KR20220127778A - Polymer electrolyte membrane water electrolysis anode and method for preparing the same using IrO₂electrodeposited porous carbon material, polymer electrolyte membrane water electrolysis apparatus and method using the same - Google Patents

Abstract

Provided are an anode for water electrolysis of a polymer electrolyte membrane in which IrO_2 is electrolytically plated on a hydrophilic porous carbon material and manufacturing method thereof, and a device and method for water electrolysis of a polymer electrolyte membrane using the same. Accordingly, as the IrO_2 loading amount used in the anode of water electrolysis of a polymer electrolyte membrane can be lowered, the amount of iridium, which is a precious metal, used can be reduced and excellent current density (excellent water electrolysis performance) can be exhibited. In addition, when applied to the anode of water electrolysis of a polymer electrolyte membrane, carbon corrosion can be reduced while exhibiting good catalytic activity. Moreover, a manufacturing process is very simple compared to the prior art, and a manufacturing cost can be greatly reduced.

Description

Polymer electrolyte membrane water electrolysis anode and method for preparing the same using IrO₂electrodeposited porous carbon material, polymer electrolyte membrane water electrolysis apparatus and method using the same}

The present specification describes an anode for water electrolysis of a polymer electrolyte membrane using a porous carbon material electrolytically plated with iridium oxide, a manufacturing method thereof, and an apparatus and method for water electrolysis of a polymer electrolyte membrane using the same.

With global climate change and the depletion of fossil fuels, the transition to a hydrogen economy has recently received a lot of attention. Hydrogen has many advantages as an alternative energy, does not produce environmental pollutants, and can be stored for a long time without significant loss.

Hydrogen is currently produced by steam reforming of natural gas, but a significant amount of CO ₂ is also produced here. As a sustainable and environmentally friendly alternative, water electrolysis combined with a renewable energy source such as wind or solar power is expected as a realistic alternative for hydrogen production.

However, the cost of hydrogen production by water electrolysis is 2-3 times more expensive compared to the reforming process. Currently, about 96% of hydrogen is produced by fossil fuel-based technologies (natural gas reforming 48%, partial oxidation 30%, coal gasification (18%)), and only 4% of total hydrogen production is produced by electrolysis.

Among the various types of water electrolysis technology, the polymer electrolyte membrane water electrolysis (PEMWE) method has high purity of produced hydrogen (about 99.99% or more), high production rate, small system volume, and ecological There are many advantages, such as the use of harmless neutral water.

In a typical PEMWE, iridium or ruthenium-based electrocatalysts are used for the oxygen evolution reaction (OER) at the anode (1.0 - 5.0 mg/cm ² ) and at the cathode Platinum catalysts are used for the hydrogen evolution reaction (HER) (0.4 - 0.8 mg/cm ² ), and these noble metal-based electrocatalysts are one of the reasons for the high system cost of PEMWE. There is a need to lower the manufacturing cost.

However, in the conventional spraying method [spraying method (eg, non-patent document 4, 6)] and sputtering method [membrane electrode assembly (MEA) using a PEMWE membrane prepared by (eg, non-patent document 7), Ir or IrO ₂ As the loading decreases, the single cell performance also decreases significantly, so Ir or IrO ₂ Reducing the loading is also difficult.

For example, in Non-Patent Document 6, IrO ₂ is loaded using a spraying method on the membrane during MEA production, and IrO ₂ loading is 3.0 mg/cm ² at 0.5 When reducing to mg/cm ² , the current density at 1.6 V was 1.33 to 0.67 A/cm ² is reported to decrease.

A. Marshall, S. Sunde, M. Tsypkin, R. Tunold, International Journal of Hydrogen Energy 32 (2007) 2320-2324. S. Song, H. Zhang, X. Ma, Z. Shao, R.T. Baker, B. Yi, International Journal of Hydrogen Energy 33 (2008) 4955-4961. J. Cheng, H. Zhang, G. Chen, Y. Zhang, Electrochimica Acta 54 (2009) 6250-6256. L. Ma, S. Sui, Y. Zhai, International Journal of Hydrogen Energy 34 (2009) 678-684. G. Wei, Y. Wang, C. Huang, Q. Gao, Z. Wang, L. Xu, International Journal of Hydrogen Energy 35 (2010) 3951-3957. H. Su, B.J. Bladergroen, V. Linkov, S. Pasupati, S. Ji, International Journal of Hydrogen Energy 36 (2011) 15081-15088. E. Slavcheva, I. Radev, S. Bliznakov, G. Topalov, P. Andreev, E. Budevski, Electrochimica Acta 52 (2007) 3889-3894. V. Antonucci, A. Di Blasi, V. Baglio, R. Ornelas, F. Matteucci, J. Ledesma-Garcia, L. G. Arriaga, A. S. Arico, Electrochimica Acta 53 (2008) 7350-7356. Wu Xu, Keith Scotta, Suddhasatwa Basu, Journal of Power Sources 196 (2011) 8918-8924. V. Baglio, R. Ornelas, F. Matteucci, F. Martina, G. Ciccarella, I. Zama, L. G. Arriaga, V. Antonucci, A. S. Arico FUEL CELLS 09, 2009, No. 3, 247-252. Anita Skulimowska, Marc Dupont, Marta Zaton, Svein Sunde, Luca Merlo, Deborah J. Jones, Jacques Roziere, International Journal of Hydrogen Energy 39 (2014) 6307-6316. David Aili, Martin Kalmar Hansen, Chao Pan, Qingfeng Li, Erik Christensen, Jens Oluf Jensen, Niels J. Bjerrum, International Journal of Hydrogen Energy 36 (2011) 6985-6993. Varagunapandiyan Natarajan, Suddhasatwa Basu, Keith Scott, International Journal of Hydrogen Energy 38 (2013) 16623-16630. Martin Kalmar Hansen, David Aili, Erik Christensen, Chao Pan, Soren Eriksen, Jens Oluf Jensen, Jens H. von Barner, Qingfeng Li, Niels J. Bjerrum, International Journal of Hydrogen Energy 37 (2012) 10992-11000.

In embodiments of the present invention, in one aspect, a polymer electrolyte membrane capable of achieving excellent current density (excellent water electrolysis performance) while reducing the IrO ₂ loading amount used for the anode of the polymer electrolyte membrane water electrolysis Provided are an anode for water electrolysis, a method for manufacturing the same, and an apparatus and method for water electrolysis using the same.

In embodiments of the present invention, in another aspect, an anode for water electrolysis of a polymer electrolyte membrane capable of reducing carbon corrosion and having good catalytic activity when applied to the anode of water electrolysis of a polymer electrolyte membrane, and a method for manufacturing the same, using the same A polymer electrolyte membrane water electrolysis apparatus and method are provided.

In embodiments of the present invention, in another aspect, an anode for water electrolysis of a polymer electrolyte membrane and a manufacturing method thereof, a polymer electrolyte membrane water electrolysis device using the same, and the manufacturing process is simple and the manufacturing cost can be greatly reduced provide a way

In embodiments of the present invention, IrO ₂ in the hydrophilic porous carbon material It provides an anode for water electrolysis of a polymer electrolyte membrane, characterized in that provided, in particular, provided by electrolytic plating.

In embodiments of the present invention, also in the hydrophilic porous carbon material IrO ₂ It provides a method for producing an anode for water electrolysis of a polymer electrolyte membrane, characterized in that it comprises the step of electrolytic plating.

In embodiments of the present invention, it also includes a polymer electrolyte membrane, a cathode formed on one side of the membrane, and an anode formed on the other side of the membrane, wherein the anode is IrO ₂ on a hydrophilic porous carbon material. It provides a single cell water electrolysis polymer electrolyte membrane, characterized in that the electrolytic plating, and a device comprising the same.

Embodiments of the present invention also provide a polymer electrolyte membrane water electrolysis method using the polymer electrolyte membrane water electrolysis device.

According to embodiments of the present invention, the amount of IrO ₂ used in the anode of the polymer electrolyte membrane water electrolysis can be lowered, so that the amount of use of iridium, a precious metal, can be reduced while providing excellent current density (excellent water electrolysis performance) can indicate In addition, when applied to the anode of the polymer electrolyte membrane water electrolysis, it can exhibit good catalytic activity and reduce carbon corrosion. In addition, the manufacturing process is very simple compared to the prior art, and the manufacturing cost can be greatly reduced.

1 is a linear potential scanning (LSV) curve for a CP electrode in an electrolytic plating solution (iridium chloride hydrate 0.1M, oxalic acid 0.04M, hydrogen peroxide 0.01M) and pH-adjusted water in an embodiment of the present invention [Fig. 1a] and a graph showing the current density [Fig. 1b] during electrolytic plating under constant potentials of 0.6 V, 0.7 V, 0.8 V and 0.9 V.
2 is an SEM image of a bare carbon paper that is not plated in Examples and Comparative Examples of the present invention [FIG. 2a], an SEM image of an IrO ₂ /CP electrode prepared by electroplating according to the electrolytic plating potential; [Fig. 2b (0.6V), Fig. 2c (0.7V), Fig. 2d (0.8V), Fig. 2e (0.9V)]. For reference, the electrolytic plating time for the IrO ₂ /CP electrode is 60 seconds.
3 is a graph showing Ir4f XPS (X-ray photoelectron spectra) of IrO ₂ electrolytically plated on carbon paper in an embodiment of the present invention.
FIG. 4 is a function of electric charge for electroplating and current density during electroplating at 0.7 V for various electrolytic plating times from 1 minute to 30 minutes [ FIG. 4 a ] in an embodiment of the present invention; FIG. for electrodeposition) as a graph showing the amount of IrO ₂ [Fig. 4b].
5 is IrO ₂ /CP prepared by electroplating at 0.7 V for 1 minute [FIG. 5A], 10 minutes [FIG. 5B], 20 minutes [FIG. 5C], 30 minutes [FIG. 5D] in an embodiment of the present invention It shows the SEM image of the electrode.
Figure 6 is, in an embodiment of the present invention, IrO ₂ /CP electrode electroplated at 0.7 V, IrO ₂ Cyclic voltammogram curves [Fig. 6a] and Ir(V) peak current decrease [Fig. 6b] are shown as a function of loading amount (expressed as electroplating time).
7 shows the polarization curves of a PEMWE single cell having an IrO ₂ /CP anode in an embodiment of the present invention ( E _dep = 0.7 V; t _dep = 1 ~ 30 min).
8 is a current density at 1.45V (closed circle) and 1.6V (open circle) in an embodiment of the present invention [ FIG. 8a ] and activity per mass as a function of anode loading at 1.6V (mass) activity) [Fig. 8b]. In FIG. 8B , data of the related art are also displayed.
9 is a graph showing the high-temperature water electrolysis performance of Examples and Comparative Examples in Experiment 2; The X-axis represents current density (unit Acm ^{- 2} ) and the Y-axis represents voltage (Voltage: unit V).
10 is a graph showing the results of Table 2 in Experiment 2; In FIG. 10 , the X axis represents the loading amount (unit: mg cm ⁻² ), and the Y axis represents the current density at 1.6V (unit: ^A cm ⁻² ). In FIG. 10, data of the related art are also displayed.

Exemplary embodiments of the present invention are detailed below.

The present inventors, as an anode material of a polymer electrolyte membrane water electrolysis device, IrO ₂ on a porous carbon material By using a material formed through the formation of, in particular, electrolytic plating, IrO ₂ It was confirmed that it was possible to achieve excellent current density (excellent water electrolysis performance) while significantly reducing the content of iridium, a precious metal, by reducing the loading amount.

Accordingly, in embodiments of the present invention, in one aspect, a hydrophilic porous carbon material is provided with IrO ₂ (present), in particular, an anode for water electrolysis of a polymer electrolyte membrane, characterized in that it is provided (present) by an electrolytic plating (electrodeposition) provides

IrO ₂ in hydrophilic porous carbon material IrO ₂ on the corresponding porous carbon material if it is electrolytically plated It has a characteristic (or morphology) or structure of electrolytic plating that is distinct from the case of using other manufacturing methods (eg, a spray method or a decal method) for formation.

That is, IrO ₂ in the porous carbon material When formed by electroplating, IrO ₂ IrO ₂ on the surface of the porous carbon material as particles (eg spherical particles) begin to form. Particles are generated and grown in the form of a film, so that the surface of the porous carbon material is IrO ₂ layer (or IrO ₂ It can also be expressed as a film) covered with (ie, surface coating), and the IrO ₂ particles further formed by electroplating are the corresponding IrO ₂ It has a form (structure) attached (or deposited) to the layer.

Therefore, in an exemplary embodiment, the anode for water electrolysis of a polymer electrolyte membrane prepared by electrolytic plating has a carbon material surface of IrO ₂ covered with a layer, the corresponding IrO ₂ IrO ₂ in the layer It can be expressed as a structure in which particles are attached (or deposited).

In an exemplary embodiment, the IrO ₂ The thickness of the layer is 0.01-1 μm, preferably 10-210 nm, more preferably 70-210 nm, IrO ₂ The particle size is 0.1 to 3 μm, preferably 0.25 to 1.2 μm.

In an exemplary embodiment, IrO ₂ on the porous carbon material The loading amount may be 0.01 to 1.00 mg cm ^-2 or 0.01 to 0.54 mg cm ^-2 .

On the other hand, in order to increase the catalytically active surface area, a porous material is used as the carbon material. In addition, since an aqueous solution-based electrolytic plating process is applied, the porous carbon material has hydrophilicity. In an exemplary embodiment, the porous carbon material is carbon paper, preferably composed of carbon fibers.

In an exemplary embodiment, the IrO ₂ The layer covers the surface of the porous carbon material, but preferably covers such that the porous carbon material is not exposed. That is, the preferred anode structure is the IrO ₂ surface of the hydrophilic porous carbon material. It is a structure that is covered by a layer but has no carbon exposure free structure.

In an exemplary embodiment, the IrO ₂ the layer covers the surface of the porous carbon material, and IrO ₂ The layer preferably has a crack free structure. That is, the preferred anode structure is the IrO ₂ surface of the hydrophilic porous carbon material. layer to cover but IrO ₂ The layer is a crack free structure.

In embodiments of the present invention, in another aspect, the hydrophilic porous carbon material IrO ₂ It provides a method for producing an anode for water electrolysis of a polymer electrolyte membrane, characterized in that it comprises the step of electrolytic plating.

In an exemplary embodiment, when electrolytic plating on the porous carbon material, at least one of a plating voltage and a plating time may be adjusted.

In an exemplary embodiment, the plating voltage is preferably 0.6 to 0.9 V. In addition, the plating time is preferably 1 to 30 minutes.

On the other hand, in embodiments of the present invention, in another aspect, a polymer electrolyte membrane, a cathode formed on one side of the membrane, and an anode formed on the other side of the membrane, wherein the anode is IrO ₂ on a porous carbon material It provides a polymer electrolyte membrane water electrolysis device, characterized in that provided.

In an exemplary embodiment, an anode made of the IrO ₂ electroplated porous carbon material (eg, carbon paper as described above) is formed on one side of a polymer electrolyte membrane (eg, Nafion membrane) and a cathode (commercial cathode) on the other side For example, a membrane electrode assembly is prepared by forming Pt/C) formed by spraying platinum on carbon paper, a bipolar plate is coupled thereto, and an end plate is mounted to a polymer electrolyte membrane water electrolysis device (cell) can be produced.

In an exemplary embodiment, the polymer electrolyte membrane water electrolysis device has a small catalytic amount (small IrO ₂ loading) can achieve high performance.

For example, IrO ₂ When the loading amount is 0.01 to 1.00 mg cm ^-2 preferably 0.01 ^to 0.54 mg cm ^-2 , 0.33 at 1.6 V, 90° C., 1.0 to 700 bar (or, for example, 1.0 to 50 bar or 1.0 to 30 bar or 1.0 to 2.5 bar) It can represent a current density of A cm ^-2 to 1.6 A cm ^-2 . In this case, as the cathode and the membrane, a conventional cathode (eg, Pt/C: the cathode catalytic amount may also be a conventional catalytic amount, eg, 0.4 mg/cm ² ) and a membrane (Nafion) may be used.

or, anode IrO ₂ When the loading amount is 0.01 to 1.00 mg cm ^-2 preferably 0.01 to 0.54 mg cm ^-2 , at 1.6 V, 120° C., 1.0 to 700 bar (or, for example, 1.0 to 50 bar or 1.0 to 30 bar or 1.0 to 2.5 bar) It can represent a current density of 1.5 A cm ^-2 to 2.5 A cm ^-2 . In this case, as the cathode and the membrane, a conventional cathode (eg, Pt/C: the cathode catalytic amount may also be a conventional catalytic amount, eg, 0.4 mg/cm ² ) and a membrane (Nafion) may be used.

As such, the characteristic that the anode of the embodiments of the present invention exhibits high performance even with a small catalytic amount can be expressed at various temperatures of a lower low temperature or a higher high temperature as well as the above temperature.

In an exemplary embodiment, the polymer electrolyte membrane water electrolysis device is anode IrO ₂ When the loading amount is 0.01 ~ 1.00 mg cm ^-2 preferably 0.01 ^~ 0.54 mg cm ^-2 , 1.6 V, 90 ℃, 1.0 ~ 700 bar (or, for example, may exhibit a mass activity (MA) of 74.7 to 0.64 A mg ^-1 at 1.0 to 50 bar or 1.0 to 30 bar or 1.0 to 2.5 bar). In this case, as the cathode and the membrane, a conventional cathode (eg, Pt/C: the cathode catalytic amount may also be a conventional catalytic amount, eg, 0.4 mg/cm ² ) and a membrane (Nafion) may be used.

In addition, the anode IrO ₂ When the loading amount is 0.01 to 1.00 mg cm ^-2 preferably 0.01 to 0.54 mg cm ^-2 , 1.6 V, 120° C., 1.0 bar to 700 bar (or, for example, 1.0 to 50 bar or 1.0 to 30 bar or 1.0 to 2.5 bar) can exhibit an activity per mass of 3.2 A mg ^-1 to 117 A mg ^-1 in In this case, as the cathode and the membrane, a conventional cathode (eg, Pt/C: the cathode catalytic amount may also be a conventional catalytic amount, eg, 0.4 mg/cm ² ) and a membrane (Nafion) may be used.

In addition, in embodiments of the present invention, in another aspect, there is provided a method for electrolysis of water for a polymer electrolyte membrane using the water electrolysis device for a polymer electrolyte membrane.

Hereinafter, it will be described in more detail through examples and experiments, but the present invention is not limited to the contents described below.

[Experiment 1]

anode electroplating ( anodic electrodeposition )through IrO ₂ / CP Produce

To prepare an electrolytic plating solution, 0.1M iridium chloride hydrate [iridium chloride hydrate (IrCl ₄ ·H ₂ O)] was dissolved in deionized water (DI water) and stirred/mixed in a magnetic stirrer for 30 minutes. Then oxalic acid ((COOH) ₂ ·2H ₂ O: 5 g L ^-1 ) and hydrogen peroxide (35% H ₂ O ₂ : 10 g L ^-1 ) were added, and the resulting solution was mixed for 10 minutes. After adjusting the pH of the solution to 10.5 by adding anhydrous potassium carbonate, the electrodeposition solution was stirred for 3 days to be stabilized under stirring.

An anodic electrodeposition was performed using a three-electrode electrochemical cell. In this tripolar electrochemical cell, a SIGNADUR® glassy carbon rod electrode (diameter: 4 mm, HTW Germany) and a saturated caramel electrode (SCE, Hanna instruments Ltd.) were used as counter and reference electrodes, respectively. became A porous carbon material, Carbon Paper (CP) (thickness: 280 um, TGPH-090, Toray Inc.) was placed on the bottom of the electrolytic plating cell.

A plating potential was applied on the carbon paper through an aluminum foil with a potentiostat instrument (AUT302N, AUTO LAB Ltd.). Linear sweep voltammetry (LSV) was performed in the plating solution in the range of 0.2V to 1.4V, and the scan rate was 50 mV s ⁻¹ . IrO ₂ Electrolytic plating was performed for various plating times (1 to 30 min) by applying a constant potential (0.6 V to 0.9 V).

IrO ₂ / CP Electrode Characterization

Cyclic voltammetry (CV) at a scan rate of 5 mV s ^-1 in the range of -0.5V to 1.5V in 0.1M HClO ₄ solution [Cyclic voltammetry (CV)] (AUT302N, AUTO LAB Ltd.) was performed.

The morphology and composition of the IrO ₂ /CP electrode were analyzed by scanning electron microscopy (SEM, S-4100, Hitachi Ltd.) and inductively coupled plasma mass spectrometry (ICP-MS, iCAP 6300 series, Thermo Ltd)], respectively. In addition, the composition of deposits was analyzed by X-ray photoelectron spectroscopy (XPS, PHI 5000 VersaProbe, Ulvac-PHI Ltd.) using Al Kα (1486.6 eV) radiation.

IrO ₂ / CP using an electrode PEMWE single cell test

IrO ₂ /CP anode and Pt/C cathode with GDL (thickness: 280 um, 5% PTFE, 10 BC, SGL group) were placed on both sides of a Nafion 212 membrane (thickness: 50 um, DuPont co.). Polyelectrolyte membrane water electrolysis (PEMWE) single cells were fabricated.

Pt/C cathodes were prepared by spraying catalyst ink on 10 BC (SGL carbon Ltd.). The catalyst ink was prepared by mixing 46.3% Pt/C (TKK) and deionized water, and adding isopropanol alcohol and 5wt% Nafion ionomer (DuPont co.).

The active area was 4 cm ² , and the Pt loading on the cathode side was fixed at 0.4 mg cm ^-2 . After cell combination, the cell temperature was increased to 90° C. and the polarization curve for water electrolysis was measured (HCP-803, Biologics Ltd.). Pre-heated deionized water was injected into the anode side (15 mL min ⁻¹ ), and the current was stabilized at various cell potentials from 1.35V to 2.0V (0.05V interval).

Results and discussion

1 is a linear potential scanning (LSV) curve [Fig. 1a] and a graph showing the current density [Fig. 1b] during electrolytic plating under constant potentials of 0.6 V, 0.7 V, 0.8 V and 0.9 V.

Referring to FIG. 1a, when the electrode potential was anodically swept toward the anode at 0 V (scan speed: 50 mV s ^{−1 )} , the anode current shown at about 0.3 V was polarized and gradually decreased, and at about 0.8 V increased rapidly. In an electrolytic plating solution, the anode current is due to electrochemical oxidation of a ligand in an Ir complex compound. Accordingly, CO ₂ and IrO ₂ are formed, and OER (oxygen evolution reaction, hereinafter may be referred to as OER) of the electrolytically plated IrO ₂ appears. For water with a similar pH (pH=10.5), no significant current was observed.

For reference, Scheme 1 below shows CO ₂ and IrO ₂ during electroplating represents a formation reaction.

[Scheme 1]

[Ir(COO) ₂ (OH) ₄ ] ^2- -> IrO ₂ + 2CO ₂ + 2H ₂ O + 2e ^-

Anode electroplating (anodic electrodeposition) was performed for 60 seconds at various electrolytic plating potentials [( E _dep ) (0.6 ~ 0.9 V)].

As shown in FIG. 1B , at more positive potentials (ie, greater anode over potential) the current density decreased slowly: after 60 seconds the current density was 0.2 mA cm ⁻² (0.6 V) -> 1.2 mA cm ^-2 (0.7 V) -> 2.5 mA cm ^-2 (0.8 V) -> 3.8 mA cm ^-2 (0.9 V). However, while oxygen evolution also occurred in the corresponding potential range, the current density (or anodic charge) at each plating potential was not directly correlated with the amount of IrO ₂ .

When OER is also significant, it is expected that the generated oxygen bubbles may block the surface of the electrolytically plated IrO ₂ and even physically separate from the IrO ₂ thin film.

2 is an SEM image of an unplated bare carbon paper (comparative example) in Examples and Comparative Examples of the present invention [Fig. 2a], IrO ₂ /CP prepared by electroplating according to the electrolytic plating potential SEM images of the electrodes [Fig. 2b (0.6V), Fig. 2c (0.7V), Fig. 2d (0.8V), Fig. 2e (0.9V)]. For reference, the electrolytic plating time for the IrO ₂ /CP electrode is 60 seconds.

Referring to FIG. 2 , compared to the initial surface morphology of CP (see FIG. 2a ), morphological changes at 0.6V plating potential were not significant (see FIG. 2b ), and a small number of IrO ₂ Only adsorbed particles were observed. In this regard, if, for example, a spray method is used, the already prepared IrO ₂ Although it is a method in which the particles are dispersed, when the plating method is used, IrO ₂ is separated from the plating solution at a specific potential and generated as adsorbed particles on the surface of the porous carbon material. will achieve

When the electroplating potential increases to 0.7 V (Fig. 2c), IrO ₂ The plating amount also increased significantly, which coincides with a significant increase in current when the plating potential increased from 0.6V to 0.7V. In the case of an anode potential of 0.8V ( FIG. 2d ), the morphology of the IrO ₂ cover portion was similar to that of 0.7 V, but the electrolytically plated IrO ₂ A large number of cracks were observed in the layer. Although the overall current density was the highest, when the plating potential was increased to 0.9 V, IrO ₂ The surface coverage of the particles was almost reduced (see Fig. 2e). This means that the IrO ₂ plating was almost interrupted by the rapid oxygen evolution. That is, the IrO ₂ plating reaction and the oxygen evolution reaction occur together. When the potential is increased to 0.9 V, both reactions are accelerated, but the oxygen evolution reaction is more rapidly accelerated. Accordingly, the generation of oxygen bubbles becomes very intense, and IrO ₂ blocks the surface to be plated, and also applies a physical impact to the already plated IrO ₂ , which is thought to occur in two phenomena of separation from the electrode.

On the other hand, the reason why the total current density is highest here is that the side reaction OER starts from about 0.61V (based on pH 10.5) and this reaction increases as the voltage increases. This is because the current density increased.

For the sample prepared by electroplating at 0.7V for 5 minutes, XPS analysis was performed, and the binding energy region of Ir4f is shown in FIG. 3 .

3 is a graph showing Ir4f XPS (X-ray photoelectron spectra) of IrO ₂ electrolytically plated on carbon paper in an embodiment of the present invention.

Major peaks were observed around binding energies of 65.4 eV and 62.5 eV, assigned to 4f _{5 /2} and 4f _{7 /2} , respectively. From the peak position, it was confirmed that the plating produced by the electrolytic plating was IrO ₂ . For reference, Ir4f _{7 /2} of IrO ₂ appears at 62.0 ~ 63.7 eV, and Ir metal appears at 60.6 eV and 61.0 eV.

E _dep was fixed at 0.7V, and the effect according to the plating time ( t _dep ) was observed (1 min to 30 min).

FIG. 4 is a function of electric charge for electroplating and current density during electroplating at 0.7 V for various electrolytic plating times from 1 minute to 30 minutes [ FIG. 4 a ] in an embodiment of the present invention; FIG. for electrodeposition) as a graph showing the amount of IrO ₂ [Fig. 4b].

Referring to Figure 4a, it is shown that the electrolytic plating can be regenerated. The anodic current density initially increased and stabilized at about 1.5 mA cm ^-2 after 5 minutes.

The amount of catalyst plated on CP during various plating times was analyzed by ICP, and the corresponding IrO ₂ loading was plotted as a function of integrated electric charge density (see FIG. 4b ).

As the plating time increased, the loading amount increased almost linearly, reaching 0.541 mg cm ⁻² ( t _dep = 30 min).

The anode current was used only to form IrO ₂ , and the IrO ₂ loading slope with respect to electric charge (electric charge) (slope in IrO ₂ ) loading vs. electric charge) was expected ^to be about 0.181 C mg ^-1 .

When the experimental data points were analyzed through linear regression, the slope value was 0.181 mg C ⁻¹ , indicating that the apparent coulombic efficiency of IrO ₂ plating was about 15.6%. This indicates that oxygen evolution is significant at 0.7V. In addition, it indicates that the electrolytically plated IrO ₂ according to the charge consumption can be separated, especially in the case of severe oxygen evolution.

Figure 5 shows the morphology of the IrO ₂ /CP electrode electrolytically plated for various plating times in an embodiment of the present invention, at 0.7 V for 1 minute [Figure 5a], 10 minutes [Figure 5b], 20 minutes [ Figure 5c], 30 minutes [Figure 5d] shows the SEM image of the IrO ₂ /CP electrode prepared by electroplating. After the electrolytic plating was performed for 1 minute, IrO ₂ plating in the form of a film with a small number of particles was observed. When the electrolytic plating time was increased to 10 minutes, a large number of spherical particles were formed. This means that the surface area of IrO ₂ increased. As the plating time increased, the particle size gradually increased from about 0.7 μm ( t _dep = 10 min) to 1.7 μm ( t _dep = 30 min), and many cracks were formed to expose the carbon surface.

Figure 6 is, in an embodiment of the present invention, IrO ₂ /CP electrode electroplated at 0.7 V, IrO ₂ Cyclic voltammogram [Fig. 6a] and Ir(V) peak current decrease [Fig. 6b] are shown as a function of loading amount (expressed as electroplating time).

Specifically, FIG. 6a shows a CV curve of an IrO ₂ /CP electrode in a 0.1 M HClO ₄ solution. smallest IrO ₂ For the sample with loading ( t _dep = 1 min), anode (0.8 V and 1.15 V) and cathodic (0.75 V) peaks for the Ir(III)/Ir(IV) redox were clearly observed (Fig. 6a, inset). Regarding the Ir(IV)/Ir(V) redox, which activates only for surface atoms, the cathode peak was 1.35V. However, the corresponding anode peak overlapped significantly with the OER peak. Therefore, the intensity of the cathode peak at 1.3~1.1V is IrO ₂ was used to measure the change in the active area (see Fig. 6b). The cathode current density increased linearly with IrO ₂ loading for plating times up to 10 minutes.

However, when additional loading of IrO ₂ was performed ( t _dep : 20 min and 30 min), the increase in peak current density was slowed, which, as expected from the large particle size on the SEM image, of IrO ₂ indicates less use. It should be noted that when the cathode peaks overlap ( t _dep = 20 min and 30 min), the measured peak current is higher than the actual current for Ir(IV)/Ir(V). Moreover, IrO ₂ /CP samples with t _dep of 20 min and 30 min showed that the cathode peak potential shifted in the negative direction. This means that there is a stronger overlap with the bulk decrease from Ir(IV) to Ir(III) as the particle size increases.

A single cell was fabricated using an IrO ₂ /CP electrode with various IrO ₂ loadings as an anode, and water electrolysis performance was measured.

7 shows the polarization curves of a PEMWE single cell having an IrO ₂ /CP anode in an embodiment of the present invention ( E _dep = 0.7 V; t _dep = 1 ~ 30 min).

For all cells, the cathode was prepared by spraying catalyst ink (commercial Pt/C and ionomer) onto the CP. As the plating time increased to 10 min, the current density gradually improved, which is thought to be due to the higher catalytic activity for the oxygen evolution reaction (see Fig. 7). IrO ₂ When the loading amount further increased ( t _dep > 10 min), the current density at low cell voltages (< 1.5 V) still increased. However, the performance at typical operating voltages (1.8 - 2.0 V) was rather reduced.

8 is a current density at 1.45V (closed circle) and 1.6V (open circle) in an embodiment of the present invention [ FIG. 8a ] and activity per mass as a function of anode loading at 1.6V (mass) activity) [Fig. 8b].

Referring first to FIG. 8A, current densities at 1.45 V and 1.60 V are shown, where 1.45 V is a region mainly determined by activation overpotential, and 1.6 V corresponds to a practical operating voltage.

In addition, it can be seen that the low overpotential performance increases rapidly with increasing the loading amount (increasing the plating time to 5 min). However, when the plating time was longer than 5 minutes (ie, when the loading amount was increased), the degree of performance improvement was relatively small. This is, IrO ₂ It means less use. The current density at 1.6 V showed a maximum at an IrO ₂ loading of 0.1 mg cm ^-2 ( t _dep = 10 min).

When the plating time is greater than 10 min, IrO ₂ It appears that the carbon substrates exposed between the platings degrade at high operating voltages. This effect of carbon corrosion could be observed more clearly in the case of a single cell with the smallest IrO ₂ loading ( t _dep = 1 min). Therefore, it can be concluded that preventing carbon exposure with crack formation at low or also high loading of IrO ₂ is very important to obtain high cell performance with good catalytic activity and low carbon corrosion.

Contrast with previous literature results

On the other hand, IrO ₂ [Non-Patent Documents 1, 2, 3, 6, 7] and Iridium Black [Non-Patent Documents 2, 4, 5] In comparison with the results of prior literature reports on anodes, the electrolytically plated IrO of this embodiment ₂ The PEMWE performance of the /CP electrode was evaluated and the results are shown in Table 1. For reference, the values in parentheses in the table below mean anode loading (anode portion and current density portion below) or cathode loading (cathode portion below), and the unit is mg cm ^{- 2} .

MEA manufacturing method anode cathode membrane Temperature (℃) Current density at 1.6V
(A cm ^-2 ) non-patent
Document 1 spray method
(Spraying) IrO ₂ (2.0) Pt/C (0.4) N115 80 0.75 Non-patent document 2 spray method
(Spraying) Ir, IrO ₂ (3.0) Pt/C (0.5) N112 80 0.52 non-patent
Document 3 spray method
(Spraying) IrO ₂ (1.5) Pt/C (0.5) N1035 80 0.68 Non-patent document 4 brush method
(Brushing) Ir (1.5) Pt (1.0) N112 80 0.5 Non-patent document 5 decal method
(Decal) Ir (3.8) Pt (2.3) N112 60 0.25 non-patent
Literature 6 spray method
(Spraying) IrO ₂ (0.5~4.0) Pt/C (0.5) N212 80 1.32
(3.0) Non-patent document 7 sputtering method
(Sputtering) IrO ₂ (0.2) Pt/C (N.A.) N117 80 0.3 Example electroplating method
(Electrodeposition) IrO _{2 /} /CP
(0.01~0.54) Pt/C (0.4) N212 90 1.01 (0.1)

For reference, briefly describing the methods listed in the table above, the spray method is a method of depositing a catalyst used as an electrode in the form of a slurry and spraying it on a film or GDL through a spray gun, and the brush method is a method of depositing the prepared slurry using a brush. This is a method of depositing on a film or GDL. The decal method is a method of depositing the prepared slurry on the material to be transferred (usually Teflon or Kapton material) with a blade and then hot pressing it on a film or GDL to deposit it. The sputtering method is a method in which ionized argon or the like is collided with a target using plasma in a vacuum chamber, and atoms ejected by the collision are deposited on a substrate.

The prior literature reports current densities of 0.25-1.32 A cm ^-2 at 1.6V for the case of high Ir or IrO ₂ loading ⁽ 1.5-3.0 mg cm ^-2 ).

In contrast, in embodiments of the present invention, IrO ₂ Although the loading was greatly reduced to 0.1 mg cm ^-2 , the PEMWE performance (1.01 A cm ^-2 at 1.6 V) of the electroplated IrO ₂ /CP was very good, which is a promising result. That is, the PEMWE performance achievable in the case of a significantly higher anode loading (> 1.5 mg cm ^{−2 )} in the prior art can be achieved at a significantly lower loading level.

Meanwhile, the current density at 1.6 V was divided according to the anode loading and the resulting mass activity (MA) is shown in FIG. 8B . In FIG. 8b, the activity per mass of each anode of Non-Patent Documents 1 to 7 shown in the table is also displayed. In the case of Non-Patent Document 2, the case of using Ir as the anode is indicated by a black square, and the case of using IrO ₂ as the anode is indicated by a white square.

In the case of conventional documents, the anode loading in submicron units is 1.4 A mg ^-1 (0.5 mg cm ^-2 ) [Non-Patent Document 6] and 1.5 A mg ^-1 (0.2 mg cm ^-2 ) [Non-Patent Document 7] It provides improved MA, with a slow increase in MA with smaller loadings. On the other hand, in the case of IrO ₂ /CP having an IrO ₂ loading amount ^of 0.03 mg cm ⁻² of the example of the present invention, MA of 20.4 A mg ⁻¹ was shown to provide stable cell performance.

[Experiment 2]

In addition to Experiment 1, this time, water electrolysis performance was evaluated at a high temperature (120° C.).

Except for evaluating the high temperature (120 ℃) water electrolysis performance, other anode manufacturing and performance evaluation methods were the same as in Experiment 1. That is, as in Experiment 1, a PEMWE single cell having an IrO ₂ /CP anode ( E _dep = 0.7 V; t _dep = 10 min, plating amount: 0.1 mg cm ^{- 2} ) was prepared by the electrolytic plating method, and the polarization curves were ) was measured at 120 ^o C and the performance according to pressure (1.5 to 2.5 bar) was observed (Example of this experiment 2: denoted as EP in FIG. 9). And, compared to the PEMWE single cell (Comparative Example of this experiment 2) employing IrO ₂ /CP anode (plating amount: 2.0 mg cm ^{- 2} ) prepared by the spray method, the performance at 120 ° C., 2.5 bar was compared. (marked as Spray in Figure 9).

In general, as the temperature increases, the kinetics of OER increases and the thermodynamic energy required for the reaction can be lowered according to the Nernst equation, so that the performance of water electrolysis increases.

9 is a graph showing the high-temperature water electrolysis performance of Examples and Comparative Examples in Experiment 2; The X-axis represents current density (unit Acm ^{- 2} ) and the Y-axis represents voltage (Voltage: unit V).

As can be seen in FIG. 9, when the pressure is increased to 1.5 bar or more to supply water as a liquid, the performance is 1.71 A cm ^-2 at 1.5 bar at 1.6 V, 1.73 A cm ^-2 at 2.0 bar at 2.5 bar It is greatly improved to 1.79 A cm ^-2 and shows a better aspect than the performance at 90° C. (1.01 A cm ^-2 ). In addition, the results showed similar performance to MEA (1.86 ^A cm ^-2 ) prepared by spraying using a fairly large amount of plating, 2.0 mg cm ^-2 .

On the other hand, IrO ₂ , RuO ₂ and RuIrO ₂ In contrast to the results reported in the prior literature on anodes, the PEMWE performance of the electrolytically plated IrO ₂ /CP electrode of this example was evaluated at 120 ° C. 2: Water electrolysis performance evaluation at 120°C).

membrane Temperature (℃) pressure (bar) loading amount
(mg cm ^-2 ) Current density at 1.6V
(A cm ^-2 ) Non-Patent Document 8: Antonucci et al. Nafion + SiO ₂ 120 3.0 IrO ₂
5.0 0.75 Non-Patent Document 9: Xu et al. Nafion + SiO ₂ 120 3.0 Ru IrO ₂
2.5 1.10 Non-Patent Document 10: Baglio et al. Nafion + TiO ₂ 120 3.0 IrO ₂
5.0 0.63 Non-Patent Document 11: Skulimowska et al. Aquivion 120 7.0 IrO ₂
2.0 1.24 Non-Patent Document 12: Aili et el. PA doping
PBI 130 1.0 IrO ₂
4.0 0.30 Non-Patent Document 13: Natarajan et al. PA doping
PBI 120 2.5 RuO ₂
1.5 0.45 Non-Patent Document 14: Hansel et al PA doping
Aquivion 130 1.0 IrO ₂
1.0 0.41 of this experiment 2
Example Nafion 120 2.5 IrO ₂
0.1 1.82

For reference, FIG. 10 is a graph showing the results of Table 2 in Experiment 2. In FIG. 10 , the X-axis represents the loading amount (unit: mg cm ^-2 ), and the Y-axis represents the current density at 1.6V (unit: A cm ^-2 ).

As can be seen from Table 2 and FIG. 10 , the conventional literature has a current density at 1.6V and 120° C. from 0.30 to 0.30 for high IrO ₂ , RuO ₂ and RuIrO ₂ loadings (1.0 ^to 5.0 mg cm ⁻² ). It is reported as 1.24 A cm ^-2 .

In contrast, according to embodiments of the present invention, IrO ₂ The high PEMWE performance (1.82 A cm ^-2 at 1.6 V, 120° C.) of the electroplated IrO ₂ /CP even though the loading was greatly reduced to 0.1 mg cm ^-2 is very good and is a promising result. That is, the PEMWE performance achievable in the case of a significantly high anode loading (> 2.0 mg cm ^{−2 )} can be achieved at a significantly lower loading level, similarly in the high temperature water electrolysis performance as well as the low temperature water electrolysis performance. will be.

As described above, IrO ₂ /CP electrodes were manufactured through anode electroplating for various plating voltages and plating times, and surface morphology and Coulombic effect were analyzed by SEM, ICP, and CV.

In embodiments of the present invention, the surface of the porous carbon material through electrolytic plating is IrO ₂ This covers and IrO ₂ It was possible to provide a structure in which the particles were formed. At voltages and plating times above a certain range, cracks were formed to expose the carbon material, but at voltages and plating times within a certain range, cracks were not formed and thus there was no exposure of the carbon material. Thereby, good catalytic activity can be obtained while preventing carbon corrosion. In addition, it can be seen that the PEMWE cell using the anode provided a fairly high current density under various temperature conditions in spite of a very small loading amount and exhibited very good activity per mass.

Although non-limiting and exemplary embodiments of the present invention have been described above, the technical spirit of the present invention is not limited to the accompanying drawings or the above description. It will be apparent to those skilled in the art that various types of modifications are possible within the scope without departing from the technical spirit of the present invention, and also, such modifications will fall within the scope of the claims of the present invention.

Claims (13)

IrO ₂ on the surface of the hydrophilic porous carbon material Anode for water electrolysis of a polymer electrolyte membrane, characterized in that it is electrolytically plated.
The method of claim 1,
IrO ₂ on the carbon paper surface Anode for water electrolysis of a polymer electrolyte membrane, characterized in that it is electrolytically plated.
3. The method of claim 2,
Carbon paper surface is IrO ₂ covered by a layer, the IrO ₂ IrO ₂ in the layer Polyelectrolyte membrane water electrolysis anode, characterized in that the particles are attached.
4. The method of claim 3,
IrO ₂ The anode for water electrolysis of a polymer electrolyte membrane, characterized in that the layer has a carbon exposure free structure.
4. The method of claim 3,
IrO ₂ An anode for water electrolysis of a polymer electrolyte membrane, characterized in that the layer has a crack free structure.
4. The method of claim 3,
IrO ₂ The thickness of the layer is 0.01 ~ 1㎛, IrO ₂ Anode for water electrolysis of a polymer electrolyte membrane, characterized in that the particle size is 0.1 ~ 3㎛.
3. The method of claim 2,
IrO ₂ on carbon paper The loading amount is 0.01 ~ 1.00 mg cm ^{- 2} or 0.01 ~ 0.54 mg cm ^{- 2} , characterized in that the anode for water electrolysis of a polymer electrolyte membrane.
polymer electrolyte membrane;
a cathode formed on one side of the film;
Comprising an anode formed on the other side of the membrane,
The anode is a polyelectrolyte membrane water electrolysis single cell, characterized in that the anode of any one of claims 1 to 7.
Polyelectrolyte membrane water electrolysis device according to claim 8, characterized in that it comprises a single cell for water electrolysis.
IrO ₂ in hydrophilic porous carbon material A method for producing an anode for water electrolysis of a polymer electrolyte membrane, comprising the step of electrolytic plating.
11. The method of claim 10,
IrO ₂ on carbon paper is electroplating, and during electroplating, at least one of the plating voltage and the plating time is adjusted, but the plating voltage is 0.6 to 0.8 V (vs. SCE), and the plating time is 3 to 30 minutes, characterized in that A method for preparing an anode for water electrolysis of a polymer electrolyte membrane.
IrO ₂ on hydrophilic porous carbon material A method of reducing the loading of iridium oxide of the anode for water electrolysis of a polymer electrolyte membrane, characterized in that electrolytic plating.
13. The method of claim 12,
During electrolytic plating, a method for reducing the loading of iridium oxide of an anode for water electrolysis of a polymer electrolyte membrane, characterized in that the electrolytic plating is performed to prevent crack formation and carbon exposure by controlling at least one of a plating voltage and a plating time.

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