Two-dimensional / two-dimensional structure composite photocatalyst and preparation method and application thereof

Abstract

The application provides a two-dimensional / two-dimensional structure composite photocatalyst and a preparation method and application thereof, and relates to the technical field of photocatalysis.The two-dimensional / two-dimensional structure composite photocatalyst comprises two-dimensional TiO2 nanosheets and ultrathin two-dimensional Ni metal nanosheets loaded on the two-dimensional TiO2 nanosheets.The ultrathin two-dimensional Ni metal nanosheets are used as cocatalysts, the ultrathin two-dimensional Ni metal nanosheets can form a two-dimensional / two-dimensional structure with the two-dimensional TiO2 nanosheets, can significantly improve the separation and migration efficiency of photo-generated carriers, and can further improve the photocatalytic hydrogen production performance.The results of examples show that the hydrogen production performance of the two-dimensional / two-dimensional structure composite photocatalyst is improved compared with the performance of a noble metal Pt loaded TiO2 photocatalyst, and therefore the composite photocatalyst can become a more efficient and relatively inexpensive catalyst for replacing the noble metal Pt loaded TiO2 in the field of photocatalysis.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photocatalysis, in particular to a two-dimensional / two-dimensional structure composite photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] Hydrogen energy, as a clean, efficient and renewable energy form, has attracted widespread attention. At present, the key to realizing green hydrogen production lies in developing low-cost and high-efficiency hydrogen production technology. Among them, the photocatalytic water splitting driven by solar energy is considered as one of the most potential hydrogen production paths in the future due to its advantages such as abundant resources, environmentally friendly process and pure product. The core of this technology lies in the construction of high-performance photocatalytic materials, especially photocatalysts with high carrier separation efficiency and excellent light response capability. Among numerous photocatalytic materials, TiO2 is widely used in the field of hydrogen production by water splitting due to its good chemical stability, non-toxicity, low cost and suitable band structure for photocatalytic reaction. In recent years, it has been found that the regulation of TiO2 into two-dimensional nanosheet structure can significantly increase its specific surface area and surface active sites, and shorten the diffusion path of photo-generated carriers, which is beneficial to improve the catalytic efficiency. However, there are still two outstanding problems with two-dimensional TiO2: one is that its band gap is wide, mainly responding to ultraviolet light, and the solar energy utilization efficiency is low; the other is that the recombination rate of photo-generated electrons and holes is high, which limits its photocatalytic activity.

[0003] In order to overcome the above defects, it is usually necessary to introduce a cocatalyst on the surface of TiO2 to promote the spatial separation of electrons and holes and improve the carrier migration rate. At present, the introduced cocatalyst is mainly platinum and other noble metals, which has high cost. Nickel metal has wide application potential in the field of catalysis due to its abundant reserves and low price. However, the catalytic activity of nickel metal is much lower than that of platinum and other noble metals, which seriously limits its application in high-efficiency catalytic reactions. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a two-dimensional / two-dimensional structure composite photocatalyst and a preparation method and application thereof. The two-dimensional / two-dimensional structure composite photocatalyst provided by the present application has excellent photocatalytic hydrogen production performance and low cost.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0006] The present application provides a two-dimensional / two-dimensional structure composite photocatalyst, which comprises two-dimensional TiO2 nanosheets and ultrathin two-dimensional Ni metal nanosheets loaded on the two-dimensional TiO2 nanosheets.

[0007] Preferably, the mass of the ultrathin two-dimensional Ni metal nanosheets is 1-15% of the mass of the two-dimensional TiO2 nanosheets.

[0008] Preferably, the size of the ultrathin two-dimensional Ni metal nanosheet is 40-60 nm.

[0009] The application provides a preparation method of the two-dimensional / two-dimensional structure composite photocatalyst.

[0010] The nickel source, oleylamine, tungsten hexacarbonyl and ascorbic acid are mixed to obtain a first precursor solution;

[0011] The titanium source and hydrofluoric acid are mixed to obtain a second precursor solution;

[0012] The first precursor solution and the second precursor solution are mixed to perform a hydrothermal reaction to obtain the two-dimensional / two-dimensional structure composite photocatalyst.

[0013] Preferably, the nickel source comprises nickel acetylacetonate; the concentration of the nickel source in the first precursor solution is 4-25 mmol·L -1 The molar ratio of ascorbic acid to the nickel source is 3-18:1, and the molar ratio of ascorbic acid to tungsten hexacarbonyl is 9:1.

[0014] Preferably, the mixing of the nickel source, oleylamine, tungsten hexacarbonyl and ascorbic acid is performed under ultrasonic conditions.

[0015] Preferably, the titanium source comprises tetrabutyl titanate; the mass fraction of the hydrofluoric acid is 40%, and the dosage ratio of the titanium source to the hydrofluoric acid is 2 mmol:2 mL.

[0016] Preferably, the mass ratio of the nickel source in the first precursor solution to the titanium source in the second precursor solution is 1:5-32.

[0017] Preferably, the temperature of the hydrothermal reaction is 180-200 DEG C, and the time is 14-16 h.

[0018] The application provides an application of the two-dimensional / two-dimensional structure composite photocatalyst in photocatalytic decomposition of water to produce hydrogen.

[0019] The application provides a two-dimensional / two-dimensional structure composite photocatalyst, and has the following beneficial effects compared with the prior art: the two-dimensional / two-dimensional structure composite photocatalyst uses ultrathin two-dimensional Ni metal nanosheets as a cocatalyst, the ultrathin two-dimensional Ni metal nanosheets can form a two-dimensional / two-dimensional structure with two-dimensional TiO2 nanosheets, and can significantly improve the separation and migration efficiency of photo-generated carriers, and further improve the photocatalytic hydrogen production performance; the two-dimensional / two-dimensional coupling interface between the ultrathin two-dimensional Ni metal nanosheets and the two-dimensional TiO2 nanosheets is constructed, so that the cocatalyst and the two-dimensional TiO2 nanosheets have good matching and strong synergistic effect, and have excellent photocatalytic hydrogen production performance and low cost; and the results of the examples show that the two-dimensional / two-dimensional structure composite photocatalyst (ultrathin two-dimensional Ni metal nanosheet loading amount is 6wt%) provided by the application has improved hydrogen production performance compared with the performance of a noble metal Pt loaded TiO2 photocatalyst, so that the two-dimensional / two-dimensional structure composite photocatalyst provided by the application can become an ideal more efficient and relatively inexpensive catalyst to replace the noble metal Pt loaded TiO2 in the field of photocatalysis.

[0020] The application provides a preparation method of the two-dimensional / two-dimensional structure composite photocatalyst, and the preparation method is based on a wet chemical path, uses oleylamine as a solvent, uses a nickel source as a metal source, combines ascorbic acid reduction, introduces a titanium source, and synthesizes the two-dimensional / two-dimensional structure composite photocatalyst with high hydrogen production efficiency by one-step hydrothermal method; and the preparation method has the advantages of easy availability of raw materials, easy control of process conditions, low cost and easy mass production.

[0021] The application provides an application of the two-dimensional / two-dimensional structure composite photocatalyst or the two-dimensional / two-dimensional structure composite photocatalyst prepared by the preparation method in photocatalytic decomposition of water to produce hydrogen; the composite photocatalyst has the advantages of a unique two-dimensional structure, efficient photo-generated electron separation capacity, a large specific surface area, excellent mass transfer performance, high space charge separation and photo-generated carrier transport efficiency, low cost and high stability, and thus has excellent performance in photocatalytic decomposition of water to produce hydrogen and a wide application prospect in the field of solar-driven water decomposition to produce hydrogen. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A TEM diagram of a two-dimensional / two-dimensional structure Ni-ene / TiO2 composite photocatalyst prepared in Example 1;

[0023] Figure 2 A hydrogen production rate comparison diagram of the two-dimensional / two-dimensional structure Ni-ene / TiO2 composite photocatalysts with different nickel metal loading amounts prepared in Example 1, pure TiO2 nanosheets prepared in a comparative example and a Pt / TiO2 catalyst prepared by a photodeposition method;

[0024] Figure 3Stability test results of the two-dimensional / two-dimensional structure Ni-ene / TiO2 (6wt%) composite photocatalyst prepared for example 1. DETAILED DESCRIPTION

[0025] The application provides a two-dimensional / two-dimensional structure composite photocatalyst, which comprises two-dimensional TiO2 nanosheets and ultrathin two-dimensional Ni metal nanosheets loaded on the two-dimensional TiO2 nanosheets.

[0026] In the application, the size of the ultrathin two-dimensional Ni metal nanosheet (which is considered to be an ultrathin nanosheet in the art with a thickness of 5 nm or less) is preferably 40-60 nm.

[0027] In the application, the mass of the ultrathin two-dimensional Ni metal nanosheet is preferably 1-15% of the mass of the two-dimensional TiO2 nanosheet, and can be 1%, 2%, 4%, 6%, 8% or 10%, and is more preferably 6%. In the application, the ultrathin two-dimensional Ni metal nanosheet acts as a cocatalyst to improve the performance of the photocatalyst, but too high or too low a loading amount of the metal cocatalyst is not conducive to improving the performance of the photocatalyst: on the one hand, too low a loading amount of the cocatalyst will result in insufficient synergistic catalysis, failing to fully play the role of the cocatalyst; on the other hand, too high a loading amount of the cocatalyst will cover the surface of the TiO2 photocatalyst, affecting its light absorption efficiency, thereby reducing the number of photogenerated electron-hole pairs, leading to a decrease in photocatalytic activity.

[0028] The catalyst provided by the application is a two-dimensional / two-dimensional (i.e. 2D / 2D) composite constructed from ultrathin Ni metal nanosheets and TiO2 nanosheets, the ultrathin two-dimensional Ni metal nanosheets being loaded on the two-dimensional TiO2 nanosheets to form parallel two-dimensional / two-dimensional structures. In the application, the ultrathin two-dimensional Ni metal nanosheets match and combine with the surface of the two-dimensional TiO2 nanosheets, are highly coupled with TiO2, and form excellent contact with the surface of TiO2, which is conducive to the rapid transfer of photogenerated electrons to the surface of the ultrathin two-dimensional Ni metal nanosheets. The two-dimensional / two-dimensional structure composite photocatalyst provided by the application can effectively reduce the recombination of photogenerated electrons and holes, improve the transport efficiency of photogenerated carriers, and has high efficiency and good photocatalytic cyclic stability in the reaction of photocatalytic decomposition of water to produce hydrogen.

[0029] In the application, the ultrathin two-dimensional Ni metal nanosheet is also a nickel metal ene (denoted as Ni-ene), and therefore the two-dimensional / two-dimensional structure composite photocatalyst is also referred to as a two-dimensional / two-dimensional structure nickel metal ene modified TiO2 composite photocatalyst (abbreviated as Ni-ene / TiO2) in the examples of the application.

[0030] The application provides a preparation method of the two-dimensional / two-dimensional structure composite photocatalyst described in the above technical solution, which comprises the following steps:

[0031] The nickel source, oleylamine, tungsten hexacarbonyl and ascorbic acid are mixed to obtain a first precursor solution;

[0032] The titanium source and hydrofluoric acid are mixed to obtain a second precursor solution;

[0033] The first precursor solution and the second precursor solution are mixed to perform a hydrothermal reaction to obtain the two-dimensional / two-dimensional structure composite photocatalyst.

[0034] In the present application, the raw materials involved are all commercially available goods well known to those skilled in the art, unless otherwise specified.

[0035] The nickel source, oleylamine, tungsten hexacarbonyl and ascorbic acid are mixed to obtain a first precursor solution (referred to as a solution in the examples of the present application).

[0036] In the present application, the nickel source preferably includes nickel acetylacetonate (Ni(acac)2). In the present application, the concentration of the nickel source in the first precursor solution is preferably 4-25 mmol·L -1 , the molar ratio of ascorbic acid to nickel source is preferably 3-18:1, which can be 3:1, 4.5:1, 9:1 or 18:1, and the molar ratio of ascorbic acid to tungsten hexacarbonyl (W(CO)6) is preferably 9:1.

[0037] In the present application, the mixing of the nickel source, oleylamine, tungsten hexacarbonyl and ascorbic acid is preferably carried out under ultrasonic conditions, and the specific operation of the mixing is preferably as follows: the nickel source is added to oleylamine, and stirred at room temperature until completely dissolved; then tungsten hexacarbonyl and ascorbic acid are added to the obtained solution for ultrasonic treatment. In the present application, the ultrasonic treatment is carried out in an ultrasonic crushing instrument, the time of the ultrasonic treatment is preferably 30 min, the energy intensity of the ultrasonic crushing instrument is preferably 50%, and the ultrasonic treatment is carried out with an interval of 40 s after each ultrasonic crushing for 20 s.

[0038] In the present application, the oleylamine serves as a solvent, the ascorbic acid serves as a reducing agent, and the tungsten carbonyl releases CO in the subsequent hydrothermal reaction, which is hybridized with the metal d orbit by π backbonding, and preferentially binds to high-energy crystal faces, thereby inhibiting the growth of nickel along the thickness direction.

[0039] The titanium source and hydrofluoric acid are mixed to obtain a second precursor solution (referred to as b solution in the examples of the present application).

[0040] In the present application, the titanium source preferably includes tetrabutyl titanate (Ti(OBu)4); the mass fraction of the hydrofluoric acid is preferably 40%, and the dosage ratio of the titanium source to hydrofluoric acid is preferably 2 mmol:2 mL.

[0041] In the present application, the mixing method of the titanium source and the hydrofluoric acid is preferably: placing the titanium source in an inert atmosphere, slowly adding the hydrofluoric acid dropwise thereto, and stirring while adding; the dropwise adding rate of the hydrofluoric acid is preferably 1 mL / 3 min.

[0042] In the present application, the hydrofluoric acid provides an acidic environment, which can inhibit the rapid hydrolysis of the titanium source, avoid the formation of disordered or agglomerated precipitates, and help to generate regular and well-dispersed nanostructures. In the mixing process of the titanium source and the hydrofluoric acid, the following reaction exists: Ti 4+ + 6F - → [TiF6] 2- , regulates the crystal nucleation and growth rate, thereby controlling the crystal form, size and morphology of TiO2, and further generates TiO2 nanosheets in the subsequent hydrothermal reaction.

[0043] After obtaining the first precursor solution and the second precursor solution, the present application mixes the first precursor solution and the second precursor solution to perform a hydrothermal reaction, thereby obtaining the two-dimensional / two-dimensional structure composite photocatalyst.

[0044] In the present application, the mass ratio of the nickel source in the first precursor solution to the titanium source in the second precursor solution is preferably 1:5-32, which can be 1:5, 1:8, 1:16 or 1:32.

[0045] The present application preferably transfers the mixed solution obtained by mixing the first precursor solution and the second precursor solution to a polytetrafluoroethylene-lined high-pressure reaction kettle, seals it and performs a hydrothermal reaction. In the present application, the temperature of the hydrothermal reaction is preferably 180-200℃, and the time is preferably 14-16 h, which can be 14, 15 or 16 h. In the process of the hydrothermal reaction, the nickel source is reduced to form ultra-thin two-dimensional Ni metal nanosheets under the action of CO (from tungsten hexacarbonyl) and ascorbic acid, and grows on the TiO2 nanosheets further condensed from the titanium source.

[0046] After the hydrothermal reaction is completed, the present application preferably naturally cools the obtained reaction solution to room temperature, and then sequentially performs centrifugation, solid-phase washing and drying, thereby obtaining the two-dimensional / two-dimensional structure composite photocatalyst. In the present application, the solid-phase washing preferably adopts repeated washing with ethanol and cyclohexane for 3 times to remove unreacted components and organic residues; the drying is preferably freeze-drying under vacuum conditions, and the time of the freeze-drying can be 24 h.

[0047] The preparation method provided by the present application has the advantages of simple process, easy control of process parameters, low equipment requirement, short cycle, low cost, and is conducive to realizing large-scale production.

[0048] The application provides application of the two-dimensional / two-dimensional structure composite photocatalyst in photocatalytic decomposition of water to produce hydrogen. The application method is not particularly required, and a method known by those skilled in the art can be used. The two-dimensional / two-dimensional structure composite photocatalyst provided by the application has excellent visible light response ability and carrier separation efficiency, is low in cost, high in stability, and has a wide application prospect in the field of solar-driven water decomposition to produce hydrogen.

[0049] In order to further illustrate the application, the two-dimensional / two-dimensional structure composite photocatalyst, the preparation method and the application thereof provided by the application are described in detail below in combination with examples, but they should not be understood as limitations to the protection scope of the application.

[0050] Example 1

[0051] A two-dimensional / two-dimensional structure composite photocatalyst (namely, a Ni-ene / TiO2 composite photocatalyst) is prepared, and the steps are as follows:

[0052] (1) Preparation of a liquid (namely, a first precursor liquid): 0.5 mmol of nickel acetylacetonate (Ni(acac)2) is weighed and added into 20 mL of oleylamine, and then magnetically stirred at room temperature until completely dissolved. Subsequently, 0.167 mmol of tungsten hexacarbonyl (W(CO)6) and 1.5 mmol of ascorbic acid are added. The obtained mixed solution is treated in an ultrasonic crusher for 30 min, and the energy intensity is set to 50%, the working time is set to 20 s, and the interval time is set to 40 s, to obtain a uniform a liquid.

[0053] (2) Preparation of a b liquid (namely, a second precursor liquid): 2 mmol of tetrabutyl titanate (Ti(OBu)4) is placed in an inert atmosphere (argon), and 2 mL of 40wt% hydrofluoric acid is slowly added dropwise while stirring, to obtain a b liquid.

[0054] (3) One-step hydrothermal reaction synthesis: the a liquid and the b liquid are mixed and transferred to a 50 mL polytetrafluoroethylene-lined high-pressure reaction kettle, and then sealed and subjected to hydrothermal reaction at 180℃ for 16 h. After the reaction is completed, the obtained solid is naturally cooled to room temperature, washed with ethanol and cyclohexane repeatedly for 3 times to remove unreacted components and organic residues, and then subjected to freeze-drying under vacuum for 24 h, to obtain a gray two-dimensional / two-dimensional structure Ni-ene / TiO2 composite photocatalyst powder. The mass of the two-dimensional Ni metal nanosheet in the obtained catalyst is 6% of the mass of the two-dimensional TiO2 nanosheet, which is denoted as Ni-ene / TiO2 (6wt%).

[0055] The composite photocatalyst prepared in Example 1 is composed of ultrathin two-dimensional Ni metal ene and two-dimensional TiO2 nanosheet, which are tightly coupled to form a stable interface structure. Figure 1 The TEM image of the two-dimensional / two-dimensional structure Ni-ene / TiO2 composite photocatalyst prepared in Example 1 shows that the Ni metal ene presents a typical two-dimensional sheet structure with a size of 40-60 nm and a thickness of about 1 nm; the TiO2 presents a sheet-shaped crystal with a uniform size (a size of 20-30 nm and a thickness of 2-3 nm) and is well dispersed in a stacked state. Figure 1 The TEM image of the two-dimensional / two-dimensional structure Ni-ene / TiO2 composite photocatalyst prepared in Example 1 shows that the Ni metal ene presents a typical two-dimensional sheet structure with a size of 40-60 nm and a thickness of about 1 nm; the TiO2 presents a sheet-shaped crystal with a uniform size (a size of 20-30 nm and a thickness of 2-3 nm) and is well dispersed in a stacked state.

[0056] Example 2

[0057] A two-dimensional / two-dimensional structure composite photocatalyst (i.e., a Ni-ene / TiO2 composite photocatalyst) is prepared by the following steps:

[0058] (1) Preparation of a liquid: 0.084 mmol of nickel acetylacetonate (Ni(acac)2) is weighed into 20 mL of oleylamine, and stirred at room temperature until completely dissolved. Then, 0.167 mmol of tungsten hexacarbonyl (W(CO)6) and 1.5 mmol of ascorbic acid are added. The resulting mixed solution is treated in an ultrasonic crusher for 30 min, with an energy intensity of 50%, a working time of 20 s, and an interval time of 40 s, to obtain a uniform a liquid.

[0059] (2) Preparation of a b liquid: 2 mmol of tetrabutyl titanate (Ti(OBu)4) is placed in an inert atmosphere (argon), and 2 mL of 40 wt% hydrofluoric acid is slowly added dropwise while stirring (a dropwise addition rate of 1 mL / 3 min) to obtain a b liquid.

[0060] (3) One-step hydrothermal reaction synthesis: The a liquid and the b liquid are mixed and transferred to a 50 mL polytetrafluoroethylene-lined high-pressure reaction kettle, which is sealed and subjected to a hydrothermal reaction at 180°C for 16 h. After the reaction is completed, the resulting solid is naturally cooled to room temperature, centrifuged, and washed repeatedly with ethanol and cyclohexane for 3 times to remove unreacted components and organic residues. Then, the resulting solid is freeze-dried under vacuum for 24 h to obtain a gray two-dimensional / two-dimensional structure Ni-ene / TiO2 composite photocatalyst powder. The mass of the two-dimensional Ni metal nanosheet in the obtained catalyst is 1% of the mass of the two-dimensional TiO2 nanosheet, which is denoted as Ni-ene / TiO2 (1 wt%).

[0061] Example 3

[0062] A two-dimensional / two-dimensional structure composite photocatalyst (i.e., a Ni-ene / TiO2 composite photocatalyst) is prepared by the following steps:

[0063] (1) Preparation of solution a: 0.167 mmol of nickel acetylacetonate (Ni(acac)2) was weighed and added to 20 mL of oleylamine, and then stirred at room temperature until completely dissolved. Then 0.167 mmol of tungsten hexacarbonyl (W(CO)6) and 1.5 mmol of ascorbic acid were added. The resulting mixed solution was treated in an ultrasonic cell disruptor for 30 min, with an energy intensity of 50%, a working time of 20 s, and an interval time of 40 s, to obtain a uniform solution a.

[0064] (2) Preparation of solution b: 2 mmol of tetrabutyl titanate (Ti(OBu)4) was placed in an inert atmosphere (argon), and 2 mL of 40 wt% hydrofluoric acid was slowly added dropwise while stirring (addition rate 1 mL / 3 min) to obtain solution b.

[0065] (3) One-step hydrothermal synthesis: solutions a and b were mixed and transferred to a 50 mL polytetrafluoroethylene-lined high-pressure reaction kettle, which was sealed and subjected to hydrothermal reaction at 180°C for 16 h. After the reaction was completed, the resulting solid was naturally cooled to room temperature, washed with ethanol and cyclohexane for 3 times to remove unreacted components and organic residues, and then freeze-dried under vacuum for 24 h to obtain a gray two-dimensional / two-dimensional structure Ni-ene / TiO2 composite photocatalyst powder. The mass of the two-dimensional Ni metal nanosheet in the obtained catalyst was 2% of the mass of the two-dimensional TiO2 nanosheet, which was recorded as Ni-ene / TiO2 (2 wt%).

[0066] Example 4

[0067] A two-dimensional / two-dimensional structure composite photocatalyst (i.e., a Ni-ene / TiO2 composite photocatalyst) was prepared according to the following steps:

[0068] (1) Preparation of solution a: 0.334 mmol of nickel acetylacetonate (Ni(acac)2) was weighed and added to 20 mL of oleylamine, and then stirred at room temperature until completely dissolved. Then 0.167 mmol of tungsten hexacarbonyl (W(CO)6) and 1.5 mmol of ascorbic acid were added. The resulting mixed solution was treated in an ultrasonic cell disruptor for 30 min, with an energy intensity of 50%, a working time of 20 s, and an interval time of 40 s, to obtain a uniform solution a.

[0069] (2) Preparation of solution b: 2 mmol of tetrabutyl titanate (Ti(OBu)4) was placed in an inert atmosphere (argon), and 2 mL of 40 wt% hydrofluoric acid was slowly added dropwise while stirring (addition rate 1 mL / 3 min) to obtain solution b.

[0070] (3) One-step hydrothermal reaction synthesis: a liquid and b liquid were mixed and transferred to a 50 mL polytetrafluoroethylene-lined high-pressure reaction kettle, which was sealed and hydrothermally reacted at 180 °C for 16 h. After the reaction was completed, it was naturally cooled to room temperature, and the obtained solid was separated by centrifugation, washed with ethanol and cyclohexane for 3 times to remove unreacted components and organic residues, and then freeze-dried under vacuum for 24 h to obtain a gray two-dimensional / two-dimensional structure Ni-ene / TiO2 composite photocatalyst powder. The mass of two-dimensional Ni metal nanosheets in the obtained catalyst was 4% of the mass of two-dimensional TiO2 nanosheets, which was recorded as Ni-ene / TiO2 (4 wt%).

[0071] Comparative Example 1

[0072] Preparation of pure TiO2 nanosheets (recorded as TiO2):

[0073] 2 mmol of tetrabutyl titanate (Ti(OBu)4) was placed in an inert atmosphere (argon), 2 mL of 40 wt% hydrofluoric acid was slowly added (addition rate 1 mL / 3 min), 20 mL of anhydrous ethanol was added, and the mixture was transferred to a 50 mL polytetrafluoroethylene-lined high-pressure reaction kettle, which was sealed and hydrothermally reacted at 180 °C for 16 h. After the reaction was completed, it was naturally cooled to room temperature, and the obtained solid was separated by centrifugation, washed with deionized water for 3 times to remove unreacted components and organic residues, and then freeze-dried under vacuum for 24 h to obtain a white pure TiO2 nanosheet powder.

[0074] Comparative Example 2

[0075] Preparation of Pt / TiO2 catalyst (recorded as Pt / TiO2 (1 wt%)) by photodeposition method, as follows:

[0076] 0.1 g of TiO2 nanosheet powder (prepared in Comparative Example 1) was dispersed in 100 mL of deionized water, ultrasonically dispersed, and 2 mL of chloroplatinic acid aqueous solution (1 mg / mL) was added under stirring. The stirring was maintained, and the mixture was irradiated with a xenon lamp for 2 h. The mixture was centrifuged at 10000 rpm for 2 times, and freeze-dried to obtain Pt / TiO2 (1 wt%, i.e. the mass of Pt was 1% of the mass of TiO2 as determined by icp).

[0077] Comparative Example 3

[0078] Preparation of Ni particle / two-dimensional TiO2 catalyst (recorded as Ni-particle / TiO2 (6 wt%)):

[0079] Firstly, 30 mg of nickel nitrate hexahydrate was dissolved in 5 mL of deionized water. Then 2 mL of ammonia water (volume percentage 28%) was added to the mixed solution and mixed well, and then 45 mL of diethylene glycol was added and stirred for 10 min. 0.1 g of TiO2 nanosheet powder (prepared in Comparative Example 1) was added to the obtained mixed solution and ultrasonically treated for 5 min, and then transferred to a 200°C oil bath and stirred until boiling. Then it was cooled to room temperature for 30 s, centrifuged at 8000 rpm and washed 5 times, and dried in a vacuum oven at 60°C for 12 h. Then the sample was placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min under an argon-hydrogen gas flow (hydrogen to argon volume ratio 5:95) for 2 h to obtain a Ni-particle / TiO2 (6 wt%, i.e. the mass of Ni particles is 6% of the mass of TiO2) photocatalyst.

[0080] The Ni-ene / TiO2 composite photocatalysts with different nickel metal loading prepared in the examples, pure TiO2 nanosheet prepared in the comparative example, Pt / TiO2 catalyst prepared by photodeposition method and Ni particle / 2D TiO2 catalyst were subjected to photocatalytic hydrogen production experiment. The photocatalytic hydrogen production experiment was carried out in a sealed quartz reactor with a lateral light transmission window, and the light source was a 300W xenon lamp (PLS-SXE300, Beijing Perfectlight). The simulated sunlight irradiation condition was used, and the experimental process was as follows: 10 mg of catalyst was dispersed in 50 mL of aqueous solution containing 10% (volume percentage) triethanolamine (triethanolamine as a sacrificial agent). The reactor was maintained at 15°C by a condensation circulation system, and argon was introduced for 20 min before the experiment to exclude air. The hydrogen production amount was detected by gas chromatograph (GC-2060) with argon as the carrier gas. Under the continuous irradiation of the light source, the gas sample was collected every 30 min, and the hydrogen production was detected by gas chromatography, and the rate was calculated.

[0081] Figure 2 The hydrogen production rate comparison chart of the Ni-ene / TiO2 composite photocatalysts with different nickel metal loading prepared in the examples, pure TiO2 nanosheet prepared in the comparative example, and Pt / TiO2 catalyst prepared by photodeposition method. Figure 2The two-dimensional / two-dimensional structure Ni-ene / TiO2 (6wt%) composite photocatalyst obtained by example 1 has good photocatalytic hydrogen production performance, and the production reaches 8273 μmol / h / g, which is obviously better than the photocatalytic hydrogen production performance of original TiO2 nanosheet (345 μmol / h / g) and the photocatalytic hydrogen production performance of Pt / TiO2 nanoparticles (7713 μmol / h / g), that is, the photocatalytic cocatalytic performance of two-dimensional nickel metalene is obviously better than that of noble metal Pt nanoparticles, which is conducive to replacing noble metal in actual production and reducing the cost of the catalyst. The hydrogen production efficiency of the Ni-particle / two-dimensional TiO2 (6wt%) catalyst prepared in comparative example 3 is only 743 μmol / h / g.

[0082] The two-dimensional / two-dimensional structure Ni-ene / TiO2 (6wt%) composite photocatalyst was subjected to a cycle stability test, and the test conditions were the same as those of the above-mentioned photocatalytic hydrogen production experiment. In the stability test, after completing one cycle, argon was passed for 15 min to remove the hydrogen generated in the reaction, and 5mL of triethanolamine was supplemented to ensure that the reaction conditions were consistent.

[0083] The cycle stability test results are shown in Figure 3 As can be seen from Figure 3 , in each cycle process, the amount of photocatalytic hydrogen production will be steadily increased with the reaction time, and after 3 cycles, it can still reach 8300 μmol / h / g, indicating that the catalyst has good stability.

[0084] The above only describes the preferred embodiments of the present application, and does not limit the present application in any form. It should be noted that for ordinary skilled persons in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A two-dimensional / two-dimensional composite photocatalyst, characterized in that, It includes two-dimensional TiO2 nanosheets and ultrathin two-dimensional Ni metal nanosheets loaded on the two-dimensional TiO2 nanosheets.

2. The two-dimensional / two-dimensional composite photocatalyst according to claim 1, characterized in that, The mass of the ultrathin two-dimensional Ni metal nanosheet is 1 to 15% of the mass of the two-dimensional TiO2 nanosheet.

3. The two-dimensional / two-dimensional composite photocatalyst according to claim 1 or 2, characterized in that, The ultrathin two-dimensional Ni metal nanosheets have a size of 40~60 nm.

4. The method for preparing the two-dimensional / two-dimensional structured composite photocatalyst according to any one of claims 1 to 3, characterized in that, Includes the following steps: The nickel source, oleylamine, hexacarbonyl tungsten, and ascorbic acid were mixed to obtain the first precursor solution; The titanium source and hydrofluoric acid were mixed to obtain the second precursor solution; The first precursor solution and the second precursor solution are mixed and subjected to a hydrothermal reaction to obtain the two-dimensional / two-dimensional structured composite photocatalyst.

5. The preparation method according to claim 4, characterized in that, The nickel source includes nickel acetylacetone; the concentration of the nickel source in the first precursor solution is 4~25 mmol·L⁻¹. -1 The molar ratio of ascorbic acid to nickel source is 3~18:1, and the molar ratio of ascorbic acid to hexacarbonyltungsten is 9:

1.

6. The preparation method according to claim 4 or 5, characterized in that, The nickel source, oleylamine, hexacarbonyltungsten, and ascorbic acid are mixed and subjected to ultrasonic treatment.

7. The preparation method according to claim 4, characterized in that, The titanium source includes tetrabutyl titanate; the hydrofluoric acid has a mass fraction of 40%, and the ratio of the titanium source to the hydrofluoric acid is 2 mmol: 2 mL.

8. The preparation method according to claim 4, 5 or 7, characterized in that, The mass ratio of nickel source in the first precursor solution to titanium source in the second precursor solution is 1:5~32.

9. The preparation method according to claim 4, characterized in that, The hydrothermal reaction is carried out at a temperature of 180~200℃ for 14~16 hours.

10. The application of the two-dimensional / two-dimensional composite photocatalyst according to any one of claims 1 to 3 or the two-dimensional / two-dimensional composite photocatalyst prepared by the preparation method according to any one of claims 4 to 9 in photocatalytic water splitting for hydrogen production.

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