Prediction of Adsorption Probability of Oxidizing and Reducing Species on 2-D Hybrid Junction of rGO-ZnO From First Principle Analysis

The target of this paper is to theoretically investigate the probability of gas (both oxidizing and reducing) adsorption on the van der Waals heterojunction formed between p-type reduced graphene oxide (rGO) and n-type two-dimensional monolayer of ZnO (2D-ZnO), using density functional theory-based first principle calculation employing Virtual Nanolab Atomistix Toolkit (v2016.4). Two types of heterostructures are considered, viz., heterostructure type-1, where hydroxyl group (sp
²
) is at the edge of the rGO and heterostructure type-2, where hydroxyl group (sp
³
) is perpendicular to the plane of rGO. Adsorption energy, charge transfer, and the distance of the nearest atom from the adsorbent are calculated for oxidizing (NO
₂
as the test case) and reducing (NH
₃
as the test case) species and compared with that of oxygen on rGO/2D-ZnO heterostructures as well as on its individual constituent (rGO nanoflakes and 2D-ZnO, separately). Like 2D-ZnO, heterostructure type-1 was also found to be selective towards NO
₂
with almost three times and five times higher adsorption energy than that of 2D-ZnO and rGO, respectively. On the other hand, it was found that charge distribution in the underlying 2D-ZnO of heterostructure type-2 remained almost unaltered even after gas adsorption and therefore lead to insignificant improvement compared to its 2D-ZnO counterpart.