On the comparison of oxygen and sulfur transfer reactivities in phosphine and phosphorene: the case of R3Sb(X) carriers (X = O or S)

Abstract

Functionalization is one of the most powerful tools in materials science for the development of new and innovative materials with tailored properties purposefully designed to enhance the overall stability of the system. This is particularly true for exfoliated black phosphorus, which suffers from easy decomposition by air and moisture, hampering its highly desirable applications, especially in electronics. The present work suggests an innovative approach to the functionalization process of this 2D-material based on the selective introduction of chalcogen atoms on the material surface through a reaction with suitable molecular precursors such as stibine chalcogenides (R₃Sb(X), X = O or S; R = organyl group). These molecules may readily act as chalcogen-transfer agents and, upon releasing the chalcogen atom atop the bP surface, leave stable stibines (R₃Sb) as byproducts, which may be easily removed from the functionalized bP surface. The work provides an overview of all the possible structural, electronic and energy aspects associated with the chalcogen-atom transfer from the stibine to phosphorus based compounds, exemplified by trialkyl phosphines and single layer exfoliated black phosphorus, i.e. phosphorene, P_n. In both cases the oxygen transfer is more exergonic than the sulfur transfer, with the associated free energy barrier for the phosphine process being higher. Although the sulfur transfer for the P_n is found to be endergonic (ca. +3.6 kcal mol⁻¹), the process may surely occur at high temperature. The evolution of the band structure upon the chalcogen transfer has been depicted in detail.