Preparation method of Au nanoparticle-modified TiO2 plasma composite electrode

Abstract

The present invention relates to a method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles. The method comprises the following steps: (1) preparing a planar or curved TiO2 electrode: using spray pyrolysis to prepare a TiO2 electrode or a SiO2@TiO2 two-dimensional photonic crystal on an ITO glass substrate; (2) depositing Au nanoparticles: using vacuum evaporation to deposit Au nanoparticles on the substrate in a single step, strictly limiting the evaporation rate, to produce the Au nanoparticle-modified TiO2 plasma composite electrode. This preparation method optimizes the Au nanoparticle deposition process, avoiding the subsequent high-energy calcination process that affects the physical properties of the Au nanoparticles. It also allows for controllable adjustment of the Au nanoparticle size, resulting in a plasma electrode with a wide visible light absorption range, strong light absorption capacity, and excellent photoelectric performance.

Description

Technical Field

[0001] The present invention relates to the technical field of composite electrode preparation for inorganic photoelectrocatalysis, and in particular to a method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles. Technical Background

[0002] Photoelectric water splitting for hydrogen production has garnered widespread attention due to its green and low-energy characteristics. Its core objective is to develop photoanodes with low electron-hole recombination rates and visible light responsiveness. TiO2, with its excellent physicochemical properties, is often used as a photoelectrocatalyst for this purpose. However, due to its large bandgap (3.2 eV), it exhibits good photoelectric performance only under ultraviolet light. Numerous studies have demonstrated that TiO2's low visible light utilization and severe carrier recombination issues can be mitigated through surface modification with precious metal nanoparticles.

[0003] In 2005, Tian Yang and Tatsuma discovered that when precious metal Au nanoparticles are loaded onto TiO2, the localized surface plasmon effect (LSPR) of the Au nanoparticles absorbs visible light, and the generated hot electrons can migrate across the interface between Au and TiO2 and transfer to the conduction band of TiO2, achieving the separation of hole-electron pairs. This process is called the plasmon-induced charge separation (PICS) effect (Tian Y., Tatsuma T., Journal of the American Chemical Society ,2005, 127, 7632-7637). Based on the PICS effect, Au nanoparticle-modified TiO2 plasma composite electrodes can achieve photoelectrocatalytic decomposition of water to produce hydrogen under visible light. Therefore, how to use a simple and feasible method to uniformly disperse Au nanoparticles with LSPR absorption on the TiO2 surface has become a research hotspot. Tanaka et al. successfully deposited Au nanoparticles on TiO2 spheres using photodeposition (Tanaka A., Teramura K. et al., Chemical Science , 2017, 8, 2574-2580), but Au nanoparticles prepared by photodeposition are prone to agglomeration, have poor reproducibility, and are difficult to control. Vacuum evaporation is a simple and controllable coating method, but this method can usually only deposit a dense metal nanofilm on TiO2, which does not have LSPR absorption. For example, Alexander et al. deposited an Au nanofilm layer using vacuum evaporation, but it had to be calcined at 550℃ for 10h to obtain Au nanoparticles (Alexander BT, Alexander V. et al, Journal of Physical Chemistry C, 2011, 115, 24642). Jiang Lin et al. were only able to deposit a continuous Au film on TiO2 nanopillars by vacuum evaporation (Jiang Lin, Liang Zhiqiang et al., A TiO2 Nanopillar-Au Nanoparticle Composite Array, Preparation Method, and Application, CN108767113B[P]). Subsequent calcination at 300°C was still required to form Au nanoparticles. Although vacuum evaporation-calcination can produce Au nanoparticle-modified TiO2 plasma composite electrodes, this method requires high-temperature calcination, which is a cumbersome process. Furthermore, calcination in air may form an oxide layer on the nanoparticle surface. Furthermore, the Au nanoparticle loading is not high enough, resulting in a narrow absorption range in the visible light range. All of these factors lead to poor photoelectric performance of the prepared TiO2 / Au. Summary of the Invention

[0004] The present invention aims to provide a method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles. The preparation method optimizes the Au nanoparticle deposition process, avoids the subsequent calcination process that consumes a lot of energy and affects the physical properties of the Au nanoparticles, and can also controllably adjust the particle size of the Au nanoparticles to obtain a plasma electrode with a wide visible light absorption range, strong light absorption capacity, and excellent photoelectric performance.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles, characterized by comprising the following steps in sequence:

[0007] 1) Preparation of flat or curved TiO2 electrodes

[0008] TiO2 electrodes or SiO2@TiO2 two-dimensional photonic crystals were prepared on ITO glass using spray pyrolysis as a substrate;

[0009] 2) Deposition of Au nanoparticles

[0010] By using a vacuum evaporation method and controlling the evaporation rate, Au nanoparticles are deposited on a substrate in one step, thereby preparing the Au nanoparticle-modified TiO2 plasma composite electrode (denoted as TiO2 / Au or SiO2@TiO2 / Au).

[0011] As a further optimization, the above vacuum evaporation method uses a tungsten boat as the evaporation source, and the deposition rate during the evaporation process is controlled to be 0.005~0.03 nm·s -1 , the evaporation time is 200~2500 s, and the evaporation pressure is 8×10 -5 ~4×10 -4 The Au wire should have a gold content of no less than 99.999%.

[0012] The preparation method of the present invention regulates the deposition rate of the evaporation process. In the competition process between the formation of crystal nuclei and the growth of crystal nuclei in the early stage of crystallization, the nucleation of Au nanoparticles is promoted and the growth of grains is slowed down based on the "polycrystalline nucleus and slow growth" characteristics of the crystallization process. Large-scale agglomeration of nanoparticles caused by the generation of large particles during the formation process is avoided, and nanoparticles with smaller grain sizes are grown in one step, thereby ensuring high dispersion and high loading of the generated nanoparticles on the substrate. At the same time, the problem that the traditional vacuum evaporation method can only obtain a continuous Au nanofilm first and must undergo a subsequent high-temperature annealing process to obtain Au nanoparticles with LSPR absorption is overcome.

[0013] To further clarify, in the preparation of the above-mentioned planar or curved TiO2 electrode, the planar TiO2 electrode is a TiO2 thin film obtained by spray pyrolysis on the surface of ITO glass, that is, a planar TiO2 electrode; the curved TiO2 electrode is a SiO2 two-dimensional photonic crystal prepared by deposition using a gas-liquid interface self-assembly method on the surface of the planar TiO2 electrode, and then a SiO2@TiO2 two-dimensional photonic crystal film is obtained by spray pyrolysis, that is, a curved TiO2 electrode.

[0014] As a further optimization, the preparation process of the above SiO2 two-dimensional photonic crystal is to first add 30~50 μL of 0.8~1.5 mol·L -1 A sodium dodecyl sulfate aqueous solution was used as a surfactant, and a n-butanol dispersion of SiO2 beads was slowly added dropwise. This led to the self-assembly of a SiO2 two-dimensional photonic crystal at the air-liquid interface, which was then transferred to a planar TiO2 electrode. The SiO2 beads were synthesized using the Stöber method and had a particle size of 250-600 nm.

[0015] As a further optimization, before depositing the above-mentioned SiO2 two-dimensional photonic crystal, the planar TiO2 electrode was irradiated with ultraviolet light for 15 to 30 minutes to obtain a hydrophilic surface.

[0016] As a further optimization, the nitrogen spray pressure in the spray pyrolysis method was controlled at 0.10-0.15 MPa, the single spraying time was 1 s, the next spraying was performed after 60 s, the number of sprayings was 2-5 times, and the calcination temperature was 480-550 o C, calcination time is 30~60 min.

[0017] As a further optimization, in the process of preparing planar TiO2 electrodes by spray pyrolysis, the precursor solution used was a mixed solution of isopropyl alcohol and di(acetylacetonato) diisopropyl titanate with a volume ratio of 4~5:1.

[0018] As a further optimization, the above-mentioned ITO glass was pretreated by ultrasonic cleaning with ultrapure water and anhydrous ethanol for 10 to 20 minutes respectively before use.

[0019] More specifically, a method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles is characterized by the following steps:

[0020] 1) Preparation of planar TiO2 electrodes:

[0021] The ITO glass treated with ultrapure water and anhydrous ethanol for 10 min was used as the substrate. A mixed solution of isopropyl alcohol and diisopropyl di(acetylacetonate) titanate with a volume ratio of 4 to 5:1 was used as the precursor. The nitrogen spray pressure was controlled at 0.12 MPa. The ITO glass surface was sprayed for 1 s and then the spraying step was repeated for 60 s. Finally, the sprayed sample was placed at 500 oC After calcination for 45 min, a planar TiO2 electrode was obtained;

[0022] 2) Preparation of Au nanoparticles by vacuum evaporation:

[0023] The obtained planar TiO2 electrode was placed as a substrate in a vacuum thermal evaporation chamber, and the evaporation source Au wire was placed in a tungsten boat. The evaporation deposition rate was controlled to 0.01 nm·s -1 , the pressure is 2×10 -4 Pa, the evaporation time was 1000 s, and Au nanoparticles were directly deposited onto the TiO2 electrode to prepare a TiO2 / Au-10 nm composite electrode.

[0024] The present invention has the following beneficial effects:

[0025] The present invention provides a method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles, which optimizes and improves the traditional vacuum evaporation method by strictly limiting the evaporation deposition rate of Au (≤0.03 nm·s -1 ) and other specific parameters control the priority of nucleation and nucleus growth of the nanoparticles during the initial crystallization process, promoting the nucleation of Au nanoparticles and slowing down grain growth. In a single step, Au nanoparticles with a high LSPR effect, high loading, high dispersion, and high density are controllably produced, eliminating the subsequent calcination process required by traditional vacuum evaporation methods, which is energy-intensive and affects the physical properties of the Au nanoparticles. The preparation process also allows for controllable adjustment of the particle size of the Au nanoparticles, resulting in a plasma composite electrode with strong light absorption throughout the visible and near-infrared regions, high photoelectric conversion efficiency, and excellent photoelectrochemical performance. Furthermore, the method is simple, controllable, and universally applicable, capable of directly depositing Au nanoparticles not only on flat TiO2 films but also on the curved surfaces of SiO2@TiO2 two-dimensional photonic crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 SEM images of TiO2 / Au of different sizes prepared in the examples of the present invention, corresponding to: (a) TiO2 / Au-5 nm; (b) TiO2 / Au-10 nm; (c) TiO2 / Au-15 nm; (d) TiO2 / Au-20 nm.

[0027] Figure 2 SEM images of SiO2@TiO2 / Au of different sizes prepared in the examples of the present invention, corresponding to: (a) SiO2@TiO2 / Au-10 nm; (b) SiO2@TiO2 / Au-20 nm.

[0028] Figure 3 This is the solid UV-visible absorption spectrum of TiO2 / Au prepared in the embodiment of the present invention.

[0029] Figure 4 This is a graph showing the photoelectric conversion efficiency (IPCE) of TiO2 / Au prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention is described in detail below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-mentioned contents of the present invention.

[0031] Example 1

[0032] A method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles is carried out according to the following steps:

[0033] 1) Preparation of TiO2 electrode:

[0034] The ITO glass treated with ultrapure water and anhydrous ethanol for 10 min was used as the substrate. A mixed solution of isopropyl alcohol and diisopropyl di(acetylacetonate) titanate with a volume ratio of 4.5:1 was used as the precursor solution. The nitrogen spray pressure was controlled at 0.12 MPa. The ITO surface was sprayed for 1 s and then the spraying was repeated for 60 s. Finally, the sprayed sample was heated at 500°C. oC After calcination for 45 min, a planar TiO2 electrode was obtained;

[0035] 2) Preparation of Au nanoparticles by vacuum evaporation: The TiO2 electrode obtained in step 1) was placed in a vacuum thermal evaporation chamber as a substrate. The evaporation source Au wire (99.999%) was placed in a tungsten boat. The evaporation deposition rate was controlled to 0.01 nm·s -1 , the pressure is 2×10 -4 Pa, the evaporation time was 500 s, and Au nanoparticles were directly deposited onto the TiO2 electrode to prepare TiO2 / Au-5nm.

[0036] Example 2

[0037] A method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles is carried out according to the following steps:

[0038] 1) The preparation of the TiO2 electrode is the same as in Example 1;

[0039] 2) Preparation of Au nanoparticles by vacuum evaporation: The TiO2 electrode obtained in step 1) was placed in a vacuum thermal evaporation chamber as a substrate. The evaporation source Au wire was placed in a tungsten boat. The evaporation deposition rate was controlled to 0.01 nm·s. -1 , the pressure is 2×10 -4 Pa, the evaporation time was 1000 s, and Au nanoparticles were directly deposited onto the TiO2 electrode to prepare TiO2 / Au-10nm.

[0040] Example 3

[0041] A method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles is carried out according to the following steps:

[0042] 1) The preparation of the TiO2 electrode is the same as in Example 1;

[0043] 2) Preparation of Au nanoparticles by vacuum evaporation: The TiO2 electrode obtained in step 1) was placed in a vacuum thermal evaporation chamber as a substrate. The evaporation source Au wire was placed in a tungsten boat. The evaporation deposition rate was controlled to 0.01 nm·s. -1 , the pressure is 2×10 -4 Pa, the evaporation time was 1500 s, and Au nanoparticles were directly deposited onto the TiO2 electrode to prepare TiO2 / Au-15nm.

[0044] Example 4

[0045] A method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles is carried out according to the following steps:

[0046] 1) The preparation of the TiO2 electrode is the same as in Example 1;

[0047] 2) Preparation of Au nanoparticles by vacuum evaporation: The TiO2 electrode obtained in step 1) was placed in a vacuum thermal evaporation chamber as a substrate. The evaporation source Au wire was placed in a tungsten boat. The evaporation deposition rate was controlled to 0.01 nm·s. -1 , the pressure is 2×10 -4 Pa, the evaporation time was 2000 s, and Au nanoparticles were directly deposited onto the TiO2 electrode to prepare TiO2 / Au-20nm.

[0048] Experimental Example 5

[0049] A method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles is carried out according to the following steps:

[0050] 1) Preparation of SiO2@TiO2 two-dimensional photonic crystal electrode: First, fill a beaker with a certain volume of water, then add 45 μL of 1 mol·L -1 A sodium dodecyl sulfate aqueous solution was prepared, and a n-butanol dispersion of SiO2 beads with a particle size of 370 nm synthesized by the Stöber method was slowly dripped onto the liquid surface, self-assembling a layer of SiO2 two-dimensional photonic crystals at the air-liquid interface. A previously prepared planar TiO2 electrode was irradiated with ultraviolet light for 30 minutes to obtain a hydrophilic surface. The treated planar TiO2 electrode was inserted into a beaker and slowly pulled up, transferring the SiO2 two-dimensional photonic crystals at the air-liquid interface to the planar TiO2 electrode. After drying, a SiO2@TiO2 two-dimensional photonic crystal electrode was obtained.

[0051] 2) Preparation of Au nanoparticles by vacuum evaporation: The SiO2@TiO2 two-dimensional photonic crystal electrode obtained in step 1) was placed in a vacuum thermal evaporation chamber as a substrate. The evaporation source Au wire was placed in a tungsten boat, and the evaporation deposition rate was controlled to 0.01 nm·s. -1 , the pressure is 2×10 -4 Pa, the evaporation time was 1000 s, and Au nanoparticles were directly deposited onto the SiO2@TiO2 two-dimensional photonic crystal electrode to prepare SiO2@TiO2 / Au-10nm.

[0052] Experimental Example 6

[0053] A method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles is carried out according to the following steps:

[0054] 1) Preparation of SiO2@TiO2 two-dimensional photonic crystals is the same as in Example 5;

[0055] 2) Preparation of Au nanoparticles by vacuum evaporation: The SiO2@TiO2 two-dimensional photonic crystal electrode obtained in step 1) was placed in a vacuum thermal evaporation chamber as a substrate. The evaporation source Au wire was placed in a tungsten boat, and the evaporation deposition rate was controlled to 0.01 nm·s. -1 , the pressure is 2×10 -4 Pa, the evaporation time was 2000 s, and Au nanoparticles were directly deposited onto the SiO2@TiO2 two-dimensional photonic crystal electrode to prepare SiO2@TiO2 / Au-20nm.

[0056] From the attached Figure 1 It can be seen that the Au nanoparticles on the TiO2 / Au prepared in the present invention are evenly distributed on the TiO2 surface, have good dispersion and high density.

[0057] From the attached Figure 2 It can be seen that the dispersion of Au nanoparticles is still good when the substrate is changed to SiO2@TiO2 two-dimensional photonic crystal, which shows that the preparation method has universal applicability for depositing Au nanoparticles on different TiO2 substrates in one step.

[0058] Attachment Figure 3 It can be seen that after the deposition of Au nanoparticles, Au / TiO2 has strong light absorption in the entire visible light region to the near-infrared region, and a relatively wide LSPR characteristic peak appears around 600 nm, indicating that the Au deposited in the present invention is nanoparticles, rather than an Au metal layer.

[0059] Attachment Figure 4 It can be seen that the shape of the photoelectric conversion efficiency of the prepared TiO2 / Au is basically consistent with the light absorption, indicating that the photocurrent comes from the LSPR absorption of Au nanoparticles. The electrode shows a large photoelectric conversion efficiency in the entire visible light range.

Claims

1. A method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles, characterized in that: The following steps are included in sequence: 1) Preparation of flat or curved TiO2 electrodes TiO2 electrodes or SiO2@TiO2 two-dimensional photonic crystals were prepared on ITO glass using spray pyrolysis as a substrate; 2) Deposition of Au nanoparticles Au nanoparticles were deposited on the substrate in one step by controlling the evaporation rate using a vacuum evaporation method. A tungsten boat was used for evaporation, and an Au wire was used as the evaporation source. The deposition rate during the evaporation process was controlled to be 0.005-0.03 nm·s -1 , the evaporation time is 200~2500 s, and the evaporation pressure is 8×10 -5 ~4×10 -4 Pa.

2. The method for preparing the Au nanoparticle-modified TiO2 plasma composite electrode according to claim 1, wherein: In the preparation of the planar or curved TiO2 electrode, the planar TiO2 electrode is prepared by spray pyrolysis on the surface of ITO glass to obtain a TiO2 thin film; the curved TiO2 electrode is prepared by depositing SiO2 two-dimensional photonic crystals on the surface of the planar TiO2 electrode using a gas-liquid interface self-assembly method, and then spray pyrolysis is used to obtain a SiO2@TiO2 two-dimensional photonic crystal film.

3. The method for preparing the Au nanoparticle-modified TiO2 plasma composite electrode according to claim 2, wherein: The preparation process of the SiO2 two-dimensional photonic crystal is to first add 30~50 μL of 0.8~1.5 mol·L -1 An aqueous solution of sodium dodecyl sulfate was used as a surfactant, and then a n-butanol dispersion of SiO2 beads was slowly added, self-assembling a layer of SiO2 two-dimensional photonic crystals at the air-liquid interface, and finally transferred it to a planar TiO2 electrode; the SiO2 beads used were synthesized by the Stöber method, with a particle size of 250~600 nm.

4. The method for preparing the Au nanoparticle-modified TiO2 plasma composite electrode according to claim 2 or 3, wherein: Before depositing the SiO2 two-dimensional photonic crystal, the planar TiO2 electrode is irradiated with ultraviolet light for 15 to 30 minutes.

5. The method for preparing the Au nanoparticle-modified TiO2 plasma composite electrode according to any one of claims 1 to 4, characterized in that: In the spray pyrolysis method, the nitrogen spray pressure is controlled at 0.10-0.15 MPa, the single spraying time is 1 s, the next spraying is performed after 60 s, the number of spraying is 2-5 times, and the calcination temperature is 480-550 o C, the calcination time is 30~60 min.

6. The method for preparing the Au nanoparticle-modified TiO2 plasma composite electrode according to any one of claims 1 to 5, characterized in that: In the process of preparing planar TiO2 electrodes by spray pyrolysis, the precursor solution used is a mixed solution of isopropyl alcohol and di(acetylacetonato) diisopropyl titanate with a volume ratio of 4~5:

1.

7. The method for preparing the Au nanoparticle-modified TiO2 plasma composite electrode according to any one of claims 1 to 6, characterized in that: The ITO glass was pretreated by ultrasonic cleaning with ultrapure water and anhydrous ethanol for 10 to 20 minutes respectively before use.

8. A method for preparing a TiO2 plasma composite electrode modified with Au nanoparticles, characterized in that: Proceed as follows: 1) Preparation of planar TiO2 electrodes: The ITO glass treated with ultrapure water and anhydrous ethanol for 10 min was used as the substrate. A mixed solution of isopropyl alcohol and diisopropyl di(acetylacetonate) titanate with a volume ratio of 4 to 5:1 was used as the precursor. The nitrogen spray pressure was controlled at 0.12 MPa. The ITO glass surface was sprayed for 1 s and then the spraying step was repeated for 60 s. Finally, the sprayed sample was placed at 500 o C roasted for 45 min; 2) Preparation of Au nanoparticles by vacuum evaporation: The obtained planar TiO2 electrode was placed as a substrate in a vacuum thermal evaporation chamber, and the evaporation source Au wire was placed in a tungsten boat. The evaporation deposition rate was controlled to 0.01 nm·s -1 , the pressure is 2×10 -4 Pa, the evaporation time was 1000 s, and Au nanoparticles were directly deposited onto the TiO2 electrode.

Images