An in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system

Abstract

The application is suitable for the technical field of carbon neutralization testing, and provides an in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system, which comprises an electrochemical electrolytic cell system, a first reflection time-of-flight mass spectrometer and a second reflection time-of-flight mass spectrometer, the electrochemical electrolytic cell system is connected with the first reflection time-of-flight mass spectrometer and the second reflection time-of-flight mass spectrometer through a vacuum system; the electrochemical electrolytic cell system comprises an electrolytic cell, a cathode electrolyte circulating unit and an anode electrolyte circulating unit. The system provides a new mass spectrometry detection system, has a time resolution of seconds, does not need a deconvolution data processing process, and can accurately track the real-time reactant consumption rate of electrocatalytic CO2 reduction on a copper electrode and the change trend of the generation rate of nine products.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon neutralization testing, and particularly relates to an in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system. BACKGROUND

[0002] Utilizing renewable energy to reduce greenhouse gas CO2 (CO2RR) into carbon-based fuels and high-value chemicals is considered as a promising way to close the human carbon cycle. In order to accelerate the development of CO2RR technology, it is necessary to solve the main obstacles such as relatively low energy efficiency and poor reaction selectivity.

[0003] The main challenge of this technology development comes from the fierce competition of hydrogen evolution reaction at negative potential, and the slow reaction kinetics of proton-electron cooperative transfer step. In addition, with the negative scanning of potential, the continuous consumption of protons and reactants CO2 on the cathode surface will cause significant concentration polarization, which largely limits the electrocatalytic CO2 conversion rate. It is worth noting that all the above challenges involve the electrode-electrolyte interface near the cathode and the material distribution in the diffusion layer changes with the potential, how to monitor and optimize the microenvironment is a more in-depth core problem.

[0004] For product analysis, gas chromatography and nuclear magnetic resonance are the most commonly used quantitative analysis techniques, but limited by their column separation time, they can only analyze the averaged product efficiency, and it is difficult to provide time-resolved information of the near-electrode surface species in the CO2RR reaction stimulated by potential and current, and it is urgent to develop high-sensitivity in-situ characterization methods and in-situ testing systems to monitor the dynamic evolution information of CO2RR reactants and products in real time. SUMMARY

[0005] The purpose of the embodiment of the application is to provide an in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system, which aims to solve the problems raised in the above background.

[0006] The embodiment of the application is implemented as follows: an in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system, comprising an electrochemical electrolytic cell system, a first reflective time-of-flight mass spectrometer and a second reflective time-of-flight mass spectrometer, wherein the electrochemical electrolytic cell system is connected with the first reflective time-of-flight mass spectrometer and the second reflective time-of-flight mass spectrometer through a vacuum system.

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

[0008] The anode electrolyte in the electrolytic cell adopts 01.M CsHCO3, and the cathode electrolyte adopts 0.1M CsHCO3 saturated with 50sccm CO2 continuously introduced, the anode adopts Pt mesh as the counter electrode to occur oxygen evolution reaction, and the cathode adopts Speed magnetron sputtering of 300 nm Cu, the substrate is used as a working electrode, and a Ag / AgCl reference electrode is inserted into the cathode chamber to control the reaction potential;

[0009] The anode electrolyte circulation unit is used for anode electrolyte circulation;

[0010] The cathode electrolyte circulation unit is used for cathode electrolyte circulation, and a part of the reaction product (mainly hydrogen) is blown into the capillary to directly enter the second reflective time-of-flight mass spectrometer for detection;

[0011] The first reflective time-of-flight mass spectrometer is used for detecting other products in the electrolysis cell except hydrogen.

[0012] The second reflective time-of-flight mass spectrometer is used for detecting hydrogen.

[0013] Further technical solutions, 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] Further technical solutions, the cathode electrolyte circulation unit includes a cathode circulation pump, a cathode electrolyte storage tank and a blowing unit, the liquid inlet of the cathode circulation pump is connected with the cathode electrolyte storage tank, the liquid outlet of the cathode circulation pump is connected with the cathode electrolyte inlet in the electrolysis cell, and the cathode electrolyte outlet of the electrolysis cell is connected with the cathode electrolyte storage tank, and the blowing unit is connected with the cathode electrolyte storage tank, and is used for blowing the gas in the cathode electrolyte storage tank into the second reflective time-of-flight mass spectrometer.

[0015] Further technical solutions, the blowing unit includes a CO2 storage tank and a gas pump, and the CO2 gas in the CO2 storage tank is blown into the cathode electrolyte storage tank through the gas pump, so that the reaction product in the cathode electrolyte storage tank is blown into the second reflective time-of-flight mass spectrometer, and the CO2 is introduced into the cathode electrolyte storage tank at a rate of 50 sccm.

[0016] Further technical solutions, the anode electrolyte circulation unit includes an anode circulation pump and an anode electrolyte storage tank, the liquid inlet of the anode circulation pump is connected with the anode electrolyte storage tank, the liquid outlet of the anode circulation pump is connected with the anode electrolyte inlet in the electrolysis cell, and the anode electrolyte outlet in the electrolysis cell is connected with the anode electrolyte storage tank.

[0017] Further technical solutions, the first reflective time-of-flight mass spectrometer includes a sampling area, an ionization area and a flight detection area, and the second reflective time-of-flight mass spectrometer includes an ionization area and a flight detection area.

[0018] This invention provides an in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system. This system offers a novel mass spectrometry detection system with second-level time resolution and a data processing procedure that does not require deconvolution. It can also accurately track the real-time reaction consumption rate and the generation rate of nine products of electrocatalytic CO2 reduction on a copper electrode. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure 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 were detected by in-situ SVUV-PIMS.

[0021] In the attached figures: 1. Electrochemical electrolysis cell system; 2. First reflection time-of-flight mass spectrometer; 3. Second reflection time-of-flight mass spectrometer. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0024] like Figure 1 As shown, an in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system provided in an embodiment of the present invention includes an electrochemical electrolysis cell system 1, a first reflection time-of-flight mass spectrometer 2, and a second reflection time-of-flight mass spectrometer 3. The electrochemical electrolysis 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 through a vacuum system.

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

[0026] The anolyte in the electrolytic cell is 0.1M CsHCO3, while the cathode electrolyte is 0.1M CsHCO3 saturated with CO2 continuously introduced at 50 sccm. A Pt mesh is used as the counter electrode for the oxygen evolution reaction, and a Pt mesh is used as the cathode. Speed magnetron sputtering of 300nm Cu, the substrate uses porous PTFE film as working electrode, and inserts Ag / AgCl reference electrode in cathode chamber to control reaction potential;

[0027] The anode electrolyte circulation unit is used for anode electrolyte circulation;

[0028] The cathode electrolyte circulation unit is used for cathode electrolyte circulation, and a part of the generated reaction product (mainly hydrogen) is blown into the capillary to directly enter the second reflective time-of-flight mass spectrometer 3 for detection;

[0029] The first reflective time-of-flight mass spectrometer 2 is used for detecting other products except hydrogen in the electrolytic cell.

[0030] The second reflective time-of-flight mass spectrometer 3 is used for detecting hydrogen generated in the reaction.

[0031] In the embodiment of the application, the circulation flow rates of the cathode electrolyte circulation unit and the anode electrolyte circulation unit are both set to 128mL / min -1 The anode uses Pt mesh as the counter electrode to generate oxygen evolution reaction, and the product is exhausted and not detected. Speed magnetron sputtering of 300nm Cu, the substrate uses porous PTFE film as working electrode, and inserts Ag / AgCl reference electrode in cathode chamber to control reaction potential.

[0032] When testing, the gas and electrolyte of the electrochemical electrolytic cell system 1 are first circulated, then the two mass spectrometers are started, the ultraviolet light energy is set (different values are set according to different detection substances, 15.6eV ultraviolet light energy is set for ionizing H2, 14.5eV energy is set for ionizing CO2, CO and CH4 species, 11.0eV energy is set for ionizing C2H4, C2H5OH, CH3CHO, C2H5CHO, CH2CH=CH2OH and C3H7OH species, to obtain the highest signal-to-noise ratio), after the baseline is stable, the electrochemical signal is applied by the electrochemical workstation to scan the linear voltammetry curve, the time-of-flight signals of the two mass spectrometers are recorded synchronously (corresponding to different molecular ion peaks), the relative abundance changes of different substances are attributed, and the relative generation rate of the electrochemical reaction process is corresponded.

[0033] As Figure 1As shown, in a preferred embodiment of the present invention, the cathode electrolyte circulation unit includes a cathode circulation pump, a cathode electrolyte storage tank, and a purging unit. The inlet of the cathode circulation pump is connected to the cathode electrolyte storage tank, the 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. The purging 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 3.

[0034] In this embodiment of the invention, the cathode electrolyte is circulated between the cathode electrolyte storage tank and the cathode chamber of the electrolytic cell using a cathode circulation pump. A portion of the products from the cathode chamber of the electrolytic cell are circulated back into the airtight cathode electrolyte storage tank. The CO2 gas stream output from the purging unit then purges the analyte (mainly hydrogen) into a capillary tube, where it is directly detected by the second reflection time-of-flight mass spectrometer 3.

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

[0036] like Figure 1 As shown, in a preferred embodiment of the present invention, the anolyte circulation unit includes an anolyte circulation pump and an anolyte storage tank. The inlet of the anolyte circulation pump is connected to the anolyte storage tank, the 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 this embodiment of the invention, the electrolyte can be circulated between the anode of the anolyte storage tank and the anode of the electrolytic cell by means of an anode circulation pump.

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

[0039] In this embodiment of the invention, gases and volatile substances pass through a Cu / PTFE membrane (which also serves as the working electrode) into the first time-of-flight mass spectrometer 2 and are placed in the sampling area (~10). -2 Stainless steel transfer tube (~10 Pa, blue area) 4Pa). Then, the sample passed through a 100 pm nozzle at the end of the transfer tube, forming an ultrasonic molecular beam, and was further collimated by a 2 mm nickel filter into the ionization chamber (10 -4 Pa). Subsequently, the sample stream crossed perpendicularly with the SVUV light, the molecules were photoionized, focused by ion lenses, and finally detected by a Re-TOF-MS (10 -5 Pa). Among them, the incident light energy of 15.6 eV was set for ionizing H2, the incident light energy of 14.5 eV was set for ionizing CO2, CO and CH4 species, and the incident light energy of 11.0 eV was set for ionizing 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 reflectron time-of-flight mass spectrometer 3) was calibrated by using the headspace cell with direct injection of the capillary, and CO2 gas was used to sweep the mixed gas containing the product into the ionization chamber of the second reflectron time-of-flight mass spectrometer 3, and then was ionized and detected by SVUV light. In order to shorten the residence time of the mass spectrum signal and the actual product generation rate, the electrolyte reservoir was set close to the cathode outlet, the actual test distance was set to 10 cm, the gas flow was increased (50 sccm CO2 flow), and the headspace volume was reduced (set to ~ 20 mL). Unlike the first reflectron time-of-flight mass spectrometer 2, the gas was directly introduced into the ionization zone, and H2 was ionized at an energy of 15.6 eV, avoiding the mass discrimination of hydrogen in the ultrasonic molecular beam sampling, thereby realizing high sensitivity detection of H2. The data acquisition frequency of the two mass spectrometers was 30 kHz, and the mass resolution (m / Am) was 2000.

[0041] The system was calibrated by using the main product produced during the reduction of CO2RR to prepare a standard gas and a standard solution, the sampling time of the system was fixed at 30 s, the relationship between the flight time and the accurate mass number was determined, the conversion between the two in the test stage was completed, and the signals of different substances were optimized by optimizing different light source energies. Subsequently, an electrochemical linear voltammetry curve signal was applied in situ, the scanning range was -0.2 V to -1.4 V vs. RHE, and the scanning rate was 1 mV s -1 . Figure 2The system in-situ detects the distribution of the products of Cu-catalyzed CO2RR with potential scanning. The signal intensity in the peak range of each product is integrated, and the spectrum interval is set to 30 s, which is equivalent to a potential resolution of 30 mV. The most suitable ionization energy is selected for each product to detect. It can be seen that H2 starts to generate at about -0.4 V, and with the negative scanning of the potential, CO product starts to be detected at -0.6 V; in the negative potential scanning, with the consumption of CO2, ethylene and alcohol are generated in large quantities near -1.0 V, aldehydes and methane are generated at more negative potentials, and all products continue to increase with the negative scanning of the potential after the initial potential, and the growth of CO and acetaldehyde slows down when the scanning approaches the end. The initial potential and relative distribution of the products are consistent with the previous test results, indicating that the method can accurately detect the complex CO2RR product distribution under fast time resolution.

[0042] The above merely describes preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An in-situ electrochemical ultraviolet photoionization time-of-flight mass spectrometry system, characterized by, The system comprises an electrochemical electrolytic cell system, a first reflective time-of-flight mass spectrometer and a second reflective time-of-flight mass spectrometer, and the electrochemical electrolytic cell system is connected with the first reflective time-of-flight mass spectrometer and the second reflective time-of-flight mass spectrometer through a vacuum system; The electrochemical electrolytic cell system comprises an electrolytic cell, a cathode electrolyte circulating unit and an anode electrolyte circulating unit; The anolyte in the electrolytic cell is 0.1 M CsHCO3, and the catholyte is 0.1 M CsHCO3 saturated with 50 sccm CO2 continuously, the anode is Pt mesh as the counter electrode to generate oxygen evolution reaction, and the cathode is 300 nm Cu deposited by speed magnetron sputtering, the porous PTFE film is used as the working electrode, and the Ag / AgCl reference electrode is inserted into the cathode chamber to control the reaction potential. The anolyte in the electrolytic cell is 0.1 M CsHCO3, and the catholyte is 0.1 M CsHCO3 saturated with 50 sccm CO2 continuously, the anode is Pt mesh as the counter electrode to generate oxygen evolution reaction, and the cathode is 300 nm Cu deposited by speed magnetron sputtering, the porous PTFE film is used as the working electrode, and the Ag / AgCl reference electrode is inserted into the cathode chamber to control the reaction potential. The anode electrolyte circulating unit is used for anode electrolyte circulation; The cathode electrolyte circulating unit is used for cathode electrolyte circulation and blowing a part of the reaction product into the capillary to directly enter the second reflective time-of-flight mass spectrometer for detection; The first reflective time-of-flight mass spectrometer is used for detecting other products except hydrogen in the electrolytic cell; The second reflective time-of-flight mass spectrometer is used for detecting hydrogen.

2. The ambient electrochemical UV photoionization time-of-flight mass spectrometer system of claim 1, wherein, The circulation flow rate of the cathode electrolyte circulation unit and the anode electrolyte circulation unit is set to 128 mL / min -1 .

3. The ambient electrochemical UV photoionization time-of-flight mass spectrometer system of claim 2, wherein, The cathode electrolyte circulating unit comprises a cathode circulating pump, a cathode electrolyte storage tank and a blowing unit, the liquid inlet of the cathode circulating pump is connected with the cathode electrolyte storage tank, the liquid outlet of the cathode circulating pump is connected with the cathode electrolyte inlet of the electrolytic cell, and the cathode electrolyte outlet of the electrolytic cell is connected with the cathode electrolyte storage tank, and the blowing unit is connected with the cathode electrolyte storage tank and used for blowing the gas in the cathode electrolyte storage tank into the second reflective time-of-flight mass spectrometer.

4. The ambient electrochemical UV photoionization time-of-flight mass spectrometer system of claim 3, wherein, The blowing unit comprises a CO2 storage tank and a gas pump, and the CO2 gas in the CO2 storage tank is blown into the cathode electrolyte storage tank through the gas pump, so that the reaction product in the cathode electrolyte storage tank is blown into the second reflective time-of-flight mass spectrometer, and the CO2 is introduced into the cathode electrolyte storage tank at a rate of 50 sccm.

5. The ambient electrochemical UV photoionization time-of-flight mass spectrometer system of claim 1, wherein, The anode electrolyte circulating unit comprises an anode circulating pump and an anode electrolyte storage tank, the liquid inlet of the anode circulating pump is connected with the anode electrolyte storage tank, and the liquid outlet of the anode circulating pump is connected with the anode electrolyte inlet of the electrolytic cell.

6. The ambient electrochemical ultraviolet photoionization time-of-flight mass spectrometer system of claim 1, wherein, The first reflective time-of-flight mass spectrometer comprises a sampling area, an ionization area and a flight detection area, and the second reflective time-of-flight mass spectrometer comprises an ionization area and a flight detection area.

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