Direct electrolysis seawater hydrogen production method that effectively inhibits precipitation

Abstract

The present invention provides a direct electrolysis seawater hydrogen production method that effectively inhibits precipitation. In the present invention, natural seawater is used as an electrolyte; an alternating current is applied to an electrode; the polarity of the electrode is periodically and alternately converted between a cathode state and an anode state by utilizing the periodic change of the voltage of the alternating current; and when the electrode is in the anode state, OH- generated by means of a hydrogen evolution reaction in the cathode state is consumed to inhibit precipitation and a catalytic activity decrease of the electrode. The present invention further provides a solution electrolysis hydrogen production method that generates a precipitate under alkaline conditions.

Description

A method for producing hydrogen by direct electrolysis of seawater with effective suppression of precipitation Technical Field

[0001] The present invention belongs to the technical field of electrolysis of seawater, and specifically comprises a method for producing hydrogen by direct electrolysis of seawater which effectively inhibits precipitation. Background Art

[0002] As the first choice to meet energy needs in the future, hydrogen energy has the advantages of high combustion calorific value, clean and pollution-free, environmentally friendly, and convenient transportation. The main sources of hydrogen are fossil fuel hydrogen production, industrial by-product hydrogen production, and water electrolysis hydrogen production. Among them, fossil fuel hydrogen production and industrial by-product hydrogen production have limited raw material reserves, and the carbon emissions of the hydrogen production process are relatively high, which does not meet the "dual carbon" goals. The entire process of hydrogen production by electrolysis of water has no greenhouse gas emissions, and the produced hydrogen is of high purity, so it is the main development direction in the future. Considering the scarcity of fresh water, as the global demand for hydrogen increases dramatically, it will be more promising to produce hydrogen with abundant seawater resources (accounting for 96.5% of the world's total water). In the process of direct electrolysis of seawater to produce hydrogen, a hydrogen evolution reaction occurs at the cathode to produce hydrogen, and at the same time, hydroxide ions (OH - ). OH accumulated on the cathode surface - The Mg present in large quantities in natural seawater 2+ and Ca 2+ The combination of these insoluble precipitates produces Mg(OH)2 and Ca(OH)2 precipitates around the cathode. These insoluble precipitates physically block the active sites of the catalyst, leading to catalyst deactivation, clogging of the diaphragm, increased ohmic losses in the electrolyzer, and deterioration of the long-term stability of the electrode performance. It has been reported that these insoluble precipitates covering the cathode surface can reduce the current density of seawater electrolysis by 50%. Therefore, the generation of insoluble precipitates during the H2 production process, which leads to catalyst deactivation and performance degradation, is a key issue that needs to be addressed in the direct electrolysis of seawater to produce H2.

[0003] There are three strategies to eliminate or reduce the generation of insoluble precipitates during H2 electrolysis. (1) Seawater pretreatment. This involves adding KOH / NaOH to natural seawater or precipitating Mg through a pre-electrocatalytic process. 2+ and Ca 2+ , and then removed by filtration. Although effective, the high price of KOH and NaOH and the complexity of the pretreatment process will greatly increase the cost of H2 production. (2) Equipment improvement. By using a selective permeable membrane to prevent unfavorable ions from entering the reaction system from seawater, precipitation is hindered or reduced, which requires additional costs related to membrane replacement and equipment maintenance. (3) Electrocatalyst improvement. A research team introduced a Lewis acid layer (Cr2O3) on the surface of the transition metal oxide catalyst, using the Lewis acid layer to react with OH in the double layer on the anode surface. - The strong binding of OH- and Mg 2+ , Ca 2+ However, the Lewis acid layer and OH - The binding capacity of α-D-glucan is limited, and this method cannot completely inhibit the formation of precipitates.

[0004] Despite significant progress, current methods either fail to fully address the precipitation issue during H2 production from seawater electrolysis or significantly increase H2 production costs due to the use of specialized equipment and complex processes. Therefore, developing more efficient and cost-effective strategies to address the precipitation issue during direct seawater electrolysis is of great significance for hydrogen production from direct seawater electrolysis. Summary of the Invention

[0005] In view of the above problems existing in the prior art, the present invention aims to provide a method for producing hydrogen by direct electrolysis of seawater which effectively inhibits precipitation. The method utilizes the periodic variation of alternating current to timely eliminate the OH generated by the electrode in the cathode state. - , avoiding the precipitation of calcium and magnesium ions on the electrode surface, thereby ensuring the long-term reaction activity of the electrode and increasing the service life of the electrode.

[0006] Due to the periodic change of the AC voltage, the polarity of the electrode will switch alternately between the cathode state and the anode state. In the present invention, for the same electrode, the cathode state refers to the electrode performing the hydrogen evolution reaction as the cathode at this voltage, and the anode state refers to the electrode performing the oxygen evolution reaction and / or the chlorine oxidation reaction as the anode at this voltage. Furthermore, the anode state refers to the electrode performing the electrochemical oxidation reaction as the anode at this voltage, including but not limited to the oxygen evolution reaction and / or the chlorine oxidation reaction.

[0007] To achieve the above objectives, the technical solutions adopted by the present invention include:

[0008] The present invention discloses a method for effectively inhibiting precipitation during the direct electrolysis of seawater to produce hydrogen. Natural seawater is used as an electrolyte, alternating current is applied to electrodes, and the polarity of the electrodes is periodically switched between cathode and anode states by utilizing the periodic change of the alternating current voltage. When the electrodes are in the anode state, OH generated by the hydrogen evolution reaction in the cathode state is consumed. - To inhibit precipitation and the decline of electrode catalytic activity.

[0009] Since seawater is rich in calcium and magnesium ions, if direct current is used to electrolyze seawater to produce hydrogen, the OH generated on the cathode surface during the hydrogen evolution reaction will - Mg in seawater 2+ and Ca 2+The combination generates an insoluble precipitate that covers the electrode surface, causing a series of problems such as catalyst deactivation, increased ohmic loss, and reduced electrode stability, making it difficult to maintain the electrode's catalytic activity for a long time. To this end, the present invention provides a simple treatment method, which cleverly utilizes the periodic changes of alternating current. By controlling the waveform, voltage, and period of the alternating current, the electrode is periodically switched between the cathode state and the anode state. When the electrode is in the cathode state, a hydrogen evolution reaction occurs near the electrode, producing hydrogen and OH. - When the electrode is converted to the anode state, oxygen evolution reaction and / or chlorine oxidation reaction occur near the electrode, consuming the OH generated in the cathode state. - , thereby eliminating the OH produced by the electrode in the cathode state - .

[0010] Furthermore, in the present invention, there are two reactions occurring near the electrodes:

[0011] When the electrode is in the cathode state: 2H2O+2e - →H2↑+2OH -

[0012] When the electrode is in the anode state: 4OH - →O2↑+2H2O+4e -

[0013] Or Cl - +2OH - →ClO - +H2O+2e -

[0014] Furthermore, the waveform of the alternating current is selected from square wave, sine wave or triangle wave; preferably square wave.

[0015] Furthermore, the voltage of the AC power is 1.8-4V; illustratively, the voltage of the AC power can be 1.8V, 2V, 2.2V, 2.4V, 2.6V, 2.8V, 3V, 3.2V, 3.4V, 3.6V, 3.8V, 4V, etc.

[0016] Furthermore, the cycle of the alternating current is 0.01-2s; illustratively, the cycle of the alternating current can be 0.01s, 0.02s, 0.05s, 0.1s, 0.2s, 0.5s, 0.8s, 1s, 1.2s, 1.5s, 1.8s, 2s, etc.

[0017] It should be noted that the present invention does not specifically limit the electrode material. Electrode materials commonly used by those skilled in the art can be used in this method. They can be loaded electrodes or unloaded electrodes. At the same time, the present invention does not specifically limit the source of the electrode material. It can be a commercially available electrode or an electrode prepared by itself with reference to the disclosed preparation method, all of which are within the protection scope of the present invention. Exemplarily, the electrode is selected from one of RuO2@foam nickel electrode, foam nickel electrode, nickel sheet electrode, platinum electrode, platinum-rhodium alloy electrode, graphite electrode, titanium electrode, foam titanium electrode, carbon paper electrode, and graphene electrode.

[0018] Furthermore, the precipitate is Ca(OH)2 and Mg(OH)2.

[0019] Furthermore, the temperature of the electrolyte is 5-95°C; illustratively, it can be 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, etc.

[0020] Furthermore, the voltage of the AC power is 1.2-380V. For example, the voltage of the AC power is 1.2V, 1.5V, 5V, 10V, 50V, 100V, 220V, 380V, etc. Preferably, the voltage of the AC power is 1.2-1.8V. Preferably, the voltage of the AC power is 1.8-4V. Preferably, the voltage of the AC power is 4-380V.

[0021] Furthermore, the period of the alternating current is 0.001-2s. For example, the period of the alternating current is 0.001s, 0.002s, 0.003s, 0.004s, 0.005s, 0.006s, 0.007s, 0.008s, 0.009s, etc. Preferably, the period of the alternating current is 0.001-0.01s. Preferably, the period of the alternating current is 0.01-2s.

[0022] It should be noted that the present invention does not specifically limit the source of seawater. Natural seawater from any region on Earth can be used directly in the electrolytic hydrogen production reaction without the need for additional operations such as removing calcium and magnesium ions.

[0023] According to another aspect of the present invention, the present invention also provides a method for producing hydrogen by electrolysis of a solution that generates a precipitate under alkaline conditions, using a solution that generates a precipitate under alkaline conditions other than natural seawater as an electrolyte, applying alternating current to the electrodes, and utilizing the periodic change of the alternating current voltage to periodically switch the polarity of the electrodes between the cathode state and the anode state. When the electrodes are in the anode state, OH generated by the hydrogen evolution reaction in the cathode state is consumed. -To inhibit precipitation and decrease in electrode catalytic activity;

[0024] The other solutions that generate precipitates under alkaline conditions include solutions containing ions that can be precipitated under alkaline conditions.

[0025] The solution that generates precipitation under alkaline conditions refers to a solution containing ions (such as Ca 2+ Mg 2+ When the solution is alkaline, these ions react with OH - The alkaline condition refers to the pH of the solution being greater than 7.

[0026] Preferably, the other solution that generates a precipitate under alkaline conditions is selected from the group consisting of 2+ Solutions and / or Mg-containing 2+ of solution.

[0027] Preferably, the other solution that generates precipitates under alkaline conditions is selected from any one or more of the following: river water, salt lake water, mine water, industrial wastewater, and domestic sewage.

[0028] Preferably, the Ca 2+ and / or Mg 2+ The solution is selected from any one or more of the following: river water, salt lake water, mine water, industrial wastewater, and domestic sewage.

[0029] Preferably, the cycle of the alternating current is 0.001-2s.

[0030] Preferably, the cycle of the alternating current is 0.001-0.01s.

[0031] Preferably, the cycle of the alternating current is 0.01-2s.

[0032] Preferably, the voltage of the alternating current is 1.2-380V.

[0033] Preferably, the voltage of the alternating current is 1.2-1.8V.

[0034] Preferably, the voltage of the alternating current is 1.8-4V.

[0035] Preferably, the voltage of the alternating current is 4-380V.

[0036] Furthermore, the waveform of the alternating current is selected from a square wave, a sine wave or a triangle wave.

[0037] Preferably, the waveform of the alternating current is selected from a square wave.

[0038] Furthermore, the electrode is selected from one of RuO2@foam nickel electrode, foam nickel electrode, nickel sheet electrode, platinum electrode, platinum-rhodium alloy electrode, graphite electrode, titanium electrode, foam titanium electrode, carbon paper electrode, and graphene electrode.

[0039] Furthermore, the temperature of the electrolyte is 5-95°C.

[0040] Beneficial effects of the present invention:

[0041] In order to solve the problems of catalyst deactivation, increased ohmic loss, and reduced electrode stability in direct current electrolysis of seawater for hydrogen production, the present invention proposes a technology for direct seawater electrolysis for hydrogen production using alternating current. By utilizing the periodic changes of alternating current, the OH generated by the hydrogen evolution reaction can be consumed in situ and in real time. - , which prevents calcium and magnesium ions from precipitating on the electrode surface, and at the same time achieves the purpose of long-term electrolysis of seawater to produce hydrogen, greatly improving the efficiency of direct electrolysis of seawater to produce hydrogen and the service life of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0043] FIG1 is a schematic diagram of the principle of hydrogen production by electrolyzing seawater with alternating current according to the present invention.

[0044] FIG2 is a schematic diagram showing the square waveform AC input applied in Example 1. FIG.

[0045] FIG3 shows the effect before and after the electrolysis of seawater using square waveform alternating current in Example 1. FIG.

[0046] FIG4 shows a current density-time curve of seawater electrolysis using square waveform alternating current in Example 1.

[0047] FIG5 shows a gas chromatogram of gaseous products of seawater electrolysis by square wave alternating current in Example 1.

[0048] FIG6 shows a graph of hydrogen evolution efficiency in seawater electrolysis using square waveform alternating current of different periods in Examples 1-4.

[0049] FIG. 7 is a schematic diagram showing the sinusoidal AC input applied in Example 5. FIG.

[0050] FIG8 is a schematic diagram showing the triangular wave AC input applied in Example 6. FIG.

[0051] FIG9 shows the effect diagram before and after using direct current to electrolyze seawater in Comparative Example 1.

[0052] FIG10 shows a current density-time curve of the electrolysis of seawater using direct current in Comparative Example 1.

[0053] FIG11 shows a curve showing the voltage variation over time (one period T) of the sinusoidal alternating current applied to the two electrodes shown in FIG1 in Example 19, the data being recorded by an oscilloscope.

[0054] FIG12 shows a curve of current density changing with time in Example 19.

[0055] FIG13 shows a curve showing the change of current density over time during one cycle in Example 19.

[0056] FIG14 shows a curve showing the time variation of the voltage of the triangular wave alternating current applied to the two electrodes shown in FIG1 in Example 23 (one period T), the data being recorded by an oscilloscope.

[0057] FIG15 shows a curve showing the change of current density over time in Example 23.

[0058] FIG16 shows a curve showing the change of current density over time during one cycle in Example 23. DETAILED DESCRIPTION

[0059] To more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. It should be understood that the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0060] In addition, unless otherwise specified, the raw materials used in the present invention can be obtained commercially, and any range recorded in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0061] Example 1

[0062] Referring to Figure 1, natural seawater was used as the electrolyte, RuO2@ nickel foam electrodes were used as the two electrodes, and square waveform alternating current (Figure 2) was used as the power supply to electrolyze natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8 V and -1.8 V, respectively. The cycle T was 1 s, and the electrolyte temperature was room temperature (25°C).

[0063] During the electrolysis process, bubbles were observed to continuously form on both electrodes. After 40 minutes of electrolysis, no precipitation formed on the electrode surfaces (Figure 3; the left image in Figure 3 shows the image before AC electrolysis, and the right image shows the image after AC electrolysis). The current was stable during this process (Figure 4). The generated gas was collected using the drainage method and analyzed by high-performance gas chromatography, confirming that the collected gas was pure hydrogen (Figure 5).

[0064] Figure 6 monitors the changes in hydrogen evolution during 100 minutes of continuous electrolysis. The maximum hydrogen evolution efficiency reaches 76.01%, and the hydrogen evolution efficiency is 58.55% at the end of electrolysis.

[0065] Example 2

[0066] Referring to Figure 1, natural seawater was used as the electrolyte, RuO2@ nickel foam electrodes were used as the two electrodes, and square waveform alternating current (Figure 2) was used as the power supply to electrolyze natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8 V and -1.8 V, respectively. The cycle T was 2 s, and the electrolyte temperature was room temperature (25°C).

[0067] During the electrolysis process, bubbles were observed to be continuously generated on both electrodes without precipitation, and the current was stable during the process.

[0068] Figure 6 monitors the changes in hydrogen evolution during 60 min of continuous electrolysis, with the highest hydrogen evolution efficiency reaching 78.45%.

[0069] Example 3

[0070] Referring to Figure 1, natural seawater was used as the electrolyte, RuO2@ nickel foam electrodes were used as the two electrodes, and square waveform alternating current (Figure 2) was used as the power supply to electrolyze natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8 V and -1.8 V, respectively. The cycle T was 0.5 s, and the electrolyte temperature was room temperature (25°C).

[0071] During the electrolysis process, bubbles were observed to be continuously generated on both electrodes without precipitation, and the current was stable during the process.

[0072] Figure 6 monitors the changes in hydrogen evolution during 80 minutes of continuous electrolysis, and the hydrogen evolution efficiency remains stable at around 12.80%.

[0073] Example 4

[0074] Referring to Figure 1, natural seawater is used as the electrolyte, titanium foam electrodes are used as the two electrodes, and square waveform alternating current (Figure 2) is used as the power supply to electrolyze natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) are 4V and -4V respectively, the cycle T is 0.2s, and the electrolyte temperature is room temperature (25°C).

[0075] During the electrolysis process, bubbles were observed to be continuously generated on both electrodes without precipitation, and the current was stable during the process.

[0076] Figure 6 monitors the changes in hydrogen evolution during 60 minutes of continuous electrolysis, and the hydrogen evolution efficiency remains stable at around 6.64%.

[0077] Example 5

[0078] Referring to Figure 1, natural seawater was used as the electrolyte, RuO2@ nickel foam electrodes were used as the two electrodes, and square waveform alternating current (Figure 2) was used as the power supply to electrolyze natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8 V and -1.8 V, respectively. The cycle T was 0.01 s, and the electrolyte temperature was room temperature (25°C).

[0079] During the 100 min electrolysis, bubbles were observed to be continuously generated on both electrodes, and no precipitation was generated. The current remained stable during the electrolysis process.

[0080] The changes in hydrogen evolution during 60 minutes of continuous electrolysis were monitored, and the hydrogen evolution efficiency remained stable at around 1.05%.

[0081] Example 6

[0082] Referring to Figure 1, natural seawater was used as the electrolyte, Pt electrodes were used as the two electrodes, and a sinusoidal alternating current (Figure 7) was used as the power source for electrolysis of natural seawater. As shown in Figure 7, Ea was 4V, the cycle T was 1s, and the electrolyte temperature was room temperature (25°C). Over a 5-hour electrolysis period, bubbles were observed to continuously form at both electrodes, with no precipitation observed. The current remained stable throughout the electrolysis process.

[0083] Example 7

[0084] Referring to FIG1 , natural seawater is used as the electrolyte, PtRh electrodes are used as the two electrodes, and triangular wave alternating current ( FIG8 ) is used as the power supply to electrolyze natural seawater. As shown in FIG8 , Ea is 3 V, the period T is 1 s, and the electrolyte temperature is room temperature (25° C.).

[0085] During the 10 h of electrolysis, bubbles were observed to be continuously generated on both electrodes, and no precipitation was generated. The current remained stable during the electrolysis process.

[0086] Comparative Example 1

[0087] Natural seawater was used as the electrolyte, RuO2@nickel foam electrodes were used as the two electrodes, and direct current was used as the power source to electrolyze natural seawater. The constant voltage was 1.8V, and the electrolyte temperature was room temperature (25°C). During the electrolysis process, bubbles were observed at the cathode, and a certain amount of white precipitate was observed on the electrode surface after 10 minutes of electrolysis (Figure 9, the left image in Figure 9 is the image before direct current electrolysis, and the right image is the image after direct current electrolysis). During this electrolysis process, the current density dropped significantly by 60% after 800 seconds of electrolysis (Figure 10).

[0088] Comparative Example 2

[0089] As shown in Figure 1, natural seawater was used as the electrolyte, RuO2@nickel foam electrodes were used as the two electrodes, and a square wave AC current (Figure 1) was used as the power source. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8V and -1.8V, respectively. The cycle T was 4 seconds, and the electrolyte temperature was room temperature (25°C). During the electrolysis process, bubbles were observed to continuously form at both electrodes, but this process was accompanied by precipitation. After 20 minutes, significant precipitation was observed to accumulate around the electrodes, possibly due to the long cycle time.

[0090] FIG1 of the present invention shows a schematic diagram of the principle of producing hydrogen by electrolyzing seawater with alternating current.

[0091] As shown in FIG1 , the method for producing hydrogen by electrolysis of water of the present invention is described by taking the electrolysis of seawater as an example. The method comprises: using natural seawater as an electrolyte, applying alternating current to the electrodes, and utilizing the periodic change of the alternating current voltage to periodically switch the polarity of the electrodes between the cathode state and the anode state. When the electrodes are in the anode state, OH generated by the hydrogen evolution reaction in the cathode state is consumed. - To suppress precipitation and electrode catalytic activity decline. In Figure 1, the electrolyte is seawater, and alternating current is applied between the left and right electrodes. In the first half cycle of alternating current, the white arrow near the left electrode indicates the hydrogen evolution reaction that occurs during the cathode state of the electrode. At the same time, the right electrode is in the anode state and oxygen evolution reaction or chlorine-oxygen reaction occurs (as shown by the white arrow near the right electrode); in the second half cycle of alternating current, the black arrow near the left electrode indicates the oxygen evolution reaction or chlorine-oxygen reaction that occurs during the anode state of the electrode. At the same time, the right electrode is in the cathode state and hydrogen evolution reaction occurs (as shown by the black arrow near the right electrode). Due to the periodic change of the alternating current voltage, the polarity of the electrode will be caused to switch alternately between the cathode state and the anode state. In the present invention, with respect to the same electrode, the cathode state refers to the electrode performing hydrogen evolution reaction as a cathode at this moment voltage, and the anode state refers to the electrode performing electrochemical oxidation reaction as an anode at this moment voltage, including but not limited to oxygen evolution reaction and / or chlorine oxidation reaction.

[0092] Preferably, the cycle of the present invention is set to 0.01-2s. More preferably, the cycle of the present invention is set to 0.2-2s; and even more preferably, the cycle of the present invention is set to 0.25-2s.

[0093] FIG2 shows a schematic diagram of square wave alternating current.

[0094] Wherein, Ea represents the voltage of the positive half cycle, Ec represents the voltage of the negative half cycle, and the period is T.

[0095] FIG7 shows a schematic diagram of a sinusoidal alternating current.

[0096] Wherein, Ea represents the peak voltage of the positive half cycle, Ec represents the peak voltage of the negative half cycle, and the period is T.

[0097] FIG8 shows a schematic diagram of a triangular wave alternating current.

[0098] Wherein, Ea represents the peak voltage of the positive half cycle, Ec represents the peak voltage of the negative half cycle, and the period is T.

[0099] As shown in Figures 2, 7, and 8, the ordinate is voltage U and the abscissa is time t. The waveform of the alternating current is selected from any one of a square wave, a sine wave, or a triangular wave. A square wave is preferred.

[0100] Figure 3 shows the effects of seawater electrolysis using a square-wave AC current before and after use in Example 1. As shown in Figure 3, the electrolyte in the electrolytic cell remained clear after 40 minutes of electrolysis, with no insoluble precipitate formed on the electrode surfaces. The clarity of the electrolyte was no significantly different from that before the start of electrolysis, i.e., at 0 minutes.

[0101] Figure 4 shows a current density-time curve for electrolyzing seawater using a square waveform alternating current in Example 1. In the current density-time curve shown in Figure 4 , the ordinate is current density and the abscissa is time.

[0102] Figure 5 shows a gas chromatogram of gaseous products of seawater electrolysis by square wave alternating current in Example 1. As shown in Figure 5 , the collected gas is pure hydrogen.

[0103] FIG6 shows a graph of hydrogen evolution efficiency in seawater electrolysis using square waveform alternating current of different periods in Examples 1-4.

[0104] Figure 9 shows a comparison of the electrolytic cell before and after direct current electrolysis of seawater. As shown in Figure 9, in Comparative Example 1, after 10 minutes of direct current electrolysis, a certain amount of white precipitate was observed on the electrode surface, and a large amount of white precipitate was observed at the bottom of the electrolytic cell.

[0105] Figure 10 shows a schematic diagram of the change in current density during direct current electrolysis of seawater. As shown in Figure 10 , the ordinate represents current density, and the abscissa represents time. In Comparative Example 1, the current density dropped significantly by 60% after 800 seconds of electrolysis, indicating that the sediment adversely affected the current density.

[0106] FIG11 shows a curve showing the voltage variation over time (one period T) of the sinusoidal alternating current applied to the two electrodes shown in FIG1 in Example 19, the data being recorded by an oscilloscope.

[0107] Figure 12 shows the curve of current density changing with time in Example 19. During the test time (60 min), the current density remained stable.

[0108] FIG13 shows a curve showing the change of current density over time in one cycle in Example 19.

[0109] FIG14 shows a curve showing the time variation of the voltage of the triangular wave alternating current applied to the two electrodes shown in FIG1 in Example 23 (one period T), the data being recorded by an oscilloscope.

[0110] Figure 15 shows the current density versus time curve in Example 23. During the test time (60 min), the current density remained stable.

[0111] FIG16 shows a curve showing the change of current density over time during one cycle in Example 23.

[0112] It should be noted that the seawater selected for the examples of natural seawater in the present invention was taken from Qingdao, Shandong Province, Weihai, Shandong Province, and Sanya, Hainan Province. The seawater from different regions had no significant effect on the experimental results.

[0113] Electrochemical signal generation and collection: A function generator (model Tektronix AFG3022C) and an electrochemical workstation (CHI660E, Shanghai Chenhua) were used to output alternating current and direct current. The electrochemical workstation was used to record electrochemical information such as current and voltage. An oscilloscope (model Tektronix TDS2022B) was used to record the voltage information actually applied to the two electrodes by the alternating current output by the function generator.

[0114] Gas product collection and analysis: The gas products produced by the electrolysis of seawater were collected by the drainage method, and the composition of the gas products produced by the electrolysis of seawater was tested and analyzed using a gas chromatograph (Shimadzu GC2030).

[0115] Sediment analysis: The precipitation during the electrolysis process was observed with the naked eye, and a dynamic light scattering instrument (DynaPro NanoStar, Wyatt, USA) was used to further qualitatively analyze the precipitation in the solution after seawater electrolysis.

[0116] The present invention does not limit the electrolytic cell required for the embodiments; it can be any commercially available electrolytic cell. In the embodiments of the present invention, the electrolysis device used was a 6 cm × 6 cm × 6 cm square electrolytic cell, configured with corresponding electrodes to form the electrolysis device. Experimental results indicate that the size of the electrolytic cell and electrodes did not affect the experimental results of the embodiments of the present invention.

[0117] The hydrogen evolution efficiency in the present invention refers to the Faraday efficiency of the hydrogen evolution reaction. The level of hydrogen evolution efficiency directly affects the efficiency of converting electrical energy into hydrogen.

[0118] Faradaic efficiency refers to the percentage of actual products to theoretical products in an electrochemical reaction, reflecting the utilization efficiency of energy conversion.

[0119] The electrode material provided by the present invention includes: a RuO2@nickel foam electrode: the nickel foam is ultrasonically cleaned in acetone, anhydrous ethanol, and a 3 mol / L HCl aqueous solution for 15 minutes, then repeatedly rinsed with deionized water and blown dry with an N2 gun for later use. RuCl3 is dissolved in isopropanol with stirring to prepare a 2 wt% RuCl3 isopropanol solution. The pretreated nickel foam (0.5 cm × 3 cm) is placed in a porcelain boat (10 mm × 100 mm × 10 mm), and the 2 wt% RuCl3 isopropanol solution is dripped into the boat until the nickel foam is just submerged. Then, in an N2 atmosphere, a tube furnace is heated to 60°C at a heating rate of 5°C / min and maintained at this temperature for 1 hour to allow the solution to evaporate. Subsequently, the sample is placed in a muffle furnace, heated to 400°C at a heating rate of 5°C / min, maintained at 400°C for 2 hours, and then naturally cooled to room temperature to produce the RuO2@nickel foam electrode.

[0120] PtRh alloy electrode: PtRh alloy wire, diameter 0.27 mm, Rh content 11% (atomic ratio), purchased from Shanghai Boxiang Electric Instrument Co., Ltd.

[0121] Nickel foam electrodes, nickel sheet electrodes, platinum electrodes, graphite electrodes, titanium electrodes, titanium foam electrodes, carbon paper electrodes, and graphene electrodes are common commercially available electrodes, and there are no special requirements for electrode shape and size.

[0122] In Examples 8-11 and Comparative Example 3, experiments were conducted with periods T set to 0.1s, 0.2s, 0.8s, 1.5s, and 3s, and other conditions were the same as in Example 1.

[0123] Example 8

[0124] Referring to Figure 1, natural seawater was used as the electrolyte, RuO2@ nickel foam electrodes were used as the two electrodes, and square waveform alternating current (Figure 2) was used as the power supply to electrolyze natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8 V and -1.8 V, respectively. The cycle T was 0.1 s, and the electrolyte temperature was room temperature (25°C).

[0125] After 60 minutes of electrolysis, bubbles were observed to be continuously generated on both electrodes without precipitation. The current remained stable during the electrolysis process, and the hydrogen evolution efficiency was approximately 3.23%.

[0126] Example 9

[0127] Referring to Figure 1, natural seawater was used as the electrolyte, RuO2@ nickel foam electrodes were used as the two electrodes, and square waveform alternating current (Figure 2) was used as the power supply to electrolyze natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8 V and -1.8 V, respectively. The cycle T was 0.2 s, and the electrolyte temperature was room temperature (25°C).

[0128] After 60 minutes of electrolysis, bubbles were observed to be continuously generated on both electrodes without precipitation. The current remained stable during the electrolysis process, and the hydrogen evolution efficiency was approximately 5.57%.

[0129] Example 10

[0130] Referring to Figure 1, natural seawater was used as the electrolyte, RuO2@ nickel foam electrodes were used as the two electrodes, and square waveform alternating current (Figure 2) was used as the power supply to electrolyze natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8 V and -1.8 V, respectively. The cycle T was 0.8 s, and the electrolyte temperature was room temperature (25°C).

[0131] After 60 minutes of electrolysis, bubbles were observed to be continuously generated on both electrodes without precipitation. The current remained stable during the electrolysis process, and the hydrogen evolution efficiency was approximately 59.74%.

[0132] Example 11

[0133] Referring to Figure 1, natural seawater was used as the electrolyte, RuO2@ nickel foam electrodes were used as the two electrodes, and square waveform alternating current (Figure 2) was used as the power supply to electrolyze natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8 V and -1.8 V, respectively. The cycle T was 1.5 s, and the electrolyte temperature was room temperature (25°C).

[0134] After 60 minutes of electrolysis, bubbles were observed to be continuously generated on both electrodes without precipitation. The current remained stable during the electrolysis process, and the hydrogen evolution efficiency was approximately 77.32%.

[0135] Comparative Example 3

[0136] Referring to Figure 1, natural seawater was used as the electrolyte, RuO2@ nickel foam electrodes were used as the two electrodes, and square waveform alternating current (Figure 2) was used as the power supply to electrolyze natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8 V and -1.8 V, respectively. The cycle T was 3 s, and the electrolyte temperature was room temperature (25°C).

[0137] After 60 minutes of electrolysis, bubbles were observed to be continuously generated on both electrodes, and white precipitates were produced as the reaction proceeded.

[0138] The gases produced in Examples 1-11 were collected by drainage method, and gas chromatography analysis showed that the gases in Examples 1-3, 5, 8-11 were pure hydrogen, while the gases in Examples 4, 6, and 7 were mixed gases of hydrogen and oxygen.

[0139] Table 1: Comparison of the changes in hydrogen evolution efficiency and the effects of inhibiting precipitation in Examples 1-3, 5, 8-11 and Comparative Examples 2 and 3:

[0140] Table 1

[0141] Conclusion: Direct seawater electrolysis for hydrogen production with an AC cycle of 0.01-2s does not produce precipitation, and the hydrogen production efficiency increases with increasing cycle. Precipitation occurs when the cycle increases to 3s and 4s.

[0142] Example 12

[0143] Referring to Figure 1, natural seawater was used as the electrolyte, RuO2@ nickel foam electrodes were used as the two electrodes, and square waveform alternating current (Figure 2) was used as the power supply to electrolyze natural seawater. The electrolyte temperature was room temperature (25°C), and the voltage Ea (anode voltage), Ec (cathode voltage), and period T were changed for the experiment.

[0144] The gas produced by the electrolysis of each step 1-8 in Example 12 was collected by drainage method, and the gas products were analyzed by gas chromatography. The experimental results are shown in the following table:

[0145] Table 2

[0146] As can be seen from Table 2, when the voltage of the AC power is 1.8-4V and the cycle is 0.01-2s, direct seawater electrolysis to produce hydrogen does not produce precipitation and the hydrogen evolution efficiency is greater than 1%.

[0147] Further, on the basis of Example 12, in order to verify that the cycle is 0.01-2s, and the voltage is electrolysis in the range of 1.8-4V, other conditions change and have an impact on the technical effect, each time selecting one of the voltage and cycle ratios in 1-8 of Table 2 of Example 12, and each time only changing one of the following experimental conditions to carry out orthogonal experiments: electrolyte temperature (respectively 5°C, 20°C, 50°C, 70°C, 95°C), waveform (square wave, sine wave, triangle wave), electrode material (respectively using nickel foam, nickel sheet, Pt, PtRh alloy, carbon paper, graphite, titanium foam, titanium sheet, RuO2@ nickel foam as two electrodes). By multiple groups of orthogonal experiments, no matter how other conditions change, when the cycle of alternating current is 0.01-2s and the voltage is electrolysis in the range of 1.8-4V, it is possible to achieve direct electrolysis of seawater to produce hydrogen, without precipitation, and the technical effect of hydrogen evolution efficiency being greater than 1%. The gas products were analyzed by gas chromatography. The gas products produced when RuO2 / foam nickel electrode was used as the electrode were pure hydrogen, while the gas products produced when other materials were used as electrodes were a mixture of hydrogen and oxygen.

[0148] Example 13

[0149] Only the electrode materials were changed, and other conditions were the same as in Example 1, and an experiment was conducted (see FIG1 , natural seawater was used as the electrolyte, and square waveform alternating current ( FIG2 ) was used as the power source for electrolysis of natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were 3 V and −3 V, respectively, the cycle T was 1 s, and the electrolyte temperature was room temperature (25° C.). The generated gas was collected by the drainage method. Electrode materials used were nickel foam, nickel sheet, Pt, PtRh alloy, carbon paper, graphite, titanium foam, titanium sheet, and RuO2@nickel foam as the two electrodes):

[0150] Table 3

[0151] In experiments 1-9 in Table 3, after 40 min of electrolysis, it was observed that bubbles continued to be generated on both electrodes, and no precipitate was formed.

[0152] Gases produced by electrolysis of various electrode materials 1-9 in Example 13 were collected using a drainage method. Gas chromatography analysis demonstrated that direct electrolysis of seawater using alternating current (AC) for hydrogen production was possible at all electrodes, with continuous hydrogen production and no precipitation. The RuO2 / nickel foam electrode produced pure hydrogen, while the other electrode materials produced a mixture of hydrogen and oxygen.

[0153] Example 14

[0154] All other conditions were the same as in Example 1, except that the electrolyte temperature was varied. This temperature was maintained in a constant-temperature water bath, and the gases generated during electrolysis were collected. (See Figure 1 . Natural seawater was used as the electrolyte, and a square-wave alternating current (Figure 2) was used as the power source for electrolysis of natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8 V and -1.8 V, respectively, with a cycle T of 1 s. The generated gases were collected using the drainage method. The electrolyte temperatures were 5°C, 20°C, 50°C, 70°C, and 95°C.)

[0155] Table 4

[0156] After 40 minutes of electrolysis, bubbles were observed to continuously form at both electrodes in each experiment shown in Table 4, with no precipitation observed. The resulting gaseous products were collected by the drainage method, and the gas volumes at the end of the reaction are listed in Table 4.

[0157] Direct seawater electrolysis using alternating current to produce hydrogen at temperatures ranging from 5 to 95°C produced no precipitation over 40 minutes. The volume of collected gas increased with increasing temperature, as the electrochemical reaction speeds up, producing more gas per unit time. Analysis of the collected gas products by gas chromatography revealed pure hydrogen.

[0158] Example 15

[0159] Other conditions were the same as in Example 1, except that the voltage was changed. Gas was collected at the end of the reaction (see FIG1 . Natural seawater was used as the electrolyte, RuO2@ nickel foam electrodes were used as the two electrodes, and square waveform alternating current ( FIG2 ) was used as the power source for electrolysis of natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage) were shown in Table 5. The cycle T was 1 s, and the electrolyte temperature was room temperature (25° C.). The generated gas products were collected by the drainage method.

[0160] The effects of direct seawater electrolysis with AC current at different AC voltages are compared as follows:

[0161] Table 5

[0162] After 40 minutes of electrolysis, bubbles were observed to continuously form at both electrodes, with no precipitation observed. The gas volumes at the end of the reaction are shown in Table 5.

[0163] Conclusion: Direct seawater electrolysis for hydrogen production using AC current at voltages ranging from 1.8 to 4 V produced no precipitation over 40 minutes. The volume of collected gas increased with increasing voltage, as the electrochemical reaction speeds up, resulting in more gas produced per unit time. Gas chromatography analysis of the gas product confirmed pure hydrogen.

[0164] Example 16

[0165] Electrolysis was performed using natural seawater as the electrolyte, with Example 1 as the reference, except for the differences shown in Table 6. (Natural seawater was used as the electrolyte and square-wave AC power was used as the power source. The voltages Ea (anode voltage) and Ec (cathode voltage), AC cycle, electrolyte temperature, and electrode materials were all shown in Table 6. The generated gas was collected using the drainage method.

[0166] The electrode materials include RuO2@nickel foam electrodes and other electrode materials. Other electrode materials are selected from any one of the following: nickel sheet electrodes; platinum electrodes; platinum-rhodium alloy electrodes; graphite electrodes; titanium electrodes; titanium foam electrodes; carbon paper electrodes; or graphene electrodes. The definition of "other electrodes" in the following embodiments is as described in this embodiment.

[0167] Table 6

[0168] Based on Table 6, further changing the waveform from a square wave to a sine wave or a triangle wave can also achieve the technical effect of no precipitation and a hydrogen evolution efficiency greater than 1%. At the same time, pure H2 is collected when the RuO2@nickel foam electrode is used as the electrode, and a mixed gas of H2 and O2 is collected when other electrode materials are used as the electrode.

[0169] Furthermore, the present invention provides embodiments of sine waves and triangular waves at different periods, and the gas prepared in embodiments 17-24 is collected by the drainage method.

[0170] Example 17

[0171] As shown in Figure 1, natural seawater was electrolyzed using RuO2@nickel foam as the two electrodes, and a sinusoidal AC power supply. Ea ​​(anode voltage) and Ec (cathode voltage) were 3V and -3V, respectively, with a cycle time of 0.2s and an electrolyte temperature of room temperature (25°C). During the electrolysis process, bubbles were continuously generated at both electrodes, with no precipitation observed, and the current remained stable.

[0172] The changes in hydrogen evolution were monitored during 60 minutes of continuous electrolysis, and the hydrogen evolution efficiency remained stable at around 6.17%.

[0173] Example 18

[0174] As shown in Figure 1, natural seawater was electrolyzed using RuO2@nickel foam as the two electrodes, and a sinusoidal AC power supply. Ea ​​(anode voltage) and Ec (cathode voltage) were 3V and -3V, respectively, with a cycle time of 0.5s and an electrolyte temperature of room temperature (25°C). During the electrolysis process, bubbles were continuously generated at both electrodes, with no precipitation observed, and the current remained stable.

[0175] The changes in hydrogen evolution were monitored during 60 minutes of continuous electrolysis, and the hydrogen evolution efficiency remained stable at around 13.03%.

[0176] Example 19

[0177] As shown in Figure 1, natural seawater was electrolyzed using RuO2@nickel foam as the two electrodes, and a sinusoidal AC power supply. Ea ​​(anode voltage) and Ec (cathode voltage) were 3V and -3V, respectively, with a cycle T of 1s. The electrolyte temperature was room temperature (25°C). During the electrolysis process, bubbles were continuously generated at both electrodes, with no precipitation observed. The current remained stable throughout the process.

[0178] The changes in hydrogen evolution during 60 minutes of continuous electrolysis were monitored, and the hydrogen evolution efficiency remained stable at around 18.60%.

[0179] Example 20

[0180] As shown in Figure 1, natural seawater was electrolyzed using RuO2@nickel foam as the two electrodes, and a sinusoidal AC power source. Ea (anode voltage) and Ec (cathode voltage) were 3V and -3V, respectively, with a cycle T of 2s and an electrolyte temperature of room temperature (25°C). During the electrolysis process, bubbles were continuously generated at both electrodes, with no precipitation observed, and the current remained stable.

[0181] The changes in hydrogen evolution during 60 minutes of continuous electrolysis were monitored, and the hydrogen evolution efficiency was stable at around 33.78%.

[0182] Example 21

[0183] As shown in Figure 1, natural seawater was electrolyzed using RuO2@nickel foam as the two electrodes, and triangular AC as the power source. Ea (anode voltage) and Ec (cathode voltage) were 3V and -3V, respectively, with a cycle time of 0.2s and an electrolyte temperature of room temperature (25°C). During the electrolysis process, bubbles were continuously generated at both electrodes, with no precipitation observed, and the current remained stable.

[0184] The changes in hydrogen evolution were monitored during 60 minutes of continuous electrolysis, and the hydrogen evolution efficiency remained stable at around 3.04%.

[0185] Example 22

[0186] As shown in Figure 1, natural seawater was electrolyzed using RuO2@nickel foam as the two electrodes, and triangular AC as the power source. Ea (anode voltage) and Ec (cathode voltage) were 3V and -3V, respectively, with a cycle time of 0.5s and an electrolyte temperature of room temperature (25°C). During the electrolysis process, bubbles were continuously generated at both electrodes, with no precipitation observed, and the current remained stable.

[0187] The changes in hydrogen evolution were monitored during 60 minutes of continuous electrolysis, and the hydrogen evolution efficiency remained stable at around 5.48%.

[0188] Example 23

[0189] As shown in Figure 1, natural seawater was used as the electrolyte, RuO2@nickel foam was used as the two electrodes, and triangular AC was used as the power source. Ea (anode voltage) and Ec (cathode voltage) were 3V and -3V, respectively, with a cycle T of 1s, and the electrolyte temperature was room temperature (25°C). During the electrolysis process, bubbles were continuously generated at both electrodes, with no precipitation observed, and the current remained stable.

[0190] The changes in hydrogen evolution during 60 minutes of continuous electrolysis were monitored, and the hydrogen evolution efficiency remained stable at around 7.05%.

[0191] Example 24

[0192] As shown in Figure 1, natural seawater was electrolyzed using RuO2@nickel foam as the two electrodes, and triangular AC as the power source. Ea (anode voltage) and Ec (cathode voltage) were 3V and -3V, respectively, with a cycle T of 2s and the electrolyte temperature at room temperature (25°C). During the electrolysis process, bubbles were continuously generated at both electrodes, with no precipitation observed, and the current remained stable.

[0193] The changes in hydrogen evolution during 60 minutes of continuous electrolysis were monitored, and the hydrogen evolution efficiency was stable at around 20.42%.

[0194] The gas products prepared in Examples 17-24 were analyzed by gas chromatography and all were found to be pure hydrogen.

[0195] The present invention also provides a method for producing hydrogen by electrolysis of a solution that generates a precipitate under alkaline conditions, wherein a solution that generates a precipitate under alkaline conditions other than natural seawater is used as an electrolyte, an alternating current is applied to the electrodes, and the polarity of the electrodes is periodically switched between a cathode state and an anode state by utilizing the periodic change of the alternating current voltage. When the electrodes are in the anode state, the OH generated by the hydrogen evolution reaction in the cathode state is consumed. - To inhibit precipitation and the decrease of electrode catalytic activity; the other solution that generates precipitates under alkaline conditions includes a solution containing ions that can be precipitated under alkaline conditions.

[0196] By adopting the method of the present invention, river water, salt lake water, mine water, industrial wastewater, domestic sewage, etc. can be directly used to prepare hydrogen, achieving the technical effects of abundant electrolyte sources, low cost, simple preparation method and high efficiency.

[0197] Preferably, the other solution that generates a precipitate under alkaline conditions is selected from the group consisting of 2+ Solutions and / or Mg-containing 2+ of solution.

[0198] Preferably, the other solution that generates precipitates under alkaline conditions is selected from any one or more of the following: river water, salt lake water, mine water, industrial wastewater, and domestic sewage.

[0199] Preferably, the Ca 2+ and / or Mg 2+ The solution is selected from any one or more of the following: river water, salt lake water, mine water, industrial wastewater, and domestic sewage.

[0200] Preferably, the cycle of the alternating current is 0.001-2s.

[0201] Preferably, the cycle of the alternating current is 0.001-0.01s.

[0202] Preferably, the cycle of the alternating current is 0.01-2s.

[0203] Preferably, the voltage of the alternating current is 1.2-380V.

[0204] Preferably, the voltage of the alternating current is 1.2-1.8V.

[0205] Preferably, the voltage of the alternating current is 1.8-4V.

[0206] Preferably, the voltage of the alternating current is 4-380V.

[0207] Preferably, the waveform of the alternating current is selected from square wave, sine wave or triangle wave.

[0208] Preferably, the electrode is selected from one of RuO2@nickel foam electrode, nickel foam electrode, nickel sheet electrode, platinum electrode, platinum-rhodium alloy electrode, graphite electrode, titanium electrode, titanium foam electrode, carbon paper electrode, and graphene electrode.

[0209] Furthermore, the type of electrolyte is changed to produce hydrogen, and the following embodiments are provided:

[0210] Example 25

[0211] The researchers replaced seawater with salt lake water, using the salt lake water as the electrolyte, RuO2@nickel foam as the two electrodes, and a square waveform alternating current as the power source. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8V and -1.8V, respectively, with a cycle T of 1s and the electrolyte at room temperature (25°C). The generated gas was collected using the water displacement method.

[0212] After 60 minutes of electrolysis, bubbles were observed to continuously form on both electrodes, and no precipitate was formed. The hydrogen evolution efficiency was greater than 1%. Analysis of the gas product produced in this example by gas chromatography revealed pure hydrogen.

[0213] The present invention does not specifically limit the source of the salt lake water, and salt lake water from any region on Earth can be used. The effect of the present invention will not be affected by the choice of lake water.

[0214] Example 26

[0215] The experimental methods for Example 26 were the same as those for Example 25, with the differences shown in Table 7. (Brine water was used as the electrolyte, and square-wave AC power was used as the power source for electrolysis of the salt lake water. The voltages Ea (anode voltage) and Ec (cathode voltage), AC cycle, electrolyte temperature, and electrode materials were all shown in Table 7.)

[0216] Table 7

[0217] The results of experiments 1-10 in Example 26 show that no precipitation occurs when the alternating current cycle is within the range of 0.01-2 seconds, and the hydrogen evolution efficiency is greater than 1%. Gas chromatography analysis of the gas product shows that when a RuO2@nickel foam electrode is used as the electrode material, the gas product is pure hydrogen. When other electrode materials (nickel sheet electrode; platinum electrode; platinum-rhodium alloy electrode; graphite electrode; titanium electrode; titanium foam electrode; carbon paper electrode; or graphene electrode) are used as the electrode material, the gas product is a mixture of hydrogen and oxygen.

[0218] Based on Examples 1-10 in Table 7, further changing the waveform from a square wave to a sine wave or a triangular wave can also achieve the technical effect of no precipitation; the hydrogen evolution efficiency is greater than 1%. At the same time, pure H2 is collected when the RuO2@nickel foam electrode is used as the electrode, and a mixed gas of H2 and O2 is collected when other electrode materials are used as the electrode.

[0219] Example 27

[0220] As shown in Figure 1, seawater was replaced with filtered mine water as the electrolyte, RuO2@nickel foam was used as the two electrodes, and a square waveform alternating current (Figure 2) was used as the power source for electrolysis of the mine water. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8V and -1.8V, respectively, with a cycle T of 1s and the electrolyte temperature at room temperature (25°C). The generated gas was collected using the water displacement method.

[0221] After 60 minutes of electrolysis, bubbles were observed to continuously form at both electrodes, with no precipitation observed. The hydrogen evolution efficiency was greater than 1%. Analysis of the gaseous product by gas chromatography revealed pure hydrogen.

[0222] Mine water filtration is used to remove large particles such as sand, silt, algae, and garbage from the water to prevent them from adversely affecting hydrogen production through electrolysis. Filtering methods include filtering the solution with ordinary filter paper.

[0223] The present invention does not specifically limit the source of the mine water, and mine water from any region on Earth can be used. The selected mine water will not affect the effect of the present invention.

[0224] Example 28

[0225] The experimental methods of Example 28 are the same as those of Example 27, with the differences shown in Table 8:

[0226] Table 8

[0227] The results of experiments 1-10 in Example 28 show that no precipitation occurs when the AC cycle is within the range of 0.01-2 seconds, and the hydrogen evolution efficiency is greater than 1%. It is also shown that when RuO2@nickel foam electrodes are used as the electrode material, pure hydrogen can be collected. When other electrode materials (nickel sheet electrodes; platinum electrodes; platinum-rhodium alloy electrodes; graphite electrodes; titanium electrodes; titanium foam electrodes; carbon paper electrodes; or graphene electrodes) are used as electrodes, a mixture of hydrogen and oxygen is collected.

[0228] Based on Table 8, further experiments were conducted by changing the waveform from a square wave to a sine wave or a triangle wave. The experimental results show that the same technical effects as those in Table 8 can be achieved. No precipitation is generated, and the hydrogen evolution efficiency is greater than 1%. At the same time, pure H2 is collected when the RuO2@nickel foam electrode is used as the electrode, while a mixture of H2 and O2 is collected when other electrode materials are used as the electrode.

[0229] Example 29

[0230] As shown in Figure 1, industrial wastewater was replaced with seawater. Filtered industrial wastewater served as the electrolyte, and RuO2@nickel foam was used as the two electrodes. A square waveform alternating current (Figure 2) was used as the power source for electrolysis. The voltages Ea (anode voltage) and Ec (cathode voltage) were 1.8 V and -1.8 V, respectively, with a cycle T of 1 second and the electrolyte at room temperature (25°C). The generated gas was collected using the drainage method.

[0231] After 60 minutes of electrolysis, bubbles were observed to continuously form at both electrodes, with no precipitation observed. The hydrogen evolution efficiency was greater than 1%. Analysis of the gaseous product by gas chromatography revealed pure hydrogen.

[0232] The present invention does not specifically limit the source of industrial wastewater, and can be derived from any industrial wastewater containing high concentrations of calcium ions, magnesium ions, and other metal ions that are easily precipitated under alkaline conditions. The effect of the present invention will not be affected by the choice of industrial wastewater.

[0233] Example 30

[0234] The experimental methods of Example 30 are the same as those of Example 29, with the differences shown in Table 9:

[0235] Table 9

[0236] The results of experiments 1-10 in Example 30 show that no precipitation occurs when the alternating current cycle is within the range of 0.01-2 seconds, and the hydrogen evolution efficiency is greater than 1%. Gas chromatography analysis of the gas product shows that when a RuO2@nickel foam electrode is used as the electrode material, the gas product is pure hydrogen. When other electrode materials (nickel sheet electrode; platinum electrode; platinum-rhodium alloy electrode; graphite electrode; titanium electrode; titanium foam electrode; carbon paper electrode; or graphene electrode) are used as the electrode material, the gas product is a mixture of hydrogen and oxygen.

[0237] The purpose of filtering industrial wastewater is to filter out large particles of impurities in industrial wastewater, thereby improving efficiency.

[0238] Based on Table 9, experiments were further conducted by changing the waveform from a square wave to a sine wave or a triangle wave. The experimental results show that the same technical effect of no precipitation and a hydrogen evolution efficiency greater than 1% can be achieved. At the same time, pure H2 is collected when the RuO2@nickel foam electrode is used as the electrode, and a mixed gas of H2 and O2 is collected when other electrode materials are used as the electrode.

[0239] By adopting the method of the present invention, river water, domestic sewage, etc. are used as the electrolyte to prepare hydrogen, and the same technical effects as those of Examples 25-30 can also be achieved.

[0240] Example 31

[0241] Electrolysis was performed using natural seawater as the electrolyte, using Example 1 as a reference. The differences are shown in parentheses and in Table 10. (Natural seawater was used as the electrolyte and square-wave alternating current was used as the power source. The voltages Ea (anode voltage) and Ec (cathode voltage) were 3V and -3V, respectively. The electrodes were made of a platinum-rhodium alloy. The AC cycle and electrolyte temperature were as shown in Table 10.) The generated gas was collected using the drainage method.

[0242] Table 10

[0243] Based on the embodiments in Table 10, the waveform is further changed from a square wave to a sine wave or a triangle wave, or the electrolyte is changed to other solutions that generate precipitates under alkaline conditions, such as river water, salt lake water, mine water, industrial wastewater, and domestic sewage. The technical effect of collecting a mixed gas of H2 and O2 and not generating precipitation during the electrolysis process can also be achieved.

[0244] When RuO2@nickel foam electrode is used as an electrode, the technical effect of collecting H2 can be achieved. However, other electrodes collect a mixture of H2 and O2.

[0245] In combination with other embodiments of the present invention, it can be seen that when the AC cycle range is 0.001-2s, even if other conditions change, the technical effect of no precipitation and production of hydrogen can be achieved.

[0246] Example 32

[0247] Electrolysis was performed using natural seawater as the electrolyte, using Example 1 as a benchmark. The differences are shown in parentheses and in Table 11. (Natural seawater was used as the electrolyte, and square-wave alternating current was used as the power source. The AC cycle was 1 second. The electrodes were platinum-rhodium alloy electrodes. The voltages Ea (anode voltage) and Ec (cathode voltage), as well as the electrolyte temperature, were as shown in Table 11. The generated gas was collected using the drainage method.

[0248] Table 11

[0249] On the basis of Table 11, the waveform can be further changed from a square wave to a sine wave or a triangle wave, or the electrolyte can be changed to river water, salt lake water, mine water, industrial wastewater, domestic sewage and other solutions that generate precipitation under alkaline conditions. The technical effect of collecting H2 and O2 mixed gas and not generating precipitation during the electrolysis process can also be achieved.

[0250] When RuO2@nickel foam electrode is used as an electrode, the technical effect of collecting H2 can be achieved. However, other electrodes collect a mixture of H2 and O2.

[0251] In combination with other embodiments of the present invention, it can be seen that when the voltage range is 1.2-380V, even if other conditions change, the technical effect of no precipitation and production of hydrogen can be achieved.

[0252] Example 33

[0253] The experimental methods for Example 33 were the same as those for Example 32, with the differences noted in parentheses and shown in Table 12. (Natural seawater was used as the electrolyte, and square-wave AC power was used as the power source for electrolysis of natural seawater. The voltages Ea (anode voltage) and Ec (cathode voltage), AC cycle, electrolyte temperature, and electrode materials were all shown in Table 12.)

[0254] Table 12

[0255] As shown in Table 12 in combination with other embodiments of the present invention, when the voltage of the AC power is 1.2-380V and the cycle is 0.001-2s, direct seawater electrolysis to produce hydrogen does not produce precipitation and hydrogen can be collected.

[0256] When RuO2@nickel foam electrode is used as an electrode, the technical effect of collecting H2 can be achieved. However, other electrodes collect a mixture of H2 and O2.

[0257] On the basis of Table 12, the waveform can be further changed from a square wave to a sine wave or a triangle wave, or the electrolyte can be changed to river water, salt lake water, mine water, industrial wastewater, domestic sewage and other solutions that generate precipitation under alkaline conditions. The technical effect of collecting H2 and not generating precipitation during the electrolysis process can also be achieved.

[0258] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for directly electrolyzing seawater to produce hydrogen with effective precipitation inhibition, characterized in that, Using natural seawater as the electrolyte and applying an alternating current to the electrode, by virtue of the periodic change of the alternating current voltage, the polarity of the electrode is periodically and alternately switched between the cathode state and the anode state. When the electrode is in the anode state, it consumes the OH generated by the hydrogen evolution reaction in the cathode state - to inhibit the precipitation and the decline of the catalytic activity of the electrode.

2. The method according to claim 1, characterized in that, The waveform of the alternating current is selected from a square wave, a sine wave or a triangular wave.

3. The method according to claim 1, wherein The waveform of the alternating current is a square wave.

4. The method according to claim 1, characterized in that, The voltage of the alternating current is 1.8 - 4V.

5. The method according to claim 1, characterized in that The period of the alternating current is 0.01 - 2s.

6. The method according to claim 1, wherein The electrode is selected from one of a RuO2@nickel foam electrode, a nickel foam electrode, a nickel sheet electrode, a platinum electrode, a platinum-rhodium alloy electrode, a graphite electrode, a titanium electrode, a titanium foam electrode, a carbon paper electrode, and a graphene electrode.

7. The method according to claim 1, wherein The precipitate is Ca(OH)2 and Mg(OH)2.

8. The method according to claim 1, characterized in that, The temperature of the electrolyte is 5 - 95°C.

9. The method according to claim 1, wherein The electrolyte is sourced from natural seawater in any region on Earth.

10. The method according to claim 1, characterized in that, The specific working mode of the method is as follows: When the electrode is in the cathode state, a hydrogen evolution reaction occurs near the electrode, generating hydrogen and OH - , when the electrode is converted to the anode state, an oxygen evolution reaction and / or a chlorine oxidation reaction occur near the electrode, consuming the OH generated in the cathode state - .

11. The method according to claim 1, wherein The voltage of the alternating current is 1.2 - 380V.

12. The method according to claim 1, wherein The period of the alternating current is 0.001 - 2s.

13. A method for electrolytic hydrogen production from a solution that forms a precipitate under alkaline conditions, characterized in that, Using a solution that forms a precipitate under alkaline conditions other than natural seawater as the electrolyte, applying an alternating current to the electrode, and utilizing the periodic change of the alternating current voltage to cause the polarity of the electrode to periodically alternate between the cathode state and the anode state. When the electrode is in the anode state, it consumes the OH generated by the hydrogen evolution reaction in the cathode state - to inhibit the precipitation of the precipitate and the decline of the catalytic activity of the electrode; The other solutions that form precipitates under alkaline conditions include solutions containing ions that can precipitate under alkaline conditions.

14. The method according to claim 13, wherein The other solutions that form precipitates under alkaline conditions are selected from any one or more of the following: river water, salt lake water, mine water, industrial wastewater, domestic sewage; preferably, the other solutions that form precipitates under alkaline conditions are selected from solutions containing Ca 2+ and / or solutions containing Mg 2+ .

15. The method according to claim 13, characterized in that, The period of the alternating current is 0.01 - 2s.

16. The method according to claim 13, wherein The voltage of the alternating current is 1.8 - 4V.

17. The method according to claim 13, wherein The period of the alternating current is 0.001 - 2s.

18. The method according to claim 13, characterized in that, The voltage of the alternating current is 1.2 - 380V.

19. The method according to claim 13, characterized in that, The waveform of the alternating current is selected from a square wave, a sine wave or a triangular wave.

20. The method according to claim 13, characterized in that The electrode is selected from one of a RuO2@nickel foam electrode, a nickel foam electrode, a nickel sheet electrode, a platinum electrode, a platinum-rhodium alloy electrode, a graphite electrode, a titanium electrode, a titanium foam electrode, a carbon paper electrode, and a graphene electrode.

21. The method according to any one of claims 13-20, characterized in that, The temperature of the electrolyte is 5 - 95°C.

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