Facile synthesis of hierarchical porous carbon/MnO composites for supercapacitor electrode materials

The hierarchical porous carbon/MnO composites were prepared from the homogenous mixture of potassium humate and manganese nitrate via one-step carbonization at 700 °C. Manganese nitrate in precursors has a synergistic catalysis effect with potassium element on the pore forming, also leads to an increased oxygen content of as-prepared composite. The PH-Mn-0.1 displays a hierarchical porosity with a moderate surface area of 776 m2 g−1 and total pore volume of 0.487 cm3 g−1, and MnO nanoparticles were uniformly deposited on the porous carbon matrix with a Mn content of 6.7 wt%. When used as electrode material for two-electrode symmetric supercapacitor, the PH-Mn-0.1 delivers higher volumetric capacitance of 276 F cm−3 at a current density of 50 mA g−1, consisting of pseudocapacitance related to MnO nanoparticles and electric double layer capacitance, a maximum energy density of 7.45 Wh kg−1 and low electrochemical resistance. Moreover, the PH-Mn-0.1 shows an enhanced rate capability due to its improved wettability, and novel cycle performance with an increasing specific capacitance during the 1000 charge–discharge cycles at 2500 mA g−1.