CN113215609A

CN113215609A - Preparation of silver nanocluster sensitized titanium dioxide composite photo-anode for photoelectrocatalysis

Info

Publication number: CN113215609A
Application number: CN202110489857.4A
Authority: CN
Inventors: 肖方兴; 汤博; 梁昊; 刘必坚
Original assignee: Fuzhou University
Current assignee: Fuzhou University
Priority date: 2021-05-06
Filing date: 2021-05-06
Publication date: 2021-08-06
Anticipated expiration: 2041-05-06
Also published as: CN113215609B

Abstract

The invention discloses a silver nanocluster sensitized TiO for photoelectrocatalysis₂The preparation method of the composite photoanode comprises the step of carrying out electrostatic layer-by-layer self-assembly on silver nanoclusters, polymer PDDA and TiO₂The nanorod arrays are bonded together to obtain a photoanode that can be used in photoelectrocatalysis. The invention firstly uses PDDA/Ag_xNCs for modifying TiO₂The method has the advantages of simple preparation process, reliable design principle, low generation cost and short period, and is beneficial to the sustainable development of environment and energy.

Description

Preparation of silver nanocluster sensitized titanium dioxide composite photo-anode for photoelectrocatalysis

Technical Field

The invention belongs to the technical field of preparation of a photoelectric catalytic material and photoelectric catalysis, and particularly relates to a silver nanocluster (Ag) for photoelectric catalysis_xNCs) sensitized TiO₂A preparation method of a composite photo-anode.

Background

Titanium dioxide (TiO) was discovered by Fujishima and Honda in Japan since 1972₂) The production of hydrogen by photocatalytic decomposition of water has become a major concern since water can be decomposed into hydrogen and oxygen under the excitation of ultraviolet light.

The titanium dioxide is used as a mature semiconductor, is superior to other semiconductors in the aspects of chemical stability, light corrosion resistance, nontoxicity, low cost and the like, particularly has the advantages of large specific surface area, large length-diameter ratio and the like due to a unique one-dimensional nano structure, shows excellent properties outstanding to zero-dimensional and two-dimensional structures, and can be used as a photoanode with good photoelectrocatalysis performance. However, due to TiO₂The solar cell has a larger band gap (3.0-3.2 eV), and can excite and transfer electrons on a valence band to a conduction band only by needing high energy input, so that the problems of high carrier recombination rate, insensitivity to visible light with low energy and near infrared solar spectrum and the like are caused.

Depositing Polyelectrolyte (PE) on the semiconductor surface to regulate the electrical properties of the surface termination while controlling the electron transport channels is an effective strategy to achieve higher charge separation efficiency. Meanwhile, the micro ligand protection metal nanocluster is a novel functional material with abundant coordination chemical characteristics, consists of a small number of metal atoms, is protected by stable ligands, and has special atom accumulation, quantum confinement effect and discrete molecular band structure, so that the property of the metal nanocluster is completely different from that of large-size nanoparticles, and the metal nanocluster has more excellent catalytic performance and photoelectric performance.

Layer-by-layer self-assembly (LbL) as a multifunctional bottom-up approach can precisely control the spontaneous assembly of small molecules into the desired complex multilayer structure. The use of electrostatic interactions between components of different charges as the primary driving force to enable loading of components on a substrate in an ordered manner by alternate deposition to achieve the desired multilayer nanostructures has been widely used.

Disclosure of Invention

The invention aims to provide PDDA/Ag NCs which have the advantages of low manufacturing cost, simple production process and environmental friendliness_xPreparation method of modified TNRAs photoanode and PDDA/Ag prepared by preparation method_xThe NCs modified TNRAs photoanode has the characteristic of capability of performing photoelectrocatalysis under visible light, and has high catalytic activity.

In order to achieve the purpose, the invention adopts the following technical scheme:

silver nanocluster sensitized TiO for photoelectrocatalysis₂The preparation method of the composite photo-anode comprises the following steps:

(1) silver nanoclusters (Ag)_xNCs) preparation:

to 200 mL of deionized water was added 12.5 mL of 20 mM AgNO₃Stirring and mixing the solution and 7.5 mL of 50 mM reduced glutathione for 2 min, then adding 1M NaOH solution to adjust the pH value to 11, heating the solution at 70-90 ℃ for 1h under the condition of 500-1000 r/min, then naturally cooling to room temperature, adding 1M HCl solution to adjust the pH value to 3.75, aging at room temperature for 24h, and finally separatingRemoving the precipitate to obtain silver nanocluster Ag_xAqueous solutions of NCs; the average grain diameter of the obtained silver nanocluster is 1-2 nm;

(2) preparation of titanium dioxide nanorod arrays (TNRAs):

pouring 15ml of ultrapure water and 15ml of concentrated hydrochloric acid solution with the concentration of 36.5-38 wt% into a lining of a 50ml reaction kettle, stirring and mixing for 5min at the speed of 1000r/min, then adding 0.45-0.5 ml of tetrabutyl titanate as a titanium source, stirring for 15min, completely immersing the cleaned FTO substrate into the obtained solution in a manner that a conductive surface faces downwards, then putting the lining into the reaction kettle, heating for 12-24h in an electric furnace with the temperature of 120-;

(3) preparing a composite light anode:

immersing the TNRAs obtained in the step (2) into 0.5-2mg/ml of PDDA aqueous solution (containing 0.5M NaCl) with positive charge for 5min, and then washing the TNRAs with deionized water for 1 min to prepare the PDDA modified TNRAs (TNRAs/(PDDA)₁) Subsequently, it is immersed in the negatively charged Ag obtained in step (1)_xNCs water solution for 5min, washing with deionized water for 1 min, and drying with nitrogen to obtain double-layer TNRAs/(PDDA/Ag)_x NCs)₁。

(4) By repeating the step (3), the multilayer composite photoanode TNRAs/(PDDA/Ag) can be obtained_xNCs)_n。

PDDA/Ag with different layers prepared by the method_xThe NCs modified TNRAs composite photoanode can be subjected to photoelectrocatalysis under visible light. The photoelectric catalytic performance is optimal when the number of layers is 4, and the photocurrent density can reach 18 mu A cm^-2。

In the process of preparing the silver nanoclusters, after heating under alkaline conditions, the pH is further adjusted to 3.75 by adding 1M HCl solution and aging is performed for 24 hours, in order to make monovalent silver gather around zero-valent silver by changing the pH conditions.

In the process of preparing the titanium dioxide nanorod array, the temperature is kept for 12-24 hours at the temperature of 120-plus-one and 150 ℃ by a hydrothermal method, and then kept for 1 hour at the temperature of 400-plus-one and 500 ℃ so that the nanorod can grow fully and the rutile type titanium dioxide nanorod is prepared.

According to the invention, polydiallyl dimethyl ammonium chloride (PDDA) and Ag NCs are alternately deposited on the surface of titanium dioxide in a layer-by-layer self-assembly manner so as to modify the surface of the titanium dioxide, so that the double effects that the charges of the PDDA and the Ag NCs are opposite and easy to adhere, and the PDDA can form a unique electron transmission channel so as to accelerate electron migration are exerted, and the photoelectrocatalysis performance of the prepared photo-anode is improved.

The invention has the following remarkable advantages:

(1) in the invention, Ag is mixed with_xThe NCs are applied to visible light-activated PDDA modified TNRAs, so that the obtained composite light anode has higher catalytic efficiency, can generate larger photocurrent, and is beneficial to sustainable development of environment and energy.

(2) PDDA/Ag obtained by the invention_xThe NCs modified TNRAs photoanode has the advantages of high photoelectrocatalysis activity, low manufacturing cost, simple production process, macroscopic preparation, environmental friendliness and easiness in recovery.

Drawings

FIG. 1 shows Ag prepared in example 1_xParticle size distribution of NCs.

FIG. 2 shows Ag prepared in example 1_xXPS pattern of Ag element in NCs.

FIG. 3 is a scanning electron micrograph of a surface (a) and a cross-section (b) of TNRAs prepared in example 1;

FIG. 4 shows a 4-layer composite photoanode T (PA) prepared in example 2₄Transmission electron microscopy images of;

FIG. 5 shows composite anodes T (PA) with different layers_xThe photocurrent density graph of (1.0V vs. RHE, chopping cycle 10 s);

FIG. 6 shows the TNRAs substrate, TP prepared in example 2₄、TA₄And T (PA)₄The photocurrent density graph of (1.0V vs. RHE, chopping cycle 10 s);

FIG. 7 shows the TNRAs substrate, TP prepared in example 2₄、TA₄And T (PA)₄Comparative photoelectric conversion efficiency (IPCE) of (a).

Detailed Description

In order to make the present invention more comprehensible, the technical solutions of the present invention are further described below with reference to specific embodiments, but the present invention is not limited thereto.

The photoelectrocatalysis performance test is carried out on an electrochemical workstation by adopting a three-electrode cell, and specifically, Na is used for testing the photoelectrocatalysis performance₂SO₄(0.5M) is electrolyte, a silver/silver chloride electrode and a platinum sheet are respectively a reference electrode and a counter electrode, the prepared composite light anode (1 multiplied by 1 cm) is used as a working electrode, and a 300w xenon lamp (lambda) adopting a band-pass filter is adopted>420 nm) as visible light irradiation, the PEC performance was evaluated.

Example 1

To 200 mL of deionized water was added 12.5 mL of 20 mM AgNO₃Stirring and mixing the solution and 7.5 mL of 50 mM reduced Glutathione (GSH) for 2 min, then adding 1M NaOH solution to adjust the pH value to 11, heating the solution at 90 ℃ for 1h at 500 r/min, naturally cooling to room temperature, adding 1M HCl solution to adjust the pH value to 3.75, aging at room temperature for 24h, and finally removing precipitates by centrifugation to obtain the silver nanoclusters (Ag nanoclusters)_xNCs) aqueous solution;

pouring 15ml of ultrapure water and 15ml of concentrated hydrochloric acid solution with the concentration of 36.5-38 wt% into a lining of a 50ml reaction kettle, stirring and mixing for 5min at the speed of 1000r/min, then adding 0.45ml of tetrabutyl titanate serving as a titanium source, stirring for 15min, completely immersing a cleaned FTO substrate into the obtained solution in a manner that a conductive surface faces downwards, then putting the lining into the reaction kettle, heating for 12h in an electric furnace at the temperature of 150 ℃, cooling to room temperature, taking out the FTO substrate, cleaning with deionized water, drying with nitrogen, heating to 500 ℃ in a muffle furnace, preserving heat for 1h, and cooling to obtain a titanium dioxide nanorod array (TNRAs);

the obtained TNRAs were immersed in 0.5 mg/ml of a positively charged PDDA aqueous solution (containing 0.5M NaCl) for 5min, followed by washing with deionized water for 1 min to prepare PDDA-modified TNRAs (TNRAs/(PDDA)₁) Subsequently, it is dipped into a tapeAg of negative charge_xNCs water solution for 5min, washing with deionized water for 1 min, and drying with nitrogen to obtain double-layer TNRAs/(PDDA/Ag)_x NCs)₁(ii) a Then repeating the above steps to obtain PDDA and Ag_xNCs are alternately deposited on the TNRAs to obtain 4-layer and 8-layer composite photoanodes which are respectively marked as T (PA)₂，T(PA)₄，T(PA)₈。

After the photoelectrocatalysis performance test, 4 layers of T (PA)₄The highest photocurrent density of 18 muA cm is shown^-2。

Example 2

the obtained TNRAs were immersed in 0.5 mg/ml of a positively charged PDDA aqueous solution (containing 0.5M NaCl) for 5min, followed by washing with deionized water for 1 min to prepare PDDA-modified TNRAs (TNRAs/(PDDA)₁) Subsequently, it is immersed in Ag having a negative charge_xNCs water solution for 5min, washing with deionized water for 1 min, and drying with nitrogen to obtain double-layer TNRAs/(PDDA/Ag)_x NCs)₁(ii) a Then repeating the above steps 2 times to obtain PDDAAg_xNCs are alternately deposited on the TNRAs to obtain a 4-layer composite photoanode T (PA)₄。

PDDA and Ag_xNCs were repeatedly deposited on TNRAs to obtain 4 layers of TNRAs/(PDDA)₄ [TP₄]And TNRAs/(Ag)_x)₄ [TA₄]。

After the photoelectrocatalysis performance test, T (PA)₄Exhibits the highest photocurrent density, while measuring T (PA)₄IPCE of (a) is also maximal, reaching 18%.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.

Claims

1. Silver nanocluster sensitized TiO for photoelectrocatalysis₂The preparation method of the composite photo-anode is characterized by comprising the following steps: the method comprises the following steps:

(1) preparing the silver nanoclusters:

to 200 mL of deionized water was added 12.5 mL of 20 mM AgNO₃Stirring and mixing the solution and 7.5 mL of 50 mM reduced glutathione for 2 min, then adding 1M NaOH solution to adjust the pH value to 11, heating the solution at 70-90 ℃ for 1h under the condition of 500-plus-one 1000r/min, then naturally cooling to room temperature, adding 1M HCl solution to adjust the pH value to 3.75, aging at room temperature for 24h, and finally removing precipitates by centrifugation to obtain the silver nanocluster Ag_xAqueous solutions of NCs;

(2) preparing a titanium dioxide nanorod array:

stirring and mixing 15ml of ultrapure water and 15ml of concentrated hydrochloric acid solution with the concentration of 36.5-38 wt% at the speed of 1000r/min for 5min, then adding 0.45-0.5 ml of tetrabutyl titanate, stirring for 15min, completely immersing the cleaned FTO substrate into the obtained solution in a manner that the conductive surface faces downwards, heating the FTO substrate in a reaction kettle at the temperature of 120-150 ℃ for 12-24h, cooling to room temperature, taking out the FTO substrate, cleaning with deionized water, drying with nitrogen, heating to the temperature of 400-500 ℃ in a muffle furnace, preserving heat for 1h, and cooling to obtain the titanium dioxide nanorod array TNRAs;

(3) preparing a composite light anode:

immersing the TNRAs obtained in the step (2) into a PDDA aqueous solution of 0.5-2mg/ml for 5min, then washing with deionized water for 1 min to prepare PDDA modified TNRAs, and then immersing the TNRAs into the Ag obtained in the step (1)_xAnd (3) carrying out nitrogen drying after the NCs aqueous solution is washed for 1 min by deionized water, thus obtaining the composite light anode.

2. The method for preparing the composite photoanode as claimed in claim 1, wherein: the average grain diameter of the silver nanocluster obtained in the step (1) is 1-2 nm.

3. The method for preparing the composite photoanode as claimed in claim 1, wherein: the aqueous PDDA solution used in step (3) contains 0.5M NaCl.

4. The method for preparing the composite photoanode as claimed in claim 1, wherein: and (4) repeating the step (3) to obtain the multilayer composite light anode.