Effects of carbon structure on electrochemical behaviour of polyluminol-based redox active composites- a comparative study

Redox-active carbon composites are promising for their excellent energy storage and their potential to leverage diverse, sustainable, low-cost, carbon substrates. This work investigated the impact of the surface structure of porous carbon substrates on the electrochemical capacitive performance of polyluminol‑carbon composites. The three carbon substrates were ordered mesoporous CMK-8, micropore rich YP-50F, and a micro- and mesoporous spent tea-based activated carbon (Tea AC). The Tea AC was developed using 2-step KOH-based activation, resulting in a high surface area with a higher microporosity compared to CMK-8, and a higher mesoporosity than YP-50F. The comparison of the 3 carbon substrates revealed that the Tea AC provided increased electrochemical energy storage with good rate performance due to effective polymer coating distribution, enhanced ion transport, and reduced diffusion limitations. The volumetric charges in the 3-electrode cells were notably higher in the polyluminol on Tea AC (374 ± 19C cm −3 ) than those of the polyluminol on CMK-8 (148 ± 7C cm −3 ) and the polyluminol on YP-50F (345 ± 21C cm −3 ). Redox kinetics analyses confirmed faster, surface-controlled processes in a larger mesopore and micropore combination, over predominantly micropores. This trend remained after scaling up from microelectrodes to asymmetric devices, leading to greater energy storage, faster kinetics and higher stability for the polyluminol on Tea AC-composite based device compared to the polyluminol on YP-50F-composite. The insights from this study highlight the importance of designing carbon substrate pore structures to complement the composite synthesis process and increasing energy density in the composite electrodes in energy storage applications. • Structure & chemistry of 3 carbons: meso-, micro-, & micro/mesoporous were studied. • A thin polyluminol coating increased charge stored in the order: Tea AC > YP AC > CMK-8. • Higher surface area & mesoporosity of Tea AC led to more polymer loading over YP AC. • Combined micro-/mesopores promote higher charge storage and faster redox reactions.