Revealing the structural properties of hydrogenated black TiO2 nanocrystals

Our recent discovery of hydrogenated black TiO2 nanocrystals has triggered intense research interests for many applications. The understanding of the properties of this new material, however, falls far from satisfactory. We present here a novel and quantitative structural analysis of hydrogenated black TiO2 nanocrystals from X-ray diffraction (XRD) based crystal morphology modeling assisted with high-resolution transmission electron microscopy measurements. This analysis method provides an in-depth understanding of the structural properties of the hydrogenated black TiO2 nanocrystals, which is otherwise hardly achievable in a quantitative way. Specifically, the percentage of various crystalline facets and the ratio of the crystalline/amorphous phases are clearly revealed, besides the surface excess pressure and stress over the crystalline phase, and the stabilizing function of the amorphous shell. This study thus sheds more light on the black TiO2 nanocrystals and may inspire more applications based on the newly revealed structural properties. We also demonstrate that the unique analysis method of XRD-derived crystal morphology modeling would be extremely useful to gain an in-depth understanding of the structural properties and behaviors of nanocrystals, especially in the case where only XRD is available and other direct measuring methods or high-end instruments are not available or are cost-prohibitive. Thus, it would promote great research interest in nanomaterials research with rich structural information, even under budget-limiting situations.