Method for synthesizing ammonia through metal-mediated catalysis without externally introducing hydrogen

Abstract

The invention discloses a metal-mediated catalytic synthesis ammonia method without external introduction of hydrogen, which comprises the following steps: firstly, an anode, a cathode, an anolyte, a catholyte and a proton exchange membrane are assembled into a reaction system, the anolyte contains a proton source, and the proton source comprises an alcohol organic compound or an aldehyde organic compound; the anode and the cathode are made of the same materials and are transition metal loaded catalysts; then introducing nitrogen into the cathode electrolyte, electrifying a reaction system, and heating and pressurizing; performing electrochemical oxidation reaction on the proton source to generate acid and release protons; and the protons are directionally transmitted into the catholyte through the proton exchange membrane, and are subjected to an electrocatalytic reduction reaction with nitrogen on the surface of the catalyst to generate nitrogen. According to the method, the protons are supplied in situ through oxidation of the anolyte, and the metal is combined to catalyze nitrogen reduction, so that ammonia can be synthesized under the condition of no exogenous hydrogen, the energy consumption of a reaction system is reduced, and the yield of the synthesized ammonia is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ammonia synthesis, and particularly relates to a method for metal-mediated catalytic ammonia synthesis without external hydrogen supply. Background Art

[0002] Currently, traditional ammonia synthesis methods mainly include the Haber-Bosch method, the electrochemical ammonia synthesis method in aqueous systems, and the metal-mediated catalytic ammonia synthesis method. Most of these synthesis methods face problems such as high energy consumption, large emissions, and low ammonia production rates. Among them: The Haber-Bosch method for ammonia synthesis relies on high temperature and high pressure (400 - 500 °C, 15 - 25 MPa) and requires hydrogen as a raw material, with high energy consumption and large carbon emissions. The electrochemical ammonia synthesis method in aqueous systems can achieve the reduction of N2 to ammonia at room temperature and normal pressure, but is limited by the high dissociation energy of the N≡N bond, resulting in low ammonia production rates.

[0003] The metal-mediated catalytic ammonia synthesis method generates an MN x intermediate through the reaction of metal (M) with N2, which can effectively improve the activation efficiency of the N≡N bond. However, in the prior art, this reaction system requires external hydrogen supply or the addition of a proton source in the organic electrolyte system of the same reaction chamber. Therefore, the composition of the electrolyte usually includes various components such as organic solvents, organic proton donors, and organic conductive aids, with extremely complex components. The low dissociation efficiency of the organic proton donor to release protons leads to low ammonia synthesis efficiency, difficult separation and purification of ammonia, and high cost of ammonia synthesis. In addition, due to the poor conductivity of the organic solution, the ammonia synthesis efficiency of the existing metal-mediated catalytic ammonia synthesis technology is low. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above prior art. For this purpose, the present invention provides a method for metal-mediated catalytic ammonia synthesis without external hydrogen supply. This method oxidizes the anode electrolyte to supply protons in situ and combines with metal-catalyzed nitrogen reduction to achieve ammonia synthesis under the condition of no external hydrogen source, which not only reduces the energy consumption of the reaction system but also improves the ammonia production rate.

[0005] The inventive concept of the present invention is as follows: In the traditional method of metal-mediated catalytic ammonia synthesis, either hydrogen is externally supplied, resulting in high energy consumption; or a proton source is added to the organic electrolyte system in the same reaction chamber, requiring the simultaneous progress of cathode nitrogen reduction and proton source dissociation. Not only is it difficult to dissociate protons, but the process of dissociating protons competes with the process of nitrogen reduction, leading to a low ammonia synthesis yield. In the present invention, an alcohol organic compound or an aldehyde organic compound is used as the anolyte. The alcohol or aldehyde is oxidized to an acid at the anode and dissociates protons. The protons pass through the proton exchange membrane into the cathode and directly serve as the proton donor for cathode nitrogen reduction, participating in the metal-mediated ammonia synthesis reaction. Therefore, by replacing the hydrogen oxidation reaction with in-situ generated protons, the present invention not only eliminates the need for external hydrogen supply and saves the energy consumption of the hydrogen synthesis process, but also the acid generated by anodic oxidation can efficiently dissociate protons and supply them to the cathode ammonia synthesis reaction, greatly improving the ammonia synthesis yield.

[0006] To solve the above technical problems, a first aspect of the present invention provides a method for metal-mediated catalytic ammonia synthesis, comprising the following steps:

[0007] (1) Assemble an anode, a cathode, an anolyte, a catholyte, and a proton exchange membrane into a reaction system, and the proton exchange membrane is disposed between the anolyte and the catholyte;

[0008] The anolyte contains a proton source, and the proton source includes an alcohol organic compound or an aldehyde organic compound; the materials of the anode and the cathode are the same, and both are catalysts loaded with transition metals;

[0009] (2) Introduce nitrogen into the catholyte, and power on, heat, and pressurize the reaction system assembled in step (1); the proton source undergoes an electrochemical oxidation reaction to generate an acid and release protons; the protons are directionally transported through the proton exchange membrane into the catholyte and electrocatalytically reduce with nitrogen on the surface of the catalyst to synthesize the nitrogen.

[0010] In some embodiments of the present invention, in step (1), the alcohol organic compound is selected from at least one of C1-C6 alcohols. Preferably, it is at least one of methanol, ethanol, propanol, and benzyl alcohol.

[0011] In some embodiments of the present invention, in step (1), the aldehyde organic compound is selected from at least one of C1-C6 aldehydes. Preferably, it is at least one of formaldehyde, acetaldehyde, propionaldehyde, and benzaldehyde.

[0012] In some embodiments of the present invention, in step (1), the anolyte further contains an organic solvent, and in the anolyte, the concentration of the proton source is 0.1-9 mol / L.

[0013] In some embodiments of the present invention, in step (1), the catholyte contains a soluble metal salt and an organic solvent, and the soluble metal salt is selected from at least one of hexafluorophosphate, bis(fluorosulfonyl)imide salt, chloride salt, and fluoride salt.

[0014] In some embodiments of the present invention, the metal ion of the soluble metal salt is selected from Li + , Na + , K + , Rb + , Cs + , Ca 2+ , Mg 2+ and at least one of them. These metal ions are beneficial to promoting the activation of nitrogen and further improving the efficiency of ammonia synthesis.

[0015] In some embodiments of the present invention, in the catholyte, the concentration of the metal ion is 0.001 - 3 mol / L.

[0016] In some embodiments of the present invention, the organic solvents in the anolyte and catholyte are the same, and are each selected from at least one of propylene carbonate, dimethyl carbonate, ethylene carbonate, tetrahydrofuran, methyl propyl carbonate, methyl formate, dimethyl phthalate, γ-butyrolactone, and maleic anhydride.

[0017] In some embodiments of the present invention, in step (1), the transition metal supported on the catalyst is selected from any one of Fe, Ru, Mo, Ni, Co, Bi, and Cu as a single metal or an alloy of at least two of them. These transition metals all have good nitrogen activation ability.

[0018] In some embodiments of the present invention, the loading amount of the transition metal is 0.1 - 5 wt%.

[0019] In some embodiments of the present invention, the catalyst further includes a support, and the metal is supported on the support; the support sequentially includes a conductive substrate, a transition metal layer, and a surface modification layer from bottom to top. Preferably, the conductive substrate is carbon cloth, the transition metal layer is an Fe2O3 layer, and the surface modification layer is a CeO2 layer.

[0020] In some embodiments of the present invention, the preparation method of the catalyst includes the following steps:

[0021] 1) Add an aqueous solution of a soluble iron salt and carbon cloth into a reaction kettle, carry out a hydrothermal reaction, and dry the reaction product to obtain an Fe2O3 precursor grown on the carbon cloth;

[0022] 2) Disperse the Fe2O3 precursor prepared in step 1) in an aqueous solution of a soluble cerium salt to obtain a mixed solution, and carry out a hydrothermal reaction to obtain a Fe2O3 / CeO2 precursor grown on carbon cloth;

[0023] 3) Calcinate the Fe2O3 / CeO2 precursor prepared in step 2) in an air atmosphere to obtain Fe2O3 / CeO2 grown on carbon cloth, i.e., the carrier;

[0024] 4) Add the carrier prepared in step 3) and a reducing agent to an aqueous solution of a soluble transition metal salt to obtain a carrier loaded with a transition metal, i.e., the catalyst.

[0025] In some embodiments of the present invention, in step 1), the concentration of the aqueous solution of the soluble iron salt is 0.01 - 0.03 mol / L.

[0026] In some embodiments of the present invention, in step 2), the concentration of the aqueous solution of the soluble cerium salt is 0.01 - 0.03 mol / L.

[0027] In some embodiments of the present invention, in step 2), in the mixed solution, the molar ratio of Fe 3+ and Ce 4+ is (3 - 5):1.

[0028] In some embodiments of the present invention, in steps 1) and 2), the temperature of the hydrothermal reaction is 120 - 140 °C, and the reaction time is 6 - 10 hours.

[0029] In some embodiments of the present invention, in step 3), the calcination temperature is 300 - 400 °C, and the calcination time is 1 - 3 hours.

[0030] In some embodiments of the present invention, in step 4), the aqueous solution of the soluble transition metal salt is selected from the aqueous solutions of soluble salts of at least one transition metal among Fe, Ru, Mo, Ni, Co, Bi, and Cu.

[0031] In some embodiments of the present invention, the concentration of the aqueous solution of the soluble transition metal salt is 0.01 - 0.5 mmol / L.

[0032] In some embodiments of the present invention, the reducing agent includes sodium borohydride.

[0033] In some embodiments of the present invention, in step (1), the proton exchange membrane is a perfluorosulfonic acid-based composite membrane.

[0034] In some embodiments of the present invention, in step (1), the thickness of the proton exchange membrane is 50 - 200 μm, and the proton conductivity ≥ 0.1 S / cm.

[0035] In some embodiments of the present invention, in step (2), the heating temperature is 25 - 100 °C.

[0036] In some embodiments of the present invention, in step (2), the pressure of pressurization is 0.1 - 5 MPa.

[0037] The above technical solution of the present invention has at least the following technical effects or advantages compared with the prior art:

[0038] (1) In the present invention, an alcohol organic compound or an aldehyde organic compound is used as the anolyte. The alcohol or aldehyde is oxidized to an acid at the anode and dissociates protons. The protons enter the cathode through the proton exchange membrane and directly serve as the proton donor for the reduction of nitrogen at the cathode, participating in the reaction of metal-mediated ammonia synthesis without externally introducing hydrogen, saving the energy consumption of the hydrogen synthesis process.

[0039] (2) The method for synthesizing ammonia in the present invention does not require adding a proton source to the catholyte, simplifies the composition of the electrolyte, makes it easy to separate and purify the acid product and the ammonia product, thereby improving the yield of ammonia synthesis and reducing the cost of ammonia synthesis. At the same time, the oxidation reaction of the alcohol or aldehyde at the anode can also obtain high-value-added acid products.

[0040] (3) In the present invention, the oxidation of alcohol or aldehyde at the anode generates an acid, which can efficiently dissociate protons in situ and provide them to the ammonia synthesis reaction at the cathode; moreover, the proton dissociation process and the nitrogen reduction process are carried out separately without competition; thus, the yield of ammonia synthesis is greatly improved, and the ammonia yield can reach 1.03×10 -8 mol / (cm 2 ·s) to 9.2×10 -8 mol / (cm 2 ·s). BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the reaction of metal-mediated catalytic ammonia synthesis of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The present invention will be specifically described below in conjunction with embodiments for the understanding of those skilled in the art. It is necessary to specifically point out here that the embodiments are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Those skilled in the art, based on the above-mentioned inventive content, make non-essential improvements and adjustments to the present invention, which should still fall within the protection scope of the present invention. At the same time, for the raw materials not specifically described below, they are all commercially available products; for the process steps or preparation methods not specifically mentioned, they are all process steps or preparation methods known to those skilled in the art.

[0043] Example 1

[0044] A method for metal-mediated catalytic ammonia synthesis, comprising the following steps:

[0045] (1) Preparation of the catalyst (FeRu / CeO2 / Fe2O3 grown on a carbon cloth conductive substrate)

[0046] Dissolve 1 mmol of iron nitrate in 60 mL of deionized water, then pour it into a hydrothermal reaction kettle containing carbon cloth, and react at 120 °C for 6 hours to obtain the Fe2O3 precursor grown on the carbon cloth. Then dissolve 0.5 mmol of cerium nitrate in 30 mL of deionized water, add the Fe2O3 precursor, and react at 140 °C for 8 hours to obtain the Fe2O3 / CeO2 precursor. Then calcine the Fe2O3 / CeO2 precursor in an air atmosphere at 350 °C for 2 hours to obtain Fe2O3 / CeO2 grown on the carbon cloth. Prepare 20 mL of a mixed aqueous solution of iron nitrate and ruthenium nitrate with a total concentration of 0.01 mmol / L, and the molar ratio of iron to ruthenium is 1:1. After adding Fe2O3 / CeO2 and stirring for 30 minutes, add 10 mL of a 0.01 mmol / L aqueous solution of sodium borohydride dropwise, and continue stirring for 1 hour to obtain the FeRu / CeO2 / Fe2O3 catalyst grown on the carbon cloth conductive substrate. The content of Ru in the catalyst is 0.03 wt%, and the content of Fe in the catalyst is 0.01 wt%.

[0047] (2) Assembly of the reaction system

[0048] Assemble the anode, cathode, anolyte, catholyte, and proton exchange membrane into a reaction system, where: the proton exchange membrane is disposed between the anolyte and the catholyte; the cathode and the anode are the catalysts prepared in step (1), with an area of 1 cm 2 ; the anolyte is propylene carbonate dissolved with 0.1 mol / L of formaldehyde, the catholyte is propylene carbonate dissolved with 0.001 mol / L of lithium hexafluorophosphate; the proton exchange membrane is a perfluorosulfonic acid-based composite membrane with a thickness of 50 μm and a proton conductivity of 2.0 S / cm.

[0049] (3) Metal-mediated catalytic ammonia synthesis

[0050] Introduce nitrogen into the catholyte of the reaction system assembled in step (2), and at 25 °C and 0.1 MPa conditions, apply a working voltage of 1.0 V. Formaldehyde undergoes an electrochemical oxidation reaction to generate acid and release protons; the protons are directionally transported through the proton exchange membrane to the catholyte, and electrocatalytic reduction reaction occurs with nitrogen on the catalyst surface to generate nitrogen, and its reaction schematic diagram is as Figure 1 shown.

[0051] Example 2

[0052] A method for metal-mediated catalytic ammonia synthesis, comprising the following steps:

[0053] (1) Preparation of the catalyst (Ni / CeO2 / Fe2O3 grown on a carbon cloth conductive substrate)

[0054] Dissolve 1 mmol of iron nitrate in 60 mL of deionized water, then pour it into a hydrothermal reaction kettle containing carbon cloth, and react at 120 °C for 6 hours to obtain the Fe2O3 precursor grown on the carbon cloth. Then dissolve 0.5 mmol of cerium nitrate in 30 mL of deionized water, add the Fe2O3 precursor, and react at 140 °C for 8 hours to obtain the Fe2O3 / CeO2 precursor. Then calcine the Fe2O3 / CeO2 precursor in an air atmosphere at 350 °C for 2 hours to obtain Fe2O3 / CeO2 grown on the carbon cloth. Prepare 20 mL of an aqueous nickel nitrate solution with a concentration of 0.1 mmol / L, add Fe2O3 / CeO2 and stir for 30 minutes, then dropwise add 10 mL of an aqueous sodium borohydride solution with a concentration of 0.01 mmol / L, and continue to stir for 1 hour to obtain the Ni / CeO2 / Fe2O3 catalyst grown on the carbon cloth conductive substrate. The content of Ni in the catalyst is 2.1 wt%.

[0055] (2) Assembly of the reaction system

[0056] Assemble the anode, cathode, anolyte, catholyte, and proton exchange membrane into a reaction system, where: the proton exchange membrane is disposed between the anolyte and the catholyte; the cathode and anode are the catalysts prepared in step (1), with an area of 1 cm 2 ; the anolyte is dimethyl carbonate dissolved with 1 mol / L of methanol, and the catholyte is dimethyl carbonate dissolved with 0.1 mol / L of cesium chloride; the proton exchange membrane is a perfluorosulfonic acid-based composite membrane with a thickness of 100 μm and a proton conductivity of 1.0 S / cm.

[0057] (3) Metal-mediated catalytic ammonia synthesis

[0058] Introduce nitrogen into the catholyte of the reaction system assembled in step (2), and under the conditions of 40 °C and 0.1 MPa, apply a working voltage of 1.0 V. Methanol undergoes an electrochemical oxidation reaction to generate acid and release protons; the protons are directionally transported through the proton exchange membrane into the catholyte, and react with nitrogen on the catalyst surface to generate nitrogen through an electrocatalytic reduction reaction. The reaction schematic diagram is as Figure 1 shown.

[0059] Example 3

[0060] A method for metal-mediated catalytic ammonia synthesis, comprising the following steps:

[0061] (1) Preparation of catalyst (BiCu / CeO2 / Fe2O3 grown on carbon cloth conductive substrate)

[0062] Dissolve 1 mmol of iron nitrate in 60 mL of deionized water, then pour it into a hydrothermal reactor containing carbon cloth, and react at 120 °C for 6 hours to obtain the Fe2O3 precursor grown on the carbon cloth. Then dissolve 0.5 mmol of cerium nitrate in 30 mL of deionized water, add the Fe2O3 precursor, and react at 140 °C for 8 hours to obtain the Fe2O3 / CeO2 precursor. Then calcine the Fe2O3 / CeO2 precursor in an air atmosphere at 350 °C for 2 hours to obtain Fe2O3 / CeO2 grown on the carbon cloth. Prepare 20 mL of a mixed aqueous solution of molybdenum nitrate and cobalt nitrate with a total concentration of 0.05 mmol / L, and the molar ratio of molybdenum to cobalt is 1:1. After adding Fe2O3 / CeO2 and stirring for 30 minutes, add 10 mL of a 0.05 mmol / L aqueous solution of sodium borohydride dropwise, and continue stirring for 1 hour to obtain the MoCo / CeO2 / Fe2O3 catalyst grown on the carbon cloth conductive substrate. The content of Mo in the catalyst is 0.1 wt%, and the content of Co in the catalyst is 0.15 wt%.

[0063] (2) Assembly of the reaction system

[0064] Assemble the anode, cathode, anolyte, catholyte, and proton exchange membrane into a reaction system, where: the proton exchange membrane is arranged between the anolyte and the catholyte; the cathode and the anode are the catalysts prepared in step (1), with an area of 1 cm 2 ; the anolyte is ethylene carbonate dissolved with 1 mol / L ethanol, the catholyte is ethylene carbonate dissolved with 1 mol / L sodium chloride; the proton exchange membrane is a perfluorosulfonic acid-based composite membrane with a thickness of 100 μm and a proton conductivity of 1.0 S / cm.

[0065] (3) Metal-mediated catalytic synthesis of ammonia

[0066] Introduce nitrogen into the catholyte of the reaction system assembled in step (2), and under the conditions of 60 °C and 1 MPa, apply a working voltage of 1.0 V. Ethanol undergoes an electrochemical oxidation reaction to generate acid and release protons; the protons are transported directionally through the proton exchange membrane to the catholyte, and react with nitrogen on the catalyst surface to generate nitrogen through an electrocatalytic reduction reaction. The reaction schematic diagram is as Figure 1 shown.

[0067] Example 4

[0068] A method for metal-mediated catalytic synthesis of ammonia, comprising the following steps:

[0069] (1) Preparation of catalyst (BiCu / CeO2 / Fe2O3 grown on carbon cloth conductive substrate)

[0070] Dissolve 1 mmol of iron nitrate in 60 mL of deionized water, then pour it into a hydrothermal reactor containing carbon cloth, and react at 120 °C for 6 hours to obtain the Fe2O3 precursor grown on the carbon cloth. Then dissolve 0.5 mmol of cerium nitrate in 30 mL of deionized water, add the Fe2O3 precursor, and react at 140 °C for 8 hours to obtain the Fe2O3 / CeO2 precursor. Then calcine the Fe2O3 / CeO2 precursor in an air atmosphere at 350 °C for 2 hours to obtain Fe2O3 / CeO2 grown on the carbon cloth. Prepare a 20 mL mixed ethylene glycol and aqueous solution of bismuth nitrate and cobalt nitrate with a total concentration of 0.5 mmol / L, and the molar ratio of bismuth to cobalt is 1:1. After adding Fe2O3 / CeO2 and stirring for 30 minutes, dropwise add 10 mL of 0.5 mmol / L sodium borohydride aqueous solution, and continue stirring for 1 hour to obtain the BiCu / CeO2 / Fe2O3 catalyst grown on the carbon cloth conductive substrate. The content of Bi in the catalyst is 0.2 wt%, and the content of Cu in the catalyst is 5 wt%.

[0071] (2) Assembly of the reaction system

[0072] Assemble the anode, cathode, anolyte, catholyte, and proton exchange membrane into a reaction system, where: the proton exchange membrane is disposed between the anolyte and the catholyte; the cathode and the anode are the catalysts prepared in step (1), with an area of 1 cm 2 ; the anolyte is ethylene carbonate dissolved with 9 mol / L acetaldehyde, and the catholyte is ethylene carbonate dissolved with 3 mol / L potassium chloride; the proton exchange membrane is a perfluorosulfonic acid-based composite membrane with a thickness of 100 μm and a proton conductivity of 1.0 S / cm.

[0073] (3) Metal-mediated catalytic ammonia synthesis

[0074] Introduce nitrogen into the catholyte of the reaction system assembled in step (2), and at 100 °C and 0.5 MPa conditions, apply a working voltage of 1.0 V. Acetaldehyde undergoes an electrochemical oxidation reaction to generate acid and release protons; the protons are directionally transported through the proton exchange membrane into the catholyte, and electrocatalytic reduction reaction occurs with nitrogen on the catalyst surface to generate nitrogen, and its reaction schematic diagram is as Figure 1 shown.

[0075] Example 5

[0076] A method for metal-mediated catalytic ammonia synthesis, comprising the following steps:

[0077] (1) Prepare a catalyst (BiCu / CeO2 / Fe2O3 grown on a carbon cloth conductive substrate) using the same preparation method as in Example 4.

[0078] (2) Assembly of the reaction system

[0079] Assemble the anode, cathode, anolyte, catholyte, and proton exchange membrane into a reaction system, where: The proton exchange membrane is disposed between the anolyte and the catholyte; The cathode and anode are the catalysts prepared in step (1), with an area of 1 cm 2 ; The anolyte is tetrahydrofuran dissolved with 9 mol / L propanol, and the catholyte is tetrahydrofuran dissolved with 3 mol / L potassium chloride; The proton exchange membrane is a perfluorosulfonic acid-based composite membrane with a thickness of 200 μm and a proton conductivity of 0.1 S / cm.

[0080] (3) Metal-mediated catalytic ammonia synthesis

[0081] Introduce nitrogen into the catholyte of the reaction system assembled in step (2). Under the conditions of 40 °C and 2 MPa, apply a working voltage of 1.0 V. Propanol undergoes an electrochemical oxidation reaction to generate acid and release protons; The protons are directionally transported through the proton exchange membrane into the catholyte and undergo an electrocatalytic reduction reaction with nitrogen on the surface of the catalyst to generate nitrogen. The reaction schematic diagram is as Figure 1 shown.

[0082] Example 6

[0083] A method for metal-mediated catalytic ammonia synthesis, comprising the following steps:

[0084] (1) Prepare a catalyst (BiCu / CeO2 / Fe2O3 grown on a carbon cloth conductive substrate) using the same preparation method as in Example 4.

[0085] (2) Assembly of the reaction system

[0086] Assemble the anode, cathode, anolyte, catholyte, and proton exchange membrane into a reaction system, where: The proton exchange membrane is disposed between the anolyte and the catholyte; The cathode and anode are the catalysts prepared in step (1), with an area of 1 cm 2 ; The anolyte is methyl propyl carbonate dissolved with 9 mol / L propionaldehyde, and the catholyte is methyl propyl carbonate dissolved with 3 mol / L potassium chloride; The proton exchange membrane is a perfluorosulfonic acid-based composite membrane with a thickness of 200 μm and a proton conductivity of 0.1 S / cm.

[0087] (3) Metal-mediated catalytic ammonia synthesis

[0088] Introduce nitrogen into the catholyte of the reaction system assembled in step (2). Under the conditions of 25 °C and 0.1 MPa, apply a working voltage of 1.0 V. Propionaldehyde undergoes an electrochemical oxidation reaction to generate acid and release protons; The protons are directionally transported through the proton exchange membrane into the catholyte and undergo an electrocatalytic reduction reaction with nitrogen on the surface of the catalyst to generate nitrogen. The reaction schematic diagram is asFigure 1 as shown

[0089] Example 7

[0090] A method for metal-mediated catalytic ammonia synthesis, comprising the following steps:

[0091] (1) Prepare a catalyst (BiCu / CeO2 / Fe2O3 grown on a carbon cloth conductive substrate) using the same preparation method as in Example 4.

[0092] (2) Assembly of the reaction system

[0093] Assemble the anode, cathode, anolyte, catholyte, and proton exchange membrane into a reaction system, where: the proton exchange membrane is disposed between the anolyte and the catholyte; the cathode and anode are the catalysts prepared in step (1), with an area of 1 cm 2 ; the anolyte is methyl formate dissolved with 9 mol / L methanol, the catholyte is methyl formate dissolved with 3 mol / L potassium chloride; the proton exchange membrane is a perfluorosulfonic acid-based composite membrane with a thickness of 200 μm and a proton conductivity of 0.1 S / cm.

[0094] (3) Metal-mediated catalytic ammonia synthesis

[0095] Introduce nitrogen into the catholyte of the reaction system assembled in step (2). Under the conditions of 25 °C and 0.1 MPa, with a working voltage of 1.0 V. Methanol undergoes an electrochemical oxidation reaction to generate acid and release protons; the protons are directionally transported through the proton exchange membrane into the catholyte, and electrocatalytic reduction reaction occurs with nitrogen on the catalyst surface to generate nitrogen, and its reaction schematic diagram is as Figure 1 shown

[0096] Example 8

[0097] A method for metal-mediated catalytic ammonia synthesis, comprising the following steps:

[0098] (1) Prepare a catalyst (BiCu / CeO2 / Fe2O3 grown on a carbon cloth conductive substrate) using the same preparation method as in Example 4.

[0099] (2) Assembly of the reaction system

[0100] Assemble the anode, cathode, anolyte, catholyte, and proton exchange membrane into a reaction system, where: the proton exchange membrane is disposed between the anolyte and the catholyte; the cathode and anode are the catalysts prepared in step (1), with an area of 1 cm 2; The anolyte is dimethyl phthalate dissolved with 9 mol / L benzaldehyde, and the catholyte is dimethyl phthalate dissolved with 3 mol / L potassium chloride; The proton exchange membrane is a perfluorosulfonic acid composite membrane with a thickness of 200 μm and a proton conductivity of 0.1 S / cm.

[0101] (3) Metal-mediated catalytic ammonia synthesis

[0102] Introduce nitrogen into the catholyte of the reaction system assembled in step (2). Under the conditions of 25 °C and 0.1 MPa, with a working voltage of 1.0 V. Benzaldehyde undergoes an electrochemical oxidation reaction to produce an acid and release protons; The protons are transported directionally through the proton exchange membrane into the catholyte, and electrocatalytic reduction reaction occurs with nitrogen on the catalyst surface to generate nitrogen. The reaction schematic diagram is as Figure 1 shown.

[0103] Example 9

[0104] A method for metal-mediated catalytic ammonia synthesis, comprising the following steps:

[0105] (1) Prepare the catalyst (BiCu / CeO2 / Fe2O3 grown on a carbon cloth conductive substrate) using the same preparation method as in Example 4.

[0106] (2) Assembly of the reaction system

[0107] Assemble the anode, cathode, anolyte, catholyte, and proton exchange membrane into a reaction system, where: The proton exchange membrane is arranged between the anolyte and the catholyte; The cathode and anode are the catalysts prepared in step (1), with an area of 1 cm 2 ; The anolyte is γ-butyrolactone dissolved with 9 mol / L benzaldehyde, and the catholyte is γ-butyrolactone dissolved with 3 mol / L potassium chloride; The proton exchange membrane is a perfluorosulfonic acid composite membrane with a thickness of 200 μm and a proton conductivity of 0.1 S / cm.

[0108] (3) Metal-mediated catalytic ammonia synthesis

[0109] Introduce nitrogen into the catholyte of the reaction system assembled in step (2). Under the conditions of 25 °C and 0.1 MPa, with a working voltage of 1.0 V. Benzaldehyde undergoes an electrochemical oxidation reaction to produce an acid and release protons; The protons are transported directionally through the proton exchange membrane into the catholyte, and electrocatalytic reduction reaction occurs with nitrogen on the catalyst surface to generate nitrogen. The reaction schematic diagram is as Figure 1 shown.

[0110] Example 10

[0111] A method for metal-mediated catalytic ammonia synthesis, comprising the following steps:

[0112] (1) Prepare the catalyst (BiCu / CeO2 / Fe2O3 grown on a carbon cloth conductive substrate) using the same preparation method as in Example 4.

[0113] (2) Assembly of the reaction system

[0114] Assemble the anode, cathode, anolyte, catholyte, and proton exchange membrane into a reaction system, where: the proton exchange membrane is disposed between the anolyte and catholyte; the cathode and anode are the catalysts prepared in step (1), with an area of 1 cm 2 ; the anolyte is maleic anhydride dissolved with 9 mol / L benzaldehyde, the catholyte is maleic anhydride dissolved with 3 mol / L potassium chloride; the proton exchange membrane is a perfluorosulfonic acid-based composite membrane with a thickness of 200 μm and a proton conductivity of 0.1 S / cm.

[0115] (3) Metal-mediated catalytic ammonia synthesis

[0116] Introduce nitrogen into the catholyte of the reaction system assembled in step (2). At 25 °C and 0.1 MPa, with a working voltage of 1.0 V. Benzaldehyde undergoes an electrochemical oxidation reaction to generate an acid and release protons; the protons are directionally transported through the proton exchange membrane into the catholyte and react electrocatalytically with nitrogen on the catalyst surface to generate nitrogen. The reaction schematic diagram is as Figure 1 shown.

[0117] Comparative Example 1

[0118] A method for metal-mediated catalytic ammonia synthesis, comprising the following steps:

[0119] (1) Prepare the catalyst (FeRu / CeO2 / Fe2O3 grown on a carbon cloth conductive substrate) using the same preparation method as in Example 1.

[0120] (2) Assembly of the reaction system

[0121] Assemble the anode, cathode, anolyte, catholyte, and proton exchange membrane into a reaction system, where: the cathode and anode are the catalysts prepared in step (1), with an area of 1 cm 2 ; the anolyte is propylene carbonate, the catholyte is propylene carbonate with 0.001 mol / L lithium hexafluorophosphate; the proton exchange membrane is a perfluorosulfonic acid-based composite membrane with a thickness of 200 μm and a proton conductivity of 0.1 S / cm.

[0122] (3) Metal-mediated catalytic ammonia synthesis

[0123] Hydrogen is introduced into the anolyte of the reaction system assembled in step (2), and nitrogen is introduced into the catholyte. Ammonia is synthesized at 25 °C and 0.1 MPa under a working voltage of 1.0 V.

[0124] The difference between Comparative Example 1 and Example 1 is that formaldehyde is not contained in the anolyte, but hydrogen is introduced.

[0125] Comparative Example 2

[0126] A method for metal-mediated catalytic synthesis of ammonia, comprising the following steps:

[0127] (1) Prepare a catalyst (Ni / CeO2 / Fe2O3 grown on a carbon cloth conductive substrate) using the same preparation method as in Example 2.

[0128] (2) Assembly of the reaction system

[0129] An anode, a cathode, and an electrolyte are assembled into a reaction system, where: the cathode and the anode are the catalysts prepared in step (1), with an area of 1 cm 2 ; the electrolyte is dimethyl carbonate dissolved with 1 mol / L methanol and 0.1 mol / L cesium chloride.

[0130] (3) Metal-mediated catalytic synthesis of ammonia

[0131] Nitrogen is introduced into the catholyte of the reaction system assembled in step (2). Ammonia is synthesized at 40 °C and 0.1 MPa under a working voltage of 1.0 V.

[0132] The difference between Comparative Example 2 and Example 2 is that during the synthesis of ammonia, the reduction of nitrogen at the cathode and the dissociation of the proton donor of methanol at the anode proceed synchronously.

[0133] Performance test

[0134] The ammonia products synthesized in Examples 1-10 and Comparative Examples 1-2 are calibrated by the indophenol blue colorimetric method, and the ammonia yield after 2 hours of catalytic ammonia synthesis is calculated. The results are shown in Table 1.

[0135] Table 1:

[0136]

[0137]

[0138] As can be seen from Table 1, Examples 1-10 combine the oxidation of a proton source (alcoholic organic compound or aldehyde organic compound) with metal-mediated nitrogen reduction. By in-situ generation and directional transport of protons, the long-standing hydrogen dependence problem in the field of electro-synthesis of ammonia is broken through, providing a new technical path for green synthesis of ammonia, and the ammonia yield can reach 1.03×10 -8to 9.2×10 -8 mol / (cm 2 ·s), which is much higher than the yield of the traditional metal-mediated ammonia synthesis in Comparative Examples 1-2.

[0139] For those of ordinary skill in the art to which the present invention pertains, several simple deductions or substitutions can be made without departing from the concept of the present invention, without the need for creative labor. Therefore, any simple improvements made by those skilled in the art based on the disclosure of the present invention should fall within the protection scope of the present invention. The above embodiments are the preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made thereto shall fall within the protection scope of the present invention.

Claims

1. A method for metal-mediated catalytic ammonia synthesis, characterized in that, It includes the following steps: (1) Assemble an anode, a cathode, an anolyte, a catholyte, and a proton exchange membrane into a reaction system, with the proton exchange membrane disposed between the anolyte and the catholyte; The anolyte contains a proton source, and the proton source includes an alcohol organic compound or an aldehyde organic compound; the materials of the anode and the cathode are the same, both being a catalyst loaded with a transition metal; (2) Introduce nitrogen into the catholyte, and power on, heat, and pressurize the reaction system assembled in step (1); the proton source undergoes an electrochemical oxidation reaction to generate an acid and release protons; the protons are directionally transported through the proton exchange membrane into the catholyte, and electrocatalytic reduction reaction occurs with nitrogen on the surface of the catalyst to synthesize the nitrogen.

2. The method for metal-mediated catalytic ammonia synthesis according to claim 1, wherein In step (1), the alcohol organic compound is selected from at least one of C1-C6 alcohols; and / or, the aldehyde organic compound is selected from at least one of C1-C6 aldehydes.

3. The method for metal-mediated catalytic ammonia synthesis according to claim 2, wherein The alcohol organic compound is selected from at least one of methanol, ethanol, propanol, and benzyl alcohol; and / or, the aldehyde organic compound is selected from at least one of formaldehyde, acetaldehyde, propionaldehyde, and benzaldehyde.

4. The method for metal-mediated catalytic ammonia synthesis according to claim 1, wherein In step (1), the catholyte contains a soluble metal salt and an organic solvent, and the soluble metal salt is selected from at least one of hexafluorophosphate, bis(fluorosulfonyl)imide salt, chloride salt, and fluoride salt.

5. The method for metal-mediated catalytic ammonia synthesis according to claim 4, wherein The metal ions of the soluble metal salt are selected from at least one of Li + , Na + , K + , Rb + , Cs + , Ca 2+ , Mg 2+ ; in the cathode electrolyte, the concentration of the metal ions is 0.001-3 mol / L.

6. The method for metal-mediated catalytic ammonia synthesis according to claim 4, wherein The organic solvent is selected from at least one of propylene carbonate, dimethyl carbonate, ethylene carbonate, tetrahydrofuran, methyl propyl carbonate, methyl formate, dimethyl phthalate, γ-butyrolactone, and maleic anhydride.

7. The method for metal-mediated catalytic ammonia synthesis according to claim 1, wherein, In step (1), the transition metal loaded on the catalyst is selected from any one of single metals of Fe, Ru, Mo, Ni, Co, Bi, Cu or an alloy of at least two of them; and / or, the loading amount of the transition metal is 0.1-5 wt%.

8. The method for metal-mediated catalytic ammonia synthesis according to claim 1 or 7, characterized in that, The catalyst further includes a support, and the transition metal is loaded on the support; the support successively includes a conductive substrate, a transition metal layer, and a surface modification layer from bottom to top.

9. The method for metal-mediated catalytic ammonia synthesis according to claim 1, wherein In step (1), the proton exchange membrane is a perfluorosulfonic acid type composite membrane.

10. The method for metal-mediated catalytic ammonia synthesis according to claim 1, characterized in that, In step (2), the heating temperature is 25-100 °C; and / or, the pressurizing pressure is 0.1-5 MPa.

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