CN115369438A

CN115369438A - Method for preparing CoTi oxide alloy electrocatalyst by using cotton fibers

Info

Publication number: CN115369438A
Application number: CN202211231658.4A
Authority: CN
Inventors: 樊丽权; 张为超; 蘧延庆; 王宇威; 巴学巍; 张德庆; 贾宏葛
Original assignee: Qiqihar University
Current assignee: Qiqihar University
Priority date: 2022-10-08
Filing date: 2022-10-08
Publication date: 2022-11-22

Abstract

A method for preparing a CoTi oxide alloy electrocatalyst by using cotton fibers relates to a method for preparing an air cathode of a metal battery. The method aims to solve the technical problems of high cost, low reserve and low catalytic activity of the existing metal catalyst applied to the cathode of the metal-air battery. The method comprises the following steps: 1. preparing impregnation liquid by utilizing cobalt nitrate hexahydrate, tetrabutyl titanate and acetamide; 2. soaking cotton fibers in a soaking solution to prepare a precursor; 3. precursor is in N ₂ Sintering in the atmosphere to obtain the CoTi oxide alloy electrocatalyst. The catalyst is used for preparing a cathode of a metal-air battery. The cathode reaches or exceeds the performance of noble metal iridium-based metal oxide and platinum-based catalyst, has wide raw material source and low price, and can be used in the field of metal-air batteries.

Description

Method for preparing CoTi oxide alloy electrocatalyst by using cotton fibers

Technical Field

The invention relates to a preparation method of an air cathode of a metal battery.

Background

Environmental issues and energy crisis have driven the rapid development of efficient and clean energy conversion and storage applications. Metal air batteries have gained wide attention due to their high safety, low cost, and zero carbon emissions. Metal-air batteries are of interest for all energy storage and conversion applications due to their high theoretical specific energy and low cost, however, oxygen Evolution Reaction (OER) and Oxygen Reduction Reaction (ORR) are considered key factors in solving metal-air batteries because they have multiple proton-coupled electron transfer steps and high energy intermediates. Therefore, it is critical to study the efficient and stable OER and ORR performance. The OER and ORR catalysts now commercially available are noble metal iridium-based metal oxides and platinum-based catalysts, which are not suitable for widespread use due to their high cost and natural scarcity. Therefore, the preparation of high-efficiency bifunctional catalysts using transition metals rich in the earth has been a hot research.

The metal-air battery is a special fuel battery which takes metal as fuel and generates oxidation-reduction reaction with oxygen in the air to generate electric energy. The metal air battery is made of abundant raw materials. The metal-air battery that has been currently under development mainly includes an aluminum-air battery, a magnesium-air battery, a zinc-air battery, a lithium-air battery, and the like. The metal catalysts applied to the cathode of the metal-air battery are Ru/Ir-based and Pt-based catalysts, and the catalysts have the defects of low reserve, high cost, insufficient dual-function catalytic activity and the like.

Disclosure of Invention

The invention provides a method for preparing a CoTi oxide alloy electrocatalyst by using cotton fibers, aiming at solving the technical problems of high cost, low reserve and low catalytic activity of the existing metal catalyst applied to a cathode of a metal-air battery. The catalyst of the invention uses non-noble metal catalyst to replace part or all of noble metal, so that the performance of the catalyst is close to or exceeds the level of the noble metal catalyst; the price is low, the source is wide and the reserve is sufficient in the aspect of cost; is superior to noble metal catalysts in terms of stability and other properties.

The method for preparing the CoTi oxide alloy electrocatalyst by using the cotton fibers comprises the following steps of:

1. preparing an impregnation liquid: according to the molar ratio of Co atoms to Ti atoms to N atoms of (3-6): 1: (1-3) respectively weighing cobalt nitrate hexahydrate, tetrabutyl titanate and acetamide, adding the cobalt nitrate hexahydrate, the tetrabutyl titanate and the acetamide into N, N-dimethylformamide, and stirring at room temperature until the cobalt nitrate hexahydrate, the tetrabutyl titanate and the acetamide are completely dissolved to obtain an impregnation liquid;

2. preparing impregnated cotton fibers: soaking cotton fiber as a C source into the soaking solution obtained in the step one for 12 to 24 hours at the temperature of between 20 and 35 ℃ and the relative humidity of between 20 and 35 percent, and drying to obtain a precursor;

3. preparation of CoTi oxide alloy electrocatalyst: the precursor is put into a tube furnace at N ₂ And (3) in the atmosphere, heating to 700-900 ℃, and sintering at constant temperature for 1-2 h to obtain the CoTi oxide alloy electrocatalyst, which is represented by CoTiCN.

Furthermore, the total mass concentration of cobalt nitrate hexahydrate and tetrabutyl titanate acetamide in the impregnation liquid in the step one is 10-30%.

Furthermore, the drying in the second step is drying in an oven at 80 ℃ for 12-24 hours.

Further, the temperature rise in the third step is performed at a speed of 4 to 5 ℃/min.

The CoTi oxide alloy electrocatalyst prepared by the method is applied to preparing a cathode of a metal-air battery by using the catalyst.

Further, a method for preparing a cathode of a metal-air battery by using the CoTi oxide alloy electrocatalyst comprises the following steps:

1. firstly, sequentially polishing a glassy carbon electrode on a chamois by using alumina powder with the grain sizes of 1.0, 0.3 and 0.05 micron until the surface of the electrode is smooth and flat without scratches, then cleaning the surface of the electrode by using deionized water, cleaning the surface of the electrode by using an ultrasonic mode for 10s, and finally drying the electrode for later use;

2. weighing 3mg CoTi oxide alloy electrocatalyst powder, adding the powder into 1mL Nafion aqueous solution with the mass percentage concentration of 0.5%, and performing ultrasonic dispersion for 30min to obtain a catalyst suspension with the concentration of 3 mg/mL;

3. and dropwise adding the catalyst suspension on the polished glassy carbon electrode, standing for 1h at room temperature, and obtaining the metal-air battery cathode after the catalyst is dried to form a film.

The method uses cotton fiber as a template, the cotton fiber is soaked in a solution containing metal and doping elements, nonmetal elements C and N are used for doping and modifying the CoTi oxide, the surface structure of the catalyst is changed by combining a high-temperature calcination mode, pyridine nitrogen and graphite nitrogen are generated, the surface metal and the nonmetal elements present good dispersibility, the specific surface area is increased, a mesoporous structure is generated, and the electrochemical performance of the CoTi oxide alloy electrocatalyst is improved.

The invention applies a CoTi oxide alloy electrocatalyst metal-air battery cathode, which has excellent difunctional electrochemical performance and excellent stability to oxygen reduction reaction.

The CoTi oxide alloy electrocatalyst of the invention reaches or exceeds the performance of noble metal iridium-based metal oxide and platinum-based catalyst, and has wide raw material source and low price, and can be used in the field of metal-air batteries.

Drawings

FIG. 1 is a scanning electron micrograph of CoTiCN prepared in example 1;

FIG. 2 is a scanning electron micrograph of CoTi prepared in comparative example 1;

FIG. 3 is a scanning electron micrograph of CoTiC prepared in comparative example 1;

FIG. 4 is a scanning electron micrograph of CoTiCS prepared in comparative example 2;

FIG. 5 is a scanning electron micrograph of CoTiCNS prepared in comparative example 3;

FIG. 6 is an XRD spectrum of CoTiCN, coTi, coTiC, coTiCS and CoTiCNS prepared in example 1 and comparative example;

FIG. 7 is a BET plot of CoTiCN, coTi, coTiC, coTiCS and CoTiCNS prepared in example 1 and comparative example;

FIG. 8 is a plot of pore size distribution of CoTiCN, coTi, coTiC, coTiCS and CoTiCNS prepared in example 1 and comparative example;

FIG. 9 is an XPS survey of CoTiCN, coTi, coTiC, coTiCS and CoTiCNS prepared in example 1 and comparative example;

FIG. 10 is a high resolution N1s spectrum of CoTiCN and CoTiCNS prepared in example 1 and comparative example

FIG. 11 is a graph of OER LSV for a catalytic glassy carbon electrode made using CoTiCN, coTi, coTiC, coTiCS, and CoTiCNS;

FIG. 12 is a graph of the OER LSV TaPhell slope for catalytic glassy carbon electrodes made with CoTiCN, coTi, coTiC, coTiCS and CoTiCNS;

FIG. 13 is an impedance spectrum of a catalytic glassy carbon electrode made with CoTiCN, coTi, coTiC, coTiCS, and CoTiCNS;

FIG. 14 is a ORR LSV plot for catalytic glassy carbon electrodes made with CoTiCN, coTi, coTiC, coTiCS and CoTiCNS;

FIG. 15 is a graph of the ORR LSV fiell slope for catalytic glassy carbon electrodes made with CoTiCN, coTi, coTiC, coTiCS, and CoTiCNS;

FIG. 16 is a graph of the number of transferred electrons and hydrogen peroxide yield for a catalytic glassy carbon electrode made using CoTiCN, coTi, coTiC, coTiCS, and CoTiCNS;

FIG. 17 is a graph of differential capacitance measurements of a catalyzed glassy carbon electrode made with CoTiCN, coTi, coTiC, coTiCS, and CoTiCNS;

FIG. 18 is a graph of the stability of CoTiCN oxide alloy electrocatalyst, prepared in example 1, before and after cycling.

Detailed Description

The following examples are used to demonstrate the beneficial effects of the present invention.

Example 1: the method for preparing the CoTi oxide alloy electrocatalyst by using the cotton fibers comprises the following steps:

1. preparing an impregnation liquid: according to the molar ratio of Co, ti and N atoms of 4:1:3, respectively weighing cobalt nitrate hexahydrate and acetamide of tetrabutyl titanate, adding the weighed materials into N, N-dimethylformamide, and stirring at room temperature until the materials are completely dissolved to obtain an impregnation liquid; wherein the total mass percentage concentration of the cobalt nitrate hexahydrate, the tetrabutyl titanate and the acetamide in the impregnation liquid is 10 percent;

2. preparing impregnated cotton fibers: soaking cotton fibers into the soaking solution obtained in the first step for 12 hours at the temperature of 30 ℃ and the relative humidity of 30%, taking out the cotton fibers, putting the cotton fibers into an oven, drying the cotton fibers for 24 hours at the temperature of 80 ℃, and taking out the cotton fibers to obtain a precursor;

3. preparation of CoTi oxide alloy electrocatalyst: the precursor is put into a tube furnace, and the reaction is carried out in N ₂ And (3) in the atmosphere, heating to 800 ℃ at the speed of 5 ℃/min, and sintering at constant temperature for 2h to obtain the CoTi oxide alloy electrocatalyst which is expressed by CoTiCN.

Comparative example 1: the difference between the embodiment and the embodiment 1 is that the components of the impregnation liquid are different, and the specific steps are as follows:

1. preparing an impregnation liquid: according to the molar ratio of Co to Ti of 4:1, respectively weighing cobalt nitrate hexahydrate and tetrabutyl titanate, adding the cobalt nitrate hexahydrate and the tetrabutyl titanate into N, N-dimethylformamide, and stirring at room temperature until the cobalt nitrate hexahydrate and the tetrabutyl titanate are completely dissolved to obtain an impregnation liquid; wherein the total mass percentage concentration of cobalt nitrate hexahydrate, tetrabutyl titanate and acetamide in the impregnation liquid is 10%;

2. preparing impregnated cotton fibers: soaking cotton fibers into the soaking solution obtained in the first step for 12 hours at the temperature of 30 ℃ and the relative humidity of 30%, taking out the cotton fibers, drying the cotton fibers in an oven at the temperature of 80 ℃ for 24 hours, and taking out the cotton fibers to obtain a precursor;

3. preparation of CoTi oxide alloy electrocatalyst:

the precursor is put into a tube furnace at N ₂ And (3) in the atmosphere, heating to 800 ℃ at the speed of 5 ℃/min, and sintering at constant temperature for 2h to obtain the CoTi oxide alloy electrocatalyst, which is expressed by CoTiC.

The precursor is put into a tube furnace at O ₂ And (3) in the atmosphere, heating to 800 ℃ at the speed of 5 ℃/min, and sintering at constant temperature for 2h to obtain the CoTi oxide alloy electrocatalyst, which is expressed by CoTi.

Comparative example 2: the difference between the embodiment and the embodiment 1 is that the components of the impregnation liquid are different, and the specific steps are as follows:

1. preparing an impregnation liquid: according to the molar ratio of Co, ti and S of 4:1:0.5 respectively weighing cobalt nitrate hexahydrate, tetrabutyl titanate and thiourea, adding the cobalt nitrate hexahydrate, the tetrabutyl titanate and the thiourea into N, N-dimethylformamide, and stirring at room temperature until the cobalt nitrate, the tetrabutyl titanate and the thiourea are completely dissolved to obtain an impregnation solution; wherein the total mass percentage concentration of cobalt nitrate hexahydrate, tetrabutyl titanate and thiourea in the impregnation liquid is 10%;

2. preparing impregnated cotton fibers: soaking cotton fibers into the soaking solution obtained in the first step for 12 hours at the temperature of 30 ℃ and the relative humidity of 30%, taking out the cotton fibers, putting the cotton fibers into a drying oven, drying the cotton fibers for 24 hours at the temperature of 80 ℃, and taking out the cotton fibers to obtain a precursor;

3. the precursor is put into a tube furnace at N ₂ And (3) in the atmosphere, heating to 800 ℃ at the speed of 5 ℃/min, and sintering at constant temperature for 2h to obtain the CoTi oxide alloy electrocatalyst which is expressed by CoTiCS.

Comparative example 3: the difference between the embodiment and the embodiment 1 is that the components of the impregnation liquid are different, and the specific steps are as follows:

1. preparing an impregnation liquid: according to the molar ratio of Co, ti, N and S of 4:1:3:0.5 respectively weighing cobalt nitrate hexahydrate, tetrabutyl titanate, acetamide and thiourea, adding the cobalt nitrate hexahydrate, the tetrabutyl titanate, the acetamide and the thiourea into N, N-dimethylformamide, and stirring at room temperature until the cobalt nitrate, the tetrabutyl titanate, the acetamide and the thiourea are completely dissolved to obtain an impregnation solution; wherein the total mass percentage concentration of cobalt nitrate hexahydrate, tetrabutyl titanate, acetamide and thiourea in the impregnation liquid is 10%;

3. preparation of CoTi oxide alloy electrocatalyst:

the precursor is put into a tube furnace at N ₂ And (3) in the atmosphere, heating to 800 ℃ at the speed of 5 ℃/min, and sintering at constant temperature for 2h to obtain the CoTi oxide alloy electrocatalyst, which is marked as CoTiCNS.

The CoTiCN, coTi, coTiC, coTiCS and CoTiCNS prepared in example 1 and comparative example were subjected to scanning electron microscopy, wherein the scanning electron micrograph of CoTiCN is shown in FIG. 1, the scanning electron micrograph of CoTi is shown in FIG. 2, the scanning electron micrograph of CoTiC is shown in FIG. 3, the scanning electron micrograph of CoTiCS is shown in FIG. 4, and the scanning electron micrograph of CoTiCNS is shown in FIG. 5. As can be seen from fig. 1 to 5, the cotton fiber is soaked in the solution containing the metal and the doping element, and then the metal and the doping element are adsorbed on the surface of the cotton fiber through high-temperature calcination. By observing the scanning electron microscope picture, the CoTi is calcined at high temperature in the air, the cotton fiber structure which is not high in temperature resistance in the catalyst is oxidized, and only metal and oxide thereof are left, so that the surface of the catalyst structure is in a crushed shape. The CoTiCN, coTiC, coTiCS and CoTiCNS all present the structural morphology of cotton fibers, the surfaces of the structures are observed, the surfaces of the CoTiCS and CoTiCN are agglomerated, the metal and nonmetal elements on the surfaces of the CoTiCN structures present good dispersibility, the particle dispersibility is superior to that of CoTi, coTiC, coTiCS and CoTiCN catalysts, the surface roughness is high, and the structure effectively increases the contact area between the catalysts and reactants and improves the electrochemical performance.

XRD tests of CoTiCN, coTi, coTiC, coTiCS and CoTiCNS prepared in example 1 and comparative example are carried out, and XRD spectrums are shown in FIG. 6, and it can be seen from FIG. 6 that the objects of metal simple substance, oxide and compound appear in the sample. In which sharp CoCo appears in the CoTiCN sample ₂ O ₄ And the phase of the simple substance Co is calcined at high temperature in an inert gas environment to generate metal oxide and the phase of the simple substance metal which are embedded and carried in a cotton fiber carbon structure, so that the electrocatalytic performance is improved.

The BET tests of CoTiCN, coTi, coTiC, coTiCS and CoTiCNS prepared in example 1 and comparative example resulted in a BET plot as shown in FIG. 7, which is seen in FIG. 7 for N ₂ In the protected environment, coTiCN, coTiC, coTiCS and CoTiCNS all present four types of nitrogen adsorption curves, which indicates that CoTiCN, coTiC, coTiCS and CoTiCNS are mesoporous structures.

The CoTiCN, coTi, coTiC, coTiCS and CoTiCNS prepared in example 1 and comparative example were subjected to pore size distribution test, and the obtained pore size distribution curve is shown in fig. 8, and the specific surface area and pore size data are shown in table 1. As can be seen from fig. 8 and table 1, the sample structure is a hierarchical pore, mainly mesoporous. The CoTiCN has higher specific surface area and mesoporous structure, is favorable for improving the transmission rate of ions and electrons in the catalytic reaction process, and increases diffusion channels of reactants, products and electrolyte in the reaction process.

TABLE 1 results of specific surface area and pore size testing of CoTiCN, coTi, coTiC, coTiCS and CoTiCNS prepared in example 1 and comparative examples

Sample (I)	Specific surface area (m) ² g ^-1 )	Pore size (nm)
			CoTiCN	110.578	3.828
CoTi	10.147	1.69
			CoTiC	65.116	3.833
CoTiCS	42.958	3.826
			CoTiCNS	111.5	1.423

The XPS survey of the CoTiCN, coTi, coTiC, coTiCS and CoTiCNS prepared in example 1 and the comparative examples gave XPS spectra as shown in fig. 9, in which the presence of metallic elements and non-metallic elements for modification in the sample was observed.

From the high-resolution N1s energy spectra of CoTiCN and CoTiCNS prepared in example 1 and the comparative example, it can be seen from fig. 10 that pyridine nitrogen and graphite nitrogen exist in CoTiCN and CoTiCNS, and their existence is favorable for improving the dual-functional electrocatalytic activity of OER and ORR, while nitrogen oxide and pyrrole nitrogen do not have obvious enhancement effect on the catalytic activity of OER and ORR. Wherein the content ratio of pyridine nitrogen and graphite nitrogen of the CoTiCN is larger than that of CoTiCNS.

The CoTiCN, coTi, coTiC, coTiCS and CoTiCNS prepared in example 1 and comparative example are used as catalysts to prepare electrodes respectively, and the specific method is as follows: the glassy carbon electrode adopts a rotating circular ring disk electrode with the diameter of 4mm, and the glassy carbon electrode is repeatedly polished in a splayed or circular shape on chamois leather by using alumina powder with the grain sizes of 1.0, 0.3 and 0.05 microns in sequence until the surface of the electrode is smooth and flat without scratches. Then, cleaning the surface of the electrode by using deionized water, cleaning the surface of the electrode by using an ultrasonic mode for 10s, and finally drying the electrode by using an ear suction ball for later use; weighing 3mg of catalyst powder, adding the catalyst powder into 1mL of Nafion aqueous solution with the mass percentage concentration of 0.5%, and performing ultrasonic dispersion for 30min to obtain a catalyst suspension with the concentration of 3 mg/mL; sucking 10 mu L of catalyst suspension by a microsyringe, dripping the catalyst suspension on the polished glassy carbon electrode, standing for 1h at room temperature, and obtaining a cathode of the metal-air battery, namely the catalytic glassy carbon electrode after the catalyst is dried to form a film, wherein the surface area of the glassy carbon electrode is 0.1256cm ² 。

At room temperature, the following electrochemical test was performed using a standard three-electrode system, with a catalytic glassy carbon electrode as the working electrode, an Ag/AgCl electrode as the reference electrode, a platinum wire as the auxiliary electrode, and 0.1M KOH solution as the electrolyte.

Using electrochemical stations and spindlesThe swivel plate electrode assembly was subjected to electrochemical testing. During OER test, the rotation speed of the electrode is 1600rpm, the scanning speed is 5mV/s, and the scanning potential interval is 0.2 to 1.0V. The resulting OER LSV curve is shown in FIG. 11, and it can be seen from FIG. 11 that at 10mA cm ^-2 At current density, the performance of CoTiCN was superior to the other samples.

The tafel slopes of the catalytic glassy carbon electrodes using CoTiCN, coTi, coTiC, coTiCS and CoTiCNS as catalysts, respectively, are shown in fig. 12, and the influence of the doping of non-metallic elements of the CoTi oxide alloy electrocatalyst on the catalyst reaction kinetic performance can be seen from the tafel slopes. The CoTiCN has a relatively low Tafel slope, and the result proves that the N-doped CoTi oxide alloy catalyst has excellent OER catalytic reaction kinetic performance.

The impedance spectrum test is carried out on the catalytic glassy carbon electrodes respectively taking CoTiCN, coTi, coTiC, coTiCS and CoTiCNS as catalysts, the frequency range is 0.1-10000 Hz, the amplitude is 5mV, and the obtained impedance spectrum 13 is shown in the figure 13.

The CoTiCN, coTi, coTiC, coTiCS and CoTiCNS are respectively used as catalytic glassy carbon electrodes of the catalyst to carry out an ORR LSV curve test, the obtained ORR LSV curve is shown in fig. 14, and as seen from fig. 14, the CoTiCN has the highest half-wave potential and the largest limiting current density, which indicates that the CoTiCN catalyst has high catalytic activity.

The influence of the doping of non-metallic elements of the CoTi oxide alloy electrocatalyst on the reaction kinetic performance of the catalyst is researched by calculating the Tafel slope, and CoTiCN has a relatively low Tafel slope as shown in FIG. 15, and the result proves that the N-doped CoTi oxide alloy catalyst has excellent ORR catalytic reaction kinetic performance.

To further study the reaction path of the ORR catalyzed process, the electron transfer number (n) and hydrogen peroxide yield of the catalyst were calculated by a rotating ring disk electrode method (RRDE) test, and the resulting plots of the electron transfer number and hydrogen peroxide yield are shown in fig. 16, and compared to other catalysts, the CoTiCN catalyst had a minimum hydrogen peroxide yield of less than 1.5% at 0.3 to 0.5V and a higher electron transfer number of greater than 3.9, indicating that the ORR reaction process of the CoTiCN catalyst followed the four electron transfer pathway. The lower hydrogen peroxide yield is advantageous to prevent hydrogen peroxide corrosion of the carbon support and during the cell during the reaction.

Double layer differential capacitance (C) of CoTiCN oxide alloy electrocatalyst prepared in example 1 _dl ) Values to evaluate the electrochemically active specific surface area of the catalyst are shown in fig. 17. The potential scan range of CV test is 1.25-1.35V, and the scan speed range is 20-100 mV s ^-1 . The adsorption and desorption behaviors of the surface of the electrode can be researched through the non-faradaic current in the range, and the real active specific surface area of the electrode is measured. Wherein the electrochemical active area of the CoTiCN is much larger than that of other catalysts. The results demonstrate that the electrochemical activity specific surface area of the N-doped CoTi oxide alloy electrocatalyst is remarkably increased, mainly because the co-doping can generate more phase interfaces and defect structures, and further remarkably increase the number of active sites.

The cycling curve of the CoTiCN oxide alloy electrocatalyst prepared in example 1 is shown in fig. 18, and it can be seen from fig. 18 that the electrochemical performance of CoTiCN did not significantly decrease after 1000 CV cycles.

From the comparison experiment of different non-metal element doped catalysts, it can be seen that the catalytic activity of CoTiCN is higher than that of CoTi, coTiC, coTiCS and CoTiCN, because the morphology, composition and structure of CoTiCN are different from those of other materials, the CoTiCN catalyst has highly dispersed active sites, and excellent OER/ORR dual-functional catalytic activity is obtained.

Claims

1. The method for preparing the CoTi oxide alloy electrocatalyst by using the cotton fiber is characterized by comprising the following steps of:

3. preparation of CoTi oxide alloy electrocatalyst: the precursor is put into a tube furnace at N ₂ And (3) in the atmosphere, heating to 700-900 ℃, and sintering at constant temperature for 1-2 h to obtain the CoTi oxide alloy electrocatalyst which is expressed by CoTiCN.

2. The method of claim 1, wherein the total mass concentration of cobalt nitrate hexahydrate and tetrabutyl titanate acetamide in the impregnation solution in the first step is 10-30%.

3. The method for preparing the CoTi oxide alloy electrocatalyst with cotton fiber according to claim 1 or 2, characterized in that the drying in step two is drying in an oven at 80 ℃ for 12-24 hours.

4. The method for preparing the CoTi oxide alloy electrocatalyst using cotton fiber according to claim 1 or 2, wherein the temperature rise in step three is at a rate of 4-5 ℃/min.

5. Use of a CoTi oxide alloy electrocatalyst prepared by the process of claim 1, characterized in that the use is for the preparation of a metal-air battery cathode using the catalyst.

6. The use of a CoTi oxide alloy electrocatalyst according to claim 5, wherein the method of making a metal-air battery cathode using a CoTi oxide alloy electrocatalyst is performed by:

1. firstly, sequentially polishing a glassy carbon electrode on chamois by using alumina powder with the grain sizes of 1.0, 0.3 and 0.05 microns until the surface of the electrode is smooth and flat without scratches, then cleaning the surface of the electrode by using deionized water, cleaning the surface of the electrode by using an ultrasonic mode for 10s, and finally drying the electrode for later use;