An in-situ Raman study method for oxygen evolution reaction using Fe-Ni composite metal oxides

Abstract

The present invention discloses a research method for in-situ Raman of Fe-Ni composite metal oxide for oxygen evolution reaction, comprising the following steps: (1) synthesizing Au nanoparticles, (2) synthesizing Au@Fe x Ni 1‑x particles, (3) preparing an electrode, and (4) combining with an electrochemical CV curve, applying a corresponding oxidation potential, and performing in-situ Raman testing. By preparing a special core-shell structure Au@Fe x Ni 1‑x O and combining with in-situ Raman technology, the present invention explores the OER process of NiFe catalyst. This method is systematic and scientific, the obtained Raman signal is clear, the changes of the catalyst during the OER process are characterized in-situ, the catalytic mechanism is explored, and further, it assists in designing more excellent catalysts.

Description

Technical Field

[0001] The invention belongs to the technical field of Raman testing, and in particular relates to a method for studying in-situ Raman of an Fe-Ni composite metal oxide for oxygen evolution reaction. Background Art

[0002] Surface enhanced Raman scattering (SERS) is a powerful spectral technology that can provide ultra-high sensitivity fingerprint vibration information, making the inherent low detection sensitivity of surface Raman spectroscopy no longer its fatal disadvantage. SERS is an important analytical method for studying molecular structure. It not only has most of the advantages of Raman spectroscopy, but also can provide richer structural information of chemical molecules, can realize real-time and in-situ detection, and has high sensitivity, simple data processing, high accuracy, and is a very powerful trace detection tool. It has been widely used in surface science, material science, biology, medicine, food safety, environmental monitoring and national security.

[0003] Water electrolysis technology has become one of the green hydrogen production methods with application prospects due to its environmental friendliness, high product purity and zero carbon emissions. In recent years, as one of the half reactions of water electrolysis, the hydrogen evolution reaction (HER) has developed rapidly; however, the other half reaction, the oxygen evolution reaction (OER), has become a bottleneck restricting the overall efficiency of the water electrolysis reaction due to its complex four-electron oxidation process and the resulting slow kinetic characteristics. Therefore, it is of great significance to deeply study the reaction mechanism of oxygen evolution reaction (OER) from the molecular level with the help of surface enhanced Raman scattering. However, Au, which can produce a large SERS effect, cannot work under high potential conditions during the oxygen evolution reaction, which seriously limits the practical application of SERS.

[0004] In order to better study the catalytic mechanism of oxygen evolution reaction (OER) at the molecular level, capture the signals of OER intermediate species, and ensure enhanced Raman signals at high potentials, it is very necessary to prepare a special compound that can also in situ explore the OER process of NiFe catalysts at high potentials and monitor the changes in the surface species and overall structure of NiFe catalysts under OER potentials in real time. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a method for studying the in-situ Raman spectroscopy of the oxygen evolution reaction using Fe-Ni composite metal oxides. x Ni 1-x O, combined with in situ Raman technology, to explore the OER process of NiFe catalyst.

[0006] In order to achieve the above purpose, the technical solution of the present invention is: a method for studying in-situ Raman spectroscopy of oxygen evolution reaction using Fe-Ni composite metal oxide, which specifically comprises the following steps:

[0007] (1) Synthesis of Au nanoparticles: Au nanoparticle sol is obtained by heating an aqueous solution of chloroauric acid and an aqueous solution of sodium citrate to react;

[0008] (2) Synthesis of Au@Fe x Ni 1-x Particles: Take the gold nanoparticles obtained in step (1), add Ni and Fe salts in different molar feed ratios, add alkaline solution, and then use a reducing agent to reduce them under alkaline conditions to obtain Au@Fe x Ni 1-x The particles were finally dried in an oven to obtain Au@Fe with different NiFe ratios. x Ni 1-x O;

[0009] (3) Electrode preparation: The Au@Fe synthesized in step (2) x Ni 1-x O is prepared into ink and dropped on the glassy carbon electrode. After drying, the electrode preparation is completed.

[0010] (4) In-situ Raman testing: Combined with the electrochemical CV curve, the corresponding oxidation potential is applied to perform in-situ Raman testing.

[0011] Furthermore, the Au nanoparticles obtained in step (1) have a particle size of 50 to 60 nm.

[0012] Furthermore, the synthesis method of Au nanoparticles in step (1) is as follows: prepare HAuCl4 aqueous solution, add the HAuCl4 aqueous solution into 200 mL of water, then add sodium citrate solution, maintain at 98-100°C for 40 minutes, stop the reaction to obtain 55 nm Au nanoparticles.

[0013] Furthermore, the concentration of the HAuCl4 aqueous solution is 28.0-30.0 mmol / L, the amount of the HAuCl4 aqueous solution added is 2.0-3.0 ml, the amount of the sodium citrate aqueous solution added is 1.4-2 ml, and the mass fraction of the sodium citrate aqueous solution is 1%.

[0014] Furthermore, in step (2), Au@Fe x Ni 1-x The specific synthesis method of Au@Fe is as follows: 35-45 mL of 55 nm Au is centrifuged at high speed, the supernatant is removed, and 4-6 ml of anhydrous ethanol is added to the solution to redisperse it; then, anhydrous ethanol solutions of Ni and Fe salts with different molar feed ratios are added, and then stirred at 60-70 ° C for 5 min, and a certain concentration of hydrazine hydrate and NaOH mixed ethanol solution is added, and the reaction is carried out at 65 ° C for a certain time to obtain Au@Fe x Ni 1-xThe particles are then washed several times with anhydrous ethanol; finally, Au@Fe is obtained by drying in an oven for 24 hours. x Ni 1-x O.

[0015] Furthermore, the Ni salt added in step (2) is one of nickel nitrate or nickel chloride, and the Fe salt is one of ferric chloride hexahydrate (FeCl3·6H2O) or ferric nitrate nonahydrate (FeNO3·9H2O), wherein the molar ratio of the NiFe salt is Ni: x Fe 1-x , where x ranges from 0 to 1, so the amount of Ni and Fe salts added only needs to meet x, 1-x.

[0016] Furthermore, the alkaline solution in step (2) is a mixed solution of hydrazine hydrate ethanol solution and sodium hydroxide ethanol solution, specifically 0.3 mL of hydrazine hydrate ethanol solution with a mass fraction of 50% and 1 mL of 0.5 mol / L NaOH ethanol solution.

[0017] The drying method mentioned above mainly refers to ordinary heating oven drying.

[0018] Furthermore, the preparation method of the ink in step (3) is as follows: prepare Au@Fe x Ni 1-x O ink, Au@Fe x Ni 1-x O was added to a solvent prepared by ultrapure water, anhydrous ethanol and a commercial Nafion solution with a mass fraction of 5% in a volume ratio of 4:5:1 to prepare a 5 mg / ml Au@Fe x Ni 1-x OInk.

[0019] Nafion is a polymer with a specific chemical formula (C7HF 13 O5S.C2F4)x, after drying, a polymer film will be formed to prevent the catalyst from falling off during testing.

[0020] Furthermore, the glassy carbon electrode refers to an in-situ Raman glassy carbon electrode specially customized by this laboratory. The modified electrode surface method is to directly drop ink onto the surface of the glassy carbon electrode and dry it. The drying method is mainly one of three methods: natural air drying, infrared lamp drying or heating oven drying.

[0021] Furthermore, in the step (4), the CV curve is obtained by applying an oxidation potential using an electrochemical workstation CHI 760e, with a potential range of 1-1.6 V (Vs.RHE), a scan rate range of 50-100 mV / s, and a cycle number of 2-4 cycles to perform cyclic voltammetry scanning, and the final curve obtained is the CV curve.

[0022] Furthermore, the instrument used for the in-situ Raman test in step (4) is Xplora Plus, the excitation light is 638nm, the laser power is 1-10%, and after fixing the specific oxidation potential with an electrochemical workstation, the potential range is 1-1.6V (Vs.RHE), and Raman scanning is performed at the current potential to obtain the Raman spectrum of the corresponding potential.

[0023] A multifunctional FeNi oxide-coated gold nanoparticle, Au@FexNi1-xO, wherein the value of x ranges from 0 to 1.

[0024] Furthermore, the oxidized FeNi gold-coated multifunctional nanoparticles are used as catalysts for oxygen evolution reactions.

[0025] Furthermore, the oxidized FeNi gold-coated multifunctional nanoparticles are used as oxygen evolution reaction catalysts in in-situ Raman analysis.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. Au@Fe prepared by the present invention x Ni 1-x O compounds, the OER process of NiFe catalysts can be explored in situ at high potentials, and the changes in the surface species and overall structure of NiFe catalysts under OER potentials can be monitored in real time;

[0028] 2. The method of the present invention is systematic and scientific, the obtained Raman signal is clear, and the changes of the catalyst during the OER process are characterized in situ, the catalytic mechanism is explored, and then more excellent catalysts can be designed;

[0029] 3. The present invention uses surface Raman enhancement technology to rationally design the core-shell structure to explore the OER process of NiFe catalysts and in situ explore the changes in the catalysts;

[0030] 4. The method of the present invention can understand the OER principle of NiFe catalysts as long as the in-situ changes of the catalyst are mastered, thereby guiding the design of better NiFe catalysts for oxygen evolution;

[0031] 5. The method of the present invention can master the oxygen evolution principle of OER, overcome the difficulties of electrochemical hydrogen production, and make the use and preparation of hydrogen energy more economical and efficient;

[0032] 6. The present invention is carried out under alkaline conditions, and RuO2 or IrO2 is generally used as a commercial OER catalyst, but its price is dozens or even hundreds of times that of NiFe catalyst. Therefore, mastering the oxygen evolution principle of FeNi catalyst and developing NiFe-based catalysts to replace traditional precious metal oxides has great application prospects and commercial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The CV curve of 55 nm Au prepared in Example 1, the transmission electron microscope image of Au@Fe0Ni1O and the cyclic voltammogram of Au@Fe0Ni1O;

[0034] Figure 2 This is the in-situ Raman spectrum of Au@Fe0Ni1O prepared in Example 1;

[0035] Figure 3 The Au@Fe prepared in Example 2 0.7 Ni 0.3 Transmission electron microscopy images of O and the corresponding cyclic voltammograms;

[0036] Figure 4 The Au@Fe prepared in Example 2 0.7 Ni 0.3 In situ Raman spectrum of O;

[0037] Figure 5 It is the transmission electron microscope image of Au@Fe1Ni0O prepared in Example 3 and the corresponding cyclic voltammogram. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is described in more detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0039] A method for studying in-situ Raman spectroscopy of oxygen evolution reaction using Fe-Ni composite metal oxides, comprising the following steps:

[0040] (1) Synthesis of Au nanoparticles: Au nanoparticle sol is obtained by heating an aqueous solution of chloroauric acid and an aqueous solution of sodium citrate to react;

[0041] (2) Synthesis of Au@Fe x Ni 1-x Particles: The Au nanoparticle sol obtained in step (1) is dispersed in anhydrous ethanol, an anhydrous ethanol solution of Ni salt and Fe salt is added, and then an alkaline solution is added, and then a reducing agent is used for reduction, and Au@Fe is obtained after drying. x Ni 1-x particle;

[0042] (3) Electrode preparation: The Au@Fe synthesized in step (2) x Ni 1-x O is prepared into ink and dropped on the glassy carbon electrode, and the electrode is prepared after drying;

[0043] (4) In-situ Raman testing: Combined with the electrochemical CV curve, the corresponding oxidation potential is applied to perform in-situ Raman testing.

[0044] Example 1

[0045] (1) 1 g of HClO4 was dissolved in a 100 volumetric flask, 2.4 mL was added to 200 mL of ultrapure water, and 1.4 mL of 1% sodium citrate was added. The mixture was kept at 99°C for 40 minutes, and the flask was taken out and placed at room temperature to obtain 55 nm Au nanoparticles. The CV test of 55 nm Au was first performed to observe the oxidation potential of 55 nm Au.

[0046] (2) Take 40mL of 55nm gold solution, centrifuge for 15 minutes, remove the supernatant, disperse the concentrate in 5mL of anhydrous ethanol, add 1.8mL of 1mmol / L NiCl2, then add 0mL of 1mmol / L FeCl3, stir evenly, and finally add 0.3mL of 50% hydrazine hydrate ethanol solution and 1mL of 0.5mol / L NaOH ethanol solution, and keep warm at 65℃ for 15min. Put the washed particles in an oven for 24 hours to obtain Au@Fe0Ni1O;

[0047] (3) Take 5 mg of Au@Fe0Ni1O particles, add 500 uL of anhydrous ethanol, 450 uL of ultrapure water, and 50 uL of Nafion (produced by SPAKE, with a concentration of 5% wt) solution to prepare 5 mg / mL ink, drop the ink onto the surface of the glassy carbon electrode, and dry it to obtain the modified Au@Fe0Ni1O glassy carbon electrode.

[0048] (4) In the in-situ Raman test, the potential range is 1-1.6V (Vs.RHE), the potential interval is 50mV, the laser wavelength is 638nm, the laser power is 10%, the spectrum acquisition time is 20s, the number of cycles is 3, and the grating number is 1200T. After each adjustment of the potential, the Raman spectrum is acquired, and finally the in-situ Raman spectrum of Au@Fe0Ni1O can be obtained.

[0049] Figure 1In Example 1, it can be seen that the oxidation peak of Au is around 1.26V, but after being coated with Fe0Ni1O, there is no obvious oxidation peak at 1.26V, indicating that the coated Fe0Ni1O can protect Au from oxidation. Then the transmission electron microscope photo of Au@Fe0Ni1O shows that NiO is coated on the surface of nano-Au, and its particle size is about 60nm, indicating that the shell thickness is about 5nm. Overall, it can be seen that the coated NiO is uniform and the coating effect is obvious. Figure 1 The CV of Au@Fe0Ni1O shows an obvious oxidation peak when the potential reaches 1.4 V, indicating that Ni(II) is oxidized to Ni(III). When the potential reaches 1.55 V, the current density increases sharply, indicating that oxygen evolution has begun at this time.

[0050] Figure 2 This is the in-situ Raman spectrum of Au@Fe0Ni1O. From the spectrum, we can see that with the increase of potential, 3580cm -1 A peak appears near 470cm, which is the stretching vibration of OH, indicating that NiO is first transformed into Ni(OH)2. As the potential increases, after 0.4V, the sample changes from Ni(OH)2 to NiOOH, and the OH stretching vibration of the lattice disappears, and a peak at 470cm -1 and 555cm -1 New peaks appeared, so we described the entire change process of Au@Fe0Ni1O by in situ Raman enhancement technology, which is of great significance to our understanding of the OER mechanism. In addition, due to the coating of Fe0Ni1O, no 580cm -1 The appearance of Au-O on the left and right indicates that the shell prevents the oxidation of Au.

[0051] Example 2

[0052] (1) 1 g of HClO4 was dissolved in a 100 volumetric flask, 2.4 mL was added to 200 mL of ultrapure water, and 1.4 mL of 1% sodium citrate was added. The mixture was kept at 99°C for 40 minutes, and the flask was taken out and left at room temperature to obtain 55 nm Au nanoparticles;

[0053] (2) Take 40mL of 55nm gold solution, centrifuge for 15 minutes, remove the supernatant, disperse the concentrate in 5mL of anhydrous ethanol, add 0.54mL of 1mmol / L NiCl2, then add 1.26mL of 1mmol / L FeCl3, stir evenly, and finally add 0.3mL of 50% hydrazine hydrate ethanol solution and 1mL of 0.5mol / L NaOH ethanol solution, keep warm at 65℃ for 15min. Put the washed particles in an oven for 24 hours to obtain Au@Fe 0.7 Ni 0.3 O;

[0054] (3) Take 5mgAu@Fe 0.7 Ni 0.3 O particles, add 500uL of anhydrous ethanol, 450uL of ultrapure water, and 50uL of Nafion (produced by SPAKE, with a concentration of 5% wt) solution to prepare a 5mg / mL ink, drop the ink onto the surface of the glassy carbon electrode, and dry it to obtain the modified Au@Fe 0.7 Ni 0.3 O glassy carbon electrode.

[0055] (4) In the in-situ Raman test, the potential range is 1-1.6V (Vs.RHE), the potential interval is 50mV, the laser wavelength is 638nm, the laser power is 10%, the spectrum acquisition time is 20s, the number of cycles is 3, and the grating number is 1200T. After each adjustment of the potential, the Raman spectrum is acquired, and finally Au@Fe 0.7 Ni 0.3 In situ Raman spectroscopy of O.

[0056] Figure 3 The Au@Fe 0.7 Ni 0.3 TEM of O, from Figure 3 It can be seen that the shell thickness is uniform, about 5nm, and the core-shell structure is complete; the CV graph shows that the oxidation peak has shifted significantly after Fe doping, indicating that the oxidation of Ni requires a larger potential at this time, indicating that Ni(II) to Ni(III) is close to 0.5V, and then it can be seen that when Ni is oxidized to +3, oxygen evolution begins.

[0057] Figure 4 Au@Fe 0.7 Ni 0.3 In the in-situ Raman spectrum of O, we can see that two peaks of NiOOH appear after the potential reaches 560 mV, at 474 cm -1 and 556cm -1 , representing the bending vibration and stretching vibration of Ni(III)-O. The stretching vibration intensity of OH in the high wave number region gradually decreases until it disappears after the potential reaches 560mV. Among them, Fe-O has no obvious change at 670mV. This peak is the Fe-O stretching vibration of Fe3O4. Therefore, we described the Au@Fe 0.7 Ni 0.3 O, which is of great significance for explaining the OER mechanism.

[0058] Example 3

[0059] (1) 1 g of HClO4 was dissolved in a 100 volumetric flask, 2.4 mL was added to 200 mL of ultrapure water, and 1.4 mL of 1% sodium citrate was added. The mixture was kept at 99°C for 40 minutes, and the flask was taken out and left at room temperature to obtain 55 nm Au nanoparticles;

[0060] (2) Take 40mL of 55nm gold solution, centrifuge for 15 minutes, remove the supernatant, disperse the concentrate in 5mL of anhydrous ethanol, add 0ml of 1mmol / L NiCl2, then add 1.8mL of 1mmol / L FeCl3, stir evenly, and finally add 0.3mL of 50% hydrazine hydrate ethanol solution and 1mL of 0.5mol / L NaOH ethanol solution, and keep warm at 70℃ for 15min. Put the washed particles in an oven for 24 hours to obtain Au@Fe1Ni0O;

[0061] (3) Take 5 mg of particles, add 500 uL of anhydrous ethanol, 450 uL of ultrapure water, and 50 uL of Nafion (produced by SPAKE, with a concentration of 5% wt) solution to prepare 5 mg / mL ink, drop the ink onto the surface of the glassy carbon electrode, and dry it to obtain a glassy carbon electrode modified with Au@Fe1Ni0O.

[0062] (4) In the in-situ Raman test, the potential range is 1-1.6V (Vs.RHE), the potential interval is 50mV, the laser wavelength is 638nm, the laser power is 10%, the spectrum acquisition time is 20s, the number of cycles is 3, and the grating number is 1200T. Raman spectrum acquisition is performed after each potential adjustment, and finally the in-situ Raman spectrum of Au@Fe1Ni0O can be obtained.

[0063] Figure 5 is the TEM of Au@Fe1Ni0O in Example 3, from Figure 3 It can be seen that the shell thickness is uniform, about 5nm, the core-shell structure is complete, and FeO x It is more inclined to island growth, the shell is not smooth but the growth is basically continuous; the subsequent CV curve shows that there is no oxidation peak under the oxidation potential, and the current density is relatively small, indicating that the oxygen evolution performance is poor.

[0064] The above embodiments are preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement modes and shall be included in the protection scope of the present invention.

Claims

1. A method for studying in-situ Raman spectroscopy of oxygen evolution reaction using Fe-Ni composite metal oxides, characterized in that: The steps include: (1) Synthesis of Au nanoparticles: Au nanoparticle sol is obtained by heating an aqueous solution of chloroauric acid and an aqueous solution of sodium citrate to react; (2) Synthesis of Au@Fe x Ni 1-x Particles: The Au nanoparticle sol obtained in step (1) is dispersed in anhydrous ethanol, an anhydrous ethanol solution of Ni salt and Fe salt is added, and then an alkaline solution is added, and then a reducing agent is used for reduction, and Au@Fe is obtained after drying. x Ni 1-x The Ni salt is nickel nitrate or nickel chloride, the Fe salt is ferric chloride hexahydrate or ferric nitrate nonahydrate, and the molar ratio of the Ni salt to the Fe salt can be expressed as Ni x Fe 1-x , x ranges from 0 to 1; (3) Electrode preparation: The Au@Fe synthesized in step (2) x Ni 1-x O is prepared into ink and dropped on the glassy carbon electrode, and the electrode is prepared after drying; (4) In-situ Raman testing: Combined with the electrochemical CV curve, the corresponding oxidation potential is applied in the potential range of 1-1.6 V Vs. RHE to perform in-situ Raman testing.

2. The method for studying in-situ Raman spectroscopy of oxygen evolution reaction using a Fe-Ni composite metal oxide according to claim 1, characterized in that: In the step (2), the volume ratio of the Au nanoparticle sol to the ethanol used for dispersion is 35-45:4-6.

3. The method for studying in-situ Raman spectroscopy of oxygen evolution reaction using a Fe-Ni composite metal oxide according to claim 1, characterized in that: In the step (2), the reducing agent is hydrazine hydrate, and the alkaline solution is a mixed solution of hydrazine hydrate ethanol solution and sodium hydroxide ethanol solution, specifically 0.3 mL of hydrazine hydrate ethanol solution with a mass fraction of 50% and 1 mL of 0.5 mol / L NaOH ethanol solution.

4. The method for studying in-situ Raman spectroscopy of oxygen evolution reaction using a Fe-Ni composite metal oxide according to claim 1, characterized in that: The glassy carbon electrode in step (3) is a customized in-situ Raman glassy carbon electrode.

5. The method for studying in-situ Raman spectroscopy of oxygen evolution reaction using a Fe-Ni composite metal oxide according to claim 1, characterized in that: In the step (4), the CV curve is scanned by applying an oxidation potential using an electrochemical workstation CHI 760e, with a potential range of 1-1.6 V Vs.RHE, a scan rate range of 50-100 mV / s, and a cycle number of 2-4 cycles.

6. The method for studying in-situ Raman spectroscopy of oxygen evolution reaction using a Fe-Ni composite metal oxide according to claim 1, characterized in that: The instrument used for the in-situ Raman test in step (4) is Xplora Plus, the excitation light is 638nm, the laser power is 1-10%, and after fixing the specific oxidation potential with an electrochemical workstation, the potential range is 1-1.6V, and Raman scanning is performed at the current potential to obtain the Raman spectrum of the corresponding potential.

7. An oxidized FeNi gold-coated multifunctional nanoparticle Au@Fe for an in-situ Raman study of oxygen evolution reaction as claimed in any one of claims 1 to 6 x Ni 1-x O, where The value range of x is 0-1.

8. Use of the oxidized FeNi gold-coated multifunctional nanoparticles as claimed in claim 7 as a catalyst for oxygen evolution reaction.

9. Use of the oxidized FeNi gold-coated multifunctional nanoparticles as claimed in claim 7 as an oxygen evolution reaction catalyst in in-situ Raman.

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