Iridium complex as well as preparation method and application thereof

Abstract

The invention relates to the technical field of photocatalysis, in particular to an iridium complex and a preparation method and application thereof. The novel iridium diphenylphosphonic acid catalyst for photocatalytic hydrogen production is prepared by taking iridium salt and diphenylphosphonic acid as raw materials through solvothermal reaction, the synthesis method is simple, the reaction condition is mild, the raw materials are easy to obtain, the iridium complex can be prepared by utilizing basic chemical raw materials, and the iridium complex has good photocatalytic water splitting hydrogen production activity and stability, and is suitable for industrial production. Wide application prospects are realized.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis technology, and in particular to an iridium complex and a preparation method and application thereof. Background Art

[0002] Photocatalytic technology is a truly environmentally friendly green technology with broad application prospects in both the energy and environmental sectors. In the energy sector, it can be used to produce hydrogen and reduce carbon dioxide using solar energy; in the environmental sector, it can be used to degrade and mineralize organic and inorganic pollutants in the environment. Photocatalytic hydrogen production, which can produce green hydrogen, is an effective way to obtain renewable energy, and green hydrogen production has garnered widespread attention.

[0003] Photocatalysts play a crucial role in photocatalytic hydrogen production technology and are a key element in the catalytic process, improving reaction efficiency and increasing product purity. Numerous studies have shown that photocatalysts still suffer from low solar energy utilization and high recombination rates of photogenerated electrons and holes. To address these issues, researchers are improving the catalytic performance of photocatalysts through methods such as semiconductor composites, morphology and structure control, co-catalyst loading, and element doping.

[0004] Therefore, it is crucial to develop high-efficiency catalysts, improve photocatalytic efficiency, and promote the further development of photocatalytic technology. Summary of the Invention

[0005] Through the rational design of the energy gap structure, the present invention prepares a novel diphenylphosphonate iridium catalyst for photocatalytic hydrogen production. The catalyst is an iridium complex. The preparation method includes: dissolving an iridium salt and diphenylphosphonic acid (DPPA) in an alcohol solvent and performing a solvothermal reaction to obtain the iridium complex.

[0006] In some embodiments, the iridium salt is iridium chloride hexahydrate.

[0007] In some embodiments, the alcohol solvent is ethanol.

[0008] In some embodiments, the molar ratio of the iridium salt to diphenylphosphonic acid is 1:(2-5).

[0009] Preferably, the molar ratio of the iridium salt to diphenylphosphonic acid is 1:(2.5-3.5).

[0010] In some embodiments, the temperature of the solvothermal reaction is 150°C to 200°C.

[0011] Preferably, the temperature of the solvothermal reaction is 175°C to 185°C.

[0012] In some embodiments, the solvothermal reaction time is more than 72 hours.

[0013] In some embodiments, the solvothermal reaction is carried out in a polytetrafluoroethylene-lined reactor.

[0014] In some embodiments, after the solvothermal reaction is completed, the reactor is taken out and naturally cooled to room temperature. The reactor is opened and the iridium complex is obtained after filtration, washing with anhydrous ethanol, and drying in air.

[0015] Furthermore, the present invention provides an iridium complex prepared by the preparation method.

[0016] Furthermore, the present invention provides the use of the iridium complex in photocatalytic water splitting.

[0017] Furthermore, the present invention provides the use of the iridium complex in photocatalytic water splitting to produce hydrogen.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention prepares a novel iridium diphenylphosphonate catalyst for photocatalytic hydrogen production. The synthesis method is simple, the reaction conditions are mild, the raw materials are readily available, and the catalyst can be prepared using basic chemical raw materials. The iridium complex has good photocatalytic water splitting hydrogen production activity and stability, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 These are scanning electron micrographs of iridium diphenylphosphonate; (a) is a 2.5 μm scale bar, and (b) is a 1.0 μm scale bar.

[0020] Figure 2 This is the XRD pattern of iridium diphenylphosphonate.

[0021] Figure 3 This is the infrared absorption spectrum of iridium diphenylphosphonate.

[0022] Figure 4 These are the optical property characterization results of iridium diphenylphosphonate; (a) is the UV-visible diffuse reflectance spectrum; (b) is the band gap spectrum.

[0023] Figure 5 This is the photocatalytic hydrogen production cycle reaction diagram of iridium diphenylphosphonate.

[0024] Figure 6 This is the XRD spectrum of diphenylphosphonic acid iridium before and after photocatalytic hydrogen production.

[0025] Figure 7 This is a schematic diagram of the photocatalytic hydrogen production mechanism of iridium diphenylphosphonate under ultraviolet-visible light irradiation. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below. Obviously, the described embodiments are part of embodiments of the present invention, rather than all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. In the embodiments provided in this specification, those without specifying specific techniques or conditions are described in accordance with the techniques or conditions described in the literature in this area, or are carried out according to product specifications. Reagents or instruments used are not specified by manufacturer and are conventional products that can be purchased through regular channels.

[0027] Example 1 The present invention provides an iridium complex, and the preparation method is as follows: (1) Iridium chloride hexahydrate YCl3·6H2O (0.1517 g, 0.5 mmol) and diphenylphosphonic acid DPPA (0.3273 g, 1.5 mmol) were dissolved in 7 mL of anhydrous ethanol, and the mixture was stirred at room temperature for 20 min until homogeneous.

[0028] (2) The mixture was transferred to a 15 mL polytetrafluoroethylene-lined stainless steel autoclave, which was placed in a muffle furnace. The reactor was kept at a constant temperature of 180°C for 72 h.

[0029] (3) After the reaction time is over, the autoclave is taken out and cooled naturally to room temperature. The autoclave is opened, filtered, washed with anhydrous ethanol, and dried in air to obtain a white sample iridium complex (iridium diphenylphosphonate), which is labeled as YDPPA.

[0030] The reaction equation of the present embodiment is as follows: Example 2 The present invention provides an iridium complex, the preparation method of which differs from that of Example 1 only in that: The amount of iridium chloride hexahydrate YCl3·6H2O was 0.5 mmol, and the amount of diphenylphosphonic acid DPPA was 1.0 mmol.

[0031] Example 3 The present invention provides an iridium complex, the preparation method of which differs from that of Example 1 only in that: Iridium chloride hexahydrate YCl3·6H2O is 1 mmol, and diphenylphosphonic acid DPPA is 5 mmol.

[0032] Example 4 The present invention provides an iridium complex, the preparation method of which differs from that of Example 1 only in that: The reactor was kept at a constant temperature of 150 °C for 72 h.

[0033] Example 5 The present invention provides an iridium complex, the preparation method of which differs from that of Example 1 only in that: The reactor was kept at a constant temperature of 200 °C for 72 h.

[0034] Comparative Example The present invention provides a complex, the preparation method of which is different from that of Example 1 only in that: The iron diphenylphosphonate complex was synthesized under the same experimental conditions by replacing iridium chloride hexahydrate with an equal amount of ferric chloride hexahydrate.

[0035] Test Example 1 Taking the iridium complex of Example 1 as an example, the morphology of iridium diphenylphosphonate was analyzed using a scanning electron microscope (SEM). Figure 1 As shown, the morphology of the complex is rod-shaped, with a relatively smooth surface and uniform distribution.

[0036] Test Example 2 Taking the iridium complex of Example 1 as a representative, the X-ray diffraction technique (XRD) was used to determine the iridium diphenylphosphonate ( Figure 2 ). As can be seen from the figure, the complex is a crystalline compound, and there is a strong diffraction peak at 2θ=7.27°, which is attributed to the characteristic diffraction peak of metal iridium diphenylphosphonate.

[0037] Test Example 3 Taking the iridium complex of Example 1 as an example, in order to further determine the chemical composition of iridium diphenylphosphonate, the complex was subjected to infrared absorption spectrum measurement. Figure 3 It can be seen that at 3036 cm -1 and 1593 cm -1 There is a strong absorption peak at 1437 cm -1 There is a strong absorption peak at 1059 cm, which is the characteristic absorption peak of the vibration of the benzene ring skeleton; -1 There is a strong absorption peak at , which is the characteristic absorption peak of YOP. Therefore, the characteristic absorption peak in the infrared absorption spectrum further confirms the presence of important functional groups in the composition and structure of iridium diphenylphosphonate.

[0038] Test Example 4 Taking the iridium complex of Example 1 as an example, the optical properties of iridium diphenylphosphonate were studied using UV-visible diffuse reflectance spectroscopy. Figure 4 As shown, the absorption of diphenylphosphonic acid and diphenylphosphonic acid iridium is mainly located in the ultraviolet region. By using the Tauc equation (αhν=A(hν-Eg) 2) and the UV-visible absorption data of the compound, by making (αhν) 1 / 2 By taking a tangent to the curve and extending it to the x-axis, we can determine the band gap of the complex. Using this approach, we determined that the band gap of iridium diphenylphosphonate is 4.31 eV.

[0039] Test Example 5 Photocatalytic water splitting for hydrogen production was tested in a fully automated online trace gas analysis closed-circuit system. A 300 W xenon lamp was used as the light source. The specific testing steps were as follows: 50 mg of the complexes prepared in the Examples and Comparative Examples and 1 mL of triethanolamine (TEOA) were mixed in 99 mL of water with continuous stirring. The suspension was sealed in a 200 mL quartz container and purged with N2 for 30 minutes to remove residual oxygen. The reaction temperature was maintained at 10°C with cooling water. The products were periodically analyzed using an Agilent 7890B gas chromatograph with a TCD detector.

[0040] After irradiation with UV-visible light for 3 h, the hydrogen production of the catalysts prepared in different embodiments and comparative examples is shown in Table 1.

[0041] Table 1

[0042] Cyclic performance test results are as follows Figure 5 As shown, the iridium diphenylphosphonate of Example 1 still maintained a relatively stable hydrogen production capacity after 4 cycles of 12 h, and the hydrogen production efficiency was maintained at 97%.

[0043] The stability of the photocatalytic water splitting and hydrogen production of diphenylphosphonic acid iridium in Example 1 was evaluated by XRD. Figure 6 As shown, by comparing the XRD spectra of the complex before and after photocatalytic hydrogen production, it can be seen that the XRD spectrum of diphenylphosphonate iridium before and after photocatalytic hydrogen production remains basically unchanged, which shows that the complex has good stability.

[0044] Further, the photocatalytic mechanism of the iridium complex of the present invention is analyzed: Based on the above test characterization analysis, a possible mechanism of photocatalytic water splitting to produce hydrogen by diphenylphosphonate iridium was proposed ( Figure 7 During the photocatalytic water splitting process to produce hydrogen, an electron transfer mechanism occurs from the ligand to the metal. This process is divided into three stages: Under UV-visible light irradiation, the benzene ring of diphenylphosphonic acid absorbs photons to generate photogenerated electron-hole pairs. The electrons on the diphenylphosphonic acid benzene ring are transferred to Y(III), forming Y(II). Simultaneously, the holes are captured by the sacrificial agent triethanolamine. Y(II) is highly reactive and undergoes a redox reaction with water to produce hydrogen, completing the photocatalytic water splitting reaction to produce hydrogen.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing an iridium complex, characterized in that: include: Iridium salt and diphenylphosphonic acid are dissolved in an alcohol solvent to carry out a solvent thermal reaction to prepare the iridium complex.

2. The preparation method according to claim 1, characterized in that The iridium salt is iridium chloride hexahydrate.

3. The preparation method according to claim 1, characterized in that The alcohol solvent is ethanol.

4. The preparation method according to claim 1, characterized in that The molar ratio of the iridium salt to diphenylphosphonic acid is 1:(2-5).

5. The preparation method according to claim 1, characterized in that The temperature of the solvent thermal reaction is 150°C to 200°C.

6. The preparation method according to claim 1, characterized in that The solvent thermal reaction time is more than 72 hours.

7. The preparation method according to claim 1, characterized in that The solvothermal reaction was carried out in a polytetrafluoroethylene-lined reactor.

8. An iridium complex obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the iridium complex according to claim 8 in photocatalytic water splitting.

10. Use of the iridium complex according to claim 8 in photocatalytic water splitting to produce hydrogen.

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