Pd / S-SnO2 (at) BTAB / PPy / GO nano material, preparation method thereof and application of Pd / S-SnO2 (at) BTAB / PPy / GO nano material in electro-catalytic air synthesis of nitrate
By using Pd/S-SnO2@BTAB/PPy/GO nanomaterials to electrocatalyze nitrogen oxidation in an air-saturated alkaline electrolyte, the problems of high energy consumption and environmental unfriendliness in nitrate production have been solved, achieving efficient nitrate synthesis at room temperature and pressure with high yield and high Faraday efficiency.
Patent Information
- Application Number
- CN202511844075.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-02-27
AI Technical Summary
In existing technologies, the high temperature and high pressure conditions for nitrate production are harsh, energy-intensive, and environmentally unfriendly. Electrochemical nitrogen oxidation (NOR) is limited by the high activation energy barrier of N2, intense competitive oxygen evolution reaction, low NO3- concentration of products, and low Faraday efficiency, and lacks efficient electrocatalysts.
Using Pd/S-SnO2@BTAB/PPy/GO nanomaterials as an electrocatalyst, an electrochemical nitrogen oxidation reaction was carried out in an air-saturated alkaline electrolyte, with palladium as the active center, to improve the efficiency and selectivity of nitrate formation.
This method achieves efficient catalytic oxidation of nitrogen to nitrate at ambient temperature and pressure, reducing energy consumption and environmental pollution. It features high yield, high Faraday efficiency, and excellent selectivity, providing a green and sustainable nitrate synthesis route.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of new energy and electrochemical catalysis, specifically involving Pd / S-SnO2@BTAB / PPy / GO nanomaterials, their preparation methods, and their application in the electrocatalytic synthesis of nitrates from air. Background Technology
[0002] Nitrate (NO3) - Nitrogen (N2) is the world's largest source of mineral nitrogen, with an annual consumption exceeding 100 million tons. It is widely used in key areas such as fertilizers, gunpowder, dyes, photovoltaic etching solutions, and energy storage electrolytes. Although atmospheric nitrogen (N2) accounts for as much as 78% of the total nitrogen content, its intramolecular N≡N bond energy is as high as 941 kJ / mol. -1 This makes activation at room temperature and pressure extremely difficult, becoming a natural bottleneck restricting the nitrogen fixation process. Since the Ostwald process was introduced in the early 20th century, industrial nitrate production has still followed the two-step route of "Haber-Bosch ammonia synthesis → high-temperature catalytic oxidation of nitric acid". However, such high-pressure and high-temperature conditions are too harsh and costly. Moreover, the reaction is exothermic, energy-intensive, and accompanied by the emission of large amounts of greenhouse gases, which is very unfriendly to the environment and runs counter to the goals of sustainable development.
[0003] In contrast, electrochemical nitrogen oxidation (NOR) can directly utilize renewable electricity to oxidize N2 to NO3 in an aqueous system at ambient temperature and pressure. - This method possesses significant advantages, including mild reaction conditions, compact process modules, zero carbon emissions, and ease of coupling with distributed energy sources such as wind, solar, and tidal power. It is considered one of the most promising routes to replace traditional high-temperature oxidation and achieve green nitrogen fixation. Current research focuses on converting intermittent green electricity from hydropower, solar power, wind power, and tidal power into chemical energy, but is limited by the high activation energy barrier of N2, the intense competitive oxygen evolution reaction, and the presence of NO3 as a product. - Bottlenecks such as low concentration and generally low Faraday efficiency make the design of efficient electrocatalysts a core challenge determining the economic viability of NOR technology. Transition metals, due to their tunable d-orbitals and good chemical stability, have always been a research focus in NOR catalysis systems; the palladium site stands out in NOR reactions because its 4d electronic structure can simultaneously "attract" N2 and oxygen-containing intermediates. Constructing a Pd-Sn synergistic interface not only simultaneously improves nitrate yield and Faraday efficiency, but also provides a practical route for green electricity-driven distributed nitrate synthesis that balances performance and cost. Summary of the Invention
[0004] One objective of this invention is to provide a Pd / S-SnO2@BTAB / PPy / GO nanomaterial with high catalytic performance. Palladium (Pd) serves as the active center, significantly improving the efficiency and selectivity of nitrate formation. Highly efficient nitrate synthesis is achieved through an electrochemical nitrogen oxidation (NOR) reaction in an air-saturated electrolyte, with significantly higher yield and Faraday efficiency than reactions conducted under a conventional nitrogen atmosphere.
[0005] The second objective of this invention is to provide a method for preparing a NOR electrocatalytic modified electrode using Pd / S-SnO2@BTAB / PPy / GO nanomaterials for electrocatalytic nitrogen oxidation. Traditional nitrate production methods are energy-intensive and generate large amounts of carbon dioxide emissions, while this invention provides a sustainable and low-energy-consumption alternative.
[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows: Pd / S-SnO2@BTAB / PPy / GO nanomaterials are prepared by the following steps: 1) Graphene oxide (GO) was prepared and purified using the Hummers method; 2) Under ultrasonic radiation, pyrrole (Py) was chemically polymerized in situ onto GO nanosheets to obtain PPy / GO nanosheets; 3) PPy / GO nanosheets were added to N,N-dimethylformamide and ultrasonically dispersed. Then 1,4-dibromobutane and KOH were added and ultrasonically dispersed. The mixture was stirred and reacted. After the reaction was completed, the mixture was centrifuged with ethanol, washed, and then triethylamine was added. The mixture was centrifuged, washed, vacuum dried, and ground to obtain black BTAB / PPy / GO nanosheet powder. 4) A small amount of BTAB / PPy / GO nanosheets were dispersed in water, and then K2PdCl6, SnCl4·5H2O and thioacetamide were added in sequence. The mixture was stirred until homogeneous, and the resulting reaction system was subjected to hydrothermal reaction. The product was washed with distilled water and anhydrous ethanol in sequence, centrifuged, and vacuum dried to obtain Pd / S-SnO2@BTAB / PPy / GO nanomaterials.
[0007] In the aforementioned Pd / S-SnO2@BTAB / PPy / GO nanomaterial, the mass ratio of graphene oxide to pyrrole is 1:1.
[0008] In step 3) of the above-mentioned Pd / S-SnO2@BTAB / PPy / GO nanomaterial, the stirring reaction is carried out at 60°C for 24 h.
[0009] In the above-mentioned Pd / S-SnO2@BTAB / PPy / GO nanomaterial, in step 4), the molar ratio of K2PdCl6, SnCl4·5H2O and thioacetamide is 1:1:7.5.
[0010] In step 4) of the above-mentioned Pd / S-SnO2@BTAB / PPy / GO nanomaterials, the hydrothermal reaction is as follows: the obtained reaction system is placed in a Teflon reaction vessel with a polytetrafluoroethylene liner and hydrothermally reacted at 200°C for 24 h.
[0011] A NOR electrocatalytic modified electrode based on Pd / S-SnO2@BTAB / PPy / GO nanomaterials is characterized in that it is a Pd / S-SnO2@BTAB / PPy / GO modified electrode made by attaching the above-mentioned Pd / S-SnO2@BTAB / PPy / GO nanomaterials onto carbon cloth as a substrate.
[0012] A method for preparing a NOR electrocatalytic modified electrode based on Pd / S-SnO2@BTAB / PPy / GO nanomaterials, characterized in that the preparation method includes the following steps: 1) The above-mentioned Pd / S-SnO2@BTAB / PPy / GO nanomaterials were ultrasonically dispersed in a mixed solution of anhydrous ethanol and Nafion to obtain a uniformly dispersed composite modifier. 2) The uniformly dispersed composite modifier was drop-coated onto a clean carbon cloth surface and dried at room temperature to obtain a Pd / S-SnO2@BTAB / PPy / GO modified electrode.
[0013] In the above preparation method, the volume ratio of anhydrous ethanol to Nafion solution is 92:8.
[0014] The above-mentioned NOR electrocatalytic modified electrode based on Pd / S-SnO2@BTAB / PPy / GO nanomaterials is used in the electrocatalytic synthesis of nitrate from air.
[0015] The above method is as follows: using the NOR electrocatalytic modified electrode based on Pd / S-SnO2@BTAB / PPy / GO nanomaterial as the working electrode, the Hg / HgO electrode as the reference electrode, and the platinum sheet electrode as the auxiliary electrode, a three-electrode system is formed to realize the electrocatalytic oxidation of nitrogen in the air to synthesize nitrate in 0.1 M potassium hydroxide solution.
[0016] The Pd / S-SnO2@BTAB / PPy / GO nanomaterial disclosed in this invention is Pd 2+ and S 2- Co-doped SnO2 nanoparticles are supported on a quaternary ammonium salt-functionalized polypyrrole / graphene oxide composite carrier. This material can efficiently catalyze the oxidation of nitrogen to nitrate in an air-saturated alkaline electrolyte at room temperature and pressure, exhibiting high yield, high Faradaic efficiency, excellent selectivity, and stability. This invention provides a new route for the green and sustainable electrochemical synthesis of nitrates and has promising application prospects.
[0017] Compared with the prior art, the present invention has the following significant advantages: 1. The NOR electrocatalytic modified electrode based on Pd / S-SnO2@BTAB / PPy / GO nanomaterials prepared in this invention, due to Pd 2+ The presence of nitrogen allows N2 to be oxidized to produce nitrates, achieving nitrogen oxidation at room temperature and pressure, thus reducing energy consumption and environmental pollution.
[0018] 2. The NOR electrocatalytic modified electrode based on Pd / S-SnO2@BTAB / PPy / GO nanomaterials prepared in this invention exhibits advantages such as strong electrochemical performance, good stability, and good linearity.
[0019] 3. The NOR electrocatalytic modified electrode based on Pd / S-SnO2@BTAB / PPy / GO nanomaterial prepared in this invention enables the electrocatalytic oxidation of nitrogen to synthesize nitrate, providing a new idea and method for practical application of electrocatalytic nitrogen fixation.
[0020] 4. In this invention, tin is relatively inexpensive and has a large storage capacity. At the same time, the tin and palladium sulfide-organic conductive complex synthesized by using n-butyltriethylammonium bromide-functionalized polypyrrole / graphene oxide (BTAB / PPy / GO) as a substrate promotes the dispersion of tin and palladium sulfides on organic conductive polymers and the electron mobility in electrochemical catalysis, thereby further improving the catalytic performance of metal sulfides.
[0021] 5. The modified electrode prepared by this invention is inexpensive, has good stability, is easy to operate, and has a fast reaction speed. Attached Figure Description
[0022] Figure 1 Electron micrograph of Pd / S-SnO2@BTAB / PPy / GO nanosheets; Among them, (a) is a scanning electron microscope (SEM) image of Pd / S-SnO2@BTAB / PPy / GO nanosheets; (b) Transmission electron microscopy (TEM) image of Pd / S-SnO2@BTAB / PPy / GO nanosheets.
[0023] Figure 2 (a) shows the XRD patterns of Pd / S-SnO2@BTAB / PPy / GO nanomaterials before and after 30 hours of electrolysis in air-saturated electrolyte; (b) shows the energy dispersive spectroscopy (EDS) spectra of Pd / S-SnO2@BTAB / PPy / GO nanomaterials before and after 30 hours of electrolysis in air-saturated electrolyte. (Top: before nitrogen oxidation reaction; Bottom: after 30 hours of electrolysis in air-saturated electrolyte)
[0024] Figure 3 XPS spectra of Pd / S-SnO2@BTAB / PPy / GO before and after 30 hours of electrolysis in air-saturated electrolyte: (a) Sn 3d; (b) Pd 3d. (Top: before nitrogen oxidation reaction; Bottom: after 30 hours of electrolysis in air-saturated electrolyte)
[0025] Figure 4 (a) Pd K-edge XANES spectrum based on synchrotron radiation (inset: magnified absorption edge) and (b) k3-weighted Fourier transform spectrum of Pd K-edge EXAFS, corresponding to: (i) Pd foil, Pd / S-SnO2@BTAB / PPy / GO (ii) before and (iii) after electrolysis (before and after NOR treatment) and (iv) PdO; (c) wavelet transform EXAFS spectra of Pd foil, PdO, and Pd / S-SnO2@BTAB / PPy / GO before and after electrolysis (before and after NOR treatment).
[0026] Figure 5 LSV plots of Pd / S-SnO2@BTAB / PPy / GO modified electrodes in saturated air, N2, and Ar.
[0027] Figure 6 The nitrate yield and Faraday efficiency of the Pd / S-SnO2@BTAB / PPy / GO modified electrode at different voltages are shown.
[0028] Figure 7 The values of nitrate yield and Faradaic efficiency for the Pd / S-SnO2@BTAB / PPy / GO modified electrode after ten consecutive catalytic cycles for two hours at the same voltage are given. Detailed Implementation
[0029] The present invention will be further described in detail below with reference to preferred embodiments and accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0030] Example 1: Pd / S-SnO2@BTAB / PPy / GO nanomaterials
[0031] (a) The preparation method is as follows: 1) Preparation of GO nanosheets: 67.5 mL of concentrated sulfuric acid, 2.0 g of high-purity graphite, and 1.6 g of NaNO3 were added to a three-necked flask and stirred until homogeneous. The system temperature was kept below 5 °C. 9 g of KMnO4 was slowly and continuously added to the mixed solution over one hour, and then the mixture was placed in a 36 °C water bath for 0.5 h. After standing at room temperature for two weeks, the solution was diluted with 560 mL of 60 °C water, and H2O2 was added dropwise until the solution turned bright yellow. The solution was then centrifuged while hot (rpm=10000), washed until neutral, and dried under vacuum at 50 °C to obtain GO nanosheets.
[0032] 2) PPy / GO nanosheets: Add 0.2 g of GO nanosheets to 100 mL of deionized water, disperse by ultrasonication, then add 0.2 g of pyrrole (Py), disperse by ultrasonication again, then add 0.6 g of FeCl3·6H2O, continue ultrasonication for 0.5 h, centrifuge, wash and vacuum dry to obtain PPy / GO nanosheets.
[0033] 3) BTAB / PPy / GO nanosheets: 0.03 g of PPy / GO nanosheets were added to 25 mL of DMF (N,N-dimethylformamide), followed by 0.08 mL of 1,4-dibromobutane and 0.0504 g of KOH. The mixture was ultrasonically dispersed for 0.5 h, then transferred to an oil bath and magnetically stirred at 60 °C for 24 h. After the reaction was complete, the mixture was centrifuged with ethanol, then 20 mL of triethylamine was added, and the mixture was ultrasonicated for one hour before centrifugation. The resulting sample was washed three times with ethanol and then transferred to a vacuum drying oven to dry for 24 h (T=50 °C). Finally, it was ground with an agate mortar to obtain black BTAB / PPy / GO powder.
[0034] 4) Preparation of Pd / S-SnO2@BTAB / PPy / GO nanomaterials: 0.02 g BTAB / PPy / GO was dispersed in 30 mL of water, and then 0.02979 g K2PdCl6, 0.02635 g SnCl4·5H2O, 0.056 g thioacetamide (TAA), and 20 mL of deionized water were added sequentially. The mixture was stirred until homogeneous, and the resulting reaction system was transferred to a Teflon reactor and subjected to hydrothermal reaction at 200℃ for 24 h. After the reaction was completed, the product was washed sequentially with distilled water and ethanol, centrifuged, and vacuum dried to obtain Pd / S-SnO2@BTAB / PPy / GO nanomaterials.
[0035] (II) Testing
[0036] 1. For example Figure 1 As shown, Figure 1 Image a in the middle is a scanning electron microscope (SEM) image of the Pd / S-SnO2@BTAB / PPy / GO nanomaterial; Figure 1Figure 1b shows a transmission electron microscope (TEM) image of the Pd / S-SnO2@BTAB / PPy / GO nanomaterial. As shown in Figure 1a, the synthesized Pd / S-SnO2@BTAB / PPy / GO exhibits a typical layered structure with a rough surface; while in Figure 1b, numerous small nanoparticles with a diameter of approximately 3 nanometers are uniformly distributed on the surface of the large layered structure, indicating that the obtained Pd / S-SnO2@BTAB / PPy / GO possesses a typical hierarchical micro / nano structure. Figure 1 As shown in the lower figures of a and b, the morphology of the electrocatalyst did not change after a long period of nitrogen oxidation reaction in an air-saturated electrolyte.
[0037] 2. For example Figure 2 As shown in Figure 2a (top), the XRD pattern of the synthesized Pd / S-SnO2@BTAB / PPy / GO shows five distinct diffraction peaks at 26.3°, 33.9°, 37.9°, 51.8°, and 64.7°. These peaks exhibit significant broadening and correspond perfectly to JCPDS file number 41-1445, indicating the presence of very small tetragonal cassiterite (SnO2). In Figure 2b (top), in addition to carbon, nitrogen, oxygen, and tin, palladium and sulfur are also clearly detected in its energy dispersive spectroscopy (EDS). After prolonged nitrogen oxidation in an air-saturated electrolyte, the crystal structure and elemental composition of the electrocatalyst remained unchanged, as shown in the lower parts of Figures 2a and 2b.
[0038] 3. Figure 3 XPS spectra of Pd / S-SnO2@BTAB / PPy / GO before and after 30 hours of electrolysis in air-saturated electrolyte: (a) Sn 3d; (b) Pd 3d. (Top: before NOR reaction, Bottom: after 30 hours of electrolysis in air-saturated electrolyte) As shown in Figure 3, compared with the electrocatalyst that has not undergone electrosynthesis, the high-resolution Pd 3d spectrum of Pd / S-SnO2@BTAB / PPy / GO showed a significant change after 30 hours of electrolysis in air-saturated electrolyte, while no change was observed in its high-resolution Sn 3d spectrum (Figure 3a-ii), indicating that NOR cannot occur at the Sn site.
[0039] Meanwhile, a distinct redshift can be clearly observed in Figure 3b of the two independent peaks corresponding to the Pd 3d5 / 2 and Pd 3d3 / 2 spin orbitals. New peaks at 336.8 and 342.1 eV are detected, attributed to the palladium 3d5 / 2 and palladium 3d3 / 2 spin orbital energy levels of the palladium-N bond, indicating a NOR reaction occurring at the palladium site of Pd / S-SnO2@BTAB / PPy / GO.
[0040] 4. (a) Pd K-edge XANES spectrum based on synchrotron radiation (inset: magnified absorption edge) and (b) k3-weighted Fourier transform spectrum of Pd K-edge EXAFS, corresponding to: (i) Pd foil, Pd / S-SnO2@BTAB / PPy / GO (ii) before and (iii) after electrolysis (before and after NOR treatment) and (iv) PdO; (c) wavelet transform EXAFS spectra of Pd foil, PdO, and Pd / S-SnO2@BTAB / PPy / GO before and after electrolysis (before and after NOR treatment).
[0041] To further verify that the palladium site is the actual catalytic center for the nitrogen oxidation reaction (NOR), we used X-ray absorption spectroscopy (XAS) in transmission mode to detect the oxidation state and coordination environment of Pd / S-SnO2@BTAB / PPy / GO at the palladium K energy edge (24350 eV) before and after NOR. The results show that in the X-ray absorption near-edge (XANES) spectra (Figure 4a), the absorption energies of Pd / S-SnO2@BTAB / PPy / GO at the palladium K energy edge before and after NOR are very close to those of PdO, with the order being: metallic palladium < Pd / S-SnO2@BTAB / PPy / GO after NOR < Pd / S-SnO2@BTAB / PPy / GO < PdO. Figure 4b shows the Fourier transform extended X-ray absorption fine structure spectroscopy analysis, and the corresponding wavelet transform EXAFS spectrum in Figure 4c is similar. Figure 1Further evidence shows that Pd / S-SnO2@BTAB / PPy / GO before NOR is significantly different from metallic palladium (palladium foil), which only shows a single dominant Pd-Pd peak at 2.44 Å (Fig. 3b-i). The FT-EXAFS spectrum of Pd / S-SnO2@BTAB / PPy / GO before NOR shows a distinct peak at 1.58 Å in the first shell (Fig. 3b-ii). Compared with the Pd-O peak at 1.62 Å of PdO in Fig. 3b-iv, this slight shift is likely due to the influence of S, which leads to the asymmetric expansion of the first shell. Before NOR, the Pd-Pd peak of Pd / S-SnO2@BTAB / PPy / GO appears at 2.70 Å in Fig. 3b-ii, consistent with the case of PdO in Fig. 3b-iv. However, after NOR, a new peak at 1.96 Å appears in Figures 3b-iii, which is attributed to the formation of Pd-N bonds. Simultaneously, peaks for O-Pd-S and Pd-Pd appear at 1.55 Å and 2.65 Å, respectively, indicating a charge transfer from nitrogen to Pd during NOR at the Pd site due to the formation of Pd-N bonds. This is consistent with the order of energy absorption at the Pd K-side before and after NOR in Figure 3a for Pd / S-SnO2@BTAB / PPy / GO.
[0042] Example 2: NOR electrocatalytic modified electrode based on Pd / S-SnO2@BTAB / PPy / GO nanomaterials
[0043] (a) The preparation method is as follows: 1) Take 1.5 mg of the dried Pd / S-SnO2@BTAB / PPy / GO nanomaterial prepared in Example 1, add 460 μL of anhydrous ethanol and 40 μL of Nafion solution, and sonicate for 30 min to obtain a black suspension with a concentration of 3 mg / mL, which is the composite modifier, for later use.
[0044] 2) Electrode preparation: Cut the carbon cloth into 1 cm × 1.5 cm pieces for later use.
[0045] 3) Preparation of modified electrode: The composite modifier prepared in step 1) was repeatedly transferred using a dropper and applied to the surface of a clean carbon cloth. It was then allowed to air dry at room temperature to obtain a Pd / S-SnO2@BTAB / PPy / GO nanomaterial electrocatalytic modified electrode.
[0046] (II) Electrochemical performance testing
[0047] 1. Comparison of linear sweep voltammetry curves of Pd / S-SnO2@BTAB / PPy / GO nanomaterial electrocatalytic modified electrode in saturated Ar and N2 and air.
[0048] Methods: In an electrolytic cell containing 0.1 M KOH solution, a Pd / S-SnO2@BTAB / PPy / GO nanomaterial electrocatalytically modified electrode was used as the working electrode, a Hg / HgO electrode as the reference electrode, and a platinum sheet electrode as the auxiliary electrode. The experiment was conducted on a CHI1040e electrochemical workstation, with its accompanying computer software used for data acquisition and processing. Linear sweep voltammetry was performed in the potential range of 1.4 V to 2.57 V (vs. RHE), and stable linear sweep voltammetric diagrams were recorded.
[0049] like Figure 5 The figure shows the linear sweep voltammetry (LSV) comparisons of the Pd / S-SnO2@BTAB / PPy / GO nanomaterial electrocatalytic modified electrode under saturated N2, saturated Ar, and air conditions. The upper curve is the LSV comparison under saturated air conditions, the middle curve is the LSV comparison under saturated N2 conditions, and the lower curve is the LSV comparison under saturated Ar conditions. Within the potential range of 1.67V to 2.57V (vs. RHE), the current density under air conditions is significantly higher than that under saturated N2 and saturated Ar conditions. This indicates that the prepared Pd / S-SnO2@BTAB / PPy / GO nanomaterial electrocatalytic modified electrode possesses NOR activity, and the NOR activity of the Pd / S-SnO2@BTAB / PPy / GO nanomaterial electrocatalytic modified electrode under saturated air conditions is significantly better than that under saturated N2 and saturated Ar conditions.
[0050] 2. Study on the optimal catalytic voltage of the electrocatalytically modified electrode made of Pd / S-SnO2@BTAB / PPy / GO nanomaterials
[0051] The working electrode was a Pd / S-SnO2@BTAB / PPy / GO nanomaterial electrocatalytically modified electrode, the reference electrode was a Hg / HgO electrode, and the auxiliary electrode was a platinum sheet electrode. The experiment was conducted on a CHI1040e electrochemical workstation, including the acquisition and processing of experimental data. Nitrogen gas was introduced into 0.1 M KOH solution, and the voltage value was taken at 0.1 V intervals within the potential range of 1.67 V to 2.17 V (vs. RHE) for two hours of chronoamperometry.
[0052] like Figure 6The figure shows the nitrate yield and Faradaic efficiency of the Pd / S-SnO2@BTAB / PPy / GO nanomaterial electrocatalytically modified electrode at different voltages. The highest NO3 yield obtained in air-saturated electrolyte was achieved at 1.77 V. - The yield and optimal Faraday efficiency were 17.21 μg h⁻¹. -1 cm -2 The value was 4.23%, which is 3.71 times the value obtained in N2 saturated electrolyte, indicating that introducing excess O2 into the NOR system can promote nitrate formation. Figure 3 , 4 The palladium site was confirmed as the actual catalytic center for the nitrogen oxidation reaction (NOR). Inductively coupled plasma atomic emission spectrometry (ICP-OES) determined the Pd content in Pd / S-SnO2@BTAB / PPy / GO to be 16.19%. Therefore, the highest nitrate yield obtained in air-saturated electrolyte was calculated to be 106.30 μg h⁻¹. -1 mg -1 act .
[0053] 3. Stability measurement of catalysts
[0054] The working electrode was a NOR electrocatalytically modified electrode made of Pd / S-SnO2@BTAB / PPy / GO nanomaterials, the reference electrode was a Hg / HgO electrode, and the auxiliary electrode was a platinum sheet electrode. The experiment was carried out on a CHI1040e electrochemical workstation, including the acquisition and processing of experimental data. Ten consecutive chronoamperometry tests were conducted for two hours each in 0.1 M KOH solution at a potential of 1.77 V (vs. RHE).
[0055] Figure 7 The values of nitrate yield and Faradaic efficiency of the electrocatalytically modified electrode of Pd / S-SnO2@BTAB / PPy / GO nanomaterial were obtained after ten consecutive catalytic cycles for two hours under the same voltage. It can be seen that the nitrate yield and Faradaic efficiency were still 70% after the tenth catalytic cycle, which proves that the prepared Pd / S-SnO2@BTAB / PPy / GO nanomaterial has good stability.
[0056] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalent alterations can be made within the spirit and scope defined by the claims of the present invention, but all such changes will fall within the protection scope of the present invention.
Claims
1. Pd / S-SnO2@BTAB / PPy / GO nanomaterials, characterized in that, The preparation method includes the following steps: 1) Graphene oxide (GO) was prepared and purified using the Hummers method; 2) Under ultrasonic radiation, pyrrole (Py) was chemically polymerized in situ onto GO nanosheets to obtain PPy / GO nanosheets; 3) PPy / GO nanosheets were added to N,N-dimethylformamide and ultrasonically dispersed. Then 1,4-dibromobutane and KOH were added and ultrasonically dispersed. The mixture was stirred and reacted. After the reaction was completed, the mixture was centrifuged with ethanol, washed, and then triethylamine was added. The mixture was centrifuged, washed, vacuum dried, and ground to obtain black BTAB / PPy / GO nanosheet powder. 4) A small amount of BTAB / PPy / GO nanosheets were dispersed in water, and then K2PdCl6, SnCl4·5H2O and thioacetamide were added in sequence. The mixture was stirred until homogeneous, and the resulting reaction system was subjected to hydrothermal reaction. The product was washed with distilled water and anhydrous ethanol in sequence, centrifuged, and vacuum dried to obtain Pd / S-SnO2@BTAB / PPy / GO nanomaterials.
2. The Pd / S-SnO2@BTAB / PPy / GO nanomaterial according to claim 1, characterized in that, The mass ratio of graphene oxide to pyrrole is 1:
1.
3. The Pd / S-SnO2@BTAB / PPy / GO nanomaterial according to claim 1, characterized in that, In step 3), the stirring reaction is carried out at 60°C for 24 h.
4. The Pd / S-SnO2@BTAB / PPy / GO nanomaterial according to claim 1, characterized in that, In step 4), the molar ratio of K2PdCl6, SnCl4·5H2O and thioacetamide is 1:1:7.
5.
5. The Pd / S-SnO2@BTAB / PPy / GO nanomaterial according to claim 1, characterized in that, In step 4), the hydrothermal reaction is as follows: the obtained reaction system is placed in a Teflon reactor with a polytetrafluoroethylene liner and hydrothermally reacted at 200°C for 24 h.
6. A method based on Pd / S-Sn The NOR electrocatalytic modified electrode of @BTAB / PPy / GO nanomaterials is characterized by... The electrode is a Pd / S-SnO2@BTAB / PPy / GO modified electrode made by attaching the Pd / S-SnO2@BTAB / PPy / GO nanomaterial as described in any one of claims 1-5 onto a carbon cloth substrate.
7. A method for preparing a NOR electrocatalytically modified electrode based on Pd / S-SnO2@BTAB / PPy / GO nanomaterials, characterized in that, The preparation method includes the following steps: 1) The Pd / S-SnO2@BTAB / PPy / GO nanomaterial described in any one of claims 1-5 is ultrasonically dispersed in a mixed solution of anhydrous ethanol and Nafion to obtain a uniformly dispersed composite modifier. 2) The uniformly dispersed composite modifier was drop-coated onto a clean carbon cloth surface and dried at room temperature to obtain a Pd / S-SnO2@BTAB / PPy / GO modified electrode.
8. The preparation method according to claim 7, characterized in that, The volume ratio of anhydrous ethanol to Nafion solution is 92:
8.
9. The application of the Pd / S-SnO2@BTAB / PPy / GO nanomaterials as described in claim 6 in the electrocatalytic synthesis of nitrates from air.
10. The application according to claim 9, characterized in that, The method is as follows: The NOR electrocatalytic modified electrode based on Pd / S-SnO2@BTAB / PPy / GO nanomaterials as described in claim 6 is used as the working electrode, the Hg / HgO electrode is used as the reference electrode, and the platinum sheet electrode is used as the auxiliary electrode to form a three-electrode system. The electrocatalytic oxidation of nitrogen in the air to synthesize nitrate is achieved in 0.1 M potassium hydroxide solution.