Utilization of high‑sulfur-containing petroleum coke for making sulfur-doped porous carbon composite material and its application in supercapacitors

As a by-product generated in a large amount in petroleum refining, high‑sulfur petroleum coke has very limited applications except being used as a fuel for combustion. To extend its applications, various utilization pathways have been seeking for many years. In this work, an attempt was made for the preparation of a sulfur-doped hierarchical porous carbon (HPC) directly from the high‑sulfur petroleum coke without using the external sulfur. A HPC with a surface area of 3318 m2 g−1 was successfully prepared by the one-step method, which has excellent electrochemical performance with a specific capacitance of 327 F g−1 at the current density of 1 A g−1. Moreover, the HPC was further modified with MnO2 nanowires to form a porous composite material, which was used for making high-performance supercapacitors. Amazingly, a higher specific capacitance of 480 F g−1 was achieved at the current density of 1 A g−1. The asymmetric supercapacitor that was assembled using the HPC/MnO2 and HPC as the positive and negative electrode respectively in 1 M Na2SO4 solution had achieved a maximum energy density of 49.7 Wh kg−1 at the power density of 450 W kg−1, which is better than most of the data reported in literature. This study suggested that the high‑sulfur petroleum coke could be a suitable source for making sulfur doped porous carbon composite materials, which are very promising for applications in supercapacitors.