Surface chemistry of liquid bismuth under oxygen and water vapor studied by ambient pressure X-ray photoelectron spectroscopy

Abstract Bismuth (Bi) has a fairly low melting point of 544 K making it practical as a liquid metal medium in a number of applications. Under ambient atmospheric conditions the surface of solid Bi oxidizes. While the solid Bi interface has been fairly well characterized with surface science studies upon exposure to oxygen, to date little is known about the molecular level reactivity of the liquid interface. Using ambient pressure X-ray photoelectron spectroscopy the liquid–gas interfacial chemistry of Bi was examined upon exposure to oxygen gas and water vapor at 550 K up to a maximum pressure of 0.5 Torr. Water vapor remained unreactive towards the liquid interface over the entire pressure range. Oxygen remined unreactive up to 10−4 Torr, whereas above this pressure oxidation was observed forming Bi2O3. The oxidation exposure onset was > 5 × 105 Langmuirs, significantly higher than what is required for solid Bi interfaces.