阅读说明：本技术 一种CoP/Si析氢催化材料及其制备方法 (CoP/Si hydrogen evolution catalytic material and preparation method thereof ) 是由 王喜娜 王德坚 张文 刘涛 何云存 袁慧 彭小牛 于 2019-10-31 设计创作，主要内容包括：本发明涉及光电催化制氢技术领域,具体公开了一种CoP/Si析氢催化材料及其制备方法,所述CoP为纳米片结构且呈网格状均匀分布在硅片表面,CoP层的厚度为3～5μm；本发明还提供了该材料的制备方法,具体包括以下步骤：S1、硅片表面预处理；S2、电沉积制备Si-Co盐前驱体；S3、高温磷化。本发明提供的CoP/Si析氢催化材料将硅吸光特性和CoP的电催化特性有效结合,显示出了优异的光电催化析氢性能,而且制备方法简单、可重复性好以及与硅工艺兼容。(The invention relates to the technical field of photoelectrocatalytic hydrogen production, and particularly discloses a CoP/Si hydrogen evolution catalytic material and a preparation method thereof, wherein CoP is of a nanosheet structure and is uniformly distributed on the surface of a silicon wafer in a latticed manner, and the thickness of a CoP layer is 3-5 microns; the invention also provides a preparation method of the material, which comprises the following steps: s1, pretreating the surface of the silicon wafer; s2, preparing a Si-Co salt precursor by electrodeposition; s3, high-temperature phosphorization. The CoP/Si hydrogen evolution catalytic material provided by the invention effectively combines the silicon light absorption characteristic with the electrocatalytic characteristic of CoP, shows excellent photoelectrocatalytic hydrogen evolution performance, and has the advantages of simple preparation method, good repeatability and compatibility with a silicon process.)

1. The CoP/Si hydrogen evolution catalytic material is characterized in that CoP is of a nanosheet structure and is uniformly distributed on the surface of a silicon wafer in a latticed manner, and the thickness of a CoP layer is 3-5 microns.

2. The CoP/Si hydrogen evolution catalytic material according to claim 1, wherein the thickness of the CoP nanosheet is 20-50 nm.

3. The preparation method of CoP/Si hydrogen evolution catalytic material according to any claim 1-2, characterized by comprising the following steps:

s1, pretreating the surface of the silicon wafer;

s2, depositing the pretreated silicon wafer in a cobalt nitrate aqueous solution at (-0.5) - (-3V) voltage for 15-50min, taking out the silicon wafer, cleaning and drying to obtain a Si-Co salt precursor;

and S3, putting the precursor obtained in the step S2 into a quartz tube filled with sodium hypophosphite, transferring the quartz tube into a vacuum tube furnace, reacting for 1-3 hours at 200-700 ℃ under nitrogen, cooling, and drying by using nitrogen.

4. The preparation method of the CoP/Si hydrogen evolution catalytic material according to claim 3, wherein the pretreatment method of S1 comprises the steps of sequentially putting a silicon wafer into acetone, alcohol and deionized water, ultrasonically cleaning for 10-20 min, and then blowing with nitrogen.

5. The preparation method of the CoP/Si hydrogen evolution catalytic material according to claim 3, wherein the concentration of the cobalt nitrate aqueous solution S2 is 0.2-0.005 mol/L.

6. The preparation method of the CoP/Si hydrogen evolution catalytic material according to claim 5, wherein the concentration of the cobalt nitrate aqueous solution S2 is 0.01-0.04 mol/L.

7. The method for preparing the CoP/Si hydrogen evolution catalytic material according to claim 3, wherein the temperature of the vacuum tube furnace S3 is 400 ℃.

Technical Field

The invention relates to the technical field of photoelectrocatalytic hydrogen production, in particular to a CoP/Si hydrogen evolution catalytic material and a preparation method thereof.

Background

The photocatalytic water splitting hydrogen production such as photocatalytic hydrogen production and photoelectrocatalysis hydrogen production mainly utilizes solar energy to split water into hydrogen, the hydrogen is water after combustion, the method is a renewable green energy conversion mode, and the method has obvious advantages in the aspects of energy conservation, environmental protection and cost reduction. The Si material is one of the most important light absorption materials in the solar cell, has the advantages of rich yield, stable performance, high light absorption rate, high integration level and the like, and has important application potential in the aspect of photoelectrocatalysis hydrogen production. At present, the technical scheme adopted by the electrocatalytic hydrogen evolution of the silicon-based battery is mainly that the external silicon-based battery is connected with an electrocatalyst electrode in an electrochemical reactor in series, a certain voltage is generated by utilizing the photovoltaic effect of the silicon-based battery, and when the voltage is greater than the voltage threshold of electrolyzed water, hydrogen and oxygen are generated on the electrocatalyst electrode (generally comprising an anode and a cathode). The method not only requires the battery to be a complete device, namely a strict electrode process, but also needs to be connected with the substrate of the electrocatalyst through an external circuit, and a Si-lead electrode, a lead-electrocatalyst substrate loop, contact resistance, the resistance of various interfaces of the electrocatalyst/the substrate and the like are respectively introduced, so that the efficiency of the photoelectrocatalysis hydrogen production is reduced, and the complexity and the material cost of the preparation process are improved. Compared with the prior art, if the electrocatalyst is directly prepared on the Si light absorption layer, the lead-in electrodes on Si and the conductive substrate of the electrocatalyst can be effectively avoided, so that the cost is effectively reduced, the efficiency is improved, and the application potential is great.

In recent years, transition metal phosphide (such as NiP, CoP, Fe-P and the like) is considered to be one of ideal non-noble metal hydrogen evolution materials due to excellent hydrogen evolution performance and stability. Among them, CoP is favored by researchers because of its low price, good stability, high hydrogen evolution performance, environmental friendliness and easy preparation, and is widely used in the fields of electrocatalysis and photoelectrocatalysis. For example, Wang et al used a sourceThe CoP nano particles are deposited and synthesized on the carbon nano material by an electro-deposition method, and the Tafel slope of the CoP nano particles is 60mV/dec and is-10 mA/cm²The overpotential is 160 mV; zhen Fang et al synthesized porous flower-like CoP/C nanosheets by in-situ pyrolysis and phosphorization, with a Tafel slope of 128mV/dec and-10 mA/cm²The overpotential is 151 mV; besides being directly used as an electrocatalyst, CoP can be compounded with semiconductor materials for photoelectric hydrogen evolution. For example, the CoP thin film synthesized by Thomas F.Jaramillo et al on a silicon substrate by vapor deposition phosphorization method utilizes the good light absorption of silicon to research the photoelectrocatalysis performance of the silicon, and the dark state is-10 mA/cm²The corresponding overpotential is 202mV, the Tafel slope is 61mV/decade, and the potential under light is +345mV at-10 mA/cm 2.

Although the various nanostructured cops (nanoparticles, nanofilms, flower-like nanoplates, etc.) described above all exhibit good hydrogen evolution performance, their use in photoelectrocatalysis has been less studied by taking advantage of the light absorption properties of silicon when combined with a silicon substrate. Moreover, the preparation method of the CoP often involves high-temperature evaporation and other processes, and the preparation process is relatively complex and has high cost. Therefore, a simple and convenient preparation method compatible with the silicon process is sought, and the application of photoelectrocatalytic hydrogen evolution combined with Si is very necessary.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a CoP/Si hydrogen evolution catalytic material and a preparation method thereof, wherein the material effectively combines the light absorption characteristic of silicon and the electrocatalytic characteristic of CoP, shows excellent photoelectrocatalytic hydrogen evolution performance, and has the advantages of simple preparation method, good repeatability and compatibility with a silicon process.

The invention provides a CoP/Si hydrogen evolution catalytic material, wherein CoP is of a nanosheet structure and is uniformly distributed on the surface of a silicon wafer in a latticed manner, and the thickness of a CoP layer is 3-5 mu m.

Preferably, the CoP nanosheets are tetragonal, and have a thickness of 20-50 nm.

The invention also provides a preparation method of the CoP/Si hydrogen evolution catalytic material, which comprises the following steps:

s1, pretreating the surface of the silicon wafer;

s2, depositing the pretreated silicon wafer in a cobalt nitrate aqueous solution at (-0.5) - (-3V) voltage for 15-50min, taking out the silicon wafer, cleaning and drying to obtain a Si-Co salt precursor;

and S3, putting the precursor obtained in the step S2 and sodium hypophosphite into a vacuum tube furnace, reacting for 1-3 h at 200-700 ℃ under the condition of nitrogen, naturally cooling to room temperature, taking out, and drying by using nitrogen to obtain the CoP/Si hydrogen evolution catalytic material.

Preferably, the pretreatment method of S1 is specifically that the silicon wafer is sequentially placed in acetone, alcohol and deionized water for ultrasonic cleaning for 10-20 min, and then dried with nitrogen.

Preferably, the concentration of the cobalt nitrate aqueous solution of S2 is 0.2-0.005 mol/L.

More preferably, the concentration of the cobalt nitrate aqueous solution of S2 is 0.01 to 0.04 mol/L.

Preferably, the electrodeposition method specifically comprises: by utilizing an electrochemical workstation and adopting a three-electrode system, a silicon wafer, a platinum sheet and Ag/AgCl are respectively used as a working electrode, a counter electrode and a reference electrode, and deposition reaction is carried out for 15-50min under the condition of constant pressure of minus 0.5-minus 3V relative to the reference electrode.

Preferably, the mass of the sodium hypophosphite S3 is 0.6-1.5 g, and the temperature of the vacuum tube furnace S3 is 400 ℃.

Compared with the prior art, the invention has the beneficial effects that: the method is characterized in that a silicon wafer is used as a substrate, a CoP nanosheet is obtained by depositing and phosphorizing on the surface of the silicon wafer, Si absorbs the photon to generate a photo-generated electron, the photo-generated electron is transmitted to the CoP through a Si-CoP interface under the external bias voltage, and the photo-generated electron is coordinated with the external electron to reduce water into hydrogen, so that the energy utilization rate can be effectively improved, and the Si-based electrode treatment process is simplified. In addition, the preparation method provided by the invention adopts the silicon wafer as the substrate, the cobalt nitrate and the sodium hypophosphite as the cobalt source and the phosphorus source, the purity is higher, the raw materials are rich, the cost is lower, meanwhile, compared with other methods such as evaporation, pyrolysis and the like, the electrodeposition method is lower in cost and simple to operate, and the used phosphating process is compatible with the Si process.

Description of the drawings:

FIG. 1 is a schematic diagram of the structure and preparation process of a CoP/Si hydrogen evolution catalytic material in the invention;

FIG. 2 is an XRD pattern of a CoP/Si hydrogen evolution catalytic material in the present invention;

FIG. 3 is a high power SEM image of a CoP/Si hydrogen evolution catalytic material in accordance with the present invention;

FIG. 4 is a sectional SEM image of a CoP/Si hydrogen evolution catalytic material in the invention;

FIG. 5 is a TEM morphology of a single-piece nanosheet of the CoP/Si hydrogen evolution catalytic material of the present invention;

FIG. 6 is a high power TEM image of the CoP/Si hydrogen evolution catalytic material of the present invention.

FIG. 7 is a HER performance test chart of CoP/Si hydrogen evolution catalytic material obtained by different phosphating temperature treatment in the invention;

FIG. 8 is a HER performance test chart of CoP/Si hydrogen evolution catalytic material prepared under different deposition electric quantities in the invention;

FIG. 9 is a diagram of a test of the photoelectrocatalytic hydrogen evolution performance of CoP/Si hydrogen evolution catalytic material prepared by different deposition electric quantities.

Detailed Description

The present invention will be described in more detail below with reference to experimental embodiments. In the present invention, unless otherwise specified, the experimental raw materials used are commercially available, and the instruments and equipment used for material preparation, characterization and related performance tests are all experimental equipment commonly used in the art.