阅读说明：本技术 一种镍铁基磷化物电催化材料及其制备方法和应用 (Nickel-iron-based phosphide electrocatalytic material and preparation method and application thereof ) 是由 黄明华 王岩 汪兴坤 张树聪 于 2021-07-19 设计创作，主要内容包括：本发明提供了一种镍铁基磷化物电催化材料及其制备方法和应用,首先通过低温磷化法得到磷化镍纳米棒修饰的镍泡沫材料(Ni-(x)P/NF),随后通过电沉积方法在Ni-(x)P/NF上均匀生长非晶态镍铁(氧)氢氧化物(Ni,Fe)OOH纳米颗粒,即得到(Ni,Fe)OOH@Ni-(x)P/NF异质结构OER电催化剂。通过该方法得到的(Ni,Fe)OOH@Ni-(x)P/NF材料具有明显的异质界面、丰富的活性位点以及快速的电荷传输能力,在碱性海水中展现了优异的电催化OER活性。同时,该催化剂在电化学反应过程中可以形成磷酸根阴离子来抵抗海水中氯离子的腐蚀,进而使其表现出长期稳定性。(Ni,Fe)OOH@Ni-(x)P/NF制备方法简单高效且成本低廉,这对于开发新型电解海水OER电催化剂具有重要意义。(The invention provides a nickel-iron-based phosphide electrocatalytic material and a preparation method and application thereof x P/NF) followed by electrodeposition on Ni x Uniformly growing amorphous ferronickel (oxygen) hydroxide (Ni, Fe) OOH nano particles on P/NF to obtain (Ni, Fe) OOH @ Ni x P/NF heterostructure OER electrocatalysts. (Ni, Fe) OOH @ Ni obtained by the method x The P/NF material has obvious heterogeneous interface, rich active sites and rapid charge transmission capability, and shows excellent electrocatalytic OER activity in alkaline seawater. Meanwhile, the catalyst can form phosphate anions to resist corrosion of chloride ions in seawater in the electrochemical reaction process, so that the catalyst shows long-term stability. (Ni, Fe) OOH @ Ni x The preparation method of the P/NF is simple, efficient and low in cost, and is suitable for developing the novel electrolytic seawater OER (organic electroluminescent device) electrocatalysisThe reagent is of great significance.)

1. The preparation method of the nickel-iron-based phosphide electrocatalytic material is characterized by comprising the following steps of:

(1) the pretreatment process comprises the following steps: the size is 1 × 1cm²～2×2cm²Respectively ultrasonically cleaning NF for 5-20 min by using absolute ethyl alcohol and deionized water, removing impurities on the surface of the NF, and drying the NF subjected to ultrasonic treatment in vacuum at 40-80 ℃ to obtain clean NF;

(2) and (3) phosphorization process: placing the NF and the sodium hypophosphite obtained in the step (1) into a tubular furnace, heating to 100-600 ℃ by a heating program of 1-10 ℃/min under the protection of argon gas, preserving the heat for 30-180 min, naturally cooling to room temperature, performing ultrasonic treatment, cleaning with deionized water, and drying to obtain the nickel foam electrode Ni modified by the nickel phosphide nanorod_xP/NF；

(3) And (3) an electrodeposition process: mixing Ni in the step (2)_xThe P/NF is put into a prepared ferronickel deposition solution, the total amount of ferronickel ions in the deposition solution is 0.1-2 mM, and the ferronickel ionsThe molar concentration ratio of (1-9: 1), and depositing for 5-60 min at a voltage of-2.0V and a stirring speed of 100-500 rpm to obtain amorphous (Ni, Fe) OOH modified Ni_xP/NF electrode, noted as (Ni, Fe) OOH @ Ni_xP/NF。

2. The method for preparing a nickel iron-based phosphide electrocatalytic material as set forth in claim 1, wherein the size of NF in the step (1) is 1 x 2cm²The ultrasonic cleaning time of absolute ethyl alcohol and deionized water is 5-15 min, and the vacuum drying temperature is 40-70 ℃.

3. The method for preparing the nickel-iron-based phosphide electrocatalytic material as set forth in claim 1, wherein NF and NaH in the step (2)₂PO₂The mass ratio of the components is 1: 3-6, the heating rate is 1-4 ℃/min, the heating temperature is 150-400 ℃, and the heat preservation time is 30-90 min.

4. The method for preparing the nickel-iron-based phosphide electro-catalytic material as claimed in claim 1, wherein the stirring speed in the step (3) is 100-300 rpm, the deposition time is 5-35 min, the total amount of nickel-iron ions in the deposition solution is 0.2-0.8 mM, and the molar concentration ratio of the nickel-iron ions is 2-5: 1.

5. A nickel iron-based phosphide electrocatalytic material prepared by the preparation method as set forth in any one of claims 1 to 4.

6. The use of a nickel iron based phosphide electrocatalytic material as claimed in claim 5 in electrolysis of seawater for oxygen evolution reaction.

7. The use of the nickel-iron-based phosphide electrocatalytic material as set forth in claim 6 in the electrolytic seawater oxygen evolution reaction, wherein said nickel-iron-based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni_xThe P/NF is used as a working electrode, and the electrolyte in the electrocatalysis process is seawater.

8. The use of the nickel-iron based phosphide electrocatalytic material as set forth in claim 7 in electrolysis of seawater for oxygen evolution reaction, wherein said seawater electrolyte is alkaline seawater.

9. The application of the nickel-iron-based phosphide electro-catalytic material in seawater electrolysis oxygen evolution reaction according to claim 8, wherein the alkaline seawater is prepared from 0.1-1.0M KOH and natural seawater.

Technical Field

The invention belongs to the field of electrochemical energy materials, particularly relates to a nickel-iron-based phosphide electrocatalytic material and a preparation method and application thereof, and particularly relates to a nickel-iron-based phosphide electrocatalytic material for seawater electrolysis and oxygen evolution and a preparation method thereof.

Background

In order to deal with global environment deterioration and energy crisis caused by the transitional consumption of fossil fuels, China puts forward the aim that the emission of carbon dioxide reaches the peak value in 2030 years, strives to achieve the solemn double-carbon target promise of carbon neutralization in 2060 years, and the renewable clean energy is more and more widely concerned by people. Hydrogen (H)₂) As a clean, pollution-free, widely-available and abundantly-applied green energy source, the green energy source is considered to be the most ideal and most potential energy carrier in the future, so that the development and utilization of hydrogen energy are important media for accelerating the realization of the carbon peak-reaching, carbon neutralization and double-carbon targets in China. The hydrogen production by electrolysis of water is a very effective and sustainable technology with simple equipment and H production₂High purity, high conversion efficiency and the like, and shows vigorous vitality. It is mainly composed of two basic reactions, the cathodic Hydrogen Evolution Reaction (HER) and the anodic Oxygen Evolution Reaction (OER). Compared with HER, OER reaction involves a complex multi-proton/electron coupling process, the reaction kinetics is slow, which becomes a main bottleneck restricting the hydrogen production efficiency by water electrolysis, and the development of an excellent electrocatalyst to improve the reaction kinetics of OER has a very important meaning. The most commonly used OER electrocatalysts at present are still noble metal based materials (e.g., RuO)₂，IrO₂) But the price is high and the reserves are scarce, so that the large-scale application and development of the composite material are limited. In order to improve the efficiency of hydrogen production by water electrolysis and reduce the cost of hydrogen production, the development of an efficient, stable and cheap electro-catalyst for oxygen evolution by water electrolysis is urgently needed.

In the past decade, many researchers have been dedicated to search for low-cost, efficient and stable non-noble metal-based electrocatalysts (such as selenides, phosphides, and transition metal (oxygen) hydroxides) for reducing the overpotential required for water electrolysis OER, thereby improving the hydrogen production efficiency of water electrolysis. Transition Metal Phosphides (TMPs) have shown great development prospects in the field of hydrogen production by electrolyzing water due to their inherent catalytic activity, adjustable structure and composition, ideal electrical conductivity and good mechanical stability. Specifically, the TMPs catalyst and hydrogenase have structuresSimilarly, metal and phosphorus sites on the surface are respectively used as proton acceptors and hydride acceptor centers, so that the electronic structure of the hydrogen production system can be remarkably changed, the electrochemical reaction kinetics is accelerated, and the hydrogen production system is widely applied to the field of hydrogen production by water electrolysis. For example, Tian et al (Journal of the Taiwan Institute of Chemical Engineers.2019,97,200-₁Fe_0.8PNSs at a current density of 10mA cm^-2The required OER overpotential is 237 mV. Lv et al (adv.Funct.Mater.2020,30,1910830.) use a strategy of combining pH-controlled wet-chemical treatment, heat treatment and phosphating treatment to prepare a large-size, porous and ultrathin NiCoP nanosheet. The catalyst has a current density of 10mA cm in 1M KOH^-2The required OER overpotential is 245 mV. Yang et al (ACS appl. energy Mater.2020,3,3577-3585.) prepared Fe-deficient ultrathin FeP nanosheets by growing 2D-FeOOH on a nickel phosphide foam substrate. The catalyst has a current density of 10mA cm in 1M KOH^-2The required OER overpotential is only 220 mV.

It is known that the above reported electrocatalytic materials are mainly applied in solutions for electrolyzing fresh water resources, but the fresh water resources are increasingly scarce and unevenly distributed on the earth, and large-scale fresh water consumption brings heavy environmental pressure. Ocean water resources account for 96.5% of the total amount of water resources on earth, and are considered to be an incompletely developed and almost unlimited chemical resource treasury. The direct electrolysis of seawater can not only produce clean energy, but also has great significance for seawater desalination, especially for coastal areas with high shortage of fresh water resources and hot arid areas. However, compared to the cathode HER for electrolyzing seawater, the anode OER is more challenging, mainly expressed in the following aspects: (1) the average salinity of seawater was about 3.5% (wherein Cl^-About 0.5M) resulting in the possibility of severe oxychlorination (ClER) or hypochlorite (ClO) in the anode OER^-) Side reaction; (2) chloride ions and small amount of Mg in seawater²⁺And SO₄ ^2-Microorganisms and bacteria can cause corrosion of the metal-based catalyst. In view of the foregoing, it is desirable to develop active sites having large specific surface areasThe OER electrocatalyst with multiple points and strong corrosion resistance ensures that the OER electrocatalyst can realize the oxygen evolution of seawater electrolysis under the dynamic overpotential far lower than 490 mV.

Due to the above problems, few electrocatalysts having excellent OER performance for the electrolysis of seawater have been reported. For example Yu et al (nat. Commun.2019,10,5106.) have prepared a NiMoN @ NiFeN electrocatalyst with a three-dimensional core-shell structure with a current density of 500mA cm in alkaline seawater^-2The required OER overvoltage is 347 mV; the Ren group (Energy environ. Sci.,2020,13,3439-3446.) prepared S- (Ni, Fe) OOH electrocatalysts at room temperature using a simple, scalable, one-step liquid phase process with current densities of 100 and 500mA cm in alkaline seawater^-2The overpotential of OER needed in the process is respectively 300mV and 398 mV; wu et al (adv. Funct. Mater.2021,31,2006484.) synthesized Ni₂P-Fe₂The current density of the P/NF bifunctional electrocatalyst in alkaline seawater is 100mA cm^-2The required OER/HER overpotentials were 305mV/252mV, respectively. Despite the above advances, the reported non-noble metal-based electrolytic alkaline seawater OER electrocatalysts still suffer from the following problems: (1) cl present in seawater^-Small amount of Mg²⁺And SO₄ ^2-Microorganisms, bacteria and the like can corrode the metal-based catalyst, so that the stability of the metal-based catalyst is poor; (2) cl present in seawater^-Severe oxychlorination (ClER) or hypochlorite (ClO) may occur during OER^-) Side reactions, resulting in poor OER selectivity; (3) the synthesis process of the electrocatalyst is complex, the process is complicated, the preparation period is long, and the requirements of practical application cannot be met. Therefore, it is very necessary to prepare an electrolytic seawater OER catalyst with high activity, good stability and low cost by a simple and convenient synthesis strategy.

Disclosure of Invention

Aiming at the problems, the invention provides a nickel-iron-based phosphide electrocatalytic material and a preparation method and application thereof. The method has the advantages that the used raw materials are low in price, the reserves are rich, the synthesis method is simple, the obtained nickel-iron-based phosphide electrocatalytic material has rich active sites and rapid charge transmission capability, shows excellent electrocatalytic OER performance in alkaline seawater, and has certain guiding significance for the commercial application of the electrolyzed seawater.

In order to solve the technical problems, the invention adopts the technical scheme that:

the invention provides a preparation method of a nickel-iron-based phosphide electrocatalytic material, which comprises the following steps:

(1) the pretreatment process comprises the following steps: the size is 1 × 1cm²～2×2cm²Respectively ultrasonically cleaning NF for 5-20 min by using absolute ethyl alcohol and deionized water, removing impurities on the surface of the NF, and drying the NF subjected to ultrasonic treatment in vacuum at 40-80 ℃ to obtain clean NF;

(2) and (3) phosphorization process: placing the NF and the sodium hypophosphite obtained in the step (1) into a tubular furnace, heating to 100-600 ℃ by a heating program of 1-10 ℃/min under the protection of argon gas, preserving the heat for 30-180 min, naturally cooling to room temperature, performing ultrasonic treatment, cleaning with deionized water, and drying to obtain the nickel foam electrode Ni modified by the nickel phosphide nanorod_xP/NF；

(3) And (3) an electrodeposition process: mixing Ni in the step (2)_xPutting P/NF into a prepared ferronickel deposition solution, wherein the total amount of ferronickel ions in the deposition solution is 0.1-2 mM, the molar concentration ratio of the ferronickel ions is 1-9: 1, and depositing for 5-60 min at a stirring speed of 100-500 rpm under a voltage of-2.0V to obtain amorphous (Ni, Fe) OOH modified Ni_xP/NF electrode, noted as (Ni, Fe) OOH @ Ni_xP/NF。

Preferably, the size of NF in the step (1) is 1X 2cm²The ultrasonic cleaning time of absolute ethyl alcohol and deionized water is 5-15 min, and the vacuum drying temperature is 40-70 ℃.

Preferably, NF and NaH are used in step (2)₂PO₂The mass ratio of the components is 1: 3-6, the heating rate is 1-4 ℃/min, the heating temperature is 150-400 ℃, and the heat preservation time is 30-90 min.

Preferably, in the step (3), the stirring speed is 100-300 rpm, the deposition time is 5-35 min, the total amount of nickel iron ions in the deposition solution is 0.2-0.8 mM, and the molar concentration ratio of the nickel iron ions is 2-5: 1.

The invention also provides a nickel-iron-based phosphide electrocatalytic material prepared by adopting the preparation methodThe nickel-iron-based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni prepared by the method_xP/NF amorphous (Ni, Fe) OOH modified Ni_xP/NF electrode, and (Ni, Fe) OOH and Ni_xP has a distinct heterogeneous interface.

The nickel-iron-based phosphide electrocatalytic material prepared by the technical scheme has rich active sites and rapid charge transmission capability, and shows excellent electrocatalytic OER activity in alkaline seawater. Meanwhile, the catalyst can form phosphate anions to resist corrosion of chloride ions in seawater in the electrochemical reaction process, and the catalyst shows excellent long-term stability, so that the catalyst has potential application value in the field of seawater electrolysis.

The invention also provides application of the nickel-iron-based phosphide electrocatalytic material in seawater electrolysis and oxygen evolution reaction. Specifically, the nickel-iron-based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni_xThe P/NF is used as a working electrode, and the electrolyte in the electrocatalysis process is seawater.

Preferably, the seawater electrolyte is alkaline seawater.

Preferably, the alkaline seawater is prepared from 0.1-1.0M KOH and natural seawater.

The nickel-iron-based phosphide electro-catalytic material is applied to the field of seawater electrolysis OER, and the electrolyte is not prepared from fresh water, but is alkaline seawater prepared from natural seawater with the pH value of about 8.5 and 1M KOH. However, the composition of seawater in which various ions exist is complicated, which accelerates the corrosion of the electrode and hinders the occurrence of OER, resulting in a significant decrease in the activity and stability of the catalyst.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention provides a nickel-iron-based phosphide catalytic material (Ni, Fe) OOH @ Ni_xP/NF can form phosphate radical anions to resist the corrosion of chloride ions in seawater in the electrochemical reaction process, so that the P/NF can show long-term stability in alkaline seawater;

(2) the invention provides a nickel-iron-based phosphide electro-catalytic material (Ni, Fe) OOH @ Ni_xP/NF with (Ni, Fe) OOH as true activityA sexual site exhibiting the electrocatalytic activity of OER; ni_xThe P has a structure similar to that of hydrogenase, has changeable composition and structural characteristics, and metal and phosphorus sites on the surface are respectively used as proton acceptor and hydride acceptor centers, so that the electronic structure of the P can be remarkably changed, and charge transfer is accelerated; (Ni, Fe) OOH and Ni_xThe obvious heterogeneous interface formed between the P generates stronger electronic interaction, enhances the charge transmission capability, provides more active sites, further improves the kinetics of the electrolyzed seawater OER, and shows that the electrolyzed seawater OER is superior to the commercial RuO₂More excellent OER activity of the electrolyzed seawater;

(3) the invention provides a nickel-iron-based phosphide electro-catalytic material (Ni, Fe) OOH @ Ni_xP/NF, the adopted raw materials have rich reserves, low price, short preparation period and simple process, and has important significance for the development of the seawater electrolysis hydrogen production technology.

Drawings

The invention will be further described with reference to the accompanying drawings in which:

FIG. 1 shows OOH @ Ni nickel-iron-based phosphide electrocatalytic materials (Ni, Fe) prepared in examples 1-4_xLSV polarization curve of P/NF in alkaline seawater;

FIG. 2 shows OOH @ Ni of the nickel iron-based phosphide electrocatalytic material (Ni, Fe) prepared in example 2_xSEM image of P/NF (FIG. 2 a); nickel-iron-based phosphide electro-catalytic material (Ni, Fe) OOH @ Ni_xTEM and HR-TEM images of P/NF (FIGS. 2 b-d);

FIG. 3 shows OOH @ Ni of the nickel iron-based phosphide electrocatalytic material (Ni, Fe) prepared in example 2_xXRD pattern of P/NF;

FIG. 4 shows OOH @ Ni of the nickel iron-based phosphide electrocatalytic material (Ni, Fe) prepared in example 2_xP/NF and Ni of comparative example 1_xP/NF, (Ni, Fe) OOH/NF of comparative example 2, RuO of comparative example 3₂LSV polarization curve of NF in alkaline seawater;

FIG. 5 shows OOH @ Ni of the nickel iron-based phosphide electrocatalytic material (Ni, Fe) prepared in example 2_xStability profile of P/NF in alkaline seawater;

FIG. 6 shows the nickel-iron-based phosphide prepared in example 2ClO of electrocatalytic material (Ni, Fe) OOH @ NixP/NF after electrocatalytic OER reaction in alkaline seawater^-And (6) detecting.

Detailed Description

In order to make the advantages and technical solutions of the present invention clearer and clearer, the present invention is further described below with reference to specific embodiments and accompanying drawings, but the present invention is not limited to the embodiments.

Comparative example 1 Nickel phosphide nanorod-modified nickel foam electrode (Ni)_xPreparation of P/NF)

To compare the nickel-iron-based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni_xP/NF, (Ni, Fe) OOH/NF and Ni_xThe performance difference between P/NF provides a preparation method of nickel foam electrode modified by nickel phosphide nano-rod, comprising the following steps:

(1) the pretreatment process comprises the following steps: the size is 1X 2cm²Respectively ultrasonically cleaning NF for 10min by using absolute ethyl alcohol and deionized water, removing impurities on the surface of the NF, and drying the NF subjected to ultrasonic treatment in vacuum at 50 ℃ to obtain clean NF;

(2) and (3) phosphorization process: weighing the NF mass in the step (1) and recording the mass as m₁Weighing NaH 0.0515g₂PO₂Mass of (a) is recorded as m₂，m₂＝5m₁0.2575 g; placing the two into a tube furnace, heating to 350 ℃ by a heating program of 2 ℃/min under the protection of argon gas, preserving the heat for 60min, naturally cooling to room temperature, carrying out ultrasonic treatment for 1min, cleaning with deionized water, and drying to obtain the nickel foam electrode Ni modified by the nickel phosphide nano-rod_xP/NF。

Comparative example 2 preparation of Nickel iron (oxy) hydroxide modified Nickel foam electrode ((Ni, Fe) OOH/NF)

To compare the nickel-iron-based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni_xP/NF, (Ni, Fe) OOH/NF and Ni_xThe performance difference between P/NF provides a preparation method of nickel iron (oxygen) hydroxide modified nickel foam electrode, which comprises the following steps:

(1) the pretreatment process comprises the following steps: the size is 1X 2cm²Respectively ultrasonically cleaning NF with absolute ethyl alcohol and deionized water for 10min to remove impurities on the surface of the NF, and ultrasonically cleaning the NFThe NF was dried under vacuum at 50 ℃ to give a clean NF;

(2) and (3) an electrodeposition process: 0.0873g of Ni (NO)₃)₂·6H₂O and 0.0404g of Fe (NO)₃)₃·9H₂Adding O into a beaker filled with 100mL of deionized water to prepare ferronickel deposition liquid with the total content of ferronickel ions of 0.4mM (the molar concentration ratio of the ferronickel ions is 3: 1); and then 50mL of ferronickel deposition solution is taken to be placed in an electrolytic cell, and deposition is carried out for 25min at the stirring speed of 100rpm under the voltage of-2.0V, so as to obtain the amorphous (Ni, Fe) OOH modified nickel foam electrode which is marked as (Ni, Fe) OOH/NF.

Comparative example 3 ruthenium dioxide modified Nickel foam electrode (RuO)₂Preparation of/NF)

To compare the nickel-iron-based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni_xP/NF, (Ni, Fe) OOH/NF and Ni_xThe performance difference between P and NF provides a preparation method of a nickel foam electrode modified by ruthenium dioxide, which comprises the following steps:

(1) the pretreatment process comprises the following steps: the size is 1X 2cm²Respectively ultrasonically cleaning NF for 10min by using absolute ethyl alcohol and deionized water, removing impurities on the surface of the NF, and drying the NF subjected to ultrasonic treatment in vacuum at 50 ℃ to obtain clean NF;

(2) and (3) dispersing: commercial RuO purchased in 10mg scale₂Catalyst powder dispersed in 10. mu.L of a mixed solvent of 5 wt% Nafion, 792. mu.L of deionized water and 198. mu.L of isopropyl alcohol;

(3) RuO to be uniformly dispersed₂Dripping the solution on the surface of clean NF, and drying in the air to obtain the ruthenium dioxide modified nickel foam electrode which is marked as RuO₂/NF。

Example 1 Nickel iron based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni_xPreparation of P/NF

A preparation method of a nickel-iron-based phosphide electrocatalytic material comprises the following steps:

(1) the pretreatment process comprises the following steps: the size is 1X 2cm²Respectively ultrasonically cleaning NF for 10min by using absolute ethyl alcohol and deionized water, removing impurities on the surface of the NF, and drying the NF subjected to ultrasonic treatment in vacuum at 50 ℃ to obtain clean NF;

(2) and (3) phosphorization process: weighing the NF mass in the step (1) and recording the mass as m₁Weighing NaH 0.0515g₂PO₂Mass of (a) is recorded as m₂，m₂＝5m₁0.2575 g; placing the two into a tube furnace, heating to 350 ℃ by a heating program of 2 ℃/min under the protection of argon gas, preserving the heat for 60min, naturally cooling to room temperature, carrying out ultrasonic treatment for 1min, cleaning with deionized water, and drying to obtain the nickel foam electrode Ni modified by the nickel phosphide nano-rod_xP/NF；

(3) And (3) an electrodeposition process: 0.0771g of Ni (NO)₃)₂·6H₂O and 0.0539g of Fe (NO)₃)₃·9H₂Adding O into a beaker filled with 100mL of deionized water to prepare ferronickel deposition liquid with the total content of ferronickel ions of 0.4mM (the molar concentration ratio of the ferronickel ions is 2: 1); then 50mL of ferronickel deposition solution is taken to be deposited in an electrolytic cell under the voltage of-2.0V and the stirring speed of 100rpm for 25min, and amorphous state (Ni, Fe) OOH modified Ni is obtained_xP/NF electrode, noted as (Ni, Fe) OOH @ Ni_xP/NF。

The molar concentration ratio of the nickel iron ions in the nickel iron deposition solution in the embodiment 1 is 2: 1.

Example 2 Nickel iron based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni_xPreparation of P/NF

A preparation method of a nickel-iron-based phosphide electrocatalytic material comprises the following steps:

(1) the pretreatment process comprises the following steps: the size is 1X 2cm²Respectively ultrasonically cleaning NF for 10min by using absolute ethyl alcohol and deionized water, removing impurities on the surface of the NF, and drying the NF subjected to ultrasonic treatment in vacuum at 50 ℃ to obtain clean NF;

(2) and (3) phosphorization process: weighing the NF mass in the step (1) and recording the mass as m₁Weighing NaH 0.0515g₂PO₂Mass of (a) is recorded as m₂，m₂＝5m₁0.2575 g; placing the two into a tube furnace, heating to 350 deg.C with a heating program of 2 deg.C/min under the protection of argon gas, maintaining the temperature for 60min, naturally cooling to room temperature, ultrasonically treating for 1min, washing with deionized water, and drying to obtain nickel foam modified by nickel phosphide nanorodElectrode Ni_xP/NF；

(3) And (3) an electrodeposition process: 0.0873g of Ni (NO)₃)₂·6H₂O and 0.0404g of Fe (NO)₃)₃·9H₂Adding O into a beaker filled with 100mL of deionized water to prepare ferronickel deposition liquid with the total content of ferronickel ions of 0.4mM (the molar concentration ratio of the ferronickel ions is 3: 1); then 50mL of ferronickel deposition solution is taken to be deposited in an electrolytic cell under the voltage of-2.0V and the stirring speed of 100rpm for 25min, and amorphous state (Ni, Fe) OOH modified Ni is obtained_xP/NF electrode, noted as (Ni, Fe) OOH @ Ni_xP/NF。

The molar concentration ratio of the nickel iron ions in the nickel iron deposition solution in the embodiment 2 is 3: 1.

Example 3 Nickel iron based phosphide electrocatalytic Material (Ni, Fe) OOH @ Ni_xPreparation of P/NF

A preparation method of a nickel-iron-based phosphide electrocatalytic material comprises the following steps:

(1) the pretreatment process comprises the following steps: the size is 1X 2cm²Respectively ultrasonically cleaning NF for 10min by using absolute ethyl alcohol and deionized water, removing impurities on the surface of the NF, and drying the NF subjected to ultrasonic treatment in vacuum at 50 ℃ to obtain clean NF;

(2) and (3) phosphorization process: weighing the NF mass in the step (1) and recording the mass as m₁Weighing NaH 0.0515g₂PO₂Mass of (a) is recorded as m₂，m₂＝5m₁0.2575 g; placing the two into a tube furnace, heating to 350 ℃ by a heating program of 2 ℃/min under the protection of argon gas, preserving the heat for 60min, naturally cooling to room temperature, carrying out ultrasonic treatment for 1min, cleaning with deionized water, and drying to obtain the nickel foam electrode Ni modified by the nickel phosphide nano-rod_xP/NF；

(3) And (3) an electrodeposition process: 0.0971g of Ni (NO)₃)₂·6H₂O and 0.0269g Fe (NO)₃)₃·9H₂Adding O into a beaker filled with 100mL of deionized water to prepare ferronickel deposition liquid with the total content of ferronickel ions of 0.4mM (the molar concentration ratio of the ferronickel ions is 5: 1); then 50mL of ferronickel deposition solution is taken to be deposited in an electrolytic cell under the voltage of-2.0V and at the stirring speed of 100rpm for 25min to obtain the nickel-iron-nickel alloyCrystalline (Ni, Fe) OOH modified Ni_xP/NF electrode, noted as (Ni, Fe) OOH @ Ni_xP/NF。

The molar concentration ratio of the nickel iron ions in the nickel iron deposition solution in the embodiment 3 is 5: 1.

Example 4 Nickel iron based phosphide electrocatalytic Material (Ni, Fe) OOH @ Ni_xPreparation of P/NF

A preparation method of a nickel-iron-based phosphide electrocatalytic material comprises the following steps:

(1) the pretreatment process comprises the following steps: the size is 1X 2cm²Respectively ultrasonically cleaning NF for 10min by using absolute ethyl alcohol and deionized water, removing impurities on the surface of the NF, and drying the NF subjected to ultrasonic treatment in vacuum at 50 ℃ to obtain clean NF;

(2) and (3) phosphorization process: weighing the NF mass in the step (1) and recording the mass as m₁Weighing NaH 0.0515g₂PO₂Mass of (a) is recorded as m₂，m₂＝5m₁0.2575 g; placing the two into a tube furnace, heating to 350 ℃ by a heating program of 2 ℃/min under the protection of argon gas, preserving the heat for 60min, naturally cooling to room temperature, carrying out ultrasonic treatment for 1min, cleaning with deionized water, and drying to obtain the nickel foam electrode Ni modified by the nickel phosphide nano-rod_xP/NF；

(3) And (3) an electrodeposition process: 0.1048g of Ni (NO)₃)₂·6H₂O and 0.0166g Fe (NO)₃)₃·9H₂Adding O into a beaker filled with 100mL of deionized water to prepare ferronickel deposition liquid with the total content of ferronickel ions of 0.4mM (the molar concentration ratio of the ferronickel ions is 9: 1); then 50mL of ferronickel deposition solution is taken to be deposited in an electrolytic cell under the voltage of-2.0V and the stirring speed of 100rpm for 25min, and amorphous state (Ni, Fe) OOH modified Ni is obtained_xP/NF electrode, noted as (Ni, Fe) OOH @ Ni_xP/NF。

The molar concentration ratio of the nickel iron ions in the nickel iron deposition solution in the embodiment 4 is 9: 1.

(Ni, Fe) OOH @ Ni for different molar concentration ratios of nickel iron ions in examples 1,2, 3 and 4 were determined_xLSV polarization curve of P/NF oxygen evolution electrocatalyst in alkaline seawater is shown in figure 1, and it can be seen from figure 1 that molar concentration ratio of nickel iron ionThe OER performance is better when the ratio is 3: 1.

Example 5 Nickel iron based phosphide electrocatalytic Material (Ni, Fe) OOH @ Ni_xStructural analysis of P/NF

FIG. 2 shows a nickel-iron-based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni_xMicroscopic morphology of P/NF. From SEM image of FIG. 2a, it can be observed that a large amount of (Ni, Fe) OOH nanoparticles are attached to Ni foam electrode modified by nickel phosphide nanorod Ni_xP/NF. From TEM images (FIGS. 2b-c) and HR-TEM images (FIG. 2d), it can be found that the catalyst is composed of crystalline Ni with orderly atomic arrangement_xP and amorphous (Ni, Fe) OOH, with a distinct heterointerface between them.

FIG. 3 shows OOH @ Ni of Ni-Fe-based phosphide electrocatalytic material_xXRD pattern of P/NF from which Ni can be observed_xP is made of Ni₂P and Ni₁₂P₅Two components, and (Ni, Fe) OOH @ Ni_xP/NF and Ni_xThe XRD patterns of P/NF were almost identical, suggesting that the deposited (Ni, Fe) OOH may be amorphous. In addition, no distinct characteristic peak was observed from the XRD pattern of (Ni, Fe) OOH, thereby further confirming that the (Ni, Fe) OOH deposited was an amorphous substance.

Example 6 Nickel iron based phosphide electrocatalytic Material (Ni, Fe) OOH @ Ni_xPerformance testing of P/NF

FIG. 4 shows the nickel-iron-based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni of example 2_xLSV polarization curve of P/NF: in 1M KOH electrolyte prepared from natural seawater (pH is about 8.5), a three-electrode system is adopted to carry out (Ni, Fe) OOH @ Ni_xThe P/NF electrocatalytic materials were subjected to electrochemical testing. The specific operation is as follows: taking 1M KOH electrolyte prepared from proper amount of natural seawater into an electrolytic cell, and adding nickel-iron-based phosphide electro-catalytic material (Ni, Fe) OOH @ Ni_xP/NF is used as a working electrode, a saturated Hg/HgO electrode is used as a reference electrode, a carbon rod is used as a counter electrode, and an LSV polarization curve test is carried out on the electro-catalytic material by adopting a Shanghai Hua CHI-760E electrochemical workstation at room temperature. Ni of comparative example 1_xP/NF, (Ni, Fe) OOH/NF of comparative example 2 and RuO of comparative example 3₂In comparison with (Ni, Fe) OOH @ Ni_xP/NF in alkaline seaThe best OER activity in water, specifically (Ni, Fe) OOH @ Ni_xP/NF at a current density of 100mA cm^-2The required overpotential is only 262 mV; at 500mA cm^-2The required overpotential is only 318mV under the large current density; for (Ni, Fe) OOH oxygen evolution electrocatalyst at a current density of 100mA cm^-2The required overpotential is 315 mV; for Ni_xP/NF oxygen evolution electrocatalyst with current density of 100mA cm^-2When the voltage is higher than the threshold voltage, the required overpotential is 445 mV; for RuO₂/NF oxygen evolution electrocatalyst at a current density of 100mA cm^-2The desired overpotential is 432 mV.

FIG. 5 shows OOH @ Ni of Ni-Fe-based phosphide electrocatalytic material_xStability test of P/NF: at a current density of 500mA cm^-2In the process, the performance is almost unchanged after 100h stability test, which shows that the electrocatalytic material has excellent stability in alkaline seawater. The reason is that phosphate anions are formed on the surface of the nickel-iron-based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni, and can generate repulsion action with chloride ions in seawater_xP/NF has the ability to resist corrosion by chloride ions.

By combining the above embodiments and analysis and test results, the nickel-iron-based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni provided by the invention_xP/NF, wherein (Ni, Fe) OOH is used as a real active site, and shows the electrocatalytic activity of OER; ni_xP has a structure similar to hydrogenase, and metal and phosphorus sites on the surface are respectively used as proton acceptors and hydride acceptor centers, so that the electronic structure of the P can be remarkably changed, and charge transmission is accelerated; (Ni, Fe) OOH and Ni_xAn obvious heterogeneous interface formed between the P generates stronger electronic interaction, enhances the charge transmission capability, provides more active sites, further improves the kinetics of seawater OER electrolysis, and shows excellent electrocatalytic OER activity in alkaline seawater. Meanwhile, the electrocatalytic material can form phosphate anions to resist corrosion of chloride ions in seawater in the electrochemical reaction process, and shows long-term stability. Furthermore, (Ni, Fe) OOH @ Ni_xThe preparation method of the P/NF is simple, efficient and low in costTherefore, a new idea is provided for developing a novel electrolytic seawater OER electrocatalyst.

Example 7 Nickel iron-based phosphide Material (Ni, Fe) OOH @ Ni_xClO after P/NF electrocatalysis OER reaction^-Detection of

For detecting (Ni, Fe) OOH @ Ni_xWhether the P/NF electrocatalytic material generates ClO after oxygen evolution reaction^-The measurement was carried out by the following method.

The (Ni, Fe) OOH @ Ni prepared in example 2_xCarrying out stability test on the P/NF electro-catalytic material in alkaline seawater for 48h, and then titrating the alkaline seawater electrolyte subjected to the stability test to be neutral (pH is about 7) by using 2M hydrochloric acid, and recording as a solution A; deionized water was used as a blank control, i.e., six standard solutions with concentrations of 0.001%, 0.002%, 0.003%, 0.005%, 0.007%, and 0.01% of NaClO were prepared, respectively, as solution 1, and as solution 2-7. ClO was carried out according to the following procedure^-Detection of (2):

(1) adding 1mL of 2M hydrochloric acid and 1mL of 2% potassium iodide into the colorless standard solution 1-7 and the solution A respectively;

(2) gently shaking the standard solutions 1-7 and solution A in step (1), if the solution turns yellow, iodine I is indicated₂Generating;

(3) continuing to add 0.5mL of 0.05% Rhodamine B (pink) to each of the standard solutions 1-7 and solution A in step (2);

(4) continuing to add 2mL of 1M sodium acetate to the standard solutions 1-7 and solution A in step (3), respectively;

(5) shaking the standard solutions 1-7 and the solution A in the step (4) for 2min respectively.

In the detection method, sodium hypochlorite reacts with hydrochloric acid to generate hypochlorous acid; reacting potassium iodide with hydrochloric acid to generate hydroiodic acid; reacting the generated hypochlorous acid with hydriodic acid to obtain I₂，I₂Fading is produced on Rhodamine B. The higher the NaClO concentration, the higher I is produced₂The more the fading effect is, the more remarkable. As can be seen in FIG. 6, ClO^-The standard solutions 1 to 7 with increasing concentrations gradually fade to show the color of iodine. The color of the solution A after detection is changed into pinkThe color of the solution is the same as that of the detected solution 1 (the concentration of NaClO is 0), which shows that the nickel-iron-based phosphide electrocatalytic material (Ni, Fe) OOH @ Ni_xP/NF has no ClO after seawater OER electrolysis reaction^-So that the electrocatalytic material can realize selective oxygen evolution in alkaline seawater.

ClO after the above electrocatalytic OER reaction^-The detection method is low in cost, simple and convenient, and whether ClO is generated or not after the subsequent OER reaction is detected^-And (3) detecting the solution to be detected according to the steps and observing whether the color of the solution changes.

While there have been shown and described what are at present considered the fundamental principles of the invention, its essential features and advantages, it will be understood by those skilled in the art that the invention is not limited by the embodiments described above, which are merely illustrative of the principles of the invention, but various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.