HYDROGEN EVOLUTION ELECTRODE AND PREPARATION METHOD THEREOF

Abstract

The present disclosure provides a hydrogen evolution electrode and a preparation method thereof. The preparation method includes the following steps: providing an electrolyte including Co(NO.sub.3).sub.2.Math.6H.sub.2O with a Co(NO.sub.3).sub.2 concentration of 0.005 mol L.sup.−1 to 0.015 mol L.sup.−1, MnCl.sub.2.Math.4H.sub.2O with a MnCl.sub.2 concentration of 0.005 mol L.sup.−1 to 0.01 mol L.sup.−1, KCl with a concentration of 0.003 mol L.sup.−1 to 0.008 mol L.sup.−1, and CH.sub.3CSNH.sub.2 with a concentration of 0.04 mol L.sup.−1 to 0.06 mol L.sup.−1; adjusting the electrolyte to a pH value of 6 to 7; providing a cathode in the form of a substrate; and conducting electrolysis in a cyclic voltammetry mode, thereby preparing the electrode for hydrogen production by water electrolysis through electrochemical deposition of a Co.sub.9-xMn.sub.xS.sub.8 nanosheet catalyst on the cathode substrate, where 1≤X≤7.

Claims

1. A preparation method of an electrode for hydrogen production by water electrolysis, comprising the following steps: providing an electrolyte comprising Co(NO.sub.3).sub.2.Math.6H.sub.2O with a Co(NO.sub.3).sub.2 concentration of 0.005 mol L.sup.−1 to 0.015 mol L.sup.−1, MnCl.sub.2.Math.4H.sub.2O with a MnCl.sub.2 concentration of 0.005 mol L.sup.−1 to 0.01 mol L.sup.−1, KCl with a concentration of 0.003 mol L.sup.−1 to 0.008 mol L.sup.−1, and CH.sub.3CSNH.sub.2 with a concentration of 0.04 mol L.sup.−1 to 0.06 mol L.sup.−1; adjusting the electrolyte to a pH value of 6 to 7; providing a cathode in a substrate form; and conducting electrolysis in a cyclic voltammetry mode, thereby preparing the electrode for hydrogen production by water electrolysis through electrochemical deposition of a Co.sub.9-xMn.sub.xS.sub.8 nanosheet catalyst on the cathode substrate, wherein 1≤X≤7.

2. The preparation method according to claim 1, wherein the electrolysis is conducted in the cyclic voltammetry mode by scanning at a potential window of −1 V vs RHE to 1 V vs RHE and a scan rate of 1 mV s.sup.−1 to 3 mV s.sup.−1 with 5 to 7 scan segments.

3. The preparation method according to claim 1, wherein the electrolysis is conducted with the electrolyte at a constant temperature of 20° C. to 30° C. for 30 min to 40 min.

4. The preparation method according to claim 1, further comprising providing an anode that is spaced from the cathode by 2 cm to 5 cm.

5. The production method according to claim 1, wherein a titanium substrate is provided as the cathode.

6. The preparation method according to claim 1, wherein a thickness of the Co.sub.9-xMn.sub.xS.sub.8 nanosheet is adjusted by controlling a molar ratio of Co and Mn in the electrolyte.

7. The preparation method according to claim 6, wherein Co and Mn in the electrolyte have a molar ratio of 1:1, namely X is 4.5.

8. An electrode for hydrogen production by water electrolysis, prepared by the preparation method according to claim 1.

9. The electrode for hydrogen production by water electrolysis according to claim 8, wherein the electrolysis is conducted in the cyclic voltammetry mode by scanning at a potential window of −1 V vs RHE to 1 V vs RHE and a scan rate of 1 mV s.sup.−1 to 3 mV s.sup.−1 with 5 to 7 scan segments.

10. The electrode for hydrogen production by water electrolysis according to claim 8, wherein the electrolysis is conducted with the electrolyte at a constant temperature of 20° C. to 30° C. for 30 min to 40 min.

11. The electrode for hydrogen production by water electrolysis according to claim 8, further comprising providing an anode that is spaced from the cathode by 2 cm to 5 cm.

12. The electrode for hydrogen production by water electrolysis according to claim 8, wherein a titanium substrate is provided as the cathode.

13. The electrode for hydrogen production by water electrolysis according to claim 8, wherein a thickness of the Co.sub.9-xMn.sub.xS.sub.8 nanosheet is adjusted by controlling a molar ratio of Co and Mn in the electrolyte.

14. The electrode for hydrogen production by water electrolysis according to claim 13, wherein Co and Mn in the electrolyte have a molar ratio of 1:1, namely X is 4.5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 shows a cyclic voltammetry curve recorded during deposition of a Co.sub.9-xMn.sub.xS.sub.8 nanogrid (array) according to the present disclosure;

[0027] FIG. 2A and FIG. 2B are a scanning electron microscopy (SEM) image of a Co.sub.9-xMn.sub.xS.sub.8 (x=3, with a thickness of 9 nm) nanogrid on an electrode prepared according to the present disclosure and a corresponding partially-enlarged annotation image, respectively;

[0028] FIG. 3A and FIG. 3B are a SEM image of a Co.sub.9-xMn.sub.xS.sub.8 (x=4.5, with a thickness of 30 nm) nanogrid on the electrode prepared according to the present disclosure and a corresponding partially-enlarged annotation image, respectively;

[0029] FIG. 4A and FIG. 4B are a SEM image of the Co.sub.9-xMn.sub.xS.sub.8 (x=6, with a thickness of 45 nm) nanogrid on the electrode prepared according to the present disclosure and a corresponding partially-enlarged annotation image, respectively;

[0030] FIG. 5 shows X-ray diffraction (XRD)-based phase analysis diagrams of the Co.sub.9-xMn.sub.xS.sub.8 (x=4.5 and 6) nanogrids on the electrode prepared according to the present disclosure and pure Co.sub.9S.sub.8; and

[0031] FIG. 6A to FIG. 6D are hydrogen evolution reaction (HER) performance test comparison curves of the bimetallic sulfide Co.sub.9-xMn.sub.xS.sub.8 (x=3, 4.5, and 6)-based nanogrid catalysts and the monobimetallic sulfide Co.sub.9S.sub.8 in strongly acidic and strongly alkaline media in Examples 1 to 3 of the present disclosure, respectively; where A and B are a linear sweep voltammetry (LSV) curve and a Tafel curve of the corresponding catalysts in a H.sub.2-saturated 0.5 M H.sub.2SO.sub.4 medium, respectively; and C and D are an LSV curve and a Tafel curve of the corresponding catalysts in a H.sub.2-saturated 1 M KOH medium, respectively.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The present disclosure will be further described below with reference to the examples and accompanying drawings. It should be understood by those skilled in the art that the examples and accompanying drawings are only for a better understanding of the present disclosure, and are not used for any limiting purpose.

One-Step Preparation of a Co.SUB.9-x.Mn.SUB.x.S.SUB.8 .(x=3) Nanosheet Array Grid-Typed Hydrogen Evolution Electrode by Cyclic Voltammetry Slow Electrodynamics Deposition

Example 1

[0033] (1) A substrate Ti sheet was pretreated, cut to 1 cm.sup.2×2 cm.sup.2, placed in 18% dilute hydrochloric acid to conduct an ultrasonic treatment for 20 min, ultrasonically cleaned with absolute ethanol and deionized water for 20 min, and then dried in a stream of nitrogen.

[0034] (2) A standard three-electrode system of an electrochemical workstation (CHI660D) was used, with a graphite sheet (2 cm.sup.2×2 cm.sup.2), a silver/silver chloride (3 M KCl) electrode, and the Ti sheet as a counter electrode, a reference electrode, and a working electrode, respectively; a distance between the substrate Ti sheet and the counter electrode was controlled at 2.5 cm, and an infiltration area was kept at 1 cm.sup.2×1 cm.sup.2.

[0035] (3) A deposition electrolyte was configured, and an electrolytic cell was provided with a mixed solution containing 0.01 mol L.sup.−1 of Co(NO.sub.3).sub.2, 0.005 mol L.sup.−1 of MnCl.sub.2, 0.0503 mol L.sup.−1 of CH.sub.3CSNH.sub.2, and 0.005 mol L.sup.−1 of KCl, at a constant temperature of 25° C. with a pH value adjusted to 6.5 with sodium hydroxide, and the electrolyte remained still throughout the deposition.

[0036] (4) Under a one-step cyclic voltammetry electrodynamic deposition mode, the electrochemical deposition was conducted at a potential window of −1.2 V vs Ag/AgCl to 0.2 V vs Ag/AgCl and a scan rate of 2 mV s.sup.−1 with 6 scan segments for 35 min, and a Co.sub.9-xMn.sub.xS.sub.8 (x=3) nanogrid was deposited on the Ti substrate to form a uniform black film.

[0037] (5) The deposited electrode film was rinsed with deionized water for 3 min, and placed in magnetically-stirring deionized water to remove residual electrolyte on an electrode surface by vortex, and then dried in a vacuum drying box for 10 h to obtain a final product. The Co.sub.9-xMn.sub.xS.sub.8 (x=3) nanosheet array was uniformly and vertically distributed on the Ti substrate (forming the electrode) to constitute a grid structure, where the nanosheet had an average thickness of 9 nm and an average pore size of 240 nm.

[0038] (6) The dried electrode was placed in 0.5 M H.sub.2SO.sub.4 and 1 M KOH media separately, to conduct subsequent electrochemical tests of the cathodic HER by water electrolysis.

Example 2

[0039] (1) A substrate Ti sheet was pretreated, cut to 1 cm.sup.2×2 cm.sup.2, placed in 18% dilute hydrochloric acid to conduct an ultrasonic treatment for 20 min, ultrasonically cleaned with absolute ethanol and deionized water for 20 min, and then dried in a stream of nitrogen.

[0040] (2) A standard three-electrode system of an electrochemical workstation (CHI660D) was used, with a graphite sheet (2 cm.sup.2×2 cm.sup.2), a silver/silver chloride (3 M KCl) electrode, and the Ti sheet as a counter electrode, a reference electrode, and a working electrode, respectively; a distance between the substrate Ti sheet and the counter electrode was controlled at 2.5 cm, and an infiltration area was kept at 1 cm.sup.2×1 cm.sup.2.

[0041] (3) A deposition electrolyte was configured, and an electrolytic cell was provided with a mixed solution containing 0.0075 mol L.sup.−1 of Co(NO.sub.3).sub.2, 0.0075 mol L.sup.−1 of MnCl.sub.2, 0.0503 mol L.sup.−1 of CH.sub.3CSNH.sub.2, and 0.005 mol L.sup.−1 of KCl, at a constant temperature of 25° C. with a pH value adjusted to 6.5, and the electrolyte remained still throughout the deposition.

[0042] (4) Under a one-step cyclic voltammetry electrodynamic deposition mode, the electrochemical deposition was conducted at a potential window of −1.2 V vs Ag/AgCl to 0.2 V vs Ag/AgCl and a scan rate of 2 mV s.sup.−1 with 6 scan segments for 35 min, and a Co.sub.9-xMn.sub.xS.sub.8 (x=4.5) nanogrid was deposited on the Ti substrate to form a uniform black film.

[0043] (5) The deposited electrode film was rinsed with deionized water for 3 min, and placed in magnetically-stirring deionized water to remove residual electrolyte on an electrode surface by vortex, and then dried in a vacuum drying box for 10 h to obtain a final product. The Co.sub.9-xMn.sub.xS.sub.8 (x=4.5) nanosheet array was uniformly and vertically distributed on the Ti substrate to constitute a grid structure, the nanosheet had an average thickness of 30 nm and an average pore size of 280 nm.

[0044] (6) The dried electrode was placed in 0.5 M H.sub.2SO.sub.4 and 1 M KOH media separately, to conduct subsequent electrochemical tests of the cathodic HER by water electrolysis.

Example 3

[0045] (1) A substrate Ti sheet was pretreated, cut to 1 cm.sup.2×2 cm.sup.2, placed in 18% dilute hydrochloric acid to conduct an ultrasonic treatment for 20 min, ultrasonically cleaned with absolute ethanol and deionized water for 20 min, and then dried in a stream of nitrogen.

[0046] (2) A standard three-electrode system of an electrochemical workstation (CHI660D) was used, with a graphite sheet (2 cm.sup.2×2 cm.sup.2), a silver/silver chloride (3 M KCl) electrode, and the Ti sheet as a counter electrode, a reference electrode, and a working electrode, respectively; a distance between the substrate Ti sheet and the counter electrode was controlled at 2.5 cm, and an infiltration area was kept at 1 cm.sup.2×1 cm.sup.2.

[0047] (3) A deposition electrolyte was configured, and an electrolytic cell was provided with a mixed solution containing 0.01 mol L.sup.−1 of Co(NO.sub.3).sub.2, 0.005 mol L.sup.−1 of MnCl.sub.2, 0.0503 mol L.sup.−1 of CH.sub.3CSNH.sub.2, and 0.005 mol L.sup.−1 of KCl, at a constant temperature of 25° C. with a pH value adjusted to 6.5, and the electrolyte remained still throughout the deposition.

[0048] (4) Under a one-step cyclic voltammetry electrodynamic deposition mode, the electrochemical deposition was conducted at a potential window of −1.2 V vs Ag/AgCl to 0.2 V vs Ag/AgCl and a scan rate of 2 mV s.sup.−1 with 6 scan segments for 35 min, and a Co.sub.9-xMn.sub.xS.sub.8 (x=6) nanogrid was deposited on the Ti substrate to form a uniform black film.

[0049] (5) The deposited electrode film was rinsed with deionized water for 3 min, and placed in magnetically-stirring deionized water to remove residual electrolyte on an electrode surface by vortex, and then dried in a vacuum drying box for 10 h to obtain a final product. The Co.sub.9-xMn.sub.xS.sub.8 (x=6) nanosheet array was uniformly and vertically distributed on the Ti substrate to constitute a grid structure, the nanosheet had an average thickness of 45 nm and an average pore size of 560 nm.

[0050] (6) The dried electrode was placed in 0.5 M H.sub.2SO.sub.4 and 1 M KOH media separately, to conduct subsequent electrochemical tests of the cathodic HER by water electrolysis.

One-Step Preparation of a Co.SUB.9-x.Mn.SUB.x.S.SUB.8 .(x=4.5) Nanosheet Array Grid-Typed Hydrogen Evolution Electrode by Cyclic Voltammetry Rapid Electrodynamics Deposition

Comparative Example 4

[0051] (1) A substrate Ti sheet was pretreated, cut to 1 cm.sup.2×2 cm.sup.2, placed in 18% dilute hydrochloric acid to conduct an ultrasonic treatment for 20 min, ultrasonically cleaned with absolute ethanol and deionized water for 20 min, and then dried in a stream of nitrogen.

[0052] (2) A standard three-electrode system of an electrochemical workstation (CHI660D) was used, with a graphite sheet (2 cm.sup.2×2 cm.sup.2), a silver/silver chloride (3 M KCl) electrode, and the Ti sheet as a counter electrode, a reference electrode, and a working electrode, respectively; a distance between the substrate Ti sheet and the counter electrode was controlled at 2.5 cm, and an infiltration area was kept at 1 cm.sup.2×1 cm.sup.2.

[0053] (3) A deposition electrolyte was configured, and an electrolytic cell was provided with a mixed solution containing 0.0075 mol L.sup.−1 of Co(NO.sub.3).sub.2, 0.0075 mol L.sup.−1 of MnCl.sub.2, 0.0503 mol L.sup.−1 of CH.sub.3CSNH.sub.2, and 0.005 mol L.sup.−1 of KCl, at a constant temperature of 25° C. with a pH value adjusted to 6.5, and the electrolyte remained still throughout the deposition.

[0054] (4) Under a one-step cyclic voltammetry electrodynamic deposition mode, the electrochemical deposition was conducted at a potential window of −1.2 V vs Ag/AgCl to 0.2 V vs Ag/AgCl and a scan rate of 8 mV s.sup.−1 with 6 scan segments for 9 min, and a Co.sub.9-xMn.sub.xS.sub.8 (x=4.5) nanogrid was deposited on the Ti substrate to form a uniform black film.

[0055] (5) The deposited electrode film was rinsed with deionized water for 3 min, and placed in magnetically-stirring deionized water to remove residual electrolyte on an electrode surface by vortex, and then dried in a vacuum drying box for 10 h to obtain a final product, where the Co.sub.9-xMn.sub.xS.sub.8 (x=4.5) nanosheets were non-uniformly distributed on the Ti substrate to form a grid structure.

[0056] (6) The dried electrode was placed in 0.5 M H.sub.2SO.sub.4 and 1 M KOH media separately, to conduct subsequent electrochemical tests of the cathodic HER by water electrolysis.

Preparation of a Co.SUB.9-x.Mn.SUB.x.S.SUB.8 .(x=4.5) Nanosheet Array Grid-Typed Hydrogen Evolution Electrode by Chronoamperometry Deposition

Example 5

[0057] (1) A substrate Ti sheet was pretreated, cut to 1 cm.sup.2×2 cm.sup.2, placed in 18% dilute hydrochloric acid to conduct an ultrasonic treatment for 20 min, ultrasonically cleaned with absolute ethanol and deionized water for 20 min, and then dried in a stream of nitrogen.

[0058] (2) A standard three-electrode system of an electrochemical workstation (CHI660D) was used, with a graphite sheet (2 cm.sup.2×2 cm.sup.2), a silver/silver chloride (3 M KCl) electrode, and the Ti sheet as a counter electrode, a reference electrode, and a working electrode, respectively; a distance between the substrate Ti sheet and the counter electrode was controlled at 2.5 cm, and an infiltration area was kept at 1 cm.sup.2×1 cm.sup.2.

[0059] (3) A deposition electrolyte was configured, and an electrolytic cell was provided with a mixed solution containing 0.0075 mol L.sup.−1 of Co(NO.sub.3).sub.2, 0.0075 mol L.sup.−1 of MnCl.sub.2, 0.0503 mol L.sup.−1 of CH.sub.3CSNH.sub.2, and 0.005 mol L.sup.−1 of KCl, at a constant temperature of 25° C. with a pH value adjusted to 6.5, and the electrolyte remained still throughout the deposition.

[0060] (4) Under a one-step chronoamperogalvanic deposition mode, the electrochemical deposition was conducted at a constant potential of −0.6 V vs Ag/AgCl for 10 min, and a Co.sub.9-xMn.sub.xS.sub.8 (x=4.5) nanogrid was deposited on the Ti substrate to form a uniform black film.

[0061] (5) The deposited electrode film was rinsed with deionized water for 3 min, and placed in magnetically-stirring deionized water to remove residual electrolyte on an electrode surface by vortex, and then dried in a vacuum drying box for 10 h to obtain a final product.

[0062] (6) The dried electrode was placed in 0.5 M H.sub.2SO.sub.4 and 1 M KOH media separately, to conduct subsequent electrochemical tests of the cathodic HER by water electrolysis.

[0063] FIG. 1 showed a cyclic voltammetry curve recorded during cyclic voltammetry electrodynamic deposition of a Co.sub.9-xMn.sub.xS.sub.8 nanogrid prepared at a room temperature. FIG. 2A and FIG. 2B, FIG. 3A and FIG. 3B, as well as FIG. 4A and FIG. 4B were SEM images of the Co.sub.9-xMn.sub.xS.sub.8 nanogrids on the electrodes prepared in Examples 1 to 3 and the corresponding partially-enlarged annotation images, respectively. By adjusting a content of manganese ions in the reaction system, three Co.sub.9-xMn.sub.xS.sub.8 nanogrids with different compositions and sizes were prepared, each with a complete crystal structure and uniform morphology. FIG. 5 showed XRD-based phase analysis diagrams of Co.sub.9-xMn.sub.xS.sub.8 (x=4.5 and 6) nanogrids on the electrodes prepared in Examples 2 and 3 and pure Co.sub.9S.sub.8. The Co.sub.9-xMn.sub.xS.sub.8 nanogrid had a diffraction peak that was completely consistent with a standard diffraction peak of the Co.sub.9S.sub.8 (JCPDS 02-1459), and exhibited a slight low-angle shift, which was caused by the introduction of manganese ions into the lattice. In the present disclosure, 2θ diffraction angles of the representative sample Co.sub.9-xMn.sub.xS.sub.8 (x=4.5) were 35.3°, 38.6°, 40.3°, 53.1°, 63.0°, 70.7°, and 76.1°, respectively, corresponding to (400), (331), (420), (531), (622), (642), and (800) planes of the Co.sub.9S.sub.8. FIG. 6 showed a comparison of LSV and Tafel curves of the Co.sub.9-xMn.sub.xS.sub.8 (x=3, 4.5, and 6) nanogrid-based hydrogen evolution electrodes on the electrodes prepared in Examples 1 to 3 and the pure Co.sub.9S.sub.8-based electrode, respectively. In the range of a hydrogen evolution potential, the Co.sub.9-xMn.sub.xS.sub.8 (x=4.5)-based hydrogen evolution electrode had lower onset potential and overpotential, and greater current density compared with those of the Co.sub.9S.sub.8-based electrode, indicating that manganese ions could significantly promote a hydrogen evolution catalytic performance of the host materials.