Electrolytic cell device and method for simultaneous desalination and electrocatalytic reduction of nitrate and electrode

Abstract

This disclosure provides an electrolytic cell device and method for simultaneously achieving desalination and electrocatalytic nitrate reduction, belonging to the field of electrochemical technology. The device uses activated carbon (AC) as the anode and a halogen-modified copper electrode as the cathode, physically separated into two electrochemically coupled chambers by a metal Pt or activated carbon interlayer. For the first time, it couples the electrocatalytic nitrate reduction to ammonia (NRA) module and the desalination module into an integrated system. This device can simultaneously achieve highly efficient desalination and electrocatalytic nitrate reduction, with a desalination rate reaching 188 μg / cm³. ‑ ²min ‑ ¹, Ammonia yield reached 1.16 mgh ‑ ¹cm ‑ ², adaptable to a wide salinity range, solving the problems of low desalination rate and narrow salinity adaptability in existing coupled systems, and achieving efficient synergy between nitrate resource recovery and seawater desalination. This disclosure is applicable to the treatment of marine wastewater or industrial wastewater containing nitrates.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and in particular to a system that combines the electrocatalytic reduction of nitrate to ammonia (NRA) reaction with seawater desalination. Specifically, it relates to an electrolytic cell device and method for simultaneously achieving desalination and electrocatalytic reduction of nitrate, as well as the electrodes used. Background Technology

[0002] In recent years, the continuous expansion of industrial and agricultural activities has led to excessive nitrate emissions, while the traditional ammonia synthesis process is accompanied by large amounts of carbon emissions, posing a serious challenge to environmental safety and human health. At the same time, the global shortage of freshwater resources is becoming increasingly prominent. Seawater desalination, as an important way to obtain freshwater resources, suffers from drawbacks such as high energy consumption and greenhouse gas emissions due to its traditional technologies (such as multi-stage flash distillation and reverse osmosis).

[0003] Against this backdrop, coupling electrocatalytic reactions with seawater desalination processes to construct multifunctional integrated systems has become an emerging research direction for simultaneously addressing resource and environmental issues. Existing studies have reported combining photoelectric driving, electroosmosis, and desalination processes, utilizing the ion concentration gradient formed during the reaction to promote salt ion migration, thereby achieving synergistic treatment and resource recovery. However, existing coupled systems still have significant drawbacks: 1) limited desalination rates, making it difficult to meet the needs of industrial applications; 2) narrow adaptability to water salinity, with desalination rates significantly decreasing in high-salinity (salinity > 30 g / L) or low-salinity (salinity < 5 g / L) environments. Summary of the Invention

[0004] This invention provides an electrolytic cell device and method for simultaneously achieving desalination and electrocatalytic nitrate reduction. For the first time, the electrocatalytic nitrate reduction module and the desalination module are electrochemically coupled. Through electrochemical action, the desalination reaction and the electrocatalytic nitrate reduction to ammonia synthesis reaction are driven simultaneously, which can achieve efficient desalination and electrocatalytic nitrate reduction to ammonia synthesis at the same time, while improving the desalination rate.

[0005] On one hand, the present invention provides an electrolytic cell device for simultaneously achieving desalination and electrocatalytic nitrate reduction, comprising a cathode, an anode, and an intermediate spacer.

[0006] The anode is an activated carbon electrode. The cathode is a halogen-modified copper electrode. The intermediate spacer layer, made of metal Pt or activated carbon, physically divides the electrolytic cell into an electrocatalytic nitrate reduction to ammonia synthesis chamber and a desalination chamber. The electrocatalytic nitrate reduction to ammonia synthesis chamber and the desalination chamber are electrochemically coupled. The electrocatalytic nitrate reduction to ammonia chamber realizes the electrocatalytic reduction of nitrate to ammonia, the desalination chamber realizes desalination, and the electrolytic cell device simultaneously realizes desalination and electrocatalytic nitrate reduction to ammonia.

[0007] Furthermore, the electrocatalytic nitrate reduction ammonia synthesis chamber is provided with a nitrate reduction tank, a proton exchange membrane, and a nitrate reduction anode tank in sequence from the near cathode side.

[0008] Furthermore, the desalination chamber is provided with a first electrolyte tank, a first cation exchange membrane, a fresh water tank, an anion exchange membrane, a concentrated water tank, a second cation exchange membrane, and a second electrolyte tank in sequence from the side near the middle spacer layer.

[0009] Furthermore, the voltage of the electrolytic cell device during operation is -8V, and the liquid flow rate in the desalination chamber is 0.1~0.4mL / min. -¹ The initial nitrate concentration is 0.05~0.5M.

[0010] Furthermore, the desalination chamber is provided with a first electrolyte tank, a first cation exchange membrane, a low-concentration nitrate tank, an anion exchange membrane, a high-concentration nitrate tank, a second cation exchange membrane, and a second electrolyte tank in sequence from the side near the middle partition layer. The high-concentration nitrate tank is connected in series with the electrocatalytic nitrate reduction to ammonia synthesis chamber.

[0011] The high-concentration nitrate tank is connected in series with the electrocatalytic nitrate reduction and ammonia synthesis chamber via a peristaltic pump.

[0012] In another aspect, the present invention provides a method for simultaneously realizing desalination and electrocatalytic nitrate reduction. Based on any of the aforementioned electrolytic cell devices, the electrocatalytic nitrate reduction module and the desalination module are electrochemically coupled, and the desalination reaction and the electrocatalytic nitrate reduction to ammonia synthesis reaction are simultaneously driven by electrochemical action.

[0013] A method for simultaneously achieving desalting and electrocatalytic nitrate reduction uses a halogen-modified copper electrode as the cathode and activated carbon as the anode, with metal Pt or activated carbon as the intermediate spacer. The electrocatalytic nitrate reduction to ammonia synthesis unit and the desalting unit are electrochemically coupled. The left side of the intermediate spacer is the electrocatalytic nitrate reduction to ammonia synthesis unit, where hydroxide ion catalytic oxidation occurs; the right side is the desalting unit, where Fe³⁺ ions react. + Ion-catalyzed reduction reaction; a nitrate-containing solution is introduced into the electrocatalytic nitrate reduction to ammonia synthesis unit, and initial seawater is introduced into the desalination unit, causing nitrate reduction to occur on the cathode surface to generate ammonia, and Fe²⁺ to occur on the anode surface. + The catalytic oxidation reaction occurs simultaneously with ion migration within the desalting unit, ultimately achieving simultaneous desalting and electrocatalytic reduction of nitrate to synthesize ammonia.

[0014] In another aspect, the present invention provides a copper electrode for any of the aforementioned electrolytic cell devices, wherein the copper electrode is a halogen-modified copper electrode Cu@Cu-I, used as the cathode of the electrolytic cell device.

[0015] In another aspect, the present invention provides a method for preparing a copper electrode, the method comprising: Step S1, CuX precursor preparation: Using copper foam as a substrate, after cleaning, it is immersed in a mixture of sodium halide (NaX) and copper sulfate pentahydrate (CuSO4). The CuX precursor was soaked in a mixed solution of 5H2O and sulfuric acid H2SO4, then washed and dried to obtain a CuX precursor loaded on copper foam. Furthermore, the cleaning process involves sequentially ultrasonically cleaning for 10 minutes each in dilute hydrochloric acid, acetone, ethanol, and deionized water.

[0016] Furthermore, sodium halide (NaX) and copper sulfate pentahydrate (CuSO4) The molar ratio of sulfuric acid to sulfuric acid (5H2O) is 1.05:1, the concentration of sulfuric acid is 1M, and the amount added is 5.4% of the total volume of the mixed solution.

[0017] Furthermore, the immersion is made of sodium halide (NaX) and copper sulfate pentahydrate (CuSO4). Specifically, in a mixed solution of sodium halide (NaX) and sulfuric acid (H2SO4), solution A is obtained by dissolving sodium halide (NaX) in deionized water; and solution B is obtained by dissolving copper sulfate pentahydrate (CuSO4). Solution A is dissolved in deionized water to obtain solution B. While stirring continuously, solution A is slowly poured into solution B and mixed evenly. Then, sulfuric acid (H2SO4) solution is added and stirred evenly. Let stand for 15 minutes to obtain a mixed solution of the three. The cleaned copper foam substrate is immersed in the above mixed solution and taken out after soaking for about 200 seconds.

[0018] Further, after soaking and removal, the sample is washed several times alternately with deionized water and anhydrous ethanol, and finally dried in a vacuum drying oven at 60°C to obtain the Cu-X precursor loaded on copper foam.

[0019] Step S2, electrochemical reduction to prepare halogen-modified Cu electrode: Using the Cu-X precursor as the working electrode, the copper electrode Cu@Cu-X was obtained by constant potential electrochemical reduction treatment in sodium bicarbonate electrolyte.

[0020] Cu-X is grown in situ on the surface of copper foam, so the final electrode is Cu@Cu-X, where "@" indicates that Cu-X is coated with Cu.

[0021] Furthermore, the concentration of the sodium bicarbonate electrolyte was 0.1 M, the electrochemical reduction constant potential was -0.8 V (vs. RHE), the reduction time was 400 seconds, and the reduction process was carried out at room temperature and pressure. -0.8 V (vs. RHE) is relative to -0.8 V at the reversible hydrogen electrode.

[0022] Specifically, an aqueous solution of sodium bicarbonate (NaHCO3) was prepared as the electrolyte. A standard three-electrode system was used, with the Cu-X precursor as the working electrode. Chronoamperometry reduction was performed at a constant potential of -0.8 V (relative to the reversible hydrogen electrode, vs. RHE) for approximately 400 seconds. After reduction, the electrode was removed, rinsed with deionized water, and dried with nitrogen to obtain the target catalyst Cu-X.

[0023] This disclosure provides an electrolytic cell apparatus and method for simultaneously achieving desalination and electrocatalytic nitrate reduction, which has the following advantages compared with the prior art.

[0024] 1) The electrolytic cell device provided by the present invention is an integrated system that couples a desalination module and an electrochemical nitrate reduction module. It can achieve rapid desalination while efficiently synthesizing ammonia, providing a novel and integrated technical solution for solving the problems of nitrogen cycle imbalance and freshwater shortage.

[0025] 2) Existing coupling systems still suffer from limited desalination rates. This invention provides an electrolytic cell device that electrochemically couples an electrocatalytic nitrate reduction module with a desalination module. A halogen (Cl, Br, I) modified copper-based electrode is used as the cathode, and this copper-based electrode also serves as a catalyst for the electrocatalytic reduction of nitrate to ammonia (NRA) reaction. Halogen modification effectively modulates the electronic structure of copper, enhancing the adsorption of nitrate ions and promoting the water dissociation process, thereby significantly improving the activity and selectivity of the electrocatalytic ammonia synthesis, and simultaneously increasing the desalination rate while achieving both desalination and electrocatalytic nitrate reduction.

[0026] 3) Existing coupling systems have limited adaptability to water salinity. The inventors of this invention discovered that the activity and selectivity of electrocatalytic reduction to ammonia (NRA) are insufficient under low nitrate concentration (<0.1M) conditions. This invention improves the electrolytic cell device that electrochemically couples a desalination module and an electrochemical nitrate reduction module by introducing an in-situ nitrate enrichment unit, achieving a series synergistic operation of "enrichment-reduction," and significantly enhancing the continuous ammonia production capacity under low nitrate concentration conditions.

[0027] 4) The electrolytic cell device provided by the present invention can be used without a proton exchange membrane (PEM). It can ensure a sufficiently high desalination rate and continuous ammonia production capacity without a PEM, simplifying the structure, reducing costs by more than 30%, and avoiding membrane fouling problems.

[0028] 5) The electrolytic cell device provided by this invention can achieve a desalination rate of up to 188 μg. cm - ² min -¹, Ammonia yield can reach 1.16 mg h - ¹ cm - ², adaptable to a wide salinity range, this invention solves the problems of low desalination rate and narrow salinity adaptability in existing coupled systems, achieving efficient synergy between nitrate resource recovery and seawater desalination. The electrolytic cell device provided by this invention is suitable for treating marine wastewater or industrial wastewater containing nitrates. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A schematic diagram of the structure of an electrolytic cell device according to an embodiment of the present invention is shown.

[0031] Figure 2 A schematic diagram illustrating the working principle of the electrolytic cell device shown in an embodiment of the present invention is presented.

[0032] Figure 3 A schematic diagram of the structure of an electrolytic cell device according to another embodiment of the present invention is shown.

[0033] Figure 4 The SEM image of the halogen-modified copper electrode shown in the embodiment of the present invention is illustrated.

[0034] Figure 5 The effect of the intermediate spacer on the operating performance of the unit is shown, with the ammonia yield on the vertical axis.

[0035] Figure 6 The effects of the intermediate spacer and the addition of PEM on the device's performance are shown, where the horizontal axis represents desalination time and the vertical axis represents the current density of the entire desalination device.

[0036] Figure 7 The effect of operating voltage on the device's performance is shown, with the horizontal axis representing voltage and the vertical axis representing desalination rate.

[0037] Figure 8 The effect of operating voltage on the performance of the device is shown, where the horizontal axis represents voltage and the vertical axis represents ammonia yield.

[0038] Figure 9 The effect of operating voltage on the device's performance is shown, where the horizontal axis represents the device's operating time and the vertical axis represents the current density.

[0039] Figure 10 The effect of electrolyte flow rate on the device's performance is shown, where the horizontal axis represents the desalination rate and the vertical axis represents the desalination rate.

[0040] Figure 11 The effect of electrolyte flow rate on the device's performance is shown, with the horizontal axis representing flow rate and the vertical axis representing ammonia yield and nitrite concentration.

[0041] Figure 12 The effect of electrolyte flow rate on device performance is shown, where the horizontal axis represents operating time and the vertical axis represents current density and sodium chloride concentration.

[0042] Figure 13 The effect of initial nitrate concentration on the operating performance of the device is shown, with the horizontal axis representing nitrate concentration and the vertical axis representing desalination rate.

[0043] Figure 14 The effect of initial nitrate concentration on the operating performance of the device is shown. The horizontal axis represents nitrate concentration, and the vertical axis represents desalination rate and ammonia yield.

[0044] Figure 15 The effect of initial nitrate concentration on the device's performance is shown, with the horizontal axis representing operating time and the vertical axis representing current density and sodium chloride concentration.

[0045] Figure 16 A schematic diagram of the structure of an electrolytic cell device according to another embodiment of the present invention is shown.

[0046] Figure 17 The illustration shows an electrolytic cell device for treating marine wastewater according to an embodiment of the present invention. The horizontal axis represents the working time, and the vertical axis represents the nitrate concentration.

[0047] Figure 18 The illustration shows an electrolytic cell device for treating marine wastewater according to an embodiment of the present invention. The horizontal axis represents the working time, and the vertical axis represents the ammonia yield.

[0048] The components include: Cu@Cu-I cathode 1, anode 2, intermediate spacer 3, nitrate reduction tank 11, PEM proton exchange membrane 12, nitrate reduction anode tank 13, first electrolyte tank 21, first cation exchange membrane 22, freshwater tank 23, anion exchange membrane 24, concentrated brine tank 25, second cation exchange membrane 26, second electrolyte tank 27, water inlet 111 of nitrate reduction tank 11, water outlet 112 of nitrate reduction tank 11, low-concentration nitrate tank 28, high-concentration nitrate tank 29, power supply 4, peristaltic pump 5, and connecting pipe 6. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0050] Example 1: Construction of Electrolytic Cell Apparatus like Figure 1 As shown, this embodiment of the invention provides an electrolytic cell device. The electrolytic cell device uses a halogen I-modified copper electrode Cu@Cu-I as the cathode 1 and activated carbon (AC) as the anode 2. The electrolytic cell device is physically divided into an electrocatalytic nitrate reduction to ammonia (NRA) chamber and a desalination chamber by an intermediate partition 3. The electrocatalytic nitrate reduction to ammonia chamber and the desalination chamber are electrochemically coupled, and the electrocatalytic nitrate reduction module and the desalination module are electrochemically coupled into an integrated system. This electrolytic cell device can simultaneously realize desalination and electrocatalytic reduction of nitrate. The intermediate partition 3 is made of metal Pt.

[0051] like Figure 1 As shown, the electrocatalytic nitrate reduction ammonia synthesis chamber is provided with the following in sequence from the side near the cathode 1: nitrate reduction tank (flowing tank plate, with water inlet 111 on the side and water outlet 112 at the top) 11, proton exchange membrane 12, and nitrate reduction anode tank (flowing tank plate, with water inlet on the side and water outlet at the top) 13; the desalination chamber is provided with the following in sequence from the side near the middle partition 3: first electrolyte tank (flowing tank plate, with water inlet on the side and water outlet at the top) 21, first cation exchange membrane 22, desalinated water tank (flowing tank plate, with water inlet on the side and water outlet at the top) 23, anion exchange membrane 24, concentrated water tank (flowing tank plate, with water inlet on the side and water outlet at the top) 25, second cation exchange membrane 26, and second electrolyte tank (flowing tank plate, with water inlet on the side and water outlet at the top) 27.

[0052] The NRA chamber uses a surface-modified copper electrode (Cu@Cu-I) as the cathode to drive the nitrate reduction to ammonia synthesis reaction. The desalination chamber uses activated carbon (AC) as the anode to drive the Fe²⁺ in the electrolyte... + Oxidized to Fe³ + The resulting ion concentration gradient is the primary driving force for desalination. On either side of the intermediate spacer, the oxygen evolution reaction (OER) and Fe³⁺ reaction occur, respectively. + Reduced to Fe² + The reactions constitute a complete electrochemical cycle. For example... Figure 1 and Figure 2As shown, a reduction reaction (nitrate reduction) occurs on the surface of cathode 1. The proton exchange membrane (PEM) only allows hydrogen ions to pass through, ensuring that the ammonium ions reduced by cathode 1 do not migrate to other tanks and can only flow out from the outlet 112 of the nitrate reduction tank 11. In the intermediate partition 3, hydroxide catalytic oxidation occurs on the left and Fe³⁺ catalytic oxidation occurs on the right. + Ion-catalyzed reduction reaction. Anode 2 catalyzes the oxidation of Fe2+. Initial seawater enters from the inlet of the freshwater tank and the inlet of the concentrated water tank, with the initial concentrations of both streams being the same. Na and Cl ions are removed from the seawater entering through the freshwater tank inlet, resulting in freshwater that flows out from the freshwater tank outlet. Seawater entering through inlet 17 of the concentrated brine tank receives ions from the freshwater stream, becoming concentrated brine, which flows out from the concentrated brine tank outlet. Nitrate reduction occurs on the cathode surface to produce ammonia, while Fe2+ oxidation occurs on the anode surface. + The catalytic oxidation reaction occurs simultaneously with ion migration within the desalination chamber, ultimately achieving simultaneous desalination of the water and electrocatalytic reduction of nitrate to synthesize ammonia.

[0053] Two bosses of the same thickness as the plate are provided on the top and side of the flow tank plate for installing pipelines.

[0054] The electrolyte is Fe 2+ / F e3+ Electrolytes, containing Fe²⁺ + / Fe³ + Electrolytes with redox pairs.

[0055] like Figure 3 As shown, the proton exchange membrane 12 can be omitted from the electrocatalytic nitrate reduction ammonia synthesis chamber. The electrocatalytic nitrate reduction ammonia synthesis chamber is equipped with a nitrate reduction tank 11, but does not have a proton exchange membrane.

[0056] Example 2: Preparation of Cu@Cu-I Electrode 1) Preparation of precursor CuI First, the copper foam substrate (approximately 1 cm × 1.5 cm in size) was cleaned. It was ultrasonically cleaned for 10 minutes each in dilute hydrochloric acid, acetone, ethanol, and deionized water in sequence to thoroughly remove the surface oxide layer and organic stains. After cleaning, it was dried with nitrogen gas for later use.

[0057] Subsequently, the reaction solutions were prepared: 3.74 g of sodium iodide (NaI) was dissolved in 25 mL of deionized water to obtain solution A; 1.25 g of copper sulfate pentahydrate (CuSO4·5H2O) was dissolved in 25 mL of deionized water to obtain solution B.

[0058] While stirring continuously, slowly pour solution A into solution B and mix thoroughly. Then add 2.7 mL of 1 M sulfuric acid (H2SO4) solution and continue stirring until the mixture is homogeneous. Let stand for 15 minutes.

[0059] The pre-treated copper foam was immersed in the above mixed solution for about 200 seconds and then removed. The removed material was washed several times alternately with deionized water and anhydrous ethanol, and finally dried in a vacuum drying oven at 60°C to obtain the CuI precursor loaded on the copper foam.

[0060] 2) Electrochemical reduction preparation of halogen-modified Cu electrode Cu@Cu-I A 0.1 M sodium bicarbonate (NaHCO3) aqueous solution was prepared as the electrolyte. A standard three-electrode system was used, with the CuI precursor as the working electrode. Chronoamperometry reduction was performed at a constant potential of -0.8 V (relative to the reversible hydrogen electrode, vs. RHE) for approximately 400 seconds. After reduction, the electrode was removed, rinsed with deionized water, and dried under nitrogen to obtain the target catalyst Cu@Cu-I.

[0061] Figure 4 High-magnification SEM images of CuI and Cu-I are shown. CuI exhibits a polyhedral nanoparticle morphology with an average particle size of approximately 500 nm. Reduced Cu-I exhibits a nanoparticle morphology with a surface composed of nanospheres, which may provide more reactive sites for the electrocatalytic NRA reaction.

[0062] The Influence of the Spacer Layer on the Performance of the Electrolytic Cell Device in Example 3 Device construction: Adopted from Example 1 respectively Figure 1 and Figure 3 The electrolytic cell apparatus shown has one set of intermediate spacers made of metal Pt and another set of intermediate spacers made of activated carbon AC.

[0063] like Figure 5-6 As shown, when the intermediate layer is Pt, the NRA activity of the device is significantly higher than that when the AC intermediate layer is used, while the overall desalination performance and system current density are less affected.

[0064] Example 4: The effect of setting a proton exchange membrane (PEM) on the working performance of the electrolyzer device Device construction: using Example 1 Figure 1 and Figure 3 The electrolytic cell apparatus shown has one set of intermediate spacers made of metal Pt and another set of intermediate spacers made of activated carbon AC.

[0065] In traditional NRA modules, the role of the PEM is to conduct protons and isolate the anion and anodic reactions, preventing the generation of NH4. + It is oxidized at the anode. This example investigates the effect of having and not having PEM in the NRA on the performance of the electrolytic cell apparatus. Figures 5-6As shown, while removing PEM reduces NRA activity (especially under Pt separator conditions) by approximately 31%, its impact on desalination performance and overall system current density is limited. Timely capture of the product NH3 effectively avoids NH4+. + The loss of PEM (Potentially Differentiated Module) is a significant issue. In complex flow fields integrating multiple independent chambers, using PEM increases system complexity and cost. Therefore, the electrolytic cell device of this invention can remove the PEM, simplifying the structure and greatly reducing costs.

[0066] Example 5: The Influence of Voltage on the Operating Performance of an Electrolytic Cell Unit Device construction: using Example 1 Figure 3 The electrolytic cell device shown has a metal Pt intermediate layer and no proton exchange membrane (PEM).

[0067] This embodiment studies the effect of voltages ranging from -5V to -9V on the operating performance of an electrolytic cell device. For example... Figure 7-9 As shown, at higher external voltages (e.g., -8 V vs. OC at two electrodes), the system achieves higher desalination rates and ammonia yields. Comparison reveals that the maximum and minimum ammonia yields differ by 55% and the desalination rates by 58% under different voltages. Considering all factors, the -8 V vs. OC voltage ensures a relatively high ammonia yield (1.16 mg h⁻¹). - ¹ cm - While maintaining a high desalination rate, ²)

[0068] Example 6: The effect of flow rate variation on the operating performance of the electrolytic cell device Device construction: using Example 1 Figure 3 The electrolytic cell device shown has a Pt metal spacer in the middle, no proton exchange membrane (PEM), and a voltage of -8V.

[0069] like Figure 10-12 As shown, changes in the liquid flow rate within the NRA chamber have a relatively small impact on the system's desalination performance (the difference between the maximum and minimum desalination rates is only 16%), but a significant impact on the NRA performance (the difference between the maximum and minimum ammonia yields is 85%). Lower flow rates (e.g., 0.1 mL / min) are more effective. - ¹) It helps to inhibit nitrite (NO2) - The accumulation of byproducts such as ammonia significantly improves the selectivity and yield of ammonia.

[0070] Example 7: Effect of initial nitrate concentration on the performance of the electrolytic cell device Device construction: using Example 1 Figure 3 The electrolytic cell apparatus shown has a Pt intermediate spacer, no PEM (proton exchange membrane), a voltage of -8V, and a flow rate of 0.1 mL / min. - ¹.

[0071] like Figures 13-15 As shown, the initial nitrate concentration has almost no effect on desalination performance, but it has a decisive impact on NRA activity (the difference between the maximum and minimum ammonia yield is 93%). At low concentrations, it is difficult to establish a dynamic equilibrium between nitrate ions and active hydrogen at the reaction site, leading to decreased activity. At a concentration of 0.5 M, the ammonia yield has already reached a relatively high level, and the increase in yield from further increasing the concentration slows down. Considering all factors, a nitrate concentration of 0.5 M is preferred.

[0072] Example 8: Practical Application Experiment in Seawater Device construction: using Example 1 Figure 3 The electrolytic cell apparatus shown has a Pt intermediate spacer, no PEM (proton exchange membrane), a voltage of -8V, and a flow rate of 0.1 mL / min. - ¹, The NRA chamber is filled with seawater with an initial nitrate concentration of 0.5M.

[0073] Experimental results: Ammonia yield 1.16 mg / h - ¹ cm - ² and desalination rate 188 μg cm - ² min - ¹, the salinity of the desalinated freshwater is <1g / L, which meets the drinking water standard, proving the adaptability of the device to seawater.

[0074] Example 9: Electrolytic cell device specifically designed for low-concentration nitrates like Figure 16 As shown, another embodiment of the present invention provides an electrolytic cell device 1 specifically for low-concentration nitrates, wherein the desalination chamber includes a low-concentration nitrate pool (L-NO3). - Pool 28 and high-concentration nitrate pool (H-NO3) - The high-concentration nitrate pool 29 is connected in series with the electrocatalytic nitrate reduction ammonia synthesis chamber 14. The high-concentration nitrate pool 29 and the low-concentration nitrate pool 28 are electrochemically connected. Based on the ion gradient generated by electrochemistry, nitrate ions are driven to migrate from the low-concentration nitrate pool 28 to the high-concentration nitrate pool 29 through the anion exchange membrane 24. Then, the high-concentration nitrate pool 29 enters the nitrate reduction pool 11 of the electrocatalytic nitrate reduction ammonia synthesis chamber via the peristaltic pump 5 and the connecting pipeline 6. At this point, the low-concentration nitrate is enriched in situ to a high concentration and enters the electrocatalytic nitrate reduction ammonia synthesis chamber to be electrocatalytically reduced to ammonia and discharged from the outlet of the nitrate reduction pool.

[0075] Performance testing: at -8 V vs. OC voltage and 0.1 mL min - ¹The flow rate in the experiment refers to the liquid flow rate of the NRA. In this embodiment, the flow rate of the NRA is consistent with the brine flow rate of the nitrate enrichment module, such as... Figure 17The device shown can remove 50 mM of NO3 within 1 hour. - The solution was enriched to 71.9 mM and stably discharged. The stable ammonia yield after enrichment reached 700.6 μg / h. -1 cm -2 ,like Figure 18 As shown, compared to before enrichment (151.6 μg h), -1 cm -2 It increased by about 4.6 times and can achieve continuous and stable ammonia production.

[0076] The system first utilizes an electrochemically generated ion gradient to drive NO3 - Transmission of L-NO3 through anion exchange membrane - Pool direction H-NO3 - The pool is migrated to achieve pre-concentration of nitrates. Subsequently, the concentrating H-NO3 is... - The tank is connected in series with the NRA reaction tank to provide high-concentration raw materials for the NRA reaction.

[0077] This embodiment effectively overcomes the technical bottleneck of low reduction efficiency of low-concentration nitrates, greatly expanding the application scope and practicality of this integrated system.

[0078] This embodiment successfully constructed an integrated platform capable of simultaneously and efficiently synthesizing ammonia and desalinating seawater through ingenious system design, optimized selection of key components, and precise control of operating parameters, and provides an effective solution for treating low-concentration nitrate wastewater.

[0079] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the invention. The scope of the present invention is defined by the appended claims and their equivalents.

[0080] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An electrolytic cell device for simultaneously achieving desalination and electrocatalytic nitrate reduction, characterized in that, Includes cathode, anode, and intermediate spacer. The anode is an activated carbon electrode. The cathode is a halogen-modified copper electrode. The intermediate spacer layer, made of metal Pt or activated carbon, physically divides the electrolytic cell into an electrocatalytic nitrate reduction to ammonia synthesis chamber and a desalination chamber. The electrocatalytic nitrate reduction to ammonia synthesis chamber and the desalination chamber are electrochemically coupled. The electrocatalytic nitrate reduction to ammonia chamber is used to drive the nitrate reduction to ammonia reaction with a halogen-modified copper electrode as the cathode; the desalting chamber is used to drive the Fe²⁺ in the electrolyte with activated carbon as the anode. + Oxidized to Fe³ + The resulting ion concentration gradient from the reaction acts as the driving force for desalination; on both sides of the intermediate spacer, oxygen evolution reaction and Fe³⁺ reaction occur, respectively. + Reduced to Fe² + The reaction.

2. The apparatus according to claim 1, characterized in that, The electrocatalytic nitrate reduction to ammonia synthesis chamber is provided with a nitrate reduction cell, a proton exchange membrane, and a nitrate reduction anode cell in sequence from the near cathode side.

3. The apparatus according to claim 1, characterized in that, The electrocatalytic nitrate reduction to ammonia synthesis chamber is not equipped with a proton exchange membrane, but is equipped with a nitrate reduction tank.

4. The apparatus according to claim 2 or 3, characterized in that, The desalination chamber is provided with a first electrolyte tank, a first cation exchange membrane, a fresh water tank, an anion exchange membrane, a concentrated brine tank, a second cation exchange membrane, and a second electrolyte tank in sequence from the side near the middle partition layer.

5. The apparatus according to claim 4, characterized in that, The electrolytic cell operates at a voltage of -8V, and the liquid flow rate within the electrocatalytic nitrate reduction to ammonia synthesis chamber is 0.1~0.4 mL / min. - ¹, The initial nitrate concentration is 0.05~0.5M.

6. The apparatus according to claim 2 or 3, characterized in that, The desalination chamber is provided with a first electrolyte tank, a first cation exchange membrane, a low-concentration nitrate tank, an anion exchange membrane, a high-concentration nitrate tank, a second cation exchange membrane, and a second electrolyte tank in sequence from the side near the middle partition layer. The high-concentration nitrate tank is connected in series with the electrocatalytic nitrate reduction to ammonia synthesis chamber.

7. The electrolytic cell apparatus according to claim 6, characterized in that, The high-concentration nitrate tank is connected in series with the electrocatalytic nitrate reduction and ammonia synthesis chamber via a peristaltic pump.

8. A method for simultaneously achieving desalination and electrocatalytic nitrate reduction, characterized in that, Using a halogen-modified copper electrode as the cathode and activated carbon as the anode, with metal Pt or activated carbon as the intermediate spacer, the electrocatalytic nitrate reduction to ammonia synthesis unit and the desalination unit are electrochemically coupled. The left side of the intermediate spacer is the electrocatalytic nitrate reduction to ammonia synthesis unit, where the oxygen evolution reaction occurs, and the right side is the desalination unit, where the Fe³⁺ reaction occurs. + Ion-catalyzed reduction reaction; The electrocatalytic nitrate reduction to ammonia synthesis unit uses a surface-modified copper electrode as the cathode to drive the nitrate reduction to ammonia synthesis reaction; The desalination unit uses activated carbon as the anode to drive Fe²⁺ in the electrolyte. + Oxidized to Fe³ + The resulting ion concentration gradient is the driving force for desalination.

9. A copper electrode for the electrolytic cell apparatus of claim 1, characterized in that, The copper electrode is a halogen-modified copper electrode Cu@Cu-X, used as the cathode of the electrolytic cell device, and the halogen X is selected from Cl, Br, and I.

10. The copper electrode according to claim 9, characterized in that, It was prepared according to the following method: (1) Preparation of CuX precursor: Using copper foam as a substrate, after cleaning, it is immersed in a mixture of sodium halide NaX and copper sulfate pentahydrate CuSO4. The CuX precursor was obtained by soaking, washing, and drying in a mixed solution of 5H2O and sulfuric acid H2SO4 on copper foam. (2) Electrochemical reduction: Using the CuX precursor as the working electrode, the copper electrode Cu@Cu-X is obtained by constant potential electrochemical reduction in sodium bicarbonate electrolyte.

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