A preparation method of a ruthenium cluster modified titanium oxide coated titanium nitride material for photocatalytic dry reforming of methane

Abstract

Preparation method of ruthenium cluster modified titanium oxide coated titanium nitride material for efficient photocatalytic methane dry reforming The present application provides a preparation method of a methane dry reforming photocatalytic material, which can convert two greenhouse gases, carbon dioxide and methane, into synthesis gas (H2 and CO) under mild conditions, providing raw materials for Fischer-Tropsch synthesis or preparation of higher value chemicals. The present application uses ruthenium chloride and commercial titanium nitride as raw materials, and the surface of the commercial titanium nitride is partially oxidized into titanium nitride by air oxidation to obtain a titanium oxide coated titanium nitride material (TiN@TiO2), and then Ru clusters are loaded on the titanium oxide coated titanium nitride material (TiN@TiO2) using a photodeposition method, thereby obtaining a Ru cluster modified titanium oxide coated titanium nitride material (TiN@TiO2-Ru). The titanium oxide coating layer and the ruthenium cluster modification are beneficial to enhance the efficient adsorption of carbon dioxide and methane molecules, and compared with unmodified titanium nitride, the TiN@TiO2-Ru material has better activation ability and charge separation efficiency of carbon dioxide and methane molecules, and exhibits excellent methane dry reforming activity and stability under light conditions.

Description

TECHNICAL FIELD

[0001] The application relates to a ruthenium cluster modified titanium oxide coated titanium nitride material for photocatalytic dry reforming of methane, and belongs to the fields of nanomaterials and photocatalysis. BACKGROUND

[0002] The dry reforming of methane (DRM) reaction, which converts two greenhouse gases, methane and carbon dioxide, into syngas (H2 and CO), has recently attracted extensive attention in the field of catalysis. The dry reforming of methane reaction is highly endothermic, and thus must be carried out at a high temperature of 1073K or above. In addition, carbon deposition is a serious problem in the DRM reaction. Compared with traditional thermal catalytic DRM, photocatalysis can make the reaction proceed under relatively mild conditions, and is a green, environmentally friendly, non-toxic and low-energy-consumption method for preparing syngas. However, the efficiency of photocatalytic DRM is still far lower than the requirement for practical application, and thus it is necessary to develop a high-efficiency and stable photocatalyst for DRM.

[0003] TiN is an ideal photocatalytic material, and has the advantages of strong light absorption capacity, non-toxicity, no secondary pollution, low cost and long-term stability. However, TiN lacks catalytic active sites, and has poor activity for the photocatalytic DRM reaction. In addition, TiN has weak adsorption capacity for carbon dioxide and methane molecules, and the photo-generated carriers are prone to recombination, and thus it is difficult to achieve efficient production of syngas. At present, there are few studies on photocatalytic transition metal nitride materials, and the use of TiN for photocatalytic DRM reaction still needs to be explored.

[0004] Therefore, based on the above research background, the ruthenium cluster modified titanium oxide coated titanium nitride material is prepared from the aspects of constructing active sites and improving stability. The material is compared with other metal-loaded modified titanium oxide coated titanium nitride materials and unmodified TiN and TiO2 materials. On the one hand, the modified ruthenium cluster can improve the adsorption capacity for methane and carbon dioxide, and promote the activation of methane and carbon dioxide. On the other hand, the coating of TiO2 material can enhance the electron transfer between TiN and Ru, and stabilize the surface deposited Ru cluster, so as to improve the stability. The ruthenium cluster modified titanium oxide coated titanium nitride material prepared in the application realizes efficient and stable photocatalytic DRM under mild conditions. SUMMARY

[0005] The application adopts a light deposition method to load ruthenium in the form of clusters in partially oxidized titanium nitride material, first, commercial titanium nitride is washed with a mixed solution of hydrogen peroxide and ammonia to remove surface antioxidants, then the titanium nitride powder is programmed to oxidize, and then cooled to room temperature to prepare a partially oxidized titanium nitride material. Then the partially oxidized titanium nitride material is added to a 1:1 ethanol solution with ruthenium chloride and stirred for 30 minutes, then a 2000mW / cm -2 The light intensity is irradiated for 30 minutes, and after multiple centrifugal drying, the ruthenium cluster modified titanium oxide coated titanium nitride material can be obtained.

[0006] The method of titanium nitride used in the application is as follows: commercial nano-TiN is soaked in a mixed solution of hydrogen peroxide and ammonia for 10 minutes, then washed with deionized water and ethanol multiple times, dried under argon atmosphere by infrared lamp to obtain TiN powder.

[0007] The method of partially oxidized titanium nitride used in the application is as follows: 400mg of commercial titanium nitride is placed in a porcelain square canister, calcined in a muffle furnace at 350℃ for 1h, the heating rate is 5℃ / min, then cooled to room temperature to collect the powder, marked as TiN@TiO2.

[0008] The method of constructing the ruthenium cluster modified titanium oxide coated titanium nitride material involved in the application is as follows: 200mg of TiN@TiO2 is dispersed in a mixed solution of 15mL ethanol and 15mL water, then ruthenium chloride solution is added, stirred for 30 minutes, and then a 2000mW / cm -2 The light intensity is irradiated for 30 minutes. Then the reacted sample is washed three times with a mixed solution of ethanol:water=1:1, and then placed in a 70℃ oven for 8h to obtain the finished product TiN@TiO2-Ru.

[0009] The method of preparing different metal loaded partially oxidized titanium nitride material involved in the application is as follows: other metal loaded partially oxidized titanium nitride material is prepared according to the method of ruthenium cluster loading, and ruthenium trichloride is replaced by chloroplatinic acid and chloroauric acid respectively.

[0010] The method of preparing ruthenium cluster loaded different carrier material involved in the application is as follows: 200mg of metal oxide is dispersed in 30mL of water, then ruthenium trichloride solution is added and stirred for 4h. Then washed three times with deionized water, dried and placed in a muffle furnace at 400℃ for 1h, the heating rate is 5℃ / min, then cooled to room temperature to collect the powder, which is the ruthenium cluster loaded different carrier.

[0011] The advantages of the application are

[0012] 1. Adopting typical metal nitride titanium nitride as a photocatalytic semiconductor, it has similar optical properties with Au, Ag and other noble metals in the optical range, showing unique localized plasmon resonance effect (LSPR) and full sunlight spectrum absorption capacity. Meanwhile, titanium nitride also has strong photo-thermal effect, which can convert infrared light that traditional semiconductor materials cannot utilize into heat energy, improving the temperature of catalytic sites and being conducive to the progress of photo-thermal methane dry reforming reaction.

[0013] 2. The partially oxidized titanium nitride forms a structure of titanium nitride core and titanium oxide shell, i.e. the coating of titanium oxide is conducive to the stability of titanium nitride at high temperature and in oxidizing atmosphere, so as to maintain the structure of the catalyst unchanged and improve the stability of photo-thermal methane dry reforming reaction.

[0014] 3. Loading ruthenium in the form of clusters on the titanium oxide coated titanium nitride can improve the adsorption capacity of the material to methane and carbon dioxide, thereby promoting activation.

[0015] 4. Through the design of the structure, the absorption of light can be improved through the synergistic effect of the titanium oxide intermediate layer and Ru clusters, the separation and migration of photo-generated carriers are promoted, and the lifetime of photo-generated carriers is improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 a is a TEM image of titanium nitride in Example 1, with a diameter of about 30-80 nm. Figure 1 b is a TEM image of partially oxidized titanium nitride in Example 2, and it can be seen that the surface of the oxidized sample has an obvious oxidation layer, which belongs to anatase TiO2. Figure 1 c is an HRTEM image of the TiN@TiO2-Ru (1%) sample in Example 3, and it can be clearly seen that after loading Ru, the morphology of the sample does not change obviously, and the Ru clusters are uniformly dispersed on the surface of TiO2, with a size of 0.95 nm. Figure 1 d is an XRD image of the Ru cluster modified TiN sample with different oxidation degrees in Example 3, and the peaks at 36.6°, 42.59°, 61.81°, 74.07°, 93.17° correspond to the (111), (200), (220), (311), (222) crystal faces of titanium nitride (JCPDS No. 98-000-0339), and the peak at 25.3° corresponds to the (101) crystal face of anatase titanium oxide (JCPDS No. 98-000-0081). No peak of Ru cluster is observed, which confirms the high dispersion of Ru. Figure 1 e is a BET image of the Ru cluster modified TiN sample with different oxidation degrees in Example 3, and it can be seen that there is a H1 type hysteresis loop.

[0017] Figure 2a is the photocatalytic DRM activity of TiN materials with different Ru loading ratios under 300 W Xe lamp. TiN samples show no catalytic activity, and the production rates of CO and H2 show a volcano trend with the increase of Ru loading, and the activity is best when the Ru loading is 1%, which indicates that Ru is the main active site for the activation of CO2 and CH4. With the increase of TiO2 content, the production rates of CO and H2 also show a volcano trend, which indicates that only a suitable ratio of TiN and TiO2 can further promote the progress of the methane dry reforming reaction Figure 2 b. Figure 2 c is the photocatalytic DRM activity of TiN@TiO2-Ru(1%) materials under different light intensities. It can be seen that with the increase of light intensity, the production rates of H2 and CO increase synchronously, which confirms the light-driven nature of the reaction. In order to confirm the importance of metal Ru and TiN materials, Figure 2 d shows the photocatalytic DRM activity results of TiN materials loaded with different metal elements and other oxide materials loaded with Ru. Compared with Ru-loaded samples, Pt-loaded TiN materials only show weak DRM activity. Au-loaded TiN materials and Ru-loaded SiO2 and Al2O3 materials also show no DRM activity. The above activity tests prove that Ru loading and titanium nitride carrier synergistically improve the photocatalytic DRM reaction performance, and compared with other metals, Ru loading can provide more adsorption and activation sites for CO2 and CH4 molecules. In order to explore the stability of the catalyst, TiN-Ru(1%) and TiN@TiO2-Ru(1%) were used for the cyclic stability test of photocatalytic methane dry reforming Figure 2 e and Figure 2 f). The results show that after 20 h, the catalytic rate only decreases by 6%, which is significantly lower than that of TiN@TiO2-Ru(1%) and TiN-Ru(1%) (25%), indicating that the TiN@TiO2-Ru(1%) catalyst has good cyclic stability.

[0018] Figure 3 a and Figure 3 b are the CO2-TPD and CH4-TPD spectra of TiN, TiN-Ru(1%) and TiN@TiO2-Ru(1%) samples. It can be seen that Ru clusters are the main adsorption sites for CO2 and CH4, and in addition, TiO2 plays a supplementary adsorption role for CH4. Figure 3c-f are the in-situ XPS of TiN@TiO2-Ru (1%), it can be seen that the N, Ti, O of the sample have obvious positive shift after light irradiation, while the negative shift of Ru is more obvious, because the content of Ru is much smaller than that of N, Ti, O. The above results confirm that the electrons will migrate from TiN to TiO2 and finally enrich on the Ru site, and the intermediate layer of titanium oxide plays an important role in electron transport, thereby improving the photocatalytic activity.

[0019] Figure 4 a is the UV-Vis diffuse reflectance spectrum of TiN, TiO2 and TiN@TiO2-Ru (1%) material, it can be seen that TiN has very strong light absorption ability, it not only has strong absorption in the visible region, but also can absorb in the near infrared region. Although part of the oxidation and loading of Ru reduces the light absorption of the sample, the sample still maintains the wide spectrum absorption ability. Figure 4 b is the transient photocurrent spectrum of TiN, TiO2 and TiN@TiO2-Ru (1%) material, the strong photocurrent response of TiN@TiO2-Ru (1%) indicates that the Ru loading and TiO2 modified sample can promote the separation of photo-generated charges. Figure 4 c-f are the electrochemical impedance diagrams of TiN, TiO2 and TiN@TiO2-Ru (1%) material, the Ru loading and TiO2 modified sample shows lower electrochemical impedance, which means that the Ru cluster and TiO2 intermediate layer reduce the electron transfer barrier of the material, which helps to improve the photo-generated carrier mobility. Figure 4 g and Figure 4 h is the fluorescence emission and time-resolved fluorescence lifetime diagram of TiN, TiO2 and TiN@TiO2-Ru (1%) material. The lower fluorescence intensity means that the photo-generated electrons and holes of the TiN@TiO2-Ru (1%) sample are not easy to recombine; the longer fluorescence lifetime of the TiN@TiO2-Ru (1%) sample indicates that the photo-generated carriers have a longer lifetime. This shows that the Ru loading and TiO2 modified sample can promote the separation and migration of photo-generated charges, thereby improving the catalytic activity.

[0020] The above experimental results prove that the Ru cluster loaded titanium oxide modified titanium nitride material synthesized by us has excellent photocatalytic DRM performance and stability.

[0021] Although the content of the present application has been described in detail by the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present application. Specific embodiments

[0022] The present application will be described in more detail below through specific examples, but the protection scope of the present application is not limited to these examples.

[0023] Example 1

[0024] Synthesis of titanium nitride

[0025] Commercially available nano-TiN was immersed in a mixed solution of hydrogen peroxide and ammonia for 10 min, then rinsed with deionized water and ethanol several times, and dried under argon atmosphere by infrared lamp to obtain TiN powder.

[0026] Example 2

[0027] Synthesis of partially oxidized titanium nitride

[0028] 400 mg of TiN was placed in a porcelain boat and calcined in a muffle furnace at 350 °C for 1 h at a heating rate of 5 °C / min, then cooled to room temperature to collect the powder, which was denoted as TiN@TiO2.

[0029] Example 3

[0030] Synthesis of ruthenium cluster loaded titanium oxide coated titanium nitride material

[0031] 200 mg of TiN@TiO2 was dispersed in 15 mL of ethanol and 15 mL of water, stirred for 30 min, then a ruthenium trichloride solution was added, the mixed solution was continuously stirred for 30 min, then the solution was irradiated with a 300 W xenon lamp for 1 h (2000 mW / cm -2 ). Then the reacted sample was washed three times with a mixed solution of ethanol:water = 1:1, then placed in a 70 °C oven for 8 h to obtain the finished product TiN@TiO2-Ru.

[0032] Comparative Example 1

[0033] Synthesis of titanium dioxide material

[0034] 400 mg of TiN was placed in a porcelain boat and calcined in a muffle furnace at 500 °C for 4 h at a heating rate of 5 °C / min, then cooled to room temperature to collect the powder, which was denoted as TiO2.

[0035] Comparative Example 2

[0036] Synthesis of ruthenium loaded titanium dioxide material

[0037] 200 mg of TiO2 was dispersed in 15 mL of ethanol and 15 mL of water, stirred for 30 min, then a ruthenium trichloride solution was added, the mixed solution was continuously stirred for 30 min, then the solution was irradiated with a 300 W xenon lamp for 1 h (2000 mW / cm -2 ). Then the reacted sample was washed three times with a mixed solution of ethanol:water = 1:1, then placed in a 70 °C oven for 8 h to obtain the finished product TiO2-Ru.

[0038] Comparative Example 3

[0039] Synthesis of ruthenium supported titanium nitride material

[0040] Disperse 200 mg of commercial TiN in 15 mL of ethanol and 15 mL of water, stir for 30 min, then add a ruthenium trichloride solution, continue to stir the mixed solution for 30 min, then irradiate the solution with a 300 W xenon lamp (2000 mW / cm -2 ) for 1 h. Then wash the reacted sample with a mixed solution of ethanol:water = 1:1 three times, then place it in a 70°C oven for 8 h to obtain the finished product TiN-Ru.

[0041] Comparative Example 4

[0042] Synthesis of ruthenium supported metal oxide material

[0043] Disperse 200 mg of Al2O3 and SiO2 in 30 mL of water, then add a ruthenium trichloride solution and stir for 4 h. Then wash with deionized water three times, dry, then place it in a muffle furnace and calcine at 400°C for 1 h, the temperature rising speed is 5°C / min, then cool to room temperature to collect the powder to obtain the finished products Al2O3-Ru and SiO2-Ru.

[0044] Comparative Example 5

[0045] Synthesis of titanium nitride coated titanium oxide (TiN@TiO2-M) material supported by different metals

[0046] Disperse 200 mg of TiN@TiO2 in 15 mL of ethanol and 15 mL of water, stir for 30 min, then add chloroplatinic acid and chloroauric acid solutions respectively, continue to stir the mixed solution for 30 min, then irradiate the solution with a 300 W xenon lamp (2000 mW / cm -2 ) for 1 h. Then wash the reacted sample with a mixed solution of ethanol:water = 1:1 three times, then place it in a 70°C oven for 8 h to obtain the finished product TiN@TiO2-M (M = Pt, Au).

[0047] Experiments and data

[0048] The method for investigating the activity of the photocatalytic methane dry reforming provided by the present application is as follows:

[0049] Place 10 mg of catalyst in a flow type photo-thermal catalytic reaction device (PLR-PTSR II), and flow 10 mL min -1The flow rate of 100 mL / min of a mixture of CH4:CO2:Ar (5:5:90, volume ratio) was passed through the reactor. The adsorption saturation was maintained in the dark for 30 min, followed by the activity test under 300 W xenon lamp simulated light. The photo-thermal reaction temperature during light was constant at 300 °C by the temperature control assembly, and the pressure was constant at 0.3 MPa. The outlet of the reactor was connected to a gas chromatograph, and the reaction products were detected in the automatic sampling mode. The detection of CO used a flame ionization detector, and the detection of H2 used a thermal conductivity detector.

Claims

1. A method for preparing a ruthenium cluster decorated titanium oxide coated titanium nitride material for photocatalytic dry reforming of methane, characterized in that For commercial titanium nitride material, a surface titanium oxide coating layer is prepared by temperature control calcination to realize partial oxidation of titanium nitride, then Ru cluster deposition is carried out in an ethanol solution containing ruthenium trichloride by controlling light intensity, and finally a ruthenium cluster modified titanium oxide coated titanium nitride material is obtained by washing and drying; The prepared material has excellent light energy utilization and methane and carbon dioxide adsorption capacity, and can exhibit good photocatalytic methane dry reforming performance; Specifically comprising the following steps: First step: immerse commercial nano TiN in a mixed solution of hydrogen peroxide and ammonia water for 10 min, then rinse with deionized water and ethanol for several times, dry under argon atmosphere by infrared lamp, and obtain TiN powder; Second step: put 400 mg of TiN powder treated in the first step into a porcelain square canister, calcine in a muffle furnace at 350 DEG C for 1 h, the heating rate is 5 DEG C / min, then cool to room temperature to collect the powder, marked as TiN@TiO2; Third step: 200 mg of TiN@TiO2 was dispersed in 15 ml of ethanol and 15 ml of water, stirred for 30 min, then a solution of ruthenium trichloride was added, the mixed solution was continuously stirred for 30 min, then the solution was irradiated for 1 h using a 300 W xenon lamp with a light intensity of 2000 mW / cm 2 , then the reacted sample was washed three times using a mixed solution of ethanol:water = 1:1, then it was placed in a 70 °C oven for 8 h to obtain the finished product TiN@TiO2-Ru.

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