A cerium dioxide-nano-gold catalyst and its preparation method and application

Abstract

The present invention provides a ceria-nano-gold catalyst that uses ceria with strong oxidizing properties as an outer shell. Even after a large amount of oxygen is lost in the ceria lattice and a large number of oxygen vacancies are formed, it is easily reoxidized to ceria by contact with oxygen in the environment. The ceria is wrapped around the surface of gold decahedron nanoparticles to avoid the aggregation of the core gold decahedron nanoparticles, thereby improving the catalytic activity and repeatability of the gold decahedron nanoparticles, while preventing the ceria-nano-gold catalyst from being poisoned and improving the performance stability of the catalyst. When used for photolysis of water to produce oxygen, the catalytic activity and conversion frequency are as high as 271.38 mol O2 ·mol Au ‑1 ·h ‑1 .

Description

Technical Field

[0001] The present invention relates to the field of catalytic materials, and in particular to a cerium dioxide-nano-gold catalyst and a preparation method and application thereof. Background Art

[0002] The process of photocatalytic water production of hydrogen and oxygen is as follows: after the semiconductor photocatalyst absorbs photon radiation with energy equal to or greater than its own band gap width, the electrons in the ground state of the valence band (HOMO) absorb energy and become excited, and then jump to the conduction band (LUMO) to form photogenerated electrons. After the electron jumps, a hole is left in the valence band. Among them, the electron has a reducing effect, H + To obtain electrons and form hydrogen, the conduction band position of the semiconductor must be above the reduction potential of water, and the higher the position, the greater the difference, and the stronger the reducing property. And the holes have an oxidizing effect, taking away O2 - The electrons on the valence band generate oxygen, so the valence band position of the semiconductor is lower than the oxidation potential position of water, and the lower the position, the greater the difference, the stronger the oxidizing property.

[0003] Photocatalytic water splitting to produce oxygen can realize the conversion of solar energy into thermal energy by using oxygen as a medium. Therefore, visible light catalytic water splitting has always been a hot area of research for scientists. At present, the types of semiconductor materials that can have excellent catalytic activity under visible light conditions are still very limited, and most of the research is on improving titanium dioxide. In addition, in the process of water splitting, the energy barrier for producing oxygen is higher than the energy barrier for producing hydrogen. Compared with the difficulty of producing hydrogen, photocatalytic water splitting to produce oxygen is more challenging. Therefore, the photocatalysts in the existing technology generally have the problem of low activity in the process of photocatalytic water splitting to produce oxygen. Summary of the Invention

[0004] The purpose of the present invention is to provide a cerium dioxide-nano-gold catalyst and its preparation method and application. The cerium dioxide-nano-gold catalyst provided by the present invention can photolyze water to produce oxygen and has high catalytic activity.

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

[0006] The invention provides a ceria-nano-gold catalyst, comprising nano-gold and ceria coated on the surface of the nano-gold; the nano-gold is gold decahedron nanoparticles.

[0007] Preferably, the thickness of the ceria is 10 to 60 nm; and the particle size of the ceria-nano-gold catalyst is 20 to 80 nm.

[0008] The present invention also provides a method for preparing the cerium dioxide-nano-gold catalyst described in the above technical solution, comprising the following steps:

[0009] (1) mixing a gold precursor solution, a surfactant solution, and a reducing agent solution to obtain a mixed solution;

[0010] (2) adding a gold seed solution to the mixed solution obtained in step (1) to perform a reduction reaction to obtain a gold decahedral nanoparticle dispersion;

[0011] (3) The gold decahedron nanoparticle dispersion obtained in step (2), water and a cerium source solution are mixed, and a hydrolysis reaction is carried out in a sealed environment to obtain a cerium dioxide-nano-gold catalyst.

[0012] Preferably, the concentration of the gold precursor solution in step (1) is 0.005-0.03 mM.

[0013] Preferably, the concentration of the surfactant solution in step (1) is 0.01 to 0.2 mM.

[0014] Preferably, the concentration of the reducing agent solution in step (1) is 0.01 to 0.3 mM.

[0015] Preferably, in step (1), the volume ratio of the gold precursor solution, the surfactant solution and the reducing agent solution is (15-25):(300-500):(1-5).

[0016] Preferably, the temperature of the reduction reaction in step (2) is room temperature, and the reduction reaction time is 0.5 to 13 minutes.

[0017] Preferably, the temperature of the hydrolysis reaction in step (3) is 90-110° C., and the time of the hydrolysis reaction is 40-80 min.

[0018] The present invention also provides the use of the cerium dioxide-nano-gold catalyst described in the above technical solution or the cerium dioxide-nano-gold catalyst prepared by the preparation method in photolysis of water to produce oxygen.

[0019] The invention provides a ceria-nano-gold catalyst. Ceria is used as an outer shell. The structure of the ceria is a cubic arrangement with metal atoms as face centers. All tetrahedral cavities are filled with oxygen, and the catalyst has strong oxidizing property. Even after a large amount of oxygen is lost in the crystal lattice of the ceria and a large number of oxygen vacancies are formed, the fluorite crystal structure of the ceria does not change. Moreover, these subcarboxylates are easily reoxidized to form ceria upon contact with oxygen in the environment. The ceria is wrapped around the surface of gold decahedral nanoparticles, which can avoid the aggregation of the gold decahedral nanoparticles in the inner core, thereby improving the catalytic activity and repeatability of the gold decahedral nanoparticles. At the same time, poisoning of the ceria-nano-gold catalyst is prevented, and the performance stability of the catalyst is improved. The results of the embodiment show that the cerium dioxide-nano-gold catalyst provided by the present invention has a catalytic activity when used for photolysis of water to produce oxygen. The oxygen production is 0.9umol at 30 minutes, 2.8umol at 45 minutes, 4.5umol at 55 minutes, and 5.8umol at 65 minutes, with a conversion frequency of up to 271.38mol O2 ·mol Au -1 ·h -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 TEM image of the cerium dioxide-nano-gold catalyst 100MT-Au prepared in Example 2 of the present invention;

[0021] Figure 2 TEM image of the cerium dioxide-nano-gold catalyst 150MT-Au prepared in Example 4 of the present invention;

[0022] Figure 3 TEM image of gold decahedral nanoparticles MT-Au prepared in a comparative example of the present invention;

[0023] Figure 4 A graph showing the change in oxygen production over time for photolysis of water to produce oxygen using 100MT-Au and 150MT-Au prepared in Examples 2 and 4 of the present invention, and MT-Au prepared in a comparative example;

[0024] Figure 5 This is a graph showing the change in conversion frequency over time for photolysis of water to produce oxygen using 100MT-Au and 150MT-Au prepared in Examples 2 and 4 of the present invention, and MT-Au prepared in the comparative example. DETAILED DESCRIPTION

[0025] The invention provides a ceria-nano-gold catalyst, comprising nano-gold and ceria coated on the surface of the nano-gold; the nano-gold is gold decahedron nanoparticles.

[0026] The ceria-nano-gold catalyst provided by the present invention comprises nano-gold, which is a gold decahedron nanoparticle. In the present invention, the nano-gold preferably has a particle size of 20 to 80 nm, more preferably 40 to 60 nm. In the present invention, the nano-gold acts as a seed, coated with ceria, and also serves as the active component of the catalyst to produce oxygen.

[0027] The ceria-nano-gold catalyst provided by the present invention further comprises ceria coated on the surface of the nano-gold. In the present invention, the ceria acts as a carrier to coat the gold decahedron nanoparticles to prevent them from agglomerating.

[0028] In the present invention, the thickness of the ceria is preferably 10 to 60 nm, more preferably 20 to 50 nm. The present invention controls the thickness of the ceria coated on the surface of the nano-gold within the above range, which is beneficial to avoid the agglomeration of the nano-gold while maintaining a high catalytic activity site.

[0029] In the present invention, the particle size of the ceria-nano-gold catalyst is 30 to 180 nm, more preferably 80 to 160 nm. Controlling the particle size of the ceria-nano-gold catalyst within the above range is beneficial for preventing agglomeration, protecting the nano-gold, and maintaining high catalytic activity of the nano-gold active centers.

[0030] The ceria-nano-gold catalyst provided by the present invention can photolyze water to produce oxygen and has high catalytic activity. In addition, ceria is wrapped on the surface of gold decahedron nanoparticles to avoid the aggregation of the inner core gold decahedron nanoparticles, thereby improving the catalytic activity and repeatability of the gold decahedron nanoparticles, and at the same time preventing the ceria-nano-gold catalyst from being poisoned, thereby improving the performance stability of the catalyst.

[0031] The present invention also provides a method for preparing the catalyst described in the above technical solution, comprising the following steps:

[0032] (1) mixing a gold precursor solution, a surfactant solution, and a reducing agent solution to obtain a mixed solution;

[0033] (2) adding a gold seed solution to the mixed solution obtained in step (1) to perform a reduction reaction to obtain a gold decahedral nanoparticle dispersion;

[0034] (3) mixing the gold decahedral nanoparticle dispersion obtained in step (2), water, and a cerium source solution, and performing a hydrolysis reaction in a sealed environment to obtain a ceria-nano-gold catalyst;

[0035] In the present invention, unless otherwise specified, the raw materials used are conventional commercial products in the field.

[0036] The present invention mixes a gold precursor solution, a surfactant solution and a reducing agent solution to obtain a mixed solution.

[0037] In the present invention, the gold precursor in the gold precursor solution is preferably one or more of chloroauric acid, sodium tetrachloroaurate dihydrate, gold acetate, gold (III) chloride and gold (I) sodium thiosulfate hydrate, more preferably chloroauric acid. In the present invention, the solvent of the gold precursor solution is preferably deionized water. The present invention has no special restrictions on the preparation of the gold precursor solution, and conventional technical solutions in the field can be adopted. In the present invention, the concentration of the gold precursor solution is preferably 0.005-0.03mM, more preferably 0.0055-0.011mM. The present invention controls the concentration of the gold precursor solution within the above range, which is conducive to controlling the morphology of nanogold and obtaining gold decahedral nanoparticles.

[0038] In the present invention, the surfactant in the surfactant solution is preferably one or more of cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, cetyltrimethylammonium hydrogen sulfate, sodium lauryl sulfonate, polyether and polyvinyl pyrrolidone, more preferably cetyltrimethylammonium chloride. In the present invention, the solvent of the surfactant solution is preferably deionized water. The present invention has no special restrictions on the preparation of the surfactant solution, and conventional technical solutions in the field can be adopted. In the present invention, the concentration of the surfactant solution is preferably 0.01 to 0.2 mM, more preferably 0.05 to 0.12 mM. The present invention controls the concentration of the surfactant solution within the above range, which is conducive to preventing the agglomeration of nanogold.

[0039] In the present invention, the reducing agent in the reducing agent solution is preferably one or more of ascorbic acid, sodium citrate, citric acid, sodium borohydride and hydrazine hydrate, more preferably ascorbic acid. In the present invention, the solvent of the reducing agent solution is preferably deionized water. The present invention has no special restrictions on the preparation of the reducing agent solution, and conventional technical solutions in the field can be adopted. In the present invention, the concentration of the reducing agent solution is preferably 0.01 to 0.3 mM, more preferably 0.05 to 0.12 mM. The present invention controls the concentration of the reducing agent solution within the above range, which is conducive to preventing the agglomeration of nanogold.

[0040] In the present invention, the volume ratio of the gold precursor solution, the surfactant solution, and the reducing agent solution is preferably (15-25): (300-500): (1-5), and preferably (18-22): (350-450): (2-4). The present invention controls the volume ratio of the gold precursor solution, the surfactant solution, and the reducing agent solution within the above range to control the growth rate of the gold decahedral nanoparticles, thereby controlling the size of the gold decahedral nanoparticles, avoiding too low a ratio that prevents the formation of gold decahedral nanoparticles, and avoiding too high a ratio that causes the formation of overly large gold decahedral nanoparticles.

[0041] In the present invention, the mixing of the gold precursor solution, the surfactant solution, and the reducing agent solution is preferably carried out under stirring. The present invention has no particular limitation on the stirring rate, as long as the components are uniformly mixed.

[0042] After obtaining the mixed solution, the present invention adds a gold seed solution to the mixed solution to carry out a reduction reaction to obtain a gold decahedron nanoparticle dispersion.

[0043] In the present invention, the preparation of the gold seed solution preferably comprises:

[0044] An ice water solution of sodium borohydride, a gold precursor solution and a surfactant solution are mixed and subjected to a reduction reaction to obtain a gold seed solution.

[0045] In the present invention, the sodium borohydride icy water solution is preferably prepared freshly. The present invention uses sodium borohydride as a reducing agent and prepares the sodium borohydride icy water solution to reduce the rate of the reduction reaction between the sodium borohydride and the gold precursor, thereby facilitating the production of small-particle gold seed crystals and preventing agglomeration of the gold seed crystals. This facilitates the production of well-dispersed, small-sized gold decahedral nanoparticles after subsequent crystal growth (reduction reaction).

[0046] In the present invention, the concentration of the sodium borohydride ice-water solution is preferably 1 to 20 mM, more preferably 8 to 11 mM. Controlling the concentration of the sodium borohydride ice-water solution within the above range is beneficial for controlling the reduction reaction rate, inhibiting the rapid synthesis of gold seeds, and facilitating the production of small gold seeds.

[0047] In the present invention, the gold precursor in the gold precursor solution is preferably one or more of chloroauric acid, sodium tetrachloroaurate dihydrate, gold acetate, gold (III) chloride and gold (I) sodium thiosulfate hydrate, more preferably chloroauric acid. In the present invention, the solvent of the gold precursor solution is preferably deionized water. The present invention has no special restrictions on the preparation of the gold precursor solution, and conventional technical solutions in the field can be adopted. In the present invention, the concentration of the gold precursor solution is preferably 5 to 15 mM, more preferably 8 to 11 mM. The present invention controls the concentration of the gold precursor solution within the above range, which is conducive to controlling the formation of the gold seed morphology and obtaining small-particle gold seeds.

[0048] In the present invention, the surfactant in the surfactant solution is preferably one or more of cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, cetyltrimethylammonium hydrogen sulfate, sodium lauryl sulfonate, polyether and polyvinyl pyrrolidone, more preferably cetyltrimethylammonium chloride. In the present invention, the solvent of the surfactant solution is preferably deionized water. The present invention has no special restrictions on the preparation of the surfactant solution, and conventional technical solutions in the field can be adopted. In the present invention, the concentration of the surfactant solution is preferably 50 to 200 mM, more preferably 80 to 110 mM. The present invention controls the concentration of the surfactant solution within the above range, which is beneficial to prevent the agglomeration of gold seeds.

[0049] In the present invention, the volume ratio of the sodium borohydride ice water solution, the gold precursor solution, and the surfactant solution is preferably (1-5):1:(20-50), and more preferably (2-4):1:(35-43). The present invention controls the volume ratio of the sodium borohydride ice water solution, the gold precursor solution, and the surfactant solution within the above range to control the formation rate of gold seeds, thereby controlling the particle size of the gold seeds, avoiding too low a ratio that prevents the formation of gold seeds, while avoiding too high a ratio that results in the formation of gold seeds with excessively large particles.

[0050] In the present invention, the mixing of the sodium borohydride ice water solution, the gold precursor solution, and the surfactant solution is preferably carried out under stirring. The present invention has no particular limitation on the stirring rate, as long as the components are uniformly mixed.

[0051] In the present invention, the reduction reaction for preparing the gold seed solution is preferably carried out under stirring. The present invention has no particular limitation on the stirring rate; a conventional rate may be employed. In the present invention, the temperature of the reduction reaction is preferably room temperature. In the present invention, the reduction reaction time is preferably 0.5 to 13 minutes, more preferably 1 to 10 minutes. Controlling the temperature and time of the reduction reaction within the above-mentioned ranges facilitates the formation of a sufficient number of gold seed crystals with a smaller particle size, thereby avoiding the formation of gold seed crystals with excessively large particles.

[0052] After the reduction reaction is completed, the present invention preferably allows the product of the reduction reaction to stand at room temperature to obtain a gold seed solution.

[0053] In the present invention, the standing time is preferably 1.5 to 4.5 hours. In the present invention, the standing time is controlled within the above range, which is conducive to stabilizing the prepared gold seed crystals and facilitating subsequent crystal growth (reduction reaction).

[0054] In the present invention, the gold seed solution is preferably added to the mixed solution under stirring. The present invention has no particular limitation on the stirring rate, as long as the components are uniformly mixed.

[0055] In the present invention, the volume ratio of the gold seed solution to the mixed solution is preferably 1:(0.2-0.8), more preferably 1:(0.4-0.5). In the present invention, controlling the volume ratio of the gold seed solution to the mixed solution within the above range is conducive to the formation of gold decahedral nanoparticle morphology.

[0056] In the present invention, the reduction reaction for preparing the gold decahedron nanoparticle dispersion is preferably carried out under stirring conditions. The present invention has no special restrictions on the stirring rate, and a conventional rate can be used. In the present invention, the temperature of the reduction reaction is preferably room temperature. In the present invention, the time of the reduction reaction is preferably 0.5 to 13 minutes, more preferably 1 to 10 minutes. The present invention controls the temperature and time of the reduction reaction within the above-mentioned range, which is conducive to controlling the growth rate of the gold decahedron nanoparticles, thereby controlling the size of the gold decahedron nanoparticles, avoiding the failure to form gold decahedron nanoparticles due to too low temperature and too short reaction time, and avoiding the formation of gold decahedron nanoparticles due to too high temperature and too long reaction time.

[0057] In the present invention, the average diameter of the gold decahedron nanoparticles in the gold decahedron nanoparticle dispersion is preferably 20 to 80 nanometers, more preferably 30 to 60 nanometers.

[0058] After the reduction reaction of the gold decahedron nanoparticle dispersion is completed, the present invention preferably allows the reduction reaction product to stand at room temperature.

[0059] In the present invention, the standing time is preferably 1.5 to 4.5 hours. The present invention controls the standing time within the above range, which is conducive to stabilizing the prepared gold decahedron nanoparticles and facilitating the subsequent coating of the gold decahedron nanoparticles with ceria.

[0060] After obtaining the gold decahedron nanoparticle dispersion, the present invention mixes the gold decahedron nanoparticle dispersion, water and a cerium source solution, and performs a hydrolysis reaction in a sealed environment to obtain a ceria-nano-gold catalyst.

[0061] In the present invention, the water is preferably ultrapure water.

[0062] In the present invention, the cerium source in the cerium source solution is preferably one or more of cerium acetate, cerium nitrate, and cerium chloride. In the present invention, the solvent of the cerium source solution is preferably deionized water. The present invention has no particular restrictions on the preparation of the cerium source solution; conventional techniques in the art may be employed. In the present invention, the concentration of the cerium source solution is preferably 0.01 to 0.2 mM, more preferably 0.05 to 0.12 mM. Controlling the concentration of the reducing agent solution within the above range helps prevent agglomeration of the gold decahedral nanoparticles.

[0063] In the present invention, the volume ratio of the gold decahedral nanoparticle dispersion to the cerium source solution is preferably (100-300):(50-500), and more preferably (150-250):(80-160). Controlling the volume ratio of the gold decahedral nanoparticle dispersion to the cerium source solution within the above range helps prevent the formation of an excessively thick ceria coating layer, which could reduce the activity of the catalyst.

[0064] In the present invention, the hydrolysis reaction is preferably carried out under stirring conditions. The present invention has no special restrictions on the stirring rate, and a conventional rate can be used. In the present invention, the temperature of the hydrolysis reaction is preferably 90 to 110°C, more preferably 95 to 105°C. In the present invention, the time of the hydrolysis reaction is preferably 40 to 80 minutes, more preferably 50 to 70 minutes. The present invention controls the temperature and time of the hydrolysis reaction within the above-mentioned range, which is beneficial to controlling the rate at which the cerium source generates ceria, thereby facilitating the generation of ceria to completely wrap the gold decahedral nanoparticles, and controlling the thickness and uniformity of the outer layer of ceria, which is beneficial to improving the catalytic activity of the prepared ceria-nano-gold catalyst.

[0065] After the hydrolysis reaction is completed, the present invention preferably sequentially cools, ultrasonicates, heats, centrifuges, and separates the product of the hydrolysis reaction to obtain a ceria-nano-gold catalyst.

[0066] In the present invention, the cooling method is preferably natural cooling to room temperature. In the present invention, the ultrasonic time is preferably 1 to 5 minutes. The present invention has no special restrictions on the ultrasonic rate, and the conventional rate in the field can be used. In the present invention, the centrifugal speed is preferably 5000 to 10000 rpm, more preferably 6000 to 9000 rpm. In the present invention, the centrifugal time is preferably 3 to 20 minutes, more preferably 5 to 15 minutes. The present invention has no special restrictions on the solid-liquid separation method, as long as the purpose of removing the liquid is achieved.

[0067] The method provided in this application is simple to operate, has a wide range of raw materials, and is suitable for large-scale production.

[0068] The present invention also provides the use of the cerium dioxide-nano-gold catalyst described in the above technical solution or the cerium dioxide-nano-gold catalyst prepared by the preparation method in photolysis of water to produce oxygen.

[0069] The present invention has no special limitation on the operation of producing oxygen by photolysis of water, and the technical solutions well known to those skilled in the art can be adopted.

[0070] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0071] Example 1

[0072] Cerium dioxide-nano-gold catalyst:

[0073] It is composed of nano-gold and cerium dioxide coated on the surface of the nano-gold; the nano-gold is a gold decahedron nanoparticle with a particle size of 50nm;

[0074] The particle size of the cerium dioxide-nano-gold catalyst is 100 nm; the thickness of the cerium dioxide coated on the surface of the nano-gold is 25 nm.

[0075] Example 2

[0076] Preparation method of cerium dioxide-nano-gold catalyst described in Example 1:

[0077] (1) mixing a chloroauric acid solution (i.e., a gold precursor solution, 0.01 mM, 500 μL), a dodecyldimethylbenzyl ammonium chloride solution (i.e., a surfactant solution, 0.1 mM, 10 mL), and an ascorbic acid solution (i.e., a reducing agent solution, 0.1 mM, 75 μL) under stirring to obtain a mixed solution;

[0078] The volume ratio of the gold precursor solution, the surfactant solution and the reducing agent solution is 20:400:3;

[0079] (2) adding 20 μL of gold seed solution to the mixed solution obtained in step (1) under stirring, performing a reduction reaction at room temperature for 5 minutes under stirring, and allowing the reduction reaction product to stand at room temperature for 2 hours to obtain a dispersion of gold decahedral nanoparticles;

[0080] The average diameter of the gold decahedron nanoparticles is 50 nanometers;

[0081] The volume ratio of the gold seed solution to the mixed solution is 1:0.47;

[0082] The gold seed solution is prepared by mixing an ice water solution of sodium borohydride (10 mM, 600 μL) prepared with ice water, a chloroauric acid solution (i.e., a gold precursor solution, 10 mM, 250 μL), and cetyltrimethylammonium bromide (i.e., a surfactant solution, 0.1 M, 9.75 mL) under stirring, then stirring at room temperature for a reduction reaction for 2 minutes, and allowing the reduction reaction product to stand at room temperature for 2 hours to obtain a gold seed solution;

[0083] The volume ratio of the sodium borohydride ice water solution, the gold precursor solution and the surfactant solution is 2.4:1:39;

[0084] (3) In a centrifuge tube, 200 μL of the gold decahedron nanoparticle dispersion obtained in step (2), 1 mL of ultrapure water and a cerium acetate solution (0.1 mM, 100 μL) were mixed. The mouth of the centrifuge tube was sealed with a sealing strip, and the lid of the centrifuge tube was covered. The centrifuge tube was placed in an oven at 100° C. in a sealed environment for hydrolysis reaction for 1 hour. The centrifuge tube was taken out and cooled to room temperature. The melted sealing film at the mouth of the centrifuge tube was removed, and the lid of the centrifuge tube was covered and placed in ultrasound for 3 minutes. The centrifuge tube was taken out and heated with a hot air gun until the solution in the centrifuge tube was clear. The centrifuge tube was centrifuged at a speed of 8000 rpm for 10 minutes. After the centrifugation, the upper clear liquid was aspirated with a rubber-tipped dropper and discarded. The bottom layer was retained to obtain a dark red crystalline cerium dioxide-nano-gold catalyst, which was recorded as 100MT-Au.

[0085] The volume ratio of the gold decahedron nanoparticle dispersion to the cerium acetate solution is 200:100;

[0086] Figure 1 TEM image of the cerium dioxide-nano-gold catalyst 100MT-Au prepared in Example 2, Figure 1 It can be seen that the catalyst prepared in Example 2 has a core of gold decahedral nanoparticles, and the outer layer of cerium dioxide completely covers the gold decahedral nanoparticles with a uniform thickness.

[0087] Application Example 1

[0088] The catalytic activity of the cerium dioxide-nano-gold catalyst prepared in Example 2 for photolysis of water to produce oxygen was tested as follows:

[0089] AgNO3 was used as a sacrificial reagent. 100MT-Au was added to 50mL (0.01M) AgNO3, placed in a three-necked flask and a magnet was placed in it. The mouth of the three-necked flask was sealed with a sealing stopper to form a closed system. One end of a hose was connected to a double-ended needle and inserted into the sealing stopper. The other end was connected to an inverted measuring cylinder filled with water in a sink. The volume of the produced oxygen was converted from the volume of the water discharged. The experiment was started after the airtightness was tested. A xenon lamp was used to illuminate the body of the three-necked flask at a current of 13.0A. The magnetic stirring device was turned on, acting as a visible light source to catalyze water splitting. The oxygen production of the system was tested over time and the conversion frequency (i.e., the molar amount of oxygen produced per mole of 100MT-Au per hour) was measured. The specific results are shown in [1]. Figure 4 and Figure 5 .

[0090] Example 3

[0091] Cerium dioxide-nano-gold catalyst:

[0092] It is composed of nano-gold and cerium dioxide coated on the surface of the nano-gold; the nano-gold is a gold decahedron nanoparticle with a particle size of 50nm;

[0093] The particle size of the cerium dioxide-nano-gold catalyst is 150 nm; the thickness of the cerium dioxide coated on the surface of the nano-gold is 50 nm.

[0094] Example 4

[0095] The cerium dioxide-nano-gold catalyst described in Example 3 was prepared according to the method of Example 2 and was recorded as 150MT-Au;

[0096] The difference from Example 2 is that the volume of the cerium acetate solution in step (3) is 150uL.

[0097] The volume ratio of the gold decahedron nanoparticle dispersion to the cerium acetate solution is preferably 200:150.

[0098] Figure 2 TEM image of the cerium dioxide-nano-gold catalyst 150MT-Au prepared in Example 4, Figure 2 It can be seen that the catalyst prepared in Example 4 has a core of gold decahedral nanoparticles, and the outer layer of cerium dioxide completely covers the gold decahedral nanoparticles with a uniform thickness. Figure 1 In comparison, the outer layer of cerium dioxide of the catalyst prepared in Example 4 is thicker.

[0099] Application Example 2

[0100] The catalytic activity of the cerium dioxide-nano-gold catalyst prepared in Example 4 for photocatalytic water splitting to produce oxygen was tested according to the method of Application Example 1. The specific results are shown in Figure 4and Figure 5 .

[0101] Comparative Example

[0102] A dispersion of gold decahedron nanoparticles was prepared according to steps (1) to (2) of the method of Example 1, and solid-liquid separation was performed to obtain gold decahedron nanoparticles, which were recorded as MT-Au;

[0103] The catalytic activity of MT-Au for photocatalytic water splitting to produce oxygen was tested according to the method of Application Example 1. The specific results are shown in Figure 4 and Figure 5 .

[0104] Figure 3 TEM image of gold decahedron nanoparticles MT-Au prepared in comparative example, Figure 3 It can be seen that the gold nanoparticles prepared in the comparative example are decahedral and have an average diameter of 50 nanometers.

[0105] Figure 4 The oxygen production of 100MT-Au and 150MT-Au prepared in Examples 2 and 4 and MT-Au prepared in the comparative example is changed over time for photolysis of water to produce oxygen. Figure 3 It can be seen that as time goes by, the oxygen production of MT-Au used for photolysis of water to produce oxygen is very small, which is 0umol, and the catalytic activity is very low; the amount of oxygen produced by 150MT-Au used for photolysis of water to produce oxygen is the largest, with an oxygen production of 0.2umol at 30 minutes, 0.5umol at 45 minutes, 0.7umol at 55 minutes, and 1.0umol at 65 minutes; the amount of oxygen produced by 100MT-Au used for photolysis of water to produce oxygen has always remained the largest, and the catalytic activity is the highest, with an oxygen production of 0.9umol at 30 minutes, 2.8umol at 45 minutes, 4.5umol at 55 minutes, and 5.8umol at 65 minutes.

[0106] Figure 5 The conversion frequency diagram of 100MT-Au and 150MT-Au prepared in Examples 2 and 4 and MT-Au prepared in the comparative example for photolysis of water to produce oxygen is shown in FIG. Figure 3 It can be seen that the conversion frequency of MT-Au for photolysis of water to produce oxygen is as low as 0.54 mol O2 ·mol Au -1 ·h -1 The conversion rate of 150MT-Au for photolysis of water to produce oxygen is 55.61 mol O2 ·mol Au -1 ·h -1 The conversion rate of 100MT-Au for photolysis of water to produce oxygen is as high as 271.38molO2 ·mol Au -1 ·h -1 .

[0107] It can be seen from the embodiments, application examples and comparative examples that the cerium dioxide-nano-gold catalyst provided by the present invention is used for photolysis of water to produce oxygen. The catalytic activity is 0.9umol of oxygen at 30 minutes, 2.8umol of oxygen at 45 minutes, 4.5umol of oxygen at 55 minutes, and 5.8umol of oxygen at 65 minutes, with a conversion frequency of up to 271.38mol O2 ·mol Au -1 ·h -1 The present invention provides a ceria-nano-gold catalyst, which uses ceria as an outer shell. The structure of ceria is a cubic arrangement with metal atoms as the face center, and all tetrahedral holes are filled with oxygen, which has strong oxidizing properties. Even after a large amount of oxygen is lost in the ceria lattice and a large number of oxygen vacancies are formed, the fluorite crystal structure of ceria does not change, and these subcarboxylates are easily reoxidized to form ceria by contacting with oxygen in the environment. By wrapping ceria on the surface of gold decahedral nanoparticles, the aggregation of the inner core gold decahedral nanoparticles can be avoided, thereby improving the catalytic activity and repeatability of the gold decahedral nanoparticles, and preventing the ceria-nano-gold catalyst from being poisoned, thereby improving the performance stability of the catalyst.

[0108] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A ceria-nano-gold catalyst for the photocatalytic production of oxygen from water, the ceria-nano-gold catalyst comprising nano-gold and ceria coated on the surface of the nano-gold; the nano-gold is a gold decahedron nanoparticle; The thickness of the cerium dioxide is 20 to 50 nm; The preparation method of the cerium dioxide-nano-gold catalyst comprises the following steps: (1) mixing a gold precursor solution, a surfactant solution, and a reducing agent solution to obtain a mixed solution; The concentration of the gold precursor solution in step (1) is 0.005-0.03 mM; (2) adding a gold seed solution to the mixed solution obtained in step (1) to perform a reduction reaction, and allowing the product of the reduction reaction to stand at room temperature to obtain a dispersion of gold decahedron nanoparticles; (3) mixing the gold decahedron nanoparticle dispersion obtained in step (2), water and a cerium source solution, performing a hydrolysis reaction in a sealed environment, and sequentially cooling, ultrasonicating, heating, centrifuging and solid-liquid separation the product of the hydrolysis reaction to obtain a cerium dioxide-nano-gold catalyst.

2. The use according to claim 1, characterized in that The particle size of the cerium dioxide-nano-gold catalyst is 20-80 nm.

3. The use according to claim 1, characterized in that The concentration of the surfactant solution in step (1) is 0.01-0.2 mM.

4. The use according to claim 1, characterized in that The concentration of the reducing agent solution in step (1) is 0.01-0.3 mM.

5. The use according to any one of claims 3 to 4, characterized in that In the step (1), the volume ratio of the gold precursor solution, the surfactant solution and the reducing agent solution is (15-25):(300-500):(1-5).

6. The use according to claim 1, characterized in that The temperature of the reduction reaction in step (2) is room temperature, and the time of the reduction reaction is 0.5 to 13 minutes.

7. The use according to claim 1, characterized in that The temperature of the hydrolysis reaction in step (3) is 90-110° C., and the time of the hydrolysis reaction is 40-80 min.

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