The Influence of Inert Ions on the Reactivity of Manganese Oxides

Inert ion doping is a possible method to modify electrical conductivity and catalytic activity of transition-metal oxide electrocatalysts. Despite the importance of dopants, little is known about the underlying mechanisms for the change of the system properties. We have performed density functional theory calculations to investigate the influence of different valent ions on the O2 evolution reaction activity of β-MnO2 and Mn2O3. While Mn2O3 is unaffected by dopants, β-MnO2 is strongly affected by ions placed in a subsurface position. Doping does not affect the ion charge at the active site, but instead it effects the bond character. This is concluded through an analysis of the density overlap regions indicator and the density of states showing that the partially covalent nature of the bonds in β-MnO2 is responsible for the changes in the adsorbate binding energies. This mechanism is not active in the mostly ionic Mn2O3. These results highlight the need to explicitly consider the detailed bonding situation...