Carbon felt-based phosphorus-doped bimetallic catalytic electrode as well as preparation method and application thereof

Abstract

The invention discloses a carbon felt-based phosphorus-doped bimetallic catalytic electrode and a preparation method and application thereof.The preparation method of the carbon felt-based phosphorus-doped bimetallic catalytic electrode comprises the steps that copper salt, platinum salt and first water are mixed to be uniform, then ammonium fluoride and urea are added, the mixture is mixed to be uniform, and a transparent solution is obtained; under the ultrasonic condition, the activated carbon fiber felt is soaked in the transparent solution and subjected to ultrasonic treatment, a first mixture is obtained, the first mixture is subjected to standing at the temperature of 120-140 DEG C and dried, and a bimetal co-loaded intermediate is obtained; enabling gas flow of inert gas to pass through the furnace body and forming an inert gas atmosphere in the furnace body, placing the bimetallic co-loaded intermediate at the downstream of the gas flow, placing a phosphorus source at the upstream of the gas flow, calcining the phosphorus source at 350-400 DEG C and calcining the bimetallic co-loaded intermediate at 350-400 DEG C to obtain the carbon felt-based phosphorus-doped bimetallic catalytic electrode. The ammonia yield of the prepared carbon felt-based phosphorus-doped bimetallic catalytic electrode reaches 25.24 mg / h / cm < 2 >, and meanwhile, the carbon felt-based phosphorus-doped bimetallic catalytic electrode has ultrahigh Faraday efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a carbon felt-based phosphorus-doped bimetallic catalytic electrode and a preparation method and application thereof. Background Art

[0002] Ammonia (NH3) has long been a vital chemical feedstock for human life, playing a crucial role in industry, agricultural production, energy storage, and conversion. Global demand for NH3 exceeds 150 million tons annually. Currently, large-scale NH3 production relies primarily on the traditional Haber-Bosch process. However, this method not only involves demanding process conditions, such as high temperatures (300-500°C) and high pressures (150-300 atm), but also requires significant energy input, resulting in low conversion and yield rates and causing serious environmental problems.

[0003] The NO bond in the nitrate redox reaction (NO₃-RR) has a lower bond energy (204 kJ / mol), making it more susceptible to breakage from a thermodynamic perspective. Furthermore, nitrate is one of the most common pollutants in our natural aquatic environment, seriously endangering human health and significantly disrupting the nitrogen balance in ecosystems. Therefore, utilizing renewable energy and electricity to synthesize NH₃ from nitrates in wastewater at room temperature and pressure is a green alternative to the traditional Haber-Bosch process, simultaneously achieving waste resource conversion and environmental remediation.

[0004] In recent years, research on electrocatalytic NO₃-RR has become increasingly widespread. However, because NO₃-RR involves eight electron transfers, it has low reaction kinetics and efficiency. Furthermore, the competition from side reactions such as hydrogen evolution and nitrite formation complicates the NO₃-RR reaction pathway. Consequently, the NH₃ generation rate, Faradaic efficiency, and energy efficiency in current research are relatively low, far from meeting industrial requirements. Furthermore, current research on NO₃-RR has primarily focused on alkaline environments, while studies on NO₃-RR under neutral conditions, such as groundwater, are limited. Achieving highly selective and efficient NH₃ synthesis from neutral nitrate wastewater remains a significant challenge. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for preparing a carbon felt-based phosphorus-doped bimetallic catalytic electrode.

[0006] Another object of the present invention is to provide a carbon felt-based phosphorus-doped bimetallic catalytic electrode obtained by the above preparation method, wherein the carbon felt-based phosphorus-doped bimetallic catalytic electrode is a Pt and P-doped Cu-based bimetallic catalytic electrode (Cu-Pt-P).

[0007] Another object of the present invention is to provide the application of the above-mentioned carbon felt-based phosphorus-doped bimetallic catalytic electrode in NO3-RR ammonia synthesis to solve the current problems of poor catalytic performance and poor selectivity of NO3-RR under neutral conditions.

[0008] The purpose of the present invention is achieved through the following technical solutions.

[0009] A method for preparing a carbon felt-based phosphorus-doped bimetallic catalytic electrode comprises the following steps:

[0010] Step 1: Mixing a copper salt, a platinum salt, and a first water until uniform, then adding ammonium fluoride and urea, and mixing until uniform to obtain a transparent solution, wherein the ratio of copper element in the copper salt to platinum element in the platinum salt is 0.24: (0.073-0.13) based on the amount of substance;

[0011] In step 1, the ratio of the amount of copper element in the copper salt, the mass of urea and the mass of ammonium fluoride is 0.24: (0.45-0.5): (0.14-0.16), the unit of the amount of substance is mmol, and the unit of the mass is g.

[0012] In step 1, the ratio of the amount of copper element in the copper salt to the volume of the first water is 0.24:(25-30), the unit of the amount of copper is mmol, and the unit of the volume is mL.

[0013] In step 1, the copper salt is copper nitrate, and the platinum salt is chloroplatinic acid.

[0014] Step 2: activating the carbon fiber felt to increase the oxygen-containing groups on its surface to obtain activated carbon fiber felt. Under ultrasonic conditions, the activated carbon fiber felt is immersed in the transparent solution and ultrasonicated for at least 3 minutes to obtain a first mixture (a heterogeneous mixed solution). The first mixture is allowed to stand at 120-140°C for 6-7 hours and dried to obtain a bimetallic co-loaded intermediate (the bimetallic co-loaded intermediate is a carbon fiber felt loaded with bimetallic elements, and the bimetallic elements are Cu and Pt). The ratio of the volume fraction of the activated carbon fiber felt to the amount of copper element in the copper salt is 1.2:0.24, and the unit of volume fraction is cm 3 , the unit of the amount of substance is mmol;

[0015] In step 2, the method for obtaining activated carbon fiber felt includes: immersing the carbon fiber felt in a mixed solution of methanol and a second water, standing at 60 to 80°C for 6 to 12 hours, drying, and then immersing it in a mixed solution of sulfuric acid, nitric acid and a third water, standing at 60 to 80°C for 12 to 24 hours to obtain activated carbon fiber felt.

[0016] In the method for obtaining activated carbon fiber felt, the ratio of methanol to the second water is (30-40):70 by volume.

[0017] In the method for obtaining activated carbon fiber felt, the ratio of nitric acid, sulfuric acid and the third water is (5-6):(10-20):45 by volume.

[0018] In the method for obtaining the activated carbon fiber felt, the concentration of nitric acid is 0.1-0.5M, and the concentration of sulfuric acid is 0.1-0.5M.

[0019] In step 2, the size of the carbon fiber felt is 20 mm×20 mm×3 mm.

[0020] Step 3: Pass an inert gas flow through the furnace body to form an inert gas atmosphere in the furnace body, place the bimetallic co-loaded intermediate downstream of the gas flow, place the phosphorus source upstream of the gas flow, calcine the phosphorus source at 350-400°C and calcine the bimetallic co-loaded intermediate at 350-400°C at the same time to obtain a carbon felt-based phosphorus-doped bimetallic catalytic electrode, wherein the calcination time is 2-2.5 hours, and the ratio of copper element in the bimetallic co-loaded intermediate to phosphorus element in the phosphorus source is 0.24:(0.94-1.88) based on the amount of substance.

[0021] In step 3, the phosphorus source is sodium hypophosphite.

[0022] In step 3, the temperature is raised to 350-400° C. at a rate of 4-6° C. / min.

[0023] The carbon felt-based phosphorus-doped bimetallic catalytic electrode obtained by the above preparation method.

[0024] The application of the above-mentioned carbon felt-based phosphorus-doped bimetallic catalytic electrode in the synthesis of ammonia by the redox reaction of nitrate.

[0025] In the above technical solution, ammonia is synthesized in a neutral environment using a carbon felt-based phosphorus-doped bimetallic catalytic electrode.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. The carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared by the present invention has a high redox potential in a neutral environment, and its starting potential (the current density corresponding to the starting potential is -10mA / cm 2 ) is 0.78 V vs. RHE, and the current density is -100 mA / cm 2 The overpotential is 0.567 V vs. RHE.

[0028] 2. The carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared by the present invention has an ammonia production of up to 25.24 mg / h / cm in an H-type electrolytic cell.2 , and also has ultra-high Faraday efficiency (91.9%).

[0029] 3. The carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared by the present invention has a wide range of NO3 - It has high ammonia production performance within the concentration range (10-2000mM) and has ultra-high selectivity and applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 LSV curves of the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1, the phosphorus-doped copper-based catalytic electrode prepared in Example 2, the bimetallic catalytic electrode prepared in Example 3, and the phosphorus-doped platinum-based catalytic electrode prepared in Example 4 as working electrodes;

[0031] Figure 2 The Tafel curves of the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1, the phosphorus-doped copper-based catalytic electrode prepared in Example 2, the bimetallic catalytic electrode prepared in Example 3, and the phosphorus-doped platinum-based catalytic electrode prepared in Example 4 as working electrodes are shown;

[0032] Figure 3 The carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 was used as the working electrode under different NO3 - LSV curve under concentration;

[0033] Figure 4 NH3 production in NO3-RR test at -0.3V vs. RHE using the carbon felt-based phosphorus-doped bimetallic catalytic electrodes prepared in Examples 1 and 5 to 9 as working electrodes;

[0034] Figure 5 The carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 was used as the working electrode to measure the NH3 production, the Faradaic efficiency of synthesizing NH3, and the Faradaic efficiency of synthesizing nitrite in the NO3-RR test at different voltages;

[0035] Figure 6 The carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 was used as the working electrode under different NO3 - NH3 production and Faradaic efficiency of synthesized NH3 in NO3-RR test under different concentration conditions;

[0036] Figure 7 The NH3 production in the NO3-RR test at different voltages using the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1, the phosphorus-doped copper-based catalytic electrode prepared in Example 2, the bimetallic catalytic electrode prepared in Example 3, and the phosphorus-doped platinum-based catalytic electrode prepared in Example 4 as working electrodes respectively;

[0037] Figure 8 The carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1, the phosphorus-doped copper-based catalytic electrode prepared in Example 2, the bimetallic catalytic electrode prepared in Example 3, and the phosphorus-doped platinum-based catalytic electrode prepared in Example 4 were used as working electrodes to test the Faradaic efficiency of NH3 under NO3-RR at different voltages;

[0038] Figure 9 The carbon felt-based phosphorus-doped bimetallic catalytic electrode of Example 1 was used as the working electrode for NO3-RR test and the resulting electrolyte was analyzed by hydrogen nuclear magnetic resonance spectrum;

[0039] Figure 10 The carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 was tested for NO3 in NO3-RR. - 、NO2 - and NH3 concentration changes;

[0040] Figure 11 X-ray photoelectron spectrum of the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1;

[0041] Figure 12 The element content test results of the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1;

[0042] Figure 13 This is the X-ray diffraction spectrum of the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further described below with reference to specific embodiments.

[0044] The purity and purchasing manufacturers of the drugs involved in the following examples are as follows:

[0045]

[0046]

[0047]

[0048] The models and manufacturers of the instruments involved in the following embodiments are as follows:

[0049] Model / Specifications Instruments / Equipment Manufacturer CJB-S140 magnetic stirrer Tianjin Kono Instrument Equipment Co., Ltd. 101-3A Electric constant temperature drying oven Shanghai Shengke Instrument Equipment Co., Ltd. TG16-WS Desktop high-speed centrifuge Hunan Xiangyi Centrifuge Company 150ml beaker Zhengzhou Xinyuan Glass Instruments Thermo Kalpha X-ray photoelectron spectrometer Thermo Fisher Scientific U-3900H UV-visible spectrophotometer Hitachi Corporation CHI660E Electrochemical workstation Shanghai Chenhua Instrument Co., Ltd. Thermo Fisher Scientific Aquion Ion chromatography Thermo Fisher Scientific OTF-1200X-S Tube furnace Hefei Kejing Materials Technology Co., Ltd.

[0050] In the following examples, water is deionized water.

[0051] Example 1 and Examples 5 to 9

[0052] A method for preparing a carbon felt-based phosphorus-doped bimetallic catalytic electrode comprises the following steps:

[0053] Step 1, uniformly dispersing a copper salt and a platinum salt in a first water (i.e., water), then adding ammonium fluoride and urea, and mixing until uniform to obtain a transparent solution, wherein the ratio of the copper element in the copper salt to the platinum element in the platinum salt is X, the ratio of the amount of copper element in the copper salt, the mass fraction of urea, and the mass fraction of ammonium fluoride is 0.24:0.45:0.15, the unit of the amount of substance is mmol, the unit of mass fraction is g, the ratio of the amount of copper element in the copper salt to the volume fraction of the first water is 0.24:25, the unit of the amount of substance is mmol, the unit of volume fraction is mL, the copper salt is copper nitrate, and the platinum salt is chloroplatinic acid;

[0054] Step 2: Under ultrasonic conditions, immerse the activated carbon fiber felt in a transparent solution, ultrasonicate for 10 minutes to obtain a first mixture (a heterogeneous mixed solution), place the first mixture in an oven, and let it stand at 120°C for 7 hours. Take out the carbon fiber felt and dry it at 60°C for 12 hours to obtain a bimetallic co-loaded intermediate (the bimetallic co-loaded intermediate is a carbon fiber felt loaded with bimetallic elements, and the bimetallic elements are Cu and Pt). The ratio of the volume fraction of the activated carbon fiber felt to the amount of copper element in the copper salt is 1.2:0.24, and the unit of the volume fraction is cm 3 , the unit of amount of substance is mmol,

[0055] The method for obtaining an activated carbon fiber felt (activating the carbon fiber felt to increase the oxygen-containing groups on its surface) comprises: immersing the carbon fiber felt in a mixed solution of methanol and a second water (i.e., water) (mixing methanol and the second water, ultrasonically treating for 3 minutes until uniform, to obtain a mixed solution of methanol and the second water), standing in a water bath at 80°C for 6 hours, taking out the carbon fiber felt and drying it at 60°C for 12 hours, and then immersing it in a mixed solution of sulfuric acid, nitric acid, and a third water (i.e., water) (mixing nitric acid, sulfuric acid, and the third water, ultrasonically treating for 3 minutes until uniform, to obtain a mixed solution of sulfuric acid, nitric acid, and the third water), standing in a water bath at 80°C for 12 hours to obtain an activated carbon fiber felt, wherein the ratio of methanol to the second water is 30:70 by volume, the ratio of nitric acid, sulfuric acid, and the third water is 5:10:45 by volume, the concentration of HNO3 in nitric acid is 0.1M, the concentration of H2SO4 in sulfuric acid is 0.1M, and the size of the carbon fiber felt is 20mm×20mm×3mm;

[0056] Step 3: pass an inert gas flow through the furnace body (muffle furnace) and form an inert gas atmosphere in the furnace body, place the bimetallic co-loaded intermediate and the phosphorus source at both ends of the porcelain boat respectively, place the porcelain boat in the furnace body, place the bimetallic co-loaded intermediate downstream of the airflow, place the phosphorus source upstream of the airflow, heat the temperature to 350°C at a rate of 5°C / min, calcine the phosphorus source at 350°C and calcine the bimetallic co-loaded intermediate at 350°C at the same time to obtain a carbon felt-based phosphorus-doped bimetallic catalytic electrode, wherein the inert gas is argon, the calcination time is 2h, and the ratio of copper element in the bimetallic co-loaded intermediate to phosphorus element in the phosphorus source is Y in terms of amount of substance, and the phosphorus source is sodium hypophosphite.

[0057] X and Y are shown in Table 1.

[0058] Table 1

[0059]

[0060] The surface element composition of the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 was characterized by X-ray photoelectron spectroscopy. Figure 11 As shown in the figure, the surface of the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 showed obvious Cu 2p 、P 2p , Pt 4f Characteristic peaks indicate that platinum and phosphorus have been successfully doped into the copper substrate. Figure 13 The X-ray diffraction shown further illustrates the doping mode of different elements in the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1, indicating that Pt and P are doped in the copper substrate in the form of PtP2 and Cu3P, respectively.

[0061] Figure 12 The element content test results of the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 (used to characterize the content of metal element Cu, metal element Pt and non-metal element P) are as follows: Figure 12 As shown, the Cu content is 12.4 wt%, the Pt content is 6.2 wt%, and the P content is 81.4 wt%.

[0062] Example 2

[0063] A method for preparing a phosphorus-doped copper-based catalytic electrode is basically the same as that of Example 1, except that no platinum salt (chloroplatinic acid) is added in Example 2.

[0064] Example 3

[0065] A method for preparing a bimetallic catalytic electrode comprises: placing the bimetallic co-loaded intermediate prepared in Example 1 in a muffle furnace, heating it to 350° C. at a rate of 5° C. / min, and calcining it at 350° C. for 2 h to obtain a bimetallic catalytic electrode.

[0066] Example 4

[0067] A method for preparing a phosphorus-doped platinum-based catalytic electrode is basically the same as that of Example 1, with the only difference being that no copper salt (copper nitrate) is added in Example 4.

[0068] Example 10

[0069] NO3-RR test: At room temperature, an electrochemical workstation was used to conduct the redox reaction of nitrate using a three-electrode system in an H-type electrolytic cell. The three electrodes were a working electrode, a counter electrode, and a reference electrode. The counter electrode was a platinum electrode, and the reference electrode was a saturated silver chloride electrode. The working electrode (the working electrode size was 10 mm × 10 mm × 3 mm) and the reference electrode were placed in the cathode chamber, and the counter electrode was placed in the anode chamber. The cathode chamber and the anode chamber were separated by a proton exchange membrane. 30 ml of electrolyte was added to each of the cathode chamber and the anode chamber. Argon was introduced into the cathode chamber in advance to prevent the influence of other substances such as dissolved oxygen. The electrolyte in the cathode chamber was sodium sulfate, sodium nitrate- 14 N(Na 14 NO3) and water mixed solution (Na2SO4 and Na 14 The concentration of NO3 is 0.1M), and the electrolyte in the anode chamber is sodium sulfate solution (the sodium sulfate solution is a mixture of anhydrous sodium sulfate and water, and the concentration of Na2SO4 in the sodium sulfate solution is 0.1M).

[0070] In the NO3-RR test of this embodiment, the voltage was set to 0.3-0.9 V vs. RHE, and the working electrode was one of the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1, the phosphorus-doped copper-based catalytic electrode prepared in Example 2, the bimetallic catalytic electrode prepared in Example 3, and the phosphorus-doped platinum-based catalytic electrode prepared in Example 4. The obtained LSV curve is shown in FIG. Figure 1 As shown by Figure 1 The LSV curve shown is fitted to calculate the Tafel slope. The Tafel slope is as follows: Figure 2 As shown in Table 3 ( Figure 2 In the examples, “Cu-Pt-P” represents Example 1, “Cu-P” represents Example 2, “Cu-Pt” represents Example 3, and “Pt-P” represents Example 4).

[0071] like Figure 1 As shown in Table 2, when the current density is -100 mA / cm 2When the overpotential of the working electrode of Example 1 is 0.567V vs. RHE, which is higher than that of Examples 2 to 4, the carbon felt-based phosphorus-doped bimetallic catalytic electrode has a very high NO3 - Electroreduction ability.

[0072] Table 2

[0073] Working electrode Overpotential (V vs. RHE) Example 1 0.567 Implementation Column 2 0.511 Example 3 0.409 Example 4 0.348

[0074] Depend on Figure 2 As can be seen from Table 3, the Tafel slope of the carbon felt-based phosphorus-doped bimetallic catalytic electrode of Example 1 is 141 mV / dec, which is much lower than that of Examples 2 to 4, indicating that the NO3-RR kinetic rate of the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 is the fastest, and the doping of phosphorus and platinum synergistically improves the NO3-RR performance.

[0075] Table 3

[0076] Working electrode Tafel slope (mV / dec) Example 1 ( Figure 2 (Cu-Pt-P) 141 Implementation 2( Figure 2 (Cu-P) 159 Example 3 ( Figure 2 ("Cu-Pt") 188 Example 4 ( Figure 2 ("Pt-P") 192

[0077] Example 11

[0078] The carbon felt-based phosphorus-doped bimetallic catalytic electrode of Example 1 was placed in the cathode chamber with different NO3 - The NO3-RR test was carried out under the condition of the electrolyte with a concentration of 0.05. The NO3-RR test in Example 11 was basically the same as that in Example 10, except that the NO3 in the electrolyte in the cathode chamber was - The concentration of the electrolyte in the cathode chamber of this embodiment is different. 14 NO3 - The concentrations are 0M, 0.1M and 0.2M respectively. The LSV curve of the NO3-RR test in Example 11 is as follows: Figure 3 As shown. Figure 3 It can be seen that the current density of the carbon felt-based phosphorus-doped bimetallic catalytic electrode of Example 1 is - This indicates that NO3-RR indeed occurs on the surface of the carbon felt-based phosphorus-doped bimetallic catalytic electrode.

[0079] pass Figure 3 The LSV curve shown is obtained at a current density of -100 mA / cm 2 As shown in Table 4, the overpotential of the carbon felt-based phosphorus-doped bimetallic catalytic electrode of Example 1 is increased when the NO3 - The concentration has an increasing trend, so the carbon felt-based phosphorus-doped bimetallic catalytic electrode has a - It has strong catalytic activity in the environment.

[0080] Table 4

[0081]

[0082] Example 12

[0083] In the following embodiments, the method for measuring the ammonium ion concentration in the electrolyte in the cathode chamber after the NO3-RR test is completed includes:

[0084] ① Prepare standard ammonium sulfate aqueous solutions with ammonium sulfate concentrations of 0.0005mM, 0.025mM, 0.05mM and 0.125mM, respectively. Use UV-visible spectrophotometer to analyze the absorption spectra of the standard ammonium sulfate aqueous solutions with ammonium sulfate concentrations of 0.0005mM, 0.025mM, 0.05mM and 0.125mM, respectively, and obtain the absorbance at 650nm. The absorbance is used as the horizontal axis and the ammonium ion (NH4 + ) concentration as the vertical axis to generate the first standard curve.

[0085] ② Determine ammonia (NH3) production by absorption spectroscopy using an indigo blue method using a UV-visible spectrophotometer. The determination method is as follows: dissolve 5 g of salicylic acid and 5 g of sodium citrate dihydrate in 100 mL of a first sodium hydroxide aqueous solution (the concentration of NaOH in the first sodium hydroxide aqueous solution is 1 M) to obtain a first indigo blue solution; dissolve 1.861 g of sodium hypochlorite in 100 mL of a second sodium hydroxide aqueous solution (the concentration of NaOH in the second sodium hydroxide aqueous solution is 2 M) to obtain a second indigo blue solution; and dissolve 0.1 g of sodium nitrosoferricyanide dihydrate in 100 mL of water to obtain a third indigo blue solution. Mix 2 mL of the first indigo blue solution, 1 mL of the second indigo blue solution, and 0.2 mL of the third indigo blue solution to obtain 3.2 mL of the indigo blue mixed solution.

[0086] ③After the NO3-RR test, take 2 mL of the electrolyte in the cathode chamber and add 3.2 mL of the indophenol blue mixed solution. Shake well and let it stand for two hours. Then perform absorption spectrum analysis and substitute the absorbance at 650 nm into the first standard curve to obtain the ammonium ion concentration in the electrolyte in the cathode chamber.

[0087] Since ammonium ions can be converted into ammonia (NH3) by bubbling or heating, the concentration of ammonia (NH3) is usually expressed by the concentration of ammonium ions in this field, and the ammonia yield (mg cm -2 h -1 ).

[0088] The carbon felt-based phosphorus-doped bimetallic catalytic electrodes of Examples 1 and 5 to 9 were used as working electrodes to perform NO3-RR tests at a constant voltage (basically the same as the "NO3-RR test" of Example 10, except that the voltage was -0.3 V vs. RHE). The NO3-RR test reaction lasted for 0.5 h. After the NO3-RR test, the ammonium ion concentration in the electrolyte in the cathode chamber was measured, and the ammonia production (mg cm) was obtained based on the ammonium ion concentration. -2 h -1 ), the NH3 production in the NO3-RR test under -0.3V vs.RHE conditions was as follows: Figure 4 As shown. Figure 4 It can be seen that the NH3 production of the carbon felt-based phosphorus-doped bimetallic catalytic electrode as the working electrode in Example 1 is slightly higher than that in Example 5, and much higher than that in Examples 6 to 9, indicating that the ammonia production is highest when the molar ratio of copper nitrate to chloroplatinic acid is 0.24:0.088.

[0089] Example 13

[0090] The test method for the concentration of nitrite in the electrolyte in the cathode chamber after the NO3-RR test includes:

[0091] ① Calibration of the absorbance corresponding to different concentrations of nitrite: Standard sodium nitrite aqueous solutions with nitrite concentrations of 0.001 mM, 0.005 mM, 0.01 mM and 0.025 mM were prepared. The absorption spectra of the standard sodium nitrite aqueous solutions with nitrite concentrations of 0.001 mM, 0.005 mM, 0.01 mM and 0.025 mM were analyzed using a UV-visible spectrophotometer to obtain the absorbance at 540 nm. A second standard curve was generated with the absorbance as the horizontal axis and the nitrite concentration as the vertical axis.

[0092] 2. carry out absorption spectrum analysis and measure nitrite concentration with UV-Vis spectrophotometer, and measuring method is: 4g p-aminobenzenesulfonamide, 0.2g N-(1-naphthyl)ethylenediamine dihydrochloride, 10mL phosphoric acid (75wt%) and 50mL deionized water are mixed to obtain naphthylethylenediamine hydrochloride mixed solution. Working electrode is placed in the cathode compartment of H type electrolytic cell and carries out NO3-RR test, NO3-RR test finishes after getting electrolyte in 5mL cathode compartment and adding it to 0.1mL naphthylethylenediamine hydrochloride mixed solution, shake up and leave standstill two hours, carry out absorption spectrum analysis, the absorbance at 540nm place is substituted into the second standard curve, obtain the concentration of nitrite in electrolyte in the cathode compartment.

[0093] Example 14

[0094] The carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 was used as a working electrode. Referring to the "NO3-RR test" of Example 10, the redox reaction of nitrate was carried out at a constant voltage of 0.2, 0.1, 0, -0.1, -0.2, -0.3, -0.4, -0.5, -0.6 or -0.7 V vs. RHE. The ammonia yield and the Faradaic efficiency of NH3 synthesis ( Figure 5 "FE-NH3") and the Faradaic efficiency of synthetic nitrite ( Figure 5 Medium "FE-NO2 - ")like Figure 5 As shown in the figure, the ammonia production increases with the decrease of voltage and reaches the highest value (25.24 mg / h / cm 2 ), and its Faradaic efficiency for synthesizing NH3 is greater than 91%. In addition, the Faradaic efficiency of nitrite is less than 7% in all voltage ranges, indicating that the carbon felt-based phosphorus-doped bimetallic catalytic electrode has high selectivity for synthesizing ammonia from NO3-RR in a wider voltage range.

[0095] Example 15

[0096] The concentration of nitrate in textile wastewater is 10-20 mM, the concentration of nitrate in industrial wastewater is 30-50 mM, and the concentration of nitrate in nuclear wastewater is 100-2000 mM. Considering that the concentration of nitrate in different wastewaters may be different, the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 was used as the working electrode. At a constant voltage of -0.3 V vs. RHE, the redox reaction of nitrate was carried out with reference to the "NO3-RR test" of Example 10. In this embodiment, the electrolyte in the cathode chamber in the NO3-RR test was 14 NO3 - The concentrations are 10mM, 20mM, 30mM, 40mM, 50mM, 100mM, 500mM, 1000mM, 1500mM and 2000mM respectively. The ammonia production and the Faradaic efficiency of synthesized NH3 at different nitrate concentrations using the carbon felt-based phosphorus-doped bimetallic catalytic electrode of Example 1 as the working electrode are shown in FIG. Figure 6 As shown. Figure 6 It can be seen that although the ammonia production fluctuates slightly with the change of nitrate concentration, the ammonia production corresponding to the working electrode of Example 1 is higher than 8.5 mg / h / cm in the wastewater system with nitrate concentration of 10-2000 mM. 2 , and the Faradaic efficiency is greater than 80%. Therefore, the carbon felt-based phosphorus-doped bimetallic catalytic electrode can effectively remove nitrate pollutants of various concentrations under neutral conditions and has great practical application value.

[0097] Example 16

[0098] In order to clarify the role of phosphorus and platinum doping, the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1, the phosphorus-doped copper-based catalytic electrode prepared in Example 2, the bimetallic catalytic electrode prepared in Example 3, and the phosphorus-doped platinum-based catalytic electrode prepared in Example 4 were used as working electrodes, respectively. The redox reaction of nitrate was carried out at a constant voltage with the voltage of 0.2, 0.1, 0, -0.1, -0.2, or -0.3 V vs. RHE according to the "NO3-RR test" in Example 10. The ammonia yield in the NO3-RR test is shown in FIG. Figure 7 As shown, the Faraday efficiency is Figure 8 As shown in the figure, within a wide voltage range, Example 1 has the highest ammonia production and its Faradaic efficiency remains above 91%. Therefore, the carbon felt-based phosphorus-doped bimetallic catalytic electrode has the best NO3-RR performance and high intrinsic activity. Secondly, the phosphorus-doped copper-based catalytic electrode of Example 2 and the bimetallic catalytic electrode of Example 3 both exhibit slightly lower ammonia production and Faradaic efficiency, indicating that the simultaneous doping of phosphorus and platinum is the main reason for improving the NO3-RR performance.

[0099] Example 17

[0100] Proton nuclear magnetic resonance spectrum test: At a voltage of -0.3 V vs. RHE, the NO3-RR test was performed using the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 as the working electrode. The NO3-RR test in Example 17 was basically the same as the NO3-RR test in the aforementioned Example 10, with the only difference being that the electrolyte in the cathode chamber was different. The electrolyte in the cathode chamber in Example 17 was the first cathode chamber electrolyte or the second cathode chamber electrolyte.

[0101] The electrolyte in the first cathode chamber is sodium sulfate, sodium nitrate- 14 N(Na 14 NO3) and water mixed solution (Na2SO4 and Na 14 The concentration of NO3 is 0.1M); the electrolyte in the second cathode chamber is sodium sulfate, sodium nitrate- 15 N(Na 15 NO3) and water mixed solution (Na2SO4 and Na 15 The concentration of NO3 is 0.1M).

[0102] The NO3-RR test was carried out under the conditions of the first cathode chamber electrolyte or the second cathode chamber electrolyte. After the reaction for 1 hour, 5 mL of the cathode chamber electrolyte was mixed with 2 mL of sulfuric acid (the concentration of H2SO4 in sulfuric acid was 4 M) and the nuclear magnetic resonance hydrogen spectrum test was carried out. Figure 9 shown.

[0103] The H NMR spectrum of the electrolyte in the first cathode chamber showed an obvious 14 NH4 + The characteristic peak of the second cathode chamber electrolyte is also only 15 NH4 + There are no other characteristic peaks, which indicates that in the NO3-RR process, NO3 in the electrolyte - It is the only source of synthesized ammonium ions (not from other substances), indicating that carbon felt-based phosphorus-doped bimetallic catalytic electrode has great application potential in the treatment of nitric acid wastewater.

[0104] Example 18

[0105] In order to evaluate the removal of NO3 in low nitrate concentration solution, a carbon felt-based phosphorus-doped bimetallic catalytic electrode was used. - The NO3-RR test was carried out at a voltage of -0.3 V vs. RHE using the carbon felt-based phosphorus-doped bimetallic catalytic electrode prepared in Example 1 as the working electrode. The NO3-RR test in Example 18 was basically the same as that in Example 10, except that the NO3 in the electrolyte in the cathode chamber was - The concentration was 5mM, and the electrolyte in the cathode chamber at 0min, 10min, 20min, 30min, 40min, 50min and 60min of NO3-RR test was taken for NO2 - concentration( Figure 10 "NO2 - ”), NO3 - concentration( Figure 10 "NO3 - ”) and NH4 + concentration( Figure 10 Determination of "NH3" in Figure 10 shown.

[0106] Depend on Figure 10 It can be seen that as the reaction time increases, NO3 - Converted into NH3, which shows that at very low NO3 - In an environment with high concentration, the carbon felt-based phosphorus-doped bimetallic catalytic electrode can also exert excellent NO3-RR performance. After the reaction, the nitrate concentration in the electrolyte of the cathode chamber was measured to be 0.14mM (8.68mg / L) (the nitrate concentration was measured by ion chromatography), and NH4 +The concentration was 3.16mM, and the nitrite concentration was maintained at around 0.018mM (0.82mg / L), which was significantly lower than the drinking water standard of the World Health Organization (nitrate - 11.3mg / L; nitrite - 0.91mg / L). This shows that the carbon felt-based phosphorus-doped bimetallic catalytic electrode is effective in completely removing NO3 - and conversion into NH3 has good application potential.

[0107] This invention utilizes a carbon-felt-based phosphorus-doped bimetallic catalytic electrode for the first time to enhance NO₃-RR performance. The resulting carbon-felt-based phosphorus-doped bimetallic catalytic electrode exhibits maximum redox current density and onset potential, along with excellent redox activity. In particular, under neutral conditions, it exhibits extremely high ammonia conversion and selectivity over a wide range of nitrate concentrations, demonstrating promising potential for application in the treatment of nitric acid wastewater.

[0108] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor falls within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon felt-based phosphorus-doped bimetallic catalytic electrode, characterized in that: The following steps are involved: Step 1: Mixing a copper salt, a platinum salt, and a first water until uniform, then adding ammonium fluoride and urea, and mixing until uniform to obtain a transparent solution, wherein the ratio of copper element in the copper salt to platinum element in the platinum salt is 0.24: (0.073-0.13) based on the amount of substance; Step 2: activating the carbon fiber felt to increase the oxygen-containing groups on its surface to obtain an activated carbon fiber felt. Under ultrasonic conditions, the activated carbon fiber felt is immersed in the transparent solution and ultrasonicated for at least 3 minutes to obtain a first mixture. The first mixture is allowed to stand at 120-140°C for 6-7 hours and dried to obtain a bimetallic co-loaded intermediate. The ratio of the volume fraction of the activated carbon fiber felt to the amount of copper element in the copper salt is 1.2:0.24, and the unit of volume fraction is cm 3 , the unit of the amount of substance is mmol; Step 3: Pass an inert gas flow through the furnace body to form an inert gas atmosphere in the furnace body, place the bimetallic co-loaded intermediate downstream of the gas flow, place the phosphorus source upstream of the gas flow, calcine the phosphorus source at 350-400°C and calcine the bimetallic co-loaded intermediate at 350-400°C at the same time to obtain a carbon felt-based phosphorus-doped bimetallic catalytic electrode, wherein the calcination time is 2-2.5 hours, and the ratio of copper element in the bimetallic co-loaded intermediate to phosphorus element in the phosphorus source is 0.24:(0.94-1.88) based on the amount of substance.

2. The preparation method according to claim 1, characterized in that In step 1, the ratio of the amount of copper element in the copper salt, the mass of urea and the mass of ammonium fluoride is 0.24: (0.45-0.5): (0.14-0.16), the unit of the amount of substance is mmol, and the unit of the mass is g.

3. The preparation method according to claim 1, characterized in that In step 1, the ratio of the amount of copper element in the copper salt to the volume of the first water is 0.24:(25-30), the unit of the amount of copper is mmol, and the unit of the volume is mL.

4. The preparation method according to claim 1, characterized in that In step 1, the copper salt is copper nitrate, and the platinum salt is chloroplatinic acid.

5. The preparation method according to claim 1, characterized in that In step 2, the method for obtaining activated carbon fiber felt includes: immersing the carbon fiber felt in a mixed solution of methanol and a second water, standing at 60 to 80°C for 6 to 12 hours, drying, and then immersing it in a mixed solution of sulfuric acid, nitric acid and a third water, standing at 60 to 80°C for 12 to 24 hours to obtain activated carbon fiber felt.

6. The preparation method according to claim 1, characterized in that In step 3, the phosphorus source is sodium hypophosphite.

7. The preparation method according to claim 1, characterized in that In step 2, the size of the carbon fiber felt is 20 mm×20 mm×3 mm.

8. The carbon felt-based phosphorus-doped bimetallic catalytic electrode obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the carbon felt-based phosphorus-doped bimetallic catalytic electrode as claimed in claim 8 in synthesizing ammonia through redox reaction of nitrates.

10. The use according to claim 9, characterized in that Carbon felt-based phosphorus-doped bimetallic catalytic electrode for ammonia synthesis under neutral conditions.

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