In-situ raman spectrum detection method for inner interface water of double electric layer on surface of Cu single crystal

Abstract

The application discloses a kind of Cu monocrystal surface double electric layer inner interface water in-situ raman spectrum detection method, belong to spectral detection technical field, specifically includes the following steps: assembly nanoparticle, Cu monocrystal hydrogen evolution impurity, detect interface water raman spectrum, assemble in-situ raman spectrum detection device, detect the interface water configuration of Cu monocrystal.The application can detect the raman spectrum information of double electric layer inner interface water by regulating in-situ electrolytic cell and accurately regulating Cu monocrystal electrode liquid layer distance, while avoiding the bubble interference spectrum acquisition in hydrogen evolution reaction process.The application can be applied in the configuration monitoring of in-situ interface water in different electrocatalytic reaction process of Cu monocrystal, thereby having direct experimental guidance help to the design of electrocatalyst.

Description

Technical Field

[0001] This invention belongs to the field of spectroscopic detection technology, specifically relating to an in-situ Raman spectroscopy detection method for water at the interface within the double electric layer on a Cu single crystal surface. Background Technology

[0002] In aqueous systems, the proton source for CO2RR and NRR processes on Cu(hkl) single crystal surfaces is primarily H2O molecules from the electric double layer. However, H2O molecules are also the main competitors for active sites during reduction. Therefore, studying the HER process on Cu(hkl) single crystal surfaces helps us better understand the complex reaction mechanisms within the electric double layer region. HER is the process by which adsorbed H2O molecules decompose to produce H2 at the cathode. Understanding the configurational changes of interfacial water within the electric double layer region of the electrode surface is crucial. However, studying interfacial H2O molecules is very difficult, as the inner Helmholtz layer is only a few [units of distance] from the electrode surface. Within this layer, interfacial water participates in the reaction processes on the electrode surface. Interfacial H2O molecules play an important role in cellular reactions, catalytic reactions, electrolysis reactions, and metal oxidation reactions.

[0003] In-situ Raman spectroscopy is an important technique for detecting interfacial water on Cu single crystal surfaces. However, a local potential difference exists at the electrode-electrolyte interface, caused by the electrochemical double layer, a specific structure composed of water and ions on the electrode surface and in the electrolyte. During electrocatalysis, a large amount of bulk water and ordered interfacial water exist within the double layer. In-situ Raman spectroscopy detects the entire signal within this region, and since the content of bulk water is much greater than that of interfacial water, the detected water signal is almost entirely from the bulk phase. However, bulk water cannot directly participate in the electrocatalytic reaction. Therefore, it is necessary to develop an in-situ Raman spectroscopy method for detecting interfacial water within the double layer of Cu single crystal surfaces to address this problem. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the existing technology and provide a method for detecting in-situ Raman spectra of interfacial water in the double electric layer on the surface of Cu single crystal, which can observe the configurational changes of interfacial water in Cu single crystal during electrocatalysis.

[0005] To achieve the above objectives, the technical solution of the present invention is: an in-situ Raman spectroscopy detection method for interface water within the electric double layer on a Cu single crystal surface, specifically comprising the following steps:

[0006] (1) Assembling nanoparticles: Au@SiO2 nanospheres were added to the surface of a Cu single crystal and vacuum dried to obtain assembled nanoparticles.

[0007] Cu single crystals with rice-sized particles;

[0008] (2) Cu single crystal hydrogen evolution and impurity removal: Cu single crystal assembled in step (1) is hydrogen evolved and impurity removed. During the hydrogen evolution process, the protective agent on the particle surface is removed, and a large number of bubbles generated will carry away most of the aggregated particles, so that the assembled nanoparticles are monolayer or sub-monolayer.

[0009] (3) Detection of interface water Raman spectrum: The Cu single crystal after hydrogen evolution and impurity removal in step (2) is assembled into a Raman in-situ electrolytic cell, the liquid layer distance is controlled by laser focusing, and then the interface water Raman spectrum is detected.

[0010] (4) Assemble the in-situ Raman spectroscopy detection device: Convert the vertical laser of the confocal Raman instrument into a horizontal laser, and the electrolytic cell also needs to be placed vertically so that the single crystal surface and the laser direction are perpendicular to each other.

[0011] (5) Detection of interfacial water configuration of Cu single crystal: The interfacial water configuration of Cu single crystal was detected at the designed potential in the hydrogen evolution potential range (vs. SCE potential is below -1.2V).

[0012] In a preferred embodiment of the present invention, in step (1), the Cu single crystal is first electropolished in phosphoric acid with a mass fraction of 60-80% to remove the surface oxide layer, and then rapidly dried by N2.

[0013] In a preferred embodiment of the present invention, the amount of Au@SiO2 nanospheres added to the Cu single crystal surface in step (1) is 1.0–2.0 μL / mm. 2 .

[0014] In a preferred embodiment of the present invention, in step (1), the Au@SiO2 nanospheres are Au cores with a particle size of 55-120 nm encapsulated by a SiO2 shell with a thickness of 1.5-2.0 nm.

[0015] In a preferred embodiment of the present invention, in step (1), Au@SiO2 nanospheres are prepared as a suspension with a concentration of 2-5 mg / L and added.

[0016] In a preferred embodiment of the present invention, the vacuum drying time in step (1) is 30 to 60 minutes and the vacuum degree is -0.05 to -0.08. The purpose of vacuum drying is to avoid oxidation and corrosion of the Cu single crystal surface.

[0017] In a preferred embodiment of the present invention, the hydrogen evolution and impurity removal of Cu single crystals in step (2) is carried out in 0.05-0.15M KCl solution, with a potential range of vs. RHE-0.5V to -1.1V, and the impurity removal is performed 1-5 times, with the electrolyte needing to be replaced each time.

[0018] In a preferred embodiment of the present invention, the laser intensity in step (3) is 0.03 to 0.05 mW, the scanning speed is 50 mV / S, and the time is 2 to 5 min.

[0019] In a preferred embodiment of the present invention, the laser focusing control of the liquid layer distance in step (3) specifically involves first focusing the laser onto the Z-axis of the single crystal electrode surface to adjust to 0, and then focusing it onto the upper surface of the window to calculate the liquid layer distance.

[0020] In a preferred embodiment of the present invention, the distance between the laser focusing and the liquid layer in step (3) is within 50 μm.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. This invention can detect the Raman spectrum information of the interface water in the double layer by adjusting the horizontal direction of the laser to enter the in-situ electrolytic cell and by using the laser to focus and test the liquid layer thickness to precisely control the distance of the Cu single crystal electrode liquid layer, while avoiding the interference of bubble spectral acquisition during the hydrogen evolution reaction.

[0023] 2. This invention can be applied to in-situ monitoring of the configuration of interfacial water in different electrocatalytic reaction processes of Cu single crystals, thereby providing direct experimental guidance for the design of electrocatalysts. Attached Figure Description

[0024] Figure 1 This is a SEM image of Au@SiO2 nanoparticles assembled in Cu single crystal according to the present invention;

[0025] Figure 2 The Raman spectra of in-situ interface water and bulk water obtained in Example 1 of this invention;

[0026] Figure 3 The in-situ Raman spectrum of the interfacial water OH stretching vibration of Cu(111) single crystal in Example 2 of this invention;

[0027] Figure 4 This is the in-situ Raman spectrum of the OH stretching vibration of the interfacial water in Cu(110) single crystal in Example 3 of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0029] An in-situ Raman spectroscopy method for detecting interfacial water within the electric double layer on a Cu single crystal surface, comprising the following steps:

[0030] (1) Assembling nanoparticles: Au@SiO2 nanospheres were added to the surface of Cu single crystals and vacuum dried to obtain Cu single crystals with assembled nanoparticles;

[0031] (2) Cu single crystal hydrogen evolution and impurity removal: Cu single crystal assembled with nanoparticles in step (1) is subjected to hydrogen evolution and impurity removal. During the hydrogen evolution process, the surface protectant of the particles is removed, and a large number of bubbles generated will carry away most of the aggregated particles. The surface protectant is removed and the assembled nanoparticles are made into a single layer or a sub-single layer.

[0032] (3) Detection of interface water Raman spectrum: The Cu single crystal after hydrogen evolution and impurity removal in step (2) is assembled into a Raman in-situ electrolytic cell, the liquid layer distance is controlled by laser focusing, and then the interface water Raman spectrum is detected.

[0033] (4) Assemble the in-situ Raman spectroscopy detection device: Convert the vertical laser of the confocal Raman instrument into a horizontal laser, and the electrolytic cell also needs to be placed vertically so that the single crystal surface and the laser direction are perpendicular to each other.

[0034] (5) Detection of interfacial water configuration of Cu single crystal: The interfacial water configuration of Cu single crystal was detected at the designed potential in the hydrogen evolution potential range.

[0035] In step (1), the Cu single crystal is first electropolished in phosphoric acid with a mass fraction of 60-80% to remove the surface oxide layer, and then quickly dried by blowing with N2.

[0036] In step (1), the amount of Au@SiO2 nanospheres added to the Cu single crystal surface is 1.0–2.0 μL / mm. 2 .

[0037] In step (1), the Au@SiO2 nanospheres consist of an Au core with a particle size of 55-120 nm encapsulated by a SiO2 shell with a thickness of 1.5-2.0 nm.

[0038] In step (1), Au@SiO2 nanospheres are prepared as a suspension with a concentration of 2-5 mg / L and added.

[0039] In step (1), the vacuum drying time is 30 to 60 minutes and the vacuum degree is -0.05 to -0.08. The purpose of vacuum drying is to avoid oxidation and corrosion of the Cu single crystal surface.

[0040] In step (2), the hydrogen evolution and impurity removal of Cu single crystals is carried out in 0.05-0.15M KCl solution, with a potential range of vs. RHE-0.5V to -1.1V. The impurity removal is performed 1-5 times, and the electrolyte needs to be replaced each time.

[0041] In step (3), the laser intensity is 0.03-0.05mW, the scanning speed is 50mV / S, and the time is 2-5min.

[0042] In step (3), the laser focusing to control the liquid layer distance is specifically achieved by first focusing the laser onto the surface of the single crystal electrode and adjusting the Z-axis to 0, and then focusing it onto the upper surface of the window to calculate the liquid layer distance.

[0043] In step (3), the distance between the laser-focused liquid layer and the liquid layer is within 50 μm.

[0044] Example 1

[0045] In-situ Raman spectroscopy of interface water and bulk water in Cu(111) single crystals was performed using the following method:

[0046] (1) The Cu(111) single crystal to be tested was first electropolished in 70% phosphoric acid to remove the surface oxide layer, and then dried by N2. Then, 1.8 μL Au@SiO2 nanospheres (shell SiO2 thickness 2.0 nm, core Au nanosphere particle size 55 nm) were dropped on the surface of the single crystal and placed in a vacuum dryer for 30 mins.

[0047] (2) The assembled Cu single crystal with nanoparticles was purified by hydrogen evolution in 0.1M KCl solution with a potential range of vs. RHE-1.0V. The purification was carried out 3 times, and the electrolyte was replaced with clean electrolyte each time.

[0048] (3) The Cu single crystal after hydrogen evolution and impurity removal is assembled into a self-made Raman in-situ electrolytic cell. The liquid layer distance is controlled by laser focusing. A laser with an intensity of 0.03mW is used. First, the Z-axis of the single crystal electrode surface is adjusted to 0, and then the liquid layer distance is calculated by focusing on the upper surface of the window. The liquid layer distance needs to be precisely controlled to 100μm to detect the Raman spectrum of bulk water and controlled to within 50μm to detect the Raman spectrum of interface water.

[0049] (4) The vertical laser of the confocal Raman instrument is converted into a horizontal laser by the optical path conversion lens, and the electrolytic cell is placed vertically so that the single crystal surface and the laser direction are perpendicular to each other.

[0050] (5) After assembling the in-situ Raman spectroscopy detection device using the above method, the device is designed to detect the OH stretching vibration of water in Cu(111) single crystal at a potential of vs. SCE-1.2V. Figure 2 As shown, curve a mainly represents the OH stretching vibration of interfacial water, while curve b mainly represents the signal of bulk water.

[0051] The interface water configurations in this embodiment are 2H·H₂O, 4H·H₂O, and negatively charged Na·H₂O.

[0052] It is known that bulk water does not change with potential, while the content of interfacial water changes due to electric field factors; the detection methods for bulk water and interfacial water are different; the content of bulk water accounts for a very high proportion of the total water, exceeding 99.99%, and its detection is very simple; the purpose of detecting bulk water is to identify the vibrational configurations of different hydrogen bonds in water, as well as to distinguish the criteria for interfacial water.

[0053] Example 2

[0054] The in-situ Raman spectrum of the water at the hydrogen evolution reaction interface of Cu(111) single crystal in a neutral electrolyte was tested according to the method in Example 1. The electrolyte was a 0.01M phosphate buffer solution, which can avoid local pH changes caused by hydrogen evolution in a short period of time. Figure 3 As shown, the interfacial water in Cu(111) single crystals reacts at a velocity of 3314 cm⁻¹ during the HER process. -1 The four hydrogen bonds are mainly composed of 4H·H₂O, gradually changing to 3423cm⁻¹. -1 Water at the interface with two hydrogen bonds.

[0055] Example 3

[0056] The in-situ Raman spectrum of the water at the hydrogen evolution reaction interface of Cu(110) single crystal in a neutral electrolyte was tested according to the method in Example 1. The electrolyte was a 0.01M phosphate buffer solution. Figure 4 As shown, the interfacial water content of the four hydrogen bonds in Cu(110) single crystal gradually decreases, while the water content of the two hydrogen bonds does not change significantly, and the content of cation-bound water increases.

[0057] The above embodiments are merely optimized implementations of the present invention, used to illustrate the principles and effects of the present invention, and are not intended to limit the present invention. It should be noted that any modifications made to the above embodiments by those skilled in the art without departing from the spirit and scope of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for in-situ Raman spectroscopy detection of water in the inner interface of the double electric layer on the surface of a Cu single crystal, characterized by, It comprises the following steps: (1) Assembling nanoparticles: adding Au@SiO2 nanospheres to the surface of Cu single crystal, and vacuum drying to obtain Cu single crystal with assembled nanoparticles; (2) Hydrogen evolution of Cu single crystal: hydrogen evolution of the Cu single crystal with assembled nanoparticles in step (1) to make the assembled nanoparticles monolayer or sub-monolayer; (3) Detecting interfacial water Raman spectrum: assembling the Cu single crystal after hydrogen evolution in step (2) into a Raman in-situ electrolytic cell, adjusting the liquid layer distance by laser focusing, and then detecting the interfacial water Raman spectrum; (4) Assembling in-situ Raman spectrum detection device: converting the vertical laser of the confocal Raman instrument into horizontal laser, vertically placing the electrolytic cell, and keeping the surface of the single crystal and the direction of the laser perpendicular; (5) Detecting the interfacial water configuration of Cu single crystal: designing the potential in the hydrogen evolution potential range to detect the interfacial water configuration of Cu single crystal.

2. The in situ Raman spectral measurement method according to Claim 1, wherein In step (1), the Cu single crystal is first electro-polished in phosphoric acid with a mass fraction of 60-80% to remove the surface oxide layer, and then dried by blowing N2.

3. The method for in situ Raman spectral measurement according to claim 1, wherein The amount of Au@SiO2nanoparticle added to the surface of the Cu single crystal in step (1) is 1.0 to 2.0 μL / mm 2 .

4. The method for in situ Raman spectral measurement according to claim 1, wherein In step (1), the Au@SiO2 nanospheres are Au core with a particle size of 55-120 nm wrapped by a SiO2 shell with a thickness of 1.5-2.0 nm.

5. The method for in situ Raman spectral measurement according to claim 1, wherein In step (1), the Au@SiO2 nanospheres are prepared into a suspension with a concentration of 2-5 mg / L for addition.

6. The method for in situ Raman spectral measurement according to claim 1, wherein In step (1), the vacuum drying time is 30-60 min, and the vacuum degree is -0.05 to -0.

08.

7. The method for in situ Raman spectral measurement according to claim 1, wherein In step (2), the hydrogen evolution of Cu single crystal is carried out in 0.05-0.15 M KCl solution, and the potential range is vs. RHE-0.5 V to -1.1 V. The hydrogen evolution is carried out for 1-5 times, and the electrolyte needs to be replaced each time.

8. The method for in situ Raman spectral measurement according to claim 1, wherein In step (3), the laser intensity is 0.03-0.05 mW, the scanning speed is 50 mV / S, and the time is 2-5 min.

9. The method for in situ Raman spectral measurement according to claim 1, wherein In step (3), the laser focusing step for adjusting the liquid layer distance is first focusing the laser to the surface of the single crystal electrode with Z-axis adjustment of 0, and then focusing the laser to the upper surface of the window piece to calculate the liquid layer distance.

10. The method for in situ Raman spectral measurement according to claim 1, wherein In step (3), the laser focusing for adjusting the liquid layer distance is within 50 μm.

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