Recently a new group of two-dimensional (2D) materials, originating from the group V elements (pnictogens), has gained global attention owing to their outstanding properties. Due to a high surface-volume ratio and extraordinary chemical activity, 2D pnictogens such as phosphorene and antimonene are highly sensitive to exposure to the environment. Hence, upon the exposure to oxygen and water molecules, they may easily oxidize, which leads to the degradation of their structure. In this work, we perform a first-principles investigation on the effects of the environmental oxygen and water molecules on the structural stability of newly emerged group V 2D material bismuthene. It is proposed that the oxidation process of bismuthene and other 2D pnictogens at ambient сonditions сan involve three general steps: adsorption of oxygen moleсules; dissoсiation of oxygen moleсules; interaсtion of water moleсules with the oxygen speсies anсhored at the surface to form acids. Importantly, recent experiments reported on high stability of bismuthene even at high temperatures. Here we show that the underlying reason for such structural stability of bismuthene may have similar roots as the stability of antimonene which originates from an acceptor role of water molecules on that material while in the case of materials with the lower stability, like phosphorene and InSe, water molecules act as donors. The present work uncovers the oxidation mechanisms and suggests the ways for maintaining the stability of bismuthene and its 2D pnictogens counterparts, which may be important for their fabrication, storage, and applications.

Arsenene, a new group-V two-dimensional (2D) semiconducting material beyond phosphorene and antimonene, has recently gained an increasing attention owning to its various interesting properties which can be altered or intentionally functionalized by chemical reactions with various molecules. This work provides a systematic study on the interactions of arsenene with the small molecules, including H 2 , NH 3 , O 2 , H 2 O, NO, and NO 2 . It is predicted that O 2 , H 2 O, NO, and NO 2 are strong acceptors, while NH 3 serves as a donor. Importantly, it is shown a negligible charge transfer between H 2 and arsenene which is ten times lower than that between H 2 and phosphorene and about thousand times lower than that between H 2 and InSe and antimonene. The calculated energy barrier for O 2 splitting on arsenene is found to be as low as 0.67 eV. Thus, pristine arsenene may easily oxidize in ambient conditions as other group V 2D materials. On the other hand, the acceptor role of H 2 O on arsenene, similarly to the cases of antimonene and InSe, may help to prevent the proton transfer between H 2 O and OÀ species by forming acids, which suppresses further structural degradation of arsenene. The structural decomposition of the 2D layers upon interaction with the environment may be avoided due to the acceptor role of H 2 O molecules as the study predicts from the comparison of common group V 2D materials. However, the protection for arsenene is still required due to its strong interaction with other small environmental molecules. The present work renders the possible ways to protect arsenene from structure degradation and to modulate its electronic properties, which is useful for the material synthesis, storage and applications.

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Recently emerging two-dimensional (2D) bismuth, bismuthene, has excited the world scientific community. It has been successfully synthesized to show high structural stability. Bismuthene possesses enhanced interaction with gas molecules due to its large surface area, which is a characteristic feature of 2D materials. This work performs a systematic firstprinciples study on the effects of the environmental gas molecules (CO, NO, NO 2 , H 2 , and NH 3 ) on the electronic structure and chemical activity of bismuthene. It is found that CO, NO, and NO 2 serve as charge acceptors. Furthermore, the adsorption of NO and NO 2 can produce noticeable modifications in the band structure of bismuthene. H 2 and NH 3 act as charge donors to bismuthene. Importantly, there is a large amount of transferred charge and a low adsorption energy of H 2 on bismuthene. Thereby, our study suggests bismuthene as a promising material for gas sensing applications and production of hydrogen storage devices.[a] Dr.

New structures made on the basis of CZTS by substitution with Cr, Ti, V, and Mo were investigated by using density functional theory. The total substitution of Zn by Cr...