CoS2 / MoS2 self-supporting heterojunction catalyst and its preparation method and application

Abstract

The present invention discloses a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst and its preparation method and application. Single-crystal CoMoO4 nanorods are synthesized on nickel foam by a hydrothermal method to obtain a precursor CoMoO4 / NF; the precursor CoMoO4 / NF is cut and placed downstream of a tube furnace, and subjected to a thermal vulcanization treatment in an inert atmosphere to obtain a CoS2 / MoS2 / CoMoO4 / NF catalyst. The CoS2 / MoS2 self-supporting heterojunction catalyst provided by the present invention is a bimetallic sulfide heterojunction catalyst, and its components have a synergistic effect, can regulate the electronic state and improve the catalytic activity, and at the same time have more catalytic active sites and excellent SOR catalytic activity. More importantly, the heterojunction of the CoS2 / MoS2 / CoMoO4 / NF catalyst of the present invention is conducive to regulating spin polarization and improving SOR catalytic activity.

Description

Technical Field

[0001] The present invention relates to the fields of new energy material technology and electrochemical catalysis technology, and specifically to a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst; it also relates to a method for preparing the catalyst and its application in the sulfide ion oxidation reaction in electrocatalytic seawater electrolysis to produce hydrogen. Background Art

[0002] Hydrogen has a high energy density (142MJ·kg -1 ), zero carbon emissions and renewability, and is considered to be a very promising clean energy carrier. Seawater electrolysis (SWE) can achieve sustainable production of high-purity hydrogen and help protect scarce freshwater resources. However, the inherent slow kinetics of the anodic oxygen evolution reaction (OER) and the chlorine evolution reaction (CER) limit its development. In this case, small molecule electrocatalytic oxidation instead of slow water oxidation is a promising energy-saving and clean hydrogen production strategy, in which the more thermodynamically favorable sulfur ion oxidation reaction (SOR, S 2- =S+2e - , -0.48V vs.RHE) to replace the anode OER is conducive to reducing the electrolysis voltage to achieve energy-saving hydrogen production, and can also avoid CER. In addition, SOR can quickly degrade sulfur-containing wastewater (0.1 to 4wt.% S 2- ) and converts it into the value-added product S8 without the need for additional oxidants or laborious separation. The hybrid seawater electrolyzer (HSE) constructed by coupling the sulfide oxidation reaction (SOR) with the cathode hydrogen evolution reaction (HER) provides an innovative approach to achieve efficient and energy-saving hydrogen production and degradation of sulfur-containing wastewater, with both economic and environmental benefits.

[0003] However, there are few studies on SOR-assisted water electrolysis for hydrogen production, and since SOR is a complex reaction process involving multiple electron transfers and the formation of multiple polysulfide intermediates, S 2-It is easy to corrode or poison the catalyst, resulting in poor activity and stability of the catalyst, which cannot meet the actual high-current industrial application. Therefore, the development of highly active, stable and low-cost SOR and HER bifunctional catalysts still faces huge challenges. In the prior art, catalysts based on transition metal oxides, phosphides and sulfides have excellent catalytic activity and are widely concerned. Among them, transition metal sulfides are a very promising catalyst in the field of SOR due to their high conductivity and ability to promote the conversion of polysulfides. For example, the journal "Green Chemistry" (DOI: 10.1039 / d1gc01857d) reported that Cu2S microsheet catalysts (Cu2S / NF) supported on nickel foam (NF) substrates were used to catalyze SOR-assisted electrochemical water decomposition, which required a voltage of 0.26V (vs.RHE) to drive 10mA·cm -2 The current density is low, and its catalytic performance is poor. In the journal Chemical Engineering Journal (DOI: 10.1016 / j.cej.2021.134472), a leaf-shaped cobalt-doped nickel sulfide (Co-Ni3S2) was synthesized on a nickel mesh by first using an electrodeposition method, followed by a simple hydrothermal sulfurization. The Co-Ni3S2 electrocatalyst was used for SOR, which drove 100 mA cm -2 The current density required was 0.59 V (vs. RHE) and stable operation for 24 hours, but its catalytic activity and cyclic stability were poor. In summary, existing transition metal-based SOR catalysts have poor catalytic activity and stability, and the development of highly active and stable catalysts still faces great challenges. Summary of the Invention

[0004] In view of the above-mentioned shortcomings, the present invention provides a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst and its preparation method and application. The present invention successfully synthesized a spin-polarized CoS2 / MoS2 heterojunction catalyst on a single crystal CoMoO4 precursor through a hydrothermal method and a thermal sulfurization method. The study found that the bimetallic sulfide heterojunction catalyst has a synergistic effect between its components, which can regulate the electronic state and improve the catalytic activity. At the same time, it has more abundant catalytic active sites and has excellent SOR catalytic activity. More importantly, the present invention found that CoS2 / MoS2 heterogeneity is conducive to regulating spin polarization and improving SOR catalytic activity.

[0005] In order to achieve the above object, the present invention provides a method for preparing a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst, comprising the following steps:

[0006] S1. Preparation of CoMoO4 / NF precursor:

[0007] Co(NO3)2·6H2O and (NH4)6Mo7O 24 4H2O is hydrothermally treated to produce single-crystalline CoMoO4 nanorods on nickel foam NF to obtain a precursor CoMoO4 / NF; wherein the nickel foam NF is pretreated nickel foam;

[0008] Preparation of S2, CoS2 / MoS2 / CoMoO4 / NF catalysts:

[0009] The precursor CoMoO4 / NF is cut and placed downstream of a tube furnace, and subjected to thermal sulfurization treatment in an inert atmosphere to obtain a CoS2 / MoS2 / CoMoO4 / NF catalyst; wherein sublimated sulfur powder is placed upstream of the tube furnace; the CoS2 / MoS2 / CoMoO4 / NF catalyst is a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst.

[0010] According to one aspect of the present invention, in step S1, the temperature of the hydrothermal treatment is 120-150° C., and the time is 4-8 hours.

[0011] According to one aspect of the present invention, in step S1, the Co(NO3)2·6H2O and (NH4)6Mo7O 24 ·4H2O molar ratio is 5:1-9:1.

[0012] According to one aspect of the present invention, in step S1, the pretreatment is specifically: ultrasonicating the nickel foam NF in hydrochloric acid, washing it with deionized water and ethanol for multiple times, and then drying it.

[0013] According to one aspect of the present invention, in step S2, the temperature of the thermal vulcanization treatment is 300-500° C., and the time is 2-5 hours.

[0014] According to one aspect of the present invention, in step S2, the heating rate of the tube furnace is 1-5°C·min -1 .

[0015] According to one aspect of the present invention, in step S2, the inert atmosphere is one or more of nitrogen or argon.

[0016] Based on the same inventive concept, the present invention also provides a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst prepared by any of the above preparation methods.

[0017] Based on the same inventive concept, the present invention also provides an application of a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst prepared by any of the above preparation methods in electrocatalytic seawater electrolysis to produce hydrogen.

[0018] Beneficial effects of the present invention:

[0019] (1) The present invention is the first to successfully synthesize a spin-polarized CoS2 / MoS2 heterojunction catalyst on a single-crystal CoMoO4 precursor by thermal sulfurization, and for the first time to apply this CoS2 / MoS2 heterojunction to the field of sulfur ion oxidation-assisted seawater electrolysis for hydrogen production;

[0020] (2) The CoS2 / MoS2 / CoMoO4 / NF catalyst prepared by the present invention is superior to the reported SOR catalysts (such as Figure 9 As shown in Figure 2, the CoS2 / MoS2 / CoMoO4 / NF catalyst with spin polarization characteristics and interfacial synergistic effect is beneficial to improving the electron transfer rate and more abundant catalytic active sites, thereby improving the SOR catalytic activity;

[0021] (3) The spin polarization characteristics of the CoS2 / MoS2 / CoMoO4 / NF catalyst prepared by the present invention are beneficial to promoting the migration of electrons on the catalyst surface and can improve the adsorption capacity of polysulfide intermediates;

[0022] (4) The CoS2 / MoS2 / CoMoO4 / NF catalyst prepared by the present invention can also operate stably for more than 70 hours under high current, showing excellent stability. The present invention is suitable for large-scale industrial water electrolysis hydrogen production applications;

[0023] (5) The present invention uses a SOR coupled HER hybrid seawater electrolyzer constructed using CoS2 / MoS2 / CoMoO4 / NF catalyst ( Figure 13 ) can simultaneously achieve energy-saving hydrogen production. In addition, SOR can quickly degrade sulfur ions and convert them into high-value sulfur (S8) ( Figure 15 ), achieving the purification of sulfur-rich wastewater without the need for additional oxidants or laborious separation. The invention has economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Flow chart for the preparation of the spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst of the present invention;

[0025] Figure 2 Physical pictures of the pretreated nickel foam NF, CoMoO4 / NF sample and CoS2 / MoS2 / CoMoO4 / NF catalyst prepared in Example 1 of the present invention;

[0026] Figure 3The following are SEM images of the products prepared in Example 1 and Comparative Example 2 of the present invention; wherein (a) is the precursor CoMoO4 / NF sample prepared in Comparative Example 2; (b) is the CoS2 / MoS2 / CoMoO4 / NF catalyst prepared in Example 1;

[0027] Figure 4 HRTEM images of different selected areas of the product prepared in Example 1 of the present invention and HRTEM images of the product prepared in Comparative Example 2; wherein (a) is an HRTEM image of the first selected area of ​​the CoS2 / MoS2 / CoMoO4 / NF catalyst prepared in Example 1; (b) is an HRTEM image of the second selected area of ​​the CoS2 / MoS2 / CoMoO4 / NF catalyst prepared in Example 1; (c) is the precursor CoMoO4 / NF sample prepared in Comparative Example 2;

[0028] Figure 5 The XRD patterns of the final products prepared in Example 1 and Comparative Examples 2-4 of the present invention are shown; wherein (a) is the XRD pattern of the final products obtained in Example 1 and Comparative Example 2; and (b) is the XRD pattern of the final products obtained in Comparative Examples 3-4.

[0029] Figure 6 This is the SOR linear scanning curve of the CoS2 / MoS2 / CoMoO4 / NF catalyst of Example 1 of the present invention in 1.0MNaOH electrolyte containing different concentrations of Na2S;

[0030] Figure 7 The SOR linear scanning curves of the final products prepared in Example 1 and Comparative Examples 2-4 of the present invention in an electrolyte containing 1.0 M Na2S and 1.0 M NaOH;

[0031] Figure 8 Comparison of the SOR and OER linear scan curves of the CoS2 / MoS2 / CoMoO4 / NF catalyst of Example 1 of the present invention;

[0032] Figure 9 This is a comparison chart of the SOR activity of the CoS2 / MoS2 / CoMoO4 / NF catalyst prepared in Example 1 of the present invention and reported;

[0033] Figure 10 The CoS2 / MoS2 / CoMoO4 / NF catalyst of Example 1 of the present invention was heated at a current density of 100 mA·cm -2 SOR stability test curve in 1.0M NaOH+1.0M Na2S electrolyte under the conditions;

[0034] Figure 11The CoS2 / MoS2 / CoMoO4 / NF catalyst of Example 1 of the present invention was heated at a current density of 300 mA·cm -2 SOR stability test curve in 1.0M NaOH+1.0M Na2S electrolyte under the conditions;

[0035] Figure 12 This is the linear scanning curve of the final product prepared in Example 1 and Comparative Examples 2-4 of the present invention in 1.0M NaOH+0.5M NaCl electrolyte;

[0036] Figure 13 This is a physical picture of a hybrid seawater electrolyzer assembled using the CoS2 / MoS2 / CoMoO4 / NF catalyst prepared in Example 1 of the present invention;

[0037] Figure 14 Comparison of the linear scan curves of a hybrid seawater electrolyzer (HSE) assembled with the CoS2 / MoS2 / CoMoO4 / NF catalyst prepared in Example 1 and an alkaline seawater electrolyzer (ASE) according to the present invention;

[0038] Figure 15 The XRD pattern and physical image of the sulfur product obtained from the electrolyte after the CoS2 / MoS2 / CoMoO4 / NF catalyst prepared in Example 1 of the present invention is treated with concentrated sulfuric acid;

[0039] Figure 16 The corresponding density maps of MoS2, CoS2 and CoS2 / MoS2 of the present invention; wherein (a) is a catalyst containing CoS2; (b) is a catalyst containing MoS2; (c) is a catalyst containing CoS2 / MoS2;

[0040] Figure 17 It is the free energy required for each step of SOR catalyzed by MoS2, CoS2 and CoS2 / MoS2 in the present invention. DETAILED DESCRIPTION

[0041] To make the present invention easier to understand, the present invention is further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the professional terms used below are consistent with the meanings understood by professional and technical personnel in this field; unless otherwise specified, the raw materials and reagents involved in this article can be purchased from the market or prepared by known methods.

[0042] The present invention provides a method for preparing a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst, comprising the following steps:

[0043] S1. Preparation of CoMoO4 / NF precursor:

[0044] Co(NO3)2·6H2O and (NH4)6Mo7O 24 4H2O is hydrothermally treated to produce single-crystalline CoMoO4 nanorods on nickel foam NF to obtain a precursor CoMoO4 / NF; wherein the nickel foam NF is pretreated nickel foam;

[0045] Preparation of S2, CoS2 / MoS2 / CoMoO4 / NF catalysts:

[0046] The precursor CoMoO4 / NF is cut and placed downstream of a tube furnace, and subjected to thermal sulfurization treatment in an inert atmosphere to obtain a CoS2 / MoS2 / CoMoO4 / NF catalyst; wherein sublimated sulfur powder is placed upstream of the tube furnace; the CoS2 / MoS2 / CoMoO4 / NF catalyst is a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst.

[0047] In one embodiment of the present invention, in step S1, the temperature of the hydrothermal treatment is 120-150° C., and the time is 4-8 hours.

[0048] In one embodiment of the present invention, in step S1, the Co(NO3)2·6H2O and (NH4)6Mo7O 24 ·4H2O molar ratio is 5:1-9:1.

[0049] In one embodiment of the present invention, in step S1, the amount of Co(NO3)2·6H2O is 1.2-1.8 mmol, (NH4)6Mo7O 24 The amount of 4H2O used is 0.1-0.5mmol.

[0050] In one embodiment of the present invention, in step S1, the pretreatment is specifically: ultrasonicating the nickel foam NF in hydrochloric acid, washing it with deionized water and ethanol for multiple times, and then drying it.

[0051] In one embodiment of the present invention, in step S2, the temperature of the thermal vulcanization treatment is 300-500° C., and the time is 2-5 hours.

[0052] In one embodiment of the present invention, in step S2, the heating rate of the tube furnace is 1-5°C·min -1 .

[0053] In one embodiment of the present invention, in step S2, the inert atmosphere is one or more of nitrogen and argon.

[0054] The following is further described with reference to specific embodiments and comparative examples.

[0055] Example 1

[0056] Preparation of CoS2 / MoS2 / CoMoO4 / NF catalyst, the preparation flow chart is as follows Figure 1 As shown:

[0057] Pretreatment of nickel foam:

[0058] The nickel foam was ultrasonically treated in 3 mol / L hydrochloric acid for 10 minutes to remove surface impurities, then washed with deionized water and ethanol for more than three times, and dried in an oven at 60° C. to obtain pretreated nickel foam NF.

[0059] Preparation of CoMoO4 / NF precursor:

[0060] Weigh 1.5mmol Co(NO3)2·6H2O and 0.3mmol (NH4)6Mo7O 24 4H2O was added to 30mL of deionized water. The pretreated nickel foam NF was placed into the vigorously stirred and thoroughly dissolved solution. The solution was then transferred to a 50mL polytetrafluoroethylene-lined autoclave and maintained at 150°C for 6 hours. After the reaction was complete, the resulting CoMoO4 / NF was rinsed with deionized water and dried at 60°C for 12 hours to obtain a purple precursor CoMoO4 / NF sample.

[0061] Preparation of CoS2 / MoS2 / CoMoO4 / NF catalyst:

[0062] The precursor CoMoO4 / NF obtained by the reaction was cut into 1×1cm 2 The small piece was placed in a porcelain boat, and then the sample was placed downstream of the tube furnace and 0.5g of sublimed sulfur powder was placed upstream. The tube furnace was heated at 2℃·min -1 The tube furnace was heated to 300 °C at a heating rate of 100 °C and maintained in a N2 atmosphere for 2 h. After the tube furnace was cooled to room temperature, the black CoS2 / MoS2 / CoMoO4 / NF catalyst was taken out.

[0063] Among them, the pretreated nickel foam NF, CoMoO4 / NF sample and CoS2 / MoS2 / CoMoO4 / NF catalyst prepared in the above steps are as follows Figure 2 shown.

[0064] Comparative Example 1

[0065] Preparation of pretreated nickel foam NF

[0066] The nickel foam was ultrasonically treated in 3 mol / L hydrochloric acid for 10 minutes to remove surface impurities, then washed with deionized water and ethanol for more than three times, and dried in an oven at 60° C. to obtain pretreated nickel foam NF.

[0067] Comparative Example 2

[0068] Preparation of CoMoO4 / NF precursor

[0069] Pretreatment of nickel foam:

[0070] The nickel foam was ultrasonically treated in 3 mol / L hydrochloric acid for 10 minutes to remove surface impurities, then washed with deionized water and ethanol for more than three times, and dried in an oven at 60° C. to obtain pretreated nickel foam NF.

[0071] Preparation of CoMoO4 / NF precursor:

[0072] Weigh 1.5mmol Co(NO3)2·6H2O and 0.3mmol (NH4)6Mo7O 24 4H2O was added to 30mL of deionized water. The pretreated nickel foam NF was placed into the vigorously stirred and thoroughly dissolved solution. The solution was then transferred to a 50mL polytetrafluoroethylene-lined autoclave and maintained at 150°C for 6 hours. After the reaction was complete, the resulting CoMoO4 / NF was rinsed with deionized water and dried at 60°C for 12 hours to obtain a purple precursor CoMoO4 / NF sample.

[0073] Comparative Example 3

[0074] Preparation of CoS2 / NF catalyst

[0075] Pretreatment of nickel foam:

[0076] The nickel foam was ultrasonically treated in 3 mol / L hydrochloric acid for 10 minutes to remove surface impurities, then washed with deionized water and ethanol for more than three times, and dried in an oven at 60° C. to obtain pretreated nickel foam NF.

[0077] Preparation of CoS2 / NF catalyst:

[0078] Dissolve 6 mmol Co(NO₃)₂·6H₂O, 4 mmol NH₄F, and 20 mmol urea in 40 mL of deionized water. Transfer the resulting solution to a 50 mL container lined with a polytetrafluoroethylene autoclave. Place the pretreated nickel foam NF into the solution and maintain it at 110°C for 8 hours. After the reaction is complete, remove the resulting pink precursor, Co(OH)₂ / NF, wash it several times with deionized water, and dry it in a 60°C oven overnight.

[0079] The Co(OH)2 / NF precursor obtained by the reaction was cut into 1×1cm 2 The small piece was placed in a porcelain boat, and then the sample was placed downstream of the tube furnace and 1.0g of sublimed sulfur powder was placed upstream. The tube furnace was heated at 5℃·min -1 The tube furnace was heated to 400 °C at a heating rate of 100 °C and maintained in a N2 atmosphere for 2 h. After the tube furnace was cooled to room temperature, the black CoS2 / NF catalyst was taken out.

[0080] Comparative Example 4

[0081] Preparation of MoS2 / NF catalyst

[0082] Pretreatment of nickel foam:

[0083] The nickel foam was ultrasonically treated in 3 mol / L hydrochloric acid for 10 minutes to remove surface impurities, then washed with deionized water and ethanol for more than three times, and dried in an oven at 60° C. to obtain pretreated nickel foam NF.

[0084] Preparation of MoS2 / NF catalyst:

[0085] 0.6 g of Na₂MoO₄·2H₂O and 0.7 g of thioacetamide were weighed and dissolved in 40 mL of deionized water with stirring for 2 hours. The solution was then transferred to a 50 mL polytetrafluoroethylene-lined autoclave. The pretreated NF was placed into the solution and maintained at 180°C for 18 hours. After the reaction was complete, the NF was removed, washed several times with deionized water, and dried in a 60°C oven overnight to obtain a black MoS₂ / NF catalyst.

[0086] Performance testing and result analysis:

[0087] Morphological characterization:

[0088] The final materials obtained in Example 1 and Comparative Example 2 were subjected to scanning electron microscope microstructure analysis. Figure 3 ,like Figure 3 As shown in Figure 3, the CoMoO4 nanorod arrays are evenly distributed on the entire nickel foam substrate. After thermal sulfurization, the nanorod morphology of the CoS2 / MoS2 / CoMoO4 / NF catalyst is well maintained, but the nanorods are slightly cracked and their surface becomes rougher.

[0089] The final materials obtained in Example 1 and Comparative Example 2 were subjected to high-resolution transmission electron microscopy microstructure analysis. Figure 4 ,Depend on Figure 4As shown in (c), the present application prepares single-crystal CoMoO4 nanorods on nickel foam NF through hydrothermal treatment. Its obvious single-crystal property can provide a fast transmission path for ions or electrons. As shown in Figure (a), the lattice fringes with a plane spacing of 0.360nm are related to the (002) crystal plane of CoMoO4, the lattice fringes of 0.264nm and 0.252nm are related to the (101) and (102) crystal planes of MoS2, respectively, and the lattice fringes of 0.325nm correspond to the (111) crystal plane of CoS2. Figure 4 (b) shows that the lattice fringes with a lattice spacing of 0.266 nm are associated with the (101) plane of MoS2, while the lattice fringes with lattice spacings of 0.272 nm and 0.275 nm are associated with the (200) plane of CoS2. Notably, the HRTEM image reveals distinct interfaces between CoS2, MoS2, and CoMoO4. This demonstrates that we have successfully prepared a heterojunction CoS2 / MoS2 / CoMoO4 / NF catalyst on the precursor CoMoO4 / NF.

[0090] The final materials obtained in Example 1 and Comparative Examples 2-4 were subjected to XRD analysis. Figure 5 As shown in the figure, the CoMoO4 precursor is mainly composed of three strong diffraction peaks of CoMoO4 (PDF#25-1434) and NF (PDF#87-0712). After thermal sulfurization, the diffraction peaks in the XRD spectrum of the catalyst correspond to CoS2 (PDF#41-1471), MoS2 (PDF#37-1492) and CoMoO4 (PDF#25-1434), which indicates that the precursor CoMoO4 / NF was successfully prepared into a heterojunction CoS2 / MoS2 / CoMoO4 / NF catalyst after thermal sulfurization. In addition, Figure 5 It can be seen that Comparative Examples 3 and 4 successfully prepared CoS2 (PDF#41-1471) catalyst and MoS2 (PDF#37-1492) catalyst.

[0091] Electrochemical performance test:

[0092] The material finally obtained in Example 1 was subjected to three-electrode electrochemical reaction at 2 mV·s in 1.0 M NaOH+0.1 M Na2S, 1.0 M NaOH+0.5 M Na2S and 1.0 M NaOH+1.0 M Na2S solutions. -1 SOR linear sweep voltammetry (LSV) test was performed at a scan rate of Figure 6 ; The results show that the CoS2 / MoS2 / CoMoO4 / NF catalyst finally obtained in Example 1 exhibits excellent SOR activity in 1.0M NaOH electrolyte containing different concentrations of Na2S, and with the increase of S 2-With the increase of ion concentration, SOR activity was significantly enhanced.

[0093] The materials finally obtained from Example 1 and Comparative Examples 2-4 were subjected to a three-electrode reaction at 2 mV·s in 1.0 M NaOH + 1.0 M Na2S. -1 SOR linear sweep voltammetry (LSV) test was performed at a scan rate of Figure 7 , Table 1; CoS2 / MoS2 / CoMoO4 / NF catalyst exhibits excellent SOR activity in 1.0MNaOH+1.0M Na2S electrolyte, requiring only extremely low potentials of 0.258 and 0.326 V vs. RHE to drive current densities of 100 and 300 mA cm -2 , its SOR catalytic activity is significantly better than that of comparative examples 2-4 (CoS2 / NF, MoS2 / NF and CoMoO4 / NF). Figure 7 The catalyst in Example 1 was reacted in 1.0M NaOH+1.0M Na2S with a three-electrode at 2mV·s -1 The SOR linear sweep voltammetry (LSV) test was performed at a scan rate of 1.5 % and compared with the OER linear sweep voltammetry (LSV) test under the same conditions. The results are shown in Figure 2. Figure 8 As shown by Figure 8 It can be seen that the linear scanning curves of CoS2 / MoS2 / CoMoO4 / NF catalyst in 1.0M NaOH electrolyte with or without Na2S can reach 100 and 300 mA·cm -2 At the current density of 1.55 and 1.67 V vs. RHE, the voltage required for OER is 1.55 and 1.67 V vs. RHE. However, when 1.0 M Na2S is added to the alkaline electrolyte, the anode SOR potential required to achieve the same current density is greatly reduced to 0.258 and 0.326 V, indicating that SOR replacing OER is beneficial to achieve energy-saving hydrogen production.

[0094] Table 1 Different catalysts driving 100 mA·cm -2 and 300mA·cm -2 The voltage required for the current density

[0095]

[0096] The CoS2 / MoS2 / CoMoO4 / NF catalyst obtained in Example 1 was subjected to chronoamperometry (CP) in a three-electrode system in a 1.0 M NaOH+1.0 M Na2S solution at 100 mA cm -2 and 300mA·cm -2 Stability test was carried out at a current density of Figure 10-11; It shows that the CoS2 / MoS2 / CoMoO4 / NF catalyst of Example 1 has excellent stability and high current density of 300mA cm -2 It can run stably for more than 70 hours under high temperature and can meet the requirements of large current applications in actual industrialization.

[0097] The materials finally obtained from Example 1 and Comparative Examples 2-4 were subjected to a three-electrode reaction at 2 mV·s in 1.0 M NaOH + 0.5 M NaCl. -1 HER linear sweep voltammetry (LSV) test was performed at a scan rate of Figure 12 The CoS2 / MoS2 / CoMoO4 / NF catalyst only requires potentials of 0.204 and 0.286 V vs. RHE to drive current densities of 100 and 300 mA cm in 1.0 M NaOH + 0.5 M NaCl electrolyte. -2 , and its HER catalytic activity is significantly better than that of CoS2 / NF and CoMoO4 / NF.

[0098] Based on the high HER and SOR activity of the CoS2 / MoS2 / CoMoO4 / NF catalyst prepared in Example 1, it was used for hydrogen evolution from seawater at the cathode (1.0 M NaOH + 0.5 M NaCl) and sulfur ion oxidation at the anode (1.0 M NaOH + 1.0 M Na2S). Figure 13 The hybrid seawater electrolyzer (HSE) shown in FIG. can realize energy-saving hydrogen production from seawater and sulfur-containing wastewater treatment. Figure 13 As shown, the cation exchange membrane (Nafion 117) is Na + Provide channels to separate the cathode and anode regions. Figure 14 As shown, HSE only needs a low voltage of 0.772V to reach 100mA·cm -2 ,Compared with the voltage of 1.733V required by the alkaline seawater tank, ,HSE reduces the energy consumption by 56%.,SOR assisted seawater electrolysis can achieve the effect of energy-saving ,hydrogen production.

[0099] The electrolyte of the catalyst prepared in Example 1 after 80h CP test in SOR was treated with concentrated sulfuric acid: concentrated H2SO4 solution was dripped into the electrolyte after SOR in an ice bath until the pH was 1. Sulfur was precipitated as a yellow product and separated by filtration to obtain a light yellow powder product ( Figure 15 In addition, Figure 15 The XRD spectrum of the product confirmed that the powder collected by acid treatment corresponds to elemental sulfur (S8, PDF#78-1889).

[0100] DFT theoretical calculations were used to study the SOR activity on different polysulfide intermediates, namely MoS2, CoS2 and CoS2 / MoS2. Figure 16 This indicates that compared to MoS2, spin-polarized CoS2 and CoS2 / MoS2 require lower energy barriers at each step of the SOR reaction. More importantly, the energy barrier that CoS2 / MoS2 needs to overcome is lower, indicating that the CoS2 / MoS2 heterojunction catalyst is more conducive to the adsorption of sulfur and the catalysis of polysulfides and has excellent SOR catalytic performance. Figure 16 (a)-(c) show that there are significant differences in the local DOS around the Fermi level (EF). The wide band gap of MoS2 at the Fermi level limits its electron transfer. However, CoS2 and CoS2 / MoS2 have no band gap at the Fermi level and exhibit high conductivity. In addition, Figure 16 Figures (a) and 16 (c) show a significant difference in the density of states of spin-up and spin-down electrons near the Fermi level EF, indicating that CoS2 and CoS2 / MoS2 are spin-polarized magnetic materials. This spin-polarized property is beneficial for promoting the migration of electrons on the catalyst surface and improving the adsorption capacity of polysulfide intermediates.

[0101] Experiments and DFT calculations reveal that the heterojunction modulates the spin polarization of CoS2 / MoS2, optimizes the free energy and adsorption energy of the reaction intermediates, and thus enhances the SOR activity. Figure 16 and Figure 12 As shown in Figure 2, compared with CoS2 and MoS2, the spin-polarized heterojunction catalyst containing CoS2 / MoS2 has better SOR and HER activities. Figure 11 As shown, CoS2 / MoS2 / CoMoO4 / NF can operate stably for more than 70 hours even at high current, showing excellent stability. The present invention is suitable for large-scale industrial water electrolysis hydrogen production applications.

[0102] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst, characterized in that: The following steps are involved: S1. Preparation of CoMoO4 / NF precursor: Co(NO3)2·6H2O and (NH4)6Mo7O 24 4H2O is hydrothermally treated to produce single-crystalline CoMoO4 nanorods on nickel foam NF to obtain a precursor CoMoO4 / NF; wherein the nickel foam NF is pretreated nickel foam; Preparation of S2, CoS2 / MoS2 / CoMoO4 / NF catalysts: The precursor CoMoO4 / NF is cut and placed downstream of a tube furnace, and subjected to thermal sulfurization treatment in an inert atmosphere to obtain a CoS2 / MoS2 / CoMoO4 / NF catalyst; wherein sublimated sulfur powder is placed upstream of the tube furnace; the CoS2 / MoS2 / CoMoO4 / NF catalyst is a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst.

2. The method for preparing a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst according to claim 1, characterized in that: In step S1, the temperature of the hydrothermal treatment is 120-150° C., and the time is 4-8 hours.

3. The method for preparing a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst according to claim 2, characterized in that: In step S1, the Co(NO3)2·6H2O and (NH4)6Mo7O 24 ·4H2O molar ratio is 5:1-9:

1.

4. The method for preparing a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst according to claim 1, characterized in that: In step S1, the pretreatment specifically includes: ultrasonicating the nickel foam NF in hydrochloric acid, washing it with deionized water and ethanol for multiple times, and then drying it.

5. The method for preparing a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst according to claim 1, characterized in that: In step S2, the temperature of the thermal vulcanization treatment is 300-500° C., and the time is 2-5 hours.

6. The method for preparing a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst according to claim 1, characterized in that: In step S2, the heating rate of the tube furnace is 1-5°C·min -1 .

7. The method for preparing a spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst according to claim 1, characterized in that: In step S2, the inert atmosphere is one or more of nitrogen and argon.

8. A spin-polarized CoS2 / MoS2 self-supporting heterojunction catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of a CoS2 / MoS2 self-supporting heterojunction catalyst prepared by the preparation method according to any one of claims 1 to 7 or the CoS2 / MoS2 self-supporting heterojunction catalyst according to claim 8 in electrocatalytic seawater electrolysis to produce hydrogen.

Images