why is Fe not used in the preparation of H₂ ?

• Metals like Fe, Ni, Co, Sn can react only when steam is passed over red hot metals.

3Fe + 4H₂O (steam) →         Fe₃O₄         + 4H₂

   Ferrosoferric oxide

• All active metals which lie above hydrogen in electrochemical series, can displace hydrogen gas from dilute mineral acids like HCl, H₂SO₄.

Fe + 2HCl → FeCl₂ + H₂

So, Fe is used in the preparation of hydrogen gas.