Oxygen Defect Modulated Titanium Niobium Oxide on Graphene Arrays: An Open-Door for High-Performance 1.4 V Symmetric Supercapacitor in Acidic Aqueous Electrolyte

Despite appealing supercapacitive properties, the acidic aqueous supercapacitors (SCs) are still suffering from low operating voltage (<1 V) leading to unsatisfactory energy densities. Herein, for the first time, it is reported that the oxygen defect modulated Ti 2 Nb 10 O 29− x (TNO x ) on interlinked graphene array (denoted as TNO x G) can achieve a wide potential window up to 1.8 V in 1 m H 2 SO 4 electrolyte and deliver an extremely high capacitance up to 368.9 F g −1 at 0.5 A g −1 . Accompanying the improved charge transfer efficiency and preferable H ion diffusion, the oxygen defects in TNO x G are capable of stimulating more pseudocapacitive behavior and simultaneously suppressing oxygen evolution reaction. Furthermore, a 1.4 V high voltage quasi-solid-state TNO x G-based symmetric supercapacitor is demonstrated, yielding a maximum energy density of 0.58 mWh cm −3 at a power density of 0.57 W cm −3 and exceptionally excellent cycling durability. It is believed that this strategy of oxygen defect modulation to optimize reaction kinetics will lead to further improvements in the performance of high-voltage aqueous SCs.