High-throughput surface segregation across ternary alloy composition space

Multicomponent alloys have gained attention in catalysis due to their improved performance over conventional monometallic counterparts. These improvements arise from their resistance to poisoning and deactivation, enhanced thermal properties, particle stability, and the ability to tune surface composition to control selectivity. The design of multicomponent catalysts is complicated by surface segregation, in which the surface becomes enriched or depleted in one or more components. Researchers have studied segregation in binary alloys, both experimentally and computationally, and some have employed composition spreads to understand the effects of bulk composition on segregation trends. However, few have examined segregation in ternary or higher-order alloys.

This work investigates surface segregation in five catalytically relevant ternary systems under ultra-high vacuum conditions. A high-throughput approach is employed by pairing composition spread thin films with spatially resolved spectroscopies of varying depth sensitivity: energy dispersive X-ray spectroscopy, low-energy ion scattering spectroscopy, and X-ray photoelectron spectroscopy. Trends are discussed, and an empirical method for predicting ternary surface compositions from binary measurements is proposed. Finally, changes in surface composition resulting from environmental changes are addressed in two separate experiments: first, by exposing alloys to hydrogen flow and measuring their response, and second, by measuring segregation kinetics in response to a rapid change in temperature.