C, N-FeNbO4 / NF microrod derived on basis of in-situ 001 crystal face of foamed nickel and derivation method and application of C, N-FeNbO4 / NF microrod

Abstract

The invention discloses a C, N-FeNbO4 / NF microrod based on foamed nickel in-situ 001 crystal face derivation and a derivation method and application thereof, and the method comprises the following steps: in a hydrothermal reaction, hydrolyzing urea to release OH-to replace oxalate in niobium oxalate so as to form a Nb-OH monomer; meanwhile, Fe < 3 + > is hydrolyzed into Fe (OH) 3 colloid; the preparation method comprises the following steps: performing liquid phase nucleation on Nb-OH and Fe (OH) 3 under a hydrothermal condition to form a FeNbO4 precursor, and growing the FeNbO4 precursor on foamed nickel (NF) in situ; in this way, the 001 crystal face of FeNbO4 is accurately regulated and controlled through the strong coordination effect of F <-> to form a rod structure. Under high-temperature (900 DEG C) carbonization, the FeNbO4 is further crystallized into an acid-resistant and alkali-resistant monoclinic crystal type three-dimensional microrod (C, N-FeNbO4 / NF) with C and N co-doped (C, N-FeNbO4) composite NF. According to the method disclosed by the invention, the agglomeration phenomenon of FeNbO4 is relieved; the microrod structure exposes more catalytic active sites, so that the catalytic activity is improved. In addition, the catalyst shows high conductivity by co-doping C and N with synergistic high-conductivity NF. Based on the regulation and control, the C, N-FeNbO4 / NF shows good electrochemical performance in the oxygen evolution reaction.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis catalyst technology, specifically to a C,N-FeNbO4 / NF microrod derived from the in-situ 001 crystal plane of nickel foam, and its derivation method and application. Background Technology

[0002] Developing high-performance catalysts to accelerate the oxygen evolution reaction (OER) is one of the effective strategies to promote the development of water electrolysis technology. Currently, the reactivity and stability of anode OER catalysts still cannot meet the demands of clean energy development. This is especially true in seawater electrolysis, where high concentrations of Cl... - With OH - A competing reaction occurs, leading to chlorine evolution reaction (CER), which generates gaseous pollution and reduces oxygen production efficiency. Furthermore, corrosive byproducts (HClO) are produced in the CER, severely damaging electrodes and electrolyzer components. Theoretically, the voltage for water decomposition (H₂O → O₂) is 1.23 V vs. RHE, and the voltage for CER (ClO) is... - →Cl2) generates an oxygen production potential of approximately 1.36 V vs. RHE. In fact, in alkaline seawater (pH > 7.5), the overpotential of CER (approximately 490 mV) is higher than that of OER, and the equilibrium potential of CER is independent of pH. Therefore, developing OER catalysts with low onset potentials is crucial to avoiding CER. In conclusion, in the electrolysis of seawater for OER, developing non-precious metal catalysts with high activity, corrosion resistance, and strong stability is the primary task for improving OER oxygen production efficiency.

[0003] Studies have shown that transition metal oxides, hydroxides, sulfides, and phosphides exhibit high catalytic activity for oxygen efflux reaction (OER). Transition metal oxides, in particular, are considered one of the most ideal catalysts for alkaline OER due to their tunable electronic structure and feasibility for industrial applications. In alkaline seawater OER, condensation efflux reaction (CER) occurs due to excessively high potential, accompanied by ClO₂. - The formation of [a substance] causes severe corrosion to the catalyst. Here, the iron-niobium oxide composed of Fe and Nb exhibits a well-defined crystal structure. Among them, Fe... 3+ (0.645 Å) and Nb 5+ (0.640 Å) have similar ionic radii. The [FeO6] and [NbO6] octahedra form the monoclinic FeNbO4 crystal system, exhibiting high corrosion resistance. Meanwhile, the high-valence Nb... 5+ This can effectively alleviate the excessive oxidation of Fe in OER, thereby enabling the reuse of active sites and improving stability. Previous literature reports the preparation of porous FeNb nanosheets through morphology optimization and microstructure modification. 11 O 29-x@C exhibits excellent electrochemical performance in OER. FeNbO4 was in situ grown on FeNbO4 constructed from honey-derived porous carbon. 4-x @NC requires only 254 mV overpotential to achieve 10 mA cm⁻¹ -2 The current density. At the same time, Ni-FeNbO4@NC synthesized through interface optimization and Ni doping achieved a super-strong stability of 50 h. However, FeNbO4 still faces the following problems in seawater electrolysis OER: (1) easy agglomeration: When synthesizing special crystal structures (orthorhombic, tetragonal and monoclinic) FeNbO4, a high temperature (>600 ℃) is required. At high temperature, due to the high surface energy of FeNbO4, oxides often agglomerate, thus exhibiting a low specific surface area. (2) low reaction activity: Due to the agglomeration of iron niobium oxides, the specific surface area is low, making it difficult to expose abundant active sites, thereby reducing the reaction activity of the catalyst. At the same time, the reaction activity of conventional catalyst FeNbO4 coated on glassy carbon electrode is difficult to meet the current density (400 mA cm⁻¹) required for industrial application. -2 (3) Poor conductivity: In FeNbO4, Fe 3+ and Nb 5+ O around the hexagonal close-packed structure 2- This results in its low intrinsic conductivity (approximately 3 × 10⁻⁶). -8 S cm -1 High energy is required to excite electrons to the conduction band to participate in the catalytic reaction, which will generate a large ohmic overpotential, thereby reducing the reaction kinetics. Summary of the Invention

[0004] To address the shortcomings, this invention aims to provide a C,N-FeNbO4 / NF microrod derived from the in-situ 001 crystal plane of nickel foam, along with its derivation method and applications. This method utilizes F... - The coordination with Fe / Nb creates multiple 001 crystal planes with high catalytic activity in FeNbO4, alleviating the aggregation of FeNbO4 and thus increasing the specific surface area of ​​the material; the microrod structure exposes more catalytic active sites, thereby increasing the catalytic activity of the oxygen evolution reaction (OER); in addition, the co-doping of C and N with highly conductive NF makes the catalyst exhibit high conductivity.

[0005] To address the problems in the existing technology, the technical solution adopted by this invention is as follows: A method for deriving C,N-FeNbO4 / NF microrods based on the in-situ 001 crystal plane of nickel foam includes the following steps: (1) Niobium oxalate, FeCl3·6H2O, NH4F and urea were added to water and stirred to obtain a uniform mixture. (2) Add nickel foam to the mixture prepared in step (1), stir and then obtain C, N-FeNbO4 / NF precursor through hydrothermal reaction; (3) The C,N-FeNbO4 / NF precursor prepared in step (2) was annealed in an argon atmosphere to obtain a three-dimensional rod-shaped C,N-FeNbO4 / NF.

[0006] Preferably, in step (1), the mass ratio of niobium oxalate: FeCl3·6H2O: urea: ammonium fluoride is 3:1.5:3:1~4:2:3.5:1; the concentration of the mixture is 0.02 g / mL. -1 ~ 0.04 g mL -1 Stirring time: 6 h to 8 h.

[0007] Preferably, in step (1), the mass ratio of niobium oxalate: FeCl3·6H2O: urea: ammonium fluoride is 3.6:1.8:3.2:1.

[0008] Preferably, in step (2), the size of the nickel foam is 2×2 cm. 2 ~4×4 cm 2 The stirring time was 1 h to 3 h, the hydrothermal reaction temperature was 120 ºC to 180 ºC, and the hydrothermal treatment time was 8 h to 16 h.

[0009] Preferably, in step (2), the size of the nickel foam is 2×2 cm. 2 The hydrothermal reaction temperature was 150 ºC, and the hydrothermal treatment time was 6 hours.

[0010] Preferably, in step (3), the C,N-FeNbO4 / NF precursor is annealed in argon at 900 ºC ± 20 ºC for 3 h.

[0011] The C,N-FeNbO4 / NF microrods derived from the method described in any of the preceding claims are characterized in that the C,N-FeNbO4 / NF microrods are mainly composed of C, N, O, Fe, Ni and Nb elements, exhibit NO and CO peaks, are uniformly distributed microrod arrays on the surface, contain porous structures, and have an electrochemically active specific surface area of ​​0.45 cm². 2 .

[0012] The aforementioned C,N-FeNbO4 / NF microrods are used as catalysts in the electrolysis of water / seawater to produce oxygen.

[0013] Preferably, the C,N-FeNbO4 / NF microrods exhibit 284 mV@50 mA cm⁻¹ in 1 M KOH. -2 The overpotential is 31.6 mV dec.-1 The Tafel slope and stability over 100 h.

[0014] Preferably, the C,N-FeNbO4 / NF exhibits high corrosion resistance in natural seawater, a corrosion potential of -0.17V, low overpotential, and good stability.

[0015] This invention designs and prepares an in-situ self-grown (along the FeNbO4 (001) crystal plane) and C, N co-doped micron rod-shaped iron-niobium oxide composite foam nickel C, N-FeNbO4 / NF catalyst, which exhibits high activity, corrosion resistance, and strong stability, and is used for water / seawater electrolysis OER. Specifically, to alleviate the aggregation of FeNbO4, the morphology of FeNbO4 is optimized through the synergistic effect of ammonium fluoride and urea. At the atomic level, through F... - Adsorbed on the 001 crystal plane of FeNbO4, the surface energy of this plane is reduced, and FeNbO4 microrods are grown along the z-axis. Simultaneously, the solution contains abundant C sources (from niobium oxalate) and N sources (from ammonium fluoride and urea), which can dope FeNbO4, thereby further improving its intrinsic conductivity and catalytic activity. Next, C,N-FeNbO4 is deposited on high-specific-surface-area and highly conductive nickel foam (NF) via a simple hydrothermal reaction. Finally, under high-temperature carbonization, a C,N co-doped FeNbO4 microrod composite NF catalyst, C,N-FeNbO4 / NF, is obtained. This catalyst has the following advantages: Crystal plane manipulation of microrods: via F - The strong coordination effect (electronegativity of 3.98) binds to the 001 crystal plane of the metal oxide FeNbO4 to form MF covalent bonds, thereby reducing the surface energy of this crystal plane. Under hydrothermal reaction, FeNbO4 crystallizes along the z-axis of the 001 crystal plane to form a micron rod-like structure, thereby suppressing agglomeration. Corrosion resistance and high activity: The Nb-O bond enhances the structural stability of FeNbO4, effectively mitigating the effects of acidity, alkaliness, and Cl. - This reduces corrosion and improves stability. The microrod-like structure of FeNbO4 provides a large specific surface area and exposes abundant active sites. Simultaneously, C and N introduce non-metallic active sites to enhance oxygen production efficiency. 3) High conductivity: FeNbO4 is grown in situ on highly conductive NF (1.0 × 10⁻⁶). 6 S m -1 This enables rapid electron transport and high reaction kinetics. Furthermore, C,N co-doping enhances the intrinsic conductivity of FeNbO4, thereby reducing the ohmic overpotential. Beneficial effects

[0016] Compared with existing technologies, this invention represents the first synthesis of C,N-FeNbO4 microrods; it constructs multiple 001 crystal planes with high catalytic activity in FeNbO4 through the coordination of F- with Fe / Nb; furthermore, the in-situ doping of C and N into the FeNbO4 lattice enhances conductivity and catalytic activity. Specifically, C,N-FeNbO4 / NF exhibits a low overpotential (284 mV @ 50 mA cm⁻¹) in 1 M KOH. -2 ), small Tafel slope (31.6 mV dec) -1 Furthermore, C,N-FeNbO4 / NF exhibits high corrosion resistance (corrosion potential -0.17 V), low overpotential, and good stability (100 h) in natural seawater. Further highlighting this, C,N-FeNbO4 / NF demonstrates excellent electrochemical performance in water electrolysis / seawater OER. Attached Figure Description

[0017] Figure 1 This is a scanning electron microscope image of nickel foam.

[0018] Figure 2 The image shows a scanning electron microscope (SEM) image of C,N-FeNbO4 / NF synthesized in Example 1.

[0019] Figure 3 The image shows a transmission electron microscope (TEM) image of C,N-FeNbO4 / NF synthesized in Example 1.

[0020] Figure 4 Mapping diagram of C,N-FeNbO4 / NF synthesized in Example 1.

[0021] Figure 5 XPS plot of C,N-FeNbO4 / NF synthesized in Example 1.

[0022] Figure 6 The image shows a scanning electron microscope (SEM) image of the synthesized N-Fe₂O₃ / NF as shown in Comparative Example 1.

[0023] Figure 7 Scanning electron microscope (SEM) image of C,N-Nb2O5 / NF synthesized in Comparative Example 2.

[0024] Figure 8 The image shows the XRD pattern of the example sample.

[0025] Figure 9 The image shows the Raman spectroscopy of the example sample.

[0026] Figure 10 The image shows the infrared curve of the sample used in the example.

[0027] Figure 11 The image shows the polarization curves of the catalyst used in this example.

[0028] Figure 12 This is an overpotential diagram of the catalyst in the example.

[0029] Figure 13 The image shows the Tafel slope of the catalyst in the example.

[0030] Figure 14 The impedance diagram is shown for the catalyst in the example.

[0031] Figure 15 The image shows the double-layer capacitance of the catalyst prepared in the example.

[0032] Figure 16 The electrochemical activity specific surface area diagram of the catalysts prepared in the examples is shown.

[0033] Figure 17 Example 1: Synthesis of C,N-FeNbO4 / NF under alkaline conditions I - t Stability test chart.

[0034] Figure 18 Tafel polarization curves of the catalyst prepared in the example with 1M KOH and seawater.

[0035] Figure 19 The polarization curves of C,N-FeNbO4 / NF synthesized in Example 1 under different conditions are shown.

[0036] Figure 20 Example 1: Synthesis of C,N-FeNbO4 / NF using 1M KOH and seawater I - t Stability test chart. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the embodiments.

[0038] The preparation method of the three-dimensional microrod structure C,N-FeNbO4 / NF described in this invention comprises the following specific steps: 1) Add niobium oxalate: FeCl3·6H2O: urea: ammonium fluoride in a mass ratio of 3.6:1.8:3.2:1 to water, and stir for 6-8 hours to form a solution with a concentration of 0.03 g / mL. -1 A mixed solution; 2) Cut the nickel foam into 2×2 cm pieces. 2 The sample was placed in the mixture prepared in step 1), stirred for 1 h to 3 h, and then hydrothermally reacted at 120 ºC to 180 ºC for 8 h to 16 h to obtain the C, N-FeNbO4 / NF precursor. 3) The C,N-FeNbO4 / NF precursor was annealed in argon at 900 ºC ± 20 ºC for 3 h to obtain three-dimensional micron rod-shaped C,N-FeNbO4 / NF.

[0039] Example 1

[0040] 1) Dissolve 0.14 g of FeCl3·6H2O, 0.27 g of niobium oxalate, 0.24 g of urea and 0.07 g of NH4F in 25 mL of water and stir for 6 h to form a homogeneous mixture; set aside.

[0041] 2) Cut the nickel foam into 2×2 cm pieces. 2 The sample was placed in the mixture prepared in step 1), stirred for 1 h, and then subjected to a hydrothermal reaction for 12 h at a temperature of 150 ºC. After the reaction was completed, the precipitate was collected by centrifugation and dried in a vacuum oven at 80 ℃ for 12 h to obtain the C,N-FeNbO4 / NF precursor. 3) Place the C,N-FeNbO4 / NF precursor into a quartz boat and continuously purge with argon gas to create an inert atmosphere, at 3℃ min. -1 The temperature was raised to 900 °C and held for 3 h to finally obtain three-dimensional micron rod-shaped C,N-FeNbO4 / NF.

[0042] The performance of three-dimensional micron-shaped C,N-FeNbO4 / NF was characterized, and the results are as follows: Figure 2-5 As shown.

[0043] Figure 1 This is a scanning electron microscope (SEM) image of the nickel foam used in step 2) of the embodiment. A smooth three-dimensional skeleton can be observed.

[0044] Figure 2 This is a scanning electron microscope (SEM) image of the three-dimensional microrod-shaped C,N-FeNbO4 / NF synthesized in this embodiment. A uniform array of microrods can be observed on the surface of the C,N-FeNbO4 / NF, and the rods contain porous structures.

[0045] Figure 3 This is a transmission electron microscope (TEM) image of the three-dimensional microrod-shaped C,N-FeNbO4 / NF synthesized in this embodiment. The C,N-FeNbO4 microrods and porosity can be clearly observed.

[0046] Figure 4 This is a mapping diagram of the three-dimensional micron-shaped C,N-FeNbO4 / NF synthesized in this embodiment. Uniform distribution of C, N, O, Fe, Ni, and Nb elements can be observed.

[0047] Figure 5 The XPS image shows the synthesized C,N-FeNbO4 / NF in this embodiment. It can be seen that the prepared material is mainly composed of C, N, O, Fe, Ni, and Nb elements.

[0048] Comparative Example 1: 1) Dissolve 0.14 g of FeCl3·6H2O, 0.24 g of urea and 0.07 g of NH4F in 25 mL of water and stir for 6 h to form a homogeneous mixture for later use.

[0049] 2) Cut the nickel foam into 2×2 cm pieces. 2 The sample was placed in the mixture prepared in step 1), stirred for 1 h, and then subjected to a hydrothermal reaction for 12 h at a temperature of 150 ºC. After the reaction was completed, the precipitate was collected by centrifugation and dried in a vacuum oven at 80 ℃ for 12 h to obtain the N-Fe2O3 / NF precursor. 3) Place the N-Fe2O3 / NF precursor into a quartz boat and continuously purge with argon gas to create an inert atmosphere, at 3 °C for min. -1 The temperature was raised to 900 °C and held for 3 hours to finally obtain N-Fe2O3 / NF.

[0050] Figure 6 This is a scanning electron microscope (SEM) image of N-Fe₂O₃ / NF. The image shows that no rod-like structure is formed without niobium oxalate. Additionally, the nickel foam surface has fewer particles.

[0051] Comparative Example 2: 1) Dissolve 0.27 g of niobium oxalate, 0.24 g of urea and 0.07 g of NH4F in 25 mL of water and stir for 6 h to form a homogeneous mixture for later use.

[0052] 2) Cut the nickel foam into 2×2 cm pieces. 2 The sample was placed in the mixture prepared in step 1), stirred for 1 h, and then subjected to a hydrothermal reaction for 12 h at a hydrothermal temperature of 150 ºC. After the reaction was completed, the precipitate was collected by centrifugation and dried in a vacuum oven at 80 ℃ for 12 h to obtain the C,N-Nb2O5 / NF precursor. 3) Place the C,N-Nb2O5 / NF precursor into a quartz boat and continuously purge with argon gas to create an inert atmosphere, at 3 ℃ for min. -1 The temperature was raised to 900 ℃ and held for 3 h to finally obtain C, N-Nb2O5 / NF.

[0053] Figure 7The image shows a scanning electron microscope (SEM) image of C,N-Nb2O5 / NF. Since C,N-Nb2O5 / NF does not contain Fe, its morphology consists of irregular nanoparticles and does not exhibit a micron-shaped rod structure.

[0054] Figure 8 The XRD patterns of the catalysts prepared in Example 1 and Comparative Examples 1-2 are shown. As can be seen from the figures, the N-Fe₂O₃ spectrum exhibits distinct peaks at 30.3°, 35.6°, 43.3°, 57.3°, and 62.9°, corresponding to the (220), (311), (400), (511), and (440) crystal planes of the Fe₃O₄ cubic crystal system (PDF#85-1436), respectively. Under high-temperature N doping, the N-Fe₂O₃ partially contains Fe 3+ Reduced to Fe 2+ Generally, multivalent Fe is beneficial for increasing OER reaction kinetics. For the XRD of C,N-Nb2O5, the characteristic peaks at 22.5°, 28.4°, 36.6°, 46.1°, 50.5°, 55.3° and 70.8° correspond to the (001), (200), (181), (002), (321), (202) and (481) crystal planes of the Nb2O5 orthorhombic crystal system (PDF#71-0336), respectively. Meanwhile, in the C, N-FeNbO4 spectrum, the peaks at 18.9, 24.5, 30.4, 31.4, 36.3, 44.1, 53.8, 60.7, and 64.4 respectively index the (011), (110), (-111), (020), (021), (112), (-202), (-113), and (023) crystal planes of the FeNbO4 monoclinic system. This further demonstrates that the catalyst of the present invention does not change the crystal structure of Nb2O5 and FeNbO4 under C and N co-doping.

[0055] Figure 9 Raman spectra of the catalysts prepared in Example 1 and Comparative Examples 1-2. Compared with N-Fe2O3 and C,N-Nb2O5, the metallic peak (MO, 228.6 cm⁻¹) of C,N-FeNbO4 is significantly different. -1 and 706.4 cm -1 The highest strength indicates its good crystallinity. Meanwhile, C,N-FeNbO4 exhibits the highest D band (1366 cm⁻¹). -1 ) and G-band (1627 cm) -1 Peak intensity. Here, the introduction of C into the FeNbO4 lattice can increase its intrinsic conductivity and catalytic activity.

[0056] Figure 10 Infrared spectroscopy curves of the catalysts prepared in Example 1 and Comparative Examples 1-2 are shown. (Infrared spectroscopy curves are displayed at 500 cm⁻¹.) -1-4000 cm -1 The functional groups of the catalysts were analyzed by infrared spectroscopy within a certain range. A NO peak (1354 cm⁻¹) was observed in all three catalysts. -1 and 1575cm -1 The presence of the functional group indicates successful N doping. In comparison, C,N-Nb2O5 and C,N-FeNbO4 exhibit a CO peak (2824 cm⁻¹). -1 No carbon-containing functional groups were observed in N-Fe2O3. This is because the carbon-containing functional groups originated from carbon in niobium oxalate entering the Nb2O5 and FeNbO4 lattices.

[0057] It needs to be explained that Figure 8 , Figure 9 and Figure 10 To avoid the Ni peak being too strong and masking the peaks of the metal oxide, the final catalyst material was ultrasonically treated with high-power ultrasound before XRD and Raman analysis. Therefore, NF was no longer added to the sample label.

[0058] Example 2

[0059] Parallel experiments were conducted using the electrode material prepared in Example 1: Electrolysis of water / seawater: Electrochemical performance tests were performed in a typical three-electrode system at room temperature (approximately 25°C). The prepared nickel foam catalyst was used as the working electrode, a graphite rod as the counter electrode, and Hg / HgO as the reference electrode to test the electrochemical performance of the OER. All reported potentials can be converted to the reversible hydrogen electrode (RHE) potential using the following formula: E (RHE) = E (Hg / HgO) +0.0591*pH +0.098 V. All electrochemical tests were performed on a CHI660E electrochemical workstation (Shanghai). To enhance the comparability of water / seawater OER, commercial catalysts IrO2 / NF and nickel foam NF were also tested. The IrO2 used here was purchased from Aladdin Shanghai Co., Ltd., analytical grade. The NF was purchased from Hefei Kejing Materials Technology Co., Ltd., 0.5mm thick * 250mm wide * 200mm long.

[0060] Figure 11 The figures show the polarization curves of different catalysts. As can be seen from the figures, the linear sweep voltammetry (LSV) curves of the catalysts show that the current density gradually increases with increasing potential. The OER activity order of the prepared catalysts is: C, N-FeNbO4 / NF > N-Fe2O3 / NF > IrO2 / NF > C, N-Nb2O5 / NF > NF. The catalytic activity of C, N-FeNbO4 / NF is superior to that of the commercial catalyst IrO2 / NF.

[0061] Figure 12 Overpotential diagrams of different catalysts. As can be seen from the figure, the overpotentials of C, N-FeNbO4 / NF at current densities of 50 mA cm -2 , 100 mA cm -2 and 200 mA cm -2 are 284 mV, 325 mV and 389 mV respectively, all lower than those of C, N-Nb2O5 / NF (338 mV, 384 mV and 458 mV), N-Fe2O3 / NF (291 mV, 338 mV and 413 mV), IrO2 / NF and NF (309 mV, 355 mV and 426 mV) at the same current density. The above results indicate that C, N-FeNbO4 / NF has the best OER performance. This is because the micro-rods have a large specific surface area, thus providing abundant active sites for OER. At the same time, C, N doping not only increases the carrier concentration of FeNbO4, but also adds additional catalytic sites, effectively improving the electrocatalytic performance.

[0062] Figure 13 Tafel slope diagrams of different catalysts. Compared with N-Fe2O3 / NF (43.9 mV dec -1 ), IrO2 / NF (57.4 mV dec -1 ), C, N-Nb2O5 / NF (70.3 mV dec -1 ) and NF (92.8 mV dec -1 ), C, N-FeNbO4 / NF exhibits the lowest Tafel slope (31.6 mV dec -1 ). Based on the results of the Tafel slope, C, N-FeNbO4 / NF requires the smallest overpotential to increase the current, thus showing high kinetic performance.

[0063] Figure 14 Impedance diagrams of different catalysts. The order of the charge transfer resistance ( R ct ) is C, N-FeNbO4 / NF < N-Fe2O3 / NF < IrO2 / NF < C, N-Nb2O5 / NF < NF. Compared with other catalysts, C, N-FeNbO4 / NF has a higher charge / ion transfer rate.

[0064] Figure 15 Double-layer capacitance of different catalysts. The double-layer capacitance values of C, N-FeNbO4 / NF, N-Fe2O3 / NF, IrO2 / NF, C, N-Nb2O5 / NF and NF are 18.1 mF cm-2 16.6 mF cm -2 12.8 mF cm -2 9.4 mFcm -2 and 7.3 mF cm -2 C,N-FeNbO4 / NF exhibits a high double-layer capacitance.

[0065] Figure 16 The values ​​represent the electrochemically active specific surface area (ECSA) of different catalysts. C,N-FeNbO4 / NF exhibits the largest ECSA (0.45 cm⁻¹). 2 This indicates its good catalytic activity.

[0066] Figure 17 Example 1: Synthesis of C,N-FeNbO4 / NF in 1 M KOH solution I - t The curve shows that the current of C,N-FeNbO4 / NF decreased to only 2.54% after 100 h of continuous electrolysis, indicating its excellent stability.

[0067] Figure 18 Tafel polarization curves for 1M KOH and seawater with different catalysts. (Tafel curve log) i corr The lowest point corresponds to E corr and i corr These represent corrosion potential and corrosion current density, respectively. E corr The more negative the value, the worse the catalyst's corrosion resistance, and vice versa. This applies to NF, IrO2 / NF, N-Fe2O3 / NF, C,N-Nb2O5 / NF, and C,N-FeNbO4 / NF. E corr The values ​​were -0.60 V, -0.46 V, -0.31 V, -0.21 V, and -0.18 V, respectively. The results indicate that C,N-FeNbO4 / NF exhibits the best corrosion resistance potential.

[0068] Figure 19 The image shows the polarization curves of C,N-FeNbO4 / NF synthesized in Example 1 under different conditions. C,N-FeNbO4 / NF maintained significant OER activity in simulated seawater electrolyte (1 M KOH + 0.5 M NaCl), requiring only overpotentials of 286 mV, 329 mV, and 401 mV to reach 50 mA cm⁻¹, respectively. -2 100 mA cm -2 and 200 mA cm-2 The current density is close to that of the catalyst in 1 M KOH electrolyte. In natural seawater, the OER activity of C,N-FeNbO4 / NF decreases, requiring 293 mV, 339 mV, and 414 mV respectively to achieve 50 mA cm⁻¹. -2 100 mA cm -2 and 200mA cm -2 The current density is likely due to small particles, bacteria, microorganisms, and insoluble precipitates loaded on the active sites of the catalyst electrode surface.

[0069] Figure 20 Example 1: Synthesis of C,N-FeNbO4 / NF with 1M KOH and seawater I - t Stability test results. After 100 h of continuous operation in natural seawater electrolyte, C, N-FeNbO4 / NF showed small fluctuations in current density and remained consistently stable.

[0070] In summary, this invention successfully fabricated C,N-FeNbO4 microrod arrays on self-supporting NF via in-situ derivatization. In-situ growth of C,N-FeNbO4 improves stability and conductivity, while its three-dimensional rod-like structure increases specific surface area and exposes abundant active sites, thus exhibiting excellent catalytic activity. In-situ C and N doping enhances the intrinsic conductivity of FeNbO4. Specifically, the synergistic effect of constructing more 001 crystal planes of FeNbO4 in situ, C,N doping, and highly conductive NF results in rapid reaction kinetics for C,N-FeNbO4 / NF in water / seawater electrolysis. Based on these advantages, C,N-FeNbO4 / NF requires only 325 mV overpotential to achieve a 100 mA cm⁻¹ reaction in 1 M KOH electrolyte solution. -2 The current density (simulated seawater: 329 mV, natural seawater: 339 mV), and the low Tafel slope (31.6 mV dec) are also noteworthy. -1 It exhibits strong stability (97.5% initial activity). Furthermore, in natural seawater, C,N-FeNbO4 / NF demonstrates good corrosion resistance (corrosion potential: 0.17 V) and durability.

Claims

1. A method for in-situ 001 facet derived C, N-FeNbO4 / NF microrods based on foamed nickel, characterized in that, The method comprises the following steps: (1) adding niobium oxalate, FeCl3·6H2O, NH4F and urea into water, stirring and treating to obtain a uniform mixed solution; (2) adding foamed nickel into the mixed solution prepared in step (1), stirring and treating, and then obtaining a C, N-FeNbO4 / NF precursor through a hydrothermal reaction; (3) annealing the C, N-FeNbO4 / NF precursor prepared in step (2) under an argon atmosphere to obtain three-dimensional rod-shaped C, N-FeNbO4 / NF.

2. The method of claim 1, wherein, In step (1), the mass ratio of niobium oxalate: FeCl3-6H2O: urea: ammonium fluoride is 3: 1.5: 3: 1~4: 2: 3.5: 1; the concentration of the mixed solution is 0.02 g mL -1 ~ 0.04 g mL -1 ; the stirring time is 6 h~8 h.

3. The method of claim 1, wherein, In step (1), the mass ratio of niobium oxalate: FeCl3·6H2O: urea: ammonium fluoride is 3.6:1.8:3.2:

1.

4. The method of claim 1, wherein, In step (2), the size of the foamed nickel is 2 x 2 cm 2 4 x 4 cm 2 ; the stirring time is 1 h~3 h, the temperature of the hydrothermal reaction is 120 °C~180 °C, and the hydrothermal treatment time is 8 h~16 h.

5. The method of claim 1, wherein, In step (2), the size of the foamed nickel was 2 x 2 cm 2 ; the temperature of the hydrothermal reaction was 150 °C and the hydrothermal treatment time was 6 h.

6. The method of claim 1, wherein, In step (3), the C, N-FeNbO4 / NF precursor is annealed in argon at 900 ºC±20 ºC for 3 h.

7. The C, N-FeNb04 / NF microrods derived from the method according to any one of claims 1-4, characterized in that, C, N-FeNbO4 / NF microrods mainly consist of C, N, O, Fe, Ni and Nb elements, exist N-O peaks and C-O peaks, uniformly distributed microrod arrays on the surface, and the rods contain porous structures, and the electrochemical active specific surface area is 0.45 cm 2 .

8. Application of the C, N-FeNbO4 / NF microrod as claimed in claim 7 as a catalyst for electrolysis of water / sea water to produce oxygen.

9. Use according to claim 8, characterized in that, The C,N-FeNbO4 / NF microrods exhibit 284 mV@50 mA cm⁻¹ in 1 M KOH. -2 The overpotential is 31.6 mV dec. -1 The Tafel slope and stability over 100 h.

10. Use according to claim 8, characterized in that, The C, N-FeNbO4 / NF has high corrosion resistance in natural seawater, a low overpotential and good stability with a corrosion potential of-0.17 V.

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