A Pt atom substitution-induced MoS2 phase transition method for enhancing hydrogen production performance in water electrolysis.

Abstract

This invention belongs to the field of catalyst preparation technology and discloses a Pt atom substitution-induced MoS2 phase transition method for enhancing the performance of water electrolysis for hydrogen production. Specifically, it relates to a method for preparing a low-platinum-loaded 1T-MoS2 composite material (Pt@1T-MoS2 / C) decorated with uniformly substituted platinum atoms on a conductive porous carbon electrocatalyst and its application in the field of electrocatalytic hydrogen evolution. By introducing Pt single atoms into the basal surface of highly conductive carbon-supported 2H-MoS2, a phase transition from 2H-MoS2 to 1T-MoS2 is achieved. This results in the synthesis of a highly efficient and economical low-platinum-loaded Pt@1T-MoS2 / C composite material that combines high conductivity, large specific surface area, high activity, and high stability. This material offers advantages of low cost, high activity, and high stability, effectively solving the problem of balancing activity and stability in MoS2 catalysts for electrocatalytic hydrogen evolution. It has significant implications and promising applications in reducing the cost of water electrolysis hydrogen evolution catalysts, improving hydrogen production efficiency, and reducing reaction energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic material synthesis technology, specifically relating to a Pt atom substitution-induced MoS2 phase transition method for preparing efficient, stable and economical water electrolysis hydrogen production catalytic materials. Background Technology

[0002] With the rapid progress and development of society, the energy crisis facing humanity is becoming increasingly severe. Hydrogen energy, due to its high calorific value and pollution-free products, is considered an ideal carrier for future energy storage and supply, and a promising clean energy source to replace fossil fuels. In particular, water electrolysis for hydrogen production, driven by renewable energy, is considered one of the most economical, cleanest, and most promising methods for large-scale production of high-purity green hydrogen, but its electrode reaction kinetics are slow. Water electrolysis for hydrogen production involves two half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. In actual electrolysis, a large overpotential is required to activate and overcome the initial reaction energy barrier, resulting in high energy consumption. To enhance reaction activity and reduce energy consumption, it is necessary to develop efficient catalysts to accelerate the reaction process and improve overall catalytic decomposition efficiency. Currently, noble metal Pt-based catalysts are widely recognized as the most efficient HER electrocatalysts, but their scarcity and durability limit their large-scale application. Therefore, developing efficient, stable, and economical HER catalysts is key to improving the efficiency of water electrolysis for hydrogen production.

[0003] As a typical two-dimensional transition metal sulfide, 2H-MoS2 is considered the optimal potential replacement for platinum in HER (Hydrogen Emission Reactor) catalysts due to its abundant reserves and relatively excellent chemical stability. However, its inherent semiconductor properties and basal inertness result in unsatisfactory catalytic performance in HER. In contrast, 1T-MoS2, with its metallic properties, has active sites not only distributed at the edges and but also on the basal surface. However, the poor stability of 1T-MoS2 as a metastable state prevents its large-scale application in catalysis. Therefore, optimizing the MoS2 phase structure, activating and strengthening basal active sites through surface / interface engineering strategies are effective ways to improve the activity and stability of MoS2 catalysts, which is crucial for reducing the energy consumption of water electrolysis for hydrogen production. Summary of the Invention

[0004] To address the existing technical challenges and overcome the shortcomings and deficiencies of 2H-MoS2 materials in catalyst applications, such as poor intrinsic conductivity, few active sites, and structural instability, this invention aims to provide a Pt atom substitution-induced phase transformation strategy. By introducing Pt single atoms into the basal plane of highly conductive carbon-supported 2H-MoS2, a phase transformation from 2H-MoS2 to 1T-MoS2 is achieved. This results in the synthesis of a highly efficient and economical low-platinum-loading Pt@1T-MoS2 / C composite material that combines high conductivity, large specific surface area, high activity, and high stability. This material offers advantages of low cost, high activity, and stability, achieving two goals at once. It effectively solves the problem of balancing activity and stability in the electrocatalytic hydrogen evolution field of MoS2 catalysts, and has significant implications and promising application prospects in reducing the cost of hydrogen evolution catalysts for water electrolysis, improving hydrogen production efficiency, and reducing reaction energy consumption.

[0005] The purpose of this invention is to provide a method for preparing MoS2 phase transformation by using a Pt atom substitution-induced phase transformation strategy.

[0006] Another object of the present invention is to provide the application of the obtained Pt@1T-MoS2 / C catalyst in the field of hydrogen production by water electrolysis.

[0007] To achieve the above objectives, the present invention employs the following technical solution: a method for Pt atom substitution-induced phase transformation to prepare low-platinum-loaded Pt@1T-MoS2 / C composite materials. The specific steps are as follows:

[0008] (1) Preparation of molybdate ion-polydopamine (MoO4) by room temperature self-polymerization 2- -PDA) self-assembly: Molybdate is dissolved in an aqueous solution, and dopamine hydrochloride is dissolved in ethanol. The two are mixed with stirring at room temperature, and self-assembled with the assistance of ammonia to form molybdate ion-polydopamine (MoO4). 2- -PDA) multi-level hierarchical nanosphere precursor.

[0009] (2) Preparation of pre-oxidized precursor MoO x / C: MoO4 2- - The PDA was transferred to a vacuum tube furnace and subjected to programmed temperature-controlled pyrolysis under an inert atmosphere to obtain MoO. x / C nanoflower balls.

[0010] (3) High-temperature vulcanization strategy for preparing 2H-MoS2 / C composite materials: Weigh MoO2 according to a certain proportion x / C and sublimed sulfur were transferred to a vacuum tube furnace and subjected to high-temperature sulfidation under programmed temperature control in an inert atmosphere to obtain 2H-MoS2 / C.

[0011] (4) Preparation of Pt@1T-MoS2 / C composite material by impregnation-low temperature pyrolysis reduction method: Weigh 2H-MoS2 / C, impregnate it in a Pt salt solution of a certain concentration, stir at room temperature for 30 min, then freeze the above liquid rapidly, freeze dry it and transfer it to a vacuum tube furnace, and carry out low temperature reduction under a reducing atmosphere to finally obtain Pt@1T-MoS2 / C composite material.

[0012] Preferably, the molybdenum salt described in step (1) includes, but is not limited to, ammonium molybdate, sodium molybdate, and their hydrates.

[0013] Preferably, the molar ratio of molybdate ions to dopamine hydrochloride in step (1) is controlled between 2 and 3, and MoO4 2- - The morphology of the PDA self-assembled body is a multi-level layered nanoflower.

[0014] Preferably, the temperature control setting of the pre-oxidation program in step (2) is as follows: at room temperature, the temperature is increased to 450°C at a heating rate of 5°C / min, and then naturally cooled after annealing for 2 hours.

[0015] Preferably, the MoO2 described in step (3) x The mass ratio of C to sublimed sulfur was controlled at 1:x. <x<20。

[0016] Preferably, the high-temperature vulcanization in step (3) adopts an upstream and downstream vulcanization method, with sublimed sulfur placed upstream and MoO2 placed downstream. x / C, the high-temperature vulcanization program is set as follows: at room temperature, the temperature is increased to 800℃ at a heating rate of 5℃ / min, and then annealed for 3 hours before naturally cooling down.

[0017] Preferably, the platinum salts mentioned in step (4) include, but are not limited to, potassium chloroplatinate, platinum acetylacetonate, chloroplatinic acid and its hydrate, platinum nitrate and its hydrate, platinum tetrachloride and its hydrate, etc. The concentration of platinum salts is controlled at 0.1 to 0.5 mol / L, instantaneous freezing is achieved by liquid nitrogen, and the sample is processed by freeze-drying technology.

[0018] Preferably, the reducing atmosphere in step (4) is a mixed gas with a volume ratio of H2 / Ar of 92 / 8, the flow rate is controlled at 80-100 mL / min, and the low-temperature reduction program is set as follows: at room temperature, the temperature is increased to 400℃ at a heating rate of 5℃ / min, and then naturally cooled down after 1 hour.

[0019] Compared with existing technologies, this invention provides a low-platinum-loading Pt@1T-MoS2 / C composite electrocatalyst, its preparation method, and its applications, achieving the following effective results:

[0020] (1) The Pt@1T-MoS2 / C electrocatalyst obtained in this invention has the morphological characteristics of few-layer 1T-MoS2 grown in situ on the surface of highly conductive multi-level layered nanospheres, which greatly strengthens the interface before the 1T-MoS2 / C conductive substrate and solves the problems of poor stability and poor intrinsic conductivity of the catalyst caused by the weak interaction between the catalyst and the conductive substrate.

[0021] (2) The Pt@1T-MoS2 / C electrocatalyst obtained in this invention has the morphological characteristics of in-situ growth of few-layer 1T-MoS2 on the surface of highly conductive multi-level layered nanospheres, which can provide abundant specific surface area and anchoring sites for single-atom Pt. As an excellent support for high-efficiency hydrogen evolution electrocatalyst with low platinum loading, it can improve the utilization rate of Pt to achieve single-atom loading, reduce costs and improve the overall efficiency of the catalyst, thus combining high efficiency and economy.

[0022] (3) The Pt@1T-MoS2 / C electrocatalyst obtained in this invention has Pt atoms that have achieved atomic-level uniform substitution on the 1T-MoS2 / C basal plane, which induces 2H-MoS2 / C to undergo phase transformation to generate 1T-MoS2 / C, further optimizing the phase structure of MoS2, optimizing the hydrogen adsorption free energy in the hydrogen evolution reaction process, reducing the hydrogen evolution reaction overpotential, and improving the overall energy efficiency.

[0023] (4) The Pt@1T-MoS2 / C electrocatalyst obtained in this invention exhibits excellent catalytic performance in the electrocatalytic hydrogen evolution reaction, possessing ultra-low overpotential and long-term stability comparable to commercial Pt / C catalysts, and has been successfully applied to the reaction system of photocatalytic solar cells driving electrocatalytic hydrogen evolution. This invention is expected to promote the application of low-platinum-loading hydrogen evolution electrocatalysts in practical water electrolysis hydrogen evolution technology. Attached Figure Description

[0024] Figure 1 These are field emission scanning electron microscope (SEM) images of the composite material in the embodiments of the present invention, wherein (a) is the prepared MoO4. 2- - SEM image of the PDA self-assembled precursor, (b) is the pre-oxidized product MoO x SEM images of Pt@1T-MoS2 / C, (c) is the SEM image of the high-temperature sulfurized composite product 2H-MoS2 / C, and (d) and (e) are the SEM images of Pt@1T-MoS2 / C at different scales.

[0025] Figure 2 Transmission electron microscope (TEM) images of Pt@1T-MoS2 / C prepared for Examples 1 and 2 of this invention;

[0026] Figure 3The powder X-ray diffraction (XRD) spectra of the 2H-MoS2 / C and Pt@1T-MoS2 / C composite materials prepared in the embodiments of the present invention are shown below.

[0027] Figure 4 The Raman spectra of the 2H-MoS2 / C and Pt@1T-MoS2 / C composite materials prepared in the embodiments of the present invention are shown.

[0028] Figure 5 The Nyquist plots of the 2H-MoS2 / C and Pt@1T-MoS2 / C composite materials prepared in the embodiments of the present invention are shown below.

[0029] Figure 6 The polarization curves and Tafel slope diagrams of the 2H-MoS2 / C, Pt@1T-MoS2 / C composite materials and Pt / C samples prepared in the embodiments of the present invention are shown.

[0030] Figure 7 The current density-time variation graph is shown for the Pt@1T-MoS2 / C composite material prepared in Example 1 of this invention.

[0031] Figure 8 The Pt@1T-MoS2 / C composite material prepared in Example 1 of this invention is applied to a photovoltaic coupled water electrolysis hydrogen production system. Detailed Implementation

[0032] The present invention will now be described in conjunction with the accompanying drawings and examples, but the specific embodiments of the present invention are not limited thereto.

[0033] Example 1

[0034] A surface / interface engineering strategy for preparing low-platinum-loaded Pt@1T-MoS2 / C composite electrocatalysts:

[0035] (1) Preparation of MoO4 by room temperature self-polymerization 2- - PDA self-assembled body: At room temperature, 270 mg ammonium molybdate was dissolved in 72 mL of deionized water, and 270 mg dopamine hydrochloride was dissolved in 144 mL of ethanol. The two solutions were mixed under magnetic stirring, and then 1 mL of ammonia was added. After polymerization for 6 h, centrifugation was performed to obtain MoO4. 2- -PDA precursor.

[0036] (2) Pre-oxidized precursor MoO x / C: MoO4 2- The PDA was transferred to a vacuum tube furnace and heated to 450°C at a rate of 5°C / min in an Ar atmosphere. It was annealed for 2 hours and then allowed to cool naturally to obtain MoO. x / C nanoflower balls.

[0037] (3) High-temperature vulcanization strategy for preparing 2H-MoS2 / C composite materials: MoO2 was weighed at a ratio of 1:10. x / C and sublimed sulfur were sulfided in a vacuum tube furnace using an upstream and downstream method, heated to 800℃ in an Ar atmosphere at a heating rate of 5℃ / min, and annealed for 3h to obtain 2H-MoS2 / C.

[0038] (4) Preparation of Pt@1T-MoS2 / C composite material by impregnation-low temperature pyrolysis reduction method: Weigh 20mg 2H-MoS2 / C and disperse it in 20ml aqueous solution containing 4μmol chloroplatinic acid. After stirring at room temperature for 30min, the above liquid is rapidly frozen under the action of liquid nitrogen. After freeze drying, it is transferred to a vacuum tube furnace and heated to 400℃ at a heating rate of 5℃ / min under H2 / Ar mixed atmosphere. After reduction for 60min, it is naturally cooled to obtain Pt@1T-MoS2 / C composite material.

[0039] Example 2

[0040] The preparation method of the composite material is the same as that in Example 1, except that Pt species are not supported, resulting in a 2H-MoS2 / C composite electrocatalyst.

[0041] Example 3

[0042] The preparation method of the composite material was the same as in Example 1, except that the high-temperature sulfidation temperature was 600℃, resulting in the Pt@MoS2 / C-600 composite electrocatalyst. The morphology and structure of the obtained catalyst were not significantly different, but it exhibited poor conductivity and catalytic activity.

[0043] Comparison with Example 1

[0044] Commercial Pt / C catalysts:

[0045] A 20 wt% commercially available Pt / C catalyst was used as a control sample for evaluating the electrocatalytic hydrogen evolution performance. The test method was the same as that in Example 1, and the catalyst was labeled as Pt / C.

[0046] Structural analysis:

[0047] Figure 1 (a) Self-assembled MoO4 2- - SEM image of the PDA precursor, showing a hierarchical multilayer nanofloral structure with nanofloral sizes ranging from 500 to 800 nm. Figure 1 (b) is the pre-oxidized product MoO x SEM image of / C, maintaining MoO4 2- - Morphology, structure and size of multi-level hierarchical nanofloral balls of PDA precursor. Figure 1(c) is a SEM image of the 2H-MoS2 / C composite material, which shows that it still maintains a multi-level hierarchical nanofloral structure, but compared with MoO2... x The tiered and layered nanospheres of / C exhibit larger lattice areas, particularly those of 2H-MoS2 / C. This is because two-dimensional MoS2 lattices are formed during high-temperature vulcanization, and these lattices continue to grow epitaxially on the original lattice structure, resulting in a larger lattice area. Figure 1 (d) and (e) show SEM images of the Pt@1T-MoS2 / C composite material at different scales. It can be clearly observed that the Pt@1T-MoS2 / C composite material still maintains the morphological structure of multi-level layered nanoflowers with a large lamellar area.

[0048] Figure 2 The TEM image of Pt@1T-MoS2 / C shows that it has a hollow structure.

[0049] Figure 3 The XRD patterns confirmed that the main phase composition of the 2H-MoS2 / C composite material and the Pt@1T-MoS2 / C composite material is MoS2 and conductive carbon, and no diffraction peaks of Pt nanoparticles were found.

[0050] Figure 4 The Raman diagram shows that the MoS2 phase in the 2H-MoS2 / C composite material is mainly the semiconductor phase 2H-MoS2, while Pt@1T-MoS2 / C undergoes a phase transformation, changing from the 2H phase to the 1T metallic phase, indicating that the introduction of Pt can induce the transformation of 2H-MoS2 to 1T-MoS2.

[0051] Performance testing: A three-electrode system was used, with a reversible hydrogen electrode as the reference electrode, a carbon rod as the counter electrode, and a glassy carbon electrode or carbon paper with a catalyst supported as the working electrode, and the test was carried out in a 0.5M H2SO4 system.

[0052] Figure 5 The Nyquist plot shows that Pt@1T-MoS2 / C improves its intrinsic conductivity compared to 2H-MoS2 / C.

[0053] Figure 6 The LSV curve in (a) shows that the low platinum loading (Pt≈3.5wt%) Pt@1T-MoS2 / C has an apparent catalytic activity comparable to that of a commercial 20wt% Pt / C catalyst. Figure 6 The LSV curve in (b) shows that Pt@1T-MoS2 / C with low platinum loading (Pt≈3.5wt%) has the highest catalytic activity. Figure 6 Tafel in (c) indicates that Pt@1T-MoS2 / C has faster reaction kinetics, which can accelerate the hydrogen evolution reaction and reduce reaction energy consumption.

[0054] Figure 7 The current-time curves in the figure demonstrate that Pt@1T-MoS2 / C exhibits excellent stability.

[0055] Figure 8 This demonstrates the successful application of Pt@1T-MoS2 / C as a cathode catalyst in a photovoltaic-coupled water electrolysis hydrogen production system.

[0056] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A method for preparing a Pt@1T-MoS2 / C hydrogen evolution electrocatalyst by Pt atom substitution induced MoS2 phase transition, characterized in that: (4) a Pt@1T-MoS2 / C composite material is prepared by an impregnation-low temperature pyrolysis reduction method: 2H-MoS2 / C is weighed and immersed in a Pt salt solution of a certain concentration, the liquid is instantaneously frozen by liquid nitrogen treatment after stirring at room temperature, and low temperature reduction is performed under a H2 / Ar reduction atmosphere after freeze-drying, finally obtaining a Pt@1T-MoS2 / C composite material. (1) Preparation of molybdate ion-polydopamine (MoO4 2- -PDA) self-assembly: dissolve molybdate salt in aqueous solution, dissolve dopamine hydrochloride in ethanol, mix the two under stirring at room temperature, and self-assemble into molybdate ion-polydopamine (MoO4 2- -PDA) multi-level layered nanosphere precursor under the assistance of ammonia. (2) Preparation of pre-oxidized precursor MoO x / C: MoO4 2- -PDA was transferred to a vacuum tube furnace, and MoO x / C nanoflower balls; (3) Preparation of 2H-MoS2 / C composite: MoO x / C and sublimed sulfur were weighed according to a certain proportion, transferred to a vacuum tube furnace, and vulcanized at 800°C to obtain 2H-MoS2 / C; The molybdate in step (1) is one of ammonium molybdate, sodium molybdate and their hydrates.

2. The production method according to claim 1, wherein The temperature of the pre-oxidation pyrolysis in step (2) is controlled at 200-500℃.

3. The production method according to claim 1, wherein The molar ratio of molybdate ions and dopamine hydrochloride in step (1) is controlled between 2 and 3, MoO4 2- The morphology of the PDA self-assembly is a multi-level layered nanoflower ball.

4. The production method according to claim 1, wherein The Pt salt in step (4) is one of potassium chloroplatinate, platinum acetylacetonate, chloroplatinic acid and its hydrate, platinum nitrate and its hydrate, and platinum tetrachloride and its hydrate.

5. The production method according to claim 1, wherein MoO x The mass ratio of / C and sublimed sulfur is controlled at 1 : x, 1 < x < 20.

6. The production method according to claim 1, wherein The low temperature reduction in step (4) is performed under a H2 / Ar reduction atmosphere, and the temperature is controlled at 200-400℃.

7. The production method according to claim 1, wherein The structure of the Pt@1T-MoS2 / C composite material is that platinum monatomic atoms are loaded on carbon-supported molybdenum disulfide nanosheets.

8. The production method according to any one of claims 1 to 7, characterized by, ​

Images