Oxygen defects, morphology, and surface chemistry of metal oxides: a deep insight through a joint experimental and theoretical perspective

Abstract

Comprehending the relationship between structure and function of materials is the main goal of materials science for the rational design of their enhanced performance. Despite being unavoidable, defects in materials are not considered an enemy of materials anymore, as some beneficial effects regarding their optimal properties, and consequently potential applications, have been observed. This suggests that the presence of defects is far from being completely understood. In this context, studying the basic interactions of defects in materials can provide a deeper comprehension of this conundrum. Thus, the consonance between the deviations of real materials and the ideal models are constant challenges to be addressed in solid-state science, which has for many decades demanded intense efforts from researchers regarding the control and exploitation of such imperfections. On the other hand, the morphology of materials is generally considered the key to modulate their functional properties. However, for semiconducting structures, morphology is as important as size and composition for the determination of the electronic structure. The exposed surfaces at the morphology are closely related to the physicochemical properties and distinct from the bulk of the material because they are constituted of undercoordinated atoms corresponding to oxygen vacancies and defects. The morphology control and manipulation at each exposed surface with a given surface energy provides a degree of freedom for harvesting and tailoring the functional properties of metal oxides, but this is usually a nontrivial task. Therefore, it is fundamental to understand how the local coordination of atoms at the exposed surfaces, that is, undercoordinated clusters of semiconductor metal oxides with oxygen vacancies, impacts the chemistry and physics of these semiconductors. Here, we investigate the relationship among oxygen defects, morphology, and surface chemistry of metal oxides using a combined experimental and theoretical strategy to unveil their peculiar technological applications as photoluminescent emission, photocatalysts, and antibacterial agents.