CN108183228A - A kind of nitrogen-doped carbon nano-array/cobalt ferrite material - Google Patents

Abstract

It the present invention provides a kind of nitrogen-doped carbon nano-array/cobalt ferrite material, is calcined and obtained by polyaniline iron cobalt metal organic framework, nano material is double oxide, large specific surface area, catalytic site are more, catalytic efficiency higher；By the excellent compatibility of metal organic framework and each metal ion species, it is readily synthesized uniform more metal spinelles to the present invention, bimetallic oxide and conducting polymer are combined with this, advantage be combined with each other between can making different type electrodes material, polyaniline can form the carbon of doping nitrogen by calcining simultaneously, it further improves electric conductivity, solves iron cobalt/cobalt oxide poorly conductive, the defects of stability is poor.

Description

A nitrogen-doped carbon nanoarray/cobalt ferrite material

technical field

The invention belongs to the field of electrode material preparation and relates to a nitrogen-doped carbon nano-array material loaded with cobalt ferrite.

Background technique

The electrocatalytic conversion between oxygen and water is a critical step in new energy technologies such as metal-air batteries, fuel cells, and water splitting. Currently, platinum and platinum composites are considered to be the best catalysts for the oxygen reduction reaction (ORR), while ruthenium and iridium oxides are the best catalysts for the oxygen evolution reaction (OER). However, these materials are costly and have poor durability, making them difficult to be widely used. Therefore, current research focuses on transition metal oxides as catalysts for OER. Ferrite MFe ₂ O ₄ (M = Co, Ni, Cu, etc.) has many advantages, such as: low cost, high abundance, low toxicity, etc., but its poor conductivity in the electrochemical process limits its catalytic activity and Stability, so it is necessary to find a way to overcome the problem of poor conductivity.

Contents of the invention

Aiming at the current problem of poor electrical conductivity of ferrite, the invention provides a nanomaterial based on an iron-cobalt polyaniline array, which has higher catalytic efficiency and better electrical conductivity.

The present invention also provides a preparation method of the above-mentioned electrode material.

In order to achieve the above object, the present invention adopts the following technical solutions.

A nitrogen-doped carbon nanoarray/cobalt ferrite (NC@CoFe ₂ O ₄ ) material obtained by calcination of polyaniline-iron-cobalt metal-organic framework (PANI-Fe/Co MOF) under protective gas.

The calcination temperature is 300-500°C, preferably 400°C; the calcination time is preferably 2-4h.

The protective gas is selected from nitrogen or inert gases, such as helium and argon.

The metal-organic framework of the iron-cobalt-polyaniline is prepared by the following method:

(1) Rinse and dry the carbon paper after pickling;

The acid is nitric acid. The concentration of the acid is 1 mol/L.

Pickling temperature is 60-90°C.

(2) On the surface of the carbon paper obtained in step (1), polyaniline nanoarrays (N-CNAs) were prepared by electrodeposition using perchloric acid and aniline as raw materials, and then rinsed and dried;

The mol ratio of described perchloric acid and aniline is 10:1.

The current in electrodeposition is 0.15mA/cm ² , and the deposition time is 5400s.

(3) Hydrothermal method On the surface of the carbon paper obtained in step (2), prepare polyaniline-iron-cobalt metal organics with iron salts, cobalt salts and DOBDC (2,5-dioxo-1,4-benzenedicarboxylic acid) skeleton.

The iron salt is preferably a ferrous salt, selected from ferrous chloride tetrahydrate.

The cobalt salt is selected from cobalt nitrate hexahydrate.

The molar ratio of the iron ion, cobalt ion and DOBDC is 56:29:25.

The hydrothermal temperature is 120° C., and the reaction time is 24 hours.

An application of the above-mentioned nitrogen-doped carbon nano-array/cobalt ferrite material in the preparation of an oxygen evolution reaction electrode.

An application of the above-mentioned nitrogen-doped carbon nano-array/cobalt ferrite material in battery electrodes and decomposing water.

The present invention has the following advantages:

The invention provides a nitrogen-doped carbon nanoarray material (NC@CoFe ₂ O ₄ ) based on cobalt ferrite loaded on the basis of polyaniline-iron-cobalt metal-organic framework (PANI-Fe/Co MOF) calcined under protective gas Obtained, the obtained material is a double oxide, with a large specific surface area, many catalytic sites, and higher catalytic efficiency; the present invention makes it easy to synthesize a uniform multi-metallic spinel through the good compatibility of the metal organic framework and various metal ions In this way, the combination of double metal oxide and conductive polymer can combine the advantages of different types of electrode materials. At the same time, polyaniline can form carbon doped with nitrogen through calcination, which further improves the conductivity and solves the problem of iron and cobalt oxidation. The defects of poor electrical conductivity and poor stability. In addition, the preparation method of the electrode material is simple, the cost is low, the stability is good, and its performance is excellent under alkaline conditions.

Description of drawings

Figure 1 is a scanning electron microscope image of N-CNAs and NC@CoFe ₂ O ₄ ; where a is for N-CNAs, b is for NC@CoFe ₂ O ₄ ;

Figure 2 shows the linear voltammetry sweep curves of NC@CoFe ₂ O ₄ and N-CNAs tested in 1M KOH electrolyte solution;

Figure 3 is the cyclic voltammetry curve of NC@CoFe ₂ O ₄ tested in 1M KOH electrolyte solution;

Figure 4 is the sweep current diagram of NC@CoFe ₂ O ₄ ;

Figure 5 is the long-term stability curve of NC@CoFe ₂ O ₄ in 1M KOH electrolyte solution;

Fig. 6 is the impedance diagram of NC@CoFe ₂ O ₄ , N-CNAs and carbon paper.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings, but the present invention is not limited by the following embodiments.

Example 1 Preparation of nitrogen-doped carbon nanoarray/cobalt ferrite material.

1.1 Preparation of carbon paper

Take an appropriate amount of water and put it into a large beaker, put the prepared carbon paper into a 50mL beaker, take 20mL of ultrapure water and add it to the beaker, then slowly add 1.345mL of HNO ₃ with a mass fraction of 68% to the beaker middle. Put the small beaker into the beaker, put it on a magnetic stirrer for heating in a water bath, boil the carbon paper with acid at 90°C for 1 hour; take out the boiled carbon paper, mark it on the carbon paper, and take a 50mL small beaker Clean it up, and add an appropriate amount of ultrapure water to it, add the marked carbon paper to it, perform ultrasonic cleaning for 5-10 minutes, then replace the ultrapure water with ethanol and ultrasonically clean for 5 minutes; then put it in an oven for drying .

1.2 Preparation of polyaniline nanoarrays (N-CNAs)

Take 50mL of ultra-pure water into the beaker, place the beaker on a magnetic stirrer and start stirring, take 4.310mL of HClO ₄ into the beaker with a pipette gun, and then add 0.460mL of aniline solution into the previous beaker , continue to stir until the solution is completely mixed; pour the above solution into the cleaned electrolytic cell, use the prepared carbon paper as the working electrode, take the Ag/AgCl reference electrode, install the graphite electrode on the electrolytic cell, and then use The electrochemical workstation performs 0.15mA/cm ² , 5400s constant current electrochemical deposition; after the deposition is completed, the obtained carbon paper is removed, rinsed with ultrapure water, and then dried in an oven to finally obtain green carbon paper.

1.3 Preparation of polyaniline-iron-cobalt metal-organic framework (PANI-Fe/Co MOF)

Take 10mL of DMF solution into the beaker, pipette gun to take 2.000mL of absolute ethanol and 1.000mL of ultrapure water into the beaker, place the beaker on a magnetic stirrer, stir the solution and mix evenly; use an electronic balance to weigh 40mg of DOBDC , 90mgFeCl ₂ ·4H ₂ O, 68mg Co(NO ₃ ) ₂ ·6H ₂ O were added to the above solution, and continued to stir until the solid was completely dissolved, and the solution turned dark blue at this time; the carbon paper obtained in 1.2 Stand vertically in a hydrothermal kettle, pour the above dark blue solution into the reaction kettle, and then place the reaction kettle in an oven at 120°C for hydrothermal reaction for 24 hours; after the reaction is completed, take out the obtained sample and wash it with ethanol for more times, and then vacuum-dried at 60°C for 12 hours.

1.4 Calcination

The sample obtained in 1.3 was calcined in a tube furnace at 400°C for 2 hours in an argon atmosphere to obtain cobalt ferrite supported on nitrogen-doped carbon nanoarray material (NC@CoFe ₂ O ₄ ).

Example 2 Physicochemical properties of nitrogen-doped carbon nanoarray/cobalt ferrite material (NC@CoFe ₂ O ₄ ).

In Example 1, polyaniline nanoarrays and Figure 1, a) is a scanning electron microscope picture of polyaniline nanoarray materials (N-CNAs) during the synthesis process, b) is a nitrogen-doped carbon nanoarray/cobalt ferrite material (NC @CoFe ₂ O ₄ ) scanning electron microscope pictures, it can be seen that N-CNAs and NC@CoFe ₂ O ₄ were successfully prepared.

Example 3 Catalytic activity of nitrogen-doped carbon nanoarray/cobalt ferrite material (NC@CoFe ₂ O ₄ ).

3.1 Linear sweep voltammetry

The linear sweep voltammetry curves corresponding to the detection (0V~0.8V vs.Ag/AgCl) of N-CNAs and NC@CoFe ₂ O ₄ in 1M KOH electrolyte solution are shown in Figure 2: the starting point of NC@CoFe ₂ O ₄ The initial overpotential is 1.42V, and that of N-CNAs is 1.57V. The initial overpotential of NC@CoFe ₂ O ₄ is relatively low, and the potential required for oxygen evolution reaction is relatively low. It can be seen that the OER catalytic activity of NC@CoFe ₂ O ₄ is stronger than that of N-CNAs.

3.2 Electrochemical surface active area

The cyclic voltammetry curve (0V~0.8V vs.Ag/AgCl) of NC@CoFe ₂ O ₄ tested in 1M KOH electrolyte solution is shown in Figure 3, and it was detected in 1M KOH electrolyte solution (-0.05V~0.05V vs .Ag/AgCl, the scan rate is 20, 40, 60, 80, 100mV/s) the scan rate current of NC@CoFe ₂ O ₄ , combined with Figure 4, its electrochemical surface active area is 8.3784, indicating that NC@CoFe ₂ O ₄ has more active sites for electrochemical reactions.

3.3 i-t long-term stability

The long-term stability of it of NC@CoFe ₂ O ₄ was detected in 1M KOH electrolyte solution (0.6V vs. Ag/AgCl, time 36000s), as shown in Figure 5. It can be seen from the figure that the curve is relatively flat, indicating that NC@CoFe ₂ O ₄ can remain stable for a long time, that is, the stability is better.

3.4 Impedance

The impedance of NC@CoFe ₂ O ₄ , N-CNAs and carbon paper was detected in 1M KOH solution, and the impedance Nyquist plot was obtained, as shown in Figure 6: From the figure, it can be seen that the slope of the curve of pure carbon paper is the largest, That is, the impedance is the smallest, and the impedance of NC@CoFe ₂ O ₄ is the largest, but the difference between the three is not large. At the same time, the impedance of the three is smaller than that of other reported materials, because the nano-array structure formed by polyaniline can effectively prevent aggregation and stacking, and reduce the internal resistance.

Claims (9)

1. A nitrogen-doped carbon nanoarray/cobalt ferrite material, characterized in that it is obtained by calcining polyaniline-iron-cobalt metal-organic frameworks under protective gas. 2. The nitrogen-doped carbon nanoarray/cobalt ferrite material according to claim 1, characterized in that the calcination temperature is 300-500°C. 3. The nitrogen-doped carbon nanoarray/cobalt ferrite material according to claim 1, wherein the protective gas is selected from nitrogen or an inert gas. 4. The nitrogen-doped carbon nanoarray/cobalt ferrite material according to claim 1, wherein the metal-organic framework of the iron-cobalt-polyaniline is prepared by the following method: (1) Rinse and dry the carbon paper after pickling; (2) On the surface of the carbon paper obtained in step (1), prepare polyaniline nano-arrays by electrodeposition using perchloric acid and aniline as raw materials, then rinse and dry; (3) Hydrothermal method On the surface of the carbon paper obtained in step (2), polyaniline-iron-cobalt metal-organic frameworks were prepared with iron salts, cobalt salts, and DOBDC. 5 . The nitrogen-doped carbon nanoarray/cobalt ferrite material according to claim 4 , wherein the pickling temperature in step (1) is 60-90° C. 6. nitrogen-doped carbon nanoarray/cobalt ferrite material according to claim 4, is characterized in that, the mol ratio of described perchloric acid and aniline is 10:1; The electric current of electrodeposition is 0.15mA/ ^cm , the deposition time is 5400s. 7. The nitrogen-doped carbon nanoarray/cobalt ferrite material according to claim 4, wherein the molar ratio of the iron ion, cobalt ion and DOBDC is 56:29:25; the hydrothermal temperature is 120°C , The reaction time is 24h. 8. An application of the nitrogen-doped carbon nanoarray/cobalt ferrite material as claimed in any one of claims 1-8 in the preparation of an oxygen evolution reaction electrode. 9. An application of the nitrogen-doped carbon nanoarray/cobalt ferrite material as claimed in any one of claims 1-8 in battery electrodes and decomposed water.