Porous carbon spheres with high specific surface area (2955 m(2) g(-1)) and large pore volume (1.65 cm(3) g(-1)) were prepared by incorporating boron in spherical polymeric precursors followed by reactive H3PO4 activation. In such a process H3PO4 acted as both an activating agent to activate the polymeric precursors and a reactant to extract out the pre-embedded boron from the carbonized spheres through formation of base dissolvable BPO4, hence generated additional pores in the carbon spheres and also widened the pore diameters. With these improved texture properties, the porous carbon spheres exhibited much enhanced energy storage capacities as electrode of symmetrical electrochemical capacitor in 1 M TEABF(4)/PC electrolyte. Energy densities of 31.3 and 20.3 Wh kg(-1) were obtained at power densities of 259 and 11,000 W kg(-1) (based on the active mass of both electrodes), respectively, which were much higher than those of the porous carbon spheres prepared without boron template and commercial activated carbons (YP-50F, Kuraray). This study provided a versatile strategy to tune the texture properties of porous carbons by combining element incorporation and reactive chemical activations, thus could be potentially used to fabricate high performance carbonaceous electrode materials for electrochemical energy storage devices.