Electrolyte for activating oxygen evolution catalyst, activating method, activated oxygen evolution catalyst and application of activated oxygen evolution catalyst
By electrochemical activation of the transition metal-based oxygen precipitation catalyst in an activated electrode solution containing a mixture of potassium and sodium salts of isoanions, the problem of poor intrinsic electrocatalytic performance of the catalyst is solved, significantly reducing overpotential and resistance, and improving catalytic efficiency.
Patent Information
- Application Number
- CN202411752475.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-02
- Publication Date
- 2025-03-07
AI Technical Summary
The intrinsic electrocatalytic performance of existing transition metal-based oxygen precipitation catalysts is poor, resulting in a high overpotential and low electrocatalytic water decomposition reaction efficiency.
The transition metal-based oxygen precipitation catalyst is activated in an activated electrode solution containing a mixture of potassium and sodium salts of isoanions, and the catalyst structure is reconstructed by electrochemical methods, exposing more active sites and optimizing the electronic structure.
The overpotential and resistance of the transition metal-based oxygen precipitation catalyst are significantly reduced, the catalytic efficiency is improved, and excellent catalytic performance is achieved.
Smart Images
Figure CN119571362A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of oxygen evolution catalysts, and in particular to an electrolyte for activating an oxygen evolution catalyst and an activation method, an activated oxygen evolution catalyst and applications thereof. Background Art
[0002] In recent years, energy crisis and environmental problems have become increasingly prominent, posing a huge threat to the ecological environment and the sustainable development of human society. It is urgent to build a clean, low-carbon, safe and efficient energy system. Hydrogen has long been considered a sustainable and clean energy carrier. Water electrolysis is one of the most promising and cleanest methods for producing hydrogen as an industrial energy supply. However, in the current water electrolysis reaction, the oxygen evolution reaction occurring on the anode is a four-electron transfer process with slow kinetics and high reaction energy barriers. Therefore, the oxygen evolution reaction on the anode is severely restricted, which seriously affects the efficiency of water electrolysis to produce hydrogen. In addition, during the water electrolysis process, due to the influence of electrode polarization, solution resistance and wire resistance, the actual electrolysis voltage is far from the equilibrium voltage, that is, there is an overpotential, and the higher the overpotential, the lower the efficiency. Therefore, in order to improve the electrolysis efficiency, it can be achieved by designing and developing efficient catalysts or by adding additives to the electrolyte.
[0003] Regarding the method of adding additives to the electrolyte, CN117305858A discloses a water electrolysis method capable of promoting the anode oxygen evolution reaction, which mainly adopts an electrolyte containing carboxylic acid additives, and the carboxylic acid additives are used to promote the anode oxygen evolution reaction in the process of water electrolysis. The carboxylic acid additives used include a large number of carboxylic acid ligands, which can adjust the electronic structure, redistribute the charge, and promote proton transfer by forming hydrogen bonds with coordinated water. The negatively charged carboxylate ions can be well used as proton transfer media and co-catalysts, that is, to promote OH - The transport, activation and dissociation of nickel foam electrodes can accelerate the reaction kinetics, reduce the overpotential and improve the efficiency of water electrolysis. However, the additives used are all organic matter, and the presence of organic matter will inevitably produce organic pollutants, which is not conducive to environmental protection. In addition, it mainly targets the oxygen evolution reaction of nickel foam electrodes, and the adapter electrode is single, which has limitations.
[0004] In the way of designing and developing efficient catalysts, the oxygen evolution reaction electrocatalysts used at the current industrial level are highly dependent on precious metal catalysts, mainly based on iridium and ruthenium catalysts. However, since iridium and ruthenium are precious metals, their reserves are low and their prices are expensive, and their cyclic stability is poor under certain conditions, which seriously limits their large-scale application. Therefore, non-precious metal catalysts with high activity and good stability are gradually being widely used, mainly based on transition metal-based catalysts, but one of the main problems with transition metal-based catalysts is that their intrinsic electrocatalytic performance is poor, resulting in a high overpotential, which will also limit the efficiency of the electrocatalytic reaction to a certain extent.
[0005] Therefore, how to improve the poor intrinsic electrocatalytic performance of transition metal-based oxygen evolution catalysts, which leads to high overpotential and low efficiency of electrocatalytic water decomposition reaction, has become a problem that needs to be solved urgently. Summary of the invention
[0006] In order to solve the above technical problems, the present invention provides an electrolyte for activating an oxygen evolution catalyst and an activation method, an activated oxygen evolution catalyst and applications thereof. The present invention activates a transition metal-based oxygen evolution catalyst in an activation electrode solution containing a mixture of potassium salt and sodium salt of the same anion. The structure of the oxygen evolution catalyst after activation by the activation electrolyte is reconstructed, which can expose more active sites, form a favorable morphology and an optimized electronic structure, thereby enhancing the activity of the oxygen evolution catalyst, reducing the overpotential of the transition metal-based oxygen evolution catalyst, improving the catalytic efficiency, and achieving excellent catalytic performance.
[0007] To achieve this object, the present invention adopts the following technical solutions:
[0008] In a first aspect, the present invention provides an electrolyte for activating an oxygen evolution catalyst, wherein the electrolyte for activating an oxygen evolution catalyst comprises an alkaline solvent and an additive;
[0009] The additive includes a mixture of potassium and sodium salts containing the same anion.
[0010] In the present invention, the presence of strongly negatively charged anions can optimize the local electronic structure of the active site and promote surface reconstruction, thereby improving the surface activity of the oxygen evolution catalyst; the cations in the electrolyte for activating the oxygen evolution catalyst exist in the catalyst in an embedded manner, which can stretch the transition metal-oxygen bond length, thereby enhancing the oxidation state of the transition metal and inducing the formation of active transition metal oxyhydroxide species, thereby further improving the oxygen evolution performance of the catalyst. At the same time, the synergistic effect of potassium ions and sodium ions can further stretch the transition metal-oxygen bond length, making the structural reconstruction more thorough, and then the activation more thorough, so that the activated oxygen evolution catalyst achieves better catalytic performance.
[0011] As a preferred technical solution of the present invention, the anion includes SO42- 、CO3 2- 、F - Br - , Cl - ,I - PO4 3- , BO3 3- 、NO3 - or SeO4 2- Any one or a combination of at least two of the following.
[0012] Preferably, the alkaline solvent comprises potassium hydroxide solution or sodium hydroxide solution.
[0013] Preferably, in the electrolyte for activating the oxygen evolution catalyst, the concentration of the alkaline solvent is 0.01 mol / L-1 mol / L, for example, 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L or 1 mol / L.
[0014] As a preferred technical solution of the present invention, in the electrolyte for activating the oxygen evolution catalyst, the concentration of the additive is 0.01 mol / L-saturated, for example, 0.01 mol / L, 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 1 mol / L, 3 mol / L, 5 mol / L, 8 mol / L or 10 mol / L, etc.
[0015] Preferably, in the additive, the molar ratio of the potassium salt to the sodium salt is (0.3-3):1, for example, 0.3:1, 0.5:1, 0.8:1, 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, etc.
[0016] In a second aspect, the present invention further provides a method for activating an oxygen evolution catalyst, the activation method comprising the following steps:
[0017] The oxygen evolution catalyst is placed in the electrolyte for activating the oxygen evolution catalyst described in the first aspect to electrochemically activate the oxygen evolution catalyst.
[0018] As a preferred technical solution of the present invention, the oxygen evolution catalyst includes a transition metal compound or a transition metal alloy.
[0019] Preferably, the transition metal in the transition metal compound includes any one of Ni, Fe, Co, Mn, W, Mo or Cu, or a combination of at least two thereof.
[0020] Preferably, the compound in the transition metal compound includes any one of hydroxide, oxide, sulfide, phosphide, selenide or nitride, or a combination of at least two thereof.
[0021] Preferably, the transition metal alloy includes any one of a nickel-based alloy, an iron-based alloy, a cobalt-based alloy, a manganese-based alloy, a tungsten-based alloy or a molybdenum-based alloy, or a combination of at least two thereof.
[0022] As a preferred technical solution of the present invention, the electrochemical activation method includes any one of cyclic voltammetry, linear sweep voltammetry, constant current method, constant voltage method, fast current pulse method or fast potential pulse method, preferably any one of linear sweep voltammetry, cyclic voltammetry or constant voltage method.
[0023] As a preferred technical solution of the present invention, the scanning speed of the linear scanning voltammetry is 1mV / s-1000mV / s, for example, 1mV / s, 50mV / s, 100mV / s, 200mV / s, 300mV / s, 400mV / s, 500mV / s, 600mV / s, 700mV / s, 800mV / s, 900mV / s or 1000mV / s, etc.
[0024] Preferably, the scanning number of the linear sweep voltammetry is 50-10000 cycles, for example 50 cycles, 100 cycles, 300 cycles, 500 cycles, 800 cycles, 1000 cycles, 1300 cycles, 1500 cycles, 2000 cycles, 5000 cycles, 8000 cycles or 10000 cycles, etc.
[0025] In the present invention, the scanning number of the linear sweep voltammetry is adjusted to 50-10000, which can make the activation more thorough without causing (partial) shedding of the activation layer, thus avoiding the problem of decreased performance of the activated oxygen evolution catalyst.
[0026] It should be noted that the voltage range of the linear sweep voltammetry method is not specifically required or limited in the present invention. As long as it is a voltage range commonly used by those skilled in the art, it is applicable to the present invention. For example, the voltage range may be 1.1V-1.6V.
[0027] Preferably, the scan rate of the cyclic voltammetry is 1 mV / s-1000 mV / s, for example, 1 mV / s, 50 mV / s, 100 mV / s, 200 mV / s, 300 mV / s, 400 mV / s, 500 mV / s, 600 mV / s, 700 mV / s, 800 mV / s, 900 mV / s or 1000 mV / s, etc.
[0028] Preferably, the scanning number of the cyclic voltammetry is 50-10000 cycles, for example 50 cycles, 100 cycles, 300 cycles, 500 cycles, 800 cycles, 1000 cycles, 1300 cycles, 1500 cycles, 2000 cycles, 5000 cycles, 8000 cycles or 10000 cycles.
[0029] In the present invention, the scanning number of cyclic voltammetry is regulated to be 50-10000, which can make the activation more thorough without causing (partial) shedding of the activation layer, thus avoiding the problem of decreased performance of the activated oxygen evolution catalyst.
[0030] It should be noted that the present invention does not make any specific requirements or special limitations on the voltage range of the cyclic voltammetry. As long as it is a voltage range commonly used by those skilled in the art, it is applicable to the present invention. For example, the voltage range may be 1.1V-1.6V.
[0031] As a preferred technical solution of the present invention, the voltage of the constant voltage method is 0-5V, and is not 0, such as 0.5V, 1V, 2V, 3V, 4V or 5V.
[0032] Preferably, the activation time of the constant voltage method is 5 min-600 min, for example, 5 min, 60 min, 100 min, 200 min, 300 min, 400 min, 500 min or 600 min.
[0033] In the present invention, the activation time of the constant voltage method is regulated to be 5 min-600 min, which can achieve a better activation effect, and the activated oxygen evolution catalyst after activation has better performance and better oxygen evolution performance.
[0034] Preferably, the current density of the constant current method is 0-1A / cm 2 , and not 0, for example 0.1A / cm 2 , 0.3A / cm 2 , 0.5A / cm 2 , 0.8A / cm 2 or 1A / cm 2 wait.
[0035] Preferably, the activation time of the constant current method is 5 min-600 min, for example, 5 min, 60 min, 100 min, 200 min, 300 min, 400 min, 500 min or 600 min.
[0036] In a third aspect, the present invention further provides an activated oxygen evolution catalyst, wherein the activated oxygen evolution catalyst is activated according to the activation method of the oxygen evolution catalyst described in the second aspect.
[0037] In a fourth aspect, the present invention further provides a use of the activated oxygen evolution catalyst according to the third aspect, wherein the activated oxygen evolution catalyst is applied to electrocatalytic water decomposition and used as an electrocatalytic water decomposition catalyst.
[0038] Compared with the prior art, the present invention has at least the following beneficial effects:
[0039] 1) The present invention activates the transition metal-based oxygen evolution catalyst in an activation electrode solution containing a mixture of potassium salt and sodium salt of the same anion. The structure of the oxygen evolution catalyst after activation by the activation electrolyte is reconstructed, which can expose more active sites, form a favorable morphology and an optimized electronic structure, thereby enhancing the catalyst activity, significantly reducing the overpotential and resistance, thereby improving the catalytic efficiency and achieving excellent catalytic performance.
[0040] 2) The activation electrolyte used in the present invention has a simple formula, and the activation method is also simple to operate, has a wide range of applications, and significantly improves the catalytic performance after activation. It is suitable for the modification of various transition metal-based electrocatalysts and has potential application prospects in electrocatalytic water decomposition and electrochemical energy storage. BRIEF DESCRIPTION OF THE DRAWINGS
[0041] Figure 1 It is a schematic diagram of the activation process of the oxygen evolution catalyst in Example 1 of the present invention.
[0042] Figure 2 It is a comparison diagram of the electrochemical oxygen evolution polarization curves of the activated oxygen evolution catalysts of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 5 of the present invention, and the electrochemical oxygen evolution polarization curve of the unactivated oxygen evolution catalyst of Comparative Example 4.
[0043] Figure 3 It is a comparison chart of the electrochemical impedance of the activated oxygen evolution catalysts of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 5 of the present invention, and the electrochemical impedance of the unactivated oxygen evolution catalyst of Comparative Example 4. DETAILED DESCRIPTION
[0044] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.
[0045] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.
[0046] Example 1
[0047] This embodiment provides an electrolyte for activating an oxygen evolution catalyst and an activation method, activating an oxygen evolution catalyst, wherein the electrolyte for activating the oxygen evolution catalyst contains a potassium hydroxide solution (1M), and additives: potassium sulfate (0.1M) and sodium sulfate (0.1M);
[0048] The activation method comprises the following steps:
[0049] 0.7842 g of potassium sulfate and 0.6392 g of sodium sulfate were weighed and dissolved in 45 mL of 1 mol / L potassium hydroxide solution. After stirring with a magnetic stirrer for 2 h, 30 mL was poured into a single-chamber electrolytic cell. The iron-nickel alloy sheet was then placed in the electrolytic cell. Linear sweep voltammetry was used for electrochemical activation at a voltage of 1.1 V to 1.6 V vs. RHE, a sweep rate of 500 mV / s, and 5000 turns. After the activation was completed, an activated oxygen evolution catalyst was obtained.
[0050] Figure 1 A schematic diagram of the activation process of the oxygen evolution catalyst of Example 1 of the present invention is shown. As can be seen from the figure, a mixture additive of potassium sulfate and sodium sulfate is added to a potassium hydroxide electrolyte. After electrochemical activation, the sulfate ions in the additive can effectively regulate the solid-liquid interface and accelerate the surface reconstruction process of the catalyst to expose more active sites, thereby enhancing the oxygen evolution reaction activity of the catalyst and obtaining the target catalyst.
[0051] Example 2
[0052] This embodiment provides an electrolyte for activating an oxygen evolution catalyst and an activation method, activating an oxygen evolution catalyst, wherein the electrolyte for activating the oxygen evolution catalyst contains a potassium hydroxide solution (1M), and additives: potassium carbonate (0.1M) and sodium carbonate (0.1M);
[0053] The activation method comprises the following steps:
[0054] Weigh 0.4146 g of potassium carbonate and 0.3180 g of sodium carbonate and dissolve them in 30 mL of 1 mol / L potassium hydroxide solution. After stirring with a magnetic stirrer for 2 h, take 30 mL and pour it into a single-chamber electrolytic cell. Then put the iron-nickel supported on the carbon cloth into the electrolytic cell and use linear sweep voltammetry for electrochemical activation with a voltage of 1.1 V-1.6 V vs. RHE, a sweep rate of 100 mV / s, and 100 turns. After the activation is completed, an activated oxygen evolution catalyst is obtained.
[0055] Example 3
[0056] This embodiment provides an electrolyte for activating an oxygen evolution catalyst and an activation method, activating an oxygen evolution catalyst, wherein the electrolyte for activating the oxygen evolution catalyst contains a potassium hydroxide solution (1M), and additives: potassium bromide (0.1M) and sodium bromide (0.1M);
[0057] The activation method comprises the following steps:
[0058] Weigh 0.3570 g of potassium bromide and 0.3087 g of sodium bromide and dissolve them in 30 mL of 1 mol / L potassium hydroxide solution. After stirring with a magnetic stirrer for 2 h, take 30 mL and pour it into a single-chamber electrolytic cell. Then put the iron-nickel alloy sheet into the electrolytic cell and use linear sweep voltammetry for electrochemical activation. The voltage is 1.1 V-1.6 V vs. RHE, the sweep rate is 500 mV / s, the number of circles is 5000, and the activation is completed to obtain an activated oxygen evolution catalyst.
[0059] Example 4
[0060] This embodiment provides an electrolyte for activating an oxygen evolution catalyst and an activation method, which activates the oxygen evolution catalyst, wherein the electrolyte for activating the oxygen evolution catalyst contains a potassium hydroxide solution (1M), and additives: potassium chloride (0.15M) and sodium chloride (0.05M);
[0061] The activation method comprises the following steps:
[0062] Weigh 0.3355 g potassium chloride and 0.0877 g sodium chloride and dissolve them in 30 mL of 1 mol / L potassium hydroxide solution. After stirring with a magnetic stirrer for 2 h, take 30 mL and pour it into a single-chamber electrolytic cell. Then put the iron-nickel-scandium alloy sheet into the electrolytic cell and perform electrochemical activation by cyclic voltammetry at a voltage of 1.1 V to 1.6 V vs. RHE, a scan rate of 50 mV / s, and 500 cycles. After the activation is completed, an activated oxygen evolution catalyst is obtained.
[0063] Example 5
[0064] This embodiment provides an electrolyte for activating an oxygen evolution catalyst and an activation method, which activates the oxygen evolution catalyst. The electrolyte for activating the oxygen evolution catalyst contains a potassium hydroxide solution (0.01M), and additives: potassium phosphate (0.15M) and sodium phosphate (0.05M);
[0065] The activation method comprises the following steps:
[0066] 0.9552 g of potassium phosphate and 0.2459 g of sodium phosphate were weighed and dissolved in 30 mL of 0.01 mol / L potassium hydroxide solution. After stirring for 2 h using a magnetic stirrer, 30 mL was poured into a single-chamber electrolytic cell. The iron-nickel alloy sheet was then placed in the electrolytic cell and electrochemically activated using a constant voltage method at a voltage of 1.5 V vs. RHE for 60 min. After the activation was completed, an activated oxygen evolution catalyst was obtained.
[0067] Example 6
[0068] This embodiment provides an electrolyte for activating an oxygen evolution catalyst and an activation method to activate the oxygen evolution catalyst. The components and content of the electrolyte for activating the oxygen evolution catalyst are consistent with those in Example 1.
[0069] The difference between the activation method and Example 1 is that the activation scan rate is 10 mV / s, the number of cycles is 10,000, and the other activation methods and parameters are consistent with Example 1.
[0070] Example 7
[0071] This embodiment provides an electrolyte for activating an oxygen evolution catalyst and an activation method to activate the oxygen evolution catalyst. The components and content of the electrolyte for activating the oxygen evolution catalyst are consistent with those in Example 1.
[0072] The difference between the activation method and Example 1 is that the activation scan rate is 100 mV / s, the number of turns is 50, and the other activation methods and parameters are consistent with Example 1.
[0073] Example 8
[0074] This embodiment provides an electrolyte for activating an oxygen evolution catalyst and an activation method to activate the oxygen evolution catalyst. The components and content of the electrolyte for activating the oxygen evolution catalyst are consistent with those in Example 1.
[0075] The difference between the activation method and Example 1 is that the number of activation cycles is 12,000, and the other activation methods and parameters are consistent with Example 1.
[0076] Example 9
[0077] This embodiment provides an electrolyte for activating an oxygen evolution catalyst and an activation method to activate the oxygen evolution catalyst. The components and content of the electrolyte for activating the oxygen evolution catalyst are consistent with those in Example 5.
[0078] The difference between the activation method and Example 5 is that the activation time is 720 min, and the other activation methods and parameters are consistent with Example 1.
[0079] Comparative Example 1
[0080] This comparative example provides an electrolyte for activating an oxygen evolution catalyst and an activation method, which activates the oxygen evolution catalyst. The electrolyte for activating the oxygen evolution catalyst is different from that in Example 1 in that it contains only potassium hydroxide solution (1M) and sodium sulfate (0.2M);
[0081] The activation method comprises the following steps:
[0082] 1.27836 g of sodium sulfate was weighed and dissolved in 45 mL of 1 mol / L potassium hydroxide solution. After stirring with a magnetic stirrer for 2 h, 30 mL was poured into a single-chamber electrolytic cell. The iron-nickel alloy sheet was then placed in the electrolytic cell. Linear sweep voltammetry was used for electrochemical activation at a voltage of 1.1 V to 1.6 V vs. RHE, a sweep rate of 500 mV / s, and 5000 turns. After the activation was completed, an activated oxygen evolution catalyst was obtained.
[0083] Comparative Example 2
[0084] This comparative example provides an electrolyte for activating an oxygen evolution catalyst and an activation method to activate the oxygen evolution catalyst. The electrolyte for activating the oxygen evolution catalyst differs from that in Example 1 in that it contains only potassium hydroxide solution (1M) and potassium sulfate (0.2M).
[0085] The activation method comprises the following steps:
[0086] 1.56834 g of potassium sulfate was weighed and dissolved in 45 mL of 1 mol / L potassium hydroxide solution. After stirring for 2 h with a magnetic stirrer, 30 mL was poured into a single-chamber electrolytic cell. The iron-nickel alloy sheet was then placed in the electrolytic cell. Linear sweep voltammetry was used for electrochemical activation at a voltage of 1.1 V to 1.6 V vs. RHE, a sweep rate of 500 mV / s, and 5000 turns. After the activation was completed, an activated oxygen evolution catalyst was obtained.
[0087] Comparative Example 3
[0088] This comparative example provides an electrolyte for activating an oxygen evolution catalyst and an activation method to activate the oxygen evolution catalyst. The electrolyte for activating the oxygen evolution catalyst differs from that of Example 1 in that it contains only a potassium hydroxide solution (1M);
[0089] The activation method comprises the following steps:
[0090] 30 mL of 1 mol / L potassium hydroxide was poured into a single-chamber electrolytic cell, and then the iron-nickel alloy sheet was placed in the electrolytic cell. Linear sweep voltammetry was used for electrochemical activation at a voltage of 1.1 V to 1.6 V vs. RHE, a sweep rate of 500 mV / s, and 5000 cycles. After the activation was completed, an activated oxygen evolution catalyst was obtained.
[0091] Comparative Example 4
[0092] This comparative example provides a non-activated oxygen evolution catalyst, that is, an iron-nickel alloy sheet that has not been treated in any way.
[0093] Comparative Example 5
[0094] This comparative example provides an electrolyte for activating an oxygen evolution catalyst and an activation method, activating an oxygen evolution catalyst, wherein the electrolyte for activating the oxygen evolution catalyst contains a potassium hydroxide solution (1M), and additives: potassium sulfate (0.1M) and sodium carbonate (0.1M);
[0095] The activation method comprises the following steps:
[0096] 0.5228 g of potassium sulfate and 0.3180 g of sodium carbonate were weighed and dissolved in 30 mL of 1 mol / L potassium hydroxide solution. After stirring for 2 h using a magnetic stirrer, 30 mL was poured into a single-chamber electrolytic cell. The iron-nickel alloy sheet was then placed in the electrolytic cell. Linear sweep voltammetry was used for electrochemical activation at a voltage of 1.1 V to 1.6 V vs. RHE, a sweep rate of 500 mV / s, and 5000 turns. After the activation was completed, an activated oxygen evolution catalyst was obtained.
[0097] The activated oxygen evolution catalysts provided in Examples 1-9 and Comparative Examples 1-3 and 5 were washed with deionized water and then the electrochemical oxygen evolution polarization curves were tested. 1 mol / L potassium hydroxide solution was used as the electrolyte. The test voltage was 1.1 V-1.6 V vs. RHE. The scan rate was 1 mV / s. The resistance was also tested.
[0098] The unactivated oxygen evolution catalyst provided in Comparative Example 4 was tested for electrochemical oxygen evolution polarization curve, using 1 mol / L potassium hydroxide solution as electrolyte, the test voltage was 1.1 V-1.6 V vs. RHE, the scan rate was 1 mV / s, and the resistance was tested.
[0099] Figure 2 The electrochemical oxygen evolution polarization curves of the activated oxygen evolution catalysts of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 5 of the present invention and the electrochemical oxygen evolution polarization curves of the unactivated oxygen evolution catalyst of Comparative Example 4 are shown. It can be seen from the figure that the activation effect of the activated electrolyte containing the mixed additive of sodium sulfate and potassium sulfate is better than that of the electrolyte containing only sodium sulfate and only potassium sulfate additives, and lower overpotentials can be achieved at both low current density and high current density. At 10 mA / cm 2 Under this condition, the overpotential of the electrolyte containing mixed additives of sodium sulfate and potassium sulfate after activation is only 268mV.
[0100] Figure 3 A comparison diagram of the electrochemical impedance of the activated oxygen evolution catalysts of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 5 of the present invention and the electrochemical impedance of the unactivated oxygen evolution catalyst of Comparative Example 4 is shown. It can be seen from the figure that the resistance of the oxygen evolution catalyst is significantly reduced after electrochemical activation in the activation electrolyte containing a mixed additive of sodium sulfate and potassium sulfate.
[0101] Table 1
[0102]
[0103]
[0104] The test results show that:
[0105] (1) It can be seen from Examples 1 to 7 that the present invention activates the transition metal-based oxygen evolution catalyst in an activation electrolyte containing a mixture of potassium salt and sodium salt of the same anion, and the structure of the oxygen evolution catalyst after activation by the activation electrolyte is reconstructed, which can expose more active sites, form a favorable morphology and an optimized electronic structure, and thus enhance the activity of the oxygen evolution catalyst. When potassium sulfate and sodium sulfate are used as additives, the activated oxygen evolution catalyst is at 10 mA / cm 2 At a current density of 1.38 W, the overpotential is as low as 268 mA and the charge transfer resistance is as low as 4.29 Ω.
[0106] (2) It can be seen from Examples 1 and 8, 5 and 9 that the present invention can make the activation more thorough by further adjusting the number of scan cycles of the cyclic voltammetry method to 50-10000 cycles and adjusting the activation time of the constant voltage method to 5 min-600 min, but will not cause the activation layer (partial) to fall off, thereby avoiding the problem of decreased performance of the activated oxygen evolution catalyst.
[0107] (3) It can be seen from Example 1 and Comparative Examples 1-2 that the present invention further stretches the transition metal-oxygen bond length by adding potassium salt and sodium salt to the sodium hydroxide solution, so that the structural reconstruction is more thorough, and then the activation is more thorough, so that the activated oxygen evolution catalyst achieves better catalytic performance;
[0108] However, when only an equal amount of sodium salt or an equal amount of potassium salt is added alone, it cannot further stretch the transition metal-oxygen bond length, so the performance of the activated oxygen evolution catalyst will decrease, the overpotential will decrease, and the resistance value will increase.
[0109] (4) It can be seen from Example 1 and Comparative Examples 3-4 that when the present invention uses only potassium hydroxide solution without adding additives to obtain an activated oxygen evolution catalyst, or uses an unactivated oxygen evolution catalyst, the catalytic performance is significantly reduced, and the overpotential and resistance value cannot be reduced.
[0110] (5) It can be seen from Example 1 and Comparative Example 5 that when the present invention uses a mixture of potassium salts and sodium salts of different anions as an additive, that is, when sodium sulfate is replaced by sodium carbonate, different anions compete with each other in promoting the reconstruction of the catalyst surface, which will play a resistance role. Therefore, the catalytic performance of the activated oxygen evolution catalyst will be significantly reduced.
[0111] In summary, the present invention activates the transition metal-based oxygen evolution catalyst in an activation electrode solution containing a mixture of potassium salt and sodium salt of the same anion, and reconstructs the structure of the activated oxygen evolution catalyst after activation by the activation electrolyte, thereby exposing more active sites, forming a favorable morphology and an optimized electronic structure, thereby enhancing the activity of the oxygen evolution catalyst, reducing the overpotential of the transition metal-based oxygen evolution catalyst, improving the catalytic efficiency, and achieving excellent catalytic performance.
[0112] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.
Claims
1. An electrolyte for activating an oxygen evolution catalyst, characterized in that: The electrolyte for activating the oxygen evolution catalyst comprises an alkaline solvent and an additive; The additive includes a mixture of potassium and sodium salts containing the same anion.
2. The electrolyte for activating the oxygen evolution catalyst according to claim 1, characterized in that: The anions include SO4 2- 、CO3 2- 、F - Br - , Cl - ,I - PO4 3- , BO3 3- 、NO3 - or SeO4 2- Any one or a combination of at least two of the following: Preferably, the alkaline solvent comprises potassium hydroxide solution or sodium hydroxide solution; Preferably, in the electrolyte for activating the oxygen evolution catalyst, the concentration of the alkaline solvent is 0.01 mol / L-1 mol / L.
3. The oxygen evolution catalyst activation electrolyte according to claim 1 or 2, characterized in that: In the electrolyte for activating the oxygen evolution catalyst, the concentration of the additive is 0.01 mol / L-saturated; Preferably, in the additive, the molar ratio of the potassium salt to the sodium salt is (0.3-3):
1.
4. A method for activating an oxygen evolution catalyst, characterized in that: The activation method comprises the following steps: The oxygen evolution catalyst is placed in the electrolyte for activating the oxygen evolution catalyst according to any one of claims 1 to 3, and the oxygen evolution catalyst is electrochemically activated.
5. The activation method according to claim 4, characterized in that The oxygen evolution catalyst comprises a transition metal compound or a transition metal alloy; Preferably, the transition metal in the transition metal compound includes any one or a combination of at least two of Ni, Fe, Co, Mn, W, Mo or Cu; Preferably, the compound in the transition metal compound includes any one of hydroxide, oxide, sulfide, phosphide, selenide or nitride, or a combination of at least two thereof; Preferably, the transition metal alloy includes any one of a nickel-based alloy, an iron-based alloy, a cobalt-based alloy, a manganese-based alloy, a tungsten-based alloy or a molybdenum-based alloy, or a combination of at least two thereof.
6. The activation method according to claim 4 or 5, characterized in that: The electrochemical activation method includes any one of cyclic voltammetry, linear sweep voltammetry, constant current method, constant voltage method, rapid current pulse method or rapid potential pulse method.
7. The activation method according to claim 6, characterized in that: The scanning speed of the linear scanning voltammetry is 1mV / s-1000mV / s; Preferably, the scanning number of the linear sweep voltammetry is 50 to 10,000; Preferably, the scanning speed of the cyclic voltammetry is 1 mV / s-1000 mV / s; Preferably, the scanning number of the cyclic voltammetry is 50 to 10,000 cycles.
8. The activation method according to claim 6, characterized in that The voltage of the constant voltage method is 0-5V and is not 0; Preferably, the activation time of the constant voltage method is 5 min-600 min; Preferably, the current density of the constant current method is 0-1A / cm 2 , and not 0; Preferably, the activation time of the constant current method is 5 min-600 min.
9. An activated oxygen evolution catalyst, characterized in that The activated oxygen evolution catalyst is obtained by activation according to the activation method of the oxygen evolution catalyst according to any one of claims 4 to 8.
10. Use of the activated oxygen evolution catalyst according to claim 9, characterized in that: The activated oxygen evolution catalyst is applied to electrocatalytic water decomposition and used as an electrocatalytic water decomposition catalyst.