A YNiCoS x / NCF catalyst and its preparation method

Abstract

This invention discloses a YNiCoS x / NCF catalyst and its preparation method, relating to the field of catalyst technology, includes: cleaning and drying NiCo foam; mixing Y(NO3)2·6H2O, sulfur powder, N2H4 and deionized water to form a homogeneous mixture; placing NiCo foam into the mixture and reacting it at a certain temperature to obtain YNiCoS x / NCF. The beneficial effect of this invention is the in-situ preparation of a multiphase YNiCo trimetallic sulfide with excellent electrical conductivity, structural stability, and hydrolysis performance on a NiCo foam matrix using a one-step hydrothermal method. This catalyst exhibits excellent water splitting electrocatalytic activity under alkaline conditions. By introducing the Y element, YNiCoS... x The HER and OER performance of the catalyst was significantly enhanced.

Description

Technical Field

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

[0002] The rational design and synthesis of efficient and low-cost bifunctional catalysts for water electrolysis remains a challenge. Transition metal sulfides (TMSs) with good electrical conductivity and tunable electronic structures are potential candidate materials, and are expected to replace noble metal electrocatalysts. In the latest research on oxygen evolution reaction (OER) catalysts based on metal chalcogenides, nickel (Ni) and cobalt (Co)-rich chalcogenides have attracted much attention due to their excellent OER activity and stability. Jiang et al. prepared three crystalline nickel sulfides, NiS, NiS2, and Ni3S2, via a microwave-assisted approach. Electrochemical studies showed that Ni3S2 exhibited the highest HER activity among the three forms, attributed to its structural advantages, including unique surface chemistry, a large electrochemical active area, and high electrical conductivity.

[0003] Furthermore, the performance and stability of alloys can be improved by introducing foreign elements. In recent years, the catalytic performance of rare earth catalytic materials has been extensively studied worldwide. Rare earth elements, encompassing the lanthanides (atomic numbers 57 to 71) and scandium and yttrium with similar electronic structures and chemical properties, exhibit superior multifaceted properties due to their unfilled 4f electron orbitals. These characteristics give rare earths unique chemical properties in the field of catalysis. Recent studies emphasize that the special electronic structure of rare earths has a significant impact on energy conversion and storage capabilities in catalysis, especially in enhancing activity and stability. Rare earth elements have also promoted the development of new properties, including intermetallic compound formation, adsorption / desorption processes, reaction selectivity, surface interactions, and improved hydrogenation / oxidation kinetics, opening up new research and application prospects in materials science and catalytic chemistry.

[0004] Among these rare earth elements, yttrium (Y) has an empty 5d orbital in its electronic structure, exhibiting strong redox capabilities and serving as an electron transfer station in catalytic reactions. Furthermore, the addition of small amounts of yttrium can improve the mechanical strength, electrical conductivity, and thermal stability of the catalyst. Therefore, utilizing inexpensive yttrium as a substitute for noble metals to prepare water splitting electrocatalysts has significant research value. However, current research on the introduction of Y as a water electrolysis catalyst is limited, and the effects of Y incorporation on non-noble metal-based compounds and its mechanism of action remain unclear, requiring further extensive research. 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 YNiCoS x / NCF catalyst and its preparation method. A multiphase YNiCo trimetallic sulfide, named YNiCoS, was prepared in situ by introducing Y and S into a NiCo foam matrix using a one-step hydrothermal method. x / NCF catalyst, where x represents the number of S atoms. This catalyst exhibits excellent electrocatalytic activity for water splitting under alkaline conditions. By introducing the Y element, YNiCoS x The HER and OER performance of the catalyst was significantly enhanced. In 1M KOH, j 10 and j 1000 The overpotentials required for the current density are as low as 75 mV and 332 mV (HER), and 90 mV and 399 mV (OER), respectively. At high current densities, this is significantly better than currently commercially available Pt / C and RuO2. Meanwhile, this catalyst exhibits good electrocatalytic stability in HER, at j 100 After running for 50 hours under the specified conditions, there was no significant degradation. Furthermore, YNiCoS... x NCF||YNiCoS x NCF batteries only require 1.64V in an alkaline electrolyzer to generate 50mA / cm². 2 The current density.

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

[0007] This invention provides a YNiCoS x The preparation method of / NCF catalyst includes the following steps:

[0008] Clean the NiCo foam thoroughly and dry it.

[0009] Y(NO3)2·6H2O, sulfur powder, N2H4 and deionized water are mixed to form a homogeneous mixture.

[0010] NiCo foam is placed into the mixture and reacted at a certain temperature to obtain YNiCoS. x / NCF.

[0011] Preferably, the NiCo foam cleaning method includes: ultrasonically cleaning the NiCo foam with acetone and hydrochloric acid respectively, followed by rinsing with deionized water and anhydrous ethanol alternately.

[0012] Preferably, the ultrasonic cleaning time is 10 to 20 minutes.

[0013] Preferably, the ratio of Y(NO3)2·6H2O, sulfur powder, N2H4 and deionized water is 0.06-0.18g: 0.03-0.07g: 1-4ml: 18-21ml.

[0014] Preferably, the ratio of Y(NO3)2·6H2O, sulfur powder, N2H4 and deionized water is 0.1-0.14g: 0.04-0.06g: 2-3ml: 19-20ml.

[0015] Preferably, the ratio of Y(NO3)2·6H2O, sulfur powder, N2H4 and deionized water is 0.12g:0.05g:2ml:20ml.

[0016] Preferably, the mixing process of Y(NO3)2·6H2O, sulfur powder, N2H4 and deionized water includes: first stirring with a magnetic stirrer for 10-20 minutes, followed by ultrasonic treatment at 80-120W for 10-20 minutes.

[0017] Preferably, the reaction temperature is 160–200°C and the reaction time is 5–15 h.

[0018] Preferably, the reaction temperature is 180°C and the reaction time is 10 hours.

[0019] A second aspect of the present invention provides a YNiCoS prepared by the above method. x / NCF catalyst. Through the treatment of YNiCoS x EDX elemental energy dispersive spectroscopy analysis of the / NCF catalyst revealed that sulfur (S) was uniformly dispersed on the catalyst surface. The weight percentages of S, Co, Ni, and Y in the catalyst were 33.46%, 49.44%, 16.47%, and 0.63%, respectively, further confirming the presence of YNiCo sulfides.

[0020] The YNiCoS of the present invention x The / NCF catalyst exhibits superior electrocatalytic activity, which can be attributed to the following factors: First, compared to single-metal sulfides, NiCo alloys exhibit higher structural stability due to the synergistic effect between metals, effectively addressing the challenges of high current densities. Second, the introduction of the rare earth element yttrium (Y) modifies the NiCo sulfide catalyst by leveraging its unique redox capabilities. The introduction of Yttrium alters the crystal phase and morphology of the NiCo sulfide, exposing more active sites and thus increasing the electrochemically active surface area of ​​the catalyst. Third, the abundant heterogeneous interfaces within the catalyst facilitate the adsorption of hydrogen intermediates and enhance the inherent activity of the catalyst surface active sites. Fourth, the in-situ growth of ternary metal sulfides on the NiCo foam substrate ensures good electrical conductivity and accelerates electron transport rates.

[0021] This invention has at least one of the following beneficial effects:

[0022] This invention employs a one-step hydrothermal method to prepare a multiphase YNiCo trimetallic sulfide with excellent electrical conductivity, structural stability, and hydrolysis performance in situ on a NiCo foam matrix. This catalyst exhibits excellent water splitting electrocatalytic activity under alkaline conditions. By introducing the Y element, YNiCoS… x The HER and OER performance of the catalyst was significantly enhanced. Attached Figure Description

[0023] Figure 1 The YNiCoS of this invention x / NCF catalyst preparation process flow diagram.

[0024] Figure 2 This is a comparison of the HER (a) and OER (b) performance of the catalysts prepared in Example 1 and Comparative Examples 1-2.

[0025] Figure 3 The comparison shows the HER (a) and OER (b) performance of the catalysts prepared in Examples 1-5 under different holding times, as well as the HER (c) and OER (d) performance at different temperatures.

[0026] Figure 4 This is a comparison of the HER (a) and OER (b) performance of the catalysts prepared in Examples 1, 6-7.

[0027] Figure 5 This is a comparison of the HER (a) and OER (b) performance of the catalysts prepared in Examples 1, 8 and 9.

[0028] Figure 6 This is a comparison of the HER (a) and OER (b) performance of the catalysts prepared in Examples 1, 10 and 11.

[0029] Figure 7 This is an XRD image of the catalyst prepared in Example 1.

[0030] Figure 8 The images show the morphology and structure of the catalyst prepared in Example 1. (a-c) SEM images at different magnifications, (d) TEM image, (e) HRTEM image, (f) TEM image, (g) SAED image, and (h) elemental energy spectrum.

[0031] Figure 9 The morphology and structure of the catalyst prepared in Example 1 are shown. (a, b) SEM images at different magnifications, (c) XRD image.

[0032] Figure 10 The morphology and structure of the catalyst prepared in Comparative Example 3 are shown. (a, b) SEM images at different magnifications, (c) XRD image.

[0033] Figure 11 The above are XPS spectra of the catalyst prepared in Example 1. (a) Full XPS spectrum, (b) Co 2p, (c) Ni 2p, (d) Y 3d, (e) S 2p and (f) O 1s.

[0034] Figure 12 These are the HER performance test graphs of the catalysts prepared in Example 1 and the comparative example in 1 M KOH. (a) LSV curve, (b) comparison of overpotential of the catalysts at different current densities, (c) Tafel curve, (d) electrochemical impedance spectroscopy, (e) MA curve and (f) TOF curve.

[0035] Figure 13 These are Cdl diagrams of the catalysts prepared in Example 1 and Comparative Examples 3-4. (a) YNiCoS x / NCF, (b)NiCoS x / NCF, (c) YNiCo / NCF, (d) NCF.

[0036] Figure 14 The catalyst prepared in Example 1 was reacted with 1 M KOH. j 100 The It curve at current density.

[0037] Figure 15 This is an XRD image of the catalyst It prepared in Example 1 after testing.

[0038] Figure 16 These are OER performance test graphs of the catalysts prepared in Examples 1 and Comparative Examples 3-4 in 1 M KOH. (a) LSV curve, (b) comparison of overpotential of catalysts at different current densities, (c) Tafel curve, (d) electrochemical impedance spectroscopy, (e) MA curve, (f) TOF curve.

[0039] Figure 17 This is a graph showing the sustainability and long-term stability of the catalyst prepared in Example 1 during the OER process. (a) YNiCoS x / NCF catalyst in 1 M KOH j 100 It curve under current density, (b) YNiCoS x / NCF|| YNiCoS x LSV curves of the overall water electrolysis of / NCF and Pt / C||RuO2 in 1 M KOH. Detailed Implementation

[0040] 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.

[0041] The nickel-cobalt foam (NCF) is from Suzhou Taili Co., Ltd., and has a thickness of 1mm.

[0042] The nickel foam (NF) is sourced from Suzhou Taili Co., Ltd., and has a thickness of 1 mm.

[0043] The cobalt foam is sourced from Suzhou Taili Co., Ltd., and has a thickness of 1mm.

[0044] Yttrium nitrate Y(NO3)2·6H2O, AR 99.9%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0045] Sulfur powder, AR 98.5%, purchased from Aladdin Reagent (Shanghai) Co., Ltd.

[0046] Hydrazine hydrate, AR 80%, purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd.

[0047] Acetone, AR 99.5%, purchased from Hangzhou Shuanglin Chemical Reagent Co., Ltd.

[0048] Hydrochloric acid, AR 36%, purchased from Hangzhou Shuanglin Chemical Reagent Co., Ltd.

[0049] Example 1

[0050] First, cut the NiCo foam (NCF) into 1cm×1cm thin slices, then ultrasonically clean it with acetone and hydrochloric acid for 15 minutes each, followed by rinsing with deionized water and anhydrous ethanol alternately, and then drying it for later use.

[0051] 0.12g Y(NO3)2 6H2O, 0.05g sulfur powder, and 2ml N2H4 were placed into the inner liner of a polytetrafluoroethylene reactor containing 20ml of deionized water. The mixture was stirred with a magnetic stirrer for 15 minutes, followed by ultrasonic treatment at 100W for 15 minutes to form a homogeneous mixture.

[0052] The dried NCF was placed into the inner liner of the reactor and then packaged into a stainless steel high-pressure reactor. It was then transferred to an oven at 180°C and kept at that temperature for 10 hours. While the reactor cooled, it was alternately rinsed with deionized water and anhydrous ethanol to obtain YNiCoS. x / NCF.

[0053] Example 2

[0054] The difference from Example 1 is that: it is then transferred to an oven at 180°C for heat preservation. 5h Everything else is the same as in Example 1.

[0055] Example 3

[0056] The difference from Example 1 is that: it is then transferred to an oven at 180°C for heat preservation. 15h Everything else is the same as in Example 1.

[0057] Example 4

[0058] The difference from Example 1 is that: then transferred to 160℃ The oven was kept warm for 10 hours. Everything else was the same as in Example 1.

[0059] Example 5

[0060] The difference from Example 1 is that: then transferred to 200℃ The oven was kept warm for 10 hours. Everything else was the same as in Example 1.

[0061] Example 6

[0062] The difference from Example 1 is that 0.12g Y(NO3)2 6H2O, 0.05g sulfur powder, 4ml N2H4 was inserted into the device 18ml The deionized water was placed in the inner liner of a polytetrafluoroethylene reactor. Everything else was the same as in Example 1.

[0063] Example 7

[0064] The difference from Example 1 is that 0.12g Y(NO3)2 6H2O, 0.05g sulfur powder, 1ml N2H4 was inserted into the device 21ml The deionized water was placed in the inner liner of a polytetrafluoroethylene reactor. Everything else was the same as in Example 1.

[0065] Example 8

[0066] The difference from Example 1 is that 0.12g of Y(NO3)2 6H2O was added. 0.03g Sulfur powder and 2 ml of N2H4 were placed into the inner liner of a polytetrafluoroethylene reactor containing 20 ml of deionized water. Everything else was the same as in Example 1.

[0067] Example 9

[0068] The difference from Example 1 is that 0.12g of Y(NO3)2 6H2O was added. 0.07g Sulfur powder and 2 ml of N2H4 were placed into the inner liner of a polytetrafluoroethylene reactor containing 20 ml of deionized water. Everything else was the same as in Example 1.

[0069] Example 10

[0070] The difference from Example 1 is that: 0.06g Y(NO3)2 6H2O, 0.05g sulfur powder, and 2ml N2H4 were placed in the inner liner of a polytetrafluoroethylene reactor containing 20ml of deionized water. Everything else was the same as in Example 1.

[0071] Example 11

[0072] The difference from Example 1 is that: 0.18g Y(NO3)2 6H2O, 0.05g sulfur powder, and 2ml N2H4 were placed in the inner liner of a polytetrafluoroethylene reactor containing 20ml of deionized water. Everything else was the same as in Example 1.

[0073] Comparative Example 1

[0074] The difference from Example 1 is that "NiCo foam" is replaced with "Ni foam". Everything else is the same as in Example 1.

[0075] Comparative Example 2

[0076] The difference from Example 1 is that "NiCo foam" is replaced with "Co foam". Everything else is the same as in Example 1.

[0077] Comparative Example 3

[0078] The difference from Example 1 is that sulfur powder is not added, and YNiCo / NCF is prepared. Everything else is the same as in Example 1.

[0079] Comparative Example 4

[0080] The difference from Example 1 is that Y(NO3)2 6H2O is not added, and NiCoS is prepared. x / NCF. Everything else is the same as in Example 1.

[0081] Test and Results Analysis

[0082] The catalysts prepared in Examples 1-10 and Comparative Examples 1-4 were subjected to the following tests.

[0083] I. Test Method Description

[0084] 1. Morphology and phase characterization

[0085] The morphology of the synthesized catalyst was analyzed using field emission scanning electron microscopy (SEM), and the distribution of surface elements was observed using energy dispersive spectroscopy (EDS). Transmission electron microscopy (TEM) was used to further investigate the microstructure and interplanar spacing of the catalyst. X-ray diffraction (XRD) was used to characterize the crystal structure to assess the phase composition and crystallinity of the sample. X-ray photoelectron spectroscopy (XPS) was used to determine the elemental composition and content of the material, thereby identifying the chemical composition and evolution of the compound state of the catalyst.

[0086] 2. Electrochemical performance testing

[0087] Electrochemical performance testing was performed using a typical three-electrode setup, utilizing a CHI 660E / 750E electrochemical workstation from Shanghai Chenhua at room temperature and atmospheric pressure. The system consisted of a catalyst working electrode, a mercuric oxide electrode (reference electrode), and a carbon rod counter electrode, with 1M KOH (pH = 14) as the electrolyte. Electrochemical tests included cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (It). First, the prepared electrodes were pretreated using CV, undergoing 500 cycles of activation at a scan rate of 50 mV / s to ensure the stability and accuracy of the results. Then, the voltammetry was performed at 1 mV / s... -1 LSV tests were performed at sweep rates within voltage ranges of -2.4 to 0 V and 0 to 1.2 V to obtain HER and OER performance. All polarization curves were IR compensated based on ohmic resistance to correct for potential (E). c From formula E c =E m -IRs calculation, where E m For experimental potential measurement, Rs is the solution resistance derived from the curve, and I is the current. The measured potential is calibrated as the overpotential under the reversible hydrogen electrode (RHE), and the calculation formula is E vs RHE = E vs Hg / HgO + 0.098 + 0.059 × pH. Simultaneously, EIS technology was used at 10... 5 Electrochemical impedance spectroscopy (EIS) reflecting the HER kinetics was plotted within a frequency range of ~0.01 Hz and an AC voltage amplitude of 5 mV. The long-term stability and durability of the catalyst were assessed at 10 mV s⁻¹. -1 Perform 10 consecutive scans at a certain speed 4 The cyclic CV and long-term It curves at different current densities were used to evaluate the catalyst. Finally, the catalyst was assembled into a dual-electrode system with anode and cathode to explore the overall water splitting performance of the catalyst.

[0088] II. Test Results and Analysis

[0089] 1. YNiCoS x Parameter optimization of NCF catalyst

[0090] To explore the optimal catalyst synthesis method, this invention investigated the morphology and HER and OER activities of metal sulfides synthesized under different conditions.

[0091] (1) Types of foam

[0092] like Figure 2As shown, the electrochemical performance of metal sulfides prepared from different metal foam substrates varies considerably. The metal sulfide prepared using pure nickel foam (Comparative Example 1) exhibits the worst performance in the OER reaction. This result may be attributed to the poor structural stability of a single metal, leading to catalyst detachment under high current density tests. The metal sulfide prepared using pure cobalt foam (Comparative Example 2) is superior to that prepared using pure nickel foam (Comparative Example 1). Furthermore, using a nickel-cobalt alloy foam (Example 1) as a self-supporting framework demonstrates better stability due to the alloy structure, enabling stable hydrogen and oxygen evolution at high current densities.

[0093] (2) Temperature and time of hydrothermal reaction

[0094] This invention also explores the effects of temperature and time on the hydrothermal reaction of YNiCoS x The effect of / NCF catalyst on catalytic activity.

[0095] Figure 3 (a, b) shows the HER and OER performance after holding the hydrothermal reaction for 5 h, 10 h, and 15 h, with the results showing that the reaction activity was best at 10 h.

[0096] Figure 3 (c, d) show the electrocatalytic performance under reaction conditions of 160℃, 180℃, and 200℃. It was found that the HER and OER activities were optimal at 180℃. This may be because the structure and morphology of the catalyst under suitable temperature and growth time lead to more active sites, which is beneficial to the hydrogen evolution and oxygen evolution reactions.

[0097] (3) Concentration of hydrazine hydrate

[0098] The concentration of hydrazine hydrate provides different environments for catalyst growth. For example... Figure 4 As shown, the N2H4 to deionized water volume ratio of 2:20 is significantly better than that of 1:21 and 4:18, indicating that both excessively high and low concentrations of hydrazine hydrate lead to a decrease in the performance of the prepared catalyst. This may be because a suitable concentration ratio allows the reaction to proceed more fully.

[0099] (4) Amount of sulfur powder and amount of Y(NO3)2 6H2O

[0100] By comparing the magnitudes of the catalyst overpotential at the same current density, the results are as follows: Figures 5-6 As shown.

[0101] Depend on Figures 5-6It can be seen that 0.05g sulfur powder and 0.12g Y(NO3)2 6H2O are superior to 0.03g sulfur powder and 0.06g Y(NO3)2 6H2O and 0.07g sulfur powder and 0.18g Y(NO3)2 6H2O, respectively, yielding the optimal parameters of 0.05g sulfur powder and 0.12g Y(NO3)2 6H2O. This is likely because a suitable solvent concentration plays a crucial role in the growth and distribution of the catalyst.

[0102] 2. YNiCoS x Morphology and structural analysis of NCF catalysts

[0103] To further explore YNiCoS x The relationship between the structure of / NCF catalyst and its electrocatalytic performance was analyzed using XRD on the YNiCoS catalyst prepared in Example 1. x The crystal structure of the / NCF catalyst was characterized.

[0104] like Figure 7 As shown, the diffraction peaks at 32.7°, 55.7°, 75.7°, and 87.2° correspond to the (200), (311), (331), and (422) crystal planes of YS (JCPDS NO. 18-1478). The diffraction peaks at 29.8°, 31.1°, 39.4°, 47.5°, 51.9°, 61.7°, 72.9°, 76.8°, and 84.5° belong to the (311), (222), (331), (511), (440), (622), (731), (800), and (751) crystal planes of Co4S3 (JCPDS NO. 02-1338). The peaks at 29.6° and 49.3° are attributed to the (111) and (220) crystal planes of Ni3S2 (JCPDS NO. 27-0341). These results demonstrate the successful synthesis of YNiCo sulfides via a one-step hydrothermal method. Furthermore, the diffraction peaks at 29.7°, 41.3°, 43.8°, and 84.1° belong to the (201), (202), (020), and (521) crystal planes of NiY (JCPDS NO. 65-5276), which is consistent with the NiY alloy synthesized in the comparative sample YNiCo.

[0105] In addition, for YNiCoS x The morphology of the / NCF catalyst was characterized. Figure 8 (a~c) represents YNiCoS x SEM images of the / NCF catalyst at different magnifications reveal spheres composed of numerous irregular nanoparticles grown in situ on the NiCo foam framework, with rectangular nanosheets interspersed at the edges of the spheres. To further investigate its structure, transmission electron microscopy was used for characterization. Figure 8(d) shows a low-magnification TEM image, revealing rectangular nanosheets and irregular particles. These two morphologies were analyzed using high-magnification transmission electron microscopy. Figure 8 (e) is a rectangular slice. The figure shows the (200) crystal plane of YS, the (220) crystal plane of Ni3S2, the (222) crystal plane of Co4S3, and the (211) crystal plane of NiY, which is consistent with the results in XRD. Figure 8 (f) is a high-magnification TEM image of the irregular particles, in which the (311) and (211) crystal planes corresponding to Co4S3 and the (111) crystal plane of Ni3S2 can be found. Furthermore, Figure 8 In (e, f), interlaced stripes can be observed at the junctions between crystal planes, indicating that a rich heterogeneous interface is formed in the catalyst. The heterogeneous interface and stacking faults formed can usually adapt to the stress in the crystal material, which plays an important role in regulating the catalytic active sites. Figure 8 (g) is the selected area electron diffraction (SAED) pattern for the corresponding region, from which the (400) crystal plane of Co4S3, the (111) crystal plane of Ni3S2, and the (303) and (020) crystal planes of NiY can be observed. These results indicate that YNiCo trimetallic sulfide was successfully synthesized in one step, and this sulfide has a complex heterostructure, which is of great significance for improving the catalytic activity of HER and OER. To investigate YNiCoS x The elemental distribution of the NCF catalyst was determined by EDX elemental energy dispersive spectroscopy analysis of the catalyst surface. The results are as follows: Figure 8 As shown in (h), S is uniformly dispersed on the catalyst surface. The weight percentages of S, Co, Ni, and Y in the catalyst are 33.46%, 49.44%, 16.47%, and 0.63%, respectively, which further confirms the presence of YNiCo sulfides.

[0106] To investigate the effect of Y element addition on the morphology and structure of the catalyst, the NiCoS prepared in Example 1 was subjected to... x The morphology and crystal structure of the / NCF catalyst were characterized.

[0107] Figure 9 (a) shows NiCoS x SEM images of the / NCF catalyst show that spherical structures composed of irregular particles also grow on the NiCo foam framework, similar to... Figure 8 (a, b) shows YNiCoS xUnlike the NCF catalyst, the edges of these spherical structures do not form rectangular nanosheets; instead, they consist of irregular particles. By comparing the morphologies of the two catalysts, it can be inferred that the addition of Y element provided new nuclei for catalyst growth, leading to the different morphologies.

[0108] By analyzing NiCoS x XRD images of / NCF were obtained, further exploring the influence of the Y element on the catalyst structure. From Figure 9 (c) shows that it is related to YNiCoS x Compared to NCF catalysts, NiCoS x / NCF has different Co sulfide crystal phases, with diffraction peaks at 35.3°, 46.7°, 51.9°, and 74.3° corresponding to the (101), (102), (003), and (202) crystal planes of Co4S3 (JCPDS NO.02-1458), respectively. Diffraction peaks at 29.9°, 30.8°, 43.5°, 64.3°, and 72.5° correspond to the (100), (002), (102), (004), and (104) crystal planes of CoS (JCPDS NO.65-0407), respectively. The crystal phase of Ni3S2 is similar to that of YNiCo. x The crystal phases of the NCF catalyst are consistent, which suggests that the addition of Y element alters the crystal phase of Co sulfides, while the crystal phase of Ni sulfides remains unchanged.

[0109] In comparison, the morphology and structure of the catalyst synthesized in Comparative Example 3 (without sulfur powder as a reactant) were also investigated. Figure 10 Images (a, b) show SEM images of YNiCo / NCF, revealing irregularly shaped particles growing on a NiCo foam framework. Under high magnification, groove-like structures were observed on the surface of the foam framework. The crystal structure of the YNiCo / NCF catalyst was subsequently characterized. Figure 10 The XRD pattern in (c) shows that the diffraction peaks correspond to the NiY (JCPDS NO.65-5276) and Co5Y (JCPDS NO.17-0078) crystal phases. It can be reasonably inferred that, without sulfur powder as a reactant, the catalyst synthesized under the same other parameters is an alloy of Ni, Co, and Y.

[0110] X-ray photoelectron spectroscopy (XPS) was used to analyze the YNiCoS prepared in Example 1. x The chemical state and composition of the / NCF catalyst were characterized, and the results are as follows: Figure 11 As shown. Among them. Figure 11 (a) indicates the presence of Ni, Co, S, Y and O elements in the sample. Figure 11(b) shows the high-resolution XPS spectrum of Co 2p. The core level spectrum in the figure can be deconvolved into two oscillating satellite peaks (approximately 786.5 eV and 802.3 eV) and four main peaks. Among them, there are two unique spin-orbit peaks at 778.3 and 793.4 eV, corresponding to Co 2p and 802.3 eV respectively. 0 Co 2p 3 / 2 and Co 2p 1 / 2 Meanwhile, the other two peaks, 781.0 eV and 796.8 eV, are attributed to Co, respectively. 2+ Co 2p valence state 3 / 2 and Co 2p 1 / 2 .

[0111] Figure 11 (c) shows the high-resolution XPS spectrum of Ni, where 853.1 eV and 870.2 eV are attributed to Ni. 2+ Ni 2p valence state 3 / 2 and Ni 2p 1 / 2 The peaks at 855.8 eV and 873.6 eV are attributed to Ni. 3+ Ni 2p 3 / 2 and Ni 2p 1 / 2 In addition, the peaks at 861.5 and 879.6 are two oscillating satellite peaks of Ni. Figure 11 (d) shows the signal peaks of Y 3d, with the fitted peaks at 156.7 eV and 158.1 eV corresponding to Y 3d. 5 / 2 and Y3d 3 / 2 The consistent chemical states indicate that Y and element were successfully loaded into the YNiCo sulfide catalyst. The chemical state of S is as follows: Figure 11 As shown in (e), the peaks at 161.6 eV and 162.8 eV are attributed to S. 2- S2p 3 / 2 and S2p 1 / 3 The peaks at 162.2 eV and 163.1 eV are attributed to S2. 2- S2p 3 / 2 and S2p 1 / 3 This indicates that metal sulfides were successfully synthesized via a one-step hydrothermal method, consistent with the results shown by XRD. The peaks appearing at 168.2 eV and 169.3 eV are attributed to SO42-. 2- The SO bond in the [structure / structure]. A possible reason is that sulfides exposed to air are oxidized to form SO4. 2- . Figure 11(f) shows the XPS peak spectrum of O1s, where the peak at 531.5 eV is attributed to the CO bond, and the peak at 532.7 eV is attributed to the COH bond. Quantitative analysis of each element using XPS revealed that the atomic percentages of Co 2p, Ni 2p, Y 3d, and S 2p were 9.94%, 6.14%, 3.73%, and 15.84%, respectively, indirectly confirming the successful addition of Y to YNiCoS. x / NCF catalyst.

[0112] 3. YNiCoS x Electrochemical performance of NCF catalysts

[0113] The HER performance of the catalyst prepared in Example 1 in 1M KOH electrolyte was studied using a standard three-electrode configuration. Figure 12 (a) shows the YNiCoS after IR correction. x / NCF, NiCoS x Linear sweep voltammetry (LSV) polarization curves of NCF, YNiCo / NCF, NCF and Pt / C catalysts.

[0114] Figure 12 (b) shows the different catalysts at j 10 j 100 and j 1000 Overpotential comparison diagram under current density. Note that YNiCoS x / NCF exhibits excellent electrocatalytic performance, driving j 10 and j 100 The overpotentials are only 75mV and 209mV, which is significantly lower than that of NiCoS. x / NCF(109mV / j 10 282mV / j 100 ), YNiCo / NCF(182mV / j 10 323mV / j 100 ), NCF(163mV / j 10 317mV / j 100 More importantly, YNiCoS x / NCF maintains j 500 and j 1000 The high current density requires only 291mV and 332mV overpotentials, respectively, which is superior to Pt / C (356mV / j). 500 498mV / j 1000 This meets the potential application requirements for H2 production under industrial conditions. The Tafel value is of great significance in analyzing electrochemical reaction kinetics.

[0115] Figure 12(c) shows the output by Figure 12 (a) Tafel slopes of different derived catalysts, showing that YNiCoS prepared in Example 1 x The Tafel slope of / NCF is 112.5mV dec. -1 This is much smaller than the NiCoS prepared in Comparative Example 4. x / NCF(163.7mV dec -1 YNiCo / NCF (189.9 mV dec) prepared in Comparative Example 3 -1 ) and NCF (192.3mV dec -1 This indicates that the catalyst exhibits a faster reaction kinetics. The Tafel slopes corresponding to the three elementary reactions of HER in alkaline electrolyte are as follows: the Tafel value for the Volmer reaction is greater than 120 mV dec. -1 The Tafel values ​​for the Heyrovsky reaction range from 40 to 120 mV dec. -1 The Tafel value of the reaction with Tafel is less than 30 mV dec. -1 According to YNiCoS x / NCF(112.5mV dec -1 The Tafel slope is between 40 and 120 mV dec. -1 Based on the results, it can be determined that the HER reaction kinetics in alkaline media follows the Volmer-Heyrovsky mechanism.

[0116] In addition, we investigated the electrocatalytic kinetics of different catalysts using electrochemical impedance spectroscopy (EIS). Figure 12 The electrochemical impedance spectroscopy in (d) indicates that YNiCoS x / NCF interfacial charge transfer resistance (R ct The Ω is only 7.3 Ω, which is much smaller than that of NiCoS. x / NCF (11.9Ω), YNiCo / NCF (48.3Ω) and NCF (61.4Ω), which makes YNiCoS x / NCF catalysts exhibit higher electrical conductivity, enabling faster electron transfer and thus higher catalytic activity. Mass activity (MA) and time-to-flight (TOF) are two other important parameters for evaluating catalytic activity, such as... Figure 12 As shown in (e), YNiCoS x / NCF exhibits significantly higher mass activity than NiCoS at the same voltage. x / NCF and YNiCo / NCF. Specifically, at an overpotential of 300mV, YNiCoS x The mass activity of NCF is 92.2 Ag.-1 And NiCoS x / NCF and YNiCo / NCF each contain only 16.7Ag. -1 and 8.75Ag -1 This indicates that, in the same mass of catalyst, YNiCoS x / NCF catalysts achieve higher hydrogen evolution efficiency. To better explore the intrinsic activity of the catalysts, the catalyst turnover frequency was compared, such as... Figure 12 As shown in (f), compared to NiCoS x / NCF and YNiCo / NCF, YNiCoS x / NCF has a larger turnover frequency at the same overpotential, possibly because NiCoS x / NCF has abundant heterogeneous interfaces, which is more conducive to the adsorption of hydrogen intermediates and enhances the inherent activity of active sites exposed on the catalyst surface.

[0117] To further investigate the reasons for the improved HER activity, this invention calculated the electrochemical surface area (ECSA) of the catalysts prepared in Example 1 and Comparative Examples 3-4 using the double-layer capacitance method (Cdl). Figure 13 As shown, the scan rate ranges from 20 to 200 mV / s within the non-Radichter interval. -1 The CV curve (left) and its calculated Cdl value (right). Among them, YNiCoS x The Cdl value of / NCF was 51.4 mF cm. -2 Compared to NiCoS x / NCF(36.4mF cm -2 ), YNiCo / NCF (4.3mF cm) -2 ) and NCF (4.9mF cm -2 The values ​​were 1.3, 10.9, and 9.4 times larger, respectively. It is noteworthy that the introduction of Y element altered the original morphology and structure of NiCo sulfides. The resulting rectangular nanosheets increased the specific surface area of ​​the catalyst. Comparison of the electrochemical surface areas between the catalysts further confirmed the presence of YNiCoS... x The multiphase structure of / NCF exposes more active sites, resulting in higher catalytic efficiency.

[0118] Besides catalytic activity, the stability of electrocatalytic hydrogen evolution is also an important indicator for evaluating electrode materials. The chronoamperometry (It) was used to investigate the YNiCoS prepared in Example 1. x Long-term stability and durability of / NCF catalysts. Figure 14 Demonstrating YNiCoS xThe process of changing the current density of / NCF catalyst at a fixed voltage and 100mA over 50 h was investigated. According to the experimental results, after 50 h of continuous hydrogen evolution reaction, the current density decreased by only 4%, indicating that the YNiCoS catalyst prepared via a one-step method... x The / NCF catalyst exhibits excellent stability in HER precipitation.

[0119] In addition, the crystal phase of the samples after stability testing was characterized, from Figure 15 As can be seen from the It test, after maintaining a current density of 100mA for 50h, YNiCoS x The XRD diffraction peaks of the / NCF catalyst were attributed to YS (JCPDS NO.18-1478), Co4S3 (JCPDS NO.02-1338), Ni3S2 (JCPDS NO.27-0341), and NiY (JCPDS NO.65-5276), respectively, which are consistent with the crystal structure of the catalyst before the It test. This indicates that the properties of the catalyst did not change before and after the reaction, which indirectly confirms the YNiCoS x / NCF catalysts exhibit excellent stability in alkaline hydrogen evolution reactions and can adapt to environments with long-term continuous hydrogen evolution.

[0120] In addition, the present invention also investigated the OER performance of the catalysts prepared in Example 1 and Comparative Examples 3-4 in 1M KOH electrolyte. Figure 16 (a) YNiCoS after IR correction x / NCF, NiCoS x Linear sweep voltammetry (LSV) polarization curves of NCF, YNiCo / NCF, NCF and Pt / C catalysts. Figure 16 (b) shows the different catalysts at j 10 j 100 and j 800 Overpotential comparison diagram under current density. Among them, YNiCoS x / NCF exhibits excellent electrocatalytic performance, driving j 10 and j 100 The overpotentials are only 90mV and 290mV, which is significantly lower than that of NiCoS. x / NCF(122mV / j 10 329mV / j 100 ), YNiCo / NCF(314mV / j 10 323mV / j 100 ) and NCF (320mV / j 10 388mV / j 100 In addition, YNiCoS x / NCF maintains j500 and j 800 The high current density requires only 368mV and 399mV overpotentials, respectively, which is superior to RuO2 (429mV / j). 500 482mV / j 800 At high current densities, YNiCoS x / NCF exhibits superior performance compared to RuO2, likely due to the in-situ growth of the catalyst on the foam framework, resulting in better structural stability and stable oxygen evolution at high current densities. This also indirectly confirms the feasibility of the in-situ engineering strategy. The Tafel value reflects information about OER kinetics. Figure 16 (c) shows the output by Figure 16 (a) Calculated Tafel slopes for different catalysts; a smaller Tafel slope suggests a faster reaction kinetic process. It can be seen that YNiCoS x The Tafel slope of / NCF is 114.7mV dec. -1 This is smaller than NiCoS x / NCF(136.4mV dec -1 ), YNiCo / NCF(119.1mV dec) -1 ), NCF (169.2mV dec) -1 ) and RuO2 (160.7mV dec -1 ), indicating that YNiCoS x / NCF catalysts exhibit faster reaction kinetics.

[0121] Electrochemical impedance spectroscopy (EIS) allows us to investigate the reaction kinetics of different catalysts. For example... Figure 16 The electrochemical impedance spectroscopy (EIS) in (d) shows that YNiCoS x The interfacial charge transfer resistance (Rct) of / NCF is only 0.98Ω, which is much smaller than that of NiCoS. x / NCF (1.58Ω), YNiCo / NCF (19.09Ω), NCF (38.59Ω) and RuO2 (2.13Ω), which makes YNiCoS x / NCF catalysts have a faster electron transfer rate, resulting in better catalytic activity.

[0122] Here, we also use mass activity (MA) and time-to-flight (TOF) to evaluate the intrinsic catalytic activity of the catalyst, such as... Figure 16 As shown in (e), YNiCoS x / NCF exhibits significantly higher mass activity than NiCoS at the same voltage. x / NCF and YNiCo / NCF. Specifically, at an overpotential of 300mV, YNiCoSx The mass activity of NCF was 19.6 Ag. -1 And NiCoS x / NCF and YNiCo / NCF each have only 8.0Ag. -1 and 0.8Ag -1 To better investigate the intrinsic activity of the catalysts, we compared the catalyst turnover frequencies, such as... Figure 16 As shown in (f), compared to NiCoS x / NCF and YNiCo / NCF, YNiCoS x / NCF exhibits a higher turnover frequency at the same overpotential. Data from MA and TOF show that the intrinsic catalytic activity of NiCo sulfides is significantly higher than that of the NiCoY alloy, indicating that sulfides are more advantageous than metal alloys in the OER process. Furthermore, the introduction of Y alters the original NiCo sulfide crystal structure, and the in-situ growth of YNiCo heterogeneous metal sulfides on the catalyst surface provides abundant heterogeneous interface structures. This facilitates the regulation of catalytic active sites, resulting in considerable catalytic activity in the OER process, even significantly higher than RuO2 at high current densities. This further confirms that introducing foreign elements can improve the performance and stability of alloys.

[0123] Furthermore, this invention explored the sustainability and long-term stability of the prepared catalyst in the OER process under test conditions similar to HER. Figure 17 (a) is YNiCoS x The It curve of the / NCF catalyst at a current density of 100mA in 1M KOH. It can be seen that the current density decreases after 5h of oxygen evolution reaction, indicating that although the synthesized catalyst has considerable performance in the LSV test of OER, its stability needs to be improved in a continuous oxygen evolution environment.

[0124] On the other hand, YNiCoS x / NCF catalyst, used as both cathode and anode electrodes, can enhance the overall water splitting performance of its dual-electrode system. Figure 17 (b) shows the current density j used to construct the battery. 50 The obtained cell voltage was approximately 1.64V, which is similar to the cell voltage (1.63V) of a cell containing a noble metal Pt / C and RuO2 catalyst. This observation indicates that, through proper design, non-noble metal-based bifunctional catalysts with performance comparable to commercial noble metal catalysts can be prepared, offering hope for replacing noble metal catalysts.

[0125] In summary, this invention successfully synthesized a YNiCo ternary multiphase sulfide with excellent electrical conductivity, structural stability, and hydrolysis performance via a one-step hydrothermal method. At high current densities, its performance even surpasses that of some noble metal-based catalysts. This invention not only explores the influence of the rare earth element yttrium on the structure of non-noble metal-based sulfides and their hydrogen and oxygen evolution performance in water electrolysis, but also provides valuable reference for further research on yttrium in the field of water electrolysis.

[0126] 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 YNiCoS x The method for preparing / NCF catalyst is characterized by, Includes the following steps: Clean the NiCo foam thoroughly and dry it. Y(NO3)2·6H2O, sulfur powder, N2H4 and deionized water are mixed to form a homogeneous mixture. NiCo foam is placed into the mixture and reacted at a certain temperature to obtain YNiCoS. x / NCF; The ratio of Y(NO3)2·6H2O, sulfur powder, N2H4 and deionized water is 0.06~0.18 g : 0.03~0.07 g : 1~4 ml : 18~21 ml.

2. A YNiCoS as described in claim 1 x The method for preparing / NCF catalyst is characterized by, The NiCo foam cleaning method includes: ultrasonically cleaning the NiCo foam with acetone and hydrochloric acid respectively, followed by rinsing with deionized water and anhydrous ethanol alternately.

3. A YNiCoS as described in claim 2 x The method for preparing / NCF catalyst is characterized by, The ultrasonic cleaning time is 10-20 minutes.

4. A YNiCoS as described in claim 1 x The method for preparing / NCF catalyst is characterized by, The ratio of Y(NO3)2·6H2O, sulfur powder, N2H4 and deionized water is 0.1~0.14 g : 0.04~0.06 g : 2~3 ml : 19~20 ml.

5. A YNiCoS as described in claim 1 x The method for preparing / NCF catalyst is characterized by, The ratio of Y(NO3)2·6H2O, sulfur powder, N2H4 and deionized water is 0.12 g : 0.05 g, 2 ml : 20 ml.

6. A YNiCoS as described in claim 1 x The method for preparing / NCF catalyst is characterized by, The mixing process of Y(NO3)2·6H2O, sulfur powder, N2H4 and deionized water includes: first stirring with a magnetic stirrer for 10-20 minutes, followed by ultrasonic treatment at 80-120 W for 10-20 minutes.

7. A YNiCoS as described in claim 1 x The method for preparing / NCF catalyst is characterized by, The reaction temperature is 160~200 ℃, and the reaction time is 5~15 h.

8. A YNiCoS as described in claim 1 x The method for preparing / NCF catalyst is characterized by, The reaction temperature was 180 °C and the reaction time was 10 h.

9. A YNiCoS prepared by the method according to any one of claims 1 to 8 x / NCF catalyst.

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