First-principles study of surface segregation in bimetallic Ni3M (M = Mo, Co, Fe) alloys with chemisorbed atomic oxygen

Segregation at metal alloy surfaces has an important impact on their catalytic and chemical properties. We have performed density-functional theory calculations to investigate the surface segregation behaviors of Ni3M (M = Mo, Co, Fe) alloys in the presence of chemisorbed atomic oxygen. The calculated results show that the segregation trend at a Ni3M(111) surface can be substantially modified by reactive gaseous environments. At an oxygen coverage of 1/4 ML, both the Ni-segregated and M-segregated surfaces are still less stable than the nonsegregated one for Ni3Fe alloy, while an M-segregated surface is more stable than the nonsegregated one for Ni3M (M = Mo, Co) alloys. Furthermore, the analysis of oxygen adsorption trends and surface electronic structures explains that the surface segregation trend is directly correlated to the surface-adsorbate binding strength. The present study provides valuable insight for exploring practical applications of Ni-based alloys as hydrogenevolution electrodes. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim