FeCoMoPC amorphous alloy for alkaline full-hydrolysis and preparation method thereof
Technical Field
The invention relates to an amorphous alloy and a preparation method thereof, in particular to a FeCoMoPC amorphous alloy for alkaline full-hydrolysis and a preparation method thereof, belonging to the technical field of catalysts for hydrogen production by water electrolysis.
Background
The problems of energy shortage and environmental pollution caused by economic development are increasingly serious, and in order to realize sustainable development of society, development of green new energy is urgently needed, and compared with renewable energy sources such as wind energy, solar energy, biomass energy and the like, hydrogen is a clean and efficient energy carrier, has high energy density, high combustion heat value and a clean combustion product H2And O. The water electrolysis hydrogen production has simple process and zero emission of pollution gas, so the method is regarded as the most promising technology for producing high-purity hydrogen and developing sustainable green energy. Water electrolysis is mainly composed of two half-reactions: the method comprises the following steps of cathodic Hydrogen Evolution (HER) and anodic Oxygen Evolution (OER), wherein the OER relates to a four-electron transfer process, slow dynamics of the OER is a key factor for restricting the hydrogen production efficiency by water electrolysis, and the development of an OER catalyst is crucial to reducing the energy consumption of hydrogen production by water electrolysis and improving the energy conversion rate.
Noble metals Pt, Ir or oxides thereof have high catalytic activity, but are expensive and scarce in reserves, so that the wide application of noble metal-based catalysts is greatly limited. In recent years, non-noble metal-based catalysts have been studied around mainly transition metals (Fe, Co, Ni) and their compounds, and amorphous alloys with special physical, mechanical and chemical properties have also attracted attention. Compared with the traditional crystalline material, the amorphous material has rich active sites and good corrosion resistance as an electrocatalyst, so that the amorphous alloy catalyst prepared by a transition metal system is expected to show excellent electrocatalytic activity. In addition, the tough amorphous strip prepared by the melt spinning method can be self-supported and directly used as an electrode, has no problem of stability loss caused by peeling from a substrate, and is more suitable for industrial application.
The FeCoPC series amorphous alloy strip is a hydrogen evolution reaction electrocatalyst with good electrocatalytic activity discovered in recent years. The existing research finds that FeCoPC amorphous alloy shows better acidic hydrogen evolution activity; however, in an acidic environment, a device is easily corroded, and in an alkaline environment, since catalytic electrolysis of water can protect the device and OER, which is an important limiting step for water electrolysis efficiency, generally has higher catalytic activity in an alkaline environment, development of a HER and OER catalyst suitable for use in an alkaline environment based on fecoppc amorphous alloy having acidic hydrogen evolution activity is more industrially applicable.
In addition, the specific surface area of the amorphous alloy strip is small, and based on the advantage of self-supporting, how to further increase the number of surface active sites and further improve the catalytic activity is also an important problem. According to the report that the amorphous alloy strip is used as a catalyst at present, the nano structure prepared by the dealloying method is an effective strategy for improving the catalytic activity of the block. For example, chinese patent application publication No. CN 111118523 a discloses a method for improving catalytic activity of Fe-based amorphous alloy in hydrogen evolution by electrolysis water through dealloying treatment, in which Fe-based amorphous alloy is immersed in strong alkaline solution for dealloying treatment to obtain nano porous structure with Fe as a component78Si13B9The amorphous alloy strip has the best performance, and the current density is 10mA cm-2The alkaline hydrogen evolution overpotential is 201 mV. However, the free dealloying method used in this patent is not only long in time and high in the concentration of the etching solution, but also requires stirring to make the etching uniform.
Based on the above, the applicant improves the existing amorphous alloy components and preparation method, and the technology of the invention is formed.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the problems that the existing FeCoPC amorphous alloy only shows acidic hydrogen evolution activity, the active specific surface area of a strip is small, and the electrocatalytic effect is poor, the invention provides the FeCoMoPC amorphous alloy for alkaline full-hydrolysis and the preparation method of the amorphous alloy, so that the activity of the amorphous alloy can be effectively improved, and the electrocatalytic effect is improved.
The technical scheme is as follows: the FeCoMoPC amorphous alloy for alkaline total hydrolysis has the chemical molecular formula (Fe) according to atomic percentage0.5Co0.5)80-xMoxP13C7Wherein the atomic percentage of Fe and Co is 1:1, and x is more than or equal to 0 and less than or equal to 10. Preferably, x is more than or equal to 3 and less than or equal to 7, and the FeCoMoPC amorphous alloy has better full-hydrolytic property.
The invention relates to a preparation method of FeCoMoPC amorphous alloy for alkaline full-hydrolysis, which comprises the following steps:
(1) prepared according to the percentage of each atom (Fe)0.5Co0.5)80-xMoxP13C7An amorphous alloy ribbon;
(2) adopting an electrochemical workstation three-electrode system to carry out the treatment on the (Fe) prepared in the step (1)0.5Co0.5)80-xMoxP13C7Carrying out constant potential corrosion on the amorphous alloy strip, taking out and cleaning a sample after the corrosion is finished, and drying at room temperature to obtain porous (Fe)0.5Co0.5)80-xMoxP13C7The amorphous alloy strip is the FeCoMoPC amorphous alloy for the alkaline full-hydrolysis.
In the above step (1), (Fe)0.5Co0.5)80-xMoxP13C7The preparation process of the amorphous alloy strip comprises the following steps: taking high-purity Fe, Co, Mo, FeP and C as raw materials, preparing a master alloy ingot by adopting electric arc melting and induction melting under the atmosphere of high-purity argon, and remelting the master alloy ingot for multiple times to ensure that the alloy components are uniform; remelting the obtained alloy ingot by a melt spinning method, spraying and quenching to obtain (Fe)0.5Co0.5)80-xMoxP13C7Is an amorphous alloy strip. Preferably, when the amorphous alloy strip is prepared by the melt spinning method, the rotating speed of the copper roller is controlled to be 3600-4200 revolutions per minute.
In the step (2), the electrochemical workstation adopts a three-electrode system of (Fe)0.5Co0.5)80-xMoxP13C7The amorphous alloy strip is taken as a working electrode, and preferably Ag/AgCl is taken as a reference electrode, and a graphite rod is taken as a counter electrode. Preferably, when the potentiostatic etching is carried out, the applied potential value is (Fe)0.5Co0.5)80-xMoxP13C7The potential interval corresponding to the active dissolution area of the polarization curve of the amorphous alloy. Further, the electrolyte for constant potential corrosion can be 0.5-1.0M H2SO4The etching time can be 8-130min, and the etching temperature can be room temperature.
Has the advantages that: compared with the prior art, the invention has the advantages that: (1) according to the invention, a small amount of Mo is doped in the FeCoPC amorphous alloy, the atomic percentage of Fe and Co is controlled to be 1:1, and the FeCoMoPC amorphous alloy with specific component content can simultaneously catalyze hydrogen evolution and oxygen evolution in an alkaline environment and can be used as a full-hydrolysis dual-function catalyst; (2) according to the invention, the FeCoMoPC amorphous alloy strip is subjected to dealloying treatment by the electrochemical method of constant potential corrosion, so that the active specific surface area of the amorphous alloy strip is obviously increased, and the electrocatalytic activity of the amorphous alloy is improved; compared with the existing free dealloying method, the treatment method provided by the invention is simple and easy to operate, has small harm, is uniform and efficient in corrosion, and the prepared FeCoMoPC amorphous alloy strip shows excellent catalytic activity and long-term stability, so that the method has an important significance in the application of the amorphous alloy strip in the aspect of catalyzing and electrolyzing water.
Drawings
FIG. 1 is (Fe) prepared in example0.5Co0.5)80-xMoxP13C7(X ═ 0,3,5,7,9) the X-ray diffraction pattern of the amorphous alloy ribbon;
FIG. 2 is (Fe) prepared in example0.5Co0.5)80-xMoxP13C7(x ═ 0,3,5,7,9) polarization curves for amorphous alloy ribbons;
FIG. 3 shows (Fe) before and after the electrochemical dealloying treatment in the examples0.5Co0.5)80P13C7OER linear scanning voltammetry of the amorphous alloy strip in 1.0M KOH electrolyte;
FIG. 4 shows (Fe) before and after the electrochemical dealloying treatment in the examples0.5Co0.5)80P13C7HER linear sweep voltammetry of the amorphous alloy strip in 1.0M KOH electrolyte;
FIG. 5 shows (Fe) after electrochemical dealloying in the examples0.5Co0.5)80-xMoxP13C7(x ═ 3,5,7,9) OER linear sweep voltammogram of amorphous alloy ribbons in 1.0M KOH electrolyte;
FIG. 6 shows (Fe) after electrochemical dealloying in the examples0.5Co0.5)80-xMoxP13C7(x ═ 3,5,7,9) HER linear sweep voltammogram of amorphous alloy ribbons in 1.0M KOH electrolyte;
FIG. 7 shows (Fe) after electrochemical dealloying in the examples0.5Co0.5)75Mo5P13C7Scanning electron microscope pictures of the amorphous alloy strip after linear scanning voltammetry activation: (a) after OER activation, (b) after HER activation;
FIG. 8 shows (Fe) after electrochemical dealloying in the examples0.5Co0.5)75Mo5P13C7Fully-hydrolyzed linear sweep voltammetry of the amorphous alloy strip in 1.0M KOH electrolyte;
FIG. 9 shows (Fe) after electrochemical dealloying in the examples0.5Co0.5)75Mo5P13C7The amorphous alloy strip is 10mA cm in 1.0M KOH electrolyte-2V-t curve at current density.
Detailed Description
The technical solution of the present invention is further described in detail with reference to the accompanying drawings and embodiments.
Examples
(1) Preparation of (Fe)0.5Co0.5)80-xMoxP13C7(x ═ 0,3,5,7,9) amorphous alloy ribbonThe preparation process comprises the following steps:
firstly, converting and weighing required high-purity Fe, Co, Mo, FeP and C according to atomic percent, firstly, smelting the Fe, Co, Mo and C into alloy ingots by electric arc in the atmosphere of high-purity argon, remelting the alloy ingots for at least 4 times to ensure that the alloy components are uniform, then, mixing the alloy ingots with the FeP, and carrying out induction smelting to obtain (Fe)0.5Co0.5)80-xMoxP13C7(x is 0,3,5,7,9) a master alloy ingot.
② adopting single-roller strip-throwing equipment to make mother alloy ingot (Fe)0.5Co0.5)80-xMoxP13C7(x is 0,3,5,7,9) induction melting in argon atmosphere, spraying the molten metal onto copper roller with 3600-4200 rpm by instantaneous pressure difference (0.02MPa), to obtain (Fe) with width of 1-2mm and thickness of 20-30 μm0.5Co0.5)80-xMoxP13C7An alloy strip.
FIG. 1 is (Fe) prepared0.5Co0.5)80-xMoxP13C7The X-ray diffraction pattern of the (X ═ 0,3,5,7,9) alloy strip shows only diffuse scattering peaks on the XRD pattern, indicating that the (Fe) produced is0.5Co0.5)80-xMoxP13C7The alloy strip is in an amorphous structure.
FIG. 2 is (Fe) prepared0.5Co0.5)80-xMoxP13C7Polarization curve of (x ═ 0,3,5,7,9) alloy strip, it can be seen that as Mo content increases, (Fe) increases0.5Co0.5)80-xMoxP13C7The corrosion resistance of (2) is improved.
(2) For (Fe) prepared as described above0.5Co0.5)80-xMoxP13C7The (x ═ 0,3,5,7,9) amorphous alloy strip is subjected to electrochemical dealloying treatment, and the treatment process is as follows:
to prepare (Fe)0.5Co0.5)80-xMoxP13C7The amorphous alloy strip is used as a working electrode, Ag/AgClAs reference electrode, graphite rod as counter electrode, electrolyte 0.5M H2SO4Corrosion potential of (Fe)0.5Co0.5)80-xMoxP13C7The active dissolution region of the polarization curve, corrosion potential in this example, was 0.11V. The etching time was as follows: (Fe)0.5Co0.5)80P13C7The corrosion time is 8-10min, (Fe)0.5Co0.5)77Mo3P13C7The corrosion time is 30-40min, (Fe)0.5Co0.5)75Mo5P13C7The corrosion time is 60-70min, (Fe)0.5Co0.5)73Mo7P13C7The corrosion time is 90-100min, (Fe)0.5Co0.5)71Mo9P13C7The etching time is 120-130 min.
After electrochemical dealloying (Fe)0.5Co0.5)80-xMoxP13C7Taking out the amorphous alloy strip, sequentially cleaning with deionized water and absolute ethyl alcohol to remove residual chemical substances on the surface of the amorphous alloy strip, and naturally drying to obtain porous (Fe)0.5Co0.5)80-xMoxP13C7。
Test one: comparison of electrochemical properties of amorphous alloy strips before and after electrochemical dealloying
Before and after electrochemical dealloying treatment (Fe)0.5Co0.5)80P13C7Carrying out electrochemical performance test on the amorphous alloy strip: adopting a three-electrode working system to perform electrochemical dealloying treatment on the (Fe) before and after0.5Co0.5)80P13C7The amorphous alloy strip is taken as a working electrode, Ag/AgCl is taken as a reference electrode, a graphite rod is taken as a counter electrode, and the working electrode is placed in a 1.0M KOH solution at 5mV s-1Linear voltammetric scans were performed at the sweep rate of (1).
FIGS. 3 and 4 show the electrochemical dealloying before and after (Fe)0.5Co0.5)80P13C7Amorphous alloyThe OER and HER linear sweep voltammograms of the strip, as seen from the graph, at a current density of 10mA cm-2When (Fe) is removed from the alloy0.5Co0.5)80P13C7The OER overpotential is reduced from 379mV before dealloying to 299mV, and the HER overpotential is reduced from 352mV to 121mV, which shows that the catalytic performance of the sample can be obviously improved through electrochemical dealloying.
And (2) test II: influence of Mo content on electrochemical performance of amorphous alloy strip
After electrochemical dealloying (Fe)0.5Co0.5)80-xMoxP13C7(x ═ 3,5,7,9) amorphous alloy ribbons were subjected to electrochemical performance testing: adopting a three-electrode working system, respectively adopting electrochemical dealloying treatment to obtain the product with different Mo contents0.5Co0.5)80-xMoxP13C7The amorphous alloy strip is taken as a working electrode, Ag/AgCl is taken as a reference electrode, a graphite rod is taken as a counter electrode, and the working electrode is placed in a 1.0M KOH solution at 5mV s-1Linear voltammetric scans were performed at the sweep rate of (1).
FIG. 5 shows the result of electrochemical dealloying (Fe)0.5Co0.5)80-xMoxP13C7(x ═ 3,5,7,9) OER linear sweep voltammogram of the amorphous alloy ribbon, as can be seen from FIG. 5, at a current density of 10mA cm-2When x is 3, x is 5, x is 7 and x is 9, the OER overpotentials of the FeCoMoPC amorphous alloy strip are respectively as follows: 260mV, 249mV, 241mV and 258 mV. FIG. 6 shows the result of electrochemical dealloying (Fe)0.5Co0.5)80-xMoxP13C7(x ═ 3,5,7,9) HER linear sweep voltammogram of the amorphous alloy ribbon, as can be seen from fig. 6, at a current density of 10mA cm-2When x is 3, x is 5, x is 7 and x is 9, the HER overpotentials of the FeCoMoPC amorphous alloy ribbon are respectively as follows: 123mV,126mV, 152mV and 177 mV. The above results show that the introduction of Mo in the FeCoPC system is favorable for oxygen evolution reaction but unfavorable for hydrogen evolution reaction.
FIG. 7 is electrochemical dealloying (Fe) activated by 3-cycle linear sweep voltammogram0.5Co0.5)75Mo5P13C7In the SEM image of (a), it can be observed that the sample surface is very rough, especially the OER activated sample has a large number of nanopores, significantly increasing the active area.
FIG. 8 shows the alloy after electrochemical dealloying (Fe)0.5Co0.5)75Mo5P13C7The test is to use two-electrode system to electrochemically strip (Fe)0.5Co0.5)75Mo5P13C7As can be seen from FIG. 8, the current density was 10mA cm and the current density was measured as an anode and a cathode, respectively-2When (Fe)0.5Co0.5)75Mo5P13C7The total hydrolysis potential of (1.617) V.
FIG. 9 shows the alloy after electrochemical dealloying (Fe)0.5Co0.5)75Mo5P13C7The result of the V-t curve chart shows that the sample still maintains better stability after 36h of full hydrolysis reaction.
From the above, the FeCoMoPC amorphous alloy strip is treated by electrochemical dealloying, so that the active specific surface area of the FeCoMoPC amorphous alloy strip can be remarkably increased, and the catalytic performance is improved; in which electrochemical dealloying (Fe)0.5Co0.5)75Mo5P13C7Has the best full-hydrolytic performance, and shows excellent catalytic activity and long-term stability.