A tunable infrared spectroscopy device with microsecond time resolution and continuous spectral acquisition

Abstract

The application discloses a tunable infrared spectrum device with microsecond time resolution and continuous spectrum acquisition, which is based on the wide-band continuous spectrum acquisition of a conventional Fourier transform infrared spectrometer, but the time resolution of the electrochemical reaction system is more than 100 milliseconds, and the in-situ / working condition infrared spectrum characterization capability for the double-layer potential response and the microsecond to millisecond time resolution of the lithium ion battery interface process is lacked, through coupling monochromatic infrared laser, the advantage of high repetition frequency, and automatic triggering and high-speed acquisition card, in-situ / working condition infrared detection with high time resolution and continuous spectrum acquisition can be realized simultaneously. The application also discloses a method for eliminating the power fluctuation of monochromatic infrared laser, based on the problem of large power fluctuation of monochromatic infrared laser, the laser is divided into a reference light and a detection light, the laser fluctuation noise is eliminated through difference spectrum, and stable, high signal-to-noise ratio and high time resolution infrared signal acquisition is realized.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical infrared spectroscopy measurement with microsecond time resolution and continuous spectrum acquisition, and in particular to a microsecond time resolution infrared spectroscopy device. Background Art

[0002] Infrared spectroscopy can effectively identify electrochemical processes and reactive species at multiphase interfaces in electrochemical systems using its unique infrared fingerprint characteristics and surface selection laws. This technology is of great significance for deepening the understanding of electrochemical reaction mechanisms and interfacial processes, and guiding the controllable construction of electrode materials. However, the response time of existing conventional infrared spectrometers for electrochemical reaction systems is over 100 milliseconds, which is far from sufficient for detecting electrochemical processes with microsecond time resolution, such as the potential response of the double layer, electrode process dynamics, and interfacial processes in lithium-ion batteries.

[0003] Currently, there are two main categories of infrared spectroscopy techniques aimed at achieving high time resolution. One category, including rapid scanning, ultra-rapid scanning, step scanning, stroboscopic sampling, and asynchronous sampling, primarily improves time resolution by controlling the interferometer's moving mirror drive mode or pulse sampling sequence. While asynchronous sampling, stroboscopic sampling, and step scanning can achieve nanosecond time resolution, they require the reaction system to be reversible and the reaction to be rapidly repeatable, making them less applicable to the complex in situ / operating electrochemical reaction interface studies. Rapid scanning and ultra-rapid scanning, while unrestricted by the reaction system, only achieve millisecond time resolution, far from sufficient for detecting electrochemical responses. The other category relies on dispersive infrared spectrometers, measuring the infrared intensity at a fixed wavelength during electrochemical processes. While the theoretical time resolution of these techniques is limited only by the detector's response speed and the ADC conversion cycle, they can easily achieve microsecond time resolution. However, due to the weak infrared light intensity, multiple spectrum acquisitions and averaging are required, resulting in a somewhat reduced actual time resolution. Summary of the Invention

[0004] The purpose of the present invention is to address the insufficient capability of existing infrared spectrometers for in-situ / operating infrared spectroscopy characterization of the double-layer potential response and interfacial processes in electrochemical reactions with microsecond to millisecond time resolution, and to design and provide a tunable infrared spectroscopy device that can combine microsecond time resolution and continuous spectral sampling and synchronous detection.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A tunable infrared spectroscopy device with microsecond time resolution and continuous spectrum acquisition includes:

[0007] Continuous spectrum infrared testing system: After the infrared light source generates a broadband continuous light source, the motor drives the aperture to adjust the light flux and then deflects it through the angle mirror to enter the Michelson interferometer. The infrared light after interference is reflected by the angle mirror into the sample chamber to collect the in-situ / working condition electrochemical reaction surface interface information, and then reflected by the angle mirror into the detector for detecting infrared signals;

[0008] High time-resolution infrared detection system (including dual-optical path noise reduction system): The infrared laser generates high-repetition-rate monochromatic light or monochromatic continuous light, which is divided into a reference light and a detection light by a beam splitter. The reference light is reflected by the corner mirror and directly enters the detector to generate a reference spectrum; the detection light is transmitted through the corner mirror with an opening in the optical center into the sample chamber to synchronously collect the in-situ / working-state double-layer potential response and electrode interface process information in the microsecond to millisecond range, and then enters the detector. The interface response signal is obtained by subtracting the detection spectrum from the reference spectrum.

[0009] Visible light path calibration system: The HeNe lasers equipped in the two test systems generate visible lasers, which are reflected / transmitted through the corner mirrors and coaxial with the broadband continuous infrared light and the monochromatic infrared laser, respectively, to adjust and calibrate the infrared optical path.

[0010] Preferably, the broadband continuous infrared light source is a thermal radiation mid-infrared light source, which can provide continuous and stable mid-infrared light.

[0011] Preferably, the motor drives the aperture, and controls the size of the light hole by electrically driving blades to adjust the light flux to an optimal value.

[0012] Preferably, in the Michelson interferometer, after the continuous infrared light is incident on the beam splitter, it is split into two beams of light that respectively irradiate the fixed mirror and the moving mirror. The two beams of light reflected back have an optical path difference and thus form interference.

[0013] Preferably, the corner mirrors are 45° gold-plated plane corner mirrors and concave spherical corner mirrors for light beam steering and parallel light beam focusing.

[0014] Preferably, the detector of the continuous spectrum infrared testing system is a liquid nitrogen cooled MCT detector (HgCdTe, MCT) with a detection range of 1-25 μm.

[0015] Preferably, the infrared laser is a Quantum Cascade Laser (QCL) infrared laser / grating spectrometer, which can output high-repetition-rate and high-power monochromatic light / continuous monochromatic light, and can obtain a spectrum signal with a high signal-to-noise ratio without multiple spectrum superposition and averaging, and can achieve microsecond time resolution.

[0016] Preferably, the beam splitter of the high time resolution infrared detection system can be made of ZnSe, gold-plated Si wafer, etc. according to the wavelength of the infrared laser, and is used to split the light beam into a reference light and a detection light.

[0017] Preferably, the sample chamber's front and rear corner mirrors are 45° gold-plated concave spherical mirrors with a 2mm through-hole at their optical center. The 45° gold-plated concave spherical surface is used to redirect a broadband, continuous mid-infrared beam into the sample chamber and reflect infrared light emitted from the sample chamber to the detector for signal collection and processing. The 2mm through-hole, while not affecting mid-infrared light reflection, allows monochromatic infrared laser light to pass directly through the sample chamber, where it is absorbed by the sample and then transmitted through the rear corner mirror's through-hole into the detector, enabling continuous spectral acquisition and simultaneous high-time-resolution acquisition.

[0018] Preferably, the detector of the high time-resolution infrared detection system can be selected from liquid nitrogen-cooled MCT detectors and broadband DTGS detectors according to the laser wavelength requirements, and can be matched with automatic triggering and high-speed acquisition cards, which effectively reduces the impact of detector response speed and ADC conversion cycle, and achieves microsecond time resolution.

[0019] Preferably, the visible laser is a helium-neon (HeNe) laser, which provides visible laser light and adjusts the visible laser light to be coaxial with the infrared beam and the monochromatic beam through components such as a beam splitter, an angle mirror, and a flat reflector to calibrate the optical path.

[0020] The present invention also provides a dual-path noise reduction method that can effectively eliminate power fluctuations of high-repetition-rate lasers. The method includes the following steps:

[0021] S1 uses a beam splitter to split the monochromatic infrared laser into two beams, one for reference light and the other for detection light;

[0022] The S2 reference beam is reflected by the corner mirror and enters the detector directly to generate a reference spectrum;

[0023] The S3 detection beam enters the sample chamber through the 2mm optical through-hole of the front corner mirror of the sample chamber, is absorbed by the sample, and then enters the detector through the optical through-hole of the rear corner mirror to obtain the detection spectrum;

[0024] S4 eliminates the high noise caused by high power fluctuations by performing spectrum subtraction on the spectra at the same time and space scales, achieving stable and high signal-to-noise ratio infrared signal acquisition.

[0025] The present invention designs a tunable infrared spectroscopy device with both microsecond time resolution and continuous spectrum sampling. The present invention is based on the characteristics of conventional Fourier transform infrared spectrometers that can continuously sample spectrum over a wide band, combined with the advantages of high repetition frequency of monochromatic infrared lasers, with automatic triggering and high-speed acquisition cards, and through a unique optical path design, the two types of spectrum acquisition are coupled together to achieve in-situ / working condition infrared detection with high time resolution and continuous spectrum sampling simultaneously. In addition, although high repetition rate infrared lasers have the advantages of high output average power and short pulse time, this does not bring low noise indicators to the laser, which greatly hinders its application in the field of infrared measurement. The present invention designs a method for eliminating power fluctuations of high repetition rate lasers, dividing the laser into a reference light and a detection light, and eliminating the high noise caused by high power fluctuations by performing spectrum difference on the spectrum at the same time and space scales, thereby achieving stable, high signal-to-noise ratio, and high time resolution infrared signal acquisition.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. The present invention uses a QCL infrared laser / grating spectrometer to generate high-repetition-rate infrared laser light with high average output power and short pulse duration. This solves the problem of traditional dispersive infrared spectrometers, which suffer from weak infrared light intensity and low temporal resolution after spectral averaging, making it impossible to achieve in-situ / operating infrared detection of double-layer potential response and interfacial processes with microsecond-level time resolution.

[0028] 2. The present invention is based on the conventional Fourier transform infrared spectrometer capable of broadband continuous spectrum acquisition, combined with the infrared laser high time resolution infrared detection system, and through a unique optical path design, it can achieve broadband continuous spectrum acquisition and microsecond time resolution synchronous acquisition.

[0029] 3. The present invention also provides a method for eliminating infrared laser noise, which solves the high noise problem caused by high repetition rate, realizes infrared signal acquisition with high signal-to-noise ratio, and ensures in-situ / working condition infrared detection with high time resolution. The method is simple, widely applicable, and highly expandable. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below with reference to the accompanying drawings and examples.

[0031] Figure 1 A schematic diagram of an implementation of a tunable infrared spectroscopy device with microsecond-level time resolution and continuous spectrum acquisition and synchronous detection provided by the present invention;

[0032] Among them, 1-thermal radiation mid-infrared light source, 2-motor-driven aperture, 3-gold-plated corner mirror, 4-Michelson interferometer, 5-gold-plated corner mirror, 6 and 7-gold-plated corner mirrors with optical center opening, 8-MCT detector, 9-QCL infrared laser, 10-beam splitter, 11-gold-plated corner mirror, 12 and 13-MCT detector, 14 and 15-He-Ne laser, 16-beam splitter, 17 and 18-gold-plated flat mirrors, 19-sample chamber, L1-broadband infrared beam, L2-monochromatic infrared laser, L3-visible laser.

[0033] Figure 2 A schematic diagram of an implementation of a tunable infrared spectroscopy device with microsecond-level time resolution and continuous spectrum acquisition and synchronous detection provided by the present invention.

[0034] Figure 3 This is the infrared detection device and noise reduction system of the present invention.

[0035] Figure 4 Figure 3 is the CO adsorption on the Cu surface observed by the infrared detection device and noise reduction system of the present invention, where a is the tunable free electron laser spectrum of the Cu thin film catalyst in 0.5M KHCO3 saturated with CO2; b is the spectrum at different potential differences. DETAILED DESCRIPTION

[0036] In order to clearly illustrate the purpose, technical solutions and advantages of the present invention, the present invention is further described in detail below with reference to the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate the present invention, but are not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the scope of protection of the present invention.

[0037] The present invention provides a tunable infrared spectroscopy device with both microsecond time resolution and continuous spectrum sampling and synchronous detection, which consists of a continuous spectrum sampling infrared testing system, a high time resolution infrared detection system (including a dual-light path noise reduction system) and a visible light path calibration system.

[0038] like Figure 1 As shown in the solid line frame, the continuous spectrum infrared testing system of the present invention adopts the structure of conventional Fourier transform infrared spectroscopy. First, a thermal radiation mid-infrared light source 1 generates a beam of 7800-350cm -1The mid- and far-infrared light beam L1 is then collimated to become parallel light. After the motor drives the aperture 2 to adjust the light flux to an appropriate size, it is deflected by the angle mirror 3 and enters the Michelson interferometer 4. It is incident on the beam splitter at a 45-degree angle. Half of the light is reflected by the beam splitter onto the fixed mirror, and the other half passes through the beam splitter and hits the moving mirror. After reflection by the fixed mirror and the moving mirror, the two beams are merged together to form coherent light with interference light characteristics. At this time, the light beam is reflected by the angle mirror 5 and the gold-plated angle mirror 6 with an opening in the optical center and enters the sample chamber 19. After being absorbed by the sample, it is reflected by the gold-plated angle mirror 7 with an opening in the optical center and enters the MCT detector 8. The detection range is 4000-600cm. -1 Obtain broadband infrared spectrum signals.

[0039] like Figure 1 As shown in the dotted box, the present invention provides a high time resolution infrared detection system (including a dual optical path noise reduction system), the QCL infrared laser 9 generates a beam of 3700-1800 cm -1 A tunable monochromatic infrared laser L2 is split by a beam splitter 10 into two beams of equal intensity. One beam, a reference beam, is reflected by a corner mirror 11 and enters an MCT detector 12 to produce a reference spectrum. The other beam, a detection beam, passes through a 2mm optical aperture at the center of a gold-plated corner mirror 6 and enters a sample chamber 19 to collect the sample signal. Subsequently, it passes through a 2mm optical aperture at the center of a gold-plated corner mirror 7 and enters an MCT detector 13 to produce a detection spectrum containing sample information. To achieve microsecond time resolution, MCT detectors 12 and 13 are paired with an automatic trigger and a high-speed acquisition card to minimize the impact of detector response speed and ADC conversion cycle on temporal resolution. To eliminate noise introduced by high-repetition-rate infrared laser power fluctuations, the reference spectrum and detection spectrum, acquired simultaneously on a spatial scale, are subtracted to obtain highly time-resolved potential response and interfacial process information at the electrochemical reaction interface.

[0040] like Figure 1 The present invention provides a visible light optical path calibration system. First, the optical path calibration of the continuous spectrum infrared test system uses a HeNe laser 14 to generate a visible laser L3. After being reflected by a beam splitter 16, the visible laser L3 is coaxial with the infrared beam to calibrate the position of the infrared beam and optimize the optical path. The optical path calibration of the high time resolution infrared detection system uses a HeNe laser 15 to generate a visible laser L3. After being reflected by gold-plated flat mirrors 17 and 18, the visible laser L3 is coaxial with the monochromatic infrared laser to calibrate the infrared laser.

[0041] The present invention is further described below with reference to specific embodiments.

[0042] The above-mentioned continuous spectrum infrared test system and high time resolution infrared detection system (including dual optical path noise reduction system) are used to in situ monitor the evolution process of the interface intermediate species in the carbon dioxide reduction reaction (CO2RR) of Cu electrocatalyst, including the following steps:

[0043] according to Figure 1 The continuous spectrum infrared testing system of the present invention adopts a conventional Fourier transform infrared spectrometer to continuously track the evolution of intermediate species on the surface reaction of Cu catalyst in CO2RR during different potential steps in a wide band (such as Figure 2 ). The sample chamber 19 uses a laboratory-made attenuated total reflection electrolytic cell and optical path accessories, and an external electrochemical workstation and gas path provide the necessary reaction conditions for the reaction system. In this embodiment, commercial Cu nanoparticles are used as catalysts, Pt foil is used as the counter electrode, AgCl is used as the reference electrode, and CO2-saturated 0.5M KHCO3 is used as the supporting electrolyte. A multi-step test method is used, and the reference potential is set to 0V (vs RHE), and the detection potential is -0.1 to -1.3V (vs RHE); the continuous spectrum scanning range is: 4000-800cm -1 , Resolution: 8cm -1 . Figure 2 This is a broadband in-situ infrared spectrum of commercial Cu nanoparticles provided in an embodiment of the present invention in 0.5M KHCO3 saturated with CO2. It can be seen from the infrared spectrum that as the potential gradually becomes negative, the 2000-2100 cm -1 *CO was observed between L In the evolution process of Cu surface, in addition, 1300-1500cm -1 HCO3 was also observed - and CO3 2- transformation and consumption process.

[0044] according to Figure 1 The high time resolution infrared detection system of the present invention (including dual optical path noise reduction system) was built at the Infrared Free Electron Laser Energy Chemistry Research Center. Figure 3 The infrared detection device and noise reduction system shown in the figure. This embodiment uses a free electron laser light source to observe the adsorption of *CO on the Cu surface. Figure 4 The tunable free electron laser spectrum and different potential difference spectra of the Cu thin film catalyst provided in the embodiment of the present invention in 0.5M KHCO3 saturated with CO2. Figure 4 As shown, at 410cm -1 The infrared signal of the Cu-C bond in Cu-CO was observed nearby. The above series of results demonstrate that the tunable infrared spectroscopy device with microsecond time resolution and continuous spectrum acquisition and synchronous detection provided by the present invention has good applicability for electrochemical in-situ / operating infrared detection.

Claims

1. A tunable infrared spectroscopy device with both microsecond time resolution and continuous spectrum acquisition, characterized in that: It includes a continuous spectrum infrared test system, a high time resolution infrared detection system with a dual optical path noise reduction system, and a visible light path calibration system; among them, The continuous spectrum sampling infrared testing system comprises an infrared light source (1), wherein the infrared light source (1) generates a broadband continuous light source (L1), which is then driven by a motor to drive an aperture (2) to adjust the light flux and then deflected by an angle mirror (3) to enter a Michelson interferometer (4). The infrared light after interference is passed through angle mirrors (5, 6) into a sample chamber (19) to collect in-situ / working condition electrochemical reaction surface interface information, and then passes through an angle mirror (7) into a detector (8) for infrared signal detection. The high time resolution infrared detection system including the dual optical path noise reduction system comprises a beam of high repetition rate monochromatic light or monochromatic continuous light (L2) generated by an infrared laser (9), which is divided into two beams by a beam splitter (10), one beam being a reference light which directly enters a detector (12) through an angle mirror (11) to generate a reference spectrum; the other beam being a detection light which enters a sample chamber (19) through an angle mirror (6) with an optical center opening to synchronously collect in-situ / working state double electric layer potential response and electrode interface process information at the microsecond to millisecond level with high time resolution, and then enters a detector (13) through an angle mirror (7) with an optical center opening, and obtains an interface response signal by subtracting the detection spectrum from the reference spectrum. The visible light path calibration system comprises two beams of visible laser light (L3) generated by lasers (14, 15), which are respectively reflected by beam splitters (16, 10), interferometers (4), angle mirrors (5, 6, 7, 11) and flat reflectors (17, 18) and then coaxial with broadband continuous infrared light (L1) and monochromatic infrared laser light (L2), for adjusting and calibrating the infrared light path.

2. The tunable infrared spectroscopy device with microsecond time resolution and continuous spectrum acquisition according to claim 1, characterized in that: The infrared light source is a thermal conductivity type mid-infrared light source.

3. The tunable infrared spectroscopy device with microsecond time resolution and continuous spectrum acquisition according to claim 1, characterized in that: The infrared laser is a quantum cascade infrared laser / grating spectrometer that outputs high repetition rate / continuous monochromatic light; the high repetition rate monochromatic light, combined with automatic triggering and a high-speed acquisition card, enables infrared signal acquisition with microsecond time resolution.

4. The tunable infrared spectroscopy device with microsecond time resolution and continuous spectrum acquisition according to claim 1, characterized in that: The detector (8) of the continuous spectrum infrared testing system is a liquid nitrogen cooled mercury cadmium telluride detector with a detection range of 1-25 μm.

5. The tunable infrared spectroscopy device with microsecond time resolution and continuous spectrum acquisition according to claim 1, characterized in that: The dual-path noise reduction system uses a beam splitter to split monochromatic infrared light into two beams of monochromatic light of equal intensity. One beam serves as reference light and enters the detector directly, while the other enters the sample chamber to collect signals and then enters the detector. The two obtained spectra are then subtracted to eliminate noise caused by laser power fluctuations.

6. The tunable infrared spectroscopy device with microsecond time resolution and continuous spectrum acquisition according to claim 1, characterized in that: The corner mirror with an opening in the optical center is provided with a light through hole in the optical center of the front and rear corner mirrors of the sample chamber in the continuous spectrum infrared testing system. While not affecting the reflection of broadband continuous infrared light, it allows monochromatic infrared light to pass directly and enter the sample chamber coaxially with the broadband continuous infrared light, thereby realizing the synchronous acquisition of continuous spectrum and microsecond time-resolved spectrum.

7. The tunable infrared spectrometer with microsecond time resolution and continuous spectrum acquisition according to claim 1, characterized in that: The laser in the visible light path calibration system is a helium-neon laser that emits visible laser light to calibrate the light path.

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