CN111889117B - Core-shell copper selenide@nickel-iron hydrotalcite electrocatalyst, preparation method and water electrolysis application - Google Patents

Abstract

The invention discloses a core-shell Cu₂Se @ NiFe-LDH electrocatalyst, and a preparation method and application thereof. Firstly, using foamed copper as substrate, in the alkaline medium and adopting chemical oxidation method to make in-situ growth of Cu (OH) on its surface₂Selenizing the nano-wire by selenium powder in a tube furnace to convert the nano-wire into copper selenide nano-wire, finally growing the nickel-iron hydrotalcite nano-sheet on the surface of the nano-wire by adopting an electrodeposition method, and preparing the core-shell copper selenide @ nickel-iron hydrotalcite nano-sheet electrocatalyst by adopting a two-step method of gas phase selenization and electrodeposition. The obtained core-shell copper selenide @ ferronickel hydrotalcite nanosheet catalyst is in a nanowire shape, and the diameter of the core-shell copper selenide @ ferronickel hydrotalcite nanosheet catalyst is 150-250 nm; with Cu₂Se is taken as a core, NiFe-LDH sheets are taken as shells, and the thickness of the NiFe-LDH sheets is less than 10 nm; the catalytic activity of the nickel-iron hydrotalcite nanosheets and the composite materials thereof in the 1mol/L KOH electrolyte solution through oxygen evolution reaction, hydrogen evolution reaction and full hydrolysis is higher than that of the nickel-iron hydrotalcite nanosheets and the composite materials thereof prepared by other traditional methods.

Description

Core-shell copper selenide@nickel-iron-based hydrotalcite electrocatalyst, preparation method and water electrolysis application

Technical field:

The invention relates to a core-shell copper selenide@nickel-iron hydrotalcite (Cu ₂ Se@NiFe-LDH) electrocatalyst that can effectively improve the efficiency of electrolysis of water and a preparation method thereof, and the core-shell selenium obtained by the preparation method The catalytic effect of Cu@NiFe hydrotalcite electrocatalyst on oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under alkaline conditions belongs to the field of electrocatalysis.

Background technique:

Electrolyzed water is of great significance for reducing petrochemical energy demand and protecting the environment. However, in acidic and alkaline electrolytes, electrolysis of water needs to break the OH bond and release electrons to form the O=O double bond. This kinetic process is very slow and usually requires a potential higher than 1.23V, that is, a large overpotential. Therefore, highly active catalysts are required to reduce overpotentials for efficient water splitting. Oxygen evolution reaction (OER) is the bottleneck of water splitting. Although there are noble metal catalysts, such as RuO ₂ and IrO ₂ , they are expensive, scarce, and require large overpotentials to drive OER. Therefore, the development of efficient, abundant, and inexpensive OER non-precious metal catalysts is one of the topics of current renewable energy research.

Transition double metal hydroxides (LDHs) have potential applications due to their compositional diversity and stability. Studies have shown that bimetallic NiFe-LDH has higher catalytic activity and lower overpotential than LDH containing only a single Ni or Fe component. However, the HER performance of NiFe-LDH is not satisfactory. Studies have shown that strong interactions between transition metal hydroxides and other metal compounds play an important role in the structural and electrochemical properties of the constructed composites. Transition metal selenides are considered to be a promising class of support materials because of their unique electronic configurations and fairly good catalytic activities, which can act to tune the OER and HER performance of LDHs. The specific surface area, electrical conductivity, and stability of the composite catalyst can be improved through rational structural design, which further promotes its electrocatalytic activity.

In the invention, Cu ₂ Se is used as a supporting carrier, and a core-shell Cu ₂ Se@NiFe hydrotalcite composite Cu ₂ Se@NiFe-LDH is prepared by an electrodeposition method. In the invention, the deposition conditions are optimized by controlling the deposition time, the concentration and ratio of the metal ions in the electrolyte, and the electrochemical properties of CuSe@NiFe-LDH with different deposition times are tested to compare and analyze the influence of the deposition time on the morphology and catalytic performance of the catalyst. ; Through the performance test of Cu ₂ Se@NiFe-LDH prepared with different metal ion concentrations, the effect of metal ion concentration on the morphology and catalytic performance of the catalyst was compared and analyzed _; LDH performance test, comparative analysis of the effect of metal ion ratio on catalyst morphology and catalytic performance, obtained the best conditions for electrodeposition, prepared core-shell Cu ₂ Se@NiFe-LDH electrode material, and its electrolytic water performance A systematic study has been carried out, and the related research work has not been reported yet.

Invention content:

In view of the deficiencies of the prior art and the needs of research and application in the field, one of the objects of the present invention is to provide a core-shell copper selenide@nickel-iron hydrotalcite electrocatalyst, which is characterized in that the catalyst is made of foamed copper As the substrate, Cu(OH) ₂ nanowires were grown in situ on its surface by chemical oxidation in an alkaline medium, and then selenized into copper selenide nanowires with selenium powder in a tube furnace, and finally electro-deposition method was used. Nickel-iron hydrotalcite was grown on its surface; copper foam was recorded as CF, copper selenide as Cu ₂ Se, nickel-iron hydrotalcite as NiFe-LDH, copper selenide@nickel-iron hydrotalcite as Cu ₂ Se @NiFe-LDH;

The second purpose of the present invention is to provide a kind of preparation method of core-shell copper selenide@nickel-iron hydrotalcite electrocatalyst, specifically comprising the following steps:

(1) Preparation of Cu ₂ Se/CF

Soak commercial copper foam with a size of 3cm×4cm in a 37% hydrochloric acid solution for 10 minutes, and wash it with deionized water and absolute ethanol for several times; put the cleaned copper foam into 80mL of NaOH and (NH ₄ ) Soak in the mixed solution of ₂ S ₂ O ₈ for 20 min to grow light blue Cu(OH) ₂ nanowires on the surface in situ, take out the copper foam with Cu(OH) ₂ nanowires grown and rinse it with deionized water. Dry in an oven at 60 °C for 6 h; place the dried Cu(OH) ₂ nanowires in a tube furnace, and put 0.1 g of selenium powder at the front of the tube furnace at a rate of 5 °C/min under a nitrogen atmosphere. The temperature was raised to 400 °C and kept for 30 min. After the tube furnace was naturally cooled, the sample was taken out, washed with deionized water and ethanol for several times to obtain Cu ₂ Se/CF, which was dried for later use;

(2) Preparation of Cu ₂ Se@NiFe-LDH/CF

With Cu ₂ Se/CF as the working electrode, platinum wire electrode as the counter electrode, saturated calomel electrode as the reference electrode, the electrolyte is a mixed aqueous solution of Ni(NO ₃ ) ₂ and FeSO ₄ , and electrified at a potential of -1.0V The electrodeposition reaction was carried out for 60-150 s to grow NiFe-LDH on the surface, and the core-shell Cu ₂ Se@NiFe-LDH/CF catalyst was prepared;

Wherein the molar concentrations of NaOH and (NH ₄ ) ₂ S ₂ O ₈ in the mixed solution of NaOH and (NH ₄ ) ₂ S ₂ O ₈ in step (1) are 2.5 and 0.125 mol/L respectively; in step (2), Ni The total concentration of metal ions in the mixed aqueous solution of (NO ₃ ) ₂ and FeSO ₄ is 0.15-0.45 mol/L, and the molar ratio of Ni(NO ₃ ) ₂ and FeSO ₄ is 1-6:2.

The electrocatalyst prepared by the above preparation method is in the shape of nanowires with a diameter of 150-250nm; with Cu ₂ Se as the core and NiFe-LDH flakes as the shell, the thickness of the NiFe-LDH flakes is less than 10nm.

The core _- shell Cu ₂ Se@NiFe-LDH electrocatalyst prepared by the above preparation method is suitable for catalyzing oxygen evolution reaction and hydrogen evolution reaction in alkaline electrolyte. The electrocatalyst was added to 1 mol/L KOH solution as the working electrode, the saturated calomel electrode was used as the reference electrode, and the platinum sheet was used as the counter electrode to test its catalytic activity for oxygen evolution reaction and hydrogen evolution reaction, and its use as a bifunctional electrode full water splitting performance.

Compared with the prior art, the main beneficial effects and advantages of the present invention are:

(1) The core-shell Cu ₂ Se@NiFe-LDH electrocatalyst preparation method of the present invention solves the problems of aggregation, large particle size, wide particle size distribution range and high ratio of nickel-iron hydrotalcite existing in the traditional co-precipitation method. Small surface area and other defects, showing the characteristics of large specific surface area, uniform size, thin lamellae and good mechanical stability.

(2) In the core-shell Cu ₂ Se@NiFe-LDH electrocatalyst, Se element changes the electronic structure of Cu, so that Cu ₂ Se has good electrical conductivity and catalytic activity, and Cu ₂ Se as support obviously improves NiFe -The conductivity and dispersibility of LDH material, which improves the catalytic performance.

(3) The core-shell Cu ₂ Se@NiFe-LDH electrocatalyst preparation method, the NiFe-LDH flakes prepared by the electrodeposition method have a certain mechanical strength, and the NiFe-LDH is cross-distributed on the Cu ₂ Se nanowires, making the active The fully exposed sites are not only favorable for the access of ^OH- , but also for the escape of gaseous products.

(4) In the core-shell Cu ₂ Se@NiFe-LDH electrocatalyst, the synergistic effect between Cu ₂ Se and NiFe-LDH improves the charge transport of NiFe-based hydrotalcite nanosheets, which solves the problem of pure NiFe-LDH. The disadvantages of poor conductivity and easy aggregation of nanosheets improve the catalytic performance of the composite structure.

Description of drawings:

1 is the XRD diffraction pattern of the Cu ₂ Se and Cu ₂ Se@NiFe-LDH samples obtained in Example 1.

FIG. 2 is a scanning electron microscope photograph of the Cu ₂ Se sample obtained in Example 1. FIG.

FIG. 3 is a scanning electron microscope photograph of the Cu ₂ Se@NiFe-LDH sample obtained in Example 1. FIG.

4 is a transmission electron microscope photograph of the sample obtained in Example 1.

5 is a high-resolution transmission electron microscope photograph of the sample obtained in Example 1.

6 is the OER linear scan voltammogram of the four samples obtained in Example 1, Example 2, Example 3 and Example 4 in 1 mol/L KOH solution.

7 is the OER linear scan voltammogram of the three samples obtained in Example 1, Example 5 and Example 6 in 1 mol/L KOH solution.

Fig. 8 is the OER linear scan of the Cu ₂ Se and Cu ₂ Se@NiFe-LDH samples obtained in Example 1, the six samples obtained in Example 7, Example 8, Example 9 and Comparative Example 1 in 1 mol/L KOH solution voltammogram.

FIG. 9 is a graph of the constant voltage It test of the Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH/CF electrode obtained in Example 1 in 1 mol/L KOH electrolyte at 1.45 V (vs RHE).

10 is a multi-step chronopotentiometry diagram of the Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH/CF electrode obtained in Example 1 in 1 mol/L KOH electrolyte.

Figure 11 shows the electrochemical impedances of Cu ₂ Se and Cu ₂ Se@NiFe-LDH samples obtained in Example 1, six samples obtained in Example 7, Example 8, Example 9 and Comparative Example 1 in 1 mol/L KOH solution picture.

FIG. 12 shows the linear scan voltammograms of HER of Cu ₂ Se and Cu ₂ Se@NiFe-LDH samples obtained in Example 1, and five samples obtained in Comparative Example 1, Comparative Example 2 and Comparative Example 3 in 1 mol/L KOH solution.

Figure 13 is the OER linear scan voltammogram of five samples obtained in Example 1, Example 2, Comparative Example 9, Comparative Example 10 and Comparative Example 11 when used as electrolysis water catalysts in 1 mol/L KOH solution

Detailed ways:

In order to further understand the present invention, the present invention is further described below with reference to the accompanying drawings and embodiments, but does not limit the present invention in any way.

Example 1:

(1) Preparation of Cu ₂ Se/CF

Immerse commercial copper foam with a size of 3cm×4cm in a 37% hydrochloric acid solution for 10 minutes, and wash it with deionized water and absolute ethanol for several times; put the cleaned copper foam into 80mL of NaOH and (NH ₄ ) ₂ Soak in the mixed solution of S ₂ O ₈ for 20 min to grow light blue Cu(OH) ₂ nanowires on the surface in situ, take out the copper foam with Cu(OH) ₂ nanowires grown and rinse it with deionized water. Dry in an oven at 60 °C for 6 h; place the dried Cu(OH) ₂ nanowires in a tube furnace, at the same time put 0.1 g of selenium powder at the front end of the tube furnace, and heat up at a rate of 5 °C/min in a nitrogen atmosphere To 400 ℃, hold for 30min, take out the sample after natural cooling in the tube furnace, rinse with deionized water and ethanol several times to obtain Cu ₂ Se/CF, dry for use;

(2) Preparation of Cu ₂ Se@NiFe-LDH/CF

Using Cu ₂ Se/CF as the working electrode, platinum wire electrode as the counter electrode, saturated calomel electrode as the reference electrode, the electrolyte is a mixed aqueous solution of Ni(NO ₃ ) ₂ and FeSO ₄ , Ni(NO ₃ ) ₂ and FeSO ₄ The concentration of 0.2M and 0.1M respectively, under the condition of potential of -1.0V for 120s, the electrodeposition reaction was carried out to grow NiFe-LDH on the surface, and the core-shell Cu ₂ Se@Ni _{2/ 3} Fe _1/3 - LDH/CF catalyst.

Example 2:

(1) Preparation of Cu ₂ Se/CF

Prepare according to the method and conditions of step (1) in Example 1.

(2) Preparation of Cu ₂ Se@NiFe-LDH/CF

Referring to the method and preparation conditions of step (2) in Example 1, the electrodeposition time was set to 60s to obtain a copper selenide@nickel-iron hydrotalcite nanosheet electrocatalyst, denoted as Cu ₂ Se@Ni _2/3 Fe 1/ ₃ -LDH/CF-60;

Example 3:

(1) Preparation of Cu ₂ Se/CF

Prepare according to the method and conditions of step (1) in Example 1.

(2) Preparation of Cu ₂ Se@NiFe-LDH/CF

Referring to the method and preparation conditions of step (2) in Example 1, the electrodeposition time was set to 90s to obtain copper selenide@nickel-iron hydrotalcite nanosheet electrocatalyst, denoted as Cu ₂ Se@Ni _2/3 Fe 1/ ₃ -LDH/CF-90;

Example 4:

(1) Preparation of Cu ₂ Se/CF

Prepare according to the method and conditions of step (1) in Example 1.

(2) Preparation of Cu ₂ Se@NiFe-LDH/CF

Referring to the method and preparation conditions of step (2) in Example 1, the electrodeposition time was set to 150s to obtain copper selenide@nickel-iron hydrotalcite nanosheet electrocatalyst, denoted as Cu ₂ Se@Ni _2/3 Fe 1/ ₃ -LDH/CF-150;

Example 5:

(1) Preparation of Cu ₂ Se/CF

Prepare according to the method and conditions of step (1) in Example 1.

(2) Preparation of Cu ₂ Se@NiFe-LDH/CF

Referring to the method and preparation conditions of step (2) in Example 1, except that the concentrations of Ni(NO ₃ ) ₂ and FeSO ₄ in the electrolyte solution were changed to 0.2M and 0.05M, respectively, copper selenide@nickel-iron hydrotalcite was obtained Nanosheet electrocatalyst, denoted as Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH/CF-0.15;

Example 6:

(1) Preparation of Cu ₂ Se/CF

Prepare according to the method and conditions of step (1) in Example 1.

(2) Preparation of Cu ₂ Se@NiFe-LDH/CF

Referring to the method and preparation conditions of step (2) in Example 1, except that the concentrations of Ni(NO ₃ ) ₂ and FeSO ₄ in the electrolyte solution were changed to 0.3M and 0.15M, respectively, copper selenide@nickel-iron hydrotalcite was obtained Nanosheet electrocatalyst, denoted as Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH/CF-0.45;

Example 7:

(1) Preparation of Cu ₂ Se/CF

Prepare according to the method and conditions of step (1) in Example 1.

(2) Preparation of Cu ₂ Se@NiFe-LDH/CF

Referring to the method and preparation conditions of step (2) in Example 1, except that the concentrations of Ni(NO ₃ ) ₂ and FeSO ₄ in the electrolyte solution were changed to 0.1M and 0.2M, respectively, copper selenide@nickel-iron hydrotalcite was obtained Nanosheet electrocatalyst, denoted as Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH/CF-1:2;

Example 8:

(1) Preparation of Cu ₂ Se/CF

Prepare according to the method and conditions of step (1) in Example 1.

(2) Preparation of Cu ₂ Se@NiFe-LDH/CF

Referring to the method and preparation conditions of step (2) in Example 1, except that the concentrations of Ni(NO ₃ ) ₂ and FeSO ₄ in the electrolyte solution were changed to 0.15M and 0.15M, respectively, copper selenide@nickel-iron hydrotalcite was obtained Nanosheet electrocatalyst, denoted as Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH/CF-1:1;

Example 9:

(1) Preparation of Cu ₂ Se/CF

Prepare according to the method and conditions of step (1) in Example 1.

(2) Preparation of Cu ₂ Se@NiFe-LDH/CF

Referring to the method and preparation conditions of step (2) in Example 1, except that the concentrations of Ni(NO ₃ ) ₂ and FeSO ₄ in the electrolyte solution were changed to 0.225M and 0.075M, respectively, copper selenide@nickel-iron hydrotalcite was obtained Nanosheet electrocatalyst, denoted as Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH/CF-3:1;

Comparative Example 1:

With reference to the method and preparation conditions in Example 2, the only difference is that the nickel-iron hydrotalcite nanosheets are directly electrodeposited on the surface of the treated foam copper, denoted as Ni _2/3 Fe _1/3 -LDH/CF;

Comparative Example 2:

Immerse commercial copper foam with a size of 1cm×2cm in a 37% hydrochloric acid solution for 10 minutes, and wash it with deionized water and absolute ethanol for several times; put the cleaned copper foam into 80mL of NaOH and (NH ₄ ) ₂ Soaked in the mixed solution of S ₂ O ₈ for 20 min, light blue Cu(OH) ₂ nanowires were grown in situ on the surface, denoted as Cu(OH) ₂ NWs/CF;

Comparative Example 3:

Soak commercial copper foam with a size of 1cm × 2cm in a hydrochloric acid solution with a concentration of 37% for 10 minutes, wash it with deionized water and absolute ethanol for several times, and record it as Cu foam;

1 is the XRD test chart of the Cu ₂ Se and Cu ₂ Se@NiFe-LDH samples obtained in Example 1. It can be seen from the figure that the Cu ₂ Se catalyst has obvious characteristic peaks at 36.50°, 42.69°, 61.5° and 73.69°, doped with a small amount of CuO, and its 111, 200, 220 and 311 faces appear in the figure Diffraction peaks, indicating the presence of copper oxide in the sample. The catalyst has obvious characteristic peaks at 25.41° and 43.91°, corresponding to the 222 and 504 faces of Cu ₂ Se. Besides the characteristic peaks of CuO and Cu ₂ Se, Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH samples also showed NiFe-LDH 003 at 11.58°, 23.33°, 34.51°, 39.59° and 46.55° , 006, 012, 015 and 018 surface characteristic peaks, proving the successful preparation of core-shell CuSe@NiFe-based hydrotalcite nanosheet electrocatalysts.

FIG. 2 is a scanning electron microscope image of the Cu ₂ Se nanowire sample obtained in Example 1. FIG. It can be seen from the figure that the nanowires grow uniformly on the surface of the copper foam, the diameter of the nanowires is between 150 and 250 nm, the morphology is relatively regular, the size is uniform and the density is high, which is very beneficial to the deposition of hydrotalcite. According to the literature, copper selenide has good electron transport ability and certain catalytic activity for oxygen evolution reaction, which is very beneficial to the improvement of OER catalytic activity of the catalyst.

FIG. 3 is a scanning electron microscope image of the core-shell Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH sample obtained in Example 1. FIG. It can be seen from the figure that the hydrotalcite nanosheets grow uniformly and staggered on the Cu ₂ Se nanowires. This ordered three-dimensional structure greatly increases the specific surface area of the catalyst, which is beneficial to the approach of OH ^- and the release of gaseous products. The thickness of the nanosheets is less than 10 nm, and this ultrathin structure is beneficial to the exposure of active sites and the enhancement of electrocatalytic performance.

4 is a transmission electron microscope image of the core-shell Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH sample obtained in Example 1. It can be seen from the figure that the length of NiFe-LDH nanosheets deposited on the Cu ₂ Se nanowires is about 100-150 nm, the thickness of the nanosheets is less than 10 nm, the distribution is uniform, and the morphology is good, which is consistent with the scanning electron microscope image in Figure 3. Consistent.

5 is a high-resolution transmission electron microscope image of the core-shell Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH sample obtained in Example 1. The lattice fringes can be clearly observed from the figure. The lattice fringes of 0.25 nm correspond to the (012) crystal plane of NiFe-LDH, and the lattice fringes of 0.34 nm correspond to the (112) crystal plane of Cu ₂ Se. The existence of these characteristic peaks proves the successful deposition of NiFe-LDH nanosheets on the surface of Cu ₂ Se.

Fig. 6 is the OER linear scanning voltammogram of the four samples obtained in Example 1, Example ₂ , Example 3, and Example 4 in 1 mol/L KOH electrolyte. @NiFe-LDH electrocatalyst OER activity, it was found that at a current density of 50 mA cm ^-2 , the as-prepared sample Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH-120 had a higher deposition time of 120 s. The onset potential is the smallest, and the catalyst has the best catalytic activity.

Fig. 7 is the OER linear scanning voltammogram of the three samples obtained in Example 1, Example 5 and Example 6 in 1 mol/L KOH electrolyte. The effect of the oxygen evolution reaction activity of the Cu ₂ Se@NiFe-LDH electrocatalyst was investigated, and it was found that the Cu ₂ Se@Ni _2/3 Fe ₁ obtained when the total molar concentration of metal ions was 0.3 M at a current density of 50 mA·cm ^-2 _The /3-LDH-0.30 sample has the smallest onset potential, and this catalyst has the best catalytic activity.

Fig. 8 shows the linear scan volts of six samples obtained in Example 1, Cu ₂ Se and Cu ₂ Se@NiFe-LDH, Example 7, Example 8, Example 9 and Comparative Example 1 in 1 mol/L KOH electrolyte Antu. It can be seen from the figure that under the condition that the total metal ion concentration of nickel and iron is kept constant at ^0.3M , only the ratio of metal nickel and iron ions is changed. When the molar ratio of Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH is 2:1, the onset potential is the smallest and the steepness is the largest. Therefore, the catalyst with this ratio has the best catalytic activity.

Figure 9 is a time-current curve diagram of the Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH electrocatalyst obtained in Example 1 at a constant voltage of 1.45V (vs RHE). As shown in the figure, after 80 hours of In the test, there is almost no obvious decrease in the current density, which indicates that the catalyst has good long-term stability and durability.

Figure 10 is a multi-step chronopotentiometry diagram of the Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH electrocatalyst obtained in Example 1. As shown in the figure, the current density is from 100 mA·cm ^-2 to 190 mA·cm ^-2 , The increase range is 10 mA·cm ^-2 every two hours. The current density basically does not change in the first two hours, and the current density changes relatively smoothly in the next twenty hours without obvious fluctuation. This indicates that the Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH electrocatalyst has good catalytic activity and stability in the catalytic OER process.

Figure 11 shows the electrocatalysts with different ratios of Cu ₂ Se and Cu ₂ Se@NiFe-LDH obtained in Example 1 of the present invention, Example 7, Example 8, Example 9 and Comparative Example 1 in 1 mol/L KOH electrolyte The electrochemical impedance spectrum of the open circuit potential of 1.48V (vs RHE), the electrochemical impedance of the catalyst was measured at the open potential in a stable 1mol/L KOH solution. It can be seen from the figure that the charge transfer resistance of Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH is the smallest, which is smaller than that of Cu ₂ Se@NiFe-LDH with other metal ratios, and also smaller than that of Cu ₂ Se/CF and Ni _2/3 Fe _1/3 -LDH/CF. This indicates that the kinetic process of Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH is faster than other catalysts.

12 is the HER linear scan of the electrocatalysts of different ratios obtained in Example 1 of the present invention Cu ₂ Se and Cu ₂ Se@NiFe-LDH, Comparative Example 1, Comparative Example 2 and Comparative Example 3 in 1 mol/L KOH electrolyte The voltammetry curve, as shown in the figure, among these electrocatalysts, Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH electrocatalyst has the smallest onset potential and the highest catalytic activity at 10 mA·cm ^-2 good. Although the onset potential is smaller than that of commercial Pt/C electrodes, it also has good application potential at large current densities.

Fig. 13 is a scanning voltammogram of Cu ₂ Se and Cu ₂ Se@NiFe-LDH obtained in Example 1, five samples obtained in Comparative Example 1, Comparative Example 2 and Comparative Example 3 for fully electrolyzed water under a two-electrode system Among these five electrocatalysts, Cu ₂ Se@Ni _2/3 Fe _1/3 -LDH has the smallest onset potential and the highest catalytic activity, which is a very promising bifunctional electrocatalyst.

All the above electrocatalytic performance tests used saturated calomel electrode as the reference electrode, Pt electrode as the counter electrode, the scan rate was 5mV/s, the electrolyte was 1mol/LKOH electrolyte, and all potentials were converted into reversible hydrogen potential (RHE) , the conversion formula is

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (4)

1. a core-shell copper selenide@nickel-iron class hydrotalcite electrocatalyst, it is characterized in that described catalyzer is based on foamed copper, in alkaline medium by chemical oxidation method on its surface in-situ growth Cu(OH) ) ₂ nanowires, and then selenized into copper selenide nanowires with selenium powder in a tube furnace, and finally used electrodeposition to grow nickel-iron hydrotalcite on its surface; the foamed copper is recorded as CF, and the copper selenide is recorded as Cu ₂ Se, nickel-iron hydrotalcite is denoted as NiFe-LDH, and copper selenide@nickel-iron hydrotalcite is denoted as Cu ₂ Se@NiFe-LDH; The preparation method of the core-shell copper selenide@nickel-iron hydrotalcite electrocatalyst is characterized in that, comprising the following steps: (1) Preparation of Cu ₂ Se/CF Immerse commercial copper foam with a size of 3 cm × 4 cm in 37% hydrochloric acid solution for 10 minutes, and wash it with deionized water and absolute ethanol for several times; put the cleaned copper foam into 80 mL of NaOH and ( Soak in the mixed solution of NH ₄ ) ₂ S ₂ O ₈ for 20 min to grow light blue Cu(OH) ₂ nanowires on the surface in situ, take out the copper foam with Cu(OH) ₂ nanowires grown with deionization Rinse with water and dry in an oven at 60 °C for 6 h; place the dried Cu(OH) ₂ nanowires in a tube furnace, and put 0.1 g of selenium powder at the front of the tube furnace at the same time. The temperature was raised to 400 °C at a rate of ℃/min and held for 30 min. After the tube furnace was naturally cooled, the sample was taken out, rinsed with deionized water and ethanol several times to obtain Cu ₂ Se/CF, which was dried for use; (2) Preparation of Cu ₂ Se@NiFe-LDH/CF Using Cu ₂ Se/CF as the working electrode, platinum wire electrode as the counter electrode, saturated calomel electrode as the reference electrode, the electrolyte is a mixed aqueous solution of Ni(NO ₃ ) ₂ and FeSO ₄ , and electrified at a potential of -1.0 V The electrodeposition reaction was carried out for 60~150 s to grow NiFe-LDH on the surface, and the core-shell Cu ₂ Se@NiFe-LDH/CF catalyst was prepared. 2. a kind of core-shell copper selenide@nickel-iron hydrotalcite electrocatalyst according to claim 1 is characterized in that in the step (1) of the preparation method, NaOH and (NH ₄ ) ₂ S ₂ O ₈ The molar concentrations of NaOH and (NH ₄ ) ₂ S ₂ O ₈ in the mixed solution are 2.5 and 0.125 mol/L, respectively; the total concentration of metal ions in the mixed aqueous solution of Ni(NO ₃ ) ₂ and FeSO ₄ in step (2) is 0.15~0.45 mol/L, the molar ratio of Ni(NO ₃ ) ₂ and FeSO ₄ is 1~6:2. 3. a kind of core-shell copper selenide@nickel-iron hydrotalcite electrocatalyst according to claim 1, it is characterized in that this catalyst is in nanowire shape, and its diameter is 150～250 nm; Take Cu ₂ Se as core , with NiFe-LDH flakes as shells, and the thickness of NiFe-LDH flakes is less than 10 nm. 4. a kind of core-shell copper selenide@nickel iron hydrotalcite electrocatalyst according to any one of claim 1～3, it is characterized in that described electrocatalyst is used for alkaline electrolyzed water anode oxygen evolution reaction.

Images