Method for manufacturing water electrolysis catalyst

Abstract

The present invention relates to a copper-nickel-iron double layer hydroxide nanoprism, a manufacturing method thereof, and a use thereof as a water electrolysis catalyst. The present invention discloses a catalytic electrode for water electrolysis, the catalytic electrode comprising: a metal foam; and a composite transition metal chalcogenide heterostructure formed on the metal foam. This catalytic electrode for water electrolysis can exhibit improved electrochemical catalytic activity for both a hydrogen evolution reaction (HER) and an oxygen evolution reaction (OER) in a water electrolysis reaction, can efficiently produce hydrogen with a lower energy supply than conventional noble metal electrodes, and can be used in both anion exchange membrane water electrolyzers and solar cell-water electrolysis systems. The present invention relates to a nanosphere hybrid structure containing nickel cobalt selenide and molybdenum selenide, and a use thereof as a water electrolysis catalyst. The present invention relates to a water electrolysis catalyst in which zinc cobalt sulfide and molybdenum disulfide are hetero-bonded, and a manufacturing method thereof.

Description

Method for manufacturing a water electrolysis catalyst

[0001] The present invention relates to copper-nickel-iron double-layer hydroxide nanoprisms, a method for producing the same, and a use thereof as a water electrolysis catalyst.

[0002] The present invention relates to a catalyst for electrolysis comprising a complex transition metal chalcogenide, a method for producing the same, and a use thereof.

[0003] The present invention relates to a hybrid structure having a nanosphere structure comprising nickel cobalt selenide and molybdenum selenide and its use as a water electrolysis catalyst.

[0004] The present invention relates to a water electrolysis catalyst in which zinc cobalt sulfide and molybdenum disulfide are hetero-bonded, and a method for producing the same.

[0005] While the use of fossil fuels has led to economic and industrial development, it has also resulted in numerous problems, including various environmental pollution. In particular, greenhouse gases and pollutants generated by the combustion of fossil fuels are contributing to global warming. Accordingly, extensive research is being conducted worldwide to develop clean, renewable energy sources. Recently, hydrogen energy has emerged as an eco-friendly energy source that can address environmental issues caused by fossil fuels. Water electrolysis, in particular, is attracting attention as an eco-friendly and efficient hydrogen production technology. Electrochemical water electrolysis involves two half-cell reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. Precious metal-based catalysts (Pt / C, IrO2) have been used as commercial electrocatalysts for HER and OER, respectively. However, the high cost of these precious metals poses a significant obstacle to the development of efficient catalysts.

[0006] Among transition metal-based materials with outstanding OER catalytic properties, metal-organic frameworks (MOFs) offer numerous advantages, including unique structures and morphologies, pore sizes of varying sizes, and easily tunable chemical structures. However, recent research trends in OER catalysts demonstrate that beyond the application of MOFs alone, research is being conducted toward enhancing catalytic activity through various post-treatments, such as phosphorylation and sulfur treatment.

[0007] The Industrial Revolution led to a significant increase in energy demand, and fossil fuels have primarily been used to meet this rapidly growing demand. Excessive fossil fuel consumption has released harmful gases such as nitrogen oxides, sulfur dioxide, carbon dioxide, and carbon monoxide into the atmosphere, causing environmental pollution and respiratory diseases. Furthermore, carbon dioxide emissions have accelerated global warming. Therefore, the development of new and renewable energy sources, such as wind, solar, hydrogen, and fuel cells, that can replace existing energy sources is essential. Hydrogen is emerging as a promising clean and renewable energy source to replace fossil fuels. However, efficiently producing hydrogen to meet commercial-scale demand remains a key challenge. Water electrolysis offers a promising route to efficient hydrogen production in terms of energy conversion and storage, and catalysts or electrodes play a crucial role. Therefore, the development of active, stable, and inexpensive electrodes or electrocatalysts is a prerequisite for achieving the desired electrocatalytic hydrogen production in electrolysis for practical use, and has become a central focus of recent research.

[0008] Hydrogen energy is produced through thermal (natural gas reforming, renewable liquid and bio-oil processing, biomass and coal gasification), electrolysis (water splitting using various energy sources), and photolysis (biological and electrochemical materials), among which electrolysis is considered a promising technology due to the green nature of the H2 energy produced through this process.

[0009] Depending on the type of electrolyte, electrolysis systems are divided into alkaline electrolysis, proton exchange membrane (PEM) electrolysis, and anion exchange membrane (AEM) electrolysis.

[0010] AEM electrolysis is easy to operate under high pressure and differential pressure, can operate at high current densities, and allows for miniaturization of the device. Furthermore, unlike PEM electrolysis, AEM electrolysis operates in an alkaline environment, allowing the use of inexpensive, naturally abundant non-precious metal catalysts rather than platinum-based catalysts. This contributes to the economic feasibility of green hydrogen production. However, AEM electrolysis is still in the research and development phase, and commercialization requires overcoming performance issues such as the low ionic conductivity of the anion exchange membrane and the long-term stability and reliability of non-precious metal catalysts.

[0011] Transition metal dichalcogenides (TMDs) have attracted significant interest in electrocatalysis due to their unique physical and chemical properties. These compounds have the general chemical formula MX2 (M = transition metal, X = chalcogen) and are bonded by strong intralayer (covalent) and weak interlayer bonds. In MX2, M is often from groups 3 to 12 of the periodic table, and X is typically S, Se, or Te (group 16 of the periodic table). As expected, various MX2s have diverse electronic properties, including insulators (e.g., HfS2), semiconductors (e.g., MoS2 and WS2), semimetals (e.g., WTe2 and TiSe2), and pure metals (e.g., NbS2 and VSe2). Depending on the constituent atoms, TMD materials exhibit metallic, superconducting, or semiconducting properties, and semiconductor materials such as sulfides, selenides, and tellurides are of interest for AEM electrocatalysis due to their high stability.

[0012] TMD-based electrolysis catalysts have several advantages: their large surface area provides abundant HER reaction sites; the measured in-plane resistance of two-dimensional TMDs is lower than that across the basal plane, allowing electrons to more easily migrate along the basal plane to reach the catalytic sites at the edges; and the diverse transition orbitals of different transition metals contribute to the diverse electronic structures of TMDs, ultimately resulting in unique catalytic behaviors for electrolysis. Therefore, significant research is focused on designing novel non-precious metal electrocatalysts for more efficient AWE.

[0013] [Prior Art Document] [Patent Document] Republic of Korea Publication No. 10-2023-0070401

[0014] Accordingly, the inventors of the present invention synthesized Cu-mediated NiFe-LDH (CuNiFe-LDH) nanoprisms using a conductive metal-organic framework (MOF) through a simple method and confirmed their electrolytic catalytic activity, thereby completing the present invention.

[0015] Accordingly, the purpose of the present invention is to provide a copper-nickel-iron double-layer hydroxide nanoprism, a method for producing the same, and a use thereof as a water electrolysis catalyst.

[0016] Accordingly, the present invention has completed the present invention by manufacturing a catalyst for electrolysis including a transition metal chalcogenide compound to solve the above-described activity and stability problems.

[0017] Accordingly, the present invention aims to provide a catalyst for water electrolysis comprising a transition metal chalcogenide compound, a method for producing the same, and a use thereof.

[0018] Accordingly, the inventor of the present invention completed the present invention by manufacturing a new heterojunction hybrid structure of metallic molybdenum selenide nanospheres and nickel cobalt selenide through a simple two-step sequential method.

[0019] Accordingly, the present invention aims to provide a hybrid structure having a nanosphere structure including nickel cobalt selenide and molybdenum selenide, a method for producing the same, and a use thereof.

[0020] Accordingly, the inventor of the present invention completed the present invention by manufacturing a hybrid electrolysis catalyst in which zinc cobalt sulfide and molybdenum disulfide are hetero-bonded through a simple two-step hydrothermal method.

[0021] Accordingly, the present invention aims to provide a water electrolysis catalyst comprising zinc cobalt sulfide and molybdenum disulfide, a method for producing the same, and a use thereof.

[0022] In order to achieve the above-described object, the present invention provides a method for producing copper-nickel-iron double-layer hydroxide nanoprisms, comprising: a first step of synthesizing an iron metal-organic framework by mixing an iron precursor and fumaric acid and then subjecting the mixture to a hydrothermal reaction; and a second step of synthesizing a copper-nickel-iron double-layer hydroxide by mixing the iron metal-organic framework with a nickel precursor and a copper precursor and then subjecting the mixture to a hydrothermal reaction.

[0023] In addition, the present invention provides a copper-nickel-iron double layer hydroxide nanoprism manufactured by a manufacturing method according to the present invention.

[0024] In addition, the present invention provides a water electrolysis catalyst comprising copper-nickel-iron double-layer hydroxide nanoprisms according to the present invention.

[0025] In addition, the present invention provides an anion exchange membrane electrolysis anode comprising a electrolysis catalyst according to the present invention.

[0026] Furthermore, the present invention provides an anion exchange membrane electrolysis device comprising: an anode comprising an OER electrolysis catalyst including copper-nickel-iron double-layer hydroxide nanoprisms according to the present invention; a cathode comprising an HER electrolysis catalyst; and an anion exchange membrane positioned between the anode and the cathode.

[0027] The present invention also provides a solar-electrochemical cell comprising a copper-nickel-iron double-layer hydroxide nanoprism according to the present invention.

[0028] Specific details of other embodiments are included in the detailed description and drawings.

[0029] As a means for achieving the above-described object, the present invention provides a method for producing a catalyst for electrolysis, comprising: a first step of hydrothermally synthesizing a transition metal double layer hydroxide on a metal foam in a solvent containing a transition metal precursor; and a second step of hydrothermally synthesizing the transition metal double layer hydroxide in a solution containing a transition metal and a chalcogen compound to form a composite transition metal chalcogenide.

[0030] In the second step, the composite transition metal chalcogenide may be a heterojunction of two or more transition metal chalcogenide structures.

[0031] In the first and second steps, the transition metal may be at least one transition metal selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Ir, Pt, Os, and Au.

[0032] In the second step, the chalcogen compound may include at least one chalcogen atom selected from the group consisting of S, Se, and Te.

[0033] The above complex transition metal chalcogenide may include at least one selected from the group consisting of CuCo2S4, CuCo2Te4, ZnFeTe, VTe2, FeTe, WS2, WSe2, WTe2, ZnS2, ZnSe2, ZnTe2, MoS2, MoSe2, MoTe2, ZrS2, ZrSe2, HfS2, HfSe2, NbSe2, and ReSe2.

[0034] The above composite transition metal chalcogenide may be any one material selected from the group consisting of VTe2@ZnFeTe, FeTe@ZnFeTe, and MoTe2@ZnFeTe.

[0035] The present invention also provides a catalyst for electrolysis of water, comprising a metal foam and a composite transition metal chalcogenide formed on the metal foam, as a means for achieving the above object.

[0036] The present invention also provides a water electrolysis catalyst comprising a composite transition metal chalcogenide structure, which is manufactured by the manufacturing method of the present invention as a means for achieving the above-mentioned purpose.

[0037] The above composite transition metal chalcogenide may be a heterojunction of two or more transition metal chalcogenide structures.

[0038] The above complex transition metal chalcogenide may include at least one selected from the group consisting of CuCo2S4, CuCo2Te4, ZnFeTe, VTe2, FeTe, WS2, WSe2, WTe2, ZnS2, ZnSe2, ZnTe2, MoS2, MoSe2, MoTe2, ZrS2, ZrSe2, HfS2, HfSe2, NbSe2, and ReSe2.

[0039] The above composite transition metal chalcogenide may be any one material selected from the group consisting of VTe2@ZnFeTe, FeTe@ZnFeTe, and MoTe2@ZnFeTe.

[0040] The above complex transition metal chalcogenide may include a transition metal chalcogen compound having a nanosheet structure.

[0041] The above electrolysis catalyst has an oxygen generation reaction of 20 mA / cm 2 It can exhibit an overpotential of 240 mV at an electrode current density of .

[0042] In addition, the present invention provides a water electrolysis catalyst electrode including the water electrolysis catalyst of the present invention as a means for achieving the above-described purpose.

[0043] In addition, the present invention provides a solar cell-water electrolysis system including the water electrolysis catalyst of the present invention as a means for achieving the above-described purpose.

[0044] In addition, the present invention provides a membrane electrode assembly comprising a cathode as a means for achieving the above-described purpose; an anion exchange membrane formed on the cathode; and an anode formed on the anion exchange membrane, wherein the cathode and the anode include a water electrolysis catalyst of the present invention.

[0045] As a means for achieving the above-described object, the present invention provides a method for producing a hybrid nanostructure, comprising: a first step of synthesizing a nickel-cobalt precursor by hydrothermal synthesis of a precursor solution prepared by dispersing a nickel precursor, a cobalt precursor, and glycerol in a solvent; and a second step of forming nanospheres including nickel-cobalt selenide and molybdenum selenide by adding the nickel-cobalt precursor to a solution containing a molybdenum precursor and a selenite precursor and then hydrothermally synthesizing the precursor solution.

[0046] In addition, the present invention provides a hybrid nanostructure comprising a nanosphere structure including nickel cobalt selenide and molybdenum selenide, which is manufactured by the manufacturing method of the present invention.

[0047] In addition, the present invention provides a water electrolysis catalyst comprising the hybrid nanostructure of the present invention.

[0048] In addition, the present invention provides a water electrolysis catalyst electrode comprising the water electrolysis catalyst of the present invention.

[0049] In addition, the present invention provides a solar cell-water electrolysis system comprising the water electrolysis catalyst of the present invention.

[0050] In addition, the present invention provides a membrane electrode assembly comprising a cathode; an anion exchange membrane formed on the cathode; and an anode formed on the anion exchange membrane, wherein the cathode and the anode include a water electrolysis catalyst of the present invention.

[0051] Additionally, the present invention provides an electrocatalyst for urea oxidation reaction (UOR) comprising the hybrid nanostructure of the present invention.

[0052] As a means for achieving the above-described object, the present invention provides a method for producing a catalyst for electrolysis, comprising: a first step of hydrothermally synthesizing a zinc-cobalt double layer hydroxide on a metal foam using a solution containing a zinc precursor and a cobalt precursor; and a second step of hydrothermally synthesizing the zinc-cobalt double layer hydroxide in a solution containing a molybdenum precursor and a sulfur precursor to form a hybrid structure.

[0053] In addition, the present invention provides a water electrolysis catalyst, which is manufactured by the manufacturing method of the present invention and is a hybrid structure comprising zinc cobalt sulfide and molybdenum disulfide.

[0054] In addition, the present invention provides a water electrolysis catalyst electrode comprising the water electrolysis catalyst of the present invention.

[0055] In addition, the present invention provides a solar cell-water electrolysis system comprising the water electrolysis catalyst of the present invention.

[0056] In addition, the present invention provides a membrane electrode assembly comprising: a cathode; an anion exchange membrane formed on the cathode; and an anode formed on the anion exchange membrane, wherein the cathode and the anode include a water electrolysis catalyst of the present invention.

[0057] The present invention can exhibit excellent OER performance with low activation energy by using Cu-mediated NiFe-LDH nano prisms as a water electrolysis catalyst, and thus has the effect of showing promising efficiency and durability with excellent stable operation while also showing high hydrogen production.

[0058] When conducting a water electrolysis reaction using the water electrolysis catalyst of the present invention, improved electrochemical catalytic activity can be exhibited in both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Furthermore, the water electrolysis catalyst of the present invention can efficiently produce hydrogen with a lower energy supply compared to conventional precious metal electrodes, and can be used in both anion exchange membrane water electrolysis and solar cell-water electrolysis systems.

[0059] FIG. 1 is a schematic diagram illustrating high-performance solar-coupled alkaline water electrolysis using a Cu-mediated NiFe-LDH nano-prism electrocatalyst and a Ni fiber paper non-precious metal electrode according to one embodiment of the present invention.

[0060] Figure 2 is a schematic diagram showing a synthesis process of CuNiFe-LDH according to one embodiment of the present invention.

[0061] Figure 3 shows FESEM images of (a) Fe-MOF, (b) NiFe-LDH nanoprisms, and (c) CuNiFe-LDH nanoprisms, (df) TEM image and corresponding EDX elemental mapping image of Fe-MOF, (gj) TEM image and corresponding EDX elemental mapping image of NiFe-LDH, and (kp) TEM image, HRTEM image of selected area electron diffraction pattern, and corresponding EDX elemental mapping image of CuNiFe-LDH.

[0062] Figure 4 shows the XPS spectra of CuNiFe-LDH: (a) survey spectrum, (b) Ni 2p, (c) Fe 2p, and (d) Cu 2p; (e) schematic diagram of electronic interactions between Ni, Fe, Cu, and O in NiFe-LDH and CuNiFe-LDH.

[0063] Figure 5 shows the electrochemical OER activities of Fe-MOF, NiFe-LDH, and CuNiFe-LDH: (a) linear sweep voltammetry curves, (b) 10 and 20 mA cm -2 (c) Chronoamperometric stability test of CuNiFe-LDH, (d) Tafel slope, (e) comparison with a recently reported high-performance system, (f) current density at various scan rates for electrochemical double-layer capacitance analysis, (g) Arrhenius plot of current at various potentials, (h) activation energy (Ea) calculation, (i) comparison of Ea for NiFe-LDH, CuNiFe-LDH, and CeNiFe-LDH. Experimental conditions: argon-saturated 1 M KOH, 20°C, ~200 and ~185 μg cm for GC and Ni electrodes, respectively. -2 Catalyst loading of .

[0064] Figure 6 shows (a) a schematic diagram of AEMWE operation, (b) polarization curves of AEMWE systems with various MEAs, (c) comparison with previously reported high-performance systems, and (d) Ohmic overpotential (η ohm ), exercise overpotential (η kin ) divided by the total AEMWE overpotential, and low, medium and high j values ​​(300, 600 and 900 mA cm, respectively). -2 ) at mass transfer overpotential (η) mass ), (e) calculated cell efficiency at various j values, (f) long-term stability of the studied MEAs, (g) electricity consumed to produce 1 kg of H2. (Experimental conditions): 1 m KOH, 50°C, ~ 2.5 mg / cm -2 Catalyst loading, ~ 0.5 mg / cm-2 Pt / C loading and ~ 1 mg / cm -2 (RuO2 loading).

[0065] Figure 7 is a flowchart illustrating a manufacturing process of a catalyst electrode for water electrolysis of the present invention.

[0066] Figure 8 is a SEM image of a catalyst electrode for water electrolysis of the present invention.

[0067] Figure 9 is a TEM image of a catalyst electrode for water electrolysis of the present invention.

[0068] Figure 10 is a schematic diagram illustrating a manufacturing process of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention.

[0069] Figure 11 is an HR-TEM image of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention.

[0070] FIG. 12 is an EDAX mapping image of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention.

[0071] Figure 13 is an XRD pattern and XPS spectrum of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention.

[0072] Figure 14 is an XPS spectrum for each atom of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention.

[0073] Fig. 15 is a photograph showing the contact angle of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention.

[0074] Figure 16 is a graph evaluating the OER overpotential of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention.

[0075] Figure 17 shows a Tafel curve during OER operation of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention.

[0076] Figure 18 is a graph evaluating the stability of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention during OER operation.

[0077] FIG. 19 is an EDAX mapping image after OER operation of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention.

[0078] Figure 20 is a graph evaluating the HER overpotential of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention.

[0079] Figure 21 shows a Tafel curve during HER operation of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention.

[0080] Figure 22 is a graph evaluating the stability of a catalyst electrode for electrolysis manufactured according to one embodiment of the present invention during HER operation.

[0081] Figure 23 is a graph evaluating the overpotential and stability of an anion exchange membrane electrolysis device manufactured according to one embodiment of the present invention.

[0082] Figure 24 shows the volume and faradaic efficiency (C) of gases (H2 and O2) produced from anion exchange membrane electrolysis manufactured according to one embodiment of the present invention.

[0083] Figure 25 shows (a) the synthesis process of NCSMS nanospheres, (bd) SEM capture images of NCSMS, (e) elemental mapping of NCSMS nanospheres, (fg) TEM capture images of NCSMS nanospheres, (h) HR-TEM capture images of NCSMS nanospheres, and (i) the elemental mapping results.

[0084] Figure 26 shows the results of (a) XRD, (b) Raman spectrum, (c) BET analysis, (d) pore-diameter distribution, (e) survey of XPS pattern, (f) Co 2p, (g) Ni 2p, (h) Mo 3d and (i) Se 2p high-resolution XPS spectra evaluation.

[0085] Figure 27 shows (a) LSV plot of NCSMS as OER, (b) overvoltage, (c) Tafel slope, (d) it plot, (e) LSV before and after stability test, (f) ECSA numerical plot, (g) LSV plot of NCSMS as HER, (h) overvoltage, (i) Tafel slope, (j) it plot, (k) LSV before and after stability test, (l) 10 to 100 mA cm -2 The results of the chronoampere measurement test are shown in .

[0086] Figure 28 shows (a) comparison of LSV polarization curves of MoSe2 / NF (+) || MoSe2 / NF (-), NCS / NF (+) || NCS / NF (-), NCSMS hybrid (+) || NCSMS hybrid (-), and Pt / C / NF (-) || RuO2 / NF (+), (b) half-cell LSV plot, (c) it test of NCSMS hybrid (+) || NCSMS hybrid (-), (d) LSV determination of S hybrid (+) || NCSMS hybrid (-) electrolyzer before and after 72 h it test, (e) gas evolution, (f) schematic diagram of two-electrode electrolyzer of NCSMS hybrid (+) || NCSMS hybrid (-), and (g) comparison results with recently published water electrolysis electrodes.

[0087] Figure 29 shows (a) LSV curves, (b) overpotential, (c) Tafel comparison, (d) ECSA values, (e) chronoamperometric plot (it), and (f) LSV polarization evaluation analysis results of NCSMS hybrids after initial and 72 h it tests in 1 m KOH and 0.33 M urea electrolytes.

[0088] Figure 30 shows (a) assembly diagram of AEMWE, (b) LSV curve of NCSMS, (c) LSV curve after stability test, (d) stability test of NCSMS, (e) image of AEMWE, (f) image of AEMWE system, (g) IV curve of solar cell, (hj) side view of atomic structure of MoSe2, NCS, and NCSMS, (km) plan view of atomic structure of MoSe2, NCS, and NCSMS hybrid, (n) DOS values ​​of MoSe2, NCS, and NCSMS, (o) △G of different active sites in structure of NCSMS. H *, (p) Gibbs free-energy changes of the NCSMS at different active sites of the NCSMS.

[0089] Figure 31 (a) MoS2@Zn 0.76 Co 0.24 Synthesis mechanism of S, (be) MoS2@Zn at various resolutions 0.76 Co 0.24 FE-SEM images of S hybrid, and (f) MoS2@Zn 0.76 Co 0.24 The corresponding EDX map of the S hybrid is shown.

[0090] Figure 32 (a,b) MoS2@Zn 0.76 Co 0.24 FE-TEM images of S hybrid, (c,d) MoS2@Zn 0.76 Co 0.24 HR-TEM images of S hybrid, and (f,h) MoS2@Zn 0.76 Co 0.24 This shows the EDX mapping image of the elements included in the S hybrid.

[0091] Fig. 33 is MoS2@Zn 0.76 Co 0.24 S, Zn 0.76 Co 0.24(a) XRD plot, (b) Raman shift, (c) BET analysis, and d) pore-diameter distribution of S and MoS2, and MoS2@Zn 0.76 Co 0.24 (e) Co 2p, (f) Mo 3d, (g) Zn 2p, and (h) S 2p XPS spectra of the S hybrid are shown.

[0092] Figure 34 shows the results of (a) LSV plot, (b) η, (c) Tafel plot, and (d) ECSA analysis plot, (e) MoS2@Zn 0.76 Co 0.24 Chromatographic plots of S / NF nanohybrid (it), (f) MoS2@Zn initial and after 48 h it test 0.76 Co 0.24 This shows the LSV plot of the S / NF nanohybrid.

[0093] Figure 35 shows MoS2@Zn during HER. 0.76 Co 0.24 (a) LSV plot, (b) η, (c) Tafel slope comparison, and (d) stability plot of S / NF hybrid, (e) MoS2@Zn 0.76 Co 0.24 Comparative LSV plots of the S / NF hybrid at initial and 48 h post-treatment, (f) overpotential comparison results of recently reported HER electrodes.

[0094] Figure 36 (a) MoS2(+) || MoS2(-), Zn 0.76 Co 0.24 S (+) || Zn 0.76 Co 0.24 S (-), MoS2@Zn 0.76 Co 0.24 S (+) || MoS2@Zn 0.76 Co 0.24 Half-cell LSV plots of (a) MoS2(+) || MoS2(-), and (b) Pt / C(-) || RuO2 hybrids, Zn 0.76 Co 0.24 S (+) || Zn0.76 Co 0.24 S(-) and MoS2@Zn 0.76 Co 0.24 S (+) || MoS2@Zn 0.76 Co 0.24 LSV plots of S(-) electrolyzer and commercial Pt / C(-) || RuO2(+), (c) MoS2@Zn 0.76 Co 0.24 S (+) || MoS2@Zn 0.76 Co 0.24 Results of the it test of S (-) electrolytic cell, (d) MoS2@Zn after initial and 48-hour it test 0.76 Co 0.24 S (+) || MoS2@Zn 0.76 Co 0.24 LSV determination of S(-), (e) oxygen evolution graph, (f) comparison with cell overvoltages from recent literature, (g) schematic of the two-electrode electrolyzer, (h) photograph of two electrodes in one actuator, and (i) photograph of each electrode in another actuator os.

[0095] Figure 37 shows (a) the assembly diagram of AEMWE, (b) comparison with recent literature, and (c) MoS2@Zn 0.76 Co 0.24 IV curve of S, (d) MoS2@Zn 0.76 Co 0.24 Results of the stability test of S: (e) LSV curve after stability test, (f) image of AEMWE system, (g) self-standing solar cell and electrode assembly, and (h) IV curve of solar cell.

[0096] The present invention is susceptible to various modifications and 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 invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. In describing the present invention, detailed descriptions of related known technologies will be omitted if they are deemed to obscure the gist of the present invention.

[0097] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0098] Terms such as first, second, etc. may be used to describe various components, but these components should not be limited by these terms. These terms are used solely to distinguish one component from another.

[0099] The present invention may be better understood by the following examples, which are provided for illustrative purposes only and are not intended to limit the scope of protection defined by the appended claims.

[0100]

[0101] Examples of the first embodiment of the present invention are as follows.

[0102] The present invention relates to a method for producing copper-nickel-iron double-layer hydroxide nanoprisms, comprising: a first step of synthesizing an iron metal-organic framework by mixing an iron precursor and fumaric acid and then subjecting the mixture to a hydrothermal reaction; and a second step of synthesizing a copper-nickel-iron double-layer hydroxide by mixing the iron metal-organic framework with a nickel precursor and a copper precursor and then subjecting the mixture to a hydrothermal reaction.

[0103] In the first step, the iron precursor and fumaric acid may be mixed for 1 to 4 days, for example, 3 days, but is not limited thereto.

[0104] In the second step, the nickel precursor and the copper precursor may be mixed in a mass ratio of 3:1 to 4, but is not limited thereto.

[0105] In addition, the present invention relates to copper-nickel-iron double layer hydroxide nanoprisms manufactured by the manufacturing method according to the present invention.

[0106] In addition, the present invention relates to a water electrolysis catalyst comprising copper-nickel-iron double-layer hydroxide nanoprisms according to the present invention.

[0107] The above electrolysis catalyst can be used for oxygen evolution reaction (OER) of fresh water, alkaline water or seawater, but is not limited thereto.

[0108] The above electrolysis catalyst may be a non-precious metal electrolysis catalyst, but is not limited thereto.

[0109] In addition, the present invention relates to an anion exchange membrane electrolysis anode comprising a electrolysis catalyst according to the present invention.

[0110] Furthermore, the present invention relates to an anion exchange membrane electrolysis device comprising: an anode comprising an OER electrolysis catalyst comprising copper-nickel-iron double-layer hydroxide nanoprisms according to the present invention; a cathode comprising an HER electrolysis catalyst; and an anion exchange membrane positioned between the anode and the cathode.

[0111] The above HER electrolysis catalyst may include, but is not limited to, NiFe2O4.

[0112] The present invention also relates to a solar-electrochemical cell comprising a copper-nickel-iron double layer hydroxide nanoprism according to the present invention.

[0113] Example 1.1: Catalyst synthesis

[0114] 1.1.1. Fabrication of MIL-88A metal-organic frameworks (MOFs)

[0115] Typically, Fe(NO3)3-9H2O (320 mg) and fumaric acid (160 mg) were mixed in DMF (25 mL) / H2O (5 mL) for 3 days to form a reddish-yellow solution. The resulting solution was transferred to a Teflon-lined stainless steel autoclave (50 mL) and hydrothermally reacted at 90°C for 6 h. The precipitate was collected by centrifugation, washed three times with a water / ethanol (1:1) mixture, and dried at 60°C for 10 h.

[0116] 1.1.2. Fabrication of NiFe-LDH nanoprisms

[0117] Solution A was prepared by dispersing MIL-88A (14 mg) in DMF (20 mL). Solution B was prepared by dissolving urea (200 mg) and Ni(NO3)3-6H2O (150 mg) in water (20 mL). Solution C, prepared by mixing Solutions A and B, was heated at 90°C for 6 h in a completely sealed Teflon-lined stainless steel autoclave (50 mL). The resulting product was washed three times with a water / ethanol (1:1) mixture and then dried at 60°C for 10 h.

[0118] 1.1.3. Fabrication of CuNiFe-LDH nanoprisms

[0119] Solution A was prepared by dispersing MIL-88A (14 mg) in DMF (20 mL). Solution B was prepared by dissolving urea (200 mg), Ni(NO3)3-6H2O (150 mg), and Cu(NO3)3-3H2O (100 mg) in water (20 mL). Solution C, prepared by mixing Solutions A and B, was heated at 90°C for 6 h in a completely sealed Teflon-lined stainless steel autoclave (50 mL). The obtained product was washed three times with a water / ethanol (1:1) mixture and dried at 60°C for 10 h.

[0120] Example 1.2: Alkaline water electrolyzer setup and operation

[0121] 1.2.1. Cleaning and pretreatment of Ni fiber paper electrode

[0122] Activated nickel fiber paper (NFP) electrodes have been used as anode and cathode gas diffusion electrodes in electrochemical reactions. 1 × 1 and 5 × 5 cm 2 NFP pieces of the appropriate size were cut from commercial NFP. The NFP pieces were immersed in hydrochloric acid (0.1 m), sonicated for 15 min, rinsed with deionized water and ethanol, and dried in an oven at 60°C for 6 h.

[0123] 1.2.2. Manufacturing of Gas Diffusion Electrode (GDL)

[0124] The electrodes were fabricated using a catalyst coating method. To prepare the anode, the catalyst (20 mg) was mixed with water (1 mL), isopropyl alcohol (2 mL), and anion exchange binder (Sustainion® XC-1, 100 μL) by sonication for 30 min. A similar method was used to produce the NiFe2O4 coated cathode. The catalyst loading of the anode and cathode was ~2.5 mg cm -2 The homogeneous catalyst ink was coated on the NFP GDL using a spray coating method on a hot plate (60°C). The active area of ​​the electrode was 5 × 5 cm 2For comparison, RuO2-coated NFP (catalyst loading: ~1 mg cm -2 ) and 20% Pt / C coated NFP (catalyst loading: ~0.5 mg cm -2 ) were used as the positive and negative electrodes, respectively.

[0125] 1.2.3. Conventional two-electrode system

[0126] A typical water electrolyzer test was performed using a two-electrode single-chamber apparatus. CuNiFe-LDH / NFP and NiFe2O4 / NFP were used as the anode and cathode, respectively, and the electrolyzer was tested at 1.45–1.9 V.

[0127] 1.2.4. Wireless solar-powered water electrolyzer

[0128] Double-sided a-Si:H / a-Si:H / μc-Si:H triple-junction single-crystal solar cells were fabricated using a laser scribing machine. The Ag side of the solar cell was cleaned with soldering flux. Copper tape welded to one end of the solar panel (front and back) was used for connection. The IV characteristics of the solar cell were measured from the open-circuit voltage to the short-circuit current in the direction of 5 mV s. -1 100 mW cm with a scan rate of -2The PV-EC system was tested under simulated AM 15G light (Oriel Sol3A Solar Simulator) using a Keithley 4200 source measure unit. The light intensity was calculated using a 91150 V Reference Cell and Meter (Newport). The bias voltage at steady state was selected as the average maximum power point voltage during the IV measurements. The solar cells (types A, B1, B2, B3, B4, B5, and their combinations) showed voltages of 0.35, 0.35, 0.35, 0.35, 0.35, and 21 V, respectively. Two types of solar cell devices (flat and semicircular) were fabricated. Finally, the PV-EC system was sealed with steel-welded epoxy (Hardex, Malaysia).

[0129] 1.2.5. Commercial Anion Exchange Membrane Water Electrolyzer (AEMWE)

[0130] Membrane electrode assemblies (MEAs) were fabricated by placing a membrane (Sustainion™ X37-50 RT) between two catalyst-coated substrates (catalyst-coated NFP electrodes) using a hot press method (2 MPa, 40°C, 1 min). For comparison, MEAs were also fabricated using the catalyst-coated membrane (CCM) method and the catalyst-coated substrate (CCS) method. In the CCM method, the catalyst loading on the top of the membrane was approximately 1.0 mg cm -2 am.

[0131] Example 1.3: Physical Characterization

[0132] Field emission scanning electron microscopy (FESEM) confirmed that the Fe-MOF had a smooth spindle shape (Fig. 3a). The Fe-MOF was then converted to NiFe-LDH nanoprisms (Fig. 3b) or CuNiFe-LDH nanoprisms (Fig. 3c). Energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of Cu, Ni, and Fe in the CuNiFe-LDH nanoprisms. In the XRD pattern of the CuNiFe-LDH nanoprisms, the diffraction peaks at 11.3°, 22.7°, and 34.5° correspond to the (003), (006), and (012) planes of CuNiFe-LDH, respectively (JCPDS No. 40-0215). Transmission electron microscopy (TEM) image (Fig. 3) showed interconnected Fe-MOF nanoprisms, and EDX elemental mapping confirmed the presence of Fe (Fig. 3e,f). Similarly, the TEM image (Fig. 3g) and EDX elemental mapping (Figs. 3h-j) of the NiFe-LDH nanoprisms show the uniform distribution of Ni and Fe. The TEM image (Fig. 3k) of CuNiFe-LDH confirmed the successful synthesis of hierarchical nanoprisms by showing a loosely packed porous structure. In addition, the high-resolution TEM (HRTEM) image (Fig. 3l) indicates the presence of two phases: 012 (0.26 nm) and 006 (0.347 nm). Finally, the EDX elemental mapping (Figs. 3m-p) of CuNiFe-LDH confirmed the uniform distribution of Cu, Ni, and Fe throughout the porous nanoprisms.

[0133] Example 1.4: Elemental composition and phase analysis

[0134] The electronic structure and composition of CuNiFe-LDH were studied using X-ray photoelectron spectroscopy (XPS). The XPS spectrum of CuNiFe-LDH in Fig. 4a confirmed the presence of Ni, Fe, Cu, and O without impurities. Deconvoluted Ni 2p spectrum of CuNiFe-LDH (Fig. 4b) showed 856.1 (2p 3 / 2 ) and 873.9 eV(2p1 / 2 ) show two peaks, which shift to higher binding energy compared to NiFe-LDH. The Fe 2p spectrum of CuNiFe-LDH (Fig. 4c) shows Fe 2p 3 / 2 and Fe 2p 1 / 2 peaks, which shifted to lower binding energies of 713.6 and 724.4 eV, respectively, compared to NiFe-LDH. 932.6 eV (Cu 2p 3 / 2 ) and 953.3 eV (Cu 2p 1 / 2 ) The observation of high intensity Cu peaks in CuNiFe-LDH 2+ The presence of Cu was confirmed (Fig. 4d). The observation of opposite shifts of the Ni 2p and Fe 2p peaks indicates that partial electron transfer occurs from the Ni site to the Fe site when Cu is present in CuNiFe-LDH.

[0135] As shown in Fig. 4e, the electron-electron interactions between Ni, Fe, and Cu ions in CuNiFe-LDH can be explained by the electronic structure of the metal ions. Ni 2+ is an atomic electron state d8(t 2g 6 e g 2 ), where the fully occupied π-symmetric d-orbital (t 2g ) is Ni 2+ Wow O 2- It causes electronic repulsion between Fe. Also, Fe 3+ is a π-symmetric d-orbital (d5; t 2g 3 e g 2) has unpaired electrons, promoting π-back donation and Fe-O bond formation. This interaction can accelerate partial charge transfer from Ni to Fe and lead to Ni-O-Fe bridge formation, which is supported by XPS results. Cu doping promoted electron transfer from Ni and Cu to Fe through O atoms in the electron accepting sites of CuNiFe-LDH. Consequently, Cu 2+ (t 2g 6 e g 3 ) formed Ni-O-Fe-O-Cu through the d-orbital (π-symmetry), which caused electron-electron repulsion. When combined with Ni and Fe, the electron-rich d-orbital of Cu can modify the electronic state and change the electronic structure and conductivity of CuNiFe-LDH, thereby improving the OER activity.

[0136] Example 1.5: Electrochemical performance

[0137] The OER activities of CuNiFe-LDH, NiFe-LDH, Fe-MOF, and bare glassy carbon (GC) electrodes were compared at the same mass loading (geometric area: ~200 μg cm-2) using a three-electrode array. As shown in Fig. 5a,b, CuNiFe-LDH showed a higher OER activity than NiFe-LDH (10 mA cm -2 At 254mV, 20mA cm -2 at 330 mV), Fe-MOF (10 mA cm -2 At 330mV, 20mA cm -2 ) and lower η values ​​(j = 10 and 20 mA cm) than bare GC (negligible). -2 It was confirmed that the reversible hydrogen electrode (RHE) showed 204 and 289 mV, respectively. In addition, the η value of CuNiFe-LDH was similar to that of RuO2 (10 mA cm -2 192mV at 20mA cm -2293 mV). Also, chronoamperometry (Ni electrode, catalyst load: ~185 μg cm) was performed at a constant applied voltage of 1.5 V. -2 ) was used to evaluate the stability of the catalyst (Fig. 5c). In addition, the Tafel slopes of Fe-MOF, NiFe-LDH, and CuNiFe-LDH were 48.3, 40.1, and 34.2 mV dec, respectively. -1 was (Fig. 5d). RuO2 (29.8 mV dec -1 ) and the lower Tafel slope of CuNiFe-LDH, similar to that of CuNiFe-LDH, indicate that this catalyst exhibits faster OER reaction kinetics and higher activity.

[0138] As shown in Fig. 5e, CuNiFe-LDH had lower η than Co-NiFe-LDH (238 mV), Ce@NiFe-LDH (205 mV), graphene-NiFe-LDH (220 mV), FeNiP / NCH (250 mV), Ce-NiFe-LDH (242 mV), Ni / Ni2P@N-CNF (285 mV), and NiFe-LDH (272 mV). The j versus scan rate plot (Fig. 3f) showed η of 0.8, 1.02, and 1.42 mF cm for Fe-MOF, NiFe-LDH, and CuNiFe-LDH, respectively. -2 The Cdl value of geo was obtained. Typically, the average specific capacitance of a flat surface is 40 μF cm -2 As can be seen in Fig. 5i, the Ea value of CuNiFe-LDH (15.45 kJ mol -1 ) is NiFe-LDH(43.4kJ mol -1 ) and CeNiFe-LDH (27.6 kJ mol -1 ) was lower than that of CuNiFe-LDH. These results indicate that CuNiFe-LDH has a lower kinetic barrier to OER.

[0139] Example 1.6: Performance of a Commercial Zero-Gap Single-Cell Alkaline Anion-Exchange Membrane Water Electrolyzer

[0140] In this invention, we developed a non-precious metal-based AEMWE device for low-cost commercial hydrogen production that can replace PEMWE (Fig. 6a). The membrane electrode assembly (MEA) was fabricated by combining the previously reported NiFe2O4HER electrocatalyst and CuNiFe-LDH OER electrocatalyst in 1 m KOH using a commercially available anion exchange membrane (Sustainion™ X37-50 RT) as an ion separation membrane. Key criteria for improving the MEA, as well as the interface between the membrane layer (ML) and the catalyst layer (CL), are as follows: (i) a high three-phase (solid-liquid-gas) boundary to create a large reaction area that facilitates ion and mass transport; (ii) an efficient OH- transport pathway between the ML and CL; and (iii) excellent adhesion properties between the CL and ML to prevent catalyst loss during electrolysis. (iv) By binding the catalyst to the CL using an anion exchange ionomer binder (Sustainion™ XC-1, Dioxide Materials, USA), catalyst separation was prevented and OH transport microchannels were constructed in the CL.

[0141] A method for directly depositing a catalyst on a membrane (CCM) was developed for MEA fabrication. The CCM method is suitable for fabricating porous CLs with high ion, gas, and electrolyte permeability. Uniform CLs were formed on the membrane surface on the anode (CuNiFe-LDH) and cathode (NiFe2O4). In the CCS method, CuNiFe-LDH / NFP and NiFe2O4 / NFP electrodes were fabricated as the anode and cathode, respectively. Figure 6b shows the loading curves of AEMWEs using various MEAs with 1 m KOH as a circulating medium and an operating temperature of 50°C. At 1.85 V, the MEA activity of AEMWEs follows the trend: MEA-CCM-3 (1131 mA cm -2 ) > MEA-CCS-4(1080mA cm -2 ) > MEA-CCM-1(1053mA cm -2) > MEA-CCS-2(947mA cm -2 ) in order. The j values ​​of the CuNiFe-LDH / NFP||NiFe2O4 / NFP(+ / -)-CCM-1 and CuNiFe-LDH / NFP||NiFe2O4 / NFP(+ / -)-CCS-2 electrolytic cell systems are 1053 and 947 mA cm, respectively. -2 , and 1053 and 1047 mA cm at 1.85 V, respectively. -2 , which is a high-grade commercial RuO2 / NFP||Pt / C / NFP(+ / -)-CCS-4 electrode pair (j = 1080 mA cm at 1.85 V). -2 ) is similar to that of the most recently reported system. Therefore, the AEMWE device showed superior performance compared to the most recently reported system (Fig. 6c).

[0142] <Conclusion of Embodiment 1>

[0143] In the present invention, Cu-mediated NiFe-LDH (CuNiFe-LDH) nanoprisms were fabricated using a simple method as a conductive metal-organic framework (MOF; NiFe MIL-88A). The initial MOF structure was stabilized by electronic bonding and Cu ion coordination. The CuNiFe-LDH nanoprisms were fabricated under a 10 mA cm -2 At a current density of 204 mV and an overpotential of 15.45 kJ mol -1 It exhibited excellent OER performance with low activation energy. Mechanistic investigation using density functional theory calculations demonstrated that the Cu site of CuNiFe-LDH was very efficient for OER, and CuNiFe-LDH had a lower theoretical overpotential than NiFe-LDH. The wireless solar-electrochemical cell developed using CuNiFe-LDH / Ni fiber paper (NFP) anode and NiFe2O4 / NFP cathode achieved a solar-to-hydrogen efficiency of 11.08%. In addition, the OER efficiency was 974 mA cm at 1.85 V. -2The excellent performance of an anion exchange membrane electrolyzer using CuNiFe-LDH catalyst, such as power consumption of 46.9 kWh per 1 kg of hydrogen production, and the reproducible self-templating method were introduced to fabricate CuNiFe-LDH nanoprisms with excellent OER activity. The advanced LDH structure of CuNiFe-LDH microprisms has j = 10 mA cm -2 At an overpotential of 204 mV, low activation energy (Ea = 15.45 kJ mol -1 ) and provided high stability for 24 h. The desired nanoprisms could be easily produced through Cu-mediated structural modification of the NiFe-LDH structure and MOF modification. DFT calculations demonstrated that the high specific activity of CuNiFe-LDH was due to the close proximity of the binding energy, a key explanatory variable for predicting the OER performance of the Cu site in CuNiFe-LDH, to the ideal value. The fabricated PV cell was combined with an EC cell composed of CuNiFe-LDH / NFP and NiFe2O4 / NFP electrodes to form a PV-EC device that achieved excellent stability and STH efficiency of 11.08% for 20 h. This wireless PV-EC device set a new benchmark for PV-based solar hydrogen generators. In addition, an AEMWE with a non-precious metal electrode (anode / cathode) for H2 production using the CuNiFe-LDH catalyst was fabricated. The fabricated device exhibited an electrochemical performance of 974 mA cm at 1.85 V. -2 With a stable operation time of over 120 hours and a high J value, the AEMWE demonstrated promising efficiency and durability. Furthermore, only 46.9 kWh of electricity was consumed to produce 1 kg of H2, demonstrating that this AEMWE could provide a low-cost and sustainable approach to H2 production.

[0144]

[0145] Examples of the second embodiment of the present invention are as follows.

[0146] <Catalyst electrode for water electrolysis>

[0147] As a means for achieving the aforementioned purpose, the present invention provides a water electrolysis catalyst including a composite transition metal chalcogenide structure formed on a metal foam and a catalyst electrode including the same.

[0148] The catalyst electrode of the present invention can be used, for example, in anion exchange membrane (AEM) electrolysis. The AEM electrolysis is composed of a membrane, an ionomer, a membrane electrode assembly (MEA), and a gas diffusion layer (GDL), and the membrane electrode assembly is further composed of a cathode, anion exchange membrane, and an anode. The catalyst electrode of the present invention can be utilized as the cathode and anode of the membrane electrode assembly.

[0149] In addition, the catalyst electrode of the present invention can be used, for example, in a photovoltaic-electrolysis (PV-EC) system. The PV-EC system is a method of producing hydrogen through water electrolysis after generating electricity using a solar cell. The PV-EC system is composed of a photovoltaic cell, an oxidation catalyst electrode, a reduction catalyst electrode, an ion separation membrane, and an aqueous electrolyte. The catalyst electrode of the present invention can be used as an oxidation catalyst electrode and a reduction catalyst electrode in the PV-EC system.

[0150] The above metal foam is a fully open porous metal structure in which all pores are connected, and is characterized by various pore sizes, low specific weight, and high processability. Here, the metal foam may be at least one selected from the group consisting of Ni foam, Fe foam, Cu foam, Ag foam, and Ti foam, but is not limited thereto.

[0151] Here, the above-mentioned composite transition metal chalcogenide may be a heterojunction of two or more transition metal chalcogen compounds. The heterojunction refers to a contact between two substances with different energy levels, such as a junction between two different semiconductors such as a gallium arsenide (GaAs) element and germanium (Ge), or a junction between a semiconductor and a metal. In order for a heterojunction to exhibit its unique properties, the crystal structure or thermal expansion coefficient between the two substances to be joined must be very similar. Otherwise, the unique properties of the junction may be lost as various interface states are formed at the junction.

[0152] Here, the transition metal may be at least one transition metal selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Ir, Pt, Os, and Au, but is not limited thereto.

[0153] The above chalcogen compound may be at least one chalcogen atom selected from the group consisting of S, Se, and Te, but is not limited thereto.

[0154] The above n may be an integer from 1 to 10, and the above m may be an integer from 1 to 10.

[0155] Here, the above-mentioned complex transition metal chalcogenide may include any one material selected from the group consisting of CuCo2S4, ZnFeTe, VTe2, FeTe, CuCo2Te4, WS2, WSe2, WTe2, ZnS2, ZnSe2, ZnTe2, MoS2, MoSe2, MoTe2, ZrS2, ZrSe2, HfS2, HfSe2, NbSe2, and ReSe2 and combinations thereof, but is not limited thereto.

[0156] Here, the complex transition metal chalcogenide heterostructure may include a transition metal chalcogenide compound having a nanosheet structure. The nanosheet refers to a sheet structure having a size in the nanometer scale. It generally includes nanosheets having a diameter of several nanometers to several hundred nanometers, and there is no particular limitation on the length. There are various types of nanosheets, such as metals (Ni, Pt, Au, etc.), semiconductors (Si, InP, GaN, ZnO, etc.), and insulators (SiO2, TiO2, etc.). In the present invention, the transition metal chalcogenide heterostructure having the nanosheet structure may be, for example, ZnFeTe.

[0157] A more specific composite transition metal chalcogenide heterostructure may be, for example, one material selected from the group consisting of VTe2@ZnFeTe, FeTe@ZnFeTe and MoTe2@ZnFeTe.

[0158] Here, the catalyst electrode for water electrolysis can be characterized by exhibiting an overpotential of 119 mV at an electrode current density of 20 mA / cm2 in the hydrogen evolution reaction. More specifically, at an electrode current density of 20 mA / cm 2 At an overpotential of 119 mV and an electrode current density of 50 mA / cm 2 It can exhibit an overpotential of 217 mV.

[0159] In addition, the catalyst electrode for water electrolysis can be characterized by exhibiting an overpotential of 240 mV at an electrode current density of 20 mA / cm2 in the oxygen evolution reaction. More specifically, at an electrode current density of 20 mA / cm 2 At an overpotential of 240 mV and an electrode current density of 50 mA / cm 2 It can exhibit an overpotential of 300 mV.

[0160] More specific details regarding the overpotential of the electrolysis catalyst electrode of the present invention will be described in more detail in {Examples and Evaluation} below.

[0161] Here, the contact angle of the electrolysis catalyst electrode may be 0° to 5°, and more preferably 0.01° to 3°. The contact angle indicates the degree of hydrophilicity of the electrode surface, and is defined as superhydrophobic when the contact angle is 160° or more, hydrophobic when the contact angle is 90° or more and less than 160°, hydrophilic when the contact angle is 20° or more and less than 90°, and hydrophilic when the contact angle is less than 20°. The smaller the contact angle value of the electrolysis catalyst electrode, the more hydrophilic it is, and the more hydrophilic the electrolysis catalyst electrode is, the better the contact efficiency with the electrolyte solution, thereby providing faster charge transport and improved conductivity. Specific details related to the contact angle of the electrolysis catalyst electrode of the present invention will be described in more detail in {Examples and Evaluation} below.

[0162] <Method for producing a catalyst for water electrolysis>

[0163] The present invention provides a method for producing a catalyst for electrolysis, comprising the steps of: a first step of hydrothermally synthesizing a transition metal double layer hydroxide on a metal foam in a solvent containing a transition metal precursor; and a second step of hydrothermally synthesizing the transition metal double layer hydroxide in a solution containing a transition metal and a chalcogen compound to form a composite transition metal chalcogenide.

[0164] Figure 7 is a flow chart illustrating a process for manufacturing a catalyst for electrolysis of the present invention. Referring to Figure 7, it can be seen that the method for manufacturing a catalyst for electrolysis of the present invention includes a step of forming a transition metal double-layer hydroxide nanosheet on a metal foam; and a step of forming a transition complex transition metal chalcogenide on the transition metal double-layer hydroxide nanosheet.

[0165] Here, the step of forming the transition metal double-layer hydroxide nanosheet and the step of forming the composite transition metal chalcogenide can be performed through a simple hydrothermal synthesis method. Hereinafter, the method of manufacturing the water electrolysis catalyst of the present invention will be described in detail, step by step.

[0166] Hydrothermal synthesis refers to the synthesis of materials using hydrothermal reactions. Hydrothermal reactions utilize water under high temperatures and pressures, typically around 100°C and over 1 atm. Performing such hydrothermal reactions typically requires a high-temperature, high-pressure vessel, commonly called an autoclave. Under saturated vapor pressure, the density, viscosity, surface tension, and dielectric constant of water continuously decrease with increasing temperature. Furthermore, the number of ions in water increases with increasing temperature, reaching a maximum at approximately 270°C. Thus, high-temperature, high-pressure water has the property of dissolving organic compounds while simultaneously serving as a solvent that forms a reaction field suitable for ionic reactions, facilitating the diffusion of ions and molecules and achieving high reaction rates. The hydrothermal method described above is used to synthesize various catalysts.

[0167] Here, the step of forming the transition metal nanosheet may be heating the metal foam substrate in an aqueous solution containing a first thermal transition metal precursor.

[0168] Here, the first transition metal precursor may be any transition metal precursor capable of forming the nanosheet structure, and the any transition metal precursor capable of forming the nanosheet structure may include, but is not limited to, one or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Ir, Pt, Os, and Au. More specific examples may include zinc nitrate (Zn(NO3)2), zinc acetate (Zn(CH3COO)2), zinc chloride (ZnCl2), iron nitrate (Fe(NO3)3), iron acetate (Fe(CH3COO)3), iron chloride (FeCl3), and the like.

[0169] The heating temperature may be 100 to 200°C. When the heating temperature is less than 100°C and more than 200°C, it may be difficult for the first transition metal precursor to be formed into the nanosheet structure.

[0170] The step of forming the above transition metal chalcogenide compound may be a step of heating a metal foam having the above transition metal nanosheets formed in an aqueous solution containing a second transition metal precursor and a telluride precursor.

[0171] The second transition metal precursor may include, but is not limited to, one or more selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Ir, Pt, Os and Au. More specific second transition metal precursors may include, for example, sodium tungstate, potassium tungstate, ammonium tungstate, carbonyl tungstate, dimethyl zinc, diethyl zinc, zinc acetate, zinc iodide, zinc bromide, zinc chloride, zinc nitrate, zinc oxide, zinc sulfate, ammonium molybdate, ammonium sodium, metabananadate, and the like.

[0172] The telluride precursor may be, for example, potassium tellurite, sodium tellurite or the like, and any precursor that is soluble in water and can release tellurium ions may be used without limitation.

[0173] In addition, the method for manufacturing a catalyst electrode for water electrolysis of the present invention is characterized by further comprising the steps of: placing a metal foam on which the transition metal nanosheets are formed in an aqueous solution containing a second transition metal precursor; and a telluride precursor; and a heating step in which the transition metal nanosheets and telluride ions form a bond to form a transition metal chalcogenide heterostructure having a nanosheet structure. In addition, as another transition metal chalcogenide compound from the second transition metal precursor is formed on the transition metal chalcogenide compound having a nanosheet structure, a composite transition metal chalcogenide compound can ultimately be formed.

[0174] Specific examples of complex transition metal chalcogenides may include VTe2@ZnFeTe, FeTe@ZnFeTe, MoTe2@ZnFeTe, etc., as described above.

[0175] Fig. 8 is a SEM image of a catalyst electrode for water electrolysis of the present invention. More specifically, Fig. 8a illustrates a catalyst electrode for water electrolysis having a size of 5 μm (inset), and Fig. 8b illustrates a catalyst electrode for water electrolysis having a size of 2 μm (inset). Referring to Fig. 8, it can be seen that the catalyst electrode for water electrolysis of the present invention exhibits a nanosheet shape with a thick and rough appearance. In addition, it can be seen that the catalyst electrode for water electrolysis of the present invention has mesopores and macropores. These pores increase the specific surface area of ​​the electrode of the present invention, allowing it to be more exposed to solvents and ions, thereby enabling faster electron transfer.

[0176] Figure 9 is a TEM image of a catalyst electrode for water electrolysis of the present invention. Referring to Figure 9, it can be seen that the catalyst electrode for water electrolysis of the present invention has a nanosheet structure of a transition metal chalcogenide compound prepared from a first transition metal precursor, and a transition metal chalcogenide compound prepared from a second transition metal precursor is fixed on the surface of the nanosheet, so that the surface of the nanosheet is formed non-uniformly.

[0177] <Membrane electrode assembly including a catalyst electrode for water electrolysis>

[0178] The present invention provides a membrane electrode assembly comprising: a cathode; an anion exchange membrane formed on the cathode; and an anode formed on the anion exchange membrane, wherein the cathode and the anode include a metal foam and a composite transition metal chalcogenide heterostructure formed on the metal foam.

[0179] The above membrane electrode assembly, as described above, is a component of AEM water electrolysis, and includes a cathode, an anion exchange membrane, and an anode, and may include a catalyst electrode for water electrolysis of the present invention. At the anode, a hydrogen evolution reaction (HER) occurs simultaneously as a half-cell reaction, and at the cathode, an oxygen evolution reaction (OER) occurs simultaneously. That is, water is reduced at the anode and reacts with electrons to form hydrogen and hydroxide ions, the generated hydroxide ions diffuse to the cathode through the anion exchange membrane, and the electrons are transferred to the cathode through an external circuit. At the cathode, the hydroxide ions lose electrons and recombine into water and oxygen, and the electrons are released from the cathode surface to proceed with the reaction. The water decomposition process that occurs at the anode and cathode is as follows.

[0180] Anode: 4OH - → O2+ 2H2O + 4e - E 0= 0.401 V

[0181] Cathode: 4H2O + 4e - → 2H2+ 4OH - E 0 = -0.828 V

[0182] Overall: 2H2O → H2+ O2E 0 = 1.23 V

[0183] An AEM electrolyzer comprising a membrane electrode assembly of the present invention as a cathode and an anode uses a metal foam, a catalyst electrode for an electrolyzer comprising a composite transition metal chalcogenide heterostructure formed on the metal foam, and a catalyst electrode for an electrolyzer capable of increasing the efficiency of hydrogen and oxygen generation by improving charge transport and conductivity.

[0184] <Solar cell-water electrolysis system including a catalyst electrode for water electrolysis>

[0185] In addition, the catalyst electrode for water electrolysis of the present invention can be utilized in a photovoltaic-electrolysis (PV-EC) system as described above. The PV-EC system is composed of a photovoltaic cell, an anode, a cathode electrode, an ion separator, and an aqueous electrolyte.

[0186] The PV-EC system can produce hydrogen by a process in which, when light is irradiated onto the photovoltaic cell, the photovoltaic cell absorbs the light to generate electrons and holes, which are then transferred to oxidation (oxygen generation electrode) and reduction (hydrogen generation electrode) catalyst electrodes located inside an aqueous electrolyte solution to decompose water, thereby separating oxygen at the oxidation electrode and hydrogen at the reduction electrode. The catalyst electrode for water electrolysis of the present invention can be utilized as an oxidation catalyst electrode and a reduction catalyst electrode in the PV-EC system.

[0187] The above photovoltaic cell may use any of the existing solar cells developed and used, which include a semiconductor material capable of absorbing light to create electron-hole pairs. For example, a photovoltaic solar cell using a silicon semiconductor, a dye-sensitized solar cell, a chalcogenide solar cell, an oxide thin-film solar cell, an organic semiconductor solar cell, or a combination thereof may be used.

[0188] The size of the above photovoltaic cell can vary from 1 cm Х 1 cm to 100 cm Х 100 cm, and can be appropriately determined under optimal light-to-hydrogen efficiency conditions. Depending on the type of photovoltaic cell, a separate additional photovoltaic cell may be used if the generated voltage is lower than the potential required for water decomposition.

[0189] A solar cell-water electrolysis system including a catalyst electrode for water electrolysis of the present invention can increase the efficiency of hydrogen and oxygen generation by improving charge transport and conductivity, since the catalyst electrode for water electrolysis includes an oxidation catalyst electrode and a reduction catalyst electrode, a metal foam, and a composite transition metal chalcogenide heterostructure formed on the metal foam.

[0190] Hereinafter, the claims of the present specification will be described in more detail with reference to the attached drawings and embodiments. However, since the drawings and embodiments presented in this specification may be modified in various ways by those skilled in the art and may have various forms, the matters described in the present invention should not be considered to limit the present invention to a specific disclosed form, but to include all equivalents and substitutes included in the spirit and technical scope of the present invention. In addition, the attached drawings are presented to help those skilled in the art understand the present invention more accurately, and may be depicted in an exaggerated or reduced form compared to the actual form.

[0191] {Example 2 and Evaluation}

[0192] <Example 2>

[0193] Example 2 (VTe2@ZnFeTe / NF)

[0194] 2.1. ZnFe / NF fabrication

[0195] Several 3D-NF pieces measuring (1 x 1) and (5 x 5) cm were cut from commercially available 3D-NF sheets. Some of the 3D-NF pieces were immersed in hydrochloric acid (1 M) and then sonicated in an ultrasonic bath for 15 min. After sonication, the washed 3D-NF were rinsed with deionized water and ethanol and then dried in an oven for 6 h.

[0196] The Ni foam was immersed in an aqueous solution containing 0.03 M zinc nitrate, 0.04 M iron nitrate, 0.07 M ammonium fluoride, and 0.2 M urea, and then transferred to a 60 mL Teflon-lined stainless steel autoclave and maintained at 120 °C for 12 h. After cooling the sample to room temperature, the ZnFe / NF composite was washed with deionized water and ethanol.

[0197] 2.2. Fabrication of VTe2@ZnFeTe / NF

[0198] Then, the prepared ZnFe / NF composite was immersed in an aqueous solution containing 0.07 M ammonium metavanadate, 0.04 M potassium tellurate, and 2 ml hydrazine hydrate, transferred to a Teflon-lined stainless steel autoclave, and maintained at 180°C for 24 h. After the sample was cooled to room temperature, the VTe2@ZnFeTe / NF composite was washed with deionized water and ethanol. The final product was obtained after drying at 60°C for 12 h.

[0199] The catalyst loading of NF is about 1.25 mg / cm 2Prior to the electrochemical experiment, the electrode was coated with 5% Nafion® binder to prevent mechanical loss of the catalyst during electrolysis, resulting in a concentration of 0.25 mg / cm 2 got the loading of .

[0200] Figure 10 schematically illustrates a manufacturing process of a catalyst electrode for water electrolysis manufactured according to an embodiment of the present invention. Referring to Figure 10, the catalyst electrode for water electrolysis of the present invention comprises 1) Zn 2+ and Fe 3+ After forming transition metal (ZnFe) nanosheets on the Ni foam by hydrothermal synthesis of Ni foam in an aqueous solution containing 2) V 5+ It can be seen that the method includes a process of hydrothermally synthesizing Ni foam on which the ZnFe nanosheets are formed by placing the Ni foam in an aqueous solution containing potassium tellurate. It can be seen that the method forms a complex transition metal chalcogenide heterostructure in the form of VTe2@ZnFeTe on the Ni foam.

[0201] Comparative Example 1 (VTe2 / NF)

[0202] To synthesize VTe2 / NF hybrids, ammonium metavanadate (0.14 M), ammonium fluoride (0.07 M), and urea (0.2 M) were dissolved in 60 mL of distilled water to form a clear solution. The precursor solution was poured into an autoclave (60 mL) containing pretreated NF (2 x 4 cm, sonicated with 3 M HCl, EtOH, and distilled water for 30 min each), sealed, and heat-treated at 120 °C for 12 h. Subsequently, the obtained vanadium precursor was added to a 60 mL dispersion of potassium tellurate (0.04 M) and hydrazine hydrate (2 mL) and heated at 180 °C for 24 h to obtain VTe2 / NF. Finally, the product was washed sequentially with distilled water and EtOH and dried at 60 °C for 12 h to obtain clean VTe2 / NF nanosheets.

[0203] The catalyst loading of NF is about 1.25 mg / cm 2 Before the electrochemical experiment, the electrode was coated with 5% Nafion® binder to prevent mechanical loss of the catalyst during electrolysis, and 0.25 mg / cm 2 The loading of was obtained (hereinafter referred to as “Comparative Example 1”).

[0204] Comparative Example 2 (ZnFeTe / NF)

[0205] Zinc nitrate (0.03 M), iron nitrate (0.04 M), ammonium fluoride (0.07 M), and urea (0.2 M) were dissolved in 60 mL of distilled water to form a clear solution. The precursor solution was poured into an autoclave (60 mL) containing pretreated NF (2 Х 4 cm, sonicated with 3 M HCl, EtOH, and distilled water for 30 min each), sealed, and heat-treated at 120 °C for 12 h. After that, the obtained ZnFe LDH / NF was added to a 60 mL dispersion of potassium tellurate (0.04 M) and hydrazine hydrate (2 mL), and heated at 180 °C for 24 h to obtain ZnFeTe / NF. Finally, the product was washed sequentially with distilled water and EtOH and then dried at 60°C for 12 hours to obtain clean ZnFeTe / NF nanosheets (hereinafter referred to as “Comparative Example 2”).

[0206] Comparative Example 3 (NF)

[0207] Several 3D-NF pieces measuring (1 x 1) and (5 x 5) cm were cut from commercially available 3D-NF sheets. Some of the 3D-NF pieces were immersed in hydrochloric acid (1 M) and then sonicated in an ultrasonic bath for 15 min. After sonication, the washed 3D-NF were rinsed with deionized water and ethanol and then dried in an oven for 6 h.

[0208] Next, a 5% Nafion® binder was coated on the above NF to manufacture a catalyst electrode for water electrolysis (hereinafter referred to as “Comparative Example 3”).

[0209] Comparative Example 4 (RuO2 / NF)

[0210] A commercial RuO2 catalyst and 5% Nafion® were dispersed in ethanol. The catalyst dispersed in ethanol was applied to the NF layer (catalyst loading was approximately 0.3 mg / cm 2 ) and thus, a catalyst electrode coated with RuO2 catalyst was manufactured (hereinafter referred to as “Comparative Example 5”).

[0211] Comparative Example 5 (Pt / C / NF)

[0212] A commercial Pt / C catalyst and 5% Nafion® were dispersed in ethanol. The catalyst dispersed in ethanol was applied to the NF layer (catalyst loading was approximately 0.3 mg / cm 2 ) and a catalyst electrode coated with a Pt / C catalyst was manufactured (hereinafter referred to as “Comparative Example 4”).

[0213] The configurations of each of the above examples and comparative examples are summarized in Table 1 below.

[0214] [Table 1]

[0215]

[0216] Manufacturing Example 1

[0217] Example 2 was used as the cathode and anode, and an anion exchange membrane (Sustainion X37-50 Grade RT) was inserted between the cathode and anode by a hot press method (40°C, 2 MPa) to manufacture a membrane electrode assembly (MEA). Gold-plated nickel was used as the current collector and end plate.

[0218] The single anion-exchange membrane water electrolyzer (AEMWE) cell manufactured in this way was operated at 50°C using a 1 M KOH aqueous medium. The electrolyte performance was evaluated by obtaining a load curve at an applied potential of 1.5–2.0 V, and the stability of the catalyst was evaluated under alkaline water electrolysis conditions at a constant applied potential.

[0219] Comparative manufacturing example 1 (VTe2(+)∥VTe2(-))

[0220] An anion exchange membrane electrolysis device was manufactured in the same manner as the above manufacturing example, except that Comparative Example 1 was included as the cathode and anode (hereinafter referred to as “Comparative Manufacturing Example 1”).

[0221] Comparative manufacturing example 2 (ZnFeTe(+)∥ZnFeTe(-))

[0222] An anion exchange membrane electrolysis device was manufactured in the same manner as the above manufacturing example, except that Comparative Example 2 was included as the cathode and anode (hereinafter referred to as “Comparative Manufacturing Example 2”).

[0223] Comparative manufacturing example 3 (RuO2 / NF(+)∥Pt / C / NF(-))

[0224] An anion exchange membrane electrolysis device was manufactured in the same manner as the above manufacturing example, except that Comparative Example 4 was included as the cathode and Comparative Example 5 was included as the anode (hereinafter referred to as “Comparative Manufacturing Example 3”).

[0225] The compositions of the above manufacturing examples and comparative manufacturing examples are summarized in Table 2 below.

[0226] [Table 2]

[0227]

[0228] <Evaluation of the Second Embodiment>

[0229] 2.1. Physical properties evaluation

[0230] FIG. 11 is a HR-TEM image of a catalyst electrode for water electrolysis manufactured according to an embodiment of the present invention. More specifically, FIG. 11a shows Example 2 observed at a 20 nm scale, and FIGS. 11b and 11c show Example 2 observed at a 1 nm scale, showing the lattice pattern of Example 2. Referring to FIG. 11, it can be seen that a heterostructure of VTe2 and ZnFeTe is formed on the nanosheet structure. In addition, referring to FIG. 11a, it can be seen that VTe2 is bonded to ZnFeTe to form a heterojunction structure. In addition, it can be seen that Example 2 has various types of lattice patterns, which are respectively due to the (200) plane of ZnFeTe and the (002) plane of VTe2.

[0231] Fig. 12 is an EDAX mapping image of a catalyst electrode for water electrolysis manufactured according to an embodiment of the present invention. More specifically, Fig. 12A shows the overall distribution of atoms in Example 2, and Fig. 12B shows the distribution of each atom. Referring to Fig. 12, it can be seen that the catalyst electrode for water electrolysis of the present invention has Zn, Fe, V, and Te evenly distributed.

[0232] FIG. 13 is an XRD pattern and an XPS spectrum of a catalyst electrode for water electrolysis manufactured according to an embodiment of the present invention. More specifically, FIG. 13a illustrates the XRD patterns of Example 2, Comparative Example 1, and Comparative Example 2, and FIG. 13b illustrates the XPS spectrum of Example 2. Referring to FIG. 13, the XRD pattern of Example 2 identifies ZnFeTe of (200), (222), and (400) planes at 35.3°, 56.9°, and 62.5°. In addition, the (002) and (003) planes of VTe2 at 2e values ​​of 36.5° and 42.9° can be found only in Example 2 and Comparative Example 1, which means that VTe2 exists in Example 2, which ultimately means that a heterojunction structure of ZnFeTe and VTe2 is formed in Example 2.

[0233] Fig. 14 is an XPS spectrum for each atom of a catalyst electrode for water electrolysis manufactured according to an embodiment of the present invention. More specifically, Fig. 14a is an XPS spectrum of Zn in Example 2, Fig. 14b is an XPS spectrum of Fe in Example 2, Fig. 14c is an XPS spectrum of V in Example 2, and Fig. 14d is an XPS spectrum of Te atoms in Example 2. Referring to Fig. 14, it can be seen that in Example 2, VTe2@ZnFeTe is bonded, so that Zn, Fe, V, and Te in various oxidation states exist simultaneously.

[0234] 2.2. Contact angle evaluation

[0235] FIG. 15 is a photograph illustrating the contact angle of a catalyst electrode for water electrolysis manufactured according to an embodiment of the present invention. More specifically, FIG. 15A shows the contact angle of Comparative Example 3, FIG. 15B shows Comparative Example 1, FIG. 15C shows Comparative Example 2, and FIG. 15D shows Comparative Example 1. Referring to FIG. 15, it can be seen that each contact angle is about 139.4° for Comparative Example 3, about 99.3° for Comparative Example 1, about 113.1° for Comparative Example 2, and about 0° for Example 2. The results indicate that hydrophilicity increases in the order of Comparative Example 3 < Comparative Example 2 < Comparative Example 1 < Example 2. From these results, it can be seen that the surface wettability is improved in Example 2 due to the heterojunction of the electrode surface, and ultimately, Example 2 becomes superhydrophilic with a reduced contact angle. That is, the electrolyte solution in the electrolytic cell may have difficulty penetrating into Example 3, which has a hydrophobic, smooth surface. On the other hand, the electrolyte solution can rapidly diffuse into Example 2, which has a somewhat rough, hydrophilic surface, thereby maximizing the exposure of the catalytically active sites of the electrode to the electrolyte solution, and thus, an improvement in the HER reaction kinetics can be expected.

[0236] 2.3. OER Evaluation

[0237] Figure 16 is a graph evaluating the OER overpotential of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention. More specifically, Figure 16a is a graph showing the OER response of Example 2 and Comparative Examples 1 to 4 evaluated by linear sweep voltammetry (LSV), and Figure 16b is a graph showing the OER response of Example 2, Comparative Examples 1, Comparative Examples 2, and Comparative Examples 4 at a current density of 20 mA / cm. 2 and 50 mA / cm 2 This is a graph showing the OER overpotential value. Referring to Fig. 16, Comparative Examples 1, 2, and 3 are 20 mA / cm 2 In each case, the overpotential values ​​are 300 mV, 290 mV and 310 mV and 50 mA / cm 2 It can be seen that the overpotential values ​​are 400 mV, 360 mV and 400 mV, respectively. On the other hand, Example 2 shows 20 mA / cm 2 At 240mV, 50mA / cm 2 It can be seen that the overpotential value is significantly lower at 300 mV.

[0238] FIG. 17 illustrates Tafel curves during OER operation of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention. More specifically, in order to better recognize the catalytic results of Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 4, the suitability for the LSV polarization curve was evaluated using the Tafel correlation η = b log (J / J0). Here, J0 is the exchange current density, J is the current density, η is the overpotential, and b is the Tafel slope. Referring to FIG. 17, it can be seen that the Tafel slope of Example 2 is 98.1 mV / dec, which is lower than 164.5 mV / dec of Comparative Example 1 and 113.1 mV / dec of Comparative Example 2. These results indicate that the catalyst electrode for water electrolysis of the present invention exhibits improved OER kinetics due to the formation of the heterostructure of VTe2@ZnFeTe.

[0239] Fig. 18 is a graph evaluating the stability of a catalyst electrode for water electrolysis manufactured according to an embodiment of the present invention during OER operation. More specifically, Fig. 18a is a graph showing the change in current density over time for Example 2 (test potential 1.45 V), and Fig. 18b is a graph comparing the current density value as a function of potential for Example 2 with the value after 20 hours of cycling from the initial value. Referring to Fig. 18, it can be seen that Example 2 showed no significant current damage for 20 hours. In addition, when comparing the initial current density value of Example 2 with the value after 20 hours of cycling, it can be seen that almost the same overpotential and current are shown.

[0240] FIG. 19 is a TEM and EDAX mapping image of a catalyst electrode for water electrolysis manufactured according to an embodiment of the present invention after OER operation. More specifically, FIG. 19a is a TEM image of Example 2 after a 20-hour cycle, FIG. 19b is a mapping of other atoms after a 20-hour cycle of Example 2, and FIG. 19b is a mapping of Zn, Fe, V, and Te atoms after a 20-hour cycle of Example 2. Referring to FIG. 19, it can be seen that Example 2 after 20 hours of cycling has a uniform distribution of Zn, Fe, V, and Te. Compared to FIG. 12, which is an EDAX mapping image immediately after manufacture, there is no significant difference in the distribution.

[0241] 2.4. HER Evaluation

[0242] Fig. 20 is a graph evaluating the HER overpotential of a catalyst electrode for water electrolysis manufactured according to one embodiment of the present invention. More specifically, Fig. 20a is a graph evaluating the HER reactions of Example 2, Comparative Examples 1 to 3, and Comparative Example 5 through linear sweep voltammetry (LSV), and Fig. 20b is a graph showing the HER overpotential values ​​at current densities of 20 mA / cm2 and 50 mA / cm2 of Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 5. Referring to Fig. 20, it can be confirmed that Comparative Example 1, Comparative Example 2, and Comparative Example 5 exhibit overpotential values ​​of 303 mV, 207 mV, and 215 mV at 20 mA / cm2, and 412 mV, 306 mV, and 316 mV at 50 mA / cm2, respectively. On the other hand, it can be confirmed that Example 2 exhibits somewhat lower overpotential values ​​of 202 mV at 20 mA / cm2 and 299 mV at 50 mA / cm2.

[0243] FIG. 21 illustrates a Tafel curve during HER operation of a water electrolysis catalyst electrode manufactured according to one embodiment of the present invention. More specifically, the HER kinetics determined by rate were explored using a Tafel plot by determining the slope through the Tafel relationship: η = a + b log J, where b characterizes the Tafel slope. Referring to FIG. 21 , it can be seen that the Tafel slope of Example 2 is small at 133.8 mV / dec. This result is similar to that of Comparative Example 5, a commercially available water electrolysis catalyst electrode, at 116.8 mV / dec, and is superior to that of Comparative Example 2 at 219.1 mV / dec.

[0244] FIG. 22 is a graph evaluating the stability of a water electrolysis catalyst electrode manufactured according to an embodiment of the present invention during HER operation. More specifically, FIG. 22a is a graph showing the change in current density over time for Example 2 (test potential -0.2 V), and FIG. 22b is a graph comparing the current density values ​​as a function of potential for Example 2 with the initial value and the value after 20 hours of cycling. Referring to FIG. 22, it can be seen that Example 2 has excellent long-term stability with no significant change in current for 20 hours. In addition, when comparing the initial value of the current density of Example 2 with the value after 20 hours of cycling, it can be seen that the overpotential values ​​for providing current densities of 20 and 50 mA / cm2 are slightly lower, but these values ​​show that the stability and reliability of the water electrolysis catalyst electrode of the present invention can be used routinely without major difficulties.

[0245] 2.5. Electrolysis performance evaluation

[0246] Figure 23 is a graph evaluating the overpotential and stability of anion exchange membrane electrolyzers manufactured according to one embodiment of the present invention. More specifically, Figure 23a is a graph evaluating Manufacturing Example 1 and Comparative Manufacturing Examples 1 to 3 using linear sweep voltammetry (LSV), Figure 23b is a graph showing the change in current density over time for Manufacturing Example 1 (test potential 1.5 V), and Figure 23c is a graph comparing the current density values ​​according to the change in potential between the initial value and the value after 20 hours of cycling for Manufacturing Example 1. Referring to Figure 23a, at a current density of 10 mA / cm 2It can be seen that in order to achieve this, an overpotential value of 1.58 V is required for Comparative Example 1, 1.61 V for Comparative Example 2, and 1.54 V for Comparative Example 3. Here, Example 2 shows a value of 1.58 V, which is consistent with the commercially available Comparative Example 3. In addition, referring to FIG. 23b, it can be seen that Example 2 shows a continuous current for 20 hours, indicating good long-term performance. In addition, referring to FIG. 23c, when comparing the initial value of the current density with the value after 20 hours of cycling, it can be seen that Example 2 has almost the same overpotential and current, confirming that the water electrolysis including the water electrolysis catalyst electrode of the present invention has excellent long-term stability.

[0247] FIG. 24 is a diagram showing the volume of gases (H2 and O2) produced in an anion exchange membrane electrolysis according to one embodiment of the present invention. More specifically, FIG. 24a shows the amount of H2 and O2 gases produced over time when producing Example 2, and FIG. 24b shows a performance comparison of the electrolysis according to Example 2. Referring to FIG. 24, it can be seen that the volume of H2 and O2 gradually increases with reaction time and linearly increases with the actual current density, and it can be seen that the theoretically calculated volume of H2 and O2 gases is relatively similar to the experimentally measured results. In addition, the electrolysis performance comparison of Example 2 also presented the requirement of the minimum cell turnout for efficient H2 and O2 production. These results indicate that most of the energy in the catalyst system of Example 2 is used to produce H2 and O2 for water decomposition.

[0248] When a water decomposition reaction is performed using the catalyst electrode for water electrolysis of the present invention, improved electrochemical catalytic activity can be exhibited in both the hydrogen production reaction (HER) and the oxygen production reaction (OER).

[0249] In addition, the catalyst electrode for water electrolysis of the present invention can efficiently produce hydrogen with a lower energy supply compared to existing precious metal electrodes.

[0250] In addition, the catalyst electrode for water electrolysis of the present invention can be used in both anion exchange membrane water electrolysis and solar cell-water electrolysis systems.

[0251]

[0252] Examples of the third embodiment of the present invention are as follows.

[0253] The present invention relates to a method for producing a hybrid nanostructure, comprising: a first step of synthesizing a nickel-cobalt precursor by hydrothermal synthesis of a precursor solution prepared by dispersing a nickel precursor, a cobalt precursor, and glycerol in a solvent; and a second step of forming nanospheres comprising nickel cobalt selenide and molybdenum selenide by adding the nickel-cobalt precursor to a solution containing a molybdenum precursor and a selenite precursor and then hydrothermally synthesizing the precursor solution; and a hybrid nanostructure having a nanosphere structure comprising nickel cobalt selenide and molybdenum selenide produced by the method.

[0254] In the first step, the nickel precursor and cobalt precursor may be used in a molar ratio of 1:1, but is not limited thereto.

[0255] In the second step, the molybdenum precursor and the selenite precursor may be used in a molar ratio of 1:3, but is not limited thereto.

[0256] In the first step, the nickel-cobalt precursor may have a nanosphere structure, but is not limited thereto.

[0257] The above nanosphere may have a structure in which molybdenum selenide is bonded to the outer surface of a nickel cobalt selenide nanosphere, but is not limited thereto.

[0258] The above nanospheres may be porous, for example, but not limited to, having formed pores such as various pores, mesopores and macropores.

[0259] The present invention relates to a water electrolysis catalyst comprising the hybrid nanostructure of the present invention and a water electrolysis catalyst electrode comprising the water electrolysis catalyst.

[0260] The catalyst electrode of the present invention can be used, for example, in anion exchange membrane (AEM) electrolysis. The AEM electrolysis is composed of a membrane, an ionomer, a membrane electrode assembly (MEA), and a gas diffusion layer (GDL), and the membrane electrode assembly is further composed of a cathode, anion exchange membrane, and an anode. The catalyst electrode of the present invention can be utilized as the cathode and anode of the membrane electrode assembly, but is not limited thereto.

[0261] In addition, the catalyst electrode of the present invention can be used, for example, in a photovoltaic-electrolysis (PV-EC) system. The PV-EC system is a method of producing hydrogen through water electrolysis after generating electricity using a solar cell. The PV-EC system is composed of a photovoltaic cell, an oxidation catalyst electrode, a reduction catalyst electrode, an ion separation membrane, and an aqueous electrolyte. The catalyst electrode of the present invention can be used as an oxidation catalyst electrode and a reduction catalyst electrode in the PV-EC system, but is not limited thereto.

[0262] The present invention relates to a membrane electrode assembly comprising: a cathode; an anion exchange membrane formed on the cathode; and an anode formed on the anion exchange membrane, wherein the cathode and the anode include a water electrolysis catalyst of the present invention.

[0263] The above membrane electrode assembly, as described above, is a component of AEM water electrolysis, and includes a cathode, an anion exchange membrane, and an anode, and may include a catalyst electrode for water electrolysis of the present invention. At the anode, a hydrogen evolution reaction (HER) occurs simultaneously as a half-cell reaction, and at the cathode, an oxygen evolution reaction (OER) occurs simultaneously. That is, water is reduced at the anode and reacts with electrons to form hydrogen and hydroxide ions, the generated hydroxide ions diffuse to the cathode through the anion exchange membrane, and the electrons are transferred to the cathode through an external circuit. At the cathode, the hydroxide ions lose electrons and recombine into water and oxygen, and the electrons are released from the cathode surface to proceed with the reaction. The water decomposition process that occurs at the anode and cathode is as follows.

[0264] Anode: 4OH - → O2+ 2H2O + 4e - E 0 = 0.401 V

[0265] Cathode: 4H2O + 4e - → 2H2+ 4OH - E 0 = -0.828 V

[0266] Overall: 2H2O → H2+ O2E 0 = 1.23 V

[0267] An AEM electrolyzer comprising a membrane electrode assembly of the present invention as a cathode and an anode uses a metal foam, a catalyst electrode for an electrolyzer comprising a composite transition metal chalcogenide heterostructure formed on the metal foam, and a catalyst electrode for an electrolyzer capable of increasing the efficiency of hydrogen and oxygen generation by improving charge transport and conductivity.

[0268] In addition, the catalyst electrode for water electrolysis of the present invention can be utilized in a photovoltaic-electrolysis (PV-EC) system as described above. The PV-EC system is composed of a photovoltaic cell, an anode, a cathode electrode, an ion separator, and an aqueous electrolyte.

[0269] The PV-EC system can produce hydrogen by a process in which, when light is irradiated onto the photovoltaic cell, the photovoltaic cell absorbs the light to generate electrons and holes, which are then transferred to oxidation (oxygen generation electrode) and reduction (hydrogen generation electrode) catalyst electrodes located inside an aqueous electrolyte solution to decompose water, thereby separating oxygen at the oxidation electrode and hydrogen at the reduction electrode. The catalyst electrode for water electrolysis of the present invention can be utilized as an oxidation catalyst electrode and a reduction catalyst electrode in the PV-EC system.

[0270] The above photovoltaic cell may use any of the existing solar cells developed and used, which include a semiconductor material capable of absorbing light to create electron-hole pairs. For example, a photovoltaic solar cell using a silicon semiconductor, a dye-sensitized solar cell, a chalcogenide solar cell, an oxide thin-film solar cell, an organic semiconductor solar cell, or a combination thereof may be used.

[0271] The size of the above photovoltaic cell can vary from 1 cm Х 1 cm to 100 cm Х 100 cm, and can be appropriately determined under optimal light-to-hydrogen efficiency conditions. Depending on the type of photovoltaic cell, a separate additional photovoltaic cell may be used if the generated voltage is lower than the potential required for water decomposition.

[0272] A solar cell-water electrolysis system including a catalyst electrode for water electrolysis of the present invention can increase the efficiency of hydrogen and oxygen generation by improving charge transport and conductivity, since the catalyst electrode for water electrolysis includes an oxidation catalyst electrode and a reduction catalyst electrode, a metal foam, and a composite transition metal chalcogenide heterostructure formed on the metal foam.

[0273] The present invention relates to an electrocatalyst for urea oxidation reaction (UOR) comprising the hybrid nanostructure of the present invention.

[0274] Hydrogen can be produced using the electrocatalyst for the above element oxidation reaction, but is not limited thereto.

[0275] Hereinafter, the claims of the present specification will be described in more detail with reference to the attached drawings and embodiments. However, since the drawings and embodiments presented in this specification may be modified in various ways by those skilled in the art and may have various forms, the matters described in the present invention should not be considered to limit the present invention to a specific disclosed form, but to include all equivalents and substitutes included in the spirit and technical scope of the present invention. In addition, the attached drawings are presented to help those skilled in the art understand the present invention more accurately, and may be depicted in an exaggerated or reduced form compared to the actual form.

[0276] {Example 3 and Evaluation}

[0277] Example 3.1. Synthesis of nickel-cobalt-selenide and molybdenum-selenide nanospheres

[0278] 3.1.1. Materials

[0279] Nickel nitrate (Ni(NO3)2·6H2O, 98%), cobalt nitrate (Co(NO3)2·6H2O, 97%), sodium molybdate (Na2MoO4·2H2O, 99.9%), sodium borate (NaBH4), selenide, platinum / carbon catalyst, industry standard Nafion, ruthenium oxide (RuO2, 99.9%), ethanol (C2H5OH, 99.9%), methanol (CH3OH, 99.9%), hydrochloric acid (HCl, 35–37%), potassium hydroxide (KOH ≥ 99.5%), and nickel foam substrate were purchased from Sigma Aldrich.

[0280] 3.1.2. Synthesis of nickel-cobalt-selenide and molybdenum-selenide nanospheres

[0281] The nanosphere structure of NCSMS was fabricated by a simple and easy method as shown in Fig. 25a.

[0282] To synthesize NCSMS nanosphere heterojunctions, a precursor solution was prepared by dispersing (0.7 mmol), cobalt nitrate (0.7 mmol), and 8 ml glycerol in 40 ml isopropanol at a 1:1 molar ratio. The precursor solution was placed in an 80 ml autoclave and hydrothermally synthesized at 180°C for 6 h. Upon completion of the hydrothermal reaction, a nickel-cobalt precursor was obtained, which was repeatedly washed with distilled water and ethanol. The synthesized nickel-cobalt precursor was added to a solution containing sodium molybdate (2 mmol), sodium borohydride (10 mmol), and selenide (6 mmol) powders, and hydrothermally synthesized at 190°C for 14 h to obtain NCSMS nanosphere hybrids. The synthesized NCSMS nanospheres were repeatedly washed with purified water and ethanol and dehydrated at 60°C for 6 h to obtain dry NCSMS nanosphere heterojunctions. For comparison, NiCo, MoSe2, and NCS nanospheres were also prepared under the same reaction conditions. Commercial Pt / C and RuO2 catalysts were also prepared.

[0283] Example 3.2. Structural and morphological characterization

[0284] The nanosphere structure of NCSMS was manufactured as in Example 3. First, nickel-cobalt nanospheres were hydrothermally synthesized, and then sodium molybdate, sodium borohydride, and selenide powders were added and poured into an 80 mL non-stick steel autoclave to undergo a two-step hydrothermal process. NCSMS nanospheres were successfully synthesized through a simple and easy two-step hydrothermal process.

[0285] The structure and microstructure of the newly synthesized sample were analyzed using field emission scanning electron microscopy (FE-SEM), as shown in Fig. 25. In addition, field emission transmission electron microscopy (FE-TEM) characteristics were used to investigate the characteristics of the NCSMS nanospheres. After the second hydrothermal treatment step, MoSe2 was firmly and uniformly anchored to the outer surface of the NCS nanospheres, forming NCSMS hybrid nanospheres. As verified by SEM images, uniform NCSMS nanospheres were synthesized (Fig. 25b-d). The presence of pores and a rough surface was also confirmed in the SEM images. The formation of hybrid NCSMS nanospheres resulted in the formation of various pores and voids (mesopores and macropores) that enhanced the contact point intermediate region (electrode and electrolyte), thereby enhancing the electrocatalytic performance.

[0286] The morphology and structure of a material play a crucial role in influencing electron transport performance in electrocatalysis. Nanospheres enhance ion / molecule transport channels for electrodes, electrode sheet-electrolyte contacts, and electroactive centers, ultimately enhancing electrocatalytic performance. A current collector comprising a three-dimensional porous composition of electroactive materials enhances ion / electron transport rates and facilitates the removal of gases generated from the catalyst layer. Therefore, the development of superior heterostructures derived from non-precious metals can significantly enhance the electrocatalytic performance of catalysts.

[0287] Additionally, atomic arrangement analysis of the NCSMS heterojunction was performed using elemental mapping and EDX analysis (Fig. 25e). The elemental mapping results of the NCSMS hybrid show a balanced allocation of Ni, Co, Mo, and Se, demonstrating the effectiveness of existing synthesis techniques in the fabrication of NCSM.

[0288] FE-TEM images of NCSMS (Fig. 25f-g) showed the morphology and structure of regular NCSMS nanospheres. Compared with NiCo and nickel-cobalt-selenide (NCS) nanospheres, NCSMS nanospheres were larger and had rougher surfaces. After the secondary hydrothermal process, MoSe2 was uniformly and firmly anchored on the outer surface of NCS, resulting in a rougher surface of NCS. In addition, HR-TEM capture (Fig. 25h) showed various types of lattice patterns attributed to the (110) plane of NCS and the (102) plane of MoSe2. Finally, EDX elemental mapping analysis (Fig. 25i) demonstrated the presence of Ni, Co, Mo, and Se atoms, providing further evidence for the successful formation of NCS heterojunction nanospheres.

[0289] The crystal properties of MoSe2, NCS, and NCSMS nanospheres were measured using XRD. The XRD pattern of MoSe2 (Fig. 26a) showed strong reflections at two θ positions of 16.4°, 26.7°, 38.3°, and 55.8°, which were aligned with the (002), (100), (103), and (110) crystal planes, indicating the presence of a metallic phase of MoSe2 (JCPDS Card No. 87-2419). In addition, the reflections at two θ positions of 31.5°, 38.1°, 44.3°, 50.6°, 59.1°, 60.8°, and 69.5° corresponding to the (101), (102), (110), (103), (201), and (202) planes are attributed to NCS (JCPDS Card No. 70-2851). Therefore, the XRD characterization of NCSMS nanospheres showed peaks for both MoSe2 and NCS, indicating the formation of a hybrid of NCS and MoSe2 (Fig. 26a). In addition, the Raman spectrum showed peaks at 144.5, 278.3, and 286.8 cm , which are attributed to the metallic phase of MoSe2. -1 It shows peaks at (Fig. 26b). Also, as can be seen in Fig. 26b, 235.2 and 5001.7 cm -1 The peaks were observed to confirm the presence of NCS. The Raman analysis results showed a peak shift of MoSe2 due to the formation of a hybrid of NCS and MoSe2 and its integration with NCS. Alternatively, the pore size and pore distribution of the NCSMS nanospheres were estimated using the adsorption-desorption isotherms and BET (Brunauer-Emmett-Teller) characteristics. As shown in Fig. 26c, the nitrogen adsorption-desorption isotherms of the NCSMS nanospheres presented a distinct type-IV hysteresis loop, which confirmed the mesoporous structure. According to the BET surface area estimation, the surface areas of NCSMS, NCS, and MoSe2 were 133, 71.3, and 42.5 m2 g, respectively. -1Furthermore, pore size studies demonstrated the mesoporous nature of the NCS nanospheres, as shown in Figure 26d. The high external surface area and mesoporous nature of the NCS hybrid enhanced the catalytic efficiency for OER and HER. Consequently, more electrocatalytic active centers and charge-transfer channels were created.

[0290] To obtain a comprehensive understanding of the NCS heterojunction, X-ray photoelectron spectroscopy (XPS) was used to analyze the multi-valence states and composition. The XPS spectrum of the NCSMS nanospheres showed the presence of multiple elements such as Ni, Co, Mo, and Se, as shown in Fig. 26e. Figure 27f shows the XPS spectrum of cobalt, which exhibited two distinct peaks at 778.84 and 794.15 eV, which were assigned to the Co2p 3 / 2 and Co2p 1 / 2 Co of the orbit 3+ corresponds to the state. Also, the peaks at 781.39 and 798 eV correspond to Co 2+ The presence of the cobalt 2p state indicated that the oxidation state of cobalt was +2. The detailed XPS spectrum of nickel (Fig. 26g) showed two distinct peaks at 852.9 and 872.06 eV, which were assigned to Ni 2p, respectively. 3 / 2 and Ni 2p 1 / 2, which is attributed to . In addition, two additional peaks were observed at 858.56 and 878.57 eV, indicating the +2-oxidation state of nickel. The precise spectrum of molybdenum (Fig. 26h) shows a pair of peaks at 232.52 and 228.18 eV, corresponding to Mo 3d3 / 2 and Mo 3d5 / 2, respectively, suggesting the +4-oxidation state of Mo in the NCS hybrid. Finally, Fig. 26i shows the XPS spectrum of selenium, which shows two primary peaks at 55.71 and 54.92 eV, representing Se 3d3 / 2 and Se 3d5 / 2, respectively. This indicates that the surface of selenium is in the -2-oxidation state. Collectively, the XPS data showed the coexistence of various oxidation states of nickel, cobalt, molybdenum, and selenium in the hybrid nanospheres of the NCS hybrid.

[0291] Example 3.3. Catalytic performance

[0292] 3.3.1. Evaluation of electrochemical reactions of OER and HER

[0293] The overall water splitting mechanism mainly depends on the OER performance. Therefore, the activity of the OER catalyst is a key factor in the water splitting process. Consequently, the OER activity of MoSe2, NCS, and NCSMS heterojunctions was studied by conducting experiments with a standard three-electrode setup in an electrolyte solution containing 1.0 M KOH. First, before measuring the OER performance, a 20 mV s -1 Cyclic voltammetry (CV) (100 cycles) was performed to stabilize the electrode at the scan rate.

[0294] Scan rate 10 mV s -1 Linear sweep voltammetry (LSV) studies on MoSe2, NCS, NCSMS nanohybrid, and commercial RuO2 catalysts are shown in Fig. 27a. The LSV results for NCS showed the best performance compared to MoSe2, NCS, and commercial RuO2 catalysts at 50 mA cm -2Wow 100 mA cm -2 In MoSe2, NCS, NCSMS, RuO 2 The overpotentials of NCS and 1T-MoSe2 were 440 and 540, 400 and 470, 290 and 370, and 330 and 40 mV, respectively (Fig. 27b). Therefore, due to the synergistic effect of NCS and 1T-MoSe2, NCS had the smallest overpotential compared to MoSe2, NCS, and commercial RuO2 catalysts. In addition, due to the cooperative effect of the heterointerface between NCS and 1T-MoSe2, the excellent performance of NCS hybrid as an OER contrasted with that of the counterpart catalyst. In addition, the catalytic properties of the NCSMS heterojunction were evaluated using the Tafel curve. The Tafel curve was obtained by applying the Tafel relation η = blog (J / J0) to the LSV polarization curve (see Fig. 27c). The Tafel slopes of MoSe2, NCS, NCSMS nanohybrid, and commercial RuO2 are 125.3, 123.5, 33.25, and 60.25 mV dec, respectively. -1 . Notably, the NCSMS hybrid nanospheres exhibited the lowest Tafel slope, indicating excellent OER kinetics. The Tafel slope and overpotential values ​​of the NCSMS nanosphere hybrids were lower than those of the MoSe2, NCS, and RuO2 catalysts under the same analytical conditions (see Fig. 27b, c). These results suggest that the unique hybrid nanospheres of NCS and MoSe2 possess great potential as anode electrodes for OER in alkaline electrolytes. Previous studies have shown that modifying the heterointerface can significantly improve the OER activity, leading to significant improvements.

[0295] Therefore, the NCSMS electrode hybrid has the effect of improving the OER performance by utilizing the electrical conductivity and electroactive sites. The present invention showed that the surface properties, structure, voids and porosity of the NCSMS nanosphere hybrid have a decisive influence on the electrocatalysis of the electrode, and the heterostructure of the NCSMS nanosphere with the resulting non-uniform surface and excellent conductivity provides electrocatalytic active centers to increase the electrocatalytic activity. In addition, the electrochemical double layer capacitance (C) of the electrode dl ) was used to analyze the activity of the catalyst. The ECSA values ​​of NCS, MoSe2, and NCSMS hybrids were 4.1, 6.4, and 21.3 cm, respectively. 2 , and was calculated to be between 1.0 and 1.2 V (Fig. 27d). ECSA analysis provides evidence that NCSMS acts as an excellent electrode, and ECSA plays a significant role in improving the electrochemical properties. The rough, pore-rich, and porous morphology of NCSMS also contributes significantly to promoting the efficient evolution of O2 during OER. The electrocatalytically active sites of NCSMS electrode facilitate the easy evolution of oxygen bubbles, thereby promoting the next step of the OER process. In addition, the morphology of NCSMS nanospheres is favorable for O2 bubble diffusion, which is further beneficial for OER. In addition to morphology, the electronic configuration of nanospheres is also very important for the OER process. The "d" electrons of Ni and Co significantly affect the adsorbent adhesion. Therefore, NCSMS nanospheres can enhance the d-electron transfer and electrochemical activity.

[0296] One of the challenges in obtaining effective catalysts for water splitting is their long-term stability. Therefore, to assess the reliability of NCSMS nanospheres in 1 M KOH for 72 hours, chronoamperometric (i.t.) analysis was performed. Figure 27e shows the i.t. results of the NCSMS nanospheres, which showed no significant current degradation over 72 hours, confirming their excellent durability for EWS and their potential as promising OER catalysts. Furthermore, to assess the stability of the NCSMS nanosphere hybrid, LSV curves were obtained before and after 72 hours of i.t. analysis, as shown in Figure 27f. These results show nearly identical LSV polarization curves after 72 hours, demonstrating their promising potential for OER applications. Furthermore, to investigate the stability of these nanospheres as OER electrodes, post-treatment characteristics of the NCSMS nanospheres were examined using field-effect scanning electron microscopy (FE-SEM), field-effect transduction spectroscopy (FE-TEM), and XRD analyses. The excellent performance and durability of the NCSMS nanospheres could be attributed to several factors:

[0297] (i) ECSA and OER are unique hybrids of NCSMS nanospheres, which have a rough, porous and hollow morphology and structure.

[0298] (ii) NCSMS nanospheres synthesized with a mixture of NCS and MoSe2 catalysts showed increased catalytic efficiency due to an increase in catalytic active sites, and showed faster electron transfer and superior performance compared to NCS and MoSe2 catalysts.

[0299] (iii) The presence of Ni, Mo, and Co with different valences in the NCSMS nanospheres enhanced the OER performance by generating more favorable binding energies of MO and simplifying the production of OER intermediates. The oxygen generation process involves several intermediate reactions, including M-OHAD, MO, M-O2H, and M-OO. These reactions occur due to the different oxidation states of the elements present in the nanohybrid. As a result, the nanohybrid exhibits a strong attraction to OH- anions, making it a highly effective catalyst for OER. These properties can enhance the overall performance of the NCSMS nanohybrid in promoting oxygen generation.

[0300] The overall effectiveness of the electrolysis process is also limited by the HER activity of the catalyst. The HER activities of MoSe2, NCS, and NCSMS nanospheres were measured using a standard three-electrode setup in an electrolyte solution containing 1.0 M KOH. Figure 27g shows the LSV polarization curves of MoSe2, NCS, and NCSMS nanospheres. The potentials of MoSe2, NCS, and NCSMS nanospheres were estimated from the LVS data and plotted as shown in Figure 27h. 50 mA cm -2 Wow 100 mA cm -2 The overpotential values ​​of MoSe2, NCS, NCSMS, and Pt / C in j are 336, 426, 302, 388, 244, 304, 256, and 325 mV, respectively (Fig. 27h). These results show that NCSMS nanospheres exhibit the lowest overpotential compared to MoSe2, NCS, and Pt / C, indicating a better HER effect of the nanohybrid. In addition, the HER kinetics was investigated using the Tafel plot (η = a + b log J, where b represents the Tafel slope). The Tafel slope plot presented in Fig. 27i shows that NCS (41.6 mV dec -1 ) nanospheres MoSe2(119.5 mV dec -1), NCS(116.8 mV dec -1 ), Pt / C(52.7 mV dec -1 ) shows the lowest value compared to the NCSMS catalyst. The Tafel coefficient is an important parameter for evaluating HER kinetics. A low Tafel coefficient indicates faster reaction kinetics at the electrode-electrolyte interface. This is because it occurs at a low overpotential possible due to the low activation energy requirement. To promote the HER kinetics, the NCSMS catalyst exhibits a low Tafel slope, which means that it requires a small activation energy. Previous studies suggest that the HER promoted by NCSMS follows the Volmer–Heyrowski pathway in alkaline electrolytes, in which water electrolytically dissociates into hydroxide (OH-) ions and a desorption step occurs during the HER kinetics.

[0301] Nevertheless, the robustness of the electrode is essential for practical applications. Therefore, a chronoampere measurement test was performed by applying it for 72 hours. The stability test results (Fig. 27j) showed minimal degradation, indicating that the NCSMS is a durable electrode. The LSV polarization curve was measured after 72 hours of cycling and compared with the initial LSV curve, as shown in Fig. 27k. These results verified the stability and reliability of the NCSMS hybrid for practical applications in water splitting. Finally, the chronoampere measurement test results, as shown in Fig. 27l, showed that NCSMS required a lower potential than NCS and MoSe2.

[0302] The excellent activity of NCSMS nanospheres as HER electrodes can be attributed to the synergistic effects of the interconnected heterostructure of NCS and 1T-MoSe2 and the enhanced electrical properties, electroactive surface area, and number of active electrocatalytic sites. Tafel slope analysis revealed that the NCSMS catalyst required a low activation energy, promoting the kinetics of HER via the Volmer-Heyrovsky pathway in alkaline electrolytes, as previously reported (R. Anand et al., Adv. Energy Mater., 11 (2021) 2102388). Electrochemical impedance spectroscopy (EIS) revealed that NCSMS had a higher conductivity and charge transport rate with a lower Rs value than MoSe2 and NCS. Furthermore, the durability of NCSMS was analyzed by chronoperometry for 72 h, which showed minimal degradation, indicating that it is a durable electrode for practical applications. The stability of the catalyst was assessed by measuring the LSV polarization curve after 72 hours of cycling. The results showed no significant changes compared to the initial curve, confirming the stability of the catalyst throughout the test period. Chronopherometry testing further confirmed that NCS required a lower potential than NCS and MoSe2, as shown in Figure 27l.

[0303] 3.3.2. Electrochemical performance evaluation for overall water splitting

[0304] The NCSMS hybrid material showed high potential as both HER and OER electrodes in a standard three-electrode system, suggesting that it could be a potential candidate for complete water splitting. NCSMS nanospheres can also be utilized as a two-electrode electrolyzer for efficient OER and HER. The LSV polarization test (Fig. 28a) of the two-electrode system showed that the NCSMS hybrid exhibited high current efficiencies of 10 mA cm at a cell potential of 1.5 V. -2It was confirmed that the j of 10 mA cm was obtained, which was impressive compared to MoSe2(+) || MoSe2(-), NCS(+) || Pt / C / NF(-) || RuO2 / NF(+), which require higher cell potentials to obtain the same j. -2 The cell potentials of MoSe2(+) || MoSe2(-) (1.61), NCS(+) || NCS(-) (1.53), Pt / C / NF(+) || RuO2 / NF(+) (1.34), and NCSMS (+) || NCSMS(-) (1.3) in are shown in Fig. 28b. These results clearly demonstrate the superior performance of the NCSMS hybrid in dual-functional water splitting. This means that the hybrid material exhibits excellent dual activities in the fields of HER, OER, and EWS. In addition, the stability was evaluated for 72 hours, and the result showed no change in current density, as shown in Fig. 28c, suggesting that the hybrid material has long-term durability for practical implementation.

[0305] In order to confirm the durability of the NCSMS (+) || NCSMS (-) electrolyzer, the LSV curve was measured before and after 72 hours (Fig. 28d) to show the stability of the hybrid for electrochemical catalyst, and the amount of gas produced was also quantitatively measured. In conclusion, the NCSMS hybrid material has excellent water splitting performance, suggesting that it has great potential for application in energy conversion and storage fields. The results, as shown in Fig. 28e, show the amount of H2 and O2 produced while comparing the experimental and theoretically obtained gas volumes. A schematic diagram of the two-electrode electrolyzer system is given in Fig. 28f, which shows the charge transfer mechanism between the electrodes and the gas evolution. In addition, the cell potential of the NCSMS (+) || NCSMS (-) heterojunction electrolyzer is in contrast to that of a recently reported transition metal-based electrolyzer. NCSMS (+) || The cell potential of NCSMS (-) is 1.5 V superior to that of the currently reported electrode, as shown in Fig. 28g. The main reasons for the bifunctional properties and long-term durability of NCSMS (+) || NCSMS (-) are as follows:

[0306] (i) The presence of 1T-MoSe2 improves the electrochemical behavior and catalytic efficiency of the hybrid material by changing the electrical conductivity and charge transfer properties (Fig. 28f).

[0307] (ii) O2 and H2 bubbles are easily formed because the selenide matrix reduces the kinetic energy barrier and promotes intermediate reactions.

[0308] (iii) As can be seen from the SEM and TEM images, the morphology of the NCSMS nanospheres is porous, hollow, and rough, providing more active sites to facilitate the formation of O2 and H2 (Fig. 28d).

[0309] (iv) Co on the octahedral surface 3+The presence of high-spin elements such as ions can enhance the catalytic potential for both OER and HER, which is evidenced by the Co2p XPS spectrum presented in Fig. 26c.

[0310] 3.3.3. Electrochemical performance evaluation for UOR

[0311] The electrochemical activity of NCSMS nanospheres as urea oxidation reaction (UOR) was measured using a three-electrode system in 1.0 M KOH and 0.33 M urea electrolyte. Figure 29a shows the LSV polarization curves of the NCSMS hybrid with and without urea electrolyte. NCS nanospheres exhibited excellent UOR performance in urea electrolyte with overpotentials of 62, 170, and 260 mV, which were higher than those in alkaline electrolytes (90, 350, and 420 mV) at 10, 50, and 100 mA cm -2 Each current density can be obtained, showing that the element electrolyte performance of the NCSMS hybrid is improved. In addition, as shown in Fig. 29c, the Tafel slope (29.1 mV dec) of NCSMS in the element electrolyte -1 ) is the Tafel slope of the alkaline electrolyte (32.25 mV dec -1 ) was smaller than that of the UOR dynamics. In addition, various scan rates (10-60 mV s -1 ) was measured to analyze the ECSA based on the CV curve. As shown in Fig. 29d, the NCSMS nanospheres were 24.5 cm in the element electrolyte. -2 The Cdl value of alkaline electrolyte (21.3 cm- 2) was higher than that of the element electrolyte, indicating that the catalytic activity was enhanced. The catalytic stability of NCSMS was investigated by applying a constant voltage for 72 hours. The results, as shown in Fig. 29e, demonstrate that NCSMS has remarkable stability over the given period, and the potential of NCSMS remains almost the same before and after the stability test, as shown in Fig. 29f.

[0312] 3.3.4. Alkaline electrolyzers, solar-electrochemical systems, and computational research

[0313] The efficiency and resilience of the synthesized electrocatalyst were observed for a zero-gap single AEMWE cell, confirming its excellent electrocatalytic activity (Fig. 30). As part of the AEMWE performance evaluation, a membrane electrode assembly (MEA) was used, which used a non-precious metal catalyst as the cathode and anode catalyst, respectively, as a gas diffusion layer (GDL) manufactured from nanofibers. The assembly diagram shown in Fig. 30a shows the components of the alkaline anion exchange electrolyzer. This device is used for electrolysis and consists of several major components that play essential roles in its operation. The main components are (1) the electrode chamber, which is divided into two separate compartments: the cathode chamber and the anode chamber. These compartments each contain an electrode, a cathode, and an anode. The electrodes catalyze the electrochemical reactions that occur during electrolysis. (2) The anion exchange membrane is located between the cathode and anode compartments and allows the flow of ions required for the electrolysis process while maintaining the separation between the two compartments. (3) The electrolyte solution that fills the electrode compartments. Electrolyte solutions typically contain alkali metal hydroxides, such as potassium hydroxide (KOH). These solutions provide the ions necessary for electrochemical reactions and ensure conductivity within the electrolysis device. In an MEA using a non-precious metal catalyst, a cell efficiency of 69.13% at 1.85 V was achieved, reaching 408 mA cm. -2A current density of 100 kJ / cm was achieved (Fig. 30b). From a commercial perspective, the electrolysis device of the present invention offers distinct advantages due to its minimal catalyst loading and lower operating temperature, which can reduce capital and operating costs.

[0314] Furthermore, we evaluated the durability of the catalyst within the electrolyzer system, as well as the consistency of the experimental measurements. The results, as shown in Figure 30d, demonstrated that the NCSMS electrode exhibited remarkable resilience while maintaining a potential of 1.85 V for 72 hours. This demonstrates that the current loss observed during the test was minimal. In conclusion, these results highlight the excellent activity of the NCSMS electrode, making it a promising candidate for various commercial applications. The actual assembly is shown in Figure 30e. Furthermore, as shown in Figure 30f, the mixture of non-precious metal catalysts is assembled with a solar cell. The solar cell is connected to the electrode without wires (solar cell, electrode), simplifying the water splitting system and reducing the required input energy. Therefore, the system design of the present invention is simple and convenient. Figure 30g shows the IV curve of the solar cell. The fabricated solar cell has an open-circuit voltage of 1.6 V, and the sample of the present invention demonstrated high performance using this voltage as the input power source.

[0315] Density functional theory (DFT) was used to elucidate the synergistic effect of MoSe2 and NCS on electrochemical performance. Based on experimental data, models of MoSe2, NCS, and NCSMS were constructed, as shown in Figures 30h-m. The density of states (DOS) was calculated to examine the influence on the electronic structure. Around the Fermi level, NCSMS exhibited a higher DOS than MoSe2 and NCS, suggesting that the combination of MoSe2 and NCS significantly enhanced electrical conductivity and electron transport (Figure 30n). To further investigate this synergistic effect, DFT calculations of the Gibbs free energies of HER and OER were performed. When the Gibbs free energy of H adsorption (DGH*) is close to zero, it is an important parameter for investigating HER kinetics. In fact, the calculated DGH* values ​​for MoSe2, NCS, and NCSMS are 0.18, -0.17, and -0.07 eV, respectively (Fig. 30o). While the hydrogen adsorption on NCS is relatively strong due to its negative value, the relatively weak adsorption observed on MoSe2 further inhibits the HER. Notably, the thermoneutral DGH* of NCSMS ensures fast H adsorption / desorption kinetics, favoring the HER activity. From the perspective of the Gibbs free energy diagram of the OER process, all electron transfer steps are endothermic with an uphill free energy path, thus promoting water oxidation. It is noteworthy that the conversion of O* to OOH* is the rate-limiting step in the OER process for all configuration models. In this regard, the theoretical overpotentials for MoSe2 and NCS are estimated to be 1.54 V and 2.12 V, respectively. In contrast, NCSMS showed the most energetically favorable intermediate bond, resulting in a low theoretical overpotential of 0.92 V (Fig. 29p).Through DFT calculations, we conclude that the NCSMS hybrid can enhance HER and OER activities by promoting the slow kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) processes through modulation of the electronic configuration and control of the Gibbs free energy of intermediates, along with enhanced electrical conductivity.

[0316] <Conclusion of the Third Embodiment>

[0317] A two-step hydrothermal method was used to synthesize highly efficient, durable, and novel nanosphere structures containing NCSMS heterojunctions. The synthesized nanospheres exhibited remarkable electrochemical performance. For OER, the nanospheres exhibited an OER of 50 mA cm in a 1.0 M potassium hydroxide solution. -2 Wow 100 mA cm -2 showed low overpotentials of 290 mV and 370 mV, respectively. Similarly, for HER, 50 mA cm -2 Wow 100 mA cm -2 In , the overpotentials were 244 mV and 304 mV, respectively. In addition, during the urea electrolysis, the nanospheres also exhibited a 50 mA cm in 1.0 M potassium hydroxide and 0.33 M urea electrolytes. -2 Wow 100 mA cm -2 They exhibited low overpotentials of 170 mV and 260 mV, respectively. When used in NCSMS-based electrolytes, the required operating power is 10 mA cm -2 is only 1.5 V. In addition, when the NCSMS catalyst is integrated into the membrane electrode assembly, the current of 408 mA cm at 1.85 V is achieved. -2A high current density of 69.13% was achieved, resulting in a cell efficiency of 69.13%. Consequently, the combination of MS and NCS electrodes offers numerous advantages in terms of suitable design, manufacturing, and environmental friendliness. Furthermore, the integration of wireless electrodes and solar cell connections simplifies and enhances the efficiency of the water splitting system. Therefore, the present invention presents an innovative approach to fabricating a non-precious metal-based hybrid electrolysis device through a simple design strategy. The objective is to investigate high-performance bifunctional electrochemical catalysts and enhance hydrogen fuel production using abundant water resources.

[0318]

[0319] Examples of the fourth embodiment of the present invention are as follows.

[0320] The present invention relates to a method for producing a catalyst for electrolysis, comprising a first step of hydrothermally synthesizing a zinc-cobalt double layer hydroxide on a metal foam using a solution containing a zinc precursor and a cobalt precursor; and a second step of hydrothermally synthesizing the zinc-cobalt double layer hydroxide in a solution containing a molybdenum precursor and a sulfur precursor to form a hybrid structure; and a water electrolysis catalyst having a hybrid structure containing zinc cobalt sulfide and molybdenum disulfide produced by the method.

[0321] In the first step, the zinc precursor and the cobalt precursor may be used in a weight ratio of 1:2, but is not limited thereto.

[0322] In the second step, the molybdenum precursor and the sulfur precursor may be used in a weight ratio of 1:2, but is not limited thereto.

[0323] In the first step, the solution containing the zinc precursor and cobalt precursor may include, but is not limited to, ammonium and urea. Urea can be gradually released by hydrolyzing ammonia under hydrothermal conditions in an aqueous solution, and an octahedral metal complex can be formed by the reaction of ammonia and a metal cation. Then, the nuclei of Zn / Co hydroxides can be assembled with each other to form ZnCo double layer hydroxide (LDH). Finally, in the second step, an ion exchange process occurs between the hydroxide and the sulfide to form a metal sulfide, through which MoS2@Zn 0.76 Co 0.24 S nanowire heterojunction structures can be formed.

[0324] In the first step, the zinc-cobalt double layer hydroxide may have a nanowire structure, but is not limited thereto. The zinc-cobalt layered double hydroxide (ZnCo LDH) nanowires are initially formed in the hydrothermal reaction of the first step, and then undergo an ion exchange process in the hydrothermal step of the second step to form MoS2@Zn 0.76 Co 0.24 S nanowire hybrid structures can be formed.

[0325] The above electrolysis catalyst may be a metal foam; and a zinc cobalt sulfide and molybdenum disulfide hybrid structure formed on the metal foam, but is not limited thereto.

[0326] The above metal foam is a fully open porous metal structure in which all pores are connected, and is characterized by various pore sizes, low specific weight, and high processability. Here, the metal foam may be at least one selected from the group consisting of Ni foam, Fe foam, Cu foam, Ag foam, and Ti foam, but is not limited thereto.

[0327] The above electrolysis catalyst may be porous, for example, having pores such as mesopores and macropores, but is not limited thereto.

[0328] The above electrolysis catalyst may be a bifunctional catalyst used as an oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalyst, but is not limited thereto.

[0329] The above electrolysis catalyst may have a nanowire structure, which may be a heterostructure in which zinc cobalt sulfide and molybdenum disulfide are joined, for example, MoS2@Zn 0.76 Co 0.24 It may be a hybrid structure represented by the S structure, but is not limited thereto.

[0330] The present invention relates to a water electrolysis catalyst electrode comprising the water electrolysis catalyst of the present invention.

[0331] The catalyst electrode of the present invention can be used, for example, in anion exchange membrane (AEM) electrolysis. The AEM electrolysis is composed of a membrane, an ionomer, a membrane electrode assembly (MEA), and a gas diffusion layer (GDL), and the membrane electrode assembly is further composed of a cathode, anion exchange membrane, and an anode. The catalyst electrode of the present invention can be utilized as the cathode and anode of the membrane electrode assembly, but is not limited thereto.

[0332] In addition, the catalyst electrode of the present invention can be used, for example, in a photovoltaic-electrolysis (PV-EC) system. The PV-EC system is a method of producing hydrogen through water electrolysis after generating electricity using a solar cell. The PV-EC system is composed of a photovoltaic cell, an oxidation catalyst electrode, a reduction catalyst electrode, an ion separation membrane, and an aqueous electrolyte. The catalyst electrode of the present invention can be used as an oxidation catalyst electrode and a reduction catalyst electrode in the PV-EC system, but is not limited thereto.

[0333] The present invention relates to a membrane electrode assembly comprising: a cathode; an anion exchange membrane formed on the cathode; and an anode formed on the anion exchange membrane, wherein the cathode and the anode include a water electrolysis catalyst of the present invention.

[0334] The above membrane electrode assembly, as described above, is a component of AEM water electrolysis, and includes a cathode, an anion exchange membrane, and an anode, and may include a catalyst electrode for water electrolysis of the present invention. At the anode, a hydrogen evolution reaction (HER) occurs simultaneously as a half-cell reaction, and at the cathode, an oxygen evolution reaction (OER) occurs simultaneously. That is, water is reduced at the anode and reacts with electrons to form hydrogen and hydroxide ions, the generated hydroxide ions diffuse to the cathode through the anion exchange membrane, and the electrons are transferred to the cathode through an external circuit. At the cathode, the hydroxide ions lose electrons and recombine into water and oxygen, and the electrons are released from the cathode surface to proceed with the reaction. The water decomposition process that occurs at the anode and cathode is as follows.

[0335] Anode: 4OH - → O2+ 2H2O + 4e - E0 = 0.401 V

[0336] Cathode: 4H2O + 4e - → 2H2+ 4OH - E 0 = -0.828 V

[0337] Overall: 2H2O → H2+ O2E 0 = 1.23 V

[0338] An AEM electrolyzer comprising a membrane electrode assembly of the present invention as a cathode and an anode uses a metal foam, a catalyst electrode for an electrolyzer comprising a composite transition metal chalcogenide heterostructure formed on the metal foam, and a catalyst electrode for an electrolyzer capable of increasing the efficiency of hydrogen and oxygen generation by improving charge transport and conductivity.

[0339] In addition, the catalyst electrode for water electrolysis of the present invention can be utilized in a photovoltaic-electrolysis (PV-EC) system as described above. The PV-EC system is composed of a photovoltaic cell, an anode, a cathode electrode, an ion separator, and an aqueous electrolyte.

[0340] The PV-EC system can produce hydrogen by a process in which, when light is irradiated onto the photovoltaic cell, the photovoltaic cell absorbs the light to generate electrons and holes, which are then transferred to oxidation (oxygen generation electrode) and reduction (hydrogen generation electrode) catalyst electrodes located inside an aqueous electrolyte solution to decompose water, thereby separating oxygen at the oxidation electrode and hydrogen at the reduction electrode. The catalyst electrode for water electrolysis of the present invention can be utilized as an oxidation catalyst electrode and a reduction catalyst electrode in the PV-EC system.

[0341] The above photovoltaic cell can use any of the existing solar cells developed and used, which include a semiconductor material that can absorb light to create electron-hole pairs. For example, a photovoltaic solar cell using a silicon semiconductor, a dye-sensitized solar cell, a chalcogenide solar cell, an oxide thin-film solar cell, an organic semiconductor solar cell, or a combination thereof can be used.

[0342] The size of the above photovoltaic cell can vary from 1 cm Х 1 cm to 100 cm Х 100 cm and can be appropriately determined under optimal light-to-hydrogen efficiency conditions. Depending on the type of photovoltaic cell, a separate additional photovoltaic cell may be used if the generated voltage is lower than the potential required for water decomposition.

[0343] A solar cell-water electrolysis system including a catalyst electrode for water electrolysis of the present invention can increase the efficiency of hydrogen and oxygen generation by improving charge transport and conductivity, since the catalyst electrode for water electrolysis includes an oxidation catalyst electrode and a reduction catalyst electrode, a metal foam, and a composite transition metal chalcogenide heterostructure formed on the metal foam.

[0344] <Example 4>

[0345] Example 4.1 MoS2@Zn 0.76 Co 0.24 S synthesis

[0346] 4.1.1. Materials

[0347] Zinc nitrate (Zn(NO3)2·6H2O, 98%), ammonium fluoride (NH4F, ≥99.99%), cobalt nitrate (Co(NO3)2·6H2O, 97%), platinum / carbon (5.0 wt%), urea (NH2)2CO, ≥99%), ruthenium oxide (RuO2, 99.9%), sodium tungstate (Na2WO4·2H2O, 99.9%), Nafion (5.0 wt%), ethanol (C2H5OH, 99.9%), methanol (CH3OH, 99.9%), hydrochloric acid (HCl, 35–37%), potassium hydroxide (KOH, ≥99.5%), and NF substrate were purchased from Sigma-Aldrich.

[0348] 4.1.2. MoS2@Zn on Ni foam 0.76 Co 0.24 S synthesis

[0349] MoS2@Zn as shown in Fig. 31a 0.76 Co 0.24 S heterojunction structures were fabricated. Chemicals were used without further purification. Initially, Ni foam (NF) was washed with 3 M HCl, ethanol, and distilled water, sonicated for 30 min, and then dried in an autoclave. MoS2@Zn 0.76 Co 0.24 For S heterojunction, zinc nitrate (0.3 g), cobalt nitrate (0.6 g), ammonium fluoride (0.1 g), and urea (1 g) were dissolved and diffused to prepare a precursor, and then the precursor solution was transferred to an autoclave (80 mL) and hydrothermal treatment was performed at 120°C for 6 h. After the hydrothermal treatment was completed, the zinc-cobalt precursor grown on NF was repeatedly washed with distilled water and ethanol. The zinc-cobalt precursor synthesized on NF was added to a solution of 0.5 g of sodium molybdate and 1 g of sodium sulfide in 8 mL of propionic acid and 16 mL of deionized water, and hydrothermal treatment was performed at 180°C for 14 h to obtain MoS2@Zn 0.76 Co 0.24 S hybrid was obtained. MoS2@Zn synthesized on nanofiber substrate 0.76 Co 0.24The S nanowire heterojunction was dried by heating at 70°C for 6 h after rinsing with distilled water several times, and then dried MoS2@Zn 0.76 Co 0.24 S heterojunction was formed. For comparison, Zn 0.76 Co 0.24 S nanowire heterostructures and MoS2 monolayers were fabricated on nanofiber substrates using identical reaction conditions except for the molybdenum and zinc-cobalt precursors, respectively.

[0350] Example 4.2. Morphological and topological analysis

[0351] Figure 31a is MoS2@Zn 0.76 Co 0.24 We demonstrate a facile and scalable synthesis of S heterojunctions. MoS2@Zn was synthesized by a two-step hydrothermal process on porous and spongy NF substrates. 0.76 Co 0.24 S heterojunction was synthesized. ZnCo layered double hydroxide (ZnCo LDH) nanowires were initially formed in a hydrothermal reaction, and then MoS2@Zn through an ion exchange process in the hydrothermal stage. 0.76 Co 0.24 S nanowire hybrid structure is formed. The element has a great effect of stepwise releasing ammonia by hydrolysis under hydrothermal conditions in an aqueous solution. An octahedral metal complex was formed by the reaction of ammonia and metal cations. Afterwards, ZnCo LDH was formed as the nuclei of Zn / Co hydroxides were assembled with each other. Finally, an ion exchange process occurs between the hydroxides and sulfides to form metal sulfides, through which MoS2@Zn 0.76 Co 0.24 S nanowire heterojunctions were formed.

[0352] Figure 31a shows MoS2@Zn on NF. 0.76 Co 0.24The synthesis mechanism of S is shown. MoS2@Zn was observed using field emission scanning electron microscopy (FE-SEM) and field emission transmission electron microscopy (FE-TEM). 0.76 Co 0.24 The surface morphology and microstructure of S were investigated. Figures 31b-e show Zn 0.76 Co 0.24 MoS2@Zn on NF with the same characteristics as S / NF 0.76 Co 0.24 The FE-SEM image of S shows that the nanowires are rougher and thicker, and no sharpness is detected on the surface and tip of the nanowires. Also, MoS2@Zn 0.76 Co 0.24 Multiple pores / voids (mesopores and macropores) were observed from the heterojunction of S / NF, increasing the area exposed to the electrolyte. This type of surface nanostructure plays a pivotal role in improving the electrocatalytic function. MoS2@Zn 0.76 Co 0.24 The rough and porous nanowires of the S / NF hybrid can facilitate electron transport. The nanowires can increase the exposed area of ​​the electrode, current collector, and electrolyte, and contribute to direct ion / molecule transport pathways to the electroactive centers, thereby enhancing the electrocatalytic activity. The use of electroactive materials composed of 3D porous current collectors can enhance ion / electron transport rates and facilitate gas evolution on the catalyst surface. Therefore, developing a non-precious metal-derived catalyst with a hybrid nanowire structure on NF can alter the electrocatalytic activity. MoS2@Zn 0.76 Co 0.24 EDX and corresponding mapping studies of the S / NF hybrid were also performed to evaluate the elemental composition of the nanohybrid (Fig. 31f). MoS2@Zn 0.76 Co 0.24 The EDX results of the S / NF hybrid show a uniform and consistent distribution of Zn, Co, Mo, and S, and MoS2@Zn on the NF. 0.76 Co0.24 It is to prove the suitability when synthesizing S.

[0353] MoS2@Zn using FE-TEM analysis 0.76 Co 0.24 The internal and external structures of the S hybrid were analyzed. MoS2@Zn 0.76 Co 0.24 FE-TEM images of S (Fig. 32a, b) show that MoS2 is Zn 0.76 Co 0.24 Zn fixed on the outside of S 0.76 Co 0.24 Zn, thicker and rougher than S 0.76 Co 0.24 It shows slightly different features from S. HR-TEM images (Fig. 32c, d) show the (111) plane Zn of MoS2 0.76 Co 0.24 It showed various types of lattice patterns attributed to S and (002) planes. The EDX spectrum and corresponding mapping images (Fig. 32e, f) showed the presence of Zn, Co, Mo, and S, indicating that MoS2@Zn 0.76 Co 0.24 The synthesis of S hybrid was verified.

[0354] MoS2, Zn using X-ray diffraction (XRD) 0.76 Co 0.24 S and heterojunction MoS2@Zn 0.76 Co 0.24 The crystal phase of S was measured (Fig. 33a). The XRD results of MoS2 / NF showed peaks at two θ values ​​of 14.1, 32.1, 37.2, 50.6 and (Fig. 33a) assigned to the (002), (100), (110), (103), and (111) planes, which correspond to the (002), (100), (110), and (111) planes (Fig. 33a) demonstrating the metallic phase of MoS2 ((JCPDS No. 42-1450) [6]. XRD showed peaks at 2 θ = 28.66, 47.68, 56.60, and 77.06 °, which are assigned to Zn 0.76 Co 0.24It corresponds to the (111), (220), (311) and (331) planes of MoS2@Zn (JCPDS card no.47-1656). 0.76 Co 0.24 XRD patterns of S are 1T MoS2 and Zn 0.76 Co 0.24 S shows peaks in all Zn 0.76 Co 0.24 The formation of a heterostructure containing S and MoS2 was qualitatively verified (Fig. 33a). Finally, two intense peaks with θ values ​​of 45.2, 52.6, and 76.9° were consistent with NF, indicating that the nanohybrid was formed on 3D NF. In addition, the Raman spectrum showed J2, J3, and E of MoS2, as shown in Fig. 33b. 1g , E 2g , and A 1g It contained peaks. However, peaks J1, J2, J3, and E1g were as in Fig. 33b. However, peaks J1, J2, J3, and E 1g The peak represents 1T-MoS2 (Fig. 33b). Instead, adsorption-desorption isotherm and Brunauer-Emmett-Teller (BET) characterization were performed to characterize MoS2@Zn 0.76 Co 0.24 The pore size and pore distribution of the S heterojunction were evaluated. MoS2@Zn 0.76 Co 0.24 The nitrogen adsorption-desorption isotherm of S showed a clear type IV hysteresis curve, which indicated the mesopore structure, as shown in Fig. 33c. Based on BET surface-area calculations, the surface areas of the MoS2@Zn 0.76 Co 0.24 S Hybrid (146.3 m 2 g -1 ), Zn 0.76 Co 0.24 S (91.2 m 2 g -1 ), and MoS2(62.4 m 2 g-1 ) was confirmed. In addition, in the pore-size test, the pore-size distribution was highest in the 10 nm region, which is MoS2@Zn 0.76 Co 0.24 The menophore properties of the S hybrid were confirmed (Fig. 33d). MoS2@Zn 0.76 Co 0.24 The higher surface area and mesoporous nature of the S heterojunction improved the OER and HER performance. Therefore, more electrocatalytic active sites and ion / electron transport channels were created. MoS2@Zn 0.76 Co 0.24 The elemental composition and valence state of the S hybrid were analyzed using X-ray photoelectron spectroscopy (XPS). XPS analysis of the Co 2p spectrum (Fig. 33e) showed the presence of two distinct peaks observed at energy levels of 778.5 eV and 794.1 eV. These peaks were assigned to Co 2p, respectively. 3 / 2 and Co 2p 1 / 2 Co of 3+ corresponds to the state. In addition, additional satellite peaks with vibrational patterns are observed at about 781.3 eV and 798.1 eV, which correspond to the Co 2+ It can be seen that this is due to the presence of MoS2@Zn 0.76 Co 0.24 Detailed Mo 3d scan of the S composite (Fig. 33f) shows two prominent peaks, particularly Mo 3d 3 / 2 (about 231.4 eV) and Mo 3d 5 / 2 (approximately 228.6 eV). These peaks were MoS2@Zn 0.76 Co 0.24 Evidence for the presence of +4-valent Mo within the S hybrid was provided. XPS examination of the Zn 2p spectrum (Fig. 33g) revealed a peak at 1044.8 eV (Zn 2p 1 / 2 ) and 1021.7 eV (Zn 2p 3 / 2 ) showed the presence of two primary peaks. These peaks were Zn 2+It may be due to the oxidation state. In addition, XPS analysis (Fig. 33h) showed that S 2p 3 / 2 (about 162.3 eV) and S 2p 1 / 2 (approximately 163.7 eV) showed a peak.

[0355] Example 4.3. Electrochemical performance

[0356] 4.3.1. OER catalyst performance

[0357] OER activity plays an important role in the water-splitting process. Therefore, MoS2, Zn 0.76 Co 0.24 S and MoS2@Zn 0.76 Co 0.24 The OER activity of the S hybrid was investigated using a standard three-electrode setup in 1.0 M KOH electrolyte. To prepare a stable electrode, a 15 mV s electrode was applied prior to the acquisition of electrocatalytic study data. -1 One hundred cyclic voltammograms were performed at a scan rate of 20 mA cm and Fig. 34a shows the LSV results for all catalysts. -2 , 50 mA cm -2 , 100 mA cm -2 The calculated overpotentials at various current densities (Fig. 34b) are: 290 mV, 360 mV, and 460 mV for MoS2, Zn 0.76 Co 0.24 270 mV, 330 mV, and 420 mV in S, MoS2@Zn 0.76 Co 0.24 90 mV, 170 mV and 240 mV in S. MoS2@Zn due to the synergistic effect 0.76 Co 0.24 S is MoS2, Zn 0.76 Co 0.24 It showed the lowest overpotential compared to S and bare NF. Individual MoS2 and Zn 0.76 Co 0.24 Unlike the S structure, MoS2@Zn 0.76 Co 0.24 S / NF nanohybrid is Zn 0.76 Co0.24 The combined effect of the heterointerface between S and MoS2 resulted in excellent electrocatalytic activity for OER. This synergistic effect induced atomic-level reorganization of the catalyst, leading to optimal electrocatalytic performance. Tafel curve analysis showed that MoS2@Zn 0.76 Co 0.24 To further analyze the activity of the S / NF hybrid, the overpotential (η) = blog (J / J0) was measured and calculated (Fig. 34c). MoS2@Zn 0.76 Co 0.24 Tafel slope of S hybrid 57 mV dec -1 Ro, Zn 0.76 Co 0.24 S (131.1), MoS2 (124.6), and RuO2 (62.3), which were lower than those of MoS2@Zn under the same measurement conditions. 0.76 Co 0.24 This shows the boosted OER dynamics of the S hybrid. MoS2@Zn 0.76 Co 0.24 The S nanohybrid showed the smallest η and Tafel slope values ​​compared to the other secondary catalysts (Fig. 34b, c). MoS2@Zn 0.76 Co 0.24 LSV, η, and Tafel analysis results of S / NF nanohybrid as an OER electrode @Zn 0.76 Co 0.24 The excellent performance of S / NF was confirmed. This is Zn 0.76 Co 0.24 This is due to the unique heterostructure of S nanowires and MoS2. Previous theoretical and practical studies have shown that heterointerface engineering plays a crucial role in enhancing OER performance.

[0358] As a result, MoS2 and Zn 0.76 Co 0.24 The hybrid of S catalyst promotes OER activity by increasing charge transport and catalytic activity, but MoS2@Zn for OER 0.76 Co0.24 The performance of S / NF heterostructures has not yet achieved significant results. In this study, MoS2@Zn 0.76 Co 0.24 Through the study on S / NF nanohybrid, it was revealed that the morphological characteristics and porosity significantly affect the reaction acceleration of the electrode. In addition, MoS2@Zn 0.76 Co 0.24 The synthesized hybrid of S / NF and hierarchically porous nanowires with rough morphology and excellent conductivity facilitated the formation of electrocatalytically active centers and enhanced the electrocatalytic activity. In addition, the electrochemically active surface area (ECSA) is a key indicator in catalytic research, and the ECSA was estimated using the electrochemical double layer capacitance (Cdl) of the electrode. The ECSA values ​​were recorded at 0.92–1.12 V (Fig. 34d), and the Cdl was calculated using CV. MoS2@Zn 0.76 Co 0.24 S Nanohybrid (24.21 cm) 2 ) > Zn 0.76 Co 0.24 S(7.6 cm 2 ) > MoS2(4.6 cm 2 ) is presented in Fig. 34d. MoS2@Zn 0.76 Co 0.24 The S nanohybrid is clearly an excellent electrode because it significantly accelerates HER and OER. The porous structure of the electrode material plays a crucial role, acting as a reservoir for the electrolyte and facilitating the release of oxygen. This is particularly important when anode bubbles are released from the outer surface of the electrode, blocking the electrocatalytic active sites and degrading anode activity. Nevertheless, the mesoporous MoS2@Zn nanowires are clearly an excellent electrode because they significantly accelerate HER and OER.

[0359] One of the variables affecting the practical implementation of electrodes for EWS is the stability of the catalyst, and long-term durability is very important. To measure the durability of the electrode, the success of the catalyst in the EWS process must be estimated by repeating the reaction. Therefore, chronoampere measurements were used for 48 hours to evaluate the success of the catalyst in the EWS process. 0.76 Co 0.24 The stability of the S / NF hybrid was estimated. Figure 34e shows MoS2@Zn with no significant current loss for 48 hours. 0.76 Co 0.24 The stability measurement results of the S / NF hybrid were presented, confirming the excellent durability and effectiveness of the catalyst for EWS application. In addition, the current density (Fig. 34f) was measured after 48 hours of use as an OER. A similar LSV polarization curve was measured after 48 hours to confirm the MoS2@Zn 0.76 Co 0.24 The long durability of S nanohybrid was confirmed. In addition, MoS2@Zn for OER 0.76 Co 0.24 To further verify the durability of S nanohybrid, MoS2@Zn 0.76 Co 0.24 S nanohybrid was prepared by MoS2@Zn for 48 hours 0.76 Co 0.24 After using the S nanohybrid as an anode, the post-characterization studies using FE-SEM, FE-TEM, EDX elemental mapping, and XRD analysis showed similar structures, morphologies, XRD peak patterns, and identical elements, further demonstrating the long-term stability of the hybrid. MoS2@Zn 0.76 Co 0.24 The excellent OER catalytic effect and long-term robustness of S nanohybrid may be attributed to the following reasons.

[0360] (i) MoS2@Zn using heterogeneous external Ni template 0.76 Co 0.24 The excellent catalytic activity of S porous nanowires enhanced the water, ECSA, and O2 liberation processes.

[0361] (ii) Zn 0.76 Co 0.24 Unlike S and MoS2, MoS2@Zn 0.76 Co 0.24 The heterogeneity of the S hybrid accelerates electron transport and enhances performance due to the large catalytically active sites.

[0362] (iii) MoS2@Zn 0.76 Co 0.24 The utilization of Zn, Mo, and Co elements with various valences in the S hybrid enhanced the formation of metal oxides and attracted the generation of anode-step reactions such as l M-OH, MO, M-O2H, and M-OO, which promoted the catalytic activity. Therefore, the catalyst that attracted more OH promoted greater OER activity. MoS2@Zn 0.76 Co 0.24 In S nanohybrid, other oxidation states of elements are also OH - It can be very similar to the anion, which is MoS2@Zn 0.76 Co 0.24 This suggests that S nanohybrid is an excellent catalyst for OER.

[0363] 4.3.2. HER catalytic activity

[0364] The HER performance of all samples was evaluated using LSV in 1.0 M KOH electrolyte (Fig. 35a). MoS2, Zn 0.76 Co 0.24 S, MoS2@Zn 0.76 Co 0.24 Overpotential values ​​(η) for S hybrid and Pt / C are 20, 50, and 100 mA cm -2 were measured at the current density. Similarly, the corresponding overpotential values ​​are presented in Fig. 35b. For MoS2, the overpotential values ​​were 335 mV, 364 mV, and 464 mV. Zn 0.76 Co 0.24 For S, the overpotential values ​​were 242 mV, 273 mV, and 442 mV. MoS2@Zn 0.76 Co0.24 For S, the overpotential values ​​were 169 mV, 237 mV, and 301 mV. For Pt / C, the overpotential values ​​were 186 mV, 247 mV, and 342 mV. MoS2@Zn 0.76 Co 0.24 The S hybrid exhibited excellent performance as a HER electrode with the lowest η value. Similarly, the HER kinetics was investigated based on the Tafel curve by estimating the slope curve (η = a + b log J) as shown in Fig. 35c. MoS2@Zn 0.76 Co 0.24 S hybrid is commercial Pt / C (48.6), Zn 0.76 Co 0.24 It showed the lowest Tafel slope (39.7 mV dec-1) among S(91.8) and MoS2(101.5). Also, Fig. 35c shows that MoS2@Zn 0.76 Co 0.24 S shows that S is a good electrode for HER kinetics. The Tafel slope is an important indicator of HER kinetics, and a small value indicates that the reaction kinetics is accelerated at the electrode-electrolyte interface with a low overpotential due to low activation preconditions. In addition, MoS2@Zn 0.76 Co 0.24 S (29.7 mV dec -1 ) requires less energy to initiate the HER reaction, as shown in the Tafel slope: this is MoS2@Zn 0.76 Co 0.24 S-catalyzed HER reaction suggests that it follows the Volmer-Heyrovsky pathway in alkaline electrolytes. In general, the kinetics of HER in alkaline solutions are dependent on adsorption, OH of water - It includes electrochemical decomposition and desorption steps into ions.

[0365] In addition, the long-term stability of the catalyst plays a key role in practical applications. As shown in Fig. 35d, the catalyst exhibited good stability for 48 h, while the current density did not change significantly, confirming excellent long-term durability for HER. In addition, after 48 h of cycling, MoS2@Zn 0.76 Co 0.24 The S electrode (Fig. 35e) produced an LSV curve with a current density almost identical to the initial curve, indicating that MoS2@Zn is suitable for practical applications. 0.76 Co 0.24 The S Hybrid has proven its good stability and reliability.

[0366] MoS2@Zn 0.76 Co 0.24 MoS2@Zn for long-term application post-analysis of S / NF hybrids 0.76 Co 0.24 To further investigate the excellent structural reliability of the S / NF hybrid, a 48-hour post-treatment was performed. The detection of zinc, cobalt, molybdenum, sulfur, and oxygen atoms serves as strong evidence for the excellent structural stability and durability of the electrode. In particular, the MoS2@Zn 0.76 Co 0.24 The S / NF hybrid exhibited excellent HER activity in contrast to recently reported metal-sulfide-based hybrids, as shown in Fig. 35f. MoS2@Zn 0.76 Co 0.24 The remarkable HER effect of S / NF hybrid is Zn 0.76 Co 0.24 This is attributed to the synergistic effect of S and MoS2 and the enhanced synergistic effect, electrical conductivity and electrocatalytic active sites.

[0367] 4.3.3. Overall hydrolysis catalytic activity

[0368] MoS2@Zn 0.76 Co 0.24As can be seen from the three-electrode performance analysis, the S hybrid exhibited strong dual-functional electrocatalytic activities for HER and OER in a 1.0 M KOH solution. Therefore, the hybrid of the present invention can serve as an effective catalyst for both the anode and cathode in a two-electrode electrolyzer in an alkaline solution. MoS2(+) || MoS2(-), Zn 0.76 Co 0.24 S(+) || Zn 0.76 Co 0.24 S(-), Pt / C(-) || RuO2(+) and MoS2@Zn 0.76 Co 0.24 The standard Ecell value of S(-) was determined from the total voltage difference between the HER and OER half-cell overpotentials as given in Fig. 36a. In particular, MoS2@Zn 0.76 Co 0.24 S hybrid electrode 10 mA cm -2 It showed excellent activity with Ecell value of about 100. These results show that MoS2@Zn 0.76 Co 0.24 This suggests that the S hybrid has tremendous potential to achieve efficient dual-functional EWS activity. To determine the actual ESW characteristics, LSV analysis was performed at 1.0–1.8 V, and the actual ESW characteristics were confirmed as shown in Fig. 36b. MoS2(+) || Zn 0.76 Co 0.24 S(-), Pt / C(-) || RuO2(+) and MoS2@Zn 0.76 Co 0.24 S(-) hybrid electrode 10 mA cm -2 To achieve j, total Ecells of 1.64 V, 1.63 V, 1.55 V and 1.45 J were required, respectively.

[0369] MoS2@Zn 0.76 Co 0.24The S hybrid generated H2 and O2 gases at a low potential of 1.45 V, demonstrating excellent dual functionality as both anode and cathode for EWS. Furthermore, stability tests showed that MoS2@Zn 0.76 Co 0.24 S(+) || MoS2@Zn 0.76 Co 0.24 The S(-) hybrid electric vehicle maintained a stable current for 48 hours, demonstrating impressive long-term operation (Fig. 36c). LSV comparison (Fig. 36d) showed consistent j and overpotential both initially and after the 48-hour it test, indicating that MoS2@Zn 0.76 Co 0.24 S(+) || MoS2@Zn 0.76 Co 0.24 The excellent durability of the S(-) hybrid cell was further confirmed. In addition, MoS2@Zn 0.76 Co 0.24 S(+) || MoS2@Zn 0.76 Co 0.24 The EIS analysis results of S(-) showed very low electrode-electrolyte interfacial resistance and excellent conductivity of MoS2@Zn 0.76 Co 0.24 The excellent bifunctionality and durability of the S hybrid were confirmed. Finally, the amount of generated gas was measured (Fig. 36e), and the experimental and theoretical gas volumes of H2 and O2 were confirmed. MoS2@Zn 0.76 Co 0.24 S(+) || MoS2@Zn 0.76 Co 0.24 Comparison of the cell potentials of recently reported alkaline EVs with S(-) hybrid EVs and transition metal-sulfide electrodes, MoS2@Zn in alkaline electrolyte and bifunctional 0.76 Co 0.24 The cell potential of the S(-) hybrid electric vehicle was much lower at 1.45 V (Fig. 36f), which is lower than that of MoS2@Zn 0.76 Co 0.24 The S Hybrid demonstrated excellent performance:

[0370] (i) MoS2 and Zn 0.76 Co 0.24 The hybrid of S improved the electrical conductivity, reduced the electron transfer resistance, and facilitated additional catalytic sites for OER and HER (Fig. 36g).

[0371] (ii) The sulfur atom of the hybrid rearranges the electron configuration and frees the kinetic energy barrier, allowing O2 and H2 to be easily released from the reaction intermediates.

[0372] (iii) MoS2@Zn 0.76 Co 0.24 Sponge nanofibers containing S nanowire hybrids exhibited unique porous properties, exposing a high density of active sites (Fig. 36g).

[0373] (iv) MoS2@Zn on NFs 0.76 Co 0.24 Direct synthesis of the S hybrid confirmed that the electroactive catalyst interacted directly with the template, promoting efficient charge-transfer rates.

[0374] Cathode (MoS2@Zn 0.76 Co 0.24 S) and anode (MoS2@Zn 0.76 Co 0.24 The oxygen and hydrogen bubbles generated in S) were analyzed by gas chromatography (GC), respectively. In the present invention, 80.36% pure hydrogen (Fig. 36h, gas evolution, in one reactor) was obtained, which is less pure than commercial hydrogen (99.999%). In contrast, 93.86% pure hydrogen was generated at each electrode of the other reactor (Fig. 36i, photographs of each electrode of the other reactor).

[0375] 4.3.4. Alkaline anion exchange electrolyzer and solar electrochemical system

[0376] To secure excellent electrocatalytic activity, a study was conducted to evaluate the efficiency and resilience of the electrocatalyst synthesized in a zero-gap single AEMWE cell. To evaluate the AEMWE performance, a non-precious metal catalyst (MoS2@Zn) was used as the anode and cathode catalyst. 0.76 Co 0.24 A gas diffusion layer (GDL) made of S) and nanofibers and an anion exchange membrane made of Sustainion X37-50 RT were used. Figure 37a shows the assembly diagram of the alkaline anion exchange electrolytic cell.

[0377] MoS2@Zn 0.76 Co 0.24 The MEA using S achieved 405 mA cm with 68.28% cell efficiency at 1.85 V, the standard voltage for industrial alkaline water electrolyzers. - It was analyzed that a current density of 2 was achieved (Fig. 37c). The electrolyzer of the present invention showed similar performance to other recently reported advanced AEMWE systems (Fig. 37b), but it showed competitive advantages in terms of low catalyst loading and operating temperature, resulting in lower capital and operating costs. Gas chromatography analysis demonstrated that the system of the present invention could produce hydrogen at a rate of 3.1 mL / min with a purity of 99.997%, meeting commercial standards. To evaluate the catalytic resilience and reproducibility of experimental measurements in the electrolyzer system, MoS2@Zn 0.76 Co 0.24 The S electrode was tested and demonstrated high resilience at a potential of 1.85 V for 72 h with minimal current loss (Fig. 37d). These results indicate that MoS2@Zn 0.76 Co 0.24 The excellent performance of the S electrode is demonstrated, indicating its suitability for commercial applications. In addition, MoS2@Zn is suitable for use in anion exchange membrane electrolysis devices in alkaline environments. 0.76 Co 0.24 The stability of S is supported by the observed LSV curve as shown in Fig. 37e, and the AEMWE of the present invention is as shown in Fig. 37f.

[0378] Furthermore, by assembling a mixture of non-precious metal catalysts into a solar cell, as shown in Figure 37g, the water electrolysis system was simplified and the required input energy was reduced. By connecting the solar cell to the electrodes without wires, a simple and convenient system design was achieved. Figure 37h shows the IV curve of the solar cell. The fabricated solar cell exhibited an open-circuit voltage of 1.6 V, and our sample demonstrated high performance using this voltage as the input power source.

[0379] <Conclusion of Embodiment 4>

[0380] In summary, a novel, highly efficient, and powerful bifunctional MoS2@Zn 0.76 Co 0.24 The S hybrid catalyst was synthesized using a hydrothermal method. The metal phase of molybdenum disulfide was MoS2@Zn 0.76 Co 0.24 The electronic conductivity of S was greatly improved, resulting in a significantly lower overpotential. 20, 50, and 100 mA cm -2 In the OER of MoS2@Zn, the overpotentials in 1.0 M potassium hydroxide solution were only 90, 170, and 240 mV, respectively. Similarly, for HER in the same current density and electrolyte, the overpotentials were 169, 237, and 301 mV. 0.76 Co 0.24 S electrolyte exhibits excellent performance as a catalyst in alkaline electrolytes, operating at 1.45 V and providing 10 mA cm -2 was achieved. Noteworthy is that 405 mA cm -2 At a current density of , the system produced hydrogen with an amazing purity of 99.997% at a rate of 3.1 mL / min. This resulted in an excellent cell efficiency of 68.28% and a voltage of 1.85%. ZnCoS (10 mA cm -2 ) and MoS2-Co9S9 (10 mA cm -2 Compared to previous studies such as MoS2@Zn (at 210 mV) 0.76 Co0.24 S has improved performance. MoS2 and Zn 0.76 Co 0.24 The heterostructure of S catalysts offers numerous advantages for convenient and cost-effective design and fabrication without environmental impact. The presented study provides an innovative direction for the fabrication of electrolytes based on heterostructures of transition metal chalcogenides with excellent dual-functional catalytic activity. This approach can enhance the production of H2 fuel through a complete water splitting process. Future research should focus on the synergy of heterostructures for the modification of the electronic interface.

[0381] The above description is merely an example of the technical idea of ​​the present invention, and those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential characteristics of the present invention.

[0382] Accordingly, the embodiments disclosed in the present invention are intended to illustrate, rather than limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical concepts within the scope equivalent thereto should be construed as being included within the scope of the present invention.

Claims

1. A first step of synthesizing an iron metal organic framework by mixing an iron precursor and fumaric acid and then conducting a hydrothermal reaction; and A second step of synthesizing a copper-nickel-iron double layer hydroxide by mixing the iron metal-organic framework with a nickel precursor and a copper precursor and then performing a hydrothermal reaction; A method for producing copper-nickel-iron double-layer hydroxide nanoprisms comprising:

2. In paragraph 1, A method wherein the iron precursor and fumaric acid are mixed for 1 to 4 days in the first step.

3. In paragraph 1, A method wherein, in the second step, the nickel precursor and the copper precursor are mixed in a mass ratio of 3:1 to 4.

4. Copper-nickel-iron double layer hydroxide nanoprism manufactured by the manufacturing method of any one of claims 1 to 3.

5. A water electrolysis catalyst comprising the copper-nickel-iron double-layer hydroxide nanoprism of clause 4.

6. In paragraph 5, The above water electrolysis catalyst is a catalyst used in the oxygen evolution reaction (OER) of fresh water, alkaline water or seawater.

7. In paragraph 5, The above electrolysis catalyst is a non-precious metal electrolysis catalyst.

8. Anion exchange membrane electrolysis anode containing the electrolysis catalyst of clause 5.

9. A solar-electrochemical cell comprising the copper-nickel-iron double-layer hydroxide nanoprism of paragraph 4.

10. A first step of hydrothermally synthesizing a transition metal double layer hydroxide on a metal foam in a solvent containing a transition metal precursor; and A second step of forming a composite transition metal chalcogenide by hydrothermally synthesizing the above transition metal double layer hydroxide in a solution containing a transition metal and a chalcogen compound; A method for producing a catalyst for electrolysis comprising:

11. In paragraph 10, A method in which the composite transition metal chalcogenide in the second step is a heterojunction of two or more transition metal chalcogenide structures.

12. In paragraph 10, A method wherein in the second step, the chalcogen compound comprises at least one chalcogen atom selected from the group consisting of S, Se, and Te.

13. In paragraph 10, A method wherein the above complex transition metal chalcogenide is selected from the group consisting of VTe2@ZnFeTe, FeTe@ZnFeTe and MoTe2@ZnFeTe.

14. Metal foam; and A catalyst for water electrolysis comprising a composite transition metal chalcogenide formed on the above metal foam.

15. A catalyst for water electrolysis comprising a complex transition metal chalcogenide structure, manufactured by the manufacturing method of any one of claims 10 to 14.

16. In paragraph 15, The above composite transition metal chalcogenide is a catalyst for water electrolysis, wherein two or more transition metal chalcogenide structures are hetero-bonded.

17. A first step of synthesizing a nickel-cobalt precursor by hydrothermal synthesis of a precursor solution prepared by dispersing a nickel precursor, a cobalt precursor, and glycerol in a solvent; and A second step of forming nanospheres containing nickel cobalt selenide and molybdenum selenide by adding the nickel-cobalt precursor to a solution containing a molybdenum precursor and a selenite precursor and then performing hydrothermal synthesis; A method for manufacturing a hybrid nanostructure including:

18. In paragraph 17, A method wherein in the first step, the nickel precursor and the cobalt precursor are used in a molar ratio of 1:

1.

19. In paragraph 17, A method wherein in the second step, the molybdenum precursor and the selenite precursor are used in a molar ratio of 1:

3.

20. In paragraph 17, A method wherein in the first step, the nickel-cobalt precursor has a nanosphere structure.

21. A hybrid nanostructure comprising a nanosphere structure comprising nickel cobalt selenide and molybdenum selenide, manufactured by the manufacturing method of any one of claims 17 to 20.

22. In paragraph 21, The above nanosphere is a hybrid nanostructure that is porous.

23. A first step of hydrothermally synthesizing a zinc-cobalt double layer hydroxide on a metal foam using a solution containing a zinc precursor and a cobalt precursor; and A second step of forming a hybrid structure by hydrothermally synthesizing the zinc-cobalt double layer hydroxide in a solution containing a molybdenum precursor and a sulfur precursor; A method for producing a catalyst for electrolysis comprising:

24. In paragraph 23, A method wherein in the first step, the zinc precursor and the cobalt precursor are used in a weight ratio of 1:

2.

25. In paragraph 23, A method wherein in the second step, the molybdenum precursor and the sulfur precursor are used in a weight ratio of 1:

2.

26. In paragraph 23, In the above first step, the zinc-cobalt double layer hydroxide has a nanowire structure.

27. In paragraph 23, A method wherein the solution containing the zinc precursor and the cobalt precursor in the first step contains ammonium and urea.

28. A water electrolysis catalyst manufactured by any one of the manufacturing methods of Articles 23 to 27, and having a hybrid structure comprising zinc cobalt sulfide and molybdenum disulfide.

29. In paragraph 28, A catalyst for electrolysis comprising a metal foam and a zinc cobalt sulfide and molybdenum disulfide hybrid structure formed on the metal foam.

30. In paragraph 28, The above electrolysis catalyst is a hydrolysis catalyst in which zinc cobalt sulfide and molybdenum disulfide are hetero-bonded.

31. In paragraph 28, The above electrolysis catalyst is MoS2@Zn 0.76 Co 0.24 A catalyst for electrolysis, which is a hybrid structure with an S structural element.

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