Preparation method and application of low-rhodium-content platinum-rhodium bimetallic supported CdS photocatalytic material

Abstract

The application relates to a preparation method and application of a low-rh-content platinum-rh bimetallic supported CdS photocatalytic material, and relates to a preparation method and application of a CdS photocatalytic material.The application aims to solve the problems of large rare metal consumption and slow hydrogen evolution rate of existing photocatalytic hydrogen production catalysts.The method comprises the following steps: one, preparing CdS; and two, compounding.The low-rh-content platinum-rh bimetallic supported CdS photocatalytic material is applied to photocatalytic materials in water photolysis hydrogen production.The application utilizes the PtRh bimetallic active site to decompose water to produce hydrogen, can change the CdS from the original poor catalytic activity into a photocatalytic material with high catalytic activity, inhibits the serious carrier recombination problem of the CdS itself, obtains strong hydrogen production performance, and the product H2 is considered as an important energy source in the future, has the advantages of cleanness, non-toxicity and high energy density compared with other energy sources.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method and application of a CdS photocatalytic material. BACKGROUND

[0002] Photochemical water splitting for hydrogen production is an important part of future green hydrogen industry. This technology has the characteristics of simple equipment, mild reaction conditions and greenness. Common photocatalytic materials for photochemical water splitting for hydrogen production include TiO2, Al:SrTiO3 and CdS. Compared with TiO2 and Al:SrTiO3, CdS has a wider light absorption range, and thus can generate more photo-generated charges for water oxidation and reduction reactions. However, single photocatalysts have problems such as high photo-generated charge recombination probability and lack of effective active sites. Therefore, when an excellent photocatalyst for photochemical water splitting for hydrogen production is found, it needs to be modified.

[0003] Loading active sites is a common and effective modification method. It can maximize the separation and use of photo-generated carriers by the difference in work function with the base material and the easier promotion of photo-induced redox reactions. Rh, Pt and other platinum group metals have been proven to be excellent hydrogen evolution active sites. In 2021, Japanese scholar Kazunari Domen used Rh 0.1 wt% to load Al:SrTiO3 to complete 100 m 2 Photochemical water splitting for hydrogen production pilot test. The Rh loading of 0.1 wt% is still high, so it is necessary to further find a way to reduce the Rh loading. SUMMARY

[0004] The purpose of the present application is to solve the problems of large use of rare metals and slow hydrogen evolution rate of existing photocatalytic hydrogen production catalysts, and to provide a preparation method and application of a low-rh-content platinum-rh-bimetal-loaded CdS photocatalytic material.

[0005] Based on the synergistic effect of bimetallic, the present application develops a low-rh-content platinum-rh-bimetal-loaded CdS photocatalytic material. Compared with single Rh or Pt loaded CdS with the same content, the PtRh loaded CdS in the present application has a significantly higher hydrogen evolution rate, which can effectively complete the task of photochemical water splitting for hydrogen production.

[0006] A preparation method of a low-rh-content platinum-rh-bimetal-loaded CdS photocatalytic material, which is completed according to the following steps:

[0007] I. Preparation of CdS:

[0008] ①, Cd(NO3)2·4H2O and Na2S·9H2O are added to deionized water, stirred for a period of time, and a mixed solution is obtained;

[0009] ②, transfer the mixed solution to the inner lining of a polytetrafluoroethylene reactor, seal, and then heat the polytetrafluoroethylene reactor to 200-220 DEG C, react at 200-220 DEG C for a period of time, and obtain a reaction product; wash and dry the reaction product to obtain CdS;

[0010] II. Compound:

[0011] CdS and Cl3H6O3Rh are added to deionized water, vacuumed for a period of time, then argon is introduced into the system, vacuumed again, and the air in the system is completely removed, irradiated under a xenon lamp for a period of time, K2PtCl6 is added to the system, and irradiated under a xenon lamp for a period of time to obtain a reaction product; the reaction product is washed and dried to obtain a low-rh-content platinum-rh bimetallic supported CdS photocatalytic material.

[0012] Principle of the application:

[0013] The application improves the water-splitting hydrogen production performance of CdS photocatalyst by regulating the types, proportions and deposition sequence of active site species on the surface of CdS photocatalyst. The electronic structure of the metal site is adjusted by the difference in the work function of the metal, the H2O molecule adsorption configuration is optimized, the H-O bond activation is promoted, the generation rate of hydrogen radicals and the rate of hydrogen radicals combining to form H2 are improved, and the desorption ability of H2 generation is also strengthened by the electronic structure of the metal site, thereby enhancing the hydrogen production performance. By combining and screening different metals, it is found that Pt and Rh can be perfectly matched and used to complete the efficient water-splitting hydrogen production application. At the same time, Rh has the characteristics of low loading in the bimetallic group, which can effectively reduce the use cost of the catalytic material.

[0014] Advantages of the application:

[0015] I. The application uses PtRh bimetallic active sites to decompose water to produce hydrogen, which can convert CdS from a previously poor catalytic activity to a high-catalytic-activity photocatalytic material, inhibits the serious carrier recombination problem of CdS itself, and obtains strong hydrogen production performance. The product H2 is considered to be an important energy source in the future, and has the advantages of cleanliness, non-toxicity and high energy density compared with other energy sources. Water-splitting hydrogen production by solar photocatalysis is one of the most promising solutions to environmental problems and sustainable clean energy problems;

[0016] II. The low-rh-content platinum-rh bimetallic supported CdS photocatalytic material prepared by the application is used for photocatalytic decomposition of water to produce hydrogen, and the water-splitting hydrogen production rate can reach 72.16 mmol·g -1 ·h -1 ;

[0017] III. The application provides a possibility for commercialization of large-scale water-splitting hydrogen production. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 XRD patterns of CdS samples prepared on the surface of CdS and different promoters;

[0019] Figure 2 XPS patterns of the low-rh-content platinum-rhodium bimetallic supported CdS photocatalytic material PtRh / CdS prepared in Example 1, in which (a) is Cd 3d, (b) is S 2p, (c) is Rh 3d, and (d) is Pt 4f;

[0020] Figure 3 Performance comparison chart of CdS samples prepared on the surface of CdS and different promoters;

[0021] Figure 4 Hydrogen production performance chart of the low-rh-content platinum-rhodium bimetallic supported CdS photocatalytic material PtRh / CdS prepared in Example 1 in a cycle experiment. DETAILED DESCRIPTION

[0022] Specific embodiment one: a preparation method of the low-rh-content platinum-rhodium bimetallic supported CdS photocatalytic material according to the embodiment, which is completed according to the following steps:

[0023] I. Preparation of CdS:

[0024] ①Cd(NO3)2·4H2O and Na2S·9H2O were added to deionized water, stirred for a period of time, and a mixed solution was obtained;

[0025] ②The mixed solution was transferred to the inner lining of a polytetrafluoroethylene reactor, sealed, and the polytetrafluoroethylene reactor was heated to 200-220°C. The reaction was carried out at 200-220°C for a period of time, and the reaction product was obtained. The reaction product was washed and dried to obtain CdS;

[0026] II. Compound:

[0027] CdS and Cl3H6O3Rh were added to deionized water, vacuumed for a period of time, then argon was introduced into the system, vacuumed again to completely remove the air in the system, and irradiated under a xenon lamp for a period of time. K2PtCl6 was added to the system and irradiated under a xenon lamp for a period of time to obtain a reaction product. The reaction product was washed and dried to obtain a low-rh-content platinum-rhodium bimetallic supported CdS photocatalytic material.

[0028] Embodiment two: the difference between this embodiment and embodiment one is that the mass and volume ratio of Cd(NO3)2·4H2O to deionized water in step 1 1 is (1g~3.1g):(1mL~25mL); the mass and volume ratio of Na2S·9H2O to deionized water in step 1 1 is (4g~12.1g):(1mL~25mL). The other steps are the same as embodiment one.

[0029] Embodiment three: the difference between this embodiment and one of embodiment one or two is that the stirring time in step 1 1 is 30min~60min. The other steps are the same as embodiment one or two.

[0030] Embodiment four: the difference between this embodiment and one of embodiment one to three is that the reaction time at 200℃~220℃ in step 1 2 is 12h~20h. The other steps are the same as embodiment one to three.

[0031] Embodiment five: the difference between this embodiment and one of embodiment one to four is that the reaction product is washed with deionized water and anhydrous ethanol for 3 times~5 times in step 1 2; the drying temperature in step 1 2 is 40℃~60℃, and the drying time is 6h~12h. The other steps are the same as embodiment one to four.

[0032] Embodiment six: the difference between this embodiment and one of embodiment one to five is that the molar ratio of K2PtCl6 to Cl3H6O3Rh in step 2 is (0.5~0.7):(0.05~0.07). The other steps are the same as embodiment one to five.

[0033] Embodiment seven: the difference between this embodiment and one of embodiment one to six is that the mass and volume ratio of CdS to deionized water in step 2 is (0.05g~0.1g):50mL. The other steps are the same as embodiment one to six.

[0034] Specific embodiment eight: the difference between this embodiment and one of the specific embodiments one to seven is that in step two, CdS and Cl3H6O3Rh are added to deionized water, vacuumed for 5 min~10 min, then argon gas is introduced into the system for 5 min~10 min, vacuumed again for 10 min~15 min to completely remove the air in the system, irradiated under a xenon lamp for 5 min~10 min, K2PtCl6 is added to the system, and irradiated under a xenon lamp for 15 min~30 min to obtain a reaction product; the reaction product is washed with deionized water and anhydrous ethanol for 3 times~5 times respectively, and then dried at 40℃~60℃ for 6 h~12 h to obtain a low-rhodium-content platinum-rhodium bimetallic loaded CdS photocatalytic material. The other steps are the same as those in the specific embodiments one to seven.

[0035] Specific embodiment nine: the application of a low-rhodium-content platinum-rhodium bimetallic loaded CdS photocatalytic material as a photocatalytic material in the water splitting for hydrogen production.

[0036] The following examples are used to verify the beneficial effects of the present application:

[0037] Example 1: a preparation method of a low-rhodium-content platinum-rhodium bimetallic loaded CdS photocatalytic material (PtRh / CdS), which is completed according to the following steps:

[0038] I. Preparation of CdS:

[0039] ①, 3.0848 g of Cd(NO3)2·4H2O and 12.009 g of Na2S·9H2O are added to 25 mL of deionized water, stirred for 60 min to obtain a mixed solution;

[0040] ②, the mixed solution is transferred to the inner lining of a polytetrafluoroethylene reaction kettle, sealed, and the polytetrafluoroethylene reaction kettle is heated to 200℃, and reacted at 200℃ for 20 h to obtain a reaction product; the reaction product is washed with deionized water and anhydrous ethanol for 3 times respectively, and then dried at 60℃ for 12 h to obtain CdS;

[0041] II. Compound:

[0042] 0.1 g of CdS and 0.000091 g of Cl3H6O3Rh are added to 50 mL of deionized water, vacuumed for 10 min, then argon gas is introduced into the system for 10 min, vacuumed again for 10 min to completely remove the air in the system, irradiated under a xenon lamp for 10 min, 0.00168 g of K2PtCl6 is added to the system, and irradiated under a xenon lamp for 30 min to obtain a reaction product; the reaction product is washed with deionized water and anhydrous ethanol for 3 times respectively, and then dried at 60℃ for 12 h to obtain a low-rhodium-content platinum-rhodium bimetallic loaded CdS photocatalytic material (PtRh / CdS).

[0043] Comparative Example 1: The preparation method of RhPt / CdS is completed according to the following steps:

[0044] I. Preparation of CdS:

[0045] ①, 3.0848g Cd(NO3)2·4H2O and 12.009g Na2S·9H2O were added to 25mL deionized water, stirred for 60min, to obtain a mixed solution;

[0046] ②, the mixed solution was transferred to the inner liner of a polytetrafluoroethylene reactor, sealed, and the polytetrafluoroethylene reactor was heated to 200℃, and reacted at 200℃ for 20h to obtain a reaction product; the reaction product was washed with deionized water and anhydrous ethanol for 3 times respectively, and then dried at 60℃ for 12h to obtain CdS;

[0047] II. Complexing:

[0048] 0.1g CdS and 0.00168g K2PtCl6 were added to 50mL deionized water, vacuumed for 10min, then argon was introduced into the system for 10min, and then vacuumed for 10min to completely remove the air in the system, and irradiated under xenon lamp for 30min, 0.000091g Cl3H6O3Rh was added to the system, and irradiated under xenon lamp for 10min to obtain a reaction product; the reaction product was washed with deionized water and anhydrous ethanol for 3 times respectively, and then dried at 60℃ for 12h to obtain RhPt / CdS.

[0049] Comparative Example 2: The preparation method of Pt / CdS is completed according to the following steps:

[0050] I. Preparation of CdS:

[0051] ①, 3.0848g Cd(NO3)2·4H2O and 12.009g Na2S·9H2O were added to 25mL deionized water, stirred for 60min, to obtain a mixed solution;

[0052] ②, the mixed solution was transferred to the inner liner of a polytetrafluoroethylene reactor, sealed, and the polytetrafluoroethylene reactor was heated to 200℃, and reacted at 200℃ for 20h to obtain a reaction product; the reaction product was washed with deionized water and anhydrous ethanol for 3 times respectively, and then dried at 60℃ for 12h to obtain CdS;

[0053] II. Complexing:

[0054] 0.1 g of CdS and 0.00168 g of K2PtCl6 were added to 50 mL of deionized water, vacuumed for 10 min, then argon was bubbled into the system for 10 min, vacuumed again for 10 min to completely remove the air in the system, and irradiated under a xenon lamp for 30 min to obtain a reaction product; the reaction product was washed with deionized water and anhydrous ethanol for 3 times respectively, and then dried at 60°C for 12 h to obtain Pt / CdS.

[0055] Comparative Example 3: The preparation method of Rh / CdS was completed according to the following steps:

[0056] I. Preparation of CdS:

[0057] ①, 3.0848 g of Cd(NO3)2·4H2O and 12.009 g of Na2S·9H2O were added to 25 mL of deionized water, stirred for 60 min to obtain a mixed solution;

[0058] ②, the mixed solution was transferred to the inner liner of a polytetrafluoroethylene reaction kettle, sealed, and the polytetrafluoroethylene reaction kettle was heated to 200°C, and reacted at 200°C for 20 h to obtain a reaction product; the reaction product was washed with deionized water and anhydrous ethanol for 3 times respectively, and then dried at 60°C for 12 h to obtain CdS;

[0059] II. Compound:

[0060] 0.1 g of CdS and 0.000091 g of Cl3H6O3Rh were added to 50 mL of deionized water, vacuumed for 10 min, then argon was bubbled into the system for 10 min, vacuumed again for 10 min to completely remove the air in the system, and irradiated under a xenon lamp for 10 min to obtain a reaction product; the reaction product was washed with deionized water and anhydrous ethanol for 3 times respectively, and then dried at 60°C for 12 h to obtain Rh / CdS.

[0061] Comparative Example 4: The preparation method of CdS was completed according to the following steps:

[0062] I. Preparation of CdS:

[0063] ①, 3.0848 g of Cd(NO3)2·4H2O and 12.009 g of Na2S·9H2O were added to 25 mL of deionized water, stirred for 60 min to obtain a mixed solution;

[0064] ②, the mixed solution was transferred to the inner liner of a polytetrafluoroethylene reaction kettle, sealed, and the polytetrafluoroethylene reaction kettle was heated to 200°C, and reacted at 200°C for 20 h to obtain a reaction product; the reaction product was washed with deionized water and anhydrous ethanol for 3 times respectively, and then dried at 60°C for 12 h to obtain CdS.

[0065] Figure 1 XRD patterns of CdS and different cocatalyst surface construction CdS samples;

[0066] From Figure 1 It can be seen that CdS, PtRh / CdS, RhPt / CdS, Pt / CdS, Rh / CdS are hexagonal phase, and no metal characteristic peaks are detected in the metal loaded samples, which is because of small loading amount and high dispersion of the metal.

[0067] Figure 2 XPS patterns of the low rhodium content platinum-rhodium bimetal loaded CdS photocatalytic material PtRh / CdS prepared in Example 1, in which (a) is Cd 3d, (b) is S 2p, (c) is Rh 3d, and (d) is Pt 4f;

[0068] Figure 2 a indicates that Cd is divalent, Figure 2 b indicates that S is divalent. Compared with CdS, the elements of Cd and S in PtRh / CdS move to the high binding energy direction, indicating that the loaded metal has strong interaction with the substrate CdS, and due to the larger work function of the metal, the electrons on the CdS are transferred to the metal sites. Figure 2 c and d are the XPS fine spectra of Rh and Pt, and Pt and Rh can be directly seen in the sample, indicating that Pt and Rh are successfully loaded.

[0069] Photocatalytic water splitting hydrogen production test:

[0070] 0.03g of CdS, 0.03g of PtRh / CdS, 0.03g of RhPt / CdS, 0.03g of Pt / CdS, and 0.03g of Rh / CdS were weighed and added into 100mL of a sacrificial agent (a mixed solution of 0.35mol / L Na2S·9H2O and 0.25mol / L Na2SO3), and ultrasonic was applied for 5min to disperse the CdS uniformly. The mixed solution was added into a reactor (POFIELabsolar-6A), cooling circulating water was started to keep the temperature of the reactor at 5℃, the reactor was vacuumized for 10min to remove the air in the reactor, argon was added to make the gas pressure in the reactor 5.5kPa, and irradiation was carried out under a xenon lamp with an AM1.5G filter. The hydrogen production was detected by gas chromatography every 60min.

[0071] Figure 3 Performance comparison chart of CdS and different cocatalyst surface construction CdS samples;

[0072] From Figure 3It can be seen that CdS can only decompose trace amount of water into H2, while Rh / CdS sample shows slightly higher hydrogen production efficiency after loading Rh; Pt / CdS shows higher hydrogen production performance after loading Pt, while RhPt / CdS has a small amount of improvement in hydrogen production performance compared with Pt / CdS when loading Rh first and then loading Pt; PtRh / CdS has a large amount of improvement in hydrogen production performance compared with Pt / CdS when loading Rh first and then loading Pt, which shows that the type and loading order of the supported co-catalyst on PtRh / CdS have a great influence on the hydrogen production performance of CdS.

[0073] Figure 4 The hydrogen production performance chart of the low-rh-content platinum-rhodium bimetallic supported CdS photocatalytic material PtRh / CdS prepared in Example 1 in the cycle experiment.

[0074] From Figure 4 It can be seen that the sample has no decrease in hydrogen evolution activity after 16 hours of 4-cycle hydrogen evolution experiment, which shows that the prepared sample has excellent light stability.

Claims

1. A method for preparing a low-rhodium-content platinum-rhodium bimetallic supported CdS photocatalytic material, characterized by The preparation method is specifically completed according to the following steps: I. Preparation of CdS: ①, Cd (NO3) 2·4H2O and Na2S·9H2O are added to deionized water, stirred for 30 min~60 min, and a mixed solution is obtained; ②, the mixed solution is transferred to the inner lining of a polytetrafluoroethylene reactor, sealed, and the polytetrafluoroethylene reactor is heated to 200℃~220℃, and the reaction is carried out at 200℃~220℃ for 12h~20h, to obtain a reaction product; the reaction product is washed and dried to obtain CdS; II. Compound: 0.1g CdS and 0.000091g Cl3H6O3Rh are added to deionized water, vacuumed for 5min~10min, then argon is introduced into the system for 5min~10min, vacuumed again for 10min~15min, the air in the system is completely removed, and the system is irradiated under a xenon lamp for 5min~10min, K2PtCl6 is added to the system, and irradiated under a xenon lamp for 15min~30min to obtain a reaction product; the reaction product is washed and dried to obtain a low-rh-content platinum-rh-bimetallic supported CdS photocatalytic material.

2. The method for preparing a low-Rh-content Pt-Rh bimetallic supported CdS photocatalytic material according to claim 1, characterized in that The mass of Cd (NO3) 2·4H2O to the volume of deionized water in step 1① is (1g~3.1g):(1mL~25mL); the mass of Na2S·9H2O to the volume of deionized water in step 1① is (4g~12.1g):(1mL~25mL).

3. The method for preparing a low-Rh-content Pt-Rh bimetallic supported CdS photocatalytic material according to claim 1, characterized in that In step 1②, the reaction product is washed with deionized water and anhydrous ethanol for 3~5 times; the drying temperature in step 1② is 40℃~60℃, and the drying time is 6h~12h.

4. The method for preparing a low-Rh-content Pt-Rh bimetallic supported CdS photocatalytic material according to claim 1, characterized in that The molar ratio of CdS to Cl3H6O3Rh in step 2 is 1:(0.05~0.07).

5. The method for preparing a low-rhodium-content platinum-rhodium bimetallic supported CdS photocatalytic material according to claim 1, characterized in that... The molar ratio of K2PtCl6 to Cl3H6O3Rh in step 2 is (0.5~0.7):(0.05~0.07).

6. The method for preparing a low-Rh-content Pt-Rh bimetallic supported CdS photocatalytic material according to claim 1, characterized in that The mass of CdS to the volume of deionized water in step 2 is (0.05g~0.1g):50mL.

7. The method for preparing a low-rhodium-content platinum-rhodium bimetallic supported CdS photocatalytic material according to claim 1, characterized in that... In step 2, the reaction product is washed with deionized water and anhydrous ethanol for 3~5 times, and then dried at 40℃~60℃ for 6h~12h to obtain a low-rh-content platinum-rh-bimetallic supported CdS photocatalytic material.

8. The application of the low-rhodium-content platinum-rhodium bimetallic supported CdS photocatalytic material prepared by the preparation method of claim 1, characterized in that A low-rh-content platinum-rh-bimetallic supported CdS photocatalytic material is applied as a photocatalytic material in the production of hydrogen by water photolysis.

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