An iridium cluster loaded gallium oxide material, a preparation method and application thereof

Abstract

The application belongs to the technical field of electrocatalysis, and particularly relates to an iridium cluster loaded gallium oxide material and a preparation method and application thereof. The iridium cluster loaded gallium oxide material comprises sheet-shaped gallium oxide and iridium clusters loaded on the surface of the gallium oxide; the mass percentage of iridium in the iridium cluster loaded gallium oxide material is less than or equal to 50%. The mass percentage of the noble metal Ir in the material is less than or equal to 50%, which can reduce the cost; in the electrocatalytic oxygen evolution reaction, after the voltage is applied, the iridium cluster loaded gallium oxide material (Ir@Ga2O3) can generate in-situ reconstructed Ga-O-Ir interfaces through bias-induced Ga leaching, the Ga-O-Ir interfaces significantly reduce the energy barrier of the oxygen evolution reaction, greatly improve the reaction activity, and significantly improve the electrochemical performance (overpotential and cycle stability).

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrocatalysis, and particularly relates to an iridium cluster loaded gallium oxide material and a preparation method and application thereof. BACKGROUND

[0002] Proton exchange membrane water electrolyzer (PEMWE) has the advantages of high working current density and H2 purity, low resistance loss, etc., making it the preferred technology for high-efficiency and small-area electrolyzers. However, the working conditions of strong acidity and oxidation environment of PEMWE pose substantial challenges to the activity and stability of catalysts. These challenges are related to the slow kinetics of the oxygen evolution reaction (OER) and the dependence on the key catalyst of iridium oxide (IrO2). For example, the anode catalyst of iridium oxide, which is popular so far due to its stability. On the one hand, the mass fraction of Ir in the current commercial supported iridium oxide catalyst is more than 75%, and Ir is one of the rarest metals on earth, which is high in cost, on the other hand, the electrochemical performance of IrO2 cannot be efficiently and stably operated for a long time under the working conditions of PEMWE, thereby making the PEMWE relying on iridium oxide catalysts not market competitive. Therefore, it is urgent to develop an electrocatalyst with intrinsic activity, acid stability and low iridium to improve the competitiveness of PEMWE devices. SUMMARY

[0003] Therefore, the purpose of the present application is to provide an iridium cluster loaded gallium oxide material and a preparation method and application thereof. The iridium cluster loaded gallium oxide material provided by the present application has a low Ir content (≤50wt%) and excellent electrochemical performance. As a catalyst, the iridium cluster loaded gallium oxide material has enhanced electrocatalytic activity and good long-term stability under the working conditions of PEMWE.

[0004] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0005] The present application provides an iridium cluster loaded gallium oxide material, which comprises sheet-shaped gallium oxide and iridium clusters loaded on the surface of the gallium oxide.

[0006] The mass percentage of iridium in the iridium cluster loaded gallium oxide material is ≤50%.

[0007] Preferably, the crystal form of the gallium oxide is ε-Ga2O3, the crystal lattice structure is cubic structure, and the space group is Fd-3m (227).

[0008] The present application provides a preparation method of the iridium cluster loaded gallium oxide material described in the above technical solutions, which comprises the following steps:

[0009] The Ir source, gallium salt, alkali source, organic alcohol and water are mixed to perform one-step hydrothermal reaction to obtain the gallium oxide material loaded with iridium clusters.

[0010] Preferably, the Ir source is iridium chloric acid.

[0011] Preferably, the gallium salt is gallium nitrate.

[0012] Preferably, the alkali source is potassium hydroxide.

[0013] Preferably, the organic alcohol is ethylene glycol.

[0014] Preferably, the one-step hydrothermal reaction has a temperature of 160-220 DEG C and a holding time of 12-36 h.

[0015] Preferably, the molar ratio of Ir in the Ir source to Ga in the gallium salt is (1-2):(1-8).

[0016] The application provides application of the gallium oxide material loaded with iridium clusters as a catalyst in a proton exchange membrane water electrolyzer.

[0017] The application provides a gallium oxide material loaded with iridium clusters, which comprises flaky gallium oxide and iridium clusters loaded on the surface of the gallium oxide; the mass percentage of iridium in the gallium oxide material loaded with iridium clusters is less than or equal to 50%. The application uses Ga2O3 as a base material and is combined with noble metal Ir, so that the mass percentage of the noble metal Ir in the composite material can be significantly reduced (less than or equal to 50%) and the cost can be reduced. In an oxygen evolution reaction of electrocatalysis, after a voltage is applied, the gallium oxide material loaded with iridium clusters (Ir@Ga2O3) can generate an in-situ reconstructed Ga-O-Ir interface through bias-induced Ga leaching. The Ga-O-Ir interface significantly reduces the energy barrier of the oxygen evolution reaction, greatly improves the reaction activity, and significantly improves the electrochemical performance (overpotential and cycle stability). The gallium oxide material loaded with iridium clusters can be used as a catalyst to be operated efficiently and stably for more than 1000 h under the working conditions of a proton exchange membrane water electrolyzer (PEMWE), which is much longer than the performance and the longest operation time of a commercial catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A spherical aberration transmission electron microscope image of the gallium oxide material loaded with iridium clusters (Ir@Ga2O3 (1:1)) prepared in Example 1;

[0019] Figure 2 An XRD graph of the gallium oxide material loaded with iridium clusters (Ir@Ga2O3) prepared in Example 1;

[0020] Figure 3OER polarization curve of the iridium cluster supported gallium oxide material prepared for Examples 1-5 and C-IrO2;

[0021] Figure 4 OER polarization curve of the iridium cluster supported gallium oxide material (Ir@Ga2O3 (1:1)) prepared for Example 1 and Ga2O3 prepared for Comparative Example 1;

[0022] Figure 5 Polarization curve of the iridium cluster supported gallium oxide material (Ir@Ga2O3) prepared for Example 1 and commercial catalyst IrO2 (C-IrO2) in PEM WE;

[0023] Figure 6 Chronoamperometric curve of the iridium cluster supported gallium oxide material (Ir@Ga2O3) prepared for Example 1 in PEM WE. DETAILED DESCRIPTION

[0024] The present application provides an iridium cluster supported gallium oxide material, comprising sheet-shaped gallium oxide and iridium clusters supported on the surface of the gallium oxide:

[0025] The mass percentage of iridium in the iridium cluster supported gallium oxide material is ≤50%.

[0026] Unless otherwise specified, the present application does not have special requirements for the source of the raw materials used, and commercially available products known to those skilled in the art can be used.

[0027] The iridium cluster supported gallium oxide material provided by the present application comprises sheet-shaped gallium oxide.

[0028] As an embodiment, the crystal form of the gallium oxide is ε-Ga2O3, the crystal lattice structure is cubic structure, and the space group is Fd-3m (227).

[0029] The iridium cluster supported gallium oxide material provided by the present application comprises iridium clusters supported on the surface of the gallium oxide.

[0030] As an embodiment, the mass percentage of iridium in the iridium cluster supported gallium oxide material is ≤50%.

[0031] The present application also provides a preparation method of the iridium cluster supported gallium oxide material described in the above technical solution, comprising the following steps:

[0032] The iridium source, gallium salt, alkali source, organic alcohol and water are mixed to perform one-step hydrothermal reaction to obtain the iridium cluster supported gallium oxide material.

[0033] As an embodiment, the Ir source is iridium chlorate (H2IrCl6); the gallium salt is gallium nitrate (Ga(NO3)3); the alkali source is potassium hydroxide (KOH); and the organic alcohol is ethylene glycol (EG). The organic alcohol plays the role of reducing agent and template in the one-step hydrothermal reaction.

[0034] As an embodiment, the molar ratio of Ir in the Ir source to Ga in the gallium salt is (1-2):(1-8), and in specific embodiments, 1:1, 2:1, 1:2, 1:4 or 1:8.

[0035] As an embodiment, the mass ratio of the gallium salt to the alkali source is (2-1):(1-2), and in specific embodiments, 2:1; the mass ratio of the gallium salt to the organic alcohol is (0.02-0.32):(10-15), and in specific embodiments, 0.04:11.3; and the mass ratio of the gallium salt to water is (0.01-0.32):(10-30), and in specific embodiments, 0.04:25.

[0036] As an embodiment, the mixing is as follows: first, the Ir source and the gallium salt are dispersed in water, then the alkali source is added for first stirring, and finally the organic alcohol is added for second stirring. As an embodiment, the first stirring is at a speed of 3000-5000 rpm, and in specific embodiments, 5000 rpm, for 5 min; and the second stirring is at a speed of 3000-5000 rpm, and in specific embodiments, 5000 rpm, for 30 min.

[0037] As an embodiment, the temperature of the one-step hydrothermal reaction is 160-220°C, and the holding time is 12-36 h. In specific embodiments, the temperature of the one-step hydrothermal reaction is 180°C, and the holding time is 24 h.

[0038] As an embodiment, the equipment used in the one-step hydrothermal reaction is a Teflon-lined stainless steel autoclave.

[0039] As an embodiment, after the one-step hydrothermal reaction, the method further comprises: after the product obtained in the one-step hydrothermal reaction is cooled to room temperature, washing and solid-liquid separation are performed to obtain the gallium oxide material loaded with iridium clusters.

[0040] As an embodiment, the reagents used in the washing are water and ethanol; the number of times of washing and solid-liquid separation using each reagent is independently 2 times; the solid-liquid separation is centrifugal separation; the centrifugal separation is at a speed of 11000 rpm for 5 min.

[0041] The application further provides application of the iridium cluster loaded gallium oxide material in a proton exchange membrane water electrolyzer as a catalyst.

[0042] In the application, the application of the iridium cluster loaded gallium oxide material in the proton exchange membrane water electrolyzer as a catalyst is preferably application of the iridium cluster loaded gallium oxide material in the proton exchange membrane water electrolyzer in electrolysis of water to produce hydrogen as a catalyst.

[0043] The application of the iridium cluster loaded gallium oxide material in the proton exchange membrane water electrolyzer as a catalyst is not particularly limited in the application, and a method well known in the art can be used.

[0044] In the electrocatalytic oxygen evolution reaction, after a voltage is applied, the iridium cluster loaded gallium oxide material generates an in-situ reconstructed Ga-O-Ir interface through Ga leaching induced by bias, which significantly reduces the energy barrier of the oxygen evolution reaction and greatly improves the reaction activity, so that the iridium cluster loaded gallium oxide material has excellent electrochemical performance.

[0045] The technical solutions in the application will be described clearly and completely in combination with the embodiments in the application, but they should not be understood as limitations to the protection scope of the application.

[0046] Iridium chloric acid (H2IrCl6), hydrated gallium nitrate (Ga(NO3)3·xH2O), ethylene glycol (EG) and potassium hydroxide (KOH) were purchased from Aladdin, analytical grade.

[0047] Example 1

[0048] First, 65 mg of H2IrCl6 and 40 mg of Ga(NO3)3·xH2O were dispersed in 25 mL of water, the molar ratio of Ir in H2IrCl6 to Ga in Ga(NO3)3 was 1:1, 20 mg of KOH was added to the obtained solution, stirred at 5000 rpm for 5 min, 10 mL of ethylene glycol (1.13 g / mL) was added, stirred at 5000 rpm for 30 min, the obtained solution was transferred to a 50 mL Teflon-lined stainless steel autoclave, one-step hydrothermal reaction was carried out at 180℃ for 24 h, the obtained product was cooled to room temperature, then washed with water and ethanol, centrifuged for 2 times, the centrifugal speed was 11000 rpm, the time was 5 min, and the iridium cluster loaded gallium oxide material (Ir@Ga2O3(1:1)) was obtained.

[0049] Example 2

[0050] The difference from Example 1 is that the molar ratio of Ir in H2IrCl6 to Ga in Ga(NO3)3xH2O is 2:1.

[0051] Example 3

[0052] The difference from Example 1 is that the molar ratio of Ir in H2IrCl6 to Ga in Ga(NO3)3xH2O is 1:2.

[0053] Example 4

[0054] The difference from Example 1 is that the molar ratio of Ir in H2IrCl6 to Ga in Ga(NO3)3xH2O is 1:4.

[0055] Example 5

[0056] The difference from Example 1 is that the molar ratio of Ir in H2IrCl6 to Ga in Ga(NO3)3xH2O is 1:8.

[0057] Comparative Example 1

[0058] 40 mg of Ga(NO3)3xH2O was dispersed in 25 mL of water, 20 mg of KOH was added to the resulting solution, stirred at 5000 rpm for 5 min, 10 mL of ethylene glycol was added, stirred at 5000 rpm for 30 min, the resulting solution was transferred to a 50 mL Teflon-lined stainless steel autoclave, and a one-step hydrothermal reaction was carried out at 180°C for 24 h, the resulting product was cooled to room temperature, then washed with water and ethanol and centrifuged twice, the centrifugal speed was 11000 rpm, the time was 5 min, and Ga2O3 was obtained.

[0059] Comparative Example 2

[0060] A commercial catalyst IrO2 was used as a comparative example.

[0061] Performance test

[0062] (1) Figure 1 The spherical aberration transmission electron microscope image of the iridium cluster loaded gallium oxide material (Ir@Ga2O3(1:1)) prepared in Example 1, wherein a is the HAADF-STEM image of Ir@Ga2O3, b is the EDS mapping image of Ir, O and Ga in Ir@Ga2O3, c is the EDS mapping image of Ga in Ir@Ga2O3, d is the HAADF-STEM image of Ir@Ga2O3, e is the EDS mapping image of O in Ir@Ga2O3, and f is the EDS mapping image of Ir in Ir@Ga2O3. From the images, it can be seen that the Ir@Ga2O3(1:1) material is a core-shell structure, and the core is Ir, and the shell is Ga2O3. Figure 1It can be seen from the above that the iridium cluster loaded gallium oxide material prepared in the present application has iridium mainly in the form of clusters loaded on the carrier Ga2O3.

[0063] (2) Figure 2 The XRD pattern of the iridium cluster loaded gallium oxide material (Ir@Ga2O3) prepared in Example 1. It can be seen from the above that the XRD spectrum of the material prepared in the present application mainly shows the peak spectrum of Ga2O3, and the crystal form of the gallium oxide is ε-Ga2O3, and the crystal lattice structure is cubic structure, and the space group is Fd-3m (227). Figure 2

[0064] (3) Figure 3 The OER polarization curve diagram of the iridium cluster loaded gallium oxide material prepared in Examples 1-5 and the commercial catalyst IrO2 (C-IrO2). It can be seen from the above that the OER performance of the materials of different examples is different, wherein the Ir@Ga2O3 (1:1) prepared in Example 1 has the optimal OER performance, and it can be intuitively found that the OER performance is obviously improved by loading the iridium cluster on the gallium oxide material. Figure 3

[0065] (4) Figure 4 The OER polarization curve diagram of the iridium cluster loaded gallium oxide material (Ir@Ga2O3 (1:1)) prepared in Example 1 and the Ga2O3 prepared in Comparative Example 1. It can be seen from the above that the Ga2O3 as the comparative example has almost no OER performance. Figure 4

[0066] (5) Figure 5 The polarization curve diagram of the iridium cluster loaded gallium oxide material (Ir@Ga2O3) prepared in Example 1 and the commercial catalyst IrO2 (C-IrO2) in PEMWE. It can be seen from the above that the Ir@Ga2O3 prepared in the present application reaches 2A·cm Figure 5 -2 at 80℃ under the working condition of PEMWE, only 1.76V is needed to reach 1A·cm -2 at 80℃ under the working condition of PEMWE, only 1.63V is needed to reach 1A·cm -2 at 80℃ under the working condition of PEMWE, 1.72V is needed to reach 1A·cm. It shows that the Ir@Ga2O3 prepared in the present application performs much better than the commercial catalyst IrO2 in the proton exchange membrane water electrolysis cell (PEMWE).

[0067] (6) Figure 6 The chronoamperometric curve diagram of the iridium cluster loaded gallium oxide material (Ir@Ga2O3) prepared in Example 1 in PEMWE. It can be seen from the above that the Ir@Ga2O3 prepared in the present application can reach 1A·cm Figure 6 -2 ​​​​​The degradation rate is only 11.5 μV·h after 1000 h of stable operation -1 However, the commercial catalyst IrO2 can only operate for less than 400 h.

[0068] Although the above embodiments have been described in detail, they are only some embodiments of the present application but not all embodiments. Other embodiments can be obtained by those skilled in the art without creativity on the basis of the above embodiments, and these embodiments also belong to the protection scope of the present application.

Claims

1. The application of gallium oxide material supported on iridium clusters as a catalyst in a proton exchange membrane water electrolyzer, characterized in that, The gallium oxide material loaded with iridium clusters includes plate-like gallium oxide and iridium clusters loaded on the surface of gallium oxide: The mass percentage of iridium in the gallium oxide material loaded with iridium clusters is ≤50%; The method for preparing the gallium oxide material loaded with iridium clusters includes the following steps: An Ir source, gallium salt, alkali source, organic alcohol, and water are mixed and subjected to a one-step hydrothermal reaction to obtain the gallium oxide material loaded with iridium clusters.

2. The application according to claim 1, characterized in that, The gallium oxide has the crystal form ε-Ga2O3, the lattice structure is cubic, and the space group is Fd-3m(227).

3. The application according to claim 1, characterized in that, The Ir source is iridium chloride.

4. The application according to claim 1, characterized in that, The gallium salt is gallium nitrate.

5. The application according to claim 1, characterized in that, The alkali source is potassium hydroxide.

6. The application according to claim 1, characterized in that, The organic alcohol is ethylene glycol.

7. The application according to claim 1, characterized in that, The temperature of the first-step hydrothermal reaction is 160~220℃, and the holding time is 12~36h.

8. The application according to claim 1, characterized in that, The molar ratio of Ir in the Ir source to Ga in the gallium salt is (1~2):(1~8).

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