Iron complex, preparation method and application thereof

Abstract

The application belongs to the technical field of photocatalysts, and relates to an iron complex and a preparation method and application thereof, the preparation method of the iron complex being as follows: dissolving ferric chloride hydrate and phenylphosphonic acid in a solvent to perform a solvothermal reaction; and the molar ratio of the ferric chloride hydrate and the phenylphosphonic acid being 1:(1-4). The application selects phenylphosphonic acid and ferric chloride hydrate as raw materials, takes iron as a coordination center ion, takes phenylphosphonic acid as a ligand, and synthesizes an iron complex for photocatalytic splitting of water to produce hydrogen through a solvothermal method. The synthesis method is simple, the reaction condition is mild, raw materials are easy to obtain, and the iron complex can be prepared by using basic chemical raw materials. The iron complex has good photocatalytic splitting of water to produce hydrogen activity and stability.

Description

Technical Field

[0001] This invention belongs to the field of photocatalyst technology, and relates to an iron complex, its preparation method and application. Background Technology

[0002] Hydrogen energy plays a crucial role in the "dual carbon" goal and is a key driver of energy transformation. As an indispensable link in the hydrogen energy industry chain, photocatalysis is one of the effective ways to obtain green hydrogen. The photocatalytic hydrogen production process consists of three steps: light absorption, charge migration and separation, and surface redox reactions. Among these, the photocatalyst is a key component in the reaction process, but most catalysts suffer from poor stability, narrow light absorption range, and low catalytic activity. Synthesizing catalysts with high photocatalytic efficiency and high stability is a pressing issue that needs to be addressed in photocatalysis technology.

[0003] Therefore, we need to synthesize a photocatalyst with good photocatalytic activity and stability in water splitting for hydrogen production. Summary of the Invention

[0004] The main objective of this invention is to overcome the deficiencies in the prior art and provide an iron complex, its preparation method, and its application.

[0005] To achieve the above objectives, the specific technical solution is as follows: An iron complex with iron as the coordinating center ion and phenylphosphine as the ligand, the chemical formula of the iron complex is FeC. 12 H 13 P2O7.

[0006] The present invention provides an iron complex with iron as the coordination center ion and phenylphosphine as the ligand, which has good photocatalytic water splitting activity and stability for hydrogen production.

[0007] Furthermore, the iron complex is a crystalline compound, and the powder X-ray diffraction pattern of the iron complex shows a diffraction peak at 2θ = 5.86°.

[0008] Furthermore, the iron complex has a plate-like morphology with a relatively smooth surface and uniform distribution.

[0009] The present invention also provides a method for preparing an iron complex, wherein hydrated ferric chloride (FeCl3·6H2O) and phenylphosphoric acid are dissolved in a solvent and subjected to a solvothermal reaction; wherein the molar ratio of hydrated ferric chloride to phenylphosphoric acid is 1:(1-4).

[0010] This invention uses phenylphosphoric acid and hydrated ferric chloride as raw materials to synthesize a new iron complex through solvothermal synthesis. This complex exhibits good photocatalytic activity and stability in water splitting for hydrogen production. The synthesis method is simple, the reaction conditions are mild, the raw materials are readily available, and it can be prepared using basic chemical raw materials.

[0011] Furthermore, the molar ratio of hydrated ferric chloride to phenylphosphoric acid is 1:(1-3), preferably 1:(1-1.5).

[0012] By using the above-mentioned preferred molar ratio of hydrated ferric chloride and phenylphosphoric acid, the present invention can obtain a target product with better crystallinity and purer phase, reduce the generation of impurities caused by the imbalance of raw material ratio, and further increase the specific surface area of ​​the product, providing more active sites for photocatalytic reaction, ensuring catalytic activity without causing unnecessary waste of raw materials, and reducing synthesis cost.

[0013] Furthermore, the reaction temperature of the solvothermal reaction is 175-190℃, and the reaction time of the solvothermal reaction is 70-80h.

[0014] This invention utilizes the aforementioned reaction temperature and time range for a solvothermal reaction, ensuring that the raw materials react fully to generate the target iron complex. This avoids insufficient conversion of raw materials and insufficient crystallinity of the product due to excessively low temperature or insufficient reaction time, which would affect the final catalytic performance. It also avoids energy waste and increased production energy consumption and costs due to excessively high temperature or excessively long reaction time. Furthermore, it prevents the product structure from being damaged, ensuring that the prepared iron complex has good crystallinity and a stable chemical structure, thereby guaranteeing its excellent photocatalytic water splitting and hydrogen production performance and stability.

[0015] Preferably, the temperature of the solvothermal reaction is 180°C and the reaction time is 72 h.

[0016] Furthermore, the solvent is anhydrous ethanol.

[0017] The solvents used in this invention effectively promote the dissolution and dispersion of raw materials, allowing hydrated ferric chloride and phenylphosphoric acid to fully contact and react in the system. This avoids introducing other difficult-to-remove impurity ions, and the target product with high purity can be obtained without additional impurity removal steps. At the same time, anhydrous ethanol, as a low-boiling-point polar solvent, has a low boiling point and is easier to remove through washing and drying in the post-processing stage. It will not remain in the product's pore structure and occupy active sites, thus better preserving the porous structure and active sites of the product, ensuring the specific surface area and catalytic activity of the final product. Moreover, the solvents mentioned above are inexpensive and have low toxicity, making them more suitable for the needs of large-scale production.

[0018] Further, the molar volume ratio of the hydrated ferric chloride to the solvent is 1 mmol: (10-20) ml, preferably 1 mmol: 14 ml.

[0019] The present invention uses the above-mentioned molar volume ratio of hydrated ferric chloride and solvent, which can ensure that the raw materials are fully dispersed and dissolved in the reaction system, allowing the coordination reaction to proceed more completely, avoiding the problems of raw material agglomeration and uneven product crystallization caused by excessive concentration, and at the same time, it will not reduce the reaction rate due to excessive solvent ratio. The final product has better crystallinity and better photocatalytic performance.

[0020] Furthermore, the method for preparing the iron complex includes the following steps: (1) Dissolve ferric chloride hexahydrate and phenylphosphoric acid in a solvent and stir at room temperature for 10-30 min to obtain a mixture; (2) The mixture is subjected to a solvothermal reaction at 175-190℃ for 70-80h; (3) After the reaction is complete, the mixture is allowed to cool naturally to room temperature, then filtered, washed and dried.

[0021] The present invention further provides the application of the above-mentioned iron complex in photocatalytic water splitting for hydrogen production.

[0022] Furthermore, the iron complex is subjected to photocatalytic water splitting to produce hydrogen under ultraviolet-visible light irradiation.

[0023] The iron complex of this invention, as a photocatalyst, produces 132.3 μmol / g of hydrogen from water splitting under UV-Vis irradiation for 3 h; after four cycles of 12 h, it still maintains a relatively stable hydrogen production capacity, with a hydrogen production efficiency of 97%; and the XRD spectrum of the iron complex before and after photocatalytic hydrogen production remains basically unchanged, indicating that the complex has good stability.

[0024] Compared with the prior art, the present invention has the following significant advantages: This invention provides an iron complex for photocatalytic water splitting to produce hydrogen. The synthesis method is simple, the reaction conditions are mild, and the raw materials are readily available and can be obtained using basic chemical raw materials. The iron complex has good photocatalytic water splitting activity and stability. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 Here is a SEM image of the iron complex phenyl ferric phosphate prepared in Example 1 of this invention; Figure 2This is the XRD pattern of the iron complex phenyl iron phosphate prepared in Example 1 of this invention; Figure 3 This is the Fourier transform infrared spectrum of the iron complex phenyl ferric phosphate prepared in Example 1 of this invention; Figure 4 These are (a) a broad XPS spectrum and (b) a high-resolution spectrum of Fe 2p of the iron complex phenyl iron phosphate prepared in Example 1 of this invention; Figure 5 These are the TG and DTG diagrams of the iron complex phenyl ferric phosphate prepared in Example 1 of this invention; Figure 6 This is the UV-Vis DRS image of the iron complex phenyl ferric phosphate prepared in Example 1 of this invention; Figure 7 This is the band gap diagram of the iron complex phenyl ferric phosphate prepared in Example 1 of the present invention; Figure 8 These are the diagrams of (a) catalytic hydrogen production under UV-Vis irradiation and (b) photocatalytic hydrogen production cycle of the iron complex phenyl iron phosphate prepared in Example 1 of this invention; Figure 9 These are the XRD patterns of the iron complex phenyl iron phosphate prepared in Example 1 of this invention before and after photocatalytic hydrogen production. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] Unless otherwise specified in the embodiments of the present invention, the techniques or conditions described in the literature in this field or the product instructions shall be followed; if the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased through legitimate channels.

[0029] Example 1 This embodiment provides an iron complex and its preparation method. The iron complex is phenylferric phosphate with the chemical formula FeC. 12 H 13 P2O7; The method for preparing the iron complex includes the following steps: (1) Dissolve ferric chloride hexahydrate FeCl3·6H2O (0.1351 g, 0.5 mmol) and phenyl phosphoric acid (0.1186 g, 0.75 mmol) in 7 mL of anhydrous ethanol and stir the mixture at room temperature for 20 min until homogeneous; (2) Transfer the mixture to a 15 mL polytetrafluoroethylene-lined stainless steel high-pressure reactor, place the reactor in a muffle furnace, and keep the reactor at a constant temperature of 180°C for 72 h. (3) After the reaction time is over, the high-pressure reactor is removed and allowed to cool naturally to room temperature. The reactor is then opened, filtered, washed with anhydrous ethanol, and dried in the air to obtain the white iron complex phenyl ferric phosphate.

[0030] The synthesis reaction equation for iron complexes is shown below: .

[0031] The elemental analysis data of the iron complex of the present invention are as follows: theoretical value of C (%) 36.90, theoretical value of H (%) 3.61; actual value of C (%) 36.46; actual value of H (%) 3.69.

[0032] 1. Characterization of the iron complex of the present invention The morphology of the complex was first analyzed using scanning electron microscopy (SEM). For example... Figure 1 As shown, the complex has a plate-like morphology with a relatively smooth surface and uniform distribution.

[0033] The complex was determined using X-ray diffraction (XRD). Figure 2 As shown in the figure, the complex is a crystalline compound, and there is a strong diffraction peak at 2θ = 5.86°, which is a characteristic diffraction peak of phenyl phosphate metallic iron.

[0034] To further determine the chemical composition of the complex, infrared absorption spectroscopy was performed on it. Figure 3 As shown in the figure, at 3054 cm... -1 and 1597 cm -1 There are strong absorption peaks at 1438 cm⁻¹, which are characteristic absorptions of the CH and C=C bonds on the benzene ring; -1 There is a strong absorption peak at 1119 cm⁻¹, which is a characteristic absorption peak of the benzene ring skeletal vibration; -1 There is a strong absorption peak at this location, which is a characteristic absorption peak of Fe-OP. Therefore, the characteristic absorption peak in the infrared absorption spectrum further confirms the presence of important functional groups in the composition and structure of phenyl iron phosphate.

[0035] Based on infrared absorption spectroscopy analysis, XPS tests were performed on the complex. Figure 4The bonding modes of the elements in the coordination compound were further investigated. XPS broadband data of the coordination compound showed that... Figure 4 a) The complex contains four elements: C (1s), P (2p), O (1s), and Fe (2p). In the high-resolution Fe 2p spectrum of the complex ( Figure 4 (b) The binding energy peaks of Fe 2p3 / 2 and Fe 2p1 / 2 are 712.6 and 727.8 eV, respectively, and the spin-orbit separation energy between the two peaks is 15.2 eV. This result indicates that iron exists in the complex in the chemical form of ferric iron.

[0036] 2. Thermal behavior analysis of the iron complex of the present invention Thermogravimetric analysis (TG) was used to analyze the thermal behavior of the complex. The TG curve of the complex showed five distinct weight loss intervals. Figure 5 The highest weight loss temperatures of the complex in the five weight loss ranges were 151.6℃, 217.8℃, 304.7℃, 493.8℃, and 959.3℃, with weight losses of 3.94%, 2.54%, 13.33%, 29.51%, and 33.81%, respectively. At 1115℃, the total weight loss and residual amount of the complex were 26.88% and 73.12%, respectively. This demonstrates that the complex exhibits excellent thermal stability under a N2 atmosphere.

[0037] 3. Characterization of the optical properties of the iron complexes of the present invention The optical properties of the complex were investigated using ultraviolet-visible diffuse reflectance spectroscopy. For example... Figure 6 As shown, the absorption of phenyl ferric phosphate is mainly located in the ultraviolet region.

[0038] Using the Tauc equation (αhν=A(hν-Eg)) 2 The UV-Vis absorption data of the compound were obtained by making (αhν) 1 / 2 By tangent to the curve and extending it to the X-axis, the band gap value of the complex can be determined. Using this method, the band gap value of phenylferric phosphate was determined to be 2.91 eV. Figure 7 ).

[0039] 4. Study on the photocatalytic performance of the iron complex of the present invention The photocatalytic performance of the complex as a photocatalyst for hydrogen production via water splitting was investigated under UV-Vis irradiation. After 3 h of UV-Vis irradiation, the hydrogen production of the complex was 132.3 μmol / g. Figure 8 a); Cyclic performance test results show that the complex maintained a relatively stable hydrogen production capacity after four cycles of 12 h, with a hydrogen production efficiency of 97% ( Figure 8 b).

[0040] The stability of the complex for photocatalytic water splitting to hydrogen production was evaluated using XRD. Figure 9 By comparing the XRD spectra of the complex before and after photocatalytic hydrogen production, it can be seen that the XRD spectra of the complex remain basically unchanged before and after photocatalytic hydrogen production, which indicates that the complex has good stability.

[0041] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An iron complex, characterized in that, With iron as the coordinating center ion and phenylphosphoric acid as the ligand, the chemical formula of the iron complex is FeC. 12 H 13 P2O7.

2. The iron complex according to claim 1, characterized in that, The iron complex is a crystalline compound, and the powder X-ray diffraction pattern of the iron complex shows a diffraction peak at 2θ = 5.86°.

3. A method for preparing an iron complex, characterized in that, Hydrated ferric chloride and phenyl phosphoric acid are dissolved in a solvent and subjected to a solvothermal reaction; the molar ratio of hydrated ferric chloride and phenyl phosphoric acid is 1:(1-4).

4. The method for preparing the iron complex according to claim 3, characterized in that, The molar ratio of hydrated ferric chloride to phenylphosphoric acid is 1:(1-3), preferably 1:1.

5.

5. The method for preparing the iron complex according to claim 3 or 4, characterized in that, The reaction temperature of the solvothermal reaction is 175-190℃, and the reaction time is 70-80h.

6. The method for preparing the iron complex according to claim 5, characterized in that, The solvent is anhydrous ethanol.

7. The method for preparing the iron complex according to claim 6, characterized in that, The molar volume ratio of the hydrated ferric chloride to the solvent is 1 mmol: (10-20) ml, preferably 1 mmol: 14 ml.

8. The method for preparing the iron complex according to claim 7, characterized in that, The method for preparing the iron complex includes the following steps: (1) Dissolve ferric chloride hexahydrate and phenylphosphoric acid in a solvent and stir at room temperature for 10-30 min to obtain a mixture; (2) The mixture is subjected to a solvothermal reaction at 175-190℃ for 70-80h; (3) After the reaction is complete, the mixture is allowed to cool naturally to room temperature, then filtered, washed and dried.

9. The application of the iron complex as described in claim 1 or 2, or the iron complex prepared by the method described in any one of claims 3 to 8, in photocatalytic water splitting for hydrogen production.

10. The application according to claim 9, characterized in that, The iron complex is subjected to photocatalytic water splitting to produce hydrogen under ultraviolet-visible light irradiation.

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