Mesoporous In-Sn binary oxides of crystalline framework with extended compositional variation

Abstract

Indium-tin oxide is considered a highly promising mixed-metal oxide system, because it shows good performance in various industrial processes. Therefore, it will be of great importance to explore the possibility of obtaining new In-Sn oxides with controlled contents whose properties could be tailored. However, In or Sn content in In-Sn oxides has generally been restricted to <10% because of their low solid solubility into counterpart metal oxide framework. Herein, we report for the first solvothermal synthesis of crystalline mesoporous In-Sn oxides with a broad range of In/Sn ratios and their opto-electrochemical properties. For the synthesis, we use phenolic polymer as a structure-directing agent. Surprisingly, we observe that the phenolic polymer plays a critical role in overcoming their low solubility by manipulating kinetics of crystal nucleation and subsequet growth. As a result, we obtain In-rich rutile SnO2 phase without phase separation with up to 50% In content and Sn-rich rhombohedral In2O3 structure with higher In content. The synthesized materials are highly transparent regardless of In content. The electrochemical properties are sensitive to In content. Our strategy offers possibility of realizing crystalline mesoporous mixed-metal oxides with tunable contents, thus opening a new perspective for the development of optoelectronic materials.