Asymmetric electrolyte type efficient nitrogen fixation ammonia synthesis device and method
By using an asymmetric electrolyte-based device and method, the problems of nitrogen-nitrogen triple bond activation and hydrogen evolution competition in the electrochemical synthesis of ammonia were solved, improving ammonia yield and current efficiency, achieving efficient nitrogen dissolution and proton source supply, and enhancing the performance of ammonia synthesis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-28
- Publication Date
- 2026-03-31
AI Technical Summary
Existing electrochemical ammonia synthesis technologies suffer from low ammonia yield and current efficiency due to the difficulty in activating nitrogen-nitrogen triple bonds and strong hydrogen evolution competition reactions under mild conditions, coupled with insufficient nitrogen solubility, making it difficult to achieve efficient ammonia synthesis.
The device employs an asymmetric electrolyte type, utilizing high-nitrogen gas in the cathode chamber to dissolve the organic electrolyte and the aqueous electrolyte in the anode chamber, separated by a proton exchange membrane. The cathode chamber is loaded with a catalyst, and the anode chamber provides the proton source. Electrolysis is carried out at a potential controlled between -0.1V and -1.5V. By combining specific catalysts such as black phosphorus nanodots or MXene, the solubility of nitrogen gas is improved and hydrogen evolution competition is avoided.
This approach achieves higher ammonia yield and Faraday efficiency, reduces hydrogen evolution competition in the anhydrous cathode chamber, and provides a continuous proton source in the anode chamber, thus enhancing the practical value of ammonia synthesis.
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Abstract
Description
Technical Field
[0001] This invention relates to a process for synthesizing ammonia, specifically to an apparatus and method for high-efficiency nitrogen fixation and ammonia synthesis using an asymmetric electrolyte. Background Technology
[0002] Ammonia is an important inorganic chemical raw material, and due to its high hydrogen content (17.6%), it is considered an ideal hydrogen carrier. However, the Haber process, currently the only industrial-scale ammonia synthesis method, requires high temperature and pressure conditions (300–500℃, 200–300 atm), resulting in extremely high energy consumption, accounting for nearly 2% of the world's total annual energy consumption, and accompanied by significant CO2 emissions. Therefore, given the increasingly serious energy and environmental problems, it is essential to develop sustainable and green ammonia synthesis technologies. Among many potential alternatives to ammonia synthesis, electrochemical ammonia synthesis, especially electrocatalytic direct nitrogen reduction, is considered the most ideal technology because it can be carried out under mild conditions and can directly use water as a hydrogen source.
[0003] In recent years, although extensive research has been conducted on the electrochemical nitrogen fixation to ammonia synthesis reaction (electrocatalytic nitrogen reduction to ammonia), the low ammonia yield and current efficiency achieved so far are limited by the difficulty in activating the nitrogen-nitrogen triple bond under mild conditions, coupled with the highly competitive hydrogen evolution reaction. These figures are still far from meeting the parameters required for practical applications. Furthermore, simultaneously improving both the current efficiency and ammonia production rate in electrochemical ammonia synthesis appears extremely difficult, primarily due to the following reasons:
[0004] 1) Hydrogen ions are more easily activated than nitrogen-nitrogen triple bonds, but hydrogen is indispensable as a reactant. The unavoidable hydrogen evolution competition reaction makes it difficult to obtain nitrogen reduction catalysts with both high activity and high selectivity at the same time.
[0005] 2) In conventional aqueous electrolyte solutions, due to the low solubility of nitrogen and the enrichment and overflow of hydrogen, the amount of nitrogen available for reaction and its diffusion and adsorption are limited, making it difficult to achieve a high ammonia yield in terms of the amount of reactants.
[0006] Clearly, to overcome the aforementioned bottlenecks, it is necessary to seek more efficient nitrogen reduction electrocatalysts or to transform the electrochemical ammonia synthesis reaction system. Summary of the Invention
[0007] The purpose of this invention is to overcome the shortcomings and deficiencies of the prior art and to provide an apparatus and method for efficient nitrogen fixation and ammonia synthesis using an asymmetric electrolyte.
[0008] This invention is achieved through the following technical solution:
[0009] An apparatus for efficient nitrogen fixation and ammonia synthesis using an asymmetric electrolyte type includes a cathode chamber 4 and an anode chamber 6; the cathode chamber 4 and the anode chamber 6 are connected by a pipeline, and a diaphragm 5 is installed in the pipeline;
[0010] The cathode chamber 4 is filled with a high-nitrogen dissolved organic electrolyte and is equipped with a working electrode 1 and a reference electrode 2; the working electrode 1 is loaded with a catalyst.
[0011] The anode chamber 6 is filled with an aqueous electrolyte and is equipped with a counter electrode 3;
[0012] The counter electrode 3, reference electrode 2 and working electrode 1 are electrically connected to the electrochemical workstation;
[0013] The cathode chamber 4 is provided with an air inlet and an air outlet at the top.
[0014] The diaphragm 5 is a proton exchange membrane.
[0015] The catalyst can be a metal or a non-metal catalyst.
[0016] The nitrogen gas in the cathode chamber 4 dissolves organic electrolytes such as methanol, ethanol, propanol, etc., and the solute is a conductive salt that can dissolve in alcohol, such as lithium chloride, sodium chloride, lithium carbonate, lithium sulfate, sodium sulfate, etc.
[0017] The reference electrode 2 is an Ag / AgCl electrode filled with electrolyte or a silver wire electrode.
[0018] The counter electrode 3 is an inert electrode. The inert electrode is a platinum electrode, a gold electrode, or a carbon electrode.
[0019] The aqueous electrolyte in the anode chamber 6 is an acidic solution such as hydrochloric acid or sulfuric acid, an alkaline solution such as sodium hydroxide or potassium hydroxide, or a neutral solution such as sodium sulfate or PBS.
[0020] An efficient nitrogen fixation and ammonia synthesis method using an asymmetric electrolyte system includes the following steps:
[0021] S1. Insert the nitrogen gas inlet tube through the gas outlet into the bottom of the nitrogen-dissolving organic electrolyte in the cathode chamber 4, and continuously ventilate at a flow rate of 10-100 mL / min; connect the gas outlet of the cathode chamber 4 to the absorption bottle containing the acidic solution.
[0022] S2. Simultaneously turn on the electrochemical workstation, set the potential of the electrochemical workstation to -0.1V to -1.5V (potential relative to the reference electrode), and the time is 1 to 4 hours;
[0023] S3. Collect the electrolyte and absorbent after electrolysis and mix them. Quantitatively detect the ammonia product in the electrolyte. The detection equipment is ultraviolet-near-infrared spectrometer with indophenol blue method, Nessler reagent spectrophotometry, or nuclear magnetic resonance spectrometer.
[0024] S4. To avoid the influence of organic solvents on the quantitative detection of ammonia, the electrolyte after electrolysis needs to be pretreated: the electrolyte is adjusted to acidity with hydrochloric acid, and then the acidic electrolyte is heated to completely evaporate the organic solvent, leaving ammonium chloride and the corresponding solute salt solid; then, water of the same amount as the original electrolyte is added to the dried solid salt; finally, the ammonium chloride aqueous solution is quantitatively detected by ultraviolet spectrophotometry.
[0025] Compared with the prior art, the present invention has the following advantages and effects:
[0026] The reaction system (device) proposed in this invention can not only improve the solubility of nitrogen, but also avoid the strong hydrogen evolution competition reaction in the anhydrous environment of the cathode chamber, thus achieving a high ammonia yield and Faraday efficiency.
[0027] In the reaction system of this invention, the proton source required for ammonia synthesis at the cathode can be continuously supplied by water electrolysis at the anode, making it more practical. Attached Figure Description
[0028] Figure 1 This is a schematic diagram of the apparatus for efficient nitrogen fixation and ammonia synthesis using an asymmetric electrolyte type according to the present invention.
[0029] Figure 2 This is a flowchart of the ammonia detection method in the ammonia synthesis method of the present invention.
[0030] Figure 3 The graphs show the ammonia synthesis performance measured in Examples 1-4. Detailed Implementation
[0031] The present invention will now be described with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.
[0032] Unless otherwise specified in the examples, standard conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0033] like Figure 1 As shown, the present invention discloses an apparatus for efficient nitrogen fixation and ammonia synthesis using an asymmetric electrolyte, comprising a cathode chamber 4 and an anode chamber 6; the cathode chamber 4 and the anode chamber 6 are connected by a pipeline, and a diaphragm 5 is provided in the pipeline;
[0034] The cathode chamber 4 is filled with a high-nitrogen dissolved organic electrolyte and is equipped with a working electrode 1 and a reference electrode 2; the working electrode 1 is loaded with a catalyst.
[0035] The anode chamber 6 is filled with an aqueous electrolyte and is equipped with a counter electrode 3;
[0036] The counter electrode 3, reference electrode 2 and working electrode 1 are electrically connected to the electrochemical workstation;
[0037] The cathode chamber 4 is provided with an air inlet and an air outlet at the top.
[0038] The diaphragm 5 is a proton exchange membrane.
[0039] The catalyst can be a metal or a non-metal catalyst.
[0040] The nitrogen gas in the cathode chamber 4 dissolves organic electrolytes such as methanol, ethanol, propanol, etc., and the solute is a conductive salt that can dissolve in alcohol, such as lithium chloride, sodium chloride, lithium carbonate, lithium sulfate, sodium sulfate, etc.
[0041] The reference electrode 2 is an Ag / AgCl electrode filled with electrolyte or a silver wire electrode.
[0042] The counter electrode 3 is an inert electrode. The inert electrode is a platinum electrode, a gold electrode, or a carbon electrode.
[0043] The aqueous electrolyte in the anode chamber 6 is an acidic solution such as hydrochloric acid or sulfuric acid, an alkaline solution such as sodium hydroxide or potassium hydroxide, or a neutral solution such as sodium sulfate or PBS.
[0044] The present invention will be further described below with reference to the embodiments.
[0045] Example 1
[0046] like Figure 1 As shown in the diagram, this embodiment exemplarily provides an apparatus diagram for a highly efficient nitrogen-fixing ammonia synthesis system using an asymmetric electrolyte. It includes a cathode chamber 4 containing an organic electrolyte and an anode chamber 6 containing an aqueous electrolyte, separated by a proton exchange membrane 5. The working electrode 1, reference electrode 2, and counter electrode 3 are connected to an electrochemical workstation.
[0047] In this embodiment, the electrolyte in the cathode chamber is a 0.5M LiSO4 anhydrous methanol solution, and the electrolyte in the anode chamber is a 0.5M NaOH aqueous solution. A carbon cloth loaded with black phosphorus nanodots is clamped onto a platinum electrode holder as the working electrode. The counter electrode is a platinum sheet, and the reference electrode is Ag / AgCl containing the cathode electrolyte. Electrolysis was conducted under continuous nitrogen flow, with the potential set to -0.7V vs. Ag / AgCl, and the electrolysis time was 2 hours. An absorbent containing 2M HCl was introduced into the cathode chamber outlet. After electrolysis, to avoid the influence of methanol on ammonia detection, the absorbent and cathode electrolytes were mixed, using a method as follows: Figure 2 The process shown pretreats the mixture. After heating as shown in step ①, methanol evaporates, leaving solid LiSO4 and NH4Cl. In step ②, an aqueous solution of equal volume to the original electrolyte is added to the solid to obtain an aqueous solution of LiSO4 and NH4Cl. Finally, the ammonia concentration of the aqueous solution is detected and analyzed.
[0048] Example 2
[0049] In this embodiment, the electrolyte in the cathode chamber is an anhydrous methanol solution of 0.5M NaCl, and the electrolyte in the anode chamber is an aqueous solution of 0.5M HCl. A carbon cloth loaded with black phosphorus nanodots is clamped onto a platinum electrode holder as the working electrode. The counter electrode is a platinum sheet, and the reference electrode is Ag / AgCl containing the cathode electrolyte. Electrolysis is performed under continuous nitrogen flow, with the potential set to -0.7V vs. Ag / AgCl, and the electrolysis time is 2 hours. An absorbent containing 2M HCl is introduced into the cathode chamber outlet. After electrolysis, to avoid the influence of methanol on ammonia detection, the absorbent and cathode electrolytes are mixed, using a method such as… Figure 2 The process shown pretreats the mixture. After heating as shown in step ①, methanol evaporates, leaving NaCl and NH4Cl solids. In step ②, an aqueous solution of equal volume to the original electrolyte is added to the solids to obtain an aqueous solution of NaCl and NH4Cl. Finally, the ammonia concentration of the aqueous solution is detected and analyzed.
[0050] Example 3
[0051] In this embodiment, the electrolyte in the cathode chamber is a 0.5M LiCl anhydrous methanol solution, and the electrolyte in the anode chamber is a 0.5M PBS aqueous solution. A carbon cloth loaded with MXene is clamped onto a platinum electrode holder as the working electrode. The counter electrode is a platinum sheet, and the reference electrode is Ag / AgCl containing the cathode electrolyte. Electrolysis was conducted under continuous nitrogen flow, with the potential set to -0.7V vs. Ag / AgCl, and the electrolysis time was 2 hours. An absorbent containing 2M HCl was introduced into the cathode chamber outlet. After electrolysis, to avoid the influence of methanol on ammonia detection, the absorbent and cathode electrolytes were mixed using a method such as… Figure 2 The process shown pretreats the mixture. After heating as shown in step ①, methanol evaporates, leaving solid LiCl and NH4Cl. In step ②, an aqueous solution of equal volume to the original electrolyte is added to the solid to obtain an aqueous solution of LiCl and NH4Cl. Finally, the ammonia concentration of the aqueous solution is detected and analyzed.
[0052] Example 4
[0053] In this embodiment, the electrolyte in the cathode chamber is a 0.5M LiCl anhydrous methanol solution, and the electrolyte in the anode chamber is a 0.5M H2SO4 aqueous solution. A composite carbon cloth loaded with MXene and black phosphorus nanodots is clamped onto a platinum electrode holder as the working electrode. The counter electrode is a platinum sheet, and the reference electrode is Ag / AgCl containing the cathode electrolyte. Electrolysis was conducted under continuous nitrogen flow, with the potential set to -0.7V vs. Ag / AgCl, and the electrolysis time was 2 hours. An absorbent containing 2M HCl was introduced into the cathode chamber outlet. After electrolysis, to avoid the influence of methanol on ammonia detection, the absorbent and cathode electrolytes were mixed using a method such as… Figure 2 The process shown pretreats the mixture. After heating as shown in step ①, methanol evaporates, leaving solid LiCl and NH4Cl. In step ②, an aqueous solution of equal volume to the original electrolyte is added to the solid to obtain an aqueous solution of LiCl and NH4Cl. Finally, the ammonia concentration of the aqueous solution is detected and analyzed.
[0054] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. An apparatus for high efficiency nitrogen fixation for ammonia synthesis of asymmetric electrolyte type, characterized by: It comprises a cathode chamber (4) and an anode chamber (6); the cathode chamber (4) and the anode chamber (6) are connected through a pipeline, and a diaphragm (5) is arranged in the pipeline; The cathode chamber (4) is filled with nitrogen-dissolved organic electrolyte, and is provided with a working electrode (1) and a reference electrode (2); the working electrode (1) is loaded with a catalyst; The anode chamber (6) is filled with aqueous electrolyte, and is provided with a counter electrode (3); The counter electrode (3), the reference electrode (2) and the working electrode (1) are electrically connected to an electrochemical workstation.
2. The apparatus for asymmetric electrolyte type high efficient nitrogen fixation and ammonia synthesis according to claim 1, characterized in that: The cathode chamber (4) is provided with an air inlet hole and an air outlet hole at the top.
3. The apparatus for asymmetric electrolyte type high efficient nitrogen fixation and ammonia synthesis according to claim 1, characterized in that: The diaphragm (5) is a proton exchange membrane.
4. The apparatus for asymmetric electrolyte type high efficient nitrogen fixation and ammonia synthesis according to claim 1, characterized in that: The catalyst is a metal or non-metal catalyst.
5. The apparatus for asymmetric electrolyte type high efficient nitrogen fixation and ammonia synthesis according to claim 1, characterized in that: The nitrogen-dissolved organic electrolyte in the cathode chamber (4) is an alcohol.
6. The apparatus for asymmetric electrolyte type high efficient nitrogen fixation and ammonia synthesis according to claim 1, characterized in that: The reference electrode (2) is an Ag / AgCl electrode or a silver wire electrode filled with electrolyte.
7. The apparatus for asymmetric electrolyte type high efficient nitrogen fixation and ammonia synthesis according to claim 1, characterized in that: The counter electrode (3) is an inert electrode.
8. The apparatus for asymmetric electrolyte type high efficient nitrogen fixation and ammonia synthesis according to claim 1, characterized in that: The aqueous electrolyte in the anode chamber (6) is an acidic, alkaline or neutral aqueous solution.
9. The apparatus for asymmetric electrolyte type high efficient nitrogen fixation and ammonia synthesis according to claim 7, characterized in that: The inert electrode is a platinum electrode, a gold electrode or a carbon electrode.
10. A method of efficient nitrogen fixation for ammonia synthesis in asymmetric electrolyte system, characterized by The device is realized by any one of claims 1-9, comprising the following steps: S1, a nitrogen gas inlet pipe is inserted into the bottom of the nitrogen-dissolved organic electrolyte in the cathode chamber (4) from the air outlet hole, and the nitrogen gas is continuously supplied at a flow rate of 10-100 mL / min; the air outlet hole of the cathode chamber (4) is connected to an absorption bottle containing an acidic solution; S2, the electrochemical workstation is turned on at the same time, and the potential of the electrochemical workstation is set to-0.1V to-1.5V for 1-4h; S3, the electrolyzed electrolyte and the absorption liquid are collected and mixed, and the product ammonia in the electrolyte is quantitatively detected; the detection equipment is an ultraviolet-near infrared spectrometer or a nuclear magnetic resonance spectrometer; S4, in order to avoid the influence of the existence of organic solvent on the quantitative detection of ammonia, the electrolyzed electrolyte needs to be pretreated: the electrolyte is adjusted to be acidic by hydrochloric acid, then the acidic electrolyte is heated to completely volatilize the organic solvent, leaving ammonium chloride and the corresponding solute salt solid; then an equal amount of water as the original electrolyte is added to the dried solid salt; finally, the ammonium chloride aqueous solution is quantitatively detected by ultraviolet spectrophotometry.