A method for controllable formation of single CO nanobubbles by electroreduction of CO2 in an ionic liquid system

Abstract

The present invention provides a method for the controlled formation of single CO nanobubbles through the electroreduction of CO2 in an ionic liquid system. An appropriate amount of water is added to the ionic liquid solvent, and CO2 is introduced. The current, voltage, and scan rate are adjusted to generate single CO nanobubbles on the surface of a nanometer-sized gold electrode through the electroreduction of CO2. This method can stably generate and monitor the behavior of single CO nanobubbles, featuring controllable nanobubble generation and high detection accuracy. It provides a simple and efficient method for studying the nucleation behavior and evolution of interfacial nanobubbles, as well as the mechanism of gas evolution at the interface. Furthermore, it can improve the efficiency of CO2 electroreduction by regulating bubble behavior.

Description

Technical Field

[0001] The present invention relates to the fields of electroanalytical chemistry and microscopic interface nanoscience, and in particular to a method for controllably forming single CO nanobubbles by electroreducing CO2 in an ionic liquid system. Background Art

[0002] Bubbles are widely present in processes such as green chemical production, efficient energy conversion, and high-end material synthesis. Their behavior significantly impacts material conversion and energy utilization efficiency. According to classical nucleation theory, bubbles at gas-liquid-solid interfaces have lower nucleation barriers than bubbles in the bulk phase, are more widespread, and have a greater impact on the process.

[0003] Especially during electrocatalytic reactions, gas is usually produced or consumed on the electrode surface. In gas-producing reactions, bubbles need to diffuse and overflow quickly to release active sites on the electrode surface and maintain the stability of the electrode surface reaction. In gas-consuming reactions, it is hoped that bubbles will spread evenly on the electrode surface to form a rich "gas-liquid-solid" three-phase interface to achieve an increase in reaction rate and selectivity. Therefore, understanding its essential characteristics and movement laws is the key to the precise design of new structural reactors, which is of great significance to energy conservation, emission reduction and improving product quality.

[0004] Currently, people have a deep understanding of the behavior of bubbles larger than micrometers, but research on smaller nanobubbles is still blank. One of the reasons is that nanobubbles are small in size and have an extremely short nucleation time. Existing instruments cannot accurately obtain the size of nanobubbles, and it is also difficult to quickly capture them at the nanoscale and conduct real-time dynamic observation and research on their microscopic behavior.

[0005] In view of the rapid evolution of the interfacial nanobubble formation process, the present invention uses nanoelectrodes to carry out CO2 electroreduction reaction in an ionic liquid system to control the production of single CO nanobubbles with good reproducibility and stability, providing a simple and efficient method for studying the nucleation behavior, evolution law and gas escape mechanism of interfacial nanobubbles. Summary of the Invention

[0006] The present invention proposes a method for controllably forming single CO nanobubbles by electroreducing CO2 in an ionic liquid system. An ionic liquid solution is used as an electrolyte, a nanometer-sized electrode is used as a working electrode, CO2 is introduced to carry out an electroreduction reaction, and the nucleation process of single CO nanobubbles is obtained by regulating factors such as the ionic liquid type, water content, electrode radius, and voltage sweep rate in the reaction system. Single CO nanobubbles are controllably generated on the surface of the nanometer-sized electrode.

[0007] Specific implementation scheme of the present invention is as follows:

[0008] A certain amount of ionic liquid is compounded with acetonitrile solvent, and then an appropriate amount of water is added; argon gas is introduced into the ionic liquid solution to remove oxygen in the liquid phase, and then CO2 is introduced for saturation; using a three-electrode system, a voltammetric scan is performed in the CO2-saturated ionic liquid solution to monitor current changes and determine bubble formation.

[0009] The cations in the used ionic liquid are imidazolium cations: 3-methylimidazole, 1-ethyl-3-methylimidazole, 1-butyl-3-methylimidazole; the anions are tetrafluoroborate, hexafluorophosphate, bistrifluoromethanesulfonimide, and the ionic liquid is composed of one or more of the anions and cations. The ionic liquid is added to anhydrous acetonitrile to prepare a composite ionic liquid with a concentration of 0.1 to 1 mol / L. Deionized water is added to the composite solution to prepare a water content of 1 to 10 percent by weight of the solution.

[0010] After argon is deoxygenated, CO2 is introduced for saturation. After saturation, the CO2 gas line is removed to above the liquid surface to ensure that the electrolytic cell is in a CO2-saturated atmosphere.

[0011] The voltammetric scan was performed in a double-layer Faraday shield cage. The nanoelectrodes used were 20nm to 250nm in size. The voltammetric test voltage sweep rate was 10mV / s to 500mV / s, and the voltage range was 0 to -3.0V. The electrochemical reduction of CO2 was performed by monitoring the current change. A sudden change in the current indicated the formation of a single CO nanobubble, and the overpotential and peak current at the time of the sudden change were recorded. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is the CV test curve of CO nanobubble nucleation;

[0013] Figure 2 is the CV test curve without nanobubble nucleation; DETAILED DESCRIPTION

[0014] The following is a clear and complete description of the technical solutions of the present invention in conjunction with the embodiments. The described embodiments are only some of the embodiments of the present invention, rather than all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also included in the present invention.

[0015] Example 1

[0016] A method for controllably forming single CO nanobubbles by electroreduction of CO2 in an ionic liquid system comprises the following steps:

[0017] The ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) was mixed with acetonitrile at a concentration of 1 mol / L. Water was added to a 5% wt% concentration, and argon was introduced at a rate of 80 ml / min for 15 minutes for deoxygenation. The solution was saturated with CO2 at 50 ml / min for 15 minutes. After saturation, the CO2 gas was removed to the surface of the liquid. A gold nanoelectrode with an apparent radius of 31 nm was used as the working electrode, an Ag / AgCl reference electrode, and a Pt wire counter electrode. Cyclic voltammetry was performed over a voltage range of 0 to -2.5 V at a scan rate of 100 mV / s.

[0018] After the nanobubbles are nucleated, they quickly cover the electrode surface, causing a sudden change in current. The CV curve of CO nanobubble nucleation is shown in Figure 2. Figure 1 As shown in the figure, when the voltage is scanned negatively, the current suddenly changes and there is only one peak current, indicating that a single CO nanobubble is formed on the gold nanoelectrode. The current sudden change can be used as a characteristic basis for the nucleation of nanobubbles. Compared with the system without CO2, Figure 2 No current mutation occurs, indicating that no nanobubbles are formed. Therefore, in the present invention, a single CO nanobubble is formed on the 31 nm gold electrode, with a nucleation overpotential of -2.36 V and a nucleation critical current of -16.28 nA.

[0019] Example 2

[0020] A method for controllably forming single CO nanobubbles by electroreduction of CO2 in an ionic liquid system comprises the following steps:

[0021] The ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Bmim][NTF2]) was mixed with acetonitrile at a concentration of 1 mol / L. Water was added at a 5% wt% argon flow rate of 80 ml / min, and deoxygenation was performed for 15 minutes. The solution was saturated with CO2 at 50 ml / min for 15 minutes. After saturation, the CO2 gas was removed to above the liquid surface. A gold nanoelectrode with an apparent radius of 20 nm was used as the working electrode, an Ag / AgCl reference electrode, and a Pt wire as the counter electrode. Cyclic voltammetry was performed over a voltage range of 0 to -2.5 V at a scan rate of 100 mV / s. The nucleation process was performed in a double-layer Faraday cage to shield the solution from external electromagnetic interference.

[0022] After nucleation, CO nanobubbles quickly cover the electrode surface, resulting in a sudden change in current. The nucleation overpotential of the formed CO nanobubbles is -2.31 V, and the nucleation critical current is -15.05 nA.

[0023] Example 3

[0024] A method for controllably forming single CO nanobubbles by electroreduction of CO2 in an ionic liquid system comprises the following steps:

[0025] The ionic liquid [Bmim][BF4] was mixed with acetonitrile at a concentration of 1 mol / L. Water was added at a 5% wt% argon flow rate of 80 ml / min, and deoxygenation was performed for 15 minutes. The solution was saturated with CO2 at 50 ml / min for 15 minutes. After saturation, the CO2 gas was removed to above the liquid surface. A gold nanoelectrode with an apparent radius of 46 nm was used as the working electrode for the electrode apparent radius test. Ag / AgCl was used as the reference electrode, and a Pt wire was used as the counter electrode. Cyclic voltammetry was performed over a voltage range of 0 to -3.0 V at a scan rate of 100 mV / s. The nucleation process was performed in a double-layer Faraday cage to shield the solution from external electromagnetic interference.

[0026] After nucleation, CO nanobubbles quickly cover the electrode surface, resulting in a sudden change in current. The nucleation overpotential of the formed CO nanobubbles is -2.43 V, and the nucleation critical current is -20.54 nA.

[0027] Example 4

[0028] A method for controllably forming single CO nanobubbles by electroreduction of CO2 in an ionic liquid system comprises the following steps:

[0029] The ionic liquid [Bmim][BF4] was mixed with acetonitrile at a concentration of 1 mol / L. Water was added at a 5% wt% argon flow rate of 80 ml / min, and deoxygenation was performed for 15 minutes. The solution was saturated with CO2 at 50 ml / min for 15 minutes. After saturation, the CO2 gas was removed to above the liquid surface. A gold nanoelectrode with an apparent radius of 120 nm was used as the working electrode, an Ag / AgCl reference electrode, and a Pt wire as the counter electrode. Cyclic voltammetry was performed over a voltage range of 0 to -2.7 V at a scan rate of 100 mV / s. The nucleation process was performed in a double-layer Faraday cage to shield the solution from external electromagnetic interference.

[0030] After nucleation, CO nanobubbles quickly cover the electrode surface, resulting in a sudden change in current. The nucleation overpotential of the formed CO nanobubbles is -2.29 V, and the nucleation critical current is -64.43 nA.

[0031] Example 5

[0032] A method for controllably forming single CO nanobubbles by electroreduction of CO2 in an ionic liquid system comprises the following steps:

[0033] The ionic liquid [Bmim][BF4] was mixed with acetonitrile at a concentration of 1 mol / L. Water was added at a 5% wt% argon flow rate of 80 ml / min, and deoxygenation was performed for 15 minutes. The solution was saturated with CO2 at 50 ml / min for 15 minutes. After saturation, the CO2 gas was removed to above the liquid surface. A gold nanoelectrode with an apparent radius of 120 nm was used as the working electrode, an Ag / AgCl reference electrode, and a Pt wire as the counter electrode. Cyclic voltammetry was performed over a voltage range of 0 to -2.7 V at a scan rate of 500 mV / s. The nucleation process was performed in a double-layer Faraday cage to shield the solution from external electromagnetic interference.

[0034] After nucleation, CO nanobubbles quickly cover the electrode surface, resulting in a sudden change in current. The nucleation overpotential of the formed CO nanobubbles is -2.40 V, and the nucleation critical current is -65.99 nA.

[0035] Example 6

[0036] A method for controllably forming single CO nanobubbles by electroreduction of CO2 in an ionic liquid system comprises the following steps:

[0037] The ionic liquid [Bmim][BF4] was mixed with acetonitrile at a concentration of 1 mol / L. Water was added at a 6% wt% argon flow rate of 80 ml / min, and deoxygenation was performed for 15 minutes. The solution was saturated with CO2 at 50 ml / min for 15 minutes. After saturation, the CO2 gas was removed to above the liquid surface. A gold nanoelectrode with an apparent radius of 215 nm was used as the working electrode, an Ag / AgCl reference electrode, and a Pt wire as the counter electrode. Cyclic voltammetry was performed over a voltage range of 0 to -2.7 V at a scan rate of 100 mV / s. The nucleation process was performed in a double-layer Faraday cage to shield the solution from external electromagnetic interference.

[0038] After nucleation, CO nanobubbles quickly cover the electrode surface, resulting in a sudden change in current. The nucleation overpotential of the formed CO nanobubbles is -2.60 V, and the nucleation critical current is -131.00 nA.

[0039] Example 7

[0040] A method for controllably forming single CO nanobubbles by electroreduction of CO2 in an ionic liquid system comprises the following steps:

[0041] The ionic liquid [Bmim][BF4] was mixed with acetonitrile at a concentration of 1 mol / L. Water was added at a 7% wt% argon flow rate of 80 ml / min, and deoxygenation was performed for 15 minutes. The solution was saturated with CO2 at 50 ml / min for 15 minutes. After saturation, the CO2 gas was removed to above the liquid surface. A gold nanoelectrode with an apparent radius of 215 nm was used as the working electrode, an Ag / AgCl reference electrode, and a Pt wire counter electrode. Cyclic voltammetry was performed over a voltage range of 0 to -2.7 V at a scan rate of 100 mV / s. The nucleation process was performed in a double-layer Faraday cage to shield the solution from external electromagnetic interference.

[0042] After nucleation, CO nanobubbles quickly cover the electrode surface, resulting in a sudden change in current. The nucleation overpotential of the formed CO nanobubbles is -2.59 V, and the nucleation critical current is -102.90 nA.

Claims

1. A method for controllably forming single CO nanobubbles by electroreduction of CO2 in an ionic liquid system, characterized in that: Using a negative voltage sweep method, with an ionic liquid solution as the electrolyte, CO2 gas is introduced. By adjusting the voltage sweep rate and monitoring the current change, CO2 reduction reaction occurs, generating single CO nanobubbles on the nanometer-sized electrode surface. The specific steps are as follows: 1) Prepare an ionic liquid solution by mixing a certain amount of ionic liquid with acetonitrile solvent, and then adding an appropriate amount of water; 2) introducing argon into the ionic liquid solution to remove oxygen in the liquid phase, then introducing CO2 to saturate the solution, and after saturation, removing the CO2 gas line to above the liquid surface; 3) Using a three-electrode system, a voltammetric scan was performed in a CO2-saturated ionic liquid solution. The entire process was carried out in a double-layer Faraday shield cage, and the current changes were monitored. A sudden change in the current indicated the formation of a single CO nanobubble. The ionic liquid in step 1) is composed of anions and cations, wherein the cation is an imidazole cation: 3-methylimidazole, 1-ethyl-3-methylimidazole or 1-butyl-3-methylimidazole, and the anion is: tetrafluoroborate, hexafluorophosphate or bistrifluoromethanesulfonyl imide; the ionic liquid is added to anhydrous acetonitrile to prepare a composite ionic liquid with a concentration of 0.1 to 1 mol / L; and the amount of water added to the composite solution is 1% wt to 10% wt of the solution mass.

2. The method according to claim 1, characterized in that Step 2) There is no oxygen in the electrolytic cell and it is in a CO2 saturated atmosphere.

3. The method according to claim 1, characterized in that The working electrode used in step 3) is made of gold, silver or copper nanoelectrode with a size of 5nm to 250nm, the counter electrode is a platinum or graphite electrode, and the reference electrode is an Ag electrode coated with an AgCl layer, a calomel electrode or an Ag / AgCl non-aqueous electrode. The voltammetric test voltage sweep rate is 10mV / s to 1000mV / s, and the voltage range is 0 to -3.0V. The electrochemical reduction of CO2 reaction is carried out, and the current change is monitored in real time. When the current suddenly changes, a single CO nanobubble is formed, and the overpotential and peak current when the current suddenly changes are recorded.

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