In-situ monitoring method for dynamic morphology and activity of nitrate reduction reaction catalyst

Abstract

The invention discloses an in-situ monitoring method for dynamic morphology and activity of a nitrate reduction reaction catalyst, and belongs to the technical field of electro-catalytic material characterization. And in combination with a modified electrolytic tank and a linkage strategy of'potential output-morphology scanning-activity detection ', in-situ co-positioning accurate monitoring of nanoscale morphology evolution and local activity distribution on the surface of the catalyst in the nitrate radical reduction reaction process is realized, and the method has high stability and compatibility and excellent dynamic quantitative characterization capability. According to the in-situ monitoring method developed by the invention, the technical bottleneck that the morphology and the activity are difficult to synchronously monitor by a traditional characterization technology is solved, and a brand-new dynamic analysis platform is provided for dynamic identification of active sites of a nitrate reduction reaction catalyst, analysis of a reaction mechanism and optimization of catalytic performance.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic material characterization technology, specifically to a method for in-situ monitoring of the dynamic morphology and activity of nitrate reduction reaction catalysts. Background Technology

[0002] NO3RR (nitrate reduction reaction) is a key electrochemical process for solving nitrate pollution in water bodies and achieving low-cost synthesis of "green ammonia." Its catalytic performance hinges on the dynamic evolution of active sites (such as edges, wrinkles, and defect structures) during the reaction. Currently, characterization techniques for NO3RR catalysts mainly rely on the individual use or simple combinations of commercial detection equipment, such as traditional electrochemical methods (e.g., cyclic voltammetry, electrochemical impedance spectroscopy) or spectroscopic techniques (e.g., X-ray absorption spectroscopy), which struggle to comprehensively analyze the dynamic changes of active sites.

[0003] To overcome this bottleneck, some studies have attempted to combine atomic force microscopy (AFM) with scanning electrochemical microscopy (SECM). However, these existing technologies still have limitations in practical applications: they are mainly designed for static surface analysis (such as metal corrosion monitoring) and have not yet been adapted to the dynamic and complex scenario of "liquid-phase electrocatalysis" of NO3RR; the electrolytic cell design of traditional EC-AFM-SECM devices cannot meet the high alkalinity environment of NO3RR (pH up to 13), which easily leads to electrode corrosion and electrolyte leakage; the probes used are mostly based on feedback mode, which is a single mode and cannot achieve co-localization of "morphology-product detection" at the same time, while the probes based on ultramicroelectrodes (UMEs) are large in size, resulting in poor spatial resolution and difficulty in accurately identifying the dynamic changes of active sites. Summary of the Invention

[0004] Therefore, the present invention aims to provide a method for in-situ monitoring of the dynamic morphology and activity of nitrate reduction reaction catalysts, mainly addressing two core defects in the detection technology of NO3RR catalysts based on commercial modules: first, the spatiotemporal disconnect between morphology characterization and activity detection; and second, the lack of scenario adaptability.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: (1) Integrating AFM, SECM probes and electrochemical workstations, in-situ co-location monitoring of the catalyst’s “nanoscale morphology evolution” and “local activity distribution” during the NO3RR process is achieved, breaking the spatiotemporal decoupling of structure and activity; (2) Slightly modify and optimize the operation of the electrolytic cell to build a test environment (liquid phase system, pH compatibility: 1~13) suitable for NO3RR, and ensure the stability and repeatability of the activity signal; (3) Design a three-linkage strategy of “potential output - morphology scanning - activity detection” to accurately capture the synchronous changes in morphology and activity in the key potential range of NO3RR; (4) Improve the versatility of the device so that it can be extended to the characterization of a variety of electrocatalysts.

[0006] Specifically: A method for in-situ monitoring of the dynamic morphology and activity of a catalyst for nitrate reduction reaction includes the following steps: Step 1: Test System Setup and Preprocessing A conductive substrate coated with a nitrate reduction catalyst was prepared; a scanning electrochemical microscope (SECM) probe was fixed to an atomic force microscope (AFM) to obtain an integrated AFM-SECM probe. Using this integrated probe as the first working electrode and the conductive substrate coated with the nitrate reduction catalyst as the second working electrode, an electrolyte was injected to complete the assembly of the electrolytic cell; the integrated AFM-SECM probe, the electrochemical workstation, and the control computer were connected, the system was initialized, and the lift-up height and detection potential of the integrated probe were set. Step 2: In-situ synchronous detection process The potential programs for the first and second working electrodes were set in the electrochemical workstation software, and the scanning parameters were set in the atomic force microscopy (AFM) software. The lift-up height of the integrated probe of the atomic force microscopy (AFM)-scanning electrochemical microscopy (SECM) was controlled by the software to switch between morphology scanning and lift-up scanning modes. At the same time, the morphology and current signal channels were opened to record the contact current and lift-up current of the integrated probe in real time, so as to realize the synchronous acquisition of three-dimensional data of "potential-morphology-activity". The storage path was set to save the experimental data. Step 3: Morphology-activity association analysis and active site identification The surface morphology images at different potentials were analyzed using atomic force microscopy software to extract morphological features. At the same time, the lift-up current signals at each potential were analyzed to establish the correspondence between morphological features and activity signals. By combining the atomic force microscopy morphology images with electrochemical current-thermal maps, the active sites of the catalyst could be accurately located.

[0007] Preferably, the conductive substrate coated with the nitrate reduction catalyst is prepared as follows: Take nitrate reduction catalyst powder with a thickness of 1~20nm, add anhydrous ethanol to prepare a dispersion of 0.1mg / mL, and sonicate for 30min; take 10μL of dispersion with a pipette, uniformly drop it onto a conductive substrate, and vacuum dry at 60℃ for 2h to form a monodisperse catalyst coating, thus obtaining the conductive substrate of nitrate reduction catalyst.

[0008] Preferably, the electrolytic cell comprises: The base has a shell screwed to its top, and a sealed liquid space is formed between the base and the shell, which contains an electrolyte. An inner pool is installed on top of the base, and the inner pool is disposed in the liquid space, forming an installation space between the inner pool and the base; A substrate is installed in the installation space, and a detachable electrode module is installed on the top of the substrate. The substrate and the inner tank are made of polytetrafluoroethylene. A quartz cover plate is installed on the top of the housing. An O-ring is installed between the quartz cover plate and the housing. The O-ring has two interfaces, which are respectively connected to the Ag wire reference electrode and the Pt wire counter electrode. The tip of the Ag wire reference electrode is close to the working electrode and immersed in the electrolyte. The Pt wire counter electrode is wound around the inner wall of the housing to enhance electron transport. The O-ring is made of fluorinated rubber, and the interfaces are naturally sealed to ensure no electrolyte leakage.

[0009] Preferably, the Ag wire reference electrode is immersed to a depth of 10 mm.

[0010] Preferably, the electrode module supports highly oriented pyrolytic graphite (HOPG), gold-plated silicon wafers, or glassy carbon electrode (GC) conductive substrates.

[0011] Preferably, the electrolyte in step 1 is pre-purged with argon gas for more than 30 minutes (to remove dissolved oxygen), sealed, and stored at low temperature and away from light.

[0012] Preferably, the conductive substrate in step 1 has a size of 10mm × 10mm.

[0013] Preferably, the lift height of the integrated probe in step 1 is 0~100nm. The specific operation is as follows: using the AFM peak force tapping mode, the probe lightly touches the HOPG surface. The AFM lift mode switch is turned on and adjusted to the target height to maintain a constant distance between the probe and the catalyst surface, so as to avoid interference of the activity signal by the distance change.

[0014] Preferably, the detection potential of the integrated probe in step 1 ( E tip ) is 0.6V vs. Ag is used in response to the oxidation signal of NO3RR products.

[0015] Preferably, the scanning parameters in step 2 are: a scanning range of 5×5μm, a scanning rate of 1.0Hz, a resolution of 256×256 pixels, and a peak force tapping mode (to ensure topographic resolution).

[0016] The present invention has the following advantages: This application solves the core problem of "morphology-activity spatiotemporal disconnect" in existing technologies by "synchronous integration of commercial modules + minor modification of electrolyzers + linkage scanning strategy," and the beneficial effects on NO3RR catalyst detection are as follows: (1) Improved spatiotemporal co-localization accuracy: The ultra-high nanoscale morphology resolution of AFM matches the 100nm activity detection resolution of SECM. Combined with "contact-non-contact" linked scanning, spatial co-localization of "nanoscale morphology-local activity" in the NO3RR process is achieved for the first time, solving the problem of "structure-activity decoupling" in traditional techniques. For example, the wrinkled areas of α-SnO2 / GO can be directly observed. I tip It is approximately 100 times larger than the flat area, clearly defining the structural characteristics of the active site; (2) Optimization of underwater compatibility and potential adaptability: The corrosion-resistant electrode system (PTFE electrolytic cell) can operate stably for >6h in electrolytes with pH 1~13 without electrolyte leakage or electrode oxidation; the potential control system supports -10~+10V. vs. Due to the wide window of Ag and the tolerance properties of the probe, the practical application range is typically -2.0 to +2.0 V. vs. Within the range of Ag, it can cover the entire reduction potential range of NO3RR, avoiding the interference current problem of traditional devices. For example, under strongly alkaline conditions at pH=13, the device can still stably record the roughness changes of α-SnO2 / GO (improved by 59.0%). (3) Quantitative characterization capability of dynamic processes: Through synchronous acquisition of "potential-morphology-current", the dynamic structure-activity relationship of NO3RR was established. For example, it was found that α-SnO2 / GO in E sample The thickness reduction rate is fastest at -0.6V (corresponding to Sn). 4+ →Sn 2+ The peak value of the restoration), and at this time I tip The upward trend provides direct evidence for the "structural reconstruction → active site generation" model. (4) High versatility: The device supports catalysts of various forms such as nanosheets and particles (e.g., Sn-based and Bi-based nanosheets), and can be adapted to different NO3RR reaction conditions by adjusting the electrolyte composition (e.g., KNO3 concentration, electrolyte type, pH); at the same time, the "morphology-activity co-localization" principle of the device can be extended to other electrocatalytic reactions such as CO2 reduction and water electrolysis, providing a universal platform for catalyst characterization in multiple scenarios. Attached Figure Description

[0017] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0018] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0019] Figure 1 The diagram shows the core electrochemical cell of the EC-AFM-SECM of this invention (left) and its application in NO3RR (right). The AFM-SECM integrated probe serves as the first working electrode for local electrochemical activity imaging; the sample (a conductive substrate coated with the catalyst) serves as the second working electrode for macroscopic electrocatalytic performance testing; a silver wire serves as the reference electrode; and a platinum wire serves as the counter electrode. Figure 2 This is a schematic diagram of the electrolytic cell structure of the present invention; Figure 3 The NO3RR of amorphous a-SnO2 / GO nanosheets, crystalline c-SnO2 / GO nanosheets, and GO nanosheets in Examples 1-3 of this invention at different potentials in a weakly alkaline solution (the electrolyte is a mixture of 1M KNO3 and 0.1M KHCO3, pH=8.3) is described. I tip Signal response curve; Figure 4 This is an in-situ discrimination diagram of the NO3RR activity in different regions of amorphous a-SnO2 / GO nanosheets obtained by SG / TC mode testing based on the EC-AFM-SECM in-situ platform in Example 1 of this invention; Top: AFM morphology diagram, Bottom: SECM morphology diagram. I tip Heat map; Figure 5 This is an in-situ discrimination diagram of NO3RR activity in different regions of amorphous a-SnO2 / GO nanosheets obtained by feedback mode testing based on the EC-AFM-SECM in-situ platform in Example 1 of this invention. Top: AFM morphology; Bottom: SECM morphology. I tip Heat map. Detailed Implementation

[0020] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] A method for in-situ monitoring of the dynamic morphology and activity of a catalyst for nitrate reduction reaction includes the following steps (see details below for the specific principle). Figure 1 ): Step 1: Test System Setup and Preprocessing A conductive substrate coated with a nitrate reduction catalyst was prepared; a scanning electrochemical microscope (SECM) probe was fixed to an atomic force microscope (AFM) to obtain an AFM-SECM integrated probe. Using this integrated probe as the first working electrode and the conductive substrate coated with the nitrate reduction catalyst as the second working electrode, an electrolyte was injected to complete the assembly of the electrolytic cell; the AFM-SECM integrated probe, the electrochemical workstation, and the control computer were connected, the system was initialized, and the lift-up height and detection potential of the integrated probe were set. Step 2: In-situ synchronous detection process The potential programs for the first and second working electrodes were set in the electrochemical workstation software, and the scanning parameters were set in the atomic force microscope software. The lift-up height of the AFM-SECM integrated probe was controlled by the software to switch between morphology scanning and lift-up scanning modes. At the same time, the morphology and current signal channels were opened to record the contact current and lift-up current of the integrated probe in real time, so as to realize the synchronous acquisition of three-dimensional data of "potential-morphology-activity". The storage path was set to save the experimental data. Step 3: Morphology-activity association analysis and active site identification The surface morphology images at different potentials were analyzed using atomic force microscopy software to extract morphological features. At the same time, the lift-up current signals at each potential were analyzed to establish the correspondence between morphological features and activity signals. By combining the atomic force microscopy morphology images with electrochemical current-thermal maps, the active sites of the catalyst could be accurately located.

[0022] Preferably, the conductive substrate coated with the nitrate reduction reaction catalyst is prepared as follows: Take nitrate reduction catalyst powder with a thickness of 1~20nm, add anhydrous ethanol to prepare a dispersion of 0.1mg / mL, and sonicate for 30min; take 10μL of dispersion with a pipette, uniformly drop it onto a conductive substrate, and vacuum dry at 60℃ for 2h to form a monodisperse catalyst coating, thus obtaining the conductive substrate of nitrate reduction catalyst.

[0023] Preferably, the electrolytic cell comprises: The base has a shell screwed to the top, and a sealed liquid space is formed between the base and the shell, which contains electrolyte. The inner pool is installed on top of the base and is placed in the liquid space, forming an installation space between the inner pool and the base; The substrate is installed in the installation space. A detachable electrode module is installed on the top of the substrate. The substrate and the inner tank are made of polytetrafluoroethylene. A quartz cover plate is installed on the top of the housing. An O-ring is installed between the quartz cover plate and the housing. The O-ring has two interfaces, which are connected to the Ag wire reference electrode and the Pt wire counter electrode, respectively. The tip of the Ag wire reference electrode is close to the working electrode and immersed in the electrolyte. The Pt wire counter electrode is wound around the inner wall of the housing to enhance electron transmission. The O-ring is made of fluorinated rubber, and the interfaces are naturally sealed to ensure no electrolyte leakage.

[0024] Preferably, the Ag wire reference electrode is immersed to a depth of 10 mm.

[0025] Preferably, the electrode module supports a conductive substrate of highly oriented pyrolytic graphite (HOPG), gold-plated silicon wafer, or glassy carbon electrode (GC).

[0026] Preferably, in step 1, the electrolyte is purged with argon gas for at least 30 minutes beforehand (to remove dissolved oxygen), sealed, and stored at low temperature and away from light.

[0027] Preferably, the size of the conductive substrate in step 1 is 10mm × 10mm.

[0028] Preferably, the lift height of the integrated probe in step 1 is 0~100nm. The specific operation is as follows: using the AFM peak force tapping mode, the probe lightly touches the HOPG surface. The AFM lift mode switch is turned on and adjusted to the target height to maintain a constant distance between the probe and the catalyst surface, so as to avoid interference of distance changes with the activity signal.

[0029] Preferably, the detection potential of the integrated probe in step 1 ( E tip ) is 0.6V vs. Ag is used in response to the oxidation signal of NO3RR products.

[0030] Preferably, the scanning parameters in step 2 are: a scanning range of 5×5μm, a scanning rate of 1.0Hz, a resolution of 256×256 pixels, and a peak force tapping mode (to ensure topographic resolution).

[0031] The AFM used in this invention is a Bruker Dimension Icon atomic force microscope, used for surface morphology imaging; The commercial model of SECM is PFT-SECM, which is a Pt microprobe. The probe has an exposed tip diameter of ~100nm, and the rest is covered with insulating Si3N4. The cantilever beam length is ~40μm, and it is used to detect local active signals. The electrochemical workstation is a Shanghai Chenhua CHI760E dual potentiostat, which supports a four-electrode system and has a potential output range of -10 to 10V. It is used to control the working electrode potential of the catalyst and the detection potential of the SECM probe.

[0032] Example 1 A method for in-situ monitoring of the dynamic morphology and activity of a catalyst for nitrate reduction reaction includes the following steps (see details below for the specific principle). Figure 1 ): Step 1: Test System Setup and Preprocessing (1) Catalyst sample preparation: A 15.8 nm thick a-SnO2 / GO powder was added to anhydrous ethanol to prepare a 0.1 mg / mL dispersion, which was then ultrasonically dispersed for 30 min. 10 μL of the dispersion was taken with a pipette and uniformly dropped onto a HOPG substrate (10 × 10 mm in size). The substrate was then vacuum dried at 60 °C for 2 h. Monodisperse amorphous a-SnO2 / GO nanosheets were formed on the surface of the HOPG substrate. The thickness and dispersion uniformity were confirmed by AFM pre-scan. (2) Electrolytic cell assembly (see structural diagram) Figure 1 and Figure 2 Electrolyte preparation: The HOPG substrate, which forms monodisperse amorphous a-SnO2 / GO nanosheets, was fixed at the bottom of the electrolytic cell as the second working electrode. The SECM probe was fixed to the AFM to obtain the AFM-SECM integrated probe, which served as the first working electrode. A Pt wire electrode, wound into a spiral shape, was inserted into the electrolytic cell to improve current uniformity. A modified Ag wire reference electrode was used, and 2.5 mL of electrolyte, which was a mixture of 1 M KNO3 and 0.1 M KHCO3 with pH 8.3, was injected into the electrolytic cell. The electrolyte was purged with Ar gas for more than 30 minutes in advance to remove dissolved oxygen. The electrolyte was then sealed and stored in a cool, dark place. (3) Module connection and synchronization initialization: Connect the control computer, AFM-SECM integrated probe, and electrochemical workstation using a USB cable. Install the commercial device control software Bruker NanoScope Analysis 2.0 and CHI760E Software. Manually turn on the electrochemical workstation and AFM instrument for signal collection. Use the AFM peak force tapping mode to gently touch the AFM-SECM integrated probe to the HOPG surface. Turn on the AFM Lift mode switch and adjust the height to 50 nm to maintain a constant distance between the AFM-SECM integrated probe and the catalyst surface to avoid interference from distance changes on the activity signal. Set the SECM probe accordingly. E tip 0.6V vs. Ag is used in response to the oxidation signal of NO3RR products; Step 2: EC-AFM-SECM in-situ platform Configure the electrochemical workstation software as follows: Potential of the first working electrode (SECM, Pt probe): 0.6V vs. Ag; The second working electrode E sample Program: Initial potential is OCP, termination potential is -1.0V vs. Ag, step size 0.1V, dwell time per step 1024s; In the AFM software, set the scanning parameters as follows: scanning range 5×5μm, scanning rate 1.0Hz, resolution 256×256 pixels, and scanning mode to peak force tapping mode to ensure topographic resolution. Activate the SECM probe lift-off mode in the AFM software, set the lift-off height to 50 nm, and allow the probe to alternate between morphology scanning and lift-off scanning. Open the morphology acquisition channel and the tip current acquisition channel, and simultaneously record the probe contact current and... I tip Simultaneously collect "potential-morphology-activity" data and set the data storage path; Step 3: Morphology-activity association analysis and active site identification Extracting morphological features Morphology images at various potentials were analyzed using AFM software: Surface roughness of amorphous α-SnO2 / GO nanosheets at OCP. R q =2.4nm, average thickness=15.8nm; E sample At -0.8V, R qThe thickness was further increased to 3.4 nm (an improvement of 41.7%), while the thickness decreased to 11.4 nm (a reduction of 27.8%). This indicates that cathode polarization induces surface reconstruction with increased catalyst roughness and reduced thickness.

[0033] Activity signal association when E sample When the voltage is -0.7V, the measured value is... I tip =~12pA; when E sample At -0.8V, I tip It can reach ~16pA.

[0034] Active site localization AFM topography image and SECM I tip Heatmap comparison, using Nanoscop Analysis software I tip Values ​​are mapped to black, with local edges and wrinkle locations. I tip It can reach ~400pA, which is a highly active region.

[0035] Example 2 A method for in-situ monitoring of the dynamic morphology and activity of a catalyst for nitrate reduction reaction includes the following steps (see details below for the specific principle). Figure 1 ): Step 1: Test System Setup and Preprocessing (1) Catalyst sample preparation A 16.5 nm thick c-SnO2 / GO powder was added to anhydrous ethanol to prepare a 0.1 mg / mL dispersion, which was then ultrasonically dispersed for 30 min. 10 μL of the dispersion was taken with a pipette and uniformly dropped onto a HOPG substrate (10 × 10 mm in size). The substrate was then vacuum dried at 60 °C for 2 h. Monodisperse crystalline c-SnO2 / GO nanosheets were formed on the surface of the HOPG substrate. The thickness and dispersion uniformity were confirmed by AFM pre-scan. (2) Electrolytic cell assembly (see structural diagram) Figure 1 and Figure 2 Electrolyte preparation: The HOPG substrate, which forms monodisperse crystalline c-SnO2 / GO nanosheets, was fixed at the bottom of the electrolytic cell as the second working electrode. The SECM probe was fixed to the AFM to obtain the AFM-SECM integrated probe, which served as the first working electrode. A spiral-wound Pt wire was inserted into the electrolytic cell to improve current uniformity. A modified Ag wire reference electrode was used, and 2.5 mL of electrolyte was injected into the electrolytic cell. The electrolyte was a mixture of 1 M KNO3 and 0.1 M KHCO3 with a pH of 8.3. The electrolyte was purged with Ar gas for more than 30 minutes in advance to remove dissolved oxygen. The electrolyte was then sealed and stored in a cool, dark place. (3) Module connection and synchronization initialization: Connect the control computer, AFM-SECM integrated probe, and electrochemical workstation using a USB cable. Install the commercial device control software Bruker NanoScope Analysis 2.0 and CHI760E Software. Manually turn on the electrochemical workstation and AFM instrument for signal collection. Use the AFM peak force tapping mode to gently touch the AFM-SECM integrated probe to the HOPG surface. Turn on the AFM Lift mode switch and adjust the height to 50 nm to maintain a constant distance between the AFM-SECM integrated probe and the catalyst surface to avoid interference from distance changes on the activity signal. Set the SECM probe accordingly. E tip 0.6V vs. Ag is used in response to the oxidation signal of NO3RR products; Step 2: EC-AFM-SECM in-situ platform Configure the electrochemical workstation software as follows: Potential of the first working electrode (SECM, Pt probe): 0.6V vs. Ag; The second working electrode E sample Program: Initial potential is OCP, termination potential is -1.5V vs. Ag, step size 0.1V, dwell time per step 1024s; In the AFM software, set the scanning parameters as follows: scanning range 5×5μm, scanning rate 1.0Hz, resolution 256×256 pixels, and scanning mode to peak force tapping mode to ensure topographic resolution. Activate the SECM probe lift-off mode in the AFM software, set the lift-off height to 50 nm, and enable the probe to alternate between morphology scanning and lift-off scanning. Open the morphology acquisition channel and the tip current acquisition channel, and simultaneously record the probe contact current and lift-off current. I tip Simultaneously collect "potential-morphology-activity" data and set the data storage path; Step 3: Morphology-activity association analysis and active site identification Extracting morphological features Morphology images at various potentials were analyzed using AFM software: Surface roughness of c-SnO2 / GO nanosheets at OCP. R q =2.15nm, average thickness =16.5nm; E sample At -0.8V, R q The thickness was reduced to 2.05nm (a decrease of 4.6%) and the thickness was reduced to 13.6nm (a decrease of 17.6%).

[0036] Activity signal association when E sample =-1.5V vs. Ag time I tip The current can only reach ~16pA.

[0037] Active site localization AFM topography image and SECM I tip Heatmap comparison, using Nanoscop Analysis software I tip The value is mapped to black, and no obvious high-activity region was found, indicating its low NO3RR activity.

[0038] Example 3 A method for in-situ monitoring of the dynamic morphology and activity of a catalyst for nitrate reduction reaction includes the following steps (see details below for the specific principle). Figure 1 ): Step 1: Test System Setup and Preprocessing (1) Catalyst sample preparation Take GO powder with a thickness of 1.0 nm, add anhydrous ethanol to prepare a dispersion of 0.1 mg / mL, and sonicate for 30 min. Take 10 μL of the dispersion with a pipette and uniformly drop it onto a HOPG substrate (size 10 × 10 mm). Dry it under vacuum at 60 °C for 2 h. Monodisperse GO nanosheets are formed on the surface of the HOPG substrate. The thickness and dispersion uniformity are confirmed by AFM pre-scan. (2) Electrolytic cell assembly (see structural diagram) Figure 1 and Figure 2 Electrolyte preparation: The HOPG substrate forming monodisperse GO nanosheets was fixed at the bottom of the electrolytic cell as the second working electrode; the SECM probe was fixed on the AFM to obtain the AFM-SECM integrated probe, which served as the first working electrode; a Pt wire electrode was inserted into the electrolytic cell in a spiral shape to improve current uniformity; a modified Ag wire reference electrode was used; and 2.5 mL of electrolyte was injected into the electrolytic cell. The electrolyte was a mixture of 1 M KNO3 and 0.1 M KHCO3 with a pH of 8.3. The electrolyte was purged with Ar gas for more than 30 minutes in advance to remove dissolved oxygen, and then sealed and stored in the dark at low temperature. (3) Module connection and synchronization initialization: Connect the control computer, AFM-SECM integrated probe, and electrochemical workstation using a USB cable. Install the commercial device control software Bruker NanoScope Analysis 2.0 and CHI760E Software. Manually turn on the electrochemical workstation and AFM instrument for signal collection. Use the AFM peak force tapping mode to gently touch the AFM-SECM integrated probe to the HOPG surface. Turn on the AFM Lift mode switch and adjust the height to 50 nm to maintain a constant distance between the AFM-SECM integrated probe and the catalyst surface to avoid interference from distance changes on the activity signal. Set the SECM probe accordingly. E tip 0.6V vs. Ag is used in response to the oxidation signal of NO3RR products; Step 2: EC-AFM-SECM in-situ platform Configure the electrochemical workstation software as follows: Potential of the first working electrode (SECM, Pt probe): 0.6V vs. Ag; The second working electrode E sample Program: Initial potential is OCP, termination potential is -1.5V vs. Ag, step size 0.1V, dwell time per step 1024s; In the AFM software, set the scanning parameters as follows: scanning range 5×5μm, scanning rate 1.0Hz, resolution 256×256 pixels, and scanning mode to peak force tapping mode to ensure topographic resolution. Activate the SECM probe lift-off mode in the AFM software, set the lift-off height to 50 nm, and enable the probe to alternate between morphology scanning and lift-off scanning. Open the morphology acquisition channel and the tip current acquisition channel, and simultaneously record the probe contact current and lift-off current. I tip Simultaneously collect "potential-morphology-activity" data and set the data storage path; Step 3: Morphology-activity association analysis and active site identification Extracting morphological features Morphology images at various potentials were analyzed using AFM software: Surface roughness of GO nanosheets at OCP. Rq =0.18nm, average thickness =1.0nm; E sample At -0.8V, Rq There was no change in thickness.

[0039] Activity signal association When E sample V range: -0.4 to -1.5 vs. Within the Ag range, none I tip The change in current signal proves that it is inactive in NO3RR.

[0040] Example 4 A method for in-situ monitoring of the dynamic morphology and activity of a catalyst for nitrate reduction reaction includes the following steps (see details below for the specific principle). Figure 1 ): Step 1: Test System Setup and Preprocessing (1) Catalyst sample preparation Take a-BiO with a thickness of 3.2 nm. x / GO powder was dissolved in anhydrous ethanol to prepare a dispersion of 0.1 mg / mL, and ultrasonically dispersed for 30 min. 10 μL of the dispersion was pipetted and uniformly drop-coated onto a HOPG substrate (10 × 10 mm). The substrate was then vacuum-dried at 60 °C for 2 h, resulting in a monodisperse amorphous α-BiO₂ on the HOPG substrate surface. x / GO nanosheets, thickness and dispersion uniformity were confirmed by AFM pre-scanning; (2) Electrolytic cell assembly (see structural diagram) Figure 1 and Figure 2 Electrolyte preparation: The above forms a monodisperse amorphous α-BiO x / GO nanosheets were fixed to the bottom of the electrolytic cell as the second working electrode; the SECM probe was fixed to the AFM to obtain the AFM-SECM integrated probe, which served as the first working electrode; a Pt wire coiled into a spiral shape was inserted into the electrolytic cell to improve current uniformity; a modified Ag wire reference electrode was used; and 2.5 mL of electrolyte was injected into the electrolytic cell. The electrolyte was a mixture of 1 M KNO3 and 0.1 M KHCO3 with a pH of 8.3. The electrolyte was purged with Ar gas for more than 30 minutes in advance to remove dissolved oxygen, and then sealed and stored at low temperature in the dark. (3) Module connection and synchronization initialization: Connect the control computer, AFM-SECM integrated probe, and electrochemical workstation using a USB cable. Install the commercial device control software Bruker NanoScope Analysis 2.0 and CHI760E Software. Manually turn on the electrochemical workstation and AFM instrument for signal collection. Use the AFM peak force tapping mode to gently touch the AFM-SECM integrated probe to the HOPG surface. Turn on the AFM Lift mode switch and adjust the height to 50 nm to maintain a constant distance between the AFM-SECM integrated probe and the catalyst surface to avoid interference from distance changes on the activity signal. Set the SECM probe accordingly. E tip 0.6V vs. Ag is used in response to the oxidation signal of NO3RR products; Step 2: EC-AFM-SECM in-situ platform Configure the electrochemical workstation software as follows: Potential of the first working electrode (SECM, Pt probe): 0.6V vs. Ag; The second working electrode E sample Program: Initial potential is OCP, termination potential is -1.0V vs. Ag, step size 0.1V, dwell time per step 1024s; In the AFM software, set the scanning parameters as follows: scanning range 5×5μm, scanning rate 0.5Hz, resolution 256×256 pixels, and the scanning mode to the "tap mode" of commercial AFM for non-contact scanning to ensure morphological stability. Activate the SECM probe lift-off mode in the AFM software, set the lift-off height to 50 nm, and enable the probe to alternate between morphology scanning and lift-off scanning. Open the morphology acquisition channel and the tip current acquisition channel, and simultaneously record the probe contact current and lift-off current. I tip Simultaneously collect "potential-morphology-activity" data and set the data storage path; Step 3: Morphology-activity association analysis and active site identification Extracting morphological features Morphology images at various potentials were analyzed using AFM software: At OCP, amorphous α-BiO x Surface roughness of / GO nanosheets Rq =0.58nm, average thickness =3.2nm; E sample At -0.8V, Rq The thickness was further increased to 0.67nm (an improvement of 15.5%), while the thickness was reduced to 2.8nm (a reduction of 12.5%).

[0041] Activity signal association In E sample At -0.8V, it can be detected synchronously. I tip Current signal ~13.5 pA.

[0042] Active site localization AFM topography image and SECM I tip Heatmap comparison, using Nanoscop Analysis software I tip The value is mapped to black, revealing the local edges and wrinkle locations. I tip The value was higher than ~2 pA in the flat region, which was identified as the main active site of NO3RR.

[0043] Example 5 A method for in-situ monitoring of the dynamic morphology and activity of a catalyst for nitrate reduction reaction includes the following steps (see details below for the specific principle). Figure 1 ): Step 1: Test System Setup and Preprocessing (1) Catalyst sample preparation A 4.5 nm thick a-SnO2 / GO powder was added to anhydrous ethanol to prepare a 0.1 mg / mL dispersion, which was then ultrasonically dispersed for 30 min. 10 μL of the dispersion was taken with a pipette and uniformly dropped onto a HOPG substrate (10 × 10 mm in size). The substrate was then vacuum dried at 60 °C for 2 h. Monodisperse amorphous a-SnO2 / GO nanosheets were formed on the surface of the HOPG substrate. The thickness and dispersion uniformity were confirmed by AFM pre-scan. (2) Electrolytic cell assembly (see structural diagram) Figure 1 and Figure 2 Electrolyte preparation: The HOPG substrate, which forms monodisperse amorphous a-SnO2 / GO nanosheets, was fixed at the bottom of the electrolytic cell as the second working electrode. The SECM probe was fixed on the AFM to obtain the AFM-SECM integrated probe, which served as the first working electrode. A Pt wire electrode, wound into a spiral shape, was inserted into the electrolytic cell to improve current uniformity. A modified Ag wire reference electrode was used, and 2.5 mL of electrolyte, which was a mixture of 1 M KNO3 and 0.1 M KOH with pH=13, was injected into the electrolytic cell. The electrolyte was purged with Ar gas for more than 30 minutes in advance to remove dissolved oxygen, and then sealed and stored at low temperature in the dark. (3) Module connection and synchronization initialization: Connect the control computer, AFM-SECM integrated probe, and electrochemical workstation using a USB cable. Install the commercial device control software Bruker NanoScope Analysis 2.0 and CHI760E Software. Manually turn on the electrochemical workstation and AFM instrument for signal collection. Use the AFM peak force tapping mode to gently touch the AFM-SECM integrated probe to the HOPG surface. Turn on the AFM Lift mode switch and adjust the height to 50 nm to maintain a constant distance between the AFM-SECM integrated probe and the catalyst surface to avoid interference from distance changes on the activity signal. Set the SECM probe accordingly. E tip The voltage is 0.6V vs. Ag, used to respond to the oxidation signal of NO3RR products; Step 2: EC-AFM-SECM in-situ platform Configure the electrochemical workstation software as follows: Potential of the first working electrode (SECM, Pt probe): 0.6V vs. Ag; The second working electrode E sample Program: Initial potential is OCP, termination potential is -1.0V vs. Ag, step size 0.1V, dwell time per step 1024s; In the AFM software, set the scanning parameters as follows: scanning range 5×5μm, scanning rate 1.0Hz, resolution 256×256 pixels, and scanning mode to peak force tapping mode to ensure topographic resolution. Activate the SECM probe lift-off mode in the AFM software, set the lift-off height to 50 nm, and enable the probe to alternate between morphology scanning and lift-off scanning. Open the morphology acquisition channel and the tip current acquisition channel, and simultaneously record the probe contact current and lift-off current. I tip Simultaneously collect "potential-morphology-activity" data and set the data storage path; Step 3: Morphology-activity association analysis and active site identification Extracting morphological features Morphology images at various potentials were analyzed using AFM software: Surface roughness of amorphous α-SnO2 / GO nanosheets at OCP. R q =1.4nm, average thickness =4.5nm; E sample At -0.8V, R qThe nanometer size was further increased to 2.56 nm (an 82.9% improvement), and the thickness became 3.4 nm (a 24.4% decrease), gradually transforming the amorphous a-SnO2 / GO nanosheet structure into a network structure.

[0044] Activity signal association Simultaneous analysis of each potential I tip Signal: when E sample When the voltage is -0.7V, the measured value is... I tip =~12pA; when E sample At -0.8V, I tip It can reach ~16pA.

[0045] Active site localization AFM topography image and SECM I tip Heatmap comparison, using Nanoscop Analysis software I tip The value is mapped to black, revealing the local edges and wrinkle locations. I tip It can reach ~400pA and has been identified as the main active site of NO3RR.

[0046] Example 6 A method for in-situ monitoring of the dynamic morphology and activity of a catalyst for nitrate reduction reaction includes the following steps (see details below for the specific principle). Figure 1 ): Step 1: Test System Setup and Preprocessing (1) Catalyst sample preparation A 13.5 nm thick a-SnO2 / GO powder was added to anhydrous ethanol to prepare a 0.1 mg / mL dispersion, which was then ultrasonically dispersed for 30 min. 10 μL of the dispersion was taken with a pipette and uniformly dropped onto a highly oriented pyrolytic graphite (HOPG) substrate (10 × 10 mm in size). The substrate was then vacuum dried at 60 °C for 2 h. Monodisperse amorphous a-SnO2 / GO nanosheets were formed on the surface of the HOPG substrate. The thickness and dispersion uniformity were confirmed by AFM pre-scan. (2) Electrolytic cell assembly (see structural diagram) Figure 1 and Figure 2 Electrolyte preparation: The HOPG substrate, which forms monodisperse amorphous a-SnO2 / GO nanosheets, was fixed at the bottom of the electrolytic cell as the second working electrode. The SECM probe was fixed to the AFM to obtain the AFM-SECM integrated probe, which served as the first working electrode. A Pt wire electrode was inserted into the electrolytic cell in a spiral shape to improve the current uniformity. A modified Ag wire reference electrode was used. 2.5 mL of electrolyte, which was a mixture of 10 mM [Ru(NH3)6]Cl3 and 0.1 M KCl, with pH=7.0, was injected into the electrolytic cell. (3) Module connection and synchronization initialization: Connect the control computer, AFM-SECM integrated probe, and electrochemical workstation using a USB cable. Install the commercial device control software Bruker NanoScope Analysis 2.0 and CHI760E Software. Manually turn on the electrochemical workstation and AFM instrument for signal collection. Use the AFM peak force tapping mode to gently touch the AFM-SECM integrated probe to the HOPG surface. Turn on the AFM Lift mode switch and adjust the height to 50 nm to maintain a constant distance between the AFM-SECM integrated probe and the catalyst surface to avoid interference from distance changes on the activity signal. Set the SECM probe accordingly. E tip -0.4V vs Ag is used in response to the oxidation signal of NO3RR products; Step 2: EC-AFM-SECM in-situ platform Configure the electrochemical workstation software as follows: Potential of the first working electrode (SECM, Pt probe): -0.4V vs. Ag; The second working electrode E sample Program: Set the potential to OCP; In the AFM software, set the scanning parameters as follows: scanning range 5×5μm, scanning rate 1.0Hz, resolution 256×256 pixels, and scanning mode to peak force tapping mode to ensure topographic resolution. Activate the SECM probe lift-off mode in the AFM software, set the lift-off height to 50 nm, and enable the probe to alternate between morphology scanning and lift-off scanning. Open the morphology acquisition channel and the tip current acquisition channel, and simultaneously record the probe contact current and lift-off current. I tip Simultaneously collect "potential-morphology-activity" data and set the data storage path; Step 3: Morphology-activity association analysis and active site identification Extracting morphological features Morphology images at various potentials were analyzed using AFM software: Surface roughness of amorphous α-SnO2 / GO nanosheets at OCP. R q =2.5nm, average thickness =13.5nm.

[0047] Activity signal association Areas such as nanosheet edges, wrinkles, and rough particles I tip The current is significantly higher than that in the flat area. I tip The current difference is between 2 and 4 pA, indicating a strong electron transport capability in the roughness region, which explains its highly active NO3RR performance.

[0048] from Figure 3 The NO3RR responses of amorphous a-SnO2 / GO nanosheets (Example 1), crystalline c-SnO2 / GO nanosheets (Example 2), and GO nanosheets (Example 3) at different potentials in a weakly alkaline solution (the electrolyte was a mixture of 1M KNO3 and 0.1M KHCO3, pH=8.3) show that the three different catalysts... E sample Between -0.4 and -0.7V vs. Within the Ag range, I tip =~10pA; when E sample Between -0.7 and -1.1V vs. Within the Ag range, amorphous α-SnO2 / GO nanosheets I tip The anode pressure was increased to ~25 pA for crystalline c-SnO2 / GO nanosheets and GO nanosheets. I tip Basically unchanged; when E sample Between -1.1 and -1.5V vs. Within the Ag range, crystalline c-SnO2 / GO nanosheets I tip Increased to ~15pA, GO nanosheets I tip Basically unchanged.

[0049] AFM morphology and SECM were performed on the amorphous a-SnO2 / GO nanosheets in Example 1. I tip Comparative analysis of heat maps, from the SG / TC mode based on the EC-AFM-SECM in-situ platform ( Figure 4 ) and feedback patterns ( Figure 5In-situ discrimination of NO3RR activity in different regions of amorphous a-SnO2 / GO nanosheets obtained by testing shows that the brown / black regions correspond to higher NO3RR activity. I tip The signal (~400 pA) is ~100 times stronger than that at the substrate site. This highly active region is consistent with the spatial distribution of the edges, rough particles, wrinkles, and stacked structures of the amorphous a-SnO2 / GO nanosheets. This triple coupling relationship of "potential-morphology-activity" confirms that the edge / wrinkled structure is the main active site of NO3RR.

[0050] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for in-situ monitoring of the dynamic morphology and activity of a catalyst for nitrate reduction reaction, characterized in that, Includes the following steps: Step 1: Test System Setup and Preprocessing Prepare a conductive substrate coated with a catalyst for nitrate reduction reaction; A scanning electrochemical microscope probe was fixed to an atomic force microscope to obtain an integrated atomic force microscope-scanning electrochemical microscope probe. The integrated probe was used as the first working electrode, and a conductive substrate coated with a nitrate reduction catalyst was used as the second working electrode. Electrolyte was injected to complete the assembly of the electrolytic cell. The integrated atomic force microscope-scanning electrochemical microscope probe, the electrochemical workstation, and the control computer were connected to initialize the system and set the lift-up height and detection potential of the integrated probe. Step 2: In-situ synchronous detection process The potential programs for the first and second working electrodes were set in the electrochemical workstation software, and the scanning parameters were set in the atomic force microscope software. The lift-up height of the integrated probe of the atomic force microscope-scanning electrochemical microscope was controlled by the software to switch between morphology scanning and lift-up scanning modes. At the same time, the morphology and current signal channels were opened to record the contact current and lift-up current of the integrated probe in real time, so as to realize the synchronous acquisition of three-dimensional data of "potential-morphology-activity". Set the storage path to save the experimental data; Step 3: Morphology-activity association analysis and active site identification The surface morphology images at different potentials were analyzed using atomic force microscopy software to extract morphological features. At the same time, the lift-up current signals at each potential were analyzed to establish the correspondence between morphological features and activity signals. By combining the atomic force microscopy morphology images with electrochemical current-thermal maps, the active sites of the catalyst could be accurately located.

2. The method for in-situ monitoring of the dynamic morphology and activity of the nitrate reduction catalyst as described in claim 1, characterized in that, The method for preparing the conductive substrate coated with the nitrate reduction catalyst is as follows: Take nitrate reduction reaction catalyst powder with a thickness of 1~20nm, add anhydrous ethanol to prepare a dispersion of 0.1mg / mL, and sonicate for 30min; take 10μL of dispersion with a pipette, drop it evenly onto a conductive substrate, and vacuum dry at 60℃ for 2h to form a monodisperse catalyst coating, thus obtaining a conductive substrate coated with catalyst.

3. The method for in-situ monitoring of the dynamic morphology and activity of the nitrate reduction catalyst as described in claim 1, characterized in that, The electrolytic cell includes: The base (1) is screwed to the top of the outer shell (5), and a sealed liquid space is formed between the base (1) and the outer shell (5), and the liquid space contains electrolyte; An inner pool (4) is installed on top of the base (1), and the inner pool (4) is disposed in the liquid space, forming an installation space between the inner pool (4) and the base (1); A substrate (2) is installed in the installation space. A detachable electrode module (3) is installed on the top of the substrate (2). The substrate (2) and the inner tank (4) are made of polytetrafluoroethylene. A quartz cover plate (7) is installed on the top of the outer shell (5). An O-ring gasket (6) is installed between the quartz cover plate (7) and the outer shell (5). The O-ring gasket (6) has two interfaces, which are respectively connected to the Ag wire reference electrode and the Pt wire electrode. The tip of the Ag wire reference electrode is close to the working electrode and immersed in the electrolyte. The Pt wire electrode is wound around the inner wall of the outer shell (5). The O-ring gasket (6) is made of fluorinated rubber, and the interface is naturally sealed.

4. The method for in-situ monitoring of the dynamic morphology and activity of the nitrate reduction catalyst as described in claim 3, characterized in that, The Ag wire reference electrode is immersed to a depth of 10 mm.

5. The method for in-situ monitoring of the dynamic morphology and activity of the nitrate reduction catalyst as described in claim 3, characterized in that, The electrode module supports highly oriented pyrolytic graphite, gold-plated silicon wafers, or glassy carbon electrode conductive substrates.

6. The method for in-situ monitoring of the dynamic morphology and activity of the nitrate reduction catalyst as described in claim 1, characterized in that, The electrolyte described in step 1 is pre-purged with argon gas for at least 30 minutes, sealed, and stored at low temperature and away from light.

7. The method for in-situ monitoring of the dynamic morphology and activity of the nitrate reduction catalyst as described in claim 1, characterized in that, The conductive substrate coated with the nitrate reduction catalyst in step 1 has a size of 10 mm × 10 mm.

8. The method for in-situ monitoring of the dynamic morphology and activity of the nitrate reduction catalyst as described in claim 1, characterized in that, The lift-up height of the integrated probe described in step 1 is 0~100nm.

9. The method for in-situ monitoring of the dynamic morphology and activity of the nitrate reduction catalyst as described in claim 1, characterized in that, The detection potential of the integrated probe in step 1 is 0.6V. vs. Ag.

10. The method for in-situ monitoring of the dynamic morphology and activity of the nitrate reduction catalyst as described in claim 1, characterized in that, The scanning parameters described in step 2 are: scanning range of 5×5μm, scanning rate of 1.0Hz, resolution of 256×256 pixels, and scanning mode of peak force tapping mode.

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