Fabrication of a NiO@NF supported free-standing porous carbon supercapacitor electrode using temperature-controlled phase separation method.

To address the problem that capacitor electrode being low in capacitance and reliant on binder to retain shape, a binder-free, self-supporting supercapacitor electrode is made via pyrolysis of porous polyacrylonitrile (PAN) formed by phase separation, supported by hydrothermally treated nickel foam backbone. The role of hydrothermal reaction time and PAN solution concentration on electrochemical properties was thoroughly studied, and the results indicate a generally peaked capacitance at 4 h of hydrothermal reaction time, but after a certain threshold, a supposed micro-domain buffering mechanism would take over and enhance the pseudocapacitance from NiO to reach a specific capacitance as high as 152 F/g at a high active material mass load of 14.98 mg/cm, providing the area specific capacitance up to 1.98 F/cm. The use of temperature-controlled phase separation and incorporation of nickel oxide together guarantees the electrode sufficient ion and electron transportation pathway while improving its capacitance by redox electrochemical reactions.