Flexible carbon fiber/reduced-TiO2 composites for constructing remarkable performance supercapacitors

In this paper, we synthesize honeycomb structure titanium dioxide (TiO2) grafted with carbon fiber (CF) composites (CF/TiO2) for flexible supercapacitors (SCs), which evidently boosts specific surface areas (SSA) of CF. In addition, we put forward an effective strategy for enhancing conductivity of TiO2 relying on construction of oxygen defects in NaBH4 solution. Amazingly, the reduced-TiO2 supporting on CF electrode (CF/R–TiO2) obtains from optimum conditions (2 M 4h) and exhibits the highest specific capacitance of 115.2 F g−1 at 1200 mA g−1, suggesting ultra-utilization of R–TiO2 for SC. Interestingly, its capacitance retention still remains 98.37% after 10000 cycles, which declares prominent cycling stability. Furthermore, we conduct density functional theory (DFT) analysis to reveal the enhancement mechanism of R–TiO2. With the reduction process, Fermi energy (EF) can obviously move conduction band (CB), which indicates increments of electronic conductivity of TiO2. Moreover, the aqueous symmetric SC based on CF/R–TiO2 (CF/R–TiO2-SC) expresses a high energy density of 49.6 Wh kg−1 at a power density of 1440 W kg−1. Meanwhile, the all-solid-state flexible supercapacitor (CF/R–TiO2-AFSC) further presents favorable flexibility in tested bending angles. Our results demonstrate that CF/R–TiO2 is provided with introduction of oxygen defects and honeycomb structure, which might have tremendous potential for SC.