A density functional theory study on influence of 3d alloying elements on electrochemical properties of cobalt-base alloys

The paper systematically studies the impact of the 3d transition metals Ti, V, Cr, Mn, Fe, Ni and Cu on electrochemical stability of non-passivated cobalt-base alloys {0 0 0 1} surface by evaluating the chemical potential and the electrode potential shift relative to pure cobalt metal using density functional theory calculations. Cr, Fe, Mn, and V are found to make the Co atoms more stable on the {0 0 0 1} surfaces of the corresponding alloys compared to pure Co {0 0 0 1} surfaces, whereas Ti, Ni, and Cu make Co atoms much less stable. Among all the considered alloying elements, chrome is the most beneficial to the stability enhancement of alloys. Furthermore, the effects of water and hydroxyl adsorption on the electrochemical stability are considered. It is found that the surface adsorption properties may be considerably modified by introducing the Cr atoms. Our results indicate that water or hydroxyl adsorption destabilizes both the Co–Cr alloy and pure Co surface. However, the Co–Cr alloy surface is still more stable than the pure Co surface in the presence of adsorbed water, while the pure Co surface is more stable than the Co–Cr alloy surface in the presence of adsorbed hydroxyl. Our calculation reveals that the electrochemical corrosion property of the Co–Cr alloy is insensitive to water adsorption and sensitive to hydroxyl adsorption in comparison with the pure Co metal.