Co-Fe @ FeF catalyst and two-dimensional nano-array synthesis method
阅读说明：本技术 一种Co-Fe@FeF催化剂及二维纳米阵列合成方法 (Co-Fe @ FeF catalyst and two-dimensional nano-array synthesis method ) 是由 黄金 邵兵 庞卫 谭晓琼 唐聪 于 2019-11-14 设计创作，主要内容包括：本发明涉及无机化学以及电催化研究领域,具体为一种Co-Fe@FeF催化剂及二维纳米阵列合成方法,通过泡沫铁浸泡在硝酸钴和过氧化氢的混合溶液中,原位生长得到在泡沫铁表面形成呈二维纳米阵列的无定形Co/Fe羟基氧化物,具有优异的电化学稳定性,在高电流密度下使用寿命长,同时展现出潜在工业应用价值前景。(The invention relates to the field of inorganic chemistry and electrocatalysis research, in particular to a Co-Fe @ FeF catalyst and a two-dimensional nano-array synthesis method.)
1. A Co-Fe @ FeF catalyst comprising a composite of a Co/Fe oxyhydroxide and a foamed iron, wherein the Co/Fe oxyhydroxide forms a two-dimensional nanoarray in an amorphous state on the surface of the foamed iron.
2. A method for synthesizing a two-dimensional nano array of a Co-Fe @ FeF catalyst is characterized by at least comprising the following steps of: and sequentially soaking the foamed iron in HCl solution, ethanol and acetone for ultrasonic treatment, then washing with deionized water, and then placing in a vacuum oven for drying to obtain the Co/Fe oxyhydroxide with a gray black surface.
3. The preparation method of claim 2, wherein the treated foam iron is soaked in a mixed solution of cobalt nitrate and hydrogen peroxide, and the growth of the two-dimensional nano-array of mixed metal oxyhydroxide is controlled by controlling the soaking time.
4. The method according to claim 3, wherein the mixed solution is in a ratio of Co (NO)3)2·6H2O (0.7275 g, 2.5 mmol) and 5% H2O2(25 mL)。
5. The method according to claim 4, wherein the soaking time is 1 to 10 minutes.
Technical Field
The invention relates to the field of inorganic chemistry and electrocatalysis research, in particular to a Co-Fe @ FeF catalyst and a two-dimensional nano-array synthesis method.
Background
In order to solve the problems of energy crisis and environmental pollution caused by excessive consumption of the traditional fossil fuels, the development of efficient and environment-friendly energy conversion and storage technology is important. The electrocatalytic Oxygen Evolution Reaction (OER) is a core process of energy storage and conversion such as hydrogen production by water electrolysis and metal-air batteries, and the reaction involves transfer of four electrons, is a kinetic slow reaction, and requires to design and prepare a high-efficiency catalyst to reduce the overpotential of the reaction. Noble metal-based OER electrocatalysts represented by Ru and Ir have excellent electrocatalytic properties, but their high price and scarce reserves hinder their industrial applications. The first transition metal elements of cobalt (Co), nickel (Ni) and iron (Fe) are abundant and cheap, and the oxide or oxyhydroxide thereof shows good OER performance under alkaline conditions. Particularly, some hydroxyl compound two-dimensional nanomaterials of Co, Ni and Fe mixed metal show noble metal catalysts comparable to Ru-based and Ir-based catalysts due to large specific surface, complete exposure of active sites and excellent electron conductivity, and are considered to be one of the most promising OER electrocatalysts. However, the synthesis methods of these catalysts are mostly solvothermal methods or high-temperature calcination methods, which require a large amount of energy, generally require a long preparation time and multiple steps, and are not suitable for large-scale industrial production.
Moreover, most of the OER electro-catalysts with excellent performance can only be used at a current density of 10 mA cm–2Operating under the conditions of (1). However, the electrocatalysts required for industrialization require current densities of up to 500 mA cm at overpotentials of less than 300 mV–2The electrode material has good stability, and only a few electrode materials meet the requirement at present. In order to prepare an OER electrode material satisfying the industrial requirements, the following four approaches are generally used: (1) use of materials with high OER intrinsic catalytic activity; (2) the catalytically active sites are fully exposed to the surface of the material; (3) being able to withstand high intensity oxidation conditions; (4) readily adsorb the substrate and rapidly desorb the product. In addition, during OER, the catalyst must adhere to the electrode substrate to prevent detachment under conditions of substantial oxygen evolution. However, it is extremely difficult to prepare an electrode material capable of satisfying the above criteria at the same time. Therefore, it is still challenging to synthesize an OER electrode material with high electrochemical activity, good stability and low cost rapidly and environmentally.
Disclosure of Invention
The invention aims to provide a Co-Fe @ FeF catalyst and a two-dimensional nano-array synthesis method, and solves the problems in the background art.
In order to achieve the purpose, the invention provides the following technical scheme:
a Co-Fe @ FeF catalyst comprising a composite of a Co/Fe oxyhydroxide and a foamed iron, the Co/Fe oxyhydroxide forming a two-dimensional nanoarray in an amorphous state on the surface of the foamed iron.
A method for synthesizing a two-dimensional nano array of a Co-Fe @ FeF catalyst at least comprises the following steps of: and sequentially soaking the foamed iron in HCl solution, ethanol and acetone for ultrasonic treatment, then washing with deionized water, and then placing in a vacuum oven for drying to obtain the Co/Fe oxyhydroxide with a gray black surface.
Furthermore, the processed foam iron is soaked in a mixed solution of cobalt nitrate and hydrogen peroxide, and the growth of the mixed metal oxyhydroxide two-dimensional nano array is regulated and controlled by controlling the soaking time.
Further, the ratio of the mixed solution is Co (NO)3)2·6H2O (0.7275 g, 2.5 mmol) and 5% H2O2(25 mL)。
Furthermore, the soaking time is 1-10 minutes.
Compared with the prior art, the invention has the beneficial effects that:
the preparation method is unique and simple, the amorphous Co/Fe oxyhydroxide which is in a two-dimensional nano array is formed on the surface of the foamed iron by soaking the foamed iron in the mixed solution of the cobalt nitrate and the hydrogen peroxide and growing in situ, the electrochemical stability is excellent, the service life is long under high current density, and the potential industrial application value prospect is shown.
Drawings
FIG. 1 is an SEM photograph (a), a TEM photograph (b) and an electron diffraction photograph (c) of Co + Fe @ FeF-5 according to an embodiment of the present invention;
FIG. 2 is a schematic process flow diagram of the present invention;
FIG. 3 is a Raman spectrum of Co + Fe @ FeF-5 according to an example of the present invention;
FIG. 4 is an XPS spectrum of Co 2p for Co + Fe @ FeF-5 of an example of the present invention;
FIG. 5 is an XPS spectrum of Fe 2p for Co + Fe @ FeF-5 of an example of the present invention;
FIG. 6 is an XPS spectrum of O1 s for Co + Fe @ FeF-5 of an example of the present invention;
FIG. 7 is an LSV curve of FeF, Co-Fe @ FeF and RuO2 according to the present invention;
FIG. 8 is a CC curve for Co-Fe @ FeF-5 in accordance with an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described below with reference to the drawings in the embodiments of the present invention.
Referring to fig. 1 to 8, the technical solution provided by the present invention:
first, example 1(Co + Fe @ FeF-1):
(1) treating the foamed iron: firstly, soaking foam iron (Fe foam, FeF for short) with the area of S = 3 cm × 1cm in 0.1M HCl solution, ethanol and acetone in sequence for 3 minutes by ultrasonic treatment, then washing the foam iron three times by deionized water to remove oxides and oil stains on the surface of the FeF, and placing the foam iron on a 25-degree-of-freedom (25-degree-of-freedom) rackoCAnd drying in a vacuum oven for 12 hours to obtain the foam iron with a gray black surface.
(2) Soaking the treated FeF in Co (NO)3)2·6H2O (0.7275 g, 2.5 mmol) and 5% H2O2(25 mL) of the solution, after 1 minute at room temperature, there was almost no change in the surface of the gray-brown foam iron (the resulting reactant was named Co + Fe @ FeF-1).
Third, example 2 (Co + Fe @ FeF-5):
(1) treating the foamed iron: firstly, soaking foam iron (Fe foam, FeF for short) with the area of S = 3 cm × 1cm in 0.1M HCl solution, ethanol and acetone in sequence for 3 minutes by ultrasonic treatment, then washing the foam iron three times by deionized water to remove oxides and oil stains on the surface of the FeF, and placing the foam iron on a 25-degree-of-freedom (25-degree-of-freedom) rackoCAnd drying in a vacuum oven for 12 hours to obtain the foam iron with a gray black surface.
(2) Soaking the treated FeF in Co (NO)3)2·6H2O (0.7275 g, 2.5 mmol) and 5% H2O2(25 mL) in a solution, and after 5 minutes at room temperature, it was blackish blackThe surface of the colored foamy iron became reddish brown (the resulting reactant was named Co + Fe @ FeF-5).
Third, example 3 (Co + Fe @ FeF-10):
(1) treating the foamed iron: firstly, soaking foam iron (Fe foam, FeF for short) with the area of S = 3 cm × 1cm in 0.1M HCl solution, ethanol and acetone in sequence for 3 minutes by ultrasonic treatment, then washing the foam iron three times by deionized water to remove oxides and oil stains on the surface of the FeF, and placing the foam iron in a vacuum oven at 25 ℃ for drying for 12 hours to obtain the foam iron with a gray black surface.
(2) Soaking the treated FeF in Co (NO)3)2·6H2O (0.7275 g, 2.5 mmol) and 5% H2O2(25 mL) of the reaction mixture, after 10 minutes at room temperature, the reddish brown color on the surface of the gray black foam iron was darkened (the resulting reaction mixture was named Co + Fe @ FeF-10).
Second, observation and analysis of the embodiment:
and (3) observing Co + Fe @ FeF-5 by a scanning electron microscope and a transmission electron microscope, forming a two-dimensional nano array on the surface of the foamed iron, and enabling the product to be in an amorphous state (figure 1).
To determine the structure of the product, the product contained Co-O bonds (450 and 525 cm) as determined by Raman spectroscopy (FIG. 3)−1) And Fe-O bonds (660 cm)−1) And preliminarily determining that the product is Co/Fe oxyhydroxide.
In order to further confirm that the product is Co/Fe oxyhydroxide, the product contains the following components by the attribution of peaks through the X-ray photoelectron spectrum (figures 4-6) of a test product: co2+And Co3+(780.5 eV to 795.5 eV are respectively assigned as Co 2p3/2And Co 2p1/2The peak of (a) is Co at each of satellite peaks of-787.0 eV and-803.0 eV2+And Co3+Characteristic peak of) Fe2+And Fe3+(724.5 eV and 726.5 eV are respectively assigned to Fe2+And Fe3+Fe 2p of1/2Peaks at 711.0 eV and 713.5 eV are respectively assigned to Fe2+And Fe3+Peak of) and O and OH–(-) -531.0 eV and ~532.5 eV are respectively assigned to O and OH–Characteristic peak of). And combining the Raman spectrum and the X-ray photoelectron spectrum to show that the two-dimensional nano array grown on the surface of the foamed iron in situ is amorphous Co/Fe oxyhydroxide.
Secondly, electrochemical test:
the electrochemical test is carried out by collecting with CHI 660E electrochemical workstation, using saturated Ag/AgCl electrode as reference electrode, platinum wire as counter electrode, and working electrode of S = 1cm2The electrolyte solution of (1) was a KOH solution of 1 mol/L. The voltage windows of CV and LSV scanning are both 0.1-0.6V, and the scanning speeds are respectively 50 mV s−1And 5 mV s−1The anode current values of CC were 10 mA, 100 mA and 500 mA, respectively.
The mathematical expression for converting the potential of a Reversible Hydrogen Electrode (RHE) is as follows:
E(RHE) =E(Ag/AgCl) + 0.197 V + 0.059pH –IR u
in the formula:Ifor the purpose of the current to be tested,R uthe solution impedance is.
Activating the sample by cyclic voltammetry, performing linear scanning on the sample after the CV curves are overlapped, and converting LSV into RHE, Co + Fe @ FeF-5 at 10 mA cm−2And 500 mA cm−2The overpotential of the alloy is respectively 208 mV and 298 mV, which are superior to that of Co + Fe @ FeF-1, Co + Fe @ FeF-10 and noble metal RuO2Performance of (fig. 7).
Sequentially at 10 mA cm−2、100 mA cm−2And 500 mA cm−2The voltage is hardly increased after the electrolysis for 60 hours under the current density condition, the electrochemical stability is excellent (figure 8), the electrocatalytic OER performance of Co + Fe @ FeF-5 obtained by collecting the oxygen amount is calculated to meet the requirement of industrial production, and the potential industrial application value is realized.
In conclusion, the amorphous Co/Fe oxyhydroxide in a two-dimensional nano array is formed on the surface of the foam iron by soaking the foam iron in the mixed solution of cobalt nitrate and hydrogen peroxide and growing in situ, so that the amorphous Co/Fe oxyhydroxide has excellent electrochemical stability and long service life under high current density, and shows potential industrial application value prospects.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention, and it is to be understood that the invention is not limited thereto, but may be modified within the scope of the appended claims.