A Fe-NiCoSe x / NCFF catalyst and its preparation method

Abstract

This invention discloses a Fe-NiCoSe x The preparation method of NCFF catalyst relates to the field of catalyst technology and includes the following steps: cleaning and drying NCFF foam; mixing selenium powder, hydrazine hydrate and deionized water evenly, adding the NCFF foam, and reacting at a certain temperature to obtain Fe-NiCoSe. x / NCFF catalyst. The beneficial effects of this invention are the use of nickel-cobalt-iron trimetallic alloy foam, which, through a simple one-step hydrothermal process, grows selenide nanoparticles to construct a Fe-NiCoSe nanoparticle structure rich in CoSe2-Ni3Se4 heterostructure, uniformly doped with iron, and containing both crystalline and amorphous phases. x The / NCFF catalyst exhibits superior HER and OER activities, outperforming most reported transition metal-based catalysts.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a Fe-NiCoSe catalyst. x / NCFF catalyst and its preparation method. Background Technology

[0002] To address challenges such as the energy crisis and reduce environmental pollution, water splitting for hydrogen production has become a common method. Currently, the three most common methods for achieving water splitting for hydrogen production are based on electrocatalytic electrolysis, solid oxide electrolyzers (SOEC), and photoelectrochemical electrolysis (PEC). Among these methods, electrocatalytic water splitting has attracted significant attention due to its relatively environmentally friendly and economical characteristics. However, electrocatalytic water splitting involves two half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. HER involves two-electron transfer, while OER involves four-electron transfer, leading to slow kinetics, especially in alkaline media. Although noble metal-based materials (such as Pt, IrO2, and RuO2) are considered leading electrocatalysts for HER and OER, their scarcity and high cost limit their widespread application and commercialization. Therefore, developing efficient non-noble metal electrocatalysts for alkaline HER and OER is promising but remains a significant challenge.

[0003] Recently, transition metal compounds have become a focus of extensive research due to their advantages such as low cost, multiple valence states, and suitable electronic structures, and are considered effective electrocatalysts for HER and OER. Among transition metal compounds, selenides (TMSes) have attracted widespread attention due to their good performance and excellent catalytic stability in HER and OER. It has been reported that Ni3Se2 nanostructures grown on Ni substrates exhibit excellent catalytic activity and durability in both HER and OER. Furthermore, testing and DFT calculations have revealed that NiSe2-FeSe2 heterostructure nanosheets also exhibit highly efficient total hydrolysis performance and long-term stability. However, compared with noble metal-based catalysts, the activity of TMSes is still insufficient, and there is a significant gap between its performance and the requirements of high current density industrial applications.

[0004] Constructing heterostructures and designing elemental doping have always been effective approaches for developing highly efficient bifunctional electrocatalysts. For example, Wang's NiTe-NiSe heterostructure catalyst... 10Both HER and OER exhibited remarkably high activity, requiring only 76 mV and 164 mV overpotentials, respectively. The hierarchical Ni2P / (Co,Ni)OOH heterointerface developed by Zhang et al. demonstrated high activity and stability in the alkaline hydrogen evolution reaction. Furthermore, Fe doping was also confirmed by Zhao's team to effectively improve the catalytic activity of NiSe nanowires. Sergio Battiato successfully promoted the oxygen evolution reaction by chemically depositing iron-doped nickel oxide microflowers with controlled composition. However, to adapt to industrial applications, in addition to high catalytic activity, catalytic stability at high current densities is also crucial. Therefore, the development of non-noble metal-based bifunctional electrocatalysts that can maintain high catalytic activity at high current densities is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a Fe-NiCoSe x / NCFF catalyst and its preparation method. This invention proposes a novel method with an extremely simple process for preparing TMSes electrocatalysts, named Fe-NiCoSe. x / NCFF, where x represents a mixture of various selenides of different trimetallic components. This invention uses a nickel-cobalt-iron trimetallic alloy foam with an Fe content of only 0.5%. Selenide nanoparticles are grown using a very simple one-step hydrothermal process to construct a Fe-NiCoSe nanoparticle structure rich in a CoSe2-Ni3Se4 heterostructure, uniformly doped with iron, and containing both crystalline and amorphous phases. x / NCFF catalyst. Electrochemical testing confirmed its extremely high water electrolysis activity, mainly manifested in the achievement of j at low overpotentials of 36mV and 210mV. 10 The HER and OER processes can even achieve j in HER and OER at only 328mV and 345mV respectively. 1000 All of them can maintain high stability for 20 hours or more. Overall, compared with the commonly used laboratory j 10 and j 100 Activity test, Fe-NiCoSe x / NCFF in j 1000 It exhibits significant advantages and is therefore more suitable for industrial applications. DFT calculations also demonstrate the superior electron density and reaction intermediate adsorption capacity of the CoSe2(210)-Ni3Se4(202) heterojunction, while showcasing its HER (-0.384eV) and OER (ΔG). 1st 0.243 eV, ΔG 2nd The process requires an extremely low energy barrier (0.376 eV).

[0006] The technical solution of the present invention is as follows:

[0007] The first aspect of the present invention provides a Fe-NiCoSe x The preparation method of / NCFF catalyst includes the following steps:

[0008] Clean the NCFF foam thoroughly and dry it;

[0009] Selenium powder, hydrazine hydrate, and deionized water were mixed evenly, and then the NCFF foam was added. The mixture was reacted at a certain temperature to obtain Fe-NiCoSe. x / NCFF catalyst.

[0010] Preferably, the NCFF foam cleaning method includes: ultrasonically cleaning the NCFF foam in acetone solvent and HCl solution for 5-15 minutes respectively, and then taking out the NCFF and rinsing the surface with anhydrous ethanol and deionized water alternately.

[0011] Preferably, the NCFF foam drying method includes: drying the cleaned NCFF in a drying oven at 45-55°C for 10-20 minutes.

[0012] Preferably, the ratio of selenium powder, hydrazine hydrate and deionized water is 0.06-0.1g: 1.5-2.5ml: 18-22ml.

[0013] Preferably, the ratio of selenium powder, hydrazine hydrate and deionized water is 0.07-0.09g: 1.8-2.2ml: 19-21ml.

[0014] Preferably, the ratio of selenium powder, hydrazine hydrate, and deionized water is 0.08g:2ml:20ml.

[0015] Preferably, the reaction is carried out at 160–200°C in a forced-air drying oven for 20–28 hours.

[0016] Preferably, the reaction is carried out at 180°C for 24 hours in a forced-air drying oven.

[0017] Preferably, the size of the NCFF foam is 0.5-1.5cm × 0.5-1.5cm.

[0018] A second aspect of the present invention provides Fe-NiCoSe obtained by the above preparation method. x / NCFF catalyst. Morphologically, Ni, Co, Fe, Se, and O elements are uniformly distributed. In terms of content, Ni atoms account for 5.56%, Co atoms 36.51%, Fe atoms 0.78%, Se atoms 47.34%, and O atoms 9.81%.

[0019] This invention has at least one of the following beneficial effects:

[0020] This invention utilizes a nickel-cobalt-iron trimetallic alloy foam to grow selenide nanoparticles using a simple one-step hydrothermal process. This constructs a Fe-NiCoSe nanoparticle structure rich in CoSe2-Ni3Se4 heterostructures, uniformly doped with iron, and containing both crystalline and amorphous phases. x / NCFF catalyst.

[0021] The Fe-NiCoSex / NCFF catalyst prepared by this invention via a simple one-step process exhibits superior HER and OER activities, outperforming most reported transition metal-based catalysts. This catalyst possesses uniformly dense, micron-sized selenide particles and dense nanowires on its surface, providing a large reaction surface area and abundant active sites, resulting in an extremely large electrochemically active specific surface area. The incorporation of trace amounts of Fe allows the catalyst to grow into a richer selenide structure during selenization, with the nickel-cobalt-iron trimetallic alloy forming micron-sized particles that integrate crystalline and amorphous phases, significantly enhancing electrochemical performance. Attached Figure Description

[0022] Figure 1 The Fe-NiCoSe of the present invention x Flowchart of the preparation process of / NCFF catalyst.

[0023] Figure 2 The graph shows a comparison of the HER(a) and OER(b) performance of the catalysts prepared in Examples 1-3.

[0024] Figure 3 This is a comparison chart of the HER(a) and OER(b) performance of the catalysts prepared in Examples 1, 4-5.

[0025] Figure 4 This is a comparison chart of the HER(a) and OER(b) performance of the catalysts prepared in Examples 1, 6-7.

[0026] Figures 5-6 These are the XRD patterns of the catalysts prepared in Example 1 and Comparative Examples 1-2.

[0027] Figure 7 These are morphology images of the catalyst prepared in Example 1. a is a low-resolution morphology image, b is a high-resolution SEM image, c is a framework mapping image, d is a low-resolution TEM and elemental energy spectrum, and e and f are high-resolution TEM images.

[0028] Figure 8 These are the XPS spectra of the catalyst prepared in Example 1. a is the full XPS spectrum, and bf are the high-resolution spectra of each element.

[0029] Figure 9These are electrocatalytic performance test graphs of the catalysts prepared in Examples 1 and Comparative Examples 1-3, and the two substrates NCFF and NCF. a is the LSV curve, b is the Tafel slope data, c is the electrochemical impedance spectroscopy (EIS) Nyquist plot, d is the LSV curve of the sample after 10,000 cyclic voltammetry (CV) scans, and e is the... 10 j 100 and j 1000 The timing current curve below.

[0030] Figure 10 SEM low-resolution and high-resolution images of the catalyst prepared in Example 1 after It test. a is a low-resolution SEM image, b is a high-resolution SEM image.

[0031] Figure 11 This is the XRD pattern of the crystal structure of the sample prepared by catalyst It in Example 1.

[0032] Figure 12 The figures show the performance test results of the catalysts prepared in Examples 1 and Comparative Examples 1-3, and the two substrates NCFF and NCF used as OER working electrodes. a is the LSV curve, b is the Tafel slope, c is the electrochemical impedance spectroscopy, d is the LSV curve after 10,000 voltammetric cycles (CV), and e is the constant voltage chronoamperometry curve.

[0033] Figure 13 These are morphological images of the catalyst prepared in Example 1 after the OER reaction and It test. a is a low-resolution scanning electron microscope image, and b is a high-resolution scanning electron microscope image.

[0034] Figure 14 The image shows the XRD pattern of the catalyst prepared in Example 1 after the OER reaction was tested.

[0035] Figure 15 These are bilayer capacitance current (Cdl) graphs for the catalysts prepared in Example 1 and Comparative Example 1. a-b represent Fe-NiCoSe... x / NCFF, c~d is NiCoSe x / NCF, e~f is NCFF.

[0036] Figure 16 It is an atomic model of the CoSe2(210), Ni3Se4(202) and CoSe2(210)-Ni3Se4(202) heterojunction of the catalyst prepared in Example 1.

[0037] Figure 17 This is the DOS diagram of the catalyst prepared in Example 1.

[0038] Figure 18This is a Gibbs free energy evolution diagram of the CoSe2(210), Ni3Se4(202) and CoSe2(210)-Ni3Se4(202) heterojunction in the HER of the catalyst prepared in Example 1.

[0039] Figure 19 This is a Gibbs free energy evolution diagram of the CoSe2(210), Ni3Se4(202), and CoSe2(210)-Ni3Se4(202) heterostructures in the OER of the catalyst prepared in Example 1. Detailed Implementation

[0040] This invention is achieved through Figure 1 The method shown successfully synthesized Fe-NiCoSe using a one-step hydrothermal selenization reaction of nickel-cobalt-iron trimetallic alloy foam (NCFF). x / NCFF.

[0041] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following specific embodiments.

[0042] All chemical reagents used in the following examples were of analytical grade, and the water was deionized water. Acetone (CH3COCH3, AR, 99.5%), hydrochloric acid (HCl, AR, 36%), and anhydrous ethanol (CH3CH2OH, AR, 99.7%) were purchased from Hangzhou Shuanglin Chemical Reagent Co., Ltd. Hydrazine hydrate (N2H4H2O, AR, 50%) and potassium hydroxide (KOH, AR, 90%) were purchased from Shandong Xiya Chemical Industry Co., Ltd. Selenium powder (Se, AR, 99.9%), platinum carbon (Pt / C, AR, 20wt%), ruthenium oxide (RuO2, AR 99.9%), and perfluorosulfonic acid (Nafion) were purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Nickel-cobalt-iron alloy foam (NCFF) was purchased from Suzhou Taili Foam Factory.

[0043] Example 1

[0044] NCFF foam with a size of 1×1cm was ultrasonically cleaned for 10 min each in acetone and 1 mol / L HCl solution. After removal, the NCFF was rinsed three times each with anhydrous ethanol and deionized water, and then dried in a drying oven at 50℃ for 15 min to obtain contamination-free NCFF foam.

[0045] Add 20ml of deionized water, 0.08g of selenium powder and 2ml of hydrazine hydrate to the inner liner of the reactor. After mixing evenly, add the cleaned NCFF foam and transfer the inner liner to the autoclave reactor. React at 180℃ for 24h in a forced-air drying oven.

[0046] After the reactor cooled to room temperature, the sample was removed and washed to obtain Fe-NiCoSe.x / NCFF catalyst.

[0047] Example 2

[0048] The difference from Example 1 is that the amount of selenium powder added is changed to 0.06g, while the rest is the same as Example 1.

[0049] Example 3

[0050] The difference from Example 1 is that the amount of selenium powder added is changed to 0.1g, while the rest is the same as Example 1.

[0051] Example 4

[0052] The difference from Example 1 is that the reaction temperature is changed to 160°C, otherwise it is the same as Example 1.

[0053] Example 5

[0054] The difference from Example 1 is that the reaction temperature is changed to 200°C, while the rest is the same as Example 1.

[0055] Example 6

[0056] The difference from Example 1 is that the reaction time is changed to 20 hours, otherwise it is the same as Example 1.

[0057] Example 7

[0058] The difference from Example 1 is that the reaction time is changed to 28 hours, otherwise it is the same as Example 1.

[0059] Comparative Example 1

[0060] The difference from Example 1 is that NCFF foam is replaced with NCF foam, otherwise it is the same as Example 1, resulting in NiCoSe. x / NCF catalyst.

[0061] Comparative Example 2

[0062] The difference from Example 1 is that NCFF foam is replaced with FCF foam, otherwise it is the same as Example 1, resulting in FeCoSe. x / FCF catalyst.

[0063] Comparative Example 3

[0064] The difference from Example 1 is that commercially available precious metals are loaded onto the NCFF foam. The specific loading method is as follows: Pt / C is ultrasonically dispersed in ethanol and perfluorosulfonic acid is added. After being dropped onto the NCFF surface and dried, a Pt / C-NCFF catalyst is obtained.

[0065] Test and Results Analysis

[0066] The catalysts prepared in Examples 1-7 and Comparative Examples 1-3 were subjected to the following tests.

[0067] I. Test Method Description

[0068] 1. Material Characterization

[0069] The morphology and surface features of the catalyst were observed in detail using field emission scanning electron microscopy (SEM, JSM-6700F, JEOL, Japan). The crystal structure and interplanar distances of the sample were studied using transmission electron microscopy (TEM, JSM 2100, JEOL, Japan), while its elemental composition and content were analyzed using energy dispersive spectroscopy (EDX). X-ray diffraction (XRD, Thermo Fisher Scientific, USA) and X-ray photoelectron spectroscopy (XPS, K-Alpha, USA) were used to detect the crystal phase and elemental state of the sample, respectively.

[0070] 2. Electrocatalytic evaluation

[0071] Electrochemical characteristics were measured using a CHI 660E electrochemical workstation at 1.0 M KOH solution (pH = 14) and room temperature (25°C). The experimental setup included a three-electrode system, with the catalyst sample as the working electrode, the carbon rod as the counter electrode, and Hg / HgO as the reference electrode. Notably, all test samples were 0.25 cm in size. 2 The working electrode was activated by cyclic voltammetry (CV) at a scan rate of 1 mV / s. Linear sweep voltammetry (LSV) was used to record the current-voltage curves. Electrochemical impedance spectroscopy (EIS) was performed at different potentials over a frequency range of 0.02 Hz to 100 kHz with an AC voltage amplitude of 5 mV. All potentials in the experimental data were corrected relative to the reversible hydrogen electrode (RHE) according to the Nernst equation, expressed as: E vsRHE =E vsHg / HgO +0.095 +0.059 pH. For the experimental data, 100% internal resistance (iR) compensation was performed, and the corrected potential expression is E. Corrected =E Raw -IRs, where E Corrected It is the corrected potential, E Raw Rs is the original measured potential, and Rs is the solution resistance. The double-layer capacitance (Cdl) is calculated to estimate the electrochemically active surface area (ECSA). The time-to-flight (TOF) frequency of the hydrogen release reaction (HER) and oxygen release reaction (OER) is based on the TOF... HER =jS / 2nF and TOF OER=jS / 4nF, where S, j, n, and F represent the electrode surface area, current density, amount of substance, and Faraday constant (96485 C mol), respectively. -1 The HER and OER performance of Pt / C and RuO2 powder-coated samples with the same catalyst mass loading were compared. Hydrogen and oxygen production were determined by measuring gas emissions every 10 minutes. The HER or OER stability of the catalysts at different current densities was evaluated using chronoamperometry (TFC) curves. Finally, the catalyst samples were assembled into a two-electrode system to assess their overall hydrolysis performance, and their stability was investigated by measuring the It curve under constant pressure.

[0072] 3. Theoretical Calculation

[0073] All calculations were performed within the framework of density functional theory, employing the projector augmented-wave method, as implemented in VASP (see: Kresse, G.; Joubert, D. From ultrasoft pseudopotentials to the projector augmented-wave method. Physical Review B 1999, 59, 1758-177.). The generalized gradient approximation proposed by Perdew, Burke, and Ernzerhof (see: Heyd, J.; Scuseria, GE; Ernzerhof, M. Hybrid Functionals Based on a Screened Coulomb Potential J. Chem. Phys. 2003, 118, 8207.) was chosen as the hybrid density functional selected by the exchange correlation potential (see: Perdew, JP; Burke, K.; Ernzerhof, M. Generalized gradient approximation made simple. Physical Review Letters 1996, 77, 3865-3868.). Van der Waals interactions are described by the DFT-D3 method (References: Grimme, S.; Antony, J.; Ehrlich, S. and Krieg, H.A., HA. consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. Journal of Chemical Physics 2010, 132, 154104.). The cutoff energy for plane waves is set to 400 eV. In the iterative solution of the Kohn-Sham equation, the energy criterion is set to 10⁻⁴ eV. Perpendicular to the sheet, [the following is a description of the addition of...]. A vacuum layer was used to avoid artificial interactions between periodic images. Brillouin zone integration was performed using a 2x2x1K mesh. All structures were relaxed until the residual forces on the atoms decreased to less than [value missing]. The calculation methods for HER and OER are consistent with our previous calculation methods (Reference: Li T, Yu Y, Pei M. Dual-Atom Doping Carbon Materials as Highly Efficient Electrocatalysts for Lithium-Sulfur Batteries: Bimetallic Cooperation Mechanism[J].The Journal of Physical Chemistry C,2023,127(13):6271-6279.).

[0074] II. Test Results and Analysis

[0075] 1. Structure and Representation

[0076] To determine the optimal growth conditions for multiphase selenides with high water electrolysis activity, we controlled three variables: selenium powder content in the reaction solution, temperature and time of the hydrothermal reaction, and prepared corresponding samples. Then, we tested the LSV polarization curves of their HER and OER reactions.

[0077] according to Figure 2 The results showed that when 0.08 g of selenium powder was uniformly dispersed in the reaction solution, the sample exhibited the highest HER and OER activities, indicating that the selenium powder concentration at this point was most suitable for the growth of multiphase selenides.

[0078] And from Figure 3 As can be seen, the prepared sample exhibits the best bifunctional performance when the hydrothermal temperature is 180℃, which may be because the selenide forms the most complete morphology and crystal phase at 180℃.

[0079] Finally, according to Figure 4 The results showed that the sample exhibited the best HER and OER performance when the reaction time was 24 hours. This indicates that the morphology and crystal structure of the selenide grew to the optimal state at the most suitable selenium powder concentration and reaction temperature, and continued reaction may lead to structural damage.

[0080] After determining the optimal parameters for the selenization reaction, this invention analyzed the Fe-NiCoSe prepared in Example 1 using XRD patterns. x Iron-free NiCoSe was grown on NCF prepared in both NCFF and Comparative Example 1. x The specific crystal structure of the NCF sample, such as Figure 5The results show that the crystal structures of the two are basically the same. The peak shapes of the spectra can be indexed to CoSe2 (JCPDS No. 09-0234), CoSe2 (JCPDS No. 10-0408), Co3Se4 (JCPDS No. 89-2001) and Ni3Se4 (JCPDS No. 18-0890). Specifically, the peaks at 34.2°, 51.8°, 63.4°, 72.0° and 76.0° correspond to the (210), (311), (400), (420) and (332) crystal planes of CoSe2 (JCPDS No. 09-0234), and the four peaks at 30.8°, 34.7°, 36.3° and 47.8° correspond to the (110), (111), (012) and (121) planes of CoSe2 (JCPDS No. 10-0408), respectively. In addition to CoSe2, several crystal planes of Co3Se4 (JCPDS No. 89-2001), namely (400), (511), (440), (444), (731), (733), and (840), also correspond to the peaks at 35.2°, 46.2°, 50.6°, 63.1°, 70.9°, 76.4°, and 85.0° in the spectrum. For the nickel crystal phase Ni3Se4 (JCPDS No. 18-0890), corresponding peaks at 33.2°, 33.7°, 35.6°, 44.8°, 45.3°, 50.7°, 60.4°, 70.0°, 72.0°, and 84.4° can be found in the XRD spectrum for (-112), (202), (013), (-114), (204), (310), (-116), (-125), (008), and (109). These XRD data indicate the successful synthesis of the nickel-cobalt bimetallic selenide. Furthermore, the XRD peaks clearly show the presence of Fe-NiCoSe synthesized on the trimetallic substrate. x The peak phases of / NCFF near four positions (33.8°, 45.4°, 51.2°, and 84.4°) are compared with those of the iron-free NiCoSe sample. x The / NCF values ​​showed a slight shift, all deviating to the right by about 0.1°. This confirms that Fe participated in the synthesis of selenide particles, either as an element or as a compound, and this incorporation is also highly beneficial for improving their catalytic performance. According to... Figure 6We can clearly observe that the sample prepared using nickel-free iron-cobalt alloy foam as a substrate significantly lacks the key main peak corresponding to the (-114) plane of the Ni3Se4 crystalline phase (JCPDS No. 18-0890). However, other peaks still exist and correspond well to the crystal planes of CoSe2. This proves that nickel selenides have been successfully synthesized on the NCF or NCFF surface, thus forming a heterogeneous interface with cobalt selenides, thereby significantly improving the catalyst activity. Figure 6 As can be seen, the sample prepared using nickel-free iron-cobalt alloy foam as a substrate clearly lacks the key main peak corresponding to the (-114) plane of the Ni3Se4 (JCPDS No. 18-0890) crystalline phase. However, other peaks are still present and correspond well to the crystal plane of CoSe2. This confirms that nickel selenides are successfully synthesized on the NCF or NCFF surface, thus forming a heterogeneous interface with cobalt selenides and significantly improving catalyst activity.

[0081] To investigate and analyze the microstructure and surface partial crystal phase structure of the Fe-NiCoSe prepared in Example 1, SEM and TEM were used to study its microstructure. x The / NCFF catalyst was studied in detail. Figure 7 a is Fe-NiCoSe x The morphology of NCFF under low resolution SEM shows that the foam skeleton of NCFF is covered with uniform and dense particles with a size of about 3-5 μm and an irregular geometric shape with protruding edges. Figure 7 b is a high-resolution SEM image. At higher magnification, it is clear that the particle surface is densely covered with extremely fine and short nanowires. These extremely fine and densely distributed nanowires can provide a large reaction area and expose a large number of active sites, thereby significantly improving the reaction efficiency of Fe-NiCoSe. x The catalytic activity of / NCFF. From Figure 7 The skeletal mapping diagram of c shows that Ni, Co, Fe, Se, and O are evenly distributed, indicating that the generated polymetallic selenides are very uniformly distributed on the skeletal structure. Although the amount of Fe is extremely small, it is also uniformly present on the foam skeletal structure. From Figure 7 As can be seen from the low-resolution TEM and elemental energy spectrum in d, Ni, Co, Fe, Se and O elements are also uniformly distributed in the particle fragments and nanowires observed in SEM. Although Table 1 shows that the iron content is only 0.78%, it can still be said that the three metals nickel, cobalt and iron all participated in the formation of selenide particles.

[0082] Figure 7 e and Figure 7f is a high-resolution TEM image, showing clear crystal planes in both images. The interplanar spacings of 0.266 nm, 0.202 nm, and 0.252 nm can be attributed to Ni3Se4, corresponding to the (202), (-114), and (013) crystal planes, respectively. Furthermore, the interplanar spacings of 0.262 nm, 0.190 nm, and 0.290 nm correspond to the (210), (121), and (110) crystal planes of CoSe2, respectively. It is noteworthy that, based on the crystal plane distribution in the image, it is clearly visible that the (202) crystal plane of Ni3Se4 and the (210) crystal plane of CoSe2, the (121) crystal plane of CoSe2 and the (013) crystal plane of Ni3Se4, and the (110) crystal plane of CoSe2 and the (013) crystal plane of Ni3Se4 form heterojunction interfaces at three locations, indicating the presence of selenide (Fe-NiCoSe). x The crystal structure of the selenide exhibits an abundance of heterogeneous interfaces, which is highly beneficial for improving catalyst performance. Furthermore, in addition to numerous crystal faces, the high-resolution TEM images clearly show many amorphous phases, indicating that the selenide particles are composed of both crystalline and amorphous phases. Therefore, although no crystalline iron phase was found, combined with... Figure 7 The mapping diagram in d still indicates that iron may exist uniformly in the Fe-NiCoSe phase as single atoms or amorphous selenides. x In the middle. Overall, Fe-NiCoSe x This amorphous and crystalline phase hybrid structure has a highly positive impact on electrocatalytic performance. SEM and TEM results jointly demonstrate the successful synthesis of nickel-cobalt-iron trimetallic polyhedralite particles covered with extremely fine nanowires on the NCFF surface.

[0083] Table 1

[0084]

[0085] To further investigate the Fe-NiCoSe prepared in Example 1 x To determine the chemical composition and bonding state of the / NCFF surface, we measured the XPS spectra of the samples. Figure 8 XPS full spectrum in a and Figure 8 High-resolution spectra of each element in bf. For example... Figure 8 In b, the two peaks at energy positions of 879.42 eV and 861.77 eV are first fitted as two satellite peaks, and the remaining four peaks are attributed to Ni in the metal compound. 2+ (Ni 2p 1 / 2 873.37 eV, Ni 2p 3 / 2 (855.67eV) and Ni 3+ (Ni 2p 1 / 2869.97 eV, Ni 2p 3 / 2 (852.86eV) Ni 2p 1 / 2 and Ni 2p 3 / 2 Track. Similarly, Figure 8 The high-resolution spectrum of Co2p in c was fitted to six peaks. First, satellite peaks corresponding to the energies of 802.48 eV and 785.52 eV were excluded. The two peaks at 797.13 eV and 781.20 eV can be attributed to Co. 2+ Co 2p 1 / 2 and Co 2p 3 / 2 The two peaks at the remaining positions of 793.21 eV and 778.4 eV were then correlated with Co. 3+ Co 2p 1 / 2 and Co 2p 3 / 2 track. Figure 8 Figure d shows the various chemical states of iron, including Fe2+ , except for the two satellite peaks corresponding to the energy positions of 733.23 eV and 716.54 eV. 3+ Fe 2p 1 / 2 (722.20eV) and Fe 2p 3 / 2 (713.60 eV) orbital, and Fe 2+ Fe 2p 1 / 2 (719.46eV) and Fe2p 3 / 2 (711.13 eV) orbital. This indicates that Fe-NiCoSe x During the preparation of the / NCFF catalyst, iron forms amorphous compounds such as iron selenide or iron oxide, rather than existing solely in elemental form, further proving the existence of Fe-NiCoSe. x / NCFF is a nickel-cobalt-iron trimetallic selenide catalyst containing abundant heterojunction interfaces and a combination of crystalline and amorphous phases. Furthermore, Figure 8 The values ​​at eV indicate the chemical state of Se. The peak at 58.71 eV is initially attributed to a Se-O bond, while the remaining peaks at 55.39 eV and 54.49 eV correspond to the chemical states of Se 3d. 3 / 2 and Se 3d 5 / 2 The orbits can be agreed upon. Figure 8 The peaks at 530.00 eV, 530.83 eV, and 532.30 eV in f indicate Fe-NiCoSe x The oxygen element in the / NCFF catalyst exists in three forms: metal-oxygen bond, hydrogen-oxygen bond, and adsorbed oxygen.

[0086] 2. Fe-NiCoSe x HER and OER performance of / NCFF catalysts

[0087] Fe-NiCoSe prepared in Example 1 x The electrocatalytic performance of the / NCFF catalyst was tested in a 1MKOH three-electrode system as the working electrode.

[0088] Figure 9 a is the Fe-NiCoSe prepared in Example 1 x Samples prepared with / NCFF catalyst and substrate replaced by FCF and NCF (FeCoSe) x / FCF and NiCoSe x Linear sweep voltammetry (LSV) of HER was performed on Pt / C-NCFF, a commercial noble metal catalyst, and NCFF and NCF substrates. Firstly, it is clearly evident that NCFF exhibits a significant improvement in HER activity compared to the NCF substrate itself, directly demonstrating the positive impact of trace Fe incorporation on HER performance. Secondly, after selenization treatment, the HER activity of the three different substrates was significantly improved in both low and high current density regions, showing a strong Fe-NiCoSe ratio. x / NCFF and NiCoSe x / NCF requires only overpotentials of 36.07mV and 50.07mV respectively to reach j 10 The comparison between the two substrates, NCFF (118.53mV) and NCF (159.4mV), clearly shows a significant improvement. It's worth mentioning that FeCoSe... x The LSV curve of the / FCF sample exhibits a significant reduction peak in the low current density region, thus making it impossible to obtain an accurate j. 10 Overpotential, which may be attributed to the presence of side reactions during the electrochemical process. In j 1000 At that time, Fe-NiCoSe x / NCFF, FeCoSe x / FCF and NiCoSe x / NCF requires only 328mV, 396mV, and 385mV overpotentials respectively, showing a significant advantage compared to NCFF (514mV) and NCF (692mV). This demonstrates that selenides of nickel, cobalt, and iron all play a substantial role in improving HER performance. Among them, Fe-NiCoSe x The performance of / NCFF in each stage of the hydrogen evolution reaction (including j) 100 193mV, j 500 The optimal value is 299mV, which benefits from the rich heterojunction interface constructed by nickel-cobalt selenide and the incorporation of amorphous iron selenide.

[0089] Figure 9b compiled the Tafel slope data calculated for each sample. It should be noted that FeCoSe... x The Tafel slope value calculated from the FCF sample (18.96 mV dec) -1 ) far below or even including Fe-NiCoSe x For all samples, including / NCFF, this data is clearly affected by side reactions due to the presence of reduction peaks in their LSV curves, and therefore does not accurately reflect the kinetic rate of the HER process; thus, it is not included in the comparison. Furthermore, Fe-NiCoSe... x / NCFF has the lowest Tafel slope value (33.7mV dec). -1 (), lower than NiCoSe x / NCF(45.06mV dec -1 ), NCFF(102.98mV dec -1 ) and NCF (142.39mV dec -1 (), even slightly lower than the commercially available precious metal catalyst Pt / C (34.37 mV dec) -1 This indicates that Fe-NiCoSe x The / NCFF catalyst exhibited significant advantages in the electrochemical reaction kinetics of the HER process in a 1M KOH environment. The process followed the Volmer-Heyrovsky mechanism.

[0090] To further investigate the electrochemical reaction kinetics of the HER process in the catalyst samples, their electrochemical impedance (EIS) Nyquist plots were tested. Figure 9 c). Fe-NiCoSe can be seen in the figure. x The Rct value of / NCFF is 2.5Ω, which is higher than that of NiCoSe. x / NCF(2.79Ω), FeCoSe x / FCF (2.88Ω) and even Pt / C (3.98Ω) have a slight advantage, and are far lower than NCFF (9.35Ω) and NCF (18Ω). Generally speaking, a smaller Rct means stronger metallicity and electron transfer ability, which can lead to higher hydrogen evolution reaction efficiency. This also shows that growing trimetallic selenide self-supported catalysts from iron-doped nickel-cobalt alloy foams is an effective way to prepare high-performance HER catalysts.

[0091] To test Fe-NiCoSe x The HER stability and durability of the / NCFF sample were first tested by measuring the LSV curves of the sample after 10,000 cyclic voltammetric (CV) scans. Figure 9d) It can be seen that the activity of the sample hardly decreased after long-term cyclic scanning, especially in the low current density region, where the LSV curve almost overlapped with the original. In the high current density region, there were only very small changes, which reflects the excellent performance of Fe-NiCoSe. x The NCFF sample exhibits exceptional durability under prolonged cycling current.

[0092] To further verify the stability of the sample, we tested j 10 j 100 and j 1000 The timing current curve below, as shown Figure 9 As shown in the stepped three-segment curve in e, the sample at j 10 After a 50-hour constant voltage HER reaction test, the current density even increased by 14.8%. 1000 Even after 20 hours, there was a 19.6% increase, which may be attributed to the activation of the active material under the current, thereby exposing more active surface area. In j 100 Although there was a slight decrease, the decrease was only about 2%, which fully demonstrates the effectiveness of Fe-NiCoSe. x The NCFF sample exhibits exceptional durability and stability.

[0093] In addition, in order to investigate Fe-NiCoSe x To investigate the source of NCFF stability, we characterized the morphology, phase structure, and chemical composition of the samples after the It test. Figure 10 The images show low-resolution and high-resolution SEM images of the samples after the It test. Figure 10 The low-resolution scanning electron microscope image in a shows Fe-NiCoSe x After a prolonged HER process, the microscopic particle structure of / NCFF remained essentially unchanged, and its morphology was similar to that before the reaction. Figure 7 a) They remain largely consistent. Figure 10 Further magnification revealed that the originally upright nanowires on the particle surface had collapsed and were now cross-linked to the particle surface. However, the nanowires were clearly still present and had not been destroyed or disappeared during the HER reaction; they had simply changed from an upright to a collapsed state. This demonstrates that the catalyst's microstructure had not changed significantly due to the prolonged HER process, indicating its stability in microscopic physical structure. Furthermore, XRD patterns (…) Figure 11 Analysis of the crystal structure of the sample after It was performed revealed that Fe-NiCoSe was found through comparison. x The main peaks corresponding to all crystalline phases and crystal planes of / NCFF still exist, with only minor changes in the peak height of some peaks. This proves that Fe-NiCoSe xThe crystal structure of / NCFF is extremely stable in the HER reaction, showing virtually no change after 120 hours of iodine (IT) testing.

[0094] The performance of each catalyst was also tested as the working electrode for the OER. Figure 12 a represents the LSV curve. Clearly, Fe-NiCoSe... x / NCFF exhibited superior OER activity (j 10 210mV, j 1000 : 345mV), although in the low current region compared with commercial noble metal catalyst RuO2 (j 10 While the current density (137mV) is still insufficient, it performs better at higher current densities. Notably, the trimetallic foam NCFF, doped with trace amounts of Fe, also exhibits significantly better activity than NCF in the OER, demonstrating that Fe incorporation is highly beneficial for both the OER and HER processes. All three selenized samples again showed significant activity enhancement in the OER, indicating the great potential of transition metal selenides (TMSes) for both water electrolysis reactions. Figure 12 b shows Fe-NiCoSe x The lowest Tafel slope (55.92 mV dec) of / NCFF was observed in all samples. -1 ), compared to FeCoSe x / FCF(63.21mV dec -1 ), NiCoSe x / NCF(74.13mV dec -1 ) and RuO2 / NCFF (125.28mV dec -1 It has advantages in all aspects, far exceeding the substrate NCFF (90.57mV dec). -1 ) and NCF (126.29mV dec -1 This shows Fe-NiCoSe x The rapid kinetics of / NCFF in the OER process. Additionally, Figure 12 The extremely low Rct (1.26 Ω) shown in c makes Fe-NiCoSe x / NCFF possesses the ability to rapidly transfer electrons, which is more conducive to the oxygen evolution process. Other samples, such as FeCoSe... x / FCF(1.56Ω), NiCoSe x / NCF (1.44Ω) and RuO2 / NCFF (3.3Ω) are slightly worse.

[0095] To investigate Fe-NiCoSe xTo investigate whether the advantages of the / NCFF catalyst at high current densities in the OER reaction can be maintained stably over a long period, we tested its LSV curve after 10,000 voltammetric cycles (CV). Figure 12 d), the data shows that its activity only decreased by a very small amount, j 1000 The overpotential of 359 mV increased by only 14 mV compared to before cycling. We also tested Fe-NiCoSe. x / NCFF constant voltage chronocurrent curve in the high current density region ( Figure 12 e) Under 25 hours of high current density oxygen evolution reaction operation, the measured It curve, although fluctuating, did not show significant overall attenuation, proving that Fe-NiCoSe x / NCFF’s superior durability in OER processes.

[0096] To investigate the potential factors contributing to the superior durability of the samples during the OER reaction, we also characterized the morphology and structure of the samples after the It test. Figure 13 It can be observed that the prolonged oxygen evolution reaction did not change the micron-level morphology of the catalyst surface; the selenide particles remained uniformly and densely distributed on the foam skeleton. Furthermore, at the more microscopic nanoscale morphology... Figure 13 b) The selenide surface no longer shows obvious nanowire morphology, but instead has a honeycomb morphology similar to that formed by cross-linking of nanosheets. This morphology also exposes a large number of active sites and reaction area, thus greatly preserving the OER activity of the catalyst.

[0097] pass Figure 14 The XRD patterns show that after a long OER reaction, the peak heights of many peaks changed, but the peaks corresponding to the key crystal planes of all major crystal phases remained, and some peaks were even more prominent. This means that although the surface structure of the catalyst changed during the OER process, the crystal phases were not destroyed. While some crystal planes decreased, others were exposed more. For example, the peak height corresponding to the (-114) crystal plane of Ni3Se4 (JCPDS No. 18-0890) increased significantly. This also means that more heterointerfaces can be retained, so there is no significant loss of catalyst activity.

[0098] The above electrochemical performance test data indicate that Fe-NiCoSe x / NCFF catalysts exhibit superior performance in both HER and OER processes. From Figure 15 The measured double-layer capacitance current (Cdl) value revealed that Fe-NiCoSe x The Cdl value of / NCFF is 61.58 mF cm. -2 The value is much higher than that of NiCoSe samples without iron doping.x / NCF(46.08mF cm -2 ) and NCFF substrate (12.34mF cm) -2 From this, the ECSA value (electrochemically active specific surface area) of each sample can be calculated, which are Fe-NiCoSe x / NCFF: 1529.5cm -1 ECSA NiCoSe x / NCF:1152cm -1 ECSA NCFF: 246.8cm -1 ECSA The large electrochemical active surface area provides a large number of reactive sites, which also supports Fe-NiCoSe x The high performance of / NCFF catalyst in two reactions of water electrolysis.

[0099] 3. DFT calculation

[0100] To further elucidate Fe-NiCoSe x The performance of selenide crystals on the surface of the / NCFF catalyst relative to the HER and OER processes was analyzed by DFT calculations, based on XRD and TEM results, to determine the crystal phase and the resulting heterostructure. Figure 16 Atomic models of the main highly active crystal planes CoSe2(210), Ni3Se4(202) and CoSe2(210)-Ni3Se4(202) heterojunctions are shown, established using the VASP calculation package.

[0101] Since the density of states (DOS) is the projection of the band structure onto the vertical axis, Figure 17 The DOS diagram shown can be used to quantify the correlation between CoSe2(210), Ni3Se4(202), and CoSe2(210)-Ni3Se4(202) heterojunctions and HER activity. The diagram clearly shows that all three exceed the Fermi level, reflecting their inherent low electrical resistance and other metallic properties. Compared to monolayer phases, the CoSe2(210)-Ni3Se4(202) heterojunction exhibits a significantly larger DOS value. The high density of states indicates that the construction of the heterojunction interface enhances the electron density, thus facilitating the HER process. It is evident that the heterojunction can significantly increase the concentration of free electrons in both spin-down and spin-up states. This is likely the main factor reducing the binding strength of intermediate substances such as H*, OH*, O*, and OOH* on the catalyst surface during electrocatalysis.

[0102] The hydrogen adsorption free energy (ΔGH*) is an important parameter for evaluating electrocatalytic activity; ideally, |ΔGH*| should approach 0 during the HER process. Figure 18The ΔGH* value of the CoSe2(210)-Ni3Se4(202) heterojunction is -0.384 eV, which is much lower than the -0.624 eV of the two monolayer phases CoSe2(210) and -1.386 eV of Ni3Se4(202). This indicates that the CoSe2(210)-Ni3Se4(202) heterojunction adsorbs H during the HER process. + It has an extremely low energy barrier and extremely high hydrogen release efficiency. Furthermore... Figure 19 The energy changes in the four stages of the OER reaction are shown. For the OER evolution process, the rate-determining step for both the Ni3Se4(202) and CoSe2(210)-Ni3Se4(202) heterojunctions is the second step of O* generation, while for CoSe2(210), the rate-determining process is influenced by the third step of OOH* generation. In comparison, the energy barrier (ΔG) of the CoSe2(210)-Ni3Se4(202) heterojunction is... 1st 0.243 eV, ΔG 2nd (0.376eV) is much smaller than CoSe2(210)(ΔG) 2nd 0.661 eV, ΔG 3rd :1.162eV) and Ni3Se4(202)(ΔG 2nd 1.168 eV, ΔG 3rd The energy barrier of the CoSe2(210)-Ni3Se4(202) heterojunction is 0.213 eV. This data shows that the collective effect brought about by the CoSe2(210)-Ni3Se4(202) heterojunction significantly optimizes the energy barrier required for the OER process, which is particularly evident in the conversion of OH* to O* and the generation of O* to OOH*.

[0103] Based on theoretical calculations and experimental characterization and testing data, it can be found that the two-phase heterostructure CoSe2-Ni3Se4 significantly increases the free electron concentration, and the energy barriers required for both HER and OER processes are significantly reduced, thus both can be driven at lower overpotentials.

[0104] Analysis based on electrochemical test results indicates that Fe-NiCoSe x / NCFF exhibits superior activity and stability for both HER and OER. The reasons for this can be summarized through analysis of various characterization test results as follows:

[0105] (1) Fe-NiCoSe x The uniform and densely distributed micron-sized selenide particles and their dense nanowires on the surface of / NCFF provide a huge reaction area and extremely rich active sites, with a calculated reaction depth of 1529.5 cm⁻¹. -1 ECSAThe large ECSA value also indicates that it has a very large electrochemically active specific surface area. Furthermore, its microstructure remained intact under prolonged high current density HER and OER conditions, providing it with strong electrocatalytic stability.

[0106] (2) The incorporation of trace amounts of Fe element enabled the catalyst to grow into a richer selenide structure during the selenization process. XPS and TEM analysis showed that the nickel-cobalt-iron trimetallic compounds formed micron-sized particles that integrated crystalline and amorphous phases. This is extremely beneficial for improving electrochemical performance.

[0107] (3) Fe-NiCoSe x The extremely low Tafel value of the / NCFF catalyst supports its rapid electrochemical kinetics, and the low Rct value indicates its inherent metallic properties, which is beneficial for accelerating the transfer of electrons from the electrode to the electrolyte, thereby providing a more efficient electrocatalytic reaction process.

[0108] (4) DFT calculations show the high electron density and strong adsorption capacity of the two-phase heterostructure CoSe2(210)-Ni3Se4(202) for reaction intermediates, and also indicate its adsorption of H during the HER process. + The energy barriers for the decisive steps in the OER process are extremely low.

[0109] In summary, the Fe-NiCoSex / NCFF catalyst, prepared via a simple one-step process, exhibits superior HER and OER activities compared to most reported transition metal-based catalysts. This catalyst possesses uniformly dense micron-sized selenide particles and dense nanowires on its surface, providing a large reaction surface area and abundant active sites. Furthermore, XPS and TEM results show that the catalyst is composed of nickel, cobalt, and iron, forming micron-sized particles that integrate crystalline and amorphous phases, further enhancing its electrochemical performance. DET results reveal that the CoSe2(210)-Ni3Se4(202) heterojunction exhibits a higher density of states, indicating that the formation of the heterojunction increases the electron density, thus favoring the HER and OER processes. More notably, Fe-NiCoSex / NCFF demonstrates excellent stability in both HER and OER reactions at high current densities, which is significant for the commercial application of transition metal-based catalysts.

[0110] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A Fe-NiCoSe x The method for preparing / NCFF catalyst is characterized by, Includes the following steps: Clean the NCFF foam thoroughly and dry it; Selenium powder, hydrazine hydrate, and deionized water were mixed evenly, and then the NCFF foam was added. The mixture was reacted at a certain temperature to obtain Fe-NiCoSe. x / NCFF catalyst; The NCFF foam is a nickel-cobalt-iron trimetallic alloy foam; The x represents a mixture of various selenides composed of nickel, cobalt, and iron.

2. The Fe-NiCoSe according to claim 1 x The method for preparing / NCFF catalyst is characterized by, The NCFF foam cleaning method includes: ultrasonically cleaning the NCFF foam in acetone solvent and HCl solution for 5-15 minutes respectively, and then taking out the NCFF and rinsing the surface with anhydrous ethanol and deionized water alternately.

3. The Fe-NiCoSe according to claim 1 x The method for preparing / NCFF catalyst is characterized by, The NCFF foam drying method includes drying the cleaned NCFF in a drying oven at 45-55°C for 10-20 minutes.

4. The Fe-NiCoSe according to claim 1 x The method for preparing / NCFF catalyst is characterized by, The ratio of selenium powder, hydrazine hydrate, and deionized water is 0.06–0.1 g: 1.5–2.5 ml: 18–22 ml.

5. The Fe-NiCoSe according to claim 1 x The method for preparing / NCFF catalyst is characterized by, The ratio of selenium powder, hydrazine hydrate, and deionized water is 0.07–0.09 g: 1.8–2.2 ml: 19–21 ml.

6. The Fe-NiCoSe according to claim 1 x The method for preparing / NCFF catalyst is characterized by, The ratio of selenium powder, hydrazine hydrate, and deionized water is 0.08g:2ml:20ml.

7. The Fe-NiCoSe according to claim 1 x The method for preparing / NCFF catalyst is characterized by, React at 160–200°C in a forced-air drying oven for 20–28 hours.

8. The Fe-NiCoSe according to claim 1 x The method for preparing / NCFF catalyst is characterized by, React at 180°C for 24 hours in a forced-air drying oven.

9. The Fe-NiCoSe according to claim 1 x The method for preparing / NCFF catalyst is characterized by, The NCFF foam has a size of 0.5-1.5cm × 0.5-1.5cm.

10. A Fe-NiCoSe prepared by any one of the preparation methods described in claims 1 to 9 x / NCFF catalyst.

Images