Investigation on Pesudocapacitance Mechanism of Magnéli Oxide Ti4O7 in Aqueous Electrolyte

Possessing high electronic conductivity and the nature of chemical inertness, the Magnéli phase titanium oxide Ti4O7 is a promising material for various electrochemical applications. Herein, the Ti4O7 electrode in aqueous Li2SO4 electrolyte is characterized for its supercapacitor applications. The oxide electrode exhibits pseudocapacitive behavior over a wide potential range of ±1.0 V (vs. Ag/AgCl), showing a specific capacitance of 105 F g−1, equivalent to 85 µF cm−2–oxide, along with outstanding high-rate performance and cycle stability (96 % capacitance retention after 5000 cycles). In situ X-ray absorption near-edge spectroscopy analysis on the Ti K-edge absorption reveals that the pseudocapacitance does not involve the redox reaction of the oxide electrode material. A pseudocapacitance mechanism attributed to the reversible redox reactions of the hydrogen and oxygen atoms adsorbed on the oxide surface is proposed.