Method for preparing porous nickel electrode through electrodeposition of nickel-zinc-phosphorus alloy and application

Abstract

The invention discloses a method for preparing a porous nickel electrode by electrodepositing nickel-zinc-phosphorus alloy, which comprises the following steps: taking a nickel-based substrate as a cathode, and carrying out electrochemical deposition reaction in an electrolytic bath filled with an electroplating solution which comprises nickel salt, zinc salt and a phosphorus source; carrying out heat treatment on the nickel-based substrate subjected to electrochemical deposition; and the nickel-based substrate subjected to heat treatment is put into alkali liquor to be activated. The phosphorus source is introduced into the electroplating solution, the phosphorus element can be doped into alloy crystal lattices, and the dissolution efficiency of zinc is improved during activation, so that the residual quantity of the zinc element is effectively reduced, the activation time is shortened, sufficient formation of a porous structure is facilitated on the premise of ensuring the uniformity of the porous structure, the catalytic performance of the electrode is improved, and the service life of the electrode is prolonged. And the residual zinc element is prevented from polluting the electrolyte.

Description

Technical Field

[0001] The present application belongs to the technical field of alkaline water electrolysis, and specifically relates to a method for preparing a porous nickel electrode by electrodeposition of a nickel-zinc-phosphorus alloy and its application. Background Art

[0002] At present, the mainstream hydrogen production technology is mainly based on traditional fossil energy as raw materials. Although this method is mature and easy to scale up, it does not meet the requirements of environmental protection and sustainable development. Alkaline water electrolysis hydrogen production technology is both environmentally friendly and low-cost, and can produce high-purity hydrogen. The technology is relatively mature. The water electrolysis reaction consists of two half reactions, the hydrogen evolution reaction (HER) occurring at the cathode and the oxygen evolution reaction (OER) occurring at the anode, with a theoretical voltage of 1.23V; because the process is usually affected by factors such as polarization, a certain overpotential is required to decompose water into hydrogen and oxygen.

[0003] In order to reduce the overpotential required for the electrolysis of water, a catalyst needs to be coated on the electrode surface to accelerate the reaction. Currently, the most widely used commercial catalyst is the Raney nickel catalyst, and its preparation method is mainly to spray a Raney nickel catalyst with a certain nickel-aluminum ratio on a nickel-based substrate by thermal spraying, plasma spraying, etc., so that the nickel-based electrode has higher catalytic activity. However, the existing nickel-aluminum Raney nickel catalyst reacts violently during the activation process. Due to the rapid reaction, the new phase crystal nucleus is non-uniformly nucleated and grown, and the crystal nucleus is mainly concentrated in solid impurities or near the surface, which is easily affected by impurities, has poor stability, and the pores formed are uneven, which affects the performance and service life of the electrode. Summary of the invention

[0004] The purpose of the present application is to provide a method and application for preparing a porous nickel electrode by electrodeposition of nickel-zinc-phosphorus alloy, so as to solve the technical problems in the prior art that the nickel-aluminum Raney nickel catalyst reacts violently during the activation process, resulting in the non-uniform nucleation and growth of new phase nuclei, and the nuclei are mainly concentrated in solid impurities or near the surface, which is easily affected by impurities, has poor stability, and the pores formed are uneven, which affects the performance and service life of the electrode.

[0005] In order to achieve the above-mentioned object, the first aspect of the present application provides a method for preparing a porous nickel electrode by electrodeposition of a nickel-zinc-phosphorus alloy, comprising:

[0006] Using a nickel-based substrate as a cathode, an electrochemical deposition reaction is carried out in an electrolytic cell filled with an electroplating solution, wherein the electroplating solution includes a nickel salt, a zinc salt and a phosphorus source;

[0007] heat treating the electrochemically deposited nickel-based substrate;

[0008] The heat-treated nickel-based substrate is placed in an alkaline solution for activation to obtain a porous nickel electrode.

[0009] In one or more embodiments, the nickel salt includes one or more combinations of nickel sulfate, nickel chloride, and nickel nitrate.

[0010] In one or more embodiments, the zinc salt includes one or more combinations of zinc sulfate, zinc chloride, and zinc nitrate.

[0011] In one or more embodiments, the phosphorus source includes one or more combinations of sodium hypophosphite, sodium phosphite and sodium phosphate.

[0012] In one or more embodiments, the concentration of the nickel salt is 100-150 g / L, the concentration of the zinc salt is 1-10 g / L, and the concentration of the phosphorus source is 50-70 g / L.

[0013] In one or more embodiments, the pH value of the plating solution is 4.5-5.5, and the plating solution also includes additives, the additives include boric acid, ammonium chloride and a crystallization regulator, the concentration of the boric acid is 10-30 g / L, the concentration of the ammonium chloride is 20-50 g / L, and the concentration of the crystallization regulator is 45-55 g / L.

[0014] In one or more embodiments, the step of using the nickel-based substrate as a cathode and performing an electrochemical deposition reaction in an electrolytic cell filled with an electroplating solution further comprises:

[0015] Pre-treating the nickel-based substrate;

[0016] The step of pre-treating the nickel-based substrate comprises:

[0017] placing the nickel-based substrate in a surfactant for ultrasonic treatment;

[0018] The ultrasonically treated nickel-based substrate is immersed in acid and then taken out and cleaned.

[0019] In one or more embodiments, the nickel-based substrate is a nickel mesh, nickel foam or nickel felt. In the electrochemical deposition reaction, the anode is a pure nickel electrode, and the current density is 5 to 20 mA / cm 2 The reaction time is 1 to 2 hours and the reaction temperature is room temperature.

[0020] In one or more embodiments, in the step of heat treating the electrochemically deposited nickel-based substrate, the heat treatment temperature is 200 to 350° C. and the time is 1 to 2 hours.

[0021] In one or more embodiments, in the step of activating the heat-treated nickel-based substrate in an alkali solution, the alkali solution is a potassium hydroxide solution or a sodium hydroxide solution with a concentration of 10-30%, the activation time is 12-24 hours, and the activation temperature is 70-100°C.

[0022] In order to achieve the above-mentioned purpose, the second aspect of the present application provides a porous nickel electrode prepared by the method described in any of the above-mentioned embodiments.

[0023] In order to achieve the above-mentioned purpose, the third aspect of the present application provides an application of the porous nickel electrode described in any of the above-mentioned embodiments as a hydrogen evolution electrode in an alkaline water electrolysis reaction.

[0024] Different from the prior art, the beneficial effects of this application are:

[0025] The present application introduces a phosphorus source into the electroplating solution. The phosphorus element can be doped into the alloy lattice and improve the dissolution efficiency of zinc during activation, thereby effectively reducing the residual amount of zinc element and shortening the activation time while ensuring the uniformity of the pore structure, which is conducive to the full formation of the porous structure, improves the catalytic performance of the electrode, and avoids residual zinc element from contaminating the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is a schematic flow chart of an embodiment of a method for preparing a porous nickel electrode by electrodeposition of a nickel-zinc-phosphorus alloy according to the present application;

[0028] Figure 2 Surface SEM images of the porous nickel electrodes of Example 1 and Comparative Example 1, in which a is the porous nickel electrode of Example 1 and b is the porous nickel electrode of Comparative Example 1;

[0029] Figure 3 1 is the LSV curve of the porous nickel electrode of Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0031] At present, the widely used Raney nickel electrode is prepared by thermal spraying nickel-aluminum alloy. The activation reaction is rapid during the removal of aluminum, and the nickel-aluminum phase nuclei nucleate and grow non-uniformly. After activation, uneven pore morphology appears, the performance is difficult to improve, and the coating life is limited.

[0032] In order to solve the above problems, the applicant uses zinc instead of aluminum, and grows a nickel-zinc material layer on a nickel-based substrate by electroplating, and then performs heat treatment to allow the nickel and zinc metals to diffuse into each other to form a Ni-Zn alloy layer. The electrode is then soaked in alkali for activation treatment. The zinc atoms react with hydroxide ions to generate corresponding zinc salts and hydrogen, thereby removing the zinc element in the electrode to form a porous nickel electrode.

[0033] Since the zinc element reacts slowly and evenly during the activation process, the nickel-zinc crystal nuclei can be uniformly nucleated and grown, and a uniform pore structure can be formed after activation, which greatly increases the active area of ​​the catalyst and improves the hydrogen reaction rate.

[0034] However, in actual application, it was found that although the lower activation rate of zinc element is conducive to the uniform nucleation and growth of nickel-zinc crystal nuclei and the uniformity of subsequent pore structure, the lower activation rate also leads to a large amount of zinc element residue on the electrode after a short activation time (about 20-30% of zinc remains on the electrode). The activation is not thorough, resulting in insufficient formation of the porous structure, affecting the catalytic performance of the electrode, and also causing pollution to the alkaline solution of the electrolytic cell during operation.

[0035] Therefore, in order to increase the dissolution rate and amount of Zn in nickel-zinc alloy and reduce the residual amount of Zn after activation, the applicant has developed a new method for preparing a porous nickel electrode. This preparation method effectively increases the dissolution rate of zinc during the activation process by improving the electroplating solution, thereby shortening the activation time, reducing the residual Zn on the electrode, and contributing to the full formation of the porous structure, thereby improving the catalytic performance of the electrode.

[0036] Specifically, see Figure 1 , Figure 1 It is a schematic flow chart of an embodiment of a method for preparing a porous nickel electrode by electroplating a nickel-zinc-phosphorus alloy in the present application.

[0037] like Figure 1 As shown, the method includes:

[0038] S100, pre-treating the nickel-based substrate.

[0039] The nickel-based substrate may be a commonly used substrate material in the art, such as nickel mesh, nickel foam, and nickel felt.

[0040] The purpose of pretreatment is to remove impurities such as oil stains and oxide layers remaining on the surface of the nickel-based substrate to avoid affecting the adhesion of subsequent plating layers on the nickel-based substrate and to improve the bonding strength of the electroplated coating.

[0041] Specifically, in one embodiment, the preprocessing method may include:

[0042] The nickel-based substrate is placed in a surfactant and sonicated;

[0043] The ultrasonically treated nickel-based substrate is immersed in acid and then taken out and cleaned.

[0044] The surfactant may be any surfactant commonly used in the art, such as conventional soapy water, which is used to remove oil stains on the surface of the nickel-based substrate. In one embodiment, the ultrasonic treatment time may be 30 minutes.

[0045] The acid may be any common acid such as hydrochloric acid, and the soaking time may be 10 minutes, which is used to remove the oxide layer on the surface of the nickel-based substrate.

[0046] In other embodiments, other pretreatment methods commonly used in the art may also be used to ensure that the oil stains and oxide layer on the surface of the nickel-based substrate are fully removed, and the effect of this embodiment can be achieved.

[0047] S200, using the pretreated nickel-based substrate as a cathode to perform an electrochemical deposition reaction in an electrolytic cell filled with an electroplating solution.

[0048] The electroplating solution includes nickel salt, zinc salt and phosphorus source.

[0049] In one embodiment, the nickel salt may include one or more combinations of nickel sulfate, nickel chloride, and nickel nitrate.

[0050] In one embodiment, the zinc salt may include one or more combinations of zinc sulfate, zinc chloride, and zinc nitrate.

[0051] In one embodiment, the phosphorus source may include one or more combinations of sodium hypophosphite, sodium phosphite, and sodium phosphate.

[0052] More specifically, in order to ensure a suitable ratio of nickel, zinc and phosphorus, which helps to optimize the pore ratio and distribution of the subsequently prepared porous nickel electrode, in one embodiment, the concentration of the nickel salt can be 100-150 g / L, the concentration of the zinc salt can be 1-10 g / L, and the concentration of the phosphorus source can be 50-70 g / L.

[0053] In one embodiment, the pH value of the electroplating solution may be 4.5-5.5, the solvent of the electroplating solution may be water, and the solute may further include additives, and the additives include boric acid, ammonium chloride, and a crystal modifier.

[0054] Among them, the concentration of boric acid can be 10-30 g / L, the concentration of ammonium chloride can be 20-50 g / L, and the crystallization regulator can be ethylamine hydrochloride and other commonly used crystallization regulators in the art, and its concentration can be 45-55 g / L.

[0055] In one embodiment, in order to optimize the reaction rate of the electrochemical deposition reaction, the anode can be a pure nickel electrode, and the current density can be 5-20 mA / cm 2 The reaction time can be 1 to 2 hours, and the reaction temperature can be room temperature.

[0056] It can be understood that in the above electrochemical deposition reaction, a nickel-zinc-phosphorus material layer can be deposited on the surface of the nickel-based substrate.

[0057] S300, heat treating the electrochemically deposited nickel-based substrate.

[0058] In S200, a nickel-zinc-phosphorus material layer is deposited on the surface of the nickel-based substrate. After heat treatment, the nickel-zinc metals can diffuse into each other to form an alloy. At the same time, phosphorus elements with a smaller radius can also be doped into the alloy lattice to form Zn3P2 and Ni-Zn-P alloys.

[0059] In one embodiment, the heat treatment temperature may be 200 to 350° C., and the time may be 1 to 2 hours.

[0060] S400, placing the heat-treated nickel-based substrate into an alkaline solution for activation to obtain a porous nickel electrode.

[0061] After S300 forms an alloy phase, the zinc element can be removed by activation in alkaline solution, thereby constructing a porous structure and increasing the catalyst active area on the surface of the nickel-based substrate.

[0062] Due to the presence of Zn3P2 and Ni-Zn-P alloy, the P element can accelerate the dissolution of the Zn element and achieve a faster dissolution rate, thereby effectively shortening the activation time and reducing the amount of zinc residue while ensuring the uniformity of the pore structure, which is conducive to the full formation of the porous structure and thus improves the catalytic performance of the electrode.

[0063] In one embodiment, the alkali solution is a potassium hydroxide solution or a sodium hydroxide solution with a concentration of 10-30%, the activation time is 12-24 hours, and the activation temperature is 70-100°C.

[0064] Based on the methods of the above-mentioned embodiments, by introducing a phosphorus source into the electroplating solution, the dissolution rate of the zinc element during the activation process is effectively increased, thereby effectively reducing the residual amount of the zinc element while ensuring the uniformity of the pore structure, shortening the activation time, and contributing to the full formation of the porous structure, thereby improving the catalytic performance of the electrode and avoiding residual zinc elements from contaminating the electrolyte.

[0065] The beneficial effects of the technical solution of the present application are further elaborated in detail below in conjunction with specific embodiments.

[0066] Embodiment 1:

[0067] A porous nickel electrode is prepared by the following steps:

[0068] 1) Pretreatment: A 46-mesh twill weave, 0.25 mm wire diameter nickel mesh was ultrasonically treated in soapy water for 30 min to remove oil and then cleaned with pure water. It was then immersed in 3M HCl for 10 min to remove surface oxides. It was then rinsed with pure water and placed in pure water for later use.

[0069] 2) Electroplating: at 5mA / cm 2 At a current density of , in a plating solution containing 100 g / L nickel sulfate, 5 g / L zinc chloride, 60 g / L sodium hypophosphite, 30 g / L boric acid, 50 g / L ammonium chloride, and 50 g / L ethylamine hydrochloride, with a pH of 5, the previously treated electrode was used as the cathode and the pure nickel material was used as the anode for electroplating for 2 hours at room temperature to form a Ni-Zn-P material layer.

[0070] 3) Heat treatment: Rinse the electroplated electrode with pure water and then perform heat treatment at a temperature of 300° C. for 1.5 h to form a Ni-Zn-P intermetallic compound alloy layer.

[0071] 4) Activation: The heat-treated electrode was activated by soaking in 20% NaOH for 20 h at a temperature of 80° C. to construct a porous structure.

[0072] 5) Rinse the activated electrode and dry it to obtain a porous nickel electrode.

[0073] Embodiment 2:

[0074] A porous nickel electrode, the preparation method is basically the same as that of Example 1, except that:

[0075] The nickel-based substrate uses a 40-mesh plain weave, 0.19mm wire diameter nickel mesh;

[0076] The plating solution includes: 130g / L nickel sulfate, 8g / L zinc chloride, 50g / L sodium hypophosphite, 30g / L boric acid, 50g / L ammonium chloride, pH 4.5;

[0077] The heat treatment temperature is 250°C and the time is 2h.

[0078] Embodiment 3:

[0079] A porous nickel electrode, the preparation method is basically the same as that of Example 1, except that:

[0080] The plating solution includes: 150g / L nickel chloride, 10g / L zinc sulfate, 70g / L sodium phosphite, 10g / L boric acid, 20g / L ammonium chloride, 45g / L ethylamine hydrochloride;

[0081] The heat treatment temperature is 200°C and the time is 2h.

[0082] Embodiment 4:

[0083] A porous nickel electrode, the preparation method is basically the same as that of Example 1, except that:

[0084] The plating solution includes: 100g / L nickel nitrate, 2g / L zinc nitrate, 60g / L sodium phosphate, 20g / L boric acid, 30g / L ammonium chloride, 55g / L ethylamine hydrochloride;

[0085] The heat treatment temperature is 200°C and the time is 2h.

[0086] Comparative Example 1:

[0087] A porous nickel electrode, the preparation method is basically the same as that of Example 1, except that:

[0088] The plating solution does not include sodium hypophosphite.

[0089] Effect Example 1: Characterization Analysis

[0090] The porous nickel electrodes of Example 1 and Comparative Example 1 were characterized and analyzed to obtain Figure 2 , Figure 2 Surface SEM images of the porous nickel electrodes of Example 1 and Comparative Example 1, in which a is the porous nickel electrode of Example 1 and b is the porous nickel electrode of Comparative Example 1.

[0091] like Figure 2 As shown, the surface of the porous nickel electrode of Example 1 has a richer pore structure, which is mainly because the Zn element of the porous nickel electrode of Example 1 is dissolved more thoroughly during the activation process and the pore structure is fully formed.

[0092] Effect Example 2: Element Analysis

[0093] The element content of the porous nickel electrodes of Example 1 and Comparative Example 1 was analyzed to obtain the data in the following table.

[0094]

[0095] As shown in the above table, the residual amount of Zn in the porous nickel electrode of Example 1 is only 1.9%, while the residual amount of Zn in the porous nickel electrode of Comparative Example 1 reaches 23.2%.

[0096] The above data show that the addition of a phosphorus source to the electroplating solution of Example 1 can significantly reduce the residual amount of Zn, which is mainly due to the fact that the P element can be doped into the alloy lattice and improve the dissolution efficiency of Zn during activation.

[0097] Effect Example 3: Electrochemical Performance Analysis

[0098] Using a Bio-Logic electrochemical workstation and a saturated calomel reference electrode, the LSV curves of the porous nickel electrodes of Example 1 and Comparative Example 1 were tested in a 30wt% KOH solution at 80°C. Figure 3 , Figure 3 1 is the LSV curve of the porous nickel electrode of Example 1 and Comparative Example 1 of the present application.

[0099] like Figure 3 As shown, the overpotential of the electrode of Example 1 is significantly lower than that of Comparative Example 1, wherein at a current density of -500 mA / cm 2 Under the above conditions, the overpotential of the porous nickel electrode of Example 1 is 28 mV lower than that of Comparative Example 1, and the effect is obvious.

[0100] The above data show that the present application can promote the dissolution of Zn during activation by doping a phosphorus source during the electroplating process, reduce the residual Zn content, facilitate the formation of a pore structure, and improve the hydrogen evolution catalytic performance of the electrode.

[0101] It is obvious to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential features of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present application. Any reference numeral in a claim should not be regarded as limiting the claim to which it relates.

[0102] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a porous nickel electrode by electrodeposition of a nickel-zinc-phosphorus alloy, characterized in that: include: Using a nickel-based substrate as a cathode, an electrochemical deposition reaction is carried out in an electrolytic cell filled with an electroplating solution, wherein the electroplating solution includes a nickel salt, a zinc salt and a phosphorus source; heat treating the electrochemically deposited nickel-based substrate; The heat-treated nickel-based substrate is placed in an alkaline solution for activation to obtain a porous nickel electrode.

2. The method according to claim 1, characterized in that The nickel salt comprises one or more combinations of nickel sulfate, nickel chloride and nickel nitrate; and / or, The zinc salt comprises one or more combinations of zinc sulfate, zinc chloride and zinc nitrate; and / or, The phosphorus source includes one or more combinations of sodium hypophosphite, sodium phosphite and sodium phosphate.

3. The method according to claim 1, characterized in that The concentration of the nickel salt is 100-150 g / L, the concentration of the zinc salt is 1-10 g / L, and the concentration of the phosphorus source is 50-70 g / L.

4. The method according to claim 1, characterized in that: The pH value of the electroplating solution is 4.5-5.5, and the electroplating solution also includes additives, the additives include boric acid, ammonium chloride and a crystallization regulator, the concentration of the boric acid is 10-30 g / L, the concentration of the ammonium chloride is 20-50 g / L, and the concentration of the crystallization regulator is 45-55 g / L.

5. The method according to claim 1, characterized in that The method further comprises the following steps before the step of using the nickel-based substrate as a cathode and performing an electrochemical deposition reaction in an electrolytic cell filled with an electroplating solution: Pre-treating the nickel-based substrate; The step of pre-treating the nickel-based substrate comprises: placing the nickel-based substrate in a surfactant for ultrasonic treatment; The ultrasonically treated nickel-based substrate is immersed in acid and then taken out and cleaned.

6. The method according to claim 1, characterized in that The nickel-based substrate is a nickel mesh, nickel foam or nickel felt. In the electrochemical deposition reaction, the anode is a pure nickel electrode, and the current density is 5-20 mA / cm 2 The reaction time is 1 to 2 hours and the reaction temperature is room temperature.

7. The method according to claim 1, characterized in that In the step of heat treating the electrochemically deposited nickel-based substrate, the heat treatment temperature is 200-350° C. and the time is 1-2 hours.

8. The method according to claim 1, characterized in that In the step of placing the heat-treated nickel-based substrate into an alkali solution for activation, the alkali solution is a potassium hydroxide solution or a sodium hydroxide solution with a concentration of 10-30%, the activation time is 12-24 hours, and the activation temperature is 70-100°C.

9. A porous nickel electrode prepared by the method according to any one of claims 1 to 8.

10. Use of the porous nickel electrode according to claim 9 as a hydrogen evolution electrode in an alkaline water electrolysis reaction.

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