Coal-based graphitized activated carbon for solar energy powered supercapacitor IoT applications

Solar cells show promise as energy conversion gadgets, but their extended use is limited by intermittent sunlight. Self-powered solar cell integration with an electrical energy storage system could be one solution to this problem. Therefore, we have developed a coin cell supercapacitor (SC) device based on coal-based graphitized carbon materials and integrated with solar cells to assess its efficiency for energy transformation and storage for practical validity. Supercapacitor carbon electrode was developed from a naturally abundant carbon precursor i. e. low-grade coal using molasses as binder, for the fabrication of high-quality SC devices. The fabricated supercapacitor exhibits a notable 127 F g- 1 specific capacitance, maintaining 92 % of its initial value for up to 10,000 charge/discharge cycles at 5 A g- 1 , and a maximum energy density of 70.57 Wh kg- 1 and power density of 2000.17 W kg- 1 . In order to create a self-sustaining power pack, the SCs (4 V) are integrated with a commercial solar cell (6 V, 750 mAh). Importantly, in the presence of natural sunlight, the solar-powered as-fabricated supercapacitor bank can significantly power a commercial IoT module (4-6 V, 600 mAh) demonstrating its potential for successful solar-to-electric energy transformation and storage. The findings demonstrate that solar- powered coal-based SC can be explored as an incredibly rapid future-proof energy storage technology that can help reduce energy demand in the foreseeable future.