Iron oxide-based nanotube arrays derived from sacrificial template-accelerated hydrolysis: Large-area design and reversible lithium storage

We report a novel "sacrificial template-accelerated hydrolysis" (STAH) approach to the synthesis of iron oxide-based nanotube arrays including hematite Ot-Fe₂O₃ and magnetite Fe₃O ₄ on centimeter-scale conducting alloy substrates. ZnO nanowire arrays are chosen as the inexpensive and sacrificial templates that do not contribute to the component of final iron oxide nanotubes but can be in situ dissolved by the acid produced from the Fe³⁺ precursor hydrolysis. Interestingly, the ZnO template dissolution in turn accelerates the Fe ³⁺ hydrolysis, which is essential to initiating the nanotube formation. Such a STAH approach provides a morphology-reservation transformation, when various shaped ZnO templates are adopted. Moreover, by introducing glucose into the precursor solution, we also successfully obtain carbon/hematite(C/α-Fe₂O₃) composite nanotube arrays on large-area flexible alloy substrate, with a large number of pores and uniform carbon distribution at a nanoscale in the nanotube walls. These arrays have been demonstrated as excellent additive-free anode materials for lithium ion batteries in terms of good cycling performance up to 150 times (659 mA h g^-1) and outstanding rate capability. Our result presents not only a new route for inorganic nanotube formation but also an insight for rational design of advanced electrode materials for electrochemical batteries and sensors.