Synergistic Effect of Oxygen and Water on the Environmental Reactivity of 2D Layered GeAs

We investigated the reactivity of layered GeAs in the presence of oxygen or water using synchrotron-based X-ray photoelectron spectroscopy and ab initio calculations. By performing experiments at near-ambient pressure (up to 20 mbar), we gained detailed insights into the material’s stability under realistic conditions. GeAs showed limited reactivity with dry O2 and deaerated H2O. However, a small amount of humidity (Rw = 0.5% at T = 20 °C) in an O2 atmosphere significantly enhanced reactivity. This synergistic effect was well captured by density functional theory calculations, which revealed a strongly exothermic formation energy for the simultaneous chemisorption of O2 and H2O, compared to the adsorption of each molecule individually.