阅读说明：本技术 一种用于酸性电解水析氧的过渡金属磷化物复合材料及其制备方法 (Transition metal phosphide composite material for acidic electrolyzed water oxygen evolution and preparation method thereof ) 是由 闫海静 付宏刚 王雨 焦艳淸 于 2021-10-09 设计创作，主要内容包括：本发明公开了一种用于酸性电解水析氧的过渡金属磷化物复合材料的制备方法,属于非贵金属析氧催化剂的技术领域。本发明要解决目前酸性电解水析氧催化剂价格高昂、活性较低及稳定性差等问题。本发明的复合材料是由碳布和钴钼双金属磷化物组成的纳米片组成。本发明方法：一、对碳布进行酸洗预处理；二、将硝酸钴和磷钼酸溶解在蒸馏水中,搅拌均匀,溶液颜色变为褐色,得到钴钼多酸簇中间体；三、然后转移至水热釜中,水热后溶液颜色变成紫色,形成钴钼双金属氧化物/碳布复合体；四、然后高温磷化,冷却后洗涤。本发明的磷化钴钼/碳布材料具有高导电性、大电化学表面积、高化学稳定性和耐酸抗腐蚀的特点,并且表现出优异的酸性电解水析氧活性。(The invention discloses a preparation method of a transition metal phosphide composite material for acidic electrolyzed water oxygen evolution, belonging to the technical field of non-noble metal oxygen evolution catalysts. The invention aims to solve the problems of high price, low activity, poor stability and the like of the existing acidic electrolyzed water oxygen evolution catalyst. The composite material consists of carbon cloth and nano sheets consisting of cobalt-molybdenum double-metal phosphide. The method comprises the following steps: firstly, carrying out acid pickling pretreatment on the carbon cloth; dissolving cobalt nitrate and phosphomolybdic acid in distilled water, uniformly stirring, and changing the color of the solution into brown to obtain a cobalt-molybdenum polyacid cluster intermediate; thirdly, transferring the solution into a hydrothermal kettle, and changing the color of the solution into purple after hydrothermal to form a cobalt-molybdenum bimetal oxide/carbon cloth complex; fourthly, high-temperature phosphorization is carried out, and washing is carried out after cooling. The cobalt molybdenum phosphide/carbon cloth material has the characteristics of high conductivity, large electrochemical surface area, high chemical stability, acid resistance and corrosion resistance, and shows excellent acidic electrolyzed water oxygen evolution activity.)

1. A transition metal phosphide composite material for acidic electrolyzed water oxygen evolution is characterized by comprising carbon cloth and nanosheets, wherein nanosheet arrays grow on the carbon cloth in an orderly manner, and the nanosheets are formed by cobalt-molybdenum bimetallic phosphide.

2. Composite according to claim 1, characterized in that said nanosheets have a thickness of between 60nm and 80 nm.

3. The method for preparing the transition metal phosphide composite material for acidic electrolyzed water oxygen evolution as set forth in claim 1, characterized in that the preparation method is realized by the following steps:

step one, pretreatment of carbon cloth: carrying out acid treatment on the carbon cloth by using a mixed solution of concentrated hydrochloric acid and concentrated sulfuric acid, washing by using distilled water, and drying in an oven to finish pretreatment;

dissolving cobalt salt and molybdate in distilled water, and uniformly stirring to change the color of the solution into brown so as to form a cobalt-molybdenum polyacid cluster intermediate;

step three, transferring the reaction liquid obtained in the step two to a hydrothermal kettle with a polytetrafluoroethylene lining, then putting the hydrothermal kettle into pretreated carbon cloth, and carrying out hydrothermal treatment to generate a cobalt-molybdenum bimetal oxide/carbon cloth complex;

and step four, putting the cobalt-molybdenum bimetal oxide/carbon cloth composite obtained in the step three into a tubular furnace for phosphating, and then naturally cooling to room temperature to obtain the non-noble metal supported transition metal phosphide composite material.

4. The production method according to claim 3, wherein the volume ratio of the concentrated hydrochloric acid to the concentrated sulfuric acid in the mixed solution in the step one is 1: 3.

5. The production method according to claim 3 or 4, characterized in that the acid treatment of the first step is an ultrasonic cleaning of the carbon cloth in the mixed solution for 30min, followed by a standing acid treatment for 4 hours.

6. The method according to claim 3, wherein the mass ratio of the cobaltous salt to the molybdate in the step (1-10) is 1, and the mass ratio of the cobaltous salt to the distilled water is 1: (50-100).

7. The method according to claim 3, wherein the stirring time in the second step is 1 to 10 hours.

8. The method according to claim 3, wherein the cobalt salt in the second step is cobalt nitrate, cobalt chloride or cobalt acetate, and the molybdate is phosphomolybdic acid, ammonium molybdate or sodium molybdate.

9. The process according to claim 3, wherein the hydrothermal treatment is carried out at 100 to 180 ℃ for 2 to 10 hours in the third step.

10. The method according to claim 3, wherein the phosphating treatment in the fourth step is carried out by calcining at 400 to 800 ℃ for 1 to 4 hours.

Technical Field

The invention belongs to the technical field of non-noble metal oxygen evolution catalysts; in particular to a transition metal phosphide composite material for oxygen evolution of acidic electrolyzed water and a preparation method thereof.

Background

The hydrogen energy is a novel green energy source and has the advantages of environmental protection, high efficiency, sustainability and the like. The electrochemical catalytic decomposition of water to produce hydrogen is one of the cleanest, simple and efficient methods at present. The process of decomposing water involves two important reactions, namely the oxygen evolution reaction at the anode and the hydrogen evolution reaction at the cathode. Compared with the alkaline water splitting hydrogen production, the proton exchange membrane water electrolysis (PEM) device operated in an acidic medium has the advantages of high current density, low operation temperature, low gas transmittance, simple electrolytic cell design and the like compared with the traditional Alkaline Water Electrolysis (AWE) or solid oxide water electrolysis (SOE) device, and meanwhile, the proton exchange membrane technology has achieved huge achievements and is produced and applied in large quantities, so the acidic water splitting hydrogen production is very promising in application. However, the bottle neck for oxygen evolution of acidic electrolyzed water seriously hinders the development of hydrogen production by acidic decomposed water. The traditional noble metal-based (Pt, Ir, Ru and the like) materials are high in price and cannot achieve ideal stability when being used for acid decomposition of water, so that development of cheap, efficient and stable oxygen evolution catalysts in acid media is imperative.

At present, the bottle neck for oxygen evolution of acidic electrolyzed water seriously hinders the development of hydrogen production by acidic decomposed water. The traditional noble metal-based (Pt, Ir, Ru and the like) materials are high in price and cannot achieve ideal stability when being used for acid decomposition of water, so that development of cheap, efficient and stable oxygen evolution catalysts in acid media is imperative. However, there are currently few reports of non-noble metal-based catalysts for acidic electrolysis of water for oxygen evolution, indicating that the design and synthesis of such materials remains a challenging task.

Currently, transition phosphides, especially cobalt-based phosphides, have been extensively studied for use in acidic HER and OER due to their high conductivity, diverse compositions and excellent chemical stability. However, the conventional transition metal phosphide preparation process is complicated and it is difficult to achieve high performance and high stability in an acidic medium. Therefore, the method for exploring the simple and efficient phosphide electrocatalyst synthesis method and applying the method to practical industrial application has very important theoretical and practical significance, and not only can greatly save the production cost, but also can simplify the production process.

Disclosure of Invention

The invention aims to solve the problems of high price, low activity, poor stability and the like of the existing acidic electrolyzed water oxygen evolution catalyst; and provides a non-noble metal supported transition metal phosphide composite material and a preparation method thereof.

The invention reduces the cost of hydrogen production by acidic water decomposition and improves the activity of the hydrogen production; the method is realized by the following scheme:

a transition metal phosphide composite material for acidic electrolyzed water oxygen evolution is composed of carbon cloth and nanosheets, wherein nanosheet arrays grow on the carbon cloth in order, and the nanosheets are composed of cobalt-molybdenum bimetallic phosphide.

Further limited, the thickness of the nano-sheet is 60 nm-80 nm.

The invention discloses a preparation method of a transition metal phosphide composite material for acidic electrolyzed water oxygen evolution, which is characterized by comprising the following steps:

step one, pretreatment of carbon cloth: carrying out acid treatment on the carbon cloth by using a mixed solution of concentrated hydrochloric acid and concentrated sulfuric acid, washing by using distilled water, and drying in an oven to finish pretreatment;

dissolving cobalt salt and molybdate in distilled water, and uniformly stirring to change the color of the solution into brown so as to form a cobalt-molybdenum polyacid cluster intermediate;

step three, transferring the reaction liquid obtained in the step two to a hydrothermal kettle with a polytetrafluoroethylene lining, then putting the hydrothermal kettle into pretreated carbon cloth, and carrying out hydrothermal treatment to generate a cobalt-molybdenum bimetal oxide/carbon cloth complex;

and step four, putting the cobalt-molybdenum bimetal oxide/carbon cloth composite obtained in the step three into a tubular furnace for phosphating, and then naturally cooling to room temperature to obtain the non-noble metal supported transition metal phosphide composite material.

Further limiting, the volume ratio of the concentrated hydrochloric acid to the concentrated sulfuric acid in the mixed solution in the step one is 1:3, the mass fraction of the concentrated hydrochloric acid is 36-38%, and the mass fraction of the concentrated sulfuric acid is 98.3%.

Further defined, the acid treatment of the first step is to place the carbon cloth in the mixed solution for ultrasonic cleaning for 30min, and then to stand for acid treatment for 4 hours.

Further limiting, the mass ratio of the cobaltous salt to the molybdate in the step (1-10) is 1, and the mass ratio of the cobaltous salt to the distilled water is 1: (50-100).

Further limiting, the stirring speed of the second step is 1000 rpm-4000 rpm, and the stirring time is 1 h-10 h.

Further, the cobalt salt in the second step is cobalt nitrate, cobalt chloride or cobalt acetate), and the molybdate is phosphomolybdic acid, ammonium molybdate or sodium molybdate.

Further limiting, in the third step, carrying out hydrothermal treatment for 2-10 h at 100-180 ℃.

Further limited, the phosphorization treatment of the step four is calcination for 1-4 h at 400-800 ℃.

The phosphide electrocatalyst material is prepared by a simple and efficient method. The phosphide electrocatalyst material prepared by the invention has good performance in the aspect of electrocatalytic decomposition of water and oxygen evolution, and the cobalt-molybdenum bimetallic phosphide/carbon cloth complex has excellent OER catalytic activity at 10mAcm^-2Has an overpotential of 261mV and an activity higher than that of commercial RuO₂A catalyst, which indicates that the cobalt molybdenum bimetallic phosphide/carbon cloth composite can be used as a high efficiency non-noble metal oxygen generation catalyst. It is worth mentioning that the activity of the cobalt molybdenum bimetallic phosphide/carbon cloth catalyst is superior to that of the commercial RuO₂A catalyst. This indicates that cobalt molybdenum bimetallic phosphide/carbon cloth can be used as a highly efficient non-noble metal oxygen generating catalyst.

The transition metal phosphide complex prepared by the method disclosed by the invention has the advantages that the transition metal phosphide uniformly grows on the carbon cloth, the transition metal phosphide and the carbon cloth are easy to combine, and the excellent catalytic activity of water electrolysis and oxygen evolution is shown.

The invention does not use any noble metal, thereby greatly reducing the cost expenditure and having important guiding significance for the design and the practical application of the electrocatalytic acidic decomposition water in the future.

The invention does not use any adhesive and does not pollute the environment.

The cobalt-molybdenum bimetallic phosphide material is prepared by a strategy of growing metal on carbon cloth in situ. The operation method and the reaction equipment are relatively simple, and the large-scale preparation of the catalyst material is facilitated.

The invention can realize the regulation and control of the size, the shape and the metal ratio of the cobalt-molybdenum bimetal phosphide/carbon cloth composite by adjusting the raw material ratio, the hydrothermal condition (time and temperature) and the calcining condition (time and temperature).

The cobalt molybdenum phosphide/carbon cloth material prepared by the method has the characteristics of high conductivity, large electrochemical surface area, high chemical stability, acid resistance and corrosion resistance, and shows excellent acidic electrolyzed water oxygen evolution activity.

Drawings

FIG. 1 is a scanning electron microscope image of the cobalt molybdenum bimetallic phosphide/carbon cloth composite obtained in example 1;

FIG. 2 is a magnified higher magnification scanning electron microscope image of the cobalt molybdenum bimetallic phosphide/carbon cloth composite obtained in example 1;

FIG. 3 is an X-ray diffraction pattern of the cobalt molybdenum bimetallic phosphide/carbon cloth composite obtained in example 1;

figure 4 is a graph of the oxygen evolution performance of different catalysts.

Detailed Description

Example 1: the preparation method of the transition metal phosphide complex of the embodiment is realized by the following steps:

cutting a carbon cloth into small cubes with the size of 3cm multiplied by 3cm, then placing the cubes into a mixed solution prepared from 36% by mass of concentrated hydrochloric acid and 98.3% by mass of concentrated sulfuric acid for ultrasonic cleaning for 30min, then standing the cubes for acid treatment for 4 hours, then washing the cubes with distilled water again, and placing the cubes in a drying oven for drying at 60 ℃ for 4 hours to obtain pretreated carbon cloth; the volume ratio of the concentrated hydrochloric acid to the concentrated sulfuric acid in the mixed solution is 1: 3.

Dissolving 0.3g of cobalt nitrate and 0.2g of phosphomolybdic acid in 25mL of distilled water, uniformly stirring, and changing the color of the solution into brown to form a cobalt-molybdenum polyacid cluster intermediate;

step three, transferring the reaction liquid obtained in the step two into a hydrothermal kettle with a polytetrafluoroethylene lining, then putting the hydrothermal kettle into a pretreatment carbon cloth, and carrying out hydrothermal treatment at 120 ℃ for 4 hours until the color of the solution is changed into purple, so as to generate a cobalt-molybdenum bimetal oxide/carbon cloth complex;

and step four, putting the cobalt-molybdenum bimetal oxide/carbon cloth composite obtained in the step three into a tubular furnace, carrying out phosphating treatment for 2 hours at the temperature of 600 ℃, and then naturally cooling to room temperature to obtain the cobalt-molybdenum phosphide/carbon cloth composite.

Fig. 1 shows a scanning electron microscope picture of the cobalt molybdenum phosphide/carbon cloth composite obtained in example 1, and it can be seen from the picture that a nanosheet array structure composed of cobalt molybdenum bimetallic phosphide uniformly grows on the carbon cloth, which proves that an ordered cobalt molybdenum bimetallic phosphide nanosheet composite material is formed.

A scanning electron microscope picture of higher magnification of the cobalt molybdenum phosphide/carbon cloth composite obtained in example 1 is shown in fig. 2, and it can be seen from the figure that a nanosheet array structure composed of cobalt molybdenum bi-metal phosphide is orderly grown on the carbon cloth, and the nanosheet thickness is about 60 nm. The ultrathin cobalt-molybdenum bimetallic phosphide nanosheet composite material is proved to be formed.

The powder X-ray diffraction pattern of the cobalt molybdenum phosphide/carbon cloth composite obtained in example 1 is shown in FIG. 3, and it can be seen that these diffraction peaks are assigned to CoP respectively₂(PDF #77-0263), MoP (PDF #24-0771), demonstrates the successful preparation of a cobalt molybdenum bimetallic oxide/carbon cloth composite.

The oxygen evolution performance of the different catalysts is shown in FIG. 4 at 0.5MH₂SO₄The performance of the cobalt molybdenum bimetallic phosphide/carbon cloth composites in catalyzing OER was evaluated using a classical three-electrode system at room temperature in solution. Using both carbon cloth and commercial RuO₂As a comparative sample. At a sweep rate of 5mVs^-1Lower carbon cloth, cobalt molybdenum bimetallic phosphide/carbon cloth and RuO₂Of catalystsPolarization curve. As can be seen from the figure, the activity of the carbon cloth is poor, while the cobalt molybdenum bimetallic phosphide/carbon cloth shows superior to the commercial RuO₂Has an initial overpotential of 220 mV and 240mV at 10mAcm, 50 mAcm and 100mAcm^-2The overpotentials at current densities of 221, 473, and 606mV and 261, 536, and 656mV, respectively. The cobalt-molybdenum bimetallic phosphide/carbon cloth can be used as a high-efficiency non-noble metal oxygen evolution catalyst, can greatly reduce the production cost and has a certain application prospect.