Fe-doped MoS.SUB.2 .nano-material, preparation method therefor and use thereof

Abstract

The invention discloses a method for preparing a Fe-doped MoS.sub.2 nano-material, which comprises the following steps: dissolving a ferric salt and ammonium tetrathiomolybdate in DMF and reacting at 180-200° C. for 6-24 hrs to obtain a Fe-doped MoS.sub.2 nano-material. The present invention also provides a Fe-doped MoS.sub.2 nano-material supported by nickel foam, which includes a nickel foam substrate and the Fe-doped MoS.sub.2 nano-material loaded on the nickel foam substrate. Furthermore, the present invention also provides a preparation method and use of the above materials. In the invention, the desired product can be obtained by a one-pot solvothermal reaction, and thus the operation is simple. There is no need to introduce a surfactant for morphological control during the preparation process, and the resulting product has a clean surface and is easy to wash.

Claims

1. A method for preparing a Fe-doped MoS.sub.2 nano-material, comprising steps of: dissolving a ferric salt and ammonium tetrathiomolybdate in DMF and reacting at 180-200° C. for 6-24 hrs to obtain the Fe-doped MoS.sub.2 nano-material.

2. The method according to claim 1, wherein the ferric salt is ferric chloride hexahydrate.

3. The method according to claim 1, wherein the molar ratio of the ferric salt to ammonium tetrathiomolybdate is 1-5:5.

4. The method according to claim 1, wherein the method further comprises the steps of washing, centrifuging and drying the reaction product.

5. The method according to claim 4, wherein the solvents used in the washing step are deionized water and anhydrous ethanol.

6. The method according to claim 4, wherein the rotation speed for centrifugation is 8000-12000 rpm, the centrifugation time is not less than 3 minutes; the drying temperature is 40-60° C., and the drying time is 2-12 hrs.

7. A Fe-doped MoS.sub.2 nano-material prepared by the preparation method according to claim 1.

8. A Fe-doped MoS.sub.2 nano-material supported by nickel foam, comprising a nickel foam substrate and the Fe-doped MoS.sub.2 nano-material according to claim 7 which is loaded on the nickel foam substrate.

9. A method for preparing a Fe-doped MoS.sub.2 nano-material supported by nickel foam according to claim 8, comprising steps of: dissolving a ferric salt and ammonium tetrathiomolybdate in DMF, immersing a nickel foam in the resulting solution and reacting at 180-200° C. for 6-24 hrs to obtain the Fe-doped MoS.sub.2 nano-material supported by the nickel foam.

10. An electrocatalyst for catalyzing an hydrogen evolution reaction, an oxygen evolution reaction and a full hydrolysis reaction, comprising the Fe-doped MoS.sub.2 nano-material supported by nickel foam according to claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a scanning electron microscopy (SEM) image of Fe-doped molybdenum disulfide nanocanopies;

(2) FIG. 2 is a transmission electron microscopy (TEM) image of Fe-doped molybdenum disulfide nanocanopies;

(3) FIG. 3 is an X-ray powder diffraction (PXRD) pattern of Fe-doped molybdenum disulfide nanocanopies;

(4) FIG. 4 is an energy dispersive X-ray spectrum (EDX) diagram of Fe-doped molybdenum disulfide nanocanopies;

(5) FIG. 5 is an element distribution diagram of Fe-doped molybdenum disulfide nanocanopies;

(6) FIG. 6 is an X-ray photoelectron spectroscopy (XPS) diagram of Fe-doped molybdenum disulfide nanocanopies;

(7) FIG. 7 shows a linear scanning voltammetry curve (a), a Tafel slope diagram (b), a double-layer capacitance diagram (c) of Fe-doped molybdenum disulfide nanocanopies in 0.5M H.sub.2SO.sub.4, and a control diagram of polarization curves of Fe.sub.0.05—MoS.sub.2 before and after 1000 cycles (d);

(8) FIG. 8 is a scanning electron microscopy (SEM) image of a Fe-doped molybdenum disulfide supported by nickel foam;

(9) FIG. 9 is an X-ray powder diffraction (PXRD) pattern of a Fe-doped molybdenum disulfide supported by nickel foam;

(10) FIG. 10 shows an HER polarization curve (a), an HER corresponding Tafel slope diagram (b), an OER polarization curve (c), an OER corresponding Tafel slope diagram (d) and a double-layer capacitance diagram (e) of a Fe-doped molybdenum disulfide supported by nickel foam in 1.0M KOH electrolyte, and a chronopotentiometric measurement (f) of the OER reaction catalyzed by the Fe-doped molybdenum disulfide supported by nickel foam;

(11) FIG. 11 shows an apparatus (a) for overall water splitting by using the Fe-doped molybdenum disulfide supported by nickel foam in 1.0M KOH electrolyte, and a polarization curve (b) of the overall water splitting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) The invention will be further illustrated in more detail with reference to the accompanying drawings and embodiments, so that those skilled in the art can better understand and implement the present invention. However, It is noted that, the following embodiments are not intended to limit the scope of the present invention.

Example 1: Preparation of Fe-Doped Molybdenum Disulfide Nanocanopies

(13) 13 mg (0.05 mmol) of ammonium tetrathiomolybdate and 13.5 mg (0.05 mmol) of ferric chloride hexahydrate solid were weighed and dissolved in 12 mL of N, N-dimethylformamide (DMF) to form a solution. The solution was then transferred to a Teflon-lined stainless autoclave. The kettle is then placed in an oven after being sealed and reacted at 200° C. for 12 hrs. After the reaction was completed, it was naturally cooled to room temperature. After being washed with deionized water and ethanol and subjected to centrifuging separation and drying process, black powdered Fe-doped molybdenum disulfide nanocanopies were obtained, named as Fe.sub.0.05—MoS.sub.2, wherein Fe represents iron ions and 0.05 represents the molar amount of the iron salt is 0.05 mmol, and MoS.sub.2 represents molybdenum disulfide.

(14) As shown in FIG. 1 and FIG. 2, the Fe-doped molybdenum disulfide nanocanopies have a uniform morphology, as well as high quality and high yield, and have a diameter of less than 200 nm and a thickness of about 30 nm.

(15) As shown in FIG. 3, the X-ray powder diffraction (PXRD) pattern of the Fe-doped molybdenum disulfide nanocanopies is conformed with the reported interlayer spacing of 9.4 Å of molybdenum disulfide in the literature (See K. Ai, C. Ruan, M. Shen, L. Lu, Adv. Funct. Mater. 2016, 265542-5549.).

(16) As shown in FIG. 4 and FIG. 5, the Fe-doped molybdenum disulfide nanocanopies are composed of Mo, Fe, S, and O, and each element is evenly distributed.

(17) As shown in FIG. 6, the photoelectron spectroscopy (XPS) of the Fe-doped molybdenum disulfide nanocanopies shows that the valences of Mo, Fe, S, and O are +4, +2, −2, and −2, respectively.

Example 2: Preparation of a Fe-Doped Molybdenum Disulfide Nanocanopy Electrocatalyst

(18) 2.5 mg solid powder of the Fe-doped molybdenum disulfide nanocanopies and 2.5 mg of commercial available carbon black were weighed and mixed, then 970 μL of isopropanol and 30 μL of 5 wt. % Nafion solution were added, the resulting mixture was sonicated for 1 h so that it was uniformly dispersed to form an ink-like solution. 20 μL of the solution was added dropwise in batches onto the surface of the polished glassy carbon electrode, and then air-dried for later use.

(19) As a control, 2.5 mg of the molybdenum disulfide solid powder and 2.5 mg of commercial available carbon black were weighed and mixed, then 970 μL of isopropanol and 30 μL of 5 wt. % Nafion solution were added, and the resulting mixture was sonicated for 1 h so that it was uniformly dispersed to form an ink-like solution. 20 μL of the solution was added dropwise in batches onto the surface of the polished glassy carbon electrode, and then air-dried for later use.

(20) As a control, 5.0 mg of commercial available Pt/C (5 wt. % Pt) was weighed and added with 970 μL of isopropanol and 30 μL of 5 wt. % Nafion solution, the resulting mixture was sonicated for 1 h so that it was uniformly dispersed to form an ink-like solution. 20 μL of the solution was added dropwise in batches onto the surface of the polished glassy carbon electrode, and then air-dried for later use.

Example 3: HER Performance Test in an Acidic Electrolyte

(21) The entire electrocatalytic test was performed under a standard three-electrode system, wherein the working electrode was the glassy carbon electrode prepared in Example 2, the reference electrode was an Ag/AgCl (saturated KCl solution) electrode, and the counter electrode was a platinum wire electrode. The electrolyte solution used for the linear scanning voltammetry (LSV) test is a 0.5M H.sub.2SO.sub.4 solution, with a potential scanning range of −0.7-0 V and a scanning speed of 5 mV/s. All the measured data was subjected to an iR-compensation.

(22) As shown in FIG. 7, compared with pure molybdenum disulfide, the Fe-doped molybdenum disulfide nanocanopies show excellent HER electrocatalytic performance. At a current density of 10 mA.Math.cm.sup.−2, the over-potential value is only 173 mV, and the Tafel slope is also as low as 41.1 mV.Math.dec.sup.−1. The double-layer capacitance value is 39.8 mF.Math.cm.sup.−2 and higher than molybdenum disulfide, which demonstrates that Fe.sub.0.05—MoS.sub.2 has more HER active sites than pure MoS.sub.2. After 1000 cycles, the performance did not decrease significantly.

Example 4: Preparation of a Fe-Doped Molybdenum Disulfide Supported by Nickel Foam

(23) 13 mg (0.05 mmol) of ammonium tetrathiomolybdate and 13.5 mg (0.05 mmol) of ferric chloride hexahydrate solid were weighed and dissolved in 12 mL of N, N-dimethylformamide (DMF) to form a solution. The solution was then transferred to a Teflon-lined stainless autoclave and a piece of nickel foam (1 cm*2 cm) was immersed in it. The kettle was then sealed and placed in an oven and reacted at 200° C. for 12 hrs. After the reaction was completed, it was naturally cooled to room temperature. After being washed by deionized water and ethanol and dried in a blast drying oven at 60° C., a Fe-doped molybdenum disulfide supported by nickel foam was obtained, which was named as Fe.sub.0.05—MoS.sub.2/NF, wherein Fe represents ferric ions, 0.05 represents the molar amount of the ferric salt is 0.05 mmol, MoS.sub.2 represents molybdenum disulfide, and NF represents nickel foam (nickle foam).

(24) As shown in FIG. 8, the Fe-doped molybdenum disulfide supported by nickel foam is dense amorphous particulates.

(25) As shown in FIG. 9, the powder diffraction pattern (PXRD) of the Fe-doped molybdenum disulfide supported by nickel foam is corresponding to that of the metallic nickel and molybdenum disulfide.

Example 5: HER Performance Test in an Alkaline Electrolyte

(26) The entire electrocatalytic test was performed under a standard three-electrode system, wherein the working electrode was the Fe-doped molybdenum disulfide supported by nickel foam (with an effective area of 0.5 cm.sup.2), the reference electrode was an Ag/AgCl (saturated KCl solution) electrode, and the counter electrode was a platinum wire electrode. The electrolyte solution used for the linear scanning voltammetry (LSV) test is 1M KOH solution, with a potential scanning range of −1.6 to −1 V and a scanning speed of 2 mV/s. All the measured data was subjected to an iR-compensation.

(27) As shown in FIGS. 10 (a) and (b), compared with pure molybdenum disulfide and pure nickel foam, the Fe-doped molybdenum disulfide supported by nickel foam shows excellent HER electrocatalytic performance. At a current density of 10 mA.Math.cm.sup.−2, the over-potential value is only 153 mV, and the Tafel slope is also as low as 85.6 mV.Math.dec.sup.−1.

Example 6: The OER Performance Test in an Alkaline Electrolyte

(28) The entire electrocatalytic test was performed under a standard three-electrode system, wherein the working electrode was the Fe-doped molybdenum disulfide supported by nickel foam (with an effective area of 0.5 cm.sup.2), the reference electrode was an Ag/AgCl (saturated KCl solution) electrode, and the counter electrode was a platinum wire electrode. The electrolyte solution used for the linear scanning voltammetry (LSV) test is 1M KOH solution, with a potential scanning range of 0-0.8 V and a scanning speed of 2 mV/s. All the measured data was subjected to an iR-compensation.

(29) As shown in FIGS. 10 (c), (d), (e), and (f), the Fe-doped molybdenum disulfide supported by nickel foam exhibits excellent OER electrocatalytic performance. At a current density of 20 mA.Math.cm.sup.−2, the over-potential value is only 230 mV, and the Tafel slope is also as low as 78.7 mV.Math.dec.sup.−1. The Fe-doped molybdenum disulfide supported by nickel foam also shows an excellent stability. And the electrocatalytic performance did not decrease significantly after 140 hrs of the constant current chronopotential test.

Example 7: Overall Water Splitting Test in an Alkaline Electrolyte

(30) The entire electrocatalytic test was performed under a double-electrode system, wherein both electrodes were the Fe-doped molybdenum disulfide supported by nickel foam (with an effective area of 0.5 cm.sup.2). The electrolyte solution used for the linear scanning voltammetry (LSV) test is 1M KOH solution, with a potential scanning range of 0.8-2 V and a scanning speed of 5 mV/s.

(31) As shown in FIG. 11, the Fe-doped molybdenum disulfide supported by nickel foam shows excellent total hydrolysis catalytic performance, and it can reach a current density of 10 mA.Math.cm.sup.−2 at only 1.52 V.

(32) The above descriptions are only preferred embodiments of the present invention and not intended to limit the present invention, it should be noted that those of ordinary skill in the art can further make various modifications and variations without departing from the technical principles of the present invention, and these modifications and variations also should be considered to be within the scope of protection of the present invention. The protection scope of the present invention is defined by the claims.