CN106179392A - A kind of preparation method of the cobaltous tungstate nanometer rods eelctro-catalyst of iron ion doping - Google Patents

Abstract

The invention discloses a preparation method of cobalt tungstate nanorod electrocatalyst doped with iron ions, which is synthesized by using cobalt chloride, ferrous chloride or ferric chloride, sodium tungstate and ammonia water as raw materials. The invention has the advantages of simple operation, green raw materials, abundant sources, low cost, short product preparation period and good repeatability. The iron ion-doped cobalt tungstate nanorod electrocatalyst prepared by the present invention has good electrocatalytic activity of decomposing water to generate oxygen, and can be widely used in the field of energy conversion.

Description

A kind of preparation method of iron ion doped cobalt tungstate nanorod electrocatalyst

technical field

The invention relates to the technical field of inorganic nanometer electrocatalytic materials, in particular to a method for preparing an efficient iron ion-doped cobalt tungstate nanorod electrocatalyst.

Background technique

Electrocatalysis is a heterogeneous catalysis that occurs at the interface between electrodes and electrolytes, and it involves the cross-discipline of many scientific branches such as electrochemistry, surface science, and materials science. Electrocatalysis is widely used in energy conversion and storage (fuel cells, chemical batteries, supercapacitors, hydrogen energy), environmental protection (sewage treatment, electrochemical sensors, degradation of organic waste, ozone generation, etc.), new substance synthesis and material preparation , electrochemical engineering (chlor-alkali industry, metal processing, forming, finishing, etc.) and electrochemical processes in the fields of biology and analysis.

Electrolyzed water mainly includes two parts: cathode hydrogen evolution and anode oxygen evolution, in which the efficiency of electrolysis water is determined by the anode oxygen evolution reaction. The anodic oxygen evolution reaction involves a 4-electron transfer process, which is a complex and slow kinetic process. A high-efficiency electrochemical oxygen evolution reaction catalyst can solve the slow kinetic process of splitting water.

Although noble metals and noble metal oxides have shown good performance in the electrocatalytic oxygen evolution reaction, these noble metals are relatively expensive, and noble metal oxides are relatively easy to corrode in alkaline media, which to some extent hinders their use as an oxygen evolution reaction. Wide application of oxygen anode electrodes. Therefore, various non-noble metal catalysts have been developed as substitutes for noble metals and their oxides. Generally, non-noble metal catalysts mainly include spinel-type oxides and perovskite-type transition metal oxides and their derivatives, layered double metal hydroxides, carbon-based non-metallic catalysts, and some transition metal complexes.

Cobalt tungstate belongs to divalent transition metal tungstate, and cobalt tungstate crystal is a typical wolframite P2/c monoclinic space group structure. The current research work mainly adopts hydrothermal/solvothermal method to synthesize. Relevant research results show that cobalt tungstate micro-nano materials play an important role in magnetic materials, microwave dielectric ceramics, photoelectric display materials, and catalytic decomposition of organic pollutants such as rhodamine, methyl orange, and phenol. It is also reported in the literature that cobalt tungstate can electrocatalytically split water to produce oxygen, but its activity is low.

The oxygen evolution performance of the material is closely related to its adsorption of hydroxide ions. Too weak or too strong interaction with hydroxide ions is not conducive to the improvement of its electrocatalytic activity. The oxygen evolution performance of cobalt tungstate is weak, on the one hand, it is due to its weak force on hydroxide ions.

Contents of the invention

Aiming at the deficiencies in the prior art, the present invention aims to provide a method for preparing iron ion-doped cobalt tungstate nanorod electrocatalysts, by doping iron ions into cobalt tungstate nanorods to optimize its reaction to hydroxide ions The adsorption effect, thereby improving its electrocatalytic activity, and the invention is simple in operation, rich in raw material sources, low in cost, short in product preparation cycle, and good in repeatability.

In order to achieve the above object, the present invention adopts the following technical solutions:

A preparation method of iron ion doped cobalt tungstate nanorod electrocatalysts, comprising the steps of:

S1 Under stirring conditions, dissolve ferrous chloride or ferric chloride, cobalt chloride and sodium tungstate in water, then add ammonia water, stir and mix to obtain a mixed solution;

S2 transfers the mixed solution obtained in step S1 to a polytetrafluoroethylene-lined reaction kettle, seals it and reacts it in a blast drying oven; after the reaction is cooled to room temperature, the obtained powder is centrifuged, and deionized water and no Alternately washed with water and ethanol for several times, placed in a vacuum drying oven to dry to obtain a solid product, which is the electrocatalyst of cobalt tungstate nanorods doped with iron ions.

It should be noted that, in step S1, the amount of cobalt chloride is 1mmoL, the amount of sodium tungstate is 1mmoL, the amount of ferrous chloride or ferric chloride is 0.05mmoL, the amount of water is 40mL, and the amount of ammonia water is 0.5 mL.

It should be noted that, in step S2, the reaction temperature in the forced air drying oven was 180° C., and the reaction time was 12 hours.

It should be noted that, in step S2, the drying temperature in a vacuum drying oven is 60° C., and the drying time is 4 hours.

The beneficial effects of the present invention are: by doping iron ions into cobalt tungstate nanorods to optimize its adsorption to hydroxide ions, thereby improving its electrocatalytic activity, and the present invention is simple in operation, rich in raw material sources, and low in cost , the product preparation cycle is short and the repeatability is good.

Description of drawings

Figure 1a is a scanning electron image of the pure-phase cobalt tungstate nanorods prepared in Comparative Example 1, and Figure 1b is an XRD diffraction pattern of the corresponding product.

Figures 2a and 2b are the scanning electron images and the corresponding XRD patterns of the cobalt tungstate nanoparticles prepared without using ammonia water in Comparative Example 2, respectively.

Figure 3a is a scanning electron image of Fe ²⁺ ion-doped cobalt tungstate nanorods prepared in Example 1, and Figure 3b is an XRD diffraction pattern of the corresponding product.

4a and 4b are scanning electron images and corresponding XRD patterns of iron ion-doped cobalt tungstate nanorods prepared under the condition of using Fe ³⁺ ions as dopants in Example 2 of the present invention, respectively.

Figure 5 is the linear voltammetry curves of pure-phase cobalt tungstate nanorods and nanoparticles.

Figure 6 is the nitrogen adsorption-desorption curves of pure-phase cobalt tungstate nanorods and nanoparticles.

Figure 7 is the linear voltammetry curves of cobalt tungstate nanorods doped with Fe ²⁺ and Fe ³⁺ ions respectively.

8 is a linear voltammetry curve of cobalt tungstate nanorods and Fe ²⁺ ion-doped cobalt tungstate nanorods.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution, and provides detailed implementation and specific operation process, but the protection scope of the present invention is not limited to the present invention. Example.

A preparation method of iron ion doped cobalt tungstate nanorod electrocatalysts, comprising the steps of:

S1 Under stirring conditions, dissolve ferrous chloride or ferric chloride, cobalt chloride and sodium tungstate in water, then add ammonia water, stir and mix to obtain a mixed solution;

S2 transfers the mixed solution obtained in step S1 to a polytetrafluoroethylene-lined reaction kettle, seals it and reacts it in a blast drying oven; after the reaction is cooled to room temperature, the obtained powder is centrifuged, and deionized water and no Alternately washed with water and ethanol for several times, placed in a vacuum drying oven to dry to obtain a solid product, which is the electrocatalyst of cobalt tungstate nanorods doped with iron ions,

It should be noted that, in step S1, the amount of cobalt chloride is 1mmoL, the amount of sodium tungstate is 1mmoL, the amount of ferrous chloride or ferric chloride is 0.05mmol, the amount of water is 40mL, and the amount of ammonia water is 0.5mL. mL.

It should be noted that, in step S2, the reaction temperature in the forced air drying oven was 180° C., and the reaction time was 12 hours.

It should be noted that, in step S2, the drying temperature in a vacuum drying oven is 60° C., and the drying time is 4 hours.

The following demonstrates the performance of the present invention through experiments.

Comparative example one:

The synthesis process of pure phase cobalt tungstate nanorods is as follows:

Dissolve 1mmol cobalt chloride and 1mmol sodium tungstate in 40mL water under stirring. Add 0.5mL ammonia water to the above mixed solution, stir and mix well. The mixed solution was transferred to a polytetrafluoroethylene-lined autoclave (V=50mL), and reacted at 180°C for 12h. After the reaction was finished, it was naturally cooled to room temperature, and the product was taken out, washed several times with high-purity water and absolute ethanol respectively, and the product cleaned by centrifugation was placed in a vacuum drying oven to dry.

It can be seen from the scanning electron image of Figure 1a that the product is a nanorod structure. It can be seen from Figure 1b that the main diffraction peaks of the product can be indexed as monoclinic cobalt tungstate, which is consistent with the standard card (JCPDS No.15-0687).

Comparative example two:

The synthesis process of cobalt tungstate nanoparticles prepared under the condition of not using ammonia water:

Dissolve 1mmol cobalt chloride and 1mmol sodium tungstate in 40mL water, stir and mix. The solution was put into an autoclave (V=50mL) lined with a polytetrafluoroethylene liner, and reacted at 180°C for 12h. After the reaction was finished, it was naturally cooled to room temperature, and the product was taken out, washed several times with high-purity water and absolute ethanol respectively, and the product cleaned by centrifugation was placed in a vacuum drying oven to dry.

Scanning electron microscopy (Fig. 2a) observations showed that the product was nanoparticles. The XRD analysis results showed (Fig. 2b), consistent with cobalt tungstate nanorods, that the product was pure phase cobalt tungstate.

Embodiment one

The synthesis process of Fe ²⁺ ion-doped cobalt tungstate nanorods is as follows:

Add 1mmol of cobalt chloride, 1mmol of sodium tungstate, and 0.05mmol of ferrous chloride into a high-pressure reactor (V=50mL) lined with a polytetrafluoroethylene liner, and stir to dissolve. Then add 0.5mL ammonia water to the reaction kettle, stir and mix well. After the reaction kettle was screwed tightly and sealed, it was placed in an electric heating constant temperature blast drying oven, and reacted at 180° C. for 12 hours. After the reaction was finished, it was naturally cooled to room temperature, and the product was taken out. Wash several times with high-purity water and absolute ethanol respectively, and dry the product cleaned by centrifugation in a vacuum drying oven.

As shown in Figure 3a, the doping of a small amount of Fe ^ions does not affect the morphology of cobalt tungstate nanorods. The XRD pattern of the product is consistent with that of undoped cobalt tungstate nanorods (Figure 3b), and no new diffraction peaks appear, which indicates that Fe ²⁺ ions are doped into the cobalt tungstate nanorod lattice.

Embodiment two

Synthesis process of Fe ³⁺ ion-doped cobalt tungstate nanorods:

Dissolve 1mmol of cobalt chloride, 1mmol of sodium tungstate, and 0.05mmol of ferric chloride in 40mL of water, and stir to mix. Add 0.5mL ammonia water to the above mixed solution, stir and mix well. The mixed solution was transferred to a high-pressure reaction kettle lined with polytetrafluoroethylene liner (V=50mL), the reaction kettle was screwed tightly and sealed, and then placed in an electric constant temperature blast drying oven for reaction at 180°C for 12h. After the reaction was finished, it was naturally cooled to room temperature, and the product was taken out, washed several times with high-purity water and absolute ethanol respectively, and the product cleaned by centrifugation was placed in a vacuum drying oven to dry.

Scanning electron mirror (Fig. 4a) observation results show that the product is a nanorod. XRD analysis results show (Figure 4b) that the product is pure phase cobalt tungstate.

The catalysts prepared in Comparative Example 1, Comparative Example 2, Embodiment 1 and Embodiment 2 were subjected to an electrocatalytic oxygen production experiment, and the reaction conditions were as follows:

The catalytic performance of the electrocatalyst was tested by linear voltammetry (LSV). The electrochemical performance tests were all carried out on the CHI660D electrochemical workstation of Beijing Huake Putian Technology Co., Ltd., with platinum wire as the counter electrode and saturated calomel as the reference electrode. Weigh 5 mg of the catalyst and dissolve it in 1 mL (V isopropanol: V water = 2: 1), sonicate for 30 minutes, then add 40 μL of naphthol, and continue to sonicate for 30 minutes. Use a pipette gun to pipette 5 μL on the prepared glassy carbon electrode, and measure its electrochemical performance after standing overnight. The electrolyte of the test system is 0.5M KOH, and the sweep rate of the LSV is 10mV/s. The electrode potential adopts the RHE standard, E(RHE)=E(SCE)+0.242+0.059×pH.

Analysis of the linear voltammetry curves of pure-phase cobalt tungstate nanorods and nanoparticles in Comparative Example 1 and Comparative Example 2 (Figure 5) shows that cobalt tungstate nanorods have better electrocatalytic oxygen generation performance. The good electrocatalytic activity of cobalt tungstate nanorods can be attributed to its one-dimensional nanostructure that facilitates carrier transport and large specific surface area (Figure 6).

Analyze the linear voltammetry curve (Fig. 7) of the cobalt tungstate nanorod (Fig. 7) of doping Fe ²⁺ and Fe ³⁺ ion doping in embodiment 2, the result shows that Fe ²⁺ and Fe ³⁺ ion doping Cobalt tungstate nanorods have similar electrocatalytic activity, and the doping of ferrous ions or ferric ions has little effect on the electrocatalytic oxygen evolution performance of cobalt tungstate nanorods.

Analyze the linear voltammetry curve (Fig. 8) of the cobalt tungstate nanorod of comparative example one and the Fe ²⁺ ion-doped cobalt tungstate nanorod of embodiment one, the result shows that Fe ²⁺ ion-doped cobalt tungstate Nanorods have significantly enhanced electrocatalytic activity. The current density can reach 72mA·cm ^-2 at 1.95V (vs RHE), which is more than 5 times that of undoped cobalt tungstate nanorods. The good electrocatalytic activity stems from the fact that the doping of iron ions regulates the electronic structure of cobalt tungstate, which facilitates the adsorption of hydroxide ions, thereby enhancing its electrocatalytic oxygen evolution performance.

For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and ideas, and all these changes and modifications should be included in the protection scope of the claims of the present invention.

For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and ideas, and all these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims (4)

1. the preparation method of the cobaltous tungstate nanometer rods eelctro-catalyst of an iron ion doping, it is characterised in that comprise the steps:

S1 under agitation, by ferrous chloride or iron chloride, is jointly dissolved in water together with cobaltous chloride and sodium tungstate, then adds Enter ammonia, after stirring and evenly mixing, obtain mixed solution；

The mixed solution that step S1 obtains is transferred in teflon-lined reactor by S2, in air dry oven after sealing In react；Question response is cooled to by gained powder centrifugation after room temperature, with deionized water and dehydrated alcohol alternately washing For several times, it is placed in vacuum drying oven and is dried, obtain solid product, be the cobaltous tungstate nanometer rods eelctro-catalyst of iron ion doping.

The preparation method of the wolframic acid nanometer rods eelctro-catalyst of a kind of iron ion doping the most according to claim 1, its feature Being, in step S1, the amount of cobaltous chloride is 1mmoL, and the amount of sodium tungstate is that the amount of 1mmoL, ferrous chloride or iron chloride is 0.05mmoL, the amount of water is 40mL, and the amount of ammonia is 0.5mL.

The preparation method of the wolframic acid nanometer rods eelctro-catalyst of a kind of iron ion doping the most according to claim 1, its feature Being, in step S2, in air dry oven, the temperature of reaction is 180 DEG C, and the response time is 12 hours.

The preparation method of the wolframic acid nanometer rods eelctro-catalyst of a kind of iron ion doping the most according to claim 1, its feature Being, in step S2, the temperature being dried in vacuum drying oven is 60 DEG C, and the time is 4 hours.