A self-supporting one-dimensional nanorod array composite material, its preparation method and application

Abstract

This invention provides a self-supporting one-dimensional nanorod array composite material, its preparation method, and its application, belonging to the field of clean energy harvesting technology. The preparation method provided by this invention includes the following steps: mixing soluble nickel salt, soluble molybdate, and water, and carrying out a hydrothermal reaction to obtain a NiMo precursor; heat-treating the NiMo precursor and a modifier under a protective atmosphere to obtain the self-supporting one-dimensional nanorod array composite material. Experimental results show that the composite material prepared by the method provided by this invention has excellent electrocatalytic water splitting activity and operational stability, and photo-assisted synthesis further enhances the electrocatalytic water splitting activity of the composite material, making it applicable to solar-driven electrocatalytic water splitting.

Description

Technical Field

[0001] This invention relates to the field of clean energy harvesting technology, and in particular to a self-supporting one-dimensional nanorod array composite material, its preparation method, and its application. Background Technology

[0002] Currently, the ever-increasing energy demands and unbearable environmental pressures of industrial society make the development of clean energy conversion and storage technologies an urgent priority. Solar-driven electrocatalytic water splitting, with its high theoretical energy conversion efficiency, is considered a promising option for solving the energy crisis. Noble metal-based materials are relatively ideal water electrolysis catalysts; however, their natural scarcity, high cost, and instability limit their further large-scale application. Therefore, the rational development of low-cost, highly active, and stable water splitting electrocatalysts to replace noble metal-based materials is crucial.

[0003] There are two main methods for designing and improving the catalytic activity of catalysts. On the one hand, catalyst activity can be improved by controlling the morphology (such as nanowires, nanosheets, and heterostructures) and growth substrate to increase the number of supported active sites, conductivity, and stability of the electrocatalyst. On the other hand, catalyst activity can be improved by enhancing the inherent catalytic properties of each site, for example, through interface engineering, cation engineering, defect engineering, and multi-anion engineering.

[0004] Due to limitations such as low loading mass, easy agglomeration, and unavoidable use of polymer binders, powdered electrocatalysts often suffer from low loading capacity, agglomeration, and the unavoidable use of polymer binders. Therefore, constructing nanoarrays on conductive substrates (such as metal foams, carbon cloth, and metal foils) to form self-supporting electrodes is considered an effective strategy to avoid the defects of powdered materials. This not only increases the specific surface area and catalyst loading but also provides a "high-speed" channel for electron transport. Furthermore, uniformly arranged nanoarrays facilitate the diffusion of electrolytes and bubbles. Currently, research on multi-heterointerface and multi-anion electrocatalysts, including transition metal carbides / borides / nitrides / oxides / selenides / phosphides, has been extensively studied. Among these electrocatalysts, transition metal phosphides (TMPs) are considered promising because they exhibit high activity and stability. The metal and phosphorus atoms on the surface of metal phosphides act as proton and electron acceptor centers, improving the electronic structure of these electrocatalysts. Meanwhile, transition metals (TMDCs), especially Ni and Mo, have become important candidates for water splitting electrocatalysts due to their high electronic conductivity and theoretically high catalytic activity. Despite the significant advantages of combining Ni and Mo, the activity and stability of most NiMo-based electrocatalysts still fall far short of the requirements for practical applications. Summary of the Invention

[0005] The purpose of this invention is to provide a self-supporting one-dimensional nanorod array composite material, its preparation method, and its applications. The self-supporting one-dimensional nanorod array composite material provided by this invention enables the combination of NiMo-based materials and phosphorus sulfidation, exhibiting excellent electrocatalytic water splitting activity and operational stability.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a self-supporting one-dimensional nanorod array composite material, comprising the following steps:

[0008] Soluble nickel salt, soluble molybdate, and water are mixed and subjected to a hydrothermal reaction to obtain the NiMo precursor.

[0009] The NiMo precursor and modifier were heat-treated under a protective atmosphere to obtain the self-supporting one-dimensional nanorod array composite material.

[0010] Preferably, the mass ratio of the soluble nickel salt to the soluble molybdate is (0.605–1.05):(0.862–1.362).

[0011] Preferably, the mixing is carried out under stirring conditions;

[0012] The stirring time is 20 to 50 minutes.

[0013] Preferably, the hydrothermal reaction is carried out at a temperature of 120–180°C for 6–12 hours.

[0014] Preferably, after the hydrothermal reaction is completed, the process further includes sequential washing and drying;

[0015] The drying temperature is 60–80°C, and the time is 6–12 hours.

[0016] Preferably, the modifier comprises hypophosphite and / or elemental sulfur.

[0017] Preferably, the mass ratio of the hypophosphite to the total mass of the modifier is (0-1):1.

[0018] Preferably, the heat treatment temperature is 300–500°C, the holding time is 1–3 hours, and the heating rate to the heat treatment temperature is 2–5°C / min.

[0019] The present invention also provides a self-supporting one-dimensional nanorod array composite material prepared by the preparation method described above, wherein the surface of the nanorods in the self-supporting one-dimensional nanorod array composite material is a modified layer;

[0020] The diameter of the nanorods is 1.25–2.85 μm, and the thickness of the modified layer is 25–80 nm.

[0021] The modified layer is a phosphorus-sulfurized modified layer, a phosphorus-modified modified layer, or a sulfur-modified modified layer.

[0022] The present invention also provides the application of the self-supporting one-dimensional nanorod array composite material described above in solar-driven electrocatalytic water splitting.

[0023] This invention provides a method for preparing a self-supporting one-dimensional nanorod array composite material, comprising the following steps: mixing soluble nickel salt, soluble molybdate and water, and carrying out a hydrothermal reaction to obtain a NiMo precursor; and heat-treating the NiMo precursor and a modifier under a protective atmosphere to obtain the self-supporting one-dimensional nanorod array composite material. The method for preparing a self-supporting one-dimensional nanorod array composite material provided by this invention involves heat treatment of a NiMo precursor. This process disrupts some of the NiMo precursor's surface structure upon high-temperature heating, leading to dehydration / oxidation and the generation of a large amount of Mo oxide on the nanorod surface. This Mo oxide reacts with a modifier to form a multiphase heterogeneous structure. This results in a self-supporting one-dimensional nanorod array composite material that not only inherits the excellent physicochemical properties of the NiMo precursor but also generates abundant active sites after modification, enhancing its electrocatalytic water splitting activity. The strong interfacial contact between the modified layer and the NiMo precursor in the composite material obtained after heat treatment provides better interfacial coupling, further improving ion and electron transport. The modification process allows the active sites to preferentially grow along the surface of the NiMo precursor nanorods, forming a smooth and uniform deposition surface. This not only increases the contact area between the active surface and the electrolyte but also achieves excellent stability during long-term operation. Experimental results show that the composite material prepared by the method provided by this invention, when subjected to hydrogen evolution reaction with 1 mol / L KOH solution as the electrolyte, exhibits good performance at a current density of 10 mA / cm². 2 ~100mA / cm 2 At this time, the overpotential can reach 35mV to 233mV; using 1mol / L KOH solution as the electrolyte for the oxygen evolution reaction, at a current density of 10mA / cm², the overpotential can reach 35mV to 233mV; 2 ~100mA / cm 2 At this time, the overpotential can reach 211.8mV~288mV; using composite materials as the anode and cathode of the electrolytic cell, electrocatalytic water splitting was carried out in a 1mol / L KOH solution at a current density of 10mA / cm². 2 ~100mA / cm 2 The voltage can reach 1.391V to 1.711V, exhibiting excellent electrocatalytic water splitting activity and operational stability.

[0024] This invention combines NiMo-based materials with phosphorus sulfide, endowing the composite material with excellent physicochemical properties and abundant phosphorus sulfide active sites. This enhances the electrocatalytic water splitting activity of the composite material, and it can also be applied to solar-driven electrocatalytic water splitting, where solar energy can further improve catalytic activity. Experimental results show that the self-supporting one-dimensional nanorod array composite material provided by this invention exhibits photo-assisted electrocatalytic hydrogen evolution reaction in 1 mol / L KOH solution at a current density of 10 mA / cm². 2 ~100mA / cm 2 At this time, the overpotential under light assistance can reach 44mV to 190mV; in the photo-assisted electrocatalytic oxygen evolution reaction in 1 mol / L KOH solution, at a current density of 10 mA / cm², the overpotential can reach 44mV to 190mV. 2 ~100mA / cm 2 At this time, the overpotential under light assistance can reach 180mV~242.8mV; in 1mol / L KOH solution, light-assisted electrocatalytic water splitting at a current density of 10mA / cm³ can achieve an overpotential of 180mV~242.8mV. 2 ~100mA / cm 2 When the photo-assisted potential reaches 1.239V to 1.629V, it indicates that photo-assisted electrocatalytic water splitting activity of the composite material is significantly improved. Attached Figure Description

[0025] Figure 1 A scanning electron microscope image of the composite material prepared in Example 1 of this invention;

[0026] Figure 2 The X-ray diffraction patterns are those of the materials prepared in Examples 1-3 and the comparative examples of this invention.

[0027] Figure 3 Linear voltammetric curves of the hydrogen evolution reaction of nickel foam and 20 wt% Pt / C in 1 mol / L KOH solution for the materials prepared in Examples 1-3 and the comparative examples of the present invention;

[0028] Figure 4 Linear voltammetric curves of oxygen evolution reaction of nickel foam and RuO2 in 1 mol / L KOH solution for the materials prepared in Examples 1-3 and the comparative examples of the present invention;

[0029] Figure 5 The linear voltammetric curves of the composite material prepared in Example 1 of this invention and Pt / C||RuO2 in 1 mol / L KOH solution for electrocatalytic water splitting are shown.

[0030] Figure 6 The linear voltammetric curve of the composite material prepared in Example 1 of this invention and 20 wt% Pt / C in 1 mol / L KOH solution for photo-assisted electrocatalytic hydrogen evolution reaction is shown.

[0031] Figure 7 The linear voltammetric curve of the composite material prepared in Example 1 of this invention and RuO2 in 1 mol / L KOH solution for photo-assisted electrocatalytic oxygen evolution reaction is shown.

[0032] Figure 8 The linear voltammetric curves of the composite material prepared in Example 1 of this invention and Pt / C||RuO2 in 1 mol / L KOH solution for photo-assisted electrocatalytic water splitting are shown.

[0033] Figure 9 An optical photograph of the composite material prepared according to one embodiment of the present invention, showing solar-driven integral water splitting. Detailed Implementation

[0034] This invention provides a method for preparing a self-supporting one-dimensional nanorod array composite material, comprising the following steps:

[0035] Soluble nickel salt, soluble molybdate, and water are mixed and subjected to a hydrothermal reaction to obtain the NiMo precursor.

[0036] The NiMo precursor and modifier were heat-treated under a protective atmosphere to obtain the self-supporting one-dimensional nanorod array composite material.

[0037] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0038] This invention involves mixing soluble nickel salt, soluble molybdate, and water, and then carrying out a hydrothermal reaction to obtain a NiMo precursor.

[0039] In this invention, the preferred mass ratio of the soluble nickel salt to the soluble molybdate is (0.605–1.05):(0.862–1.362), more preferably (0.705–1.005):(0.962–1.262), and even more preferably (0.8–0.9):(1.1–1.22). Limiting the mass ratio of the soluble nickel salt to the soluble molybdate to the above range is more advantageous for obtaining a NiMo precursor with a one-dimensional nanorod array structure.

[0040] In this invention, the preferred volume ratio of the soluble nickel salt, the soluble molybdate, and water is (0.605–1.05) g : (0.862–1.362) g : (40–80) mL, more preferably (0.705–1.005) g : (0.962–1.262) g : (45–75) mL, and even more preferably (0.8–0.9) g : (1.1–1.22) g : (50–70) mL. This invention limits the volume ratio of the soluble nickel salt, the soluble molybdate, and water to the above ranges to ensure the formation of a NiMo precursor with a one-dimensional nanorod array structure.

[0041] In this invention, the soluble nickel salt is preferably NiCl2·6H2O; the soluble molybdate is preferably (NH4)6Mo7O. 24 • 4H₂O; the water is preferably deionized water. This invention limits the soluble nickel salt, soluble molybdate, and water to the above-mentioned types to better facilitate the hydrothermal reaction.

[0042] In this invention, the mixing is preferably carried out under stirring conditions; the stirring time is preferably 20-50 min, more preferably 30-50 min; the stirring speed is preferably 1000-2500 rpm / min; and the stirring temperature is preferably room temperature. This invention does not impose any special limitations on the stirring equipment and operation; equipment and operation familiar to those skilled in the art can be used.

[0043] In this invention, the temperature of the hydrothermal reaction is preferably 120–180°C, more preferably 140–160°C; the time of the hydrothermal reaction is preferably 6–12 h, more preferably 6–8 h. Limiting the temperature and time of the hydrothermal reaction to the above ranges allows for a more complete hydrothermal reaction, which is beneficial for obtaining a NiMo precursor with a one-dimensional nanorod array structure.

[0044] In this invention, the heating rate to the hydrothermal reaction temperature is preferably 4–7 °C / min, more preferably 5–6 °C / min. Limiting the heating rate to the hydrothermal reaction temperature to the above range in this invention is beneficial for obtaining a NiMo precursor with a one-dimensional nanorod array structure.

[0045] In this invention, the hydrothermal reaction is preferably carried out in a hydrothermal reactor; the hydrothermal reactor also includes nickel foam vertically fixed to the bottom of the reactor; the nickel foam is preferably cleaned before use. This invention does not have specific limitations on the cleaning steps for the nickel foam; cleaning operations well known to those skilled in the art can be used.

[0046] In this invention, after the hydrothermal reaction is completed, it is preferable to further include washing and drying in sequence.

[0047] In this invention, the washing process preferably involves sequentially washing with anhydrous ethanol and deionized water; more preferably, the hydrothermal reaction product is washed with anhydrous ethanol 3-5 times, followed by washing with deionized water 3-5 times. This invention effectively removes excess ions from the hydrothermal reaction product through the above washing operations.

[0048] In this invention, the drying is preferably carried out under vacuum conditions; the drying temperature is preferably 60–80°C, more preferably 60–75°C, and even more preferably 60–70°C; the drying time is preferably 6–12 hours, more preferably 8–12 hours, and even more preferably 10–12 hours. Setting the drying temperature and time within the above ranges allows for better drying of the NiMo precursor.

[0049] In this invention, the structure of the NiMo precursor is preferably a one-dimensional nanorod array structure, more preferably a tetragonal prism nanorod array. This invention limits the structure of the NiMo precursor to the above-mentioned structure, which is beneficial for obtaining self-supporting one-dimensional nanorod array composite materials.

[0050] After obtaining the NiMo precursor, the present invention heat-treats the NiMo precursor and the modifier under a protective atmosphere to obtain the self-supporting one-dimensional nanorod array composite material.

[0051] In this invention, the modifier preferably comprises hypophosphite and / or elemental sulfur, more preferably hypophosphite and elemental sulfur. By limiting the modifier to the above-mentioned types, this invention ensures the formation of abundant activation sites on the NiMo precursor surface.

[0052] In this invention, the preferred mass ratio of hypophosphite to the total mass of the modifier is (0-1):1, more preferably 0.67:1. By limiting the mass ratio of hypophosphite to the total mass of the modifier to the above range, this invention allows for better modification of the NiMo precursor by P and S elements.

[0053] In this invention, the hypophosphite is preferably sodium hypophosphite monohydrate; the elemental sulfur is preferably sulfur powder. Limiting the hypophosphite and elemental sulfur to the aforementioned types ensures the phosphorus-sulfurization modification of the NiMo precursor.

[0054] In this invention, the protective atmosphere is preferably a high-purity nitrogen atmosphere. By setting a protective atmosphere, this invention can avoid introducing impurities into the composite material, thus preventing any impact on the composite material's catalytic performance.

[0055] In this invention, the heat treatment is preferably carried out in a horizontal tube furnace.

[0056] The preferred method of heat-treating the NiMo precursor, hypophosphite, and elemental sulfur under a protective atmosphere in this invention is to place the NiMo precursor downstream of a tube furnace and the hypophosphite and elemental sulfur upstream of the furnace, and then perform heat treatment under a protective atmosphere. By placing the NiMo precursor, hypophosphite, and elemental sulfur separately, this invention ensures that the PH3 and H2S gases generated by the hypophosphite and elemental sulfur fully react with the NiMo precursor and preferentially grow on the surface of the NiMo precursor nanorods, forming a smooth and uniform deposition surface, thereby improving the catalytic performance and operational stability of the composite material.

[0057] In this invention, the NiMo precursor is preferably placed in a small ceramic boat downstream of the tube furnace; the hypophosphite and elemental sulfur are preferably placed in separate small ceramic boats upstream of the tube furnace. This invention does not impose any particular limitation on the placement of the hypophosphite and elemental sulfur upstream of the tube furnace, as long as their positions relative to the NiMo precursor are upstream of the tube furnace. This separate placement facilitates the formation of a smooth and uniform deposition surface.

[0058] In this invention, the heat treatment temperature is preferably 300–500°C, more preferably 350–450°C, and even more preferably 300–350°C; the heat treatment time is preferably 1–3 h, more preferably 1–2.5 h, and even more preferably 2–2.5 h; the heating rate to the heat treatment temperature is preferably 2–5°C / min, more preferably 2–4.5°C / min, and even more preferably 2–3°C / min. This invention, through heat treatment, can destroy some of the structural components of the NiMo precursor surface after high-temperature heating. After dehydration / oxidation, a large amount of Mo oxide is generated on the nanorod surface. The sublimated elemental sulfur decomposes into H2S under a nitrogen atmosphere, and hypophosphite decomposes into PH3. The H2S and PH3 gases react with the components on the nanorod surface to form a heterogeneous structure, generating abundant phosphorus sulfide active sites and improving the catalytic performance of the composite material.

[0059] In this invention, the heat treatment is preferably followed by a cooling treatment after completion; the present invention does not have a special limitation on the cooling treatment process, and any cooling process known to those skilled in the art can be used.

[0060] This invention involves heat-treating the NiMo precursor, which disrupts some of its surface structure upon high-temperature heating. Following dehydration / oxidation, a large amount of Mo oxide is generated on the nanorod surface, reacting with a modifier to form a multiphase heterogeneous structure. This results in a self-supporting one-dimensional nanorod array composite material that not only inherits the excellent physicochemical properties of the NiMo precursor but also generates abundant active sites after modification, enhancing its electrocatalytic water splitting activity. The robust interfacial contact between the modified layer and the NiMo precursor in the heat-treated composite material provides better interfacial coupling, further improving ion and electron transport. Simultaneous modification allows the active sites to preferentially grow along the surface of the NiMo precursor nanorods, forming a smooth and uniform deposition surface. This not only increases the contact area between the active surface and the electrolyte but also achieves excellent stability during long-term operation.

[0061] The present invention also provides a self-supporting one-dimensional nanorod array composite material prepared by the preparation method described above. The structure of the self-supporting one-dimensional nanorod array composite material is preferably a tetragonal prism nanorod array structure. The surface of the nanorods in the self-supporting one-dimensional nanorod array composite material is a modified layer. The diameter of the nanorods is 1.25-2.85 μm, and the thickness of the modified layer is 25-80 nm. The modified layer is one of a phosphorus-sulfurized modified layer, a phosphorus-modified modified layer, or a sulfur-modified modified layer, preferably a phosphorus-sulfurized modified layer.

[0062] The present invention also provides the application of the self-supporting one-dimensional nanorod array composite material described in the above technical solution in solar-driven electrocatalytic water splitting.

[0063] This invention combines NiMo-based materials with phosphorus sulfide to endow the composite material with excellent physicochemical properties and abundant phosphorus sulfide active sites, which can enhance the electrocatalytic water splitting activity of the composite material. Furthermore, the composite material can also be applied to solar-driven electrocatalytic water splitting, where solar energy can enhance catalytic activity.

[0064] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0065] Example 1

[0066] A method for preparing a self-supporting one-dimensional nanorod array composite material comprises the following steps:

[0067] 0.855 g of nickel chloride hexahydrate, 1.112 g of ammonium molybdate tetrahydrate and 60 mL of deionized water were mixed and magnetically stirred for 30 min at room temperature to obtain a light green homogeneous solution; the stirring speed was 1500 rpm / min.

[0068] The cleaned nickel foam was vertically fixed at the bottom of a 100mL polytetrafluoroethylene-lined reactor. The resulting light green homogeneous solution was poured into the reactor and kept at 160℃ for 6 hours in a hydrothermal oven to carry out the hydrothermal reaction. After the hydrothermal reaction was completed, the hydrothermal reaction product was washed three times with anhydrous ethanol, and then washed three times with deionized water. Finally, it was dried in a vacuum oven at 60℃ for 12 hours to obtain the NiMo precursor. The heating rate to the hydrothermal reaction temperature was 5℃ / min.

[0069] The NiMo precursor was placed in a small porcelain boat and positioned downstream of a tube furnace. 1.0 g of sodium hypophosphite monohydrate and 0.5 g of sulfur powder were placed in different small porcelain boats and positioned upstream of the tube furnace. The furnace was then subjected to heat treatment under high-purity nitrogen at a temperature of 300 °C for 2 h. The heating rate to the heat treatment temperature was 2 °C / min. The self-supporting one-dimensional nanorod array composite material was obtained and denoted as NiMo-(S,P)@NF composite material.

[0070] The prepared NiMo-(S,P)@NF composite material was observed by scanning electron microscopy, and the obtained SEM images are as follows: Figure 1 As shown;

[0071] from Figure 1 As can be seen, the morphology of the NiMo-(S,P)@NF material is a tetragonal prism nanorod array. The nanorods have a uniform diameter of 1.25 to 1.55 μm, and the surface of the nanorods is a phosphorus sulfide modified layer with a thickness of 40 nm.

[0072] Example 2

[0073] A method for preparing a self-supporting one-dimensional nanorod array composite material comprises the following steps:

[0074] 0.605 g of nickel chloride hexahydrate, 0.862 g of ammonium molybdate tetrahydrate, and 50 mL of deionized water were mixed and magnetically stirred for 20 min at room temperature to obtain a pale green homogeneous solution; the stirring speed was 1000 rpm / min.

[0075] The cleaned nickel foam was vertically fixed at the bottom of a 100mL polytetrafluoroethylene-lined reactor. The resulting light green homogeneous solution was poured into the reactor, and the mixture was kept at 120℃ for 12 hours in a hydrothermal oven to carry out the hydrothermal reaction. After the hydrothermal reaction was completed, the hydrothermal reaction product was washed three times with anhydrous ethanol, and then washed three times with deionized water. Finally, it was dried in a vacuum oven at 70℃ for 10 hours to obtain the NiMo precursor. The heating rate to the hydrothermal reaction temperature was 4℃ / min.

[0076] The NiMo precursor was placed in a small porcelain boat and placed downstream of a tube furnace. 1.5g of sulfur powder was placed in different small porcelain boats and placed upstream of the tube furnace. Heat treatment was carried out under high-purity nitrogen at a temperature of 350℃ for 1.5h. The heating rate to the heat treatment temperature was 3℃ / min. The self-supporting one-dimensional nanorod array composite material was obtained, denoted as NiMo-S@NF composite material.

[0077] The morphology of the NiMo-S@NF composite material is similar to that of Example 1, which is a tetragonal prism nanorod array structure. The nanorods have a uniform diameter of 1.65 to 1.85 μm and a sulfurized modified layer on the surface of the nanorods with a thickness of 50 nm.

[0078] Example 3

[0079] A method for preparing a self-supporting one-dimensional nanorod array composite material comprises the following steps:

[0080] 0.9 g of nickel chloride hexahydrate, 1.212 g of ammonium molybdate tetrahydrate and 70 mL of deionized water were mixed and magnetically stirred for 40 min at room temperature to obtain a light green homogeneous solution; the stirring speed was 2000 rpm / min.

[0081] The cleaned nickel foam was vertically fixed at the bottom of a 100mL polytetrafluoroethylene-lined reactor. The resulting light green homogeneous solution was poured into the reactor and kept at 140℃ for 10 hours in a hydrothermal oven to carry out the hydrothermal reaction. After the hydrothermal reaction was completed, the hydrothermal reaction product was washed three times with anhydrous ethanol, and then washed three times with deionized water. Finally, it was dried in a vacuum oven at 75℃ for 8 hours to obtain the NiMo precursor. The heating rate to the hydrothermal reaction temperature was 6℃ / min.

[0082] The NiMo precursor was placed in a small porcelain boat and placed downstream of a tube furnace. 1.5g of sodium hypophosphite monohydrate was placed in different small porcelain boats and placed upstream of the tube furnace. The furnace was then subjected to heat treatment under high-purity nitrogen at a temperature of 400℃ for 3 hours. The heating rate to the heat treatment temperature was 4℃ / min. The self-supporting one-dimensional nanorod array composite material was obtained and denoted as NiMo-P@NF composite material.

[0083] The morphology of the NiMo-P@NF composite material is similar to that of Example 1, which is a tetragonal prism nanorod array structure with a uniform diameter of 2.05 to 2.35 μm. The surface of the nanorods is a phosphating modified layer with a thickness of 35 nm.

[0084] Comparative Example

[0085] A method for preparing a self-supporting one-dimensional nanorod array composite material comprises the following steps:

[0086] 1.05 g of nickel chloride hexahydrate, 1.362 g of ammonium molybdate tetrahydrate and 80 mL of deionized water were mixed and magnetically stirred for 50 min at room temperature to obtain a light green homogeneous solution; the stirring speed was 2500 rpm / min.

[0087] The cleaned nickel foam was vertically fixed at the bottom of a 100mL polytetrafluoroethylene-lined reactor. The resulting light green homogeneous solution was poured into the reactor and kept at 180℃ for 8 hours in a hydrothermal oven to carry out the hydrothermal reaction. After the hydrothermal reaction was completed, the hydrothermal reaction product was washed three times with anhydrous ethanol, and then washed three times with deionized water. Finally, it was dried in a vacuum oven at 80℃ for 6 hours to obtain the NiMo precursor. The heating rate to the hydrothermal reaction temperature was 7℃ / min.

[0088] The NiMo precursor was placed in a small porcelain boat and placed downstream of a tube furnace. It was then heat-treated under high-purity nitrogen at a temperature of 500°C for 1 hour. The heating rate to the heat treatment temperature was 5°C / min. The self-supporting one-dimensional nanorod array material was obtained, denoted as NiMo@NF material.

[0089] The morphology of the NiMo@NF material is similar to that of Example 1, which is a tetragonal prism nanorod array structure with uniform nanorod diameters of 2.40–2.85 μm.

[0090] X-ray diffraction analysis was performed on the materials prepared in Examples 1-3 and the comparative examples, and the obtained XRD patterns are as follows: Figure 2 As shown.

[0091] from Figure 2As can be seen from the data, the NiMo-(S,P)@NF composite material contains characteristic peaks of β-NiMoO4 (45-0142), α-NiMoO4 (33-0948), MoO3 (21-0569), MoP4 (26-1273), Ni3S2 (44-1418), and Ni (04-0850), confirming the successful preparation of the NiMo-(S,P)@NF composite material. The NiMo-S@NF composite material also contains characteristic peaks of β-NiMoO4 (45-0142), α-NiMoO4 (33-0948), MoO3 (21-0569), Ni3S2 (44-1418), and Ni (04-0850). The presence of characteristic peaks in the NiMo-P@NF composite material confirms the successful preparation of the NiMo-S@NF composite material. The NiMo-P@NF composite material contains characteristic peaks of β-NiMoO4 (45-0142), α-NiMoO4 (33-0948), MoO3 (21-0569), MoP4 (26-1273), and Ni (04-0850), confirming the successful preparation of the NiMo-P@NF composite material. Similarly, the presence of characteristic peaks in the NiMo@NF material confirms the successful preparation of the NiMo@NF material.

[0092] Electrochemical tests were performed on the materials prepared in Examples 1-3 and the comparative examples:

[0093] Using the materials prepared in Examples 1-3 and the comparative example as working electrodes, a three-electrode system was assembled with 1 mol / L KOH solution (deionized water as solvent), carbon rod as counter electrode, and Hg / HgO as reference electrode, and the three-electrode electrochemical performance was tested.

[0094] Using the materials prepared in Examples 1-3 and the comparative example as anodes and cathodes, and 1 mol / L KOH solution (deionized water as solvent) as electrolyte, a dual-electrode system was assembled and the dual-electrode electrochemical performance was tested.

[0095] Figure 3 Linear voltammetric curves of hydrogen evolution reaction of nickel foam (NF) and 20 wt% Pt / C in 1 mol / L KOH solution for the materials prepared in Examples 1-3 and the comparative examples of the present invention.

[0096] from Figure 3 As can be seen from this, at a current density of 10 mA / cm² 2 and 100mA / cm 2At that time, the overpotentials of Example 1 were 35mV and 233mV, respectively, which were less than those of Example 2 (79mV, 249mV), Example 3 (88mV, 320mV), Comparative Example (162mV, 315mV) and Nickel Foam (222mV, 409mV), and were close to those of 20% Pt / C (25mV, 162mV), indicating that the NiMo-(S,P)@NF composite material has the best electrocatalytic hydrogen evolution activity.

[0097] Figure 4 Linear voltammetric curves of oxygen evolution reaction of nickel foam and RuO2 in 1 mol / L KOH solution for the materials prepared in Examples 1-3 and the comparative examples of the present invention.

[0098] from Figure 4 As can be seen from this, at a current density of 100 mA / cm² 2 At that time, the overpotential of Example 1 was 288mV, which was less than that of Example 2 (296mV), Example 3 (307mV), Comparative Example (310V), and Nickel Foam (590mV, 50mA / cm). 2 The overpotential of NiMo-(S,P)@NF is close to that of RuO2 (277mV). This indicates that the NiMo-(S,P)@NF composite material exhibits the best electrocatalytic oxygen evolution activity.

[0099] Figure 5 The linear voltammetric curves of NiMo-(S,P)@NF||NiMo-(S,P)@NF and Pt / C||RuO2, composed of the NiMo-(S,P)@NF material prepared in Example 1 of this invention, for electrocatalytic water splitting in 1 mol / L KOH solution are shown.

[0100] from Figure 5 As can be seen from this, at a current density of 10 mA / cm² 2 and 100mA / cm 2 At that time, the voltages of NiMo-(S,P)@NF||NiMo-(S,P)@NF were 1.391V and 1.711V, respectively, which are much smaller than those of Pt / C||RuO2 (1.571V and 1.821V). This indicates that the NiMo-(S,P)@NF composite material has superior water-splitting activity compared to noble metals.

[0101] Figure 6 The linear voltammetric curves of the NiMo-(S,P)@NF material prepared in Example 1 of this invention and 20wt% Pt / C in 1mol / L KOH solution for photo-assisted electrocatalytic hydrogen evolution reaction are shown.

[0102] from Figure 6 As can be seen from this, at a current density of 100 mA / cm² 2At that time, the overpotential of the NiMo-(S,P)@NF material prepared in Example 1 under light assistance was 190mV, which was less than the overpotential of the NiMo-(S,P)@NF material prepared in Example 1 without light assistance (233mV) and close to the overpotential of 20wt% Pt / C (162mV). This indicates that light assistance can significantly improve the hydrogen evolution activity of the electrocatalyst.

[0103] Figure 7 The linear voltammetric curve of the photo-assisted electrocatalytic oxygen evolution reaction of NiMo-(S,P)@NF material and RuO2 prepared in Example 1 of this invention in 1 mol / L KOH solution is shown.

[0104] from Figure 7 As can be seen from this, at a current density of 100 mA / cm² 2 At that time, the overpotential of the NiMo-(S,P)@NF material prepared in Example 1 under photo-assisted conditions was 242.8 mV, which was much smaller than the overpotential of the NiMo-(S,P)@NF material prepared in Example 1 without photo-assisted conditions (288.8 mV) and the overpotential of RuO2 (275.8 mV). This indicates that photo-assisted conditions can significantly improve the oxygen evolution activity of the electrocatalyst.

[0105] Figure 8 The linear voltammetric curves of NiMo-(S,P)@NF||NiMo-(S,P)@NF and Pt / C||RuO2 prepared in Example 1 of this invention for photo-assisted electrocatalytic water splitting in 1 mol / L KOH solution are shown.

[0106] from Figure 8 As can be seen from this, at a current density of 10 mA / cm² 2 and 100mA / cm 2 At that time, the voltages of Example 1 under light assistance were 1.239V and 1.629V, respectively, which were much lower than the voltages of Example 1 without light assistance (1.239V and 1.629V) and the voltages of RuO2 (1.571V and 1.821V), indicating that light assistance significantly improves the water splitting activity of the electrocatalyst.

[0107] Figure 9 An optical photograph of the NiMo-(S,P)@NF composite material prepared in one embodiment of the present invention, showing solar-driven integral water splitting.

[0108] from Figure 9 As can be seen, a relatively low voltage of 1.578V can drive the generation of obvious H2 / O2 bubbles on the electrode plate, indicating that solar-driven electrocatalytic water splitting has the potential for large-scale practical application.

[0109] The self-supporting one-dimensional nanorod array composite material prepared by the method provided in this invention is a highly efficient solar-driven electrocatalytic water splitting catalyst. It has excellent catalytic activity and working stability, and has great application prospects.

[0110] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a self-supporting one-dimensional nanorod array composite material, comprising the following steps: Soluble nickel salt and soluble molybdate are mixed with water and subjected to a hydrothermal reaction to obtain the NiMo precursor. The NiMo precursor and modifier were heat-treated under a protective atmosphere to obtain the self-supporting one-dimensional nanorod array composite material. The modifier is hypophosphite and elemental sulfur; the mass ratio of hypophosphite to the total mass of the modifier is 0.67:1; The heat treatment temperature is 300~500℃, the holding time is 1~3h, and the heating rate to the heat treatment temperature is 2~4.5℃ / min.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the soluble nickel salt to the soluble molybdate is (0.605~1.05):(0.862~1.362).

3. The preparation method according to claim 1 or 2, characterized in that, The mixing is carried out under stirring conditions; The stirring time is 20-50 minutes.

4. The preparation method according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 120~180℃ for 6~12 hours.

5. The preparation method according to claim 4, characterized in that, After the hydrothermal reaction is completed, the process also includes washing and drying in sequence. The drying temperature is 60~80℃, and the time is 6~12h.

6. The self-supporting one-dimensional nanorod array composite material prepared by the preparation method according to any one of claims 1 to 5, wherein the surface of the nanorods in the self-supporting one-dimensional nanorod array composite material is a modified layer; The diameter of the nanorods is 1.25~2.85μm, and the thickness of the modified layer is 25~80nm; The modified layer is a phosphorus sulfide modified layer.

7. The application of the self-supporting one-dimensional nanorod array composite material according to claim 6 in solar-driven electrocatalytic water splitting.

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