Oxygen vacancy induced fast lithium storage and efficient organics photodegradation over ultrathin TiO2 nanolayers grafted graphene sheets

Abstract In this work we have developed a unique structure of ultrathin (5 nm) TiO 2 nanolayers grafted graphene nanosheets (TiO 2 /G) and integrated oxygen vacancy (V O ) into TiO 2 to enhance its lithium storage and photocatalytic performances. The defective TiO 2 /G was synthesized by a solvothermal and subsequent thermal treatment method. When treated in a H 2 atmosphere, the resulting TiO 2-x /G(H 2 ) has lower crystallinity, smaller crystal size, richer surface V O , higher surface area, larger pore volume, and lower charge transfer resistance than that reduced by NaBH 4 solid, i.e., TiO 2-x /G(NaBH 4 ). More importantly, the surface V O in the TiO 2-x /G(H 2 ) could remarkably inhibit the recombination of photogenerated electron-hole pairs compared with the bulk Vo in the TiO 2-x /G(NaBH 4 ). As a result, the combination of all the factors contributed to the superiority of TiO 2-x /G(H 2 ), which demonstrated not only 70% higher specific capacity, longer cycling performance (1000 cycles) and better rate capability for lithium-ion battery, but also higher photocatalytic activity and 1.5 times faster degradation rate for organic pollutants removal than TiO 2-x /G(NaBH 4 ). The findings in this work will benefit the fundamental understanding of TiO 2 /G surface chemistry and advance the design and preparation of functional materials for energy storage and water treatment.