Catalytic electrode and method of forming the same and electrolysis device

Abstract

A catalytic electrode includes a nickel-based porous base material, and a plurality of catalytic alloy balls of nickel and another metal doped with elements, in which the another metal includes iron, the elements include C, F, and S, and the catalytic alloy balls are dispersed on the surface of the nickel-based porous base material. The catalytic electrode also includes a plurality of metal phosphide particles covering the nickel-based porous base material and the catalytic alloy balls, and the metal phosphide particle includes nickel phosphide, nickel iron phosphide, nickel cobalt phosphide, nickel copper phosphide, or nickel zinc phosphide.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is based on, and claims priority from, Taiwan Application Serial Number 113145978, filed on Nov. 28, 2024, the disclosure of which is hereby incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] The technical field relates to catalytic electrodes and a method of forming the same.BACKGROUND

[0003] An oxygen evolution reaction (OER) is a multi-step electron transfer process with a slow reaction dynamic and a high overpotential. Noble metal-based catalysts (e.g., IrO2 and RuO2) are considered as the most advanced OER electrocatalysts, as they have high catalytic performance under harsh reaction conditions. However, the noble metal-based ones are rare and expensive, which hinder their large-scale application in electrolysis technology. The abundant transition metal (especially nickel-based catalysts) serving as alternatives to noble metal catalysts are promising candidates for OER catalysts due to their low cost and high catalytic activity. However, an enhancement is still needed in the number and catalytic activity of the active sites to further improve the electrochemical performance of nickel-based catalysts.SUMMARY

[0004] One embodiment of the disclosure provides a catalytic electrode, including: a nickel-based porous base material; a plurality of catalytic alloy balls of nickel and another metal doped with elements, wherein the another metal includes iron, the elements include C, F, and S, and the catalytic alloy balls are dispersed on the surface of the nickel-based porous base material; and a plurality of metal phosphide particles covering the nickel-based porous base material and the catalytic alloy balls, and the metal phosphide particles include nickel phosphide, nickel iron phosphide, nickel cobalt phosphide, nickel copper phosphide, or nickel zinc phosphide.

[0005] In some embodiments, the nickel-based porous base material includes nickel mesh, nickel foam, or nickel felt.

[0006] In some embodiments, the nickel and the iron in the catalytic alloy balls have a molar ratio of 2:1 to 4:1.

[0007] In some embodiments, the another metal in the catalytic alloy balls further includes cobalt, and the cobalt and the iron in the catalytic alloy balls have a molar ratio of greater than 0 and less than or equal to 6:1.

[0008] In some embodiments, the doped C occupies 1 to 25 atomic % of the catalytic alloy balls, the doped F occupies 1 to 25 atomic % of the catalytic alloy balls, and the doped S occupies 1 to 15 atomic % of the catalytic alloy balls.

[0009] In some embodiments, the elements doped in the catalytic alloy balls further include P, and the doped P occupies greater than 0 and less than or equal to 15 atomic % of the catalytic alloy balls.

[0010] One embodiment of the disclosure provides an electrolysis device, including: an anode; a cathode; and an aqueous solution in contact with the anode and the cathode, wherein the anode or the cathode is the described catalytic electrode.

[0011] One embodiment of the disclosure provides a method of forming a catalytic electrode, including: mixing layered double hydroxide (LDH) and metal hydroxide (M(OH)x) of nickel and another metal with solvent and binder to form an ink, wherein the another metal includes iron; coating the ink onto a nickel-based porous base material, baking the ink dry and then sintering the dried ink under hydrogen, thereby alloying the nickel and the another metal to form a plurality of catalytic alloy balls dispersed on the surface of the nickel-based porous base material, and doping elements of the binder into the catalytic alloy balls, wherein the elements include C, F, and S; and forming a plurality of metal phosphide particles to cover the nickel-based porous base material and the catalytic alloy balls, and the metal phosphide particles include nickel phosphide, nickel iron phosphide, nickel cobalt phosphide, nickel copper phosphide, or nickel zinc phosphide.

[0012] In some embodiments, the layered double hydroxide and metal hydroxide of nickel and another metal are formed by following step: mixing an aqueous solution of nickel salt and another metal salt with an alkaline solution containing sodium hydroxide.

[0013] In some embodiments, the ink further includes an anionic surfactant, a neutral surfactant, or a combination thereof, and the step of sintering the dried ink under hydrogen dopes elements of the anionic surfactant, neutral surfactant, or a combination thereof into the catalytic alloy balls, and the elements of the anionic surfactant, neutral surfactant, or a combination thereof include C, S, P, or a combination thereof.

[0014] In some embodiments, the binder includes a copolymer of perfluorosulfonic acid and tetrafluoroethylene, polytetrafluoroethylene, or a combination thereof.

[0015] A detailed description is given in the following embodiments.DETAILED DESCRIPTION

[0016] In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details.

[0017] One embodiment of the disclosure provides a method of forming a catalytic electrode, including: mixing layered double hydroxide (LDH) and metal hydroxide (M(OH)x) of nickel and another metal with solvent and binder to form an ink, wherein the another metal includes iron. For example, mixing sodium hydroxide and sodium carbonate (or sodium phosphate or sodium hypophosphite) in water to form an alkaline solution. Nickle salt (e.g., nickel chloride or nickel nitrate) and another metal salt (e.g., iron chloride or iron nitrate) are dissolved in water to form an aqueous solution. In some embodiments, the nickel and the iron have a molar ratio of 2:1 to 4:1. If the nickel amount is too low, the active sites will be insufficient. If the nickel amount is too high, the catalyst will aggregate. In some embodiments, the another metal may further include cobalt, and the another metal salt may include cobalt chloride or cobalt nitrate. In some embodiments, the cobalt and the iron have a molar ratio of greater than 0 and less than or equal to 6:1. If the cobalt amount is too high, the catalytic activity of the subsequently formed LDH and metal hydroxide will be low. The aqueous solution of the metal salt is heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of the metal salt until the pH value reaching 8.5 to 12, thereby forming LDH and metal hydroxide of nickel and another metal through a reaction. The reaction result is centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid (e.g., LDH and metal hydroxide of nickel and another metal) is heated until dry. Note that the above method of forming LDH and metal hydroxide of nickel and another metal is only for illustration rather than liming the disclosure thereto. One skilled in the art my adopt any suitable method to form LDH and metal hydroxide of nickel and another metal, and is not limited by the above method.

[0018] Subsequently, the solid (e.g., LDH and metal hydroxide of nickel and another metal), the solvent, and the binder can be mixed to form an ink. In some embodiments, the solvent includes water and alcohol. In some embodiments, the solid (e.g., LDH and metal hydroxide of nickel and another metal) and the solvent have a weight ratio of 1:400 to 1:450. If the solvent amount is too less, the precipitation will occur due the insufficient dispersity. If the solvent is too much, it may take too much time to prepare the catalytic electrode. In some embodiments, the binder includes a copolymer of perfluorosulfonic acid and tetrafluoroethylene (e.g., Nafion), polytetrafluoroethylene (PTFE), or a combination thereof. If the binder amount is too less, the catalyst will have a poor adhesion and be easily spalled during electrolysis. If the binder is too much, it may cover the active sites of the catalyst, block the electrode, and cause mass transfer issues.

[0019] The ink was coated onto a nickel-based porous base material, heated until dry, and then sintered under hydrogen, thereby alloying the nickel and the another metal to form a plurality of catalytic alloy balls dispersed on the surface of the nickel-based porous base material, and doping elements of the binder into the catalytic alloy balls. The nickel-based porous base material can be nickel mesh, nickel foam, or nickel felt. The sintering temperature can be 400° C. to 500° C. If the sintering temperature is too low, the nickel and the another metal cannot be alloyed to form the catalytic alloy balls, and the binder cannot be decomposed to dope the elements (e.g., C, F, and S elements of Nafion) into the catalytic alloy. If the sintering temperature is too high, the catalytic particles will be too large, and the reaction surface area will be decreased.

[0020] Subsequently, a plurality of metal phosphide particles are formed to cover the nickel-based porous base material and the catalytic alloy balls, and the metal phosphide particles include nickel phosphide, nickel iron phosphide, nickel cobalt phosphide, nickel copper phosphide, or nickel zinc phosphide. In some embodiments, the metal phosphide particles may connect to each other, but pores (such as parts that are not connected) are remained between the metal phosphide particles. For example, nickel sulfate, sodium acetate, lactic acid, saccharin, surfactant (e.g., anionic surfactant, neutral surfactant, or a combination thereof), and de-ionized water are formulated to form an aqueous solution, and its pH value was adjusted to 4.0 to 5.5. Sodium hypophosphite is dissolved in deionized water. The aqueous solution containing nickel ions is heated to 60° C. to 100° C., and the nickel-based porous base material with the catalytic alloy balls loaded thereon is disposed in the aqueous solution containing nickel ions. Subsequently, the aqueous solution of sodium hypophosphite is added to the aqueous solution containing nickel ions, thereby growing nickel phosphide particles to cover the nickel-based porous base material and the catalytic alloy balls. In some embodiments, the aqueous solution containing nickel ions is heated to 80° C. to 85° C., and the nickel-based porous base material with the catalytic alloy balls loaded thereon is disposed in the aqueous solution containing nickel ions. Subsequently, the aqueous solution of sodium hypophosphite is added to the aqueous solution containing nickel ions, thereby growing nickel phosphide particles to cover the nickel-based porous base material and the catalytic alloy balls.

[0021] Alternatively, the nickel sulfate, copper chloride, cobalt chloride, zinc sulfate, ammonium ferrous sulfate, disodium succinate, sodium sulfate, sodium hypophosphite, and deionized water are formulated to prepare an aqueous solution. Subsequently, the nickel-based porous base material with the catalytic alloy balls loaded thereon is disposed in the aqueous solution containing metal ions, thereby growing metal phosphide particles to cover the nickel-based porous base material and the catalytic alloy balls. The metal phosphide particles include nickel phosphide, nickel iron phosphide, nickel cobalt phosphide, nickel copper phosphide, or nickel zinc phosphide, which may prevent the catalytic alloy balls from spalling from the nickel-based porous base material. The metal phosphide will not degrade the catalytic activity of the catalytic alloy balls. It should be understood that the method of forming the metal phosphide particles is only for illustration rather than limiting the disclosure thereto. One skilled in the art my adopt any suitable method to form the metal phosphide particles, and is not limited by the above method.

[0022] In some embodiments, the ink further includes an anionic surfactant, neutral surfactant, or a combination thereof. In some embodiments, the solid (e.g., LDH and metal hydroxide of nickel and another metal) and the surfactant have a weight ratio of greater than 0 and less than or equal to 1:4. If the surfactant amount is too high, it will block the active sites of the catalyst. The step of sintering under hydrogen will dope several elements of the anionic surfactant, the neutral surfactant, or a combination thereof into the catalytic alloy balls, and the elements of the surfactant include C, S, P, or a combination thereof. For example, the anionic surfactant can be sodium dodecyl sulfate (SDS), dioctyl sodium sulfosuccinate (DSS), lauryl phosphate (LP), or a combination thereof. The neutral surfactant includes polyoxyethylene sorbitan monolaurate (Tween20), polyoxyethylene sorbitan monooleate (Tween80), octylphenyl polyoxyethylene ether (Triton X-100), polyoxyethylene (5) nonylphenyl ether (IGEPAL CO-520), sorbitan laurate (Span20), lauryl alcohol polyoxyethylene ether (Brij-30), or a combination thereof.

[0023] The catalytic electrode obtained from the described method may include a nickel-based porous base material; a plurality of catalytic alloy balls of nickel and another metal doped with elements, wherein the another metal includes iron, the elements include C, F, and S, and the catalytic alloy balls are dispersed on the surface of the nickel-based porous base material; and a plurality of metal phosphide particles covering the nickel-based porous base material and the catalytic alloy balls, and the metal phosphide particles include nickel phosphide, nickel iron phosphide, nickel cobalt phosphide, nickel copper phosphide, or nickel zinc phosphide.

[0024] In some embodiments, the doped C occupies 1 to 25 atomic % of the catalytic alloy balls, the doped F occupies 1 to 25 atomic % of the catalytic alloy balls, and the doped S occupies 1 to 15 atomic % of the catalytic alloy balls. If the amount of the doped C and the doped F in the catalytic alloy balls is too low, the metal will aggregate. If the amount of the doped C in the catalytic alloy balls is too high, the active sites of the alloy balls will be blocked. If the amount of the doped S in the catalytic alloy balls is too low, it will not be beneficial to form Ni of high valent state, and the electron synergy cannot be efficiently achieved. If the amount of the doped S in the catalytic alloy balls is too high, the active sites of the alloy balls will be blocked. In some embodiments, the elements doped in the catalytic alloy balls further include P, and the doped P occupies greater than 0 and less than or equal to 15 atomic % of the catalytic alloy balls. If the amount of the doped P in the catalytic alloy balls is too high, the active sites of the alloy balls will be blocked. It should be understood that the doping elements in the catalytic alloy balls mainly come from the binder and the optional anionic surfactant, neutral surfactant, or a combination thereof in the ink of the described method. In other words, the amount of the doping elements that is too low or too high means that the binder amount (and the surfactant amount) is too low or too high.

[0025] One embodiment of the disclosure provides an electrolysis device, including: an anode; a cathode; and an aqueous solution in contact with the anode and the cathode, wherein the anode or the cathode is the described catalytic electrode. In some embodiments, the anode is the described catalytic electrode. As shown in experiments, the catalytic electrode of the disclosure may greatly improve the performance of the electrolysis device such as an AEM stack.

[0026] Below, exemplary embodiments will be described in detail so as to be easily realized by a person having ordinary knowledge in the art. The inventive concept may be embodied in various forms without being limited to the exemplary embodiments set forth herein.EXAMPLES

[0027] In following Examples, the electrocatalytic characteristics of the three electrodes were measured by the parameters as below. The working electrode was the self-prepared electrode of 1×1 cm2. The reference electrode was Hg / HgO. The counter electrode was Pt wire. The electrolyte was 1M KOH. The testing temperature was 25° C. The scan rate of linear sweep voltammetry (LSV) was 5 mV / s, the scan range of OER was 1.2 V to 2.0 V (vs. RHE), and the scan range of HER was 0.1 V to −0.70 V (vs. RHE). The data were compensated with iR ranging from 85% to 95% (85% was major in experiments). The above measurement may refer to Catalysts 2023, 13 (3), 586.

[0028] In following examples, the element ratios of the catalyst were analyzed by EDS, and the structures of the catalyst were analyzed by SEM.Example 1-1

[0029] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscillation was applied for 30 minutes, and 0.05 mL of Nafion solution (5 wt % of a copolymer of perfluorosulfonic acid and tetrafluoroethylene, D2020CS commercially available from Chemours) was added to the mixture and then ultrasonic oscillation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 252 mV for a current density of 10 mA / cm2, an overpotential of 312 mV for a current density of 50 mA / cm2, and an overpotential of 348 mV for a current density of 100 mA / cm2. By the way, the nickel mesh (without the solid loaded thereon) had an overpotential of 348 mV for a current density of 10 mA / cm2, an overpotential of 428 mV for a current density of 50 mA / cm2, and an overpotential for a current density of 100 mA / cm2 could not be measured in the electro catalytic measurement range due to the poor performance of the nickel mesh. The ruthenium oxide (loaded on the nickel mesh) had an overpotential of 275 mV for a current density of 10 mA / cm2, an overpotential of 368 mV for a current density of 50 mA / cm2, and an overpotential of 427 mV for a current density of 100 mA / cm2.

[0030] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O, 2.70 g of FeCl3·6H2O, and 1.19 g of CoCl2·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:0.5) was 2 mg / cm2. This catalyst had an overpotential of 284 mV for a current density of 10 mA / cm2, an overpotential of 343 mV for a current density of 50 mA / cm2, and an overpotential of 386 mV for a current density of 100 mA / cm2.

[0031] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O, 2.70 g of FeCl3·6H2O, and 2.38 g of CoCl2·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:1) was 2 mg / cm2. This catalyst had an overpotential of 291 mV for a current density of 10 mA / cm2, an overpotential of 353 mV for a current density of 50 mA / cm2, and an overpotential of 394 mV for a current density of 100 mA / cm2.

[0032] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O, 2.70 g of FeCl3·6H2O, and 4.76 g of CoCl2·6H2O were dissolved in 500 ml of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:2) was 2 mg / cm2. This catalyst had an overpotential of 294 mV for a current density of 10 mA / cm2, an overpotential of 358 mV for a current density of 50 mA / cm2, and an overpotential of 405 mV for a current density of 100 mA / cm2.

[0033] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O, 2.70 g of FeCl3·6H2O, and 9.52 g of CoCl2·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:4) was 2 mg / cm2. This catalyst had an overpotential of 307 mV for a current density of 10 mA / cm2, an overpotential of 368 mV for a current density of 50 mA / cm2, and an overpotential of 412 mV for a current density of 100 mA / cm2.

[0034] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O, 2.70 g of FeCl3·6H2O, and 14.28 g of CoCl2·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:6) was 2 mg / cm2. This catalyst had an overpotential of 313 mV for a current density of 10 mA / cm2, an overpotential of 379 mV for a current density of 50 mA / cm2, and an overpotential of 423 mV for a current density of 100 mA / cm2.

[0035] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 9.52 g of CoCl2·6H2O was dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., cobalt hydroxide) was 2 mg / cm2. This catalyst had an overpotential of 356 mV for a current density of 10 mA / cm2, an overpotential of 428 mV for a current density of 50 mA / cm2, and an overpotential for a current density of 100 mA / cm2 could not be measured in the electrocatalytic measurement range due to the poor performance of the catalyst.

[0036] As shown in Example 1-1, the catalytic activity of LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions was higher than that of RuO2. When LDH and metal hydroxide further included cobalt, the catalytic activity of LDH and metal hydroxide was decreased as the cobalt amount increased, but its catalytic activity was still higher than that of RuO2.Example 1-2

[0037] The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) loaded on the nickel mesh in Example 1-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 242 mV for a current density of 10 mA / cm2, an overpotential of 283 mV for a current density of 50 mA / cm2, and an overpotential of 304 mV for a current density of 100 mA / cm2. By the way, the nickel mesh (without catalyst loaded thereon) after being sintered at 400° C. under hydrogen for 5 hours had an overpotential of 320 mV for a current density of 10 mA / cm2, an overpotential of 376 mV for a current density of 50 mA / cm2, and an overpotential of 410 mV for a current density of 100 mA / cm2.

[0038] The solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:0.5) loaded on the nickel mesh in Example 1-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel, iron, and cobalt to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 239 mV for a current density of 10 mA / cm2, an overpotential of 279 mV for a current density of 50 mA / cm2, and an overpotential of 301 mV for a current density of 100 mA / cm2.

[0039] The solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:1) loaded on the nickel mesh in Example 1-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel, iron, and cobalt to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 249 mV for a current density of 10 mA / cm2, an overpotential of 291 mV for a current density of 50 mA / cm2, and an overpotential of 314 mV for a current density of 100 mA / cm2.

[0040] The solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:2) loaded on the nickel mesh in Example 1-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel, iron, and cobalt to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 252 mV for a current density of 10 mA / cm2, an overpotential of 294 mV for a current density of 50 mA / cm2, and an overpotential of 318 mV for a current density of 100 mA / cm2.

[0041] The solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:4) loaded on the nickel mesh in Example 1-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel, iron, and cobalt to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 249 mV for a current density of 10 mA / cm2, an overpotential of 287 mV for a current density of 50 mA / cm2, and an overpotential of 310 mV for a current density of 100 mA / cm2.

[0042] The solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:6) loaded on the nickel mesh in Example 1-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel, iron, and cobalt to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 255 mV for a current density of 10 mA / cm2, an overpotential of 294 mV for a current density of 50 mA / cm2, and an overpotential of 321 mV for a current density of 100 mA / cm2.

[0043] As shown in Example 1-2, the catalytic activity of the catalytic alloy after being sintered under hydrogen was better than that of LDH and metal hydroxide before being sintered under hydrogen. The amount of cobalt did not influence the catalytic activity of the catalytic alloy.Example 2-1

[0044] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 252 mV for a current density of 10 mA / cm2, an overpotential of 312 mV for a current density of 50 mA / cm2, and an overpotential of 348 mV for a current density of 100 mA / cm2.

[0045] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 7.13 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 3:1) was 2 mg / cm2. This catalyst had an overpotential of 239 mV for a current density of 10 mA / cm2, an overpotential of 314 mV for a current density of 50 mA / cm2, and an overpotential of 357 mV for a current density of 100 mA / cm2.

[0046] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 9.51 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 4:1) was 2 mg / cm2. This catalyst had an overpotential of 233 mV for a current density of 10 mA / cm2, an overpotential of 304 mV for a current density of 50 mA / cm2, and an overpotential of 342 mV for a current density of 100 mA / cm2.

[0047] As shown in Example 2-1, when the iron and the nickel in LDH and metal hydroxide had a molar ratio of 2:1 to 4:1, the catalyst had similar catalytic activities.Example 2-2

[0048] The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) loaded on the nickel mesh in Example 2-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 257 mV for a current density of 50 mA / cm2 and an overpotential of 280 mV for a current density of 100 mA / cm2.

[0049] The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 3:1) loaded on the nickel mesh in Example 2-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 268 mV for a current density of 50 mA / cm2 and an overpotential of 295 mV for a current density of 100 mA / cm2.

[0050] The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 4:1) loaded on the nickel mesh in Example 2-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 257 mV for a current density of 50 mA / cm2 and an overpotential of 282 mV for a current density of 100 mA / cm2.

[0051] As shown in Example 2-2, the catalytic activity of the catalytic alloy after being sintered under hydrogen was better than that of LDH and metal hydroxide before being sintered under hydrogen. The catalytic alloy with different ratios of nickel and iron had similar catalytic activities.Example 3-1

[0052] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 252 mV for a current density of 10 mA / cm2, an overpotential of 312 mV for a current density of 50 mA / cm2, and an overpotential of 348 mV for a current density of 100 mA / cm2.

[0053] 5.76 g of sodium hydroxide and 5.72 g of sodium hypophosphite (NaH2PO2·H2O) were dissolved in 80 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 80 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and hypophosphite ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 239 mV for a current density of 10 mA / cm2, an overpotential of 295 mV for a current density of 50 mA / cm2, and an overpotential of 322 mV for a current density of 100 mA / cm2.

[0054] 5.76 g of sodium hydroxide and 20.52 g of sodium phosphate (Na3PO4. 12H2O) were dissolved in 160 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 80 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and phosphate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 243 mV for a current density of 10 mA / cm2, an overpotential of 317 mV for a current density of 50 mA / cm2, and an overpotential of 357 mV for a current density of 100 mA / cm2.

[0055] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 5.82 g of Ni(NO3)2·6H2O and 4.04 g of Fe(NO3)3·9H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, nitrate ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 222 mV for a current density of 10 mA / cm2, an overpotential of 304 mV for a current density of 50 mA / cm2, and an overpotential of 342 mV for a current density of 100 mA / cm2.

[0056] 5.76 g of sodium hydroxide and 5.72 g of sodium hypophosphite were dissolved in 80 mL of water to form an alkaline solution. 5.82 g of Ni(NO3)2·6H2O and 4.04 g of Fe(NO3)3·9H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, nitrate ions, and hypophosphite ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 211 mV for a current density of 10 mA / cm2, an overpotential of 309 mV for a current density of 50 mA / cm2, and an overpotential of 352 mV for a current density of 100 mA / cm2.Example 3-2

[0057] The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) loaded on the nickel mesh in Example 3-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 281 mV for a current density of 50 mA / cm2 and an overpotential of 305 mV for a current density of 100 mA / cm2.

[0058] The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and hypophosphite ions, in which the nickel and the iron had a molar ratio of 2:1) loaded on the nickel mesh in Example 3-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 284 mV for a current density of 50 mA / cm2 and an overpotential of 305 mV for a current density of 100 mA / cm2. In the catalytic alloy, the doped C occupied 5.7 atomic %, the doped F occupied 16.7 atomic %, the doped S occupied 1.64 atomic %, and the doped P occupied 9.84 atomic % (from the hypophosphite ions).

[0059] The aqueous solution of metal salt in Example 3-1 was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 8.5, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, nitrate ions, and hypophosphite ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and hypophosphite ions, in which the nickel and the iron had a molar ratio of 2:1) loaded on the nickel mesh in Example 3-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 289 mV for a current density of 50 mA / cm2 and an overpotential of 310 mV for a current density of 100 mA / cm2.

[0060] The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and phosphate ions, in which the nickel and the iron had a molar ratio of 2:1) loaded on the nickel mesh in Example 3-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 300 mV for a current density of 50 mA / cm2 and an overpotential of 323 mV for a current density of 100 mA / cm2.

[0061] As shown in Example 3-2, the catalytic activity of the catalytic alloy after being sintered under hydrogen was better than that of LDH and metal hydroxide before being sintered under hydrogen. The catalytic alloy formed from sintering LDH and metal hydroxide of different cations had similar catalytic activities. In addition, the pH value of synthesizing the catalyst could be 8.5 to 12.Example 4-1

[0062] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry.

[0063] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was precipitated after being left to stand for 1 hour. The ink was coated onto a nickel mesh immediately after being prepared and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 321 mV for a current density of 50 mA / cm2, and an overpotential of 441 mV for a current density of 300 mA / cm2.

[0064] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.01 g of sodium dodecyl sulfate (SDS, anionic surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was not precipitated after being left to stand over 24 hours. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 289 mV for a current density of 50 mA / cm2, and an overpotential of 379 mV for a current density of 300 mA / cm2.

[0065] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was not precipitated after being left to stand over 24 hours. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 275 mV for a current density of 50 mA / cm2, and an overpotential of 363 mV for a current density of 300 mA / cm2.

[0066] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.05 g of SDS solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was not precipitated after being left to stand over 24 hours. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 282 mV for a current density of 50 mA / cm2, and an overpotential of 367 mV for a current density of 300 mA / cm2.

[0067] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.10 g of SDS solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was not precipitated after being left to stand over 24 hours. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 306 mV for a current density of 50 mA / cm2, and an overpotential of 396 mV for a current density of 300 mA / cm2.

[0068] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.20 g of SDS solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was not precipitated after being left to stand over 24 hours. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 311 mV for a current density of 50 mA / cm2, and an overpotential of 435 mV for a current density of 300 mA / cm2.

[0069] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.40 g of SDS solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was not precipitated after being left to stand over 24 hours. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 313 mV for a current density of 50 mA / cm2, and an overpotential for a current density of 300 mA / cm2 could not be measured in the electro catalytic measurement range.

[0070] As shown in Example 4-1, the surfactant such as SDS could be added to the ink to further improve the catalytic activity of LDH and metal hydroxide.Example 4-2

[0071] The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) loaded on the nickel mesh and free of SDS in Example 4-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 265 mV for a current density of 50 mA / cm2 and an overpotential of 355 mV for a current density of 300 mA / cm2. In the catalytic alloy, the doped C occupied 15.5 atomic %, the doped F occupied 7.28 atomic %, and the doped S occupied 4.36 atomic %.

[0072] The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) loaded on the nickel mesh and formed by utilizing 0.01 g of SDS solution in Example 4-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. This catalyst had an overpotential of 278 mV for a current density of 50 mA / cm2 and an overpotential of 351 mV for a current density of 300 mA / cm2.

[0073] The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) loaded on the nickel mesh and formed by utilizing 0.02 g of SDS solution in Example 4-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. This catalyst had an overpotential of 262 mV for a current density of 50 mA / cm2 and an overpotential of 312 mV for a current density of 300 mA / cm2. In the catalytic alloy, the doped C occupied 10.08 atomic %, the doped F occupied 19.05 atomic %, and the doped S occupied 10.06 atomic %.

[0074] The solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) loaded on the nickel mesh and formed by utilizing 0.05 g of SDS solution in Example 4-1 was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. This catalyst had an overpotential of 262 mV for a current density of 50 mA / cm2 and an overpotential of 331 mV for a current density of 300 mA / cm2.

[0075] As shown in Example 4-2, the catalytic alloy formed by sintering the ink with additional SDS and further doped with sulfur, which may improve the catalytic activity of the catalyst for the high current density.Example 5

[0076] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry.

[0077] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. 0.02 g of cetyltrimethylammonium bromide (CTAB, cationic surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was severely precipitated. The ink was coated onto a nickel mesh and then heated until dry to obtain an uneven and easily-spalled coating layer, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and N elements of CTAB into the catalytic alloy. This catalyst had an overpotential of 292 mV for a current density of 50 mA / cm2 and an overpotential of 380 mV for a current density of 300 mA / cm2.

[0078] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. 0.02 g of decyltrimethylammonium bromide (DTAB, cationic surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was severely precipitated. The ink was coated onto a nickel mesh and then heated until dry to obtain an uneven and easily-spalled coating layer, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and N elements of DTAB into the catalytic alloy. This catalyst had an overpotential of 317 mV for a current density of 50 mA / cm2 and an overpotential of 399 mV for a current density of 300 mA / cm2.

[0079] As shown in Example 5, the cationic surfactant was improper for the ink of the disclosure.Example 6

[0080] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry.

[0081] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 292 mV for a current density of 50 mA / cm2 and an overpotential of 375 mV for a current density of 300 mA / cm2.

[0082] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. This catalyst had an overpotential of 269 mV for a current density of 50 mA / cm2 and an overpotential of 340 mV for a current density of 300 mA / cm2.

[0083] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of dioctyl sodium sulfosuccinate (DSS, anionic surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant DSS into the catalytic alloy. This catalyst had an overpotential of 281 mV for a current density of 50 mA / cm2 and an overpotential of 372 mV for a current density of 300 mA / cm2.

[0084] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of lauryl phosphate (LP, anionic surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and P elements of the surfactant LP into the catalytic alloy. This catalyst had an overpotential of 272 mV for a current density of 50 mA / cm2 and an overpotential of 336 mV for a current density of 300 mA / cm2.

[0085] As shown in Example 6, the ink with additional anionic surfactant could further improve the catalytic activity of the catalytic alloy.Example 7

[0086] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry.

[0087] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 292 mV for a current density of 50 mA / cm2 and an overpotential of 375 mV for a current density of 300 mA / cm2.

[0088] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of polyoxyethylene sorbitan monolaurate (Tween20, neutral surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C element of the surfactant Tween20 into the catalytic alloy. This catalyst had an overpotential of 289 mV for a current density of 50 mA / cm2 and an overpotential of 354 mV for a current density of 300 mA / cm2.

[0089] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of polyoxyethylene sorbitan monooleate (Tween80, neutral surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C element of the surfactant Tween80 into the catalytic alloy. This catalyst had an overpotential of 276 mV for a current density of 50 mA / cm2 and an overpotential of 349 mV for a current density of 300 mA / cm2.

[0090] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of octylphenyl polyoxyethylene ether (Triton X-100, neutral surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C element of the surfactant Triton X-100 into the catalytic alloy. This catalyst had an overpotential of 276 mV for a current density of 50 mA / cm2 and an overpotential of 350 mV for a current density of 300 mA / cm2.

[0091] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of polyoxyethylene (5) nonylphenyl ether (IGEPAL CO-520, neutral surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C element of the surfactant IGEPAL CO-520 into the catalytic alloy. This catalyst had an overpotential of 273 mV for a current density of 50 mA / cm2 and an overpotential of 351 mV for a current density of 300 mA / cm2.

[0092] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of sorbitan laurate (Span20, neutral surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C element of the surfactant Span20 into the catalytic alloy. This catalyst had an overpotential of 290 mV for a current density of 50 mA / cm2 and an overpotential of 374 mV for a current density of 300 mA / cm2.

[0093] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of lauryl alcohol polyoxyethylene ether (Brij-30, neutral surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C element of the surfactant Brij-30 into the catalytic alloy. This catalyst had an overpotential of 286 mV for a current density of 50 mA / cm2 and an overpotential of 361 mV for a current density of 300 mA / cm2.

[0094] As shown in Example 7, adding the neutral surfactant to the ink could improve the catalytic activity of the catalytic alloy.Example 8

[0095] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry.

[0096] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 292 mV for a current density of 50 mA / cm2 and an overpotential of 375 mV for a current density of 300 mA / cm2.

[0097] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of 3-decyldimethylammonium propane sulfonate (Sulfobetaine 10, amphoteric surfactant) solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C, N, and S element of the surfactant Sulfobetaine 10 into the catalytic alloy. This catalyst had an overpotential of 298 mV for a current density of 50 mA / cm2 and an overpotential of 373 mV for a current density of 300 mA / cm2.

[0098] As shown in Example 8, adding the amphoteric surfactant to the ink had a limited effect on improving the catalytic activity of the catalytic alloy.Example 9

[0099] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry.

[0100] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 292 mV for a current density of 50 mA / cm2 and an overpotential of 375 mV for a current density of 300 mA / cm2.

[0101] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. This catalyst had an overpotential of 269 mV for a current density of 50 mA / cm2 and an overpotential of 340 mV for a current density of 300 mA / cm2.

[0102] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of polytetrafluoroethylene (PTFE) solution (5 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C and F elements of PTFE in the ink into the catalytic alloy. This catalyst had an overpotential of 291 mV for a current density of 50 mA / cm2 and an overpotential of 390 mV for a current density of 300 mA / cm2.

[0103] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of PTFE solution (5 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C and F elements of PTFE in the ink and C and S elements of the surfactant SDS into the catalytic alloy. This catalyst had an overpotential of 280 mV for a current density of 50 mA / cm2 and an overpotential of 354 mV for a current density of 300 mA / cm2.

[0104] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of hexamethylterphenyl polydimethylbenzimidazole (HMT-PMBI) solution (5 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C and N elements of HMT-PMBI in the ink into the catalytic alloy. This catalyst had an overpotential of 309 mV for a current density of 50 mA / cm2 and an overpotential of 414 mV for a current density of 300 mA / cm2.

[0105] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of HMT-PMBI solution (5 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was then added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C and N elements of HMT-PMBI in the ink and C and S elements of the surfactant SDS into the catalytic alloy. This catalyst had an overpotential of 304 mV for a current density of 50 mA / cm2 and an overpotential of 387 mV for a current density of 300 mA / cm2.

[0106] As shown in Example 9, the fluorine-containing polymer such as Nafion and PTFE could serve as the binder in the ink.Example 10

[0107] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry.

[0108] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 252 mV for a current density of 10 mA / cm2, an overpotential of 310 mV for a current density of 50 mA / cm2, and an overpotential of 347 mV for a current density of 100 mA / cm2. This catalyst was sheet-shaped. The catalyst had a BET surface area of 133.31 m2 / g, an average pore size for adsorption of 120.19 Å, and an average pore size for desorption of 120.43 Å (measured by TriStar II plus of micromeritics).

[0109] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under air for 5 hours to form nickel iron oxide from the nickel and the iron, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the nickel iron oxide catalyst. This catalyst had an overpotential of 257 mV for a current density of 10 mA / cm2, an overpotential of 298 mV for a current density of 50 mA / cm2, and an overpotential of 319 mV for a current density of 100 mA / cm2. The catalyst was sheet-shaped.

[0110] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under nitrogen for 5 hours to form nickel iron oxide from the nickel and the iron, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the nickel iron oxide catalyst. This catalyst had an overpotential of 269 mV for a current density of 10 mA / cm2, an overpotential of 308 mV for a current density of 50 mA / cm2, and an overpotential of 329 mV for a current density of 100 mA / cm2.

[0111] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 257 mV for a current density of 50 mA / cm2 and an overpotential of 280 mV for a current density of 100 mA / cm2. The catalyst was ball-shaped. The catalyst had a BET surface area of 20.75 m2 / g, an average pore size for adsorption of 409.43 Å, and an average pore size for desorption of 418.15 Å (measured by TriStar II plus of micromeritics). As shown in XPS analysis, the catalytic alloy included Ni0, Ni2+, Ni3+, Fe0, Fe2+, and Fe3+, included carbon doping but no metal-carbon bonding, and included a little amount of sulfur doping.

[0112] As shown in Example 10, the catalytic alloy formed by sintering LDH and metal hydroxide under hydrogen had a better catalytic activity. In addition, the catalytic alloy after being sintered under hydrogen could expose more catalytic active sites.Example 11

[0113] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry.

[0114] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 252 mV for a current density of 10 mA / cm2, an overpotential of 310 mV for a current density of 50 mA / cm2, and an overpotential of 347 mV for a current density of 100 mA / cm2.

[0115] 200 mg of the solid, 70 mL of deionized water, and 25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 5 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto glass and then heated until dry and ground. 2 mg of the dried catalyst, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 252 mV for a current density of 10 mA / cm2, an overpotential of 342 mV for a current density of 50 mA / cm2, and an overpotential of 385 mV for a current density of 100 mA / cm2. As shown above, too much Nafion might cover active sites of the catalyst and reduce the catalytic activity of the catalyst.Example 12

[0116] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry.

[0117] 200 mg of the solid, 70 mL of deionized water, and 25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 5 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto glass, heated until dry and ground. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. 2 mg of the catalytic alloy, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the catalyst (the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. This catalyst had an overpotential of 310 mV for a current density of 50 mA / cm2 and an overpotential of 340 mV for a current density of 100 mA / cm2.

[0118] 200 mg of the solid was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy. 2 mg of the catalytic alloy, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry. This catalyst had an overpotential of 344 mV for a current density of 50 mA / cm2 and an overpotential of 379 mV for a current density of 100 mA / cm2.

[0119] As shown in Example 12, when the solid of LDH and metal hydroxide included the binder such as Nafion, C, S, and F elements could be doped into the catalytic alloy as the catalyst was being sintered, and the catalytic activity could be efficiently improved.Example 13

[0120] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O, 2.70 g of FeCl3·6H2O, and 4.759 g of CoCl2·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:2) was 2 mg / cm2. This catalyst had an overpotential of 293 mV for a current density of 10 mA / cm2, an overpotential of 340 mV for a current density of 50 mA / cm2, and an overpotential of 363 mV for a current density of 100 mA / cm2.

[0121] The ink was coated onto a nickel felt and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:2) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel, iron, and cobalt to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. This catalyst had an overpotential of 246 mV for a current density of 10 mA / cm2, an overpotential of 275 mV for a current density of 50 mA / cm2, and an overpotential of 291 mV for a current density of 100 mA / cm2.

[0122] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O, 2.70 g of FeCl3·6H2O, and 4.759 g of CoCl2·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. A nickel felt was immersed in the aqueous solution of metal salt, the aqueous solution of metal salt was then heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours to form solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:2) on the nickel felt. This catalyst had an overpotential of 259 mV for a current density of 10 mA / cm2, an overpotential of 289 mV for a current density of 50 mA / cm2, and an overpotential of 305 mV for a current density of 100 mA / cm2. Because Nafion was not required in this process, the active sites would not be covered by Nafion. As such, the catalytic activity of the catalyst was higher.

[0123] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O, 2.70 g of FeCl3·6H2O, and 4.759 g of CoCl2·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. A nickel felt was immersed in the aqueous solution of metal salt, the aqueous solution of metal salt was then heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours to form solid (e.g., LDH and metal hydroxide of nickel, iron, cobalt, chlorine ions, and carbonate ions, in which the nickel, the iron, and the cobalt had a molar ratio of 2:1:2) on the nickel felt. The nickel felt was taken out of the solution of metal salt and dried, and then sintered at 400° C. under hydrogen for 5 hours to alloy nickel, iron, and cobalt to form a catalytic alloy. This catalyst had an overpotential of 266 mV for a current density of 10 mA / cm2, an overpotential of 294 mV for a current density of 50 mA / cm2, and an overpotential of 310 mV for a current density of 100 mA / cm2. The catalytic activity of the catalyst after sintering was lower than before sintering due to lacking of Nafion and its doping effect.Example 14

[0124] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry.

[0125] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 250° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy. This catalyst had an overpotential of 264 mV for a current density of 10 mA / cm2, an overpotential of 322 mV for a current density of 50 mA / cm2, and an overpotential of 369 mV for a current density of 100 mA / cm2.

[0126] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 330° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy. This catalyst had an overpotential of 279 mV for a current density of 10 mA / cm2, an overpotential of 337 mV for a current density of 50 mA / cm2, and an overpotential of 387 mV for a current density of 100 mA / cm2.

[0127] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and Nafion was initially cracked to dope C, S, and F elements of Nafion into the catalytic alloy. This catalyst had an overpotential of 244 mV for a current density of 10 mA / cm2, an overpotential of 283 mV for a current density of 50 mA / cm2, and an overpotential of 305 mV for a current density of 100 mA / cm2.

[0128] As shown in Example 14, if the sintering temperature was too low, the catalytic activity of the catalytic alloy could not be efficiently improved. The catalyst sintered at 400 under hydrogen had a better performance.Example 15

[0129] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry.

[0130] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. In oxygen evolution reaction (OER), this catalyst had an overpotential of 285 mV for a current density of 50 mA / cm2, an overpotential of 306 mV for a current density of 100 mA / cm2, and an overpotential of 362 mV for a current density of 300 mA / cm2. A tape was attached to the nickel mesh, it was found that some catalytic alloy was adhered on the tape after removing the tape from the nickel mesh. In addition, water droplets obviously remained on the catalyst surface when water is dropped on the catalyst, it means that the catalyst had a low hydrophilicity. In addition, the catalytic alloy spalled from the nickel mesh after being continuously operated by a constant current density of 50 mA / cm2 and a voltage of about 1.49 V to 1.50 V for 24 hours. Next, in hydrogen evolution reaction (HER), this catalyst had an overpotential of 266 mV for a current density of 100 mA / cm2, an overpotential of 296 mV for a current density of 150 mA / cm2, and an overpotential of 326 mV for a current density of 200 mA / cm2.

[0131] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. 3.25 g of NiSO4·6H2O, 3.75 g of sodium acetate, 2.5 mL of lactic acid, 0.25 g of saccharin, 0.25 mL of SDS solution (0.1 wt %), and 112.5 mL of deionized water were formulated to form an aqueous solution, and its pH value was adjusted to 4.8. 3 g of sodium hypophosphite was dissolved in 12.5 mL of deionized water. The aqueous solution containing nickel ions was heated to 80° C. to 85° C., the sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions, and the aqueous solution of sodium hypophosphite was then added to the aqueous solution containing nickel ions, thereby growing nickel phosphide particles (3.0 mg, in which phosphorous and nickel had a molar ratio of 1:6 to 1:7) to cover the nickel mesh and the catalytic alloy. In oxygen evolution reaction (OER), this catalyst had an overpotential of 273 mV for a current density of 50 mA / cm2, an overpotential of 296 mV for a current density of 100 mA / cm2, and an overpotential of 349 mV for a current density of 300 mA / cm2. A tape was attached to the nickel mesh, it was found that no catalytic alloy or nickel phosphide particles was adhered on the tape after removing the tape from the nickel mesh. In addition, water permeated into the catalyst when water is dropped on the catalyst, it means that the catalyst had a high hydrophilicity. In the catalytic alloy, the doped C occupied 19.73 atomic %, the doped F occupied 4.02 atomic %, the doped S occupied 2.47 atomic %, and the doped P occupied 3.21 atomic % (from the metal phosphide particles). Next, in hydrogen evolution reaction (HER), this catalyst had an overpotential of 254 mV for a current density of 100 mA / cm2, an overpotential of 278 mV for a current density of 150 mA / cm2, and an overpotential of 301 mV for a current density of 200 mA / cm2.

[0132] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. 3.25 g of NiSO4·6H2O, 3.75 g of sodium acetate, 2.5 mL of lactic acid, 0.25 g of saccharin, 0.25 mL of SDS solution (0.1 wt %), and 112.5 mL of deionized water were formulated to form an aqueous solution, and its pH value was adjusted to 4.8. 3 g of sodium hypophosphite was dissolved in 12.5 mL of deionized water. The aqueous solution containing nickel ions was heated to 80° C. to 85° C., the sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions, and the aqueous solution of sodium hypophosphite was then added to the aqueous solution containing nickel ions, thereby growing nickel phosphide particles (3.8 mg, in which phosphorous and nickel had a molar ratio of 1:6 to 1:7) to cover the nickel mesh and the catalytic alloy. In oxygen evolution reaction (OER), this catalyst had an overpotential of 286 mV for a current density of 50 mA / cm2, an overpotential of 309 mV for a current density of 100 mA / cm2, and an overpotential of 365 mV for a current density of 300 mA / cm2. A tape was attached to the nickel mesh, it was found that no catalytic alloy or nickel phosphide particles was adhered on the tape after removing the tape from the nickel mesh. Next, in hydrogen evolution reaction (HER), this catalyst had an overpotential of 264 mV for a current density of 100 mA / cm2, an overpotential of 281 mV for a current density of 150 mA / cm2, and an overpotential of 296 mV for a current density of 200 mA / cm2.

[0133] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. 3.25 g of NiSO4·6H2O, 3.75 g of sodium acetate, 2.5 mL of lactic acid, 0.25 g of saccharin, 0.25 mL of SDS solution (0.1 wt %), and 112.5 mL of deionized water were formulated to form an aqueous solution, and its pH value was adjusted to 4.8. 3 g of sodium hypophosphite was dissolved in 12.5 mL of deionized water. The aqueous solution containing nickel ions was heated to 80° C. to 85° C., the sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions, and the aqueous solution of sodium hypophosphite was then added to the aqueous solution containing nickel ions, thereby growing nickel phosphide particles (4.2 mg, in which phosphorous and nickel had a molar ratio of 1:6 to 1:7) to cover the nickel mesh and the catalytic alloy. In oxygen evolution reaction (OER), this catalyst had an overpotential of 285 mV for a current density of 50 mA / cm2, an overpotential of 306 mV for a current density of 100 mA / cm2, and an overpotential of 364 mV for a current density of 300 mA / cm2.

[0134] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. 3.25 g of NiSO4·6H2O, 3.75 g of sodium acetate, 2.5 mL of lactic acid, 0.25 g of saccharin, 0.25 mL of SDS solution (0.1 wt %), and 112.5 mL of deionized water were formulated to form an aqueous solution, and its pH value was adjusted to 4.8. 3 g of sodium hypophosphite was dissolved in 12.5 mL of deionized water. The aqueous solution containing nickel ions was heated to 80° C. to 85° C., the sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions, and the aqueous solution of sodium hypophosphite was then added to the aqueous solution containing nickel ions, thereby growing nickel phosphide particles (5.6 mg, in which phosphorous and nickel had a molar ratio of 1:6 to 1:7) to cover the nickel mesh and the catalytic alloy. In oxygen evolution reaction (OER), this catalyst had an overpotential of 281 mV for a current density of 50 mA / cm2, an overpotential of 304 mV for a current density of 100 mA / cm2, and an overpotential of 356 mV for a current density of 300 mA / cm2.

[0135] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. 3.25 g of NiSO4·6H2O, 3.75 g of sodium acetate, 2.5 mL of lactic acid, 0.25 g of saccharin, 0.25 mL of SDS solution (0.1 wt %), and 112.5 mL of deionized water were formulated to form an aqueous solution, and its pH value was adjusted to 4.8. 3 g of sodium hypophosphite was dissolved in 12.5 mL of deionized water. The aqueous solution containing nickel ions was heated to 80° C. to 85° C., the sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions, and the aqueous solution of sodium hypophosphite was then added to the aqueous solution containing nickel ions, thereby growing nickel phosphide particles (17.8 mg, in which phosphorous and nickel had a molar ratio of 1:6 to 1:7) to cover the nickel mesh and the catalytic alloy. In oxygen evolution reaction (OER), this catalyst had an overpotential of 294 mV for a current density of 50 mA / cm2, an overpotential of 327 mV for a current density of 100 mA / cm2, and an overpotential of 400 mV for a current density of 300 mA / cm2.

[0136] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. In oxygen evolution reaction (OER), this catalyst had an overpotential of 269 mV for a current density of 50 mA / cm2, an overpotential of 290 mV for a current density of 100 mA / cm2, and an overpotential of 340 mV for a current density of 300 mA / cm2. In addition, the catalytic alloy spalled from the nickel mesh after being continuously operated by a constant current density of 50 mA / cm2 and a voltage of about 1.49 V to 1.50 V for 24 hours. Next, in hydrogen evolution reaction (HER), this catalyst had an overpotential of 319 mV for a current density of 100 mA / cm2, an overpotential of 349 mV for a current density of 150 mA / cm2, and an overpotential of 365 mV for a current density of 200 mA / cm2.

[0137] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. 1.31 g of NiSO4·6H2O, 2.5 g of disodium succinate, 1.5 g of sodium sulfate, 3.1 g of sodium hypophosphite, and 100 mL of deionized water were formulated to form an aqueous solution. The sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions, and the aqueous solution of sodium hypophosphite was then added to the aqueous solution containing nickel ions, thereby growing nickel phosphide particles (2.0 mg) to cover the nickel mesh and the catalytic alloy. In oxygen evolution reaction (OER), this catalyst had an overpotential of 263 mV for a current density of 50 mA / cm2, an overpotential of 288 mV for a current density of 100 mA / cm2, and an overpotential of 346 mV for a current density of 300 mA / cm2. In addition, the catalytic alloy was stable and not spalling from the nickel mesh after being continuously operated by a constant current density of 50 mA / cm2 and a voltage of about 1.49 V to 1.50 V for 24 hours. Next, in hydrogen evolution reaction (HER), this catalyst had an overpotential of 278 mV for a current density of 100 mA / cm2, an overpotential of 303 mV for a current density of 150 mA / cm2, and an overpotential of 321 mV for a current density of 200 mA / cm2.

[0138] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. 1.31 g of NiSO4·6H2O, 2.5 g of disodium succinate, 1.5 g of sodium sulfate, 3.1 g of sodium hypophosphite, and 100 mL of deionized water were formulated to form an aqueous solution. The sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions, and the aqueous solution of sodium hypophosphite was then added to the aqueous solution containing nickel ions, thereby growing nickel phosphide particles (3.5 mg) to cover the nickel mesh and the catalytic alloy. In oxygen evolution reaction (OER), this catalyst had an overpotential of 267 mV for a current density of 50 mA / cm2, an overpotential of 300 mV for a current density of 100 mA / cm2, and an overpotential of 352 mV for a current density of 300 mA / cm2

[0139] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. 1.31 g of NiSO4·6H2O, 1.96 g of (NH4)2Fe(SO4)2·6H2O, 2.5 g of disodium succinate, 1.5 g of sodium sulfate, 3.1 g of sodium hypophosphite, and 100 mL of deionized water were formulated to form an aqueous solution. The sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions and iron ions, and the aqueous solution of sodium hypophosphite was then added to the aqueous solution containing nickel ions and iron ions, thereby growing nickel iron phosphide particles (2.1 mg, in which phosphorous and nickel had a molar ratio of 1:3.6 to 1:4.0, and phosphorus and iron had a molar ratio of 1:0.1 to 1:0.15) to cover the nickel mesh and the catalytic alloy. In oxygen evolution reaction (OER), this catalyst had an overpotential of 266 mV for a current density of 50 mA / cm2, an overpotential of 288 mV for a current density of 100 mA / cm2, and an overpotential of 343 mV for a current density of 300 mA / cm2.

[0140] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. 1.31 g of NiSO4·6H2O, 1.96 g of (NH4)2Fe(SO4)2·6H2O, 2.5 g of disodium succinate, 1.5 g of sodium sulfate, 3.1 g of sodium hypophosphite, and 100 mL of deionized water were formulated to form an aqueous solution. The sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions and iron ions, and the aqueous solution of sodium hypophosphite was then added to the aqueous solution containing nickel ions and iron ions, thereby growing nickel iron phosphide particles (3.0 mg, in which phosphorous and nickel had a molar ratio of 1:3.6 to 1:4.0, and phosphorus and iron had a molar ratio of 1:0.1 to 1:0.15) to cover the nickel mesh and the catalytic alloy. In oxygen evolution reaction (OER), this catalyst had an overpotential of 257 mV for a current density of 50 mA / cm2, an overpotential of 279 mV for a current density of 100 mA / cm2, and an overpotential of 329 mV for a current density of 300 mA / cm2.

[0141] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. 1.31 g of NiSO4·6H2O, 1.19 g of CoCl2·6H2O, 2.5 g of disodium succinate, 1.5 g of sodium sulfate, 3.1 g of sodium hypophosphite, and 100 mL of deionized water were formulated to form an aqueous solution. The sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions and cobalt ions, thereby growing nickel cobalt phosphide particles (4.9 mg) to cover the nickel mesh and the catalytic alloy. In hydrogen evolution reaction (HER), this catalyst had an overpotential of 298 mV for a current density of 100 mA / cm2, an overpotential of 327 mV for a current density of 150 mA / cm2, and an overpotential of 352 mV for a current density of 200 mA / cm2.

[0142] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. 1.31 g of NiSO4·6H2O, 0.85 g of CuCl2, 2.5 g of disodium succinate, 1.5 g of sodium sulfate, 3.1 g of sodium hypophosphite, and 100 mL of deionized water were formulated to form an aqueous solution. The sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions and copper ions, thereby growing nickel copper phosphide particles (5.6 mg) to cover the nickel mesh and the catalytic alloy. In hydrogen evolution reaction (HER), this catalyst had an overpotential of 278 mV for a current density of 100 mA / cm2, an overpotential of 302 mV for a current density of 150 mA / cm2, and an overpotential of 326 mV for a current density of 200 mA / cm2.

[0143] 2 mg of the solid, 0.70 mL of deionized water, and 0.25 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 0.05 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes. 0.02 g of SDS solution (10 wt %) was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel mesh and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The catalyst was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink and C and S elements of the surfactant SDS into the catalytic alloy. 1.31 g of NiSO4·6H2O, 1.47 g of ZnSO4·7H2O, 2.5 g of disodium succinate, 1.5 g of sodium sulfate, 3.1 g of sodium hypophosphite, and 100 mL of deionized water were formulated to form an aqueous solution. The sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions and zinc ions, thereby growing nickel zinc phosphide particles (1.7 mg) to cover the nickel mesh and the catalytic alloy. In hydrogen evolution reaction (HER), this catalyst had an overpotential of 274 mV for a current density of 100 mA / cm2, an overpotential of 308 mV for a current density of 150 mA / cm2, and an overpotential of 340 mV for a current density of 200 mA / cm2.

[0144] As shown in Example 15, growing an appropriate weight (2 mg to 6 mg) of nickel phosphide or nickel iron phosphide to cover the nickel mesh and the catalytic alloy, would prevent the catalytic alloy from spalling from the nickel mesh. The nickel phosphide or nickel iron phosphide would not degrade the catalytic activity of the oxygen evolution reaction. In addition, growing 1.7 mg to 5.6 mg of nickel phosphide, nickel cobalt phosphide, or nickel zinc phosphide to cover the nickel mesh and the catalytic alloy could enhance the catalytic activity of the hydrogen evolution reaction.Example 16

[0145] Test factors of anionic exchange membrane (AEM) stack are shown below. The anode was a self-prepared electrode (63.6 cm2). The cathode was Pt / C. The separator film was anionic exchange film. The electrolyte was an aqueous solution of 1 wt % KOH or 5.6 wt % KOH. The test temperature was 55° C. The test temperature was 1.5 V to 2.0 V. The stack was assembled as below. An end plate, a bipolar plate, a gas diffusion layer, the anode, the separator, the cathode, another gas diffusion layer, another bipolar plate, and another end plate were assembled in sequence. The stack and the test method may refer to Chem. Soc. Rev., 2022, 51, 9620.

[0146] 5.76 g of sodium hydroxide and 5.71 g of sodium carbonate were dissolved in 180 mL of water to form an alkaline solution. 4.75 g of NiCl2·6H2O and 2.70 g of FeCl3·6H2O were dissolved in 500 mL of water to form an aqueous solution of metal salt. The aqueous solution of metal salt was heated to 50° C. to 55° C., and the alkaline solution was slowly added to the aqueous solution of metal salt until the pH value reaching 12, and then reacted at 50° C. to 55° C. for 5 hours. The reaction result was centrifuged to collect solid, and the solid was washed with deionized water. The centrifugation and washing steps were repeated several times. The solid was heated until dry. 1 g of the solid, 350 mL of deionized water, and 125 mL of isopropyl alcohol were mixed and then ultrasonic oscilliation was applied for 30 minutes, and 25 mL of Nafion solution D2020CS was added to the mixture and then ultrasonic oscilliation was applied for 10 minutes to prepare an ink. The ink was coated onto a nickel felt and then heated until dry, and the loading amount of the solid (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was 2 mg / cm2. The nickel felt with LDH and metal hydroxide loaded thereon was served as an anode, and KOH solution (1 wt %) was served as an electrolyte in the stack. The stack had a current density of 435.2 mA / cm2 at a voltage of 1.8V, and a current density of 849.1 mA / cm2 at a voltage 2.0 V.

[0147] The nickel felt with LDH and metal hydroxide loaded thereon (e.g., LDH and metal hydroxide of nickel, iron, chlorine ions, and carbonate ions, in which the nickel and the iron had a molar ratio of 2:1) was sintered at 400° C. under hydrogen for 5 hours to alloy nickel and iron to form a catalytic alloy, and dope C, S, and F elements of Nafion solution D2020CS in the ink into the catalytic alloy. The hydrogen sintered nickel felt was served as an anode, and KOH solution (1 wt %) was served as an electrolyte in the stack. The stack had a current density of 962.3 mA / cm2 at a voltage of 1.8V, and a current density of 1849.1 mA / cm2 at a voltage 2.0 V. The hydrogen sintered nickel felt was served as an anode, and KOH solution (5.6 wt %) was served as an electrolyte in the stack. The stack had a current density of 1455.0 mA / cm2 at a voltage of 1.8V, and a current density of 2558.6 mA / cm2 at a voltage 2.0 V.

[0148] 11.79 g of NiSO4·6H2O, 22.5 g of disodium succinate, 13.5 g of sodium sulfate, 27.9 g of sodium hypophosphite, and 900 mL of deionized water were formulated to form an aqueous solution. The sintered catalytic alloy electrode was immersed in the aqueous solution containing nickel ions, thereby growing nickel phosphide particles to cover the nickel felt and the catalytic alloy. The nickel felt with nickel phosphide particles grown thereon was served as an anode, and KOH solution (1 wt %) was served as an electrolyte in the stack. The stack had a current density of 998.9 mA / cm2 at a voltage of 1.8V, and a current density of 1464.7 mA / cm2 at a voltage 1.9 V.

[0149] As shown Example 16, the hydrogen sintered catalytic electrode could efficiently improve the stack performance. In the electrode of the nickel felt and the catalytic alloy covered by the nickel phosphide particles, the nickel phosphide particles would not block the active sites of the catalytic alloy, and the stack performance would not be decreased.

[0150] It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed methods and materials. It is intended that the specification and examples be considered as exemplary only, with the true scope of the disclosure being indicated by the following claims and their equivalents.

Claims

1. A catalytic electrode, comprising:a nickel-based porous base material;a plurality of catalytic alloy balls of nickel and another metal doped with elements, wherein the another metal includes iron, the elements include C, F, and S, and the catalytic alloy balls are dispersed on the surface of the nickel-based porous base material; anda plurality of metal phosphide particles covering the nickel-based porous base material and the catalytic alloy balls, wherein the metal phosphide particles include nickel phosphide, nickel iron phosphide, nickel cobalt phosphide, nickel copper phosphide, or nickel zinc phosphide.

2. The catalytic electrode as claimed in claim 1, wherein the nickel-based porous base material includes nickel mesh, nickel foam, or nickel felt.

3. The catalytic electrode as claimed in claim 1, wherein the nickel and the iron in the catalytic alloy balls have a molar ratio of 2:1 to 4:1.

4. The catalytic electrode as claimed in claim 1, wherein the another metal in the catalytic alloy balls further includes cobalt, and the cobalt and the iron in the catalytic alloy balls have a molar ratio of greater than 0 and less than or equal to 6:1.

5. The catalytic electrode as claimed in claim 1, wherein the doped C occupies 1 to 25 atomic % of the catalytic alloy balls, the doped F occupies 1 to 25 atomic % of the catalytic alloy balls, and the doped S occupies 1 to 15 atomic % of the catalytic alloy balls.

6. The catalytic electrode as claimed in claim 1, wherein the elements doped in the catalytic alloy balls further include P, and the doped P occupies greater than 0 and less than or equal to 15 atomic % of the catalytic alloy balls.

7. An electrolysis device, comprising:an anode;a cathode; andan aqueous solution in contact with the anode and the cathode,wherein the anode or the cathode is the catalytic electrode as claimed in claim 1.

8. A method of forming a catalytic electrode, comprising:mixing layered double hydroxide and metal hydroxide of nickel and another metal with solvent and binder to form an ink, wherein the another metal includes iron;coating the ink onto a nickel-based porous base material, baking dry the ink and then sintering the dried ink under hydrogen, thereby alloying the nickel and the another metal to form a plurality of catalytic alloy balls dispersed on the surface of the nickel-based porous base material, and doping elements of the binder into the catalytic alloy balls, wherein the elements include C, F, and S; andforming a plurality of metal phosphide particles to cover the nickel-based porous base material and the catalytic alloy balls, wherein the metal phosphide particles include nickel phosphide, nickel iron phosphide, nickel cobalt phosphide, nickel copper phosphide, or nickel zinc phosphide.

9. The method as claimed in claim 8, wherein the layered double hydroxide and metal hydroxide of nickel and another metal are formed by following step:mixing an aqueous solution of nickel salt and another metal salt with an alkaline solution containing sodium hydroxide.

10. The method as claimed in claim 8, wherein the ink further includes anionic surfactant, neutral surfactant, or a combination thereof, and the step of sintering the dried ink dopes elements of the anionic surfactant, neutral surfactant, or a combination thereof into the catalytic alloy balls, and the elements of the anionic surfactant, neutral surfactant, or a combination thereof include C, S, P, or a combination thereof.

11. The method as claimed as claimed in claim 8, wherein the binder includes copolymer of perfluorosulfonic acid and tetrafluoroethylene, polytetrafluoroethylene, or a combination thereof.