Ultrafast and sustainable upcycling of low-rank coal into functional porous carbon for enhanced pseudocapacitive performance

Ultrafast Joule heating integrated molten-salt technique is developed. • This technique can transform bituminous coal into carbon materials in seconds. • The carbon material exhibits desirable capacitive energy storage performance. • Life-cycle assessment highlights both economic and environmental advantages. Low-rank bituminous coal remains largely underexploited for producing high-value carbon materials, primarily because its high ash content imposes energy-intensive purification steps and intricate downstream processing. Here, we have developed a catalyst-free, one-pot molten-salt synthesis protocol to convert raw coal directly into oxygen-rich, hierarchically porous carbons in a matter of seconds. Mechanistically, the exceptionally rapid heating and cooling rates (>100 K s −1 ) prove pivotal in generating curved nanosheet morphologies with hierarchical pore networks and an oxygen-enriched surface, both of which are instrumental in enhancing pseudocapacitive charge storage. When tested in 6 M KOH, the resultant carbon affords a specific capacitance of 264.1 F g −1 , appreciably higher than the 203.5 F g −1 obtained from carbons prepared via conventional molten-salt routes. Additionally, the ample oxygen-containing functionalities firmly immobilize polyoxometalate redox species within the porous matrix, and the substantial adsorption energies not only raise the capacitance further but also ensure outstanding cyclability. A thorough life-cycle assessment reinforces the pronounced economic and environmental merits of this methodology, thereby establishing it as a scalable and sustainable solution for valorizing low-rank coal into functional carbons. A catalyst-free, one-step strategy that integrates flash Joule heating into molten-salt synthesis has been proposed. This rapid activation process directly converts raw bituminous coal into high-purity, oxygen-rich hierarchical porous carbon in a short duration of seconds. The resulting material delivers a high capacitance of 264.1 F g −1 , markedly surpassing carbons produced by conventional molten-salt methods. Download: Download high-res image (105KB) Download: Download full-size image