Hierarchical Micro/Mesoporous Carbons Synthesized with a ZnO Template and Petroleum Pitch via a Solvent-Free Process for a High-Performance Supercapacitor

Hierarchical micro/mesoporous carbons were prepared using ZnO nanoparticles as hard templates and a petroleum industrial-residual pitch as the carbon source via a solvent-free process. The ZnO templates can be easily removed using HCl(aq), thereby avoiding limitations present in conventional porous silica templating approaches that require highly corrosive HF(aq) for template removal. Notably, the proposed solvent-free synthetic method from low-cost pitch to high-value porous carbons is a friendly process with respect to our overexploited environment. With the combination of ZnO nanoparticles and pitch, the surface area (76-548 m² g^-1) of the resultant mesoporous carbons increases with an increase in the weight ratios of ZnO to pitch. Furthermore, the hierarchical micro/mesoporous carbons with a large surface area (854-1979 m² g^-1) can be feasibly fabricated by only adding an appropriate amount of an activating agent. Meanwhile, N-doped hierarchical porous carbons can be achieved by carbonizing the blend of these materials with melamine. For supercapacitor application, the resultant carbons exhibit a high capacitance up to 200.5 F g^-1 at 5 mV s^-1 using LiClO₄/PC as the electrolyte in a symmetrical two-electrode cell. More importantly, the coin-cell supercapacitor based on porous carbons achieved a capacitance of 94 F g^-1 at 5 mV s^-1 and 63% capacitance retention at 500 mV s^-1, thereby holding the potential for commercialization.