Method for manufacturing of three-dimensional freestanding porous thin-graphite with hierarchical porosity

A three dimensional graphite structure with a controlled porosity made by a method comprising:

• plating a metal layer on at least one of a nickel, an iron or a cobalt foam substrate;
• annealing the metal and the nickel, iron or cobalt foam into a porous metal-nickel, iron or cobalt catalyst, wherein the catalyst has a smooth and a porous surface;
• etching smooth surface of the annealed porous metal-nickel, iron or cobalt catalyst;
• growing a graphite layer on the porous surface of the annealed porous metal-nickel, iron or cobalt catalyst;
• and
• completely etching the porous metal-nickel, iron or cobalt catalyst to obtain the graphite layer,
• wherein the three dimensional graphite structure has multiple levels of pores having different porosities comprising a first level of pores and a second level of pores wherein the second level of pores have a smaller pore size and are disposed on the walls of said first level of pores.