CN109852994B

CN109852994B - Co9S8Preparation method of nitrogen-doped carbon composite array electrode

Info

Publication number: CN109852994B
Application number: CN201910130122.5A
Authority: CN
Inventors: 黄妞; 闫术芳; 曹星明
Original assignee: China Three Gorges University CTGU
Current assignee: China Three Gorges University CTGU
Priority date: 2019-02-21
Filing date: 2019-02-21
Publication date: 2021-02-02
Anticipated expiration: 2039-02-21
Also published as: CN109852994A

Abstract

The invention provides a dual functionCo of (A)₉S₈The preparation method of the nitrogen-doped carbon composite array electrode comprises the steps of preparing a basic cobalt salt needle array in-situ electrode by using a chemical bath deposition method, growing polydopamine on the surface of the basic cobalt salt array by using dopamine, adding thiourea in a protective atmosphere, carrying out a vulcanization reaction by using a CVD method, converting the polydopamine into a nitrogen-doped carbon material in the reaction process, and converting the basic cobalt salt into Co under the thiourea atmosphere₉S₈. The product obtained by the technical scheme of the invention has various high electrocatalytic active sites, including nitrogen-doped active sites in the carbon material and other lattice defects caused by the nitrogen-doped active sites, and has excellent electrocatalytic oxygen reduction (ORR) performance; co₉S₈The method has better performance of electrocatalytic Oxygen Evolution Reaction (OER); furthermore Co₉S₈The heterojunction formed with carbon material also has excellent electrocatalytic OER and OER properties.

Description

Co9S8Preparation method of nitrogen-doped carbon composite array electrode

Technical Field

The invention relates to an in-situ electrode and preparation thereof, belonging to the field of energy storage and conversion materials and devices.

Background

With the increasing demand of people for clean energy and sustainable energy, the development of renewable energy technologies with low cost, high activity and durability, such as fuel cells, metal-air batteries and the like, is a scientific challenge in modern society. It is noteworthy that the technologies that enable these advances are highly dependent on a range of electrochemical reactions in our daily lives, such as Oxygen Evolution Reaction (OER) and Oxygen Reduction Reaction (ORR). However, these oxygen-based electrochemical reactions are limited by the slow kinetics and efficiency in renewable energy technologies. Noble metal-based electrocatalysts discovered to date (e.g., Pt/C, RuO)₂Ir/C) has higher catalytic activity on ORR or OER. However, none of the commercial catalysts satisfactorily performs both reactions simultaneously. In addition, the poor long-term durability of the catalytic center due to structural degradation or poisoning during electrochemical operation has also prevented its widespread use. In recent years, some cobalt oxide, cobalt sulfide, cobalt-based nanocomposites have been reported to have bifunctional electrocatalytic properties. Among these cobalt compounds, cobalt-rich sulfide (Co)₉S₈) The method is attracting attention of researchers due to attractive application of the method in aspects of water desulfurization and the like. However, due to pure Co₉S₈The specific surface area of the nano particles is small, the conductivity is insufficient, the nano particles are easy to agglomerate, the stability in an alkaline medium is poor, the inherent active sites are lack, and the like, and the bifunctional catalytic performance realized by utilizing the nano particles is far from insufficient.

Disclosure of Invention

In view of the above, the object of the present invention is to provide a Co₉S₈The preparation method of the nitrogen-doped carbon composite array electrode has the advantages of low equipment requirement, low cost of required raw materials, easy control of reaction conditions, simple production process, good stability of formed products, small environmental pollution and the like, can be used for the double-function electrocatalyst of OER and ORR, and has great significance for batch production of in-situ electrodes.

Therefore, the invention provides a basic cobalt salt array electrode prepared by chemical bath, and strong interface coupling Co is prepared by annealing in the atmosphere of thiourea driven by inert gas after dopamine is polymerized and deposited₉S₈The method for compounding the array electrode with the nitrogen-doped carbon comprises the following steps:

firstly, dissolving cobalt chloride and urea in deionized water at room temperature, wherein the concentration of the cobalt chloride is 50-200 mM; the mass fraction of the urea is 3-10%, and a needle-shaped basic cobalt salt array is grown on a conductive substrate in the aqueous solution by a chemical bath deposition method, wherein the chemical bath temperature is 70-100 ℃, and the chemical bath deposition time is 1-6 h.

The cobalt salt of the array is simply and rapidly grown on the conductive substrate by a chemical bath deposition method, and the array is uniform and firm. Taking carbon paper as an example, basic cobalt salt arrays are uniformly grown on each carbon fiber and graphite sheet in the carbon paper, and the basic cobalt salt is complex in composition and is an extremely advantageous precursor.

And secondly, depositing and polymerizing dopamine on the substrate on which the basic cobalt salt array grows, enabling the polydopamine to be uniformly coated on the surface of the basic cobalt salt array, flushing and drying the polydopamine, and then carrying out annealing reaction in an atmosphere of thiourea driven by inert gas, wherein the annealing temperature is 600-900 ℃ and the annealing time is 0.5-4 h.

The concentration of cobalt chloride in the chemical bath one-step solution is 50-200 mM, and the mass fraction of urea is 3-10%. The chemical bath deposition time is 1-6 h, and the water bath temperature is 70-100 ℃.

The dopamine polymerization condition is that the dopamine is slowly stirred in an alkalescent Tris buffer solution at room temperature, the polymerization time is 10-30 h, and the dopamine concentration is 0.1-10 mg/mL.

The inert gas is Ar gas or N₂The gas and sulfur atmosphere is thiourea. Wherein the annealing reaction temperature is 500-900 ℃, and the annealing reaction time is 0.5-4 h. The mass of thiourea used in the annealing process is 3-50 times of that of dopamine.

The polydopamine forms a nitrogen-doped carbon material in thiourea atmosphere, and basic cobalt salt is converted into Co in the atmosphere₉S₈. Poly-dopamine originally has higher polymerization degree, and carbon formed after carbonization has high graphitization degree and strong conductivity, thereby facilitating the generation of catalytic reaction; n elements contained in polydopamine and thiourea can be doped into a carbon skeleton or form graphitized nitrogen or pyrrole nitrogen or pyridine nitrogen on the surface in the carbon material forming process, so that the OER and ORR catalytic performance of the electrode can be improved; thirdly, thiourea evaporates at high temperature and dopes into the carbon skeleton to form nitrogen-doped carbon material, and Co is generated at the same time₉S₈. Fourthly, nitrogen-containing micromolecules released in the process of converting polydopamine into carbon material are favorable for forming Co-N_xAnd a Co-O bond.

In the technical scheme of the invention, Co is mixed₉S₈Compounding with conductive carbon and carbon-based materials is one of the effective ways to improve performance and stability, expand and improve their applications. These materials not only increase Co₉S₈Due to the redox cycling properties of the carbon atoms, the catalytic activity and stability are improved, and the ORR potential is lowered. In addition, doping of hetero atoms (N, O, S) into the carbon-based material can effectively generate active sites because high positive charge density induces charge transfer between adjacent carbon atoms and also changes O₂Adsorption mode, weakening the O-O bond, thereby achieving the purpose of high-efficiency ORR. Therefore, the invention aims to prepare the low-cost, high-efficiency and stable bifunctional electrocatalystOne kind of Co₉S₈With the compound array of nitrogen-doped carbon, wherein cobalt sulfide plays the function of catalysis OER and ORR reaction, and nitrogen-doped carbon plays the function of catalysis ORR reaction, can improve the whole electric conductivity of combined material simultaneously, accelerate electron transport and then improve catalytic reaction speed. In addition, after the cobalt sulfide is compounded with the carbon material, the intrinsic catalytic capability of the interface of the composite material can be improved due to the strong interface coupling effect of the cobalt sulfide and the carbon material.

Drawings

FIG. 1 OER-ORR Linear voltammetric Scan (LSV) of the sample prepared in example 1.

Figure 2 XRD pattern of the sample prepared in example 1.

FIG. 3 SEM image of sample prepared in example 1.

FIG. 4 OER-ORR linear voltammetric scan (LSV) of the sample prepared in example 2.

FIG. 5 OER-ORR Linear voltammetric Scan (LSV) of the sample prepared in example 3.

Detailed Description

The method for testing the OER and ORR performance LSV in the embodiment of the invention comprises the following steps: with Co₉S₈The nitrogen-doped carbon composite array electrode is used as a working electrode, a carbon rod is used as a counter electrode, a saturated Hg/HgO electrode is used as a reference electrode, the electrolyte is a 1M KOH aqueous solution, and the scanning speed is 10 mV/s. In the OER and ORR tests, oxygen was bubbled through the solution to saturate the oxygen naturally in aqueous KOH, and additionally, stirring was accompanied by 200 r.p.m. during the test.

Example 1:

0.15M CoCl was added at room temperature₂∙ 6H₂O, 6.25% by mass of urea was dissolved in 40 mL of deionized water. And soaking the carbon paper in the solution, reacting in a water bath at 90 ℃ for 2h, naturally cooling to room temperature, taking out the carbon paper, washing with deionized water for three times, and drying for later use. Soaking the carbon paper prepared in the above manner in 50 mL of Tris base with the concentration of 0.01M and the pH value of 8.5, adding 40 mg of dopamine, stirring for 24 hours at room temperature, washing the sample with deionized water for three times, and drying. Putting the carbon paper into a tube furnace, reacting at 350 ℃ for 2h under thiourea (0.2 g) airflow, then continuously heating to 700 ℃ for reacting for 2h, and naturally reactingCooling to room temperature and taking out to obtain CFP/Co₉S₈@ C in situ electrode.

FIG. 1 is a graph of the OER, ORR linear voltammetric scans (LSV) of the electrodes prepared in example 1. The current density when the electrode passes through is 10 mA/cm²When the potential corresponding to the oxygen production by the OER reaction in the alkaline aqueous solution is E₁₀= 1.550V, half-wave potential corresponding to ORR reaction in alkaline aqueous solution is E_1/2= 0.713V, the limiting current density can reach 6.0 mA/cm²，ΔE = E₁₀ - E_1/2 = 0.837 V。

FIG. 2 shows Co prepared in example 1₉S₈XRD pattern of the array electrode compounded with nitrogen-doped carbon. Comparison of Standard cards Co₉S₈PDF # -19-0364 and Graphite-PDF # -41-1487 show that the main component of the electrode prepared by this example is Co₉S₈And carbon, indicating that the electrode is made of Co₉S₈And carbon.

FIG. 3 shows Co prepared in example 1₉S₈SEM image of the array electrode composited with nitrogen-doped carbon. The combination of XRD shows that the Co-coated carbon electrode is prepared by this example₉S₈The outer layer of the particles is firmly wrapped and has pores, which is beneficial to the electron diffusion in the practical application of the electrode.

Example 2:

0.15M CoCl was added at room temperature₂∙ 6H₂O, 6.25% by mass of urea was dissolved in 40 mL of deionized water. And soaking the carbon paper in the solution, reacting in a water bath at 90 ℃ for 2h, naturally cooling to room temperature, taking out the carbon paper, washing with deionized water for three times, and drying for later use. Soaking the carbon paper prepared in the above manner in 50 mL of Tris base with the concentration of 0.01M and the pH value of 8.5, adding 30 mg of dopamine, stirring at room temperature for 24 hours, washing the sample with deionized water for three times, and drying. Putting the carbon paper into a tube furnace, reacting for 2 hours at 350 ℃ under thiourea (0.2 g) airflow, then continuously heating to 700 ℃ for reacting for 2 hours, naturally cooling to room temperature, and taking out to obtain CFP/Co₉S₈@ C in situ electrode.

FIG. 4 is a graph of the OER, ORR linear voltammetric scans (LSV) of the electrodes prepared in example 2. The current is known from the figureThe current density of the electrode passing through is 10 mA/cm²When the potential corresponding to the oxygen production by the OER reaction in the alkaline aqueous solution is E₁₀= 1.472V, half-wave potential corresponding to ORR reaction in alkaline aqueous solution is E_1/2= 0.743V, the limiting current density can reach 35.0 mA/cm²，ΔE = E₁₀ - E_1/2 = 0.729 V。

Example 3:

0.15M CoCl was added at room temperature₂∙ 6H₂O, 6.25% by mass of urea was dissolved in 40 mL of deionized water. And soaking the carbon paper in the solution, reacting in a water bath at 90 ℃ for 2h, naturally cooling to room temperature, taking out the carbon paper, washing with deionized water for three times, and drying for later use. Soaking the carbon paper prepared in the above manner in 50 mL of Tris base with the concentration of 0.01M and the pH value of 8.5, adding 50 mg of dopamine, stirring at room temperature for 24 hours, washing the sample with deionized water for three times, and drying. Putting the carbon paper into a tube furnace, reacting for 2 hours at 350 ℃ under thiourea (0.2 g) airflow, then continuously heating to 700 ℃ for reacting for 2 hours, naturally cooling to room temperature, and taking out to obtain CFP/Co₉S₈@ C in situ electrode.

FIG. 5 is a graph of the OER, ORR linear voltammetric scans (LSV) of the electrodes prepared in example 3. The current density when the electrode passes through is 10 mA/cm²When the potential corresponding to the oxygen production by the OER reaction in the alkaline aqueous solution is E₁₀= 1.539V, the half-wave potential corresponding to the ORR reaction in the alkaline aqueous solution is E_1/2= 0.736V, the limiting current density can reach 35.0 mA/cm²，ΔE = E₁₀ - E_1/2 = 0.803 V。

Claims

1. Co₉S₈The preparation method of the nitrogen-doped carbon composite array electrode is characterized by comprising the following steps:

(1) dissolving cobalt chloride and urea in deionized water, and growing a needle-shaped basic cobalt salt array on a conductive substrate by using a chemical bath deposition method, wherein the concentration of the cobalt chloride is 50-200 mM, the mass fraction of the urea is 3-10%, the chemical bath deposition time is 1-6 h, and the water bath temperature is 70-100 ℃;

(2) making dopamine in alkalescenceAfter polymerizing the buffer solution on the substrate on which the basic cobalt salt array grows in the protective atmosphere, adding thiourea in the buffer solution, and carrying out a vulcanization reaction by using a CVD method, wherein the weak alkaline buffer solution is Tris buffer solution with the concentration of 0.005-0.02M and the concentration of dopamine is 0.1-10 mg/mL, and the protective gas is Ar gas or N gas₂The atmosphere of gas and sulfur is thiourea, wherein the annealing reaction temperature is 500-900 ℃, the annealing reaction time is 0.5-4 h, and the mass of thiourea used in the annealing process is 3-50 times that of dopamine, so that Co is obtained₉S₈And nitrogen-doped carbon composite array electrodes.

2. Co according to claim 1₉S₈The preparation method of the nitrogen-doped carbon composite array electrode is characterized in that the conductive substrate comprises any one of carbon paper, carbon cloth, graphite paper, copper foam or nickel.

3. Co according to claim 1₉S₈The preparation method of the nitrogen-doped carbon composite array electrode is characterized in that the polymerization time of dopamine is 10-30 h, and the polymerization condition is stirring at room temperature.