Hierarchical porous carbon nanosheet derived from waste engine oil for high-performance supercapacitor application

The utilization of electrode materials with high-performance and low-cost is crucial for the development of electrochemical energy storage devices. Waste engine oil is a toxic and hazardous waste; it is estimated that about 45 million tons of waste engine oil are generated per year worldwide. Herein, waste engine oil was first recycled as a raw material to fabricate hierarchical porous carbon nanosheets. The obtained material exhibited high specific surface area (up to 2276 m(2) g(-1)), hierarchical porous structure, and excellent capacitance performance. Its specific capacitance reached 352 F g(-1), and more than 87.7% of initial capacitance was retained when the current density was increased from 0.5 to 20 A g(-1). In addition, no apparent capacitance drop was observed after 5000 charge and discharge cycles. The superior capacitance performance than that of the commercial activated carbon and most of the waste-derived porous carbons, cheap and readily available raw materials, and environmental benefit due to proper recycling of the hazardous waste make the reported hierarchical porous carbon nanosheet a promising energy storage material.