Shape-controlled iron oxide nanocrystals: synthesis, magnetic properties and energy conversion applications

Iron oxide nanocrystals (IONCs) with various geometric morphologies show excellent physical and chemical properties and have received extensive attention in recent years. The various shape-induced magnetic and electrochemical properties of the IONCs make them suitable for diverse applications. Understanding the correlation between the physicochemical properties and morphology of IONCs is a prerequisite for their widespread applications. Hence, this review focuses on current research progress regarding shape-controlled IONCs in different dimensions, and the corresponding shape-dependent magnetic, catalytic and gas-sensor properties are discussed. Furthermore, the general preparation methods, shape-guided growth mechanisms and energy conversion applications in photoelectrochemical water splitting, dye-sensitized solar cells (DSSCs) and lithium-ion batteries (LIBs) of these IONCs (alpha-Fe2O3, gamma-Fe2O3, Fe3O4) are also discussed. Finally, the perspectives of IONCs in promising research directions are proposed.