Coral reef-like nickel phosphide-tungsten oxide nanocomposite, method for preparing the coral reef-like nickel phosphide-tungsten oxide nanocomposite and catalyst for electrochemical water splitting including the coral reef-like nickel phosphide-tungsten oxide nanocomposite

Patent metadata

Field	Value
Publication number	US-2023002921-A1
Application number	US-202117545412-A
Country	US
Kind code	A1
Filing date	Dec 8, 2021
Priority date	Jul 2, 2021
Publication date	Jan 5, 2023
Grant date	—

Abstract

A coral reef-like nickel phosphide-tungsten oxide nanocomposite is disclosed. The coral reef-like nickel phosphide-tungsten oxide nanocomposite has a structure in which algae-like transition metal-doped nickel phosphide nanosheets are deposited on coral-like tungsten oxide nanostructures grown vertically on a substrate. This structure allows the coral reef-like nickel phosphide-tungsten oxide nanocomposite to have a large surface area, which leads to a significant increase in the number of catalytic active sites, and ensures high conductivity and electrochemical stability of the coral reef-like nickel phosphide-tungsten oxide nanocomposite. Due to these advantages, the coral reef-like nickel phosphide-tungsten oxide nanocomposite has a low overpotential and superior hydrogen evolution reaction or oxygen evolution reaction efficiency when applied to a water splitting catalyst under alkaline conditions. Also disclosed are a method for preparing the coral reef-like nickel phosphide-tungsten oxide nanocomposite and a catalyst for electrochemical water splitting including the coral reef-like nickel phosphide-tungsten oxide nanocomposite.

First claim

What is claimed is:

1 . A coral reef-like nickel phosphide-tungsten oxide nanocomposite comprising a substrate, a core comprising a plurality of tungsten oxide nanostructures grown vertically on the substrate, and a shell comprising transition metal-doped nickel phosphide nanosheets covering a portion or the entirety of the surface of the core.

2 . The coral reef-like nickel phosphide-tungsten oxide nanocomposite according to claim 1 , wherein the substrate is a nickel foam.

3 . The coral reef-like nickel phosphide-tungsten oxide nanocomposite according to claim 1 , wherein the tungsten oxide nanostructures are in the form of nanowires, nanotubes or nanorods.

4 . The coral reef-like nickel phosphide-tungsten oxide nanocomposite according to claim 1 , wherein the tungsten oxide nanostructures have an average length of 20 to 100 μm and a thickness of 0.5 to 10 μm.

5 . The coral reef-like nickel phosphide-tungsten oxide nanocomposite according to claim 1 , wherein the tungsten oxide nanostructures have an interplanar distance (d-spacing) of 0.1 to 0.6 nm, as measured by X-ray diffraction.

6 . The coral reef-like nickel phosphide-tungsten oxide nanocomposite according to claim 1 , wherein the transition metal-doped nickel phosphide nanosheets have a structure in which a portion or the entirety of the surface of the nickel phosphide nanosheets is doped with at least one transition metal selected from the group consisting of Co, Fe, and Mo.

7 . The coral reef-like nickel phosphide-tungsten oxide nanocomposite according to claim 6 , wherein the transition metal is doped in an amount of 1 to 10 atomic %, based on 100 atomic % of the coral reef-like nickel phosphide-tungsten oxide nanocomposite.

8 . The coral reef-like nickel phosphide-tungsten oxide nanocomposite according to claim 1 , wherein the nickel phosphide of the transition metal-doped nickel phosphide nanosheets is NiP, Ni 2 P or a mixture thereof.

9 . The coral reef-like nickel phosphide-tungsten oxide nanocomposite according to claim 1 , wherein the amount of metal atoms in the shell is 25 to 45 atomic %, based on 100 atomic % of the coral reef-like nickel phosphide-tungsten oxide nanocomposite.

10 . A catalyst for electrochemical water splitting comprising the coral reef-like nickel phosphide-tungsten oxide nanocomposite according to claim 1 .

11 . The catalyst according to claim 10 , wherein the catalyst is for the hydrogen evolution reaction or oxygen evolution reaction.

12 . An electrode comprising the catalyst according to claim 10 .

13 . An electrochemical water splitting system comprising the electrode according to claim 12 , a counter electrode, and an electrolyte or ionic liquid.

14 . A method for preparing a coral reef-like nickel phosphide-tungsten oxide nanocomposite, comprising:
(A) introducing a tungsten oxide precursor on a substrate, followed by primary thermal treatment under vacuum conditions to form a core comprising a plurality of tungsten oxide nanostructures grown along a vertical direction on the substrate; (B) introducing a nickel precursor and a transition metal precursor on the tungsten oxide nanostructures, followed by electrodeposition to form a nickel hydroxide-tungsten oxide intermediate in which a shell comprising transition metal-doped nickel hydroxide nanosheets is deposited on the tungsten oxide nanostructures; and (C) introducing a phosphorus precursor into the nickel hydroxide-tungsten oxide intermediate, followed by secondary thermal treatment.

15 . The method according to claim 14 , wherein the substrate is a nickel foam.

16 . The method according to claim 14 , wherein the tungsten oxide precursor is selected from the group consisting of WO 3 , WO 2 , W 18 O 49 , and mixtures thereof.

17 . The method according to claim 14 , wherein the core comprising tungsten oxide nanostructures is grown by thermal evaporation.

18 . The method according to claim 17 , wherein the thermal evaporation is performed for 30 minutes to 2 hours after heating to 800 to 1200° C. at a ramp rate of 10 to 25° C./min under a vacuum of 0.07 mbar or less.

19 . The method according to claim 14 , wherein the nickel precursor is selected from the group consisting of nickel acetate, nickel halides, nickel nitrate, nickel chloride hexahydrate, nickel carbonyl complexes, and mixtures thereof.

20 . The method according to claim 14 , wherein the transition metal precursor is MCl x .6H 2 O or M(NO 3 ) x .6H 2 O (where M is Fe, Co, Mo or V and x is 1≤x≤10).

21 . The method according to claim 14 , wherein the nickel precursor and the transition metal precursor are mixed in a molar ratio of 1:1 to 6:1.

22 . The method according to claim 14 , wherein the electrodeposition is performed at −1.1 to −0.9 V for 250 to 350 seconds in the step (B).

23 . The method according to claim 14 , wherein the phosphorus precursor is selected from the group consisting of sodium hypophosphite (NaPO 2 H 2 .H 2 O), phosphate (H 3 PO 4 ), monoammonium phosphate (NH 4 H 2 PO 4 ), diammonium phosphate ((NH 4 ) 2 HPO 4 ), triethylphosphine ((C 2 H 5 ) 3 P), trimethylphosphine ((CH 3 ) 3 P), and mixtures thereof.

24 . The method according to claim 14 , wherein the transition metal is doped in an amount of 1 to 10 atomic %, based on 100 atomic % of the coral reef-like nickel phosphide-tungsten oxide nanocomposite.

25 . The method according to claim 14 , wherein the amount of metal atoms in the shell is 25 to 45 atomic %, based on 100 atomic % of the coral reef-like nickel phosphide-tungsten oxide nanocomposite.

26 . The method according to claim 14 , wherein the secondary thermal treatment is performed for phosphorization under an inert atmosphere at 100 to 500° C. for 1 to 3 hours.

27 . The method according to claim 14 , wherein the substrate is a nickel foam, the tungsten oxide precursor is WO 3 , the tungsten oxide nanostructures are grown by thermal evaporation for 50 to 70 minutes after heating to 1000 to 1100° C. at a ramp rate of 17 to 18° C./min under a vacuum of 0.06 mbar or less, the tungsten oxide nanostructures have an average length of 45 to 55 μm and a thickness of 1.5 to 2.5 the tungsten oxide nanostructures have an interplanar distance (d-spacing) of 0.31 to 0.42 nm, as measured by X-ray diffraction, the nickel precursor is nickel chloride hexahydrate, the transition metal precursor is FeCl 3 .6H 2 O or CoCl 2 .6H 2 O, the nickel precursor and the transition metal precursor are mixed in a molar ratio of 2:1 to 4:1, the nickel hydroxide-tungsten oxide intermediate is formed by electrodeposition at −1.1 to −0.9 V for 250 to 350 seconds, the phosphorus precursor is sodium hypophosphite (NaPO 2 H 2 .H 2 O), the secondary thermal treatment is performed for phosphorization under an inert atmosphere at 280 to 320° C. for 1.8 to 2.2 hours, the amount of the transition metal doped is 3.31 to 7.22 atomic %, based on 100 atomic % of the coral reef-like nickel phosphide-tungsten oxide nanocomposite, and the amount of metal atoms in the shell is 36 to 40 atomic %, based on 100 atomic % of the coral-like nickel phosphide-tungsten oxide nanocomposite.

Assignees

• S Oil Corp
• Postech Res & Business Dev Found

Inventors

• Paik Sang Cheol
• Yong Kijung
• Kim Dokyoung

Classifications

• C23C14/083

  of refractory metals or yttrium · CPC title

• C25B11/053

  characterised by multilayer electrocatalytic coatings · CPC title

• C25B11/091

  consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds · CPC title

• C25B1/04 Primary

  by electrolysis of water · CPC title

• C23C28/042

  including a refractory ceramic layer, e.g. refractory metal oxides, ZrO2, rare earth oxides · CPC title