KR102000974B1 - Hydrogen evolution reaction catalyst electrode comprising vertical graphene nano hills and preparing method of the same - Google Patents

Abstract

The present invention relates to a substrate; Seed metal nano-agglomerates scattered on one surface of the substrate; And a vertically grown graphene disposed on the seed metal nano-agglomerate. The present invention also relates to a method of preparing the same. Water electrolysis and the like can be facilitated, and graphene encapsulates the seed metal to ensure corrosion stability, durability and a very small mass.

Description

TECHNICAL FIELD [0001] The present invention relates to a hydrogen generating reaction catalyst electrode containing graphene grown vertically, and a method for producing the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a hydrogen generating reaction catalyst electrode including vertically grown graphene and a method for producing the same.

Hydrogen, the simplest and richest element on the planet, is well known for its potential to produce green energy as a secondary energy carrier and has the following advantages: First, even when there is a very small amount of NOx as it is burned when hydrogen is used as fuel, no other air pollutants are generated. Second, hydrogen can be transported to gas or liquid, and it is easy to store in various forms. Third, hydrogen is not depleted because it is produced through water splitting reaction using water, which is an infinite resource. Fourth, hydrogen energy sources are being applied not only to general fuels but also to various energy systems such as hydrogen cars and hydrogen planes. The development of hydrogen catalysts is essential for effective generation of these hydrogen energy sources. The platinum catalyst, which is now commercially available as a hydrogen catalyst, has excellent catalytic activity but has disadvantages of high cost and scarcity. To overcome these shortcomings, recently transition metal (eg Co, Ni, Fe, Mo) compounds have been developed as excellent non-noble metal catalysts.

Water electrolysis is the reaction of water to hydrogen and oxygen when electricity is applied. That is, when a voltage is applied to the electrode material, an oxidation-reduction reaction occurs electrochemically. At this time, oxygen is generated at the oxidizing electrode and hydrogen is generated at the reducing electrode.

The process of decomposing water to produce hydrogen and oxygen is an endothermic reaction due to an increase in large free energy and corresponds to an involuntary reaction. Therefore, in order to proceed the water decomposition reaction, it is necessary to externally apply a potential corresponding to 1.23 V. Actually, depending on the electrode catalyst, more overvoltage is required than the ideal potential.

Water electrolysis is the simplest way to produce hydrogen, and because it uses water as a raw material, mass production and high purity hydrogen can be obtained. However, when hydrogen is produced by water electrolysis, power consumption can be increased, and thus it is difficult to be practically used. For this purpose, it is necessary to develop a system to increase the efficiency of hydrogen production through water electrolysis and to study the technology of manufacturing electrode catalyst with high activity for hydrogen generation.

Hydrogen Evolution Reaction (HER) is a phenomenon in which hydrogen is generated through a catalyst. The required voltage and performance are determined by electrode material and surface conditions. The reversible electrochemical reactions on the electrode surface are as follows.

= 0V vs. SHEH ⁺ (aq) + e-? 1 / 2H ₂ (g), E

= 0V vs.. SHE

Based on the hydrogen reduction electrode, hydrogen is generated when the voltage is 0V.

It occurs through three mechanisms when hydrogen is generated on the electrode surface.

Basically, hydrogen ions are reduced and adsorbed on the electrode surface in the form of hydrogen atoms (Volmer reaction). Here, it is divided into two paths. Hydrogen is generated by binding hydrogen atoms adsorbed and hydrogen ions in a solution (Heyrowsky reaction) or by bonding hydrogen atoms (Tafel reaction) between adsorbed hydrogen atoms. Tafel slope is also used as a value to identify the mechanism of hydrogen generation reaction.

The equation related to the factors affecting the hydrogen catalytic activity is as follows.

η = b log ( j / j _o )

In this expression, η: it means the exchange current density (exchange current density): over-voltage, b: tapel slope, j: current density (current density), j _o. Based on this equation, an ideal hydrogen catalyst has a low Tappel slope and a high exchange current density.

Overvoltage is the most important factor affecting the catalytic activity. Overvoltage is the most significant contributor to the charge transfer reaction and depends on the overvoltage value depending on the speed and overcoming the energy barrier in the catalyst activation. The better the catalyst activation, the lower the overvoltage value. In the case of commercially available platinum electrodes, the voltage at which hydrogen is generated is close to 0V. However, hydrogen catalysts are under study to overcome the disadvantages of platinum electrodes and minimize overvoltages as much as platinum electrodes.

In order to satisfy the development of the hydrogen catalyst, it should be a material having the advantages of low cost and abundance that can compensate for the disadvantages of the platinum and have a good catalytic activity to replace the platinum.

Graphene is useful in a variety of electrochemical applications due to its high electrical conductivity, wide surface area and lightness, chemical stability in acidic and alkaline electrolytes, natural abundance and other inherent characteristics. However, graphene itself is known not to have sufficient activity for HER. Therefore, in order to improve the HER performance of the graphene catalyst, graphene was functionalized by additionally doping and / or dispersing the HER active material on the graphene. When doped with heteroatoms (such as N, S, B and P), graphene showed excellent performance in electrolysis due to the customized spin and charge distribution by adjacent dopants. However, even after doping, the HER activity of graphene is far behind that of modern electrocatalysts, so it was necessary to make a hybrid structure with HER active materials to show competitive performance. At the same time, efforts have been made to modify the electrode design to reduce the weight and volume of the catalyst. For higher participation of active sites in electrolysis, vertically oriented nanosheets have been proposed for two-dimensional dicalcogenide materials. Similarly, vertical Graphene Nano Hills (VGNHs) could generate dense open edges of graphene as active sites in electrolysis and, unlike flat graphene, Surface.

Korean Patent No. 1389925

It is an object of the present invention to provide a hydrogen generation reaction catalyst electrode which utilizes vertical grains having a height of several tens of nanometers grown on a seed metal as a hydrogen generation reaction catalyst to lower the onset potential and increase the current density.

The present invention aims at providing a hydrogen generating reaction catalyst electrode in which graphene encapsulates a seed metal and the seed metal is not corroded.

The present invention aims at providing a hydrogen generating reaction catalyst electrode having durability and a very small mass.

1. a substrate; Seed metal nano-agglomerates scattered on one surface of the substrate; And a vertically grown graphene positioned on the seed metal nano-agglomerate.

2. The method of claim 1, wherein the substrate is selected from the group consisting of glassy carbon (GC), Ni, Co, Fe, Pt, Pd, Au, Al, Cr, Cu, Mn, Mo, Rh, Ir, , U, V, Zr, Si , GaAs, GaN, silica (SiO _2), silica (quartz), glass (glass), sapphire (Al ₂ O _3), mica (mica), PI (polyimide) , PEEK (polyetheretherketone ), PES (polyethersulfone), PEI (polyetherimide), PC (polycarbonate) and PEN (polyethylenenaphthalate).

3. The hydrogen storage alloy according to item 1, wherein the seed metal is selected from the group consisting of Al, Ti, Cr, Fe, Co, Ni, Fe, Cu, Zn, Pd, Pt, Au, Ag, Generated Reaction Catalyst Electrode.

4. The hydrogen generation reaction catalyst electrode according to 3 above, wherein the seed metal is Co.

5. The hydrogen generation reaction catalyst electrode according to 1 above, wherein said seed metal nano-agglomerate has an average diameter of 20 nm or less.

6. The hydrogen generation catalyst electrode according to 1 above, wherein the hydrogen generating reaction catalyst electrode has a voltage of 0.4 V or less at a current density of 100 mA / cm 2.

7. The hydrogen generation reaction catalyst electrode of 1 above, further comprising a buffering graphene layer between the seed metal nano-aggregate and the vertically grown graphene.

8. depositing a seed metal on a substrate to form seed metal nano-agglomerates scattered on the substrate; And growing graphene vertically on the seed metal nano-agglomerate.

9. The hydrogen storage alloy according to the above 8, wherein the seed metal is selected from the group consisting of Al, Ti, Cr, Fe, Co, Ni, Fe, Cu, Zn, Pd, Pt, Au, Ag, (EN) METHOD FOR MANUFACTURING GENERATION REACTION.

10. The method of producing a hydrogen generation reaction catalyst electrode according to the above 9, wherein the seed metal is Co.

11. The method of claim 8, wherein the deposition is performed so that the average diameter of the seed metal nano-agglomerates is 20 nm or less.

12. The method of claim 8, further comprising forming a buffering graphene layer on the seed metal agglomerate prior to the step of vertically growing the graphene on the seed metal nanoaggregate. Gt;

According to one embodiment of the present invention, the hydrogen generation reaction catalyst electrode of the present invention can grow the vertically grown graphene with the seed metal as a template and facilitate water electrolysis or the like by using it as a catalyst for the hydrogen generation reaction .

According to an embodiment of the present invention, the hydrogen generating reaction catalyst electrode of the present invention encapsulates the seed metal by graphene to ensure corrosion stability.

According to an embodiment of the present invention, the hydrogen generating reaction catalyst electrode of the present invention may have durability and a very small mass.

FIG. 1 is a schematic cross-sectional view of a hydrogen generating reaction catalyst electrode according to an embodiment of the present invention, (b) to (c) an FESEM image of the surface of VGNHs, (d) FIG.
2 shows a seed metal nano-agglomerate scattered on one surface of a substrate.
Fig. 3 (a) is an LSV curve of Co, Ni and Fe-seeded VGNHs at 0.5 MH ₂ SO ₄ , Fig. 3 (b) is a Nyquist plot at -0.4 V, Fig. 3 The position of the G peak in the study is shown.
Figure 4 shows the LSV curves of Pt wire, Pt and Pt-seeded VGNHs at 0.55 MH ₂ SO ₄ .
Figure 5 shows vertically grown graphene.
FIG. 6 is a graph showing the relationship between a VGNHs / Co (250s) electrode, a VGNHs / Co (100s) electrode, a VGNHs / Co (250s) electrode prepared by varying the deposition time to a hydrogen generating reaction catalyst electrode according to an embodiment of the present invention, (A) low starting potential and (b) overvoltage of the Pt electrode and the Pt electrode.
Fig. 7 (a) shows the Nyquist impedance and equivalent circuit model (inserted figure) of the Co seed VGNHs at an operating voltage of -0.25 V for interpreting the EIS results, and Fig. 7 (b) shows the VGNHs / The plot of the LSV curve of Co (50s) and the graph of current density (j) versus time (h) curves at -0.160V.
(C) the VGNHs / Co (100s) electrode of Example 2; (d) the VGNHs / Co (100s) electrode of Example 2; The AFM image of the VGNHs / Co (250s) electrode is shown.
Fig. 9 shows (a) the XPS profile of Co 2p (upper panel) and C 1s (lower panel) for Co seed VGNHs, (b) VGNHs / GC, VGNHs / Co (50s, 100s, (C) Raman peak position as a function of Co deposition time for G peak (top panel), D peak (middle panel) and 2D peak (bottom panel), and d) Raman peak intensity ratio as a function of Co deposition time for ID / IG (top panel) and I2D / IG (bottom panel).

The present invention relates to a hydrogen generating reaction catalyst electrode and a method for producing the same, and is capable of facilitating water electrolysis and the like by using a seed metal as a template to grow vertically grown graphene as a catalyst for hydrogen generation reaction. The present invention relates to a hydrogen generating catalyst electrode capable of ensuring corrosion stability by encapsulating a seed metal and having durability and a very small mass, and a method for producing the same.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. And shall not be construed as limited to such matters.

The term " vertical " in this specification includes not only cases where they are mathematically vertical but also cases where ordinary descriptors can be recognized substantially vertically.

In this specification, 'vertically grown graphene' means graphene grown on the upper surface of the substrate.

In the present specification, the directional expression of the upper side, the upper side (upper side), the upper side, and the like can be understood as meaning lower, lower (lower), lower, etc. according to the standard. That is, the expression of the spatial direction should be understood in the relative direction and should not be construed as limiting in the absolute direction.

A hydrogen generating reaction catalyst electrode according to an embodiment of the present invention includes a substrate; A seed metal nano-agglomerate 200 scattered on one surface of the substrate 100; And vertically grown graphene (400) located on the seed metal nanoaggregate.

FIG. 1 (a) is a schematic cross-sectional view of a hydrogen generating reaction catalyst electrode according to the present invention.

According to one embodiment of the present invention, the substrate 100 serves as an electrode for the hydrogen generation reaction. The electrode material known in the art can be used without limitation, and a material such as a known conductor, semiconductor, . Examples of the conductor include glassy carbon (GC) or a metal such as Ni, Co, Fe, Pt, Pd, Au, Al, Cr, Cu, Mn, Mo, Rh, Ir, Ta, Ti, Zr, and may be at least one selected from the group consisting of Si, GaAs, GaN, silica (SiO ₂ ), quartz, glass, sapphire (Al ₂ O ₃ ) And at least one selected from the group consisting of polyimide, polyetheretherketone (PEEK), polyethersulfone (PES), polyetherimide (PEI), polycarbonate (PC) and polyethylenenaphthalate (PEN) It can be one.

As illustrated in FIG. 2, the seed metal nano-agglomerates 200 are scattered on one surface of the substrate 100.

According to an embodiment of the present invention, the seed metal may be selected from the group consisting of Al, Ti, Cr, Fe, Co, Ni, Fe, Cu, Zn, Pd, Pt, Au, Ag, Co can be used in view of exhibiting a low starting potential and a high current density, preferably Co, Ni or Fe, more preferably Co showing a fast and large charge transfer (see FIG. 3).

The seed metal nano-agglomerates 200 serve to change the electrical properties of graphene through electron mobility and / or deformation.

As illustrated in FIG. 6, graphene itself does not have sufficient activity for HER, but in vertically grown graphene 400 located on the seed metal nano-agglomerate 200, by interaction at the interface with the seed metal The electrical characteristics of the graphene are changed so that the hydrogen generation reaction catalyst electrode exhibits a low initiation potential and a high current density, thereby improving the HER activity.

The seed metal may be one that can change the electrical characteristics of the graphene. In general, all the metals may have such a difference, but they may change the electrical characteristics of the graphene in contact with it by charge transfer or the like. The kind of seed metal is not limited as above.

In the case of Pt, the VGNHs electrode vertically grown on the Pt seed metal exhibited a higher current density than the electrode prepared by depositing only Pt (see FIG. 4).

The seed metal nano-agglomerates 200 may have a diameter of, for example, 1 nm to 40 nm, an average diameter of 20 nm or less, and preferably an average diameter of 5 nm or less. When the average diameter is 5 nm or less, the HER activity is remarkably excellent.

The seed metal nano-agglomerates 200 may be prepared according to methods known in the art and may be formed by sputtering, e-beam deposition, chemical vapor deposition Method (Chemical Vapor Deposition (CVD)), or the like.

In the case of forming by deposition, the seed metal nano-agglomerate 200 of the diameter may be formed by adjusting the deposition time to a short time, but is not limited thereto.

The vertically grown graphene 400 is located on the seed metal nano-agglomerate 200.

5, vertically grown graphene 400 is shown.

The height of the vertically grown graphene 400 may be 5 nm to 50 nm. Within the above range, the vertically grown graphene 400 may be connected to each other to be more firmly formed on the seed metal nano-agglomerate 200.

The hydrogen generating reaction catalyst electrode of the present invention having the above structure can exhibit a high current density even at a low voltage. For example, a current density of 100 mA / cm < 2 > may be exhibited even at a voltage of 0.4 V or lower, but the present invention is not limited thereto.

If necessary, the hydrogen generating reaction catalyst electrode of the present invention may further include a buffered graphene (BG) layer 300 between the seed metal nano-agglomerate 200 and the vertical growth graphene 400.

The buffering graphene layer 300 is a non-uniform layer formed on the seed metal nano-agglomerate 200 scattered on one surface of the substrate 100. The buffering graphene layer 300 enhances the HER activity by promoting electron transfer of the seed metal.

The present invention also provides a method of forming a seed metal nano-agglutinate, comprising: depositing a seed metal on a substrate to form seed metal nano-agglomerates dispersed on the substrate; And vertically growing graphene on the seed metal nano-agglomerate; The present invention also provides a method for producing a hydrogen generating reaction catalyst electrode.

The step of depositing the seed metal on the substrate and forming the seed metal nano-agglomerate on the substrate may be one which has been produced according to a method known in the art as described above, For example, by a known deposition method such as a sputtering method, an e-beam deposition method, and a chemical vapor deposition method (CVD).

When formed by deposition, the seed metal nano-agglomerate of the diameter may be formed by, for example, controlling the deposition time to be short, but is not limited thereto.

The seed metal nano-agglomerates may be formed, for example, to have a diameter of 1 nm to 40 nm and an average diameter of 20 nm or less, preferably an average diameter of 5 nm or less. When the average diameter is 5 nm or less, the HER activity is remarkably excellent.

The step of vertically growing the graphene on the seed metal nano-agglomerate may be performed according to a method known in the art. Examples of the step of forming the graphene by sputtering, electron beam evaporation e-beam deposition, and chemical vapor deposition (CVD).

If necessary, the method may further include forming a buffering graphene layer on the seed metal agglomerate prior to the step of vertically growing the graphene on the seed metal nano agglomerate.

The step of forming the buffering graphene layer may be performed according to a method known in the art. Examples of the forming method include sputtering, e-beam deposition and chemical vapor deposition And may be manufactured by a known deposition method such as Chemical Vapor Deposition (CVD).

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples.

Example  One: VGNHs / Co (50s) Electrode Fabrication

Deposition of seed metal

Cobalt was deposited on a glassy carbon (GC) substrate with electron beam deposition technology for 50 seconds. Solid Co (99.99%, Alfa Aesar) was sublimated in an alumina crucible in a high vacuum chamber. During the deposition process, the chamber pressure was maintained at about 9 x ^10-6 Torr. The nominal deposition rate determined from the thickest film was 1 nm / 50 s. The resulting film was classified as the deposition time instead of the nominal thickness because the shorter the deposition time, the more granular the granules.

Vertical growth Of graphene (VGNHs)  growth

Vertically grown graphene (VGNHs) were grown directly using a plasma-enhanced chemical vapor deposition (PECVD) method. Hydrogen (H ₂ , 20 sccm) was injected at 50 W of radio frequency (RF) power to remove unwanted contaminants from the substrate and treated with plasma. After the plasma treatment, hydrogen (H ₂ , 20 sccm) and methane (CH ₄ , 10 sccm) were injected as carbon precursors; The VGNHs / Co (50s) electrode was fabricated by growing the VGNHs to release the gas mixture at 50 ° C for 30 minutes at 750 ° C with RF power.

Example  2: VGNHs / Co (100s) Electrode Fabrication

Was prepared in the same manner as in Example 1 except that cobalt was deposited on a glassy carbon (GC) substrate with an electron beam deposition technique for 100 seconds.

Example  3: VGNHs / Co (250s) Electrode Fabrication

Was prepared in the same manner as in Example 1, except that cobalt was deposited on a glassy carbon (GC) substrate by electron beam deposition technique for 250 seconds.

Comparative Example  One: GC  electrode

A GC substrate was used as the working electrode.

Comparative Example  2: VGNHs  electrode

VGNHs electrodes were prepared by directly growing VGNHs on a GC substrate except for the deposition of the seed metal of Example 1.

Comparative Example  3: Pt electrode

A Pt electrode was used as the working electrode.

Experimental Example  1: Measurement of electrochemical characteristics

All electrochemical characterization measurements were performed with the catalyst electrodes of Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3 at room temperature acidic electrolyte (0.5MH ₂ SO ₄ ); The catalytic electrode was used as the working electrode, the Ag / AgCl electrode was used as the reference electrode, and the spiral Pt wire was used as the counter electrode. HER activity was measured by Linear Sweep Voltammetry (LSV) at 10 mV s ^-1 scan rate using a workstation (Biologic SP-300, Biologic Science Instruments). The measured potentials were converted based on the RHE (Reversible Hydrogen Electrode) electrode according to the equation E (RHE) = E (Ag / AgCl ° + Ag / AgCl) at 0.5 MH ₂ SO ₄ . The polarization curves were collected after iR correction at 0.5 MH ₂ SO ₄ . The current density was calculated from the geometric operating area of the GC electrode (~ 0.30 cm 2). The supported amount of the catalyst was estimated to be 5.6 cm cm ^-2 , much smaller than the typical usage. Nyquist impedance was measured at a voltage amplitude of 10 mV and a frequency range of 1 Hz to 1 MHz.

FIG. 6 shows the VGNHs of Comparative Example 1, the VGNHs electrode of Comparative Example 2, the Pt electrode of Comparative Example 3, and the VGNHs of Example 1, which were prepared by varying the deposition time of the hydrogen generating reaction catalyst electrode according to one embodiment of the present invention. (A) low starting potential and (b) overvoltage of the Co / 50s electrode, the VGNHs / Co (100s) electrode of Example 2, and the VGNHs / Co (250s) electrode of Example 3 are shown.

The GC electrode of Comparative Example 1 exhibited negligible electrocatalytic performance with a high initiation potential (~ 305 mV). The VGNHs directly grown on the GC surface of Comparative Example 2 showed HER performance similar to that of Comparative Example 1, suggesting that HER inactivity of graphene can not be improved simply by structural modification. In contrast, VGNHs deposited with a Co seed on GC as a hydrogen generating reaction catalyst electrode according to an embodiment of the invention exhibited improved HER activity and high current density. A nominal thickness of 5 nm Co seed (250 seconds deposition) of Example 3 was able to reduce the initiation potential to ~ 280 mV. However, the increase in Co thickness before VGNH growth did not improve HER performance. In addition, the HER activity steadily increased when the Co deposition time was reduced. In particular, the starting voltage was improved to 93 mV at VGNHs / Co (100 seconds of deposition) and to 62 mV at VGNHs / Co (50 seconds of deposition) (see FIG. 6 (a)). This means that very little energy consumption has occurred in the catalytic process and is better than reported for non-noble metal catalysts.

In addition, the enhanced HER activity is reflected in the reduced Tafel slope, as in Figure 6 (b). The slope value is reduced from 182mV decade ^-1 (VGNHs Co is not deposited) to 83mV decade ^-1 (nominal thickness 1nm Co VGNHs seed) showed a higher current density at a lower voltage. The smallest Tafel slope value is larger than the value of the Pt electrode but similar to the value of the hybrid catalyst composed of graphene doped with HER active material. In particular, the maximum overvoltage of the hydrogen generating reaction catalyst electrode according to an embodiment of the present invention was 160 mV @ 10 mAcm ^-2 .

In addition, as can be inferred from the cross-sectional HRTEM image, Co nano-clusters were completely encapsulated by BG and VGNH (see Figures 1 (d) to 1 (f)).

Fig. 7 (a) shows the Nyquist impedance of the Co seed VGNHs and the equivalent circuit model (inserted figure) at an operating voltage of -0.25 V for interpreting the EIS results. The semicircle of VGNHs / Co (50s) was found to be the smallest, indicating high electrical conductivity in electrolysis and faster transfer of electrons from the electrode. Fig. 7 (b) shows the LSV curve of VGNHs / Co (50s) around 1000 cycles, and the graph plotting the current density (j) versus time (h) curve, operating at -0.160 V, Excellent stability was observed over time.

Experimental Example  2: Other characteristics

Field Emission-Sanning Electron Microscopy (FESEM) measurements were performed using a Hitachi S4700 system (operating at 15 kV) with electron scattering spectroscopy (EDS, Horiba EMAX) Respectively. High-Resolution Transmission Electron Microscopy (HRTEM) measurements were performed with the Oxford EDS system using JEM-2100F (operating at 200 kV). Surface morphology was obtained by Atomic Force Microscopy (AFM; n-Tracer system, Nano Focus Inc.) operating in a non-contact mode. Carbon structure analysis was performed using a Raman spectroscopy (Renishaw, in Via system) using a 514.5 nm excitation laser operating at 0.75 mW. Chemical bonds were analyzed by X-ray photoelectron spectroscopy (XPS) system with AlKa (1486.6 eV) line.

(C) a VGNHs / Co (100s) electrode of Example 2; (d) a VGNHs / Co (100s) electrode of Example 2; An AFM image of the VGNHs / Co (250s) electrode is shown. The height of VGNHs increased proportionally with increasing Co thickness. When the Co is very thin, the VGNHs are composed of small hills and valleys. However, as the Co is thicker, the shape of the VGNHs is gradually changed into huge aggregates by interconnecting the hills.

Figure 9 (a) shows the XPS profile of Co 2p (top panel) and C 1s (bottom panel) for Co seed VGNHs. The C 1s spectrum is fit for sp ² and sp ³ bonds and the relative fractions of these bonds are shown: sp ² CC is the red line, sp ³ CC is the green line, and the total fit line is the dotted line.

The presence of the Co Co 2p _3/2 and 2p _1/2 respectively correspond to the level found in a particular peak of 781.3eV, and 792.63eV (upper panel of Figure 9 (a)). This indicated that Co was in a metallic state and no CoOx phase. The C 1s spectrum (~ 284.37 eV) from VGNHs showed sp2 and sp3 carbon bonds (bottom panel in Figure 9 (a)) and the relative ratio is typical for directly grown graphene with many defects, OC = O (289 eV), C = O (288 eV), and CO (287 eV) were not noticeable. However, whether the VGNHs were doped due to the Co seed could not be determined from the current XPS profile due to the detection limit. Instead, in the case of graphene, Raman spectra are more sensitive to doping and defect density.

Figure 9 (b) shows Raman spectra of VGNHs / GC, VGNHs / Co (50s, 100s, 250s) / GC as reference electrodes and a GC electrode with nothing deposited. All samples showed three distinct peaks, D, G and 2D. These peaks are well known characteristics of graphite structures; The primary in-plane vibration of sp ² hybrid (G peak ~ 1600cm ^-1), of the longitudinal phonons by defect inter-valley transition (D peak ~ 1350cm ^-1), 2 car according to the conservation of momentum of the two phonon wave number vector having the opposite The peak position and relative intensity of the D peak (2D peak ~ 2700 cm ^-1 ) can be used to obtain indirect information on the graphene layer, such as defects, deformation or internal / external doping.

Figure 9 (c) shows Raman peak positions as a function of Co deposition time for G peak (top panel), D peak (middle panel) and 2D peak (bottom panel). For all Co-seeded VGNHs, a significant blue shift of the G, D and 2D peaks was observed (wavelengths of the spectral lines were shifted to blue than the standard wavelength) (samples with a Co deposition time of 0 were not seeded VGNH). In general, the blue shift of the G and 2D peaks is interpreted as an indication of p-type doping of the graphene. In this sense, it can be expected that the Co seed brought the unintended doping effect to the VGNHs through charge transfer and / or deformation. Interestingly, the amount of blue-shift or doping effect increased as the amount of Co seed decreased, consistent with the trend of HER enhancement. However, it is known that the doping effect alone can not achieve the HER performance presented here. Another factor affecting HER activity may be related to defect density because the edge density of VGNH will determine the number of catalytically active sites.

Figure 9 (d) shows the Raman peak intensity ratio as a function of Co deposition times for ID / IG (top panel) and I2D / IG (bottom panel). The intensity ratio of ID / IG (defect density) increased, while the ratio of I2D / IG (affinity to graphene) decreased with thinner Co seeds (greater HER activity). It can be expected that high activity for HER in Co-seeded VGNHs results from the combined effect of unintended doping and increased active catalytic site.

100: substrate
200: seed metal nano-aggregate
300: buffer graphene layer
400: Vertically grown graphene

Claims (12)

Board;
Seed metal nano-agglomerates scattered on one surface of the substrate;
And a vertically grown graphene positioned on the seed metal nano-agglomerate. The substrate according to claim 1, wherein the substrate is made of glassy carbon (GC), Ni, Co, Fe, Pt, Pd, Au, Al, Cr, Cu, Mn, Mo, Rh, Ir, Ta, , V, Zr, Si, GaAs , GaN, silica (SiO _2), silica (quartz), glass (glass), sapphire (Al ₂ O _3), mica (mica), PI (polyimide) , PEEK (polyetheretherketone), Wherein the substrate is a substrate of at least one material selected from the group consisting of PES (polyethersulfone), PEI (polyetherimide), PC (polycarbonate) and PEN (polyethylenenaphthalate). The hydrogen generation reaction according to claim 1, wherein the seed metal is selected from the group consisting of Al, Ti, Cr, Fe, Co, Ni, Fe, Cu, Zn, Pd, Pt, Au, Ag, Catalytic electrode. 4. The hydrogen generation reaction catalyst electrode according to claim 3, wherein the seed metal is Co. The hydrogen generation reaction catalyst electrode according to claim 1, wherein the seed metal nano-agglomerate has an average diameter of 20 nm or less. The hydrogen generation catalyst electrode according to claim 1, wherein the hydrogen generating reaction catalyst electrode has a voltage of 0.4 V or less at a current density of 100 mA / cm 2. The hydrogen generation reaction catalyst electrode according to claim 1, further comprising a buffering graphene layer between the seed metal nano-aggregate and the vertically grown graphene. Depositing seed metal on the substrate to form seed metal nano-agglomerates dispersed on the substrate;
And growing graphene vertically on the seed metal nano-agglomerate. The hydrogen generation reaction according to claim 8, wherein the seed metal is selected from the group consisting of Al, Ti, Cr, Fe, Co, Ni, Fe, Cu, Zn, Pd, Pt, Au, Ag, A method of manufacturing a catalyst electrode. 10. The method according to claim 9, wherein the seed metal is Co. 9. The method according to claim 8, wherein the deposition is performed so that the average diameter of the seed metal nano-agglomerates is 20 nm or less. 9. The method of claim 8, further comprising forming a buffering graphene layer on the seed metal agglomerate prior to the step of vertically growing the graphene on the seed metal nanoaggregate, .

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