CN114005999A

CN114005999A - A kind of bifunctional electrocatalyst and its preparation method and application

Info

Publication number: CN114005999A
Application number: CN202111037583.1A
Authority: CN
Inventors: 贺贝贝; 潘国宏; 赵凌; 公衍生; 王欢文; 汪锐
Original assignee: Zhejiang Research Institute China University Of Geosciences Wuhan; China University of Geosciences
Current assignee: Zhejiang Research Institute China University Of Geosciences Wuhan; China University of Geosciences
Priority date: 2021-09-06
Filing date: 2021-09-06
Publication date: 2022-02-01
Anticipated expiration: 2041-09-06
Also published as: CN114005999B

Abstract

The invention discloses a bifunctional electrocatalyst and a preparation method and application thereof. The inner core of the bifunctional electrocatalyst is a perovskite-like oxide nanofiber, chemical formula 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, and the Fe doping ratio is x=0-0.3. The method first obtains the perovskite-like oxide nanofiber PSNC, puts the nanofiber PSNC into the cavity of the ALD system to heat up in vacuum, and performs cyclic deposition on the nanofiber PSNC to obtain the iron-doped cerium oxide deposited on the nanofiber PSNC. material film. The bifunctional electrocatalyst of the present invention can maintain excellent ORR/OER catalytic activity under alkaline conditions, and shows good rate and cycle performance when applied to the cathode catalyst of a zinc-air battery.

Description

Bifunctional electrocatalyst and preparation method and application thereof

Technical Field

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

Background

Metal-air batteries have received much attention in the energy storage and conversion field because of their green, clean, high energy density, recyclable and other advantages. The zinc air battery has a large-scale application commercial prospect due to the abundant earth reserves, low price and strong corrosion resistance in alkaline electrolyte. Oxygen Evolution Reaction (OER) and Oxygen Reduction Reaction (ORR) are used as two important half reactions of the cathode of the zinc-air battery, and due to the fact that an electron transfer process is complex, the reaction has high overpotential, and energy efficiency of the zinc-air battery is low, and therefore research on corresponding bifunctional electrocatalysts is very important.

Although the noble metal-based catalyst has high catalytic activity, the noble metal-based catalyst has less reserves, high price and single function, thereby causing difficulty for large-scale application of the noble metal-based catalyst. The research of non-noble metal-based catalysts has become a hot spot in this field. The perovskite type oxide has low price, abundant reserves and adjustable electronic structure, thereby having higher potential electrocatalytic activity. However, the electronic conductivity and intrinsic catalytic activity of the perovskite material prepared by the traditional solid phase reaction method are low, and the nano-sized catalyst introduced on the surface of the oxide can obviously increase active sites and improve the catalytic activity, so that the high-efficiency and stable catalyst meeting the commercial requirement is expected to be obtained.

The current methods for nano-modification of catalysts are generally mechanical mixing and grinding method, impregnation method and chemical vapor deposition method. The contact area between the nano particles and the oxide electrode particles is small, the adhesion force is weak, and the long-term stability of the modified compound is poor; the impregnation method and the vapor deposition method require subsequent high-temperature treatment to deposit the nano catalyst on the particle surface, which may damage the structure and the original morphology of the oxide; not only the modified species are not distributed uniformly, but also the impregnation amount is poor in controllability, the modified amount is not easy to control, the process period is long, and the preparation cost is high, so that the practical application of the modified species is limited.

Disclosure of Invention

The invention aims to provide a bifunctional electrocatalyst which maintains excellent ORR/OER catalytic activity under alkaline conditions and shows good multiplying power and cycle performance when applied to a zinc-air battery cathode catalyst, and a preparation method and application thereof, aiming at the defects in the prior art.

The invention relates to a bifunctional electrocatalyst, the inner core of which is perovskite-like oxide nano fiber with a chemical formula of Pr_zSr_2-zNi_yCo_1-yO_2-εZ is 0-2, y is 0-1, epsilon is 0-0.25, and the outer layer is hetero-atom doped CeO deposited by ALD technology₂Film Fe_xCe_1-xO_2-δWherein the doping ratio x of the metal Fe is 0-0.3, and the doping ratio delta is 0-0.1.

Further, 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, comprising the following steps:

s1: according to the chemical formula Pr_zSr_2-zNi_yCo_1-yO_2-εRespectively weighing Pr source, Sr source, Ni source and Co source according to stoichiometric ratio, sequentially dissolving in organic solvent, stirring until completely dissolved, adding polyvinylpyrrolidone, and continuously stirring until the solution is viscous;

s2: spinning the solution by using an electrostatic spinning technology, and drying after the spinning is finished;

s3: the dried spinning is pre-oxidized and kept warm to form a phase, and the perovskite-like oxide nanofiber Pr is obtained_0.5Sr_1.5Ni_0.5Co_0.5O_2-εRecorded as PSNC;

s4: putting the nanofiber PSNC into an ALD system cavity, raising the temperature in vacuum, performing cyclic deposition on the nanofiber PSNC by adopting an atomic layer deposition technology to obtain a layer of iron-doped cerium oxide film which is uniformly deposited on the nanofiber PSNC, and controlling the thickness of the deposited film by the number of cycles; and controlling the proportion of Fe and Ce in the film according to the circulation times of each element in the circulation ring.

Further, the Pr source in step S1 is Pr (NO)₃)₃·6H₂O, Sr source is Sr (NO)₃)₃The Ni source is Ni (NO)₃)₂·6H₂O or Ni (CH)₃COO)₂·4H₂O, Co sources including Co (NO)₃)₂·6H₂O; the Pr (NO)₃)₃·6H₂O，Sr(NO₃)₃，Ni(NO₃)₂·6H₂O，Co(NO₃)₂·6H₂The molar ratio of O is 1:3:1: 1; the organic solvent is N, N-dimethylformamide.

Further, the electrostatic spinning technology in the step S2 adopts a negative pressure of 2.5-3 kV, a positive pressure of 15-20 kV, a receiving distance of 15-20 cm and a pushing speed of 0.06-0.08 mm min^-1。

Further, in step S3, at 0.5 deg.C for min^-1Raising the temperature to 220 ℃ at the heating rate, preserving the heat for 2 hours for pre-oxidation, and finally carrying out pre-oxidation at the temperature of 0.5 ℃ for min^-1Heating to 850-900 ℃, and preserving heat for 5 hours to form a phase to obtain the nano fiber PSNC;

further, in step S4, the iron source used is ferrocene Fe (Cp)₂The cerium source is Ce (iPrCp)₂(iPr-amd)。

Further, the specific operation of performing the cyclic deposition on the nanofiber PSNC in step S4 is: o is₃Pulse 0.5s → dwell 8s → Fe (Cp)₂Pulse 1s → dwell 15s → N₂Purge 2s → nx (H)₂O pulse 0.02s → dwell 30s → Ce (iPrCp)₂(iPr-amd) pulse 0.5s → dwell 20s → N₂Purge 2s), the value of n is determined by the compositional proportion of the deposit.

Further, in step S4, the atomic layer deposition parameters are: the ALD system has a chamber pressure of 1Torr, a deposition window temperature of 150-. High-purity nitrogen is used as carrier gas for deposition, the flow rate of ozone is 400sccm, and the number of cycles is 26-105.

The application of the bifunctional electrocatalyst is coated on carbon paper of a positive current collector of a zinc-air battery.

The bifunctional electrocatalyst can keep excellent ORR/OER catalytic activity under an alkaline condition, shows good multiplying power and cycle performance when being applied to a zinc-air battery cathode catalyst, can obviously reduce the overpotential on an air electrode, improves the energy density and power efficiency, and enhances the long-term charge and discharge stability when being applied to the assembly and test of a zinc-air battery.

The preparation method of the invention is to deposit a layer of cerium oxide with different iron doping amounts outside the nanofiber prepared by electrostatic spinning by utilizing an atomic layer deposition technology, and can carry out precise modification on the composition and thickness of a coating layer of the cerium oxide. According to the preparation method, the surface modification of the nano catalyst can be efficiently and quickly realized through the ALD technology, the components, the proportion and the thickness of the deposit can be accurately controlled, the ALD-modified perovskite-based composite material is applied to the cathode catalyst of the zinc-air battery, and the commercial application approach of the zinc-air battery can be expanded.

Drawings

FIG. 1 is the PSNC @ Fe prepared in example 2_0.1Ce_0.9O_2-δ-79cycles X-ray powder diffractionA map;

FIG. 2a is PSNC @ Fe prepared in example 2_0.1Ce_0.9O_2-δSEM (scanning Electron microscope) picture of 79 cycles;

FIGS. 2b and 2c are PSNC @ Fe prepared in example 2_0.1Ce_0.9O_2-δTEM (transmission electron microscopy) images of 79 cycles;

FIG. 2d is the PSNC @ Fe prepared in example 2_0.1Ce_0.9O_2-δ-79cycles of element maps;

FIG. 3a is PSNC @ Fe prepared in example 2_0.1Ce_0.9O_2-δ79cycles with PSNC and commercial iridium oxide catalyst at 0.1mol L^-1LSV curve of OER performance in KOH solution;

FIG. 3b is the PSNC @ Fe prepared in example 2_0.1Ce_0.9O_2-δ79cycles with PSNC and commercial iridium oxide catalyst at 0.1mol L^-1LSV curve of ORR performance in KOH solution;

FIG. 4 shows PSNC @ Fe prepared in example 2_0.1Ce_0.9O_2-δ-79cycles and PSNC nanofibers assembled zinc air cell polarization performance test curve;

FIG. 5 shows PSNC @ Fe prepared in example 2_0.1Ce_0.9O_2-δ-79cycles and PSNC nanofibers assembled zinc air battery to carry out rate capability test curve;

FIG. 6 shows PSNC @ Fe prepared in example 2_0.1Ce_0.9O_2-δZinc air battery assembled by-79 cycles and PSNC nano-fiber at current density of 5mA cm^-2A discharge performance test curve performed under the condition;

FIG. 7 shows PSNC @ Fe prepared in example 2_0.1Ce_0.9O_2-δThe zinc-air battery assembled by-79 cycles and PSNC nano fibers is at 10mA cm^-2The cycle performance test curve performed under the conditions of (1).

Detailed Description

The following are specific embodiments of the present invention and are further described with reference to the drawings, but the present invention is not limited to these embodiments.

Example 1:

according to the chemical formula Pr_0.5Sr_1.5Ni_0.5Co_0.5O_4-εSeparately weighing Pr (NO) according to stoichiometric ratio₃)₃·6H₂O，Sr(NO₃)₃，Ni(NO₃)₂·6H₂O，Co(NO₃)₂·6H₂Dissolving O in 20mL of N, N-dimethylformamide in sequence, stirring until the O is completely dissolved, adding 2.2g of polyvinylpyrrolidone, continuously stirring for 10 hours until the solution is in a viscous state, and spinning by using an electrostatic spinning technology, wherein the parameters of a spinning machine are set to be 3kV of negative pressure, 16kV of positive pressure, 30% of humidity, 20cm of receiving distance and 0.08mm min of injection speed^-1. After spinning, the fiber was dried in a 60 ℃ forced air drying oven for 12 hours and then at 0.5 ℃ for min^-1Raising the temperature to 220 ℃ at the heating rate, preserving the heat for 2 hours for pre-oxidation, and finally carrying out pre-oxidation at the temperature of 0.5 ℃ for min^-1And (4) heating to 850 ℃, and keeping the temperature for 5 hours to carry out phase formation to obtain the PSNC nanofiber.

PSNC nanofibers are placed in an ALD cavity to be heated in vacuum, CeO with different Fe doping contents is deposited after nitrogen purging and cleaning₂Coating to obtain PSNC @ Fe_xCe_1-xO_2-δThe optimum Fe doping ratio was determined, wherein the metal Fe doping ratio x is 0, 0.1, 0.2, 0.3. The ALD system chamber pressure during deposition is about 1Torr, the deposition window temperature is 150-. High-purity nitrogen (99.999%) is used as carrier gas for deposition, the flow rate of ozone is 400sccm, and the thickness of a deposited film is controlled by the number of cycles; the proportion of Fe to Ce in the composite film was controlled by the number of small cycles of each element in the cycle, and the number of deposition cycles in this example was 26 cycles. Fe_xCe_1-xO_2-δOne deposition turn of (a) is in the order: o is₃Pulse 0.5s → dwell 8s → Fe (Cp)₂Pulse 1s → dwell 15s → N₂Purge 2s → nx (H)₂O pulse 0.02s → dwell 30s → Ce (iPrCp)₂(iPr-amd) pulse0.5s → dwell 20s → N₂Purge 2s), the value of n is determined by the compositional proportion of the deposit. PSNC @ CeO is obtained after ALD deposition is finished₂-26cycles、PSNC@Fe_0.1Ce_0.9O_2-δ-26cycles、PSNC@Fe_0.2Ce_0.8O_2-δ-26cycles, and PSNC @ Fe_0.3Ce_0.7O_2-δ-26cycles bifunctional catalytic material.

The OER and ORR performance of the electrocatalyst materials for each different iron doping ratio is shown in table 1. It can be seen that PSNC @ Fe is obtained when the iron doping molar ratio is 0.1_0.1Ce_0.9O_2-δOER performance of 26cycles with an initial potential of 1.48V at 10mA cm^-2The corresponding potential is 1.68V, which is obviously lower than other iron doping content; among ORR properties, PSNC @ Fe_0.1Ce_0.9O_2-δHalf-wave potential of-26 cycles is 0.7V, and limiting current density is-4.67 mA cm^-2Also, it is superior to other iron doping ratios, indicating that the electrocatalytic activity is the highest and the oxygen exchange kinetics are faster when the iron doping ratio is 0.1 in the iron-doped cerium oxide, and thus the optimum iron doping amount is determined to be 0.1.

TABLE 1 summary of OER and ORR Performance of deposition of cerium oxides of different iron doping ratios on PSNC nanofibers according to the invention

Example 2:

according to the chemical formula Pr_0.5Sr_1.5Ni_0.5Co_0.5O_4-εSeparately weighing Pr (NO) according to stoichiometric ratio₃)₃·6H₂O，Sr(NO₃)₃，Ni(NO₃)₂·6H₂O，Co(NO₃)₂·6H₂O is dissolved in 20mL of N, N-dimethylformamide in turnAnd (2) stirring to completely dissolve, adding 2.2g of polyvinylpyrrolidone, continuously stirring for 10 hours until the solution is in a viscous state, spinning by using an electrostatic spinning technology, wherein the parameters of a spinning machine are set to 3kV of negative pressure, 16kV of positive pressure, 30% of humidity, 20cm of receiving distance and 0.08mm min of injection speed^-1. After spinning, the fiber was dried in a 60 ℃ forced air drying oven for 12 hours and then at 0.5 ℃ for min^-1Raising the temperature to 220 ℃ at the heating rate, preserving the heat for 2 hours for pre-oxidation, and finally carrying out pre-oxidation at the temperature of 0.5 ℃ for min^-1And (4) heating to 850 ℃, and keeping the temperature for 5 hours to carry out phase formation to obtain the PSNC nanofiber.

PSNC nanofibers are placed in an ALD cavity to be heated in vacuum, and after nitrogen purging and cleaning, iron oxide and cerium oxide are alternately deposited. The ALD system has a chamber pressure of about 1Torr, a deposition window temperature of 150-. High-purity nitrogen (99.999%) is used as carrier gas for deposition, the flow rate of ozone is 400sccm, and the thickness of a deposited film is controlled by the number of cycles; the proportion of Fe and Ce in the composite film is controlled by the small circulation times of each element in the circulation ring. The deposition cycle sequence of the Fe/Ce oxide in this example is: o is₃Pulse 0.5s → dwell 8s → Fe (Cp)₂Pulse 1s → dwell 15s → N₂Purge 2s → H₂O pulse 0.02s → dwell 30s → Ce (iPrCp)₂(iPr-amd) pulse 0.5s → dwell 20s → N₂Purge 2s, deposition number 79cycles in this example. PSNC @ Fe is obtained after ALD deposition is finished_0.1Ce_0.9O_2-δ-79cycles bifunctional catalytic material.

Referring to the attached FIG. 1, PSNC @ Fe prepared according to the technical scheme of the embodiment_0.1Ce_0.9O_2-δAn X-ray powder diffraction pattern of-79 cycles, which shows a one-to-one correspondence with the peaks of PSNC, but does not show particularly distinct peaks of iron oxide or cerium oxide, which may be related to the amorphous structure of the outer coating layer and the very small amount of coating.

Referring to the attached FIG. 2a, PSNC @ Fe prepared according to the technical scheme of the embodiment_0.1Ce_0.9O_2-δ-79cycles ofSEM (scanning electron microscope) picture, from which it can be seen that it is a one-dimensional nanofiber structure with a diameter of about 250nm and is distributed relatively uniformly. FIGS. 2b and 2c are PSNC @ Fe prepared according to the embodiment_0.1Ce_0.9O_2-δTEM (Transmission Electron microscopy) image of 79cycles, from which it can be seen that the nanofibers have a uniform amorphous coating outside, the thickness of the coating being related to the number of ALD depositions cycles, indicating the successful preparation of the core-shell structure. FIG. 2d is PSNC @ Fe_0.1Ce_0.9O_2-δThe element mapping of 79cycles can observe that each element is distributed more uniformly and has no segregation, and in addition, a small amount of Fe and Ce elements are distributed on the fiber, thereby further explaining the existence of the surface coating layer.

To demonstrate the electrocatalytic properties of the catalyst, the amount of the catalyst was 0.1mol L^-1Oxygen evolution and oxygen reduction performance tests were performed in KOH solution at 1600 rpm. The test is completed by using a three-electrode test system, wherein a reference electrode is a saturated calomel electrode, a counter electrode is a platinum electrode, and a working electrode is formed by coating 2 mu L of catalyst slurry on a platinum-carbon electrode. The catalyst slurry was prepared by mixing 40mg of catalyst, 10mg of Ketjen black, 5mL of ethanol, and 250. mu.L of Nafion solution and sonicating for two hours.

Referring to FIG. 3a, PSNC @ Fe prepared according to the technical scheme of the embodiment_0.1Ce_0.9O_2-δ79cycles with PSNC and commercial iridium oxide catalyst at 0.1mol L^-1LSV curve of OER performance in KOH solution. PSNC @ Fe_0.1Ce_0.9O_2-δThe-79 cycles show excellent OER catalytic activity, the initial potential is 1.4V, and compared with 1.5V of iridium oxide, the catalyst has lower cost and higher commercial value. At 10mA cm^-2PSNC @ Fe at a current density of_0.1Ce_0.9O_2-δThe potential for the-79 cycles is 1.55V, which is clearly lower than PSNC (1.72V) and the commercial catalyst iridium oxide (1.69V), indicating a faster oxygen exchange kinetics. Referring to FIG. 3b, PSNC @ Fe prepared according to the technical scheme of the embodiment_0.1Ce_0.9O_2-δ79cycles with PSNC and commercial iridium oxide catalyst at 0.1mol L^-1ORR behavior in KOH solutionLSV curve. Comparison with PSNC (0.67V, 4.51mA cm^-2) And platinum carbon (0.89V, 5.26mA cm)^-2)，PSNC@Fe_0.1Ce_0.9O_2-δ-79cycles(0.72V，5.56mA cm^-2) Has higher half-wave potential and limiting current density, and shows that the catalyst has optimal ORR catalytic activity.

The zinc-air battery is a liquid water system zinc-air battery assembled by taking a zinc sheet as a negative electrode and air as an electrochemical reaction substance of a positive electrode and taking the prepared bifunctional electrocatalyst as an air cathode catalyst. After 25mg of the catalyst and 6.25mg of ketjen black were mixed and ground for 20 minutes, 1mL of ethanol and 380mL of Nafion solution were added and mixed thoroughly, and then the mixture was uniformly coated on 10 pieces of 2 × 2cm carbon paper, and dried in a vacuum oven at 60 ℃ for 10 hours for standby. The negative electrode of the zinc-air battery uses a zinc sheet, and the electrolyte is 6mol L^-1KOH and 0.2mol L of^-1The mixed solution of zinc acetate. And assembling the positive electrode, the negative electrode, the electrolyte, the diaphragm and the like into the zinc-air battery for testing.

See FIG. 4 for PSNC @ Fe_0.1Ce_0.9O_2-δPolarization performance test curve of zinc-air battery assembled by 79cycles and PSNC nano-fibers, as can be seen from the figure, PSNC @ Fe_0.1Ce_0.9O_2-δThe maximum power density of a zinc-air battery assembled by 79cycles of catalyst can reach 195mW cm^-2Is obviously higher than PSNC 102mW cm^-2Is also higher than the commercial catalyst Pt/C + IrO₂84mW cm^-2Its good output performance may be due to the excellent bifunctional catalytic activity of the catalyst itself.

See FIG. 5 for PSNC @ Fe_0.1Ce_0.9O_2-δ-79cycles and PSNC nanofibers assembled zinc air battery to carry out rate performance test curve. Shown in the figure, PSNC @ Fe_0.1Ce_0.9O_2-δThe 79cycles catalyst showed a relatively smooth plateau at each current density plateau and when the current density was returned to 1mA cm^-2When the voltage was recovered to 1.24V, it was confirmed that the zinc-air cell was excellent in reversibility.

See FIG. 6 for PSNC@Fe_0.1Ce_0.9O_2-δThe zinc-air battery assembled by the-79 cycles and the PSNC nano fibers is at 5mA cm^-2Discharge performance test curve performed under the conditions of (1). PSNC @ Fe is shown in the figure_0.1Ce_0.9O_2-δThe-79 cycles discharge continuously for nearly 39 hours, better than 27 hours for PSNC, and the voltage is more stable without significant drop.

See FIG. 7 for PSNC @ Fe_0.1Ce_0.9O_2-δThe zinc-air battery assembled by-79 cycles and PSNC nano fibers is at 10mA cm^-2The cycle performance test curve performed under the conditions of (1). Load PSNC @ Fe_0.1Ce_0.9O_2-δThe zinc-air battery of the-79 cycles catalyst is continuously charged and discharged for about 280 hours, 1375 cycle periods, and has better cycle stability than PSNC.

PSNC@Fe_0.1Ce_0.9O_2-δThe 79cycles catalyst has excellent OER and ORR dual-function catalytic activity and zinc-air battery performance, because the ohmic loss is reduced due to the doping of Fe in the coating layer, the ionic conductivity is improved, and meanwhile, the substrate with the fiber structure also provides larger surface area and exposes more active sites.

Example 3:

according to the chemical formula Pr_0.5Sr_1.5Ni_0.5Co_0.5O_4-εSeparately weighing Pr (NO) according to stoichiometric ratio₃)₃·6H₂O，Sr(NO₃)₃，Ni(NO₃)₂·6H₂O，Co(NO₃)₂·6H₂Dissolving O in 20mL of N, N-dimethylformamide in sequence, stirring until the O is completely dissolved, adding 2.2g of polyvinylpyrrolidone, continuously stirring for 10 hours until the solution is in a viscous state, and spinning by using an electrostatic spinning technology, wherein the parameters of a spinning machine are set to be 3kV of negative pressure, 16kV of positive pressure, 30% of humidity, 20cm of receiving distance and 0.08mm min of injection speed^-1. After spinning, the fiber was dried in a 60 ℃ forced air drying oven for 12 hours and then at 0.5 ℃ for min^-1Raising the temperature to 220 ℃ at a heating rate, preserving the heat for 2 hours for pre-oxidation, and finallyAt 0.5 deg.C for min^-1And (4) heating to 850 ℃, and keeping the temperature for 5 hours to carry out phase formation to obtain the PSNC nanofiber.

PSNC nanofibers are placed in an ALD cavity to be heated in vacuum, and after nitrogen purging and cleaning, iron oxide and cerium oxide are alternately deposited. The ALD system has a chamber pressure of about 1Torr, a deposition window temperature of 150-. High-purity nitrogen (99.999%) is used as carrier gas for deposition, the flow rate of ozone is 400sccm, and the thickness of a deposited film is controlled by the number of cycles; the proportion of Fe and Ce in the composite film is controlled by the small circulation times of each element in the circulation ring. The deposition cycle sequence of the Fe/Ce oxide in this example is: o is₃Pulse 0.5s → dwell 8s → Fe (Cp)₂Pulse 1s → dwell 15s → N₂Purge 2s → H₂O pulse 0.02s → dwell 30s → Ce (iPrCp)₂(iPr-amd) pulse 0.5s → dwell 20s → N₂Purge 2s, deposition turns 53 in this example. PSNC @ Fe is obtained after ALD deposition is finished_0.1Ce_0.9O_2-δ-53cycles bifunctional catalytic material.

The main XRD structure and SEM appearance of the catalyst are similar to those of example 2, and the electrocatalytic performance and zinc-air battery performance of the catalyst are superior to those of a PSNC catalyst, but not superior to those of the PSNC @ Fe_0.1Ce_0.9O_2-δ79cycles of catalysts, e.g. PSNC @ Fe_0.1Ce_0.9O_2-δOER curves at 10mA cm for-53 cycles^-2The corresponding potential is 1.66V at the current density of (2), and the half-wave potential and the limiting current density in the ORR test are 0.69V and 5.22mA cm^-2。

Example 4:

according to the chemical formula Pr_0.5Sr_1.5Ni_0.5Co_0.5O_4-εSeparately weighing Pr (NO) according to stoichiometric ratio₃)₃·6H₂O，Sr(NO₃)₃，Ni(NO₃)₂·6H₂O，Co(NO₃)₂·6H₂Dissolving O in 20mL of N, N-dimethylformamide in sequence, stirring to dissolve completely, adding 2.2g of polyvinylpyrrolidone, and stirring for 10 timesSpinning by using an electrostatic spinning technology after the solution is viscous for hours, wherein the parameters of a spinning machine are set to 3kV of negative pressure, 16kV of positive pressure, 30% of humidity, 20cm of receiving distance and 0.08mm min of injection speed^-1. After spinning, the fiber was dried in a 60 ℃ forced air drying oven for 12 hours and then at 0.5 ℃ for min^-1Raising the temperature to 220 ℃ at the heating rate, preserving the heat for 2 hours for pre-oxidation, and finally carrying out pre-oxidation at the temperature of 0.5 ℃ for min^-1And (4) heating to 850 ℃, and keeping the temperature for 5 hours to carry out phase formation to obtain the PSNC nanofiber.

PSNC nanofibers are placed in an ALD cavity to be heated in vacuum, and after nitrogen purging and cleaning, iron oxide and cerium oxide are alternately deposited. The ALD system has a chamber pressure of about 1Torr, a deposition window temperature of 150-. High-purity nitrogen (99.999%) is used as carrier gas for deposition, the flow rate of ozone is 400sccm, and the thickness of a deposited film is controlled by the number of cycles; the proportion of Fe and Ce in the composite film is controlled by the small circulation times of each element in the circulation ring. The deposition cycle sequence of the Fe/Ce oxide in this example is: o is₃Pulse 0.5s → dwell 8s → Fe (Cp)₂Pulse 1s → dwell 15s → N₂Purge 2s → H₂O pulse 0.02s → dwell 30s → Ce (iPrCp)₂(iPr-amd) pulse 0.5s → dwell 20s → N₂Purge 2s, deposition turns of 105 in this example. PSNC @ Fe is obtained after ALD deposition is finished_0.1Ce_0.9O_2-δ-105cycles bifunctional catalytic material.

The main XRD structure and SEM appearance of the catalyst are similar to those of example 1, the electrocatalytic performance and the zinc-air battery performance of the catalyst are superior to those of a PSNC catalyst, but the electrocatalytic performance and the zinc-air battery performance of the catalyst are not as good as those of the PSNC @ Fe_0.1Ce_0.9O_2-δ79cycles of catalysts, e.g. PSNC @ Fe_0.1Ce_0.9O_2-δOER curve at 10mAcm for-105 cycles^-2The corresponding potential is 1.64V at the current density of (2), and the half-wave potential and the limiting current density in the ORR test are 0.7V and 5.46mA cm^-2。

Example 5:

according to the chemical formula Pr_1.0Sr_1.0Ni_0.5Co_0.5O_4-εSeparately weighing Pr (NO) according to stoichiometric ratio₃)₃·6H₂O，Sr(NO₃)₃，Ni(NO₃)₂·6H₂O，Co(NO₃)₂·6H₂Dissolving O in 20mL of N, N-dimethylformamide in sequence, stirring until the O is completely dissolved, adding 2.2g of polyvinylpyrrolidone, continuously stirring for 10 hours until the solution is in a viscous state, and spinning by using an electrostatic spinning technology, wherein the parameters of a spinning machine are set to be 3kV of negative pressure, 16kV of positive pressure, 30% of humidity, 20cm of receiving distance and 0.08mm min of injection speed^-1. After spinning, the fiber was dried in a 60 ℃ forced air drying oven for 12 hours and then at 0.5 ℃ for min^-1Raising the temperature to 220 ℃ at the heating rate, preserving the heat for 2 hours for pre-oxidation, and finally carrying out pre-oxidation at the temperature of 0.5 ℃ for min^-1And (4) heating to 850 ℃, and keeping the temperature for 5 hours to carry out phase formation to obtain the PSNC nanofiber.

PSNC nanofibers are placed in an ALD cavity to be heated in vacuum, and after nitrogen purging and cleaning, iron oxide and cerium oxide are alternately deposited. The ALD system has a chamber pressure of about 1Torr, a deposition window temperature of 150-. High-purity nitrogen (99.999%) is used as carrier gas for deposition, the flow rate of ozone is 400sccm, and the thickness of a deposited film is controlled by the number of cycles; the proportion of Fe and Ce in the composite film is controlled by the small circulation times of each element in the circulation ring. The deposition cycle sequence of the Fe/Ce oxide in this example is: o is₃Pulse 0.5s → dwell 8s → Fe (Cp)₂Pulse 1s → dwell 15s → N₂Purge 2s → H₂O pulse 0.02s → dwell 30s → Ce (iPrCp)₂(iPr-amd) pulse 0.5s → dwell 20s → N₂Purge 2s, deposition number 79cycles in this example. Pr after ALD deposition_1.0Sr_1.0Ni_0.5Co_0.5O_4-ε@Fe_0.1Ce_0.9O_2-δ-79cycles bifunctional catalytic material.

The main XRD structure and SEM appearance of the zinc-air battery are similar to those of example 2, and the electrocatalytic performance and the zinc-air battery performance of the zinc-air battery are superior to those of the zinc-air battery which is not precipitatedAccumulated pure Pr_1.0Sr_1.0Ni_0.5Co_0.5O_4-εCatalyst but with a higher OER-ORR potential difference than PSNC @ Fe in example 2_0.1Ce_0.9O_2-δ79cycles catalyst.

Example 6:

according to the chemical formula Pr_1.5Sr_0.5Ni_0.5Co_0.5O_4-εSeparately weighing Pr (NO) according to stoichiometric ratio₃)₃·6H₂O，Sr(NO₃)₃，Ni(NO₃)₂·6H₂O，Co(NO₃)₂·6H₂Dissolving O in 20mL of N, N-dimethylformamide in sequence, stirring until the O is completely dissolved, adding 2.2g of polyvinylpyrrolidone, continuously stirring for 10 hours until the solution is in a viscous state, and spinning by using an electrostatic spinning technology, wherein the parameters of a spinning machine are set to be 3kV of negative pressure, 16kV of positive pressure, 30% of humidity, 20cm of receiving distance and 0.08mm min of injection speed^-1. After spinning, the fiber was dried in a 60 ℃ forced air drying oven for 12 hours and then at 0.5 ℃ for min^-1Raising the temperature to 220 ℃ at the heating rate, preserving the heat for 2 hours for pre-oxidation, and finally carrying out pre-oxidation at the temperature of 0.5 ℃ for min^-1And (4) heating to 850 ℃, and keeping the temperature for 5 hours to carry out phase formation to obtain the PSNC nanofiber.

PSNC nanofibers are placed in an ALD cavity to be heated in vacuum, and after nitrogen purging and cleaning, iron oxide and cerium oxide are alternately deposited. The ALD system has a chamber pressure of about 1Torr, a deposition window temperature of 150-. High-purity nitrogen (99.999%) is used as carrier gas for deposition, the flow rate of ozone is 400sccm, and the thickness of a deposited film is controlled by the number of cycles; the proportion of Fe and Ce in the composite film is controlled by the small circulation times of each element in the circulation ring. The deposition cycle sequence of the Fe/Ce oxide in this example is: o is₃Pulse 0.5s → dwell 8s → Fe (Cp)₂Pulse 1s → dwell 15s → N₂Purge 2s → H₂O pulse 0.02s → dwell 30s → Ce (iPrCp)₂(iPr-amd) pulse 0.5s → dwell 20s → N₂Purge 2s, deposition ring in this exampleThe number is 79 turns. Pr after ALD deposition_1.5Sr_0.5Ni_0.5Co_0.5O_4-ε@Fe_0.1Ce_0.9O_2-δ-79cycles bifunctional catalytic material.

The main XRD structure and SEM appearance of the zinc-air battery are similar to those of example 2, and the electrocatalytic performance and the zinc-air battery performance of the zinc-air battery are superior to those of undeposited pure Pr_1.5Sr_0.5Ni_0.5Co_0.5O_4-εCatalyst but with a higher OER-ORR potential difference than PSNC @ Fe in example 2_0.1Ce_0.9O_2-δ79cycles catalyst.

Example 7:

Putting the PSNC nano-fiber into an ALD (atomic layer deposition) cavity, heating in vacuum, purging and cleaning by nitrogen, and depositing titanium oxide and cerium oxide alternately. Wherein the ALD system has a chamber pressure of about 1Torr, a deposition window temperature of 150 deg.C, a manifold temperature of 150 deg.C, a cerium source heating temperature of 150 deg.C, and a titanium source TDMAT heating temperature of 75 deg.C to provide sufficient saturated vapor pressure. The deposition uses high-purity nitrogen (99.999%) as carrier gas, and the thickness of the deposited film is controlled by the number of cycles; controlling composite films with small cycle times of elements within a cycle circleThe ratio of Ti to Ce in the alloy. The deposition cycle sequence of the Ti/Ce oxide in this example is: h₂O pulse 0.02s → dwell 30s → Ti (NMe)₂)₄Pulse 0.4s → dwell 20s → N₂Purge 2s → H₂O pulse 0.02s → dwell 30s → Ce (iPrCp)₂(iPr-amd) pulse 0.5s → dwell 20s → N₂Purge 2s, deposition number 79cycles in this example. PSNC @ Ti is obtained after ALD deposition is finished_0.1Ce_0.9O_2-δ-79cycles bifunctional catalytic material. The main XRD structure and SEM appearance are similar to those of example 2.

Example 8:

Putting the PSNC nano-fiber into an ALD (atomic layer deposition) cavity, heating in vacuum, purging and cleaning by nitrogen, and simultaneously alternately depositing zinc oxide and cerium oxide. The ALD system has a chamber pressure of about 1Torr, a deposition window temperature of 150-. The deposition uses high-purity nitrogen (99.999%) as carrier gas, and the thickness of the deposited film is controlled by the number of cycles; the proportion of Zn and Ce in the composite film is controlled by the small circulation times of each element in the circulation ring. Deposition ring in this exampleThe number is 79 turns. PSNC @ Zn is obtained after ALD deposition is finished_0.1Ce_0.9O_2-δ-79cycles bifunctional catalytic material. The main XRD structure and SEM appearance are similar to those of example 2.

Example 9:

Putting the PSNC nano-fiber into an ALD (atomic layer deposition) cavity, raising the temperature in vacuum, purging and cleaning by nitrogen, and simultaneously alternately depositing aluminum oxide and cerium oxide. The ALD system has a chamber pressure of about 1Torr, a deposition window temperature of 150-. The deposition uses high-purity nitrogen (99.999%) as carrier gas, and the thickness of the deposited film is controlled by the number of cycles; the proportion of Al and Ce in the composite film is controlled by the small circulation times of each element in the circulation ring. The number of deposition turns in this example was 79. PSNC @ Al is obtained after ALD deposition is finished_0.1Ce_0.9O_2-δ-79cycles bifunctional catalytic material. The main XRD structure and SEM appearance are similar to those of example 2.

The above is not relevant and is applicable to the prior art.

While certain specific embodiments of the present invention have been described in detail by way of illustration, it will be understood by those skilled in the art that the foregoing is illustrative only and is not limiting of the scope of the invention, as various modifications or additions may be made to the specific embodiments described and substituted in a similar manner by those skilled in the art without departing from the scope of the invention as defined in the appending claims. It should be understood by those skilled in the art that any modifications, equivalents, improvements and the like made to the above embodiments in accordance with the technical spirit of the present invention are included in the scope of the present invention.

Claims

1. a bifunctional electrocatalyst, is characterized in that: the inner core of described bifunctional electrocatalyst is class perovskite oxide nanofiber, and its chemical formula 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 film F _x Ce _1-x O _2-δ deposited by ALD technology, and the doping ratio of metal Fe is x=0～0.3, δ=0～0.1.

2 . The bifunctional electrocatalyst according to claim 1 , wherein the 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 .

3. a preparation method of bifunctional electrocatalyst as claimed in claim 1 or 2, is characterized in that: comprise the steps:

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

S2: spin the solution by using electrospinning technology, and dry it after spinning;

S3: spinning the dried, pre-oxidized, and thermally insulated 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 for vacuum heating, and use atomic layer deposition technology to perform cyclic deposition on the nanofiber PSNC to obtain a uniform layer of iron-doped cerium oxide film on the nanofiber PSNC. The thickness of the deposited film is controlled by the large number of cycles; the ratio of Fe and Ce in the film is controlled by the number of cycles of each element in the cycle.

4 . The method for preparing a bifunctional electrocatalyst according to claim 3 , wherein the Pr source in step S1 is Pr(NO ₃ ) ₃ .6H ₂ O, and the Sr source is Sr(NO ₃ ) ₃ . 5 . , the Ni source is Ni(NO ₃ ) ₂ ·6H ₂ O or Ni(CH ₃ COO) ₂ ·4H ₂ O, and the 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 bifunctional electrocatalyst according to claim 4, wherein the negative pressure used by the electrospinning technology in step S2 is 2.5-3 kV, the positive pressure is 15-20 kV, and the receiving distance is 15～20cm, the bolus rate is 0.06～0.08mm min ^-1 .

6. the preparation method of a kind of bifunctional electrocatalyst as claimed in claim 3, it is characterized in that: in step S3, with the temperature rise rate of 0.5 ℃ min ^-1 is heated up to 220 ℃ of insulation 2 hours to carry out pre-oxidation, and finally with The temperature was raised to 850-900°C at 0.5°C min ^-1 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 , and cerium source is Ce(iPrCp) ₂ ( iPr-amd).

8. the preparation method of a kind of bifunctional electrocatalyst as claimed in claim 7 is characterized in that: in step S4, the concrete operation of cyclic deposition on nanofiber _PSNC is: O pulse 0.5s→stay 8s→Fe ( Cp) ₂ pulses 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 method for preparing a bifunctional electrocatalyst according to claim 8 , wherein in step S4 , the atomic layer deposition technical parameters are: the chamber pressure of the ALD system is 1 Torr, the deposition window temperature 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 to provide sufficient saturated vapor pressure. The deposition uses high-purity nitrogen as the carrier gas, the ozone flow rate is 400sccm, and the number of cycles is 26 to 105. .

10. The application of a bifunctional electrocatalyst according to claim 1, characterized in that: it is coated on the carbon paper of the positive current collector of the zinc-air battery.