Controlled-Synthesis and Photocatalytic Properties of h-In2O3and c-In2O3

Figure 1. XRD patterns of the (a) InOOH, (b) In(OH)3, (c) h-In2O3, and (d) c-In2O3 products that were obtained using the hydrothermal method and thermal oxidation. Indium oxide (In2O3) is an important semiconductor with a wide band-gap of 3.6 eV that has been widely used in solar cells, gas sensors, optoelectronics, and photocatalysis. Many efforts have been devoted to the synthesis of In2O3 with various morphologies, such as nanocubes, nanotubes, nanotowers, nanorods, and hollow spheres. In2O3 has two phases of hexagonal In2O3 (h-In2O3) and cubic In2O3 (c-In2O3). Most of the synthetic methods have focused on preparing one of the two In2O3 phases. However, relatively little is known about the controlled synthetic method for the two specific phases of In2O3 that is carried out by adjusting the synthetic conditions. In this study, simple methods were reported for the production of InOOH and In(OH)3 using hydrothermal reactions in aqueous solutions containing InCl3, ethylenediamine (EDA), and N,N,N',N'-tetraethylethylenediamine (TEEDA). The selective formation of InOOH or In(OH)3 was controlled by varying the amount of water. h-In2O3 and c-In2O3 were also selectively synthesized through the thermal oxidation of the InOOH and In(OH)3 products, respectively as precursors. The photocatalytic properties of the h-In2O3 and c-In2O3 products that were fabricated this work were also examined.