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 F 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.