Electrolyte additive for improving water electrolysis reaction performance, electrolyte, electrolyte solution, and method for improving water electrolysis reaction performance

Abstract

The present invention relates to the technical field of water electrolysis, and particularly to an electrolyte additive for improving water electrolysis reaction performance, an electrolyte, an electrolyte solution, and a method for improving water electrolysis reaction performance. The additive includes a non-metal oxyacid salt (sulfate, phosphate, borate, selenate, silicate, carbonate, perchlorate, trifluoroacetate, etc.) and an aqueous solution thereof, and an oxometallate (molybdate, tungstate, vanadate, chromate, niobate, ferricyanate, zincate, aluminate, stannate, etc.) and an aqueous solution thereof, as electrolyte solution additives for a water electrolysis reaction. The present invention provides a use of an oxyacid salt for improving the activity and stability of oxygen evolution during water electrolysis. In particular, the oxyacid salt is also suitable for electrolysis reactions carried out at high and low temperatures. Due to the addition of the oxyacid salt, the present invention reduces the oxygen evolution reaction potential and the charge transfer resistance, increases the electron transport rate, and exhibits relatively fast chemical reaction kinetics, thereby facilitating the improvement of the reaction activity.

Description

Electrolyte additive for improving performance of water electrolysis reaction, electrolyte and electrolyte solution and method for improving performance of water electrolysis reaction TECHNICAL FIELD

[0001] The present application belongs to the technical field of water electrolysis, and particularly relates to an electrolyte additive for improving performance of water electrolysis reaction, an electrolyte and an electrolyte solution, and a method for improving performance of water electrolysis reaction. BACKGROUND

[0002] With the growing global energy demand, clean energy and renewable energy are attracting much attention. Hydrogen energy is one of the most promising energy sources to replace fossil fuels. Water electrolysis can produce high-purity hydrogen on a large scale, avoiding carbon dioxide emissions. However, due to the relatively high cost of water electrolysis, many researchers focus on achieving a low-cost, high-efficiency water electrolysis process. To improve the competitiveness of water electrolysis, it is crucial to reduce the OER overpotential to reduce energy consumption. Due to the slow kinetics of OER, the energy efficiency loss of alkaline water electrolysis (ALK) is mostly from the OER side. Among the catalysts for alkaline water electrolysis, NiFe-LDH (hydrotalcite-like), IrO2 (noble metal-like), NiFe-MOF (metal-organic framework-like), Co3O4 (transition metal oxide-like), LaCoO3 (perovskite-like), and Ni(OH)2 (over metal hydroxide-like) are all efficient OER catalysts. As the most mature hydrogen production device, alkaline water electrolysis cell (ALKWE) is one of the most practical methods to achieve carbon neutralization. ALKWE usually operates at 80℃ to improve the reaction thermodynamics and kinetics, ultimately reducing power consumption. In low-temperature harsh environments, water electrolysis needs to be started normally in the presence of a large heat preservation device, and the catalyst and substrate are more prone to fall off at low temperatures due to brittleness. However, anodes with high oxygen evolution reaction (OER) activity, such as NiFe-LDH (hydrotalcite-like), IrO2 (noble metal-like), NiFe-MOF (metal-organic framework-like), Co3O4 (transition metal oxide-like), LaCoO3 (perovskite-like), and Ni(OH)2 (over metal hydroxide-like), are prone to performance degradation and ultimately lead to system failure at high and low temperatures after a relatively long period of operation. This limitation greatly hinders the development of high-performance ALKWE.

[0003] In addition, among the many hydrogen production methods, water electrolysis is considered the most effective way to produce green hydrogen. However, freshwater resources account for only three percent of global water resources, while seawater resources are inexhaustible. Therefore, due to the limited freshwater reserves, using renewable energy to electrolyze seawater to produce hydrogen is a more sustainable solution.

[0004] Direct electrolysis of seawater has certain challenges. The main component of seawater is sodium chloride (concentration of about 0.5 mol per liter), and the presence of chloride ions will cause corrosion and chlorine oxidation at the anode, poison the active site, and corrode the electrode base. At the same time, direct use of seawater as an electrolyte will cause the salt concentration of the electrolyte to continue to rise during the electrolysis process until it is saturated.

[0005] Therefore, it is necessary to desalinate seawater. Even if seawater is desalinated, there will still be several ppm of residue, and long-term electrolysis will still cause accumulation of chloride ions, causing corrosion of the tank. The current alkaline tank has to be replaced with an electrolyte when the chloride ion concentration reaches several hundred ppm. The nickel foam electrode in the alkaline water electrolysis industry will be corroded in less than ten hours of operation in high-concentration brine.

[0006] Therefore, in order to promote the further development of seawater electrolysis hydrogen production technology, it is urgent to develop an anode catalyst or additive that can work stably in a high-concentration brine environment. In recent years, significant progress has been made in the development of seawater electrolysis anode catalysts, and each catalyst has its unique corrosion prevention mechanism and ability, but no paradigm has been formed. Therefore, if an anode corrosion prevention additive for electrolysis of seawater can be invented, which can universally improve the stability of the electrolysis seawater anode and avoid the cumbersome catalyst preparation and design process, it will play a promoting role in the progress of seawater electrolysis technology.

[0007] To solve one or more of the above problems, the present application is proposed. SUMMARY

[0008] In recent years, a lot of work has been done to improve the stability of the anode. It is worth noting that most of the research only focuses on electrolysis at room temperature, and little attention is paid to temperature stability related to actual industrial applications (such as -30°C, 80°C, etc.). The gap between the current research status and industrial needs highlights the need to reveal the performance degradation law of the anode and develop new strategies to mitigate the degradation of the anode at high and low temperatures. Electrolyte additives for alkaline water electrolysis mainly focus on surfactant-type organic substances, which are relatively stable and have the effect of accelerating the rapid detachment of bubbles, and can improve the electrode performance to a certain extent. However, inorganic salt-containing oxygen acids have no such obvious effect on bubbles, so their role is easily overlooked. In addition, some researchers have added macromolecular organic salts (such as sodium polyacrylate) to the electrolyte, which has improved the performance of the electrode, but macromolecular organic salts can easily increase the viscosity of the electrolyte and affect the ion conduction rate.

[0009] Applicants found in the process of implementing the present application that small molecule organic and inorganic oxoacid salts have high electron affinity, and the strong interaction between the anions and the cations on the electrode surface helps to form stable substances on the electrode surface, and is conducive to the occurrence of anode reconstruction and the improvement of electrode stability. Therefore, the prepared K3PO4, K2CO3, KB(OH)4, K2SO4, KClO4, CF3COOK, potassium pentafluoropropionate, potassium heptafluorobutyrate, potassium nonafluoropentanoate, potassium perfluorohexanoate solution or Na3PO4, Na2CO3, NaB(OH)4, Na2SO4, NaClO4, CF3COONa, Na2SeO4, Na2SiO3 solution was taken in different amounts and added to the prepared KOH (or NaOH, or simulated seawater (mainly composed of NaCl) + NaOH or KOH or other alkali) solution to obtain the corresponding oxygen evolution reaction electrolyte with different oxoacid ions and different concentrations. NiFe-LDH (hydrotalcite), IrO2 (noble metal), NiFe-MOF (metal organic framework), Co3O4 (transition metal oxide), LaCoO3 (perovskite), and Ni(OH)2 (transition metal hydroxide) were used as working electrodes, platinum sheet electrode as counter electrode, and mercury-mercury oxide electrode as reference electrode. In a three-electrode system, the OER activity of different electrolyte formulations was tested, and in a two-electrode system, the water electrolysis stability of different electrolyte formulations was tested at 400 mA cm -2

[0010] The present application found that through the above electrolyte regulation, the oxygen evolution reaction activity and stability of water electrolysis were greatly improved. The precipitate formed by high valence cations and high valence anions is more stable, and therefore the addition of oxoacid ions such as phosphate is more conducive to the formation of high-activity and high-stability substances (such as hydroxyapatite), which are adsorbed on the electrode surface without being separated from the electrode, which is conducive to being activated again as active sites, anode reconstruction and enhancing anode dissolution resistance.

[0011] The first aspect of the present application provides an electrolyte additive for water electrolysis reaction performance, which comprises an oxoacid radical. The oxoacid radical is one or more of non-metal oxoacid radical or metal oxoacid radical.

[0012] The above performance refers to activity and / or stability.

[0013] The oxoacid radical can exist in the form of an oxoacid radical aqueous solution.

[0014] Preferably, the oxoacid radical is selected from one or more of inorganic oxoacid radical or organic oxoacid radical.

[0015] ​Preferably, the inorganic oxygen-containing acid radical is selected from one or more of: phosphate, carbonate, borate, sulfate, perchlorate. The organic oxygen-containing acid radical is selected from one or more of: trifluoroacetate, potassium pentafluoropropionate, potassium heptafluorobutyrate, potassium nonafluoropentanoate, potassium perfluorohexanoate.

[0016] The metal oxygen-containing acid radical is selected from one or more of: molybdate, tungstate, vanadate, niobate, ferricyanide, zincate, aluminate, stannate.

[0017] Preferably, the oxygen-containing acid radical is from an oxygen-containing acid salt. The metal oxygen-containing acid radical can be from a metal oxyacid salt, such as molybdate, tungstate, vanadate, niobate, ferricyanide, zincate, aluminate, stannate, etc.

[0018] Preferably, the oxygen-containing acid salt is selected from one or more of: K3PO4, K2CO3, KB(OH)4, K2SO4, KClO4, CF3COOK, Na3PO4, Na2CO3, NaB(OH)4, Na2SO4, NaClO4, CF3COONa, Na2SeO4, Na2SiO3, potassium pentafluoropropionate, potassium heptafluorobutyrate, potassium nonafluoropentanoate, potassium perfluorohexanoate, sodium pentafluoropropionate, sodium heptafluorobutyrate, sodium nonafluoropentanoate, sodium perfluorohexanoate.

[0019] Preferably, the temperature of the electrolytic water oxygen evolution reaction is -30-100°C.

[0020] The second aspect of the present application provides an electrolyte for improving the performance of an electrolytic water reaction, the electrolyte comprising a base and a non-metallic oxygen-containing acid salt. The base is sodium hydroxide or potassium hydroxide.

[0021] The third aspect of the present application provides a method for improving the performance of an electrolytic water oxygen evolution reaction, the method comprising: using a solution containing an oxygen-containing acid radical as an electrolyte for an electrolytic water oxygen evolution reaction.

[0022] The oxygen-containing acid radical is a non-metallic oxygen-containing acid radical or a metal oxygen-containing acid radical.

[0023] The oxygen-containing acid radical is from an oxygen-containing acid salt.

[0024] The above-mentioned performance refers to activity and / or stability.

[0025] The metal oxygen-containing acid radical is selected from one or more of: molybdate, tungstate, vanadate, niobate, ferricyanide, zincate, aluminate, stannate.

[0026] Preferably, the oxygen-containing acid radical is from an oxygen-containing acid salt. The metal oxygen-containing acid radical can be from a metal oxyacid salt, such as molybdate, tungstate, vanadate, niobate, ferricyanide, zincate, aluminate, stannate, etc.

[0027] Preferably, the electrolyte for the water electrolysis oxygen evolution reaction is an alkaline solution (one or more of KOH, NaOH).

[0028] Preferably, the oxygen-containing acid salt is selected from one or more of non-metallic inorganic oxygen-containing acid salts or non-metallic organic oxygen-containing acid salts.

[0029] The above-mentioned organic oxygen-containing acid salt is preferably a small-molecule organic oxygen-containing acid salt.

[0030] Preferably, the inorganic oxygen-containing acid salt is selected from one or more of phosphate, carbonate, borate, sulfate, perchlorate, silicate, selenate;

[0031] The organic oxygen-containing acid salt is selected from one or more of trifluoroacetate, pentafluoropropionate, heptafluorobutyrate, nonafluoropentanoate, perfluorohexanoate.

[0032] Preferably, the amount of the oxygen-containing acid salt added in the electrolyte for the water electrolysis oxygen evolution reaction is 1-2000 mM. In other words, the concentration of the oxygen-containing acid salt in the electrolyte for the water electrolysis oxygen evolution reaction is 1-2000 mM.

[0033] Preferably, the oxygen-containing acid salt is selected from one or more of K3PO4, K2CO3, KB(OH)4, K2SO4, KClO4, CF3COOK, Na3PO4, Na2CO3, NaB(OH)4, Na2SO4, NaClO4, CF3COONa, Na2SeO4, Na2SiO3, potassium pentafluoropropionate, potassium heptafluorobutyrate, potassium nonafluoropentanoate, potassium perfluorohexanoate, sodium pentafluoropropionate, sodium heptafluorobutyrate, sodium nonafluoropentanoate, sodium perfluorohexanoate.

[0034] Preferably, the electrolyte for the water electrolysis oxygen evolution reaction contains 0.1-9 M KOH solution, or contains 0.1-9 M NaOH solution, or contains simulated seawater + KOH, NaOH or other alkali.

[0035] Preferably, the catalyst for the water electrolysis oxygen evolution reaction is selected from one or more of hydrotalcite, noble metal, metal-organic framework, transition metal oxide, perovskite.

[0036] The fourth aspect of the present application provides an electrolyte for water electrolysis oxygen evolution, wherein the electrolyte contains an oxygen-containing acid root.

[0037] The oxygen-containing acid root is derived from an oxygen-containing acid salt. The oxygen-containing acid root is a non-metallic oxygen-containing acid root or a metallic oxygen-containing acid root.

[0038] The oxygen-containing acid salt is selected from one or more of non-metallic inorganic oxygen-containing acid salts or non-metallic organic oxygen-containing acid salts.

[0039] The inorganic oxyacid salt is selected from one or more of the following: phosphate, carbonate, borate, sulfate, perchlorate, silicate, selenate;

[0040] The organic oxyacid salt is selected from one or more of the following: trifluoroacetate, pentafluoropropionate, heptafluorobutyrate, nonafluoropentanoate, perfluorohexanoate.

[0041] Preferably, the electrolyte for electrolysis of water for oxygen evolution reaction contains an alkaline substance.

[0042] Preferably, the electrolyte solution is an inorganic strong alkali solution.

[0043] The inorganic oxyacid salt is selected from one or more of the following: phosphate, carbonate, borate, sulfate, perchlorate, silicate, nitrate, selenate;

[0044] The organic oxyacid salt is selected from one or more of the following: trifluoroacetate, pentafluoropropionate, heptafluorobutyrate, nonafluoropentanoate, perfluorohexanoate.

[0045] Preferably, the content of the oxyacid salt in the electrolyte for electrolysis of water for oxygen evolution reaction is 1-2000 mM.

[0046] The oxyacid salt is selected from one or more of the following: K3PO4, K2CO3, KB(OH)4, K2SO4, KClO4, CF3COOK, Na3PO4, Na2CO3, NaB(OH)4, Na2SO4, NaClO4, CF3COONa, Na2SeO4, Na2SiO3, potassium pentafluoropropionate, potassium heptafluorobutyrate, potassium nonafluoropentanoate, potassium perfluorohexanoate, sodium pentafluoropropionate, sodium heptafluorobutyrate, sodium nonafluoropentanoate, sodium perfluorohexanoate.

[0047] Preferably, the electrolyte for electrolysis of water for oxygen evolution reaction contains 0.1-9 M KOH solution, or 0.1-9 M NaOH solution, or simulated seawater + KOH, NaOH or other alkali.

[0048] The fifth aspect of the present application also provides a method for electrolysis of water for oxygen evolution, comprising the following steps:

[0049] The electrolyte for electrolysis of water for oxygen evolution is electrolyzed using a three-electrode system to obtain oxygen.

[0050] The electrolysis temperature is -30-100℃.

[0051] When the electrolyte for electrolysis of water for oxygen evolution reaction contains chloride ions, one of the important indicators of the above performance is to prevent anodic corrosion of electrolyzed seawater.

[0052] Therefore, the following is a specific description of preventing anodic corrosion of electrolyzed seawater:

[0053] The sixth aspect of the present application provides an electrolyte additive for preventing anodic corrosion of electrolysis seawater, wherein the electrolyte additive contains silicate negative ions.

[0054] Preferably, the silicate negative ions are derived from water-soluble silicates.

[0055] Preferably, the water-soluble silicates are selected from one or more of sodium silicate, potassium silicate, and lithium silicate.

[0056] The seventh aspect of the present application provides an electrolyte for preventing anodic corrosion of electrolysis seawater, wherein the electrolyte is an electrolyte containing silicate negative ions and a base.

[0057] The eighth aspect of the present application provides a method for preventing anodic corrosion of electrolysis seawater, wherein the method comprises using an electrolyte containing silicate negative ions and a base to electrolyze water to produce hydrogen, and the anode can resist corrosion of high concentrations of chloride ions.

[0058] Preferably, the silicate negative ions are derived from water-soluble silicates.

[0059] Preferably, the water-soluble silicates are selected from one or more of sodium silicate, potassium silicate, and lithium silicate, and the concentration of the water-soluble silicates in the basic electrolyte is 0.1-2000 millimoles per liter.

[0060] Preferably, the base electrolyte contains an alkali metal, and the concentration of the alkali metal base is 0.1-6.0 moles per liter.

[0061] Preferably, the concentration of chloride ions in the electrolyte is 0.0001-3.0 moles per liter.

[0062] Preferably, the alkali metal base is selected from one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0063] Preferably, the method can make the anode of electrolysis seawater resistant to corrosion of salts with a chloride ion concentration of 0.0001-3.0 moles per liter.

[0064] The ninth aspect of the present application provides an electrolyte for preventing anodic corrosion of electrolysis seawater, wherein the electrolyte comprises silicates and a base. The silicates are water-soluble silicates. The complex electrolyte can make the anode resistant to corrosion of high concentrations of chloride ions.

[0065] In the process of electrolysis of seawater, the silicate negative ions are adsorbed on the surface of the anode, repel chloride ions, stabilize the electrode composition, effectively resist chloride ion corrosion and competitive reactions, and improve the operating stability of the electrode in high-salt seawater electrolyte.

[0066] When the oxygen-containing acid radical is a metal oxygen-containing acid radical, the present application further discloses the following content:

[0067] The application also provides a basic water electrolysis anode catalyst and a metal oxyanion electrolyte additive, which aims to improve the activity and stability of basic water electrolysis to be applicable to long-time working conditions.

[0068] The application also provides a preparation method of a nickel-iron hydrotalcite intercalated with different interlayer intercalated oxyanions, and the material prepared by using the method is used for catalyzing the anode oxygen evolution reaction of basic water electrolysis, which can greatly improve the electrochemical reaction efficiency of the oxygen evolution reaction under high temperature and large current and stabilize hydrogen production.

[0069] The tenth aspect of the application provides a nickel-iron hydrotalcite intercalated with metal oxyanions, wherein the nickel-iron hydrotalcite is intercalated with metal oxyanions, and the metal oxyanions are selected from one or more of vanadate, chromate, molybdate and tungstate.

[0070] Preferably, the nickel-iron hydrotalcite has a sheet structure with a size of 40-1000 nm and a thickness of 5-20 nm.

[0071] More preferably, the nickel-iron hydrotalcite is formed by stacking a plurality of curled or uncurled sheet structures, the size of a single sheet structure is distributed in 40-1000 nm, the thickness is distributed in 5-30 nm, and the total content of metal elements accounts for 40-60 wt% of the total elements. The content of metal elements can be calculated according to the element composition of the specific layered metal hydroxide.

[0072] The eleventh aspect of the application provides a preparation method of the nickel-iron hydrotalcite intercalated with metal oxyanions according to the tenth aspect, and the preparation method comprises the following steps:

[0073] (1) dissolving nickel salt and iron salt in water from which CO2 has been removed to prepare solution A; dissolving nucleating agent and oxyanion metal salt in water to obtain solution B;

[0074] The concentration of nickel salt and iron salt in solution A is 0.01-0.2 mol / L;

[0075] The concentration of nucleating agent in solution B is 0.05-0.8 mol / L, and the concentration of oxyanion metal salt is 0.01-0.1 mol / L;

[0076] (2) under the conditions of stirring, nitrogen or inert gas, and water bath at 60-80℃, mixing solution A and B in step (1) into decarburized water C to obtain a mixed solution, maintaining the pH of the mixed solution at 8.5-11.5 during the dropping process, and continuously stirring for 20 minutes-24 hours after the dropping is completed to obtain a suspension;

[0077] (3) the suspension is subjected to multiple centrifugal washing, and the obtained gelatinous product is subjected to freeze vacuum drying to obtain the nickel-iron hydrotalcite;

[0078] The metal salt of oxygen-containing acid comprises one or more of KVO3, NaVO3, Na2CrO4, K2CrO4, Na2MoO4, K2MoO4, NaWO4, KWO4, Na2W2O7, and K2W2O7.

[0079] The nucleating agent is selected from one or both of potassium hydroxide and sodium hydroxide.

[0080] The twelfth aspect of the present application provides a method for improving the performance of water electrolysis reaction, which comprises using the nickel-iron hydrotalcite of the first aspect as an anode catalyst for alkaline water electrolysis.

[0081] Preferably, a platinum sheet is used as a counter electrode.

[0082] A three-electrode or two-electrode system is used.

[0083] The three-electrode system uses mercury / mercury oxide as a reference electrode.

[0084] A sodium hydroxide or potassium hydroxide solution is used as an alkaline solution.

[0085] The electrolysis temperature is -30-100℃.

[0086] The above performance includes activity and / or stability.

[0087] The thirteenth aspect of the present application provides an electrolyte additive for improving the performance of alkaline water electrolysis reaction, which contains a metal salt of oxygen-containing acid, and the metal salt of oxygen-containing acid is selected from one or more of vanadate, chromate, molybdate, and tungstate.

[0088] The fourteenth aspect of the present application provides an electrolyte for improving the performance of alkaline water electrolysis reaction, which contains sodium hydroxide or potassium hydroxide and a metal salt of oxygen-containing acid.

[0089] The concentration of the sodium hydroxide or potassium hydroxide is 1 mol / L.

[0090] The concentration of the metal salt of oxygen-containing acid is 0-1 mmol / L, and the metal salt of oxygen-containing acid is selected from one or more of vanadate, chromate, molybdate, and tungstate.

[0091] The fifteenth aspect of the present application provides a method for improving the performance of water electrolysis reaction, which comprises using an alkaline solution containing a metal salt of oxygen-containing acid as an anode electrolyte for water electrolysis oxygen evolution reaction, and the electrolysis temperature is -30-100℃, and the concentration of the metal salt of oxygen-containing acid is 0-1 mmol / L.

[0092] Preferably, a nickel-iron hydrotalcite intercalated with metal oxyanions is used as an anode catalyst, the nickel-iron hydrotalcite being intercalated with metal oxyanions selected from one or more of vanadate, chromate, molybdate, tungstate.

[0093] Preferably, a platinum sheet is used as a counter electrode;

[0094] A three-electrode or two-electrode system is used;

[0095] The three-electrode system uses mercury / mercuric oxide as a reference electrode;

[0096] A sodium hydroxide or potassium hydroxide solution is used as an alkaline solution.

[0097] The performance in this application includes activity and / or stability.

[0098] For the prior art, the present application has the following beneficial effects:

[0099] 1. The present application provides the use of oxyanions to improve the activity and stability of water electrolysis oxygen evolution. In particular, it is also applicable to electrolysis reactions at high and low temperatures. The addition of oxyanions in the present application reduces the oxygen evolution reaction potential, reduces the charge transfer resistance, accelerates the electron transfer rate, and has faster chemical reaction kinetics, all of which are beneficial to the improvement of reaction activity.

[0100] 2. In this application, during the high and low temperature stability test, the addition of oxyanions enhances the anode's resistance to dissolution, reduces the dissolution of metal ions, and reduces the deposition of metal ions on the platinum sheet, thereby improving the stability of the catalyst.

[0101] 3. In particular, the present application also finds that the adsorption of oxyanion ions on the catalyst is beneficial to the reconstruction of the anode and the generation of highly active substances (such as hydroxyl oxyanions), which is beneficial to the reduction of the reaction potential and the preservation of active sites, and is beneficial to the improvement of activity and stability. The added oxyanion ions have certain electronic attraction properties and resistance to dissolution, which can keep the metal ions in a higher valence state, which is more conducive to oxidation and promotes the next reaction.

[0102] 4. The present application provides an electrolyte for water electrolysis oxygen evolution, which comprises oxyanions and an electrolyte solution, and the electrolyte solution is KOH or NaOH or simulated seawater + NaOH, KOH or other alkali. The electrolyte for water electrolysis oxygen evolution provided by the present application uses oxyanions as an additive to improve the activity and stability of high-temperature water electrolysis, thereby improving the efficiency and stability of the electrochemical reaction.

[0103] When the electrolyte for water electrolysis oxygen evolution reaction contains chloride ions, one of the important indicators of the above performance is to prevent anode corrosion during electrolysis of seawater.

[0104] Therefore, the following is specifically described for preventing anodic corrosion of electrolytic seawater:

[0105] 1. The present application first proposes to use silicate negative ion additives for electrocatalytic seawater electrolysis anode corrosion prevention. Compared with the design of corrosion-resistant catalysts, the present application is universally applicable to all electrolytic seawater anode electrode corrosion prevention. Silicate negative ions will be adsorbed on the surface of the catalyst and the substrate during electrolysis. Due to its moderate molecular radius and large number of charges, it effectively resists chloride ion attack by using charge repulsion and steric effect, thereby achieving chloride ion exclusion under high-concentration brine and industrial current density, inhibiting chloride ion corrosion of the substrate and chlorine oxidation competitive side reactions.

[0106] 2. The embodiments of the present application prove that:

[0107] By adding 10 millimoles per liter of silicate to the electrolyte, the nickel-iron layered double hydroxide electrode loaded on the nickel foam can be stably operated for 1000 hours in 1.0 mole per liter of sodium hydroxide and 0.5 mole per liter of sodium chloride alkaline brine, while it can only work for 200 hours without silicate additives, with a five-fold increase in stability.

[0108] By adding 500 millimoles per liter of silicate to the electrolyte, the nickel-iron layered double hydroxide electrode loaded on the nickel foam can be stably operated for 1000 hours in 1 mole per liter of sodium hydroxide and 2.5 moles per liter of sodium chloride alkaline high-concentration brine, which is the longest time reported for alkaline brine electrolysis at this concentration, while it can only work for 2 hours without silicate additives. At the same time, the electrode still maintains the original physical structure after 1000 hours of reaction, and the electrolyte is clear, without catalyst falling off, so the silicate can also effectively reduce the falling off and dissolution of the catalyst on the electrode surface, anchor the catalyst, and realize long-term stable electrolysis process in high salt concentration.

[0109] When the oxygen-containing acid radical is a metal oxygen-containing acid radical, the present application also has the following beneficial effects for the prior art:

[0110] 1. Although previous work has systematically studied the interlayer anions of nickel-iron hydrotalcite, it is mostly limited to organic anions and non-metallic oxygen-containing acid radicals. The present application unexpectedly found that metal oxygen-containing acid radicals as interlayer anions of hydrotalcite can further improve the activity and stability of alkaline electrolytic water compared to organic anions and non-metallic oxygen-containing acid radicals.

[0111] 2. The nickel-iron layered double hydroxide (LDH) with intercalated metal oxyacid anions provided by this invention, compared with traditional nickel-iron LDH, has a smaller size, more dispersed structure, and larger interlayer spacing because the ionic radius of the metal oxyacid anions is larger than that of the traditional intercalated carbonate anions. This is beneficial for exposing edge active sites, thereby increasing the number of active sites on the material surface. On the other hand, most of the metals in the metal oxyacid anions are in a higher valence state and have a certain degree of oxidizing property, which can help increase the valence state of nickel, the active site for oxygen evolution reaction, thereby changing the electronic structure of the material and improving its intrinsic activity.

[0112] The electrolyte containing metal oxyacid anions provided by this invention can exchange positions with the interlayer anions of nickel-iron hydrotalcite during the reaction process, thereby also undergoing the above-mentioned mechanism, which similarly enhances the activity of the oxygen evolution reaction.

[0113] 3. The nickel-iron hydrotalcite provided by this invention is used as an anode catalyst for alkaline water electrolysis and as an electrolyte additive for the electrolyte of water electrolysis. Both alone and in combination, they improve the stability of the oxygen evolution reaction and are suitable for a wide temperature range (-30 to 100°C).

[0114] Under the same temperature and current density conditions, when the nickel-iron hydrotalcite provided by this invention and conventional hydrotalcite were subjected to water electrolysis reactions for the same duration, the former showed a significantly reduced catalyst dissolution rate in the electrolyte compared to the latter. Using an anolyte catalyst to catalyze the oxygen evolution reaction in electrolytes with and without electrolyte additives under the aforementioned electrolysis conditions, it was found that the electrolyte additives could protect the catalyst from dissolution. In-situ and ex-situ characterization results indicate that the electrolyte additives help the catalyst maintain a stable morphology. The reduction in catalyst dissolution allows the electrolysis system to operate more stably and sustainably.

[0115] 4. The precursors required for nickel-iron hydrotalcite with different metal oxyanion intercalation provided in this invention are inexpensive and readily available, and the reaction operation is simple and easy to perform, making it suitable for large-scale industrial production.

[0116] 5. The electrolyte additives provided in this invention all have upstream industrial chains, and the additives themselves do not require reaction treatment and are simple to use. Attached Figure Description

[0117] Figure 1 shows the LSV curve of the OER reaction in Example 1 under K3PO4-controlled conditions;

[0118] Figure 2 shows the LSV curve of the OER reaction in Example 2 under Na2CO3 controlled conditions;

[0119] Figure 3 shows the LSV curve of the OER reaction in Example 3 under KB(OH)4 controlled conditions;

[0120] Figure 4 is a LSV curve of Example 4 for OER reaction under Na2SO4 regulation condition;

[0121] Figure 5 is a LSV curve of Example 5 for OER reaction under KClO4 regulation condition;

[0122] Figure 6 is a LSV curve of Example 6 for OER reaction under CF3COOK regulation condition;

[0123] Figure 7 is a LSV curve of Example 7 for OER reaction under Na2SiO3 regulation condition;

[0124] Figure 8 is a LSV curve of Example 8 for OER reaction under Na2SeO4 regulation condition;

[0125] Figure 9 is a CV curve of Example 9 for OER reaction under potassium pentafluoropropionate regulation condition;

[0126] Figure 10 is a CV curve of Example 10 for OER reaction under potassium heptafluorobutyrate regulation condition;

[0127] Figure 11 is a CV curve of Example 11 for OER reaction under potassium nonafluoropentanoate regulation condition;

[0128] Figure 12 is a CV curve of Example 12 for OER reaction under potassium perfluorohexanoate regulation condition;

[0129] Figure 13 is a stability curve of Example 13 for OER reaction under K3PO4 regulation condition;

[0130] Figure 14 is a stability curve of Example 14 for OER reaction under Na2CO3 regulation condition;

[0131] Figure 15 is a stability curve of Example 15 for OER reaction under KB(OH)4 regulation condition;

[0132] Figure 16 is a stability curve of Example 16 for OER reaction under Na2SO4 regulation condition;

[0133] Figure 17 is a stability curve of Example 17 for OER reaction under KClO4 regulation condition;

[0134] Figure 18 is a stability curve of Example 18 for OER reaction under CF3COOK regulation condition;

[0135] Figure 19 is an XPS spectrum of Example 19 after OER stability test reaction under K3PO4 regulation condition;

[0136] Figure 20 is an EDS elemental mapping of Example 19 after OER stability test reaction under K3P04mediated conditions.

[0137] Figure 21 is a CV curve of Example 20 nickel-iron layered double hydroxide electrode supported on nickel foam for OER reaction.

[0138] Figure 22 is a CV curve of Example 20 electrode after addition of silicate for OER reaction.

[0139] Figure 23 is a stability test curve of Example 20 and Comparative Example 1 electrodes for OER reaction in alkaline brine with or without addition of silicate.

[0140] Figure 24 is a stability test curve of Example 21 and Comparative Example 2 electrodes for OER reaction in alkaline brine with or without addition of silicate.

[0141] Figure 25 is a stability test curve of Example 22 and Comparative Example 3 electrodes for OER reaction in alkaline brine with or without addition of silicate.

[0142] Figure 26 is a photograph of Example 22 electrode and electrolyte after stability test in alkaline brine with addition of silicate.

[0143] Figure 27 is a stability curve of Example 23 and Comparative Example 4 electrodes for OER reaction in alkaline brine with or without addition of silicate.

[0144] Figure 28 is a photograph of Comparative Example 3 electrode and electrolyte after stability test in alkaline brine without addition of silicate.

[0145] Figure 29 is a stability curve of Example 24 electrode for OER reaction in low concentration alkaline brine with addition of silicate.

[0146] Figure 30 is a SEM image of CO3 2- Intercalated nickel-iron hydrotalcite;

[0147] Figure 31 is a SEM image of VO3 - Intercalated nickel-iron hydrotalcite;

[0148] Figure 32 is a SEM image of CrO4 2- Intercalated nickel-iron hydrotalcite;

[0149] Figure 33 is a SEM image of MoO4 2- Intercalated nickel-iron hydrotalcite;

[0150] Figure 34 is a SEM image of WO4 - Intercalated nickel-iron hydrotalcite;

[0151] Figure 35 W2O7 in Example 30 2- SEM image of intercalated nickel iron hydrotalcite;

[0152] Figure 36 CO3 in Example 25 2- XRD of intercalated nickel iron hydrotalcite compared to standard card;

[0153] Figure 37 VO3 in Example 26 - XRD of intercalated nickel iron hydrotalcite compared to standard card;

[0154] Figure 38 CrO4 in Example 27 2- XRD of intercalated nickel iron hydrotalcite compared to standard card;

[0155] Figure 39 MoO4 in Example 28 2- XRD of intercalated nickel iron hydrotalcite compared to standard card;

[0156] Figure 40 WO4 in Example 29 - XRD of intercalated nickel iron hydrotalcite compared to standard card;

[0157] Figure 41 W2O7 in Example 30 2- XRD of intercalated nickel iron hydrotalcite compared to standard card;

[0158] Figure 42 CO3 in Example 25 2- CV curve of intercalated nickel iron hydrotalcite for OER reaction under NaVO3 regulation;

[0159] Figure 43 VO3 in Example 26 - CV curve of intercalated nickel iron hydrotalcite for OER reaction under NaVO3 regulation;

[0160] Figure 44 CrO4 in Example 27 2- CV curve of intercalated nickel iron hydrotalcite for OER reaction under Na2CrO4 regulation;

[0161] Figure 45 MoO4 in Example 28 2- CV curve of intercalated nickel iron hydrotalcite for OER reaction under Na2MoO4 regulation;

[0162] Figure 46 WO4 in Example 29 - LSV curve of intercalated nickel iron hydrotalcite for OER reaction under NaWO4 regulation;

[0163] Figure 47 W2O7 in Example 30 2- CV curve of intercalated nickel iron hydrotalcite for OER reaction under Na2W2O7 regulation;

[0164] Figure 48 is VO3in application example 1 - Stability curve of intercalated nickel iron hydrotalcite under NaVO3regulation for OER reaction;

[0165] Figure 49 is CrO4in application example 2 2- Stability curve of intercalated nickel iron hydrotalcite under Na2CrO4regulation for OER reaction;

[0166] Figure 50 is MoO4in application example 3 2- Stability curve of intercalated nickel iron hydrotalcite under Na2MoO4regulation for OER reaction;

[0167] Figure 51 is WO4in application example 4 - Stability curve of intercalated nickel iron hydrotalcite under NaWO4regulation for OER reaction;

[0168] Figure 52 is W2O7in application example 5 2- Stability curve of intercalated nickel iron hydrotalcite under Na2W2O7regulation for OER reaction;

[0169] Figure 53 is the dissolution amount of catalyst in the electrolyte after stability test under NaVO3regulation in application example 1

[0170] Figure 54 is VO3in example 25 - XPS image of intercalated nickel iron hydrotalcite nickel;

[0171] Figure 55 is VO3in example 25 - Raman image of intercalated nickel iron hydrotalcite;

[0172] Figure 56 is CO3in comparative example 1 2- Intercalated nickel iron hydrotalcite and VO3 - CV comparison curve of intercalated nickel iron hydrotalcite for OER reaction in 1MKOH.

[0173] Figure 57 is the high-temperature OER (oxygen evolution) reaction stability curve of the electrode in the electrolyte additionally added with niobate, ferricyanide, zincate, aluminate, stannate, respectively.

[0174] Figure 58 is the low-temperature OER (oxygen evolution) reaction stability curve of the electrode in the electrolyte additionally added with niobate, ferricyanide, zincate, aluminate, stannate, respectively.

[0175] Figure 59 is the high-temperature OER (oxygen evolution) reaction stability curve of the electrode in the electrolyte additionally added with sodium silicate, potassium trifluoroacetate, and tin chloride, respectively. DETAILED DESCRIPTION

[0176] The present application will be described with respect to the following examples, but the embodiments of the application are not limited to only the examples. Unless otherwise noted, the experimental methods in the examples were carried out according to conventional conditions and conditions described in manuals, or using general equipment, materials, reagents, etc. recommended by the manufacturers, and were obtained commercially, unless otherwise noted. The starting materials used in the following examples and comparative examples were all commercially available.

[0177] The ranges disclosed herein are defined by the lower and upper limits of the range, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. Ranges defined by the lower and upper limits can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. In addition, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing each and every intervening real number between the upper and lower limits of that range, wherein a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand way of describing those numerical combinations. In addition, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0178] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of the present application can be combined to form new technical solutions. Unless otherwise specified, all steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0179] As used in this application, the terms "comprises", "comprising", "includes", "including" or "contains", "containing" where used should be interpreted as being inclusive (i.e. meaning "including but not limited to") unless there are other base entities explicitly listed. Similarly as used in this application, the term "exemplary" is intended to be exemplary (e.g. a exemplary embodiment) only. Thus, the exemplary is not to be construed as preferred or advantageous over other embodiments.

[0180] 6M KOH solution refers to 20wt% KOH solution. NiFe-LDH nanorarray electrode, nickel foam electrode, platinum plate, nickel iron layered double hydroxide electrode loaded on nickel foam in this application can be obtained by market purchase or existing method. When referring to molar concentration unit, M represents mol / L.

[0181] Example 1

[0182] Prepare 6M KOH solution and 2M K3PO4 solution, take a certain amount of the above K3PO4 solution into 6M KOH solution to obtain electrolyte, so that the K3PO4 concentration in the electrolyte is 0mM, 1mM, 2mM, 3mM, 4mM, 5mM, 6mM, 7mM, 8mM, 9mM, 10mM, 11mM, 12mM. The KOH concentration in the electrolyte is basically 6M (because the amount of K3PO4 solution added is very small), and the total volume of the electrolyte is 50mL.

[0183] Use the above 13 kinds of solutions as electrolyte for electrolysis of water, take platinum plate as counter electrode, NiFe-LDH nanorarray electrode as working electrode, and mercury-mercury oxide electrode as reference electrode to form a three-electrode system. At 80℃, OER is carried out, and the LSV curves of the above 13 kinds of solutions are measured, and the results are shown in Figure 1; at 10mA cm -2 The corresponding voltage is shown in Table 1.

[0184] Table 1 Current density is 10mA cm -2 Voltage under different K3PO4 contents

[0185] As can be seen from Figure 1 and Table 1, with the increase of K3PO4 concentration, the reaction voltage decreases and the activity increases. When the K3PO4 concentration in the electrolyte is 10mM, the best performance is obtained. When the K3PO4 concentration is higher, the NiFe-LDH OER performance is basically unchanged, which may be due to the excessive addition of phosphate, which affects the mass transfer and does not help the performance improvement.

[0186] Example 2

[0187] Except that the working electrode is replaced by IrO2, K3PO4 is replaced by Na2CO3, after adding Na2CO3, the concentration of Na2CO3 in the electrolyte is 0 mM, 1 mM, 2 mM, 3 mM, 4 mM, 5 mM, 10 mM, 6M KOH is replaced by 6M NaOH, and the others are the same as in Example 1.

[0188] Table 2 Current density is 10 mA cm -2 Voltage under different Na2CO3 contents

[0189] As can be seen from FIG. 2 and Table 2, as the concentration of Na2CO3 increases, the reaction voltage decreases and the activity increases, and the best performance is obtained when the concentration of Na2CO3 in the electrolyte is 4 mM, and the performance of IrO2 OER decreases when the concentration of Na2CO3 is higher, which may be due to the excessive addition of carbonate, affecting the mass transfer.

[0190] Example 3

[0191] Except that the working electrode is replaced by Ni(OH)2, K3PO4 is replaced by KB(OH)4, after adding KB(OH)4, the concentration of KB(OH)4 in the electrolyte is 0 mM, 1 mM, 3 mM, 5 mM, 10 mM, and the others are the same as in Example 1.

[0192] Table 3 Current density is 10 mA cm -2 Voltage under different KB(OH)4 contents

[0193] As can be seen from FIG. 3 and Table 3, as the concentration of KB(OH)4 increases, the reaction voltage decreases and the activity increases, and the best performance is obtained when the concentration of KB(OH)4 in the electrolyte is 1 mM, and the performance of Ni(OH)2 OER decreases when the concentration of KB(OH)4 is higher, which may be due to the excessive addition of borate, affecting the mass transfer.

[0194] Example 4

[0195] Except that the working electrode is replaced by Co3O4, K3PO4 is replaced by Na2SO4, the concentration of Na2SO4 in the electrolyte is replaced by 0 mM, 2 mM, 4 mM, 6 mM, 8 mM, 10 mM, 12 mM, and 6M KOH solution is replaced by 2.8M NaCl (to simulate seawater) + 6M NaOH. The others are the same as in Example 1.

[0196] 2.8M NaCl (to simulate seawater) + 6M NaOH means: a mixed solution of NaCl and NaOH, in the mixed solution, the concentration of NaCl is 2.8M, and the concentration of NaOH is 6M.

[0197] Table 4. Voltage at current density of 10 mA cm -2 Voltage at different Na2SO4 contents

[0198] As can be seen from FIG. 4 and Table 4, with the increase of the concentration of Na2SO4, the reaction voltage decreases, and the activity increases. When the concentration of Na2SO4 in the electrolyte is 10 mM, the best performance is obtained. When the concentration of Na2SO4 is higher, the Co3O4 OER performance decreases, which may be due to the excessive addition of sulfate, affecting the mass transfer.

[0199] Example 5

[0200] Except that the working electrode is changed from the NiFe-LDH nanometer array electrode to the NiFe-MOF, K3PO4 is changed to KClO4, and after adding KClO4, the concentration of KClO4 in the electrolyte is 0 mM, 1 mM, 2 mM, 3 mM, 4 mM, 5 mM, 10 mM, and the others are the same as in Example 1.

[0201] Table 5. Voltage at current density of 10 mA cm -2 Voltage at different KClO4 contents

[0202] As can be seen from FIG. 5 and Table 5, with the increase of the concentration of KClO4, the reaction voltage decreases, and the activity increases. When the concentration of KClO4 in the electrolyte is 4 mM, the best performance is obtained. When the concentration of KClO4 is higher, the NiFe-MOF OER performance decreases, which may be due to the excessive addition of perchlorate, affecting the mass transfer.

[0203] Example 6

[0204] Except that the working electrode is changed from the NiFe-LDH nanometer array electrode to LaCoO3, K3PO4 is changed to CF3COOK, and after adding CF3COOK, the concentration of CF3COOK in the electrolyte is 0 mM, 1 mM, 3 mM, 5 mM, 8 mM, 10 mM, 15 mM, 20 mM, 25 mM, and the others are the same as in Example 1.

[0205] Table 6. Voltage at current density of 10 mA cm -2 Voltage at different CF3COOK contents

[0206] As can be seen from FIG. 6 and Table 6, as the concentration of CF3COOK increases, the reaction voltage decreases and the activity increases, and when the concentration of CF3COOK is 15 mM, the best performance is achieved. When the concentration of CF3COOK is higher, the performance of LaCoO3 OER decreases, which may be due to the excessive addition of trifluoroacetate, affecting the mass transfer.

[0207] Example 7

[0208] Except that K3PO4 is replaced by Na2SiO3, the addition concentration is changed to 0 mM, 1 mM, 3 mM, 5 mM, 7 mM, 9 mM, and the others are the same as in Example 1.

[0209] Table 7 Voltage under different Na2SiO3 contents when the current density is 10 mA cm-2 -2

[0210] As can be seen from FIG. 7 and Table 7, as the concentration of Na2SiO3 increases, the reaction voltage decreases and the activity increases, and when 7 mM Na2SiO3 is added, the best performance is achieved. When Na2SiO3 is continuously added, the performance of NiFe-LDH OER decreases, which may be due to the excessive addition of silicate, affecting the mass transfer.

[0211] Example 8

[0212] Except that K3PO4 is replaced by Na2SeO4, the addition concentration is changed to 0 mM, 1 mM, 3 mM, 5 mM, 7 mM, 9 mM, 11 mM, 13 mM, 15 mM, 17 mM, and the others are the same as in Example 1.

[0213] Table 8 Voltage under different Na2SeO4 contents when the current density is 10 mA cm-2 -2

[0214] As can be seen from FIG. 8 and Table 8, as the concentration of Na2SeO4 increases, the reaction voltage decreases and the activity increases, and when 13 mM Na2SeO4 is added, the best performance is achieved. When Na2SeO4 is continuously added, the performance of NiFe-LDH OER decreases, which may be due to the excessive addition of selenate, affecting the mass transfer.

[0215] Example 9

[0216] Except that K3PO4 is replaced by potassium pentafluoropropionate, the addition concentration is changed to 0 mM, 2 mM, 4 mM, 6 mM, and the others are the same as in Example 1.

[0217] Table 9 Voltage under different potassium pentafluoropropionate contents when the current density is 10 mA cm-2 -2 ​​​

[0218] As can be seen from FIG. 9 and Table 9, as the concentration of potassium pentafluoropropionate increases, the reaction voltage decreases and the activity increases, and the best performance is achieved when 4 mM of potassium pentafluoropropionate is added. When more potassium pentafluoropropionate is added, the OER performance of the NiFe-LDH decreases, which may be due to the excessive addition of pentafluoropropionate, affecting the mass transfer.

[0219] Example 10

[0220] Except that K3PO4 is changed to potassium heptafluorobutyrate, the addition concentration is changed to 0 mM, 10 mM, 20 mM, and 30 mM, and the other conditions are the same as in Example 1.

[0221] Table 10 Voltage under different potassium heptafluorobutyrate contents at a current density of 10 mA cm-2 -2

[0222] As can be seen from FIG. 10 and Table 10, as the concentration of potassium heptafluorobutyrate increases, the reaction voltage decreases and the activity increases, and the best performance is achieved when 20 mM of potassium heptafluorobutyrate is added. When more potassium heptafluorobutyrate is added, the OER performance of the NiFe-LDH decreases, which may be due to the excessive addition of heptafluorobutyrate, affecting the mass transfer.

[0223] Example 11

[0224] Except that K3PO4 is changed to potassium nonafluoropentanoate, the addition concentration is changed to 0 mM, 3 mM, 6 mM, and 9 mM, and the other conditions are the same as in Example 1.

[0225] Table 11 Voltage under different potassium nonafluoropentanoate contents at a current density of 10 mA cm-2 -2

[0226] As can be seen from FIG. 11 and Table 11, as the concentration of potassium nonafluoropentanoate increases, the reaction voltage decreases and the activity increases, and the best performance is achieved when 6 mM of potassium nonafluoropentanoate is added. When more potassium nonafluoropentanoate is added, the OER performance of the NiFe-LDH decreases, which may be due to the excessive addition of nonafluoropentanoate, affecting the mass transfer.

[0227] Example 12

[0228] Except that K3PO4 is changed to potassium perfluorohexanoate, the addition concentration is changed to 0 mM, 2 mM, 4 mM, and 6 mM, and the other conditions are the same as in Example 1.

[0229] Table 12 Voltage under different potassium perfluorohexanoate contents at a current density of 10 mA cm-2 -2

[0230] ​​​As can be seen from FIG. 12 and Table 12, as the concentration of potassium perfluorohexanoate increases, the reaction voltage decreases and the activity increases, and the best performance is achieved when 4 mM of potassium perfluorohexanoate is added. When more potassium perfluorohexanoate is added, the OER performance of the NiFe-LDH decreases, which may be due to the excessive addition of perfluorohexanoate, affecting the mass transfer.

[0231] Example 13

[0232] A 6M KOH solution and a 2M K3PO4 solution were prepared, and a certain amount of the above K3PO4 solution was added to the 6M KOH solution to obtain an electrolyte, so that the K3PO4 concentration in the electrolyte was 0 mM, 2 mM, 3 mM, 4 mM, 10 mM, 30 mM, 60 mM, and 2000 mM, respectively, and the total volume of the electrolyte was 50 mL.

[0233] The above eight solutions were used as electrolytes for electrolysis of water, a platinum sheet was used as a counter electrode, and a NiFe-LDH nanometer array electrode was used as a working electrode to form a two-electrode system. The electrolysis of water was carried out at 100°C and 400 mA cm -2 Next, the stability of the electrolysis of water was tested, and the stability curves of the above eight electrolytes were measured. The results are shown in FIG. 13, and the voltage increase values after 20 h of stability testing are shown in Table 13.

[0234] Table 13 Voltage increase amount under different K3PO4 contents after 20 h of stability testing

[0235] As can be seen from FIG. 13 and Table 13, as the concentration of K3PO4 increases, the initial voltage of the stability gradually decreases, indicating that the activity increases. When the K3PO4 concentration in the electrolyte is 3 mM, the best stability is achieved, and the voltage increase amount is the smallest. When the K3PO4 concentration is higher, the stability increase amount increases, which may be due to the excessive addition of phosphate, the increase of the solution resistance, the excessive occupation of active sites on the electrode surface by the adsorption of phosphate, and the influence on the mass transfer.

[0236] Example 14

[0237] Except that the working electrode was changed to an IrO2 electrode, K3PO4 was changed to Na2CO3, the concentration was changed to 0 mM, 2 mM, 5 mM, and 10 mM, 6M KOH was changed to 0.1M NaOH, the temperature was changed to 80°C, and the others were the same as in Example 13.

[0238] Table 14 Voltage increase amount under different Na2CO3 contents after 20 h of stability testing

[0239] As can be seen from FIG. 14 and Table 14, as the concentration of Na2CO3 increases, the initial voltage decreases and the stability improves. The electrolyte with a concentration of 5 mM Na2CO3 has the best stability. When the concentration of Na2CO3 is higher, the stability decreases, which may be due to the excessive addition of carbonate, the increase of solution resistance, and the influence on mass transfer.

[0240] Example 15

[0241] Except that the working electrode is replaced by a Ni(OH)2 electrode, K3PO4 is replaced by KB(OH)4, and after the addition of KB(OH)4, the concentration of KB(OH)4 in the electrolyte is 0 mM, 2 mM, 3 mM, 5 mM, the temperature is changed from 100°C to 80°C, and the other conditions are the same as in Example 13.

[0242] Table 15 Voltage increase after 20h stability test under different KB(OH)4 contents

[0243] As can be seen from FIG. 15 and Table 15, as the concentration of KB(OH)4 increases, the initial voltage decreases and the stability improves. The electrolyte with a concentration of 3 mM KB(OH)4 has the best stability. When the concentration of KB(OH)4 is higher, the stability decreases, which may be due to the excessive addition of borate, the increase of solution resistance, and the influence on mass transfer.

[0244] Example 16

[0245] Except that the working electrode is replaced by a Co3O4 electrode, K3PO4 is replaced by Na2SO4, and after the addition of Na2SO4, the concentration is changed to 0 mM, 2 mM, 5 mM, 10 mM, 6M KOH is replaced by 2.8M NaCl (to simulate seawater) + 6M NaOH, the temperature is changed from 100°C to 80°C, and the other conditions are the same as in Example 13.

[0246] 2.8M NaCl (to simulate seawater) + 6M NaOH means a mixed solution of NaCl and NaOH, in which the concentration of NaCl is 2.8M and the concentration of NaOH is 6M.

[0247] Table 16 Voltage increase after 20h stability test under different Na2SO4 contents

[0248] As can be seen from FIG. 16 and Table 16, as the concentration of Na2SO4 increases, the initial voltage decreases and the stability improves. The electrolyte with a concentration of 5 mM Na2SO4 has the best stability. When the concentration of Na2SO4 is higher, the stability decreases, which may be due to the excessive addition of sulfate, the increase of solution resistance, and the influence on mass transfer.

[0249] Example 17

[0250] Except that the working electrode is replaced by NiFe-MOF, K3PO4 is replaced by KClO4, after adding KClO4, the concentration of KClO4 in the electrolyte is 0mM, 10mM, 15mM, 6M KOH is replaced by 9M KOH, the temperature is changed from 100℃ to -30℃, and the others are the same as Example 13.

[0251] Table 17 Voltage increase after 20h stability test under different KClO4 content

[0252] As can be seen from Figure 17 and Table 17, with the increase of KClO4 concentration, the initial voltage decreases and the stability improves, and when the concentration of KClO4 in the electrolyte is 10mM, it has the best stability, and when the concentration of KClO4 is higher, the stability decreases, which may be due to the excessive addition of perchlorate, the increase of solution resistance, and the influence of mass transfer.

[0253] Example 18

[0254] Except that the working electrode is replaced by LaCoO3, K3PO4 is replaced by CF3COOK, and the concentration is changed to 0mM, 5mM, 10mM, 20mM, 25mM, the temperature is changed from 100℃ to 80℃, and the others are the same as Example 13.

[0255] Table 18 Voltage increase after 20h stability test under different CF3COOK content

[0256] As can be seen from Figure 18 and Table 18, with the increase of CF3COOK concentration, the initial voltage decreases and the stability improves, and when the concentration of CF3COOK in the electrolyte is 10mM, it has the best stability, and when the concentration of CF3COOK is higher, the stability decreases, which may be due to the excessive addition of trifluoroacetate, the increase of solution resistance, and the influence of mass transfer.

[0257] Example 19

[0258] Prepare 6M KOH solution and add K3PO4 solution to get electrolyte, so that the concentration of K3PO4 in the electrolyte is 60mM, and the concentration of KOH is 6M solution with a total volume of 50mL.

[0259] Use the above solution as electrolyte for electrolysis of water, platinum sheet as counter electrode, NiFe-LDH nanometer array electrode as working electrode, to form a two-electrode system. At 80℃, 400mA cm -2Next, the electrolytic water stability test was performed, the stability curve of the above solution was measured, and the NiFe-LDH electrode after the stability test was rinsed and dried for XPS and EDS element mapping characterization, and the results are shown in Figures 19 and 20. It can be shown by XPS and EDS element mapping that after the stability test, the phosphate is adsorbed on the electrode surface. Since the adsorption can still be detected after being washed clean, it indicates that chemical adsorption occurs and forms a bond on the electrode surface, which is beneficial to the stability of the catalyst.

[0260] From the above analysis, it can be seen that the listed oxygen-containing acid salts have obvious promotion effect on the OER activity and stability under high temperature conditions, and different types of oxygen-containing acid salts correspond to the best concentration. The oxygen-containing acid salts include phosphate, carbonate, borate, sulfate, perchlorate, silicate, selenate, trifluoroacetate, pentafluoropropionate, heptafluorobutyrate, nonafluoropentanoate, perfluorohexanoate and other oxygen-containing acid salts. Since the oxygen-containing acid anion works, when there is no obvious effect on the electrolyte pH, adding the corresponding acid appropriately still has the same effect, for example, trifluoroacetic acid, pentafluoropropionic acid, etc. At the same time, adding one or more of them is also applicable. Among the above experimental electrolyte solutions are KOH solutions, which are also applicable to other alkali solutions, such as NaOH, simulated seawater or real seawater + NaOH or KOH or other alkalis, etc. The cations in the oxygen-containing acid salts can also be replaced by potassium ions with other cations, such as sodium ions, etc. The temperature used in this experiment is -30-100°C, which means close to the conditions of industrial application, so other similar industrial application temperatures are also applicable. The model catalyst used in this experiment is NiFe-LDH, which is also applicable to other hydrotalcites or other oxide catalysts. This experiment is carried out in a general electrolytic cell, which is also applicable to devices, etc.

[0261] Example 20

[0262] 1.1 Nickel-iron layered double hydroxide electrode loaded on nickel foam for oxygen evolution reaction activity test

[0263] A nickel-iron layered double hydroxide electrode loaded on nickel foam was prepared by a hydrothermal method. 1 millimole of nickel nitrate, 1 millimole of iron nitrate, and 8 millimoles of urea were added to 36 milliliters of water, and the solution was ultrasonically dissolved uniformly. Then the solution was transferred to a hydrothermal kettle, and a 2*3 cm 2 nickel foam was placed in the kettle. The reaction was carried out at 120 degrees Celsius for 12 hours, and the product after the reaction was a nickel-iron layered double hydroxide electrode loaded on nickel foam.

[0264] The activity of the nickel-iron layered double hydroxide supported on the nickel foam for oxygen evolution in electrolysis of seawater was tested using a standard three-electrode system. Mercury oxide was used as the reference electrode, the counter electrode was a nickel foam, and the electrolyte was an alkaline brine solution of 1.0 mole per liter sodium hydroxide and 0.5 mole per liter sodium chloride. A cyclic voltammetry scan was first performed at a scan rate of 100 millivolts per second in the range of 1.1-2 V vs RHE until the electrode reached a stable state. Then, a linear sweep was performed at a scan rate of 5 millivolts per second in the range of 1.1-2 V vs RHE. The linear sweep voltammetry curve obtained is shown in FIG. 21. As shown in FIG. 21, the overpotential of the electrode in the alkaline brine solution at a current density of 10 milliamperes per square centimeter was 268 millivolts.

[0265] 1.2 Effect of Silicate Additive on Oxygen Evolution Reaction Activity

[0266] The above experimental conditions were unchanged, and sodium silicate was additionally added to the electrolyte, so that the concentration of sodium silicate was 10 millimoles per liter. It was determined whether the addition of the silicate additive affected the oxygen evolution reaction activity of the electrode. The linear sweep voltammetry curve obtained is shown in FIG. 22. As shown in FIG. 22, the overpotential of the nickel-iron layered double hydroxide electrode supported on the nickel foam in the alkaline brine solution containing the silicate additive at a current density of 10 milliamperes per square centimeter was 268 millivolts. This indicates that the silicate additive does not affect the oxygen evolution reaction activity, and that the addition of silicate does not affect the transport of hydroxyl ions on the surface of the electrode.

[0267] 1.3 Stability Test of Oxygen Evolution Reaction after Addition of Silicate Additive in Alkaline Brine

[0268] The stability of the oxygen evolution reaction of the electrode in the alkaline brine after the addition of the silicate additive was evaluated using a two-electrode system. The nickel foam was used as the counter electrode, and the nickel-iron layered double hydroxide electrode supported on the nickel foam was used as the working electrode. The electrolyte was an alkaline brine solution containing the silicate additive, sodium hydroxide, and sodium chloride. The concentration of sodium hydroxide in the alkaline brine solution was 1.0 mole per liter, the concentration of sodium chloride was 0.5 mole per liter, and the concentration of silicate was 10 millimoles per liter. The silicate was specifically sodium silicate. The stability test was performed at a current density of 1 ampere per square centimeter, and the results are shown in FIG. 23. In the alkaline brine containing the silicate additive, the electrode could be stably operated for 1000 hours without voltage decay. This indicates that the silicate additive will be adsorbed on the surface of the electrode during electrolysis, effectively repelling chloride ions and preventing corrosion of the substrate and catalyst by the chloride ions.

[0269] Example 21 Stability Test of Oxygen Evolution Reaction after Addition of Silicate Additive in Alkaline Brine

[0270] To further increase the salt concentration to evaluate the most severe conditions that silicate additive can tolerate, the stability of the electrode in the alkaline brine after adding silicate additive was evaluated using a two-electrode system. The nickel-iron layered double hydroxide electrode loaded on the nickel foam was used as the working electrode, and the nickel foam was used as the counter electrode. The electrolyte was an alkaline brine solution containing silicate additive, sodium hydroxide, and sodium chloride. The alkaline brine solution contained 1.0 mole per liter of sodium hydroxide, 1.0 mole per liter of sodium chloride, and 10 millimoles per liter of sodium silicate. The stability test was performed at a current density of 1 ampere per square centimeter, and the results are shown in FIG. 24. In the alkaline brine containing silicate additive, the electrode can be stably operated for 500 hours without voltage decay, indicating that the silicate additive will be adsorbed on the electrode surface during electrolysis, effectively repelling chloride ions and preventing chloride ion corrosion of the substrate and catalyst.

[0271] Example 22 Stability test of oxygen evolution reaction in alkaline brine after adding silicate

[0272] To further increase the salt concentration to evaluate the most severe conditions that silicate additive can tolerate, the stability of the electrode in the alkaline brine after adding silicate additive was evaluated using a two-electrode system. The nickel-iron layered double hydroxide electrode loaded on the nickel foam was used as the working electrode, and the nickel foam was used as the counter electrode. The electrolyte was an alkaline brine solution containing silicate additive, sodium hydroxide, and sodium chloride. The alkaline brine solution contained 1.0 mole per liter of sodium hydroxide, 1.0 mole per liter of sodium chloride, and 10 millimoles per liter of sodium silicate. The stability test was performed at a current density of 1 ampere per square centimeter, and the results are shown in FIG. 24. In the alkaline brine containing silicate additive, the electrode can be stably operated for 500 hours without voltage decay, indicating that the silicate additive will be adsorbed on the electrode surface during electrolysis, effectively repelling chloride ions and preventing chloride ion corrosion of the substrate and catalyst.

[0273] FIG. 26 is a photograph of the electrode and electrolyte after 1000 hours of reaction. The electrode surface has no catalyst falling off and still maintains the original hardness, and the electrolyte remains clear. It is worth noting that the salt concentration in this example is an extremely severe test condition, indicating that silicate can effectively adsorb on the electrode surface to protect the electrode, and at an industrial current density, it is immune to the attack of high-concentration chloride ions on the catalyst and substrate, preventing corrosion and poisoning.

[0274] Example 23 Stability test of oxygen evolution reaction in alkaline brine after adding silicate

[0275] In industrial conditions, the concentration of sodium hydroxide is 6.0 moles per liter, if seawater is used as electrolyte, with water being continuously decomposed, the salt concentration in the electrolyte will continue to rise until saturation. In order to test the ability of silicate additives to repel chloride ions in saturated brine, the stability of the oxygen evolution reaction of the electrode after adding silicate additives in the alkaline brine under industrial conditions was evaluated using a two-electrode system. The counter electrode was foamed nickel, and the working electrode was foamed nickel electrode. The electrolyte was an alkaline brine solution containing silicate additives, sodium hydroxide and sodium chloride. The alkaline brine solution contains: sodium hydroxide 6.0 moles per liter, sodium chloride 3.0 moles per liter, lithium silicate 10 millimoles per liter. The stability test was carried out at 80°C and a current density of 1 ampere per square centimeter. The results are shown in Figure 27, which shows that the electrode can be operated stably for 200 hours without corrosion. This shows that the silicate anion additive corrosion prevention strategy can be applied universally to high temperature, high concentration alkaline brine environment, industrial electrodes, and silicate adsorbed on the electrode surface can effectively resist the corrosion and poisoning of chloride ions on the substrate, preventing the substrate from being corroded and disintegrated in a high concentration brine environment.

[0276] Example 24 Stability test of oxygen evolution reaction after adding silicate in alkaline low concentration brine

[0277] In order to test the corrosion prevention ability of silicate additives in ppm level low concentration alkaline brine, the electrolyte was an alkaline brine solution containing silicate additives, sodium hydroxide and low concentration sodium chloride. The alkaline brine solution contains: sodium hydroxide 1.0 moles per liter, sodium chloride 0.0001 moles per liter (0.1 millimoles per liter), sodium silicate 0.0001 moles per liter (0.1 millimoles per liter). The working electrode was a nickel-iron layered double hydroxide electrode loaded on foamed nickel. The stability test was carried out at a current density of 1 ampere per square centimeter. The results are shown in Figure 29, which shows that the electrode can be operated stably for hundreds of hours without voltage decay, proving that silicate additives not only make the anode resistant to high concentration brine corrosion, but also protect the electrode in low concentration brine, and can realize long-term stable electrolysis when desalinated seawater is used as feedstock.

[0278] Comparative Example 1 Stability test of oxygen evolution reaction without adding silicate in alkaline brine

[0279] The conditions in Example 20.3 were unchanged, but no silicate was added. The results (Figure 23) show that the nickel-iron layered double hydroxide electrode loaded on foamed nickel can only be operated for 200 hours in an alkaline brine solution containing 1.0 moles per liter of sodium hydroxide and 0.5 moles per liter of sodium chloride before being corroded, and the electrode is in a powdery state. This shows that the electrode cannot work stably under these conditions without silicate, while the electrode can be operated stably for 1000 hours without decay after adding silicate, proving the important role of silicate in corrosion prevention.

[0280] Example 2 Stability test of oxygen evolution reaction in alkaline brine without adding silicate

[0281] Example 21 The conditions remain unchanged, but no silicate is added, and the results show (Figure 24) that the nickel-iron layered double hydroxide electrode loaded on the nickel foam is corroded by chloride ions in 1.0 mol / L sodium hydroxide and 1.0 mol / L sodium chloride in the alkaline brine solution within 3 hours, while the electrode can work stably for 500 hours after adding silicate, the stability is greatly improved, which shows that silicate can be adsorbed on the surface of the electrode and can resist the attack of high-concentration chloride ions under high current density.

[0282] Example 3 Stability test of oxygen evolution reaction in alkaline brine without adding silicate

[0283] Example 22 The conditions remain unchanged, but no silicate is added, and the results show (Figure 25) that the nickel-iron layered double hydroxide electrode loaded on the nickel foam is corroded by chloride ions in 1.0 mol / L sodium hydroxide and 2.5 mol / L sodium chloride in the alkaline brine solution within 2 hours. The electrode and electrolyte photos are shown in Figure 28, which shows that in the absence of silicate, the electrode is easily attacked by chloride ions, causing the substrate to be corroded and ulcerated, and the electrode to be broken.

[0284] However, in the presence of silicate, the electrode can stably operate in such harsh environment for 1000 hours and still maintain the original physical structure (Figure 26), and no catalyst powder shedding is observed in the electrolyte, which shows that silicate not only can adsorb on the surface of the electrode to repel chloride ions, but also can stabilize the electrode structure to a certain extent to avoid catalyst shedding.

[0285] Example 4 Stability test of oxygen evolution reaction in alkaline brine without adding silicate

[0286] Example 23 The conditions remain unchanged, but no silicate is added, and the results show (Figure 27) that the nickel foam electrode is corroded by chloride ions in 1 A / cm2 current density, 80°C, in the electrolyte of 6.0 mol / L sodium hydroxide and 3.0 mol / L sodium chloride in the alkaline brine solution within 15 hours, while the electrode can stably operate for 200 hours without attenuation after adding silicate, which further proves the important role of silicate in corrosion protection.

[0287] From the above analysis, the silicate additive has obvious effect on the stability of the anode in seawater electrolysis, and the silicate including sodium silicate, potassium silicate, lithium silicate and other soluble silicates are also applicable, and adding one or more of them is also applicable. The electrolyte solution in the above experiment is an alkaline salt water solution of sodium hydroxide and sodium chloride. In essence, the key to causing electrode corrosion is the corrosion of chloride ions in alkaline salt water to the substrate. The present application confirms the anode corrosion prevention effect of silicate negative ions in electrolysis of high-concentration salt water, so other alkaline salt water solutions are also applicable, such as potassium hydroxide + sodium chloride, potassium hydroxide + potassium chloride, sodium hydroxide + real seawater, potassium hydroxide + real seawater, etc. The present experiment uses room temperature and industrial application temperature of 80°C, and other similar industrial application temperatures such as 60°C and 120°C are also applicable.

[0288] The model catalyst used in the experiment is a nickel-iron layered double hydroxide electrode supported on foamed nickel and a foamed nickel electrode. Silicate negative ions will be adsorbed on the surface of the catalyst and the substrate during the electrolysis process. Due to its large molecular radius and large number of charges, it effectively utilizes charge repulsion and steric effect to resist chloride ion attack, thereby achieving exclusion of chloride ions in high-concentration salt water and industrial current density, inhibiting corrosion of chloride ions to the substrate and chlor-oxidation competitive side reaction, and can be universally applied to all seawater electrolysis anode electrodes and catalysts. Therefore, it can be predicted that other alkaline water electrolysis industrial application metal electrodes such as foamed iron, foamed nickel-iron, nickel mesh, nickel felt, and all other metal electrodes are also applicable, and the above metal electrodes as the substrate loaded with iridium dioxide, ruthenium dioxide, nickel-iron hydrotalcite nanometer array, or other hydroxides, oxides, or any water electrolysis oxygen evolution catalyst to form seawater electrolysis oxygen evolution electrode are also applicable.

[0289] The experiment is carried out in a common electrolytic cell, and the same device is also applicable.

[0290] Example 25-NaVO3 as electrolyte additive

[0291] Preparation of CO3 2- Interlayered nickel-iron hydrotalcite

[0292] (1) 2 mmol of nickel chloride hexahydrate and 1 mmol of iron chloride nonahydrate were dissolved in 30 mL of deionized water from which CO2 had been removed (referred to as carbon-free water, and the carbon removal operation was to pass nitrogen gas at 80°C for 1 h) to prepare solution A; 0.6 g of potassium hydroxide and 0.6 g of Na2CO3 were dissolved in 30 mL of carbon-free water (deionized water from which CO2 had been removed) to obtain solution B;

[0293] (2) Under the conditions of magnetic stirring, nitrogen flow, and water bath at 60°C, the solution A and B in step (1) were mixed into 30 mL of decarbonated C by double drop method, and the pH of the mixed solution C was maintained at about 8.5, and the stirring was continued for 24 h;

[0294] (3) The obtained suspension after stirring was centrifuged for 5 times, and the washing liquid was decarbonated. The obtained gel-like product was freeze-dried to obtain CO3 2- Intercalated nickel-iron hydrotalcite.

[0295] The nickel-iron hydrotalcite was characterized:

[0296] As shown in the SEM image of FIG. 30, the CO3 2- The intercalated nickel-iron hydrotalcite was stacked by a plurality of curled or uncurled sheet-like structures, and a single sheet-like structure (sheet) was basically hexagonal, the radius of the circumscribed circle of the hexagon was 100-500 nm, that is, the size of a single sheet-like structure was 200-1000 nm, and the thickness of a single sheet-like structure was 10-20 nm. As shown in the XRD characterization of FIG. 36, the CO3 2- The intercalated nickel-iron hydrotalcite could be well compared with the standard hydrotalcite card. The inductively coupled plasma (ICP) element analysis of the hydrotalcite showed that the metal accounted for 53% as shown in Table 1.

[0297] Table 1 CO3 2- ICP element analysis table of the intercalated nickel-iron hydrotalcite

[0298] The CO3 2- The intercalated nickel-iron hydrotalcite was subjected to electrochemical activity test under the regulation of NaVO3 as an additive:

[0299] First, a working electrode was prepared. 5 mg of the prepared CO3 2- The intercalated nickel-iron hydrotalcite was placed in a small centrifuge tube, 1 mL of ethanol was added for ultrasonic dispersion, and 20 μL of 5% Nafion was added as an adhesive after uniform dispersion. The above prepared slurry was uniformly dropped on a 1 cm x 1 cm nickel foam to obtain a working electrode.

[0300] Secondly, 1M KOH solution and 0.25M NaVO3 solution were prepared, and a certain amount of NaVO3 solution was added to 1M KOH solution to obtain an electrolyte, so that the concentration of NaVO3 in the electrolyte was 0mM, 0.25mM, 0.50mM, and 0.75mM respectively. The concentration of KOH in the electrolyte was basically 1M (because the amount of NaVO3 solution added was very small), and the total volume of the electrolyte was 50 mL.

[0301] Finally, at 25°C, a three-electrode system was used, with foam nickel with catalyst dropped on it as the working electrode, a platinum sheet as the counter electrode, and mercury-mercury oxide as the reference electrode, and the above-mentioned five electrolytes as the electrolyte. The OER test was performed on the system connected to the electrochemical workstation, and the specific test item was the LSV curve. The results are shown in FIG. 42. As can be seen from FIG. 42, as the concentration of NaVO3increases, the onset potential of OER gradually decreases, meaning that the activity is improved. When the concentration of NaVO3in the electrolyte is 0.75 mM, the CO3 2- The intercalated nickel-iron hydrotalcite exhibits the best activity, with an overpotential of 341 mV.

[0302] Example 26

[0303] Preparation of VO3 - Intercalated nickel-iron hydrotalcite

[0304] (1) 2 mmol of nickel nitrate hexahydrate and 1 mmol of iron nitrate nonahydrate were weighed and dissolved in 30 mL of deionized water from which CO2had been removed (referred to as de-carbonated water, the de-carbonation operation being nitrogen bubbling for 1 h at 80°C) to obtain solution A; 0.6 g of potassium hydroxide and 0.6 g of NaVO3were dissolved in 30 mL of de-carbonated water to obtain solution B;

[0305] The concentration of the nickel salt in solution A was 0.06 mol / L, and the concentration of the iron salt was 0.03 mol / L.

[0306] The concentration of the nucleating agent potassium hydroxide in solution B was 0.35 mol / L, and the concentration of the oxygen-containing acid radical metal salt was 0.1 mol / L.

[0307] (2) Under the conditions of magnetic stirring, nitrogen bubbling, and water bath at 80°C, solutions A and B in step (1) were mixed into 30 mL of de-carbonated water C using a double-dropping method, and the pH of the mixed solution C was maintained at about 11.5, and the stirring was continued for 20 minutes;

[0308] (3) The suspension obtained after stirring was centrifuged and washed 5 times with de-carbonated water, and the obtained gel-like product was freeze-dried under vacuum to obtain VO3 - Intercalated nickel-iron hydrotalcite.

[0309] The nickel-iron hydrotalcite was characterized as follows:

[0310] As can be seen from the SEM image of FIG. 31, the VO3 - The intercalated nickel-iron hydrotalcite is formed by the stacking of multiple curled or uncurled sheet-like structures, and a single sheet-like structure (flake) is basically hexagonal, with the radius of the circumscribed circle of the hexagon being 100-500 nm, i.e., the size of a single sheet-like structure being 200-1000 nm, and the thickness of a single sheet-like structure being 10-20 nm. As can be seen from the XRD characterization of FIG. 37, the VO3- The (003) crystal plane diffraction peak of the intercalated nickel-iron hydrotalcite is shifted to a low angle compared to the conventional carbonate intercalated nickel-iron hydrotalcite, proving that VO3 - is successfully intercalated into the interlayer of the nickel-iron hydrotalcite. The results of the inductively coupled plasma (ICP) elemental analysis of the hydrotalcite are shown in Table 2, and the proportion of metals is 54.7%.

[0311] Table 2 VO3 - ICP elemental analysis table of intercalated nickel-iron hydrotalcite

[0312] VO3 - Electrochemical activity test of intercalated nickel-iron hydrotalcite under the regulation of NaVO3 as an additive:

[0313] First, the working electrode is prepared. 5 mg of the VO3 - The intercalated nickel-iron hydrotalcite is placed in a small centrifuge tube, 1 mL of ethanol is added and ultrasonically dispersed, 20 μL of 5% Nafion is added as an adhesive after uniform dispersion, and the mixture is shaken thoroughly. The prepared slurry is uniformly dropped on a 1 cm x 1 cm nickel foam to obtain a working electrode.

[0314] Secondly, 1M KOH solution and 0.25M NaVO3 solution are prepared, and a certain amount of the above NaVO3 solution is added to the 1M KOH solution to obtain an electrolyte, so that the concentration of NaVO3 in the electrolyte is 0mM, 0.25mM, 0.50mM, 0.75mM and 1mM respectively. The concentration of KOH in the electrolyte is basically 1M (because the amount of NaVO3 solution added is very small), and the total volume of the electrolyte is 50mL.

[0315] Finally, at 25°C, in a three-electrode system, the nickel foam with catalyst dropped on it is used as the working electrode, platinum sheet is used as the counter electrode, and mercury-mercury oxide is used as the reference electrode, and the above five electrolytes are used as electrolytes. The above system is connected to an electrochemical workstation for OER test, and the specific test item is CV curve. The results are shown in Figure 43. As can be seen from Figure 14, as the concentration of NaVO3 increases, the onset potential of OER gradually decreases, which means that the activity is improved. When the concentration of NaVO3 in the electrolyte is 1mM, VO3 - The intercalated nickel-iron hydrotalcite exhibits the best activity, with an overpotential of 234mV.

[0316] Example 27

[0317] Preparation of CrO4 2- Intercalated nickel-iron hydrotalcite

[0318] (1) 0.4 mmol of nickel sulfate hexahydrate and 0.2 mmol of iron sulfate nonahydrate were dissolved in 30 mL of deionized water from which CO2 had been removed (referred to as de-carbonated water, and the de-carbonation operation was carried out by passing nitrogen gas at 80°C for 1 h) to prepare solution A; 0.086 g of potassium hydroxide and 0.06 g of Na2CrO4 were dissolved in 30 mL of de-carbonated water to obtain solution B;

[0319] The concentration of the nickel salt in solution A was 0.05 mol / L, and the concentration of the iron salt was 0.025 mol / L.

[0320] The concentration of the nucleating agent potassium hydroxide in solution B was 0.05 mol / L, and the concentration of the oxygen-containing acid radical metal salt was 0.01 mol / L.

[0321] (2) Under the conditions of magnetic stirring, passing nitrogen gas, and water bath at 80°C, solutions A and B in step (1) were mixed into 30 mL of de-carbonated water C using a double-dropping method, and the pH of the mixed solution C was maintained at about 10.0, and stirring was continued for 20 minutes;

[0322] (3) The suspension obtained after stirring was centrifuged for 5 times, and the washing liquid was de-carbonated water. The obtained gel-like product was freeze-dried in vacuum to obtain CrO4 2- intercalated nickel-iron hydrotalcite.

[0323] The nickel-iron hydrotalcite was characterized as follows:

[0324] As shown in the SEM image of FIG. 32, the CrO4 2- intercalated nickel-iron hydrotalcite was stacked by multiple curled or non-curved sheet-like structures, and a single sheet-like structure (sheet) was basically hexagonal, the radius of the circumscribed circle of the hexagon was 100-400 nm, i.e., the size of a single sheet-like structure was 200-800 nm, and the thickness of a single sheet-like structure was 10-15 nm. As shown in the XRD characterization of FIG. 38, the CrO4 2- intercalated nickel-iron hydrotalcite had a (003) crystal face diffraction peak that was offset to a low angle compared to the traditional carbonate intercalated nickel-iron hydrotalcite, which proved that the CrO4 2- was successfully intercalated into the interlayer of the nickel-iron hydrotalcite.

[0325] The CrO4 2- intercalated nickel-iron hydrotalcite was subjected to electrochemical test under the regulation of the additive Na2CrO4:

[0326] First, a working electrode was prepared. 5 mg of the above-prepared CrO4 2-The intercalated nickel-iron hydrotalcite was placed in a small centrifuge tube, 1 mL of ethanol was added and ultrasonically dispersed, 20 μL of 5% Nafion was added as an adhesive, and the mixture was shaken well. The above prepared slurry was evenly dropped on a 1 cm x 1 cm nickel foam to obtain a working electrode.

[0327] Secondly, 1M KOH solution and 0.25M Na2CrO4 solution were prepared, and a certain amount of the above Na2CrO4 solution was added to the 1M KOH solution to obtain an electrolyte, so that the concentration of Na2CrO4 in the electrolyte was 0 mM, 0.25 mM, 0.50 mM, 0.75 mM and 1 mM, respectively. The concentration of KOH in the electrolyte was basically 1M (because the amount of Na2CrO4 solution added was very small), and the total volume of the electrolyte was 50 mL.

[0328] Finally, at 25°C, a three-electrode system was used, the nickel foam with catalyst was used as the working electrode, platinum was used as the counter electrode, and mercury-mercury oxide was used as the reference electrode, and the above five electrolytes were used as the electrolyte. The above system was connected to an electrochemical workstation for OER test, and the specific test item was CV curve. The results are shown in FIG. 44. As can be seen from FIG. 44, after adding Na2CrO4 to the electrolyte, the onset potential of OER is reduced, which means that the activity is improved. Unlike Example 2, the activity does not change much after increasing the concentration of Na2CrO4 in the electrolyte, which shows that a small amount of Na2CrO4 is enough to promote the OER reaction activity, and the minimum overpotential is 289 mV.

[0329] Example 28

[0330] Preparation of MoO4 2- Intercalated nickel-iron hydrotalcite

[0331] (1) 6 mmol of nickel nitrate hexahydrate and 3 mmol of iron nitrate nonahydrate were dissolved in 30 mL of deionized water (decarbonated water) to prepare solution A; 1.2 g of potassium hydroxide and 0.6 g of Na2MoO4 were dissolved in 30 mL of decarbonated water to prepare solution B;

[0332] The concentration of nickel salt in solution A was 0.06 mol / L, and the concentration of iron salt was 0.03 mol / L

[0333] The concentration of nucleating agent potassium hydroxide in solution B was 0.8 mol / L, and the concentration of oxygen-containing acid metal salt was 0.1 mol / L.

[0334] (2) Under the conditions of magnetic stirring, nitrogen flow and water bath at 80°C, solution A and B in step (1) were mixed into 30 mL of decarbonated water C by double drop method, and the pH of the mixed solution C was maintained at about 10.0, and the stirring was continued for 20 minutes;

[0335] (3) The obtained suspension after stirring was centrifugally washed for 5 times with de-carbonated water, and the obtained gel-like product was freeze-dried to obtain MoO4 2- Intercalated nickel-iron hydrotalcite

[0336] The nickel-iron hydrotalcite was characterized:

[0337] As shown in the SEM image of FIG. 33, the MoO4 2- The intercalated nickel-iron hydrotalcite was stacked by multiple curled or uncurled sheet-like structures, and the single sheet-like structure (sheet) was basically hexagonal, the radius of the circumscribed circle of the hexagon was 150-500 nm, i.e. the size of the single sheet-like structure was 300-1000 nm, and the thickness of the single sheet-like structure was 12-25 nm. As shown in the XRD characterization of FIG. 39, the MoO4 2- The (003) crystal face diffraction peak of the intercalated nickel-iron hydrotalcite was shifted to a low angle compared with the traditional carbonate intercalated nickel-iron hydrotalcite, which proved that the MoO4 2- was successfully intercalated into the interlayer of the nickel-iron hydrotalcite.

[0338] The MoO4 2- The intercalated nickel-iron hydrotalcite was subjected to electrochemical test under the regulation of the additive Na2MoO4:

[0339] First, the working electrode was prepared. 5 mg of the MoO4 2- The intercalated nickel-iron hydrotalcite was placed in a small centrifuge tube, 1 mL of ethanol was added and ultrasonically dispersed, 20 μL of 5% Nafion was added as an adhesive after uniform dispersion, and the mixture was shaken thoroughly. The above prepared slurry was uniformly dropped on a 1 cm x 1 cm foam nickel to obtain a working electrode.

[0340] Secondly, 1M KOH solution and 0.25M Na2MoO4 solution were prepared, and a certain amount of the above Na2MoO4 solution was added to the 1M KOH solution to obtain an electrolyte, so that the concentration of Na2MoO4 in the electrolyte was 0 mM, 0.25 mM, 0.50 mM, 0.75 mM and 1 mM respectively. The concentration of KOH in the electrolyte was basically 1M (because the amount of Na2MoO4 solution added was very small), and the total volume of the electrolyte was 50 mL.

[0341] Finally, at 100°C, a three-electrode system was used, with the foam nickel with catalyst as the working electrode, a platinum plate as the counter electrode, and a mercury-mercury oxide electrode as the reference electrode, and the above-mentioned five electrolytes as the electrolyte. The OER test was performed on the system connected to the electrochemical workstation, and the specific test item was the CV curve. The results are shown in FIG. 45. As can be seen from FIG. 45, after adding Na2MoO4 to the electrolyte, the onset potential of OER was reduced, indicating that the activity was improved. As in Example 27, after increasing the concentration of Na2MoO4 in the electrolyte, the activity did not change much, indicating that a small amount of Na2MoO4 was sufficient to promote the OER reaction activity, and the overpotential was as small as 299 mV.

[0342] Example 29

[0343] Preparation of WO4 - Intercalated nickel-iron hydrotalcite

[0344] (1) 2 mmol of nickel nitrate hexahydrate and 1 mmol of iron nitrate nonahydrate were weighed and dissolved in 30 mL of deionized water from which CO2 had been removed (referred to as de-carbonated water, and the de-carbonation operation was performed by passing nitrogen gas at 80°C for 1 h) to obtain solution A; 0.6 g of potassium hydroxide and 0.6 g of NaWO4 were dissolved in 30 mL of de-carbonated water to obtain solution B;

[0345] (2) Under the conditions of magnetic stirring, passing nitrogen gas, and a water bath at 80°C, solutions A and B in step (1) were mixed into 30 mL of de-carbonated water C by a double-dropping method, and the pH of the mixed solution C was maintained at about 10.0, and the stirring was continued for 20 minutes;

[0346] (3) The obtained suspension after stirring was centrifuged and washed for 5 times, and the washing liquid was de-carbonated water. The obtained gelatinous product was freeze-dried to obtain WO4 - Intercalated nickel-iron hydrotalcite.

[0347] The nickel-iron hydrotalcite was characterized as follows:

[0348] As can be seen from the SEM image of FIG. 35, the WO4 - The intercalated nickel-iron hydrotalcite was stacked by multiple curled or non-curling sheet-like structures, and the single sheet-like structure (sheet) was basically hexagonal, the radius of the circumscribed circle of the hexagon was 130-450 nm, that is, the size of the single sheet-like structure was 200-700 nm, and the thickness of the single sheet-like structure was 17-26 nm. As can be seen from the XRD characterization of FIG. 40, the WO4 - The (003) crystal face diffraction peak of the intercalated nickel-iron hydrotalcite was shifted to a low angle compared with the traditional carbonate intercalated nickel-iron hydrotalcite, which proved that the WO4 - was successfully intercalated into the interlayer of the nickel-iron hydrotalcite.

[0349] WO4 - The intercalated nickel-iron hydrotalcite was electrochemically tested under the regulation of the additive NaWO4:

[0350] First, the working electrode was prepared. 5 mg of the above-prepared WO4 - The intercalated nickel-iron hydrotalcite was placed in a small centrifuge tube, 1 mL of ethanol was added and ultrasonically dispersed, 20 μL of 5% Nafion was added as an adhesive after uniform dispersion, and the mixture was shaken thoroughly. The above-prepared slurry was uniformly dropped on a 1 cm x 1 cm nickel foam to obtain a working electrode.

[0351] Secondly, 1M KOH solution and 1M NaWO4 solution were prepared, a certain amount of the above NaWO4 solution was added to the 1M KOH solution to obtain an electrolyte, and the concentration of NaWO4 in the electrolyte was 0 mM, 0.5 mM, 1 mM and 2 mM, respectively. The concentration of KOH in the electrolyte was basically 1M (because the amount of NaWO4 solution added was very small), and the total volume of the electrolyte was 50 mL.

[0352] Finally, under a three-electrode system at -30°C, the nickel foam with the catalyst dropped thereon was used as the working electrode, a platinum sheet was used as the counter electrode, mercury-mercury oxide was used as the reference electrode, and the above four electrolytes were used as the electrolyte. The above system was connected to an electrochemical workstation for OER test, and the specific test item was LSV curve. The results are shown in FIG. 46. As can be seen from FIG. 46, as the concentration of NaWO4 increases, the onset potential of OER gradually decreases, which means that the activity is improved. When the concentration of NaWO4 in the electrolyte is 1 mM, the WO4 - The intercalated nickel-iron hydrotalcite showed the best activity, and the overpotential was the smallest, being 328 mV.

[0353] Example 30

[0354] Preparation of W2O7 2- Intercalated nickel-iron hydrotalcite

[0355] (1) 2 mmol of nickel nitrate hexahydrate and 1 mmol of iron nitrate nonahydrate were weighed and dissolved in 30 mL of deionized water from which CO2 had been removed (referred to as de-carbonated water, and the de-carbonation operation was carried out by passing nitrogen gas at 80°C for 1 h) to prepare solution A; 0.6 g of potassium hydroxide and 0.6 g of Na2W2O7 were dissolved in 30 mL of de-carbonated water to obtain solution B;

[0356] The concentration of nickel salt in solution A was 0.06 mol / L, and the concentration of iron salt was 0.03 mol / L

[0357] The concentration of nucleating agent potassium hydroxide in solution B was 0.35 mol / L, and the concentration of oxygen-containing acid radical metal salt was 0.1 mol / L.

[0358] (2) Under the conditions of magnetic stirring, nitrogen flow, and water bath at 60°C, the solution A and B in step (1) were mixed into 30 mL of decarbonated C by double-dropping method, and the pH of the mixed solution C was maintained at about 8.5, and the stirring was continued for 24 h;

[0359] (3) The obtained suspension after stirring was centrifuged for 5 times, and the washing liquid was decarbonated. The obtained gel-like product was freeze-dried to obtain W2O7 2- The intercalated nickel-iron hydrotalcite.

[0360] The nickel-iron hydrotalcite was characterized:

[0361] The SEM image of FIG. 35 shows that the W2O7 2- The intercalated nickel-iron hydrotalcite was stacked by multiple curled or uncurled sheet-like structures. The single sheet-like structure (sheet) was basically hexagonal, and the radius of the circumscribed circle of the hexagon was 130-450 nm, i.e., the size of the single sheet-like structure was 200-700 nm, and the thickness of the single sheet-like structure was 17-26 nm. The XRD characterization of FIG. 41 shows that the W2O7 2- The (003) crystal face diffraction peak of the intercalated nickel-iron hydrotalcite was shifted to a low angle compared with the traditional carbonate intercalated nickel-iron hydrotalcite, which proved that the W2O7 2- was successfully intercalated into the interlayer of the nickel-iron hydrotalcite.

[0362] The W2O7 2- The intercalated nickel-iron hydrotalcite was subjected to electrochemical test under the regulation of the additive Na2W2O7:

[0363] First, the working electrode was prepared. 5 mg of the prepared W2O7 2- The intercalated nickel-iron hydrotalcite was placed in a small centrifuge tube, 1 mL of ethanol was added for ultrasonic dispersion, and 20 μL of 5% Nafion was added as an adhesive after uniform dispersion. The above prepared slurry was uniformly dropped on a 1 cm x 1 cm nickel foam to obtain a working electrode.

[0364] Secondly, 1M KOH solution and 0.25M Na2W2O7 solution were prepared, and a certain amount of Na2W2O7 solution was added to the 1M KOH solution to obtain an electrolyte, so that the concentration of Na2W2O7 in the electrolyte was 0 mM, 0.25 mM, 0.50 mM, 0.75 mM, and 1 mM, respectively. The concentration of KOH in the electrolyte was basically 1M (because the amount of Na2W2O7 solution added was very small), and the total volume of the electrolyte was 50 mL.

[0365] Finally, at 25°C, the three-electrode system, drop the catalyst on the foam nickel as the working electrode, platinum as the counter electrode, mercury-mercury oxide as the reference electrode, using the above five kinds of electrolyte as electrolyte. The above system connected to the electrochemical workstation for OER test, the specific test project is CV curve. The results are shown in Figure 47. As can be seen from Figure 47, with the increase of Na2W2O7 concentration, the onset potential of OER gradually decreases, which means that the activity is improved. When the concentration of Na2W2O7 in the electrolyte is 1 mM, W2O7 2- The intercalated nickel-iron hydrotalcite exhibits the best activity, and the overpotential is the smallest, which is 293 mV.

[0366] Application Example 1

[0367] The VO3 - The intercalated nickel-iron hydrotalcite is subjected to electrochemical stability test under the regulation of NaVO3 additive.

[0368] First, the working electrode is prepared. Take 5 mg of the prepared VO3 - The intercalated nickel-iron hydrotalcite is placed in a small centrifuge tube, 1 mL of ethanol is added and ultrasonically dispersed, 20 μL of 5% Nafion is added as an adhesive after uniform dispersion, and the mixture is shaken thoroughly. The prepared slurry is uniformly dropped on the 1 cm x 1 cm foam nickel to obtain the working electrode.

[0369] Secondly, 1M KOH solution and 0.25M NaVO3 solution are prepared, and a certain amount of NaVO3 solution is added to 1M KOH solution to obtain electrolyte, so that the concentration of NaVO3 in the electrolyte is 0 mM, 0.25 mM, 0.50 mM, 0.75 mM and 1 mM respectively. The concentration of KOH in the electrolyte is basically 1M (because the amount of NaVO3 solution added is very small), and the total volume of the electrolyte is 50 mL.

[0370] Finally, at 80°C, the two-electrode system, drop the catalyst on the foam nickel as the working electrode, platinum as the counter electrode, using the above five kinds of electrolyte as electrolyte. The above system is connected to the stability test system, and the specific test project is 400mA cm -2 Constant current. The results are shown in Figure 48. As can be seen from Figure 48, the average voltage of the curve with 0.75 mM NaVO3 additive in the electrolyte is the lowest, and the curve with 1 mM NaVO3 additive in the electrolyte is the most stable. It shows that the addition of NaVO3 helps OER to proceed more stably, and the voltage even decreases by 0.06V in the test range.

[0371] Application Example 2 - The prepared CrO4 2-The intercalated nickel-iron hydrotalcite is subjected to electrochemical stability test under the regulation of an additive Na2CrO4.

[0372] First, the working electrode is prepared. 5 mg of the prepared CrO4 2- The intercalated nickel-iron hydrotalcite is placed in a small centrifuge tube, 1 mL of ethanol is added and ultrasonically dispersed, 20 μL of 5% Nafion is taken as an adhesive, and the slurry is uniformly dropped on a 1 cm x 1 cm foam nickel to obtain a working electrode.

[0373] Secondly, 1M KOH solution and 0.25M Na2CrO4 solution are prepared, and a certain amount of the above Na2CrO4 solution is added to the 1M KOH solution to obtain an electrolyte, so that the concentration of Na2CrO4 in the electrolyte is 0 mM, 0.25 mM, 0.50 mM, 0.75 mM and 1 mM respectively. The concentration of KOH in the electrolyte is basically 1M (because the amount of Na2CrO4 solution added is very small), and the total volume of the electrolyte is 50 mL.

[0374] Finally, under the condition of 25℃ and two-electrode system, the foam nickel with catalyst is used as the working electrode, the platinum sheet is used as the counter electrode, and the above five electrolytes are used as the electrolyte. The above system is connected to the stability test system, and the specific test items are 400mA cm -2 Constant current. The results are shown in Figure 49. As can be seen from Figure 49, the average voltage of the curve with 0.75 mM Na2CrO4 as the electrolyte additive is the lowest, and the curve with 0.75 mM Na2CrO4 as the electrolyte additive is the most stable. Subsequent addition of Na2CrO4 will increase the mass transfer burden. It shows that the addition of a certain amount of Na2CrO4 helps the OER to proceed more stably, and the voltage even decreases by 0.05V in the test range.

[0375] Application Example 3

[0376] The prepared MoO4 2- The intercalated nickel-iron hydrotalcite is subjected to electrochemical stability test under the regulation of an additive Na2MoO4.

[0377] First, the working electrode is prepared. 5 mg of the prepared MoO4 2- The intercalated nickel-iron hydrotalcite is placed in a small centrifuge tube, 1 mL of ethanol is added and ultrasonically dispersed, 20 μL of 5% Nafion is taken as an adhesive, and the slurry is uniformly dropped on a 1 cm x 1 cm foam nickel to obtain a working electrode.

[0378] Secondly, 1M KOH solution and 0.25M Na2MoO4 solution were configured, and a certain amount of the above Na2MoO4 solution was added to the 1M KOH solution to obtain an electrolyte, so that the concentration of Na2MoO4 in the electrolyte was 0mM, 0.25mM, 0.50mM, 0.75mM and 1mM respectively. The concentration of KOH in the electrolyte was basically 1M (because the amount of Na2MoO4 solution added was very small), and the total volume of the electrolyte was 50mL.

[0379] Finally, at -30℃, the foam nickel with catalyst dropped on it was used as the working electrode and platinum sheet as the counter electrode in a two-electrode system, and the above five electrolytes were used as electrolytes. The above system was connected to the stability test system, and the specific test item was 400mA cm -2 constant current. The results are shown in Figure 50. As can be seen from Figure 50, the average voltage of the curve with 1mM Na2MoO4 as the electrolyte additive is the lowest, and the curve with 1mM Na2MoO4 as the electrolyte additive is the most stable. It shows that the addition of Na2MoO4 helps the OER to proceed more stably, and the voltage even decreases by 0.07V in the test range.

[0380] Application Example 4

[0381] The prepared WO4 - The intercalated nickel-iron hydrotalcite was subjected to electrochemical stability test under the regulation of NaWO4 as an additive.

[0382] First, the working electrode was prepared. 5mg of the above prepared WO4 - The intercalated nickel-iron hydrotalcite was placed in a small centrifuge tube, 1mL of ethanol was added and ultrasonically dispersed, 20μL of 5% Nafion was added as an adhesive after uniform dispersion, and the mixture was shaken thoroughly. The above prepared slurry was uniformly dropped on the 1cm x 1cm foam nickel to obtain the working electrode.

[0383] Secondly, 1M KOH solution and 1M NaWO4 solution were configured, and a certain amount of the above NaWO4 solution was added to the 1M KOH solution to obtain an electrolyte, so that the concentration of NaWO4 in the electrolyte was 0mM, 0.5mM, 1mM and 2mM respectively. The concentration of KOH in the electrolyte was basically 1M (because the amount of NaWO4 solution added was very small), and the total volume of the electrolyte was 50mL.

[0384] Finally, at 100℃, the foam nickel with catalyst dropped on it was used as the working electrode and platinum sheet as the counter electrode in a two-electrode system, and the above four electrolytes were used as electrolytes. The above system was connected to the stability test system, and the specific test item was 400mA cm -2Constant current. The results obtained are shown in Figure 51. As can be seen from Figure 51, the lowest average voltage is the curve with 0.25 mM NaWO4 as electrolyte additive, and the most stable is the curve with 1 mM NaWO4 as electrolyte additive. This shows that the addition of NaWO4 helps the OER to proceed more stably, and the voltage even decreases by 0.03 V in the test range.

[0385] Application Example 5

[0386] The W2O7 prepared as shown in Example 30 was subjected to a stability test. 2- The intercalated nickel-iron hydrotalcite was subjected to an electrochemical stability test under the regulation of Na2W2O7 as an additive.

[0387] First, the working electrode was prepared. 5 mg of the W2O7 prepared above was taken and dispersed in 1 mL of ethanol by ultrasonic treatment. 20 μL of 5% Nafion was added as an adhesive, and the mixture was shaken well. The prepared slurry was dropped onto a 1 cm x 1 cm foam nickel to obtain the working electrode. 2- The intercalated nickel-iron hydrotalcite was placed in a small centrifuge tube, 1 mL of ethanol was added and ultrasonically dispersed, and 20 μL of 5% Nafion was added as an adhesive, and the mixture was shaken well. The prepared slurry was dropped onto a 1 cm x 1 cm foam nickel to obtain the working electrode.

[0388] Second, 1 M KOH solution and 0.25 M Na2W2O7 solution were prepared, and a certain amount of the above Na2W2O7 solution was added to the 1 M KOH solution to obtain an electrolyte, so that the concentration of Na2W2O7 in the electrolyte was 0 mM, 0.25 mM, 0.50 mM, 0.75 mM, and 1 mM, respectively. The concentration of KOH in the electrolyte was basically 1 M (because the amount of Na2W2O7 solution added was very small), and the total volume of the electrolyte was 50 mL.

[0389] Finally, at -30°C, the foam nickel with the catalyst dropped thereon was used as the working electrode, and platinum was used as the counter electrode, and the above five electrolytes were used as the electrolyte. The above system was connected to the stability test system, and the constant current was tested. The results obtained are shown in Figure 52. As can be seen from Figure 52, the lowest average voltage is the curve with 1 mM Na2W2O7 as electrolyte additive, and the most stable is the curve with 1 mM Na2W2O7 as electrolyte additive. This shows that the addition of Na2W2O7 helps the OER to proceed more stably, and the voltage decay is 0.01 V in the test range.

[0390] Application Example 6

[0391] The VO3 prepared after the stability test of Application Example 1 was subjected to a stability test. - The intercalated nickel-iron hydrotalcite was subjected to an electrochemical stability test under the regulation of Na2W2O7 as an additive.

[0392] Figure 53 is an inductively coupled plasma mass spectrometry test of the electrolyte after the stability test of Example 1, which shows that the addition of NaVO3to the electrolyte can help reduce the dissolution of the nickel and iron catalytic sites. - Figure 25 shows the X-ray photoelectron spectroscopy test of the intercalated nickel-iron hydrotalcite sample, which shows that the nickel main peak of the sample shifts to a higher binding energy relative to the conventional carbonate intercalated nickel-iron hydrotalcite, indicating that the nickel element is slightly oxidized. This slight oxidation changes the electronic structure of the nickel-iron hydrotalcite, making it have faster electron transport during the OER process, resulting in a lower onset potential for OER and faster reaction kinetics.

[0393] Figure 27 shows the Raman spectroscopy test of the VO3 - Figure 55 shows the Raman spectroscopy test of the intercalated nickel-iron hydrotalcite, which shows two high-intensity peaks at 800 cm -1 -1 belonging to metavanadate, indicating successful intercalation of metavanadate. The two peaks at 470 cm -1 -1 and 570 cm -1 -1 are peaks of nickel-iron hydrotalcite, and the former peak is smaller than that of carbonate intercalated hydrotalcite, indicating that the sample has a larger bond length, which is consistent with the XRD image in Figure 37. All the characterizations show that the intercalation of metal oxides increases the interlayer distance and exposes more edge active sites, and the oxidizing property of metal oxides oxidizes nickel, making the intrinsic active sites more active, which ultimately leads to better activity. The presence of metal oxoacid ions as additives in the electrolyte can help nickel-iron hydrotalcite exchange interlayer anions during OER to obtain greater activity, and can help stabilize nickel-iron hydrotalcite to reduce dissolution, ultimately achieving the effect of stabilizing the catalyst.

[0394] Comparative Example 5

[0395] Figure 27 shows the Raman spectroscopy test of the VO3 2- intercalated nickel-iron hydrotalcite prepared as shown in Example 25 and the VO3 - intercalated nickel-iron hydrotalcite prepared as shown in Example 26. First, prepare the working electrode as shown in Examples 25 and 26; second, prepare 50 mL of 1M KOH solution; finally, in a three-electrode system with mercury oxide as the reference electrode, platinum sheet as the counter electrode, and the prepared electrode as the working electrode, connect the electrochemical workstation for testing. The obtained CV results are shown in Figure 56, which shows that by changing the non-metallic oxygen-containing acid intercalated in the hydrotalcite to a metallic oxygen-containing acid, higher activity can be obtained without adding any additives to the electrolyte, which helps to accelerate the OER process.

[0396] Based on all the above examples and analysis, it is found that in the temperature range of -30~100℃ (meaning close to the conditions of industrial application), metal oxides as interlayer anions of nickel-iron oxide and as electrolyte additives of alkaline solution can help to significantly improve the activity and stability of the nickel-iron hydrotalcite catalytic OER system. In this experiment, nickel-iron hydrotalcite is used as a model catalyst, and other hydrotalcites or other metal hydroxides and other catalysts also have this effect. This experiment is carried out in a common electrolytic cell, and the same applies to transducer devices.

[0397] Example 31 High-temperature, high-salt, and high-alkaline concentration with the addition of metal oxysalt

[0398] The working electrode is a NiFe-LDH nanometer array electrode, the counter electrode is a nickel foam electrode, and the electrolyte is an aqueous solution containing NaOH and NaCl, with the concentration of NaOH being 8M and the concentration of NaCl being 2M. The operating temperature is 100℃, and the current density is 1A cm -2 The ammonium niobium oxalate, potassium ferricyanide, zinc chloride, sodium aluminate, and tin chloride are added to the electrolyte, and the concentration of each is 0.01M. Figure 57 is a high-temperature OER (oxygen evolution) reaction stability curve of the electrode in the electrolyte with the additional addition of niobate, ferricyanide, zincate, aluminate, and stannate.

[0399] As can be seen from Figure 57, the electrode can be stably operated for 100 hours without significant voltage decay, which confirms the role of metal oxysalt in maintaining the stability of the electrode under high-temperature, high-salt concentration, and high-alkaline concentration conditions.

[0400] Example 32 Low-temperature, high-alkaline concentration with the addition of metal oxysalt

[0401] The working electrode is a NiFe-LDH nanometer array electrode, and the counter electrode is a nickel foam electrode. The electrolyte is a 6M NaOH aqueous solution, and the operating temperature is -30℃, and the current density is 0.1A cm -2 The ammonium niobium oxalate, sodium ferricyanide, zinc nitrate, aluminum chloride, and tin nitrate are added to the electrolyte, and the concentration of each is 0.01M. Figure 58 is a low-temperature OER (oxygen evolution) reaction stability curve of the electrode in the electrolyte with the additional addition of niobate, ferricyanide, zincate, aluminate, and stannate.

[0402] As can be seen from Figure 58, the electrode can be stably operated for 100 hours without significant voltage decay, which confirms the role of metal oxysalt in maintaining the stability of the electrode under low-temperature conditions.

[0403] Example 33 Mixed addition of non-metal, metal, and organic oxysalt

[0404] The working electrode is a NiFe-LDH nanorarray electrode, and the counter electrode is a nickel foam electrode. The electrolyte is an aqueous solution containing NaOH and NaCl, the concentration of NaOH is 8 M, and the concentration of NaCl is 2 M. The operating temperature is 100°C, and the current density is 1 A cm -2 Sodium silicate, potassium trifluoroacetate, and tin chloride were additionally added to the electrolyte, respectively. After the addition, the concentration of sodium silicate was 5 mM, the concentration of potassium trifluoroacetate was 5 mM, and the concentration of stannate was 5 mM. FIG. 59 is a high-temperature OER (oxygen evolution) reaction stability curve of the electrode in the electrolyte additionally containing sodium silicate, potassium trifluoroacetate, and tin chloride, respectively. As shown in FIG. 59, the electrode can be stably operated for 100 hours without obvious voltage attenuation, which confirms the effect of mixed addition of nonmetallic oxygen-containing acid radicals and metallic oxygen-containing acid radicals on maintaining the stability of the electrode under high temperature, high salt concentration, and high alkali concentration.

[0405] It can be proved that the nonmetallic oxygen-containing acid radicals and the metallic oxygen-containing acid radicals in the application can be used alone or in any combination to maintain the stability of the electrode.

[0406] The above examples are only examples for clear illustration, and do not limit the embodiments, and the obvious changes or changes derived therefrom are still within the protection scope of the application.

[0407] In summary, the application provides an electrolyte additive for improving the performance of water electrolysis reaction, an electrolyte and an electrolyte solution, and a method for improving the performance of water electrolysis reaction. The additive is a nonmetallic oxygen acid salt (sulfate, phosphate, borate, selenate, silicate, carbonate, perchlorate, trifluoroacetate, etc.) and an aqueous solution thereof, and a metallic oxygen acid salt (molybdate, tungstate, vanadate, chromate, niobate, ferricyanide, zincate, aluminate, stannate, etc.) and an aqueous solution thereof, which are used as an electrolyte additive for water electrolysis reaction. The application also provides the use of oxygen acid salts for improving the oxygen evolution activity and stability of water electrolysis. In particular, it is also applicable to electrolysis reactions at high and low temperatures (-30-100°C). The addition of the oxygen acid salts in the application reduces the oxygen evolution reaction potential, reduces the charge transfer resistance, accelerates the electron transfer rate, and has faster chemical reaction kinetics, which are all conducive to the improvement of the reaction activity.

Claims

1. An electrolyte additive for improving the performance of an electrolytic water reaction, characterized by, The electrolyte additive comprises one or several non-metallic oxyanions or metallic oxyanions.

2. The electrolyte additive according to claim 1, characterized in that, The non-metallic oxyanions are selected from one or several inorganic oxyanions or organic oxyanions.

3. The electrolyte additive according to claim 2, characterized in that, The inorganic oxyanions are selected from one or several of phosphates, carbonates, borates, sulfates, perchlorates, selenates, silicates. The organic oxyanions are selected from one or several of trifluoroacetates, pentafluoropropionates, heptafluorobutyrates, nonafluoropentanoates, perfluorohexanoates.

4. The electrolyte additive according to claim 1, characterized in that, The metallic oxyanions are selected from one or several of molybdates, tungstates, vanadates, chromates, niobates, ferricyanides, zincates, aluminates, stannates.

5. The electrolyte additive according to claim 1, characterized in that, The metallic oxyanions are from metallic oxyanion salts selected from one or several of vanadates, chromates, molybdates, tungstates, niobates, ferricyanides, zincates, aluminates, stannates.

6. The electrolyte additive according to claim 1, characterized in that, The improvement of the electrolysis water reaction performance refers to preventing the anode corrosion of electrolysis seawater. The non-metallic oxyanions are silicate anions, which are derived from water-soluble silicates.

7. An electrolyte for improving the performance of an electrolytic water reaction, characterized by, The electrolyte comprises alkali and non-metallic oxyanion salts.

8. The electrolyte of claim 6, wherein, The improvement of the electrolysis water reaction performance refers to preventing the anode corrosion of electrolysis seawater. The non-metallic oxyanions are silicates.

9. A method of improving the performance of an electrolysis water reaction, characterized by, The method comprises using a solution containing oxyanions as the electrolyte for the electrolysis water oxygen evolution reaction.

10. The method of claim 9, wherein, The electrolyte is an alkaline solution. The oxyanions are selected from one or several inorganic oxyanions or organic oxyanions.

11. The method of claim 9, wherein, The inorganic oxyanions are selected from one or several of phosphates, carbonates, borates, sulfates, perchlorates, selenates, silicates; the organic oxyanions are selected from one or several of trifluoroacetates, pentafluoropropionates, heptafluorobutyrates, nonafluoropentanoates, perfluorohexanoates.

12. The method of claim 9, wherein, The oxyanions are derived from oxyanion salts selected from one or several of K3PO4, K2CO3, KB(OH)4, K2SO4, KClO4, CF3COOK, Na3PO4, Na2CO3, NaB(OH)4, Na2SO4, NaClO4, CF3COONa, Na2SeO4, Na2SiO3, potassium pentafluoropropionate, potassium heptafluorobutyrate, potassium nonafluoropentanoate, potassium perfluorohexanoate; the electrolysis water oxygen evolution reaction temperature is -30-100℃.

13. The method of claim 9, wherein, The improvement of the electrolysis water reaction performance refers to preventing the anode corrosion of electrolysis seawater. The oxyanions are silicate anions, and the electrolyte is an alkaline electrolyte.

14. The method of claim 13, wherein, The method can make the anode of electrolysis seawater resistant to corrosion of salts with a chlorine ion concentration of 0.0001-3.0 moles per liter.

15. A method of improving the performance of an electrolysis water reaction, characterized by, The method comprises using nickel-iron hydrotalcite as the anode catalyst for alkaline electrolysis water. The nickel-iron hydrotalcite is intercalated with metallic oxyanions selected from one or several of vanadates, chromates, molybdates, tungstates.

16. An electrolyte for electrolysis of water for oxygen evolution, characterized by The electrolyte comprises oxyanions.

17. A method of oxygen evolution from water electrolysis, characterized by, The electrolyte containing oxyanion salts is electrolyzed at a temperature of -30-100℃.

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