A Ni-doped rare earth metal-type nano-oxide, its preparation method and application

Abstract

The present invention provides a Ni-doped rare earth metal-based nano-oxide, a preparation method thereof and an application. In the present invention, after directly mixing a rare earth metal source and a Ni source, a precursor is prepared and then reduced. In the obtained nano-oxide, Ni is atomically dispersed, mainly in the form of Ni<supgt;2+< / supgt;, and a rich, uniformly distributed and stable Ni-O active site can be constructed. In addition, by using the above method, the content of Ni element in the Ni-doped rare earth metal-based nano-oxide can reach about 10 wt%, which is much higher than the prior art level. In addition, the preparation method provided by the present invention has easily available synthetic raw materials, is simple, convenient and time-consuming, and is easy to realize large-scale production. After testing, the Ni-doped rare earth metal-based nano-oxide has excellent photothermal catalytic activity.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterial synthesis, and particularly relates to a Ni-doped rare earth metal type nano-oxide, a preparation method thereof, and an application thereof, and more particularly to a Ni / CeO x nano-oxide, a preparation method thereof, and an application thereof. Background Art

[0002] Dry reforming of methane (DRM) can simultaneously utilize two major greenhouse gases, CO 2 and CH 4 to produce valuable syngas (CO + H 2 ), and thus has been proposed and studied (Chem Rev. 2017, 117(13), 8497-8520). Syngas can be further synthesized into important raw materials for high-value chemicals such as olefins and gasoline through the Fischer-Tropsch synthesis method. Therefore, the DRM reaction can not only effectively alleviate the greenhouse effect, but also may provide a viable alternative to traditional fossil fuels, thereby promoting the sustainable development of future energy. In addition, the progress of this technology makes it possible to effectively exploit natural gas with a high carbon dioxide content, paving the way for its wider application, while it is difficult to utilize this resource with the traditional steam reforming method.

[0003] Since CO 2 and CH 4 are very stable and difficult to activate, the energy requirement for DRM is as high as 247 kJ mol -1 , usually requiring a high temperature of 700-1000 °C and a pressure of 1-30 atmospheres to drive the reaction, resulting in more energy consumption. Therefore, in order to promote the occurrence of low-temperature DRM reaction, clean and sustainable light energy can be introduced as an alternative energy source. So far, various catalysts for light-driven DRM have been developed. Among various catalysts, Ni-based materials exhibit excellent methane cracking ability, and their activity is comparable to that of noble metal catalysts, and the price is much lower than that of noble metals. However, Ni-based catalysts are prone to sintering, resulting in a reduction in the number of active sites. In addition, excessive carbon deposition will cause obvious deactivation of the catalyst after several cycles. This is because, compared with noble metals, the equilibrium constant of the methane cracking reaction on the Ni surface is higher, thus promoting the formation and growth of inactive carbon nanotubes and graphite carbon layers, blocking the catalyst active sites.

[0004] Based on the above problems, Akri et al. prepared a single-atom catalyst Ni / HAP-Ce catalyst to inhibit carbon deposition caused by excessive cracking of methane, but when the Ni loading was increased to 10 wt%, Ni particles were still formed (Nat Commun. 2019, 10, 5181). Tavasoli et al. selectively phosphated CeO 2 Nanorod support surface to adjust Ni-CeO 2 Photocatalytic performance, but its activity is still low (Nat Commun. 2023, 14, 1435). Therefore, how to further improve the stability of Ni-based catalysts while retaining their high activity through simple and effective methods is still an urgent requirement for their practical application. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a Ni-doped rare earth metal nano-oxide and a preparation method and application thereof. The Ni-doped rare earth metal nano-oxide has excellent stability and high activity for photothermal catalytic methane dry reforming reaction.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a Ni-doped rare earth metal nano-oxide, which is prepared by heating a mixture of a rare earth metal source and a Ni source to form a precursor, followed by reduction.

[0008] Preferably, the mass content of Ni element in the rare earth metal nano-oxide is 8.5-10 wt%.

[0009] Preferably, the rare earth metal in the rare earth metal source is selected from any one or more of Ce, La, Sm or Nd, preferably Ce.

[0010] In a second aspect, the present invention provides a method for preparing the above-mentioned Ni-doped rare earth metal type nano oxide, comprising the following steps:

[0011] S1: After mixing a rare earth metal source, a Ni source and a solvent, the obtained mixture is reacted under heating conditions to obtain a precursor;

[0012] S2: After reducing the precursor, Ni-doped rare earth metal nano-oxide is obtained.

[0013] Preferably, the rare earth metal source is selected from Ce(NO 3 ) 3 6H 2 O、La(NO 3 ) 2 6H 2 O、Sm(NO3 ) 2 ·6H 2 O, Nd(NO 3 ) 2 ·6H 2 O, CeCl 3 ·7H 2 O, LaCl 3 ·7H 2 O, SmCl 3 ·6H 2 O or NdCl 3 ·6H 2 O, or any one or more of the following.

[0014] Preferably, the Ni source is selected from Ni(NO 3 ) 2 ·6H 2 O and / or NiCl 2 ·6H 2 O.

[0015] Preferably, the solvent is selected from triethylene glycol and / or ethylene glycol.

[0016] Preferably, the molar ratio of the rare earth metal source to the Ni source is (3.0~3.6):1.

[0017] Preferably, after the rare earth metal source is completely dissolved in the solvent, it is mixed with the Ni source to obtain a mixture.

[0018] Preferably, the dissolution is carried out under the condition that the temperature is raised from room temperature to 80~100°C.

[0019] Preferably, the temperature of the heating condition is 160~200°C; the time for heating to the temperature of the heating condition is 5~10 min.

[0020] Preferably, the reaction time is 0.5~3 h.

[0021] Preferably, the reduction is carried out in an atmosphere containing hydrogen.

[0022] Preferably, the reduction temperature is 300~400°C and the time is 1~5 h.

[0023] In the third aspect, the present invention provides an application of the above Ni-doped rare earth metal type nano-oxide in the photo-thermal catalytic dry reforming of methane.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] The present invention provides a Ni-doped rare earth metal-based nano-oxide, which is prepared by heating a mixture of a rare earth metal source and a Ni source to form a precursor and then reducing it. By directly mixing the rare earth metal source and the Ni source, preparing the precursor, and then performing reduction, in the obtained nano-oxide, N is atomically dispersed and mainly exists as Ni 2+ , and a rich, uniformly distributed, and stable Ni-O active site can be constructed. In addition, by using the above method, the content of Ni element in the Ni-doped rare earth metal-based nano-oxide can reach about 10 wt%, which is much higher than the prior art level. In addition, the preparation method provided by the present invention has easily available synthetic raw materials, is simple, convenient, and time-consuming, and is easy to realize large-scale production.

[0026] The present invention uses the above Ni-doped rare earth metal-based nano-oxide as a catalyst in the reaction of photothermal catalytic dry reforming of methane. The existing Ni-O active sites are beneficial to the formation of CH X O* (1 ≤ x ≤ 3) intermediate, avoiding deep dehydrogenation of methane to produce carbon deposition, thereby reducing catalyst deactivation caused by carbon deposition. In addition, the presence of rare earth metal oxides is beneficial to the adsorption and activation of CO 2 , facilitating catalysis by the Ni-O active site, and further promoting the conversion of the CH X O* intermediate.

[0027] After testing, the Ni-doped rare earth metal-based nano-oxide provided by the present invention is used as a catalyst in the reaction of photothermal catalytic dry reforming of methane. Under the light intensity of 4 W cm -2 , the H 2 and CO yields are as high as 626.5 and 728.5 mmol g cat -1 h -1 , and it has good photothermal conversion ability and can operate stably for 100 h, indicating its good stability and lifespan for photothermal catalytic dry reforming of methane. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 X-ray diffraction pattern of the Ni / CeO x precursor and the Ni / CeO x -350 sample prepared in Example 1;

[0029] Figure 2 Element distribution pattern of the Ni / CeO x -350 sample prepared in Example 1;

[0030] Figure 3 Ni / CeO prepared in Example 1 x-350 as a catalyst for the photo-thermal catalytic dry reforming of methane to produce CO and H 2 Yield result diagram;

[0031] Figure 4 Ni / CeO prepared in Example 1 x -350 and Ni obtained in Comparative Example 1 NP / CeO 2 As a catalyst for the photo-thermal catalytic dry reforming of methane, the long-cycle stability test result diagram under the light intensity of 4 W cm -2 . Detailed implementation manners

[0032] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0033] Aiming at the problems of poor coke resistance and easy carbon deposition inactivation of existing Ni-based catalysts, the present invention provides a Ni-doped rare earth metal-based nano-oxide, which is preferably prepared by heating a mixture of a rare earth metal source and a Ni source to form a precursor and then reducing it.

[0034] In the present invention, the mass content of Ni element in the rare earth metal-based nano-oxide is 8.5-10 wt%.

[0035] In the present invention, the rare earth metal in the rare earth metal source is selected from any one or more of Ce, La, Sm or Nd, and preferably Ce.

[0036] The rare earth metal in the rare earth metal source in the present invention is denoted as M, then the Ni-doped rare earth metal-based nano-oxide can be denoted as: Ni / MO x , and the value of subscript x is generally between 1 and 2.

[0037] In some embodiments of the present invention, when M is selected from Ce, the Ni-doped rare earth metal-based nano-oxide can be denoted as: Ni / CeO x (the value of x is between 1 and 2).

[0038] The present invention also provides a preparation method of the above-mentioned Ni-doped rare earth metal-based nano-oxide, including the following steps:

[0039] S1: After mixing the rare earth metal source, the Ni source and the solvent, react the obtained mixture under heating conditions to obtain a precursor;

[0040] S2: After reducing the precursor, Ni-doped rare-earth metal-type nano-oxides are obtained.

[0041] According to the present invention, first, a rare-earth metal source, a Ni source and a solvent are mixed to obtain a mixture.

[0042] In some embodiments of the present invention, the rare-earth metal source is selected from Ce(NO 3 ) 3 ·6H 2 O, La(NO 3 ) 2 ·6H 2 O, Sm(NO 3 ) 2 ·6H 2 O, Nd(NO 3 ) 2 ·6H 2 O, CeCl 3 ·7H 2 O, LaCl 3 ·7H 2 O, SmCl 3 ·6H 2 O or NdCl 3 ·6H 2 O, and any one or more of them are preferred to be Ce(NO 3 ) 3 ·6H 2 O and / or CeCl 3 ·7H 2 O; the Ni source is selected from Ni(NO 3 ) 2 ·6H 2 O and / or NiCl 2 ·6H 2 O; the solvent is selected from triethylene glycol or other alcohol reagents such as ethylene glycol.

[0043] In some specific embodiments of the present invention, the rare-earth metal source is selected from Ce(NO 3 ) 3 ·6H 2 O; the Ni source is selected from Ni(NO 3 ) 2 ·6H 2 O; the solvent is selected from triethylene glycol to facilitate the formation of CeO with specific exposed (111) and (200) crystal planes 2 .

[0044] In some preferred embodiments of the present invention, to ensure the highly atomic-level dispersion of the doped Ni, the present invention uses Ce(NO 3 ) 3 ·6H2 Add triethylene glycol, keep the temperature at 80 - 100 °C and stir to dissolve it completely. Then add Ni(NO 3 ) 2 ·6H 2 O. Similarly, keep the temperature at 80 - 100 °C and stir to dissolve and mix evenly to obtain a mixture.

[0045] In the present invention, the molar ratio of the rare earth metal source to the Ni source is (3.0 - 3.6):1. In some embodiments of the present invention, it is preferred that the molar ratio of Ce(NO 3 ) 3 ·6H 2 O to Ni(NO 3 ) 2 ·6H 2 O is (3.0 - 3.6):1, preferably (3.0 - 3.3):1, and more preferably 3.0:1.

[0046] After obtaining the mixture, according to the present invention, quickly raise the temperature of the mixture to 160 - 200 °C (specifically, it can be 160 °C, 170 °C, 180 °C, 190 °C, 200 °C), and keep the temperature at this temperature for 0.5 - 3 h, preferably 1 - 2 h, to obtain a precursor. In the present invention, the temperature increase needs to be carried out quickly, and the time for temperature increase is generally controlled within 5 - 10 min, preferably 5 - 7 min. The present invention preferably controls the time for temperature increase because rapid temperature increase is conducive to the formation of a large number of crystal nuclei, and at the same time, shortening the operation time is more convenient. During the experiment, if the temperature is not increased quickly, it may cause the growth time of some crystal nuclei to be too long, which is not conducive to controlling the crystallinity and the size of the catalyst.

[0047] In the present invention, after obtaining the precursor, it can be reduced. In some embodiments of the present invention, preferably, the precursor is treated before reduction.

[0048] The treatment of the precursor preferably includes: adding a mixed solution of ethanol and ethyl acetate in a certain proportion to the obtained precursor solution to precipitate the product, ultrasonically dispersing the above sample with ethanol, and then adding a certain amount of mixed solution of ethanol and ethyl acetate (ethanol:ethyl acetate is 30:40, volume ratio) for centrifugal separation. Repeat this cleaning process, and then dry to obtain the precursor.

[0049] The above ultrasonic dispersion can make the precursor more evenly dispersed and the cleaning more thorough, and can avoid excessive solvent residue. The ratio of ethanol to ethyl acetate can be adjusted according to the actual situation, and ethanol and ethyl acetate can also use other similar reagents, which are not specifically limited in the present invention.

[0050] The drying is preferably vacuum drying, and the temperature of the vacuum drying is 50 to 70 °C, preferably 60 °C.

[0051] Finally, according to the present invention, the obtained precursor can be reduced.

[0052] In the present invention, the role of the reduction is to activate the catalyst and further adjust the surface structure and Ni valence state of the catalyst.

[0053] The temperature required for the reduction is 300 to 400 °C, such as 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 370 °C, 380 °C, 390 °C or 400 °C, etc., preferably 350 °C. In the present invention, if the reduction temperature is too high, it will cause the material to sinter, Ni to precipitate, and the catalyst structure to be damaged.

[0054] The reduction gas flow is a gas flow containing hydrogen, preferably a hydrogen-argon mixture or a hydrogen-helium mixture. To ensure experimental safety, generally the proportion of hydrogen in the hydrogen-argon mixture or hydrogen-helium mixture should not be too high and can be adjusted as needed. For example, specifically it can be: 10% H 2 / 90% Ar.

[0055] In some embodiments of the present invention, it is preferred to place the prepared precursor in a tubular furnace, continuously pass a reduction gas flow for 0.5 to 2 h at room temperature to remove the air in the tubular furnace, and then heat it at a rate of 5 to 10 °C min -1 to 300 to 400 °C for hydrogen reduction for 1 to 5 h, preferably 2 to 4 h, and collect the target product.

[0056] In summary, in some specific embodiments of the present invention, a method for preparing Ni / CeO x nanoxide is provided, and the steps are as follows:

[0057] a) Precursor synthesis: Using triethylene glycol as a solvent and a surfactant, and using the polyol-mediated method, heating and dissolving and uniformly mixing Ce(NO 3 ) 3 ·6H 2 O and Ni(NO 3 ) 2 ·6H 2 O, quickly heating to 170 °C to prepare the Ni / CeO x precursor for use;

[0058] b) Precursor treatment: Add a mixed solution of ethanol and ethyl acetate in a certain proportion to the precursor solution in step a) to form a product precipitate. Ultrasonically disperse the above sample with ethanol, then add a certain amount of the mixed solution of ethanol and ethyl acetate for centrifugal separation. Repeat this cleaning process, and then perform vacuum drying to obtain the precursor;

[0059] c) Sample reduction: Reduce the sample prepared in step b) with hydrogen at a certain temperature, and collect to obtain the Ni / CeO x series of nano-oxides.

[0060] The synthesis raw materials provided by the present invention are easily available, the method is simple, convenient and time-consuming, and it is easy to realize large-scale production.

[0061] The present invention also provides an application of the above-mentioned Ni-doped rare earth metal type nano-oxide in the dry reforming of methane by photothermal catalysis.

[0062] After testing, the Ni-doped rare earth metal type nano-oxide provided by the present invention is used as a catalyst in the reaction of dry reforming of methane by photothermal catalysis. Under the light intensity of 4 W cm -2 The yields of H 2 and CO are as high as 626.5 and 728.5 mmol g cat -1 h -1 , and it has good photothermal conversion ability and can operate stably for 100 h, indicating its good stability and lifespan in the dry reforming of methane by photothermal catalysis.

[0063] It can be seen that the Ni-doped rare earth metal type nano-oxide has enhanced photothermal catalytic activity after optimization, which is at the same level as noble metal catalytic materials. At the same time, the catalytic stability is greatly improved compared with the Ni particle catalyst prepared by the traditional impregnation method.

[0064] To further illustrate the present invention, the following examples are used for detailed description. The experimental raw materials used in the following examples of the present invention are all general commercially available products.

[0065] Example 1

[0066] 1) The preparation method of Ni / CeO x nano-oxide is as follows:

[0067] First, add 2 mmol Ce(NO 3 ) 3 ·6H 2 O to a 150 mL three-necked flask, and add 50 mL of triethylene glycol. Rapidly heat from room temperature to 100 °C under strong magnetic stirring and keep it for 30 minutes to fully dissolve it. Then add 0.6 mmol Ni(NO3 ) 2 ·6H 2 O, stir for 30 minutes while maintaining the temperature at 100 °C. Rapidly heat the resulting solution from 100 °C to 170 °C within 7 minutes, and stir for 1 h to prepare the Ni / CeO x precursor for use (the molar ratio of Ni to Ce is 3:10). After the solution cools, add a mixed solution of appropriate ethanol and ethyl acetate (volume ratio 3:40) to precipitate the precursor. After centrifugation, add appropriate ethanol to ultrasonically disperse the above sample, and then use the ethanol and ethyl acetate mixed solution for centrifugal separation again. Repeat this washing process, and finally dry in vacuum at 60 °C to obtain the precursor. Place 50 mg of the prepared precursor sample in a tubular furnace, and continuously pass a reducing gas stream (10% H 2 / 90% Ar) at room temperature for 0.5 h to remove the air in the tubular furnace. Subsequently, heat it to 350 °C at a rate of 5 °C min -1 for hydrogen reduction for 2 h, and collect the product Ni / CeO x -350.

[0068] Figure 1 This is the X-ray diffraction pattern of the Ni / CeO x precursor and the Ni / CeO x -350 sample prepared in this example. It can be seen from this that the product prepared in this example has a relatively low crystallinity and overall shows the CeO 2 crystal form, and no diffraction signal of Ni particles is detected. Figure 2 This is the elemental distribution pattern of the Ni / CeO x -350 sample prepared in this example. It can be found from this that the prepared sample shows a highly dispersed Ni distribution, further indicating the successful synthesis of Ni / CeO x nano-oxide with uniformly dispersed Ni element.

[0069] 2) Photothermal catalytic performance test of methane dry reforming reaction:

[0070] Take 5 mg of Ni / CeO x -350 catalyst, add 400 μL of distilled water, ultrasonically disperse it, and then uniformly drip it onto a glass fiber disc for sample preparation. Subsequently, dry it on a hot plate at 100 °C. Place the sample on a quartz support inside a flow reactor equipped with a quartz window to allow light irradiation, and use a 300 W xenon lamp as the light source. Use CH 4 :CO 2 :Ar (1:1:8) as the feed gas, check the airtightness of the flow device, and adjust the gas flow rate to 20 mL min -1Continuously introduce it into the reactor. After fixing the reactor and the xenon lamp, adjust the light intensity to 4 W cm -2 using a light power meter. Detect the components and contents of each gas in the effluent phase through an on-line gas chromatograph, and calculate the product yield and the conversion rate of the raw material gas. It is measured that the yields of H -2 and CO of the sample under the light intensity of 4 W cm 2 are as high as 626.5 and 728.5 mmol g cat -1 h -1 .

[0071] Figure 3 Using Ni / CeO x -350 prepared in Example 1 as a catalyst for the photocatalytic dry reforming of methane to produce CO and H 2 yields, it can be found that the activity of this material increases continuously with the increase of light intensity.

[0072] 3) Photothermal temperature measurement of Ni / CeO x nano-oxide:

[0073] Take 5 mg of Ni / CeO x -350 catalyst, add 400 μL of distilled water, ultrasonically disperse it and then evenly drip it on a glass fiber disc for sample preparation, and then dry it on a 100°C heating plate. Fix the sample on a 200°C heating stage. After the temperature of the sample is measured and stabilized by a K-type thin-film thermocouple, use an infrared thermal imager to measure the photothermal temperature of the sample surface and correct its emissivity to 0.08 according to the thermocouple data. Place the sample in a CH -1 :CO 4 :Ar(1:1:8) gas flow rate of 20 mL min 2 , and use the corrected infrared thermal imager to measure the photothermal temperature of the sample surface under the irradiation of 4 W cm -2 light intensity, which is 520.2°C, indicating that the Ni / CeO x -350 catalyst has good photothermal conversion ability.

[0074] Example 2

[0075] The specific process is the same as that of Example 1, except that in step 1), the obtained solution is rapidly heated from 100°C to 180°C within 7 minutes, stirred for 1 h to prepare the Ni / CeO x precursor, and the subsequent steps are the same. It is measured that the catalytic activity of this catalyst for the dry reforming of methane is close to that of Ni / CeO x -350 obtained in Example 1.

[0076] Example 3

[0077] The specific process is the same as that in Example 1, except that in step 1), the obtained solution is rapidly heated from 100 °C to 190 °C within 7 minutes, stirred for 1 h to prepare the Ni / CeO x precursor, and the subsequent steps are the same. The catalytic activity of this catalyst for dry reforming of methane is measured to be close to that of the Ni / CeO x -350 obtained in Example 1.

[0078] Example 4

[0079] 1) The preparation method of Ni NP / CeO x nano-oxide is as follows:

[0080] First, add 2 mmol of Ce(NO 3 ) 3 ·6H 2 O to a 150 mL three-necked flask, and add 50 mL of triethylene glycol. Rapidly heat from room temperature to 100 °C under strong magnetic stirring and keep it for 30 minutes to fully dissolve. Then rapidly raise the temperature to 170 °C within 7 minutes, continue stirring for 1 h, and then naturally cool to 100 °C. Then add 0.6 mmol of Ni(NO 3 ) 2 ·6H 2 O, stir for 30 minutes, and keep the temperature at 100 °C. Subsequently, rapidly heat the obtained solution from 100 °C to 170 °C within 7 minutes, stir for 1 h to prepare the Ni NP / CeO x precursor for use (the molar ratio of Ni to Ce is 3:10). After the solution is cooled, add a mixed solution of appropriate ethanol and ethyl acetate (volume ratio 3:40) to precipitate the precursor. After centrifugation, add appropriate ethanol to ultrasonically disperse the above sample, and then use the ethanol and ethyl acetate mixed solution for centrifugal separation again. Repeat this cleaning process, and finally dry in vacuum at 60 °C to obtain the precursor. Place 50 mg of the prepared precursor sample in a tubular furnace, continuously pass a reducing gas stream (10% H 2 / 90% Ar) at room temperature for 0.5 h to remove the air in the tubular furnace, and then heat it to 400 °C at a rate of 5 °C min -1 for hydrogen reduction for 2 h to collect the product Ni NP / CeO x (1 ≤ x ≤ 2).

[0081] 2) Photothermal catalytic performance test for dry reforming of methane:

[0082] It is the same as in Example 1, but the test results show that the activity of Ni NP / CeO x nano-oxide is very low.

[0083] Example 5

[0084] The specific process is the same as that of Example 1, except that in steps 2) and 3), the xenon lamp intensity is adjusted to 2 W cm by using a light power meter -2 , and the photothermal temperature of the sample surface measured by the emissivity-corrected thermal imager is 360.1 °C. The H 2 and CO yields under the light intensity are 11.4 and 47.8 mmol g cat -1 h -1 respectively.

[0085] Example 6

[0086] The specific process is the same as that of Example 1, except that in steps 2) and 3), the xenon lamp intensity is adjusted to 2.5 W cm by using a light power meter -2 , and the photothermal temperature of the sample surface measured by the emissivity-corrected thermal imager is 400.0 °C. The H 2 and CO yields under the light intensity are 52.0 and 145.8 mmol g cat -1 h -1 respectively.

[0087] Example 7

[0088] The specific process is the same as that of Example 1, except that in steps 2) and 3), the xenon lamp intensity is adjusted to 3 W cm by using a light power meter -2 , and the photothermal temperature of the sample surface measured by the emissivity-corrected thermal imager is 430.1 °C. The H 2 and CO yields under the light intensity are 180.0 and 347.0 mmol g cat -1 h -1 respectively.

[0089] Example 8

[0090] The specific process is the same as that of Example 1, except that in steps 2) and 3), the xenon lamp intensity is adjusted to 3.5 W cm by using a light power meter -2 , and the photothermal temperature of the sample surface measured by the emissivity-corrected thermal imager is 485.7 °C. The H 2 and CO yields under the light intensity are 279.9 and 469.9 mmol g cat -1 h -1 respectively.

[0091] Comparative Example 1

[0092] 1) Ni NP / CeO 2The preparation method of the impregnated sample is as follows:

[0093] Take 0.5 g of commercial CeO 2 and put it into a 100 mL beaker. Add 20 mL of deionized water, and continuously stir for 30 min after ultrasonic treatment to make it evenly dispersed. Take 1.45 g of Ni(NO 3 ) 2 ·6H 2 O, add 10 mL of deionized water, and ultrasonic until dissolved to prepare a solution with a Ni element content of 0.5 M. Then take 1.7 mL and add it to the CeO 2 dispersed in deionized water, and continuously stir. After the mixed solution is stirred for 1 h, transfer it to a hot plate, set the temperature to 70 - 80 °C and continuously stir for several hours until the liquid is evaporated to dryness. Take out the solid, fully grind it to obtain the precursor. Place 50 mg of the prepared precursor sample in a tubular furnace, continuously pass a reducing gas stream (10% H 2 / 90% Ar) at room temperature for 0.5 h to remove the air in the tubular furnace, and then heat it up to 400 °C at a rate of 5 °C min -1 for hydrogen reduction for 2 h, and collect the product Ni NP / CeO 2 .

[0094] 2) Photothermal catalytic dry reforming of methane reaction performance test:

[0095] Same as Example 1, the initial catalytic activity of this catalyst for the dry reforming of methane reaction is slightly lower than that of Ni / CeO x -350. At a light intensity of 4 W cm -2 , the H 2 and CO yields are 522.5 and 651.4 mmol g cat -1 h -1 respectively, and the catalyst undergoes rapid deactivation, and the activity drops sharply as the reaction proceeds.

[0096] Figure 4 To use the Ni / CeO x -350 prepared in Example 1 and the Ni NP / CeO 2 prepared in Comparative Example 1 as catalysts for the long-cycle stability test of photothermal catalytic dry reforming of methane at a light intensity of 4 W cm -2 . Ni NP / CeO 2 undergoes rapid deactivation within 20 h, and the catalytic activity drops sharply; while Ni / CeO x -350 can operate stably for 100 h, indicating its good stability and lifespan for photothermal catalytic dry reforming of methane.

[0097] The foregoing description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A Ni-doped rare earth metal nano-oxide, characterized in that: In the Ni-doped rare earth metal nano-oxide, Ni is dispersed at the atomic level; The Ni-doped rare earth metal nano-oxide is prepared according to the following method: S1: After mixing a rare earth metal source, a Ni source and a solvent, the obtained mixture is reacted under heating conditions to obtain a precursor; S2: After reducing the precursor, Ni-doped rare earth metal nano-oxide is obtained; The rare earth metal in the rare earth metal source is selected from any one or more of Ce, La, Sm or Nd; the solvent is selected from triethylene glycol; The temperature of the heating condition is 160-200°C; the time of heating to the temperature of the heating condition is 5-10 min; the reaction time is 0.5-3 h; The reduction is carried out in an atmosphere containing hydrogen, and the temperature of the reduction is 300-400°C.

2. The Ni-doped rare earth metal type nano-oxide according to claim 1, characterized in that: The mass content of Ni element in the rare earth metal nano-oxide is 8.5-10 wt %.

3. A method for preparing Ni-doped rare earth metal nano-oxide according to claim 1 or 2, characterized in that: The following steps are involved: S1: After mixing a rare earth metal source, a Ni source and a solvent, the obtained mixture is reacted under heating conditions to obtain a precursor; S2: After reducing the precursor, Ni-doped rare earth metal nano-oxide is obtained; The rare earth metal in the rare earth metal source is selected from any one or more of Ce, La, Sm or Nd; the solvent is selected from triethylene glycol; The temperature of the heating condition is 160-200°C; the time of heating to the temperature of the heating condition is 5-10 min; the reaction time is 0.5-3 h; The reduction is carried out in an atmosphere containing hydrogen, and the temperature of the reduction is 300-400°C.

4. The preparation method according to claim 3, characterized in that: The rare earth metal source is selected from any one or more of Ce(NO3)3·6H2O, CeCl3·7H2O, LaCl3·7H2O, SmCl3·6H2O or NdCl3·6H2O; The Ni source is selected from Ni(NO3)2·6H2O and / or NiCl2·6H2O.

5. The preparation method according to claim 3 or 4, characterized in that: The molar ratio of the rare earth metal source to the Ni source is (3.0-3.6):

1.

6. The preparation method according to claim 3, characterized in that: After the rare earth metal source is completely dissolved in the solvent, it is mixed with the Ni source to obtain a mixture; The dissolution is carried out under the condition of increasing the temperature from room temperature to 80-100°C.

7. The preparation method according to claim 3, characterized in that: The reduction time is 1 to 5 h.

8. Use of the Ni-doped rare earth metal nano-oxide according to claim 1 or 2 or the Ni-doped rare earth metal nano-oxide prepared by the preparation method according to any one of claims 3 to 7 in photothermal catalytic methane dry reforming.

Images