Flexible Hf₆Ta₂O₁₇@ acidified carbon nanotube composite films with enhanced interfacial interaction for high-performance supercapacitors

Recently, various transition metal oxides (TMOs) have been introduced to modify carbon nanotubes (CNTs), demonstrating great potential for high energy storage performance. Herein, we designed a novel flexible composite film based on Hf₆Ta₂O₁₇ (HTO) and CNTs to leverage their complementary advantages. HTO nanocrystals were prepared by the polymer derived ceramics (PDC) method, which could be uniformly distributed and firmly embedded on the surface of carboxy functionalized single-wall carbon nanotubes (SWCNTs). More importantly, we developed a new way to enhance the interfacial interaction between the TMOs and the carbon materials to optimize the energy storage performance of the resulting composites. Finally, the composite supercapacitor showed the maximum specific capacitance of 5862.5 mF cm⁻² at the current density of 5 mA cm⁻² with a potential window of 2 V, which was much higher than those obtained from the two materials alone. Furthermore, the synergistic effect was confirmed to efficiently reduce the work function of the composite as well as the energy required by the electronic transition. Our results implied that the composite materials based on TMO and carbon materials (e.g. nanotubes or graphene), including the flexible HTO@ acidified carbon nanotube composite film, holds real promise for the applications as promising energy storage materials.