A test method for analyzing electrocatalytic processes on the nanosecond time scale

Abstract

The application discloses a test method for analyzing electrocatalytic process on a nanosecond time scale. The method comprises the following steps: firstly, a pulse voltage with a frequency of 1 kHz is applied between a working electrode and a counter electrode in an electrolytic cell, a synchronous signal of the pulse voltage is input into a time sequence card to convert the signal into a 2 kHz synchronous signal, and a pulse super-continuous white light source is triggered. The pulse white light generated by the light source is focused on a sample to be measured in the electrolytic cell, and the white light passing through the sample is collected by a high-speed spectrometer. The high-speed spectrometer is synchronous with the trigger signal of the super-continuous white light source, and a pulse white light spectrum is recorded every 450 us. The white light spectrum before and after the pulse voltage is applied is recorded by the high-speed spectrometer respectively, and the influence of the pulse voltage on the sample absorption spectrum is calculated. The time delay between the pulse voltage and the pulse white light is changed by the time sequence card, and the spectrum change at different moments is recorded.

Description

Technical Field

[0001] This invention belongs to the field of characterization methods for electron transfer processes in electrocatalysis, specifically a testing method for analyzing electrocatalytic processes on a nanosecond timescale. Background Technology

[0002] With increasing energy demand, traditional fossil fuels face depletion and environmental pollution, making clean energy (such as wind, solar, and hydrogen energy) a key focus. Electrocatalysis plays a crucial role in clean energy utilization, environmental protection, and energy conversion. With the development of renewable energy technologies, performance optimization of electrocatalytic materials has become a research priority. Since electrocatalytic processes typically involve multiple reaction intermediates and rapid electron transfer processes, and these reaction steps may occur on nanosecond or even shorter timescales, research on electrocatalytic processes on the nanosecond timescale is particularly important. However, current research on catalytic reaction processes on the nanosecond timescale is still limited.

[0003] Nanosecond transient absorption is often combined with pulsed excitation techniques. By precisely controlling the pulse voltage or laser pulse, specific electrochemical reactions or excited states are induced, and then the transfer of electrons and energy within the system is tracked by spectroscopic detection. Therefore, the application of nanosecond time-resolved spectroscopy in electrocatalysis has received increasing attention in recent years. This technique combines rapid spectroscopic measurements and electrochemical reaction monitoring, enabling the acquisition of dynamic information on electrocatalytic reaction processes within a nanosecond timescale. It can also help optimize catalyst design, improving its reaction efficiency and selectivity. In summary, the application of nanosecond time-resolved spectroscopy in electrocatalysis provides a powerful tool for studying the dynamic processes of electrocatalytic reactions. Summary of the Invention

[0004] The purpose of this invention is to provide a method that combines nanosecond transient absorption with an electrocatalytic device to enable analysis of the electrocatalytic process on a nanosecond timescale.

[0005] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0006] A testing method for analyzing electrocatalytic processes on a nanosecond timescale includes the following steps:

[0007] 1) Build a test system;

[0008] 2) Place the sample to be tested in the electrolytic cell, and then place the electrolytic cell into the testing system to begin the test;

[0009] 3) Analyze the test results to obtain the effect of the applied voltage on the absorbance of the sample.

[0010] Step 1) specifically refers to:

[0011] A convex lens 1, a convex lens 2, a convex lens 3, and a high-speed spectrometer are placed sequentially in the optical path emitted by the supercontinuum white light laser. The timing card is connected to the supercontinuum white light laser, the function generator, and the high-speed spectrometer via data cables.

[0012] The positive terminal of the pulse voltage output by the function generator is connected to the platinum electrode via an ammeter, and the negative terminal is connected to the reference electrode via a voltmeter. The negative terminal is also connected to the sample to be tested.

[0013] Step 2) includes the following steps:

[0014] 2.1) The electrolytic cell is placed between convex lens 1 and convex lens 2. The pulsed white light is focused onto the surface of the sample through convex lens 1. The white light passing through the sample becomes a parallel beam after passing through convex lens 2. Then, the parallel beam is focused by convex lens 2 and enters the high-speed spectrometer.

[0015] 2.2) The timing card acquires the electrical pulse signal emitted by the function generator, and then controls the frequency of the supercontinuous white light laser and the high-speed spectrometer so that the frequency of the electrical pulse and the high-speed spectrometer are the same, both being 0.5 times the frequency of the pulsed white light, to ensure that there are two pulsed white light within the period of a single pulse voltage, and that they appear once each when there is no pulse voltage.

[0016] 2.3) Obtain the intensity of the probe light and the intensity of the reference light at different times.

[0017] Step 3) specifically refers to:

[0018] The effect of the applied voltage on the sample absorbance was calculated based on the intensity of the probe light and the intensity of the reference light at different times.

[0019]

[0020] Where ΔA is the change in sample absorbance under pulse voltage, Ipump-probe is the intensity of probe light when pulse voltage is applied, Ipump-ref is the intensity of reference light when pulse voltage is applied, Iunpump-probe is the intensity of probe light when no pulse voltage is applied, and Iunpump-ref is the intensity of reference light when no pulse voltage is applied.

[0021] The present invention has the following beneficial effects and advantages:

[0022] This invention combines nanosecond transient absorption with pulsed excitation techniques, enabling the detection of electron and energy transfer on a nanosecond timescale. This method can also aid in the study of reaction mechanisms in electrocatalysis, such as the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). Spectroscopic characterization reveals the dynamics of nanosecond-level electrochemical reactions, contributing to the design of more efficient catalysts and the optimization of reaction conditions. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the test method.

[0024] Figure 2 This is a schematic diagram of the UV-Vis absorption spectrum of MOS2 in Example 1;

[0025] Figure 3 The nanosecond transient absorption spectrum and kinetic curves of the MOS2 electrocatalytic reaction process in Example 1 are shown.

[0026] Among them, a) time-division spectra at a reaction voltage of 1.6V; b) kinetic curves at wavelengths of 605nm and 652nm; c) nanosecond transient absorption spectra at different voltages at 200 microseconds; d) kinetic curves at different voltages at 200 microseconds (652nm). Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0028] A testing method for analyzing electrocatalytic processes on a nanosecond timescale, specifically:

[0029] (1) In-situ detection of electrocatalytic processes: High-speed spectrometers collect the detection light that passes through and is focused onto the sample, and record the intensity of the detection light.

[0030] (2) A pulsed voltage was applied to the working electrode and the counter electrode, and a timing card was used to trigger the generation of white light with a repetition rate of twice that of the applied voltage. The white light spectra before and after the application of the pulsed voltage were measured using a high-speed spectrometer, and the effect of the pulsed voltage on the absorption spectrum was calculated. By adjusting the time delay between the pulsed voltage and the white light pulse using the timing card, the changes in the absorption spectrum when the pulsed voltage was applied at different time points could be obtained, and the transient absorption kinetics of the electrocatalytic reaction could be recorded.

[0031] This invention adds an electrocatalytic reaction device to the optical path.

[0032] This invention utilizes 2kHz pulsed white light as the probe light, which is focused and transmitted through the sample. The intensity of the probe light is then collected by a high-speed spectrometer.

[0033] Step (1) is as follows: place the electrolytic cell in the optical path, connect the positive terminal of the pulse voltage output by the function generator to the counter electrode, and connect the negative terminal to the working electrode (taking the hydrogen evolution reaction as an example to connect the positive and negative terminals); focus the pulsed white light onto the surface of the sample to be measured, and the white light passing through the sample becomes a parallel beam after passing through the convex lens, and then focus the parallel beam into the high-speed spectrometer.

[0034] Step (2) specifically involves: the frequency of the electrical pulse is the same as that of the high-speed spectrometer, which is 0.5 times the frequency of the pulsed white light, ensuring that there are two pulses of white light within the period of a single pulse voltage, and that the pulses occur once each with and without a pulse voltage, according to the formula... The effect of applied voltage on sample absorbance can be calculated, where ΔA is the change in sample absorbance under pulsed voltage, and I... pump-probe It is the intensity of the probe light when a pulse voltage is applied, I pump-ref It is the intensity of the reference light when a pulse voltage is applied, I unpump-probe The intensity of the probe light when no pulse voltage is applied, I unpump-ref It is the intensity of the reference light when no pulse voltage is applied.

[0035] Example 1:

[0036] All reagents and materials used in the experiment were purchased commercially. To better verify the feasibility of the experimental setup, MoS2, with its good catalytic performance and photosensitivity, was selected as the electrocatalyst to be tested. First, the exciton peak positions of MoS2 were determined using UV-Vis absorption spectroscopy, serving as a reference for nanosecond transient absorption. Figure 2 As shown, its characteristic absorption peaks are located at 610 nm and 650 nm. According to... Figure 1 After assembling the equipment, the MoS2 sample was placed in an electrolytic cell containing an electrolyte solution of 0.5M H2SO4 for testing. Figure 3 a shows the nanosecond transient absorption spectrum of the MoS2 catalyst during the reaction process. The main features of the spectrum are two bleaching peaks, A and B, centered at 652 nm and 605 nm, respectively. Photoinduced absorption of electrons was observed between 450 nm and 550 nm. The test results are consistent with... Figure 2 The characteristic absorption peak position of MoS2 in the mid-UV-Vis absorption spectrum shifted compared to the previous observation. This is because electron injection under electrocatalytic conditions causes a change in the energy band of MoS2, resulting in a shift in the exciton peak position. (Comparison) Figure 3 and Figure 2 The results verify the feasibility of the experimental method.

[0037] Figure 3 a is the time-division spectrum at a reaction voltage of 1.6 V, revealing that electron injection is a relatively slow process during the reaction. Kinetic analysis shows that electron injection begins at 85 microseconds (e.g., ...). Figure 3 b) This is because when no power is applied, the electrons in the MOS2 in the sulfuric acid solution are depleted, resulting in increased resistance and making it difficult to inject electrons when voltage is applied. Figure 3 b indicates that there is no significant difference in dynamics between the two wavelengths, so they can be analyzed separately using any exciton peak. Figure 3c shows the nanosecond transient absorption spectra at different potentials. The signal gradually increases with the increase of potential. According to the MOS2 reaction potential, there is still an electron transfer process even when the hydrogen evolution reaction does not occur. Figure 3 Figure d shows the kinetic changes of MOS2 at different voltages at a wavelength of 652 nm. As the voltage increases, the injection process gradually accelerates, and the time at which electron injection begins shortens. In summary, this testing method can analyze the electron transfer process in electrocatalytic reactions on a nanosecond timescale.

Claims

1. A testing method for analyzing electrocatalytic processes on a nanosecond timescale, characterized in that, Includes the following steps: 1) Build a test system; 2) Place the sample to be tested in the electrolytic cell, and then place the electrolytic cell into the testing system to begin the test; 3) Analyze the test results to obtain the effect of the applied voltage on the absorbance of the sample.

2. The test method for analyzing electrocatalytic processes on a nanosecond timescale according to claim 1, characterized in that, Step 1) specifically refers to: A convex lens 1, a convex lens 2, a convex lens 3, and a high-speed spectrometer are placed sequentially in the optical path emitted by the supercontinuum white light laser. The timing card is connected to the supercontinuum white light laser, the function generator, and the high-speed spectrometer via data cables.

3. The test method for analyzing electrocatalytic processes on a nanosecond timescale according to claim 2, characterized in that, The positive terminal of the pulse voltage output by the function generator is connected to the platinum electrode via an ammeter, and the negative terminal is connected to the reference electrode via a voltmeter. The negative terminal is also connected to the sample to be tested.

4. The test method for analyzing electrocatalytic processes on a nanosecond timescale according to claim 1, characterized in that, Step 2) includes the following steps: 2.1) The electrolytic cell is placed between convex lens 1 and convex lens 2. The pulsed white light is focused onto the surface of the sample through convex lens 1. The white light passing through the sample becomes a parallel beam after passing through convex lens 2. Then, the parallel beam is focused by convex lens 2 and enters the high-speed spectrometer. 2.2) The timing card acquires the electrical pulse signal emitted by the function generator, and then controls the frequency of the supercontinuous white light laser and the high-speed spectrometer so that the frequency of the electrical pulse and the high-speed spectrometer are the same, both being 0.5 times the frequency of the pulsed white light, to ensure that there are two pulsed white light within the period of a single pulse voltage, and that they appear once each when there is no pulse voltage. 2.3) Obtain the intensity of the probe light and the intensity of the reference light at different times.

5. The test method for analyzing electrocatalytic processes on a nanosecond timescale according to claim 1, characterized in that, Step 3) specifically refers to: The effect of the applied voltage on the sample absorbance was calculated based on the intensity of the probe light and the intensity of the reference light at different times. Where ΔA is the change in sample absorbance under pulse voltage, Ipump-probe is the intensity of probe light when pulse voltage is applied, Ipump-ref is the intensity of reference light when pulse voltage is applied, Iunpump-probe is the intensity of probe light when no pulse voltage is applied, and Iunpump-ref is the intensity of reference light when no pulse voltage is applied.

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