CN111101151A

CN111101151A - Preparation and application of molybdenum-doped cobalt selenide foam nickel composite electrode for water electrolysis

Info

Publication number: CN111101151A
Application number: CN201911292172.XA
Authority: CN
Inventors: 张小华; 陈金华; 王诗乐; 聂建行
Original assignee: Hunan University
Current assignee: Hunan University
Priority date: 2019-12-16
Filing date: 2019-12-16
Publication date: 2020-05-05

Abstract

The invention discloses preparation and application of a molybdenum-doped cobalt selenide foam nickel composite electrode for water electrolysis; the composite electrode is formed by depositing molybdenum-doped cobalt selenide composite on a foamed nickel electrode and is marked as Mo-CoSe₂NS @ NF. the electrode is applied to water electrolysis, and has good electrocatalytic performance and stability on hydrogen evolution and oxygen evolution, namely η catalytic hydrogen evolution₁₀89mV, Tafel slope 69mV dec^‑1Catalytic oxygen evolution η₁₀234mV, Tafel slope 58mV dec^‑1The cathode and the anode are used for constructing an electrolytic cell, and the current density in an alkaline medium reaches 10mA cm^‑2The electrolytic voltage was only 1.56V. The composite electrode catalytic active substance is directly deposited on the foamed nickel electrode, and the synthesis method is simple, green and environment-friendly, and has high-efficiency bifunctional catalysisThe water electrolyzer designed by the method has simple structure and is suitable for industrial scale application of water electrolysis.

Description

Preparation and application of molybdenum-doped cobalt selenide foam nickel composite electrode for water electrolysis

Technical Field

The invention relates to a water electrolysis electrocatalysis composite electrode, in particular to a preparation method and application of a high-efficiency electrocatalysis electrolysis water hydrogen evolution and oxygen evolution double-function composite electrode of molybdenum-doped cobalt selenide foam nickel, belonging to the field of electrolysis water.

Background

With the improvement of the living standard of human beings and the improvement of the degree of social civilization, the requirements of various aspects on energy supply and ecological environment quality are continuously improved. At present, how to solve economic and technical challenges and problems related to energy and environment in time has become an important problem facing the whole human society, and clean and renewable energy conversion and storage systems including fuel cells, metal air batteries and electrochemical water diversion devices have been greatly stimulated and developed. Among these systems, electrolyzers are one of the most promising methods for clean production of hydrogen and oxygen. However, in order to realize efficient water electrolysis and large-scale application of hydrogen energy, an efficient hydrogen and oxygen evolution catalyst is urgently needed.

Currently, noble metals and noble metal oxide alloys or metal oxides (e.g., Pt and IrO)₂) Have proven to be the most advanced electrolytic water catalysts, but their large-scale application is limited by scarcity of scarce resources and high costs. In order to develop clean energy technology, the current situation mainly of fossil energy is changed, and the search for efficient, stable and low-cost catalysts for water electrolysis and hydrogen and oxygen evolution is imperative. The double-function catalyst can make the water electrolysis equipment simpler and greatly reduce the operation cost, so the development of the double-function catalyst for water electrolysis has more important significance.

Transition metal oxides, transition metal chalcogenides, phosphides, hydroxides, etc. have attracted much attention in recent years in the research of bifunctional electrocatalysts because of their advantages such as high catalytic efficiency, low manufacturing cost, and promotion of kinetics of HER and OER. Among the numerous transition metal chalcogenides, CoSe₂Due to its abundant global resources, low cost, and excellent stability, it has attracted particular attention in the energy conversion and storage fields such as water electrolysis, lithium ion batteries, zinc-air batteries, and Polymer Electrolyte Membrane Fuel Cells (PEMFCs). However, to drive both OER and HER more efficiently, CoSe-based₂The development of the dual-function electrocatalyst for water electrolysis is still an important work.

Disclosure of Invention

The invention provides a preparation method and application of a molybdenum-doped cobalt selenide foam nickel composite electrode for water electrolysis, the electrode is a dual-function electrode, can simultaneously catalyze hydrogen evolution and oxygen evolution reactions of water electrolysis, has the characteristics of simple preparation, low cost, excellent performance and environmental friendliness, and is suitable for industrial production and application.

The invention is mainly realized by adopting the following technical scheme:

a preparation method of a molybdenum-doped cobalt selenide foam nickel composite electrode comprises the following steps:

1) pretreatment of foamed nickel: the foamed nickel cut into certain size is acid-washed, ultrasonically cleaned and dried for later use.

2)Co(OH)₂Preparation of NS @ NF: using water solution containing divalent cobalt salt as electrolyte, using constant current electrolysis method with certain current density at room temperature, electrodepositing Co (OH) on NF₂Nanosheet (Co (OH)₂NS @ NF), the product was dried in a 60 ℃ drying oven.

3)Mo-CoSe₂NS @ NF was prepared by dissolving a divalent cobalt salt and molybdate in 30ml of ultrapure water, stirring for 30min, and transferring to a 50ml Teflon autoclave. Then the cleaned Co (OH)₂NS is immersed in the reaction kettle, and the high-pressure reaction kettle is sealed and put into an air-blast drying box for hydrothermal reaction. The autoclave was cooled to room temperature, the sample was rinsed with ultrapure water, and unreacted materials were washed off and dried overnight at 60 ℃. Finally, the sample is placed in the middle of a vacuum tube furnace, a certain amount of Se powder is placed at the tail end of a quartz tube, and the vacuum tube furnace is heated at 5 ℃ for min in Ar atmosphere^-1Heating to proper temperature at a heating rate and keeping for 2 hours to obtain the molybdenum-doped cobalt selenide foam nickel composite electrode marked as Mo-CoSe₂NS@NF。

Preferably, in the step 1), the specification thickness of the foamed nickel is 0.5-10mm, the pore size is 0.1-10mm, and the pore size is 40-130 PPI.

Preferably, in the step 1), the acid washing solution is 1M-2.5M HCl solution, the acid washing time is 10-30min, the ultrasonic cleaning sequence is that acetone cleaning is carried out after ultrapure water cleaning, ultrasonic cleaning is carried out for 10-30min respectively, and drying is carried out for standby.

Preferably, in the step 2), the concentration of the electrolytic solution of the divalent cobalt aqueous solution is 0.1M, and the current density is 0.5-3.0mA cm^-2The electrodeposition time is 20min-60min, and the drying time is 24 hours.

Preferably, in the step 3), the molar ratio of the molybdate to the divalent cobalt salt is 0.4-1.0: 1, the hydrothermal reaction temperature is 140-. The molar ratio of the reactant to the Se powder is 5-20 times, and the temperature is 350-500 ℃. The invention also discloses Mo-CoSe₂The NS @ NF electrode is applied to electrolysis of water to separate out hydrogen and oxygen. The result of hydrogen evolution test in 1M KOH solution shows that Mo-CoSe₂The current density of hydrogen evolution catalyzed by NS @ NF electrode reaches 10mA cm^-2The overpotential is only 89 mV; the catalytic oxygen evolution current density reaches 10mA cm^-2The overpotential is only 234 mV; the current density at 1.56V reaches 10mA cm in the water electrolysis process catalyzed by the water splitting electrolytic cell using the alkaline medium assembled by the anode and the cathode at room temperature^-2. And exhibits excellent stability during a 10 hour constant current test.

Compared with the prior art, the invention has the following advantages:

1.Mo-CoSe₂the NS @ NF electrode has low hydrogen evolution over potential and 10mA cm in 1M KOH solution^-2The overpotential was only 89 mV.

2.Mo-CoSe₂NS @ NF electrode has low oxygen evolution over potential and 10mA cm in 1M KOH solution^-2The overpotential is only 234 mV.

3.Mo-CoSe₂The electrolytic water electrolysis voltage of the NS @ NF electrode is low, and the electrolytic water current density in 1M KOH solution reaches 10mA cm^-2The voltage is only 1.56V.

4.Mo-CoSe₂The NS @ NF electrode has the characteristics of simple preparation, low cost, excellent performance, environmental friendliness and the like, and is suitable for industrial large-scale production and application.

Description of the drawings

Fig. 1 SEM images of different magnifications of a molybdenum doped cobalt selenide foamed nickel electrode prepared by the present invention.

Detailed Description

The following examples are given to illustrate the present invention in more detail, but do not limit the scope of the claims of the present invention.

Example 1

(1) preparing foamed nickel: cutting foam Nickel (NF) into certain size (2cm × 1cm), ultrasonic cleaning foam nickel in 1M HCl solution, ultrapure water and acetone for 20min, and drying.

(2) Preparation of Co (OH)₂NS @ NF: performing electrodeposition on NF surface, and performing electrodeposition with 0.1M Co (NO)₃)₂As an electrolyte, a current density of 1.0mA cm was used at room temperature^-2Constant current electrolysis of NF by electrodeposition of Co (OH)₂Nanosheet (Co (OH)₂NS @ NF) for 30min, and the product was dried in a 60 ℃ drying oven for 24 hours.

(3) Preparation of Mo-CoSe₂NS@NF

Mixing Na at a molar ratio of 0.6: 1₂MoO₄·2H₂O and Co (NO)₃)₂·6H₂O was dissolved in 30mL of ultrapure water, stirred for 30min and then transferred to a 50mL Teflon autoclave. Then the cleaned Co (OH)₂NS @ NF is immersed in the reaction kettle, the high-pressure reaction kettle is sealed and placed in an air-blast drying oven, and hydrothermal reaction is carried out for 12 hours at 160 ℃. After the autoclave was cooled to room temperature, the sample was rinsed with ultrapure water to remove unreacted materials, and dried at 60 ℃ overnight. Then placing the sample in the middle of a vacuum tube furnace, placing 1g of Se powder at the tail end of a quartz tube, heating the vacuum tube furnace to 400 ℃ at a heating rate of 5 ℃ min < -1 > in Ar atmosphere, and keeping the temperature for 2 hours to obtain a product Mo-CoSe₂NS @ NF. Fig. 1 is SEM images of different magnifications of a molybdenum doped cobalt selenide foamed nickel electrode prepared by the present invention.

Example 2

(1) preparing foamed nickel: cutting foam Nickel (NF) into certain size (2cm × 1cm), ultrasonic cleaning foam nickel in 1.5MHCl solution, ultrapure water and acetone for 30min, and drying.

(2) Preparation of Co (OH)₂NS @ NF: performing electrodeposition on NF surface, and performing electrodeposition with 0.1M Co (NO)₃)₂Is an electrolyte and is used at room temperatureWith a current density of 2.0mA cm^-2Constant current electrolysis of NF by electrodeposition of Co (OH)₂Nanosheet (Co (OH)₂NS @ NF) for 20min, and the product was dried in a 60 ℃ drying oven for 24 hours.

(3) Preparation of Mo-CoSe₂NS@NF

Mixing Na at a molar ratio of 0.6: 1₂MoO₄·2H₂O and Co (NO)₃)₂·6H₂O was dissolved in 30mL of ultrapure water, stirred for 30min and then transferred to a 50mL Teflon autoclave. Then the cleaned Co (OH)₂NS @ NF is immersed in the reaction kettle, the high-pressure reaction kettle is sealed and placed in an air-blast drying oven, and hydrothermal reaction is carried out for 8 hours at 180 ℃. After the autoclave was cooled to room temperature, the sample was rinsed with ultrapure water to remove unreacted materials, and dried at 60 ℃ overnight. Then, the sample was placed in the middle of a vacuum tube furnace, 2g of Se powder was placed at the end of a quartz tube, and the vacuum tube furnace was heated at 5 ℃ for min in Ar atmosphere^-1Heating rate of (2) to 450 ℃ and holding for 2 hours to obtain the product Mo-CoSe₂NS@NF。

Example 3

(1) preparing foamed nickel: cutting foam Nickel (NF) into certain size (2cm × 1cm), ultrasonic cleaning foam nickel in 2.5MHCl solution, ultrapure water and acetone for 30min, and drying.

(2) Preparation of Co (OH)₂NS @ NF: performing electrodeposition on NF surface, and performing electrodeposition with 0.1M Co (NO)₃)₂As an electrolyte, a current density of 2.5mA cm was used at room temperature^-2Constant current electrolysis of NF by electrodeposition of Co (OH)₂Nanosheet (Co (OH)₂NS @ NF) for 15min, and the product was dried in a 60 ℃ drying oven for 24 hours.

(3) Preparation of Mo-CoSe₂NS@NF

Mixing Na at a molar ratio of 0.4: 1₂MoO₄·2H₂O and Co (NO)₃)₂·6H₂O was dissolved in 30ml of ultrapure water, stirred for 30min and transferred to a 50ml Teflon autoclave. Then cleaning the Co (O)H)₂NS @ NF is immersed in the reaction kettle, the high-pressure reaction kettle is sealed and placed in an air-blast drying oven, and hydrothermal reaction is carried out for 6 hours at 200 ℃. After the autoclave was cooled to room temperature, the sample was rinsed with ultrapure water to remove unreacted materials, and dried at 60 ℃ overnight. Then, the sample was placed in the middle of a vacuum tube furnace, 2.5g of Se powder was placed at the end of a quartz tube, and the vacuum tube furnace was heated at 5 ℃ for min in Ar atmosphere^-1Heating rate of (2) to 450 ℃ and holding for 2 hours to obtain the product Mo-CoSe₂NS@NF。

Claims

1. A preparation method of a molybdenum-doped cobalt selenide foam nickel composite electrode for water electrolysis is characterized in that foam nickel is used as a matrix electrode.

2. The method of claim 1, wherein the nickel foam has a thickness of 0.5-10mm, a pore size of 0.1-10mm, and a pore size of 40-130 PPI.

3. A preparation method of a molybdenum-doped cobalt selenide foam nickel composite electrode for water electrolysis is characterized by comprising the following steps:

3)Mo-CoSe₂NS @ NF was prepared by dissolving a divalent cobalt salt and molybdate in 30mL of ultrapure water, stirring for 30min, and transferring to a 50mL Teflon autoclave. Then the cleaned Co (OH)₂NS is immersed in the reaction kettle, and the high-pressure reaction kettle is sealed and put into an air-blast drying box for hydrothermal reaction. The autoclave was cooled to room temperature, the sample was rinsed with ultrapure water, and unreacted materials were washed off and dried overnight at 60 ℃. Finally, the sample is placed in the middle of the vacuum tube furnace, andplacing a certain amount of Se powder at the tail end of a quartz tube, and heating the vacuum tube furnace at 5 ℃ for min in Ar atmosphere^-1Heating to proper temperature at a heating rate and keeping for 2 hours to obtain the molybdenum-doped cobalt selenide foam nickel composite electrode marked as Mo-CoSe₂NS@NF。

4. The method for preparing the molybdenum-doped cobalt selenide foamed nickel composite electrode for electrolytic water according to claim 3, wherein in the step 1), the acid washing solution is 1M-2.5M HCl solution, the acid washing time is 10-30min, the ultrasonic cleaning sequence is that acetone cleaning is performed after ultrapure water cleaning, ultrasonic cleaning is performed for 10-30min respectively, and drying is performed for later use.

5. The method for preparing the molybdenum-doped cobalt selenide foam nickel composite electrode for electrolyzing water as claimed in claim 3, wherein the electrolyte containing divalent cobalt salt in the step 2) is CoCl₂、Co(NO₃)₂、CoSO₄And the like.

6. The method for preparing a molybdenum-doped cobalt selenide foam nickel composite electrode for electrolyzing water as claimed in claim 3, wherein the concentration of the cobalt salt-containing electrolyte in the step 2) is 0.1M, and the current density is 0.5-5.0mA cm/cm^-2The electrodeposition time is 20min to 60min, and the drying time is 12 to 24 hours.

7. The method for preparing the iron-doped cobalt diselenide composite nitrogen-doped carbon material according to claim 1, wherein in the step 3), the divalent cobalt salt is CoCl₂、Co(NO₃)₂、CoSO₄And the like.

8. The method for preparing the iron-doped cobalt diselenide composite nitrogen-doped carbon material according to claim 1, wherein in the step 3), the molybdate is (NH)₄)₂MoO₄、Na₂MoO₄、K₂MoO₄And the like.

9. The method as claimed in claim 1, wherein in the step 3), the molar ratio of the cobalt (II) salt to the molybdate is 0.4-1.0, the hydrothermal reaction temperature is 140 ℃ to 200 ℃, and the hydrothermal reaction time is 6-16 hours. The molar ratio of the Se powder to the reactants is 5-20 times, and the temperature is 350-500 ℃.

10. The preparation method of the molybdenum-doped cobalt selenide foam nickel composite electrode as claimed in claim 1, which is applied to the field of electrocatalytic oxygen evolution, hydrogen evolution or hydrogen evolution/oxygen evolution catalysts.