Shape-controlled Synthesis And Performance Of Efficient Visiblelight-responsive AgI Photocatalysts

The depletion trend of coal, oil, and natural gas and the deteriorating ecological environment are important issues to be solved currently, which resulted from the increasing population and frequent human activities. Photocatalytic technology becomes the research focus of world-wide scientists due to its characteristics of mild condition, sustainability and pollution-free. The morphology, size and structure of photocatalyst usual y have significant effects on the photocatalytic performance. Therefore, special functions of the photocatalysts can be achieved through controlling their morphology.In this paper, an organic amine assisted wet homogeneous precipitation method has been developed to prepare AgI micro/nanoparticles, with water was used as solvent, ethylenediamine to coordinate silver ions, and PVP to guide the growth orientation of uniform sized AgI polyhedra. By adjusting the concentration of ethylenediamine, the reaction temperature and dropping rate of KI solution, different morphologies of AgI micro/nanoparticles were obtained. SEM, TEM, UV-vis DRS and XRD measurements were carried out to examine the morphology, optical properties and structures of AgI particles. In addition, we investigated the relationship between morphologies of silver iodide and their photocatalytic activities for the degradation of rhodamine B. The formation mechanism of AgI crystals was studied. It is proposed that white crystals of silver iodide-ethylenediamine complex formed firstly, and then water treatment condition would induce the complex to decompose and generate regular-shaped AgI. It is interesting that morphologies of AgI crystals can be controlled through treatments on complexes by solvents with different polarities.We extended organic amine assisted homogeneous precipitation method, substituting ethanol and ethylene glycol for water as solvent respectively to prepare AgI particles with shaped morphology and uniform size. SEM, TEM, UV-vis DRS and XRD measurements were carried out to examine the morphology, optical properties and structures of AgI particles. Particularly, the selective synthesis of spherical and concave spherical silver iodide has been realized through applying alcohol as solvent. Their photocatalytic activities for the degradation of rhodamine B have been tested by photo-electrochemical measurements. Additionally, this method can be also used to synthesize AgCl and AgBr cubes.Graphene oxide can exhibit its super conductivity in composed photocatalys. In this paper, we adapted one-step alcohol heating method to wrap spherical AgI to form graphene-AgI composite, where the graphene oxide has been firstly prepared using modified Hummers method. SEM, XRD, UV-vis DRS measurements were used to characterize its structure and composition. In addition, the influence of the amount of graphene loaded on the photocatalytic performance was studied.