CN112968187A - Mesoporous rhodium hollow nanofiber electrocatalyst and preparation method thereof - Google Patents

Abstract

A mesoporous rhodium hollow nanofiber electrocatalyst is prepared by the following method: firstly, preparing potassium chlororhodate, nickel chloride and hydrochloric acid solution, then dissolving the nickel chloride solution in ethylene glycol under magnetic stirring, uniformly mixing, placing the reaction solution in an oil bath pan, adding hydrazine hydrate for reaction, cooling to room temperature, uniformly mixing with ethanol, centrifuging the obtained nickel nano fiber with water, washing again in water for later use, ultrasonically dispersing PEO-b-PMMA in tetrahydrofuran, dropwise adding water, the potassium chlororhodate solution and hydrochloric acid into the solution, then carrying out ultrasound treatment, finally adding the nickel nano fiber, carrying out water bath reaction on the mixed solution, centrifuging and washing the obtained product with water, and drying in a vacuum oven. And provides a preparation method of the mesoporous rhodium hollow nanofiber electrocatalyst. The invention has simple preparation process, good repeatability and high product yield, can be synthesized in large dose and is convenient for industrial production.

Description

Mesoporous rhodium hollow nanofiber electrocatalyst and preparation method thereof

(I) technical field

The invention relates to a mesoporous rhodium hollow nanofiber electrocatalyst and a preparation method thereof, and the mesoporous rhodium hollow nanofiber electrocatalyst can be used for the research of electrochemical catalytic methanol oxidation reaction.

(II) background of the invention

Global energy crisis and ecological issues have driven the need for renewable energy technologies. Currently, alkaline fuel cells are receiving much attention due to their high energy density, high conversion efficiency, good portability, and low emissions. However, the slow methanol oxidation reaction kinetics of the anode have hindered the large scale commercialization of alkaline fuel cells. To date, platinum-based nanoelectrocatalysts have been considered as one of the most effective electrocatalysts in alkaline methanol oxidation reactions (Nie, Y.; Li, L.; Wei, Z., recovery enhancements in Pt and Pt-free catalysts for oxidative reaction. chem. Soc. Rev.2015,44, 2168-. However, platinum catalysts generally have a high overpotential and a weak CO resistance, resulting in a great reduction in electrochemical durability. Therefore, the development of an efficient and highly stable electrocatalyst for methanol oxidation reaction is urgently needed and is also a great challenge.

In the methanol oxidation reaction, CO adsorbed on the surface of the oxophilic metal rhodium can be easily removed, so that the rhodium-based electrocatalyst exhibits better resistance to CO poisoning, but has lower electrochemical activity. In order to improve the performance of rhodium-based electrocatalysts, research has been carried out in recent years to synthesize rhodium-based electrocatalysts of different structures, such as Hollow rhodium Nanospheres (Kang, y.q.; Xue, q.; Zhao, y.; Li, x.f.; Jin, p.j.; Chen, y.selective engineered Synthesis of Hollow Rh Nanospheres for electrochemical reaction, small 2018,14,1801239) and rhodium Nanosheets (Zhu, j. -y.; Chen s., s.; Xue, q.; Li, f. -m.; Yao, h. -, c.; Xu, l.; chenn, y.h. -, Rh Nanospheres for Methanol reaction, oxygen. 2020,264,118520) and the like. Among them, the one-dimensional nanofiber structure is considered to have the effects of promoting electron transfer, promoting mass transfer, prolonging service life, inhibiting mechanical degradation, accelerating electrochemical response, and the like. In recent years, Shu macro topic group reports that Noble Metal nano-fibers such as palladium, platinum, gold, silver and the like are synthesized by an electrodeposition method by using anodized aluminum as a hard template (Cui, C.H.; Li, H.H.; Yu, S.H.A General application to Electrochemical Deposition of High Quality Free-stacking mineral Metal (Pd, Pt, Au, Ag) Sub-Micron Tubes composite of Nanoparticles in Polar organic solvent. chem. Commun.2010,46, 940-2). However, the method has the defects of difficult control of the growth speed and complex synthesis process, and limits the wide application of the method. Thus, the sacrificial templating approach is an efficient and convenient strategy for synthesizing nanofibers. The mesoporous nano structure has the characteristics of high porosity, high-distribution open pore structure, rich specific surface area and the like, and is widely researched. The hard template method using mesoporous silica as a template is considered to be an effective method for preparing regular mesopores. The method has more synthesis steps and the pore structure is blocked, so that the change of the polymer micelle template is another effective strategy for realizing the mesoporous structure of the catalyst. However, rhodium has larger surface energy than other noble metals, so that the rhodium-based nanomaterial with mesopores is difficult to prepare by the method. Therefore, designing rhodium nanostructures with regular mesopores is challenging.

Disclosure of the invention

In order to overcome the defects of the prior art, the invention provides a mesoporous rhodium hollow nanofiber electrocatalyst and a preparation method thereof, and researches on catalytic electrochemical methanol oxidation reaction.

The technical scheme adopted by the invention is as follows:

a mesoporous rhodium hollow nanofiber electrocatalyst is prepared by the following method:

(1) respectively preparing 1-50 mM potassium chlororhodate, 0.1-2M nickel chloride and 0.1-2M hydrochloric acid solution;

(2) dissolving 20-200 mu L of nickel chloride solution into 2-20 mL of ethylene glycol under magnetic stirring, and uniformly mixing; placing the reaction solution in an oil bath kettle at 90-150 ℃, adding 0.1-1 mL of hydrazine hydrate, reacting for 5-30 minutes, cooling to room temperature after the reaction is finished, uniformly mixing with ethanol, centrifuging the obtained nickel nanofiber with water, and dispersing in 0.2-2 mL of water for later use;

(3) ultrasonically dispersing 1-10 mg of PEO-b-PMMA in 0.2-2 mL of tetrahydrofuran, dropwise adding 1.5-15 mL of water, 0.2-2 mL of potassium chlororhodate solution and 0.5-5 mL of hydrochloric acid into the solution after dissolving the PEO-b-PMMA, and then ultrasonically treating the solution at 20-50 ℃ for 0.5-2 hours;

(4) adding 0.1-1 mL of nickel nano fiber into the solution, reacting the mixed solution in a water bath at 10-100 ℃ for 0.5-5 hours, finally, centrifugally washing the obtained product with water, and drying in a vacuum oven at 10-100 ℃ for 5-20 hours.

The nickel nano-fiber and the surfactant PEO-b-PMMA play a key role in forming the mesoporous rhodium hollow nano-fiber structure. The nickel nano-fiber is used as a sacrificial template, and has the following advantages: the synthesis method has mild condition, high speed and high yield. Due to the advantages, the method provides possibility for batch production of the mesoporous rhodium hollow nanofiber electrocatalyst. The surfactant PEO-b-PMMA is widely used for synthesizing mesoporous materials such as alloys, metal oxides and the like. The diblock copolymer PEO-b-PMMA has the unique characteristic of forming spherical micelles with hydrophilic appearance and hydrophobic interior in an aqueous solution, and the surface mesoporous structure is obtained by washing away the surfactant with a solvent after the metal is reduced. In the preparation process, the nickel nano-fiber serves as a sacrificial membrane plate, and the surfactant PEO-b-PMMA serves as a soft template. The unique mesoporous rhodium hollow nano-fiber material is prepared by utilizing the synthesis strategy of combining the double templates.

The invention also relates to a preparation method of the mesoporous rhodium hollow nanofiber electrocatalyst, which comprises the following steps:

(1) respectively preparing 1-50 mM potassium chlororhodate, 0.1-2M nickel chloride and 0.1-2M hydrochloric acid solution;

(2) dissolving 20-200 mu L of nickel chloride solution into 2-20 mL of ethylene glycol under magnetic stirring, and uniformly mixing; placing the reaction solution in an oil bath kettle at 90-150 ℃, adding 0.1-1 mL of hydrazine hydrate, reacting for 5-30 minutes, cooling to room temperature after the reaction is finished, uniformly mixing with ethanol, centrifuging the obtained nickel nanofiber with water, and dispersing in 0.2-2 mL of water for later use;

(3) ultrasonically dispersing 1-10 mg of PEO-b-PMMA in 0.2-2 mL of tetrahydrofuran, dropwise adding 1.5-15 mL of water, 0.2-2 mL of potassium chlororhodate solution and 0.5-5 mL of hydrochloric acid into the solution after dissolving the PEO-b-PMMA, and then ultrasonically treating the solution at 20-50 ℃ for 0.5-2 hours;

(4) adding 0.1-1 mL of nickel nano fiber into the solution, reacting the mixed solution in a water bath at 10-100 ℃ for 0.5-5 hours, finally, centrifugally washing the obtained product with water, and drying in a vacuum oven at 10-100 ℃ for 5-20 hours.

Further, the concentration and volume of potassium chlororhodate and nickel nano-fiber, the kind of surfactant, and the temperature and time of reaction are controlled to control the appearance and structure of the mesoporous fiber.

The electrochemical catalytic methanol oxidation reaction is carried out at normal temperature and normal pressure, and the specific performance test operation process is as follows:

1) the cyclic voltammogram of methanol oxidation was measured by a conventional three-electrode system cell, and the measured electrode potentials were converted to reversible hydrogen electrode potentials. Wherein three electrodes include: mercury/mercury oxide reference electrode, working electrode, platinum wire counter electrode. The preparation method of the working electrode comprises the following steps of weighing 1-10 mg of catalyst sample, ultrasonically dispersing the catalyst sample in 1-5 mL of deionized water, dripping 1-10 mu L of slurry on the surface of a glassy carbon electrode, drying, then dripping 1-10 mu L of Nafion solution (0.5 wt%), and drying for later use.

2) In the electrochemical test, firstly, a proper amount of 1.0M potassium hydroxide solution is added into an electrolytic cell, nitrogen is introduced to saturate the solution with nitrogen, and then a cyclic voltammetry test procedure is selected. Next, the cyclic voltammograms of the catalyst and of the different sweep rates were tested continuously in a 1.0M potassium hydroxide solution containing 1.0M methanol. And introducing carbon monoxide gas into the solution to saturate the solution, introducing nitrogen to remove the carbon monoxide in the solution, and testing the desorption cyclic voltammetry curve of the carbon monoxide on the surface of the catalyst. Thereafter, the stability of the catalyst was tested by chronoamperometry on a 1.0M potassium hydroxide solution containing 1.0M methanol. Finally, the methanol oxidation performance of the catalyst can be evaluated by calculating the mass activity and the specific activity according to the cyclic voltammogram.

The invention has the following beneficial effects:

(1) the mesoporous rhodium hollow nanofiber electrocatalyst is simple in synthesis method, mild in condition, good in repeatability, high in product yield, capable of being synthesized in large dose and convenient for industrial production.

(2) The shape and structure of the rhodium hollow nano-fiber can be controlled by changing the concentration and volume of the precursors of potassium chlororhodate and hydrochloric acid.

(3) The synthesized mesoporous rhodium hollow nanofiber electrocatalyst replaces the use of noble metal platinum in methanol oxidation reaction, and simultaneously shows excellent catalyst activity, stability and carbon monoxide toxicity resistance, so that the rhodium-based material has a very high application prospect as the electrocatalyst for methanol oxidation.

(IV) description of the drawings

Fig. 1 is an SEM image of mesoporous rhodium hollow nanofibers according to embodiment 1 of the present invention.

Fig. 2 is TEM, HRTEM and selected area electron diffraction patterns of mesoporous rhodium hollow nanofibers according to embodiment 1 of the present invention.

Fig. 3 is XRD and XPS charts of mesoporous rhodium hollow nanofibers according to embodiment 1 of the present invention.

Fig. 4 is a cyclic voltammetry curve of mesoporous rhodium hollow nanofibers at a sweep rate of 50 mv in embodiment 1 of the present invention.

Fig. 5 is a mass-normalized cyclic voltammetry curve and an electrochemically active area-normalized cyclic voltammetry curve of mesoporous rhodium hollow nanofibers at a sweep rate of 50 mv according to embodiment 1 of the present invention.

Fig. 6 is a cyclic voltammetry curve of mesoporous rhodium hollow nanofibers at different scanning speeds and a corresponding curve of forward peak current and square root of scanning speed in embodiment 1 of the present invention.

Fig. 7 is a carbon monoxide desorption cyclic voltammetry curve and a chronoamperometric curve of mesoporous rhodium hollow nanofibers according to embodiment 1 of the present invention.

Fig. 8 is an SEM of mesoporous rhodium hollow nanofibers according to embodiment 2 of the present invention.

Fig. 9 is a mass-normalized cyclic voltammetry curve and an electrochemically active area-normalized cyclic voltammetry curve of mesoporous rhodium hollow nanofibers according to example 2 of the present invention.

Fig. 10 is an SEM image of mesoporous rhodium hollow nanofibers according to embodiment 3 of the present invention.

Fig. 11 is an SEM image of mesoporous rhodium hollow nanofibers according to embodiment 4 of the present invention.

(V) detailed description of the preferred embodiments

The invention will be further described with reference to specific examples, but the scope of the invention is not limited thereto:

referring to fig. 1 to 11, a mesoporous rhodium hollow nanofiber electrocatalyst is prepared by the following method:

(1) respectively preparing 1-50 mM potassium chlororhodate, 0.1-2M nickel chloride and 0.1-2M hydrochloric acid solution;

(2) dissolving 20-200 mu L of nickel chloride solution into 2-20 mL of ethylene glycol under magnetic stirring, and uniformly mixing; placing the reaction solution in an oil bath kettle at 90-150 ℃, adding 0.1-1 mL of hydrazine hydrate, reacting for 5-30 minutes, cooling to room temperature after the reaction is finished, uniformly mixing with ethanol, centrifuging the obtained nickel nanofiber with water, and dispersing in 0.2-2 mL of water for later use;

(3) ultrasonically dispersing 1-10 mg of PEO-b-PMMA in 0.2-2 mL of tetrahydrofuran, dropwise adding 1.5-15 mL of water, 0.2-2 mL of potassium chlororhodate solution and 0.5-5 mL of hydrochloric acid into the solution after dissolving the PEO-b-PMMA, and then ultrasonically treating the solution at 20-50 ℃ for 0.5-2 hours;

(4) adding 0.1-1 mL of nickel nano fiber into the solution, reacting the mixed solution in a water bath at 10-100 ℃ for 0.5-5 hours, finally, centrifugally washing the obtained product with water, and drying in a vacuum oven at 10-100 ℃ for 5-20 hours.

In this embodiment, the performance test of the oxidation-reduction of the mesoporous rhodium hollow nanofiber material is performed on a CHI 660E electrochemical workstation, and the operation process is as follows:

1) the cyclic voltammogram of methanol oxidation was measured by a conventional three-electrode system cell, and the measured electrode potentials were converted to reversible hydrogen electrode potentials. Wherein three electrodes include: mercury/mercury oxide reference electrode, working electrode, platinum wire counter electrode. The preparation method of the working electrode comprises the following steps of weighing 2mg of catalyst sample, ultrasonically dispersing the catalyst sample in 1mL of deionized water, dripping 5 mu L of slurry on the surface of the glassy carbon electrode, drying, then dripping 5 mu L of Nafion solution (0.5 wt%), and drying for later use.

2) In the electrochemical test, firstly, a proper amount of 1.0M potassium hydroxide solution is added into an electrolytic cell, nitrogen is introduced to saturate the solution with nitrogen, and then a cyclic voltammetry test procedure is selected. Next, the cyclic voltammograms of the catalyst and of the different sweep rates were tested continuously in a 1.0M potassium hydroxide solution containing 1.0M methanol. And introducing carbon monoxide gas into the solution to saturate the solution, introducing nitrogen to remove the carbon monoxide in the solution, and testing the desorption cyclic voltammetry curve of the carbon monoxide on the surface of the catalyst. Thereafter, the stability of the catalyst was tested by chronoamperometry on a 1.0M potassium hydroxide solution containing 1.0M methanol. Finally, the methanol oxidation performance of the catalyst can be evaluated by calculating the mass activity and the specific activity according to the cyclic voltammogram.

Example 1:

a preparation method of a mesoporous rhodium hollow nanofiber electrocatalyst comprises the following steps:

(1) respectively preparing 40mM potassium chlororhodate, 1M nickel chloride and 1M hydrochloric acid solution;

(2) dissolving 75 mu L of nickel chloride solution in 7.5mL of ethylene glycol under magnetic stirring, uniformly mixing, placing the reaction solution in an oil bath kettle at 135 ℃, adding 0.5mL of hydrazine hydrate, reacting for 20 minutes, cooling to room temperature after the reaction is finished, uniformly mixing with ethanol, centrifuging, washing the obtained product with water, and dispersing in 1mL of water for later use;

(3) ultrasonically dispersing 2mg of PEO-b-PMMA in 0.5mL of tetrahydrofuran, dropwise adding 3.5mL of water, 0.5mL of potassium chlororhodate solution and 1mL of hydrochloric acid into the solution after the PEO-b-PMMA is dissolved, and then ultrasonically treating the solution at 35 ℃ for 1 hour;

(4) 0.4mL of nickel nanofibers was added to the above solution, the mixture was reacted in a water bath at 25 ℃ for 1 hour, and finally the resulting product was washed with water by centrifugation and then dried in a vacuum oven at 50 ℃ for 10 hours.

The SEM image of the obtained mesoporous rhodium hollow nanofiber is shown in fig. 1. The obtained TEM, HRTEM and selected area electron diffraction patterns of the mesoporous rhodium hollow nanofiber are shown in fig. 2. The XRD and XPS patterns of the obtained mesoporous rhodium hollow nanofibers are shown in fig. 3. The cyclic voltammetry curve of the obtained mesoporous rhodium hollow nanofiber at a sweep rate of 50 millivolts is shown in figure 4. The obtained cyclic voltammetry curve of the mesoporous rhodium hollow nanofiber with the normalized mass and the cyclic voltammetry curve with the normalized electrochemical active area under the sweep rate of 50 millivolts are shown in figure 5. The cyclic voltammetry curves of the obtained mesoporous rhodium hollow nanofibers at different scanning speeds and the corresponding curve graph of the forward peak current and the square root of the scanning speed are shown in fig. 6. The carbon monoxide desorption cyclic voltammetry curve and the chronoamperometric curve of the obtained mesoporous rhodium hollow nano-fiber are shown in figure 7.

The SEM image clearly shows that rhodium has a good one-dimensional mesoporous structure, and the TEM image shows that a huge one-dimensional cavity is formed in the nanofiber structure. The mesoporous hollow structure of the rhodium nanofiber electrocatalyst can be confirmed by combining SEM and TEM images. HRTEM, selective area electron diffraction and XRD can confirm the polycrystalline structure, and XPS data can confirm that no nickel remains in the mesoporous rhodium hollow nano-fiber. The cyclic voltammetry curve can be obtained, and the mesoporous rhodium hollow nano-fiber has a higher electrochemical active area. The mass activity and the specific activity of the mesoporous rhodium hollow nanofiber electrocatalyst which are respectively 0.54mA cm can be obtained according to a cyclic voltammetry diagram of the mesoporous rhodium hollow nanofiber electrocatalyst in methanol^-2And 325mA mg^-1. Through cyclic voltammetry curves at different rotating speeds, the mesoporous rhodium hollow nanofiber has great improvement on proton kinetics. Through the stability tests of the carbon monoxide desorption cyclic voltammetry and the chronoamperometry, the mesoporous rhodium hollow nanofiber electrocatalyst with good electrochemical stability can be seenAnd resistance to toxicity.

Example 2:

a preparation method of a mesoporous rhodium hollow nanofiber electrocatalyst comprises the following steps:

(1) respectively preparing 1mM potassium chlororhodate, 0.1M nickel chloride and 0.1M hydrochloric acid solution;

(2) dissolving 20 mu L of nickel chloride solution in 2mL of ethylene glycol under magnetic stirring, uniformly mixing, placing the reaction solution in an oil bath kettle at 90 ℃, adding 0.1mL of hydrazine hydrate, reacting for 5 minutes, cooling to room temperature after the reaction is finished, uniformly mixing with ethanol, centrifuging, washing the obtained product with water, and dispersing in 0.2mL of water for later use;

(3) taking 1mg of PEO-b-PMMA, ultrasonically dispersing in 0.2mL of tetrahydrofuran, dropwise adding 1.5mL of water, 0.2mL of potassium chlororhodate solution and 0.5mL of hydrochloric acid into the solution after the PEO-b-PMMA is dissolved, and then ultrasonically treating the solution at the temperature of 20 ℃ for 0.5 hour;

(4) 0.1mL of nickel nanofibers was added to the above solution, the mixture was reacted in a water bath at 25 ℃ for 0.5 hour, and finally the resulting product was washed with water by centrifugation and then dried in a vacuum oven at 10 ℃ for 5 hours.

The SEM image of the obtained mesoporous rhodium hollow nanofiber is shown in fig. 8. The obtained cyclic voltammogram of the mesoporous rhodium hollow nanofiber with the normalized mass and the normalized electrochemical active area at the sweep rate of 50 millivolts is shown in a graph of fig. 9.

From the SEM image, it can be seen that the rhodium hollow nanofibers with fine mesopores are formed. This is mainly due to the varying amounts of reactants and reaction times. According to the cyclic voltammetry curve with normalized mass and the cyclic voltammetry curve with normalized electrochemical active area, the methanol oxidation performance of the rhodium hollow nanofiber catalyst with fine mesopores is not as good as that of the rhodium hollow nanofiber with mesopores, which is mainly caused by different pore channel structures of the catalyst.

Example 3:

a preparation method of a mesoporous rhodium hollow nanofiber electrocatalyst comprises the following steps:

(1) respectively preparing 50mM potassium chlororhodate, 2M nickel chloride and 0.1M hydrochloric acid solution;

(2) dissolving 200 mu L of nickel chloride solution in 20mL of ethylene glycol under magnetic stirring, uniformly mixing, placing the reaction solution in an oil bath kettle at 150 ℃, adding 1mL of hydrazine hydrate, reacting for 30 minutes, cooling to room temperature after the reaction is finished, uniformly mixing with ethanol, centrifuging, washing the obtained nickel nanofiber with water in a centrifugal mode, and dispersing in 2mL of water for later use;

(3) 10mg of PEO-b-PMMA was ultrasonically dispersed in 2mL of tetrahydrofuran. After PEO-b-PMMA was dissolved, 15mL of water, 2mL of potassium chlororhodate solution and 0.5mL of hydrochloric acid were added dropwise to the above solution, followed by sonication at 50 ℃ for 0.5 hour;

(4) 1mL of nickel nanofibers was added to the above solution, the mixture was reacted in a water bath at 100 ℃ for 0.5 hour, and finally the resulting product was washed with water by centrifugation and then dried in a vacuum oven at 100 ℃ for 5 hours.

During the synthesis process, the ratio of hydrochloric acid, surfactant and potassium chlororhodate is not proper when the rhodium nanofiber is synthesized, and the synthesis time is too short and the reaction temperature is too high, so that the rhodium nanofiber with the mesoporous hollow structure cannot be synthesized.

Example 4:

a preparation method of a mesoporous rhodium hollow nanofiber electrocatalyst comprises the following steps:

(1) respectively preparing 50mM potassium chlororhodate, 2M nickel chloride and 2M hydrochloric acid solution;

(2) dissolving 200 mu L of nickel chloride solution in 20mL of ethylene glycol under magnetic stirring, uniformly mixing, placing the reaction solution in an oil bath kettle at 90 ℃, adding 1mL of hydrazine hydrate, reacting for 30 minutes, cooling to room temperature after the reaction is finished, uniformly mixing with ethanol, centrifuging, washing the obtained nickel nanofiber with water in a centrifugal mode, and dispersing in 2mL of water for later use;

(3) ultrasonically dispersing 10mg of PEO-b-PMMA in 2mL of tetrahydrofuran, dropwise adding 15mL of water, 2mL of potassium chlororhodate solution and 5mL of hydrochloric acid into the solution after the PEO-b-PMMA is dissolved, and then ultrasonically treating the solution at the temperature of 20 ℃ for 2 hours;

(4) 1mL of nickel nanofibers was added to the above solution, the mixture was reacted in a water bath at 10 ℃ for 5 hours, and finally the resulting product was washed by centrifugation with water and then dried in a vacuum oven at 10 ℃ for 20 hours.

In the synthesis process, the proportion of hydrochloric acid, surfactant and potassium chlororhodate is not proper when the rhodium nanofiber is synthesized, the synthesis time is too long, and the reaction temperature is too low, so that impurity particles are generated while the mesoporous rhodium hollow nanofiber is synthesized.

Claims (3)

1. A mesoporous rhodium hollow nanofiber electrocatalyst is prepared by the following method:

(1) respectively preparing 1-50 mM potassium chlororhodate, 0.1-2M nickel chloride and 0.1-2M hydrochloric acid solution;

(2) dissolving 20-200 mu L of nickel chloride solution into 2-20 mL of ethylene glycol under magnetic stirring, and uniformly mixing; placing the reaction solution in an oil bath kettle at 90-150 ℃, adding 0.1-1 mL of hydrazine hydrate, reacting for 5-30 minutes, cooling to room temperature after the reaction is finished, uniformly mixing with ethanol, centrifuging the obtained nickel nanofiber with water, and dispersing in 0.2-2 mL of water for later use;

(3) ultrasonically dispersing 1-10 mg of PEO-b-PMMA in 0.2-2 mL of tetrahydrofuran, dropwise adding 1.5-15 mL of water, 0.2-2 mL of potassium chlororhodate solution and 0.5-5 mL of hydrochloric acid into the solution after dissolving the PEO-b-PMMA, and then ultrasonically treating the solution at 20-50 ℃ for 0.5-2 hours;

(4) adding 0.1-1 mL of nickel nano fiber into the solution, reacting the mixed solution in a water bath at 10-100 ℃ for 0.5-5 hours, finally, centrifugally washing the obtained product with water, and drying in a vacuum oven at 10-100 ℃ for 5-20 hours.

2. The preparation method of the mesoporous rhodium hollow nanofiber electrocatalyst according to claim 1, characterized by comprising the following steps:

(1) respectively preparing 1-50 mM potassium chlororhodate, 0.1-2M nickel chloride and 0.1-2M hydrochloric acid solution;

(2) dissolving 20-200 mu L of nickel chloride solution into 2-20 mL of ethylene glycol under magnetic stirring, and uniformly mixing; placing the reaction solution in an oil bath kettle at 90-150 ℃, adding 0.1-1 mL of hydrazine hydrate, reacting for 5-30 minutes, cooling to room temperature after the reaction is finished, uniformly mixing with ethanol, centrifuging the obtained nickel nanofiber with water, and dispersing in 0.2-2 mL of water for later use;

(3) ultrasonically dispersing 1-10 mg of PEO-b-PMMA in 0.2-2 mL of tetrahydrofuran, dropwise adding 1.5-15 mL of water, 0.2-2 mL of potassium chlororhodate solution and 0.5-5 mL of hydrochloric acid into the solution after dissolving the PEO-b-PMMA, and then ultrasonically treating the solution at 20-50 ℃ for 0.5-2 hours;

(4) adding 0.1-1 mL of nickel nano fiber into the solution, reacting the mixed solution in a water bath at 10-100 ℃ for 0.5-5 hours, finally, centrifugally washing the obtained product with water, and drying in a vacuum oven at 10-100 ℃ for 5-20 hours.

3. The method of claim 2, wherein the concentration and volume of potassium chlororhodate and nickel nanofibers, the type of surfactant, and the temperature and time of the reaction are controlled to control the morphology and structure of the mesoporous fibers.

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