Tailoring the Surface Chemical Reactivity of Transition‐Metal Dichalcogenide PtTe₂ Crystals

PtTe 2 is a novel transition‐metal dichalcogenide hosting type‐II Dirac fermions that displays application capabilities in optoelectronics and hydrogen evolution reaction. Here it is shown, by combining surface science experiments and density functional theory, that the pristine surface of PtTe 2 is chemically inert toward the most common ambient gases (oxygen and water) and even in air. It is demonstrated that the creation of Te vacancies leads to the appearance of tellurium‐oxide phases upon exposing defected PtTe 2 surfaces to oxygen or ambient atmosphere, which is detrimental for the ambient stability of uncapped PtTe 2 ‐based devices. On the contrary, in PtTe 2 surfaces modified by the joint presence of Te vacancies and substitutional carbon atoms, the stable adsorption of hydroxyl groups is observed, an essential step for water splitting and the water–gas shift reaction. These results thus pave the way toward the exploitation of this class of Dirac materials in catalysis.