Electrochemical performance evaluation of pine sawdust derived carbons by incorporating with Mn, Mn–Fe or Mn–Ni oxides

The hybrid electrode material of transition metal oxide/carbon has good potential for the remarkable performance of supercapacitors. Here pine sawdust derived carbons were prepared with highly dispersed Mn, Mn–Fe or Mn–Ni oxides and hierarchical porous structure by CO2 gasification. Effects of the CO2 gasification conditions (including the gasification temperature, gasification reaction time and the metal loading amount) were investigated on the surface metal species, pore structures and morphology of the hybrid materials. The as-prepared hybrid materials show the total metal content less than 6.5 wt% but display good electrochemical performance, along with the specific capacitance up to 369.5–750.6 F g−1 at 0.5 A g−1 in the three-electrode system. Those doped with Mn–Fe or Mn–Ni binary metal composite can be a better candidate than that doped with the unary metal. The assembled asymmetric supercapacitor presents a high energy density of 13.9 Wh kg−1 at 375.9 W kg−1 in a potential window of 0–1.5 V. Besides, excellent cycling performance can be achieved with the capacitance retention rate of 92.8% after 5000 charge-discharge cycles at 5 A g−1. The synergism of the introduced metal oxides and carbon skeleton with the hierarchical porous structure enables the hybrid materials to provide the desirable specific capacitance, outstanding rate capability and cycling performance.