High-current-density hydrogen evolution electrode for alkaline water electrolysis as well as preparation method and application of high-current-density hydrogen evolution electrode

Abstract

The invention discloses a high-current-density hydrogen evolution electrode for alkaline water electrolysis as well as a preparation method and application of the high-current-density hydrogen evolution electrode, and belongs to the technical field of hydrogen production by water electrolysis. The nano-catalyst hydrogen evolution electrode prepared by the invention has a sandwich structure, the outermost layer is the nano cobaltosic oxide catalyst, and the nano-catalyst hydrogen evolution electrode has large specific surface area and high porosity, is beneficial to active site exposure, electrolyte permeation and gas product overflow, promotes mass transfer power and improves current density. And the nanosheet catalyst grows on the metal cobalt interlayer in an in-situ rooting manner, so that the interface bonding and charge transfer of the catalyst are enhanced, and the mechanical stability and the charge transfer power of the catalyst are improved. The prepared electrode material HER is high in activity and good in stability, key, large-current-density catalysis can be achieved under low overpotential, the performance is remarkably superior to that of a commercial # imgabs0 # nickel electrode, and the key bottleneck that the running current density of an ALK electrolytic cell is low is hopeful to be solved. And moreover, the electroplating preparation process is simple, time and energy are saved, the cost is low, and large-scale production can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen production by electrolysis of water, and specifically relates to a high current density hydrogen evolution electrode for alkaline water electrolysis and a preparation method and application thereof. Background Art

[0002] Hydrogen production by water electrolysis is an effective way to prepare green hydrogen fuel, which is expected to solve the storage and consumption problems of renewable energy power generation and help achieve the "dual carbon" goals. Alkaline water (ALK) electrolyzers and proton exchange membrane (PEM) electrolyzers are currently more mature water electrolysis technologies. Among them, ALK occupies a large market share due to its advantages such as low equipment cost and high technical maturity. However, the operating current density of ALK technology is low, which leads to problems such as large equipment size, high manufacturing cost, and low working efficiency, which seriously restricts its application development. Specifically, most commercial ALK electrolyzers use Raney prepared by thermal spraying. Nickel electrodes usually require a large overpotential of 300-500mV to drive 500mA / cm 2 The current density of the ALK electrolyzer is usually limited to 500 mA / cm 2 Therefore, in order to meet the scale of production, industrial ALK water electrolysis hydrogen production can only enlarge the equipment size, which will lead to a series of adverse consequences, such as: increased equipment manufacturing costs and difficulty, increased gas cross-permeability, high power consumption and low efficiency of hydrogen production. In addition, commercial The preparation method of nickel electrodes includes a two-step process of thermal spraying nickel-aluminum alloy particles and strong alkali etching activation, which has the "three highs" problems of high pollution, high waste and high energy consumption. Summary of the invention

[0003] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0004] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0005] Therefore, the object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a high current density hydrogen evolution electrode for alkaline water electrolysis.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions, including:

[0007] The cleaned porous metal mesh and metal plate are used as cathode and anode respectively to construct a two-electrode system for electroplating, and the cathode is taken out and repeatedly washed with clean water, and then dried to obtain a sandwich structure hydrogen evolution electrode;

[0008] Wherein, the electroplating solution is a mixed aqueous solution of a cobalt source, ammonium chloride and thiourea; the molar concentration of the cobalt source is 0.07-0.12 mol / L;

[0009] The sandwich structure comprises a porous metal substrate layer, a cobalt metal middle layer and a nano-cobalt tetroxide catalyst outermost layer.

[0010] As a preferred embodiment of the method for preparing the high current density hydrogen evolution electrode for alkaline water electrolysis of the present invention, the cobalt source comprises one or more of cobalt acetate, cobalt chloride and cobalt sulfate.

[0011] As a preferred embodiment of the method for preparing the high current density hydrogen evolution electrode for alkaline water electrolysis of the present invention, the cleaning is performed by soaking in dilute hydrochloric acid for 15 to 25 minutes and then rinsing with clean water.

[0012] As a preferred embodiment of the method for preparing the high current density hydrogen evolution electrode for alkaline water electrolysis of the present invention, the cathode comprises one of nickel wire mesh, nickel foam and nickel felt; and the anode comprises one of titanium plate, nickel plate and stainless steel plate.

[0013] As a preferred embodiment of the method for preparing the high current density hydrogen evolution electrode for alkaline water electrolysis of the present invention, the molar concentration of ammonium chloride in the electroplating solution is 1.8-2.3 mol / L; the molar concentration of thiourea is 0.1 mol / L.

[0014] As a preferred embodiment of the method for preparing the high current density hydrogen evolution electrode for alkaline water electrolysis of the present invention, the electroplating process adopts constant current chronopotentiometry, wherein the current density is 200 mA / cm 2 , the electroplating deposition time is 10 to 20 minutes.

[0015] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a high current density hydrogen evolution electrode for alkaline water electrolysis. The high current density hydrogen evolution electrode for alkaline water electrolysis has a sandwich structure, with a porous metal as a substrate layer, cobalt metal as an intermediate layer, and a nano-cobalt oxide catalyst as an outermost layer.

[0016] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an application of a high current density hydrogen evolution electrode for alkaline water electrolysis in the electrolysis of alkaline water for hydrogen evolution.

[0017] As a preferred application of the high current density hydrogen evolution electrode for alkaline water electrolysis of the present invention, the catalytic activity of the hydrogen evolution electrode during the electrolysis of alkaline water for hydrogen evolution is 207mV overpotential, i.e., it can reach 1A / cm 2 high current density.

[0018] As a preferred application of the high current density hydrogen evolution electrode for alkaline water electrolysis of the present invention, the hydrogen evolution electrode is 2 The hydrogen evolution catalyst operated stably at a high current density for 300 hours without attenuation.

[0019] Beneficial effects of the present invention:

[0020] The nano catalyst hydrogen evolution electrode prepared by the present invention has a sandwich structure, the outermost layer is a nano cobalt tetroxide catalyst, which has a large specific surface area and high porosity, is conducive to the exposure of active sites and electrolyte penetration and gas product overflow, promotes mass transfer power, and improves current density. In addition, the nano sheet catalyst is rooted and grown in situ on the metal cobalt interlayer, which enhances the interface bonding and charge transfer of the catalyst, and improves the mechanical stability and charge transfer power of the catalyst.

[0021] The electrode material prepared by the present invention has high HER activity and good stability. The key is that it can achieve high current density catalysis at low overpotential, and its performance is significantly superior to commercial Nickel electrodes are expected to solve the key bottleneck of low operating current density of ALK electrolytic cells. Moreover, the electroplating preparation process is simple, time-saving and energy-saving, low-cost and scalable. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0023] Figure 1 This is a scanning electron microscope top view of the electrode material obtained in Example 1 of the present invention.

[0024] Figure 2 This is a top view of the electrode material obtained in Example 1 of the present invention, magnified by a scanning electron microscope.

[0025] Figure 3 This is a scanning electron microscope cross-sectional view of the electrode material obtained in Example 1 of the present invention.

[0026] Figure 4 This is a perspective electron microscope image of the electrode material obtained in Example 1 of the present invention.

[0027] Figure 5 This is a high-resolution transmission electron microscope image of the electrode material obtained in Example 1 of the present invention.

[0028] Figure 6 This is the selected area electron diffraction pattern of the electrode material obtained in Example 1 of the present invention.

[0029] Figure 7 The electrode material obtained in Example 1 of the present invention runs at 1A / cm 2 Stability at high current density.

[0030] Figure 8 It is a comparison of HER activities of different samples prepared by adjusting the concentration of the plating solution in Examples 1 to 3 of the present invention.

[0031] Fig. 9 It is a comparison of HER activities of different samples prepared by adjusting the electroplating time in Examples 1, 4, and 5 of the present invention.

[0032] Fig.10 The electrode material obtained in Example 1 of the present invention is the same as the commercial Comparison of HER performance of nickel electrodes. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0034] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0035] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0036] The raw materials used in the present invention are all commercially available unless otherwise specified.

[0037] The substrate used in the present invention is a 46-mesh nickel wire mesh provided by Jiangsu Green Hydrogen Electrode Co., Ltd.

[0038] Example 1

[0039] This embodiment provides a method for preparing a high current density hydrogen evolution (HER) electrode for alkaline water electrolysis, specifically:

[0040] A nickel wire mesh (1 cm×3 cm) was immersed in dilute hydrochloric acid (5 wt.%) for 20 min for surface treatment, and then taken out and rinsed thoroughly with clean water.

[0041] Weigh 7 mmol of cobalt acetate, 140 mmol of ammonium chloride, and 7 mmol of thiourea, dissolve them in 70 ml of deionized water, and stir vigorously for 30 min to fully dissolve them to obtain a uniform mixed electroplating solution.

[0042] Build a two-electrode circuit, connect the nickel wire mesh to the cathode and the titanium plate to the anode. Control the two electrodes of the same area (1cm×2cm) to be immersed in the electroplating solution, and apply a rectifier power supply of 200mA / cm 2 The constant current was applied and the electroplating was continued for 15 min. The nickel wire mesh was removed and the surface attachments were washed with clean water. After drying, the nanocatalyst electrode of this embodiment was obtained.

[0043] Figure 1 This is a SEM top view of the electrode material obtained in this embodiment. It can be seen that dense micron flower balls grow on the nickel wire mesh substrate. Figure 2 The magnified SEM photo shows that the micron flower ball is composed of nanosheets. This multi-scale pore structure amplifies the specific surface area, increases the exposure of active sites, and is conducive to electrolyte penetration and gas escape.

[0044] Figure 3 This is a SEM cross-sectional photo of the electrode material obtained in this example. It can be seen that the electrode presents a layered sandwich structure, with the bottom layer being a nickel wire mesh substrate, the middle layer being a metal cobalt layer, and the outermost layer being cobalt oxide nanosheets. The rooted growth of the nanocatalyst ensures mechanical bonding and charge transfer at the interface, promoting mass transfer / charge transfer dynamics when operating at high current density.

[0045] Figure 4 This is a TEM photo of the electrode material prepared in this example. It can be seen that the catalyst is a two-dimensional ultra-thin nanosheet. Figure 5 This is a HRTEM image, showing that the internal crystalline phase of the nanosheet belongs to the spinel structure Co3O4 (JCPDS#43-1003) crystal. Figure 6 The SAED spectrum shows that the (111), (220) and (311) planes of Co3O4 crystals are identified, which is consistent with the results of HRTEM. These characterizations clearly confirm that the catalyst is Co3O4 nanosheets.

[0046] The stability of the electrode prepared in Example 1 of the present invention was evaluated by chronopotentiometry, and the current density was controlled at 1 A / cm 2 The electrolyte was 1M KOH solution and the temperature was room temperature 25°C. The results were as follows Fig.10 As shown. Figure 7 It can be seen that the electrode of the present invention is 1A / cm 2 It runs smoothly at high current density, and there is no sign of performance degradation during the 300-hour test.

[0047] Example 2

[0048] The difference between this embodiment and embodiment 1 is that the dosage of cobalt acetate in the electroplating solution is adjusted to 5 mmol, that is, the concentration of cobalt acetate in the electroplating solution is 0.07 mol / L, and the rest of the preparation process is the same as that in embodiment 1 to prepare a hydrogen evolution electrode.

[0049] Example 3

[0050] The difference between this embodiment and embodiment 1 is that the dosage of cobalt acetate in the electroplating solution is adjusted to 9 mmol, that is, the concentration of cobalt acetate in the electroplating solution is 0.12 mol / L, and the rest of the preparation process is the same as that in embodiment 1 to prepare a hydrogen evolution electrode.

[0051] Figure 8 The HER performance of the hydrogen evolution electrodes prepared in Examples 1 to 3 is compared. Examples 2 and 3 achieve 0.5 A / cm 2 The required overpotential is shown in Table 1.

[0052] Table 1

[0053]

[0054] As can be seen from Table 1, the effect of adjusting the concentration of cobalt acetate in the electroplating solution on the performance of the prepared hydrogen evolution electrode material is significant, because the cobalt ion concentration in the solution determines the sample composition and morphology formed by electroplating under the same conditions. When the cobalt acetate solution is too high, the concentration of cobalt ions is excessive in the entire electroplating process, so that only a cobalt metal layer can be formed by electroplating, and a cobalt oxide catalytic layer cannot be formed, so that HER lacks reaction sites. When the cobalt acetate solution is too low, a cobalt metal layer will not be formed, and cobalt oxide nanosheets will only be formed on the surface of the metal substrate, which will reduce the mechanical bonding and charge transfer intensity, and will not be conducive to the occurrence of HER. In short, too low or too high cobalt acetate concentration will affect the formation of the "sandwich" structure. According to the results of Table 1, the best technical effect can be obtained when the concentration of cobalt acetate in the electroplating solution in the present invention is 0.1mol / L.

[0055] Example 4

[0056] The difference between this embodiment and embodiment 1 is that the electroplating time is adjusted to 10 minutes, and the rest of the preparation process is the same as that of embodiment 1 to prepare a hydrogen evolution electrode.

[0057] Example 5

[0058] The difference between this embodiment and embodiment 1 is that the electroplating time is adjusted to 20 minutes, and the rest of the preparation process is the same as that of embodiment 1 to prepare a hydrogen evolution electrode.

[0059] Fig. 9 The HER performance of the hydrogen evolution electrodes prepared in Examples 1, 4, and 5 is compared. Examples 4 and 5 achieve 0.5 A / cm 2The required overpotential is shown in Table 2.

[0060] Table 2

[0061]

[0062] As can be seen from Table 2, adjusting the electroplating time has a significant effect on the performance of the prepared hydrogen evolution electrode material. This is because when other conditions are the same, the length of the electroplating time will affect the final proportion of the cobalt metal layer and the cobalt tetroxide catalytic surface in the "sandwich" structure. Too short an electroplating time makes it impossible for the electroplated sample to form a cobalt tetroxide catalytic surface on the surface, while too long an electroplating time will cause the cobalt tetroxide nanoflowers to form a large number of aggregates, which will affect its charge transfer ability and be unfavorable for the occurrence of the reaction. According to the results in Table 2, the best technical effect can be obtained when the electroplating time in the present invention is 15 minutes.

[0063] Example 6

[0064] The difference between this embodiment and embodiment 1 is that the cobalt source is adjusted to cobalt chloride, and the rest of the preparation process is the same as that of embodiment 1 to prepare a hydrogen evolution electrode.

[0065] Example 7

[0066] The difference between this embodiment and embodiment 1 is that the cobalt source is adjusted to cobalt sulfate, and the rest of the preparation process is the same as that of embodiment 1 to prepare a hydrogen evolution electrode.

[0067] Examples 6 and 7 achieve 0.5A / cm 2 The required overpotential is shown in Table 3.

[0068] Table 3

[0069]

[0070] As can be seen from the above table, adjusting the type of cobalt source has a significant effect on the performance of the prepared hydrogen evolution electrode material, because the ligands and hydrates carried by different cobalt sources will affect the actual performance of the electron transmission capacity in the electroplating solution, as well as the adsorption of the groups during the electroplating process. In summary, the best technical effect can be obtained when the cobalt source in the present invention is cobalt acetate.

[0071] Comparative Example 1

[0072] This comparative example provides a thermal spraying preparation Nickel electrode, provided by Jiangsu Green Hydrogen Electrode Co., Ltd.

[0073] The hydrogen evolution electrode prepared in Example 1 and the commercial electrode in Comparative Example 1 were applied to electrolyze alkaline water, specifically:

[0074] The electrode prepared in Example 1 is similar to the commercial The nickel electrodes were used as cathode hydrogen evolution electrodes, and their cathode hydrogen evolution activities were evaluated by linear scanning voltammetric polarization curves. The scanning rate was controlled at 5 mV / s, the electrolyte was 1 M KOH solution, and the temperature was room temperature 25 °C. The results are shown in Fig. 9 shown.

[0075] Fig.10 It can be seen that the electrode prepared in Example 1 of the present invention exhibits excellent HER performance, especially high current density performance, achieving 0.5 A / cm 2 and 1A / cm 2 The overpotentials required for the current density are 184mV and 207mV respectively, which are far better than commercial Nickel electrode.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 1 is that the content of thiourea in the electroplating solution is adjusted to 0, and the rest of the preparation process is the same as that of Example 1 to prepare a hydrogen evolution electrode.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 1 is that the current density of the electroplating is adjusted to 100 mA / cm 2 The remaining preparation processes are the same as those in Example 1 to obtain a hydrogen evolution electrode.

[0080] Comparative Example 4

[0081] The difference between this comparative example and Example 1 is that the current density of the electroplating is adjusted to 300 mA / cm 2 The remaining preparation processes are the same as those in Example 1 to obtain a hydrogen evolution electrode.

[0082] Comparative Example 5

[0083] This comparative example provides a conventional cobalt tetroxide electrode, specifically:

[0084] Platinum-modified cobalt tetroxide nanospheres were synthesized in one step using the PLAL method. In a typical synthesis, a cobalt target was placed in a 50μm platinum salt aqueous solution with a volume of 10mL by a Nd:YAG (Surelite-II) pulsed laser. A laser with a base wavelength of 1064nm and a pulse power of 100mJ / s was used, and it was focused on the surface of the cobalt target through a lens with a focal length of 30mm. After 30 minutes of PLAL treatment, the colloidal solution was centrifuged at 22430×g and washed with water and ethanol several times. Finally, the platinum-modified cobalt tetroxide nanosphere sample was dried overnight at 100°C to obtain a cobalt tetroxide electrode.

[0085] The overpotential and service life required for achieving different current densities in the above comparative examples are shown in Table 4.

[0086] Table 4

[0087]

[0088] It can be seen from the above table that the ratio of cobalt salt, conductive agent and electroplating current used in the present invention are the best choices. Compared with nickel electrodes and conventional cobalt tetroxide electrode catalysts, the cobalt tetroxide catalytic electrode described in the present invention has a lower overpotential and a more energy-saving preparation method under high current conditions, showing good commercial application prospects.

[0089] The cobalt in the electroplating solution of the present invention is the metal source for generating the cobalt metal layer and the cobalt tetroxide catalyst layer, and plays a major role. The role of ammonium chloride and thiourea is to increase the conductivity and electronic regulation ability of the electroplating solution.

[0090] The nano catalyst hydrogen evolution electrode prepared by the present invention has a sandwich structure, the outermost layer is a nano cobalt tetroxide catalyst, which has a large specific surface area and high porosity, is conducive to the exposure of active sites and electrolyte penetration and gas product overflow, promotes mass transfer power, and improves current density. In addition, the nano sheet catalyst is rooted and grown in situ on the metal cobalt interlayer, which enhances the interface bonding and charge transfer of the catalyst, and improves the mechanical stability and charge transfer power of the catalyst.

[0091] The electrode material prepared by the present invention has high HER activity and good stability. The key is that it can achieve high current density catalysis at low overpotential, and its performance is significantly superior to commercial Nickel electrodes are expected to solve the key bottleneck of low operating current density of ALK electrolytic cells. Moreover, the electroplating preparation process is simple, time-saving and energy-saving, low-cost and scalable.

[0092] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a high current density hydrogen evolution electrode for alkaline water electrolysis, characterized in that: include, The cleaned porous metal mesh and metal plate are used as cathode and anode respectively to construct a two-electrode system for electroplating, and the cathode is taken out and repeatedly washed with clean water, and then dried to obtain a sandwich structure hydrogen evolution electrode; The electroplating solution is a mixed aqueous solution of a cobalt source, ammonium chloride and thiourea; the molar concentration of the cobalt source is 0.07-0.12 mol / L.

2. The preparation method of high current density hydrogen evolution electrode for alkaline water electrolysis as claimed in claim 1, wherein: The cobalt source includes one or more of cobalt acetate, cobalt chloride, and cobalt sulfate.

3. The preparation method of high current density hydrogen evolution electrode for alkaline water electrolysis as claimed in claim 1, wherein: The cleaning comprises soaking in dilute hydrochloric acid for 15 to 25 minutes and then rinsing with clean water.

4. The preparation method of high current density hydrogen evolution electrode for alkaline water electrolysis as claimed in claim 1, wherein: The cathode includes one of nickel wire mesh, nickel foam and nickel felt; the anode includes one of titanium plate, nickel plate and stainless steel plate.

5. The preparation method of high current density hydrogen evolution electrode for alkaline water electrolysis as claimed in claim 1, characterized in that: The molar concentration of ammonium chloride in the electroplating solution is 1.8-2.3 mol / L; the molar concentration of thiourea is 0.1 mol / L.

6. The preparation method of high current density hydrogen evolution electrode for alkaline water electrolysis as claimed in claim 1, characterized in that: The electroplating process adopts constant current chronopotentiometry, where the current density is 200 mA / cm 2 , the electroplating deposition time is 10 to 20 minutes.

7. A high current density hydrogen evolution electrode for alkaline water electrolysis prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The high current density hydrogen evolution electrode for alkaline water electrolysis has a sandwich structure, with porous metal as the substrate layer, cobalt metal as the middle interlayer, and nano cobalt tetroxide catalyst as the outermost layer.

8. Use of the high current density hydrogen evolution electrode for alkaline water electrolysis as claimed in any one of claims 1 to 6 in the electrolysis of alkaline water for hydrogen evolution.

9. The application of the high current density hydrogen evolution electrode for alkaline water electrolysis as claimed in claim 8, characterized in that: The catalytic activity of the hydrogen evolution electrode during the electrolysis of alkaline water for hydrogen evolution is 207 mV overpotential, i.e., it can reach 1 A / cm 2 high current density.

10. The use of a high current density hydrogen evolution electrode for alkaline water electrolysis as claimed in claim 8, characterized in that: The hydrogen evolution electrode is at 1A / cm 2 The hydrogen evolution catalyst operated stably at a high current density for 300 hours without attenuation.

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