Supercapacitive performance of homogeneous Co3O4/TiO2 nanotube arrays enhanced by carbon layer and oxygen vacancies

Self-supported and binder-free electrodes based on homogeneous Co3O4/TiO2 nanotube arrays enhanced by carbon layer and oxygen vacancies (Co3O4/co-modified TiO2 nanotube arrays (m-TNAs)) are prepared via a simple and cost-effective method in this paper. The highly ordered TNAs offer direct pathways for electron and ion transport and can be used as 3D substrate for the decoration of electroactive materials without any binders. Then, by a facile one-step calcination process, the electrochemical performance of the as-obtained carbon layer and oxygen vacancy m-TNAs is approximately 83 times higher than that of pristine TNAs. In addition, Co3O4 nanoparticles are uniformly deposited onto the m-TNAs by a universal chemical bath deposition (CBD) process to further improve the supercapacitive performance. Due to the synergistic effect of m-TNAs and Co3O4 nanoparticles, a maximum specific capacitance of 662.7 F g(-1) can be achieved, which is much higher than that of Co3O4 decorated on pristine TNAs (Co3O4/TNAs; 166.2 F g(-1)). Furthermore, the specific capacitance retains 86.0 % of the initial capacitance after 4000 cycles under a high current density of 10 A g(-1), revealing the excellent long-term electrochemical cycling stability of Co3O4/m-TNAs. Thus, this kind of heterostructured Co3O4/m-TNAs could be considered as promising candidates for high-performance supercapacitor electrodes.