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Water-Induced Bimetallic Alloy Surface Segregation: A First Principle Study

Bimetallic alloys have drawn extensive attentions in materials science due to their widespread applications in electronics, engineering and catalysis. A very fundamental question of alloy is its surface segregation phenomenon. Many recent observations have shown that reactive gases or supports may have strong effects on alloy segregation. However, segregation in water, the most common solvent and environment, has not received enough attention. In this paper we give the quantitative descriptions on the surface segregation energies of 23 transition-metal impurities in Cu hosts under the conditions of water adsorption by performing density functional theory (DFT) calculations. The general trends in the changes of segregation energies caused by water adsorption are established. Our results show water adsorption could induce strong surface segregation tendencies for early and middle transition metals in Cu alloys. This finding not only prompts us to re-examine the potential effects of water on bimetallic alloy surfaces, but would be also very helpful as a guide for the further theoretical and experimental studies in this field.