The role of H ₂ O and O ₂ molecules and phosphorus vacancies in the structure instability of phosphorene

Abstract

The poor structural stability of phosphorene in air was commonly ascribed to humidity and oxygen molecules. Recent exfoliation of phosphorene in deoxygenated water promotes the need to re-examine the role of H2O and O2 molecules. Considering the presence of high population of vacancies in phosphorene, we investigate the interaction of H2O and O2 molecules with vacancy-contained phosphorene using first-principles calculations. In contrast to the common notion that physisorbed molecules tend to have a stronger adsorption at vacancy sites, we show that H2O has nearly the same adsorption energy at the vacancy site as that at the perfect one. Charge transfer analysis shows that O2 is a strong electron scavenger, which transfers the lone-pair electrons of the phosphorus atoms to the 2π * antibonding orbital of O2. As a result, the barrier for the O-O bond splitting to form O-P bonds is reduced from 0.81 eV at the perfect site to 0.59 eV at the defect site, leading to an about 5000 faster oxidizing rate at the defect site than at the perfect site at room temperature. Hence, our work reveals that the vacancy in phosphorene shows a stronger oxygen affinity than the perfect phosphorene lattice site. Structural degradation of phosphorene due to oxidization may occur rapidly at edges and grain boundaries where vacancies tend to agglomerate.2

Opto‐electronic properties of blue phosphorene oxide with and without oxygen vacancies

“…This value is within the range reported for some pure metallic oxides, which runs between 1 and 3 eV . This demonstrates the viability for the formation of the vacancy and the crucial role that it has for applications of BPO in adsorption, catalysis, and gas sensors …”

“…Up to this date, there is no report in the literature regarding the formation of the oxygen vacancy in the BPO. Indeed, many studies have considered defects in phosphorene, but they have mainly focused on the vacancy of phosphorous atoms . To evaluate the formation energy for the oxygen vacancy, we make use of the following expression: where E BPO–V is the equilibrium energy of the BPO with the oxygen vacancy created.…”

Two-Dimensional Black Phosphorus Carbide: Rippling and Formation of Nanotubes

“…However, these materials are chemically active and structurally unstable in standard ambient conditions. [27][28][29][30][31][32] For this reason, a new class of materials, the hybridized composites that combine the advantages and counteract the disadvantages of its constituent compounds are currently in the spotlight. [33][34][35][36][37][38] These materials can exist as heterostructures consisting of several layered 2D materials 33,[39][40][41] such as graphene/phosphorene, graphene/InSe, and boron nitride/phosphorene or 2D layers consisting of atoms of different elements.…”

Atomic-scale mechanisms of defect- and light-induced oxidation and degradation of InSe

“…6,12,13 Phosphorene is a well-known example which shows a rapid oxidation due to chemical adsorption of O2 molecules, 14 photo-oxidation, 4,5 and defect-assisted oxidation. 15 Indium selenide (InSe), a recently emerging layered metal monochalcogenide III-VI compound with each InSe layer composed of covalently bonded Se-In-In-Se atomic planes, has attracted great attention, 16,17 owing to its intriguing electronic properties and dramatically different behaviors compared with other 2D materials. 18,19 For instance, in sharp contrast to MoS2 with the well-known direct (monolayer)-indirect (multilayer) transition, InSe has an opposite thicknessdependent behavior with an indirect band gap for monolayer while a direct band gap for multilayer sheets when exceeding a critical thickness.…”