CN115928122A - Nickel phosphide electrocatalytic material and preparation method thereof - Google Patents

Abstract

The invention relates to a nickel phosphide electrocatalytic composite material and a preparation method thereof, belonging to the technical field of electrocatalytic hydrogen production. The invention adopts an in-situ self-growth strategy and prepares nickel phosphide/nickel foam (Ni) with the characteristics of good substrate adhesion, mechanical stability, conductivity and the like by a simple two-step method of in-situ synthesis and low-temperature phosphorization ₂ P/NF) electrocatalytic composite material. Under alkaline condition, ni prepared by the invention ₂ The P/NF electrocatalytic composite material has the current density of 10 mA/cm ² The overpotential of the capacitor is only 189mV, and the electric double layer capacitor (C) _dl ) The value is as high as 30.68 mF/cm ² Provides a new material design and synthesis technology for efficiently obtaining clean hydrogen energy.

Description

A kind of nickel phosphide electrocatalytic material and preparation method thereof

technical field

The invention relates to a nickel phosphide electrocatalytic composite material and a preparation method thereof, belonging to the technical field of electrocatalytic hydrogen production.

Background technique

The massive exploitation of global fossil fuels has led to serious energy crisis and environmental pollution, so people have put forward an urgent demand for clean, economical and sustainable energy. As an inexhaustible clean energy with wide sources and high energy density, hydrogen energy can gradually replace strategic energy commodities such as oil and natural gas, and can ensure energy security and diversification. It is an ideal energy category to form an efficient, safe and stable multi-energy complementary energy system, and will play an important role in realizing the goal of "carbon peaking and carbon neutrality". Hydrogen production by electrolysis of water has attracted much attention due to its low energy consumption, low greenhouse gas emissions during the entire production process, high purity of hydrogen produced, and low impurity content.

At present, platinum (Pt)-based noble metals are the best electrocatalysts for hydrogen evolution reaction (HER), but their high price and scarce resources limit their large-scale application. Therefore, the preparation of low-cost, high-efficiency, and stable non-noble metal catalysts has become one of the current research hotspots. Among them, transition metal compounds (including transition metal carbides, transition metal sulfides, transition metal nitrides, transition metal oxides, transition metal phosphides and transition metal selenides) have unique physical and chemical properties, a wide range of sources, and low prices. characteristics have attracted much attention. However, most metals show poor hydrogen evolution performance due to the strong force between the adsorbed hydrogen and the metal surface in the process of hydrogen production by electrolysis of water. However, in transition metal phosphides, P can enter the metal lattice, "dilute" the metal atoms and maintain the electronic structure of the metal basically unchanged, thereby reducing the free energy of hydrogen adsorption and facilitating the desorption of hydrogen. At the same time, P has high electronegativity and can capture electrons from metal elements. Negatively charged P can also be used as an active site for absorbing hydrogen, and the formed covalent bond (metal-phosphorus bond) can also improve the energy efficiency of metal phosphides. stability.

Nickel phosphide has a variety of different component chemical formulas and a catalytic mechanism similar to hydrogenase. Scholars at home and abroad have carried out a lot of research in this field. For example, the publication number is CN 110512228 A, which uses electroless plating to prepare nickel hydroxide/foam nickel precursor containing nickel phosphorus coating, and then prepares nickel phosphide/foam nickel self-supporting electrode by phosphating. The operation process is complicated, and the precursor Many raw materials are used in the preparation process, and nickel sulfate needs to be added as a nickel source. The formed precursor has weak adhesion to the nickel foam substrate, resulting in poor stability of the prepared nickel phosphide/nickel foam self-supporting electrode. Publication No. CN113881964 A discloses a preparation method of sheet-like nickel phosphide array electrode material. First, cetyltrimethylammonium bromide and hydrogen peroxide are used to activate foamed nickel to obtain sheet-shaped nickel hydroxide array/foamed nickel The precursor was phosphated at 400°C for 1 hour to obtain a nickel phosphide/nickel foam electrode. There is no need to add nickel source in the preparation process, but the preparation period is long, the operation process is complicated, and surfactants are required.

In view of some of the above problems, it is particularly important to prepare an efficient, stable, green and economical electrocatalytic composite material through a simple process.

The nickel foam used in the present invention directly provides a nickel source for the formation of Ni(OH) ₂ without adding an additional nickel source. Therefore, the prepared precursor can be rooted in NF, has good substrate adhesion, electrical conductivity and mechanical stability, and these characteristics can still be maintained after low-temperature in-situ phosphating.

Contents of the invention

The first technical problem solved by the present invention is to provide an electrocatalytic composite material with good substrate adhesion, electrical conductivity and mechanical stability prepared by adopting a self-growth strategy.

The second technical problem solved by the present invention is to provide a method for preparing an electrocatalytic composite material, comprising the following steps:

a. Dissolve urea (CO(NH ₂ ) ₂ ) and ammonium fluoride (NH ₄ F) in 70 mL of deionized water, and stir evenly to obtain a mixed solution;

b. Transfer the mixed solution obtained in step a together with the processed nickel foam (NF) sheet to a polytetrafluoroethylene-lined hydrothermal kettle, put it into an oven for hydrothermal reaction, and cool it down after the hydrothermal treatment ends to room temperature, washed with deionized water and ethanol, and vacuum-dried to obtain a Ni(OH) ₂ /NF precursor;

c. Use sodium hypophosphite (NaH ₂ PO ₂ ·H ₂ O) as the phosphorus source and place it at the tail of the quartz boat, place the precursor obtained in step b on the top of the quartz boat, and transfer it to a tube furnace with a nitrogen atmosphere Heating and phosphating, washing with deionized water and ethanol after cooling down to room temperature, and drying to obtain Ni ₂ P/NF electrocatalytic composite material.

In one embodiment, in step a, the urea concentration is 5-20 mmol/L; preferably, the urea concentration is 15 mmol/L.

In one embodiment, in step b, the hydrothermal temperature is 125°C to 200°C; preferably, the hydrothermal temperature is 150°C.

In one embodiment, in step b, the hydrothermal time is 6-12 hours; preferably, the hydrothermal time is 8 hours.

In one embodiment, in step c, the amount of phosphorus source is 8:1-16:1; preferably, the amount of phosphorus source is 10:1.

In one embodiment, in step c, the heating rate is 1° C./min˜5° C./min; preferably, the heating rate is 1° C./min.

In one embodiment, in step c, the heating temperature is 240°C-300°C; preferably, the holding time is 290°C.

In one embodiment, in step c, the heating and holding time is 1 to 3 hours; preferably, the holding time is 2 hours.

The third technical problem solved by the present invention is to provide an application of the electrocatalytic composite material, which is used for high-efficiency electrolysis of water to produce hydrogen.

Beneficial effects of the present invention:

1. In the electrocatalytic composite material of the present invention, NF itself is used as Ni source, and ammonium fluoride is used as an etchant to release Ni ions from NF, Ni ions slowly precipitate, and react in situ to form Ni(OH) ₂ precursors, This self-growth strategy increases the adhesion between the catalyst and the conductive substrate, effectively improving the durability and stability of the material.

2. The present invention adopts low-cost hydrothermal method and low-temperature phosphating method, the preparation method is simple, the conditions are mild, the source of raw materials is wide, and the cost is low.

Description of drawings

FIG. 1 is the XRD pattern of the Ni ₂ P/NF-8:1 electrocatalytic composite material obtained in Example 1.

Fig. 2 is the LSV curve of the Ni ₂ P/NF-8:1 electrocatalytic composite material obtained in Example 1.

Fig. 3 is the C _dl diagram of the Ni ₂ P/NF-8:1 electrocatalytic composite material obtained in Example 1.

Fig. 4 is the XRD pattern of Ni ₂ P/NF-10:1 electrocatalytic composite material obtained in embodiment 2

Fig. 5 is the LSV curve of the Ni ₂ P/NF-10:1 electrocatalytic composite material obtained in Example 2.

Fig. 6 is the C _dl diagram of the Ni ₂ P/NF-10:1 electrocatalytic composite material obtained in Example 2.

FIG. 7 is the XRD pattern of the Ni ₂ P/NF-12:1 electrocatalytic composite material obtained in Example 3.

Fig. 8 is the LSV curve of the Ni ₂ P/NF-12:1 electrocatalytic composite material obtained in Example 3.

FIG. 9 is the C _dl diagram of the Ni ₂ P/NF-12:1 electrocatalytic composite material obtained in Example 1.

Detailed ways

The specific implementation of the present invention will be further described below in conjunction with the examples, and the present invention is not limited to the scope of the examples.

Electrocatalytic test

The electrocatalytic hydrogen evolution reaction test was carried out in a KOH solution with a concentration of 1M. The size of the Ni ₂ P/NF composite material was 1*1cm, with a carbon rod as the counter electrode, Hg/HgO as the reference electrode, and a glassy carbon electrode clamp. The Ni ₂ P/NF composite material was used as the working electrode, and the electrochemical performance test was carried out on an electrochemical workstation DH7000 (Donghua Test).

Example 1

Synthesis:

a. Dissolve 0.047g of urea (CO(NH ₂ ) ₂ ) and 0.023g of ammonium fluoride (NH ₄ F) in 70mL of deionized water, and stir evenly to obtain a mixed solution;

b. Transfer the mixed solution obtained in step a together with the processed nickel foam (NF) sheet to a polytetrafluoroethylene-lined hydrothermal kettle, put it in an oven at 125°C for 6 hours, and cool it down after the hydrothermal treatment ends to room temperature, washed with deionized water and ethanol, and vacuum-dried at 60°C to obtain a Ni(OH) ₂ /NF precursor;

c. Use sodium hypophosphite (NaH ₂ PO ₂ ·H ₂ O) with a mass ratio of 8:1 as the phosphorus source and place it at the tail of the quartz boat, place the precursor obtained in step b on the top of the quartz boat, and transfer to In a tube furnace in a nitrogen atmosphere, the temperature was raised to 300 °C for 1 h at 2 °C/min, and after cooling down to room temperature, it was washed with deionized water and ethanol, and dried to obtain a Ni ₂ P/NF-8:1 electrocatalytic composite material.

Fig. 1 is the XRD pattern of Ni ₂ P/NF-8:1 electrocatalytic composite material obtained in Example 1 of the present invention, as can be seen from Fig. 1, the XRD of Ni ₂ P/NF-8:1 prepared in Example 1 The results are consistent with the standard diffraction peaks, and there are no other impurities, which proves the success of phosphating.

Fig. 2 is the LSV diagram of the Ni ₂ P/NF-8:1 electrocatalytic composite material obtained in Example 1 of the present invention, as can be seen from Fig. 2, the Ni ₂ P/NF-8:1 electrocatalytic composite material obtained in Example 1 The overpotential is 263mV when the current density is 10mA cm ^-2 .

Fig. 3 is the C _dl value of Ni ₂ P/NF-8:1 electrocatalytic composite material obtained in Example 1 of the present invention, as can be seen from Fig. 3, the Ni ₂ P/NF-8:1 that embodiment 1 makes The C _dl value is 14.83 mF/cm ² .

Example 2

Synthesis:

a. Dissolve 0.063g of urea (CO(NH ₂ ) ₂ ) and 0.023g of ammonium fluoride (NH ₄ F) in 70mL of deionized water, and stir evenly to obtain a mixed solution;

b. Transfer the mixed solution obtained in step a together with the processed nickel foam (NF) sheet to a polytetrafluoroethylene-lined hydrothermal kettle, put it in an oven at 150°C for 8 hours, and cool it after the hydrothermal treatment ends to room temperature, washed with deionized water and ethanol, and vacuum-dried at 60°C to obtain a Ni(OH) ₂ /NF precursor;

c. Use sodium hypophosphite (NaH ₂ PO ₂ ·H ₂ O) with a mass ratio of 10:1 as the phosphorus source and place it at the tail of the quartz boat, place the precursor obtained in step b on the top of the quartz boat, and transfer to In a tube furnace in a nitrogen atmosphere, the temperature was raised to 290 °C for 2 h at 1 °C/min, and after cooling down to room temperature, it was washed with deionized water and ethanol, and dried to obtain a Ni ₂ P/NF-10:1 electrocatalytic composite material.

Fig. 4 is the XRD pattern of Ni ₂ P/NF-10:1 electrocatalytic composite material obtained in Example 2 of the present invention, as can be seen from Fig. 4, the XRD of Ni ₂ P/NF-10:1 prepared in Example 2 The results are consistent with the standard diffraction peaks, and there are no other impurities, which proves the success of phosphating.

Fig. 5 is the LSV diagram of the Ni ₂ P/NF-10:1 electrocatalytic composite material obtained in Example 2 of the present invention, as can be seen from Fig. 5, the Ni ₂ P/NF-10:1 electrocatalytic composite material obtained in Example 2 The overpotential is 189mV at a current density of 10mA cm ^-2 .

Fig. 6 is the C _dl value of the Ni ₂ P/NF-10:1 electrocatalytic composite material obtained in Example 2 of the present invention, as can be seen from Fig. 6, the Ni ₂ P/NF-10:1 that the embodiment 2 makes The C _dl value is 30.18 mF/cm ² .

Example 3

Synthesis:

a. Dissolve 0.084g of urea (CO(NH ₂ ) ₂ ) and 0.023g of ammonium fluoride (NH ₄ F) in 70mL of deionized water, and stir evenly to obtain a mixed solution;

b. Transfer the mixed solution obtained in step a together with the processed nickel foam (NF) sheet to a polytetrafluoroethylene-lined hydrothermal kettle, put it in an oven at 175°C and keep it warm for 10h, and cool it down after the hydrothermal treatment ends to room temperature, washed with deionized water and ethanol, and vacuum-dried at 60°C to obtain a Ni(OH) ₂ /NF precursor;

c. Use sodium hypophosphite (NaH ₂ PO ₂ ·H ₂ O) with a mass ratio of 12:1 as the phosphorus source and place it at the tail of the quartz boat, place the precursor obtained in step b on the top of the quartz boat, and transfer to In a nitrogen atmosphere tube furnace, the temperature was raised to 280°C for 3h at 5°C/min, and after cooling down to room temperature, it was washed with deionized water and ethanol, and dried to obtain Ni ₂ P/NF-12:1 electrocatalytic composite material.

Fig. 7 is the XRD pattern of the Ni ₂ P/NF-12:1 electrocatalytic composite material obtained in Example 3 of the present invention, as can be seen from Fig. 7, the XRD of Ni ₂ P/NF-12:1 prepared in Example 3 The results are consistent with the standard diffraction peaks, and there are no other impurities, which proves the success of phosphating.

Fig. 8 is the LSV diagram of the Ni2P/NF-12:1 electrocatalytic composite material obtained in Example 3 of the present invention, as can be seen from Fig. 8, the _Ni2P /NF-12:1 electrocatalytic composite material obtained in Example 3 is The overpotential at a density of 10mA cm ^-2 is 216mV.

Fig. 9 is the C _dl value of Ni ₂ P/NF-12:1 electrocatalytic composite material obtained in Example 3 of the present invention, as can be seen from Fig. 9, Ni ₂ P/NF-12:1 prepared in Example 3 The C _dl value is 19.33 mF/cm ² .

Claims (10)

1. A nickel phosphide electrocatalytic composite material and a preparation method thereof are characterized in that: the invention adopts a self-growth strategy and prepares nickel phosphide/nickel foam (Ni) with the characteristics of good substrate adhesion, mechanical stability, conductivity and the like by a simple two-step method of in-situ synthesis and low-temperature phosphorization ₂ P/NF) electrocatalytic composite material to realize excellent hydrogen production performance by electrocatalytic decomposition of water.

2. The nickel phosphide electrocatalytic composite material as set forth in claim 1 and the preparation method thereof, characterized by comprising the steps of:

a. taking urea (CO (NH) ₂ ) ₂ ) Ammonium fluoride (NH) ₄ F) Dissolving in 70mL of deionized water, and uniformly stirring to obtain a mixed solution;

b. mixing the mixed solution obtained in the step a with treated foam Nickel (NF)) Transferring the slices into a hydrothermal kettle with a polytetrafluoroethylene lining, putting the hydrothermal kettle into an oven for hydrothermal reaction, cooling to room temperature after hydrothermal reaction, washing with deionized water and ethanol, and vacuum drying to obtain Ni (OH) ₂ a/NF precursor;

c. with sodium hypophosphite (NaH) ₂ PO ₂ ·H ₂ O) is used as a phosphorus source and is placed at the tail part of the quartz boat, the precursor obtained in the step b is placed at the top of the quartz boat, the quartz boat is transferred into a tube furnace with nitrogen atmosphere for heating and phosphorization, the temperature is reduced to room temperature, then deionized water and ethanol are used for cleaning, and drying is carried out to obtain Ni ₂ P/NF electrocatalytic composite material.

3. The nickel phosphide electrocatalytic composite material and the preparation method thereof as claimed in claim 2, wherein: in the step a, the concentration of the urea is 5-20 mmol/L.

4. The nickel phosphide electrocatalytic composite material and the preparation method thereof as claimed in claim 2, wherein: in the step b, the hydrothermal temperature is 125-200 ℃.

5. The nickel phosphide electrocatalytic composite material and the preparation method thereof as claimed in claim 2, wherein: in the step b, the hydrothermal time is 6-12 h.

6. The nickel phosphide electrocatalytic composite material and the preparation method thereof as claimed in claim 2, wherein the nickel phosphide electrocatalytic composite material comprises the following components in percentage by weight: in the step c, the dosage of the phosphorus source is 8:1-16 by mass ratio.

7. The nickel phosphide electrocatalytic composite material and the preparation method thereof as claimed in claim 2, wherein: in the step c, the heating rate is 1-5 ℃/min.

8. The nickel phosphide electrocatalytic composite material and the preparation method thereof as claimed in claim 2, wherein: in the step c, the heating temperature is 240-300 ℃.

9. The nickel phosphide electrocatalytic composite material and the preparation method thereof as claimed in claim 2, wherein: in the step c, the heating and heat preservation time is 1-3 h.

10. Use of a nickel phosphide electrocatalytic composite material as set forth in claim 1 or prepared by the preparation method as set forth in any one of claims 2 to 8 as an electrocatalytic water decomposition catalyst.

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