CN110833840A

CN110833840A - Method for producing electrocatalysts by single-step electrodeposition and electrocatalysts produced thereby

Info

Publication number: CN110833840A
Application number: CN201811353380.1A
Authority: CN
Inventors: 朴丈秀; 黄英恩; 白正民; 金熙濬; 李台源
Original assignee: Hyundai Motor Co; Kia Motors Corp; UNIST Academy Industry Research Corp
Current assignee: Hyundai Motor Co; UNIST Academy Industry Research Corp; Kia Corp
Priority date: 2018-08-16
Filing date: 2018-11-14
Publication date: 2020-02-25
Also published as: KR102589924B1; US20200056296A1; KR20200020152A

Abstract

The present invention discloses a method for producing an electrocatalyst by single-step electrodeposition and the electrocatalyst produced thereby. Specifically, the method may include forming a metal layer on a substrate, treating the substrate of the metal layer and forming a catalyst layer on the metal layer by applying an electrical potential to an aqueous deposition solution comprising a nickel precursor, a copper precursor, a phosphorus precursor, and an additive, wherein a molar ratio of the nickel precursor to the copper precursor may be greater than about 49: 1. Therefore, the present invention is advantageous in that the process for producing the electrocatalyst may be simplified.

Description

Method for producing electrocatalysts by single-step electrodeposition and electrocatalysts produced thereby

Reference to related applications

The present application claims the priority of korean patent application No.10-2018-0095514 filed by the korean intellectual property office at 2018, month 8 and 16 under the clause 35 u.s.c. § 119, the disclosure of which is incorporated herein by reference in its entirety.

Technical Field

The present invention relates to a method for producing electrocatalysts by electrodeposition.

Background

Since hydrogen energy is currently attracting attention as an environmentally friendly energy source that can replace fossil fuels, and since hydrogen energy can be generated only by electrolyzing water, research interest in electrocatalysts (electrocatalysts) for generating hydrogen energy by electrolyzing water has been increased.

Generally, electrocatalysts consist of a Hydrogen Evolution Reaction (HER) electrode and an Oxygen Evolution Reaction (OER) electrode. As a material for each electrode, platinum (Pt) is most widely known. However, since platinum is a noble metal and has a limited reserve, studies have been actively conducted to use abundant metals such as iron (Fe), nickel (Ni), copper (Cu), and cobalt (Co) as elements replacing platinum, in particular, to use dissimilar metals as materials for electrocatalysts.

For example, in the related art, cobalt phosphide (cobalt phosphide) doped with copper has been used. However, the production method is complicated, it uses Metal Organic Framework (MOF) as a precursor, a carbonization process is performed at 800 ℃ and a heat post-treatment process is performed at 300 ℃, and it has been reported to be active only in a strong base (pH 13.5) electrolyte.

In addition, in the related art, a material in which nickel (Ni) foam has been doped with cobalt may include a complicated process such as forming a layered nanostructure (three-layered morphology) on the surface of the nickel foam using a ball lithography method. Furthermore, the material is amorphous and has been reported to be active only in strong base (pH 13.5) electrolytes.

Further, in the related art, materials have been prepared by electrodepositing nickel and copper on a stainless steel foil, and then applying a phosphide treatment thereto (so-called two-step process). However, the addition of phosphorus requires a process of 300 ℃, and is not efficient in terms of cost.

Although the use of nickel precursors, copper precursors, and phosphorus precursors that can be electrodeposited have been introduced in the related art, electrolysis and removal of liquid or vapor water molecules (water vapor) may be limited because the invention exhibits superhydrophobicity and is used for surface waterproofing. In addition, due to the use of additives for various purposes, e.g. SDS and Na₂SO₄As an ionic enhancer and ammonia water as a pH adjuster, the process may not be simple.

Disclosure of Invention

In a preferred aspect, the present invention can provide a simplified method of producing an electrocatalyst and reduce the use of additives in electrodeposition. In addition, the present invention may provide a method of producing an electrocatalyst for removal of water vapor.

In one aspect, a method of producing an electrocatalyst is provided. The method may include forming a metal layer on a substrate, treating a surface of the metal layer and forming a catalyst layer on the metal layer by applying an electric potential to an aqueous deposition solution including a nickel precursor, a copper precursor, a phosphorus precursor, and an additive. Specifically, the molar ratio of nickel precursor to copper precursor can be greater than about 49:1 to 499:1, or more preferably between about 99:1 to about 499: 1.

"aqueous deposition solution" refers to a mixture or solution containing water or a water-based solvent for dispersing other materials or components.

The metal layer may suitably comprise a nickel layer or a copper layer.

And processing the surface of the metal layer. Preferably, the treatment may provide a hydrophilic surface, for example, the hydrophilic surface treatment may suitably comprise a UV-ozone cleaning treatment.

The potential may be applied by cyclic voltammetry.

Preferably, the potential may range from about-1.2 to 0.2V, including from about-1.0V to 0.2V, -0.8V to 0.2V, or-0.6V to 0.2V.

The frequency of the applied potential range may suitably be about 3 to 15 times.

The molar concentration of the nickel precursor may be about 0.02 to 0.5M, including 0.05 to 0.2M or 0.1 to 0.15M.

The nickel precursor may suitably comprise one or more selected from nickel sulphate, nickel nitrate and nickel acetate.

The concentration of the copper precursor may be about 0.001 to 0.02M.

The copper precursor may suitably comprise one or more selected from copper sulphate, copper nitrate, copper acetate and copper acetylacetonate.

The additive may suitably comprise sodium acetate, and may also comprise glycine or citric acid.

The molar ratio of nickel precursor to sodium acetate, glycine, or citric acid can be about 1: about 0.5 or higher and about 1: less than about 2.

The molar concentration of each of sodium acetate, glycine, and citric acid may be about 0.05 or more and less than about 0.2M.

The molar ratio of nickel precursor to phosphorus precursor can be from about 1: about 5 to about 1: about 20, more preferably, from about 1: about 5 to about 1: about 10.

The molar concentration of the phosphorus precursor can be from about 0.01M to about 2.0M, from about 0.05 to about 1.5M, or more preferably, from about 0.1 to 1.25M.

The phosphorus precursor may suitably comprise sodium hypophosphite.

The substrate on which the nickel copper-phosphide catalyst layer is deposited may be pretreated. The pretreatment may be an oxygen plasma etching process.

In another aspect, there is provided an electrocatalyst comprising an oxygen evolution reaction electrode and a hydrogen evolution reaction electrode, producible by the method described herein. At least one of the electrodes may include a substrate and a catalyst layer electrodeposited on the substrate, and the catalyst layer may include greater than about 65 at% nickel based on 100 at% metal atoms; and less than about 35 at% copper. In a preferred aspect, the catalyst layer may include greater than about 66, 70, 75, 80, 85, 90, or 95 at% Ni and include less than about 34, 30, 25, 20, 15, 10, or 5 at% Cu, based on 100 at% total metal atoms. In general, the catalyst layer will contain copper, i.e., the amount of copper will be greater than 0 at% or preferably will be at least about 0.0.5 at% or higher, based on 100 at% metal atoms.

The electrocatalyst may comprise a metal layer located between the substrate and the catalyst layer. The metal layer may suitably comprise a nickel layer or a copper layer.

According to various exemplary embodiments, the present invention may provide a simplified method of producing an electrocatalyst and an additive used during electrodeposition. In addition, the methods disclosed herein can remove moisture.

Also provided are vehicle components that may include an electrocatalyst as described herein. Exemplary vehicle components may include headlights. A vehicle comprising a vehicle component as disclosed herein is also provided.

Other aspects of the invention are disclosed below.

Drawings

FIG. 1 is a flow diagram of an exemplary method for producing an exemplary electrocatalyst by one-step electrodeposition according to an exemplary embodiment of the invention.

FIG. 2 is a graph of hydrogen evolution reaction (H) as measured by nickel layer thickness when forming a nickel layer on a conductive substrate₂SO₄0.5M).

FIG. 3 is a graph showing the measurement of hydrogen evolution reaction (H) according to cycle frequency when the potential range and the scanning rate are-1.2 to 0.2V and 10mV/s, respectively₂SO₄0.5M).

Fig. 4 is a graph showing the molar ratio of nickel precursor to copper precursor, the ratio of nickel atoms to copper atoms (at%) in an exemplary catalyst layer, according to an exemplary embodiment of the present invention.

Fig. 5 is a graph of Linear Sweep Voltammetry (LSV) according to the ratio (at%) of nickel atoms and copper atoms.

Fig. 6A shows an XRD pattern and crystal analysis according to the ratio (at%) of nickel atoms and copper atoms in an exemplary embodiment of the present invention, and fig. 6B magnifies the XRD pattern of fig. 6A at diffraction angles between about 43 ° and about 45.5 °. FIG. 6C is an enlarged view of Ni shown in FIG. 6A₈₉Cu₁₁-XRD pattern of P.

FIG. 7A is a graph in which exemplary Ni₆₅Cu₃₅Transmission Electron Microscope (TEM) image of the portion of the P catalyst layer where Ni-rich nickel copper-phosphide appears in the exemplary embodiment of the present invention, and fig. 7B is the fast fourier transform image of fig. 7A.

FIG. 8A is a graph in which Ni is exemplified₆₅Cu₃₅Transmission electron microscopy of the portion of the P catalyst layer where Cu-rich nickel copper-phosphide appears in the exemplary embodiment of the present invention, and fig. 8B is the fast fourier transform graph of fig. 8A.

FIG. 9A is a graph in which exemplary Ni₆₅Cu₃₅Ni in P catalyst layer₁₂P₅A transmission electron microscope image of a portion where crystals appear in an exemplary embodiment of the present invention, and fig. 9B is a fast fourier transform image of fig. 9A.

FIG. 10A is a graph in which exemplary Ni₆₅Cu₃₅Ni in P catalyst layer₃A transmission electron microscope image of a portion of a P crystal appearing in an exemplary embodiment of the present invention, and fig. 10B is a fast fourier transform image of fig. 10A.

FIG. 11 is a graph showing that the hydrogen evolution reaction (H) was measured based on the concentration of sodium acetate when the concentration of the nickel precursor was 0.1M₂SO₄0.5M).

FIG. 12 is a graph showing that when the concentration of the nickel precursor was 0.1M, the hydrogen evolution reaction (H) was measured based on the concentration of glycine₂SO₄0.5M).

FIG. 13 is a graph of measuring hydrogen evolution reaction (H) according to the concentration of citric acid when the concentration of nickel precursor is 0.1M₂SO₄0.5M).

FIG. 14 is a graph measuring hydrogen evolution reaction (H) based on the molar ratio of nickel precursor to phosphorus precursor₂SO₄0.5M).

Fig. 15A is a picture captured by a Scanning Electron Microscope (SEM) after 10 minutes of applying 10V to the pre-treated OER electrode, and fig. 15B, 15C, and 15D are pictures captured by enlarging the pictures in fig. 15A.

Fig. 16A is a picture captured by a scanning electron microscope after 10 minutes of applying 10V to a non-pretreated OER electrode, and fig. 16B, 16C and 16D are pictures captured by enlarging the picture in fig. 16A.

FIG. 17 is a comparative exemplary Ni₉₁Cu₉-a graph of the electrical conductivity of the P electrocatalyst and the electrical conductivity of the Ni-P electrocatalyst in an exemplary embodiment of the invention.

FIG. 18 is a comparative exemplary Ni₉₁Cu₉A plot of charge mobility of the P electrocatalyst and charge mobility of the Ni-P electrocatalyst in exemplary embodiments of the present invention.

FIG. 19 is a graph measuring exemplary Ni in an exemplary embodiment of the invention₉₁Cu₉Hydrogen evolution reaction (H) of-P electrocatalyst, Pt electrocatalyst, Ni-P electrocatalyst, NiCu electrocatalyst, Ni electrocatalyst and Cu electrocatalyst₂SO₄0.5M).

FIG. 20 is a graph measuring exemplary Ni in an exemplary embodiment of the invention₉₁Cu₉Graphs of hydrogen evolution reactions (KOH 1M) for P electrocatalyst, Pt electrocatalyst, Ni-P electrocatalyst, NiCu electrocatalyst, Ni electrocatalyst and Cu electrocatalyst.

FIG. 21 is a graph of the voltage when a 10V potential is applied to exemplary Ni in an exemplary embodiment of the invention₉₁Cu₉-scanning electron microscopy at 10 min of an exemplary HER electrode for P electrocatalyst.

FIG. 22 is a graph of the voltage when a 10V potential is applied to exemplary Ni in an exemplary embodiment of the invention₉₁Cu₉-scanning electron microscopy images of exemplary OER electrodes for P electrocatalyst at 10 min.

FIG. 23 illustrates an exemplary embodiment of the present inventionAccording to application to exemplary Ni₉₁Cu₉-current density of the potential of the P electrocatalyst.

FIG. 24A shows exemplary Ni mounted on a headlamp in an exemplary embodiment of the invention₉₁Cu₉-P electrocatalyst and water vapour, and fig. 24B shows Ni therein₉₁Cu₉-a region around the P electrocatalyst from which water vapour has been removed.

FIG. 25 is a graph of exemplary Ni in accordance with an exemplary embodiment of the present invention₉₁Cu₉-graph of humidity measurement current density of P electrocatalyst.

Detailed Description

Hereinafter, the present invention will be described in detail. However, the present invention is not limited or restricted to the exemplary embodiments, and objects and effects of the present invention will be naturally understood or will become apparent from the following description, and the objects and effects of the present invention are not limited only to the following description. Further, in the description of the present invention, when it is determined that detailed description of publicly known techniques related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," "including," "has," "having," and the like, when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

It is to be understood that the term "vehicle" or "vehicular" or other similar terms as used herein include motor vehicles, generally such as passenger automobiles, including Sport Utility Vehicles (SUVs), buses, trucks, various commercial vehicles, marine vessels, including various boats and ships, aircraft, and the like, and including hybrid cars, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, for example, gasoline-powered and electric-powered vehicles.

Further, unless specifically stated or otherwise apparent from the context, as used herein, the term "about" should be understood to be within the normal allowed range of the art, e.g., within 2 standard deviations of the mean. "about" can be understood as being within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.01%, 0.05% or 0.01% of the stated value. Unless otherwise apparent from the context, all numbers provided herein are modified by the term "about".

FIG. 1 is a flow chart of the present invention for producing an exemplary electrocatalyst by one-step electrodeposition in an exemplary embodiment of the present invention. As shown in fig. 1, the present invention may include forming a metal layer on a substrate (S101), treating a surface of the metal layer, for example, hydrophilic surface treatment (S102) and forming a catalyst layer, for example, a nickel copper-phosphide catalyst layer, on the metal layer by applying an electric potential to an aqueous deposition solution (S103) containing a nickel precursor, a copper precursor, a phosphorus precursor and an additive.

The one-step electrodeposition may suitably include forming the nickel copper-phosphide catalyst layer with a single electrodeposition, and the nickel copper-phosphide catalyst layer may suitably include a catalyst layer having a crystal structure in which phosphorus can be deposited into interstitial sites of nickel, and copper ions can be deposited by substituting nickel atoms located in the nickel interstitial sites with copper ions.

A glass sheet or a silicon sheet may be suitably used as the substrate, and the metal layer formed on the substrate may suitably include a nickel layer or a copper layer. Further, the metal layer may be formed by sputtering or electron beam. However, the deposition method may not necessarily be limited thereto as long as the deposition method does not affect the electrodeposition of the deposition aqueous solution.

FIG. 2 is a graph of hydrogen evolution reaction (H) as measured by nickel layer thickness when forming a nickel layer on a conductive substrate₂SO₄0.5M). The nickel layer may suitably have a thickness of about 50 to 300nm, as shown in fig. 2. Since the metal layer (e.g., nickel layer) serves as a channel for transferring charges during electrodeposition, its thickness is not necessarily limited to 50 to 300 nm.

The treatment of the metal layer, such as a hydrophilic surface treatment, may be a UV-ozone cleaning treatment. The hydrophilic surface treatment may improve the bonding strength between the surface of the substrate and the aqueous deposition solution containing the precursor by surface modification, for example, formation of hydroxyl groups (-OH). In addition, the hydrophilic surface treatment can prevent the generation of bubbles on the surface of the substrate during electrodeposition. However, the hydrophilic surface treatment is not limited thereto, and a surface treatment to which plasma or the like is applied may be suitably used.

When the nickel copper-phosphide catalyst layer was formed, an electric potential was applied by cyclic voltammetry. The applied potential may be set to be less than the reduction potential of nickel, copper and phosphorus (e.g., +0.272V, +0.859V and 0.348V, respectively, with respect to Ag/AgCl), and preferably, the potential may range from about-1.2 to 0.2V.

The frequency (cycle frequency) when applying about-1.2 to 0.2V may be about 3 to 15 times. When the cycle frequency is less than 3 times, nucleation before growth of the ionic catalyst layer may not uniformly occur throughout the entire metal layer region, and when the cycle frequency is more than 15 times, the catalyst characteristics may be deteriorated.

FIG. 3 is a graph showing the measurement of hydrogen evolution reaction (H) according to cycle frequency when the potential range and the scanning rate are-1.2 to 0.2V and 10mV/s, respectively₂SO₄0.5M). As shown in fig. 3, the hydrogen generation effect of the electrocatalyst produced by setting the cycle frequency to 3 to 15 times may be superior to those of the electrocatalysts produced when the cycle frequency is set to 1, 2 and 20 times.

When the cycle frequency is set to 3 to 15 times, the catalyst layer may be uniformly formed over the entire area of the metal layer, and the catalyst characteristics may not be deteriorated. However, a constant current method (10 to 20 mA/cm) may also be used²) Instead of cyclic voltammetry, a nickel copper-phosphide catalyst layer was formed.

The molar ratio of nickel precursor to copper precursor contained in the aqueous deposition solution of the present invention may be greater than about 49: 1. The molar ratio will be described in detail below.

Fig. 4 is a graph showing the ratio (at%) of nickel atoms to copper atoms in the catalyst layer according to the molar ratio of the nickel precursor to the copper precursor, and fig. 5 is a graph of linear sweep voltammetry according to the ratio (at%) of nickel atoms to copper atoms. Tables 1 and 2 show the results of measuring the ratio of nickel atoms to copper atoms in the catalyst layer according to the molar ratio of the nickel precursor to the copper precursor by EDX, and at 10mA/cm when each catalyst layer was used as a catalyst layer of a hydrogen evolution reaction electrode, respectively²And (4) overvoltage under the condition of voltage.

TABLE 1

TABLE 2

As shown in fig. 4 and 5 and tables 1 and 2, a nickel precursor and a copper precursor may be suitably contained in the deposition aqueous solution in a molar ratio of about 199:1, and when the nickel copper-phosphide catalyst layer is composed of about 91 at% of nickel and about 9 at% of copper, based on 100 at% of metal atoms, that is, when Ni is Ni₉₁Cu₉When the-P catalyst layer is used as a catalyst layer of a hydrogen evolution reaction electrode, the concentration of the catalyst is 10mA/cm²The overvoltage measured for the current density of-48 mV, which is the minimum value.

Ni formed from an aqueous deposition solution wherein the molar ratio of nickel precursor to copper precursor is 499:1, 199:1, or 99:1₉₃Cu₇-P catalyst layer, Ni₉₁Cu₉-P catalyst layer or Ni₈₉Cu₁₁The overvoltage measured for the P-catalyst layer is lower than the overvoltage measured for a Ni-P catalyst layer formed from an aqueous deposition solution that does not contain a copper precursor.

These results are shown because the charge build-up between nickel and phosphorus is reduced by doping the nickel-phosphorus catalyst layer with copper. In other words, free electrons may be increased, and the hydrogen adsorption energy may converge to 0.

Meanwhile, when the molar ratio of the nickel precursor to the copper precursor in the deposition aqueous solution is equal to or less than about 49:1, i.e., the ratio of copper atoms is about 35 at% or more, the catalyst characteristics may be rapidly deteriorated. For example, as described below, since copper-phosphide is first deposited on a metal layer, a nickel-copper alloy-phosphide layer having a uniform composition is not formed, and thus phase separation occurs.

Therefore, the nickel precursor and the copper precursor may be contained in a ratio of a molar ratio of the nickel precursor to the copper precursor contained in the aqueous deposition solution of the present invention of more than about 49:1 where the catalyst characteristics are rapidly deteriorated.

Fig. 6A shows an XRD pattern and crystal analysis according to the ratio (at%) of nickel atoms and copper atoms, and fig. 6B magnifies the XRD pattern of fig. 6A with diffraction angles between about 43 ° and about 45.5 °. FIG. 6C is an enlarged view of Ni shown in FIG. 6A₈₉Cu₁₁-XRD pattern of P catalyst layer. Table 3 shows the crystals and peak positions where the peaks occur.

TABLE 3

	Cu(200)	Ni(200)	Cu(111)	Ni(111)
					Peak angle	43.63°	44.66°	50.95°	51.98°

As shown in fig. 6A to 6C and table 3, when the catalyst layer contains 7 at% or more of copper atoms, peaks occur at 44.66 ° and 51.98 °, which correspond to the Ni (200) surface and the Ni (111) surface, and thus, a nickel copper-phosphide catalyst layer can be formed by XRD pattern analysis.

In Ni₈₉Cu₁₁In the P catalyst layer, peaks appear at 44.66 ° and 51.98 °, whereas peaks appear very finely at 43.63 ° and 50.95 °, which correspond to the copper (200) surface and the copper (111) surface. For example, since copper-phosphide is first deposited on a metal layer, phase separation occurs finely with copper-phosphide and nickel-phosphide. However, due to Ni₈₉Cu₁₁The P catalyst layer exhibits an overvoltage lower than that of the Ni-P catalyst layer and Ni₉₃Cu₇The overvoltage of the P catalyst layer, and thus the effect of improving the conductivity according to the addition (doping) of copper may be more significant than the effect produced by forming an uneven catalyst layer.

Ni at atomic ratio of copper greater than about 11 at%₆₅Cu₃₅-P catalyst layer, Ni₃₆Cu₆₄-P catalyst layer and Ni₂₃Cu₇₇In the-P catalyst layer, the peaks clearly appear at 43.63 ° and 50.95 °. Phase separation of the copper phosphide apparently occurred due to the high concentration of copper precursor contained in the aqueous deposition solution. Since the catalyst characteristics (overvoltage) of each catalyst layer rapidly deteriorate, the nickel precursor and the copper precursor cannot be contained at a copper atomic ratio of more than about 35 at% or at a molar ratio of the nickel precursor to the copper precursor in the deposition aqueous solution (which may be equal to or less than about 49: 1). Hereinafter, Ni will be described in detail₆₅Cu₃₅-phase separation in the P catalyst layer.

FIG. 7A is a graph in which Ni₆₅Cu₃₅-transmission electron microscopy of the portion of the P catalyst layer where Ni-rich nickel copper-phosphide appeared, and fig. 7B is the fast fourier transform plot of fig. 7A. As shown in fig. 7A and 7BMay be in Ni₆₅Cu₃₅The Ni-rich nickel copper-phosphide was formed in the P catalyst layer because the reciprocal of the length of each of the arrow mark indicating the direction of about 8 o ' clock and the arrow mark indicating the direction between about 4 o ' clock and about 5 o ' clock was the same as the (200) surface and the (111) surface corresponding to the crystal surface of the Ni-rich nickel copper-phosphide.

FIG. 8A is a graph in which Ni₆₅Cu₃₅-transmission electron microscopy of the portion of the P catalyst layer where Cu-rich nickel copper-phosphide occurred, and fig. 8B is the fast fourier transform plot of fig. 8A. As shown in fig. 8A and 8B, may be in Ni₆₅Cu₃₅The Cu-rich nickel copper-phosphide is formed in the P catalyst layer because the reciprocal of the length of each of the arrow mark indicating the direction of about 6 o ' clock and the arrow mark indicating the direction between about 2 o ' clock and about 3 o ' clock is the same as the (100) surface and the (200) surface corresponding to the crystal surface of the Cu-rich nickel copper-phosphide.

FIG. 9A is a drawing in which Ni₆₅Cu₃₅Ni in P catalyst layer₁₂P₅A transmission electron microscope image of a portion where the crystal appears, and fig. 9B is a fast fourier transform image of fig. 9A. As shown in fig. 9A-9B, may be in Ni₆₅Cu₃₅Formation of Ni in P catalyst layer₁₂P₅A crystal, because the reciprocal of the length of each of the arrow mark indicating the direction of about 1 o ' clock and the arrow mark indicating the direction between about 7 o ' clock and about 8 o ' clock corresponds to Ni₁₂P₅The (420) and (321) surfaces of the crystal surface are the same.

FIG. 10A is a drawing in which Ni₆₅Cu₃₅Ni in P catalyst layer₃A transmission electron microscope image of a portion where the P crystal appears, and fig. 10B is a fast fourier transform image of fig. 10A. As shown in fig. 10A-10B, may be in Ni₆₅Cu₃₅Formation of Ni in P catalyst layer₃P crystal because the reciprocal of the length of each of the arrow mark indicating the direction of about 1 o 'clock and the arrow mark indicating the direction of about 7 o' clock corresponds to Ni₃The (330) and (321) surfaces of the P crystal surface are the same.

Meanwhile, the molar concentration of the nickel precursor may be about 0.02 to 0.5M, and the nickel precursor may be at least one or more of nickel sulfate, nickel nitrate, or nickel acetate.

The concentration of the copper precursor may be about 0.001 to 0.02M, and the copper precursor may suitably comprise one or more selected from copper sulfate, copper nitrate, copper acetate and copper acetylacetonate.

The additive contained in the aqueous deposition solution of the present invention includes sodium acetate, and may also include glycine or citric acid. Sodium acetate as used herein can adjust the reduction rate of metal ions by maintaining pH and adjusting the deposition reaction, while glycine and citric acid can be so-called complexing agents that can inhibit the binding of metal ions to oxygen, hydrogen, etc., which can be easily bound and promote the binding of metal ions to phosphorus (P).

The molar ratio of nickel precursor to sodium acetate, glycine, or citric acid contained in the aqueous deposition solution of the present invention can be about 1: about 0.5 or higher and about 1: less than about 2. When the molar ratio is about 1: about 2 or more, the bonding strength between the metal ions and the additive may be increased, and thus uniform electrodeposition may not be achieved. Therefore, the catalyst characteristics may deteriorate.

FIG. 11 is a graph showing that the hydrogen evolution reaction (H) was measured based on the concentration of sodium acetate when the concentration of the nickel precursor was 0.1M₂SO₄0.5M), and fig. 12 is a graph in which the hydrogen evolution reaction (H) is measured according to the concentration of glycine when the concentration of nickel precursor is 0.1M₂SO₄0.5M), and fig. 13 is a graph in which the hydrogen evolution reaction (H) is measured according to the concentration of citric acid when the concentration of the nickel precursor is 0.1M₂SO₄0.5M).

As shown in fig. 11 to 13, when the molar ratio of the nickel precursor to sodium acetate, glycine, or citric acid is about 1:0.5 and 1:1, an excellent hydrogen generation effect may be exhibited, but when the molar ratio is about 1:2, the hydrogen generating effect is deteriorated.

Meanwhile, each of sodium acetate, glycine and citric acid may be about 0.05 to 0.1M in molar concentration, and glycine or citric acid may be suitably used. However, glycine and citric acid may be used in combination as long as the binding and reaction between glycine and citric acid may not affect the action of the complexing agent.

The aqueous deposition solution of the present invention may be an aqueous solution having a molar ratio of nickel precursor to phosphorus precursor of about 1: about 5 or more and about 1: less than about 20. When the molar ratio is 1:5 or more, it is possible to use no ion enhancer (e.g., SDS, Na) for electrodeposition₂SO₄Etc.) and a pH adjuster (e.g., ammonia water), and when the molar ratio is 1:20 or more, the characteristics of the electrocatalyst may deteriorate.

FIG. 14 is a graph measuring hydrogen evolution reaction (H) based on the molar ratio of nickel precursor to phosphorus precursor₂SO₄0.5M), and table 4 shows the results at 10mA/cm when the molar ratio of the nickel precursor to the phosphorus precursor is different²The measured overvoltage.

TABLE 4

Molar ratio of nickel precursor to phosphorus precursor	1:2	1:5	1:10	1:20
					Overvoltage (mV)	-85	-82	-74	-84

As shown in fig. 14 and table 4, when the molar ratio of the nickel precursor to the phosphorus precursor is 1:5 and 1:10, the hydrogen generation effect may be significantly improved, and when the molar ratio of the precursors is 1:2 or 1:20, the hydrogen generation effect may be deteriorated. Meanwhile, the molar concentration of the phosphorus precursor may be about 0.1 to 1.25M, and the phosphorus precursor may be sodium hypophosphite.

The substrate on which the nickel copper-phosphide catalyst layer is deposited may be pretreated, for example, the substrate used as an OER electrode may be pretreated. When the electrocatalyst is etched at a high potential, the electrocatalyst may be damaged due to a sharp increase in current, so that the electrocatalyst may be pretreated to improve the durability of the electrocatalyst. The pretreatment may be an oxygen plasma etching method, but is not limited thereto.

Fig. 15A is a picture captured by a scanning electron microscope after 10 minutes of applying 10V to the pre-treated OER electrode, and fig. 15B to 15D are pictures captured by enlarging the picture in fig. 15A. As shown in fig. 15A to 15D, catalytic reaction was observed at the central vertical axis and the central horizontal axis in fig. 15A and 15B, but no dry cracking was observed.

Fig. 16A is a picture captured by a scanning electron microscope after 10 minutes of applying 10V to a non-pretreated OER electrode, and fig. 16B to 16D are pictures captured by enlarging the picture in fig. 16A. As shown in fig. 16A-16D, various cracks were observed.

Therefore, as the pretreatment, for example, oxygen plasma etching, is performed, the durability of the electrocatalyst including the nickel-copper phosphide catalyst layer can be improved, and the durability against the 10V potential can be obtained.

Examples

Hereinafter, production of Ni as an example of the present invention will be described in detail₉₁Cu₉-a P catalyst layer. However, the following examples are provided only for specifically illustrating or explaining the present invention, and the present invention is not limited thereto.

A nickel layer having a thickness of 50nm was formed on a silicon wafer by using an electron beam deposition apparatus, and a UV ozone cleaner (AC-6, 15 to 20 mW/cm)²) The substrate was subjected to hydrophilic surface treatment for 10 minutes.

The aqueous deposition solution was prepared by mixing nickel sulfate, copper sulfate, and sodium hypophosphite as a nickel precursor, a copper precursor, and a phosphorus precursor, respectively, and sodium acetate and citric acid as additives with distilled water. The molar ratio of the nickel precursor to the copper precursor was adjusted to 199:1, the molar ratio of the nickel precursor to each additive was adjusted to 1:1, and the molar ratio of the nickel precursor to the phosphorus precursor was adjusted to 1: 10.

After purging the deposition aqueous solution with nitrogen for 20 minutes, Ni was formed by using an electroplating apparatus₉₁Cu₉-a P catalyst layer. In the formation of the catalyst layer, three-electrode (counter electrode: graphite rod, reference electrode: Ag/AgCl) cyclic voltammetry was used. The potential to be applied ranged from-1.2 to 0.2V, the cycle frequency was set to 3 times, and the sweep rate was set to 10 mV/s.

The substrate on which the catalyst layer was formed after electrodeposition was washed with ethanol and distilled water (in this order), and then dried at room temperature. In the produced substrate, by using a Reactive Ion Etcher (RIE) apparatus, at 100W, 20Pa and 100sccm O₂The substrate to be used as an OER electrode was subjected to oxygen plasma etching for 30 minutes.

Ni to be mentioned below₉₁Cu₉-P electrocatalyst refers to an electrocatalyst such that: ni produced according to the above examples₉₁Cu₉-the P catalyst layer serves as a catalyst layer for the HER electrode and/or OER electrode of the electrocatalyst.

FIG. 17 and FIG. 18 are a drawing showing the reaction of Ni₉₁Cu₉-graph comparing the conductivity and charge mobility of P electrocatalyst with the conductivity and charge mobility of Ni-P electrocatalyst. As shown in FIGS. 17 and 18, Ni is present over the entire potential region₉₁Cu₉the-P electrocatalyst has a conductivity greater than that of the Ni-P electrocatalyst and is due to the fact that Ni is present in comparison to the Ni-P electrocatalyst₉₁Cu₉The circle drawn by the-P electrocatalyst towards the x-axis has a relatively smaller diameter, thus Ni₉₁Cu₉the-P electrocatalyst has a low electrical resistance.

FIG. 19 is a graph for measuring Ni₉₁Cu₉-P electrocatalyst, Pt electrocatalyst, Ni-P electrocatalyst, NiCu electrocatalyst, Ni electrocatalyst and Cu electrocatalystHydrogen evolution reaction (H) of electrocatalyst₂SO₄0.5M). Table 5 shows the current density of 10mA/cm for each electrocatalyst²The measured overvoltage.

TABLE 5

Composition of electrocatalyst	Ni₉₁Cu₉-P	Pt	Ni-P	NiCu	Ni	Cu
							Overvoltage (mV)	-48	-129	-82	-406	-338	-439

As shown in FIG. 19 and Table 5, Ni₉₁Cu₉The measured overvoltage level of the-P electrocatalyst is lower than that of the Pt electrocatalyst, which can be the representative electrocatalyst, and the measured overvoltage level is lower than that of the Ni-P electrocatalyst. By FIG. 19 and Table 5, Ni₉₁Cu₉-P electrocatalyst inHas excellent effect in hydrogen evolution reaction.

FIG. 20 is a graph for measuring Ni₉₁Cu₉Graphs of oxygen evolution reactions (KOH 1M) of P electrocatalyst, Pt electrocatalyst, Ni-P electrocatalyst, NiCu electrocatalyst, Ni electrocatalyst and Cu electrocatalyst. Table 6 shows that when the current density of each electrocatalyst was 10mA/cm²The measured overvoltage.

TABLE 6

Composition of electrocatalyst

Ni₉₁Cu₉-P

Pt

Ni-P

NiCu

Ni

Cu

Overvoltage (mV)

290

>1,000

450

650

590

620

As shown in FIG. 20 and Table 6, Ni was added in the oxygen evolution reaction₉₁Cu₉The overvoltage level measured by the-P electrocatalyst is also lower than that of the Pt electrocatalystThe overvoltage of the agent and its measured overvoltage level is lower than the overvoltage of the Ni-P electrocatalyst. By FIG. 20 and Table 6, Ni₉₁Cu₉the-P electrocatalyst also has excellent effects in oxygen evolution reactions.

FIGS. 21 and 22 are diagrams when a 10V potential is applied to Ni₉₁Cu₉-scanning electron microscopy images of HER and OER electrodes of P electrocatalyst at 10 min. As shown in fig. 21 and 22, the HER electrode and the OER electrode may be durable at high potentials because no drying cracks are observed on the HER electrode surface and the OER electrode surface.

FIG. 23 shows a graph according to the application to Ni₉₁Cu₉-current density of the potential of the P electrocatalyst. Table 7 shows the current densities at potentials of 2V, 5V, 7V and 10V.

TABLE 7

As shown in FIG. 23 and Table 7, due to Ni₉₁Cu₉The P-electrocatalyst exhibits a predetermined current density at a potential of 10V or less, and thus the electrocatalyst can stably operate even if a high potential is applied to the electrocatalyst.

FIG. 24A shows Ni mounted on a headlamp₉₁Cu₉-P electrocatalyst 10, and fig. 24B shows Ni therein₉₁Cu₉-P regions 11 around the electrocatalyst where water vapour is removed. As shown in FIGS. 24A-24B, Ni₉₁Cu₉the-P electrocatalyst 10 may be mounted on a lower portion of an inner surface of the headlamp lens, preferably, on a lower end portion of the inner surface of the lens. Since moisture may remain in the end portion of the headlamp when the lamp is lit, the electrocatalyst may be mounted in the lower portion of the inner surface of the headlamp lens because moisture generated on the surface of the electrocatalyst device may be removed and water flowing down the inner surface of the lens may be decomposed (be baked down). However, the location of the electrocatalyst is not limited as long as the operation of the headlamps and the line of sight of the driver are not obstructed.

FIG. 25 is a graph based on Ni₉₁Cu₉-graph of humidity measurement current density of P electrocatalyst. Table 8 shows the current densities when a 10V potential was applied and the humidities were 20%, 70%, 90%, and 99%.

TABLE 8

As shown in fig. 25 and table 8, as the humidity rises, the current density can be increased, and the current density at each humidity can be constantly displayed. Further, the ability to remove moisture can be constantly maintained while Ni₉₁Cu₉The P electrocatalyst operates stably at 10V potential. At the same time, in Ni₉₁Cu₉-P electrocatalyst, 0.1. mu.l of water are removed per hour at 99% humidity.

The present invention has been described in detail through representative embodiments, but it will be understood by those skilled in the art that various modifications in the above embodiments are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be determined by the claims to be described below and variations or modifications derived from the claims and their equivalents.

Interpretation of reference numerals and symbols

10：Ni₉₁Cu₉-P electrocatalyst

11: region in which water vapor is removed

Claims

1. A method of producing an electrocatalyst, comprising:

forming a metal layer on a substrate;

processing the surface of the metal layer; and

forming a catalyst layer on the surface-treated metal layer by applying an electric potential to a deposition aqueous solution containing a nickel precursor, a copper precursor, a phosphorus precursor and an additive,

wherein the molar ratio of the nickel precursor to the copper precursor is greater than 49: 1.

2. The method of claim 1, wherein the metal layer comprises a nickel layer or a copper layer.

3. The method of claim 1, wherein treating the surface comprises treating the surface using a UV-ozone cleaning treatment.

4. The method of claim 1, wherein the potential is applied by cyclic voltammetry.

5. The method of claim 4, wherein the potential ranges from-1.2 to 0.2V.

6. The method of claim 5, wherein the range of electrical potentials is applied at a frequency of 3 to 15 times.

7. The method of claim 1, wherein the molar concentration of the nickel precursor is 0.02 to 0.5M.

8. The method of claim 1, wherein the nickel precursor comprises one or more of nickel sulfate, nickel nitrate, and nickel acetate.

9. The method of claim 1, wherein the molar concentration of the copper precursor is 0.001 to 0.02M.

10. The method of claim 1, wherein the copper precursor comprises one or more of copper sulfate, copper nitrate, copper acetate, and copper acetylacetonate.

11. The method of claim 1, wherein the additive comprises sodium acetate and further comprises glycine or citric acid.

12. The method of claim 11, wherein the molar ratio of the nickel precursor to sodium acetate, glycine, or citric acid is 1:0.5 or higher and 1: less than 2.

13. The method of claim 11, wherein the molar concentration of each of sodium acetate, glycine, and citric acid is 0.05 or more and less than 0.2M.

14. The method of claim 1, wherein the molar ratio of the nickel precursor to the phosphorus precursor is from 1:5 to 1: 20.

15. The method of claim 1, wherein the molar concentration of the phosphorus precursor is 0.1 to 1.25M.

16. The method of claim 1, wherein the phosphorus precursor comprises sodium hypophosphite.

17. The method of claim 1, wherein the substrate is pretreated using an oxygen plasma etching process.

18. An electrocatalyst comprising an oxygen evolution reaction electrode and a hydrogen evolution reaction electrode,

wherein at least one of the electrodes comprises a substrate and a catalyst layer electrodeposited on the substrate and comprising greater than 65 at% nickel based on 100 at% metal atoms; and less than 35 at% copper.

19. The electrocatalyst according to claim 18, further comprising a metal layer positioned between the substrate and the catalyst layer.

20. The electrocatalyst of claim 19, wherein the metal layer comprises a nickel layer or a copper layer.

21. A vehicle component comprising the electrocatalyst of claim 19.