In-situ electrochemical ultraviolet light ionization time-of-flight mass spectrometry system

Abstract

The invention is suitable for the technical field of carbon neutralization test, and provides an in-situ electrochemical ultraviolet light ionization time-of-flight mass spectrometry system, which comprises an electrochemical electrolytic tank system, a first reflection time-of-flight mass spectrometry and a second reflection time-of-flight mass spectrometry, the electrochemical electrolytic cell system is connected with the first reflection time-of-flight mass spectrum and the second reflection time-of-flight mass spectrum through the vacuum system; the electrochemical electrolytic tank system comprises an electrolytic tank, a catholyte circulating unit and an anolyte circulating unit. The system provides a brand new mass spectrum detection system, has second-level time resolution and a data processing process without deconvolution, and can accurately track the change trend of the real-time reactant consumption rate and nine product generation rates of electrocatalytic CO2 reduction on a copper electrode.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon neutrality testing, and in particular relates to an in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system. Background Art

[0002] Reduction of greenhouse gas CO2 (CO2RR) to carbon-based fuels and high-value-added chemicals using renewable energy to generate electricity is considered a promising way to close the anthropogenic carbon cycle. In order to accelerate the development of CO2RR technology, major obstacles such as relatively low energy efficiency and poor reaction selectivity need to be addressed.

[0003] The main challenges in the development of this technology come from the fierce competition of the hydrogen evolution reaction at negative potentials and the slow reaction kinetics of the proton-electron cooperative transfer step. In addition, as the potential is swept negatively, protons and reactant CO2 are continuously consumed on the cathode surface, resulting in significant concentration polarization, which greatly limits the electrocatalytic CO2 conversion rate. It is worth noting that all of the above challenges involve the distribution of substances in the electrode-electrolyte interface and diffusion layer near the cathode as the potential changes. How to monitor and optimize the microenvironment is a deeper core issue.

[0004] For product analysis, gas chromatography and nuclear magnetic resonance are the most commonly used quantitative analysis techniques. However, due to the limitation of their column separation time, they can only analyze the averaged product efficiency and it is difficult to provide time-resolved information on the rapid evolution of near-electrode surface species in the CO2RR reaction with potential and current excitation. It is urgent to develop highly sensitive in situ characterization methods and in situ testing systems to monitor the dynamic evolution information of CO2RR reactants and products in real time. Summary of the invention

[0005] The purpose of the embodiments of the present invention is to provide an in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system, aiming to solve the problems raised in the above background technology.

[0006] The embodiment of the present invention is implemented as follows: an in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system includes an electrochemical electrolytic cell system, a first reflection time-of-flight mass spectrometer, and a second reflection time-of-flight mass spectrometer, wherein the electrochemical electrolytic cell system is connected to the first reflection time-of-flight mass spectrometer and the second reflection time-of-flight mass spectrometer via a vacuum system;

[0007] The electrochemical electrolytic cell system comprises an electrolytic cell, a cathode electrolyte circulation unit and an anolyte circulation unit;

[0008] The anode electrolyte in the electrolytic cell is 0.1M CsHCO3, the cathode electrolyte is 0.1M CsHCO3 saturated with 50 sccm CO2 continuously introduced, the anode uses a Pt mesh as a counter electrode to produce oxygen evolution reaction, and the cathode uses 300nm Cu was sputtered by speed magnetron, and the substrate used a porous PTFE film as the working electrode, and an Ag / AgCl reference electrode was inserted in the cathode chamber to control the reaction potential;

[0009] The anolyte circulation unit is used for circulating the anolyte;

[0010] The cathode electrolyte circulation unit is used to circulate the cathode electrolyte and purge a portion of the substance to be tested (mainly hydrogen) produced by the reaction into the capillary tube to directly enter the second reflection time-of-flight mass spectrometer for detection;

[0011] The first reflection time-of-flight mass spectrometer is used to detect other products other than hydrogen that are volatilized into the electrolytic cell;

[0012] The second reflection time-of-flight mass spectrometer is used to detect the hydrogen produced by the reaction.

[0013] In a further technical solution, the circulation flow rates of the cathode electrolyte circulation unit and the anode electrolyte circulation unit are both set to 128 mL min -1 .

[0014] A further technical solution is that the cathode electrolyte circulation unit includes a cathode circulation pump, a cathode electrolyte storage tank and a purge unit, the liquid inlet of the cathode circulation pump is connected to the cathode electrolyte storage tank, the liquid outlet of the cathode circulation pump is connected to the cathode electrolyte inlet in the electrolytic cell, and the cathode electrolyte outlet of the electrolytic cell is connected to the cathode electrolyte storage tank, and the purge unit is connected to the cathode electrolyte storage tank for blowing the gas in the cathode electrolyte storage tank into the second reflection time-of-flight mass spectrometer.

[0015] According to a further technical solution, the purge unit includes a CO2 storage tank and an air pump, and the CO2 gas in the CO2 storage tank is blown into the cathode electrolyte storage tank by the air pump, thereby blowing the reaction products in the cathode electrolyte storage tank into the second reflection time-of-flight mass spectrometer, and CO2 is introduced into the cathode electrolyte storage tank at a rate of 50 sccm.

[0016] According to a further technical solution, the anode electrolyte circulation unit comprises an anode circulation pump and an anode electrolyte storage tank, the liquid inlet of the anode circulation pump is connected to the anode electrolyte storage tank, the liquid outlet of the anode circulation pump is connected to the anode electrolyte inlet in the electrolytic cell, and the anode electrolyte outlet in the electrolytic cell is connected to the anode electrolyte storage tank.

[0017] According to a further technical solution, the first reflection time-of-flight mass spectrometer includes a sampling region, an ionization region and a flight detection region, and the second reflection time-of-flight mass spectrometer includes an ionization region and a flight detection region.

[0018] An in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system is provided in an embodiment of the present invention. The system provides a new mass spectrometry detection system with a time resolution of seconds and a data processing process that does not require deconvolution. At the same time, it can accurately track the real-time reactant consumption rate and the changing trends of the nine product generation rates of the electrocatalytic CO2 reduction on the copper electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic structural diagram of an in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system provided in an embodiment of the present invention;

[0020] Figure 2 The changes in the potential scan of Cu-catalyzed CO2RR products detected by in situ SVUV-PIMS.

[0021] In the drawings: an electrochemical cell system 1; a first reflection time-of-flight mass spectrometer 2; and a second reflection time-of-flight mass spectrometer 3. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0024] like Figure 1 As shown, an in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system provided by one embodiment of the present invention comprises an electrochemical electrolytic cell system 1, a first reflection time-of-flight mass spectrometer 2 and a second reflection time-of-flight mass spectrometer 3, wherein the electrochemical electrolytic cell system 1 is connected to the first reflection time-of-flight mass spectrometer 2 and the second reflection time-of-flight mass spectrometer 3 via a vacuum system;

[0025] The electrochemical electrolytic cell system 1 includes an electrolytic cell (the specific structure can refer to the Chinese invention patent application number 202111286256.X "A Differential Electrochemical Mass Spectrometry Flow Electrolytic Cell for Carbon Neutrality Testing and Its Design Method"), a cathode electrolyte circulation unit and an anode electrolyte circulation unit;

[0026] The anode electrolyte in the electrolytic cell is 0.1M CsHCO3, the cathode electrolyte is 0.1M CsHCO3 saturated with 50 sccm CO2 continuously introduced, the anode uses a Pt mesh as a counter electrode to produce oxygen evolution reaction, and the cathode uses 300nm Cu was sputtered by speed magnetron, and the substrate used a porous PTFE film as the working electrode, and an Ag / AgCl reference electrode was inserted in the cathode chamber to control the reaction potential;

[0027] The anolyte circulation unit is used for circulating the anolyte;

[0028] The cathode electrolyte circulation unit is used to circulate the cathode electrolyte and purge a portion of the substance to be tested (mainly hydrogen) produced by the reaction into the capillary tube and directly enter the second reflection time-of-flight mass spectrometer 3 for detection;

[0029] The first reflection time-of-flight mass spectrometer 2 is used to detect other products other than hydrogen that are volatilized into the electrolytic cell;

[0030] The second reflection time-of-flight mass spectrometer 3 is used to detect the hydrogen produced by the reaction.

[0031] In the embodiment of the present invention, the circulation flow rates of the cathode electrolyte circulation unit and the anode electrolyte circulation unit are both set to 128 mL min -1 The anode uses Pt mesh as the counter electrode to produce oxygen evolution reaction, and the product is discharged without detection. The cathode uses 300nm Cu is sputtered by speed magnetron, and the substrate uses a porous PTFE film as the working electrode, which separates the reaction interface and the vacuum system at the same time. The reaction products are generated at the membrane interface, and a part of them (other products except hydrogen) enter the first reflection flight time mass spectrometer 2 for detection through volatilization, and the other part is circulated to blow the test substance (mainly hydrogen detection) into the capillary and directly enter the ultraviolet photoionization chamber of the second reflection flight time mass spectrometer 3.

[0032] During the test, the gas and electrolyte of the electrochemical cell system 1 first began to circulate, and then the two mass spectrometers were turned on, and the energy of the ultraviolet light was set (different values ​​were set according to different detection substances, 15.6eV ultraviolet light energy was set for ionizing H2, 14.5eV energy was used for ionizing CO2, CO and CH4 species, and 11.0eV energy was used for ionizing C2H4, C2H5OH, CH3CHO, C2H5CHO, CH2CH=CH2OH and C3H7OH species to obtain the highest signal-to-noise ratio), and after waiting for the baseline to stabilize, the electrochemical workstation was used to apply the electrochemical signal to scan the linear voltammetric curve, and the signal changes of the different flight times (corresponding to different molecular ion peaks) of the two mass spectrometers were synchronously recorded, and the relative abundance changes attributed to different substances corresponded to the relative generation rates of their electrochemical reaction processes.

[0033] like Figure 1As shown, as a preferred embodiment of the present invention, the cathode electrolyte circulation unit includes a cathode circulation pump, a cathode electrolyte storage tank and a purge unit, the liquid inlet of the cathode circulation pump is connected to the cathode electrolyte storage tank, the liquid outlet of the cathode circulation pump is connected to the cathode electrolyte inlet in the electrolytic cell, and the cathode electrolyte outlet of the electrolytic cell is connected to the cathode electrolyte storage tank, and the purge unit is connected to the cathode electrolyte storage tank for blowing the gas in the cathode electrolyte storage tank into the second reflection time-of-flight mass spectrometer 3.

[0034] In the embodiment of the present invention, the cathode electrolyte is circulated between the cathode electrolyte storage tank and the cathode chamber of the electrolytic cell by a cathode circulation pump. Part of the product of the cathode chamber of the electrolytic cell enters the airtight cathode electrolyte storage tank through circulation, and the CO2 gas flow output by the purge unit purges the substance to be tested (mainly hydrogen) into the capillary and directly enters the second reflection flight time mass spectrometer 3 for detection.

[0035] like Figure 1 As shown, as a preferred embodiment of the present invention, the purge unit includes a CO2 storage tank and an air pump, and the CO2 gas in the CO2 storage tank is blown into the cathode electrolyte storage tank by the air pump, thereby blowing the reaction products in the cathode electrolyte storage tank into the second reflection time-of-flight mass spectrometer 3, and CO2 is introduced into the cathode electrolyte storage tank at a rate of 50sccm.

[0036] like Figure 1 As shown, as a preferred embodiment of the present invention, the anolyte circulation unit includes an anolyte circulation pump and an anolyte storage tank, the liquid inlet of the anolyte circulation pump is connected to the anolyte storage tank, the liquid outlet of the anolyte circulation pump is connected to the anolyte inlet in the electrolytic cell, and the anolyte outlet in the electrolytic cell is connected to the anolyte storage tank.

[0037] In the embodiment of the present invention, the electrolyte can be circulated between the anode electrolyte storage tank and the anode of the electrolytic cell by an anode circulation pump.

[0038] like Figure 1 As shown, as a preferred embodiment of the present invention, the first reflection time-of-flight mass spectrometer 2 includes a sampling area (blue area), an ionization area (yellow area) and a flight detection area (green area), and the second reflection time-of-flight mass spectrometer 3 includes an ionization area (yellow area) and a flight detection area (green area).

[0039] In the embodiment of the present invention, the gas and volatile substances enter the first reflection time-of-flight mass spectrometer 2 through the Cu / PTFE membrane (also serving as the working electrode) and are placed in the sampling area (~10 -2 Pa, blue area) in a stainless steel transfer tube (~10 4Then, the sample passes through the 100 μm nozzle at the end of the transfer tube to form an ultrasonic molecular beam, and is further arranged into the ionization chamber (10 -4 Pa). The sample flow then intersects the SVUV light perpendicularly, the molecules are photoionized, focused by the ion lens, and finally detected by Re-TOF-MS (10 -5 The incident light energy of 15.6 eV was set to ionize H2, the incident light energy of 14.5 eV was set to ionize CO2, CO and CH4 species, and the incident light energy of 11.0 eV was set to ionize C2H4, C2H5OH, CH3CHO, C2H5CHO, CH2CH=CH2OH and C3H7OH species to obtain the highest signal-to-noise ratio.

[0040] Another mass spectrometer (i.e., the second reflection time-of-flight mass spectrometer 3) directly injects samples through a headspace cell in combination with a capillary. The CO2 gas purges the mixed gas containing the product and is introduced into the ionization chamber of the second reflection time-of-flight mass spectrometer 3 through a capillary, and is then photoionized and detected by SVUV. In order to shorten the residence time of the mass spectrometer signal and the actual product generation rate, the electrolyte storage tank needs to be set close to the cathode outlet, and the actual test distance is set to 10 cm. At the same time, the gas flow rate is increased (50 sccm CO2 flow rate) and the headspace volume is reduced (set to ~20 mL). Different from the first reflection time-of-flight mass spectrometer 2, the gas is directly introduced into the ionization zone, and H2 is ionized at an energy of 15.6 eV, avoiding mass discrimination against hydrogen in ultrasonic molecular beam sampling, thereby achieving high-sensitivity detection of H2. The data acquisition frequency of the two mass spectrometers is 30 kHz, and the mass resolution (m / Δm) is 2000.

[0041] The system was calibrated by preparing standard gas and standard solution using the main products produced during CO2RR reduction. The system sampling time was fixed at 30s, and the relationship between flight time and accurate mass number was determined. The conversion between the two in the test phase was completed. By optimizing different light source energies, the signals of different substances were optimized. Subsequently, an electrochemical linear voltammetric scanning curve signal was applied in situ, with a scanning range of -0.2V to -1.4V vs. RHE and a scanning rate of 1mV s -1 . Figure 2The system was demonstrated to detect the distribution of products of Cu-catalyzed CO2RR in situ with potential scanning. The signal intensity within the peak range of each product was integrated, and the spectrum sampling interval was set to 30s, which is equivalent to a potential resolution of 30mV. Each product was selectively detected at the most appropriate ionization energy. It can be seen that H2 began to be generated at ~-0.4V. With the negative potential scan, CO products began to be detected at -0.6V. In the further negative potential scan, along with the consumption of CO2, ethylene and alcohols were generated in large quantities near -1.0V, and aldehydes and methane were produced at more negative potentials. All products continued to increase with the negative potential scan after the starting potential. When the scan was near the end, the growth of CO and acetaldehyde tended to slow down. The starting potential and relative distribution of the products are consistent with the previous test results, indicating that this method can accurately detect the distribution of complex CO2RR products at a faster time resolution.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system, characterized in that: It includes an electrochemical electrolytic cell system, a first reflection time-of-flight mass spectrometer and a second reflection time-of-flight mass spectrometer, wherein the electrochemical electrolytic cell system is connected to the first reflection time-of-flight mass spectrometer and the second reflection time-of-flight mass spectrometer via a vacuum system; The electrochemical electrolytic cell system comprises an electrolytic cell, a cathode electrolyte circulation unit and an anolyte circulation unit; The anode electrolyte in the electrolytic cell is 0.1M CsHCO3, the cathode electrolyte is 0.1M CsHCO3 saturated with 50 sccm CO2 continuously introduced, the anode uses a Pt mesh as a counter electrode to produce oxygen evolution reaction, and the cathode uses 300nm Cu was sputtered by speed magnetron, and the substrate used a porous PTFE film as the working electrode, and an Ag / AgCl reference electrode was inserted in the cathode chamber to control the reaction potential; The anolyte circulation unit is used for circulating the anolyte; The cathode electrolyte circulation unit is used to circulate the cathode electrolyte and to purge a portion of the substance to be tested produced by the reaction into the capillary tube and directly enter the second reflection time-of-flight mass spectrometer for detection; The first reflection time-of-flight mass spectrometer is used to detect other products other than hydrogen that are volatilized into the electrolytic cell; The second reflection time-of-flight mass spectrometer is used to detect the hydrogen produced by the reaction.

2. The in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system according to claim 1, characterized in that: The circulation flow rates of the cathode electrolyte circulation unit and the anolyte circulation unit were both set to 128 mL min -1 .

3. The in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system according to claim 2, characterized in that: The cathode electrolyte circulation unit includes a cathode circulation pump, a cathode electrolyte storage tank and a purge unit, wherein the liquid inlet of the cathode circulation pump is connected to the cathode electrolyte storage tank, the liquid outlet of the cathode circulation pump is connected to the cathode electrolyte inlet in the electrolytic cell, and the cathode electrolyte outlet of the electrolytic cell is connected to the cathode electrolyte storage tank, and the purge unit is connected to the cathode electrolyte storage tank and is used to blow the gas in the cathode electrolyte storage tank into the second reflection time-of-flight mass spectrometer.

4. The in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system according to claim 3, characterized in that: The purge unit includes a CO2 storage tank and an air pump, and the CO2 gas in the CO2 storage tank is blown into the cathode electrolyte storage tank by the air pump, thereby blowing the reaction products in the cathode electrolyte storage tank into the second reflection time-of-flight mass spectrometer, and CO2 is introduced into the cathode electrolyte storage tank at a rate of 50sccm.

5. The in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system according to claim 1, characterized in that: The anode electrolyte circulation unit comprises an anode circulation pump and an anode electrolyte storage tank, wherein the liquid inlet of the anode circulation pump is connected to the anode electrolyte storage tank, the liquid outlet of the anode circulation pump is connected to the anode electrolyte inlet in the electrolytic cell, and the anode electrolyte outlet in the electrolytic cell is connected to the anode electrolyte storage tank.

6. The in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system according to claim 1, characterized in that: The first reflection time-of-flight mass spectrometer includes a sampling region, an ionization region and a flight detection region, and the second reflection time-of-flight mass spectrometer includes an ionization region and a flight detection region.

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