CN113293407B

CN113293407B - Iron-rich nanobelt oxygen evolution electrocatalyst and preparation method thereof

Info

Publication number: CN113293407B
Application number: CN202110629867.3A
Authority: CN
Inventors: 刘伟; 李传明
Original assignee: Linyi University
Current assignee: Linyi University
Priority date: 2021-06-07
Filing date: 2021-06-07
Publication date: 2022-02-22
Anticipated expiration: 2041-06-07
Also published as: CN113293407A

Abstract

The invention discloses an iron-rich nanobelt oxygen evolution electrocatalyst and a preparation method thereof, belonging to the technical field of catalysts. In 1.0M KOH solution, the catalyst exhibits excellent OER catalytic performance: overpotential η at low specific current density₁₀＝230mV,η₅₀₀322mV and low Tafel 47.6mV/dec, and can be operated continuously and stably for 50 h. The catalyst has the shape of an ultrathin nanobelt, has a large specific surface area, is simple in preparation method, does not need high temperature or external voltage, and is efficient and energy-saving.

Description

Iron-rich nanobelt oxygen evolution electrocatalyst and preparation method thereof

Technical Field

The invention belongs to the technical field of catalysts, and particularly relates to an iron-rich nanobelt oxygen evolution electrocatalyst and a preparation method thereof.

Background

Hydrogen, as an environmentally friendly secondary energy, has the advantages of high combustion heat value, large application potential and the like, and is considered to be an ultimate energy source required by the human society. The method for producing hydrogen by electrocatalytic decomposition of water has the characteristics of green and mild method and high hydrogen production purity, and has a wide application prospect.

However, the anode reaction (oxygen evolution reaction, OER) for electrocatalytic decomposition of water is a four-electron transfer reaction, which requires a high reaction barrier, increases the energy consumption for electrolysis of water to produce hydrogen, and limits the large-scale application of the technology for electrocatalytic decomposition of water to produce hydrogen. The efficient oxygen evolution electrocatalyst can effectively reduce the overpotential of the OER reaction, thereby greatly reducing the energy consumption of water electrolysis hydrogen production.

Currently, noble metal oxides (RuO)₂Or IrO₂) Is the best performing OER catalyst, but its high price limits its large scale application. In recent years, transition metal-based OER catalysts have attracted extensive attention from researchers. Among the transition metal-based OER catalysts of the prior art, nickel-based and cobalt-based catalysts exhibit unusual OER catalytic performance. Iron, the second most abundant metal on earth, is less expensive than nickel and cobalt, but the iron-based OER catalysts are less active. In addition, the preparation process of the OER catalyst is largeHigh temperature or external voltage is needed, which increases the production cost of the catalyst. Therefore, the production of iron-based OER catalysts by a simple, efficient and energy-saving preparation process is essential for large-scale application of electrocatalytic decomposition of water to produce hydrogen.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a low-cost and high-efficiency iron-rich nanobelt oxygen evolution electrocatalyst capable of effectively reducing the overpotential of the OER reaction, and simultaneously provides a simple, high-efficiency and convenient preparation method of the catalyst.

In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:

an iron-rich nanobelt oxygen evolution electrocatalyst, which is a Co and/or V modified iron-rich nanobelt oxygen evolution electrocatalyst.

Preferably, the catalyst is an iron-rich nanobelt oxygen evolution electrocatalyst comprising Co and V modifications.

A preparation method of an iron-rich nanobelt oxygen evolution electrocatalyst comprises the following preparation steps:

(1) primary battery reaction system construction: adding CoCl₂·6H₂O solution and/or VCl₃Dissolving the solution in NaCl solution as electrolyte, soaking foamed nickel and foamed iron in the electrolyte and connecting them in series through conducting wire; because the chemically active types of nickel and iron are different, a closed loop is formed under the condition that a lead and an electrolyte exist, and thus a primary battery is formed;

(2) preparing an iron-rich nanobelt catalyst: and (2) placing the primary battery reaction system set up in the step (1) on a magnetic stirrer, and reacting at normal temperature to obtain the iron-rich nanobelt oxygen evolution electrocatalyst growing on the foamed nickel.

Preferably, the concentration of the NaCl solution in step (1) is 1M.

Preferably, the CoCl is used in the step (1)₂·6H₂The concentration of the O solution was 5mM, VCl₃The concentration of the solution was 5 mM.

Preferably, the CoCl is used in the step (1)₂·6H₂O solution and VCl₃The volume ratio of the solution is 10:1, CoCl₂·6H₂O solution and VCl₃The volume ratio of the solution mixed solution to the NaCl solution is 1: 1.

Preferably, the reaction time in step (2) is 8 hours.

The iron-rich nanobelt oxygen evolution electrocatalyst is applied to electrolyzed water.

The catalyst is prepared by connecting two different chemically active metals (Ni and Fe) and building a galvanic cell in the presence of electrolyte. Fe is oxidized into Fe under the action of a primary cell as an anode²⁺Ni as cathode and takes reduction reaction on its surface to generate OH^-While the metal ions (Co) in the electrolyte solution are simultaneously under the action of the galvanic cell²⁺And V³⁺) And Fe produced²⁺Will migrate to the relatively inert Ni surface and react with dissolved oxygen and OH generated^-Reacting and depositing on the surface of Ni to form the electrocatalyst.

Advantageous effects

(1) The preparation method is simple, efficient and energy-saving, the catalyst is prepared by a primary battery-driven method, the growth period is short, high temperature or external voltage is not needed, and the preparation method is efficient and energy-saving; in 1.0M KOH solution, the catalyst exhibits excellent OER catalytic performance: overpotential (eta) at low specific current density₁₀＝230mV,η₅₀₀322mV) and low Tafel (47.6mV/dec), and can be operated continuously and stably for 50 h; therefore, the iron-rich oxygen evolution catalyst obtained by the energy-saving primary battery driving method effectively reduces the overpotential and the energy consumption of the OER reaction;

(2) the catalyst is obtained by modifying cheap FeOOH with a small amount of Co and/or V, has low production cost and low reaction overpotential, and enables the electrocatalytic water decomposition reaction to be carried out under low applied voltage, thereby generating more O₂And H₂(ii) a At a current density of 10mA/cm²And 500mA/cm²The overpotential required is 230 mV and 322mV respectively;

(3) the catalyst has the shape of an ultrathin nanobelt, and electrochemical tests and DFT calculation show that the catalyst has a large specific surface area, is beneficial to contact reactants and diffusion of the reactants, and has excellent conductivity and appropriate Gibbs free energy to reaction intermediate products, so that the catalyst shows excellent OER catalytic performance.

Drawings

FIG. 1 is a morphology of (Co, V) -FeOOH obtained by scanning electron microscopy in example 1 of the present invention;

FIG. 2 is an XRD pattern of (Co, V) -FeOOH obtained by X-ray diffraction in example 1 of the present invention;

FIG. 3 is an XPS plot of (Co, V) -FeOOH obtained by X-ray photoelectron spectroscopy in example 1 of the present invention;

FIG. 4 is a morphology chart of Co-FeOOH obtained by scanning electron microscopy in example 2 of the present invention;

FIG. 5 is an XRD pattern of Co-FeOOH obtained by X-ray diffraction in example 2 of the present invention;

FIG. 6 is a morphology chart of V-FeOOH obtained by scanning electron microscopy in example 3 of the present invention;

FIG. 7 is an XRD pattern of V-FeOOH obtained by X-ray diffraction in example 3 of the present invention;

FIG. 8 is a morphology of FeOOH obtained by scanning electron microscopy in comparative example 1;

FIG. 9 is an XRD pattern of FeOOH obtained by X-ray diffraction in comparative example 1;

FIG. 10 is the LSV curve of comparative example 2 obtained by LSV test for samples of different precursor ratios;

FIG. 11 is an LSV curve of (Co, V) -FeOOH obtained by the LSV test of comparative example 2 at different reaction times;

FIG. 12 is a LSV curve of a sample doped with different elements;

FIG. 13 is Tafel of samples doped with different elements;

FIG. 14 is an electrochemical impedance spectrum of a sample doped with different elements;

FIG. 15 is a graph of the stability of (Co, V) -FeOOH;

FIG. 16 is a DOS plot of (Co, V) -FeOOH and FeOOH electrocatalysts;

FIG. 17 is a graph showing the free energies of adsorption of (Co, V) -FeOOH and FeOOH.

Detailed Description

The technical solution of the present invention is further described below with reference to specific embodiments, but is not limited thereto.

Example 1

And ultrasonically cleaning the foamed nickel with the length of 20mm and the width of 5mm for 30 minutes by using acetone, 1M HCl, absolute ethyl alcohol and deionized water in sequence to remove impurities on the surface. And ultrasonically cleaning the foamed iron with the same size for 30 minutes by using acetone, absolute ethyl alcohol and deionized water in sequence to remove impurities on the surface. And connecting the foamed nickel and the foamed iron by using a lead.

20mL of 1M NaCl, 18.2mL of 5mM CoCl were added to the reactor₂·6H₂O and 1.8mL of 5mM VCl₃. I.e. CoCl₂·6H₂O and VCl₃Is 10: 1. Reacting for 8h under the condition of room temperature and stirring, and obtaining the (Co, V) -FeOOH nano charged catalyst after the reaction is finished. The nano-sheet morphology of (Co, V) -FeOOH is obtained by using a scanning electron microscope, as shown in FIG. 1. The crystal structure of (Co, V) -FeOOH was obtained by X-ray diffraction, and as shown in FIG. 2, a small amount of doping of Co and V did not cause a change in the crystal structure. An XPS map of (Co, V) -FeOOH was obtained using X-ray photoelectron spectroscopy, and as shown in FIG. 3, the elemental ratio was close to Fe: co: v is approximately equal to 3:1.1:0.09, which shows that the content of Fe in the catalyst is far larger than that of Co and V.

Example 2

The experimental procedure was the same as in example 1, except that the electrolytes were prepared from 20mL of 1M NaCl and 20mL of 5mM CoCl₂·6H₂And O. After the reaction is finished, a small amount of Co-FeOOH nano charged catalyst with a Co modified FeOOH matrix is obtained. The morphology of the Co-FeOOH nanosheets is obtained by a scanning electron microscope, as shown in FIG. 4. The crystal structure of Co-FeOOH was obtained by X-ray diffraction, as shown in FIG. 5, indicating that a small amount of Co doping did not cause a change in the crystal structure.

Example 3

The experimental procedure was the same as in example 1, except that the electrolytes were made of 20mL of 1M NaCl and 20mL of 5mM VCl₃And (4) forming. After the reaction is finished, a small amount of V-FeOOH nano charged catalyst of V modified FeOOH matrix is obtained. The morphology of the nanosheet of V-FeOOH was obtained by scanning electron microscopy, as shown in FIG. 6. The crystal structure of V-FeOOH was obtained by X-ray diffraction, as shown in FIG. 7, illustrating the small amount of V doped with noCausing a change in the crystal structure.

Comparative example 1

And ultrasonically cleaning the foamed nickel with the length of 20mm and the width of 5mm for 30 minutes by using acetone, 1M HCl, absolute ethyl alcohol and deionized water in sequence to remove impurities on the surface. And ultrasonically cleaning the foamed iron with the same size for 30 minutes by using acetone, absolute ethyl alcohol and deionized water in sequence to remove impurities on the surface. And connecting the foamed nickel and the foamed iron by using a lead. A galvanic reaction system was constructed by adding 40mL of 0.5M NaCl as an electrolyte to the reactor and immersing the nickel foam and the iron foam connected to the lead wires into the above solution to a depth of 10 mm. The reaction was carried out for 8h with stirring at room temperature. After the reaction is finished, the FeOOH electrocatalyst is obtained. The nano-morphology of FeOOH is obtained by using a scanning electron microscope, as shown in FIG. 8; the crystal structure of FeOOH was obtained by X-ray diffraction, as shown in fig. 9.

Comparative example 2

The pretreatment of nickel foam and iron foam and the construction of the galvanic cell reaction system were performed in the same manner as in example 1, with the changes being electrolyte solution: changing CoCl in electrolyte solution₂·6H₂O and VCl₃The ratio of (1) to (2) was 16.7mL of 5mM CoCl₂·6H₂O and 3.3mL of 5mM VCl₃18.7mL of 5mM CoCl₂·6H₂O and 1.3mL of 5mM VCl₃I.e. CoCl₂·6H₂O and VCl₃Are 5:1 and 15:1, respectively.

Using the LSV curve, it was found that when CoCl was used as shown in FIG. 10₂·6H₂O and VCl₃The best catalytic performance was obtained for the sample obtained with a volume ratio of 10: 1. In addition, the growth time of the electrocatalyst was changed, and it was found using the LSV curve that the catalytic performance of the electrocatalyst was the best when the deposition time was 8h, as shown in fig. 11.

Test example 1

In a KOH solution with the concentration of 1M, the catalyst obtained under the different preparation conditions is used as a working electrode, the Hg/HgO electrode is used as a reference electrode, and a stone grinding rod is used as a counter electrode, so that the oxygen production performance of the sample by electrocatalytic decomposition of water is successfully tested. LSV curves of the electrocatalysts are shown in FIG. 12, with a small Co-doping of Co and VThe electrocatalyst (Co, V) -FeOOH of (2) exhibits optimum catalytic performance at currents of 10 and 500mAcm^-2The overpotentials required were 230 and 322 mV. FIG. 13 shows Tafel curves for different catalysts, with the Tafel slope for (Co, V) -FeOOH being 47.6 mV/dec. As shown in FIG. 14, which is a graph of electrochemical impedance of different catalysts, studies have shown that (Co, V) -FeOOH exhibits the smallest electrochemical AC impedance. The stability test is shown in FIG. 15, and after 50 hours of continuous operation, (Co, V) -FeOOH activity is not obviously reduced.

Test example 2

The catalysts (Co, V) -FeOOH and FeOOH obtained in example 1 were investigated as objects, and the electronic structures of the catalysts were investigated by the first principle. Calculation of Gibbs free energy

The formula: Δ G ═ E_DFT+ Δ ZPE-T Δ S. As shown in FIGS. 16 and 17, the band gap of (Co, V) -FeOOH is close to 0 compared with FeOOH, indicating a significant improvement in conductivity. As shown in FIG. 14, the adsorption free energy of (Co, V) -FeOOH to the reaction intermediate was significantly decreased.

It should be noted that the above-mentioned embodiments are only some of the preferred modes for implementing the invention, and not all of them. Obviously, all other embodiments obtained by persons of ordinary skill in the art based on the above-mentioned embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.

Claims

1. A preparation method of an iron-rich nanobelt oxygen evolution electrocatalyst is characterized in that the catalyst is a Co and/or V modified iron-rich nanobelt oxygen evolution electrocatalyst, and comprises the following preparation steps:

(1) primary battery reaction system construction: adding CoCl₂·6H₂O solution and/or VCl₃Dissolving the solution in NaCl solution as electrolyte, soaking foamed nickel and foamed iron in the electrolyte and connecting them in series through conducting wire;

(2) preparing an iron-rich nanobelt catalyst: placing the primary battery reaction system set up in the step (1) on a magnetic stirrer, and reacting at normal temperature to obtain an iron-rich nanobelt oxygen evolution electrocatalyst growing on foamed nickel;

the concentration of the NaCl solution in the step (1) is 1M;

CoCl described in step (1)₂·6H₂The concentration of the O solution was 5mM, VCl₃The concentration of the solution was 5 mM.

2. The method for preparing the oxygen evolution electrocatalyst for the iron-rich nanobelt according to claim 1, wherein the CoCl of step (1)₂·6H₂O solution and VCl₃The volume ratio of the solution is 10:1, CoCl₂·6H₂O solution and VCl₃The volume ratio of the solution mixed solution to the NaCl solution is 1: 1.

3. The method for preparing the oxygen evolution electrocatalyst with rich iron nanobelts according to claim 1, wherein the reaction time in the step (2) is 8 hours.