invention.
Claims
1. A multi-metal alloy / Mo2C heterojunction nanomaterial, characterized in that: The nanomaterial comprises a multi-metal alloy phase and a Mo2C phase, and a heterojunction interface is formed between the multi-metal alloy phase and the Mo2C phase.
2. The multi-metal alloy / Mo2C heterojunction nanomaterial according to claim 1, characterized in that: The multi-metal alloy is a bimetallic alloy, a trimetallic alloy or a high entropy alloy; The multi-metal alloy phase and the Mo2C phase in the multi-metal alloy / Mo2C heterojunction nanomaterial form a uniform heterojunction structure.
3. The multi-metal alloy / Mo2C heterojunction nanomaterial according to claim 1, characterized in that: The metal is selected from Fe, Co, Ni or Cu; The high entropy alloy is an alloy of Fe, Co, Ni and Cu; The molar ratio between the metals in the multi-metal alloy is 1:1; The molar ratio between the multi-metal alloy and Mo2C is 1:2~2:
1.
4. A method for preparing a multi-metal alloy / Mo2C heterojunction nanomaterial as claimed in any one of claims 1 to 3, characterized in that: The method comprises: (1) subjecting a metal source of a plurality of metal ions to a solvothermal reaction with a molybdenum salt and 2,5-dihydroxyterephthalic acid in a solvent, and then collecting the reaction product, washing it, and drying it; (2) The dried product obtained in step (1) is subjected to Joule heating to obtain the multi-metal alloy / Mo2C heterojunction nanomaterial.
5. The method according to claim 4, characterized in that The metal sources of the plurality of metal ions are hydrochlorides, nitrates, sulfates or acetates of at least two of Fe, Co, Ni and Cu, and the molybdenum salt is hydrochloride, nitrate, sulfate or acetate of molybdenum.
6. The method according to claim 4, characterized in that The solvent is selected from one or more of water, ethanol, ethylene glycol, dimethylformamide and dimethylacetamide.
7. The method according to claim 4, characterized in that The solvent thermal reaction is carried out at 100-150° C. for 12-36 hours.
8. The method according to claim 4, characterized in that The conditions for the Joule heating are: applying a current of 90-120A, a discharge time of 15-60s, and an actual heating temperature of 600-800°C.
9. Use of the multi-metal alloy / Mo2C heterojunction nanomaterial according to any one of claims 1 to 3 or the multi-metal alloy / Mo2C heterojunction nanomaterial prepared by the method according to any one of claims 4 to 8 in water electrolysis or seawater electrolysis.
10. The use according to claim 9, characterized in that: The multi-metal alloy / Mo2C heterojunction nanomaterial is used to prepare an OER electrocatalyst.