| dc.description.abstract | Defect engineering has been shown as an efficient way to activate inert basal planes of 2D materials, as surface defects are typically active sites. In this study, we show that the reactivity of PtTe2 basal plane is enhanced by introducing surface Te-vacancies, corresponding to under-coordinated surface Pt (Ptuc), and the defect density can be controlled with Argon ion (Ar+) bombardment. With reflection high energy electron diffraction (RHEED), photoelectron spectroscopy (PES), and ambient pressure X-ray photoelectron spectroscopy (APXPS), we demonstrate that the Ar+ bombardment produces primarily surface Te-vacancies and the number of Ptuc grows almost in linear proportion with the Ar+ bombardment time. These spectra also indicate the decomposition of methanol adsorbed on the defective PtTe2 surface, evidenced by the formation of CHxO and CHx, and a highly positive correlation between the numbers of decomposed methanol and Ptuc, implying Ptuc as an active site toward the methanol decomposition. The surface reactivity of PtTe2 can therefore be manipulated by controlling the number of Ptuc through the Ar+ bombardment. With synchrotron-based APXPS, we show that the surface Te-vacancies on PtTe2 were enhanced by adsorbed methanol. The increased surface Te-vacancies were indicated by the decreased ratio of the Te 4d to Pt 4f core-level signals and increased Pt 4f signals at smaller binding energy, reflecting increased undercoordinated Pt (Ptuc). With increasing methanol exposure from high vacuum to near-ambient pressure (up to 0.1 mbar), both methanol decomposition, indicated by the production of atomic carbons and CHx, and the number of Te-vacancies were significantly promoted, implying that these processes could promote each other. We also noted that the number of Te-vacancies was saturated at about methanol pressure 0.01 mbar. The result implies, in addition to traditional defect engineering strategies (e.g., annealing, ion bombardment or plasma treatment), an alternative approach to engineer surface defects on layered 2D materials. | en_US |