Conductive Nanosized Magnéli-Phase Ti₄O₇ with a Core@Shell Structure

Magnéli-phase Ti₄O₇, known for its high electrical conductivity and corrosion resistance, is typically prepared by hydrogen reduction at high temperatures (∼1000 °C), leading to large particles. Nanosized Ti₄O₇ have been explored for application toward high specific surface area electrode materials and electrocatalyst supports; nonetheless, the particle size of Ti₄O₇ is still insufficient for utilization as a support. In this study, we have pursued a novel synthetic approach for nanosized Ti₄O₇ platelets with a length of 10-80 nm and thickness of 3-10 nm even under high-temperature conditions. We herein describe the use of SiO₂ beads as a core to obtain a SiO₂ core coated with multilayers of TiO₂ nanosheets exfoliated from layered H₂Ti₄O₇ which is subsequently subjected to high-temperature reduction to prepare a SiO₂-core@Ti₄O₇-shell structure. The pair distribution function technique has proven that the shell is transformed to single-phase Ti₄O₇. The electrical double layer capacitance of SiO₂-core@Ti₄O₇-shell was much larger than that of conventionally synthesized Ti₄O₇ particles with a micrometer size. The results show the beneficial effects of the SiO₂-core@Ti₄O₇-shell structure, and it is the first example of the synthesis for conductive Ti₄O₇ with a high specific surface area even under conditions of high-temperature synthesis.