CN114005999B - Bifunctional electrocatalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a bifunctional electrocatalyst and a preparation method and application thereof. The core of the bifunctional electrocatalyst is perovskite-like oxide nano-fiber with a chemical formula of Pr _z Sr _2‑z Ni _y Co _{1‑ y} O _2‑ε Z = 0-2, y = 0-1, epsilon = 0-0.25, and the outer layer is hetero-atom doped CeO deposited by ALD technology ₂ Film Fe _x Ce _{1‑ x} O _2‑δ And the Fe doping ratio x = 0-0.3. The preparation method comprises the steps of firstly obtaining the perovskite-like oxide nano-fiber PSNC, placing the nano-fiber PSNC into an ALD system cavity, heating in vacuum, and carrying out cyclic deposition on the nano-fiber PSNC to obtain the iron-doped cerium oxide film deposited on the nano-fiber PSNC. The bifunctional electrocatalyst disclosed by the invention can keep excellent ORR/OER catalytic activity under an alkaline condition, and shows good multiplying power and cycle performance when being applied to a zinc-air battery cathode catalyst.

Description

A kind of bifunctional electrocatalyst and its preparation method and application

technical field

The invention relates to the technical field of catalysts, in particular to a bifunctional electrocatalyst and its preparation method and application.

Background technique

Metal-air batteries have attracted much attention in the field of energy storage and conversion due to their advantages of greenness, cleanliness, high energy density and recyclability. Zinc-air batteries have commercial prospects for large-scale applications due to their earth-abundant reserves, low price, and strong corrosion resistance in alkaline electrolytes. Oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are two important half-reactions of the zinc-air battery cathode. Due to the complex electron transfer process, the reaction has a high overpotential, which leads to the energy efficiency of the zinc-air battery. Therefore, the research on corresponding bifunctional electrocatalysts is particularly important.

Although noble metal-based catalysts have high catalytic activity, their large-scale application is difficult due to their limited reserves, high price and single function. At present, the research on non-precious metal-based catalysts has become a hot spot in this field. Perovskite-type oxides are inexpensive and abundant, with tunable electronic structures and thus high potential electrocatalytic activity. However, the electronic conductivity and intrinsic catalytic activity of perovskite materials prepared by traditional solid-state reaction methods are low. The introduction of nano-sized catalysts on the surface of oxides can significantly increase active sites and improve catalytic activity, which is expected to meet commercial An efficient and stable catalyst for chemical needs.

At present, the methods of nano-modified catalysts are generally mechanical mixing method, impregnation method and chemical vapor deposition method. The contact area between the nanoparticles introduced by the mechanical mixing method and the oxide electrode particles is small, the adhesion force is weak, and the long-term stability of the modified composite is poor; the impregnation method and the vapor deposition method require subsequent high-temperature treatment. Nano-catalysts are deposited on the surface of the particles, which may destroy the structure and original morphology of the oxide; not only the distribution of modified species is uneven, the impregnation amount is poorly controllable, it is not easy to control the amount of modification, and the process cycle is longer and the preparation cost is higher. limit its practical application.

Contents of the invention

The purpose of the present invention is to address the above-mentioned deficiencies in the prior art, to propose a bifunctional battery that maintains excellent ORR/OER catalytic activity under alkaline conditions and is applied to the cathode catalyst of a zinc-air battery to exhibit good rate and cycle performance. Catalyst and its preparation method and application.

A bifunctional electrocatalyst of the present invention, the core of the bifunctional electrocatalyst is a perovskite-like oxide nanofiber, and its chemical formula is Pr _z Sr _2-z Ni _y Co _1-y O _2-ε , z=0 ~2, y=0~1, ε=0~0.25, the outer layer is a heteroatom-doped CeO ₂ thin film Fe _x Ce _1-x O _2-δ deposited by ALD technology, wherein the metal Fe doping ratio x=0 ~0.3, δ=0~0.1.

Further, said z is 0.5, 1.0 or 1.5, y is 0.5, and x is 0, 0.1, 0.2 or 0.3.

A method for preparing the bifunctional electrocatalyst as described above, comprising the steps of:

S1: According to the chemical formula Pr _z Sr _2-z Ni _y Co _1-y O _2-ε , respectively weigh the Pr source, Sr source, Ni source and Co source according to the stoichiometric ratio and dissolve them in the organic solvent in sequence, and stir until completely dissolved Finally, add polyvinylpyrrolidone and continue to stir until the solution is viscous;

S2: The solution is spun by electrospinning technology, and dried after spinning;

S3: Spinning after drying, pre-oxidation, and heat preservation to form a phase to obtain perovskite-like oxide nanofibers Pr _0.5 Sr _1.5 Ni _0.5 Co _0.5 O _2-ε , denoted as PSNC;

S4: Put the nanofiber PSNC into the cavity of the ALD system to raise the temperature under vacuum, and use the atomic layer deposition technology to perform cyclic deposition on the nanofiber PSNC, and obtain a layer of iron-doped cerium oxide film uniformly deposited on the nanofiber PSNC, and use The thickness of the deposited film is controlled by the number of cycles; the ratio of Fe and Ce in the film is controlled by the cycle number of each element in the cycle.

Further, the Pr source in step S1 is Pr(NO ₃ ) ₃ ·6H ₂ O, the Sr source is Sr(NO ₃ ) ₃ , the Ni source is Ni(NO ₃ ) ₂ ·6H ₂ O or Ni(CH ₃ COO ) ₂ ·4H ₂ O, the Co source includes Co(NO ₃ ) ₂ ·6H ₂ O; the Pr(NO ₃ ) ₃ ·6H ₂ O, Sr(NO ₃ ) ₃ , Ni(NO ₃ ) ₂ ·6H ₂ The molar ratio of O, Co(NO ₃ ) ₂ ·6H ₂ O is 1:3:1:1; the organic solvent is N,N-dimethylformamide.

Further, the electrospinning technique in step S2 uses a negative pressure of 2.5-3 kV, a positive pressure of 15-20 kV, a receiving distance of 15-20 cm, and a bolus injection speed of 0.06-0.08 mm min ^-1 .

Further, in step S3, the temperature is raised to 220°C for 2 hours at a heating rate of 0.5°C min ^-1 for pre-oxidation, and finally the temperature is raised to 850-900°C for 5 hours ^at 0.5°C min -1 for phase formation, and Nanofiber PSNC;

Further, in step S4, the iron source used is ferrocene Fe(Cp) ₂ , and the cerium source is Ce(iPrCp) ₂ (iPr-amd).

Further, the specific operation of cyclic deposition on the nanofiber PSNC in step S4 is: O ₃ pulse 0.5s → dwell 8s → Fe(Cp) ₂ pulse 1s → dwell 15s → N ₂ purge 2s → n×(H ₂ O pulse 0.02s → dwell 30s → Ce(iPrCp) ₂ (iPr-amd) pulse 0.5s → dwell 20s → N ₂ purge 2s), the value of n is determined by the composition ratio of the sediment.

Further, in step S4, the technical parameters of atomic layer deposition are: ALD system chamber pressure 1 Torr, deposition window temperature 150-250°C, pipeline temperature 150°C, cerium source heating temperature 150°C, iron source heating temperature 80°C, to provide sufficient saturation vapor pressure. The deposition uses high-purity nitrogen as the carrier gas, the ozone flow rate is 400 sccm, and the number of cycles is 26 to 105 cycles.

The application of the above-mentioned bifunctional electrocatalyst is applied on the positive electrode current collector carbon paper of the zinc-air battery.

The bifunctional electrocatalyst of the present invention can maintain excellent ORR/OER catalytic activity under alkaline conditions, and can be applied to zinc-air battery cathode catalysts to show good rate and cycle performance, and can be used in the assembly and testing of zinc-air batteries. Significantly reduce the overpotential on the air electrode, improve energy density and power efficiency, and enhance its long-term charge-discharge stability.

The preparation method of the present invention uses atomic layer deposition technology to deposit a layer of cerium oxides with different doping amounts of iron on the nanofibers prepared by electrospinning, and can precisely modify the composition and thickness of the coating layer. The bifunctional electrocatalyst prepared by this method is a three-dimensional network framework composed of one-dimensional nanofibers. After being modified by ALD, a core-shell structure is formed, and an effective heterogeneous interface is constructed. The coating thickness can be precisely controlled. The preparation method of the present application can efficiently and quickly realize the surface modification of nano-catalysts through ALD technology, and can also precisely control the composition, proportion and thickness of deposits. Applying ALD-modified perovskite-based composite materials to zinc-air battery cathode catalysts can Expand the commercial application path of zinc-air batteries.

Description of drawings

Figure 1 is the X-ray powder diffraction pattern of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared in Example 2;

Figure 2a is the SEM (scanning electron microscope) image of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared in Example 2;

Figures 2b and 2c are TEM (transmission electron microscope) images of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared in Example 2;

Figure 2d is the elemental map of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared in Example 2;

Figure 3a is the LSV curve of the OER performance of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared in Example 2 and PSNC and commercial iridium oxide catalyst in 0.1mol L ^-1 KOH solution;

Figure 3b is the LSV curve of the ORR performance of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared in Example 2 and PSNC and commercial iridium oxide catalyst in 0.1mol L ^-1 KOH solution;

Figure 4 is the polarization performance test curve of the zinc-air battery assembled with PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared in Example 2 and PSNC nanofibers;

Figure 5 is the rate performance test curve of the zinc-air battery assembled with PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared in Example 2 and PSNC nanofibers;

Figure 6 is the discharge performance test curve of the zinc-air battery assembled with PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared in Example 2 and PSNC nanofibers under the condition of a current density of 5 mA cm ^-2 ;

Figure 7 is the cycle performance test curve of the zinc-air battery assembled by PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared in Example 2 and PSNC nanofibers under the condition of 10mA cm ^-2 .

Detailed ways

The following are specific embodiments of the present invention and in conjunction with the accompanying drawings, the technical solutions of the present invention are further described, but the present invention is not limited to these embodiments.

Example 1:

According to the chemical formula Pr _0.5 Sr _1.5 Ni _0.5 Co _0.5 O _4-ε , weigh Pr(NO ₃ ) ₃ 6H ₂ O, Sr(NO ₃ ) ₃ , Ni(NO ₃ ) ₂ 6H ₂ O according to the stoichiometric ratio , Co(NO ₃ ) ₂ 6H ₂ O were dissolved in 20mL N,N-dimethylformamide in turn, stirred until completely dissolved, then added 2.2g polyvinylpyrrolidone, and continued to stir for 10 hours until the solution was viscous , using electrospinning technology for spinning, the spinning machine parameters are set as negative pressure 3kV, positive pressure 16kV, humidity 30%, receiving distance 20cm, injection speed 0.08mm min ^-1 . After spinning, ^it was dried in a blast drying oven at 60°C for 12 hours, then heated to 220°C for 2 hours at a rate of 0.5°C ^min The temperature was raised to 850° C. and kept for 5 hours for phase formation to obtain PSNC nanofibers.

Put the PSNC nanofibers into the ALD cavity to raise the temperature under vacuum, and after purging and cleaning with nitrogen, deposit CeO ₂ cladding layers with different Fe doping contents to obtain PSNC@Fe _x Ce _1-x O _2-δ , which is used to explore the most A good Fe doping ratio, wherein the metal Fe doping ratio x=0, 0.1, 0.2, 0.3. During the deposition process, the chamber pressure of the ALD system is about 1 Torr, the deposition window temperature is 150-250°C, the pipeline temperature is 150°C, the cerium source heating temperature is 150°C, and the iron source heating temperature is 80°C to provide sufficient saturated vapor pressure. The deposition uses high-purity nitrogen (99.999%) as the carrier gas, and the ozone flow rate is 400 sccm. The thickness of the deposited film is controlled by the number of cycles; the ratio of Fe and Ce in the composite film is controlled by the small number of cycles of each element in the cycle. In this embodiment, the number of deposition circles is 26 circles. A deposition cycle sequence of Fe _x Ce _1-x O _2-δ is: O ₃ pulse 0.5s → dwell 8s → Fe(Cp) ₂ pulse 1s → dwell 15s → N ₂ purge 2s → n×(H ₂ O pulse 0.02s→stay 30s→Ce(iPrCp) ₂ (iPr-amd) pulse 0.5s→stay 20s→N ₂ purge 2s), the value of n is determined by the composition ratio of the sediment. After ALD deposition, PSNC@CeO ₂ -26cycles, PSNC@Fe _0.1 Ce _0.9 O _2-δ -26cycles, PSNC@Fe _0.2 Ce _0.8 O _2-δ -26cycles, and PSNC@Fe _0.3 Ce _0.7 O _2-δ - 26cycles bifunctional catalytic material.

The OER and ORR performances of electrocatalyst materials with different iron doping ratios are shown in Table 1. It can be seen that when the molar ratio of iron doping is 0.1, the onset potential of PSNC@Fe _0.1 Ce _0.9 O _2-δ -26cycles OER performance is 1.48V, and at a current density of 10mAcm ^-2 , the corresponding potential It is 1.68V, which is obviously lower than other iron doping contents; in the ORR performance, the half-wave potential of PSNC@Fe _0.1 Ce _0.9 O _2-δ -26cycles is 0.7V, and the limiting current density is -4.67mA cm ^-2 , It is also superior to other iron doping ratios, indicating that in iron-doped cerium oxide, when the iron doping ratio is 0.1, its electrocatalytic activity is the highest, and the oxygen exchange kinetics is faster. Therefore, the optimal iron doping ratio is determined. The impurity is 0.1.

Table 1 Summary of OER and ORR performance of cerium oxide deposited on PSNC nanofibers with different iron doping ratios in the present invention

Example 2:

According to the chemical formula Pr _0.5 Sr _1.5 Ni _0.5 Co _0.5 O _4-ε , weigh Pr(NO ₃ ) ₃ 6H ₂ O, Sr(NO ₃ ) ₃ , Ni(NO ₃ ) ₂ 6H ₂ O according to the stoichiometric ratio , Co(NO ₃ ) ₂ 6H ₂ O were dissolved in 20mL N,N-dimethylformamide in turn, stirred until completely dissolved, then added 2.2g polyvinylpyrrolidone, and continued to stir for 10 hours until the solution was viscous , using electrospinning technology for spinning, the spinning machine parameters are set as negative pressure 3kV, positive pressure 16kV, humidity 30%, receiving distance 20cm, injection speed 0.08mm min ^-1 . After spinning, ^it was dried in a blast drying oven at 60°C for 12 hours, then heated to 220°C for 2 hours at a rate of 0.5°C ^min The temperature was raised to 850° C. and kept for 5 hours for phase formation to obtain PSNC nanofibers.

The PSNC nanofibers were put into the ALD cavity to raise the temperature under vacuum, and after nitrogen purging and cleaning, iron oxide and cerium oxide were deposited alternately at the same time. The chamber pressure of the ALD system is about 1 Torr, the temperature of the deposition window is 150-250°C, the temperature of the pipeline is 150°C, the heating temperature of the cerium source is 150°C, and the heating temperature of the iron source is 80°C, so as to provide sufficient saturated vapor pressure. The deposition uses high-purity nitrogen (99.999%) as the carrier gas, and the ozone flow rate is 400 sccm. The thickness of the deposited film is controlled by the number of cycles; the ratio of Fe and Ce in the composite film is controlled by the small number of cycles of each element in the cycle. The order of the deposition circle of Fe/Ce oxide in this example is: O ₃ pulse 0.5s → dwell 8s → Fe(Cp) ₂ pulse 1s → dwell 15s → N ₂ purge 2s → H ₂ O pulse 0.02s → dwell 30s → Ce(iPrCp) ₂ (iPr-amd) pulse for 0.5s → dwell for 20s → N ₂ purge for 2s, the number of deposition cycles in this embodiment is 79 cycles. After the ALD deposition, the PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles bifunctional catalytic material was obtained.

Referring to accompanying drawing 1, it is the X-ray powder diffraction pattern of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared according to the technical scheme of this example. Obvious iron oxide or cerium oxide peaks, which may be related to the amorphous structure of the outer coating layer and the very little coating amount.

Referring to accompanying drawing 2a, it is the SEM (scanning electron microscope) picture of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared according to the technical scheme of this embodiment, it can be seen from the figure that it is a one-dimensional structure with a diameter of about 250nm Nanofibrous structure and relatively uniform distribution. Accompanying drawings 2b and 2c are TEM (transmission electron microscope) images of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared according to the technical scheme of this example. It can be seen from the figure that there is a uniform amorphous package outside the nanofiber. The cladding layer, the thickness of the cladding layer is related to the number of turns deposited by ALD, indicating the successful preparation of the core-shell structure. Attached Figure 2d is the element mapping diagram of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles. It can be observed that the distribution of each element is relatively uniform without segregation. In addition, a small amount of Fe and Ce are distributed on the fiber. Further The presence of a surface coating is illustrated.

To demonstrate the electrocatalytic performance of the catalyst, oxygen evolution and oxygen reduction performance tests were carried out in 0.1mol L ^-1 KOH solution at 1600rpm. The tests were all completed with a three-electrode test system. The reference electrode was a saturated calomel electrode, the counter electrode was a platinum electrode, and the working electrode was composed of 2 μL of catalyst slurry coated on a platinum carbon electrode. The catalyst slurry was prepared by mixing 40 mg of catalyst, 10 mg of Ketjen black, 5 mL of ethanol and 250 μL of Nafion solution and ultrasonically for two hours.

Referring to Figure 3a, it is the LSV curve of the OER performance of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared according to the technical scheme of this example and PSNC and commercial iridium oxide catalyst in 0.1mol L ^-1 KOH solution. PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles exhibited excellent OER catalytic activity with an onset potential of 1.4 V, compared with 1.5 V of iridium oxide, with lower cost and higher commercial value. At a current density of 10 mA cm ^-2 , the potential corresponding to PSNC@Fe _0.1 Ce _0.9 O _2-δ -79 cycles is 1.55 V, which is significantly lower than that of PSNC (1.72 V) and the commercial catalyst iridium oxide (1.69 V), indicating that Its faster oxygen exchange kinetics. Referring to Figure 3b, it is the LSV curve of the ORR performance of PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles prepared according to the technical scheme of this example and PSNC and commercial iridium oxide catalyst in 0.1mol L ^-1 KOH solution. Compared with PSNC (0.67V, 4.51mA cm ^-2 ) and platinum carbon (0.89V, 5.26mA cm ^-2 ), PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles (0.72V, 5.56mA cm ^-2 ) has Higher half-wave potential and limiting current density indicate that it has the best catalytic activity for ORR.

The zinc-air battery of the present invention is a liquid water-based zinc-air battery assembled with zinc flakes as the negative electrode, air as the positive electrode electrochemical reaction substance, and the bifunctional electrocatalyst prepared by the present invention as an air cathode catalyst. Mix and grind 25mg of catalyst and 6.25mg of Ketjen black for 20 minutes, add 1mL of ethanol and 380mL of Nafion solution and mix thoroughly, then evenly coat on 10 pieces of 2×2cm carbon paper, and dry in a vacuum oven at 60°C for 10 Hours to spare. The negative electrode of the zinc-air battery uses zinc flakes, and the electrolyte is a mixed solution of 6 mol L ^-1 KOH and 0.2 mol L ^-1 zinc acetate. Assemble the positive electrode, negative electrode, electrolyte, separator, etc. into a zinc-air battery for testing.

See Figure 4, the polarization performance test curve for the zinc-air battery assembled by PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles and PSNC nanofibers. It can be seen from the figure that PSNC@Fe _0.1 Ce _0.9 The maximum power density of Zn-air batteries assembled with O _2-δ -79cycles catalyst can reach 195mW cm ^-2 , which is significantly higher than 102mW cm ^-2 of PSNC and 84mW cm ^-2 of commercial catalyst Pt/C+IrO ₂ . The good output performance may be attributed to the excellent bifunctional catalytic activity of the catalyst itself.

See Figure 5, the rate performance test curve for the zinc-air battery assembled by PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles and PSNC nanofibers. The figure shows that the PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles catalyst shows a relatively stable platform at each current density platform, and when the current density returns to 1mA cm ^-2 , its voltage also returns to 1.24V, This demonstrates the excellent reversibility of this Zn-air battery.

See Figure 6, the discharge performance test curve of the zinc-air battery assembled by PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles and PSNC nanofibers under the condition of 5mA cm ^-2 . The figure shows that PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles has been discharged for nearly 39 hours, which is better than PSNC's 27 hours, and its voltage is relatively stable without significant drop.

See Figure 7, the cycle performance test curve of the zinc-air battery assembled by PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles and PSNC nanofibers under the condition of 10mA cm ^-2 . The Zn-air battery loaded with PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles catalyst lasted for about 280 hours, 1375 cycles, and had better cycle stability than PSNC.

The PSNC@Fe _0.1 Ce _0.9 O _2-δ -79 cycles catalyst has excellent OER and ORR bifunctional catalytic activity and Zn-air battery performance, which is due to the Fe doping in the cladding layer to reduce the ohmic loss and improve the ionic conductivity , and the substrate of the fibrous structure also provides a larger surface area, exposing more active sites.

Example 3:

According to the chemical formula Pr _0.5 Sr _1.5 Ni _0.5 Co _0.5 O _4-ε , weigh Pr(NO ₃ ) ₃ 6H ₂ O, Sr(NO ₃ ) ₃ , Ni(NO ₃ ) ₂ 6H ₂ O according to the stoichiometric ratio , Co(NO ₃ ) ₂ 6H ₂ O were dissolved in 20mL N,N-dimethylformamide in turn, stirred until completely dissolved, then added 2.2g polyvinylpyrrolidone, and continued to stir for 10 hours until the solution was viscous , using electrospinning technology for spinning, the spinning machine parameters are set as negative pressure 3kV, positive pressure 16kV, humidity 30%, receiving distance 20cm, injection speed 0.08mm min ^-1 . After spinning, ^it was dried in a blast drying oven at 60°C for 12 hours, then heated to 220°C for 2 hours at a rate of 0.5°C ^min The temperature was raised to 850° C. and kept for 5 hours for phase formation to obtain PSNC nanofibers.

The PSNC nanofibers were put into the ALD cavity to raise the temperature under vacuum, and after nitrogen purging and cleaning, iron oxide and cerium oxide were deposited alternately at the same time. The chamber pressure of the ALD system is about 1 Torr, the temperature of the deposition window is 150-250°C, the temperature of the pipeline is 150°C, the heating temperature of the cerium source is 150°C, and the heating temperature of the iron source is 80°C, so as to provide sufficient saturated vapor pressure. The deposition uses high-purity nitrogen (99.999%) as the carrier gas, and the ozone flow rate is 400 sccm. The thickness of the deposited film is controlled by the number of cycles; the ratio of Fe and Ce in the composite film is controlled by the small number of cycles of each element in the cycle. The order of the deposition circle of Fe/Ce oxide in this example is: O ₃ pulse 0.5s → dwell 8s → Fe(Cp) ₂ pulse 1s → dwell 15s → N ₂ purge 2s → H ₂ O pulse 0.02s → dwell 30s → Ce(iPrCp) ₂ (iPr-amd) pulse for 0.5s → dwell for 20s → N ₂ purge for 2s, the number of deposition cycles in this embodiment is 53 cycles. After the ALD deposition, the PSNC@Fe _0.1 Ce _0.9 O _2-δ -53cycles bifunctional catalytic material was obtained.

Its main XRD structure and SEM morphology are similar to Example 2, and its electrocatalytic performance and zinc-air battery performance are better than PSNC catalysts, but not as good as PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles catalysts, such as PSNC@Fe _0.1 Ce The OER curve of _0.9 O _2-δ -53cycles corresponds to a potential of 1.66V at a current density of 10mA cm ^-2 . In the ORR test, its half-wave potential and limiting current density are 0.69V and 5.22mA cm ^{-2 ,} respectively.

Example 4:

According to the chemical formula Pr _0.5 Sr _1.5 Ni _0.5 Co _0.5 O _4-ε , weigh Pr(NO ₃ ) ₃ 6H ₂ O, Sr(NO ₃ ) ₃ , Ni(NO ₃ ) ₂ 6H ₂ O according to the stoichiometric ratio , Co(NO ₃ ) ₂ 6H ₂ O were dissolved in 20mL N,N-dimethylformamide in turn, stirred until completely dissolved, then added 2.2g polyvinylpyrrolidone, and continued to stir for 10 hours until the solution was viscous , using electrospinning technology for spinning, the spinning machine parameters are set as negative pressure 3kV, positive pressure 16kV, humidity 30%, receiving distance 20cm, injection speed 0.08mm min ^-1 . After spinning, ^it was dried in a blast drying oven at 60°C for 12 hours, then heated to 220°C for 2 hours at a rate of 0.5°C ^min The temperature was raised to 850° C. and kept for 5 hours for phase formation to obtain PSNC nanofibers.

The PSNC nanofibers were put into the ALD cavity to raise the temperature under vacuum, and after nitrogen purging and cleaning, iron oxide and cerium oxide were deposited alternately at the same time. The chamber pressure of the ALD system is about 1 Torr, the temperature of the deposition window is 150-250°C, the temperature of the pipeline is 150°C, the heating temperature of the cerium source is 150°C, and the heating temperature of the iron source is 80°C, so as to provide sufficient saturated vapor pressure. The deposition uses high-purity nitrogen (99.999%) as the carrier gas, and the ozone flow rate is 400 sccm. The thickness of the deposited film is controlled by the number of cycles; the ratio of Fe and Ce in the composite film is controlled by the small number of cycles of each element in the cycle. The order of the deposition circle of Fe/Ce oxide in this example is: O ₃ pulse 0.5s → dwell 8s → Fe(Cp) ₂ pulse 1s → dwell 15s → N ₂ purge 2s → H ₂ O pulse 0.02s → dwell 30s → Ce(iPrCp) ₂ (iPr-amd) pulse for 0.5s → dwell for 20s → N ₂ purge for 2s, the number of deposition cycles in this embodiment is 105 cycles. After the ALD deposition, the PSNC@Fe _0.1 Ce _0.9 O _2-δ -105cycles bifunctional catalytic material was obtained.

Its main XRD structure and SEM morphology are similar to those of Example 1, and its electrocatalytic performance and zinc-air battery performance are better than PSNC catalysts, but not as good as PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles catalysts, such as PSNC@Fe _0.1 Ce The OER curve of _0.9 O _2-δ -105cycles corresponds to a potential of 1.64V at a current density of 10mAcm ^-2 . In the ORR test, its half-wave potential and limiting current density are 0.7V and 5.46mA cm ^{-2 ,} respectively.

Example 5:

According to the chemical formula Pr _1.0 Sr _1.0 Ni _0.5 Co _0.5 O _4-ε , weigh Pr(NO ₃ ) ₃ 6H ₂ O, Sr(NO ₃ ) ₃ , Ni(NO ₃ ) ₂ 6H ₂ O according to the stoichiometric ratio , Co(NO ₃ ) ₂ 6H ₂ O were dissolved in 20mL N,N-dimethylformamide in turn, stirred until completely dissolved, then added 2.2g polyvinylpyrrolidone, and continued to stir for 10 hours until the solution was viscous , using electrospinning technology for spinning, the spinning machine parameters are set as negative pressure 3kV, positive pressure 16kV, humidity 30%, receiving distance 20cm, injection speed 0.08mm min ^-1 . After spinning, ^it was dried in a blast drying oven at 60°C for 12 hours, then heated to 220°C for 2 hours at a rate of 0.5°C ^min The temperature was raised to 850° C. and kept for 5 hours for phase formation to obtain PSNC nanofibers.

The PSNC nanofibers were put into the ALD cavity to raise the temperature under vacuum, and after nitrogen purging and cleaning, iron oxide and cerium oxide were deposited alternately at the same time. The chamber pressure of the ALD system is about 1 Torr, the temperature of the deposition window is 150-250°C, the temperature of the pipeline is 150°C, the heating temperature of the cerium source is 150°C, and the heating temperature of the iron source is 80°C, so as to provide sufficient saturated vapor pressure. The deposition uses high-purity nitrogen (99.999%) as the carrier gas, and the ozone flow rate is 400 sccm. The thickness of the deposited film is controlled by the number of cycles; the ratio of Fe and Ce in the composite film is controlled by the small number of cycles of each element in the cycle. The order of the deposition circle of Fe/Ce oxide in this example is: O ₃ pulse 0.5s → dwell 8s → Fe(Cp) ₂ pulse 1s → dwell 15s → N ₂ purge 2s → H ₂ O pulse 0.02s → dwell 30s → Ce(iPrCp) ₂ (iPr-amd) pulse for 0.5s → dwell for 20s → N ₂ purge for 2s, the number of deposition cycles in this embodiment is 79 cycles. After ALD deposition, Pr _1.0 Sr _1.0 Ni _0.5 Co _0.5 O _4-ε @Fe _0.1 Ce _0.9 O _2-δ -79cycles bifunctional catalytic material was obtained.

Its main XRD structure and SEM morphology are similar to Example 2, and its electrocatalytic performance and zinc-air battery performance are better than those of undeposited pure Pr _1.0 Sr _1.0 Ni _0.5 Co _0.5 O _4-ε catalyst, but its OER-ORR potential difference is high In Example 2, PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles catalyst.

Embodiment 6:

According to the chemical formula Pr _1.5 Sr _0.5 Ni _0.5 Co _0.5 O _4-ε , weigh Pr(NO ₃ ) ₃ 6H ₂ O, Sr(NO ₃ ) ₃ , Ni(NO ₃ ) ₂ 6H ₂ O according to the stoichiometric ratio , Co(NO ₃ ) ₂ 6H ₂ O were dissolved in 20mL N,N-dimethylformamide in turn, stirred until completely dissolved, then added 2.2g polyvinylpyrrolidone, and continued to stir for 10 hours until the solution was viscous , using electrospinning technology for spinning, the spinning machine parameters are set as negative pressure 3kV, positive pressure 16kV, humidity 30%, receiving distance 20cm, injection speed 0.08mm min ^-1 . After spinning, ^it was dried in a blast drying oven at 60°C for 12 hours, then heated to 220°C for 2 hours at a rate of 0.5°C ^min The temperature was raised to 850° C. and kept for 5 hours for phase formation to obtain PSNC nanofibers.

The PSNC nanofibers were put into the ALD cavity to raise the temperature under vacuum, and after nitrogen purging and cleaning, iron oxide and cerium oxide were deposited alternately at the same time. The chamber pressure of the ALD system is about 1 Torr, the temperature of the deposition window is 150-250°C, the temperature of the pipeline is 150°C, the heating temperature of the cerium source is 150°C, and the heating temperature of the iron source is 80°C, so as to provide sufficient saturated vapor pressure. The deposition uses high-purity nitrogen (99.999%) as the carrier gas, and the ozone flow rate is 400 sccm. The thickness of the deposited film is controlled by the number of cycles; the ratio of Fe and Ce in the composite film is controlled by the small number of cycles of each element in the cycle. The order of the deposition circle of Fe/Ce oxide in this example is: O ₃ pulse 0.5s → dwell 8s → Fe(Cp) ₂ pulse 1s → dwell 15s → N ₂ purge 2s → H ₂ O pulse 0.02s → dwell 30s → Ce(iPrCp) ₂ (iPr-amd) pulse for 0.5s → dwell for 20s → N ₂ purge for 2s, the number of deposition cycles in this embodiment is 79 cycles. After ALD deposition, Pr _1.5 Sr _0.5 Ni _0.5 Co _0.5 O _4-ε @Fe _0.1 Ce _0.9 O _2-δ -79cycles bifunctional catalytic material was obtained.

Its main XRD structure and SEM morphology are similar to Example 2, and its electrocatalytic performance and zinc-air battery performance are better than those of undeposited pure Pr _1.5 Sr _0.5 Ni _0.5 Co _0.5 O _4-ε catalyst, but its OER-ORR potential difference is high In Example 2, PSNC@Fe _0.1 Ce _0.9 O _2-δ -79cycles catalyst.

Embodiment 7:

According to the chemical formula Pr _0.5 Sr _1.5 Ni _0.5 Co _0.5 O _4-ε , weigh Pr(NO ₃ ) ₃ 6H ₂ O, Sr(NO ₃ ) ₃ , Ni(NO ₃ ) ₂ 6H ₂ O according to the stoichiometric ratio , Co(NO ₃ ) ₂ 6H ₂ O were dissolved in 20mL N,N-dimethylformamide in turn, stirred until completely dissolved, then added 2.2g polyvinylpyrrolidone, and continued to stir for 10 hours until the solution was viscous , using electrospinning technology for spinning, the spinning machine parameters are set as negative pressure 3kV, positive pressure 16kV, humidity 30%, receiving distance 20cm, injection speed 0.08mm min ^-1 . After spinning, ^it was dried in a blast drying oven at 60°C for 12 hours, then heated to 220°C for 2 hours at a rate of 0.5°C ^min The temperature was raised to 850° C. and kept for 5 hours for phase formation to obtain PSNC nanofibers.

The PSNC nanofibers were put into the ALD cavity to raise the temperature under vacuum, and after nitrogen purging and cleaning, titanium oxide and cerium oxide were deposited alternately at the same time. The chamber pressure of the ALD system is about 1 Torr, the deposition window temperature is 150°C, the pipeline temperature is 150°C, the cerium source heating temperature is 150°C, and the titanium source TDMAT heating temperature is 75°C to provide sufficient saturated vapor pressure. The deposition uses high-purity nitrogen (99.999%) as the carrier gas, and the thickness of the deposited film is controlled by the number of cycles; the ratio of Ti and Ce in the composite film is controlled by the small number of cycles of each element in the cycle. The order of the deposition circle of Ti/Ce oxide in this example is: H ₂ O pulse 0.02s→stay 30s→Ti(NMe ₂ ) ₄ pulse 0.4s→stay 20s→N ₂ purge 2s→H ₂ O pulse 0.02s→ Dwell for 30s→Ce(iPrCp) ₂ (iPr-amd) pulse for 0.5s→dwell for 20s→N ₂ purge for 2s. The number of deposition cycles in this embodiment is 79. After ALD deposition, the PSNC@Ti _0.1 Ce _0.9 O _2-δ -79cycles bifunctional catalytic material was obtained. Its main XRD structure and SEM morphology are similar to Example 2.

Embodiment 8:

According to the chemical formula Pr _0.5 Sr _1.5 Ni _0.5 Co _0.5 O _4-ε , weigh Pr(NO ₃ ) ₃ 6H ₂ O, Sr(NO ₃ ) ₃ , Ni(NO ₃ ) ₂ 6H ₂ O according to the stoichiometric ratio , Co(NO ₃ ) ₂ 6H ₂ O were dissolved in 20mL N,N-dimethylformamide in turn, stirred until completely dissolved, then added 2.2g polyvinylpyrrolidone, and continued to stir for 10 hours until the solution was viscous , using electrospinning technology for spinning, the spinning machine parameters are set as negative pressure 3kV, positive pressure 16kV, humidity 30%, receiving distance 20cm, injection speed 0.08mm min ^-1 . After the spinning was completed, it was dried in a blast drying oven at 60°C for 12 hours, and then heated to 220°C at a heating rate of 0.5°C min ^-1 for 2 hours for pre-oxidation, and finally 0.5°C min ^-1 The temperature was raised to 850° C. and kept for 5 hours for phase formation to obtain PSNC nanofibers.

The PSNC nanofibers were put into the ALD cavity to raise the temperature under vacuum, and after nitrogen purging and cleaning, zinc oxide and cerium oxide were deposited alternately at the same time. The chamber pressure of the ALD system is about 1 Torr, the temperature of the deposition window is 150-170°C, the temperature of the pipeline is 150°C, and the heating temperature of the cerium source is 150°C to provide sufficient saturated vapor pressure, and the zinc source DEZ does not need to be heated. The deposition uses high-purity nitrogen (99.999%) as the carrier gas, and the thickness of the deposited film is controlled by the number of cycles; the ratio of Zn and Ce in the composite film is controlled by the small number of cycles of each element in the cycle. In this embodiment, the number of deposition circles is 79 circles. After ALD deposition, the PSNC@Zn _0.1 Ce _0.9 O _2-δ -79cycles bifunctional catalytic material was obtained. Its main XRD structure and SEM morphology are similar to Example 2.

Embodiment 9:

According to the chemical formula Pr _0.5 Sr _1.5 Ni _0.5 Co _0.5 O _4-ε , weigh Pr(NO ₃ ) ₃ 6H ₂ O, Sr(NO ₃ ) ₃ , Ni(NO ₃ ) ₂ 6H ₂ O according to the stoichiometric ratio , Co(NO ₃ ) ₂ 6H ₂ O were dissolved in 20mL N,N-dimethylformamide in turn, stirred until completely dissolved, then added 2.2g polyvinylpyrrolidone, and continued to stir for 10 hours until the solution was viscous , using electrospinning technology for spinning, the spinning machine parameters are set as negative pressure 3kV, positive pressure 16kV, humidity 30%, receiving distance 20cm, injection speed 0.08mm min ^-1 . After spinning, ^it was dried in a blast drying oven at 60°C for 12 hours, then heated to 220°C for 2 hours at a rate of 0.5°C ^min The temperature was raised to 850° C. and kept for 5 hours for phase formation to obtain PSNC nanofibers.

The PSNC nanofibers were put into the ALD cavity to raise the temperature under vacuum, and after being purged and cleaned by nitrogen, aluminum oxide and cerium oxide were deposited alternately at the same time. The chamber pressure of the ALD system is about 1 Torr, the temperature of the deposition window is 150-250°C, the temperature of the pipeline is 150°C, and the heating temperature of the cerium source is 150°C to provide sufficient saturated vapor pressure, and the aluminum source TMA does not need to be heated. The deposition uses high-purity nitrogen (99.999%) as the carrier gas, and the thickness of the deposited film is controlled by the number of cycles; the ratio of Al to Ce in the composite film is controlled by the small number of cycles of each element in the cycle. In this embodiment, the number of deposition circles is 79 circles. After the ALD deposition, the PSNC@Al _0.1 Ce _0.9 O _2-δ -79cycles bifunctional catalytic material was obtained. Its main XRD structure and SEM morphology are similar to Example 2.

What is not involved above is applicable to the prior art.

Although some specific embodiments of the present invention have been described in detail by examples, those skilled in the art should understand that the above examples are only for illustration, rather than for limiting the scope of the present invention. Various modifications or additions or similar substitutions can be made to the described specific embodiments without departing from the direction of the present invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent replacements, improvements, etc. made to the above implementations based on the technical essence of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. A bifunctional electrocatalyst, characterized in that: the core of the bifunctional electrocatalyst is a perovskite-like oxide nanofiber, and its chemical formula is Pr _z Sr _2-z Ni _y Co _1-y O _2-ε , z=0~2, y=0~1, ε=0~0.25, the outer layer is a heteroatom-doped CeO ₂ thin film Fe _x Ce _1-x O _2-δ deposited by ALD technology, in which the metal Fe doping ratio x=0-0.3, δ=0-0.1. 2. A bifunctional electrocatalyst according to claim 1, characterized in that: said z is 0.5, 1.0 or 1.5, y is 0.5, and x is 0, 0.1, 0.2 or 0.3. 3. a preparation method of the bifunctional electrocatalyst as claimed in claim 1 or 2, is characterized in that: comprises the steps: S1: According to the chemical formula Pr _z Sr _2-z Ni _y Co _1-y O _2-ε , respectively weigh the Pr source, Sr source, Ni source and Co source according to the stoichiometric ratio and dissolve them in the organic solvent in sequence, and stir until completely dissolved Finally, add polyvinylpyrrolidone and continue to stir until the solution is viscous; S2: The solution is spun by electrospinning technology, and dried after spinning; S3: Spinning after drying, pre-oxidizing, and keeping warm to form a phase to obtain perovskite-like oxide nanofibers Pr _z Sr _2-z Ni _y Co _{1- y} O _2-ε , denoted as PSNC; S4: Put the nanofiber PSNC into the cavity of the ALD system to raise the temperature under vacuum, and use the atomic layer deposition technology to perform cyclic deposition on the nanofiber PSNC, and obtain a layer of iron-doped cerium oxide film uniformly deposited on the nanofiber PSNC, and use The thickness of the deposited film is controlled by a large number of cycles; the ratio of Fe and Ce in the film is controlled by the cycle number of each element in the cycle. 4. The preparation method of a bifunctional electrocatalyst according to claim 3, characterized in that: the Pr source in step S1 is Pr(NO ₃ ) ₃ 6H ₂ O, and the Sr source is Sr(NO ₃ ) ₃ , Ni source is Ni(NO ₃ ) ₂ ·6H ₂ O or Ni(CH ₃ COO) ₂ ·4H ₂ O, Co source includes Co(NO ₃ ) ₂ ·6H ₂ O; the Pr(NO ₃ ) ₃ · The molar ratio of 6H ₂ O, Sr(NO ₃ ) ₃ , Ni(NO ₃ ) ₂ 6H ₂ O, Co(NO ₃ ) ₂ 6H ₂ O is 1:3:1:1; the organic solvent is N,N-Dimethylformamide. 5. The preparation method of a kind of bifunctional electrocatalyst as claimed in claim 4, it is characterized in that: the negative pressure that the electrospinning technique in step S2 adopts is 2.5～3kV, and positive pressure is 15～20kV, and the receiving distance is 15-20cm, the injection speed is 0.06-0.08mm min ^-1 . 6. The preparation method of a bifunctional electrocatalyst as claimed in claim 3, characterized in that: in step S3, the temperature is raised to 220°C at a heating rate of 0.5°C min ^-1 for 2 hours for pre-oxidation, and finally 0.5 ℃ min ^-1 heating up to 850-900 ℃ for 5 hours for phase formation to obtain nanofiber PSNC. 7. The preparation method of a kind of bifunctional electrocatalyst as claimed in claim 3, is characterized in that: in step S4, used iron source is ferrocene Fe(Cp) ₂ , cerium source is Ce(iPrCp) ₂ ( iPr-amd). 8. the preparation method of a kind of bifunctional electrocatalyst as claimed in claim 7, it is characterized in that: in the step S4, carry out the specific operation of cyclic deposition on nanofiber PSNC: _O pulse 0.5s→stay 8s→Fe( Cp) ₂ pulse 1s→dwell 15s→N ₂ purge 2s→n×(H ₂ O pulse 0.02s→dwell 30s→Ce(iPrCp) ₂ (iPr-amd) pulse 0.5s→dwell 20s→N ₂ purge 2s ), the value of n is determined by the composition ratio of the sediment. 9. The preparation method of a bifunctional electrocatalyst as claimed in claim 8, characterized in that: in step S4, the technical parameters of atomic layer deposition are: ALD system chamber pressure 1 Torr, deposition window temperature 150-250 °C, The temperature of the pipeline is 150°C, the heating temperature of the cerium source is 150°C, and the heating temperature of the iron source is 80°C to provide sufficient saturated vapor pressure. The deposition uses high-purity nitrogen as the carrier gas, the ozone flow rate is 400 sccm, and the number of cycles is 26 to 105. . 10. The application of a bifunctional electrocatalyst as claimed in claim 1, characterized in that: it is coated on the carbon paper of the positive electrode current collector of the zinc-air battery.

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