Pulse broadening transient raman probing system for studying electrode electrocatalysis processes

Abstract

This invention relates to a pulse-broadened transient Raman detection system for studying electrocatalytic processes at electrodes, belonging to the field of Raman spectroscopy technology. It includes a resistor, digital oscilloscope, computer, electrochemical workstation, signal generator, femtosecond laser, silver mirror one, silver mirror two, crystal, dichroic mirror, pulse broadener, aperture, narrowband filter, silver mirror six, Raman filter one, reflection to aperture, objective lens, pulse delayer, silver mirror seven, Raman filter two, cemented doublet lens, electrolytic cell, and charge-coupled device. Its advantages lie in using transient Raman spectroscopy with a pulse broadener, combined with electrical excitation and time-resolved measurement methods during the electrochemical reaction process, to detect reaction intermediates on and around the electrode surface with high temporal and spatial resolution. It can detect Raman signals of reaction intermediates on the electrode surface on a femtosecond timescale, thus providing a new approach to understanding the mechanism of electrocatalytic reactions.

Description

Technical Field

[0001] This invention belongs to the field of Raman spectroscopy technology, specifically relating to a pulse-broadened transient Raman detection system for studying electrode electrocatalytic processes. Background Technology

[0002] Electrocatalysis plays a crucial role in many fields, particularly in energy conversion, storage, and environmental protection, such as fuel cells, water electrolysis for hydrogen production, and carbon dioxide reduction. However, the complexity of electrocatalytic reactions makes their reaction mechanisms and kinetics difficult to understand in detail, especially the formation, transformation, and diffusion of electrochemical reaction intermediates occurring at the electrode surface. These processes are often accompanied by rapid mass and energy exchanges, and the evolution of reaction intermediates, especially on short timescales, directly affects electrocatalytic performance and reaction efficiency. Therefore, accurately probing the behavior of these reaction intermediates is key to understanding the mechanisms of electrocatalytic reactions.

[0003] In existing technologies, Raman spectroscopy, as a non-contact, non-destructive analytical tool, has been widely applied in materials science and electrochemical reaction research. By detecting molecular vibrational modes, Raman spectroscopy can provide crucial information about the chemical composition, molecular structure, and bonding state of the research object. However, traditional Raman spectroscopy suffers from insufficient spatial and temporal resolution, making it difficult to effectively observe reaction processes over short periods, especially in electrocatalytic reactions where the generation and disappearance of reaction intermediates are transient, often occurring on nanosecond or even shorter timescales. To better probe the dynamic behavior of these electrocatalytic processes, it is necessary to combine time-resolved Raman spectroscopy with electrochemical methods to capture the formation and evolution of reaction intermediates at a higher temporal resolution. Furthermore, the complexity of the electrode surface in electrochemical reactions necessitates the resolution and detection of reaction intermediates in different spatial regions. The electric field near the electrode surface, the diffusion of reactants, the formation of products, and the distribution of current density can all lead to different local reaction behaviors. Therefore, in-depth research on electrocatalytic reactions requires not only time-resolved analytical methods but also high-precision measurements of the three-dimensional spatial information of the electrode surface and its surrounding areas. This need has prompted researchers to develop detection systems that can achieve both high temporal and spatial resolution simultaneously.

[0004] In the field of electrochemistry, researchers often use a three-electrode system (including a working electrode, a reference electrode, and a counter electrode) to study electrocatalytic reactions on electrode surfaces. However, electrocatalytic reactions occur at the electrode-electrolyte interface, and the reaction intermediates in this process are often in high-energy and short-lived states, making them extremely difficult to detect directly. Although electrochemical workstations can provide real-time current-voltage (IV) curves to analyze electrochemical reactions occurring on the electrode surface, they cannot directly provide structural information about the reaction intermediates. Therefore, combining spectroscopic analysis techniques with electrochemical systems is a viable approach to understanding these complex electrochemical reaction mechanisms. While Raman spectroscopy, due to its sensitivity to molecular structure, can provide information on molecular vibrational modes and is suitable as a tool for detecting intermediates in electrocatalytic reactions, Raman detection in electrochemical systems faces several challenges. First, electrochemical reactions are often dynamic, and the intermediates in the reaction process have transient characteristics, making them difficult to detect with static Raman spectroscopy. Second, the formation, diffusion, and disappearance of reaction intermediates on the electrode surface is a very short-lived process, requiring high temporal resolution detection methods. The temporal resolution of traditional Raman spectroscopy is typically in the millisecond range, far lower than the temporal resolution required for electrocatalytic reactions. Summary of the Invention

[0005] This invention provides a pulse-broadened transient Raman detection system for studying electrode electrocatalytic processes, in order to solve the current problems faced in Raman detection in electrochemical systems, namely, that intermediates in the reaction process have transient characteristics and are difficult to detect by static Raman spectroscopy, and that the time resolution of traditional Raman spectroscopy is usually in the millisecond range, which is far lower than the time resolution required for electrocatalytic reactions.

[0006] The technical solution adopted in this invention includes a circuit section, a transient Raman spectroscopy testing section, an electrolytic cell, and a charge-coupled device (CCD). The circuit section includes a resistor, a digital oscilloscope, a computer, an electrochemical workstation, and a signal generator. The signal generator is electrically connected to the electrochemical workstation, and the computer is connected to the USB interface of the electrochemical workstation via a USB-to-square data cable. A resistor is connected in series between the electrochemical workstation and the electrolytic cell, and a digital oscilloscope is connected in parallel across the resistor. The transient Raman spectroscopy testing section includes a femtosecond laser, a silver mirror (first and second), a BBO crystal, a dichroic mirror, a pulse stretcher, an aperture (first), a narrowband filter, a silver mirror (sixth), a Raman filter (first), an aperture (second), an objective lens, a pulse delayer, a silver mirror (seventh), and a Raman filter (second). The system consists of a cemented doublet lens, in which a pulse delayer is electrically connected to a femtosecond laser. The femtosecond pulse laser emitted by the femtosecond laser is reflected by silver mirrors one and two, and then converted into 515nm green light by a BBO crystal. This green light passes through a dichroic mirror, is split into beams 1 and 2 by a pulse stretcher, and then passes through a narrowband filter. It is then reflected by silver mirror six and Raman filter one to aperture two. The objective lens focuses the beam into the electrolytic cell, illuminating the spatial region on the electrode surface where the reaction intermediate to be tested is located. The light scattered by the reaction intermediate passes through the objective lens, aperture two, and Raman filter one to reach silver mirror seven. The beam is reflected by silver mirror seven and passes through Raman filter two and the cemented doublet lens to be focused onto the charge-coupled device, thus obtaining the Raman spectral signal of the reaction intermediate.

[0007] The pulse stretcher includes a third silver mirror, a fourth silver mirror, a fifth silver mirror, and a beam splitter. 50% of the laser light reflected by the third silver mirror is directly reflected by the beam splitter into the first aperture, which is called light number 1. The other 50% of the laser light reflected by the third silver mirror passes through the beam splitter, is reflected again by the fourth and fifth silver mirrors, reaches the beam splitter, and is incident into the first aperture, which is called light number 2.

[0008] The signal generator outputs a square wave electrical signal with a high level of 5V and a low level of 0.8V.

[0009] The high-level 5V output of the signal generator is the normal state, and the low-level 0.8V is the trigger state.

[0010] The resistor has a resistance of 100Ω.

[0011] The signal generator is electrically connected to the pulse delayer.

[0012] The narrowband filter is used to filter out unwanted light, allowing only light within a specific wavelength range to pass through, in order to ensure the purity and accuracy of the Raman signal.

[0013] During the current decay phase after the electrical pulse signal ends, a pulse delay device is used to precisely control the time Δ. t The Raman signal of the reaction intermediate is detected by femtosecond laser pulses.

[0014] The Raman filter one and Raman filter two are used to block the excitation light, allowing only the longer wavelength Raman scattering signal to pass through.

[0015] A resistor is connected in series between the green clamp d and the counter electrode c in the electrolytic cell of the electrochemical workstation; the red clamp f is connected to the working electrode a in the electrolytic cell; and the white clamp e is connected to the reference electrode b.

[0016] The beneficial effects of this invention are:

[0017] This invention utilizes transient Raman spectroscopy equipped with a pulse broadening device, combined with electrical excitation and time-resolved measurement methods during electrochemical reactions, to detect reaction intermediates on and near the electrode surface with high temporal and spatial resolution. This innovative multi-pulse "pump-probe" measurement method enables the detection of Raman signals of reaction intermediates on the electrode surface on a femtosecond timescale, thus providing a new approach to understanding the mechanisms of electrocatalytic reactions.

[0018] This invention offers excellent adjustability and ease of use. Utilizing an open-type transient Raman system with pulse broadening, it detects the Raman signals of reaction intermediates generated during electrochemical reactions under the influence of electrical pulses. This allows for precise monitoring and analysis of the dynamic processes of electrocatalytic reactions, providing a powerful tool for studying electrochemical reaction mechanisms. The highly adjustable signal generator of this invention enables flexible control of the electrochemical reaction process. Furthermore, after applying a single electrical pulse signal to the electrochemical system, the diffusion of reaction intermediates can be detected at different times and spatial locations using femtosecond laser pulses.

[0019] This invention achieves highly efficient detection of reaction intermediates during electrocatalytic reactions. By introducing femtosecond laser pulses, transient processes in electrocatalytic reactions can be detected with femtosecond-level temporal resolution, overcoming the limitation of traditional Raman spectroscopy in capturing fast reaction intermediates. Furthermore, a pulse stretcher is introduced: by broadening short laser pulses, the probability of capturing Raman signals is increased. This process also reduces peak power, avoiding damage to optical components. By adjusting the objective lens focus position, precise three-dimensional spatial detection of the electrode surface and its surrounding area can be achieved, realizing high spatial resolution and better revealing the spatial distribution of reaction intermediates.

[0020] This invention organically combines an electrochemical workstation with a Raman spectroscopy system, enabling comprehensive monitoring of the generation, diffusion, and disappearance of substances in electrochemical reactions. It provides a powerful tool for the study of electrocatalytic reactions, offers more complete information on the electrocatalytic reaction process, and is expected to promote further development in this field. Attached Figure Description

[0021] Figure 1 This is a system schematic diagram of the present invention. Detailed Implementation

[0022] See Figure 1 The system includes a circuit section, a transient Raman spectroscopy testing section, an electrolytic cell 16, and a charge-coupled device (CCD) 20. The circuit section includes a resistor 17, a digital oscilloscope 18, a computer 19, an electrochemical workstation 21, and a signal generator 22. The signal generator 22 is electrically connected to the electrochemical workstation 21. The computer 19 is connected to the USB interface of the electrochemical workstation 21 via a USB-to-square data cable to ensure precise control of the pulse voltage. After the trigger signal arrives at the electrochemical workstation 21, under the control of the computer 19, the electrochemical workstation 21 outputs the required pulse voltage signal for measuring electrochemical reactions. In response to transient current changes during the process, a 100Ω resistor 17 is connected in series between the green clamp d of the electrochemical workstation 21 and the counter electrode c in the electrolytic cell 16. The red clamp f is connected to the working electrode a in the electrolytic cell 16, and the white clamp e is connected to the reference electrode b. A digital oscilloscope 18 is connected in parallel across the resistor 17. The voltage change across the resistor 17 is monitored in real time by the digital oscilloscope 18, and the transient current response under the action of the pulse voltage is recorded. After a single electrical pulse signal is applied, the current in the electrochemical reaction system will gradually decay as the reaction intermediate diffuses. During the current decay process, a specific time Δt is selected to detect the Raman signal of the reaction intermediate in order to obtain key information in the electrochemical reaction process.

[0023] The transient Raman spectroscopy testing section includes a femtosecond laser 1, silver mirror 1 2, silver mirror 2 3, BBO crystal 4, dichroic mirror 5, pulse stretcher A, aperture 1 9, narrowband filter 11, silver mirror 6 12, Raman filter 1 13, aperture 2 14, objective lens 15, pulse delayer 23, silver mirror 7 24, Raman filter 2 25, and cemented doublet lens 26. The pulse delayer 23 is electrically connected to the femtosecond laser 1. Raman signal detection is achieved through the pulse delayer DG535 (23), which is used to precisely adjust the relative delay between the femtosecond laser 1 and the signal generator 22, synchronizing the emission of the femtosecond pulsed laser with the time of the electrochemical reaction. The femtosecond pulsed laser emitted by the femtosecond laser 1 passes through silver mirror 1... The light beam is reflected by mirror 2 and silver mirror 3, and then converted into 515nm green light by BBO crystal 4. This green light passes through dichroic mirror 5, is split into light 1 and light 2 by pulse stretcher, and then passes through narrowband filter 11. It is then reflected by silver mirror 6 12 and Raman filter 13 to aperture 2 14. The objective lens 15 focuses the light beam into electrolytic cell 16, illuminating the spatial region of the reaction intermediate to be tested on the electrode surface. The light scattered by the reaction intermediate (indicated by dashed lines) passes through objective lens 15, aperture 2 14, and Raman filter 13 to reach silver mirror 7 24. The light beam is reflected by silver mirror 7 24 and passes through Raman filter 2 25 and cemented doublet lens 26 to be focused onto charge-coupled device CCD 20, thus obtaining the Raman spectrum signal of the reaction intermediate.

[0024] The pulse stretcher A includes silver mirror 3 (6), silver mirror 4 (7), silver mirror 5 (8), and beam splitter 10. 50% of the laser light reflected by silver mirror 3 (6) is directly reflected by beam splitter 10 to aperture 9, referred to as beam 1. The other 50% of the laser light reflected by silver mirror 3 (6) passes through beam splitter 10, is reflected again by silver mirror 4 (7) and silver mirror 5 (8), and then incident on aperture 9, referred to as beam 2. Because the two beams have different optical path lengths, their arrival times at the sample surface differ. This results in an extra beam within a single pulse to detect the Raman signal of the reaction intermediate. During the sample's reaction, multiple pulses are used to detect the signal, thus increasing the number of additional beams for signal detection. This significantly increases the probability of detecting the reaction intermediate signal. Since the laser's output power overflows, the presence of beam splitter 10 does not need to be considered in relation to the light intensity or power.

[0025] The signal generator 22 outputs a square wave electrical signal with a high level of 5V and a low level of 0.8V. This signal is transmitted to the electrochemical workstation 21 through the circuit to trigger its operation.

[0026] The high level of 5V output by the signal generator 22 is the normal state, and the low level of 0.8V is the trigger state.

[0027] The resistor 17 has a resistance of 100Ω.

[0028] The signal generator 22 is electrically connected to the pulse delay unit 23.

[0029] Narrowband filter 11 is used to filter out unwanted light, allowing only light within a specific wavelength range to pass through, in order to ensure the purity and accuracy of the Raman signal.

[0030] During the current decay phase after the electrical pulse signal ends, the pulse delay unit 23 is used to precisely control the time Δ. t The Raman signal of the reaction intermediate is detected by femtosecond laser pulses.

[0031] Raman filter 13 and Raman filter 25 are used to block the excitation light and only allow the longer wavelength Raman scattering signal to pass through.

[0032] System working principle

[0033] This invention is used to study the electrocatalytic process on the electrode surface. It adopts the "pump-probe" principle in transient spectroscopy to detect the Raman spectra of reaction intermediates generated at different times after electrical excitation, thereby revealing the electrocatalytic reaction mechanism near the electrode under diffusion-driven conditions.

[0034] This invention incorporates a pulse stretcher in a transient Raman system, consisting of three silver mirrors and a beam splitter 10. The split beam propagates in a delay arm formed by the three silver mirrors. Due to the different number of times the beam passes through the silver mirror 7, the optical path length varies, resulting in different propagation speeds even in the same medium. For example, the beam that does not pass through the silver mirror 7 has the shortest optical path and propagation time; the beam that passes through the silver mirror 7 once has a longer optical path and propagation time. Thus, light that originally departed simultaneously from the beam splitter has a time difference when it reaches the beam splitter again, naturally resulting in a time difference when it reaches the sample. This effectively delays and replicates the isochronous short pulse beam from the laser. Since the number of beams increases over time, this significantly increases the probability of Raman signal capture. In summary, by incorporating a pulse stretcher A in an open optical path, the different optical path lengths of the beams passing through the beam splitter 10 result in different arrival times at the sample. This adds a large number of additional beams during Raman signal detection, greatly increasing the probability of Raman signal capture.

[0035] Pulse-spanning transient Raman spectroscopy is a technique that combines time-resolved measurements with Raman spectroscopy. Its basic principle is that short-pulse laser light passes through a pulse stretcher and other optical components, including a beam splitter and total reflection mirrors, to collect Raman signals at different time delays, thereby enabling the detection of transient processes in the sample. The presence of the pulse stretcher significantly increases the probability of measuring Raman signals from chemical reaction intermediates. Furthermore, the accumulated time difference lengthens the pulse in the time domain, reducing peak power and preventing damage to optical components. To achieve this, a pulse stretcher consisting of three mirrors and a beam splitter is first introduced into an open optical path, where the optical path length can be adjusted by the researchers. Different optical path lengths can be adjusted for different samples, thus selecting different pulse stretching techniques.

[0036] This invention introduces a measurement scheme similar to a "pump-probe" technique. An electrochemical workstation generates electrical pulses via a signal generator, which are applied to the electrode as a "pump" signal to trigger the electrochemical reaction. Simultaneously, a femtosecond-level pulsed laser acts as a "probe" signal, scanning the electrode surface and its surrounding area to detect reaction intermediates generated during the electrode reaction. By precisely controlling the time delay between the laser pulse and the electrical pulse, Raman spectra of reaction intermediates in a specific region of the electrode surface at different times can be obtained. Analysis of these time-resolved Raman signals allows researchers to understand the dynamic processes of reaction intermediate formation, diffusion, and disappearance.

[0037] This invention is based on the "pump-probe" principle of transient spectroscopy. A step potential is applied as a "pump" signal to the electrode at a specific time point t=0 to trigger the electrochemical reaction. Simultaneously, a femtosecond laser pulse is used as the probe light, and a charge-coupled device (CCD) records the Raman spectrum of a reaction intermediate at a spatial location on the electrode surface at a delay time t=Δt, thereby confirming key information about the electrocatalytic reactants. Furthermore, the system monitors the current-time (I–T) curve of the entire electrochemical reaction system using a digital oscilloscope. This electrochemical reaction system employs a three-electrode configuration, including a counter electrode, a working electrode, and a reference electrode, to ensure precise control of the electrochemical reaction.

[0038] High and low level signals are generated by signal generator 22 to trigger the electrochemical workstation to output electrical pulse signals, driving the electrochemical reaction. A 100Ω small-amplitude resistor is connected in series in the entire circuit. The current change across the resistor is monitored in real time using a digital oscilloscope, thereby recording the transient current response of the electrochemical reaction system under the action of the electrical pulse signal. After applying a single electrical pulse signal, the system current gradually decreases as the intermediate diffuses in the electrochemical cell. The behavior of the reaction intermediate is analyzed by detecting the Raman signal during the process.

[0039] The Raman signal is detected by adjusting the relative delay between the femtosecond laser 1 and the signal generator 22 using a pulse delayer 23. The pulsed laser emitted by the femtosecond laser passes through a series of optical elements to reach the objective lens and is focused onto the reaction intermediate to be tested. The light scattered by the reaction intermediate passes through the objective lens and the silver mirror and is then converged into the CCD, thereby acquiring Raman signals at different time points and spatial locations.

[0040] After a pulsed voltage is applied to the electrode, an electrochemical reaction occurs within the electrochemical workstation 21. The generated reaction intermediates diffuse in the electrolyte. This diffusion process is dominated by molecular diffusion and has a relatively slow timescale. Therefore, the Raman signal of the reaction intermediates can be detected using femtosecond laser pulses at different delay times. Through time-resolved detection, key information about the reactants can be obtained. Simultaneously, by utilizing the changes in Raman signal intensity detected at different times, the concentration changes of the reaction intermediates can be inferred, thereby further deducing the mechanism and pathway of the electrocatalytic reaction on the electrode surface. In addition to time-resolved detection, by changing the focal point of the objective lens, the Raman signal of the reaction intermediates at different spatial locations near the electrode can be detected, thus obtaining three-dimensional spatial concentration distribution information of the reaction intermediates or products. This invention achieves the detection of reaction intermediates in different spatial regions of the electrode surface by adjusting the focal point position of the objective lens. This technology can provide three-dimensional spatial concentration distribution information of the electrode surface and its surrounding areas, providing important evidence for understanding the spatial heterogeneity of electrocatalytic reactions.

[0041] By combining time-resolved and spatial-resolved detection methods, researchers can not only detect the generation time of reaction intermediates, but also understand their spatial diffusion behavior. This combination provides a new perspective for revealing the local dynamics in complex electrochemical reactions.

Claims

1. A pulse-broadened transient Raman detection system for studying electrode electrocatalytic processes, characterized in that: The system includes a circuit section, a transient Raman spectroscopy testing section, an electrolytic cell, and a charge-coupled device (CCD). The circuit section includes a resistor, a digital oscilloscope, a computer, an electrochemical workstation, and a signal generator. The signal generator is electrically connected to the electrochemical workstation. The computer is connected to the electrochemical workstation's USB interface via a USB-to-square data cable. A resistor is connected in series between the electrochemical workstation and the electrolytic cell, and the digital oscilloscope is connected in parallel across the resistor. The transient Raman spectroscopy testing section includes a femtosecond laser, two silver mirrors (one and two), a BBO crystal, a dichroic mirror, a pulse stretcher, an aperture (one), a narrowband filter, a silver mirror (six), a Raman filter (one), an aperture (two), an objective lens, a pulse delayer, a silver mirror (seven), a Raman filter (two), and a cemented doublet lens. The pulse delayer is electrically connected to the femtosecond laser. The femtosecond pulse laser emitted by the femtosecond laser is reflected by silver mirror 1 and silver mirror 2, and then converted into 515nm green light by BBO crystal. The green light passes through a dichroic mirror, is split into light 1 and light 2 by a pulse stretcher and enters aperture 1. It then passes through a narrowband filter, is reflected by silver mirror 6 and Raman filter 1 and enters aperture 2. The objective lens focuses the beam into the electrolytic cell and illuminates the spatial region where the reaction intermediate to be tested is located on the electrode surface. The light scattered by the reaction intermediate passes through the objective lens, aperture 2, Raman filter 1 and reaches silver mirror 7. The beam is reflected by silver mirror 7 and passes through Raman filter 2 and cemented doublet lens and is focused onto the charge-coupled device to obtain the Raman spectrum signal of the reaction intermediate. The pulse stretcher includes a third silver mirror, a fourth silver mirror, a fifth silver mirror, and a beam splitter. 50% of the laser light reflected by the third silver mirror is directly reflected by the beam splitter into the first aperture, which is called light number 1. The other 50% of the laser light reflected by the third silver mirror passes through the beam splitter, is reflected again by the fourth and fifth silver mirrors, reaches the beam splitter, and is incident into the first aperture, which is called light number 2.

2. The pulse-broadened transient Raman detection system for studying electrode electrocatalytic processes according to claim 1, characterized in that: The signal generator outputs a square wave electrical signal with a high level of 5V and a low level of 0.8V.

3. The pulse-broadened transient Raman detection system for studying electrode electrocatalytic processes according to claim 2, characterized in that: The high-level 5V output of the signal generator is the normal state, and the low-level 0.8V is the trigger state.

4. The pulse-broadened transient Raman detection system for studying electrode electrocatalytic processes according to claim 1, characterized in that: The resistor has a resistance of 100Ω.

5. The pulse-broadened transient Raman detection system for studying electrode electrocatalytic processes according to claim 1, characterized in that: The signal generator is electrically connected to the pulse delayer.

6. The pulse-broadened transient Raman detection system for studying electrode electrocatalytic processes according to claim 1, characterized in that: The narrowband filter is used to filter out unwanted light, allowing only light within a specific wavelength range to pass through, in order to ensure the purity and accuracy of the Raman signal.

7. The pulse-broadened transient Raman detection system for studying electrode electrocatalytic processes according to claim 1, characterized in that: During the current decay phase after the electrical pulse signal ends, a pulse delay device is used to precisely control the time Δ. t The Raman signal of the reaction intermediate is detected by femtosecond laser pulses.

8. The pulse-broadened transient Raman detection system for studying electrode electrocatalytic processes according to claim 1, characterized in that: The Raman filter one and Raman filter two are used to block the excitation light, allowing only the longer wavelength Raman scattering signal to pass through.

9. The pulse-broadened transient Raman detection system for studying electrode electrocatalytic processes according to claim 1, characterized in that: A resistor is connected in series between the green clamp d and the counter electrode c in the electrolytic cell of the electrochemical workstation; the red clamp f is connected to the working electrode a in the electrolytic cell; and the white clamp e is connected to the reference electrode b.

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