An oxygen-bridged iron-silicon diatomic electrocatalyst, and a preparation method and application thereof

Abstract

The application relates to a preparation method of an oxygen-bridged iron-silicon diatomic electrocatalyst, which comprises the following steps: stirring and complexing an iron source and a silicon source, mixing a complexing solution with a graphene oxide solution to obtain a precursor solution through ultrasonic treatment, carrying out hydrothermal reaction on the precursor solution to obtain a reaction product, and carrying out freeze-drying treatment on the reaction product, and then carrying out high-temperature nitriding through a chemical vapor deposition method to obtain the oxygen-bridged iron-silicon diatomic electrocatalyst. The oxygen-bridged iron-silicon diatomic electrocatalyst prepared by the method has excellent four-electron oxygen reduction electrocatalytic performance under acidic and alkaline conditions, and has high activity, strong selectivity and stable performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical catalysis, and particularly relates to an oxygen-bridged iron-silicon diatomic electrocatalyst as well as a preparation method and application thereof. BACKGROUND

[0002] Four-electron cathode oxygen reduction reaction (4e - )ORR is commonly used in proton exchange membrane fuel cells (PEMFC), anion exchange membrane fuel cells (AEMFC) and zinc-air batteries (ZABs), however, due to the slow kinetics of ORR, expensive platinum group metals are required as catalysts, which greatly hinders the application of various hydrogen energy batteries.

[0003] Therefore, developing a non-noble metal catalyst with high activity, high stability and high durability has become one of the primary goals of all parties, and currently, single-atom (SAC) or diatomic catalysts (DACs) with a metal-nitrogen-carbon (M-N-C, M = Fe, Co, Cu, Mn, Ni, etc.) coordination structure have a large atomic utilization rate and a special coordination environment. Although the Fe-N-C catalyst has high ORR performance, the active sites are easily deactivated due to the occurrence of a Fenton reaction, which seriously affects the activity and stability of the catalyst, and therefore, a more efficient and stable catalyst needs to be designed to replace the platinum-based catalyst.

[0004] Studies have shown that adjusting the coordination structure of the active site is one of the methods to optimize the ORR catalytic performance, and adding an additional dopant near the active site of the M-N-C catalyst can reduce the electron delocalization around the catalytic center and improve the interaction with oxygen, thereby reducing the ORR reaction energy barrier. Therefore, developing a simple and effective synthesis method to regulate the coordination environment of the active site of the transition metal single-atom or diatomic catalyst is one of the important methods for the current research and development of non-noble metal catalysts. SUMMARY

[0005] The purpose of the present application is to provide an oxygen-bridged iron-silicon diatomic electrocatalyst as well as a preparation method and application thereof, which can solve the technical problem of difficult regulation of the coordination structure of the diatomic catalyst.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of an oxygen-bridged iron-silicon diatomic electrocatalyst, comprising the following steps:

[0008] S1, after stirring and complexing the ferric nitrate solution and the sodium silicate solution, the complexing solution is mixed with the graphene oxide solution by an ultrasonic disperser to obtain a precursor solution; the precursor solution is subjected to a hydrothermal reaction to obtain a black columnar reaction product, wherein the stirring time is 20-40 min, and the ultrasonic time is 15-40 min;

[0009] S2. The reaction product is freeze-dried and then subjected to high-temperature nitridation using a chemical vapor deposition method to obtain an oxygen-bridged iron-silicon diatomic electrocatalyst.

[0010] Preferably, the percentage of iron in the ferric nitrate to the mass of graphene oxide in the graphene oxide solution is 1-20%; the percentage of silicon in the sodium silicate to the mass of graphene oxide in the graphene oxide solution is 1-7%, wherein the ferric nitrate solution is dissolved by anhydrous ethanol and the sodium silicate solution is dissolved by deionized water.

[0011] Preferably, the preparation method of the graphene oxide solution is: dispersing the graphene oxide solid in deionized water, ultrasonicating for 4-6 hours to obtain the graphene oxide solution; the concentration of the graphene oxide solution is 1-4 mg mL -1 .

[0012] Preferably, in step S1, the temperature of the hydrothermal reaction is 160-200° C., and the time of the hydrothermal reaction is 10-15 h.

[0013] Preferably, in step S2, the freeze-drying treatment time is 3-15 hours.

[0014] Preferably, in step S2, the high-temperature nitridation using the chemical vapor deposition method includes the following steps: nitridation is performed in a mixed atmosphere of argon and ammonia, the reaction temperature is 700-900°C, the reaction time is 1-3h, the argon flow rate is 100±10sccm, and the ammonia flow rate is 50±10sccm.

[0015] In another aspect, the present invention provides an oxygen-bridged iron-silicon diatomic electrocatalyst prepared by the above-mentioned preparation method.

[0016] In another aspect, the present invention provides the use of the oxygen-bridged iron-silicon diatomic electrocatalyst as a catalyst for the four-electron oxygen reduction reaction to produce water.

[0017] Another aspect of the present invention provides the use of the above-mentioned oxygen-bridged iron-silicon diatomic electrocatalyst as a cathode catalyst for a zinc-air battery.

[0018] The present invention uses ferric nitrate (Fe(NO3)3) as an iron source, sodium silicate (NaSiO3) as a silicon source, and ammonia (NH3) as a nitrogen source, and adopts a hydrothermal method and chemical vapor deposition technology (CVD) to synthesize an oxygen-bridged iron-silicon diatomic electrocatalyst.

[0019] The application takes graphene as a carrier, and forms a positively charged complex structure by stirring iron ions and silicate ions to uniformly complex, in a hydrothermal process, the iron-silicon complex is inlaid into the deprotonated graphene oxide defect site, and then the coordination structure of the active site is regulated by a chemical vapor deposition (CVD) technology to synthesize a low-cost, special coordination oxygen-bridged iron-silicon diatomic electrocatalyst; in the synthesis process, graphene oxide has more defects than graphene, which can provide a large number of sites for the anchoring of iron atoms, and can inhibit the generation of metal clusters or nanometal, forming a diatomic catalyst with rich active sites and excellent stability; and in the stirring process, the iron ions and silicate ions form a stable precursor by complexation, and with the hydrothermal and high-temperature nitriding process, the iron element and the silicon element are completely anchored on the surface of graphene, thereby forming an oxygen-bridged iron-silicon diatomic structure.

[0020] The application has simple synthesis, short preparation time, inexpensive and abundant precursor; and the oxygen-bridged iron-silicon diatomic electrocatalyst can be obtained by simple hydrothermal and chemical vapor deposition.

[0021] The oxygen-bridged iron-silicon diatomic electrocatalyst prepared by the application has excellent four-electron oxygen reduction electrocatalytic performance under acidic and alkaline conditions, high activity, strong selectivity, stable performance, and far exceeds the commercial Pt / C catalyst under alkaline conditions, and approaches the commercial Pt / C catalyst under acidic conditions; and when the catalyst is applied to the cathode catalyst of a zinc-air battery, it exhibits excellent power density and stability. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The XRD pattern of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared for Example 1;

[0023] Figure 2 The Raman spectrum of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared for Example 1;

[0024] Figure 3 The infrared spectrum of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared for Example 1;

[0025] Figure 4 The XRD pattern of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared for Example 4;

[0026] Figure 5 The Raman spectrum of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared for Example 5;

[0027] Figure 6 The infrared spectrum of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared for Example 5;

[0028] Figure 7TEM image of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1, where: a-200 nm, b-2 nm;

[0029] Figure 8 Schematic diagram of the element content of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1;

[0030] Figure 9 The XPS fine structure peaks of N1s and Fe2p of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1, where: aN 1s, b-Fe 2p;

[0031] Figure 10 The oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1 was - ORR performance, including: a-polarization curve, b-number of transferred electrons and H2O2 selectivity;

[0032] Figure 11 The oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1 was - ORR performance, where: a-Tafel slope plot, b-stability curve;

[0033] Figure 12 The oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1 was - ORR performance, including: a-polarization curve, b-number of transferred electrons and H2O2 selectivity;

[0034] Figure 13 The oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1 was - ORR performance, where: a-Tafel slope plot, b-stability curve;

[0035] Figure 14 This is the discharge polarization curve and power density diagram of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1 in a zinc-air battery device. DETAILED DESCRIPTION

[0036] The present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0037] The graphene oxide in the following examples was prepared by a modified Hummers method, and the specific process was as follows: a three-necked flask was placed in a water pot filled with cold water, 3 g of graphite powder and a mixed solution of concentrated H2SO4 and H3PO4 (volume ratio 9:1) were added thereto, and 18 g of KMnO4 was slowly added at a rotation speed of 200-350 rpm.

[0038] The mixture was stirred in a water bath at 50°C for 12 h at a stirring speed of 200-350 rpm. After the solution temperature dropped to room temperature, it was poured into 400 mL of pre-chilled deionized water and stirred evenly. H2O2 was slowly added in small amounts several times under stirring until the solution turned bright yellow. The mixture was washed repeatedly with 30% by mass HCl solution, deionized water, anhydrous ethanol and diethyl ether. After vacuum drying at room temperature for 24 h, a light yellow graphene oxide solid was obtained.

[0039] Example 1

[0040] A method for preparing an oxygen-bridged iron-silicon diatomic electrocatalyst comprises the following steps:

[0041] 0.16 g of graphene oxide solid was added to 80 mL of deionized water, and a light brown graphene oxide solution was obtained after ultrasonic dispersion for 6 hours. At the same time, 7 mL of ferric nitrate nonahydrate solution and 1.45 mL of sodium silicate solution were mixed and stirred for 30 minutes and then added to the graphene oxide solution. The mass of iron and silicon elements accounted for 7% and 5% of the mass of graphene oxide, respectively. After ultrasonication for 15 minutes, a uniformly dispersed precursor solution was obtained.

[0042] The uniformly mixed precursor solution was transferred to the inner lining of the hydrothermal reactor, and the reaction temperature was set to 180°C and the reaction time was 12 h.

[0043] The hydrothermal product was freeze-dried for 12 hours. The resulting black column was then placed in a tube furnace and subjected to a high-temperature nitridation reaction using chemical vapor deposition (CVD) in an atmosphere of argon and ammonia. The reaction parameters were: a tube furnace temperature of 800°C, a gas flow rate of 50 sccm of NH3 and 100 sccm of Ar, and a nitridation time of 2 hours. This resulted in an oxygen-bridged iron-silicon diatomic electrocatalyst (FeSiNC-5.0).

[0044] Example 2

[0045] A method for preparing an oxygen-bridged iron-silicon diatomic electrocatalyst comprises the following steps:

[0046] 0.16 g of graphene oxide solid was added to 80 mL of deionized water, and a light brown graphene oxide solution was obtained after ultrasonic dispersion for 6 h. At the same time, 7 mL of ferric nitrate nonahydrate solution and 0.87 mL of sodium silicate solution were mixed and stirred for 30 min and then added to the graphene oxide solution. The mass of iron and silicon elements accounted for 7% and 3% of the mass of graphene oxide, respectively. After ultrasonication for 15 min, a uniformly dispersed precursor solution was obtained.

[0047] The uniformly mixed precursor solution was transferred to the inner lining of the hydrothermal reactor, and the reaction temperature was set to 180°C and the reaction time was 12 h.

[0048] The hydrothermal product was freeze-dried for 12 hours. The resulting black column was then placed in a tube furnace and subjected to a high-temperature nitridation reaction using chemical vapor deposition (CVD) in an atmosphere of argon and ammonia. The reaction parameters were: a tube furnace temperature of 800°C, a gas flow rate of 50 sccm of NH3 and 100 sccm of Ar, and a nitridation time of 2 hours. This yielded an iron-silicon diatomic electrocatalyst (FeSiNC-3.0).

[0049] Example 3

[0050] A method for preparing an oxygen-bridged iron-silicon diatomic electrocatalyst comprises the following steps:

[0051] 0.16 g of graphene oxide solid was added to 80 mL of deionized water, and a light brown graphene oxide solution was obtained after ultrasonic dispersion for 6 h. At the same time, 7 mL of ferric nitrate nonahydrate solution and 0.29 mL of sodium silicate solution were mixed and stirred for 30 min and then added to the graphene oxide solution. The mass of iron and silicon elements accounted for 7% and 1% of the mass of graphene oxide, respectively. After ultrasonication for 15 min, a uniformly dispersed precursor solution was obtained.

[0052] The uniformly mixed precursor solution was transferred to the inner lining of the hydrothermal reactor, and the reaction temperature was set to 180°C and the reaction time was 12 h.

[0053] The hydrothermal product was freeze-dried for 12 hours. The resulting black column was then placed in a tube furnace and subjected to a high-temperature nitridation reaction using chemical vapor deposition (CVD) in an atmosphere of argon and ammonia. The reaction parameters were: a tube furnace temperature of 800°C, a gas flow rate of 50 sccm of NH3 and 100 sccm of Ar, and a nitridation time of 2 hours. This yielded an iron-silicon diatomic electrocatalyst (FeSiNC-1.0).

[0054] Example 4

[0055] A method for preparing an oxygen-bridged iron-silicon diatomic electrocatalyst comprises the following steps:

[0056] 0.16 g of graphene oxide solid was added to 80 mL of deionized water, and a light brown graphene oxide solution was obtained after ultrasonic dispersion for 6 hours. At the same time, 20 mL of ferric nitrate nonahydrate solution and 1.45 mL of sodium silicate solution were mixed and stirred for 30 minutes and then added to the graphene oxide solution. The mass of iron and silicon elements accounted for 20% and 5% of the mass of graphene oxide, respectively. After ultrasonication for 15 minutes, a uniformly dispersed precursor solution was obtained.

[0057] The uniformly mixed precursor solution was transferred to the inner lining of the hydrothermal reactor, and the reaction temperature was set to 180°C and the reaction time was 12 h.

[0058] The hydrothermal product was freeze-dried for 12 hours. The resulting black column was then placed in a tube furnace and subjected to a high-temperature nitridation reaction using chemical vapor deposition (CVD) in an atmosphere of argon and ammonia. The reaction parameters were: a tube furnace temperature of 800°C, a gas flow rate of 50 sccm of NH3 and 100 sccm of Ar, and a nitridation time of 2 hours. This yielded an iron-silicon diatomic electrocatalyst (FeSiNC-5.0).

[0059] Example 5

[0060] A method for preparing an oxygen-bridged iron-silicon diatomic electrocatalyst comprises the following steps:

[0061] 0.16 g of graphene oxide solid was added to 80 mL of deionized water, and a light brown graphene oxide solution was obtained after ultrasonic dispersion for 6 hours. At the same time, 5 mL of ferric nitrate nonahydrate solution and 1.45 mL of sodium silicate solution were mixed and stirred for 30 minutes and then added to the graphene oxide solution. The mass of iron and silicon elements accounted for 5% and 5% of the mass of graphene oxide, respectively. After ultrasonication for 15 minutes, a uniformly dispersed precursor solution was obtained.

[0062] The uniformly mixed precursor solution was transferred to the inner lining of the hydrothermal reactor, and the reaction temperature was set to 180°C and the reaction time was 12 h.

[0063] The hydrothermal product was freeze-dried for 12 hours. The resulting black column was then placed in a tube furnace and subjected to a high-temperature nitridation reaction using chemical vapor deposition (CVD) in an atmosphere of argon and ammonia. The reaction parameters were: a tube furnace temperature of 800°C, a gas flow rate of 50 sccm of NH3 and 100 sccm of Ar, and a nitridation time of 2 hours. This yielded an iron-silicon diatomic electrocatalyst (FeSiNC-5.0).

[0064] Example 6

[0065] A method for preparing an oxygen-bridged iron-silicon diatomic electrocatalyst comprises the following steps:

[0066] 0.16 g of graphene oxide solid was added to 80 mL of deionized water, and a light brown graphene oxide solution was obtained after ultrasonic dispersion for 6 h. At the same time, 1 mL of ferric nitrate nonahydrate solution and 1.45 mL of sodium silicate solution were mixed and stirred for 30 min and then added to the graphene oxide solution. The mass of iron and silicon elements accounted for 1% and 5% of the mass of graphene oxide, respectively. After ultrasonication for 15 min, a uniformly dispersed precursor solution was obtained.

[0067] The uniformly mixed precursor solution was transferred to the inner lining of the hydrothermal reactor, and the reaction temperature was set to 150°C and the reaction time was 12 h.

[0068] The hydrothermal product was freeze-dried for 12 hours. The resulting black column was then placed in a tube furnace and subjected to a high-temperature nitridation reaction using chemical vapor deposition (CVD) in an atmosphere of argon and ammonia. The reaction parameters were: a tube furnace temperature of 600°C, a gas flow rate of 50 sccm of NH3 and 100 sccm of Ar, and a nitridation time of 1 hour. This yielded an iron-silicon diatomic electrocatalyst (FeSiNC-5.0).

[0069] Example 7

[0070] A method for preparing an oxygen-bridged iron-silicon diatomic electrocatalyst comprises the following steps:

[0071] 0.16 g of graphene oxide solid was added to 80 mL of deionized water, and a light brown graphene oxide solution was obtained after ultrasonic dispersion for 6 hours. At the same time, 10 mL of ferric nitrate nonahydrate solution and 1.74 mL of sodium silicate solution were mixed and stirred for 30 minutes and then added to the graphene oxide solution. The mass of iron and silicon elements accounted for 10% and 6% of the mass of graphene oxide, respectively. After ultrasonication for 15 minutes, a uniformly dispersed precursor solution was obtained.

[0072] The uniformly mixed precursor solution was transferred to the inner lining of the hydrothermal reactor, and the reaction temperature was set to 160°C and the reaction time was 12 h.

[0073] The hydrothermal product was freeze-dried for 12 hours. The resulting black column was then placed in a tube furnace and subjected to a high-temperature nitridation reaction using chemical vapor deposition (CVD) in an atmosphere of argon and ammonia. The reaction parameters were: a tube furnace temperature of 1000°C, gas flows of 50 sccm NH3 and 100 sccm Ar, and a nitridation time of 1 hour. This yielded an iron-silicon diatomic electrocatalyst (FeSiNC-6.0).

[0074] The catalyst performance evaluation and characterization of the examples are as follows:

[0075] The oxygen-bridged iron-silicon diatomic electrocatalyst was used as a catalyst material for the four-electron oxygen reduction reaction to produce water: the test instrument used a pine rotating disk electrode device (Rotating disk electrode, RDE and Rotating ring-disk electrode, RRDE; electrode model: AFE6R2) and zinc-air batteries (ZABs) to perform electrochemical tests related to four-electron oxygen reduction. The dispersion formulation is as follows: 1 mg of catalyst solid was added to 100 μL of deionized water, 100 μL of anhydrous ethanol, and 20 μL of Nafion solution, then mixed and ultrasonicated for 1 hour. 2.5 μL of the dispersion droplet was applied to the disk electrode (disk area of ​​RDE: 0.196 cm 2 Or the disk area of ​​RRDE: 0.2376 cm 2The area of ​​the platinum ring is 0.2356 cm 2 ), after the first dispersion was dried, 2.5 μL of the dispersion was taken and dropped onto the rotating disk electrode surface (the area mass loading of the electrocatalyst was 0.12 mg cm -2 (RDE) or 0.10 mg cm -2 (RRDE)), and then dried naturally for 12 hours before conducting relevant experimental tests. A platinum wire electrode was used as the counter electrode, Ag / AgCl (3M potassium chloride solution as a salt bridge) was used as the reference electrode, and a disk electrode or ring disk electrode coated with an oxygen-bridged iron-silicon diatomic electrocatalyst was used as the working electrode to assemble a three-electrode system. Before the experiment began, nitrogen or oxygen was introduced into the electrolyte until saturated. Different pH electrolytes (acidic electrolyte: 0.5M H2SO4; alkaline electrolyte: 0.1M KOH) were selected according to different experimental conditions. The electrolyte was charged at 100mV s -1 The cyclic voltammetry (CV) test was performed to activate the catalyst for about 30 min until there was no air on the catalyst surface. In an oxygen-saturated electrolyte, different speeds (225-2025 rpm) were set, and the voltage range was 0.2-1.1 V at a rate of 5 mV s -1 Enter the scan rate to perform linear voltammetry (LSV).

[0076] Zinc-air battery assembly and testing: Cathode electrode: 5 mg of homemade catalyst and 5 mg of carbon black powder were added to 50 μL of isopropyl alcohol, 25 μL of polytetrafluoroethylene (PTFE) solution, and 0.95 mL of deionized water. Ultrasonic dispersion was performed for 3-5 hours to disperse the mixture uniformly. The resulting dispersion was drop-coated on a 2.5 x 2.5 cm hydrophilic carbon paper with a drop-coating area of ​​1 x 1 cm and a loading of 1.0 mg cm. -2 Anode: Polish the zinc plate surface clean and ultrasonically clean it with anhydrous ethanol and then acetone for 30 minutes. Electrolyte: Mixture of 6M KOH and 0.2M ZnCl2.

[0077] Under acidic conditions: the half-wave potential can reach 0.66 V and the current density is 5.07 mA cm -2 , with good stability and low H2O2 selectivity, demonstrating good 4e - ORR performance.

[0078] Under alkaline conditions, the half-wave potential can reach 0.84 V and the current density is 6.11 mA cm -2 , with good stability and very low H2O2 selectivity, demonstrating good 4e - ORR performance.

[0079] Figure 1Shown is the XRD pattern of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1. There are only two diffraction peaks in the figure, located at around 25° and 44°, representing the (002) and (001) planes of graphitic carbon, respectively. There are no diffraction peaks of other metals and their compounds, which indicates that iron is anchored on graphene in the form of single atoms or clusters.

[0080] Figure 2 The Raman spectrum of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1 is shown. The D peak (1350 cm -1 around) is stronger than the G peak (1580cm -1 The intensity ratio of the D peak to the G peak (ID / IG) reached 1.145, which indicates that the prepared oxygen-bridged iron-silicon diatomic electrocatalyst is defect-enriched.

[0081] Figure 3 The figure shows the infrared spectrum of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1. It can be seen from the figure that the oxygen-bridged iron-silicon diatomic electrocatalyst has abundant oxygen functional groups.

[0082] Figure 4 Shown is the XRD pattern of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 4, in which not only the (002) and (100) crystal planes of graphene are observed, but also obvious diffraction peaks of elemental iron and iron carbide are observed, which proves that excess iron is not completely anchored to the surface by graphene, and may exist in the form of elemental iron and iron carbide.

[0083] Figure 5 The figure shows the Raman spectrum of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 5. The intensity ratio of the D peak to the G peak (ID / IG) reaches 1.107, which indicates that the prepared oxygen-bridged iron-silicon diatomic electrocatalyst is defect-enriched.

[0084] Figure 6 The infrared spectrum of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 6 is shown, which also shows that the catalyst has rich oxygen-containing functional groups, but the degree of nitridation is low due to the low reaction temperature and short reaction time.

[0085] Figure 7 a and 7b are the low-magnification and high-magnification TEM images of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1, respectively, which show that there are abundant wrinkles on the surface of the prepared oxygen-bridged iron-silicon diatomic electrocatalyst, which is conducive to exposing more reaction active sites and facilitating the electrochemical reaction.

[0086] Figure 8The elemental content of the oxygen-bridged Fe-Si bimetallic electrocatalyst prepared in Example 1 is shown, wherein Fe: 0.3, Si: 0.6, C: 78.4, N: 5.8, O: 14.9, which indicates that both Fe and Si elements are successfully doped into graphene.

[0087] Figure 9 The XPS spectra of the oxygen-bridged Fe-Si bimetallic electrocatalyst prepared in Example 1 are shown, wherein Figure 9 The N 1s spectra of a show characteristic peaks near 398.2, 399.4, 400.2, and 401.2 eV, which are attributed to pyridinic nitrogen, iron-nitrogen, pyrrolic nitrogen and graphitic nitrogen components, respectively; wherein the pyridinic nitrogen and iron-nitrogen components are beneficial for 4e – ORR reaction. Figure 9 The Fe 2p fine spectra of b show characteristic peaks of Fe 2+ at 710.3-722.1 eV, and after doping with Si element, the Fe 2+ characteristic peaks of the catalyst shift to low binding energy by 1.2 eV, which may be due to the formation of more Fe-O-Si structure, Fe 2+ obtaining electrons from O atoms.

[0088] Figure 10 The performance of the oxygen-bridged Fe-Si bimetallic electrocatalyst prepared in Example 1 in acidic 4e - ORR is shown, wherein Figure 10 a and Figure 10 b are the polarization curves in 0.5 M H2SO4 electrolyte, respectively, wherein the catalyst has a high half-wave potential (E 1 / 2 , 0.64 V) and a limiting current density (J D , 5.08 mA cm -2 ); the number of electron transfer (n) is 3.78 and the H2O2 selectivity is 10-15%, which all indicate that the catalyst is an ideal four-electron transfer path under acidic conditions.

[0089] Figure 11 The performance of the oxygen-bridged Fe-Si bimetallic electrocatalyst prepared in Example 1 in acidic 4e - ORR is shown, wherein Figure 11 a and Figure 11 b are the Tafel slope graph and stability curve in 0.5 M H2SO4 electrolyte, respectively, and the calculated Tafel slope is 128 mV dec -1 , which indicates that the catalyst has superior kinetic performance, and the catalyst can maintain high stability for up to 10 hours of continuous operation without significant decay of current density (91%), and the oxygen-bridged Fe-Si bimetallic electrocatalyst has excellent 4e- ORR activity and stability.

[0090] Figure 12 The oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1 is shown in alkaline 4e - ORR performance, where Figure 12 a and Figure 12 b are polarization curves in 0.1 M KOH electrolyte, where the catalyst has a high half-wave potential (E 1 / 2 , 0.85V) and limiting current density (J D , 6.05 mA cm -2 ); the electron transfer number (n) is 3.92 and the H2O2 selectivity is 1-5%, which indicates that the catalyst is an ideal four-electron transfer pathway under alkaline conditions.

[0091] Figure 13 The oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1 is shown in alkaline 4e - ORR performance, where Figure 13 a and Figure 13 b are the Tafel slope graph and stability curve in 0.1M KOH electrolyte, respectively. The calculated Tafel slope is 115mV dec -1 , which shows that the catalyst has excellent kinetic properties, and the catalyst can maintain high stability in continuous operation for up to 10 hours, and the current density does not decay significantly (90%). In summary, the oxygen-bridged iron-silicon diatomic electrocatalyst has excellent 4e - ORR activity and stability.

[0092] Figure 14 The figure shows the polarization curve and power density of the oxygen-bridged iron-silicon diatomic electrocatalyst prepared in Example 1, which can reach 80 mW cm -2 Peak power density, with excellent power density and stability.

Claims

1. A method for preparing an oxygen-bridged iron-silicon diatomic electrocatalyst, characterized in that: The following steps are involved: S1. After the iron source and the silicon source are stirred and complexed, the complex solution is mixed with the graphene oxide solution and ultrasonically mixed to obtain a precursor solution; subjecting the precursor solution to a hydrothermal reaction to obtain a reaction product; S2. The reaction product is freeze-dried and then subjected to high-temperature nitridation using a chemical vapor deposition method to obtain an oxygen-bridged iron-silicon diatomic electrocatalyst.

2. The preparation method according to claim 1, characterized in that The percentage of iron in the iron source to the mass of graphene oxide in the graphene oxide solution is 1-20%; the percentage of silicon in the silicon source to the mass of graphene oxide in the graphene oxide solution is 1-7%.

3. The preparation method according to claim 1 or 2, characterized in that The iron source is ferric nitrate; the silicon source is sodium silicate.

4. The preparation method according to claim 1, characterized in that In step S1, the graphene oxide solution is prepared by dispersing graphene oxide solid in deionized water and ultrasonicating for 4-6 h to obtain a graphene oxide solution; the concentration of the graphene oxide solution is 1-4 mg mL -1 .

5. The preparation method according to claim 1, characterized in that In step S1, the temperature of the hydrothermal reaction is 160-200° C., and the time of the hydrothermal reaction is 10-15 h.

6. The preparation method according to claim 1, characterized in that In step S2, the freeze-drying treatment time is 3-15 h.

7. The preparation method according to claim 1, characterized in that In step S2, the high-temperature nitridation using the chemical vapor deposition method includes the following steps: nitridation is performed in a mixed atmosphere of argon and ammonia, the reaction temperature is 700-900°C, the reaction time is 1-3 hours, the argon flow rate is 100±10 sccm, and the ammonia flow rate is 50±10 sccm.

8. An oxygen-bridged iron-silicon diatomic electrocatalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the oxygen-bridged iron-silicon diatomic electrocatalyst according to claim 8 as a catalyst for producing water in a four-electron oxygen reduction reaction.

10. Use of the oxygen-bridged iron-silicon diatomic electrocatalyst according to claim 8 as a cathode catalyst for a zinc-air battery.

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