Reactions Activated by Surface Under-coordinated X on Layered XTe2 (X = Pt, Pd and Ni)

We present an investigation of surface reactions catalyzed on layered transition metal dichalcogenides (TMDs) under both ultrahigh vacuum (UHV) and near-ambient-pressure (NAP) conditions, with scanning tunnelling microscopy, synchrotron-based photoelectron spectroscopy (PES), NAP-PES, NAP-mass spectroscopy and density-functional-theory modelling. In the design of ideal catalysts, a structure that provides the largest active surface for reactions but consumes minimal materials is highly desired. TMDs, owing to their two-dimensional structures, possess great advantages for such ideal catalysts. The present work sheds light on the catalytic properties of TMDs, including PtTe2, PdTe2 and NiTe2, and their potential as catalysts. Our results show that the under-coordinated X (Xuc; X = Pt, Pd and Ni) at the surface Te vacancies on XTe2 served as active sites for the reactions of adsorbed methanol, methane and carbon dioxide. Great reaction probabilities and varied selectivities were exhibited and associated with peculiar geometric and electronic effects — the hexagonal-lattice positioning and partial oxidation of the Xuc. The results suggest that these investigated TMDs surfaces can serve as efficient catalysts toward varied hydrocarbon reactions.