KR102530075B1 - Multiple complex compound for hydrogen generating, hydrogen generating device comprising the same and producing method of the same - Google Patents

Abstract

The present invention relates to an N-doped graphitic matrix including one or more Ru single particles and one or more Cu single particles; and
It relates to a multi-composite compound including Ru nanoparticles including at least one Cu-N ₃ -Ru bond, a hydrogen generating device including the same, and a manufacturing method thereof.

Description

Multiple complex compound for hydrogen generating, hydrogen generating device comprising the same and producing method of the same}

It relates to a multi-complex compound for generating hydrogen, a hydrogen generating device including the same, and a manufacturing method thereof.

Demand for renewable and clean fuels has grown rapidly over the past few decades and is expected to grow even more in the future. Hydrogen (H ₂ ) is considered an abundant, renewable and clean fuel as a promising chemical energy carrier alternative to fossil fuels. Electrocatalytic water separation is one of the inexpensive, clean and silent technologies for efficient industrial-grade H ₂ production. Pt-based catalysts in acid and alkali solvents are most effective for water electrolysis in the hydrogen evolution reaction (HER) (2H ⁺ + 2e ^- → H ₂ ↑). However, considering the high price of Pt and its unsatisfactory efficiency, a low-cost, high-efficiency, and stable HER electrocatalyst to replace Pt is required. Recently, non-noble metal-based electrocatalysts-based catalysts have shown reasonable HER activity, but their practical applications are still limited due to insufficient acid stability. In addition, several Pt and Ru-based catalysts showed promising HER properties, but still Ru-based catalysts require large amounts of Ru to compete with Pt catalysts.

Thus, there is still a need for a catalyst that not only exhibits better activity than commercial 20 wt% Pt/C or current Ru-based catalysts, but also has high mass activity and durability.

An object of the present invention is to provide a multi-complex compound having excellent mass activity and high stability as a catalyst used in a hydrogen generating device, a hydrogen generating device including the same, and a method for producing the same.

According to one aspect, an N-doped graphitic matrix including one or more Ru single particles and one or more Cu single particles; and

A multi-composite compound is provided, comprising Ru nanoparticles comprising at least one Cu-N ₃ -Ru bond.

According to another aspect, a hydrogen generating device including a cathode including the multi-complex compound is provided.

According to another aspect, mixing melamine, glucose, Ru precursor and Cu precursor to obtain a mixture; and

There is provided a method for producing a multi-complex compound comprising; heat-treating the mixture.

The multiple complex compound according to one aspect has excellent catalytic performance and stability and excellent mass activity in both acidic and basic electrolytes. In addition, Cu atoms improve the electrical conductivity of the graphite matrix by the presence of Ru nanoparticles, and the coordination of Cu particles connected to the surface of Ru nanoparticles by the immisicibility of Cu-Ru creates a new active site (active site). site) is introduced, and aggregation of Ru nanoparticles is prevented to have high durability, and the hydrogen generating device including the multi-composite compound has a long lifespan.

1 is a TEM image of compound 1.
2a and 2b are HAADF-STEM images and EELS spectra of Compound 1, respectively. Figure 2c is the Ru K-edge EXAFS spectra and their fitting results for compound 1 (red) and Cu-foil (blue). 2D is a soft XAS spectrum for Cu 2p L ₃ and L ₂ normalized intensities of compounds 1 and 5. 2f to 2h show structures calculated according to DFT results of (f) Cu-N ₃ -Ru(0001), (g) Ru-N ₂ C ₂ -G _N , and (h) Cu-N ₄ -G _N , respectively. am.
3 is an HRTEM image of compound 1 and compound 2.
Figure 4a is a polarization curve of the hydrogen evolution reaction (HER) of Example 1-1 and Comparative Examples 1-1 to 1-3. Figure 4b is a polarization curve of the hydrogen generation reaction (HER) of Example 2-1 and Comparative Examples 2-1 to 2-3. Figure 4c is the Tafel slope of Figures 4a and 4b. 4D is a mass activity of Example 1-1, Comparative Example 1-1 to Comparative Example 1-3, Example 2-1 and Comparative Example 2-1 to 2-3. 4E and 4F show hydrogen production measured by gas chromatography (GC) in Examples 1-1 and 2-1 at a fixed cathode current of 10 mA*cm ^-2 and Faradaic efficiency calculated based thereon am.
5A and 5B show chronoamperometry versus time for Examples 1-1 and 2-1, respectively, and FIGS. 5C and 5D show chronoamperometry for Comparative Examples 1-1 and 2-1, respectively. It shows the current density vs.
6A is a Nyquist diagram of Examples 1-1 and 2-1, FIG. 6B is a Nyquist diagram of Comparative Examples 1-1 and 2-1, and FIG. 6C is a Nyquist diagram of Comparative Examples 1-3 and 2 Figure 6d is a Nyquist diagram of Comparative Example 1-4 and Comparative Example 2-4, respectively, overpotentials having an amplitude of 10 mV in the frequency range of 10 mHz to 100 KHz -10 and -5 measured in mV (versus RHE) of 0.5MH ₂ SO ₄ and 1M KOH solutions.
7a to 7c show RuC ₂ N ₂ -G _N , RuC ₂ N ₂ (CuN ₄ ) ₂ -G _N and (CuN ₃ ) in Cu(SA)/Ru(NP)-G _N according to Boltzmann transport theory, respectively. These are the geometric and electronic structures of ₂ Ru ₄₉ /RuC ₂ N ₂ (CuN ₄ ) ₂ -G _N .

Since the present inventive concept described below can be applied with various transformations and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present creative idea to a specific embodiment, and should be understood to include all transformations, equivalents, or substitutes included in the technical scope of the present creative idea.

Terms used below are only used to describe specific embodiments, and are not intended to limit the present inventive idea. Singular expressions include plural expressions unless the context clearly dictates otherwise. Hereinafter, terms such as “comprise” or “have” are intended to indicate that there is a feature, number, step, operation, component, part, component, material, or combination thereof described in the specification, but one or the other It should be understood that the presence or addition of the above other features, numbers, steps, operations, components, parts, components, materials, or combinations thereof is not precluded.

Also, terms such as first and second may be used throughout the specification to describe various components, but the components should not be limited by the terms.

In the drawings, the thickness is enlarged or reduced to clearly express various layers and regions. Like reference numerals have been assigned to like parts throughout the specification. Throughout the specification, when a part such as a layer, film, region, plate, etc. is said to be "on" or "above" another part, this includes not only the case directly on top of the other part, but also the case where there is another part in the middle thereof. . Terms are used only to distinguish one component from another.

Until now, the most efficient electrocatalyst for hydrogen-evolution-reaction (HER) is a Pt-based catalyst, but its application in a wide range of industrial/technical fields has been limited due to its high cost and insufficient HER efficiency. The present inventors, N- doped graphite matrix (N-doped graphitic matrix) including one or more Ru single particles, one or more Cu single particles; and Ru nanoparticles containing at least one Cu-N ₃ -Ru bond, which have excellent HER activity in both acidic and basic solvents and significantly improved durability (retention of more than 600 hours in strong acidic solutions) and high mass It was found to exhibit activity, and the present invention was completed through research in this respect. Multiple complex compounds according to one embodiment of the present invention have a low "negative overpotential" (-η = |η| = 12.5/10 mV at 10 mA*cm ^-2 ) in a 0.5MH ₂ SO ₄ /1M-KOH solution. and long-term operational durability (constant current density over 600 hours in acidic solution), very high mass activity (N ₂ for acidic and basic solution) compared to Pt/C catalyst and other Ru catalysts in both acidic and basic solution -/H ₂ - 3.02/4.17 and 2.2/3.0 A*mg _Ru ^-1 ) in a saturated environment. This suggests the possibility of application as a HER catalyst.

Hereinafter, multiple complex compounds according to an aspect of the present invention will be described in detail.

The multi-composite compound may include an N-doped graphitic matrix including one or more Ru single particles and one or more Cu single particles; and Ru nanoparticles including at least one Cu-N ₃ -Ru bond.

For example, in the Ru K-edge EXAFS spectrum for an N-doped graphitic matrix including one or more Cu single particles and one or more Ru nanoparticles, a secondary peak occurs at 2.69 Å, This is CuN ₃ Ru(0001) according to DFT calculation ^. Since it corresponds to 2.44 Å corresponding to the Ru distance, it can be seen that the Ru nanoparticles include at least one Cu—N ₃ -Ru bond.

The multiple composite compound according to an embodiment of the present invention includes Cu single particles together with Ru nanoparticles, thereby improving electrical conduction or charge transfer rate of the graphite matrix. In addition, since the multi-composite compound according to an embodiment of the present invention includes Ru nanoparticles including at least one Cu-N ₃ -Ru bond, the coordination of N-linked Cu single particles on the surface of the Ru nanoparticles is a new activity. It has long-term stability (more than 600 hours in an acidic medium) by introducing a site and preventing aggregation of Ru nanoparticles.

According to one embodiment, the Ru nanoparticles may be Ru nanoparticles in which a plurality of Ru single particles are formed by a metal-metal bond.

According to one embodiment, the Ru nanoparticles may include Cu single particles connected to the surface of the Ru nanoparticles through N atoms.

In the multiple composite compound according to an embodiment of the present invention, due to immiscibility between Ru and Cu, Cu single particles are connected to the surface of Ru nanoparticles through N atoms, and Cu atoms are single, not nanoparticles. It can exist in the form of particles.

In addition, the non-mixability between Ru and Cu can be confirmed through the fact that the total number of bonds between Ru and Cu calculated by the UPBE0-D3/def2-TZVP theory is zero.

In the multicomposite compound according to an embodiment of the present invention, a new active site may be introduced into the Ru nanoparticles due to Cu single particles N-linked to the surface of the Ru nanoparticles.

According to one embodiment, the Cu—N ₃ may have a regular tetrahedral crystal structure.

According to one embodiment, the Ru nanoparticles may be located on the N-doped graphite matrix.

For example, the Ru nanoparticles may be placed in direct contact with the N-doped graphite matrix.

According to one embodiment, the N-doped graphite matrix may be a melamine-derived N-doped graphite matrix.

For example, the N atoms of the N-doped graphite matrix may be derived from melamine.

According to one embodiment, the N-doped graphite matrix may be a glucose-derived N-doped graphite matrix.

For example, some or all of the C atoms of the N-doped graphite matrix may be derived from glucose.

According to one embodiment, the N-doped graphite matrix is pyridine N (pyridinic N), pyrrolic N (pyrrolic N), quaternary N (quaternary N) and pyridine-oxidized N (pyridine-oxidized N) may contain one or more.

According to one embodiment, the N-doped graphite matrix may include pyridinic N.

According to one embodiment, the one or more Ru single particles and/or the one or more Cu single particles may coordinately bond with the pyridinic N.

According to one embodiment, at least one of the Ru single particles included in the N-doped graphite matrix may be connected to two N atoms through a coordination bond and two C atoms through a covalent bond.

For example, the Ru single particle may be expressed in the form of RuSA(-C ₂ N ₂ -G _N ).

According to one embodiment, at least one of the Cu single particles included in the N-doped graphite matrix may be connected to four N atoms through a coordinate bond.

For example, the Cu single particle may be expressed in the form of CuSA-N ₄ -G _N .

In the multi-composite compound according to an embodiment of the present invention, Cu single particles exist as planar CuN ₄ to suppress protrusion of the graphite matrix, thereby increasing the conductivity of the system.

According to one embodiment, the weight ratio of Ru atoms and Cu atoms included in the multi-composite compound may be 1:10 to 10:1, but is not limited thereto.

According to one embodiment, the Ru nanoparticles may have a particle diameter of 1.5 to 3.0 nm.

For example, the Ru nanoparticles may have an average diameter of 2.3 nm, but are not limited thereto.

According to one embodiment, the size of the Ru nanoparticles may be uniform.

According to another aspect, a hydrogen generating device including the aforementioned multi-complex compound is provided. The multi-complex compound can function as a hydrogen evolution catalyst in both acidic and basic solvents.

For example, the hydrogen generator may include an aqueous solution having a pH of 1 to 14 as an electrolyte.

According to another aspect, as a method for producing the multi-complex compound, obtaining a mixture by mixing melamine, glucose, Ru precursor and Cu precursor; And heat-treating the mixture; a method for producing a multi-complex compound comprising a may be provided.

According to one embodiment, the method for preparing the multi-complex compound may further include calcining the mixture under an inert gas atmosphere after the heat treatment step.

According to one embodiment, the inert gas of the calcination step may include nitrogen, argon, helium, or a combination thereof.

According to one embodiment, the Ru precursor may include a halide, a sulfur oxide, a nitroxide, a carbonate, a hydroxide, a phosphorus oxide, a selenide, or any combination thereof of metal Ru.

According to one embodiment, the Cu precursor may include a halide, a sulfur oxide, a nitroxide, a carbonate, a hydroxide, a phosphorus oxide, a selenide, or any combination thereof of metal Cu.

According to one embodiment, the step of obtaining the mixture may be performed in a solution process.

According to one embodiment, the solution process may include stirring the melamine, glucose, and Ru precursor in a solvent (eg, deionized water).

According to one embodiment, the heat treatment includes a first heat treatment step and a second heat treatment step;

A heat treatment temperature of the first heat treatment step may be lower than a heat treatment temperature of the second heat treatment step.

According to one embodiment, the first heat treatment step may be a hydrothermal reaction and may include a drying step.

According to one embodiment, the first heat treatment step may be performed at 150 to 200 °C.

According to one embodiment, the second heat treatment step may be performed at 700 to 900 °C.

For example, the second heat treatment step may be performed at 750 to 850 °C. When the heat treatment temperature is within the above range, an N-doped graphite matrix is formed with glucose and melamine, and Cu single particles bonded to the surface of the Ru nanoparticles with N atoms are introduced, thereby improving HER activity and stability.

According to one embodiment, the first heat treatment step may be performed for 18 to 36 hours.

According to one embodiment, the second heat treatment step may be performed for 3 to 5 hours.

According to one embodiment, the second heat treatment step may include annealing the product of the first heat treatment step in a furnace tube, discharging it in a sulfuric acid solution, filtering it, and washing it. there is.

By including the above step, remaining reactants and impurities may be removed.

Hereinafter, synthesis examples and examples will be described in more detail with respect to multiple complex compounds according to one embodiment of the present invention.

Raw material

Ruthenium (III) chloride hydrate, 99.999% Copper (II) sulfate pentahydrate, D-(+) glucose, 99% melamine, 95% sulfuric acid and 90% potassium hydroxide were purchased from Sigma-Aldrich. 20% Pt on Vulcan XC-72 and 20% Ir on Vulcan XC-72 were purchased from Permetek Co.

[Synthesis Example]

Synthesis Example 1

Melamine (4 g), glucose (2 g), and Ru precursor (Ruthenium (III) chloride hydrate, 400 mg, 1.93 mmol) were mixed with Cu precursor (Copper (II) sulfate pentahydrate, 100 mg, 0.4 mmol) in deionized water. (15 mL), and the mixture was put into a Teflon-lined stainless steel autoclave (50 mL) and stirred at room temperature for 3 hours. After stirring, the mixture was sealed and incubated at 180°C for 24 hours and then dried at 80°C. To activate the product, the temperature was raised to 800 °C in a furnace tube at a heating rate of 3 °C min ^-1 and left for 4 hours. After cooling the product to room temperature under Ar gas, it was placed in 80°C, 9M H ₂ SO ₄ (15 mL) for 12 hours to remove impurities. Afterwards, it was filtered and washed in ethanol and hot deionized water (80° C.), and the powder was dried in vacuo overnight. The activated product was calcined at 800° C. for 4 hours under Ar gas to obtain Compound 1 (Cu/Ru@G _N ).

Synthesis Example 2

Compound 2 (Ru@G _N ) was obtained in the same manner as in Synthesis Example 1, except that the Cu precursor was not included.

Synthesis Example 3

Compound 3 (Ru ^* @G _N ) was obtained in the same manner as in Synthesis Example 1, except that the Cu precursor was not included and 0.8 g of the Ru precursor was used.

Synthesis Example 4

Compound 4 (Cu ^* /Ru@G _N ) was obtained in the same manner as in Synthesis Example 1, except that 300 mg of the Cu precursor was used.

Synthesis Example 5

Compound 5 (Cu@G _N ) was obtained in the same manner as in Synthesis Example 1, except that the Ru precursor was not included.

[Evaluation Example 1: Physical/chemical properties of multiple complex compounds]

(Assessment Methods)

To perform HRTEM, STEM and EELS, a transmission electron microscope (TEM, FEI Titan3 G2 60-300) was used with a monochromator at a voltage of 80 kV.

EXAFS analysis was performed with an ionization detector (Oxford) of the Pohang Accelerator Laboratory (PAL).

X-ray absorption spectra (XAS) for the Ru K-edge were acquired at room temperature using PAL's beamline 6D.

Background subtraction, normalization and Fourier-transform were performed by standard procedures in the ATHENA program.

Extracted EXAFS signals (χ(r) and k ³ χ(k)) were analyzed for all compounds, and EXAFS fitting was performed using the Artemis program.

(Evaluation results)

1 is a TEM image of Compound 1, showing that Ru nanoparticles are uniformly distributed with an average diameter of 2.3 nm in the graphite matrix.

2a and 2b are HAADF-STEM images and EELS spectra of Compound 1, respectively. In FIG. 2A, a blue “+” indicates a region in which Ru nanoparticles are present, and a green box indicates a region in Compound 1 in which Ru nanoparticles are not present. Figure 2b shows the EELS spectrum (blue spectrum) for the portion marked with a blue "+" and the EELS spectrum (green spectrum) for the portion marked with a green box, respectively. The blue spectrum shows a strong Ru peak, a weak Cu peak, and unbranched N-π ^* and N-σ ^* peaks, indicating that Ru nanoparticles, Cu single particles, and non-planar N atoms are involved in metal bonding. In addition, the spectrum for the green box region without Ru nanoparticles shows a weak Ru peak, a weak Cu peak, and moderately branched N-π ^* and N-σ ^* peaks, which indicate that Ru and Cu single particles are almost It shows that it is connected to the planar N atom.

Figure 2c is the Ru K-edge EXAFS spectra and their fitting results for compound 1 (red) and Cu-foil (blue). Compound 1 shows a prominent peak at 1.7 Å, and the peak originates from a 1 ^st -shell Cu-N bond with a high coordination number (CN) of 3 to 4, corresponding to d(Cu-N) = 2.0 Å. . Cu-foil shows a prominent peak at 2.24 Å, which originates from the Cu-Cu bond, corresponding to d(Cu-Cu) = 2.56 Å. In Compound 1, no peak is observed at around 2.24 Å, where a prominent peak of the Cu-foil appears, indicating that Cu nanoparticles do not exist in Compound 1 and Cu atoms exist only in the form of Cu single particles. In addition, compound 1 shows a secondary peak at 2.69Å, which is CuN ₃ Ru (0001) to Cu ^... Corresponds to 2.44 Å, which corresponds to the Ru distance (not Cu-Ru bonds). Therefore, it can be confirmed that a Cu-N ₃ -Ru bond exists in Compound 1.

Figure 2d is the soft XAS spectrum for Cu 2p L ₃ and L ₂ normalized intensities of compounds 1 and 5, and Figure 2e is CuN ₄ in graphite matrix (G _N ) and CuN ₃ in Ru(0001) slab system. It is an XAS spectrum calculated according to PBE0/ROCIS for In FIG. 2D, it is shown that Cu single particles on the graphite matrix (G _N ) in both Compounds 1 and 5 are coordinated by approximately 4 N atoms to form planar CuN ₄ . However, since Cu single particles in Compound 1 are present in both Ru nanoparticles and G _N , the Cu L ₃ and L ₂ intensity peaks are red-shifted by about 0.3 eV compared to Compound 5 in which only Cu single particles in G _N exist. indicates This value agrees with the predicted redshift based on PBE044 in Fig. 2e.

2f to 2h show structures calculated according to DFT results of (f) Cu-N ₃ -Ru(0001), (g) Ru-N ₂ C ₂ -G _N , and (h) Cu-N ₄ -G _N , respectively. am.

3 is an HRTEM image of compound 1 and compound 2, (a) and (b) are HRTEM images of compound 1, (c) and (d) are HRTEM images of compound 2, (a) and (b) ), Ru nanoparticles of compound 1 are indicated by red circles, Ru nanoparticles of compound 2 in (c) and (d) are indicated by blue circles, and black dotted circles are guide lines to help track the blue circles. . (a) and (c) are HRTEM images before irradiation with an electron beam, and (b) and (d) are HERTEM images after irradiation with an electron beam. However, in Compound 1, Ru nanoparticles were not combined due to the presence of Cu single particles even when the electron beam was irradiated for a long time of 5 minutes or more, but in the case of Compound 2, it was confirmed that they were rapidly merged within 1 minute. This shows that as long as Cu single particles of Compound 1 are located on N ₃ Ru(NP), the Cu single particles prevent aggregation of Cu—N ₃ Ru(NP) by non-mixing between Ru and Cu atoms.

Table 1 shows the weight percent of Ru atoms and Cu atoms of Compounds 1 to 5, and shows values calculated by inductively-coupled-plasma atomic-emission-spectroscopy (ICP-AES).

Ru (% by weight) Cu (% by weight) compound 1 2.9 1.48 compound 2 7.8 - compound 3 15.7 - compound 4 2.0 2.08 compound 5 - 2.16

[Example]

Example 1-1: Preparation of 3-electrode system in acidic solution

A glassy carbon electrode (GCE) with a diameter of 3 mm was used as the working electrode loaded with Compound 1, a saturated calomel electrode and a graphite rod were used as reference and counter electrodes, and a three-electrode using an acidic solvent (0.5MH ₂ SO ₄ ) was used. system was made.

Comparative Examples 1-1 to 1-4

A three-electrode system was prepared in the same manner as in Example 1-1, except that Compounds 2 to 4 and commercial 20% by weight Pt/C in Table 2 were used instead of Compound 1 in Example 1-1.

Compound loaded on the working electrode Example 1-1 One Comparative Example 1-1 2 Comparative Example 1-2 3 Comparative Example 1-3 4 Comparative Example 1-4 Commercial 20 wt% Pt/C

Example 2-1: Preparation of 3-electrode system in basic solution

A glassy carbon electrode (GCE) with a diameter of 3 mm was used as a working electrode loaded with Compound 1, a saturated calomel electrode and a graphite rod were used as reference and counter electrodes, and a three-electrode system using a basic solvent (1M KOH) was prepared. did

Comparative Examples 2-1 to 2-4

A three-electrode system was prepared in the same manner as in Example 2-1, except that Compounds 2 to 4 shown in Table 3 and commercial 20% by weight Pt/C were used instead of Compound 1 in Example 2-1.

Compound loaded on the working electrode Example 2-1 One Comparative Example 2-1 2 Comparative Example 2-2 3 Comparative Example 2-3 4 Comparative Example 2-4 Commercial 20 wt% Pt/C

[Evaluation Example 2: Electrochemical performance evaluation]

(Assessment Methods)

Linear scan voltammogram (LSV)

In order to measure HER activity, VSP-Modular 2 Channels Potentiostat/ Galvanostat/EIS (Bio-Logic Science Instruments) was performed.

All data collected were 85% iR compensated unless otherwise stated, and 85% iR compensated potential at j = 10 mAcm ^-2 for H ₂ saturated 0.5MH ₂ SO ₄ and 1M KOH with solution resistances of 8.4 and 10 Ω. was calculated as 5 and 6 mV, and the current density was normalized to the cross section of RDE (0.07065 cm ² ).

LSV was performed in H ₂ saturated 0.5MH ₂ SO ₄ and H ₂ saturated 1M KOH solvents from -0.4 to 0.1 V (versus RHE) and a scan rate of 2 mV/s.

In addition, the Tafel slope values for Example 1-1, Comparative Examples 1-1 to 1-4, Example 2-1, and Comparative Examples 2-2 to 2-4 represent the steady-state potential data after iR compensation. was calculated using

chronoamperometry

For the durability test, it was performed on a VSP-Modular 2 Channels Potentiostat/Galvanostat/EIS (Bio-Logic Science Instruments) using Examples 1-1 and 2-1 at room temperature.

In H ₂ saturated 0.5 MH ₂ SO ₄ and H ₂ saturated 1 M KOH solvents without iR correction, constant overpotentials of −20 and −35 mV in H ₂ saturated 0.5 MH ₂ SO ₄ respectively for 12 days, in H ₂ saturated 1 M KOH - It was performed for 60 h with a constant overpotential of 15 mV.

For Comparative Examples 1-1 and 1-2, the overpotential proceeded in the same manner, except that the overpotential progressed to -60 mV in an acidic solution and -35 mV in a basic solution for 24 hours.

Electrochemical Impedance Spectroscopy (EIS)

EIS spectra were measured using Examples 1-1 and 2-1 and Comparative Examples 1-1, 1-2, 1-4, 2-1, 2-2 and 2-4. EIS was measured in 0.5 MH ₂ SO ₄ and 1 M KOH solutions at overpotentials of −10 and −5 mV (versus RHE), respectively, with an amplitude of 10 mV in the frequency range of 10 mHz to 100 KHz.

(Evaluation results)

Linear sweep voltammogram (LSV)

In order to evaluate the HER activity of the three-electrode system fabricated in Example 1-1, Comparative Example 1-1 to Comparative Example 1-3, Example 2-1 and Comparative Example 2-1 to 2-3, LSV was performed.

Figure 4a is a polarization curve (acidic solvent) of the hydrogen generation reaction (HER) of Example 1-1 and Comparative Examples 1-1 to 1-3, Figure 4b is Example 2-1 and Comparative Examples 2-1 to 2 The polarization curve (basic solvent) of the hydrogen evolution reaction (HER) of -3, and FIG. 4c is the Tafel slope of FIGS. 4a and 4b. The overpotential (-η) of Example 1-1 is 12.5 1 mV, which is lower than the 18 mV of Comparative Example 1-4, and the overpotential (-η) of Example 2-1 is 10 1 mV, Comparative Example Since it is lower than 43 mV of 2-4, it can be seen that compound 1 has improved HER activity than Pt/C catalyst in both acidic and basic solutions.

compound compound loading
(mg/cm ² ) Overpotential (-η) (mV)
(at 10 mA/cm ² ) 0.5 H ₂ SO ₄ /1M KOH;
injection rate, gas Example 1-1 One 0.283 12.5ㅁ1 2 mV/s, H ₂ (1600 rpm);
0.07065 cm ² Comparative Example 1-2 3 0.283 16.5 2 mV/s, H ₂ (1600 rpm);
0.07065 cm ² Comparative Example 1-4 Commercial 20 wt% Pt/C 0.283 18 2 mV/s, H ₂ (1600 rpm);
0.07065 cm ² Example 2-1 One 0.283 10ㅁ1 2 mV/s, H ₂ (1600 rpm);
0.07065 cm ² Comparative Example 2-2 3 0.283 14 2 mV/s, H ₂ (1600 rpm);
0.07065 cm ² Comparative Example 2-4 Commercial 20 wt% Pt/C 0.283 43 mV 2 mV/s, H ₂ (1600 rpm);
0.07065 cm ²

4D shows the mass activity of Example 1-1, Comparative Example 1-1 to Comparative Example 1-3, Example 2-1 and Comparative Example 2-1 to 2-3, the mass activity was calculated by the following formula.

The superior performance of Examples 1-1 and 2-1 is comparable to the mass activity (1.05 / 0.08 A*mg _Pt ^-1 ) of Comparative Examples 1-4 and 2-4 employing commercial 20 wt% Pt/C and other Ru-based catalysts. Compared to Comparative Examples 1-1 to 1-3 and 2-1 to 2-5 employing , it can be seen by confirming that they have a large mass activity of 2.2 / 3.0 A*mg _Ru ^-1 , respectively.

4E and 4F show the hydrogen production amount and Faraday efficiency in Examples 1-1 and 2-1 at a fixed cathode current of 10 mA*cm ^-2 . The Faraday efficiency was calculated by dividing the volume of hydrogen generated by the calculated theoretical charge value at a fixed current of 10 mA*cm ^-2 , which is a measure of the purity of generated hydrogen, and is a 0.5MH ₂ SO ₄ and 1M KOH solution. In , the average efficiency of compound 1 was 95 ± 1%, showing that the current applied to the HER process was almost completely utilized.

chronoamperometry

In order to evaluate the stability of the three-electrode system fabricated in Examples 1-1 and 2-1, a chronoamperometric ( it ) response was performed.

Figure 5a shows that the current density is maintained at a constant current density for 600 hours as a result of measuring the current density for a total of 12 days in Example 1-1. That is, it can be seen that Example 1-2 has excellent stability in acidic solvents.

Figure 5b shows that as a result of measuring the current density for a total of 60 hours in Example 2-1, it is maintained at a constant current density for more than 48 hours. That is, it can be seen that Example 2-1 has excellent stability even in basic solvents.

5c and 5d show current densities measured over time for Comparative Examples 1-1 and 2-1, respectively. After 24 hours, current densities reduced by 35% and 48%, respectively, were measured.

Electrochemical Impedance Spectroscopy (EIS)

Charge transfer resistance ( R _ct ) of the 3-electrode system fabricated in Examples 1-1 and 2-1 and Comparative Examples 1-1, 1-3, 1-4, 2-1, 2-3 and 2-4 To evaluate, EIS was performed.

6A is a Nyquist diagram of Examples 1-1 and 2-1, FIG. 6B is a Nyquist diagram of Comparative Examples 1-1 and 2-1, and FIG. 6C is a Nyquist diagram of Comparative Examples 1-3 and 2 It is a Nyquist diagram of -3, and FIG. 6d is a Nyquist diagram of Comparative Examples 1-4 and 2-4. The calculation of R _CT through FIGS. 6A to 6D is shown in Table 5 below.

Charge transfer resistance (R _CT ) Example 1-1 4.3 Comparative Example 1-1 79.3 Comparative Example 1-3 74.6 Comparative Example 1-4 12.4 Example 2-1 4.9 Comparative Example 2-1 52.3 Comparative Example 2-3 29.3 Comparative Example 2-4 41.6

Through Table 5, it can be confirmed that the charge transfer resistance (R _ct ) of Examples 1-1 and 2-1 is significantly smaller than that of other comparative examples, and therefore, during the HER reaction, fast charge in both acid and basic solutions movement can occur. That is, it shows that the high conductivity of Compound 1, which is indicated by the presence of Cu single atoms, provides fast catalytic kinetics for HER.

[Evaluation Example 3: Atomic Evaluation]

In order to explain the excellent electron transport ability of the multi-complex compound according to one embodiment of the present invention due to the existence of a single atom of Cu, the electronic structure calculation for electrical conductivity (σ) was performed according to the Boltzmann transport theory, and the calculation The geometric and electronic structures of the H-adsorbed Cu single particle/Ru nanoparticle-graphite matrix system (Cu(SA)/Ru(NP)-G _N ) are shown in FIGS. 7a to 7c. That is, FIGS. 7a to 7c show RuC ₂ N ₂ -G _N , RuC ₂ N ₂ (CuN ₄ ) ₂ -G _N and (CuN) in Cu(SA)/Ru(NP)-G _N according to Boltzmann transport theory, respectively. ₃ ) ₂ Ru ₄₉ /RuC ₂ N ₂ (CuN ₄ ) These are the geometric and electronic structures of ₂ -G _N.

In FIGS. 7A to 7C , Ru is shown in gray, Cu is orange, N is blue, C is brown, and H is cyan in relation to the three-dimensional structure, and in relation to the electronic structure, Ru is represented by a red dot curve and Cu is blue. Represented by a dot curve, the Fermi level E _F corresponds to 0 eV.

7a shows that the extended π orbital plane of the graphite matrix is interrupted due to the protrusion of RuN ₂ C ₂ , but in FIGS. 7b and 7c, Cu single particles are present as planar CuN ₄ and are tense without interruption around E _F It can be confirmed that a band is formed. In addition, the electrical conductivity of RuC ₂ N ₂ -G _N in FIG. 7a, the electrical conductivity of RuC ₂ N ₂ (CuN ₄ ) ₂ -G _N in FIG. 7b, and the electrical conductivity of (CuN ₃ ) ₂ Ru ₄₉ /RuC ₂ N ₂ in FIG. 7c When comparing the electrical conductivity of (CuN ₄ ) ₂ -G _N , the ratio is 1 : 5.22 : 6.13. That is, through the above results, it can be seen that the planar CuN ₄ suppresses the protrusion of the graphite matrix to increase the conductivity of the system.

In addition, the Cu-s orbitals show more scattering bands for the local Ru-d orbitals around the Fermi energy (E _F ), which in the graphite matrix It clearly shows the role of Cu single particles in enhancing electron transport. Therefore, not only do Ru single particles have highly enhanced electron transport/conductivity by Cu single particles, resulting in ΔG _H near zero, but also Cu single particles form new fcc-active sites (ΔG _H near zero) on Ru nanoparticles. It can be seen that a multicomposite compound in which non-mixable Cu and Ru single particles exist in the presence of Ru nanoparticles can be used as a high-performance electrocatalyst.

In conclusion, according to the foregoing examples and comparative examples, the multi-complex compound is an excellent electrocatalyst for hydrogen production. The multicomplex compound exhibits excellent HER activity and long-term operational durability in both acidic and basic solutions. In acidic solution (0.5MH ₂ SO ₄ ), the multi-complex compound exhibits low overpotential (-η, 12.5 mV) and long-term operating durability (maintaining constant current density over 600 hours), and in basic solution (1M KOH) , the multicomplex compound exhibits a low overpotential (−η, 10 mV). In addition, the multi-complex compound has a very high mass activity (N ₂ -/H ₂ - 3.02/4.17 and 2.2/3.0 A*mg _Ru in a saturated environment) compared to the Pt/C catalyst and other Ru catalysts in both acidic and basic solutions. ^-1 ).

That is, in the _multi -composite compound, ΔG _H of the fcc-active site on the surface of the Ru nanoparticles close to Cu single particles (Cu SAs) is close to 0 (H-absorption/ facilitates desorption), the presence of Cu single particles on the matrix increases the conductivity at the Ru(-N ₂ C ₂ -G _N ) single particle site (faster charge/electron transfer for faster H ⁺ reduction) In particular, Cu single particles prevent oxidation and aggregation of the metal, improving long-term operational durability. ＊

Therefore, the multi-composite compound is an electrocatalyst with improved stability and catalytic activity, showing that it can be used in high-efficiency energy devices ready for industrial applications.

In the above, preferred embodiments according to the present invention have been described with reference to drawings and embodiments, but this is only exemplary, and those skilled in the art can make various modifications and equivalent other implementations therefrom. will be able to understand Therefore, the scope of protection of the present invention should be defined by the appended claims.

<References>

[1] Q. Lu, A.-L. Wang, Y. Gong, W. Hao, H. Cheng, J. Chen, B. Li, N. Yang, W. Niu, J. Wang, Y. Yu, X. Zhang, Y. Chen, Z. Fan, X. -J. Wu, J. Chen, J. Luo, S. Li, L. Gu, H. Zhang, Nat. Chem., 2018, 10 , 456-461.

[2] C.-H. Chen, D. Wu, Z. Li, R. Zhang, C.-G. Kuai, X. -R. Zhao, C.-K. Dong, S.-Z. Qiao, H. Liu and X.-W. Du, Adv. Energy Mater , 2019, 9 , 1803913.

[3] B. Huang, H. Kobayashi, T. Yamamoto, S. Matsumura, Y. Nishida, K. Sato, K. Nagaoka, S. Kawaguchi, Y. Kubota and H. Kitagawa, J. Am. Chem. Soc. , 2017, 139 , 4643-4646.

[4] J. Deng, H. Li, J. Xiao, Y. Tu, D. Deng, H. Yang, H. Tian, J. Li, P. Ren and X. Bao, Energ. Environ. Sci. , 2015, 8 , 1594-1601.

[5] Y. Pan, S. Liu, K. Sun, X. Chen, B. Wang, K. Wu, X. Cao, W.-C. Cheong, R. Shen, A. Han, Z. Chen, L. Zheng, J. Luo, Y. Lin, Y. Liu, D. Wang, Q. Peng, Q. Zhang, C. Chen, Y. Li, Angew. Chem. Int. Ed. 2018 , 57 , 8614

[6] S. Sultan, J. N. Tiwari, J.-H. Jang, AM Harzandi, F. Salehnia, SJ Yoo and KS Kim, Adv. Energy Mater. , 2018, 8 , 1801002.

[7] JN Tiwari, WG Lee, S. Sultan, M. Yousuf, AM Harzandi, V. Vij and KS Kim, ACS Nano , 2017, 11 , 7729-7735.

[8] J. A. Turner, Science , 2004, 305 , 972.

[9] D. Voiry, HS Shin, KP Loh and M. Chhowalla, Nat. Rev. Chem. , 2018, 2 , 0105.

[10] JN Tiwari, S. Sultan, CW Myung, T. Yoon, N. Li, M. Ha, AM Harzandi, HJ Park, DY Kim, SS Chandrasekaran, WG Lee, V. Vij, H. Kang, TJ Shin , HS Shin, G. Lee, Z. Lee and KS Kim, Nat. Energy , 2018, 3 , 773-782.

[11] D. Liu, X. Li, S. Chen, H. Yan, C. Wang, C. Wu, Y. A. Haleem, S. Duan, J. Lu, B. Ge, PM Ajayan, Y. Luo, J. Jiang and L. Song, Nat. Energy , 2019, 4 , 512-518.

[12] H. Yin, S. Zhao, K. Zhao, A. Muqsit, H. Tang, L. Chang, H. Zhao, Y. Gao and Z. Tang, Nat. Commun. , 2015, 6 , 6430.

[13] X. Cheng, Y. Li, L. Zheng, Y. Yan, Y. Zhang, G. Chen, S. Sun and J. Zhang, Energ. Environ. Sci. , 2017, 10 , 2450-2458.

[14] N. Cheng, S. Stambula, D. Wang, M. N. Banis, J. Liu, A. Riese, B. Xiao, R. Li, T.-K. Sham, L. -M. Liu, G. A. Botton and X. Sun, Nat. Commun. , 2016, 7 , 13638.

[15] M. Li, K. Duanmu, C. Wan, T. Cheng, L. Zhang, S. Dai, W. Chen, Z. Zhao, P. Li, H. Fei, Y. Zhu, R. Yu , J. Luo, K. Zang, Z. Lin, M. Ding, J. Huang, H. Sun, J. Guo, X. Pan, W. A. Goddard, P. Sautet, Y. Huang and X. Duan, Nat. Catal. , 2019, 2 , 495-503.

[16] V. Vij, S. Sultan, AM Harzandi, A. Meena, JN Tiwari, W.-G. Lee, T. Yoon and KS Kim, ACS Catal. , 2017, 7 , 7196-7225.

[17] Y. Zheng, Y. Jiao, Y. Zhu, LH Li, Y. Han, Y. Chen, A. Du, M. Jaroniec and SZ Qiao, Nat. Commun. 2014, 5 , 3783.

[18] J. Mahmood, F. Li, S.-M. Jung, MS Okyay, I. Ahmad, S.-J. Kim, N. Park, H.Y. Jeong and J.-B. Baek, Nat. Nanotechnol. , 2017, 12 , 441-446.

[19] Y. Zheng, Y. Jiao, Y. Zhu, LH Li, Y. Han, Y. Chen, M. Jaroniec and S.-Z. Qiao, J. Am. Chem. Soc. , 2016, 138 , 16174-16181.

[20] J. Xu, T. Liu, J. Li, B. Li, Y. Liu, B. Zhang, D. Xiong, I. Amorim, W. Li and L. Liu, Energ. Environ. Sci. , 2018, 11 , 1819-1827.

[21] J. Su, Y. Yang, G. Xia, J. Chen, P. Jiang and Q. Chen, Nat. Commun. , 2017, 8 , 14969.

[22] T. Liu, B. Feng, X. Wu, Y. Niu, W. Hu and CM Li, ACS Appl. Energy Mater. , 2018, 1 , 3143-3150.

[23] R. Ye, Y. Liu, Z. Peng, T. Wang, AS Jalilov, B.I. Yakobson, S.-H. Wei and JM Tour, ACS Appl. Mater. Inter. , 2017, 9 , 3785-3791.

[24] K. Li, Y. Li, Y. Wang, J. Ge, C. Liu and W. Xing, Energ. Environ. Sci. , 2018, 11 , 1232-1239.

[25] B. Lu, L. Guo, F. Wu, Y. Peng, JE Lu, TJ Smart, N. Wang, YZ Finfrock, D. Morris, P. Zhang, N. Li, P. Gao, Y. Ping and S. Chen, Nat. Commun. , 2019, 10 , 631.

[26] J. N. Tiwari, A. M. Harzandi, M. Ha, S. Sultan, C. W. Myung, H. J. Park, D. Y. Kim, P. Thangavel, A. N. Singh, P. Sharma, S. S. Chandrasekaran, F. Salehnia, J.-W. Jang, HS Shin, Z. Lee and KS Kim, Adv. Energy Mater. , 2019, 9 , 1900931.

[27] J. Mao, C.-T. He, J. Pei, W. Chen, D. He, Y. He, Z. Zhuang, C. Chen, Q. Peng, D. Wang and Y. Li, Nat. Commun. , 2018, 9 , 4958.

[28] C.-T. Dinh, A. Jain, FPG de Arquer, P. De Luna, J. Li, N. Wang, X. Zheng, J. Cai, BZ Gregory, O. Voznyy, B. Zhang, M. Liu, D. Sinton, EJ Crumlin and EH Sargent, Nat. Energy , 2019, 4 , 107-114.

[29] C. Zhang, J. Sha, H. Fei, M. Liu, S. Yazdi, J. Zhang, Q. Zhong, X. Zou, N. Zhao, H. Yu, Z. Jiang, E. Ringe , B.I. Yakobson, J. Dong, D. Chen and JM Tour, ACS Nano , 2017, 11 , 6930-6941.

[30] X. Cui, W. Li, P. Ryabchuk, K. Junge and M. Beller, Nat. Catal. , 2018, 1 , 385-397.

[31] J. Zhang, Y. Zhao, X. Guo, C. Chen, C.-L. Dong, R.-S. Liu, C.-P. Han, Y. Li, Y. Gogotsi and G. Wang, Nat. Catal. , 2018, 1 , 985-992.

[32] L. Cao, Q. Luo, W. Liu, Y. Lin, X. Liu, Y. Cao, W. Zhang, Y. Wu, J. Yang, T. Yao and S. Wei, Nat. Catal. , 2018, 2 , 134-141.

[33] N. Aoki, H. Inoue, H. Kawasaki, H. Daimon, T. Doi and M. Inaba, J. Electrochem. Soc. , 2018, 165 , F737-F747.

[34] J. Hu, L. Wu, KA Kuttiyiel, KR Goodman, C. Zhang, Y. Zhu, MB Vukmirovic, MG White, K. Sasaki and RR Adzic, J. Am. Chem. Soc. , 2016, 138 , 9294-9300.

[35] Y.-T. Kim, P. P. Lopes, S.-A. Park, A Y Lee, J. Lim, H. Lee, S. Back, Y. Jung, N. Danilovic, V. Stamenkovic, J. Erlebacher, J. Snyder and NM Markovic, Nat. Commun. , 2017, 8 , 1449.

[36] X. Yang, J.-K. Sun, M. Kitta, H. Pang and Q. Xu, Nat. Catal. , 2018, 1 , 214-220.

[37] W. Liu, E. Hu, H. Jiang, Y. Xiang, Z. Weng, M. Li, Q. Fan, X. Yu, E.I. Altman and H. Wang, Nat. Commun. , 2016, 7 , 10771.

[38] J.N. Tiwari, Y.-K. Seo, T. Yoon, WG Lee, WJ Cho, M. Yousuf, AM Harzandi, D.-S. Kang, K.-Y. Kim, P. -G. Suh and KS Kim, ACS Nano , 2017, 11 , 742-751.

[39] Y. Lin, X. Pan, W. Qi, B. Zhang and DS Su, J. Mater. Chem. A , 2014, 2 , 12475-12483.

[40] K. Suenaga, E. Sandro, C. Colliex, CJ Pickard, H. Kataura and S. Iijima, Phys. Rev. B , 2001, 63 , 165408.

[41] B. Hammer, L. B. Hansen and J. K. Nørskov, Phys. Rev. B , 1999, 59 , 7413-7421.

[42] A. Tkatchenko and M. Scheffler, Phys. Rev. Lett. , 2009, 102 , 073005.

[43] H. Shi, K. Jacobi and G. Ertl, J. Chem. Phys. , 1993, 99 , 9248-9254.

[44] JP Perdew, M. Ernzerhof and K. Burke, J. Chem. Phys. , 1996, 105 , 9982-9985.

[45] JP Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett. , 1996, 77 , 3865-3868.

[46] F. Neese, Wiley Interdiscipp Rev. Comput. Mol. Sci. , 2012, 2 , 73-78.

[47] JR Lombardi and B. Davis, Chem. Rev. , 2002, 102 , 2431-2460.

[48] JH Sinfelt, GH Via, FW Lytle and RB Greegor, J. Chem. Phys. , 1981, 75 , 5527-5537.

[49] J. Zheng, Y. Yan and B. Xu, J. Electrochem. Soc. 2015, 162 , 14, F1470-F1481

[50] S. Sultan, J. N. Tiwari, A. N. Singh, S. Zhumagali, M. Ha, C. W. Myung, P. Thangavel and K. S. Kim, Adv. Energy Mater. , 2019, 9 , 1900624.

Claims (20)

an N-doped graphitic matrix including one or more Ru single particles and one or more Cu single particles; and
Ru nanoparticles comprising at least one Cu-N ₃ -Ru bond;
The Ru nanoparticles include Cu single particles connected to the surface through N atoms, a multi-composite compound. According to claim 1,
The Ru nanoparticles are Ru nanoparticles in which a plurality of Ru single particles are formed by metal-metal bonding. delete According to claim 1,
The Cu—N ₃ has a tetrahedral crystal structure, a multi-complex compound. According to claim 1,
Wherein the Ru nanoparticles are located on the N-doped graphite matrix. According to claim 1,
Wherein the N-doped graphite matrix is a melamine-derived N-doped graphite matrix. According to claim 1,
The N-doped graphite matrix includes pyridinic N,
The one or more Ru single particles and / or the one or more Cu single particles coordinately bonded to the pyridinic N, multiple complex compounds. According to claim 1,
At least one of the Ru single particles included in the N-doped graphite matrix is linked to two N atoms by a coordinate bond and two C atoms by a covalent bond. According to claim 1,
At least one of the Cu single particles included in the N-doped graphite matrix is connected to four N atoms by a coordinate bond, a multi-composite compound. According to claim 1,
A weight ratio of Ru atoms and Cu atoms included in the multi-composite compound is 1:10 to 10:1, a multi-composite compound. According to claim 1,
The Ru nanoparticles have a particle diameter of 1.5 to 3.0 nm, a multi-composite compound. Claims 1, 2 and 4 to 11, a hydrogen generating device comprising a cathode comprising a multi-composite compound according to any one of claims. According to claim 12,
The hydrogen generating device comprises an aqueous solution having a pH of 1 to 14 as an electrolyte.

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