Three-dimensional CuO (at) Ni (OH) 2 (at) FeOOH multistage nanowire array electrode and preparation method and application thereof

Abstract

The invention relates to a three-dimensional CuO (at) Ni (OH) 2 (at) FeOOH multistage nanowire array electrode and a preparation method and application thereof, and belongs to the field of water electrolysis and new energy materials. The method comprises the following steps: firstly, placing foamy copper in a mixed solution of potassium hydroxide (sodium hydroxide) and ammonium persulfate for reaction to prepare a Cu (OH) 2 nanowire array electrode; secondly, calcining the electrode in a muffle furnace to obtain a CuO nanowire array electrode; and then, electrically depositing a Ni (OH) 2 nano layer and a FeOOH nano layer on the CuO nano wire in sequence to obtain the three-dimensional CuO (at) Ni (OH) 2 (at) FeOOH multi-stage nano wire array electrode. In the catalyst, the Ni (OH) 2 nano layer and the CuO nano wire are tightly combined and fully contacted, and the FeOOH and the Ni (OH) 2 nano layer are tightly combined and fully contacted, so that a unique three-layer cable structure is formed. The self-supporting electrode material prepared by the invention has excellent conductivity and electrocatalytic activity, and good structural stability. The method is simple in process and high in controllability, and has a non-negligible application prospect in the fields of water electrolysis and new energy.

Description

Technical Field

[0001] The present invention belongs to the technical field of water electrolysis and new energy materials, and in particular relates to a three-dimensional CuO@Ni(OH)2@FeOOH multi-level nanowire array electrode and a preparation method and application thereof. Background Art

[0002] Hydrogen production by water electrolysis is an effective method to achieve innovative substitution of energy forms, and can effectively store sustainable but intermittent energy such as solar energy and wind energy. However, due to the high energy barriers of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), especially the slow kinetics and high overpotential of OER, the electrolysis voltage in practical applications is much higher than the theoretical value (1.23V). Precious metals are usually required to achieve high electrocatalytic activity and low overpotential, but the scarcity of precious metals further hinders large-scale application. Therefore, in recent years, a large number of studies have been devoted to the development of transition metal-based electrocatalysts to replace precious metal-based catalysts. Among various non-precious metal electrocatalysts, nickel-iron-based nanomaterials have attracted widespread attention due to their low cost and abundant reserves. For example, nickel-iron-based (oxy)hydroxides are a promising class of precious metal substitutes due to their unique layered structure and tunable electronic structure. The catalytic activity of electrocatalysts is mainly affected by two aspects. One is the intrinsic activity of the catalytic active sites, which depends on the geometric / electronic structure of the active species. The other is the number of active sites, which is highly related to the micro / nanostructure of the catalytic electrode. In order to improve catalytic performance, people have conducted research on various strategies, including morphology, defects, heterogeneous structures, etc. at different scales.

[0003] In addition, the study showed that replacing water molecules with more easily oxidized small organic molecules such as urea, ethanol, amines and hydrazine also opened up another way for energy-saving hydrogen production. In particular, compared with the traditional OER, the urea oxidation reaction (UOR: CO(NH2)2+6OH - →N2+5H2O+CO2+6e - ) has an ultra-low theoretical decomposition voltage (0.37 V vs. RHE). It can be seen that urea oxidation coupled with water electrolysis is a promising energy-saving hydrogen production technology. Summary of the invention

[0004] The main purpose of the present invention is to provide a preparation method and application of a three-dimensional CuO@Ni(OH)2@FeOOH multi-level nanowire array electrode to solve the problems of slow reaction rate and poor stability of existing water electrolysis anode materials.

[0005] According to an embodiment of the present invention, a method for preparing a three-dimensional CuO@Ni(OH)2@FeOOH multi-level nanowire array electrode is proposed, which includes: placing pretreated foam copper in a mixed solution of potassium hydroxide or sodium hydroxide and ammonium persulfate of a certain concentration to react for a period of time to obtain a Cu(OH)2 nanowire array electrode; placing the electrode in a muffle furnace and heating it to a target temperature and maintaining it for a certain period of time to obtain a CuO nanowire array electrode; placing the CuO nanowire array electrode in a nickel salt-based electrolyte solution, and electrodepositing it at a specific potential to obtain a CuO@Ni(OH)2 nanowire array electrode; placing the CuO@Ni(OH)2 nanowire array electrode in an electrolyte solution, and electrodepositing it at a specific potential to obtain a CuO@Ni(OH)2@FeOOH nanowire array electrode.

[0006] The concentration of potassium hydroxide or sodium hydroxide is 1 to 3 M, the concentration of ammonium persulfate is 0.05 to 0.15 M, the total volume of the mixed solution is 50 to 200 mL, and the reaction time is 10 to 60 min.

[0007] Among them, the heating rate of the muffle furnace is 2~10℃·min -1 ; The target temperature is 100-250℃; The insulation time is 0.5-3h.

[0008] The nickel salt includes but is not limited to nickel nitrate, nickel sulfate, and nickel chloride; the solution concentration is 0.1 to 0.3 M; the solution volume is 80 to 150 mL; the deposition potential is -0.9 to -1.5 V vs. RHE; and the electrodeposition time is 60 to 600 s.

[0009] The electrolyte is a mixed solution of acetate and ferrous salt, wherein acetate includes but is not limited to potassium acetate and sodium acetate, and the concentration is 5 to 20 mM. Ferrous salts include but are not limited to ferrous sulfate, ferrous nitrate, and ferrous chloride, and the concentration is 0.5 to 3 mM. The total volume of the solution is 80 to 150 mL; the electrodeposition potential is -0.9 to -1.5 V vs. RHE; and the electrodeposition time is 10 to 300 s.

[0010] According to an embodiment of the present invention, a three-dimensional CuO@Ni(OH)2@FeOOH nanowire array electrode obtained according to the preparation method described above is also provided, which is used as an anode material for oxygen evolution reaction and urea electro-oxidation reaction.

[0011] According to the technical solution of the present invention, by combining chemical oxidation-heat treatment-electrodeposition, the obtained three-dimensional nanoarray electrode has a hierarchical porous structure and a high specific surface area, exhibits excellent electrocatalytic activity and durability, and broadens the synthesis strategy of Ni-Fe bimetallic materials as anode catalytic materials for water electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments are briefly introduced below.

[0013] Figure 1 The XRD spectra of the samples prepared in Example 1, Example 2 and Comparative Example 1 are shown.

[0014] Figure 2 The SEM images of the samples prepared in Example 1, Example 2, Example 3 and Comparative Example 1 and the TEM images of Example 1 and Comparative Example 1 are shown.

[0015] Figure 3 CV curves of OER performance of samples prepared in Example 1, Example 2, Example 3 and Comparative Example 1 in N2-saturated 1M KOH electrolyte.

[0016] Figure 4 LSV curves of UOR performance of samples prepared in Example 1, Example 2, Example 3 and Comparative Example 1 in N2-saturated 1M KOH+0.5MUREA electrolyte.

[0017] Figure 5 This is a graph showing the test results of water electrolysis and urea electrolysis of the sample prepared in Example 1. DETAILED DESCRIPTION

[0018] The present invention is described in detail below in conjunction with the embodiments, but the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only partial embodiments of the present invention, and for those skilled in the art, other similar embodiments obtained without creative work all fall within the protection scope of the present invention.

[0019] Embodiment 1:

[0020] A method for preparing a three-dimensional CuO@Ni(OH)2@FeOOH multi-level nanowire array electrode mainly comprises the following steps:

[0021] (1) A 1×4 cm copper foam was sequentially treated with 30 mL of deionized water, acetone, 2 M hydrochloric acid, and anhydrous ethanol for 15 min by ultrasonication and dried naturally. It was then placed in a 100 mL mixed solution of 2.5 M potassium hydroxide or sodium hydroxide and 0.125 M ammonium persulfate for 30 min to obtain blue Cu(OH)2NWs / CF on the surface of the copper foam.

[0022] (2) Place the Cu(OH)2NWs / CF in a muffle furnace and heat at 5℃·min -1 The temperature was raised to 180 °C and calcined for 1 h to obtain black CuO NWs / CF.

[0023] (3) The chronoamperometric electrodeposition was performed on 1×1 cm CuO NWs / CF. During the deposition process, a saturated calomel electrode (SCE) was used as the reference electrode, a graphite sheet was used as the counter electrode, the deposition solution was 100 mL of 0.15 M nickel nitrate hexahydrate solution, and the deposition time was 480 s to obtain CuO@Ni(OH)2NWs / CF.

[0024] (4) On the basis of electrodepositing a layer of Ni(OH)2, a layer of FeOOH was further deposited. The electrolyte was a mixed solution of 100 mL, 10 mM potassium acetate and 0.5 mM ferrous sulfate. The deposition time was 150 s, and a CuO@Ni(OH)2@FeOOH NWs / CF three-dimensional nanowire array catalyst was obtained.

[0025] Embodiment 2:

[0026] The experimental steps of this embodiment are the same as those of embodiment 1, except that one less layer of FeOOH is deposited.

[0027] Embodiment 3:

[0028] The experimental steps of this embodiment are the same as those of embodiment 1, with the only difference being that one less layer of Ni(OH)2 is deposited.

[0029] Comparative Example 1:

[0030] The experiment of this embodiment is the same as that of embodiment 1, except that no electrodeposition is performed.

[0031] Figure 1 XRD diagrams of samples prepared in Example 1, Example 2 and Comparative Example 1; it can be seen from the figure that with the deposition of Ni(OH)2 and FeOOH, the peak of the CuO substrate of the sample of Example 1 becomes weaker, indicating successful electrodeposition and an increase in the deposited material, which weakens the CuO signal.

[0032] Figure 2 The SEM images of the samples prepared in Example 1, Example 2, Example 3 and Comparative Example 1 and the TEM images of Example 1 and Comparative Example 1; wherein (a) is the SEM image of the CuO@Ni(OH)2@FeOOH NWs / CF in Example 1, and (b), (c) and (d) are the SEM images of Example 2, Example 3 and Comparative Example 1, respectively. It can be seen from the figure that the structure of the nanowires is maintained before and after chemical oxidation and electrodeposition. Among them, (e) and (f) are TEM images of Example 1 and Comparative Example 1. It can be seen from the TEM images of the two that, relative to Comparative Example 1, Example 1 has an obvious layered interface, with the inner layer being CuO and the outer layers being Ni(OH)2 and FeOOH, respectively, proving that the sample obtained in Example 1 is a layered three-dimensional nanowire array structure similar to a cable structure.

[0033] Figure 3 The CV curves of the OER performance of the samples prepared in Example 1, Example 2, Example 3 and Comparative Example 1 in a 1M KOH electrolyte saturated with N2 are shown in Figure 1. As can be seen from the figure, Example 1 has the best OER performance, which is 100 mA cm -2 The corresponding voltage is the minimum (1.54V).

[0034] Figure 4 The UOR performance LSV curves of the samples prepared in Example 1, Example 2, Example 3 and Comparative Example 1 in N2-saturated 1M KOH+0.5M UREA electrolyte are shown in the figure. As can be seen from the figure, Example 1 has the best UOR performance at a current density of 10 mA·cm -2 and 100mA·cm -2 The corresponding voltages are 1.32V and 1.37V respectively.

[0035] Figure 5 The test results of water electrolysis and urea electrolysis of the sample of Example 1 are shown in Figure (a). From Figure (a), it can be seen that urea electrolysis (HER and UOR) requires 1.37V to reach 100mA·cm -2 The current density is 2.447 W / m. In contrast, water electrolysis (HER and OER) requires a higher cell voltage to achieve the same current density, which reflects the advantage of energy-saving hydrogen production using UOR at the anode. As can be seen from Figure (b), whether in 1M KOH or 1M KOH+0.5M UREA electrolyte, the stability test maintained a relatively stable trend, indicating that the prepared CuO@Ni(OH)2@FeOOH NWs / CF catalyst has good electrocatalytic stability.

[0036] It should be noted that the above embodiments are only for further illustrating the content of the present invention and should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, modifications or substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention.

Claims

1. A method for preparing a three-dimensional CuO@Ni(OH)2@FeOOH multi-level nanowire array electrode, characterized in that The following steps are involved: S1: placing the pretreated copper foam in a mixed solution of potassium hydroxide or sodium hydroxide and ammonium persulfate at a certain concentration for a period of time to prepare a Cu(OH)2 nanowire array electrode; S2: placing the Cu(OH)2 nanowire array electrode in a muffle furnace and heating it to a target temperature and maintaining it for a certain period of time to obtain a CuO nanowire array electrode; S3: placing the CuO nanowire array electrode in a nickel salt-based electrolyte solution, and electrodepositing at a specific potential to obtain a CuO@Ni(OH)2 nanowire array electrode; S4: placing the CuO@Ni(OH)2 nanowire array electrode in an electrolyte solution, and electro-depositing the CuO@Ni(OH)2@FeOOH nanowire array electrode at a specific potential.

2. The preparation method according to claim 1, characterized in that: In step S1, the concentration of potassium hydroxide or sodium hydroxide is 1 to 3 M, and the concentration of ammonium persulfate is 0.05 to 0.15 M. The total volume of the mixed solution is 50 to 200 mL, and the reaction time is 10 to 60 min.

3. The preparation method according to claim 1, characterized in that: In step S2, the heating rate is 2-10°C·min -1 ; The target temperature is 100-250℃; The insulation time is 0.5-3h.

4. The preparation method according to claim 1, characterized in that: In step S3, the nickel salt includes but is not limited to nickel nitrate, nickel sulfate, and nickel chloride; the solution concentration is 0.1 to 0.3 M; the solution volume is 80 to 150 mL; the deposition potential is -0.9 to -1.5 V vs. RHE; and the electrodeposition time is 60 to 600 s.

5. The preparation method according to claim 1, characterized in that: In step S4, the electrolyte is a mixed solution of acetate and ferrous salt, wherein acetate includes but is not limited to potassium acetate and sodium acetate, and the concentration is 5 to 20 mM. Ferrous salts include but are not limited to ferrous sulfate, ferrous nitrate, and ferrous chloride, and the concentration is 0.5 to 3 mM. The total volume of the solution is 80 to 150 mL; the electrodeposition potential is -0.9 to -1.5 V vs. RHE; and the electrodeposition time is 10 to 300 s.

6. A three-dimensional CuO@Ni(OH)2@FeOOH multi-level nanowire array electrode material prepared by the preparation method according to any one of claims 1 to 5.

7. Application of the three-dimensional CuO@Ni(OH)2@FeOOH multi-level nanowire array electrode according to claim 6 in the fields of water electrolysis and new energy materials.

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