U.S. patent application number 16/545927 was filed with the patent office on 2020-07-02 for devices for hydrogen production and methods of fabricating a hydrogen catalyst layer.
The applicant listed for this patent is Samsung Electronics Co., Ltd. Research & Business Foundation Sungkyunkwan University. Invention is credited to Hyoungsub Kim, Jinbum Kim, Taejin Park.
Application Number | 20200208279 16/545927 |
Document ID | / |
Family ID | 71123979 |
Filed Date | 2020-07-02 |
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United States Patent
Application |
20200208279 |
Kind Code |
A1 |
Park; Taejin ; et
al. |
July 2, 2020 |
DEVICES FOR HYDROGEN PRODUCTION AND METHODS OF FABRICATING A
HYDROGEN CATALYST LAYER
Abstract
Disclosed herein are devices for hydrogen production and methods
of fabricating hydrogen catalyst layers. The method may comprise
forming on a substrate a first horizontal crystal and a first
standing crystal that include each molybdenum oxide; forming a
second horizontal crystal, a second standing crystal, and a
preliminary layer on the second horizontal and standing crystals by
supplying a sulfur gas onto the first horizontal crystal and the
first standing crystal, the preliminary layer including molybdenum
disulfide (MoS.sub.2); and removing the second horizontal crystal
and the second standing crystal.
Inventors: |
Park; Taejin; (Yongin-si,
KR) ; Kim; Jinbum; (Seoul, KR) ; Kim;
Hyoungsub; (Suwon-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd.
Research & Business Foundation Sungkyunkwan University |
Suwon-si
Suwon-si |
|
KR
KR |
|
|
Family ID: |
71123979 |
Appl. No.: |
16/545927 |
Filed: |
August 20, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25B 11/0478 20130101;
C25B 11/02 20130101; C25B 1/04 20130101; C25B 11/0447 20130101;
B01J 23/00 20130101; C25B 11/0405 20130101 |
International
Class: |
C25B 11/02 20060101
C25B011/02; C25B 1/04 20060101 C25B001/04; C25B 11/04 20060101
C25B011/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 31, 2018 |
KR |
10-2018-0173442 |
Claims
1. A method of fabricating a hydrogen catalyst layer, the method
comprising: providing a substrate comprising a first horizontal
crystal and a first standing crystal that each include molybdenum
oxide; forming a second horizontal crystal, a second standing
crystal, and a preliminary layer on the second horizontal and
second standing crystals by supplying a sulfur gas onto the first
horizontal crystal and the first standing crystal, the preliminary
layer including molybdenum disulfide (MoS.sub.2); and removing the
second horizontal crystal and the second standing crystal.
2. The method of claim 1, wherein forming the second horizontal
crystal and the second standing crystal includes reducing at least
a portion of oxygen atoms in the first horizontal crystal and in
the first standing crystal.
3. The method of claim 1, wherein the second horizontal crystal and
the second standing crystal include molybdenum dioxide
(MoO.sub.2).
4. The method of claim 1, wherein the molybdenum oxide in the first
horizontal crystal and the first standing crystal has a chemical
formula of Mo.sub.aO.sub.b, wherein a and b are each independently
an integer equal to or greater than 1, and a ratio of b/a is from 2
to 3.
5. The method of claim 1, wherein providing the substrate
comprising the first horizontal crystal and the first standing
crystal includes supplying the substrate with an inert gas and a
molybdenum oxide gas.
6. The method of claim 1, wherein removing the second horizontal
crystal and the second standing crystal includes spraying the
substrate with an etchant that etches the second horizontal crystal
and the second standing crystal.
7. The method of claim 1, wherein forming the second horizontal
crystal and the second standing crystal includes increasing a
temperature of the substrate.
8. A method of fabricating a hydrogen catalyst layer, the method
comprising: forming on a substrate a first horizontal crystal and a
first standing crystal that each include molybdenum dioxide
(MoO.sub.2); forming a preliminary layer on the first horizontal
crystal and the first standing crystal; and removing the first
horizontal crystal and the first standing crystal, wherein the
preliminary layer includes molybdenum disulfide (MoS.sub.2).
9. The method of claim 8, wherein the first horizontal crystal
extends in a first direction that is parallel to a top surface of
the substrate, and the first standing crystal extends in a second
direction that intersects the top surface of the substrate.
10. The method of claim 8, wherein forming the preliminary layer on
the first horizontal crystal and the first standing crystal
includes supplying a sulfur gas onto the substrate.
11. The method of claim 8, wherein forming on the substrate the
first horizontal crystal and the first standing crystal includes:
forming on the substrate a second horizontal crystal and a second
standing crystal; and reducing at least a portion of oxygen atoms
in the second horizontal crystal and in the second standing
crystal.
12. The method of claim 8, wherein removing the first horizontal
crystal and the first standing crystal includes spraying the
substrate with an etchant that etches the first horizontal crystal
and the first standing crystal.
13. The method of claim 8, wherein removing the first horizontal
crystal and the first standing crystal includes forming a standing
structure, wherein the standing structure includes: a first
standing segment that extends in a direction intersecting a top
surface of the substrate; a second standing segment that extends in
the direction intersecting the top surface of the substrate; and a
first void between the first standing segment and the second
standing segment.
14. The method of claim 13, wherein the first standing segment and
the second standing segment are parallel to each other.
15. A device for hydrogen production, the device comprising: a
substrate; a horizontal structure that lies on the substrate and
extends in a first direction that is parallel to a top surface of
the substrate; and a first standing structure and a second standing
structure that each extend in a direction that intersects the top
surface of the substrate, wherein each of the first and second
standing structures includes: a first standing segment and a second
standing segment that are parallel to each other; and a first void
between the first standing segment and the second standing segment,
wherein extending directions of the first and second standing
structures cross each other.
16. The device of claim 15, wherein the horizontal structure, the
first standing segment, and the second standing segment each
include molybdenum disulfide (MoS.sub.2).
17. The device of claim 15, wherein a thickness of each of the
first and second standing segments is less than a shortest interval
between the first standing segment and the second standing
segment.
18. The device of claim 15, wherein the first standing segment
includes a first inner sidewall facing the second standing segment,
the second standing segment includes a second inner sidewall facing
the first standing segment, and the first void completely exposes
the first and second inner sidewalls.
19. The device of claim 15, wherein the horizontal structure, the
first standing segment, and the second standing segment each have a
plate shape.
20. The device of claim 15, wherein a second void is provided
between the first standing structure and the second standing
structure.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This U.S. nonprovisional application claims priority under
35 U.S.C .sctn. 119 to Korean Patent Application No.
10-2018-0173442 filed on Dec. 31, 2018 in the Korean Intellectual
Property Office, the entire contents of which are hereby
incorporated by reference.
FIELD
[0002] The present inventive concepts generally relate to a device
for hydrogen production and a method of fabricating a hydrogen
catalyst layer. More particularly, the present inventive concepts
relate to a device for hydrogen production including molybdenum
disulfide and a method of fabricating a hydrogen catalyst layer
including molybdenum disulfide.
BACKGROUND
[0003] Hydrogen is known as a future eco-friendly energy resource.
At present, hydrogen is mostly generated by a chemical byproduct
hydrogen production method in which toxic byproducts are formed.
Eco-friendly water electrolysis using platinum exhibits a high
efficiency of hydrogen production, but has disadvantages in that
expensive platinum must be used. Recently, due to its relatively
low price resulting from rich reserves and its high efficiency in
hydrogen production, molybdenum disulfide (MoS.sub.2) has been
actively studied as a catalyst used for eco-friendly water
electrolysis for hydrogen production.
SUMMARY
[0004] Some example embodiments of the present inventive concepts
provide a device for hydrogen production with high efficiency.
[0005] According to some example embodiments of the present
inventive concepts, a method of fabricating a hydrogen catalyst
layer may comprise: providing a substrate comprising a first
horizontal crystal and a first standing crystal that each include
molybdenum oxide; forming a second horizontal crystal, a second
standing crystal, and a preliminary layer by supplying a sulfur gas
onto the first horizontal crystal and the first standing crystal,
wherein the preliminary layer is on the second horizontal and
second standing crystals and includes molybdenum disulfide
(MoS.sub.2); and removing the second horizontal crystal and the
second standing crystal.
[0006] According to some example embodiments of the present
inventive concepts, a method of fabricating a hydrogen catalyst
layer may comprise: forming on a substrate a first horizontal
crystal and a first standing crystal that each include molybdenum
dioxide (MoO.sub.2); forming a preliminary layer on the first
horizontal crystal and the first standing crystal; and removing the
first horizontal crystal and the first standing crystal. The
preliminary layer may include molybdenum disulfide (MoS.sub.2).
[0007] According to some example embodiments of the present
inventive concepts, a device for hydrogen production may comprise:
a substrate; a horizontal structure that lies on the substrate and
extends in a first direction that is parallel to a top surface of
the substrate; and a first standing structure and a second standing
structure that extend in a second direction that intersects the top
surface of the substrate. Each of the first and second standing
structures may include: a first standing segment and a second
standing segment that are parallel to each other; and a first void
between the first standing segment and the second standing segment.
Extending directions of the first and second standing structures
may cross each other.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 illustrates a perspective view showing a device for
hydrogen production according to some example embodiments of the
present inventive concepts.
[0009] FIG. 2A illustrates a cross-sectional view showing a device
for hydrogen production according to some example embodiments of
the present inventive concepts.
[0010] FIG. 2B illustrates an enlarged view showing section A of
FIG. 2A.
[0011] FIGS. 3A, 4A, 5A, and 6 illustrate schematic diagrams
showing a method of fabricating a hydrogen catalyst layer according
to some example embodiments of the present inventive concepts.
[0012] FIGS. 3B, 4B, and 5B illustrate enlarged views showing
section A of FIGS. 3A, 4A, and 5A, respectively.
[0013] FIGS. 7 and 8 illustrate schematic diagrams showing a method
of fabricating a hydrogen catalyst layer according to some example
embodiments of the present inventive concepts.
[0014] FIG. 9 is a SEM image showing preliminary layers of
molybdenum disulfide (MoS.sub.2) on horizontal and standing
crystals of molybdenum dioxide (MoO.sub.2) in accordance with
Experimental Example 1.
[0015] FIG. 10 is a SEM image showing MoS.sub.2 following removal
of horizontal and standing crystals of molybdenum dioxide
(MoO.sub.2) in accordance with Experimental Example 1.
[0016] FIG. 11 is a graph showing Raman analysis results of a state
in which preliminary layers of molybdenum disulfide (MoS.sub.2) are
formed on horizontal and standing crystals of molybdenum dioxide
(MoO.sub.2) in accordance with Experimental Example 1.
[0017] FIG. 12 is a graph showing Raman analysis results of a state
in which horizontal and standing crystals of molybdenum dioxide
(MoO.sub.2) are removed in accordance with Experimental Example
1.
[0018] FIG. 13 illustrates a schematic diagram showing a process
for hydrogen reduction using a device for hydrogen production
according to some example embodiments of the present inventive
concepts.
[0019] FIG. 14 is a graph showing hydrogen reduction efficiency for
a device for hydrogen production according to some example
embodiments of the present inventive concepts.
DETAILED DESCRIPTION OF EMBODIMENTS
[0020] FIG. 1 illustrates a perspective view of a device for
hydrogen production according to some example embodiments of the
present inventive concepts. FIG. 2A illustrates a cross-sectional
view of a device for hydrogen production according to some example
embodiments of the present inventive concepts. FIG. 2B illustrates
an enlarged view showing section A of FIG. 2A.
[0021] Referring to FIGS. 1, 2A, and 2B, a device for hydrogen
production according to some example embodiments of the present
inventive concepts may include a substrate 100 and a hydrogen
catalyst layer on the substrate 100. The hydrogen catalyst layer
may include horizontal structures 210 and standing structures 220.
The horizontal structures 210 and the standing structures 220 may
be catalysts for reducing hydrogen ions (H.sup.+).
[0022] In certain embodiments, the substrate 100 may be a
conductive substrate. The conductive substrate may include a metal
or non-metal. The metal may be, for example, gold (Au). The
non-metal may be, for example, graphene.
[0023] In other embodiments, the substrate 100 may be a dielectric
substrate. The dielectric substrate may include a dielectric
material. For example, the dielectric material may be silicon oxide
(SiO.sub.x, 0<x<2).
[0024] The substrate 100 may be provided with the horizontal
structures 210 and the standing structures 220. The horizontal
structures 210 and the standing structures 220 may be irregularly
arranged on the substrate 100. In some embodiments, the horizontal
structures 210 and the standing structures 220 may be formed on the
substrate 100.
[0025] The horizontal structure 210 may have a first thickness T1.
The horizontal structure 210 may be shaped like a plate. For
example, the first thickness T1 of the horizontal structure 210 may
be less than a width of the horizontal structure 210. One or more
horizontal structures 210 may extend in a direction parallel to a
top surface 110 of the substrate 100.
[0026] The standing structure 220 may include a first standing
segment 221, a second standing segment 222, and a first void VO1.
The first and second standing segments 221 and 222 may be spaced
apart from each other. The first void VO1 may be provided between
the first and second standing segments 221 and 222. The first void
VO1 may be a substantially hollow space.
[0027] One or more standing structures 220 may extend in a
direction intersecting the top surface 110 of the substrate 100.
For example, at least one of the standing structures 220 may extend
in a direction perpendicular to the top surface 110 of the
substrate 100. The first and second standing segments 221 and 222
of the standing structure 220 may also extend in a direction
intersecting the top surface 110 of the substrate 100.
[0028] In some embodiments, two or more of the standing structures
220 may extend in a direction in which the two or more standing
structures 220 would cross each other, if extended. For example, an
extending direction of a first standing structure 220 may intersect
an extending direction of a second standing structure 220. In this
sense, the first standing structure 220 and the second standing
structure 220 may not extend in parallel to each other.
[0029] The first and second standing segments 221 and 222 may each
have a second thickness T2. Each of the first and second standing
segments 221 and 222 may be shaped like a plate. Each of the first
and second standing segments 221 and 222 may have a shape similar
to that of the horizontal structure 210 when standing.
[0030] The first and second standing segments 221 and 222 may be
parallel to each other. A first length L1 may be defined to refer
to a shortest interval between the first and second standing
segments 221 and 222. The first length L1 may be greater than the
second thickness T2.
[0031] The first standing segment 221 may have a first inner
sidewall 2211 facing the second standing segment 222. The second
standing segment 222 may have a second inner sidewall 2221 facing
the first standing segment 221. The first and second inner
sidewalls 2211 and 2221 may be completely exposed to the first void
VO1. The first void VO1 may be defined by the first and second
inner sidewalls 2211 and 2221.
[0032] A second void VO2 may be provided between the standing
structures 220. The second void VO2 may be a substantially hollow
space.
[0033] The horizontal structures 210, the first standing segments
221, and/or the second standing segments 222 may include (or
contain) molybdenum disulfide (MoS.sub.2). The horizontal
structures 210, the first standing segments 221, and/or the second
standing segments 222 may include a monolayer or a multilayer
(e.g., 2 or more layers) of molybdenum disulfide (MoS.sub.2). The
multilayer of MoS.sub.2 may have a structure in which a plurality
of monolayers of MoS.sub.2 are stacked and connected by Van der
Waals force(s).
[0034] In a device for hydrogen production according to some
example embodiments of the present inventive concepts, because the
first and second inner sidewalls 2211 and 2221 are exposed to the
first void VO1, each of the first and second standing segments 221
and 222 may have a relatively large surface area. As a result,
according to some example embodiments of the present inventive
concepts, the device for hydrogen production may achieve relatively
high efficiency in hydrogen reduction.
[0035] FIGS. 3A, 4A, 5A, and 6 illustrate schematic diagrams
showing a method of fabricating a hydrogen catalyst layer according
to some example embodiments of the present inventive concepts.
FIGS. 3B, 4B, and 5B illustrate enlarged views showing section A of
FIGS. 3A, 4A, and 5A, respectively.
[0036] Referring to FIGS. 3A and 3B, a substrate 100 may be
disposed in a chamber 300. For example, the substrate 100 may be a
conductive substrate. For another example, the substrate 100 may be
a dielectric substrate. The chamber 300 may maintain a high vacuum
state. For example, the chamber 300 may maintain a pressure below
about 0.01 Torr.
[0037] An inert gas IG and a molybdenum oxide gas MOG may be
supplied to the chamber 300 through an inlet 310 thereof. For
example, the inert gas IG may include argon (Ar) and/or nitrogen
(N). The molybdenum oxide gas MOG may include molybdenum oxide of a
single species or a combination of molybdenum oxides of multiple
species. The molybdenum oxide gas MOG may include molybdenum oxide
having a chemical formula of Mo.sub.aO.sub.b, wherein a and b may
each independently be an integer equal to or greater than 1, and a
ratio of b/a may be from 2 to 3. In some embodiments, the ratio of
b/a may be between 2 and 3. For example, the molybdenum oxide gas
MOG may be selected from the group consisting of MoO.sub.2,
MoO.sub.3, Mo.sub.2O.sub.5, and a combination thereof However, the
molybdenum oxide gas MOG may not include MoO.sub.2 alone. When the
molybdenum oxide gas MOG includes MoO.sub.2 alone, the chamber 300
may be additionally supplied with one or both of MoO.sub.3 and
Mo.sub.2O.sub.5. In some embodiments, the molybdenum oxide gas MOG
and/or chamber 300 comprises MoO.sub.2 and MoO.sub.3 and/or
Mo.sub.2O.sub.5.
[0038] The inert gas IG may be supplied at a flow rate of about 200
sccm to about 500 sccm. When the chamber 300 is supplied with the
inert gas IG and the molybdenum oxide gas MOG, a supply amount of
the molybdenum oxide gas MOG may be controlled to maintain the
chamber 300 at a pressure of about 1 Torr to about 1.2 Torr. Gases
may be discharged through an outlet 320 from the chamber 300.
[0039] When the inert gas IG and the molybdenum oxide gas MOG are
supplied, first horizontal crystals 410 and first standing crystals
420 may be formed on the substrate 100. For example, the formation
of the first horizontal crystals 410 and the first standing
crystals 420 may depend on a difference in temperature between the
molybdenum oxide gas MOG and the substrate 100 and on a partial
pressure of the molybdenum oxide gas MOG. The first horizontal
crystals 410 and the first standing crystals 420 may include
molybdenum oxide of a single species or a combination of molybdenum
oxides of multiple species. The first horizontal crystals 410 and
the first standing crystals 420 may each include molybdenum oxide
having a chemical formula of Mo.sub.cO.sub.d, wherein c and d may
each independently be an integer equal to or greater than 1, and a
ratio of d/c may be from 2 to 3. In some embodiments, the ratio of
d/c may be between 2 and 3. For example, the molybdenum oxide gas
MOG may be selected from the group consisting of MoO.sub.2,
MoO.sub.3, Mo.sub.2O.sub.5, and a combination thereof. However, the
molybdenum oxide gas MOG may not include MoO.sub.2 alone. When the
molybdenum oxide gas MOG includes MoO.sub.2 alone, the chamber 300
may be additionally supplied with one or both of MoO.sub.3 and
Mo.sub.2O.sub.5. In some embodiments, the molybdenum oxide gas MOG
and/or chamber 300 comprises MoO.sub.2 and MoO.sub.3 and/or
Mo.sub.2O.sub.5.
[0040] The first horizontal crystals 410 and the first standing
crystals 420 may be irregularly arranged on the substrate 100. The
first horizontal crystals 410 and the first standing crystals 420
may each have a plate shape. The first horizontal crystals 410 may
extend in a direction parallel to a top surface 110 of the
substrate 100. The first standing crystals 420 may extend in a
direction intersecting the top surface 110 of the substrate
100.
[0041] Referring to FIGS. 4A and 4B, heating may be performed to
increase a temperature of the substrate 100. A temperature rising
rate of the substrate 100 may fall in a range of about 50.degree.
C./min to about 55.degree. C./min. When the temperature rising rate
of the substrate 100 is set at about 50.degree. C./min to about
55.degree. C./min, the first horizontal crystals 410 and the first
standing crystals 420 may be prevented from their loss due to
sublimation. In some embodiments, the temperature rising rate of
the substrate 100 is set between about 50.degree. C./min and about
55.degree. C./min.
[0042] When the temperature of the substrate 100 reaches about
650.degree. C. to about 780.degree. C., a sulfur gas SG may be
supplied through the inlet 310 to the chamber 300. The sulfur gas
SG may be supplied at a flow rate above about 50 sccm.
[0043] When the sulfur gas SG is supplied, the first horizontal
crystals 410 and the first standing crystals 420 may react with the
sulfur gas SG. When the first horizontal crystals 410 and the first
standing crystals 420 react with the sulfur gas SG, oxygen (O)
atoms in the first horizontal crystals 410 and/or the first
standing crystals 420 may be at least partially reduced. The
reduction of oxygen (O) may convert the first horizontal crystals
410 into second horizontal crystals 510 and also convert the first
standing crystals 420 into second standing crystals 520.
[0044] The second horizontal crystals 510 and the second standing
crystals 520 may include molybdenum dioxide (MoO.sub.2). The
molybdenum dioxide (MoO.sub.2) in the second horizontal crystals
510 and the second standing crystals 520 may be formed when oxygen
(O) is at least partially reduced from molybdenum oxide having a
chemical formula of Mo.sub.cO.sub.d. The second horizontal crystals
510 and the second standing crystals 520 may each be shaped like a
plate. The second horizontal crystal 510 may have a third thickness
T3. The third thickness T3 may be, on average, less than a
thickness T3' of the first horizontal crystal 410. The second
standing crystal 520 may have a fourth thickness T4. The fourth
thickness T4 may be, on average, less than a thickness T4' of the
first standing crystal 420. The second horizontal crystals 510 may
extend in the direction parallel to the top surface 110 of the
substrate 100. The second standing crystals 520 may extend in the
direction intersecting the top surface 110 of the substrate
100.
[0045] Each of the second horizontal crystals 510 may include a
first surface 511 perpendicular to a direction along the third
thickness T3 and also include second surfaces 512 parallel to the
direction along the third thickness T3. Each of the second standing
crystals 520 may include third surfaces 521 perpendicular to a
direction along the fourth thickness T4 and also include fourth
surfaces 522 parallel to the direction along the fourth thickness
T4.
[0046] Referring to FIGS. 5A and 5B, the temperature of the
substrate 100 may be increased. While the temperature of the
substrate 100 is increased, the sulfur gas SG may be continuously
supplied. The temperature of the substrate 100 may be increased up
to a maximum temperature of about 900.degree. C. to about
1100.degree. C. The maximum temperature of the substrate 100 may be
kept for about 10 minutes or more.
[0047] When the temperature of the substrate 100 reaches the
maximum temperature, the sulfur gas SG may react with the second
horizontal crystals 510 and the second standing crystals 520. When
the second horizontal crystals 510 and the second standing crystals
520 react with the sulfur gas SG, a preliminary layer 600 may be
formed on the second horizontal crystals 510 and the second
standing crystals 520. The preliminary layer 600 may be conformally
formed on the first and second surfaces 511 and 512 of the second
horizontal crystals 510 and on the third and fourth surfaces 521
and 522 of the second standing crystals 520. In some embodiments,
the preliminary layer 600 is conformally formed on exposed surfaces
(e.g., surfaces exposed to and/or contacted with the sulfur gas SG)
of the second horizontal crystals 510 and the second standing
crystals 520.
[0048] The preliminary layer 600 may include molybdenum disulfide
(MoS.sub.2). The preliminary layer 600 may be a monolayer of
molybdenum disulfide (MoS.sub.2) or a multilayer of molybdenum
disulfide (MoS.sub.2). The multilayer may have a structure in which
a plurality of monolayers are stacked and connected by Van der
Waals force(s). The longer the time in which the maximum
temperature of the substrate 100 is maintained, the greater the
number of stacked molecular layers of the preliminary layer
600.
[0049] The preliminary layer 600 may include first segments 610
formed on the second surfaces 512 of the second horizontal crystals
510 and also include second segments 620 formed on the fourth
surfaces 522 of the second standing crystals 520. The second
segment 620 on the second standing crystal 520 may have a second
length L2 in the direction along the fourth thickness T4 of the
second standing crystal 520.
[0050] Referring to FIG. 6, an etchant EC may be used to remove the
second horizontal crystals 510 and the second standing crystals
520. The etchant EC may include a material capable of etching
molybdenum dioxide (MoO.sub.2). For example, the etchant EC may
include a buffered oxide etchant (BOE) and/or hydrofluoric acid
(HF).
[0051] When the etchant EC is sprayed onto the substrate 100, the
etchant EC may pass through the preliminary layer 600 to remove the
second horizontal crystals 510 and the second standing crystals 520
within the preliminary layer 600.
[0052] Referring back to FIGS. 1, 2A, and 2B, when the second
horizontal crystals 510 are removed, the first segments 610 of the
preliminary layer 600 may also be removed from the second surfaces
512 of the second horizontal crystals 510. When the second standing
crystals 520 are removed, the second segments 620 of the
preliminary layer 600 may also be removed from the fourth surfaces
522 of the second standing crystals 520.
[0053] The preliminary layer 600 may be formed and/or transformed
into horizontal structures 210 and standing structures 220. The
horizontal structure 210 may be on and/or attached to the top
surface 110 of the substrate 100 because of the removal of the
second horizontal crystals 510 and the first segments 610 of the
preliminary layer 600. A first void VO1 may be formed between a
first standing segment 221 and a second standing segment 222 of the
standing structure 220 because of the removal of the second
standing crystals 520 and the second segments 620 of the
preliminary layer 600. The formation of the first void VO1 may
expose a first inner sidewall 2211 of the first standing segment
221 and also expose a second inner sidewall 2221 of the second
standing segment 222.
[0054] FIGS. 7 and 8 illustrate schematic diagrams showing a method
of fabricating a hydrogen catalyst layer according to some example
embodiments of the present inventive concepts. Except for that
discussed below, a method of fabricating a hydrogen catalyst layer
according to some example embodiments of the present inventive
concepts is similar to that according to the embodiment discussed
above with reference to FIGS. 3A, 4A, and 5A.
[0055] Referring to FIG. 7, the inert gas IG may be supplied
through the inlet 310 to the chamber 300.
[0056] A molybdenum oxide powder MOP may be in and/or provided in
the chamber 300. The molybdenum oxide powder MOP may include
molybdenum oxide of a single species or a combination of molybdenum
oxides of multiple species. The molybdenum oxide powder MOP may
include molybdenum oxide having a chemical formula of
Mo.sub.aO.sub.b, wherein a and b may each independently be an
integer equal to or greater than 1, and a ratio of b/a may be from
2 to 3. In some embodiments, the ratio of b/a may be between 2 and
3. For example, the molybdenum oxide powder MOP may be selected
from the group consisting of MoO.sub.2, MoO.sub.3, Mo.sub.2O.sub.5,
and a combination thereof. However, in some embodiments, the
molybdenum oxide powder MOP may not include MoO.sub.2 alone. When
the molybdenum oxide powder MOP includes only MoO.sub.2 as the
molybdenum oxide species, the chamber 300 may additionally be
supplied with one or both of MoO.sub.3 and Mo.sub.2O.sub.5. In some
embodiments, the molybdenum oxide powder MOP and/or chamber 300
comprises MoO.sub.2 and MoO.sub.3 and/or Mo.sub.2O.sub.5.
[0057] The molybdenum oxide powder MOP may be vaporized due to an
increase in temperature of the chamber 300. As the molybdenum oxide
powder MOP is vaporized, the chamber 300 may be supplied with
gaseous molybdenum oxide such as MoO.sub.n, wherein n is less than
or equal to 3.
[0058] Referring to FIG. 8, a sulfur powder SP may be in and/or
provided in the chamber 300. The sulfur powder SP may be vaporized
due to an increase in temperature of the chamber 300. As the sulfur
powder SP is vaporized, the chamber 300 may be supplied with
gaseous sulfur (S).
[0059] The following will describe an experimental example
utilizing a device for hydrogen reduction according to some example
embodiments of the present inventive concepts.
EXPERIMENTAL EXAMPLE 1
[0060] A graphene substrate was loaded in a chamber maintained at a
pressure of 0.01 Torr. The chamber was supplied with nitrogen (N)
gas at a flow rate of 500 sccm. A molybdenum trioxide (MoO.sub.3)
gas was supplied to the chamber, the chamber was maintained at a
pressure of 1 Torr, and horizontal and standing crystals of
molybdenum trioxide (MoO.sub.3) were formed.
[0061] A temperature of the substrate was increased at a rate of
50.degree. C./min. A sulfur (S) powder was vaporized in the
chamber. As the sulfur (S) powder was vaporized, a sulfur (S) gas
reacted with the horizontal and standing crystals of molybdenum
trioxide (MoO.sub.3). Horizontal and standing crystals of
molybdenum dioxide (MoO.sub.2) were formed by the reaction of the
sulfur (S) gas with the horizontal and standing crystals of
molybdenum trioxide (MoO.sub.3).
[0062] The temperature of the substrate was increased to
1000.degree. C. The substrate was maintained at a temperature of
1000.degree. C. for 10 minutes. The sulfur (S) gas and the
horizontal and standing crystals of molybdenum dioxide (MoO.sub.2)
were reacted to form a preliminary layer containing molybdenum
disulfide (MoS.sub.2) on the horizontal and standing crystals of
molybdenum dioxide (MoO.sub.2).
[0063] A buffered oxide etchant (BOE) was used to remove the
horizontal and standing crystals of molybdenum dioxide
(MoO.sub.2).
[0064] FIG. 9 illustrates a SEM image showing molybdenum disulfide
(MoS.sub.2) preliminary layers formed on horizontal and standing
crystals of molybdenum dioxide (MoO.sub.2) in accordance with
Experimental Example 1. FIG. 10 illustrates a SEM image showing a
state in which horizontal and standing crystals of molybdenum
dioxide (MoO.sub.2) have been removed in accordance with
Experimental Example 1.
[0065] FIG. 9 may show the preliminary layers of molybdenum
disulfide (MoS.sub.2) covering the horizontal and standing crystals
of molybdenum dioxide (MoO.sub.2), and FIG. 10 may show horizontal
structures and standing segments of molybdenum disulfide
(MoS.sub.2). Comparing FIG. 9 and FIG. 10, it may be ascertained
that each second length (see L2 of FIG. 5B) of second segments (see
620 of FIG. 5B) in the preliminary layers of molybdenum disulfide
(MoS.sub.2) is relatively greater than each second thickness (see
T2 of FIG. 2B) of the standing segments (see 221 and 222 of FIG.
2B).
[0066] FIG. 11 illustrates a graph showing Raman analysis results
of a state in which the preliminary layers of molybdenum disulfide
(MoS.sub.2) are formed on the horizontal and standing crystals of
molybdenum dioxide (MoO.sub.2) in accordance with Experimental
Example 1. FIG. 12 illustrates a graph showing Raman analysis
results of a state in which the horizontal and standing crystals of
molybdenum dioxide (MoO.sub.2) have been removed in accordance with
Experimental Example 1.
[0067] Referring to FIG. 11, Raman analysis may confirm the
presence of molybdenum dioxide (MoO.sub.2) and molybdenum disulfide
(MoS.sub.2).
[0068] Referring to FIG. 12, Raman analysis may confirm the absence
of molybdenum dioxide (MoO.sub.2) and the presence of molybdenum
disulfide (MoS.sub.2).
[0069] FIG. 13 illustrates a schematic diagram showing a process
for hydrogen reduction using a device for hydrogen production
according to some example embodiments of the present inventive
concepts.
[0070] Referring to FIG. 13, a solution 720 may be provided and/or
prepared in a vessel 710. The solution 720 may include a hydrogen
ion (H.sup.+). For example, the solution 720 may include water
(H.sub.2O) and/or sulfuric acid (H.sub.2SO.sub.4). When the
substrate 100, on which the horizontal structures 210 and the
standing structures 220 are provided, is immersed in the solution
720 and supplied with a voltage, the hydrogen ion (H.sup.+) in the
solution 720 may be reduced by the horizontal structures 210 and
the standing structures 220. A current resulting from the reduction
of the hydrogen ion (H.sup.+) may be measured to obtain hydrogen
reduction efficiency of a device for hydrogen production.
[0071] FIG. 14 illustrates a graph showing hydrogen reduction
efficiency of a device for hydrogen production according to some
example embodiments of the present inventive concepts.
[0072] FIG. 14 may show how hydrogen reduction efficiency depends
on the kind of catalyst. In FIG. 14, the expression of "Au" may
indicate an experimental result of hydrogen reduction catalyzed by
gold (Au), the expression of "Lateral MoS.sub.2" may indicate an
experimental result of hydrogen reduction catalyzed by molybdenum
disulfide (MoS.sub.2) horizontally grown on a substrate, the
expression of "Vertical MoO.sub.2/MoS.sub.2" may indicate an
experimental result of hydrogen reduction catalyzed by horizontal
and standing crystals of molybdenum dioxide (MoO.sub.2) and
preliminary layers of molybdenum disulfide (MoS.sub.2) that are
formed in accordance with Experimental Example 1, and the
expression of "Vertical MoS.sub.2" may indicate an experimental
result of hydrogen reduction catalyzed by molybdenum disulfide
(MoS.sub.2) from which horizontal and standing crystals of
molybdenum dioxide (MoO.sub.2) are removed in accordance with
Experimental Example 1.
[0073] When a substrate and catalysts are provided into a solution
of 0.5 M sulfuric acid, and when a hydrogen reduction current (J)
is measured while the substrate is supplied with a voltage (V), it
may be confirmed that the result expressed by Vertical MoS.sub.2
has the highest efficiency of hydrogen reduction.
[0074] According to some example embodiments of the present
inventive concepts, a device for hydrogen production may be
configured to allow molybdenum disulfide to have a relatively large
surface area to achieve high efficiency of hydrogen reduction.
[0075] Although some example embodiments of the present inventive
concepts have been discussed with reference to accompanying
figures, it will be understood that various changes in form and
details may be made therein without departing from the spirit and
scope of the present inventive concepts. It therefore will be
understood that the some example embodiments described above are
just illustrative but not limitative in all aspects.
* * * * *