Reduction process of copper oxide film by formic acid

The reduction of a copper oxide surface film by formic acid was investigated in situ using a spectroscopic ellipsometer. The activation energy of the reduction of the copper oxide film by formic acid was 97.4 kJ mol−1, and the reduction rate increased with increasing formic acid partial pressure. From experimental results, we assumed that the hydrogen atoms dissociated from the formic acid molecules that were adsorbed on the copper surface and reacted with the oxygen atoms, and the oxygen atoms desorbed as water. Furthermore, it was predicted that the reduction proceeds by the diffusion of oxygen atoms from bulk copper oxide to the copper surface, and the dissociation of hydrogen atoms from the formic acid molecules was the rate-determining step. Based on this prediction, the reduction rate was mathematically calculated, which was in good agreement with the experimental data.