阅读说明：本技术 一种中空CoOOH/FeOOH纳米颗粒催化剂的制备方法 (Preparation method of hollow CoOOH/FeOOH nanoparticle catalyst ) 是由 秦伟 张旭东 贾鑫 卢松涛 康红军 于 2021-09-10 设计创作，主要内容包括：本发明公开了一种中空CoOOH/FeOOH纳米颗粒催化剂的制备方法,属于新能源材料技术以及电化学催化领域。本发明通过自模板的方法进行合成,首先在室温下通过络合反应合成铁参杂的普鲁士蓝类似物CoFe PBA,作为催化剂前驱体,再经过电场的作用和碱诱导制备中空结构的CoOOH/FeOOH催化剂,合成的CoOOH/FeOOH催化剂在碱性条件具有优良的析氧(OER)催化性能、优异的稳定性。该制备方法所用原料成本低、方法简单,易于操作,便于大规模生产。(The invention discloses a preparation method of a hollow CoOOH/FeOOH nanoparticle catalyst, belonging to the fields of new energy material technology and electrochemical catalysis. The method is synthesized by a self-template method, firstly, iron-doped Prussian blue analogue CoFe PBA is synthesized at room temperature through a complexation reaction and is used as a catalyst precursor, and then a CoOOH/FeOOH catalyst with a hollow structure is prepared through the action of an electric field and alkali induction, wherein the synthesized CoOOH/FeOOH catalyst has excellent Oxygen Evolution (OER) catalytic performance and excellent stability under an alkaline condition. The preparation method has the advantages of low cost of raw materials, simple method, easy operation and convenient large-scale production.)

1. A preparation method of a hollow CoOOH/FeOOH nanoparticle catalyst is characterized in that the method synthesizes an iron-doped Prussian blue analogue precursor CoFe PBA through a complexation reaction at room temperature, and the precursor is subjected to an electric field effect and an alkali induction to prepare the hollow CoOOH/FeOOH nanoparticle catalyst.

2. The method of claim 1, wherein the method comprises the steps of:

step 1, preparing CoFe PBA;

mixing Co (CN)₆ ^3-And Fe (CN)₆ ^3-Preparing reaction solution according to the proportion, and then adding Co²⁺Carrying out complex reaction with the reaction solution at room temperature to obtain CoFe PBA;

step 2, preparing CoOOH/FeOOH;

mixing CoFe PBA prepared in the step 1, ethanol, water and Nafion to obtain a dispersion solution, dripping the dispersion solution on carbon paper to prepare an electrode, and performing OER treatment by taking the prepared electrode as an anode in a three-electrode system with an electrolyte of a 1mol/L KOH solution to enable CoFe PBA to perform redox reaction to form CoOOH/FeOOH and obtain a CoOOH/FeOOH electrode;

step 3, preparing hollow CoOOH/FeOOH;

and (3) applying current to the CoOOH/FeOOH electrode obtained in the step (2) to enable the CoOOH/FeOOH to generate the kirkendalk effect on the solid CoOOH/FeOOH to form CoOOH/FeOOH with a hollow structure, and marking the CoOOH/FeOOH as CoOOH/FeOOH NB.

3. The method for preparing a hollow CoOOH/FeOOH nanoparticle catalyst as claimed in claim 1, wherein the Co (CN) in step 1₆ ^3-And Fe (CN)₆ ^3-In a molar ratio of X: (5-X), wherein X is 1, 2, 3, 4 or 5.

4. The method for preparing a hollow CoOOH/FeOOH nanoparticle catalyst according to claim 1, wherein the step of preparing is carried outCo (CN) in step 1₆ ^3-And Fe (CN)₆ ^3-In a molar ratio of 4: 1.

5. the method for preparing a hollow CoOOH/FeOOH nanoparticle catalyst as claimed in claim 1, wherein the molar ratio of the reactants in the complexation reaction in step 1 is n (Co)²⁺)：n(C₆H₅Na₃O₇)：n(Co(CN)₆ ^3-+Fe(CN)₆ ^3-)＝4：1：1。

6. The method for preparing a hollow CoOOH/FeOOH nanoparticle catalyst according to claim 1, wherein the OER treatment parameters in step 2 are as follows: the sweep rate is 5mV/s, and the voltage is 0-0.7V.

7. The method for preparing a hollow CoOOH/FeOOH nanoparticle catalyst according to claim 1, wherein the current in step 3 is 10mA, and the current application time is 3 h.

Technical Field

The invention relates to a preparation method of a hollow CoOOH/FeOOH nanoparticle catalyst, belonging to the fields of new energy material technology and electrochemical catalysis.

Background

Hydrogen energy is a new clean energy source, and has the advantages of high energy density, abundant reserves, easy availability and the like, so that the hydrogen energy becomes one of important substitutes of fossil fuels. At present, three methods of steam methane reforming, coal gasification and water electrolysis exist as methods for preparing hydrogen energy, and the former two methods account for 95 percent of the hydrogen production industry at the present stage. The two methods of steam methane reforming and coal gasification have the defects of high energy consumption and pollution, the raw material used by water electrolysis is water, and other byproducts cannot be generated in the process of preparing hydrogen, so that the hydrogen production by water electrolysis is valued by people. At present, due to the defects of the technology and the like, the cost of the electrolyzed water is high, and the electrolyzed water is not easy to realize, so that the electrolyzed water only accounts for a small part of the hydrogen production industry.

When water is electrolyzed to prepare hydrogen, an electrolytic reaction is carried out under the standard potential of 1.23V to generate the hydrogen. The electrolytic water process involves two half-reactions: the oxygen evolution reaction of the anode is a four-electron reaction mechanism, a complex proton-coupled electron transfer process is involved in the oxygen evolution reaction process, so that an additional voltage is needed to overcome a reaction barrier, the voltage of the actual electrolyzed water is higher than 1.23V, and the extra part is called overpotential. In order to reduce the overpotential and the waste of energy, research on the mechanism of water electrolysis is focused, and the research finds that the electrode material is an important factor influencing the magnitude of the overpotential.

Currently, commonly used electrode materials are Ru/Ir-based materials and Pt-based materials, which are used in OER and HER processes, respectively, but due to scarcity, high cost and low stability, there is a need to find a good quality and cheap catalytic material to replace.

Disclosure of Invention

The invention provides a preparation method of a hollow CoOOH/FeOOH nanoparticle catalyst, aiming at solving the technical problems in the prior art.

The technical scheme of the invention is as follows:

a preparation method of a hollow CoOOH/FeOOH nanoparticle catalyst is characterized in that an iron-doped cobalt-based Prussian blue analogue CoFe PBA precursor is synthesized at room temperature through a complexation reaction, and the precursor is subjected to electric field assistance and alkali induction to prepare the hollow CoOOH/FeOOH catalyst which is marked as CoOOH/FeOOH NB.

Further defined, the method includes the steps of:

step 1, preparing CoFe PBA;

mixing Co (CN)₆ ^3-And Fe (CN)₆ ^3-Preparing reaction solution according to the proportion, and then adding Co²⁺Carrying out complex reaction with the reaction solution at room temperature to obtain CoFe PBA;

step 2, preparing CoOOH/FeOOH;

mixing CoFe PBA prepared in the step 1, ethanol, water and Nafion to obtain a dispersion solution, dripping the dispersion solution on carbon paper to prepare an electrode, and performing OER treatment by taking the prepared electrode as a positive electrode in a three-electrode system with an electrolyte of 1mol/LKOH solution to enable CoFe PBA redox reaction to form CoOOH/FeOOH, thereby obtaining an electrode with a surface of CoOOH/FeOOH and an inner part of CoFe PBA;

step 3, preparing hollow CoOOH/FeOOH;

and (3) applying current to the CoOOH/FeOOH electrode obtained in the step (2) to enable the CoOOH/FeOOH to generate the kirkendalk effect on the solid CoOOH/FeOOH, and recording the CoOOH/FeOOH with anion exchange forming a hollow structure as CoOOH/FeOOH NB.

Further limited, step 1 Co (CN)₆ ^3-And Fe (CN)₆ ^3-In a molar ratio of X: (5-X), wherein X is 1, 2, 3, 4 or 5.

Further limited, step 1 Co (CN)₆ ^3-And Fe (CN)₆ ^3-Is 4: 1.

further limiting, the molar ratio of the reactants in the complexation reaction in step 1 is n (Co)²⁺)：n(C₆H₅Na₃O₇)：n(Co(CN)₆ ^3-+Fe(CN)₆ ^3-)＝4：1：1。

Further defined, the OER processing parameters in step 2 are: the sweep rate is 5mV/s, and the voltage is 0-0.7V.

Further limiting, the current in step 3 is 10mA, and the current application time is 3 h.

The invention has the following beneficial effects:

(1) a new method for doping metal is provided. At room temperature, by controlling Co (CN)₆ ^3-And Fe (CN)₆ ^3-The ratio of the components realizes the control of element doping, lattice distortion and defects in the Prussian blue analogue CoFe PBA.

(2) The change of prussian blue analogue in the OER process was extensively studied. Reasonable assumptions are made about ion transfer in the OER process and are characterized in a reasonable manner.

Drawings

FIG. 1 is a flow chart and a mechanism diagram for the preparation of CoOOH/FeOOH NB;

FIG. 2 is an X-ray diffraction pattern of CoOOH/FeOOH NB and CoFe PBA;

FIG. 3 is a Fourier transform infrared spectrum of CoOOH/FeOOH NB and CoFe PBA;

FIG. 4 is a Linear Scanning Voltammogram (LSV) of CoOOH/FeOOH NB, CoOOH/FeOOH, CoFe PBA and carbon paper;

FIG. 5 is a Tafel plot for different electrode materials;

FIG. 6 is an electrochemical impedance plot (EIS) of different electrode materials;

FIG. 7 is an electrochemical surface area plot (ECSA) of CoOOH/FeOOH NB and CoFe PBA;

FIG. 8 is a time duration measurement of a CoOOH/FeOOHNB catalyst at a current density of 20 mV/s;

FIG. 9 is an SEM image of CoFe PBA;

FIG. 10 is a TEM image of CoFe PBA;

FIG. 11 is an SEM image of CoOOH/FeOOH NB;

FIG. 12 is a TEM image of CoOOH/FeOOH NB;

FIG. 13 is an electron diffraction pattern of CoOOH/FeOOH NB.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The experimental procedures used in the following examples are conventional unless otherwise specified. The materials, reagents, methods and apparatus used, unless otherwise specified, are conventional in the art and are commercially available to those skilled in the art.

Example 1:

(1) synthesis of CoFe PBA:

0.1538g of CoCl were weighed out₂·6H₂O and 0.04753g of C₆H₅Na₃O₇·2H₂O (sodium citrate), to 100ml of deionized water to prepare a solution A, 0.0105889g of K were weighed again₃FeC₆N₆(Potassium ferricyanide) and 0.043406g of K₃CoC₆N₆(Potassium cobalt cyanide) (Co (CN))₆ ^3-:Fe(CN)₆ ^3-4: 1) added to 100ml of deionized water to form a solution B. And putting the solutions A and B into ultrasound to uniformly disperse the solutions. And (3) dripping B into A in an ultrasonic environment, continuously carrying out ultrasonic treatment for 1h, then aging at room temperature for 24h, washing the powder obtained by the reaction with water and alcohol, and drying in an oven at the temperature of 70 ℃ overnight to obtain CoFe PBA. SEM and TEM of CoFe PBA are shown in FIG. 9 and FIG. 10, respectively.

(2) Preparation of CoOOH/FeOOH:

5mg of the synthesized CoFe PBA is weighed, 300 mu L of deionized water, 680 mu L of ethanol and 100 mu L of an Afion solution are added, ultrasonic treatment is carried out for 30min, then a uniformly dispersed solution is prepared, 120 mu L of the solution is uniformly coated on the treated carbon paper, and the treated carbon paper is dried. Taking the prepared electrode as a positive electrode to carry out oxygen evolution reaction, wherein the potential is 0-0.7V, the scanning speed is 5mV/s, the surface reacts under the assistance of an electric field, a lamellar structure CoOOH/FeOOH is generated in situ, and the cubic center is dissolved to form a hollow framework structure.

(3) Preparation of CoOOH/FeOHNB:

the current applied to the electrode was 10mA/cm²And (4) activating. After 3h of oxygen evolution reaction at the electrode, CoOOH/FeOOH NB with high exposed active sites is obtained. SEM, TEM and electron diffraction patterns of CoOOH/FeOOH NB are shown in FIGS. 11-13, respectively.

The performance analysis of CoFe PBA, CoOOH/FeOOH and CoOOH/FeOOH NB obtained in the above experimental process:

(1) x-ray diffraction analysis (XRD)

X-ray diffraction analysis is carried out on the prepared CoOOH/FeOOH NB and CoFe PBA, the result is shown in figure 2, compared with a standard map, three strong peaks of the CoFe PBA prepared by the complex reaction are shifted, namely crystal faces (200), (220) and (400) corresponding to the three strong peaks are distorted, and the fact that the prepared cobalt-based Prussian blue analogue CoFe PBA doped with iron is proved. In the X-ray diffraction curve of the sample CoOOH/FeOOH NB, the three strong peaks correspond to the (111), (110) and (221) crystal planes respectively. Compared with the standard PDF card of CoOOH, the CoOOH/FeOOH NB has larger peak position shift, and the peak position is not sharp and has amorphous characteristics, which indicates that other phases exist, because another straight metal element in the catalyst is Fe, FeOOH is supposed to be generated, namely the prepared CoOOH contains FeOOH substances, and the lattice distortion is serious.

(2) Fourier transform Infrared Spectroscopy (FT-IR spectra)

Fourier transform infrared spectroscopy analysis is carried out on the prepared CoOOH/FeOOH NB and CoFe PBA, the results are shown in figure 3, the precursor CoFe PBA is respectively 2170cm^-1And 2090cm^-1Has a peak corresponding to Co^Ⅲ-CN-Co^ⅡAnd Fe^Ⅲ-CN-Co^ⅡTensile vibration of the bond at 1650cm^-1The peak position at (b) corresponds to the stretching vibration of-OH. The CoOOH/FeOOH NB sample obtained after the electric field assisted preparation is only 1650cm^-1Shows a tensile vibration peak corresponding to-OH, and proves that under the assistance of an electric field, Co (CN)₆ ^3-And Fe (CN)₆ ^3-The ions are leached out and the CoFe PBA is converted to CoOOH/FeOHNB.

(3) Linear Sweep Voltammetry (LSV)

Scanning with Linear Sweep Voltammetry (LSV) at a scan rate of 5mV/sThe electrochemical activity of CoOOH/FeOOH was studied in 1.0M KOH, as shown in FIG. 4. The overpotential of activated CoOOH/FeOOH can reach the reference current of 10mA/cm only by 271mV, while the overpotentials of the precursors CoCo PBA, CoOOH/FeOOH and carbon paper are much higher, namely 330mV, 310mV and 440 mV. Simultaneously with IrO₂Compared with the electrocatalyst, the activated CoOOH/FeOOH NB also has high electrocatalytic performance.

(4) Tafel curve

As shown in FIG. 5, the slope of Tafel of CoOOH/FeOOH NB was 34.4mVdec at the lowest^-1And CoOOH/FeOOH particles (55.9 mVdec)^-1)、CoFe PBA(75.4mVdec^-1)。

(5) Electrochemical Impedance Spectroscopy (EIS)

FIG. 6 is the Electrochemical Impedance Spectroscopy (EIS) at 275mV overpotential, from which CoOOH/FeOOH NB has a smaller charge transfer resistance Rct. The 1.66 Ω of CoOOH/FeOOH NB is attributed to the larger contact area of CoOOH/FeOOH NB during OER, faster built-in conduction process.

(6) Electrochemical surface area (ECSA)

The electrochemical surface area (ECSA) was measured by calculating the electrochemical double layer capacitance (Cdl). Several CVs were performed in a small potential window between 1.187 and 1.287v (vsche), without any faraday process involved. Cdl values were observed for the following sequence (fig. 7): CoOOH/FeOOH NB (34 mF/cm)²)>CoFe PBA(24mF/cm²) It is shown that CoOOH/FeOHNB has larger catalytic activity area and more catalytic activity.

(7) Stability curve

Durability tests showed that CoOOH/FeOOH had good stability in 1M KOH, and the prepared catalytic material was maintained at 20mA/cm²At the next 50h, there was no significant performance degradation.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.