A tungsten carbonitride substrate-based coherent heterostructure catalyst material and a method for preparing the same

Abstract

The application relates to a tungsten carbonitride substrate-based coherent heterostructure catalyst material and a preparation method thereof, and belongs to the field of catalysts. A solution containing platinum and doped metal salt, namely A solution, is prepared; a reducing agent solution containing a surfactant, namely B solution, is prepared. A WCN substrate sheet is placed in the B solution, the B solution is heated to 220-250 DEG C, then the A solution is gradually added dropwise into the B solution, constant-temperature reaction is carried out until the dropping is completed, stirring and cooling to room temperature, in-situ Pt-based nano-catalyst particles with coherent heterostructure are generated on the WCN nano structure; the catalyst and the substrate material form a coherent interface structure, promote interface charge distribution and transfer, and further improve the activity and stability of the nano catalyst.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic material preparation and application, and particularly to a coherent heterostructure catalyst composite thin film electrode electrocatalytic hydrogen evolution material and its in-situ growth synthesis method. Background Technology

[0002] Electrocatalytic water splitting is a promising technology for producing clean hydrogen fuels. Developing cost-effective, efficient, and durable hydrogen evolution reaction (HER) electrocatalysts plays a crucial role in water splitting. Platinum-based electrocatalysts exhibit good electrocatalytic activity in both acidic and alkaline media, but their economic cost limits their further application. Recent studies have shown that heterostructured electrocatalysts also demonstrate the potential for highly efficient HER electrocatalysis. The degree of interfacial matching in heterostructured electrocatalysts affects their interfacial electronic structure, which in turn determines the kinetics and activity of the HER reaction. Therefore, developing methods for constructing coherent interfacial heterostructured electrocatalysts for HER electrocatalysis is both significant and challenging. Summary of the Invention

[0003] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a method for in-situ synthesis of coherent heterostructure nanocatalyst composite thin film electrode materials. The purpose is to construct a coherent interface structure between the catalyst and the substrate material, promote the distribution and transfer of interfacial charge, and thereby improve the activity and stability of the nanocatalyst, thus solving the technical problem of performance degradation during electrocatalysis.

[0004] To achieve the above objectives, according to one aspect of the present invention, a method for preparing and synthesizing a coherent heterostructure catalyst composite electrode is provided, comprising the following steps:

[0005] (1) Place the platinum-containing salt and the salt corresponding to the doped metal in water, stir and sonicate to disperse evenly, and record it as solution A;

[0006] (2) Place the reducing agent in a container, add a small amount of surface active protectant, stir until completely dissolved, and record it as solution B; triethylene glycol serves as a reducing agent and solvent to provide a reduction reaction environment for the subsequent metal precursor, and polyvinylpyrrolidone (PVP) is added as a surface active protectant to increase the catalyst nucleation sites on the substrate material, making it easier for the catalyst crystals to grow in situ on the substrate.

[0007] (3) Prepare or purchase sheet-like tungsten carbonitride (WCN) as a substrate material;

[0008] Patent 202311680121.0 discloses a method for preparing nanoscale high-conductivity tungsten carbonitride heterojunction thin films. According to the process described therein, tungsten carbonitride (WCN) with a high specific surface area is prepared as a substrate material for subsequent in-situ growth of Pt-based catalysts.

[0009] (4) Place the substrate in solution B, heat solution B to 220-250°C, and then gradually add solution A to solution B. Keep the reaction at a constant temperature until the addition is complete, stir and cool to room temperature. Pt-based nanocatalyst particles with coherent heterostructure can be generated in situ on the WCN nanostructure.

[0010] In further step (1), the doping metal is one or more of copper, cobalt, nickel, and zinc, preferably four; wherein the concentration of copper, cobalt, nickel, and zinc is 1-20 times that of platinum; and the concentration of platinum is 1-5 mM.

[0011] In step (2), add 1 to 1.2 grams of PVP for every 100 to 300 mL of triethylene glycol solution.

[0012] In further step (4), each cm 2 5–20 μg of platinum were grown in situ on a tungsten carbonitride (WCN) substrate of a certain area. The platinum loading was relatively low.

[0013] The coherent heterostructure catalyst material based on tungsten carbonitride substrate obtained in this invention can be directly used as an electrocatalytic electrode for hydrogen evolution reaction (HER) in water electrolysis to produce hydrogen.

[0014] Compared with the prior art, the advantages and significant effects of the present invention are as follows:

[0015] (1) This invention is the first to prepare a coherent heterostructure Pt-based nanocatalyst composite thin film electrode material (the interface between the prepared Pt-based catalyst and the WCN substrate material is coherent). This coherent interface structure will cause electron redistribution at the interface between the catalyst and the substrate material, forming a continuous electronic conduction pathway, thereby regulating the electronic structure of the catalyst and making it closer to the optimal state of the hydrogen evolution reaction.

[0016] (2) The interface coherent heterostructure proposed in this invention has excellent crystal plane matching at the catalyst-substrate phase interface, which improves the structural stability of the electrode material under long-term electrocatalytic reaction cycle.

[0017] (3) The interfacial coherent heterostructure proposed in this invention will generate a synergistic effect at the interface between the catalyst and the substrate. The substrate material can enrich electrons on its surface and adsorb and dissociate hydrogen species (H*) in the solution, and participate in the hydrogen evolution reaction together with the catalyst, thereby improving the overall efficiency of the electrocatalytic hydrogen evolution reaction.

[0018] (4) The interfacial coherent heterostructure proposed in this invention provides good electronic conductivity for the WCN substrate material and abundant active sites for the catalyst. The combination of the two can achieve a more efficient hydrogen evolution reaction.

[0019] (5) This invention significantly reduces the amount of precious metal platinum used by controlling the content of the platinum precursor or by introducing doping with four transition metal elements: cobalt, nickel, copper, and zinc. Simultaneously, the combination of multiple elements allows the metal alloy catalyst to possess a tunable electronic structure and extremely excellent structural stability.

[0020] (6) The electrocatalytic hydrogen evolution performance of the material of the present invention is superior to that of the best commercially available platinum-carbon catalyst. Attached Figure Description

[0021] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the specific examples will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram illustrating the principle of material preparation and synthesis according to the present invention.

[0023] Figure 2 The X-ray diffraction (XRD) patterns of the catalyst materials grown in situ on tungsten carbonitride in all examples of the present invention are shown in Figure (b). Figure (b) is an enlargement of the dashed area in Figure (a). The dashed line in Figure (b) represents the standard diffraction peak of platinum. It can be seen that the diffraction peak positions of the catalyst composite thin film electrode and the substrate are basically consistent, and the peak positions of the Pt-based catalyst coincide with those of the substrate.

[0024] Figure 3 The high-resolution transmission electron microscope (HRTEM) image of the material PtCoNiCuZn / WCN described in Example 1 of this invention and its corresponding elemental distribution map show that the particles are uniformly distributed on the substrate material.

[0025] Figure 4 The figure shows the atomic structure characterization of a single nanoparticle of the PtCoNiCuZn / WCN catalytic material described in Example 1 of this invention. The larger and brighter atoms in the figure are Pt, and the smaller and darker atoms are Co, Ni, Cu, or Zn elements. It can be seen from (a) and (b) that the content of noble metal atoms Pt is significantly higher than that of non-noble metal atoms (Co, Ni, Cu, or Zn, mainly because the reducing agent has a greater reducing power for Pt than Co, Ni, Cu, or Zn when the metal is grown on the substrate by in-situ reduction, and it is also easier to grow in-situ on the substrate). The two are arranged randomly and irregularly, thus forming a crystal structure of non-noble metal atoms doped with noble metals.

[0026] Figure 5This is a high-resolution transmission electron microscope (HRTEM) image of the coherent heterostructure of the catalyst and substrate described in Example 1 of this invention, which corresponds to the XRD pattern. The interplanar spacings of the substrates WC(100) and WN(100) are respectively... and The interplanar spacing of the catalyst particles (111) is approximately [value missing]. The interface mismatch between the two is 0.05 < δ < 0.5, which falls within the category of coherent relationship.

[0027] Figure 6 This is a comparison chart of the mass activity of the materials described in all examples of this invention, specifically including Pt / WCN, PtCu / WCN, PtCoNiCuZn / WCN, and a commercial Pt / C (20%) catalyst. The chart shows the normalized mass activity of the noble metals in the hydrogen evolution reaction catalyzed in 0.5 molar sulfuric acid solution, with a reversible hydrogen electrode (RHE) as the reference electrode. At an overpotential of 50 mV, the noble metal mass activity of the best-performing material shown in this invention is 4.63 A / mg (mass activity is a common performance comparison standard for noble metal-based catalysts, usually referring to the ratio of the current density per unit area of ​​electrode material at a certain overpotential to the mass of catalyst on it; the mass activity described in this patent is at an overpotential of 50 mV, and the current density unit is mA / cm²). 2 The loading of noble metals in the catalyst per unit area is 8.8 μg / cm². 2 Therefore, the ratio of the two is converted to amperes per milligram (mg), which is 22 times that of commercial Pt / C (20%) catalysts. This demonstrates that the material of the present invention has a high utilization rate of precious metals and excellent performance when used as an electrocatalytic hydrogen evolution reaction catalyst.

[0028] Figure 7 The image shows the chronopotential curve of the material described in Example 1 of this invention for the electrocatalytic hydrogen evolution reaction in a 0.5 mol / L sulfuric acid solution. It can be seen that, compared to commercial Pt / C catalysts, the potential of the material described in this invention shows almost no decay after 300 hours. Therefore, the material of this invention exhibits higher stability. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only a part of the examples of the present invention, and not all of them. Specific conditions are not specified in the examples, and the experimental methods used are generally based on routine laboratory conditions, conditions described in manuals, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used can be obtained commercially unless otherwise specified. Furthermore, based on the examples of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0030] Example 1

[0031] Catalyst composite thin film electrode materials with coherent heterostructures were prepared by the following steps:

[0032] Step (1): Prepare a precursor solution containing a mixture of 2 mM chloroplatinic acid hexahydrate, 20 mM cobalt chloride hexahydrate, 20 mM nickel chloride hexahydrate, 20 mM copper chloride dihydrate, and 20 mM zinc chloride. Stir and sonicate to mix evenly.

[0033] Step (2): Prepare the reaction solution by adding 100-300 mL of triethylene glycol solution to the reaction vessel, adding 1-1.2 g of PVP, and stirring continuously until completely dissolved to obtain a reducing mixed reaction solution containing a surfactant. The purpose of triethylene glycol is to create conditions for the formation of corresponding metallic atoms from various metal ions in the aforementioned metal precursor solution. Adding a surfactant can improve the hydrophilicity / hydrophobicity of the substrate material, increasing the active sites of the substrate material and the nucleation sites of catalyst atoms.

[0034] Step (3): Cut the WCN substrate into 1×1cm pieces and place them in the mixed reaction solution obtained in step (2). Heat the reaction vessel to 230°C in a magnetically stirred oil bath. Then, add the 90mL precursor solution from step (1) at a rate of 1mL·min. -1 The metal precursor is added dropwise continuously to the reaction solution while the mixture is vigorously stirred continuously. The purpose of dropwise addition is to ensure that the ionic state of the metal precursor can be fully reduced to the metallic state under the action of the reducing agent. Vigorous stirring is to ensure that the atoms reduced to the metallic state are dispersed in a timely manner, inhibiting their aggregation in the solution.

[0035] Step (4): Following the steps in step (3), the precursor solution is dripped in and then the constant temperature of 230℃ is ended. The mixture is then allowed to cool naturally to room temperature while continuously stirring. Finally, the in-situ grown PtCoNiCuZn / WCN interfacial coherent heterostructure catalyst composite electrode is obtained.

[0036] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the catalytic material obtained in this example. Compared with the WCN substrate, the dashed line corresponds to the standard diffraction peak position of metallic Pt, which is basically consistent with the diffraction peak position intensity of the WCN substrate. This indicates that the low loading of the catalyst and the similar interplanar spacing with the substrate, and the slight shift in peak position are caused by the doping of transition elements.

[0037] Figure 3The image shows a high-resolution transmission electron microscope (HRTEM) image of the catalytic material obtained in this example and its corresponding elemental energy spectrum distribution map, which clearly shows that the particles are uniformly loaded on the substrate, the elements are uniformly distributed in the nanoparticles, and there is no phase separation.

[0038] Figure 4 The figure shows the atomic structure characterization diagram of the single nanoparticle of the catalytic material obtained in this example. As can be seen from Figures (a) and (b), the larger and brighter Pt atoms are more abundant than the smaller and darker Co, Ni, Cu or Zn atoms, and the two are randomly arranged in an irregular manner, which constitutes the doping of the noble metal structure by non-noble metal elements.

[0039] Figure 5 The image shows a high-resolution transmission electron microscope (HRTEM) image of the coherent heterostructure of the catalytic material obtained in this example. The area marked by the dashed line corresponds to the interfacial mismatch between the substrate and the catalyst, which falls within the range of coherent relationships. This corresponds to the XRD pattern.

[0040] Figure 6 The figure shows the mass activity graph of the catalytic material obtained in this example, which shows that the mass activity is about 22 times higher than that of commercial Pt / C (20%) catalyst at an overpotential of 50 mV vs. RHE.

[0041] Figure 7 The figure shows the chronopotential results of the catalyst material obtained in this example. It can be seen that, compared with the curve of Pt / C (20%), the overpotential of the material in this example hardly decays after 300 hours of long cycling.

[0042] Example 2

[0043] Referring to the method in Example 1, the catalyst composite thin film electrode material with a coherent heterostructure is prepared by the following steps:

[0044] Step (1): Prepare a precursor solution containing a mixture of 2 mM chloroplatinic acid hexahydrate and 20 mM copper chloride dihydrate, stir and sonicate until homogeneous.

[0045] Step (2): Prepare the reaction solution by adding 100-300 mL of triethylene glycol solution to the container to be reacted, adding 1-1.2 g of PVP, and stirring continuously until it is completely dissolved to obtain a reducing mixed reaction solution containing surfactant.

[0046] Step (3): Place the 1×1cm WCN substrate sheet into the mixed reaction solution obtained in step (2), heat the reaction vessel to 230°C in a magnetically stirred oil bath, and then add the 90mL precursor solution from step (1) at a rate of 1mL·min. -1The solution is continuously added drop by drop to the reaction solution while the mixture is stirred vigorously.

[0047] Step (4): Following the steps in step (3), the precursor solution is dripped in and then the constant temperature of 230℃ is ended. The mixture is then allowed to cool naturally to room temperature while continuously stirring. Finally, the in-situ grown PtCu / WCN interfacial coherent heterostructure catalyst composite electrode is obtained.

[0048] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the catalytic material obtained in this example. Compared with the WCN substrate, the dashed line corresponds to the standard diffraction peak position of metallic Pt, which is basically consistent with the diffraction peak position intensity of the WCN substrate. This indicates that the low loading of the catalyst and the similar interplanar spacing with the substrate, and the slight shift in peak position are caused by the doping of transition elements.

[0049] Figure 6 The figure shows the mass activity graph of the catalytic material obtained in this example, which shows an improvement of approximately 7.4 times in mass activity compared to commercial Pt / C (20%) catalysts at an overpotential of 50 mV vs. RHE.

[0050] Example 3

[0051] Referring to the method in the above examples, the catalyst composite thin film electrode material with a coherent heterostructure is prepared by the following steps:

[0052] Step (1): Prepare a precursor solution containing 2 mM chloroplatinic acid hexahydrate solution, stir and sonicate to mix evenly.

[0053] Step (2): Prepare the reaction solution by adding triethylene glycol solution to the reaction vessel, adding 1 to 1.2 grams of PVP, and stirring continuously until it is completely dissolved to obtain a reducing mixed reaction solution containing surfactant.

[0054] Step (3): Place WCN substrates of different sizes into the mixed reaction solution obtained in step (2), heat the reaction vessel to 230°C in a magnetically stirred oil bath, and then add the precursor solution from step (1) at a rate of 1 mL / min. -1 The solution is continuously added drop by drop to the reaction solution while the mixture is stirred vigorously.

[0055] Step (4): Following the steps in step (3), the precursor solution is dripped in and then the constant temperature of 230℃ is ended. The mixture is then allowed to cool naturally to room temperature while continuously stirring. Finally, the in-situ grown Pt / WCN interfacial coherent heterostructure catalyst composite electrode is obtained.

[0056] Figure 2The image shows the X-ray diffraction (XRD) pattern of the catalytic material obtained in this example. Compared with the WCN substrate, the dashed line corresponds to the standard diffraction peak position of metallic Pt, which is basically consistent with the diffraction peak position intensity of the WCN substrate. This indicates that the low loading of the catalyst and the similar interplanar spacing with the substrate, and the slight shift in peak position are caused by the doping of transition elements.

[0057] Figure 6 The figure shows the mass activity graph of the catalytic material obtained in this example, which is about 4.9 times higher than that of commercial Pt / C (20%) catalyst at an overpotential of 50 mV vs. RHE.

[0058] The above are specific implementation examples of the present invention.

[0059] The experimental data shown in the accompanying figures fully demonstrate the excellent performance of the coherent heterostructure catalyst of the present invention. In many aspects of physicochemical properties, it has greatly surpassed the currently commercially available Pt / C catalysts, which is a major breakthrough in the field of electrocatalytic materials and has considerable prospects for practical applications.

Claims

1. A method for preparing a coherent heterostructure catalyst material based on a tungsten carbonitride substrate, characterized in that, Includes the following steps: (1) Place the platinum-containing salt and the salt corresponding to the doped metal in water, stir and sonicate to disperse evenly, and record it as solution A; (2) Place the reducing agent in a container, add a small amount of surface active protectant, stir until completely dissolved, and record it as solution B; triethylene glycol serves as a reducing agent and solvent to provide a reduction reaction environment for the subsequent metal precursor; polyvinylpyrrolidone (PVP) is added as a surface active protectant to increase the catalyst nucleation sites on the substrate material, making it easier for the catalyst crystals to grow in situ on the substrate. (3) Prepare sheet-like tungsten carbonitride (WCN) as a substrate material; (4) Place the substrate in solution B, heat solution B to 220~250℃, and then gradually add solution A to solution B. Keep the reaction at a constant temperature until the addition is complete, stir and cool to room temperature. Pt-based nanocatalyst particles with coherent heterostructure can be generated in situ on WCN nanostructure. In step (1), the doping metals are copper, cobalt, nickel and zinc; the concentrations of copper, cobalt, nickel and zinc are 1-20 times that of platinum; the concentration of platinum is 1-5 mM.

2. The method for preparing a coherent heterostructure catalyst material based on a tungsten carbonitride substrate according to claim 1, wherein in step (4) each cm 2 5-20 μg of platinum were grown in situ on a tungsten carbonitride WCN substrate with an area of ​​[area missing].

3. A coherent heterostructure catalyst material based on a tungsten carbonitride substrate prepared by the method according to any one of claims 1-2.

4. The application of a coherent heterostructure catalyst material based on a tungsten carbonitride substrate prepared according to any one of claims 1-2, which is directly used as an electrocatalytic electrode for hydrogen evolution reaction (HER) in water electrolysis to produce hydrogen.

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