A method for reactivating a deactivated sodium borohydride hydrolysis catalyst for hydrogen production.

Abstract

This invention belongs to the field of catalyst remediation technology, specifically relating to a method for reactivating a deactivated sodium borohydride hydrolysis catalyst for hydrogen production. In this invention, using an alkaline solution as the electrolyte on an electrochemical workstation, constant-voltage DC electrolysis is employed in a three-electrode system to effectively electrolytically reduce sodium metaborate, a hydrolysis byproduct remaining on the surface of the deactivated sodium borohydride hydrolysis catalyst, to water-soluble sodium borohydride. This effectively removes the sodium metaborate, which facilitates the re-exposure of active sites covered by sodium metaborate, thereby restoring the performance of the deactivated sodium borohydride hydrolysis catalyst to a reusable state. The reactivation method of this invention is characterized by mild conditions, minimal disruption to the original structure of the sodium borohydride hydrolysis catalyst, and a stable and controllable process, making it highly suitable for supported deactivated sodium borohydride hydrolysis catalysts.

Description

Technical Field

[0001] This invention belongs to the field of catalyst remediation technology, specifically relating to a method for reactivating a deactivated sodium borohydride hydrolysis catalyst for hydrogen production. More specifically, this invention relates to a method for restoring the performance of a supported sodium borohydride hydrolysis catalyst for hydrogen production, and the method of this invention can partially restore the performance of the deactivated sodium borohydride hydrolysis catalyst for hydrogen production. Background Technology

[0002] As the global energy structure shifts towards cleaner and lower-carbon energy, hydrogen energy, with its high energy density and zero carbon emissions, has become one of the most promising green energy carriers. Sodium borohydride hydrolysis for hydrogen production is considered a crucial solution for portable and miniaturized hydrogen energy applications due to its high hydrogen storage density, mild reaction conditions, and high hydrogen purity. In the reaction NaBH4 + 2H2O → NaBO2 + 4H2↑, the catalyst is the core material, and its activity and stability directly determine the hydrogen production efficiency and cost. However, existing catalysts, such as precious metals, transition metals, and their oxides, suffer from significant performance degradation over long-term use due to the deposition of sodium metaborate as a byproduct on the surface. This deposition covers some active sites, blocking the hydrogen production pathway and ultimately leading to a substantial decline in hydrogen production performance. Traditional solutions often involve directly replacing the catalyst, but the high cost of precious metals severely restricts the large-scale application of this technology. Therefore, developing efficient and low-cost catalyst repair methods is crucial for promoting the commercialization of sodium borohydride hydrogen production technology.

[0003] Currently, research on the reactivation of deactivated catalysts mainly focuses on physical cleaning and heat treatment. For example, low-concentration acid washing is used to remove surface-adsorbed borate byproducts, or low-temperature calcination is used to continuously eliminate the passivation layer and re-expose the hydrolysis hydrogen production active sites. However, these methods have significant limitations: acid washing corrodes the catalyst support and destroys structural stability; heating easily induces metal particle agglomeration, which reduces activity. Summary of the Invention

[0004] To address the deactivation problem of sodium borohydride hydrolysis hydrogen production catalysts after multiple cycles due to the accumulation of sodium metaborate, a byproduct of the hydrolysis reaction, on the catalyst surface, this invention provides a method for reactivating deactivated sodium borohydride hydrolysis hydrogen production catalysts. This invention uses the deactivated sodium borohydride hydrolysis hydrogen production catalyst as the cathode and employs a three-electrode system for constant-voltage DC electrolysis. The deactivated catalyst is repaired through an electroreduction reaction of sodium metaborate on the cathode surface. This invention provides a mild, efficient, and economical repair method that can precisely restore the active sites and surface characteristics of the deactivated sodium borohydride hydrolysis hydrogen production catalyst while avoiding secondary damage. This ensures the catalyst remains in a high-activity range for most of the operating time, preventing slow performance degradation, significantly delaying the catalyst's final failure time, and reducing replacement frequency. Because the repair process cost is far lower than the catalyst replacement cost, and the catalyst remains in a high-activity range for a longer period during operation, this technology is expected to significantly reduce the overall cost of sodium borohydride hydrogen production technology, providing technical support for the application of sodium borohydride in fuel cells and mobile power sources.

[0005] To achieve the above-mentioned technical objectives and effects, the present invention adopts the following technical solution: On an electrochemical workstation, using an alkaline solution as the electrolyte, constant-voltage DC electrolysis was employed in a three-electrode system to effectively electrolytically reduce sodium metaborate, a residual hydrolysis byproduct on the surface of the deactivated sodium borohydride hydrolysis hydrogen production catalyst, and reduce it to water-soluble sodium borohydride, thereby removing sodium metaborate and partially restoring the hydrogen production rate of the deactivated sodium borohydride hydrolysis hydrogen production catalyst.

[0006] This invention protects a method for reactivating a deactivated sodium borohydride hydrolysis catalyst for hydrogen production, comprising the following steps: A deactivated sodium borohydride hydrolysis hydrogen production catalyst is used as the cathode, and a three-electrode system consisting of a cathode, an anode, and a reference electrode is adopted; wherein, the deactivated sodium borohydride hydrolysis hydrogen production catalyst is a sodium borohydride hydrolysis hydrogen production catalyst with sodium metaborate deposited on its surface.

[0007] Using an alkaline solution as the electrolyte, which provides an alkaline environment for the electrochemical reaction and dissolves subsequent reduction products, a three-electrode system was immersed at one end in the electrolyte, while the other end was electrically connected to an electrochemical workstation. Constant-voltage DC electrolysis was employed to electroreduce sodium metaborate on the cathode surface, converting it into water-soluble sodium borohydride. Because sodium borohydride is readily soluble in the alkaline electrolyte, it detaches from the surface of the sodium borohydride hydrolysis hydrogen production catalyst, thus exposing the covered active sites and obtaining a repaired sodium borohydride hydrolysis hydrogen production catalyst. The repaired catalyst can be reused in the sodium borohydride hydrolysis hydrogen production reaction, and its catalytic activity is restored.

[0008] Preferably, the deactivated sodium borohydride hydrolysis catalyst used as the cathode is a supported catalyst.

[0009] Preferably, the support for the supported catalyst is selected from one of the following: copper sheet, copper foam, nickel mesh, nickel foam, stainless steel mesh, titanium mesh, titanium felt, titanium foam, carbon cloth, and carbon paper. The support has a certain mechanical strength and can be easily clamped onto the electrode clamp and used directly as an electrode material.

[0010] Preferably, the surface of the supported catalyst is wholly or partially covered with sodium metaborate; the support is also supported with one or more of Pt, Ru, Pd, Rh, Co, Fe, Mo, Ni, W, Mn, and Cu.

[0011] Preferably, the alkaline solution is selected from NaOH solution or KOH solution, the concentration of the alkaline solution is 10 mmol / L to 1000 mmol / L, the volume of the electrolyte is 50 mL to 1000 mL, and the pH of the electrolyte is 12 to 14.

[0012] Preferably, the anode is a graphite rod, which is a material with stable conductivity. Other materials with stable conductivity can also be used as the anode of the present invention. The reference electrode is an Hg / HgO electrode, and other standard reference electrodes can also be selected.

[0013] Preferably, the conditions for DC electrolysis are: an electrolysis voltage of 0.5V (vs. Hg / HgO) to 1.5V (vs. Hg / HgO) and an electrolysis temperature of 20℃ to 50℃, for 5 min to 60 min.

[0014] Preferably, after electrolysis, the repaired sodium borohydride hydrolysis hydrogen production catalyst is rinsed with deionized water until there is no residual electrolyte or reduction product on the surface, and then placed in an oven to dry to constant weight.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention uses a deactivated sodium borohydride hydrolysis catalyst as the cathode and employs a three-electrode system for constant-voltage DC electrolysis. The deactivated sodium borohydride hydrolysis catalyst is repaired through an electroreduction reaction of sodium metaborate on the cathode surface. This repair method is low-cost, mild, and does not easily damage the original structure of the sodium borohydride hydrolysis catalyst. The process is stable and controllable, making it highly suitable for supported deactivated sodium borohydride hydrolysis catalysts. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the three-electrode system used in the present invention to repair the sodium borohydride hydrolysis hydrogen production catalyst.

[0017] Figure 2This is a schematic diagram of an apparatus for determining the hydrogen production rate of sodium borohydride hydrolysis catalyst and a restored deactivated sodium borohydride hydrolysis catalyst by the water displacement method.

[0018] Figure 3 This is a graph showing the proportion of hydrogen production rates relative to the initial values ​​of the deactivated sodium borohydride hydrolysis hydrogen production catalysts repaired under different electrolysis voltages in Examples 1 to 5.

[0019] Figure 4 This is a graph showing the ratio of hydrogen production rate to the initial value for the deactivated sodium borohydride hydrolysis hydrogen production catalyst repaired at different electrolysis times in Examples 3 and 6-9.

[0020] Figure 5 This is a graph showing the proportion of hydrogen production rates relative to the initial values ​​measured at different electrolysis temperatures for the deactivated sodium borohydride hydrolysis hydrogen production catalysts repaired in Examples 8 and 10-13. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. The invention will now be described in detail with reference to the accompanying drawings: This invention aims to repair sodium borohydride hydrolysis catalysts for hydrogen production and to study the performance of the repaired catalysts. The deposition of sodium metaborate, a byproduct, on the surface of the sodium borohydride hydrolysis catalyst is one of the important reasons for its deactivation. This invention provides a method for removing the passivation layer on the surface of a sodium borohydride hydrolysis catalyst to repair its catalytic performance in sodium borohydride hydrolysis. The method includes the following steps: electrolysis using a three-electrode system, such as... Figure 1 As shown, the deactivated sodium borohydride hydrolysis catalyst was clamped with electrode clips and partially immersed in an electrolytic cell with an alkaline electrolyte. It was then connected to the cathode of an electrochemical workstation. A graphite rod and Hg / HgO were used as the anode and reference electrode, respectively. A constant voltage electrolysis potential and time were set. After the electrolysis, the repaired sodium borohydride hydrolysis catalyst was removed from the electrolytic cell and washed with deionized water to remove any residual alkaline solution from its surface. This partially restores the performance of the deactivated sodium borohydride hydrolysis catalyst; for example, the hydrogen production rate is restored by 20%–30%.

[0022] During electrolysis, in addition to the hydrogen evolution reaction during water electrolysis, an electroreduction reaction of NaBO2 also occurs on the surface of the deactivated sodium borohydride hydrolysis hydrogen production catalyst. The reaction process is as follows: BO2 - +6H2O+8e - →BH4 - +8OH -In this way, the sodium metaborate passivation layer is electro-reduced into water-soluble sodium borohydride and removed, and the previously covered surface active sites are re-exposed. When they re-participate in the sodium borohydride hydrolysis reaction, the hydrogen production rate is expected to be partially restored.

[0023] The technical solution of the present invention will be further studied using the following embodiments. The specific research methods and results are shown below: In this embodiment of the invention, the carbon fiber cloth-supported CoMoP sodium borohydride hydrolysis hydrogen production catalyst disclosed in patent CN107413360B is used as an example for research. Hydrolysis hydrogen production is carried out using the carbon fiber cloth-supported CoMoP sodium borohydride hydrolysis hydrogen production catalyst and it is cycled 10 times. The test results show that the hydrogen production rate of the catalyst after 10 cycles decreases to 60.4% of the initial value. The catalyst after 10 cycles is taken as the research object, and it is assumed in the embodiment to be a deactivated sodium borohydride hydrolysis hydrogen production catalyst.

[0024] Example 1 A method for reactivating a deactivated sodium borohydride hydrolysis catalyst for hydrogen production includes the following steps: After clamping the deactivated sodium borohydride hydrolysis hydrogen production catalyst with electrode clamps, the catalyst was partially immersed in an electrolytic cell with NaOH solution as the electrolyte and connected to the cathode of an electrochemical workstation. Graphite rod and Hg / HgO were used as the anode and reference electrode, respectively. The electrolysis voltage was set to 0.7V (vs. Hg / HgO), the electrolysis time to 20min, and the electrolysis temperature to 25℃, thus obtaining the repaired sodium borohydride hydrolysis hydrogen production catalyst.

[0025] Example 2 A method for reactivating a deactivated sodium borohydride hydrolysis hydrogen production catalyst is the same as the repair steps in Example 1, except that the electrolysis voltage is replaced by 0.8V (vs. Hg / HgO) instead of 0.7V (vs. Hg / HgO).

[0026] Example 3 A method for reactivating a deactivated sodium borohydride hydrolysis hydrogen production catalyst is the same as the repair steps in Example 1, except that the electrolysis voltage is replaced by 0.9V (vs. Hg / HgO) instead of 0.7V (vs. Hg / HgO).

[0027] Example 4 A method for reactivating a deactivated sodium borohydride hydrolysis hydrogen production catalyst is the same as the repair steps in Example 1, except that the electrolysis voltage is replaced by 1.0V (vs. Hg / HgO) instead of 0.7V (vs. Hg / HgO).

[0028] Example 5 A method for reactivating a deactivated sodium borohydride hydrolysis hydrogen production catalyst is the same as the repair steps in Example 1, except that the electrolysis voltage is replaced by 1.1V (vs. Hg / HgO) instead of 0.7V (vs. Hg / HgO).

[0029] Example 6 A method for reactivating a deactivated sodium borohydride hydrolysis catalyst for hydrogen production includes the following steps: After clamping the deactivated sodium borohydride hydrolysis hydrogen production catalyst with electrode clamps, the catalyst was partially immersed in an electrolytic cell with NaOH solution as the electrolyte and connected to the cathode of an electrochemical workstation. Graphite rod and Hg / HgO were used as the anode and reference electrode, respectively. The electrolysis time was set to 5 min, the electrolysis voltage to 0.9 V (vs. Hg / HgO), and the electrolysis temperature to 25 °C, thus obtaining the repaired sodium borohydride hydrolysis hydrogen production catalyst.

[0030] Example 7 A method for reactivating a deactivated sodium borohydride hydrolysis hydrogen production catalyst is the same as the repair steps in Example 6, except that the electrolysis time is changed from 5 min to 10 min.

[0031] Example 8 A method for reactivating a deactivated sodium borohydride hydrolysis hydrogen production catalyst is the same as the repair steps in Example 6, except that the electrolysis time is changed from 5 min to 15 min.

[0032] Example 9 A method for reactivating a deactivated sodium borohydride hydrolysis hydrogen production catalyst is the same as the repair steps in Example 6, except that the electrolysis time is replaced by 25 minutes instead of 5 minutes.

[0033] Example 10 A method for reactivating a deactivated sodium borohydride hydrolysis catalyst for hydrogen production includes the following steps: After clamping the deactivated sodium borohydride hydrolysis hydrogen production catalyst with electrode clamps, the catalyst was partially immersed in an electrolytic cell with NaOH solution as the electrolyte and connected to the cathode of an electrochemical workstation. Graphite rod and Hg / HgO were used as the anode and reference electrode, respectively. The electrolysis temperature was set to 20℃, the electrolysis voltage to 0.9V (vs. Hg / HgO), and the electrolysis time to 15min, thus obtaining the repaired sodium borohydride hydrolysis hydrogen production catalyst.

[0034] Example 11 A method for reactivating a deactivated sodium borohydride hydrolysis hydrogen production catalyst is the same as the repair steps in Example 10, except that the electrolysis temperature is changed from 20°C to 30°C.

[0035] Example 12 A method for reactivating a deactivated sodium borohydride hydrolysis hydrogen production catalyst is the same as the repair steps in Example 10, except that the electrolysis temperature is replaced by 35°C instead of 20°C.

[0036] Example 13 A method for reactivating a deactivated sodium borohydride hydrolysis hydrogen production catalyst is the same as the repair steps in Example 10, except that the electrolysis temperature is changed from 20°C to 40°C.

[0037] Example 14 A method for reactivating a deactivated sodium borohydride hydrolysis catalyst for hydrogen production includes the following steps: After clamping the deactivated sodium borohydride hydrolysis hydrogen production catalyst with electrode clamps, the catalyst was partially immersed in an electrolytic cell with NaOH solution as the electrolyte and connected to the cathode of an electrochemical workstation. Graphite rod and Hg / HgO were used as the anode and reference electrode, respectively. The electrolysis temperature was set to 50℃, the electrolysis voltage to 0.5V (vs. Hg / HgO), and the electrolysis time to 5min, thus obtaining the repaired sodium borohydride hydrolysis hydrogen production catalyst.

[0038] Example 15 A method for reactivating a deactivated sodium borohydride hydrolysis catalyst for hydrogen production includes the following steps: After clamping the deactivated sodium borohydride hydrolysis hydrogen production catalyst with electrode clamps, the catalyst was partially immersed in an electrolytic cell with NaOH solution as the electrolyte and connected to the cathode of an electrochemical workstation. Graphite rod and Hg / HgO were used as the anode and reference electrode, respectively. The electrolysis temperature was set to 20℃, the electrolysis voltage to 1.5V (vs. Hg / HgO), and the electrolysis time to 60min, thus obtaining the repaired sodium borohydride hydrolysis hydrogen production catalyst.

[0039] This invention employs a three-electrode system for the reactivation of a deactivated sodium borohydride hydrolysis catalyst for hydrogen production. The three-electrode system structure diagram is shown below. Figure 1 As shown, Examples 1 through 15 all yielded repaired sodium borohydride hydrolysis hydrogen production catalysts. The following research uses the repaired sodium borohydride hydrolysis hydrogen production catalysts from Examples 1 through 13 as examples. Specific research methods and results are shown below: Performance testing: such as Figure 2 As shown, the method for determining the performance of sodium borohydride hydrolysis hydrogen production catalyst is the classical water displacement method. Specifically, it is necessary to calculate the volume of hydrogen produced per unit mass of catalyst per unit time. The volume of water displaced is equal to the volume of hydrogen produced, i.e., the hydrogen production rate HGR. According to the formula HGR = V / (t*m), the final result is expressed in L·min. -1 ·g -1A higher hydrogen production rate indicates better catalyst performance. The hydrogen production performance of the carbon fiber cloth-supported CoMoP sodium borohydride hydrolysis catalyst needs to be tested beforehand to compare with the effect after repair. Specifically: Prepare 50 mL of 5 wt.% sodium borohydride solution, place a 1 cm × 1 cm unused carbon fiber cloth-supported CoMoP sodium borohydride hydrolysis catalyst in the sodium borohydride solution, and at 50℃, complete reaction of the sodium borohydride constitutes one cycle. Calculate the hydrogen production rate as the initial value, then repeat the second, third, ..., nth cycle, each with a certain decrease compared to the previous cycle, recording the hydrogen production rate for a total of 10 cycles. The test shows that after 10 cycles, the hydrogen production rate of the catalyst decreases to 60.4% of the initial value. Then, remove the catalyst from the solution, rinse it completely with deionized water, and then apply it... Figure 1 The three-electrode system shown is used to repair the sodium borohydride hydrolysis hydrogen production catalyst device.

[0040] Corresponding to the performance of the sodium borohydride hydrolysis hydrogen production catalysts repaired using different electrolysis voltages in Examples 1-5, the repaired sodium borohydride hydrolysis hydrogen production catalyst exhibited the best performance at 0.9V (vs. Hg / HgO). The testing method for the repaired sodium borohydride hydrolysis hydrogen production catalyst was completely consistent with that described above; only the initial hydrogen production rate needed to be recorded and compared with the initial hydrogen production rate measured by the previously virgin carbon fiber cloth-supported CoMoP sodium borohydride hydrolysis hydrogen production catalyst and the data after the 10th cycle. Figure 3 It can be seen that the hydrogen production rate after 20 min of electrolysis at 0.9V (vs. Hg / HgO) and 1.0V (vs. Hg / HgO) is as high as 94.5% and 86.3% of the initial value, respectively, while there are significant differences at other electrolysis potentials. This means that by optimizing the potential window, the competition for HER side reactions can be significantly reduced, and the efficiency of the cathode electroreduction reaction can be improved.

[0041] Corresponding to the performance of the sodium borohydride hydrolysis hydrogen production catalyst repaired with different electrolysis times in Examples 3 and 6-9, such as Figure 4 As shown, the performance of the repaired sodium borohydride hydrolysis hydrogen production catalyst was continuously improved under electrolysis times of 5 min, 10 min, and 15 min, while the performance remained stable under electrolysis times of 20 min and 25 min. This indicates that the surface passivation layer of the repaired sodium borohydride hydrolysis hydrogen production catalyst was continuously eliminated under continuous electrolysis.

[0042] Corresponding to Examples 8 and 10-13, the performance of the sodium borohydride hydrolysis hydrogen production catalyst repaired using different electrolysis temperatures was analyzed. Figure 5 The results show that temperature has little effect on the remediation effect, and the sodium borohydride hydrolysis hydrogen production catalyst with the best performance is obtained by electrolysis at 30℃.

[0043] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for reactivating a deactivated sodium borohydride hydrolysis catalyst for hydrogen production, characterized in that, Includes the following steps: A three-electrode system consisting of a cathode, an anode, and a reference electrode was used to produce hydrogen by hydrolysis of deactivated sodium borohydride catalyst as the cathode. Among them, the deactivated sodium borohydride hydrolysis hydrogen production catalyst is a sodium borohydride hydrolysis hydrogen production catalyst with sodium metaborate deposited on the surface. Using an alkaline solution as the electrolyte, one end of the three-electrode system was immersed in the electrolyte, and the other end was electrically connected to an electrochemical workstation. Constant voltage DC electrolysis was used to cause sodium metaborate on the cathode surface to undergo an electroreduction reaction and be converted into sodium borohydride, which is easily soluble in water, thus obtaining the repaired sodium borohydride hydrolysis hydrogen production catalyst.

2. The reactivation method for the deactivated sodium borohydride hydrolysis hydrogen production catalyst according to claim 1, characterized in that, The deactivated sodium borohydride hydrolysis catalyst used as the cathode is a supported catalyst.

3. The reactivation method for the deactivated sodium borohydride hydrolysis hydrogen production catalyst according to claim 2, characterized in that, The support for the supported catalyst is selected from one of the following: copper sheet, copper foam, nickel mesh, nickel foam, stainless steel mesh, titanium mesh, titanium felt, titanium foam, carbon cloth, and carbon paper.

4. The reactivation method for the deactivated sodium borohydride hydrolysis hydrogen production catalyst according to claim 3, characterized in that, The surface of the supported catalyst is completely or partially covered by sodium metaborate.

5. The method for reactivating the deactivated sodium borohydride hydrolysis hydrogen production catalyst according to claim 1, characterized in that, The alkaline solution is selected from NaOH solution or KOH solution.

6. The method for reactivating the deactivated sodium borohydride hydrolysis hydrogen production catalyst according to claim 5, characterized in that, When the alkaline solution is selected from NaOH or KOH solutions, the concentration is 10 mmol / L to 1000 mmol / L, the volume is 50 mL to 1000 mL, and the pH is 12 to 14.

7. The method for reactivating the deactivated sodium borohydride hydrolysis hydrogen production catalyst according to claim 1, characterized in that, The anode is a graphite rod, and the reference electrode is an Hg / HgO electrode.

8. The method for reactivating the deactivated sodium borohydride hydrolysis hydrogen production catalyst according to claim 1, characterized in that, The conditions for DC electrolysis are: an electrolysis voltage of 0.5V (vs. Hg / HgO) to 1.5V (vs. Hg / HgO) and an electrolysis temperature of 20℃ to 50℃, for 5 min to 60 min.

9. The method for reactivating the deactivated sodium borohydride hydrolysis hydrogen production catalyst according to claim 1, characterized in that, After electrolysis, the repaired sodium borohydride hydrolysis hydrogen production catalyst is rinsed with deionized water until there is no residual electrolyte or reduction product on the surface, and then placed in an oven to dry to constant weight.

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