Metal Organic frameworks and conducting polymer based materials for energy and sensing applications

Abstract

Supercapacitors are promising energy-storage devices owing to their high power density, rapid charge-discharge capability, and excellent cycling stability, but their relatively low energy density limits their applications. This thesis focuses on the development of metal-organic frameworks (MOFs) and conducting polymer (CP)-based composites for energy storage, with the conducting polymer-based composites further investigated for self-sensing applications. We synthesised a nitrogen-enriched Ni MOF using polyvinylpyrrolidone (PVP) as a nitrogen source and morphology-directing agent. Polypyrrole (PPy) and polyaniline (PANI) were combined with nitrogen-doped graphene quantum dots (NGQDs) to improve their electrochemical stability. NGQDs were synthesized by a simple hydrothermal method using PPy as the precursor and incorporated into PPy and PANI matrices through chemical oxidative polymerization. Among the NGQDs/PPy composites, the NPP-50 composite exhibited a specific capacitance of 664 F g⁻¹ at 0.8 A g⁻¹, an energy density of 90.2 Wh kg⁻¹, a power density of 600.4 W kg⁻¹, and 93% capacitance retention after 3000 cycles. Among the NGQDs/PANI composites, the NPA-25 composite achieved 947 F g⁻¹ at 1 A g⁻¹, an energy density of 67.6 Wh kg⁻¹, a power density of 599.7 W kg⁻¹, and 94% retention after 3000 cycles. Furthermore, both composites demonstrated current-sensing capability, highlighting their potential for integrated energy- storage and sensing applications. Overall, the developed Ni MOF and NGQD- based conducting polymer composites show promise as multifunctional electrode materials for advanced supercapacitors and self-sensing devices.