نبذة مختصرة : PtTe2 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 PtTe2 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 PtTe2 surfaces to oxygen or ambient atmosphere, which is detrimental for the ambient stability of uncapped PtTe2-based devices. On the contrary, in PtTe2 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. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ; Horizon 2020 Framework Programme, H2020: 696656-GrapheneCore1 ; A.P. and G.C. thank Vito Fabio for technical support and Marilena Zappia for having participated in HREELS experiments. This work was partly performed in the framework of the Nanoscience Foundry and Fine Analysis (NFFA-MIUR Italy Progetti Internazionali) project under Proposal No. 2017004. This project received funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 696656-GrapheneCore1.
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