Combination of rGO/S, N/TiO2 for the Enhancement of Visible Light-Driven Toluene Photocatalytic Degradation

Toluene is one type of common volatile organic compound (VOC) that is produced by daily products and is harmful to human health. Therefore, the degradation of toluene is critical to improving indoor air quality value. Photocatalytic degradation is considered an efficient and safe method to convert toluene into water and carbon dioxide without the formation of a secondary pollutant. Performance improvement of TiO2, a typically applied photocatalyst, has advantages in light absorption and electron transfer process. In this study, the TiO2 improvement was carried out by the doping of sulfur and nitrogen (S, N) elements along with various reduced graphene oxide (rGO). The composition of 0.1wt%rGO/S0.05N0.1TiO2 performed higher photocatalytic degradation of toluene due to the elevation of specific surface area, formation of oxygen-containing functional group, and chemical defect structure. However, a higher amount of rGO addition creates the shielding effect and inhibits the light penetration. Moreover, the relative humidity and applied temperature influence the photocatalytic activity through the competitive adsorption or increase the collisions frequency, respectively. During the photocatalytic degradation using 0.1wt%rGO/S0.05N0.1TiO2, toluene will be converted into benzyl alcohol, benzaldehyde, benzoic acid, water, and carbon dioxide.

Simulating droplet motion on virtual leaf surfaces

A curvilinear thin film model is used to simulate the motion of droplets on a virtual leaf surface, with a view to better understand the retention of agricultural sprays on plants. The governing model, adapted from Roy et al. (2002 J. Fluid Mech. 454, 235–261 ( doi:10.1017/S0022112001007133 )) with the addition of a disjoining pressure term, describes the gravity- and curvature-driven flow of a small droplet on a complex substrate: a cotton leaf reconstructed from digitized scan data. Coalescence is the key mechanism behind spray coating of foliage, and our simulations demonstrate that various experimentally observed coalescence behaviours can be reproduced qualitatively. By varying the contact angle over the domain, we also demonstrate that the presence of a chemical defect can act as an obstacle to the droplet's path, causing break-up. In simulations on the virtual leaf, it is found that the movement of a typical spray size droplet is driven almost exclusively by substrate curvature gradients. It is not until droplet mass is sufficiently increased via coalescence that gravity becomes the dominating force.