Method for improving efficiency of hydrogen evolution from water electrolysis and method for characterizing efficiency of hydrogen evolution from water electrolysis

Abstract

The application discloses a method for improving water electrolysis hydrogen evolution efficiency and a water electrolysis hydrogen evolution efficiency characterization method. A block polymer is added to an electrolyte to strengthen hydrogen bubble desorption on a hydrogen evolution electrode surface, so that the water electrolysis hydrogen evolution efficiency is improved. By introducing a trace amount of block polymer, the application effectively reduces hydrogen bubble adhesion on a platinum electrode surface, promotes rapid desorption, and improves the water electrolysis hydrogen evolution efficiency. The hydrogen bubble desorption quantitative characterization method based on voltage fluctuation analysis is established, and the characterization method can be completed on a conventional electrochemical workstation without high-speed photography or microscopic imaging. The characterization result is intuitive and reliable, and the operation is simple, so that the method is convenient for industrial application and process monitoring.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis, specifically relating to a method for improving the hydrogen evolution efficiency of water electrolysis and a method for characterizing the hydrogen evolution efficiency of water electrolysis. Background Technology

[0002] Hydrogen, as a renewable and clean energy source, is considered an ideal alternative to fossil fuels. Compared to traditional fossil fuel-based hydrogen production, water electrolysis offers abundant feedstock and produces no carbon dioxide emissions, demonstrating enormous potential.

[0003] To improve the electrocatalytic performance of water electrolysis, much research currently focuses on developing catalysts with high catalytic activity. However, these processes are complex and costly, making large-scale preparation and industrial application difficult. In actual water electrolysis for hydrogen evolution, severe adhesion of hydrogen bubbles to the electrode surface can block active sites, increase electrode overpotential, and even strip the catalyst from the substrate, causing catalyst deactivation, compromising its stability, and severely impacting the hydrogen evolution efficiency. Therefore, to reduce the cost of hydrogen production through water electrolysis and improve hydrogen evolution efficiency, it is necessary to improve and quantitatively characterize the process from the perspective of hydrogen bubble desorption on the hydrogen evolution electrode surface.

[0004] The adhesion of bubbles on the surface of the hydrogen evolution electrode is related not only to the type of electrode material and the properties of the electrode surface, but also to the cost and efficiency of hydrogen production. Summary of the Invention

[0005] One objective of this invention is to provide a method for improving the hydrogen evolution efficiency of water electrolysis. This method is reliable in principle, low in cost, and easy to operate. It provides a practical solution to the problem of severe hydrogen bubble adhesion on the electrode surface, which restricts electrocatalytic efficiency, and has broad application prospects.

[0006] The method for improving hydrogen evolution efficiency in water electrolysis provided by this invention includes the following steps:

[0007] Adding block polymers to the electrolyte enhances the desorption of hydrogen bubbles on the surface of the hydrogen evolution electrode, thereby improving the hydrogen evolution efficiency of water electrolysis.

[0008] The block polymer may be an amphiphilic block polymer, specifically a polyoxyethylene-polyoxypropylene block copolymer, and more specifically F-68.

[0009] In the electrolyte, the concentration of the block polymer can be 1-500 μmol / L, specifically 100 μmol / L.

[0010] The electrolyte can be an alkaline electrolyte, specifically a 0.5-1.5 mol / L potassium hydroxide solution, more specifically a 1 mol / L potassium hydroxide solution.

[0011] The hydrogen evolution electrode can specifically be a platinum electrode.

[0012] This invention introduces a block polymer into the electrolyte and adjusts the concentration of the block polymer to adsorb at the hydrogen bubble / water interface to form a sufficiently strong "molecular brush" structure, which hinders the adhesion of hydrogen bubbles to the electrode surface and the merging of small and large hydrogen bubbles, thereby enhancing the desorption of hydrogen bubbles on the surface of the hydrogen evolution electrode and improving the electrocatalytic performance of water electrolysis.

[0013] The present invention also provides a method for quantitatively characterizing the desorption behavior of hydrogen bubbles.

[0014] The method for quantitatively characterizing hydrogen bubble desorption behavior provided by this invention includes the following steps: In an alkaline electrolyte, a three-electrode measurement system is used to apply a constant current density to the working electrode. The voltage change of the working electrode over time is monitored in real time by an electrochemical workstation, and the hydrogen bubble desorption behavior is quantitatively characterized by the fluctuation characteristics of the voltage signal. In the three-electrode measurement system, the counter electrode is a carbon electrode, the working electrode is a platinum electrode, and the reference electrode is a Hg / HgO electrode. The working electrode applies a constant current density between -20 and -200 mA / cm². 2 Preferably -50mA / cm 2 ; The method of quantitatively characterizing bubble desorption behavior by utilizing the fluctuation characteristics of voltage signals indicates that small average voltage fluctuations and short durations of average voltage fluctuations indicate rapid desorption of hydrogen bubbles from the electrode surface and high efficiency of hydrogen evolution in water electrolysis; large average voltage fluctuations and long durations of average voltage fluctuations indicate slow desorption of hydrogen bubbles from the electrode surface and low efficiency of hydrogen evolution in water electrolysis.

[0015] A block polymer is added to the alkaline electrolyte, and the hydrogen bubble desorption behavior before and after the addition of the block polymer is compared by utilizing the fluctuation characteristics of the voltage signal, thereby determining the effect of the addition of the block polymer on the hydrogen bubble desorption behavior.

[0016] The present invention also provides an apparatus for quantitatively characterizing the desorption behavior of hydrogen bubbles.

[0017] The device for quantitatively characterizing the desorption behavior of hydrogen bubbles includes: a three-electrode measurement system, an electrochemical workstation 5, an electrolyte, an H-type electrolytic cell 13, a gas pipeline 9, a rubber tube 10, a water tank 11, and a measuring cylinder 12. The three-electrode measurement system includes a counter electrode 6, a working electrode 7, and a reference electrode 8, which are respectively connected to an electrochemical workstation 5. The three-electrode measurement system and electrolyte are placed in an H-type electrolytic cell 13; The gas pipeline 9 is connected to the rubber tube 10; The measuring cylinder 12 is filled with water and placed upside down in the water tank 11. When H2 is generated at the cathode of water electrolysis, the gas passes through the gas pipe 9 and the rubber tube 10 to discharge the water in the measuring cylinder 12, thus obtaining the volume of the generated H2 gas. A constant current density is applied to the electrochemical workstation, and the voltage change of the working electrode over time is monitored in real time by the electrochemical workstation. The fluctuation characteristics of the voltage signal are used to quantitatively characterize the bubble desorption behavior.

[0018] The counter electrode is a carbon electrode; The working electrode is a platinum electrode; The reference electrode is an Hg / HgO electrode; The electrolyte is a potassium hydroxide solution, specifically a 0.5-1.5 mol / L potassium hydroxide solution, more specifically a 1 mol / L potassium hydroxide solution.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention effectively reduces the adhesion of hydrogen bubbles to the surface of the platinum electrode by introducing a trace amount of block polymer, promotes their rapid desorption, and improves the efficiency of hydrogen evolution in water electrolysis.

[0020] 2. The block polymer used in this invention is inexpensive and readily available. Its introduction requires no complex process modification and has good prospects for technology transfer.

[0021] 3. The quantitative characterization method for hydrogen bubble desorption based on voltage fluctuation analysis established in this invention does not require high-speed photography or microscopic imaging. It can be completed on a conventional electrochemical workstation. The characterization results are intuitive and reliable, the operation is simple, and it is convenient for industrial application and process monitoring. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the atomic force microscope experiment for measuring the interaction between hydrogen bubbles and the surface of a platinum electrode in Embodiment 1 of the present invention. Figure 2 The image shows the results of atomic microscopy measurements of the interaction between hydrogen bubbles and the platinum electrode surface in a 500mM NaNO3 solution containing 10μM block polymer F68 as the continuous phase in Example 1 of this invention. Figure 3 The image shows the results of atomic microscopy measurements of the interaction between hydrogen bubbles and the platinum electrode surface in a 500mM NaNO3 solution containing 100μM block polymer F68 as the continuous phase in Example 1 of this invention. Figure 4 This is a diagram illustrating the bubble desorption mechanism on the surface of the block polymer-reinforced hydrogen evolution electrode in Example 1. Figure 5 In Example 2 of this invention, the electrochemical workstation measured a current density of -50 mA / cm². 2A schematic diagram showing the voltage change in 1 mol / L potassium hydroxide solutions with and without 100 μM block polymer F68. Meanwhile, Figure 5 Also shown is the experimental setup for measuring hydrogen production over 30 minutes under a constant voltage of 5V as described in Example 3.

[0023] Figure 6 This is a graph showing the change in current density applied by the electrochemical workstation in Example 2 over time.

[0024] Figure 7 In Example 2, the current density measured by the electrochemical workstation was -50 mA / cm². 2 The graph shows the voltage change over time in a 1 mol / L potassium hydroxide solution without the addition of block polymer F68. Graph a shows the voltage change over time recorded during water electrolysis, and graph b is a magnified view of the voltage change over time during the last 200 seconds after water electrolysis stabilizes.

[0025] Figure 8 In Example 2, the current density measured by the electrochemical workstation was -50 mA / cm². 2 The voltage changes over time in a 1 mol / L potassium hydroxide solution containing 100 μM block polymer F68 were recorded. Figure a shows the voltage changes over time during water electrolysis, and Figure b is a magnified view of the voltage changes over the last 200 seconds after water electrolysis stabilized.

[0026] Figure 9 Figure a shows the hydrogen production results when a constant voltage of 5V is applied externally in Example 3. Figure a shows the change in gas production over time, and Figure b shows a comparison of hydrogen production over 30 minutes.

[0027] The attached figures are labeled as follows: 1-Laser; 2-Hydrogen bubble; 3-Probe; 4-Substrate; 5-Electrochemical workstation; 6-Counter electrode; 7-Working electrode; 8-Reference electrode; 9-Gas line; 10-Rubber tubing; 11-Water tank; 12-Grating cylinder; 13-H-type electrolytic cell. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0030] This invention provides a method for improving the hydrogen evolution efficiency of water electrolysis, comprising the following steps: adding a block polymer to the electrolyte, wherein the concentration of the block polymer is 1-500. The electrolyte is an alkaline electrolyte, which enhances the desorption of bubbles on the surface of the hydrogen evolution electrode by using a concentration of mol / L to improve the efficiency of hydrogen evolution in water electrolysis.

[0031] Furthermore, the block polymer is preferably a polyoxyethylene polyoxypropylene block copolymer PEO-PPO-PEO, and more specifically, it can be F68.

[0032] Furthermore, the concentration of the added block polymer F68 is preferably 100 μmol / L.

[0033] Furthermore, the alkaline electrolyte is a 0.5-1.5 mol / L potassium hydroxide solution, more specifically a 1 mol / L potassium hydroxide solution.

[0034] The present invention also provides a method for quantitatively characterizing the desorption behavior of hydrogen bubbles.

[0035] The method for quantitatively characterizing the desorption behavior of hydrogen bubbles includes the following steps: In an alkaline electrolyte, a three-electrode measurement system is used to apply a constant current density to the working electrode. The voltage change of the working electrode over time is monitored in real time by an electrochemical workstation, and the hydrogen bubble desorption behavior is quantitatively characterized by the fluctuation characteristics of the voltage signal. Furthermore, in the three-electrode measurement system, the counter electrode is a carbon electrode, the working electrode is a platinum electrode, and the reference electrode is an Hg / HgO electrode.

[0036] Furthermore, the constant current density applied to the working electrode is -20 to -200 mA / cm². 2 Preferably -50mA / cm 2 .

[0037] Furthermore, the method of quantitatively characterizing bubble desorption behavior using the fluctuation characteristics of voltage signals indicates that small average voltage fluctuations and short durations of average voltage fluctuations lead to rapid desorption of hydrogen bubbles from the electrode surface and higher efficiency of hydrogen evolution in water electrolysis; conversely, large average voltage fluctuations and long durations of average voltage fluctuations lead to slow desorption of hydrogen bubbles from the electrode surface and lower efficiency of hydrogen evolution in water electrolysis.

[0038] In the implementation of this invention, the key to the successful implementation of this invention is that the introduction of block polymer F68 into the electrolyte can enhance the desorption of hydrogen bubbles on the surface of the hydrogen evolution electrode. The mechanism of hydrogen bubble desorption on the surface of the hydrogen evolution electrode enhanced by block polymer is explained in Example 1 below.

[0039] Example 1: Block polymer F68 inhibits the adhesion of hydrogen bubbles to the surface of a platinum electrode. Combination Figure 1 The effect of the block polymer F68 on the interaction forces between micron-sized hydrogen bubbles and a platinum surface was measured using atomic force microscopy (AFM). A magnetron sputtered platinum-coated silicon wafer was used as substrate 4. The nanoscale smoothness of the magnetron sputtered silicon wafer surface eliminated the influence of roughness on the results. A 500 mM NaNO3 solution was used, at a concentration that completely shielded the influence of the electric double layer forces, similar to the shielding effect of a 1 mol / L potassium hydroxide solution. The 500 mM NaNO3 solution was drawn up using a dropper and dripped onto the platinum-coated silicon wafer substrate 4 to form 8 mm diameter droplets, serving as the continuous phase environment. Hydrogen gas was drawn up using a custom-made ultra-sharp syringe, subsequently generating hydrogen bubbles 2 with radii ranging from 30 to 100 micrometers on the platinum-coated silicon wafer substrate 4. This created an environment where the 500 mM NaNO3 solution served as the continuous phase, and the micron-sized hydrogen bubbles served as the dispersed phase.

[0040] Using an atomic force microscope, probe 3 is suspended directly above hydrogen bubbles 2 dispersed in the continuous phase of a 500 mM NaNO3 solution. Probe 3 is then brought into contact with hydrogen bubbles 2 on a platinum-plated silicon substrate 4. Because probe 3 is more hydrophobic, and hydrogen bubbles are also hydrophobic, attraction exists between hydrophobic substances. The hydrogen bubbles 2 on the platinum-plated silicon substrate 4 are thus transferred to probe 3. Probe 3 is then lifted and moved above the clean platinum-plated silicon substrate 4. Figure 1 As shown.

[0041] Set the atomic force microscope probe 3 to 1 Hydrogen bubbles 2, propelled by a velocity of m / s, move downwards towards the platinum-plated silicon substrate 4. Excluding the influence of hydrodynamics, the peak force is set to 5 nN. When the atomic force microscope detects the force, the laser 1 deflects, and the deflected signal is received by the laser receiver and converted into force information. Once the force measured by the atomic force microscope reaches the set peak force, it retracts, moving away from the platinum-plated silicon substrate 2.

[0042] like Figure 2As shown, when 10 μmol / L block polymer F68 is added to the solution, initially, the hydrogen bubble 2 is far from the platinum-plated silicon substrate 4, so the detected force is 0. As the hydrogen bubble 2 approaches, a positive force is initially detected, followed by a "jump-in" phenomenon. In the figure, the repulsive force is positive, and the attractive force is negative. This positive force, i.e., the weak repulsive force, may be the slight resistance generated by the hydrogen bubble discharging. The subsequent "jump-in" phenomenon indicates that the hydrogen bubble 2 adheres to the platinum-plated silicon substrate 4 under a strong attractive force. At this concentration, the block polymer F68 cannot prevent the adhesion of the hydrogen bubble 2.

[0043] Combination Figure 3 When 100 μmol / L block polymer F68 was added to the solution, a strong repulsive force was detected throughout the process of the atomic force microscope probe 3 bringing hydrogen bubbles 2 close to the platinum-plated silicon substrate 4, with only a weak attractive force detected during the withdrawal. This indicates that the addition of 100 μmol / L block polymer F68 can inhibit the adhesion of hydrogen bubbles to the platinum-plated surface.

[0044] Figure 4 This study demonstrates the mechanism by which block polymer F68 enhances hydrogen bubble desorption on the surface of a hydrogen evolution electrode. Block polymer F68 comprises a hydrophilic PEO segment and a hydrophobic PPO segment. When block polymer F68 adsorbs at the gas-liquid interface, the hydrophilic PEO segment enters the aqueous phase and extends within it, while the hydrophobic PPO segment is submerged in the gas phase. As the concentration of block polymer F68 increases, the amount of F68 adsorbed at the gas-liquid interface also increases, resulting in a denser arrangement and forming a tight "molecular brush" structure on the surface of the hydrogen bubbles. This structure hinders the adhesion of hydrogen bubbles to the platinum-plated surface. Furthermore, this "molecular brush" structure provides additional steric repulsion for the interactions between hydrogen bubbles, preventing smaller hydrogen bubbles from immediately merging with larger ones during water electrolysis; instead, smaller bubbles separate directly from the electrode surface. This is how block polymer F68 enhances hydrogen bubble desorption on the surface of the hydrogen evolution electrode.

[0045] Example 2: Quantitative characterization of hydrogen bubble desorption on the surface of hydrogen evolution electrode using an electrochemical workstation Combination Figure 5 A three-electrode measurement system was used, with a carbon electrode as the counter electrode (6), a platinum electrode as the working electrode (7), and an Hg / HgO electrode as the reference electrode (8), all connected to an electrochemical workstation (5). The electrolyte was a 1 mol / L potassium hydroxide solution placed in an H-type electrolytic cell (13). A gas line (9) was connected to a rubber tube (10). A graduated cylinder (12) filled with water was inverted in a water tank (11). When H2 was generated at the cathode of the water electrolysis, the gas passed through the gas line (9), then through the rubber tube (10), and was discharged from the water in the graduated cylinder (12), allowing the measurement of the generated H2 gas volume.

[0046] When the electrochemical workstation applies -50mA / cm 2 At current density ( Figure 6 The electrolyte was a 1M potassium hydroxide solution. Voltage changes over time were recorded for both the absence of block polymer F68 and the addition of 100 μmol / L block polymer F68. Figure 7 ,8).

[0047] When the block polymer F68 is not added, the voltage change over time is as follows: Figure 7 As shown. Figure 7 Plot a shows the voltage change over time recorded throughout the entire water electrolysis process. Plot b is a magnified view of the voltage change over time during the last 200 seconds after the water electrolysis stabilized. Figure 7 As can be clearly seen in Figure b, although the voltage decreases overall over time, this process is accompanied by fluctuations. This is because hydrogen bubbles adhere to the surface of the hydrogen evolution platinum electrode, blocking the active sites on the electrode surface and increasing the electrode overpotential. When hydrogen bubbles grow and desorb on the surface of the hydrogen evolution platinum electrode, the active sites on the electrode surface blocked by hydrogen bubbles can continue to undergo water electrolysis. Therefore, voltage fluctuations are formed. By analyzing this fluctuating voltage change, the average hydrogen bubble desorption time and the resulting average voltage change value can be quantitatively characterized. Without the addition of block polymer F68, the average voltage fluctuation is 2.180 mV, and the average voltage fluctuation duration is 0.146 s. After adding 100 μmol / L block polymer F68, the voltage changes over time as follows: Figure 8 As shown, the average voltage fluctuation was 0.059 mV, and the average voltage fluctuation duration was 0.060 s. Clearly, the addition of the block polymer F68 reduced both the average voltage fluctuation and the average voltage fluctuation duration, indicating that hydrogen bubbles desorbed more quickly from the electrode surface, resulting in higher hydrogen evolution efficiency.

[0048] Example 3: Comparison of hydrogen production from water electrolysis after a period of time with and without 100 μmol / L block polymer F68 in a 1 mol / L potassium hydroxide solution. Combination Figure 5 A constant voltage of 5V was applied to the carbon counter electrode 6 and the platinum working electrode 7. The hydrogen production from water electrolysis was compared between the results obtained in graduated cylinder 12 after a period of time with and without 100μmol / L of 1mol / L potassium hydroxide solution containing block polymer F68. Figure 9 ).like Figure 9As shown in Figure a, graph a represents the change in hydrogen production over time, and graph b represents a comparison of hydrogen production after 30 minutes. Without the addition of block polymer F68, 7.88 ml of hydrogen gas could be collected after 30 minutes of water electrolysis. However, after adding 100 μmol / L block polymer F68, 9.13 ml of hydrogen gas could be collected after 30 minutes of water electrolysis, representing a 15.86% increase in hydrogen production. This indicates that adding 100 μmol / L block polymer F68 to a 1 mol / L potassium hydroxide solution can significantly improve the hydrogen evolution efficiency of water electrolysis.

[0049] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A method for improving the hydrogen evolution efficiency of water electrolysis, comprising the following steps: Adding block polymers to the electrolyte enhances the desorption of hydrogen bubbles on the surface of the hydrogen evolution electrode, thereby improving the hydrogen evolution efficiency of water electrolysis.

2. The method according to claim 1, characterized in that, The block polymer is an amphiphilic block polymer, specifically a polyoxyethylene-polyoxypropylene block copolymer.

3. The method according to claim 2, characterized in that, The block polymer is F-68.

4. The method according to claim 1, characterized in that, The concentration of the block polymer in the electrolyte is 1-500 μmol / L.

5. The method according to claim 1, characterized in that, The electrolyte is an alkaline electrolyte, specifically a 0.5-1.5 mol / L potassium hydroxide solution.

6. A method for quantitatively characterizing the desorption behavior of hydrogen bubbles, comprising the following steps: In an alkaline electrolyte, a three-electrode measurement system is used to apply a constant current density to the working electrode. The voltage change of the working electrode over time is monitored in real time by an electrochemical workstation, and the hydrogen bubble desorption behavior is quantitatively characterized by the fluctuation characteristics of the voltage signal.

7. The method according to claim 6, characterized in that, In the three-electrode measurement system, the counter electrode is a carbon electrode, the working electrode is a platinum electrode, and the reference electrode is a Hg / HgO electrode. The working electrode applies a constant current density between -20 and -200 mA / cm². 2 .

8. The method according to claim 6, characterized in that, Small average voltage fluctuations and short durations of average voltage fluctuations indicate rapid desorption of hydrogen bubbles from the electrode surface and high efficiency of hydrogen evolution in water electrolysis; large average voltage fluctuations and long durations of average voltage fluctuations indicate slow desorption of hydrogen bubbles from the electrode surface and low efficiency of hydrogen evolution in water electrolysis.

9. An apparatus for quantitatively characterizing the desorption behavior of hydrogen bubbles, comprising: The three-electrode measurement system includes an electrochemical workstation 5, an electrolyte, an H-type electrolytic cell 13, a gas pipeline 9, a rubber tube 10, a water tank 11, and a graduated cylinder 12. The three-electrode measurement system includes a counter electrode 6, a working electrode 7, and a reference electrode 8, which are connected to an electrochemical workstation 5. The three-electrode measurement system and electrolyte are placed in an H-type electrolytic cell 13; The gas pipeline 9 is connected to the rubber tube 10; The measuring cylinder 12 is filled with water and placed upside down in the water tank 11. When H2 is generated at the cathode of water electrolysis, the gas passes through the gas pipe 9 and the rubber tube 10 to discharge the water in the measuring cylinder 12, thus obtaining the volume of the generated H2 gas. A constant current density is applied to the electrochemical workstation, and the voltage change of the working electrode over time is monitored in real time by the electrochemical workstation. The fluctuation characteristics of the voltage signal are used to quantitatively characterize the bubble desorption behavior.

10. The apparatus according to claim 9, characterized in that, The counter electrode is a carbon electrode; The working electrode is a platinum electrode; The reference electrode is an Hg / HgO electrode; The electrolyte is a potassium hydroxide solution, specifically a 0.5-1.5 mol / L potassium hydroxide solution.

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