Segregation at the surfaces of CuxPd1 − x alloys in the presence of adsorbed S

► Composition Spread Alloy Films applied to high throughput study of segregation. ► Cu segregation to the clean CuxPd1 − x alloy surface is exothermic over all x. ► Adsorbed S reduces the extent of Cu segregation to the CuxPd1 − x surface. ► Cu segregation to the S-treated CuxPd1 − x surface is driven by entropy.