Electrocatalytic interface nanostructured electrode film based on photothermal effect and application

Abstract

This invention discloses an electrocatalytic interface nanostructure electrode film based on photothermal effect and its application, belonging to the field of electrocatalysis. The electrode film includes a hydrophobic photothermal gel layer HPG for ammonia evaporation and a nickel single-atom modified cuprous oxide catalyst layer NiCu-SA for catalytic nitrate reduction. It solves the problems of additional introduction of anions and high energy consumption in the prior art.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis, specifically to electrocatalytic interface nanostructure electrode films based on photothermal effects and their applications. Background Technology

[0002] Green ammonia production holds the promise of making a significant contribution to the transition to a zero-emission future through its decarbonization in key applications such as fertilizer production and fuel sources. Currently, global ammonia production is approximately 183 million tons per year, primarily produced via the Haber-Bosch process, which requires high temperatures (450-650°C) and high pressures (>100 atmospheres). This process heavily relies on fossil fuels as the primary hydrogen source, resulting in approximately 500 million tons of carbon dioxide emissions, accounting for 1-2% of global greenhouse gas emissions. These emissions, coupled with the impact of ammonia production on the global nitrogen cycle, are considered a potential contributor to global biodiversity loss and air quality deterioration. Records from the early 21st century show that human activities fix approximately 213 teragrams of nitrogen annually, exceeding the natural nitrogen fixation rate (approximately 203 teragrams per year). Despite these environmental problems, global demand for ammonia continues to rise annually due to population growth, presenting significant challenges related to uneven ammonia distribution. In many parts of the world, intensive agricultural activities result in substantial waste emissions, particularly from fertilizer use. These emissions have adverse environmental impacts, including soil acidification, ecosystem degradation, and increased air pollutants. Conversely, some developing regions face persistent challenges of insufficient access to agricultural fertilizers and inadequate soil fertility due to cost and affordability issues. Therefore, there is an urgent need to conduct research aimed at developing efficient ammonia production technologies to enable decentralized production via the Haber-Bosch process.

[0003] While the Haber-Bosch process has a mature industrial base in ammonia production, its reliance presents significant challenges. This method, characterized by high energy consumption and substantial greenhouse gas emissions, underscores the urgent need for sustainable alternatives. Emerging technologies such as direct electrochemical nitrogen reduction (DET) and lithium-mediated DET offer promising pathways to reducing environmental impact. However, DET faces challenges related to catalyst efficiency and selectivity, while lithium-mediated DET involves complex operational requirements, cost considerations in non-aqueous systems, and inherent energy efficiency issues. In contrast, the electrochemical reduction of nitrates to ammonia offers unique advantages. This method utilizes nitrates as a feedstock, which are readily available from wastewater and groundwater, or can be obtained by plasma ionization of air to form water-soluble nitrogen oxides. This approach offers milder reaction conditions and higher selectivity, potentially enabling decentralized production facilities and reducing the environmental footprint associated with ammonia production. Furthermore, nitrate reduction is crucial to the current global nitrogen cycle. By converting nitrates to ammonia and purifying them, this process has the potential to reduce nitrogen pollution and improve the utilization of nitrogen resources, thereby supporting the sustainable development of the water-energy-food link. Despite these advantages, a major challenge remains: due to the limited concentration of nitrates, the concentration of ammonia formed by electroreduction is extremely low, requiring a large energy input for purification. Current common solutions focus on using stripping methods or direct contact membrane distillation, where dilute acid absorbs the electrochemically reduced ammonia, followed by high-temperature evaporation to obtain the ammonium salt. However, these methods require the introduction of additional anions, and the recovery of the ammonium salt requires a considerable amount of thermal energy input. The resulting product contains Cl... - and SO4 2- Anions, such as those found in platinum-based noble metals, have been shown to poison the ammonia fuel cell market, thus limiting its potential applications. This issue is particularly important because large quantities of ammonia are expected to be used in the energy sector in the future, and aqueous or liquid ammonia solutions are highly favored. Addressing this challenge is crucial to realizing the full potential of electrochemical nitrate reduction as a viable alternative to traditional ammonia production methods. Summary of the Invention

[0004] This invention provides an electrocatalytic interface nanostructure electrode film based on photothermal effect and its application, which solves the problems of additional introduction of anions and high energy consumption in the prior art.

[0005] To solve this technical problem, the present invention provides the following technical solution:

[0006] The photothermal electrocatalytic interface nanostructure electrode film includes a hydrophobic photothermal gel layer HPG for ammonia evaporation and a nickel single-atom modified cuprous oxide catalyst layer NiCu-SA for catalytic nitrate reduction.

[0007] Preferably, the hydrophobic photothermal gel layer and the nickel single-atom modified cuprous oxide catalyst layer NiCu-SA are bonded together by a PVA solution to form a Janus structure.

[0008] Preferably, the nickel single-atom modified cuprous oxide catalyst layer NiCu-SA is a nickel single-atom anchored cuprous oxide nanowire electrode.

[0009] Preferably, the hydrophobic photothermal gel layer HPG comprises polypyrrole hydrophobically treated with an octadecyltrichlorosilane solution.

[0010] Preferably, the hydrophobic photothermal gel layer HPG is prepared by blending polyvinyl alcohol as the polymer backbone with polypyrrole, cross-linking with glutaraldehyde, and then immersing in an octadecyltrichlorosilane solution at room temperature.

[0011] This scheme also provides a method for preparing electrocatalytic interfacial nanostructure electrode films based on photothermal effects, including the following steps:

[0012] S1. Preparation of nickel-doped cuprous oxide catalyst layer NiCu-SA: First, a copper mesh was immersed in a solution composed of sodium hydroxide, ammonium persulfate, and deionized water to grow copper hydroxide nanowires on the mesh. The resulting copper hydroxide nanowires were then immersed in a nickel chloride solution for ion exchange. After ion exchange, nickel-doped copper oxide was obtained. Finally, the nickel-doped copper oxide was electrochemically reduced in an electrolyte using a chronoamperometry method at a potential of -0.50 V relative to the reversible hydrogen electrode to obtain the nickel-doped cuprous oxide catalyst layer NiCu-SA.

[0013] S2. Preparation of the hydrophobic photothermal gel layer: Pyrrole was added to water and ultrasonically treated to form solution A; then ammonium persulfate was ultrasonically dissolved in water to prepare solution B; solutions A and B were added to hydrochloric acid and stirred, and pyrrole rapidly polymerized into polypyrrole. After washing and filtering, the polypyrrole was ultrasonically dissolved in water to form solution C; polyvinyl alcohol was dissolved in water by heating and stirring, and hydrochloric acid, glutaraldehyde and solution C were added to the polyvinyl alcohol solution. After thorough mixing, the mixture was quickly poured into a mold for cross-linking and curing; the resulting material was freeze-dried.

[0014] Water was added to octadecyltrichlorosilane and then diluted with n-hexane; the freeze-dried material was immersed in the diluted octadecyltrichlorosilane solution for reaction, and after the reaction, it was washed with n-hexane and dried to obtain the hydrophobic photothermal gel layer HPG;

[0015] S3. A hydrophobic photothermal gel layer HPG is bonded to a nickel single-atom modified cuprous oxide catalyst layer NiCu-SA using a PVA solution to form an electrocatalytic interface nanostructure electrode film based on the photothermal effect.

[0016] Preferably, in step S1, the concentration of sodium hydroxide is 10.0 M; the concentration of ammonium persulfate is 1.0 M; the concentration of nickel chloride solution is 20.0 mM; and the electrolyte contains 200 ppm NO3. - 0.5M Na2SO4.

[0017] Preferably, the preparation process of solution A in step S2 is as follows: 1 mL of pyrrole is added to 10 mL of water and ultrasonically treated for 15 minutes to form solution A; the preparation process of solution B is as follows: 3.304 g of ammonium persulfate is ultrasonically dissolved in 10 mL of water to prepare solution B; the mass fraction of solution C is 1 wt%; the mass-volume ratio of polyvinyl alcohol to water is 0.8:10 g / mL.

[0018] Preferably, in step S2, the volume ratio of water to octadecyltrichlorosilane is 1:100; and the ratio of octadecyltrichlorosilane to hexane is 10 times.

[0019] This solution also provides the application of the above-mentioned photothermal effect-based electrocatalytic interface nanostructure electrode film and the photothermal effect-based electrocatalytic interface nanostructure electrode film obtained by the above preparation method in environmental nitrogen resource recovery.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] This scheme provides a photothermal-electrocatalytic interface (PTEI) based on Janus hybrid nanostructure electrodes, which exhibits a synergistic enhancement effect in ammonia yield and evaporation performance. The system integrating the photothermal-electrocatalytic interface can continuously produce and purify a pure ammonia solution with a concentration of approximately 2 M from plasma-ionized air, achieving a yield as high as 13.7 mg / cm³. - 2 h -1 0.36 M ammonia can be recovered from simulated industrial wastewater, with a total nitrogen recovery rate of 80%.

[0022] A Janus hybrid nanostructure PTEI system utilizes solar energy to reduce energy consumption and purifies low-concentration ammonia from the NOxRR process, enabling continuous electrified production from environmental sources such as air and wastewater. The introduction of nickel single atoms into the cuprous oxide substrate significantly improves ammonia yield—at 200 ppm NO3—by promoting the generation of active hydrogen and the dissociation of NOxRR intermediates. - The Faraday efficiency (FE) in the -N solution exceeds 90%, and the yield (YR) exceeds 2.8 mg / cm³. -2 h -1By optimizing the hydrophobicity of the interface, we ensured stable and continuous ammonia production and purification within the integrated PTEI system. Scanning electrochemical microscopy (SECM) confirmed a 3.3-fold increase in ammonia evaporation rate under photothermal conditions. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0024] Figure 1 a is a schematic diagram of a hybrid nanostructure floating on the water surface used for interfacial nitrate-ammonia electrocatalysis and thermally driven evaporation;

[0025] Figure 1 b is a scanning electron microscope (SEM) image of NiCu-SA: 50 μm;

[0026] Figure 1 c is a scanning electron microscope (SEM) image of NiCu-SA: 5μm;

[0027] Figure 1 d represents the atomic-level high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of NiCu-SA and the pixel intensity integral;

[0028] Figure 1 e represents the Ni K-side Fourier transform extended X-ray absorption fine structure (FT-EXAFS) spectra of Ni(OH)2, nickel foil, NiO, and NiCu-SA;

[0029] Figure 1 f is a scanning electron microscope (SEM) image of the hydrophobic photothermal gel (HPG): 100 μm;

[0030] Figure 1 Scanning electron microscope (SEM) image of hydrophobic photothermal gel (HPG) at 400 nm;

[0031] Figure 1 h represents the N2 adsorption isotherm and pore size distribution of HPG;

[0032] Figure 1 i represents the contact angle test and surface Si / O ratio of the gel after treatment with OTS solution of different concentrations;

[0033] Figure 2 'a' represents NO3 under neutral conditions. - The Faradaic efficiency of NiCu-SA and Cu2O in PTEI for the formation of ammonia and nitrite products when the -N concentration is 200 ppm;

[0034] Figure 2 b represents the ammonia Faraday efficiency and yield of NiCu-SA at different temperatures at -0.5 V;

[0035] Figure 2 c is the Gibbs free energy calculation diagram of the reaction pathway for the reduction of nitrate to ammonia on the NiCu-SA and Cu2O surfaces;

[0036] Figure 2 d is a snapshot of the differential charge density of nitrite ions on the surfaces of NiCu-SA and Cu2O and the Hamiltonian population COHP of the NO crystal orbitals;

[0037] Figure 3 a shows the temperature change curves of gels with different wetting properties under 1 sun illumination over time, as well as the infrared thermal images of PG and OG2;

[0038] Figure 3 b represents the ammonia evaporation rate of different modified electrodes obtained from experimental measurements and finite element simulations;

[0039] Figure 3 c represents the molecular dynamics simulation of the evaporation process in hydrophobic and hydrophilic modified pores;

[0040] Figure 3 d represents the evolution of the number of hydrogen bonds at the hydrophilic / hydrophobic model interface over time and its average value (dashed line), as well as the adsorption energy of ammonia molecules on the hydrophilic / hydrophobic chain;

[0041] Figure 4 a is a schematic diagram of PTEI ammonia collection based on a batch reactor;

[0042] Figure 4 b represents the nitrogen collection efficiency and ammonia recovery rate of the system under 0, 0.5, 1, and 2 sun light intensities;

[0043] Figure 4 c represents laboratory-prepared concentrations of 50, 100, 200, and 500 ppm (NO3). - Evaluation of nitrogen collection efficiency and ammonia recovery rate in nitrate solutions and simulated industrial wastewater (IW) and textile wastewater (TW);

[0044] Figure 4 d represents the residual nitrogen content analysis of wastewater with initial nitrate concentrations of 50, 100, 200, and 500 ppm, as well as the treated IW and TW nitrogen-containing wastewater.

[0045] Figure 4e is a schematic diagram of using a platinum ultramicroelectrode (Pt-UME) in substrate generation-tip collection (SG / TC) mode to operate a scanning electrochemical microscope (SECM) to detect NH3 generated during the NO3RR process on PTEI;

[0046] Figure 4 f represents the current and the fitted curve when the tip approaches the substrate;

[0047] Figure 4 g represents a snapshot of ammonia generated on the substrate via NO3RR and its simulated diffusion coefficient in air;

[0048] Figure 5 a is a schematic diagram of the photothermal-electrocatalytic interface of the cascaded plasma ionization air generator in a flow electrolyzer;

[0049] Figure 5 b represents the use of 1 M KOH as the supporting electrolyte and 200 mW cm⁻¹. -2 Long-term stability test of the system relative to the reversible hydrogen electrode (RHE) at a potential of -0.6 V under optical power density illumination;

[0050] Figure 5 c represents the change in ammonia concentration extracted from the air or simulated wastewater over 24 hours;

[0051] Figure 5 d represents the application of ammonia extracted from air or simulated wastewater in a direct ammonia fuel cell, where both the cathode and anode use a loading of 0.4 mg PGM cm⁻¹. -2 Pt / C catalyst. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0053] Example 1

[0054] (1) Synthesis of NiCu-SA:

[0055] First, treat a 300-mesh copper mesh (~0.022 g / cm²) with approximately 20 mL of 0.5 M sulfuric acid solution. 2 The copper mesh was then rinsed with ethanol. Next, the copper mesh was immersed in a solution consisting of 4.0 mL of 10.0 M sodium hydroxide, 2.0 mL of 1.0 M ammonium persulfate and 9.0 mL of deionized water for 20 minutes to grow copper hydroxide (Cu(OH)2) nanowires on the copper mesh.

[0056] The obtained copper hydroxide nanowires were washed with deionized water and dried at 60°C for 1 hour, and then immersed in a 20.0 mM nickel chloride (NiCl2) solution for 12 hours to promote the ion exchange process. After ion exchange, the nickel-doped copper hydroxide nanowires were dried at 80°C for 1 hour, and then heat-treated at 200°C in air atmosphere to obtain nickel-doped copper oxide (Ni-CuO).

[0057] Finally, nickel-doped copper oxide was electrochemically reduced for 2 hours in a 0.5 M Na2SO4-200 ppm NaNO3 electrolyte using a chronoamperometry method at a potential of -0.50 V relative to the reversible hydrogen electrode (RHE) to obtain a nickel-copper single-atom catalyst (NiCu-SA).

[0058] (2) Preparation of PTEI

[0059] HPG was synthesized using a typical method: 1 mL of pyrrole was added to 10 mL of water and sonicated for 15 minutes to form solution A; subsequently, 3.304 g of ammonium persulfate was sonicated to dissolve in 10 mL of water to prepare solution B. Solutions A and B were added to 50 mL of 1.2 M hydrochloric acid and stirred for 10 minutes, where the pyrrole rapidly polymerized into polypyrrole (PPy). After washing with water and filtering, the PPy was sonicated in water to form solution C (1 wt%). 0.8 g of polyvinyl alcohol (PVA) was dissolved in 10 mL of water by heating and stirring. 0.5 mL of 1.2 M hydrochloric acid, 1.25 mL of glutaraldehyde, and 3 mL of solution C were added to this solution. After thorough mixing, the mixture was quickly poured into a mold and crosslinked and cured for 2 hours. The resulting material was carefully cut into 1×1 cm pieces. 2 Or 3×3 cm 2 The cubes were then freeze-dried.

[0060] Next, hydrophobication treatment was performed: 20 μL of water was added to 2 mL of octadecyltrichlorosilane, sonicated for 10 seconds, and allowed to stand for 2 hours. The solution was then diluted with n-hexane at 1, 10, 100, and 1000 times, respectively. The lyophilized material was immersed in the diluted solution for 20 minutes, washed with n-hexane, and dried. The HPGs were named OG1, OG2, OG3, and OG4 according to the dilution factor from low to high.

[0061] Finally, HPG and NiCu-SA were bonded together using a PVA solution to form a Janus structure. Figure 1 a).

[0062] Comparative Example 1

[0063] The difference between this comparative example and Example 1 is that the hydrophobication treatment step is not included. The freeze-dried PVA gel without hydrophobication treatment is named PG, where PG0.6, PG0.8, PG1.0 and PG1.2 represent PVA:H2O mass ratios of 0.6:10, 0.8:10, 1.0:10 and 1.2:10, respectively.

[0064] Comparative Example 2

[0065] The difference between this comparative example and Example 1 is that the synthesis of cuprous oxide (Cu2O) involves the same heat treatment and electrochemical reduction of copper hydroxide nanowires, but does not include the nickel ion exchange step.

[0066] Example 2

[0067] An electrolytic cell for testing the catalytic performance of nitrate to ammonia conversion was assembled, comprising an anode chamber, a cathode chamber, and an electrolyte. The cathode chamber used a thermo-electrocatalytic interface nanostructure electrode prepared in Example 1, and the anode used a graphite rod electrode. The electrolyte was wastewater containing nitrate (concentration 50-5000 ppm). The cathode potential was -0.2 V to -0.6 V.

[0068] Example 3

[0069] HPG used in the flowing electrolytic cell was prepared by the following steps: A photothermal coating was applied to a commercially available porous polytetrafluoroethylene (PTFE) membrane. A PPy solution was centrifuged, dried, and ground into powder, and then mixed with conductive carbon black XC-72R at a mass ratio of 1:3. 10 mg of the mixed powder was ultrasonically dispersed in 1 mL of isopropanol solution and sprayed onto the PTFE membrane (50% porosity, 150 μm thickness) with a loading of approximately 0.4 mg cm⁻¹. -2 Subsequently, a diluted octadecyltrichlorosilane solution was uniformly sprayed onto the surface of the photothermal coating, and HPG and NiCu-SA were directly clamped and fixed together using electrode plates.

[0070] The above materials were characterized as follows: Atomic-level characterization: Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images were obtained using JEOL NEOARM. Spectroscopic analysis: UV-Vis absorption spectra were acquired using a UNICO UV-4800 spectrophotometer; X-ray absorption fine structure (XAFS) analysis was performed at the Shanghai Synchrotron Radiation Facility (China), and extended X-ray absorption fine structure (EXAFS) data were processed using the IFEFFIT package; X-ray photoelectron spectroscopy (XPS) was measured using Thermo Scientific K-Alpha (USA). Morphology and structure: Scanning electron microscopy (SEM) images were acquired using a ZEISS GeminiSEM 300; specific surface area analysis (BET) was performed on a Quantachrome EVO (USA). Physical properties: Contact angle tests were performed using a Zhongchen JC2000D1; compressive mechanical properties of the materials were tested using an INSTRON 5982 (USA). 1 H nuclear magnetic resonance (NMR) 1 The H NMR spectrum was recorded using a Bruker 600 MHz spectrometer (Germany).

[0071] First, the surface morphology of NiCu-SA was observed using scanning electron microscopy (SEM). Figure 1 b and Figure 1 c). The copper mesh consists of copper wires with a diameter of approximately 50 μm, on which a densely packed array of nanowires is grown. To further characterize the atomic structure of the catalyst, we obtained high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images. The results show that the lattice spacing between Cu atoms is approximately 0.3 nm, which is consistent with... Figure 1 The (011) crystal plane of Cu₂O shown in d corresponds to this. Auger electron spectroscopy (AES) and energy-dispersive X-ray spectroscopy (EDS) mapping results also support that the copper nanowires are mainly composed of Cu₂O. In principle, the brightness of the atomic pillars in the HAADF-STEM image is proportional to the square of the atomic number, which makes it possible to distinguish Ni and Cu atoms based on the Z-contrast between adjacent atomic pillars. The intensity distribution also confirms the anchoring of nickel monomers on the surface. This indicates that... Figure 1 The structure shown in d contains single-atom nickel species. Fourier transform extended X-ray absorption fine structure (FT-EXAFS) analysis of the K-edge of nickel (Ni) in NiCu-SA was performed. Figure 1e) shows that the Ni bond length is 1.44 Å. This value is shorter than the Ni-O bond length in NiO and Ni(OH)₂, and the Ni-Ni bond length in bulk nickel foil. Furthermore, the relatively low intensity of the Ni scattering peak in NiCu-SA indicates a low coordination number of nickel, suggesting that nickel species are atomically anchored on the Cu₂O surface. Further analysis of O1s X-ray photoelectron spectroscopy (XPS) shows that the oxygen vacancy concentration in NiCu-SA is significantly higher than that in Cu₂O, which provides a basis for the high-valence Ni... 2+ The successful incorporation of Cu2O into the lattice provides direct evidence.

[0072] Scanning electron microscopy images provide further evidence for the three-dimensional hierarchical pore structure of the gel membrane. Figure 1 f、 Figure 1 g). The results showed that macropores ranging from tens to hundreds of micrometers existed in the gel membrane, while mesoporous structures of tens of nanometers were uniformly distributed along the gel wall. This characteristic hierarchical structure is attributed to the dispersing effect of PVA, a surfactant in the solution, on PPy. Therefore, the PVA-PPy clusters formed a structure with gaps after gelation. To gain a deeper understanding of the hierarchical porous structure of HPG, Brunol-Emmett-Teller (BET) analysis was used, such as... Figure 1 As shown in figure h, the N2 adsorption isotherm exhibits type II isotherm characteristics, indicating that the material is predominantly macroporous. Further analysis of the pore size distribution (inset) shows that the most common pore size in the material is approximately 1.4 nm. Furthermore, the wettability was controlled by immersing the original PVA gel material (PG) in OTS solutions of different dilution ratios (0, 10, 100, and 1000 times) (denoted as OG1, OG2, OG3, and OG4, respectively). The OTS modification coverage on the surface of the material after OTS treatment was detected by X-ray photoelectron spectroscopy (XPS). Figure 1 The results show that the coverage of OTS increases significantly with increasing solution concentration, with OG1 showing slightly higher coverage than OG2. We used contact angle measurements to investigate the wettability of the sample groups. The results show that the water contact angle from PG to the OG2 surface increases significantly with increasing OTS content, while the contact angle of OG1 is slightly lower than that of OG2. This trend is consistent with previous studies, highlighting the influence of surface microstructure on material wettability. Based on these findings, we can conclude that a 10-fold dilution of OTS solution provides a suitable treatment concentration.

[0073] The catalytic performance of nitrate reduction at different concentrations was evaluated under neutral conditions. Figure 2 a) These concentrations are close to those found in common agricultural and industrial wastewater. Specifically, NO2 is mainly generated at low overpotentials. -This is consistent with previous reports on copper-based materials. In the potential range of -0.2V to -0.6V, NiCu-SA exhibits a significantly higher ammonia Faradaic efficiency (FE), indicating that the introduction of isolated nickel species promotes the conversion of nitrate to ammonia at low overpotentials. Furthermore, NiCu-SA exhibits high efficiency over a wide concentration range (50-5000 ppm NO3). - NiCu-SA exhibits stable ammonia production performance within the -N range. Durability assessments show that NiCu-SA achieves a Faradaic efficiency exceeding 90% during electrochemical NO3RR in ten consecutive catalytic cycles, demonstrating its excellent stability in nitrate electrolysis. We hypothesize that during illumination, photothermal generation may be transferred from the upper HPG layer to NiCu-SA, causing temperature changes and potentially affecting ammonia production performance. Therefore, we investigated the nitrate electroreduction performance at different temperatures at a given potential of -0.5V. Figure 2 (b) The results showed that temperature had little effect on the Faradaic efficiency of ammonia at this potential, but the ammonia yield (YR) increased significantly with increasing temperature. Notably, in previous studies, increasing temperature at low overpotentials improved the Faradaic efficiency of NO3RR, attributed to differences in solution pH and operating potential. To ensure measurement accuracy, ¹H nuclear magnetic resonance (NMR) spectroscopy was used to qualitatively confirm that all ammonia originated from the electroreduction of nitrate in solution, while ion chromatography (IC) was used to quantitatively verify the accuracy of the indophenol blue method. Further characterization of the NiCu-SA after testing revealed that the Ni2pXPS spectrum was almost identical before and after testing, indicating that the chemical environment of the Ni species did not change significantly. Furthermore, scanning electron microscopy analysis confirmed that the nanowire array morphology of the catalyst remained intact, with no collapse or aggregation observed.

[0074] To gain a deeper understanding of the mechanism behind the performance improvement of NiCu-SA, density functional theory (DFT) calculations were performed. Cu₂O(110) models with and without single-atom Ni site modification were constructed. Typically, the nitrate reduction pathway includes nitrate adsorption, hydrogenation of NOx intermediates, and deoxygenation, ultimately ending with ammonia desorption. Figure 2c shows the effect of Ni single-atom modification on the NO3RR and hydrogen evolution reaction (HER), with calculations considering a pH of 12. Specifically, the nitrate adsorption free energy on NiCu-SA is approximately 0.15 eV lower than that on Cu2O, indicating that the process is thermodynamically more favorable. Furthermore, the positive free energy change of the NO to NHOH step is considered a potential-determining step (PDS), with this value for Cu2O (1.06 eV) being higher than that for NiCu-SA (1.01 eV). Energy analysis of the HER pathway indicates that the water splitting reaction on pure Cu2O is suppressed. In contrast, NiCu-SA exhibits a significant thermodynamic advantage in water adsorption and dissociation, enabling its surface to generate abundant active hydrogen atoms (H) for NOx hydrogenation. To further investigate the source of NiCu-SA's superior ability to activate NOx intermediates, we investigated NO2... - Adsorption on the NiCu-SA surface ( Figure 2 d). NO2 - It is one of the most common byproducts of copper-based catalysts in the NO3RR process, therefore the reaction substrate is related to adsorbed NO2. - Its catalytic ability is crucial. Differential charge density simulations show that the introduction of single-atom Ni sites leads to NO2... - Asymmetric adsorption at copper sites was observed. For the Cu₂O model, the total charge transfer during substrate-NO₂ binding was calculated to be 0.257 e⁻, with each copper atom contributing 0.106 e⁻ and 0.109 e⁻, respectively. In contrast, the total charge transfer in the NiCu-SA model was 0.243 e⁻, with copper and nickel atoms contributing 0.102 e⁻ and 0.131 e⁻, respectively. Furthermore, crystal orbital Hamiltonian population (COHP) analysis of the NO orbitals in NO₂ showed that, compared to Cu₂O, the antibonding orbitals of NO in NiCu-SA shifted to lower energies, with a -ICOHP value of 1.46 eV. This provides supporting evidence that the synergistic effect of isolated nickel atoms and the Cu₂O surface promotes NO bond activation. - The negative shift of the Fermi level of NiCu-SA relative to Cu2O after adsorption further supports this conclusion.

[0075] The photothermal evaporation performance of HPG for ammonia was studied as follows. In solar-driven water evaporation, controlling the wettability of the gel membrane is crucial, as surface wettability plays a key role in the binding mode between water molecules and the surface. To improve ammonia-water separation performance, we used an immersion treatment method with different concentrations of OTS solution to adjust the gel wettability. Figure 3The image shows the temperature fluctuations of the floating gels under solar radiation: the surface temperatures of the highly hydrophobic OG1, OG2, and OG3 rise rapidly, exceeding 40°C within 10 seconds and reaching approximately 48°C after 10 minutes; in contrast, the hydrophilic PG and OG4 require approximately 10 minutes to reach thermal equilibrium. Furthermore, the surface temperatures of the more hydrophobic gels are significantly higher than those of the hydrophilic film under light irradiation. This is attributed to the large amount of liquid water in the hydrophilic gel maintaining a low temperature through surface evaporation and heat absorption, while the infrared image shows that PG loses heat to the bulk water, indicating convection between it and the underlying water body; the heat of OG2 is mainly concentrated on the surface, which is conducive to the in-situ evaporation of ammonia.

[0076] Figure 3 b shows the illumination (1 sun, 100 mW / cm²) -2 Under different wettability gels, the evaporation rate of 200 ppm (NH3-N) ammonia solution showed two distinct trends: In the first stage (white area), the evaporation rate first increased and then decreased with decreasing OTS hydrophobic treatment concentration, with OG2 exhibiting the highest ammonia evaporation rate, approximately 1.32 ± 0.14 gh. -1 m -2 In the second stage (blue area), the evaporation rate of PG was significantly higher than that of OG4. For further analysis, we simulated the effect of hydrophobicity on ammonia evaporation performance using finite element analysis. The model fixed the gel film on the surface of an ammonia solution and examined the relationship between the relative humidity of the gel and the normalized ammonia evaporation rate. The results showed that the ammonia evaporation capacity decreased with decreasing hydrophobicity, but the normalized evaporation rate was lowest at a relative humidity of approximately 0.8. Figure 3 b). Further analysis revealed that when both liquid and gas phases coexist in the porous gel, the liquid phase (water) dominates at high relative humidity (>0.8), and the ammonia evaporation rate is determined by the liquid phase ammonia flux; at low relative humidity (<0.8), the gas phase ammonia flux is the primary controller. Furthermore, increased relative humidity leads to a significant decrease in liquid phase ammonia flux, while the confined space in the gas phase results in a tortuous ammonia diffusion path.

[0077] Hydrophobic modified materials exhibited significantly better mechanical stability compared to untreated PG: OG1 had the highest elastic modulus (185.3 MPa), while OG2 maintained acceptable mechanical strength (166.2 MPa) and significantly improved ammonia evaporation efficiency and selectivity. Figure 3 (b) and exhibited high thermal stability during long-term testing (ammonia evaporation rate remained above 90%).

[0078] Molecular dynamics simulations were used to elucidate the mechanism by which the wettability of porous gels affects ammonia evaporation at the microscale. A solution chamber containing 14,700 water molecules and 300 ammonia molecules was constructed. Figure 3c) A metal layer was placed below the solution chamber to restrict molecular movement, and two pore models were constructed above it: a hydrophilic pore model composed of PVA chains and a hydrophobic pore model composed of alkane chains. The pore width was set to approximately 1 nm based on BET results. To prevent water or ammonia molecules from rebounding into the solution during evaporation, a constraint force was applied above the pore model, and periodic boundary conditions were used to confine the molecules within a specified simulation region.

[0079] Significant differences were observed after a 500ps evaporation simulation: in the hydrophilic model, water molecules gradually penetrated into the PVA pores, causing a significant upward shift of the liquid level; in the hydrophobic model, the liquid level remained almost unchanged throughout the simulation. The amount of ammonia molecules evaporated in the hydrophobic model (17 molecules) was higher than that in the hydrophilic model (11 molecules). Given that hydrogen bonds are the main interaction between ammonia and water molecules, we extracted hydrogen bond data of ammonia molecules at the interface (…). Figure 3 d). The results showed that during the 500 ps simulation, the average number of hydrogen bonds for ammonia molecules at the liquid surface in the hydrophobic model (1.82) was lower than that in the hydrophilic model (1.97), indicating that the hydrophobic system weakened the hydrogen bonding between ammonia and water molecules at the interface, thereby promoting the desorption of ammonia molecules from the solution. Furthermore, the adsorption energy of ammonia molecules by the hydrophilic chain was significantly higher than that of the hydrophobic chain, suggesting that the hydrophilic pores may create greater resistance to ammonia evaporation, hindering the evaporation process.

[0080] This solution develops a custom battery for PTEI ammonia evaporation. Figure 4 a) This battery is based on an H-type electrolytic cell design, consisting of a cathode chamber and an anode chamber. Our main research focus is on the recovery of ammonia via photothermal coupling electrosynthesis in the cathode chamber. To allow solar radiation to reach the PTEI, a quartz window was installed at the top of the cathode chamber. When a potential is applied to the NiCu-SA, the NO3RR reaction occurs on the NiCu-SA, leading to the dissociation of surface water molecules and the generation of a large amount of OH⁻. The locally high pH value promotes the existence of NH3 in molecular form. In addition, photothermal generation increases the temperature of the gas-liquid interface, accelerating the evaporation of ammonia molecules from the liquid surface.

[0081] To account for the differences in solar irradiance in different regions, we studied the ammonia collection capacity of NiCu-SA under different light intensities. Figure 4 (b) The nitrogen collection efficiency was determined by measuring the ammonia nitrogen content in the acidic solution after collecting the tail gas. In an electrolyte solution with an initial nitrate nitrogen concentration of 200 ppm, the nitrogen collection efficiency under no-light conditions was only about 40%. In contrast, the overall nitrogen collection efficiency increased to 64.2% under a light intensity of 0.5 sun. At higher irradiances of 1 sun and 2 sun, the efficiencies reached 74.1% and 80.8%, respectively, with ammonia collection rates recorded as 0.073 mgh. -1 cm -2 and 0.082mgh -1 cm-2 Furthermore, we investigated the system's nitrogen resource collection capacity for solutions with different nitrate concentrations. Figure 4 c). Specifically, at a concentration of 50 ppm, the nitrogen resource collection rate was 50.8%. Under higher conditions approaching industrial wastewater concentrations, the ammonia capture efficiency exceeded 70%, with an ammonia collection rate reaching 0.184 mgh. -1 cm -2 In addition, we prepared two more complex wastewater samples to simulate actual industrial wastewater (IW) and textile wastewater (TW). This was particularly important for samples containing NO3. - The IW treatment results for -N (~580ppm), NH3-N (~400ppm), and Cl⁻ (~460ppm) showed that the total nitrogen collection efficiency reached 78.8%, and the ammonia recovery rate was 0.43 mgh. -1 cm -2 In the TW (total nitrogen) phase, the nitrate nitrogen content was approximately 104 ppm, with a nitrogen collection efficiency of 54.5%. This difference can be attributed to the inherently higher ammonia concentration in the IW (individual nitrogen) phase, resulting in a higher total nitrogen collection efficiency. Residual nitrate species in the liquid phase were analyzed after treatment. Figure 4 d). The level of residual nitrate in the solution is directly related to the initial nitrate concentration. After treatment, the nitrate ion removal efficiency of all components except TW exceeded 90%. The nitrate nitrogen removal efficiency in TW was slightly lower, possibly due to its significantly higher Cl⁻ content compared to nitrate ions. We used multiphysics finite element simulations to gain a deeper understanding of the transport behavior of reactant species in the batch reactor. Analysis showed that the pH at the interface rapidly increased to above 11, indicating that even under neutral conditions, the OH⁻ generated by electroreduction was sufficient to maintain the molecular form of ammonia at the interface. By analyzing the concentration changes of the main nitrogen-containing species (including ammonia molecules, ammonium ions, and nitrate ions) in the cell, we observed that the rate of decrease in ammonia concentration gradually stabilized over time during photo-evaporation, indicating that the evaporation rate of ammonia is affected by its own concentration. Furthermore, the study found that temperature contributes to the evaporation of ammonia at the interface.

[0082] To obtain direct evidence that PTEI promotes ammonia evaporation, we performed scanning electrochemical microscopy (SECM) experiments in surface generation / tip collection mode (SG / TC). Figure 4As shown in Figure e, a negative potential was applied to the NiCu-SA surface to initiate NO3RR and generate ammonia. NiCu-SA was integrated with a polytetrafluoroethylene film coated with hydrophobic photothermal gel (HPG) to form a PTEI. The distance between the tip and the substrate was calibrated using 1 mM ferrocene methanol as a reference. Three different scenarios were investigated: Scenario I included NO3RR, illumination, and purging to promote ammonia evaporation; Scenario II included NO3RR and purging; and Scenario III involved only NO3RR. A positive potential was applied to a 25 μm platinum microelectrode (Pt-UME) to detect the ammonia generated on the NiCu-SA. Because the Pt-UME is smaller than the substrate below, the current on the Pt-UME as the tip gradually approaches the substrate originates entirely from the oxidation reaction of ammonia generated on the substrate. Numerical simulations of the gradual change in tip current were used to fit the surface ammonia concentration and its diffusion rate at the photothermal interface.

[0083] like Figure 4 As shown in f, when the tip gradually approaches the substrate, the tip current in scenario I is significantly lower than that in scenarios II and III, indicating that a large amount of ammonia on the substrate evaporates through the photothermal interface. The fitting results show that the ammonia diffusion rate in scenario II (without illumination) is 5.36 × 10⁻⁶. -7 cm 2 s -1 The diffusion rate at the photothermal interface is 1.78 × 10⁻⁶. -6 cm 2 s -1 This indicates that the photothermal interface in scenario I increases the ammonia evaporation rate by more than three times. Figure 4 The visualization of the two-dimensional concentration distribution of g further reveals that, compared with scenarios II and III, a large amount of ammonia evaporates from the photothermal electrocatalytic interface in gaseous form in scenario I.

[0084] In summary, we have demonstrated the application of PTEI in batch reactors for water purification and denitrification. However, the mismatch between the ammonia evaporation rate and the production rate resulted in suboptimal ammonia production efficiency. In contrast, flow reactors offer advantages in production efficiency and integration, making them more suitable for practical industrial applications. By combining a plasma-mediated nitrogen oxide generation system with PTEI (P-PE-NOxRR) for NOx reduction, we designed a system capable of continuously producing high-purity concentrated ammonia water from air, further expanding the potential of PTEI systems. Figure 5 a).

[0085] The P-PE-NOxRR operated continuously and stably for 30 hours, and the current stabilized at 200 mAcm after the initial 30 minutes. -2 h -1 The above indicates that the formation and consumption of nitrate at the cathode have reached equilibrium. After 4 hours, due to the accumulation of ammonia in the cathode tank, the ammonia collection rate gradually stabilized, eventually reaching 13.7 mg / cm³.-2 h -1 The balance value ( Figure 5 b). During the 24-hour collection period, the P-PE-NOxRR collected approximately 23 mL of pure ammonia solution with a concentration of 1.96 M (~3.25 wt%), which is comparable to the ammonia concentration previously reported for ammonia fuel cells. In this system, industrial simulated wastewater (IW) was used as the nitrate nitrogen source (W-PE-NOxRR), and approximately 25 mL of ammonia solution with a concentration of 0.36 M (~0.61 wt%) was collected. Figure 5 c).

[0086] Ammonia obtained from air and simulated wastewater is mixed with 10M NaOH at a volume ratio of 9:1 for use in ammonia fuel cells. Figure 5 d). The peak power densities of fuel cells directly driven by ammonia generated by P-PE-NOxRR and W-PE-NOxRR are 1.77 mW / cm³, respectively. -2 and 1.32mWcm -2 It is important to note that this is only a proof of concept; in reality, optimizing the catalyst can significantly improve the power density of direct ammonia fuel cells (DAFCs).

[0087] In summary, this scheme developed a Janus hybrid nanostructure PTEI system that utilizes solar energy to reduce energy consumption and purifies low-concentration ammonia from the NOxRR process, achieving continuous electrified production from environmental sources such as air and wastewater. The introduction of nickel single atoms into the cuprous oxide substrate significantly improved ammonia yield—at 200 ppm NO3—by promoting the generation of active hydrogen and the dissociation of NOxRR intermediates. - The Faraday efficiency (FE) in the -N solution exceeds 90%, and the yield (YR) exceeds 2.8 mg / cm³. -2 h -1 By optimizing the hydrophobicity of the interface, we ensured stable and continuous ammonia production and purification within the integrated PTEI system. Scanning electrochemical microscopy (SECM) confirmed a 3.3-fold increase in ammonia evaporation rate under photothermal conditions. When using air as the nitrogen source, the ammonia extraction rate of the PTEI system reached as high as 13.7 mg / cm³. -2 h -1 This process produces an ammonia solution with a concentration of approximately 2M. Furthermore, treating simulated industrial wastewater yields a 0.36M ammonia solution with a total nitrogen recovery rate exceeding 80%. This synergistic innovation in material and device design drives the development of a multifunctional platform for water treatment, chemical synthesis, and separation and purification, providing a sustainable strategy for advancing the Water-Energy-Food Link (WEFNexus). Moreover, this method holds promise for extension to other low-boiling-point product reactions, such as carbon dioxide reduction (CO2RR) and nitrogen reduction (NRR).

[0088] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrocatalytic interface nanostructure electrode film based on photothermal effect, characterized in that, It includes a hydrophobic photothermal gel layer HPG for ammonia evaporation and a nickel single-atom modified cuprous oxide catalyst layer NiCu-SA for catalytic nitrate reduction; The hydrophobic photothermal gel layer HPG and the nickel single-atom modified cuprous oxide catalyst layer NiCu-SA are bonded together by PVA solution to form a Janus structure; The nickel single-atom modified cuprous oxide catalyst layer NiCu-SA is a nickel single-atom anchored cuprous oxide nanowire electrode. The hydrophobic photothermal gel layer HPG is prepared by blending polyvinyl alcohol with polypyrrole, cross-linking with glutaraldehyde, and then immersing in an octadecyltrichlorosilane solution at room temperature.

2. The method for preparing the electrocatalytic interface nanostructure electrode film based on photothermal effect as described in claim 1, characterized in that, Includes the following steps: S1. Preparation of nickel-doped cuprous oxide catalyst layer NiCu-SA: First, a copper mesh was immersed in a solution composed of sodium hydroxide, ammonium persulfate, and deionized water to grow copper hydroxide nanowires on the mesh. The resulting copper hydroxide nanowires were then immersed in a nickel chloride solution for ion exchange. After ion exchange, nickel-doped copper oxide was obtained. Finally, the nickel-doped copper oxide was electrochemically reduced in an electrolyte using a chronoamperometry method at a potential of -0.50 V relative to the reversible hydrogen electrode to obtain the nickel-doped cuprous oxide catalyst layer NiCu-SA. S2. Preparation of hydrophobic photothermal gel layer HPG: Pyrrole is added to water and ultrasonically treated to form solution A; then ammonium persulfate is ultrasonically dissolved in water to prepare solution B; solutions A and B are added to hydrochloric acid and stirred, and pyrrole rapidly polymerizes into polypyrrole. After washing and filtering, polypyrrole is ultrasonically treated in water to form solution C. Polyvinyl alcohol was dissolved in water by heating and stirring. Hydrochloric acid, glutaraldehyde, and solution C were added to the polyvinyl alcohol solution. After thorough mixing, the mixture was quickly poured into a mold for cross-linking and curing. The resulting material was then freeze-dried. Water was added to octadecyltrichlorosilane and then diluted with n-hexane; the freeze-dried material was immersed in the diluted octadecyltrichlorosilane solution for reaction, and after the reaction, it was washed with n-hexane and dried to obtain the hydrophobic photothermal gel layer HPG; S3. A hydrophobic photothermal gel layer HPG is bonded to a nickel single-atom modified cuprous oxide catalyst layer NiCu-SA using PVA solution to form an electrocatalytic interface nanostructure electrode film based on photothermal effect.

3. The method for preparing the electrocatalytic interface nanostructure electrode film based on photothermal effect as described in claim 2, characterized in that, In step S1, the concentration of sodium hydroxide is 10.0 M; the concentration of ammonium persulfate is 1.0 M; the concentration of nickel chloride solution is 20.0 mM; and the electrolyte contains 200 ppm NO3. - 0.5M Na2SO4.

4. The method for preparing the electrocatalytic interface nanostructure electrode film based on photothermal effect as described in claim 2, characterized in that, The preparation process of solution A in step S2 is as follows: 1 mL of pyrrole is added to 10 mL of water and ultrasonically treated for 15 minutes to form solution A; the preparation process of solution B is as follows: 3.304 g of ammonium persulfate is ultrasonically dissolved in 10 mL of water to prepare solution B; the mass fraction of solution C is 1 wt%; the mass-volume ratio of polyvinyl alcohol to water is 0.8:10 g / mL.

5. The method for preparing the electrocatalytic interface nanostructure electrode film based on photothermal effect as described in claim 2, characterized in that, In step S2, the volume ratio of water to octadecyltrichlorosilane is 1:100; the ratio of octadecyltrichlorosilane to hexane is 10.

6. The application of the photothermal electrocatalytic interface nanostructure electrode film based on the photothermal effect as described in claim 1 and the photothermal electrocatalytic interface nanostructure electrode film obtained by the preparation method described in any one of claims 2-5 in the recovery of nitrogen resources in the environment.

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