Method for treating a surface of a metallic structure

1. A method for treating a surface of a metallic structure, the metallic structure being made of a first metallic material; the method comprising the steps of:

(a) bonding an alloy material made of the first metallic material and a second metallic material with the structure; and

(b) etching away at least some of the first metallic material from a structure obtained after step (a) so as to obtain a treated structure with an increased specific surface area compared with the metallic structure before treatment.

2. The method of claim 1 , wherein the treated structure has a nanostructured surface with nano-pores.

3. The method of claim 2 , wherein step (a) comprises electrodepositing the alloy material onto the metallic structure.

4. The method of claim 3 , wherein an electrochemical cell is used for electrodepositing the alloy material onto the metallic structure; the electrochemical cell comprises a first electrode, a second electrode and an electrolyte in electrical connection; wherein the metallic structure to be treated being connected as the first electrode; and the electrolyte comprises a solution with ions of the first metallic material and ions of the second metallic material.

5. The method of claim 4 , wherein the solution of the electrolyte further comprises an acid.

6. The method of claim 4 , wherein step (b) comprises electrochemically de-alloying at least some of the first metallic material.

7. The method of claim 6 , wherein the de-alloying in step (b) is carried out in a solution with ions of the first metallic material, ions of the second metallic material and an acid.

8. The method of claim 6 , wherein the de-alloying in step (b) is carried out in an acidic solution comprising HC 1 , HNO 3 , H 2 SO 4 , or ammonium.

9. The method of claim 7 , wherein the electrodeposition in step (a) is carried out by applying a first voltage for a first duration to the metallic structure; and the de-alloying in step (b) is carried out by applying a second voltage different from the first voltage for a second duration to the structure obtained after step (a).

10. The method of claim 9 , wherein the first duration is 1-60 seconds.

11. The method of claim 9 , wherein the second duration is 1-60 seconds.

12. The method of claim 9 , wherein one of the first voltage and the second voltage is a negative voltage, and another of the first voltage and the second voltage is a positive voltage.

13. The method of claim 1 , wherein in step (b) at least some or all of the second metallic material is detached from the structure obtained after step (a) as the first metallic material is etched away.

14. The method of claim 13 , wherein the second metallic material detached from the structure obtained after step (a) is in a form of particles.

15. The method of claim 14 , wherein the detached second metallic material particles have nano-pores.

16. The method of claim 1 , further comprising the step of:

(c) repeating steps (a) and (b).

17. The method of claim 16 , wherein steps (a) and (b) are repeated for 20 to 160 times.

18. The method of claim 1 , wherein the alloy material is the form of micro-isles.

19. The method of claim 1 , wherein the first metallic material is chemically more reactive than the second metallic material.

20. The method of claim 19 , wherein the first metallic material is an aluminium-based material, a copper-based material, a zinc-based material, or a silver-based material; and the second metallic material is a nickel-based material, platinum, or gold.

21. The method of claim 1 , wherein the metallic structure is porous.

22. The method of claim 21 , wherein the metallic structure is in the form of a foam, a foil, a wire, or a mesh.

23. The method of claim 21 , wherein the metallic structure is an open-cell metal foam.

24. The method of claim 1 , further comprising the step of:

(d) generating, bonding or coating a metallic or metallic oxide material on a surface of the treated structure.

25. The method of claim 1 , further comprising the step of:

(e) generating, bonding or coating an electro-active or photocatalytic oxide material on a surface of the treated structure.

26. The method of claim 1 , further comprising the step of:

(f) modifying a surface of the treated structure using thermal treatment.

27. A method for treating a surface of an open-cell metal foam, the open-cell metal foam being made of a first metallic material; the method comprising the steps of:

(a) electrodepositing alloy material micro-isles made of the first metallic material and a second metallic material onto the open-cell metal foam; and

(b) electrochemically de-alloying at least some of the first metallic material from a structure obtained after step (a) so as obtain a treated open-cell metal foam with a nanostructured surface having nano-pores.

28. The method of claim 27 , further comprising the step of:

(c) repeating steps (a) and (b).

29. The method of claim 27 , further comprising at least one of the following step:

(d) generating, bonding or coating a metallic or metallic oxide material on a surface of the treated open-cell metal foam;

(e) generating, bonding or coating an electro-active or photocatalytic oxide material on a surface of the treated open-cell metal foam; and

(f) modifying a surface of the treated open-cell metal foam using thermal treatment.

30. The method in claim 27 , wherein in step (b) at least some or all of the second metallic material is detached from the structure obtained after step (a) as the first metallic material is de-alloyed, and wherein the detached second metallic material is a form of particles having nano-pores.

31. The method in claim 27 , wherein the first metallic material is an aluminium-based material, a copper-based material, a zinc-based material, or a silver-based material; and

the second metallic material is a nickel-based material, platinum, or gold.