Inductive Effect in Mn-Doped NiO Nanosheet Arrays for Enhanced Capacitive and Highly Stable Hybrid Supercapacitor

The inductive effect related to foreign metal substitution has great effect on the redox behavior of transition metal oxides, which plays an important role in their electrochemical activities. In this work, we demonstrate the inductive effect in nickel oxide nanosheet arrays (NSAs) via doping with the lower electronegative element Mn, which has greatly improved their electrochemical capacitance and stability. Density functional theory (DFT) calculations show that the inductive effect in Mn–NiO increases the electron transport efficiency, enhances the adsorption energy of OH^–, and also makes the compound more covalent. Therefore, Mn–NiO NSAs demonstrated a dramatically improved specific capacitance twofold better than that of pure NiO NSAs at a current density of 5 mA cm^–2 and higher stability without any decay of capacitance after 10 000 cycles at 30 mA cm^–2. Moreover, the hybrid supercapacitor device of Mn–NiO NSAs//graphene–CNT exhibited an excellent recycling stability after 50 000 cycles of charging/discharging at 6 A g^–1 with comparative energy density and power density.