Anhydrous proton electrolyte for electrochemical reduction and application thereof

Abstract

The invention discloses an anhydrous proton electrolyte for electrochemical reduction and application thereof.The electrolyte is formed by compounding inorganic acid / salt and an organic solvent, a stable proton source is provided, high ionic conductivity and a wide electrochemical stability window are shown, the electrolyte adapts to various electrosynthesis systems, and the electrochemical reduction performance is improved. Various electrode materials can be supported, stable operation under a relatively high potential can be realized, and a substrate range and operation conditions of an electrochemical reduction reaction are effectively expanded.

Description

Technical Field

[0001] This invention relates to the field of electrochemical synthesis technology, and in particular to an anhydrous proton electrolyte for electrochemical reduction and its application. Background Technology

[0002] Electrochemical reduction synthesis, as a green synthetic method, has shown significant potential in energy conversion and the preparation of high-value-added chemicals. Traditional electrochemical reduction processes often employ aqueous electrolyte solutions, especially in reactions involving protons (such as the electrochemical hydrogenation of organic compounds, carbon dioxide reduction, and nitrogen reduction to ammonia), where water serves as both a solvent and a proton source. However, aqueous systems have significant limitations: firstly, the electrochemical window of water is narrow, severely restricting the applicable electrode materials and reaction types; secondly, the overpotential of the hydrogen evolution reaction (HER) in water is low, fiercely competing with the target reduction reaction, leading to decreased current efficiency, lower selectivity, and lower yield of the target product; and thirdly, water molecules themselves may participate in side reactions, causing decomposition of certain water-sensitive substrates or intermediates.

[0003] To overcome the inherent limitations of aqueous systems, research on anhydrous proton electrolytes has gradually gained attention. These electrolytes are typically composed of inorganic acids (such as sulfuric acid and phosphoric acid) dissolved in non-aqueous organic solvents (such as acetonitrile, propylene carbonate, and alcohols), and supporting electrolytes (such as quaternary ammonium salts and inorganic salts) can be added to improve ionic conductivity. Anhydrous proton electrolytes offer a wide electrochemical window, controllable proton activity, and good substrate solubility, creating a favorable environment for efficient electrochemical reduction.

[0004] In existing technologies, although some studies have attempted to use combinations of non-aqueous solvents and acids, for example, existing literature has used 1M phosphoric acid / acetonitrile electrolytes in batteries with an ionic conductivity of 0.5 mS / cm. -1 While currently used in electrochemical reduction reactions, anhydrous proton electrolytes still face challenges such as ineffective suppression of hydrogen evolution, low proton transport efficiency, and insufficient ionic conductivity, which limit their application in large-scale electrosynthesis. Therefore, developing an anhydrous proton electrolyte that can effectively suppress hydrogen evolution, promote efficient proton transport, and possess high ionic conductivity has become a key challenge in advancing electrochemical reduction synthesis technology. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an anhydrous proton electrolyte for electrochemical reduction that effectively suppresses hydrogen evolution, has high ionic conductivity and a wide electrochemical stability window, and its application.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: An anhydrous proton electrolyte for electrochemical reduction, comprising an inorganic acid as a solute dissolved in an organic solvent; the concentration of the solute is 20-100 mg / mL, which is the molar amount of solute per unit volume of solvent; the inorganic acid includes one or more of polyphosphoric acid, phosphoric acid, sulfuric acid, nitric acid, and hydrochloric acid; the organic solvent includes one or more of alcohols containing hydroxyl groups, phenols containing hydroxyl groups, aldehydes containing carbonyl groups, esters containing ester groups, organic acids containing acid radicals, and nitrile compounds containing cyanide radicals.

[0007] As a further improvement to the aforementioned technical solution: It also includes inorganic salts, which include one or more alkali metal salts or alkaline earth metal salts of phosphoric acid, sulfuric acid, nitric acid, and hydrochloric acid.

[0008] The alcohols containing hydroxyl groups include one or more of monohydric alcohols, dihydric alcohols, trihydric alcohols, primary alcohols, secondary alcohols, and tertiary alcohols; The phenols containing hydroxyl groups include one or more monohydric phenols and polyhydric phenols.

[0009] The carbonyl-containing aldehydes include one or more of aliphatic aldehydes, aromatic aldehydes, and alicyclic aldehydes.

[0010] The esters containing ester groups include one or more of carboxylic acid esters, inorganic acid esters, and lactones.

[0011] The organic acids containing acid radicals include one or more of fatty acids, aromatic acids, and alicyclic acids.

[0012] The cyanide-containing nitrile compounds include one or more of aliphatic nitriles, aromatic nitriles, and unsaturated nitriles.

[0013] The alcohols containing hydroxyl groups include one or more of methanol, ethanol, isopropanol, tert-butanol, ethylene glycol, and glycerol.

[0014] The phenols containing hydroxyl groups include one or more of phenol, methylphenol, hydroquinone, catechol, and phloroglucinol.

[0015] The carbonyl-containing aldehydes include one or more of formaldehyde, acetaldehyde, acrolein, and benzaldehyde.

[0016] The esters containing ester groups include one or more of ethyl acetate, nitroglycerin, adenosine triphosphate, and γ-butyrolactone.

[0017] The organic acids containing an acid radical include one or more of acetic acid, palmitic acid, stearic acid, oleic acid, benzoic acid, and cyclohexanecarboxylic acid.

[0018] The cyanide-containing nitrile compounds include one or more of acetonitrile, benzonitrile, and acrylonitrile.

[0019] The solute is phosphoric acid, and the organic solvent is anhydrous ethyl acetate or anhydrous ethylene glycol.

[0020] The concentration of the inorganic salt is 0.1-10 mg.

[0021] Application of the aforementioned anhydrous proton electrolyte for electrochemical reduction in electrochemical reduction reactions.

[0022] As a further improvement to the aforementioned technical solution: The electrochemical reduction reaction is a reduction reaction that requires a proton source, including at least one of the following: electroreduction of carbon dioxide to synthesize organic matter, electrochemical synthesis of ammonia, reduction of unsaturated bonds, biomass molecular conversion, and dehalogenation of halogenated organic pollutants.

[0023] The electrochemical reduction reaction is the electroreduction of carbon dioxide to synthesize organic matter or the electroreduction to synthesize ammonia.

[0024] When the electrochemical reduction reaction is the electroreduction of carbon dioxide to synthesize organic matter, it includes a cathode chamber and an anode chamber separated by a proton exchange membrane, a gas diffusion electrode as the working electrode, a platinum electrode as the auxiliary electrode, a silver / silver chloride electrode as the reference electrode, CuS as the catalyst in the cathode chamber, CO2 gas is introduced into the cathode chamber, and an anhydrous proton electrolyte according to the above-described method for electrochemical reduction is used as the electrolyte, and a working voltage is applied. When the electrochemical reduction reaction is the electrochemical synthesis of ammonia, it is carried out in a two-chamber electrolytic cell consisting of a cathode chamber and an anode chamber separated by an anion exchange membrane. A carbon paper gas diffusion electrode is used as the working electrode, a platinum mesh as the counter electrode, and a silver / silver chloride electrode as the reference electrode. MoS2 nanomaterials are used as the cathode chamber catalyst. N2 gas is continuously introduced into the cathode chamber, and an anhydrous proton electrolyte as described above for electrochemical reduction is used as the electrolyte. A working voltage is applied.

[0025] The electrolyte system of inorganic acid and organic solvent described in this invention achieves its universal technical effect through the jointly constructed "confined proton environment." This environment possesses two major characteristics: controlled proton activity and stable solvent molecules. Performance breakthroughs are achieved through the following mechanisms: 1. Suppression of hydrogen evolution: In organic solvents, the dissociation of inorganic acids is restricted, and protons mainly exist in the form of ion pairs or solvated clusters, significantly reducing their activity. This "confined" state greatly enhances the proton reduction barrier, fundamentally suppressing hydrogen evolution side reactions. 2. Widening of the electrochemical window: The molecular orbital energy levels of organic solvents are stable, and their intrinsic decomposition potential is much higher than that of water, naturally providing a wide electrochemical window. High-concentration inorganic acids further enhance the ionic strength of the system, synergistically suppressing solvent decomposition. 3. Promotion of proton transport: High-concentration acid molecules form a dynamic hydrogen bond network with organic solvents containing lone pairs of electrons / active hydrogen, enabling efficient proton transport along this network. This process does not rely on high dissociation, achieving efficient proton conduction. In summary, this invention, by replacing water with organic solvents and combining them with high-concentration inorganic acids, comprehensively reconstructs the physicochemical environment of the system. Any combination that meets the basic requirements of "acid providing a proton source, solvent forming a hydrogen bond network and being stable on its own" can form a "confined proton environment" and consistently achieve the technical effects of suppressing hydrogen evolution, providing a wide window, and efficiently transporting protons.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: The anhydrous proton electrolyte for electrochemical reduction of the present invention is composed of inorganic acids / salts and organic solvents, which not only provides a stable source of protons, but also exhibits high ionic conductivity (3.5-25 mS / cm). -1 The conductivity of conventional anhydrous proton electrolytes is around 3.5 mS / cm. -1 With a wide electrochemical stability window (≥2.5 V), it is adaptable to a variety of electrosynthesis systems, supports a variety of electrode materials and operates stably at higher potentials, effectively expanding the substrate range and operating conditions of electrochemical reduction reactions.

[0027] The anhydrous proton electrolyte of this invention effectively suppresses the hydrogen evolution reaction (HER) in electrochemical reduction reactions, significantly improving the selectivity and yield of the target product. By optimizing proton activity and transport pathways, it significantly reduces the kinetic rate of the HER, allowing protons to preferentially participate in the target reduction reaction (such as electrochemical hydrogenation of organic matter, CO2 reduction, and nitrogen reduction to ammonia synthesis). Experiments show that in typical electrocatalytic hydrogenation reactions, compared to traditional acidic water electrolytes, the electrolyte system provided by this invention reduces the current efficiency of the HER side reaction and improves the Faraday efficiency of the target product under the catalysis of a catalyst. Attached Figure Description

[0028] Figure 1 Schematic diagrams of phosphoric acid / ethyl acetate electrolytes at different concentrations and their corresponding ionic conductivity diagrams. Figure 1 (a) is a schematic diagram of the electrolyte. Figure 1 (b) is the ionic conductivity diagram.

[0029] Figure 2 The conductivity window diagrams are for Comparative Example 1, Comparative Example 2, and Examples 1 and 7.

[0030] Figure 3 The figure shows the Faraday efficiency of hydrogen gas, a byproduct of the electrolytes in Comparative Examples 3 and 6, during the carbon dioxide electroreduction reaction.

[0031] Figure 4 The diagram shows the Faraday efficiency of hydrogen as a byproduct in the carbon dioxide electroreduction reaction of the electrolytes of Example 7 and Comparative Example 7.

[0032] Figure 5 The diagram shows the Faraday efficiency of the formic acid product in the electrolyte of Comparative Examples 3 and 6 during the carbon dioxide electroreduction reaction.

[0033] Figure 6 The diagram shows the Faraday efficiency of the formic acid product in the electroreduction reaction of the electrolytes in Example 7 and Comparative Example 7.

[0034] Figure 7 The diagram shows the Faraday efficiency of the electrolytes in Comparative Examples 3, 7, 6, and 7 for the byproduct hydrogen and product ammonia in the nitrogen electroreduction of ammonia. Detailed Implementation

[0035] The present invention will be further described in detail below. Unless otherwise specified, the instruments or materials used in the present invention are commercially available.

[0036] Example 1 The anhydrous proton electrolyte for electrochemical reduction in this embodiment uses crystalline phosphoric acid as the solute and anhydrous ethyl acetate as the organic solvent, with a solute concentration of 20 m. In this document, solution concentration is defined as the molar amount of solute per unit volume of solvent (e.g., 1 m represents 1 mole of H3PO4 in 1 liter of ethyl acetate).

[0037] The method for preparing anhydrous proton electrolyte for electrochemical reduction in this embodiment includes the following steps: 196 g of crystalline phosphoric acid (H3PO4, purity ≥99.0%) is weighed and added to 100 mL of anhydrous ethyl acetate (EA, purity 99.8%), and stirred continuously until the solid solute completely disappears and the solution becomes optically transparent, thus preparing a phosphoric acid / ethyl acetate electrolyte with a concentration of 20 mg / mL. The entire preparation process is completed in a glove box (moisture content <0.1 ppm).

[0038] Comparative Example 1 The anhydrous proton electrolyte used for electrochemical reduction in this comparative example ( Figure 1 (a) EA), which is largely the same as in Example 1, except that there is no acid solute, only organic solvent.

[0039] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that crystalline phosphoric acid is not added.

[0040] Comparative Example 2 The anhydrous proton electrolyte used for electrochemical reduction in this embodiment ( Figure 1 (a) 1m), with crystalline phosphoric acid as the solute and anhydrous ethyl acetate as the organic solvent, the concentration of the solute is 1 m. In this article, the solution concentration is defined as the molar amount of solute in a unit volume of solvent (for example, 1 m means that 1 liter of ethyl acetate contains 1 mole of H3PO4).

[0041] The method for preparing anhydrous proton electrolyte for electrochemical reduction in this embodiment includes the following steps: 9.8 g of crystalline phosphoric acid (H3PO4, purity ≥99.0%) is weighed and added to 100 mL of anhydrous ethyl acetate (EA, purity 99.8%), and stirred continuously until the solid solute completely disappears and the solution becomes optically transparent, thus preparing a phosphoric acid / ethyl acetate electrolyte with a concentration of 1 m. The entire preparation process is completed in a glove box (moisture content <0.1 ppm).

[0042] Comparative Example 3 The anhydrous proton electrolyte used for electrochemical reduction in this embodiment ( Figure 1 (a) is 10m), which is roughly the same as in Example 1, except that the concentration of the solute is 10 m.

[0043] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the mass of crystalline phosphoric acid is 98 g.

[0044] Example 2 The anhydrous proton electrolyte used for electrochemical reduction in this embodiment ( Figure 1 (a) is 30m), which is roughly the same as in Example 1, except that the concentration of the solute is 30 m.

[0045] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the mass of crystalline phosphoric acid is 294 g.

[0046] Example 3 The anhydrous proton electrolyte used for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the concentration of the solute is 40 mg.

[0047] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the mass of crystalline phosphoric acid is 392 g.

[0048] Example 4 The anhydrous proton electrolyte used for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the concentration of the solute is 50 mg.

[0049] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the mass of crystalline phosphoric acid is 490 g.

[0050] Example 5 The anhydrous proton electrolyte used for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the concentration of the solute is 60 mg.

[0051] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the mass of crystalline phosphoric acid is 588 g.

[0052] Example 6 The anhydrous proton electrolyte used for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the concentration of the solute is 70 mg.

[0053] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the mass of crystalline phosphoric acid is 686 g.

[0054] Example 7 The anhydrous proton electrolyte used for electrochemical reduction in this embodiment ( Figure 1 (a) is 80m), which is roughly the same as in Example 1, except that the concentration of the solute is 80 m.

[0055] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the mass of crystalline phosphoric acid is 784 g.

[0056] Example 8 The anhydrous proton electrolyte used for electrochemical reduction in this embodiment ( Figure 1 (a) is 85m), which is roughly the same as in Example 1, except that the concentration of the added solute is 85m.

[0057] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the mass of crystalline phosphoric acid is 833 g.

[0058] Example 9 The anhydrous proton electrolyte used for electrochemical reduction in this embodiment ( Figure 1 (a) is 100m), which is roughly the same as in Example 1, except that the concentration of the added solute is 100 m.

[0059] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the mass of crystalline phosphoric acid is 980 g.

[0060] Images of phosphoric acid / ethyl acetate electrolytes with different concentration gradients and their corresponding ionic conductivity (tested at room temperature) for various embodiments and comparative examples of this invention are shown below. Figure 1 As shown, from Figure 1 As shown in (a), when the phosphoric acid concentration is higher than 80m (starting from 85m, excluding 80m), solid phosphoric acid cannot dissolve further and cannot form a colorless, transparent, homogeneous electrolyte. Figure 1 (b) It can be seen that when the concentrations are 1m, 10m, 20m, 30m, 40m, 50m, 60m, 70m, and 80m, the ionic conductivity is 0.0036 mS / cm. -1 1.06mS cm -1 3.83mS cm -1 7.19mS cm -1 10.77mS cm -1 14.12mS cm -1 16.95mS cm -1 19.32mS cm -1 21.77mS cm -1 The ionic conductivity gradually increases, and when it reaches 85 m and 100 m, the ionic conductivity of the supernatant no longer increases because phosphoric acid has reached saturation.

[0061] Figure 2 Electrochemical window diagrams of Comparative Example 1, Comparative Example 2, and Examples 1 and 7 are shown. As can be seen from the diagrams, the high-concentration anhydrous proton electrolytes (20m, 80m) prepared in the examples can maintain a wide electrochemical window (>2.5V) while improving ionic conductivity.

[0062] Example 10: The anhydrous proton electrolyte used for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the organic solvent is anhydrous ethylene glycol.

[0063] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 10, except that the organic solvent is anhydrous ethylene glycol (EG, purity 99.8%).

[0064] Comparative Example 4: The anhydrous proton electrolyte used for electrochemical reduction in this embodiment is largely the same as that in Example 10, except that the concentration of the solute is 1 m.

[0065] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 10, except that the mass of crystalline phosphoric acid is 9.8 g.

[0066] Example 11: The anhydrous proton electrolyte used for electrochemical reduction in this embodiment is largely the same as that in Example 10, except that the concentration of the solute is 80 mg.

[0067] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 10, except that the mass of crystalline phosphoric acid is 784 g.

[0068] The ionic conductivity of Comparative Example 4, Example 10, and Example 11 were 0.004 mS / cm, respectively. -1 4.5mS cm -1 23.6mS cm -1 .

[0069] Example 12: The anhydrous proton electrolyte used for electrochemical reduction in this embodiment is largely the same as that in Example 1, except that the solute is concentrated sulfuric acid.

[0070] The method for preparing anhydrous proton electrolyte for electrochemical reduction in this embodiment includes the following steps: First, 200 g of concentrated sulfuric acid (H2SO4, purity ≥98.0%) is weighed and added to 100 mL of anhydrous ethyl acetate (EA, purity 99.8%). The mixture is stirred continuously until the solid solute completely disappears and the solution becomes optically transparent, thus preparing a sulfuric acid / ethyl acetate electrolyte with a concentration of 20 μM. The entire preparation process is completed in a glove box (moisture content <0.1 ppm).

[0071] Comparative Example 5: The anhydrous proton electrolyte used for electrochemical reduction in this comparative example is largely the same as that in Example 12, except that the concentration of the solute is 1 m.

[0072] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this comparative example is largely the same as that in Example 12, except that the mass of concentrated sulfuric acid (H2SO4, purity ≥98.0%) is 10g.

[0073] Example 13: The anhydrous proton electrolyte used for electrochemical reduction in this embodiment is largely the same as that in Example 12, except that the concentration of the solute is 80 mg.

[0074] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment is largely the same as that in Example 10, except that the mass of concentrated sulfuric acid is 800 g.

[0075] The ionic conductivity of Comparative Example 5, Example 12, and Example 13 were 0.007 mS / cm, respectively. -1 5.8mS cm -1 24.8mS cm -1 .

[0076] Example 14: The anhydrous proton electrolyte for electrochemical reduction in this embodiment uses crystalline phosphoric acid as the solute, anhydrous ethyl acetate as the organic solvent, and potassium dihydrogen phosphate as the additive salt. In this embodiment, the concentration of the solute is 20 m and the concentration of the additive salt is 0.1 m. In this document, the solution concentration is defined as the molar amount of solute / additive salt per unit volume of solvent (for example, 1 m means 1 mole of H3PO4 in 1 liter of ethyl acetate).

[0077] The method for preparing anhydrous proton electrolyte for electrochemical reduction in this embodiment includes the following steps: 196 g of crystalline phosphoric acid (H3PO4, purity ≥99.0%) and 1.36 g of potassium dihydrogen phosphate are weighed and added to 100 mL of anhydrous ethyl acetate (EA, purity 99.8%). The mixture is stirred continuously until the solid solute completely disappears and the solution becomes optically transparent, thus preparing a phosphoric acid / ethyl acetate electrolyte with a concentration of 20 mg (containing 0.1 mg of potassium dihydrogen phosphate). The entire preparation process is completed in a glove box (moisture content <0.1 ppm).

[0078] Example 15: The anhydrous proton electrolyte for electrochemical reduction in this embodiment uses crystalline phosphoric acid as the solute, anhydrous ethyl acetate as the organic solvent, and potassium dihydrogen phosphate as the additive salt. In this embodiment, the concentration of the solute is 20 m and the concentration of the additive salt is 2 m. In this document, the solution concentration is defined as the molar amount of solute / additive salt per unit volume of solvent (for example, 1 m means that 1 liter of ethyl acetate contains 1 mole of H3PO4).

[0079] The preparation method of the anhydrous proton electrolyte for electrochemical reduction in this embodiment includes the following steps: 196g of crystalline phosphoric acid (H3PO4, purity ≥99.0%) and 27.218g of potassium dihydrogen phosphate are weighed and added to 100mL of anhydrous ethyl acetate (EA, purity 99.8%). The mixture is stirred continuously until the solid solute completely disappears and the solution becomes optically transparent, thus preparing a phosphoric acid / ethyl acetate electrolyte with a concentration of 20m (containing 2m of potassium dihydrogen phosphate). The entire preparation process is completed in a glove box (moisture content <0.1 ppm).

[0080] Examples 14 and 15 are the same as Example 1, using the same solute and organic solvent, except that potassium dihydrogen phosphate is added. The ionic conductivity of Example 14 is 3.9 S cm⁻¹. -1 The ionic conductivity of Example 15 was 4.1 mS / cm. -1 Compared to Example 1, the addition of potassium dihydrogen phosphate increases the number of mobile ions in the solution and further improves the ionic conductivity.

[0081] In Examples 14 and 15, the concentration of the additive salt was in the range of 0.1-10m. If it was greater than 10m, when the salt concentration was close to or exceeded its solubility limit, crystals would easily precipitate, and the viscosity of the high-concentration salt solution would increase.

[0082] Comparative Example 6: The electrolyte used in this comparative example for electrochemical reduction uses crystalline phosphoric acid as the solute and water as the solvent, with a solute concentration of 10m. In this paper, solution concentration is defined as the molar amount of solute per unit volume of solvent (for example, 1m means 1 mole of H3PO4 in 1 liter of water).

[0083] The preparation method of the electrolyte for electrochemical reduction in this comparative example includes the following steps: weigh 98 g of crystalline phosphoric acid (H3PO4, purity ≥99.0%) and add it to 100 mL of deionized water, and stir continuously until the solid solute completely disappears and the solution reaches an optically transparent state to obtain 10 mL of phosphoric acid aqueous solution.

[0084] Comparative Example 7: The electrolyte used in this comparative example for electrochemical reduction uses crystalline phosphoric acid as the solute and water as the solvent, with a solute concentration of 80m. In this paper, solution concentration is defined as the molar amount of solute per unit volume of solvent (for example, 1m means 1 mole of H3PO4 in 1 liter of water).

[0085] The preparation method of the electrolyte for electrochemical reduction in this comparative example includes the following steps: weigh 784 g of crystalline phosphoric acid (H3PO4, purity ≥99.0%) and add it to 100 mL of deionized water, and stir continuously until the solid solute completely disappears and the solution reaches an optically transparent state to obtain an 80 mL phosphoric acid aqueous solution.

[0086] Example 16 The application of the electrolytes in the various embodiments and comparative examples of this invention in electrochemical reduction reactions, wherein the electrochemical reduction reaction is a carbon dioxide electroreduction reaction, including: Using 10 mL of EA / H3PO4 solution from Comparative Example 3, 80 mL of EA / H3PO4 solution from Example 7, 10 mL of H3PO4 aqueous solution from Comparative Example 6, and 80 mL of H3PO4 aqueous solution from Comparative Example 7 as electrolytes in the CO2 reduction device, a flow cell experiment was conducted. CuS was used as the catalyst in the cathode chamber, and CO2 gas was introduced into the cathode chamber. The gas diffusion layer (1 cm × 3 cm), the Pt sheet (1 cm × 3 cm), and the Ag / AgCl (saturated KCl) electrode were used as the working electrode, counter electrode, and reference electrode, respectively, with a working area of ​​1 cm². 2 The cathode and anode chambers are separated by a proton exchange membrane (Nafion 117), and a mass flow controller adjusts the gas flow rate to 30 mL / min. -1 The peristaltic pump maintains the electrolyte flow rate at 10 mL / min. -1 .

[0087] The hydrogen content of the byproduct was detected in real time using gas chromatography-mass spectrometry. The hydrogen Faraday efficiency at different current densities in Comparative Examples 3 and 6 was as follows: Figure 3 As shown, at all current densities, the hydrogen Faraday efficiency is lower when using the anhydrous proton electrolyte proposed in this invention, indicating that this electrolyte can effectively suppress the occurrence of hydrogen side reactions in electroreduction reactions. Examples 7 and 7 show the hydrogen Faraday efficiencies at different current densities. Figure 4 As shown, at the same current density, the hydrogen Faradaic efficiency of the 80m EA / H3PO4 electrolyte in Example 7 is lower than that of the 80m EA / H2O electrolyte in Comparative Example 7. Figure 3 and Figure 4 It can be seen that the hydrogen Faraday efficiency of the 80m EA / H3PO4 electrolyte in Example 7 is lower than that of the 10m EA / H3PO4 solution in Comparative Example 3, indicating that the concentration and ratio of the electrolyte affect the effectiveness of suppressing the occurrence of hydrogen side reactions in the electroreduction reaction.

[0088] Electroreduction synthesis using the anhydrous proton electrolyte provided by this invention is environmentally friendly, safe to operate, and easy to scale up. It avoids the use of high-pressure hydrogen as a hydrogen source, significantly improving process safety. Simultaneously, the anhydrous nature prevents the decomposition of water-sensitive substrates or products, simplifies post-reaction processing, and allows for the recycling of electrolyte components, demonstrating good process compatibility and scalability potential. It exhibits universal catalytic enhancement effects on different types of reactions (such as the reduction of C=O bonds, C=C bonds, nitrile groups, and carboxyl groups), making it highly valuable for widespread application.

[0089] Example 17 The application of the electrolytes in the various embodiments and comparative examples of this invention in electrochemical reduction reactions, wherein the electrochemical reduction reaction is a carbon dioxide electroreduction reaction, including: Using 10 mL of EA / H3PO4 solution from Comparative Example 3, 80 mL of EA / H3PO4 solution from Example 7, 10 mL of H3PO4 aqueous solution from Comparative Example 6, and 80 mL of H3PO4 aqueous solution from Comparative Example 7 as electrolytes in the CO2 reduction device, a flow cell experiment was conducted. CuS was used as the catalyst in the cathode chamber, and CO2 gas was introduced into the cathode chamber. The gas diffusion layer (1 cm × 3 cm), the Pt sheet (1 cm × 3 cm), and the Ag / AgCl (saturated KCl) electrode were used as the working electrode, counter electrode, and reference electrode, respectively, with a working area of ​​1 cm². 2 The cathode and anode chambers are separated by a proton exchange membrane (Nafion 117), and a mass flow controller adjusts the gas flow rate to 30 mL / min. -1 The peristaltic pump maintains the electrolyte flow rate at 10 mL / min. -1 .

[0090] The content of the target product formic acid was detected by liquid nuclear magnetic resonance. The formic acid Faraday efficiency at different current densities in Comparative Examples 3 and 6 is as follows: Figure 5 As shown, the formic acid Faradaic efficiency is higher when using the anhydrous proton electrolyte proposed in this invention at all current densities, indicating that this electrolyte can effectively improve the selectivity and yield of the target product in the CO2 electroreduction reaction. The formic acid Faradaic efficiencies at different current densities in Examples 7 and 7 are shown below. Figure 6 As shown, at the same current density, the formic acid faradaic efficiency of the 80m EA / H3PO4 electrolyte in Example 7 is higher than that of the 80m EA / H2O electrolyte in Comparative Example 7. (Combined) Figure 5 and Figure 6 It can be seen that the formic acid faradaic efficiency of the 80m EA / H3PO4 electrolyte in Example 7 is higher than that of the 10m EA / H3PO4 solution in Comparative Example 3, indicating that the concentration and ratio of the electrolyte have an effect on the reaction pathway and selectivity in the electroreduction reaction.

[0091] Example 18 The application of the electrolytes in the various embodiments and comparative examples of this invention in electrochemical reduction reactions, including the electrochemical reduction of nitrogen to synthesize ammonia, comprising: The 10 mL EA / H3PO4 solution from Comparative Example 3, the 80 mL EA / H3PO4 solution from Example 7, the 10 mL H3PO4 aqueous solution from Comparative Example 6, and the 80 mL H3PO4 aqueous solution from Comparative Example 7 were used as electrolytes in a nitrogen electroreduction ammonia synthesis apparatus, and tests were conducted using a flow cell system. Fe-doped MoS2 nanosheet array material was used as the cathode catalyst. High-purity N2 gas was continuously introduced into the cathode chamber. A gas diffusion electrode (1 cm × 3 cm), a Pt mesh electrode (1 cm × 3 cm), and Ag / AgCl (saturated KCl) were used as the working electrode, counter electrode, and reference electrode, respectively, with an effective working area of ​​1 cm². The cathode chamber and anode chamber were separated by an anion exchange membrane, and the N2 gas flow rate was controlled at 30 mL / min using a mass flow controller. - ¹, The peristaltic pump maintains the electrolyte flow rate at 10 mL / min. - ¹.

[0092] The generation amounts of the target product ammonia and the byproduct hydrogen were monitored in real time using gas chromatography. Comparative Examples 3, 6, and 7 were compared under the same current density (100 mA cm⁻¹). -2 The Faraday efficiency of hydrogen and the Faraday efficiency of ammonia are as follows: Figure 7 As shown, at all current densities, when using the anhydrous proton-type EA / H3PO4 electrolyte described in this invention, the hydrogen Faraday efficiency is significantly lower than that of the traditional aqueous phosphoric acid electrolyte, while the ammonia Faraday efficiency is significantly higher than that of the traditional aqueous phosphoric acid electrolyte. This indicates that the non-aqueous electrolyte system can effectively suppress the occurrence of hydrogen evolution side reaction during nitrogen electroreduction and improve ammonia yield.

[0093] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. An anhydrous proton electrolyte for electrochemical reduction, characterized in that: An inorganic acid is used as the solute, which is dissolved in an organic solvent; the concentration of the solute is 20-100 mg, which is the molar amount of solute per unit volume of solvent. The inorganic acid includes one or more of polyphosphoric acid, phosphoric acid, sulfuric acid, nitric acid, and hydrochloric acid; The organic solvent includes one or more of the following: alcohols containing hydroxyl groups, phenols containing hydroxyl groups, aldehydes containing carbonyl groups, esters containing ester groups, organic acids containing acid radicals, and nitrile compounds containing cyanide radicals.

2. The anhydrous proton electrolyte for electrochemical reduction according to claim 1, characterized in that: It also includes inorganic salts, which include one or more alkali metal salts or alkaline earth metal salts of phosphoric acid, sulfuric acid, nitric acid, and hydrochloric acid.

3. The anhydrous proton electrolyte for electrochemical reduction according to claim 1 or 2, characterized in that: The alcohols containing hydroxyl groups include one or more of monohydric alcohols, dihydric alcohols, trihydric alcohols, primary alcohols, secondary alcohols, and tertiary alcohols; The phenols containing hydroxyl groups include one or more of monohydric phenols and polyhydric phenols; The carbonyl-containing aldehydes include one or more of aliphatic aldehydes, aromatic aldehydes, and alicyclic aldehydes; The esters containing ester groups include one or more of carboxylic acid esters, inorganic acid esters, and lactones; The organic acids containing acid radicals include one or more of fatty acids, aromatic acids, and alicyclic acids; The cyanide-containing nitrile compounds include one or more of aliphatic nitriles, aromatic nitriles, and unsaturated nitriles.

4. The anhydrous proton electrolyte for electrochemical reduction according to claim 3, characterized in that: The alcohols containing hydroxyl groups include one or more of methanol, ethanol, isopropanol, tert-butanol, ethylene glycol, and glycerol. The phenols containing hydroxyl groups include one or more of phenol, methylphenol, hydroquinone, catechol, and phloroglucinol; The carbonyl-containing aldehydes include one or more of formaldehyde, acetaldehyde, acrolein, and benzaldehyde; The esters containing ester groups include one or more of ethyl acetate, nitroglycerin, adenosine triphosphate, and γ-butyrolactone; The organic acids containing acid radicals include one or more of acetic acid, palmitic acid, stearic acid, oleic acid, benzoic acid, and cyclohexanecarboxylic acid; The cyanide-containing nitrile compounds include one or more of acetonitrile, benzonitrile, and acrylonitrile.

5. The anhydrous proton electrolyte for electrochemical reduction according to claim 4, characterized in that: The solute is phosphoric acid, and the organic solvent is anhydrous ethyl acetate or anhydrous ethylene glycol.

6. The anhydrous proton electrolyte for electrochemical reduction according to claim 2, characterized in that: The concentration of the inorganic salt is 0.1-10 mg.

7. The application of an anhydrous proton electrolyte for electrochemical reduction according to any one of claims 1 to 6 in an electrochemical reduction reaction.

8. The application according to claim 7, characterized in that: The electrochemical reduction reaction is a reduction reaction that requires a proton source, including at least one of the following: electroreduction of carbon dioxide to synthesize organic matter, electrochemical synthesis of ammonia, reduction of unsaturated bonds, biomass molecular conversion, and dehalogenation of halogenated organic pollutants.

9. The application according to claim 8, characterized in that: The electrochemical reduction reaction is the electroreduction of carbon dioxide to synthesize organic matter or the electroreduction to synthesize ammonia.

10. The application according to claim 9, characterized in that: When the electrochemical reduction reaction is the electroreduction of carbon dioxide to synthesize organic matter, it includes a cathode chamber and an anode chamber separated by a proton exchange membrane, a gas diffusion electrode as the working electrode, a platinum electrode as the auxiliary electrode, a silver / silver chloride electrode as the reference electrode, CuS as the catalyst in the cathode chamber, CO2 gas is introduced into the cathode chamber, and an anhydrous proton electrolyte for electrochemical reduction according to any one of claims 1 to 6 is used as the electrolyte, and a working voltage is applied. When the electrochemical reduction reaction is an electrochemical synthesis of ammonia, it is carried out in a dual-chamber electrolytic cell consisting of a cathode chamber and an anode chamber separated by an anion exchange membrane. A carbon paper gas diffusion electrode is used as the working electrode, a platinum mesh as the counter electrode, a silver / silver chloride electrode as the reference electrode, and MoS2 nanomaterials as the cathode chamber catalyst. N2 gas is continuously introduced into the cathode chamber, and an anhydrous proton electrolyte for electrochemical reduction according to any one of claims 1 to 6 is used as the electrolyte. A working voltage is applied.

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