KR101952585B1 - Extensive water oxidation to reduction of ultra-durable non-precious electrocatalysts for alkaline water electrolysis - Google Patents

Abstract

The in-situ hybridization of the electrochemical catalyst-current collector is active with a low reaction barrier in water electrolysis and functions as a very stable electrode. It exists in a large amount and Ni ₃ Se ₂ / NF electrodes formed characters of cheap non-noble metal is from 1 100 mA cm voltage of 315 mV (against a reversible hydrogen electrode) at M KOH ^- an oxygen generating an anode current density of ^2. At a constant current density of 100 mA cm ^-2 , the Ni 3 Se 2 / NF electrode shows good OER stability for 285 hours with a slight potential loss of 5.5% in the strongly alkaline electrolyte. Thus, alkaline water electrolysis cells constructed with Ni ₃ Se ₂ / NF and NiCo ₂ S ₄ / NF require 1.58 V to produce a current density of 10 mA cm ^-2 at 500 Mh of continuous operation at 1 M KOH. In alkaline water electrolysis systems, mineral oil water degradation using solar panels can be a promising approach to promote independence from electricity in terms of improving hydrogen fuel economy. Overall, this method is one of the energy-efficient methods to lower the cost of the water separator because it can simplify various processes and equipment.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to the oxidation of a wide range of water for the reduction of high durability noble metal electrochemical catalysts for alkaline water electrolysis,

 Various embodiments of the present invention are directed to an electrode for water electrolysis, a water electrolyzer comprising the same, and a solar-to-hydrogen module comprising the same.

Hydrogen is attracting attention as a future energy source, such as fuel cells, and hydrogen production technology is also attracting attention. Currently, technologies for leading hydrogen production include steam reforming of natural gas, gasification of coal and petroleum coke, and gasification and reforming of heavy oil.

Water electrolysis, one of the hydrogen production technologies, has been known for nearly 200 years but contributes only 4% of the world's hydrogen production. In addition, it has been difficult to mass-produce hydrogen due to the disadvantage of requiring a lot of electricity for water electrolysis or using a noble metal catalyst such as platinum. Water electrolysis works well when using electricity derived from renewable energy sources and is fully sustainable.

Until now, the catalyst preparation process has resulted in high cost for practical applications because of the instability of the coating and the inability to make an efficient electrode-electrical interface at the membrane electrode assembly (MEA).

On the other hand, an electrolyzer combined with a solar cell for solar to hydrogen generation is one of the suitable ways to reduce the cost for water electrolysis. Further, studies are being actively carried out to improve the electrode material and to lower the hydrogen production cost by various simplified processes and equipments.

In various embodiments of the present invention, in order to solve the problem, it is desired to provide a low-cost and high-efficiency electrode. Also, a solar-to-hydrogen module in which a water electrolytic cell composed of such an electrode and a solar cell are combined is provided.

An electrode for water electrolysis according to various embodiments of the present invention comprises: a support; And nickel selenide (Ni ₃ Se ₂ ) formed on the support.

A water electrolyzer according to various embodiments of the present invention includes a cathode comprising a support and a nickel cobalt sulfide (NiCo ₂ S ₄ ) formed on the support; And an anode comprising a support and nickel selenium (Ni ₃ Se ₂ ) formed on the support.

A solar-to-hydrogen module according to various embodiments of the present invention includes a water electrolytic cell including a cathode and an anode; And a solar cell including a cathode terminal and a cathode terminal directly connected to the cathode and the anode, wherein the cathode comprises: a support; And a nickel cobalt sulfide (NiCo ₂ S ₄ ) formed on the support, wherein the anode comprises: a support; And nickel selenide (Ni ₃ Se ₂ ) formed on the support.

The electrode according to various embodiments of the present invention is applicable to an anode that generates oxygen in an alkali electrolyte, has low overvoltage and excellent stability.

According to various embodiments of the present invention, Ni ₃ Se ₂ is directly formed on the surface of the nickel foam as a support. Thus, the catalyst electrode has a lower charge transfer resistance.

According to various embodiments of the present invention, the cost for water electrolysis can be reduced by providing a module for solar to hydrogen generation through an electrolytic cell coupled with a solar cell.

Figure 1 is a schematic diagram of in situ formation of a Ni ₃ Se ₂ / NF electrocatalyst by hydrothermal method.
2A is an XRD graph of Ni ₃ Se ₂ / NF.
Figure 2b shows the crystal structure between nickel and selenium atoms.
2C is a SEM photograph of the Ni ₃ Se ₂ electrode.
Figure 3 shows the surface morphology of a nickel foam and Ni ₃ Se ₂ formed thereon.
4 is an XPS (X-ray photoelectron spectroscopy) graph of Ni ₃ Se ₂ / NF.
Figure 5a shows the OER LSV of Ni ₃ Se ₂ / NF, NiSe / NF, NF and RuO ₂ / GC electrodes in oxygen saturated 1 M KOH.
5B shows the Tafel slope of Ni ₃ Se ₂ / NF, NiSe / NF, NF and RuO ₂ / GC electrodes.
FIG. 5C is a graph showing the continuous durability of the Ni ₃ Se ₂ / NF electrode for 285 hours.
5D is a graph showing the potential shift, the potential loss, and the retention ratio of the Ni ₃ Se ₂ / NF electrode.
5E is a graph of overvoltage shift measurement of a Ni ₃ Se ₂ / NF electrode.
6 is an XRD graph of a Ni ₃ Se ₂ / NF electrode after a 285 hour continuous durability test.
FIG. 7 is a SEM photograph of a Ni ₃ Se ₂ / NF electrode after 285 hours of continuous durability test.
8 is the XPS spectrum of the Ni ₃ Se ₂ / NF electrode after a 285 hour continuous durability test.
Figure 9 is the EIS spectra of a Ni ₃ Se ₂ / NF electrode after a 285 hour continuous durability test.
10 shows the result of ECSA analysis of the Ni ₃ Se ₂ / NF electrode after the 285-hour continuous durability test.
Figure 11 is a Nyquist plot of Ni ₃ Se ₂ / NF electrodes recorded at an open circuit voltage (OCV) and 1.597 V (vs RHE) as ELS spectra.
12A is a photograph of a two-electrode system of an alkaline water electrolyzer.
FIG. 12B shows a case where RuO ₂ / NF is applied as an anode material and Pt / C (40%) / NF is applied as a cathode material (hereinafter referred to as RuO ₂ / NF // Pt / C (40% Cell voltage (iR compensation) of the two-electrode system and the Ni ₃ Se ₂ / NF // NiCo ₂ S ₄ / NF two-electrode system.
12C is a graph for a long term durability test.
13 is a diagram of a solar-to-hydrogen module in which a water electrolyzer and a solar cell are combined.

Hereinafter, various embodiments of the present document will be described with reference to the accompanying drawings. It is to be understood that the embodiments and terminologies used herein are not intended to limit the invention to the particular embodiments described, but to include various modifications, equivalents, and / or alternatives of the embodiments.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention provides an electrode comprising a 3D porous current collector and nickel selenium (Ni ₃ Se ₂ ). The electrodes according to various embodiments of the present invention have low overvoltage and excellent stability.

According to various embodiments of the present invention, nickel selenium (Ni ₃ Se ₂ ) is directly grown on the surface of the support nickel foam. Thus, the catalyst electrode has a lower charge transfer resistance.

According to various embodiments of the present invention, it is possible to provide a water electrolyzer comprising a cathode and an anode. At this time, the cathode may include a support and a nickel cobalt sulfide (NiCo ₂ S ₄ ) formed on the support. The anode may comprise a support and nickel selenium (Ni ₃ Se ₂ ) formed on the support. The support acts as a current collector and the nickel cobalt sulphide (NiCo ₂ S ₄ ) or nickel selenium (Ni ₃ Se ₂ ) can act as a catalyst.

According to various embodiments of the present invention, a solar-to-hydrogen module with a water electrolyzer and a solar cell connected thereto can be provided. In this case, the solar-to-hydrogen module may include a solar cell including a cathode and a cathode terminal directly connected to the cathode and the anode of the water electrolyzer.

Hereinafter, the electrode for water electrolysis of the present invention will be described in more detail with reference to Examples.

Example - Nickel Foam (nickel form, NF Lt; RTI ID = 0.0 > selenium < / RTI & Ni ₃ Se ₂ )

Selenium (Se) powder and ethylenediamine (99%, C ₂ H ₈ N ₂ ) were manufactured by Alfa Aesar. Nickel foam (> 99.99%, 80 μm) was purchased from MTI Korea and used as a support and nickel material.

The nickel foams (1 cm x 1 cm) pieces were washed with 3 M hydrochloric acid, ethanol and deionized water, respectively, in order to dissolve the surface oxidized nickel and expose the nickel metal. Selenium powder (0.022 g) was dispersed in a mixture of ethylenediamine (25 mL) and deionized water (15 mL) by sonication for 30 min. The selenium solution was then transferred to a Teflon container and the washed nickel foam (0.0441 g) was immersed in the solution. The Teflon vessel was then sealed and maintained in a Parr autoclave at 160 DEG C for 25 hours. After 25 hours, a sample of nickel foam (hereinafter referred to as Ni ₃ Se ₂ / NF) with Ni ₃ Se ₂ formed was taken out and washed several times with deionized water to remove the solvent and unreacted selenium. To remove moisture, Ni ₃ Se ₂ / NF was dried under vacuum at 60 ° C overnight.

Comparative Example

Except that NiSe (hereinafter referred to as NiSe / NF) formed on a nickel foam was produced by changing the amount of selenium.

Figure 1 is a schematic diagram of in situ formation of a Ni ₃ Se ₂ / NF electrocatalyst by hydrothermal method. Surface cleaned porous 3D nickel foam (NF) was used as a support as well as a Ni source. Referring to FIG. 1A, the crystal structure indicates dense nickel atoms, and the Ni-Ni bonds in metallic nickel are very short as shown in the figure. To improve the reaction, the selenium powder was dispersed in a mixture of deionized water and ethylenediamine (3: 5) and transferred to a Teflon-lined Parr autoclave.

Referring to FIG. 1B, the nickel foam was immersed in the solution and surrounded by Se element. Referring to FIG. 1C, at 160 DEG C, Ni ions on the NF surface react with selenium ions to form Ni-Se bonds. Specifically, each Ni atom bonds with four Se atoms in the crystal structure. During the 25 hour continuous reaction, all Se ions react with Ni ions and the NF surface is completely converted to Ni ₃ Se ₂ .

As shown in Fig. 1d, the surface Ni reacts with Se and is completely converted to Ni ₃ Se ₂ , which is strongly bound to unreacted Ni atoms. The Ni ₃ Se ₂ crystal structure shows the tetrahedral arrangement of Ni and Se atoms.

2A is an XRD graph of Ni ₃ Se ₂ / NF.

Referring to FIG. 2A, it is shown that a Ni ₃ Se ₂ phase is formed with Rhombohedral crystal structure (JCPS: 01-085-0754). Three strong characteristic peaks at 2θ values of 44.3 ^° , 51.6 ^° and 76.2 ^° are associated with the nickel foam support (JCPDS: 98-004-3397). XRD phase analysis confirms the reaction between selenium and nickel ions on the formation of pure Ni ₃ Se ₂ electrocatalyst in impurity-free nickel foams.

Figure 2b shows the crystal structure between nickel and selenium atoms. Referring to FIG. 2B, there is shown a potential ionic bond between a nickel atomic position and a nickel (blue) and selenium (gold) atom. In the crystal structure, each nickel atom is bonded to four selenium atoms in a tetrahedral environment. 2C is a SEM photograph of the Ni ₃ Se ₂ electrode. Referring to FIG. 2C, it is shown that the nickel foam surface successfully converted to Ni ₃ Se ₂ .

Figure 3 shows the surface morphology of a nickel foam and Ni ₃ Se ₂ formed thereon.

Figure 3a shows a smooth surface of a porous 3D nickel foam. Figures 3b and 3c show a uniform formation of a porous Ni ₃ Se ₂ electrocatalyst having multiple voids and a low magnification image of the electrode surface. FIG. 3D shows a cauliflower shape of an electrocatalyst having a rough surface, as a high magnification image. The size of each shape is ~ 1.5μm and the pore size is ~ 300nm. The rough porous electrode can increase the electrochemical performance of the catalyst due to more active site exposure and electrolyte accessibility. In addition, this can create a good path for draining gas bubbles formed from the electrode surface without physical damage to the electrode catalyst material on the electrode surface. Also, Ni ₃ Se ₂ / NF is more strongly bonded to the support than to Ni and Se ions deposited on the support surface. More specifically, the Se ions can interact with the Ni ions of the support to form a Ni ₃ Se ₂ / NF electrode catalyst. Compared to other forms of electrocatalysts such as nanorods, nanowires, and nanotubes, this form is more stable from chemical and physical disturbances.

4 is an XPS (X-ray photoelectron spectroscopy) graph of Ni ₃ Se ₂ / NF. Various electronic states of Ni and Se elements near the surface of the synthesized Ni ₃ Se ₂ / NF electrocatalyst were further investigated using X-ray photoelectron spectroscopy.

Referring to FIG. 4a, Ni ₃ Ni 2p spectrum of the Se ₂ electrocatalyst is a spin of the two peak shakeup - may be entangled with 2p _3/2 and 2p _1/2 doublets due to orbital coupling. In the peak fit analysis, the binding energy at 854.7 eV for Ni2p _3/2 and 872.1eV Ni2p _1/3 is the spin-orbit characteristics of Ni ^{+ 2.} Ni 2p spectrum is also the elimination of the possible presence of Ni ^{3 +.} It clearly shows that most of Ni exists in the form of Ni ^{2 +} states. The appearance of intense peaks in the Ni 2p spectrum is another evidence for the predominant presence of Ni ^{2 +} in Ni ₃ Se ₂ electrode catalysts.

Figure 4b shows a detailed analysis of the Se 3d high resolution XPS spectrum. In particular, the Ni ₃ Se ₂ Se 3d spectrum may have better fit 3d _5/2 and 3d _3/2 doublet. Specifically, the dual energy separation is ~0.8 V and is perfectly consistent with standard observations. So we check the bivalent state of Se (Se ^2- ) and make one kind of metal-selenide bond (Ni-Se) as possible. From this, it can be seen that the Ni-Se compound was successfully formed in the form of Ni ₃ Se ₂ .

Figure 5a shows the OER LSV of Ni ₃ Se ₂ / NF, NiSe / NF, NF and RuO ₂ / GC electrodes in oxygen saturated 1 M KOH. The oxygen evolution reaction (OER) activity of the electrodes prepared according to the examples was evaluated using a three-electrode system having platinum and saturated calomel electrodes as counter electrodes and reference electrodes, respectively.

Referring to Figure 5a, strong oxidation peaks were found at ~ 1.38 V due to Ni (II) -Ni (III) conversion during electrochemical performance. Surface Ni atoms were partially oxidized to NiOOH on the surface of the Ni ₃ Se ₂ / NF electrode. Interestingly, the oxidation peak is higher than other electrode catalysts and means that many active sites (NiOOH) are formed on the Ni ₃ Se ₂ / NF surface. Oxygen overvoltage measurements at 10 mA cm ^-2 current density were not difficult or precise due to intense Ni oxide [Ni (II) -Ni (III)] peaks at ~ 1.38 V (vs RHE). Therefore, in this experiment, the overvoltage was measured at a high current density of 100 mA cm ^-2 . The results are shown in Table 1 below.

Catalyst OER Overpotential
(mV)
@ 100mVcm ^-2 Tafel Slope
(mV dec ^-1 ) Specific Activity
(mV cm _{( geo )} ^-2 )
@ 1.60V vs RHE Ni ₃ Se ₂ / NF 315 32.3 241.1 NiSe / NF 411 40.3 49.8 RuO ₂ 420 63.2 29.7 NF - 116.9 6.2

Referring to Table 1, the Ni ₃ Se ₂ / NF electrode provides an oxygen emission current density of 100 mA cm ^-2 at 315 mV overvoltage. Overvoltages of 411 mV and 420 mV are required to obtain a current density of 100 mA cm ^-2 for NiSe / NF and RuO ₂ / GC electrodes, respectively, and NF is very low even at 1.7 V vs RHE at 1 M KOH (~ 50 mA cm ^{- 2} ). The specific activity of all electrocatalysts was calculated from the OER curve at 1.60 V vs RHE. Referring to Table 1, the Ni ₃ Se ₂ / NF electrocatalyst exhibited a maximum of 241.1 mA cm (geo) ^-2 , 8 times and 5 times higher than the RuO ₂ / GC and NiSe / NF electrode catalyst, respectively. A significant improvement in the catalytic activity of the Ni ₃ Se ₂ / NF electrode catalyst may be due to an increase in surface area. In addition, the Ni ₃ Se ₂ / NF electrode is activated for the hydrogen evolution reaction and exhibits an initial overvoltage of 150 mV in the same alkaline environment (1 M KOH). That is, it means that the Ni ₃ Se ₂ / NF electrocatalyst has an activity favorable to the total water decomposition.

This comparison shows that the Ni ₃ Se ₂ / NF electrocatalyst exhibits a much lower overvoltage than the more expensive electrode catalyst RuO ₂ / GC, with a difference of ~105 mV at ~100 mc ^-2 at ~ 100 mc ^-2 . Also, NiS / NF, Ni-B / NF, Co 0. ₁₃ Ni _{0 .} Recently reported electrode catalysts such as ₈₇ Se ₂ / Ti mesh require very high overvoltage to reach a current density of 100 mA cm ^-2 . Thus, Ni3Se2 / NF electrodes require very low overvoltage for higher cathode current density.

5B shows the Tafel slope of Ni ₃ Se ₂ / NF, NiSe / NF, NF and RuO ₂ / GC electrodes.

Referring to FIG. 5B, the Ni ₃ Se ₂ / NF electrode exhibits a Tafel slope of 32.3 mVdel ^-1 . However, the Tafel slope values for NiSe / NF and RuO ₂ / GC are 40.3 mVdec ^-1 and 63.2 mVdec ^-1 , respectively. NF showed a very high Tafel slope of 116.9 mVdel-1. Therefore, the Ni ₃ Se ₂ / NF electrode exhibits a very low Tafel gradient compared to other electrode catalysts, and as a result, the Ni ₃ Se ₂ / NF electrode easily has OER dynamics. The Tafel slope can also determine the rate determining step in the OER mechanism.

FIG. 5C is a graph showing the continuous durability of the Ni ₃ Se ₂ / NF electrode for 285 hours. 5D is a graph showing the potential shift, the potential loss, and the retention ratio of the Ni ₃ Se ₂ / NF electrode.

To understand the changes in dislocation, phase and surface morphology, the time durability of Ni ₃ Se ₂ / NF electrodes was evaluated by chronopotentiometry at a current density of 100 mA cm ^-2 . Initially, the Ni ₃ Se ₂ / NF electrode provides an OER current density of 100 mA cm ^-2 at an electrode potential of ~ 1.61 V vs RHE. Specifically, a sharp increase up to ~10 hours occurred at a potential of ~ 1.61V ~ 1.66V, possibly due to the partial wettability of the electrode surface and the new electrode environment. After a certain period of time, however, even after 285 h continuous durability test at 100 mA cm ^-2 , it showed almost stable potential with very small loss. The black graph shows a potential change from ~ 45 mV (50 hours) to ~ 90 mV (285 hours). After 50 to 100 hours, the potential rapidly increases from ~ 45 mV to ~ 57 mV with time. However, after 100 hours, the potential change was negligibly small as compared with the previous step. Over 250 hours, the potential increased sharply within ~ 35 hours from ~ 77 mV to ~ 90 mV. Also, referring to the blue graph, the potential loss was very small at 1% at 50 hours. After 100 hours, the dislocation loss gradually increased to 285 hours. Ultimately, the maximum potential loss was 5.5%, that is, the retention rate was 94.5%. Thus, it showed a potential loss of only 5.5% after a long term durability of 285 hours at a high current density of 100 mA cm < ² >

5E is a graph of overvoltage shift measurement of a Ni ₃ Se ₂ / NF electrode.

Over-voltage shifts were measured before and after the 285-hour test by overlaying the LSV trace to further confirm the stability of the Ni ₃ Se ₂ / NF electrocatalyst after the 285-hour endurance test. The electrode after the test required an additional overvoltage of 54 mV (369 mV) to provide a current density of 100 mA cm ^-2 compared to the overvoltage (315 mV) of the electrode before the test. Therefore, the stability of the Ni ₃ Se ₂ / NF electrode catalyst electrode was confirmed by low overvoltage shift of the LSV measurement.

6 is an XRD graph of a Ni ₃ Se ₂ / NF electrode after a 285 hour continuous durability test. Referring to FIG. 6, it was confirmed that the Ni ₃ Se ₂ phase of the rombhohedral was still maintained even after the 285-hour continuous durability test. The strength of the nickel foam by the nickel phase increased slightly due to small changes in electrode shape.

FIG. 7 is a SEM photograph of a Ni ₃ Se ₂ / NF electrode after 285 hours of continuous durability test. 7A and 7B are low magnification photographs, and c and d are high magnification photographs.

Referring to FIG. 7, it clearly shows the prominent morphological change of the electrode catalyst without peeling off the electrode surface from the cauliflower shape to the small particle clusters.

8 is the XPS spectrum of the Ni ₃ Se ₂ / NF electrode after a 285 hour continuous durability test. Referring to FIG. 8A, a new peak appears at a binding energy of 856.3 and 873.9 eV after the peak fitting analysis because NiOOH is formed on the electrode surface. Similarly, referring to Figure 8b, the Se 3d post-XPS spectrum shows that selenium is the major conversion to selenium oxide.

Figure 9 is the EIS spectra of a Ni ₃ Se ₂ / NF electrode after a 285 hour continuous durability test. Referring to FIG. 9, the EIS result after the durability test is slightly higher than the sample Rct value (3.7?) Before the durability test, with the Rct value of 2.6?.

10 shows the result of ECSA analysis of the Ni ₃ Se ₂ / NF electrode after the 285-hour continuous durability test. Referring to Fig. 10, it can be seen that the electrochemically active surface area calculated after ECSA measurement (3.3 mF cm < ² & gt ^; ) does not greatly change the electrode surface area.

Figure 11 is a Nyquist plot of Ni ₃ Se ₂ / NF electrodes recorded at an open circuit voltage (OCV) and 1.597 V (vs RHE) as ELS spectra.

Referring to FIG. 11A, a Randles equivalent circuit matches the EIS spectrum and is designed to match the electrolyte resistance Rs in the higher frequency range, the charge transfer resistance Rct in the lower frequency range, and the exact double layer capacitance Cdl of the electrode Was used to evaluate the value. In the Z-fitted curves, Rs and Rct values were relatively low, ~ 2 Ω and ~ 1.75 Ω, respectively. Thus, it is evident that the formation of Ni ₃ Se ₂ / NF is more advantageous for electron transfer and can significantly help overcome reaction barriers during OER at 1 M KOH. The electrolyte resistance is also used for iR calibration of all OER linear sweep voltammograms (LSV).

11B is a cyclic voltammogram of a Ni ₃ Se ₂ / NF electrode with a scan rate of 100, 200, 300, 400 and 500 mVs ^-1 at 0.63 V to 0.73 V versus RHE. 11C is a graph of the current density of i _a and i _c at 0.68 V versus RHE. Figures 11B and 11C are graphs for electrochemically active surface aera (ECSA) analysis. ECSA was calculated by measuring the electrical double-layer capacitance (EDLC) of the Ni ₃ Se ₂ / NF electrode at 1 M KOH and is another important evidence of the superior OER activity of the Ni ₃ Se ₂ / NF electrode to be.

Referring to FIG. 11B, the CV curves show perfect rectangular behavior at each scan rate and the existence of double layer capacitance (EDLC) can be confirmed by the high electrochemically active surface area (ECSA) of the electrode. The current density (CV area) of the anode (i _a ) and the cathode (i _c ) linearly increases to 2 mA cm ^-2 from _a low scan rate (100 mV s-1) to a high scan rate (500 mV s- Respectively.

Referring to FIG. 11C, the electrochemical surface area and roughness coefficients of 16.2 cm ² and 90 were in good agreement with the surface morphology shown in the SEM photograph, showing a capacitance value of 3.6 mF cm ^-2 . This high roughness can increase the electrocatalyst and electrolyte interactions. Therefore, it can be seen that the electrode catalyst grown on the 3D nickel foam improves the OER dynamics of the Ni ₃ Se ₂ / NF electrode to provide excellent activity at low voltage.

12A is a photograph of a two-electrode system of an alkaline water electrolyzer. The active area of the exposed electrode in the electrolyte was 1.8 cm ² . Referring to Figure 12a, performance was tested in a 1M KOH environment comprising two electrodes, close to the actual scale for large scale production of pure hydrogen. Ni ₃ Se ₂ / NF is applied as an anode material and NiCo ₂ S ₄ / NF is applied as a cathode material (hereinafter referred to as Ni ₃ Se ₂ / NF // NiCo ₂ S ₄ / NF).

FIG. 12B shows a case where RuO ₂ / NF is applied as an anode material and Pt / C (40%) / NF is applied as a cathode material (hereinafter referred to as RuO ₂ / NF // Pt / C (40% Cell voltage (iR compensation) of the two-electrode system and the Ni ₃ Se ₂ / NF // NiCo ₂ S ₄ / NF two-electrode system. Ni ₃ Se ₂ / NF // The two-electrode system of NiCo ₂ S ₄ / NF requires a voltage of 1.58 V to achieve a current density of 10 mAcm ^-2 , but RuO ₂ / NF // Pt / C (40% ) / NF electrode, a voltage of 1.53 V was required to obtain the same current density. In other words, the Ni ₃ S ₂ / NF // NiCo ₂ S ₄ / NF electrode exhibits similar performance to the much more expensive RuO ₂ / NF // Pt / C (40%) / NF electrode.

12C is a graph for a long term durability test. Referring to FIG. 12C, a current density of 10 mA cm ^-2 was initially obtained at a voltage of 1.76 V, and gradually increased to 1.8 V within 10 hours. It was maintained without significant increase in voltage from 10 hours to 365 hours, and gradually increased to 1.82 V in the 500 hour continuous durability test. Finally, after a 500 hour durability test, only 1.82 V was needed to provide a current density of 10 mA cm ^-2 .

13 is a diagram of a solar-to-hydrogen module in which a water electrolyzer and a solar cell are combined. Water electrolysis using voltage from solar energy is one of the energy-efficient ways to increase hydrogen production. Referring to FIG. 9, the water electrolyzer of the two-electrode system of Ni ₃ Se ₂ / NF // NiCo ₂ S ₄ / NF is directly connected to the anode and cathode terminals of the solar cell (GaAs thin film). For solar to hydrogen generation, a stable potential of 3.65 V was applied to the two-electrode water bath connected to the solar cell. At this potential, it can be seen that oxygen and hydrogen gas are generated continuously in the cathode and the anode, respectively.

The features, structures, effects and the like described in the foregoing embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. Further, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention. It can be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiments may be modified and implemented. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

delete

Claims (9)

A support that is a porous nickel foam; And
Wherein Ni ions on the surface of the support react with selenium ions to form Ni-Se bonds, thereby converting the nickel selenide (Ni ₃ Se ₂ ).


delete The method according to claim 1,
Wherein the support acts as a current collector and the nickel selenide (Ni ₃ Se ₂ ) acts as a catalyst.
A cathode comprising a cathode support and a nickel cobalt sulfide (NiCo ₂ S ₄ ) formed on the cathode support; And
An anode comprising a nickel selenium (Ni ₃ Se ₂ ) modified by the reaction of selenium ions to form an Ni-Se bond, the anode support being a porous nickel foil and the Ni ion on the anode support surface Water electrolyzer.
5. The method of claim 4,
Wherein the cathode support is a porous nickel foam.
5. The method of claim 4,
Wherein the cathode support or the anode support acts as a current collector and the nickel cobalt sulfide (NiCo ₂ S ₄ ) or nickel selenium (Ni ₃ Se ₂ ) acts as a catalyst.
And a solar cell including a cathode and a cathode terminal directly connected to the anode,
The cathode may further comprise:
A cathode support; And
And nickel cobalt sulfide (NiCo ₂ S ₄ ) formed on the cathode support,
The anode,
An anode support that is a porous nickel foam; And
A solar-to-hydrogen module comprising transformed nickel selenium (Ni ₃ Se ₂ ), whereby Ni ions on the anode support surface react with selenium ions to form Ni-Se bonds.
8. The method of claim 7,
Wherein the cathode support is a porous nickel foam. ≪ RTI ID = 0.0 > 8. < / RTI >
8. The method of claim 7,
Wherein the cathode support or the anode support acts as a current collector and the nickel cobalt sulphide (NiCo ₂ S ₄ ) or nickel selenium (Ni ₃ Se ₂ ) acts as a solar- hydrogen module.

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