Tunable infrared spectrum device with microsecond-level time resolution and continuous spectrum acquisition functions

Abstract

The invention discloses a tunable infrared spectrum device with microsecond-level time resolution and continuous spectrum acquisition, which can realize broadband continuous spectrum acquisition based on a conventional Fourier transform infrared spectrometer, but the time resolution of an electrochemical reaction system is more than 100 milliseconds. The in-situ / working condition infrared spectroscopy characterization capability aiming at microsecond-to-millisecond-level time resolution in the double-electrode-layer potential response and lithium ion battery interface process is lacked, the advantages of single-color infrared laser coupling and high repetition frequency are matched with automatic triggering and a high-speed acquisition card, and the in-situ / working condition infrared spectroscopy characterization capability of the lithium ion battery interface process is improved. In-situ / working condition infrared detection with high time resolution and continuous spectrum acquisition synchronization can be realized. The invention further discloses a method for eliminating monochromatic infrared laser power fluctuation, based on the problem that monochromatic infrared laser power fluctuation is large, laser is divided into a beam of reference light and a beam of detection light, laser fluctuation noise is eliminated through the differential spectrum, and stable infrared signal collection with the high signal-to-noise ratio and the high time resolution is achieved.

Description

Technical Field

[0001] The 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 technology can effectively identify the information of electrochemical processes and reaction species at multiphase interfaces in electrochemical systems by using unique infrared fingerprint characteristics and surface selection laws, which is of great guiding significance for in-depth understanding of electrochemical reaction mechanisms and interface processes, and guiding the controllable construction of electrode materials. However, the response time of existing conventional infrared spectrometers to electrochemical reaction systems is more than 100 milliseconds, which is far from meeting the requirements of electrochemical process detection with microsecond time resolution, such as the potential response of the double layer, electrode process kinetics, and lithium-ion battery interface processes.

[0003] At present, there are two main types of infrared spectroscopy technologies for high time resolution. One type includes fast scanning, ultrafast scanning, step scanning, stroboscopic sampling, asynchronous sampling, etc., which mainly improve the time resolution by controlling the driving mode of the interferometer moving mirror or the pulse sampling sequence. Although asynchronous sampling, stroboscopic sampling and step scanning can achieve nanosecond time resolution, the reaction system must be reversible and the reaction can be repeated quickly, which is less universal for the current complex in-situ / operating electrochemical reaction interface research. Although fast scanning and ultrafast scanning have no restrictions on the reaction system, they can only achieve millisecond time resolution, which is far from realizing the detection of electrochemical response. The other type is based on a dispersive infrared spectrometer to measure the infrared intensity of a fixed wavelength in the electrochemical process. The theoretical time resolution of this type of technology is only affected by the response speed of the detector and the ADC conversion cycle, so it is easy to achieve microsecond time resolution, but it is limited by the weak infrared light intensity and requires multiple spectrum superposition and averaging, so the actual time resolution will be reduced to a certain extent. Summary of the invention

[0004] The purpose of the present invention is to provide a tunable infrared spectrometer that has both microsecond time resolution and continuous spectral acquisition and synchronous detection, in view of the insufficient capability of existing infrared spectrometers in in-situ / operating infrared spectroscopy characterization with microsecond to millisecond time resolution of the double layer potential response and interface processes in electrochemical reactions.

[0005] The objective 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 table 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 a corner mirror and directly enters the detector to generate a reference spectrum; the detection light is transmitted through the corner mirror with a hole in the optical center into the sample chamber to synchronously collect the in-situ / working condition double-layer potential response and electrode interface process information at the microsecond to millisecond level, 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 coaxial with broadband continuous infrared light and monochromatic infrared laser after being reflected / transmitted through corner mirrors, 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, which 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 may be made of ZnSe, gold-plated Si sheet, etc., according to the wavelength of the infrared laser, and is used to split the light beam into a reference light beam and a detection light beam.

[0017] Preferably, the sample chamber front and rear corner mirrors are 45° gold-plated concave spherical corner mirrors, and a 2mm through hole is opened at the optical center. The 45° gold-plated concave spherical surface is used to redirect the broadband continuous mid-infrared light beam to enter the sample chamber and reflect the infrared light emitted from the sample chamber to the detector for signal collection and processing. The 2mm optical through hole allows the monochromatic infrared laser to directly transmit through without affecting the reflection of the mid-infrared light, enter the sample chamber, be absorbed by the sample, and then transmit into the detector through the optical through hole of the rear corner mirror, so as to realize continuous spectral acquisition and high time resolution synchronous 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 and adjusts the visible laser 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-optical path noise reduction method, which can effectively eliminate the power fluctuation of a high-repetition-rate laser. The method comprises 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 directly enters the detector to produce a reference spectrum;

[0023] The S3 detection beam is transmitted into the sample chamber through the 2mm optical through hole of the corner mirror in front of the sample chamber, and after being absorbed by the sample, it is transmitted into 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, thus achieving stable infrared signal acquisition with high signal-to-noise ratio.

[0025] The present invention designs a tunable infrared spectrometer with both microsecond time resolution and continuous spectrum acquisition. The present invention is based on the characteristics of wide-band continuous spectrum acquisition of conventional Fourier transform infrared spectrometers, 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 spectrum acquisitions are coupled together to achieve in-situ / working condition infrared detection with high time resolution and continuous spectrum acquisition simultaneously. In addition, although high-repetition-rate infrared lasers have the advantages of high average output 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 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 generates high repetition rate infrared laser based on QCL infrared laser / grating spectrometer, with high output average power and short pulse time. It solves the problem that the traditional dispersive infrared spectrometer has weak infrared light intensity, low time resolution after averaging, and cannot realize in-situ / operating infrared detection of double electric layer potential response and interface process with microsecond time resolution;

[0028] 2. The present invention is based on the conventional Fourier transform infrared spectrometer capable of wide-band continuous spectrum acquisition, combined with an infrared laser high time resolution infrared detection system, and through a unique optical path design, can achieve wide-band 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, has a wide range of applicability, and is highly expansible. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] Figure 1 A schematic diagram of an implementation of a tunable infrared spectroscopy device with microsecond 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, 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, 13-MCT detector, 14, 15-He-Ne laser, 16-beam splitter, 17, 18-gold-plated flat mirrors, 19-sample chamber, L1-broadband infrared beam, L2-monochromatic infrared laser, L3-visible laser.

[0033] Figure 2 The present invention provides a schematic diagram of an implementation of a tunable infrared spectroscopy device with both microsecond time resolution and continuous spectrum acquisition and synchronous detection.

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

[0035] Figure 4 This 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 with different potential differences. DETAILED DESCRIPTION

[0036] In order to clearly explain the purpose, technical solutions and advantages of the present invention, the present invention is further described in detail below in conjunction with the embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain 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 should be included in the protection scope of the present invention.

[0037] The invention discloses a tunable infrared spectrum device with microsecond time resolution and continuous spectrum sampling synchronous detection, which is composed of a continuous spectrum sampling infrared test 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 diverted by the angle mirror 3 and enters the Michelson interferometer 4. It is incident on the beam splitter at 45 degrees. Half of the light is reflected by the beam splitter to the fixed mirror, and the other half of the light is incident on the moving mirror through the beam splitter. After being reflected 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 then 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 wide-band 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 3700-1800cm -1 The tunable monochromatic infrared laser L2 is split into two beams of light with the same intensity by the beam splitter 10. One beam is the reference beam, which enters the MCT detector 12 after being reflected by the corner mirror 11 to obtain the reference spectrum. The other beam is the detection beam, which enters the sample chamber 19 through the 2mm optical through hole in the center of the gold-plated corner mirror 6 to collect the sample signal, and then enters the MCT detector 13 through the 2mm optical through hole in the center of the gold-plated corner mirror 7 to obtain the detection spectrum with sample information. In order to achieve microsecond time resolution, the MCT detectors 12 and 13 are equipped with automatic triggering and high-speed acquisition cards to reduce the impact of the detector response speed and ADC conversion cycle on the time resolution. In order to eliminate the noise caused by the high-repetition-rate infrared laser power fluctuation, the reference spectrum collected at the same spatial scale is subtracted from the detection spectrum to obtain the potential response and interface process information of the electrochemical reaction interface with high time resolution.

[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, which is coaxial with the infrared light beam after being reflected by a beam splitter 16, so as to calibrate the position of the infrared light 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, which is coaxial with the monochromatic infrared laser after being reflected by gold-plated flat mirrors 17 and 18, so as 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 the 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 of the Cu catalyst in the 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 step test method is used, and the reference potential is set to 0V (vs RHE), and the detection potential is -0.1~-1.3V (vs RHE); continuous spectrum scanning range: 4000-800cm -1 , Resolution: 8cm -1 . Figure 2 The broadband in-situ infrared spectrum of the commercial Cu nanoparticles provided in the 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 2000-2100cm -1 *CO was observed between L In the evolution process of Cu surface, in addition, 1300-1500cm -1 It was also observed that HCO3 - 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 prove that the tunable infrared spectroscopic device with microsecond time resolution and continuous spectrum acquisition 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 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). After the infrared light source (1) generates a broadband continuous light source (L1), the light flux is adjusted by a motor-driven aperture (2) and then diverted through 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 / operating state electrochemical reaction surface interface information, and then passed 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), the beam of light is divided into two beams by a beam splitter (10), one beam is a reference light, which directly enters a detector (12) through an angle mirror (11) to generate a reference spectrum; the other beam is a detection light, which enters a sample chamber (19) through an angle mirror (6) with an optical center opening, synchronously collects microsecond to millisecond level in-situ / operating double electric layer potential response and electrode interface process information, 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 optical 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), and are used for adjusting and calibrating the infrared optical path.

2. The tunable infrared spectrometer with microsecond time resolution and continuous spectrum acquisition according to claim 1, characterized in that: The continuous spectrum sampling infrared testing system comprises an infrared light source, an aperture, a Michelson interferometer, a detector and an optical path part which are arranged in sequence.

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

4. The tunable infrared spectrometer with microsecond time resolution and continuous spectrum acquisition according to claim 1, characterized in that: The high time resolution infrared detection system containing a dual-optical path noise reduction system comprises an infrared laser, a beam splitter, an angle mirror with an optical center opening, a detector and an optical path part which are arranged in sequence.

5. The tunable infrared spectrometer with microsecond time resolution and continuous spectrum acquisition according to claim 1 or 4, characterized in that: The infrared laser is a quantum cascade infrared laser / grating spectrometer, which outputs high repetition rate / continuous monochromatic light; the high repetition rate monochromatic light, in combination with automatic triggering and a high-speed acquisition card, realizes infrared signal acquisition with microsecond time resolution.

6. The tunable infrared spectrometer with microsecond time resolution and continuous spectrum acquisition according to claim 1, 2 or 4, characterized in that: The detector is a liquid nitrogen cooled mercury cadmium telluride detector with a detection range of 25-1 μm.

7. The tunable infrared spectrometer with microsecond time resolution and continuous spectrum acquisition according to claim 1 or 4, characterized in that: The dual-optical path noise reduction system divides the monochromatic infrared light into two monochromatic lights of equal intensity through a beam splitter. One beam directly enters the detector as a reference light, and the other beam enters the sample chamber to collect signals and then enters the detector. The two obtained spectra are subtracted to eliminate the noise caused by laser power fluctuations.

8. The tunable infrared spectrometer with microsecond time resolution and continuous spectrum acquisition according to claim 1 or 4, characterized in that: The corner mirror with a hole in the optical center is provided with a light through hole in the optical center of the corner mirrors before and after the sample chamber in the continuous spectrum infrared testing system, which allows monochromatic infrared light to pass directly without affecting the reflection of broadband continuous infrared light, and enters the sample chamber coaxially with the broadband continuous infrared light, thereby realizing the synchronous collection of continuous spectrum and microsecond time-resolved spectrum.

9. 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 optical path calibration system is a helium-neon laser that emits visible laser to calibrate the optical path.

10. A dual-path noise reduction method for eliminating power fluctuations of a high repetition rate laser, comprising the following steps: S1 uses a beam splitter to split the monochromatic infrared laser into two beams, one for reference light and the other for detection light; The S2 reference beam is reflected by the corner mirror and directly enters the detector to produce a reference spectrum; The S3 detection beam is transmitted into the sample chamber through the light through hole of the corner mirror in front of the sample chamber, and after being absorbed by the sample, it is transmitted into the detector through the light through hole of the rear corner mirror to obtain the detection spectrum; S4 achieves infrared signal acquisition by performing spectrum subtraction on the spectra at the same time and space scales to eliminate the high noise caused by high power fluctuations.

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