Reduction of copper oxides by carbon monoxide at an applied potential

Abstract

Application of a potential to a gas phase reaction catalyst is one of the possible methods of catalytic activity control. Since this approach is not popular, there are few publications about the effect of applied potential and some aspects of this phenomenon have not been considered at all. However, it is of great interest to identify the factors that increase the activity of the reaction under conditions of applied potential. In this study, the activity of copper oxide reduction by carbon monoxide at an applied potential was analyzed by quantum-chemical calculations. According to the estimates, the highest activity should be observed for Cu₂O; the activity of CuO allotropes should be substantially lower. Low potentials of about one volt affect the binding energies of CO with oxides and the energy of the oxide reduction reaction, which eventually determines the activity of oxide reduction. A detailed analysis of the electronic structure of oxides does not allow us to draw clear conclusions about the activity. The electric field is assumed to be able to affect reduction when the oxides reach potentials of ∼±2 V. In the case of Cu₂O and CuO allotropes, the negative potential promotes the reduction reaction, which is consistent with the experiment. Calculations also showed that the differences in the reduction reaction energies of CuO allotropes at different potentials are due to the local changes in the interatomic bonding in these systems.