Sol‐gel derived mixed phase (Mn, Ti)‐oxides/graphene nanoplatelets for hybrid supercapacitors

Summary In this investigation, (Mn, Ti)‐ oxides were prepared using pluronic 123 templating assisted sol‐gel method. Sol‐A with Ti precursor in ethanol was acidified with HCl whereas sol‐B containing Mn precursor was prepared in ethanol containing 5 wt% pluronic 123 surfactant. Gelation was accomplished by the addition of de‐ionized water. As‐prepared gels were aged for 24 hours, dried at 80°C for 12 hours and calcined at 500°C to 1200°C for 5 hours to obtain powdered electrode materials, which were analyzed by x‐ray diffraction, scanning electron microscopy/energy‐dispersive x‐ray, and Brunauer‐Emmett‐Teller (BET) surface area analysis. Hybrid supercapacitors were fabricated using the sol‐gel derived (Mn, Ti)‐ oxides and Gr‐nanoplatelets electrodes with aqueous KOH (potassium hydroxide) as electrolyte. Fabricated supercapacitors were charged with 2.0 V and 0.01 A for 10 minutes. Charged supercapacitors were tested via cyclic voltammetry to determine specific capacitance. For the powdered materials prepared with Mn:Ti at 65:35 wt% and calcined at 500°C, x‐ray diffraction analysis revealed the presence of TiO2‐rutile, Mn2O3 and Mn3O4 as 20%, 60%, and 18%, respectively. At higher calcination temperature, TiO2‐rutile and Mn2O3 phases were found to be absent with the presence of higher perovskite (TiMnO3) phase. Both pore volume and BET specific surface area was found to decrease with increase in calcination temperature. The specific capacitance was found be dependent on Mn:Ti wt% used to prepare the powdered materials as well as the calcination conditions. The gel prepared with Mn:Ti of 30:70 wt% followed by 2‐step calcination yielded a maximum specific capacitance.