CN111632606A - A kind of preparation method of multilayer stacked nanosheet CoS-CeO2 nitrogen reduction catalyst - Google Patents

Abstract

The synthesis of NH ₃ is mainly controlled by the traditional energy-consuming Haber-Bosch process, but it has great drawbacks. It emits a large amount of CO ₂ to cause the greenhouse effect and requires severe reaction conditions, such as high temperature and high pressure. The electrochemical nitrogen reduction reaction under ambient conditions provides us with a friendly route to artificially synthesize _NH3 , however, stable and efficient catalysts are required for the nitrogen reduction reaction. Noble metals such as Au, Ru, Ag and Rh can be effectively used for electrolytic nitrogen reduction, while the expensive price of these catalysts limits their use. Transition metal oxides happen to solve this kind of expensiveness, and they are non-toxic and easy to prepare, but the accompanying problem is that their poor electrical conductivity adversely affects the catalytic performance. The invention provides a preparation method of a multi-layer stacked nano-sheet catalyst material cobalt sulfide cerium oxide hybrid CoS-CeO ₂ and its electrocatalytic nitrogen reduction application. First, a specific proportion of cobalt and cerium reagents are added to a special reaction solution, and the cobalt and cerium precursors are obtained by heating and reacting by the hydrothermal synthesis method; then, the cobalt and cerium precursors are placed in a tube furnace with a specific nitrogen flow rate. Sulfiding treatment, finally obtains cobalt sulfide cerium oxide hybrid CoS-CeO ₂ . The CoS‑CeO ₂ catalyst exhibits excellent catalytic activity in the field of electrocatalytic nitrogen reduction NRR, with an ammonia yield of 40.6 µg h ^–1 mg ^–1 _cat and a Faradaic efficiency of 10.2% at ‑0.2 V relative to a standard hydrogen electrode .

Description

A kind of preparation method of multilayer stacked nanosheet CoS-CeO2 nitrogen reduction catalyst

technical field

The invention relates to the field of preparation and application of inorganic nanomaterials, in particular to a method for preparing a multi-layer stacked nanosheet catalyst material cobalt sulfide cerium oxide hybrid CoS-CeO ₂ based on a hydrothermal method, which is realized in the field of electrocatalytic nitrogen reduction Applications.

Background technique

As one of the most important industrial chemicals, _NH3 has been used in pharmaceuticals, fertilizers, fuels, and explosives, etc.; as a nitrogen compound precursor, it has played an important role in agriculture, pharmaceuticals, and textile industries. Meanwhile, ammonia gas is an emerging energy carrier with a hydrogen content of 17.6% in liquid ammonia and a methanol content of 12.5%. Ammonia gas is likely to be a promising candidate for the future hydrogen economy. Therefore, ammonia occupies an indispensable position in the future population development. According to statistics, more than 140 million tons of ammonia are produced in industry every year, and the demand is still growing. Today, the large demand for ammonia gas has developed into an imminent social problem, which has stimulated in-depth research on the large-scale production technology of artificial ammonia gas.

However, due to the chemical inertness of nitrogen and the high energy barrier of N≡N bond cleavage, the synthesis of ammonia mainly relies on the traditional energy-intensive Haber-Bosch process, which requires harsh conditions at 350-550 °C and At the same time, the input of _H2 and energy consumption are mainly from fossil fuels, which leads to a large amount of carbon dioxide emissions, with an average of 1.87 tons of carbon dioxide per ton of ammonia, which cannot be ignored. The traditional Haber-Bosch process reportedly consumes about 2% of the world's energy supply and accounts for 1.5% of global greenhouse gas emissions. Therefore, the search for sustainable and efficient ammonia production methods under mild conditions remains a huge impetus.

In recent years, electrochemical nitrogen reduction reaction NRR has attracted much attention. Compared with the traditional Haber-Bosch process, NRR has the following advantages: ambient working conditions, soil-rich feedstocks, namely nitrogen and water, simplified equipment, and minimal carbon emissions, but it requires efficient nitrogen reduction electrocatalysts. To date, theoretical and experimental studies on NRR with heterogeneous catalysts have mainly focused on noble metals, transition metal oxides/nitrides/carbides/chalcogenides, and metal-free catalysts. Many noble metals, such as Au, Ru, Rh, and Pd, can effectively catalyze nitrogen reduction reactions with high yields, but the expensiveness of these catalysts has limited their widespread use. Therefore, more attention has begun to focus on the design and research of non-precious metal catalysts, especially transition metals, which have outstanding advantages, stability, non-toxicity, low cost and easy preparation.

Due to their unique size, nanomaterials endow materials with many novel properties and exhibit excellent activity in the field of electrocatalysis. In addition, as a commonly used regulation method, coupled with the synergistic effect of metals, the catalytic properties produced by doping will surely make further breakthroughs in electrocatalytic nitrogen reduction. In view of this, the present invention provides a multi-layer stacked nanosheet catalyst material cobalt sulfide ceria hybrid CoS-CeO ₂ applied as an efficient electrocatalytic nitrogen reduction catalyst.

SUMMARY OF THE INVENTION

One of the objectives of the present invention is a novel preparation method of a multi-layer stacked nanosheet CoS-CeO ₂ nitrogen reduction catalyst.

The second objective of the present invention is to apply the synthesized multilayer stacked nanosheet catalyst to an electrocatalytic nitrogen reduction system.

The third purpose of the present invention is to design a brand-new single-chamber membrane electrode nitrogen reduction electrocatalytic testing system through repeated testing and processing.

Description of drawings

FIG. 1 is a schematic structural diagram of a self-designed single-chamber membrane electrode nitrogen reduction electrocatalytic test system provided by the present invention.

The technical scheme of the present invention is as follows:

1. a multi-layer stacking nano-sheet catalyst material cobalt sulfide cerium oxide hybrid CoS-CeO ₂ preparation method, is characterized in that, preparation step is as follows:

(1) Add cobalt and cerium reagents in a fixed ratio of 10:1 to 1:1 to a specific reaction solution, that is, a mixed solution of urea and thiourea to prepare a pre-reaction solution, and use the hydrothermal synthesis method to heat the pre-reaction solution at a certain temperature. For a certain period of time, naturally cool, wash and dry the collected cobalt-cerium precursor. In this process, the use of a mixed solution of urea and thiourea can effectively adjust the pH of the solution, promote the formation of multi-layer stacked nanosheets, and control the nanomaterials at the same time. The morphology of the resulting cobalt-cerium precursor shows a very thin physical structure;

(2) The cobalt-cerium precursor is placed in a tube furnace, the nitrogen flow rate is fixed at 10 ~ 50 mL/min, the calcination temperature is 300 ^o C ~ 600 ^o C, and the sublimation sulfur is added as the sulfidation reagent to carry out the sulfidation reaction, wherein the sulfidation reagent and The mass ratio of cobalt-cerium precursors is 1:10 ~ 1:100, the sulfidation temperature is 300 ^o C ~ 600 ^o C, the sulfidation time is 1 ~ 6 h, and the heating rate is 0.5 ^o C/min to obtain multilayer stacked nanosheets CoS-CeO ₂ , in this process, sublimated sulfur as a sulfidation reagent can not only promote the formation of multi-layer stacked nanosheets of CoS-CeO ₂ , but also improve the conductivity of the catalyst, while exposing the generated CoS-CeO ₂ to more catalytic The active site is beneficial to the subsequent electrocatalytic process.

2. A method for preparing a multi-layer stacked nanosheet CoS-CeO ₂ nitrogen reduction catalyst, characterized in that, adopting a single-chamber membrane electrode nitrogen reduction electrocatalytic performance test, the steps are as follows:

(1) CoS-CeO ₂ was prepared into 0.1 ~ 5 mg/mL ink liquid, which was dripped on the proton exchange membrane and dried at room temperature; The surface of the CoS-CeO ₂ , that is, the electrocatalytic nitrogen reduction membrane electrode is prepared. During this process, the proton exchange membrane only allows H ⁺ to permeate directionally, and directly interacts with the catalyst on the membrane electrode under the nitrogen atmosphere, which greatly shortens the time. Reaction time;

(2) Using the above-mentioned membrane electrode as the working electrode, the graphite electrode as the counter electrode, the Ag/AgCl electrode as the reference electrode, and the 0.1-2 mol/L sodium sulfate-lithium perchlorate mixed solution as the electrolyte, electrocatalysis was carried out. Nitrogen reduction process. In this process, the mixed solution of sodium sulfate and lithium perchlorate is used as the electrolyte, which improves the selectivity of the reaction, that is, it can effectively suppress the hydrogen evolution reaction and promote the nitrogen reduction reaction. It is the first time that the mixed solution of the two is applied to In the nitrogen reduction electrocatalytic test, the results show that the effect is excellent.

3. Using a novel single-chamber membrane electrode nitrogen reduction electrocatalytic test system, in which the proton exchange membrane is used as the working electrode, the CoS _- CeO2 catalyst is drop-coated on the outside of the membrane electrode, and H ⁺ is continuously supplied through the sodium sulfate-lithium perchlorate mixed electrolyte Supply, the micro funnel receiver collects the ammonia solution produced, this test system can improve the utilization rate of the electrocatalytic nitrogen reduction catalyst, prevent excessive consumption of the catalyst, and at the same time can effectively improve the Faradaic efficiency of the reaction.

4. The performance of CoS-CeO ₂ multilayer stacked nanosheets, the ammonia yield of electrocatalytic nitrogen reduction reaction reaches 40.6 µg h ^–1 mg ^–1 , and the Faradaic efficiency is as high as 10.2 %, with better ammonia yield and Faradaic efficiency.

specific embodiment

In order to further understand the present invention, the preferred embodiments of the present invention are described below with reference to the examples. These descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

Example 1

Step 1: Take a beaker and add 100 mL of deionized water, add urea (0.781 g, 13 mmol) and stir for 30 min to form a clear and transparent solution, then add cobalt nitrate hexahydrate (0.582 g, 2 mmol), hexahydrate cobalt nitrate (0.582 g, 2 mmol), hexahydrate Cerium nitrate (0.434 g, 1.0 mmol) was stirred for 30 min, and then 40 mL was transferred to a polytetrafluoroethylene liner. After sealing the hydrothermal autoclave, it was placed in an oven at 100 °C for 8 h. After natural cooling, washing with deionized water and absolute ethanol, and vacuum drying, the cobalt-cerium precursor supported on the titanium mesh was obtained.

The second step: The cobalt-cerium precursor and 1 g of sublimated sulfur were placed in a tube furnace, calcined at 300 ^o C for 1 h under nitrogen atmosphere, the heating rate was 0.5 ^o C/min, and the nitrogen flow was 10 mL/min. Multilayer stacked nanosheets of CoS-CeO ₂ are obtained.

Step 3: Multi-layer stacked nanosheets CoS-CeO ₂ for water electrolysis application

1. Prepare CoS-CeO ₂ as 0.1 ~ 5 mg/mL ink solution, drop on the proton exchange membrane, and dry at room temperature; configure 0 ~ 1 mg/mL Nafion solution, drop on the above slightly dry ink CoS-CeO ₂ surface, namely the electrocatalytic nitrogen reduction membrane electrode was prepared.

2. Using the above-mentioned membrane electrode as the working electrode, the graphite electrode as the counter electrode, the Ag/AgCl electrode as the reference electrode, and the 0.1 ~ 2 mol/L sodium sulfate-lithium perchlorate mixed solution as the electrolyte, electrocatalytic nitrogen restore process. The cyclic voltammetry test voltage range is 0 ~ -1.0 V, the highest potential is 0 V, the lowest potential is -1.0 V, the starting potential is 0 V, and the ending potential is -1.0 V. The scan rate is 0.05 V/s. The sampling interval is 0.001 V, the rest time is 2 s, and the number of sweep segments is 500.

3. Perform a linear voltage sweep test with a voltage range of 0 ~ -1.0 V. The initial potential was 0 V and the termination potential was -1.0 V. The scan rate is 5 mV/s. The sampling interval is 0.001 V. The resting time was 2 s. First, argon gas was passed into the electrolyte for 30 min, and the first linear voltage sweep test was performed after the argon gas was saturated. Then, nitrogen gas was introduced into the electrolyte for 30 min, and the second linear voltage sweep test was performed after the nitrogen gas was saturated.

4. Using the membrane electrode as the working electrode, the catalyst was subjected to a long-term nitrogen reduction test, and the potentials were set to -0.35 V, -0.45 V, -0.55 V, -0.65 V, and -0.75 V, respectively, and the running time was 7200 s.

Step 4: Ammonia production test

1. Drawing of working curve: using NH ₄ Cl as standard reagent to prepare 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 in 0.1 mol/L sodium sulfate-lithium perchlorate mixed solution, respectively , 1.0 μg/mL standard solution and color reaction test absorbance. Take 4 mL of standard solution and add 50 μL of oxidant (including 75 wt% NaOH and 75 wt% NaClO), 500 μL of colorant (including 40 wt% of sodium salicylate and 32 wt% of NaOH), 50 μL of catalyst (5 wt% Na ₂ [Fe(NO)(CN) ₅ ]·2H ₂ O). After standing in the dark at room temperature for 1 h, the spectrum was scanned with a UV-Vis spectrophotometer in the wavelength range of 550 nm to 800 nm, and the absorbance value at 660 nm was recorded and the concentration was plotted to obtain a standard curve.

2. Ammonia production test: take 4 mL of the electrolyte after running for 2 h at each potential, add 50 μL oxidant (including 75 wt% NaOH and 75 wt% NaClO), 500 μL colorant (including 40 wt% NaClO) in turn sodium salicylate and 32 wt% NaOH), 50 μL catalyst (5 wt% Na ₂ [Fe(NO)(CN) ₅ ] · 2H ₂ O). After standing in the dark at room temperature for 1 h, the UV-visible spectrophotometer was used for spectral scanning in the wavelength range of 550 nm to 800 nm, and the absorbance value at 660 nm was recorded, and finally the concentration of ammonia was obtained. After data processing and calculation, the multi-layer stacked nanosheet CoS-CeO ₂ has excellent effect on NRR, the ammonia yield reaches 40.6 µg h ^–1 mg ^–1 _cat. at -0.2 V (relative to standard hydrogen electrode), and the Faradaic efficiency is as high as 10.2%.

Example 2

Step 1: Take a beaker and add 100 mL of deionized water, add urea (0.901 g, 15 mmol), and stir for 30 min to form a clear and transparent solution, then add cobalt chloride hexahydrate (0.476 g, 2 mmol), Hydrate cerium nitrate (0.434 g, 1.0 mmol), stir for 30 min, and transfer 40 mL into a polytetrafluoroethylene liner. After sealing the hydrothermal autoclave, it was placed in an oven at 110 °C for 10 h. After natural cooling, the cobalt-cerium precursor was obtained after washing with deionized water and absolute ethanol respectively, and vacuum drying.

The second step: take the cobalt-cerium precursor and 1.5g of sublimated sulfur in a tube furnace, calcined at 350 ^o C for 1 h in a nitrogen atmosphere, the heating rate is 0.5 ^o C/min, and the nitrogen flow rate is 10 mL/min. Multilayer stacked nanosheets of CoS-CeO ₂ are obtained.

Step 3: Multi-layer stacked nanosheets CoS-CeO ₂ for water electrolysis application

1. Prepare CoS-CeO ₂ as 0.1 ~ 5 mg/mL ink solution, drop on the proton exchange membrane, and dry at room temperature; configure 0 ~ 1 mg/mL Nafion solution, drop on the above slightly dry ink CoS-CeO ₂ surface, namely the electrocatalytic nitrogen reduction membrane electrode was prepared.

2. Using the above-mentioned membrane electrode as the working electrode, the graphite electrode as the counter electrode, the Ag/AgCl electrode as the reference electrode, and the 0.1 ~ 2 mol/L sodium sulfate-lithium perchlorate mixed solution as the electrolyte, electrocatalytic nitrogen restore process. The cyclic voltammetry test voltage range is 0 ~ -1.0 V, the highest potential is 0 V, the lowest potential is -1.0 V, the starting potential is 0 V, and the ending potential is -1.0 V. The scan rate is 0.05 V/s. The sampling interval is 0.001 V, the rest time is 2 s, and the number of sweep segments is 500.

3. Perform a linear voltage sweep test with a voltage range of 0 ~ -1.0 V. The initial potential was 0 V and the termination potential was -1.0 V. The scan rate is 5 mV/s. The sampling interval is 0.001 V. The resting time was 2 s. First, argon gas was passed into the electrolyte for 30 min, and the first linear voltage sweep test was performed after the argon gas was saturated. Then, nitrogen gas was introduced into the electrolyte for 30 min, and the second linear voltage sweep test was performed after the nitrogen gas was saturated.

4. Using the membrane electrode as the working electrode, the catalyst was subjected to a long-term nitrogen reduction test, and the potentials were set to -0.35 V, -0.45 V, -0.55 V, -0.65 V, and -0.75 V, respectively, and the running time was 7200 s.

Step 4: Ammonia production test

1. Drawing of working curve: using NH ₄ Cl as standard reagent to prepare 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 in 0.1 mol/L sodium sulfate-lithium perchlorate mixed solution, respectively , 1.0 μg/mL standard solution and color reaction test absorbance. Take 4 mL of standard solution and add 50 μL of oxidant (including 75 wt% NaOH and 75 wt% NaClO), 500 μL of colorant (including 40 wt% of sodium salicylate and 32 wt% of NaOH), 50 μL of catalyst (5 wt% Na ₂ [Fe(NO)(CN) ₅ ]·2H ₂ O). After standing in the dark at room temperature for 1 h, the spectrum was scanned with a UV-Vis spectrophotometer in the wavelength range of 550 nm to 800 nm, and the absorbance value at 660 nm was recorded and the concentration was plotted to obtain a standard curve.

2. Ammonia production test: take 4 mL of the electrolyte after running for 2 h at each potential, add 50 μL oxidant (including 75 wt% NaOH and 75 wt% NaClO), 500 μL colorant (including 40 wt% NaClO) in turn sodium salicylate and 32 wt% NaOH), 50 μL catalyst (5 wt% Na ₂ [Fe(NO)(CN) ₅ ] · 2H ₂ O). After standing in the dark at room temperature for 1 h, the UV-visible spectrophotometer was used for spectral scanning in the wavelength range of 550 nm to 800 nm, and the absorbance value at 660 nm was recorded, and finally the concentration of ammonia was obtained. After data processing and calculation, the multi-layer stacked nanosheet CoS-CeO ₂ has excellent effect on NRR, the ammonia yield reaches 40.2µg h ^–1 mg ^–1 _cat. at -0.2 V (relative to standard hydrogen electrode), and the Faradaic efficiency up to 10.1%.

Example 3

Step 1: Take a beaker and add 100 mL of deionized water, add urea (0.961 g, 16 mmol), and stir for 30 min to form a clear and transparent solution, then add cobalt nitrate hexahydrate (0.582 g, 2 mmol) and cerium sulfate in sequence under stirring. (0.498 g, 1.5 mmol), stirred for 30 min, and then transferred 40 mL into a polytetrafluoroethylene liner. After sealing the hydrothermal autoclave, it was placed in an oven at 110 °C for 8 h. After natural cooling, the cobalt-cerium precursor was obtained after washing with deionized water and absolute ethanol respectively, and vacuum drying.

The second step: The cobalt-cerium precursor and 2 g of sublimated sulfur were placed in a tube furnace, calcined at 300 ^o C for 1 h under nitrogen atmosphere, the heating rate was 0.5 ^o C/min, and the nitrogen flow was 10 mL/min. Multilayer stacked nanosheets of CoS-CeO ₂ are obtained.

Step 3: Multi-layer stacked nanosheets CoS-CeO ₂ for water electrolysis application

1. Prepare CoS-CeO ₂ as 0.1 ~ 5 mg/mL ink solution, drop on the proton exchange membrane, and dry at room temperature; configure 0 ~ 1 mg/mL Nafion solution, drop on the above slightly dry ink CoS-CeO ₂ surface, namely the electrocatalytic nitrogen reduction membrane electrode was prepared.

2. Using the above-mentioned membrane electrode as the working electrode, the graphite electrode as the counter electrode, the Ag/AgCl electrode as the reference electrode, and the 0.1 ~ 2 mol/L sodium sulfate-lithium perchlorate mixed solution as the electrolyte, electrocatalytic nitrogen restore process. The cyclic voltammetry test voltage range is 0 ~ -1.0 V, the highest potential is 0 V, the lowest potential is -1.0 V, the starting potential is 0 V, and the ending potential is -1.0 V. The scan rate is 0.05 V/s. The sampling interval is 0.001 V, the rest time is 2 s, and the number of sweep segments is 500.

3. Perform a linear voltage sweep test with a voltage range of 0 ~ -1.0 V. The initial potential was 0 V and the termination potential was -1.0 V. The scan rate is 5 mV/s. The sampling interval is 0.001 V. The resting time was 2 s. First, argon gas was passed into the electrolyte for 30 min, and the first linear voltage sweep test was performed after the argon gas was saturated. Then, nitrogen gas was introduced into the electrolyte for 30 min, and the second linear voltage sweep test was performed after the nitrogen gas was saturated.

4. Using the membrane electrode as the working electrode, the catalyst was subjected to a long-term nitrogen reduction test, and the potentials were set to -0.35 V, -0.45 V, -0.55 V, -0.65 V, and -0.75 V, respectively, and the running time was 7200 s.

Step 4: Ammonia production test

1. Drawing of working curve: using NH ₄ Cl as standard reagent to prepare 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 in 0.1 mol/L sodium sulfate-lithium perchlorate mixed solution, respectively , 1.0 μg/mL standard solution and color reaction test absorbance. Take 4 mL of standard solution and add 50 μL of oxidant (including 75 wt% NaOH and 75 wt% NaClO), 500 μL of colorant (including 40 wt% of sodium salicylate and 32 wt% of NaOH), 50 μL of catalyst (5 wt% Na ₂ [Fe(NO)(CN) ₅ ]·2H ₂ O). After standing in the dark at room temperature for 1 h, the spectrum was scanned with a UV-Vis spectrophotometer in the wavelength range of 550 nm to 800 nm, and the absorbance value at 660 nm was recorded and the concentration was plotted to obtain a standard curve.

2. Ammonia production test: take 4 mL of the electrolyte after running for 2 h at each potential, add 50 μL oxidant (including 75 wt% NaOH and 75 wt% NaClO), 500 μL colorant (including 40 wt% NaClO) in turn sodium salicylate and 32 wt% NaOH), 500 μL colorant (containing 40 wt% sodium salicylate and 32 wt% NaOH), 50 μL catalyst (5 wt% Na ₂ [Fe(NO)(CN) ₅ ] · 2H ₂ O). After standing in the dark at room temperature for 1 h, the UV-visible spectrophotometer was used for spectral scanning in the wavelength range of 550 nm to 800 nm, and the absorbance value at 660 nm was recorded, and finally the concentration of ammonia was obtained. After data processing and calculation, the application of multilayer stacked nanosheets CoS-CeO ₂ to NRR is excellent, the ammonia yield reaches 40.3 µg h ^–1 mg ^–1 _cat. at -0.2 V (relative to standard hydrogen electrode), and the Faradaic efficiency is as high as 10.2%.

Example 4

Step 1: Take a beaker and add 100 mL of deionized water, add urea (1.051 g, 17.5 mmol) and stir for 30 min to form a clear and transparent solution, then add cobalt nitrate hexahydrate (1.019 g, 3.5 mmol), hexahydrate Cerium nitrate (0.76 g, 1.75 mmol) was stirred for 30 min, and then 40 mL was transferred to a polytetrafluoroethylene liner. After sealing the hydrothermal autoclave, it was placed in an oven at 120 °C for 10 h. After natural cooling, the cobalt-cerium precursor was obtained after washing with deionized water and absolute ethanol respectively, and vacuum drying.

The second step: The cobalt-cerium precursor and 1 g of sublimated sulfur were placed in a tube furnace, calcined at 400 ^o C for 1 h under nitrogen atmosphere, the heating rate was 0.5 ^o C/min, and the nitrogen flow was 10 mL/min. Multilayer stacked nanosheets of CoS-CeO ₂ are obtained.

Step 3: Multi-layer stacked nanosheets CoS-CeO ₂ for water electrolysis application

1. Prepare CoS-CeO ₂ as 0.1 ~ 5 mg/mL ink solution, drop on the proton exchange membrane, and dry at room temperature; configure 0 ~ 1 mg/mL Nafion solution, drop on the above slightly dry ink CoS-CeO ₂ surface, namely the electrocatalytic nitrogen reduction membrane electrode was prepared.

2. Using the above-mentioned membrane electrode as the working electrode, the graphite electrode as the counter electrode, the Ag/AgCl electrode as the reference electrode, and the 0.1 ~ 2 mol/L sodium sulfate-lithium perchlorate mixed solution as the electrolyte, electrocatalytic nitrogen restore process. The cyclic voltammetry test voltage range is 0 ~ -1.0 V, the highest potential is 0 V, the lowest potential is -1.0 V, the starting potential is 0 V, and the ending potential is -1.0 V. The scan rate is 0.05 V/s. The sampling interval is 0.001 V, the rest time is 2 s, and the number of sweep segments is 500.

3. Perform a linear voltage sweep test with a voltage range of 0 ~ -1.0 V. The initial potential was 0 V and the termination potential was -1.0 V. The scan rate is 5 mV/s. The sampling interval is 0.001 V. The resting time was 2 s. First, argon gas was passed into the electrolyte for 30 min, and the first linear voltage sweep test was performed after the argon gas was saturated. Then, nitrogen gas was introduced into the electrolyte for 30 min, and the second linear voltage sweep test was performed after the nitrogen gas was saturated.

4. Using the membrane electrode as the working electrode, the catalyst was subjected to a long-term nitrogen reduction test, and the potentials were set to -0.35 V, -0.45 V, -0.55 V, -0.65 V, and -0.75 V, respectively, and the running time was 7200 s.

Step 4: Ammonia production test

1. Drawing of working curve: using NH ₄ Cl as standard reagent to prepare 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 in 0.1 mol/L sodium sulfate-lithium perchlorate mixed solution, respectively , 1.0 μg/mL standard solution and color reaction test absorbance. Take 4 mL of standard solution and add 50 μL of oxidant (including 75 wt% NaOH and 75 wt% NaClO), 500 μL of colorant (including 40 wt% of sodium salicylate and 32 wt% of NaOH), 50 μL of catalyst (5 wt% Na ₂ [Fe(NO)(CN) ₅ ]·2H ₂ O). After standing in the dark at room temperature for 1 h, the spectrum was scanned with a UV-Vis spectrophotometer in the wavelength range of 550 nm to 800 nm, and the absorbance value at 660 nm was recorded and the concentration was plotted to obtain a standard curve.

2. Ammonia production test: take 4 mL of the electrolyte after running for 2 h at each potential, add 50 μL oxidant (including 75 wt% NaOH and 75 wt% NaClO), 500 μL colorant (including 40 wt% NaClO) in turn sodium salicylate and 32 wt% NaOH), 50 μL catalyst (5 wt% Na ₂ [Fe(NO)(CN) ₅ ] · 2H ₂ O). After standing in the dark at room temperature for 1 h, the UV-visible spectrophotometer was used for spectral scanning in the wavelength range of 550 nm to 800 nm, and the absorbance value at 660 nm was recorded, and finally the concentration of ammonia was obtained. After data processing and calculation, the multi-layer stacked nanosheet CoS-CeO ₂ has excellent effect on NRR, the ammonia yield reaches 40.5 µg h ^–1 mg ^–1 _cat. at -0.2 V (relative to standard hydrogen electrode), and the Faradaic efficiency is as high as 10.1%.

Claims (4)

1. a multi-layer stacking nanosheet CoS-CeO _The preparation method of nitrogen reduction catalyst, is characterized in that, preparation step is as follows: (1) Add a fixed proportion of cobalt and cerium reagents to a specific reaction solution to prepare a pre-reaction solution, and use the hydrothermal synthesis method to heat the pre-reaction solution at a certain temperature for a certain period of time, naturally cool, wash and dry the collected cobalt-cerium precursor ; (2) The cobalt-cerium precursor is placed in a tube furnace, the nitrogen flow rate and calcination temperature are fixed, and sulfur powder is added as a sulfidation reagent to carry out the sulfidation reaction, and the multi-layer stacked nanosheet catalyst material cobalt sulfide cerium oxide hybrid CoS-CeO ₂ is obtained. . 2. the multi-layer stacking nanosheet CoS-CeO according to claim ₁ The preparation method of nitrogen reduction catalyst is characterized in that: In the step (1), the specific reaction solution is a mixed solution of urea and thiourea; the cobalt source reagent is one or more of cobalt nitrate hexahydrate, cobalt chloride, cobalt acetylacetonate, cobalt sulfate, and cobalt acetate. The concentration of the source solution is 0.005 to 0.04 mol/L; the cerium source is one or more of cerium ammonium nitrate, hexahydrate cerium nitrate, cerium chloride heptahydrate, cerium sulfate, and cerium acetate, and the concentration of the cerium source solution is 0.002 ~ 0.02mol/L; the molar ratio of cobalt source and cerium source is 10:1 ~ 1:1; the reaction temperature of the cobalt-cerium pre-reaction solution is 100 ^o C ~ 180 ^o C, and the reaction time is 6 ~ 14 h; In the step (2), the nitrogen flow rate is 10-50 mL/min; the sulfidation reagent used is sublimated sulfur, wherein the mass ratio of the sulfidation reagent to the cobalt-cerium precursor is 1:10-1:100; the cobalt-cerium precursor is 1:10-1:100. The vulcanization temperature of the body in the tube furnace is 300 ^o C ~ 600 ^o C, the vulcanization time is 1 ~ 6 h, and the heating rate is 0.5 ^o C/min. 3. A method for preparing a multi-layer stacked nanosheet CoS-CeO ₂ nitrogen reduction catalyst, characterized in that, adopting a single-chamber membrane electrode nitrogen reduction electrocatalytic performance test, the steps are as follows: (1) CoS-CeO ₂ was prepared into 0.1 ~ 5 mg/mL ink liquid, which was dripped on the proton exchange membrane and dried at room temperature; the surface of CoS-CeO ₂ , namely the electrocatalytic nitrogen reduction membrane electrode; (2) Using the above-mentioned membrane electrode as the working electrode, the graphite electrode as the counter electrode, the Ag/AgCl electrode as the reference electrode, and the 0.1-2 mol/L sodium sulfate-lithium perchlorate mixed solution as the electrolyte, electrocatalysis was carried out. Nitrogen reduction process. 4. A method for preparing a multi-layer stacked nanosheet CoS-CeO ₂ nitrogen reduction catalyst, characterized in that the single-chamber membrane electrode nitrogen reduction electrocatalysis test system is shown in Figure 1, (1) is a fixed base ; ( ₂ ) is the membrane electrode with the CoS-CeO2 catalyst on the outside of the single-chamber electrolytic cell; (3) is the micro funnel receiver; (4) is the ammonia solution reservoir; (5) is the sodium sulfate- Lithium perchlorate mixed electrolyte; (6) is a single-chamber electrolytic cell; (7) is an inlet pipe; (8) is a counter electrode; (9) is a reference electrode; (10) is an air pressure balance outlet; (11) ) is the working electrode lead; (12) is the micro dropper; (13) is the nitrogen delivery channel.

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