Plasma / transition metal sulfide composite material and its preparation method and application

Abstract

This invention belongs to the field of energy technology and discloses a plasma / transition metal sulfide composite material, its preparation method, and its application. The introduction of the Au-Cu2O plasma core-shell structure with unique optical properties enhances the visible light absorption of the transition metal sulfide, and its hot carrier separation effect can significantly improve the charge separation efficiency of the composite material. Under light irradiation, the prepared Au-Cu2O / NiCoS composite catalyst exhibits high oxygen evolution kinetics, with its oxygen evolution performance improved by approximately 12 times.

Description

Technical Field

[0001] The present invention belongs to the field of energy technology, and in particular relates to a plasma / transition metal sulfide composite material and a preparation method and application thereof. Background Art

[0002] Common methods for producing hydrogen include: reforming fossil fuels, electrolyzing water, and producing hydrogen from renewable energy. However, reforming fossil fuels often consumes large amounts of fossil fuels, resulting in significant carbon dioxide emissions and irreversible damage to natural resources due to excessive fossil energy consumption. Electrolyzing water consumes significant amounts of electricity and is prohibitively expensive, making it unsuitable for large-scale production. Therefore, the optimal solution currently is to utilize renewable sunlight and water electrolysis to produce hydrogen. In recent years, converting solar energy into chemical fuels through water splitting has become an important energy production method. This process does not emit greenhouse gases and generates energy cleanly. Therefore, utilizing solar radiation to photocatalytically generate clean H2 from water is of great significance.

[0003] Studies have shown that photoelectrochemical (PEC) water splitting has the potential to convert solar energy into hydrogen energy (STH) because hydrogen and oxygen gases can be easily quantified in PEC. When designing light-absorbing materials, semiconductors are the preferred materials because they can be excited to produce excitons (electron-hole pairs) under sunlight to drive electrolysis. However, pure semiconductor materials have problems such as carrier recombination, poor light harvesting, and electrode degradation, and are still far from practical applications. Constructing a heterojunction is a common way to improve the charge separation efficiency of catalysts. Generally speaking, the driving force for charge transfer in a heterojunction is the potential difference between energy levels, and the loss of potential energy during electron-hole transfer will weaken the oxidation and reduction ability of the composite photocatalyst. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a plasma / transition metal sulfide composite material and a preparation method thereof, wherein the plasma / transition metal sulfide composite material has better photoelectrocatalytic water splitting performance.

[0005] In order to solve the above problems, the present invention provides the following technical solutions:

[0006] A method for preparing a plasma / transition metal sulfide composite material comprises the following main steps:

[0007] S1. The pretreated nickel foam was immersed in a mixture containing a Co salt and a S source with magnetic stirring. The foam was then transferred to a Teflon-lined stainless steel autoclave and hydrothermally treated at 110°C to 200°C for 6 to 24 hours to obtain nickel-cobalt-sulfur nanosheets supported on the nickel foam.

[0008] S2. Stirring the mixture of chloroauric acid, sodium borohydride, and PVP at 25°C to 55°C for 1 to 5 hours to obtain an Au nanoparticle solution;

[0009] S3. A mixture containing a copper salt and a reducing agent was added to the Au nanoparticle solution and stirred evenly for 1 to 5 hours. The color changed from pink to dark green to obtain an aqueous suspension containing Au-Cu2O, Au-Cu2O having a core-shell structure;

[0010] S4. Immersing the nickel foam-supported nickel cobalt sulfur nanosheets in the aqueous suspension containing Au-Cu2O for 1 h to 4 h, and obtaining a self-supporting Au-Cu2O / NiCoS composite material of nickel foam under the action of electrostatics, namely the plasma / transition metal sulfide composite material.

[0011] Furthermore, in step S1, the specific method of the pretreatment is: soaking the nickel foam in a 1M hydrochloric acid solution and ultrasonically treating it for 20 minutes to remove its surface oxide, then ultrasonically rinsing it with acetone, ethanol, isopropanol and ultrapure water for 10 minutes respectively, and then placing it in a vacuum drying oven at 60°C for 6 hours to obtain the pretreated nickel foam.

[0012] Furthermore, in step S1, the Co salt is a water-soluble cobalt salt or a hydrate thereof, and the S source is a water-soluble S salt or a hydrate thereof.

[0013] Furthermore, in step S1, the water-soluble cobalt salt is one or more of CoCl2·6H2O, CoCl2, CoBr2, CoI2, CoCO3, Co(NO3)2 and CoSO4, and the water-soluble S salt is one or more of thiourea, sulfur powder and 2,2-diaminodiphenyl disulfide.

[0014] Furthermore, in step S2, the mixed solution containing chloroauric acid, sodium borohydride and PVP also contains sodium citrate.

[0015] Furthermore, in step S2, the molar ratio of Co salt to S is 8:1 to 1:8.

[0016] The present invention also provides a plasma / transition metal sulfide prepared by the above preparation method.

[0017] The present invention also provides an application of the above plasma / transition metal sulfide in photoelectrocatalytic hydrogen evolution materials.

[0018] The beneficial effects of the present invention are:

[0019] The plasma / transition metal sulfide composite material provided by the present invention broadens the absorption of semiconductor catalysts in the visible light range by introducing plasma materials, thereby improving the charge separation efficiency of the material. Its unique hot carrier effect facilitates the transmission between electrons and holes, effectively improving the electrocatalytic performance. It has high catalytic efficiency at both low and high current densities, and exhibits high catalytic kinetics under light conditions. Its Tafel slope is only 49.4mV dec -1 The catalyst has high long-term stability. After 1,000 cycles of testing, its performance showed no attenuation. Moreover, after 50 hours of continuous testing, it still maintained a current density of ~99.23%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings.

[0021] Figure 1 This is a SEM image of the Au-Cu2O / NiCoS sample prepared in Example 1 of the present invention;

[0022] Figure 2 TEM image of the Au-Cu2O / NiCoS sample prepared in Example 1 of the present invention;

[0023] Figure 3 XRD pattern of the Au-Cu2O / NiCoS sample prepared in Example 1 of the present invention;

[0024] Figure 4 This is the XPS graph of the Au-Cu2O / NiCoS sample prepared in Example 1 of the present invention;

[0025] Figure 5 This is the UV-visible absorption graph of the plasma material Au-Cu2O prepared in Example 1 of the present invention;

[0026] Figure 6 This is a graph showing the photoelectrocatalytic performance of the Au-Cu2O / NiCoS sample prepared in Example 1 of the present invention;

[0027] Figure 7 This is a comparison chart of the photocurrent response of the plasma material Au-Cu2O and its comparative material;

[0028] Figure 8 This is a catalytic stability test chart of the Au-Cu2O / NiCoS sample prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The present invention will now be further described with reference to specific examples. The following examples are intended to illustrate the present invention rather than to further limit the present invention.

[0030] Instruments and reagents:

[0031] The microstructure of the catalysts was characterized using field emission scanning electron microscopy (FESEM, ZEISS Gemini SEM 300) and transmission electron microscopy (TEM, JEOL JEM-2100). The samples were characterized using a powder X-ray diffractometer (BRUKER AXSD8Advance, Cu Kα radiation source). The chemical composition of the samples was analyzed using X-ray photoelectron spectroscopy (Escalab 250Xi, Thermo Fisher Scientific). UV-Vis absorption spectra of all samples were measured using a UV-Vis spectrophotometer (Cary 500Scan, Varian, USA).

[0032] Copper sulfate was purchased from Shanghai Mairui Chemical Technology Co., Ltd.

[0033] Sodium hydroxide was purchased from Shanghai Mairui Chemical Technology Co., Ltd.

[0034] Potassium hydroxide was purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd.

[0035] Ethanol was purchased from Zhongke Jinyan (Beijing) Technology Co., Ltd.

[0036] Sodium citrate was purchased from Shanghai Aladdin Reagent Co., Ltd.

[0037] Gold chloride trihydrate was purchased from Xilong Scientific Co., Ltd.

[0038] Cobalt chloride was purchased from Shanghai Mairui Chemical Technology Co., Ltd.

[0039] Cobalt bromide was purchased from Shanghai Mairui Chemical Technology Co., Ltd.

[0040] Thiourea was purchased from Shanghai Mairui Chemical Technology Co., Ltd.

[0041] Nickel nitrate was purchased from Shanghai Aladdin Reagent Co., Ltd.

[0042] Ferric nitrate was purchased from Shanghai Aladdin Reagent Co., Ltd.

[0043] Sodium borohydride was purchased from Shanghai Aladdin Reagent Co., Ltd.

[0044] Example 1

[0045] Step S1. NiCoS catalyst-loaded NFs were fabricated via a facile and scalable one-step hydrothermal method.

[0046] First, nickel foam (NF, 1×3 cm 2) were treated with 1.0 M HCl, acetone, ethanol, isopropanol, and deionized water for 10 min each to remove contaminants and the oxide layer, and then dried in a vacuum oven to obtain clean NFs ready for use.

[0047] 0.15 mmol CoCl2·6H2O and 0.5 mmol CH4N2S were dissolved in 10 mL of deionized water and magnetically stirred for 30 minutes. The mixed solution was then transferred to a 25 mL stainless steel autoclave, where a piece of clean NF was added and maintained at 150°C for 12 hours. In the hydrothermal reaction, CoCl2·6H2O and CH4N2S served as Co and S sources, while the NF served as a Ni source and self-supporting support.

[0048] Step S2. In the synthesis of Au-Cu2O core-shell templates, AuNPs were synthesized using a typical citrate reduction method.

[0049] Under continuous stirring, 2 mL of sodium citrate (38 mM) was added to 100 mL of HAuCl4·3H2O (0.1 wt%) solution. After 2 minutes, 1 mL of freshly prepared NaBH4 (0.08 wt%) solution was slowly added. After stirring for 5 minutes, PVP solution (10 mL, 1 mg / mL) was added and stirred for another 12 hours. Next, 3.0 mL of PVP-protected AuNP colloids were dispersed in a 35°C CuSO4 aqueous solution (2.0 mL, 0.01 M), followed by the addition of NaOH (1.5 mL, 0.1 M) and the reducing agent L-ascorbic acid (LAA, 0.5 mL, 0.1 M). As the Au-Cu2O core-shell structure successfully formed, the color of the solution changed from pink to dark green.

[0050] Step S3. The nickel foam was immersed in an aqueous suspension of Au-Cu2O for 1 hour. The negatively charged Au-Cu2O nanosheets were electrostatically adsorbed onto the positively charged NF. Finally, the resulting Au-Cu2O / NF was vacuum dried at 60°C for 12 hours. Simultaneously, NiCoS was decorated onto the Au-Cu2O through electrostatic interactions. The NiCoS supported on the Ni foam was immersed in a colloidal suspension of Au-Cu2O and gently shaken until the colloid turned colorless. After the Au-Cu2O was completely fixed to the NiCoS, the Au-Cu2O / NiCoS nanocomposite was dried in air.

[0051] Figure 1 TEM images of the Au-Cu2O / NiCoS sample prepared in Example 1 of the present invention (Figure a) and (b) a high-resolution TEM image of the material. As can be seen from the figures, the prepared catalyst exhibits an egg-shaped core-shell structure encapsulated by ultrathin transition metal sulfide nanosheets.

[0052] Figure 2 SEM images of the Au-Cu2O / NiCoS sample prepared in Example 1 of the present invention. Figure a shows an SEM image of the composite material supported on nickel foam, Figure b shows an SEM image of Au-Cu2O, Figure c shows an SEM image of two-dimensional NiCoS nanosheets, and Figure d shows an SEM image of the Au-Cu2O / NiCoS sample at high magnification. Combined with TEM, the morphology of the prepared plasma / transition metal sulfide can be demonstrated.

[0053] Figure 3 Powder X-ray diffraction (PXRD) patterns of the Au-Cu2O / NiCoS sample prepared in Example 1 of the present invention, Figure a is the PXRD diffraction pattern of Au-Cu2O, and Figure b is the PXRD pattern of the Au-Cu2O / NiCoS composite material. Figure 3 In a, PXRD shows typical diffraction peaks of Au and Cu2O nanocrystals. Figure 3 b As can be seen, the XRD pattern of the synthesized Au-Cu2O / NiCoS composite material shows the characteristic diffraction peaks of Ni3S2 (JPCDS No.44-1418), Co3S4 (JPCDS No.02-1338), Au (JPCDS No.04-0784) and Cu2O (JPCDS No.05-0667), proving that we have successfully synthesized the target material.

[0054] Figure 4 This is the X-ray photoelectron spectroscopy (XPS) diagram of the Au-Cu2O / NiCoS sample prepared in Example 1 of the present invention. Figure 4 It can be seen that nickel, cobalt, sulfur, oxygen, gold and copper elements are all present in the full XPS spectrum of the sample, which also indirectly proves the synthesis of our material. Figure 4 b is the S2p spectrum, in which the two characteristic peaks at 162.03 and 163.4 eV are attributed to the divalent S species in Ni3S2 and Co3S4. Figure 4 c) There are two main peaks at 853.6 / 872.2eV and 855.4 / 873.2eV respectively. 2+ and Ni 3+ The analysis showed that the nickel atoms in the composite material were mainly in the +2 valence state. Figure 4 d is the high-resolution energy spectrum of Co2p, and the binding energies at 780.8 / 796.7eV and 775.8 / 792.2eV are attributed to Co 2+ and Co 3+ The weak satellite peaks indicate that the Co in the composite material is mainly in the +3 valence state. For the Cu2p high-resolution energy spectrum, the two peaks at 932.5 and 952.4 eV are attributed to Cu2p 3 / 2 and Cu2p1 / 2 , confirming the existence of +1 Cu ( Figure 4 e). Figure 4 In Figure 5, the two peaks at 83.2 and 87.8 eV are the typical results of the spin-orbit splitting of the Au 4f energy level, which match well with the values of metallic Au(0).

[0055] Figure 5 This is the UV-visible absorption graph of the plasma material Au-Cu2O prepared in Example 1 of the present invention. Figure 5 As shown, pure Cu2O exhibits weak absorption at about 450nm. Due to the strong plasma coupling between Au and Cu2O nanoparticles, the prepared Au-Cu2O core-shell structure plasmon has strong absorption in the visible light (650nm) range.

[0056] Figure 6 This is a photoelectrocatalytic performance diagram of the Au-Cu2O / NiCoS sample prepared in Example 1 of the present invention, as shown in FIG. Figure 6 As shown in Figure a, the Au-Cu2O / NiCoS electrode has high OER activity under both laser illumination and non-laser illumination conditions, with large current and low overpotential. Since the plasma Au-Cu2O generates hot carriers under laser irradiation, the OER performance under illumination will be further improved, resulting in the overpotential of Au-Cu2O / NiCoS being 100 mA cm -2 The blue shift from 345 mV to 338 mV was observed. In addition, the blue shift was observed when compared with the NiCoS electrode (119.2 mV dec -1 ), the electrode exhibited a lower Tafel slope of 86.4 mV dec under light illumination. -1 ( Figure 6 b). The Au-Cu2O / NiCoS electrode exhibits a photocurrent response 12 times higher than that of pure NiCoS and 24.5 times higher than that of pure Au-Cu2O during continuous light switching. Figure 6 c), which is mainly due to the Schottky junction formed at the interface between the Au-Cu2O and NiCoS composites, which largely promotes the electron transfer and the hot carriers induced by the surface plasmon of Au-Cu2O nanoparticles, further effectively enhancing the OER performance.

[0057] Figure 7 Comparison of the photocurrent responses of the plasmonic material Au-Cu2O and its comparative materials. (a) UV-Vis absorption of Au-Cu2O, Au, and Cu2O. (b) UV-Vis absorption at a power density of 100 mW cm -2 (c&d) Photocurrent response of Au-Cu2O, Au, and Cu2O electrodes under laser irradiation.

[0058] Figure 8 The catalytic stability test data of the Au-Cu2O / NiCoS sample prepared in the present invention, Figure a is a curve diagram of the composite material before and after the linear cyclic voltammetry test of 1000, Figure b is a graph of the oxygen evolution performance at different current densities, Figure c is a PXRD diffraction pattern of the material after continuous testing for 50 hours, and Figure d is a comparison of the oxygen evolution performance of this catalyst and other related catalytic materials. Figure 7 It can be seen that Au-Cu2O / NiCoS at 60mA cm -2 The Au-Cu2O / NiCoS electrode was tested stably and continuously for up to 50 hours at a current density of 1000 nm, showing high stability and no degradation of performance after 1000 cycles. In addition, after about 50 hours of continuous current testing, the nanostructure, element valence and composition of the Au-Cu2O / NiCoS electrode remained almost unchanged ( Figure 8 c), reflecting its excellent long-term electrocatalytic stability. Compared with previously reported catalysts ( Figure 8 d), its high activity, good kinetics, and high stability indicate that the Au-Cu2O / NiCoS catalyst has potential commercial application prospects.

[0059] To further illustrate the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort shall fall within the scope of protection of the present invention.

[0060] The above examples describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a plasma / transition metal sulfide composite material, characterized in that: The main steps include: S1. The pretreated nickel foam was immersed in a mixture containing a Co salt and a S source with magnetic stirring. The foam was then transferred to a Teflon-lined stainless steel autoclave and hydrothermally treated at 110°C to 200°C for 6 to 24 hours to obtain nickel-cobalt-sulfur nanosheets supported on the nickel foam. S2. The mixture containing chloroauric acid, sodium borohydride and PVP was stirred uniformly at 25°C~55°C for 1h~5h to obtain an Au nanoparticle solution; the mixture containing chloroauric acid, sodium borohydride and PVP also contained sodium citrate; S3. A mixture of a copper salt and a reducing agent was added to the Au nanoparticle solution and stirred evenly for 1 h to 5 h, and the color changed from pink to dark green to obtain an aqueous suspension containing Au-Cu2O, Au-Cu2O having a core-shell structure; S4. Immersing the nickel foam-supported nickel cobalt sulfur nanosheets in the aqueous suspension containing Au-Cu2O for 1 h to 4 h, and obtaining a self-supporting Au-Cu2O / NiCoS composite material of nickel foam under the action of electrostatics, that is, the plasma / transition metal sulfide composite material.

2. The preparation method according to claim 1, characterized in that In step S1, the specific method of the pretreatment is: soaking the nickel foam in a 1M hydrochloric acid solution and ultrasonically treating it for 20 minutes to remove the surface oxide, then ultrasonically rinsing it with acetone, ethanol, isopropanol and ultrapure water for 10 minutes respectively, and then placing it in a vacuum drying oven at 60°C for 6 hours to obtain the pretreated nickel foam.

3. The preparation method according to claim 1, characterized in that In step S1, the Co salt is one or more of CoCl2·6H2O, CoCl2, CoBr2, CoI2, CoCO3, Co(NO3)2 and CoSO4, and the S source is one or more of thiourea, sulfur powder and 2,2-diaminodiphenyl disulfide.

4. The preparation method according to claim 1, characterized in that In step S1, the molar ratio of the Co salt to the S source is 8:1 to 1:

8.

5. The plasma / transition metal sulfide prepared by the preparation method according to any one of claims 1 to 4.

6. Use of the plasma / transition metal sulfide according to claim 5 in photoelectrocatalytic hydrogen evolution materials.

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