[CdS4] structurally distorted piezoelectric-photocatalytic water splitting hydrogen production Cu-P / CdS catalyst and its preparation method and application

Abstract

The present invention discloses a piezoelectric-photocatalytic water decomposition hydrogen production Cu-P / CdS catalyst with a distorted [CdS4] structure and its preparation method and application, belonging to the field of catalyst and hydrogen energy technology. The present invention provides a water decomposition hydrogen production Cu-P / CdS catalyst, the preparation method of which includes: dispersing a cadmium source and a sulfur source in water, heating to 130-150°C for reaction, and preparing CdS; CdS is dispersed in a copper source aqueous solution and dried to obtain a powder; the powder is mixed with a phosphorus source and calcined to obtain a piezoelectric-photocatalyst. The present invention suppresses electron-hole recombination by embedding an electron-withdrawing group Cu-P on the surface of non-centrosymmetric CdS, forming a [0001] direction piezoelectric polarization, causing [CdS4] to be distorted and forming an electronic dipole moment, providing electron-hole migration and separation driving force, greatly improving hydrogen production activity and stability, and without the need for loading precious metals, reducing production costs.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts and hydrogen energy, and specifically relates to a Cu-P / CdS catalyst for piezoelectric-photocatalytic water decomposition and hydrogen production with local electron regulation of [CdS4] structural distortion, as well as a preparation method and application thereof. Background Art

[0002] With the development of industrial society, the development of new renewable clean energy is urgent. Among them, hydrogen energy is abundant in reserves, high in specific heat, renewable, and pollution-free, making it a very ideal clean energy source. Scientific research shows that solar energy is inexhaustible. The hydrogen produced by water decomposition still produces water after combustion, without any pollutants and can be recycled. Therefore, using solar energy to decompose water to produce hydrogen is the most ideal way to obtain hydrogen energy. In 1972, scientists discovered that using semiconductor materials as photocatalysts can realize solar photocatalytic water decomposition to produce hydrogen. The reaction process of photocatalytic water decomposition to produce hydrogen is as follows: (1) When irradiated with light with energy equal to or greater than the band gap width (Eg), the bound electrons in the valence band of the semiconductor are excited by the light and jump to the conduction band to become free electrons, leaving an equal number of positively charged holes in the valence band; (2) The photogenerated electrons and holes migrate in opposite directions under the action of the electric field, and some electrons and holes recombine under the action of Coulomb force; (4) The electrons and holes that migrate to the catalyst surface undergo redox reactions with the adsorbed substances on the surface. Among them, semiconductor photocatalysts are important media for converting solar energy into chemical energy, and the selection criteria for efficient hydrogen production catalysts are mainly: (1) having a wide solar spectrum response range, so that they can fully absorb solar energy; (2) having a suitable band gap width: theoretically, the band gap width of the semiconductor required for photocatalytic water decomposition is about 1.8eV, and the more negative the conduction band potential, the stronger the reduction ability; (3) high efficiency of photogenerated electron-hole separation; (4) since the photocatalytic reaction mainly occurs at the surface active sites of the catalyst, highly active surface reaction sites are required.

[0003] The semiconductor material CdS has become a very promising photocatalyst due to its suitable energy band structure and conduction band potential (Eg=2.40V, CB=-0.52V, VB=1.88V). However, CdS still has disadvantages such as high hydrogen production overpotential, easy recombination of photogenerated electrons and holes, weak electron transport performance, poor conductivity, and photocorrosion, resulting in low photoquantum conversion efficiency, thereby limiting its activity and stability in photocatalytic water decomposition to produce hydrogen.

[0004] In response to the above-mentioned problems of photocatalysts, most studies at this stage have tried to improve these problems by loading precious metal co-catalysts, constructing heterojunctions, doping, and morphology control. However, the effect of improving performance is not particularly significant and is far from meeting the standards of industrial production. The main problems at this stage are: (1) The cost of loading precious metal co-catalysts (Au, Ag, Pt, etc.) is too high and is not suitable for industrial application; (2) Constructing heterojunctions cannot fundamentally solve the problem of easy recombination of photogenerated electrons and holes in CdS and photocorrosion, nor can it improve the kinetic performance of electrons or optimize the hydrogen adsorption and desorption performance of surface sites; (3) Doping makes it difficult to control the potential of impurity energy levels. If deep impurity energy levels are formed, they will become electron-hole recombination centers, which will in turn reduce performance; (4) Although smaller particle size will expose more active sites of the catalyst, it will also lead to particle agglomeration and changes in the band gap, thus failing to significantly improve performance.

[0005] For example, CN201910706168.7 discloses a novel single-atom photohydrogen production catalyst having an ultra-thin porous sheet structure, and the Pt single atom is reduced in situ by a group rich in the surface of carbon dots (CDs). The resulting catalyst expression is CdS@CDs / Pt-SAs, which can greatly improve the efficiency of hydrogen production using sunlight. CN202110752625.3 discloses a novel Pd single-atom-loaded graphite phase carbon nitride photocatalytic water splitting catalyst, which has better photocatalytic water splitting performance and stability than pure graphite phase carbon nitride and Pd nanoparticle-loaded graphite phase carbon nitride. However, these methods often require the use of precious metals, which significantly increases the cost and does not essentially solve the problems of CdS itself. Therefore, the performance improvement is not very obvious and is far from meeting the standards for industrial applications. Summary of the Invention

[0006] Based on the problems of the prior art, the technical problems to be solved by the present invention are: (1) fundamentally solving the problems of easy recombination of electrons and holes, poor electron transport performance, and photocorrosion in the main catalyst CdS, and further improving its hydrogen production activity; (2) developing a photocatalyst system that can significantly improve the hydrogen production activity and stability of CdS without the use of precious metal co-catalysts, reducing costs and facilitating industrial application; (3) artificially constructing the electric dipole moment to enhance the macroscopic polarization intensity of non-centrosymmetric hexagonal CdS and provide direct driving force for the separation of photogenerated electrons and holes; (4) designing and regulating the local surface of the photocatalysis to optimize the kinetic performance, reduction performance and hydrogen adsorption and desorption performance of the electrons in its active sites and the surface atoms. (5) fully exploring the spontaneous piezoelectric polarization characteristics of non-centrosymmetric CdS and artificially regulating it to facilitate the separation and migration of photogenerated electrons and holes.

[0007] To solve the above technical problems, the present invention first provides a method for preparing a Cu-P / CdS catalyst for piezoelectric photocatalytic water decomposition and hydrogen production with local electron regulation of [CdS4] structural distortion, which comprises the following steps:

[0008] A. Disperse the cadmium source and the sulfur source in water, heat to 130-150°C for reaction, cool, separate the solid and liquid, wash, and dry and grind the resulting solid to obtain CdS;

[0009] B. Dispersing the CdS obtained in step A in a copper source aqueous solution to obtain a mixed solution, drying the mixed solution, and grinding the solid obtained after drying to obtain a powder sample;

[0010] C. Grind the powder sample obtained in step B and the phosphorus source until they are uniformly mixed, and then calcine them under the protection of inert gas. After the calcination is completed, wash and dry them to obtain a Cu-P / CdS photocatalyst.

[0011] Wherein, in the above preparation method, in step A, the cadmium source is at least one of cadmium acetate, cadmium chloride, cadmium bromide, cadmium iodide, cadmium sulfate, and cadmium nitrate.

[0012] Preferably, in the above preparation method, in step A, the cadmium source is cadmium acetate.

[0013] Wherein, in the above preparation method, in step A, the sulfur source is at least one of thiourea, sodium sulfide, thioacetamide, sodium thioacetate, and potassium thioacetate.

[0014] Preferably, in the above preparation method, in step A, the sulfur source is thiourea.

[0015] In the above preparation method, in step A, the amounts of the cadmium source and the sulfur source are based on a molar ratio of Cd in the cadmium source to S in the sulfur source of 1.4-1.8:7.0-9.0.

[0016] Wherein, in the above preparation method, in step A, the amount of water used is 8 to 18 mL / mmol Cd in the cadmium source.

[0017] Wherein, in the above preparation method, in step A, the dispersion is ultrasonic dispersion.

[0018] In the above preparation method, in step A, after dispersion, stirring is performed for 1 to 3 hours, and then heating is performed for reaction.

[0019] Wherein, in the above preparation method, in step A, the reaction time is 20 to 28 hours.

[0020] Wherein, in the above preparation method, in step A, the drying temperature is 90-110°C.

[0021] Wherein, in the above preparation method, in step A, the drying time is 6 to 8 hours.

[0022] Wherein, in the above preparation method, in step B, the copper source is at least one of copper chloride, copper nitrate, copper sulfate, and copper acetate.

[0023] Preferably, in the above preparation method, in step B, the copper source is copper chloride.

[0024] Wherein, in the above preparation method, in step B, the Cu concentration of the copper source aqueous solution is 0.05 to 0.15 mmol / L.

[0025] Wherein, in the above preparation method, in step B, the amount of the copper source aqueous solution is used to control the mass percentage of Cu element in the Cu-P / CdS photocatalyst obtained in step C to be 0.1 to 0.5 wt%.

[0026] Wherein, in the above preparation method, the mass ratio of the CdS obtained in step A used in step B to the phosphorus source used in step C is 1-3:1-3.

[0027] Wherein, in the above preparation method, in step B, the dispersion is ultrasonic dispersion.

[0028] Wherein, in the above preparation method, in step B, the drying temperature is 50-70°C.

[0029] Wherein, in the above preparation method, in step B, the drying time is 20 to 30 hours.

[0030] Wherein, in the above preparation method, in step C, the phosphorus source is at least one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium monohydrogen phosphate, and potassium monohydrogen phosphate.

[0031] Preferably, in the above preparation method, in step C, the phosphorus source is sodium dihydrogen phosphate or potassium dihydrogen phosphate.

[0032] Wherein, in the above preparation method, in step C, the calcination temperature is 350-450°C, and the heating rate is 4-6°C.

[0033] Wherein, in the above preparation method, in step C, the calcination time is 5 to 15 minutes.

[0034] Wherein, in the above preparation method, in step C, the washing is performed by washing with water and ethanol 2 to 4 times.

[0035] Wherein, in the above preparation method, in step C, the drying temperature is 70-90°C.

[0036] Wherein, in the above preparation method, in step C, the drying time is 8 to 10 hours.

[0037] Based on the above preparation method, the present invention also provides a Cu-P / CdS catalyst for piezoelectric-photocatalytic water decomposition and hydrogen production with local electron-controlled [CdS4] structural distortion prepared by the above preparation method.

[0038] The present invention significantly improves the catalyst performance by embedding electron-withdrawing groups Cu-P on the non-centrosymmetric CdS surface. Therefore, the present invention also provides the above-mentioned piezoelectric-photocatalytic water decomposition and hydrogen production Cu-P / CdS catalyst with local electron regulation [CdS4] structural distortion, and its application in photocatalytic water decomposition and hydrogen production, photocatalytic decomposition of organic matter and hydrogen production, photocatalytic reduction of CO2, photocatalytic degradation of organic pollutants, photoelectrocatalytic water decomposition and hydrogen production, photoelectrocatalytic decomposition of organic matter and hydrogen production, photoelectrocatalytic reduction of CO2 or photoelectrocatalytic degradation of organic pollutants.

[0039] In particular, the above catalyst has been greatly improved in hydrogen production activity and stability. Therefore, preferably, the present invention provides its use in photocatalytic water decomposition to produce hydrogen or photoelectrocatalytic water decomposition to produce hydrogen.

[0040] Beneficial effects of the present invention:

[0041] 1. The Cu and P elements introduced in the present invention can attract electrons in CdS, overcome the Coulomb force inside the bulk CdS, and enable the photogenerated electrons to quickly migrate to the active sites on the catalyst surface, thereby solving the problem of easy recombination of photogenerated electrons and holes in CdS due to Coulomb attraction;

[0042] 2. In the present invention, the electrons generated by CdS are first transferred to Cu and then to P atoms. That is, Cu atoms serve as electron transfer media and P atoms serve as electron receivers. This constructs a Cd-S-Cu-P electron transfer path, solving the problem of poor electron transfer kinetics.

[0043] 3. The XRD diffraction peak of Cu-P / CdS in the present invention shifts to a higher angle than that of CdS, indicating that the interplanar spacing is reduced and the lattice shrinks, i.e., compressive stress exists, which aggravates the distortion of the structural unit and increases the macroscopic polarization of CdS, thus solving the problem of electron-hole recombination caused by Coulomb force.

[0044] 4. The present invention embeds electron-withdrawing Cu-P groups on the surface of non-centrosymmetric CdS. The compressive stress generated by electrostatic attraction causes the [CdS4] tetrahedron in the hexagonal CdS to be distorted and form an electronic dipole moment.

[0045] 5. The present invention regulates the electronic behavior of the localized CdS surface to generate a piezoelectric polarization phenomenon along the

[0001] direction, thereby forming a polarization electric field. The polarization electric field perpendicular to the

[0001] crystal plane provides the driving force for electron-hole migration and separation.

[0046] 6. The present invention does not require the loading of any precious metal co-catalysts. Under the action of the Cu-P electron-withdrawing group, it synergistically regulates the kinetic properties of the electrons in the active site and intensifies the lattice distortion of the asymmetric material CdS to generate a polarization electric field, providing a direct driving force for the separation of photogenerated electrons and holes, thereby achieving ultra-high hydrogen production activity of 316.5 mmol / h / g, which is much higher than the existing literature reports.

[0047] In summary, the present invention embeds electron-withdrawing groups Cu-P on the surface of non-centrosymmetric CdS, which not only suppresses the electron-hole recombination caused by bulk Coulomb attraction, but also forms piezoelectric polarization along the

[0001] direction of CdS due to the compressive stress generated by electrostatic attraction, so that the [CdS4] tetrahedron in the hexagonal CdS is distorted and an electronic dipole moment is formed. The polarized electric field provides the driving force for electron-hole migration and separation, and the synergistic piezoelectric photocatalysis has greatly improved the hydrogen production activity and stability. Without the need to load precious metal co-catalysts, the production cost is reduced, which is conducive to promoting the industrialization process of photocatalytic water decomposition to produce hydrogen technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a preparation route for the piezoelectric Cu-P / CdS photocatalyst of the present invention.

[0049] Figure 2 XRD patterns of Cu-P / CdS and CdS.

[0050] Figure 3 Steady-state fluorescence spectra of Cu-P / CdS and CdS.

[0051] Figure 4 This is the full X-ray photoelectron spectrum of Cu-P / CdS.

[0052] Figure 5 SEM images of CdS and Cu-P / CdS; the left one is CdS and the right one is Cu-P / CdS.

[0053] Figure 6 Schematic diagram of the [CdS4] structural distortion obtained by theoretical calculation.

[0054] Figure 7 This is the charge density difference diagram of the Cu-P / CdS system.

[0055] Figure 8 Activity diagram of photocatalytic water decomposition and hydrogen production of different control samples. DETAILED DESCRIPTION

[0056] Specifically, the preparation method of the piezoelectric-photocatalytic water decomposition hydrogen production Cu-P / CdS catalyst with local electron regulation of [CdS4] structural distortion includes the following steps:

[0057] A. Disperse the cadmium source and the sulfur source in water (generally deionized water), heat to 130-150°C for reaction (generally in a reactor), cool, separate the solid and liquid, and wash, and then dry and grind the resulting solid to obtain CdS;

[0058] B. Dispersing the CdS obtained in step A in a copper source aqueous solution to obtain a mixed solution, drying the mixed solution, and grinding the solid obtained after drying to obtain a powder sample;

[0059] C. Grind the powder sample obtained in step B and the phosphorus source until they are uniformly mixed, and then calcine them under the protection of inert gas. After the calcination is completed, wash and dry them to obtain a Cu-P / CdS photocatalyst.

[0060] The present invention considers that the redox reaction in the photocatalytic process mainly occurs at the active sites on the catalyst surface. Therefore, it is envisioned to perform local surface modification to regulate the reducing ability of surface electrons and the adsorption and desorption properties of surface active sites, which may effectively improve the performance of water decomposition and hydrogen evolution. The present invention further considers the asymmetric characteristics and intrinsic polarization properties of hexagonal CdS (CdS has two crystal forms, tetragonal and hexagonal, and the tetragonal crystal is a centrosymmetric structure with no intrinsic polarization properties). If the [CdS4] tetrahedron undergoes structural distortion under the action of an external force, generating an electronic dipole moment, the macroscopic polarization will be enhanced. The polarized electric field will drive charge transfer and separation, thereby providing the driving force for the separation and migration of photogenerated electrons and holes. Therefore, the present invention has designed a method that can simultaneously regulate the distortion of the wurtzite CdS structural unit [CdS4] and regulate the reducing ability of surface electrons and the adsorption and desorption properties of surface active sites, thereby artificially constructing a favorable electron transport path.

[0061] Various CdS preparation processes have been reported in the field. Although CdS synthesized using existing processes or commercially available CdS may also undergo structural distortion under the influence of Cu-P, the intrinsic properties of CdS synthesized by different processes vary, resulting in different hydrogen production rates in the final composite photocatalyst. Therefore, to obtain a composite photocatalyst with superior performance, the present invention utilizes a unique preparation method in Step A to control the CdS morphology to a hexagonal, dendritic structure, resulting in superior performance compared to CdS synthesized using other processes or commercially available CdS.

[0062] In step A of the present invention, the cadmium source is controlled to be at least one of cadmium acetate, cadmium chloride, cadmium bromide, cadmium iodide, cadmium sulfate, and cadmium nitrate, preferably cadmium acetate; the sulfur source is controlled to be at least one of thiourea, sodium sulfide, thioacetamide, sodium thioacetate, and potassium thioacetate, preferably thiourea; and the amount of the cadmium source and the sulfur source is controlled to be based on the molar ratio of Cd in the cadmium source to S in the sulfur source of 1.4 to 1.8:7.0 to 9.0. In the present invention, each specific cadmium source can be an anhydrous cadmium salt or a hydrated cadmium salt, which does not affect the target product. However, since the anhydrous compound is generally expensive, a hydrated salt such as cadmium acetate dihydrate, hydrated cadmium chloride, or hydrated cadmium sulfate is generally used.

[0063] In step A of the present invention, the amount of water is controlled to be 8-18 mL / mmol of Cd in the cadmium source.

[0064] In step A of the present invention, ultrasonic dispersion is used to ensure the dispersion effect; at the same time, in order to make the reaction more complete, stirring is performed for 1 to 3 hours after ultrasonic dispersion, and then heating is performed for reaction.

[0065] In step A of the present invention, the reaction time is 20 to 28 hours; the drying temperature is 90 to 110° C.; and the drying time is 6 to 8 hours.

[0066] In step B of the present invention, the copper source is controlled to be at least one of copper chloride, copper nitrate, copper sulfate, and copper acetate, preferably copper chloride. Similar to the cadmium source, in the present invention, each specific copper source can be an anhydrous copper salt or a hydrated copper salt, without affecting the target product. However, since anhydrous compounds are generally expensive, hydrated salts such as copper chloride dihydrate and copper acetate monohydrate are generally used.

[0067] In the present invention, the concentration of the copper source aqueous solution affects the dispersibility of the system. Since the copper loading is low in the present invention, a low concentration is used to make the Cu more evenly dispersed and reduce agglomeration. In addition, the copper loading affects the performance of the catalyst. If the loading is too low, the catalyst cannot fully function. If the loading is too high, it will cause agglomeration, shielding light absorption, etc., reducing the atomic utilization rate. Therefore, the present invention controls the Cu concentration of the copper source aqueous solution to 0.05-0.15 mmol / L, and the amount of the copper source aqueous solution is used to control the mass percentage of the Cu element in the Cu-P / CdS photocatalyst obtained in step C to 0.1-0.5 wt%.

[0068] In the present invention, the P content is similar to controlling the Cu loading amount. At the same time, part of the gas generated by the phosphorus source during the calcination process will be discharged with the argon gas in the tube furnace. Therefore, through experiments, the present invention controls the mass ratio of the CdS obtained in step A used in step B to the phosphorus source used in step C to be 1-3:1-3, which is more conducive to the coordination of phosphorus atoms with copper.

[0069] In step B of the present invention, ultrasonic dispersion is used to ensure a uniform dispersion effect; and to ensure uniform dispersion, the mixed solution is continuously stirred before drying.

[0070] In steps B and C of the present invention, while the mixed solution can be directly subjected to the subsequent phosphorus source mixing and calcination steps, or high-temperature drying, provided the catalyst does not decompose, this can easily lead to CdS agglomeration or grain growth. Therefore, the present invention opts for drying at a relatively mild temperature to remove moisture before proceeding to the next calcination step, thereby obtaining a catalyst with excellent performance. Therefore, in step B of the present invention, the drying temperature is controlled to be 50-70°C, and the drying time is 20-30 hours.

[0071] In step C of the present invention, the phosphorus source is at least one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium monohydrogen phosphate, and potassium monohydrogen phosphate, preferably sodium dihydrogen phosphate or potassium dihydrogen phosphate.

[0072] In step C of the present invention, the calcination temperature is 350-450° C., the heating rate is 4-6° C., the calcination time is 5-15 minutes, the washing is performed 2-4 times with water and ethanol, the drying temperature is 70-90° C., and the drying time is 8-10 hours.

[0073] Based on the above preparation method, the present invention also provides a piezoelectric-photocatalytic water splitting hydrogen production Cu-P / CdS catalyst prepared using the above preparation method, wherein the localized electrons modulate the structural distortion of [CdS4]. The catalyst of the present invention is a material that can be used in a reduction reaction, i.e., a cathode. For example, in a photocatalytic reaction, the catalyst of the present invention can be referred to as a photocathode.

[0074] The present invention significantly improves the performance of the catalyst by embedding the electron-withdrawing group Cu-P on the non-centrosymmetric CdS surface. Therefore, the present invention also provides the piezoelectric-photocatalytic water decomposition hydrogen production Cu-P / CdS catalyst with the above-mentioned local electron-controlled [CdS4] structural distortion, and its application in photocatalytic water decomposition hydrogen production, photocatalytic decomposition of organic matter hydrogen production, photocatalytic reduction of CO2, photocatalytic degradation of organic pollutants, photoelectrocatalytic water decomposition hydrogen production, photoelectrocatalytic decomposition of organic matter hydrogen production, photoelectrocatalytic reduction of CO2, or photoelectrocatalytic degradation of organic pollutants. Among them, decomposition of organic matter to produce hydrogen and degradation of organic pollutants both belong to the decomposition of organic matter, but the two have different purposes. Photocatalytic or photoelectrocatalytic decomposition of organic matter to produce hydrogen, for example, can decompose ethanol, methanol, formic acid or formaldehyde; photocatalytic or photoelectrocatalytic degradation of organic pollutants can degrade rhodamine, sunset yellow, tetracycline, nitrogen oxides, benzene, toluene or acetone.

[0075] The present invention embeds Cu and P, elements with strong electron-withdrawing properties, on the surface of hexagonal CdS. Cu acts as a bridge for electron transfer, and Cu-P acts as an electron capture device to transfer the photogenerated electrons generated by light-excited CdS to the P site on the catalyst surface, thereby suppressing the recombination of electrons and holes in the bulk phase. At the same time, due to the electronic attraction between Cu-P and CdS, compressive stress is formed, which aggravates the [CdS4] tetrahedral distortion in CdS, generates an electronic dipole moment, and thus forms a macroscopic polarization, providing a direct driving force for the separation of photogenerated electrons and holes, and ultimately greatly improving the catalytic water decomposition and hydrogen evolution performance of CdS. Therefore, preferably, the present invention provides its application in photocatalytic water decomposition and hydrogen production or photoelectrocatalytic water decomposition and hydrogen production.

[0076] The present invention is further described in detail below through examples, but the protection scope of the present invention is not limited to the scope of the examples.

[0077] Example 1

[0078] 1. Ultrasonic dispersion of 1.4 mmol Cd(CH3COO)2·2H2O and 7.0 mmol thiourea in 15 ml deionized water, stirring for 2 h;

[0079] 2. Transfer the above solution into a reactor, heat to 140°C and keep the reaction for 20 hours. After the reaction is completed, cool it naturally to room temperature;

[0080] 3. The product obtained in step 2 was centrifuged and washed, dried in a drying oven at 90°C for several hours, and fully ground to obtain a CdS catalyst;

[0081] 4. Prepare a 0.05 mmol / L CuCl2·2H2O solution in a volumetric flask, labeled as solution A. Weigh 0.1 g of the CdS obtained in step 3 and ultrasonically disperse it in a certain volume of solution A so that the mass percentage of Cu element in the composite photocatalyst is 0.1 wt%, and continue stirring.

[0082] 5. Dry the mixture obtained in step 4 at 50°C for 20 hours, and grind the solid obtained after drying thoroughly;

[0083] 6. The powder sample obtained in step 5 was thoroughly ground with 0.1 g of NaH2PO2 to mix evenly, and then placed in a tube furnace and calcined to 350°C under an Ar atmosphere at a heating rate of 4°C for 5 min. The powder sample was then cooled to room temperature and collected.

[0084] 7. The powder obtained in step 6 was washed twice with deionized water and ethanol, and dried in a drying oven at 70° C. for 8 h to finally obtain the Cu-P / CdS photocatalyst.

[0085] Example 2

[0086] 1. Ultrasonic dispersion of 1.8 mmol Cd(CH3COO)2·2H2O and 9.0 mmol thiourea in 25 ml deionized water, stirring for 3 h;

[0087] 2. Transfer the above solution into a reactor, heat to 150°C and keep the reaction for 28 hours. After the reaction is completed, cool it naturally to room temperature;

[0088] 3. The product obtained in step 2 was centrifuged and washed, dried in a drying oven at 90°C for several hours, and fully ground to obtain a CdS catalyst;

[0089] 4. Prepare a 0.05 mmol / L CuCl2·2H2O solution in a volumetric flask, labeled as solution A. Weigh 0.2 g of the CdS obtained in step 3 and ultrasonically disperse it in a certain volume of solution A so that the mass percentage of Cu element in the composite photocatalyst is 0.5 wt%, and continue stirring.

[0090] 5. Dry the mixture obtained in step 4 at 70°C for 30 hours, and grind the solid obtained after drying thoroughly;

[0091] 6. The powder sample obtained in step 5 was thoroughly ground with 0.2 g of NaH2PO2 to mix evenly, and then placed in a tube furnace and calcined to 450 ° C under Ar atmosphere at a heating rate of 6 ° C for 5 min. The powder sample was cooled to room temperature and collected;

[0092] 7. The powder obtained in step 6 was washed with deionized water and ethanol 4 times, and dried in a drying oven at 90° C. for 10 h to finally obtain the Cu-P / CdS photocatalyst.

[0093] Example 3

[0094] 1. Ultrasonic dispersion of 1.4 mmol Cd(CH3COO)2·2H2O and 8.0 mmol thiourea in 20 ml deionized water, stirring for 1 h;

[0095] 2. Transfer the above solution into a reactor, heat to 130°C and keep the reaction for 24 hours. After the reaction is completed, cool it naturally to room temperature;

[0096] 3. The product obtained in step 2 was centrifuged and washed, dried in a drying oven at 100°C for several hours, and fully ground to obtain a CdS catalyst;

[0097] 4. Prepare a 0.15 mmol / L CuCl2·2H2O solution in a volumetric flask, labeled as solution A. Weigh 0.1 g of the CdS obtained in step 3 and ultrasonically disperse it in a certain volume of solution A so that the mass percentage of the Cu element in the composite photocatalyst is 0.3 wt%, and continue stirring.

[0098] 5. Dry the mixture obtained in step 4 at 70°C for 24 hours, and grind the solid obtained after drying thoroughly;

[0099] 6. The powder sample obtained in step 5 was thoroughly ground with 0.3 g of NaH2PO2 to mix evenly, and then placed in a tube furnace and calcined to 350 ° C under Ar atmosphere at a heating rate of 4 ° C for 10 min. After cooling to room temperature, the powder sample was collected;

[0100] 7. The powder obtained in step 6 was washed with deionized water and ethanol three times, and dried in a drying oven at 80° C. for 10 h to finally obtain the Cu-P / CdS photocatalyst.

[0101] Example 4

[0102] 1. Ultrasonic dispersion of 1.6 mmol Cd(CH3COO)2·2H2O and 8.0 mmol thiourea in 20 ml deionized water, stirring for 3 h;

[0103] 2. Transfer the above solution into a reactor, heat to 140°C and keep the reaction for 24 hours. After the reaction is completed, cool it naturally to room temperature;

[0104] 3. The product obtained in step 2 was centrifuged and washed, dried in a drying oven at 110° C. for several hours, and fully ground to obtain a CdS catalyst;

[0105] 4. Prepare a 0.10 mmol / L CuCl2·2H2O solution in a volumetric flask, labeled as solution A. Weigh 0.3 g of the CdS obtained in step 3 and ultrasonically disperse it in a certain volume of solution A so that the mass percentage of Cu element in the composite photocatalyst is 0.3 wt%, and continue stirring.

[0106] 5. Dry the mixture obtained in step 4 at 60°C for 30 hours, and grind the solid obtained after drying thoroughly;

[0107] 6. The powder sample obtained in step 5 was thoroughly ground with 0.1 g of NaH2PO2 to mix evenly, and then placed in a tube furnace and calcined to 450 ° C under Ar atmosphere at a heating rate of 6 ° C for 15 min. The powder sample was cooled to room temperature and collected;

[0108] 7. The powder obtained in step 6 was washed twice with deionized water and ethanol, and dried in a drying oven at 100° C. for 10 h to finally obtain the Cu-P / CdS photocatalyst.

[0109] Example 5

[0110] 1. Ultrasonic dispersion of 1.6 mmol Cd(CH3COO)2·2H2O and 8.0 mmol thiourea in 20 ml deionized water, stirring for 2 h;

[0111] 2. Transfer the above solution into a reactor, heat to 140°C and keep the reaction for 24 hours. After the reaction is completed, cool it naturally to room temperature;

[0112] 3. The product obtained in step 2 was centrifuged and washed, dried in a drying oven at 100°C for several hours, and fully ground to obtain a CdS catalyst;

[0113] 4. Prepare a 0.10 mmol / L CuCl2·2H2O solution in a volumetric flask, labeled as solution A. Weigh 0.2 g of the CdS obtained in step 3 and ultrasonically disperse it in a certain volume of solution A so that the mass percentage of Cu element in the composite photocatalyst is 0.3 wt%, and continue stirring.

[0114] 5. Dry the mixture obtained in step 4 at 60°C for 24 hours, and grind the solid obtained after drying thoroughly;

[0115] 6. The powder sample obtained in step 5 was thoroughly ground with 0.2 g of NaH2PO2 to mix evenly, and then placed in a tube furnace and calcined to 400 ° C under Ar atmosphere at a heating rate of 5 ° C for 10 min. After cooling to room temperature, the powder sample was collected;

[0116] 7. The powder obtained in step 6 was washed with deionized water and ethanol three times, and dried in a drying oven at 90° C. for 9 h to finally obtain the Cu-P / CdS photocatalyst.

[0117] Example 6

[0118] 1. Ultrasonic dispersion of 1.4 mmol Cd(CH3COO)2·2H2O and 9.0 mmol thiourea in 25 ml deionized water, stirring for 3 h;

[0119] 2. Transfer the above solution into a reactor, heat to 150°C and keep the reaction for 20 hours. After the reaction is completed, cool it naturally to room temperature;

[0120] 3. The product obtained in step 2 was centrifuged and washed, dried in a drying oven at 110° C. for several hours, and fully ground to obtain a CdS catalyst;

[0121] 4. Prepare a 0.15 mmol / L CuCl2·2H2O solution in a volumetric flask, labeled as solution A. Weigh 0.3 g of the CdS obtained in step 3 and ultrasonically disperse it in a certain volume of solution A so that the mass percentage of Cu element in the composite photocatalyst is 0.1 wt%, and continue stirring.

[0122] 5. Dry the mixture obtained in step 4 at 70°C for 20 hours, and grind the solid obtained after drying thoroughly;

[0123] 6. The powder sample obtained in step 5 was thoroughly ground with 0.2 g of NaH2PO2 to mix evenly, and then placed in a tube furnace and calcined to 400 ° C under Ar atmosphere at a heating rate of 6 ° C for 10 min. The powder sample was cooled to room temperature and collected;

[0124] 7. The powder obtained in step 6 was washed with deionized water and ethanol 4 times, and dried in a drying oven at 90° C. for 10 h to finally obtain the Cu-P / CdS photocatalyst.

[0125] Example 7

[0126] 1. Ultrasonic dispersion of 1.8 mmol Cd(CH3COO)2·2H2O and 9.0 mmol thiourea in 25 ml deionized water, stirring for 1 h;

[0127] 2. Transfer the above solution into a reactor, heat to 150°C and keep the reaction for 28 hours. After the reaction is completed, cool it naturally to room temperature;

[0128] 3. The product obtained in step 2 was centrifuged and washed, dried in a drying oven at 110° C. for several hours, and fully ground to obtain a CdS catalyst;

[0129] 4. Prepare a 0.15 mmol / L CuCl2·2H2O solution in a volumetric flask, labeled as solution A. Weigh 0.3 g of the CdS obtained in step 3 and ultrasonically disperse it in a certain volume of solution A so that the mass percentage of Cu element in the composite photocatalyst is 0.5 wt%, and continue stirring.

[0130] 5. Dry the mixture obtained in step 4 at 70°C for 30 hours, and grind the solid obtained after drying thoroughly;

[0131] 6. The powder sample obtained in step 5 was thoroughly ground with 0.3 g of NaH2PO2 to mix evenly, and then placed in a tube furnace and calcined to 450 ° C under Ar atmosphere at a heating rate of 6 ° C for 15 min. The powder sample was cooled to room temperature and collected;

[0132] 7. The powder obtained in step 6 was washed with deionized water and ethanol three times, and dried in a drying oven at 90° C. for 10 h to finally obtain the Cu-P / CdS photocatalyst.

[0133] Detection of the Cu-P / CdS photocatalyst obtained in Example 5

[0134] Figure 2 The XRD patterns of Cu-P / CdS and CdS are shown in the figure below. From the local enlarged image on the right, we can see that the main diffraction peaks of Cu-P / CdS are shifted to high angles, indicating that the interplanar spacing becomes smaller and the lattice shrinks. This proves that the introduction of Cu-P causes compressive stress in the CdS system, which can induce lattice distortion and ultimately enhance the polarization effect.

[0135] Figure 3 is the steady-state fluorescence spectra of Cu-P / CdS and CdS. It can be seen that the fluorescence intensity of Cu-P / CdS is significantly lower than that of CdS, indicating that the electronic dipole moment generated by Cu-P significantly improves the electron transport kinetics of the system and inhibits the electron-hole recombination.

[0136] Figure 4 This is the full X-ray photoelectron spectrum of Cu-P / CdS, indicating that the synthesis method successfully introduced Cu and P elements into the CdS system.

[0137] Figure 5 These are the SEM images of CdS and Cu-P / CdS; the left one is CdS and the right one is Cu-P / CdS. It can be seen that CdS is dendritic and Cu-P / CdS is a dendritic CdS with nanoparticles of very small size loaded on its surface.

[0138] Figure 6 This is a schematic diagram of the calculated structural distortion of [CdS4]. It can be seen that due to the action of the Cu-P group, the bond length of the structural unit in the

[0001] direction becomes shorter, verifying that the Cu-P group does cause the structural distortion of [CdS4].

[0139] Figure 7 This is the charge density difference diagram of the Cu-P / CdS system. Analysis shows that electrons migrate from CdS to Cu atoms and then to P atoms, verifying that in this system Cu atoms are electron transfer media and P atoms are electron receivers. The electron transfer path of Cd-S-Cu-P is constructed, solving the problem of poor electron transfer kinetics.

[0140] Figure 8 The photocatalytic water decomposition hydrogen production activity of different control samples showed that the hydrogen production rate of single CdS was 5.0 mmol / h / g, and the hydrogen production rate of Cu-P / CdS was greatly improved to 316.5 mmol / h / g.

[0141] Test example

[0142] The composite photocatalysts of Examples 1-7 were used to conduct photocatalytic water splitting hydrogen production experiments. The reaction conditions were as follows: A Pfizer LABSOLAR-6A photocatalyst comprehensive testing instrument, consisting of a light source, reaction equipment, a magnetically controlled gas circulation device, a vacuum device, a collection device, and a chromatographic testing device, was used. The photocatalytic water splitting hydrogen production system was connected to a gas chromatograph, and the generated gas was injected into the gas chromatograph for analysis. The gas chromatograph was equipped with a thermal conductivity device (TCD), using 5A molecular sieve as the chromatographic column and high-purity N2 as the carrier gas. The experimental parameters were set as follows: the TCD was set to 150°C, the vaporization chamber was set to 110°C, and the chromatographic column was set to 50°C.

[0143] The specific operation of the photocatalytic hydrogen evolution experiment is as follows: 50 mg of photocatalyst is fully dispersed in a quartz reaction device containing 90 mL of deionized water + 10 mL of lactic acid. The role of lactic acid is to consume holes. The simulated light source used is a 300W xenon lamp, and an optical filter (λ>420 nm, AM=1.5) is used to filter the light in the ultraviolet band. The hydrogen production rate is detected by gas chromatograph. Before illumination, high-purity N2 must be introduced to degas the entire system (including the solution) to discharge the O2 in the device. The temperature of the reaction system is maintained at 10 ° C using a constant temperature water bath. The hydrogen production test results are shown in Table 1, and it can be seen that the hydrogen production rate of the photocatalyst in this system reaches 316.5 mmol h -1 g -1 .

[0144] Table 1 Photocatalytic water decomposition hydrogen production rate and stability

[0145] <![CDATA[Hydrogen production rate (mmol h -1 g -1 )]]> Hydrogen production stability (h) Example 1 214.2 ≥24 Example 2 224.1 ≥24 Example 3 206.2 ≥24 Example 4 234.6 ≥24 Example 5 316.5 ≥24 Example 6 245.5 ≥24 Example 7 265.1 ≥24

[0146] Control Example

[0147] To compare the performance of the photocatalytic water decomposition and hydrogen production of the photocatalyst system of the present invention, the hydrogen production rates of the CdS system composite photocatalyst are listed below. CN112808280A discloses a S-doped TiO2-CdS composite photocatalytic hydrogen production material. Under 300W xenon lamp illumination, the optimal hydrogen production rate is about 1.31mmol h -1 g -1 CN112121834A discloses a MXene / CdS composite photocatalyst with an optimal hydrogen production rate of approximately 3.71 mmol h -1 g -1 CN113398998A discloses a Zr-MOF@CdS photocatalyst with an average optimal hydrogen production rate of approximately 1.86 mmol h -1 g -1 CN103381367A discloses a CdS / Ba 0.9 Zn 0.1TiO3 composite photocatalyst, the optimal hydrogen production rate is about 1.47mmolh -1 g -1 It can be concluded that the photocatalyst synthesized by the present invention has significantly higher photocatalytic water decomposition and hydrogen production performance.

Claims

1. A method for preparing a Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production by local electron-controlled [CdS4] structural distortion, characterized by: The following steps are involved: A. Disperse the cadmium source and the sulfur source in water, heat to 130-150°C for reaction, cool, separate the solid and liquid, wash, and dry and grind the resulting solid to obtain CdS; B. Dispersing the CdS obtained in step A in a copper source aqueous solution to obtain a mixed solution, drying the mixed solution, and grinding the solid obtained after drying to obtain a powder sample; C. Grinding the powder sample obtained in step B and the phosphorus source until uniformly mixed, and then calcining under the protection of an inert gas. After the calcination is completed, washing and drying are performed to obtain a Cu-P / CdS photocatalyst; In step A, the amount of the cadmium source and the sulfur source is based on a molar ratio of Cd in the cadmium source to S in the sulfur source of 1.4-1.8:7.0-9.0; In step A, the reaction time is 20 to 28 hours; In step B, the amount of the copper source aqueous solution is used to control the mass percentage of Cu element in the Cu-P / CdS photocatalyst obtained in step C to be 0.1-0.5 wt %.

2. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 1, characterized in that: In step A, the cadmium source is at least one of cadmium acetate, cadmium chloride, cadmium bromide, cadmium iodide, cadmium sulfate, and cadmium nitrate.

3. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 2, characterized in that: In step A, the cadmium source is cadmium acetate.

4. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 1, characterized in that: In step A, the sulfur source is at least one of thiourea, sodium sulfide, thioacetamide, sodium thioacetate, and potassium thioacetate.

5. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 4, characterized in that: In step A, the sulfur source is thiourea.

6. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 1, characterized in that: In step A, the amount of water used is 8-18 mL / mmol Cd in the cadmium source.

7. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 1, characterized in that: In step A, at least one of the following must be met: The dispersion is ultrasonic dispersion; After dispersion, stir for 1~3h, then heat to react; The drying temperature is 90-110°C; The drying time is 6 to 8 hours.

8. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 1, characterized in that: In step B, the copper source is at least one of copper chloride, copper nitrate, copper sulfate, and copper acetate.

9. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 8, characterized in that: In step B, the copper source is copper chloride.

10. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 1, characterized in that: In step B, the Cu concentration of the copper source aqueous solution is 0.05~0.15mmol / L.

11. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 1, characterized in that: The mass ratio of the CdS obtained in step A used in step B to the phosphorus source used in step C is 1-3:1-3.

12. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 1, characterized in that: In step B, at least one of the following conditions must be met: The dispersion is ultrasonic dispersion; The drying temperature is 50-70°C; The drying time is 20 to 30 hours.

13. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 1, characterized in that: In step C, the phosphorus source is at least one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium monohydrogen phosphate, and potassium monohydrogen phosphate.

14. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 13, characterized in that: In step C, the phosphorus source is sodium dihydrogen phosphate or potassium dihydrogen phosphate.

15. The method for preparing the Cu-P / CdS catalyst for piezoelectric-photocatalytic water splitting and hydrogen production with localized electron-controlled [CdS4] structural distortion according to claim 1, characterized in that: In step C, at least one of the following conditions must be met: The calcination temperature is 350-450°C, and the heating rate is 4-6°C; The calcination time is 5 to 15 minutes; The washing is performed by washing with water and ethanol 2 to 4 times; The drying temperature is 70-90°C; The drying time is 8 to 10 hours.

16. A Cu-P / CdS catalyst for piezoelectric-photocatalytic water decomposition and hydrogen production prepared by the preparation method according to any one of claims 1 to 15, wherein the obtained catalyst has a local electron-regulated [CdS4] structural distortion.

17. Use of the piezoelectric-photocatalytic water splitting and hydrogen production Cu-P / CdS catalyst with local electron-controlled [CdS4] structural distortion prepared by the preparation method according to any one of claims 1 to 15, or the piezoelectric-photocatalytic water splitting and hydrogen production Cu-P / CdS catalyst with local electron-controlled [CdS4] structural distortion according to claim 16 in photocatalytic water splitting and hydrogen production, photocatalytic degradation of organic pollutants, photoelectrocatalytic water splitting and hydrogen production, or photoelectrocatalytic degradation of organic pollutants.

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