Preparation method and application of phosphorus dichromium

Abstract

The application provides a preparation method of phosphorus dichromium, and steps of the method comprise the following: CoCl2, PCl5, NaCl, AlCl3 and aluminum powder are uniformly mixed, and then the mixture is placed in an inert atmosphere to react to obtain phosphorus dichromium. The method can prepare pure-phase phosphorus dichromium with ideal dendritic morphology, and the method has the characteristics of simplicity, low cost and scalable preparation. The phosphorus dichromium prepared by using the method has wide application potential and market prospect when used as an electrocatalyst for hydrogen evolution reaction (HER).

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method and application of phosphorus dichromium, and belongs to the technical field of catalyst materials for electrocatalytic hydrogen production. BACKGROUND

[0002] Transition metal phosphides have broad application prospects in the fields of electrocatalysis, energy storage and conversion, catalytic hydrogenation desulfurization or denitrification, etc. due to their unique structure and physical and chemical properties. Existing researches show that transition metal phosphides can be prepared by solvothermal method of organic phosphorus source (such as trioctylphosphine oxide, tributylphosphine, triphenylphosphine), thermal decomposition of inorganic phosphorus source (such as dihydrogen phosphate salt, elemental phosphorus) and hydrogen phosphide gas phase phosphidation method. However, these traditional routes have more or less the disadvantages of complex process, volatilization of toxic organic phosphorus source, release of highly toxic phosphine, and product pollution. Therefore, although facing great challenges, it is still of great significance to develop a low-toxicity, reliable, scalable and high-efficiency method for preparing transition metal phosphides. SUMMARY

[0003] According to one aspect of the application, a preparation method of phosphorus dichromium is provided, in which NaCl-AlCl3 is used as a molten salt system to construct a reaction liquid phase environment, CoCl2 is used as a cobalt source, low-toxicity PCl5 is used as a phosphorus source, and aluminum powder is used as a reducing agent, so that the phosphide of cobalt is finally prepared. The preparation method has low toxicity, low reaction temperature, repeatability and easy scaling.

[0004] The application adopts the following technical scheme:

[0005] According to another aspect of the application, a preparation method of phosphorus dichromium is provided, which comprises the following steps:

[0006] CoCl2, PCl5, NaCl, AlCl3 and aluminum powder are uniformly mixed and then placed in an inert atmosphere to react to obtain phosphorus dichromium.

[0007] Optionally, 1-3 parts by weight of CoCl2, 0.1-1 parts by weight of PCl5, 0.5-5 parts by weight of NaCl, 2-18 parts by weight of AlCl3 and 0.1-0.5 parts by weight of aluminum powder are uniformly mixed and then placed in an inert atmosphere to react.

[0008] Optionally, the reaction conditions include that the reaction temperature is 115-300 DEG C, the reaction time is 0.5-24 h, and natural cooling is performed.

[0009] Optionally, the reaction temperature is selected from any value in 115 DEG C, 140 DEG C, 170 DEG C, 200 DEG C, 230 DEG C, 260 DEG C and 300 DEG C, or a range value between any two thereof.

[0010] When the reaction temperature exceeds 300℃, the chlorides will evaporate to different degrees, the reaction will become more violent, the reaction will be rapid, which is not conducive to the control of the reaction, and there is a certain risk.

[0011] Optionally, the method further comprises washing and drying after the reaction is completed.

[0012] Optionally, the washing process comprises: adding water to the product after the reaction to wash, then centrifuging to obtain a solid, and then sequentially washing with hydrochloric acid, water, and ethanol, and then vacuum drying at room temperature.

[0013] The hydrochloric acid is prepared by mixing water and 37% concentrated hydrochloric acid at a volume ratio of 5-20:1.

[0014] Optionally, the dilute hydrochloric acid is prepared by mixing water and 37% concentrated hydrochloric acid at a volume ratio of 10:1.

[0015] Optionally, the drying is vacuum drying at room temperature.

[0016] Optionally, the reaction is carried out in a closed reactor with an inert atmosphere.

[0017] Optionally, the inert atmosphere is argon with a purity of not less than 99.99%.

[0018] Optionally, in the preparation method, the process of obtaining pure-phase di-cobalt phosphide mainly involves the following two reactions:

[0019] NaCl + AlCl3→ NaAlCl4 reaction (1)

[0020] 2CoCl2 + PCl5 + 3Al→ Co2P + 3AlCl3 reaction (2).

[0021] The above reactions undergo the following processes:

[0022] 1. NaCl and AlCl3 are melted to form a eutectic salt NaAlCl4;

[0023] 2. The reducing agent Al powder is ionized in the above molten salt Al→ Al 3+ + 3e, forming a highly active aluminum reducing substance;

[0024] 3. Co 2+ and P 5+ are co-reduced by the highly active aluminum reducing substance to P 3- , Co 1+ , Co 2+ , and finally Co2P and CoP are precipitated from the molten salt. Adjusting the corresponding reaction raw material portions within the reactant dosage range of the present application can realize the precipitation of pure-phase Co2P in the molten salt.

[0025] According to another aspect of the present application, there is provided a di-cobalt phosphide prepared according to the above preparation method, which is a particle having a nano-dendritic micro-morphology.

[0026] Optionally, the particle size of the di-cobalt phosphide particle is 0.3-5 μm.

[0027] According to yet another aspect of the present application, there is provided an application of the di-cobalt phosphide prepared according to the above preparation method as an electro-catalyst for hydrogen evolution reaction (HER).

[0028] Optionally, the loading amount of the di-cobalt phosphide as a catalyst for electro-catalytic hydrogen evolution reaction is 0.8-2 mg / cm 2 , and the catalytic reaction temperature is 25-80 °C.

[0029] Optionally, the loading amount of the di-cobalt phosphide as a catalyst for electro-catalytic hydrogen evolution reaction is 2 mg / cm 2 , and the catalytic reaction temperature is 80 °C.

[0030] The beneficial effects that can be produced by the present application include:

[0031] The preparation method of di-cobalt phosphide provided by the present application can avoid the volatilization of toxic organic phosphorus source in the preparation process of traditional transition metal phosphide, while avoiding the release of highly toxic phosphine, and can prepare pure-phase Co2P with ideal dendritic morphology in high quality. The method has the characteristics of simplicity, low cost and scale-up preparation. The di-cobalt phosphide prepared by the method has broad application potential and market prospect as an electro-catalyst for hydrogen evolution reaction (HER). BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 (a) XRD pattern and (b) SEM image of product #2 prepared in Example 2 of the present application;

[0033] Figure 2 (a) XRD pattern and (b) SEM image of product #4 prepared in Example 4 of the present application;

[0034] Figure 3 (a) XRD pattern and (b) SEM image of product #5 prepared in Example 5 of the present application;

[0035] Figure 4 (a) XRD pattern and (b) SEM image of product #6 prepared in Example 6 of the present application;

[0036] Figure 5 (a) XRD pattern and (b) SEM image of product #7 prepared in Example 7 of the present application;

[0037] Figure 6 Linear sweep voltammetry (LSV) curves of the product #7 prepared in Example 7 of this application for electrocatalytic hydrogen evolution reaction (HER) at different Co2P loadings and different temperatures;

[0038] Figure 7 The overpotential diagram for the electrocatalytic hydrogen evolution reaction (HER) of product #7 obtained in Example 7 of this application (product #7 loading is 2.0 mg cm⁻¹) -2 (The temperature is 80℃);

[0039] Figure 8 The graph shows the change in electrolytic current density over time during the electrocatalytic hydrogen evolution reaction (HER) of product #7 obtained in Example 7 of this application (product #7 loading was 2.0 mg / cm³). -2 (At a temperature of 25℃, the electrolysis potential is -0.3V);

[0040] Figure 9 This is a comparison of the linear sweep voltammetry (LSV) curves of product #7 prepared in Example 7 of this application before and after 24 hours of electrocatalytic hydrogen evolution reaction (HER) (product #7 loading was 2.0 mg / cm²). -2 (The temperature is 25℃). Detailed Implementation

[0041] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0042] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased commercially. Among them, aluminum powder, model 200 mesh, was purchased from Anaiji Chemical Technology (Shanghai) Co., Ltd.; carbon paper, model HCP120, was purchased from Shanghai Hesen Electric Co., Ltd.; carbon black, model SUPER-P, was purchased from Hefei Kejing Material Technology Co., Ltd.; and 20% Pt / C, model HPT020, was purchased from Shanghai Hesen Electric Co., Ltd.

[0043] In Examples 1 to 7 of this application, the yield (Q) of Co2P was calculated in the following manner:

[0044]

[0045] Q: Yield;

[0046] N: The number of metal atoms contained in a transition metal phosphide molecule;

[0047] m 产物 : The final mass (g) of the transition metal phosphide product obtained;

[0048] m 原料: Mass (g) of the added metal chloride raw material;

[0049] M 原料 : Relative molecular mass (g / mol) of the added metal chloride;

[0050] M 产物 : The relative atomic mass (g / mol) of the final transition metal phosphide product.

[0051] Example 1

[0052] 1.00g CoCl2 and 0.80g PCl5 were thoroughly mixed in a glove box filled with argon (99.99%) and sealed in a reactor. The reactor was then placed at 115℃ for 5 hours. After the reaction was completed, the reactor was allowed to cool naturally and then opened. No solid product was found, indicating that the raw materials did not react under the reaction conditions.

[0053] Example 2

[0054] 1.00 g CoCl2, 0.80 g PCl5, and 0.32 g aluminum powder were thoroughly mixed in a glove box filled with argon (99.99%) and sealed in a reactor. The reactor was then placed at 115 °C for 5 h. After the reaction was complete, the reactor was allowed to cool naturally. The reactor was then opened and deionized water was injected into it for washing. The mixture was then centrifuged and washed with dilute hydrochloric acid (prepared by mixing water and 37% concentrated hydrochloric acid in a volume ratio of 10:1), deionized water, and ethanol, respectively. The mixture was then vacuum dried at room temperature to obtain solid product #2.

[0055] Example 3

[0056] 1.00 g CoCl2, 0.80 g PCl5, 2.00 g NaCl, and 7.14 g AlCl3 were thoroughly mixed in a glove box filled with 99.99% argon gas and then sealed in a reactor. The reactor was then placed at 115 °C for 5 hours. After the reaction was complete, the reactor was allowed to cool naturally and then opened. No solid product was found, indicating that the raw materials did not react under the reaction conditions.

[0057] Example 4

[0058] 1.00g CoCl2, 0.80g PCl5, 2.00g NaCl, 7.14g AlCl3, and 0.32g aluminum powder were thoroughly mixed in a glove box filled with 99.99% argon gas and sealed in a reactor. The reactor was then placed at 115℃ for 5 hours. After the reaction was completed, the reactor was allowed to cool naturally. The reactor was then opened and deionized water was injected into it for washing. The mixture was then centrifuged and washed with dilute hydrochloric acid (prepared by mixing water and 37% concentrated hydrochloric acid in a volume ratio of 10:1), deionized water, and ethanol, respectively. The mixture was then vacuum dried at room temperature to obtain solid product #4.

[0059] Example 5

[0060] 1.00g CoCl2, 0.80g PCl5, 2.00g NaCl, 7.14g AlCl3, and 0.32g aluminum powder were thoroughly mixed in a glove box filled with 99.99% argon gas and sealed in a reactor. The reactor was then placed at 200℃ for 5 hours. After the reaction was completed, the reactor was allowed to cool naturally. The reactor was then opened and deionized water was injected into it for washing. The mixture was then centrifuged and washed with dilute hydrochloric acid (prepared by mixing water and 37% concentrated hydrochloric acid at a volume ratio of 10:1), deionized water, and ethanol, respectively. The mixture was then vacuum dried at room temperature to obtain solid product #5.

[0061] Example 6

[0062] 1.00g CoCl2, 0.80g PCl5, 2.00g NaCl, 7.14g AlCl3, and 0.32g aluminum powder were thoroughly mixed in a glove box filled with argon (99.99%) and sealed in a reactor. The reactor was then placed at 300℃ for 5 hours. After the reaction was completed, the reactor was allowed to cool naturally. The reactor was then opened and deionized water was injected into it for washing. The mixture was then centrifuged and washed with dilute hydrochloric acid (prepared by mixing water and 37% concentrated hydrochloric acid at a volume ratio of 10:1), deionized water, and ethanol, respectively. The mixture was then vacuum dried at room temperature to obtain solid product #6.

[0063] Example 7

[0064] 100g CoCl2, 80g PCl5, 200g NaCl, 714g AlCl3, and 32g aluminum powder were thoroughly mixed in a glove box filled with argon (99.99%) and sealed in a reactor. The reactor was then placed at 200℃ for 5 hours. After the reaction was completed, the reactor was allowed to cool naturally. The reactor was then opened and deionized water was injected into it for washing. The mixture was then centrifuged and washed with dilute hydrochloric acid (prepared by mixing water and 37% concentrated hydrochloric acid in a volume ratio of 10:1), deionized water, and ethanol, respectively. The mixture was then vacuum dried at room temperature to obtain solid product #7.

[0065] The raw material amounts and corresponding yields for preparing Co2P solid products in Examples 1-7 are shown in Table 1.

[0066] Table 1

[0067]

[0068] Test Example 1

[0069] XRD analysis was performed using a Miniflex 600 X-ray diffractometer manufactured by Rigaku Corporation of Japan.

[0070] XRD characterization was performed on the samples in Examples 2, 4 to 7. Typical characterization results are as follows: Figures 1 to 5 As shown in (a). The results show that CoCl2, PCl5, and aluminum powder can react directly at 115°C in Example 2, but the product #2 after the reaction forms a mixed phase of Co2P and CoP. When NaCl and AlCl3 molten salt are added, the solid products #4, #5, and #6 prepared by CoCl2, PCl5, and aluminum powder at 115°C (Example 4), 200°C (Example 5), and 300°C (Example 6) are all pure phase Co2P. In addition, when the synthesis scale of Example 5 is increased by 100 times at 200°C (Example 7), the product #7 prepared is also pure phase Co2P.

[0071] Test Example 2

[0072] The morphology of the products was analyzed using a scanning electron microscope (SEM) of model Zeiss-Sigma 300 manufactured by the German Zeiss Group.

[0073] SEM characterization was performed on the samples in Examples 2, 4 to 7. Typical characterization results are as follows: Figures 1 to 5 As shown in (b). The results show that the product #2, which is formed by the direct reaction of CoCl2, PCl5, and aluminum powder at 115℃, has an irregular nanoparticle morphology. When NaCl and AlCl3 molten salt are added, the solid products #4, #5, and #6 prepared by CoCl2, PCl5, and aluminum powder at 115℃ (Example 4), 200℃ (Example 5), and 300℃ (Example 6) can all form nanodendritic morphologies. In addition, when the synthesis scale is increased by 100 times at 200℃ (Example 7), the product #7 also has a nanodendritic microstructure.

[0074] Test Example 3

[0075] The performance of the electrolysis system was analyzed using an electrochemical workstation, model CHI660E, manufactured by Shanghai Chenhua Instrument Co., Ltd.

[0076] The product #7 (dendritic Co2P) prepared in Example 7 was used for performance testing of the hydrogen evolution reaction (HER) electrocatalyst. Figure 6 To determine the different dendritic Co2P loading levels (0.8 mg / cm³), -2 1.6mg cm -2 2.0mg cm -2 Linear sweep voltammetry (LSV) curves of dendritic Co2P and control samples (carbon paper, carbon black, and commercial 20% Pt / C) at different temperatures (25℃, 50℃, and 80℃) were obtained. The results showed that dendritic Co2P can electrocatalyze HER at low overpotentials, and the overpotential gradually decreases with increasing loading and temperature, especially at a loading of 2.0 mg / cm³. -2 It exhibits electrocatalytic HER performance close to that of commercially available 20% Pt / C at a temperature of 80℃. Figure 7 As shown, when the dendritic Co2P loading is 2.0 mg cm⁻¹ -2 At a temperature of 80℃, its electrocatalytic HER overpotential is only 98mV, close to the 60mV of commercial 20% Pt / C.

[0077] Figure 8 Dendritic Co2P (with a loading of 2.0 mg cm⁻¹) was observed. -2 The stability of electrocatalyzed HER (at a temperature of 25℃) was investigated. The results showed that at an electrolysis potential of -0.3V (vs. RHE), the electrolysis current density remained relatively stable over a 24-hour stability test, maintaining a current density of approximately 120 mA cm⁻¹. -2 This indicates that the electrocatalytic HER performance of dendritic Co2P remains stable. Furthermore, the LSV test was repeated on the dendritic Co2P electrode after 24 hours of electrocatalytic HER, as shown... Figure 9 As shown, the results indicate that the LSV curve of the dendritic Co2P electrode for electrocatalytic HER only showed a slight shift before and after the 24-hour stability test, further demonstrating that the dendritic Co2P has good electrocatalytic stability for HER.

[0078] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing cobalt diphosphide, characterized in that, The preparation method includes the following steps: Cobalt phosphide is obtained by mixing 1-3 parts by weight of CoCl2, 0.1-1 parts by weight of PCl5, 0.5-5 parts by weight of NaCl, 2-18 parts by weight of AlCl3, and 0.1-0.5 parts by weight of aluminum powder evenly and reacting them in an inert atmosphere. The reaction conditions include: a reaction temperature of 115~300℃, a reaction time of 0.5~24h, and natural cooling.

2. The preparation method according to claim 1, characterized in that, The inert atmosphere is argon gas with a purity of not less than 99.99%.

3. The preparation method according to claim 2, characterized in that, The steps also include washing and drying after the reaction is complete.

4. The preparation method according to claim 3, characterized in that, The washing and drying process includes: adding water to the product after the reaction for washing, then centrifuging to obtain a solid, and washing it in sequence with hydrochloric acid, water and ethanol, and then drying it under vacuum at room temperature.

5. Cobalt phosphide prepared by the preparation method according to any one of claims 1 to 4, characterized in that, The cobalt phosphide is composed of particles with a nano-dendritic microstructure. The cobalt phosphide particles have a particle size of 0.3~5μm.

6. The application of cobalt phosphide prepared by the preparation method according to any one of claims 1 to 4 as an electrocatalyst for hydrogen evolution reaction (HER).

7. The application according to claim 6, characterized in that, When cobalt phosphide is used as a catalyst in the electrocatalytic hydrogen evolution reaction, the loading is 0.8~2 mg / cm³. 2 The catalytic reaction temperature is 25~80℃.

8. The application according to claim 6, characterized in that, When cobalt phosphide is used as a catalyst in the electrocatalytic hydrogen evolution reaction, the loading is 2 mg / cm³. 2 The catalytic reaction temperature is 80℃.

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