CN112030176A

CN112030176A - Silicon photoelectric cathode modified by tungsten sulfide nano particles and preparation method thereof

Info

Publication number: CN112030176A
Application number: CN202010732234.0A
Authority: CN
Inventors: 林惠文; 常焜; 秦亚雷; 徐旺; 韩文君
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2020-07-27
Filing date: 2020-07-27
Publication date: 2020-12-04
Anticipated expiration: 2040-07-27
Also published as: CN112030176B

Abstract

The invention discloses a tungsten sulfide nanoparticle modified silicon photocathode and a preparation method thereof, belonging to the field of photoelectrocatalysis semiconductor materials. The invention specifically comprises the following steps: taking a solution of soluble thiotungstate as a reaction raw material, taking a hydrofluoric acid solution as a reaction medium, and depositing tungsten sulfide nano-particles to the surface of a silicon wafer in situ under the oxidation-reduction action of the surface of the silicon wafer which is subjected to fluorinated etching treatment and thiotungstate ions in the hydrofluoric acid medium under the normal temperature condition to prepare the silicon photocathode with the uniformly deposited ultrathin tungsten sulfide nano-particle film.

Description

Silicon photoelectric cathode modified by tungsten sulfide nano particles and preparation method thereof

Technical Field

The invention belongs to the field of photoelectrocatalysis semiconductor materials, and particularly relates to a silicon photocathode modified by tungsten sulfide nanoparticles and a preparation method thereof.

Background

Photoelectrocatalytic pure water decomposition and carbon dioxide reduction is a very effective way to develop and convert solar energy, where the key and most fundamental factor in determining photoelectrocatalytic performance is the need to use a suitable and efficient semiconductor photocathode. Among many semiconductors, silicon, which is abundant and inexpensive, is the most promising small bandgap semiconductor (1.12 eV), and its bandgap absorption almost perfectly matches the near infrared and visible light portions in the solar spectrum, and at the same time it has nearly ideal band structure, and can fully meet the requirements of photoelectrocatalysis pure water decomposition and carbon dioxide reduction on the semiconductor conduction band position. However, the photoelectrocatalysis performance of pure silicon is very poor, mainly due to the retarded hydrogen evolution and carbon dioxide reduction catalytic capability of the surface of the pure silicon, so that a modification promoter needs to be deposited on the surface of the pure silicon to meet the performance requirement of photoelectrocatalysis.

Transition metal sulfides such as tungsten sulfide have shown great potential as novel inexpensive promoters on silicon-based photocathodes. It has been reported that by synthesizing amorphous tungsten disulfide and tungsten trisulfide under high temperature condition and modifying silicon photocathode, initial photogeneration voltage close to 0.4V for standard hydrogen electrode is obtained, and 20mA ∙ cm is reached under 0V condition^-2The photo-generated current (appl. mater. inter. 2014, 6, 10408). In general, the co-catalytic properties of tungsten sulfide, and its interaction with the silicon semiconductor, determine the photo-catalytic properties of the silicon photocathode. How to improve the promoting properties of tungsten sulfide and its interaction with the silicon semiconductor depends on what technical means are used to achieve the preparation. Chemical vapor deposition (MRS Commun. 2017, 7, 272), thermal synthesis (appl. Catal. B: environ. 2018, 237, 158) or pulsed laser deposition (adv. Sci. 2019, 6, 190030)1) Etc. are the most commonly used technical means. Although silicon photocathodes satisfying the photocatalytic performance can occasionally be obtained, these technical means have disadvantages of very low deposition rate, non-uniform deposition thickness, high preparation cost, and the like.

Disclosure of Invention

The invention provides a silicon photoelectric cathode modified by tungsten sulfide nano particles and a preparation method thereof, wherein the preparation method is simple and easy to operate, the reaction condition is mild and controllable, the thickness of the obtained tungsten sulfide nano particles is 1-15nm, the tungsten sulfide nano particles can be simply controlled by changing the concentration of thiotungstate and the reaction time, and the raw material cost and the preparation efficiency are superior to those of the prior art.

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

a silicon photoelectric cathode modified by tungsten sulfide nano-particles is characterized in that tungsten sulfide nano-particles are deposited on the surface of p-type monocrystalline silicon in the photoelectric cathode, the tungsten sulfide nano-particles are uniformly distributed on the surface of the p-type monocrystalline silicon, and the thickness of the tungsten sulfide nano-particle layer is 1-15 nm.

A preparation method of a tungsten sulfide nanoparticle modified silicon photocathode comprises the following steps:

(1) putting p-type monocrystalline silicon in a mixed solution of concentrated sulfuric acid and hydrogen peroxide at 40-80%^oC, cleaning for 30-60min to remove organic pollutants on the surface, and then etching for 5-30min by using 0.5-10% fluorine-containing solution to remove a surface oxide layer;

(2) dissolving soluble thiotungstate in solvent, preparing 0.05-0.5M thiotungstate solution, standing at 5%^oC, standby;

(3) and (3) dropwise adding the thiotungstate solution prepared in the step (2) with a certain volume into a hydrofluoric acid solution to prepare thiotungstate mixed hydrofluoric acid solutions with different concentrations, horizontally placing the p-type monocrystalline silicon cleaned in the step (1) in the thiotungstate mixed hydrofluoric acid solution for 1-60min, cleaning, and drying in an argon atmosphere or vacuum to prepare the tungsten sulfide nanoparticle modified silicon photocathode.

In the above step, the fluorine-containing solution in step (1) is a hydrofluoric acid or ammonium fluoride solution; solubility in step (2)Thiotungstate is (NH4)₂WS₄、Na₂WS₄Or K₂WS₄The solvent is water or ethanol; in the step (3), the concentration of ammonium thiotungstate in the mixed solution of the thiotungstate and the hydrofluoric acid is 0.1-10mM, and the mass percentage concentration of the hydrofluoric acid is 1-10%; the thickness of the tungsten sulfide nano-particle layer is 1-15nm, and the thickness of the tungsten sulfide nano-particle layer can be controlled by changing the concentration of thiotungstate and the reaction time.

Has the advantages that: the invention provides a silicon photocathode modified by tungsten sulfide nano particles and a preparation method thereof, wherein thiotungstate is used as a raw material, amorphous tungsten sulfide nano particles are controllably deposited on the silicon photocathode in situ through simple normal-temperature liquid-phase redox reaction, the thickness of the deposited tungsten sulfide nano particle layer is 1-15nm, the thickness can be controlled simply by changing the concentration and the reaction time of the thiotungstate, and the raw material cost and the preparation efficiency are both superior to those of the prior art; the deposited tungsten sulfide nano particles and the silicon photocathode have a tight interface combination effect, so that efficient photoproduction electron transmission is realized; the method has the advantages of simple and easily-operated process, mild and controllable conditions, low cost of reagents and environmental protection, and the prepared silicon photocathode has great application potential in the fields of photoelectrocatalysis water decomposition, photoelectrocatalysis carbon dioxide reduction and the like.

Drawings

FIG. 1 is a schematic structural diagram of a silicon photocathode modified with tungsten sulfide nanoparticles according to the present invention;

FIG. 2 is an atomic force micrograph of amorphous tungsten sulfide deposited in situ on the surface of a silicon photocathode prepared in example 3 of the present invention;

fig. 3 is a profile view showing the thickness of tungsten sulfide nanoparticles in a silicon photocathode prepared in example 3 of the present invention.

Detailed Description

The invention is described in detail below with reference to specific embodiments and with reference to the following figures:

example 1

A silicon photoelectric cathode modified by tungsten sulfide nano particles and a preparation method thereof comprise the following steps:

cutting p-type monocrystalline silicon into square samples with side length of 1cm by using a glass cutter, placing the square samples in a mixed solution of 10mL of concentrated sulfuric acid and 5mL of hydrogen peroxide, and placing the mixture in a 60-mL mixed solution^oC, cleaning for 40min, and etching for 10min by using 2.0% hydrofluoric acid to obtain bare silicon without an oxide layer; 2.0mmol of ammonium thiotungstate was dissolved in 10mL of water to prepare a 0.2M ammonium thiotungstate solution, 0.05mL of the ammonium thiotungstate solution was then dropped into 10mL of a 5.0% hydrofluoric acid solution to prepare a 1.0mM ammonium thiotungstate mixed hydrofluoric acid solution, the above-mentioned oxide layer-free p-type single crystal silicon was placed in the solution for 5min, and then washed with a large amount of ultrapure water and dried with argon gas to prepare a tungsten sulfide nanoparticle thin film-modified silicon photocathode shown in FIG. 1, wherein the thickness of the obtained tungsten sulfide thin film was about 9.0 nm.

Example 2

cutting p-type monocrystalline silicon into square samples with side length of 1cm by using a glass cutter, placing the square samples in a mixed solution of 10mL of concentrated sulfuric acid and 5mL of hydrogen peroxide, and placing the mixture in a 60-mL mixed solution^oC, cleaning for 40min, and etching for 5min by using 5.0% hydrofluoric acid to obtain bare silicon without an oxide layer; 1.0mmol of ammonium thiotungstate was dissolved in 10mL of water to prepare a 0.1M ammonium thiotungstate solution, 0.02mL of the ammonium thiotungstate solution was then added dropwise to 10mL of a 6.0% hydrofluoric acid solution to prepare a 0.2mM ammonium thiotungstate mixed hydrofluoric acid solution, the above-mentioned oxide-layer-free p-type single crystal silicon was placed in the solution for 20min, and then washed with a large amount of ultrapure water and dried with argon gas to prepare a tungsten sulfide nanoparticle film-modified silicon photocathode as shown in FIG. 1, wherein the thickness of the obtained tungsten sulfide film was about 6.0 nm.

Example 3

cutting p-type monocrystalline silicon into square samples with side length of 1cm by using a glass cutter, placing the square samples in a mixed solution of 10mL of concentrated sulfuric acid and 5mL of hydrogen peroxide, and placing the mixture in a 60-mL mixed solution^oC, cleaning for 40min, and etching for 5min by using 3.0% hydrofluoric acid to obtain bare silicon without an oxide layer; 1.0mmol of ammonium thiotungstate is dissolved in 10mL of water to prepare0.1M ammonium thiotungstate solution, 0.01mL of the ammonium thiotungstate solution was then dropped into 10mL of 8.0% hydrofluoric acid solution to prepare 0.1mM ammonium thiotungstate mixed hydrofluoric acid solution, and the above-mentioned p-type single crystal silicon without an oxide layer was placed in the solution for 20min, followed by washing with a large amount of ultrapure water and drying with argon gas to prepare a tungsten sulfide nanoparticle thin film-modified silicon photocathode as shown in FIG. 1, the thickness of the obtained tungsten sulfide thin film being about 4.0 nm. As can be seen from FIG. 2, the amorphous tungsten sulfide nanoparticles prepared by the chemical in-situ self-reduction method have uniform size of about 10nm and good dispersibility, and are uniformly distributed on the surface of a Si wafer, and as can be seen from FIG. 3, the thickness of the amorphous tungsten sulfide nanoparticles modified Si surface film prepared by the chemical in-situ self-reduction method is 4-6 nm.

The foregoing is only a preferred embodiment of this invention and it should be noted that modifications can be made by those skilled in the art without departing from the principle of the invention and these modifications should also be considered as the protection scope of the invention.

Claims

1. The silicon photoelectric cathode modified by tungsten sulfide nanoparticles is characterized in that tungsten sulfide nanoparticles are deposited on the surface of p-type monocrystalline silicon in the photoelectric cathode, and the tungsten sulfide nanoparticles are uniformly distributed on the surface of the p-type monocrystalline silicon.

2. The tungsten sulfide nanoparticle modified silicon photocathode of claim 1, wherein the tungsten sulfide nanoparticle layer is 1-15nm thick.

3. A preparation method of a tungsten sulfide nanoparticle modified silicon photocathode is characterized by comprising the following steps:

(2) dissolving soluble thiotungstate in solvent, preparing 0.05-0.5M thiotungstate solution, standingIn 5^oC, standby;

4. The method for preparing the photocathode of silicon modified by tungsten sulfide nanoparticles as claimed in claim 3, wherein the fluorine-containing solution in step (1) is hydrofluoric acid or ammonium fluoride solution.

5. The method for preparing the photocathode for silicon modified by tungsten sulfide nanoparticles as claimed in claim 3, wherein the soluble thiotungstate in the step (2) is (NH4)₂WS₄、Na₂WS₄Or K₂WS₄The solvent is water or ethanol.

6. The method for preparing the photocathode for silicon modified by tungsten sulfide nanoparticles as claimed in claim 3, wherein the concentration of ammonium thiotungstate in the mixed hydrofluoric acid solution of thiotungstate in step (3) is 0.1-10mM, and the concentration of hydrofluoric acid is 1-10% by mass.

7. The method for preparing the photocathode of silicon modified by tungsten sulfide nanoparticles as claimed in claim 3, wherein the thickness of the tungsten sulfide nanoparticle layer can be controlled by changing the concentration and reaction time of thiotungstate during the preparation process.

8. The method for preparing the silicon photocathode modified by the tungsten sulfide nanoparticles as claimed in claim 3 or 7, wherein the thickness of the tungsten sulfide nanoparticles is 1-15 nm.