Iron-based catalyst for photo-thermal catalytic water gas conversion reaction as well as preparation method and application of iron-based catalyst

Abstract

The invention discloses an iron-based catalyst for a photo-thermal catalytic water gas conversion reaction as well as a preparation method and application of the iron-based catalyst. The structure of the catalyst comprises a zinc-iron composite metal oxide and clustered noble metal particles loaded on the zinc-iron composite metal oxide. According to the technical scheme, photo-thermal catalysis of a water gas conversion reaction by using the iron-based catalyst is realized for the first time, and the iron-based catalyst has relatively good hydrogen production activity at low temperature.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photo-thermal catalysis. More particularly, it relates to an iron-based catalyst for photo-thermal catalytic water-gas shift reaction and a preparation method and application thereof. BACKGROUND

[0002] It is of great significance to improve the utilization rate of fossil energy, produce clean energy and develop low-carbon economy. The water-gas shift (WGS) reaction is an important reaction for large-scale production of hydrogen energy in industry using fossil energy. Hydrogen energy, as a secondary clean energy with abundant reserves, is known as the most potential energy in the 21st century. Therefore, it is of great practical significance to promote the development of clean energy by developing efficient water-gas shift catalytic materials. At present, the commonly used industrial catalysts are divided into low-temperature copper-based catalysts (180℃-250℃) and high-temperature iron-based catalysts (350℃-700℃) according to temperature. Although the copper-based WGS reaction catalyst has high reaction activity in the low temperature zone, it is very sensitive to temperature and environment. It is easy to deactivate. Iron-based catalysts are widely used in high temperature zones due to their wide active temperature range, good thermal stability and long service life. However, the water-gas shift reaction is an exothermic reaction, so low temperature is beneficial to the reaction equilibrium. The high-temperature iron-based catalyst consumes a lot of energy and often has low conversion efficiency. Therefore, it is of great practical significance to develop iron-based catalysts with high activity in the low temperature zone. In recent years, it has been proved that using solar energy to replace traditional heat to drive water-gas reaction to produce hydrogen is a very promising new path. The conversion of solar energy into chemical energy by using solar photo-thermal catalytic technology has been considered as one of the best ways to solve the future renewable energy. However, how to obtain an iron-based catalyst that can well catalyze the water-gas shift reaction to produce hydrogen at low temperature is still a technical problem to be solved by those skilled in the art. SUMMARY

[0003] Based on the above problems, the purpose of the present application is to provide an iron-based catalyst for photo-thermal catalytic water-gas shift reaction and a preparation method and application thereof. In the technical solution of the present application, the photo-thermal catalytic water-gas shift reaction is realized for the first time using the iron-based catalyst, and the catalyst has good hydrogen production activity at low temperature.

[0004] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0005] On the one hand, the present application provides an iron-based catalyst for photo-thermal catalytic water-gas shift reaction. The structure of the catalyst comprises zinc-iron composite metal oxide and cluster-shaped noble metal particles loaded on the zinc-iron composite metal oxide.

[0006] Further, the noble metal particles are selected from one or more of gold, platinum and silver.

[0007] Further, the mass ratio of the zinc-iron composite metal oxide to the noble metal particles is 0.1-5 wt%.

[0008] In another aspect, the present application provides a preparation method of the iron-based catalyst as described above, characterized in that it comprises the following steps:

[0009] The aqueous solution of the zinc salt and the iron salt is added dropwise into the buffer solution, and a precipitant is added to the solution until the pH is 8-10, preferably 8-9.5, and more preferably 8. After the materials are fully dissolved, the solution is heated for crystallization, and then cooled to room temperature. After washing and drying, the precursor hydrotalcite is obtained.

[0010] The precursor hydrotalcite is ground, and after calcination and cooling to room temperature, the mixed metal oxide is obtained.

[0011] The mixed metal oxide is dispersed in deionized water, and an aqueous solution of a noble metal salt is added while the pH of the solution is controlled to be 8-10. After washing and drying, the noble metal-zinc-iron mixed metal oxide precursor is obtained.

[0012] The noble metal-zinc-iron mixed metal oxide precursor is heated to 100-600℃ in a hydrogen-argon mixed gas atmosphere for 2-5 h, and after completion, the atmosphere is switched to nitrogen, and the temperature is naturally cooled to room temperature. The final product, the iron-based photo-thermal catalyst, is obtained.

[0013] Further, the temperature for heating and crystallization is 40-120℃, and the time is 12-36 h.

[0014] Further, in the aqueous solution, the concentration of the zinc salt is 0.1-0.02 mol·L -1 ; the concentration of the iron salt is 0.2-0.05 mol·L -1 ; and the molar ratio of the zinc salt to the iron salt is 3-1:1.

[0015] Further, the iron salt is ferric nitrate, ferric chloride, or ferric sulfate.

[0016] Further, the zinc salt is zinc nitrate, zinc chloride, or zinc sulfate.

[0017] Further, in the buffer solution, the buffer is anhydrous sodium carbonate.

[0018] Further, the buffer solution is an aqueous solution of anhydrous sodium carbonate.

[0019] Further, the precipitant is sodium hydroxide.

[0020] Further, the washing is performed by washing with deionized water for 3-5 times.

[0021] Further, the drying is freeze-drying, and the drying time is 6-15h.

[0022] Further, in the noble metal salt, the noble metal is selected from one or more of gold and platinum. Exemplary noble metal salts include, but are not limited to, chloroplatinic acid hexahydrate, chloroauric acid tetrahydrate, and the like.

[0023] Further, the chemical formula of the precursor hydrotalcite is [Zn 2+ 1-x Fe 3+ x (OH)2] x+ ·(A n- ) x / n ·mH2O, wherein 0.2≤x≤0.33; n is the valence number of the anion; m is the number of crystal water, and the value range is 0.5-9, A n- is NO3 - or CO3 2- .

[0024] Further, in the buffer, the number of moles of the buffer is 2-8 times the total number of moles of the iron salt and the zinc salt.

[0025] Further, in the hydrogen-argon mixed gas, the volume fraction of hydrogen is 10%.

[0026] Further, the calcination conditions are: increasing the temperature to 400-600℃, preferably 300℃, at a rate of 2-5℃·min -1 , and maintaining the temperature for 2-5h.

[0027] Further, the temperature increasing rate when increasing the temperature to 100-600℃ is 2-5℃·min -1 .

[0028] Further, in the aqueous solution of the noble metal salt, the concentration of the noble metal salt is 0.1-0.05mmol·L -1 .

[0029] In another aspect, the application provides the use of the iron-based catalyst as described above in a photo-thermal catalytic water gas shift reaction.

[0030] Further, the use comprises the following steps:

[0031] In a closed reaction kettle, the iron-based catalyst is contacted with carbon monoxide gas and liquid water, and irradiated under full-spectrum conditions.

[0032] Irradiation under full-spectrum conditions, the low-temperature hydrogen production activity of the catalytic reaction is higher.

[0033] Further, the above-mentioned salts and precipitants used are all of analytical purity.

[0034] The beneficial effects of the present application are as follows:

[0035] In the technical scheme of the present application, the iron-based photo-thermal catalyst is used for the first time to realize photo-thermal water gas conversion and has very high hydrogen production activity. The iron-based photo-thermal catalyst has low cost, simple preparation and simple process, is easy to mass-produce, and is used for the first time in the photo-thermal catalytic water gas conversion reaction. The iron-based catalyst has very high hydrogen production activity at low temperature and is expected to be applied to industrial applications.

[0036] In the preparation method of the catalyst provided by the present application, the layered hydrotalcite is used as a precursor, and the topological transformation effect of the hydrotalcite itself is utilized to carry out reduction by calcination. The hydrotalcite is used as a precursor or a rigid and stable template to carry out noble metal deposition by using the induced confinement effect, so as to form a noble metal-iron-based nano photo-thermal catalyst with high dispersity and high loading. By controlling the molar ratio of zinc-iron precursor metal salt, the loading amount of noble metal and the reduction temperature, the catalyst has very high activity in the preparation of hydrogen by low-temperature photo-thermal catalytic water gas conversion. Under some preferred conditions, the hydrogen production activity at 240℃ in the low-temperature region (temperature less than 250℃) can reach 27.28μmol·gcat -1 ·s -1 , which is obviously higher than the reported iron-based catalysts. BRIEF DESCRIPTION OF DRAWINGS

[0037] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0038] Figure 1A The XRD spectra of the products obtained in Examples 1-3 and Comparative Example 1 of the present application are shown in the figure; the curves a, b, c and d in the figure correspond to the XRD spectra of the iron-based photo-thermal catalysts prepared in Examples 1-3 and Comparative Example 1, respectively; Figure 1A The curve e in the figure is the XRD spectrum of the mixed metal oxide after calcination obtained in step 3 of Example 1; Figure 1A The curve f in the figure is the XRD spectrum of the precursor hydrotalcite material (ZnFe-LDH) obtained in step 2 of Example 1.

[0039] Figure 1B The XANES spectra of the products obtained in Examples 1-3 and Comparative Example 1 of the present application are shown in the figure; the curves a, b, c and d in the figure correspond to the XANES spectra of the iron-based photo-thermal catalysts prepared in Examples 1-3 and Comparative Example 1, respectively.

[0040] Figure 1C The XPS spectra of the products obtained in Examples 1-3 and Comparative Example 1 of the present application are shown in the figure; the curves a, b, c and d in the figure correspond to the XPS spectra of the iron-based photo-thermal catalysts prepared in Examples 1-3 and Comparative Example 1, respectively.

[0041] Figure 2A The image shown is a transmission electron microscope (TEM) image of the iron-based photothermal catalyst obtained in Example 1 of the present invention.

[0042] Figure 2B The image shown is a transmission electron microscope (TEM) image of the iron-based photothermal catalyst obtained in Example 2 of the present invention.

[0043] Figure 2C The image shown is a transmission electron microscope (TEM) image of the iron-based photothermal catalyst obtained in Example 3 of the present invention.

[0044] Figure 2D The image shown is a transmission electron microscope (TEM) image of the iron-based photothermal catalyst obtained in Comparative Example 1 of the present invention.

[0045] Figure 2E The image shows a scanning electron microscope (SEM) image of the precursor hydrotalcite (ZnFe-LDH) obtained in step 2 of Embodiment 1 of the present invention.

[0046] Figure 2F The image shows a scanning electron microscope (SEM) image of the mixed metal oxide (ZnFe-MMO) obtained in step 3 of Example 1 of the present invention.

[0047] Figure 3 The diagram shows the performance of the iron-based photothermal catalysts obtained in Example 1 (0.1% Au / Fe2O3-ZnO), Example 2 (0.4% Au / Fe2O3-ZnO), Example 3 (1.0% Au / Fe2O3-ZnO), and Comparative Example 1 (Fe2O3-ZnO), as well as the precursor hydrotalcite (ZnFe-LDH) obtained in step 2 of Example 1 and the mixed metal oxide (ZnFe-MMO) obtained in step 3 of Example 1 for photothermal catalysis of water-gas conversion reaction.

[0048] Figure 4 The diagram shows the comparative performance of the iron-based photothermal catalyst obtained in Example 2 of the present invention in the photothermal catalytic water-gas conversion reaction at different temperatures (light conditions and dark reaction conditions). Detailed Implementation

[0049] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0050] Example 1

[0051] A method for preparing an iron-based photothermal catalyst for the photothermal catalytic reaction of water and gas to produce hydrogen includes the following steps:

[0052] 1) Preparation of mixed metal salt solution: Dissolve 0.01 mol ferrous chloride and 0.003 mol zinc chloride in 20 mL deionized water, slowly add dropwise to 180 mL of 0.1 mol anhydrous sodium carbonate aqueous solution, add sodium hydroxide precipitant until the pH of the solution is 8, after complete dissolution, crystallize in an oil bath at 40 °C for 24 h.

[0053] 2) After the reaction is complete, cool to room temperature, wash the crude product three times with deionized water by centrifugation, and then dry it in an oven at 80℃ for 12 hours to obtain the precursor hydrotalcite (ZnFe-LDH).

[0054] 3) The precursor hydrotalcite was thoroughly ground and placed in a muffle furnace at 5°C·min. -1 The temperature was increased to 500℃ at a heating rate and held at this temperature for 5 hours, and then allowed to cool naturally to room temperature to obtain a mixed metal oxide (ZnFe-MMO).

[0055] 4) Disperse the mixed metal oxides obtained in step 3) in deionized water, slowly add 0.01 mmol of an aqueous solution of the noble metal salt chloroauric acid tetrahydrate, and use an aqueous solution of sodium hydroxide to control the pH of the process to 8.

[0056] 5) After stirring for 2 hours, the crude product is washed three times by centrifugation with deionized water, and then freeze-dried for 12 hours to obtain the precursor of noble metal supported mixed metal oxide.

[0057] 6) The mixed metal oxides obtained above were subjected to a hydrogen-argon mixture (10% H2, v / v) at 5 °C·min. -1 The temperature was increased to 150℃ and maintained at that temperature for 5 hours. After that, the temperature was switched to N2 atmosphere and allowed to cool naturally to room temperature, thus obtaining the iron-based photothermal catalyst, denoted as 0.1% Au / Fe2O3-ZnO.

[0058] The 0.1% Au / Fe2O3-ZnO photothermal catalyst prepared according to the above method is applied to the photothermal catalytic water-gas conversion reaction. The specific method is as follows:

[0059] 10 mg of a noble metal-iron-based photothermal catalyst and 200 μL of H2O were added to a light-transmitting sealed reactor. After sealing, CO reaction gas (0.4 MPa) was introduced for full-spectrum irradiation. Gas chromatography was used to detect the changes in products over time to determine the catalyst activity and the selectivity of each product.

[0060] Figure 1A Curve a in the middle is the XRD pattern of the iron-based photothermal catalyst prepared in Example 1. Figure 1A Curve e in the middle is the XRD pattern of the calcined mixed metal oxide obtained in step 3 of Example 1. Figure 1AThe curve f is the XRD pattern of the precursor hydrotalcite material (ZnFe-LDH) obtained in step 2 of Example 1.

[0061] Figure 1B Curve a in the middle is the XANES spectrum of the iron-based photothermal catalyst prepared in Example 1.

[0062] Figure 1C Curve a is the XPS spectrum of the iron-based photothermal catalyst prepared in Example 1.

[0063] Figure 2A This is a transmission electron microscope (TEM) image of the noble metal-iron-based photothermal catalyst obtained in Example 1.

[0064] Figure 2E This is a scanning electron microscope image of the precursor hydrotalcite material (ZnFe-LDH) obtained in step 2 of Example 1.

[0065] Figure 2F The image shows a scanning electron microscope (SEM) image of the calcined mixed metal oxide (ZnFe-LDH) obtained in step 3 of Example 1.

[0066] Depend on Figure 1A As can be seen from curve f, under these conditions, the synthesized precursor hydrotalcite can form a well-structured hydrotalcite, with its (003), (006), and (110) characteristic peaks being very obvious. Figure 2E It is known that the synthesized precursor, hydrotalcite, consists of hexagonal nanosheets of approximately 400 nm in size and about 20 nm in thickness. After high-temperature calcination, the hydrotalcite structure undergoes a topological transformation, becoming a composite metal oxide of ZnO and Fe2O3, such as... Figure 1A The e-curve in the figure. Under the conditions of precious metal deposition and hydrogen reduction, such as... Figure 1A As shown by curve a in the figure, the crystal structure of the sample did not change. Figure 2A As shown, the Au nanoclusters reduced at this temperature are dispersed on Fe2O3-ZnO nanosheets. Under full-spectrum irradiation, this catalyst, after time-varying performance, achieves a water-gas conversion hydrogen production performance of 7.89 μmol·g⁻¹ at a low temperature of 240℃. cat -1 ·s -1 ,like Figure 3 As shown.

[0067] Example 2

[0068] A method for preparing an iron-based photothermal catalyst for the photothermal catalytic reaction of water and gas to produce hydrogen includes the following steps:

[0069] 1) Preparation of mixed metal salt solution: Dissolve 0.01 mol ferrous chloride and 0.003 mol zinc chloride in 20 mL deionized water, slowly add dropwise to 180 mL of 0.1 mol anhydrous sodium carbonate aqueous solution, add sodium hydroxide precipitant until the pH of the solution is 8, after complete dissolution, crystallize and reflux in an oil bath at 105 °C for 24 h.

[0070] 2) After the reaction is complete, cool to room temperature, wash the crude product three times with deionized water by centrifugation, and then dry it in an oven at 80°C for 12 hours to obtain the precursor hydrotalcite.

[0071] 3) The precursor hydrotalcite was ground and placed in a muffle furnace at 5°C·min. -1 The temperature was increased to 500℃ at a heating rate and held at this temperature for 5 hours, then allowed to cool naturally to room temperature to obtain a mixed metal oxide.

[0072] 4) Disperse the mixed metal oxides obtained in step 3) in deionized water, slowly add 0.04 mmol of aqueous solution of chloroauric acid tetrahydrate, and use aqueous solution of sodium hydroxide to control the pH of the process to 8.

[0073] 5) After stirring for 2 hours, the crude product is washed three times by centrifugation with deionized water, and then freeze-dried for 12 hours to obtain the precursor of noble metal supported mixed metal oxide.

[0074] 6) The mixed metal oxides obtained above were subjected to a hydrogen-argon mixture (10% H2, v / v) at 5 °C·min. -1 The temperature was increased to 150℃ and maintained at that temperature for 5 hours. After that, the temperature was switched to N2 atmosphere and allowed to cool naturally to room temperature, thus obtaining the iron-based photothermal catalyst, denoted as 0.4% Au / Fe2O3-ZnO.

[0075] The noble metal-iron-based photothermal catalyst prepared according to the above method is applied to the photothermal catalytic water-gas conversion reaction. The specific method is as follows:

[0076] 10 mg of a noble metal-iron-based photothermal catalyst and 200 μL of H2O were added to a light-transmitting, sealed reactor. After sealing, CO reaction gas (0.4 MPa) was introduced for full-spectrum irradiation. The changes in the product over time were detected by gas chromatography to determine the catalyst activity.

[0077] The catalyst prepared in this example was characterized as follows:

[0078] Figure 1A Curve b is the XRD pattern of 0.4% Au / Fe2O3-ZnO prepared in Example 2; Figure 1B Curve b is the XANES spectrum of 0.4% Au / Fe2O3-ZnO prepared in Example 2;Figure 1C Curve b is the XPS spectrum of 0.4% Au / Fe2O3-ZnO prepared in Example 2; Figure 2B This is a transmission electron microscope image of the noble metal-iron-based photothermal catalyst obtained in Example 2; Figure 3 The figure shows the performance of the 0.4% Au / Fe2O3-ZnO photothermal catalytic water-gas conversion reaction obtained in Example 2.

[0079] After high-temperature calcination, the precursor hydrotalcite material undergoes a topological transformation, becoming a composite metal oxide of ZnO and Fe2O3. This is followed by reduction at the reduction temperature described in this embodiment. The XRD pattern of the final product is shown below. Figure 1A The b-curve and XANES spectrum are as follows: Figure 1B The b-curve and XPS spectrum are shown below. Figure 1C In curve b, the Au portion is reduced to elemental Au; from Figure 2B As observed, the reduced noble metal-iron based catalyst at this temperature retains the layered structure of hydrotalcite, with highly loaded gold nanoclusters dispersed on Fe2O3-ZnO nanosheets. Under full-spectrum irradiation, this catalyst, after time-varying performance, achieves a water-gas conversion hydrogen production performance of 27.28 μmol·g⁻¹ at a low temperature of 240℃. cat -1 ·s -1 The results above show that, under illumination, the 0.4% Au / Fe2O3-ZnO catalyst exhibits significantly higher catalytic activity for hydrogen evolution compared to the 0.1% Au / Fe2O3-ZnO catalyst.

[0080] Example 3

[0081] A method for preparing an iron-based photothermal catalyst for the photothermal catalytic reaction of water and gas to produce hydrogen includes the following steps:

[0082] 1) Preparation of mixed metal salt solution: Dissolve 0.01 mol ferrous chloride and 0.003 mol zinc chloride in 20 mL deionized water, slowly add dropwise to 180 mL of 0.1 mol anhydrous sodium carbonate aqueous solution, add sodium hydroxide precipitant until the pH of the solution is 8, after complete dissolution, crystallize and reflux in an oil bath at 105 °C for 24 h.

[0083] 2) After the reaction is complete, cool to room temperature, wash the crude product three times with deionized water by centrifugation, and then dry it in an oven at 80°C for 12 hours to obtain the precursor hydrotalcite.

[0084] 3) The precursor hydrotalcite was ground and placed in a muffle furnace at 5°C·min. -1 The temperature was increased to 500℃ at a heating rate and held at this temperature for 5 hours, then allowed to cool naturally to room temperature to obtain a mixed metal oxide.

[0085] 4) Disperse the mixed metal oxides obtained in step 3) in deionized water, slowly add an aqueous solution of the noble metal salt chloroauric acid tetrahydrate, and use an aqueous solution of sodium hydroxide to control the pH of the process to 8.

[0086] 5) After stirring for 2 hours, the crude product is washed three times by centrifugation with deionized water, and then freeze-dried for 12 hours to obtain the precursor of noble metal supported mixed metal oxide.

[0087] 6) The mixed metal oxides obtained above were subjected to a hydrogen-argon mixture (10% H2, v / v) at 5 °C·min. -1 The temperature was increased to 150℃ and maintained at that temperature for 5 hours. After that, the temperature was switched to N2 atmosphere and allowed to cool naturally to room temperature, thus obtaining the iron-based photothermal catalyst, denoted as 1.0% Au / Fe2O3-ZnO.

[0088] The noble metal-iron-based photothermal catalyst prepared according to the above method is applied to the photothermal catalytic water-gas conversion reaction. The specific method is as follows:

[0089] 100 mg of a noble metal-iron-based photothermal catalyst and 200 μL of H2O were added to a light-transmitting, sealed reactor. After sealing, CO reaction gas (0.4 MPa) was introduced for full-spectrum irradiation. Gas chromatography was used to detect the changes in products over time to determine the catalyst activity and the selectivity of each product.

[0090] The catalyst prepared in this example was characterized as follows:

[0091] Appendix Figure 1A Curve c is the XRD pattern of 1.0% Au / Fe2O3-ZnO prepared in Example 3; (See attached image) Figure 1B Curve c is the XANES spectrum of 1.0% Au / Fe2O3-ZnO prepared in Example 3; (See attached image) Figure 1C Curve c is the XPS spectrum of 1.0% Au / Fe2O3-ZnO prepared in Example 3; Figure 2B This is a transmission electron microscope image of the noble metal-iron-based photothermal catalyst obtained in Example 3; Figure 3 The figure shows the performance of the 1.0% Au / Fe2O3-ZnO photothermal catalytic water-gas conversion reaction obtained in Example 3.

[0092] After high-temperature calcination, the precursor hydrotalcite material undergoes a topological transformation, becoming a composite metal oxide of ZnO and Fe2O3. This is followed by reduction at the reduction temperature described in this embodiment. The XRD pattern of the final product is shown below. Figure 1A The middle curve c and XANES spectrum are as follows Figure 1B The c-curve and XPS spectrum are as followsFigure 1C As shown by curve c, Au is partially reduced to elemental Au; from Figure 2B As observed, the reduced noble metal-iron based catalyst at this temperature retains the layered structure of hydrotalcite, with gold nanoparticles dispersed on Fe2O3-ZnO nanosheets. Under full-spectrum irradiation, this catalyst exhibits a water-gas conversion hydrogen production performance of 21.60 μmol·g⁻¹ at a low temperature of 240℃, after time-varying performance. cat -1 ·s -1 The results above show that, under illumination, the activity of the 1.0% Au / Fe2O3-ZnO catalyst is reduced compared to that of the 0.4% Au / Fe2O3-ZnO catalyst, but it still exhibits considerable hydrogen production activity.

[0093] Comparative Example 1

[0094] A method for preparing an iron-based photothermal catalyst for the photothermal catalytic reaction of water and gas to produce hydrogen includes the following steps:

[0095] 1) Preparation of mixed metal salt solution: Dissolve 0.01 mol ferrous chloride and 0.003 mol zinc chloride in 20 mL deionized water, slowly add dropwise to 180 mL of 0.1 mol anhydrous sodium carbonate aqueous solution, add sodium hydroxide precipitant until the pH of the solution is 8, after complete dissolution, crystallize in an oil bath at 40 °C for 24 h.

[0096] 2) After the reaction is complete, cool to room temperature, wash the crude product three times with deionized water by centrifugation, and then dry it in an oven at 80°C for 12 hours to obtain the precursor hydrotalcite.

[0097] 3) The precursor hydrotalcite was thoroughly ground and placed in a muffle furnace at 5°C·min. -1 The temperature was increased to 500℃ at a heating rate and held at this temperature for 5 hours, then allowed to cool naturally to room temperature to obtain a mixed metal oxide.

[0098] 4) The mixed metal oxides obtained above were subjected to a hydrogen-argon mixture atmosphere (10% H2, v / v) at 5 °C·min. -1 The temperature was increased to 550℃ and maintained at that temperature for 5 hours. After that, the temperature was switched to N2 atmosphere and allowed to cool naturally to room temperature, thus obtaining the iron-based photothermal catalyst, denoted as Fe2O3-ZnO.

[0099] The noble metal-iron-based photothermal catalyst prepared according to the above method is applied to the photothermal catalytic water-gas conversion reaction. The specific method is as follows:

[0100] 100 mg of a noble metal-iron-based photothermal catalyst was added to a light-transmitting sealed reactor, CO reaction gas (0.4 MPa) was introduced, 200 μL of H2O was added, the reactor was sealed, and full-spectrum light was applied. Gas chromatography was used to detect the changes in products over time to determine the catalyst activity and the selectivity of each product.

[0101] Figure 1A Curve d in the middle is the XRD pattern of the iron-based photothermal catalyst prepared in Comparative Example 1. Figure 1B Curve d in the middle is the XANES spectrum of the iron-based photothermal catalyst prepared in Comparative Example 1. Figure 1C Curve d in the middle is the XPS spectrum of Fe2O3-ZnO prepared in Comparative Example 1; Figure 2D The image shows a transmission electron microscope (TEM) image of the noble metal-iron-based photothermal catalyst obtained in Comparative Example 1. Figure 3 The diagram shows the photothermal catalytic performance of the iron-based photocatalyst obtained in Comparative Example 1 for the water-gas conversion reaction.

[0102] Depend on Figure 1A As can be seen from curve f, under these conditions, the synthesized precursor hydrotalcite can form a well-structured hydrotalcite, with its (003), (006), and (110) characteristic peaks being very obvious. Figure 2E It is known that the synthesized precursor, hydrotalcite, consists of hexagonal nanosheets of approximately 400 nm in size and about 20 nm in thickness. After high-temperature calcination, the hydrotalcite structure undergoes a topological transformation, becoming a composite metal oxide of ZnO and Fe2O3, such as... Figure 1A Curve e in the figure. Under the conditions of noble metal deposition and hydrogen reduction, such as Figure 1A As shown by curve d in the figure, the crystal structure of the sample did not change. Figure 2D The Fe2O3-ZnO structure still maintains a well-defined layered structure of hydrotalcite. Figure 3 As can be seen, the catalytic activity of the catalyst is significantly reduced, indicating that gold plays a very important role in the conversion of water gas to hydrogen.

[0103] Comparative Example 2

[0104] An iron-based photothermal catalyst for the photothermal catalytic reaction of water and gas to produce hydrogen is disclosed. The preparation method is the same as in Example 2, except that the heating method of the closed reaction vessel during the water-gas reaction is changed to pure electric heating, while the temperature remains at 240°C. Figure 4 The results showed that the catalyst's catalytic activity was significantly reduced in the dark, indicating that light irradiation plays a very important role in the photothermal catalysis of water-gas reaction to produce hydrogen using iron-based photothermal catalysts.

[0105] Comparative Example 3

[0106] A titanium-zinc based photothermal catalyst for the photothermal reaction of water and gas to produce hydrogen is disclosed in Example 2, differing only in that 0.01 mol of ferrous chloride is replaced with 0.01 mol of tetrabutyl titanate during material preparation. The resulting catalyst, under full-spectrum irradiation, exhibits a hydrogen production rate of less than 20 μmol·g⁻¹ at a low temperature of 240°C after time-varying behavior in the water-gas conversion process. cat -1 ·s -1 .

[0107] In summary, existing technologies for preparing high-hydrogen-yielding active catalysts through water-gas conversion primarily rely on high-temperature iron-based catalysts, which suffer from high energy consumption and significant environmental pollution during the reaction process. This invention, for the first time, employs photothermal catalysis of the water-gas conversion reaction. This approach is not only more environmentally friendly and energy-efficient than existing technologies, but also the first to utilize a noble metal-iron-based catalyst for photothermal catalysis of the water-gas conversion reaction, exhibiting excellent hydrogen production performance in the low-temperature region. This invention holds promise for industrial scale-up and practical application.

[0108] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. An iron-based catalyst for a photo-thermo-catalytic water gas shift reaction, characterized in that, The structure of the catalyst comprises zinc-iron composite metal oxide and cluster-shaped noble metal particles supported on the zinc-iron composite metal oxide.

2. The catalyst according to claim 1, characterized in that, The noble metal particles are selected from one or more of gold, platinum and silver.

3. The catalyst of claim 1, wherein The mass ratio of the zinc-iron composite metal oxide to the noble metal particles is 0.1-5 wt%.

4. The process for the preparation of an iron-based catalyst according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: An aqueous solution of zinc salt and iron salt is added dropwise into a buffer solution, a precipitant is added to the solution to adjust the pH to 8-10, the material is fully dissolved, then crystallization is performed by heating, and after cooling to room temperature, the precursor hydrotalcite is obtained by washing and drying; The precursor hydrotalcite is ground, calcined, and cooled to room temperature to obtain a mixed metal oxide; The mixed metal oxide is dispersed in deionized water, an aqueous solution of noble metal salt is added, and the pH of the solution is controlled to 8-10, then the noble metal-zinc-iron mixed metal oxide precursor is obtained by washing and drying; The noble metal-zinc-iron mixed metal oxide precursor is heated to 100-600℃ in a hydrogen-argon mixed gas atmosphere for 2-5 h, then switched to a nitrogen atmosphere, and naturally cooled to room temperature to obtain the final product, the iron-based photo-thermal catalyst.

5. The preparation method according to claim 4, characterized in that, The temperature for the heating crystallization is 40-120℃, and the time is 12-36 h; and / or The concentration of the zinc salt in the aqueous solution is 0.1-0.02 mol-L -1 The concentration of the iron salt in the aqueous solution is 0.2-0.05 mol-L -1 The molar ratio of the zinc salt to the iron salt is 3-1:1; and / or In the buffer solution, the number of moles of the buffer is 2-8 times the total number of moles of the iron salt and the zinc salt.

6. The preparation method according to claim 4, characterized in that, The conditions for the calcination are: temperature increase at a rate of 2-5°C·min -1 to 400-600°C and holding at this temperature for 2-5 h.

7. The preparation method according to claim 4, characterized in that, The temperature increasing rate to 100-600℃ is 2-5℃·min -1 .

8. The preparation method according to claim 4, characterized in that, The concentration of the noble metal salt in the aqueous solution of the noble metal salt is 0.1-0.05 mmol / L -1 .

9. Use of the iron-based catalyst according to any one of claims 1-3 in a photo-thermal catalytic water-gas shift reaction.

10. Use according to claim 9, characterized in that, The use comprises the following steps: The iron-based catalyst is contacted with carbon monoxide gas and liquid water in a closed reaction kettle, and irradiated under full-spectrum conditions; Preferably, the use ratio of the iron-based catalyst to liquid water is 10-100 mg: 100-500 μL; and the partial pressure of the carbon monoxide gas is 0.2-1 MPa.

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