The kinetic H/D isotope effect in electroless copper plating. An EQCM study

The effect of H/D substitution in water and formaldehyde on the rate of electroless copper plating and either cathodic deposition or anodic dissolution of copper were studied by EQCM. The kinetic H/D isotope effect (k sub(H)/k sub(D)) ca. 4.5 was found for H/D substitution in formaldehyde and of about 1 when H sub(2)O was replaced by D sub(2)O under open-circuit conditions, indicating the rupture of C - H bond of formaldehyde to be the rate-limiting step in electroless copper plating. The k sub(H)/k sub(D) value up to 3 in anodic copper dissolution and cathodic reduction of Cu(II) ions for H/D substitution in water suggests that water molecules or hydroxyl ions are involved in the formation of intermediate oxy-(hydroxy-) species. Some synergetic features of mutual enhancement of anodic formaldehyde oxidation and cathodic Cu(II) reduction half-reactions in electroless copper plating are discussed in terms of both an oxygen-containing Cu(I) intermediate and preferable surface structure formation.