Supercapacitive performance of TiO₂ boosted by a unique porous TiO₂/Ti network and activated Ti³

TiO₂ has been reported to have considerable capacity through appropriate surface modification. Previous studies of TiO₂-based supercapacitors mainly focused on anodized TiO₂ nanotubes and TiO₂ powder, even though the capacitance still lags behind that of carbon-base materials. In this work, a three-dimensional porous TiO₂/Ti (PTT) network was constructed by anodic oxidation and its capacitance was boosted by subsequent aluminum-reduction process. Activated Ti³⁺ was proved to be being successfully introduced into the surface of pristine PTT, resulting in the prominent enhancement of supercapacitive performance. An areal capacitance of 81.75 mF cm^-2 was achieved from Al-reduced PTT (Al-PTT) at 500 °C in 1 M H₂SO₄ electrolyte, which was among the highest value of pure TiO₂-based electrodes. Good electrochemical stability was also confirmed by the 3.12% loss of the highest capacity after 5000 CV cycles. More importantly, the activated Ti³⁺/Ti⁴⁺ redox couple in modified TiO₂ is solidly confirmed by being directly observed in CV curves. The capacitive mechanism of the redox reaction is also studied by electrochemical tests. The construction of a 3D porous network structure and efficient Ti³⁺ introduction provide an effective method to boost the supercapacitive performance of TiO₂-based materials for energy storage applications.