Reduction process of copper oxide film by formic acid

Abstract

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.

Advancing the Understanding of Photocatalytic Nitrate Reduction for Ammonia Synthesis: Copper Catalysts and Formic Acid Synergy

“…Despite the stability of these Cu phases, they can dissolve in diluted acids . The reaction of CuNp with formic acid has been reported to produce a copper formate complex in the reaction solution. , During light irradiation, photogenerated holes from TiO 2 reduce copper formate, resulting in the formation of reddish-colored Cu 2 O and metallic copper in the solution as shown in Figure ix. , During the initial few minutes of light irradiation, the copper-reconstituted phase forms on the TiO 2 surface, resulting in a stable TiO 2 /Cu 2 O phase with metallic copper deposition creating the catalyst. Cu 2 O is a good photocatalyst but usually suffers from low stability due to the copper’s unstable oxidation state .…”

“…Similarly, the selection of suitable sacrificial agents could play a crucial role in stabilizing copper in a lower oxidation state. Formic acid is commonly used as a sacrificial agent in nitrate reduction reactions. , Because of the reduction properties of formic acid, copper is expected to remain in its lower oxidation state, forming Cu and Cu 2 O. , Therefore, formic acid can serve multiple roles in the photocatalytic reaction.…”