Method for improving catalytic activity

1. A method for improving the catalytic activity of an oxygen evolution reaction (OER) catalyst, the OER catalyst comprising a porous substrate with a porous catalytic metallic composite coating, the method comprising:

exposing the porous metallic composite coating to a reducing agent in solution at a temperature of between 10° C. and 50° C., wherein the porous metallic composite coating is a nickel-iron composite; and

reducing the nickel-iron composite upon the exposing of the porous metallic composite coating to the reducing agent so as to form a reduced nickel-iron composite having an increased oxygen vacancy density in the reduced nickel-iron composite as compared to the nickel-iron composite.

2. The method according to claim 1 , wherein the nickel-iron composite comprises a nickel-iron oxide, a nickel-iron hydroxide, or a mixture thereof.

3. The method according to claim 1 , wherein the nickel-iron composite has a formula of Ni 2x Fe 3y (OH) 2x+3y , wherein x is a number between about 0.1 and about 2 and y is a number between about 0.1 and about 2.

4. The method according to claim 1 , wherein the metallic composite coating is amorphous.

5. The method according to claim 4 , wherein the amorphous metallic composite coating comprises nanosheets, nanoflakes, or a combination thereof.

6. The method according to claim 1 , wherein the metallic composite coating is crystalline.

7. The method according to claim 1 , wherein the reducing agent is sodium borohydride (NaBH 4 ).

8. The method according to claim 1 , wherein the substrate is an electrically conductive substrate.

9. The method according to claim 8 , wherein the electrically conductive substrate is nickel foam.